JPH06265421A - Magneto-strictive torque sensor - Google Patents

Abstract

PURPOSE:To improve the detecting sensibility of a magnetostrictive torque sensor even in the case where a magnetic aeolotropic part in a torque detecting shaft is set up to be at only one spot for composing a torque sensor. CONSTITUTION:A magnetic aeolotropic part 2 is formed at one spot on the outer periphery of a torque transmitting shaft 1, and a detecting coil 3 and an exciting coil 4 are arranged on the circumference of the magnetic aeolotropic part 2, and a torque detecting signal is obtained from the output of the detecting coil 3. A resistance 17 to fix exciting current is provided in series between the exciting coil 4 and a.c. exciting power source 5. Detecting voltage proportional to the product of the number of turns and exciting current is therefore output to the detecting coil 3. Thus the high detecting voltage can be obtained under the same exciting voltage by increasing the number of turns of the detecting coil 3, and a highly sensitive torque sensor is thereby obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor.

[0002]

2. Description of the Related Art A magnetostrictive torque sensor is known as a means for detecting the magnitude of torque applied to a torque detecting shaft. As this magnetostrictive torque sensor, a pair of magnetic anisotropic portions that are inclined in opposite directions are formed on the outer peripheral surface of the torque detection shaft, and an exciting coil and a pair of detection coils are provided around these magnetic anisotropic portions. It is generally provided with.

[0003]

On the other hand, even if the magnetic anisotropic portion is formed only at one location on the outer peripheral surface of the torque detecting shaft, the measurement sensitivity will be slightly lowered, but there is no problem in practical use. A magnetostrictive torque sensor can be configured.

However, the higher the measurement sensitivity is, the more preferable it is. Since the magnetic anisotropy portion is provided at only one place and the measurement sensitivity is high, a compact and highly sensitive torque sensor can be obtained. Is expected.

Therefore, it is an object of the present invention to improve the measurement sensitivity of a torque sensor when the torque sensor is configured with only one magnetic anisotropic portion.

[0006]

In order to achieve the above object, the present invention provides a single magnetic anisotropic portion formed on the outer peripheral surface of a torque detection shaft and a magnetic anisotropic portion provided around the magnetic anisotropic portion. An exciting coil and a detecting coil, a means for obtaining a torque detection signal from the output of the detecting coil, a means for supplying an exciting voltage to the exciting coil, and an exciting coil provided in series between the exciting coil and the exciting voltage supplying means. It has a resistance for making the current constant.

[0007]

In this structure, when torque is applied to the torque detecting shaft, the magnetic permeability of the magnetically anisotropic portion changes, which changes the impedance of the coil.
At this time, if the value of the exciting voltage of the exciting voltage supply means or the value of the resistance provided in series is set so that the exciting current flowing through the exciting coil becomes almost constant, the number of turns of this detecting coil is set in the detecting coil. A detection voltage proportional to the product of the exciting current is output. Therefore, by increasing the number of turns of the detection coil, a large detection voltage can be obtained with the same excitation voltage, and this detection voltage changes with high sensitivity depending on the torque applied to the torque detection shaft. Therefore, it is possible to obtain a torque sensor with good performance that is not easily affected by noise and drift.

[0008]

FIG. 1 shows a first embodiment of the present invention. here,
Reference numeral 1 denotes a torque detection shaft, and a magnetic anisotropic portion 2 inclined with respect to the shaft center is formed at only one location on the outer peripheral surface thereof.
A detection coil 3 and an excitation coil 4 are arranged around the magnetic anisotropic portion 2.

The exciting coil 4 is connected to an alternating current excitation power source 5 for supplying an alternating current to the exciting coil 4. A resistor 17 for keeping the exciting current constant is connected in series between the AC exciting power source 5 and the exciting coil 4. Further, a rectifier circuit 6 and a low-pass filter 7 are connected to the AC excitation power source 5 so as to be connected in parallel with the resistor 17 and the excitation coil 3 to form an excitation voltage detection circuit 8.

The output line from the detection coil 3 has a gain temperature characteristic correction circuit 11, a rectification circuit 9 and a low pass filter.
10 is connected to form a torque detection circuit 12. The output side of the filter 10 in the torque detection circuit 12 and the output side of the filter 7 in the excitation voltage detection circuit 8 are both connected to the input side of the subtractor 13. The output side of the subtractor 13 is connected to the amplifier 14.

The output side of the amplifier 14 is connected to a polarity determination circuit 15 for detecting the direction of the torque applied to the torque detection shaft 1 and a gain switching circuit 16. The gain switching circuit 16 can switch the gain of the torque detection signal from the amplifier 14 based on the direction of the torque applied to the torque detection shaft 1 in response to the output from the polarity determination circuit 15.

In such a configuration, the AC excitation power source 5
Is a resistor 17 and an exciting coil 4 which are connected in series with each other.
The excitation voltage Vex shall be supplied to. Also, the output from the detection coil 3 is V1, the output of the correction circuit 11 is V3, and the filter
The output of 10 is V2. These outputs V1, V3, V2 increase / decrease according to the magnitude of the torque applied to the shaft 1. On the other hand, it is assumed that the output V01 appears in the filter 7 in response to the excitation voltage Vex.

When torque is applied to the torque detection shaft 1,
The magnetic permeability of the magnetic anisotropic portion 2 changes, and the impedance of the coil changes accordingly, so that the magnitude of the applied torque is obtained. By the way, it is possible to configure torque sensors of various capacities using the same electronic circuit,
In that case, the shaft diameter of the torque detection shaft 1 is changed. Then, at that time, if the magnitude of the exciting voltage Vex and the value of the resistor 17 are set so that the value of the exciting current flowing through the exciting coil 4 becomes substantially constant, the number of turns of this detecting coil is set in the detecting coil 3 as well. A detection voltage V1 proportional to the product of the exciting current is output, and the detection voltage V1 changes depending on the torque applied to the torque detection shaft 1. Therefore, by increasing the number of turns of the detection coil 3, a large detection voltage V1 can be obtained with the same excitation voltage, and this detection voltage V1 changes with high sensitivity due to the torque applied to the torque detection shaft 1. Therefore, it is possible to obtain a torque sensor with good performance that is not easily affected by noise and drift.

When the excitation voltage Vex changes for some reason, the detection output V1 of the torque detection circuit 12
V3, V2 and the output V01 of the excitation voltage detection circuit 8 also change,
The rate of change thereof is equal to the rate of change of the excitation voltage Vex. On the other hand, in the subtractor 13, the output V01 of the filter 7 of the excitation voltage detection circuit 8 is the output of the filter 10 of the torque detection circuit 12.
Is subtracted from the output V2 of. Therefore, how is the excitation voltage
The advantage is that the torque output does not change even if Vex changes.

The temperature characteristics of the outputs V1, V3, V2, and V01 are measured in advance, and the gain-temperature characteristic correction circuit 11 corrects so that V2 = V01 when the torque is not applied to the shaft 1 and the torque is zero. Determine the constant. In this way, even if the torque sensor changes in temperature, the subtractor 13 outputs an output whose output fluctuation is compensated for in response to this temperature change.
V4 appears. After all, the output V4 of the subtractor 13 is one that prevents the occurrence of an error due to the fluctuation of the exciting voltage Vex of the exciting power source 5 and the temperature change, but appears with high sensitivity. The output V4 of the subtractor 13 is amplified by the amplifier 14 and becomes the output V5.

In the above description, the gain temperature characteristic correction circuit 11 is provided on the output side of the detection coil 3 in the torque detection circuit 12. However, the gain temperature characteristic correction circuit 11 is replaced by the gain temperature characteristic correction circuit 11 as shown by the broken line in FIG. Also, the same function can be obtained by providing the exciting voltage detecting circuit 8 on the input side of the rectifying circuit 6.

The output V5 of the amplifier 14 is input to the gain switching circuit 16 and the polarity determination circuit 15. Generally magnetic anisotropy part 2
When there is only one position, the torque detection sensitivity is different depending on whether the clockwise torque is applied or the counterclockwise torque is applied, and the torque output V1 or V5 is different. Therefore, the direction of the applied torque is determined from the output V5 by the polarity determination circuit 15 by a known method, and the gain switching circuit is determined based on the direction of the applied torque.
16 switches the output V5 gain. As a result, the torques in either direction are detected with equal sensitivity, the torques in both directions are correctly detected, and finally output.

FIG. 2 shows a second embodiment of the present invention. Here, the gain temperature characteristic correction circuit 11 includes a torque detection circuit 12
It is provided between the rectifier circuit 9 and the filter 10 in the above, or between the rectifier circuit 6 and the filter 7 in the excitation voltage detection circuit 8. Other configurations are similar to those of the first embodiment of FIG.

FIG. 3 shows a third embodiment of the present invention. Here, the gain temperature characteristic correction circuit 11 includes a torque detection circuit 12
Is provided on the output side of the filter 10 or on the output side of the filter 7 in the excitation voltage detection circuit 8. Other configurations are similar to those of the first embodiment of FIG.

FIG. 4 shows a fourth embodiment of the present invention. Here, the gain temperature characteristic correction circuit 11 is provided between the resistor 17 and the AC excitation power supply 5. In this embodiment, the gain-temperature characteristic correction circuit 11 is composed of a temperature-sensitive resistor whose resistance value greatly changes due to temperature change. Other configurations are similar to those of the first embodiment of FIG.

[0021]

As described above, according to the present invention, the resistance for making the exciting current constant is provided in series between the exciting coil and the exciting voltage supply means, so that the torque detecting shaft has a single magnetic difference. Despite having only a directional section, the detection coil can output a detection voltage proportional to the product of the number of turns of this detection coil and the exciting current, and the number of turns of the detection coil must be increased. With this, a large detection voltage can be obtained with the same excitation voltage, and this detection voltage can be changed with high sensitivity based on the applied torque, and a high-performance torque sensor that is less susceptible to noise and drift can be obtained. The torque detection shaft can be made short because the torque detection shaft has only a single magnetic anisotropy portion, and the number of coils and bobbins around which the coil is wound is also dependent. It can be reduced by half as compared with, those can be simplified shape of the shield case for housing, as a result, it is possible to obtain a high precision torque sensor while being compact.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a magnetostrictive torque sensor according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a magnetostrictive torque sensor according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a magnetostrictive torque sensor according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a magnetostrictive torque sensor according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Torque detection axis 2 Magnetic anisotropy part 3 Detection coil 4 Excitation coil 5 AC excitation power supply 17 Resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taro Saito 2-35, Jimmucho, Yao-shi, Osaka Kubota Kuhoji Temple Co., Ltd. (72) Inventor, Mutsumi Sunabatake 2-35-35, Jimmucho, Yao-shi, Osaka Company Kubota Kouhoji Factory

Claims (4)

[Claims] 1. A single magnetic anisotropy portion formed on an outer peripheral surface of a torque detection shaft, an exciting coil and a detection coil provided around the magnetic anisotropy portion, and a torque from an output of the detection coil. It has a means for obtaining a detection signal, a means for supplying an exciting voltage to the exciting coil, and a resistor provided in series between the exciting coil and the exciting voltage supplying means for making the exciting current constant. Magnetostrictive torque sensor. 2. An apparatus comprising: a means for obtaining an exciting voltage signal from the exciting voltage value of the exciting voltage supply means; and a computing means for computing a difference between the torque detection signal and the exciting voltage signal to compensate for the fluctuation of the exciting voltage value. The magnetostrictive torque sensor according to claim 1, wherein 3. A temperature characteristic compensating means for compensating a measurement error due to a temperature change by adjusting a gain of at least one of a torque detection signal and an exciting voltage signal. Magnetostrictive torque sensor. 4. A means for detecting the direction of the torque applied to the torque detection shaft, and a means for switching the gain of the torque detection signal based on the direction of the applied torque. The magnetostrictive torque sensor according to any one of items.