JPH07189756A - Accelerator sensor input circuit - Google Patents

Abstract

PURPOSE:To discriminate an output circuit with unjust output appropriately when two kinds of output are different from each other due to the double constitution of an accelerator sensor by providing an alarm circuit for generating alarm output when the potential of the cold side terminal of a potentiometer drops. CONSTITUTION:A signal SIG1 is taken into an analog-digital converting circuit AD1 from a middle point terminal T1 connected to the sliding piece of a potentiometer P. When a change is detected in the signal SIG1, a signal SIG2 is taken into an analog-digital converting circuit AD2 from a cold side terminal T2. A program control circuit CPU switches a switching circuit EX synchronously with the clock of a clock generating circuit CLK and takes in the signal SIG1 or SIG2. At this time, when voltage drop is detected from the voltage value of the signal SIG2, it is so judged that abnormality is generated to electrical wiring connecting the potentiometer P, or the potentiometer P and an accelerator sensor input circuit, and an alarm circuit AR is instructed to output an alarm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used to control an internal combustion engine equipped with an electronic control unit. INDUSTRIAL APPLICABILITY The present invention takes in a mechanical displacement of an accelerator pedal or other accelerator operating end of an internal combustion engine as an electric signal and utilizes it in a control circuit for controlling the rotational speed of the internal combustion engine. The invention is suitable for use in motor vehicles equipped with a gasoline engine or a diesel engine.

[0002]

2. Description of the Related Art In an electronic control unit for an internal combustion engine, it is necessary to capture a mechanical displacement of an accelerator pedal or other accelerator operating end as an electric signal. For this purpose, a potentiometer or a reactor is used as an accelerator sensor. Those using a circuit, those using a magnetically sensitive resistive element, and others are known. Among them, the one using a potentiometer is provided with two terminals connected to both ends of one resistor and a midpoint terminal for taking out a midpoint potential by a slider sliding on the surface of this resistor, The slider is mechanically connected to the accelerator pedal, and the midpoint potential changes according to the mechanical displacement of the accelerator pedal.
The input circuit of the accelerator sensor is configured to supply a constant voltage to the hot side terminal of the resistor, connect the cold side terminal to the ground potential, and use the midpoint potential as a control signal.

Although such a circuit has a simple structure and the device can be provided at a low cost, when a disconnection or a contact failure occurs in the electric circuit, the detection output is erroneous. Therefore, a circuit for detecting the disconnection or the contact failure. A device devised so as to perform control in a fail-safe manner is provided.
As an example of the conventional circuit, there is a technique disclosed in Japanese Patent Laid-Open No. 286837/1990, and in particular, FIG. 3 shows a circuit for connecting the cold side terminal of the potentiometer to the ground via another resistor. Is disclosed. However, this circuit is not configured to monitor the terminal voltage of this other resistor.

[0004]

In a circuit configured to mechanically displace the slider of the potentiometer in accordance with the displacement of the accelerator pedal and take in the midpoint potential appearing on the slider as a control input. , The contact failure between the slider and the potentiometer's resistor becomes a problem, but unless this contact disappears and the contact resistance becomes infinite, keep the input impedance of the circuit that receives the midpoint potential high. Can be relieved by That is, even if some contact failure occurs, if the impedance on the receiving circuit side is kept high, no current will flow to the midpoint terminal, and therefore the midpoint potential will not change significantly. The technology disclosed in the above publication is intended to remedy this contact failure at the midpoint potential when the contents are carefully examined.

The accelerator pedal displacement detection circuit of an automobile is
Place the potentiometer very close to the accelerator pedal to shorten the mechanical connection between the potentiometer's slider and the accelerator pedal, and connect the potentiometer and the electronic circuit that receives this signal by electrical wiring. It is convenient to configure it. This requires wires and connectors between the potentiometer and the electronic circuitry. Poor contact often occurs in this electrical wiring path, especially in the connector.

Further, there is a technique in which an accelerator sensor using a potentiometer has a dual structure so that when a contact failure occurs on one side, the output of the circuit that has become defective is cut off to prevent erroneous detection or erroneous control. Are known. When the accelerator sensor has a dual structure, and when the two sensor outputs show different outputs, it is extremely important to determine whether or not both outputs are valid values. For this reason, it has been practiced to provide a relatively expensive device such as detecting that the output value is out of the range.

The present invention has been made against such a background, in which the slider of the potentiometer is mechanically displaced according to the displacement of the accelerator pedal, and the midpoint potential appearing on the slider is controlled and input. It is an object of the present invention to detect an occurrence of a contact failure occurring in a passage of an electric wiring in a circuit configured to take in as and issue an alarm. Furthermore, the present invention avoids false detection according to this alarm output,
An object is to provide an apparatus capable of executing fail-safe processing. Further, the present invention provides a circuit capable of properly discriminating a circuit which is sending an improper output when the two outputs are in different states when the accelerator sensor has a dual structure. With the goal.

[0008]

The present invention is provided with a potentiometer in which a constant voltage is applied to a hot side terminal and the potential of a midpoint terminal changes in response to a displacement of an accelerator operating end. Is an accelerator sensor input circuit that uses as a control input.

Here, the feature of the present invention is that the cold side terminal of the potentiometer is connected to the ground potential through a resistor, and an alarm output is generated when the potential of the cold side terminal drops. It is where the alarm circuit is provided.

The program control circuit includes a digital-analog conversion circuit for converting the potential of the midpoint terminal and the potential of the cold side terminal into digital signals, respectively, and a program control circuit for executing the acquisition processing of the digital signals. Means for executing a fail-safe process for the captured potential of the midpoint terminal when the potential of the cold side terminal drops below a predetermined value when a change in the potential of the midpoint terminal is detected. Is desirable.

It is preferable that the potentiometer is provided with dual circuits for working and protection, and has circuit means for switching between working and protection when the potential of the cold side terminal drops.

[0012]

The accelerator sensor input circuit of the present invention detects that a contact failure has occurred in the path of the electrical wiring of the potentiometer interlocking with the accelerator, and issues an alarm.
Further, erroneous detection is avoided according to this alarm output, and fail-safe processing is executed. Further, in the case where the accelerator sensor has a dual structure, when the two outputs are in different states, the circuit that is sending out a legitimate output is properly determined.

Here, a method for detecting the occurrence of contact failure occurring in the path of the electric wiring of the potentiometer will be described with reference to FIG. FIG. 4 is a diagram showing an equivalent circuit for explaining the detection method. A constant voltage + V is applied to the terminal T ₀ . The terminal T ₂ is grounded via the resistor R ₃ and outputs the signal SIG2. The terminal T ₁ is connected to the slider of the potentiometer P and outputs the signal SIG1. In the actual wiring, the potentiometer P is provided with three terminals, which are connected to the terminals T ₀ , T ₁ , and T ₂ by a relay connector, respectively. Therefore, the resistances R _x , R _y , and R _z shown by broken lines in FIG. 4 represent resistances that occur unexpectedly due to poor contact of the relay connector or disconnection of electric wiring. In the following, in order to make the description easy to understand, the contact resistance of the relay connector including the resistance of the electrical wiring will be described.

If the contact failure does not occur in the relay connector, the values of the resistances R _x , R _y and R _z are so small that they can be ignored. However, if a contact failure occurs, the resistances R _x , R _y ,
The value of R _z increases greatly. Therefore, assuming that the contact failure occurs in the relay connector, when the resistance value of the resistance R _y increases, when the resistance value of the resistance R _z increases,
When the resistance value of the resistance R _x increases, the resistances R _z and R
A change in the signals SIG1 and SIG2 when the resistance value of _x simultaneously increases will be described.

[0015] E a voltage value of the constant voltage + V, the resistance value R ₁ of the resistor R _1, the resistance value R ₂ of the resistor R _2, the resistance R ₃ of the resistor R _3, the resistance value of the resistor R _x R _x, the resistance R _y of the resistance value R _y of the resistance value of the resistor R _z when R _z, when the contact of the relay connector is good, since it is _{R x = R y = R z} ≒ 0Ω, SIG1 = [E ・ (R ₂ + R ₃ )] / [R ₁ + R ₂ + R
₃ ] SIG2 = [E · R ₃ ] / [R ₁ + R ₂ + R ₃ ]. The above equations represent the voltage values of the signals SIG1 and SIG2, respectively. Here, when R _y increases, the input impedance of the circuit that receives the signal SIG1 from the terminal T ₀ is set high, so that almost no current flows through the terminal T ₀ , and R _y is infinite, that is, non-contact. Signal SIG1 unless
Is almost unchanged. Therefore, there is almost no influence on the accelerator sensor input circuit. When R _z increases, R _x = R _y ≈0 Ω, so SIG1 = [E · (R ₂ + R ₃ )] / [R _z + R ₁ + R
₂ + R ₃ ] SIG2 = [E · R ₃ ] / [R _z + R ₁ + R ₂ + R ₃ ]. In this case R _z is the signal SIG1 and SIG
Any of the above equations representing the voltage value of 2 appears in the denominator. That is, as R _z increases, the voltage values of the signals SIG1 and SIG2 respectively drop. Therefore, the signal SIG having an incorrect value is output to the accelerator sensor input circuit.
Since 1 and SIG2 are given, accurate operation of the device operating with the output signal of the accelerator sensor input circuit cannot be obtained. However, since the fall of the signal SIG1 is generally used as a signal indicating "close" of the accelerator, the risk of malfunction is small. When R _x increases, R _z = R _y ≈0Ω, so SIG1 = [E · (R ₂ + R _x + R ₃ )] / [R ₁ + R
₂ + R _x + R ₃ ] SIG2 = [E · R ₃ ] / [R ₁ + R ₂ + R _x + R ₃ ]. In this case, R _x appears in both the numerator and denominator in the expression representing the voltage value of the signal SIG1. Since the voltage value E is multiplied in the numerator, the voltage value of the signal SIG1 rises as R _x increases. In the equation representing the voltage value of the signal SIG2, R _x appears in the denominator. That is, the voltage value of the signal SIG2 drops as R _x increases. Therefore, since signals SIG1 and SIG2 having wrong values are given to the accelerator sensor input circuit, accurate operation of the device that operates with the output signal of the accelerator sensor input circuit cannot be obtained. Generally, the rise of the signal SIG1 is used as a signal indicating the "open" of the accelerator, so that the risk of malfunction is high. When R _x and R _z increase at the same time, R _y ≈0Ω, so SIG1 = [E · (R ₂ + R _x + R ₃ )] / [R _z + R
₁ + R ₂ + R _x + R ₃ ] SIG2 = [E · R ₃ ] / [R _z + R ₁ + R ₂ + R _x +
R ₃ ]. In this case, R _x appears in both the numerator and the denominator in the expression representing the voltage value of the signal SIG1, and R _z appears in the denominator. That is, the voltage value of the signal SIG1 may increase or may decrease depending on the values of R _x and R _z . In the formula representing the voltage value of the signal SIG2, R _x and R _z appear in the denominator. That is, if R _x and / or R _z increases, the voltage value of the signal SIG2 drops. Therefore, since signals SIG1 and SIG2 having wrong values are given to the accelerator sensor input circuit, accurate operation of the device that operates with the output signal of the accelerator sensor input circuit cannot be obtained.

As described above, when a contact failure occurs in the relay connector, the signal SIG is generated in any case.
Two drops are allowed. Therefore, the abnormality of the potentiometer, the relay connector, and the electric wiring can be detected by monitoring the signal SIG2.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

[0018] The present invention is provided with a potentiometer P which the potential of the middle point terminal T ₁ in response to displacement of the accelerator operation end constant voltage is applied to the hot-side terminal T ₀ is changed, the middle point terminal T ₁ It is an accelerator sensor input circuit that uses a potential as a control input.

Here, the feature of the present invention is that the cold side terminal T ₂ of the potentiometer P is connected to the ground potential via the resistor R ₃ and when the potential of the cold side terminal T ₂ drops. Circuit AR for generating alarm output to
Is in place. Analog-digital converting circuit for converting the potential of the middle point terminal T ₁ of the potential and the cold side terminal T ₂ into digital signals AD1 and AD2
And a program control circuit CPU for executing this digital signal acquisition processing. The program control circuit CPU has a predetermined potential at the cold side terminal T ₂ when a change in the potential at the midpoint terminal T ₁ is detected. When falling below the value, means for executing fail-safe processing on the fetched potential of the midpoint terminal T ₁ is provided. Each of the analog / digital conversion circuits AD1 and AD2 has a resistance value of the potentiometer P (R ₁ , R shown in FIG. 4).
₂ and R ₃ ) has a sufficiently high impedance.

Next, the operation of the program control circuit CPU will be described with reference to FIG. FIG. 2 shows a program control circuit C
It is a flowchart which shows operation | movement of PU. The signal SI is output from the terminal T ₁ connected to the slider of the potentiometer P.
G1 is taken into the analog / digital conversion circuit AD1 (S1). When a change in the signal SIG1 is detected (S
2) Then, the signal SIG2 is taken into the analog-digital conversion circuit AD2 from the terminal T ₂ (S3). The program control circuit CPU switches the switching circuit EX in synchronism with the clock of the clock generating circuit CLK and takes in the signal SIG1 or SIG2. At this time, if a voltage drop is detected from the voltage value of the signal SIG2 (S4), it is determined that an abnormality has occurred in the potentiometer P or the electrical wiring connecting the potentiometer P and the accelerator sensor input circuit, and the alarm circuit AR is alerted. The output is instructed (S6). Also,
Pre-programmed fail-safe processing is performed so that other devices that are controlled by the output signal of the accelerator sensor input circuit do not malfunction to the dangerous side (S
7). In the apparatus of the embodiment of the present invention, the program control circuit controls the throttle / rack control motor M. If the potentiometer P has a dual structure as an active spare, the active spare is switched (S8). If no voltage drop is detected in the voltage value of the signal SIG2 (S
4), potentiometer P or potentiometer P
The throttle / rack control motor M is controlled by the voltage value of the signal SIG1 previously taken in, assuming that there is no abnormality in the electrical wiring connecting the accelerator sensor input circuit with the accelerator sensor input circuit.

The above-mentioned duplexed potentiometer P will be described with reference to FIG. FIG. 3 is a block diagram of the potentiometer P having a dual configuration. Two systems of potentiometers P1 and P as working and spare
Two are provided. Potentiometers P1 and P2
Is connected to a switching circuit SW composed of semiconductor switches. The output of the potentiometer P1 or P2 is switched by an active spare switching signal from the program control circuit CPU.

[0022]

As described above, the accelerator sensor input circuit of the present invention can detect that a contact failure has occurred in the path of the electric wiring and can generate an alarm. Further, erroneous detection can be avoided and fail-safe processing can be executed according to this alarm output. Further, when the accelerator sensor has a dual structure, it is possible to properly determine and switch the circuit that is sending out a legitimate output.

This makes it possible to improve the safety of a motor vehicle equipped with a device controlled by an electronic circuit.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of a program control circuit.

FIG. 3 is a block diagram of a potentiometer having a dual configuration.

FIG. 4 is a diagram showing an equivalent circuit for explaining a detection method.

[Explanation of symbols]

AD1, AD2 Analog-digital conversion circuit AR Alarm circuit CLK Clock generation circuit CPU program control circuit EX, SW switching circuit M Throttle / rack control motor P, P1, P2 potentiometer R ₁ , R ₂ , R ₃ , R _x , R _y , R _z resistance SIG1, SIG2 signal T ₀ , T ₁ , T ₂ terminal

Claims (3)

[Claims] 1. A potentiometer (P) is provided, wherein a constant voltage is applied to a hot side terminal (T ₀ ) and the potential of a midpoint terminal (T ₁ ) changes in response to a displacement of an accelerator operating end. In the accelerator sensor input circuit that uses the potential of the terminal as a control input, the cold side terminal (T ₂ ) of the potentiometer (P)
Is connected to the ground potential via a resistor (R ₃ ), and is equipped with an alarm circuit for generating an alarm output when the potential of the cold side terminal (T ₂ ) drops. . 2. A digital-analog conversion circuit for converting the potential of the midpoint terminal (T ₁ ) and the potential of the cold side terminal (T ₂ ) into digital signals, respectively, and a program for executing this digital signal acquisition processing. The program control circuit includes a control circuit, and the potential of the cold side terminal (T ₂ ) drops below a predetermined value when a change in the potential of the midpoint terminal (T ₁ ) is detected. The accelerator sensor input circuit according to claim 1, further comprising means for executing fail-safe processing with respect to the potential of the midpoint terminal that has been taken in. 3. The potentiometer is dualized for working and protection, and comprises circuit means for switching between working and protection when the potential of the cold side terminal (T ₂ ) drops. Accelerator sensor input circuit.