JPH0467586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an operation monitoring method for monitoring the operation of an injection time measuring means for timing the opening time of a fuel injection valve of an internal combustion engine and detecting an abnormality thereof.

(Technical background and problems thereof) The valve opening time of the fuel injection valve, which is determined according to the operating state of the internal combustion engine, is set in the injection time clocking means, and this occurs while the timing means measures the set time. A fuel injection control device that opens the fuel injection valve based on a continuous activation signal is generally known.

As a method for detecting an abnormality in such a fuel injection control device, particularly in the injection time measuring means, there is a method of comparing a control signal output from the central processing unit to the time measuring means and an activation signal output from the time measuring means. Traditionally done.

More specifically, the central processing unit detects a change from on to off or from off to on in a control signal representing a valve opening time according to the engine operating state, which is output to the injection time measuring means, and detects the detected change. An abnormality in the timer is detected by determining whether or not the operating signal, which is the output of the timer, changes in response to the change in the control signal.

However, depending on a specific high-load operating state of the engine, for example, at high engine speeds when the interval between occurrences of the TDC signal as a control timing signal becomes short, the control signal input from the central processing unit to the timing means may be The on state may be maintained, and in such a case, there is a problem in that it becomes impossible to detect an abnormality in the injection time measuring means using the method described above.

(Object of the Invention) The present invention has been made in view of the above problems, has a simple configuration, and constantly monitors the operation of the injection time measuring means of the fuel injection control device regardless of the operating state of the engine. It is an object of the present invention to provide an operation monitoring method that can detect the abnormality.

(Structure of the invention) According to the present invention, in order to achieve such an object,
a central processing unit that calculates the opening time of the fuel injection valve according to the operating state of the internal combustion engine; and a central processing unit that sets the operating time of the fuel injection valve based on a control signal from the central processing unit that corresponds to the valve opening time. In the operation monitoring method for monitoring the operation of a fuel injection control device, the central processing unit calculates the valve opening time, and includes an injection time clock unit that continues to output an operation signal of the injection valve while counting the operation time. Immediately after the completion of the operation, the central processing unit generates a signal for prohibiting the output of the activation signal to the injection time measurement means for a predetermined period of time, and when the output of the activation signal is prohibited, the activation signal from the injection time measurement means is transmitted to the injection time measurement means. A method for monitoring the operation of a fuel injection time measuring means for an internal combustion engine is provided, which comprises reading the operating signal into a central processing unit and determining an abnormality in the injection time measuring means based on the read operation signal.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the circuit configuration of a fuel injection control device for an internal combustion engine (for example, a 6-cylinder engine) to which the operation monitoring method according to the present invention is applied.
The fuel injection control device is basically a central processing unit 1,
and an injection time measuring means 3, an asynchronous addition circuit 4, which are connected in series to the output side of the central processing unit 1.
It consists of a NOR/BU selection circuit 5 and a fuel injection valve 7. The central processing unit (hereinafter referred to as "CPU") 1 synchronizes with the engine rotation and determines the opening time T _OUT of the fuel injection valves (#1 to #6) 7 according to the engine operating state.
At the same time, when the engine is in a predetermined acceleration state, a valve opening time T ₂ that is not synchronized with the engine rotation for increasing the amount of acceleration fuel is calculated. The CPU 1 determines which of the fuel injection valves #1 to #6 the valve opening time T _OUT thus calculated is to be applied to, and sends a signal corresponding to the calculated valve opening time to the injection time clock via the data bus 2. and sending it to a counter corresponding to the applied injection valve of means (hereinafter referred to as "Ti timer") 3;
A signal corresponding to the valve opening time _T2 is sent to the data bus 2.
to the asynchronous counter of Ti timer 3.
The Ti timer 3 consists of a plurality of counters (for example, seven) corresponding to the number of cylinders in the engine, and the time that the counters should count is set based on the above-mentioned signal input from the CPU 1. Ti timer 3
Each counter outputs an activation signal to open the fuel injection valve while counting the set time. The operation signal output from the Ti timer 3 is sent to the asynchronous addition circuit 4, and is also sent to the CPU 1 as a signal for monitoring the operation of the Ti timer 3. For example, in the case of a 6-cylinder engine, the asynchronous addition circuit 4
Consists of six OR gates, one input terminal of each OR gate is connected to the asynchronous Ti counter of Ti timer 3, and the other input terminal is the activation signal of the corresponding fuel injection valve (#1 to #6) 7. output
It is connected to each counter (#1 to #6) of Ti timer 3. The signals representing the opening time of each of the injection valves (#1 to #6) 7, which have been asynchronously corrected by the asynchronous addition circuit 4 during a predetermined acceleration state of the engine, are further controlled during normal operation and during abnormal operation. Select one of the backup controls for
It is sent to the NOR/BU selection circuit 5. The output sides of an abnormality compensation circuit (hereinafter referred to as "BU circuit") 6 and a monitoring circuit 8 are connected to the NOR/BU selection circuit 5. The monitoring circuit 8 is a well-known watchdog timer, and its input side is connected to the CPU 1 so that an abnormality determination signal from the CPU 1 is supplied thereto.
That is, when the CPU 1 or the Ti timer 3 is operating normally, pulses generated at regular intervals as the abnormality determination signal are supplied to the monitoring circuit 8, and when the CPU 1 or the Ti timer 3 is operating abnormally, the supply of the pulses is cut off. The monitoring circuit 8 sends an abnormality signal to the NOR/BU selection circuit 5 when the pulse is cut off, and the selection circuit 5 switches the fuel injection control from the normal mode to the backup mode in response to the abnormality signal, and the BU circuit 6 Activate.

Regarding the abnormality determination of the Ti timer 3, as described above, the operation signal supplied from each counter of the Ti timer 3 to the asynchronous addition circuit 4 is also supplied to the CPU 1, and the CPU 1 uses the Ti timer described below based on this operation signal. The abnormality determination subroutine determines whether or not there is an abnormality in the Ti timer 3. When an abnormality in the Ti timer 3 is detected by this subroutine, the CPU 1 stops supplying the constant cycle pulse to the monitoring circuit 8, and the monitoring circuit 8 switches to the control mode when the supply of the pulse is stopped. Switch from normal mode to backup mode.

Next, a method for determining an abnormality in the Ti timer of a fuel injection device according to the present invention will be explained with reference to a graph showing the time change of the operating signal output from the Ti timer 3 shown in FIG. 2, and a subroutine for determining an abnormality in the Ti timer shown in FIG. This will be explained with reference to the program flowchart.

The solid line in Figure 2 indicates that the engine is in a high rotation region, etc.
The broken lines represent the changes in each signal when the control signal from the CPU 1 is in a specific operating range in which it remains on, and the broken lines represent the changes in each signal in the normal operating range.
The program shown in FIG. 3 applies to each cylinder (not shown) in which the injection valve (#1 to #6) 7 shown in FIG. 1 is arranged.
This is executed by the CPU 1 every time a signal (TDC signal) is generated at a predetermined crank angle before the start of the intake stroke.

When the TDC signal is input to CPU1 (at time t ₁ )
The valve opening time T _OUT of the fuel injection valve 7 shown in FIG. 1 is calculated according to the operating state when the TDC signal is generated (step 1). In the next step 2, CPU 1 starts the Ti timer 3 counter (#n) of the cylinder corresponding to the TDC signal this time.
Ti is a command signal that forcibly turns off the operating signal of Ti.
The signal is continuously outputted to the timer 3 for a predetermined time T (time period _t2 to _t6 ). This predetermined time T is a time shorter than the response delay time of the injection valve 7, that is, even if the injection valve 7 continues to be opened when the engine is in a high load operating state such as in a high rotation region, the above predetermined time T is It is set to a short time such that the off command signal does not substantially affect the fuel injection amount.

In this embodiment, the predetermined time T is set by the program processing time from step 2 to step 5, which will be described later. In the next step 3, Ti
In order to compensate for the response delay of the timer 3, that is, the delay in the activation signal of the Ti timer 3 (FIG. 2 b) with respect to the command signal from the CPU 1 (FIG. 2 a), a predetermined time Δt ₁ is set.
(several μs) and then proceed to step 4.
It is determined whether the activation signal of the Ti timer 3 has actually been turned off by the command signal from the CPU 1 (at time _t5 ).

Even if the engine is in the high rotation range, the Ti timer 3
During normal operation, the operating signal is off at time _t5 in FIG. 2, so the determination result in step 4 is affirmative (Yes), and in the next step 5, the control signal corresponding to the valve opening time T _OUT is That is, a signal that turns on the activation signal of the Ti timer 3 is generated from the CPU 1 (at time t ₆ ). In the next step 6, it is determined whether or not T _OUT calculated in step 1 is greater than a predetermined value T _CHK (at time t ₇ ), and the determination result is affirmative (Yes).
If so, proceed to step 7 in the same way as step 3 above.
Wait for a predetermined time Δt ₂ (several μs) longer than the response delay time of Ti timer 3 to elapse (between time t ₈ and time _{t 10} ).
After compensating for the response delay of the Ti timer 3, the process proceeds to the next step 8, where it is determined whether the actual activation signal of the Ti timer has been turned on by the command signal from the CPU 1 (at time _t10 ). In this case, when Ti timer 3 is normal, the activation signal (Fig. 2b) is on at time _t10 , so this determination result is affirmative (Yes).
Then, normal processing is performed (step 11).

On the other hand, if the determination result in step 6 is negative (No), steps 7 and 8 are skipped and the step
Go to 11. The reason why the determination in step 6 is provided in this way is that if the valve opening time T _OUT determined in step 1 is extremely short, even if the Ti timer 3 is normal, the determination in step 8 is performed ( This is because the actuation signal may turn off at t ₁₀ ).

If the determination result in either step 4 or step 8 is negative (No), proceed to step 9 and add 1 to the abnormality occurrence count N _ERR to calculate a new count.
N _ERR . The value of the number of abnormality occurrences N _ERR can be set to zero at predetermined intervals (for example, every 1 second). In the next step 10, it is determined whether the number of abnormality occurrences N _ERR obtained in step 9 is greater than or equal to a predetermined number N _Ti (for example, 3 times), and if the determination result is negative (No), normal processing is performed ( Step 11); if affirmative (Yes), abnormality processing is performed (step 12).

In this embodiment, as a process for such an abnormality,
CPU 1 stops generating constant period pulses to monitoring circuit 8 and changes the control mode from normal mode to BU circuit 6.
Switch to backup mode.

Furthermore, the operation of the asynchronous counter, which is a part of the Ti timer, can be monitored by performing the same steps as shown in FIG. 3 in synchronization with a constant cycle control signal instead of the TDC signal.

(Effects of the Invention) As detailed above, according to the method of the present invention, a central processing unit that calculates the opening time of the fuel injection valve according to the operating state of the internal combustion engine, and a Operation of a fuel injection control device comprising an injection time clock unit that sets an operating time of a fuel injection valve based on a control signal from a central processing unit and continues to output an operating signal of the injector while counting the operating time. Immediately after the central processing unit finishes calculating the valve opening time, the central processing unit generates a signal for a predetermined period of time to prohibit the output of the operating signal to the injection time measuring means. The operation signal from the injection time measuring means is read into the central processing unit when the output of the operating signal is prohibited, and an abnormality in the injection time measuring means is determined based on the read operation signal. With a device having such a configuration, it is possible to constantly monitor the operation of the injection time measuring means of the fuel injection control device regardless of the operating state of the engine, and to detect abnormalities therein.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of a fuel injection control device for an internal combustion engine to which the method of the present invention is applied, and FIG. 2 is a timing diagram showing temporal changes in the operating signal output from the Ti timer 3 in FIG. FIG. 3 is a program flowchart illustrating a Ti timer abnormality determination subroutine according to the present invention. 1...Central processing unit (CPU), 3...Injection time measuring means (Ti timer), 7...Fuel injection valve (#1~
#6), 8...Monitoring circuit.

Claims (1)

[Scope of Claims] 1. A central processing unit that calculates the valve opening time of the fuel injection valve according to the operating state of the internal combustion engine, and a central processing unit that calculates the valve opening time of the fuel injection valve based on a control signal from the central processing unit that corresponds to the valve opening time. In an operation monitoring method for monitoring the operation of a fuel injection control device, the method includes: an injection time clock means for setting an operation time of the injection valve and continuing to output an operation signal of the injection valve while counting the operation time;
Immediately after the central processing unit finishes calculating the valve opening time, the central processing unit generates a signal for prohibiting the output of the actuation signal to the injection time measuring means for a predetermined period of time, and prohibits the output of the actuation signal. A fuel injection time measuring means for an internal combustion engine, characterized in that an operating signal from the injection time measuring means is read into the central processing unit, and an abnormality in the injection time measuring means is determined based on the read operating signal. Operation monitoring method. 2. When a second predetermined time period shorter than the predetermined time period has elapsed since the generation of the signal for inhibiting the output of the actuation signal, the actuation signal from the injection time measuring means is read into the central processing unit, and the read operation signal is activated. Claim 1, characterized in that an abnormality in the injection time measuring means is determined based on the signal.
A method for monitoring the operation of a fuel injection time measuring means for an internal combustion engine as described in . 3. The method for monitoring the operation of a fuel injection time measuring means for an internal combustion engine according to claim 2, wherein the second predetermined time is longer than a response delay time of the injection time measuring means. 4. Immediately after the elapse of the predetermined time, an operating signal from the injection time measuring means is read into the central processing unit, and an abnormality in the injection time measuring means is determined based on the read operating signal. A method for monitoring the operation of a fuel injection time measuring means for an internal combustion engine according to scope 1. 5. The method for monitoring the operation of a fuel injection time measuring means for an internal combustion engine according to claim 4, wherein the predetermined time is shorter than a response delay time of the fuel injection valve.