JP3616917B2 - Torque sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torque sensor, and more particularly to an improvement of a torque sensor suitable for an automobile power steering apparatus.
[0002]
[Prior art]
FIG. 2 is a block diagram illustrating a configuration example of a conventional torque sensor. In this torque sensor, an alternating current oscillated and output from the oscillation circuit 10 is applied to the current amplification circuit 11 and the amplitude reversal current amplification circuit 12 to be amplified and amplitude reversed. A series circuit of a coil 13 whose impedance changes according to the applied torque and a coil 14 for temperature compensation, a series circuit of a resistor R1, a variable resistor VR1, and a resistor R2, and a series circuit of a resistor R3, a variable resistor VR2, and a resistor R4 The current amplified by the current amplification circuit 11 and the amplitude reversal current amplification circuit 12 and the amplitude reversal amplification are applied to both ends of the parallel circuit.
[0003]
The voltage at the connection point between the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR1 are applied to the main-side differential amplifier circuit 19, and the difference is amplified. The voltage at the connection point of the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR2 are applied to the sub-amplifier differential amplifier 23, and the difference between them is amplified.
The alternating current oscillated and output from the oscillation circuit 10 is also applied to the sampling pulse generation circuit 20, and the sampling pulse generation circuit 20 generates and outputs a sampling pulse based on the applied current.
[0004]
The differential voltage amplified by the differential amplifier circuit 19 is sampled by the sampling pulse output from the sampling pulse generating circuit 20 in the main-side sample and hold circuit 21 and output as a detected torque value via the main-side buffer 22. The
The sample and hold circuit 21 is supplied with the differential voltage amplified by the differential amplifier circuit 19, is charged by the analog switch SW1 that is operated by the sampling pulse, and the voltage sampled by the analog switch SW1, and has a positive voltage of 2.5 V through the resistor R1. And a capacitor C1 to which the constant voltage is applied, and output from the positive electrode of the capacitor C1. The negative electrode of the capacitor C1 is grounded.
[0005]
The difference voltage amplified by the differential amplifier circuit 23 is sampled by the sampling pulse output from the sampling pulse generating circuit 20 in the sub-side sample and hold circuit 25, and output as a detected torque value via the sub-side buffer 26. The
The sample hold circuit 25 is supplied with the differential voltage amplified by the differential amplifier circuit 23, is charged by the analog switch SW2 that is operated by the sampling pulse, and the voltage sampled by the analog switch SW2, and has a resistance R2 (= R1) at the positive electrode. And a capacitor C2 (= C1) to which a constant voltage of 2.5 V is applied, and outputs from the positive electrode of the capacitor C2. The negative electrode of the capacitor C2 is grounded.
The voltages output from the buffer 22 and the buffer 26 are respectively supplied to the control unit 24 of the power steering apparatus as a detected value of the steering torque.
[0006]
In the torque sensor having such a configuration, the alternating current output from the oscillation circuit 10 is supplied to the current amplification circuit 11 and the amplitude reversal current amplification circuit 12 to be amplified and amplitude reversal amplified, respectively. The alternating currents amplified and inverted in amplitude are respectively connected to a series circuit of a coil 13 and a temperature compensating coil 14, a series circuit of a resistor R1, a variable resistor VR1, and a resistor R2, a resistor R3, a variable resistor VR2, and a resistor R4. It is given to both ends of a parallel circuit with a series circuit.
[0007]
The voltage at the connection point of the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR1 are applied to the differential amplifier circuit 19. The differential amplifier circuit 19 is temperature-compensated according to the applied torque. Amplifies the voltage difference.
The voltage at the connection point of the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR2 are applied to the differential amplifier circuit 23. The differential amplifier circuit 23 is temperature-compensated according to the applied torque. Amplifies the voltage difference.
[0008]
The differential voltage amplified by the differential amplifier circuit 19 is sampled by the sample hold circuit 21, and is supplied to the control unit 24 via the buffer 22 as the detected main torque value. The control unit 24 is based on this torque value. A steering assist motor (not shown) is driven and controlled.
The differential voltage amplified by the differential amplifier circuit 23 is sampled by the sample hold circuit 25 and is supplied to the control unit 24 via the buffer 26 as a detected sub torque value.
The control unit 24 detects an abnormality of the torque sensor based on the difference between the torque values from the buffer 22 and the buffer 26 given.
[0009]
[Problems to be solved by the invention]
In the conventional torque sensor, as described above, the main-side sample and hold circuit 21 and the sub-side sample and hold circuit 25 have exactly the same circuit configuration. Therefore, when the oscillation circuit 10 breaks down and stops oscillating, both outputs become the midpoint voltage (2.5 V), the steering torque becomes 0, and the steering assist is turned off, but the oscillation circuit 10 fails. There was a problem that it could not be detected.
[0010]
In JP-A-6-88757, the voltage related to the steering torque to be detected is clamped by the clamp circuit on the main side and the sub side, and the peak detection circuit detects the peak of the clamped voltage. A “torque sensor” is disclosed in which a limiter circuit is added to an output terminal of a sub-side peak detection circuit to detect a failure of an oscillation circuit.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a torque sensor that can detect a failure of an oscillation circuit.
[0011]
[Means for Solving the Problems]
The torque sensor according to the first aspect of the invention amplifies voltages based on a change in impedance generated in the coil in accordance with the torque to be detected by the two amplifier circuits, and the two holding circuits use the sampling pulses. Each of the two holding circuits detects and holds the torque based on the voltage held by one of the two holding circuits, and the voltage held by each of the two holding circuits. In the torque sensor configured to detect an abnormality based on the difference, the other of the two holding circuits includes a step-down circuit that drops the held voltage to the first fixed potential when the sampling pulse is not applied. And an abnormality is detected when the sampling pulse is not given.
[0012]
In this torque sensor, voltages based on a change in impedance generated in the coil in accordance with the torque to be detected are amplified by two amplifier circuits. The two holding circuits sample and hold the two holding circuits by the sampling pulse given from the sampling pulse generating circuit, respectively, detect torque based on the voltage held by one of the two holding circuits, and 2 An abnormality is detected based on the difference between the voltages held by the two holding circuits. The step-down circuit provided in the other of the two holding circuits drops the held voltage to the first fixed potential when no sampling pulse is applied to the holding circuit.
As a result, when a sampling pulse is not applied to the holding circuit, a difference occurs in the voltage output from each of the holding circuits on the main side and the sub side, and the failure of the oscillation circuit that is the source of the sampling pulse can be detected. A torque sensor can be realized.
[0013]
A torque sensor according to a second aspect of the present invention includes one of the two holding circuits including a first capacitor to be charged with a sampled voltage, and the first capacitor passes through a first resistor and is higher than the first fixed potential. Two fixed potentials are applied, and the other of the two holding circuits includes a second capacitor to be charged with a sampled voltage, and a second resistor is connected in parallel to the second capacitor. And
[0014]
In this torque sensor, one of the two holding circuits is charged with the first capacitor by the sampled voltage, and a second fixed potential higher than the first fixed potential is applied to the first capacitor through the first resistor. In the other of the two holding circuits, the second capacitor is charged by the sampled voltage, and a second resistor is connected in parallel to the second capacitor.
As a result, when a sampling pulse is not applied to the holding circuit, a difference occurs in the voltage output from each of the holding circuits on the main side and the sub side, and the failure of the oscillation circuit that is the source of the sampling pulse can be detected. A torque sensor can be realized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings showing the embodiments.
FIG. 1 is a block diagram showing a configuration of an embodiment of a torque sensor according to the present invention. In this torque sensor, an alternating current oscillated and output from the oscillation circuit 10 is applied to the current amplification circuit 11 and the amplitude reversal current amplification circuit 12 to be amplified and amplitude reversed. A series circuit of a coil 13 whose impedance changes according to the applied torque and a coil 14 for temperature compensation, a series circuit of a resistor R1, a variable resistor VR1, and a resistor R2, and a series circuit of a resistor R3, a variable resistor VR2, and a resistor R4 The current amplified by the current amplification circuit 11 and the amplitude reversal current amplification circuit 12 and the amplitude reversal amplification are applied to both ends of the parallel circuit.
[0016]
The voltage at the connection point between the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR1 are applied to the main-side differential amplifier circuit 19, and the difference is amplified. The voltage at the connection point of the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR2 are applied to the sub-amplifier differential amplifier 23, and the difference between them is amplified.
The alternating current oscillated and output from the oscillation circuit 10 is also applied to the sampling pulse generation circuit 20, and the sampling pulse generation circuit 20 generates and outputs a sampling pulse based on the applied current.
[0017]
The differential voltage amplified by the differential amplifier circuit 19 is sampled by the sampling pulse output from the sampling pulse generating circuit 20 in the main-side sample-and-hold circuit 21 (holding circuit), and the main-side buffer 22 is used as a detected torque value. Is output via.
The sample and hold circuit 21 is supplied with the differential voltage amplified by the differential amplifier circuit 19, is charged by the analog switch SW1 that is operated by the sampling pulse, and the voltage sampled by the analog switch SW1, and has a positive voltage of 2.5 V through the resistor R1. And a capacitor C1 to which a constant voltage (second fixed potential) is applied, and output from the positive electrode of the capacitor C1. The negative electrode of the capacitor C1 is grounded.
[0018]
The differential voltage amplified by the differential amplifier circuit 23 is sampled by the sampling pulse output from the sampling pulse generating circuit 20 in the sub-side sample hold circuit 25a, and is output as a detected torque value via the sub-side buffer 26. The
The sample-and-hold circuit 25a (holding circuit) is supplied with the differential voltage amplified by the differential amplifier circuit 23, and operates with an analog switch SW2 that is activated by a sampling pulse, and a capacitor C3 that is charged with the voltage sampled by the analog switch SW2 Circuit) and a resistor R3 (step-down circuit) connected in parallel between the positive electrode and the negative electrode of the capacitor C3, and outputs from the positive electrode of the capacitor C3. The negative electrode of the capacitor C3 is grounded (first fixed potential).
The voltages output from the buffer 22 and the buffer 26 are respectively supplied to the control unit 24 of the power steering apparatus as a detected value of the steering torque.
[0019]
In the torque sensor having such a configuration, the alternating current output from the oscillation circuit 10 is supplied to the current amplification circuit 11 and the amplitude reversal current amplification circuit 12 to be amplified and amplitude reversal amplified, respectively. The alternating currents amplified and inverted in amplitude are respectively connected to a series circuit of a coil 13 and a temperature compensating coil 14, a series circuit of a resistor R1, a variable resistor VR1, and a resistor R2, a resistor R3, a variable resistor VR2, and a resistor R4. It is given to both ends of a parallel circuit with a series circuit.
[0020]
The voltage at the connection point of the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR1 are applied to the differential amplifier circuit 19. The differential amplifier circuit 19 is temperature-compensated according to the applied torque. Amplifies the voltage difference.
The voltage at the connection point of the coils 13 and 14 and the voltage at the variable terminal of the variable resistor VR2 are applied to the differential amplifier circuit 23. The differential amplifier circuit 23 is temperature-compensated according to the applied torque. Amplifies the voltage difference.
[0021]
The differential voltage amplified by the differential amplifier circuit 19 is sampled by the sample hold circuit 21, and is supplied to the control unit 24 via the buffer 22 as the detected main torque value. The control unit 24 is based on this torque value. A steering assist motor (not shown) is driven and controlled.
The differential voltage amplified by the differential amplifier circuit 23 is sampled by the sample and hold circuit 25a, and is supplied to the control unit 24 through the buffer 26 as the detected sub torque value.
The control unit 24 detects an abnormality of the torque sensor based on the difference between the torque values from the buffer 22 and the buffer 26 given.
[0022]
Here, the sample hold circuit 21 charges the capacitor C1 with the voltage sampled by the analog switch SW1, and outputs the charged and held voltage from the positive electrode of the capacitor C1. When the torque to be detected is 0, a midpoint voltage of 2.5 V is output.
When the oscillation circuit 10 fails and the sampling pulse is not applied to the analog switch SW1, the sample hold circuit 21 outputs a constant voltage of 2.5 V through the resistor R1.
[0023]
The sample hold circuit 25a charges the capacitor C3 with the voltage sampled by the analog switch SW2, and outputs the charged and held voltage from the positive electrode of the capacitor C3. When the torque to be detected is 0, the midpoint voltage 2.5 V maintained by the resistor R3 is output.
When the oscillation circuit 10 fails and the sampling pulse is not applied to the analog switch SW2, the sample hold circuit 25a discharges the capacitor C3 through the resistor R3, and outputs 0 V that is the ground potential after a predetermined time. Become.
[0024]
【The invention's effect】
According to the torque sensor of the present invention, when a sampling pulse is not applied to the holding circuit, a difference occurs in the voltage output from each holding circuit on the main side and the sub side, and the oscillation circuit that is the source of the sampling pulse is generated. A torque sensor that can detect a failure can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of a torque sensor according to the present invention.
FIG. 2 is a block diagram illustrating a configuration example of a conventional torque sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Oscillator 13, 14 Coil 19, 23 Differential amplifier circuit 20 Sampling pulse production circuit 21, 25a Sample hold circuit (hold circuit)
24 control unit C1 capacitor R1 resistor C3 capacitor (voltage step-down circuit)
R3 resistance (step-down circuit)
SW1, SW2 Analog switch

Claims (2)

The two amplification circuits amplify the voltage based on the impedance change generated in the coil in accordance with the torque to be detected, and the two holding circuits are obtained by the sampling pulse provided from the sampling pulse generating circuit. Each of the two holding circuits is sampled and held, the torque is detected based on the voltage held by one of the two holding circuits, and the abnormality is detected based on the difference between the voltages held by the two holding circuits. Torque sensor
The other of the two holding circuits includes a step-down circuit that drops the held voltage to a first fixed potential when the sampling pulse is not applied, and detects an abnormality when the sampling pulse is not applied. A torque sensor characterized by being made. One of the two holding circuits includes a first capacitor to be charged with a sampled voltage, and a second fixed potential higher than the first fixed potential is applied to the first capacitor through a first resistor; The torque sensor according to claim 1, wherein the other of the two holding circuits includes a second capacitor to be charged with a sampled voltage, and a second resistor is connected in parallel to the second capacitor.

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