JPH04282428A - Magnetostriction type torque sensor - Google Patents

Abstract

PURPOSE:To obtain a torque sensor reduced in the temp. drift of torque output characteristics and having stable output characteristics by setting the product of the number of patterns of the magnetostriction film of a rotary shaft, the width of each pattern and the thickness thereof to a specific range. CONSTITUTION:A magnetostriction type torque sensor has patterns constituted so that a plurality of striplike magnetostriction films 2 are provided to the surface of a rotary shaft 1 so as to be inclined in the axial direction thereof. When the number of the patterns is set to (n), the width of each pattern is set to W and the thickness thereof is set to (t), the product of (n), W and (t) is set to the range of 0.3-0.7mm<2>. A temp. drift is generated by the change of the inductance of a detection circuit due to the change of temp. under definite torque. When temp. rises, electric resistance increases and inductance reduces. Therefore, when the electric resistance and the inductance are set to such a range that the change quantities thereof are set off each other, impedance does not change by temp. That is, when the product of (n), W and (t) is within the range of 0.3-0.7mm<2>, stable torque output characteristics extremely reduced in a temp. drift are obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor that detects the torque of a rotational drive shaft or the like by detecting changes in the characteristics of a magnetostrictive film.

0002

[Prior Art] Conventionally, magnetostrictive torque sensors have been proposed as torque sensors for use in controlling rotational drive systems of automobiles, robots, manipulators, machine tools, etc., in order to make them compact and non-contact. . This method involves attaching a magnetostrictive film, which is a strip-shaped magnetic material with magnetostriction, in a spiral shape to the surface of the rotating shaft, and then changing the magnetic properties of the magnetostrictive film, which changes when torque is applied to the rotating shaft, to change the impedance. Torque is detected non-contact using a detection coil or magnetic head. This magnetostrictive film is formed on the surface of the rotating shaft by a method such as pasting amorphous foil with adhesive, sputtering, wet plating, or vacuum evaporation. magnetic anisotropy in the longitudinal direction (for example,
195323). However, compared to using adhesives, methods such as sputtering, wet plating, and vacuum evaporation have stronger adhesion to the rotating shaft and are therefore more reliable against repeated torque application.

0003

[Problems to be Solved by the Invention] However, even if a torque sensor is constructed by forming a magnetostrictive film using methods such as sputtering, wet plating, or vacuum evaporation, there is a large temperature drift in the torque output characteristics and the output is reduced. There was a problem with instability. When we investigated the cause of this in the rotating shaft, detection coil, and magnetostrictive film that make up the torque sensor, we found that the pattern shape of the magnetostrictive film has the greatest effect on temperature drift. An object of the present invention is to reduce temperature drift in the torque output characteristics of a torque sensor made of a magnetostrictive film and to provide a torque sensor with stable output characteristics.

0004

[Means for Solving the Problems] The present invention involves depositing a plurality of strip-shaped magnetostrictive films on the surface of a rotating shaft by sputtering, wet plating, or vacuum evaporation so as to be inclined with respect to the axial direction of the rotating shaft. In a magnetostrictive torque sensor equipped with a pattern, when the number of patterns of the magnetostrictive film is n, the width of the pattern is Wmm, and the thickness of the pattern is tmm, the product of the respective dimensions, n・W・t, is 0. .3~0.7mm2
It is designed to be within the range of .

[0005]

[Operation] Temperature drift occurs because the impedance of the detection circuit changes when the temperature changes under constant torque. What most influences the change in impedance Z are the electrical resistance R and inductance L of the magnetostrictive film. Impedance Z is expressed as Z=R+jωL, and as the temperature rises, electrical resistance increases and inductance decreases. Therefore, if the values of electrical resistance and inductance are selected within a range in which changes that occur in response to temperature changes cancel each other out, impedance does not change with temperature. The value of the electrical resistance and inductance is set by the pattern shape of the magnetostrictive film.The number of strip-shaped patterns is n, the width of the pattern is Wmm, and the thickness of the pattern is tmm, and the product of each is n・W・t. is 0.
When it is in the range of 3 to 0.7 mm2, temperature drift is extremely small and stable torque output characteristics can be obtained.

[0006]

[Embodiment] The present invention will be described with reference to an embodiment shown in the drawings. Ti-6Al is used as the material of the rotating shaft 1 that generates strain stress.
-4V, carbon steel S45C, and ceramics, a 45~70Ni-Fe alloy is sputtered on the outer peripheral surface of each shaft, and as shown in FIG. attached to the pattern. At that time, the number of patterns, which is the dimensional structure of the pattern, is n, and the width of the pattern is Wm.
m, the thickness of the pattern is tmm, the respective product, n
- A torque sensor was manufactured by setting W·t in the range of 0.1 to 0.9 mm 2 and providing the detection coil 3 on the magnetostrictive film 2 with an air gap in between. When we investigated the temperature fluctuation of the torque output characteristics with respect to temperature of the torque sensor of each specification when the temperature rose by 80 degrees Celsius from room temperature, we found that the product n・W・t is 0
．． Temperature drift is ±0.1 in the range of 3 to 0.7 mm2
% or less. In addition, vacuum evaporation and plating were used to attach the magnetostrictive film, and similar results were obtained. Note that the shaft material of the torque sensor does not need to be the one shown in this example as long as it is a material that can accurately transmit strain stress to the magnetostrictive film, regardless of its magnetic permeability or electrical resistance. is clear. Furthermore, it is naturally expected that similar results will be obtained even if the ion plating method or other methods are used as the magnetostrictive film forming method. Furthermore, although the above description has been about one set of multiple spiral patterns, when forming a torque sensor by arranging multiple sets of multiple spiral patterns, the product n, W, and t of each set of patterns should be set within the above range. You can set it so that

[0007]

[Effects of the Invention] As described above, according to the present invention, temperature drift can be suppressed by the simple method of adjusting the configuration of the dimensions of the pattern of the magnetostrictive film, and the technology can be easily introduced during mass production. This has the effect of providing a stable and versatile torque sensor with little temperature drift in torque output characteristics. In particular, the ability to reduce temperature drift without being affected by the material of the rotating shaft has the effect of expanding the field of application of the torque sensor of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of output characteristics of the torque sensor of the present invention.

[Explanation of symbols]

1 Rotation axis 2 Magnetostrictive film 3 Detection coil

Claims (1)

[Claims] 1. A magnetostrictive torque device comprising a pattern in which a plurality of band-shaped magnetostrictive films are attached to the surface of a rotating shaft at an angle with respect to the axial direction of the rotating shaft by sputtering, wet plating, or vacuum evaporation. In the sensor, when the number of patterns of the magnetostrictive film is n, the width of the pattern is Wmm, and the thickness of the pattern is tmm, the product of the respective dimensions is n・W
- A magnetostrictive torque sensor characterized in that t is in the range of 0.3 to 0.7 mm2.