JPH0815060A - Manufacture of magnetostrictive film for torque sensor - Google Patents

Abstract

PURPOSE:To provide a magnetostrictive film for a torque sensor with high sensitivity and low hysterisis and a manufacturing method thereof. CONSTITUTION:A magnetostrictive film having a magnetostrictive effect is formed on the surface of an axle so that a torque sensor that detects strain torque applied on the axle is formed. The magnetostrictive film has a compound structure wherein a phase made of, for example, Fe-Ni group, Co-Ni group or Fe-Al group that mainly represents a magnetostrictive effect is finely dispersed into a matrix consisting of a phase made of a boride, a borosilicate or the like of the magnetostrictive alloy that mainly represents a hardness effect.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a reverse magnetostriction effect of a magnetic alloy, and a magnetostrictive film for use in a magnetostrictive torque sensor for measuring torque transmitted to a shaft as a power transmission shaft in a non-contact manner and a method for manufacturing the same. Regarding

2. Description of the Related Art Ferromagnetic materials have the property that their dimensions are slightly deformed when they are magnetized and that their magnetic permeability is changed when they are elastically deformed by applying an external force. The former is called the magnetostrictive effect and the latter is called the inverse magnetostrictive effect. The saturation magnetostriction coefficient λs is used as a measure of the magnitude of these effects. A sensor that magnetically detects the torque applied to the rotating shaft by utilizing the inverse magnetostrictive effect is called a magnetostrictive torque sensor. Generally, in a power transmission shaft (shaft) used for a prime mover, a machine tool, etc., torque applied to the shaft is measured for output control or power fluctuation control. A magnetostrictive torque sensor is used to measure this torque. Conventionally, as a shaft with a magnetostrictive torque detector used in a magnetostrictive torque sensor, as shown in Japanese Patent Application Laid-Open No. 63-81993, a shaft constituted of a steel shaft having a magnetostrictive effect is known. Has been. Also, as disclosed in Japanese Patent Laid-Open No. 59-166827, a shaft having a magnetostrictive film as a magnetostrictive torque detecting section formed by fixing a magnetic metal ribbon to the surface of the shaft with a synthetic resin adhesive or the like. Are known. In order to detect the torque from the shaft, the stress caused by the torque acting on the shaft is transmitted to the magnetostrictive film, and the change in the magnetic permeability due to the inverse magnetostrictive effect of the magnetostrictive film at this time is detected from the outside without contact. Also,
There is also known a method of forming a nickel film on the surface of the shaft by a plating method, a vapor deposition method or a sputtering method. Further, in JP-A-4-346043, a Ni—Fe based magnetostrictive film is formed on the surface of a shaft by a thermal spraying method such as a plasma spraying method, and a heat diffusion treatment is performed at 900 to 1100 ° C. in a non-oxidizing atmosphere. Further, the above-mentioned Japanese Patent Laid-Open No. 5-5267
No. 8, in the same manner, after forming an Fe—Co based magnetostrictive film by a plasma spraying method, 800 to 800 in a non-oxidizing atmosphere.
It is disclosed that the heat diffusion treatment is performed at 850 ° C.

However, such a conventional magnetostrictive torque sensor has the following problems. First, a shaft with a magnetostrictive torque detector that utilizes the magnetostrictive effect of the shaft itself has a problem that the magnetostrictive effect is lower than that of a shaft provided with a magnetostrictive film, and as a result, the sensitivity of torque detection is low. There is. Therefore, in the torque sensor using this shaft, the processing circuit becomes complicated and expensive. On the other hand, in the case of a shaft with a separate magnetostrictive film, since the magnetostrictive film is adhered with an adhesive, the magnetostrictive film itself can have corrosion resistance, but sufficient joint strength between the magnetostrictive film and the shaft is obtained. However, there is a problem in that reliability is lost. That is, in this shaft, the joint between the magnetostrictive film and the shaft may deteriorate depending on the magnitude of the torque applied to the shaft or the operating environment conditions of high temperature and high humidity. The correlation with the change may be lost, and the torque detection accuracy may be reduced. The cause of such inconvenience is that the ratio of the torque applied to the shaft and the bonding strength of the synthetic resin adhesive decreases as the torque increases, and the stress generated in the shaft cannot be sufficiently transmitted to the magnetostrictive film. Is assumed to be from. Further, it is assumed that it is caused by a change with time of the synthetic resin adhesive itself, deterioration due to heat of the environment temperature for use, or the like. In addition, when a nickel film is formed on the surface of the shaft by a plating method, a vapor deposition method, a sputtering method, or a magnetostrictive film such as a Ni—Fe system is formed on the surface of the shaft by a plasma spraying method, sensitivity is small when the hysteresis is small. On the contrary, there is a problem that the hysteresis becomes large when trying to improve the sensitivity. The metallographic structure of the magnetostrictive film obtained by these methods has a one-phase structure. An object of the present invention is to provide a magnetostrictive film that simultaneously achieves improvement in sensitivity and reduction in hysteresis.

In order to achieve the above object, the magnetostrictive film according to the present invention forms a magnetostrictive film having a magnetostrictive effect on the surface of a shaft so that the torsion torque applied to the shaft can be reduced. A magnetostrictive film used in a magnetostrictive torque sensor for detecting, wherein the magnetostrictive film exhibits mainly a magnetostrictive effect phase (hereinafter referred to as a magnetostrictive phase) and a hardness effect, at least in its surface portion. It is characterized by having a composite structure composed of a phase (hereinafter referred to as a hardening phase). As the magnetostrictive phase, Fe-Ni system, Co-Ni system
System, Fe-Al system, rare earth metal-Fe system, rare earth metal-
1. Any magnetostrictive alloy selected from the group consisting of Co-based alloys and composite alloys thereof, or any of the alloy systems described above selected from the group consisting of Mo, W, Zr, Ta and Nb 1. It is desirable to be composed of a magnetostrictive alloy containing at least one or more metal elements. Further, it is desirable that the hardening phase is composed of the boride or borosilicate of the magnetostrictive phase. Further, the magnetostrictive phase is finely dispersed in the matrix composed of the hardened phase, more preferably 5 to 10 μm in diameter.
It is desirable that the particles exhibit a finely dispersed structure as crystal grains of a certain degree. The manufacturing method of the magnetostrictive film according to the present invention,
Magnetostrictive alloy system selected from the group consisting of Fe-Ni system, Co-Ni system, Fe-Al system, rare earth metal-Fe system, rare earth metal-Co system, and composite alloy systems thereof, or any one of the above. A composition obtained by further adding B and / or Si to the magnetostrictive alloy system containing one or more metal elements selected from the group consisting of Mo, W, Zr, Ta and Nb in the alloy system of A magnetostrictive material having
The magnetostrictive material adhered to the shaft surface is then heated to heat-bond the magnetostrictive material to the shaft surface as a magnetostrictive film, and at least at the surface portion thereof, a boride of the magnetostrictive alloy. A hardened phase composed of a borosilicate or a matrix is used as a matrix, and a magnetostrictive phase composed of the magnetostrictive alloy is finely dispersed therein to form a composite structure. The heating is carried out at a shaft surface temperature of 1050 to 1090 ° C. and a heating time of 3 to
It is desirable that the heating is performed by high frequency induction heating under a processing condition of about 6 minutes.

[Function] Generally, as a factor causing the hysteresis,
There are two types: magnetic domain wall movement in a magnetostrictive material, magnetic irreversibility associated with rotational magnetization, and microscopic plastic deformation of the material. As a countermeasure against the above, reduction of the crystal magnetic anisotropy, and the present invention is
It was made possible by uniformly dispersing the minute magnetostrictive phase (preferably in the non-magnetic phase). As a measure against the above, the material rigidity of the surface was improved, that is, the hardness of the surface was improved. With this in mind, the present invention specifically describes a system with a large magnetostriction effect (for example, Fe-
Ni, Co-Ni, Fe-Al, etc.) so that a hardening phase of boride, borosilicate, etc. can be formed in B, Si or M.
One or more elements such as o, W, Zr, Ta, and Nb are contained in advance, and the material is attached to the shaft by, for example, a thermal spraying method, and then the magnetostrictive portion is heated (for example, high frequency heating) to form the magnetostrictive portion. A hardened phase made of a boride or a borosilicate of a magnetostrictive material alloy was used as a matrix, and a phase having a large magnetostrictive effect (for example, Fe—Ni phase) was heat-welded to a shaft material under the condition that the phase was finely dispersed in the matrix. Also,
High sensitivity was achieved by precipitating crystal grains with a large magnetostriction effect. In addition, the magnetic anisotropy is reduced by making the crystal of a fine magnetostrictive phase of about 5 to 10 μm, and the rigidity of the surface layer is increased by the presence of the hardened phase forming the matrix, which results in low hysteresis. Realized the characteristics. The composite phase composed of the magnetostrictive phase and the hardened phase according to the present invention can enhance the sensitivity and solve the factors of the hysteresis at one time, so that it is possible to provide a torque sensor with high sensitivity and low hysteresis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetostrictive film for a torque sensor and the method for manufacturing the same according to the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, in a shaft 2 having a magnetostrictive torque sensor detector according to an embodiment of the present invention, a magnetostrictive film 4 is formed on the surface of the shaft 2, and the magnetostrictive film 4 is firmly attached to the shaft 2. By being melt-bonded, the magnetostrictive torque sensor detection body 6 is formed. The magnetostrictive torque sensor detection body 6 formed on the shaft 2 has two rows of slit-shaped patterns that are inclined in opposite directions with respect to the shaft center of the shaft by about 45 degrees. Exciting coils (not shown) are arranged on the outer periphery of the shaft 2 on which each pattern is formed with a gap of about 2 mm or more. These exciting coils are connected to an AC power source (not shown) of several kHz to several hundred kHz. Therefore, a sufficiently saturated AC magnetic field is applied to the magnetostrictive films 4 and 4 as the magnetostrictive torque sensor detection body 6 formed on the surface of the shaft 2 as the power transmission shaft. Around the excitation coil, detection coils 8 are arranged in correspondence with the two rows of patterns of the magnetostrictive torque sensor detection body 6 formed on the shaft. One ends of the detection coils 8 and 8 are connected to each other, and the other ends thereof are connected to the differential detection means 10, respectively, to form a magnetostrictive torque sensor. As described above, the magnetostrictive torque sensor detection body 6 is formed in a two-row slit-shaped pattern in which the axes of the shaft are inclined in opposite directions to each other by about 45 degrees, so that the shaft rotates in one direction. In this case, a compressive stress acts on one pattern and a tensile stress acts on the other pattern. Therefore, by measuring the difference in change in magnetic permeability based on these stresses with the detection coils 8 and 8 and the differential detection means 10 as the magnetostrictive torque sensor,
The torque acting on the shaft 2 can be detected.
For example, a differential amplifier is used as the differential detection means. The difference in change in magnetic permeability may be detected using a magnetic head. Next, a method for manufacturing a magnetostrictive film according to an embodiment of the present invention will be described. First, the shaft 2 is prepared as shown in FIG. The shaft 2 is not particularly limited, but may be, for example, SNCM439 or YHD5.
0 or the like is used. The shaft 2 is first washed. After cleaning the shaft 2, as shown in FIG. 2B, the magnetostrictive film 4 for forming the torque sensor detection body is temporarily fixed to the outer periphery of the shaft 2 at a predetermined axial position.
As a method of temporarily fixing the formation, a raw material is melted in advance to form an ingot of a magnetostrictive material having a predetermined alloy composition, and a magnetostrictive material powder obtained by crushing this is subjected to thermal spraying such as plasma spraying, Alternatively, the raw material is melted and rapidly drawn to form a ribbon of a magnetostrictive material having a predetermined alloy composition, which is wound around a shaft and temporarily fixed by spot welding or the like. The former method is preferable because the magnetostrictive film can be finally and firmly bonded to the shaft. Incidentally, in this way, by preparing an ingot or ribbon of a magnetostrictive material having a predetermined alloy composition in advance, the composition of the magnetostrictive film is made uniform, and even when a thermal spraying method is used, It is possible to avoid problems such as variations in alloy structure and generation of defects due to differences in melting temperature. The plasma spray method
In general, a plasma is generated with a gas such as Ar, He, N ₂ , H ₂ or the like, and powder for forming a film is put into the plasma and melted and sprayed on the surface of the base material to form a film, If necessary, the thermal spraying operation is repeated until the desired layer thickness, for example, 200 to 300 μm is reached. The layer thickness is determined from the depth of penetration of the detected magnetic flux and the thickness range in which there are few defects in the coating after heat treatment as described later. If the coating is too thin, the effect of the base material will appear, and the output characteristics will fluctuate.On the other hand, if the coating is too thick, residual stress will occur along with the thickness of the thermal spray, and defects will easily occur on the outermost surface after finishing. Since this leads to a decrease in yield, it is desired that the layer thickness be within the above range. Also in the mode of winding the ribbon, the ribbon is wound so as to have the above-mentioned layer thickness, but the film thickness of the ribbon is preferably, for example, about 50 to 100 μm from the viewpoint of operability. As the magnetostrictive material forming the magnetostrictive film, Fe-Ni-based, Co-Ni-based, Fe
-Al system, rare earth metal-Fe system, rare earth metal-Co system,
Alternatively, these complex alloy systems, and further alloy systems containing one or more metal elements such as Mo, W, Zr, Ta, and Nb in these alloy systems, and hardened phases such as boride and borosilicate For this purpose, a material obtained by adding an element such as B or Si is used. As such a magnetostrictive material,
Specifically, Fe _x B _y Si _z (although Shikichu, x + y + z = 100,65 <x <80,
20 <y + z <35 and 2 <y <33. ), The following general formula _{Fe x Ni y Mo m B n} ( however Shikichu, x + y + m + n = 100,70 <x + y
<80, 30 <x <50, 20 <m + n <30, 2 <m
<10. ) Or the following general formula: Fe _x Co _y B _m Si _n (where x + y + m + n = 100, 75 <x + y
<90, 50 <x <80, 10 <m + n <25, 9 <m
<24. The following composition can be exemplified as a preferable one. Next, the shaft 2 in which the magnetostrictive film 4 is temporarily fastened is heat-treated under reduced pressure conditions using, for example, a high-frequency fusion bonding apparatus 14 as shown in FIG. This device 14
Has a vacuum chamber 16 for housing the shaft 2,
The shaft 2 is rotated by the shaft rotating device 18. The shaft rotation device 18 is controlled by the rotation control device 20. Inside the vacuum chamber 16, a coil 22 for heating the outer circumference of the shaft 2 with high frequency is installed. The vacuum chamber 16 is connected to a turbo molecular pump 24, a rotary pump 26, other pumps 28, and various control valves for maintaining a high degree of vacuum inside. The high frequency applied to the coil 22 is 50 to 400 kHz, for example 110 kHz, and the outer peripheral temperature of the shaft 2 heated by the coil 22 is controlled by the pyrometer 30 or the like.
About 050 to 1090 ° C is suitable. This heating temperature is a temperature sufficient for diffusion-bonding the temporarily fastened magnetostrictive material to the outer periphery of the shaft 2, and is determined in view of forming the composite structure of the magnetostrictive phase and the hardened phase as described above. It In order to obtain such a heating temperature, the high frequency power is set to 0.5 to 3 kW at the above frequency. A heating time of about 3 to 6 minutes is suitable. That is, if the heating time is less than 3 minutes, the composite structure of the magnetostrictive phase and the hardened phase does not appear, while if the heating time exceeds 6 minutes, the particle size of the magnetostrictive phase dispersed in the matrix of the hardened phase. Is large, magnetic anisotropy is large, and hysteresis is also large. As also the degree of reduced pressure, 10 ^- 2 to 10 ^- 5 Torr, for example, 10 ^- 3
It is in a vacuum state of about Torr. The atmosphere gas can be replaced with an inert gas such as Ar.
Further, the shaft is rotated at about 10 to 50 rpm in order to perform the treatment almost uniformly over the entire circumference of the shaft 2. By such heat treatment, the magnetostrictive film 4 and the shaft 2 are firmly and uniformly diffused and bonded, and at least the magnetostrictive film 4 is formed.
On the surface portion of, a composite structure composed of a magnetostrictive phase and a hardening phase is formed, for example, as shown in FIG. In this composite structure, the magnetostrictive phase is preferably a fine structure having a grain size of about 5 to 10 μm in order to reduce the magnetic anisotropy and reduce the hysteresis. Further, during the heat treatment, diffusion of the shaft material component from the shaft 2 to the magnetostrictive film 4 occurs, but since the heat treatment time is extremely short, diffusion occurs only at the bonding interface, and near the outermost surface of the magnetostrictive film 4. Therefore, the inverse magnetostriction characteristic of the magnetostrictive film 4 is not deteriorated. Next, as shown in FIG. 2 (C), two rows in which the surface of the amorphous magnetostrictive film 4 is inclined along the outer periphery of the shaft 2 in directions opposite to each other with an inclination of about 45 degrees with respect to the axis. Are processed into a slit-shaped pattern to form the torque sensor detection bodies 6 and 6. Such a pattern is called a so-called chevron pattern, and means for forming this pattern is not particularly limited, but a machining method such as rolling is used. The torque sensor detectors 6 and 6 formed in this way have excellent performances of high sensitivity and low hysteresis, are bonded to the shaft 2 very firmly, and have sufficient heat resistance. Therefore, the sensitivity and linearity of the stress-magnetic characteristic conversion are excellent even in a severe operating environment such as high torque and high temperature such as an automobile engine. It should be noted that the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the present invention. For example, in the magnetostrictive film, the heating method for forming the composite structure composed of the magnetostrictive phase and the hardened phase is not limited to the high frequency induction heating method, and a vacuum electric furnace heating method or the like can be used. Further, the hardening phase does not necessarily have to be composed of a boride or borosilicate of a magnetostrictive alloy, but may be composed of, for example, a carbide or a nitride other than this. Next, more specific examples of the present invention will be described in comparison with conventional examples and comparative examples, but the present invention is not limited to these examples. Example composition Fe _40.0 Ni _38.0 Mo _3.8 B _18.2 (atomic ratio) with an average particle diameter of 30 μm as an alloy powder was used as a raw material powder, and a diameter of 7.3 m
Fe-based shaft of m (composition is Fe balance in atomic ratio; Mn13
%; Cr 10%; Ni2.2%; V2.0%; Si1.0%; C
0.6%) by thermal spraying method with a thickness of 300 μm and a width of 35 mm
A thermal sprayed film was prepared. The spraying conditions are plasma sprayer,
Ar gas flow rate 40 liters / min, plasma input power 500 A × 70 V, alloy powder supply rate 18 g / min,
Scanning was repeated at a sample (shaft) rotation speed of 650 rpm and a plasma torch scanning speed of 1.5 cm / sec.
Further, the Fe-based shaft material and the thermal spray material were melt-bonded by high frequency induction heating. The conditions for fusion bonding are as follows. Shaft material surface temperature: 1070 ° C. Vacuum degree: 10 ⁻³ Torr Temperature rising time: 10 seconds Heating time: 3 to 6 minutes Frequency: 130 kHz Power: 0.8 kW Shaft rotation speed: 10 rpm FIG. The output characteristics are shown. The sensitivity of ± 1 Nm when the gain of the amplifier is 20 times is 9
It was 8.71 mV and the hysteresis was 0.9%. FIG. 5 shows a detection part (sprayed film part) manufactured according to this embodiment.
The cross-sectional structure of is shown. It is a structure composed of two phases of a fine phase (hereinafter a phase) of about 5 to 10 μm and a matrix (hereinafter b phase). When the hardness of each phase was measured at 5 points by a 50 gf micro Vickers hardness meter, the average hardness was a phase 374 and a phase b 569. Also,
Table 1 shows the compositional analysis values of each phase by an electron beam microanalyzer. The a phase is a Fe-Ni phase generally called permalloy having a large magnetostriction effect, and the b phase is
Similarly, the main component is Fe-Ni phase, and Mo is included.
Further, B is contained in a high concentration. Powder X-ray diffraction of the separately measured magnetostrictive phase revealed that the magnetostrictive phase was the Mo ₂ FeB ₂ phase in addition to the Fe-Ni phase. Therefore b
It is considered that the phase has a large hardness because it is a boride phase, and the a phase has a small hardness because the B concentration is 0. From these facts, it can be said that a is a phase exhibiting a large magnetostriction effect, and b is a phase exhibiting a magnetostriction effect but mainly increasing the rigidity of the surface layer. Furthermore, a phase is 5 to 1
It is considered that the magnetic anisotropy is small because of the fine structure of about 0 μm. The small magnetic anisotropy reduces the hysteresis. From the above, the presence of the a phase having a high magnetostrictive effect causes an increase in sensitivity, the presence of the b phase which is a hardening phase forming a matrix, and the fine structure of the a phase cause a low hysteresis characteristic. It is clear that The structure of such a two-phase structure having a fine magnetostrictive phase is determined by the temperature and time conditions during the melt bonding, and the range is 1050 to 10 on the surface temperature of the shaft material.
It appeared to be 90 ° C for 3-6 minutes.

[Table 1] Conventional Example Using a Ni ₅₀ Fe ₅₀ (atomic ratio) powder having an average particle size of 30 μm as a raw material, a 300 μm thick film was formed on the same Fe-based shaft material as in the example by a thermal spraying method. The thermal spraying conditions were plasma spraying machine, Ar gas flow rate 43 liter / min, plasma input power 500A × 70V, alloy powder supply rate 20g /
Scanning is repeated 20 times at the following conditions: min, sample (shaft) rotation speed: 700 rpm, and plasma torch scanning speed: 1.0 cm / sec. Further, the shaft material and the thermal spray material were joined by fusion joining using the same high frequency induction heating device as in the example. The conditions for fusion bonding are as follows. Shaft material surface temperature: 1250 ° C. Vacuum degree: 10 ⁻³ Torr Heating time: 3 minutes and 30 seconds Frequency: 130 kHz Power: 2.5 kW Shaft rotation speed: 10 rpm FIG. 6 shows a load torque-output characteristic according to a conventional example. The output after passing through an amplifier with a gain of 20 is ± 1 N · m and 8
The sensitivity is relatively high at 5.97 mV, but the hysteresis is large at 5.82%. FIG. 7 shows a cross-sectional structure of a detection part (sprayed film part) manufactured by a conventional example. The structure has a grain size of about 7 to 8 μm. The average hardness measured at 5 points with a 50 gf Micro Vickers hardness meter was 152.
Further, the compositional analysis values by the electron beam microanalyzer are as shown in Table 2, Fe: 50.4 atom%, Ni: 49.
It was 6 atomic%. Therefore, it is clear that since the hardness is small, the rigidity is small and the hysteresis is large.

[Table 2] Comparative Example Composition used in Examples Fe _40.0 Ni _38.0 Mo _3.8 B _18.2
(Atomic ratio) as alloy powder as raw material powder, diameter 7.
A 3 mm Fe-based shaft was sprayed under the same conditions as in the examples. Further, the Fe-based shaft material and the thermal spray material were melt-bonded by high frequency induction heating. The conditions for fusion bonding are as follows. Shaft material surface temperature: 1150 ° C Vacuum degree: 10 ^-2 Torr Temperature rising time: 10 seconds Heating time: 7 minutes 10 seconds Frequency: 130 kHz Power: 1.2 kW Shaft rotation speed: 10 rpm Figure 8 shows load torque-output according to a comparative example. Show the characteristics. The sensitivity of ± 1 Nm when the gain of the amplifier is 20 times is 9
It was 1.75 mV and the hysteresis was 2.7%. FIG. 9 shows the cross-sectional structure of the detection part (sprayed film part) produced by the comparative example. It is a structure composed of grains (hereinafter c phase) of about 60 μm and matrix (hereinafter d phase). The average value of the hardness of each phase by a 50 gf micro Vickers hardness meter was d phase 525 versus c phase 344. Also,
Table 3 shows the compositional analysis values of each phase by an electron beam microanalyzer. Like the phase a in the example, the phase c is
The phase having a large magnetostriction effect, and the d phase, like the b phase of the embodiment, exhibits a magnetostriction effect but is a hard phase containing Mo and B. However, since the c phase has a structure of large particles of about 60 μm, it is considered that the magnetic anisotropy is larger than that in the example, and therefore the hysteresis is also larger.

[Table 3]

As described above, according to the present invention, the magnetostrictive portion has, as a matrix, a hardened phase composed of, for example, a boride or a borosilicate of a magnetostrictive material alloy, and is made of, for example, F
Since it is possible to form a magnetostrictive film in which a phase having a large magnetostriction effect such as e-Ni, Co-Ni, and Fe-Al is finely dispersed in the matrix, it is possible to simultaneously improve sensitivity and reduce hysteresis.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a magnetostrictive torque sensor.

FIG. 2 is a schematic view showing a method of manufacturing a shaft having a magnetostrictive torque sensor detector according to an embodiment of the present invention.

FIG. 3 is a schematic view of a high frequency induction heating treatment apparatus used in an embodiment of the present invention.

FIG. 4 is a graph showing load torque-output characteristics in one example of the present invention.

FIG. 5 is a photomicrograph of the cross-sectional structure (metal structure) of the sprayed film portion produced in one example of the present invention.

FIG. 6 is a graph showing load torque-output characteristics in a conventional example.

FIG. 7 is a micrograph of a cross-sectional structure (metal structure) of a sprayed film portion manufactured in a conventional example.

FIG. 8 is a graph showing load torque-output characteristics in a comparative example.

FIG. 9 is a micrograph of a cross-sectional structure (metal structure) of a sprayed film portion produced in Comparative Example.

[Explanation of symbols]

 2 ... Shaft 4 ... Magnetostrictive film 6 ... Magnetorestrictive torque sensor detector.

Claims (7)

[Claims] 1. A magnetostrictive film used in a magnetostrictive torque sensor for detecting a torsion torque applied to a shaft by forming a magnetostrictive film having a magnetostrictive effect on the surface of the shaft, wherein the magnetostrictive film comprises: A magnetostrictive film for a torque sensor, which has a composite structure mainly composed of a phase exhibiting a magnetostrictive effect and a phase mainly exhibiting a hardness effect, at least on a surface portion thereof. 2. The phase exhibiting the magnetostrictive effect is Fe--Ni.
System, Co-Ni system, Fe-Al system, rare earth metal-Fe
System, a rare earth metal-Co system, and any magnetostrictive alloy selected from the group consisting of these composite alloy systems, or any of the alloy systems described above from the group consisting of Mo, W, Zr, Ta and Nb. The magnetostrictive film for a torque sensor according to claim 1, which is composed of a magnetostrictive alloy containing one or more selected metal elements. 3. The phase exhibiting the effect of hardness is composed of a boride or borosilicate of the magnetostrictive alloy.
Alternatively, the magnetostrictive film for a torque sensor according to item 2. 4. The magnetostrictive film for a torque sensor according to claim 1, wherein the phase exhibiting the magnetostrictive effect has a structure in which the phase exhibiting the hardness effect is finely dispersed in a matrix. 5. The phase exhibiting the magnetostrictive effect has a diameter of 5 to 10
The magnetostrictive film for a torque sensor according to claim 4, wherein the magnetostrictive film has a structure in which crystal grains having a size of about μm are finely dispersed in a matrix including a phase exhibiting the effect of hardness. 6. A method of manufacturing a magnetostrictive film used in a magnetostrictive torque sensor for detecting a torsional torque applied to a shaft by forming a magnetostrictive film having a magnetostrictive effect on the surface of a shaft, comprising: Magnetostrictive alloy system selected from the group consisting of Ni-based, Co-Ni-based, Fe-Al-based, rare earth metal-Fe-based, rare earth metal-Co-based, and composite alloys thereof, or any of the alloys described above. It has a composition obtained by further adding B and / or Si to a magnetostrictive alloy system containing one or more metal elements selected from the group consisting of Mo, W, Zr, Ta and Nb in the system. Magnetostrictive material,
Adhered to the surface of the shaft, and then heating the magnetostrictive material adhered to the surface of the shaft,
The magnetostrictive material is thermally fused to the shaft surface as a magnetostrictive film, and at least the surface portion thereof has a matrix of a hardened phase made of a boride or borosilicate of the magnetostrictive alloy, and a magnetostrictive phase made of the magnetostrictive alloy is formed in the matrix. A method of manufacturing a magnetostrictive film for a torque sensor, which comprises forming a finely dispersed composite structure. 7. The heating is carried out at a shaft surface temperature of 1050 to 1090.
The method for producing a magnetostrictive film for a torque sensor according to claim 6, wherein the magnetostrictive film for a torque sensor is performed by high-frequency induction heating under processing conditions of a temperature of about 3 to 6 minutes.