JPH03210047A - Abnormality diagnosing device for sensor - Google Patents

Abstract

PURPOSE:To improve detection accuracy by detecting a variation quantity of an output voltage value after changing a current value which flows into a sensor where a power supply voltage is used as a reference voltage, and diagnosing it abnormal if it is larger than the variation quantity at a normal time preliminarily stored. CONSTITUTION:Into a sensor 1 formed of a potentiometer and the like in which a power supply voltage is used as a reference voltage, two kinds of currents with different values are supplied by varying resistance value of pull-up resistance 2 or pull-down resistance 6 by a variation means 3 so as to take the output voltage value at that time in an abnormality diagnosing means 5. When abnormality in a sensor 1, for example, at connector contact resistance and the like, only the output voltage value is decreased, and thus it is compared with output voltage value at the normal time preriminarily stored in a memory means 4 so as to diagnose whether abnormality has occurred or not. Improvement of detection accuracy is obtained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sensor abnormality diagnosing device, and more particularly to a sensor abnormality diagnosing device suitable for detecting characteristic deviations of vehicle-mounted sensors.

(Prior Art) Generally, an internal combustion engine controlled by a fuel injection MWIIJ device is equipped with various sensors such as a potentiometer and a water temperature sensor, and fuel injection control is performed based on the output values of these sensors. This makes it possible to realize fuel injection that appropriately corresponds to the lIr1J state.

Further, since the fuel injection control device performs control operations based on output signals from various sensors, if an abnormality occurs in the sensors, it becomes impossible to perform appropriate fuel injection control. Contact resistance at the connector connection portion is considered to be the cause of this abnormality. Contact resistance is resistance caused by the formation of an oxide film on the surfaces of connector contacts and contact bottles. When contact resistance is generated by this oxide film, a deviation occurs in sensor characteristics, making it impossible to obtain an appropriate sensor output corresponding to the *ra state.

Previously, the only way to confirm the occurrence of this oxide film was to remove the connector and perform a visual inspection, but when the connector was removed, the oxide film peeled off from the contacts and contact pins, making it difficult to detect. there were.

For this reason, a sensor abnormality diagnosing device has been proposed that can diagnose an abnormality in a sensor without removing the connector. Conventional abnormality diagnostic devices of this type include:
For example, Toyota technical publication publication number 3361 (issue date 1
September 29, 989).

The abnormality diagnosis device shown in the publication is for diagnosing an abnormality in a throttle sensor. This abnormality diagnosis device is
Set the reference position on the sensor that uses the power supply voltage as the reference voltage,
When the sensor reaches the reference position, it is determined whether the sensor output voltage is within a predetermined range corresponding to the reference position, and if the output voltage value is outside the predetermined range, it is determined that an abnormality has occurred. It was supposed to be configured to.

(Problem to be Solved by the Invention) However, with the above-mentioned conventional abnormality diagnosis device, it was possible to diagnose an abnormality only at a specific reference position. It is necessary to keep it stopped in a stable state at the reference position. However, the degree of opening of the throttle valve constantly changes. Therefore, it is difficult to keep the sensor stably stopped at the reference position, and it is difficult to perform accurate and stable abnormality diagnosis.

In addition, a configuration can be considered in which stable abnormality diagnosis can be performed by widening the width of the reference position so that the sensor remains at the reference position even if the sensor position changes slightly. If the width is widened, the detection accuracy will deteriorate accordingly, making it impossible to make an accurate diagnosis.

Furthermore, for sensors such as throttle sensors whose reference positions are easy to set, the conventional abnormality diagnosis device described above can be applied; however, for sensors such as pressure sensors and lubricant sensors, it is difficult to set reference positions due to structural and cost considerations. There has been a problem in that conventional abnormality diagnosis devices cannot deal with sensors that are difficult to detect.

The present invention has been made in view of the above points, and an object of the present invention is to provide a sensor abnormality diagnosing device capable of detecting sensor abnormality without providing a specific reference position.

[Means to solve the problem]

1 and 2 are diagrams of the principle of the present invention.

In order to solve the above problems, the present invention, as shown in FIG. a variable means (3) for changing the value of current flowing into the sensor (1) by varying the resistance value of the up resistor (2); The amount of change in the output voltage value of the sensor (1) when the sensor (1) is changed is detected, and the detected amount of change is compared to the amount of change in the output voltage value under normal conditions stored in the storage means (4). A sensor abnormality diagnosing device is characterized by comprising an abnormality diagnosing means (5) for diagnosing that there is an abnormality in the sensor (1) when the abnormality is large.

In addition, as shown in Figure 2 (the same components as those shown in Figure 1 are given the same reference numerals), there is a sensor (1) that uses the power supply voltage as a reference voltage, and a pull-down resistor connected to the ground. (6), variable means (31) for changing the current value flowing out from the sensor (1) by varying the resistance value of the pull-down resistor (6), ii The amount of change in the output voltage value of the sensor (1) when the current value flowing from the sensor (1) is changed is detected, and compared with the amount of change in the output voltage value under normal conditions stored in the storage means (4). , and an abnormality diagnosing means (5) for diagnosing that there is an abnormality in the sensor (1) when the detected amount of change is large.

(Operation) In the sensor abnormality diagnosis device configured as described above, by varying the resistance value of the pull-up resistor (2) or the pull-down resistor (6) using the variable means (3), the sensor (1)
Two types of currents with different values can be passed through. When an abnormality such as connector contact resistance occurs in the sensor v(1), an output voltage value (voltage drop) corresponding to the sum of the internal resistance of the sensor (1) and the connector contact resistance occurs. Therefore, by comparing this output voltage value with a predetermined output voltage value that occurs when the sensor (1) is in a normal state, it is possible to diagnose whether or not an abnormality has occurred in the sensor (1).

In addition, currents of different values are passed through the sensor (1), the difference between the output voltage values output from each is determined, and abnormality diagnosis is performed based on the amount of change in the output voltage value.
There is no need to particularly set a reference position. Therefore, it is possible to perform an abnormality diagnosis even for a sensor for which it is difficult to set a reference position.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. Third
The figure shows an abnormality diagnosis device for a sensor provided in an internal combustion engine, which is an embodiment of the present invention. In this embodiment, a case will be described in which the abnormality diagnosis device is applied to abnormality diagnosis of a throttle position sensor 10 (hereinafter referred to as a position sensor).

The position sensor 10 is a sensor that detects the opening degree of the throttle valve, and is mechanically coupled to the throttle shaft. This position sensor 10 has a built-in variable resistor, and is configured so that the value of internal resistance R1 changes in response to rotational displacement of the throttle shaft. Therefore, the opening degree of the throttle valve can be measured by using the power supply voltage Vc as a reference voltage and measuring the voltage drop due to the internal resistance R1 as the output voltage Vout.

The position sensor 10 is connected to an engine control unit 12 (hereinafter referred to as ECU) via a connector 11.
It is connected to the. The following explanation will be given assuming that a connector connection resistance R2 is generated in the connector 11.

The ECU 12 is a microprocessing unit 1- (
MPLJ) 13, read-only memory (ROM) 14,
Random access memory (RAM) 15, input port 1
6.17, output ports 18, 19, and buses 20 such as data buses and control buses for connecting these ports. Ignition switch 2 is connected to input port 16.
1. Idle switch 22, vehicle speed sensor 23. Neutral switch 24 is connected, and output port 1
A warning lamp 26 is connected to 8 via a drive circuit 25.

The abnormality diagnosis device which is a feature of the present invention is constituted by pull-up resistors R3 and R4 provided in the ECU 12, a switching transistor Tr, and an abnormality diagnosis means constituted by software. In addition, pull-up resistor R
3 is configured to be connected in parallel to the internal resistance R+ of the position sensor 10 and the connector contact resistance R2 by turning on the transistor Tr. Therefore, the transistor T whose pull-up resistance value is changed by the operation of the transistor T is connected to the output port 19 via the drive circuit 27, and is turned on and off based on instructions from the MPU 13. Also, the output voltage VOut is converted into a digital output signal by an analog-to-digital converter 28 (hereinafter referred to as an A/D converter) and then supplied to the input port 17. Note that a resistor connected in parallel with the pull-up resistor R3 R4 is a pull-up resistor for detecting an abnormality due to a short circuit, such as when the connector 11 is disconnected or a disconnection occurs.In addition, pull-up resistors R3 and R4 are connected to the internal resistor R1 of the position sensor 10. The resistance value is set to be relatively large.

Next, the operation of the abnormality diagnosis device having the above hardware configuration will be explained. FIG. 4 is a flowchart showing the operation of the abnormality diagnosis device according to the first embodiment of the present invention. When this routine is started, first in step 100 the transistor Tr is turned off and an initial state is set. Next, the MPU determines whether the ignition switch 21 is turned on in step 110, and if it is turned on, determines in step 120 whether the starter voltage (STA) is not being supplied. If it is determined in step 120 that the power is not being supplied, the process proceeds to step 130 and determines whether the idle switch 22 is turned on.

If an affirmative determination is made in each of the determiners in steps 110 to 130 above, in step 140 the transistor T
is turned on.A state in which an affirmative determination is made in each of the determiners in steps 110 to 130 is a state in which the inner mm valve is in a stopped state and the throttle valve is in a closed position.

This is because when the output value of the position sensor 10 is changing, in other words, when the internal combustion engine is running or when the throttle valve is displaced, there is a risk of incorrect diagnosis. This is because abnormality diagnosis is performed by selecting a time when the internal combustion engine is stable.

On the other hand, even when the transistor Tr is turned off, the power supply voltage Vc is applied to the position sensor 10.
An output signal based on the output voltage Vout is constantly supplied to the MPU 13. Note that the output voltage value of the output voltage vout in a state where this pull-up resistor R3 is not connected (Tr is off) is defined as Vl. As mentioned above,
In this embodiment, the connector 11 has a connector contact resistance R2.
is assumed to be occurring, this output voltage value v1
also reflects the voltage drop due to the connector contact resistance R2.

In step 140, when the transistor "[" is turned on, the pull-up resistor R3 has an internal resistance R+, a connector contact resistance R
2 in parallel, so that the current value of the current flowing through the circuit changes with respect to the current value in the state where the pull-up resistor R3 is not connected. Also, as the current value changes, the output voltage yout also changes, but the output voltage after the change is
Let the value of Out be the output voltage value v2.

In the following step 150, the output voltage value V2 after the pull-up resistor R3 is connected is subtracted from the output voltage value ■1 before the pull-up resistor R3 is connected to calculate the sensor output change amount W (W=V+V
2).

Further, in step 160, the sensor output change value W obtained in step 150 is converted to the normal sensor output change amount M (hereinafter simply referred to as normal value) stored in the ROM 14 in advance.
Compare with. Here, the normal value M is a value obtained by determining the amount of change in sensor output using a position sensor and a connector in which no abnormality such as connector contact resistance has occurred. If the sensor output variation W is abnormally large with respect to the normal value M, this indicates that some resistance such as connector contact resistance is occurring in the circuit in addition to the internal resistance R1 of the position sensor 10. Therefore, the sensor output change mW is normal ItiM
An abnormality diagnosis of the position sensor 10 can be performed by comparing with .

In other words, as in the configuration of the present application, currents of different current values are passed,
By determining each output voltage value V+, V2 and then performing an abnormality diagnosis based on the amount of change W, which is the relative value, it is possible to perform an abnormality diagnosis regardless of the value of the internal resistance R1.
Moreover, it is sufficient to store one normal value in the ROM 14. Therefore, the configuration inside the ROM 14 can be simplified, and the present abnormality diagnosis device can be applied to all kinds of sensors.

The explanation will be returned to FIG. 4. If it is determined in step 160 that the sensor output change amount W is an abnormally large value with respect to the normal value M, it is determined in step 110 whether or not the number of times this abnormality has been detected is the predetermined number N. to decide. If it is the Nth time, the warning lamp 26 is turned on in step 180. This allows the user of the abnormality diagnosis device to know that an abnormality has occurred in the position sensor 10. The reason why the warning lamp 26 is not turned on until the abnormality has been diagnosed a predetermined number of times N or more in step 170 is adopted is because it is possible that W>M due to a cause different from the original abnormality such as a disturbance. The process of step 170 prevents misdiagnosis from occurring.

In the process described above, if a negative determination is made in steps 110 to 130, the process is terminated as the internal combustion engine is not in a state suitable for abnormality diagnosis, and if a negative diagnosis is made in step 160, the process is terminated. terminates the process by determining that there is no abnormality in the position sensor 10, and further determines that there is a risk of erroneous diagnosis if a negative determination is made in step 170, increments the number of abnormality detections n in step 190, and then terminates the process. .

FIG. 5 is a flowchart showing the operation of the abnormality diagnosis device according to the second embodiment of the present invention. Note that the operation shown in the flowchart differs from the operation of the first embodiment only in the setting of the timing for performing abnormality diagnosis, so the steps for performing the same processing as in FIG. The same number of steps is shown, and the explanation thereof will be omitted.

The second embodiment can be applied to an internal combustion engine equipped with an idle speed control system (hereinafter referred to as ISO). In other words, in an internal combustion engine having an IC, even if the ignition switch 21 is turned off and the engine is stopped, the ECU 12 is still operating to perform idle speed control pulpalization, so the abnormality diagnosis can be performed using this time. It is composed of

Therefore, in step 210, it is determined whether the ignition switch 21 has changed from the on state to the off state. Even if an affirmative determination is made in step 210, since the throttle shaft may be displaced due to accelerator operation, it is further determined in step 220 whether or not the idle switch 22 is turned on. If affirmative determinations are made in both steps 210 and 220, the MPLJ 13 determines that the internal combustion mm is in a state suitable for abnormality diagnosis, and performs the abnormality diagnosis operation from step 140 onwards. Incidentally, if a negative determination is made in steps 210 and 220, it is determined that the internal combustion engine is in a state unsuitable for abnormality diagnosis, and the process is terminated.

FIG. 6 is a flowchart showing the operation of the abnormality diagnosis device according to the third embodiment of the present invention. Since this embodiment also differs from the first embodiment only in the timing at which the abnormality diagnosis is performed, the same steps as those shown in FIG. 4 will be given the same number of steps, and the explanation thereof will be omitted.

The third embodiment can be applied to an internal combustion engine equipped with an automatic transmission. Therefore, it is determined in step 130 whether the vehicle speed (SPD) is 0, and if it is determined that SPD=O, it is determined in step 320 whether the idle switch 22 is on. When it is determined that the idle switch 22 is on, it is determined in the following step 330 whether the neutral switch 24 is on, and if it is determined that the neutral switch 24 is on, it is determined that the engine is in a steady state, and the process proceeds to step 140. The following abnormality diagnosis operations are performed. Furthermore, step 310~
If a negative determination is made in step 330, the MPLJ 13 concludes that the internal combustion engine is in a state unsuitable for abnormality diagnosis and ends the process.

In the above embodiment, the current value is changed by connecting and disconnecting the pull-up resistor R3 with the transistor Tr, but the present invention is not limited to this.
As shown in the figure, connect the pull-down resistor R5 to the output voltage vOut.
It may also be arranged between the ground and the ground. Even in this configuration, the internal resistance R1 and the connector contact resistance R2
Currents of different values can be passed through the terminals, and an abnormality can be determined in the same manner as in the above-described embodiment.

Furthermore, although the above-described embodiment shows a configuration in which the abnormality diagnosis device is used to diagnose abnormalities in the position sensor 10, the present invention is not limited to this, and the abnormality diagnosis device according to the present application can be widely applied to various types of sensors. What can be obtained will be clear from the explanation given above.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to diagnose abnormalities due to sensor characteristic f such as increased connector contact resistance without providing a reference position as in the past, thereby improving detection accuracy. In addition, it has features such as being able to apply an abnormality diagnosis device to various sensors.

[Brief explanation of drawings]

1 and 2 are principle diagrams of the present invention, FIG. 3 is a configuration diagram of an abnormality diagnosis device that is an embodiment of the present invention, and FIG. 4 is a diagram of the abnormality diagnosis device that is a first embodiment of the present invention. FIG. 5 is a flow chart showing the operation of the abnormality diagnosis device according to the second embodiment of the present invention, and FIG. 6 is a flow chart showing the operation of the abnormality diagnosis device according to the second embodiment of the present invention.
A flowchart showing the operation of the abnormality diagnosing device according to the embodiment, and FIG. 7 is a configuration diagram showing the abnormality diagnosing device using a pull-down resistor. R1... Internal resistance, R2... Connector contact resistance, R
3... Pull-up resistor, R5... Pull-down resistor,
10...Position sensor, 11...Connector, 1
2...ECU (engine control unit),
26...Warning lamp.

Claims (2)

[Claims] (1) A sensor that uses a power supply voltage as a reference voltage, a pull-up resistor connected to the power supply voltage, and a variable means that changes the value of current flowing into the sensor by varying the resistance value of the pull-up resistor. , detecting the amount of change in the output voltage value of the sensor when the current value flowing into the sensor is changed by the variable means, and comparing it with the amount of change in the output voltage value under normal conditions stored in the storage means; An abnormality diagnosing device for a sensor, comprising: abnormality diagnosing means for diagnosing that there is an abnormality in the sensor when the detected amount of change is large. (2) A sensor that uses a power supply voltage as a reference voltage, a pull-down resistor connected to ground, and a variable means for varying the current value flowing out from the sensor by varying the resistance value of the pull-down resistor; The amount of change in the output voltage value of the sensor when the current value flowing out from the sensor is changed by the means is detected, and the amount of change in the output voltage value in the normal state stored in the storage means is compared with the amount of change in the output voltage value in the normal state stored in the storage means. An abnormality diagnosing device for a sensor, comprising: abnormality diagnosing means for diagnosing that there is an abnormality in the sensor when the amount of change is large.