Stator structure and electric motor

Abstract

A stator structure (20) according to an embodiment comprises a stator (30) and a stator frame (40) that is formed into a bottomed cylindrical shape having an opening and accommodates the stator (30). The stator structure (20) also comprises: a filling resin (70) that fills a space between a bottom (41) of the stator frame (40) and the stator (30); and a bearing (BR) that is disposed on the bottom (41) of the stator frame (40) and has an outer diameter larger than the inner diameter of the stator (30). The bottom (41) of the stator frame (40) comprises: a retaining wall (42) that retains the outer peripheral surface of the bearing (BR); and a resin-contacting wall (43) that is provided between the retaining wall (42) and the stator (30), extends radially inward of the retaining wall (42), and contacts the filling resin (70).

Description

Stator assembly and electric motor

[0001] The present disclosure relates to a stator assembly and an electric motor.

[0002] A stator assembly as a component of an electric motor has been known (for example, see Patent Document 1). The stator assembly in Patent Document 1 includes a stator, a cylindrical stator frame with a bottom that houses the stator, and a retaining wall that protrudes axially from the bottom of the stator frame and retains a bearing. The bearing rotatably supports an output shaft of an electric motor that includes the stator assembly.

[0003] JP 2016-163393 A

[0004] The stator frame is filled with a filler resin, which contacts the outer peripheral surface of the retaining wall. In this configuration, when the filler resin is filled and hardened, the shrinking filler resin pulls the retaining wall radially outward. This can impair the inner diameter accuracy of the retaining wall. In light of this situation, the present disclosure provides a stator assembly and an electric motor with improved inner diameter accuracy of the retaining wall that holds the bearing.

[0005] One aspect of the present disclosure relates to a stator assembly. The stator assembly includes a stator, a stator frame formed in a cylindrical shape with an opening and a bottom to house the stator, a filled resin filled in the space between the bottom of the stator frame and the stator, and a bearing disposed at the bottom of the stator frame and having an outer diameter larger than the inner diameter of the stator. The bottom of the stator frame has a retaining wall that holds the outer peripheral surface of the bearing, and a resin contact wall that is provided between the retaining wall and the stator, extends radially inward from the retaining wall, and contacts the filled resin.

[0006] Another aspect of the present disclosure relates to an electric motor including the stator assembly described above.

[0007] According to the present disclosure, it is possible to provide a stator assembly and an electric motor in which the inner diameter precision of the retaining wall that holds the bearing is improved.

[0008] Fig. 1 is a cross-sectional view schematically showing the configuration of an example of a stator assembly according to the present disclosure. Fig. 2A is a perspective view schematically showing the configuration of a stator core and a stator frame of the stator assembly of Fig. 1. Fig. 2B is a perspective view schematically showing the configuration of a segment core of the stator core of Fig. 2A. Fig. 3A is a front view schematically showing the configuration of an example of an electric motor according to the present disclosure. Fig. 3B is a side view schematically showing the configuration of an example of an electric motor according to the present disclosure.

[0009] The following describes examples of embodiments of a stator assembly and an electric motor according to the present disclosure. However, the present disclosure is not limited to the examples described below. While the following description may use specific numerical values ​​and materials, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0010] (Stator Assembly) A stator assembly according to the present disclosure includes a stator, a stator frame, a filled resin, and a bearing.

[0011] The stator may have a stator core including a plurality of teeth, an insulator covering each tooth, and a winding wound around the insulator.

[0012] The stator core may have a back yoke portion formed in a substantially cylindrical shape, and each tooth portion may protrude radially inward from the back yoke portion. The back yoke portion may be a split type or an integrated type. The stator core may be formed by stacking multiple electromagnetic steel sheets. The insulator may be made of an insulating resin material. The winding body may be made of an insulated wire with an insulating coating. The winding body may be wound using a concentrated winding method or a distributed winding method.

[0013] The stator frame is formed in a cylindrical shape with a bottom and an opening, and houses the stator. The stator frame may be made of a material with high thermal conductivity, such as aluminum or an aluminum alloy. The thermal conductivity of the material of the stator frame may be higher than the thermal conductivity of the material of the stator core.

[0014] The filled resin is filled in the space between the bottom of the stator frame and the stator. The filled resin may also be filled in the space between the inner peripheral surface of the stator frame and the outer peripheral surface of the stator core, and the space between adjacent windings. The filled resin is typically a resin composition containing multiple components and may include epoxy resin, phenolic resin, polyester resin, polyurethane resin, or the like. The filled resin may also include a filler. The filler is preferably inorganic particles, such as aluminum hydroxide. The filler content of the filled resin may be 10% by weight or more and 50% by weight or less. The thermal conductivity of the filled resin may be higher than the thermal conductivity of the insulating coating material of the insulated wire that makes up the winding. The flexural modulus of the filled resin may be lower than the flexural modulus of the material that makes up the stator frame.

[0015] The bearing is disposed at the bottom of the stator frame and has an outer diameter larger than the inner diameter of the stator. The bearing may be, for example, a radial bearing or a thrust bearing. The bearing may be, for example, a ball bearing or a roller bearing. The bearing may rotatably support an output shaft of an electric motor including the stator assembly according to the present disclosure.

[0016] The bottom of the stator frame has a retaining wall and a resin contact wall. The retaining wall holds the outer peripheral surface of the bearing. The resin contact wall is provided between the retaining wall and the stator, extends radially inward from the retaining wall, and contacts the filled resin. With this configuration, the retaining wall that holds the bearing is isolated from the filled resin by the resin contact wall, and is not pulled by the filled resin that shrinks when hardened. Therefore, the stator assembly according to the present disclosure is less likely to lose the inner diameter accuracy of the retaining wall due to the mechanism described above in relation to the conventional technology, and can improve the inner diameter accuracy of the retaining wall.

[0017] The inner diameter of the resin contact wall may be smaller than the inner diameter of the stator. With this configuration, when filling the filled resin, for example, by using a jig that abuts against the inner peripheral edge of the resin contact wall and the inner peripheral surface of the stator, the area where the retaining wall is located can be isolated from the area where the filled resin is replenished. In this case, it is possible to prevent the filled resin from unintentionally filling the area where the retaining wall is located.

[0018] The inner diameter of the filled resin may be approximately the same as the inner diameter of the stator. Here, "approximately the same" means that the ratio of the inner diameter of the stator to the inner diameter of the filled resin is 0.9 or more and 1.1 or less. With this configuration, it is possible to ensure an adequate path for dissipating heat generated in the stator to the stator frame via the filled resin.

[0019] A gap may be provided between the resin contact wall and the bearing. For example, the gap may be formed by separating the resin contact wall and the bearing in the axial direction of the stator. With this configuration, even if the resin contact wall is pulled by the shrinking filled resin, this does not affect the bearing, and therefore the positional accuracy of the bearing is less likely to be impaired.

[0020] (Electric Motor) An electric motor according to the present disclosure includes a stator assembly according to the present disclosure. The electric motor according to the present disclosure may further include components such as a rotor, an output shaft (rotating shaft), another bearing, and a bracket. The rotor having an output shaft may be disposed in an internal space of the stator assembly. One end of the output shaft may be rotatably supported by the bearing. The other bearing may be fixed to a housing portion of the bracket and rotatably support the other end of the output shaft.

[0021] As described above, according to the present disclosure, by isolating the retaining wall that holds the bearing from the filled resin by the resin contact wall, it is possible to improve the inner diameter accuracy of the retaining wall. Furthermore, according to the present disclosure, it is possible to improve the concentricity between the output shaft of the electric motor and the electric motor mounting portion (i.e., the portion for mounting the electric motor to the target device), thereby suppressing rattle of the output shaft.

[0022] An example of a stator assembly and an electric motor according to the present disclosure will be described in detail below with reference to the drawings. The components described above can be applied to the components of the example stator assembly and electric motor described below. The components of the example stator assembly and electric motor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Of the components of the example stator assembly and electric motor described below, components that are not essential to the stator assembly and electric motor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and number of actual components.

[0023] In the following, first, the stator assembly 20 of this embodiment will be described, and then the electric motor 10 of this embodiment will be described.

[0024] (Stator Assembly) Fig. 1 is a cross-sectional view schematically showing the configuration of a stator assembly 20 according to an embodiment. Fig. 2A is a perspective view schematically showing the configuration of a stator core 31 and a stator frame 40 of the stator assembly 20. Fig. 2B schematically shows the configuration of a segment core 32 of the stator core 31. As shown in Figs. 1, 2A, and 2B, the stator assembly 20 according to this embodiment includes a stator 30, a stator frame 40, a printed wiring board 50, a connector 60, a filled resin 70, and a bearing BR.

[0025] The stator 30 has a stator core 31 including a plurality of teeth 32b, an insulator 33 covering each tooth 32b, and a winding body 34 wound around the insulator 33. A third space (not shown) is formed between adjacent winding bodies 34.

[0026] As shown in Fig. 2A, the stator core 31 of this embodiment is formed by joining together a plurality of segment cores 32. As shown in Fig. 2B, each segment core 32 has a yoke portion 32a, teeth portions 32b, and a flange portion 32c. Each segment core 32 is formed by laminating a plurality of electromagnetic steel sheets. Note that Fig. 2A shows only one insulator 33 and one winding body 34.

[0027] As shown in FIG. 1 , the stator frame 40 is formed in a cylindrical shape with a bottom and an opening, and houses the stator 30. A first space S1 is formed between the bottom 41 of the stator frame 40 and the stator 30. A second space (not shown) is formed between the inner peripheral surface of the stator frame 40 and the outer peripheral surface of the stator core 31. This second space corresponds to a groove (not shown) formed in the outer peripheral surface of the stator core 31. The stator frame 40 is made of, for example, an aluminum alloy. In this embodiment, the stator frame 40 is formed as a single unit, but this is not limiting. For example, in the stator frame 40, the portion covering the outer peripheral portion of the stator 30 and the bottom 41 housing the bearing BR may be separate bodies.

[0028] The printed wiring board 50 is electrically connected to the winding body 34. The printed wiring board 50 is disposed within the stator frame 40 closer to the opening than the stator 30. The printed wiring board 50 may be formed in an annular (donut-shaped), fan-shaped (arc-shaped), C-shaped, or other shape. The printed wiring board 50 has a hollow portion in the center, through which the output shaft 80 (see FIG. 3B ) of the electric motor 10 is inserted.

[0029] The connector 60 is electrically connected to the printed wiring board 50. The connector 60 is electrically connected to the winding body 34 via the printed wiring board 50, and is connected to a power source (not shown) for supplying power to the winding body 34. The connector 60 is disposed near the opening of the stator frame 40.

[0030] The first space S1, the second space S2, and the third space S3 are filled with the filling resin 70. The filling resin 70 is, for example, but not limited to, an epoxy resin. The filling resin 70 includes a filler. The filler content of the filling resin 70 is, for example, 10% by weight or more and 50% by weight or less.

[0031] The bearing BR is disposed on the bottom 41 of the stator frame 40. The bearing BR has an outer diameter larger than the inner diameter of the stator 30. The bearing BR in this embodiment is a radial ball bearing, but is not limited to this. One axial side of the bearing BR (the lower side in FIG. 1 ) is covered by a cover 44. The bearing BR rotatably supports the output shaft 80 (see FIG. 3B ) of the electric motor 10 in this embodiment.

[0032] The bottom 41 of the stator frame 40 has a retaining wall 42 and a resin contact wall 43. The retaining wall 42 holds the outer peripheral surface of the bearing BR. In this embodiment, the resin contact wall 43 is provided between the retaining wall 42 and the stator 30, extends radially inward from the retaining wall 42, and contacts the filled resin 70. The resin contact wall 43 contacts the filled resin 70 on the surface away from the retaining wall 42 (or the surface axially facing the stator 30). Preferably, a gap G is provided between the resin contact wall 43 and the bearing BR (enlarged view of FIG. 1). The axial dimension of this gap G may be 0.3 mm or more and 0.7 mm or less. Preferably, the inner diameter of the filled resin 70 is approximately the same as the inner diameter of the stator 30. That is, the ratio of the inner diameter of the filled resin 70 to the inner diameter of the stator 30 is preferably 0.9 or more and 1.1 or less. Preferably, the inner diameter of the resin contact wall 43 is smaller than the inner diameter of the stator 30 .

[0033] (Electric Motor) Figures 3A and 3B are front and side views schematically illustrating the configuration of an electric motor 10 according to an embodiment. As shown in Figures 3A and 3B, the electric motor 10 according to this embodiment includes components such as a rotor, an output shaft 80, another bearing, and a bracket in addition to the stator assembly 20 described above. The rotor, another bearing, and bracket are not shown. The rotor having the output shaft 80 is disposed in the internal space of the stator assembly 20. Both ends of the output shaft 80 are rotatably supported by the bearing BR and another bearing. The outer ring side of the other bearing is fixed to a housing portion of the bracket.

[0034] <<Supplementary Note>> The above description of the embodiment discloses the following techniques.

[0035] (Technology 1) A stator assembly of Technology 1 includes a stator, a stator frame formed in a cylindrical shape with an opening and a bottom that houses the stator, a filled resin that fills the space between the bottom of the stator frame and the stator, and a bearing that is disposed at the bottom of the stator frame and has an outer diameter larger than the inner diameter of the stator. The bottom of the stator frame has a retaining wall that holds the outer peripheral surface of the bearing, and a resin contact wall that is provided between the retaining wall and the stator, extends radially inward beyond the retaining wall, and comes into contact with the filled resin.

[0036] (Technology 2) In the stator assembly of Technology 2, in the stator assembly described in Technology 1, the inner diameter of the resin contact wall is smaller than the inner diameter of the stator.

[0037] (Technology 3) In the stator assembly of Technology 3, in the stator assembly according to Technology 1 or 2, the ratio of the inner diameter of the stator to the inner diameter of the filled resin is 0.9 or more and 1.1 or less.

[0038] (Technology 4) The stator assembly of Technology 4 is the stator assembly according to any one of Technologies 1 to 3, in which a gap is provided between the resin contact wall and the bearing.

[0039] (Technology 5) The electric motor of Technology 5 includes the stator assembly according to any one of Technology 1 to Technology 4.

[0040] The present disclosure can be used in stator structures and electric motors.

[0041] REFERENCE SIGNS LIST 10 Electric motor 20 Stator assembly 30 Stator 31 Stator core 32 Segment core 32a Yoke portion 32b Teeth portion 32c Flange portion 33 Insulator 34 Winding body 40 Stator frame body 41 Bottom portion 42 Holding wall 43 Resin contact wall 44 Lid 50 Printed wiring board 60 Connector 70 Filled resin 80 Output shaft BR Bearing G Gap S1 First space

Claims

1. A stator assembly comprising: a stator; a stator frame formed in a bottomed cylindrical shape with an opening for housing the stator; a filling resin filled in a space between the bottom of the stator frame and the stator; and a bearing disposed at the bottom of the stator frame and having an outer diameter larger than the inner diameter of the stator. The bottom of the stator frame has a holding wall for holding the outer peripheral surface of the bearing, and a resin contact wall provided between the holding wall and the stator, extending radially inward of the holding wall and contacting the filling resin.

2. The stator assembly according to claim 1, wherein the inner diameter of the resin contact wall is smaller than the inner diameter of the stator.

3. The stator assembly according to claim 1 or 2, wherein the ratio of the inner diameter of the stator to the inner diameter of the filling resin is 0.9 or more and 1.1 or less.

4. The stator assembly according to claim 1 or 2, wherein a gap is provided between the resin contact wall and the bearing.

5. An electric motor comprising the stator assembly according to claim 1 or 2.

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