JPH0462442A - Torque measuring instrument - Google Patents

Abstract

PURPOSE:To prevent the output characteristic from being distorted even in a high torque range by controlling the amplification factor of a torque detection signal according to variation in the inductance of a search coil due to variation in the magnetic permeability of the whole shaft based upon variation in torque. CONSTITUTION:An AGC 11 is controlled according to the variation in the inductance corresponding to the applied torque of a shaft 1 of a search coil 15, provided nearby a shaft 1 corresponding to both magnetic anisotropic parts 1 and 3, corresponding to the applied torque of the shaft 1 and the amplification factor of a torque detection signal is controlled. Consequently, the torque measuring instrument which has nonlinearity corrected and no distortion of the output characteristic even in the high torque range is obtained.

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 the change in magnetic permeability of each magnetic anisotropic part when torque is applied to this shaft is measured. Detection is performed by a pair of detection coils arranged near the magnetic anisotropic portion and excited by an excitation coil, and the magnitude of the torque acting on the shaft is converted into an electrical signal from the difference between both detection signals. For example, a torque measuring device based on the
No. 334862.

In this conventional torque measuring device, the sensitivity of both detection signals is corrected by controlling the excitation current so that the sum of both detection signals becomes constant. Note that the amplification factor of the torque detection signal based on the difference between both detection signals is set to be constant.

Problems to be Solved by the Invention However, in such conventional torque measuring devices,
If the torque transmission shaft is made of a highly nonlinear material, there is a problem in that the torque-output voltage characteristic is distorted as shown in FIG. 5 when high torque is applied. For this reason, especially when the shaft diameter cannot be increased using the same shaft material, only a torque sensor with a relatively narrow torque measurement range can be realized.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a torque measuring device that does not cause distortion in output characteristics even in a high torque range.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a system that is provided near a shaft corresponding to both magnetically anisotropic portions, and that transmits light across the entire shaft based on changes in the torque applied to the shaft. The present invention includes a search coil whose inductance changes according to a change in magnetic property, and means for controlling an amplification factor of a torque detection signal based on the change in inductance of the search coil.

When torque is applied to the W shaft, a difference occurs between the increase in magnetic permeability due to the tensile force and the decrease in magnetic permeability due to the compressive force in both magnetic anisotropic parts, and the magnetic permeability of the entire shaft changes. Therefore, the inductance of the search coil changes in accordance with this change in magnetic permeability. Therefore, by detecting this change in inductance and correcting the amplification factor of the torque detection signal based on the detection result, nonlinearity can be improved.

Embodiment In FIG. 1, reference numeral 1 denotes a shaft for transmitting torque, which is made of a material having soft magnetism and magnetostriction. On the outer periphery of the shaft 1, there is a magnetic anisotropic portion 2.3 which forms an angle of about ±45 degrees with the direction of the axis of the shaft 1 and faces the furnace in opposite directions.
It is formed by many grooves. Magnetic anisotropy part 2
, 3 are provided with detection coils 45 corresponding to each magnetic anisotropic portion 2.3 and an excitation coil 6 for exciting these detection coils 4.5. The excitation coil 6 is
It is connected to an AC power source 7.

The output lines from the detection coils 4 and 5 are connected to the input terminals of low-pass filters 8 and 9, respectively, and the output sides of these low-pass filters 8 and 9 are connected to the input terminal of a differential amplifier 10. The differential amplifier 10 outputs a voltage signal corresponding to the torque acting on the shaft 1 by taking the difference between the detection signals of the rain detection coils 4 and 5.

An auto gain controller 11 and a voltage/current converter 12 are connected in this order to the output side of the differential amplifier 10, and the configuration is such that an output signal appears at an output terminal 13 of the voltage/current converter 12. There is. 14 is a load resistance.

A search coil 15 is provided near the axis 1 corresponding to both magnetic anisotropy portions 2.3, and this search coil 15 is connected to a zero oscillator 16 that constitutes a part of the time constant circuit of the oscillator 16.
The output side of is connected to one input terminal of a differential amplifier 18 via a frequency/@pressure converter 17. A reference voltage generator 19 including a Zener diode is connected to the other input terminal of the differential amplifier 18 . An output line 20 from the differential amplifier 18 is connected to the auto-gain controller 11 and can supply a gain control signal to the auto-gain controller 11.

In such a configuration, the excitation coil 6 is connected to the AC power source 7
It receives constant current control, constant voltage control, etc.

Now, when torque T is applied to shaft 1, both magnetic anisotropic parts 2,
3, a difference occurs between the increase in magnetic permeability due to the tensile force and the decrease in magnetic permeability due to the compressive force, and the overall magnetic permeability of the shaft 1 changes. Therefore, for example, under control in which the excitation current 1ex of the excitation coil 6 is kept constant, the inductance of the search coil 15 changes, and the oscillation frequency of the oscillator 16 changes. Figure 2 shows the torque T applied to shaft 1 and search coil 1.
5 shows the relationship between the inductance and the inductance.

When the oscillation frequency of the oscillator 16 changes in response to the inductance L1 of the search coil 15 at a predetermined torque t (kgf-m), this frequency is changed to a voltage by the pressure converter 17 and input to the differential amplifier 18. be done. The differential amplifier 18 sends a gain control signal corresponding to the inductance L1 at that time to the auto gain controller 11, and corrects the amplification factor as shown in FIG.

As a result, as shown in FIG. 4, the distortion of the characteristics, especially in the high torque range, is corrected, and the non-linearity of the output characteristics is improved. Therefore, the torque sensor can be constructed even if a material with large non-linearity is used for the axis l.

On the other hand, if shaft 1 is made of the same material as before,
As shown in FIG. 4, a torque sensor having a wider torque measurement range than 5 can be constructed. Furthermore, if the correlation between the signal voltage of the gain control signal and the amplification factor in the auto gain controller 11 is individually determined for each torque sensor, a torque sensor with very good linearity can be constructed.

Effects of the Invention As described above, according to the present invention, changes in the inductance of the search coil corresponding to changes in the torque applied to the shaft are detected, and the amplification factor of the torque detection signal is controlled based on the detection result. Therefore, it is possible to obtain a torque measuring device in which distortion does not occur in the output characteristics even in a high torque range.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the circuit configuration of a torque measuring device according to an embodiment of the present invention, FIGS. 2 to 4 are diagrams showing the characteristics of the circuit in FIG. 1, and FIG. 5 is a diagram showing a conventional torque measuring device. FIG. 3 is a diagram showing output characteristics. 1... Axis, 2.3... Magnetic anisotropy part, 4, 5...
Detection coil, 6... Excitation coil, 7... AC power supply,
11... Auto gain controller, 15... Search coil, 16... Oscillator. Agent Yoshihiro MorimotoFig. [4k 1≦1 Fig. 4

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 Torque is detected by a pair of detection coils placed near the anisotropic part and excited by an excitation coil, and the magnitude of the torque acting on the shaft is converted into an electrical signal based on the difference between both detection signals. A measuring device, provided near an axis corresponding to both the magnetic anisotropy portions,
a search coil whose inductance changes due to a change in the magnetic permeability of the entire shaft based on a change in the torque applied to the shaft; and means for controlling the amplification factor of the torque detection signal based on the change in the inductance of the search coil; A torque measuring device characterized by having: