MAGNETOSTRICTIVE TORQUE SENSOR SHAFT AND MANUFACTURING METHOD THEREFOR

Abstract

Provided are a magnetostrictive torque sensor shaft with excellent processing accuracy and stability of quality and a preferred method for manufacturing the shaft. The magnetostrictive torque sensor shaft has an amorphous thermal spray coating on the surface of a substrate made of a metal material, the amorphous thermal spray coating having a magnetostrictive property and being formed by thermal spraying, and the substrate surface being subjected to surface roughening by laser irradiation. The laser irradiation is performed in the surface roughening process prior to the amorphous thermal spraying and in pattern formation process after the thermal spraying.

Claims

1. A magnetostrictive torque sensor shaft having a magnetostrictive region for torque detection on a surface of the shaft, wherein the magnetostrictive torque sensor shaft comprises an amorphous thermal spray coating on the surface of a substrate made of a metal material, the amorphous thermal spray coating having a magnetostrictive property and being formed by thermal spraying, the surface of the substrate being subjected to surface roughening by laser irradiation.

2. A method of manufacturing a magnetostrictive torque sensor shaft having a magnetostrictive region for torque detection on a surface of the shaft, the method comprising processes of: surface roughening by laser irradiation on the surface of a substrate made of a metal material prior to amorphous thermal spraying; subjecting the surface of the substrate roughened by the laser irradiation to the amorphous thermal spraying; and thereafter pattern formation by the laser irradiation as with the surface roughening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a flowchart illustrating main process steps in one example of the method for manufacturing a magnetostrictive torque sensor shaft according to the present invention.

[0021] FIGS. 2A and 2B are processed sample images showing each surface condition after surface roughening (preprocessing) on the surface of a substrate in the method for manufacturing a magnetostrictive torque sensor shaft according to the present invention and the conventional method for manufacturing a magnetostrictive torque sensor shaft, respectively: FIG. 2A showing the surface condition after the substrate surface is subjected to surface roughening by laser irradiation according to the present invention; and FIG. 2B showing the surface condition after the substrate surface is subjected to the conventional surface roughening by shot blasting.

[0022] FIG. 3 is an enlarged schematic view of a part of appearance of the magnetostrictive torque sensor shaft after coating film removal (postprocessing) by laser irradiation according to the present invention.

[0023] FIG. 4 is a vertical sectional view showing the general structure of a magnetostrictive torque sensor shaft which is one example of the present invention.

DETAILED DESCRIPTION

[0024] The method of manufacturing a magnetostrictive torque sensor shaft of the present invention includes a surface roughening step (preprocessing), an amorphous thermal spraying step, and a pattern forming step (postprocessing), as illustrated in the flowchart of the manufacturing method of the magnetostrictive torque sensor shaft according to a preferred embodiment of the present invention in FIG. 1. In the surface roughening step prior to the thermal spraying, a laser irradiation is employed, instead of the conventional shot blasting with aluminum powder, on the surface roughening step (preprocessing) which is performed on the surface of a substrate (a metal material including aluminum, copper, carbon steel, and stainless steel), to improve adhesion (anchor effect) required for formation of an amorphous thermal spray coating on the surface of the substrate. In the amorphous thermal spraying step, an amorphous which is a magnetic material is subjected to thermal spraying on the surface of the roughened substrate to form a magnetostrictive region. In the pattern forming step (postprocessing), the amorphous thermal spray coating film formed by the amorphous thermal spraying step is partially removed by the laser irradiation from the substrate so as to form a desired pattern of the coating film.

[0025] That is, the method of manufacturing a magnetostrictive torque sensor shaft of the present invention uses the laser irradiation, instead of the conventional shot blasting with aluminum powder, in the surface roughening process (preprocessing) prior to the amorphous thermal spraying and in the pattern formation process (postprocessing) after the thermal spraying to achieve a magnetostrictive torque sensor shaft with superior processing accuracy and stability of quality and manufacture the shaft at low cost. The use of laser irradiation enables not only improvement in adhesion (anchor effect) required for formation of an amorphous thermal spray coating on the surface of the substrate, but also formation of an appropriately roughened surface within a short time just by adjusting the laser output, the moving velocity of the laser, and the like in the surface roughening process (preprocessing) prior to the thermal spraying, resulting in achievement of a well-finished surface of the substrate and a surface texture with accuracy and stability. In particular, regarding the finished condition (roughness) of the substrate surface, it is clearly seen from the processed sample images of FIGS. 2A and 2B that the surface condition (photo image 2A) which was obtained by the surface roughening process using the laser irradiation according to the present invention, shows that the finished surface of the substrate is good and the surface texture has significantly high reproducibility and uniformity, compared with the surface condition (photo image 2B) which was obtained by the surface roughening process using the conventional shot blasting.

[0026] The below is each surface roughness (measured by a prescribed roughness measurement) of the processed sample images showing the surface conditions in FIGS. 2A and 2B.

(1) Sample image 2A processed with laser irradiation [0027] Ra (roughness in the wide direction): 9.611 μm [0028] Ra (roughness in the lengthwise direction): 9.426 μm
(2) Sample image 2B processed with shot blasting [0029] Ra (roughness in the wide direction): 2.467 μm [0030] Ra (roughness in the lengthwise direction): 2.683 μm

[0031] As for the postprocessing included in the manufacturing method of the magnetostrictive torque sensor shaft of the present invention, the amorphous thermal spray coating film is partially removed by the laser irradiation from the substrate in the pattern forming step to form a desired pattern (design) of the coating film. In doing so, the pattern formation is carried out while controlling a reasonable amount of rotation angle of the substrate depending on the progress of the pattern formation by laser irradiation. The process makes it possible to achieve the magnetostrictive torque sensor shaft on which the desired pattern (design) of the coating film is formed. FIG. 3 illustrates a part of appearance of the magnetostrictive torque sensor shaft having the desired pattern (design) of the coating film. Reference sign 1 denotes the magnetostrictive torque sensor shaft, reference sign 2 denotes slits, and reference sign 3 denotes the magnetostrictive region.

[0032] As described above, the method of manufacturing the magnetostrictive torque sensor shaft of the present invention employs laser irradiation on the surface roughening process (preprocessing) prior to the thermal spraying and in the pattern formation process (postprocessing) after the amorphous thermal spraying, which makes it possible to produce the advantageous effects that can form the appropriately roughened surface on the substrate within a short time just by adjusting the laser output and the moving velocity of the laser and can obtain a well-finished surface of the substrate and a surface texture with accuracy and stability, and furthermore can save costs of masking sheets thanks to needlessness of the masking sheets, simplify equipment thanks to needlessness of the attachment and removal devices for masking sheets, and omit the attachment and removal work for the masking sheets in the pattern formation process (postprocessing), and thus shorten the time required for the postprocessing, thereby achieving in manufacture of the magnetostrictive torque sensor shaft with excellent processing accuracy and stability of quality at a low cost.

[0033] It goes without saying that laser processing which is performed as preprocessing in the present invention is not limited to the case where the magnetostrictive region is formed by thermal spraying, can be also applied to cases where a magnetostrictive region is formed by any ways other than thermal spraying.

REFERENCE SIGNS LIST

[0034] 1 Magnetostrictive torque sensor shaft [0035] 2 Slit [0036] 3 Magnetostrictive region