JPH0650277B2 - Self-diagnostic device for Urasuke air control system in internal combustion engine - Google Patents

Description

The present invention relates to a self-diagnosis device for an auxiliary air control system in an internal combustion engine.

<Prior Art> Generally, an intake system of an automobile internal combustion engine is provided with an auxiliary air passage that bypasses a throttle valve, and an auxiliary air control valve is interposed in the auxiliary air passage. Then, the auxiliary air flow rate is controlled by controlling the valve opening, and for example, the idle speed is controlled (see, for example, Japanese Utility Model Laid-Open No. 60-15942).

By the way, if the above-mentioned auxiliary air control system acts in a direction in which the air flow rate increases abnormally due to a failure or the like, the idle speed becomes abnormally high, and in the case of a vehicle equipped with an automatic transmission, there is a risk of runaway. Therefore, a self-diagnosis function of the auxiliary air control system as described below is provided to detect such an abnormal state and prevent the vehicle from running out of control.

The conventional self-diagnosis system uses the target idle speed N _SET
And the actual idle speed N are compared, and N> N _SET +5
When the state of 00 rpm continues for a predetermined time (for example, 10 seconds) or more, it is determined to be abnormal. Then, at the time of such an abnormality determination, a fail-safe is issued in which a control command for fully closing the auxiliary air control valve is issued.

<Problems to be Solved by the Invention> However, in a system that performs self-diagnosis by comparing a target idle speed with an actual speed as in the conventional case, even in a normal state, for example, in a state such as deceleration coasting. In some cases, the above-described abnormality determination condition may be satisfied, so that it is necessary to provide the above-described delay time. Therefore, there is a problem that it takes time from the occurrence of abnormality to the determination.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a self-diagnosis device for an auxiliary air control system in which the time from the occurrence of an abnormality to the determination is extremely short.

<Means for Solving Problems> Therefore, according to the present invention, as shown in FIG. 1, an internal combustion engine equipped with an auxiliary air control valve for controlling an auxiliary air flow rate in an auxiliary air passage bypassing a throttle valve of an engine intake system. In an auxiliary air control system self-diagnosis device for an engine, an intake air amount detection means for detecting an intake air amount of the engine, a diagnostic means for diagnosing normality / abnormality of the intake air amount detection means, and the diagnostic means are normal. When the determination is made, the intake air amount detected by the intake air amount detecting means when the throttle valve is fully closed is compared with the auxiliary air amount corresponding to the control signal of the auxiliary air control valve, and the detected value of the intake air amount detecting means is An abnormality determining means for determining an abnormality when it is large is provided.

<Operation> According to the above configuration, when the intake air amount detecting means is normal,
The intake air amount detected by the intake air amount detecting means when the throttle valve is fully closed is compared with the auxiliary air amount corresponding to the control signal of the auxiliary air control valve, and when the detected value of the intake air amount detecting means is large, the auxiliary air amount is detected. The air control system is determined to be abnormal. In this way, if the diagnosis is performed based on the amount of air taken into the engine instead of the engine speed, it is possible to make a determination of normality / abnormality in a short time.

<Example> An example of the present invention will be described below with reference to the drawings.

In FIG. 2 showing an embodiment of the present invention, an auxiliary air passage 3 that bypasses the throttle valve 2 is provided in an intake passage 1 of the engine. In the auxiliary air passage 3, an auxiliary air control valve 4 whose valve opening degree is controlled based on a control signal from a control unit 7 described later is interposed. In the intake passage on the upstream side of the throttle valve 2, for example, a hot-wire type air flow meter 5 is provided as an intake air amount detecting means for detecting the amount of intake air taken into the engine, and an air cleaner 6 is provided upstream of the air flow meter 5. It is provided.

The controller unit 7 contains a microcomputer, an air flow meter 5, a starter switch 8,
Revolution sensor 9 for detecting engine revolution N, battery
10 and each signal from the idle switch 11, etc., which is turned on when the throttle valve 4 is fully closed, is input. Then, based on these signals and the control signal to the auxiliary air control valve 4, as shown in the flow chart of FIG. 3, when the self-diagnosis result of the air flow meter 5 is normal, the self-diagnosis of the auxiliary air control system is performed. To do. Therefore, the control unit 7 has the functions of a diagnostic means of the air flow meter 5 and an abnormality determination means of the auxiliary air control system.

Next, the operation will be described based on the flowchart of FIG.

First, in step (indicated by S in the drawing, the same applies hereinafter) 1, it is determined whether or not the idle switch 11 is ON,
If ON, go to step 2.

In step 2, a self-diagnosis is made as to whether the air flow meter 5 is normal or abnormal. This self-diagnosis is performed based on the output voltage of the air flow meter 5, for example. That is, the operating voltage of the air flow meter 5 is normally 5V, and the output voltage value in the normal state is in the range of 1V to 4V. Therefore,
When the output voltage V of the air flow meter 5 is in the range of 1V ≦ V ≦ 4V, it is determined to be normal, and when it is lower than 1V or higher than 4V other than that, it is determined to be abnormal.

If the air flow meter 5 is normal in step 2, the process proceeds to step 3.

In step 3, it is determined whether or not the starter switch 8 is OFF, and when it is OFF, the process proceeds to step 4.

In step 4, it is determined whether the engine is rotating based on the signal from the rotation speed sensor 9. If the engine is rotating, the process proceeds to step 5.

In step 5, the voltage of the battery 10 is a predetermined voltage, for example
It is determined whether the voltage is 12V or higher. If it is 12V or higher, the process proceeds to step 6.

In step 6, the auxiliary air flow rate Q _ISC is obtained based on the control signal of the auxiliary air control system 4 output from the control unit 7. Here, the auxiliary air flow rate Q _ISC is searched from the duty ratio of the control signal by a map as shown. In this embodiment, the Q _ISC is set to the maximum value in the variation of the correspondence relationship between the duty ratio and the Q _ISC in consideration of the worst conditions such as atmospheric pressure and intake humidity, and the leakage flow rate in the throttle body. Of the throttle valve 2 when the idle switch 11 is ON and the leak amount from the throttle valve 2 is added, and these values are set slightly higher.

Next, in step 7, the auxiliary air flow rate Q _ISC obtained in step 6 and the intake air flow rate Q detected by the air flow meter 5 are compared. If Q _ISC ≤Q, the process proceeds to step 8 to activate the counter. The count value C is incremented by 1.

In step 9, the count value C is the preset value C ₀
It is determined whether or not the above conditions are satisfied. When C ≧ C ₀ , it is determined in step 10 that the auxiliary air control system is abnormal.

Further, if these judgments are NO in steps 1 to 5 or if Q _ISC > Q in step 7, the process goes to step 11 to clear the count value C.

As described above, in the present embodiment, when the air flow meter 5 is normal, the throttle valve opening is fully closed (at idle), the starter switch is OFF, the engine is rotating, and the battery voltage is 12.
When each condition of V or more is satisfied, the air flow meter 5
The detected value Q of Q is compared with the auxiliary air flow rate Q _ISC, and Q _ISC ≤Q
When the above condition continues for a predetermined time (for example, about 1 sec), it is determined that the auxiliary air control system is abnormal.

In this way, by performing self-diagnosis of the auxiliary air control system based on the amount of air taken into the engine, it is possible to significantly reduce the time until abnormality determination, as compared to the case of using the conventional engine speed. It is possible to reliably avoid an abnormal operating state due to a failure of the auxiliary air control system.

When it is determined that the auxiliary air control system is abnormal,
After the abnormality judgment, until the key switch is turned off, for example,
The auxiliary air control valve is fully closed, and when the engine speed is equal to or higher than a predetermined value, control such as fuel cut is performed to provide a fail-safe configuration.

In this embodiment, the air flow meter is used to detect the intake air amount, but the same effect can be obtained by using the intake air amount detected from the intake negative pressure by using the intake pressure sensor.

<Effects of the Invention> As described above, according to the present invention, since the abnormality diagnosis of the auxiliary air control system is made by comparing the intake air amount and the auxiliary air amount, not the engine speed, the occurrence of an abnormality The time to determine an abnormality can be greatly shortened. Therefore, it is possible to reliably avoid an abnormal operating state that may occur due to a failure of the auxiliary air control system.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the configuration of the present invention, FIG. 2 is a hardware configuration diagram showing an embodiment of the present invention, and FIG. 3 is a control flowchart of the same embodiment. 1 ... Intake passage, 2 ... Throttle valve, 3 ... Auxiliary air passage, 4 ... Auxiliary air control valve, 5 ... Air flow meter, 7 ... Control unit

Claims (1)

[Claims] 1. A self-diagnosis device for an auxiliary air control system in an internal combustion engine, comprising an auxiliary air control valve for controlling an auxiliary air flow rate in an auxiliary air passage bypassing a throttle valve of an engine intake system. Intake air amount detecting means for detecting, diagnostic means for diagnosing normality / abnormality of the intake air amount detecting means, and when the diagnosing means is determined to be normal, when the throttle valve detected by the intake air amount detecting means is fully closed Of the intake air amount and an auxiliary air amount corresponding to the control signal of the auxiliary air control valve, and an abnormality determination means for determining an abnormality when the detected value of the intake air amount detection means is large. Self-diagnosis device for auxiliary air control system in internal combustion engine.