JPH0634458A - Magnetostriction detector for magnetostriction type torque sensor and its manufacture - Google Patents

Abstract

(57) [Abstract] [Purpose] Magnetostrictive detector with good adhesion between the torque transmission shaft and the magnetic alloy coating, stable output characteristics against repeated stress, and excellent detection sensitivity and reproducibility, and its manufacturing method. The purpose is to provide. [Structure] On the outer peripheral surface of the torque transmission shaft, a plurality of concave lines and convex lines inclined at an angle of 45 ° with respect to the longitudinal direction of the shaft are provided at regular intervals, and a magnetic alloy is formed on the concave line and convex line surfaces. A layered magnetostrictive detector for a torque sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive detector used in a magnetostrictive torque sensor capable of non-contact torque detection and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a magnetostrictive torque sensor in which a magnetostrictive detection layer having a magnetostrictive effect is provided on the surface of a torque transmission shaft and a solenoid coil is arranged around the magnetostrictive detection layer, Japanese Patent Laid-Open No. 62-20 is known.
It is disclosed in Japanese Patent No. 6421.

In this torque sensor, when a rotational torque is applied to a shaft provided with a magnetostriction detecting layer, a principal stress is also applied to the magnetostriction detecting layer in a direction of 45 ° with respect to the rotational direction, and distortion is generated.

The change in magnetic permeability becomes magnetic anisotropy, and the change in magnetic permeability depending on the torque is output as an electric signal as the change in the inductance of the solenoid coil. And detecting the direction.

Therefore, the reliability and durability of the sensor are determined by the formation state of the magnetostriction detecting layer.

As a method for forming this magnetostriction detecting layer, there is a method in which a foil of a magnetostrictive material such as an amorphous alloy is spirally adhered to the surface of the shaft (Japanese Patent Laid-Open No. 59-166827). In this case, an adhesive or a brazing material is used to bond the foil, but there is room for improvement in terms of durability under repeated stress.

Further, a magnetostrictive alloy is sputtered on the surface of the shaft member (JP-A-60-42628), wet plating method (JP-A-62-206421), or plasma spraying method (JP-A-63-62). 297545), the magnetostrictive alloy layer is selectively removed by a cutting process or a chemical etching method so as to have a band shape with an angle of 45 °, and shape anisotropy is imparted. In these cases,
Usually, heat treatment is performed to homogenize the metallographic structure of the alloy layer and enhance the adhesiveness between the alloy layer and the shaft member.

However, since a spiral groove is formed after forming the coating, it takes time and effort to form a plurality of grooves with high dimensional accuracy without damaging the coating.
High cost.

Although it is difficult to simply compare the properties of the magnetic alloy coatings formed by the above-mentioned methods, one of the characteristics of the coating formation method is that the sputtering method provides good adhesion, but the composition of the formed film. Control is difficult and the processing time is long. In addition, although the wet plating method has good adhesion, it is difficult to form a thick film because the composition of the film tends to vary widely. The plasma spraying method has good film thickness controllability and productivity, has a small variation in film composition, and has good durability, but it is difficult to form a thin film thickness.

[0010]

As described above, the conventionally proposed magnetostrictive detector has advantages and disadvantages in stability of coating composition, stability of coating thickness, difficulty in managing manufacturing conditions, productivity, and the like. Improvements were desired in each case.

The present invention has been made in view of the above circumstances, and the adhesion between the torque transmission shaft and the magnetic alloy coating is good, and stable output characteristics are exhibited against repeated stress. Moreover, it is an object of the present invention to provide a magnetostrictive detector having excellent detection sensitivity and reproducibility with high productivity.

[0012]

In order to achieve the above object, a magnetostrictive detector for a torque sensor according to the present invention has a plurality of outer peripheral surfaces of a torque transmission shaft inclined at an angle of 45 ° with respect to the longitudinal direction of the shaft. Grooves and ridges are formed at regular intervals,
The magnetic alloy layer is formed on the concave surface and the convex surface.

Further, in the method for manufacturing a magnetostrictive detector for a torque sensor according to the present invention, a plurality of concave and convex lines inclined at an angle of 45 ° with respect to the longitudinal direction of the shaft are rolled on the outer peripheral surface of the torque transmission shaft. The magnetic alloy layer is formed at regular intervals by means of, and a magnetic alloy layer is formed on the concave and convex portions by thermal spraying, and heat treatment is performed in a non-oxidizing atmosphere.

The axis of the magnetostrictive body is rod-shaped or cylindrical, and either non-magnetic material such as stainless steel or non-ferrous alloy or ferromagnetic material such as alloy steel can be used. In the case of ferromagnetic material, magnetic alloy coating is used. A non-magnetic material is preferable because it needs to be formed thick. In this case, the coefficient of thermal expansion of the material is preferably close to that of the magnetic alloy.

The magnetic alloy is known nickel, 15 to 60.
% Fe-Ni alloy, 30-60% Co-Fe alloy,
An 8 to 18% Al-Fe alloy or the like can be applied. Considering that the magnetostriction coefficient is large and the cost is low, 50% Fe-
Ni-based alloys are suitable.

The concave line and the convex line form an angle of 45 with respect to the axis.
In the case of detecting forward / reverse rotation, one is formed at + 45 ° and the other is formed at −45 ° in the longitudinal direction of the shaft as in the conventional case.

If the thickness of the magnetic alloy portion is too thin, the stress detection characteristic becomes unstable. Therefore, when the shaft material is a non-magnetic material, it is 10
It is preferably formed to a thickness of at least μm. Further, when a ferromagnetic material is used as the shaft material, it is necessary to have a thickness such that the detected magnetic flux does not reach the shaft material. Therefore, for example, when the frequency for detecting the change in permeability is 50 KHz, the film thickness Is 30
Provide at least μm. For the same reason, the depth of the groove is 0.2
mm or more is preferable.

Next, in the manufacturing method, it is preferable to form a plurality of inclined concave lines and convex lines provided on the surface of the shaft in advance from the standpoint of workability, and a part thereof is cut.

V-shaped, sine-shaped, gear-shaped, trapezoidal, fan-shaped, etc. can be applied to the shape of the groove. The convex stripes between the concave stripes are formed so that each top surface is concentric.

When the magnetic alloy is sprayed on the shaft member having the concave and convex lines, it is desirable to remove the oil on the surface in advance. Further, in order to enhance the adhesion of the thermal spray coating, it is desirable that the surface to be sprayed is blasted to have a matte surface.

In the thermal spraying, a plasma is generated by a gas such as Ar, He, N ₂ , H ₂ and the powder for forming a coating film is put into the plasma and melted and sprayed on the surface of the shaft member to form a coating film. . A high temperature flame spraying method can also be applied.

The heat treatment strengthens the adhesion between the shaft material and the sprayed coating, promotes mutual diffusion between the sprayed particles, improves defects peculiar to the sprayed coating, normalizes the layered metal structure, and improves sensitivity and linearity. In vacuum,
It is processed in a non-oxidizing atmosphere such as hydrogen gas.

The treatment temperature is 900 to 1 for Fe-Ni alloy.
100 ° C., 800-850 ° C. for Co-Fe alloy, Al
In the case of —Fe alloy, heating at about 400 ° C. and slow cooling is the same as in the conventional case. In this case, it is known that when the processing temperature is increased, the sensitivity is improved, but the linearity and the hysteresis are deteriorated when the processing temperature is too high or too low.
Further, in order to make the components uniform, before heating and slow cooling, the Co—Fe alloy is heated to about 1200 ° C. and rapidly cooled,
The Al—Fe alloy may be heated to about 800 ° C. and then rapidly cooled.

[0024]

The magnetic alloy layer of the magnetostrictive detector according to the present invention is provided with anisotropy because it is formed on the surface of the uneven strip inclined at an angle of 45 °.

In magnetostriction detection, a change in permeability due to strain in the magnetic alloy layer near the top surface of the ridge is output as an electric signal as a change in inductance of the solenoid coil.

The shaft material and the magnetic alloy layer are formed continuously on the concave-convex line surface, and the bonding area between them is large compared to the cylindrical surface,
Durability is improved.

Since the coating is formed by the thermal spraying method, it can be formed thick with little variation in composition of each portion of the thermal sprayed coating. Further, if the metallographic structure is made uniform by heat treatment, linearity of output, hysteresis, sensitivity, as a torque sensor, Dynamic range, reproducibility, and durability are improved.

If the concavo-convex stripes of the shaft member are formed by the rolling method and the coating film is formed by the thermal spraying method, both work efficiency is good.
The magnetostrictive detector can be manufactured at low cost.

[0029]

EXAMPLES Examples of the present invention will be described below.

First, a stainless steel rod (material JIS standard SUS304) having an outer diameter of 20 mm and a length of 100 mm was prepared.

Then, as shown in FIG. 1, after forming the concave stripe 2 on the surface of the shaft 1 by rolling, the outer peripheral surface of the convex stripe 3 is cut to adjust the dimensions to obtain a shaft material.

As shown in FIG. 2, the concave stripes 2 and the convex stripes 3 are substantially trapezoidal, and the height h of the convex stripes 3 is 0.5 mm and the width W is W.
₃ and 5 mm, the sample 1, the width W ₃ formed ten on the outer periphery
Is 1 mm and 20 pieces are formed on the outer circumference, and a sample ₃ having a width W ₃ of 0.5 mm and 40 pieces is formed on the outer circumference.

The concave stripes 2 and the convex stripes 3 are formed such that one is inclined at an angle of + 45 ° and the other is inclined at an angle of -45 ° in the longitudinal direction of the shaft.

The outer peripheral surface of each shaft material was blasted by blasting corundum with compressed air to obtain a satin finish.

Next, a magnetic alloy coating film having a thickness of 0.1 mm was formed on the concave portion 2 and the convex portion 3 by thermal spraying. This thermal spray is 2
00 in Torr vacuum Ar gas atmosphere, sprayed with 50% Fe-Ni alloy powder by Ar-H ₂ plasma jet. In this composition, Fe-Ni alloy coatings of various compositions were formed by plasma spraying in preliminary experiments, and magnetostrictive characteristics were evaluated, and the characteristics were good.

Then, each sample was placed in hydrogen gas at a temperature of 100.
After heating to 0 °, it was gradually cooled to obtain a sample.

FIG. 2 schematically shows the sectional structure of the sample. The shaft 1 has a groove 2 and a groove 3 formed on the surface thereof, and the magnetic alloy layer 4 is in close contact with the surface thereof.

On the other hand, as a sample 4 for comparison, a sample by a plating method was prepared. The outer peripheral surface of a stainless steel rod having the same dimensions as described above was finished by machining to be smooth, and then alkaline degreasing was performed to make a shaft material, and 20% Fe-Ni alloy plating was applied to a thickness of 10 μm. This plating method is disclosed in JP-A-62-1
It carried out in the nickel sulfamate solution similarly to the method described in 206421.

Next, in the longitudinal direction of the shaft, one angle is +45.
And a masking agent (wax) having a width of 4 mm at an angle of −45 ° and covered with a masking agent (wax) at equal intervals, and etched with an aqueous ferric chloride solution to selectively remove the plating film. Then, a heat treatment for removing residual stress is performed at a temperature of 350 ° C. in hydrogen gas,
It was used as a comparative sample.

The alloy composition of the comparative sample was 20% Fe-
Fe-Ni was used and the heat treatment temperature was 350 ° C.
In the case of an alloy plating film, this alloy composition has a good magnetostriction detection sensitivity, and this heat treatment temperature is based on the findings obtained from preliminary experiments that the heat treatment temperature is good in terms of adhesion to a shaft material and magnetostriction detection sensitivity.

FIG. 3 schematically shows the cross-sectional structure of the comparative sample. In the figure, the magnetic alloy layers 4 are adhered to the surface of the shaft 1 at equal intervals, and the space between the magnetic alloy layers 4 is the selective removal portion 10 removed by etching.

Each of the magnetostrictive detectors thus prepared is fixed to a cantilever shaft, coils 5 and 6 are arranged as shown in FIG. 1, and one end of the sample is arranged by an electric circuit as shown in FIG. Torsional torque was applied to and the relationship between torque and output voltage was measured. In FIG. 4, reference numeral 7 is a transistor, 8 is an input terminal, and 9 is an output terminal. The number of turns of the coils 5 and 6 is 40, and the excitation conditions are a frequency of 50 KHz and a current of 1
The waveform was a sine wave at 00 mA.

Here, the sensitivity means the value of the output voltage when a torque of 1 N · m is applied, and the linearity plots the output voltage value when the torque is equally applied in the forward rotation direction and the reverse rotation direction on the graph. Then, connect the output voltage values of the maximum torque of forward and reverse with a straight line, and show the maximum deviation of the voltage value plotted from this straight line as a percentage of the full-scale voltage (difference in output voltage of the maximum torque of forward and reverse). The hysteresis is a value representing the amount of output voltage value deviation when the torque is 0 when a positive torque and a reverse torque are continuously applied, as a percentage of the full-scale voltage.

The measurement results are shown in Table 1. It can be seen that Samples 1 to 3, which are samples of the present invention, are superior to Comparative Sample 4 in each characteristic. This is because in the sample of the present invention, the tissue variation is small, and the coating is formed thick,
It is considered that the adhesion is good.

Further, when the width W _{3 of the} ridge 3 becomes small, each characteristic tends to decrease slightly.

On the other hand, in the fabrication, the comparative sample 4 is complicated in the plating process, the selective removal process and the management of these liquids, but it can be understood that the comparative sample 4 can be prepared relatively easily according to the present invention.

[0047]

[Table 1] Next, the invention sample 1 and the comparative sample 4 were set in the same manner as in the above-described test method, a forward and reverse torsion torque of 10 N · m was applied to the shaft 10 ⁸ times at a cycle of 10 Hz, and the torque conversion characteristics after that were set. It measured and investigated the deterioration condition.

As a result, in Comparative Sample 4, the sensitivity was 50%, the linearity was 5%, and the hysteresis was 7% lower, whereas in Sample 1 of the present invention, almost no deterioration was observed.

[0049]

As described above, in the magnetostrictive detector according to the present invention, since the magnetic alloy coating is formed on the entire surface of the uneven line on the outer peripheral surface of the shaft member, the adhesion between the shaft member and the coating is good. In addition, it has excellent durability, good characteristics such as sensitivity and linearity, and also has various effects such as extremely high productivity because it is produced by the rolling method and the thermal spraying method. Have.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a torque sensor used for measurement of the present invention.

FIG. 2 is a cross-sectional view of essential parts showing a magnetostrictive detector according to the present invention.

FIG. 3 is a cross-sectional view of essential parts showing a conventional magnetostrictive detector.

FIG. 4 is a torque detection circuit diagram in the torque sensor shown in FIG. 1.

[Explanation of symbols]

 1 axis 2 concave stripe 3 convex stripe 4 magnetic alloy layer 5, 6 coil 7 transistor 8 input terminal 9 output terminal

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Masayuki Doi 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Ltd. (72) Keiho Kojima 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Inside Hitachi Research Laboratory

Claims (2)

[Claims] 1. A magnetostrictive detector for a torque sensor, comprising a magnetic alloy layer having a magnetostrictive effect on the outer peripheral surface of a torque transmission shaft, wherein the outer peripheral surface of the torque transmission shaft forms an angle of 45 ° with the longitudinal direction of the shaft. A magnetostrictive detector for a torque sensor, wherein a plurality of inclined concave and convex lines are formed at regular intervals, and a magnetic alloy layer is formed on the concave and convex surfaces. 2. A magnetostrictive detector for a torque sensor comprising a magnetic alloy layer having a magnetostrictive effect on the outer peripheral surface of a torque transmitting shaft, wherein the outer peripheral surface of the torque transmitting shaft is at an angle of 45 ° with respect to the longitudinal direction of the shaft. A plurality of slanting concave and convex stripes are formed at regular intervals by rolling, a magnetic alloy layer is formed on the concave and convex stripes by thermal spraying, and heat treatment is carried out in a non-oxidizing atmosphere. Of manufacturing magnetostrictive detector for torque sensor.