JP3743340B2 - Accelerator pedal sensor failure diagnosis device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure diagnosis device for an accelerator pedal sensor in an electric throttle system in which two accelerator pedal sensors are set independently.
[0002]
[Prior art]
In the electronic throttle system, the opening of the accelerator pedal, which is the driver's will, is detected by an accelerator pedal sensor, and based on this, the opening of the throttle valve is controlled in consideration of the state of the engine and the vehicle. .
In this case, two accelerator pedal sensors are provided independently to cope with a failure of the accelerator pedal sensor (see Japanese Patent Application Laid-Open No. 10-77889).
[0003]
In addition, the failure diagnosis of the accelerator pedal sensor includes (1) inconsistency diagnosis for diagnosing a failure when the difference between inputs from both sensors exceeds a predetermined value, and (2) the input from each sensor is out of a predetermined range. In this case, an out-of-range diagnosis for diagnosing a failure is performed.
[0004]
[Problems to be solved by the invention]
However, if a failure occurs at the same time in two sensors, such as a broken harness or a poor connector, the signals from the two sensors change simultaneously in the direction corresponding to the accelerator fully closed state. A failure cannot be detected by the inconsistency diagnosis, and a failure cannot be detected until the output is outside the predetermined range even in the diagnosis outside the predetermined range of (2).
[0005]
On the other hand, in order to remove noise from the sliding portion of a potentiometer (variable resistor) that is a sensor, it is necessary to set a large time constant for the sensor signal input circuit. As a result, since the input signal from the sensor gradually decreases, it takes a long time to start the diagnosis outside the predetermined range (2).
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an accelerator pedal sensor failure diagnosis device that can quickly diagnose failure even when two sensors fail simultaneously. .
[0006]
[Means for Solving the Problems]
Therefore, in the first aspect of the invention, in the electric throttle system in which two accelerator pedal sensors are set independently, inconsistency for diagnosing a failure when the difference between inputs from both sensors exceeds a predetermined value. In an accelerator pedal sensor failure diagnosis apparatus comprising diagnosis means and diagnosis means for out-of-predetermined range for diagnosing a failure when an input from each sensor falls outside a predetermined range, each input circuit for inputting a signal of each sensor The time constants are different from each other.
[0007]
In the invention of claim 2, the time constant is a discharge time constant when the sensor and the input circuit are disconnected (including when the connector is disconnected in addition to when the harness is disconnected). To do.
According to a third aspect of the present invention, the difference between the time constants is set according to a time until a failure is diagnosed by the inconsistency diagnosing means at the time of disconnection between the sensor and the input circuit.
[0008]
According to a fourth aspect of the present invention, the difference between the time constants is set according to noise generated at a sliding portion of a potentiometer type sensor.
In the invention of claim 5, the input circuit comprises a series circuit of a first resistor and a capacitor and a second resistor arranged in parallel between the output terminal of the accelerator pedal sensor and the ground, Both accelerator pedals are configured such that the potential of the connection point between the first resistor and the capacitor is input to the CPU, the resistance values of the first and second resistors are R1 and R2, and the capacitance of the capacitor is C. In the sensor input circuit, the value of C × R1 is made equal, and the value of C × (R1 + R2) is made different.
[0009]
In the invention of claim 6, particularly in the case of the invention of claim 5, in the input circuits of both accelerator pedal sensors, the value of R2 is made equal and the values of C and R1 are made different under the condition of constant C × R1. It is characterized by.
The invention of claim 7 is characterized in that, in the case of the invention of claim 5 in particular, in the input circuits of both accelerator pedal sensors, the values of C and R1 are made equal and the values of R2 are made different.
[0010]
The invention according to claim 8 is characterized in that means for controlling the throttle valve is provided as fail-safe means for diagnosing a failure, considering the input from the accelerator pedal sensor as a value corresponding to the accelerator fully closed.
According to the ninth aspect of the present invention, there is provided a means for returning the throttle valve to the initial position set by the return spring by shutting off the power to the throttle valve control motor as a fail-safe means when diagnosing a failure. Features.
[0011]
【The invention's effect】
According to the first aspect of the present invention, by setting different time constants for each input circuit for inputting the signal of each accelerator pedal sensor, in both sensors, the disconnection between the sensor and the input circuit (harness disconnection). In addition, even if a connector disconnection or the like occurs, failure diagnosis can be performed early by inconsistency diagnosis.
[0012]
According to the second aspect of the present invention, in the input circuits of both the sensors, the discharge time constant at the time of disconnection between the sensor and the input circuit is made different, so that the failure diagnosis can be performed more reliably and quickly.
According to the invention of claim 3, it is possible to set in consideration of the time until a failure is diagnosed by inconsistency diagnosis when the sensor and the input circuit are disconnected.
[0013]
According to the invention of claim 4, it is possible to achieve both the sliding noise cut of the potentiometer type sensor and the early failure diagnosis.
According to the invention of claim 5, by making the value of C × R1 equal in the input circuits of both sensors, the characteristics of the filter for cutting the high frequency defined thereby, in other words, the responsiveness is made equal. On the other hand, by changing the value of C × (R1 + R2) in the input circuits of both sensors, the discharge time constant at the time of disconnection defined by this can be made different, and the filter characteristics at the normal time are impaired. Therefore, accurate failure diagnosis is possible.
[0014]
According to the invention of claim 6, in the input circuits of both sensors, the value of R2 is made equal, and the values of C and R1 are made different under the constant condition of C × R1, so that the sensor noise defined by R2 is reduced. The effect of Claim 5 can be acquired after unifying the reduction effect.
According to the invention of claim 7, the effects of claim 5 can be obtained by changing the values of C and R1 to be equal and making the value of R2 different in the input circuits of both sensors so that only one component (R2) is changed. Obtainable.
[0015]
According to the invention of claim 8, when a failure is diagnosed, the throttle valve is controlled by regarding the input from the accelerator pedal sensor as an accelerator fully closed equivalent value, so that the actual input is delayed by the time constant and the accelerator fully closed. Before the equivalent value is reached, it is possible to shift to idle control reliably and early.
According to the ninth aspect of the invention, when a failure is diagnosed, the throttle valve control motor is de-energized and the throttle valve is returned to the initial position set by the return spring. However, limp home travel is possible because the travel is set to be possible.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view of an electric throttle system showing an embodiment of the present invention.
The accelerator pedal 1 is biased to the accelerator fully closed position by a return spring 2.
[0017]
The electric throttle valve 3 is urged to an initial position (a neutral position on the relatively low opening side) by a return spring (torsion coil spring) 4 and is driven by a throttle control motor 5.
The engine control unit (ECU) 6 includes a CPU 7, an A / D converter 8, a motor drive circuit 9, and the like, and signals from various sensors are input to the CPU 7 via the A / D converter 8.
[0018]
The accelerator pedal sensors APS1 and APS2 are potentiometer-type sensors that generate a voltage signal corresponding to the opening degree (depression amount) of the accelerator pedal 1, and are independently provided with two systems, each of which is an A / D converter. 8 is input to the CPU 7.
The throttle position sensors TPS1 and TPS2 are potentiometer type sensors that generate a voltage signal corresponding to the opening degree of the electric throttle valve 3, and two independent systems are provided, each of which is an A / D converter. 8 is input to the CPU 7.
[0019]
In addition, signals such as engine speed, water temperature, vehicle speed, and gear position are also input from the other sensor group 100 as the operating states of the engine and the vehicle.
In the CPU 7, the target throttle opening is set according to the opening of the accelerator pedal 1 detected by the accelerator pedal sensors APS1 and APS2, and further the operating state of the engine and the vehicle, and the opening of the electric throttle valve 3 is set accordingly. Control. Specifically, the actual throttle opening detected by the throttle position sensors TPS1 and TPS2 matches the target throttle opening while controlling the supply of power (BATT) to the motor drive circuit 9 via the motor relay 10. Thus, by controlling the duty of the motor drive circuit 9, the current to the throttle control motor 5 is controlled and the opening degree of the electric throttle valve 3 is controlled.
[0020]
FIG. 2 shows an accelerator pedal sensor and an input circuit on the ECU side.
The accelerator pedal sensors APS1 and APS2 are both potentiometer-type sensors comprising a resistor RX having one end connected to a sensor power supply and the other end grounded, and a brush BR sliding on the resistor RX in conjunction with the accelerator pedal. Thus, the brush BR side serves as an output terminal, and the output voltage increases as the accelerator pedal opening increases.
[0021]
The output terminals of the accelerator pedal sensors APS1 and APS2 are connected to the input circuits INP1 and INP2 on the ECU side (the front stage of the A / D converter 8) via connectors CN, respectively. Note that the connectors CN of both sensors are integrally formed.
Both the input circuits INP1 and INP2 on the ECU side are series circuits of a first resistor R1 (R1aps1, R1aps2) and a capacitor C (Caps1, Caps2) between the output terminals of the accelerator pedal sensors APS1, APS2 and the ground. And the second resistor R2 (R2aps1, R2aps2) are arranged in parallel, and the potential at the connection point between the first resistor R1 and the capacitor C is used as an input to the CPU 7 (A / D converter 8). Yes.
[0022]
The capacitor C and the first resistor R1 are used as a filter for cutting high frequencies. If C and R1 represent a capacitor capacity and a resistance value, the filter characteristics are determined by C × R1, and C × R1 Are the same, the response is almost equal.
The second resistor R2 is set for the purpose of reducing noise generated at the sliding portion of the potentiometer type sensor. In a normal setting, the second resistor R2 is set to R2 >> R1 (about 1000 times). However, if a resistance equal to or greater than a predetermined value is set as R2, that role can be achieved.
[0023]
Therefore, the signals from the accelerator pedal sensors APS1 and APS2 pass through the input circuits INP1 and INP2, and then are input to the CPU 7 via the A / D converter 8, and the CPU 7 performs fault diagnosis based on these input signals. Do.
The failure diagnosis includes (1) inconsistency diagnosis for diagnosing a failure when the difference between inputs from both sensors exceeds a predetermined value, and (2) a failure when the input from each sensor is outside a predetermined range. Diagnosis outside the predetermined range is performed.
[0024]
If the result of failure diagnosis is normal, the opening degree of the electric throttle valve 3 is controlled based on signals from the accelerator pedal sensors APS1 and APS2, and if failure is diagnosed, predetermined fail-safe processing is performed.
Here, consider a case where the two accelerator pedal sensors APS1 and APS2 fail simultaneously.
[0025]
If the connector CN between the two accelerator pedal sensors APS1 and APS2 and the input circuits INP1 and INP2 is disconnected at the same time (the connector CN is likely to be disconnected at the same time because it is integrated), or if the harness is disconnected at the same time, the accelerator Since the input circuit of the pedal sensor has a pull-down configuration, there is no input, but the input decreases with a discharge time constant determined by the input circuit, particularly C × (R1 + R2). When the input circuit has the same characteristics, the two inputs are lowered in the same manner as if the accelerator pedal was returned (see FIG. 3). Therefore, the inconsistency diagnosis in (1) cannot detect a failure, and the above ( Although the failure can be detected when the diagnosis is out of the predetermined range in the diagnosis 2) outside the predetermined range, it is difficult to diagnose the failure until it is out of the predetermined range.
[0026]
In addition, when using a variable resistor consisting of a resistor and a brush that slides on the resistor as an accelerator pedal sensor, noise generated by friction powder or a region where wear does not progress from a frequently worn region There is a problem of noise generated when going up, and it is necessary to increase the time constant of the input circuit for noise removal, which further increases the time required for failure diagnosis.
[0027]
In FIG. 3, the time constants of the input circuits INP1 and INP2 of both accelerator pedal sensors are equal,
Capacitor Caps1 = Caps2 = 1μF
First resistor R1aps1 = R1aps2 = 1kΩ
Second resistor R2aps1 = R2aps2 = 1000kΩ
In this case, the change in the input to the CPU at the time of disconnection is shown, and it takes about 3.2 seconds before it is diagnosed as a failure because it is out of the predetermined range (below the lower limit threshold SL). It is shown that.
[0028]
Therefore, in the present invention, by making the time constants of the input circuits of the two accelerator pedal sensors different and changing the rate of decrease of the input value at the time of disconnection, the failure can be detected by inconsistency diagnosis, and the failure can be detected in a short time. Like that.
Specifically, in the input circuits of both accelerator pedal sensors, the value of C × R1 is made equal and the value of C × (R1 + R2) is made different.
[0029]
That is,
Caps1 × R1aps1 = Caps2 × R1aps2
Caps1 × (R1aps1 + R2aps1) ≠ Caps2 × (R1aps2 + R2aps2)
And
More specifically, the following measures (A) or (B) are taken.
[0030]
(A) In the input circuits of both accelerator pedal sensors, the value of R2 is made equal, and the values of C and R1 are made different under the condition of constant C × R1.
As a numerical example,
Accelerator pedal sensor APS1 side,
Capacitor Caps1 = 1μF
First resistor R1aps1 = 1kΩ
Second resistor R2aps1 = 1000kΩ
Accelerator pedal sensor APS2 side,
Capacitor Caps2 = 0.5μF
First resistor R1aps2 = 2kΩ
Second resistor R2aps2 = 1000kΩ
And
[0031]
In this case, C × R1 representing normal filter characteristics is
APS1 side: 1 μF × 1 kΩ = 1.0
APS2 side: 0.5 μF × 2 kΩ = 1.0
Thus, equal characteristics can be obtained.
R2 which shows a noise reduction effect can be obtained as R2aps1 = R2aps2 = 1000 kΩ on both the APS1 side and the APS2 side.
[0032]
The discharge time constant at the time of disconnection is determined by C × (R1 + R2),
APS1 side: 1 μF × (1 kΩ + 1000 kΩ) ≈1000
APS2 side: 0.5 μF × (2 kΩ + 1000 kΩ) ≈500
Therefore, it becomes about 1/2.
Therefore, the discharge time constant at the time of disconnection can be changed without impairing the purpose of the normal filter and sliding noise countermeasure.
[0033]
(B) In the input circuits of both accelerator pedal sensors, the values of C and R1 are made equal and the values of R2 are made different.
As a numerical example,
Accelerator pedal sensor APS1 side,
Capacitor Caps1 = 1μF
First resistor R1aps1 = 1kΩ
Second resistor R2aps1 = 1000kΩ
Accelerator pedal sensor APS2 side,
Capacitor Caps2 = 1μF
First resistor R1aps2 = 1kΩ
Second resistor R2aps2 = 500kΩ
And
[0034]
In this case, C × R1 representing normal filter characteristics is
APS1 side: 1 μF × 1 kΩ = 1.0
APS2 side: 1 μF × 1 kΩ = 1.0
Thus, equal characteristics can be obtained.
The discharge time constant at the time of disconnection is determined by C × (R1 + R2),
APS1 side: 1 μF × (1 kΩ + 1000 kΩ) ≈1000
APS2 side: 1 μF × (1 kΩ + 500 kΩ) ≈500
Therefore, it becomes about 1/2.
[0035]
R2 showing the noise reduction effect is different between the APS1 side and the APS2 side, but is sufficiently large, so that it can fulfill its role. On the other hand, since the changed part is only R2, it can be implemented more easily.
Therefore, the discharge time constant at the time of disconnection can be changed without impairing the purpose of the normal filter and sliding noise countermeasure.
[0036]
When the connector is disconnected by changing the discharge time constant at the time of disconnection as in (A) or (B) above, as shown in FIG. 4, the input from the accelerator pedal sensor APS2 is the accelerator pedal sensor. Compared with the input from the APS1, when the time difference decreases and the input difference becomes equal to or larger than a predetermined value, a failure is diagnosed by the inconsistency diagnosis of (1) above, and the predetermined of (2) above. There is no waiting for out-of-range diagnosis.
[0037]
FIG. 4 shows changes in the input to the CPU at the time of disconnection when the time constants of the input circuits INP1 and INP2 of the two accelerator pedal sensors are made different and the numerical example (A) is used. In the inconsistency diagnosis, when the difference between the inputs of the two sensors is 500 mV or more, if it is assumed that a failure is diagnosed, it is possible to diagnose in about 0.15 seconds.
[0038]
FIG. 5 is a flowchart of failure diagnosis.
In S1, the input from the accelerator pedal sensor APS1 is read, and in S2, the input from the accelerator pedal sensor APS2 is read. Hereinafter, APS1 and APS2 are input values.
In S3, an input difference ΔAPS = | APS1−APS2 | is calculated.
[0039]
In S4, it is determined whether or not the input difference ΔAPS is a predetermined value (for example, 500 mV) or more. This part corresponds to inconsistency diagnosis means. If it is less than the predetermined value, the process proceeds to S5. In S5, it is determined whether APS1 is outside a predetermined range (above the upper limit side threshold value or less than the lower limit side threshold value). If it is within the predetermined range, the process proceeds to S6. This portion corresponds to out-of-range diagnostic means.
[0040]
In S6, it is determined whether or not APS2 is outside a predetermined range (more than the upper threshold value or less than the lower threshold value). If it is within the predetermined range, the process proceeds to S7. This portion also corresponds to out-of-range diagnostic means.
In S7, since both the inconsistency diagnosis and the diagnosis outside the predetermined range are diagnosed as normal, normal throttle control is performed using a signal from the accelerator pedal sensor. In addition, when responsiveness etc. differ by different time constants, it controls based on the signal from the sensor which has the optimal responsiveness etc. among two sensors.
[0041]
On the other hand, if YES in any of S4 to S6, the process proceeds to S8.
In S8, since the failure is diagnosed in either the inconsistency diagnosis or the out-of-predetermined range diagnosis, the following (a) or (b) is executed as the fail-safe process. This part corresponds to a fail-safe means.
(A) The throttle control motor 5 controls the electric throttle valve 3 by regarding the input from the accelerator pedal sensor as an accelerator fully closed equivalent value.
[0042]
According to this, the following effects can be obtained. Conventionally, when the input from the accelerator pedal sensor decreases due to disconnection, the throttle valve closes according to the decrease, so it takes time to enter the idle state. On the other hand, when diagnosing a failure, the throttle valve is controlled immediately by considering the input from the accelerator pedal sensor as a value corresponding to the accelerator fully closed, so that the throttle valve can be closed in a short time without being affected by the input circuit. In addition, it is possible to shift to idle control at an early stage.
[0043]
(B) The motor relay 10 is forcibly turned off, the power is shut off, and the throttle control motor 5 is deenergized to return the electric throttle valve 3 to the initial position set by the return spring 4.
According to this, in addition to the effect of (a) above, since the initial position of the electric throttle valve 3 is normally set so as to be able to travel with a low opening, limp home traveling is possible.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an electric throttle system showing an embodiment of the present invention. FIG. 2 is a diagram showing an accelerator pedal sensor and an input circuit on an ECU side. FIG. 3 is an accelerator when a disconnection occurs when time constants are the same. Diagram showing changes in input from pedal sensor [Fig. 4] Diagram showing changes in input from accelerator pedal sensor at time of disconnection when time constants are different [Fig. 5] Flow chart of fault diagnosis [Explanation of symbols]
1 Accelerator pedal 3 Electric throttle valve 4 Return spring 5 Throttle control motor 6 Engine control unit (ECU)
7 CPU
8 A / D converter 9 Motor drive circuit 10 Motor relay APS1 Accelerator pedal sensor APS2 Accelerator pedal sensor TPS1 Throttle position sensor TPS2 Throttle position sensor RX Accelerator pedal sensor resistor BR Accelerator pedal sensor brush CN Connector INP1, INP2 Input circuit C (Caps1, Caps2) Capacitor R1 (R1aps1, R1aps2) First resistor R2 (R2aps1, R2aps2) Second resistor

Claims (9)

In an electric throttle system in which two accelerator pedal sensors are set independently, inconsistency diagnosis means for diagnosing a failure when the difference between inputs from both sensors exceeds a predetermined value, and inputs from each sensor In a failure diagnosis device for an accelerator pedal sensor comprising an out-of-predetermined range diagnostic means for diagnosing a failure when it is out of a predetermined range,
A failure diagnosis device for an accelerator pedal sensor, wherein different time constants are set in each input circuit for inputting a signal of each sensor. The accelerator pedal sensor failure diagnosis apparatus according to claim 1, wherein the time constant is a discharge time constant at the time of disconnection between the sensor and the input circuit. 3. The time constant difference is set according to a time until a failure is diagnosed by the inconsistency diagnosing means when a disconnection occurs between the sensor and the input circuit. Accelerator pedal sensor failure diagnosis device. The accelerator pedal sensor failure according to any one of claims 1 to 3, wherein the difference between the time constants is set according to noise generated in a sliding portion of a potentiometer type sensor. Diagnostic device. The input circuit includes a series circuit of a first resistor and a capacitor and a second resistor arranged in parallel between the output terminal of the accelerator pedal sensor and the ground, and the first resistor and the capacitor. The potential at the connection point is input to the CPU,
When the resistance values of the first and second resistors are R1 and R2, and the capacitance of the capacitor is C,
The accelerator pedal according to any one of claims 1 to 4, wherein in the input circuits of both accelerator pedal sensors, the value of CxR1 is made equal and the value of Cx (R1 + R2) is made different. Sensor failure diagnosis device. 6. The failure diagnosis device for an accelerator pedal sensor according to claim 5, wherein, in the input circuits of both accelerator pedal sensors, the values of R2 are made equal, and the values of C and R1 are made different under a constant condition of C × R1. 6. The accelerator pedal sensor failure diagnosis apparatus according to claim 5, wherein in the input circuits of both accelerator pedal sensors, the values of C and R1 are made equal and the values of R2 are made different. 8. A means for controlling a throttle valve by considering an input from an accelerator pedal sensor as an accelerator fully closed equivalent value as fail-safe means when a failure is diagnosed. The failure diagnosis device for an accelerator pedal sensor according to one. 2. A fail-safe means for diagnosing a failure is provided with means for returning the throttle valve to an initial position set by a return spring by shutting off power to the throttle valve control motor. The failure diagnosis device for an accelerator pedal sensor according to any one of claims 7 to 10.

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