Stator and production method for stator

Abstract

A stator according to the present invention has a cylindrical stator core that has a plurality of slots. The stator also has an annular channel case that is provided opposite a first end surface of the stator core and has an internal cooling channel. The stator also has a stator coil that comprises a plurality of segment conductors that are inserted into the slots and passes through the annular channel case.

Description

Stator and stator manufacturing method

[0001] The present disclosure relates to a stator and a method for manufacturing a stator.

[0002] The motor generator has a stator consisting of a stator core and a stator coil, and a rotor housed inside the stator (see Patent Documents 1 to 3). Also, a stator coil consisting of multiple segment coils has been proposed as the stator coil wound around the stator core.

[0003] JP 2011-97780 A JP 2012-90405 A JP 2015-33299 A

[0004] Since the stator coil generates heat when current is applied, it is important to actively cool the stator coil in order to ensure proper functioning of the motor-generator. To address this issue, methods such as dripping oil onto the coil ends of the stator coil or pouring oil into the coil ends covered with a cover have been considered. However, in recent years, the amount of heat generated by the stator coil has tended to increase, creating a need for efficient cooling of the stator coil.

[0005] According to the present disclosure, a stator includes a cylindrical stator core having a plurality of slots formed therein. The stator has an annular flow path case disposed facing a first end face of the stator core and defining a cooling flow path therein. The stator includes a stator coil formed of a plurality of segment conductors inserted into the slots and penetrating the annular flow path case. The annular flow path case includes a first annular plate portion disposed facing the first end face of the stator core and having a plurality of first openings formed therein facing the slots. The annular flow path case includes a second annular plate portion disposed facing the first annular plate portion and having a plurality of second openings formed therein facing the first openings. The stator coil includes a first coil end formed of the plurality of segment conductors protruding from the first end face through the annular flow path case. The stator coil includes a second coil end formed of the plurality of segment conductors protruding from a second end face of the stator core opposite the first end face. Each of the plurality of segment conductors includes a straight portion inserted into the slot, the first opening, and the second opening. Each of the plurality of segment conductors is connected to the straight portion and includes a welded end portion that constitutes the first coil end. Each of the plurality of segment conductors is connected to the straight portion and includes a folded portion that constitutes the second coil end.

[0006] According to the present disclosure, a stator manufacturing method includes a case arrangement step of arranging an annular flow passage case, the annular flow passage case defining a cooling flow passage therein, facing an end face of a cylindrical stator core, a coil insertion step of inserting a conductor group consisting of a plurality of segment conductors into a plurality of slots formed in the stator core and a plurality of openings formed in the annular flow passage case, and a coil welding step of bending and welding end portions of the plurality of segment conductors that protrude through the annular flow passage case in a circumferential direction of the stator core.

[0007] According to the present disclosure, by providing an annular flow path case through which the segment conductors pass, the stator coil can be cooled efficiently.

[0008] FIG. 1 is a diagram showing a vehicle equipped with a motor generator. FIG. 2 is a cross-sectional view showing a motor generator equipped with a stator. FIG. 3 is a cross-sectional view showing a stator along line A-A in FIG. 2. FIG. 4 is a perspective view showing a segment coil. FIG. 5 is a perspective view showing a stator. FIG. 6 is a diagram showing a connection structure of segment coils. FIG. 7 is a diagram showing an example of a wiring structure of a stator coil. FIG. 8 is a diagram showing a cooling circuit. FIG. 9 is a perspective view showing a stator core and an annular flow path case. FIG. 10 is an exploded perspective view of the stator core and the annular flow path case. FIG. 11 is a cross-sectional view showing a portion of the stator along line B-B in FIG. 8. FIG. 12 is a diagram showing a stator manufacturing method. FIG. 13 is a diagram showing the execution status of the stator manufacturing method. FIG. 14 is a diagram showing the execution status of the stator manufacturing method. FIG. 15 is a diagram showing the execution status of the stator manufacturing method. FIG. 16 is a diagram showing the execution status of the stator manufacturing method. FIG. 17 is a diagram showing a cooling circuit and a stator as a modified example.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, identical or substantially identical configurations and elements will be designated by the same reference numerals and repeated description will be omitted.

[0010] <Vehicle> Fig. 1 is a diagram showing a vehicle 11 equipped with a motor generator 10. As shown in Fig. 1, the vehicle 11 has an electric axle 13 consisting of the motor generator 10 and a differential mechanism 12. The motor generator 10 and the differential mechanism 12 are connected via a gear train (not shown), and the differential mechanism 12 is connected to wheels 15 via axles 14. The motor generator 10, which is a rotating electric machine, is connected to a battery pack 17 via an inverter 16. Note that, although the motor generator 10 of the electric axle 13 is shown as an example of a motor generator to which the stator technology of the present disclosure can be applied, the present disclosure is not limited to this. For example, the technology of the present disclosure may be applied to a motor generator provided in a transmission or the like, or to a motor generator provided in a device other than a vehicle.

[0011] <Motor Generator> Figure 2 is a cross-sectional view showing a motor generator 10 including a stator 20 according to one embodiment of the present disclosure. As shown in Figure 2, the motor generator 10 includes a cylindrical motor case 21 with a bottom, and an end cover 22 attached to the open end of the motor case 21. A stator 20 including a stator core 23 and a stator coil 24 is attached to the inner peripheral surface of the motor case 21. The stator 20 includes a cylindrical stator core 23 made of a plurality of laminated electromagnetic steel plates, and three-phase stator coils 24 wound around the stator core 23.

[0012] A bus bar unit 26 is connected to coil ends 25 of stator coil 24. Bus bar unit 26 has three power bus bars 27, 28, and 29 connected to three power points Pu, Pv, and Pw of stator coil 24, and a neutral bus bar 30 connecting three neutral points Nu, Nv, and Nw of stator coil 24 to one another. Bus bar unit 26 also has an insulating member 31 that holds power bus bars 27 to 29 and neutral bus bar 30. Furthermore, ends of power bus bars 27 to 29 protrude outside from motor case 21, and power cables 32 extending from inverter 16 are connected to each of power bus bars 27 to 29.

[0013] A cylindrical rotor 33 is rotatably housed in the center of the stator core 23. The rotor 33 has a cylindrical rotor core 34 made of a plurality of laminated electromagnetic steel plates, a plurality of permanent magnets 35 provided in the rotor core 34, and a rotor shaft 36 fixed to the center of the rotor core 34. One end of the rotor shaft 36 is supported by a bearing 38 provided in the motor case 21, and the other end of the rotor shaft 36 is supported by a bearing 39 provided in the end cover 22.

[0014] <Stator Structure> Figure 3 is a cross-sectional view showing the stator 20 taken along line A-A in Figure 2. As shown in Figure 3, a plurality of slots S1 to S48 are formed at predetermined intervals in the circumferential direction D1 on the inner periphery of the stator core 23. A segment coil (segment conductor) 40 is inserted into each of the slots S1 to S48, and the stator coil 24 is formed by connecting the plurality of segment coils 40 to each other. As will be described later, the stator coil 24 is made up of a U-phase coil Cu, a V-phase coil Cv, and a W-phase coil Cw.

[0015] The illustrated U-phase coil Cu, V-phase coil Cv, and W-phase coil Cw have the same coil structure and are assembled to the stator core 23 with a phase shift of 120°. In the illustrated example, the segment coils 40 that make up the U-phase coil Cu are housed in slots S1, S2, S7, S8, etc., the segment coils 40 that make up the V-phase coil Cv are housed in slots S3, S4, S9, S10, etc., and the segment coils 40 that make up the W-phase coil Cw are housed in slots S5, S6, S11, S12, etc.

[0016] Figure 4 is a perspective view showing a segment coil 40. As shown in Figure 4, the segment coil 40 is bent into a substantially U-shape and has a pair of coil sides (straight portions) 41 spaced apart at a predetermined pitch. One coil side 41 is housed in one of the slots (e.g., slot S7), and the other coil side 41 is housed in another slot (e.g., slot S13) spaced apart at a predetermined pitch. The segment coil 40 also has a folded portion 42 connecting the pair of coil sides 41 to each other and welded ends 43 extending from each of the pair of coil sides 41.

[0017] The segment coil 40 is made of rectangular wire made of a conductive material such as copper. As shown by the hatching in Figure 4, the segment coil 40 is provided with an insulating coating 44 made of enamel, resin coating, or the like, except for the tip of the welded end 43. In other words, the coil side 41 and the folded portion 42 are provided with an insulating coating 44 made of resin coating, or the like. The shape of the folded portion 42 that constitutes the segment coil 40 is not limited to the shape shown in the figure, and the folded portion 42 can have various shapes depending on the slot insertion position.

[0018] FIG. 5 is a perspective view of the stator 20, and FIG. 6 is a diagram showing the connection structure of the segment coil 40. As shown in FIGS. 3 and 5, multiple segment coils 40 are assembled in each slot S1 to S48 of the stator core 23. Also, as shown in FIG. 6, the welded end 43 of the segment coil 40 penetrates the annular flow path case 50 from the first end face 45 of the stator core 23 and is positioned on the power line side. Meanwhile, the folded portion 42 of the segment coil 40 protrudes from the second end face 46 of the stator core 23 and is positioned on the counter power line side. As shown in FIGS. 2 and 5, the annular flow path case 50 (described later) is provided on the first end face 45 of the stator core 23, and the annular flow path case 60 (described later) is provided on the second end face 46 located opposite the first end face 45. Note that, in this specification, the "power line side" refers to the side on which the power bus bars 27 to 29 are arranged.

[0019] As shown in Figure 6, the welded ends 43 that protrude through the annular flow path case 50 are bent so as to contact the welded ends 43 of other segment coils 40. Then, by welding the joints 47 made up of the welded ends 43 that are in contact with each other, the multiple segment coils 40 are connected to each other via the joints 47. Note that the welded joints 47 are subjected to an insulating treatment in which a resin coating or the like is formed to cover the conductors.

[0020] FIG. 7 is a diagram showing an example of the wiring structure of the stator coil 24. As shown in FIG. 7, the stator coil 24 is composed of a U-phase coil Cu, a V-phase coil Cv, and a W-phase coil Cw. The U-phase coil Cu is composed of a plurality of segment coils 40 connected in series. One end of the U-phase coil Cu is a power point Pu, and the other end of the U-phase coil Cu is a neutral point Nu. The V-phase coil Cv is also composed of a plurality of segment coils 40 connected in series. One end of the V-phase coil Cv is a power point Pv, and the other end of the V-phase coil Cv is a neutral point Nv. The W-phase coil Cw is also composed of a plurality of segment coils 40 connected in series. One end of the W-phase coil Cw is a power point Pw, and the other end of the W-phase coil Cw is a neutral point Nw.

[0021] The neutral point Nu of the U-phase coil Cu, the neutral point Nv of the V-phase coil Cv, and the neutral point Nw of the W-phase coil Cw are connected to one another via the neutral bus bar 30. This allows the phase coils Cu, Cv, and Cw to be connected to one another, and the phase coils Cu, Cv, and Cw form the stator coil 24. Note that the connection structure of the stator coil 24 is not limited to the connection structure shown in FIG. 7 , and the stator coil 24 may be formed using another connection structure.

[0022] <Cooling Circuit> The cooling circuit 70 for the stator coil 24 will now be described. FIG. 8 is a diagram showing the cooling circuit 70. FIG. 9 is a perspective view showing the stator core 23 and the annular flow path cases 50, 60, and FIG. 10 is an exploded perspective view of the stator core 23 and the annular flow path cases 50, 60. FIG. 11 is a cross-sectional view showing a portion of the stator 20 taken along line B-B in FIG. 8. In the following description, the slot reference numerals "S1 to S48" will be replaced with the reference numeral "80."

[0023] 8, 9, and 10, an annular flow path case 50 is provided on a first end face 45 of the stator core 23, and an annular flow path case (second annular flow path case) 60 is provided on a second end face 46 of the stator core 23. As shown in Fig. 8, a coil end (first coil end) 25 consisting of the welded end portion 43 of the segment coil 40 is arranged near the outside of the annular flow path case 50. In addition, a coil end (second coil end) 37 consisting of the folded portion 42 of the segment coil 40 is arranged inside the annular flow path case 60.

[0024] 10 , the annular flow path case 50 provided on the first end surface 45 of the stator core 23 has a case main body 51 provided opposite the first end surface 45 of the stator core 23, and an annular plate portion (second annular plate portion) 52 attached to the case main body 51 by adhesive or the like. The case main body 51 has an annular plate portion (first annular plate portion) 53 in which a plurality of openings (first openings) 53 a facing the plurality of slots 80 are formed, an inner peripheral wall portion 54 provided on the inner periphery of the annular plate portion 53, and an outer peripheral wall portion 55 provided on the outer periphery of the annular plate portion 53.

[0025] The annular plate portion 52 is provided opposite the annular plate portion 53, and a plurality of openings (second openings) 52a are formed in the annular plate portion 52, facing the plurality of openings 53a. An annular cooling flow path 56 is defined inside the annular flow path case 50. Furthermore, an inlet port 57 communicating with the cooling flow path 56 is provided in the outer peripheral wall portion 55 of the annular flow path case 50, and an outlet port 58 communicating with the cooling flow path 56 is also provided.

[0026] The annular flow path case 60 provided on the second end surface 46 of the stator core 23 includes a case main body 61 provided facing the second end surface 46 of the stator core 23 and an annular plate portion 62 attached to the case main body 61 by adhesive or the like. The case main body 61 includes an annular plate portion 63 having a plurality of openings 63a formed therein that face the plurality of slots 80, an inner circumferential wall portion 64 provided on the inner periphery of the annular plate portion 63, and an outer circumferential wall portion 65 provided on the outer periphery of the annular plate portion 63. An annular cooling flow path 66 is defined inside the annular flow path case 60. Furthermore, the outer circumferential wall portion 65 of the annular flow path case 60 is provided with an inlet port 67 communicating with the cooling flow path 66, and an outlet port 68 communicating with the cooling flow path 66.

[0027] As shown in FIG. 8 , the cooling circuit 70 includes annular flow path cases 50, 60, a radiator 71, a tank 72, and a coolant pump 73. A discharge port 73o of the coolant pump 73 is connected to the inlet ports 57, 67 of the annular flow path cases 50, 60 via a pipe 74. A suction port 73i of the coolant pump 73 is connected to the outlet ports 58, 68 of the annular flow path cases 50, 60 via a pipe 75, the tank 72, a pipe 76, the radiator 71, and a pipe 77. A coolant serving as a refrigerant is injected into the annular flow path cases 50, 60, the radiator 71, the tank 72, the coolant pump 73, and the pipes 74 to 77. An antifreeze liquid such as ethylene glycol or propylene glycol is used as the coolant injected into the cooling circuit 70.

[0028] 11 , the multiple coil sides 41 protruding from the first end surface 45 of the stator core 23 are inserted into the openings 52a, 53a so as to penetrate the annular flow path case 50. As shown in the enlarged portion, a sealant 82 made of hardened varnish made of resin, organic solvent, or the like is provided in the gap between the coil side 41 and the opening 53a. Similarly, a sealant 82 made of hardened varnish is provided in the gap between the coil side 41 and the opening 52a. This allows the sealant 82 to seal the gap in the annular flow path case 50, thereby preventing coolant from leaking from the annular flow path case 50.

[0029] Additionally, the multiple coil sides 41 protruding from the second end face 46 of the stator core 23 are inserted into the opening 63a of the annular flow path case 60. As shown in the enlarged view, a sealant 83 made of hardened varnish is provided in the gap between the coil side 41 and the opening 63a. This allows the sealant 83 to seal the gap in the annular flow path case 60, thereby preventing coolant from leaking from the annular flow path case 60.

[0030] By driving the coolant pump 73, coolant circulates between the annular flow path cases 50, 60 and the radiator 71, as shown by arrow FL1. This allows the coolant cooled by the radiator 71 to be supplied to the cooling flow paths 56, 66 of the annular flow path cases 50, 60, and the coolant flowing through the annular flow path cases 50, 60 to cool the stator coil 24. That is, the coolant flowing through the annular flow path case 50 actively cools the coil side 41 of the stator coil 24, and the coolant flowing through the annular flow path case 60 actively cools the coil end 37 of the stator coil 24. Furthermore, because the coil side 41 and the folded portion 42 are provided with the insulating coating 44, an antifreeze solution such as ethylene glycol can be used as the coolant, allowing the stator coil 24 to be efficiently cooled.

[0031] Furthermore, because the coil sides 41 of the stator coil 24 pass through the annular flow path case 50, the annular flow path case 50 can be disposed between the stator core 23 and the coil ends 25, allowing for efficient cooling of the stator coil 24 with a simple configuration. That is, because the power bus bars 27 to 29 that protrude outside the case are connected to the coil ends 25, it is difficult to partition the cooling flow path by covering the coil ends 25 with a cover or the like. In contrast, by disposing the annular flow path case 50 between the stator core 23 and the coil ends 25, the annular flow path case 50 can supply coolant to the coil sides 41 near the coil ends 25, allowing for efficient cooling of the stator coil 24.

[0032] <Stator Manufacturing Method> Next, a stator manufacturing method according to an embodiment of the present disclosure will be described. Fig. 12 is a diagram illustrating the stator manufacturing method. Figs. 13, 14, 15, and 16 are diagrams illustrating the execution status of the stator manufacturing method.

[0033] <Case Attachment Process> As shown in Fig. 12 , a case attachment process S100 for attaching the annular flow path cases 50, 60 to the stator core 23 is set as a process of the stator manufacturing method. As shown in Fig. 13 , in the case attachment process S100, by using a jig (not shown), the annular flow path case 50 is disposed on the first end surface 45 of the stator core 23 so that the openings 52 a, 53 a of the annular flow path case 50 face the slots 80. Also, in the case attachment process S100, by using a jig (not shown), the case main body 61 of the annular flow path case 60 is disposed on the second end surface 46 of the stator core 23 so that the openings 63 a of the annular flow path case 60 face the slots 80. In this way, in the case attachment process (case placement process) S100, the annular flow path case 50, inside which the cooling flow path 56 is defined, is disposed opposite the end surface 45 of the cylindrical stator core 23.

[0034] <Coil Insertion Process> As shown in Figure 12, the stator manufacturing method includes a coil insertion process S110 after the case attachment process S100, in which multiple segment coils 40 are inserted into the stator core 23 and the annular flow path cases 50, 60. As indicated by arrows α in Figures 13 and 14, in the coil insertion process S110, a coil group (conductor group) 85 consisting of multiple segment coils 40 is inserted in the following order: the opening 63a of the annular flow path case 60, the slot 80 of the stator core 23, the opening 53a of the annular flow path case 50, and the opening 52a of the annular flow path case 50. Note that an insulating sheet such as aramid paper, also known as an insulator, is provided between the slot 80 and the segment coil 40.

[0035] <Coil Welding Process> As shown in Figure 12, the stator manufacturing method includes a coil welding process S120 after the coil insertion process S110, in which the welding ends 43 of the segment coils 40 are bent and welded. As shown in Figure 15, in the coil welding process S120, the welding ends (ends) 43 of the segment coils 40 that protrude through the annular flow path case 50 are bent in the circumferential direction D1 of the stator core 23 to form multiple joints 47, and each joint 47 is welded by TIG welding or the like. As a result, a coil end 25 consisting of the multiple welding ends 43 is provided near the outside of the annular flow path case 50.

[0036] 12 , as a process of the stator manufacturing method, a plate attachment process S130 is set after the coil welding process S120, in which the annular plate portion 62 is attached to the case main body portion 61 of the annular flow path case 60. As indicated by the arrow β in Fig. 15 , in the plate attachment process S130, the annular plate portion 62 is attached so as to close the open end of the case main body portion 61. As a result, the coil end 37 made up of the multiple folded portions 42 is accommodated in the cooling flow path defined inside the annular flow path case 60.

[0037] 12 , the stator manufacturing method includes a varnish impregnation step S140, which is set after the plate attachment step S130, in which varnish 100 is dripped onto the coil ends 25 consisting of the welded ends 43. As shown in FIG. 16 , in the varnish impregnation step S140, varnish 100 made of resin, organic solvent, or the like is dripped onto the coil ends 25, causing the varnish to permeate along the coil sides 41 of the segment coils 40. The varnish that has permeated the annular flow path cases 50, 60 and the stator core 23 then hardens, thereby fixing the annular flow path cases 50, 60 to the stator core 23 and fixing the stator coil 24 to the stator core 23.

[0038] 16, the gap between the coil side 41 and the opening 53a is filled with a sealant 82 made of varnish, and the gap between the coil side 41 and the opening 52a is filled with a sealant 82 made of varnish. Furthermore, the varnish flows along the coil side 41 and reaches the annular flow path case 60, so the gap between the coil side 41 and the opening 63a is filled with a sealant 83 made of varnish.

[0039] <Modification of Cooling Circuit> In the example shown in FIG. 8 , two annular flow path cases 50, 60 are provided for the stator core 23, but this is not limiting. Here, FIG. 17 illustrates a modification of the cooling circuit 90 and a stator 91. As shown in FIG. 17 , the stator 91 includes the stator core 23 and an annular flow path case 50 that faces the first end face 45 of the stator core 23. The discharge port 73o of the coolant pump 73 is connected to the inlet port 57 of the annular flow path case 50 via a pipe 92. The suction port 73i of the coolant pump 73 is connected to the outlet port 58 of the annular flow path case 50 via a pipe 75, a tank 72, a pipe 76, a radiator 71, and a pipe 93. In this way, even when one annular flow path case 50 is provided for the stator core 23, the coil side 41 of the stator coil 24 can be actively cooled by the coolant flowing through the annular flow path case 50.

[0040] The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present disclosure. In the above description, an antifreeze liquid such as ethylene glycol is used as the coolant injected into the cooling circuit 70. However, this is not limited to this, and the oil in the electric axle 13 may also be used as the coolant. In the illustrated example, annular cooling flow paths 56, 66 are defined inside the annular flow path cases 50, 60. However, this is not limited to this, and arc-shaped cooling flow paths may be defined by providing partitions inside the annular flow path cases 50, 60. In addition, the annular flow path cases 50, 60 may be formed using a resin material or a metal material.

[0041] In the illustrated example, each phase coil Cu, Cv, Cw is formed by connecting multiple segment coils 40 in series, but this is not limited thereto, and each phase coil Cu, Cv, Cw may be formed by connecting multiple segment coils 40 in parallel. Also, in the illustrated example, eight segment coils 40 are inserted into one slot 80, but this is not limited thereto. For example, more than eight segment coils 40 may be inserted into one slot 80, or fewer than eight segment coils 40 may be inserted into one slot 80. Also, in the illustrated example, a stator core 23 with 48 slots is used, but this is not limited thereto, and a stator core with a different number of slots may be used.

[0042] 20... Stator, 23... Stator core, 24... Stator coil, 25... Coil end (first coil end), 27, 28, 29... Power bus bar, 37... Coil end (second coil end), 40... Segment coil (segment conductor), 41... Coil side (straight portion), 42... Folded portion, 43... Welded end (end), 44... Insulating coating, 45... First end face (end face), 46... Second end face, 50... Annular flow path case, 52... Annular plate portion (second annular plate portion), 52a...opening (second opening), 53...annular plate portion (first annular plate portion), 53a...opening (first opening), 56...cooling flow path, 60...annular flow path case (second annular flow path case), 66...cooling flow path, 80...slot, 82...sealing material, 83...sealing material, 85...coil group (conductor group), 91...stator, S1 to S48...slot, S100...case mounting process (case arrangement process), S110...coil insertion process, S120...coil welding process, D1...circumferential direction

Claims

1. A cylindrical stator core having a plurality of slots formed therein; an annular flow path case provided opposite a first end face of the stator core and defining a cooling flow path inside; and a stator coil made of a plurality of segment conductors inserted into the slots and penetrating the annular flow path case, wherein the annular flow path case comprises: a first annular plate portion provided opposite the first end face of the stator core and having a plurality of first openings formed therein that face the plurality of slots; and a second annular plate portion provided opposite the first plate portion and having a plurality of second openings formed therein that face the plurality of first openings, wherein the stator coil comprises: a first coil end made of the plurality of segment conductors protruding from the first end face through the annular flow path case; and a second coil end made of the plurality of segment conductors protruding from a second end face of the stator core opposite the first end face, wherein each of the plurality of segment conductors has a straight portion inserted into the slot, the first opening, and the second opening; and a welded end portion connected to the straight portion and constituting the first coil end. a folded portion that is connected to the straight portion and that constitutes the second coil end.

2. A stator according to claim 1, wherein a sealing material is provided in the gap between the straight portion and the first opening, and a sealing material is provided in the gap between the straight portion and the second opening.

3. A stator according to claim 1, wherein the straight portion is provided with an insulating coating.

4. A stator according to claim 1, further comprising a second annular flow path case provided opposite the second end face of the stator core and defining a cooling flow path therein for accommodating the second coil end.

5. A stator according to claim 1, wherein a power bus bar is connected to the first coil end.

6. A stator manufacturing method comprising: a case arrangement step of placing an annular flow path case, inside which a cooling flow path is defined, opposite an end face of a cylindrical stator core; a coil insertion step of inserting a group of conductors consisting of a plurality of segment conductors into a plurality of slots formed in the stator core and a plurality of openings formed in the annular flow path case; and a coil welding step of bending and welding the ends of the plurality of segment conductors that protrude through the annular flow path case in the circumferential direction of the stator core.

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