JPH04155232A - Manufacture of magnetostrictive detector for torque sensor - Google Patents

Abstract

PURPOSE:To obtain a magnetostrictive body excellent in detection accuracy with a better sticking tendency of a magnetostrictive film by a method wherein a nickel layer is provided on a torque transmission shaft, a Permalloy layer is provided thereon and then, a heat treatment is performed to remove stress. CONSTITUTION:A nickel layer is formed on an outer circumferential surface of a torque transmission shaft 1 comprising a non-magnetic alloy by a nickel strike plating and a Permalloy layer having an electrostrictive characteristic is formed thereon by electric plating. A part excluding a slit-shaped groove 3 is covered with a masking agent and etched by a ferric chloride aqueous solution to form an electrostrictive film 2 and the slit-shaped groove 3. As treatment to remove a residual stress, a heat treatment is performed in a oxidation-free atmosphere at a temperature of 350-400 deg.C. In this manner, the nickel plated layer is provided between a shaft material and the Permalloy thereby achieving a higher sticking tendency while a better stress sensitivity and reversible change in magnetic permeability.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing a magnetostrictive detector for a torque sensor that can detect torque in a non-contact manner.

<Prior art> A magneto-type 1-lux sensor having a configuration in which a magnetostrictive detection film having magnetostrictive characteristics is provided on the surface of a torque transmission shaft and a solenoid coil is arranged around the outer circumference is disclosed in, for example, Japanese Patent Laid-Open No. 62-2064.
It has been known from the prior art, for example, from Publication No. 21.

However, in this type of magneto-type torque sensor, when rotational torque is applied to the shaft, the magnetostrictive detection film is also
Strain occurs in the ° direction, which causes magnetic anisotropy and changes in magnetic permeability.

By outputting this torque-dependent change in magnetic permeability as an electrical signal as a change in the inductance of the solenoid coil, the magnitude and direction of the torque can be detected.

In addition, as the magnetostrictive detection film used in this type of torque sensor, a magnetostrictive film made of amorphous alloy or permalloy, which is an iron-nickel alloy, is formed on the surface of the shaft by sputtering or plating. A device formed by this method is disclosed in Japanese Patent Laid-Open No. 60-42628.

On the other hand, as for the method by plating,
There are those in which the shaft surface is plated with nickel in the form of strips as disclosed in Publication No. 931, etc., and those disclosed in Japanese Patent Application Laid-Open No. 62-2064.
As disclosed in Publication No. 21, etc., a permalloy film is applied to the shaft surface by electroplating and then heat treated to remove residual stress, or a nickel strike plating is applied to the shaft as a base, and Co- Examples include those in which a magnetostrictive film such as B is electrolessly plated.

By the way, when used as a magnetostrictive detection film for a magnetostrictive torque sensor, if it is plated as it is, the film has residual stress, so the sensitivity to magnetostriction is inadequate, and the adhesion between the shaft and the magnetostriction detection film is also poor. It has the property of easily peeling off due to repeated stress.゛Therefore, in order to align and alloy the bonding surfaces and to alleviate the residual stress of the plating film,
2-206421 and the like propose a method of performing heat treatment as a post-treatment.

<Problem to be solved by the invention> As described above, the magnetostrictive detector, which is heat-treated to remove residual stress after plating the shaft with a magnetostrictive film, has better detection sensitivity, reproducibility, and durability than other types of detectors. It has excellent properties such as properties.

However, if the heat treatment temperature is increased with emphasis on adhesion, thermal residual stress remains in the magnetostrictive film due to the difference in thermal expansion between the shaft material and the plated magnetostrictive detection film, which deteriorates detection sensitivity; If the temperature is lowered, there is a problem in that the adhesion of the film deteriorates.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a magnetostrictive detector that has good adhesion to a torque transmission shaft and has excellent detection sensitivity.

Means for Solving the Problems> In order to achieve the object of "two legs," the present invention provides a magnetostrictive material in which a permalloy layer having magnetostrictive properties is provided on the outer peripheral surface of a cylindrical or cylindrical torque transmission shaft. The detection object is characterized in that a nickel layer is provided on the outer surface of the torque transmission shaft made of a non-magnetic alloy, a permalloy layer is provided on the potassium nickel layer, and then residual stress removal treatment is performed.

Further, the nonmagnetic alloy is austenitic stainless steel, the nickel layer is formed by nickel strike plating, and the permalloy layer is formed by electroplating.

Furthermore, the residual stress removal treatment is carried out in a non-oxidizing atmosphere for 3
It is characterized by heat treatment within a temperature range of 50 to 400°C.

The detection sensitivity and maximum permissible torque of the torque transmission shaft are adjusted by setting its diameter or wall thickness depending on the magnitude of the torque and the mounting situation.

Further, this torque transmission shaft is selected from a shaft that is non-magnetic and has a high elastic limit under stress strain, such as austenitic stainless steel.

The magnetostrictive detection film made of a magnetic alloy is determined from the viewpoints of the required magnetostriction coefficient, magnetic permeability 1 workability, economic efficiency, film wear controllability, etc., and electroplating of iron-nickel alloy (permalloy) is preferably used. .

When permalloy plating is applied directly to the shaft material, large tensile stress remains in the film, and changes in magnetic permeability due to stress (torque) are irreversible. However, if a nickel plating layer is provided between the shaft material and the permalloy plating film, , the tensile stress of the permalloy plating film decreases, and changes in magnetic permeability due to stress become reversible.

Heat treatment reduces residual stress in the plating film and
It strengthens the adhesion between the shaft material and the plating film, thereby improving the reversibility of changes in magnetic permeability due to stress in the magnetostrictive detection film.

However, if the heat treatment temperature is lower than 350°C, the bond between the shaft material and the plating film will be insufficient, while if it is higher than 400°C, there will be a magnetic difference in the direction perpendicular to the plating film due to the difference in thermal expansion coefficient between the shaft material and the plating film. Orientation occurs, and changes in magnetic permeability due to stress (torque) are not observed, preferably at 350°C to 400°C.
is selected.

<Function> As in this invention, torque transmission is possible only when a nickel layer is first provided on the shaft material, a permalloy layer is formed on this nickel layer, and then heat treatment is performed in the optimum temperature range. In addition to aiming for the direction of adhesion between the shaft material, which is the shaft, and the magnetic 1 detection film, good stress (torque) sensitivity as a magnetostriction detection film can be obtained, and sufficient reversibility of magnetic permeability changes can be obtained. It will be done.

<Example> Examples will be explained below.

Outer diameter 251. After smoothing the outer diameter surface of a stainless steel pipe (material JIS standard 5US304) with an inner diameter of 21 mm and a length of 100 mm, the shaft material 1 that will become the torque transmission shaft is degreased and cleaned with alkali. Got ready.

Sample 1 is coated with 30% Fe by electroplating on the outer diameter of the shaft material 1.
After applying -Ni alloy to a thickness of 10 μm, parts other than the slit-like grooves were covered with a masking agent (wax) and etched with a ferric chloride aqueous solution to selectively remove the plating film.

The part left as a plating film on the shaft member 1 is considered to be the magnetostrictive film 2, but the part from which the plating film was removed has a width of 1w111!
The right part of the shaft member 1 in the longitudinal direction is at an angle of + with respect to the shaft member 1.
45℃ and the left part is a slit-shaped groove 3 tilted at an angle of -45℃
10 each are formed around the circumference.

The plating method was carried out in a nickel sulfamate solution in the same manner as described in JP-A-62-206421.

Next, for sample 2, after applying nickel plating to a thickness of 1 μm on the shaft material 1 marked J- in advance, an iron-nickel alloy plating film was applied in the same manner as in sample 1, and the film was selectively removed, and the same process as in sample 1 was performed. A magnetostrictive film 2 and slit-like grooves 3 were formed.

The nickel plating described in Item 1 is strike plating using a hydrochloric acid solution of nickel chloride.

Next, sample 1 and sample 2 were heated at a temperature of 300°C.

Heat treatment was performed at 350°C, 400°C, and 450°C for 1 hour. This heat treatment was performed in hydrogen gas.

Each of the magnetostrictive detectors produced in this way was fixed to a cantilever jig, and the coils were arranged as shown in Fig. 1.
An electrical circuit as shown in FIG. 2, that is, a transistor 7 is connected to the transistor 7 after the input terminal 6, and the coil 4.5 is connected to the switch 8 which is connected to the output terminal 9. Using a torque detection circuit, torsional torque was applied to one end of each sample 1°2, and the relationship between I·Lux and output voltage was measured.

The results are shown in FIGS. 3 and 4.

FIG. 3 compares the heat treatments of Samples 1 and 2.

In addition, graph (1) in the same figure shows the characteristics of the shaft material l whose surface is directly plated with nickel-iron alloy.
Graph (2) shows the case where the surface of the shaft material 1 is pre-plated with nickel and then plated with nickel-iron alloy.
) shows the characteristics of the material in graph (1) heat-treated at 400° C. for 1 hour, and graph (4) shows the properties of the material in graph (2) heat-treated at 400° C. for 1 hour.

From the graphs in the same figure, it can be seen that graph (4) in which nickel strike plating and heat treatment were performed is superior in linearity of torque detection.

On the other hand, FIG. 4 shows that sample 2 was heat-treated for 300 to 450
These are the measurement results at various temperatures of °C.

As is clear from this measurement result, the heat treatment temperature was 300°C.
Graph (5) The l-luke conversion characteristic is nonlinear, and it can be imagined that irreversibility remains in the change in magnetic permeability due to torque.

Graph (6) with heat treatment temperatures of 350°C and 400°C
(7) has high torque detection sensitivity and good linearity.

Graph (8) in which the heat treatment temperature is 450° C. has good linearity, but the detection sensitivity is extremely low. This is presumably because the magnetic permeability of the magnetostrictive film 2 is reduced due to perpendicular magnetic anisotropy.

As described above, the nickel-iron alloy plating film used as a magnetostrictive detector for a torque sensor can obtain good characteristics by heat-treating it at 350 to 400°C.

Next, the durability of the magnetostrictive detection film for a torque sensor was investigated.

Sample 1. The shaft member 1 in No. 2 was fixed to a cantilever jig, and a twist of ±110 N− was repeatedly applied to the other end of the shaft member 1 at a frequency of 10 Hz.

As a result, cracks occurred in the plating film of Sample 1 after 104 repetitions, whereas cracks occurred in Sample 2 according to the present invention after 104 repetitions.
When heat treated at 0° C. for 1 hour, no cracking or peeling of the plating film was observed even after 106 repeated torques, and the so-called adhesion between the magnetic film 2 and the shaft member 1 was good.

<Effects of the Invention> As explained above, according to the manufacturing method of the present invention, a nickel layer is first formed on the shaft 1 of a non-magnetic alloy as a base, and then a permalloid layer is formed on this nickel layer. Since the magnetostrictive sensing film is formed by forming a layer and then subjected to heat treatment to remove residual stress, it has excellent adhesion between the torque transmission shaft and the magnetostrictive sensing film, and has good stress sensitivity and resistance to changes in magnetic permeability. It has good reversibility, excellent output linearity and reproducibility, and has good adhesion to the torque transmission shaft.
Moreover, a method for manufacturing a magnetostrictive detector with excellent detection sensitivity can be provided.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a torque sensor, FIG. 2 is a torque detection circuit diagram, and FIGS. 3 and 4 are graphs showing torque output characteristics. 1... Shaft member 2... Magnetostrictive film 3... Slit-like groove 4.5... Coil patent applicant Hitachi Powder Metallurgy Co., Ltd.

Claims (4)

[Claims] 1. In a magnetostrictive sensor in which a permalloy layer having magnetostrictive properties is provided on the outer circumferential surface of a cylindrical or cylindrical torque transmitting shaft, a nickel layer is provided on the outer circumferential surface of the torque transmitting shaft made of a non-magnetic alloy, and the nickel A method for manufacturing a magnetostrictive detector for a torque sensor, comprising providing a permalloy layer on the layer and then performing residual stress removal treatment. 2. 2. The method of manufacturing a magnetostrictive detector for a torque sensor according to claim 1, wherein the non-magnetic alloy is austenitic stainless steel. 3. 3. The method of manufacturing a magnetostrictive detector for a torque sensor according to claim 1, wherein the nickel layer is formed by nickel strike plating, and the permalloy layer is formed by electroplating. 4. Residual stress removal treatment is carried out at 35% in a non-oxidizing atmosphere.
4. The method of manufacturing a magnetostrictive detector for a torque sensor according to claim 1, wherein the heat treatment is performed within a temperature range of 0 to 400[deg.] C.