JPH0242417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a torque sensor that detects torque without contact.

[Technical background of the invention and its problems]

In recent years, it has been required to accurately detect the torque of a rotating body. To meet this demand, a non-contact method in which the detection body does not come into contact with the rotating body is suitable.

Traditionally, non-contact type torque sensors include indirect methods that detect torque indirectly by detecting the torsion angle of the shaft using light or magnetism, or those that use a magnetic material on the rotating body and detect magnetism due to the rotation of the magnetic material. Attempts have been made to directly detect torque using strain phenomena. However, it is not suitable for practical use.

Compared to the indirect method, the direct method described above is more convenient and can detect torque during standstill, forward rotation, and reverse rotation, and is preferable in terms of application. It was difficult to detect.

By the way, recently a torque sensor has been proposed that uses the magnetostrictive properties of an amorphous magnetic alloy to directly detect torque without contact (IEE of Japan Magnetics Study Group Materials, MAG-81-71).

This is done by wrapping an amorphous magnetic alloy ribbon with large magnetostrictive properties around a rotating shaft and fixing it so that the shaft strain stress due to torque is introduced into the amorphous magnetic alloy ribbon. Torque is detected by externally detecting changes in the magnetic properties of the ribbon without contact.

That is, as shown in FIG. 1, the torque sensor has an annular magnetic core 2 made of an amorphous magnetic alloy ribbon fitted around a rotating shaft 1. Now, when torque 3 is applied to the rotating shaft 1, strain stress is applied to the rotating shaft 1 in a direction of ±45° with respect to its circumferential direction, and along with this, the annular magnetic core 2 that is in complete contact with the rotating shaft 1 is As shown in Figure 1, strain stress σ is applied in the circumferential direction.
4 occurs.

In this torque sensor, as shown in FIG.
Uniaxial magnetic anisotropy Ku(5) is introduced in advance in the direction of , to facilitate magnetization in this direction. As mentioned above, when torque 3 is applied, the induced magnetic anisotropy induced by the strain stress σ generated in the annular magnetic core 2 is added accordingly, and the uniaxial magnetic anisotropy becomes Ku
(5) changes to Ku′(6). Therefore, by electrically detecting the amount of change in this uniaxial magnetic anisotropy, the torque 3 applied to the rotating shaft 1 can be detected. Specifically, for example, an excitation winding 7 and a detection winding 8 are arranged around the annular magnetic core 2, and the excitation winding 7
A power supply circuit (not shown) is connected to the detection winding 8, and a detection circuit (not shown) is connected to the detection winding 8. Then, the annular magnetic core 2 is excited by the excitation winding 7. Rotating axis 1
When the uniaxial magnetic anisotropy of the annular magnetic core 2 changes due to the application of torque 3 to , the magnetic permeability of the annular magnetic core 2 in the magnetic flux penetration direction changes. This change in magnetic permeability is detected as a voltage change by the detection winding 7 and the detection circuit. Therefore, the torque can be detected from the correspondence between the magnitude of the torque 3 and the magnitude of the voltage change.

Note that if the uniaxial magnetic anisotropy Ku is not introduced into the annular magnetic core 2 in advance, the torque detection characteristic (voltage change) exhibits hysteresis, making it impossible to use it as a sensor.

By the way, conventionally, the above-mentioned magnetic metal ribbon was fixed to the rotating shaft using a synthetic resin adhesive.
However, when magnetic metal ribbons are fixed with adhesive, the adhesive loosens as the temperature rises, which changes the stress applied to the magnetic metal ribbons, causing fluctuations in the torque detection output and reducing the accuracy of torque detection. There was a problem.

[Purpose of the invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a torque sensor that can perform highly accurate torque detection without fluctuation in output even with temperature changes of about -30 to 150 degrees Celsius. The purpose is to

[Summary of the invention]

The torque sensor of the present invention is characterized in that a magnetic metal ribbon is encapsulated and fixed to the rotating shaft using a shape memory alloy fixing material due to its shape memory action.

Shape memory alloys include Au-Cd, Cu-Al-Ni,
Cu−Al−Zn, Cu−Sn, In−Tl, Ni−Al, Ni−
Many alloys such as Ti are known, and any of them can be used in the torque sensor of the present invention.

Fixing of the magnetic metal ribbon to the rotating shaft using the above-mentioned shape memory alloy fixing material will be explained with reference to FIGS. 3a to 3d.

First, a magnetic metal ribbon 1 is attached to a rotating shaft 11 with a diameter D ₁ .
2 (as shown in Figure 3a). On the other hand, a cylindrical body 1 having a diameter D ₂ smaller than the diameter D 1 of the rotating shaft 11 is formed by molding a shape memory alloy at a temperature _higher than the transformation point.
3 (as shown in Figure b). Next, the diameter of the cylindrical body 13 is expanded at a temperature below the transformation point, and the cylindrical body 1 has _a diameter D ₃ larger than the diameter D 1 of the rotating shaft 11.
3' is prepared (shown in c of the same figure). Next, this cylindrical body 13' is attached to the magnetic metal ribbon 12 of the rotating shaft 11.
When the cylindrical body 13' is inserted into the position where the cylindrical body 13' is wound and the entire body is exposed to a temperature above the transformation point, the cylindrical body 13' has the initial diameter _D2 due to the shape memory effect.
Since the magnetic metal ribbon 12 tends to shrink, the magnetic metal ribbon 12 is wrapped in the cylindrical body 13 and firmly fixed to the rotating shaft 11 (as shown in d of the same figure). In addition, the magnetic metal ribbon 12
The uniaxial magnetic anisotropy may be imparted to the magnetic metal ribbon 12 before or after the magnetic metal ribbon 12 is wound around the rotating shaft 11.

Since the diameter of the cylindrical body made of shape memory alloy will not become larger than _D1 at any temperature (excluding changes in shape due to thermal expansion), it will be possible to guarantee a wide range of temperatures. Torque detection accuracy is significantly improved.

The shape of the shape memory alloy fixing material used in the present invention may be any shape, such as a ring shape or a spiral shape, in addition to the above-mentioned cylindrical shape. The thickness of these shape memory alloy fixing materials must be designed according to their mechanical strength, but in the non-contact type torque sensor of the present invention, in order to maximize the detection output, magnetic metal thin strips and Since the distance between the magnetic metal thin strip and the detection coil disposed close to it must be as small as possible, it is desirable that the thickness of the shape memory alloy fixing material interposed between the two is as thin as possible.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on examples.

First, a width of 10 mm and a thickness of approximately 20 μm were obtained using the single roll method.
A thin ribbon of (Fe _0.985 Nb _0.015 ) ₈₁ Si ₆ B ₁₃ amorphous magnetic alloy was fabricated. Next, attach this thin strip to a diameter of 30 mm.
It was wrapped around the rotating shaft once and the ends were fixed with adhesive.

In addition, a thin plate of shape memory alloy NiTi (transformation point 60°C) with a thickness of 0.1 mm was rolled in advance at a temperature of 70°C, and the diameter
A 29 mm cylindrical body was manufactured. Subsequently, the diameter of this cylindrical body was expanded to a diameter of 30 mm or more of the rotating shaft at room temperature.

Next, with the rotating shaft twisted, the cylindrical body of the shape memory alloy was fitted onto the rotating shaft at the position where the amorphous magnetic alloy ribbon was wound, and the entire body was then heated to a temperature of 70°C. placed. As a result, the cylindrical body of the shape memory alloy NiTi tries to shrink to the initial cylindrical body with a diameter of 29 mm due to the shape memory effect, so the amorphous magnetic alloy ribbon is encapsulated in the cylindrical body of the shape memory alloy and rotates. firmly fixed to the shaft. Subsequently, the rotating shaft was untwisted to impart uniaxial magnetic anisotropy to the amorphous magnetic alloy ribbon.

Using the torque sensor obtained in the above manner, in which the amorphous magnetic alloy ribbon is encapsulated and fixed in the shape memory alloy cylinder, based on the principle shown in FIGS. 1 and 2 described above, The dynamic torque of the rotating shaft was detected in the temperature range of -30 to 150℃. As a result, the dynamic torque detection accuracy in the above temperature range was about ±10% with a conventional torque sensor in which an amorphous magnetic alloy ribbon was fixed to the rotating shaft using only adhesive, but when using the shape memory alloy described above, According to the torque sensor used, the dynamic torque detection accuracy in the above temperature range was within ±1%.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to detect torque with high accuracy over a wide temperature range, and it is possible to provide a torque sensor that is extremely practical in industry.

[Brief explanation of the drawing]

Figures 1 and 2 are principle diagrams of a non-contact torque sensor, and Figures 3a to 3d are explanatory diagrams showing a method of fixing a magnetic metal ribbon to a rotating shaft using a shape memory alloy fixing material in the present invention. be. 11...Rotating shaft, 12...Magnetic metal ribbon, 1
3, 13'... Shape memory alloy cylindrical body.

Claims (1)

[Claims] 1. Non-contact detection of torque is performed by fixing a magnetic metal ribbon with a large magnetostriction constant to a rotating shaft and using the fact that the magnetic properties of the magnetic metal ribbon change due to the torque applied to the rotating shaft. A torque sensor, characterized in that the magnetic metal ribbon is encapsulated and fixed to the rotating shaft using a shape memory alloy fixing material due to its shape memory action.