JPH07159257A - Torque sensor - Google Patents

Abstract

PURPOSE:To provide a torque sensor in which the reliability is enhanced with respect to torsional strength while suppressing the fluctuation in the sensitivity of output to torque. CONSTITUTION:A shaft 11 made of steel not subjected to heat treatment is applied with an amorphous metal body 12 having a plurality of slits 12a, 12b extending in the direction of + or -45 deg. with respect to the longitudinal direction of a shaft 11 and coils 14a, 14b are constituted thereon. This structure enhances the reliability in the torsional strength of a torque sensor and suppresses fluctuation in the sensitivity of output to torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor which can detect a torque transmitted to a shaft in a non-contact manner by applying a stress magnetic effect of a magnetic material.

[0002]

2. Description of the Related Art In recent years, a material whose magnetic permeability changes due to strain generated when an external force is applied, and this is often detected as a change in the self-inductance of a coil.

For example, as a conventional technique, Japanese Patent Laid-Open No. 62-2
There is a torque sensor disclosed in Japanese Patent Publication No. 98735. This torque sensor has a structure as shown in FIG.

In FIG. 6, reference numeral 1 denotes a shaft made of S35C,
Reference numeral 1a is a groove formed in the shaft 1, 2 is a magnetostrictive amorphous metal body adhered to the groove 1a, 3 is a bobbin arranged concentrically with the shaft 1, and a coil 4 is wound around the bobbin to provide torque. It constitutes a sensor.

The operation of the torque sensor configured as described above will be described below. When torque is transmitted to the shaft 1, strain is generated on the surface of the groove 1a, and the amorphous metal body 2 having magnetostriction is also strained. The magnetic permeability of this magnetostriction changes, and the excitation of the coil 4 changes the inductance. This change was detected by the coil 4 and measured by the detection circuit to detect the torque.

[0006]

However, in the above-mentioned conventional torque sensor, since the magnetic permeability of the shaft 1 varies greatly, the magnitude of the leakage magnetic flux flowing in the shaft 1 also varies, and the output of the torque sensor with respect to the torque is varied. There was a problem in that variations in sensitivity occurred.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide a torque sensor in which reliability of the torque sensor with respect to torsional strength is improved and variation in output sensitivity with respect to torque is small.

[0008]

In order to solve the above-mentioned conventional problems, the present invention provides a rotatably supported shaft and a plurality of slits in directions of 45 ° and −45 ° with respect to the longitudinal direction of the shaft. It is provided with a magnetically sensitive means having a formed magnetostriction, a coil for exciting and detecting the magnetically sensitive means facing each of the magnetically sensitive means, and a magnetic yoke provided outside the coil, and transmitted to the shaft. An electrical means for detecting a change in strain generated on the shaft surface due to torque as a change in the self-inductance of the coil through a change in the magnetic permeability of the magnetic sensing means, and detecting the magnitude of the torque from the self-inductance difference of the coil is provided. In the torque sensor of the present invention, non-heat treated steel is used as the shaft material, and the surface of the amorphous metal body having magnetostriction having a small surface roughness is arranged so as to face the coil.

[0009]

With this structure, non-heat treated steel can be used for the shaft, and reliability in torsional strength and variations in output sensitivity with respect to torque of the torque sensor are improved.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view of a main body of a torque sensor for power steering of a vehicle or the like according to an embodiment of the present invention.

In FIG. 1, reference numeral 11 denotes a shaft, which is a non-heat treated steel MICA-75 (manufactured by Sumitomo Metal Industries, Ltd.) corresponding to the strength when quenching and tempering is applied to carbon steel S35C for machine structure. ), And the shaft diameter is 18 mm. 11a is axis 1
1 is a groove formed at right angles to the longitudinal direction and has a width of 25.0
mm, the depth is 0.5 mm, and the shaft diameter of the groove 1a is 17 mm. Reference numeral 12 is an amorphous metal body having a magnetostriction, which is a magnetic sensing means, and is made by a super-quenching piece roll method with a composition of Fe-Ni-Cr-Si-B, and has a width of 24.9 mm and a length of 52 mm by etching. , + 45 ° and -45 ° with respect to the longitudinal direction of the shaft
Slits are formed in the direction of + 45 ° and the slit side is 12
a, the slit side of -45 ° is 12b, and its thickness is 20
˜30 μm, magnetostriction constant 11 × 10 ⁻⁶ , saturation magnetization 0.7
(T), a coefficient of thermal expansion of 11 × 10 ⁻⁶ (1 / ° C.), a rotating roller formed by heat treatment at a Curie temperature or higher and a crystal temperature or lower to have regular surface irregularities and small surface roughness. An adhesive having a bismaleimide triazine resin BT2164 (manufactured by Mitsubishi Gas Chemical Co., Inc.) having the same curl as the shaft diameter of 17 mm of the groove 11a so that the surface in contact with To glue. A bobbin 13 is arranged concentrically with the shaft 11 and has a coil 1 around it.
4a and 14b are wound. +45 of amorphous metal body 12
The coil on the slit 12a side in the ° direction is 14a, -45 °
The coil on the slit 12b side in the direction is 14b, and the coil 1
The ends of 4a and 14b are respectively coupled to the detection circuit.
Reference numeral 15 denotes a magnetic yoke, which constitutes two magnetic circuits including coils 14a and 14b and slits 12a and 12b provided on the amorphous metal body 12.

Here, the shaft 11 and the amorphous metal body 12 are bonded together by tightening when the amorphous metal body 12 having magnetostriction is bonded to the groove 11a through an adhesive as shown in FIG. As a jig, a Teflon-based heat-shrinkable tube (manufactured by Gunze Co., Ltd.) 1 in a loose-fitting state so as to cover the amorphous metal body 12.
After installing 6 in vacuum at 150 ℃ for 1 hour, then 1
Bond by treatment at 250 ° C. in 0 atmosphere for 3 hours. After the bonding, the heat shrinkable tube 16 is removed.

The characteristics of this torque sensor will be described below. Regarding the reliability of the torque sensor for safety,
294N, which is 30 times the maximum torque value in the torque detection range
It is necessary to guarantee the breaking strength of the shaft 11 up to the applied torque of m, and an experiment was conducted to measure the breaking torque of the shaft 11 by fixing one end of the shaft 11 and gradually applying torque from the other end. , The torque sensor according to the present invention is 363 N · m
While the breaking strength can be guaranteed up to 37 times the maximum torque value, the torque sensor based on the S35C shaft described in the conventional technique that is not subjected to quenching and tempering treatment is 274 N · m, which is 28 times the maximum torque value. It broke.

The reliability of the characteristics is 196 Nm, which is 20 times the maximum torque value in the torque detection range.
Although it is necessary to guarantee the reproducibility of the torque-output characteristics even after applying the torque of 1, the one end of the shaft 11 is fixed and the plastic deformation of the shaft 11 after applying the torque from the other end is measured to measure the elastic limit of the shaft. Of the torque sensor of the present invention, the torsional deformation of the shaft changes elastically up to 245 N · m, which is 25 times the maximum torque value. The adhered state of the crystalline metal body returns to the state before the torque is applied, and the reproducibility of the torque-output characteristic can be guaranteed, whereas the torque by the axis of S35C described in the conventional technique that is not subjected to quenching and tempering treatment. 1 for the sensor
The torsional deformation of the shaft changes elastically only up to 66 N · m and 17 times the maximum torque value, and when a torque 20 times the maximum torque value is applied, plastic deformation remains on the shaft and the magnetostriction bonded on the shaft is removed. The adhered state of the amorphous metal body does not return to the state before the torque is applied, and the reproducibility of the torque-output characteristic is not seen. As described above, the torque sensor according to the present invention can improve the cost and the reliability at the same time.

FIG. 3A shows a torque-output characteristic range (hatched portion) at room temperature of the torque sensor (n = 10) according to the present invention. The torque detection range is -9.8.
N · m to 9.8 N · m. The horizontal axis shows the torque, and the vertical axis shows the output of the torque sensor. FIG. 3B is a torque-output characteristic range (hatched portion) at room temperature of the torque sensor (n = 10) based on the shaft of S35C described in the conventional technique that is not subjected to quenching and tempering. Figure 3 (a),
As is clear from (b), since the non-heat treated steel is used for the shaft material of the shaft 11 of the torque sensor, the variation in the magnetic permeability is smaller than that of the conventional S35C that is not subjected to quenching and tempering treatment, and By reducing the variation of the leakage magnetic flux flowing, the variation of the sensitivity of the torque sensor with respect to the torque could be reduced to 1/3 or less.

FIG. 4 shows the torque-output characteristics of the torque sensor. The solid line indicates the torque sensor according to the present invention, and the dotted line indicates that the surface of the amorphous metal body 12 having magnetostriction having a large surface roughness faces the coil. The torque sensor is arranged. As shown in FIG. 5, the surface of the amorphous metal body 12 having magnetostriction that is in contact with the rotating roller and has a regular uneven surface shape and a small surface roughness is arranged so as to face the heat shrinkable tube 16. As a result, stress concentration is eliminated between the amorphous metal body 12 having magnetostriction and the heat-shrinkable tube 16, and one end of the heat-shrinkable tube 16 is first tightly fixed to the shaft due to the shrinkage variation of the heat-shrinkable tube 16 and its fixing. By mitigating the influence of the elongation in the longitudinal direction from one side to the other side, the misalignment of the amorphous metal body 12 having magnetostriction can be improved and the symmetry of the output with respect to the torque can be improved.

In the present embodiment, the magnetic sensing means has been described as an amorphous metal body, but the same effect can be obtained by using an amorphous metal body as permalloy.

[0018]

As is apparent from the above description,
Since the torque sensor of the present invention uses the shaft made of non-heat treated steel, the reliability of the torsional strength is improved, the cost is reduced by omitting the quenching and tempering process of the shaft, and the variation in the output sensitivity of the torque sensor to the torque is suppressed. Can be reduced.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a torque sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a step of adhering the shaft and the amorphous metal body, which are the main parts of the same.

FIG. 3A is a diagram showing a torque-output characteristic range of the torque sensor of the present invention. FIG. 3B is a diagram showing a torque-output characteristic range of a conventional torque sensor.

FIG. 4 is a comparative diagram showing torque-output characteristics of a torque sensor.

FIG. 5 is a diagram illustrating a bonding step in one embodiment of the present invention.

FIG. 6 is a partial sectional view of a torque sensor in a conventional example.

[Explanation of symbols]

 11 axis 12 amorphous metal body 14 coil

Claims (3)

[Claims] 1. A shaft made of non-heat treated steel rotatably supported, and 45 ° and −45 ° with respect to the longitudinal direction on the shaft.
A magnetism-sensing means having a plurality of slits formed in a direction forming a line, a coil for exciting and detecting the magnetism-sensing means facing each of the magnetism-sensing means, and a magnetic yoke provided outside the coil. A change in strain generated on the surface of the shaft due to the torque transmitted to the shaft is detected as a change in the self-inductance of the coil through a change in the magnetic permeability of the magnetic sensing means, and the magnitude of the torque is calculated from the difference in the self-inductance of the coil. A torque sensor having an electric means for detecting. 2. The torque sensor according to claim 1, wherein the magnetic sensing means is an amorphous metal body or permalloy. 3. The torque sensor according to claim 2, wherein a surface of the amorphous metal body having a small surface roughness is arranged so as to face the coil.