JP2697057B2 - 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 detecting an abnormality of a fuel injection valve or the like of an internal combustion engine.

[Prior Art] Conventionally, as this kind of abnormality diagnosis device, for example,
The thing of 62-298643 gazette is known. That is, at the time of idle speed control, the output voltage of the oxygen sensor is equal to the predetermined voltage (0.45 V) for determining whether the air-fuel ratio is rich or lean.
V) to detect the feedback frequency when crossing,
When this frequency is larger than the set value, it is determined that the fuel injection valve is abnormal.

However, in this conventional technique, since the detection determination is performed at the time of idle speed control with a low feedback frequency, not only failure due to malfunction of the fuel injection valve or clogging of the fuel passage in the fuel injection valve, but also other problems In addition, there is a problem that a slight decrease in the injection amount due to a difference in the fuel injection valve is determined to be an abnormality of the fuel injection valve. Further, in this technique, since the abnormality is diagnosed based on the feedback frequency, it is difficult to distinguish whether the abnormality is caused by the oxygen sensor or the fuel injection valve. Furthermore, in this technology, the output voltage of the oxygen sensor is a predetermined voltage (0.45V)
There is also a problem that an abnormality cannot be detected unless it is a remarkable failure that decreases to below, and for example, a slight abnormality such as a decrease in the fuel injection amount due to a minute vibration of the combustion injection valve cannot be detected.

Further, as another conventional technique, as described in Japanese Patent Application Laid-Open No. 62-107252, a lean state that appears temporarily at predetermined intervals is detected when the engine should be in a rich state at a high engine load. In some cases, a failure of one of the plurality of fuel injection valves is detected. However, in this conventional technique, since a high engine load condition is employed as a condition for performing the abnormality diagnosis, a failure due to a minute vibration of the fuel injection valve, which easily appears in a steady state, is detected. However, there is a problem that the detection ability is low.

An object of the present invention is to solve the problems of the above-described conventional technology, and to accurately detect a failure such as clogging of a fuel passage in a fuel injection valve or a minute vibration in distinction from a failure of an oxygen sensor or the like. It is an object of the present invention to provide a device for diagnosing abnormality of an internal combustion engine that can be used.

[Means for Solving the Problems] To solve the above problems, the present invention provides an air-fuel ratio detecting means provided in an exhaust passage M2 of an internal combustion engine M1, as shown in FIG.
M3 and the fuel injection valve M4 based on the output signal of the air-fuel ratio detection means M3.
And a signal output from the air-fuel ratio detecting means M3 within an engine operating state in which the frequency of the feedback control is stable within an air-fuel ratio rich reference range. A reference range determining means M6 for determining whether or not the output signal from the air-fuel ratio detecting means M3 is greater than or equal to a predetermined deviation when the reference range determining means M6 determines that the output signal is within the reference range. Abnormality determination means M7 for detecting an inverted state and outputting an abnormal signal when the inverted state is equal to or more than a predetermined number of times.

[Operation] In the present invention, the amount of fuel injected from the fuel injection means M4 is controlled by the feedback control means M5 based on the output signal of the air-fuel ratio detection means M3 provided in the exhaust passage M2 of the internal combustion engine M1. Further, the output signal from the air-fuel ratio detecting means M3 is also input to the reference range determining means M6. The determining means M6 determines whether the detection signal output from the air-fuel ratio detecting means M3 is within an air-fuel ratio rich reference range under an engine operating state in which the feedback frequency is stable, and determines whether the detection signal is within the reference range. Is determined, the result of this determination is input to the abnormality determination means M7. The abnormality judging means M7 detects an inversion state of a predetermined deviation or more of the output signal based on the judgment result, and outputs an abnormality signal when the inversion state is a predetermined number of times or more.

Therefore, even if the output signal of the oxygen sensor does not reverse between rich and lean, a failure of the fuel injection valve or the like that appears as a signal that slightly fluctuates within the rich range can be easily detected.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.
FIG. 2 is a schematic configuration diagram showing an engine to which the abnormality diagnosis device of the embodiment is applied and peripheral devices thereof. As shown in the figure, an engine 1 mixes air sucked from the atmosphere with fuel injected from a fuel injection valve 3 provided for each cylinder and guides the mixture to an intake port 5 and a spark plug 9. Fuel chamber for taking out the energy of the combustion of the air-fuel mixture ignited by the formed electric spark as a rotational movement via a piston 10
An exhaust system 13 that exhausts the burned gas through an exhaust port 12 is provided.

An air cleaner (not shown), an air flow meter 15 for detecting the amount of intake air, a throttle valve 16 for controlling the amount of intake air, and a surge tank 18 for smoothing the pulsating flow of the intake air are provided in the intake system 7 from the upstream. Have been. Normally, the intake air amount is controlled by the opening of a throttle valve 16 linked to an accelerator pedal (not shown). The intake system 7 has a throttle position sensor for detecting the operating state of the engine 1 in addition to the air flow meter 15.
23 and an intake air temperature sensor 24 are provided.

A mixture of air sucked through the throttle valve 16 and fuel injected from the fuel injection valve 3 is sucked into the combustion chamber 11, compressed by the piston 10, and then compressed by an electric spark formed in the spark plug 9. Ignite. The ignited air-fuel mixture explosively burns, drives the piston 10, becomes exhaust gas, is discharged to the exhaust system 13, is purified by a catalyst device (not shown), and is released to the atmosphere. This exhaust system 13
Is provided with an oxygen sensor 25 for detecting the oxygen concentration in the exhaust gas.

The ignition plug 9 provided in each cylinder of the engine 1 is connected to a distributor 29 that distributes a high voltage generated in the igniter 27 in synchronization with rotation of a crankshaft (not shown) by a high withstand voltage cord. In the distributor 29, a rotation speed sensor 32 for generating a pulse corresponding to the rotation speed of the engine 1 and a cylinder discrimination sensor 34 are provided. The cylinder block 38 of the engine 1 is
The temperature of the cooling water, which is being cooled by the circulating cooling water and is one of the operating states of the engine 1, is detected by a cooling water temperature sensor 39 provided in the cylinder block 38.

The output signal of each sensor that detects the operating state of the engine 1 is input to the electronic control unit 70. The electronic control unit 70
As shown in FIG. 3, a CPU 71, a ROM 72, a RAM 73, etc. are built in, an A / D converter 74, an input / output interface 7
5, 76 and a backup RAM 77 are mainly configured. The input / output interface 75 has a rotation speed sensor
32, the cylinder discrimination sensor 34 and the throttle position sensor 23 are directly connected, and the A / D conversion air 74 includes an air flow meter 15, an intake air temperature sensor 24, an oxygen sensor 25, and a cooling water temperature sensor.
39 etc. are connected, and the input / output interface 76 has
The fuel injection valve 3, the igniter 27 and the warning lamp 81 are connected via a drive circuit.

The electronic control unit 70 having such a configuration is used for the engine 1
The operation state is read to perform various controls, that is, the air-fuel ratio feedback control and the ignition timing control using the oxygen concentration in the exhaust gas are executed. The abnormality diagnosis process of the fuel injection valve 3, which is a simple process, will be described mainly with reference to FIG.

In this control, after the ignition key is turned on, initialization including the initialization of a flag, a counter, and the like indicating an abnormal state of the combustion injection valve 3 is performed, and then the processing of step 100 and thereafter is executed. First, step 100
Then, the output voltage Vg of the oxygen sensor 25 is read through the A / D converter 74 at predetermined time intervals. In the following step 105, it is determined whether the self-diagnosis condition of the fuel injection valve 3 is satisfied based on the set / reset state of the flag FA. That is, this flag FA is set by the processing shown in the flowchart of FIG. 5, and in steps 101 to 103, the cooling water temperature is determined based on the detection signal of the cooling water temperature sensor 39 during the execution of the feedback control. When the three conditions of 70 ° C. or higher and the engine speed of 2000 rpm or more are satisfied based on the output signal of the speed sensor 32, it is determined that the engine is in a steady operation state after warm-up. In step 104, a flag FA indicating that the self-diagnosis of the fuel injection valve 3 is possible is set. On the other hand, when the above three conditions are not satisfied, the flag FA is reset in step 105.

If the result of the determination in step 107 is that the condition for performing a self-diagnosis is not satisfied, that is, if the engine is not in a steady operation state, the present routine is temporarily terminated. On the other hand, when it is determined in step 107 that the self-diagnosis condition is satisfied, the process proceeds to step 110, in which it is determined whether the output voltage Vg of the oxygen sensor 25 is equal to or higher than a predetermined voltage (0.45 V), It is determined whether the air-fuel ratio is on the rich side or on the lean side. Here, if it is determined that it is on the rich side, the process proceeds to step 115, where the output voltage Vg _OLD obtained in the previous process is read from the RAM 73,
The difference ΔVg between the output voltage Vg _OLD and the current output voltage Vg is calculated.

In the following step 120, it is determined whether or not the output voltage Vg is inverted based on the positive / negative change state of the difference ΔVg. If it is determined in step 120 that it is reversed, the process proceeds to step 125, where it is determined whether or not the difference ΔVg is equal to or greater than the predetermined deviation voltage 0.1 V, and the predetermined deviation voltage
If it is 0.1 V or more, the inversion counter CA is counted up in step 130. If a negative determination is made in steps 120 and 125, the output voltage Vg
Is determined not to be inverted, and a step 145 described later is performed.
Move to.

In step 135, it is determined whether or not the inversion counter CA is 6 or more. If it is 6, the abnormality determination counter CB is counted up in step 140. That is,
When the output voltage Vg of the oxygen sensor 25 is 0.45 V or more, and the difference ΔVg is 0.1 V or more, the number of inversions is measured, and when the rotation is 6 times or more, that is, when there is a peak of 3 times or more. Then, the abnormality determination counter CB is counted up. In the following step 145, the current output voltage Vg is set to the output voltage Vg _OLD for the next processing, and this is stored in the RAM 73, followed by terminating the present routine.

On the other hand, if the output voltage Vg is less than 0.45 V, that is, if it is determined that the air-fuel ratio has switched from rich to lean, the inversion counter CA is reset in step 150. In the next step 155, the count number of the abnormality determination counter CB is determined. If the count is 10 or more, that is, if the inversion of the output voltage Vg is detected 6 times or more in total, 10 times or more is detected. It is determined to be lower. Thereafter, the abnormality processing is executed in step 160, that is, the detection result is stored in the backup RAM 77 and the driver is alerted of the abnormality by turning on the warning lamp 81, and then the present routine is terminated.

The above series of processes will be described with reference to the time chart of FIG. 6. In a rich state where the output voltage Vg of the oxygen sensor 25 exceeds 0.45 V, the number of inversions of the output voltage Vg is measured by the inversion counter CA, Is determined six times or more, it is determined that the fuel injection valve 3 is abnormal.

Therefore, the output signal of the oxygen sensor 25 is
In a state where Vg is maintained in a rich state, a failure of a combustion injection valve or the like which appears as a signal fluctuating minutely with a cycle larger than the feedback frequency can be easily detected by distinguishing abnormally from the output signal of the oxygen sensor 25. can do.

When the fuel injection amount is normal, the output voltage Vg becomes the seventh voltage.
As shown in the figure, when the voltage is 0.45 V or more, the inversion is not repeated, and the inversion counter CA does not become 2 or more.

Next, means for coping with the case where the temporary failure of the fuel injection valve 3 has been resolved will be described with reference to the flowchart of FIG. 8 which is a partial modification of the processing of FIG. That is, when the mode is switched from rich to lean in step 110, the process proceeds to step 205, where the inversion counter CA is set to 6
A determination is made as to whether or not the value is less than 6. When the counter is less than 6, the abnormality determination counter CB is counted down in step 210. In the following step 215, the abnormality determination counter CB
Is determined to be 10 or more. When it is determined to be 10 or more, the abnormality processing is executed in the same manner as in step 160 of FIG. 4. On the other hand, when it is determined to be less than 10, step 22
At 0, the fuel injection amount by the fuel injection valve 3 is determined to be normal, the warning lamp 81 is turned off, and the abnormality warning processing performed on the backup RAM 77 is canceled. In the next step 225, the inversion counter CA is cleared to prepare for the next processing.

By such a process, even if a failure such as the clogging of the fuel injection valve 3 temporarily occurs, when the failure is resolved, the warning of the abnormality is resolved.

In the above embodiment, the inverted state of the output voltage Vg of the oxygen sensor 25 is used only for detecting an abnormality of the fuel injection valve 3. However, the inverted state of the combustion state is used together with the output signal of the knocking sensor. It can also be used as one output for judgment.

Further, by detecting in which period the inversion of the output signal Vg is concentrated during the continuation of the rich state, it is possible to determine which cylinder of the fuel injection valve is abnormal.

[Effects of the Invention] According to the abnormality diagnosis device for an internal combustion engine of the present invention, the output signal from the air-fuel ratio detection means is in a rich state, and by detecting a state in which the output signal is inverted by a predetermined deviation or more, the output signal is within the rich range. Failures such as clogging of the fuel passage in the fuel injection valve and slight vibrations, which appear as a slightly fluctuating output, can be accurately detected separately from failures of the oxygen sensor and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a basic configuration of the present invention.
FIG. 3 is a configuration diagram showing an engine and peripheral devices according to an embodiment of the present invention, FIG. 3 is a control block diagram of the embodiment, FIG. 4 is a flowchart showing abnormality diagnosis processing of the embodiment,
FIG. 5 is a flowchart showing the self-diagnosis determination processing of the embodiment, FIGS. 6 and 7 are time charts showing the operation of the embodiment, and FIG. 8 is a flowchart showing the abnormality diagnosis processing of another embodiment. is there. M1 ... internal combustion engine, M2 ... exhaust passage, M3 ... air-fuel ratio detection means, M4 ... fuel injection means, M6 ... feedback control means, M7 ... abnormality determination means, 1 ... engine, 3 ... fuel Injection valve, 25 ... oxygen sensor, 70 ... electronic control unit, 81 ...
… Warning lamp

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-34331 (JP, A) JP-A-63-143353 (JP, A) JP-A-63-215854 (JP, A) JP-A-63-215854 219853 (JP, A) JP-A-63-227938 (JP, A) JP-A-63-314344 (JP, A)

Claims (1)

(57) [Claims] An air-fuel ratio detecting means provided in an exhaust passage of an internal combustion engine; a feedback control means for driving a fuel injection valve based on an output signal of the air-fuel ratio detecting means to perform feedback control of the air-fuel ratio; Under an engine operating state in which the frequency of the feedback control is stable, a reference range determination unit that determines whether a signal output from the air-fuel ratio detection unit is within an air-fuel ratio rich side reference range, and the reference range determination unit. When it is determined that the output signal is within the reference range, a state where the output signal from the air-fuel ratio detecting means has been inverted by a predetermined deviation or more is detected. An abnormality diagnosis device for an internal combustion engine, comprising: an abnormality determination unit that outputs an error.