Electric motor

Abstract

To provide an electric motor capable of reducing the number of components and the number of assembling steps.SOLUTION: An electric motor 10 comprises: a rotor housing 28 fixed on a motor shaft; a stator core 34 housed inside the rotor housing; a first bearing 50 and a second bearing 52 for rotatably supporting the motor shaft; a bearing holder 18 having a first bearing housing part for housing the first bearing; a center piece 20 having a second bearing housing part for housing the second bearing; a spring washer 66 for applying a pre-load to the second bearing; a circuit board 22 for feeding electricity to a stator; and a heat sink 26 thermally connected to the circuit board. The heat sink is electrically connected to the spring washer. The rotor housing is electrically connected to a ground part of the circuit board via the motor shaft, the second bearing, the spring washer, and the heat sink.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The technology of the present disclosure relates to electric motors. [Background technology]

[0002] Conventionally, there is an electric motor that includes a motor shaft, a rotor housing fixed to the motor shaft, a stator core accommodated inside the rotor housing, a first bearing and a second bearing that rotatably support the motor shaft, a bearing holder having a first bearing accommodating portion that accommodates the first bearing, a center piece that has a second bearing accommodating portion that accommodates the second bearing and supports the stator core and the bearing holder, and a circuit board that supplies power to the stator (see, for example, Patent Document 1).

[0003] This electric motor has a first ground path consisting of the rotor housing, motor shaft, first bearing, bearing holder, and conductive part to electrically connect the rotor housing to the ground part of the circuit board, and a second ground path consisting of the rotor housing, motor shaft, second bearing, and conductive part. The conductive part has a preload member that applies preload to the second bearing and a terminal member connected to the bearing holder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6638310 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described electric motor, in addition to the preload member, a terminal member, which is a separate member from the preload member, is used to electrically connect the rotor housing to the ground portion of the circuit board. Therefore, the number of parts and the number of assembly steps increase by the amount of the terminal member.

[0006] The technique of the present disclosure provides an electric motor that can reduce the number of components and assembly steps compared to conventional motors. [Means for solving the problem]

[0007] The technology disclosed herein is an electric motor (10, 80) including a motor shaft (12), a rotor housing (28) fixed to the motor shaft, a stator core (34) accommodated inside the rotor housing, a first bearing (50) and a second bearing (52) that rotatably support the motor shaft, a bearing holder (18) having a first bearing accommodating portion (46) that accommodates the first bearing, a center piece (20) having a second bearing accommodating portion (48) that accommodates the second bearing and that supports the stator core and the bearing holder, a spring washer (66) that applies a preload to the second bearing, a circuit board (22) that supplies power to the stator, and a heat sink (26) thermally connected to the circuit board, wherein the heat sink is electrically connected to the spring washer, and the rotor housing is electrically connected to a ground portion (54) of the circuit board via the motor shaft, the second bearing, the spring washer, and the heat sink.

[0008] According to the technique of the present disclosure, an electric motor is provided that can reduce the number of components and assembly steps compared to conventional electric motors. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a longitudinal sectional view of an electric motor according to a first embodiment of the disclosed technique. [Figure 2] FIG. 2 is an exploded perspective view showing the state before the wave washer and the heat sink are assembled to the center piece. [Figure 3] FIG. 2 is an enlarged longitudinal sectional view of part A in FIG. [Figure 4] FIG. [Figure 5]FIG. 2 is a vertical cross-sectional view showing a ground path of the electric motor. [Figure 6] FIG. 10 is an enlarged longitudinal cross-sectional view of a main part of an electric motor according to a second embodiment of the disclosed technique. [Figure 7] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] First, a first embodiment of the technique of the present disclosure will be described.

[0011] 1, an electric motor 10 according to the first embodiment includes a motor shaft 12, a rotor 14, a stator 16, a bearing holder 18, a center piece 20, a circuit board 22, a circuit case 24, and a heat sink 26. In each drawing, arrow Z1 indicates one axial side of the electric motor 10, and arrow Z2 indicates the other axial side of the electric motor 10.

[0012] The motor shaft 12 is made of a metal such as iron. The rotor 14 has a cylindrical rotor housing 28 with an opening 28A and a rotor magnet 30 fixed to the inside of the peripheral wall of the rotor housing 28. The rotor housing 28 is made of a metal such as aluminum or iron. A cylindrical fixing portion 32 is formed in the center of the ceiling of the rotor housing 28, and the motor shaft 12 is fixed to the inside of the fixing portion 32 by press-fitting. The rotor housing 28 is electrically connected to the motor shaft 12 by fixing the motor shaft 12 to the fixing portion 32. "Electrically connected" means that they are connected in a conductive manner.

[0013] The stator 16 is housed inside the rotor housing 28. The stator 16 is disposed radially inside the rotor magnet 30 and facing the rotor magnet 30. The stator 16 has a stator core 34 and a plurality of windings 36. The stator core 34 is a laminated body made of metal, formed by stacking core sheets formed of, for example, electromagnetic steel sheets. The plurality of windings 36 are wound around a plurality of teeth 38 formed radially on the stator core 34, with resin insulators 40 interposed between them. The entire stator 16, including the stator core 34 and the plurality of windings 36, is annular.

[0014] The center piece 20 is made of resin. The center piece 20 has a main body 42 that faces the opening 28A of the rotor housing 28, and a cylindrical support portion 44 that protrudes from the center of the main body 42 toward the stator 16. The main body 42 is formed in a roughly disk shape with its thickness direction aligned with the axial direction of the electric motor 10. The main body 42 is sized to face the entire opening 28A of the rotor housing 28.

[0015] The bearing holder 18 is supported by the center piece 20 by being attached to the support part 44 from one axial side of the electric motor 10. The motor shaft 12 passes through the center of the bearing holder 18 and the center piece 20. The bearing holder 18 is made of a metal such as aluminum or iron. The outer peripheral surface of the bearing holder 18 is electrically connected to the inner peripheral surface of the stator core 34.

[0016] The bearing holder 18 and the support portion 44 are inserted inside the annular stator core 34. The stator core 34 is fixed to the main body portion 42, for example, by screws, and thereby the stator core 34 is supported by the center piece 20. A first bearing accommodating portion 46 is formed in the bearing holder 18, and a second bearing accommodating portion 48 is formed in the main body portion 42. The first bearing accommodating portion 46 is formed in a recess that opens to one axial side of the electric motor 10, and the second bearing accommodating portion 48 is formed in a recess that opens to the other axial side of the electric motor 10.

[0017] The first bearing receiving portion 46 receives a first bearing 50, and the second bearing receiving portion 48 receives a second bearing 52. The first bearing 50 and the second bearing 52 are each a ball bearing made of metal. Specifically, the ball bearings used for the first bearing 50 and the second bearing 52 have an outer ring, balls, and an inner ring. The outer ring, balls, and inner ring are made of a metal such as stainless steel. The outer ring, balls, and inner ring are in contact with each other and are electrically connected.

[0018] The motor shaft 12 is press-fitted inside the first bearing 50 and the second bearing 52. The motor shaft 12 is supported by the bearing holder 18 and the support portion 44 via the first bearing 50 and the second bearing 52, and the rotor 14 is rotatably supported with respect to the centerpiece 20. The first bearing 50 is housed in the first bearing housing portion 46, and is thereby electrically connected to the bearing holder 18. Furthermore, the first bearing 50 and the second bearing 52 are electrically connected to the motor shaft 12 by the motor shaft 12 being press-fitted inside the first bearing 50 and the second bearing 52.

[0019] The circuit board 22 is disposed on the opposite side of the main body 42 from the stator 16. The circuit board 22 is fixed to the main body 42, for example, by screws. The circuit board 22 is a board for supplying power to the stator 16. Specifically, the circuit board 22 is mounted with a plurality of switching elements for switching the current supplied to the plurality of windings 36. The current supplied to the plurality of windings 36 is switched by the plurality of switching elements, thereby forming a rotating magnetic field in the stator 16. Furthermore, the formation of the rotating magnetic field in the stator 16 generates attractive and repulsive forces between the stator 16 and the rotor 14, causing the rotor 14 to rotate.

[0020] The circuit case 24 is formed in a flat container shape and is attached to the main body 42 with its opening facing the main body 42. The circuit case 24 is disposed on the opposite side of the main body 42 from the stator 16, and houses the circuit board 22. The circuit case 24 is made of a metal such as aluminum or iron.

[0021] The heat sink 26 is made of a metal with high thermal conductivity, such as aluminum. The heat sink 26 is fixed to the circuit board 22 by screws or the like. The heat sink 26 is thermally connected to the circuit board 22. Specifically, the heat sink 26 is thermally connected to a plurality of switching elements mounted on the circuit board 22. "Thermal connection" means that the heat sink 26 is connected in a manner that allows heat transfer. The heat sink 26 is also electrically connected to a ground portion 54 of the circuit board 22. The ground portion 54 is electrically connected to a ground terminal of a connector provided on the circuit board 22.

[0022] 2, the heat sink 26 has a facing portion 56 that faces the main body portion 42 in the axial direction of the electric motor 10. The facing portion 56 has a size and shape that faces the entire main body portion 42. A through hole 58 that passes through the center of the facing portion 56 in the axial direction of the electric motor 10 is formed, and the motor shaft 12 is inserted into the through hole 58. The facing portion 56 extends around the motor shaft 12.

[0023] A plurality of crimped portions 60 are formed on the main body portion 42. The number of the crimped portions 60 may be any number equal to or greater than three. In the example shown in FIG. 2, the number of the crimped portions 60 is four. Each crimped portion 60 is formed as a protrusion that protrudes toward the other axial side of the electric motor 10. The opposing portion 56 has crimped holes 62 formed at positions corresponding to each crimped portion 60. The crimped holes 62 penetrate the electric motor 10 in the axial direction. The crimped portions 60 and the crimped holes 62 form fixing portions 64 that fix the heat sink 26 to the center piece 20. Each crimped portion 60 is inserted into the crimped hole 62, and the tip end of each crimped portion 60 is crimped by thermal crimping or the like, thereby fixing the heat sink 26 to the center piece 20 by the fixing portions 64 at three or more points in the circumferential direction of the motor shaft 12.

[0024] As shown in FIG. 3, a wave washer 66 is provided on the other axial side of the electric motor 10 relative to the second bearing 52. The wave washer 66 is an example of a "spring washer" according to the technology of the present disclosure. The wave washer 66 is formed in an annular shape and has a waved shape (see also FIG. 4). The motor shaft 12 is inserted inside the wave washer 66. The wave washer 66 is made of a metal such as stainless steel. The wave washer 66 is electrically connected to the second bearing 52 by contacting the outer ring of the second bearing 52.

[0025] The wave washer 66 is disposed between the second bearing 52 and the heat sink 26, and biases the second bearing 52 toward one axial side of the electric motor 10 relative to the heat sink 26. In other words, the wave washer 66 applies a preload to the second bearing 52 toward one axial side of the electric motor 10.

[0026] The portion of the facing portion 56 of the heat sink 26 that is located around the motor shaft 12 is formed as an overlap portion 68 that overlaps the wave washer 66 in the radial direction of the wave washer 66. The heat sink 26 is electrically connected to the wave washer 66 as the overlap portion 68 comes into contact with the wave washer 66. In other words, the heat sink 26 (specifically, the overlap portion 68) is directly connected to the wave washer 66 without any other member interposed therebetween.

[0027] 5, the electric motor 10 having the above configuration has an earth path 70 formed to electrically connect the rotor housing 28 and the stator core 34 to the ground portion 54 of the circuit board 22. Specifically, the rotor housing 28 is electrically connected to the ground portion 54 via the motor shaft 12, the second bearing 52, the wave washer 66, and the heat sink 26. The stator core 34 is also electrically connected to the ground portion 54 via the bearing holder 18, the first bearing 50, the motor shaft 12, the second bearing 52, the wave washer 66, and the heat sink 26.

[0028] Next, the effects of the first embodiment will be described.

[0029] As described above in detail, the electric motor 10 according to the first embodiment includes the metal wave washer 66 electrically connected to the second bearing 52, and the heat sink 26 is electrically connected to the wave washer 66. The rotor housing 28 is electrically connected to the ground portion 54 of the circuit board 22 via the motor shaft 12, the second bearing 52, the wave washer 66, and the heat sink 26. Therefore, compared to using a terminal member that is a separate member from the wave washer 66 in addition to the wave washer 66 to electrically connect the rotor housing 28 to the ground portion 54, the number of components and the number of assembly steps can be reduced.

[0030] Furthermore, the stator core 34 is electrically connected to the ground portion 54 via the bearing holder 18, the first bearing 50, the motor shaft 12, the second bearing 52, the wave washer 66, and the heat sink 26. Therefore, compared to using a terminal member in addition to the wave washer 66 to electrically connect the stator core 34 to the ground portion 54, the number of parts and the number of assembly steps can be reduced.

[0031] Furthermore, the heat sink 26 is fixed to the center piece 20 by fixing portions 64 at three or more points in the circumferential direction of the motor shaft 12. Therefore, the parallelism of the heat sink 26 to the center piece 20, and therefore the parallelism of the wave washer 66, can be ensured, and the wave washer 66 can apply a preload to the second bearing 52 with high precision.

[0032] Furthermore, the heat sink 26 is directly connected to the wave washer 66. Therefore, the heat sink 26 can be electrically connected to the wave washer 66 without forming a terminal portion integrally with the wave washer 66.

[0033] Furthermore, the heat sink 26 has an overlap portion 68 that overlaps the wave washer 66 in the radial direction of the wave washer 66, and the overlap portion 68 is electrically connected to the wave washer 66. Therefore, by using the heat sink 26, the wave washer 66 can be electrically connected to the ground portion 54.

[0034] Next, a modification of the first embodiment will be described.

[0035] In the first embodiment, an annular wave washer 66 is used to apply a preload to the second bearing 52, but a spring washer having a shape other than the annular wave washer 66 may be used as long as it can apply a preload to the second bearing 52. For example, a spring washer having a twisted shape with part of the washer broken off may be used as the spring washer.

[0036] In addition, in the first embodiment, the fixing portion 64 having the crimping portion 60 and the crimping hole 62 is used to fix the heat sink 26 to the center piece 20, but for example, a screw or the like may be used as the fixing portion 64.

[0037] [Second embodiment] Next, a second embodiment of the technique of the present disclosure will be described.

[0038] As shown in Figures 6 and 7, the electric motor 80 according to the second embodiment has the following configuration changes compared to the electric motor 10 according to the first embodiment. The following describes the differences between the second embodiment and the first embodiment. In the second embodiment, a terminal member 100 is used instead of the wave washer 66 (see Figures 1 to 5) of the first embodiment. The terminal member 100 has a configuration in which the wave washer 66 and a terminal portion 102 are integrally formed. The terminal member 100 is made of metal, for example, stainless steel.

[0039] The wave washer 66 is provided on one axial side of the electric motor 80 with respect to the second bearing 52. The motor shaft 12 is inserted inside the wave washer 66. The wave washer 66 comes into contact with the outer ring of the second bearing 52, and is thereby electrically connected to the second bearing 52.

[0040] The wave washer 66 is disposed between the second bearing 52 and the bottom of the second bearing accommodating portion 48, and biases the second bearing 52 toward the other axial side of the electric motor 80 with respect to the bottom of the second bearing accommodating portion 48. In other words, the wave washer 66 applies a preload to the second bearing 52 toward the other axial side of the electric motor 80.

[0041] The terminal portion 102 is formed in a tongue shape and extends from the wave washer 66 to the heat sink 26 side, passing between the second bearing 52 and the peripheral wall portion of the second bearing housing portion 48. The heat sink 26 has an extension portion 104 that extends toward the second bearing 52 along the radial direction of the electric motor 80. The extension portion 104 is a portion that extends toward the second bearing 52 side with respect to multiple heat dissipation protrusions 106 provided on the heat sink 26. The extension portion 104 is electrically connected to the terminal portion 102 by coming into contact with the terminal portion 102, and thereby the heat sink 26 is electrically connected to the wave washer 66. In other words, the heat sink 26 (specifically, the extension portion 104) is connected to the wave washer 66 via the terminal portion 102 that is formed integrally with the wave washer 66.

[0042] In the electric motor 80 configured as described above, the rotor housing 28 is electrically connected to the ground portion 54 via the motor shaft 12, the second bearing 52, the wave washer 66, the terminal portion 102, and the heat sink 26. The stator core 34 is also electrically connected to the ground portion 54 via the bearing holder 18, the first bearing 50, the motor shaft 12, the second bearing 52, the wave washer 66, the terminal portion 102, and the heat sink 26.

[0043] Next, the effects of the second embodiment will be described.

[0044] As described above in detail, the electric motor 80 according to the second embodiment includes the metal wave washer 66 electrically connected to the second bearing 52, and the heat sink 26 is electrically connected to the wave washer 66 via the terminal portion 102 formed integrally with the wave washer 66. The rotor housing 28 is electrically connected to the ground portion 54 of the circuit board 22 via the motor shaft 12, the second bearing 52, the wave washer 66, the terminal portion 102, and the heat sink 26. Therefore, the number of components and the number of assembly steps can be reduced compared to when a terminal member that is a separate component from the wave washer 66 is used in addition to the wave washer 66 to electrically connect the rotor housing 28 to the ground portion 54.

[0045] Furthermore, the stator core 34 is electrically connected to the ground portion 54 via the bearing holder 18, the first bearing 50, the motor shaft 12, the second bearing 52, the wave washer 66, the terminal portion 102, and the heat sink 26. Therefore, compared to using a terminal member that is a separate member from the wave washer 66 in addition to the wave washer 66 to electrically connect the stator core 34 to the ground portion 54, the number of parts and the number of assembly steps can be reduced.

[0046] The heat sink 26 also has an extension 104 that extends toward the second bearing 52, and the extension 104 is electrically connected to the terminal portion 102. Therefore, the terminal portion 102 can be electrically connected to the heat sink 26 without increasing the length of the terminal portion 102 by the amount that the extension 104 extends toward the second bearing 52.

[0047] The above describes one embodiment of the technology of the present disclosure, but the present invention is not limited to the above, and it goes without saying that the present invention can be implemented in various modifications within the scope of the gist of the present disclosure.

[0048] Below, supplementary notes are provided regarding the technology of the present disclosure. (Appendix 1) a motor shaft (12); a rotor housing (28) fixed to the motor shaft; a stator core (34) accommodated inside the rotor housing; a first bearing (50) and a second bearing (52) that rotatably support the motor shaft; a bearing holder (18) having a first bearing accommodating portion (46) for accommodating the first bearing; a center piece (20) that has a second bearing accommodating portion (48) that accommodates the second bearing and supports the stator core and the bearing holder; a spring washer (66) that applies preload to the second bearing; a circuit board (22) that supplies power to the stator; a heat sink (26) thermally connected to the circuit board; Equipped with the heat sink is electrically connected to the spring washer; The rotor housing is electrically connected to a ground portion (54) of the circuit board via the motor shaft, the second bearing, the spring washer, and the heat sink. Electric motor (10, 80). (Appendix 2) the stator core is electrically connected to the ground portion via the bearing holder, the first bearing, the motor shaft, the second bearing, the spring washer, and the heat sink; 1. An electric motor as defined in Appendix 1. (Appendix 3) The heat sink is directly connected to the spring washer. 10. The electric motor (10) according to claim 1 or 2. (Appendix 4) The heat sink has an overlap portion (68) that overlaps with the spring washer in the radial direction of the spring washer, The overlapping portion is electrically connected to the spring washer. 1. An electric motor as described in Appendix 3. (Appendix 5) The heat sink is fixed to the center piece by fixing portions (64) at three or more points in the circumferential direction of the motor shaft. 1. An electric motor according to claim 3 or 4. (Appendix 6) The heat sink is connected to the spring washer via a terminal portion (102) formed integrally with the spring washer. 10. The electric motor (10) according to claim 1 or 2. (Appendix 7) The heat sink has an extension (104) extending toward the second bearing, The extension portion is electrically connected to the terminal portion. 6. An electric motor as defined in Appendix 6. [Explanation of symbols]

[0049] 10...electric motor, 12...motor shaft, 14...rotor, 16...stator, 18...bearing holder, 20...center piece, 22...circuit board, 24...circuit case, 26...heat sink, 28...rotor housing, 28A...opening, 30...rotor magnet, 32...fixing portion, 34...stator core, 36...winding, 38...teeth, 40...insulator, 42...main body portion, 44...support portion, 46...first bearing accommodating portion, 48...second bearing accommodating portion, 50...first bearing, 52...second bearing, 54...ground portion, 56...opposing portion, 58...through hole, 60...crimping portion, 62...crimping hole, 64...fixing portion, 66...wave washer, 68...overlapping portion, 70...earth path, 100...terminal member, 102...terminal portion, 104...extension portion, 106...heat dissipation protrusion portion

Claims

1. a motor shaft (12); a rotor housing (28) fixed to the motor shaft; a stator core (34) housed inside the rotor housing; a first bearing (50) and a second bearing (52) for rotatably supporting the motor shaft; a bearing holder (18) having a first bearing accommodating portion (46) for accommodating the first bearing; a center piece (20) that has a second bearing accommodating portion (48) that accommodates the second bearing and supports the stator core and the bearing holder; a spring washer (66) for applying a preload to the second bearing; a circuit board (22) that supplies power to the stator; a heat sink (26) thermally connected to the circuit board; Equipped with the heat sink is electrically connected to the spring washer; The rotor housing is electrically connected to a ground portion (54) of the circuit board via the motor shaft, the second bearing, the spring washer, and the heat sink. Electric motor (10, 80).

2. the stator core is electrically connected to the ground portion via the bearing holder, the first bearing, the motor shaft, the second bearing, the spring washer, and the heat sink; 2. The electric motor according to claim 1.

3. The heat sink is directly connected to the spring washer.

2. The electric motor (10) of claim 1.

4. The heat sink has an overlap portion (68) that overlaps the spring washer in the radial direction of the spring washer, The overlapping portion is electrically connected to the spring washer.

4. The electric motor according to claim 3.

5. The heat sink is fixed to the center piece by fixing portions (64) at three or more points in the circumferential direction of the motor shaft.

4. The electric motor according to claim 3.

6. The heat sink is connected to the spring washer via a terminal portion (102) formed integrally with the spring washer. The electric motor (80) of claim 1.

7. The heat sink has an extension (104) extending toward the second bearing, The extension portion is electrically connected to the terminal portion.

7. The electric motor according to claim 6.

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