JP2019211352A - Method for producing torque sensor shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a torque sensor shaft having corrosion resistance and having a stable output sensitivity. In a method of manufacturing a torque sensor shaft (10) having a magnetostrictive portion (2) formed on the outer circumference of a rotating shaft (1), an iron-based material is used as the material of the rotating shaft (1), and a passivation film is formed on the outer circumference of the rotating shaft (1). By doing so, there are provided a plating process of maintaining corrosion resistance and plating a metal having a melting point of 500 ° C. or higher, and a spraying process of spraying a magnetic material on the position where the magnetostrictive portion 2 of the rotating shaft 1 is formed. The plating is preferably electroless nickel-phosphorus plating, and it is also preferable to have a shot blasting step of removing the plating at the position where the magnetostrictive portion 2 is formed by shot blasting after the plating step and before the thermal spraying step. [Selection diagram] Figure 2

Description

  The present invention relates to a method of manufacturing a torque sensor shaft, and more particularly, to a method of manufacturing a magnetostrictive torque sensor shaft that can be suitably used for a power-assisted bicycle or the like, having corrosion resistance and stable output sensitivity. The present invention relates to a method of manufacturing a torque sensor shaft that provides a torque sensor shaft having

  Bicycles with electric motors such as electric assist bicycles output auxiliary power in accordance with the torque acting on the crankshaft, so it is necessary to assemble a torque sensor for detecting the torque. As a torque sensor shaft used for this torque sensor, a torque sensor shaft having a magnetostrictive portion provided on the outer periphery of a crankshaft is known. When this magnetostrictive part is formed by wrapping a magnetostrictive foil around the outer periphery of the crankshaft and fastening it with an adhesive, the adhesion between the magnetostrictive part and the crankshaft is not high, so sufficient torque detection characteristics can be obtained. In addition, there is a problem of short life.

  Under such circumstances, Patent Document 1 proposes a method of manufacturing a torque sensor that can improve torque detection characteristics and reduce manufacturing costs. Specifically, in manufacturing a torque sensor shaft having a magnetostriction portion including an amorphous alloy film (including a metal glass film) on the outer peripheral surface, a flame containing metal powder is injected over the amorphous alloy film forming the magnetostriction portion. A method of forming a magnetostrictive portion on the outer peripheral surface of the rotating shaft has been proposed by melting the metal powder and spraying with a cooling gas from outside before the flame reaches the outer peripheral surface of the rotating shaft. .

International Publication No. 2012/173261

  In general, the torque sensor shaft is plated with zinc or the like for the purpose of preventing rust. Therefore, as proposed in Patent Document 1, when the magnetostrictive portion of the torque sensor shaft is formed by thermal spraying of a magnetic material, the galvanization becomes a high temperature state, and in general galvanization, it is melted by heat. Possible countermeasures include not galvanizing the torque sensor shaft or galvanizing after thermal spraying of the magnetic material. However, if the torque sensor shaft is not galvanized, the output changes due to rust. In addition, when galvanization is performed after thermal spraying of the magnetic material, galvanization is formed in the magnetostrictive portion, so output sensitivity decreases, output sensitivity varies due to variations in galvanization thickness, Such a problem will occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a torque sensor shaft that eliminates such problems and that provides a torque sensor shaft having corrosion resistance and stable output sensitivity.

  As a result of diligent investigations to solve the above problems, the present inventor, when manufacturing a torque sensor shaft provided with a magnetostrictive portion on the outer periphery, before forming the magnetostrictive portion on the rotational shaft by thermal spraying, It has been found that the above-mentioned problems can be solved by applying predetermined plating, and the present invention has been completed.

That is, the torque sensor shaft manufacturing method of the present invention is a torque sensor shaft manufacturing method in which a magnetostrictive portion is formed on the outer periphery of the rotating shaft.
A plating process that uses an iron-based material as the material of the rotary shaft, can maintain corrosion resistance by forming a passive film on the outer periphery of the rotary shaft, and performs plating of a metal having a melting point of 500 ° C. or higher; Spraying a magnetic material at a position where the magnetostrictive portion of the rotating shaft is formed.

  In the torque sensor shaft manufacturing method of the present invention, the plating is preferably electroless nickel-phosphorus plating. Further, the torque sensor shaft manufacturing method of the present invention includes a shot blasting step for removing plating at a position where the magnetostrictive portion is formed by shot blasting after the plating step and before the spraying step. It is preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the torque sensor shaft from which the torque sensor shaft which has corrosion resistance and the stable output sensitivity is obtained can be provided.

It is a schematic plan view of the torque sensor shaft obtained by the torque sensor shaft manufacturing method according to a preferred embodiment of the present invention. It is a flowchart of the manufacturing method of the torque sensor shaft which concerns on one preferable embodiment of this invention.

Hereinafter, the manufacturing method of the torque sensor shaft of the present invention will be described in detail.
The torque sensor shaft manufacturing method of the present invention is a method of manufacturing a torque sensor shaft having a magnetostrictive portion on the outer periphery of a rotating shaft, and FIG. 1 is a torque sensor shaft manufacturing method according to a preferred embodiment of the present invention. It is a schematic plan view of the torque sensor axis | shaft obtained by. The illustrated torque sensor shaft 10 has a magnetostrictive portion 2 having a magnetostrictive effect formed on the outer periphery of the rotating shaft 1, and the rotating shaft disposed on the outer periphery of the magnetostrictive portion 2 in a direction perpendicular to the rotating shaft direction. A plurality of slits 3a are formed at an angle of 45 ° with respect to the direction. In the illustrated example, a plurality of slits 3a are arranged substantially in parallel along the circumferential direction, and these are arranged in three rows in the rotation axis direction. Right next to the three rows of slits 3a, there are provided a plurality of rows of slits 3b arranged substantially symmetrically with the three rows of slits. In the illustrated example, the slits 3a and 3b are arranged in three rows, but the torque sensor shaft 10 according to the torque sensor shaft manufacturing method of the present invention is not limited to this. For example, one row at a time. It may be.

  FIG. 2 shows a flowchart of a method for manufacturing a torque sensor shaft according to a preferred embodiment of the present invention. In the flowchart shown in the drawing, a plating process for plating the outer periphery of the rotating shaft 1, a shot blasting process for removing plating at a position where the magnetostrictive portion 2 is formed by shot blasting, a preheating process for preheating the rotating shaft 1, A thermal spraying process in which a magnetic material is sprayed onto the rotating shaft 1 to form the magnetostrictive portion 2; a cooling process in which the rotating shaft 1 is cooled to a predetermined temperature when the rotating shaft 1 rises to a predetermined temperature; and an outer periphery of the rotating shaft 1 The upper magnetostriction portion 2 includes a masking step for covering the portion other than the position where the slit 3 is formed, a slit formation step for forming the slit 3 in the magnetostriction portion 2 by shot blasting, and a masking removal step for removing the masking. Yes.

  The torque sensor shaft manufacturing method of the present invention uses an iron-based material as the material of the rotating shaft 1. Iron-based materials have the advantage of being inexpensive and easy to process, and for example, ordinary carbon steel can be used. In the method for manufacturing a torque sensor shaft according to the present invention, a metal film having a melting point of 500 ° C. or higher can be maintained by forming a passive film on the outer periphery of the rotary shaft 1 in the plating step. Apply plating. Thus, by plating the metal that forms the passive film on the outer periphery of the rotating shaft 1, rust of the torque sensor shaft 10 can be prevented, and the corrosion resistance of the torque sensor shaft 10 can be improved. Examples of the metal that forms such a passive film include nickel, chromium, aluminum, titanium, and copper. In the torque sensor shaft manufacturing method of the present invention, the magnetostrictive portion 2 is formed by a thermal spraying process. In this thermal spraying process, the rotary shaft 1 is heated to a high temperature. If galvanized, galvanization will melt. Therefore, it is necessary to use a metal with high heat resistance for plating on the rotating shaft 1. From such a viewpoint, as the plating used in the plating step, a metal having a melting point of 500 ° C. or higher is used.

  In the torque sensor shaft manufacturing method of the present invention, there is no particular limitation on the plating method in the plating step, and either electrolytic plating or electroless plating may be used. Electrolytic nickel-phosphorous plating (electroless Ni-P plating) is preferred. In the torque sensor shaft manufacturing method of the present invention, the electroless Ni—P plating conditions are not particularly limited, and known conditions can be employed.

  The manufacturing method of the torque sensor shaft of the present invention includes a thermal spraying process of spraying a magnetic material at a position where the magnetostrictive portion 2 of the rotary shaft 1 is formed after the above-described plating process. This thermal spraying process can be performed by, for example, injecting a flame containing magnetic material powder to melt the metal powder, and injecting the flame and the molten magnetic material onto the rotating shaft 1. Therefore, since the magnetostrictive portion 2 is directly welded to the rotating shaft 1 without interposing an adhesive or the like, the stress to the torque sensor shaft 10 is well transmitted to the magnetostrictive portion 2, thereby the sensitivity of the torque sensor. Will be good. Here, in the torque sensor shaft manufacturing method of the present invention, it is preferable that the temperature of the rotating shaft 1 in the thermal spraying process is adjusted to 300 to 500 ° C. In the torque sensor shaft manufacturing method of the present invention, since the plating applied to the rotating shaft 1 is a metal having a melting point of 500 ° C. or higher, the rotating shaft 1 is subjected to the spraying process under such conditions. It is possible to prevent the upper plating from melting.

  Moreover, when the outer peripheral plating of the rotating shaft 1 is formed by electroless Ni—P plating, the electroless Ni—P plating has the highest hardness by heat treatment at about 400 ° C., although it varies depending on the phosphorus content. Indicates. For this reason, the rotation shaft 1 is plated by electroless Ni-P plating, and the temperature of the rotation shaft 1 in the thermal spraying process is performed in the range of 300 to 500 ° C., whereby the wear resistance of the rotating sliding portion of the torque sensor shaft 10 is achieved. It is also possible to obtain an effect of improving.

  In the torque sensor shaft manufacturing method of the present invention, the magnetic material forming the magnetostrictive portion 2 is not particularly limited, and a conventionally used magnetic material having a magnetostrictive effect can be appropriately used. Examples of the magnetic material include a magnetic material having a magnetostriction effect such as an iron-based amorphous alloy, a nickel-based alloy, and a chromium-based alloy. Moreover, there is no restriction | limiting in particular as a thermal spraying apparatus in a thermal spraying process, A known thermal spraying apparatus can be used. For example, as the thermal spraying apparatus, a thermal spray gun in which a pipe for supplying magnetic powder to be sprayed together with a carrier gas such as nitrogen and a supply pipe for acetylene and oxygen as fuel are connected to each other is used. it can. Using this, the magnetostrictive portion 2 can be formed on the rotating shaft 1 by injecting the flame and the molten magnetic material onto the torque sensor shaft 10.

  In the torque sensor manufacturing method of the present invention, the shot blasting step is performed by shot blasting after the plating step and before the thermal spraying step, by removing the plating at the position where the magnetostrictive portion 2 on the rotating shaft 1 is formed. It is preferable to have. In this shot blasting process, the outer peripheral surface at the position where the magnetostrictive portion 2 is formed on the rotating shaft 10 is roughened, so that the magnetic material to be sprayed in the subsequent spraying process can be more strongly welded by the anchor effect. it can. In the torque sensor shaft manufacturing method of the present invention, the shot blasting device and shot blasting conditions in the shot blasting process are not particularly limited, and the conventional method is used. Can do.

  Moreover, in the manufacturing method of the torque sensor shaft of this invention, it is preferable to provide the preheating process which preheats the rotating shaft 1 before a thermal spraying process. By preheating the rotating shaft 1 before the spraying step, the magnetic material sprayed in the subsequent spraying step can be favorably welded to the rotating shaft 1. This preheating process can be performed by, for example, applying a flame of a spray gun used in the subsequent spraying process to the rotating shaft 1 and setting the temperature of the rotating shaft 1 to, for example, 300 to 500 ° C.

  Furthermore, in the torque sensor shaft manufacturing method of the present invention, it is preferable to provide a cooling step after the thermal spraying step. By providing the cooling step, it is possible to prevent the plating on the rotating shaft 1 from being melted due to the temperature of the rotating shaft 1 being excessively increased. In addition, although there is no restriction | limiting in particular about a cooling means, For example, the air cooling which does not require additional equipment etc. is employable. In the torque sensor shaft manufacturing method of the present invention, the thermal spraying process and the cooling process may be alternately repeated several times. That is, when the temperature of the rotating shaft 1 exceeds a predetermined temperature in the spraying process, the temperature of the rotating shaft 1 is lowered in the cooling process, and when the temperature of the rotating shaft 1 decreases to the predetermined temperature, the spraying process is performed again. May be. As described above, in the method for manufacturing a torque sensor shaft according to the present invention, the temperature of the rotary shaft 1 is preferably adjusted to 300 to 500 ° C. However, by alternately repeating the thermal spraying step and the cooling step, the rotary shaft 1 The temperature of 1 can be adjusted to 300-500 degreeC.

  Furthermore, in the method for manufacturing a torque sensor shaft according to the present invention, it is preferable to perform a slit forming step of forming slits 3 a and 3 b in the magnetostrictive portion 2 after forming the magnetostrictive portion 2 on the rotating shaft 1. The slits 3a and 3b can be formed by, for example, shot blasting. In this case, a masking step for masking the non-formed portions of the slits 3a and 3b of the magnetostrictive portion 2 before the slit forming step and a masking removing step for removing the masking after the slit forming step may be provided. Good. In the torque sensor shaft manufacturing method of the present invention, the shot blasting device and shot blasting conditions are not particularly limited even in the slit forming step, and the conventionally used shot blasting device and shot blasting conditions should be adopted. Can do.

  The manufacturing method of the torque sensor shaft of the present invention can maintain corrosion resistance by using a ferrous material as the material of the rotating shaft 1 on the outer periphery of the rotating shaft 1 and forming a passive film on the outer periphery of the rotating shaft 1, In addition, it is only important to have a plating step of plating a metal having a melting point of 500 ° C. or higher and a thermal spraying step of spraying a magnetic material at a position where the magnetostrictive portion 2 of the rotating shaft 1 is formed. There are no particular restrictions on.

  For example, the slit forming step in the torque sensor shaft manufacturing method of the present invention is not limited to shot blasting, and can be performed by a known method. In addition to shot blasting, for example, the slits 3a and 3b may be formed by chemical treatment such as etching after coating the magnetostrictive portion 2 with resin or the like, or the slits 3a and 3b may be formed by machining such as cutting. . Further, the shape of the slits 3a and 3b is not particularly limited, but it is preferably a chevron shape whose longitudinal direction is ± 45 ° with respect to the axial direction of the rotary shaft 1 as shown in FIG. Furthermore, masking in the masking process when the slit forming process is performed by shot blasting is not particularly limited, and conventional techniques can be appropriately employed.

1 Crankshaft 2 Magnetostrictive part 3 Slit 10 Torque sensor shaft

Claims (3)

In the manufacturing method of the torque sensor shaft in which the magnetostrictive portion is formed on the outer periphery of the rotating shaft,
A plating process that uses an iron-based material as the material of the rotary shaft, can maintain corrosion resistance by forming a passive film on the outer periphery of the rotary shaft, and performs plating of a metal having a melting point of 500 ° C. or higher; And a thermal spraying step of thermally spraying a magnetic material at a position where the magnetostrictive portion of the rotating shaft is formed.   The method of manufacturing a torque sensor shaft according to claim 1, wherein the plating is electroless nickel-phosphorus plating. 3. The method of manufacturing a torque sensor shaft according to claim 1, further comprising a shot blasting step of removing plating at a position where the magnetostrictive portion is formed by shot blasting after the plating step and before the spraying step.

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