Manufacturing method of rotor for rotary electric machine

Abstract

To ensure a desired interference over an axial range of a mating area.SOLUTION: A manufacturing method of a rotor for a rotary electric machine includes: an arrangement step of supporting a workpiece including a core member for a rotor core and a hollow shaft member for a rotor shaft and forming a set state in which the shaft member is arranged on the inner diameter side of the core member; and a joining step of applying force to the workpiece in the set state to join the core member and the shaft member. The joining step includes a pressing step of applying radial force from the hollow interior of the shaft member to the radially outward direction such that the shaft member contacts or is pressed against the core member, and the pressing step is performed separately at multiple axial positions on the shaft member and is started from an axially outer position of the shaft member among the multiple positions.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a rotor for a rotating electric machine. [Background technology]

[0002] A technique is known in which a urethane mandrel inserted into the hollow interior of a hollow rotor shaft is compressed in the axial direction by a die and a pad, thereby fitting the rotor shaft into a shaft hole in a rotor core (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-106797 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described conventional technology, a urethane mandrel is used and the amount of radial expansion of the mandrel is controlled by compressive forces from both axial ends, so a significant interference is generated between the rotor core and the rotor shaft over the entire axial direction of the rotor core. However, if the axial range of the fitting region between the rotor core and the rotor shaft becomes relatively long, the axial length of the mandrel becomes long, making it difficult to ensure the desired interference over the entire axial direction.

[0005] In contrast, in a method in which the axial range of the mating region is divided into multiple ranges and interference is generated for each divided range, depending on the divided range in which interference is generated first, portions of the rotor shaft in other divided ranges may deform in an undesirable manner, which may result in the rotor not achieving the desired dimensional accuracy.

[0006] Therefore, in one aspect, an object of the present disclosure is to achieve a desired dimensional accuracy in a rotor while ensuring a desired interference over the axial range of a fitting region. [Means for solving the problem]

[0007] In one aspect, there is provided a method for manufacturing a rotor for a rotating electric machine, the method comprising: an arrangement step of supporting a workpiece including a core member for a rotor core and a hollow shaft member for a rotor shaft, and forming a set state in which the shaft member is arranged on the inner diameter side of the core member; a joining step of joining the core member and the shaft member by applying a force to the workpiece in the set state, the coupling step includes a pressing step of applying a radial force from a hollow interior of the shaft member to a radially outer side in a manner that the shaft member contacts or is pressed against the core member, There is provided a manufacturing method in which the pressing step is performed separately at a plurality of axial positions on the shaft member, and starts from an axially outer position of the shaft member among the plurality of positions. [Effects of the Invention]

[0008] In one aspect, the present disclosure makes it possible to ensure a desired interference over the axial range of the fitting region. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically showing a cross-sectional structure of a motor according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a rotor manufacturing apparatus. [Figure 3] FIG. 2 is an exploded perspective view of the pressure molding mechanism as viewed from below. [Figure 4] FIG. 2 is a cross-sectional perspective view of the pressure molding mechanism taken along a plane passing through a reference axis. [Figure 5] FIG. 2 is a perspective view of the pressure molding mechanism as viewed from below. [Figure 6]1 is a schematic flowchart showing the flow of the present manufacturing method. [Figure 7] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 8] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 9] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 10] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 11] 7A to 7C are cross-sectional views further schematically illustrating the state of loads applied to the rotor shaft and the rotor core in some steps shown in FIG. 6. [Figure 12] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 13] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 14A] FIG. 14 is an enlarged view of a portion Q1 in FIG. [Figure 14B] FIG. 10 is an explanatory diagram showing the state of the cam punch in a molding and pressurizing step as viewed from above. [Figure 15] 7A to 7C are cross-sectional views further schematically illustrating the state of loads applied to the rotor shaft and the rotor core in some steps shown in FIG. 6. [Figure 16] 7A to 7C are cross-sectional views schematically showing states in some steps shown in FIG. 6. [Figure 17] 7A to 7C are cross-sectional views further schematically illustrating the state of loads applied to the rotor shaft and the rotor core in some steps shown in FIG. 6. [Figure 18] 7A to 7C are cross-sectional views further schematically illustrating the state of loads applied to the rotor shaft and the rotor core in some steps shown in FIG. 6. [Figure 19] FIG. 10 is an explanatory diagram of a problem caused by the second comparative example. [Figure 20] FIG. 10 is a diagram illustrating the effect of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are merely examples and are not intended to limit the scope of the invention. In addition, shapes and the like in the drawings may be partially exaggerated for the sake of explanation.

[0011] 1 is a cross-sectional view schematically showing the cross-sectional structure of a motor 1 according to an embodiment. In FIG. 1, an X direction is defined, as well as an X1 side of the X direction and an X2 side of the X direction.

[0012] 1 shows the rotating shaft 12 of the motor 1. In the following description of the motor 1, the axial direction refers to the direction in which the rotating shaft (center of rotation) 12 of the motor 1 extends, and is parallel to the X direction. The radial direction refers to the radial direction centered on the rotating shaft 12. Therefore, the radially outer side refers to the side away from the rotating shaft 12, and the radially inner side refers to the side toward the rotating shaft 12. The circumferential direction corresponds to the direction of rotation around the rotating shaft 12.

[0013] The motor 1 may be a motor for driving a vehicle, such as that used in a hybrid vehicle or an electric vehicle, but the motor 1 may also be used for any other purpose.

[0014] The motor 1 is an inner rotor type, and the stator 21 is provided so as to surround the radially outer side of the rotor 30. The stator 21 has the radially outer side of a stator core 22 fixed to a stator support portion 10.

[0015] The case 2 forms a space that houses the motor 1. The case 2 includes a stator support 10. The stator support 10 is joined to the radially outer surface of the stator core 22. The stator support 10 may have a flow path through which cooling water passes and / or an oil path. The stator support 10 may be formed of two or more pieces.

[0016] The stator 21 includes a stator core 22 and a stator coil 29 .

[0017] Although the stator core 22 is formed, for example, from laminated steel plates of a circular magnetic material, in a modified example, the stator core 22 may be formed from a green compact obtained by compressing and solidifying magnetic powder. The stator core 22 may be formed from a split core that is split in the circumferential direction, or may be in a form that is not split in the circumferential direction.

[0018] Stator core 22 is formed with a plurality of teeth that protrude radially inward, and has stator coils 29 wound thereon.

[0019] The stator coil 29 includes, for example, a U-phase coil, a V-phase coil, and a W-phase coil. The stator coil 29 has slot insertion portions (not shown) that are inserted into slots of the stator core 22, as well as coil ends 29A and 29B that protrude from both sides of the stator core 22 in the axial direction.

[0020] The stator coil 29 may be wound around the stator core 22 by assembling coil pieces (not shown) in the form of segment coils to the stator core 22. A segment coil is a form in which the coil of each phase is divided into units that are easy to assemble (for example, units that can be inserted into two slots). The coil pieces are formed, for example, by covering a linear conductor (rectangular wire) with a substantially rectangular cross section with an insulating coating (not shown). The linear conductor is made of copper, but in a modified example, the linear conductor may be made of another conductive material such as iron.

[0021] The rotor 30 is disposed radially inside the stator 21. The rotor 30 includes a rotor core 32 and a rotor shaft 34. The rotor core 32 is fixed to the radially outside of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor shaft 34 is rotatably supported by the case 2 via bearings 14a and 14b. Specifically, the inner peripheral surface of the rotor shaft 34 on the X1 side is supported by the bearing 14a, and the outer peripheral surface of the rotor shaft 34 on the X2 side is supported by the bearing 14b. The rotor shaft 34 defines the rotary shaft 12 of the motor 1.

[0022] The shape of the inner circumferential surface of the rotor shaft 34 may or may not be rotationally symmetrical about the rotation axis 12 when viewed from above. For example, the inner circumferential surface of the rotor shaft 34 may be circular, elliptical, or polygonal when viewed from above. Spline teeth, grooves, or the like may be formed on the inner and outer circumferential surfaces of the rotor shaft 34.

[0023] The rotor core 32 is formed, for example, from annular laminated steel plates of a magnetic material. Permanent magnets 329 are inserted inside the rotor core 32. The number and arrangement of the permanent magnets 329 are optional. In a modified example, the rotor core 32 may be formed from a green compact obtained by compressing and solidifying magnetic powder.

[0024] In this embodiment, no end plates are provided on both axial sides of the rotor core 32, but end plates may be provided. In this case, the end plates may be press-fitted onto the rotor shaft 34 to apply a slight axial force to the rotor core 32.

[0025] As shown in FIG. 1, the rotor shaft 34 has a hollow portion 34A. The hollow portion 34A extends over the entire axial length of the rotor shaft 34. The hollow portion 34A may function as an oil passage. For example, as shown by arrow R1 in FIG. 1, oil may be supplied to the hollow portion 34A from one axial end thereof, and the oil may flow along the radially inner surface of the rotor shaft 34, thereby cooling the rotor core 32 from the radially inner side. Furthermore, the oil flowing along the radially inner surface of the rotor shaft 34 may be ejected radially outward through oil holes 348, 349 formed at both ends of the rotor shaft 34 (arrows R5, R6) and used to cool the coil ends 29A, 29B.

[0026] When the axial range where the rotor shaft 34 is coupled to the rotor core 32 is defined as the coupling portion, the rotor shaft 34 may have a configuration in which one of the two ends axially outward of the coupling portion is reduced in diameter. Specifically, as shown in FIG. 1, the rotor shaft 34 is configured such that the end on the X2 side is reduced in diameter, while the end on the X1 side is not reduced in diameter. Therefore, the hollow portion 34A has a smaller inner diameter at the end on the X2 side. Specifically, the rotor shaft 34 has a first inner diameter r1 from the end face on the X1 side to the end on the X2 side, and a second inner diameter r2 at the end on the X2 side. The second inner diameter r2 is significantly smaller than the first inner diameter r1.

[0027] In this embodiment, the rotor shaft 34 has a protruding portion 340 that protrudes radially outward at the end on the X1 side. When viewed in the axial direction, the protruding portion 340 overlaps with a radially inner portion of the axial end face 320 of the rotor core 32 and abuts in the axial direction against the radially inner portion of the axial end face 320 of the rotor core 32. As will be described later, the protruding portion 340 has the function of axially positioning the rotor shaft 34 with respect to the rotor core 32 during manufacturing.

[0028] 1, the value of the first inner diameter r1 is substantially constant, and a first step 346 or the like for receiving the thrust load of the bearing 14a is formed as a step where the value of the first inner diameter r1 changes. Note that the step (radial difference) of the first step 346 may be significantly smaller than that of the second step 347 in the radial direction associated with the change (decrease) from the first inner diameter r1 to the second inner diameter r2. Note that in this embodiment, the rotor shaft 34 has an inner diameter r3 (≒ r1) at the end on the X1 side that is significantly larger than the second inner diameter r2, and therefore the bearing 14a can be disposed on the inner circumferential surface side of the rotor shaft 34.

[0029] Such a rotor shaft 34 has a relatively large first inner diameter r1 in the axial range where it joins with the rotor core 32, so that the permanent magnets 329 and the like can be efficiently cooled via oil flowing along the inner circumferential surface of the rotor shaft 34.

[0030] 1 discloses a specific oil cooling method, any method for cooling the motor 1 using oil may be used. For example, an oil supply pipe may be provided that is inserted into the hollow portion 34A, or oil may be dripped from the radially outer side toward the coil ends 29A, 29B through an oil passage that may be formed in the stator support portion 10.

[0031] Next, with reference to Figure 2 and subsequent figures, an example of a manufacturing apparatus 200 and a manufacturing method for the rotor 30 in the motor 1 of the above-described embodiment will be described. Figure 2 and other figures define the Z direction parallel to the rotation axis 12, as well as the Z1 side and Z2 side along the Z direction. Hereinafter, for the sake of explanation, as an example, the Z direction corresponds to the up-down direction during the manufacturing process, and the Z2 side is the down side. Also, Figure 2 and other figures show a reference axis I in the manufacturing apparatus 200. The reference axis I constitutes the central axis when centering the workpiece, and corresponds to the above-described rotation axis 12. Also, hereinafter, terms such as the axial direction are based on the reference axis I. Therefore, for example, the radial direction corresponds to the radial direction of the rotating body centered on the reference axis I.

[0032] Fig. 2 is a cross-sectional view that schematically shows a manufacturing apparatus 200 for the rotor 30. Figs. 3 to 5 are explanatory views of the pressure molding mechanism 25 that includes a cam punch base 256, a cam driver 258, and a cam punch 260. Fig. 3 is an exploded perspective view of the pressure molding mechanism 25 as viewed from below, Fig. 4 is a cross-sectional perspective view of the pressure molding mechanism 25 cut along a plane that passes through the reference axis I, and Fig. 5 is a perspective view of the pressure molding mechanism 25 as viewed from below. Note that in Fig. 3, some (two of four) of the cam punches 260 are not shown.

[0033] The manufacturing apparatus 200 includes a press 210 and a mold 240 .

[0034] The press 210 may have a conventional configuration, in which case the manufacturing apparatus 200 can be formed using an existing press. The press 210 has an upper slide 214 that is vertically slidable (slidable) relative to a lower bolster (bed) 212. The position of the slide 214 can be controlled in the vertical direction. The bolster 212 is provided with a bed knockout pin 2122 that can move in the vertical direction. For example, the bed knockout pin 2122 has a function of lifting the workpiece from the lower die 270 (a function of separating the workpiece from the lower die 270) and may be built into the bolster 212. The bed knockout pin 2122 may be similar to a bed knockout pin provided in a typical press. The vertical position and / or load (vertical load transmitted via the bed knockout pin 2122) of the bed knockout pin 2122 can be controlled.

[0035] The mold 240 includes an upper mold 250 , a lower mold 270 , a core holder 280 , and a shaft holder 290 .

[0036] The upper mold 250 includes an upper mold fixing portion 252 , a cam punch base 256 , a cam driver 258 , and a cam punch 260 .

[0037] The upper mold fixing part 252 is fixed to the slide 214 of the press machine 210. The upper mold fixing part 252 moves (lifts and lowers) together with the slide 214 in the up and down direction.

[0038] Cam punch base 256 is supported by upper mold fixing part 252 in a manner that allows it to move up and down relative to upper mold fixing part 252. Cam punch base 256 can also move up and down (raise and lower) integrally with upper mold fixing part 252 and slide 214.

[0039] 3 to 5, cam punch base 256 has a cylindrical shape that extends in the vertical direction, and has, on its lower end surface, a slide support portion 2562 that supports cam punch 260. As shown in FIGS. 3 and 4, slide support portion 2562 has a downward T-shaped cross section when viewed in the radial direction, and extends in the radial direction with a uniform cross section.

[0040] As shown in FIG. 4, the cam punch base 256 has a slide hole 2564 formed by a hollow interior with the reference axis I as its axis, and the slide hole 2564 extends in the vertical direction with a uniform cross section (for example, a uniform rectangular cross section when viewed from above).

[0041] The cam driver 258 functions as a driving member that drives the cam punch 260. The cam driver 258 is supported by the cam punch base 256 in a manner that allows it to move up and down relative to the cam punch base 256.

[0042] Cam driver 258 is movable vertically between an upper operating position and a lower non-operating position relative to cam punch base 256. When cam driver 258 moves between the operating position and the non-operating position, cam punch 260 is displaced in conjunction therewith between a radially outer operating position and a radially inner non-operating position.

[0043] Cam driver 258 is pushed up to an upper operating position by driver drive pin 274, which will be described later. Note that when cam driver 258 is axially separated from driver drive pin 274, which will be described later, it is located at a lower non-operating position due to the influence of gravity. Note that displacement of cam driver 258 relative to cam punch base 256, downward displacement below the lower non-operating position, may be restricted by stopper 2581 (see FIG. 2). Note that the upper operating position may be fixed or variable, as will be described later.

[0044] The cam driver 258 includes a supported portion 2582 and a driving portion 2584 .

[0045] Supported portion 2582 is inserted into slide hole 2564 of cam punch base 256. Supported portion 2582 extends in the vertical direction with a uniform cross section (for example, a uniform rectangular cross section when viewed from above) corresponding to slide hole 2564.

[0046] Driving portion 2584 extends in the vertical direction in a manner that is continuous with the lower end of supported portion 2582. Driving portion 2584 is disposed radially inside cam punch 260. Specifically, driving portion 2584 is disposed in hollow portion 262 (see FIG. 3) on the radial inside of cam punch 260.

[0047] The cross-sectional area of drive portion 2584 (the cross-sectional area when cut in a horizontal plane) increases downward. In the example shown in FIGS. 3 to 5, drive portion 2584 has a rectangular cross-sectional shape (e.g., a square cross-sectional shape). However, in modified examples, drive portion 2584 may have another cross-sectional shape, such as a polygon, depending on the division mode of cam punch 260 (and the associated cross-sectional shape of radially inner cavity 262), which will be described later.

[0048] Drive unit 2584 has, on its outer circumferential surface (side surface), second inclined surfaces 25842 that are inclined relative to the up-down direction. Second inclined surfaces 25842 are planar and form the four side surfaces (outer circumferential surfaces) of drive unit 2584. The inclination angles (for example, inclination angles relative to reference axis I; see the supplementary angle of angle θ in FIG. 14A described later) of second inclined surfaces 25842 on the four side surfaces of drive unit 2584 may be the same.

[0049] The driving portion 2584 is disposed in the cavity 262 on the radially inner side of the cam punch 260 in such a manner that the second inclined surface 25842 is in surface contact with a first inclined surface 2601 of the cam punch 260, which will be described later. In this case, the surface contact between the driving portion 2584 and the cam punch 260 may be maintained even when the cam driver 258 is in any position between the upper operating position and the lower non-operating position.

[0050] Cam punch 260 is supported by slide support portion 2562 of cam punch base 256. Cam punch 260 is supported by cam punch base 256 in a manner such that cam punch 260 is displaceable in the radial direction relative to cam punch base 256.

[0051] The cam punch 260 is radially displaceable between a radially inner inoperative position and a radially outer operative position. When the cam punch 260 is in the inoperative position, it has a shape that allows it to be positioned within the hollow portion 34A of the rotor shaft 34. When the cam punch 260 is in the radially inner inoperative position, it has an outer shape (for example, an overall substantially circular or elliptical outer shape) that corresponds to the shape of the inner circumferential surface of the rotor shaft 34 in a top view. In this case, when the cam punch 260 is in the radially inner inoperative position, it may have an outer shape that is offset radially inward from the shape of the inner circumferential surface of the rotor shaft 34 in a top view.

[0052] Cam punch 260 is normally positioned at a non-operating position on the radially inner side. An elastic ring (not shown), which is a ring-shaped elastic member, may be provided in ring groove 261 of cam punch 260. In this manner, cam punch 260 may be biased toward the non-operating position on the radially inner side by biasing means such as the elastic ring (not shown).

[0053] The radial position of the cam punch 260 changes in conjunction with the axial displacement of the cam driver 258. Specifically, when the cam driver 258 moves from the lower inoperative position to the upper operative position, the cam punch 260 moves in conjunction with this from the radially inner inoperative position to the radially outer operative position. Furthermore, when the cam driver 258 moves from the upper operative position to the lower inoperative position, the cam punch 260 moves in conjunction with this from the radially outer operative position to the radially inner inoperative position. When the cam punch 260 is in the radially outer operative position, it has an outer shape (e.g., an overall substantially circular or elliptical outer shape) that corresponds to the shape of the inner circumferential surface of the rotor shaft 34, as viewed from above. In this case, when the cam punch 260 is in the radially outer operative position, it may have an outer shape that is offset radially outward from the shape of the inner circumferential surface of the rotor shaft 34, as viewed from above (see the dashed dotted line in Figure 14B, described later).

[0054] Cam punch 260 has a hollow portion 262 on the radially inner side. Hollow portion 262 continues from slide hole 2564 of cam punch base 256 and extends in the axial direction with reference axis I as its axis. Note that hollow portion 262 has a shape corresponding to drive unit 2584 of cam driver 258 in a top view. Note that hollow portion 262 may have a cross-sectional shape that is rotationally symmetric with respect to reference axis I (a shape relating to a cross section when cut on a horizontal plane).

[0055] Cam punch 260 has first inclined surface 2601 that is inclined relative to the vertical direction on the inner circumferential surface that forms hollow portion 262. First inclined surface 2601 forms a contacted portion that comes into contact with second inclined surface 25842 of drive portion 2584 of cam driver 258. As will be described later with reference to FIG. 14A , first inclined surface 2601 has the function of converting a portion of the force that cam punch 260 receives from drive portion 2584 into a radial force.

[0056] The cam punch 260 has the function of applying a radial force to the inner peripheral surface of the rotor shaft 34, thereby expanding the diameter of the rotor shaft 34 in a manner that involves plastic deformation. To be able to appropriately perform this function, the cam punch 260 is preferably configured to have high rigidity / hardness. For example, the cam punch 260 may be formed from a metal material and be a substantially rigid body (a rigid body that does not substantially deform in the molding and pressurizing process described below). When formed from a metal material, the cam punch 260 is less susceptible to wear and tear than urethane, and can have significantly higher durability.

[0057] 3 to 5, for example, cam punch 260 is divided into four parts in the circumferential direction, and each divided part forms cam slider 2602. In a modified example, cam punch 260 may be divided into five or more parts, or into three or less parts.

[0058] Each cam slider 2602 is supported by the slide support portion 2562 of the cam punch base 256 in a manner allowing it to slide radially outward along the radial direction relative to the slide support portion 2562. In the example shown in FIGS. 3 and 4, each cam slider 2602 has an engagement groove 2604 that engages with the slide support portion 2562, and the engagement groove 2604 has a downward T-shaped cross section corresponding to the cross section of the slide support portion 2562 when viewed in the radial direction, and extends radially with a uniform cross section. Note that in the example shown in FIGS. 3 to 5, each cam slider 2602 is a divided body divided into four, and therefore the respective sliding directions may be orthogonal to each other.

[0059] Each cam slider 2602 forms the above-described first inclined surface 2601 in a one-to-one correspondence with each second inclined surface 25842 on the four side surfaces of the drive portion 2584. Moreover, the first inclined surface 2601 of each cam slider 2602 as a whole forms the radially outer boundary surface of the cavity portion 262. The inclination angle of the first inclined surface 2601 of each cam slider 2602 (for example, the inclination angle with respect to the reference axis I; see the supplementary angle of angle θ in FIG. 14A described later) may be the same for each other.

[0060] The core holder 280 is supported by the upper mold fixing part 252 in a manner that allows it to move up and down relative to the upper mold fixing part 252. The core holder 280 is in surface contact with the upper end surface of the stack of steel plates that forms the rotor core 32, and can press it downward (towards the Z2 side).

[0061] The shaft presser 290 is disposed in a manner that allows it to move up and down relative to the upper mold fixing portion 252 (and the slide 214). The shaft presser 290 comes into surface contact with the upper end surface of the shaft member that forms the rotor shaft 34, and is capable of pressing it downward (toward the Z2 side). The shaft presser 290 is capable of moving up and down independently of the upper mold fixing portion 252 (and the slide 214). Therefore, the shaft presser 290 can press the upper end surface of the shaft member that forms the rotor shaft 34 in a manner that does not depend on the pressing force of the core presser 280 (pressing force against the upper end surface of the laminate of steel plates that forms the rotor core 32).

[0062] The lower mold 270 includes a work support portion 272 and a driver drive pin 274 .

[0063] The workpiece support portion 272 is a lower die fixing portion that is fixed to the bolster 212 of the press machine 210. The workpiece support portion 272 supports the workpiece, including the rotor core 32 and the hollow rotor shaft 34, from below. At this time, the workpiece support portion 272 creates a state in which the rotor shaft 34 is disposed on the inner diameter side of the rotor core 32 (see FIG. 8 described later). In this embodiment, the workpiece support portion 272 supports the rotor shaft 34 via the rotor core 32 (i.e., does not directly support the rotor shaft 34).

[0064] The driver drive pin 274 functions as one component of the pressure molding mechanism 25. The driver drive pin 274 is movable in the vertical direction relative to the work support part 272 in a manner that allows it to abut against the lower end surface of the cam driver 258 (i.e., the lower end surface of the drive part 2584) in the vertical direction. The driver drive pin 274 may be movable in the vertical direction in a manner that allows it to be integrated with the bed knockout pin 2122.

[0065] With its upper end surface abutting against the lower end surface of the cam driver 258, the driver drive pin 274 applies an axial force to the cam driver 258 based on the axial load from the bed knockout pin 2122. In other words, the driver drive pin 274 transmits the axial load from the bed knockout pin 2122 to the cam driver 258, thereby applying an axial force (upward force) to the cam driver 258.

[0066] According to such a manufacturing apparatus 200, the rotor 30 can be manufactured with high precision by the manufacturing method described below using an existing press machine 210. In a modified example, equipment may be used instead of the press machine 210. An example of the operation of the manufacturing apparatus 200 will be described in relation to the manufacturing method described below.

[0067] FIG. 6 is a schematic flowchart showing the flow of the manufacturing method. FIGS. 7 to 10, 12, 13, and 16 are cross-sectional views schematically showing the state of the rotor shaft 34 and rotor core 32 in the manufacturing apparatus 200 at several steps shown in FIG. 6. FIGS. 11, 15, 17, and 18 are cross-sectional views further schematically showing the state of the load applied to the rotor shaft 34 and rotor core 32 at several steps shown in FIG. 6, and are schematic views showing only one side with respect to the reference axis I. FIG. 14A is an enlarged view of portion Q1 in FIG. 13 and is an explanatory diagram of the load transmission mode in the molding pressure step. FIG. 14B is an explanatory diagram showing the state of the cam punch 260 in a top view at the molding pressure step. FIG. 14B shows the cam punch 260 when it is in a non-operating position on the radially inner side, and also shows a dashed line representing the outline of the cam punch 260 when it is in an operating position on the radially outer side.

[0068] 7, this manufacturing method includes a preparation step (step S500) of preparing, as workpieces, a shaft member that forms the rotor shaft 34 and a stack of steel plates that forms the rotor core 32 (not bonded to each other). Note that, hereinafter, the shaft member that forms the rotor shaft 34 will be simply referred to as the "rotor shaft 34," and the stack of steel plates that forms the rotor core 32 will be simply referred to as the "rotor core 32."

[0069] At this stage, the rotor shaft 34 may have the protrusion 340, first step portion 346, and second step portion 347 described above. At this stage, the rotor shaft 34 has an inner diameter r1' at a portion that forms the inner circumferential surface of the first inner diameter r1 in the finished state, and the inner diameter r1' may be slightly smaller than the first inner diameter r1 (see FIG. 1) in the finished state. At this stage, the rotor shaft 34 may have an outer diameter r20 that is the same as or slightly smaller than the inner diameter r10 of the rotor core 32.

[0070] Also, like the rotor shaft 34, the rotor core 32 at this stage may have an outer diameter slightly smaller than the outer diameter in the finished product state. This is because the rotor core 32 deforms slightly radially outward as the rotor shaft 34 expands in diameter in the integration step (step S506) described below.

[0071] Next, as shown in Fig. 8, this manufacturing method includes a step (step S501) of setting the rotor shaft 34 and rotor core 32 in the manufacturing apparatus 200. At this time, the work support portion 272 of the lower mold 270 of the manufacturing apparatus 200 supports the rotor core 32 from below and restricts downward movement (displacement) of the rotor core 32. At this time, the rotor shaft 34 is supported by the rotor core 32 as the protrusion 340 abuts against the rotor core 32 in the axial direction. In this way, when step S501 is completed, the rotor shaft 34 is supported by the work support portion 272 via the rotor core 32. Fig. 8 schematically shows the state at the end of step S501.

[0072] The rotor shaft 34 and the rotor core 32 do not necessarily have to be set on the workpiece support portion 272 of the manufacturing apparatus 200 at the same time, and may be set on the workpiece support portion 272 of the manufacturing apparatus 200 in order.

[0073] Next, this manufacturing method includes a step (step S502) of applying an axial force to a radially inner portion of the rotor core 32 (a portion overlapping the protrusion 340 in an axial view) by pressing the rotor shaft 34 in the axial direction with the shaft presser 290. The shaft presser 290 may press the entire axial end surface of the rotor shaft 34 on the Z1 side toward the Z2 side. At this time, the shaft presser 290 may also press the axial end surface of the first stepped portion 346 associated with the bearing 14a (a surface that receives the thrust load of the bearing 14a) toward the Z2 side (see FIG. 11 described later). FIG. 9 schematically illustrates the state at the end of step S502. This pressing by the shaft presser 290 serves to maintain the axial positioning of the rotor shaft 34 relative to the rotor core 32 in the integration step (step S506) described later. Therefore, the pressing state by the shaft presser 290 may be maintained at least partially during the integration step (step S506) described later.

[0074] Next, the manufacturing method includes a step of lowering the upper die 250 to the preparation position and pressing the rotor core 32 in the axial direction with the core presser 280 (step S504). FIG. 10 schematically illustrates the state at the end of step S504. At this time, the core presser 280 applies an axially downward force to the rotor core 32 from the axial end surface 320. This pressing by the core presser 280 may be performed to adjust the axial thickness (stack thickness) of the rotor core 32 to a desired thickness. The core presser 280 presses in the axial direction a region of the rotor core 32 radially outward from the protruding portion 340 of the rotor shaft 34. The pressing force by the core presser 280 may be significantly smaller than the pressing force by the shaft presser 290 described above. The pressing state by the core presser 280 may be maintained during the integration step (step S506) described below.

[0075] 11, the pressing state by the core presser 280 and the pressing state by the shaft presser 290 are schematically shown by forces F110 and F111. In this embodiment, the pressing by the core presser 280 and the pressing by the shaft presser 290 are performed independently of each other, but they may also be performed simultaneously. In other words, the core presser 280 and the shaft presser 290 may be an integrated pressing member.

[0076] Next, the manufacturing method includes an integration step (step S506) of integrating the rotor core 32 and the rotor shaft 34 by expanding the diameter of the rotor shaft 34.

[0077] In this embodiment, the integration process is performed for each of the multiple axially formed target regions on the inner peripheral surface of the rotor shaft 34. In this embodiment, the integration process is started from the axially end side of the multiple axially formed target regions. For example, the integration process may be performed in order from top to bottom of the multiple axially formed target regions. Hereinafter, the region of the multiple axially formed target regions that is to be formed and pressurized in the current integration process will be referred to as the "currently formed target region."

[0078] The multiple axial forming target regions may cover the entire axial range of the rotor shaft 34 that is coupled to the rotor core 32. However, in a modified example, the multiple axial forming target regions may cover a portion of the axial range of the rotor shaft 34 that is coupled to the rotor core 32.

[0079] In this embodiment, of the multiple forming target regions in the axial direction, the forming target region on the axial end side (the uppermost forming target region) includes the upper end position of the axial range of the rotor shaft 34 that is coupled to the rotor core 32. In this case, the upper end position of the forming target region on the axial end side (the uppermost forming target region) may coincide with the upper end position of the axial range of the rotor shaft 34 that is coupled to the rotor core 32. However, in this embodiment, the forming target region on the axial end side (the uppermost forming target region) is set to include an axial range that is higher than the axial range of the rotor shaft 34 that is coupled to the rotor core 32. In other words, the forming target region on the axial end side (the uppermost forming target region) is set to overlap the protrusion 340 when viewed in the radial direction. In this case, the upper end of the forming target region on the axial end side (the uppermost forming target region) may coincide with the axial position of the first step portion 346.

[0080] The integration step (step S506) includes a molding positioning step (step S5061) of positioning the cam punch 260 relative to the rotor shaft 34 so that the cam punch 260 faces or contacts in the radial direction the current molding target area on the inner peripheral surface of the rotor shaft 34. Fig. 12 schematically shows the state at the end of step S5061 when the second molding target area from the top of the multiple molding target areas in the axial direction is the current molding target area.

[0081] 12, in parallel with the molding positioning step (step S5061), the bed knockout pin 2122 is raised to a position immediately before the driver drive pin 274 abuts against the cam driver 258. However, in a modified example, such raising of the bed knockout pin 2122 may be performed after the molding positioning step (step S5061) and before step S5062, or may be performed before the molding positioning step (step S5061).

[0082] The integration process (step S506) then includes a molding pressurizing process (step S5062) in which the axial load from the bed knockout pin 2122 is transmitted to the cam driver 258 via the driver drive pin 274 as an axial force, thereby displacing (sliding) the cam punch 260 in the radial direction. Figure 13 schematically shows the state during the molding pressurizing process (step S5062). In Figure 13, the axial load F13 applied to the cam driver 258 via the driver drive pin 274 is schematically shown by an arrow.

[0083] In the molding pressurization step (step S5062), driver drive pin 274 pushes up cam driver 258 based on the axial load from bed knockout pin 2122. When cam driver 258 is pushed up, as shown in FIG. 14A , cam punch 260 is pushed out radially outward toward the radially outer operating position with second inclined surface 25842 of cam driver 258 and first inclined surface 2601 of cam punch 260 in contact with each other.

[0084] As the cam punch 260 moves toward its radially outer operating position, the cam punch 260 radially contacts the current forming target area on the inner circumferential surface of the rotor shaft 34. When the cam punch 260 further moves toward its radially outer operating position, a force F3 perpendicular to the contact surface between the second inclined surface 25842 of the cam driver 258 and the first inclined surface 2601 of the cam punch 260 is generated in response to a reaction force (a reaction force directed radially inward) from the rotor shaft 34. As shown in FIG. 14A , this force F3 is divided into a vertical component F1 and a radial component F2 directed radially outward, the magnitude of which depends on the magnitude of the axial load from the bed knockout pin 2122. The magnitude of the radial component F2 can be expressed as F2 = F3 × sin θ. In this case, the angle θ corresponds to the inclination angle of the first inclined surface 2601 (and the second inclined surface 25842) relative to the horizontal plane, as shown in FIG. 14A .

[0085] Then, by further increasing the axial load from the bed knockout pin 2122 (i.e., by increasing the radial component F2), the cam punch 260 is further displaced radially outward toward the operating position, whereby the cam punch 260 reaches the operating position in a manner that involves plastic deformation of the rotor shaft 34. That is, the increased radial component F2 acts radially outward on the current forming target region (see region P2 in FIG. 14A ) on the inner circumferential surface of the rotor shaft 34, and the rotor shaft 34 expands in diameter accompanied by plastic deformation. In this way, when the driver drive pin 274 is pushed up to the operating position and the cam punch 260 reaches the operating position, the rotor shaft 34 expands in diameter accompanied by plastic deformation. As a result, the rotor shaft 34 expands in diameter in the axial range corresponding to the current forming target region, and the rotor core 32 and the rotor shaft 34 are integrated.

[0086] Here, the radial interference between the rotor core 32 and the rotor shaft 34 achieved in the molding and pressurizing step (step S5062) is determined by the radial displacement (slide amount) Δd (see FIG. 14B ) of the cam punch 260 from when the cam punch 260 abuts against the inner circumferential surface of the rotor shaft 34 until it reaches its operating position. This radial displacement (slide amount) Δd of the cam punch 260 is determined by the difference between the vertical position of the driver drive pin 274 when the cam punch 260 abuts against the inner circumferential surface of the rotor shaft 34 and the vertical position of the driver drive pin 274 when it reaches its operating position. The vertical movement amount related to this difference can be precisely controlled by controlling the vertical position of the bed knockout pin 2122. In this way, according to this embodiment, the radial interference between the rotor core 32 and the rotor shaft 34 can be precisely controlled by controlling the position of the bed knockout pin 2122.

[0087] The integration step (step S506) then includes a pressure release step (step S5063) in which the bed knockout pin 2122 and the driver drive pin 274 are slightly lowered to return the cam driver 258 to the inoperative position. Accordingly, the cam punch 260 is returned radially inward from the operative position to the inoperative position. Note that a ring-shaped elastic body (not shown) may be wound around the ring groove 261 (see FIG. 4) of the cam punch 260 as a return mechanism for realizing such radial movement of the cam punch 260. In this case, the elastic ring can simultaneously bias the four cam sliders 2602 radially inward toward the inoperative position.

[0088] In this embodiment, a radial force (see radial component F2) can be applied to the cam punch 260 by the drive unit 2584 of the cam driver 258 located in the cavity 262 radially inside the cam punch 260. At this time, the forming target area on the inner circumferential surface of the rotor shaft 34 (see area P2 in FIG. 14A ) overlaps the contact area between the cam punch 260 and the cam driver 258 (i.e., the contact area between the first inclined surface 2601 and the second inclined surface 25842) when viewed in the radial direction. This makes it possible to uniformize the radial force applied to the inner circumferential surface of the rotor shaft 34 via the cam punch 260 over the entire axial range of the forming target area. In this way, according to this embodiment, it is possible to appropriately control the interference between the rotor core 32 and the rotor shaft 34 over the entire axial range of the forming target area, thereby achieving a desired interference.

[0089] In this embodiment, the integration step (step S506) is repeatedly performed for each of the axially divided molding and pressure regions (step S507). For example, as shown in FIG. 13, the integration step (step S506) for the second molding and pressure region from the top is performed after the integration step (step S506) for the first molding and pressure region. After the integration step (step S506) for the second molding and pressure region is completed, the next integration step (step S506) is performed for the third molding and pressure region from the top. Specifically, the molding positioning step (step S5061) is performed for the third molding and pressure region from the top, and then the molding and pressure region (step S5062) is performed for the fourth molding and pressure region from the top. Similarly, the molding positioning process (step S5061) is performed for the lowest molding pressure area, and then, as shown in Figure 16, the molding pressure process (step S5062) is performed for the lowest molding pressure area, and the integration process (step S506) is completed.

[0090] In this embodiment, the inner peripheral surface of the rotor shaft 34 is divided into a plurality of molding and pressure regions in the axial direction, and the integration step (step S506) is performed for each molding and pressure region. Figure 17 schematically shows the forces (force by the shaft presser 290, radial forces F151 to F156 for expanding the diameter, etc.) applied by the molding and pressure step (step S5062) to the six axially divided molding and pressure regions P1 to P6.

[0091] Even with the same internal pressure, the amount of radially outward deformation of the rotor shaft 34 may vary depending on the axial position of the rotor shaft 34. This is because the rigidity of the rotor shaft 34 may vary at each axial position due to differences in the cross-sectional shape of the rotor shaft 34, etc. For example, under the same internal pressure, the amount of radially outward deformation of the rotor shaft 34 is likely to be greater at the center of the axial range of the fitting region between the rotor shaft 34 and the rotor core 32 than at the end of the axial range on the second step portion 347 side. For this reason, when the same internal pressure is applied throughout the entire axial range of the fitting region, it is difficult to uniform the interference throughout the axial range of the fitting region.

[0092] In this regard, in this embodiment, the inner peripheral surface of the rotor shaft 34 is divided into multiple molding and pressure application regions in the axial direction, and the integration process (step S506) is performed for each molding and pressure application region. Therefore, the force F3 (see FIG. 14A) applied from the cam driver 258 to the cam punch 260 via the driver drive pin 274 can be varied for each molding and pressure application region. This allows the radial component F2 (see FIG. 14A) applied to the molding and pressure application region via the cam punch 260 to be varied for each molding and pressure application region. Therefore, this embodiment makes it possible to precisely control (adjust) the interference over the axial range of the mating region. That is, this embodiment makes it possible to ensure a desired interference over the axial range of the mating region. Therefore, this embodiment also makes it possible to uniformize the interference over the entire axial range of the mating region. On the other hand, this embodiment also makes it possible to make the interference larger in a portion of the axial range of the mating region than in other portions, if necessary.

[0093] In this embodiment, the multiple molding and pressure regions in which the integration step (step S506) is performed individually as described above may be set to overlap each other in the axial direction. That is, adjacent molding and pressure regions may partially overlap in the axial direction. For example, a lower portion of the first molding and pressure region from the top may overlap with an upper portion of the second molding and pressure region from the top.

[0094] Returning to FIG. 6, once the integration step (step S506) is completed, this manufacturing method includes a step of raising upper die 250 to the top dead center (step S508).

[0095] Next, this manufacturing method includes a jet hole forming step (step S509) of forming holes corresponding to the oil holes 348, 349 in the rotor shaft 34. The jet hole forming step may be performed by machining or the like after the rotor shaft 34 is removed from the manufacturing apparatus 200. When the jet hole forming step (step S509) is completed, the final rotor shaft 34 is completed.

[0096] Next, this manufacturing method includes other finishing steps (step S510), which may include a step of fixing the permanent magnet 329, a step of magnetizing the permanent magnet 329, and the like.

[0097] In this way, according to this manufacturing method, the axial range of the mating region between the rotor shaft 34 and the rotor core 32 is divided into multiple molding and pressure regions, and the integration process is performed individually for each molding and pressure region. This allows the rotor shaft 34 and the rotor core 32 to be joined without excessively increasing the mold strength. That is, in the first comparative example, in which only one molding and pressure region is set for the axial range of the mating region between the rotor shaft 34 and the rotor core 32, the axial length of the molding and pressure region in each integration process is long. As a result, the force required to achieve the desired interference (axial load F13 as shown in FIG. 13) becomes excessively large, and excessive strength is required for each element of the pressure molding mechanism 25 (such as the driver drive pin 274). In contrast, according to this manufacturing method, the integration process (step S506) is performed for multiple divided molding and pressure regions, thereby solving the problem of the comparative example.

[0098] Here, a configuration in which the axial range of the mating region between the rotor shaft 34 and the rotor core 32 is divided into multiple molding and pressure regions has the above-mentioned advantages over a comparative example in which only one molding and pressure region is set, but can also cause the disadvantages described below. Fig. 19 is an explanatory diagram (an explanatory diagram of a second comparative example) of the disadvantages that can occur in a configuration in which the axial range of the mating region between the rotor shaft 34 and the rotor core 32 is divided into multiple molding and pressure regions. Fig. 20 is an explanatory diagram of the effects of this embodiment. Both Figs. 19 and 20 are cross-sectional views of the rotor shaft 34 and the rotor core 32, and the cam punch 260 is schematically shown in cross section.

[0099] In a configuration in which the axial range of the fitting region between the rotor shaft 34 and the rotor core 32 is divided into multiple molding and pressure regions, the following inconveniences may occur depending on which of the multiple molding and pressure regions the integration process (step S506) is started from. Specifically, when the integration process (step S506) is started from a molding and pressure region closer to the axial center, as in the second comparative example shown in FIG. 19 , the portion of the rotor shaft 34 axially outward from the molding and pressure region is pulled toward the axial center. As a result, as shown schematically in FIG. 19 , the axial length of the rotor shaft 34 is extended, and the portion of the rotor shaft 34 on the axially outer side is displaced radially inward. Note that this amount of displacement tends to increase toward the axially outer side. When this displacement occurs, the axial contact between the protrusion 340 of the rotor shaft 34 and the axial end face 320 of the rotor core 32 is released. As a result, in the joined state of the rotor shaft 34 and the rotor core 32 after the integration process involving the multiple molding and pressure regions is completed, a significant deviation (error) occurs from the normal (nominal) relationship in the axial positional relationship between the protruding portion 340 of the rotor shaft 34 and the axial end face 320 of the rotor core 32. In other words, the dimensional accuracy of the final rotor (for example, the dimensional accuracy of each part based on the protruding portion 340, such as dimensions L1 and L2 shown in FIG. 1) deteriorates.

[0100] In contrast, in this embodiment, as described above, the integration process (step S506) is started from the molding and pressure region on the axial end side of the multiple molding and pressure regions. Although the portion of the rotor shaft 34 below the molding and pressure region is pulled upward, the axial contact state between the protruding portion 340 of the rotor shaft 34 and the axial end face 320 of the rotor core 32 is maintained. In other words, although the portion of the rotor shaft 34 near the axial center is displaced radially inward, the rotor shaft 34 and the rotor core 32 are joined in the molding and pressure region while the axial contact state between the protruding portion 340 of the rotor shaft 34 and the axial end face 320 of the rotor core 32 is maintained. As a result, even if the integration process (step S506) is subsequently performed on the molding and pressure region on the axial center side of the multiple molding and pressure regions, the displacement shown in FIG. 19 does not occur.

[0101] In this way, according to this embodiment, the axial range of the mating area between the rotor shaft 34 and the rotor core 32 can be divided into multiple molding pressure areas, while significantly reducing the possibility of errors occurring in the axial positional relationship between the protrusion 340 of the rotor shaft 34 and the axial end face 320 of the rotor core 32.

[0102] Furthermore, in this embodiment, as described above, the axial contact state between the protruding portion 340 of the rotor shaft 34 and the axial end surface 320 of the rotor core 32 is maintained by the shaft presser 290, while the integration process (step S506) is started from the molding pressure region on the axial end side. This makes it possible to join the rotor shaft 34 and the rotor core 32 in the molding pressure region while reliably maintaining the axial contact state between the protruding portion 340 of the rotor shaft 34 and the axial end surface 320 of the rotor core 32.

[0103] Although each embodiment has been described in detail above, it is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of components of the above-described embodiments.

[0104] For example, in the above-described embodiment, the integration step (step S506) is performed once for each of the multiple molding and pressure application zones, but this is not limited to this. For example, the integration step (step S506) may be performed multiple times for each of the multiple molding and pressure application zones, or the integration step (step S506) may be performed once for some of the multiple molding and pressure application zones and multiple times for the remaining ones. Therefore, for example, for the molding and pressure application zones on the axial end side of the multiple molding and pressure application zones, the first integration step (step S506) may be performed in a manner that the interference is "0" (i.e., the rotor shaft 34 and the rotor core 32 are in contact), and then the second integration step (step S506) may be performed in a manner that the interference is a desired value greater than "0."

[0105] In the above-described embodiment, the integration process starts from the molding and pressure region at the axial end of the multiple molding and pressure regions, and then the target region of the integration process moves to the lower molding and pressure regions in order, but this is not limited to this. That is, as long as the integration process starts from the molding and pressure region at the axial end of the multiple molding and pressure regions, the integration process may be performed in any order for the remaining molding and pressure regions. For example, the second molding and pressure region may be the lower molding and pressure region.

[0106] Furthermore, in the above-described embodiment, the integration step (step S506) is performed in a pressed state by the shaft presser 290, but the formation of a pressed state by the shaft presser 290 (a state in which an axial force acts between the protruding portion 340 of the rotor shaft 34 and the axial end surface 320 of the rotor core 32) may be omitted. In this case, the shaft presser 290 itself may be omitted. Alternatively, instead of forming a pressed state, the shaft presser 290 may achieve the formation of an axial contact state between the rotor core 32 and the rotor shaft 34 (a state in which the axial force acting between the protruding portion 340 of the rotor shaft 34 and the axial end surface 320 of the rotor core 32 is substantially "0").

[0107] Furthermore, in the above-described embodiment, the protrusion 340 is formed integrally with the rotor shaft 34 as part of the rotor shaft 34, but it may also be a portion that is fixed to the rotor shaft 34 as a separate member (separate piece). [Explanation of symbols]

[0108] 1 motor (rotating electric machine), 30 rotor, 32 rotor core (core member), 34 rotor shaft (shaft member), 340 protrusion

Claims

1. A method of manufacturing a rotor for a rotating electric machine, comprising: an arrangement step of supporting a workpiece including a core member for a rotor core and a hollow shaft member for a rotor shaft, and forming a set state in which the shaft member is arranged on the inner diameter side of the core member; a joining step of joining the core member and the shaft member by applying a force to the workpiece in the set state, the coupling step includes a pressing step of applying a radial force from a hollow interior of the shaft member to a radially outer side in a manner that the shaft member contacts or is pressed against the core member, A manufacturing method in which the pressing step is performed separately at a plurality of axial positions on the shaft member, and starts from an axially outer position of the shaft member among the plurality of positions.

2. the shaft member has, on one axial side, a radially outward protruding portion that axially abuts against a radially inner portion of the axial end face of the core member, The manufacturing method according to claim 1 , wherein an axial range in which the shaft member contacts or is pressed against the core member in the pressing step at a start position among the plurality of positions includes an axial position of the protrusion.

3. The manufacturing method according to claim 2 , wherein the positioning step includes forming the set state in which the shaft member is supported on the core member via the protrusion.

4. The manufacturing method according to claim 1 , wherein the pressing step at the plurality of positions is performed only once for one workpiece at each of the plurality of positions.

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