JPH04359127A - Preparation of magnetic film of magnetostrictive torque sensor - Google Patents

Abstract

PURPOSE:To improve the detection sensitivity by forming a magnetic film in the state where the surface stress in the compression (pulling) direction is applied for the longitudinal direction of a magnetic film pattern, in case of the magnetic film having a positive (negative) magnetostrictive constant. CONSTITUTION:Ni-Fe allay having a positive magnetostrictive constant is used as cylindrical target 2. A torsional torque in the compression direction is applied in the direction of arrow A through a catching device 8 on a rotary shaft 6 inserted into the target 2, and a surface stress B in the compression direction for the longitudinal direction of a pattern is applied on a magnetic film formation part. After a vacuum tank 1 in which the above-described devices are accommodated is exhausted, argon gas is introduced to a prescribed value, and a voltage is applied on an electrode 3, and sputtering is carried out from the target 2. On a magnetic film 7 thus obtained, the inductive magnetic anisotropy due to a magnet device 5 and the anisotropy due to the surface stress are generated, and a large torque output value is obtained as torque sensor. When the magnetic film has a negative magnetostrictive constant, the torsional torque is applied in the pulling direction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic film used in a magnetostrictive torque sensor that detects torque applied to a rotating shaft in a non-contact manner.

0002

[Prior Art] Non-contact control is used to control robots, manipulators, and machine tools that have rotational drive systems.
In addition, a small torque sensor is required. As such a torque sensor, there is one that forms a magnetic film having a magnetostrictive effect on the outer peripheral surface of the rotating shaft and utilizes the magnetostrictive effect due to the torque applied to the rotating shaft.The schematic structure of this sensor is as shown in FIG. A magnetic film 2 having a magnetostrictive effect with magnetic anisotropy (axis of easy magnetization) K in a direction of 30 to 60 degrees with respect to the axial direction of the rotating shaft in a predetermined position range on the surface of the rotating shaft 21.
2 is provided, and an excitation coil 23 and a detection coil 24 are provided on the outer periphery of this magnetic film with a constant gap maintained therebetween. When torsional torque T is applied to this rotating shaft 21, the magnetic permeability changes due to the magnetostrictive effect of the magnetic film 22, so the induced electromotive force generated in the detection coil 24 changes, and this change in electromotive force is detected. The value of torsional torque T is detected.

As described above, as a method of obtaining a magnetic film having anisotropy, good adhesion to the rotating shaft, and excellent thickness uniformity, high energy density In some cases, the rotating shaft surface is heated and rapidly cooled by beam irradiation, and in others, a cylindrical target with a magnetostrictive effect is installed in a vacuum chamber, as shown in Japanese Patent Application Laid-Open No. 1-279755. A permanent magnet with the inner periphery of the magnetic pole surface inclined at an appropriate angle of 30 to 60 degrees with respect to the axis is placed around the outer periphery of the cylindrical target, and an inclined magnetic field is applied to the rotating shaft inserted inside the cylindrical target. A method has been proposed in which sputtering is performed in a state in which the metal is added. In addition, JP-A-2-98639 discloses that after carburizing the surface layer of a rotating shaft whose surface layer is made of alloy steel containing nickel, austempering treatment, martempering treatment, or continuous cooling quenching treatment is performed as quenching treatment. There are also those that undergo sub-zero treatment or tempering treatment.

0004

[Problems to be Solved by the Invention] However, although these methods can achieve good adhesion between the magnetic film and the rotating shaft and uniform film thickness, they cannot accurately maintain the induced magnetic anisotropy. First, since the effect of anisotropy cannot be sufficiently obtained, output fluctuations due to noise are large, making it impossible to obtain a highly sensitive torque output signal.

[0005]

[Means for Solving the Problems] Therefore, in the present invention, a magnetic film is formed by a sputtering method, an ion plating method, a wet plating method, etc., and in the case of a magnetic film having a positive magnetostriction constant, the magnetic film pattern is The magnetic film is formed by applying a surface stress in a compressive direction to the longitudinal direction, and in the case of a magnetic film having a negative magnetostriction constant, applying a surface stress in a tensile direction to the longitudinal direction of the magnetic film pattern. or heat treatment of the magnetic film portion. Also,
A magnetic film is formed in the desired pattern on the rotating shaft in advance,
Heat treatment is performed by heating only the magnetic film portion on the surface of the rotating shaft to 350 to 600° C. by high-frequency induction heating without or with surface stress in the compressive or tensile direction applied to the magnetic film.

[0006]

[Operation] Therefore, when the surface stress applied to the rotating shaft is removed after the magnetic film is formed or heat treated, stress in the longitudinal direction of the pattern is induced in the magnetic film, causing strong stress anisotropy. In addition, high-frequency induction heating heats only the surface of the rotating shaft, preventing thermal expansion due to temperature rise of the rotating shaft, increasing the contraction difference between the rotating shaft and the magnetic film, and strengthening the magnetic anisotropy that occurs during cooling. , an effect of improving detection sensitivity when used as a torque sensor can be obtained.

[0007]

[Example] Fig. 1 shows an example in which a magnetic film is formed by sputtering by imparting magnetic anisotropy using an external magnetic field. A target, 3 is an electrode, 4 is a shield surrounding the outside of the cylindrical target, 5 is a cylindrical target 2, and 30 to 6
A magnet device arranged so as to surround the magnet 51 at an angle of 0 degrees.
, 52 and a yoke 53. 6 is a rotating shaft inserted into the cylindrical target 2, 7 is a magnetic film formed on the rotating shaft, 8 is a gripping device for holding the rotating shaft 6, and K is a direction of magnetic anisotropy.

In this embodiment, a Ni--Fe alloy containing 60% by weight of Ni and having an inner diameter of 60 mm and a positive magnetostriction constant is used as the cylindrical target 2, and a rotating target with a diameter of 40 mm inserted into this cylindrical target is used. A torsion torque of -1 kgfm to -3 kgfm (force in the compressive direction is indicated by a minus sign) is applied to the shaft 6 via the gripping device 8 in the direction of arrow A, and the magnetic film forming portion is compressed in the direction of the longitudinal direction of the pattern. gives a surface stress B of . After evacuating the vacuum chamber 1 containing these devices to 1 x 10-6 Torr, argon gas was introduced at 5 x 10-3 Torr, a voltage of -500 V was applied to the electrode 3, and sputtering from the target 2 was performed. . Note that the portion of the rotating shaft 6 where the magnetic film is not formed is masked in advance.

In the magnetic film 7 thus obtained, induced magnetic anisotropy due to the magnet device 5 and stress anisotropy due to surface stress occur, and the torque of a torque sensor equipped with this magnetic film is generated. As shown in Figure 2, the output characteristics are -1 kg compared to the case where no surface stress due to torsional torque is applied.
When applying a torsion torque of fm, it is 1.2 times, -3 kg.
When a torsional torque of fm was applied, an output value of approximately 1.4 times was obtained. Note that when the magnetic film had a negative magnetostriction constant, almost the same effect was obtained by applying the torsional torque in the tensile direction (indicated by a plus sign).

FIG. 3 shows an embodiment in which a magnetic film having anisotropy is formed by heat treatment. When the attached magnetic film 7 is provided and the magnetic film 7 has a positive magnetostriction constant, the surface of the rotating shaft 6 is caused by torsional torque in the compressive direction with respect to the longitudinal direction of the magnetic film pattern, as shown by arrow A. Heat treatment is performed using a heater 9 while applying stress and applying an external magnetic field in a direction of 30 to 60 degrees using a magnet device 5.

In such a device, the magnet device 5 is attached to the magnetic film 7.
While applying an external magnetic field in the direction of 45 degrees, and applying torsion torques A of -2 kgfm and -4 kgfm to the rotating shaft 6, the anisotropy was performed by changing the heat treatment temperature in steps of 50°C from 250°C to 650°C. The torque output characteristics of a torque sensor made of this magnetic film were compared with the output of a torque sensor made of a magnetic film treated in the same way without applying external stress, and the results are shown in Table 1. As shown, no effect of surface stress was observed at 250°C, but at 300 to 600°C, by applying surface stress, the effect of magnetic anisotropy was 1.2 to 1.2% compared to the case of only magnetic anisotropy without applying torsional torque. A 1.8 times larger output characteristic was obtained. Note that the magnetic film deteriorates at 650°C.

0012

[Table 1]

When the magnetic film 7 has a negative magnetostriction constant,
Similar output characteristics can be obtained by applying torsional torque in the tensile direction relative to the direction of the magnetic film pattern. In addition, if the rotating shaft is equipped with a chevron-shaped magnetic film with bidirectional magnetic patterns, surface stress in the compressive direction is applied to the magnetic film that has a positive magnetostrictive effect on each magnetic film pattern. It is sufficient to apply a surface stress in the tensile direction to a magnetic film having a negative magnetostrictive effect. For example, when positive magnetic films 7 are provided in different pattern directions as shown in FIG. The heat treatment is performed with different torsional torques applied to the rotating shaft 6. Both ends of the rotating shaft 6 are gripped with a gripping jig 10, and an arm 11, for example, is clamped to the portion where there is no magnetic film between the magnetic films. By adding a weight 12 to this arm 11, a torsion torque A in the compression direction can be applied to perform heat treatment. Note that the torsion torque may be selected to be an appropriate value that is less than or equal to the proof stress of the magnetic film, taking into account the material of the magnetic film, the diameter of the rotating shaft, the measuring torque capacity, and the like.

FIG. 5 shows an embodiment in which a magnetic film is formed on the rotating shaft in advance and high-frequency induction heating is used to impart anisotropy to the magnetic film. S45C with a diameter of 30 mm, Ti alloy,
A magnetic film 7 made of 50Ni-Fe, 87Fe-Al alloy is formed with a thickness of 7 μm using SUS304 in a predetermined pattern by sputtering, ion plating, or wet plating. A high frequency induction heating coil 13 is provided surrounding the. Therefore, the magnetic film 7 is heated by the high frequency induction heating coil 13.
is heated, and the magnetic field of the coil is applied in the longitudinal direction of the magnetic film pattern to generate induced magnetic anisotropy. However, since only the vicinity of the surface of the rotating shaft 6 is heated, even if the magnetic film 7 shrinks due to cooling after heat treatment, the rotating shaft 6 hardly shrinks, and the shrinkage stress of the rotating shaft generates shrinkage in the magnetic film. The magnetic anisotropy can be increased.

[0015] According to this embodiment, the frequency can be increased to 350 KHz.
Samples were prepared at a temperature of 300 to 600 degrees Celsius at every 100 degrees Celsius, and the output characteristics of a torque sensor using these samples were measured. Table 2 shows the output ratio with the measured value of the torque sensor using the sample heat-treated as shown in Table 2, and it is observed that the torque output characteristics are improved by 10 to 80%.

[0016]

[Table 2]

[0017] When performing high-frequency induction heating, the above-mentioned torsion torque can be applied to the rotating shaft to increase the anisotropy.

[0018]

Effects of the Invention As described above, the present invention forms a magnetic film having a magnetostrictive effect at a predetermined position on the outer peripheral surface of a rotating shaft, changes the permeability of the magnetic film in accordance with the torque applied to the rotating shaft, and In a magnetostrictive torque sensor that detects the torque based on a change in torque, if the magnetic film has a positive magnetostrictive constant, a surface stress is applied in a compressive direction to the longitudinal direction of the magnetic film pattern, and if the magnetic film has a negative magnetostrictive constant, The magnetostrictive film is formed by magnetizing the magnetic film pattern while applying surface stress in the tensile direction to the longitudinal direction of the magnetic film pattern, or by heat treatment. By induction heating, the heating of the rotating shaft is reduced and the magnetic film portion is heated, and the shrinkage difference between the magnetic film and the rotating shaft is increased when the magnetic film is cooled. Therefore, the magnetic film is easily produced, the magnetic anisotropy is increased, the reproducibility of the output during torque detection is improved, and a highly sensitive torque sensor with less influence of noise can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example in which the present invention is applied to a sputtering method.

FIG. 2 is a characteristic curve diagram showing the output of the torque sensor made of the magnetic film produced according to FIG. 1;

FIG. 3 is a schematic side sectional view showing an example in which heat treatment is performed according to the present invention.

FIG. 4 is a schematic side sectional view showing another embodiment in which heat treatment is performed according to the present invention.

FIG. 5 is a schematic side sectional view showing another method of the present invention.

[Explanation of symbols]

1 Vacuum chamber 2 Cylindrical target 3 Electrode 4. Shield 5 Magnet device 6 Rotation axis 7 Magnetic film 8 Grasping device 9 Heater 10 Grasping jig 11 Arm 12 Weight 13 High frequency induction heating coil

Claims (5)

[Claims] 1. A magnetic film having a magnetostrictive effect is formed on the outer peripheral surface of a rotating shaft at a predetermined position, and torque is detected by utilizing the change in magnetic permeability of the magnetic film in accordance with the torque applied to the rotating shaft. In the magnetostrictive torque sensor, when forming the magnetic film, if the magnetic film has a positive magnetostrictive constant, a surface stress is applied in a compressive direction to the longitudinal direction of the magnetic film pattern to form a negative magnetostrictive constant. In the case of a magnetic film, a method for producing a magnetic film for a magnetostrictive torque sensor, characterized in that the magnetic film is formed while applying surface stress in a tensile direction to the longitudinal direction of a magnetic film pattern. 2. A magnetic film having a magnetostrictive effect is formed on the outer peripheral surface of the rotating shaft at a predetermined position, and torque is detected by utilizing the fact that the magnetic permeability of the magnetic film changes in accordance with the torque applied to the rotating shaft. In the magnetostrictive torque sensor, when forming the magnetic film, a cylindrical target surrounding a rotating shaft in a vacuum chamber and a magnet device arranged at a predetermined angle on the outside of the cylindrical target are provided, and the cylindrical target is In the case of a magnetic film with a positive magnetostriction constant, a compressive surface stress is applied in the longitudinal direction of the magnetic film pattern, and in the case of a magnetic film with a negative magnetostriction constant, a surface stress is applied in the longitudinal direction of the magnetic film pattern. A method for producing a magnetic film for a magnetostrictive torque sensor, characterized in that the magnetic film is formed by sputtering while applying surface stress in the tensile direction. 3. A magnetic film having a magnetostrictive effect is formed on the outer peripheral surface of the rotating shaft at a predetermined position, and torque is detected by utilizing the change in magnetic permeability of the magnetic film in accordance with the torque applied to the rotating shaft. In a magnetostrictive torque sensor, if the magnetic film previously formed on the rotating shaft is a magnetic film with a positive magnetostrictive constant, a surface stress in a compressive direction is applied to the longitudinal direction of the magnetic film pattern to create a negative magnetostrictive constant. In the case of magnetic films with
1. A method for producing a magnetic film for a magnetostrictive torque sensor, the method comprising heat-treating the sensor. 4. A magnetic film having a magnetostrictive effect is formed on the outer peripheral surface of the rotating shaft at a predetermined position, and torque is detected by utilizing the change in magnetic permeability of the magnetic film in accordance with the torque applied to the rotating shaft. Preparation of a magnetic film for a magnetostrictive torque sensor, characterized in that a magnetic film is formed in a desired pattern on the rotating shaft, and the magnetic film is heat-treated at 300 to 600°C by high-frequency induction heating. Method. 5. The magnetic film of the magnetostrictive torque sensor according to claim 1, wherein the magnetic film is formed by a sputtering method, an ion plating method, or a wet plating method. Fabrication method.