JP2000230453A - Temperature sensor fault diagnostics system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a remedial action to be taken at early stages when a fault occurs by performing fault diagnostics procedures as soon as an ignition switch is turned ON. SOLUTION: A minimum reference temperature TWMIN is determined (S11) according to an intake air temperature TA and a correction coefficient KESTP is calculated (S12) according to an engine stop time TESTP that extends from a time when the engine was stopped last to a time when it is started this time. A reference temperature TWREF is calculated (S13) by multiplying the minimum reference temperature TWMIN by the correction coefficient KESTP. If an output value TW of an engine coolant temperature sensor is higher than the reference temperature, it is determined that there is a fault (S15).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor failure diagnostic device for detecting the temperature of an internal combustion engine or a temperature related to the engine temperature.

[0002]

2. Description of the Related Art As a method of diagnosing a failure of a temperature sensor used for controlling an internal combustion engine, for example, a method disclosed in Japanese Patent Publication No. 3-56417 has been conventionally known. According to this method, the temperature sensor output value is compared with the predetermined discrimination value from the time when the first predetermined time has elapsed after the engine is started, and the temperature sensor output value is continuously shifted to one side with respect to the predetermined discrimination value. When the existing time exceeds the second predetermined time, it is diagnosed that the temperature sensor has failed.

[0003]

However, according to the above-mentioned conventional diagnostic method, the first predetermined time after starting the engine (until about 10 minutes is described in the above publication) elapses.
Because it is not possible to diagnose, for example, when determining the fuel supply amount at the start according to the output value of the engine temperature sensor,
If the output value indicates a temperature different from the actual temperature, for example, a temperature after warm-up is completed even during a cold start, there is a problem that the fuel supply amount is insufficient and the startability of the engine is deteriorated. Was. Therefore, it has been desired to execute the failure diagnosis earlier and execute the effective face-safe processing.

[0004] The present invention has been made in view of this point, and provides a failure diagnosis apparatus which performs a failure diagnosis immediately after an ignition switch is turned on, and can cope with a failure at an early stage. With the goal.

[0005]

In order to achieve the above object, an invention according to claim 1 is a failure diagnostic device for a temperature sensor for detecting a temperature of an internal combustion engine or a temperature related to the engine temperature. Stop time measuring means for measuring the stop time from the last stop of the engine to the present start, and determination temperature setting means for setting a determination temperature according to the stop time,
And determining means for determining that the temperature sensor has failed when the temperature detected by the temperature sensor at the time of starting this time is higher than the determination temperature.

According to this configuration, the stop time from the last stop of the engine to the present start is measured, a determination temperature is set according to the stop time, and the temperature detected by the temperature sensor at the present start is measured. However, since it is determined that the temperature sensor has failed when the temperature is higher than the determination temperature, a failure diagnosis is immediately performed when the ignition switch is turned on, and an early response can be made when a failure occurs.

The sensors for detecting the engine temperature or a temperature related to the engine temperature include, for example, a sensor for detecting an engine cooling water temperature or a lubricating oil temperature, an intake air temperature sensor, an exhaust gas temperature sensor, and the like.

The stop time measuring means is usually constituted by a timer for measuring time, but a capacitor circuit is provided in which a discharge time constant is set to a time required for the engine temperature to fall to substantially the outside temperature, and a terminal of the capacitor is provided. The stop time may be calculated from the voltage. Alternatively, when a sensor that detects a temperature related to another engine temperature, for example, an engine cooling water temperature sensor is to be subjected to failure diagnosis, a stop time is calculated according to an output value of an intake air temperature sensor or an exhaust air temperature sensor. Is also good. This is because the output values of these sensors indicate a temperature higher than the outside air temperature immediately after the engine stops, and gradually decrease to the outside air temperature with the passage of time.

Further, the determination temperature setting means includes an outside air temperature related temperature detecting means for detecting a temperature related to the outside air temperature,
It is preferable that the minimum judgment temperature is set according to the detected outside air temperature, and the minimum judgment temperature is corrected according to the stop time to set the judgment temperature.
In this case, the correction is performed such that the shorter the stop time, the higher the determination temperature.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a control device for an internal combustion engine (hereinafter, referred to as “engine”) including a temperature sensor and a failure diagnosis device thereof according to an embodiment of the present invention. In the figure, a throttle valve 3 is arranged in the intake pipe 2 of the engine 1. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, and the throttle valve opening sensor 4 outputs an electric signal corresponding to the opening of the throttle valve 3 to output an electronic control unit (hereinafter “ECU”). 5).

A fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). The ECU 5 is electrically connected to the ECU 5 and controls a valve opening time of the fuel injection valve 6 based on a signal from the ECU 5.

On the other hand, an intake pipe absolute pressure (PBA) sensor 7 is provided immediately downstream of the throttle valve 3, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is supplied to the ECU 5. . Further, an intake air temperature (TA) sensor 8 is attached downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies the electric signal to the ECU 5. Engine water temperature (T
W) The sensor 9 includes a thermistor or the like, detects an engine coolant temperature (cooling coolant temperature) TW, outputs a corresponding temperature signal, and supplies the temperature signal to the ECU 5. In the present embodiment, the engine water temperature sensor 9 is a temperature sensor to be subjected to failure diagnosis.

An engine speed (NE) sensor 10 is mounted around a camshaft or crankshaft (not shown) of the engine 1.
And a cylinder discrimination (CYL) sensor 11. The engine speed sensor 10 outputs a TDC signal pulse at a crank angle position before a predetermined crank angle with respect to the top dead center (TDC) at the start of the intake stroke of each cylinder of the engine 1 (every 180 ° crank angle in a four-cylinder engine). The cylinder discriminating sensor 11 outputs a cylinder discriminating signal pulse at a predetermined crank angle position of a specific cylinder. These signal pulses are supplied to the ECU 5. An exhaust temperature sensor 15 for detecting an exhaust gas temperature TGAS is provided in an exhaust pipe 12 of the engine 1, and a detection signal of the exhaust temperature sensor 15 is provided by an ECU.
5 is supplied.

The ECU 5 shapes input signal waveforms from various sensors, corrects voltage levels to predetermined levels, and converts analog signal values to digital signal values. 5b, a storage means 5c for storing various calculation programs executed by the CPU 5b, calculation results, and the like, an output circuit 5d for outputting control signals for the fuel injection valve 6, and the like. The storage means 5c is backed up by the battery voltage even when the ignition switch is turned off, and a backup RAM (Random Access Memory) in which stored contents are retained.
mory). In addition, the ECU 5 determines the stop time TES from the time when the engine 1 was stopped last time until the current start.
A timer 5e for measuring TP is incorporated. CPU 5b
Performs the drive control of the fuel injection valve 6, the control of the ignition timing by a not-shown spark plug, etc., based on the detection signals of the various sensors described above, and executes the failure diagnosis of the engine water temperature sensor 9 by the processing shown in FIG. I do.

The process shown in FIG. 2 is executed immediately after the ignition switch is turned on. First, at step S11, the detected value TA of the intake air temperature sensor 8, which is substantially equal to the outside temperature, is detected.
Is calculated in accordance with the following equation. Specifically, as shown in FIG. 3A, the minimum determination temperature TWMIN is slightly higher than the intake air temperature sensor detection value TA (for example, 5 ° C.).
Temperature).

Next, the KTESTP table shown in FIG. 3B is searched according to the stop time TESTP measured by the timer 5e, and a correction coefficient KTESTP is calculated (step S12). The KTESTP table indicates the stop time T
In the range where the ESTP is shorter than the predetermined time TESTP0, the setting is made to decrease as the stop time TESTP becomes longer, and is set to 1.0 in the range of TESTP ≧ TESTP0. The predetermined time TESTP0 is a time required for the engine water temperature TW to become substantially equal to the outside air temperature from the time when the engine 1 is stopped after the warm-up is completed, and is set to, for example, about 8 hours.

In the following step S13, the minimum judgment temperature T
By multiplying WMIN by the correction coefficient KTESTP, the determination temperature TWREF (= TWMIN × KTEST)
P), and then the detected value T of the engine coolant temperature sensor 9
It is determined whether W is higher than the determination temperature TWREF (step S14). If TW ≦ TWREF, this process is immediately terminated. If TW> TWREF, it is determined that the engine water temperature sensor 9 has failed (step S15), and the detected value TW is set to the failsafe specified value T.
Replace with WFS and turn on a warning lamp (not shown) for notifying the failure (steps S16, S1)
7).

As described above, according to the processing of FIG. 2, the failure diagnosis of the engine coolant temperature sensor 9 can be performed immediately after the ignition switch is turned on, and the face-safe processing can be executed at an early stage. Here, the fail-safe specified value TWFS is, for example, the determination temperature TWREF.
Equal to Thereby, an appropriate water temperature value can be set according to the outside air temperature (= TA) and the stop time TESTP. For example, the setting of the fuel supply amount at the time of starting the engine according to the water temperature value TW can be made appropriate. Can be.

FIG. 4 is a graph showing the transition of the detected value TW of the engine coolant temperature sensor 9 when the engine 1 is stopped at the time t0, wherein the solid line shows the normal characteristic and the broken line shows an example of the failure characteristic. Is shown. In this figure, water temperature TW0 is the engine water temperature after the warm-up is completed, and water temperature TW1 is the engine water temperature when it is almost equal to the outside air temperature. Time t
The time from 0 to t1 is usually about 8 hours.
This corresponds to the predetermined time TESTP0 in (b). At time t1, the correction coefficient KESTP = 1.0, and the determination temperature TWREF (t1) is set to a value slightly higher than the outside air temperature at this time. Accordingly, in the process of FIG. 2, when the sensor output value is fixed to a value indicating a high temperature as indicated by a broken line, a failure is diagnosed.

As described above, a fault that can be diagnosed by the processing in FIG. 2 is a fault in which the sensor output does not decrease. For example, a fault in which the sensor output maintains a value indicating a low temperature cannot be diagnosed. After the execution, it is desirable to further execute failure diagnosis by the method disclosed in, for example, Japanese Patent Publication No. 3-56417.

In this embodiment, the ECU 5 constitutes a stop time measuring means, a judgment temperature setting means, and a judgment means.
More specifically, the timer 5e corresponds to a stop time measuring unit, steps S11 to S13 in FIG. 2 correspond to a determination temperature setting unit, and steps S14 and S15 in FIG. 2 correspond to a determination unit.

The present invention is not limited to the embodiment described above, and various modifications are possible. For example, in the above-described embodiment, an example in which the failure diagnosis of the engine coolant temperature sensor 9 is performed has been described.
5, a temperature sensor for detecting the temperature of the engine 1 or a temperature related to the engine temperature, such as a lubricating oil temperature sensor (not shown) for detecting the temperature of the lubricating oil of the engine 1 or a sensor for directly detecting the temperature of the engine body If so, the failure diagnosis can be performed by the same method. Although the detected value TA of the intake air temperature sensor is used as the outside air temperature in step S11 in FIG. 2, an outside air temperature sensor may be separately provided and the detected value may be used as the outside air temperature.

For the measurement of the stop time TESTP, a capacitor circuit in which the time constant is set to about 8 hours without using the timer 5e, that is, a circuit in which the terminal voltage VC of the capacitor decreases in about 8 hours, is constructed. Alternatively, the stop time may be measured by the terminal voltage VC. Or,
When a sensor that detects a temperature related to another engine temperature, for example, an engine coolant temperature sensor is a target of failure diagnosis, the stop time may be calculated according to an output value of an intake air temperature sensor or an exhaust air temperature sensor. Good. This is because the output values of these sensors indicate a temperature higher than the outside air temperature immediately after the engine stops, and gradually decrease to the outside air temperature with the passage of time.

[0024]

As described above in detail, according to the present invention, the stop time from the last stop of the engine to the present start is measured, and the determination temperature is set according to the stop time. When the temperature detected by the temperature sensor is higher than the determination temperature, it is determined that the temperature sensor has failed, so that the failure diagnosis can be performed as soon as the ignition switch is turned on. Can be handled.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a control device of an internal combustion engine including a temperature difference sensor and a failure diagnosis device thereof according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process for performing a failure diagnosis of a temperature sensor.

FIG. 3 is a diagram showing a table used in the processing of FIG. 2;

FIG. 4 is a time chart for explaining the processing of FIG. 2;

[Explanation of symbols]

Reference Signs List 1 internal combustion engine 5 electronic control unit (stop time measuring means, judgment temperature setting means, judgment means) 9 engine water temperature sensor (temperature sensor)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G084 CA07 DA30 EB22 FA02 FA20 FA27 3G301 JB01 JB09 KA28 PA10B PD11B PE08B

Claims (1)

[Claims] 1. A failure diagnosis device for a temperature sensor for detecting a temperature of an internal combustion engine or a temperature related to the engine temperature, wherein a stop time for measuring a stop time from a previous stop of the engine to a present start of the engine. A measuring means, a judgment temperature setting means for setting a judgment temperature according to the stop time, and a temperature detected by the temperature sensor at the time of starting this time is higher than the judgment temperature, the temperature sensor has failed. And a determination means for determining the failure.