JPH03282338A - Manufacture of torque sensor - Google Patents

Abstract

PURPOSE:To enhance the sensitivity of the torque sensor without any problem accompanying magnetic anisotropy given to a magnetic body by performing grooving or chemical substrate processing for the surface of a torque transmission shaft and then forming the magnetic body as a film. CONSTITUTION:At two positions on the surface of the torque transmission shaft 11 which is rotated by a driving source, a couple of V grooves are formed by lathing at +45 deg. and -45 deg. to the peripheral direction of the shaft 11. The magnetic body 12 is formed as the film at the part of the shaft 11 where the grooves are formed. The magnetic body 12 is formed of the alloy film of about specific 10<-5> magnetic strain. This constitution give the magnetic body 12 axes of easy magnetization in the running directions of the grooves to have uniaxial magnetic anisotropic properties K<1>uo and K<2>uo at +45 deg. and -45 deg. to the peripheral direction of the shaft 11. Cylindrical detection coils 131 ad 132 are provided in non-countact state with the magnetic body 12 and a cylindrical exciting coil 14 is also formed. This torque sensor has excellent linearity over a wide torque range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a torque sensor that non-contactly detects torque applied to a rotating shaft or the like.

(Prior Art) Torque is used as the most basic parameter when controlling or monitoring rotary drive units such as electric motors and automobiles. For example, torque detection is also of high importance in various in-vehicle electrical systems (power steering systems, transmission control systems, engine control systems, four-wheel drive systems, steering systems) that are being actively developed.

In recent years, a torque sensor has been proposed that can detect torque without contact by utilizing the magnetostrictive effect that occurs in a ribbon of amorphous magnetic alloy (IEE of Japan Magnetics Study Group Material MAG-81-72). .

The principle of this torque sensor will be explained with reference to FIG. In FIG. 12, a magnetic body 2 made of an amorphous magnetic alloy ribbon is wound and fixed around a rotating shaft on which torque is to be detected, that is, a torque transmission shaft 1. This magnetic body 2 has an angle θ (≠0
) is the uniaxial magnetic anisotropy K with the direction of the easy magnetization axis. . has been granted.

Further, an excitation coil and a detection coil are arranged close to the magnetic body 2, and the detection coil is connected to a detection circuit (not shown).

Using the torque sensor having such a configuration, torque can be detected in the following manner. Here, in order to simplify the explanation, it is assumed that θ-45@ and the saturation magnetostriction constant λ5>0. Now, when torque T shown by the broken line arrow is applied to shaft 1,
The surface strain stress σ generated on the shaft 1 is transmitted to the magnetic body 2,
The magnetic body 2 has a diameter of +45″ with respect to the circumferential direction of the torque transmission shaft 1.
A tension force σ is generated in the direction of , and a compressive stress -σ is generated in the direction of -45''.Accompanyingly, due to the magnetostriction effect, the magnetic body 2 exhibits stress-induced magnetic anisotropy in the direction of +45°. , (K,, −3λ, ·σ) is induced. As a result,
K. Toni 1. are combined and the uniaxial magnetic anisotropy is K w
Changes to x. In this case, if the direction of the magnetic flux passing through the inside of the magnetic body 2 is constant, the magnetic permeability of the magnetic body 2 in the magnetic flux penetration direction changes as the -axis magnetic anisotropy changes. Therefore, this change in magnetic permeability can be measured by a detection coil and a detection circuit connected thereto, and the torque T applied to the shaft 1 can be determined from the measured value.

By the way, in the torque sensor based on the above-described principle, the magnetic body 2 has uniaxial magnetic anisotropy Ku in advance.

must be given. In particular, in order to use this torque sensor to detect the torque during forward rotation and reverse rotation with good linearity, it is necessary to
and -θ (excluding 0°, 90″180″270@), a pair of magnetic bodies with uniaxial magnetic anisotropy of 6° in advance, and for detecting changes in the magnetic properties of these magnetic bodies. It is necessary to construct a torque sensor using a pair of differentially coupled detection coils or detection heads.

Conventionally, in order to impart uniaxial magnetic anisotropy of 5o to a magnetic material,
The following methods are known, but all of these methods have problems.

■We fabricated an annular magnetic body made of amorphous magnetic alloy to match the diameter of the torque transmission shaft, heat-treated it to remove internal stress, and then inserted it into the torque transmission shaft to give the shaft a torsion. How to glue it in place and untwist the shaft. However, this method has the problem of complicating the process, such as the need to prepare an annular magnetic body in advance to match the diameter of the shaft and the need to twist the shaft.

■A method of introducing -axis magnetic anisotropy by subjecting the magnetic material to heat treatment and cooling in a magnetic field before adhering and fixing the magnetic material to the shaft. However, this method is very time-consuming and lacks mass productivity, and is difficult to apply to long magnetic bodies, which limits the size and shape of the magnetic body.

■For example, by hot isostatic pressing (HIP), an amorphous alloy is
), the alloy is bonded and crystallized, and then a part of this alloy is irradiated with laser pulses to form amorphous stripes (Japanese Patent Laid-Open No. 6
3-2H478). In this method, the magnetic material has a structure in which crystalline and amorphous materials are arranged alternately in stripes, so that magnetic anisotropy can be imparted to the magnetic material. In addition, this method provides good bonding durability of the magnetic material. However, this method has problems, such as requiring an expensive laser irradiation device and modifying the surface of the magnetic material with a laser, making the magnetic material more or less brittle.

(2) A method of forming a magnetic material on the surface of the shaft using a vapor phase growth method (Japanese Patent Application No. 5111-150988). This method is superior in terms of fixing the magnetic material to the surface of the shaft. However, this publication does not disclose any specific means for imparting magnetic anisotropy to the magnetic material formed on the surface of the shaft.
There is a problem with this point.

When applying torque sensors to in-vehicle electrical systems, it is extremely important to take measures against the introduction of magnetic anisotropy into magnetic materials.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing a highly sensitive torque sensor without the problems associated with introducing magnetic anisotropy into a magnetic material.

[Structure of the Invention (Means for Solving the Problems)] The method for manufacturing a torque sensor of the present invention includes rotating a magnetic material having magnetostriction on the surface of a torque transmission shaft, and applying torque to the shaft to In manufacturing a torque sensor that detects torque by utilizing changes in the magnetic properties of a body, the surface of the torque transmission link shaft is grooved or chemically coated along a predetermined direction with respect to its circumferential direction. After processing,
It is characterized in that magnetic anisotropy is produced in a predetermined direction by forming a film of a magnetic material.

In the present invention, specific processing methods for forming grooves on the torque transmission shaft include: (1) forming spiral grooves on the surface of the torque transmission shaft by lathe processing, (2) using relatively coarse abrasive paper, etc. , Method of polishing the torque transmission shaft to create polishing scratches, ■ Applying photoresist to the torque transmission shaft, exposing and
Examples include a method of developing to form a predetermined resist pattern and then etching the exposed torque transmission shaft.

The shape of the groove may be square, V-shaped, U-shaped, etc., and is not particularly limited. The width and spacing of the grooves are 10#-10■l
degree is preferred. Further, the depth of the groove is preferably about lIn to 1 fin.

In addition, a method of chemically pretreating the torque transmission shaft is to coat the torque transmission shaft with an oil film, resin, etc. that prevents the growth of magnetic substances, and then irradiate the torque transmission shaft with a high energy density beam such as a laser in a predetermined direction. Then, there is a method of removing oil film, resin, etc. from that part. In this case, when the magnetic material is formed into a film in a later step, the growth rate of the magnetic material differs depending on the area where there is an oil film, resin, etc. and the area where it is not, so that unevenness occurs in the formed magnetic material.

The width and interval of the chemical base treatment is preferably about 1- to 5■■.

Such groove processing and chemical surface treatment are performed along a predetermined direction with respect to the circumferential direction of the torque transmission shaft so that single-ring magnetic anisotropy occurs in the magnetic material that is formed in a later process. Ru.

The direction of groove machining and chemical surface treatment is preferably ±45" with respect to the principal stress direction, that is, the circumferential direction of the torque transmission shaft, but any direction greater than 0° and less than 90" with respect to the circumferential direction is preferable. Any direction that forms an angle is sufficient.

In the present invention, specific methods for forming a magnetic film on the torque transmission shaft include (1) a plating method, (2) a vapor phase growth method such as a sputtering method, and the like.

However, in order to obtain a magnetic material exhibiting soft magnetic properties, manufacturing parameters (for example, Ar
It is preferable to appropriately select the pressure (pressure, etc.). Further, the thickness of the film is preferably about 100 nm-1 μm.

(Function) In the method of the present invention, when a magnetic material is formed on the surface of the torque transmission shaft after groove processing or chemical surface treatment is performed along a predetermined direction with respect to its circumferential direction, the magnetic material is formed into a film. The magnetic material may be formed with a uniform thickness following the unevenness of the surface of the torque transmission shaft, or the magnetic material may be formed with a different thickness depending on the unevenness of the surface of the torque transmission shaft or chemical base treatment. Which of the above states the magnetic film is in depends on the width and depth of the groove, the thickness of the magnetic film, etc. In the former case, shape magnetic anisotropy occurs in the magnetic body in a predetermined direction. In the latter case, differences in magnetic properties, particularly magnetic permeability, occur due to differences in the film thickness of the magnetic material, resulting in magnetic anisotropy in a predetermined direction.

By using the method of the present invention, treatments that were conventionally required to introduce magnetic anisotropy into a magnetic material, such as manufacturing an annular magnetic material and twisting the axis, heat treatment/cooling in a magnetic field, laser treatment, etc. There is no need for beam irradiation, and the magnetic material can be firmly fixed to the torque transmission shaft. Further, the problem of embrittlement of the magnetic material due to heat treatment in a magnetic field, laser beam irradiation, etc. does not occur.

Note that, as a method similar to the method of the present invention, a method of selectively forming a film of magnetic material by masking a part of the torque transmission shaft can be considered. However, the method of masking a portion of the torque transmission shaft is far more complicated and less practical than the groove machining and chemical surface treatment in the present invention. In addition, if a part of the torque transmission shaft is masked and a magnetic material is selectively deposited, the magnetic material film will be formed discontinuously and a large magnetic resistance will be introduced into the magnetic circuit, causing torque detection. Sensitivity decreases. On the other hand, in the method of the present invention, since the magnetic film is continuously formed, the torque detection sensitivity does not decrease.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic diagram of a torque sensor according to an embodiment of the present invention. In FIG. 1, two parts of the surface of the torque transmission shaft 11 with a diameter of 20 am, which is rotated by a drive source such as a motor (not shown), are machined with a lathe to have a width of 0.5 fins and a depth as shown in FIG. 0.5mm V groove, 0
．． + in the circumferential direction of the torque transmission shaft 11 at 1 mm intervals.
One pair is provided in the 456 and -45@ directions. A magnetic material 12 is deposited on the portion of the torque transmission shaft 11 where the groove is formed.

This magnetic body 12 is formed by a sputtering method (F
eo, 2 C00, 8) 711S i s B14
It is made of an alloy film having a composition and a magnetostriction constant of about 10-5. Its film thickness is approximately 20 mm.

With such a structure, the direction in which the groove runs becomes the axis of easy magnetization of the magnetic body 12, and the magnetic body 12 has uniaxial magnetic anisotropy of 3 in the direction of +45° -45° with respect to the circumferential direction of the torque transmission shaft 11.゜, K-〇 are introduced.

A cylindrical detection winding 131 is installed on the outer periphery of the grooved portion of the torque transmission shaft 11 without contacting the magnetic body 12.
132 has been applied. In addition, the detection winding 131 13□
A cylindrical excitation winding 14 is provided on the outer periphery of the coil. These detection windings 131 and 132 and the excitation winding 14 are connected to a winding frame made of a non-magnetic material (not shown), and a conducting wire of 0.3+am diameter is connected to the excitation winding 1 100 times in the case of the detection windings 131 and 132.
In case of No. 4, it is wound 300 times.

FIG. 9 is a block diagram showing the circuit configuration of the torque sensor of this embodiment. In FIG. 5, the oscillator 21 generates 10
A sinusoidal excitation current of 0 kHz is generated, amplified by the amplifier 22, and applied to the excitation winding 14.

As a result, an alternating magnetic field is applied to the magnetic bodies 12+ and 12□. Then, according to the principle described above, the detection winding 13+
, 13□ is sent to the differential amplifier 23.
24, rectified by a synchronous detector 26 via 25,
A DC torque signal that changes in response to torque changes is obtained.

FIG. 10 shows the results of measuring the torque detection characteristics using the torque sensor configured as described above. As is clear from FIG. 10, the torque sensor of this example exhibits good linearity over a wide torque range.

Embodiment 2 Instead of forming the V-groove shown in FIG. 2 on the surface of the torque transmission shaft 11 by lathe processing, a width of 0.05 as shown in FIG.
+nm, depth 0.1w U grooves are spaced at 0.05+am intervals, +45'' and -4 in the circumferential direction of the torque transmission shaft 11.
The structure shown in FIG. 1 was formed in the same manner as in Example 1 except that one pair was provided in the 5'' direction.

The other detection winding 13113□, excitation winding 14, and circuit configuration are the same as in the first embodiment. With this torque sensor as well, torque detection characteristics with good linearity similar to those shown in FIG. 1O were obtained.

In the case of the first embodiment, as shown in FIG. 4, the magnetic body 12 is formed to have a uniform thickness following the irregularities on the surface of the torque transmission shaft 11. On the other hand, in the case of the second embodiment, as shown in FIG. 6, the magnetic body 12 is formed with different thicknesses depending on the unevenness of the surface of the torque transmission shaft 11. Moreover, as an intermediate state between FIG. 4 and FIG. 6, the magnetic body 12 may be formed as shown in FIG. 5. These differences are determined by the width and depth of the groove, and the thickness of the magnetic material 12, but in any case, magnetic anisotropy occurs in the magnetic material 12.

In addition, after applying a chemical base treatment to the torque transmission shaft 11,
Magnetic anisotropy may be introduced into the magnetic material 12 by forming the magnetic material 12 into a film. This method will be explained with reference to FIGS. 7 and 8. As shown in FIG. 7, an oil film 35 is applied to the surface of the torque transmission shaft 11. While rotating the torque transmission shaft 11, the laser beam from the laser oscillator 32 is applied to the oil film 35 on the surface of the mirror 33 and the lens 34.
irradiate while scanning. As a result, a portion 36 from which the oil film 35 has been removed is formed on the surface of the torque transmission shaft 11 along a predetermined direction with respect to its circumferential direction. After that, when the magnetic material 12 is sputtered, the growth rate of the magnetic material 12 is different between the part with the oil film 35 and the part 36 without it, so as shown in FIG. As a result, magnetic anisotropy occurs in the magnetic body 12.

Further, in the above embodiment, the excitation winding I4 was used to detect torque with the circuit configuration shown in FIG. 9, but torque detection could also be performed with the circuit configuration shown in FIG. 11 without using the excitation winding. good. In FIG. 11, a sinusoidal current generated by an oscillator 21 is amplified by an amplifier 22. In FIG.

A detection winding 13. is connected to the output terminal of the amplifier 22. and a series circuit with the resistor R1, the detection winding 132, and the resistor R2 (R2-R+)
A bridge circuit consisting of a series circuit with is connected.

Further, the sine wave current generated by the oscillator 21 is input to the reference signal generator 27, and the signal generated here is output to the phase detector 28. A differential amplifier 23 is connected to the detection end of the bridge circuit, and its output is sent to a phase detector 28.
can be detected and torque output can be obtained.

[Effects of the Invention] As detailed above, in the method for manufacturing a torque sensor of the present invention, after the surface of the torque transmission shaft is subjected to groove processing or chemical surface treatment along a predetermined direction with respect to its circumferential direction, , magnetic anisotropy can be introduced into a magnetic material by a simple means of forming a film of the magnetic material. Further, problems such as embrittlement due to the introduction of magnetic anisotropy into the magnetic material do not occur, and torque detection characteristics are also excellent.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a torque sensor according to an embodiment of the present invention, and FIGS. 2 and 3 are a schematic diagram of a torque sensor according to an embodiment of the present invention.
2 is a cross-sectional view showing the shape of the groove formed in the torque transmission shaft;
Figures 4 to 6 are explanatory diagrams showing the state of coating of the magnetic material according to the shape of the groove formed on the torque transmission shaft in the embodiment of the present invention, and Figure 7 is the torque transmission shaft in another embodiment of the present invention. FIG. 8 is an explanatory diagram showing the state of the magnetic material formed after the chemical base treatment of the torque transmission shaft, and FIG. 9 is a circuit of the torque sensor according to the present invention. FIG. 10 is a block diagram showing the configuration of the torque sensor according to the present invention; FIG. 11 is a block diagram showing the circuit configuration of the torque sensor according to another embodiment of the present invention; FIG. The figure is an explanatory diagram showing the principle of the torque sensor according to the present invention. 11... Torque transmission shaft, 12... Magnetic body, 13.
13□...Detection winding, 14...Excitation winding, 21...
Oscillator, 22... Amplifier, 23.24.25... Differential amplifier, 26... Synchronous detector, 27... Reference signal generator, 28... Phase detector. Figure 1

Claims (1)

[Claims] In manufacturing a torque sensor in which a magnetic material having magnetostriction is fixed to the surface of a torque transmission shaft and the magnetic properties of the magnetic material change due to the torque applied to the shaft, torque is detected. Generating magnetic anisotropy in a predetermined direction by forming a film of magnetic material on the surface of a torque transmission shaft after performing groove processing or chemical base treatment along a predetermined direction with respect to its circumferential direction. A method for manufacturing a torque sensor characterized by: