WO2012173261A1

WO2012173261A1 - Torque sensor and manufacturing method therefor

Info

Publication number: WO2012173261A1
Application number: PCT/JP2012/065436
Authority: WO
Inventors: 正博小牧; 広宣蔦野; 繁夫蒲田; 亮常見; 早乙女　康典; 網谷　健児
Original assignee: 株式会社中山製鋼所; 株式会社サンエテック; 国立大学法人東北大学
Priority date: 2011-06-17
Filing date: 2012-06-16
Publication date: 2012-12-20
Also published as: JPWO2012173261A1; JP5940531B2

Abstract

[Problem] To provide a torque sensor which is improved with regard to the torque detection characteristic, manufacturing cost, and the like, and a manufacturing method therefor. [Solution] This torque sensor comprises a magnetostrictive section containing an amorphous alloy film (including a metallic glass film) formed on a surface of a rotation shaft. The amorphous alloy film in the magnetostrictive section is formed on the surface of the rotation shaft by means of thermal spray wherein a metallic powder is melted by spraying flame containing the metallic powder, and the flame is cooled by a cooling gas from the outside before the flame reaches the surface of the rotation shaft.

Description

Torque sensor and manufacturing method thereof

The present invention relates to a torque sensor of a type that detects the magnitude of torque acting on a rotating shaft (drive shaft) by a change in magnetic permeability of a magnetostrictive portion provided on the surface of the rotating shaft.

A general structure of the above-described type of torque sensor is shown in FIG. A rotating shaft 1 that receives torque is supported by a housing 3 via a bearing 2, and magnetostrictive portions A and B are formed on a part of the surface of the rotating shaft 1. In addition, the coils C and D are arranged at positions near the outer circumferences of the magnetostrictive portions A and B inside the housing 3. As the magnetostrictive portions A and B, a magnetic material is formed on the surface of the shaft 1 in a spiral shape that is inclined in opposite directions with respect to the axial direction as shown in the drawing (that is, a magnetic film or protrusion is spirally formed). Are generally formed as a plurality of lines). The housing 3 is also provided with an amplifier board 4 and a signal line connector 5 as shown in the figure.
When torque is applied to the rotating shaft 1, tensile stress and compressive stress are generated in the magnetostrictive portions A and B, respectively. As a result, the magnetic permeability of each magnetostrictive portion A and B is increased and decreased by the opposing magnetostrictive effects. To do. Since the induced electromotive force of the coils C and D is generated based on the change in the magnetic permeability, a voltage output proportional to the magnitude of the torque can be obtained by performing DC conversion and differential amplification of both. .

There is the following Patent Document 1 as a document relating to such a torque sensor. In the same document 1, there is an example in which the rotating shaft itself is formed of a ferromagnetic material having a high magnetic permeability as a configuration of the magnetostrictive portion. It is shown that there is an example of thermal spraying.
An amorphous alloy (including metallic glass) is suitable as the magnetic material constituting the magnetostrictive portion. This is because the magnetostrictive portion of the torque sensor is required to have two characteristics of high permeability and high magnetostriction, and an amorphous alloy is preferable in that respect and can provide high sensitivity characteristics. About using an amorphous alloy for a magnetostriction part, it describes in following patent document 2 grade | etc., And shows that the ribbon of the amorphous alloy produced by the single roll method is fixed to the rotating shaft surface.
Patent Document 3 below describes that it is preferable to employ a high-speed spraying process such as high-speed flame spraying (HVOF) in order to form a metallic glass film on the surface of the base material (base material). .

JP 2010-2414 A Japanese Patent Publication No. 63-20031 JP 2010-10668 A

The inventors consider that the torque detection characteristics of the torque sensor are not sufficient by any of the examples described in the above-mentioned documents, and there is room for further improvement.
In other words, the magnetostrictive portion of the rotating shaft is clearly disadvantageous in terms of sensitivity compared to the case of using an amorphous alloy when it is composed of only a general magnetic material. Also, if an amorphous alloy ribbon is fixed to the surface of the rotating shaft by attaching it with an adhesive, etc., sufficient detection characteristics cannot be obtained due to poor adhesion to the rotating shaft, output hysteresis, short life It also affects the problem. Even when a metal glass film is formed on the surface of the rotating shaft by a high-speed flame spraying process such as high-speed flame spraying, the method is high-speed, so the time that the metal powder is in the flame is short, so that the metal powder does not melt Since it is laminated on the shaft surface in the supercooled liquid phase state, the adhesion between the alloy film and the rotating shaft seems to be insufficient, and the torque detection sensitivity is not high. Further, the high-speed thermal spraying process has a limitation that it is necessary to use an amorphous metal powder having a particle size of about 30 μm or less, which is disadvantageous in terms of manufacturing cost.

The present invention solves the above-described problems and provides a torque sensor improved in terms of torque detection characteristics and manufacturing cost, and a method for manufacturing the torque sensor.

The torque sensor of the present invention has a magnetostrictive part including a metal glass film on the surface of the rotating shaft, and the metal glass film in the magnetostrictive part injects a flame containing the metal powder to melt the metal powder. It is characterized in that the flame is formed on the surface of the rotary shaft by thermal spraying in which the flame is cooled by the cooling gas from outside before reaching the surface of the rotary shaft.
This torque sensor has the following operational features. That is,
a) Since the surface of the rotating shaft has a magnetostrictive portion including a metallic glass film, the magnetostrictive portion has two characteristics of high permeability and high magnetostriction. For this reason, this torque sensor exhibits superior characteristics regarding torque detection as compared with the case without the coating (see FIG. 1).
b) Since the metallic glass film is formed on the surface of the rotating shaft by thermal spraying, the hysteresis is extremely small compared to the example in which the ribbon of the alloy is fixed on the surface of the rotating shaft (see FIG. 2). Unlike the case of using an adhesive or the like for fixing the ribbon, it is considered that the adhesion between the alloy film and the rotating shaft is high. In addition, since the metallic glass film is laminated on the rotating shaft as a film simultaneously with the amorphization by thermal spraying, there is also an advantage that the magnetostrictive part is formed easily and quickly.
c) As a thermal spraying method, the above-mentioned method of injecting a flame containing metal powder to melt the metal powder and cooling the flame with a cooling gas from the outside adopts this torque sensor. The torque detection characteristics are even better than those sprayed by (see FIG. 3). It is considered that since the metal powder is once melted, the adhesion of the metal glass film to the surface of the rotating shaft is increased, and the torque of the rotating shaft is easily transmitted to the alloy film. Further, unlike the case of the high-speed spraying process, there is an advantage that even a metal powder having a large particle size (about 40 μm or more) can be used.

In the above torque sensor, it is more preferable that the rotation axis is a non-magnetic material and the amorphous alloy of the magnetostrictive portion is Fe—Co—Si—B—Nb-based metallic glass.
If the rotating shaft is a magnetic material, as described above, a magnetostrictive portion can be formed simply by forming a helical projection or the like on the surface thereof, and torque can be detected without providing a magnetic film. However, when the rotating shaft is a magnetic material, it is affected by an external magnetic field, so that the torque detection sensitivity decreases. In that respect, if a magnetostrictive part is formed by using a nonmagnetic material for the rotating shaft and forming a metallic glass film on its surface, it is less susceptible to external magnetic fields and, due to the nature of the metallic glass film, The detection characteristics are extremely high (see FIG. 4). That is, as long as a metal glass sprayed coating can be formed, any material rotation shaft can be applied as a torque sensor.
Further, when the amorphous alloy film of the magnetostrictive portion is Fe—Co—Si—B—Nb-based metallic glass, the amorphous forming ability is high, and it is advantageous in terms of magnetic characteristics and mechanical characteristics (FIG. 7A). (See (b) and (c)).

In the above torque sensor, it is preferable that a metal glass film is formed on the surface of the rotating shaft by the thermal spraying in a state where the temperature of the flame and the surface temperature of the rotating shaft are controlled to be constant.
Since the flame for thermal spraying needs to melt the metal powder and be rapidly cooled with a cooling gas, its temperature needs to be sufficiently controlled. However, according to the tests by the inventors, the surface temperature of the rotating shaft during thermal spraying must be sufficiently controlled. This is because it is confirmed that the sensitivity and hysteresis of the torque sensor including the magnetostrictive portion formed by the thermal spraying differ depending on the surface temperature of the rotating shaft during thermal spraying (see FIGS. 5 and 6). The difference between the sensitivity and hysteresis occurs because, for example, if the surface temperature is low, the degree of adhesion of the molten metal powder to the surface of the rotating shaft decreases, so hysteresis occurs, but the film becomes amorphous and the sensitivity increases. On the other hand, if the temperature is high, the degree of adhesion increases and no hysteresis occurs. However, it is presumed that the amorphous ratio of the film decreases and the sensitivity decreases. Therefore, the surface temperature of the rotating shaft during thermal spraying needs to be measured by an appropriate thermometer or the like and controlled to an appropriate temperature range (300 to 500 ° C.).

The magnetostrictive portion of the torque sensor has a configuration in which concave portions and convex portions are alternately arranged linearly on the surface of the rotating shaft, and the metal glass film is formed so as to fill the concave portions (see FIG. 10). It is preferable that the metal glass film is formed on the entire region including the concave portions and the convex portions and then polished so that the metal glass film on the surface of the convex portions adjacent to the metal glass film is eliminated.
Such a magnetostrictive part can be relatively easily manufactured by a method in which a metal glass film is widely formed by thermal spraying on the surface of the rotating shaft including irregularities, and then the film is polished. In this case, since the metallic glass film is formed so as to fit in the recess, the film is particularly highly integrated with the rotating shaft and is not easily peeled off. Will also be expensive. In addition, when the portions where the metal glass film is formed and the portions where the metal glass film is not formed are alternately arranged in a line having an acute angle of 45 degrees with respect to the rotation axis in the magnetostrictive portion, the torque detection characteristic is enhanced.

The magnetostrictive portion of the torque sensor is also configured by alternately arranging the portions where the metallic glass film is formed and the portions where the metallic glass film is not formed on the surface of the rotating shaft (see FIG. 10). After the metal glass film is formed on the entire surface, the non-formed part of the metal glass film may be removed by shot blasting by covering a part of the surface of the rotating shaft with a mask.
Such a magnetostrictive portion is also relatively easily configured by thermal spraying and then shot blasting performed by covering the magnetostrictive portion with a mask (having an opening such as a slit at a position corresponding to the non-formed portion). can do. The removal method is not limited to shot blasting, and may be a chemical process such as etching after the magnetostrictive portion is coated with a resin or a mechanical process such as cutting.

The magnetostrictive portion of the torque sensor is constructed by alternately arranging the portions where the metal glass film is formed and the portions where the metal glass film is not formed on the surface of the rotating shaft (see FIG. 10). It is also possible that the metal glass film of the above-mentioned formation part is formed by covering a part of the surface of the rotating shaft with a mask.
Such a magnetostrictive portion can also be easily configured by the above-described thermal spraying performed by covering the magnetostrictive portion with a mask (having an opening such as a slit at a position corresponding to the formation portion).
The magnetostrictive portion of the torque sensor is formed by alternately arranging the portions where the metallic glass film is formed and the portions where the metallic glass film is not formed on the surface of the rotating shaft. The metal glass film of the above-mentioned formation part may be directly formed.
Such a magnetostrictive part can also be easily configured by a precision sprayed composite machine.

The torque sensor according to the invention described above, when the magnetostrictive portion is configured on the surface of the rotating shaft, a) the rotating shaft is preheated, and b) the thermal spray is maintained on the surface with the flame temperature kept constant. To form a metallic glass film on the magnetostrictive portion by c) and repeatedly rotating the rotating shaft and applying the flame to the rotating shaft surface and deflecting from the rotating shaft surface when forming the film. Thus, it is preferable that the temperature is maintained on the surface of the rotating shaft.
By doing so, it is possible to form a preferable metallic glass film on the surface of the rotating shaft by the above thermal spraying while managing the flame temperature and the surface temperature of the rotating shaft to be constant. If the flame is continuously applied to the surface of the rotating shaft, the temperature of the surface continues to rise. However, if the flame is applied or deflected as described above, the temperature of the surface of the rotating shaft can be maintained within a certain range (see FIG. 9). That's why. By doing so, it is possible to form a metal glass film that has excellent adhesion and integrity to the surface of the rotating shaft and a high amorphization rate, and as a result, a torque sensor having excellent detection characteristics can be manufactured.

For the above thermal spraying for forming the metal glass film, a metal powder having a diameter of 40 μm or more including a crystalline powder may be used.
Such a metal powder can be obtained at a lower cost than a powder having a smaller diameter or an amorphous powder (amorphized powder), so that the cost required for thermal spraying, that is, the construction of the magnetostrictive portion can be reduced. The use of such an inexpensive metal powder is one of the advantages unique to the present invention that is different from high-speed spraying processes such as high-speed flame spraying.

According to the present invention, it is possible to provide an inexpensive torque sensor that is excellent in detection characteristics and low in cost required for the configuration of the magnetostrictive portion.

It is a diagram which shows a sensor output (vertical axis) when a torque (horizontal axis) is applied to the rotating shaft of the torque sensor, and shows a comparison between the case where the magnetostrictive portion does not have a metal film and the case where it has. It is a diagram showing a sensor output (vertical axis) when a torque (horizontal axis) is applied to the rotation axis of the torque sensor, and a case where an amorphous alloy ribbon (ribbon) is fixed to the magnetostrictive portion and a thermal sprayed metallic glass A comparison with the case where a film is provided is shown. It is a diagram showing a sensor output (vertical axis) when a torque (horizontal axis) is applied to the rotation shaft of the torque sensor, and a case where a metallic glass film is formed on the magnetostrictive portion by high-speed flame spraying, and The comparison with the case where the same film is formed by thermal spraying is shown. It is a diagram which shows a sensor output (vertical axis) when a torque (horizontal axis) is applied to the rotating shaft of the torque sensor, and shows a difference depending on the material of the rotating shaft (magnetic or non-magnetic). It is a diagram which shows a sensor output (vertical axis) when a torque (horizontal axis) is applied to the rotating shaft of the torque sensor, and shows a difference due to the surface temperature of the rotating shaft during thermal spraying of the metallic glass film. It is a diagram which shows a sensor output (vertical axis) when a torque (horizontal axis) is applied to the rotating shaft of the torque sensor, and shows a difference due to the surface temperature of the rotating shaft during thermal spraying of the metallic glass film. Each of FIGS. 7A, 7B, and 7C shows magnetostriction and holding power, mechanical properties, and amorphous forming ability of an Fe—Co—Si—B—Nb-based metallic glass as an amorphous alloy film in the magnetostrictive portion. It is a figure which shows (XRD profile). It is a side view (a part is shown with sectional drawing) which shows the outline | summary of a thermal spraying apparatus. It is a diagram (time progress is from right to left) which shows the change of the surface temperature of the rotating shaft during spraying to a magnetostriction part. It is a typical sectional view showing the structure of a magnetostrictive torque sensor.

Embodiments of the invention will be described below with reference to the drawings.
Magnetostrictive portions A and B as shown in the figure are formed by forming a metallic glass film on the partial surface of the rotary shaft 1 in the torque sensor as shown in FIG. 10 by thermal spraying. Each of the magnetostrictive portions A and B is formed by forming a metal glass film in a plurality of spiral shapes that form 45 ° with the axial direction, and alternately arranging the formed portions and the non-formed portions of the film. . The directions of the spirals of the magnetostrictive portions A and B are different from each other so that both lines are perpendicular to each other. The diameter of the rotating shaft 1 is 8 mm or more, and the line width of the spiral of the formed part and the non-formed part is about 1 to 3 mm.

The formation part and the non-formation part of the metallic glass film in the magnetostriction parts A and B are formed by the following procedure. That is, 1) By forming a plurality of grooves on the surface of the rotating shaft 1 to form a grooved shaft, concave and convex portions (not shown) along the spiral line (formed portion and non-formed portion) are formed. 2) Form a metallic glass film by spraying the entire area including the concave and convex portions, and 3) remove the convex metallic glass film by polishing the sprayed portion after that. ) Make sure that there is no step between the surface of the metallic glass film (formation part) and the surface of the convex part (non-formation part) adjacent to it.
However, the configuration procedure of the magnetostrictive portions A and B is not limited to the above example. For example, a metal glass is used by spraying the entire area of the magnetostrictive portions A and B using a shaft (rotary shaft 1) having no groove as described above. After forming the film, a part of the surface of the rotating shaft 1 is covered with a mask (having a spiral slit corresponding to a non-formed part, not shown), and shot blasting is performed, thereby forming a metal glass film forming part. It is also possible to provide a non-formed portion. Alternatively, the above thermal spraying is performed by covering a part of the surface of the rotary shaft without the groove with a mask (having a spiral slit corresponding to the formation portion, not shown), so that the same formation portion and non-formation are formed. A portion may be provided.
After shot blasting the base material, using a heat resistant paint etc. to give a chevron-like pattern, forming a sprayed coating on the surface, by removing only the sprayed coating on the shoblon pattern using a grinder or shot blast, A chevron pattern may be formed.
Further, after forming a sprayed coating on the surface of the base material, it is also possible to form a shoblon pattern after shot blasting by performing a shotblon-like masking using a shot blast resistant paint or the like.

The metal glass film is formed on the rotary shaft 1 by using a flame quenching thermal spraying device 11 shown in FIG. 8 and supported by a support device (supporting the rotary shaft 1 horizontally and rotating it around the axis, not shown). This is performed by spraying on the outer peripheral surface of the rotating shaft 1 that has been moved.
As shown in the figure, the thermal spraying device 11 has a double-pipe tubular body 15 or the like that can also be called an external cooling device attached to the front of a powder-type flame spraying gun 12. Connected to the spray gun 12 are a tube for supplying the material powder to be sprayed together with a carrier gas (for example, nitrogen), a supply tube for acetylene and oxygen as fuel, and a supply tube for an internal cooling gas (for example, nitrogen). Yes. There is a nozzle 13 at the front end of the thermal spray gun 12, from which a flame and a molten material (the melted powder) are sprayed. The internal cooling gas is blown out from a position in contact with the periphery of the nozzle 13 to cool the nozzle 13 and adjust the temperature of the flame. A flange-like front plate 14 is fixed to the thermal spray gun 12 around the nozzle 13 near the front end thereof, and a cylindrical body 15 is attached thereto. The illustrated cylindrical body 15 separates the flame F from the outside air in the first half of the flame F sprayed by the spray gun 12 (portion close to the nozzle 13; the melting region of the material powder), and flame from the tip of the double pipe. Cooling gas (for example, nitrogen) G is blown into the latter half of F to cool the flame F.
The thermal spraying device 11 sprays a flame F containing material particles from a nozzle 13, melts the material particles with the flame F, and cools the material particles with the cooling gas G, thereby forming a metallic glass film on the surface of the rotary shaft 1. Can be formed. The speed of the flame F is set to about 30 to 40 m / s, and the temperature of the flame F is set to 1000 to 1200 ° C. near the center (adjusted according to the material particles, respectively). Since the flame F reaches the base material 10 by being surrounded by the cylindrical body 15 and the cooling gas (nitrogen) G ejected therefrom, the amount of oxides in the metal glass film can be suppressed. Since the spray particles can be melted with a sufficient amount of heat, it is possible to use metal powder having a diameter of 40 μm or more (about 100 μm or less) including crystalline powder in the thermal spraying using the thermal spraying apparatus 11.

At the time of thermal spraying by the thermal spraying device 11, temperature management is performed so that the surface temperature of the rotating shaft 1 becomes constant along with the temperature of the flame F. This is because, depending on the surface temperature of the rotating shaft 1 during thermal spraying, the torque detection sensitivity of the magnetostrictive portion formed by thermal spraying is different.
The surface temperature of the rotating shaft 1 is measured by a radiation thermometer, and temperature control is performed during the spraying time t3 as well as during the preheating / falling time t1 and t2 as shown in FIG. Specifically, 1) At the preheating time t1, the rotating shaft 1 is preheated by a burner or the like before the start of spraying, and 2) the temperature lowering time between setting a baffle plate that prevents the sprayed material from scattering from a slightly higher preheating temperature. After confirming a certain temperature drop at t2, spraying is started. 3) During the spraying time t3, while rotating the rotating shaft 1, by repeatedly applying the flame F to the shaft surface and deflecting it from the shaft surface The surface temperature of the rotating shaft 1 is kept substantially constant (within a range of 300 to 500 ° C., depending on the material of the rotating shaft 1 and the sprayed material). That is, during this time t3, the flame F is applied to the rotating shaft 1 (the magnetostrictive portion forming portion) that is horizontally supported and rotated, and is sent in the axial length direction (horizontal), and the flame F is sent at one or both ends of the feed. Reciprocate in the direction perpendicular to the shaft length direction (either up or down) to deviate from the shaft surface. When the rotating shaft 1 has a small diameter and easily rises in temperature, the surface temperature may be controlled by waiting (stopping) the flame F for a while at a position deviating from the shaft surface.

The coating formed by thermal spraying is preferably made of, for example, Fe—Co—Si—B—Nb-based metallic glass. As shown in FIGS. 7 (a) to (c), the metal glass has high amorphous forming ability and is easy to be made amorphous, has excellent magnetic properties, and is difficult to be plastically deformed in mechanical properties. This is because it is preferable. That is, first, FIG. 7A is an example.
(Fe _1-x Co _x ) ₇₂ B ₂₀ Si ₄ Nb ₄ is a diagram showing magnetostriction (λs) and coercive force (Hc) in Co glass for each concentration of metal, with excellent properties. I understand. FIG. 7 (b) is an investigation of the mechanical properties of the same metallic glass in the same manner, and it can be said that it has good properties in terms of compressive strength, Young's modulus, and plastic elongation. FIG. 7C shows an XRD profile of a sprayed film obtained by performing the aforementioned rapid thermal spraying (using the thermal spraying apparatus 11 of FIG. 8) on (Fe _0.5 Co _0.5 ) ₇₂ Si ₄ B ₂₀ Nb ₄ metallic glass. Indicates. Only the amorphous phase was obtained in any of the two types of sprayed films obtained by changing the spraying conditions, and it was structurally found that the alloy can be easily obtained by spraying.
In addition, although the material of the rotating shaft 1 is not ask | required, it is advantageous to set it as nonmagnetic materials, such as titanium and stainless steel. This is because if the rotating shaft 1 is a non-magnetic material, it is not easily affected by an external magnetic field, and therefore torque detection characteristics are improved.

As described above, various comparative data on the torque detection characteristics of the torque sensor of the invention having the magnetostrictive portion as described above have been obtained.

First, the surface of the rotating shaft made of carbon steel (SK3) without using metallic glass is shown in Fig. 1 when the metallic glass is sprayed onto the rotating shaft made of carbon steel (SK3) as described above. The relationship between the torque (horizontal axis) and the sensor output (vertical axis) is shown for the case where only the irregularities extending spirally are formed to form a magnetostrictive portion. In the former example, a metal glass forming portion and a non-forming portion are provided in the magnetostrictive portion using the grooved shaft described above.
It can be seen that the former having a metallic glass film in the magnetostrictive part has a very high sensitivity although the linearity is somewhat inferior to the latter example having no film. When the sensitivity is so high, there is an advantage that the output does not need to be amplified by an amplifier, and therefore there is less noise (no noise filter is required).

In FIG. 2, the case where the metal glass is sprayed on the rotating shaft as described above to form a magnetostrictive portion and the case where an amorphous ribbon formed by a single roll method is attached to the surface of the rotating shaft to form a magnetostrictive portion. The relationship between torque and sensor output is shown. Both rotating shafts are carbon steel (SK3). In the former, the magnetostrictive portion is provided with a metal glass forming portion and a non-forming portion using the grooved shaft. The thickness of the former metallic glass is 140 to 150 μm, and the thickness of the latter amorphous ribbon is 25 μm (attached to the surface of the rotating shaft without grooves).
In the latter example in which an amorphous ribbon is pasted, it can be seen that hysteresis is more likely to occur than the former in which a metallic glass film is formed by thermal spraying because the adhesion between the ribbon and the rotating shaft is not sufficient.

FIG. 3 shows the relationship between torque and sensor output when the metallic glass film of the magnetostrictive part is formed by the above-mentioned thermal spraying and when it is formed by high-speed flame spraying (HVOF). The rotating shafts are all made of carbon steel (SK3), and the metallic glasses are all (Fe _0.5 Co _0.5 ) ₇₂ Si ₄ B ₂₀ Nb ₄ as described above.
Although HVOF is excellent in output linearity, it can be said that the sensitivity is low and hysteresis occurs. In HVOF, since the powder material is not sufficiently dissolved, it is assumed that the adhesion to the surface of the rotating shaft is not high.

FIG. 4 shows the torque and sensor output in the case where the magnetostriction portion is formed by performing the above-described thermal spraying by the apparatus 11 of FIG. 8 on each of the rotating shafts made of titanium (Ti-6Al-4V) and carbon steel (S45C). Shows the relationship. In either case, the magnetostrictive portion is provided with a metal glass forming portion and a non-forming portion using the grooved shaft. There is no difference in the thickness of the metallic glass film.
According to FIG. 4, it can be seen that when the rotating shaft is made of titanium, the linearity is slightly inferior to that of carbon steel, but the sensitivity is greatly improved. This is because the titanium material has a characteristic that it is easy to concentrate the magnetic flux produced by the coil on the magnetostrictive portion because the titanium material has a low elastic modulus and a large amount of strain as compared with the iron material and is non-magnetic.

5 and 6 show the influence of the spraying temperature on the sensor output. In other words, what effect does the temperature of the surface of the rotating shaft at the magnetostrictive part (low temperature at the spraying time t3 shown in FIG. 9) have on the relationship between torque and sensor output when forming the metallic glass film? Represents. FIG. 5 is an example in which the magnetostrictive portion is provided with a metallic glass forming portion and a non-forming portion using the spiral grooved shaft having a diameter of 30 mm, and FIG. This is an example in which the formation portion and the non-formation portion of the metal glass film are provided by performing spray blasting after performing thermal spraying on the entire area of the magnetostrictive portion and performing shot blasting as described above. In any case, the surface temperature of the rotating shaft was measured with a radiation thermometer as described above. In addition, in each of FIG. 5 and FIG. 6, the emissivity for temperature measurement is set separately.
5 and 6, it is confirmed that the sensitivity and linearity of the torque sensor vary depending on the temperature of the surface of the rotating shaft during thermal spraying. This is presumably because the degree of adhesion of the molten metal to the surface of the rotating shaft and the amorphization rate of the sprayed coating change depending on the temperature. According to the test, the optimum value of the temperature is in the range of 300 to 500 ° C., but the optimum temperature varies depending on the rotating shaft, the material of the sprayed coating, and the shape and size of the sprayed portion.

As described above, the torque sensor having the magnetostrictive portion according to the present invention is more suitable than the torque sensor adopting other methods, materials, and forms as long as the flame and the temperature of the rotating shaft surface during spraying are appropriately controlled. It can be seen that preferable torque detection characteristics can be exhibited.

1 Rotating shaft A / B Magnetostrictive part 11 Thermal spraying device

Claims

A torque sensor having a magnetostrictive portion including a metallic glass film on the surface of the rotating shaft,
The metal glass coating in the magnetostrictive part sprays a flame containing metal powder to melt the metal powder and cools the flame with a cooling gas from outside before it reaches the surface of the rotating shaft. The torque sensor is formed on the surface of the rotating shaft.
The torque sensor according to claim 1, wherein the rotating shaft is a non-magnetic material, and the metal glass of the magnetostrictive portion is Fe-Co-Si-B-Nb-based metal glass.
The magnetostrictive portion is formed by forming the metal glass film so that the concave portions and the convex portions are alternately arranged linearly on the surface of the rotating shaft and filling the concave portions. The metal glass film is formed on the entire surface including the concave and convex portions and then polished, whereby the metal glass film on the surface of the metal glass film and the convex portions adjacent thereto is eliminated. The torque sensor according to 1 or 2.
The magnetostrictive portion is formed by alternately arranging the formed portion and the non-formed portion of the metallic glass film on the surface of the rotating shaft, and the magnetostrictive portion has the metallic glass film over the entire area. After the formation, the non-formed portion of the metallic glass film is removed by chemical processing such as shot blasting or etching performed by covering a part of the film surface with a mask or machining such as cutting. The torque sensor according to claim 1 or 2, characterized in that
The magnetostrictive portion is configured by alternately arranging the portions where the metal glass film is formed and the portions where the metallic glass film is not formed on the surface of the rotational shaft, and the magnetostrictive portion rotates the thermal spray on the rotational axis. The torque sensor according to claim 1 or 2, wherein a part of the surface is covered with a mask to form a metal glass film of the formation part.
The torque sensor manufacturing method according to any one of claims 1 to 5, wherein the magnetostrictive portion is formed on the surface of the rotating shaft.
The rotating shaft is preheated, and the metal glass film on the magnetostrictive portion is formed on the surface by the thermal spraying with the flame temperature kept constant, and the rotating shaft is rotated when the coating is formed. And the temperature of the surface of the rotating shaft is maintained by repeatedly applying the flame to the surface of the rotating shaft and deflecting it from the surface of the rotating shaft.
7. The method of manufacturing a torque sensor according to claim 6, wherein a metal powder having a diameter of 40 μm or more including a crystalline powder is used for the thermal spraying for forming the metal glass film.