JP2001004464A - Torque detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reliability even upon failure of a signal processing section. SOLUTION: The torque detector 10 comprises a torque sensor 12, and signal processing sections 14, 16. The torque sensor 12 outputs an electric signal variable with the value of torque applied to a rotary shaft. The signal processing section 14 extracts an electric signal (output voltage V1) corresponding to the value of torque from an electric signal received from the torque sensor 12 and outputs the extracted electric signal from an output terminal 171. The signal processing section 16 extracts an electric signal (output voltage V2) corresponding to the value of torque from an electric signal received from the torque sensor 12 and outputs the extracted electric signal from an output terminal 172. Since the signal processing sections 14, 16 have different circuitry, a same failure results from a same factor at low possibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque detecting device used for, for example, a power steering for reducing a steering force of a vehicle.

[0002]

2. Description of the Related Art A general torque detecting device includes a torque sensor for outputting an electric signal that changes according to a torque value applied to a rotating shaft, and an electric signal corresponding to the torque value based on the electric signal output from the torque sensor. And a signal processing unit for extracting and outputting the same.

In such a torque detecting device, by providing two signal processing units having the same circuit configuration,
A device with improved reliability is known (for example, JP-A-7-260601). In this conventional torque detection device, an output terminal is provided for each signal processing unit, and even if one of the signal processing units fails, if the other signal processing unit is normal, the torque can be normally detected as a whole. Things.

[0004]

However, if one of the signal processing units fails due to, for example, overvoltage or overcurrent (a voltage or current exceeding the maximum rated value of a circuit component), the other signal processing unit also fails. I often did. Therefore, the reliability of the conventional torque detecting device has not improved as expected.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a torque detecting device capable of reliably improving reliability.

[0006]

SUMMARY OF THE INVENTION The present inventor has noticed that the limitation of the reliability improvement in the conventional torque detecting device lies in the circuit configuration of both signal processing units. That is, since both signal processing units have the same circuit configuration, the same result is obtained for the same cause of failure. Therefore, if both signal processing units have different circuit configurations, the reliability will surely be improved. The present invention has been made based on this finding.

A torque detecting device according to the present invention outputs a torque sensor that outputs an electric signal that changes according to a torque value applied to a rotating shaft, and extracts an electric signal corresponding to the torque value from the electric signal output from the torque sensor. And a plurality of signal processing units for outputting the signals. The plurality of signal processing units have different circuit configurations. Here, “plurality” means two or more, but “two” is preferable because it is realistic. The “different circuit configuration” may be entirely different or only partially different.

[0008] An electric signal that changes according to the torque value applied to the rotating shaft is output from the torque sensor. This electric signal is input to a plurality of signal processing units. In each signal processing unit, an electric signal corresponding to the torque value is separately extracted. At this time, even if one of the signal processing units fails, if the remaining signal processing units are normal, the torque can be normally detected as a whole.

Since the plurality of signal processing units have different circuit configurations, it is unlikely that the same result will be obtained for the same cause of failure. Therefore, the reliability is surely improved by that much.

[0010]

FIG. 1 is a block diagram showing a first embodiment of a torque detecting device according to the present invention. Hereinafter, description will be made based on this drawing.

The torque detecting device 10 according to the present embodiment includes a torque sensor 12, a signal processing unit 14, a signal processing unit 16, and the like. The torque sensor 12 outputs an electric signal that changes according to a torque value applied to the rotating shaft. Signal processing unit 1
4 extracts an electric signal (output voltage V1) corresponding to the torque value from the electric signal output from the torque sensor 12,
This is output from the output terminal 171. Signal processing unit 16
Extracts an electric signal (output voltage V2) corresponding to the torque value from the electric signal output from the torque sensor 12, and outputs this from an output terminal 172. The signal processing unit 14 and the signal processing unit 16 have different circuit configurations. The torque detecting device 10 is for power steering.

First, the basic operation of the torque detecting device 10 will be described.

An electric signal that changes according to the torque value applied to the rotating shaft is output from the torque sensor 12. This electric signal is input to the signal processing units 14 and 16, respectively. In the signal processing units 14 and 16, the electric signals corresponding to the torque values are separately extracted. At this time, if the signal processing unit 16 is normal even if the signal processing unit 14 fails, the torque is normally detected as a whole if the signal processing unit 14 is normal even if the signal processing unit 16 fails. it can. Since the signal processing units 14 and 16 have different circuit configurations, it is unlikely that the same result will be obtained for the same cause of failure. Therefore, the reliability is surely improved by that much.

Next, each component of the torque detecting device 10 and other operations will be described.

The torque sensor 12 is of a magnetostrictive type, and includes an excitation source 121, excitation coils 122 and 123, a sensor shaft 12
4. It is composed of detection coils 125, 126 and the like.
The sensor shaft 124 is made of a ferromagnetic material such as iron, nickel, or an alloy thereof. When torque is applied to the sensor shaft 124, tensile stress and compressive stress are applied in a direction of ± 45 degrees with respect to the center line of the sensor shaft 124. There is a difference in the magnetic permeability between the direction in which the tensile stress is applied and the direction in which the compressive stress is applied due to the magnetostriction phenomenon. That is, torque can be detected by detecting the difference in the magnetic permeability.

Therefore, the excitation coils 122 and 123 and the detection coils 125 and 126 are arranged on the surface of the sensor shaft 124, and the excitation coils 122 and 123 are excited by the AC voltage of the excitation source 121. Then, AC voltage values corresponding to the magnetic permeability in the tensile direction and the magnetic permeability in the compression direction are separately obtained from the detection coils 125 and 126, respectively. Therefore, if these AC voltages are rectified and smoothed and converted to DC, the difference between them corresponds to the torque value applied to the sensor shaft 124.
Although not shown, the sensor shaft 124 is connected between an input shaft attached to a steering wheel and an output shaft attached to a steering mechanism such as a pinion and a rack.

The signal processing unit 14 includes detection coils 125, 1
A rectifier circuit 18 for rectifying the AC voltage output from
20, a comparison circuit 22 for taking the difference between the output voltages of the rectifier circuits 18 and 20, a smoothing circuit 24 for converting the output voltage of the comparison circuit 22 into DC, a gain / middle point adjustment circuit 26 for correcting the output voltage of the smoothing circuit 24, A voltage monitoring circuit 28 having a function of monitoring the voltage, a control circuit 30 operating based on an output signal of the voltage monitoring circuit 28, an analog voltage output circuit 32 operating based on an output signal of the control circuit 30, and an output signal of the control circuit 30. The switches 34 and 36 operate on the basis of a temperature sensor 38 for detecting a temperature. The signal processing unit 16 includes rectifying / smoothing circuits 40 and 42 for rectifying and smoothing the AC voltage output from the detection coils 125 and 126, an addition / smoothing circuit 44 for obtaining a difference between output voltages of the rectification / smoothing circuits 40 and 42, and an addition / smoothing circuit. Gain to correct the output voltage
It comprises a midpoint adjustment circuit 46 and the like.

The voltage monitoring circuit 28 receives the power supply voltage, the output voltage of the smoothing circuit 24, the output voltages V1, V2, etc., and monitors these voltages. Normally, the switch 34 is closed and the switch 36 is open, and the output voltage V1 is
1 is output. Here, when the voltage monitoring circuit 28 determines that the output voltage V1 is abnormal, the control circuit 3
The switch 34 is opened by the output signal of 0 and the switch 3
6 is closed, the output voltage V2 becomes the output terminal 17
1 is output. Therefore, the output terminal 172 can be omitted. Therefore, by using only the output terminal 171, one input circuit on the EPS (Electric Power Steering) controller side connected to the torque detection device 10 becomes unnecessary.

The voltage monitoring circuit 28 stores in advance data relating to a change in gain and a midpoint due to a change in temperature. Then, the voltage monitoring circuit 28 outputs a correction signal to the gain / midpoint adjustment circuit 26 based on the output signal of the temperature sensor 38. Further, when a predetermined torque value is applied or when the torque value is zero, the voltage monitoring circuit 28 outputs a correction signal to the gain / middle point adjustment circuit 26 so that a correct gain or a middle point is obtained.

In the case of a failure or the like, the output voltage V
To force 1 high or low, the control circuit 30
, A voltage corresponding to high or low is output from the analog voltage output circuit 32.

FIG. 2 is a more specific circuit diagram of the torque detector of FIG. Hereinafter, description will be given based on FIG. 1 and FIG. However, the same parts as those in FIG.

The rectifier circuit 18 includes operational amplifiers 181, 18
2, diodes 183, 184, resistors 185 to 189
And the like, and is a full-wave rectifier using an ideal diode. The rectifier circuit 20 includes operational amplifiers 201 and 20
2, diodes 203 and 204, resistors 205 to 209
And the like, and is a full-wave rectifier using an ideal diode. The comparison circuit 22 is a subtractor that includes an operational amplifier 221, resistors 222 to 226, and the like.
The smoothing circuit 24 is a low-pass filter 24 '. The gain / midpoint adjustment circuit 26 is an A / D / D / A converter 2
6 '. The voltage monitoring circuit 28 and the control circuit 30
² is a CPU 50 having a PROM. The analog voltage output circuit 32 is a D / A converter 32 '.

The rectifying and smoothing circuit 40 includes an operational amplifier 401,
402, diodes 403 and 404, resistors 405-4
09, a full-wave rectifier with a smoothing capacitor using an ideal diode, which is constituted by a capacitor 410 and the like.
The rectifying / smoothing circuit 42 is a full-wave rectifier with a smoothing capacitor using an ideal diode, which includes operational amplifiers 421 and 422, diodes 423 and 424, resistors 425 to 429, and a capacitor 430. Diode 4
Since the connection directions of the diodes 03 and 404 and the diodes 423 and 424 are reversed, the output voltage of the rectifying / smoothing circuit 40 is positive and the output voltage of the rectifying / smoothing circuit 42 is negative. The addition smoothing circuit 44 includes an operational amplifier 441, a resistor 442,
This is an adder with a smoothing capacitor, which is constituted by 443, a capacitor 424, and the like. Gain / midpoint adjustment circuit 4
6 is an operational amplifier 461, thermistors 462, 463,
This is a temperature compensator constituted by resistors 464 to 468, variable resistors 469 and 470, and the like. Thermistor 46
2 is for adjusting the middle point, and the thermistor 463 is for adjusting the gain. The resistance values of the variable resistors 469 and 470 are adjusted in advance so as to obtain desired temperature compensation characteristics.

As described above, the signal processing unit 14 and the signal processing unit 1
6, the signal processing unit 16 outputs a normal output voltage V2 even if the CPU 50 and the A / D / D / A converter 26 'fail due to external noise or the like. The converse is also true. Similarly, since the temperature correction method is different between the signal processing unit 14 and the signal processing unit 16, even if one of the devices fails for some reason, the other can correct the temperature normally.

The CPU 50 outputs the output voltages V1 and V2.
The difference | V1−V2 | is monitored, and if this is abnormal, a fail output (0 [V] or 5 [V]) or a midpoint output (2.
By outputting a command signal of 5 [V]) to the D / A converter 32 ', a fail process or a midpoint fixing process is performed.

It should be noted that the signal processing unit 14 and the signal processing unit 16 may be configured such that each component is separate, the operational amplifier is a different type, and constants such as resistance are changed. Although the + input terminal of each operational amplifier is at the ground voltage, an offset voltage (2.5 to 4.0 [V]) may be applied.

FIG. 3 is a block diagram showing a second embodiment of the torque detecting device according to the present invention. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG. 1 and FIG.

In the first embodiment, the entire circuit configuration differs between the two signal processing units, whereas in the present embodiment, a part of the circuit configuration differs between the two signal processing units.

The torque detecting device 60 of the present embodiment includes the torque sensor 12, a signal processing unit 64, a signal processing unit 66, and the like. The torque sensor 12 outputs an electric signal that changes according to a torque value applied to the rotating shaft. Signal processing unit 6
4 extracts an electric signal (output voltage V1) corresponding to the torque value from the electric signal output from the torque sensor 12,
This is output from the output terminal 171. Signal processing unit 66
Extracts an electric signal (output voltage V2) corresponding to the torque value from the electric signal output from the torque sensor 12, and outputs this from an output terminal 172. The signal processing unit 64 and the signal processing unit 66 have different circuit configurations from each other. The torque detector 60 is for power steering.

The signal processing section 64 includes rectifier circuits 18, 20,
Comparison circuit 22, smoothing circuit 24, gain / midpoint adjustment circuit 2
6, a CPU 50, an analog voltage output circuit 32, a switch 34, a temperature sensor 38, a CPU monitoring circuit 68, and the like. The signal processing unit 66 includes the rectifier circuits 18 and 2
0, a comparison circuit 22, a smoothing circuit 24, a gain / midpoint adjustment circuit 46, and the like. That is, the rectifier circuits 18 and 20, the comparison circuit 22, and the smoothing circuit 24 are shared by the signal processing units 64 and 66.

The operation of the torque detecting device 60 is almost the same as that of the torque detecting device 10 (FIGS. 1 and 2). Therefore, the operation of the torque detecting device 60 that is not included in the torque detecting device 10 will be described.

If a failure occurs in any of the rectifier circuits 18, 20, the comparison circuit 22, and the smoothing circuit 24, the output voltage V
1 and V2 are both abnormal voltages (for example, 5 [V] or 0
[V]). Therefore, in this case, the CPU 5
0 instantaneously opens the switch 34 and outputs, for example, a midpoint voltage (for example, 2.5 [V]) from the output terminal 171 via the analog voltage output circuit 32. As a result, the midpoint voltage (for example, 2.5
[V]), and an abnormal voltage (for example, 5 [V] or 0 [V]) is output from the output terminal 172.

When the CPU 50 becomes abnormal, the CPU monitoring circuit 68 instantaneously opens the switch 34 via the analog voltage output circuit 32 and, for example, outputs the midpoint voltage (for example, 2 .5
[V]) from the output terminal 171. This allows
The output of the abnormal voltage due to the abnormality of the CPU 50 can be prevented.

Although the torque detecting device according to the present invention has been described for power steering in the above embodiment, it can be applied to general vehicles and other wide fields.

[0035]

According to the torque detecting device of the present invention,
A plurality of signal processing units that extract and output an electric signal corresponding to the torque value from the electric signal output from the torque sensor and have different circuit configurations, so that each signal processing unit is the same for the same cause of failure. Since a result can be prevented, reliability can be reliably improved.

According to the torque detecting device of the third aspect,
By providing a temperature correction circuit having a different circuit configuration for each signal processing unit, it is possible to prevent each correction circuit from having the same result for the same cause of failure, so that reliability in temperature correction can be reliably improved. .

According to the torque detecting device of the fourth aspect,
By providing the voltage monitoring circuit that monitors the voltage of the electric signal output from each signal processing unit, the abnormality of each signal processing unit can be quickly detected, so that the reliability can be more reliably improved.

According to the torque detecting device of the fifth aspect,
When the electric signal output from the first signal processing unit is abnormal and the electric signal output from the second signal processing unit is normal, the electric signal output from the second signal processing unit is Since the output from the first signal processing unit is performed, the output terminal of the second signal processing unit can be omitted, so that a system using the torque detection device can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a torque detection device according to the present invention.

FIG. 2 is a more specific circuit diagram of the torque detection device of FIG. 1;

FIG. 3 is a block diagram showing a second embodiment of the torque detection device according to the present invention.

[Explanation of symbols]

 10, 60 Torque detecting device 12 Torque sensor 14, 64 Signal processing unit (first signal processing unit) 16, 66 Signal processing unit (second signal processing unit)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kenichi Azuma 300 Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. F-term (reference) 3D033 CA03 CA11 CA16 CA28 CA31

Claims (5)

[Claims] A torque sensor that outputs an electric signal that changes in accordance with a torque value applied to a rotating shaft; an electric signal corresponding to the torque value is extracted and output from the electric signal output from the torque sensor; A torque detection device comprising: a plurality of signal processing units having circuit configurations different from each other. 2. A torque sensor that outputs an electric signal that changes in accordance with a torque value applied to a rotating shaft, and a first signal that extracts and outputs an electric signal corresponding to the torque value from the electric signal output from the torque sensor. A signal processing unit, and an electric signal corresponding to a torque value is extracted and output from the electric signal output from the torque sensor, and a second signal processing unit having a circuit configuration different from that of the first signal processing unit And a torque detecting device comprising: 3. The torque detection device according to claim 1, wherein each of the signal processing units includes a temperature correction circuit that corrects the electric signal based on a temperature, and the temperature correction circuits have different circuit configurations. 4. The torque detecting device according to claim 1, further comprising a voltage monitoring circuit that monitors a voltage of an electric signal output from each of the signal processing units. 5. A voltage monitoring circuit that monitors a voltage of an electric signal output from the first and second signal processing units, wherein the voltage monitoring circuit outputs an electric signal output from the first signal processing unit. When the signal is abnormal and the electric signal output from the second signal processing unit is normal, the electric signal output from the second signal processing unit is output from the first signal processing unit. The torque detection device according to claim 2.