Title of Invention: Work Vehicle
Technical field
[0001]
　The present invention relates to work vehicles such as tractors.
Background technology
[0002]
　2. Description of the Related Art Conventionally, a tractor equipped with a continuously variable transmission is known as disclosed in Patent Document 1. The tractor disclosed in Patent Document 1 has a hydraulic pump and a hydraulic motor, and receives power from an engine. A transmission unit and a compound planetary transmission unit for synthesizing an input transmission output and engine power to output a combined power.
prior art documents
patent literature
[0003]
Patent document 1: Japanese patent publication "JP 2019-95058"
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0004]
　In the tractor as disclosed in Patent Document 1, by controlling the swash plate angle of the hydraulic pump so that the number of rotations of the hydraulic motors is the same, the number of rotations of the hydraulic motor can be kept constant, but the load, etc. If it is large, it may be difficult to stabilize the behavior of the continuously variable transmission.
　In addition, in the tractor disclosed in Patent Document 1, connection of the compound planetary transmission unit when the tractor is braked is not taken into consideration, and the behavior (running) of the tractor during braking may change.
[0005]
　Further, a tractor as disclosed in Patent Document 1 has a structure in which a hydrostatic continuously variable transmission section transmits power to a compound planetary transmission section. When the power of the continuously variable transmission portion is transmitted to the compound planetary transmission portion, the gear shift shock may become large when the gear is changed.
　SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a working vehicle in which the behavior of a continuously variable transmission can be easily stabilized. Another object of the present invention is to provide a work vehicle equipped with a hydrostatic continuously variable transmission capable of improving the traveling performance of the tractor during braking and releasing the braking.
Means to solve problems
[0006]
　The technical means of the present invention for solving this technical problem are characterized by the following points.
　The work vehicle has a vehicle body provided with a travel device, a hydraulic pump having a swash plate whose output changes according to the swash plate angle, and an output shaft whose rotational speed changes according to the output of the hydraulic pump. A traveling motor capable of transmitting power of a shaft to the traveling device, an angle detecting device for detecting a swash plate angle that is the angle of the swash plate, control information relating to control of the swash plate angle, and detected by the angle detecting device. a swash plate control unit for controlling the swash plate angle based on the actual swash plate angle, which is the calculated swash plate angle.
[0007]
　The work vehicle includes a rotation detection device that detects the rotation speed of the output shaft of the traveling motor, and the swash plate control unit uses the rotation speed detected by the rotation detection device as the control information. The swash plate angle is controlled based on the actual swash plate angle.
　The swash plate control unit performs control to reduce the angle deviation when an angle deviation between the set angle of the swash plate determined according to the rotation speed and the actual swash plate angle is equal to or greater than a threshold value. and if the angular deviation is less than a threshold, the set angle is maintained.
[0008]
　The swash plate control unit sets, as the set angle, an angle at which the rotation speed deviation between the target rotation speed of the traveling motor and the actual rotation speed detected by the rotation detection device becomes small.
　The work vehicle is provided with a transmission that changes gears by power output from the output shaft of the travel motor, and the swash plate control unit adjusts the rotational speed deviation when the transmission changes the gears. , the change speed of the swash plate angle is controlled to be small when the rotational speed deviation is equal to or greater than the threshold value.
[0009]
　The hydraulic pump and the travel motor are hydrostatic continuously variable transmissions that steplessly change the driving force of the prime mover.
　The work vehicle includes a plurality of planetary gear transmissions that change the speed of the driving force changed by the continuously variable transmission, and the plurality of planetary gear transmissions transmit high-speed driving force to the traveling device. 1 planetary gear transmission and a second planetary gear transmission that transmits a driving force at a lower speed than the first planetary gear transmission.
[0010]
　The work vehicle has a vehicle body provided with a travel device, a hydraulic pump having a swash plate whose output changes according to the swash plate angle, and an output shaft whose rotational speed changes according to the output of the hydraulic pump. a traveling motor capable of transmitting power to the traveling device; a rotation detection device for detecting the number of rotations of the output shaft of the traveling motor; and an angle of the swash plate. an angle detection device for detecting the angle of the swash plate; a braking device for braking the traveling device; a control device for controlling the continuously variable transmission based on the actual swash plate angle, which is the swash plate angle detected by the angle detection device when the braking device is braking. ing.
[0011]
　When the braking is not performed, the control device performs rotation speed feedback control so as to reduce the deviation between the actual rotation speed detected by the rotation detection device and the target rotation speed. When it is performed, swash plate feedback control is performed so that the deviation between the actual swash plate angle, which is the swash plate angle detected by the angle detection device, and the target swash plate angle becomes small.
　The work vehicle includes a braking operation member that brakes the braking device, and the control device sets the target swash plate angle according to the amount of operation of the braking operation member.
[0012]
　The work vehicle includes a planetary gear transmission mechanism capable of shifting the driving force changed by the continuously variable transmission between high speed and low speed, and transmitting the driving force changed by the planetary gear transmission to the traveling device. a clutch mechanism that can be switched between a connected state in which it is connected to the travel transmission shaft and a disconnected state in which it is not connected to the travel transmission shaft, and the control device controls the clutch mechanism when the braking device is applied. to the disconnected state.
[0013]
　The control device disengages the clutch mechanism when the driving force of the planetary gear transmission mechanism is on the high speed side.
　The planetary gear transmission mechanism includes a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to a high speed side, and a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to the high speed side. and a second planetary gear transmission that shifts to a lower speed side than the clutch mechanism, and the clutch mechanism has a connection state in which the driving force of the first planetary gear transmission is connected to the travel transmission shaft, and a connection state in which the drive force of the first planetary gear transmission is connected to the travel transmission shaft. a first clutch device that can be switched between a disengaged state in which the driving force of the second planetary gear transmission is connected to the travel transmission shaft, and a disengaged state in which the drive force of the travel transmission shaft is not connected; and a second clutch device, wherein when the second clutch device is in the disengaged state, the control device has a rotational deviation between the number of revolutions of the travel motor and the number of revolutions of the second planetary gear transmission. The number of revolutions of the traveling motor is changed so as to decrease the number of revolutions.
[0014]
　The control device switches the second clutch device to an engaged state when the rotational speed deviation is equal to or less than a threshold value.
　The control device switches the first clutch device from the disconnected state to the connected state when the braking of the braking device is released.
　The control device switches the second clutch device from the disconnected state to the connected state when the speed of the vehicle body increases while the braking device is being applied.
[0015]
　A work vehicle includes a prime mover, a traveling device, a continuously variable transmission for steplessly shifting the driving force transmitted from the prime mover, and a planetary gear transmission mechanism for shifting the changed driving force by the continuously variable transmission. a clutch mechanism that can be switched between a connected state in which it is connected to a travel transmission shaft that transmits the driving force changed by the planetary gear transmission to the travel device, and a disconnected state in which it is not connected to the travel transmission shaft; and an automatic transmission unit for starting a switching operation of switching the clutch mechanism from the disengaged state to the connected state before the drive force output from the transmission reaches an automatic shift condition.
[0016]
　The continuously variable transmission includes a hydraulic pump having a swash plate whose output changes according to the angle of the swash plate, and an output shaft whose rotational speed changes according to the output of the hydraulic pump and which transmits the changed driving force to the planetary gear transmission mechanism. and the automatic transmission unit, before the rotation speed of the output shaft that transmits the driving force output from the continuously variable transmission reaches the switching rotation speed that is the automatic transmission condition, A switching operation of the clutch mechanism is started.
[0017]
　The work vehicle includes a rotation detection device that detects the rotation speed of the output shaft of the traveling motor, and the automatic transmission unit predicts the time required to reach the switching rotation speed from the rotation speed detected by the rotation detection device. The switching operation is performed based on at least the time predicted by the prediction unit.
　The planetary gear transmission mechanism includes a first planetary gear transmission for transmitting high-speed driving force and a second planetary gear transmission for transmitting driving force at a lower speed than the first planetary gear transmission, and the clutch The mechanism includes a first clutch device capable of transmitting the driving force of the first planetary gear transmission to the travel transmission shaft, and a second clutch device capable of transmitting the driving force of the second planetary gear transmission to the travel transmission shaft. and the automatic transmission unit, when one of the first clutch device and the second clutch device is in the connected state, the other is in the disconnected state.
[0018]
　The work vehicle includes a hydraulic pump that discharges hydraulic oil, an electromagnetic control valve into which the hydraulic oil discharged from the hydraulic pump is introduced, and an oil passage that connects the electromagnetic control valve and the clutch mechanism. , the automatic transmission portion outputs a control signal for opening the electromagnetic control valve when starting the switching operation.
　The work vehicle includes a vehicle body provided with a traveling device, a hydrostatic continuously variable transmission that continuously changes the driving force of the prime mover, and a high speed side and a low speed side of the driving force changed by the continuously variable transmission. a planetary gear transmission mechanism capable of changing speed to and from the planetary gear transmission mechanism; a connected state in which the driving force transmitted by the planetary gear transmission mechanism is connected to the travel transmission shaft; and a disconnected state in which the travel transmission shaft is not connected. A switchable clutch mechanism, a braking device that brakes the vehicle body, and a control device that brings the clutch mechanism into the disengaged state when the braking device is braked.
[0019]
　The control device disengages the clutch mechanism when the drive force of the planetary gear transmission mechanism is on the high speed side.
　The planetary gear transmission mechanism includes a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to a high speed side, and a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to the high speed side. a second planetary gear transmission that shifts to a lower speed side than the clutch mechanism, wherein the clutch mechanism is in a connected state in which the driving force of the first planetary gear transmission is connected to the travel transmission shaft, and in a connection state in which the drive force of the first planetary gear transmission is connected to the travel transmission shaft a first clutch device that can be switched between a disengaged state in which the driving force of the second planetary gear transmission is connected to the travel transmission shaft, and a disengaged state in which the drive force of the travel transmission shaft is not connected; and a second clutch device, wherein the control device disengages the first clutch device when braking of the braking device is performed.
[0020]
　The work vehicle includes a vehicle speed detection device that detects the vehicle speed of the vehicle body, and switches the clutch mechanism from the disconnected state to the connected state when the vehicle speed detected by the vehicle speed detection device is equal to or less than a threshold value.
　The planetary gear transmission mechanism includes a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to a high speed side, and a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to the high speed side. a second planetary gear transmission that shifts to a lower speed side than the clutch mechanism, wherein the clutch mechanism is in a connected state in which the driving force of the first planetary gear transmission is connected to the travel transmission shaft, and in a connection state in which the drive force of the first planetary gear transmission is connected to the travel transmission shaft a first clutch device that can be switched between a disengaged state in which the driving force of the second planetary gear transmission is connected to the travel transmission shaft, and a disengaged state in which the drive force of the travel transmission shaft is not connected; and a second clutch device, wherein the control device switches the second clutch device from the disconnected state to the connected state when the vehicle speed is equal to or less than a threshold value.
[0021]
　The hydrostatic continuously variable transmission has a hydraulic pump having a swash plate whose output changes according to the swash plate angle, and an output shaft whose rotational speed changes according to the output of the hydraulic pump. a traveling motor that can be transmitted to the traveling device, wherein the control device controls the continuously variable transmission based on the number of revolutions of the traveling motor when the braking device is not braking; When the braking device is applied, the continuously variable transmission is controlled based on the swash plate angle of the hydraulic pump.
Effect of the invention
[0022]
　According to the present invention, the behavior of a continuously variable transmission can be easily stabilized. Further, according to the present invention, in a work vehicle equipped with a hydrostatic continuously variable transmission, it is possible to improve the running performance of the tractor during braking and releasing the braking.
Brief description of the drawing
[0023]
1] A diagram showing the entire transmission. [Fig.
2 is a diagram showing a control block diagram; FIG.
3 is a diagram showing the relationship between the number of revolutions of a travel motor and the angle of a swash plate; FIG.
4 is a diagram showing the operation flow of swash plate control; FIG.
5A shows a shift state when the tractor is accelerated when the clutch mechanism is switched from the disengaged state to the engaged state before the automatic shift condition is reached. FIG.
FIG. 5B shows a shift state when the tractor is accelerated when the clutch mechanism is switched from the disengaged state to the engaged state after the automatic shift condition is reached.
6 is a diagram showing a flow of switching operation; FIG.
7A is a diagram showing an example of a switching state of a clutch mechanism in control of a braking control section; FIG.
7B] A diagram showing another example of the switching state of the clutch mechanism in the control of the braking control section. [FIG.
7C] A diagram showing another example of the switching state of the clutch mechanism in the control of the braking control section. [FIG.
7D is a diagram showing another example of the switching state of the clutch mechanism in the control of the braking control section; FIG.
8 is a diagram showing the entire tractor. FIG.
MODE FOR CARRYING OUT THE INVENTION
[0024]
　BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
　FIG. 8 shows a tractor 1 as an example of a work vehicle. Although the tractor 1 will be described as an example, the work vehicle is not limited to a tractor, but may be an agricultural machine such as a rice transplanter.
　As shown in FIG. 8 , the tractor 1 includes a vehicle body 3 having a travel device 7 , a prime mover 4 , a transmission 5 and a steering device 29 . The traveling device 7 is a device having front wheels 7F and rear wheels 7R. The front wheels 7F may be of a tire type or a crawler type. Also, the rear wheel 7R may be of a tire type or a crawler type. The prime mover 4 is an internal combustion engine such as a gasoline engine or a diesel engine. In this embodiment, prime mover 4 is a diesel engine.
[0025]
　The transmission device 5 can switch the driving force of the traveling device 7 by changing speed, and can switch the traveling device 7 between forward and reverse. A cabin 9 is provided in the vehicle body 3, and a driver's seat 10 is provided in the cabin 9. - 特許庁
　A lifting device 8 is provided at the rear portion of the vehicle body 3 . The working device 2 can be attached to and detached from the lifting device 8 . Further, the lifting device 8 is capable of lifting and lowering the work device 2 mounted thereon. The work device 2 includes a tillage device for tilling, a fertilizer spraying device for spraying fertilizer, an agricultural chemical spraying device for spraying agricultural chemicals, a harvesting device for harvesting, a harvesting device for cutting pasture grass, a spreading device for spreading pasture grass, etc. Examples include a grass collecting device for collecting pasture grass, a forming device for forming pasture grass, and the like.
[0026]
　As shown in FIG. 1 , the transmission 5 includes a continuously variable transmission 50 , a planetary gear transmission mechanism 51 , a clutch mechanism 52 and an auxiliary transmission 53 . The continuously variable transmission 50 , the planetary gear transmission mechanism 51 , the clutch mechanism 52 and the auxiliary transmission 53 are housed in the mission case 12 .
　The continuously variable transmission 50 is a device that continuously changes the speed of the driving force transmitted from the prime mover 4 . In this embodiment, the continuously variable transmission 50 is a hydrostatic continuously variable transmission.
[0027]
　The driving force transmitted from the output shaft (crankshaft) 4a of the prime mover 4 to the main shaft (propulsion shaft) 54 is changed. As shown in FIG. 1, the continuously variable transmission 50 has a hydraulic pump P1 and a travel motor M1. As shown in FIG. 2, the hydraulic pump P1 and the traveling motor M1 are connected by an oil passage (circulation oil passage) 55 through which hydraulic oil flows.
　As shown in FIG. 1, the hydraulic pump P1 has an input shaft 56a and a swash plate 56b. The hydraulic pump P1 is driven by the power transmitted to the input shaft 56a, and the output (discharge amount (flow rate) of hydraulic oil, pressure) is controlled by the angle (swash plate angle) of the swash plate 56b that is supported to be able to swing. can be changed.
[0028]
　The travel motor M1 has an output shaft 58 . The rotation speed of the output shaft 58 changes depending on the output of the hydraulic pump P1 (flow rate and pressure of hydraulic oil). The power of the output shaft 58 is transmitted to the traveling device 7 after being transmitted to the planetary gear transmission mechanism 51 and the like.
　Specifically, as shown in FIG. 1, the input shaft 56a of the hydraulic pump P1 is connected to a drive gear mechanism 59 having gears and the like that rotate with the rotation of the main shaft (propulsion shaft) 54. The power of the main shaft (propulsion shaft) 54 is transmitted through. The output is changed by the swash plate angle of the hydraulic pump P1, and the rotation speed of the output shaft 58 of the travel motor M1 is changed.
[0029]
　The planetary gear transmission mechanism 51 is a device for further changing the speed of the driving force changed by the continuously variable transmission 50 and has a plurality of planetary gear transmissions 57 . In this embodiment, the plurality of planetary gear transmissions 57 includes a first planetary gear transmission 57H and a second planetary gear transmission 57L. The first planetary gear transmission 57H is a planetary gear transmission that transmits a high-speed driving force, and the second planetary gear transmission 57L is a planetary gear that transmits a lower-speed driving force than the first planetary gear transmission 57H. It is a gearbox.
[0030]
　The first planetary gear transmission 57H has a first input shaft 61a, a first sun gear 61b, a first ring gear 61c, a plurality of first planetary gears 61d, a first carrier 61e, and a first output shaft 61f. ing. The first input shaft 61a is rotatably supported, and the driving force changed by the continuously variable transmission 50 is transmitted. The first sun gear 61b is a gear that rotates as the first input shaft 61a rotates. The first ring gear 61c is arranged coaxially with the first sun gear 61b and is rotatably supported. A plurality of first planetary gears 61d are arranged between the first ring gear 61c and the first sun gear 61b. A plurality of first planetary gears 61d are supported by a first carrier 61e. The first output shaft 61f is supported so as to rotate with the rotation of the first ring gear 43a.
[0031]
　The second planetary gear transmission 57L has a second input shaft 62a, a second sun gear 62b, a second ring gear 62c, a plurality of second planetary gears 62d, a second carrier 62e, and a second output shaft 62f. ing. The second input shaft 62a is rotatably supported, and the driving force changed by the continuously variable transmission 50 is transmitted. The second sun gear 62b is a gear that rotates as the second input shaft 62a rotates. The second ring gear 62c is arranged coaxially with the second sun gear 62b and is rotatably supported. A plurality of second planetary gears 62d are arranged between the second ring gear 62c and the second sun gear 62b. A plurality of second planetary gears 62d are supported by a second carrier 62e. The second output shaft 62f is supported so as to rotate as the second carrier 62e rotates.
[0032]
　The output side of the continuously variable transmission 50, that is, the power of the output shaft 58 of the traveling motor M1 is transmitted to the second planetary gear transmission 57L via the second input shaft 62a of the second planetary gear transmission 57L. be done. Further, the power is transmitted to the first planetary gear transmission 57H by a power transmission mechanism 63 connected to the second input shaft 62a of the second planetary gear transmission 57L. The power transmission mechanism 63 includes a gear 63a that rotates as the input shaft 62a rotates, a gear 63b that meshes with the gear 63a, and a gear 63c provided on the first input shaft 61a of the first planetary gear transmission 57H. I'm in. The gear 63b meshes with the gear 63c.
[0033]
　Therefore, the power of the output shaft 58 of the travel motor M1 is transmitted to the input shaft 61a of the first planetary gear transmission 57H via the second input shaft 62a, the gear 63a, the gear 63b and the gear 63c.
　A gear provided on the second ring gear 62c of the first planetary gear transmission 57H and a gear 64 provided on the main shaft (propulsion shaft) 54 are in mesh with each other. are engaged.
[0034]
　As described above, according to the continuously variable transmission 50 and the planetary gear transmission mechanism 51, when the driving force output from the continuously variable transmission 50 is input to the first planetary gear transmission 57H, the driving force is converted to high speed. When input to the two-planetary gear transmission 57L, it can be converted to a low speed.
　As shown in FIG. 1 , the transmission 5 has a clutch mechanism 52 . The clutch mechanism 52 can be switched between a connected state in which the driving force changed by the planetary gear transmission mechanism 51 is connected to the traveling transmission shaft 66 and a disconnected state in which the driving force is not connected to the traveling transmission shaft 66 . The clutch mechanism 52 has a first clutch device 52A and a second clutch device 52B. The first clutch device 52A is a clutch capable of transmitting the driving force of the first planetary gear transmission 57H to the traveling transmission shaft 66. As shown in FIG. The second clutch device 52B is a clutch capable of transmitting the driving force of the second planetary gear transmission 57L to the traveling transmission shaft 66. As shown in FIG.
[0035]
　The first clutch device 52A and the second clutch device 52B are hydraulic clutches that are switched between a connected state and a disconnected state by hydraulic oil.
　The first clutch device 52A includes a housing 71a rotatable integrally with the first output shaft 61f of the first planetary gear transmission 57H, a cylindrical shaft 71b, and a friction plate 71c arranged between the housing 71a and the cylindrical shaft 71b. and a pressing member 71d. The pressing member 71d is biased in a direction away from the friction plate 71c by a biasing member such as a spring (not shown).
[0036]
　An oil passage 71e for supplying and discharging hydraulic oil is connected to the housing 71a. When the hydraulic oil is supplied from the oil passage 71e to the housing 71a side, the pressing member 71d presses against the biasing force of the spring. side (connection side), the friction plate 71c is pressed against the housing 71 side, the first clutch device 52A is in a connected state, and the power of the output shaft 61f is applied to the gear 73 rotating integrally with the cylindrical shaft 71b. transmitted. On the other hand, when the hydraulic oil is discharged from the housing 71a side to the oil passage 71e, the pressing member 71d is moved to the cutting side by the biasing force of the spring, so that the friction plate 71c is separated from the housing 71a side, and the first clutch device is closed. 52A is in the disconnected state, and the power of the output shaft 61f is not transmitted to the gear 73.
[0037]
　The travel transmission shaft 66 is provided with an input gear 74 that rotates integrally with the travel transmission shaft 66. The input gear 74 meshes with the output side gear (output gear) 73 of the first clutch device 52A. When the first clutch device 52A is in the engaged state, the driving force shifted to the high speed side by the first planetary gear transmission 57H is transmitted to the traveling transmission shaft 66. As shown in FIG.
　The second clutch device 52B is a clutch that switches between forward and reverse travel, and has a forward clutch portion 75 and a reverse clutch portion 76 . The forward clutch portion 75 and the reverse clutch portion 76 have a housing 77 that rotates integrally with the second output shaft 62f of the second planetary gear transmission 57L.
[0038]
　The forward clutch portion 75 has a cylindrical shaft 75b, a friction plate 75c arranged between the housing 77 and the cylindrical shaft 75b, and a pressing member 75d. The pressing member 75d is biased in a direction away from the friction plate 75c by a biasing member such as a spring (not shown).
　An oil passage 75e for supplying and discharging working oil is connected to the housing 77 on the forward clutch portion 75 side. By moving to the pressing side (connection side) against the force, the friction plate 75c is pressed against the housing 77 side, the forward clutch portion 75 is in the connected state, and the power of the output shaft 62f is integrated with the cylindrical shaft 75b. It is transmitted to the rotating gear 78 . On the other hand, when hydraulic oil is discharged from the housing 77 side to the oil passage 75e, the pressing member 75d moves toward the cutting side due to the biasing force of the spring. is disconnected, and the power of the output shaft 62f is not transmitted to the gear 78.
[0039]
　The reverse clutch portion 76 has a cylindrical shaft 76b, a friction plate 76c arranged between the housing 77 and the cylindrical shaft 76b, and a pressing member 76d. The pressing member 76d is biased in a direction away from the friction plate 76c by a biasing member such as a spring (not shown).
　The travel transmission shaft 66 is provided with an input gear 80 that rotates integrally with the travel transmission shaft 66. The input gear 80 meshes with a gear (output gear) 78 on the output side of the forward clutch portion 75 to move forward. When the clutch portion 75 is in the engaged state, the driving force shifted to the low speed side by the second planetary gear transmission 57L is transmitted to the traveling transmission shaft 66. As shown in FIG.
[0040]
　An oil passage 76e for supplying and discharging working oil is connected to the inside of the housing 77 on the reverse clutch portion 76 side. By moving to the pressing side (connecting side) against the force, the friction plate 76c is pressed against the housing 77 side, the reverse clutch portion 76 is in the connected state, and the power of the output shaft 62f is integrated with the cylindrical shaft 76b. It is transmitted to the rotating gear 79 . On the other hand, when hydraulic oil is discharged from the housing 77 side to the oil passage 76e, the pressing member 76d moves toward the cutting side due to the biasing force of the spring. is disconnected, and the power of the output shaft 62f is not transmitted to the gear 79.
[0041]
　The auxiliary transmission 53 includes a first transmission section 95 provided between the first counter shaft 91 and the rear wheel drive shaft 93, a second transmission section 96 provided coaxially with the second counter shaft 92, and It is configured with a transmission gear linked to. The subtransmission device 53 includes a first low speed transmission gear 97a, a second low speed transmission gear 97b, a high speed transmission gear 97c and a medium speed transmission gear 97d, and has three stages of high speed, medium speed and low speed. is possible.
[0042]
　A rear wheel drive shaft 93 that has been shifted by the auxiliary transmission 53 is connected to a rear wheel differential device 100 to which a rear axle 99 that rotatably supports the rear wheels 7R is connected. , the auxiliary transmission 53 and the rear wheel drive shaft 93 to the traveling device 7 having the rear wheels 7R. Further, the driving force of the forward travel transmission shaft 66 is transmitted to the front wheel transmission shaft 101 via the front wheel transmission gear 98 provided on the rear wheel drive shaft 93 . The front wheel transmission shaft 101 is provided with a drive conversion clutch 102 that changes the rotation of the front wheels 7F. The front wheel drive shaft 103 is connected to a front wheel differential device 106 to which a front axle 105 that rotatably supports the front wheels 7F is connected. to the travel device 7 having the front wheels 7F. In the drive conversion clutch 102, the front wheels 7F and the rear wheels 7R can be rotated at a constant speed, the front wheels 7F and the rear wheels 7R can be used for 4WD, or only the rear wheels 7R can be used for 2WD. can be done.
[0043]
　A PTO clutch device 110 is provided on the propulsion shaft 54 ​​. The PTO clutch device 110 is composed of, for example, a hydraulic clutch or the like. By turning on/off the hydraulic clutch, the power of the propulsion shaft 54 ​​is transmitted to the PTO propulsion shaft 111 (connected state), and the power of the propulsion shaft 54 ​​is transferred to the PTO propulsion state. It switches to a state (disconnected state) in which the power is not transmitted to the shaft 111 . A PTO transmission device 112 for changing the driving force (rotation) of the PTO propulsion shaft 111 is provided in the middle of the PTO propulsion shaft 111, and is connected to the rotation of the PTO propulsion shaft 111, that is, to the PTO propulsion shaft 111 via a gear. The rotation of the PTO shaft 16 that is applied can be changed.
[0044]
　As shown in FIG. 2, the tractor 1 has a steering device 29 . The steering device 29 has a steering wheel (steering wheel) 30, a rotating shaft (steering shaft) 31 that rotates as the steering wheel 30 rotates, and an auxiliary mechanism (power steering mechanism) 32 that assists the steering of the steering wheel 30. is doing. The auxiliary mechanism 32 includes a hydraulic pump 33 , a control valve 34 to which hydraulic oil discharged from the hydraulic pump 33 is supplied, and a steering cylinder 35 operated by the control valve 34 . The control valve 34 is an electromagnetic valve that operates based on a control signal. The control valve 34 is, for example, a three-position switching valve that can be switched by moving a spool or the like. The control valve 34 can also be switched by steering the steering shaft 31 . The steering cylinder 35 is connected to an arm (knuckle arm) that changes the direction of the front wheels 7F.
[0045]
　Therefore, when the handle 30 is operated, the switching position and the opening degree of the control valve 34 are switched according to the handle 30, and the steering cylinder 35 expands and contracts to the left or right according to the switching position and the opening degree of the control valve 34. By doing so, the steering direction of the front wheels 7F can be changed. Note that the steering device 29 described above is merely an example, and is not limited to the configuration described above.
　The tractor 1 has a positioning device 40 . The positioning device 40 can detect its own position (positioning information including latitude and longitude) using satellite positioning systems (positioning satellites) such as D-GPS, GPS, GLONASS, Hokuto, Galileo, and Michibiki. That is, the positioning device 40 receives a satellite signal (position of the positioning satellite, transmission time, correction information, etc.) transmitted from the positioning satellite, and based on the satellite signal, determines the position of the tractor 1 (for example, latitude, longitude), That is, the vehicle body position is detected. The positioning device 40 has a receiving device 41 and an inertial measurement unit (IMU: Inertial Measurement Unit) 42 . The receiving device 41 is a device that has an antenna or the like and receives satellite signals transmitted from a positioning satellite, and is attached to the vehicle body 3 separately from the inertial measurement device 42 . In this embodiment, the receiving device 41 is attached to the vehicle body 3 , ie the cabin 9 . Note that the mounting location of the receiving device 41 is not limited to the embodiment.
[0046]
　The inertial measurement device 42 has an acceleration sensor that detects acceleration, a gyro sensor that detects angular velocity, and the like. The roll angle, pitch angle, yaw angle, etc. of the vehicle body 3 can be detected by the inertial measurement device 42 provided below the vehicle body 3 , for example, the driver's seat 10 .
　Now, as shown in FIG. The control device 120 includes a CPU, electric/electronic circuits, programs stored in the control device 120, and the like. The control device 120 performs various controls regarding the tractor 1 . The storage device 121 is composed of a nonvolatile memory or the like.
[0047]
　An angle detection device 122 and a rotation detection device 123 are connected to the control device 120 . The angle detection device 122 is a sensor that detects a swash plate angle, which is the angle of the swash plate 56b of the hydraulic pump P1. The rotation detection device 123 is a sensor that detects the actual rotation speed (actual motor rotation speed) of the output shaft 58 of the traveling motor M1. A regulator 125 that controls the angle of the swash plate is also connected to the controller 120 . The regulator 125 includes a control valve (electromagnetic control valve) 126 such as an electromagnetic valve. The electromagnetic control valve 126 has a solenoid, and is a valve whose degree of opening changes according to the current that excites the solenoid. As the current exciting the solenoid increases, the opening of the electromagnetic control valve 126 increases, and as the current exciting the solenoid decreases, the opening of the electromagnetic control valve 126 decreases. When the solenoid of the electromagnetic control valve 126 is demagnetized and no current is applied, the electromagnetic control valve 126 is fully closed.
[0048]
　The control device 120 controls the hydraulic pump P1, that is, controls the swash plate angle of the swash plate 56b of the hydraulic pump P1 (swash plate control).
　The control device 120 includes a swash plate control section 120A. The swash plate control unit 120A controls the swash plate angle so that the rotation speed (actual rotation speed) J1 detected by the rotation detection device 123 matches the target rotation speed (target rotation speed) J2 of the traveling motor M1. The swash plate control unit 120A feeds back the actual number of rotations J1 of the traveling motor M1, and the deviation between the fed back actual number of rotations J1 and the target number of rotations (target number of rotations) J2 of the predetermined number of rotations of the traveling motor M1. The swash plate angle is set, that is, the swash plate angle is set so as to be small.
[0049]
　For example, as shown in FIG. 3, the storage device 121 stores a control map, ie, a control line L1, showing the relationship between the rotation speed of the traveling motor M1 and the swash plate angle of the hydraulic pump P1.
　When driving the travel motor M1, the swash plate control unit 120A first sets the target rotation speed J2 of the travel motor M1. A setting angle (target setting angle) θ1a of the corresponding swash plate angle is obtained.
[0050]
　Next, when the target setting angle θ1a is obtained, the swash plate control section 120A determines the opening degree of the electromagnetic control valve 126 so as to achieve the target swash plate angle θ1a, and excites the solenoid of the electromagnetic control valve 126. After controlling the swash plate angle by energizing the solenoid of the electromagnetic control valve 126, the swash plate control unit 120A refers to the deviation (rotation speed deviation ΔJ) between the target rotation speed J2 and the actual rotation speed J1 to determine the rotation speed deviation. The set angle θ1a is corrected to the set angle θ1b so that ΔJ becomes small, and the opening of the electromagnetic control valve 126 is corrected so as to obtain the corrected set angle θ1b. That is, the swash plate control unit 120A controls the swash plate angle so as to achieve the target rotation speed J2 of the travel motor M1 by feeding back the actual rotation speed J1 of the travel motor M1 (revolution feedback control).
[0051]
　Now, the swash plate control unit 120A performs not only rotational speed feedback control but also control while referring to the actual swash plate angle θ2. Specifically, the swash plate control unit 120A also controls the swash plate angle based on the control information regarding control of the swash plate angle and the swash plate angle (actual swash plate angle) θ2 detected by the angle detection device 122. conduct. The control information is various parameters for determining the swash plate angle, and various information when the tractor 1 is driven. In this embodiment, the control information is the actual rotation speed J1. That is, the swash plate control section 120A controls the swash plate angle based on the actual rotation speed J1 and the actual swash plate angle θ2.
[0052]
　Specifically, when the traveling motor M1 is being driven, the swash plate control unit 120A, as shown in FIG. and the set angle (target set angle) θ1b determined corresponding to . When the deviation (angular deviation) Δθ between the actual swash plate angle θ2 (θ2a, θ2b) and the set angle (target set angle) θ1b is equal to or greater than the threshold value θ10, the swash plate control unit 120A performs control to reduce the angle deviation Δθ. is performed, and if the angle deviation Δθ is less than the threshold value θ10, the set angle θ1b is held.
[0053]
　For example, when the actual swash plate angle θ2 when the swash plate angle is controlled by the set angle θ1b is θ2a, the swash plate control unit 120A sets the angle deviation Δθ between the actual swash plate angle θ2a and the set angle θ1b. is less than the threshold θ10. Therefore, the swash plate control unit 120A performs swash plate control while performing rotational speed feedback control using the control line L1 as described above.
　On the other hand, when the actual swash plate angle θ2 when the swash plate control unit 120A sets and controls the set angle θ1b is θ2b, the angle deviation Δθ between the set angle θ1b and the actual swash plate angle θ2b is equal to or greater than the threshold value θ10. Therefore, as described above, instead of performing swash plate control while performing rotational speed feedback control using the control line L1, it is determined that the load is large, and the control line L2 different from the control line L1 is used. to control.
[0054]
　The control line L2 is a line that makes the set angle θ1c smaller than the set angle θ1b even if the target rotation speed J2 is the same as that of the control line L1. That is, the control line L2 is a control line for reducing the angular deviation Δθ between the set angle θ1c corresponding to the target rotation speed J2 and the actual swash plate angle θ2b. That is, as shown in FIG. 3, when the angular deviation Δθ becomes equal to or greater than the threshold value θ10, the swash plate control unit 120A controls the target rotation speed J2 of the traveling motor M1 and the setting value based on the control line L1 to the control line L2. The angle θ1c is obtained to control the swash plate angle. If the angle deviation Δθ continues to be equal to or greater than the threshold value θ10, the swash plate angle may be controlled so as to reach the target rotation speed J2 of the traveling motor M1 by rotation speed feedback control.
[0055]
　FIG. 4 is a diagram showing the operation flow of swash plate control.
　As shown in FIG. 4, the swash plate control unit 120A sets a swash plate angle (target swash plate angle) θ1 based on the target rotation speed J2 and the control line L1 (S1). The swash plate control unit 120A refers to the actual rotation speed J1 (S2), and calculates the rotation speed deviation ΔJ between the target rotation speed J2 and the actual rotation speed J1 (S3). The swash plate control unit 120A performs swash plate control by correcting the set angle θ1 so as to reduce the rotational speed deviation ΔJ (S4). The swash plate control unit 120A refers to the actual swash plate angle θ2 (S5), and calculates the angle deviation Δθ between the set angle θ1 and the actual swash plate angle θ2 (S6). is greater than or equal to the threshold value .theta.10 (S7). If the angular deviation .DELTA..theta. ). It is determined whether or not the tractor 1 (vehicle body 3) has stopped (running stopped, work completed) (S9). If the tractor 1 (body 3) is not stopped, the process returns to S2.
[0056]
　In addition, when changing the gear stage by the transmission 5, the swash plate control unit 120A shifts to the high speed side by the first planetary gear transmission 57H by, for example, switching the first clutch device 52A from the disconnected state to the connected state. or when shifting to the lower speed side by the second planetary gear transmission 57L by switching the forward clutch portion 75 of the second clutch device 52B from the disconnected state to the connected state, the target rotation speed J2 and the actual rotation speed J1 Refer to the deviation (rotational speed deviation ΔJ) from The swash plate control unit 120A performs control using the control line L2 instead of the control line L1 when the rotational speed deviation ΔJ is equal to or greater than the threshold, and uses the control line L1 when the rotational speed deviation ΔJ is less than the threshold. may be used for control.
[0057]
　Further, in the above-described embodiment, the swash plate control unit 120A reduces the angle deviation Δθ through the control line L2 when the angle deviation Δθ is equal to or greater than the threshold value θ10 or when the rotational speed deviation ΔJ is equal to or greater than the threshold value. However, when the rotational speed deviation ΔJ is equal to or greater than the threshold value, such as when changing the gear position by the transmission 5, the change speed of the swash plate angle may be decreased. For example, when switching the planetary gear transmission mechanism 51 to the high speed side or the low speed side, the inclination of the control line L2 is decreased (the increase in the swash plate angle per unit rotation speed is decreased).
[0058]
　The method of setting the target rotation speed J2 of the traveling motor M1 is not limited. For example, when the accelerator 127 is operated by the driver, the number of revolutions of the prime mover 4 (the number of revolutions of the prime mover) is set, and the controller 120 sets the number of revolutions of the prime mover 4 corresponding to the set number of revolutions of the prime mover (the target number of revolutions of the prime mover). Alternatively, the target rotation speed J2 of the travel motor M1 may be automatically set corresponding to the target motor rotation speed during automatic operation, or the target rotation speed of the travel motor M1 may be set according to a preset vehicle speed. The number J2 may be set and is not limited.
[0059]
　The work vehicle 1 has a vehicle body 3 provided with a travel device 7, a hydraulic pump P1 having a swash plate 56b whose output changes according to the swash plate angle, and an output shaft 58 whose rotational speed changes according to the output of the hydraulic pump P1. a traveling motor M1 capable of transmitting the power of the output shaft 58 to the traveling device 7; an angle detecting device 122 for detecting a swash plate angle that is the angle of the swash plate 56b; A swash plate control unit 120A that controls the swash plate angle based on the actual swash plate angle θ2 that is the swash plate angle detected by the detection device 122 . According to this, since the swash plate angle is controlled using both the control information related to the control of the swash plate angle and the actual swash plate angle θ2 that is the actual swash plate angle, the behavior of the continuously variable transmission can be easily performed. can be stabilized.
[0060]
　The work vehicle 1 includes a rotation detection device 123 that detects the rotation speed of the output shaft 58 of the traveling motor M1. The swash plate angle is controlled based on the number J1 and the actual swash plate angle θ2. According to this, it is possible to easily grasp the relationship between the actual rotation speed J1 of the travel motor M1 and the actual swash plate angle θ2 when the rotation speed of the travel motor M1 is controlled. That is, in control, it is possible to grasp the relationship between the actual swash plate angle θ2 on the input side and the actual rotation speed J1 on the output side, and execute control according to the situation.
[0061]
　When the angle deviation Δθ between the set angle θ1 of the swash plate angle determined according to the rotation speed and the actual swash plate angle θ2 is equal to or greater than a threshold value, the swash plate control unit 120A performs control to reduce the angle deviation Δθ. If the angular deviation Δθ is less than the threshold value θ10, the set angle θ1 is held. According to this, when the angle deviation Δθ between the set angle θ1 and the actual swash plate angle θ2 is equal to or greater than the threshold value, the actual swash plate angle θ2 is far from the set set angle θ1. It can be determined that the angular deviation .DELTA..theta. For example, it is possible to reduce the occurrence of overshoot and hunting during acceleration (acceleration) and deceleration of the tractor 1 .
[0062]
　The swash plate control unit 120A sets, as the set angle θ1, an angle at which the rotation speed deviation ΔJ between the target rotation speed J2 of the traveling motor M1 and the actual rotation speed J1 detected by the rotation detection device 123 becomes small. According to this, the rotational speed feedback control of the traveling motor M1 can be performed so as to reduce the rotational speed deviation ΔJ of the traveling motor M1, and the actual rotational speed J1 of the traveling motor M1 can be set to the intended rotational speed. .
[0063]
　The work vehicle 1 is provided with a transmission 5 that changes gears by power output from the output shaft 58 of the traveling motor M1. The deviation .DELTA.J is referred to, and if the rotational speed deviation .DELTA.J is equal to or greater than the threshold value, the change speed of the swash plate angle is controlled to be small. According to this, when the rotation speed deviation ΔJ is equal to or greater than the threshold value, the change speed of the swash plate angle is reduced, so that overshoot and hunting can be prevented when performing the rotation speed control of the traveling motor M1. can be reduced.
[0064]
　The hydraulic pump P1 and the traveling motor M1 are a hydrostatic continuously variable transmission 50 for steplessly changing the driving force of the prime mover. According to this, in the hydrostatic continuously variable transmission 50, even when the load fluctuates, the hydrostatic continuously variable transmission 50 can be operated more stably.
　The work vehicle 1 includes a plurality of planetary gear transmissions 57 that change the speed of the driving force changed by the continuously variable transmission 50 . It includes a first planetary gear transmission 57H and a second planetary gear transmission 57L that transmits driving force at a lower speed than the first planetary gear transmission. According to this, when high-speed driving force is transmitted to the traveling device 7, and when switching between high speed and low speed when transmitting low-speed driving force, control according to the load can be performed.
[0065]
　As shown in FIG. 2, the control device 120 includes an automatic transmission section 120B. Automatic transmission portion 120B starts a switching operation to switch clutch mechanism 52 from the disconnected state to the connected state before the driving force output from continuously variable transmission 50 reaches the automatic transmission condition. The automatic transmission portion 120B operates before the output shaft 58 (the output shaft 58 of the traveling motor M1) that transmits the driving force output from the continuously variable transmission 50 reaches the switching rotation speed that is the automatic transmission condition. Start switching operation.
[0066]
　The switching operation of the clutch mechanism 52 will be described in detail below.
　A plurality of electromagnetic control valves 130 that operate the clutch mechanism 52 (the first clutch device 52A and the second clutch device 52B) are connected to the control device 120 . The plurality of electromagnetic control valves 130 include a first electromagnetic control valve 130a that operates the first clutch device 52A, a second electromagnetic control valve 130b that operates the forward clutch portion 75 of the second clutch device 52B, and the second clutch device 52B. and a third electromagnetic control valve 130c that operates the reverse clutch portion 76 of.
[0067]
　Each of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c has a solenoid, and is a valve whose opening changes according to the current that energizes the solenoid. The opening of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c increases as the current exciting the solenoid increases, and decreases as the current exciting the solenoid decreases. Become. Demagnetize the solenoids of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b and the third electromagnetic control valve 130c. The control valve 130c is fully closed.
[0068]
　The first electromagnetic control valve 130a is connected to the oil passage 71e, the second electromagnetic control valve 130b is connected to the oil passage 75e, and the third electromagnetic control valve 130c is connected to the oil passage 76e. An oil passage 131 of a hydraulic pump P2 different from the hydraulic pump P1 is connected to the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c, and hydraulic oil can be supplied thereto. An oil passage 132 for discharging hydraulic oil is connected to the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c. Hydraulic oil is discharged from
[0069]
　When switching the clutch mechanism 52 (the first clutch device 52A and the second clutch device 52B), that is, when switching the planetary gear transmission mechanism 51 to the high speed side or the low speed side, the automatic transmission portion 120B switches the first clutch device 52A and the second clutch device 52A. When one of the two clutch devices 52B is connected, the other is disconnected.
　Specifically, when the planetary gear transmission mechanism 51 is set to the high speed side, a current (control signal) is output to the solenoid of the first electromagnetic control valve 130a to fully open the first electromagnetic control valve 130a. The first clutch device 52A is switched from the disconnected state to the connected state. In addition to this, when the planetary gear transmission mechanism 51 is set to the high speed side, the solenoids of the second electromagnetic control valve 130b and the third electromagnetic control valve 130c are deenergized, and the second electromagnetic control valve 130b and the third electromagnetic control valve By fully closing 130c, the second clutch device 52B is brought into a disengaged state (neutral state).
[0070]
　On the other hand, when the planetary gear transmission mechanism 51 is set to the low speed side, the solenoid of the first electromagnetic control valve 130a is deenergized and the first electromagnetic control valve 130a is fully closed, thereby disconnecting the first clutch device 52A. state. In addition to this, when the planetary gear transmission mechanism 51 is set to the low speed side, a current (control signal) is output to either the solenoid of the second electromagnetic control valve 130b or the third electromagnetic control valve 130c. For example, when the tractor 1 (vehicle body 3) is driven forward at low speed, the solenoid of the second electromagnetic control valve 130b is energized to bring the forward clutch portion 75 into the connected state. When the tractor 1 (vehicle body 3) is traveling at a low speed and in reverse, the solenoid of the third electromagnetic control valve 130c is energized and the reverse clutch 76 is connected.
[0071]
　Here, when switching the clutch mechanism 52 (the first clutch device 52A, the second clutch device 52B), the automatic transmission unit 120B is connected to the output shaft 58 of the traveling motor M1 and the output shaft (the first output shaft) of the planetary gear transmission mechanism 51. If the rotation difference (rotational deviation) between the shaft 61f and the second output shaft 62f) is large, the connection shock becomes large when the clutch mechanism 52 is switched from the disconnected state to the connected state. , the rotational speed of the output shaft 58 of the traveling motor M1 ( The switching rotation speed) is set, and the set switching rotation speed of the output shaft 58 is used as the automatic shift condition. The swash plate angle of the hydraulic pump P1 or the number of revolutions of the prime mover is changed so that the output shaft 58 of the traveling motor M1 reaches the switching revolution number J5. The number of revolutions of the output shafts (the first output shaft 61f and the second output shaft 62f) of the planetary gear transmission mechanism 51 may be detected by a sensor or the like, or may be calculated by a gear ratio or the like. not. The first threshold is a threshold for reducing shift shock when shifting.
[0072]
　On the other hand, the automatic transmission portion 120B starts switching operation to switch the clutch mechanism 52 from the disconnected state to the connected state before the output shaft 58 of the traveling motor M1 reaches the automatic shifting condition.
　5A and 5B show the state of speed change when the tractor 1 (vehicle body 3) is increased (accelerated). In FIG. 5, the vehicle speed L10 gradually increases, and the actual rotation speed J1 increases and decreases as the speed increases. 5A and 5B, before acceleration, the first clutch device 52A is in the disengaged state (zero pressure) as indicated by L20, and the forward clutch portion 75 of the second clutch device 52B is in the engaged state as indicated by L21. The description is based on the premise that
[0073]
　As shown in FIG. 5A, when speeding up the tractor 1 (body 3), the control device 120 increases the swash plate angle and the number of revolutions of the prime mover, thereby increasing the number of revolutions of the output shaft 58 of the traveling motor M1. On the other hand, the actual rotation speed J1 of the output shaft 58 of the traveling motor M1 is increased toward the switching rotation speed J5.
　Automatic transmission portion 120B starts the switching operation at time point P21 earlier than time point P20 at which actual rotation speed J1 coincides with switching rotation speed J5. In the switching operation, the automatic transmission portion 120B excites the solenoid of the first electromagnetic control valve 130a to maximize the degree of opening of the first electromagnetic control valve 130a (fully open). Then, when the first electromagnetic control valve 130a is fully opened, the housing 71a begins to be gradually filled with the hydraulic oil in the period T1, and the supply chamber (the pressing member 71d is accommodated in the housing 71a) to which the hydraulic oil is supplied. When the pressure in the space) exceeds time point P20, the pressure member 71d such as a piston gradually pushes the friction plate 71c. , the first clutch device 52A is switched to the connected state.
[0074]
　When the first clutch device 52A is in the connected state at time point P22, the forward clutch portion 75 of the second clutch device 52B is switched from the connected state to the disconnected state.
　Note that the automatic transmission unit 120B may have a prediction unit 120B1. The prediction unit 120B1 predicts the time (reaching time) from the actual rotation speed J1 to the switching rotation speed J5. When the tractor 1 (vehicle body 3) detects an operation to increase speed, or when the controller 120 acquires a signal or operation to increase speed, the prediction unit 120B1 sets the switching rotation speed J5. By referring to the actual number of revolutions, the amount of increase (inclination) of the actual number of rotations J1 per predetermined time is obtained, and the arrival time is predicted from the inclination of the actual number of rotations J1. For example, when the arrival time is predicted to be 0.3 seconds, the automatic transmission portion 120B advances the switching operation so that the pressure of the hydraulic fluid in the supply chamber within the housing 71a becomes equal to or higher than the predetermined value after 0.3 seconds. That is, when the actual number of revolutions J1 of the traveling motor M1 reaches the switching number of revolutions J5, at least the friction plate 71c and the plate provided on the housing 71 start to come into contact with each other. Start switching operation.
[0075]
　In the above-described embodiment, the case where the tractor 1 (vehicle body 3) is accelerated has been described, but the present invention can also be applied when decelerating. As for the operation in the case of deceleration, the above-mentioned acceleration can be read as deceleration.
　FIG. 6 is a diagram showing the flow of the switching operation.
　As shown in FIG. 6, when the automatic transmission unit 120B acquires a switching command for the planetary gear transmission mechanism 51, that is, a command to speed up or decelerate (S10), it sets the switching rotation speed J5 (S11 ). The setting of the switching rotation speed J5 is obtained, for example, by measuring or calculating the rotation speed of the output shafts (the first output shaft 61f and the second output shaft 62f) of the planetary gear transmission mechanism 51, and the rotation speed of the output shaft is determined by the traveling motor. A switching rotation speed J5 is set to a rotation speed that does not deviate from the actual rotation speed J1 of M1 by a predetermined amount or more. Note that the method for setting the switching rotation speed J5 is an example, and is not limited.
[0076]
　When the switching rotation speed J5 is set, the prediction unit 120B1 predicts the arrival time (S12). For example, the automatic transmission unit 120B starts the switching operation earlier than the arrival time P20 at which the actual rotation speed J1 of the traveling motor M1 reaches the switching rotation speed J5 (S13).
　The work vehicle 1 includes a prime mover 4 , a traveling device 7 , a continuously variable transmission 50 , a planetary gear transmission mechanism 51 , and a traveling transmission shaft for transmitting the driving force changed by the planetary gear transmission mechanism 51 to the traveling device 7 . A clutch mechanism 52 that can be switched between a connected state in which it is connected to the drive transmission shaft 66 and a disconnected state in which it is not connected to the travel transmission shaft 66, and a clutch mechanism 52 that can be switched before the driving force output from the continuously variable transmission 50 reaches an automatic shift condition. and an automatic transmission unit 120B that starts a switching operation for switching from the disconnected state to the connected state. According to this, in a work vehicle provided with a continuously variable transmission for steplessly changing the driving force and a planetary gear transmission mechanism for changing the speed of the driving force changed by the continuously variable transmission, at the time of gear changing, etc., the Power of the transmission can be transmitted smoothly.
[0077]
　The continuously variable transmission 50 includes a hydraulic pump P1 and a traveling motor M1, and the automatic transmission portion 120B is configured such that the rotational speed of the output shaft that transmits the driving force output from the continuously variable transmission 50 is set under the automatic transmission condition. The switching operation of the clutch mechanism 52 is started before reaching a certain switching rotation speed J5. According to this, for example, as shown in FIG. 5A, the switching operation can be started at time P21 before reaching the switching rotation speed J5, so that the rotation speed of the traveling motor M1 reaches the switching rotation speed J5. In this case, the filling of the hydraulic oil into the clutch mechanism 52 can be completed earlier, and the power of the continuously variable transmission can be smoothly transmitted. On the other hand, as shown in FIG. 5B, when the switching operation of the clutch mechanism 52 is started when the switching rotation speed J5 is reached, the clutch mechanism 52 is Since the filling of the hydraulic oil has just started, the time during which the clutch mechanism 52 cannot be connected increases even though the rotation speed of the travel motor M1 has reached the switching rotation speed J5.
[0078]
　The automatic shift section 120B has a prediction section 120B1 that predicts the time required to reach the switching rotation speed J5 from the rotation speed detected by the rotation detection device 123, and performs the switching operation based on at least the time predicted by the prediction section 120B1. . According to this, by predicting the time until the switching rotation speed J5 is reached by the prediction unit 120B1, the switching operation can be advanced more accurately and quickly.
[0079]
　The planetary gear transmission mechanism 51 includes a first planetary gear transmission 57H that transmits high-speed driving force and a second planetary gear transmission 57L that transmits low-speed driving force than the first planetary gear transmission 57H. The clutch mechanism 52 includes a first clutch device 52A capable of transmitting the driving force of the first planetary gear transmission 57H to the travel transmission shaft 66, and a first clutch device 52A capable of transmitting the driving force of the second planetary gear transmission 57L to the travel transmission shaft 66. When one of the first clutch device 52A and the second clutch device 52B is connected, the automatic transmission portion 120B disconnects the other. According to this, when one of the first clutch device 52A and the second clutch device 52B is engaged, the other is disengaged. can be prevented from being transmitted at the same time, and power can be smoothly transmitted to the traveling device 7 during acceleration or deceleration.
[0080]
　The work vehicle 1 includes a hydraulic pump P1, an electromagnetic control valve 130, and oil passages 71e, 75e, and 76e connecting the electromagnetic control valve 130 and the clutch mechanism 52, and the automatic transmission portion 120B starts switching operation. A control signal for opening the electromagnetic control valve 130 is output when the control valve 130 is to be opened. According to this, by opening the electromagnetic control valve 130 , hydraulic oil can be quickly supplied (filled) to the clutch mechanism 52 .
[0081]
　As shown in FIG. 2, the control device 120 includes a braking control section 120C. When the tractor 1 (vehicle body 3) is not braked, the braking control unit 120C controls the continuously variable transmission device 50 based on the actual rotation speed J1 detected by the rotation detection device 123, and controls the tractor 1 (vehicle body 3). is performed, the continuously variable transmission 50 is controlled based on the actual swash plate angle (actual swash plate angle) θ2 detected by the angle detection device 122 .
[0082]
　When the tractor 1 (vehicle body 3) is not braked, the braking control unit 120C performs rotation speed feedback control so that the deviation (rotation speed deviation) ΔJ between the actual rotation speed J1 and the target rotation speed J2 becomes small. , when braking is performed, swash plate feedback control is performed so as to reduce the angle deviation Δθ between the actual swash plate angle θ2 and the target swash plate angle θ1.
　The operation of the continuously variable transmission 50 during braking will be described below.
[0083]
　As shown in FIG. 1, the tractor 1 has a braking device 140 . The braking device 140 is a device that brakes the travel device 7 . The braking device 140 has a braking operation member 141, a left braking device 142F, and a right braking device 142R. The braking operation member 141 is a member that performs a braking operation and can be manually operated by the driver. The braking operation member 141 includes a left brake pedal 141F and a right brake pedal 141R. The left brake pedal 141F and the right brake pedal 141R are swingably supported by the vehicle body 3 or the like, are provided near the driver's seat 10, and can be operated by the driver. The left braking device 142F and the right braking device 142R are disk-type braking devices, and can be switched between a braking state for braking and a release state for releasing the braking. The left braking device 142F is provided on the left side of the rear axle 99 , and the right braking device 142R is provided on the right side of the rear axle 99 .
[0084]
　When the driver operates (depresses) the left brake pedal 141F, the left connecting member 143F connected to the left brake pedal 141F moves in the braking direction, and the left braking device 142F can be brought into the braking state. When the driver operates (depresses) the right brake pedal 141R, the right connecting member 143R connected to the right brake pedal 141R moves in the braking direction, and the right braking device 142R can be brought into the braking state. A connecting member that connects the left brake pedal 141F and the right brake pedal 141R can be freely engaged and disengaged (the left brake pedal 141F and the right brake pedal 141R can be engaged with each other by engaging the left brake pedal 141F and the right brake pedal 141R). and a non-connected state in which the left brake pedal 141F and the right brake pedal 141R are not engaged with each other. In this case, by depressing either the left brake pedal 141F or the right brake pedal 141R, the left brake device 142F and the right brake device 142R can be braked simultaneously, and the left brake pedal 141F and the right brake pedal can be braked simultaneously. By releasing the depression of any one of the brake pedals 141R, the braking of the left braking device 142F and the right braking device 142R can be released simultaneously.
[0085]
　As shown in FIG. 2, the control device 120 is connected to an operation amount detection device 145 that detects the amount of operation of the brake operation member 141, that is, the amount of depression of the brake operation member 141. As shown in FIG. The operation amount detection device 145 is a sensor that detects an operation amount (stepping amount) G1 when the connecting member is in the connected state.
　The braking control unit 120C sets the target swash plate angle θ1 during braking according to the operation amount (the amount of depression) G1 detected by the operation amount detection device 145. FIG. For example, the braking control unit 120C changes the target swash plate angle θ1 to reduce the rotational speed of the traveling motor M1 as the depression amount G1 increases, and changes the target swash plate angle θ1 as the depression amount G1 decreases. The rotation speed of the traveling motor M1 is changed to increase. That is, the braking control unit 120C is set in advance according to the depression amount G1 when the braking operation member 141 is operated and braking is performed with respect to the preset target swash plate angle θ1. A correction is made to decrease the target swash plate angle θ1. Note that the braking control unit 120C corrects, that is, does not change, the target swash plate angle θ1 when the braking operation member 141 is not operated.
[0086]
　For example, when the braking device 140 is applied while the tractor 1 (vehicle body 3) is moving forward, the braking control unit 120C disengages the clutch mechanism 52 .
　FIG. 7A shows the switching state of the clutch mechanism 52 under the control of the braking control section 120C.
　As shown at time P30 in FIG. 7A, when the tractor 1 (vehicle body 3) is moving forward, the driving force of the planetary gear transmission mechanism 51 is on the high speed side (the first clutch device 52A is in the engaged state), In addition, when the braking device 140 is braked, the braking control unit 120C switches the first clutch device 52A from the connected state to the disconnected state, and maintains the second clutch device 52B in the disconnected state. That is, when braking is performed while the tractor 1 (vehicle body 3) is moving forward and at high speed, the driving force of the planetary gear transmission mechanism 51 on the high speed side is not transmitted to the travel transmission shaft 66, while the second By disengaging the clutch device 52B (the forward clutch portion 75 and the reverse clutch portion 76), the driving force of the planetary gear transmission mechanism 51 on the low speed side is maintained at the neutral side, and power transmission by the planetary gear transmission mechanism 51 is prevented. cut.
[0087]
　7A, when the first clutch device 52A and the second clutch device 52B are in the disengaged state, the braking control unit 120C controls the rotation speed (actual rotation speed) J1 of the traveling motor M1 and the second The actual rotation speed J1 of the traveling motor M1 (first output shaft 58 rotation speed). As shown at time P31 in FIG. 7A, the braking control unit 120C changes the actual rotation speed J1 of the traveling motor M1 while the brake is being applied, thereby reducing the rotation speed deviation ΔJ to a threshold value (first threshold value) or less. If so, the forward clutch portion 75 of the second clutch device 52B is switched from the disconnected state to the connected state.
[0088]
　On the other hand, as shown at time P30 in FIG. 7B, when the first clutch device 52A and the second clutch device 52B are in the disengaged state and the braking of the braking device 140 is released at time P32 (the depression amount G1 is substantially zero). ), the braking control unit 120C stops the shock reduction control when executing the control (shock reduction control) to make the rotation speed deviation ΔJ equal to or less than the threshold (first threshold), and the first The clutch device 52A is switched from the disconnected state to the connected state. If the shock reduction control is not executed before time P32 in FIG. 7, the braking control section 120C switches the first clutch device 52A from the disconnected state to the connected state.
[0089]
　Further, as shown at time P33 in FIG. 7C, when the first clutch device 52A and the second clutch device 52B are in the disengaged state, the braking control unit 120C increases the speed by depressing the accelerator 127 or the like of the tractor 1 (the vehicle body 3). When doing so, the second clutch device 52B is switched from the disconnected state to the connected state.
　Now, in the embodiment described above, the clutch mechanism 52 is controlled by the braking of the braking device 140, but the clutch mechanism 52 may be controlled according to the vehicle speed of the tractor 1 (body 3). A vehicle speed detection device 146 is connected to the control device 120 . The vehicle speed detection device 146 is a sensor that detects the travel speed (vehicle speed) of the tractor 1 (body 3). For example, the vehicle speed detection device 146 may be a sensor that converts the rotation of the front axle 105 and the rear axle 99 into vehicle speed, or a sensor that converts the rotation of the front wheels 7F and the rear wheels 7R into vehicle speed. not.
[0090]
　The braking control unit 120C switches the clutch mechanism 52 from the disconnected state to the connected state when the vehicle speed V1 detected by the vehicle speed detection device 146 is equal to or less than a threshold value. For example, as shown at time P34 in FIG. 7D, the braking control unit 120C switches the second clutch device 52B from the disconnected state to the connected state when the vehicle speed V1 is equal to or lower than the threshold (vehicle speed threshold). Note that the vehicle speed threshold may be set by a setting member 150 provided near the driver's seat 10 . For example, when the vehicle speed threshold is set to zero by the setting member 150, the braking control unit 120C switches the second clutch device 52B from the disconnected state to the connected state when the vehicle speed V1 becomes zero.
[0091]
　The work vehicle 1 includes a vehicle body 3, a hydrostatic continuously variable transmission 50, a planetary gear transmission mechanism 51, a clutch mechanism 52, a braking device 140, and a clutch mechanism when the braking device 140 is applied. 52 and a control device 120 that puts 52 into a disconnected state. According to this, in a work vehicle equipped with a hydrostatic continuously variable transmission, it is possible to improve the traveling performance of the tractor during braking and releasing the braking. For example, when the braking device 140 is applied, the output of the hydrostatic continuously variable transmission 50 can be reduced according to the braking, and the work vehicle 1 can be stopped smoothly.
[0092]
　The work vehicle 1 includes a vehicle body 3, a hydrostatic continuously variable transmission 50 having a hydraulic pump P1 and a traveling motor M1, a rotation detecting device 123, an angle detecting device 122, and a braking device for braking the traveling device. 140, and when braking by the braking device 140 is not performed, the continuously variable transmission 50 is controlled based on the rotation speed detected by the rotation detection device 123, and when braking by the braking device 140 is performed, the angle detection device and a control device 120 for controlling the continuously variable transmission 50 based on the actual swash plate angle θ2 detected by 122 . According to this, during normal running without braking, the vehicle speed (running speed) of the work vehicle 1 can be stabilized. can be used to adjust the rotation speed of the traveling motor M1, and appropriate braking can be performed according to various situations.
[0093]
　When braking is not performed, the control device 120 performs rotation speed feedback control so that the deviation between the actual rotation speed J1, which is the rotation speed detected by the rotation detection device 123, and the target rotation speed J2 becomes small. When it is performed, swash plate feedback control is performed so as to reduce the deviation between the actual swash plate angle θ2 detected by the angle detection device 122 and the target swash plate angle θ1. According to this, when braking is not performed, the vehicle speed can be set to the target vehicle speed by the rotation speed feedback control, and the swash plate angle is stabilized by the swash plate feedback control during braking, and the traveling motor M1 side is driven. The number of revolutions can be made constant at a set value.
[0094]
　The work vehicle 1 includes a braking operation member 141 that applies braking to the braking device 140 , and the control device 120 sets the target swash plate angle θ1 according to the amount of operation of the braking operation member 141 . According to this, when the operation amount of the braking operation member 141 is large, the target swash plate angle θ1 is decreased according to the operation amount, and when the operation amount is small, the target swash plate angle θ1 is set to the operation amount. The working vehicle 1 can be stably driven by the strength of the braking.
[0095]
　The work vehicle 1 includes a planetary gear transmission mechanism 51 and a clutch mechanism 52, and the control device 120 disengages the clutch mechanism 52 when the braking device 140 is applied. According to this, transmission of power (transmission of driving force) to the travel device 7 can be cut off during braking.
　The control device 120 disengages the clutch mechanism 52 when the driving force of the planetary gear transmission mechanism 51 is on the high speed side. According to this, when the driving force on the high speed side is being transmitted during braking, the transmission of the driving force on the high speed side to the travel device 7 can be cut off.
[0096]
　The planetary gear transmission mechanism 51 has a first planetary gear transmission 57H and a second planetary gear transmission 57L, and the clutch mechanism 52 includes a first clutch device 52A and a second clutch device 52B, When the second clutch device 52B is in the disengaged state, the control device 120 reduces the rotational speed of the traveling motor M1 so that the rotational deviation between the rotational speed of the traveling motor M1 and the rotational speed of the second planetary gear transmission 57L becomes small. change. According to this, it is possible to reduce the switching shock when switching to the low speed side during braking.
[0097]
　The control device 120 switches the second clutch device 52B to the connected state when the rotation speed deviation is equal to or less than the threshold value. According to this, it is possible to further reduce the switching shock when switching to the low speed side.
　The control device 120 switches the first clutch device 52A from the disconnected state to the connected state when the braking of the braking device 140 is released. According to this, the work vehicle 1 can be quickly switched from deceleration due to braking to acceleration while the switching shock is applied.
[0098]
　The control device 120 switches the second clutch device 52B from the disengaged state to the connected state when the speed of the vehicle body 3 increases while the braking device 140 is braking. According to this, the work vehicle 1 can be quickly switched from deceleration due to braking to acceleration.
　The control device 120 includes a vehicle speed detection device 146 that detects the vehicle speed of the vehicle body 3, and switches the clutch mechanism 52 from the disconnected state to the connected state when the vehicle speed detected by the vehicle speed detection device 146 is equal to or less than a threshold. According to this, the clutch mechanism 52 is changed from the disengaged state to the connected state when the vehicle speed of the work vehicle 1 is sufficiently low, so that the work vehicle 1 can be stably stopped.
[0099]
　The control device 120 switches the second clutch device 52B from the disconnected state to the connected state when the vehicle speed is equal to or less than the threshold value. According to this, by switching the second clutch device 52B on the low speed side, the work vehicle 1 can be quickly stopped, and after the braking is released, the driving force can be transmitted from the low speed side to the traveling device 7. can be done.
　The hydrostatic continuously variable transmission 50 has a hydraulic pump P1 and a traveling motor M1, and the control device 120 controls the number of revolutions of the traveling motor M1 when braking by the braking device 140 is not performed. , and when braking by the braking device 140 is performed, the continuously variable transmission 50 is controlled based on the swash plate angle of the hydraulic pump P1. According to this, in a work vehicle equipped with a hydrostatic continuously variable transmission, it is possible to improve the traveling performance of the tractor during braking and releasing the braking. For example, when braking is performed by the braking device 140, the output of the hydrostatic continuously variable transmission 50 can be reduced according to the braking, and the tractor 1 can be stopped smoothly. Further, when the braking device 140 does not perform braking, the work vehicle 1 can travel.
[0100]
　In the above-described embodiment, the control device 120 capable of controlling the transmission 5 includes the swash plate control section 120A, the automatic transmission section 120B, and the braking control section 120C. It is not necessary to include all of the transmission unit 120B and the braking control unit 120C, and the transmission 5 may be controlled by combining them as appropriate.
　It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.
Code explanation
[0101]
1: Working vehicle (tractor)
3: Vehicle body
4: Prime mover
5: Transmission device
7: Travel device
33: Hydraulic pump
50: Continuously variable transmission device
56b: Swash plate
57: Planetary gear transmission device
57H: First planetary gear transmission device
57L : second planetary gear transmission
58 : output shaft
61f : output shaft
62f : output shaft
120A : swash plate control section
122 : angle detection device
123 : rotation detection device
J1 : actual rotation speed
J2 : target rotation speed
M1 : traveling motor
P1 : Hydraulic pump
P2 : Hydraulic pump
ΔJ : Rotation speed deviation
Δθ : Angle deviation
θ1 : Set angle (target swash plate angle)
θ2 : Actual swash plate angle
The scope of the claims
[Claim 1]
　A vehicle body provided with a traveling device
　, a hydraulic pump having a swash plate whose output changes according to the swash plate angle, and
　an output shaft whose rotational speed changes according to the output of the hydraulic pump, and the power of the output shaft is a travel motor that can be transmitted to the travel device;
　an angle detection device that detects a swash plate angle that is the angle of the swash plate
　; control information related to control of the swash plate angle; and a swash plate control unit that controls the swash plate angle based on an actual swash plate angle of
　.
[Claim 2]
　A rotation detection device for detecting the rotation speed of the output shaft of the traveling motor is provided, and the
　swash plate control unit uses the rotation speed detected by the rotation detection device as the control information, and the rotation speed and the actual swash plate angle. The work vehicle according to claim 1, wherein the swash plate angle is controlled based on:
[Claim 3]
　The swash plate control unit performs control to reduce the angle deviation when an angle deviation between the set angle of the swash plate determined according to the rotation speed and the actual swash plate angle is equal to or greater than a threshold value. 3. The work vehicle according to claim 2, wherein said set angle is maintained when said angle deviation is less than a threshold.
[Claim 4]
　4. The swash plate control unit sets, as the set angle, an angle at which the rotation speed deviation between the target rotation speed of the traveling motor and the actual rotation speed detected by the rotation detection device becomes small. Work vehicle as described.
[Claim 5]

　The swash plate control unit is configured to refer to the rotational speed deviation when the transmission changes the gear stage 　. 5. The work vehicle according to claim 4, wherein the speed of change of the swash plate angle is controlled to be small when the rotational speed deviation is equal to or greater than a threshold value.
[Claim 6]
　The work vehicle according to any one of claims 1 to 4, wherein the hydraulic pump and the travel motor are hydrostatic continuously variable transmissions that steplessly change the driving force of the prime mover.
[Claim 7]
　and a plurality of planetary gear transmissions for shifting the driving force shifted by the continuously variable transmission
　,
　wherein the plurality of planetary gear transmissions are first planetary gear transmissions for transmitting high-speed driving force to the traveling device. A work vehicle according to any one of claims 1 to 6, including a device and a second planetary gear transmission transmitting drive power at a lower speed than said first planetary gear transmission.
[Claim 8]
　A vehicle body provided with a travel device
　, a hydraulic pump having a swash plate whose output changes according to the swash plate angle, and an output shaft whose rotational speed changes according to the output of the hydraulic pump. a traveling motor that can be transmitted to a device;
　a rotation detecting device that detects the number of rotations of the output shaft of the traveling motor; and
　a swash plate angle that is the angle of the swash plate. a
　braking device for braking the traveling device; and when the
　braking device is not braking, the continuously variable transmission is controlled based on the rotation speed detected by the rotation detection device. and a control device for controlling the continuously variable transmission based on the actual swash plate angle, which is the
　swash plate angle detected by the angle detection device when the braking device is applied. .
[Claim 9]
　When the braking is not performed, the control device performs rotation speed feedback control so as to reduce the deviation between the actual rotation speed detected by the rotation detection device and the target rotation speed. 9. The work vehicle according to claim 8, wherein, when performed, the swash plate feedback control is performed so that the deviation between the actual swash plate angle, which is the swash plate angle detected by the angle detection device, and the target swash plate angle becomes small. .
[Claim 10]
　10.
　The work vehicle according to claim 9, further comprising a braking operation member that applies braking to the braking device, wherein the control device sets the target swash plate angle according to an amount of operation of the braking operation member.
[Claim 11]
　A planetary gear transmission mechanism capable of shifting the driving force shifted by the continuously variable transmission between high speed side and low speed side, and
　a traveling transmission shaft transmitting the driving force changed by the planetary gear transmission to the traveling device. a clutch mechanism that can be switched between a connected state in which it is connected and a disconnected state in which it is not connected to the travel transmission shaft
　,
　wherein the control device switches the clutch mechanism to the disconnected state when the braking device is braked. The work vehicle according to any one of claims 8 to 10.
[Claim 12]
　12. The work vehicle according to claim 11, wherein the control device places the clutch mechanism in the disengaged state when the driving force of the planetary gear transmission mechanism is on the high speed side.
[Claim 13]
　The planetary gear transmission mechanism includes a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to a high speed side, and a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to the high speed side. and a second planetary gear transmission that shifts to a lower speed side than the clutch mechanism, and the
　clutch mechanism has a connection state in which the driving force of the first planetary gear transmission is connected to the travel transmission shaft, and a connection state in which the driving force of the first planetary gear transmission is connected to the travel transmission shaft. a first clutch device that can be switched between a disengaged state in which
　the driving force of the second planetary gear transmission is connected to the travel transmission shaft, and a disengaged state in which the drive force of the travel transmission shaft is not connected; and a second clutch device , wherein when the second clutch device is in the disengaged state
　,
　the control device has a rotational deviation between the number of revolutions of the travel motor and the number of revolutions of the second planetary gear transmission. 13. The work vehicle according to claim 11 or 12, wherein the rotation speed of the travel motor is changed so as to decrease.
[Claim 14]
　The work vehicle according to claim 5, wherein the control device switches the second clutch device to the connected state when the rotational speed deviation is equal to or less than a threshold value.
[Claim 15]
The work vehicle according to claim 12 or 13, wherein the control device switches the first clutch device from the disconnected state to the connected state when the braking of the braking device is released.
[Claim 16]
　15. The control device according to any one of claims 12 to 14, wherein the control device switches the second clutch device from the disconnected state to the connected state when the speed of the vehicle body increases while the braking device is being applied. work vehicle.