JPH03103737A - Torque measuring instrument - Google Patents

Abstract

PURPOSE:To evade a state wherein adverse influence is imparted to sensor performance by connecting an exciting coil to a constant current source and preventing a magnetic field from varying even if the impedance of a sensor part varies with temperature. CONSTITUTION:When torque operates on a shaft 1, the difference V1-V2 between both detected voltages appears at the output side of a differential amplifier 13 as usual. The difference value V1-V2 is a voltage value, but it is V/I- converted 28 and outputted 29. At this time, the exciting coil 6 is connected to the constant current source 21, so even if the impedance of the sensor part varies owing to the temperature variation, an exciting current is constant, so a produced magnetic field is constant. Consequently, the state wherein adverse influence is imparted to the sensor performance owing to the variation in the magnetic field intensity of the shaft 1 is precluded. Here, if the characteristics of the instrument vary owing to the temperature variation and the detected voltages V1 and V2 are varied, the sum V1+V2 is compared by an adder 31 with the reference voltage of a reference voltage generation part 32. Then the sum value is fed back 33 to make the gain of an amplification part 23, etc., constant.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a torque measuring device.

Conventional technology Conventionally, as a torque measuring device, a pair of magnetic anisotropic parts are formed on the outer periphery of a torque transmission shaft, and changes in magnetic permeability of each magnetic anisotropic part are measured when torque is applied to this shaft. , detected by a pair of detection coils arranged near the magnetic anisotropic part,
For example, a system that converts the magnitude of torque acting on the shaft into an electrical signal based on the difference between the two detection @ numbers was proposed in a patent application filed in 1983.
No. 2-334862.

FIG. 2 shows a schematic structure of the torque measuring device proposed in Japanese Patent Application No. 62-334862. Here, 1 is a shaft for transmitting torque, and is made of a material having soft magnetism and magnetostriction. On the outer periphery of the shaft 1, magnetic anisotropic portions 2 and 3 are formed by a large number of grooves, etc., forming an angle of about 45 degrees with the direction of the axis of the shaft 1 and tilting in opposite directions. .

Each magnetic anisotropic portion 2.3 is provided around the magnetic anisotropic portion 2.3.
Detection coils 4.5 corresponding to these detection coils 4.5 and 4.5.
An excitation coil 6 for exciting the magnet 5 is provided.

The excitation coil 6 is connected to an AC lightning source 7, and this AC power source 7
An auto gain controller 8 is connected between the excitation coil 6 and the excitation coil 6.
is provided.

The output line 9.10 from each detection coil 4, 5 is connected to the input of a rectifier and filter device it, 12, respectively, and also to the input of a rectifier and filter device it, 1771. 1
The output side of 2 is connected to the input end of the differential amplifier 13. The differential amplifier 13 outputs a voltage corresponding to the torque acting on the shaft 1 to the output terminal 14 by taking the difference between the detection signals of both the detection coils 4 and 5. The output of the rectifier and filter device H, 12 is also connected to the input of an adder 15, the output of which is connected to the autogain controller 8 mentioned above.

like this! ? According to Section 4, changes in magnetic permeability in each magnetically anisotropic portion 2.3 based on the torque acting on the shaft 1 are detected by the detection coils 4, 5. At this time, since the magnetic anisotropic parts are inclined in opposite directions, when a tensile force is applied to one magnetic anisotropic part, a compressive force is applied to the other magnetic anisotropic part. Therefore, for example, when the detected lightning pressure (1) of one of the detection coils 4 increases as the torque increases, the detected lightning pressure V2 of the other detection coil 5 decreases accordingly. Therefore, as mentioned above, the difference amplifier 13 is used to calculate the difference V between the two detection voltages.
When t-V2 is determined, a signal corresponding to the change in torque appears at the output terminal 14.

Now, if there is a temperature change in the sensor section around axis 1, the characteristics of the device will change and there is a risk that accurate detection values will not be obtained. Therefore, in such a case, the average value of both detection voltages V1 and V2, which have slopes in opposite directions as described above, is controlled to be constant to prevent measurement errors caused by temperature changes. There is. That is, the adder 15 adds both detection voltages V1. V2 (7) Sum Vl +V2 (
The auto gain controller 8 is feedback-controlled to increase or decrease the excitation current so that this value becomes a constant value. By doing this, even if the characteristics of the device change due to temperature changes, there will be no change in the relationship between the torque acting on the shaft 1 and the detected voltages V1 and V2, and accurate measurements can be expected.

Problems to be Solved by the Invention However, in such conventional devices, the sum of detected voltages Vt
Feedback control is performed so that +V2 remains constant, resulting in constant voltage control, and the lightning current changes due to changes in the impedance of the sensor section due to temperature changes. And, by changing the excitation 1l current in this way,
The magnetic field strength of axis 1 may change, which may adversely affect sensor performance.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve these problems and to prevent the adverse effects on sensor performance caused by the above-mentioned fluctuations in excitation current.

Means for Solving the Problems In order to achieve the above object, the present invention provides an excitation coil near the magnetically oriented section, connects this excitation coil to a constant current source; , a means is provided for detecting the sum of the detection voltages of both detection coils and adjusting the gain of the amplification section on the output side of each detection coil so that this sum becomes a constant value.

According to this method, the excitation coil is controlled with a constant current, instead of being controlled by changing the excitation current as in the past, so the impedance of the sensor section changes due to temperature changes. However, the generated magnetic field is always constant and does not adversely affect the sensor characteristics. Moreover,
Then, the gain of the amplification section provided on the output side of each detection coil is adjusted to keep the sum of the detection voltages of both detection coils constant, so measurement errors due to temperature changes are eliminated. Occurrence is reliably prevented.

Embodiment In FIG. 1, the magnetic anisotropic parts 2 and 3 are of the shape li. Around the shaft 1, an excitation coil 6 and a pair of detection coils 4 are arranged.
, 5 are provided. The excitation coil 21 is connected to an alternating current constant current 8!21.

The output lines 9, 10 of both detection coils 4.5 are rectified and filtered 5111. 12 input terminals, respectively. A variable resistor 22 is connected between these output lines 9.10 to balance both sensor sections, which are comprised of detection coils 4, 5, magnetic anisotropy section 2.3, and the like.

Double rectifier and filter device 11. The denono side of 12 is
Amplifying sections 23 and 24 respectively as gain controllers
connected to. Each amplifier section 23. 24 is the resistance 25
and a transistor 26. Both amplification sections 23.2
The output side of 4 is connected to the difference IIJ amplifier 1 as in the case of FIG.
It is connected to the input terminal of 3. The output side of the differential amplifier 13 is connected to the V/I
Connected to converter 28. A current output appears at the output terminal 29 of the V/I converter 28. 30 is a resistance.

Also, both amplifying sections 23. The output side of 24 is connected to the input side of adder 31. At the inverting input terminal of the adder 31,
A reference voltage generator 32 including a Zener diode is connected. Furthermore, the output end of the sieve filter 31 is connected to the amplifier section 23.
24, that is, the base of each transistor 26, forming a feedback loop 33.

In such a configuration, when torque is applied to the shaft 1, a difference V1-V2 between the two detection voltages is generated on the output side of the differential amplifier 13.
The appearance of is the same as in the case of FIG. This difference value V1-V2 appears in the form of a voltage, which is converted into a current by the V/I converter 28, and the converted current output appears at the output terminal 29.

At this time, since the excitation coil 6 is connected to the constant current source 21, even if the impedance of the sensor section changes due to temperature changes, the excitation current is constant, so the generated magnetic field is always constant. Therefore, a situation in which the sensor performance is adversely affected by a change in the magnetic field strength of the shaft 1 is prevented from occurring.

Furthermore, if the characteristics of the device change due to temperature changes and the detection voltages V1 and V2 change accordingly,
The sum V1+V2 of these detected voltages is compared with the reference voltage from the reference voltage generator 32 in the adder 31. Then, the feedback loop 33 causes the amplifying section 23. 24 gains are adjusted to prevent fluctuations in measurement sensitivity, zero points, etc.

Effect of Brahma As described above, according to the present invention, since the excitation coil is connected to a constant current source, the generated magnetic field does not change even if the impedance of the sensor section changes due to temperature change, and therefore the magnetic field of the sensor shaft section This prevents the occurrence of a situation where the intensity changes and adversely affects sensor performance. Furthermore, since the sum of the detection voltages of both detection coils is controlled to a constant value, even if temperature changes occur in the sensor section, fluctuations in sensitivity and zero point during measurement are extremely minimized. be able to.

[Brief explanation of drawings]

FIG. 1 shows a circuit 4f of a torque measuring device according to an embodiment of the present invention.
FIG. 2, a diagram showing the four precepts, is a diagram showing a circuit configuration of a conventional torque measuring device. 1... Axis, 2.3... Magnetic anisotropy part, 4.5...
Detection coil, 6... Excitation coil, 21... Constant current source, 23. 24... Amplification section (gain controller),
31... Sifter, 33... Feedback loop.

Claims (1)

[Claims] 1. A pair of magnetically anisotropic parts are formed on the outer periphery of a torque transmission shaft, and the change in magnetic permeability of each magnetically anisotropic part when torque is applied to this shaft is calculated based on the magnetic A torque measuring device that detects with a pair of detection coils arranged near the anisotropic part and converts the magnitude of torque acting on the shaft into an electrical signal from the difference between the two detection signals, comprising: An excitation coil is provided near the magnetic anisotropy section, this excitation coil is connected to a constant current source, and the sum of detection voltages of both detection coils is detected on the output side of the detection coil, and this sum is constant. 1. A torque measuring device, comprising means for adjusting the gain of an amplification section on the output side of each detection coil so that the value of