JPH0319901B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an engine control device that uses a microcomputer to control the rotation of an engine (particularly a diesel engine), and in particular is capable of continuing to control the rotation of the engine in place of the computer when the computer runs out of control. The present invention relates to an engine control device equipped with a backup circuit.

BACKGROUND ART In recent years, there has been a remarkable wave of electronic control of internal combustion engines in automobiles and the like, and microcomputers are being used to control internal combustion engines. In an engine control circuit that uses such a computer, the computer periodically takes in information such as the accelerator opening, engine speed, and engine temperature, and controls the fuel supply valve, etc. to ensure that the appropriate amount of fuel is supplied. It is something to control.

Generally, control by a computer is performed by sequentially executing control programs stored in advance in a built-in memory, and as long as the computer is operating normally, no abnormality will occur in the control. On the other hand, when using a computer to control the engine, if the computer goes out of control, the engine speed may become abnormally high or the engine may start to rev up, making it impossible to control the engine. Not only can this damage the engine, but it can also affect human life. It is inconceivable that a computer would run out of control for no reason, but in engine control, etc., it is placed in a place with a poor electrical environment, so it is susceptible to external conditions such as noise contamination, abnormally high or low temperatures, etc. In the unlikely event that a program loop or the like occurs, the program may run out of control. Conventional computer-controlled engine control devices do not have these countermeasures, and there is a need for a solution in the unlikely event that the engine goes out of control.

In general, in the field of computer technology, in order to detect computer runaway, a runaway detection program is provided as part of the control program, or a circuit is provided to monitor the output of the bus line, and the same address is output many times in a row. If the computer outputs an address that has not been set, it is determined to be a runaway and the computer's operation is immediately disabled. However, if this is applied to an engine control device, it would be possible to stop the engine. I don't like it because it makes me feel bad. In other words, when the computer in the engine control device goes out of control, it is impossible to stop the engine immediately.
A car that has been running will have to come to a sudden stop, and while the car is moving on the road, there is a risk of rear-end collisions and other dangers to human life.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an engine control device that can control an engine in place of a computer even if the computer goes out of control.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention.

In FIG. 1, 1 is an accelerator pedal, 2 is a potentiometer that detects the amount of depression of the accelerator pedal as an electric signal PPS, and 3 is a control device incorporating a computer. 4 is a pneumatically driven actuator, 4a is a transmission shaft, 5 is a pneumatic pressure control valve, 6 is a vacuum pressure control valve, 5a and 5b are pipes attached to each pneumatic pressure control valve, and 6a and 6b are also attached to the vacuum pressure control valve. It is a pipe made of 7 is a crank, 8 is a shaft, 9 is a control lever, 10 is a spring that applies rotational force to the lever 9 in one direction, and 11 is a potentiometer that detects the amount of rotation of the shaft 8 as an electric signal SLS. 21 is a cam rotationally driven by the shaft 8, 22 is a control rack, and 23 is a plunger that controls the fuel injection amount. Movement of the control rack 22 rotates the plunger 23, changing the effective stroke of the plunger 23. , is a well-known fuel injection pump for a diesel engine that changes the amount of fuel delivered by vertical movement of a plunger 23.

Next, the operation shown in FIG. 1 will be explained. When the driver depresses the accelerator pedal 1, the potentiometer 2 also operates in conjunction with the depressing of the accelerator pedal 1, and generates an electric signal PPS of a voltage level corresponding to the amount of depressing. This electrical signal
The PPS is input to the control device 3, and then input as a depression command amount (accelerator opening amount) to a computer, which will be described later. On the other hand, the position of the control rack 22 is indicated by the rotational position of the shaft 8, and an electrical signal with a voltage level corresponding to the rotational position of the shaft 8 is generated.
The SLS is output from the potentiometer 11 and input to the computer of the control device 3, and the diesel engine rotation speed signal RS is input from a rotation speed detector (not shown). The control device 3 controls the accelerator opening amount.
A fuel injection amount signal is created from PPS and the rotational speed signal RS, the difference between the fuel injection amount signal and the rotational position signal SLS is calculated, and a valve adjustment command is given to the air pressure control valve 5 and the vacuum pressure control valve 6 based on this difference. give signal VCS,
Both control valves are controlled. As a result, the supply air pressure and the vacuum pressure regulating valve 6 are controlled by the air pressure regulating valve 5.
The degree of vacuum is adjusted by controlling the actuator 4, and the left and right vacuum degrees are controlled by the actuator 4. The driving force transmission shaft 4a moves according to the degree of vacuum, and this movement causes the crank 7 to rotate the shaft 8 against the force of the spring 10, rotate the cam 21, and move the control rack 22. and rotates the plunger 23 to increase or decrease the effective stroke of the plunger 23 to control the amount of fuel delivered. Due to the rotational movement of the shaft 8, the potentiometer 1
1 also rotates by an amount commensurate with the rotational movement of the shaft 8. The potentiometer 11 generates a voltage signal SLS corresponding to this rotation, feeds it back to the control device 3, and finally controls the control rack 2 by an amount corresponding to the amount of opening (depression) of the accelerator pedal.
When the actuator 2 moves, the difference becomes zero, and the leftward pulling force and the rightward pulling force of the actuator 4 are balanced and the actuator 4 stops. Of course, at that point, the control device 3 does not output the valve control command signal VCS to the air pressure control valve 5 and the vacuum pressure control valve 6, and these control valves are closed. These control operations are performed instantaneously. Conversely, similar control is performed when the accelerator pedal is released. In Fig. 1, the shaft 8 and the lever 9 are separated. For example, when the throttle is cold or when the throttle is activated, the accelerator is used when it is necessary to forcibly open the throttle a small amount according to the throttle valve opening. This device is capable of increasing the effective stroke of the plunger 23 independently of the position of the crank 7 based on a command from the pedal.

FIG. 2 is a block diagram of one embodiment of the control device of the present invention. In the figure, 30 is a computer, which has a microcomputer main body 301 and an input/output interface 302. Note that 303 is a bus line. The microcomputer 301 includes a processing device 301a, a control program memory 301b that stores a control program, and a data memory 301c.
It has a system that periodically reads the outputs of various sensors installed in various parts of the car at high speed (polling control).
Alternatively, predetermined arithmetic processing is performed under the control of the control program using an interrupt, and the processing results are output to operation sections (not shown). Input/output interface 3
02 converts the accelerator opening signal PPS, which indicates the amount of depression of the accelerator pedal, into a digital value PD.
AD converter 30 for digital conversion (AD conversion)
2a, a buffer register 302b that stores the digital value PD, an AD converter 302c that AD converts the rotation speed signal RS indicating the rotation speed of the diesel engine into a digital value RD, and the digital value RD.
It has a buffer register 302d that stores RD. 31 is a DA converter that converts the digital output value of the computer 30 into an analog quantity VAS;
32 is a differential amplifier that outputs the difference between the position signal SLS of the potentiometer 11 and the command value VAS of the DA converter 31; 33 is an analog-to-duty conversion circuit that generates a pulse signal of a constant period; The duty ratio of the pulse signal is changed and outputted according to the input analog quantity. For example, when the input analog quantity is zero, a pulse signal with a duty ratio of zero, that is, a pulse width of zero is output.
PT is a power transistor for amplifying the analog voltage.
The output pulse signal of the duty conversion circuit 33 is amplified into the valve control command signal VCS. 34 is a position detection circuit that converts the output of the potentiometer 11 into an analog position signal SLS, and 35 is a waveform shaping circuit that shapes the output of the rotation speed detection device and converts it into a rotation speed signal RS. . 36 is a signal generation circuit, into which the rotational speed signal RS and the accelerator pedal accelerator opening signal PPS are input, and the rotational speed signal is generated.
It generates a pulse signal with a duty ratio that is inversely proportional to RS and proportional to accelerator opening signal PPS. 37 is a runaway detection circuit, and the computer 301
connected to the bus line, receives data on the bus line,
This circuit determines that the computer has gone out of control if the same address is output on the bus line multiple times in a row, and it consists of multiple registers that receive data on the bus line and a comparison circuit that compares the contents of these registers. It's good to think that there are. AND1, AND2
is an AND gate, which constitutes a switching circuit, and when the detection output ABS of the runaway detection circuit 37 is "1" (when non-runaway is detected), the AND gate AND1 opens and the detection output
AND gate when ABS is “0” (when detecting runaway)
AND2 is what opens. NOT is an inversion gate.

To explain this operation, the accelerator opening signal PPS
is AD-converted into a digital value PD by the AD converter 302a of the input/output interface circuit 302, and then is sent to the data memory 301 at a predetermined period.
It is stored in the opening degree storage area 304 of c.

On the other hand, the rotational speed signal RS is converted into a digital value SD by the AD converter 302c and then stored in the opening degree storage area 305 of the data memory 301c. The processing device 301a constantly calculates the difference between the digital values PD and RD under the control of the control program.
A fuel injection amount command signal VAS proportional to the difference is output.

Furthermore, the detection outputs of the exhaust gas concentration sensor and the engine temperature sensor are input to the microcomputer 301, and the optimum fuel injection amount command signal VAS is determined.

This command signal VAS is converted into an analog quantity by a DA converter 31 and input to a differential amplifier 32. The differential amplifier 32 receives the position signal of the potentiometer 11.
Since the SLS is input from the position detection circuit 34, a difference signal between the command signal VAS and the position signal SLS is output. This difference signal is converted by an analog-to-duty conversion circuit into a pulse signal with a duty ratio corresponding to the analog amount of the difference signal. On the other hand, the runaway detection circuit 37 monitors the runaway of the computer 30 via the bus line 303, and when the runaway detection circuit 37 does not detect runaway, it outputs a detection output.
Since ABC is “1”, the AND gate AND1
is open, the output pulse signal of the conversion circuit 33 is transmitted to the transistor PT, amplified as the valve control command signal VCS, and the output pulse signal of the conversion circuit 33 is amplified as the valve control command signal VCS.
(Fig.) is used for driving. As a result, the actuator 4 operates as described above, the control rack 22 moves, and the plunger 23 is rotated to control the amount of fuel delivered. When the computer 30 is not running out of control, the computer determines the optimum fuel injection amount according to the accelerator opening degree, engine rotation speed, etc., and controls the injection amount of the fuel pump. The runaway detection circuit 37 constantly takes in data on the bus line 303 of the computer 30, and determines whether address information in the data is continuously the same. If the same address is output continuously, it is considered that the program is looping or the computer is running out of control, so the detection output ABS is set to "0" and a runaway detection force is generated. As a result, the AND gate AND1 is closed and the output of the conversion circuit 33 is not transmitted to the transistor PT, so that the fuel injection control by the computer 30 becomes invalid. On the other hand, the AND gate AND2 is opened when the detection output ABS is input through the inversion gate NOT, so the output of the signal generation circuit 36 is transmitted to the transistor PT and is applied to the control valves 5 and 6 as the valve control command signal VCS. It will be done. That is, the fuel injection amount is controlled by the output of the signal generation circuit 36.

The signal generation circuit 36 is shown in the block diagram of FIG.
This will be explained using the characteristic diagrams shown in FIGS. In the figure,
306 is an oscillator, and 307 is a triangular conversion circuit, which converts the oscillation output of the oscillator 306 into a triangular wave signal TWS.
(Fig. 6A), 308 is the frequency -
Voltage converter (FV converter), rotation speed signal RS
It outputs a voltage according to the frequency of , and has the rotation speed-voltage output characteristic shown in FIG. 4A. A buffer amplifier 309 amplifies the accelerator opening signal PPS and has the opening signal (PPS)-voltage output characteristic shown in FIG. 4B. 310 is a differential amplifier, which outputs the difference obtained by subtracting the rotation speed voltage output from the accelerator opening signal PPS.
Generates DFS, accelerator opening signal PPS
The relationship between and the differential output DFS has a characteristic as shown in FIG. 5, using the rotation speed as a parameter. 320 is a comparison circuit that compares the differential output DFS and the triangular wave signal TWS as shown in FIG. 6A, and outputs a level "1" when the differential output DFS is greater than the triangular wave signal TWS as shown in FIG. 6B. When it is less than that, a pulse signal VBS indicating a level "0" output is output. That is, as is clear from FIG. 6B, the output pulse signal VBS has the oscillation period of the oscillator 306 and its pulse width is proportional to the differential output DFS, and is a kind of pulse width modulation signal. To explain the operation of FIG. 3, the accelerator opening signal PPS is amplified by the buffer amplifier 309, and the differential amplifier 310
On the other hand, the rotation speed signal RS converted into a voltage is input to the differential amplifier 310, and the difference thereof is output. The output DFS of the differential amplifier 310 is a predetermined rotation speed command signal according to the opening amount of the accelerator opening signal PPS and the actual rotation speed signal RS.
It shows the difference between This differential output DFS is the triangular wave signal of the triangular wave conversion circuit 307 in the comparator circuit 320.
It is compared with TWS and converted into a pulse signal VBS with a pulse width corresponding to the magnitude of the differential output DFS. This pulse signal VBS is a fuel injection amount signal, and its pulse width is inversely proportional to the rotation speed and proportional to the accelerator opening. In other words, the duty ratio of the pulse signal is 6th
As shown in Figure C, it is inversely proportional to the rotation speed and proportional to the accelerator opening. In this way, the computer 30
Even if the engine runs out of control, the signal generation circuit 36 will control the rotation of the engine as instructed by the accelerator.
Compared to the optimal control amount of the computer 30, the control amount of the signal generation circuit 36 does not use the output of other sensors as a determining factor for the control amount, so although the hysteresis characteristics and response characteristics are inferior, engine control can be continued. Even in the worst case scenario, you can take your vehicle to a service factory by yourself. In the embodiment described above, the control valves 5 and 6 are controlled by the valve control command signal VCS.
However, two valve control command signals VCS1 and VCS are used to control control valves 5 and 6 separately.
2 may be created. For this reason, computer 3
If the command output VAS is larger than the position signal SLS, the command signal VCS1 for the control valve 6 is issued, and if it is smaller than the position signal SLS, the command signal VCS2 for the control valve 5 is issued.For example, the differential amplifier 32, analog-to-duty conversion circuit 33 , AND gate AND1, transistor
It is sufficient to provide one more PT combination. Similarly, in the signal generation circuit 36, the accelerator opening signal
If PPS is larger than the rotation speed signal RS, the command signal VCS1 of the control valve 6 is sent, and if it is smaller, the command signal VCS of the control valve 5 is sent.
For example, in FIG. 3, another set of differential amplifier 310 and comparison circuit 320 may be provided. Further, the actuators 4, 5, and 6 are not limited to the above-mentioned configuration, and other pneumatic control types, electric motors, etc. may also be used. Furthermore, the aforementioned runaway detection circuit 37 includes one that detects that an address on the bus line 303 indicates an unset address, one that detects that no data is output to the bus line 303 for a predetermined period of time, etc. can be used, and a combination of these detections may also be used.

As explained above, according to the present invention, in an engine control device having a backup circuit that controls the fuel supply amount in place of the computer when the computer that controls the fuel supply amount to the engine malfunctions, Differential means for outputting an analog signal that decreases as the rotational speed increases and increases as the depression amount increases from the speed signal and the accelerator pedal depression amount signal; and a waveform conversion device that outputs a signal with a predetermined waveform. and comparison means for generating a digital signal in which the duty ratio decreases as the rotational speed increases and increases as the amount of depression increases from the output signals of the differential means and the waveform converting means, and outputs the digital signal as the output of the backup circuit. It is possible to provide an engine control device characterized by having the following. In addition, in the engine control device according to the present invention, when the backup circuit is activated, in order to maintain the rotational speed of the engine stably according to the amount of depression of the accelerator pedal, especially when applied to a diesel engine, it acts as an electronic governor. There is no need to attach a mechanical governor. In other words, even if the computer goes out of control for some reason, the engine rotation speed can be controlled normally according to the amount of depression of the accelerator pedal, so the engine will not rotate abnormally or stop. There is no risk of damage to the vehicle or danger to human life. Furthermore, since the vehicle can be driven under its own power, the vehicle can be safely taken to a service factory or the like. Furthermore, even if the computer runs out of control, the runaway is automatically detected and the control is switched, so there is no interruption in engine control, which is also highly safe.

Although the present invention has been explained using one example, the present invention is not limited to this example, and various modifications can be made within the scope of the gist of the present invention, and these are not excluded from the scope of the present invention. do not have.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a block diagram of a signal generation circuit of the embodiment of Fig. 2, and Figs. FIG. 3 is a characteristic diagram of the main part, and FIG. 6 is an explanatory diagram of the output operation of FIG. 3. In the figure, 1... accelerator pedal, 2, 11... potentiometer, 3... control device, 4... actuator, 5, 6... control valve, 22... control rack, 23... plunger, 30... ...Computer, 36...Signal generation circuit, 37...Runaway detection circuit.

Claims (1)

[Scope of Claims] 1. In an engine control device having at least a backup circuit that controls the fuel supply amount in place of the computer when the computer that controls the fuel supply amount to the engine malfunctions, the engine rotation speed signal and the accelerator pedal differential means for outputting an analog signal that decreases as the rotational speed increases and increases as the rotational speed increases from the depression amount signal; a waveform conversion means that outputs a signal with a predetermined waveform; and comparing means for generating a digital signal in which the duty ratio decreases as the rotational speed increases and increases as the amount of depression increases from the output signal of the waveform converting means and outputs the digital signal as the output of the backup circuit. Characteristic engine control device. 2. The engine control device according to claim 1, wherein the engine is a diesel engine. 3. The engine control device according to claim 1 or 2, wherein the output of the backup circuit is provided to a fuel injection pump of the engine. 4. The engine control device according to claim 1, wherein the output signal of the waveform conversion means is a triangular wave.