ELECTRONIC CIRCUIT DEVICE AND VEHICLE USING THE ELECTRONIC CIRCUIT DEVICE
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic circuit device, and more particularly, to an electronic circuit device to be used for a control device for an internal combustion engine, and a vehicle using the electronic circuit device.
2. Description of the Related Art
Hitherto, an electronic control device for an internal combustion engine, which is called as an engine control unit (ECU) , is mounted on a vehicle. This ECU is mainly formed by a microcomputer, a power supply, a power device, an input processing circuit, an output processing circuit, and the like, and is configured to control operations relating to driving of the vehicle . Various parameters relate to such control. As one of the parameters relating to the control, external temperature information is important.
The outside air temperature is usually most accurately measured by arranging a dedicated temperature sensor at a location that faces a place outside that can be in contact with the outside air. Meanwhile, there are known technologies of indirectly estimating the outside air temperature without providing the dedicated temperature sensor in consideration of securing an arrangement place, a decrease in the cost, and the like. For example, there is known a control device for an internal combustion engine, in which a temperature sensor is arranged in an intake pipe inside a system for the internal combustion engine that is in contact with sucked intake air and the temperature sensor is used as an intake air temperature sensor without providing a dedicated temperature

sensor at a location that faces a place outside that can be in contact with the outside air, thereby estimating the outside air temperature (e.g., see Japanese Patent Application Laid-open No. 2008-45455) .
Moreover, there is known a method using three or more temperature sensors to estimate a temperature distribution on a plane, which is not limited to the internal combustion engine (e.g., see Japanese Patent Application Laid-open No. 62-170826).
The control device for an internal combustion engine disclosed in Japanese Patent Application Laid-open No. 2008-45455 uses an intake air amount sensor in addition to the intake air temperature sensor for the estimation of the outside air temperature. In other words, the control device for an internal combustion engine disclosed in Japanese Patent Application Laid-open No. 2008-45455 estimates the outside air temperature from a relationship between the intake air temperature detected by the intake air temperature sensor and the intake air amount detected by the intake air amount sensor, and reguires signals at two different timings from the intake air temperature sensor and the intake air amount sensor.
In this case, from the viewpoints of estimating precision and sensing precision, for example, there are such problems that an interval needs to be secured until a timing at which the difference between the two signal values is sufficiently large, and sensors having high precision are reguired. Thus, there is room for improvement in terms of the period reguired until the outside air temperature is estimated and the cost of the sensors.
An intra-plane temperature estimation method for estimating a temperature distribution disclosed in Japanese Patent Application Laid-open No. 62-170826 has room for considering at which locations of the vehicle the temperature sensors need to be arranged in order to realize efficient estimation of the outside air temperature of the vehicle. Moreover, the temperature estimation method disclosed in Japanese Patent Application Laid-open No. 62-170826

requires three or more temperature sensors for the temperature estimation, and there is room for improvement in terms of the cost.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned problems, and has an object to provide an electronic circuit device capable of precisely estimating an outside air temperature in a short amount of time at a low cost without arranging a dedicated temperature sensor for the outside air temperature detection at a location that faces a place outside that can be in contact with the outside air, and a vehicle using the electronic circuit device.
In order to solve the above problem, an electronic circuit device according to the present invention comprises : a power supply mounted on a circuit board and configured to supply power; a first temperature sensor mounted on the circuit board and configured to use the power supplied from the power supply so as to detect a first temperature; a second temperature sensor mounted on the circuit board, and is configured to use the power supplied from the power supply so as to detect a second temperature; and a calculator configured to calculate an estimation temperature at a position in an external region of the circuit board based on the first temperature and the second temperature, the position being on a straight line on which the first temperature sensor and second temperature sensor are connected.
Also, a vehicle according to the present invention comprises : an internal combustion engine arranged in a vehicle housing; the electronic circuit device according to claim 1; an intake passage configured to supply outside air from an outside air intake portion to the internal combustion engine; and a signal generator configured to generate a control signal for the internal combustion engine, wherein the estimation temperature calculated by the calculator

is provided to the signal generator, and the signal generator generates the control signal based on the estimation temperature. According to the present invention, the calculator is configured to calculate the circuit board external estimated temperature in the external region of the circuit board on the straight line connected between the first temperature sensor mounted on the circuit board and is configured to use the power supplied from the power supply so as to detect the first temperature, and the second temperature sensor mounted on the circuit board and is configured to use the power supplied from the power supply so as to detect the second temperature, based on the first temperature and the second temperature. Thus, the circuit board external temperature can be precisely estimated in a short amount of time at a low cost without arranging a dedicated temperature sensor for the outside air temperature detection at a location that faces a place outside that can be in contact with the outside air.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram for illustrating an entire control system for an internal combustion engine to which an electronic circuit device according to the present invention is applied;
FIG. 2 is a schematic diagram for illustrating an example of an arrangement of an ECU main body incorporating the electronic circuit device according to the present invention, and of the control system for the internal combustion engine;
FIG. 3 is a plan block diagram for illustrating an arrangement example of electronic circuit elements inside the ECU main body incorporating the electronic circuit device according to the present invention;
FIG. 4 is a graph for showing a temperature distribution around the ECU main body illustrated in FIG. 3;

FIG. 5 is a flowchart for illustrating a control algorithm when an electronic circuit device according to a second embodiment of the present invention is applied to an internal combustion engine;
FIG. 6 is a flowchart for illustrating a control algorithm when an electronic circuit device according to a third embodiment of the present invention is applied to the internal combustion engine;
FIG. 7 is a schematic diagram for illustrating a vehicle according to a fourth embodiment of the present invention; and
FIG. 8 is a schematic diagram for illustrating a vehicle according to a fifth embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS Referring to the accompanying drawings, a detailed description of an electronic circuit device and a vehicle according to various embodiments of the present invention will now be made. The embodiments described below are merely examples, and the present invention is not limited to those embodiments.

First Embodiment
FIG. 1 is a diagram for illustrating an overall configuration of a well-known control system for an internal combustion engine to which an electronic circuit device according to the present invention is applied. An internal combustion engine 100 is a four-cycle gasoline engine operated with one combustion cycle formed of four strokes, that are the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke . An air filter 102, a throttle valve 103, and an intake pressure sensor 104 for detecting an intake pressure of the air in an intake passage 101 of the internal combustion engine 100 are provided in the stated

order from an upstream side in the intake passage 101. A bypass passage 106 for allowing an upstream side and a downstream side of the throttle valve 103 to communicate with each other and an idle speed control valve 107 are provided in the intake passage 101.
An injector 110 which injects and supplies fuel drawn by a fuel pump 108 from a fuel tank 109 to the vicinity of an intake port is provided on a downstream side of the intake pressure sensor 104 in the intake passage 101.
The internal combustion engine 100 includes a combustion chamber 105. An intake valve 111 for air intake is provided in the combustion chamber 105. An ignition plug 112 having a protruded electrode is provided at an upper portion of the combustion chamber 105. A piston 113 which reciprocates upward/downward is provided in a lower portion of the combustion chamber 105. This piston 113 is connected to a crankshaft 115 via a connecting rod 114. An exhaust valve 116 is further provided in the combustion chamber 105. The combustion chamber 105 is connected to an exhaust passage 117 via the exhaust valve 116.
A crank angle sensor 118 which detects a rotation angle of the crankshaft 115 is provided in the vicinity of the crankshaft 115 of the combustion chamber 105. A three-way catalyst 119 is provided on a downstream side of the exhaust passage 117 . Moreover, an 02 sensor 120 is provided upstream of the three-way catalyst 119 . The throttle valve 103 adjusts an opening degree of a throttle. For air from which dust has been removed by the air filter 102, the throttle valve 103 controls an air flow amount supplied to the combustion chamber 105 of the internal combustion engine 100 via the intake passage 101 through the adjustment of the opening degree of the throttle. From a viewpoint from a driver side, the throttle valve 103 controls the adjustment of the throttle opening degree in accordance with an operation amount of an accelerator (not shown)

operated by the driver.
The idle speed control valve 107 provided in the bypass flow passage 106 adjusts an air flow amount flowing through the bypass flow passage 106 so as to control the number of revolutions of the internal combustion engine during an idling operation of the internal combustion engine 100.
The injector 110 injects the fuel into the air that has passed through the intake passage 101 ahead of the intake valve 111, thereby forming a mixture . The intake valve 111 supplies the formed mixture to the combustion chamber 105. The ignition plug 112 provided in the combustion chamber 105 ignites the mixture supplied to the combustion chamber 105 by a discharge spark, thereby combusting the mixture. The combustion of the mixture enables work directed to the outside to be carried out.
Specifically, the crankshaft 115 is rotated via the piston 113 and the connecting rod 114, and rotation energy is extracted from the combustion of the mixture. The exhaust valve 116 exhausts exhaust gas generated by the combustion of the mixture to the exhaust passage 117 by the opening operation. A plurality of protrusions are provided at a predetermined interval on an outer periphery of a rotor which integrally rotates with the crankshaft 115, and the crank angle sensor 118 outputs a crank signal having a rectangular shape when the protrusion passes by the crank angle sensor 118. The internal combustion engine 100 uses the above-mentioned configuration to control the timings of the fuel injection and the mixture ignition.
The three-way catalyst 119 provided in the exhaust passage 117 purifies NOx, HC, and CO contained in the combusted exhaust gas . The 02 sensor 120 on an upstream side of the three-way catalyst 119 changes an output value in accordance with an oxygen concentration in the exhaust gas, determines whether an air-fuel ratio is less or more than a theoretical air-fuel ratio, that is,

determines whether the current state is rich or lean for the combustion of the mixture, and reflects the determination in a combustion control condition.
FIG. 2 is a schematic diagram for illustrating an example of an ECU main body 121 including an electronic circuit device according to the embodiment of the present invention, which is arranged in the control system for the internal combustion engine 100 illustrated in FIG. 1. In this example, the ECU main body 121 is arranged in an outside air intake or inlet 133 of the internal combustion engine 100 . A part of the components illustrated in FIG. 1 are not illustrated in FIG. 2.
FIG. 3 is a plan block diagram for illustrating an arrangement example of electronic circuit elements inside the ECU main body 121 including the electronic circuit device according to the first embodiment of the present invention. The ECU main body 121 includes a power supply 122, a microcomputer 123, an output processing circuit 124, input processing circuits 125, an A/D conversion circuit 126, a power device 127, a communication IC 128, and the like, which are arranged on an ECU board 131. The ECU main body 121 is an example of a body on which the electronic circuit device according to the present invention is mounted, and the ECU board 131 is an example of a circuit board.
The ECU main body 121 receives input signals from the intake pressure sensor 104, the crank angle sensor 118, the 02 sensor 120, a vehicle speed sensor (not shown), and the like, and inputs the signals into the input processing circuits 125. Then, the input signal is converted from an analog signal to a digital signal by the A/D conversion circuit 126, and is input to the microcomputer 123. The microcomputer 123 carries out the combustion control for the internal combustion engine 100, for example, the fuel injection control using the injector 110 or the ignition control processing using the ignition plug 112, based on a control logic built in

advance.
In other words, a fuel injection interval (injection amount) of the injector 110 is controlled, or the timing of generating the spark on the electrode of the ignition plug 112 is controlled by transmitting a control value from the microcomputer 123 to the power device 127. For the ignition plug, such a control that a high voltage is induced on an ignition coil provided separately to thereby generate the spark based on the control from the power device 127 is to be carried out.
The microcomputer 123 has functions of, for example, a CPU, a memory, an input/output (I/O) system, and a timer, and constructs a basic control logic such as input/output to/from a data table, and various calculations. Moreover, the microcomputer 123 can generate control signals to the control system of the internal combustion engine 100. Further, the microcomputer 123 calculates a housing external estimated temperature based on the detected values of the first temperature sensor 129 and the second temperature sensor 130, which will be described later, to generate signals for controlling the internal combustion engine 100 based on the calculation result. In other words, the microcomputer 123 is an example of a calculation part as well as a signal generation part according to this embodiment.
As described above, the ECU main body 121 is configured such that the microcomputer 123 carries out the calculation of the housing external estimated temperature and the generation of the signals for controlling the internal combustion engine 100. However, the present invention is not limited to this example. The ECU main body 121 may be configured to separately include a component for carrying out the calculation of the housing external estimated temperature and a component for carrying out the generation of the signals for controlling the internal combustion engine 100. Such a configuration of the components will increase a degree of freedom

when designing the ECU main body 121.
The ECU main body 121 itself is the electronic circuit board, and so is stored in an ECU housing 121a sealed so as to cope with rainfall and the like, thereby forming the ECU main body 121. Namely, the ECU housing 121a is covered with the ECU board 131 so as to protect the electronic components from rainfall and the like with an appropriate space interposed therebetween. The ECU main body 121, the ECU board 131, and the ECU housing 121a may be considered as a single circuit board. Thus, the housing external estimated temperature can also be described as a circuit board external estimated temperature in an external region of the circuit board, and will be hereinafter referred to as "circuit board external estimated temperature".
The first temperature sensor 129 and the second temperature sensor 130 are provided on the ECU board 131 of the ECU main body 121. The first temperature sensor 129 and the second temperature sensor 130 are, for example, IC temperature sensors, and are cheaper by ten times or more than dedicated sensors for measuring the outside air temperature, reguiring a thermoelectric converter and the like .
The ECU main body 121 does not reguire an intake air amount sensor as described above, and thus improvement in the cost is expected. Moreover, in the ECU main body 121, the first temperature sensor 129 and the second temperature sensor 130 are directly mounted on the ECU board 131 without intervention of cables, and thus cables for connecting the first temperature sensor 129 and the second temperature sensor 130 to the ECU main body 121 are not reguired. As a result, a thermoelectric converter or the like for converting sensor inputs from the first temperature sensor 129 and the second temperature sensor 130 is also unnecessary, and thus improvement in the cost is expected. Further, the first temperature sensor 129 and the second temperature sensor 130 having the same configuration are used, so that improvement in work

efficiency is expected in an assembly process.
The first temperature sensor 129 is arranged so as to be adjacent to the power supply 122, while the second temperature sensor 130 is arranged in the vicinity of an outer periphery portion of the ECU housing 121a, being sufficiently separated from the first temperature sensor 129.
The first temperature sensor 129 is arranged on a straight line in X direction that connects the power supply 122 and the second temperature sensor 130 with each other, and is arranged so that a heat generation element does not exist on a straight line that connects the first temperature sensor 129 and the second temperature sensor 130 with each other. Simultaneously, there is provided such an arrangement that a local heatsink does not exist between the first temperature sensor 129 and the second temperature sensor 130. In other words, the ECU main body 121 is configured such that a region between the first temperature sensor 129 and the second temperature sensor 130 is exposed on the ECU board 131.
In other words, the ECU main body 121 is configured such that a space exists between the temperature sensors 129 and 130 and the ECU housing 121a, where it is assumed that the space on the straight line in the X direction and the space between the temperature sensors 129 and 130 are the same. As a result, even when the temperature indicated by the first temperature sensor 129 and the temperature indicated by the second temperature sensor 130 are considered as having an approximately linear relationship, an error in temperature estimation at a position set on the straight line can be decreased as much as possible.
It is to be noted that the power supply 122 is a power supply for serving the entire ECU main body 121, and is thus temporally small in temperature variation with respect to the operation state of the internal combustion engine 100, i.e., the operation state of the ECU main body 121. Thus, the power supply can be treated

as a relatively stable heat generation body.
On the other hand, the power device 12 7 and the like carry out, for example, pulse generation for the injector 110, and hence are elements that exhibit great change in heat generation amount depending on, for example, the operation state of the internal combustion engine 100 and great temperature variation as a heat generation body. Thus, it is desired that the first temperature sensor 129 be installed in the vicinity of a component having small temperature variation, for example, the power supply 122 rather than a component having great temperature variation, for example, the power device 127.
The arrangement of the first temperature sensor 129, the second temperature sensor 130, and other devices illustrated in FIG. 3 is merely an example, so that the arrangement is not limited to this example.
FIG. 4 is a graph for showing a temperature distribution curve CT around the ECU main body 121 including the electronic circuit device according to the first embodiment, showing a basic physical phenomenon at an interface on the assumption of heat transfer from a wall surface to the atmosphere. The first temperature sensor 129 and the second temperature sensor 130 are mounted on the ECU board 131, and the outside air temperature to be estimated is separated by an ECU container side wall 132, that is a part of the ECU housing 121a.
In FIG. 4, the X direction illustrated in FIG. 3 is assigned to a horizontal axis, temperature is assigned to a vertical axis, the temperature of the first temperature sensor 129 is indicated as Tl (K) , the temperature of the second temperature sensor 130 is indicated as T2 (K) , and the temperature at the position outside the housing 121a is indicated as a circuit board external estimated temperature Ta (K).
Then, the circuit board external estimated temperature Ta (K)

is defined by the following Expression 1 by using a constant U (W/K) , which is obtained by multiplying and dividing a plurality of constants acguired from the heat balance, and a coefficient h (W/K) . The microcomputer 123 uses Expression 1 to calculate the circuit board external estimated temperature Ta (K) :
Ta=T2-U/h(T1-T2) .... Expression (1)
Expression 1 is determined by a heat transfer amount determined by a temperature difference between Tl and T2 and heat conductivity, as well as a heat transfer amount determined by a temperature difference between T2 and the circuit board external estimated temperature Ta and heat conductivity. A temperature distribution in a curved form on a left side of the side wall 132 shown in FIG. 4 indicates an accurate distribution on a wall surface and in the atmosphere, where the atmospheric temperature is generally approximated so as to be independent of a distance to the wall. Thus, also in this embodiment, the distance over which the curved temperature distribution is formed is approximated to be zero. Moreover, the constant U includes pieces of position information on the first temperature sensor 129 and the second temperature sensor 130. Those pieces of position information are fixed information, and thus only need to be measured and stored in advance in the microcomputer 123 serving as the calculation part.
The ECU main body 121 is provided in an environment in which the surrounding air is less directly influenced by flowing air while the vehicle travels . For example, in a case of a two-wheeled vehicle, both of the temperature sensors are in a region surrounded by a panel at a bottom portion of a seat. In a case of a passenger vehicle, an engine room, a vehicle cabin, or the like that is not influenced by the outside air flow is conceivable. The internal combustion engine for the vehicle is preferably arranged as described above in order to avoid entrance of rainwater from the outside air intake to the combustion chamber particularly under an environment of

rainfall, for example. Further, the outside air intake is preferably directed oppositely to a forward travel direction of the vehicle for the reasons that rainwater unlikely enters the vehicle.
As a result, the outside air temperature can easily be estimated by the inexpensive temperature sensors directly mounted on the ECU substrate 131 without using a dedicated temperature sensor, wires, a thermoelectric converter, and the like in order to acquire the outside air temperature information. Moreover, the first temperature sensor 129 and the second temperature sensor 130 are arranged in the control system of the internal combustion engine 100, and are provided in the vicinity of the power supply 122 that has relatively small thermal temporal variation on the ECU board 131, and thus the temperature can be highly precisely estimated. Thus, the electronic control system of the internal combustion engine can be realized at a low cost.
On this occasion, in the example of FIG. 2, the ECU main body 121 is provided in the vicinity of the outside air intake 133 in which the air filter 102 of the internal combustion engine 100 is provided, and is arranged so that the -X direction connecting the first temperature sensor 129 and the second temperature sensor 130 to each other along a straight line approximately directs toward the outside air intake 133 . As a result, the outside air temperature to be estimated and the intake air temperature taken from the outside air intake 133 match each other in terms of position.
The outside air intake 133 thus exists in the -X direction on the ECU main body 121, so that for example, even when a temperature distribution exists in the outside air around the internal combustion engine 100, the temperature of the outside air taken into the internal combustion engine 100 can be precisely estimated.
Moreover, the state of the density of the outside air introduced into the combustion chamber 105 and the like can be

recognized more accurately by using both of the circuit board external estimated temperature and the intake pressure data of the intake pressure sensor 104 provided in the intake passage 101, resulting in a highly precise combustion control.
Second Embodiment
In a second embodiment of the present invention, the estimated value of the outside air temperature obtained in the first embodiment is used to estimate the temperature of the internal combustion engine 100. The microcomputer 123 uses the first temperature sensor 129 and the second temperature sensor 130 provided in the ECU main body 121 to estimate the outside air temperature, uses this result to estimate a main body temperature of the internal combustion engine 100, and applies those results to the combustion control.
First, the microcomputer 123 calculates the outside air temperature Ta estimated from the first temperature sensor 129 and the second temperature sensor 130 provided on the ECU board 131 and an energy balance QIN~QOUT of the main body of the internal combustion engine 100. When the temperature of the internal combustion engine main body is denoted by TENG, the following Expression 2 is established:
M-CP-ATENG/At=QIN-QouT •••• Expression (2)
Further, a total sum of the energy output from the internal combustion engine can be expressed as the following Expression 3:
QOUT=S (Qj)+(3(TENG-Ta) Expression (3)
A second term on the right side of Expression 3 represents a heat radiation amount, and a first term on the right side represents the other output energies . In Expression 3, M: mass (kg) of the internal combustion engine main body portion, CP: specific heat (J/(kg-K)) of the internal combustion engine main body portion, QiN: total sum (J/s) of the energy input to the internal combustion

engine main body portion, QOUT : total sum (J/s) of the energy output from the internal combustion engine main body portion, Q j: output energy of an individual element j from the internal combustion engine main body portion, t: time (s), and (3: constant (W/K) .
Expression 2 described above is a differential eguation of the time t and the internal combustion engine main body temperature TENG, expressing a change amount ATENG of the internal combustion engine temperature TENG with respect to a time change amount At. TENG at the time t is obtained by discretizing the energy balance of Expression 3 with respect to time. TENG after At, that is, at a time (t+At), is acguired from TENG at the time t and ATENG by discretizing the differential eguation of Expression 2. The internal combustion engine temperature TENG is successively calculated with respect to the time by repeating this calculation. TENG at a time At is initially calculated from TENG at a time t=0, and the temperature of the internal combustion engine main body portion before the combustion is thus input.
The estimated temperature TENG of the internal combustion engine main body is calculated by assigning Ta obtained from Expression 1 to Expression 3 and solving the simultaneous eguations of Expression 2 and Expression 3.
The time difference At in this case indicates, for example, a timing interval of the fuel injection in the internal combustion engine. Moreover, the temperature in the initial state, namely, the temperature at the time when the internal combustion engine is started and the combustion starts, is input in this calculation.
As the initial temperature calculation method, there are given, for example,
(1) a method of pre-storing the temperature in a stopped state, counting an elapsed period until a next operation starts, and estimating the initial temperature from the elapsed period and the heat capacity of the subject to be estimated;

(2) a method of measuring the resistance of a resistor installed previously in an electronic control device, a power device, or the like, determining the temperature of the resistor from a relationship between the resistance and the temperature associated with each other in advance, and estimating the initial temperature from the temperature of the resistor and the temperature of the subject to be estimated associated with each other in advance; and
(3) a method of acguiring a pressure value of the outside air sucked into the internal combustion engine, and estimating the initial temperature from a relationship between the pressure value and the temperature of the subject of the estimation associated with each other in advance. Those methods are merely examples of the estimation method for the initial value, and the estimation method is not limited thereto.
FIG. 5 is a flowchart for illustrating the outside air temperature estimation and the internal combustion engine main body portion temperature estimation from the ECU main body 121 including the electronic circuit device according to the second embodiment. This applies to a case where the ECU main body 121 is installed in an environment in which the surrounding temperature is less directly influenced by the flowing air when the vehicle travels. Constants used for the estimation, such as the constant U and the coefficient h are stored in a nonvolatile memory, and other reguired information is input when the power of the vehicle is turned on.
As a result, the circuit board external estimated temperature Ta according to the present invention can be calculated from the input values from the first temperature sensor 129 and the second temperature sensor 130, and the result can be used to estimate the temperature TENG of the internal combustion engine main body portion.
Namely, in FIG. 5, initial state information on the internal combustion engine before the combustion, such as information from various sensors and the estimated initial values (U, h, (3), are

firstly input to the microcomputer 123 when the power supply of the vehicle is turned on (Step SI).
Then, after the temperature of the internal combustion engine main body portion before the combustion is acquired (Step S2), the respective temperatures Tl and T2 are input from the first temperature sensor 129 and the second temperature sensor 130 (Step S3) . Then, the circuit board external estimated temperature Ta represented by Expression 1 is calculated from the above-mentioned constants and the temperatures Tl and T2 (Step S4).
Simultaneously, an internal combustion engine operation parameter is input to the microcomputer 123 (Step S5) . The microcomputer 123 uses the circuit board external estimated temperature Ta and the internal combustion engine parameter to acquire QIN and Q0UT from the energy balance equations of Expressions 2 and 3 (Step S6), and estimate the temperature TENG of the internal combustion engine main body portion after the time difference At (Step S7) . It is to be noted that the information on the circuit board external estimated temperature Ta is also used for subsequent combustion control (Step S8).
Moreover, T^NG after At is newly considered as T^NG after the time t and is used for the estimation of the next temperature of the internal combustion engine main body portion after At (Step S2) , to thereby estimate in advance the temperature of the internal combustion engine main body portion by repeating this calculation. It is to be noted that the internal combustion engine operation parameter is a parameter determined based on the operation state of the internal combustion engine, and is, for example, the number of revolutions of the internal combustion engine, the vehicle speed, and the like.
Third Embodiment
FIG. 6 is a flowchart for illustrating the estimation of the

circuit board external temperature in the electronic circuit device and the internal combustion engine main body portion temperature estimation according to a third embodiment of the present invention.
This applies to a case where the ECU main body 121 is mounted in an environment in which the surrounding temperature is well directly influenced by the flowing air when the vehicle travels. Constants used for the estimation, for example, the constant U and a constant a are pre-stored in a nonvolatile memory, and other reguired information is input when the power of the vehicle is turned on.
The circuit board external estimated temperature Ta according to the third embodiment is calculated from the input values from the first temperature sensor 129 and the second temperature sensor 130, as well as the coefficient h having the vehicle speed V as a parameter. The result can be used to estimate the temperature TENG of the internal combustion engine main body portion.
In other words, the flowchart of FIG. 6 is different from that of FIG. 5 in that when calculating the circuit board external estimated temperature Ta (Step S4), the coefficient h having the vehicle speed V as a parameter is used (Step S9) in addition to the temperatures from the first temperature sensor 129 and the second temperature sensor 130.
Namely, when the vehicle speed V is more than a threshold, the coefficient h can be expressed as an approximation eguation represented as the following Expression 4. In other words, the microcomputer 123 can use Expression 4 to calculate the circuit board external estimated temperature Ta (K):
h=aV0'8 .... Expression (4) where a is a proportional constant, and V is the vehicle speed. This vehicle speed V is input, for example, from a vehicle sensor (not shown), and means for acguiring the speed information is originally provided in the vehicle, and can thus be used.

Hitherto, a temperature sensor is mounted in the internal combustion engine main body, and combustion conditions, such as the throttle opening degree adjustment for setting the air flow amount and the like are controlled in accordance with the temperature state of the internal combustion engine main body.
According to the above respective embodiments, not only can the temperature of the internal combustion engine main body be estimated and the need for a dedicated temperature sensor for measuring the outside air temperature and wires for the sensor be eliminated, but also a dedicated temperature sensor adapted to a high temperature of the internal combustion engine main body can be eliminated. Further, the need for machining the internal combustion engine main body to mount a sensor can be eliminated, and the need for wires can be eliminated. Thus, an electronic circuit device system can be realized at a lower cost.
The respective embodiments are not limited to the specific details as mentioned and described above and the representative embodiments. Modified examples and effects easily derived by a person skilled in the art can also be included in the present invention. Thus, various changes may be made without departing from the spirt or scope of the general concept of the present invention defined by the scope of claims and eguivalents thereof.
While in the above-mentioned embodiments, the power supply 122 provided in the ECU main body 121 in the calculation of the circuit board external estimated temperature has been mentioned, the heat generation body is not limited to the power supply 122 but may the one presenting a regularly stable temperature. For example, compared with the power device 127 and the like having great operation variation during driving, the microcomputer 123 and the A/D converter are more preferred.
While in the above-mentioned embodiments, the ECU is exemplified as the electronic circuit device, the electronic

circuit device is not limited to the ECU, and a control unit such as a hybrid control unit (HCU), an electronic control unit (ECU), a motor control unit (MCU), and a transmission control unit (TCU) may be applied to a circuit board when a part or the entirety thereof are separately installed, with similar effects.
While in the above-mentioned embodiments, using the circuit board external estimated temperature to estimate the temperature of the internal combustion engine main body has been mentioned, the circuit board external estimated temperature may be used to control an air conditioner and engine cooling.

Fourth Embodiment
FIG. 7 is a schematic diagram for illustrating an example in which the electronic circuit device according to the first to third embodiments is applied to a two-wheeled motor vehicle . In this case, the internal combustion engine 100 is mounted on a two-wheeled motor vehicle 200. An ECU main body on which two temperature sensors are installed was mounted on the two-wheeled motor vehicle 200, and the difference between the circuit board external estimated temperature and an actually measured outside air temperature was examined in environments having different outside air temperatures under different driving conditions. The vehicle includes a motor vehicle and a two-wheeled vehicle.
As a result, it was found that, with this arrangement, U/h acguired from the coefficient h and the constant U used in Expression 1 can be treated as a constant value to estimate the temperature. As a result, the calculation for the temperature estimation is simplified, and a load imposed on the microcomputer 123 can be decreased in the estimation processing.
Fifth Embodiment

FIG. 8 is a schematic diagram for illustrating the two-wheeled motor vehicle 200 using the electronic circuit device according to a fifth embodiment. The configuration of the electronic circuit device is the same as that of the first and second embodiments, but the ECU main body 121 of FIG. 8 differs from the ECU main body 121 for the two-wheeled vehicle 200 according to the fourth embodiment illustrated in FIG. 7 in terms of arrangement. In other words, the ECU main body 121 of FIG. 8 is arranged in a vehicle body front portion of the two-wheeled motor vehicle 200, and is provided at a portion at which the surrounding temperature is influenced by flowing air during the travel of the vehicle.
In this case, the heat transfer from the ECU container sidewall 132 illustrated in FIG. 4 is promoted, and thus the outside air temperature can be estimated by treating the coefficient h of Expression 1 as a function of the flow speed. For example, when the flow is turbulence, the heat transfer from the ECU container sidewall 132 is considered to be proportional to the speed to the power of 0.8, where a is a proportional constant.
When the vehicle speed is high, the outside air temperature Ta (K) can be estimated in accordance with an approximation eguation represented as the following Expression 4:
As a result, it is possible to easily estimate the temperature in the external region of the circuit board by using the inexpensive first temperature sensor 129 and second temperature sensor 130 directly provided on the ECU board 131 and the vehicle speed independently of the installation location of the ECU main body 121.
As described above, according to the present invention, the circuit board external estimated temperature acguired by the electronic circuit device can be used as, for example, one of control signals in the control device of the internal combustion engine for the vehicle, and the need to arrange a dedicated temperature

sensor on the vehicle is eliminated.

What is claimed is:
1. An electronic circuit device, comprising:
a power supply mounted on a circuit board and configured to supply power;
a first temperature sensor mounted on the circuit board and configured to use the power supplied from the power supply so as to detect a first temperature;
a second temperature sensor mounted on the circuit board and configured to use the power supplied from the power supply so as to detect a second temperature; and
a calculator configured to calculate an estimation temperature at a position in an external region of the circuit board based on the first temperature and the second temperature, the position being on a straight line on which the first temperature sensor and second temperature sensor are connected.
2 . The electronic circuit device according to claim 1, wherein
when the first temperature is represented as Tl, the second
temperature is represented as T2, a constant is represented as U,
a coefficient is represented as h, and the estimation temperature
is represented as Ta, an expression
Ta=T2-U/h(T1-T2) is satisfied.
3 . The electronic circuit device according to claim 2, wherein the constant U comprises position information of the first temperature sensor and position information of the second temperature sensor, and the position information of the first temperature sensor and the position information of the second temperature sensor are stored in the calculator in advance.
4 . The electronic circuit device according to claim 1, further

comprising:
a signal generator configured to generate a control signal for an internal combustion engine,
wherein the signal generator generates the control signal based on the estimation temperature calculated by the calculator.
5 . The electronic circuit device according to claim 4, wherein the power supply, the calculator, and the signal generator are spaced away from the straight line and arranged on the circuit board.
6. The electronic circuit device according to any one of claims 1 to 5, wherein the first temperature sensor is arranged at a position near the power supply.
7. The electronic circuit device according to any one of claims 1 to 6, wherein the first temperature sensor and the second temperature sensor are arranged between the external region of the circuit board and the power supply on the straight line, and the external region of the circuit board and the power supply are on the straight line.
8 . The electronic circuit device according to any one of claims 1 to 7, wherein:
the first temperature sensor and the second temperature sensor are sealed on the circuit board from outside air, and the circuit board has an exposed region on the straight line between the first temperature sensor and the second temperature sensor.
9. The electronic circuit device according to claim 1 or 7, wherein the circuit board has an outer periphery, and the external region of the circuit board positions at a vicinity of the outer periphery.

10. The electronic circuit device according to any one of claims 1 to 9, wherein an outside air flow is generated around a vehicle in accordance with a vehicle speed, and the electric circuit device is arranged at position free from the outside air flow.
11. The electronic circuit device according to claim 4, wherein
the calculator calculates a first estimation temperature when the internal combustion engine is in an initial state and calculates a second estimation temperature when the combustion engine is in a state after the initial state as the estimation temperature, and
the signal generator generates the control signal in accordance with an energy balance of the internal combustion engine based on the first estimation temperature and the second estimation temperature so as to control the internal combustion engine.
12. The electronic circuit device according to claim 2, wherein when a vehicle speed is higher than a threshold, the calculator uses the coefficienth including the vehicle speed so as to calculate the estimation temperature Ta(K).
13. A vehicle, comprising:
an internal combustion engine arranged in a vehicle housing;
the electronic circuit device according to claim 1;
an intake passage configured to supply outside air from an outside air intake portion to the internal combustion engine; and
a signal generator configured to generate a control signal for the internal combustion engine, wherein
the estimation temperature calculated by the calculator is provided to the signal generator, and
the signal generator generates the control signal based on

the estimation temperature.
14. A vehicle according to claim 13, wherein an external region of the circuit board of the electronic circuit device positions at the outside air intake.