JPH079201B2 - Abnormality diagnosis device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality diagnosis device for an internal combustion engine, and in particular, it is provided in each cylinder by feedback controlling the air-fuel ratio by an air-fuel ratio sensor provided in an exhaust passage. The present invention relates to an abnormality diagnosis device for an internal combustion engine that injects fuel with a fuel injection valve.

[Conventional technology]

Conventionally, the basic injection amount of the fuel injection valve is calculated according to the intake air amount and the rotation speed of the engine, and the basic amount is calculated according to the air-fuel ratio correction amount calculated based on the detection symbol of the oxygen concentration in the exhaust gas of the engine. A multi-cylinder internal combustion engine equipped with an air-fuel ratio feedback type electronically controlled fuel injection device that maintains an appropriate air-fuel ratio of the engine by correcting the injection amount is known. In such a fuel injection device, the control of the injection amount is performed by the valve opening time of the fuel injection valve, and the valve opening time is determined by the energization time to the fuel injection valve.

Further, in the fuel injection device as described above, at least one fuel injection valve is arranged collectively in the intake passage portion before the collecting portion of the intake manifold mainly for cost reduction, and is common to all the cylinders. The so-called single point injection (SP
There is an I) system or a cylinder-by-cylinder injection system in which one fuel injection valve is provided for each cylinder and fuel injection is performed simultaneously or independently for each cylinder.

However, in such a fuel injection device, if any one of the plurality of fuel injection valves has an abnormality such as disconnection or clogging, or a short circuit of the output circuit of the fuel injection valve drive circuit, the injection amount becomes appropriate. There is a problem in that the air-fuel ratio is greatly changed outside the amount, and the output is greatly reduced even if the engine is stopped or is not stopped, which deteriorates drivability.

Therefore, in the SPI type fuel injection device having a plurality of fuel injection valves, when an abnormality is detected in one of them, the remaining fuel injection valves supply the same amount of fuel as the injection amount before the abnormality occurs. There are those that perform correction injection so that the above is performed (for example, JP-A-60-069243 and JP-A-60-079135).
Gazette].

[Problems to be solved by the invention]

However, in an engine equipped with a fuel injection device of a cylinder-by-cylinder injection system, since a fuel injection valve is provided for each cylinder,
There is a problem that even if one fuel injection valve fails, the other fuel injection valves cannot be rescued. Therefore, when the fuel injection valve is abnormal, its early detection is necessary. Then, for early detection of abnormality of the fuel injection valve provided for each cylinder, an abnormality diagnosis device equipped with abnormality detection means for each injection valve is required, but it is costly to realize this. There was a point.

An object of the present invention is to solve the problems of the air-fuel ratio control device for an internal combustion engine equipped with the conventional cylinder-by-cylinder injection type fuel injection device, and in the cylinder-by-cylinder fuel injection system engine, the fuel injection valve of each cylinder is abnormal. An object of the present invention is to provide an excellent internal-combustion-engine abnormality diagnosis device capable of detecting an abnormality of a fuel injection valve based on an inversion state of an air-fuel ratio without providing a detection means.

[Means for solving problems]

An abnormality diagnosis device for an internal combustion engine according to the present invention that achieves the above object, as shown in FIG. 1, is an air-fuel ratio detecting means installed in an exhaust passage of an internal combustion engine, which includes a fuel injection valve for each cylinder,
Air-fuel ratio feedback means for performing feedback control of the air-fuel ratio by the output of this air-fuel ratio detection means, idle detection means for detecting the idle operation state of the internal combustion engine, and frequency detection means for detecting the air-fuel ratio feedback frequency in the idle operation state. Comparing the detected frequency with a set value higher than the frequency that can be taken when the fuel injection valve is normal, and in this comparing means, when the detected frequency is higher than the set value, the fuel injection valve is judged to be abnormal. It is characterized in that it comprises an abnormality determining means for determining.

[Action]

The internal combustion engine abnormality diagnosis device of the present invention, when detecting the idle operation state of the engine, measures the air-fuel ratio rich, the number of lean reversal, the air-fuel ratio rich within a predetermined time, when the lean reversal number is normal. It is determined that the fuel injection valve is abnormal when it is detected that the set value is larger than the possible number of reversals.

Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

FIG. 2 is an overall schematic diagram showing an internal combustion engine to which the present invention is applied. In FIG. 2, an air flow meter 3, a throttle valve 12, and a fuel injection valve 7 are provided in the intake passage 2 of the engine body 1 in this order from the upstream side of the intake passage 2.

The air flow meter 3 directly measures the intake air amount Q, and a built-in potentiometer generates an output signal of an analog voltage proportional to the intake air amount. This output signal is the A / D converter 1 with built-in multiplexer in the control circuit 10.
Supplied to 01.

The throttle valve 12 is closed during idle operation, and the opening thereof increases as the engine load increases. The throttle valve 12 has a built-in potentiometer 13, outputs a voltage proportional to the opening of the throttle valve, and is provided with an idle switch 14 for detecting the full closing of the throttle valve. The potentiometer 13 is connected to the A / D converter 101, and the idle switch 14 is connected to the input / output interface 102. The fuel injection valve 7 is provided for each cylinder and opens when energized to supply pressurized fuel to the intake port.

Further, an analog voltage proportional to the engine water temperature THW is generated by the water temperature sensor 11 attached to the cylinder block of the engine and is supplied to the A / D converter 101. The distributor 4 has its axis converted to, for example, a crank angle of 720
A crank angle sensor 5 for generating a reference position detection pulse signal for each ° and a crank angle sensor 6 for generating an angular position detection pulse signal for every 30 ° converted into a crank angle are provided. The pulse signals of these crank angle sensors 5 and 6 are supplied to the input / output interface 102 of the control circuit 10, of which the output of the crank angle sensor 6 is supplied to the interrupt terminal of the CPU 103.

The exhaust passage 8 of the engine is provided with an O ₂ sensor 9 that generates an electric signal according to the oxygen component concentration in the exhaust gas. The output of the O ₂ sensor 9 is supplied to the input / output interface 102 via the buffer circuit 109 of the control circuit 10 and the comparison circuit 110.

Further, 112 is an engine check lamp provided on an instrument panel or the like of a driver's seat for displaying an abnormality of the fuel injection valve 7 to an occupant of the vehicle. When output, it is turned on by the drive circuit 111.

The control circuit 10 is configured as, for example, a microcomputer, and has an A / D converter 101, an input / output interface 102, and a CPU 10.
3, a buffer circuit 109, a comparison circuit 110, a drive circuit 111, a ROM 104, a RAM 105, etc. are provided.
In 10, down counter 106, flip-flop 107
The drive circuit 108 is for controlling the fuel injection valve 7. That is, when the fuel injection amount TAU is calculated,
The fuel injection amount TAU is preset in the down counter 106 and the flip-flop 107 is also set. As a result, the drive circuit 108 starts energizing the fuel injection valve 7. On the other hand, when the down counter 106 counts a clock signal (not shown) and finally the carry-out terminal thereof becomes "1" level, the flip-flop 107 is reset and the drive circuit 108 is provided with the fuel injection valve 7. Stop the momentum. That is, the fuel injection valve 7 is energized by the above-mentioned fuel injection amount TAU, and accordingly, the amount of fuel corresponding to the fuel injection amount TAU is sent to the combustion chamber of the engine body 1.

The CPU 103 generates an interrupt when the A / D conversion of the A / D converter 101 is completed, when the input / output interface 102 receives the pulse signal of the crank angle sensor 6, or the like. In addition, the intake air amount data Q and the cooling water temperature data of the air flow meter 3
THW is fetched by an A / D conversion routine executed every predetermined time and updated and stored in a predetermined area of the RAM 105.

FIG. 3 is a partial circuit diagram of FIG. In FIG.
The buffer circuit 109 includes a capacitor 1091 and a resistor 1092, and the comparison circuit 110 includes an operational amplifier 1101 and resistors 1102 and 1103 that generate a comparison voltage VR (= 0.45 V). The resistor 1092 is for limiting the maximum level of the output voltage when the element temperature of the O ₂ sensor 9 becomes excessive. As a result, the output of the O ₂ sensor 9 is temporarily stored in the buffer circuit 109 and converted into a digital signal by the comparison circuit 110. This digital signal is
It is sent to the input / output interface 102 for air-fuel ratio feedback control. In addition, Vcc is a power supply voltage of the control circuit 10, and indicates 5 V, for example.

Next, an example of the control procedure of the control circuit 10 of the present invention in FIG. 2 will be described. Before that, the reason why the present invention uses FIG. 6 and FIG. Explain what to do.

FIGS. 6 and 7 show O ₂ when the fuel injection valve 7 of the first cylinder # 1 of the multi-cylinder engine causes a flow rate decrease of −20%.
FIG. 6 shows a change waveform of the output waveform of the sensor 9 and a change waveform of the air-fuel ratio correction value FAF. FIG. 6 shows an idle operation state, and FIG. 7 shows a case of no load and 2000 rpm. When the fuel injection valve of the # 1 cylinder causes a decrease in the flow rate, only the air-fuel mixture of the # 1 cylinder becomes lean, so that the exhaust gas discharged from the # 1 cylinder is always lean. Since the exhaust gas discharged from the other cylinders is normal, the air-fuel ratio data detected by the air-fuel ratio sensor pulsates according to the lean signal of the # 1 cylinder.

This pulsation can be seen from the comparison of FIGS. 6 and 7,
It appears remarkably in the output waveform of the O ₂ sensor at the time of idling, but it does not appear remarkably because the pulsation is dampened at the time of rotation higher than that at idling (2000 rpm in the example). For the above reason, in the present invention, the abnormality diagnosis of the fuel injection valve is performed during idling.

FIG. 5 shows the output waveform of the O ₂ sensor and the change waveform of the air-fuel ratio correction value FAF when the 4-cylinder engine is in normal idle operation. From this figure, when the engine is in normal idle operation, there are three large peaks in the output waveform of the O ₂ sensor in 5 seconds, and when the judgment level of rich and lean is 0.45V, FAF shows Give feedback like. At this time, the number of inversions of the O ₂ sensor is 6 and the feedback frequency is 0.5.

However, when the fuel injection valve of the # 1 cylinder causes a flow rate decrease of -20%, the O ₂ sensor outputs a lean signal (direction in which the voltage decreases) every time the lean exhaust gas from the # 1 cylinder hits. However, since the output waveform becomes a "comb" and the number of times when it exceeds the determination level of 0.45 V increases, the output waveform of the O ₂ sensor 9 becomes as shown in FIG. The number of reversals of the O ₂ sensor in this figure is 28, which is extremely larger than the number of times when the fuel injection valve is normally operating.

Therefore, in the present invention, the number of reversals of the output of the O ₂ sensor at the time of idling, that is, the feedback frequency is measured, and the set value is set to a value higher than the frequency that the measurement frequency can take when the fuel injection valve is operating normally. When the time exceeds the limit, the fuel injection valve is diagnosed as abnormal. This will be described below using a flowchart.

FIG. 4 is a routine executed every 8 ms, and shows an example of the control procedure of the control circuit 10 in FIG. In this routine, first, at step 401, it is judged if the engine is in the idle operation state. The determination of the idle operation state is made by the potentiometer which is the throttle valve opening sensor shown in FIG.
This is performed when a minute state of the throttle valve opening degree due to the output from 13 is detected or when the throttle valve is fully closed by the idle switch 14. When the idle state is detected in step 401 (YES), the step
In step 402, the idle time counter CNT is incremented by 1.

The next step 403 is a step for determining the elapsed time after the idle state, which is 5 after the idle state.
Whether or not the second has elapsed (this routine is executed every 8 ms, so whether or not the count value has reached 5000 ms / 8 ms = 625) is determined. If it is less than 5 seconds after the idle state, the process proceeds to step 404.

Step 404 In than the O ₂ O ₂ sensor signal and the current sensor when last time through this routine, the rich from the O ₂ sensor, whether a lean signal is inverted is determined, if inverted For example, in step 405, the O ₂ sensor inversion counter COX is incremented by 1 and the process proceeds to step 406, but if it is not inverted, it is not incremented in step 406.
Proceed to.

Step 406 is a step of counting the period of the rich / lean inversion signal from the O ₂ sensor, that is, the feedback frequency. Therefore, in step 406, the O ₂
It is judged whether or not the value of the sensor reversal counter COX is larger than the set value 25 which is set to a value higher than the feedback frequency that can be taken under normal conditions. If it is 25 or more (YES), step 4
At 07, an injection valve abnormality signal is output. When it is less than 25, the abnormality signal is not output and the routine proceeds to step 409. When the injection valve abnormality signal is output, this signal is amplified by the drive circuit 111 shown in FIG. 2, and the engine check lamp 112 is turned on.

If the engine that becomes NO in step 401 is not in the idle state, or if the idle state that becomes NO in step 403 continues for 5 seconds or more, proceed to step 408 to clear the CNT and COX Proceed to 409.

Then, in this step 409, it is judged whether or not the current signal of the O ₂ sensor 9 is rich, and when it is rich (YES), the routine proceeds to step 410, where the integration constant Ki is subtracted from FAF, and when it is lean (NO). Advances to step 411 to add the integration constant Ki to FAF.

What has been described above is a flow rate reduction abnormality of the fuel injection valve, but the same applies to the flow rate change to the rich side of the injection valve due to fuel leakage due to poor liquid tightness or foreign substance intervention in the needle valve portion of the injection valve. A phenomenon occurs, which can also be detected by the device of the present invention. Further, in the detection method of the above embodiment, even if half of all the injection valves are in an abnormal state, it can be detected. Further, in the above-described embodiment, the abnormality of the fuel injection valve is diagnosed by the increase of the feedback frequency. However, even if the abnormality of the injection valve is detected by detecting that the rich / lean inversion cycle is shortened. It is a good one.

The air-fuel ratio correction value FAF described above is reflected on the fuel injection amount TAU in a fuel injection routine (not shown).

〔The invention's effect〕

As described above, according to the abnormality diagnosis device for an internal combustion engine of the present invention, in the electronically controlled engine of the method of injecting fuel for each cylinder, the fuel can be easily measured by measuring the feedback frequency when the engine is in the idle state. There is an effect that an abnormality of the injection valve can be detected.

Further, since the abnormality of the fuel injection valve can be detected only by measuring the output of the O ₂ sensor, there is no need to provide a detection means for the fuel injection valve, which is advantageous in that the cost is low.

[Brief description of drawings]

FIG. 1 is an overall block diagram for explaining the configuration of the present invention, FIG. 2 is an overall schematic diagram showing an embodiment of an internal combustion engine abnormality diagnosis apparatus according to the present invention, and FIG. 3 is a portion of FIG. FIG. 4 is a circuit diagram, FIG. 4 is a flow chart showing an example of the control procedure of the control circuit of FIG. 2, and FIG. 5 is an output waveform of the O ₂ sensor when the engine is in normal idle operation and the air-fuel ratio at that time. FIG. 6 is a waveform diagram showing a change waveform of the correction value FAF, FIG. 6 is a diagram corresponding to FIG. 5 when one fuel injection valve causes a decrease in flow rate, and FIG. 7 is an engine operating at 2000 rpm with no load. FIG. 3 is a waveform diagram showing an output waveform of the O ₂ sensor when the air-fuel ratio is changing and a change waveform of the air-fuel ratio correction value FAF at that time. 1 ... Engine body, 2 ... Intake passage, 3 ... Air flow meter, 4 ... Distributor, 7 ... Fuel injection valve,
8 ... Exhaust passage, 9 ... O ₂ sensor, 10 ... Control circuit, 12
...... Throttle valve, 13 ...... Potentiometer, 14 idle switch, 112 ...... Engine check lamp.

Continuation of the front page (56) Reference JP-A-60-69243 (JP, A) JP-A-60-79135 (JP, A) JP-A-60-26137 (JP, A) JP-A-60-57415 (JP , A) JP-A-61-34331 (JP, A) JP-A-62-107252 (JP, A)

Claims (1)

[Claims] 1. An air-fuel ratio detecting means installed in an exhaust passage of an internal combustion engine having a fuel injection valve for each cylinder; and an air-fuel ratio feedback means performing feedback control of an air-fuel ratio by the output of the air-fuel ratio detecting means. , An idle detection means for detecting the idle operation state of the internal combustion engine, a frequency detection means for detecting the air-fuel ratio feedback frequency in the idle operation state, and a detected frequency that is higher than a frequency that can be taken when the fuel injection valve is normal. An abnormality diagnosing device for an internal combustion engine, comprising: comparing means for comparing the fuel injection valve with the comparing means; and abnormality determining means for determining that the fuel injection valve is abnormal when the detected frequency is higher than the set value.