Manufacturing method of rotor

Abstract

To provide a novel technique for fixing a shaft to a core with a target axial force.SOLUTION: Disclosed is a manufacturing method for a rotor for an electric motor. The rotor comprises: a core; a shaft which is inserted through the core and provided in an upper end protruding from an upper end face of the core and includes a flange part pressing the upper end face; and a nut which is fastened to a lower end of the shaft protruding from a lower end face of the core and presses the lower end face of the core. The shaft includes a center hole extending from the upper end in an axial direction and a step surface, which is positioned in the lower end, is provided inside of the center hole. The manufacturing method includes the steps of: imposing a predetermined load on the step surface using a push-in rod, which is inserted from the upper end of the shaft to the center hole, while supporting the lower end face of the core, through which the shaft is inserted, with a jig; and fastening the nut to the lower end with predetermined torque in the state where the load is imposed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a method for manufacturing a rotor. [Background technology]

[0002] Patent Document 1 discloses a technique for fastening a bolt and nut fastener to a fastened body with a target axial force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-93119 A Summary of the Invention [Problem to be solved by the invention]

[0004] In rotors for electric motors, a core may be fastened to a shaft using a nut, thereby utilizing the axial force (axial elastic force) of the shaft to fix the shaft to the core. In such rotors, it is desirable that the shaft is fixed to the core with a target axial force. However, the influence of friction occurring on the seating surface and thread surface of the nut cannot be ignored by simply managing the fastening torque of the nut, and it is difficult to generate the target axial force on the shaft with good reproducibility.

[0005] The present specification provides a novel technique for fixing a shaft to a core at a target axial force. [Means for solving the problem]

[0006] In a first aspect of the present technology, a manufacturing method of a rotor for an electric motor is disclosed. The rotor includes a core, a shaft that is inserted into the core and is provided at an upper end protruding from an upper end surface of the core, and has a flange portion that presses the upper end surface, and a nut that is fastened to a lower end of the shaft that protrudes from a lower end surface of the core and presses the lower end surface of the core. The shaft has a central hole that extends in the axial direction from the upper end, and a stepped surface located within the lower end is provided inside the central hole. The manufacturing method includes a step of applying a predetermined load to the stepped surface using a push rod inserted from the upper end of the shaft into the central hole while supporting the lower end surface of the core through which the shaft is inserted with a jig, and a step of fastening the nut to the lower end with a predetermined torque while the load is being applied.

[0007] In the above configuration, a predetermined load is applied to the step surface located at the lower end of the shaft using a push rod inserted from the upper end of the shaft. As a result, a predetermined tensile load acts on the shaft, and the shaft is elastically deformed, generating a planned axial force in the shaft. In this state, when a nut is fastened to the lower end of the shaft with a predetermined torque, the core is fixed to the shaft. Since an axial force is already generated in the shaft, the torque required to fasten the nut can be relatively small, and as a result, the friction generated on the seat surface and thread surface of the nut can be kept small. Therefore, the effect of the friction can be eliminated or suppressed, and the target axial force can be generated in the shaft with good reproducibility. The predetermined load applied to the step surface using the push rod and the predetermined torque required to fasten the nut to the lower end of the shaft can each be set in advance according to the desired target axial force. [Brief description of the drawings]

[0008] [Figure 1] FIG. [Diagram 2] 1A to 1C are diagrams showing a method for manufacturing a rotor 2 using a manufacturing apparatus 30. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Example) (Rotor 2 Configuration) As shown in Fig. 1, the rotor 2 includes a core (rotor core) 10, a shaft (rotor shaft) 12 inserted through the core 10, and a nut (rotor nut) 14 fastened to the shaft 12. The rotor 2 is a rotor of a traction motor. The traction motor can be used in hybrid vehicles, battery-powered vehicles, fuel cell vehicles, plug-in hybrid vehicles, etc. Note that the up-down and left-right directions in Figs. 1 and 2 do not specify the actual directions.

[0010] Core 10 is formed into a cylindrical shape by laminating a plurality of electromagnetic steel plates in the vertical direction (axial direction) of rotor 2. Core 10 has a central hole 10A penetrating core 10 in the vertical direction at its center.

[0011] The shaft 12 has a cylindrical shape. The shaft 12 is composed of an upper end 12A, an intermediate portion 12B, and a lower end 12C. The upper end 12A protrudes upward from the upper end surface 10B of the core 10. The intermediate portion 12B is inserted into the central hole 10A of the core 10. The outer diameter of the intermediate portion 12B is slightly smaller than the hole diameter of the central hole 10A of the core 10. The lower end 12C protrudes downward from the lower end surface 10C of the core 10. The upper end 12A is provided with a flange portion 12D that presses the upper end surface 10B of the core 10 downward. That is, the flange portion 12D abuts against the upper end surface 10B of the core 10. The outer diameter of the flange portion 12D is larger than the hole diameter of the central hole 10A of the core 10. A nut 14 is fastened to the lower end 12C. When the nut 14 is fastened to the lower end portion 12C, the nut 14 presses the lower end surface 10C of the core 10 upward.

[0012] The shaft 12 has a central hole 16 extending downward from the upper end 12A. The central hole 16 penetrates the shaft 12 in the up-down direction. The central hole 16 is composed of a first central hole 16A and a second central hole 16B. The first central hole 16A and the second central hole 16B are separated by a step surface 18 located in the lower end 12C inside the central hole 16. The step surface 18 is located below the lower end of the nut 14 fastened to the lower end 12C. The hole diameter of the first central hole 16A is larger than the hole diameter of the second central hole 16B.

[0013] (Configuration of manufacturing device 30) With reference to FIG. 2, a manufacturing apparatus 30 for manufacturing the rotor 2 will be described. The manufacturing apparatus 30 is an apparatus for fixing the shaft 12 to the core 10. The manufacturing apparatus 30 includes a jig 32, a servo press 34, a push-in rod 36 connected to the servo press 34, and a socket 38. The jig 32 has a cylindrical shape. A center hole 32A that penetrates the jig 32 in the vertical direction is provided at the center of the jig 32. The hole diameter of the center hole 32A is larger than the hole diameter of the center hole 10A of the core 10. The servo press 34 is an apparatus for applying a predetermined load to the step surface 18 of the shaft 12 using the push-in rod 36. The push-in rod 36 has a cylindrical shape. The outer diameter of the push-in rod 36 is smaller than the hole diameter of the first center hole 16A of the shaft 12 and larger than the hole diameter of the second center hole 16B. The socket 38 is a member for fastening the nut 14 of the rotor 2 to the shaft 12.

[0014] (Manufacturing method of rotor 2) A method for manufacturing the rotor 2 using the manufacturing apparatus 30 will be described with reference to FIG.

[0015] First, as shown in FIG. 2(A), the core 10 is placed on a jig 32. Next, the shaft 12 is inserted into the core 10 from the upper end surface 10B side of the core 10. In a modified example, the core 10 with the shaft 12 inserted therein may be placed on the jig 32. As a result, the lower end surface 10C of the core 10 with the shaft 12 inserted therein is supported by the jig 32. Next, the servo press 34 is driven to insert a push rod 36 into the center hole 16 of the shaft 12 from the upper end portion 12A of the shaft 12, and a predetermined load is applied to the step surface 18 of the shaft 12. As a result, a predetermined tensile load acts on the shaft 12, and elastic deformation occurs in the shaft 12. That is, the shaft 12 extends slightly in the vertical direction (axial direction), and an axial force is generated in the shaft 12. The predetermined load is preferably set so that an axial force larger than the target axial force generated in the shaft 12 in the rotor 2, which is a completed product, is generated. With this configuration, the torque required to fasten the nut 14 to the lower end 12C of the shaft 12 can be reduced compared to when a predetermined load is set so that a target axial force is generated in the shaft 12.

[0016] Next, as shown in FIG. 2(B), in a state where a predetermined load is applied to the step surface 18, that is, in a state where an axial force is generated in the shaft 12, the nut 14 is fastened to the lower end 12C of the shaft 12 with a predetermined torque using the socket 38. The predetermined torque is set to a torque that can generate a target axial force in the shaft 12 when the load of the predetermined load on the step surface 18 is released. In this way, the predetermined load applied to the step surface 18 using the pushing rod 36 and the predetermined torque when fastening the nut 14 to the lower end 12C of the shaft 12 are each set in advance according to the desired target axial force. As a result, the shaft 12 is fixed to the core 10. That is, the shaft 12 presses the upper end surface 10B of the core 10, and the nut 14 presses the lower end surface 10C of the core 10. Thereafter, the rotor 2 is removed from the manufacturing apparatus 30, and the rotor 2 is completed (see FIG. 1).

[0017] As described above, the rotor 2 includes the core 10, the shaft 12 that is inserted through the core 10 and is provided at the upper end 12A protruding from the upper end face 10B of the core 10 and has a flange portion 12D that presses against the upper end face 10B, and the nut 14 that is fastened to the lower end 12C of the shaft 12 that protrudes from the lower end face 10C of the core 10 and presses against the lower end face 10C of the core 10. The shaft 12 has a central hole 16 that extends in the axial direction from the upper end 12A, and inside the central hole 16, a stepped surface 18 is provided that is located within the lower end 12C. A manufacturing method of a rotor 2 for an electric motor includes a step of applying a predetermined load to the step surface 18 using a pushing rod 36 inserted into the central hole 16 from the upper end 12A of the shaft 12 while supporting the lower end surface 10C of the core 10 through which the shaft 12 is inserted with a jig 32, and a step of tightening a nut 14 to the lower end 12C with a predetermined torque while the load is being applied.

[0018] According to the above configuration, a predetermined load is applied to the step surface 18 located at the lower end 12C of the shaft 12 using the push rod 36 inserted from the upper end 12A of the shaft 12. As a result, a predetermined tensile load acts on the shaft 12, and the shaft 12 is elastically deformed, so that a planned axial force is generated in the shaft 12. In this state, when the nut 14 is fastened to the lower end 12C of the shaft 12 with a predetermined torque, the core 10 is fixed to the shaft 12. Since the axial force is generated in advance in the shaft 12, the torque required to fasten the nut 14 can be relatively small, and as a result, the friction generated on the seat surface and thread surface of the nut 14 can be kept small. Therefore, the effect of the friction can be eliminated or suppressed, and the target axial force can be generated in the shaft 12 with good reproducibility. [Explanation of symbols]

[0019] 2: rotor, 10: core, 10A: center hole, 10B: upper end surface, 10C: lower end surface, 12: shaft, 12A: upper end portion, 12B: middle portion, 12C: lower end portion, 12D: flange portion, 14: nut, 16: center hole, 16A: first center hole, 16B: second center hole, 18: step surface, 30: manufacturing device, 32: jig, 32A: center hole, 34: servo press, 36: pushing rod, 38: socket

Claims

[Claim 1] 1. A method for manufacturing a rotor for an electric motor, comprising the steps of: The rotor is A core, a shaft that is inserted through the core and has a flange portion at an upper end protruding from an upper end surface of the core and pressing against the upper end surface; a nut that is fastened to a lower end of the shaft that protrudes from a lower end surface of the core and presses the lower end surface of the core, The shaft has a central hole extending axially from the upper end, and a stepped surface is provided inside the central hole and located within the lower end, The manufacturing method includes: a step of applying a predetermined load to the step surface using a push rod inserted into the central hole from the upper end of the shaft while supporting a lower end surface of the core through which the shaft is inserted by a jig; fastening the nut to the lower end portion with a predetermined torque while the load is applied; A manufacturing method comprising:

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