JPS58174132A - Fuel injection controller - Google Patents

Abstract

PURPOSE:To maintain a function of fuel injection when a crank angle sensor is in failure, by performing the fuel injection with a prescribed frequency pulse signal in no relation to a crank angle at abnormality of the crank angle sensor. CONSTITUTION:If a crank angle sensor 6 causes a trouble, a reference signal S1 or a unit angle pulse S'1 is not output. This phenomenon is decided by a cpu2, and a selective signal S7 becoming a high level at fault time is output from an I/O interface 3. A back up signal generator circuit 9 outputs a pulse signal S8 of prescribed frequency. When the crank angle sensor is in failure, if the signal S7 becomes a high level, the signal S8 is output as an injection pulse S9. In this way, self running can be performed even when the crank angle sensor is in failure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a technique for maintaining fuel injection function when a crank angle sensor fails.

As a conventional fuel injection control device, there is one shown in FIG. 1, for example.

In FIG. 1, a control circuit 1 is composed of a microcomputer including a CPU 2, an input/output interface 3, a RAM 4, and a ROM 5.

Still, the crank angle sensor 6 is linked to the crankshaft of the internal combustion engine, and the crankshaft adjusts to a fixed reference angle (4 degrees) depending on the number of cylinders.
A reference angle signal S1 is output every time the cylinder rotates by 180° (for a cylinder, 120° for a six-cylinder).

The control circuit 1 performs calculations according to a program stored in the ROM 5 in advance.

That is, the intake air amount signal S2, the water temperature signal S, the starter signal S4, the idle signal S5, and various other signals indicating the engine operating state (not shown) are input, and the fuel injection amount is calculated according to these values.

Then, in synchronization with the reference angle signal S1, an injection pulse S6 having a data (pulse width) corresponding to the above calculation result is output.

For example, when the injection pulse S6 is injected once per crankshaft rotation in a six-cylinder engine, the reference angle signal S1 is
Output each time you input.

While the injection pulse S6 is at a high level, the transistor 7 constituting the fuel injection drive circuit is turned on, and the fuel injection valve 8 is opened to inject fuel into the engine.

The fuel pressure applied to the fuel injection valve 8 is always constant. Therefore, the injection amount for the second injection is a value corresponding to the valve opening time, that is, the date of the injection pulse S6.

Note that the above fuel injection amount is calculated, for example, by the following equation (1).

......(1) C...Various correction coefficients T8...Outside voltage correction K...Constant Q depending on engine type...Intake air amount N...Engine rotation speed still above The rotational speed N is usually calculated by counting unit angular pulses S'1 (for example, a signal output every time the crankshaft rotates by 1°) given from the crank angle sensor 6.

As described above, in the conventional fuel injection control device, the calculation of the fuel injection amount and the timing control of the fuel injection are performed based on the signal from the crank angle sensor. Therefore, if the crank angle sensor fails and its signal cannot be obtained, there is a problem that only one sensor is lost.

In order to solve the above problem, it is possible to have dual crank angle sensors so that even if one fails, the other crank angle sensor will operate, but having dual crank angle sensors would increase the cost significantly. This is not a practical solution due to space issues and other issues.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a fuel injection control device that can perform fuel injection without any trouble even if the crank angle sensor fails.

In order to achieve the above object, the present invention determines that the crank angle sensor has failed when the signal from the crank angle sensor is no longer output, and in that case, fuel injection is performed based on a pulse signal of a predetermined period. It is configured to do so.

In the present invention, when it is determined that the crank angle sensor has failed, the alarm device is activated to notify the driver of the occurrence of the failure, and information on the occurrence of the failure is still stored in a non-volatile memory. It is configured to facilitate diagnosis of the failure location.

The present invention will be described in detail below based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate the same parts.

In FIG. 2, when the crank angle sensor 6 fails, the reference angle signal S1 or unit angle pulse S'1 is no longer output. This phenomenon is determined by the CPU 2, and the input/output interface 6 outputs a switching signal S7 which becomes high level at the time of failure.

The backup signal generation circuit 9 outputs a pulse signal S8 with a predetermined period (details will be described later).

The selection circuit 10 is a circuit for outputting the pulse signal S8 as the injection pulse S9 when the crank angle sensor 6 fails and the original injection pulse S6 is no longer output. For example, the selection circuit 10 is a circuit as shown in FIG. It has a structure.

In FIG. 3, 13 and 14 are AND circuits, and 15 is an OR circuit. Note that one input of the AND circuit 13 is inverted and inputted.

When the switching signal S7 is at a low level (normal), the output of the AND circuit 14 is always at a low level, and the output of the AND circuit 13 is always at a low level.
The output becomes the same as the original injection pulse S6. Therefore, the output of the OR circuit 15, ie, the injection pulse S9 given to the transistor 7 of the fuel injection valve drive circuit, becomes the same as the original injection pulse S6.

On the other hand, if the switching signal S7 becomes high level at the time of failure, the pulse signal S8 will be output as the injection pulse S9, contrary to the above case.

Next, the backup signal generation circuit 9 will be explained.

The backup signal generation circuit 9 may basically be an oscillator that outputs a pulse signal with a constant period and constant data (constant pulse width).

However, if a pulse signal with a constant period and constant data is used as the injection pulse, it cannot correspond to the dynamic characteristics of the internal combustion engine, resulting in insufficient control.

In other words, when the data is constant, the fuel injection amount is always constant, so as the intake air amount changes, the air-fuel ratio of the mixture changes, making engine rotation unstable.

Therefore, it is desirable to change at least the data depending on the amount of intake air.

Further, if only the data is changed and the cycle is always constant, the following problems arise.

In other words, if the cycle is set longer, when the rotational speed of the internal combustion engine increases, the time between fuel injections will increase.
The intake stroke occurs two or more times, and some cylinders that do not receive fuel come out and fail, resulting in a decrease in engine output.

Conversely, if the cycle is set short, the error rate of the pulse width will increase when the data (pulse width) is small at low speeds, low loads, and the air-fuel ratio will fluctuate, causing the engine to Rotation may become unstable.

In the conventional fuel injection valves currently in use, if the valve opening time is short, the driving pulse does not pulse, so if the pulse width is set to a too small value, the control becomes inaccurate.

In order to solve the above problems, the pulse signal S8
It is only necessary to change the period according to the operating state of the internal combustion engine.

FIG. 4 is a diagram showing an embodiment of the backup signal generation circuit 9 based on the above consideration, and FIG. 5 is a signal waveform diagram of the circuit of FIG. 4.

In FIG. 4, a counter 16 counts and outputs clock pulses S1o of a constant period.

Further, a digital data value is written into the data register 19 by the signal C1 from the CPU 2.
A digital period value is written into the period register 20 by a signal C2 from the CPU 2.

Next, the comparator 17 compares the output of the counter 16 and the output of the duty register 19, and outputs a signal S11 when the two match.

The comparator 18 still compares the output of the counter 16 and the output of the period register 20, and if they match, it outputs a signal S12.
Output.

The flip-flop 21 is reset by the signal S11 and set by the signal S12. Further, the counter 16 should be reset every time the signal S12 is applied.

The pulse signal S8 output from the flip-flop 21 has a pulse width τ2 corresponding to the data value of the data register 19, as shown at 88 in FIG.
This becomes a pulse with a period τ1 corresponding to the period value of the period register 20.

By changing the above data value and cycle value according to the operating state of the engine, it is possible to perform control according to the operating state.

FIG. 6 is an embodiment of a flowchart for carrying out the above control, and shows a case where the cycle is switched into two stages depending on the amount of intake air.

In FIG. 6, first, at Pl, it is determined whether or not the crank angle sensor has failed based on the presence or absence of the reference angle signal S1 (or unit angle pulse) of the crank angle sensor 6.

If Pl is NO (normal), immediately go to END and start the next calculation.

If Pl is YES (failure), P2 outputs the switching signal S7 from the input/output interface 6, and then P3
, and it is determined whether the dog is a dog or not based on the intake air amount being a predetermined value.

P3. If the answer is YES, that is, if the intake air amount is larger than the predetermined value, there is a risk that the Norms width will become too small relative to the cycle as described above, so the cycle should be set to a short value (2 (llms). ).

First, in P4, the basic injection amount TP-20msxKxQ is calculated.

As shown in equation (1) above, under normal conditions, TP
The O value is calculated based on the rotational speed N and the intake air amount Q, but when the crank angle sensor fails, unit angular pulses are not output and it is therefore difficult to obtain the rotational speed N. TP is calculated based on the quantity Q.

Next, in P5, correction coefficients C for various corrections such as increase in water temperature, increase in start-up amount, increase in amount after idling, etc. are calculated.

Next, P6te actual fuel injection amount T1=TPxC+T8(T
S is a correction amount corresponding to the value of the battery voltage).

Next, in P7, 20m5 is set as the cycle value in the cycle register 20 in FIG. 4, and in P8, the data register 19
Then, the value of TI is set as the data value.

On the other hand, if P3 is No, the period is set to a long value of 60m5.

The calculation process is shown in P, ~P13, but the above P4~P
8 is the same except for the period value.

In the embodiment shown in FIG. 6, the cycle is changed into two stages depending on whether the intake air amount Q is larger than a predetermined value.
<0) It is preferable to provide a hysteresis characteristic by changing the predetermined value to be compared depending on the case. In this way, when the engine is operated with the intake air amount Q close to the predetermined value, it is possible to prevent the cycle from switching alternately between 20 m5 and 60 m5 and causing the air-fuel ratio to fluctuate.

Further, the cycle may be continuously changed in accordance with the amount of intake air.

Further, when the throttle valve is at the idle opening degree (the idle signal S5 is "1"), it generally indicates that the engine rotational speed is low, so the cycle may be switched by the idle signal S5. In other words, when idle, the cycle is lengthened,
Other than that, just keep it short.

Since the idle signal S5 is output in response to the opening and closing of the idle switch, the structure is simplified, and the program is also simplified, so that the capacity of the program memory can be reduced.

Immediately after the start of deceleration, the rotational speed may be high even if the throttle valve is closed. However, in this case, since the engine is decelerating, there is no problem even if some cylinders do not take in fuel.

Still in the embodiment of FIG. 2, when the crank angle sensor fails, the switching signal S7 is used to switch off the transistor 1.
1 is turned on to light up a warning lamp 12 (or a buzzer, etc.) to notify the driver of the occurrence of a failure.

According to the present invention, even if the crank angle sensor fails, the driver may not notice the failure as long as the vehicle can still be driven. However, the present invention is only a safety measure in the event of a failure, and does not mean that a mixture with an appropriate air-fuel ratio can always be supplied as in the case where there is no failure.

Therefore, if the engine is operated for a long time in a condition where the crank angle sensor has failed, there is a risk of damaging the catalyst device for purifying exhaust gas, etc., which is not preferable.

Therefore, when a failure of the crank angle sensor is detected, it is desirable to issue an alarm as described above to instruct the vehicle to go to a repair shop and drive with low load.

Next, in the embodiment shown in FIG. 2, a case is illustrated in which the backup signal generation circuit 9 and the selection circuit 10 are provided as independent circuits, but the functions of both circuits may also be shared by the input/output interface 3. You can do it.

In other words, in a device using a microconbeater, such as the device shown in FIG. 2, the input/output interface 6 should be composed of an LSI with versatile functions so that it can be used for various purposes. There are many.

Therefore, by switching the operation mode of input/output interface B, the functions of both of the above circuits can be provided.

FIG. 7 is a diagram showing an embodiment of the device based on the above consideration, and the same reference numerals as in FIG. 2 indicate the same parts.

As shown in FIG. 7, by configuring the input/output interface 6 to switch between normal and faulty signals by the internal switching operation, there is no need to add special circuits such as a selection circuit, and the converter calculation can be performed easily. Since it is only necessary to change the program, the device is simplified.

FIG. 8 is an embodiment diagram showing a specific example of the input/output interface 6 in the configuration shown in FIG. 7, and FIG. 9 is a signal waveform diagram of the circuit shown in FIG.

In FIG. 8, a clock pulse oscillator 3o outputs a clock pulse S1o of a constant period.

The backup signal generating section 31 is the same as the backup signal generating circuit shown in FIG. 4, and outputs a pulse signal S8 having a period .tau.1 and a pulse width .tau.2 as shown in FIG. 5.

Next, the injection pulse generator 32 is a circuit that outputs an injection pulse S6 during normal operation.

In the injection pulse generator 32, the AND circuit 22:
Clock pulse S1 while injection pulse S6 is at high level
It outputs the same pulse signal S13 as o.

The counter 23 counts the pulse signal S16 and is set when the reference angle signal S1 from the crank angle sensor 6 is applied. 11' Meanwhile, the duty register 24 receives the signal C! from the CPU 2. A digital data value is written by l.

The comparator 25 compares the output of the counter 26 and the output of the duty register 24, and when the two match, outputs a signal S14.
Output.

The flip-flop 26 is set when the reference angle signal S1 is applied, and is set when the signal S14 is applied.

Therefore, the injection pulse S6 output from the flip-flop 26 has the same period τ as the output interval of the reference angle signal S1.
3 and a pulse width τ4 corresponding to the data value of the data register 24, resulting in a steam pulse.

Next, the mode register 63 outputs a switching signal S7, which is at a low level when normal and becomes high level when a failure occurs, in response to the signal C4 from the CPU 2.

Next, the mode switch 34 outputs the original injection pulse S6 when the switching signal S7 is at a low level, and outputs the pulse signal S8 when the switching signal S7 is at a high level.

The output of this mode switch 34 is the injection pulse S.

becomes.

Next, FIG. 10 is a diagram showing another embodiment of the present invention, and the same reference numerals as in FIG. 2 indicate the same parts.

In FIG. 10, a pulse oscillator 65 outputs a constant cycle pulse signal S15.

When the switching signal S7 is at a low level (normal state), the groove switching circuit 66 outputs the reference angle signal S1 and outputs the switching signal S7.
When is at a high level (at the time of failure), a pulse signal S15 is output.

The configuration is such that the output of this switching circuit 66 is given to the input/output interface B.

With the above configuration, the signal itself input to the input/output interface 6 is automatically switched and inputted depending on whether it is normal or not.

Therefore, the operation of the input/output interface 3 and the calculation of the fuel injection amount in the CPU 2 are exactly the same in normal conditions and in failure conditions, which has the effect of simplifying the program and saving the capacity of the program memory. .

If an oscillator with a variable cycle is used as the pulse oscillator 35, and the cycle of the pulse signal S15 is switched by switching to the idle signal S, etc., even better control can be achieved. 'Next, FIG. 11 shows still another embodiment of the present invention, in which the same reference numerals as in FIG. 10 indicate the same parts.

The embodiment shown in FIG. 11 is provided with a non-volatile memory 37 for storing the fact that the crank angle sensor 6 has failed.

A failure of the crank angle sensor 6 may be a permanent failure, but it may also be an occasional failure.

In the case of such a failure, it is extremely difficult to find the failure location.

Therefore, when it is determined that the crank angle sensor 6 has failed, it is desirable to memorize its history.

Therefore, in the embodiment shown in FIG. 11, the non-volatile memory 67 is used to store the fact that the crank angle sensor 6 has failed, thereby making it possible to easily discover the failure of the crank angle sensor at a service shop or the like. It is structured in a simple manner.

The purpose of using non-volatile memory is to prevent the stored contents from being erased when the power is turned off (when the engine is stopped).

In addition, as the non-volatile memory 67, MNOS, EE
Things that are themselves non-volatile like P ROM and CMO
It is possible to use a RAM configured to perform a backup operation on the RAM of 8.

As explained above, according to the present invention, even if the crank angle sensor fails, the fuel injection function can be maintained to the extent that the engine can operate without any problems, so it is possible to drive to the repair shop or home by yourself. become. By configuring the system to memorize the occurrence of a malfunction in the crank angle center, it becomes easy to find and repair the malfunctioning part. Further, by configuring the system to issue an alarm in the event of a failure, there are many effects such as being able to prevent damage to the catalyst device and the like due to continued operation for a long time without noticing the failure.

[Brief explanation of drawings]

Fig. 1 is a diagram of an example of a conventional fuel injection control device, Fig. 2 is a diagram of an embodiment of the present invention, Fig. 3 is a diagram of an embodiment of a selection circuit, and Fig. 4 is an embodiment of a backup signal generation circuit. 5 is a signal waveform diagram of the circuit of FIG. 4, FIG. 6 is an embodiment of a flowchart showing the calculation process, FIG. 7 is an embodiment of the present invention, and FIG. 7 shows one embodiment of the input/output interface, FIG. 9 shows a signal waveform diagram of the circuit of FIG. 8, and FIGS. 10 and 11 show other embodiments of the present invention. Explanation of symbols 1,71... Control circuit ° 2... CPU6... Input/output interface 4... RAM 5... ROM6...
Crank angle sensor 7...Transistor 8...Fuel injection valve 9...Backup signal generation circuit 10...Selection circuit 11...Transistor 1
2... Alarm lamp 16.14... AND circuit 15... OR circuit 16... Counter 17.
18... Comparator 19... Duty register 20... Period register 21... Flip-flop 22... AND circuit 26... Counter 24
... Duty register 25 ... Comparator 26 ... Flip-flop 60 ... Clock pulse oscillator 31 ... Backup signal generation section 62 ... Injection pulse generation section 66 ... Mode register 34 ... Mode switch 65
...Pulse oscillator 66...Switching circuit 37...
Nonvolatile memory Sl...Reference angle signal S6...Original injection pulse S7...Switching signal S8...Backup pulse signal S9...Injection Hals S1o...Clock pulse S15...
Constant periodic pulse signal Representative patent attorney Junnosuke Nakamura 1'1 Figure C2C. Figure 9F5; □ ″ 'rm-r, --□: Figure 19 1'IO diagram

Claims (11)

[Claims] (1) a crank angle sensor that outputs a first signal at a predetermined crank angle in synchronization with the rotation of the crankshaft of the internal combustion engine;
a first means for outputting an injection pulse synchronized with the signal;
In a fuel injection control device comprising a fuel injection valve drive circuit that drives a fuel injection valve according to the injection pulse, when at least a part of the first signal is not output and the crank angle sensor is activated, the crank angle sensor is activated. a third means for determining that the crank angle sensor has failed and applying a pulse signal of a predetermined period unrelated to the crank angle to the fuel injection valve drive circuit instead of the injection pulse; 1. A fuel injection control device that controls a fuel injection valve drive circuit to perform a fuel injection operation. (2) When the first means is configured in a microcomputer, the injection pulse and the pulse signal of a predetermined period are switched by switching the operation mode of an input/output interface in the microcomputer. Claim 1 characterized in that it is configured to output
The fuel injection control device described in . (3) The sixth means includes means for generating a pulse signal of a predetermined period, and a switching means for supplying the pulse signal to the fuel injection valve drive circuit in place of the injection pulse output from the first means when a failure occurs. A fuel injection control device according to claim 1, characterized in that it is comprised of: (4) The sixth means includes means for generating a pulse signal of a predetermined period, and switching means for supplying the pulse signal to the first means instead of the first signal of the crank angle sensor when a failure occurs. 2. The fuel injection control device according to claim 1, wherein the fuel injection control device is configured as follows. (5) The fuel according to any one of claims 1 to 4, characterized in that the period of the pulse signal having the predetermined period is configured to change depending on the operating state of the internal combustion engine. Injection control device. (6) The fuel injection control device according to claim 5, characterized in that the above-mentioned period is configured to change according to the intake air amount of the internal combustion engine. (7) The fuel injection control device according to claim 5, wherein the cycle is configured to be switched to a different value depending on whether or not the internal combustion engine is in an idle state. (8) The fuel according to any one of claims 1 to 6, characterized in that the pulse width of the pulse signal of the predetermined period is changed depending on the operating state of the internal combustion engine. Injection control device. (9) A fuel injection control device as set forth in claim 8, wherein the pulse width is configured to be changed in accordance with the intake air amount of the internal combustion engine. □ (10) a crank angle sensor that outputs a first signal at a predetermined crank angle in synchronization with the rotation of the crankshaft of the internal combustion engine; In a fuel injection control device comprising a first means for outputting an injection pulse and a fuel injection valve drive circuit for driving a fuel injection valve according to the injection pulse, at least a part of the first signal is output. sixth means for determining that the crank angle sensor has failed when the crank angle sensor is out of order and supplying a pulse signal of a predetermined period unrelated to the crank angle to the fuel injection valve drive circuit in place of the injection pulse; A fuel injection control device comprising: alarm means that is activated when the means determines that the crank angle sensor has failed to indicate the occurrence of a failure. (11) a crank angle sensor that outputs a first signal at a predetermined crank angle in synchronization with the rotation of the crankshaft of the internal combustion engine; In a fuel injection control device comprising a first means for outputting an injection pulse and a fuel injection valve drive circuit for driving a fuel injection valve according to the injection pulse, at least a part of the first signal is output. sixth means for determining that the crank angle sensor has failed when the crank angle sensor is out of order and supplying a pulse signal of a predetermined period unrelated to the crank angle to the fuel injection valve drive circuit instead of the injection pulse; A fuel injection control device comprising: a nonvolatile memory that stores failure information when the means determines that a crank angle sensor has failed.