FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] MONITORING SYSTEM MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 2 DESCRIPTION Field [0001] The present disclosure relates to a monitoring system to monitor the state of a brake apparatus for a 5 railway vehicle. Background [0002] For example, a conventional brake apparatus measures a brake cylinder pressure (BC pressure) after a 10 predetermined time has elapsed from the start of a brake release operation, and when the measured BC pressure is equal to or higher than a predetermined value, recognizes such a BC pressure as indicating a brake non-release state (see, for example, paragraph [0005] of Patent Literature 1). 15 Citation List Patent Literature [0003] Patent Literature 1: Japanese Patent Application Laid-open No. 08-290766 20 Summary Technical Problem [0004] Unfortunately, in the case of recognizing the brake non-release depending on whether or not the BC 25 pressure is equal to or higher than a predetermined value, as in the conventional technique, there is a problem of failure to recognize an anomaly or a sign of an anomaly, which is a phase preceding the brake non-release. [0005] The present disclosure has been made to solve the 30 above problem, and an object of the present disclosure is to provide a monitoring system capable of recognizing an air discharge anomaly or a sign of an air discharge anomaly, which is the phase preceding the brake non-release. 3 Furthermore, an object of the present disclosure is to provide a monitoring system capable of recognizing an air supply anomaly or a sign of an air supply anomaly, which is a phase preceding insufficient braking. 5 [0006] To achieve the above object, a monitoring system according to the present disclosure comprises: a brake cylinder pressure detection unit to detect a brake cylinder pressure indicating a pressure of a brake cylinder of a brake device to generate a mechanical braking force by 10 pressing a friction material against a rotating body provided in a vehicle; an air discharge time measurement unit to measure a brake cylinder pressure air discharge time required for the brake cylinder pressure detected by the brake cylinder pressure detection unit to fall to a 15 predetermined first reference pressure after a brake command is canceled when the vehicle stops and the brake command is input; and a diagnosis unit to determine that there is an air discharge anomaly or a sign of an air discharge anomaly when the brake cylinder pressure air 20 discharge time measured by the air discharge time measurement unit is equal to or longer than a predetermined first reference time. [0007] A monitoring system according to the present disclosure comprises: a brake cylinder pressure detection 25 unit to detect a brake cylinder pressure indicating a pressure of a brake cylinder of a brake device to generate a mechanical braking force by pressing a friction material against a rotating body provided in a vehicle; an air supply time measurement unit to measure a brake cylinder 30 pressure air supply time required for the brake cylinder pressure detected by the brake cylinder pressure detection unit to rise to a fourth reference pressure set to be lower than a target brake cylinder pressure for a brake command, 4 after the brake command is input when the vehicle stops and the brake command is not input; and a diagnosis unit to determine that there is an air supply anomaly or a sign of an air supply anomaly when the brake cylinder pressure air 5 supply time measured by the air supply time measurement unit is equal to or longer than a predetermined sixth reference time. Advantageous Effects of Invention 10 [0008] A monitoring system according to the present disclosure comprises: a brake cylinder pressure detection unit to detect a brake cylinder pressure indicating a pressure of a brake cylinder of a brake device to generate a mechanical braking force by pressing a friction material 15 against a rotating body provided in a vehicle; an air discharge time measurement unit to measure a brake cylinder pressure air discharge time required for the brake cylinder pressure detected by the brake cylinder pressure detection unit to fall to a predetermined first reference pressure 20 after a brake command is canceled when the vehicle stops and the brake command is input; and a diagnosis unit to determine that there is an air discharge anomaly or a sign of an air discharge anomaly when the brake cylinder pressure air discharge time measured by the air discharge 25 time measurement unit is equal to or longer than a predetermined first reference time. It is therefore possible to recognize an air discharge anomaly or a sign of an air discharge anomaly, which is the phase preceding the brake non-release. 30 [0009] A monitoring system according to the present disclosure comprises: a brake cylinder pressure detection unit to detect a brake cylinder pressure indicating a pressure of a brake cylinder of a brake device to generate 5 a mechanical braking force by pressing a friction material against a rotating body provided in a vehicle; an air supply time measurement unit to measure a brake cylinder pressure air supply time required for the brake cylinder 5 pressure detected by the brake cylinder pressure detection unit to rise to a fourth reference pressure set to be lower than a target brake cylinder pressure for a brake command, after the brake command is input when the vehicle stops and the brake command is not input; and a diagnosis unit to 10 determine that there is an air supply anomaly or a sign of an air supply anomaly when the brake cylinder pressure air supply time measured by the air supply time measurement unit is equal to or longer than a predetermined sixth reference time. It is therefore possible to recognize an 15 air supply anomaly or a sign of an air supply anomaly, which is the phase preceding the insufficient braking. Brief Description of Drawings [0010] FIG. 1 is a block diagram illustrating an example 20 of the configuration of a monitoring system according to a first embodiment of the present disclosure. FIG. 2 is a block diagram illustrating an example of the configuration of a brake control device according to the first embodiment of the present disclosure. 25 FIG. 3 is a diagram illustrating an example of measurement of a brake cylinder pressure air discharge time by the monitoring system according to the first embodiment of the present disclosure. FIG. 4 is a diagram illustrating another example of 30 measurement of the brake cylinder pressure air discharge time by the monitoring system according to the first embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of 6 measurement of the brake cylinder pressure air discharge time and a pressure air discharge time by the monitoring system according to the first embodiment of the present disclosure. 5 FIG. 6 is a flowchart illustrating an example of the procedure of determination of a sign of an air discharge anomaly and an air discharge anomaly using the brake cylinder pressure air discharge time by the monitoring system according to the first embodiment of the present 10 disclosure. FIG. 7 is a flowchart illustrating an example of the procedure of determination of a sign of an air discharge anomaly and an air discharge anomaly using the brake cylinder pressure air discharge time by the monitoring 15 system according to the first embodiment of the present disclosure. FIG. 8 is a diagram illustrating an example of temporal changes in brake cylinder pressure air discharge time. 20 FIG. 9 is a block diagram illustrating an example of the configuration of the brake control device according to a second embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example of measurement of a brake cylinder pressure air supply time by 25 the monitoring system according to the second embodiment of the present disclosure. FIG. 11 is a diagram illustrating another example of measurement of the brake cylinder pressure air supply time by the monitoring system according to the second embodiment 30 of the present disclosure. FIG. 12 is a diagram illustrating an example of measurement of the brake cylinder pressure air supply time and the AC pressure air supply time by the monitoring 7 system according to the second embodiment of the present disclosure. FIG. 13 is a flowchart illustrating an example of the procedure of determination of a sign of an air supply 5 anomaly and an air supply anomaly using the brake cylinder pressure air supply time by the monitoring system according to the second embodiment of the present disclosure. FIG. 14 is a flowchart illustrating an example of the procedure of determination of a sign of an air supply 10 anomaly and an air supply anomaly using the brake cylinder pressure air supply time by the monitoring system according to the second embodiment of the present disclosure. FIG. 15 is a diagram illustrating an example of temporal changes in brake cylinder pressure air supply time. 15 FIG. 16 is a diagram illustrating an example of the hardware configuration that implements each device of the monitoring system according to the first and second embodiments of the present disclosure. 20 Description of Embodiments [0011] Embodiments of a monitoring system according to the present disclosure will be hereinafter described with reference to the drawings. [0012] First Embodiment. 25 FIG. 1 is a block diagram illustrating an example of the configuration of a monitoring system according to the present first embodiment. As illustrated in FIG. 1, for example, the monitoring system 1 according to this first embodiment includes brake control devices 3, terminal 30 devices 4, a central device 5, an on-board wireless device 7, and a ground device 8, etc. The brake control device 3 controls a brake device installed in the associated vehicle 2 of a train. The terminal device 4 collects state 8 information indicating the states of a plurality of devices including the brake control device 3 installed in the associated vehicle 2. The central device 5 acquires the state information on the plurality of devices output from 5 each terminal device 4. The on-board wireless device 7 sends the state information, etc. output from the central device 5, to the ground side through wireless communication via a network 6. The ground device 8 acquires the state information, etc. from the vehicle 2 via the on-board 10 wireless device 7. In addition, the foremost vehicle 2a includes a cab 9. The cab 9 includes a control operation device (not illustrated) such as a main controller (master controller) that generates a brake command corresponding to a brake operation performed by a driver, and a monitor 15 display (not illustrated), etc. Note that although FIG. 1 illustrates only two vehicles 2, namely, the front vehicle 2a and the following vehicle 2b adjacent to the foremost vehicle 2a, but the number of vehicles 2 of the train is not limited to a particular number. 20 [0013] The central device 5 acquires the state information on a plurality of devices output from each terminal device 4 that collects the state information indicating the states of the plurality of devices installed in the associated vehicle 2. The devices installed in the 25 vehicle 2 are not illustrated in detail, but include a propulsion control device, an auxiliary power supply device, an air conditioner, a lighting device, a door, a wheel, a motor, etc. in addition to the brake control device 3, for example. Note that the types of installed devices are 30 sometimes different depending on the vehicle 2. The plurality of devices are each installed in the vehicle 2 and is connected via an in-vehicle transmission path (branch transmission path) 10 to the terminal device 4 9 provided in that vehicle 2. Each of the plurality of devices is provided with various sensors, etc. to detect the state information on the associated device. The state information on each of the plurality of devices is 5 collected by the associated terminal device 4 via these sensors, etc. The in-vehicle transmission path 10 is a transmission path disposed in the vehicle 2 and is configured using, for example, a local area network (LAN) line. In addition, each of the plurality of devices is 10 assigned device identification information for uniquely identifying the corresponding device. Likewise, each vehicle 2 having the plurality of devices installed therein is assigned vehicle identification information for uniquely identifying the corresponding vehicle. In addition, car 15 number information indicating a car number allocated to the vehicle 2 or vehicle type information indicating whether the vehicle 2 is a front vehicle, a middle vehicle, or a rear vehicle may be attached to the vehicle identification information. 20 [0014] The terminal devices 4, each of which is installed in the corresponding vehicle 2, are connected to one another via an inter-vehicle transmission path (trunk transmission path) 11. The inter-vehicle transmission path 11 is a transmission path disposed across the vehicles 2 25 and is configured using, for example, a LAN line. The terminal device 4 sends control information including a control command, etc. output from the central device 5, to each device in the vehicle 2. In addition, the terminal device 4 sends the collected state information on each 30 device to the central device 5 in accordance with a command from the central device 5. [0015] The central device 5 is installed in, for example, each of the front vehicle 2a and a rearmost vehicle 2 (not 10 illustrated). The central device 5 is connected to the terminal devices 4 and acquires and manages the state information on each device output from each terminal device 4. Then, the central device 5 sends the state information 5 on each device managed by the central device 5, to the ground device 8 via the on-board wireless device 7. [0016] In addition to the management of the state information on the plurality of devices, the central device 5 manages train information sent and received in the train. 10 The train information is, for example, train service information indicating stop information, arrival/departure station time, etc., train identification information that identifies the train, train position information indicating the position of the train, train speed information 15 indicating the speed of the train, vehicle count information indicating the number of coupled vehicles of the train, traveling direction information indicating the traveling direction of the train, vehicle length information indicating the vehicle length of each vehicle 2 20 of the train, and notch information indicating the number of notches of the main controller. In addition, the central device 5 manages door open/close information indicating open/close information on doors provided in each vehicle 2 for passengers to get on and off, as the state 25 information. The central device 5 may also manage environmental information indicating the atmospheric temperature, humidity, precipitation, wind speed, etc. around the location of the train. The central device 5 is connected to the cab 9 and sends the control information 30 input from the control operation device, etc. of the cab 9, to each device via the terminal device 4 placed in each vehicle 2 to control that device. In addition, the monitor display of the cab 9 displays information such as the speed 11 of the train, the open/close states of the doors, and the brake cylinder pressure, for example. [0017] FIG. 2 is a block diagram illustrating an example of the configuration of the brake control device according 5 to the first embodiment of the present disclosure. As illustrated in FIG. 2, the brake control device 3 includes a control unit 12, a brake control valve 13, a relay valve 14, an air spring pressure detection unit (hereinafter, referred to as “AS pressure sensor”) 15, an AC pressure 10 detection unit (hereinafter, referred to as “AC pressure sensor”) 16, a brake cylinder pressure detection unit (hereinafter, a “BC pressure sensor”) 17, etc. As illustrated in FIG. 2, in addition to the brake control device 3, the vehicle 2 is also provided with a brake 15 device 18, wheels 19, an air spring 20, a compressed air tank 21, a speed sensor 22, a temperature detection unit (temperature sensor) 23, etc. For example, a brake command output from the main controller of the cab 9 is input to the brake control device 3, and the brake control device 3 20 controls the operation of the brake device 18 on the basis of the brake command. The brake command, which is input to the brake control device 3 from the main controller operated by the driver, etc., includes, for example, a service brake command (brake notch signal) set in seven 25 stages and an emergency brake command used for emergency stop, etc. [0018] The brake device 18 is a mechanical brake that applies to each wheel 19 and is provided on an axle of each wheel 19. The brake device 18 includes a brake cylinder 24 30 and a brake shoe 25. The brake shoe is a friction material that acts in correspondence to the pressure of air inside the brake cylinder 24. When the pressure in the brake cylinder 24 of the brake device 18 is raised by the supply 12 of the compressed air to the brake cylinder 24 from the compressed air tank 21 via the brake control device 3, the brake shoe 25 is pressed against the wheel 19 to thereby generate a mechanical braking force. The wheel 19 is a 5 rotating body that rotates during the travelling of the vehicle 2. The mechanical braking force is represented by the product of a pressing force, which is a force for pressing the brake shoe 25 against the wheel 19, and a friction coefficient of a contact surface between the brake 10 shoe 25 and the wheel 19. Note that the brake device 18 may be a disc brake. In a case where the brake device 18 is a disc brake, a brake disc, which is a rotating body, is secured to an axle, etc. The brake disc is sandwiched by brake pads, which are friction materials, in accordance 15 with the BC pressure, thereby generating the mechanical braking force. [0019] Although not illustrated in detail, the brake control valve 13 is made up of, for example, an apply magnet valve (AMV) and a release magnet valve (RMV). The 20 apply magnet valve is an electromagnetic valve to supply the compressed air to the relay valve 14. The release magnet valve is an electromagnetic valve to discharge the compressed air from the relay valve 14. The brake control valve 13 opens and closes the apply valve and the release 25 valve on the basis of the compressed air from the compressed air tank 21 and an electromagnetic valve opening/closing signal from the control unit 12, thereby controlling the flow rate of the compressed air to be supplied to the relay valve 14. 30 [0020] The relay valve 14 uses the compressed air in the compressed air tank 21 to supply the brake cylinder 24 with compressed air proportional to the pressure of the compressed air from the brake control valve 13 and having 13 an amplified flow rate. [0021] The AS pressure sensor 15 is a sensor that detects an AS pressure indicating the pressure of the air spring 20 provided in the vehicle 2. The AS pressure, 5 which is the pressure of the air spring 20, is a signal indicating the weight of the vehicle 2. The AS pressure is input to the AS pressure sensor 15. The AS pressure sensor detects this AS pressure and outputs the measured value of the AS pressure to the control unit 12. In the air spring 10 20, the AS pressure to be output to the AS pressure sensor 15 varies in accordance with the load applied to the vehicle 2. For this reason, on the basis of the AS pressure, the control unit 12 can measure the load applied to the vehicle 2. 15 [0022] The AC pressure sensor 16 detects an AC pressure. The AC pressure is the pressure of the compressed air to be supplied as a brake command pressure from the brake control valve 13 to the relay valve 14. The AC pressure sensor 16 outputs the measured value of the AC pressure to the 20 control unit 12. [0023] The BC pressure sensor 17 detects a BC pressure. The BC pressure is the pressure of the compressed air to be supplied from the relay valve 14 to the brake cylinder 24. The BC pressure sensor 17 outputs the measured value of the 25 BC pressure to the control unit 12 as a brake cylinder pressure measurement value. The brake cylinder pressure measurement value is hereinafter, referred to as “BC pressure measurement value”. [0024] The speed sensor 22 is a sensor that generates a 30 speed signal indicating the speed of the vehicle 2 on the basis of the rotation speed of the wheels 19 and outputs the generated speed signal to the control unit 12. Note that, although not illustrated in FIG. 2, the speed sensors 14 22 are placed on the front and rear railroad trucks of the vehicle 2, and the vehicle 2 can detect the speed from each wheel 19. [0025] The temperature sensor 23 is a sensor that is 5 provided around the brake device 18 and detects temperature information around the brake device 18. The temperature sensor 23 detects the temperature information around the brake device 18 and outputs the detected temperature information to the control unit 12. 10 [0026] In the vehicle 2, the control unit 12 controls the brake device 18 so as to generate the mechanical braking force by pressing the brake shoe 25 against the wheel 19. The control unit 12 calculates a braking force necessary for the vehicle 2, on the basis of the brake 15 command and the AS pressure. The necessary braking force is obtained by the product of the load of the vehicle 2 and deceleration included in the brake command. Then, the control unit 12 computes a target pressure value in the brake cylinder 24, on the basis of the computed braking 20 force. The control unit 12 includes, for example, a determination unit 26, an air discharge time measurement unit 27, a position information acquisition unit 28, and an environmental information acquisition unit 29. [0027] FIG. 3 is a diagram illustrating an example of 25 measurement of a brake cylinder pressure air discharge time by the monitoring system according to the first embodiment of the present disclosure. In FIG. 3, the horizontal axis indicates the brake cylinder pressure air discharge time (hereinafter, referred to as “BC pressure air discharge 30 time”). The BC pressure air discharge time indicates the elapsed time from when the brake command is canceled and the BC pressure starts to be discharged to the brake cylinder 24. The vertical axis indicates the BC pressure 15 detected by the BC pressure sensor 17. For example, the determination unit 26 determines whether or not the brake command is canceled (for example, a brake release command is input) when the vehicle 2 stops and the brake command is 5 input. Examples of when the vehicle 2 stops include, but are not limited to, when the vehicle 2 stops at a station or when the vehicle 2 is checked in leaving the depot. As illustrated in FIG. 3, when the brake command is canceled, the BC pressure starts to fall because the BC pressure is 10 discharged. For example, when determining that the brake command is canceled, the determination unit 26 notifies the air discharge time measurement unit 27 of a brake command cancellation signal indicating that the brake command is canceled. 15 [0028] As illustrated in FIG. 3, the air discharge time measurement unit 27 measures the BC pressure air discharge time after the brake command is canceled. More specifically, when receiving the brake command cancellation signal from the determination unit 26, the air discharge 20 time measurement unit 27 first measures the BC pressure air discharge time required for the BC pressure detected by the BC pressure sensor 17 to fall to a predetermined first reference pressure P1. The first reference pressure P1, which may be the value of a pressure set to be higher than 25 a threshold value of a BC pressure used for conventional detection of brake non-release, is set to, for example, 50 kPa. The air discharge time measurement unit 27 also individually measures the BC pressure air discharge times required for the BC pressure detected by the BC pressure 30 sensor 17 to fall to a predetermined second reference pressure P2 and a predetermined third reference pressure P3. The second reference pressure P2 is a pressure value set to be lower than the first reference pressure P1, and the 16 third reference pressure P3 is a pressure value set to be lower than the second reference pressure P2. The second reference pressure P2 only needs to be set to be lower than the first reference pressure P1 and is not limited to a 5 particular value. For example, the second reference pressure P2 is set to a half value of the first reference pressure P1. In addition, the third reference pressure P3 only needs to be set to be lower than the second reference pressure P2 and is not limited to a particular value. For 10 example, the third reference pressure P3 is set to 2 to 10 [kPa]. [0029] Similarly, the air discharge time measurement unit 27 also measures an AC pressure air discharge time after the brake command is canceled. More specifically, 15 when receiving the brake command cancellation signal from the determination unit 26, the air discharge time measurement unit 27 first measures the AC pressure air discharge time required for the AC pressure detected by the AC pressure sensor 16 to fall to the first reference 20 pressure P1. The air discharge time measurement unit 27 also individually measures the AC pressure air discharge times required for the AC pressure detected by the AC pressure sensor 16 to fall to the second reference pressure P2 and the third reference pressure P3. 25 [0030] The position information acquisition unit 28 acquires, from the central device 5, the train position information indicating the position of the train, for example. In addition, the environmental information acquisition unit 29 acquires, from the central device 5, 30 the environmental information indicating the atmospheric temperature, humidity, precipitation, wind speed, and the like around the location of the train, for example. [0031] For example, the control unit 12 associates the 17 BC pressure air discharge time and the AC pressure air discharge time measured by the air discharge time measurement unit 27 with information such as the train position information, the environmental information, the 5 temperature information, date and time information, brake command information, and the door open/close information when the determination unit 26 determines that the brake command is canceled. In addition, the control unit 12 further associates the BC pressure air discharge time and 10 the AC pressure air discharge time with the vehicle identification information on the vehicle 2 having the brake device 18 installed therein, the device identification information on the brake device 18, and the device identification information on the brake control 15 device 3, and sends the associated information to the ground device 8 via the on-board wireless device 7. [0032] As illustrated in FIG. 1, the ground device 8 includes a data accumulation unit 30 and a diagnosis unit 31. The data accumulation unit 30 accumulates the BC 20 pressure air discharge time, the AC pressure air discharge time, etc. sent from the vehicle 2. Note that the data accumulation unit 30 also similarly accumulates information acquired by a brake control device 3 installed in a vehicle 2 of a train other than the vehicle 2 of the train in such 25 a manner as to distinguish the information acquired by the brake control device 3 of the former vehicle 2 from the information acquired by the brake control device 3 of the latter vehicle 2. For example, the diagnosis unit 31 determines an air discharge anomaly or a sign of an air 30 discharge anomaly relating to the BC pressure discharge operation, using the BC pressure air discharge time, etc. The diagnosis unit 31 acquires, for example, the BC pressure air discharge time and the AC pressure air 18 discharge time from the data accumulation unit 30. [0033] In FIG. 3, an air discharge time-BC pressure curve BR1 indicating the relationship between the BC pressure air discharge time and the BC pressure at the 5 normal time is indicated by the solid line. In addition, an air discharge time-BC pressure curve BR2 indicating the relationship between the BC pressure air discharge time and the BC pressure at the time of an air discharge anomaly sign is indicated by a broken line. An air discharge time10 BC pressure curve BR3 indicating the relationship between the BC pressure air discharge time and the BC pressure at the time of an air discharge anomaly is indicated by a broken line. An air discharge time-BC pressure curve BR4 indicating the relationship between the BC pressure air 15 discharge time and the BC pressure at the time of brake non-release is indicated by a broken line. [0034] Meanwhile, a first reference time T1 illustrated in FIG. 3 is a reference time which the diagnosis unit 31 uses for determining a sign of an air discharge anomaly. 20 The first reference time T1 is set to be shorter than the threshold value of the BC pressure air discharge time used for detection of brake non-release and is set to, for example, 1 to 3 [sec]. In addition, a second reference time T2 is a reference time which the diagnosis unit 31 25 uses for determining an air discharge anomaly, and is set to be longer than the first reference time T1. The second reference time T2 is set to be longer than the first reference time T1 by 1 to 2 [sec], for example. Likewise, a third reference time T3 is a reference time which the 30 diagnosis unit 31 uses for determining brake non-release, and is set to be longer than the second reference time T2. In addition, a fourth reference time T4 is a reference time which the diagnosis unit 31 uses for determining an air 19 discharge anomaly or a sign of an air discharge anomaly, and is set to be longer than the first reference time T1. Note that, although FIG. 3 illustrates an example in which the fourth reference time T4 is set to the same time as the 5 third reference time T3 (T3=T4), the fourth reference time T4 is not limited to this example. The fourth reference time T4 only needs to be set to be longer than the first reference time T1 and may be set to the same time as the second reference time T2, for example. In addition, the 10 fourth reference time T4 may be set to be shorter than the second reference time T2 or longer than the third reference time T3. A fifth reference time T5 is a reference time which the diagnosis unit 31 uses for determining an air discharge anomaly or a sign of an air discharge anomaly, 15 and is set to be longer than the third reference time T3 and the fourth reference time T4. The first to fifth reference times T1 to T5 are recorded in advance in a recording unit (not illustrated) provided in the ground device 8, for example. Note that the first to fifth 20 reference times T1 to T5 may be set for each brake control device 3. In addition, the diagnosis unit 31 may acquire the first to fifth reference times T1 to T5 from a device at the on-board side, such as the brake control device 3 provided in the vehicle 2, via the on-board wireless device 25 7. [0035] In FIG. 3, a region shorter than the first reference time T1 after the brake command is canceled is defined as a normal region. In addition, a region equal to or longer than the first reference time T1 but shorter than 30 the second reference time T2 is defined as an air discharge anomaly sign region. Likewise, a region equal to or longer than the second reference time T2 but shorter than the third reference time T3 is defined as an air discharge 20 anomaly region. In addition, a region equal to or longer than the second reference time T2 is defined as a brake non-release region. [0036] As indicated by the air discharge time-BC 5 pressure curve BR1 in FIG. 3, the diagnosis unit 31 determines that the BC air discharge time is normal, for example, when the BC pressure air discharge time is within the normal region, that is, when the BC pressure air discharge time required for the BC pressure to fall to the 10 first reference pressure P1 after the brake command is canceled is shorter than the first reference time T1. In addition, as indicated by the air discharge time-BC pressure curve BR2 in FIG. 3, the diagnosis unit 31 determines that there is a sign of an air discharge anomaly, 15 for example, when the BC pressure air discharge time is within the air discharge anomaly sign region, that is, when the BC pressure air discharge time required for the BC pressure to fall to the first reference pressure P1 after the brake command is canceled is equal to or longer than 20 the first reference time T1 but shorter than the second reference time T2. Then, when determining that there is a sign of an air discharge anomaly, for example, the diagnosis unit 31 generates and outputs an attention signal for calling attention. For example, by sending the 25 attention signal output from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information calling attention, on the monitor display of the cab 9 of the vehicle 2. [0037] In addition, as indicated by the air discharge 30 time-BC pressure curve BR3 in FIG. 3, the diagnosis unit 31 determines that there is an air discharge anomaly, for example, when the BC pressure air discharge time is within the air discharge anomaly region, that is, when the BC 21 pressure air discharge time required for the BC pressure to fall to the first reference pressure P1 after the brake command is canceled is equal to or longer than the second reference time T2 but shorter than the third reference time 5 T3. Then, when determining that there is an air discharge anomaly, for example, the diagnosis unit 31 generates and outputs an anomaly signal for notifying of the anomaly. For example, by sending the anomaly signal output from the diagnosis unit 31 to the vehicle 2 via the network 6, the 10 ground device 8 displays information notifying of the anomaly, on the monitor display of the cab 9 of the vehicle 2. [0038] In addition, as indicated by the air discharge time-BC pressure curve BR4 in FIG. 3, the diagnosis unit 31 15 determines that the brake is not released, for example, when the BC pressure air discharge time is within the brake non-release region, that is, when the BC pressure air discharge time required for the BC pressure to fall to the first reference pressure P1 after the brake command is 20 canceled is equal to or longer than the third reference time T3. Then, when determining that the brake is not released, for example, the diagnosis unit 31 generates and outputs not only a brake non-release signal for notifying that the brake is not released but also a stop command for 25 stopping the vehicle 2. For example, by sending the brake non-release signal and the stop command output from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information notifying of the brake non-release, on the monitor display of the cab 9 of the 30 vehicle 2 and additionally stops the vehicle 2 based on the stop command. [0039] FIG. 4 is a diagram illustrating another example of measurement of the brake cylinder pressure air discharge 22 time by the monitoring system according to the first embodiment of the present disclosure. As described above, as indicated by the air discharge time-BC pressure curve BR1 in FIG. 3, the diagnosis unit 31 determines that the BC 5 air discharge time is normal, for example, when the BC pressure air discharge time is within the normal region, that is, when the BC pressure air discharge time required for the BC pressure to fall to the first reference pressure P1 after the brake command is canceled is shorter than the 10 first reference time T1. However, even when the BC air discharge time is shorter than the first reference time T1, a situation where the BC pressure is not appropriately discharged for some reason is likely to occur thereafter. In FIG. 4, an air discharge time-BC pressure curve BR5 and 15 an air discharge time-BC pressure curve BR6 are indicated by broken lines. The air discharge time-BC pressure curve BR5 and the air discharge time-BC pressure curve BR6 indicate the relationship between the BC pressure air discharge time and the BC pressure when the diagnosis unit 20 31 determines that there is an air discharge anomaly or a sign of an air discharge anomaly when the BC pressure air discharge time required for the BC pressure to fall to the first reference pressure P1 after the brake command is canceled is shorter than the first reference time T1. 25 [0040] As indicated by the air discharge time-BC pressure curve BR5 in FIG. 4, for example, when the BC pressure air discharge time is within the normal region, that is, when the BC pressure air discharge time required for the BC pressure to fall to the first reference pressure 30 P1 after the brake command is canceled is shorter than the first reference time T1, the diagnosis unit 31 determines whether or not the BC pressure air discharge time required for the BC pressure to fall to the second reference 23 pressure P2 after the brake command is canceled is equal to or longer than the fourth reference time T4. When determining that the BC pressure air discharge time required for the BC pressure to fall to the second 5 reference pressure P2 after the brake command is canceled is equal to or longer than the fourth reference time T4, the diagnosis unit 31 determines that there is an air discharge anomaly or a sign of an air discharge anomaly. Then, when determining that there is an air discharge 10 anomaly or a sign of an air discharge anomaly, for example, the diagnosis unit 31 generates and outputs an anomaly signal for notifying of the air discharge anomaly or an attention signal for calling attention. For example, by sending the anomaly signal or the attention signal output 15 from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information notifying of the anomaly or information calling attention, on the monitor display of the cab 9 of the vehicle 2. Note that whether the diagnosis unit 31 determines that there is an 20 air discharge anomaly or a sign of an air discharge anomaly in such a case as indicated by the air discharge time-BC pressure curve BR5 in FIG. 4 may depend upon the values of the second reference pressure P2 and the fourth reference time T4. 25 [0041] As indicated by the air discharge time-BC pressure curve BR6 in FIG. 4, for example, when determining that the BC pressure air discharge time is within the normal region, that is, the BC pressure air discharge time required for the BC pressure to fall to the first reference 30 pressure P1 after the brake command is canceled is shorter than the first reference time T1 and determining that the BC pressure air discharge time required for the BC pressure to fall to the second reference pressure P2 after the brake 24 command is canceled is shorter than the fourth reference time T4, the diagnosis unit 31 determines whether or not the BC pressure detected by the BC pressure sensor 17 when the fifth reference time T5 has elapsed is equal to or 5 higher than the third reference pressure P3. When determining that the BC pressure detected by the BC pressure sensor 17 at a time of lapse of the fifth reference time T5 is equal to or higher than the third reference pressure P3, that is, when determining that there 10 is a residual pressure of the BC pressure, the diagnosis unit 31 determines that there is a possibility of leakage of an SR pressure (compressed air pressure) into the relay valve 14. Then, the diagnosis unit 31 generates and outputs a leak-in notification signal for notifying that 15 there is a possibility of leak-in of the SR pressure, for example. For example, by sending the leak-in notification signal output from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information notifying that there is a possibility of leak-in of the SR 20 pressure, on the monitor display of the cab 9 of the vehicle 2. [0042] FIG. 5 is a diagram illustrating an example of measurement of the brake cylinder pressure air discharge time and the AC pressure air discharge time by the 25 monitoring system according to the first embodiment of the present disclosure. For example, as indicated by the air discharge time-BC pressure curve BR2 or the air discharge time-BC pressure curve BR3 in FIG. 5, when determining that there is a sign of an air discharge anomaly or an air 30 discharge anomaly, the diagnosis unit 31 uses the AC pressure air discharge time in order to further perform determination for specifying what part is a factor of the sign of the air discharge anomaly or the air discharge 25 anomaly. In the lower diagram of FIG. 5, the horizontal axis indicates the AC pressure air discharge time indicating the elapsed time from when the brake command is canceled and the AC pressure, which is the brake command 5 pressure supplied to the relay valve 14, starts to be discharged. The vertical axis indicates the AC pressure detected by the AC pressure sensor 16. In addition, in FIG. 5, an air discharge time-AC pressure curve AR1 indicating the relationship between the AC pressure air discharge time 10 and the AC pressure at the normal time is indicated by the solid line. An air discharge time-AC pressure curve AR2 indicating the relationship between the AC pressure air discharge time and the AC pressure at the time of an air discharge anomaly sign is indicated by a broken line. An 15 air discharge time-AC pressure curve AR3 indicating the relationship between the AC pressure air discharge time and the AC pressure at the time of an air discharge anomaly is also indicated by a broken line. [0043] For example, as indicated by the air discharge 20 time-BC pressure curve BR2 or the air discharge time-BC pressure curve BR3 in FIG. 5, when determining that there is a sign of an air discharge anomaly or an air discharge anomaly, the diagnosis unit 31 determines whether or not the AC pressure air discharge time required for the AC 25 pressure to fall to the first reference pressure P1 after the brake command is canceled is equal to or longer than the first reference time T1. For example, as indicated by the air discharge time-AC pressure curve AR1 in FIG. 5, when the AC pressure air discharge time is within the 30 normal region, that is, when the AC pressure air discharge time required for the AC pressure to fall to the first reference pressure P1 after the brake command is canceled is shorter than the first reference time T1 (not equal to 26 or longer than the first reference time T1), the diagnosis unit 31 determines that the air discharge at the side of the brake control valve 13 is properly performed and determines that there is an air discharge anomaly or a sign 5 of an air discharge anomaly relating to the side of the relay valve 14. [0044] For example, as indicated by the air discharge time-AC pressure curve AR2 and the air discharge time-AC pressure curve AR3 in FIG. 5, for example, when the AC 10 pressure air discharge time is in the air discharge anomaly sign region or the air discharge anomaly region, that is, when the AC pressure air discharge time required for the AC pressure to fall to the first reference pressure P1 after the brake command is canceled is equal to or longer than 15 the first reference time T1, the diagnosis unit 31 determines that there is an air discharge anomaly or a sign of an air discharge anomaly relating to the side of the brake control valve 13. [0045] FIGS. 6 and 7 are flowcharts illustrating an 20 example of the procedure of determination of a sign of an air discharge anomaly and an air discharge anomaly using the brake cylinder pressure air discharge time by the monitoring system according to the first embodiment of the present disclosure. An example of a series of steps of 25 processing by the monitoring system 1 according to the first embodiment of the present disclosure will be hereinafter described with reference to the flowcharts in FIGS. 6 and 7. As illustrated in FIG. 6, in step S101, the determination unit 26 of the monitoring system 1 determines 30 whether or not the brake command has been canceled. [0046] When the determination unit 26 determines, in step S101, that the brake command has been canceled (Yes), the air discharge time measurement unit 27 measures, in 27 step S102, the BC pressure air discharge time and the AC pressure air discharge time after the brake command was canceled. When determining in step S101 that the brake command has not been canceled (No), the determination unit 5 26 again determines whether or not the brake command has been canceled. That is, the determination unit 26 repeats the determination in S101 until the brake command is canceled. [0047] Next, in step S103, the determination unit 26 10 determines whether or not the BC pressure detected by the BC pressure sensor 17 has fallen to the first reference pressure P1 or lower. When determining in step S103 that the BC pressure has fallen to the first reference pressure P1 or lower (Yes), the determination unit 26 sends, to the 15 diagnosis unit 31, the BC pressure air discharge time required for the BC pressure measured by the air discharge time measurement unit 27 to fall to the first reference pressure P1 and the AC pressure air discharge time required for the AC pressure to fall to the first reference pressure 20 P1 after the brake command is canceled. In step S104, the diagnosis unit 31 determines whether or not the BC pressure air discharge time is equal to or longer than the first reference time T1. When determining in step S103 that the BC pressure has not fallen to the first reference pressure 25 P1 or lower (No), the determination unit 26 again determines whether or not the BC pressure has fallen to the first reference pressure P1 or lower. That is, the determination unit 26 repeats the determination in S103 until the BC pressure falls to the first reference pressure 30 P1 or lower. [0048] When the diagnosis unit 31 determines, in step S104, that the BC pressure air discharge time is equal to or longer than the first reference time T1 (Yes), the 28 diagnosis unit 31 determines, in step S105, whether or not the BC pressure air discharge time is equal to or longer than the second reference time T2. When the diagnosis unit 31 determines, in step S105, that the BC pressure air 5 discharge time is equal to or longer than the second reference time T2 (Yes), the diagnosis unit 31 determines, in step S106, whether or not the BC pressure air discharge time is equal to or longer than the third reference time T3. [0049] When the diagnosis unit 31 determines, in step 10 S106, that the BC pressure air discharge time is equal to or longer than the third reference time T3 (Yes), the diagnosis unit 31 determines, in step S107, that the brake is not released, and generates and outputs the brake nonrelease signal for notifying that the brake is not released. 15 [0050] In addition, when the diagnosis unit 31 determines, in step S106, that the BC pressure air discharge time is not equal to or longer than the third reference time T3 (No), the diagnosis unit 31 determines, in step S108, whether or not the AC pressure air discharge 20 time required for the AC pressure to fall to the first reference pressure P1 after the brake command is canceled is equal to or longer than the first reference time T1. When the diagnosis unit 31 determines, in step S108, that the AC pressure air discharge time is equal to or longer 25 than the first reference time T1 (Yes), the diagnosis unit 31 determines, in step S109, that there is an air discharge anomaly relating to the side of the brake control valve 13, and generates and outputs the anomaly signal for notifying that there is an air discharge anomaly relating to the side 30 of the brake control valve 13, for example. When the diagnosis unit 31 determines, in step S108, that the AC pressure air discharge time is not equal to or longer than the first reference time T1 (No), the diagnosis unit 31 29 determines, in step S110, that there is an air discharge anomaly relating to the side of the relay valve 14, and generates and outputs the anomaly signal for notifying that there is an air discharge anomaly relating to the side of 5 the relay valve 14, for example. [0051] In addition, when the diagnosis unit 31 determines, in step S105, that the BC pressure air discharge time is not equal to or longer than the second reference time T2 (No), the diagnosis unit 31 determines, 10 in step S111, whether or not the AC pressure air discharge time required for the AC pressure to fall to the first reference pressure P1 after the brake command is canceled is equal to or longer than the first reference time T1. When the diagnosis unit 31 determines, in step S111, that 15 the AC pressure air discharge time is equal to or longer than the first reference time T1 (Yes), the diagnosis unit 31 determines, in step S112, that there is a sign of an air discharge anomaly relating to the side of the brake control valve 13, and generates and outputs the attention signal 20 for notifying that there is a sign of an air discharge anomaly relating to the side of the brake control valve 13, for example. When the diagnosis unit 31 determines, in step S111, that the AC pressure air discharge time is not equal to or longer than the first reference time T1 (No), 25 the diagnosis unit 31 determines, in step S113, that there is a sign of an air discharge anomaly relating to the side of the relay valve 14, and generates and outputs the attention signal for notifying that there is a sign of an air discharge anomaly relating to the side of the relay 30 valve 14, for example. [0052] In addition, when the diagnosis unit 31 determines, in step S104 that the BC pressure air discharge time is not equal to or longer than the first reference 30 time T1 (No), the diagnosis unit 31 determines, in step S114 illustrated in FIG. 7, whether or not the BC pressure has fallen to the second reference pressure P2. Note that FIG. 7 illustrates details of the subsequent process A when 5 the diagnosis unit 31 determines that the BC pressure air discharge time is not equal to or longer than the first reference time T1 in the process in step S104 in FIG. 6 (No). [0053] When the diagnosis unit 31 verifies, in step S114, 10 that the BC pressure has fallen to the second reference pressure P2 (Yes), the diagnosis unit 31 determines, in step S115, whether or not the BC pressure air discharge time required for the BC pressure to fall to the second reference pressure P2 after the brake command is canceled 15 is equal to or longer than the fourth reference time T4. When determining, in step S114, that the BC pressure has not fallen to the second reference pressure P2 or lower (No), the diagnosis unit 31 again determines whether or not the BC pressure has fallen to the second reference pressure 20 P2 or lower. That is, the determination unit 26 repeats the determination in S114 until the BC pressure falls to the second reference pressure P2 or lower. [0054] When the diagnosis unit 31 determines, in step S115, that the BC pressure air discharge time is equal to 25 or longer than the fourth reference time T4 (Yes), the diagnosis unit 31 determines, in step S116, that there is a sign of an air discharge anomaly. In addition, when the diagnosis unit 31 determines, in step S115, that the BC pressure air discharge time is not equal to or longer than 30 the fourth reference time T4 (No), the diagnosis unit 31 determines, in step S117, whether or not the BC pressure air discharge time is equal to or longer than the fifth reference time T5. 31 [0055] When the diagnosis unit 31 determines, in step S117, that the BC pressure air discharge time is equal to or longer than the fifth reference time T5 (Yes), the diagnosis unit 31 determines, in step S118, whether or not 5 the BC pressure is equal to or higher than the third reference pressure P3. When the diagnosis unit 31 determines, in step S117, that the BC pressure air discharge time is not equal to or longer than the fifth reference time T5 (No), the diagnosis unit 31 again 10 determines whether or not the BC pressure air discharge time is equal to or longer than the fifth reference time T5. That is, the determination unit 26 repeats the verification in S117 until the BC pressure air discharge time becomes equal to or longer than the fifth reference time T5. 15 [0056] When the diagnosis unit 31 determines, in step S118, that the BC pressure is equal to or higher than the third reference pressure P3 (Yes), the diagnosis unit 31 determines, in step S119, that there is a possibility of leakage of the SR pressure into the relay valve 14. When 20 the diagnosis unit 31 determines, in step S118, that the BC pressure is not equal to or higher than the third reference pressure P3 (No), the diagnosis unit 31 determines, in step S120, that the air discharge is normal. Note that, when determining, in step S103, that the BC pressure has not 25 fallen to the first reference pressure P1 or lower (No), the diagnosis unit 31 again determines whether or not the BC pressure has fallen to the first reference pressure P1 or lower. However, when the BC pressure air discharge time has become equal to or longer than the third reference time 30 T3 for determining brake non-release, the process in step S103 may stop and the diagnosis unit 31 may determine that the brake is not released. In addition, when determining in step S114 that the BC pressure has not fallen to the 32 second reference pressure P2 or lower (No), the diagnosis unit 31 again determines whether or not the BC pressure has fallen to the second reference pressure P2 or lower. However, when the BC pressure air discharge time has become 5 equal to or longer than the fifth reference time T5, the process in step S114 may stop and the diagnosis unit 31 may determine that the brake is not released or there is a possibility of leakage of the SR pressure into the relay valve 14. 10 [0057] The monitoring system 1 according to the first embodiment of the present disclosure includes: the BC pressure sensor 17 to detect the BC pressure indicating the pressure of the brake cylinder 24 of the brake device 18 to generate a mechanical braking force by pressing the brake 15 shoe 25 against the wheel 19 provided in the vehicle 2; the air discharge time measurement unit 27 to measure the BC pressure air discharge time required for the BC pressure detected by the BC pressure sensor 17 to fall to the predetermined first reference pressure P1 after the brake 20 command is canceled when the vehicle 2 stops and the brake command is input; and the diagnosis unit 31 to determine that there is an air discharge anomaly or a sign of an air discharge anomaly when the BC pressure air discharge time measured by the air discharge time measurement unit 27 is 25 equal to or longer than the predetermined first reference time T1. It is therefore possible to recognize an air discharge anomaly or a sign of an air discharge anomaly, which is a phase preceding the brake non-release. [0058] In the monitoring system 1 according to the first 30 embodiment of the present disclosure, the diagnosis unit 31 determines that there is an air discharge anomaly when the BC pressure air discharge time is equal to or longer than the second reference time T2 set to be longer than the 33 first reference time T1, and determines that there is a sign of an air discharge anomaly when the BC pressure air discharge time is equal to or longer than the first reference time T1 but shorter than the second reference 5 time T2. It is therefore possible to recognize more precisely which one of the air discharge anomaly and the sign of the air discharge anomaly, which are phases preceding the brake non-release, happens. [0059] In the monitoring system 1 according to the first 10 embodiment of the present disclosure, the diagnosis unit 31 determines that the brake is not released when the BC pressure air discharge time is equal to or longer than the third reference time T3 set to be longer than the second reference time T2. It is therefore possible to 15 appropriately recognize the brake non-release when the brake non-release occurs. [0060] In the monitoring system 1 according to the first embodiment of the present disclosure, the air discharge time measurement unit 27 measures the BC pressure air 20 discharge time after the brake command is canceled when the vehicle 2 stops at a station or when the stopping vehicle 2 is checked in leaving the depot. The air discharge time measurement unit 27 can thus measure the BC pressure air discharge time without being affected by the regenerative 25 brake. It is therefore possible to learn of occurrence of an air discharge anomaly or a sign of an air discharge anomaly relating to the brake control valve 13 or the relay valve 14, which forms an air brake unit of the brake control device 3. 30 [0061] The monitoring system 1 according to the first embodiment of the present disclosure includes the AC pressure sensor 16 to detect the AC pressure indicating the pressure of the compressed air to be supplied from the 34 brake control valve 13 to the relay valve 14 as the brake command pressure. The air discharge time measurement unit 27 measures the AC pressure air discharge time required for the AC pressure detected by the AC pressure sensor 16 to 5 fall to the first reference pressure P1 after the brake command is canceled when the brake command is input. The diagnosis unit 31 determines whether or not the AC pressure air discharge time is equal to or longer than the first reference time T1 when the BC pressure air discharge time 10 is equal to or longer than the first reference time T1, and determines that there is an air discharge anomaly or a sign of an air discharge anomaly relating to the relay valve 14 when the AC pressure air discharge time is not equal to or longer than the first reference time T1. It is therefore 15 possible to recognize an air discharge anomaly or a sign of an air discharge anomaly relating to the relay valve 14, which is a phase preceding the brake non-release. [0062] In the monitoring system 1 according to the first embodiment of the present disclosure, when the AC pressure 20 air discharge time is equal to or longer than the first reference time T1, the diagnosis unit 31 determines that there is an air discharge anomaly or a sign of an air discharge anomaly relating to the brake control valve 13. It is therefore possible to recognize an air discharge 25 anomaly or a sign of an air discharge anomaly relating to the brake control valve 13, which is a phase preceding the brake non-release. [0063] In the monitoring system 1 according to the first embodiment of the present disclosure, the air discharge 30 time measurement unit 27 measures the BC pressure air discharge time required for the BC pressure measured by the BC pressure sensor 17 to fall to the second reference pressure P2 set to be lower than the first reference 35 pressure P1. The diagnosis unit 31 determines that there is an air discharge anomaly or a sign of an air discharge anomaly when the BC pressure air discharge time is equal to or longer than the fourth reference time T4 set to be 5 longer than the first reference time T1. It is therefore possible to accurately recognize an air discharge anomaly or a sign of an air discharge anomaly, which is a phase preceding the brake non-release. [0064] In the monitoring system 1 according to the first 10 embodiment of the present disclosure, when the BC pressure measured by the BC pressure sensor 16 at the time of lapse of the fifth reference time T5 set to be longer than the third reference time T3 and the fourth reference time T4 is equal to or higher than the third reference pressure P3 set 15 to be lower than the second reference pressure P2, the diagnosis unit 31 determines that there is a possibility of leakage of the SR pressure into the relay valve 14. It is therefore possible to appropriately recognize that possibility when a residual pressure of the BC pressure 20 exists. [0065] The monitoring system 1 according to the first embodiment of the present disclosure includes the data accumulation unit 30 to accumulate the BC pressure air discharge time measured by the air discharge time 25 measurement unit 27. An air discharge anomaly or a sign of an air discharge anomaly can be therefore determined using a plurality of past BC pressure air discharge times. [0066] The monitoring system 1 according to the first embodiment of the present disclosure includes the position 30 information acquisition unit 28 to acquire position information on the vehicle 2. The data accumulation unit 30 accumulates the position information on the vehicle 2 acquired by the position information acquisition unit 28 36 when the BC pressure air discharge time is measured by the air discharge time measurement unit 27, the position information on the vehicle 2 being associated with the BC pressure air discharge time. It is therefore possible to 5 learn of where the vehicle 2 stopped when the BC pressure air discharge time was given. [0067] The monitoring system 1 according to the first embodiment of the present disclosure includes the temperature sensor 23 to detect the temperature information 10 around the brake device 18. The data accumulation unit 30 accumulates the temperature information detected by the temperature sensor 23 when the BC pressure air discharge time is measured by the air discharge time measurement unit 27, the temperature information being associated with the 15 BC pressure air discharge time. It is therefore possible to learn of how much the temperature around the brake device 18 was when the BC pressure air discharge time was given. [0068] Note that the monitoring system 1 according to 20 this first embodiment includes, by way of example, the data accumulation unit 30 and the diagnosis unit 31 provided in the ground device 8, as illustrated in FIG. 1. However, the data accumulation unit 30 and the diagnosis unit 31 are not limited to being provided in the ground device 8. For 25 example, the monitoring system 1 may be configured to have the data accumulation unit 30 and the diagnosis unit 31 provided in the brake control device 3, the central device 5, etc. provided in the vehicle 2. [0069] In the monitoring system 1 according to this 30 first embodiment, by way of example, the diagnosis unit 31 determines an air discharge anomaly or a sign of an air discharge anomaly, using a single BC pressure air discharge time measured by the air discharge time measurement unit 27 37 when the determination unit 26 determines that the brake command is canceled with the vehicle 2 stopped and the brake command input, as illustrated in FIGS. 3 to 5. However, the diagnosis unit 31 may acquire a plurality of 5 BC pressure air discharge times measured by the air discharge time measurement unit 27 in a predetermined first period and obtain the tendency of the BC pressure air discharge times within the first period, thereby determining an air discharge anomaly or a sign of an air 10 discharge anomaly. Note that, for example, the first period is a period on a one-week basis or a one-month basis or the like, but is not limited to a particular period and may be a period on a one-day basis or a one-year basis. [0070] FIG. 8 is a diagram illustrating an example of 15 temporal changes in the brake cylinder pressure air discharge time. In FIG. 8, the horizontal axis indicates the date, and the vertical axis indicates the BC pressure air discharge time required for the BC pressure detected by the BC pressure sensor 17 to fall to the first reference 20 pressure P1 after the brake command is canceled. The BC pressure air discharge time may be, for example, the BC pressure air discharge time measured by the air discharge time measurement unit 27 every time the vehicle 2 is checked in leaving the depot, or may be a statistical value 25 such as an average value of the BC pressure air discharge time for one day measured by the air discharge time measurement unit 27 every time the vehicle 2 stops at a station. FIG. 8 illustrates the BC pressure air discharge time for 10 days as an example. In FIG. 8, the dates on 30 the horizontal axis are expressed as day 1 to day 10 but may be expressed as day, month, and year. Note that the diagnosis unit 31 does not necessarily need to acquire the BC pressure air discharge time for every day and instead 38 may acquire the BC pressure air discharge time for every predetermined period (for example, for every week) set to be shorter than the first period. In addition, the diagnosis unit 31 may acquire a statistical value such as 5 an average value of a plurality of BC pressure air discharge times measured by the air discharge time measurement unit 27 in a predetermined period. Note that the plurality of BC pressure air discharge times measured by the air discharge time measurement unit 27 is 10 accumulated in the data accumulation unit 30 of the ground device 8 in association with, for example, information such as the vehicle identification information on the vehicle 2, the device identification information on the brake device 18, the device identification information on the brake 15 control device 3, the train position information, the environmental information, the temperature information, the date and time information, the brake command information, and the door open/close information. For example, as illustrated in FIG. 8, the diagnosis unit 31 may obtain a 20 temporal tendency by performing tendency estimation, etc., using the BC pressure air discharge times within the first period. In addition, to diagnose an air discharge anomaly or a sign of an air discharge anomaly, the diagnosis unit 31 may perform machine learning, combining information such 25 as the environmental information and the temperature information accumulated in the data accumulation unit 30 together with the plurality of BC pressure air discharge times. [0071] Furthermore, the diagnosis unit 31 may determine 30 that there is a sign of an air discharge anomaly relating to the BC pressure when, for example, a predetermined number or more of or a predetermined proportion or more of the BC pressure air discharge times within the first period 39 are included in the air discharge anomaly sign region in which the BC pressure air discharge time is equal to or longer than the first reference time T1 but shorter than the second reference time T2. 5 [0072] Second Embodiment. Next, the monitoring system 1 according to a second embodiment of the present disclosure will be described. FIG. 9 is a block diagram illustrating an example of the configuration of the brake control device according to the 10 second embodiment of the present disclosure. Note that components, etc. similar to those of the monitoring system 1 according to the first embodiment of the present disclosure are denoted by the same reference signs, and a detailed description thereof will be omitted. As 15 illustrated in FIG. 9, the brake control device 3 of the monitoring system 1 according to the second embodiment is different from the brake control device 3 of the monitoring system 1 according to the first embodiment illustrated in FIG. 2 in including an air supply time measurement unit 32 20 instead of the air discharge time measurement unit 27. In addition, the monitoring system 1 according to the second embodiment is different from the monitoring system 1 according to the first embodiment in that the diagnosis unit 31 determines an air supply anomaly or a sign of an 25 air supply anomaly. Note that, the control unit 12 of the brake control device 3 of the monitoring system 1 according to the second embodiment lacks the air discharge time measurement unit 27, by way of example, for simplification of description. However, the control unit 12 may be 30 configured to include the air discharge time measurement unit 27 together with the air supply time measurement unit 32. [0073] FIG. 10 is a diagram illustrating an example of 40 measurement of brake cylinder pressure air supply time by a monitoring system according to the second embodiment of the present disclosure. In FIG. 10, the horizontal axis indicates the brake cylinder pressure air supply time 5 (hereinafter, referred to as “BC pressure air supply time”) indicating the elapsed time from when the brake command is input and the BC pressure starts to be supplied to the brake cylinder 24. The vertical axis indicates the BC pressure detected by the BC pressure sensor 17. For 10 example, the determination unit 26 determines whether or not the brake command (brake notch signal) is input when the vehicle 2 stops and the brake command is not input (brake released). Examples of when the vehicle 2 stops include, but are not limited to, when the vehicle 2 is 15 checked in leaving the depot. As illustrated in FIG. 3, when the brake command is input, the BC pressure starts to rise because the BC pressure is supplied to the brake cylinder 24. For example, when determining that the brake command is input, the determination unit 26 notifies the 20 air supply time measurement unit 32 of a brake command input signal indicating that the brake command is input. [0074] As illustrated in FIG. 10, the air supply time measurement unit 32 measures the BC pressure air supply time after the brake command is input. More specifically, 25 when receiving the brake command input signal from the determination unit 26, the air supply time measurement unit 32 first measures the BC pressure air supply time required for the BC pressure detected by the BC pressure sensor 17 to rise to the predetermined fourth reference pressure P4. 30 The fourth reference pressure P4 is a value set to be lower than the target brake cylinder pressure (hereinafter, referred to as “target BC pressure”) for the brake command and is set to, for example, a value of 50 to 70% of the 41 target BC pressure. Note that the target BC pressure can be calculated, for example, by the control unit 12 on the basis of the brake command and the AS pressure. The air supply time measurement unit 32 also individually measures 5 the BC pressure air supply times required for the BC pressure detected by the BC pressure sensor 17 to rise to a predetermined fifth reference pressure P5 and a predetermined sixth reference pressure P6. The fifth reference pressure P5 is a pressure value set to be higher 10 than the fourth reference pressure P4, and the sixth reference pressure P6 is a pressure value set to be higher than the fifth reference pressure P5. The fifth reference pressure P5 only needs to be set to be higher than the fourth reference pressure P4 and is not limited to a 15 particular value. For example, the fifth reference pressure P5 is set to a value obtained by adding half of the difference between the target BC pressure and the fourth reference pressure P4 to the fourth reference pressure P4. In addition, the sixth reference pressure P6 20 only needs to be set to be higher than the fifth reference pressure P5 and is not limited to a particular value. For example, the sixth reference pressure P6 is set to be lower than the target BC pressure. [0075] Similarly, the air supply time measurement unit 25 32 also measures AC pressure air supply time after the brake command is input. More specifically, when receiving the brake command input signal from the determination unit 26, the air supply time measurement unit 32 first measures the AC pressure air supply time required for the AC 30 pressure detected by the AC pressure sensor 16 to rise to the fourth reference pressure P4. The air supply time measurement unit 32 also individually measures the AC pressure air supply times required for the AC pressure 42 detected by the AC pressure sensor 16 to rise to the fifth reference pressure P5 and the sixth reference pressure P6. [0076] In addition, for example, the control unit 12 associates the BC pressure air supply time and the AC 5 pressure air supply time measured by the air supply time measurement unit 32 with information such as the train position information, the environmental information, the temperature information, the date and time information, the brake command information, and the door open/close 10 information when the determination unit 26 determines that the brake command is input. The control unit 12 further associates the BC pressure air supply time and the AC pressure air supply time with the vehicle identification information on the vehicle 2 having the brake device 18 15 installed therein, the device identification information on the brake device 18, and the device identification information on the brake control device 3. The control unit 12 sends the associated information to the ground device 8 via the on-board wireless device 7. 20 [0077] As illustrated in FIG. 1, the ground device 8 includes the data accumulation unit 30 and the diagnosis unit 31. The data accumulation unit 30 accumulates the BC pressure air supply time, the AC pressure air supply time, etc. sent from the vehicle 2. Note that the data 25 accumulation unit 30 also similarly accumulates information acquired by the brake control device 3 installed in a vehicle 2 of a train other than the vehicle 2 of the train in such a manner as to distinguish the information acquired by the brake control device 3 of the former vehicle 2 from 30 the information acquired by the brake control device 3 of the latter vehicle 2. For example, the diagnosis unit 31 determines an air supply anomaly or a sign of an air supply anomaly relating to the BC pressure air supply action, 43 using the BC pressure air supply time, etc. The diagnosis unit 31 acquires, for example, the BC pressure air supply time and the AC pressure air supply time from the data accumulation unit 30. 5 [0078] In FIG. 10, an air supply time-BC pressure curve BA1 indicating the relationship between the BC pressure air supply time and the BC pressure at the normal time is indicated by the solid line. In addition, an air supply time-BC pressure curve BA2 indicating the relationship 10 between the BC pressure air supply time and the BC pressure at the time of an air supply anomaly sign is indicated by a broken line. An air supply time-BC pressure curve BA3 indicating the relationship between the BC pressure air supply time and the BC pressure at the time of an air 15 supply anomaly is indicated by a broken line. An air supply time-BC pressure curve BA4 indicating the relationship between the BC pressure air supply time and the BC pressure at the time of insufficient braking is indicated by a broken line. 20 [0079] Meanwhile, a sixth reference time T6 illustrated in FIG. 10 is a reference time which the diagnosis unit 31 uses for determining a sign of an air supply anomaly. The sixth reference time T6 is set to be shorter than the threshold value of the BC pressure air supply time used for 25 detection of insufficient braking and is set to, for example, 1 to 3 [sec]. In addition, a seventh reference time T7 is a reference time which the diagnosis unit 31 uses for determining an air supply anomaly, and is set to be longer than the sixth reference time T6. The seventh 30 reference time T7 is set to be longer than the sixth reference time T6 by 1 to 2 [sec], for example. In addition, an eighth reference time T8 is a reference time which the diagnosis unit 31 uses for determining 44 insufficient braking, and is set to be longer than the seventh reference time T7. In addition, a ninth reference time T9 is a reference time which the diagnosis unit 31 uses for determining an air supply anomaly or a sign of an 5 air supply anomaly, and is set to be longer than the sixth reference time T6. Note that, although FIG. 10 illustrates an example in which the ninth reference time T9 is set to the same time as the eighth reference time T8 (T8 = T9), the ninth reference time T9 is not limited to this example. 10 The ninth reference time T9 only needs to be set to be longer than the sixth reference time T6 and may be set to the same time as the seventh reference time T7, for example. In addition, the ninth reference time T9 may be set to be shorter than the seventh reference time T7 or longer than 15 the eighth reference time T8. A tenth reference time T10 is a reference time which the diagnosis unit 31 uses for determining an air supply anomaly or a sign of an air supply anomaly, and is set to be longer than the eighth reference time T8 and the ninth reference time T9. The 20 sixth to tenth reference times T6 to T10 are recorded in advance in a recording unit (not illustrated) provided in the ground device 8, for example. Note that the sixth to tenth reference times T6 to T10 may be set for each brake control device 3. In addition, the diagnosis unit 31 may 25 acquire the sixth to tenth reference times T6 to T10 from a device at the on-board side, such as the brake control device 3 provided in the vehicle 2, via the on-board wireless device 7. Meanwhile, the sixth to tenth reference times T6 to T10 may be modified according to the value of 30 the target BC pressure calculated by the control unit 12. [0080] In FIG. 10, a region shorter than the fourth reference time T4 after the brake command is input is defined as a normal region. In addition, a region equal to 45 or longer than the fourth reference time T4 but shorter than the fifth reference time T5 is defined as an air supply anomaly sign region. A region equal to or longer than the fifth reference time T5 but shorter than the sixth 5 reference time T6 is defined as an air supply anomaly region. A region equal to or longer than the sixth reference time T6 is defined as an insufficient braking region. [0081] As indicated by the air supply time-BC pressure 10 curve BA1 in FIG. 10, the diagnosis unit 31 determines that the BC air supply time is normal, for example, when the BC pressure air supply time is within the normal region, that is, when the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 15 after the brake command is input is shorter than the sixth reference time T6. In addition, as indicated by the air supply time-BC pressure curve BA2 in FIG. 10, the diagnosis unit 31 determines that there is a sign of an air supply anomaly, for example, when the BC pressure air supply time 20 is within the air supply anomaly sign region, that is, when the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 after the brake command is input is equal to or longer than the sixth reference time T6 but shorter than the seventh 25 reference time T7. Then, when determining that there is a sign of an air supply anomaly, for example, the diagnosis unit 31 generates and outputs an attention signal for calling attention. For example, by sending the attention signal output from the diagnosis unit 31 to the vehicle 2 30 via the network 6, the ground device 8 displays information calling attention, on the monitor display of the cab 9 of the vehicle 2. [0082] In addition, as indicated by the air supply time- 46 BC pressure curve BA3 in FIG. 10, the diagnosis unit 31 determines that there is an air supply anomaly, for example, when the BC pressure air supply time is within the air supply anomaly region, that is, when the BC pressure air 5 supply time required for the BC pressure to rise to the fourth reference pressure P4 after the brake command is input is equal to or longer than the seventh reference time T7 but shorter than the eighth reference time T8. Then, when determining that there is an air supply anomaly, for 10 example, the diagnosis unit 31 generates and outputs an anomaly signal for notifying of the anomaly. For example, by sending the anomaly signal output from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information notifying of the anomaly, on 15 the monitor display of the cab 9 of the vehicle 2. [0083] In addition, as indicated by the air supply timeBC pressure curve BA4 in FIG. 10, the diagnosis unit 31 determines that braking is insufficient, for example, when the BC pressure air supply time is within the insufficient 20 braking region, that is, when the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 after the brake command is input is equal to or longer than the eighth reference time T8. Then, when determining that braking is insufficient, for example, 25 the diagnosis unit 31 generates and outputs an insufficient braking signal for notifying that braking is insufficient. For example, by sending the insufficient braking signal output from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information 30 notifying of the insufficient braking, on the monitor display of the cab 9 of the vehicle 2. [0084] FIG. 11 is a diagram illustrating another example of measurement of the brake cylinder pressure air supply 47 time by the monitoring system according to the second embodiment of the present disclosure. As described above, as indicated by the air supply time-BC pressure curve BA1 in FIG. 10, the diagnosis unit 31 determines that the BC 5 air supply time is normal, for example, when the BC pressure air supply time is within the normal region, that is, when the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 after the brake command is input is shorter than the sixth 10 reference time T6. However, even when the BC air supply time is shorter than the sixth reference time T6, a situation where the BC pressure is not appropriately supplied with air for some reason is likely to occur thereafter. In FIG. 11, an air supply time-BC pressure 15 curve BA5 and an air supply time-BC pressure curve BA6 are indicated by broken lines. The air supply time-BC pressure curve BA5 and the air supply time-BC pressure curve BA6 indicate the relationship between the BC pressure air supply time and the BC pressure when the diagnosis unit 31 20 determines that there is an air supply anomaly or a sign of an air supply anomaly when the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 after the brake command is input is shorter than the sixth reference time T6. 25 [0085] As indicated by the air discharge time-BC pressure curve BA5 in FIG. 11, for example, when the BC pressure air supply time is within the normal region, that is, when the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 30 after the brake command is input is shorter than the sixth reference time T6, the diagnosis unit 31 determines whether or not the BC pressure air supply time required for the BC pressure to rise to the fifth reference pressure P5 after 48 the brake command is input is equal to or longer than the ninth reference time T9. When determining that the BC pressure air supply time required for the BC pressure to rise to the fifth reference pressure P5 after the brake 5 command is input is equal to or longer than the ninth reference time T9, the diagnosis unit 31 determines that there is an air supply anomaly or a sign of an air supply anomaly. Then, when determining that there is an air supply anomaly or a sign of an air supply anomaly, for 10 example, the diagnosis unit 31 generates and outputs an anomaly signal for notifying of the air supply anomaly or an attention signal for calling attention. For example, by sending the anomaly signal or the attention signal output from the diagnosis unit 31 to the vehicle 2 via the network 15 6, the ground device 8 displays information notifying of the anomaly or information calling attention, on the monitor display of the cab 9 of the vehicle 2. Note that whether the diagnosis unit 31 determines that there is an air supply anomaly or a sign of an air supply anomaly in 20 such a case as indicated by the air supply time-BC pressure curve BA5 in FIG. 4 may depend upon the values of the fifth reference pressure P5 and the ninth reference time T9. [0086] As indicated by the air discharge time-BC pressure curve BA6 in FIG. 11, for example, when 25 determining that the BC pressure air supply time is within the normal region, that is, the BC pressure air supply time required for the BC pressure to rise to the fourth reference pressure P4 after the brake command is input is shorter than the sixth reference time T6 and determining 30 that the BC pressure air supply time required for the BC pressure to rise to the fifth reference pressure P5 after the brake command is input is shorter than the ninth reference time T9, the diagnosis unit 31 determines whether 49 or not the BC pressure detected by the BC pressure sensor 17 when the tenth reference time T10 has elapsed is equal to or lower than the sixth reference pressure P6. When determining that the BC pressure detected by the BC 5 pressure sensor 17 when the tenth reference time T10 has elapsed is equal to or lower than the sixth reference pressure P6, that is, when determining that there is an insufficient pressure of the BC pressure, the diagnosis unit 31 determines that there is a possibility of leakage 10 of the compressed air from the pipe of the relay valve 14 or the brake cylinder 24 out to the atmosphere side. Then, the diagnosis unit 31 generates and outputs a leak-out notification signal for notifying that there is a possibility of leak-out of the compressed air, for example. 15 For example, by sending the leak-out notification signal output from the diagnosis unit 31 to the vehicle 2 via the network 6, the ground device 8 displays information notifying that there is a possibility of leak-out of the compressed air, on the monitor display of the cab 9 of the 20 vehicle 2. [0087] FIG. 12 is a diagram illustrating an example of measurement of the brake cylinder pressure air supply time and the AC pressure air supply time by the monitoring system according to the second embodiment of the present 25 disclosure. For example, as indicated by the air supply air time-BC pressure curve BA2 or the air supply time-BC pressure curve BA3 in FIG. 12, when determining that there is a sign of an air supply anomaly or an air supply anomaly, the diagnosis unit 31 uses the AC pressure air supply time 30 in order to further perform determination for specifying what part is a factor of the sign of the air supply anomaly or the air supply anomaly. In the lower diagram of FIG. 12, the horizontal axis indicates the AC pressure air supply 50 time indicating the elapsed time from when the brake command is input and the AC pressure, which is the brake command pressure supplied to the relay valve 14, starts to be supplied. The vertical axis indicates the AC pressure 5 detected by the AC pressure sensor 16. In addition, in FIG. 12, an air supply time-AC pressure curve AA1 indicating the relationship between the AC pressure air supply time and the AC pressure at the normal time is indicated by the solid line. An air supply time-AC pressure curve AA2 10 indicating the relationship between the AC pressure air supply time and the AC pressure at the time of an air supply anomaly sign is indicated by a broken line. An air supply time-AC pressure curve AA3 indicating the relationship between the AC pressure air supply time and 15 the AC pressure at the time of an air supply anomaly is indicated by a broken line. [0088] For example, as indicated by the air supply timeBC pressure curve BA2 or the air supply time-BC pressure curve BA3 in FIG. 12, when determining that there is a sign 20 of an air supply anomaly or an air supply anomaly, the diagnosis unit 31 determines whether or not the AC pressure air supply time required for the AC pressure to rise to the fourth reference pressure P4 after the brake command is input is equal to or longer than the sixth reference time 25 T6. For example, as indicated by the air supply time-AC pressure curve AA1 in FIG. 12, when the AC pressure air supply time is within the normal region, that is, when the AC pressure air supply time required for the AC pressure to rise to the fourth reference pressure P4 after the brake 30 command is input is shorter than the sixth reference time T6 (not equal to or longer than the sixth reference time T6), the diagnosis unit 31 determines that the air supply at the side of the brake control valve 13 is properly 51 performed and determines that there is an air supply anomaly or a sign of an air supply anomaly relating to the side of the relay valve 14. [0089] For example, as indicated by the air supply time5 AC pressure curve AA2 and the air supply time-AC pressure curve AA3 in FIG. 12, for example, when the AC pressure air supply time is in the air supply anomaly sign region or the air supply anomaly region, that is, when the AC pressure air supply time required for the AC pressure to rise to the 10 fourth reference pressure P4 after the brake command is input is equal to or longer than the sixth reference time T6, the diagnosis unit 31 determines that there is an air supply anomaly or a sign of an air supply anomaly relating to the side of the brake control valve 13. 15 [0090] FIGS. 13 and 14 are flowcharts illustrating an example of the procedure of determination of a sign of an air supply anomaly and an air supply anomaly using the brake cylinder pressure air supply time by the monitoring system according to the second embodiment of the present 20 disclosure. An example of a series of steps of processing by the monitoring system 1 according to the second embodiment of the present disclosure will be hereinafter described with reference to the flowcharts in FIGS. 13 and 14. As illustrated in FIG. 13, in step S201, the 25 determination unit 26 of the monitoring system 1 determines whether or not the brake command has been input. [0091] When the determination unit 26 determines, in step S201, that the brake command has been input (Yes), the air supply time measurement unit 32 measures, in step S202, 30 the BC pressure air supply time and the AC pressure air supply time after the brake command was input. When determining in step S201 that the brake command has not been input (No), the determination unit 26 again determines 52 whether or not the brake command has been input. That is, the determination unit 26 repeats the determination in S201 until the brake command is input. [0092] Next, in step S203, the determination unit 26 5 determines whether or not the BC pressure detected by the BC pressure sensor 17 has risen to the fourth reference pressure P4 or higher. When determining in step S203 that the BC pressure has risen to the fourth reference pressure P4 or higher (Yes), the determination unit 26 sends, to the 10 diagnosis unit 31, the BC pressure air supply time required for the BC pressure measured by the air supply time measurement unit 32 to rise to the fourth reference pressure P4 and the AC pressure air supply time required for the AC pressure to rise to the fourth reference 15 pressure P4 after the brake command is input. In step S204, the diagnosis unit 31 determines whether or not the BC pressure air supply time is equal to or longer than the sixth reference time T6. When determining in step S203 that the BC pressure has not risen to the fourth reference 20 pressure P4 or higher (No), the determination unit 26 again determines whether or not the BC pressure has risen to the fourth reference pressure P4 or higher. That is, the determination unit 26 repeats the determination in S203 until the BC pressure rises to the fourth reference 25 pressure P4 or higher. [0093] When the diagnosis unit 31 determines, in step S204, that the BC pressure air supply time is equal to or longer than the sixth reference time T6 (Yes), the diagnosis unit 31 determines, in step S205, whether or not 30 the BC pressure air supply time is equal to or longer than the seventh reference time T7. When the diagnosis unit 31 determines, in step S205, that the BC pressure air supply time is equal to or longer than the seventh reference time 53 T7 (Yes), the diagnosis unit 31 determines, in step S206, whether or not the BC pressure air supply time is equal to or longer than the eighth reference time T8. [0094] When the diagnosis unit 31 determines, in step 5 S206, that the BC pressure air supply time is equal to or longer than the eighth reference time T8 (Yes), the diagnosis unit 31 determines, in step S207, that braking is insufficient, and generates and outputs the insufficient braking signal for notifying that braking is insufficient. 10 [0095] In addition, when the diagnosis unit 31 determines, in step S206, that the BC pressure air supply time is not equal to nor longer than the eighth reference time T8 (No), the diagnosis unit 31 determines, in step S208, whether or not the AC pressure air supply time 15 required for the AC pressure to rise to the fourth reference pressure P4 after the brake command is input is equal to or longer than the sixth reference time T6. When the diagnosis unit 31 determines, in step S208, that the AC pressure air supply time is equal to or longer than the 20 sixth reference time T6 (Yes), the diagnosis unit 31 determines, in step S209, that there is an air supply anomaly relating to the side of the brake control valve 13, and generates and outputs the anomaly signal for notifying that there is an air supply anomaly relating to the side of 25 the brake control valve 13, for example. When the diagnosis unit 31 determines, in step S208, that the AC pressure air supply time is not equal to nor longer than the sixth reference time T6 (No), the diagnosis unit 31 determines, in step S210, that there is an air supply 30 anomaly relating to the side of the relay valve 14, and generates and outputs the anomaly signal for notifying that there is an air supply anomaly relating to the side of the relay valve 14, for example. 54 [0096] In addition, when the diagnosis unit 31 determines, in step S205, that the BC pressure air supply time is not equal to nor longer than the seventh reference time T7 (No), the diagnosis unit 31 determines, in step 5 S211, whether or not the AC pressure air supply time required for the AC pressure to rise to the fourth reference pressure P4 after the brake command is input is equal to or longer than the sixth reference time T6. When the diagnosis unit 31 determines, in step S211, that the AC 10 pressure air supply time is equal to or longer than the sixth reference time T6 (Yes), the diagnosis unit 31 determines, in step S212, that there is a sign of an air supply anomaly relating to the side of the brake control valve 13, and generates and outputs the attention signal 15 for notifying that there is a sign of an air supply anomaly relating to the side of the brake control valve 13, for example. When the diagnosis unit 31 determines, in step S211, that the AC pressure air supply time is not equal to nor longer than the sixth reference time T6 (No), the 20 diagnosis unit 31 determines, in step S213, that there is a sign of an air supply anomaly relating to the side of the relay valve 14, and generates and outputs the attention signal for notifying that there is a sign of an air supply anomaly relating to the side of the relay valve 14, for 25 example. [0097] In addition, when the diagnosis unit 31 determines, in step S204 that the BC pressure air supply time is not equal to nor longer than the sixth reference time T6 (No), the diagnosis unit 31 determines, in step 30 S214 illustrated in FIG. 14, whether or not the BC pressure has risen to the fifth reference pressure P5. Note that FIG. 14 illustrates details of the subsequent process B when the diagnosis unit 31 determines that the BC pressure 55 air supply time is not equal to or longer than the sixth reference time T6 in the process in step S204 in FIG. 13 (No). [0098] When the diagnosis unit 31 determines, in step 5 S214, that the BC pressure has risen to the fifth reference pressure P5 (Yes), the diagnosis unit 31 determines, in step S215, whether or not the BC pressure air supply time required for the BC pressure to rise to the fifth reference pressure P5 after the brake command is input is equal to or 10 longer than the ninth reference time T9. When determining in step S214 that the BC pressure has not risen to the fifth reference pressure P5 or higher (No), the diagnosis unit 31 again determines whether or not the BC pressure has fallen to the fifth reference pressure P5 or higher. That 15 is, the determination unit 26 repeats the determination in S214 until the BC pressure rises to the fifth reference pressure P5 or higher. [0099] When the diagnosis unit 31 determines, in step S215, that the BC pressure air supply time is equal to or 20 longer than the ninth reference time T9 (Yes), the diagnosis unit 31 determines, in step S216, that there is a sign of an air supply anomaly. In addition, when the diagnosis unit 31 determines, in step S215, that the BC pressure air supply time is not equal to or longer than the 25 ninth reference time T9 (No), the diagnosis unit 31 determines, in step S217, whether or not the BC pressure air supply time is equal to or longer than the tenth reference time T10. [0100] When the diagnosis unit 31 determines, in step 30 S217, that the BC pressure air supply time is equal to or longer than the tenth reference time T10 (Yes), the diagnosis unit 31 determines, in step S218, whether or not the BC pressure is equal to or lower than the sixth 56 reference pressure P6. When the diagnosis unit 31 determines, in step S217, that the BC pressure air supply time is not equal to or longer than the tenth reference time T10 (No), the diagnosis unit 31 again determines 5 whether or not the BC pressure air supply time is equal to or longer than the tenth reference time T10. That is, the determination unit 26 repeats the determination in S217 until the BC pressure air supply time becomes equal to or longer than the tenth reference time T10. 10 [0101] When the diagnosis unit 31 determines, in step S218, that the BC pressure is equal to or lower than the sixth reference pressure P6 (Yes), the diagnosis unit 31 determines, in step S219, that there is a possibility of leakage of the compressed air out to the atmosphere side. 15 When the diagnosis unit 31 determines, in step S218, that the BC pressure is not equal to or lower than the sixth reference pressure P6 (No), the diagnosis unit 31 determines, in step S220, that the air supply is normal. Note that, when determining, in step S203, that the BC 20 pressure has not risen to the fourth reference pressure P4 or higher (No), the diagnosis unit 31 again determines whether or not the BC pressure has risen to the fourth reference pressure P4 or higher. However, when the BC pressure air supply time has become equal to or longer than 25 the eighth reference time T8 for determining insufficient braking, the process in step S203 may stop and the diagnosis unit 31 may determine that braking is insufficient. In addition, when determining in step S214 that the BC pressure has not risen to the fifth reference 30 pressure P5 or higher (No), the diagnosis unit 31 again determines whether or not the BC pressure has risen to the fifth reference pressure P5 or higher. However, when the BC pressure air supply time has become equal to or longer 57 than the tenth reference time T10, the process in step S214 may stop and the diagnosis unit 31 may determine that braking is insufficient or there is a possibility of leakage of the compressed air out to the atmosphere side. 5 [0102] The monitoring system 2 according to the first embodiment of the present disclosure includes: the BC pressure sensor 17 to detect the BC pressure indicating the pressure of the brake cylinder 24 of the brake device 18 to generate a mechanical braking force by pressing the brake 10 shoe 25 against the wheel 19 provided in the vehicle 2; the air supply time measurement unit 32 to measure the BC pressure air supply time required for the BC pressure detected by the BC pressure sensor 17 to rise to the fourth reference pressure P4 set to be lower than the target BC 15 pressure for the brake command, after the brake command is input when the vehicle 2 stops and the brake command is not input; and the diagnosis unit 31 to determine that there is an air supply anomaly or a sign of an air supply anomaly when the BC pressure air supply time measured by the air 20 supply time measurement unit 32 is equal to or longer than the predetermined sixth reference time T6. It is therefore possible to recognize an air supply anomaly or a sign of an air supply anomaly, which is a phase preceding the insufficient braking. 25 [0103] In the monitoring system 2 according to the first embodiment of the present disclosure, the diagnosis unit 31 determines that there is an air supply anomaly when the BC pressure air supply time is equal to or longer than the seventh reference time T7 set to be longer than the sixth 30 reference time T6, and determines that there is a sign of an air supply anomaly when the BC pressure air supply time is equal to or longer than the sixth reference time T6 but shorter than the seventh reference time T7. It is 58 therefore possible to recognize more precisely which one of the air supply anomaly and the sign of the air supply anomaly, which are phases preceding the insufficient braking, happens. 5 [0104] In the monitoring system 2 according to the first embodiment of the present disclosure, the diagnosis unit 31 determines that braking is insufficient when the BC pressure air supply time is equal to or longer than the eighth reference time T8 set to be longer than the seventh 10 reference time T7. It is therefore possible to appropriately recognize the insufficient braking when the insufficient braking occurs. [0105] In the monitoring system 2 according to the first embodiment of the present disclosure, the air supply time 15 measurement unit 32 measures the BC pressure air supply time after the brake command is input when the stopping vehicle 2 is checked in leaving the depot. The air supply time measurement unit 32 can thus measure the BC pressure air supply time without being affected by the regenerative 20 brake. It is therefore possible to learn of occurrence of an air supply anomaly or a sign of an air supply anomaly relating to the brake control valve 13 or the relay valve 14, which forms an air brake unit of the brake control device 3. 25 [0106] The monitoring system 2 according to the first embodiment of the present disclosure includes the AC pressure sensor 16 to detect the AC pressure indicating the pressure of the compressed air to be supplied from the brake control valve 13 to the relay valve 14 as the brake 30 command pressure. The air supply time measurement unit 32 measures the AC pressure air supply time required for the AC pressure detected by the AC pressure sensor 16 to rise to the fourth reference pressure P4 after the brake command 59 is input when the vehicle 2 stops and the brake command is not input. The diagnosis unit 31 determines whether or not the AC pressure air supply time is equal to or longer than the sixth reference time T6 when the BC pressure air supply 5 time is equal to or longer than the sixth reference time T6, and determines that there is an air supply anomaly or a sign of an air supply anomaly relating to the relay valve 14 when the AC pressure air supply time is not equal to or longer than the sixth reference time T6. It is therefore 10 possible to recognize an air supply anomaly or a sign of an air supply anomaly relating to the relay valve 14, which is a phase preceding the insufficient braking. [0107] In the monitoring system 2 according to the first embodiment of the present disclosure, when the AC pressure 15 air supply time is equal to or longer than the sixth reference time T6, the diagnosis unit 31 determines that there is an air supply anomaly or a sign of an air supply anomaly relating to the brake control valve 13. It is therefore possible to recognize an air supply anomaly or a 20 sign of an air supply anomaly relating to the brake control valve 13, which is a phase preceding the insufficient braking. [0108] In the monitoring system 2 according to the first embodiment of the present disclosure, the air supply time 25 measurement unit 32 measures the BC pressure air supply time required for the BC pressure measured by the BC pressure sensor 17 to rise to the fifth reference pressure P5 set to be higher than the fourth reference pressure P4. The diagnosis unit 31 determines that there is an air 30 supply anomaly or a sign of an air supply anomaly when the BC pressure air supply time is equal to or longer than the ninth reference time T9 set to be longer than the sixth reference time T6. It is therefore possible to more 60 accurately recognize an air supply anomaly or a sign of an air supply anomaly, which is a phase preceding the insufficient braking. [0109] In the monitoring system 2 according to the first 5 embodiment of the present disclosure, when the BC pressure measured by the BC pressure sensor 17 at the time of lapse of the tenth reference time T10 set to be longer than the eighth reference time T8 and the ninth reference time T9 is equal to or lower than the sixth reference pressure P6 set 10 to be higher than the fifth reference pressure P5, the diagnosis unit 31 determines that there is a possibility of leakage of the compressed air from the pipe of the relay valve 14 or the brake cylinder 24 to the atmosphere side. It is therefore possible to appropriately recognize that 15 possibility when an insufficient pressure of the BC pressure exists. [0110] The monitoring system 2 according to the first embodiment of the present disclosure includes the data accumulation unit 30 to accumulate the BC pressure air 20 supply time measured by the air supply time measurement unit 32. An air supply anomaly or a sign of an air supply anomaly can be therefore determined using a plurality of past BC pressure air supply times. [0111] The monitoring system 2 according to the first 25 embodiment of the present disclosure includes the position information acquisition unit 28 to acquire position information on the vehicle 2. The data accumulation unit 30 accumulates the position information on the vehicle 2 acquired by the position information acquisition unit 28 30 when the BC pressure air supply time is measured by the air supply time measurement unit 32, the position information on the vehicle 2 being associated with the BC pressure air supply time. It is therefore possible to learn of where 61 the vehicle 2 stopped when the BC pressure air supply time was given. [0112] The monitoring system 2 according to the first embodiment of the present disclosure includes the 5 temperature sensor 23 to detect the temperature information around the brake device 18. The data accumulation unit 30 accumulates the temperature information detected by the temperature sensor 23 when the BC pressure air supply time is measured by the air supply time measurement unit 32, the 10 temperature information being associated with the BC pressure air supply time. It is therefore possible to learn of how much the temperature around the brake device 18 was when the BC pressure air supply time was given. [0113] Note that, the monitoring system 1 according to 15 the present second embodiment includes, by way of example, the data accumulation unit 30 and the diagnosis unit 31 are provided in the ground device 8, as illustrated in FIG. 1. However, the data accumulation unit 30 and the diagnosis unit 31 are not limited to being provided in the ground 20 device 8. For example, the monitoring system 1 may be configured to have the data accumulation unit 30 and the diagnosis unit 31 provided in the brake control device 3, the central device 5, etc. provided in the vehicle 2. [0114] In the monitoring system 1 according to this 25 first embodiment, by way of example, the diagnosis unit 31 determines an air supply anomaly or a sign of an air supply anomaly, using a single BC pressure air supply time measured by the air supply time measurement unit 32 when the determination unit 26 determines that the brake command 30 is input with the vehicle 2 stopped and the brake command not input, as illustrated in FIGS. 10 to 12,. However, the diagnosis unit 31 may acquire a plurality of the BC pressure air supply times measured by the air supply time 62 measurement unit 32 in a predetermined second period and obtain the tendency of the BC pressure air supply times within the second period, thereby determining an air supply anomaly or a sign of an air supply anomaly. Note that, for 5 example, the second period is a period on a one-week basis or a one-month basis or the like, but is not limited to a particular period and may be a period on a one-day basis or a one-year basis. [0115] FIG. 15 is a diagram illustrating an example of 10 temporal changes in the brake cylinder pressure air supply time. In FIG. 15, the horizontal axis indicates the date, and the vertical axis indicates the BC pressure air supply time required for the BC pressure detected by the BC pressure sensor 17 to rise to the fourth reference pressure 15 P4 after the brake command is input. The BC pressure air supply time is, for example, the BC pressure air supply time measured by the air supply time measurement unit 32 every time the vehicle 2 is checked in leaving the depot. FIG. 15 illustrates the BC pressure air supply time for 10 20 days as an example. In FIG. 15, the dates on the horizontal axis are expressed as day 1 to day 10 but may be expressed as day, month, and year. Note that the diagnosis unit 31 does not necessarily need to acquire the BC pressure air supply time for every day and instead may 25 acquire the BC pressure air supply time for every predetermined period (for example, for every week) set to be shorter than the second period. In addition, the diagnosis unit 31 may acquire a statistical value such as an average value of a plurality of BC pressure air supply 30 times measured by the air supply time measurement unit 32 in a predetermined period. Note that the plurality of BC pressure air supply times measured by the air supply time measurement unit 27 is accumulated in the data accumulation 63 unit 30 of the ground device 8 in association with, for example, information such as the vehicle identification information on the vehicle 2, the device identification information on the brake device 18, the device 5 identification information on the brake control device 3, the train position information, the environmental information, the temperature information, the date and time information, the brake command information, and the door open/close information. For example, as illustrated in FIG. 10 15, the diagnosis unit 31 may obtain a temporal tendency by performing tendency estimation, etc., using the BC pressure air supply times within the second period. In addition, to diagnose an air discharge anomaly or a sign of an air discharge anomaly, the diagnosis unit 31 may perform 15 machine learning, combining information such as the environmental information and the temperature information accumulated in the data accumulation unit 30 together with the plurality of BC pressure air supply times. [0116] Furthermore, the diagnosis unit 31 may determine 20 that there is a sign of an air supply anomaly relating to the BC pressure when, for example, a predetermined number or more of or a predetermined proportion or more of the BC pressure air supply times within the second period are included in the air supply anomaly sign region in which the 25 BC pressure air supply time is equal to or longer than the sixth reference time T6 but shorter than the seventh reference time T7. [0117] Note that each device of the monitoring system 1 according to the first and second embodiments of the 30 present invention includes, for example, a processor and a memory, and the operations of each device can be implemented by software. FIG. 16 is a diagram illustrating an example of the hardware configuration that implements 64 each device of the monitoring system 1 according to the first and second embodiments of the present invention. As illustrated in FIG. 16, each device of the monitoring system 1 according to the first and second embodiments of 5 the present invention includes a processor 101 and a memory 102, and the processor 101 and the memory 102 are connected by a system bus. The processor 101 performs arithmetic operations and control by software using input data, and the memory 102 stores input data or data and a program 10 necessary for the processor 101 to perform arithmetic operations and control. Note that a plurality of processors 101 and a plurality of memories 102 may be provided separately. [0118] In addition, the present disclosure is not 15 limited to the above embodiments, and each embodiment can be, for example, modified or omitted as appropriate without departing from the scope of the idea of the present disclosure. 20 Reference Signs List [0119] 1 monitoring system; 2 vehicle; 3 brake control device; 16 AC pressure sensor; 17 brake cylinder pressure detection unit; 18 brake device; 19 rotating body (wheel); 23 temperature detection unit; 24 brake 25 cylinder; 25 friction material (brake shoe); 26 determination unit; 27 air discharge time measurement unit; 28 position information acquisition unit; 29 environmental information acquisition unit; 30 data accumulation unit; 31 diagnosis unit; 32 air supply time 30 measurement unit. 65 WE CLAIM: 1. A monitoring system comprising: a brake cylinder pressure detection unit to detect a 5 brake cylinder pressure indicating a pressure of a brake cylinder of a brake device to generate a mechanical braking force by pressing a friction material against a rotating body provided in a vehicle; an air discharge time measurement unit to measure a 10 brake cylinder pressure air discharge time required for the brake cylinder pressure detected by the brake cylinder pressure detection unit to fall to a predetermined first reference pressure after a brake command is canceled when the vehicle stops and the brake command is input; and 15 a diagnosis unit to determine that there is an air discharge anomaly or a sign of an air discharge anomaly when the brake cylinder pressure air discharge time measured by the air discharge time measurement unit is equal to or longer than a predetermined first reference 20 time. 2. The monitoring system according to claim 1, wherein the diagnosis unit determines that there is the air discharge anomaly when the brake cylinder pressure air 25 discharge time is equal to or longer than a second reference time set to be longer than the first reference time; and the diagnosis unit determines that there is the sign of the air discharge anomaly when the brake cylinder 30 pressure air discharge time is equal to or longer than the first reference time but shorter than the second reference time. 66 3. The monitoring system according to claim 2, wherein the diagnosis unit determines that a brake is not released when the brake cylinder pressure air discharge time is equal to or longer than a third reference time set to be 5 longer than the second reference time. 4. The monitoring system according to any one of claims 1 to 3, wherein the air discharge time measurement unit measures the brake cylinder pressure air discharge time 10 after the brake command is canceled when the vehicle stops at a station or when the stopping vehicle is checked in leaving a depot in a stopped state. 5. The monitoring system according to any one of claims 1 15 to 4, wherein the diagnosis unit acquires a plurality of brake cylinder pressure air discharge times measured by the air discharge time measurement unit in a predetermined first period, and obtains a tendency of the brake cylinder pressure air discharge times within the first period. 20 6. The monitoring system according to claim 5, wherein the diagnosis unit determines that there is the sign of the air discharge anomaly when a predetermined number of times or more of or a predetermined proportion or more of the 25 brake cylinder pressure air discharge times within the first period are included in an air discharge anomaly sign region in which the brake cylinder pressure air discharge time is equal to or longer than the first reference time but shorter than the second reference time. 30 7. The monitoring system according to any one of claims 1 to 6, comprising an AC pressure detection unit to detect an AC pressure 67 indicating a pressure of compressed air to be supplied from a brake control valve to a relay valve as a brake command pressure, wherein the air discharge time measurement unit measures an AC 5 pressure air discharge time required for the AC pressure detected by the AC pressure detection unit to fall to the first reference pressure after the brake command is canceled when the brake command is input, and the diagnosis unit determines whether or not the AC 10 pressure air discharge time is equal to or longer than the first reference time when the brake cylinder pressure air discharge time is equal to or longer than the first reference time, and the diagnosis unit determines that there is the air 15 discharge anomaly or the sign of the air discharge anomaly relating to the relay valve when the AC pressure air discharge time is not equal to or longer than the first reference time. 20 8. The monitoring system according to claim 7, wherein the diagnosis unit determines that there is the air discharge anomaly or the sign of the air discharge anomaly relating to the brake control valve when the AC pressure air discharge time is equal to or longer than the first 25 reference time. 9. The monitoring system according to any one of claims 1 to 8, wherein the air discharge time measurement unit measures the 30 brake cylinder pressure air discharge time required for the brake cylinder pressure measured by the brake cylinder pressure detection unit to fall to a second reference pressure set to be lower than the first reference pressure, 68 and the diagnosis unit determines that there is the air discharge anomaly or the sign of the air discharge anomaly when the brake cylinder pressure air discharge time is 5 equal to or longer than a fourth reference time set to be longer than the first reference time. 10. The monitoring system according to claim 9, wherein the diagnosis unit determines that there is a possibility 10 of leakage of an SR pressure into the relay valve when the brake cylinder pressure measured by the brake cylinder pressure detection unit at a time of lapse of a fifth reference time set to be longer than the third reference time and the fourth reference time is equal to or higher 15 than a third reference pressure set to be lower than the second reference pressure. 11. A monitoring system comprising: a brake cylinder pressure detection unit to detect a 20 brake cylinder pressure indicating a pressure of a brake cylinder of a brake device to generate a mechanical braking force by pressing a friction material against a rotating body provided in a vehicle; an air supply time measurement unit to measure a brake 25 cylinder pressure air supply time required for the brake cylinder pressure detected by the brake cylinder pressure detection unit to rise to a fourth reference pressure set to be lower than a target brake cylinder pressure for a brake command, after the brake command is input when the 30 vehicle stops and the brake command is not input; and a diagnosis unit to determine that there is an air supply anomaly or a sign of an air supply anomaly when the brake cylinder pressure air supply time measured by the air 69 supply time measurement unit is equal to or longer than a predetermined sixth reference time. 12. The monitoring system according to claim 11, wherein 5 the diagnosis unit determines that there is the air supply anomaly when the brake cylinder pressure air supply time is equal to or longer than a seventh reference time set to be longer than the sixth reference time; and the diagnosis unit determines that there is the sign 10 of the air supply anomaly when the brake cylinder pressure air supply time is equal to or longer than the sixth reference time but shorter than the seventh reference time. 13. The monitoring system according to claim 12, wherein 15 the diagnosis unit determines that braking is insufficient when the brake cylinder pressure air supply time is equal to or longer than an eighth reference time set to be longer than the seventh reference time. 20 14. The monitoring system according to any one of claims 11 to 13, wherein the air supply time measurement unit measures the brake cylinder pressure air supply time after the brake command is input when the stopping vehicle is checked in leaving a depot. 25 15. The monitoring system according to any one of claims 1 to 14, wherein the diagnosis unit acquires a plurality of brake cylinder pressure air supply times measured by the air supply time measurement unit in a predetermined second 30 period, and obtains a tendency of the brake cylinder pressure air supply times within the second period. 16. The monitoring system according to claim 15, wherein 70 the diagnosis unit determines that there is the sign of the air supply anomaly when a predetermined number of times or more of or a predetermined proportion or more of the brake cylinder pressure air supply times within the second period 5 are included in an air supply anomaly sign region in which the brake cylinder pressure air supply time is equal to or longer than the sixth reference time but shorter than the seventh reference time. 10 17. The monitoring system according to any one of claims 11 to 16, comprising an AC pressure detection unit to detect an AC pressure indicating a pressure of compressed air to be supplied from a brake control valve to a relay valve as a brake command 15 pressure, wherein the air supply time measurement unit measures an AC pressure air supply time required for the AC pressure detected by the AC pressure detection unit to rise to the fourth reference pressure after the brake command is input 20 when the vehicle stops and the brake command is not input, and the diagnosis unit determines whether or not the AC pressure air supply time is equal to or longer than the sixth reference time when the brake cylinder pressure air 25 supply time is equal to or longer than the sixth reference time, and the diagnosis unit determines that there is the air supply anomaly or the sign of the air supply anomaly relating to the relay valve when the AC pressure air supply 30 time is not equal to or longer than the sixth reference time. 71 18. The monitoring system according to claim 17, wherein the diagnosis unit determines that there is the air supply anomaly or the sign of the air supply anomaly relating to the brake control valve when the AC pressure air supply 5 time is equal to or longer than the sixth reference time. 19. The monitoring system according to any one of claims 11 to 18, wherein the air supply time measurement unit measures the 10 brake cylinder pressure air supply time required for the brake cylinder pressure measured by the brake cylinder pressure detection unit to rise to a fifth reference pressure set to be higher than the fourth reference pressure, and 15 the diagnosis unit determines that there is the air supply anomaly or the sign of the air supply anomaly when the brake cylinder pressure air supply time is equal to or longer than a ninth reference time set to be longer than the sixth reference time. 20 20. The monitoring system according to claim 19, wherein the diagnosis unit determines that there is a possibility of leakage of compressed air to an atmosphere side from pipe of the relay valve or the brake cylinder when the 25 brake cylinder pressure measured by the brake cylinder pressure detection unit at a time of lapse of a tenth reference time set to be longer than the eighth reference time and the ninth reference time is equal to or lower than a sixth reference pressure set to be higher than the fifth 30 reference pressure. 72 21. The monitoring system according to any one of claims 1 to 20, comprising a data accumulation unit to accumulate the brake cylinder pressure air discharge time measured by the air discharge time measurement unit or the brake 5 cylinder pressure air supply time measured by the air supply time measurement unit. 22. The monitoring system according to claim 21, comprising 10 a position information acquisition unit to acquire position information on the vehicle, wherein the data accumulation unit accumulates the position information on the vehicle acquired by the position information acquisition unit when the brake cylinder 15 pressure air discharge time is measured by the air discharge time measurement unit or the brake cylinder pressure air supply time is measured by the air supply time measurement unit, the position information on the vehicle being associated with the brake cylinder pressure air 20 discharge time or the brake cylinder pressure air supply time. 23. The monitoring system according to claim 21 or 22, comprising 25 a temperature detection unit to detect temperature information around the brake device, wherein the data accumulation unit accumulates the temperature information detected by the temperature detection unit when the brake cylinder pressure air discharge time is measured 30 by the air discharge time measurement unit or the brake 73 cylinder pressure air supply time is measured by the air supply time measurement unit, the temperature information being associated with the brake cylinder pressure air discharge time or the brake cylinder pressure air supply 5 time.