Wound-field rotary electric machine

Abstract

This rotary electric machine comprises: a stator (50) having a stator winding (52); and a rotor (60) having a field winding (70). The rotor is disposed on the radially inner side of the stator so as to face the stator. The stator winding has a first stator coil end (SE1) on one axial end side thereof and a second stator coil end (SE2) on the other axial end side thereof. The inner diameter dimension on the radially inner side of the second stator coil end is smaller than the inner diameter dimension on the radially inner side of the first stator coil end. In the field winding, the outer diameter dimension on the radially outer side of the second rotor coil end is smaller than the outer diameter dimension on the radially outer side of the first rotor coil end. The stator winding and the field winding are arranged such that the first stator coil end and the first rotor coil end are arranged in the radial direction, and the second stator coil end and the second rotor coil end are also arranged in the radial direction.

Description

Wound-field type rotating electric machine CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-066971 filed on April 17, 2024, the contents of which are incorporated herein by reference.

[0002] The disclosure in this specification relates to a wound field type rotating electric machine.

[0003] A wound-field rotating electric machine has a stator with a stator winding and a rotor with a field winding. The rotor has a rotor core with multiple main poles (magnetic salient poles), and the field winding is wound around the main poles (see, for example, Patent Document 1). In an inner-rotor rotating electric machine, the rotor is disposed radially inward of the stator, facing it.

[0004] Japanese Patent Application Laid-Open No. 2013-9553

[0005] In a wound-field rotating electric machine, the coil ends of the stator winding and the coil ends of the field winding are arranged in radially aligned positions, which raises concerns that the coil ends of the stator winding and the field winding may interfere with each other.

[0006] Specifically, the stator winding is wound, for example, by distributed winding at a predetermined slot pitch in the circumferential direction. Furthermore, on the coil side of the stator winding (the portion of the stator slot where the conductors are housed), the conductors are arranged in multiple layers in the radial direction, while at the coil ends, the conductors are arranged more radially apart than on the coil side to prevent interference between the conductors. In this case, the coil ends of the stator winding are shifted radially inward relative to the coil side, raising concerns about interference with the coil ends of the field winding. The coil end portions are relatively prone to deformation, and technical improvements are desirable.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a wound-field rotating electric machine in which the stator and rotor can be disposed radially opposite each other in an appropriate state.

[0008] The present disclosure relates to a wound-field rotating electric machine comprising: a stator having a stator winding; and a rotor having a rotor core including a plurality of main pole portions provided for each circumferentially aligned magnetic pole, and a field winding wound around each of the main pole portions, the rotor being disposed radially inside the stator to face it, wherein the stator winding has a first stator coil end at one axial end and a second stator coil end at the other axial end, the radially inner inner diameter dimension of the second stator coil end being smaller than the radially inner inner diameter dimension of the first stator coil end; the field winding includes a plurality of pole coils provided for each magnetic pole, and has a first rotor coil end at one axial end and a second rotor coil end at the other axial end, the radially outer outer diameter dimension of the second rotor coil end being smaller than the radially outer outer diameter dimension of the first rotor coil end; The stator winding and the field winding are respectively arranged so that the first stator coil end and the first rotor coil end are aligned radially, and the second stator coil end and the second rotor coil end are aligned radially.

[0009] In an inner rotor type rotating electric machine, reducing the outer diameter of the stator winding coil ends is effective for reducing the size of the stator, and it is preferable to configure at least one stator coil end to be offset radially inward. However, considering that the rotor is assembled to the radial inside of the stator, it is undesirable for the inner diameter of the coil end on one axial side of the stator winding to be excessively small. In this regard, by making the inner diameters of the stator coil ends on both axial sides of the stator winding different, it is possible to achieve a compact stator while improving the ease of assembly of the stator and rotor.

[0010] On the other hand, it is desirable to wind the conductor wire in multiple radial and circumferential directions around the main pole of the rotor field winding to increase the number of turns of the pole coil of each magnetic pole. Furthermore, by reducing the outer diameter of one of the rotor coil ends on both axial sides of the field winding, a suitable configuration can be realized on the rotor side that takes into account ease of assembly to the stator. In this case, by arranging the stator winding and field winding so that the first stator coil end with a relatively large inner diameter and the first rotor coil end with a relatively large outer diameter are aligned radially, and the second stator coil end with a relatively small inner diameter and the second rotor coil end with a relatively small outer diameter are aligned radially, the stator and rotor can be easily assembled. As a result, the stator and rotor can be positioned radially opposite each other in an appropriate manner.

[0011] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of a control system for a rotating electric machine, Fig. 2 is a diagram showing an inverter and its peripheral configuration, Fig. 3 is a cross-sectional view of a rotor and a stator, Fig. 4 is a diagram showing an electric circuit provided in the rotor, Fig. 5 is a perspective view showing the overall configuration of the rotor, Fig. 6 is a perspective view showing the rotor with an outer peripheral coating portion and a coil end cover removed, Fig. 7 is an exploded perspective view of the rotor, Fig. 8 is a longitudinal cross-sectional view of the rotor, Fig. 9 is a perspective view showing an exploded winding unit in the rotor main portion, and Fig. 10 is a cross-sectional view showing a partial cross-sectional structure of the rotor main portion. 12 is a longitudinal cross-sectional view of the outer peripheral covering portion, FIG. 13 is a perspective view showing the rotor assembled to the stator, FIG. 14 is a longitudinal cross-sectional view showing the rotor assembled to the stator, FIG. 15 is a cross-sectional view showing the longitudinal cross-sectional configuration of the stator, FIG. 16 is a cross-sectional view showing the longitudinal cross-sectional configuration of the rotor, FIG. 17 is a side view of the winding unit, FIG. 18 is a diagram showing the winding structure of the winding unit, and FIG. 19 is a longitudinal cross-sectional view showing an enlarged portion where the second stator coil end and the second rotor coil end are aligned side by side.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wound-field rotating electric machine according to an embodiment of the present disclosure is used as a power source for driving electric vehicles such as electric vehicles and hybrid vehicles.

[0013] First, a control system including a rotating electric machine will be described with reference to Fig. 1. The control system includes a DC power supply 10, an inverter 20, a control device 30, and a rotating electric machine 40. The rotating electric machine 40 is a self-excited wound field type synchronous machine. For example, the rotating electric machine 40, the inverter 20, and the control device 30 may be configured as an electromechanical integrated drive device, or the rotating electric machine 40, the inverter 20, and the control device 30 may each be configured as a separate component.

[0014] The rotating electric machine 40 includes a housing 41, and a stator 50 and a rotor 60 housed in the housing 41. The rotating electric machine 40 of this embodiment is an inner rotor type rotating electric machine in which the rotor 60 is disposed radially inside the stator 50.

[0015] The stator 50 includes a stator core 51 and a stator winding 52. The stator winding 52 is made of, for example, copper wire, and includes U-, V-, and W-phase windings 52U, 52V, and 52W that are arranged with an electrical angle offset of 120° from one another.

[0016] The rotor 60 includes a rotor core 61 and a field winding 70. The field winding 70 is preferably made of a conductor material such as aluminum wire, which has a low specific gravity and is easily formed. The conductor material of the field winding 70 is not limited to aluminum wire, and may be copper wire or CNT (carbon nanotube), for example. A rotating shaft 32 is attached to the center hole of the rotor core 61. The rotating shaft 32 is rotatably supported by bearings 42 and 43 in the housing 41.

[0017] As shown in FIG. 2 , the inverter 20 includes a series connection of upper-arm switches SUp, SVp, and SWp for U, V, and W phases and lower-arm switches SUn, SVn, and SWn for U, V, and W phases. First ends of U-, V-, and W-phase windings 52U, 52V, and 52W are connected to the connection points between the upper-arm switches SUp, SVp, and SWp and the lower-arm switches SUn, SVn, and SWn for each phase. Second ends of the U-, V-, and W-phase windings 52U, 52V, and 52W are connected at the neutral point. That is, in this embodiment, the stator winding 52 is star-connected. However, the stator winding 52 may also be delta-connected. In this embodiment, each of the switches SUp to SWn is, for example, an IGBT. A freewheel diode is connected in antiparallel to each of the switches SUp to SWn.

[0018] The collectors of the upper arm switches SUp, SVp, SWp of each phase are connected to the positive terminal of a DC power supply 10. The emitters of the lower arm switches SUn, SVn, SWn of each phase are connected to the negative terminal of the DC power supply 10. A smoothing capacitor 11 is connected in parallel to the DC power supply 10.

[0019] Next, the stator 50 and the rotor 60 will be described with reference to FIG.

[0020] The stator 50 and the rotor 60 are both arranged coaxially with the rotating shaft 32. In the following description, the direction in which the rotating shaft 32 extends is referred to as the axial direction, the direction extending radially from the center of the rotating shaft 32 is referred to as the radial direction, and the direction extending circumferentially around the rotating shaft 32 is referred to as the circumferential direction.

[0021] The stator core 51 is made of laminated steel plates made of a soft magnetic material and has an annular back yoke 51a and multiple teeth 51b protruding radially inward from the back yoke 51a. Multiple slots 54 are formed between adjacent teeth 51b in the circumferential direction. The stator winding 52 is formed by accommodating the phase windings of each phase in a predetermined order in each of these slots 54. For example, the stator 50 may employ a segment coil structure using multiple conductor segments. However, the structure of the stator winding 52 is arbitrary.

[0022] The rotor core 61 is made of a soft magnetic material, for example, laminated steel plates. The rotor core 61 has a cylindrical portion 61a and a plurality of main pole portions 62 extending radially outward from the cylindrical portion 61a. A field winding 70 is wound around the main pole portions 62 by concentrated winding. In this embodiment, eight main pole portions 62 are provided at equal intervals in the circumferential direction.

[0023] The field winding 70 includes a first winding portion 71 and a second winding portion 72. The first winding portion 71 is wound radially outward around each main pole portion 62, and the second winding portion 72 is wound radially inward relative to the first winding portion 71. In each main pole portion 62, the winding directions of the conductor wire in the first winding portion 71 and the second winding portion 72 are the same. Furthermore, among circumferentially adjacent main pole portions 62, the winding direction of each winding portion 71, 72 wound around one is opposite to the winding direction of each winding portion 71, 72 wound around the other. Therefore, the magnetization directions of circumferentially adjacent main pole portions 62 are opposite to each other. In the rotor 60, each main pole portion 62 in the rotor core 61 and the field winding 70 wound around each main pole portion 62 form a plurality of magnetic poles (field poles) arranged circumferentially.

[0024] 4 is a diagram showing an electric circuit including the first and second winding portions 71, 72 in the rotor 60. The first winding portion 71 and the second winding portion 72 are connected in series by connecting the second end 71b of the first winding portion 71 to the first end 72a of the second winding portion 72. A diode 91 and a capacitor 92 are connected to the second end 71b of the first winding portion 71 in parallel with the second winding portion 72. A diode 93 and a capacitor 94 are connected in series to the series connection of the first winding portion 71 and the second winding portion 72. The capacitors 92, 94 are, for example, ceramic capacitors or film capacitors.

[0025] The diode 91 has a cathode connected to the first end 72a of the second winding portion 72 and an anode connected to the second end 72b of the second winding portion 72. As a result, in a closed circuit including the second winding portion 72 and the diode 91, current flows in one direction, from the anode side to the cathode side of the diode 91. Furthermore, the diode 93 has a cathode connected to the first end 71a of the first winding portion 71 and an anode connected to the second end 72b of the second winding portion 72. As a result, the field current flowing through each winding portion 71, 72 is rectified. In this embodiment, the number of windings of the second winding portion 72 is greater than the number of windings of the first winding portion 71.

[0026] Returning to the description of FIG. 2 , the control device 30 is an electronic control unit (EC) primarily composed of a microcomputer 31. The microcomputer 31 includes a central processing unit (CPU). The functions provided by the microcomputer 31 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, if the microcomputer 31 is provided by a hardware electronic circuit, the functions can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer 31 executes a program stored in a non-transitory tangible storage medium (NSS) that serves as its own storage unit. The program includes a program for controlling the rotating electric machine 40. A method corresponding to the program is executed by executing a set of instructions that constitute the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated via a communication network such as the Internet, for example, via OTA (Over the Air).

[0027] The control device 30 generates drive signals that turn on and off the switches SUp to SWn that configure the inverter 20. Specifically, the control device 30 generates drive signals that turn on and off the switches SUp to SWn and outputs the generated drive signals to the gates of the switches SUp to SWn in order to convert the DC power output from the DC power supply 10 into AC power and supply it to the U-, V-, and W-phase windings 52U, 52V, and 52W. As a result, the upper and lower arm switches in each phase are alternately turned on with dead times therebetween.

[0028] The control device 30 turns on and off the switches SUp to SWn so that a composite current of a fundamental current and a high-frequency current (specifically, a high-frequency excitation current) having a frequency higher than that of the fundamental current flows through each of the phase windings 52U, 52V, and 52W. The fundamental current is a current that mainly serves to generate torque in the rotary electric machine 40. The high-frequency current is a current that mainly serves to excite the first and second winding portions 71 and 72 that constitute the field winding 70, thereby inducing a field current in the field winding 70. The phase currents flowing through the phase windings 52U, 52V, and 52W are shifted by 120 electrical degrees.

[0029] The high-frequency current flowing through the stator winding 52 may be a harmonic current whose fluctuating frequency is N times (N is an integer of 2 or more) the frequency of the fundamental current, or may be a current whose fluctuating frequency is different from N times the frequency of the fundamental current.

[0030] When a high-frequency current flows through the stator winding 52, a voltage is induced in the first and second winding portions 71 and 72, causing a field current to flow. The induced voltages in the first and second winding portions 71 and 72 are, for example, in phase. The currents IL1 and IL2 flowing through the first and second winding portions 71 and 72 contain frequency components of the high-frequency current.

[0031] In the electric circuit shown in Figure 4, when the first and second winding portions 71, 72 are excited by energizing the stator winding 52, a current flows from the first winding portion 71 to the second winding portion 72. Furthermore, when the voltage across the second winding portion 72 exceeds the forward voltage of the diode 91, a current IL2, which is greater than the current IL1 flowing through the first winding portion 71, flows through the closed circuit including the second winding portion 72 and the diode 91. The current flowing through the closed circuit including the second winding portion 72 and the diode 91 increases the DC component of the field current. This increases the DC component of the magnetic flux of the rotor 60, thereby increasing the torque of the rotating electric machine 40.

[0032] Next, the configuration of the rotor 60 will be described in more detail. Fig. 5 is a perspective view showing the overall configuration of the rotor 60, and Fig. 6 is a perspective view showing the rotor 60 with the outer peripheral covering portion 102 that covers the rotor main portion 101 and the coil end covers 103, 104 removed. Fig. 7 is an exploded perspective view of the rotor 60, and Fig. 8 is a vertical cross-sectional view of the rotor 60.

[0033] The rotor 60 is broadly divided into a rotor main section 101, a cylindrical outer covering section 102 provided to surround the outer periphery of the rotor main section 101, coil end covers 103 and 104 attached to one and the other axial ends of the rotor main section 101, and a busbar module 105 and a circuit module 106 provided at one of both axial ends of the rotor main section 101. The rotor main section 101 includes a rotor core 61 and a field winding 70, and the rotating shaft 32 is assembled to the center hole of the rotor core 61. The field winding 70 is made up of a plurality of winding units 110 arranged circumferentially. The coil end covers 103 and 104 are provided to cover the coil ends of the field winding 70 on both axial sides.

[0034] The busbar module 105 and the circuit module 106 are fixed to the rotating shaft 32 with the rotating shaft 32 inserted through each hollow portion, so that the busbar module 105 and the circuit module 106 are provided at positions axially facing the coil end portions of the field winding 70. The busbar module 105 has a plurality of bus bars for electrically connecting the winding units 110 for each magnetic pole.

[0035] The circuit module 106 includes a component holder 107 that houses electrical components, and a heat sink 108 that is placed over the component holder 107. The component holder 107 and the heat sink 108 are integrated with their axial end faces joined together. The component holder 107 holds diodes 91 and 93 and capacitors 92 and 94 as electrical components.

[0036] The heat sink 108 is fixed to one of the axial ends of the component holder 107, opposite the rotor core 61 (the right side in the figure). The heat sink 108 is made of, for example, aluminum. By fixing the heat sink 108 to the axial end face of the component holder 107, heat generated in the diodes 91 and 93 and the capacitors 92 and 94 when current is applied to the component holder 107 is released via the heat sink 108.

[0037] The outer covering portion 102 is formed by using a metal wire 131 and winding the wire 131 in multiple layers around the outer periphery of the plurality of winding units 110 assembled to the rotor core 61 .

[0038] Fig. 9 is an exploded perspective view of the winding unit 110 in the rotor main section 101, and Fig. 10 is a cross-sectional view showing the cross-sectional structure of a portion of the rotor main section 101. Note that Fig. 10 depicts the outer circumferential covering section 102 shown in Fig. 5 and other figures as a structure for holding the field winding 70 wound around the main pole section 62 of the rotor core 61.

[0039] The rotor main section 101 has a plurality of winding units 110, one for each magnetic pole of the rotor 60. Each winding unit 110 is formed in an annular shape with the axial direction as the longitudinal direction, and is assembled to the rotor core 61 with the main pole section 62 of the rotor core 61 inserted into its hollow section. In this embodiment, the winding units 110 form a "pole coil."

[0040] The winding unit 110 has a first coil module 111 that is located on the radially outer side when attached to the main pole portion 62, and a second coil module 112 that is located on the radially inner side. The first coil module 111 is a coil module that corresponds to the first winding portion 71, and the second coil module 112 is a coil module that corresponds to the second winding portion 72.

[0041] The first coil module 111 has an annular coil body 121 formed by multiple windings of a conductor material made of a rectangular wire in the circumferential and radial directions, and a thin plate-like insulator 122 provided integrally with the coil body 121. The insulator 122 has a portion that extends circumferentially and covers the outer peripheral portions on the radially outer and inner sides of the coil body 121, and a portion that extends radially and covers the hollow portion of the coil body 121. In other words, the outer peripheral portion on the radially outer side and the inner peripheral portion and hollow portion of the coil body 121 are insulated and coated with the insulator 122.

[0042] The second coil module 112 has an annular coil body 123 formed by multiple windings of a conductor material made of a rectangular wire in the circumferential and radial directions, and a thin plate-like insulator 124 provided integrally with the coil body 123. The insulator 124 has a portion that extends circumferentially and covers the outer peripheral portions on the radially outer and inner sides of the coil body 123, and a portion that extends radially and covers the hollow portion of the coil body 123. In other words, the outer peripheral portion on the radially outer side, the inner peripheral portion on the radially inner side, and the hollow portion of the coil body 123 are insulated and coated with the insulator 124.

[0043] The coil body 121 of the first coil module 111 is, for example, an α-winding coil in which a conductive wire is wound in an α-winding manner. The coil body 123 of the second coil module 112 is a continuously wound coil in which a conductive wire is continuously wound in a predetermined circumferential direction. Two conductive wire ends 125 extend axially in the first coil module 111, and two conductive wire ends 126 extend axially in the second coil module 112. In each of the winding units 110 arranged circumferentially, the conductive wire ends 125, 126 are connected to each other, thereby connecting the multiple first coil modules 111 provided on each main pole portion 62 in series, and connecting the multiple second coil modules 112 provided on each main pole portion 62 in series.

[0044] The conductor wire used for the coil bodies 121, 123 is, for example, a flat wire having a substantially rectangular cross section (specifically, a substantially rectangular shape). The flat wire consists of a conductor portion made of aluminum or the like and an insulating layer covering the conductor portion. However, a round wire having a circular cross section can also be used as the conductor wire. The coil structure of each coil module 111, 112 is optional; for example, the coil bodies 121, 123 can both be continuous wound coils.

[0045] 10 , the first coil module 111 has two radially wound layers of conductor wire, while the second coil module 112 has twelve radially wound layers. Each of the coil modules 111, 112 may have any number of layers, but it is preferable that the number of layers in the second coil module 112 is greater than that of the first coil module 111. The coil modules 111, 112 have different numbers of circumferential windings (i.e., the number of rows of conductor wire in the circumferential direction), with the number of windings being greater on the radially outer side than on the radially inner side. This improves the space factor of the field winding 70.

[0046] Next, the outer peripheral covering portion 102 and coil end covers 103, 104 that are provided in the rotor 60 to surround the rotor core 61 and the field winding 70 will be described. The configurations of the coil end covers 103, 104 are shown in Figures 5 and 11. Figure 5 is a perspective view of the rotor 60, with the coil end cover 103 on the circuit module 106 side, of the coil end covers 103, 104 on both axial sides, facing forward, and Figure 11 is a perspective view of the rotor 60, with the coil end cover 104 on the opposite side of the circuit module 106, of the coil end covers 103, 104 on both axial sides facing forward.

[0047] The rotor 60 is provided with coil end covers 103, 104 on both axial sides of an outer circumferential covering portion 102. The axial range in which the outer circumferential covering portion 102 is provided is a range that radially overlaps with the rotor core 61, and this range X is shown in Figure 8. In range X, the main pole portions 62 and winding units 110 are lined up in the circumferential direction, and the outer circumferential covering portion 102 is formed by spirally and multiple-wound wire 131 radially outward of each main pole portion 62 and winding unit 110. Range X is a range that corresponds to the rotor coil side of the field winding 70, which is between the rotor coil ends on both axial sides.

[0048] The outer covering portion 102 may be configured as shown in FIG. 12 . FIG. 12 is a longitudinal cross-sectional view of the outer covering portion 102, with the left-right direction being the axial direction and the up-down direction being the radial direction. In FIG. 12 , the wires 131 are wound in multiple layers (four layers in the figure) radially while contacting each other axially. The wires 131 may be steel flat wires having a rectangular cross section. The wires 131 may also be magnetic materials, specifically, SUS430, SUS631, piano wire, or the like. By using flat wire as the wires 131, gaps between the wires 131 in the outer covering portion 102 are less likely to form. This prevents the wires 131 from collapsing or deforming in the outer covering portion 102. Furthermore, the space factor of the outer covering portion 102 is increased, thereby enhancing the strength of the outer covering portion 102.

[0049] Furthermore, in the outer circumferential covering portion 102, the wire rods 131 are wound in a linearly aligned state in both the axial and radial directions. In this case, because the wire rods 131 are wound in an axially aligned state, the outer circumferential surface (the radially outer circumferential surface) of the outer circumferential covering portion 102 is flat. Therefore, the mechanical space between the rotor 60 and the stator 50 (the gap between the outer circumferential surface of the outer circumferential covering portion 102 and the stator 50) can be made constant in the axial direction. Furthermore, because the wire rods 131 are wound in a radially aligned state, the outer circumferential covering portion 102 is divided at predetermined intervals in the axial direction. Therefore, eddy currents are reduced in the outer circumferential covering portion 102.

[0050] The outer covering portion 102 and the coil end covers 103, 104 are provided radially outside the main pole portion 62 and the field winding 70, and are continuous in the axial direction with their axial end faces facing each other.

[0051] 5 , the coil end cover 103 has an end plate portion 141 that is fixed to the rotating shaft 32, and an annular portion 142 that extends axially from the outer periphery of the end plate portion 141 and surrounds the coil ends (rotor coil ends) of the field winding 70 from the radially outer side. In the coil end cover 103, the end plate portion 141 is a portion that faces the rotor coil ends and the circuit module 106 in the axial direction, and the annular portion 142 is a portion that surrounds the rotor coil ends from the radially outer side. The end plate portion 141 is provided with a central hole provided in the radial center, with the rotating shaft 32 inserted through it. The annular portion 142 is assembled to the axial end of the winding unit 110 (more specifically, the axial end of the insulator 122 of the first coil module 111).

[0052] 11 , the coil end cover 104 has an end plate portion 151 that is fixed to the rotating shaft 32, and an annular portion 152 that extends axially from the outer periphery of the end plate portion 151 and surrounds the coil ends (rotor coil ends) of the field winding 70 from the radially outer side. In the coil end cover 104, the end plate portion 151 is a portion that faces the rotor coil ends in the axial direction, and the annular portion 152 is a portion that surrounds the rotor coil ends from the radially outer side. The end plate portion 151 is provided with a central hole provided in the radial center, with the rotating shaft 32 inserted through it. The annular portion 152 is assembled to the axial end of the winding unit 110 (more specifically, the axial end of the insulator 122 of the first coil module 111).

[0053] In the coil end cover 104, the outer side of the annular portion 152 is an inclined surface that is inclined with respect to the axial direction and approaches the rotor axis on the side of the end plate portion 141, and the ends of the wire 131 that form the start and end of the winding of the outer covering portion 102 are pulled out in the axial direction along this inclined surface.

[0054] In the rotating electric machine 40, the coil ends of the stator winding 52 and the coil ends of the field winding 70 are arranged side by side in radially adjacent positions at both axial ends. In this case, there is a concern that the coil ends of the stator winding 52 may interfere with members on the rotor coil end side. In particular, if the coil ends on both axial ends of the stator winding 52 have different shapes, and if the coil ends on both axial ends of the field winding 70 have different shapes, there is a concern that the coil ends of the stator winding 52 may interfere with the rotor coil end side.

[0055] Fig. 13 is a perspective view showing the rotor 60 assembled to the stator 50, and Fig. 14 is a longitudinal cross-sectional view showing the rotor 60 assembled to the stator 50. Fig. 15 is a cross-sectional view showing the longitudinal cross-sectional configuration of the stator 50, and Fig. 16 is a cross-sectional view showing the longitudinal cross-sectional configuration of the rotor 60.

[0056] The stator 50 and the rotor 60 are disposed radially opposite each other with a predetermined gap (air gap) between them. The rotor 60 rotates in conjunction with the rotation of the rotary shaft 32, radially inside the annular stator 50.

[0057] 15 , the portions of the stator winding 52 that are axially outward of the stator core 51 are stator coil ends SE1 and SE2. In the following description, of the stator coil ends on both axial sides, the stator coil end on one axial end side (lower side in the figure) is referred to as the "first stator coil end SE1," and the stator coil end on the other axial end side (upper side in the figure) is referred to as the "second stator coil end SE2." In addition, the space between the stator coil ends SE1 and SE2 in the axial direction is referred to as the stator coil side SS.

[0058] 16, the portions of the field winding 70 that are axially outward of the rotor core 61 are rotor coil ends RE1 and RE2. In the following description, of the rotor coil ends on both axial sides, the rotor coil end on one axial end side (lower side in the figure) will be referred to as the "first rotor coil end RE1," and the rotor coil end on the other axial end side (upper side in the figure) will be referred to as the "second rotor coil end RE2." Furthermore, the space between the rotor coil ends RE1 and RE2 in the axial direction will be referred to as the rotor coil side RS.

[0059] 14, rotor coil ends RE1, RE2 are arranged radially inward of stator coil ends SE1, SE2. In the stator 50 and the rotor 60, the axial lengths of the stator core 51 and the rotor core 61 are the same, and the coil side portions of the stator winding 52 and the field winding 70 that overlap with each core 51, 61 in the radial direction are the same in the axial direction.

[0060] 13 , the stator winding 52 is configured by using a plurality of conductor segments 160 as conductor wires, and by connecting the segment ends 161, which are the ends of the conductor segments 160, together by welding or the like. In the stator winding 52, a first stator coil end SE1 is configured by connecting the segment ends 161 on one axial side (the lower side of the figure), and a second stator coil end SE2 is configured by bending the conductor segments 160 on one axial side (the upper side of the figure).

[0061] At the first stator coil end SE1, the connection portions between the segment ends 161 are arranged at predetermined intervals in the circumferential direction. The stator 50 is configured such that a plurality of conductor segments 160 are housed radially in the slots 54 (see FIG. 3 ) of the stator core 51, and the plurality of segment connection portions are arranged radially.

[0062] The stator winding 52 is wound in a distributed manner at a predetermined slot pitch in the circumferential direction. In this case, the conductor wire is arranged in multiple layers in the radial direction in the stator coil side SS (the portion of the slot where the conductor is housed), and in each stator coil end SE1, SE2, the conductor segments 150 are arranged more widely in the radial direction than in the stator coil side SS to prevent interference between the conductor segments 160. In FIG. 15 , the radial width dimension (left-right direction in the figure) of each stator coil end SE1, SE2 is larger than that of the stator coil side SS. Furthermore, a portion of the second stator coil end SE2 protrudes radially inward beyond the stator coil side SS.

[0063] 15 , in the stator winding 52, the radially inner inner diameter dimension of the first stator coil end SE1 is D11, and the radially inner inner diameter dimension of the second stator coil end SE2 is D12. In this case, the inner diameter dimension D12 of the second stator coil end SE2 is smaller than the inner diameter dimension D11 of the first stator coil end SE1 (D12<D11). More specifically, the first stator coil end SE1 is formed of multi-layered conductor segments 160 in the radial direction as described above, and the second stator coil end SE2 is offset radially inward compared to the first stator coil end SE1. Therefore, the radially inner inner diameter dimensions D11, D12 differ between the first stator coil end SE1 side and the second stator coil end SE2 side. Comparing the outer diameters of the stator coil ends SE1 and SE2, the outer diameter of the first stator coil end SE1 is larger than the outer diameter of the second stator coil end SE2.

[0064] In comparison with the stator core 51, the inner diameter dimension D11 of the first stator coil end SE1 is larger than the inner diameter dimension D13 of the inner peripheral surface of the stator core 51. Furthermore, the inner diameter dimension D12 of the second stator coil end SE2 is the same as or approximately the same as the inner diameter dimension D13 of the inner peripheral surface of the stator core 51.

[0065] As described above, by offsetting the stator coil end (SE2) on one axial side radially inward, the outer diameter dimension of the coil end of the stator winding 52 can be reduced, enabling the size of the stator 50. Furthermore, in the stator winding 52, the inner diameter dimensions of the stator coil ends on both axial sides are made different, and the inner diameter dimension of the stator coil end (SE1) on the other side is not made excessively small, which improves the ease of assembling the rotor 60 to the radially inner side of the stator 50.

[0066] 16 , the rotor 60 has different outer peripheral surface shapes in the axial direction on the first rotor coil end RE1 side and the second rotor coil end RE2 side, with the radial dimension to the outer peripheral surface on the second rotor coil end RE2 side being narrower than on the first rotor coil end RE1 side. Here, the outer peripheral surface shape of the rotor 60 is determined by the shapes of the coil end cover 103 on the first rotor coil end RE1 side and the coil end cover 104 on the second rotor coil end RE2 side, and the shapes of these coil end covers 103, 104 (more specifically, the shapes of the annular portions 142, 152) correspond to the coil end shapes of the winding unit 110.

[0067] 17 is a side view of the winding unit 110. As described above, the winding unit 110 has a first coil module 111 on the radially outer side and a second coil module 112 on the radially inner side, and when the winding unit 110 is assembled to the rotor core 61, the first coil module 111 determines the outer peripheral shape of the field winding 70. In this case, the outer peripheral surface on the radially outer side of the first coil module 111, i.e., the insulator 122 on the outer peripheral side of the first coil module 111, has different shapes in side view at one axial end and the other axial end, and on the side of the first rotor coil end RE1, which is the lower side of the figure, the outer peripheral surface of the first coil module 111 is oriented to extend in the axial direction (oriented parallel to the axial direction), and on the side of the second rotor coil end RE2, which is the upper side of the figure, the outer peripheral surface of the first coil module 111 is oriented to be inclined with respect to the axial direction. At the second rotor coil end RE2, the outer periphery of the winding unit 110 is inclined relative to the axial direction, and the outer diameter dimension decreases as it moves away from the rotor core 61 in the axial direction.

[0068] 17 , in the winding unit 110, the radially outer diameter dimension of the first rotor coil end RE1 is D21, and the radially outer diameter dimension of the second rotor coil end RE2 is D22. The outer diameter dimension D22 is the average value of the axial outer diameter dimension of the second rotor coil end RE2. In other words, the outer diameter dimension D22 can also be considered the median between the maximum and minimum outer diameter dimensions of the second rotor coil end RE2. In this case, the outer diameter dimension D22 of the second rotor coil end RE2 is smaller than the outer diameter dimension D21 of the first rotor coil end RE1 (D22<D21). In the field winding 70, the coil end shapes on both axial sides of each circumferentially arranged winding unit 110 are different, so the outer diameter dimensions D21, D22 of the rotor coil ends RE1, RE2 are different from each other.

[0069] A specific winding structure of the winding unit 110 will be described below. Figures 18(a) and 18(b) are diagrams showing an example of a winding structure. These figures show the configuration of the coil body 123 of the second coil module 112. The coil body 123 is formed by concentrated winding of conductor wire, and lane changes occur as the conductor wire is wound in multiple layers (i.e., as the conductor wire is stacked). Figure 18 shows a lane change section L at one axial end of the coil body 123. A lane change refers to a shift in the winding position in a direction intersecting the winding direction of the conductor wire when stacking the conductor wire in multiple layers. In the second coil module 112, the outer peripheral surface shape of the insulator 124 depends on the shape of the coil body 123.

[0070] 18 shows the configuration of the coil body 123 of the second coil module 112 for convenience, but the coil body 121 of the first coil module 111 has a similar configuration except for the number of turns of the conductor wire. In other words, the coil body 121 of the first coil module 111 has a lane change portion L on one of both axial ends. Of the two axial ends of the winding unit 110, the axial end having the lane change portion L is the first rotor coil end RE1.

[0071] In the winding unit 110 of each magnetic pole, at the lane change portion L where the conductor changes lanes, the conductor bulges to avoid the conductor in the lower layer. In consideration of this, the axial end portion of the winding unit 110 that has the lane change portion L is designated as the first rotor coil end RE1, i.e., the rotor coil end on the side with a relatively larger outer diameter.

[0072] In the winding units 110, ends of the conductor wires are pulled out on one axial side, and these ends of the conductor wires connect the winding units 110 (the coil modules 111, 112). In the winding units 110 of each magnetic pole, the first coil modules 111 arranged in the circumferential direction are connected in series, and the second coil modules 112 arranged in the circumferential direction are connected in series. In this case, the first coil module 111, which forms the end of the first winding section 71, and the second coil module 112, which forms the end of the second winding section 72, have their ends of the conductor wires connected to electrical components mounted on the circuit module 106. In this configuration, a space is required at one axial end of the winding unit 110 for pulling out the conductor wires. Therefore, it is preferable that the axial end of the winding unit 110 from which the ends of the conductor wires are pulled out be the first rotor coil end RE1, i.e., the rotor coil end with a relatively larger outer diameter. Furthermore, even if the winding structure of the first coil module 111 is an α-winding structure, it is preferable that the wire pull-out side of the first coil module 111 be the first rotor coil end RE1, i.e., the rotor coil end with a relatively larger outer diameter.

[0073] 14 , the stator winding 52 and the field winding 70 are arranged such that the first stator coil end SE1 and the first rotor coil end RE1 are aligned radially, and the second stator coil end SE2 and the second rotor coil end RE2 are aligned radially. In this case, the stator winding 52 and the field winding 70 are arranged such that the first stator coil end SE1, which has a relatively large inner diameter, and the first rotor coil end RE1, which has a relatively large outer diameter, are aligned radially, and the second stator coil end SE2, which has a relatively small inner diameter, and the second rotor coil end RE2, which has a relatively small outer diameter, are aligned radially. This suppresses interference between the stator winding 52 and components on the rotor 60 side (particularly the coil end covers 103, 104).

[0074] Furthermore, when manufacturing the rotating electric machine 40, the rotor 60 is assembled axially into the hollow portion of the stator 50. At this time, the rotor 60 is assembled into the stator 50 from the first stator coil end SE1 side (the lower side in FIG. 14 ). Furthermore, the second rotor coil end RE2 of the rotor 60 is the leading side when assembled into the stator 50. This prevents interference between the stator 50 and the rotor 60, and allows the rotor 60 to be easily assembled into the stator 50.

[0075] FIG. 19 is an enlarged longitudinal cross-sectional view showing a portion where the second stator coil end SE2 and the second rotor coil end RE2 are aligned side by side.

[0076] 19 , in the second rotor coil end RE2, the outer peripheral surface on the radially outer side is inclined with respect to the axial direction (see Q1 in the figure), and the outer diameter dimension becomes smaller the further away in the axial direction it is from the rotor core 61. In addition, the annular portion 152 of the coil end cover 104 has the outer peripheral surface on the radially outer side inclined with respect to the axial direction (see Q2 in the figure), and the outer diameter dimension becomes smaller the further away in the axial direction it is from the rotor core 61.

[0077] The second stator coil end SE2 and the annular portion 152 of the coil end cover 104 face each other in the radial direction. The gap dimension between the second stator coil end SE2 and the annular portion 152 increases as the distance from the rotor core 61 increases in the axial direction.

[0078] Furthermore, the radial gap dimension G1 between the second stator coil end SE2 and the annular portion 152 of the coil end cover 104 is larger than the radial gap dimension G2 between the stator 50 and the outer circumferential covering portion 102 on the stator coil side SS (axially between the first stator coil end SE1 and the second stator coil end SE2). The gap dimension G1 between the second stator coil end SE2 and the annular portion 152 is preferably the average value of the separation distance between the second stator coil end SE2 and the annular portion 152 as viewed in the axial direction.

[0079] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0080] In the rotating electric machine 40, the stator winding 52 and the field winding 70 are arranged so that the first stator coil end SE1, which has a relatively large inner diameter, and the first rotor coil end RE1, which has a relatively large outer diameter, are aligned radially, and the second stator coil end SE2, which has a relatively small inner diameter, and the second rotor coil end RE2, which has a relatively small outer diameter, are aligned radially. This improves the ease of assembly of the stator 50 and the rotor 60. As a result, the stator 50 and the rotor 60 can be positioned radially opposite each other in an appropriate state.

[0081] In the winding unit 110 of each magnetic pole, at the lane change portion L where the conductor changes lanes, the conductor bulges to avoid the conductor in the lower layer. In consideration of this, the axial end of the winding unit 110 that has the lane change portion L is designated as the first rotor coil end RE1 (i.e., the rotor coil end that has a relatively large outer diameter and is aligned radially with the first stator coil end SE1 that has a relatively large inner diameter). This allows the conductor to be properly wound in the winding unit 110 while suitably suppressing interference between the stator 50 and the rotor 60.

[0082] In a configuration in which the winding unit 110 (coil modules 111, 112) and the circuit module 106 are connected, the ends of the conductor wires (conductor ends) are pulled out in the axial direction from the winding unit 110. In this case, of the two axial ends of the winding unit 110, the axial end closest to the conductor end is the first rotor coil end RE1 (i.e., the rotor coil end that has a relatively large outer diameter and is aligned radially with the first stator coil end SE1, which has a relatively large inner diameter). This allows the circuit module 106 to be properly positioned in the rotor 60, while suitably suppressing interference between the stator 50 and the rotor 60.

[0083] In the stator winding 52, a portion of the second stator coil end SE2, which has a smaller inner diameter, protrudes radially inward beyond the stator coil side SS, while in the field winding 70, in the second rotor coil end RE2, the outer diameter of each winding unit 110 decreases the further it is axially away from the rotor core 61. In this case, interference between the second stator coil end SE2 and the second rotor coil end RE2 can be avoided without reducing the conductor space factor in the field winding 70.

[0084] In the coil end cover 104, the outer peripheral surface of the annular portion 152 is inclined relative to the axial direction, and the outer diameter dimension becomes smaller the further away from the rotor core 61 in the axial direction. In other words, in the coil end cover 104, the outer peripheral surface of the annular portion 152 that faces the second stator coil end SE2 of the stator winding 52 in the radial direction is inclined in the same direction as the second rotor coil end RE2. This allows an appropriate gap to be formed between the stator winding 52 and the coil end cover 104 on the rotor 60 side.

[0085] The second stator coil end SE2 and the annular portion 152 of the coil end cover 104 are radially opposed to each other, and the gap dimension between the second stator coil end SE2 and the annular portion 152 increases axially as the distance from the rotor core 61 increases. In this case, there is a greater concern about displacement or deformation of the field winding 70 at the axial tip end side of the second stator coil end SE2 than at the base end side (rotor core side); however, the above configuration makes it possible to suitably suppress interference between the second stator coil end SE2 and the coil end cover 104.

[0086] The radial gap dimension G1 (average separation distance) between the second stator coil end SE2 and the annular portion 152 of the coil end cover 104 is made larger than the radial gap dimension G2 between the stator core 51 and the outer circumferential covering portion 102. In this case, in the stator winding 52, the second stator coil end SE2, which is radially outer than the stator core 51, is more likely to be displaced or deformed than the stator core side; however, the above configuration makes it possible to suitably suppress interference between the second stator coil end SE2 and the coil end cover 104.

[0087] (Other Embodiments) The above embodiment may be modified as follows, for example.

[0088] In the above embodiment, the winding unit 110 of the field winding 70 is configured by two coil modules 111, 112, one radially inner and one radially outer. However, this configuration may be changed. The field winding 70 may be configured by a single coil module instead of being divided into two radially inner and outer coil modules 111, 112.

[0089] In the above embodiment, the pole coils of the magnetic poles are configured by the winding units 110, but this may be changed. For example, the pole coils of the magnetic poles may be configured by continuously winding a conductive wire around each of the magnetic poles arranged in the circumferential direction.

[0090] In the stator 50, the stator core may not be provided with teeth.

[0091] The rotating electric machine is not limited to a rotating electric machine used as an in-vehicle main engine, but may be, for example, a rotating electric machine used as an ISG (Integrated Starter Generator) that is both a motor and a generator.

[0092] The moving body on which the rotating electric machine system is mounted is not limited to a vehicle, but may be, for example, an aircraft or a ship. Furthermore, the rotating electric machine system is not limited to a system mounted on a moving body, but may be a stationary system.

[0093] The technical concepts extracted from the above-described embodiments are described below. [Configuration 1] A wound-field rotating electric machine (40) comprising: a stator (50) having a stator winding (52), a rotor (60) having a rotor core (61) including a plurality of main pole portions (62) provided for each circumferentially arranged magnetic pole, and a field winding (70) wound around each of the main pole portions, the rotor being disposed radially inside the stator to face it, the stator winding having a first stator coil end (SE1) at one axial end and a second stator coil end (SE2) at the other axial end, the radially inner inner diameter of the second stator coil end being smaller than the radially inner inner diameter of the first stator coil end, a first rotor coil end (RE1) at one axial end thereof and a second rotor coil end (RE2) at the other axial end thereof, the radially outer diameter of the second rotor coil end being smaller than the radially outer diameter of the first rotor coil end, the stator winding and the field winding being respectively arranged such that the first stator coil end and the first rotor coil end are aligned radially, and the second stator coil end and the second rotor coil end are aligned radially. [Configuration 2] A wound-field rotating electric machine according to Configuration 1, wherein in the field winding, each pole coil is formed by winding a conductor material using concentrated winding, and has a lane change portion (L) at one of both axial ends thereof where a lane change occurs as the conductor material is laminated, and the axial end of the pole coil having the lane change portion is the first rotor coil end. [Configuration 3] A wound-field rotating electric machine according to Configuration 1 or 2, wherein the rotor comprises a circuit module (106) disposed on one axial end side of the rotor core and including electrical components connected to the field winding, each of the pole coils has a conductor end extending in the axial direction, the conductor end being connected to the circuit module, and the axial end of the pole coil that is closer to the conductor end of both axial ends is the first rotor coil end.[Configuration 4] The wound-field rotating electric machine according to any one of Configurations 1 to 3, wherein the stator winding has a stator coil side (SS) between the first stator coil end and the second stator coil end in the axial direction, a portion of the second stator coil end protruding radially inward beyond the stator coil side, and at the second rotor coil end, an outer periphery of each pole coil is inclined with respect to the axial direction, and the outer diameter dimension decreases with increasing axial distance from the rotor core. [Configuration 5] The wound-field rotating electric machine according to Configuration 4, wherein the rotor has a coil end cover (104) provided to cover the second rotor coil end, and the coil end cover has an end plate portion (151) axially facing the second rotor coil end, and an annular portion (152) extending axially from the outer periphery of the end plate portion and surrounding the second rotor coil end, and the outer peripheral surface of the annular portion is inclined with respect to the axial direction, and the outer diameter dimension decreases with increasing axial distance from the rotor core. [Configuration 6] The wound-field rotating electric machine according to Configuration 5, wherein the second stator coil end and the annular portion of the coil end cover face each other in the radial direction, and the dimension of the gap between the second stator coil end and the annular portion increases with increasing axial distance from the rotor core. [Configuration 7] A wound-field rotating electric machine according to any one of configurations 1 to 6, wherein the rotor has: a coil end cover (104) provided to cover the second rotor coil end; and an outer circumferential covering portion (102) provided to surround each of the main pole portions and the field winding from the radially outer side, on a rotor coil side (RS) between the first rotor coil end and the second rotor coil end in the axial direction, wherein the coil end cover has an end plate portion (151) facing the second rotor coil end in the axial direction, and an annular portion (152) extending in the axial direction from the outer circumferential portion of the end plate portion and surrounding the second rotor coil end, and a radial gap dimension between the second stator coil end and the annular portion of the coil end cover is larger than a radial gap dimension between the stator and the outer circumferential covering portion between the first stator coil end and the second stator coil end in the axial direction.

[0094] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A wound-field type rotating electric machine (40) comprising: a stator (50) having a stator winding (52); a rotor (60) having a rotor core (61) including a plurality of main pole portions (62) provided for each circumferentially arranged magnetic pole; and a field winding (70) wound around each of the main pole portions, the rotor being disposed radially inside the stator to face it; the stator winding has a first stator coil end (SE1) at one axial end and a second stator coil end (SE2) at the other axial end, the radially inner inner diameter of the second stator coil end being smaller than the radially inner inner diameter of the first stator coil end; the field winding includes a plurality of pole coils (110) provided for each magnetic pole, and has a first rotor coil end (RE1) at one axial end and a second rotor coil end (RE2) at the other axial end, the outer diameter dimension of the second rotor coil end on the radial outside is smaller than the outer diameter dimension of the first rotor coil end on the radial outside, and the stator winding and the field winding are respectively arranged so that the first stator coil end and the first rotor coil end are aligned radially, and the second stator coil end and the second rotor coil end are aligned radially.

2. A wound-field rotating electric machine as set forth in claim 1, wherein in the field winding, each of the pole coils is formed by winding conductor material using concentrated winding, and has a lane change section (L) at one of its axial ends where a lane change occurs as the conductor material is laminated, and the axial end of the pole coil having the lane change section at one of its axial ends is the first rotor coil end.

3. A wound-field rotating electric machine as set forth in claim 1, wherein the rotor comprises a circuit module (106) disposed on one axial end side of the rotor core and equipped with electrical components connected to the field winding, each of the pole coils has a conductor end extending in the axial direction, the conductor end being connected to the circuit module, and the axial end of the pole coil that is closer to the conductor end of both axial ends is the first rotor coil end.

4. A wound-field rotating electric machine according to any one of claims 1 to 3, wherein the stator winding has a stator coil side (SS) between the first stator coil end and the second stator coil end in the axial direction, a portion of the second stator coil end protruding radially inward beyond the stator coil side, and at the second rotor coil end, the outer periphery of each pole coil is inclined with respect to the axial direction, and the outer diameter dimension becomes smaller the further away from the rotor core in the axial direction.

5. A wound-field rotating electric machine as set forth in claim 4, wherein the rotor has a coil end cover (104) provided to cover the second rotor coil end, the coil end cover having an end plate portion (151) axially facing the second rotor coil end, and an annular portion (152) extending axially from the outer periphery of the end plate portion and surrounding the second rotor coil end, the annular portion having a radially outer outer peripheral surface inclined with respect to the axial direction and an outer diameter dimension that decreases axially as it moves away from the rotor core.

6. A wound-field type rotating electric motor as described in claim 5, wherein the second stator coil end and the annular portion of the coil end cover face each other radially, and the gap dimension between the second stator coil end and the annular portion increases with increasing axial distance from the rotor core.

7. A wound-field rotating electric machine according to any one of claims 1 to 3, wherein the rotor has: a coil end cover (104) provided to cover the second rotor coil end; and an outer circumferential covering portion (102) provided to surround each of the main pole portions and the field winding from the radially outer side on a rotor coil side (RS) between the first rotor coil end and the second rotor coil end in the axial direction, the coil end cover having an end plate portion (151) axially facing the second rotor coil end, and an annular portion (152) extending axially from the outer circumferential portion of the end plate portion and surrounding the second rotor coil end, and wherein the radial gap dimension between the second stator coil end and the annular portion of the coil end cover is larger than the radial gap dimension between the stator and the outer circumferential covering portion between the first stator coil end and the second stator coil end in the axial direction.

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