Method for forming rotor shaft material

Abstract

To provide a forming method for a rotor shaft material that can make machining of a key groove on a rotor shaft unnecessary or reduce the machining time while ensuring the dimensional accuracy of a final product.SOLUTION: From a flange part 33 of a rotor shaft material 3 to the end part on the side of a rotor core attachment part, by cold forging, a key groove 34 with a width of 5 to 10 mm and a depth of 1 to 10 mm for fitting a rotor core is formed at the same time as deep holes 32a, 32b are formed about the center of the rotor shaft material 3 and the flange part 33 is formed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for forming a material for a rotor shaft used in a rotating electrical machine. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, for example, a rotor shaft used in a rotating electric machine has a flange that abuts against one axial end face of the rotor to position the rotor, a rotor holding portion that holds the rotor on its outer peripheral surface and has a key groove recessed therein extending in the axial direction, and a male thread portion formed adjacent to the rotor holding portion. The key of the rotor core, which is made of a thin magnetic plate, is fitted into the key groove of the rotor holding part, and a nut threaded onto the male threaded part is tightened onto the axial end face of the rotor core, so that the rotor is positioned axially between the step and the nut and fastened to the rotor shaft.

[0003] The rotor shaft used in this type of rotating electric machine is manufactured using a broaching device, such as that disclosed in Patent Document 2, that performs broaching for keyway machining, splines, irregular holes, and the like.

[0004] Furthermore, as disclosed in Patent Document 3, after the male thread portion is formed on the rotor shaft, a key groove may be formed from the male thread portion to the rotor holding portion. This keyway allows the rotor core, which is made up of thin magnetic plates laminated on the shaft, and the rotor shaft to rotate together as a unit.

[0005] This keyway is usually machined using an end mill cutter, but compared to external diameter lathe machining, this requires special tools and takes longer to machine, which poses the problem of increased manufacturing costs. Another method is to use a side cutter, a disk-shaped cutting tool with cutting edges on the outer periphery and both sides, which has better cutting efficiency than an end mill. However, this has the drawback of cutting not only the keyway but also the flange that positions the rotor. Another method is to use a broaching machine, but this has the drawback that the broaching tool processes the keyway into a shape that interferes with the rotor holding portion. Besides cutting, there is also a method of manufacturing keyways by plastic deformation. However, this method has the drawback of first forming a hollow shaft and then forming a keyway on its outer periphery, which reduces dimensional accuracy due to deformation of the shaft itself and generates excess material at the formed end, requiring subsequent processing.

[0006] Furthermore, even when the rotor shaft material is formed by forging, which is a commonly used method for producing materials for metal products, the above-mentioned problems also exist. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-116022 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-54927 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-55470 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention solves the problem of the key groove formed on the rotor shaft used in the conventional rotating electric machine. In view of the above, the object of the present invention is to provide a method for molding a rotor shaft material that can eliminate machining of the rotor shaft keyway or shorten the machining time while ensuring the dimensional accuracy of the final product. [Means for solving the problem]

[0009] In order to achieve the above object, the method of the present invention for molding a rotor shaft material for a rotating electric machine having a rotor core mounting portion on which a rotor core is mounted and a flange portion that determines the axial mounting position of the rotor core mounting portion is characterized in that a keyway having a width of 5 to 10 mm and a depth of 1 to 10 mm for fitting the rotor core is formed by cold forging from the flange portion of the rotor shaft material to the tip on the rotor core mounting portion side.

[0010] In this case, the key groove can be formed simultaneously with the deep hole and flange portion formed in the center of the rotor shaft material.

[0011] Additionally, the keyway can be molded to meet the tolerance range of the final product. [Effects of the Invention]

[0012] According to the method for molding rotor shaft material of the present invention, the keyway formed from the flange portion of the rotor shaft material used in a rotating electric machine to the tip on the rotor core mounting portion side is formed by cold forging in addition to molding the rotor shaft material, thereby ensuring the dimensional accuracy of the final product and making it possible to eliminate the need for machining the keyway of the rotor shaft or to shorten the processing time. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram showing an example of a manufacturing process for a rotor shaft to which the method for molding a rotor shaft material of the present invention is applied. FIG. [Figure 2] 1 is an explanatory diagram of a method for forming a rotor shaft material according to the present invention. FIG. [Figure 3] (a1) is a longitudinal cross-sectional view of a rotor shaft material, (a2) is a plan view of the same, (b1) is a longitudinal cross-sectional view of a rotor shaft (final product), and (b2) is a plan view of the same. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for forming a rotor shaft material according to the present invention will be described with reference to the drawings.

[0015] FIG. 1 shows an example of a process to which the forming method of the present invention is applied, in which a rotor shaft material is manufactured using carburizing steel.

[0016] (1) Heat treatment In order to improve the cold formability of the billet (cylindrical raw material) 1, the billet (cylindrical raw material) 1 is subjected to heat treatment (annealing).

[0017] (2) Cold forging As shown in FIG. 2 , a billet (cylindrical material) 1 is cold forged (at room temperature) using a forging die (a forging die formed in a shape corresponding to the deep holes 32a and 32b, flange portion 33, and keyway 34 to be formed in the center of the rotor shaft material 3) to produce a blank 2 having holes 22a and 22b in the center in one process, which has a total length of about 150 to 300 mm and includes a shaft portion 31 (diameter: about 40 to 80 mm), deep holes 32a and 32b, a flange portion 33 (diameter: about 60 to 100 mm), and a keyway 34 (length: about 100 to 250 mm (length from the flange portion to the tip on the rotor core mounting portion side)). The rotor shaft material 3 is formed into a shape having a thickness of about 5 to 10 mm, a width of about 5 to 10 mm, and a depth of about 1 to 10 mm. Here, two key grooves 34 are formed at 180° symmetrical positions on the shaft portion 31, but one or three or more key grooves may also be formed.

[0018] (3) Heat treatment Next, in order to improve the machinability of the rotor shaft blank 3, the rotor shaft blank 3 is subjected to heat treatment (normalizing).

[0019] (4) Intermediate processing The inner peripheral surface of the shaft portion 31 of the rotor shaft material 3 on the deep hole 32b side is machined.

[0020] (5) Cold spline forming The inner peripheral surface of the shaft portion 31 of the rotor shaft material 3 on the deep hole 32b side is subjected to cold spline forming.

[0021] (6) Machining The outer surfaces of both sides of the shaft portion 31 of the rotor shaft material 3 are machined (finishing the rotor core mounting portion and bearing mounting portion and forming a male thread portion into which the nut screws), and the deep holes 32a, 32b are penetrated to obtain the rotor shaft (final product) 4 shown in Figures 3(b1) and (b2).

[0022] Here, the specifications (one example) of the manufactured rotor shaft blank 3 are shown. [Specifications of rotor shaft material 3] Total length: 212.0mm Shaft diameter 31: 55.0 mm Diameter of deep holes 32a and 32b: 29.0 mm Length of deep holes 32a and 32b: 167.0mm and 22.0mm Flange diameter 33: 75.0 mm Length of keyway 34: 170.0 mm Keyway 34 width: 7.0mm, 7.5mm Depth of keyway 34: 5.0mm, 5.0mm

[0023] This rotor shaft material 3 is used in a rotating electric machine. The keyway 34, which is formed from the flange portion 33 of the rotor shaft material 3 to the tip on the rotor core mounting side, is formed by cold forging in conjunction with the forming of the rotor shaft material 3 (forming the deep holes 32a, 32b formed in the center of the rotor shaft material 3 and the flange portion 33). This ensures the dimensional accuracy of the rotor shaft (final product) 4 (tolerance range of the width of the keyway 34: 0.1 mm or less (preferably 0.05 mm or less)). This makes it possible to eliminate the need for machining the keyway 44 of the rotor shaft (final product) 4 (net shaping by leaving the forged black surface finish) or shorten the processing time (reducing the amount of cutting).

[0024] The above describes the method for molding a rotor shaft material of the present invention based on its embodiments. However, the present invention is not limited to the configurations described in the above embodiments, and the configuration can be changed as appropriate within the scope of the spirit of the present invention. [Industrial Applicability]

[0025] The method for forming a rotor shaft material of the present invention can eliminate machining of the rotor shaft keyway or shorten the machining time while ensuring the dimensional accuracy of the final product, and therefore can be widely used to manufacture rotor shafts used in rotating electrical machines. Cut. [Explanation of symbols]

[0026] 1 Billet (cylindrical material) 2 blank 22a hole 22b hole 3 Rotor shaft materials 31 Shaft 32a deep hole 32b deep hole 33 Flange 34 Keyway 4 Rotor shaft (final product) 44 keyway

Claims

1. A method for forming a rotor shaft material for a rotating electric machine, which has a rotor core mounting portion on which a rotor core is mounted and a flange portion that determines the axial mounting position of the rotor core mounting portion, characterized in that a billet is cold forged in a single process using a forging die formed in a shape corresponding to a deep hole, flange portion, and keyway formed in the center of the rotor shaft material from both axial ends, to produce a blank having a central hole from both axial ends, and a rotor shaft material having a total length of 150 to 300 mm, a shaft portion, a deep hole from both axial ends, and flange portions, and a keyway having a width of 5 to 10 mm and a depth of 1 to 10 mm that extends from the flange portion to the tip on the rotor core mounting portion side, for fitting the rotor core.

2. 2. The method for forming a rotor shaft blank according to claim 1, wherein the keyway is formed to satisfy a tolerance range of the final product.

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