JPS5915653A - Trouble diagnostic device of detector for internal- combustion engine - Google Patents

Abstract

PURPOSE:To raise the accuracy of a trouble diagnosis by comparing an output value from a detector for detecting a prescribed operating condition of an internal-combustion engine with a normal output region under a special operating condition. CONSTITUTION:An arithmetic circuit 4 reads the number N of engine revolution from a rotary sensor 2, decides whether N=0 or not (S1), and does not make a trouble diagnosis when Nnot equal to . On the other hand, the arithmetic circuit reads any output from an AD converter 3 at N=0 to decide (S2, S3) whether an intake air flow rate signal Q from an air flow meter 1 is within the set region or not, and outputs (S4) a specific bit ''1'' of a memory 5 when said flow rate is outside the set region to alarm the troubles of the air flow meter 1 via an alarm device connected to the memory 5. It is possible in such a way to raise trouble diagnosis accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for diagnosing a failure of a detector for detecting the operating state of an internal combustion engine.

In a system that detects the operating status of an internal combustion engine and controls the engine, good control is performed when all the various detectors are operating normally, but if even one detector fails, the engine performance will be poor. may affect.

For this reason, as disclosed in Japanese Patent Application Laid-open No. 54-141926, when an abnormality occurs in the signal of the detector (temperature sensor in this case), it is detected and the output of the detector is cleared. Some devices are designed to supply a compensation signal.

However, although such a system can deal with steady failures, it is difficult to deal with unsteady failures well despite the response delay.
Because the unsteady failure cannot be detected, the same failure occurs repeatedly every time the car is driven without being able to repair it, which adversely affects driving conditions, resulting in long-term fuel loss and durability. This could lead to a decrease in the quality of the product.

In addition, as disclosed in Japanese Patent Application Laid-open No. 55-162069, there is a device that detects and displays non-stationary abnormalities in the detector, but this device detects non-stationary abnormalities in the detector and displays them. Since a failure is diagnosed only when the output range of the detector falls outside the upper and lower limits, which fluctuate greatly over If it was within the range, it was determined to be normal, resulting in poor diagnostic accuracy.

The present invention was made by focusing on such conventional problems, and by comparing the output value of a detector that detects a predetermined operating state of an internal combustion engine with a normal output range under specific operating conditions. It is an object of the present invention to provide a failure diagnosis device for a detector for an internal combustion engine, which is configured to perform failure diagnosis of the detector and thereby improves failure diagnosis accuracy.

The present invention will be explained below based on embodiments shown in the drawings.

FIG. 1 shows an embodiment of the present invention, in which an internal combustion engine (not shown) is equipped with an air flow meter 1 that detects the amount of intake air and outputs it as an analog signal, and an air flow meter 1 that generates a signal every 1 degree of the engine rotation crank angle. A rotation speed sensor 2 is provided which detects the engine rotation speed by counting signals during a certain period of time. The analog signal from the airflow meter 1 is input to an A/D (analog-digital) converter 3 and converted into a digital signal, and then input to an arithmetic circuit 4 comprised of a microcomputer. On the other hand, the signal from the rotation speed sensor 2 is input to the arithmetic circuit 4 as it is.

Further, a memory 5 is connected to the output terminal of the arithmetic circuit 4.

Here, the air flow meter 1 has an output characteristic as shown in FIG. 2, and point A in the figure indicates the engine idling time.

Next, the operation of this embodiment will be explained according to the flowchart shown in FIG.

The arithmetic circuit 4 first reads the signal of the engine rotation speed N input from the rotation speed sensor 2 and determines whether it is N20 or not.
>, N”50, failure diagnosis is not performed.

On the other hand, when it is determined to be N20, that is, when the engine is stopped, the A/D
The output from the converter 3 is read, and the intake air flow rate signal Q output from the air flow meter 1 is within the set range (for example, 5±0.
Sz, Ss
), when it is determined that it is outside the range, a signal is output that sets a specific bit in the memory 5 to 1# (S4), and a failure of the air flow meter 1 is detected via an alarm (not shown) connected to the memory 5. Alert. Also, if Q is within the set range, it is determined to be normal and the process ends.

In this way, when the engine is stopped, that is, the normal output range of the air flow meter 1 corresponding to the intake air amount O is limited to around 5V as shown in FIG. Since it is possible to perform a failure diagnosis of the air flow meter 1 by determining this, the failure diagnosis ni can be greatly improved. Further, if the output of the air flow meter 1 deviates from the normal output range even momentarily, a failure is alarmed, so that diagnosis can be performed regardless of whether the failure is steady or unsteady.

The signals from the air flow meter 1 and the rotational speed sensor 2 may be input to another control circuit, or may be processed in the performance circuit 4 to control the engine after the flow shown in FIG. 3 is completed. It has become. Furthermore, the arithmetic circuit 4 is separately provided with a routine that resets the bits of the memory 5 to '0' at the same time as the power is turned on, and therefore it is possible to detect whether a failure has occurred after the power is turned on.This can be done by the following implementation. The same applies to examples.

FIG. 4 shows a second embodiment of the invention. This thing is
In addition to the same configuration as the previous embodiment, a water temperature sensor 6 comprising a thermistor and an A/D converter to detect the engine cooling water temperature, and a throttle valve fully closed switch 7 to detect when the intake throttle valve is fully closed are provided. and input these signals to the arithmetic circuit 14 together with the signals from the A/D converter 3 and the rotation speed sensor 2. However, as will be described later, the arithmetic circuit 14 performs processing different from that of the performance 6 circuit of the embodiment.

The operation of this device will be explained according to the flowchart shown in FIG. If the cooling water temperature is 70℃ or higher (So) and the engine speed is 1
When the engine speed is 1000 rpm or less (S12), the throttle valve is fully closed (Sss), and the signal value of the air flow meter 1 is Q≦3.5V (S14), the memory 5 is counted. When the count value is 100 or more, that is, when the above state continues for more than 1 second (S+s), a specific bit in the memory 5 is set to "1" (Sts) to warn that the air flow meter 1 has failed. On the other hand, if even one of the front Me sensors is out of condition (S+y), no fault diagnosis is performed and the count in the memory 5 is reset to 0.

In other words, point B in Figure 2 is the engine speed of 120 Or after warm-up.
It shows the intake air flow rate during idle link of about pm, and the air flow meters 1 to 3 correspond to this during normal operation. Signals near the sit are output. Therefore, under the operating conditions detected by each sensor, etc. except for the air flow meter 1, the intake air flow rate decreases from the value at point B, so if the air flow meter 1 is normal, its output will be 3.5V. Therefore, it is possible to detect a failure such as locking on the high flow rate side where Q≦3.5 continues for 1 second or more.

In this example, the condition for failure diagnosis was when the cooling water temperature was 70°C or higher, which means that when the water temperature is low, air is sucked in through the air regulator even when the throttle valve is fully open. This is to exclude such cases.

FIG. 6 shows a third embodiment. In the second embodiment, instead of the throttle valve full-close switch 7, a throttle valve full-open switch 8 which is turned on when the throttle valve is fully open is provided, and the vehicle speed is controlled. A vehicle speed sensor 9 is provided to detect the vehicle speed, and its signal is input to the arithmetic circuit 24. The vehicle speed sensor 9 includes, for example, a pulse generator that detects the rotation of a vehicle speed meter cable and generates pulses, and a pulse counter that counts the pulses. Also, the water temperature sensor is omitted.

The operation of this embodiment will be explained with reference to the flowchart shown in FIG.
, the throttle valve is fully open (S22) and the vehicle speed is 30K.
m/h or more (S23), Q75 (1v or more (S2
526), and when this state continues for more than 1 second, a specific bit in the memory is set to 1.
” to warn of failure.

That is, the zero point in FIG. 2 indicates the state when the engine speed is 1800 rpm and the throttle valve is fully open, and the normal output of the air flow meter 1 at this time is about 1V.

Therefore, under the condition that the engine speed is 2000 rpm or more and the throttle valve is fully open, the normal output of the air flow meter 1 should be less than 1 v. This makes it possible to detect failures such as locking to the side.

In this embodiment, a vehicle speed sensor 9 is provided and the vehicle speed condition is set to 301.
The reason for setting the speed higher than m/h is to avoid a failure determination when so-called idling is performed.

Furthermore, if two or three of the above-mentioned embodiments are combined, the failure detection ability can be further improved.

Further, in the above embodiments, an air flow meter is used as an example of the detection means for failure diagnosis, but it goes without saying that the present invention can also be applied to failure diagnosis of other detectors for detecting operating conditions.

As explained above, according to the present invention, by detecting whether the output of a detector that detects a predetermined operating state of an internal combustion engine is within a normal range under specific operating conditions, Since the system is configured to diagnose failures, the accuracy of failure detection can be greatly improved, and by making quick repairs, the engine can be maintained at high performance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
The figure is a diagram showing the output characteristics of the airflow meter used in the embodiment of the present invention, FIG. 3 is a flowchart showing the operation of the first embodiment, and FIG. 4 is a diagram showing the second embodiment of the present invention. FIG. 5 is a block diagram showing the operation of the above embodiment, FIG. 6 is a block diagram showing the third embodiment of the present invention, and FIG. 7 is a flow chart showing the operation of the above embodiment. 1... Air flow meter 2... Rotation speed sensor 3.
...A/D converter 4.14.24...Arithmetic circuit 5
...Memory 6...Water temperature sensor 7...Throttle half-close switch 8...Throttle valve full-open switch 9...Vehicle speed sensor Patent applicant Fujio Sasashima, Patent Attorney for Nissan Motor Co., Ltd. Figure 1 Figure 2 Figure 30 Figure 4

Claims (1)

[Claims] The output of the detector that detects the predetermined operating state of the internal combustion engine is
The configuration is such that, under specific operating conditions detected by a detector other than the detector, a failure of the detector is diagnosed by detecting whether the output is within a normal output range corresponding to the operating conditions. A failure diagnosis device for a detector for an internal combustion engine, characterized by: