JPH0368826A - Magnetostrictive film type torque sensor - Google Patents

Abstract

PURPOSE:To obtain an elaborate sensor having excellent sensitivity by forming a magnetostrictive film by pressure reduced plasma flame coating. CONSTITUTION:The pressure in a pressure reduced chamber is reduced to 10 - 50Torr. Metal powder for magnetostrictive film and a carrier gas such as Ar and He are sent into a plasma flame coating gun 14 through a pipe 12. The metal in the fused state is flame-coated on the surface of a rotating driven shaft 2 from the gun 14. Therefore, air holes are hardly formed in the magnetostrictive film, and the magnetostrictive film becomes elaborate. Oxygen is hardly contained in the magnetostrictive film, and adhesion between the magnetostrictive film and the driven shaft 2 is high. Therefore, the elaborate sensor having the excellent detecting sensitivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetostrictive torque sensor capable of detecting torque without contact, and particularly to a magnetostrictive film thereof.

[Prior art]

For example, in a vehicle drive system, a steering system, a robot drive system, etc., torque applied to a passive shaft (drive shaft) is detected and mechanically or electrically controlled.

As a torque sensor for detecting such torque,
A magnetostrictive film is fixed to the surface of the passive shaft using an adhesive, and the magnetic permeability of the film, which changes due to the inverse magnetostrictive effect, is detected using a coil or the like.

There are non-contact torque sensors (for example, JP-A-60-19
No. 5430, JP-A No. 63-317732).

Furthermore, a magnetostrictive torque sensor in which the magnetostrictive film described above is directly formed on the surface of a passive shaft by thermal spraying has also been proposed (Japanese Patent Application Laid-open No. 184323/1983).

As shown in FIG. 13, in all of the above torque sensors, a magnetostrictive film 91 is fixed or formed on the surface of the passive shaft 9, and an excitation coil 93 is placed opposite the magnetostrictive film 91.
and a detection coil 94 are arranged. The above excitation coil 9
3, the magnetostrictive film 91 is subjected to high frequency excitation of, for example, 1 KH2 or more. When torque is applied to the passive shaft 9, stress is applied to the magnetostrictive film 91, and its magnetic permeability changes. In other words.

The magnetic permeability of the magnetostrictive film 91 changes due to the inverse magnetostrictive effect.

Therefore, this magnetic permeability is detected by a detection coil.

It detects torque.

Furthermore, in the latter conventional torque sensor mentioned above, the magnetostrictive film is directly provided on the passive shaft by thermal spraying, so compared to the one in which the magnetostrictive film is fixed using an adhesive as described above.
Excellent durability.

[Problem to be solved]

However, the torque sensor provided with the above thermally sprayed magnetostrictive film also has a first-order problem.

That is, the adhesion of the interface between the magnetostrictive film and the passive shaft is insufficient.

Furthermore, the fusion, ie, the density, of the sprayed magnetostrictive film is not sufficient. In other words, pores or oxides are formed inside the thermally sprayed magnetostriction I. Therefore, the density of the magnetostrictive film is low, the rate of change in inductance is low, and the detection sensitivity is low (see Examples described later).

In view of these problems, the present invention has a magnetostrictive film that is dense and has excellent detection sensitivity. The present invention aims to provide a magnetostrictive torque sensor.

(Means for solving problems) The present invention has a passive shaft with a magnetostrictive film formed on one surface.

A torque sensor comprising an excitation coil and a detection coil disposed opposite to the magnetostrictive film with a gap therebetween, wherein the magnetostrictive film is formed on the surface of the passive shaft by low-pressure plasma spraying. It's in the sensor.

The most noteworthy feature of the present invention is that the magnetostrictive film is formed by low pressure plasma spraying.

The above-mentioned reduced pressure plasma spraying is i%! This is a method of plasma spraying under pressure. For example, Ar.

The supply gas pressure of inviscid gas such as He is 30 to 10 Qps.
In an atmosphere of i, chamber pressure 1O ~ 50 Torr
Then, a metal powder (5) as a raw material for a magnetostrictive film is thermally sprayed onto the surface of the passive shaft.

The material of the magnetostrictive film is Fe-Ni alloy (Ni30~
80%), alloys to which 10% or less of elements that increase electrical resistivity such as Mo and Cr are added, Fe-Co alloys, Fe-Affi alloys, etc.

Further, the metal powder used during WI injection is preferably 50 mesh or less; if the powder is coarser than 50 mesh, the produced magnetostrictive film may not be sufficiently dense. Further, the thickness of the magnetostrictive film is preferably 20 μm or more.

If the diameter is less than 20 μm, the detection sensitivity is low.

Further, in the case of low pressure plasma spraying, it is preferable to clean the surface of the passive shaft by sandblasting or the like to make the two surfaces slightly rough.

In other words, it is preferable to set the roughness of one surface to 10 μRZ or more. This improves the adhesion of the magnetostrictive film. Also,
After base cleaning, arc cleaning is performed to remove the oxide film on the surface of the passive shaft.

Then perform low pressure plasma spraying.

[Action and effect]

In the present invention, since the magnetostrictive film is formed by low pressure plasma spraying, almost no pores are generated in the magnetostrictive film (see FIG. 5). That is, the area ratio of the arrow in the film is 5% or less (see Examples), so the magnetostrictive film is dense.

In addition, the magnetostrictive film contains almost no oxygen (7th
(see figure).

Furthermore, since the magnetostrictive film is formed by the above-mentioned low-pressure plasma spraying, the adhesion between the magnetostrictive film and the passive shaft is high.

Therefore, according to the second aspect of the present invention, a magnetostrictive film is provided which is dense and has excellent detection sensitivity. A magnetostrictive torque sensor can be provided.

〔Example〕

First Example A magnetostrictive film was formed on the surface of the passive shaft by low pressure plasma spraying, and various measurements were performed on the passive shaft and the magnetostrictive film.

In addition, for comparison, similar measurements were also performed in the case of atmospheric radiation.

First, the formation of the magnetic f2 film on the passive shaft will be described.

For low pressure plasma spraying, as shown in Figure 9,
A passive shaft 2 is mounted on a rotating table 11 in a decompression chamber 1.
Place. Then, the pressure inside the vacuum chamber 1 is reduced, and then the metal powder and carrier gas for the magnetostrictive film are sent from the pipe 12 to the plasma spray gun 14. A passive shaft 2 rotates the molten metal once from the thermal spray gun 14.
Inject to. In addition, the code|symbol 13 is an electric wire pipe.

Furthermore, before placing the passive shaft in the reduced pressure chamber 1, the surface of the passive shaft was roughened to a surface roughness of about 10μRZ by sandblasting to clean the base. This is to improve the adhesion of the thermal spray particles. Then, the passive shaft that had undergone the base cleaning was placed in a reduced pressure chamber 1, and arc cleaning was performed under reduced pressure to remove the oxide film on the surface of the passive shaft. After that, low pressure plasma spraying was performed.

The above passive shaft is made of stainless steel t1.1I (S) with a diameter of 20M.
US304). In addition, the metal powder is Fe55%-
The grain size of the 45% Ni alloy was 100 mesh or less. The carrier gas and its pressure are Ar (argon) 60
ps t, He (helium) 60 ps + was used.

Also, during thermal spraying, the pressure inside the vacuum chamber is 20
Torr, voltage 80v.

The current was 800A. However, due to the above thermal spraying.

The surface of the passive shaft 2 is coated with Fe55%-N with a thickness of 100 μm.
A magnetostrictive film of i45% alloy was formed. below.

This passive shaft is referred to as the passive shaft of the present invention.

Also, for comparison, the pressure reduction described above was not performed.

Place the inside of the decompression chamber at atmospheric pressure and under the atmosphere.

Thermal spraying was carried out in the same manner as above except that air was used as the carrier gas. Hereinafter, this passive axis will be referred to as the comparative passive axis.

Next, various measurements were performed on the above-mentioned passive shaft of the present invention and the comparative passive shaft.

(A) Inductance change rate As shown in FIG. 10, passive shaft 2 with magnetostrictive film 22 (
20 mm in diameter), a 350-turn coil 31 is arranged with a gap maintained around the magnetostrictive film 25. The coil 31 is connected to an LCR tester 30. and,
A rotational torque was applied to the passive shaft 2, and the inductance (L value) of the coil was measured. The above measurements range from lO to 100KII
I followed Z. Further, the amount of strain was expressed as the amount of strain in the 45-degree direction on the surface of the passive shaft, and was calculated from the load torque of the passive shaft.

The results are shown in FIGS. 1 and 2. As can be seen from FIG. 1, the passive shaft of the present invention exhibits a larger rate of change in inductance with respect to load torque than the comparative passive shaft.

Further, as can be seen from FIG. 2, it can be seen that the passive shaft of the present invention exhibits a higher rate of change in inductance in all frequency regions than the comparative passive shaft. That is, the passive shaft of the present invention has excellent detection sensitivity.

(B) Magnetostrictive effect The magnetostriction effect due to the direct am characteristic was measured.

For this measurement, a magnetostrictive film was formed on a plate-shaped metal substrate other than the passive shaft by thermal spraying in the same manner as described above. Then, as shown in FIG. 11, the substrate 25 on which the magnetostrictive film 26 is formed is mounted on a four-point bending jig 33. In addition, the substrate 25
A pickup coil 34 is placed around the pickup coil 34, and an excitation coil 35 is placed around the pick-up coil 34.

Then, tensile stress, no load, and compressive stress are applied to the substrate, and the output of the pickup coil 34 is determined.

The magnetic field of the excitation coil 35 was measured. In addition, tension.

7. Compression also applies to magnetostrictive films. The curvature was set so that a stress of 4 kg/nm'' was applied.

The results are summarized in the third section regarding the present invention (low-pressure plasma spraying).
FIG. 4 shows a comparative example (atmospheric pressure spraying).

As shown in Figures 3 and 4, the hysteresis loop (Figure 3) of the magnetostrictive film of the present invention has a larger slope and a larger rate of change in inductance than that of the comparative magnetostrictive film. . In other words, the two magnetostrictive films of the present invention have high detection sensitivity.

(C) Pore formation state in magnetostrictive film Regarding the passive shaft with the magnetostrictive film formed as described above.

The part where the magnetostrictive film was formed was observed under a microscope.

The results are shown in FIG. 5 for the passive shaft of the present invention and in FIG. 6 for the comparative passive shaft. The photograph shows a cross-section of the magnetostrictive film formed by etching with a ferric chloride solution, and the magnification is 200 times.

In both figures, the area above the center of the photo is the sprayed magnetostrictive film.

The lower part is the passive shaft base material.

As can be seen from FIG. 5, the magnetostrictive film of the second passive shaft of the present invention is dense with almost no pores as defects in the film. That is, the defect area ratio in the film is 1. It was 9%.

Here, the in-film defect area ratio is the area of defects in a cross section of the film magnified 400 times, measured by one image processing device.

On the other hand, the comparative passive shaft magnetostrictive film has a large number of pores in the nu, as shown in FIG.

The defect area ratio in the film reached 43%.

(D) Oxygen-containing state in the magnetostrictive film Regarding the magnetostrictive film forming portion, the oxygen-containing state in the magnetostrictive film is
Analyzed by MA. The results are shown in FIG. 7 for one inventive passive shaft and in FIG. 8 for a comparative passive shaft using EPMA photographs (200x magnification).

In both photographs, white dots indicate the locations of oxygen.

In the photograph, the upper one-third of the white part represents the embedded resin in the cross-sectional photographing piece, and the lower one-third of the black part represents the base material of the passive shaft. exists.

As can be seen from the photos of both cars, the magnetostrictive film of the passive shaft of the present invention (Fig. 7) has an extremely low oxygen content (white dots) compared to the magnetostrictive film of the comparative passive shaft (Fig. 8). . That is, the magnetostrictive film of the passive shaft of the present invention is as follows.

It contains approximately the same amount of oxygen as the base material (passive shaft).

As is known from the above, the magnetostrictive film of the passive shaft of the present invention has an extremely low pore content, that is, a defect area ratio in the film, and an extremely low oxygen content. Also, therefore 2
The magnetostrictive film of the passive shaft of the present invention exhibits excellent detection sensitivity (
1 to 4).

Second Embodiment The passive shaft of the present invention has three detection circuits as shown in FIG. 12, for example, and is used as a torque sensor.

The detection circuit in this example consists of a resonant circuit fixed to the passive shaft 2, and a detection section consisting of a human power coil 5 and an output coil 6 provided outside the passive shaft 2, and uses this to detect torque. It is something.

That is, the resonant circuit includes the magnetostrictive film 22 provided around the entire circumference of the passive shaft 2, a resonant coil 43 wound around the magnetostrictive film 22, and a capacitor 44 connected in series with the resonant coil 43. Fix it on the passive shaft 2.

Further, a detection section that detects the resonance frequency output from the resonance circuit K includes an input coil 5 connected to a drive power source,
It consists of an output coil 6 that transmits the detected signal. The human-powered coil 5 consists of a magnetic core 51 and a coil 52 wound around it, and the output coil 6 consists of a magnetic core 6] and a coil 62 wound around it. The input coil is a so-called excitation coil.

Then, a waveform shaping circuit is connected to the detection section of the resonant circuit to measure the torque fluctuation output (as shown in the diagram). For details of the measurement, see Japanese Patent Application Laid-Open No. 63317732.

[Brief explanation of drawings]

Figures 1 to 11 show the torque sensor of the first embodiment, where Figure 1 is a relationship diagram between load torque and inductance change rate, Figure 2 is a relationship diagram between frequency and inductance change rate, and Figure 3 is a relationship diagram between frequency and inductance change rate. Figures 4 and 4 are hysteresis diagrams of magnetostrictive films, and Figure 5
Figures 6 and 6 are micrographs of the metal & 11 weave cross section of the magnetostrictive film forming part, Figures 7 and 8 are X-ray photographs taken with an X-ray microanalyzer of the cross section of the magnetostrictive film forming part,
Fig. 9 is an explanatory diagram of low pressure plasma spraying, Fig. 10 is an explanatory diagram of inductance measurement, Fig. 11 is an explanatory diagram of magnetostrictive effect measurement, Fig. 12 is an explanatory diagram of the torque sensor in the second embodiment, and Fig. 13 is an explanatory diagram of the measurement of the magnetostrictive effect. FIG. 2 is an explanatory diagram of a magnetostrictive film torque sensor. 118. Decompression chamber 212. Passive axis. 24, magnetostrictive film applicant Toyota Industries Corporation

Claims (1)

[Claims] In a torque sensor comprising a passive shaft having a magnetostrictive film formed on its surface, and an excitation coil and a detection coil arranged opposite to the magnetostrictive film with an air gap, the magnetostrictive film is formed on the surface of the passive shaft by low pressure plasma spraying. A magnetostrictive torque sensor characterized by: