JPH01123487A - Torque sensor - Google Patents

Abstract

PURPOSE:To prevent magnetic field generated by a rotary shaft from entering a film, and improve output characteristics, by obtaining induction magnetic anisotropy, by using temperature together with magnetic field at the time of forming a magnetostriction film, and demagnetizing the rotary shaft. CONSTITUTION:A rotary shaft 3 is kept at a temperature of 280-500 deg.C, and magnetic field is applied to the outer periphery of the rotary shaft 3, in the direction of 30-60 deg. with respect to the axial center direction of the rotary shaft 3. In this state, an alloy 2 composed of 35wt.% Ni and residual Fe is stuck by sputtering method or ion planting method. In the case where the rotary shaft 3 is made of magnetic material, the rotary shaft 3 is demagnetized. Thereby preventing the magnetic field generated by the rotary shaft from entering a film, and improving output properties.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a torque sensor to which a magnetostrictive film is fixed for non-contact measurement of the torque of a rotating shaft of a servo motor or the like.

(Conventional technology) A conventional example of a magnetostrictive torque sensor is shown in FIG.

This torque sensor has a magnetic material 7 having a magnetostrictive effect on the surface of a shaft 3 at an angle of 30 to 60 degrees in the axial direction of the shaft.
It has a structure in which the excitation coil 8 and the detection coil 9 are attached and arranged in the .degree. direction, surrounding the magnetic body 7 and maintaining a constant gap. In a magnetostrictive torque sensor with such a structure, when torsional torque is applied to the shaft, the magnetic permeability changes due to the magnetostrictive effect of the magnetic material, so the induced electromotive force generated in the detection coil also changes, and this change in electromotive force is detected. By this, the value of the above-mentioned torsion torque can be known.

The reason why the magnetic material is arranged at an angle to the axis of the shaft is to detect the direction of torsional torque.To improve detection sensitivity, the magnetic material is discontinuously shaped with slits in the direction of the arrow. It has anisotropy.

The conditions required for the method of forming the magnetic material used in such magnetostrictive torque sensors are adhesion to the shaft, uniformity of thickness, and temperature at 500°C when attaching the magnetic material to the shaft.
One example is that there is no need to raise the temperature to a higher level, but as mentioned above, adhesion cannot be obtained with a magnetic material attached. For this reason, a method using a vapor phase growth method such as a sputtering method has been invented as a method that satisfies the above conditions. this is.

For example, it is shown in Japanese Patent Application Laid-Open No. 60-42628.

(Problems to be Solved by the Invention) The above method describes the case where an amorphous magnetic alloy is used, and it is stated that a magnetic material such as Ni-Fe alloy (permalloy) can be used. Specific conditions for each are not described, and even if a permalloy film was formed under the conditions shown in the examples, anisotropy could not be obtained.

In addition, the one-rotation shaft is made of magnetic material (maraging steel).

In the case of (shaft steel), the shaft was magnetized by the magnetic field used to create induced magnetic anisotropy, making it impossible to use it as a torque sensor.

(Means for Solving the Problems) The present invention focuses on the temperature of the shaft when forming a magnetostrictive film by sputtering or ion plating, and maintains the shaft at 280 to 500°C, and Induced magnetic anisotropy is created by applying a magnetic field in the direction in which you want to create anisotropy.

When the rotating shaft is made of a magnetic material, demagnetization is performed after film formation.

(Function) Induced magnetic anisotropy is obtained by using both temperature and magnetic field during magnetostrictive film formation, and by demagnetizing the 9 rotating shafts, the magnetic field from the rotating shafts no longer enters the film, resulting in improved output characteristics. You will be able to do it.

(Example) An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows the configuration of a sputtering apparatus used in carrying out the present invention. The vacuum chamber 1 contains Ni-F containing 35 to 65% Ni.
e-alloy target 2. Shaft 3° Shaft rotation jig 4
．． Shaft heater 5. A magnet 6 for applying a magnetic field is arranged. Details of magnetic field application are shown in FIG.

After evacuating the inside of the vacuum chamber to below 1 x 10-% Torr, argon gas was introduced at 5 x 10-' Torr.

Apply 500V to the target and apply Ni around the shaft.
-A Fe film was formed. During sputtering, the shaft is rotated at 1 revolution/min, and the direction of the magnetic field is on the shaft's outer peripheral surface relative to the axis of the shaft.

The force was applied in three directions: 30°, 45°, and 60°. The shaft is made of Ti alloy, 545C, and maraging steel, and the temperature of the shaft during formation of the Ni-Fe film is 200 to 50.
The temperature was varied within a range of 0°C.

After forming the film around the shaft, the torque-output characteristics were measured. At this time, the maraging steel was demagnetized and then measured. As shown in the table, the measurement results showed that by applying a magnetic field in a 45° direction, an output was obtained only from the torque sensor using a magnetostrictive film formed at a temperature of 280 to 500°C.

The second tendency was the same when the direction of the magnetic field was 30° and 60°.

Next, an experiment similar to the sputtering method was conducted using the ion plating method, and similar results were obtained.

The reason why good results were obtained when the shaft temperature was 280 to 500"C is thought to be that anisotropy due to induced magnetic anisotropy was created under these conditions. Anisotropy does not occur below 270"C. It is considered that no output is produced.

(Effects of the Invention) As explained above, if the magnetostrictive film forming method according to the present invention is used, the anisotropy will increase, so the output will increase and the noise resistance will improve, and if the output is the same, the size will be reduced. can do. Furthermore, there is no need for a metal mask during film formation, which helps improve workability.

[Brief explanation of the drawing]

FIG. 1 shows a sputtering apparatus used to implement the present invention. FIG. 2 shows a method of applying a magnetic field to a shaft, and FIG. 3 shows a structure of a magnetostrictive torque sensor. 2 is a Ni-Fe alloy target and 3 is a shaft. 6 is a magnet.

Claims (1)

[Claims] In a non-contact torque sensor that utilizes the fact that a magnetic metal having magnetostriction is fixed to a rotating shaft and the magnetic properties of the magnetic metal change due to the torque applied to the rotating shaft, the temperature of the rotating shaft is set to 280 to 500. ℃, and a magnetic field is applied to the outer circumferential surface of the rotating shaft in a direction of 30 to 60 degrees with respect to the axial direction of the rotating shaft, an alloy consisting of 35 to 65% by weight of Ni and the balance of Fe is heated. A torque sensor characterized in that it is manufactured by a first step of fixing the rotating shaft by a sputtering method or an ion plating method, and a second step of demagnetizing the rotating shaft if it is made of a magnetic material.