JPH10176966A - Magnetostriction-detecting body for torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability against breaking and separation, by continuously setting a magnetostriction film and a non-magnetic film at an outer circumferential face of a torque transmission shaft, and thinning an end part of the magnetostriction film gradually. SOLUTION: A masking jig is set so that a gap is formed between an inner face of the masking jig and a torque transmission shaft 5. After the masking jig is preheated, a magnetic material is plasma sprayed to form a magnetostriction film 3. A thickness of an end part of the magnetostriction film 3 is gradually reduced, so that the magnetostriction film is resistant to separation. The masking jig is separated, and a non-magnetic material is sprayed to the torque transmission shaft 5 to form a non-magnetic film 6. Thereafter, the torque transmission shaft 5 is treated with heat in vacuum. The magnetostriction film 3 is exposed and cut until the film becomes a predetermined thickness. The end part of the magnetostriction film 3 is inclined and the non-magnetic film 6 swells over the end part, whereby the magnetostriction film 3 is improved in durability. Moreover, since a part other than the magnetostriction film 3 is coated with the non-magnetic film 6, influences by a ferromagnetic body can be shut even if the ferromagnetic body is used as the torque transmission shaft 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive detector for use in a magnetostrictive torque sensor capable of detecting torque in a non-contact manner. More specifically, the present invention relates to a magnetostrictive detector of a torque sensor having a magnetostrictive film and a nonmagnetic film.

[0002]

2. Description of the Related Art Normally, when a torque is applied to a torque transmitting shaft provided with a magnetostriction detecting layer, a main stress is applied to the magnetostrictive detecting layer in a direction of 45.degree. I do. It becomes magnetically anisotropic, causing a change in magnetic permeability. By outputting the change in magnetic permeability depending on this torque as a change in the inductance of the solenoid coil as an electric signal, the magnitude and direction of the torque can be changed. It is to detect. FIG. 19 is a side view of the conventional torque transmission shaft. In the figure, reference numeral 101 denotes a magnetostrictive film provided on the outer peripheral surface of the torque transmission shaft 102.

[0003] Regarding the magnetostrictive detector of the torque sensor,
All technologies have been proposed. Of these methods, the following three methods are mainly used to form a magnetostrictive film on the outer peripheral surface of the torque transmission shaft by thermal spraying. First, there is a method of forming a magnetostrictive film 101 by spraying a magnetostrictive material onto a torque transmission shaft 102 in a predetermined shape using masking. FIG. 20 is a cross-sectional view of the torque transmission shaft 102 created by this method.
As shown in FIG. The magnetostrictive film 101 is provided discontinuously on the outer peripheral surface of the torque transmission shaft 102. Next is the magnetostrictive film 101
Is formed over the entire circumference of the shaft, and then the magnetostrictive film 101 is processed into a predetermined shape by cutting or etching. Also in this case, the cross-sectional shape of the torque transmission shaft 102 is as shown in FIG. Then, as shown in FIG. 21, a method is provided in which the surface of the torque transmission shaft 102 is processed in advance to provide the unevenness 103, and the magnetostrictive film 101 is formed on the surface.

However, the conventional magnetostrictive detector for a torque sensor has the following problems. (1) In the method of forming the magnetostrictive film 101 by masking, the adhesion area of the magnetostrictive film 101 was small and the durability was poor. When the torque transmission shaft 102 is made of a ferromagnetic material, the magnetostrictive film 101 has to be made thick to eliminate the influence. (2) In the method of cutting or etching after forming the magnetostrictive film 101, when the formed magnetostrictive film 101 is partially removed, the film strength is reduced and the durability is deteriorated. When the torque transmission shaft 102 is made of a ferromagnetic material, the magnetostrictive film 101 has to be made thick to eliminate the influence.

(3) Unevenness 10 provided on torque transmission shaft 102
In the method of forming the magnetostrictive film 101 on the surface of No. 3, the durability of the magnetostrictive film 101 was increased, but the strength of the torque transmission shaft 102 was reduced due to the provision of the irregularities 103. Further, since the magnetostrictive film 101 is formed on the entire circumference, the influence of the magnetostrictive film 101 in the concave portion is likely to occur. Explaining the reason why this effect is likely to occur, the sprayed coating varies in film thickness and surface roughness due to various factors such as aging of electrodes and difference in particle size distribution between sprayed materials. Therefore, in the case of equipment parts such as torque sensors, after providing a sufficient film thickness,
Grinding must be performed to match the set film thickness. However, in a torque sensor provided with irregularities, the thickness of the convex portions can be made constant by grinding, but the thickness and surface roughness of the magnetostrictive film in the concave portions vary widely. come. In the case of atmospheric spraying, an oxide film is formed on the surface of the magnetostrictive film in the concave portion, which adversely affects the magnetostrictive sensitivity. Therefore, in the case of a torque sensor having unevenness, unevenness larger than the theoretically necessary difference in unevenness is preliminarily processed in consideration of the unevenness of the film thickness and surface roughness at the time of thermal spraying and the influence of the oxide film on the concave surface. And the recesses must be further processed. Here, providing the irregularities more than necessary reduces the strength of the torque transmission shaft as described above. Further, when the torque transmission shaft is a ferromagnetic material, the magnetostrictive film must be thickened, and the influence of the concave portion increases.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a magnetostrictive detector for a torque sensor which is inexpensive, has good durability, and suppresses generation of iron oxide. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned object, and the gist of the present invention is to form a magnetostrictive film on the outer peripheral surface of a torque transmission shaft, and form a non-magnetic film on the magnetostrictive film. A magnetic film is provided, or a non-magnetic film is formed on the outer peripheral surface of the torque transmission shaft, a magnetostrictive film is provided on the non-magnetic film, and the magnetostrictive film and the non-magnetic film are ground. In the magnetostrictive detector for a torque sensor. Further, a magnetostrictive film is formed on a torque transmission shaft having irregularities on the outer peripheral surface, and a nonmagnetic film is provided on the magnetostrictive film, or a nonmagnetic film is formed on the torque transmitting shaft having irregularities on the outer peripheral surface. A magnetostrictive film for a torque sensor is characterized in that a magnetostrictive film is provided on a nonmagnetic film, and the magnetostrictive film and the nonmagnetic film are ground.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetostrictive detector for a torque sensor according to the present invention will be described in detail with reference to the drawings. A magnetostrictive detector for a torque sensor in which a magnetostrictive film and a nonmagnetic film are continuous on the outer peripheral surface of a torque transmission shaft is formed by a thermal spraying method.

First Embodiment In this embodiment, first, a blast process is performed on a torque transmission shaft, and a masking jig is mounted. As shown in FIGS. 1 and 2, the masking jig 1 is a hollow cylinder made of metal and has an inner diameter d slightly larger than the diameter of the torque transmission shaft. Further, a slit 2 is provided obliquely to the longitudinal direction of the cylinder. Next, the masking jig 1 is set so that a gap is formed between the inner surface of the masking jig 1 and the torque transmission shaft, and after preheating, the magnetic material is plasma-sprayed to form a magnetostrictive film. By providing a gap between the masking jig 1 and the torque transmission shaft, the masking jig 1 can be removed from the torque transmission shaft even after the formation of the magnetostrictive film. Then, as shown in FIG. 3, the thickness T of the end portion 4 of the magnetostrictive film 3 gradually decreases, and a film resistant to peeling is formed. The magnetostrictive film 3 is formed by plasma spraying a magnetic material on the torque transmission shaft 5.

Then, the masking jig 1 is removed, and a non-magnetic material is sprayed on the torque transmission shaft 5 to form a non-magnetic film. Thereafter, the torque transmission shaft 5 is heat-treated in a vacuum.
Further, the magnetostrictive film 3 is ground until the magnetostrictive film 3 is exposed and its thickness T reaches a predetermined thickness. FIG. 4 shows a cross-sectional view of the torque transmission shaft 5 thus created. In the first embodiment, the end 4 of the magnetostrictive film has the inclination angle θ as described above.
Since the nonmagnetic film 6 is overlaid on the end 4, the durability of the magnetostrictive film 3 is improved. Further, since the portion other than the magnetostrictive film 3 is covered with the non-magnetic film 6, even if a ferromagnetic material is used for the torque transmission shaft 5, the influence can be cut off.

Second Embodiment In this embodiment, as shown in FIG. 5, a magnetostrictive film and a non-magnetic film are provided on a torque transmission shaft provided with irregularities. A plurality of grooves are provided obliquely to the longitudinal direction of the torque transmission shaft 7. Next, after performing blast processing on the torque transmission shaft 7, the magnetic material is plasma-sprayed by preheating and the magnetostrictive film 3 is formed. Then, a non-magnetic material is plasma-sprayed on the torque transmission shaft 7 to form the non-magnetic film 6. Thereafter, the torque transmission shaft 7 is heat-treated in a vacuum. further,
When the torque transmission shaft 7 is ground so that the magnetostrictive film 3 is exposed and the film thickness of the magnetostrictive film 3 is constant, the nonmagnetic film 6 is formed in the groove 8 and the nonmagnetic film 6 is formed on the outer peripheral surface. A torque transmission shaft 7 having the films 6 alternately and continuously provided is created. In this method, since the magnetostrictive film 3 is formed over the entire circumference and the nonmagnetic film 6 is formed in the groove 8, the strength of the coating is increased, the peeling of the outer circumference during grinding is less likely to occur, and the durability is improved. . When the torque transmission shaft 7 is a ferromagnetic material, the non-magnetic film 6 formed in the groove 8 eliminates the influence of the magnetostrictive film 3 and the torque transmission shaft 7 thereunder, so that the magnetostrictive characteristics are improved. .

Hereinafter, Examples 1 and 2 in which the magnetostrictive detector for a torque sensor according to the present invention is manufactured based on the first or second embodiment will be described. Example 1 In this example, first, a blast process was performed on the torque transmission shaft, and a masking jig was attached. As shown in FIGS. 1 and 2, the masking jig 1 is made of S45C,
A hollow cylinder with an outer diameter D of φ12 mm and an inner diameter d
Is larger than the diameter of the torque transmission shaft by 1 to 2 mm. Further, a slit 2 having a width of 2.3 mm is provided in a direction of ± 45 ° with respect to the longitudinal direction of the cylinder. Next, 500 between the inner surface of the masking jig 1 and the torque transmitting shaft.
The masking jig 1 was set so that a gap of 1 μm to 1 mm was formed, and after preheating, a magnetic material was plasma-sprayed to form a magnetostrictive film. By providing a gap between the masking jig 1 and the torque transmission shaft, the masking jig 1 can be removed from the torque transmission shaft even after the formation of the magnetostrictive film,
In addition, the thickness T of the end portion 4 of the formed magnetostrictive film gradually decreases (that is, 10 ° ≦ θ <90 ° in FIG. 3), and a film resistant to peeling is formed. The magnetostrictive film 3 is formed by plasma spraying Fe-40Ni-6Al, which is a magnetic material, under the conditions shown in Table 1.

[0013]

[Table 1]

Then, the masking jig 1 was removed, and Al-12Si as a nonmagnetic material was sprayed on the torque transmitting shaft 5 under the conditions shown in Table 1 to form a nonmagnetic film. Thereafter, the torque transmission shaft 5 was heat-treated in a vacuum at 400 ° C. for 1 hour. Furthermore, the magnetostrictive film was ground until the magnetostrictive film was exposed and the film thickness T became 150 μm. FIG. 4 shows a cross-sectional view of the torque transmission shaft 5 thus manufactured. In the first embodiment, the end 4 of the magnetostrictive film forms the inclination angle θ as described above, and the end 4 is overlaid with Al. improves. Further, since the portion other than the magnetostrictive film 3 is covered with the non-magnetic film 6, even if a ferromagnetic material is used for the torque transmission shaft 5, the influence can be cut off.

Example 2 A torque transmission shaft 5 having a material of S45C and an outer diameter of φ12 mm, having a width of 2.4 m in a ± 45 ° direction with respect to the longitudinal direction.
Eight grooves were formed. After blasting the torque transmission shaft 7, it was preheated and the magnetic material was plasma sprayed to form the magnetostrictive film 3. At this time, the materials used and the spraying conditions were the same as those in Example 1. Next, under the same conditions as in Example 1, non-magnetic material Al-12Si was plasma-sprayed to form non-magnetic film 6. After this, 400
The torque transmission shaft 7 was heat-treated in vacuum at 1 ° C. for 1 hour.

Further, when the torque transmitting shaft 7 is ground so that the magnetostrictive film 3 is exposed and the film thickness of the magnetostrictive film 3 is constant at 150 μm, the Al nonmagnetic film 6 is formed in the groove 8 and the outer periphery is formed. A torque transmission shaft 7 having a magnetostrictive film 3 and a non-magnetic film 6 alternately and continuously provided on the surface was prepared. FIG. 5 shows a cross-sectional view of the torque transmission shaft 7. In this method, the magnetostrictive film 3
Is formed over the entire circumference and the non-magnetic film 6 is formed in the groove portion 8, so that the film strength is increased, the peeling of the outer periphery during grinding is less likely to occur, and the durability is also improved.
When the torque transmission shaft 7 is a ferromagnetic material, the non-magnetic film 6 formed in the groove 8 eliminates the influence of the magnetostrictive film 3 and the torque transmission shaft 7 thereunder, so that the magnetostrictive characteristics are improved. .

Improvement of Magnetostrictive Material Further, a magnetostrictive detector for a torque sensor in which the magnetostrictive film 3 and the nonmagnetic film 6 are sprayed on the outer peripheral surfaces of the torque transmission shafts 5 and 7 has been described. The improvement of is described below. The main conventionally used magnetostrictive material for thermal spraying is Ni, 15% to 60% Fe-Ni alloy (as disclosed in Japanese Patent Application Laid-Open No. 4-34643, particularly, hydrogen reduction for oxide reduction). In which a heat treatment at 900 ° C. to 1100 ° C. is performed), a 30% to 60% Co—Fe alloy (JP-A-5-52678), and a 5% to 15% Al—
Fe-based alloys (Japanese Unexamined Patent Publication No. Hei 5-322573) and amorphous alloys (amorphous magnetic alloys listed in Japanese Patent Publication No. 2-42418).

However, the conventional magnetostrictive material has the following problems. (1) When spraying an Fe-based material in the atmosphere, oxygen in the air was taken into the film, and iron oxide (FeO) was formed.
Thereafter, heat treatment was performed in a non-oxidizing atmosphere to remove residual stress, but the heat treatment changed the FeO into Fe ₃ O ₄ . Since Fe ₃ O ₄ is a ferromagnetic material called magnetite, there is a possibility that a magnetic field may remain during magnetostriction measurement, causing hysteresis and drift. (2) In order to suppress the generation of magnetite as described above, there is a method using reduced pressure spraying in which spraying is performed under reduced pressure. But,
This method requires a batch processing as a processing method, requires a large capital investment, and is costly. (3) Reduce iron oxide in a reducing atmosphere such as hydrogen.
Although a method of performing heat treatment at from 1 to 1100 ° C. has been proposed, the cost is high and management is difficult. Therefore, in the present invention, Fe ₃ O ₄ (magnetite) is obtained by heat-treating the Fe—Ni alloy and the Fe—Co alloy in combination with an element that suppresses the formation of iron oxide even after heat treatment for removing residual stress.
A magnetostrictive detector for a torque sensor was manufactured using a magnetostrictive sprayed material that does not generate. The third embodiment will be described.

Third Embodiment A plurality of grooves 10 are formed on a torque transmission shaft 9 in a chevron shape. As can be seen from FIG. 6, the groove 10 is formed obliquely to the axial direction of the torque transmission shaft 9.

An alloy powder is plasma-sprayed on the torque transmission shaft 9 to form a magnetostrictive film having a constant thickness. Thereafter, a non-magnetic material is sprayed to form a non-magnetic film, and a heat treatment is performed in a vacuum. Then, the magnetostrictive film and the non-magnetic film are ground.
Therefore, in the cross section of the torque transmission shaft 9, as shown in FIG. 8, a portion where the magnetostrictive film 3 is exposed and a portion where the nonmagnetic film 6 is thickened alternately exist. The build-up of the non-magnetic material blocks the magnetostriction of the groove 10 and enhances the shape magnetic anisotropy of the magnetostrictive film 3 provided on the projection 11.

Next, Examples 3 and 4 according to the third embodiment will be described. Example 3 A chevron-shaped four grooves having a width of 3 mm and a depth of 200 μm were previously formed on a torque transmission shaft having a material of S45C and a diameter of 12 mm. FIG. 6 is a side view of the torque transmission shaft.
FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG.
As can be seen from FIG. 6, this groove 10 is
At an angle of 45 ° with respect to the axial direction. This torque transmission shaft 9 is plasma-sprayed with Fe-38Ni-6Al alloy powder (hereinafter, referred to as sample 1) or Fe-40Ni alloy powder (hereinafter, referred to as sample 2) to have a film thickness of about 25.
A 0 μm magnetostrictive film was formed. Thermal spraying conditions are as shown in Table 2.

[0022]

[Table 2]

Thereafter, a non-magnetic material Al is sprayed to form a non-magnetic film 6 having a thickness of 150 μm or more, and a heat treatment is performed at 400 ° C. for 1 hour in a vacuum. Finished to 3 mm torque transmission shaft. Therefore, in the cross section of the torque transmission shaft 9, as shown in FIG. 8, a portion where the magnetostrictive film 3 is exposed and a portion where the non-magnetic film 6 is overlaid with Al are alternately present. The build-up of Al, which is a nonmagnetic material, blocks the magnetostriction of the groove 10 and enhances the shape magnetic anisotropy of the magnetostrictive film 3 provided on the convex portion 11.

Example 4 FIGS. 9 to 12 show X-ray diffraction charts of Samples 1 and 2 after thermal spraying and after heat treatment. As can be seen from these charts, Samples 1 and 2 were obtained immediately after thermal spraying.
There was iron oxide (FeO) due to entrainment of oxygen, which is common in thermal spraying in the atmosphere. However, when heat treatment was performed at 400 ° C. for 1 hour in a vacuum, in Sample 2, oxidation due to oxygen taken into the coating proceeded, and Fe ₃
It changed to O ₄ (magnetite). Since Fe ₃ O ₄ (magnetite) is a ferromagnetic material, it has a function of retaining a magnetic force, and is an undesirable substance as a magnetostrictive material. In contrast, in Sample 1, the generation of Fe ₃ O ₄ (magnetite) is suppressed by the addition of Al, the peak of Fe ₃ O ₄ (magnetite) was observed.

The method of measuring the magnetostriction will now be described measuring method of the magnetostrictive properties. As shown in FIG. 13, a coil 12
Were arranged, a torsional torque was applied to one end of the torque transmission shaft, and the relationship between the output voltages was measured. Table 3 shows the measurement conditions, and Table 4 shows the results.

[0026]

[Table 3]

[0027]

[Table 4]

In Table 4, the output sensitivity indicates an output voltage per 1 N · m. The linearity is calculated by plotting the output voltage values when the torque is applied equally in the forward and reverse directions on a graph, connecting the output voltage values of the maximum forward and reverse torques with a straight line, and plotting the voltage from this straight line. This is a value indicating the maximum deviation of the value as a percentage of the full-scale voltage.
The hysteresis is a value in which the maximum deviation amount of the voltage value is expressed as a percentage of the full-scale voltage when the same torque is applied while continuously applying the reverse torque. The temperature stability is a value indicating the output voltage fluctuation width when the sensor ambient temperature is -30 ° C to 80 ° C, as a percentage of the full-scale voltage.

The magnetostriction characteristics of a conventional torque transmission shaft in which a torque transmission shaft is machined to form a predetermined shape with a concavo-convex portion and a magnetostrictive film is formed on the surface are also shown for comparison. This torque transmission shaft is made of a material S45C, a shaft material having a groove unevenness of 500 μm, sprayed under the conditions shown in Table 1 until the film thickness becomes about 250 μm, and heat-treated in a reducing atmosphere at 1000 ° C. Is ground to a thickness of 150 μm. Compared to this conventional torque transmission shaft, the torque transmission shafts of Examples 1 and 2 have improved magnetostriction characteristics in all items of sensitivity, linearity, hysteresis, and temperature stability. This is because the effect of the concave portion of the torque transmission shaft or the magnetostrictive film can be cut off by the shielding effect of the nonmagnetic material, and the effect of the shape magnetic anisotropy of the magnetostrictive film exposed at the convex portion is enhanced. The magnetostriction sensitivity can be improved by the thickness and composition of the magnetostrictive film.

Further, under the measurement conditions shown in Table 5, the magnetostriction characteristics (output sensitivity, linearity, hysteresis, and temperature stability) of the samples 1 and 2 shown in Example 3 were measured. Table 6 shows the measurement results.

[0031]

[Table 5]

[0032]

[Table 6]

As can be seen from Table 6, Sample 2 is inferior to Sample 1 in the two magnetostrictive characteristics of linearity and hysteresis. This is Fe ₃ O ₄ (magnetite)
This is the effect of the magnetization due to generation, and the zero point shifts little by little when the application and release of the load are repeated. On the other hand, the generation of FeO is small, and Fe ₃
Sample 1 in which O ₄ (magnetite) was not generated showed excellent results in all of output sensitivity, linearity, hysteresis, and temperature stability. The heat treatment may be performed at 400 ° C. for 1 hour in a non-oxidizing atmosphere.
No heat treatment in a hydrogen atmosphere or the like is required.

Other Embodiments 1) In the first and second embodiments, eight magnetostrictive films having a width of 2.3 mm are formed on the outer peripheral surface of the torque transmission shaft. However, the width and the number of the magnetostrictive films are not limited to these. It may be changed according to the required performance. 2) In Examples 1 to 3, Fe-4 was used as the material for thermal spraying.
0Ni-6Al alloy powder, Fe-38Ni-6Al alloy powder or Fe-40Ni alloy powder was used. But,
It is not necessary to be limited to these materials, and other components such as Fe-Ni-Al-based alloys, Fe-Ni-based alloys,
The magnetostrictive film may be formed of an o-Fe alloy, an Fe-Al alloy, an amorphous material, or the like. A non-magnetic film A
Although the l film was formed, the film is not limited to the Al film, and Cu, Ti, or other materials exhibiting a magnetic shielding effect may be used.

3) The conditions for the heat treatment differ depending on the magnetostrictive film used.
1100 ° C, Co-Fe alloy is heated and quenched to about 1200 ° C in order to make the components uniform, then 800 ° C to 85 ° C.
Heat treatment at 0 ° C. In addition, it is known that, in order to make the components uniform, it is preferable that the Fe-Al alloy be heated to about 800 ° C. and rapidly cooled, then heated at 400 ° C. and then gradually cooled. However, under these conditions, non-magnetic material A
After the thermal spraying of l, it is difficult to perform a heat treatment, and it is necessary to select the nonmagnetic film 6 according to the heat treatment conditions. Fe
-In the case of a Ni-Al alloy, 4
The heat treatment may be performed at 00 ° C. for one hour in a non-oxidizing atmosphere. For this reason, Al which has good workability and is inexpensive can be used for the non-magnetic alloy, and the cost for the heat treatment is preferably inexpensive as compared with the others. 4) The forms of the magnetostrictive film 3 and the nonmagnetic film may be, for example, those shown in FIG. 14 other than those described in the first to third embodiments. In other words, the torque transmission shaft 1 having irregularities
After forming the non-magnetic film 6 on the entire surface 2 and providing the magnetostrictive film 3 thereon, heat treatment and grinding are performed to leave the magnetostrictive film 3 in the concave portion 13. In this case, since the heat treatment must be performed after the nonmagnetic film 6 is formed, care must be taken in selecting the heat treatment temperature or the material of the nonmagnetic film so that the nonmagnetic film is not softened or melted.

5) In the first embodiment, the magnetostrictive film is formed to be discontinuous as shown in FIG. 4, but the magnetostrictive film 3 may be continuous as shown in FIG. That is, irregularities may be provided in the magnetostrictive film 3 continuous in the outer peripheral direction, and the nonmagnetic film 6 may be formed in the concave portion 14. 6) Further, as shown in FIG. 16, the magnetostrictive film 3 may be provided in the concave portion 15 of the nonmagnetic film 6 having the unevenness. Further, in Example 1, as shown in FIG.
θ <90 °, but the inclination may not be constant,
FIG. 17 or FIG.

7) In the first to third embodiments, the magnetostrictive film 3 and the non-magnetic film 6 are formed by plasma spraying. However, the present invention is not limited to the plasma spraying, and arc spraying and high-speed gas flame spraying (H.
V. O. F. ) May be used. Further, the coating is not limited to thermal spraying, and a film may be formed by plating or the like.
For example, in the torque transmission shaft 4 having a sectional shape as shown in FIG. 5 or FIG. 15, the magnetostrictive film 3 may be a Fe—Ni alloy plating film, and the nonmagnetic film 6 may be a Cu plating film. In addition, in the case of the torque transmission shaft 4 having a sectional shape as shown in FIGS. 4, 5, and 15, the nonmagnetic film 5 formed in the concave portion is formed of a nonmagnetic alloy powder or a resin adhesive containing flakes. May be. However, since the magnetic shielding property is low, when applying, attention must be paid to the material and content of the nonmagnetic alloy powder or flake. 8) In Example 3, Al was added to suppress the generation of Fe ₃ O ₄ (magnetite). However, Ti or Cr, for example, may be added as long as it has the effect of suppressing the generation of iron oxide.

9) In Example 3, the thickness of the magnetostrictive film 3 was 150 μm and the thickness of the nonmagnetic film 6 (Al) was 100 μm, but these thicknesses were adjusted according to the required magnetostrictive sensitivity. Is also good. Basically, if the film thickness is increased, the magnetostriction sensitivity is improved, but the cost is also increased. Accordingly, it is preferable to set the film thickness according to the situation. 10) In Example 3, the Fe-38Ni-6Al alloy powder was used. However, the composition ratio is not limited to this, and the Fe-Ni-based alloy and Co, which are known as magnetostrictive materials, are used.
A magnetostrictive material in which 15% or less of Al is combined with an Fe-based alloy may be sprayed. Here, the reason why the content of Al is set to 15% or less is to suppress a decrease in magnetostriction sensitivity due to excessive addition of Al. It should be noted that the addition of Al in the present invention is intended only to suppress the generation of Fe ₃ O ₄ (magnetite) in the film, and does not generate a conventionally proposed magnetostrictive material of Fe ₃ Al.

[0039]

As described above, according to the magnetostrictive detector for a torque sensor according to the present invention, (1) since the magnetostrictive film and the nonmagnetic film are continuously provided on the outer peripheral surface of the torque transmission shaft, The durability against damage and peeling of the film during assembly and transport of the torque sensor is improved. (2) The durability against damage or peeling of the film is improved when the torque transmission shaft receives a torsional torque. (3) When no irregularities are provided on the torque transmission shaft main body, the strength is improved. (4) Since the non-magnetic film is provided, the magnetic influence of the magnetostrictive film and the torque transmission shaft is eliminated, and the magnetostrictive characteristics are improved. That is, since the shaft material is not particularly limited, an inexpensive material can be selected.

(5) The post-processing of the torque transmission shaft is only grinding of the outer peripheral surface, and the number of steps is small. Therefore, no labor is required and the cost is low. (6) Since the thermal spray coating is formed on the entire surface of the outer peripheral surface of the magnetostriction detecting portion, the corrosion resistance is improved. (7) The durability of the film is improved by gradually reducing the film thickness at the end of the magnetostrictive film. (8) If the torque transmission shaft is provided with irregularities in advance, grinding is performed after forming the magnetostrictive film and non-magnetic film. Are smaller. (9) When an Fe-Ni-Al alloy is used as the material of the magnetostrictive film, the heat treatment temperature may be low, so that heat treatment can be performed after spraying Al as a nonmagnetic alloy. There is no need to interpose a heat treatment between
The manufacturing process can be simplified. (10) The present application is effective in welding as well as thermal spraying in order to suppress the formation of iron oxide in the process of film formation.

(11) By compounding and spraying Al having an iron oxide suppressing action, it is possible to suppress the generation of Fe ₃ O ₄ (magnetite) without heat treatment in a redox atmosphere. For this reason, the linearity and hysteresis of the magnetostriction characteristics can be improved. (12) Due to the self-heating effect of Ni-Al, self-bonding occurs at the film formation stage, and a dense magnetostrictive film can be formed.

[Brief description of the drawings]

FIG. 1 is a side view of a masking jig according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view taken along line II-II of FIG.

FIG. 3 is a longitudinal sectional view showing the shape of the end of the magnetostrictive film in Example 1 of the present invention.

FIG. 4 is a longitudinal sectional view of a torque transmission shaft according to the first embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a torque transmission shaft according to a second embodiment of the present invention.

FIG. 6 is a side view of a torque transmission shaft main body according to a third embodiment of the present invention.

FIG. 7 is a longitudinal sectional view taken along line VII-VII in FIG. 6;

FIG. 8 is a longitudinal sectional view of a torque transmission shaft provided with a thermal spray coating according to a third embodiment of the present invention.

FIG. 9 is an X-ray diffraction chart of a sprayed coating after spraying Sample 1 in Example 3 of the present invention.

FIG. 10 is an X-ray diffraction chart of a sprayed coating after spraying Sample 2 in Example 3 of the present invention.

FIG. 11 shows a sample 1 in Example 3 of the present invention,
It is an X-ray diffraction chart of a thermal spray coating after heat treatment.

FIG. 12 shows a sample 2 in Example 3 of the present invention sprayed,
It is an X-ray diffraction chart of a thermal spray coating after heat treatment.

FIG. 13 is a conceptual diagram illustrating a method for measuring magnetostriction characteristics according to the present invention.

FIG. 14 is a cross-sectional view of another embodiment of the present invention in which a thermal spray coating is provided on a torque transmission shaft having irregularities.

FIG. 15 is a cross-sectional view of a torque transmission shaft provided with a continuous magnetostrictive film in another embodiment.

FIG. 16 is a cross-sectional view of a torque transmission shaft provided with a continuous nonmagnetic film in another embodiment.

FIG. 17 is a longitudinal sectional view showing a magnetostrictive film having a curved end in another embodiment.

FIG. 18 is a longitudinal sectional view showing a magnetostrictive film having a curved end in another embodiment.

FIG. 19 is a side view showing a conventional torque transmission shaft.

FIG. 20 is a cross-sectional view showing a conventional torque transmission shaft provided with a magnetostrictive film.

FIG. 21 is a cross-sectional view showing a conventional torque transmission shaft provided with a magnetostrictive film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Masking jig 2 Slit 3 Magnetostrictive film 4 Coating end 5 Torque transmitting shaft 6 Non-magnetic film 7 Torque transmitting shaft 8 Groove 9 Torque transmitting shaft 10 Groove 11 Convex portion 12 Coil 13 Concave portion 14 Concave portion 15 Concave portion

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Kato 300, Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. Inventor Kazuyoshi Ishikawa 300 Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd.

Claims (8)

[Claims] 1. A magnetostrictive detector for a torque sensor, wherein a magnetostrictive film and a nonmagnetic film are continuously provided on an outer peripheral surface of a torque transmission shaft. 2. A magnetostrictive film is formed on an outer peripheral surface of the torque transmission shaft, and a non-magnetic film is provided on the magnetostrictive film, or a non-magnetic film is formed on an outer peripheral surface of the torque transmission shaft. The magnetostrictive detector for a torque sensor according to claim 1, wherein a magnetostrictive film is provided on the magnetic film, and the magnetostrictive film and the nonmagnetic film are ground. 3. The magnetostrictive detector for a torque sensor according to claim 1, wherein the thickness of the end of the film of the magnetostrictive film or the nonmagnetic film is gradually reduced. 4. A magnetostrictive film is formed on a torque transmitting shaft having irregularities on the outer peripheral surface, and a nonmagnetic film is provided on the magnetostrictive film, or a nonmagnetic film is formed on the torque transmitting shaft having irregularities on the outer peripheral surface. The magnetostrictive detector for a torque sensor according to any one of claims 1 to 3, wherein a magnetostrictive film is provided on the nonmagnetic film, and the magnetostrictive film and the nonmagnetic film are ground. 5. The magnetostrictive detector for a torque sensor according to claim 1, wherein the material of the magnetostrictive film is an Fe—Ni—Al alloy. 6. The material is Fe—Ni alloy or Fe—C.
A magnetostrictive detector for a torque sensor, characterized by spraying a material obtained by compounding a material having an iron oxide suppressing effect on a magnetostrictive material which is an o-based alloy. 7. The material having an iron oxide suppressing action is A
The magnetostrictive detector for a torque sensor according to claim 6, wherein 1 is used. 8. The magnetostrictive detector for a torque sensor according to claim 7, wherein the amount of Al added is 15% or less.