Rotating electric machine

Abstract

The housing and stator are securely fixed together while suppressing the effect of compressive stress generated in the stator core on motor efficiency. [Solution] The device comprises a housing body 11 that penetrates axially through a first opening 11a and a second opening 11b, a stator 2, a rotor 3, a first end cover 12 attached to the housing body 11 and closing the first opening 11a, and a second end cover 13 attached to the housing body 11 and closing the second opening 11b. The stator 2 has a stator core 21 and coil windings 22 wound around the teeth 212 of the stator core 21. The stator 2 is supported by the first and second end covers 12 and 13 on the inner diameter side relative to the housing body 11, with the yoke portion 211 sandwiched from both sides in the axial direction by the first and second end covers 12 and 13, and the rotor 3 is rotatably supported relative to the stator 2 by the first and second covers 12 and 13.

Description

Technical Field

[0001] The present invention relates to a rotating electric machine.

Background Art

[0002] As a method of fixing a stator to a housing, a fixing method by shrink fitting is generally adopted. By shrink fitting, the adhesion between the housing and the stator, specifically, between the housing and the stator core is enhanced, and direct cooling of the stator by the cooling water flowing through the water jacket inside the housing can be achieved, ensuring the cooling performance of the entire motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the housing and the stator are fixed by shrink fitting, the following problems occur. <00 , the housing compresses the stator core radially inward over its entire circumference, resulting in compressive stress in the stator core. This compressive stress occurs throughout the entire stator core and particularly increases at the inner peripheral portion of the stator core. The electromagnetic steel sheet, which is a constituent material of the stator core, has its magnetic properties degraded under the action of the compressive stress. Since the magnetic flux formed by the coil concentrates at the inner peripheral portion of the stator core, the influence of the degradation of the magnetic properties appears significantly. < & 30>

[0006] ​​​Secondly, the roundness of the inner surface of the stator core (hereinafter referred to as "inner surface roundness") depends on the inner surface roundness of the housing. If the inner surface roundness of the housing decreases due to insufficient machining accuracy, the inner surface roundness of the stator core will also decrease accordingly. There is a concern that a decrease in the inner surface roundness of the stator core may worsen motor vibration and noise.

[0007] In view of these circumstances, the present invention aims to provide a technology for securely fixing the housing and the stator while suppressing the influence of compressive stress generated in the stator core on iron loss and motor efficiency. [Means for solving the problem]

[0008] To solve the aforementioned problems, a rotating electric machine according to one embodiment of the present invention comprises a cylindrical housing having openings on one side and the other side in the axial direction, the housing being open in the axial direction through a first opening which is the opening on one side and a second opening which is the opening on the other side; a stator disposed in the housing; a rotor disposed radially inward from the stator in the housing; a first cover attached to the housing on one side and closing the first opening; and a second cover attached to the housing on the other side and closing the second opening. The stator has a stator core having an annular outer ring portion and a plurality of protrusions projecting radially inward from the outer ring portion and arranged in the circumferential direction; and a coil wound around the plurality of protrusions. The stator is supported by the first and second covers on the radially inward side of the housing, with the outer ring portion sandwiched between the first and second covers on both sides in the axial direction, and the rotor is rotatably supported by the first and second covers relative to the stator. The housing and the first and second covers are fixedly coupled to each other. [Effects of the Invention]

[0009] According to one embodiment of the present invention, it is possible to suppress the increase in compressive stress in the inner circumference of the stator core where magnetic flux is concentrated. Therefore, while ensuring the fixing strength between the housing and the stator, it is possible to suppress the increase in iron loss due to compressive stress and improve motor efficiency.

[0010] Furthermore, it becomes possible to reduce the influence of the housing's inner circumference roundness on the stator core's inner circumference roundness. Therefore, it is possible to avoid situations where the motor's vibration and noise worsen due to insufficient housing machining accuracy or low inner circumference roundness of the housing. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing the overall configuration of a rotating electric machine (electric motor) according to one embodiment of the present invention. [Figure 2] Figure 1 is an enlarged cross-sectional view showing the configuration around the joint between the stator core and the end cover (first end cover) of the rotating electric machine. [Figure 3] This is a cross-sectional view of the first end cover. [Figure 4] This is a cross-sectional view of the housing body. [Figure 5] Figure 1 is a cross-sectional view of the rotating electric machine along line XX, showing its internal structure. [Figure 6] This is a cross-sectional view showing the overall configuration of a rotating electric machine related to a comparative example. [Figure 7] Figure 1 is a schematic diagram illustrating (a) the locations of magnetic flux concentration and (b) the locations where compressive stress occurs in the stator core of the rotating electric machine shown. [Figure 8] Figure 6 is a schematic diagram illustrating (a) the locations of magnetic flux concentration and (b) the locations of compressive stress generation in the stator core of a rotating electric machine (comparative example). [Figure 9] Figure 6 is a schematic diagram illustrating the misalignment (off-center) of the centerlines of the stator and rotor in a rotating electric machine (comparative example). [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings.

[0013] (Overall Configuration of Rotating Electric Machine) FIG. 1 is a cross-sectional view showing an overall configuration of a rotating electric machine M according to an embodiment of the present invention.

[0014] The rotating electric machine M according to the present embodiment (hereinafter sometimes referred to as an "electric motor" or simply a "motor") is a permanent magnet synchronous motor. As the rotating electric machine M, an electric motor with a driving method different from that of a permanent magnet synchronous motor, such as a wound field synchronous motor or an induction motor, can be adopted.

[0015] The rotating electric machine M according to the present embodiment is a so-called motor generator that can operate as both a prime mover and a generator. Not limited to this, the rotating electric machine M may be an electric motor that can operate only as a prime mover.

[0016] In the present embodiment, the rotating electric machine M constitutes a drive source of an electric vehicle or a hybrid vehicle. It is possible to transmit the output torque of the rotating electric machine M to the drive wheels of the vehicle and propel the vehicle forward or backward. Not limited to this, the rotating electric machine M can be applied as an in-vehicle actuator other than the drive source, and can also be applied to uses other than in-vehicle.

[0017] In the following description, the axial direction, radial direction, and circumferential direction are defined with reference to the rotation center axis A of the rotating electric machine M. Specifically, the direction along the rotation center axis A is defined as the "axial direction", the direction perpendicular to the rotation center axis A is defined as the "radial direction", and the direction along a circle centered on the rotation center axis A is defined as the "circumferential direction".

[0018] The electric motor M mainly includes a motor housing 1, a stator 2, a rotor 3, and a motor shaft 4.

[0019] The motor housing 1 is cylindrical in shape overall and is formed by dividing it into a housing body 11 and a pair of end covers 12 and 13 (first end cover 12, second end cover 13).

[0020] The housing body 11 is open at both ends in the axial direction, and a space is formed inside that penetrates in the axial direction. In other words, the housing body 11 has openings (first opening 11a, second opening 11b) on one side and the other side in the axial direction, and the internal space (hereinafter referred to as the "housing section") 11c is open in the axial direction through these openings 11a and 11b. The stator 2, rotor 3, and motor shaft 4 are housed in the housing section 11c.

[0021] The first end cover 12 is attached to the first opening 11a of the housing body 11, and the second end cover 13 is attached to the second opening 11b, respectively. The first and second openings 11a and 11b are closed by the first and second end covers 12 and 13, thus forming the motor housing 1. The first and second end covers 12 and 13 are fastened axially to the housing body 11 by fasteners such as bolts arranged in a circumferential direction. As a result, the first and second end covers 12 and 13 are coupled to the housing body 11 so as not to rotate in the circumferential direction.

[0022] The first and second end covers 12 and 13 can be configured not only as covers that simply close the openings 11a and 11b, but also as brackets used for mounting the electric motor M to the vehicle body.

[0023] In this embodiment, the housing body 11 corresponds to the "housing," the first end cover 12 corresponds to the "first cover," and the second end cover 13 corresponds to the "second cover."

[0024] The stator 2 is positioned concentrically with the housing body 11 on the inside (i.e., the inner diameter side) of the housing body 11 in the radial direction. Hereafter, the inside in the radial direction will be referred to as the "inner diameter side," and the outside as the "outer diameter side." As will be described later, the stator 2 is indirectly fixed to the housing body 11 via the first and second end covers 12 and 13, and is immobile relative to the housing body 11.

[0025] The rotor 3 is positioned concentrically with the stator 2 on the inner diameter side of the stator 2.

[0026] The support structures for the stator 2 and rotor 3 will be described in detail later.

[0027] The motor shaft 4 is press-fitted into a shaft insertion hole that penetrates the inner diameter of the rotor 3 in the axial direction, and is fixed to the rotor 3. As a result, the motor shaft 4 can rotate integrally with the rotor 3.

[0028] The motor shaft 4 is positioned coaxially with the rotational axis A and is supported by bearings (first bearing 51, second bearing 52) on each side of the rotor 3 in the axial direction relative to the motor housing 1. The first and second bearings 51 and 52 are supported by the first end cover 12 and the second end cover 13 of the motor housing 1, respectively, and the motor shaft 4 supports the rotor 3 so that it can rotate freely around the rotational axis A relative to the stator 2.

[0029] (Internal structure of a rotating electric machine) Figure 5 is a cross-sectional view of the electric motor M along the XX line shown in Figure 1, and shows the internal structure of the electric motor M.

[0030] As shown in Figure 5, the housing body 11 has an annular shape with a constant width in the radial direction when viewed in a plan view along the rotational axis A (i.e., in the axial direction). In this embodiment, the inner circumferential surface is perfectly circular in a plan view, and the overall shape is cylindrical. For cooling during the operation of the electric motor M, it is also possible to form a passage for circulating cooling water (hereinafter referred to as a "water jacket") in the housing body 11.

[0031] The stator 2 has a stator core 21 and coil windings 22 (Figure 1).

[0032] The stator core 21 consists of an iron core formed by laminating multiple thin electromagnetic steel sheets in the axial direction and joining them together, and has a yoke portion 211 and multiple teeth 212.

[0033] The yoke portion 211 is annular in shape and includes the outer circumferential surface of the stator core 21. In other words, the outer circumferential surface of the yoke portion 211 forms the outer circumferential surfaces of the stator 2 and the stator core 21.

[0034] The teeth 212 are formed on the inner diameter side of the yoke portion 211, arranged in a circumferential direction. Each of the multiple teeth 212 protrudes radially inward from the inner circumferential surface of the yoke portion 211 toward the rotational axis A.

[0035] Here, the stator core 21 corresponds to the "stator core" according to this embodiment, the yoke portion 211 corresponds to the "outer ring portion" according to this embodiment, and each of the multiple teeth 212 corresponds to the "protruding portion" according to this embodiment.

[0036] The coil winding 22 (Figure 1) is formed by winding a conductor around a plurality of teeth 212. In this embodiment, the coil winding 22 is formed, for example, by concentrated winding. The conductor wound around the teeth 212 is housed in the gap (hereinafter referred to as "slot") s formed between adjacent teeth 212. The teeth 212 and the coil winding 22 provided thereon form an electromagnetic coil. Figure 1 schematically shows the coil winding 22 with a dashed line. In other words, the dashed line in Figure 1 shows the relative position of the coil winding 22 with respect to the stator core 21.

[0037] The coil winding 22 can be formed not only by concentrated winding but also by distributed winding.

[0038] The rotor 3 has a rotor core 31 and a plurality of permanent magnets 32.

[0039] The rotor core 31 is cylindrical and fixed to the outer circumference of the motor shaft 4. As mentioned earlier, the rotor core 31 has a shaft insertion hole that penetrates its inner diameter in the axial direction, and the motor shaft 4 is inserted into and fixed to this shaft insertion hole.

[0040] The rotor core 31, like the stator core 21, is composed of an iron core formed by laminating multiple thin electromagnetic steel sheets in the axial direction and joining them together.

[0041] As shown in Figure 1, the motor shaft 4 has end plates made of non-magnetic material (first end plate 61, second end plate 62) attached to each side of the rotor 3 in the axial direction. The first and second end plates 61 and 62 sandwich the rotor core 31 or the multiple electromagnetic steel sheets that make up it from both sides in the axial direction.

[0042] The permanent magnets 32 are arranged in a circumferential direction on the outer circumference of the rotor core 31. Multiple permanent magnet insertion holes corresponding to each of the multiple permanent magnets 32 are formed on the outer circumference of the rotor core 31, and each permanent magnet 32 ​​is inserted into one of these multiple permanent magnet insertion holes and fixed to the stator core 31. The arrangement of the permanent magnets 32 is not limited to the embedded type shown in Figure 5, but may also be a surface type.

[0043] In this embodiment, two permanent magnets 32 are provided per pole, and the rotor 3 is configured as an 8-pole motor with a total of 16 permanent magnets 32. The permanent magnets 32 form one pole in pairs and are arranged in a V-shape that spreads outward in the radial direction. The total number of permanent magnets 32, the number per pole, and their arrangement in the rotor core 31 are not limited to this, and it is possible to have 4 poles or 1 magnet per pole.

[0044] (Stator support structure) The support structure of the stator 2 will be described in detail with reference to Figure 2. Figures 3 and 4 will be referenced as appropriate in the following description. Figure 3 is a cross-sectional view of the first end cover 12, and Figure 4 is a cross-sectional view of the housing body 11.

[0045] In this embodiment, the stator 2 is supported relative to the housing 1 by clamping the stator core 21 from both axial sides with the first and second end covers 12 and 13. Specifically, the yoke portion 211 of the stator core 21 is clamped by the first and second end covers 12 and 13.

[0046] The first end cover 12 and the second end cover 13 have substantially similar configurations with respect to the support of the stator 2. Therefore, the configurations of the first and second end covers 12 and 13 will be described using the first end cover 12 as a representative example. The following description of the first end cover 12 also applies to the second end cover 13.

[0047] As shown in Figure 2, the components of the first end cover 12 can be broadly classified as follows: the first end cover 12 has an outer cylindrical portion 121 located on the outer diameter side with respect to the rotational axis A, and a central plate-shaped portion 122 located on the inner diameter side of the outer cylindrical portion 121. The outer cylindrical portion 121 and the central plate-shaped portion 122 are concentric with each other, and the first end cover 12 as a whole has a bottomed cylindrical shape with the central plate-shaped portion 122 as its bottom. The outer cylindrical portion 121 forms the outer surface of this cylinder.

[0048] The central plate-shaped portion 122 is formed coaxially with the rotational axis A and has a through hole h that penetrates the inside and outside of the housing 1 in the axial direction (Figure 3). The first bearing 51 is positioned in the through hole h, and its radial position is determined by the circumferential wall surface of the central plate-shaped portion 122 that forms the through hole h. In other words, the motor shaft 4 is supported by the first bearing 51 relative to the first end cover 12.

[0049] The outer cylinder portion 121 has a larger dimension in the axial direction than the central plate-shaped portion 122. The outer end faces 121a and 122a of the outer cylinder portion 121 and the central plate-shaped portion 122 are approximately flush with each other in the axial direction relative to the inside and outside of the housing 1, in other words, the outer end faces 121a and 122a that correspond to the bottom of the cylinder (Figure 3). As a result, the inner end face 121b of the outer cylinder portion 121 extends to a position closer to the housing body 11 or stator 2 than the inner end face 122b of the central plate-shaped portion 122.

[0050] Here, a roughly cylindrical recess is formed by the inner circumferential surface 121c of the outer cylinder portion 121 facing inward in the direction of the rotational axis A, i.e., radially, and the inner end surface 122b of the central plate-shaped portion 122 facing in the direction of the stator 2, and the outer cylinder portion 121 forms the inner end surface 121b facing in the direction of the housing body 11 or the stator 2.

[0051] In this embodiment, the first end cover 12 abuts against the stator core 21 at the inner end surface 121b of the outer cylinder portion 121. Specifically, the first end cover 12 has an annular corner portion 121d that connects the inner end surface 121b and the inner circumferential surface 121c of the outer cylinder portion 121 and extends in the circumferential direction, and abuts against the yoke portion 211 of the stator core 21 at the annular corner portion 121d and the end surface portion in its vicinity.

[0052] As previously mentioned, the first end cover 12 and the second end cover 13 have substantially similar configurations with respect to supporting the stator 2, and the second end cover 13 has an annular corner portion similar to that of the first end cover 12. The first and second end covers 12 and 13 clamp the yoke portion 211 of the stator core 21 with the annular corner portion 121d and the end face portion in its vicinity. Figure 2 shows the portion where the first end cover 12 and the housing body 11 come into contact or press against each other, that is, the joint portion between the first end cover 12 and the housing body 11, indicated by a dotted frame W.

[0053] Thus, in this embodiment, the first and second end covers 12 and 13 contact the stator core 21 at their axially oriented end faces 121b, and contact a portion of the stator core 21 on the outer diameter side, specifically the outer peripheral edge and a portion of the yoke portion 211 in its vicinity. In other words, the first and second end covers 12 and 13 form an annular joint with respect to the stator core 21, with the annular corner portion 121d of the outer cylinder portion 121 as the inner peripheral edge.

[0054] In addition to the above, the first and second end covers 12 and 13 contact the housing body 11 at their radially facing end faces.

[0055] As shown in Figure 3, the first end cover 12 has an annular notch in the outer cylinder portion 121 that extends radially inward over a predetermined range from the outer circumferential surface. This notch forms an inner circumferential protrusion 1211 having an outer circumferential surface 121e that faces radially outward. The inner circumferential protrusion 1211 forms a stepped portion where the stepped surface, which is the outer circumferential surface 121e, faces radially outward, and the outer circumferential surface 121e connects two inner end surfaces 121b and 121f that are separated in the axial direction.

[0056] In contrast, as shown in Figure 4, the housing body 11 has an annular notch extending radially outward from the inner circumferential surface over a predetermined range, and this notch gives the outer peripheral projection 111 having an inner circumferential surface 11d facing radially inward. The outer peripheral projection 111 forms a stepped portion where the stepped surface, which is the inner circumferential surface 11d, faces radially inward, and the inner circumferential surface 11d connects two outer end surfaces 11e and 11f that are separated in the axial direction.

[0057] As shown in Figure 2, the first end cover 12 and the housing body 11 are joined to each other with their stepped portions interlocked, and the outer circumferential surface 121e of the inner circumferential protrusion 1211 of the first end cover 12 and the inner circumferential surface 11d of the outer circumferential protrusion 111 of the housing body 11 are in contact with each other.

[0058] A sealing material 125 is interposed between the outer circumferential surface 121e and the inner circumferential surface 11d. The sealing material 125 is provided around the entire circumference of both the inner circumferential protrusion 1211 and the outer circumferential protrusion 111. In this embodiment, a groove is formed in the outer circumferential surface 121e of the first end cover 12, and the sealing material 125 is fitted into and installed in this groove. The groove for installing the sealing material 125 can also be formed in the inner circumferential surface 11d of the housing body 11.

[0059] Furthermore, it is also possible to reverse the relative positions of the stepped portions of the first end cover 12 and the housing body 11. That is, a notch can be formed on the inner diameter side of the first end cover 12 to form an inner circumferential surface facing radially inward on the first end cover 12, while a notch can be formed on the outer diameter side of the housing body 11 to form an outer circumferential surface facing radially outward on the housing body 11.

[0060] In addition to the above, the positional relationship between the inner end face 121b and the outer circumferential surface 121e of the first end cover 12, or in other words, the positional relationship between the axial end face 121b that abuts the stator core 21 and the radial end face 121e that abuts the housing body 11 of the first end cover 12, is not limited to a relationship where they are adjacent to each other with a corner in between. The inner end face 121b and the outer circumferential surface 121e can also be formed with other end faces facing axially or radially in between.

[0061] As shown in Figure 2, in this embodiment, a radial gap is provided between the housing body 11 and the stator 2, and the heat transfer material 7 is sealed in this gap. In other words, the housing body 11 and the stator 2 are in contact with each other via the heat transfer material 7.

[0062] The heat transfer material 7 has a higher heat transfer coefficient to the constituent materials of the housing body 11 than air, promoting heat exchange between the housing body 11 and the stator 2. The heat transfer material 7 reduces the contact thermal resistance between the housing body 11 and the stator 2 to 0.001 m 2 It is preferable to reduce the power consumption to around kW.

[0063] The invention is not limited to this, and the housing body 11 and the stator 2 may be placed in close proximity to each other, or a gap may be formed between the housing body 11 and the stator 2, but without the heat transfer material 7 being interposed, and the housing body 11 and the stator 2 may be kept separated from each other by air.

[0064] Furthermore, as shown in the figure, an axial gap is provided between the end faces of the first end cover 12 and the housing body 11 that face each other in the axial direction.

[0065] Specifically, the first end cover 12 has axially oriented end faces (inner end faces 121b, 121f) on both the inner circumferential protrusion 1211 and its outer diameter side portion of the outer cylinder portion 121. On the other hand, the housing body 11 has axially oriented end faces (outer end faces 11e, 11f) on both the outer circumferential protrusion 111 and its inner diameter side portion. As shown in Figure 2, an axial gap is formed between the inner end face 121b and the outer end face 11f on the inner diameter side, and an axial gap is formed between the inner end face 121f and the outer end face 11e on the outer diameter side.

[0066] Here, the inner end faces 121d and 121f of the first end cover 12 correspond to "opposing end faces" that face the end face of the housing body 11 which is oriented in the axial direction.

[0067] (Explanation of action and effects) The electric motor M according to this embodiment has the above configuration. The effects obtained by this embodiment will be described below.

[0068] Firstly, the stator 2, specifically the yoke portion 211 of the stator core 21, is sandwiched between the first and second end covers 12 and 13, which sandwich the housing body 11 from both sides in the axial direction. The stator 2 is supported by the first and second end covers 12 and 13 on the inner diameter side of the housing body 11, and the rotor 3 is rotatably supported by the first and second end covers 12 and 13 on the inner diameter side of the stator 2.

[0069] This makes it possible to suppress the increase in compressive stress in the area where the magnetic flux formed in the yoke portion 211 by the electromagnetic coil (teeth 212, coil winding 22) is concentrated, specifically in the inner circumference of the stator core 21.

[0070] Figure 6 is a cross-sectional view showing the overall configuration of the electric motor M' according to the comparative example.

[0071] Figures 7 and 8 are schematic diagrams illustrating the locations where magnetic flux is concentrated and where compressive stress occurs in the stator core 21 of the electric motor M according to this embodiment and the electric motor M' according to a comparative example. Figure 7 shows these locations for the electric motor M according to this embodiment, and Figure 8 shows them for the electric motor M' according to a comparative example.

[0072] In Figures 7 and 8, elements or components corresponding to each other in electric motors M and M' are denoted by the same reference numeral to avoid redundant explanations.

[0073] As shown in Figure 6, in the comparative example, the motor housing 10 is configured as a housing body 101 and a pair of end covers 102 and 103. However, unlike in this embodiment, the housing body 101 is fixed to the stator 2 by shrink-fitting the housing body 101. Specifically, the housing body 101 is heated to expand radially, then fitted onto the outer circumference of the stator core 21, and then cooled to contract the housing body 101, thereby forming a fastening force between the housing body 101 and the stator core 21.

[0074] In shrink-fit fixing, the housing body 101 tightens the stator core 21 radially inward around its entire circumference, generating compressive stress in the stator core 21. This compressive stress occurs throughout the entire yoke portion 211 of the stator core 21, and is particularly increased in the inner circumference of the yoke portion 211, specifically at the base of the teeth 212. Figure 8(b) shows the force F exerted by the housing body 11 on the stator core 21 by shrink-fit, as well as the region R22 on the inner circumference of the yoke portion 211 where the compressive stress is particularly increased.

[0075] The electromagnetic steel sheet, which is a component of the stator core 21, experiences a decrease in magnetic properties under compressive stress. The effect of the decrease in magnetic properties is particularly pronounced in the inner circumference of the stator core 21, where the magnetic flux formed by the electromagnetic coils is concentrated. Figure 8(a) shows region R1 of the stator core 21 (yoke portion 211) where the magnetic flux is concentrated.

[0076] In contrast, in this embodiment, the points where force is applied to the stator core 21, in other words, the joints between the first and second end covers 12 and 13 and the housing body 11, are limited to a part of the outer diameter side of the yoke portion 211, specifically the outer peripheral edge and a part of the yoke portion 211 in its vicinity, as shown by the frame W in Figure 2. Furthermore, the direction of the force exerted by the first and second end covers 12 and 13 on the stator core 21, i.e., the fastening force, is set axially, unlike in the comparative example.

[0077] As a result, in this embodiment, as shown in Figure 7(b), the location where compressive stress occurs is limited to region R21 on the outer circumference of the yoke portion 211, where the first and second end covers 12 and 13 abut. On the other hand, in the parts of the stator core 21 other than region R21, the generation of compressive stress itself is suppressed. Region R21, that is, the outer circumference of the yoke portion 211, is located away from the inner circumference where magnetic flux is concentrated, and the magnetic flux density is sufficiently lower compared to the inner circumference, making it less susceptible to the effects of reduced magnetic properties.

[0078] Thus, according to this embodiment, the fixing strength between the housing body 11 and the stator 2 is ensured, and the stator 2 is firmly supported on the inner diameter side of the housing body 11, while suppressing the increase in iron loss that occurs in the electric motor M due to compressive stress in the stator core 21, thereby improving motor efficiency.

[0079] Secondly, the fixing structure that clamps the yoke portion 211 of the stator core 21 from both sides in the axial direction makes it possible to reduce the influence of the inner circumference roundness of the housing body 11 on the inner circumference roundness of the stator core 21. Therefore, it is possible to avoid situations in which the vibration and noise of the electric motor M worsen due to insufficient machining accuracy of the housing body 11 or low inner circumference roundness of the housing body 11.

[0080] In other words, it becomes unnecessary to perform excessively high-precision machining on the housing body 11 in order to ensure the inner circumference roundness of the stator core 21. This makes it possible to optimize the machining precision of the housing body 11 and reduce the manufacturing cost of the electric motor M.

[0081] Thirdly, by fixing the stator 2 by clamping it from both sides in the axial direction with the first and second end covers 12 and 13, it becomes possible to suppress the misalignment (off-center) that occurs between the stator 2 and the rotor 3.

[0082] Figure 9 shows the misalignment that occurs in the electric motor M' of the comparative example. Figure 9(a) shows the normal state where the centerlines of the stator 2 and rotor 3 coincide, while Figures 9(b) and (c) show the state where misalignment occurs. Figure 9(b) shows the misalignment in the eccentric mode, and Figure 9(c) shows the misalignment in the angular mode. In Figures 9(b) and (c), the original centerline of the rotor 3 is indicated by the symbol A, the centerline after eccentricity by the symbol A1, and the centerline after angular displacement by the symbol A2.

[0083] As mentioned earlier, in the comparative example, the housing body 11 and the stator 2 (stator core 21) are joined by shrink fitting, and the rotor 3 is supported by the first and second end covers 12 and 13. The housing body 11 and the first and second end covers 12 and 13 are then joined to each other by fasteners such as bolts.

[0084] Here, in order to align the housing body 11 with the first and second end covers 12 and 13, prior to fastening with bolts, knock pins fixed to the housing body 11 are inserted into engagement holes formed in the first and second end covers 12 and 13. However, deformation of the housing body 11 due to shrink fitting may cause misalignment of the knock pins.

[0085] In contrast, in this embodiment, the stator 2 is fixed by being clamped from both sides in the axial direction by the first and second end covers 12 and 13, without being restrained by the housing body 11 itself. Therefore, even if there is a misalignment of the first and second end covers 12 and 13 relative to the housing body 11, it is possible to suppress the occurrence of a misalignment (i.e., misalignment) between the stator 2 and the rotor 3.

[0086] Fourth, the yoke portion 211 of the stator core 21 was clamped around its entire circumference by the first and second brackets 12 and 13.

[0087] This makes it possible to support the stator 2 more firmly.

[0088] Fifth, the stator 2 is positioned relative to the housing body 11 with a radial gap in between.

[0089] This reliably prevents a load from being placed on the stator core 21 from the housing body 11, thereby avoiding a situation where compressive stress is generated in the stator core 21, and making it possible to further improve motor efficiency.

[0090] Sixth, a heat transfer material 7 was sealed in the gap (i.e., the radial gap) between the housing body 11 and the stator 2.

[0091] This promotes the cooling of the stator 2 by the cooling water flowing through the water jacket formed in the housing body 11, thereby enabling proper thermal management of the electric motor M.

[0092] Seventh, an axial gap was formed between the end faces of the housing body 11 facing axially (i.e., the outer end faces 11e, 11f) and the opposing end faces of the first or second end covers 12, 13 (i.e., the inner end faces 121d, 121f).

[0093] This allows the dimensional deviation, i.e., tolerance, that occurs in the stator 2 (stator core 21) in the axial direction to be absorbed by this gap, and enables the first and second end covers 12 and 13 to securely clamp the yoke portion 211 of the stator core 21.

[0094] In this embodiment, since the stator core 21 is constructed by laminating multiple thin electromagnetic steel sheets, the overall tolerance of the stator core 21 is the sum of the tolerances of the individual electromagnetic steel sheets. Therefore, it becomes difficult to control the tolerance of the stator core 21 as a whole. However, by forming an axial gap between the end face of the housing body 11 and the first and second end covers 12 and 13, it is possible to avoid a situation where the stator 2 does not fit between the first and second end covers 12 and 13, or fits difficult to fit, due to an excessively large overall tolerance.

[0095] Eighth, the annular corner portion 121d of the first or second end cover 12, 13, which connects the opposing end face 121b and the inner circumferential surface 121c of the cover 12, 13, is brought into contact with the yoke portion 211 of the stator core 21, and the stator core 21 is clamped by the annular corner portion 121d and the end face portion in its vicinity.

[0096] This concentrates the force exerted by the first and second end covers 12 and 13 on the stator core 21 on the yoke portion 211, particularly near its outer edge, making it possible to support the stator core 21 more reliably.

[0097] Ninth, the first or second end covers 12, 13 and the housing body 11 are arranged such that the inner circumferential surface 11d of the housing body 11 and the outer circumferential surface 121e of the cover 12, 13 facing this inner circumferential surface 11d are in contact.

[0098] This makes it possible to properly seal the joint between the housing body 11 and the first and second end covers 12 and 13.

[0099] Tenth, a sealing material 7 is placed between the inner circumferential surface 11d of the housing body 11 and the outer circumferential surfaces 121e of the first and second end covers 12 and 13, thereby airtightly sealing the space between the inner circumferential surface 11d and the outer circumferential surface 121e.

[0100] This makes it possible to more reliably seal the joint between the housing body 11 and the first and second end covers 12 and 13.

[0101] The embodiments described above are illustrative and do not limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, or modifications can be made without departing from the spirit of the invention. These embodiments or their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0102] M...Rotating electric machine, 1...Motor housing, 11...Housing body, 12...First end cover, 13...Second end cover, 2...Stator, 21...Stator core, 22...Coil winding, 211...Yoke section, 212...Teeth, 3...Rotor, 31...Rotor core, 32...Permanent magnet, 4...Motor shaft, 51...First bearing, 52...Second bearing, 61...First end plate, 62...Second end plate 7...heat transfer material. 11a...first opening, 11b...second opening, 11c...housing section, 11d...inner circumferential surface, 11e, 11f...outer end surface, 111...outer circumferential protrusion, 121...outer cylinder section, 122...central plate-shaped section, 121a...outer end surface, 121b, 121f...inner end surface, 121c...inner circumferential surface, 121d...annular corner section, 121e...outer circumferential surface, 1211...inner circumferential protrusion, 122a...outer end surface, 122b...inner end surface, 125...container material, 7...heat transfer material.

Claims

1. A housing that is cylindrical in shape and has openings on one side and the other side in the axial direction, with the housing opening open in the axial direction through the first opening on the one side and the second opening on the other side, A stator arranged in the aforementioned housing section, In the housing section, a rotor is positioned on the inner diameter side of the stator, A first cover is attached to one side of the housing and closes the first opening, The housing is fitted to the other side and includes a second cover that closes the second opening, The aforementioned stator is A stator core having an annular outer ring portion and a plurality of protrusions that project radially inward from the outer ring portion and are arranged in the circumferential direction, The coils are wrapped around the plurality of protrusions, The outer ring portion is sandwiched between the first and second covers from both sides in the axial direction and supported by the first and second covers on the inner diameter side relative to the housing. The rotor is rotatably supported by the first and second covers relative to the stator. A rotating electric machine in which the housing and the first and second covers are fixedly coupled to each other.

2. The rotating electric machine according to claim 1, wherein the stator is clamped around its entire circumference by the first and second covers.

3. The rotating electric machine according to claim 1, wherein the stator is disposed relative to the housing with the radial gap between them.

4. The rotating electric machine according to claim 3, wherein a heat transfer material having a higher heat transfer coefficient to the housing components than air is sealed in the radial gap.

5. The rotating electric machine according to claim 1, wherein an axial gap is formed between the end face of the housing facing one or the other side in the axial direction and the opposing end face of the first or second cover facing the end face.

6. The first or second cover is The opposing end face and the inner circumferential surface of the cover facing radially inward are connected, and the annular corner portion extends in the circumferential direction, The rotating electric machine according to claim 5, wherein the annular corner portion abuts against the outer ring portion of the stator core.

7. The rotating electric machine according to claim 1, wherein the first or second cover has an outer circumferential surface facing the inner circumferential surface of the housing which faces radially inward, and is arranged such that the outer circumferential surface is in contact with the inner circumferential surface.

8. The rotating electric machine according to claim 7, further comprising a sealing material that is arranged around the entire circumference between the inner circumferential surface and the outer circumferential surface and airtightly seals the space between the inner circumferential surface and the outer circumferential surface.

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