JPS5928048A - Self-diagnosis starting system in self diagnosing device for automobile engine control device - Google Patents

Abstract

PURPOSE:To make it possible to make a correct diagnosis by removing elements causing erroneous judgements by a method wherein when an engine is started, whether or not the power source voltage or the engine r.p.m. has been brought under a stabilized condition is detected and if yes, the self-diagnosing device is made to start its self-diagnosis. CONSTITUTION:An operation circuit 3 formed of CPU receives as an input the output of an air flow meter 1 through an A/D converter 2 and operates the flow rate Q of sucked air. Further, it operates the number N of revolutions of the engine on the base of a signal from an engine r.p.m. sensor 4 and also operates the amount of fuel injection on the base of the engine r.p.m. The operation circuit 3 judges, that is, diagnoses by itself, wherher or not the output of the A/D converter 2 is within its normal output range but in this case, it is made to judge prior to its self-diagnosis whether or not the number N of revolutions of the engine is larger than a predetermined number N0 of revolutions of the engine and if yes, the self-diagnostic operation of the circuit 3 is started while if no, the circuit 3 is inhibited to make its self-diagnostic operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-diagnosis device for an automobile engine control device, and particularly to a self-diagnosis initiation system thereof.

Conventionally, in automobile engines equipped with electronically controlled fuel injection devices, in order to diagnose whether the various sensors that detect engine operating conditions are operating normally, the outputs of these sensors are measured under specific operating conditions. Some devices are equipped with a self-diagnosis device that detects whether the output is within a corresponding normal output range.

However, in conventional self-diagnosis devices, when the engine is started, diagnosis is started immediately when the power is turned on. Self-diagnosis starts when the power supply voltage is unstable, especially when the sensor output is
When the A/D conversion value of the sensor output fluctuates greatly due to fluctuations in the power supply voltage, such as when the sensor output is input to the arithmetic circuit (CPU) via a D converter, it may be incorrectly determined that the sensor output is out of specification even if it is normal. There was a risk of doing so.

The present invention was made with the aim of solving such conventional problems, and it detects whether the power supply voltage or engine speed has reached a stable state when starting the engine (when turning on the power). However, self-diagnosis is started after a stable state is detected, and items that may cause erroneous judgments such as A/D conversion output are not diagnosed until a stable state is reached. It is something.

Examples will be described below.

Referring to FIG.
The signal from the rotation speed sensor 4 is also input to the calculation circuit 3, and the signal from the rotation speed sensor 4 is inputted to the calculation circuit 3, and is converted into a digital signal. The injection amount is calculated.

Here, the arithmetic circuit 3 determines whether the A/D conversion value of the air flow meter 1 output is within a normal output range, that is, performs a self-diagnosis, but the program in the memory 5 is The system is configured as shown in the flowchart shown in FIG. That is, in 101, a car whose rotational speed N is greater than or equal to a predetermined rotational speed No is established, and in the case of YES, 10
Self-diagnosis is performed in step 2, and if the answer is NO, self-diagnosis is not performed.

By doing this, referring to Figure 3, self-diagnosis is not performed during the initial power-on period and during the period when the power supply voltage is reduced due to the Stark Inch being turned on and the starter being started, and the rotation speed is reduced to a certain extent. Self-diagnosis is performed after the voltage has risen and the power supply voltage has become stable, thereby preventing erroneous judgments.

In this embodiment, the rotational speed is detected, but the state of the power supply voltage may be directly monitored and self-diagnosis may be started when the power supply voltage exceeds a predetermined level.

Further, in this embodiment, an air flow meter is used as an example of a sensor to be diagnosed for failure, but the present invention is of course not limited to this and can be applied to various types of sensors.

As explained above, according to the present invention, since diagnosis is started after a stable state is reached, it is possible to eliminate the element of misjudgment, and more accurate diagnosis becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a flowchart of the embodiment, and FIG. 3 is a time chart for explaining the operation of the embodiment.

Claims (1)

[Claims] In a self-diagnosis device for an automobile engine control device that detects whether the output of various sensors is within the normal output range and diagnoses the presence or absence of an abnormality in various sensors, the power supply voltage or engine rotation speed is detected when the engine is started. A self-diagnosis 117 starting system comprising means for detecting that a stable state has been reached, and configured to start self-diagnosis after the stable state is detected.