Manufacturing method of a stator for a rotating electric machine

Abstract

To efficiently reduce dripping after lifting a workpiece from a tank.SOLUTION: A method for manufacturing a stator for a rotary electric machine includes: a preparation step of preparing a workpiece in which a plurality of coil pieces forming a stator coil are attached to a stator core, a tip portion of one coil piece and a tip portion of another coil piece being joined to each other on one end side in an axial direction in the workpiece; an immersion step of immersing the workpiece in a tank of a liquid resin material so that an impregnation target site including a joint portion of the tip portions is immersed after the preparation step; and a rotation step of rotating the workpiece at a workpiece raised position where the impregnation target site is away from a tank after the immersion step. The rotation step includes rotating the workpiece so that the liquid resin material dripping downward from one circumferential position at the impregnation target site adheres to another circumferential position at the impregnation target site.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A method for manufacturing a stator for a rotating electric machine is known, in which a workpiece for a rotating electric machine is prepared in which a plurality of coil pieces that form a stator coil are attached to a stator core, the tip ends of the plurality of coil pieces are joined together at one axial end of the workpiece, the area to be impregnated, including the joint (exposed conductor portion), is impregnated with a liquid resin material, and the liquid resin material is then hardened to cover the joint with an insulating coating of resin material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-136787 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in this type of manufacturing method for forming an insulating coating of resin material, it is difficult to efficiently reduce dripping (drippage related to the liquid resin material) after the workpiece immersed in the tank of liquid resin material is pulled out.

[0005] Therefore, in one aspect, an object of the present disclosure is to efficiently reduce dripping after a workpiece is lifted from a tank. [Means for solving the problem]

[0006] In one aspect, a preparation step of preparing a workpiece in which a plurality of coil pieces forming a stator coil are attached to a stator core, the workpiece having tip ends of one of the coil pieces and another of the coil pieces joined together at one axial end side; After the preparation step, an immersion step of immersing the workpiece in a tank of liquid resin material so that an impregnation target portion including a joint portion between the tip portions is immersed; a rotation step of rotating the workpiece at a raised position where the impregnation target portion is separated from the tank after the immersion step, The method for manufacturing a stator for a rotating electric machine includes rotating the workpiece in the rotating process so that the liquid resin material dripping downward from one circumferential position in the area to be impregnated adheres to another circumferential position in the area to be impregnated. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, it is possible to efficiently reduce dripping of liquid after a workpiece is lifted from a tank. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic flowchart illustrating an example of a method for manufacturing a stator for a rotating electric machine. [Figure 2] FIG. 2 is a diagram schematically illustrating an entire workpiece for forming a stator for a rotating electric machine. [Figure 3] 10 is a cross-sectional view taken along the axial direction of the workpiece in a state in which coil pieces are assembled to a stator core. FIG. [Figure 4] FIG. [Figure 5] FIG. 2 is a schematic cross-sectional view of a coil piece. [Figure 6] FIG. 3 is an explanatory diagram of a joint, corresponding to an enlarged view of part Q1 in FIG. 2. [Figure 7] FIG. 2 is a diagram schematically illustrating a side view of a workpiece before it is immersed in a tank of liquid resin material. [Figure 8] FIG. 2 is a diagram schematically illustrating a side view of a workpiece immersed in a tank of liquid resin material. [Figure 9] FIG. 10 is a diagram showing a schematic side view of the state of the workpiece during the rotation process in an immersed state. [Figure 9A] FIG. 10 is an enlarged view of part Q9 in FIG. [Figure 9B] 9A is a cross-sectional view taken along line 9A-9A in FIG. 9A, and is a diagram schematically illustrating the state immediately after immersion (the state before the start of the rotation step in the immersed state). [Figure 9C] 9A is a cross-sectional view taken along line 9A-9A in FIG. 9A, and is a diagram schematically illustrating a state after a rotation step is performed in an immersed state. [Figure 10] FIG. 10 is a diagram showing a schematic side view of the state of the workpiece after the process of lifting it up to near the liquid surface. [Figure 11] FIG. 10 is a diagram showing a schematic side view of the workpiece during the liquid-removing rotation process. [Figure 12] FIG. 10 is an explanatory diagram of the action of the liquid-removing rotation process. [Figure 12A] FIG. 10 is an explanatory diagram of a preferred rotation direction in the liquid-removing rotation step. [Figure 13] FIG. 10 is a side view schematically showing the state of the workpiece after being pulled further upward from the position during the liquid-removing rotation process. [Figure 14] FIG. 10 is a diagram schematically illustrating a state of a workpiece in a diagonally downward orientation as viewed from the side. [Figure 15] 10 is a diagram showing a schematic side view of a workpiece in a diagonally downward orientation undergoing a reattachment rotation process; FIG. [Figure 16A] FIG. 1 is an explanatory diagram (part 1) of the action of the reattachment rotation process. [Figure 16B] FIG. 10 is an explanatory diagram (part 2) of the effect of the reattachment rotation process. [Figure 16C] FIG. 10 is an explanatory diagram (part 3) of the effect of the reattachment rotation process. [Figure 17] 10 is a diagram showing a schematic side view of a workpiece in a diagonally downward orientation with a relatively large inclination angle; FIG. [Figure 18] FIG. 10 is a diagram schematically illustrating a state of a workpiece in an obliquely upward orientation as viewed from the side. [Figure 18A] FIG. 10 is an explanatory diagram (part 1) of a preferable range of the angle α for a workpiece in an obliquely upward orientation. [Figure 18B] FIG. 10 is a diagram (part 2) illustrating a preferred range of the angle α for a workpiece in an obliquely upward orientation. [Figure 19]FIG. 10 is a diagram schematically illustrating a workpiece in an upward orientation as viewed from the side. [Figure 20] FIG. 10 is a diagram schematically illustrating a side view of a workpiece in a state in which an upper surface resin curing process is being performed. [Figure 21] FIG. 10 is a diagram schematically illustrating a side view of the workpiece in a state where an inner diameter side resin hardening process is being performed. [Figure 22] FIG. 10 is a diagram schematically illustrating the state of the workpiece as viewed from the side before the second insulating coating step. [Figure 23] FIG. 10 is a diagram schematically illustrating the state of the workpiece in a heating step as viewed from the side. [Figure 24] FIG. 2 is a diagram schematically illustrating an example of a cooling structure. [Figure 25] 10 is a schematic flowchart showing another example of a method for manufacturing a stator for a rotating electric machine. [Figure 26] 10A and 10B are explanatory diagrams illustrating the adhesion of liquid resin material to a stator core. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] The method for manufacturing a stator for a rotating electric machine described below can be applied to any stator for a rotating electric machine as long as the stator has a joint between coil pieces at the coil end portion. As a suitable application example, a method for manufacturing a stator for a rotating electric machine that can function as a power source that generates a propulsive force for a vehicle will be described below.

[0011] FIG. 1 is a schematic flowchart illustrating an example of a method for manufacturing a stator for a rotating electric machine. Note that FIG. 1 is a flowchart illustrating a schematic flow, and additional processes may be included at any stage. FIGS. 2 to 6 are explanatory diagrams of a workpiece W. FIG. 2 is a schematic diagram illustrating the entire workpiece W including a stator core 112 and a stator coil 114 for forming a stator 10 for a rotating electric machine. FIG. 3 is a cross-sectional view along the axial direction of the workpiece W in a state in which coil pieces 52 are assembled to the stator core 112. FIG. 4 is a front view of one of the coil pieces 52. FIG. 5 is a schematic cross-sectional view of the coil piece 52. FIG. 6 is an explanatory diagram of a joint 400, corresponding to an enlarged view of portion Q1 in FIG. 2. FIGS. 7 to 18 are explanatory diagrams of this manufacturing method, and FIGS. 7 to 9, 10, 11, 13 to 15, and 17 to 22 are schematic side views illustrating the state of the workpiece W at each process. 9A to 9C are explanatory diagrams of the operation of the rotation process in the immersed state. FIG. 12 is an explanatory diagram explaining the operation of the liquid-removing rotation process at part Q11 in FIG. 11. FIG. 12A is an explanatory diagram of a preferred rotation direction in the liquid-removing rotation process, and is a diagram schematically showing a part of the coil end portion 114A in a side view. FIGS. 16A to 16C are explanatory diagrams of the operation of the rotation process.

[0012] The Z direction is shown in Figure 2 and other figures. The Z direction corresponds to the up-down direction, with the Z1 side and Z2 side corresponding to the upper side and lower side, respectively. The Y direction is shown in Figure 3 and other figures. The Y direction corresponds to the radial direction, with the Y1 side corresponding to the radially outer side and the Y2 side corresponding to the radially inner side (the side closer to the central axis I of the stator core 112).

[0013] In the following description, unless otherwise specified, the axial direction refers to the direction in which the central axis I of the stator core 112 (= the central axis of the workpiece W) extends, and the radial direction refers to the radial direction centered on the central axis I. Therefore, the radially outer side refers to the side away from the central axis I, and the radially inner side refers to the side closer to the central axis I. Furthermore, the axially outer side refers to the side away from the axial center of the stator core 112, and the axially inner side refers to the side closer to the axial center of the stator core 112. Furthermore, the circumferential direction corresponds to the direction of rotation around the central axis I.

[0014] This manufacturing method first includes a preparation step (step S10) prior to the insulating coating step. In this embodiment, the preparation step (step S10) includes an assembly forming step (step S200) and a joining step (step S202). However, in a modified example, a workpiece for which the assembly forming step (step S200) has already been performed may be used (prepared), or a workpiece for which the assembly forming step (step S200) and the joining step (step S202) have already been performed may be used (prepared).

[0015] The assembly forming step (step S200) includes mounting a plurality of coil pieces 52 that form the stator coil 114 on the stator core 112 to form an assembly (hereinafter also referred to as a "workpiece W").

[0016] Here, the stator coils 114 include a U-phase coil, a V-phase coil, and a W-phase coil (hereinafter, when U, V, and W are not distinguished, they will be referred to as "phase coils"). The base end of each phase coil is connected to an input terminal (not shown), and the end of each phase coil is connected to the end of the other phase coil to form a neutral point. In other words, the stator coils 114 are star-connected. However, the connection mode of the stator coils 114 may be changed as appropriate depending on the required motor characteristics, etc. For example, the stator coils 114 may be delta-connected instead of star-connected.

[0017] Each phase coil of the stator coil 114 may be formed by joining multiple coil pieces 52. The coil pieces 52 are in the form of segment coils (segment conductors) obtained by dividing the phase coil into units that are easy to assemble (for example, units that can be inserted into two slots 23). As shown in FIG. 5, the coil pieces 52 are formed by coating a linear conductor (rectangular wire) 120 having a substantially rectangular cross section with an insulating film 130. Here, the linear conductor 120 is formed from copper, as an example. However, in a modified example, the linear conductor 120 may be formed from another conductive material such as iron. Furthermore, the cross-sectional shape of the linear conductor 120 may be other than rectangular.

[0018] In the example shown in Fig. 4, one coil piece 52 may be formed into a substantially U-shape having a pair of linear slot-accommodated portions 50 and a bridge portion 54 connecting the pair of slot-accommodated portions 50. The bridge portion 54 on the other axial side (upper side in Fig. 4) may be formed by circumferentially molding the state shown in Fig. 4. A coupling portion 40 is set at the end of the bridge portion 54 on the other axial side (upper side in Fig. 4) to be coupled to a coupling portion 40 of a bridge portion 54 of another coil piece 52. The coupling portion 40 is a portion where the insulating film 130 has been removed (i.e., a portion where the conductor portion of the linear conductor 120 is exposed).

[0019] When the coil pieces 52 are assembled to the stator core 112, the pair of slot-receiving portions 50 are inserted into the slots 23 between the teeth 22 (see FIG. 3). In this case, the coil pieces 52 can be assembled, for example, in the axial direction.

[0020] A plurality of slot-receiving portions 50 of the coil pieces 52 shown in FIG. 4 are inserted into each slot 23, lined up in the radial direction. Accordingly, a plurality of circumferentially extending bridge portions 54 are lined up in the radial direction at both axial ends of the stator core 112. The bridge portions 54 (and the connecting portions 40 that are a part of the bridge portions 54) form coil end portions 114A that protrude axially outward from the axial end faces 1120 of the stator core 112 (see FIG. 3). The coil pieces 52 may be wound around the stator core 112 in a lap winding manner, for example. In the example shown in FIG. 4, the lower bridge portions 54 may have offset portions 521B that are offset from each other by one layer in the radial direction. The upper bridge portions 54 may also have a similar offset portion 521A (see FIG. 3).

[0021] 2 to 5 show the stator core 112 and the stator coil 114 having a specific structure, the structure of the stator core 112 and the stator coil 114 is arbitrary as long as the stator coil 114 has the joint portion 40. The winding method of the stator coil 114 is also arbitrary, and may be a winding method other than the lap winding described above, such as a wave winding method.

[0022] The joining process (step S202) includes joining the joint portions 40, which are the tip portions of one coil piece 52 and another coil piece 52, at one axial end of the workpiece W. The joint portions 40 may be overlapped with each other, and the opposing sides may be joined. Any method may be used to join the joint portions 40, but welding, for example, may be used. In this case, welding may be achieved by any method, such as laser welding or TIG welding. FIG. 6 schematically shows a joint portion 400 including a welded portion 401 (joining portion) formed on two joint portions 40 overlapped in the radial direction.

[0023] For example, when four or more coil pieces 52 are mounted in each slot 23 of the stator core 112 in a radially overlapping manner, the joining process may join multiple pairs of adjacent joining portions 40 (tip ends) in the radial direction together.

[0024] The joining range of the joining portions 40 and the orientation of the joining portions 40 when joined (the orientation when overlapping) are arbitrary. For example, in Fig. 6, the joining portions 40 are vertically upright and overlapped in the radial direction, but they may be overlapped in an X-shaped crossing when viewed in the radial direction, or only the joining portions 40 may be overlapped in the radial direction in an oblique orientation. Furthermore, the joining portions 40 may be overlapped in the axial direction in an orientation extending in the radial direction.

[0025] In the joining process, not only the coil pieces 52 are joined to each other, but also the coil pieces 52 may be joined to a bus bar or a terminal block (an output bus bar for connection to an inverter, not shown). Fig. 2 shows a schematic diagram of a neutral conductor bus bar 59 as an example of such a bus bar. The neutral conductor bus bar 59 is a bus bar that forms the neutral point described above.

[0026] In this embodiment, as an example, the joint portion 400 is provided on only one axial side of the stator core 112. Hereinafter, for the sake of distinction, of both axial sides of the stator core 112 (or both axial sides of the workpiece W), the side having the joint portion 400 will also be referred to as the lead side. Note that in a modified example, the joint portion 400 may be provided on both axial sides of the stator core 112.

[0027] After the preparation step (step S10), this manufacturing method includes a step (step S204) of setting the workpiece W at a start position (workpiece loading position) for the insulation coating step. At this time, the workpiece W may be set in a position where the lead side faces up (i.e., the joint portion 400 faces up). Hereinafter, this position where the lead side faces up will also be referred to as the "upward position of the workpiece W."

[0028] Next, this manufacturing method includes, as the first step of the insulating coating process, an upside-down inversion step (step S206) in which the orientation of the workpiece W is inverted upside down. That is, the workpiece W is inverted upside down so that the lead side is on the bottom (i.e., the joint 400 is on the bottom). Hereinafter, this orientation in which the lead side is on the bottom is also referred to as the "downward orientation of the workpiece W." The upside-down inversion of the orientation of the workpiece W may be achieved by a manufacturing apparatus. Note that the manufacturing apparatus may be, for example, an articulated robot having a hand that grips the workpiece W, and a workpiece gripping unit 1000, which is part of the manufacturing apparatus, is shown in FIG. 7, etc., which will be described later.

[0029] Next, this manufacturing method includes an immersion step (step S208) in which the workpiece W is immersed in a tank 600 of liquid resin material M0. FIG. 7 is a schematic side view of the workpiece W before being immersed in the tank 600 of liquid resin material M0, and FIG. 8 is a schematic side view of the workpiece W immersed in the tank 600 of liquid resin material M0. In this manufacturing method, the liquid resin material M0 is preferably a resin material that hardens when heated and also hardens through a polymerization reaction when irradiated with ultraviolet light. Furthermore, the liquid resin material M0 has a relatively high viscosity, for example, a viscosity greater than 10 Pa·s, preferably 20 Pa·s or greater. The tank 600 may have a circular shape in top view corresponding to the circular impregnation target portion.

[0030] The immersion process is performed while the workpiece W is maintained in a downward orientation, so that the axial end (the lower end in the downward orientation) of the workpiece W to be impregnated is immersed in the liquid resin material M0 (i.e., positioned below the liquid surface 601 of the liquid resin material M0). The impregnation target portions of the workpiece W are set at the portions of the multiple coil pieces 52 of the workpiece W. Specifically, the impregnation target portions of the workpiece W are the axial end portions (lead-side end portions) of the multiple coil pieces 52, and include the joint portions 400. More specifically, the impregnation target portions of the workpiece W include the portions of each coil piece 52 of the workpiece W where the conductor (the conductor portion of the linear conductor) is exposed (portions including the joint portions 400). The impregnation target portions have an annular shape around the central axis I when viewed in the axial direction, and include a portion of the coil end portion 114A (a portion on the axial end side).

[0031] Furthermore, in this manufacturing method, the impregnation target portion is set to include the neutral bus bar 59. In this case, by encasing the neutral bus bar 59 in the liquid resin material M0, the electrical insulation of the neutral bus bar 59 can be ensured. In other words, the neutral bus bar 59 does not need to be in a form in which it has been insulated by insert molding or the like with an insulating material such as a resin material, but can be in the form of a metal sheet (with the entire conductor material exposed). This allows the electrical insulation of the neutral bus bar 59 to be efficiently ensured.

[0032] In this manufacturing method, as will be described later, the immersion process is performed twice for one workpiece W. In this case, the portion of the workpiece W to be impregnated in each immersion process may be completely the same or may be partially different. However, in a modified example, the number of times the immersion process is performed for one workpiece W may be one time, or three or more times.

[0033] In the immersion step, the workpiece W may be kept immersed in a downward position for a certain period of time by the workpiece gripping unit 1000 of the manufacturing device.

[0034] In this manufacturing method, the immersion process includes a rotation process (see arrow R9 in FIG. 9) in which the immersed workpiece W (in a downward position) is rotated around the central axis I. Hereinafter, this rotation process performed during the immersion process will also be referred to as a "rotation process in an immersed state" to distinguish it from other rotation processes described later.

[0035] 9 to 9C are explanatory diagrams of the rotation process in an immersed state, with FIG. 9 being a schematic side view of the workpiece W during the rotation process in an immersed state, and FIG. 9A being an enlarged view of portion Q9 in FIG. 9. FIGS. 9B and 9C are cross-sectional views taken along line 9A-9A in FIG. 9A, with FIG. 9B showing the state immediately after immersion (the state before the start of the rotation process in an immersed state), and FIG. 9C showing the state after the rotation process in an immersed state has been performed. In FIGS. 9B and 9C, the L direction corresponds to the circumferential direction of the workpiece W, and L1 and L2 represent opposite sides (one circumferential side and the other circumferential side).

[0036] The rotation process in the immersed state is performed to efficiently encase the neutral bus bar 59 in the liquid resin material M0. In this embodiment, the neutral bus bar 59 extends circumferentially such that the direction perpendicular to the upper surface 591 is parallel to the central axis I. As described above, the neutral bus bar 59 is electrically insulated by being covered with the liquid resin material M0. The neutral bus bar 59 may be disposed at any position relative to the coil end portion 114A. For example, the neutral bus bar 59 may be joined to the stator coil 114 so as to extend axially outward beyond the coil end portion 114A. However, in this embodiment, the neutral bus bar 59 is joined to the stator coil 114 such that the upper surface 591 in a downward orientation (hereinafter simply referred to as the "upper surface 591") is positioned between the axial end surface 1140 of the stator coil 114 and the axial end surface 1120 of the stator core 112 in the Z direction, as schematically shown in FIG. 9 and other figures. In this case, it is possible to reduce the axial size of the rotating electric machine stator 10. Note that the axial end surface 1140 of the stator coil 114 corresponds to the axial end surface of the coil end portion 114A.

[0037] Incidentally, when the neutral bus bar 59 is wrapped in the liquid resin material M0 in this manner, efficiently directing the liquid resin material M0 onto the upper surface 591 of the neutral bus bar 59 is useful in reducing the CT (cycle time).

[0038] Here, when the upper surface 591 of the neutral bus bar 59 is located closer to the Z1 side than the axial end surface 1140 of the stator coil 114 (upper side in the downward orientation), as in this embodiment, the Z1-side boundary of the impregnation target area tends to be determined by the upper surface 591 of the neutral bus bar 59. For example, the Z1-side boundary of the impregnation target area is set slightly closer to the Z1 side than the upper surface 591 of the neutral bus bar 59. In this manner of setting the impregnation target area, the upper surface 591 of the neutral bus bar 59 is only slightly below the liquid level 601 of the liquid resin material M0 in the immersed state, which makes it difficult to quickly spread the liquid resin material M0 over the upper surface 591.

[0039] However, in the present manufacturing method, by performing the rotation step in an immersed state, it is possible to quickly spread the liquid resin material M0 over the upper surface 591 of such a neutral bus bar 59.

[0040] Specifically, when the workpiece W is immersed in the immersion process so that the upper surface 591 is positioned slightly below the liquid level 601 of the liquid resin material M0, the liquid resin material M0 flows from the outer periphery of the neutral bus bar 59 to the upper surface 591 of the neutral bus bar 59, as schematically shown by arrows R91 and R92 in FIG. 9B . However, simply holding the workpiece W in an immersed state results in a slow flow rate due to the relatively high viscosity of the liquid resin material M0 as described above, and it takes a relatively long time for the liquid resin material M0 to spread over the entire upper surface 591. Furthermore, surface tension may make it difficult for the liquid resin material M0 to flow over the upper surface 591, and in such cases, it takes a relatively long time for the liquid resin material M0 to spread over the entire upper surface 591.

[0041] In contrast, according to the present manufacturing method, the rotation step in the immersed state facilitates the flow of the liquid resin material M0 from the outer periphery of the neutral bus bar 59 to the upper surface 591 of the neutral bus bar 59. For example, rotating the workpiece W in the circumferential direction L1 of FIG. 9B promotes the flow of the liquid resin material M0 in the direction of arrow R91 (the flow of the liquid resin material M0 on the upper surface 591 of the neutral bus bar 59). Rotating the workpiece W in the circumferential direction L2 of FIG. 9B promotes the flow of the liquid resin material M0 in the direction of arrow R92 (the flow of the liquid resin material M0 on the upper surface 591 of the neutral bus bar 59). As a result, compared to simply holding the workpiece W in an immersed state, it is possible to more efficiently guide the liquid resin material M0 onto the upper surface 591 of the neutral bus bar 59, thereby reducing CT.

[0042] In this manufacturing method, the rotation step in the immersed state may be achieved by rotating the workpiece W in only one direction (either rotation toward the circumferential direction L1 or rotation toward the circumferential direction L2), or may be achieved by rotating the workpiece W in two directions (rotation toward the circumferential direction L1 and rotation toward the circumferential direction L2). When the rotation is achieved in two directions, as described above with reference to FIG. 9B, the liquid resin material M0 can be guided onto the upper surface 591 of the neutral conductor busbar 59 from both circumferential sides of the neutral conductor busbar 59 (see arrows R91 and R92), making it possible to quickly spread the liquid resin material M0 over the entire upper surface 591 (see FIG. 9C).

[0043] In this manufacturing method, the liquid resin material M0 is efficiently guided onto the upper surface 591 of the neutral conductor bus bar 59 by rotating the immersed workpiece W about the central axis I, but instead of or in addition to this, the liquid resin material M0 may be efficiently guided onto the upper surface 591 of the neutral conductor bus bar 59 by any movement such as swinging the immersed workpiece W, translating the workpiece W, or a combination of these. When translating the workpiece W, the translation may be achieved by maintaining the central axis I of the workpiece W parallel to the vertical direction, or by slightly tilting the central axis I of the workpiece W relative to the vertical direction.

[0044] Furthermore, in this manufacturing method, in the rotation step in the immersed state, the rotation around the central axis I of the workpiece W is achieved by maintaining the central axis I of the workpiece W parallel to the vertical direction, but this is not limited to this. For example, the rotation around the central axis I of the workpiece W may be achieved by slightly tilting the central axis I of the workpiece W relative to the vertical direction. In this case, the tilt angle may be changed depending on the rotation position and / or rotation angle of the workpiece W.

[0045] In this manufacturing method, the rotation angle (rotation stroke) in the rotation step in the immersed state is arbitrary, but is preferably 90 degrees or more, more preferably 180 degrees or more, and may be, for example, 360 degrees. For example, by setting the angle to 360 degrees or less, the rotation step in the immersed state can be realized even when using a robot with a limited range of motion.

[0046] Furthermore, in this manufacturing method, with regard to the rotation step in the immersed state, the rotation around the central axis I of the workpiece W is performed while the upper surface 591 of the neutral conductor busbar 59 is positioned below the liquid surface 601 of the liquid resin material M0, but this is not limited to this. For example, with regard to the rotation step in the immersed state, the rotation around the central axis I of the workpiece W may be performed while the upper surface 591 of the neutral conductor busbar 59 is aligned with the liquid surface 601 of the liquid resin material M0. Furthermore, the rotation around the central axis I of the workpiece W may be performed while changing the height difference between the upper surface 591 of the neutral conductor busbar 59 and the liquid surface 601 of the liquid resin material M0 (see dimension H1 in FIG. 9A ). For example, during the process of immersing the workpiece W, the rotation of the workpiece W may be started from a state before the workpiece W reaches the most immersed state (e.g., H1 = 0 or negative).

[0047] Next, this manufacturing method includes a lifting step (step S210) in which the workpiece W is slightly lifted from the tank 600. Hereinafter, the lifting step of step S210 will also be referred to as a "lifting step to near the liquid surface" to distinguish it from the further lifting described below. The lifting of the workpiece W may be achieved by the workpiece gripping unit 1000 of the manufacturing apparatus. FIG. 10 schematically shows the workpiece W in a downward position after being lifted slightly above the liquid surface 601. After being lifted, the workpiece W in a downward position has the liquid resin material M0 (schematically shown by the hatched area M1 in FIG. 10) impregnated in the axial end (the lower end in the downward position) of the workpiece W to be impregnated.

[0048] Next, this manufacturing method includes a rotation process (step S211) in which the workpiece W is rotated about the central axis I of the workpiece W, with the workpiece W slightly raised from the tank 600 and in a downward position. Hereinafter, the rotation process of step S211 will also be referred to as the "liquid-draining rotation process" to distinguish it from other rotation processes. In Figure 11, the rotation in the liquid-draining rotation process is schematically shown by arrows R11A and R11B.

[0049] The draining rotation process is performed to quickly return the liquid resin material M0 dripping from the impregnation target portion of the workpiece W in a downward position back to the tank 600. Specifically, when the workpiece W is lifted from the tank 600, the liquid resin material M0 drips from the impregnation target portion of the workpiece W due to its own weight. However, because the liquid resin material M0 has a relatively high viscosity, it drips relatively slowly. In this case, if the workpiece W is held in a downward position and the dripping liquid resin material M0 is allowed to finish dripping, the CT is likely to increase. Furthermore, if the workpiece W is held in a downward position for a relatively long time, an excessive amount of the liquid resin material M0 adhering to (impregnating) the impregnation target portion of the workpiece W drips into the tank 600. This leads to an unnecessary increase in the number of dipping processes performed on one workpiece W (and the resulting increase in CT) in order to ensure the required thickness of the liquid resin material M0.

[0050] In contrast, in the present manufacturing method, a liquid draining rotation process is carried out, so that before the liquid resin material M0 finishes dripping from the impregnation target portion of the workpiece W due to its own weight, the liquid resin material M0 that may drip from the impregnation target portion of the workpiece W can be separated (divided) into a portion of the liquid resin material M0 that remains on the workpiece W and a portion of the liquid resin material M0 that returns to the tank 600.

[0051] Specifically, FIG. 12 shows a portion corresponding to portion Q11 in FIG. 11 (however, the neutral bus bar 59 is not shown). The upper state ST2110 shows the state before the start of the liquid-draining rotation process, and the lower state ST2111 shows the state during the liquid-draining rotation process. When the workpiece W is rotated from state ST2110, a speed difference (speed difference in the rotational direction) (arrow R2111 in FIG. 12) occurs between the liquid resin material M0 adhering to the portion of the workpiece W to be impregnated and the liquid resin material M0 in the tank 600, as shown in state ST2111. When such a speed difference (speed gradient) occurs in the shear direction, the viscosity of the liquid resin material M0 decreases at the boundary of the speed difference, and a radial recess is formed between the portion of the liquid resin material M0 adhering to the workpiece W and the portion of the liquid resin material M0 in the tank 600. When this recess is formed, the free fall of the portion of the liquid resin material M0 below the recess is promoted. Therefore, when the workpiece W is further pulled up with the recess formed, the liquid resin material M0 adhering to the portion of the workpiece W to be impregnated and the liquid resin material M0 in the tank 600 can be easily separated (divided) at the boundary of the recess.

[0052] In this way, according to this manufacturing method, the draining rotation process can promote draining by utilizing the speed difference (speed gradient) in the shear direction, thereby shortening CT while minimizing the amount of liquid resin material M0 dripping from the impregnation target portion of the workpiece W. In addition, the number and frequency of occurrence of hanging portions M12 (liquid resin material M0 dripping down in the form of "icicles"), which will be described later, can be reduced, thereby reducing the possibility of the liquid resin material M0 adhering to the stator core 112. As a result, CT can be shortened.

[0053] In this manufacturing method, the liquid-draining rotation process may be achieved by rotating the workpiece W in only one direction (either rotation toward the circumferential direction L1 or rotation toward the circumferential direction L2), or by rotating the workpiece W in two directions (both rotation toward the circumferential direction L1 and rotation toward the circumferential direction L2).

[0054] In this regard, the inclination direction of the crossover portions 54 of the coil pieces 52 on the radially outer side and the radially inner side of the coil end portion 114A may be taken into consideration. For example, FIG. 12A schematically shows four crossover portions 54 of the radially outer coil pieces 52, with the crossover portions 54 inclined in a direction such that the upper side is closer to the L2 side than the lower side. In this case, when the workpiece W is rotated toward the circumferential direction L2 (see arrow R12B), the liquid resin material M0 impregnated between the crossover portions 54 tends to flow from the coil end portion 114A toward the axially outer side (see arrow R12A). In this case, there is a risk that the liquid resin material M0 impregnated between the crossover portions 54 will be insufficient. Therefore, in the case of such an inclination direction of the crossover portions 54, in order to avoid such a problem, the rotation direction in the liquid-draining rotation process may be a direction in which the workpiece W is rotated toward the circumferential direction L1.

[0055] In this embodiment, the vertical positional relationship between the workpiece W and the liquid surface 601 during the liquid-draining rotation process is arbitrary. However, the lifted position of the workpiece W during the lifting process to near the liquid surface is preferably within a range where the liquid resin material M0 adhering to the impregnation target portion of the workpiece W and the liquid resin material M0 in the tank 600 are connected (contiguous). More specifically, the vertical positional relationship between the workpiece W and the liquid surface 601 during the liquid-draining rotation process is preferably such that the distance between the lower end position of the workpiece W (the lowest position of the lower coil end portion 114A) and the liquid surface 601 is 10 mm or less, more preferably 5 mm or less, and most preferably approximately 1 mm to 3 mm. Note that a distance greater than 10 mm is undesirable because the liquid resin material M0 dripping from the coil end portion 114A is likely to be scattered outside the tank 600 due to centrifugal force. On the other hand, a distance less than 1 mm is undesirable because it is difficult to form the aforementioned recessed portion.

[0056] In this manufacturing method, the rotation angle (rotation stroke) in the liquid-draining rotation step is arbitrary, but is preferably 90 degrees or more, more preferably 180 degrees or more, and may be, for example, 360 degrees.

[0057] Next, this manufacturing method includes a step (step S212) of changing the obliquely downward orientation of the workpiece W that has been further lifted out of the tank 600. Fig. 13 schematically shows the state of the workpiece W when it is lifted further upward from the height of the workpiece W at the time of the liquid-draining rotation step (after the lifting step to near the liquid surface), and Fig. 14 schematically shows the state of the workpiece W in the obliquely downward orientation.

[0058] In this manufacturing method, the dripping of the liquid resin material M0 due to its own weight can be reduced by the draining rotation process described above, but dripping of the liquid resin material M0 due to its own weight still occurs. In Figures 13 and 14, the liquid resin material M0 dripping due to its own weight is indicated by the symbol M12. Hereinafter, the liquid resin material M0 impregnated in the impregnation target portion of the workpiece W that is dripping due to its own weight will be referred to as the "drooping portion M12," and the other portion will be referred to as the "normal portion M13." The "drooping portion M12" has a so-called "icicle" shape, and due to the relatively high viscosity of the liquid resin material M0, it tends not to fall immediately (i.e., it tends to extend downward while remaining in the "icicle" shape). Note that in Figure 14 and other figures, the dashed line H represents a horizontal line.

[0059] Next, this manufacturing method includes a rotation process (step S213) in which the workpiece W is rotated around the central axis I of the workpiece W. Hereinafter, the rotation process of step S213 will also be referred to as the "reattachment rotation process" to distinguish it from other rotation processes. In Figure 15, the rotation in the reattachment rotation process is schematically indicated by arrow R15.

[0060] The re-adhesion rotation step includes rotating the workpiece W so that the hanging portion M12 is absorbed into the normal portion M13 (integrated with the normal portion M13 by adhering to it). That is, the re-adhesion rotation step includes rotating the workpiece W so that the liquid resin material M0 (i.e., the hanging portion M12) dripping downward from one circumferential position in the impregnation target portion adheres to another circumferential position in the impregnation target portion.

[0061] Here, the principle of the re-attachment rotation step will be described with reference to Figures 16A to 16C. Figures 16A to 16C are plan views schematically showing the workpiece W as viewed along the arrow V15 in Figure 15.

[0062] The examples shown in FIGS. 16A to 16C illustrate how two drooping portions M12 are absorbed into the normal portion M13. Specifically, when the workpiece W rotates clockwise from the state shown in FIG. 16A, the state shown in FIG. 16B is reached, where the right-side drooping portion M12 overlaps with the normal portion M13 as viewed along arrow V15. In this case, the workpiece W is still in a diagonally downward orientation (see FIG. 15). However, due to the relatively high viscosity of the liquid resin material M0, the rotation of the workpiece W causes the drooping portion M12 to be absorbed into the normal portion M13 from its base, and the entire drooping portion M12 is absorbed into the normal portion M13. Similarly, when the workpiece W is further rotated clockwise from the state shown in FIG. 16B, the state shown in FIG. 16C is reached, where the left-side drooping portion M12 overlaps with the normal portion M13 as viewed along arrow V15. In this case, the workpiece W is also in a diagonally downward position (see Figure 15), but due to the relatively high viscosity of the liquid resin material M0, the rotation of the workpiece W causes it to be absorbed into the normal part M13 from the base side of the hanging part M12, and the entire hanging part M12 is absorbed into the normal part M13.

[0063] In this way, when each drooping portion M12 reaches a rotational position where it overlaps with the normal portion M13 as viewed by arrow V15, it is entirely absorbed into the normal portion M13. As a result, each drooping portion M12 disappears, preventing inconvenience that would occur if the orientation of the workpiece W were changed to an upward orientation while the drooping portions M12 remained. Specifically, if the orientation of the workpiece W is changed to an upward orientation in the next step S214 while the drooping portions M12 remain, there is a risk that the drooping portions M12 will adhere to the stator core 112. For example, there is a possibility that the drooping portions M12 will adhere to the axial end surface 1120 (upper end surface) of the stator core 112. In this case, the liquid resin material M0 adhering to the stator core 112 must be removed separately using a scraper or the like. In contrast, according to the present manufacturing method, as described above, such inconveniences can be reduced and the CT can be shortened.

[0064] Furthermore, according to this manufacturing method, each hanging portion M12 is not removed from the workpiece W, but is returned to the impregnation target portion of the workpiece W in a manner that integrates it with the normal portion M13. Therefore, each hanging portion M12 can be eliminated without reducing the amount of liquid resin material M0 impregnated into the impregnation target portion of the workpiece W. Specifically, when each hanging portion M12 is removed from the workpiece W, the amount of liquid resin material M0 attached to (impregnated into) the impregnation target portion of the workpiece W is correspondingly reduced. In this case, an unnecessary increase in the number of dipping steps performed on one workpiece W (and the resulting increase in CT) occurs in order to ensure the required thickness of liquid resin material M0. In contrast, according to this manufacturing method, such inconveniences can be prevented while shortening the CT.

[0065] In this manufacturing method, the redeposition rotation step may be achieved by rotating the workpiece W in only one direction (for example, either clockwise or counterclockwise in the view of arrow V15), or may be achieved by rotating the workpiece W in both directions. The rotation angle (rotation stroke) involved in the redeposition rotation step is optional, but is preferably 90 degrees or more, and more preferably 180 degrees or more.

[0066] Although the above description has mainly focused on the drooping portion M12 arising from the coil end portion 114A, the same effect can be obtained by the reattachment rotation process for a similar drooping portion M12 arising from the neutral bus bar 59.

[0067] Furthermore, in the present manufacturing method, in the re-attachment rotation step, the workpiece W in an obliquely downward position may still be positioned above the tank 600 in a manner that it faces the tank 600 in the vertical direction. That is, the workpiece W in an obliquely downward position may be formed in a manner that the portion of the workpiece W to be impregnated overlaps the tank 600 when viewed in the vertical direction. In this case, even if the hanging portion M12 separates from the workpiece W and falls, it can return into the tank 600, and a decrease in the yield of the liquid resin material M0 due to the dropping of the hanging portion M12 can be prevented.

[0068] Here, in this manufacturing method, the reattachment rotation process is performed on the workpiece W in a diagonally downward orientation, and it is desirable that the angle α of the diagonally downward orientation (see FIG. 15) be relatively small. For example, if the angle α exceeds 45 degrees, as shown schematically in FIG. 17, the hanging portion M12 tends to fall downward when the workpiece W is rotated (or the hanging portion M12 simply rotates in an icicle-like state), making the above-mentioned reattachment difficult. Furthermore, when the reattachment rotation process is performed on the workpiece W in a diagonally upward orientation, as shown schematically in FIG. 18, the hanging portion M12 tends to adhere to the stator core 112. For example, the hanging portion M12 that hangs down from a circumferential position below the central axis I tends to adhere to the axial end surface 1120 of the stator core 112 radially outward of the slots 23. Furthermore, the hanging portion M12, which starts to hang down from a circumferential position above the central axis I, tends to adhere to the axial end surface 1120 and the inner circumferential surface of the stator core 112 radially inward of the slots 23. This tendency becomes more pronounced when the angle α of the obliquely downward orientation exceeds −20 degrees on the negative side. Note that the angle α is positive in the direction in which the impregnation target portion faces downward. Therefore, the angle α of the obliquely downward orientation (see FIG. 15) is preferably smaller than 45 degrees and larger than −20 degrees. Alternatively, the lower limit of the negative angle α for the obliquely upward posture may be determined from the perspective shown in FIGS. 18A and 18B. In the example shown in FIGS. 18A and 18B, the sign of the angle α is negative due to the "obliquely upward posture." FIGS. 18A and 18B show schematic cross-sectional views (cross-sectional views taken along a cross section passing through the central axis I) of the workpiece W in the obliquely upward posture during the reattachment rotation process, each showing different hanging portions M12 (labeled "hanging portion M12A" and "hanging portion M12B" for distinction). The hanging portion M12A shown in FIG. 18A hangs down vertically from the upper side of the impregnation target portion (the side farther from the stator core 112 in the axial direction), and its lower end faces the non-impregnation target portion (the portion closer to the stator core 112 in the axial direction) of the coil end portion 114A. In this case, if the hanging portion M12A drips, the liquid resin material M0 will adhere to the portion of the coil end portion 114A that is not to be impregnated. To prevent such adhesion, the negative angle α associated with the obliquely upward posture is preferably set to be larger (closer to 0 degrees) than the angle α1 (see FIG. 18A ) when the hanging portion M12A axially faces the portion of the coil end portion 114A that is not to be impregnated. Also, the hanging portion M12B shown in FIG. 18B drips vertically downward from the lower side of the portion to be impregnated (the side closer to the stator core 112 in the axial direction), with its lower end facing the inner circumferential surface of the stator core 112. In this case, if the hanging portion M12B drips, the liquid resin material M0 will adhere to the inner circumferential surface of the stator core 112. To prevent such adhesion, the negative angle α associated with the obliquely upward posture is preferably set to be larger (close to 0 degrees) than the angle α2 (see FIG. 18B ) when the hanging portion M12B axially faces the inner circumferential surface of the stator core 112. Here, the magnitude relationship between the angles α1 and α2 may vary depending on the shape of the coil end portion 114A, the range of the area to be impregnated, and the like. Therefore, the negative angle α associated with the obliquely upward posture may preferably be set to be equal to or larger than the larger of the angles α1 and α2.

[0069] Next, this manufacturing method includes an inversion step (step S214) in which the orientation of the workpiece W is changed to an upward orientation. That is, the orientation of the workpiece W is changed from a downward orientation to an obliquely downward orientation, and then to an upward orientation. Fig. 19 schematically shows the workpiece W in an upward orientation.

[0070] Incidentally, if the orientation of the workpiece W lifted from the tank 600 is inverted upside down in the inversion step (step S214) without performing the above-described re-adhesion rotation step, there is a possibility that the drooping portion M12 will adhere to the axial end surface 1120 (upper end surface) of the stator core 112. In this case, the liquid resin material M0 adhering to the stator core 112 must be removed separately using a scraper or the like. In contrast, according to the present manufacturing method, as described above, the drooping portion M12 disappears (is absorbed by the normal portion M13) in the re-adhesion rotation step before the workpiece W is placed in the upward orientation, thereby reducing this inconvenience.

[0071] Next, this manufacturing method includes an upper surface resin curing process (step S216) in which a resin curing process of the liquid resin material M0 is performed on the upper surface of the portion to be impregnated of the workpiece W in an upward orientation. Hereinafter, the resin curing process related to the upper surface resin curing process will also be referred to as the "upper surface resin curing process."

[0072] In this manufacturing method, the upper surface resin curing process includes irradiating the upper surface of the portion of the workpiece W that is to be impregnated with ultraviolet rays. FIG. 20 schematically shows a state in which the upper surface resin curing process is being performed. In the example shown in FIG. 20, the ultraviolet irradiation device 900 irradiates the upper surface of the portion of the workpiece W that is to be impregnated with ultraviolet rays (see arrow R13). This hardens the upper portion (mainly the upper surface portion) of the liquid resin material M0 that has impregnated the portion of the workpiece W that is to be impregnated.

[0073] The ultraviolet irradiation device 900 preferably irradiates ultraviolet rays over the entire circumference of the upper surface of the portion to be impregnated of the workpiece W. This allows the liquid resin material M0 in the upper portion to be cured over the entire circumference of the portion to be impregnated. In this case, the workpiece W may be rotated about the central axis I, or the ultraviolet irradiation device 900 may be rotated. Alternatively, multiple ultraviolet irradiation devices 900 may be arranged circumferentially above the workpiece W.

[0074] The ultraviolet irradiation device 900 is preferably positioned with respect to the workpiece W so that the optical axis 901 is approximately perpendicular to the upper surface of the portion of the workpiece W to be impregnated. That is, the ultraviolet irradiation device 900 is preferably positioned with respect to the workpiece W so that the optical axis 901 is located in an approximately vertical plane. Here, "approximately" is a concept that includes an error of, for example, 10% or less. The ultraviolet irradiation device 900 is preferably positioned with respect to the workpiece W so that the optical axis 901 passes through the portion of the workpiece W to be impregnated, and more preferably, is positioned with respect to the workpiece W so that the optical axis 901 passes near the center of the radial range (range from the innermost diameter position to the outermost diameter position) of the portion of the workpiece W to be impregnated. In this case, the liquid resin material M0 in the upper portion of the portion of the workpiece W to be impregnated can be efficiently cured.

[0075] In this way, according to this manufacturing method, the workpiece W is in an upward position, and the upper portion (axial end) of the liquid resin material M0 impregnated into the impregnation target portion is cured. This reduces the inconvenience that can occur when the top-surface resin curing process is performed on the workpiece W while it is in a downward position after being lifted from the vat 600. Specifically, if the resin curing process is performed on the underside of the impregnation target portion of the workpiece W while it is in a downward position after being lifted from the vat 600, the liquid resin material M0 impregnated into the impregnation target portion of the workpiece W may harden while dripping downward due to its own weight. In this case, the hardening liquid resin material M0 may return to the vat 600, affecting the fluidity of the liquid resin material M0 in the vat 600. In contrast, according to this manufacturing method, the top-surface resin curing process is performed in an upward position as described above, thereby reducing such inconvenience.

[0076] Furthermore, according to this manufacturing method, by curing the upper portion (axial end) of the liquid resin material M0 impregnated into the impregnation target portion, a thin film of the liquid resin material M0 can be formed on the corner of the rectangular cross section of the joint 40 (see FIG. 5 , hereinafter referred to as the “joint edge 122”). That is, even on the joint edge 122, where the liquid resin material M0 is difficult to form due to the influence of the wettability around the coil pieces 52, a relatively thin film of the liquid resin material M0 can be formed. The joint edge 122 on which such a film of the liquid resin material M0 is formed has high wettability due to the film. In this way, the wettability of the joint edge 122 (wettability of the liquid resin material M0) can be improved. As a result, in the subsequent second dipping process (described below), it becomes easier to ensure the required thickness of the insulating coating (cured liquid resin material M0) on the joint edge 122 of the coil pieces 52. That is, in the second dipping step, a relatively thick film can be formed also on the joint edge 122 using the film of the liquid resin material M0 formed in the first dipping step as a base.

[0077] Next, this manufacturing method includes an inner diameter side resin curing process (step S218) in which the liquid resin material M0 is cured on the radially inner side surface of the portion to be impregnated of the workpiece W that has been inverted into an upward position. Hereinafter, the resin curing process related to the inner diameter side resin curing process will also be referred to as the "inner diameter side resin curing process" to distinguish it from the above-mentioned upper surface resin curing process.

[0078] In this manufacturing method, the inner diameter side resin curing treatment includes irradiating ultraviolet rays onto the radially inner side surface of the portion of the workpiece W to be impregnated. FIG. 21 schematically shows a state in which the inner diameter side resin curing treatment is being performed. In the example shown in FIG. 21, the ultraviolet irradiation device 900 irradiates ultraviolet rays onto the radially inner side surface of the portion of the workpiece W to be impregnated (see arrow R14). This hardens the radially inner portion (mainly the surface portion) of the liquid resin material M0 that has impregnated the portion of the workpiece W to be impregnated. Note that the ultraviolet irradiation device 900 may be the same as the ultraviolet irradiation device 900 used in the above-mentioned upper surface resin curing treatment.

[0079] The ultraviolet irradiation device 900 preferably irradiates ultraviolet rays onto the radially inner side surface of the impregnation target portion of the workpiece W along the entire circumference. This allows the liquid resin material M0 in the radially inner portion to be cured along the entire circumference of the impregnation target portion. In this case, the inner diameter side resin curing process may be performed sequentially in parallel with the top surface resin curing process. Specifically, the top surface resin curing process and the inner diameter side resin curing process may be performed together for each divided circumferential range of the entire circumference of the impregnation target portion of the workpiece W. Alternatively, the inner diameter side resin curing process may be performed before the top surface resin curing process.

[0080] The ultraviolet irradiation device 900 is preferably positioned with respect to the workpiece W so that the optical axis 901 is approximately perpendicular to the radially inner side surface of the portion of the workpiece W to be impregnated. That is, the ultraviolet irradiation device 900 is preferably positioned with respect to the workpiece W so that the optical axis 901 is located in an approximately vertical plane. Here, "approximately" is a concept that includes an error of, for example, 10% or less. Furthermore, the ultraviolet irradiation device 900 is preferably positioned with respect to the workpiece W so that the optical axis 901 passes through the portion of the workpiece W to be impregnated, and more preferably, is positioned with respect to the workpiece W so that the optical axis 901 passes near the axial center of the portion of the workpiece W to be impregnated. In this case, the liquid resin material M0 on the radially inner side surface of the portion of the workpiece W to be impregnated can be efficiently cured.

[0081] However, depending on the size of the ultraviolet irradiation device 900 and the space radially inside the workpiece W, the ultraviolet irradiation device 900 may be positioned relative to the workpiece W such that the optical axis 901 intersects obliquely with the radially inside side surface of the portion to be impregnated of the workpiece W, as shown in Fig. 21. In this case, one of the inner diameter side resin curing treatment and the upper surface resin curing treatment may serve as the other.

[0082] When the inner diameter side resin hardening step (step S218) by the inner diameter side resin hardening treatment is completed, the insulation coating step for that time is completed.

[0083] Next, in this manufacturing method, it is determined whether the insulation coating process has been performed on one workpiece W a predetermined number of times (for example, twice in this manufacturing method) (step S220). This determination may be made manually or by image processing, etc. If the determination result is "YES," the process proceeds to the next step; otherwise, steps S206 to S218 are similarly performed to perform the second insulation coating process. FIG. 22 schematically shows the workpiece W that has been turned upside down in step S206 and placed in a downward position in the second insulation coating process. Thereafter, the workpiece W undergoes a second immersion process, etc.

[0084] The second insulating coating process may be exactly the same as the first insulating coating process, which can simplify the control of the manufacturing equipment, for example.

[0085] However, the second insulating coating process preferably differs from the first insulating coating process in at least the dipping step. Specifically, the dipping step in the second insulating coating process reduces the area to be impregnated compared to the dipping step in the first insulating coating process. That is, the area to be impregnated in the second dipping process may be a portion (a portion on the axial end side) of the area to be impregnated in the first dipping process. In this case, the area to be impregnated in the second dipping process may be a minimum area including the joint edge 122 of the coil piece 52. This allows an insulating coating (a cured product of the liquid resin material M0) having the required functions to be efficiently formed using a relatively small amount (e.g., a minimum) of the liquid resin material M0.

[0086] Figure 22 schematically shows the range Q15 to which the impregnation target area for the second insulation coating process belongs, relative to the range (hatched area M1) of the liquid resin material M0 impregnated into the workpiece W in the first insulation coating process.

[0087] In this way, in this manufacturing method, the insulating coating process is performed multiple times (for example, twice in this manufacturing method), which makes it possible to ensure the necessary thickness of the insulating coating (cured product of the liquid resin material M0) on the joint edges 122 of the coil pieces 52.

[0088] After the second insulating coating process is completed, this manufacturing method includes a heating process (step S222) in which the workpiece W is heated so that the liquid resin material M0 is hardened throughout the workpiece W. This heating process has the function of completely hardening the portions of the liquid resin material M0 that have not been hardened in the various resin hardening processes described above (for example, the portions inside the surface). The heating method in the heating process is arbitrary, and may be achieved, for example, by placing the workpiece W in a furnace. The liquid resin material M0 that has impregnated the impregnation portions, including the impregnation target portions of the workpiece W, is heated and completely hardened. As a result, an insulating coating of the liquid resin material M0 is formed on the stator coil 114.

[0089] The posture of the workpiece W during the heating process is arbitrary, but is preferably a downward posture as shown schematically in FIG. 23. Note that FIG. 23 also shows a state in which a plurality of workpieces W are arranged side by side in a downward posture and undergo the heating process. Note that FIG. 23 also shows a state in which a workpiece gripping unit 1000, which is part of the manufacturing apparatus, clamps a plurality of workpieces W, but the workpieces W may also be supported on a table in such a manner that the end face of the stator core 112 abuts against the upper surface (not shown) of the table. Also, in the figure, as an example, heat is radiated from below the workpiece W (see arrow R17), but the direction of heat radiation is arbitrary.

[0090] Incidentally, in the heating process, when the stator core 112 is in an upward position, the liquid resin material M0 that is in the process of hardening before it is completely hardened may drip downward due to its own weight onto the stator core 112. In this case, the liquid resin material M0 that has adhered to the stator core 112 must be removed separately using a scraper or the like.

[0091] In contrast, in the downward position, even if the liquid resin material M0 that is still in the process of hardening before it is completely hardened moves downward under its own weight, it will not reach the stator core 112. Furthermore, the portions of the liquid resin material M0 that have hardened in the upper surface resin hardening process and the inner diameter side resin hardening process function as a "bottom lid," thereby reducing the possibility that the dripping liquid resin material M0 will form icicles. In other words, the downward movement of the liquid resin material M0 that is still in the process of hardening is blocked by the portions of the liquid resin material M0 that have hardened in the upper surface resin hardening process and the inner diameter side resin hardening process. This prevents the inconvenience that can occur when the heating process is performed in the downward position.

[0092] Thus, according to this manufacturing method, by performing the heating process in a downward position, dripping of the liquid resin material M0 onto the stator core 112 is prevented, and the portions of the liquid resin material M0 hardened in the upper surface resin hardening process and the inner diameter side resin hardening process function as a "bottom lid," thereby reducing the amount of icicle-like hardened liquid resin material M0 dripping downward. Note that a similar outer diameter side resin hardening process may be performed instead of or in addition to the outer diameter side resin hardening process.

[0093] Next, with reference to FIG. 24, a cooling structure suitable for the rotating electric machine 1 incorporating the rotating electric machine stator 10 manufactured by this manufacturing method will be described.

[0094] FIG. 24 is a diagram schematically showing an example of a cooling structure, and is a diagram schematically showing a part of the cross-sectional structure of the rotating electrical machine 1.

[0095] In the example shown in FIG. 24 , oil is supplied from the radially outer and radially inner sides to coil end portions 114A at both axial ends of stator coil 114. Specifically, oil supplied to intra-case oil passage 60 of case 2 (see arrow R20A) is supplied to the radially outer side surface of coil end portion 114A via oil hole 62 penetrating radially inward (see arrow R20). Note that oil hole 62 may be positioned vertically upward to promote dripping of oil by gravity. Furthermore, oil supplied to axial center oil passage 64 of rotor shaft 112A (see arrow R21A) is supplied to the radially inner side surface of coil end portion 114A via oil hole 66 penetrating radially outward (see arrow R21).

[0096] According to this manufacturing method, as described above, the coil end portions 114A of the stator coil 114 are coated with an insulating coating of liquid resin material M0. The portions of the stator coil 114 coated with the insulating coating of liquid resin material M0 have lower thermal conductivity than the portions of the stator coil 114 that are not (i.e., the portions where the insulating film 130 is the surface). Therefore, if the exposed area of ​​the radially outer side surface of the coil end portions 114A that is not covered with the insulating coating of liquid resin material M0 becomes unnecessarily narrow, the cooling performance of the oil from the oil holes 62 described above may be unnecessarily reduced. Similarly, if the exposed area of ​​the radially inner side surface of the coil end portions 114A that is not covered with the insulating coating of liquid resin material M0 becomes unnecessarily narrow, the cooling performance of the oil from the oil holes 66 described above may be unnecessarily reduced.

[0097] In this regard, according to the present manufacturing method, as described above, the drooping portion M12 of the liquid resin material M0 impregnated into the impregnation target portion is reduced by the redeposition rotation process. Therefore, even if the workpiece W is then in an upward position, the liquid resin material M0 on the radially outer side is less likely to drip downward. This reduces the possibility that the exposed area of ​​the radially outer side surface of the coil end portion 114A that is not covered by the insulating coating of the liquid resin material M0 will be unnecessarily narrowed. As a result, the cooling performance of the coil end portion 114A by the oil from the oil hole 62 described above can be effectively improved.

[0098] Next, a more preferable manufacturing method will be described with reference to FIGS.

[0099] FIG. 25 is a schematic flow chart showing an example of another manufacturing method that may be performed instead of the manufacturing method described above with reference to FIG.

[0100] The manufacturing method shown in FIG. 25 differs from the manufacturing method described above with reference to FIG. 1 in that steps S2210 and S2211 are added between steps S220 and S222.

[0101] After the insulating coating process is performed ("YES" in step S220), the present manufacturing method includes an inspection process (step S2210) for determining whether or not the liquid resin material M0 is attached to the axial end surface 1120 of the stator core 112. The presence or absence of the liquid resin material M0 may be determined based on the results of image processing of an image from a camera (not shown) that captures an image of the workpiece W. In this case, the determination may be performed visually, based on a predetermined algorithm, or by using artificial intelligence (machine learning, etc.). In the case of artificial intelligence, the determination of a region of interest (ROI) within the image captured by the camera may also be performed based on artificial intelligence. In this case, only harmful attachment (e.g., attachment over a range greater than a threshold) may be detected.

[0102] In this inspection process, it may also be possible to inspect whether or not the liquid resin material M0 has adhered to portions (for example, the side surfaces of the stator core 112) other than the axial end surfaces 1120 of the stator core 112. Note that the adhesion material M9 adhering to the side surfaces 1122 of the stator core 112 is often also adhering to the axial end surfaces 1120, and in some cases it may be possible to detect it at the same time by inspecting the adhesion to the axial end surfaces 1120.

[0103] 26, the liquid resin material M0 adhering to the axial end surface 1120 of the stator core 112 is schematically shown as an attachment M9. Such an attachment M9 can occur when the liquid resin material M0 drips from the coil end portion 114A or the neutral bus bar 59 or when scattered liquid resin material M0 adheres to the surface.

[0104] In this manufacturing method, the possibility of the hanging portion M12 adhering to the stator core 112 can be reduced by the liquid draining rotation step (step S211) and the re-adhesion rotation step (step S213) as described above. However, if the liquid resin material M0 adheres for some reason, it can be detected in the inspection step.

[0105] If adhesion of the liquid resin material M0 to the stator core 112 (i.e., adhesion M9) is detected in this inspection process, the manufacturing method includes a process of removing the adhesion M9 (step S2211). Any method for removing the adhesion M9 may be used, for example, a scraper. However, in this manufacturing method, the process of removing the adhesion M9 is performed before the heating process (step S222). Therefore, the adhesion M9 is easily removed, and may be removed, for example, by wiping with a rag or the like. Specifically, even if the adhesion M9 is exposed to ultraviolet light during the ultraviolet irradiation process, it only hardens to a certain extent and remains in a soft, provisionally cured state. This makes it easier to remove than the fully cured state achieved by the heating process. For example, wiping with a rag or the like does not damage the stator core 112 or the like, and is easy to work with, unlike using a scraper.

[0106] Thus, according to this manufacturing method, by performing the above-described inspection step before the heating step, the liquid resin material M0 adhering to the stator core 112 can be easily removed. In particular, if the liquid resin material M0 contains epoxy resin as a main component, it becomes difficult to remove even with a scraper after it has hardened in the heating step. Even if it can be removed with a scraper, the hardened resin may scatter or crack, and the removed material (resin residue) may adhere to the workpiece W as foreign matter. There is also a risk that the scraper may scratch (damage) the workpiece W (particularly the stator core 112). In contrast, according to this manufacturing method, by performing the inspection step before the heating step as described above, these inconveniences can be effectively avoided.

[0107] In this manufacturing method, the inspection step (step S2210) and the step of removing the deposit M9 (step S2211) are performed after the ultraviolet ray irradiation step (steps S216 and S218) related to the second insulating coating step, but they may also be performed before the ultraviolet ray irradiation step (steps S216 and S218) related to the second insulating coating step and after step S214. In this case, it is possible to reduce the possibility that the liquid resin material M0 will harden (although as described above, it will only harden to a certain extent) due to ultraviolet ray irradiation in the ultraviolet ray irradiation step (steps S216 and S218) related to the second insulating coating step.

[0108] 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.

[0109] For example, in this embodiment, since the liquid draining rotation step (step S211) and the re-adhesion rotation step (step S213) are included as described above, it is possible to reduce or eliminate the amount of liquid resin material M0 that may drip onto the stator core 112 when the workpiece W is inverted from the downward position to the upward position after the immersion step (step S208) (see step S214). Therefore, in this embodiment, it is possible to reduce or eliminate the need to irradiate the portion of the workpiece W to be impregnated (e.g., the outer diameter side of the portion to be impregnated) with ultraviolet light while the workpiece W is still in the downward position after being pulled out of the tank 600. However, in a modified example, after the liquid draining rotation step of step S211, a step may be added in which the workpiece W is slightly raised while still in the downward position and then ultraviolet light is irradiated onto the outer diameter side of the portion to be impregnated. In this case, the subsequent steps S212 and S213 may be omitted.

[0110] In the above-described embodiment, both the liquid-removing rotation step (step S211) and the re-adhesion rotation step (step S213) are preferably performed, but the liquid-removing rotation step (step S211) may be omitted. [Explanation of symbols]

[0111] 1···Rotating electric machine, 10···Stator for rotating electric machine, 40···Joint portion (tip portion), 114···Stator coil, 1140···Axial end face, 112···Stator core, 1120···Axial end face, W···Workpiece, 52···Coil piece, 59···Neutral bus bar, 600···Tank, M0···Liquid resin material, I···Central axis (stator central axis)

Claims

1. a preparation step of preparing a workpiece in which a plurality of coil pieces forming a stator coil are attached to a stator core, the workpiece having tip ends of one of the coil pieces joined to another of the coil pieces at one axial end side; After the preparation step, an immersion step of immersing the workpiece in a tank of liquid resin material so that an impregnation target portion including a joint portion between the tip portions is immersed; a rotation step of rotating the workpiece at a raised position where the impregnation target portion is separated from the tank after the immersion step, The method for manufacturing a stator for a rotating electric machine, wherein the rotating step includes rotating the workpiece around a workpiece central axis corresponding to the stator central axis, with the workpiece oriented such that the portion to be impregnated faces a direction intersecting the vertical direction.

2. 2. The method for manufacturing a stator for a rotating electric machine according to claim 1, wherein the rotating process includes rotating the workpiece so that the liquid resin material dripping downward from one circumferential position in the impregnation target portion adheres to another circumferential position in the impregnation target portion.

3. 3. The manufacturing method of a stator for a rotating electric machine according to claim 2, wherein the posture in the rotation process includes a posture in which the portion to be impregnated faces diagonally downward and an angle formed between the center axis of the workpiece and a horizontal plane is 45 degrees or less.

4. The liquid resin material has the property of being hardened by irradiation with ultraviolet light, 2. The method for manufacturing a stator for a rotating electric machine according to claim 1, further comprising, after the rotating step, an irradiation step of irradiating the portion to be impregnated with ultraviolet light.

5. 5. The method for manufacturing a stator for a rotating electric machine according to claim 1, wherein the elevated position of the workpiece includes a position where the portion to be impregnated overlaps the tank when viewed in the up-down direction.

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