Stator, electric motor, compressor, and refrigeration cycle device

Abstract

This stator comprises a stator core having a slot on the inner peripheral side of an annular core back, and a winding accommodated in the slot. The stator core is fixed inside a cylindrical frame in a state of receiving stress toward the inner side in the radial direction of the stator core. The stator core has a first core part and a second core part that is positioned closer to an end part in the axial direction of the stator core than the first core part. The first core part has a first contact surface that contacts the frame. The second core part has a second contact surface that contacts the frame, and a retracted surface that is positioned more radially inward than the second contact surface. The circumferential length L1 of the first contact surface and the circumferential length L2 of the second contact surface satisfy the relationship L1 > L2. The stator core has a region in which the first contact surface and the second contact surface are continuous in the axial direction. In the second core part of the stator core, a step part is formed such that the minimum width of the core back in the radial direction is less at the second core part than at the first core part.

Description

Stator, electric motor, compressor and refrigeration cycle device

[0001] The present disclosure relates to a stator, an electric motor, a compressor, and a refrigeration cycle device.

[0002] A stator of an electric motor includes a stator core and a winding wound around the stator core. The stator core may be fixed inside a cylindrical frame of a compressor or the like. In this case, the compressive stress applied to the stator core from the frame increases iron loss in the stator core. To address this, it has been proposed to provide a recess on the outer periphery of the stator core to reduce the contact area between the stator core and the frame (see, for example, Patent Document 1).

[0003] JP 2004-274995 A (see abstract)

[0004] Here, the stator core has an annular core back and teeth extending radially inward from the core back, and windings are wound around the teeth. To shorten the circumferential length of the windings, steps are formed at the axial ends of the teeth and the core back. However, when such steps are formed, the width of the core back is locally narrowed, and there is a possibility that iron loss will increase due to compressive stress from the frame.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to shorten the circumferential length of the winding and suppress an increase in iron loss in the stator core.

[0006] The stator disclosed herein includes a stator core having an annular core back and slots formed on the inner circumferential side of the core back, and windings housed in the slots. The stator core is fixed inside a cylindrical frame in a state in which stress is applied radially inward of the stator core. The stator core includes a first core portion and a second core portion located closer to the axial end of the stator core than the first core portion. The first core portion has a first contact surface that contacts the frame. The second core portion has a second contact surface that contacts the frame and a retracted surface located radially inward of the second contact surface. The circumferential length L1 of the first contact surface of the stator core and the circumferential length L2 of the second contact surface satisfy the relationship L1 > L2. The stator core has a region in which the first contact surface and the second contact surface are continuous in the axial direction. The second core portion of the stator core is formed with a stepped portion such that the minimum width of the core back in the radial direction is narrower in the second core portion than in the first core portion.

[0007] According to the present disclosure, the step portion is formed in the second core portion, which allows the circumferential length of the winding to be shortened. Also, since the second core portion has a recessed surface, it is possible to suppress an increase in iron loss caused by a narrowing of the minimum width of the core back due to the formation of the step portion. In other words, it is possible to shorten the circumferential length of the winding and suppress an increase in iron loss in the stator core.

[0008] 9A and 9B are cross-sectional views taken along line 9A-9A and line 9B-9B in FIG. 8 . A perspective view showing a stator core, an insulating portion, and a winding according to the first embodiment. A cross-sectional view showing teeth and insulating portions according to the first embodiment. A cross-sectional view showing teeth and insulating portions according to a first comparative example, a cross-sectional view showing teeth and insulating portions according to a second comparative example, and a cross-sectional view showing teeth and insulating portions according to the first embodiment. 1A is a schematic diagram showing an enlarged portion of a first core portion of embodiment 1, and FIG. 1B is a schematic diagram showing an enlarged portion of a second core portion of embodiment 1. FIG. 1C is a schematic diagram for explaining stress applied to the stator core of embodiment 1. FIG. 1D is a plan view showing an electric motor of embodiment 2. FIG. 1E is a plan view showing a stator core of embodiment 2. FIG. 1F is a perspective view showing a portion of the stator core of embodiment 2. FIG. 1G is a cross-sectional view showing teeth and insulating portions of embodiment 2. FIG. 1G is a schematic diagram showing an enlarged portion of a first core portion of embodiment 2, a schematic diagram showing an enlarged portion of a second core portion, and a schematic diagram showing an enlarged portion of a third core portion of embodiment 2. FIG. 1A is a plan view showing a stator core of embodiment 3, and a schematic diagram showing stress distribution in the core back. FIG. 1A is a plan view showing a stator core of comparative example 3, and a schematic diagram showing stress distribution in the core back. FIG. 1B is a plan view showing a stator core of embodiment 4, and a schematic diagram showing an enlarged portion of the stator core. 10A is a schematic diagram showing stress distribution in a core back of embodiment 4, and FIG. 10B is a schematic diagram showing stress distribution in a core back of comparative example 4. FIG. 10A is a cross-sectional view showing a stator core of embodiment 5, and FIG. 10B is a schematic diagram showing an enlarged portion of the stator core.28A is a schematic diagram showing stress distribution in the core back of embodiment 5, and FIG. 28B is a schematic diagram showing stress distribution in the core back of comparative example 5. FIG. 28A is a plan view showing a stator core of embodiment 6, and FIG. 28B is a perspective view showing an enlarged portion of the stator core. FIG. 28A is a plan view showing a stator core of embodiment 7, and FIG. 28B is a perspective view showing an enlarged portion of the stator core. FIG. 28B is a longitudinal sectional view showing a compressor to which the electric motor of each embodiment can be applied. FIG. 28C is a diagram showing a refrigeration cycle device to which the compressor of FIG. 28C can be applied.

[0009] First Embodiment <Configuration of Electric Motor> First, a first embodiment will be described. Fig. 1 is a cross-sectional view showing an electric motor 3 according to the first embodiment. The electric motor 3 shown in Fig. 1 is a permanent magnet embedded synchronous motor, and is used in, for example, a compressor 8 (Fig. 28).

[0010] The electric motor 3 has a shaft 90 which is a rotating shaft, a rotor 5 fixed to the shaft 90, and a stator 1 provided to surround the rotor 5. An air gap of, for example, 0.3 to 1.0 mm is formed between the stator 1 and the rotor 5. The stator 1 is incorporated inside a cylindrical frame 81 of a compressor 8 (FIG. 28) which will be described later.

[0011] Hereinafter, the direction of the center axis Ax of the rotor 5, i.e., the center axis of the shaft 90, will be referred to as the "axial direction." The radial direction centered on the central axis Ax will be referred to as the "radial direction." The circumferential direction centered on the central axis Ax will be referred to as the "circumferential direction."

[0012] <Configuration of the Rotor> Fig. 2 is a cross-sectional view showing the rotor 5. The rotor 5 has an annular rotor core 50 centered on the central axis Ax, and permanent magnets 55 attached to the rotor core 50. The rotor core 50 has a plurality of laminated elements stacked in the axial direction. The laminated elements are, for example, electromagnetic steel sheets. The plate thickness of the laminated elements is 0.1 to 0.7 mm.

[0013] A center hole 53 is formed in the radial center of the rotor core 50. A shaft 90 (FIG. 1) is fixed in the center hole 53 of the rotor core 50 by shrink fitting, press fitting, or the like.

[0014] A plurality of magnet insertion holes 51 are formed along the outer periphery of the rotor core 50. One permanent magnet 55 is placed in each magnet insertion hole 51. One magnet insertion hole 51 corresponds to one magnetic pole. Because the rotor core 50 has six magnet insertion holes 51, the rotor 5 has six poles. However, the number of poles of the rotor 5 is not limited to six, as long as it is two or more. Furthermore, two or more permanent magnets 55 may be placed in each magnet insertion hole 51.

[0015] The permanent magnets 55 have a width in the circumferential direction of the rotor core 50 and a thickness in the radial direction. Each permanent magnet 55 is magnetized in the thickness direction. The permanent magnets 55 are made of a rare earth magnet containing, for example, neodymium (Nd), iron (Fe), and boron (B).

[0016] Dysprosium (Dy) may be added to rare earth magnets to improve coercivity. However, adding Dy increases manufacturing costs and reduces remanence, so it is desirable to keep the Dy content at 4% by weight or less, or to add no Dy at all. In other words, the Dy content is desirably 0 to 4% by weight.

[0017] The circumferential center of the magnet insertion hole 51 is the pole center P. A radial line passing through the pole center P is called the pole center line. An inter-pole portion M is formed between adjacent magnetic poles. In this example, the magnet insertion hole 51 extends linearly in a direction perpendicular to the pole center line. However, the magnet insertion hole 51 may also extend in a V-shape.

[0018] Flux barriers 52, which are gaps, are formed on both circumferential sides of the magnet insertion holes 51. Thin-walled portions are formed between the flux barriers 52 and the outer periphery of the rotor core 50. In order to reduce leakage flux between adjacent magnetic poles, the radial width of the thin-walled portions is set to be the same as the plate thickness of the laminated elements, for example.

[0019] Radially long slits 54 are formed on the radially outer side of the magnet insertion holes 51. The slits 54 are formed to control the magnetic flux density distribution on the surface of the rotor 5. Here, seven slits 54 are formed symmetrically with respect to the pole center line, but the number and arrangement of the slits 54 are arbitrary. Also, the rotor core 50 does not necessarily have to be provided with slits 54.

[0020] The crimped portions 56 that secure the laminated elements are formed at circumferential positions corresponding to the inter-polar portions M, radially inward of the flux barriers 52. However, the placement of the crimped portions 56 is not limited to these positions. Furthermore, the laminated elements of the rotor core 50 may be secured by a method other than crimping.

[0021] Through holes 57 and 58 are formed radially inside the magnet insertion holes 51. The circumferential position of the through hole 57 coincides with the pole center P, and the circumferential position of the through hole 58 coincides with the inter-pole portion M. The through holes 57 and 58 penetrate the rotor core 50 in the axial direction and are used as refrigerant passages. Note that the arrangement of the through holes 57 and 58 is not limited to the positions described here. Furthermore, the rotor core 50 does not necessarily have to have the through holes 57 and 58.

[0022] <Configuration of Stator> As shown in Fig. 1, the stator 1 has a stator core 10 that surrounds the rotor core 50 from the radial outside, and a winding 30 wound around the stator core 10. The stator core 10 has a plurality of laminated elements that are laminated in the axial direction. The laminated elements are, for example, electromagnetic steel sheets. The plate thickness of the laminated elements is 0.1 to 0.7 mm.

[0023] Fig. 3 is a plan view showing the stator core 10, and also shows a frame 81. As shown in Fig. 3, the stator core 10 has an annular core back 11 centered on the central axis Ax, and N (N is an integer of 2 or more) teeth 12 extending radially inward from the core back 11. The teeth 12 are arranged at regular intervals in the circumferential direction. Here, the number N of the teeth 12 is 9, but it may be any number equal to or greater than 2.

[0024] The teeth 12 each have an extension 12a extending radially inward from the core back 11 and a tooth tip 12b formed at the tip of the extension 12a. The circumferential width of the tooth tip 12b is greater than the circumferential width of the extension 12a. The tooth tip 12b faces the rotor 5 (FIG. 2).

[0025] Slots 13 are formed between circumferentially adjacent teeth 12. The slots 13 are areas in which windings 30 are housed. Openings 13a are formed radially inside the slots 13, i.e., between adjacent tooth tips 12b. The number of slots 13 is N, the same as the number of teeth 12, and is nine in this example.

[0026] The windings 30 (FIG. 1) are made of magnet wire and wound in concentrated winding around each tooth 12. A current having a frequency corresponding to the rotational speed of the electric motor 3 flows through the windings 30, generating a rotating magnetic field that rotates the rotor 5.

[0027] The wire diameter of the winding 30 and the number of turns around one tooth 12 are determined by the required specifications such as rotational speed and torque, the supply voltage, and the cross-sectional area of ​​the slot 13. As an example, the wire diameter of the winding 30 is 1.0 mm, and the number of turns is 80.

[0028] An insulating portion (for example, insulating portion 20 shown in FIG. 10 ) made of a resin such as polybutylene terephthalate (PBT) is provided between the stator core 10 and the windings 30. An insulating film made of a resin such as polyethylene terephthalate (PET) may also be provided on the inner surface of the slot 13.

[0029] The stator core 10 is formed by combining N split cores 14 in an annular shape. Each split core 14 is a segment including one tooth 12. The portion of the annular core back 11 included in each split core 14 is referred to as the core back portion 11a. That is, each split core 14 has the core back portion 11a and the tooth 12.

[0030] Of the N split cores 14, the split cores 14 adjacent to each other in the circumferential direction are connected by a joint portion 11c provided at the circumferential end of the core back portion 11a.

[0031] When manufacturing the stator 1, the N split cores 14 of the stator core 10 are spread out linearly, and a winding nozzle is used to wind the windings 30 around the teeth 12. After the windings 30 are wound around the teeth 12, the N split cores 14 are bent into an annular shape, and the split cores 14 at both ends are welded together to form the annular stator core 10.

[0032] 4 is a perspective view showing a part of the stator core 10, i.e., the split cores 14. As shown in FIG. 4, the axial end face of the core back 11 and the axial end faces of the teeth 12 are on the same plane, and both are part of the axial end face 101 of the stator core 10. Therefore, both the end face of the core back 11 and the end face of the teeth 12 are referred to as the end face 101. The circumferential end face of the core back portion 11a included in each split core 14 is referred to as the connecting surface 11e.

[0033] The stator core 10 has a first core portion A1 and a second core portion A2 in the axial direction. The first core portion A1 has a length LA1 in the axial direction, and the second core portion A2 has a length LA2 in the axial direction.

[0034] The first core portion A1 is formed in the axial center of the stator core 10. The second core portions A2 are formed on both axial sides of the first core portion A1. In other words, the second core portion A2 is formed at an axial end portion of the stator core 10. That is, the second core portion A2 includes an axial end face 101 of the stator core 10.

[0035] A contact surface 15a that contacts the frame 81 (FIG. 3) is formed on the outer peripheral surface of the first core portion A1. The contact surface 15a has an arc-shaped cross section in a plane perpendicular to the central axis Ax. The distance from the central axis Ax to the contact surface 15a is D1 (FIG. 3). The contact surface 15a has a length L1 in the circumferential direction. The contact surface 15a is also referred to as the first contact surface or the maximum outer diameter portion.

[0036] The second core portion A2 has an outer peripheral surface formed with a contact surface 15b that contacts the frame 81 and a retraction surface 16 that is located radially inward of the contact surface 15b. The contact surface 15b has an arc-shaped cross section in a plane perpendicular to the central axis Ax.

[0037] The distance from the central axis Ax to the contact surface 15b is the same as the distance from the central axis Ax to the contact surface 15a (i.e., D1). The contact surface 15b has a length L2 in the circumferential direction. The contact surface 15b is also referred to as a second contact surface or a maximum outer diameter portion.

[0038] The circumferential length L1 of the contact surface 15a is longer than the circumferential length L2 of the contact surface 15b. That is, L1 > L2. The stator core 10 has a region W where the contact surface 15a and the contact surface 15b are continuous in the axial direction. In the example shown in Fig. 4, the region W is a region along the circumferential end of the core back portion 11a.

[0039] The retraction surfaces 16 are formed adjacent to the contact surfaces 15b in the circumferential direction. That is, in the second core portion A2, the retraction surfaces 16 are formed radially outward of the teeth 12, and the contact surfaces 15b are formed on both circumferential sides of the retraction surfaces 16. It is also desirable that the retraction surfaces 16 be formed symmetrically with respect to a radial line (referred to as the tooth center line T) that passes through the circumferential center of the teeth 12.

[0040] The distance from the central axis Ax to the retraction surface 16 is D2 (FIG. 3). The distance D2 is shorter than the distance D1. Therefore, the retraction surface 16 is radially spaced apart from the frame 81 (FIG. 3) and does not contact the frame 81.

[0041] A step surface 15e is formed on the outer peripheral surface of the stator core 10 between the axially adjacent contact surface 15a and the retraction surface 16. The step surface 15e is an end surface perpendicular to the axial direction, extends in the circumferential direction, and has a width in the radial direction.

[0042] A step surface 15f is formed on the outer peripheral surface of the stator core 10 between the contact surface 15b and the retraction surface 16 that are adjacent in the circumferential direction. The step surface 15f is an end surface that is perpendicular to the circumferential direction, extends in the axial direction, and has a width in the radial direction.

[0043] Grooves 18 are formed on the outer peripheral surface of the stator core 10 in portions located radially outward of the teeth 12. The grooves 18 are located on the tooth center lines T. The grooves 18 form refrigerant passages through which the refrigerant flows in the axial direction.

[0044] The groove portion 18 extends in the axial direction so as to circumferentially divide both the contact surface 15a and the withdrawal surface 16 into two. Therefore, the contact surface 15a and the withdrawal surface 16 are both formed on both circumferential sides of the groove portion 18. However, the groove portion 18 does not necessarily have to be provided in the stator core 10.

[0045] 5A and 5B are plan views showing the laminated elements 41 and 42 that make up the split core 14. The split core 14 is formed by alternately stacking the laminated elements 41 shown in Fig. 5A and the laminated elements 42 shown in Fig. 5B one by one in the axial direction and integrating them at crimped portions (not shown). The laminated elements 41 and 42 have planar shapes that are symmetrical with respect to the tooth center line T.

[0046] 5A, a curved, convex abutment portion 411 is formed at one circumferential end of the core back portion 11a of the lamination element 41. A curved, concave edge portion 412 is formed at the other circumferential end of the core back portion 11a. A crimped portion 413 is formed at the abutment portion 411.

[0047] 5(B), a curved, convex abutment portion 421 is formed at one circumferential end of the core back portion 11a of the lamination element 42. A curved, concave edge portion 422 is formed at the other circumferential end of the core back portion 11a. A crimped portion 423 is formed at the abutment portion 421.

[0048] The abutting portion 421 of the laminated element 42 overlaps with the end edge portion 412 of the laminated element 41 in the axial direction. The end edge portion 422 of the laminated element 42 overlaps with the abutting portion 411 of the laminated element 41 in the axial direction.

[0049] Two adjacent split cores 14 are connected to each other by fitting the crimped portion 413 of the laminated element 41 of one split core 14 into the crimped portion 423 of the laminated element 42 of the other split core 14. This type of connection structure is called a joint lap.

[0050] 4, the portion where the abutting portion 411 of the laminated element 41 and the edge portion 422 of the laminated element 42 overlap in the axial direction is shown as a joint portion 11c, and the portion where the edge portion 412 of the laminated element 41 and the abutting portion 421 of the laminated element 42 overlap in the axial direction is shown as a crimped portion 11d. Also, the portion where the crimped portion 413 and the crimped portion 423 fit together is shown as a crimped portion 11d.

[0051] The stator core 10 is not limited to being formed by connecting a plurality of split cores 14, and the split cores 14 may be welded to one another. In this case, as shown in Fig. 6, the split cores 14 do not have joint portions 11c, and are welded to each other at connecting surfaces 11e at the circumferential ends of the core back portions 11a.

[0052] Fig. 7 is a perspective view of a part of the stator core 10, i.e., a split core 14, seen from a different direction than Fig. 4. In Fig. 7, the joint portion 11c and the crimped portion 11d shown in Fig. 4 are omitted.

[0053] 7, a step portion S1 is formed on the slot 13 side at the axial end of the stator core 10. Here, the step portion S1 is formed at both axial ends of the stator core 10, but it is sufficient that the step portion S1 is formed at at least one axial end of the stator core 10.

[0054] The core back 11 (core back portion 11a in FIG. 7) has an inner circumferential surface 110 facing the slot 13. The teeth 12 have side surfaces 120 facing the slot 13. The inner circumferential surface 110 of the core back 11 is a plane perpendicular to the side surfaces 120 of the teeth 12.

[0055] The fact that the inner peripheral surface 110 of the core back 11 is a plane perpendicular to the side surfaces 120 of the teeth 12 is advantageous in winding the winding 30 densely to the depth of the slot 13. The inner peripheral surfaces 110 of adjacent core back portions 11a abut against each other at the circumferential center of the slot 13 (see FIG. 3).

[0056] A core back step portion 111 is formed between the inner peripheral surface 110 and the end face 101 of the core back 11. A tooth step portion 121 is formed between the side surface 120 and the end face 101 of the tooth 12. The core back step portion 111 and the tooth step portion 121 are collectively referred to as step portion S1.

[0057] The core-back step portion 111 has an inner peripheral surface 111a facing the slot 13 and a step surface 111b facing the axial direction. The tooth step portion 121 has a side surface 121a facing the slot 13 and a step surface 121b facing the axial direction. The tooth step portion 121 may be formed up to the surface of the tooth tip portion 12b on the slot 13 side.

[0058] The step portion S1 (i.e., the core-back step portion 111 and the tooth step portion 121) is formed in the second core portion A2 of the stator core 10. Although the above-mentioned Fig. 4 and Fig. 6 are drawn in perspective, the axial length LS of the step portion S1 and the axial length LA2 of the second core portion A2 have the relationship LS≦LA2.

[0059] That is, it is sufficient that the step portion S1 is formed on at least a part of the second core portion A2 in the axial direction.

[0060] In the second core part A2 in which the step part S1 is formed, the radial width of the core back 11 is narrower and the circumferential width of the teeth 12 is also narrower compared to the first core part A1 in which the step part S1 is not formed.

[0061] Next, the fixing of the stator core 10 to the frame 81 will be described. Fig. 8 is an enlarged plan view showing a portion of the rotor 5, the stator 1, and the frame 81. Fig. 9(A) is a cross-sectional view taken along line 9A-9A shown in Fig. 8. Fig. 9(B) is a cross-sectional view taken along line 9B-9B shown in Fig. 8.

[0062] The stator core 10 is fixed to the frame 81 by shrink fitting. During shrink fitting, the stator core 10 is inserted into the inside of the frame 81, the inner diameter of which has been expanded by heating, and the inner diameter of the frame 81 is then reduced by cooling. Therefore, in the cross section shown in Fig. 9(A), the frame 81 comes into contact with the contact surface 15a of the stator core 10.

[0063] Portions of the frame 81 located on both axial sides of the contact surface 15a are further displaced radially inward. Step-shaped deformation portions 81a are formed in the frame 81 along step surfaces 15e on both axial sides of the contact surface 15a. Because the retraction surfaces 16 are located radially inward of the contact surfaces 15a, they do not come into contact with the frame 81 unless the shrink-fit allowance is particularly large.

[0064] 9(B), contact surfaces 15a and 15b of stator core 10 are continuous in the axial direction. Frame 81 contacts contact surfaces 15a and 15b of stator core 10. Portions of frame 81 located on both axial sides of end face 101 of stator core 10 are further displaced radially inward. Therefore, step-shaped deformation portions 81b are formed in frame 81 along end face 101 of stator core 10.

[0065] 9A and 9B, the frame 81 contacts the contact surfaces 15a and 15b of the stator core 10, the deformed portion 81a of the frame 81 engages with the step surface 15e, and the deformed portion 81b of the frame 81 engages with the end surface 101 of the stator core 10. Therefore, the holding strength of the frame 81 for the stator core 10 is improved.

[0066] 9A and 9B, a deformed portion is also formed in frame 81 that conforms to step surface 15f (FIG. 4) of stator core 10. This further improves the holding strength of stator core 10 by frame 81.

[0067] Next, the insulating portion 20 of the stator core 10 will be described. FIG. 10 is a perspective view showing the stator core 10 and the insulating portion 20. As shown in FIG. 10, the insulating portion 20 is attached to the stator core 10. The insulating portion 20 is made of a resin such as polybutylene terephthalate (PBT) or liquid crystal polymer (LCP). The insulating portion 20 is formed, for example, by integrally molding the resin with the split cores 14. Alternatively, a resin molded body may be attached to the split cores 14.

[0068] The insulating portion 20 has a body portion 22 that covers the teeth 12, a wall portion 21 arranged radially outside the body portion 22, and a flange portion 23 arranged radially inside the body portion 22. The wall portion 21 and the flange portion 23 face each other in the radial direction with the body portion 22 sandwiched therebetween.

[0069] The wall portion 21 is provided to cover the inner peripheral surface 110 of the core back 11 and further extends on both sides in the axial direction. The body portion 22 is provided to surround the extension portion 12a of the tooth 12. The flange portion 23 is provided to cover the surface of the tip portion 12b of the tooth 12 on the slot 13 side and further extends on both sides in the axial direction.

[0070] Wall portion 21 is formed with engaging portions 21a that engage with core-back step portions 111. Body portion 22 is formed with engaging portions 22a (FIG. 11) that engage with tooth step portions 121. Flange portion 23 is formed with engaging portions 23a that engage with tooth step portions 121.

[0071] A winding 30 (FIG. 1) is wound around the body portion 22. The wall portion 21 and the flange portion 23 guide the winding 30 wound around the body portion 22 from both radial sides.

[0072] 11 is a cross-sectional view showing the teeth 12 and the insulating portions 20, taken along a plane perpendicular to the extending direction of the teeth 12. The extending direction of the teeth 12 refers to the direction of the tooth center line T (FIG. 3).

[0073] In the first core portion A1 of the stator core 10, the teeth 12 have a width W1. In the second core portion A2, the teeth 12 have a width W2. The widths W1 and W2 have a relationship of W1>W2.

[0074] The insulating portion 20 has a first surface 201 which is a plane covering the end surface 101 of the tooth 12, a second surface 202 which is a plane facing the slot 13, and a third surface 203 which is a curved surface extending from the first surface 201 to the second surface 202.

[0075] <Operation> The operation of the first embodiment will be described in comparison with comparative examples 1 and 2. Fig. 12(A) is a cross-sectional view showing the teeth 12 and insulating portion 20 of comparative example 1. Fig. 12(B) is a cross-sectional view showing the teeth 12 and insulating portion 20 of comparative example 2. Fig. 12(C) is a cross-sectional view showing the teeth 12 and insulating portion 20 of the first embodiment. In Figs. 12(A) to 12(C), the components of comparative examples 1 and 2 are assigned the same reference numerals as the components of the first embodiment.

[0076] 12A shows a tooth 12 of Comparative Example 1 that does not have a step between the side surface 120 and the end surface 101. That is, a 90-degree corner is formed between the side surface 120 and the end surface 101 of the tooth 12. The insulating portion 20 has a first surface 201 that covers the end surface 101, a second surface 202 that faces the slot 13, and a third surface 203 between these surfaces 201 and 202. The third surface 203 faces the corner of the tooth 12.

[0077] As described above, the winding 30 is wound around the teeth 12 by concentrated winding. To wind the winding 30 around the insulating portion 20 without causing bulging, it is desirable that the radius of curvature r of the third surface 203 be large. However, to increase the radius of curvature r of the third surface 203, it is necessary to increase the shortest distance t from the end surface 101 of the tooth 12 to the first surface 201 of the insulating portion 20. This increases the circumferential length of the winding 30, resulting in increased copper loss.

[0078] 12B, the teeth 12 of Comparative Example 2 do not have steps at the axial ends, similar to the teeth 12 of Comparative Example 1. That is, a 90-degree corner is formed between the side surface 120 and the end face 101 of the teeth 12. In Comparative Example 2, the shortest distance t from the end face 101 of the teeth 12 to the first surface 201 of the insulating portion 20 is shorter than in Comparative Example 1.

[0079] In this comparative example 2, the shortest distance t is short, so the radius of curvature r of the third surface 203 is small, and the winding 30 is likely to bulge toward the slot 13. This increases the circumferential length of the winding 30, and makes it difficult to arrange the winding 30 densely within the slot 13.

[0080] 12(C) shows tooth 12 of embodiment 1 having tooth step portion 121 between side surface 120 and end surface 101. Insulator 20 has first surface 201 covering end surface 101, second surface 202 facing slot 13, and third surface 203 covering tooth step portion 121.

[0081] In the first embodiment, tooth step portions 121 are formed, which makes it possible to increase radius of curvature r of third surface 203 and shorten the shortest distance t from end surface 101 of tooth 12 to first surface 201 of insulating portion 20. Increasing radius of curvature r of third surface 203 makes it less likely for winding 30 to bulge, allowing winding 30 to be densely arranged within slot 13. Furthermore, shortening the shortest distance t makes it possible to shorten the circumferential length of winding 30.

[0082] Fig. 13A is a schematic diagram showing the contact portion between the first core portion A1 of the stator core 10 and the frame 81. Fig. 13B is a schematic diagram showing the contact portion between the second core portion A2 of the stator core 10 and the frame 81.

[0083] Since a step portion S1 is formed in the second core portion A2, the minimum radial width T2 (Figure 13(B)) of the core back 11 in the second core portion A2 is narrower than the minimum radial width T1 (Figure 13(A)) of the core back 11 in the first core portion A1.

[0084] When the stator core 10 is fixed to the frame 81 by shrink fitting, the stator core 10 is subjected to stress directed radially inward from the frame 81. In the second core portion A2 in which the minimum radial width T2 of the core back 11 is narrow, stress tends to concentrate particularly on the inner peripheral portion (indicated by symbol Q) of the core back 11 located at the circumferential center of the slot 13. Because the stator core 10 is formed of laminated elements such as electromagnetic steel sheets, stress concentration leads to an increase in iron loss.

[0085] Therefore, in the first embodiment, the retracted surface 16 is formed on the outer peripheral surface of the second core portion A2 of the stator core 10. By forming the retracted surface 16, the contact area between the second core portion A2 and the frame 81 becomes smaller than the contact area between the first core portion A1 and the frame 81.

[0086] Fig. 14 is a schematic diagram showing the stress that stator core 10 receives from frame 81 in the cross section shown by line segment 9A-9A in Fig. 8. In Fig. 14, the portions of stator core 10 that receive stress from frame 81 are hatched with dots.

[0087] 14, the contact surface 15a of the first core part A1 contacts the frame 81 and receives a stress F from the frame 81. In contrast, the retracted surface 16 of the second core part A2 does not contact the frame 81 and therefore does not receive the stress F from the frame 81.

[0088] In this way, by providing the retraction surface 16 in the second core portion A2 having the step portion S1 in the stator core 10, stress concentration in the core back 11 can be avoided, and an increase in iron loss due to stress concentration can be suppressed. Therefore, an increase in iron loss in the stator core 10 as a whole can be suppressed.

[0089] 4, the stator core 10 is provided with a region W where the contact surfaces 15a, 15b are continuous in the axial direction. The effect of this will be described.

[0090] If the second core portion A2 of the stator core 10 does not have the contact surface 15b, the second core portion A2 will be held without contact with the frame 81. The laminated elements of the second core portion A2 are fixed to the laminated elements of the first core portion A1 by crimping, but the crimping leaves a slight clearance, making complete integration difficult. This reduces the integrity of the stator core 10 and causes noise.

[0091] In contrast, when the second core part A2 of the stator core 10 has a contact surface 15b, the second core part A2 is held in a state in which the contact surface 15b is pressed radially inward from the frame 81, thereby improving the integrity of the stator core 10 and reducing noise.

[0092] In particular, in region W of the stator core 10, the contact surfaces 15a, 15b are continuous in the axial direction, and therefore the stress that the contact surfaces 15a, 15b of the stator core 10 receive from the frame 81 further improves the integrity of the stator core 10 and enhances the noise reduction effect.

[0093] If the inner diameter roundness of the stator core 10 decreases, the air gap between the stator core 10 and the rotor core 50 becomes non-uniform in the circumferential direction. If vibrations caused by the magnetic attraction between the stator core 10 and the rotor core 50 are transmitted to the frame 81 through the stator core 10, noise from the electric motor 3 occurs. This noise becomes more pronounced as the air gap becomes more non-uniform. Therefore, it is desirable that the inner diameter roundness of the stator core 10 be high.

[0094] On the other hand, since the stator core 10 is made by stacking laminated elements such as electromagnetic steel plates and fixing them by caulking or the like, the circularity of the stator core 10 may be reduced due to misalignment between the laminated elements or the like.

[0095] In contrast, contact surfaces 15a and 15b of stator core 10 are subjected to radially inward stress from frame 81, so that the circularity of stator core 10 improves in accordance with the circularity of frame 81. Furthermore, if retraction surface 16 is formed symmetrically with respect to tooth center line T as shown in Fig. 4, the circularity of stator core 10 is particularly improved. This increases the inner diameter circularity of stator core 10 and makes it possible to uniform the air gap.

[0096] Although the case where the second core portion A2 and the step portion S1 are provided at both axial ends of the stator core 10 has been described here, the second core portion A2 and the step portion S1 may be provided at only one axial end of the stator core 10. However, providing the second core portion A2 and the step portion S1 at both axial ends of the stator core 10 more effectively shortens the circumferential length of the windings 30 and enables the windings 30 to be arranged more densely within the slots 13.

[0097] Also, although it has been described here that the retracted surface 16b of the second core portion A2 does not contact the frame 81, depending on the shrink-fitting allowance, the retracted surface 16b may contact the frame 81. In this case as well, the stress that the retracted surface 16 receives from the frame 81 is smaller than the stress that the contact surfaces 15a and 15b receive from the frame 81, and therefore, the effect of suppressing an increase in iron loss can be obtained.

[0098] <Effects of the embodiment> As described above, the stator 1 of the first embodiment has an annular stator core 10 having slots 13 and windings 30 housed in the slots 13. The stator core 10 has a first core portion A1 and a second core portion A2, and the second core portion A2 is located on the axial end side of the stator core 10 relative to the first core portion A1. The first core portion A1 has a contact surface 15a, and the second core portion A2 has a contact surface 15b and a retracted surface 16. The circumferential length L1 of the contact surface 15a and the circumferential length L2 of the contact surface 15b satisfy L1 > L2. The stator core 10 also has a region W where the contact surfaces 15a and 15b are continuous in the axial direction. The second core portion A2 of the stator core 10 is formed with a step portion S1 such that the minimum radial width of the core back 11 is narrower in the second core portion A2 than in the first core portion A1.

[0099] As described above, the step portion S1 is formed in the second core portion A2, thereby shortening the circumferential length of the winding 30. Furthermore, the retraction surface 16 is provided in the second core portion A2, and the circumferential length L2 of the contact surface 15b of the second core portion A2 is shorter than the circumferential length L1 of the contact surface 15a of the first core portion A1. This reduces the stress that the second core portion A2, which has a narrow minimum width of the core back 11, receives from the frame 81, thereby suppressing an increase in iron loss. Furthermore, the region W where the contact surfaces 15a and 15b are continuous in the axial direction ensures a sufficient contact area between the frame 81 and the stator core 10, thereby increasing the holding force of the frame 81 to hold the stator core 10.

[0100] In particular, since the retracted surface 16 is spaced apart from the frame 81 in the radial direction, the stress that the second core portion A2 receives from the frame 81 is further reduced, and an increase in iron loss can be effectively suppressed.

[0101] Furthermore, since the retreat surface 16 is formed symmetrically with respect to the tooth center line T, the circularity of the stator core 10 is improved, the air gap between the stator 1 and the rotor 5 is made uniform, and vibration and noise can be reduced.

[0102] Furthermore, when the winding 30 is wound using distributed winding, the effect of shortening the circumferential length by providing the step portion S1 on the stator core 10 is small, but in this embodiment, the winding 30 is wound using concentrated winding, so the effect of shortening the circumferential length by providing the step portion S1 on the stator core 10 is large.

[0103] Furthermore, since the second core portion A2 is provided at both axial ends of the stator core 10 and the step portion S1 is also provided in the axial direction of the stator core 10, the circumferential length of the winding 30 can be shortened more effectively.

[0104] Embodiment 2 Fig. 15 is a plan view showing an electric motor 3A of embodiment 2. The electric motor 3A of embodiment 2 differs from the electric motor 3 of embodiment 1 in the shape of the stator core 10A.

[0105] 16 is a plan view showing stator core 10 of electric motor 3A according to embodiment 2. In embodiment 2, two steps S1 and S2 are formed on the slot 13 side of the axial end of stator core 10. Step S1 is also referred to as a first step, and step S2 is also referred to as a second step.

[0106] The step portion S1 has a core back step portion 111 formed on the inner peripheral surface of the core back 11 and a tooth step portion 121 formed on the side surface of the tooth 12. The tooth step portion 121 may reach the tip portion 12b of the tooth 12.

[0107] The step portion S2 has a core back step portion 112 formed on the inner peripheral surface of the core back 11 and a tooth step portion 122 formed on the side surface of the tooth 12. The tooth step portion 122 may reach the tip portion 12b of the tooth 12.

[0108] Fig. 17 is a perspective view showing a portion of stator core 10A (i.e., split core 14). As shown in Fig. 18, stator core 10A has a first core portion A1, a second core portion A2, and a third core portion A3 in the axial direction. The first core portion A1, the second core portion A2, and the third core portion A3 have lengths LA1, LA2, and LA3, respectively, in the axial direction.

[0109] The first core portion A1 is formed in the axial center of the stator core 10A. The second core portions A2 are formed on both axial sides of the first core portion A1. The third core portion A3 is formed at an axial end of the stator core 10A. The third core portion A3 includes an axial end face 101 of the stator core 10A.

[0110] The second core portion A2 has the above-mentioned step portion S1 formed therein, and the third core portion A3 has the above-mentioned step portion S2 formed therein.

[0111] The first core portion A1 has a contact surface 15a that contacts the frame 81. The contact surface 15a has an arc-shaped cross section in a plane perpendicular to the central axis Ax. The distance from the central axis Ax to the contact surface 15a is D1 (FIG. 16). The contact surface 15a has a length L1 in the circumferential direction. The contact surface 15a is also referred to as a first contact surface.

[0112] The second core portion A2 has a contact surface 15b that contacts the frame 81 and a retraction surface 16b that is located radially inward of the contact surface 15b. The contact surface 15b has an arc-shaped cross section in a plane perpendicular to the central axis Ax. The distance from the central axis Ax to the contact surface 15b is the same as the distance D1 from the central axis Ax to the contact surface 15a. The contact surface 15b has a length L2 in the circumferential direction. The contact surface 15b is also referred to as the second contact surface.

[0113] The third core portion A3 has a contact surface 15c that contacts the frame 81 and a retraction surface 16c that is located radially inward of the contact surface 15c. The contact surface 15c has an arc-shaped cross section in a plane perpendicular to the central axis Ax. The distance from the central axis Ax to the contact surface 15c is the same as the distance D1 from the central axis Ax to the contact surface 15a. The contact surface 15c has a length L3 in the circumferential direction. The contact surface 15c is also referred to as the third contact surface.

[0114] The circumferential lengths L1, L2, and L3 of the contact surfaces 15a, 15b, and 15c satisfy the relationship L1 > L2 > L3. The stator core 10 also has a region W where the contact surfaces 15a, 15b, and 15c are continuous in the axial direction. In the example shown in Fig. 18, the region W is a region along the circumferential end of the core back portion 11a.

[0115] The retraction surface 16b is formed adjacent to the contact surface 15b on the side of the tooth center line T in the circumferential direction. The retraction surface 16c is formed adjacent to the contact surface 15c on the side of the tooth center line T in the circumferential direction.

[0116] Both of the retracted surfaces 16b and 16c are located radially outward of the teeth 12. It is desirable that both of the retracted surfaces 16b and 16c are formed symmetrically with respect to the tooth center line T. The retracted surfaces 16b and 16c are continuous in the axial direction. Furthermore, the circumferential length of the retracted surface 16c is longer than the circumferential length of the retracted surface 16b.

[0117] The distance from the central axis Ax to the retraction surfaces 16b and 16c is D2 ( FIG. 16 ). The distance D2 is shorter than the distance D1. Therefore, the retraction surfaces 16b and 16c do not contact the frame 81. The retraction surface 16b is also referred to as a first retraction surface, and the retraction surface 16c is also referred to as a second retraction surface.

[0118] A step surface 15e is formed between the contact surface 15a and the retraction surface 16b that are adjacent in the axial direction on the outer peripheral surface of the stator core 10. The step surface 15e is an end surface that is perpendicular to the axial direction, extends in the circumferential direction, and has a width in the radial direction.

[0119] A step surface 15f is formed between the contact surface 15b and the retraction surface 16b that are adjacent in the circumferential direction on the outer peripheral surface of the stator core 10. The step surface 15f is an end surface that is perpendicular to the circumferential direction, extends in the axial direction, and has a width in the radial direction.

[0120] A step surface 15g is formed between the contact surface 15b and the retraction surface 16c that are adjacent in the axial direction on the outer peripheral surface of the stator core 10. The step surface 15g is an end surface that is perpendicular to the axial direction, extends in the circumferential direction, and has a width in the radial direction.

[0121] A step surface 15h is formed between the contact surface 15c and the retraction surface 16c that are adjacent in the circumferential direction on the outer peripheral surface of the stator core 10. The step surface 15h is an end surface that is perpendicular to the circumferential direction, extends in the axial direction, and has a width in the radial direction.

[0122] Grooves 18 are formed on the outer peripheral surface of stator core 10. The shape and arrangement of grooves 18 are as described in embodiment 1. However, grooves 18 do not necessarily have to be provided on stator core 10.

[0123] 17 is drawn in perspective, the axial length LS1 of the step portion S1 and the axial length LA2 of the second core portion A2 have a relationship of LS1≦LA2. Similarly, the axial length LS2 of the step portion S2 and the axial length LA3 of the third core portion A3 have a relationship of LS2≦LA3.

[0124] That is, the step portion S1 may be formed on at least a portion of the second core portion A2 in the axial direction, and the step portion S2 may be formed on at least a portion of the third core portion A3 in the axial direction.

[0125] 18 is a cross-sectional view showing the teeth 12 and the insulating portions 20, taken along a plane perpendicular to the extending direction of the teeth 12. The tooth steps 121 and 122 are formed between the side surfaces 120 and the end surfaces 101 of the teeth 12.

[0126] Teeth step portion 121 has a side surface 121a facing slot 13 and a step surface 121b facing the axial direction. Teeth step portion 122 has a side surface 122a facing slot 13 and a step surface 122b facing the axial direction.

[0127] The teeth 12 have a width W1 in the first core portion A1, a width W2 in the second core portion A2, and a width W3 in the third core portion A3. The width W1 is the distance between the side surfaces 120, the width W2 is the distance between the side surfaces 121a, and the width W3 is the distance between the side surfaces 122a. The widths W1, W2, and W3 have a relationship of W1 > W2 > W3.

[0128] The body portion 22 (Figure 10) of the insulating portion 20 has a first surface 201 which is a plane covering the end faces 101 of the teeth 12, a second surface 202 which is a plane facing the slot 13, and a third surface 203 which extends from the first surface 201 to the second surface 202.

[0129] The third surface 203 of the insulating portion 20 extends to cover the tooth step portions 121, 122 of the teeth 12. Therefore, the insulating portion 20 has an engaging portion 22a that engages with the tooth step portion 121 of the teeth 12 and an engaging portion 22b that engages with the tooth step portion 122.

[0130] In the first embodiment described above, a single step S1 is formed at the axial end of the stator core 10 (see FIG. 11 ). This narrows the width W2 of the axial end of each tooth 12, which makes it easier for magnetic saturation to occur within the tooth 12 and increases iron loss. Furthermore, the volume of the engaging portion 22a of the insulating portion 20 that engages with the step S1 increases, increasing the amount of resin used.

[0131] In contrast, in the second embodiment, two steps S1, S2 are formed at the axial end of the stator core 10, so that the widths W2, W3 of the axial end of the teeth 12 are gradually narrowed. This makes it difficult for magnetic saturation to occur within the teeth 12, and it is possible to suppress an increase in iron loss. Furthermore, the volume of the engaging portions 22a, 22b of the insulating portion 20 that engage with the steps S1, S2 is reduced, so it is possible to reduce the amount of resin used.

[0132] 18 shows tooth step portions 121 and 122, but core-back step portions 111 and 112 (FIG. 6) are formed in the same manner. That is, core-back step portion 111 (FIG. 16) has an inner circumferential surface 111a (FIG. 19B) facing slot 13 and a step surface facing the axial direction. Core-back step portion 112 (FIG. 16) has an inner circumferential surface 112a (FIG. 19C) facing slot 13 and a step surface facing the axial direction.

[0133] In the stator core 10 of the second embodiment, the width W3 of the core back 11 is narrowest in the third core portion A3, and therefore suppressing stress concentration in the core back 11 becomes an issue.

[0134] Fig. 19(A) is a schematic diagram showing the contact portion between the first core portion A1 of the stator core 10 and the frame 81. Fig. 19(B) is a schematic diagram showing the contact portion between the second core portion A2 and the frame 81. Fig. 19(C) is a schematic diagram showing the contact portion between the third core portion A3 and the frame 81.

[0135] As described above, the second core portion A2 has a step portion S1 (FIG. 16), and the third core portion A3 has a step portion S2 (FIG. 16). Therefore, the minimum radial widths T1, T2, and T3 of the core back 11 in the first core portion A1, the second core portion A2, and the third core portion A3 satisfy the relationship T1 > T2 > T3.

[0136] When the stator core 10 is fixed to the frame 81 by shrink fitting, the stator core 10 is subjected to stress directed radially inward from the frame 81. The narrower the radial width of the core back 11, the more likely stress is to be concentrated on the inner peripheral portion of the core back 11 located at the circumferential center of the slot 13 (indicated by symbol Q in FIGS. 19A to 19C ).

[0137] Therefore, in embodiment 2, the circumferential length L1 of the contact surface 15a in the first core portion A1, the circumferential length L2 of the contact surface 15b in the second core portion A2, and the circumferential length L3 of the contact surface 15c in the third core portion A3 are made to satisfy L1 > L2 > L3.

[0138] Since the length L2 of the contact surface 15b of the core back 11 of the second core part A2 is shorter than the length L1 of the contact surface 15a of the first core part A1 (i.e., L1 > L2), the stress that the core back 11 of the second core part A2 receives from the frame 81 is reduced, and stress concentration can be avoided.

[0139] Furthermore, since the length L3 of the contact surface 15c of the third core portion A3 is shorter than the length L2 of the contact surface 15b of the second core portion A2 (i.e., L2 > L3), the stress that the core back 11 of the third core portion A3 receives from the frame 81 is reduced, and stress concentration can be avoided.

[0140] In this way, it is possible to suppress an increase in iron loss due to stress concentration on the core back 11, and to suppress an increase in iron loss in the stator core 10 as a whole.

[0141] Except for the above-mentioned points, the electric motor 3A of the second embodiment is configured similarly to the electric motor 3 of the first embodiment.

[0142] As described above, in the second embodiment, the stator core 10 has a first core portion A1, a second core portion A2, and a third core portion A3 in the axial direction. The first core portion A1 has a contact surface 15a, the second core portion A2 has a contact surface 15b and a retracted surface 16b, and the third core portion A3 has a contact surface 15c and a retracted surface 16c. The circumferential length L1 of the contact surface 15a, the circumferential length L2 of the contact surface 15b, and the circumferential length L3 of the contact surface 15c satisfy the relationship L1 > L2 > L3. The second core portion A2 has a step S1 formed therein such that the minimum radial width of the core back 11 is narrower in the second core portion A2 than in the first core portion A1, and the third core portion A3 has a step S2 formed therein such that the minimum radial width of the core back 11 is narrower in the third core portion A3 than in the second core portion A2. This shortens the circumferential length of the winding 30, suppresses magnetic saturation in the teeth 12, and further suppresses stress concentration in the core back 11.

[0143] Although the example in which the two-stepped step portions S1, S2 are provided at both axial ends of the stator core 10 has been described, the two-stepped step portions S1, S2 may be provided at only one axial end of the stator core 10. Furthermore, instead of the two-stepped step portions S1, S2, three or more step portions may be provided.

[0144] 20A is a plan view showing a stator core 10B according to a third embodiment. While the stator core 10 according to the first embodiment is formed by combining N split cores 14 in an annular shape, the stator core 10B according to the third embodiment is formed integrally in an annular shape. In other words, the stator core 10B according to the third embodiment is formed by stacking annular laminated elements in the axial direction.

[0145] The stator core 10B has an annular core back 11 and N teeth 12 extending radially inward from the core back 11. Slots 13 are formed between the teeth 12 adjacent to each other in the circumferential direction.

[0146] Crimping portions 11f and fitting holes 11g are formed on the core back 11. The crimping portions 11f secure the laminated elements that make up the core back 11 to one another. The fitting holes 11g fit into protrusions formed on the insulating portion 20 (FIG. 10). The grooves 18 described in the first embodiment are formed on the outer peripheral surface of the core back 11.

[0147] The crimped portions 11f are formed on both circumferential sides of the groove portion 18 in the core back 11. The fitting holes 11g are formed on the radially inner side of the groove portion 18. However, the positions of the crimped portions 11f and the fitting holes 11g are not limited to the positions described here.

[0148] Stator core 10B of embodiment 3 has first core portion A1 and second core portion A2, similar to stator core 10 of embodiment 1. Contact surface 15a (FIG. 4) is formed on the outer peripheral surface of first core portion A1, and contact surface 15b and retraction surface 16 are formed on the outer peripheral surface of second core portion A2.

[0149] The retraction surfaces 16 of the second core portion A2 are located on the outer peripheral surface of the second core portion A2 radially outside the teeth 12. The retraction surfaces 16 are preferably formed symmetrically with respect to the tooth center lines T. The contact surfaces 15b are located on the outer peripheral surface of the second core portion A2 radially outside the slots 13.

[0150] The second core portion A2 is formed with a step portion S1. The step portion S1 has a core-back step portion 111 and a tooth step portion 121.

[0151] In the third embodiment, stator core 10B is integrally formed in the circumferential direction, and therefore in the winding process, a winding nozzle is inserted through openings 13a of slots 13, and windings 30 are wound around teeth 12. Therefore, compared to stator core 10 ( FIG. 3 ) in which split cores 14 are combined, the arrangement density of windings 30 within slots 13 is relatively low.

[0152] In this case, the inner circumferential surface 110 of the core back 11 of the stator core 10 is formed as a curved surface. The curved surface is, for example, an arc surface. Furthermore, a curved corner C1 is formed between the inner circumferential surface 110 of the core back 11 of the stator core 10 and the side surface 120 of the tooth 12. The radius of curvature of the corner C1 can be relatively large.

[0153] 20B is a schematic diagram showing the stress distribution in the core back 11 of the second core portion A2. In FIG. 20B, the degree of stress concentration is represented by the density of dots, and the first core portion A1 is not shown.

[0154] The inner peripheral surface 111a of the core back 11 of the second core portion A2 is part of the core back step portion 111 (FIG. 20A), and the side surface 121a of the tooth 12 is part of the tooth step portion 121 (FIG. 20A).

[0155] The inner peripheral surface 111a of the core back 11 is formed as a curved surface, similar to the above-described inner peripheral surface 110. Furthermore, the radius of curvature of the corner C1 between the inner peripheral surface 111a of the core back 11 and the side surface 121a of the tooth 12 can be made relatively large, similar to the radius of curvature of the corner C1 between the above-described inner peripheral surface 110 and the side surface 120.

[0156] As shown in Figure 20 (B), since the inner surface 111a of the core back 11 is a curved surface, the stress that the second core portion A2 of the stator core 10B receives from the frame 81 is distributed evenly along the inner surface 111a of the core back step portion 111.

[0157] Furthermore, the second core portion A2 has an outer peripheral surface formed with the recessed surface 16 radially outward of the teeth 12, which reduces the stress that the stator core 10B receives from the frame 81. As a result, the stress at the inner peripheral portion of the core back 11 located at the circumferential center of the slot 13 can be reduced.

[0158] Fig. 21(A) is a plan view showing a stator core 10G of Comparative Example 3. Fig. 21(B) is a schematic diagram showing stress distribution in the core back 11 of the stator core 10G of Comparative Example 3. In Fig. 21(B), the degree of stress concentration is represented by the density of dots, and the first core portion A1 is not shown.

[0159] 21A , stator core 10G of Comparative Example 3 differs from stator core 10B of Embodiment 3 in that second core portion A2 does not have retracted surface 16. That is, in Comparative Example 3, the outer peripheral surface of core back 11 of second core portion A2, excluding groove portion 18, serves as contact surface 15.

[0160] In the stator core 10G of Comparative Example 3, the inner peripheral surface 111a of the core back 11 is also curved, so that the effect of distributing stress evenly along the inner peripheral surface 111a of the core back 11 can be obtained.

[0161] 20(B) and 21(B), it can be seen that the stator core 10B of the third embodiment shown in Fig. 20(B) has reduced stress, particularly in the inner peripheral portion of the core back 11 at the circumferential center of the slot 13. In the stator core 10B of the third embodiment, local stress concentration in the core back 11 can be effectively suppressed, and iron loss can be reduced.

[0162] Except for the points mentioned above, the electric motor of the third embodiment is configured similarly to the electric motor 3 of the first embodiment.

[0163] As described above, the stator core 10B of the third embodiment is integrally formed in the circumferential direction and has the first core portion A1 and the second core portion A2 in the axial direction. The first core portion A1 has the contact surface 15a, and the second core portion A2 has the contact surface 15b and the retracted surface 16, which is located radially outward of the teeth 12. Therefore, stress concentration in the inner peripheral portion of the core back 11 can be suppressed, and an increase in iron loss in the core back 11 can be suppressed.

[0164] Although it has been explained here that the second core portion A2 of the stator core 10B has a step portion S1, the second core portion A2 does not necessarily have to have the step portion S1 as long as it has a contact surface 15b and a retreat surface 16.

[0165] 22A is a plan view showing a stator core 10C according to a fourth embodiment. The stator core 10C according to the fourth embodiment is formed by combining N split cores 14 in an annular shape. Adjacent split cores 14 may be fixed together by welding or by the joints 11c (FIG. 4) described in the first embodiment.

[0166] Stator core 10C of embodiment 4 has a first core portion A1 and a second core portion A2, similar to stator core 10 of embodiment 1. Contact surface 15a (FIG. 4) is formed on the outer peripheral surface of first core portion A1, and contact surface 15b and retraction surface 16 are formed on the outer peripheral surface of second core portion A2.

[0167] The retracted surface 16 of the second core portion A2 is located radially outward from the circumferential center of the slot 13. In other words, the retracted surface 16 is located radially outward from the connecting surface 11e of the split core 14. The contact surface 15b is formed on the outer peripheral surface of the second core portion A2, closer to the teeth 12 than the retracted surface 16.

[0168] The second core portion A2 is formed with a step portion S1. The step portion S1 has a core back step portion 111 and a tooth step portion 121. The core back 11 is formed with the groove portion 18 described in the first embodiment, and the crimped portion 11f and the fitting hole 11g described in the third embodiment.

[0169] 22(B) is an enlarged view of a portion of the stator core 10C. The inner circumferential surface 110 of the core back 11 is a plane extending in a direction perpendicular to the side surfaces 120 of the teeth 12. A curved corner C1 is formed between the inner circumferential surface 110 of the core back 11 and the side surfaces 120 of the teeth 12. The corner C1 has a radius of curvature R1. The curved shape is, for example, an arc shape.

[0170] The portion of the core back 11 included in each split core 14 is referred to as the core back portion 11a. The inner circumferential surfaces 110 of adjacent core back portions 11a abut against each other at an abutment portion C2 at the circumferential center of the slot 13. The abutment portion C2 has a curved shape with a curvature radius R2. The curved shape is, for example, an arc shape.

[0171] The radius of curvature R1 of the corner C1 between the inner circumferential surface 110 of the core back 11 and the side surface 120 of the tooth 12 is smaller than the radius of curvature R2 of the abutting portion C2 of the inner circumferential surface 110 of the adjacent core back portion 11a. In other words, R1 < R2 holds. For example, if the radius of curvature R1 of the corner C1 is set to ½ of the wire diameter of the winding 30, the radius of curvature R2 of the abutting portion C2 is ½ or more of the wire diameter of the winding 30.

[0172] Because the stator core 10C is formed from the split cores 14, as described in the first embodiment, the windings 30 can be wound around the teeth 12 before the N split cores 14 are combined into an annular shape. In order to arrange the windings 30 in the slots 13 with high density, it is desirable that the radius of curvature R1 of the corners C1 between the inner circumferential surface 110 of the core back 11 and the side surfaces 120 of the teeth 12 be small.

[0173] On the other hand, it is desirable that the radius of curvature R2 of the contact portion C2 be large in order to reduce stress concentration on the inner peripheral portion of the core back 11. Therefore, by making the radii of curvature R1 and R2 satisfy the relationship R1 < R2, it is possible to improve the layout density of the windings 30 and reduce stress concentration in the core back 11.

[0174] Fig. 23(A) is a schematic diagram showing stress distribution in the second core portion A2 of stator core 10C. Fig. 23(B) is a schematic diagram showing stress distribution in the second core portion A2 of stator core 10H of Comparative Example 4. In Figs. 23(A) and 23(B), the degree of stress concentration is represented by the density of dots, and the first core portion A1 is not shown.

[0175] In Figure 23 (A), the inner surface 111a of the core back 11 of the second core portion A2 is part of the core back step portion 111 (Figure 22 (A)), and the side surface 121a of the tooth 12 is part of the tooth step portion 121 (Figure 22 (A)).

[0176] Corner portions C1 between the inner peripheral surface 111a of the core back 11 and the side surfaces 121a of the teeth 12 in the second core portion A2 have a radius of curvature R1 (FIG. 22B). Contact portions C2 of the inner peripheral surface 111a of the core back 11 in the second core portion A2 have a radius of curvature R2 (FIG. 22B). The radii of curvature R1 and R2 satisfy R1<R2.

[0177] 23B , stator core 10H of comparative example 4 differs from stator core 10C of embodiment 4 in that second core portion A2 does not have retracted surface 16. That is, in comparative example 4, the outer peripheral surface of core back 11 of second core portion A2, excluding groove portion 18, serves as contact surface 15. Therefore, stress tends to concentrate at corner portion C1 and abutment portion C2.

[0178] 23A, in the fourth embodiment, the recessed surfaces 16 are formed on the radially outer sides of the slots 13 of the second core portion A2, so that stress concentration at the corners C1 can be suppressed. As a result, stress concentration at the core back 11 can be suppressed, and an increase in iron loss can be suppressed.

[0179] Except for the points mentioned above, the electric motor of the fourth embodiment is configured similarly to the electric motor 3 of the first embodiment.

[0180] As described above, the stator core 10C of the fourth embodiment is configured by combining N split cores 14 in an annular shape and has a first core portion A1 and a second core portion A2 in the axial direction. The first core portion A1 has a contact surface 15a, and the second core portion A2 has a contact surface 15b and a retracted surface 16, with the retracted surface 16 located radially outside the slot 13. Furthermore, the radius of curvature R1 of the corner C1 between the inner circumferential surface 110 of the core back 11 and the side surface 120 of the tooth 12 is smaller than the radius of curvature R2 of the abutting portion C2 of the inner circumferential surface 110 of the adjacent core back portion 11a. Therefore, stress concentration in the core back 11 can be suppressed while improving the arrangement density of the windings 30 in the slot 13.

[0181] Here, it has been explained that the second core portion A2 of the stator core 10C has a step portion S1, but the second core portion A2 does not necessarily have to have the step portion S1 as long as it has a contact surface 15b and a retreat surface 16.

[0182] 24A is a plan view showing a stator core 10D according to a fifth embodiment. The stator core 10D according to the fifth embodiment is formed by combining N split cores 14 in an annular shape. Adjacent split cores 14 may be fixed together by welding or by the joints 11c (FIG. 4) described in the first embodiment.

[0183] Stator core 10D of embodiment 5 has a first core portion A1 and a second core portion A2, similar to stator core 10 of embodiment 1. Contact surface 15a (FIG. 4) is formed on the outer peripheral surface of first core portion A1, and contact surface 15b and retraction surface 16 are formed on the outer peripheral surface of second core portion A2.

[0184] The retraction surfaces 16 of the second core portion A2 are located on the outer peripheral surface of the second core portion A2 radially outside the teeth 12. The retraction surfaces 16 are preferably formed symmetrically with respect to the tooth center lines T. The contact surfaces 15b are located on the outer peripheral surface of the second core portion A2 radially outside the slots 13.

[0185] The second core portion A2 is formed with a step portion S1. The step portion S1 has a core back step portion 111 and a tooth step portion 121. The core back 11 is formed with the groove portion 18 described in the first embodiment, and the crimped portion 11f and the fitting hole 11g described in the third embodiment.

[0186] 24(B) is an enlarged view of a portion of the stator core 10D. As described in the fourth embodiment, the inner circumferential surface 110 of the core back portion 11a is a plane extending in a direction perpendicular to the side surface 120 of the tooth 12. A corner C1 between the inner circumferential surface 110 of the core back 11 and the side surface 120 of the tooth 12 has a radius of curvature R1. Abutment portions C2 of the inner circumferential surfaces 110 of adjacent core back portions 11a have a radius of curvature R2.

[0187] In the fifth embodiment, the radius of curvature R1 of the corner C1 between the inner circumferential surface 110 of the core back 11 and the side surface 120 of the tooth 12 is equal to or greater than the radius of curvature R2 of the abutting portion C2 of the inner circumferential surface 110 of the adjacent core back portion 11 a. In other words, R1≧R2 holds.

[0188] As explained in the fourth embodiment, in order to arrange the windings 30 in the slots 13 at high density, it is desirable that the radius of curvature R1 of the corner C1 between the inner surface 110 of the core back 11 and the side surface 120 of the teeth 12 be small.

[0189] On the other hand, in order to further improve the arrangement density of the windings 30 in the slots 13, it is desirable that the radius of curvature R2 of the contact portion C2 is also small so that the winding nozzle does not come into contact with the inner end of the connecting surface 11 e of the core back portion 11 a during the winding process.

[0190] Therefore, in the fifth embodiment, the radius of curvature R1 of the corner C1 is set to be equal to or larger than the radius of curvature R2 of the contact portion C2 (i.e., R1≧R2). For example, if the radius of curvature R1 of the corner C1 is set to be half the wire diameter of the winding 30, the radius of curvature R2 of the contact portion C2 is set to be equal to or smaller than half the wire diameter of the winding 30. This makes it possible to improve the arrangement density of the winding 30 in the slot 13.

[0191] On the other hand, if the curvature radius R2 of the abutment portion C2 is small, stress tends to concentrate on the inner peripheral portion of the core back 11. Therefore, in the fifth embodiment, a retraction surface 16 is formed on the outer peripheral surface of the core back 11, radially outward from the teeth 12. By forming the retraction surface 16 on the radially outward from the teeth 12, stress concentration on the inner peripheral portion of the core back 11 can be reduced.

[0192] Fig. 25(A) is a schematic diagram showing stress distribution in the second core portion A2 of stator core 10D. Fig. 25(B) is a schematic diagram showing stress distribution in the second core portion A2 of stator core 10I of Comparative Example 5. In Figs. 25(A) and 25(B), the degree of stress concentration is represented by the density of dots, and the first core portion A1 is not shown.

[0193] In Figure 25 (A), the inner surface 111a of the core back 11 of the second core portion A2 is part of the core back step portion 111 (Figure 24 (A)), and the side surface 121a of the tooth 12 is part of the tooth step portion 121 (Figure 24 (A)).

[0194] A corner C1 between the inner peripheral surface 111a of the core back 11 and the side surface 121a of the tooth 12 in the second core portion A2 has a radius of curvature R1. A contact portion C2 of the inner peripheral surface 111a of the core back 11 in the second core portion A2 has a radius of curvature R2. The radii of curvature R1 and R2 satisfy R1≧R2.

[0195] 25(B), stator core 10I of Comparative Example 5 differs from stator core 10D of Embodiment 5 in that the outer peripheral surface of core back 11 of second core portion A2 does not have retracted surface 16. That is, in Comparative Example 4, the outer peripheral surface of core back 11 of second core portion A2, excluding groove portion 18, serves as contact surface 15. Therefore, stress tends to concentrate at corner portion C1 and abutment portion C2, and stress concentration is particularly large at abutment portion C2.

[0196] 25A, in the fifth embodiment, the recessed surface 16 is formed on the radially outer side of the slot 13 of the second core portion A2, which alleviates stress concentration at the contact portion C2 and prevents excessive stress concentration. As a result, an increase in iron loss in the core back 11 can be suppressed.

[0197] Except for the points mentioned above, the electric motor of the fifth embodiment is configured similarly to the electric motor 3 of the first embodiment.

[0198] As described above, the stator core 10D of the fifth embodiment is configured by combining N split cores 14 and has a first core portion A1 and a second core portion A2 in the axial direction. The first core portion A1 has a contact surface 15a, and the second core portion A2 has a contact surface 15b and a retreat surface 16, with the retreat surface 16 located radially outward from the teeth 12. Furthermore, the radius of curvature R1 of the corner C1 between the inner circumferential surface 110 of the core back 11 and the side surface 120 of the tooth 12 is equal to or greater than the radius of curvature R2 of the abutting portion C2 of the inner circumferential surface 110 of the adjacent core back portion 11a. This allows for improved arrangement density of the windings 30 in the slots 13 while suppressing stress concentration in the core back 11.

[0199] Here, it has been explained that the second core portion A2 of the stator core 10D has a step portion S1, but the second core portion A2 does not necessarily have to have the step portion S1 as long as it has a contact surface 15b and a retreat surface 16.

[0200] Sixth Embodiment Fig. 26(A) is a plan view showing a stator core 10E according to a sixth embodiment. The stator core 10E according to the sixth embodiment is formed by combining N split cores 14 in an annular shape. Adjacent split cores 14 are fixed by welding at their connecting surfaces 11e. The connecting surfaces 11e are circumferential end surfaces of the core back portions 11a of the split cores 14.

[0201] Fig. 26(B) is a perspective view showing a portion (i.e., split core 14) of stator core 10E according to embodiment 6. As shown in Fig. 26(B), stator core 10E according to embodiment 6 has a first core portion A1 and a second core portion A2, similar to stator core 10 according to embodiment 1.

[0202] A contact surface 15a is formed on the outer peripheral surface of the first core portion A1, and a contact surface 15b and a retraction surface 16 are formed on the outer peripheral surface of the second core portion A2. The contact surfaces 15a, 15b and the retraction surface 16 are as described in the first embodiment.

[0203] A recessed surface 17 is formed on the outer peripheral surface of the stator core 10E along the connecting surface 11e. The recessed surface 17 is located radially inward of the contact surfaces 15a and 15b. The recessed surface 17 is located radially outward from the circumferential center of the slot 13.

[0204] The distance D3 ( FIG. 26A ) from the central axis Ax to the recessed surface 17 is equal to, for example, the distance D2 from the central axis Ax to the retracted surface 16. However, the distance D3 does not necessarily have to be equal to the distance D2, and it is sufficient if it is shorter than the distance D1 from the central axis Ax to the contact surface 15 b.

[0205] The recessed surface 17 extends in the axial direction along the connecting surface 11 e. It is desirable that the recessed surface 17 be formed from one end face 101 to the other end face 101 in the axial direction of the core back portion 11 a.

[0206] The core back 11 of the stator core 10E is formed with the groove portion 18 described in the first embodiment, and the crimped portion 11f and the fitting hole 11g described in the third embodiment. In addition, the second core portion A2 of the stator core 10E is formed with a step portion S1.

[0207] When welding the split cores 14, the joining surfaces 11e of the adjacent core back portions 11a are brought into contact with each other. Depending on the welding accuracy, a small protrusion may be formed on the outer circumferential side from the joining surfaces 11e of the core back portions 11a. If the protrusion protrudes radially outward beyond the outer circumferential surface of the stator core 10E, it will hinder the stator core 10E from being fixed to the frame 81.

[0208] Therefore, in the sixth embodiment, recessed surfaces 17 are formed along connecting surfaces 11e on the outer peripheral surface of stator core 10E. This prevents protrusions generated by welding from protruding radially outward beyond contact surfaces 15a, 15b of stator core 10E, and allows stator core 10E to be reliably fixed to frame 81.

[0209] In addition, since the outer surface of the core back 11 of the stator core 10E is formed with a recessed surface 16 in addition to a recessed surface 17, the stress that the core back 11 receives from the frame 81 can be reduced and stress concentration in the core back 11 can be suppressed.

[0210] Except for the points mentioned above, the electric motor of the sixth embodiment is configured similarly to the electric motor 3 of the first embodiment.

[0211] As described above, the stator core 10E of the sixth embodiment is formed by combining N split cores 14 and has a first core portion A1 and a second core portion A2 in the axial direction. The first core portion A1 has a contact surface 15a, and the second core portion A2 has a contact surface 15b and a retraction surface 16. In addition, the outer peripheral surface of the core back portion 11a has a recessed surface 17 that does not contact the frame 81 along the circumferential end of the core back portion 11a (i.e., the connecting surface 11e). This prevents protrusions generated by welding from protruding radially outward beyond the contact surfaces 15a and 15b, thereby enabling the stator core 10E to be reliably fixed to the frame 81.

[0212] Although it has been explained here that the second core portion A2 of the stator core 10E has a step portion S1, the second core portion A2 does not necessarily have to have the step portion S1 as long as it has a contact surface 15b, a retraction surface 16, and a recessed surface 17.

[0213] Seventh Embodiment Fig. 27(A) is a plan view showing a stator core 10F according to a seventh embodiment. The stator core 10F according to the seventh embodiment is formed by combining N split cores 14 in an annular shape.

[0214] The core back 11 of the stator core 10F is formed with the groove portion 18 described in the first embodiment, and the crimped portion 11f and the fitting hole 11g described in the third embodiment. In addition, the second core portion A2 of the stator core 10E is formed with a step portion S1.

[0215] Fig. 27(B) is a perspective view showing a part (i.e., split core 14) of stator core 10F according to embodiment 7. As shown in Fig. 27(B), stator core 10F according to embodiment 7 has a first core portion A1 and a second core portion A2, similar to stator core 10 according to embodiment 1.

[0216] A contact surface 15a is formed on the outer peripheral surface of the first core portion A1, and a contact surface 15b and a retraction surface 16 are formed on the outer peripheral surface of the second core portion A2.

[0217] In the seventh embodiment, the contact surface 15b of the second core portion A2 is formed in a region H1 radially outward of the teeth 12 and a region H2 radially outward of the slots 13. The region H2 is also a region along the connecting surface 11e of the core back portion 11a. The portion of the contact surface 15b located in the region H1 is referred to as a first portion, and the portion located in the region H2 is referred to as a second portion.

[0218] The retraction surface 16 of the second core portion A2 is formed between the region H1 and the region H2 in the circumferential direction. In other words, the retraction surface 16 of the second core portion A2 is formed between the first portion and the second portion of the contact surface 15b in the circumferential direction.

[0219] In addition to the stepped surfaces 15e and 15f described in the first embodiment, a stepped surface 15j is formed on the outer peripheral surface of the stator core 10F between the contact surface 15a in the region H1 and the retreated surface 16. Therefore, when the stator core 10F is fixed to the frame 81 by shrink fitting, the number of locations where the frame 81 engages (see FIGS. 9A and 9B) increases. This increases the fitting strength between the frame 81 and the stator core 10F.

[0220] 27(B), a convex portion 19a is formed on one coupling surface 11e of the core back portion 11a, and a concave portion 19b is formed on the other coupling surface 11e. Both the convex portion 19a and the concave portion 19b extend in the axial direction. In this case, when N split cores 14 are combined in an annular shape, the convex portion 19a of one core back portion 11a fits into the concave portion 19b of the adjacent core back portion 11a. The convex portion 19a and the concave portion 19b are also referred to as fitting portions.

[0221] N split cores 14 are combined into an annular shape while fitting the convex portions 19a and concave portions 19b of adjacent split cores 14 together to form stator core 10F, which is then shrink-fitted into frame 81. By fixing stator core 10F to frame 81, N split cores 14 are reliably fixed to one another. This eliminates the need for a welding process, thereby shortening the cycle time in the manufacturing process.

[0222] Here, since the stator core 10F is formed by integrating the N split cores 14 by fitting the protrusions 19a and recesses 19b, the circularity of the inner diameter of the stator core 10F is likely to decrease.

[0223] In the seventh embodiment, as described above, the number of engagement points between frame 81 and stator core 10F is increased, so that stator core 10F can be firmly fitted to frame 81. This allows stator core 10F to be integrated without reducing the roundness of the inner diameter of stator core 10F.

[0224] Here, it has been explained that the stator core 10F is assembled by fitting the convex portion 19a and the concave portion 19b of the split core 14 together, but instead of fitting the convex portion 19a and the concave portion 19b together, the split core 14 may be fixed by welding at the connecting surface 11e.

[0225] Except for the points mentioned above, the electric motor of the seventh embodiment is configured similarly to the electric motor 3 of the first embodiment.

[0226] As described above, stator core 10F of embodiment 7 is configured by combining N split cores 14 in an annular shape and has first core portion A1 and second core portion A2 in the axial direction. First core portion A1 has contact surface 15a, and second core portion A2 has contact surface 15b and retreat surface 16. Contact surface 15b is formed in region H1 radially outward of teeth 12 and region H2 radially outward of slots 13, and retreat surface 16 is formed between regions H1 and H2. This increases the number of engagement points between frame 81 and stator core 10F, allowing stator core 10F to be firmly fitted to frame 81.

[0227] Furthermore, since the split cores 14 have mating portions (e.g., convex portions 19a and concave portions 19b) that fit together, the split cores 14 can be fixed to the frame 81 while connected to each other via the mating portions. This eliminates the need for a welding process, and the cycle time of the manufacturing process can be shortened.

[0228] Although it has been described here that the second core portion A2 of the stator core 10F has a step portion S1, the second core portion A2 does not necessarily have to have the step portion S1 as long as it has a contact surface 15b and a retreat surface 16.

[0229] The features described in the first to seventh embodiments can be combined. For example, two or more stepped portions may be provided at the axial end portions of the stator cores of the third to seventh embodiments, as described in the second embodiment. The shapes of the stator cores described in the third to fifth embodiments may also be applied to the second, sixth, and seventh embodiments. The recessed surface 17 described in the sixth embodiment may also be provided on the stator cores of the second to fifth and seventh embodiments. The contact surface 15b and the retreated surface 16 described in the seventh embodiment may also be provided on the stator cores of the second to sixth embodiments.

[0230] In the first to seventh embodiments, it has been described that stator core 10 is fixed to frame 81 by shrink fitting. However, the method is not limited to shrink fitting, and it is sufficient that stator core 10 is fixed to frame 81 in a manner in which it is subjected to stress directed radially inward.

[0231] <Compressor> Next, a compressor 8 to which the electric motors of Embodiments 1 to 7 can be applied will be described. Fig. 28 is a cross-sectional view showing the configuration of compressor 8. Compressor 8 here is a rotary compressor, and has a sealed container 80, a compression mechanism 9 disposed within sealed container 80, an electric motor 3 that drives compression mechanism 9, and a shaft 90 that connects electric motor 3 and compression mechanism 9 so as to be capable of transmitting power. Shaft 90 is the shaft 90 shown in Fig. 1 and other figures, and is fitted into center hole 53 (Fig. 1) of rotor 5 of electric motor 3.

[0232] The sealed container 80 is a sealed container made of, for example, a steel plate, and covers the electric motor 3 and the compression mechanism 9. The sealed container 80 has an upper frame 82 and a lower frame 81. Attached to the upper frame 82 are a glass terminal 83 serving as a terminal for supplying power to the electric motor 3, and a discharge pipe 85 for discharging the refrigerant compressed in the compressor 8 to the outside. The electric motor 3 and the compression mechanism 9 are housed in the frame 81.

[0233] The compression mechanism 9 has an annular first cylinder 91 and a second cylinder 92 arranged along the shaft 90. The first cylinder 91 and the second cylinder 92 are fixed to the inside of the frame 81. An annular first piston 93 is arranged on the inner periphery of the first cylinder 91, and an annular second piston 94 is arranged on the inner periphery of the second cylinder 92. The first piston 93 and the second piston 94 are rotary pistons that rotate together with the shaft 90.

[0234] A partition plate 97 is provided between the first cylinder 91 and the second cylinder 92. The partition plate 97 is a disk-shaped member with a through-hole in the center. The cylinder chambers of the first cylinder 91 and the second cylinder 92 are provided with vanes (not shown) that divide the cylinder chambers into an intake side and a compression side. The first cylinder 91, the second cylinder 92, and the partition plate 97 are fixed together with bolts 98.

[0235] An upper frame 95 is disposed above the first cylinder 91 so as to close the upper side of the cylinder chamber of the first cylinder 91. A lower frame 96 is disposed below the second cylinder 92 so as to close the lower side of the cylinder chamber of the second cylinder 92. The upper frame 95 and the lower frame 96 support the shaft 90 rotatably.

[0236] Refrigerating machine oil (not shown) for lubricating each sliding part of the compression mechanism 9 is stored in the bottom of the frame 81 of the sealed container 80. The refrigerating machine oil flows up through a hole 90a formed in the axial direction inside the shaft 90, and is supplied to each sliding part from oil supply holes 90b formed at multiple locations on the shaft 90.

[0237] The stator 1 of the electric motor 3 is attached to the inside of a frame 81 by shrink fitting. Electric power is supplied to the windings 30 of the stator 1 from glass terminals 83 attached to an upper frame 82. A shaft 90 is fixed in the central hole 53 of the rotor 5 (FIG. 1).

[0238] An accumulator 87 that stores refrigerant gas is attached to the frame 81. The accumulator 87 is held by, for example, a holder 86 provided on the outside of the frame 81. A pair of suction pipes 88, 89 are attached to the frame 81, and refrigerant gas is supplied from the accumulator 87 to cylinders 91, 92 via the suction pipes 88, 89.

[0239] As the refrigerant, for example, R410A, R407C, or R22 may be used, but from the viewpoint of preventing global warming, it is desirable to use a refrigerant with a low GWP (global warming potential). For example, the following refrigerants can be used as the low GWP refrigerant.

[0240] (1) First, a halogenated hydrocarbon having a carbon-carbon double bond in its composition, such as HFO (Hydro-Fluoro-Orefin)-1234yf (CF ３ CF=CH ２ ) can be used. The GWP of HFO-1234yf is 4. (2) Alternatively, a hydrocarbon having a carbon-carbon double bond in its composition, such as R1270 (propylene), may be used. The GWP of R1270 is 3, which is lower than that of HFO-1234yf, but its flammability is higher than that of HFO-1234yf. (3) Alternatively, a mixture containing at least one halogenated hydrocarbon having a carbon-carbon double bond in its composition or a hydrocarbon having a carbon-carbon double bond in its composition, such as a mixture of HFO-1234yf and R32, may be used. The above-mentioned HFO-1234yf is a low-pressure refrigerant and therefore tends to cause large pressure loss, which may lead to a decrease in the performance of the refrigeration cycle (especially the evaporator). Therefore, it is practically desirable to use a mixture of HFO-1234yf with R32 or R41, which are higher-pressure refrigerants than HFO-1234yf.

[0241] The basic operation of compressor 8 is as follows. Refrigerant gas supplied from accumulator 87 is supplied to each cylinder chamber of first cylinder 91 and second cylinder 92 through suction pipes 88 and 89. When electric motor 3 is driven and rotor 5 rotates, shaft 90 rotates together with rotor 5. First piston 93 and second piston 94 fitted to shaft 90 then rotate eccentrically within each cylinder chamber, compressing the refrigerant within each cylinder chamber. The compressed refrigerant passes through groove 18 of stator 1 (FIG. 1) and through holes 57 and 58 of rotor 5 (FIG. 2), rises within sealed container 80, and is discharged to the outside through discharge pipe 85.

[0242] The compressor in which the electric motor 3 is used is not limited to a rotary compressor, but may be, for example, a scroll compressor.

[0243] The electric motor 3 of each embodiment has high motor efficiency due to reduced iron loss, which can improve the operating efficiency of the compressor 8. Furthermore, the electric motor 3 of each embodiment has a high holding force of the stator core 10 by the frame 81, which can improve the reliability of the compressor 8.

[0244] <Refrigeration cycle device> Next, a refrigeration cycle device 400 having the compressor 8 shown in Fig. 28 will be described. Fig. 29 is a diagram showing the refrigeration cycle device 400. The refrigeration cycle device 400 is, for example, an air conditioner, but is not limited to this and may be, for example, a refrigerator.

[0245] 29 includes a compressor 401, a condenser 402 that condenses a refrigerant, a pressure reducing device 403 that reduces the pressure of the refrigerant, and an evaporator 404 that evaporates the refrigerant. The compressor 401, the condenser 402, and the pressure reducing device 403 are provided in an outdoor unit 410, and the evaporator 404 is provided in an indoor unit 420.

[0246] The compressor 401, the condenser 402, the pressure reducing device 403, and the evaporator 404 are connected by refrigerant piping 407 to form a refrigerant circuit. The compressor 401 is configured as the compressor 8 shown in Fig. 28. The refrigeration cycle apparatus 400 also includes an outdoor fan 405 facing the condenser 402 and an indoor fan 406 facing the evaporator 404.

[0247] The refrigeration cycle apparatus 400 operates as follows: The compressor 401 compresses the refrigerant it draws in and sends it out as high-temperature, high-pressure refrigerant gas. The condenser 402 exchanges heat between the refrigerant sent out from the compressor 401 and outdoor air sent by the outdoor air blower 405, condenses the refrigerant, and sends it out as liquid refrigerant. The pressure reducing device 403 expands the liquid refrigerant sent out from the condenser 402 and sends it out as low-temperature, low-pressure liquid refrigerant.

[0248] The evaporator 404 exchanges heat between the low-temperature, low-pressure liquid refrigerant sent from the pressure reducing device 403 and the indoor air, evaporating the refrigerant and sending it out as refrigerant gas. The air from which heat has been removed by the evaporator 404 is supplied into the room by the indoor fan 406.

[0249] Since the electric motor 3 described in each embodiment can be applied to the compressor 401 of the refrigeration cycle device 400, the operating efficiency and reliability of the refrigeration cycle device 400 can be improved.

[0250] Although the preferred embodiments have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various improvements and modifications can be made.

[0251] DESCRIPTION OF SYMBOLS 1, 1A stator, 3, 3A electric motor, 5 rotor, 8 compressor, 9 compression mechanism, 10, 10A, 10B, 10C, 10D, 10E, 10F stator core, 11 core back, 11a core back portion, 11c joint portion, 11d crimped portion, 11e connecting surface, 12 teeth, 13 slot, 14 divided core, 15a contact surface (first contact surface), 15b contact surface (second contact surface), 15c contact surface (third contact surface), 15e, 15f, 15g, 15h, 15j step surface (engagement surface), 16 retraction surface, 16b retraction surface (first retraction surface), 16c retraction surface (second retraction surface), 17 recessed surface, 18 Groove portion, 19a Convex portion (fitting portion), 19b Concave portion (fitting portion), 20 Insulating portion, 21 Wall portion, 22 Body portion, 23 Flange portion, 30 Winding, 41, 42 Laminated element, 50 Rotor core, 51 Magnet insertion hole, 52 Flux barrier, 53 Center hole, 55 Permanent magnet, 80 Sealed container, 81 Frame, 81a, 81b Deformation portion, 101 End face, 110 Inner peripheral surface, 111, 112 Core back step portion, 111a Inner peripheral surface, 111b Step surface, 120 Side surface, 121, 122 Teeth step portion, 121a, 122a Side surface, 121b, 122b Step surface, 400 Refrigeration cycle device, 401 compressor, 402 condenser, 403 pressure reducing device, 404 evaporator, A1 first core portion, A2 second core portion, A3 third core portion, S1 step portion (first step portion), S2 step portion (second step portion).

Claims

1. a stator core having an annular core back and slots formed on the inner circumferential side of the core back, and a winding housed in the slots; the stator core is fixed to the inside of a cylindrical frame in a state in which stress is applied inward in the radial direction of the stator core, the stator core has a first core portion located in a central portion of the stator core in an axial direction and a second core portion located at least at one end portion of the stator core in the axial direction, the first core portion has a first contact surface that contacts the frame, the second core portion has a second contact surface that contacts the frame and a retraction surface that is located radially inward of the second contact surface, a length L1 of the first contact surface in the circumferential direction of the stator core and a length L2 of the second contact surface in the circumferential direction satisfy L1>L2, the stator core has a region where the first contact surface and the second contact surface are continuous in the axial direction, The second core portion of the stator core has a stepped portion formed therein such that the minimum width of the core back in the radial direction is narrower in the second core portion than in the first core portion. Stator.

2. The retraction surface is spaced apart from the frame in the radial direction. The stator according to claim 1 .

3. the stator core has teeth extending radially inward from the core back and adjacent to the slots, The retraction surfaces are formed symmetrically with respect to the circumferential center of the teeth. The stator according to claim 1 .

4. the second core portions are formed at both ends of the stator core in the axial direction, The step portions are formed in the second core portion at both ends of the stator core in the axial direction. A stator according to any one of claims 1 to 3.

5. the stator core has a third core portion located closer to an end of the stator core in the axial direction than the first core portion and the second core portion, the third core portion has a third contact surface that contacts the frame and a retraction surface that is located radially inward of the third contact surface, a step portion is formed in the third core portion of the stator core such that the minimum width of the core back in the radial direction is narrower in the third core portion than in the second core portion, The length L1 of the first contact surface in the circumferential direction, the length L2 of the second contact surface in the circumferential direction, and the length L3 of the third contact surface in the circumferential direction satisfy the relationship L1>L2>L3. A stator according to any one of claims 1 to 3.

6. The stator core is integrally formed in an annular shape, the stator core has teeth extending radially inward from the core back and adjacent to the slots, The retracted surface is located on the outer side of the tooth in the radial direction. A stator according to any one of claims 1 to 3.

7. the stator core has N divided cores (N is an integer of 2 or more) connected in an annular shape, Each of the N split cores has a core back portion extending in the circumferential direction and teeth extending radially inward from the core back portion. A stator according to any one of claims 1 to 3.

8. a corner between the core back portion and the tooth has a radius of curvature R1; a contact portion where inner circumferential surfaces of the core back portions of adjacent split cores contact each other has a radius of curvature R2, R1<R2 holds true, The withdrawal surface is located on the radially outer side of the slot.

8. The stator according to claim 7.

9. a corner between the core back portion and the tooth has a radius of curvature R1; a contact portion where inner circumferential surfaces of the core back portions of adjacent split cores contact each other has a radius of curvature R2, R1≧R2 holds true, The retracted surface is located on the outer side of the tooth in the radial direction.

8. The stator according to claim 7.

10. A recessed surface that does not come into contact with the frame is formed on the outer peripheral surface of the core back portion along an end portion in the circumferential direction of the core back portion.

8. The stator according to claim 7.

11. the second contact surface of the second core portion has a first portion located radially outward of the teeth and a second portion located radially outward of the slots, The retraction surface of the second core portion is formed between the first portion and the second portion of the second contact surface in the circumferential direction.

8. The stator according to claim 7.

12. Adjacent divided cores of the N divided cores have mating portions that engage with each other.

8. The stator according to claim 7.

13. The winding is wound on the stator core in a concentrated winding manner. A stator according to any one of claims 1 to 3.

14. The step portion is formed on the side of the second core portion facing the slot. A stator according to any one of claims 1 to 3.

15. The rotor comprises an annular stator core having slots and a winding housed in the slots, the stator core is fixed to the inside of a cylindrical frame in a state in which stress is applied inward in the radial direction of the stator core, the stator core has a first core portion and a second core portion located closer to an end of the stator core in an axial direction than the first core portion, the first core portion has a first contact surface that contacts the frame, the second core portion has a second contact surface that contacts the frame and a retraction surface that is located radially inward of the second contact surface, a length L1 of the first contact surface in the circumferential direction of the stator core and a length L2 of the second contact surface in the circumferential direction satisfy L1>L2, the stator core has a region where the first contact surface and the second contact surface are continuous in the axial direction, the stator core has N divided cores (N is an integer of 2 or more) connected in an annular shape, Each of the N split cores has a core back portion extending in the circumferential direction and teeth extending radially inward from the core back portion, a corner between the core back portion and the tooth has a radius of curvature R1; a contact portion where inner circumferential surfaces of the core back portions of adjacent split cores contact each other has a radius of curvature R2, R1<R2 holds true, The withdrawal surface is located on the radially outer side of the slot. Stator.

16. The rotor comprises an annular stator core having slots and a winding housed in the slots, the stator core is fixed to the inside of a cylindrical frame in a state in which stress is applied inward in the radial direction of the stator core, the stator core has a first core portion and a second core portion located closer to an end of the stator core in an axial direction than the first core portion, the first core portion has a first contact surface that contacts the frame, the second core portion has a second contact surface that contacts the frame and a retraction surface that is located radially inward of the second contact surface, a length L1 of the first contact surface in the circumferential direction of the stator core and a length L2 of the second contact surface in the circumferential direction satisfy L1>L2, the stator core has a region where the first contact surface and the second contact surface are continuous in the axial direction, the stator core has N divided cores (N is an integer of 2 or more) connected in an annular shape, Each of the N split cores has a core back portion extending in the circumferential direction and teeth extending radially inward from the core back portion, a corner between the core back portion and the tooth has a radius of curvature R1; a contact portion where inner circumferential surfaces of the core back portions of adjacent split cores contact each other has a radius of curvature R2, R1≧R2 holds true, The retracted surface is located on the outer side of the tooth in the radial direction. Stator.

17. A stator according to any one of claims 1 to 3; a rotor disposed inside the stator; An electric motor equipped with

18. an electric motor according to claim 17; a compression mechanism driven by the electric motor; A compressor equipped with

19. A compressor comprising the compressor according to claim 18, a condenser, a pressure reducing device, and an evaporator. Refrigeration cycle equipment.