JPH08121227A - Electronic control unit of engine - Google Patents

Abstract

PURPOSE: To suppress heat generation exceeding a usable limit temperature range of a transistor for driving an inductance load to which a Zener diode for eliminating flyback voltage is connected. CONSTITUTION: A driving circuit 341 is housed in an electronic control unit 30 of an engine, which circuit 341 controls operation of a fuel injection valve 9 based on driving command output from a microcomputer 310. In such a driving circuit, a Zener diode for eliminating flyback voltage is inserted between a base and a collector of a transistor driving the fuel injection valve. Flyback energy generated at the time of setting OFF the fuel injection valve 9 is eliminated by the transistor. A thermistor 352 is arranged in the vicinity of the transistor, while temperature around the transistor is computed based on voltage between terminals of the thermistor. When the computed peripheral temperature is a specified limit value or more, a judgment value for high speed rotation fuel cut is lowered, and power generation of the transistor is limited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic control unit for an engine that electronically controls the operation of the engine, and more particularly, it is connected to a transistor that drives an inductance load such as a fuel injection valve in synchronization with the rotation of the engine. The present invention relates to an implementation of a device that includes a Zener diode that extinguishes a flyback voltage that occurs when a load is off, and that accurately realizes thermal protection of the transistor.

[0002]

2. Description of the Related Art In such an electronic control unit for an engine, the Zener diode for extinguishing the flyback voltage is inserted between the base and collector of a transistor for driving a fuel injection valve in order to further reduce the size of the engine. However, the flyback energy generated when the fuel injection valve is turned off is absorbed by the transistor.

However, when the flyback energy is absorbed by the transistor itself as described above, heat is generated by the flyback energy in addition to the heat generated when the fuel injection valve is driven, and heat resistance of the transistor is concerned. The problem is getting bigger and bigger.

That is, simply adopting such a method as the method of extinguishing the flyback voltage is extremely severe in terms of heat, and there is a possibility that the temperature range which is the limit of use of the transistor may be exceeded. .

Therefore, conventionally, heat dissipation measures have been taken such as mounting these transistors or the like on a radiation fin, or mounting a heat sink on the transistors themselves.

[0006]

By providing such a heat dissipation measure to the above-mentioned transistor for driving the fuel injection valve, not only the transistor but also the electronic control device itself incorporating the transistor is surely Reliability will be improved.

However, from the viewpoint of its economical efficiency or an electronic control device which controls a so-called special device such as an engine, such a heat radiation measure is not always a good measure.

That is, if the above method is adopted as a method of extinguishing the flyback voltage generated when the fuel injection valve is turned off, there is a possibility that the operating temperature limit of the transistor for driving the fuel injection valve may be exceeded. However, in reality, such a situation occurs when the ambient temperature is high, the resistance value of the fuel injection valve is low (that is, the temperature is low), and the engine is rotating at high speed. Only in special cases.

[0009] Therefore, even if the above heat dissipation measures are taken in preparation for such a special situation, the technical effect thereof is weak, and it is hard to say that this is an economically effective way of cost application. In addition, if the ambient temperature itself becomes high even if the heat dissipation measures in the above-described mode are taken, effective heat dissipation is not performed, and it is not a fundamental measure against the heat generation.

Not only the above-mentioned transistor for driving the fuel injection valve but also the transistor for driving the inductance load which is built in the electronic control unit and absorbs the flyback energy in the above-mentioned mode, is the same as above. Are generally common.

The present invention has been made in view of the above circumstances, and the thermal load of a transistor for driving an inductance load to which a Zener diode for arc extinguishing a flyback voltage is connected, without inconveniently dissipating heat. An object of the present invention is to provide an electronic control device for an engine that can realize protection accurately.

[0012]

In order to achieve such an object, in the invention according to claim 1, a transistor for driving an inductance load in synchronization with the rotation of an engine, and a transistor connected to the transistor to turn off the load. In an electronic control unit for an engine, which comprises a Zener diode for extinguishing a generated flyback voltage, temperature monitoring means for monitoring the temperature of the transistor or its ambient temperature, and the monitored temperature or its equivalent value A rotational speed limiting means for limiting the engine rotational speed when the rotational speed exceeds a predetermined limit value.

According to the second aspect of the present invention, the rotational speed limiting means is provided with fuel cut determination value changing means for lowering the determination value of the fuel cut rotational speed associated with the high speed rotation of the engine.

According to the third aspect of the present invention, the rotation speed limiting means is provided with fuel injection thinning means for thinning the fuel injection into the engine for a predetermined time to reduce the maximum rotation speed of the engine. Configure as.

Further, in the invention according to claim 4, the rotation speed limiting means is provided with cut-off cylinder control means for stopping the fuel injection to an arbitrary cylinder of the engine to reduce the maximum rotation speed of the engine. Configure.

Further, in the invention according to claim 5, the rotation speed limiting means is provided with injection amount reducing means for reducing the maximum number of revolutions of the engine by reducing the fuel injection amount to the engine in a predetermined manner. Configure.

Further, in the invention according to claim 6, the rotational speed limiting means comprises an intake air limiting means for forcibly driving the intake throttle valve of the engine to reduce the maximum rotational speed of the engine.

Further, in the invention according to claim 7, in the structure according to any one of the inventions according to claims 1 to 6, the temperature monitoring means is a thermistor disposed in the vicinity of the transistor, and the thermistor. And a calculating means for calculating the ambient temperature of the transistor based on the voltage between terminals.

According to the eighth aspect of the present invention, in the configuration according to any one of the first to sixth aspects of the invention, the temperature monitoring means is arranged in the electronic control unit and is driven by a constant current. And a computing means for computing the ambient temperature of the transistor based on the forward voltage of the diode.

Further, in the invention according to claim 9, in the structure of the invention according to claim 8, the diode is separately arranged as the temperature monitoring means in the electronic control unit.

According to the tenth aspect of the present invention, in the configuration of the eighth aspect of the invention, the diode which is previously arranged as a control component in the electronic control unit is used.

According to the eleventh aspect of the present invention, in the configuration of the eighth or ninth or tenth aspect of the present invention in which a diode is used, the arithmetic means is within a predetermined time after the power is turned on, and the engine is Both the cooling water temperature and the intake air temperature are equal to or lower than a predetermined first temperature and the temperature difference is equal to or lower than a second temperature, and the logical product condition that the engine is not rotating is satisfied. Means for calibrating the forward voltage-temperature characteristic of the diode,
When any one of the above conditions is no longer met, means for calculating the respective temperature as the ambient temperature of the transistor based on the calibrated forward voltage-temperature characteristic of the diode is provided. To do.

According to the twelfth aspect of the invention, in any one of the first to sixth aspects of the invention, the temperature monitoring means converts the ambient temperature of the transistor into a battery voltage value. The rotation speed limiting means limits the engine rotation speed when the converted battery voltage value becomes equal to or higher than a predetermined limit value.

Further, in the invention according to claim 13, in the configuration according to any one of the inventions according to claims 1 to 6, the temperature monitoring means is configured to extract a base potential during constant current driving of the transistor. It is configured to include extraction means and calculation means for calculating the temperature of the transistor itself based on the extracted base potential.

According to a fourteenth aspect of the invention, in the configuration of the thirteenth aspect of the invention, the arithmetic means is:
A means for detecting that the transistor is in a constant current driving state based on a lapse of a fixed time after the transistor is turned on; and the extracted base based on the detection that the transistor is in a constant current driving state. And a means for reading the potential and calculating the temperature of the transistor based on the base potential-temperature characteristic.

According to a fifteenth aspect of the present invention, in the same configuration as the thirteenth aspect of the invention, the temperature monitoring means further comprises a power supply potential extracting means for extracting the power supply potential of the load. And a means for detecting that the transistor is in a constant current drive state based on a lapse of a fixed time after the transistor is turned on, and a means for determining that the transistor is in a constant current drive state. A means for reading the extracted base potential and the power source potential based on the detection and calculating the temperature of the transistor based on the base potential-temperature characteristic corresponding to the power source potential at each time is provided.

According to the sixteenth aspect of the present invention, a transistor for driving the inductance load in synchronization with the rotation of the engine and a zener diode connected to the transistor for extinguishing the flyback voltage generated when the load is off. In the electronic control unit of the engine including
A load temperature monitoring means for monitoring the temperature of the inductance load and a rotation speed limiting means for limiting the engine rotation speed according to the monitored load temperature are provided.

According to a seventeenth aspect of the present invention, in the configuration of the above-described sixteenth aspect of the present invention, the rotation speed limiting means is used to monitor the judgment value of the fuel cut rotation speed associated with the high speed rotation of the engine. The fuel cut judgment value changing means is arranged to change according to the temperature.

According to the eighteenth aspect of the present invention, in the configuration of the sixteenth aspect of the present invention, the rotation speed limiting means sets the fuel injection to the engine at predetermined intervals according to the monitored load temperature. The fuel injection thinning means for thinning out and reducing the maximum engine speed of the engine is provided.

According to a nineteenth aspect of the invention, in the configuration of the sixteenth aspect of the invention, the rotation speed limiting means is used to inject fuel into a number of cylinders determined according to the monitored load temperature. And a cylinder reduction control means for stopping the engine to reduce the maximum engine speed.

Further, in the invention of claim 20, in the structure of the invention of claim 16, the rotational speed limiting means is provided with a predetermined amount of fuel injection amount to the engine according to the monitored load temperature. The injection amount reducing means for reducing the maximum engine speed of the engine is provided.

Further, in the invention of claim 21, in the configuration of the invention of claim 16, the rotational speed limiting means is forced by a predetermined amount according to the monitored load temperature of the intake throttle valve of the engine. It is configured to have intake restriction means that is driven to reduce the maximum engine speed.

Further, in the invention of claim 22, in the configuration of the invention of any one of claims 16 to 21, the load temperature monitoring means is arranged in the inductance load and the temperature thereof is directly measured. The temperature measuring means is provided.

Further, in the invention described in claim 23, in the configuration of the invention described in any one of claims 16 to 21, the load temperature monitoring means includes a water temperature sensor for detecting a cooling water temperature of the engine, and the detection. And an estimating means for estimating the temperature of the inductance load based on the cooling water temperature.

Further, in the invention of claim 24, in the configuration of the invention of claim 23, the estimating means is
Calculating means for calculating the cumulative rotation speed from the engine start time, and when the calculated cumulative rotation speed is equal to or more than a predetermined value, the detected cooling water temperature or the engine rotation speed limit amount corresponding to the cooling water temperature And a correction means for correcting the allowable width by increasing it to a predetermined value.

According to a twenty-fifth aspect of the invention, in the configuration of the twenty-fourth aspect of the invention, the estimating means is
Even after the engine is stopped, the accumulated rotational speed calculated as described above is held until the ignition is turned off.

[0037]

[Function] As a method of extinguishing the flyback voltage generated when the inductance load such as a fuel injection valve is turned off, when a Zener diode is connected to a transistor for driving the Zener diode, the operating temperature limit of the transistor may be exceeded. However, in reality, such a situation occurs when the ambient temperature is high, the resistance value of the fuel injection valve is low (that is, the temperature is low), and the engine is rotating at high speed. As described above, it is limited to such special cases.

Therefore, according to the invention described in claim 1, temperature monitoring means for monitoring the temperature of the transistor or its ambient temperature, and the monitored temperature or its equivalent value is equal to or greater than a predetermined limit value. In this case, if the rotational speed limiting means for limiting the engine rotational speed is provided, respectively, the electric power generated from the transistor will be naturally limited,
Even if the above-mentioned heat dissipation measure is not necessarily applied to the above-mentioned transistor, the heat generation beyond the temperature range for which it can be used can be properly suppressed.

Therefore, it becomes possible to surely protect those elements in the unlikely event that the heat dissipation is not costly. The power generated from the transistor is proportional to the on-duty of the transistor when it is on, and is proportional to the engine speed when it is off, that is, when the flyback energy is absorbed. Therefore, assuming that the on-duty does not change, the generated electric power is limited by limiting the engine speed, and the abnormal heat generation of the transistor can be suitably suppressed.

According to the second aspect of the present invention, the rotation speed limiting means is provided with: fuel cut determination value changing means for lowering the determination value of the fuel cut rotation speed associated with the high speed rotation of the engine. With this configuration, the fuel injection is completely prohibited at the rotation speed equal to or higher than the changed fuel cut determination value, and the engine rotation speed does not increase further.

Therefore, the abnormal heat generation of the transistor is suppressed without affecting the normal running of the vehicle,
Eventually, it will be possible to protect this. In addition to the rotation speed limiting means, for example, as in the invention according to claim 3, fuel injection thinning for reducing the maximum rotation speed of the engine by thinning out fuel injection to the engine for a predetermined time Those that have means. Alternatively, according to the invention as set forth in claim 4, there is provided: a cut-off cylinder control means for stopping fuel injection into an arbitrary cylinder of the engine to reduce the maximum engine speed of the engine. Alternatively, as in the invention according to claim 5, an injection amount reducing means for reducing the fuel injection amount to the engine by a predetermined amount to reduce the maximum rotation speed of the engine. Alternatively, as in the invention according to claim 6, an intake limiting means for forcibly driving an intake throttle valve (throttle valve or the like) of the engine to reduce the maximum engine speed of the engine. Can also be configured as.

Even with such a configuration as the rotation speed limiting means, the engine rotation speed can be suitably limited, and by extension, the power generated by the transistor can be limited.

On the other hand, according to the invention as set forth in claim 7, in each of the above-mentioned constitutions, the temperature monitoring means includes: a thermistor disposed in the vicinity of the transistor;
Arithmetic means for computing the ambient temperature of the transistor based on the voltage across the terminals of the thermistor. Can be configured as. With such a structure as the temperature monitoring means, it becomes possible to directly and easily monitor the ambient temperature of the transistor.

Further, according to the invention described in claim 8, the temperature monitoring means is provided as follows: based on a diode arranged in the electronic control device and driven by a constant current, and a forward voltage of the diode. Calculating means for calculating the ambient temperature of the transistor. Can also be configured as. In particular, according to such an arrangement as a temperature monitoring means, this can be achieved for the diode, eg according to the invention according to claim 9, The temperature control means is separately provided in the electronic control unit. Alternatively, as in the invention according to claim 10, B. The components that are previously arranged as control components in the electronic control unit are used. It becomes possible to use it in such a mode.

The former A. According to the above configuration, the diode can be arranged at an arbitrary position near the transistor that is the temperature monitoring target, and any constant current source can be used.

The latter B. According to the configuration, although there is no such degree of freedom, it is not necessary to newly add an electronic component, and the temperature monitoring means can be configured more economically. As a diode that is previously arranged as a control component in this electronic control device and is driven with a constant current, for example, in a waveform shaping circuit such as a vehicle speed sensor,
There is a diode or the like that generates a comparison reference potential for binarizing the sensor signal.

According to the eleventh aspect of the present invention, in these configurations in which a diode is used as the temperature monitoring means, the calculating means includes: -within a predetermined time after power-on; The diode is based on the fact that both the cooling water temperature and the intake air temperature are equal to or less than a predetermined first temperature and the temperature difference is also less than or equal to a predetermined second temperature, and the logical product condition that the engine is not rotating is satisfied. Means for calibrating the forward voltage-temperature characteristic of the transistor; and when any one of the above conditions is no longer satisfied, the respective temperature of the transistor is adjusted based on the calibrated forward voltage-temperature characteristic of the diode. If the temperature monitoring means is realized by using the diode in this way, the forward current is generated. The variation in the temperature characteristics by properly absorbed, it is possible to perform a highly accurate monitoring of the ambient temperature.

The power generated by the transistor has a strong correlation with the power supply voltage, that is, the battery voltage, and the ambient temperature allowed for the transistor can be converted into the battery voltage and monitored.

Therefore, even in the configurations of the inventions described in claims 1 to 6, as in the invention described in claim 12,
The temperature monitoring means: A device for converting the ambient temperature of the transistor into a voltage value of a battery for monitoring. The rotation speed limiting means also has the following: When the converted voltage value of the battery is equal to or higher than a predetermined limit value, the engine speed is limited. With such a configuration, the heat generation of the transistor can be suppressed and the element can be reliably protected with a very simple configuration that basically only measures the battery voltage.

On the other hand, it is known that the base potential (base-emitter voltage) of the transistor itself also changes with a strong correlation with temperature, like the forward voltage of the diode described above.

Therefore, in the structure of the inventions according to claims 1 to 6, as in the invention according to claim 13,
The temperature monitoring means, comprising: a base potential extracting means for extracting a base potential when the transistor is driven with a constant current, and a computing means for computing the temperature of the transistor itself based on the extracted base potential. . With this configuration, the temperature of the transistor to be monitored can be monitored by directly utilizing the characteristics of the transistor. That is, in this case, even if the temperature of the transistor itself suddenly rises before the ambient temperature rises, the temperature fluctuation can be accurately captured, and abnormal heat generation and the like can be surely suppressed. .

In this case, as the calculating means, for example, according to the invention of claim 14, the transistor is brought into a constant current drive state on the basis of a lapse of a fixed time after the transistor is turned on. And a means for detecting that there is a constant current and a means for reading the extracted base potential based on the detection of the constant current drive state and calculating the temperature of the transistor based on the base potential-temperature characteristic. thing. Alternatively, when the temperature monitoring means further comprises a power supply potential extracting means for extracting the power supply potential of the load, as in the invention according to claim 15, Means for detecting that the transistor is in a constant current driving state based on the passage of time, and reading the extracted base potential and power source potential based on the detection that the transistor is in a constant current driving state, and the power source for each time. Base potential according to potential-
And means for calculating the temperature of the transistor based on the temperature characteristic. Can be configured as.

Incidentally, the amount of change in the base potential with respect to temperature decreases as the base current increases, that is, the power supply potential increases. Therefore, particularly according to the configuration of the invention described in claim 15, even if the power supply potential changes,
The accuracy of the calculated temperature can be preferably maintained, and the above-mentioned temperature of the transistor itself can be monitored with higher reliability.

By the way, in any of the inventions described in claims 1 to 15, the temperature of the transistor itself or its surroundings is monitored, and when the monitored temperature or a corresponding value exceeds a predetermined limit value, the engine I tried to limit the number of rotations. However, thermal protection of the transistor can be achieved by suppressing the power generated on the side of the inductance load in addition to the power generated by the transistor itself, in a manner similar to the above.

That is, according to the sixteenth aspect of the present invention, in the electronic control unit for the engine, the load temperature monitoring means for monitoring the temperature of the inductance load, and the engine rotation according to the monitored load temperature. Also, by respectively providing the rotation speed limiting means for limiting the number, the electric power generated from the inductance load is restricted, and the electric power generated from the transistor itself is also suppressed. Even in this case, even if the above-mentioned heat dissipation measure is not necessarily applied to the transistor, heat generation beyond the temperature range where the transistor is used can be properly suppressed.

Incidentally, the electric power generated from the load is
The higher the engine speed, and the lower the temperature of the same load, the larger. On the other hand, in a transistor, the higher the temperature, the lower the energy that can be consumed. In other words, what is a thermally difficult situation for a transistor?
It can be considered that the temperature of the load is low (generated power is large) and the temperature of the transistor itself is high (consumable power is small). Therefore, in order to thermally protect the transistor assuming that the temperature of the transistor is high to some extent, it is sufficient to suppress the power generated from the load. The engine speed may be limited according to the temperature.

As a method for limiting the engine speed, the engine speed limiting means may be used, for example, according to the invention described in claim 17, as follows: And a fuel cut determination value changing means for changing the value according to the monitored load temperature. According to the above configuration, similarly to the above, the fuel injection is completely prohibited at the rotation speed equal to or higher than the changed fuel cut determination value, and the engine rotation speed does not further increase.

In this case, the fuel cut judgment value is
The value is changed to a smaller value (a value corresponding to a lower engine speed) as the temperature of the inductance load is lower, but the specific changing mode is arbitrary, for example, a. It is changed in a substantially linear relationship in the temperature range with the load. Or b. Binary or multi-valued change is made at a certain load temperature. The present invention can be embodied in various modes, etc.

Also in this case, in addition to the rotation speed limiting means, for example, according to the invention of claim 18, the fuel injection to the engine is thinned out by a predetermined time period according to the monitored load temperature. It is equipped with fuel injection thinning means that lowers the maximum engine speed. Alternatively, according to the invention as set forth in claim 19, a cut-off cylinder control means for reducing the maximum engine speed by stopping the fuel injection to the number of cylinders determined according to the monitored load temperature is provided. thing. Alternatively, according to the invention of claim 20, the fuel injection amount to the engine is reduced by a predetermined amount according to the monitored load temperature, and an injection amount reduction means for reducing the maximum engine speed is provided. . Alternatively, according to the invention of claim 21, an intake limiting means for reducing the maximum engine speed by forcibly driving the intake throttle valve of the engine by a predetermined amount according to the monitored load temperature. Can be configured as.

With such a configuration as the rotation speed limiting means, the engine rotation speed can be suitably limited, and by extension, the load and the power generated by the transistor can be limited.

Incidentally, in order to lower the maximum engine speed of the engine, in the invention of claim 18, the lower the load temperature, the longer the thinning time is set.
In the invention of claim 19, the lower the temperature of the load is, the larger the number of reduced cylinders is set. In the invention of the above-mentioned claim 20, the lower the temperature of the load is, the larger the reduction value is set. According to the invention of claim 21, a larger drive amount is set as the temperature of the load is lower. However, those specific embodiments are arbitrary, and here, a. Setting by a linear relationship as shown in, or b. It is possible to set in various modes such as a binary or multi-valued setting as shown in.

On the other hand, in each of these configurations, the load temperature monitoring means is, for example, as in the invention according to claim 22, wherein: the temperature measuring means is provided in the inductance load to directly measure the temperature. What you get. Alternatively, according to the invention of claim 23, a water temperature sensor for detecting a cooling water temperature of the engine, and an estimating means for estimating the temperature of the inductance load based on the detected cooling water temperature. Can be configured as.

According to the former aspect of the invention, the temperature of the inductance load can be accurately grasped. As the temperature measuring means, there is a thermocouple or the like.

According to the latter aspect of the invention described in claim 23, the accuracy of the temperature information itself of the same inductance load is somewhat inferior, but it is not necessary to separately provide a dedicated sensor. That is, the temperature of the same inductance load can be grasped to some extent without using the dedicated sensor. Incidentally, the output of the water temperature sensor (engine cooling water temperature) corresponds to the warm-up state of the engine body. When the temperature of the engine body is low, it can be considered that the temperature of the inductance load such as the fuel injection valve is also low.

In particular, in the latter aspect of the invention according to claim 23, the estimating means is, as in the invention according to claim 24, a calculating means for calculating a cumulative rotation speed from the engine start time, and Compensating means for correcting the detected cooling water temperature or the allowable range of the engine rotational speed limitation amount corresponding to the cooling water temperature by a predetermined increase when the calculated cumulative rotation speed is equal to or higher than a predetermined value. With this configuration, it becomes possible to execute the above-mentioned various controls for limiting the engine speed in accordance with the temperature of the inductance load which is closer to the actual condition. That is, even when the cooling water temperature is low, if the driving time of the inductance load such as the fuel injection valve reaches a certain time, the temperature is considered to be rising, and thus the cooling water temperature or By increasing and correcting the allowable range of the engine speed limit amount according to the cooling water temperature, it becomes possible to suppress the excessive limit.

Further, in such a structure of the estimating means,
According to the invention of claim 25, the estimating means holds the calculated cumulative rotation speed until the ignition is turned off even after the engine is stopped. With this configuration, even when the engine is restarted immediately after the engine stall or the like, for example, the calculation of the cumulative rotational speed does not start from "0" again,
The mode of limiting the engine speed based on the temperature of the inductance load which is closer to the actual condition is maintained. In other words, in combination with the configuration of the invention described in claim 24, the electronic control device can be operated more efficiently in terms of thermal protection of the transistor.

[0067]

【Example】

(First Embodiment) FIGS. 1 to 8 show a first embodiment of an electronic control unit for an engine according to the present invention.

The apparatus of the first embodiment is an electronic control unit for an engine in which a drive circuit for a fuel injection valve is built in, and the ambient temperature is monitored through a thermistor arranged near the output transistor of the drive circuit. However, when the temperature becomes equal to or higher than a predetermined value, the device is configured to reduce the high rotation fuel cutoff determination value of the engine.

First, with reference to FIG. 1, the structure of the engine and its peripheral devices that are controlled by the electronic control unit will be described. As shown in FIG. 1, the engine 1 is
A combustion chamber 5 is formed by the cylinder 2, the piston 3, and the cylinder head 4. A spark plug 6 is arranged in the combustion chamber 5.

In the engine 1, the intake system is connected to the intake manifold 8 communicating with the combustion chamber 5 via the intake valve 7, the fuel injection valve 9 for injecting fuel into the intake manifold 8, and the intake manifold 8. Intake pipe 10, surge tank 1 for absorbing pulsation of intake air
1, a throttle valve 12, and an air cleaner 13 are provided.

On the other hand, the exhaust system of the engine 1 has an exhaust manifold 15 which communicates with the above-mentioned combustion chamber 5 via an exhaust valve 14. Further, the engine 1 has an igniter 1 that outputs a high voltage required for ignition.
6 and a distributor 17 that supplies a high voltage generated by the igniter 16 to the ignition plugs 6 of the respective cylinders in conjunction with a crankshaft (not shown).

On the other hand, the engine 1 is also provided with the following various sensors. Water temperature sensor 20: provided in the cooling system of the engine 1 to detect the temperature of the cooling water. Intake air temperature sensor 21: The intake air temperature sensor 21 is provided in the air cleaner 13 and detects the temperature of intake air sent to the engine 1. Throttle position sensor 22: Interlocks with the throttle valve 12 to detect the opening of the throttle valve 12. Intake pipe pressure sensor 23: measures the pressure in the intake pipe 10. Oxygen concentration sensor 24: Provided in the exhaust manifold 15 to detect the residual oxygen concentration in the exhaust gas. Rotation angle sensor 25: mounted inside the distributor 17, and every 1/24 rotation of the cam shaft of the distributor 17, that is, every integer multiple of 0 ° CA (crank angle) to 30 ° CA of the crankshaft (not shown). The rotation angle signal (pulse) is output to. It also serves as a rotation speed sensor of the engine 1.・ Cylinder discrimination sensor 26: Similarly, distributor 17
The reference signal (pulse) for cylinder discrimination is output once for each rotation of the cam shaft of the distributor 17, that is, for every two rotations of a crankshaft (not shown). -Vehicle speed sensor 28: Generates a pulse corresponding to the rotation of the wheel through the signal rotor 27 provided on the axle of the vehicle on which the engine 1 is mounted.

All outputs from these sensors are input to the electronic control unit 30. The electronic control device 30 is basically a device that drives the fuel injection valve 9 and the igniter 16 based on the output contents of these sensors to control the operation of the engine 1.

Next, the configuration of the electronic control unit 30 will be described with reference to FIG. As shown in FIG. 2, the electronic control unit 30 outputs the outputs of the microcomputer 310 and the various sensors to the microcomputer 310.
It is mainly configured by a circuit for pre-processing for taking in the engine and a circuit for processing the drive command output from the microcomputer 310 to drive the fuel injection valve 9 and the igniter 16.

Here, the microcomputer 310 itself is configured as a logical operation circuit basically including a CPU 311, a ROM 312, a RAM 313 and a backup RAM 314.

Of these, the CPU 311 inputs the outputs of the various sensors according to a control program, executes a predetermined calculation based on the control program, and issues a control command for driving the fuel injection valve 9 and the igniter 16. This is the part to output.

The ROM 312 is a read-only memory in which the control program, initial data, etc. are stored in advance, and the RAM 313 is required for executing the various sensor outputs that are input and for executing calculations or controls. This is a memory in which data is temporarily stored.

The backup RAM 314 is a non-volatile RAM (random access memory) backed up by a battery. Data that is continuously used even after the key switch (not shown) is turned off and the power supply to the control device is stopped is the backup RAM.
314 will be stored.

In the microcomputer 310, the input / output port 315 and the input port 316 both output the outputs of the various sensors.
This is a part to be incorporated into 10.

On the other hand, the output port 317 is connected to the CPU 311.
The fuel injection valve 9 and the igniter 16 generated through
Is a part for outputting a drive command to the outside. Inside the microcomputer 310, the CPU 311, the ROM 312, and the RA that constitute the logical operation circuit are included.
The M313 and the backup RAM 314 are electrically and logically connected to the ports 315 to 317 by a common bus 318.

The clock generator 319 supplies the operation clock CK to each section of the microcomputer 310.
Is the part that supplies. In the electronic control unit 30, buffer circuits 321 to 324, a multiplexer 325, and A / are used as circuits for preprocessing the outputs of the various sensors to the microcomputer 310.
D converter 326, buffer 331, comparator 33
2, and there are waveform shaping circuits 333 and 334.

Here, the multiplexer 325 includes the intake pipe pressure sensor 23, the water temperature sensor 20, and the intake temperature sensor 2 which are respectively input to the buffer circuits 321 to 324.
1 and each output of the throttle position sensor 22, and an output (voltage between terminals) of a thermistor 352, which will be described later, are selected and output based on a command from the microcomputer 310. The selected sensor output or the output of the thermistor 352 is input to the A / D converter 326.

The A / D converter 326 outputs the input sensor output or the output of the thermistor 352 based on the command from the microcomputer 310.
It is a circuit for performing / D (analog / digital) conversion. The output of each sensor and the output of the thermistor 352 are thus converted into digital signals, and the input / output port 3
It will be taken into the microcomputer 310 via 15.

On the other hand, the comparator 332 is a circuit for generating a binarized signal indicating rich or lean based on the comparison between the output of the oxygen concentration sensor 24 input to the buffer circuit 331 and a predetermined reference voltage. . The generated binarized signal is a signal used as a monitor signal in the air-fuel ratio feedback control, and is taken into the microcomputer 310 via the input port 316.

The waveform shaping circuit 333 is a circuit for shaping the output signal waveforms of the cylinder discrimination sensor 26 and the rotation angle sensor 25 into binary pulse signal waveforms. Each of these waveform shaping signals is also taken into the microcomputer 310 via the input port 316.

The waveform shaping circuit 334 is a circuit which similarly shapes the output signal waveform of the vehicle speed sensor 28 into a binary pulse signal waveform. The waveform-shaped signal is also similarly input to the microcomputer 3 via the input port 316.
Taken in 10.

In the electronic control unit 30, a drive circuit 341 and a drive circuit 34 are provided as circuits for processing the drive command output from the microcomputer 310 to drive the fuel injection valve 9 and the igniter 16, respectively.
There are two.

Of these, the drive circuit 341 is a circuit for driving the fuel injection valve 9 for a predetermined time based on a drive command (time signal corresponding to the fuel injection amount) output from the microcomputer 310. In the engine 1 shown in FIG. 1, the amount of fuel pumped from a fuel pump (not shown) is proportional to the opening time of the fuel injection valve 9,
It is injected and supplied into the intake manifold 8.

The drive circuit 342 is a circuit for controlling the energization of the igniter 16 based on a drive command (ignition signal) output from the microcomputer 310 to drive (spark) the spark plug.

In the drive circuit 341, a considerably large current flows through the transistor because the flyback energy generated when the fuel injection valve 9 is turned off is absorbed by the transistor for driving the same. As described above, there is a possibility that the temperature range which is the limit of use of these elements may be exceeded.

Therefore, in the device of the first embodiment, a thermistor 352 is arranged near the output transistor of the drive circuit 341 as shown in FIG.
The ambient temperature is monitored based on the voltage between the two terminals. The thermistor 352 is a resistor 3
51 is pulled up to the power supply voltage potential of the A / D converter 326, and the potential of the connection point with the resistor 351 thus pulled up is the output voltage of the thermistor 352 via the multiplexer 325 and the A / D converter. It is designed to be taken in by 326.

Next, with reference to FIGS. 3 and 4, a circuit example of the drive circuit 341 and a physical positional relationship between the output transistor and the thermistor 352 will be described. FIG.
In addition, the drive circuit 341 and the fuel injection valve 9 driven by the drive circuit 341 (here, the exciting coil 91
(Only shown) is shown.

As shown in FIG. 3, the drive command output from the microcomputer 310 to the drive circuit 341 is amplified by the drive transistor 3413 and then the base of the power transistor (output transistor) 3417. Applied to the electrodes.

On the other hand, the fuel injection valve exciting coil 91 to which the power supply voltage + B is applied is connected to the other end of the collector electrode of the power transistor 3417. For this reason, the output of the drive transistor 3413 is applied to the base electrode of the power transistor 3417, and the exciting coil 91 is energized and the fuel injection valve 9 is opened only while the transistor 3417 is on. You will be told. As described above, the fuel pumped from the fuel pump is injected and supplied into the intake manifold 8 by an amount proportional to the valve opening time of the fuel injection valve 9.

In the drive circuit 341, the Zener diode 3415 is used as the power transistor 34.
The high voltage (flyback voltage) generated due to the fuel injection valve exciting coil 91, which is an inductance load when 17 is turned off, is applied to the collector electrode of the transistor 3417.
This is a so-called flyback diode that clamps below the withstand voltage between the emitter electrodes.

When a plurality of the fuel injection valves 9 are provided, the transistors 3413 and 3417, the flyback diode 3415, the resistors 3411 and 3412, and the resistors 3411 and 3412 are provided corresponding to the respective fuel injection valves 9.
Circuits comprising 3414 and 3416 will be provided in parallel.

Now, for the power transistor 3417 of the driving circuit 341, the thermistor 352 is used.
Are arranged in the electronic control unit 30 in the manner shown in FIG.

FIG. 4 shows an overview of the electronic control unit 30 described above, and in FIG.
Is a case of the device 30, reference numeral 302 is a connector used for connection with an external harness, reference numeral 303 is a printed circuit board on which various circuits and elements shown in FIG. 2 are mounted, and reference numeral 304 is these circuits and elements. Shown are covers for protecting the components from dust and the like.

The electronic control unit 30 having such an overview
In the above, assuming that the above-mentioned respective elements constituting the drive circuit 341 are mounted on the printed circuit board 303 in the manner shown in FIG. 4 including the resistors 3411, 3412, 3414, and 3416, the thermistor 352 and The pull-up resistor 351 is mounted near the pull-up resistor 351 in the manner shown in FIG. Especially the thermistor 352
In order to monitor and measure the ambient temperature of the power transistor 3417 (herein, the type in which the flyback diode 3415 is integrally packaged) is monitored and measured as accurately as possible, for example, 1 cm from the transistor 3417 is used.
Shall be installed within.

FIG. 5 shows the power transistor 3417.
Voltage and current chart of
With reference to FIG. 5 in combination, the power generated from the transistor 3417 and the allowable value of the monitored ambient temperature will be considered.

The drive circuit 341 shown in FIG.
As also shown, the transistor 3413 is turned on when the drive command output from the microcomputer 310 becomes the logic L (low) level, and the base current is supplied to the power transistor 3417.

By supplying the base current in this way, the power transistor 3417 is turned on and the collector-emitter voltage VCE becomes a small value.
As shown in FIG. 5B, a voltage VCEsat called a saturation voltage is generated.

At this time, the power transistor 34
A collector current (IC) as shown in FIG. 5C flows through the collector electrode of 17. FIG. 5
In (c), the current value ICO is the collector current IC
Shows the saturation value of.

Further, as shown in FIGS. 5A and 5D, if the period of the drive command, that is, the on period of the power transistor 3417 is TO, and the energization time to the transistor 3417 at that time is T, then T. , The on-duty Don is expressed as Don = (T / TO).

Therefore, the power transistor 34 is
The power generated from the transistor 3417 when 17 is on (hereinafter referred to as on-time power) is given by the following equation when Pon is used. Pon = VCEsat × ICO × Don (1) On the other hand, when the drive command output from the microcomputer 310 becomes the logical H (high) level, the transistor 3
413 is turned off, and the supply of the base current to the power transistor 3417 is also cut off.

By shutting off the base current in this way, the power transistor 3417 tends to turn off. However, since the fuel injection valve exciting coil 91 has an inductance component, the collector electrode of the transistor 3417 has the above-mentioned fly. Back voltage is generated. And
This flyback voltage is the Zener voltage VZ of the flyback diode (Zener diode) 3415.
When the voltage exceeds about 60V, for example, current is supplied to the base electrode of the transistor 3417 through the diode 3415. That is, during that time, the same transistor 3417 is maintained in the ON state,
The collector-emitter voltage VCE is 0 when the current due to the inductance component of the fuel injection valve exciting coil 91 is 0.
Until it becomes clamped at the Zener voltage VZ. This state is also shown in FIG.

During this period, if the engine speed per unit time is NE, the power generated in the power transistor 3417 during the same period, that is, when the power transistor 3417 is to be turned off (hereinafter referred to as "off-time power"), is , And when this is Poff, the following equation is obtained. Poff = VZ × ∫_ (0) ^ (Tfb) ICdt × NE (2) Here, “∫_ (0) ^ (Tfb)” is the integral from time “0” to time “Tfb”. It means that the time "Tfb" is
As shown in FIG. 5C, this is the time required for absorbing (clamping) the flyback energy.

As described above, according to the equations (1) and (2), the average value of the power generated in the power transistor 3417 is: P = Pon + Poff = VCEsat × ICO × Don + VZ × ∫_ (0) ^ (Tfb) ICdt × NE (3)

According to the equation (3), the larger the (A) collector current IC, that is, the higher the power supply voltage + B, the larger the generated power P of the power transistor 3417 becomes. Alternatively, (B) on-duty Don (=
The larger T / TO), the more power transistor 3417
Generated power P becomes large. Alternatively, (C) the higher the engine speed NE, the larger the power P generated by the power transistor 3417. I understand that.

Continuing, the power transistor 3
The permissible ambient temperature of the transistor 3417 that is naturally determined based on the generated power P of 417 will be considered. Now, each element of the equation (3) is (a) VCEsat (collector-emitter saturation voltage)
= 0.2V, (b) ICO (collector current saturation value) = 1.5A, (c) + B (fuel injection valve power supply voltage) = 16V, (d) resistance value of fuel injection valve exciting coil 91 = 10.5
Ω, (e) Don (on duty) = 90%, (f) VZ (zener voltage) = 60 V (g) VZ × ∫_ (0) ^ (Tfb) ICdt = 5 mJ (W ·
s) (h) NE (engine speed per unit time) = 70
Assuming a value such as 00 rpm, the generated power P of the power transistor 3417 is P = Pon + Poff = 0.27W + 0.58W = 0.
It becomes 85W.

Here, if the same power transistor 341
If the maximum rating of the junction temperature of No. 7 is 150 ° C. and the thermal resistance at the junction one ambient temperature is 80 ° C./W, then the transistor 3
The allowable ambient temperature of 417 is 150 ° C.-80 ° C./W×0.85 W = 82 ° C.

That is, the power transistor 341 described above.
When the generated power P of No. 7 is 0.85 W, the operating limit temperature range is not exceeded until the ambient temperature reaches 82 ° C., and the safety of the transistor 3417 is guaranteed.

A method of monitoring the ambient temperature of the power transistor 3417 through the thermistor 352 will be described with reference to FIGS. 6 and 7. The thermistor 352 has a resistance (Rx) -temperature (Ta) characteristic of Rx = 2.45 * EXP [3500 * {(1 / (273 + Ta))-(1/293)}] (4).

Here, for example, the pull-up resistor 351 is used.
Is 1 kΩ and the power supply voltage of the A / D converter 326 is 5 V, the input voltage of the A / D converter 326 with respect to the output of the thermistor 352 is input voltage = 5 V × {Rx / (1 + Rx )}, And the characteristics are as shown in FIG.

In the apparatus of this embodiment, the thermistor 352
On the basis of these characteristics of (1), the relationship between the input voltage and the temperature Ta is mapped in the manner shown in FIG. 7, for example, and is stored in the ROM 312 or the backup RAM 314 in advance. Then, the temperature Ta obtained by performing map calculation in the mode shown in FIG. 7 on the basis of the respective values A / D processed by the A / D converter 326 is monitored as the ambient temperature of the power transistor 3417 to be monitored. I am trying.

The fuel cut judgment value changing process executed in the apparatus of the first embodiment under the monitoring of the ambient temperature of the power transistor 3417 in such a mode will be described in detail below.

The predicted maximum temperature in the electronic control unit 30 (ambient temperature of the transistor 3417) is set to 90.
C., under the operating conditions illustrated as the above (a) to (h) of the engine 1, the transistor 3417 exceeds the allowable value of the junction temperature in the range of 82 to 90.degree.
There is a possibility of destruction.

Therefore, in the device of the first embodiment, by lowering the fuel cut rotation speed at the time of high rotation in accordance with the ambient temperature to be monitored, it is possible to prevent the transistor 3417 from being heated beyond its allowable value. To prevent.

That is, the fuel cut (F /
C) The rotation speed is set according to the maximum rotation speed allowed by the engine 1. However, if the rotation speed is lowered according to the ambient temperature, the power P generated by the transistor 3417 is naturally limited. Therefore, it is possible to prevent heating exceeding the allowable value.

The specific method will be described below. Here, first, the permissible generated power at the predicted maximum temperature of 90 ° C. in the electronic control unit 30 is obtained. As mentioned above,
Maximum rating of junction temperature of power transistor 3417 is 1
If the thermal resistance at 50 ° C. and the ambient temperature of the junction is 80 ° C./W, this is (150 ° C.-90 ° C.) ÷ 80 ° C./W=0.75 W.

Then, in order to suppress the generated power P of the transistor 3417 to 0.75 W, and when the on-time power Pon of the transistor 3417 does not change at this time, it is turned off from the equation (3). Hour power Po
It is necessary to set ff to Poff ≦ 0.48W (= 0.75W−0.27W). For this purpose, the engine speed NE should be NE = 7000 rpm × (0.48 W / 0.58 W) ≈5800 rpm or less. That is, if the engine speed NE is set to 5800 rpm or less, even if the ambient temperature of the transistor 3417 reaches 90 ° C., the transistor 3417 will not be heated beyond its allowable value.

FIG. 8 shows a fuel cut judgment value changing routine executed by the device of the first embodiment based on such a principle. The routine is registered in advance in the ROM 312 and is activated by, for example, a time interrupt every 16 ms.

That is, if the routine is started now, the electronic control unit 30 first causes the thermistor 35 through the multiplexer 325 and the A / D converter 326.
The output of 2 (A / D converter input voltage) is taken in. Then, based on the map shown in FIG. 7, the ambient temperature is calculated from the captured value, and it is determined whether the calculated ambient temperature is equal to or higher than the limit value (82 ° C. in this example) (step S101). ).

As a result, when it is determined that the calculated ambient temperature does not reach the limit value, the process is finished as it is. On the other hand, when it is determined that the calculated ambient temperature is equal to or higher than the limit value, for example, the determination value 7000 rpm
The high speed fuel cut rotation speed of the engine 1 set to the above is reduced to the above rotation speed of 5800 rpm (step S
102).

This high rotation fuel cutoff determination value is usually loaded from the ROM 312 to the RAM 313,
Alternatively, it is stored in the backup RAM 314 and referred to when the fuel cut control is executed.

Therefore, by reducing and updating the judgment value in this way, the electronic control unit 30 completely prohibits fuel injection at a rotational speed equal to or higher than the updated value, and the engine rotational speed is also increased. It will not rise above the updated value. As described above, if the maximum engine speed is limited, the electric power P generated by the transistor 3417 is naturally limited, and heating exceeding the permissible value can be prevented. .

As described above, according to the device of the first embodiment, the power transistor (output transistor) for driving the fuel injection valve 9 to which the flyback diode is connected is mounted on the radiation fin, or Even if an expensive transistor having heat resistance is not used as the transistor, heat generation beyond the temperature range for which it can be used can be properly suppressed.

Therefore, it becomes possible to surely protect those elements in the unlikely event that the heat radiation is not costly. Further, according to the above-described fuel cutoff determination value changing process by the device of the first embodiment, such element protection can be realized without any influence on the normal running of the vehicle.

Further, in the device of the embodiment, the thermistor is arranged in the vicinity of the transistor to be monitored, and the ambient temperature of the transistor is calculated based on the output of this thermistor. The temperature can be monitored directly and easily.

(Second Embodiment) FIGS. 9 and 10 show a second embodiment of the electronic control unit for an engine according to the present invention.

The apparatus of the second embodiment is an electronic control unit for an engine in which a drive circuit for a fuel injection valve is built in, and the ambient temperature is monitored through a thermistor arranged near the output transistor of the drive circuit. However, when the temperature becomes equal to or higher than a predetermined value, the fuel injection to the engine is thinned out by a predetermined short time.

However, even in the device of the second embodiment, the configuration shown in FIGS. 1 to 7 or the characteristics of the thermistor 352 and the power transistor 3417 are common to the device of the first embodiment. However, duplicate explanations of common elements are omitted.

Hereinafter, the power transistor 3 in the above-mentioned mode
The fuel injection thinning control executed in the apparatus of the second embodiment under the monitoring of the ambient temperature of 417 will be described in detail. For example, assuming that the allowable ambient temperature of the transistor 3417 is 82 ° C. and the predicted maximum temperature in the electronic control unit 30 is 90 ° C., the transistor 3417 has its junction in the range of 82 to 90 ° C. As described above, there is a possibility that the temperature may exceed the allowable value and the temperature may be destroyed.

In the device of the second embodiment, therefore, the fuel injection into the engine is controlled by thinning out for a predetermined short time to prevent the transistor 3417 from being heated beyond its allowable value.

That is, if the fuel injection to the engine is thinned out for a predetermined short period of time, the engine speed can be reduced without significantly affecting the operation of the engine, and thus the transistor 3417 can be reduced. It becomes possible to limit the generated power P.

The specific method will be described below. Here, first, 100 m according to the timing routine shown in FIG.
Repeat the timing of s.

This time counting routine is activated by a time interrupt every 1 ms, and each time the routine is activated, the electronic control unit 30 (CPU 311) increments the count value TC of the time counting counter (step S201). ).

As a result of this increment, if the count value TC is less than "100", the routine is exited (step S202). On the other hand, if the count value TC is greater than or equal to "100" as a result of the increment, the count value TC is reset to "0" and the routine exits (steps S202 and S203).

By repeating such a time counting routine, the count value TC of the time counting counter is “1” → “2” → “3” ... “100” → “1” → “2” every 1 ms.
The increment is repeated in such a mode. Note that this timing routine is executed by the ROM 312.
It is registered in advance in (FIG. 2).

On the other hand, the electronic control unit 30 (CPU 31
In 1), the fuel injection thinning-out routine shown in FIG. 10 is executed in parallel with such a timing routine. The fuel injection thinning-out routine is similar to the time counting routine in the ROM.
It is registered in advance in 312. However, it is assumed that the routine is started and executed at each fuel injection timing for each cylinder of the engine 1.

If the routine is started, the electronic control unit 30 operates the multiplexer 32 as described above.
5 and the A / D converter 326, the output of the thermistor 352 is taken in, and the ambient temperature is calculated from the value obtained based on the map shown in FIG. 7, and the calculated ambient temperature is a limit value (an example here). Then, it is determined whether the temperature is 82 ° C. or higher (step S211).

As a result, when it is determined that the calculated ambient temperature does not reach the limit value, the well-known normal fuel injection operation is executed (step S212). On the other hand, when it is determined that the calculated ambient temperature is equal to or higher than the limit value, the count value TC of the clock counter is referred to, and it is determined again whether the same value TC is “0 ≦ TC ≦ 30”. Yes (step S213).

As a result, the count value TC is "0≤T
When it is determined that the value is out of the range of “C ≦ 30”, the normal fuel injection operation is similarly executed (step S212).

On the other hand, if the count value TC is "0≤TC≤3.
If it is determined that it is "0", the fuel injection operation to be executed at that time is forcibly stopped (step S21).
4). By executing such a fuel injection thinning-out routine, when the calculated ambient temperature becomes equal to or higher than the limit value, the fuel injection is stopped (cut) for 100 ms for 30 ms. The engine speed will also decrease.

When the engine speed decreases in this way, the electric power P generated by the transistor 3417 is naturally limited, and in turn heating exceeding the allowable value can be prevented.

As described above, also according to the device of the second embodiment, the power transistor (output transistor) of the drive circuit 341 is mounted on the heat radiation fin, or an expensive heat resistant transistor is used as the transistor. Even if it does not occur, heat generation beyond the temperature range for which it can be used can be properly suppressed.

Therefore, even in the device of the same embodiment, it is possible to surely protect those elements in the unlikely event that the heat dissipation is not costly. (Third Embodiment) FIG. 11 shows a third embodiment of the electronic control unit for an engine according to the present invention.

The device of the third embodiment is an electronic control unit for an engine in which a drive circuit for a fuel injection valve is built in, and the ambient temperature is monitored through a thermistor arranged near the output transistor of the drive circuit. However, when the temperature is equal to or higher than a predetermined value, the fuel injection to the arbitrary cylinder of the engine is stopped, that is, the device is configured to perform the cylinder reduction control.

Further, even in the device of the third embodiment,
The configuration shown in FIGS. 1 to 7 or the thermistor 35.
2 and the characteristics of the power transistor 3417 are common to the device of the first or second embodiment, and redundant description of the common elements will be omitted.

Hereinafter, the power transistor 3 in the above-mentioned mode
The cylinder cut-off control executed in the apparatus of the third embodiment under the monitoring of the ambient temperature of 417 will be described in detail. As described above, when the allowable ambient temperature of the transistor 3417 is 82 ° C. and the predicted maximum temperature in the electronic control unit 30 is 90 ° C., for example, 82 to 9
In the range of 0 ° C., the transistor 3417 may exceed its allowable junction temperature and may be destroyed.

Therefore, in the device of the third embodiment, when the fuel is injected into the engine, by stopping the fuel injection into any cylinder of the engine, the transistor 3417 is heated beyond its allowable value. Prevent.

That is, if the cut-off cylinder control is executed in this manner, for example, in the case of a four-cylinder engine, a specific 2
By forcibly stopping the fuel injection to the cylinders or to any two randomly determined cylinders, the generated torque becomes about 1/2. Therefore, also in this case, the high rotation operation of the engine 1 can be favorably limited, and the electric power P generated by the transistor 3417 can be limited accordingly.

The specific method will be described below. In the device of the third embodiment, the electronic control unit 30 (CPU
311) executes the cut-off cylinder control routine shown in FIG. This cut-off cylinder control routine is also started and executed at each fuel injection timing for each cylinder of the engine 1, and is registered in the ROM 312 in advance.

If the routine is started, the electronic control unit 30 operates the multiplexer 32 as described above.
5 and the A / D converter 326, the output of the thermistor 352 is taken in, and the ambient temperature is calculated from the value obtained based on the map shown in FIG. 7, and the calculated ambient temperature is a limit value (an example here). Then, it is determined whether the temperature is 82 ° C. or higher (step S301).

As a result, when it is determined that the calculated ambient temperature does not reach the limit value, the well-known normal fuel injection operation is executed for all the cylinders regardless of the cylinder. (Step S302).

On the other hand, when it is determined that the calculated ambient temperature is equal to or higher than the limit value, (1) if the cylinder is the first or third cylinder, the fuel injection to those cylinders is forcibly stopped. (2) If the cylinder is the second or fourth cylinder, the fuel injection to those cylinders is executed normally. Such a cylinder reduction control is executed (step S303).

When such a cut-off cylinder control is executed, as described above, the generated torque becomes about 1/2, and the high rotation operation of the engine 1 is naturally restricted. If the high-speed operation of the engine 1 is restricted in this way, the electric power P generated by the transistor 3417 is naturally restricted, and in turn, heating exceeding its allowable value can be prevented.

As described above, also in the device of the third embodiment, as in the device of the first or second embodiment, the output transistor of the drive circuit 341 is mounted on the radiation fin, or the same transistor is used. As a result, even if an expensive transistor having heat resistance is not used, it is possible to accurately suppress heat generation beyond the temperature range for which it is used.

(Fourth Embodiment) FIG. 12 shows a fourth embodiment of the electronic control unit for an engine according to the present invention. The device of the fourth embodiment is an electronic control unit for an engine in which a drive circuit of a fuel injection valve is built in, and monitors its ambient temperature through a thermistor arranged near the output transistor of the drive circuit, It is configured as a device that reduces the amount of fuel injection into the engine when the temperature exceeds a predetermined value.

Further, even in the device of the fourth embodiment,
The configuration shown in FIGS. 1 to 7 or the thermistor 35.
The characteristics of No. 2 and the power transistor 3417 are common to the devices of the first to third embodiments, and redundant description of the common elements will be omitted.

Hereinafter, the power transistor 3 in the above-mentioned mode
The injection amount reduction control executed in the apparatus of the fourth embodiment under the monitoring of the ambient temperature of 417 will be described in detail.
For example, assuming that the allowable ambient temperature of the transistor 3417 is 82 ° C. and the predicted maximum temperature in the electronic control unit 30 is 90 ° C., the transistor 3417 has its junction in the range of 82 to 90 ° C. It has already been mentioned that there is a possibility that the temperature may be exceeded and the temperature may be exceeded.

Therefore, in the device of the fourth embodiment, when the fuel is injected into the engine, the amount of fuel injected into each cylinder of the engine is reduced so that the transistor 3417 is heated above its allowable value. Prevent that.

That is, when the fuel injection amount is reduced by 20% from the proper amount, the generated torque is also reduced accordingly. Therefore, also in this case, the maximum rotation speed of the engine 1 can be limited, and by extension, the transistor 3
It becomes possible to limit the generated power P of 417.

The specific method will be described below. In the device of the fourth embodiment, the electronic control unit 30 (CPU
311) executes the injection amount reduction routine shown in FIG. It is assumed that this injection amount reduction routine is started and executed after the calculation of the fuel injection amount for the engine 1. This is also registered in the ROM 312 in advance.

If the routine is started, the electronic control unit 30 operates the multiplexer 32 as described above.
5 and the A / D converter 326, the output of the thermistor 352 is taken in, and the ambient temperature is calculated from the value obtained based on the map shown in FIG. 7, and the calculated ambient temperature is a limit value (an example here). Then, it is determined whether the temperature is 82 ° C. or higher (step S401).

As a result, when it is determined that the calculated ambient temperature does not reach the limit value, the routine directly exits. On the other hand, when it is determined that the calculated ambient temperature is equal to or higher than the limit value, the fuel injection amount is set to a value that is 20% less than the appropriate fuel injection amount calculated by the well-known method. The data about the same fuel injection amount registered in the predetermined area of the RAM 313 is updated (step S402).

When such reduction control of the fuel injection amount is executed, the generated torque is reduced according to the reduced amount, and the maximum rotation speed of the engine 1 is naturally limited.

If the maximum engine speed of the engine 1 is limited in this way, the electric power P generated by the transistor 3417 is naturally limited, and in turn, heating exceeding its allowable value can be prevented.

As described above, also in the device of the fourth embodiment, the output transistor of the drive circuit 341 is mounted on the radiation fin or the same transistor as the device of the first to third embodiments. As a result, even if an expensive transistor having heat resistance is not used, it is possible to accurately suppress heat generation beyond the temperature range for which it is used.

(Fifth Embodiment) Next, a fifth embodiment of the electronic control unit for an engine according to the present invention will be described.

The device of the fifth embodiment is an electronic control unit for an engine in which a drive circuit for a fuel injection valve is built in, and monitors its ambient temperature through a thermistor arranged near the output transistor of the drive circuit. However, when the temperature becomes equal to or higher than a predetermined value, the intake throttle valve of the engine, that is, the throttle valve is configured to be forcibly driven to the side where the intake amount is suppressed.

The device of the fifth embodiment basically has the same structure as the device of the first to fourth embodiments, but in the case of the device of the fifth embodiment. Particularly, it is assumed that the electronic control unit 30 can control the opening degree of the throttle valve 12 shown in FIG.

That is, in the device of the fifth embodiment, when it is determined that the ambient temperature calculated as described above is equal to or higher than the limit value, the electronic control unit 30 controls the intake air amount to the engine to be suppressed. The maximum rotational speed of the engine is limited by forcibly driving the opening of the throttle valve 12.

Therefore, also in the device of the fifth embodiment, the operating temperature limit range of the power transistor (output transistor) 3417 of the drive circuit 341 is in a manner similar to the devices of the above-described first to fourth embodiments. It will be possible to accurately suppress heat generation beyond.

In addition, in addition to the configuration of the device of the fifth embodiment, in a known engine equipped with a sub-throttle, the opening of the sub-throttle may be controlled in the above manner. it can.

(Sixth Embodiment) In the first to fifth embodiments, the thermistor 352 is used to control the electronic control unit 3.
Although the ambient temperature of 0 (power transistor 3417) is monitored, if there is another diode driven by a constant current, the ambient temperature can be monitored based on the forward voltage.

13 to 16 show a sixth embodiment of the electronic control unit for an engine according to the present invention, in which the ambient temperature is monitored based on the forward voltage of the diode driven by the constant current. An example of an apparatus is shown.

In the device of the sixth embodiment, as shown in FIG. 13 and FIG. 14, in the waveform shaping circuit 334 of the vehicle speed sensor 28 as the diode driven by the constant current, the sensor signal thereof is set to 2 A diode 3342 that generates a comparison reference potential for quantifying is diverted. The forward voltage VF of the diode 3342 is applied to the multiplexer 3
25 to be taken into the A / D converter 326. The other configuration of the electronic control unit 30 shown in FIG. 13 is the same as that of the electronic control unit 30 shown in FIG.
The duplicate explanation here is omitted.

First, the outline of the waveform shaping circuit 334 will be described with reference to FIG. As shown in FIG. 14, the waveform shaping circuit 334 uses the diode 3342.
Besides, a resistor 3341 connected in series with the diode 3342 and having a power supply voltage applied to the other end, a comparator 3344, and an input resistance 3 of the comparator 3344.
343, and the output resistance 334 of the comparator 3344.
It is configured with 5 each.

In the waveform shaping circuit 334, since it is difficult to compare the power source voltage or less by the comparator 3344, the diode 3342 is used to generate a voltage floating from the ground potential by the forward voltage VF. Then, the output signal of the vehicle speed sensor (pickup coil) 28 is input to the non-inverting input terminal (+ terminal) of the comparator 3344 in a state where the potential of the inverting input terminal (-terminal) is floated by the voltage VF. A binary pulse signal having a cycle corresponding to the rotation speed of the wheel is output from the comparator 3344.

According to such a waveform shaping circuit 334,
Basically, only a current flows through the diode 3342, which is determined by the resistance value of the resistor 3341 connected in series with the diode 3342 and its applied voltage.

Therefore, in the device of the sixth embodiment, based on the forward voltage VF-temperature characteristic of the diode 3342 which is thus driven by the constant current, the temperature in the electronic control unit 30, that is, the power transistor 3417 (see FIG. 3,
The ambient temperature (Fig. 4) is monitored.

FIG. 15 shows a VF (forward voltage) -temperature characteristic when the diode 3342 is driven at a constant current. The diode 3342 ideally has the characteristics shown by the solid line in FIG. Therefore, if the resolution of the A / D converter 326 is 5 mV, the ambient temperature can be monitored with a resolution of about 3 ° C.

However, normally, there is a variation in the VF-current characteristics of the diode. The variation in the VF-current characteristic also causes variation in the VF-temperature characteristic in the manner shown by the broken line in FIG. 15, making accurate temperature measurement based on the voltage VF difficult.

Therefore, in the apparatus of the sixth embodiment, as shown in FIG.
The above variation is calibrated through the calibration / temperature-control routine shown in (1) to obtain an accurate temperature based on the calibrated characteristics. Note that this calibration / temperature-increasing routine is shown in FIG.
16 is registered in advance in the ROM 312 shown in FIG.
It shall be activated by a time interrupt every ms.

In the apparatus of the sixth embodiment, the electronic control unit 30 (CPU 311) first starts (1) in order to avoid the influence of the voltage fluctuation after turning on the power supply + B, In step S501, it is determined whether it is within a predetermined time (for example, 1 second) after the power is turned on. (2) Next, in step S502, it is determined whether the cooling water temperature and the intake air temperature are both in the range of 0 to 30 ° C. (3) Further, in step S503, it is determined whether or not the difference between the cooling water temperature and the intake air temperature is within 3 ° C. (4) Then, in step S504, the engine speed N
It is determined whether E is 0 rpm. When all the conditions (1) to (4) are satisfied, it is considered that the entire vehicle is at a constant temperature, and the next VF (forward voltage) is determined.
Perform the calibration process of.

In the calibration process, the electronic control unit 30
First, in step S511, the (CPU 311) converts the forward voltage VF of the diode 3342 into the A / D converter 3.
Read through 26.

At the time when all the above conditions (1) to (4) are satisfied, the diode 3
Since the temperature of 342 is also considered to be equal to the cooling water temperature, the ideal value of the forward voltage VF is obtained from this cooling water temperature based on the characteristics of FIG. For example, assuming that the cooling water temperature = intake air temperature = 10 ° C., the ideal forward voltage VF is “0.7” due to the characteristics of FIG.
2 "V.

The electronic control unit 30 having obtained the ideal value for the forward voltage VF in this way next determines, in step S512, the difference between the ideal value for the forward voltage VF and the actually measured value read as the offset voltage. Obtained and stored in the backup RAM 314 (FIG. 13). For example, the measured value of the read forward voltage VF is “0.
73 "V, the ideal value is" 0.72 "V
The difference “−0.01” V from the above is stored in the backup RAM 314 as an offset voltage.

On the other hand, if any one of the above conditions (1) to (4) is not satisfied, the electronic control unit 30 executes the temperature-increasing process after step S521. That is, in this temperature-increasing process, the electronic control unit 30 (CPU 31
1) First, in step S521, the forward voltage VF of the diode 3342 is converted to the A / D converter 32 in the same manner as described above.
Read through 6.

Then, in the next step S522, the read forward voltage VF is calibrated based on the stored offset voltage. For example, if the measured value of the read forward voltage VF is "0.7" V, the calibration value is "0.69" by adding the offset voltage "-0.01" V to this value. It becomes V.

The electronic control unit 30 that has obtained the calibration value for the forward voltage VF in this manner further proceeds to step S52.
At 3, the temperature to be monitored is obtained from this calibration value based on the ideal characteristics shown in FIG. In this example, a temperature of 25 ° C. is obtained as the ambient temperature based on the calibration value “0.69” V.

As described above, according to the apparatus of the sixth embodiment, the ambient temperature can be accurately obtained without providing a thermistor dedicated to temperature measurement as in the apparatus of the first to fifth embodiments. Will be able to.

Even in the apparatus of the sixth embodiment, however, after the ambient temperature is obtained in this way, based on comparison with the limit value (82 ° C. in the above example), the first to the first In a manner similar to that of the device of the fifth embodiment, the processing for limiting the power generated by the power transistor 3417 is executed, such as limiting the fuel cut rotation speed of the engine 1 or limiting the maximum rotation speed. .

In the device of the sixth embodiment, the vehicle speed sensor 2 is used as the diode for monitoring the ambient temperature.
Diode 3 used in the waveform shaping circuit 334 of FIG.
Although the 342 is used, the selection of the diodes to be used is arbitrary as long as it is driven by a constant current.

Further, for example, the ambient temperature monitoring diode may be added separately. In this case, although a little economically disadvantageous, it is possible to select the arrangement with a high degree of freedom, such as arranging the diode closer to the power transistor 3417.

(Seventh Embodiment) In the first embodiment, each element of the equation (3) is (a) VCEsat (collector-emitter saturation voltage).
= 0.2V, (b) ICO (collector current saturation value) = 1.5A, (c) + B (fuel injection valve power supply voltage) = 16V, (d) resistance value of fuel injection valve exciting coil 91 = 10.5
Ω, (e) Don (on duty) = 90%, (f) VZ (zener voltage) = 60 V (g) VZ × ∫_ (0) ^ (Tfb) ICdt = 5 mJ (W ·
s) (h) NE (engine speed per unit time) = 70
The power P generated by the power transistor 3417 was calculated by assuming a value such as 00 rpm (P = 0.85 W).

However, the power supply voltage + B is, for example, 1
Even when the voltage is 4.0 V or less, the engine 1 operates normally. In this case, each element of the equation (3) is (a) VCEsat (collector-emitter saturation voltage)
= 0.2V, (b) ICO (collector current saturation value) = 1.3A, (c) + B (fuel injection valve power supply voltage) = 14V, (d) resistance value of fuel injection valve exciting coil 91 = 10.5
Ω, (e) Don (on-duty) = 90%, (f) VZ (zener voltage) = 60 V (g) VZ × ∫_ (0) ^ (Tfb) ICdt = 4.4 mJ (W
-S) (h) NE (engine speed per unit time) = 70
Assuming a value such as 00 rpm, the power P generated by the power transistor 3417 is P = Pon + Poff = 0.23W + 0.51W = 0.
It becomes 74W.

Therefore, here again, assuming that the maximum rating of the junction temperature of the power transistor 3417 is 150 ° C. and the thermal resistance of the junction one ambient temperature is 80 ° C./W, the ambient temperature allowed for the transistor 3417 is the same. Is 150 ° C.-80 ° C./W×0.74 W = 90 ° C.

The temperature of 90 ° C. is the predicted maximum temperature in the electronic control unit 30 (the transistor 341 described above).
Ambient temperature of 7), which is equal to 90 ° C. That is, unless the power supply voltage exceeds 14V, the generated power P of the transistor 3417 never exceeds the allowable temperature 90 ° C.

Therefore, according to the example here, only when the power supply voltage exceeds 14 V, the fuel cut speed of the engine 1 is limited and the generated power P of the transistor 3417 is limited. , Its destruction, etc. will surely be avoided.

17 and 18 show a seventh embodiment of the electronic control unit for an engine according to the present invention, which is constructed based on such a principle. That is, the device of the seventh embodiment is an electronic control unit for an engine in which a drive circuit for a fuel injection valve is built, and the temperature around the output transistor of the drive circuit is converted into a battery voltage (power supply voltage). It is configured as a device that monitors and lowers the high rotation fuel cutoff determination value of the engine when the converted battery voltage becomes equal to or higher than a predetermined limit value.

The details will be described below. FIG.
As shown in FIG. 7, in the device of the seventh embodiment, the voltage is extracted from the battery 29 of the vehicle through an appropriate voltage dividing circuit, and the extracted battery voltage is applied to the multiplexer 32.
It is designed to be taken into the A / D converter 326 via the A.D.

FIG. 18 shows a fuel cut judgment value changing routine executed by the apparatus of the seventh embodiment. Note that this routine is also registered in the ROM 312 in advance, for example, 16
It shall be activated by a time interrupt every ms.

That is, if the routine is started now, the electronic control unit 30 first takes in the voltage value of the battery 29 through the multiplexer 325 and the A / D converter 326, and the taken-in voltage value corresponds to the ambient temperature. Predetermined value corresponding to the limit value (14V in this example)
It is determined whether or not this is the case (step S601).

As a result, when it is determined that the voltage value of the battery 29 has not reached the above-mentioned predetermined value, the process is finished as it is. On the other hand, when it is determined that the voltage value of the battery 29 is equal to or higher than the predetermined value, for example, the determination value 7
The high rotation fuel cut rotation speed of the engine 1 set to 000 rpm is reduced to, for example, 5800 rpm (step S602).

This high speed fuel cut judgment value is usually RO
As described above in the apparatus according to the first embodiment, the M312 is loaded into the RAM 313 or stored in the backup RAM 314 and is referred to when the fuel cut control is executed.

By thus lowering and updating the determination value, the electronic control unit 30 completely prohibits fuel injection at a rotational speed equal to or higher than the updated value, and the engine rotational speed is also updated. It will not rise above the specified value. If the maximum engine speed is limited in this way, the electric power P generated by the transistor 3417 is naturally limited, and in turn, heating exceeding the permissible value can be prevented. As described above in the apparatus of the first embodiment.

As described above, according to the device of the seventh embodiment, the power transistor (output transistor) for driving the fuel injection valve 9 to which the flyback diode is connected is mounted on the radiation fin, or Without using an expensive heat-resistant transistor as the same transistor, and further without directly monitoring the ambient temperature of the transistor, heat generation beyond the operating temperature limit can be properly suppressed. Like

In the seventh embodiment, the means for monitoring the ambient temperature by converting it into a power supply voltage (battery voltage) is monitored by the high rotation fuel cutoff judgment value obtained by the first embodiment. Is applied to the engine speed limit control for lowering the engine speed, but the monitoring means can be similarly applied to the engine speed limit control by the devices of the above-mentioned second to fifth embodiments. Of course, it is a thing.

(Eighth Embodiment) In the sixth embodiment, the electronic control unit 30 (power transistor 341) is based on the forward voltage VF of the diode driven by the constant current.
The ambient temperature of 7) was monitored.

However, even in the case of a transistor, the voltage (VBE) at the P-N junction portion between its base and emitter is
Is known to show a lower voltage value as the temperature rises, similar to the VF characteristic of the diode.

Therefore, the power transistor 34
If the base-emitter voltage of 17 itself is measured, the temperature of the transistor itself can be directly monitored.

FIGS. 19 to 25 show an eighth embodiment of the electronic control unit for an engine according to the present invention, in which the temperature of the power transistor is directly monitored based on the base-emitter voltage of the power transistor itself. An example is shown.

In the device of the eighth embodiment, as shown in FIGS. 19 and 20, the power transistor 3 of the fuel injection valve drive circuit 341 built in the electronic control unit 30.
417 base-emitter voltage VBE and power supply voltage +
B through the multiplexer 325 to the A / D converter 326
To take in.

Incidentally, also in FIG. 19, the electronic control unit 3
The other configurations of 0 are the same as those of the electronic control unit 30 shown in FIG. 2, FIG. 13 or FIG. 17, and the duplicate description of those elements will be omitted here.

First, the characteristics of the power transistor 3417, particularly the base-emitter voltage VBE, will be described with reference to FIGS. As described above with reference to FIG. 3, in the drive circuit 341, when the drive command output from the microcomputer 310 becomes the logic L (low) level, the transistor 3413 is turned on and the power transistor 3417 is turned on. Base current IB is supplied. This state is shown in FIG.
And as shown in (b).

That is, at this time, the base current increases with a time constant determined by the base resistor 3414 and the base capacitance of the transistor 3417 itself. And
As the base current IB increases, the base potential (base-emitter voltage) VBE also increases in the manner shown in FIG. These base current IB and base potential V
The increase of BE ends after a certain time Td, and then stabilizes at a certain level.

Here, the power transistor 3417 is used.
The correlation between the base potential (base-emitter voltage) VBE and the temperature occurs in the so-called constant current driving state in which the transistor 3417 is turned on and the base current IB is stable.

Therefore, it is necessary to monitor the temperature based on the base potential VBE by utilizing time Tm (FIG. 21) which is a period during which the potential VBE is stable. That is, after the transistor 3417 is turned on, the base potential V
The BE measurement will be started. Here, this waiting time Td is the resistance value R of the above-mentioned base resistor 3414.
(Ω) and the base capacitance C (F) of the transistor 3417 need to be greater than or equal to the time constant (CR).

On the other hand, the base potential VBE of the transistor 3417 is related to not only the temperature of the transistor 3417 but also its base current IB.
If B is different, the change amount ΔVBE with respect to the temperature is also different. These states are shown in FIG.

That is, as shown in FIG. 22, the variation ΔVBE (mV / mV / base temperature VBE with temperature.
C) decreases as the base current IB increases. Therefore, for example, when the base current IB increases, that is, the power supply voltage potential + B increases, the transistor 34
The decrease in the base potential VBE due to the increase in the temperature of 17 decreases, making it difficult to accurately measure the temperature based on the base potential VBE.

Therefore, in accurately monitoring the temperature based on the base potential VBE, the base current I
B, that is, the inclination correction in the mode shown in FIG. 23 based on the power supply voltage potential + B is required.

FIG. 24 shows a transistor temperature estimation routine of the device of the eighth embodiment which is executed in view of such characteristics of the base potential VBE. Next, referring to FIG. The processing procedure of the transistor temperature estimation processing by the apparatus of the embodiment will be described in detail. Note that this transistor temperature estimation routine is registered in advance in the ROM 312 shown in FIG. 19 and is activated by a time interrupt every 16 ms. The temperature estimation table based on the base potential VBE illustrated in FIG. 23 is also stored in advance in the ROM 312, the backup RAM 314, or the like.

In the apparatus of the eighth embodiment, the electronic control unit 30 (CPU 311) first determines in step S701 whether or not the transistor 3417 is turned on based on the activation of the routine. If it is determined to be on, it is further determined in step S702 whether or not the predetermined time Td has elapsed thereafter. When these conditions are not satisfied, the routine is once exited and the process waits until it is activated next time.

When it is determined that all the above conditions are satisfied, the electronic control unit 30 then proceeds to step S70.
3 and step S704, the base potential VBE,
And the power supply voltage potential + B are read. Then, in the next step S705, (1) the slope of the previous temperature estimation table (FIG. 23) is determined based on the read power supply voltage potential + B (the temperature estimation table of the corresponding slope is selected). (2) The temperature corresponding to the read base potential VBE is selected from the determined table. By performing such processing, the temperature of the transistor 3417 at each time is estimated.

FIG. 25 shows a fuel cut judgment value changing routine which is further executed by the device of the eighth embodiment based on the estimation of the transistor temperature. Note that this routine also
It is pre-registered in the OM 312 and is activated by an interrupt for every 16 ms, for example.

That is, if the routine is started now, the electronic control unit 30 first determines whether or not the estimated transistor temperature is equal to or higher than a predetermined value (82 ° C. in this example) corresponding to the limit value. Judgment (step S80
1).

As a result, when it is determined that the transistor temperature has not reached the above-mentioned predetermined value, the process is finished as it is. On the other hand, when it is determined that the transistor temperature is equal to or higher than the predetermined value, for example, the determination value 7000r
The high rotation fuel cut rotation speed of the engine 1 set to pm is lowered to, for example, the rotation speed of 5800 rpm (step S802).

By thus lowering and updating the high rotation speed fuel cutoff determination value, the maximum engine speed is limited, the electric power P generated by the transistor 3417 is also limited, and in turn, heating exceeding the allowable value or the like is caused. I've already mentioned that you'll be prevented.

As described above, according to the device of the eighth embodiment, the temperature of the transistor 3417 for driving the fuel injection valve 9 can be directly utilized to estimate and monitor its temperature. Therefore, even when the temperature of the transistor 3417 rises sharply before the ambient temperature of the transistor 3417 rises, the temperature fluctuations that cannot be monitored by the devices according to the first to sixth embodiments are responded to. You will be able to monitor it with good sexuality.

Also in this case, the transistor 3417 is mounted on the radiation fin by performing the process of lowering the high speed fuel cut judgment value through the fuel cut judgment value changing routine based on the monitoring of the transistor temperature. Even if an expensive transistor having heat resistance is not used as the transistor, heat generation beyond the temperature range for which it can be used can be properly suppressed.

In the device of the eighth embodiment, the means for monitoring the temperature of the transistor on the basis of the base-emitter voltage of the transistor is used as a means for determining the high rotation fuel cut by the device of the first embodiment. It is applied to the rotation speed limitation control that lowers the value and limits the engine rotation speed.
It goes without saying that such a temperature monitoring means can be similarly applied to each rotation speed limitation control by the devices of the above second to fifth embodiments.

In any of the above-described first to eighth embodiments, the ambient temperature of the output transistor of the drive circuit (fuel injection valve drive circuit) 341 built in the electronic control unit 30 and the temperature of the transistor itself. However, the transistor targeted for temperature monitoring is not limited to the transistor for driving the fuel injection valve.

That is, built in the electronic control unit 30,
In the case of the transistor for driving the inductance load, which absorbs the flyback energy in the above-mentioned manner, the fact that the transistor may generate heat beyond the temperature range for use is generally common. The present invention can be similarly applied to various transistors. Then, the inductance load driving transistor to be monitored can be surely protected from damage due to abnormal heat generation and the like without the need to take any special heat radiation measures.

In the end, the electronic control device essentially requires temperature monitoring means for monitoring the temperature of the transistor or its ambient temperature, and the engine speed when the monitored temperature or its equivalent value exceeds a predetermined limit value. The number of rotations for limiting the rotation speed may be limited.

The temperature monitoring means include: a thermistor arranged near the transistor;
Arithmetic means for computing the ambient temperature of the transistor based on the voltage across the terminals of the thermistor. A device provided with a diode which is arranged in the electronic control device and is driven with a constant current, and a calculation unit which calculates the ambient temperature of the transistor based on the forward voltage of the diode. A device that converts the ambient temperature of the transistor into a battery voltage value and monitors it. A means for extracting the base potential of the transistor at the time of constant current driving, and a computing means for computing the temperature of the transistor itself based on the extracted base potential. There are, etc., and as the rotation speed limiting means for limiting the electric power generated by the transistor by limiting the engine rotation speed, there are: Those that have means. The fuel injection thinning means for thinning out the fuel injection to the engine for a predetermined short time to reduce the maximum rotation speed of the engine. -A means for reducing cylinders that stops fuel injection into any cylinder of the engine to reduce the maximum engine speed. -Injection amount reduction means for reducing the maximum number of revolutions of the engine by reducing the fuel injection amount to the engine in a predetermined manner. -Intake restriction means for forcibly driving the intake throttle valve (throttle valve, sub-throttle) of the engine to reduce the maximum engine speed. And so on.

(Ninth Embodiment) In any of the first to eighth embodiments, the output transistor of the drive circuit (fuel injection valve drive circuit) 341 incorporated in the electronic control unit 30 has its ambient temperature and transistor. The temperature of the engine is monitored and the engine speed is limited in order to suppress the generated electric power. However, by suppressing the power generated on the fuel injection valve 9 (load) side in addition to the power generated by the transistor itself, the transistor can be thermally protected in a manner similar to the above.

FIG. 26 shows the electric power generated on the side of the fuel injection valve exciting coil 91. That is, this generated power is P
L, the power generated during the on-time of the output transistor is Pon, the power generated during the off-time is Poff, and the on-cycle of the transistor is T.
When it is set to O, it is expressed by the relation of PL = Pon + Poff / TO (5).

Here, as is apparent from the equation (5), the generated power PL is equal to the ON period T of the transistor.
The smaller O, that is, the higher the engine speed, the larger the value (the term “Poff / TO” increases).

Further, as the temperature of the fuel injection valve exciting coil 91 is lower, a larger current flows therethrough. Therefore, the generated power PL has a larger value as the temperature of the fuel injection valve exciting coil 91 is lower. You will also have (section "Po
n "becomes large).

On the other hand, in the transistor, the higher the temperature, the lower the energy that can be consumed. That is, it is considered that the thermally severe situation for the transistor is when the temperature of the load (fuel injection valve exciting coil 91) is low (the generated power is large) and the temperature of the transistor itself is high (the consumable power is small). be able to.

Therefore, in order to thermally protect the transistor assuming that the temperature of the transistor is high to some extent, the above load (fuel injection valve exciting coil 91)
It is understood that the electric power generated from the engine can be suppressed, and as a specific method therefor, the engine speed can be limited according to the temperature of the same load.

27 to 29 show an example of an electronic control unit for an engine according to a ninth embodiment of the present invention, in which the above-mentioned principle is used to thermally protect the transistor.

In the device of the ninth embodiment, the temperature of the load (fuel injection valve exciting coil 91) is estimated on the basis of the cooling water temperature of the engine 1 detected by the water temperature sensor 20, and the engine is rotated at high speed. The determination value of the accompanying fuel cut rotation speed is changed according to the estimated load temperature. Incidentally, the output of the water temperature sensor 20 (cooling water temperature) corresponds to the warm-up state of the engine 1 main body. Therefore, when the temperature of the engine 1 main body is low, it may be considered that the temperature of the load such as the fuel injection valve exciting coil 91 is also low.

Incidentally, also in the apparatus of the ninth embodiment,
The basic configuration of the electronic control unit 30 is as shown in FIG.
It is the same as the device shown in FIG. 13, FIG. 17, or FIG. 19, and redundant description of each element constituting the device will be omitted.

Now, in the device of this ninth embodiment,
The electronic control unit 30 calculates the cumulative rotational speed CNE after the engine 1 is started through the angle synchronization routine shown in FIG. 27, and at any time changes the fuel cut rotational speed determination value KCUT through the procedure shown in FIG.

First, in the angle synchronization routine shown in FIG. 27, the electronic control unit 30 makes a step every time the rotation angle signal fetched from the rotation angle sensor 25 reaches a timing indicating the passage of 360 ° CA (crank angle). S9
At 01, the count value CNE of the cumulative rotation speed counter is incremented (CNE ← CNE + 1).

The angle synchronization routine is started when the engine 1 is started. Further, as the cumulative rotation number counter, for example, 2 bytes of the RAM 313 in the microcomputer 310 are used. It is assumed that the counted cumulative rotation speed CNE is not cleared until the engine 1 is completely stopped, such as when the ignition is turned off, and is held in the RAM 313.

On the other hand, the electronic control unit 30 executes the angle synchronization routine in parallel with the procedure shown in FIG.
The injection routine including the change of the determination value KCUT of the fuel cut speed described above is executed. The injection routine is started and executed at each fuel injection timing for each cylinder of the engine 1.

Now, assuming that this injection routine is started, the electronic control unit 30 causes the multiplexer 3 to operate.
25 and the output of the water temperature sensor 20 through the A / D converter 326, and in step S911, a determination value KCUT of the fuel cut speed corresponding to the water temperature value is calculated.
In the apparatus of the embodiment, this judgment value KCUT is shown in FIG.
It is calculated through the map shown in FIG.

Here, as shown in FIG. 29, the judgment value KCUT of the fuel cut rotation speed is set as a value corresponding to the rotation speed "5700 rpm" when the cooling water temperature is "-30 ° C", When the cooling water temperature is “20 ° C.”, it is set as a value corresponding to the rotation speed “7000 rpm”. In the temperature range of "-30 ° C" to "20 ° C", the corresponding rotation speed is interpolated in a substantially linear relationship. The cooling water temperature is "20.
Even if the temperature exceeds "° C", the corresponding judgment value KCUT is
It is guarded to a value corresponding to the above-mentioned rotation speed "7000 rpm".

The electronic control unit 3 which obtains the judgment value KCUT of the fuel cut speed based on such a relationship with the cooling water temperature.
Next, in step S912, the count value CNE of the cumulative rotation speed counter is read, and the value CNE is 0.
For example, it is determined whether the value is “10000” or more. Then, in the same step S912, the above value C
When it is determined that NE is “10000” or more, the determination value KCUT obtained above is determined in step S913.
Is increased and corrected in the form of, for example, KCUT = KCUT + 300 rpm. This is because, even if the cooling water temperature itself is low, if the driving time of the fuel injection valve 9 reaches a certain time, it is considered that the temperature is rising. This is a process for correcting the determination value KCUT in a close form. It should be noted that the determination value KCUT of the fuel cut rotational speed that is increased and corrected is additionally shown in FIG.

When the electronic control unit 30 executes such a correction or determines in step S912 that the count value CNE of the cumulative rotation speed counter has not reached "10000", it obtains the above in step S914. Alternatively, it is further determined whether the corrected determination value KCUT exceeds the rotation speed "7000 rpm".
When it is determined that the determination value KCUT exceeds the rotation speed "7000 rpm", the next step S91
In step 5, after setting "7000 rpm" to the same determination value KCUT (after the upper limit guard), the process of step S916 is executed. On the other hand, the determination value KCUT is "700"
If it does not exceed "0 rpm", the process of step S916 is executed by using the determined value or the corrected value as the same determination value KCUT.

In the processing of step S916, the electronic control unit 30 determines whether or not the engine speed calculated based on the output of the rotation angle sensor 25 is equal to or higher than the fuel cut speed judgment value KCUT. . When it is determined that the engine speed is equal to or higher than the determination value KCUT, the fuel injection is stopped, that is, the fuel cut is executed in step S917, and the engine speed is less than the determination value KCUT. If so, step S918
To inject fuel.

By performing such processing through the apparatus of the ninth embodiment, the electric power generated from the load (fuel injection valve exciting coil 91) is naturally limited, and by extension the electric power generated from the transistor itself. It will be suppressed.

Even in this case, even if the above-mentioned heat dissipation measures are not necessarily applied to the transistor, the heat generation beyond the operating limit temperature range can be appropriately suppressed.

Further, in the apparatus of the present embodiment, the fuel cut speed determination value KC is calculated based on the cumulative rotation speed value CNE.
Since the UT is increased and corrected, it is possible to suppress an excessive restriction on the same fuel cut rotation speed.

At the time of this correction, in the apparatus of the embodiment, the judgment value KCUT of the fuel cut speed, that is, the allowable range of the engine speed limit amount according to the cooling water temperature is increased and corrected. The cooling water temperature itself may be corrected by increasing the predetermined temperature. In short, it suffices that the relative relationship between the cooling water temperature and the allowable range of the engine speed limit amount corresponding to the cooling water temperature is corrected according to the drive time of the load. Further, of course, even if such a correction is not necessarily performed, the heat generation itself beyond the use limit temperature range of the transistor can be surely suppressed.

Further, in the apparatus of the embodiment, as described above,
Until the engine 1 is completely stopped, the cumulative rotational speed value CNE is not cleared but is retained in the RAM 313. Therefore, for example, even when the engine is restarted immediately after the engine stall or the like, the cumulative rotational speed CNE will not be restarted from "0". That is, the mode of limiting the engine speed based on the temperature of the load which is closer to the actual state is maintained. The timing for clearing the cumulative rotational speed CNE may be another timing when a predetermined time has elapsed after the engine 1 was stopped.

By the way, in the ninth embodiment, as a map for calculating the judgment value KCUT of the fuel cut speed, a substantially linear relationship is obtained in the cooling water temperature range of "-30 ° C" to "20 ° C". The characteristic that the corresponding fuel cut rotation speed is interpolated is adopted. However, in the map, other specific cooling water temperature (20.degree. C. in the example of FIG. It is also possible to adopt a characteristic in which the value of the determination value KCUT that is set (map-calculated) is changed on the basis of (). Even when the value of the determination value KCUT is changed in this manner, it is possible to reliably suppress heat generation beyond the operating temperature limit range of the transistor. In this case, the judgment value K
Regarding the temperature used as the boundary for changing the value of CUT,
The point is not limited to one point (20 ° C.) as in the example of FIG. 30, but may be set to two points or more.

In addition, in the ninth embodiment, the water temperature sensor 2
Although the temperature of the load (fuel injection valve exciting coil 91) is indirectly monitored through the cooling water temperature detected by 0, for example, a thermocouple or the like is arranged in the same load and the temperature is directly monitored. Of course, it may be done. In this case, although a dedicated sensor for measuring the temperature is required, the temperature of the same load can be grasped more accurately.

On the other hand, as in the ninth embodiment, the configuration in which the temperature of the load is monitored and the engine speed is limited according to the monitored load temperature is also the above (a) second embodiment. (B) A device for thinning out fuel injection to the engine for a predetermined short time, (b) A device for stopping fuel injection to an arbitrary cylinder of the engine, that is, a device for reducing cylinder control, as in the third embodiment. ) A device for reducing the fuel injection amount to the engine as in the fourth embodiment, (d)
It can be applied in a form corresponding to the device for forcibly driving the intake throttle valve (throttle valve, sub-throttle) of the engine as in the fifth embodiment to the side where the intake amount is suppressed.

That is, in the case of thinning out the fuel injection amount as in the device of (a) above, as shown in FIG. 31, the fuel injection to the engine is thinned out every predetermined time according to the cooling water temperature. Then, the maximum rotation speed of the engine will be reduced. In this case, the lower the cooling water temperature (load temperature), the longer the thinning time is set. Then, in this case, except that the thinning time corresponding to the cooling water temperature at each time is calculated through the map as shown in FIG. 31, the process according to the previous FIGS. 9 and 10 is executed through the electronic control unit 30. The Rukoto.

Further, in the case where the cylinder reduction control is performed as in the device (b), as shown in FIG. 32, the fuel injection to the number of cylinders determined according to the cooling water temperature is stopped. The maximum rotation speed of the engine will be reduced. Incidentally, in this case, the lower the cooling water temperature (load temperature), the larger the number of cylinders to be set. And in this case
1 except that the number of reduced cylinders corresponding to each cooling water temperature is calculated through the map as shown in FIG.
The process according to 1 will be executed through the electronic control unit 30.

Further, in the case of reducing the fuel injection amount as in the device of (c) above, as shown in FIG. 33, the fuel injection amount to the engine is reduced by a predetermined amount according to the cooling water temperature. Then, the maximum rotation speed of the engine will be reduced. By the way, in this case, cooling water temperature (load temperature)
The lower is, the more weight loss value is set. Then, in this case, except that the reduction value corresponding to the cooling water temperature at each time is calculated through the map as shown in FIG. 33, the processing according to the previous FIG. 12 is executed through the electronic control unit 30. Become.

When the intake throttle valve is forcibly driven as in the above-mentioned device (d), as shown in FIG. 34, the intake throttle valve of the engine is forced by a predetermined amount according to the cooling water temperature. Driven to reduce the maximum engine speed. Incidentally, in this case, the lower the cooling water temperature (load temperature), the larger the driving amount is set. In this case, the throttle valve or the sub-throttle is opened in the same manner as in the fifth embodiment except that the driving amount corresponding to the cooling water temperature is calculated through the map as shown in FIG. Electronic control unit 3
It will be controlled by 0.

Also in each of these configurations, the values of the variables to be set can be changed in a binary or multivalued manner with a certain cooling water temperature (load temperature) as a boundary. The allowable range of the cooling water temperature or the engine speed limit amount corresponding to the cooling water temperature may be increased and corrected according to the drive time (cumulative rotation speed) of the load. -The temperature of the load may be monitored directly by a thermocouple or the like, not necessarily by the cooling water temperature. Etc. are the same as in the case of the device of the ninth embodiment.

[0269]

As described above, according to the present invention, the use limit of the transistor for driving the inductance load, which is built in the electronic control unit of the engine and connected to the Zener diode for extinguishing the flyback voltage, is reached. It is possible to accurately suppress heat generation beyond the temperature range.

For this reason, it becomes possible to surely protect these elements without inconveniently dissipating the heat.

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing an example of an engine and peripheral devices to be controlled by the present invention.

FIG. 2 is a block diagram showing the configuration of a first embodiment of the electronic control device of the present invention.

FIG. 3 is a circuit diagram showing a configuration example of a drive circuit of a fuel injection valve and an exciting coil.

FIG. 4 is a perspective view showing an example of mounting a drive circuit for a fuel injection valve on a printed circuit board.

FIG. 5 is a time chart showing voltage and current waveforms of output transistors of the drive circuit.

FIG. 6 is a schematic diagram showing an example of a temperature-voltage characteristic table of the thermistor.

FIG. 7 is a graph showing a temperature calculation map based on the temperature-voltage characteristic table.

FIG. 8 is a flowchart showing a procedure for changing a fuel cut determination value according to the first embodiment.

FIG. 9 is a flowchart showing a timing procedure according to the second embodiment of the present invention.

FIG. 10 is a flowchart showing a fuel injection thinning-out procedure according to the second embodiment.

FIG. 11 is a flowchart showing a cut-off cylinder control procedure according to the third embodiment of the present invention.

FIG. 12 is a flowchart showing a fuel injection amount reduction procedure according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram showing the configuration of a sixth embodiment of the present invention.

FIG. 14 is a circuit diagram mainly showing a configuration example of a vehicle speed sensor waveform shaping circuit.

FIG. 15 is a graph showing forward voltage-temperature characteristics when a diode is driven at a constant current.

FIG. 16: Calibration of diode characteristics according to the sixth embodiment,
3 is a flowchart showing a temperature raising procedure based on the diode characteristics.

FIG. 17 is a block diagram showing the configuration of a seventh embodiment of the present invention.

FIG. 18 is a flowchart showing a procedure for changing the fuel cutoff determination value according to the seventh embodiment.

FIG. 19 is a block diagram showing the structure of an eighth embodiment of the present invention.

FIG. 20 is a block diagram showing a manner of extracting a base potential of an output transistor.

FIG. 21 is a time chart showing a base current waveform and a base-emitter voltage waveform of the output transistor.

FIG. 22 is a graph showing changes in the base potential with respect to temperature due to changes in the base current.

FIG. 23 is a graph showing an example of a temperature estimation table based on the base potential.

FIG. 24 is a flowchart showing a procedure for estimating the transistor temperature according to the eighth embodiment.

FIG. 25 is a flowchart showing a procedure for changing the fuel cutoff determination value according to the eighth embodiment.

FIG. 26 is a time chart showing electric power generated on the load (fuel injection valve exciting coil) side.

FIG. 27 is a flowchart showing a cumulative rotational speed calculation procedure according to the ninth embodiment of the present invention.

FIG. 28 is a flowchart showing a procedure for changing the fuel cutoff determination value according to the ninth embodiment.

FIG. 29 is a graph showing how the fuel cut determination value is changed according to the cooling water temperature.

FIG. 30 is a graph showing how the fuel cut determination value is changed according to the cooling water temperature.

FIG. 31 is a graph showing how the fuel injection thinning time is set according to the cooling water temperature.

FIG. 32 is a graph showing how the number of reduced cylinders is set according to the cooling water temperature.

FIG. 33 is a graph showing how the injection amount reduction value is set according to the cooling water temperature.

FIG. 34 is a graph showing how the intake throttle valve drive amount is set according to the cooling water temperature.

[Explanation of symbols]

1 ... Engine, 2 ... Cylinder, 3 ... Piston, 4 ... Cylinder head, 5 ... Combustion chamber, 6 ... Spark plug, 7 ... Intake valve, 8 ... Intake manifold, 9 ... Fuel injection valve, 10 ...
Intake pipe, 11 ... Surge tank, 12 ... Throttle valve, 13 ... Air cleaner, 14 ... Exhaust valve, 15 ... Exhaust manifold, 16 ... Igniter, 17 ... Distributor, 20 ... Water temperature sensor, 21 ... Intake temperature sensor, 2
2 ... Throttle position sensor, 23 ... Intake pipe pressure sensor, 24 ... Oxygen concentration sensor, 25 ... Rotation angle sensor,
26 ... Cylinder discrimination sensor, 27 ... Signal rotor, 28 ...
Vehicle speed sensor, 29 ... Battery, 30 ... Electronic control device, 3
01 ... Case, 302 ... Connector, 303 ... Printed circuit board, 304 ... Cover, 310 ... Microcomputer,
311 ... CPU, 312 ... ROM, 313 ... RAM, 3
14 ... Backup RAM, 315 ... Input / output port, 3
16 ... Input port, 317 ... Output port, 318 ... Common bus, 319 ... Clock generator, 321, 322, 3
23, 324, 331 ... Buffer circuit, 325 ... Multiplexer, 326 ... A / D converter, 332 ... Comparator, 333 ... 334 ... Waveform shaping circuit, 335 ... Wiring (diode forward voltage fetch wiring), 341 ... Driving circuit ( Igniter), 342 ... Drive circuit, 343 ... Wiring (transistor base potential taking-in wiring), 351 ... Resistor (pull-up resistor), 352 ... Thermistor, 353 ... Wiring (thermistor output taking-in wiring), 361 ... Wiring (battery voltage taking-in) Wiring), 3341, 3343, 33
45, 3411, 3412, 3414, 3416 ... Resistor, 3342 ... Diode, 3344 ... Comparator,
3413, 3417 ... Transistor, 3415 ... Zener diode (flyback diode).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahide Abe 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Kengo Sugiura 1-1-1-1, Showa town, Kariya city, Aichi prefecture Nidec Within the corporation

Claims (25)

[Claims] 1. An electronic control unit for an engine, comprising: a transistor for driving an inductance load in synchronization with engine rotation; and a Zener diode connected to the transistor for extinguishing a flyback voltage generated when the load is off. A temperature monitoring means for monitoring the temperature of the transistor or its ambient temperature, and a rotation speed limiting means for limiting the engine rotation speed when the monitored temperature or its equivalent value exceeds a predetermined limit value. An electronic control unit for an engine, comprising: 2. The electronic control unit for an engine according to claim 1, wherein the rotation speed limiting means comprises a fuel cut determination value changing means for reducing a determination value of the fuel cut rotation speed associated with the high speed rotation of the engine. 3. The engine according to claim 1, wherein said rotation speed limiting means comprises fuel injection thinning-out means for thinning out fuel injection to the engine for a predetermined period of time to reduce the maximum rotation speed of the engine. Electronic control unit. 4. The engine according to claim 1, wherein the rotation speed limiting means comprises a cut-off cylinder control means for stopping fuel injection into an arbitrary cylinder of the engine to reduce the maximum rotation speed of the engine. Electronic control unit. 5. The engine according to claim 1, wherein the rotation speed limiting means comprises injection quantity reducing means for reducing the fuel injection quantity to the engine by a predetermined amount to reduce the maximum rotation speed of the engine. Electronic control unit. 6. The electronic control unit for an engine according to claim 1, wherein said rotational speed limiting means comprises an intake air limiting means for forcibly driving an intake throttle valve of the engine to reduce the maximum rotational speed of the engine. . 7. The temperature monitoring means comprises a thermistor arranged in the vicinity of the transistor, and a calculating means for calculating an ambient temperature of the transistor based on a voltage across terminals of the thermistor. Item 7. An electronic control device for an engine according to any one of items 1 to 6. 8. The temperature monitoring means comprises a diode arranged in the electronic control unit and driven by a constant current, and a computing means for computing the ambient temperature of the transistor based on the forward voltage of the diode. Claims 1 to 6 configured as
An electronic control unit for an engine according to any one of 1. 9. The diode is separately arranged as the temperature monitoring means in the electronic control unit.
Electronic control unit for the engine described. 10. The electronic control unit for an engine according to claim 8, wherein the diode is diverted from one that is previously arranged as a control component in the electronic control unit. 11. The calculation means is within a predetermined time after power-on, both the cooling water temperature of the engine and the intake air temperature are below a predetermined first temperature, and the temperature difference is also below a predetermined second temperature. And a means for calibrating the forward voltage-temperature characteristic of the diode on the basis that the logical product condition that the engine is not rotating is satisfied, and when any one of the conditions is not satisfied, 11. The electronic control of an engine according to claim 8, 9 or 10, further comprising: means for calculating the respective temperature as the ambient temperature of the transistor based on the calibrated forward voltage-temperature characteristic of the diode. apparatus. 12. The temperature monitoring means converts the ambient temperature of the transistor into a voltage value of a battery for monitoring, and the rotation speed limiting means limits the converted voltage value of the battery to a predetermined limit. 7. The electronic control unit for the engine according to claim 1, wherein the engine speed is limited when the value is equal to or more than a value. 13. The temperature monitoring means comprises base potential extracting means for extracting a base potential when the transistor is driven with a constant current, and computing means for computing the temperature of the transistor itself based on the extracted base potential. An electronic control unit for an engine according to any one of claims 1 to 6, further comprising: 14. The calculating means detects the constant current driving state of the transistor based on a lapse of a constant time after the transistor is turned on, and the constant current driving state. 14. The electronic control unit for an engine according to claim 13, further comprising means for reading the extracted base potential on the basis of the detection of, and calculating the temperature of the transistor based on the base potential-temperature characteristic. 15. The electronic control unit for the engine according to claim 13, wherein the temperature monitoring means further comprises a power supply potential extracting means for extracting a power supply potential of the load, and the computing means includes the transistor. Means for detecting that the transistor is in a constant current driving state based on the lapse of a fixed time after being turned on, and the extracted base potential and power source based on the detection that the transistor is in a constant current driving state. An electronic control unit for an engine, comprising: a unit for reading a potential and calculating the temperature of the transistor based on a base potential-temperature characteristic corresponding to a power supply potential at each time. 16. An electronic control unit for an engine, comprising: a transistor for driving an inductance load in synchronization with engine rotation; and a Zener diode connected to the transistor for extinguishing a flyback voltage generated when the load is off. A device, comprising: load temperature monitoring means for monitoring the temperature of the inductance load; and rotation speed limiting means for limiting the engine rotation speed according to the monitored load temperature. Electronic control unit. 17. The rotation speed limiting means comprises a fuel cut judgment value changing means for changing a judgment value of a fuel cut rotation speed according to a high speed rotation of an engine according to the monitored load temperature. Item 16. An electronic control unit for an engine according to item 16. 18. The engine speed limiting means comprises fuel injection thinning means for thinning fuel injection into the engine for a predetermined period of time according to the monitored load temperature to reduce the maximum engine speed of the engine. An electronic control unit for an engine according to claim 16, which is constructed. 19. The engine speed limiting means includes a cut-off cylinder control means for stopping the fuel injection to the number of cylinders determined according to the monitored load temperature to reduce the maximum engine speed of the engine. The electronic control unit for an engine according to claim 16, which is further configured. 20. The rotation speed limiting means comprises injection amount reduction means for reducing the fuel injection amount to the engine by a predetermined amount according to the monitored load temperature to reduce the maximum rotation speed of the engine. An electronic control unit for an engine according to claim 16, which is constructed. 21. The rotational speed limiting means comprises an intake air limiting means for forcibly driving an intake throttle valve of the engine by a predetermined amount according to the monitored load temperature to reduce the maximum rotational speed of the engine. The electronic control unit for the engine according to claim 16, 22. The engine electronic control according to claim 16, wherein said load temperature monitoring means is provided with temperature measuring means which is disposed in said inductance load and directly measures the temperature thereof. apparatus. 23. The load temperature monitoring means comprises a water temperature sensor for detecting a cooling water temperature of an engine, and an estimating means for estimating a temperature of the inductance load based on the detected cooling water temperature. Item 22. The engine electronic control unit according to any one of Items 16 to 21. 24. The estimating means calculates the cumulative rotation speed from the time when the engine is started, and the detected cooling water temperature or the same cooling temperature when the calculated cumulative rotation speed is a predetermined value or more. 24. The electronic control unit for the engine according to claim 23, further comprising a correction unit that corrects an allowable range of the engine speed limit amount in accordance with the water temperature by increasing the allowable range. 25. The estimating means, even after the engine is stopped,
The electronic control unit for an engine according to claim 24, wherein the calculated cumulative rotation speed is held until the ignition is turned off.