Brushless motor

Abstract

Provided is a brushless motor (10), wherein: a motor holder (22) has an extension part (62) that extends outward from a cylindrical part (54) in the radial direction of the motor holder and is formed in a duct shape; the extension part has formed at the tip thereof an intake port (64) that opens toward one side in the axial direction of the motor holder and takes in cooling air; the extension part has formed on the inner side thereof a guide flow path (66) that extends along the radial direction of the motor holder and guides the cooling air taken in from the intake port to a body part (42) of a centerpiece (18); and the extension part is provided on the inner side thereof with a wall (68) that extends along the radial direction of the motor holder and closes a space between the intake port and a rotor housing (28).

Description

Brushless motor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-089218, filed May 31, 2024, the entire contents of which are incorporated herein by reference.

[0002] The technology of the present disclosure relates to a brushless motor.

[0003] In the technical field of brushless motors, a brushless motor is known that includes a rotor having a cylindrical rotor housing with a top end, a motor shaft disposed at the axial center of the rotor, a stator housed inside the rotor housing, a centerpiece having a main body facing an opening in the rotor housing and supporting the stator and motor shaft, a circuit board disposed on the opposite side of the main body from the stator, a heat sink disposed in the main body and connected to the circuit board so as to be heat transferable, and a motor holder having a cylindrical portion surrounding the rotor housing (see, for example, Japanese Patent No. 3426151). In this brushless motor, the motor holder has a duct-shaped extension portion extending radially outward from the cylindrical portion of the motor holder. The tip of the extension portion is formed with an intake opening that opens toward one axial side of the motor holder and allows cooling air to enter. A guide channel is formed inside the extension portion and extends radially along the motor holder to guide the cooling air taken in from the intake toward the main body.

[0004] As a result of detailed investigations by the inventors, the following problem was discovered: In the brushless motor described above, the cooling air guided by the guide flow path flows into the gap between the cylindrical portion and the rotor housing, which may result in an insufficient amount of cooling air being supplied to the objects to be cooled, including the stator, heat sink, and circuit board.

[0005] The technology disclosed herein provides a brushless motor that can prevent cooling air guided by a guide flow path from flowing into the gap between the cylindrical portion and the rotor housing, thereby ensuring that cooling air is supplied to objects to be cooled, including the stator, heat sink, and circuit board.

[0006] One aspect of the technology disclosed herein is a motor comprising: a rotor having a cylindrical rotor housing with a top; a motor shaft provided at the axial center of the rotor; a stator housed inside the rotor housing; a center piece having a main body portion facing an opening of the rotor housing and supporting the stator and the motor shaft; a circuit board arranged on the opposite side of the main body portion from the stator; a heat sink provided on the main body portion and connected to the circuit board so as to be able to conduct heat; and a motor holder having a cylindrical portion surrounding the rotor housing, is a brushless motor having an extension portion formed in a duct shape that extends from the cylindrical portion radially outward of the motor holder, an intake opening that opens toward one axial side of the motor holder and takes in cooling air is formed at the tip of the extension portion, a guide flow path is formed on the inside of the extension portion that extends along the radial direction of the motor holder and guides the cooling air taken in from the intake opening toward the main body portion, and a wall is provided on the inside of the extension portion that extends along the radial direction of the motor holder and blocks the space between the intake opening and the rotor housing.

[0007] According to the technology of the present disclosure, a brushless motor is provided that can prevent the cooling air guided by the guide flow path from flowing into the gap between the cylindrical portion and the rotor housing, thereby ensuring that the cooling air is supplied to the objects to be cooled, including the stator, heat sink, and circuit board.

[0008] FIG. 1 is a plan view of a brushless motor according to one embodiment of the technology disclosed herein. FIG. 1 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 2 is an enlarged view of a main portion of FIG. 2. FIG. 2 is an enlarged view of a main portion of FIG. 2. FIG. 4 is a cross-sectional view taken along line B-B in FIG. 4. FIG. 4 is a cross-sectional view taken along line C-C in FIG. 4. FIG. 1 is a perspective view showing a main configuration of a brushless motor according to one embodiment of the technology disclosed herein. FIG. 1 is an enlarged longitudinal cross-sectional view of a main portion showing an enlarged gap between a cylindrical portion and a rotor housing in a brushless motor according to one embodiment of the technology disclosed herein. FIG. 1 is a perspective view showing a main configuration of a brushless motor according to a first comparative example. FIG. 1 is a perspective view showing a main configuration of a brushless motor according to a second comparative example. FIG. 1 is an enlarged longitudinal cross-sectional view of a main portion showing an enlarged gap between a cylindrical portion and a rotor housing in a brushless motor according to a third ...

[0009] An embodiment of the technology of the present disclosure will be described below.

[0010] The brushless motor 10 of this embodiment shown in Figure 1 is a fan motor used in a blower mounted on a vehicle such as a passenger automobile. As shown in Figures 2 and 3, the brushless motor 10 includes a motor shaft 12, a rotor 14, a stator 16, a center piece 18, a circuit board 20, a motor holder 22, a circuit case 24, and a heat sink 26. In each figure, arrow Z1 indicates one axial side of the brushless motor 10, and arrow Z2 indicates the other axial side of the brushless motor 10.

[0011] 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. A cylindrical fixing portion 32 is formed in the center of the ceiling of the rotor housing 28, and the motor shaft 12 is press-fitted into the fixing portion 32. The motor shaft 12 is press-fitted into the fixing portion 32, thereby being located at the axial center of the rotor 14. The tip of the motor shaft 12 protrudes from the rotor housing 28 to one axial side of the brushless motor 10.

[0012] 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 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.

[0013] The center piece 18 is made of resin and has a main body 42 facing the opening 28A of the rotor housing 28, a cylindrical support portion 44 protruding from the center of the main body 42 toward the stator 16, and a cylindrical support member 46 attached to the support portion 44 from one axial side of the brushless motor 10. The main body 42 is formed in a roughly disk shape with its thickness direction aligned with the axial direction of the brushless motor 10. The main body 42 is sized to face the entire opening 28A of the rotor housing 28.

[0014] The support portion 44 and the support member 46 are inserted inside the annular stator core 34. The stator core 34 is fixed to the main body portion 42, for example, by screws, so that the stator 16 is supported by the centerpiece 18. A bearing accommodating portion 48 is formed in the main body portion 42, and a bearing accommodating portion 50 is formed in the support member 46. A bearing 52 is housed in each of the bearing accommodating portions 48, 50, and the motor shaft 12 is press-fitted into the bearing 52. The motor shaft 12 is supported by the support portion 44 and the support member 46 via the bearing 52, so that the rotor 14 is rotatably supported with respect to the centerpiece 18.

[0015] The circuit board 20 is disposed on the opposite side of the main body 42 from the stator 16. The circuit board 20 is fixed to the main body 42, for example, by screws. A plurality of switching elements are mounted on the circuit board 20 to switch 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 creates attractive and repulsive forces between the stator 16 and the rotor 14, causing the rotor 14 to rotate.

[0016] The motor holder 22 is made of, for example, resin, and is provided around the rotor housing 28. The motor holder 22 has a cylindrical portion 54 that surrounds the rotor housing 28 and an annular portion 56 that extends radially outward from the cylindrical portion 54 of the motor holder 22. A gap 58 is provided between the cylindrical portion 54 and the rotor housing 28 in the radial direction of the brushless motor 10. The annular portion 56 is formed in the shape of an annular plate with its thickness direction aligned with the axial direction of the brushless motor 10. A plurality of attachment portions 60 are provided on the outer periphery of the annular portion 56. The brushless motor 10 is fixed to the object by attaching the plurality of attachment portions 60 to the object.

[0017] 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 20. The circuit case 24 is fixed to the motor holder 22 by, for example, screws.

[0018] The motor holder 22 has an extension portion 62 that extends from the cylindrical portion 54 radially outward of the brushless motor 10. The extension portion 62 is formed in a duct shape. An intake port 64 for taking in cooling air W is formed at the tip of the extension portion 62. The intake port 64 is located outside the main body portion 42 in the radial direction of the brushless motor 10 and opens toward one axial side of the brushless motor 10. The radial direction of the brushless motor 10 is the same as the radial direction of the motor holder 22, and the axial direction of the brushless motor 10 is the same as the axial direction of the motor holder 22. A guide flow path 66 extending radially of the brushless motor 10 is formed inside the extension portion 62. The guide flow path 66 extends from the intake port 64 toward the main body portion 42 and guides the cooling air W.

[0019] A wall 68 extending radially of the brushless motor 10 is provided inside the extension portion 62. The wall 68 is provided between the intake 64 and the rotor housing 28 in the radial direction of the brushless motor 10, and closes the gap between the intake 64 and the rotor housing 28. Because the rotor 14 including the rotor housing 28 rotates, a small gap is provided between the wall 68 and the rotor housing 28. The gap between the wall 68 and the rotor housing 28 is set to the smallest possible gap so that the rotor housing 28 does not interfere with the wall 68 during rotation. The wall 68 extends from the intake 64 side to a position opposite the end of the rotor housing 28 on the opening 28A side. The wall 68 forms a wall portion on one axial side of the brushless motor 10 relative to the guide flow passage 66, and the bottom of the extension portion 62 forms a wall portion on the other axial side of the brushless motor 10 relative to the guide flow passage 66.

[0020] The annular portion 56 is formed between the intake port 64 and the cylindrical portion 54 in the radial direction of the brushless motor 10, and is formed integrally with the extension portion 62. The annular portion 56 is located on one axial side of the brushless motor 10 relative to the wall 68, and a space 70 is provided between the wall 68 and the annular portion 56 in the axial direction of the brushless motor 10.

[0021] The heat sink 26 is made of a metal such as aluminum that has high thermal conductivity. The heat sink 26 is fixed to the circuit board 20 by screws or the like. The heat sink 26 is connected to the circuit board 20 in a manner that allows heat to be transferred therethrough. Specifically, the heat sink 26 is connected to a plurality of switching elements and the like on the circuit board 20 in a manner that allows heat to be transferred therethrough.

[0022] As shown in Figures 4 to 7, the heat sink 26 is provided on the main body 42. The heat sink 26 extends along the periphery of the motor shaft 12 (see Figure 6 in particular). The heat sink 26 is C-shaped when viewed in the axial direction of the brushless motor 10. The main body 42 has a ceiling 72 that covers the heat sink 26 from the stator 16 side. The ceiling 72 also extends along the periphery of the motor shaft 12 in correspondence with the heat sink 26, and is C-shaped when viewed in the axial direction of the brushless motor 10. The ceiling 72 is formed along the periphery of the support portion 44.

[0023] A cooling air flow path 74 is formed between the heat sink 26 and the ceiling portion 72, and the cooling air W is guided to the cooling air flow path 74 by the guide flow path 66. In addition, the wall 68 prevents the cooling air W taken in from the intake 64 from flowing into the gap 58 between the cylindrical portion 54 and the rotor housing 28, and guides the cooling air W to the cooling air flow path 74 between the heat sink 26 and the ceiling portion 72.

[0024] More specifically, the heat sink 26 has a facing portion 76 and a plurality of protrusions 78. The facing portion 76 faces the ceiling portion 72 in the axial direction of the main body portion 42. The plurality of protrusions 78 protrude from the facing portion 76 toward the ceiling portion 72 and are disposed in the cooling air flow path 74 between the heat sink 26 and the ceiling portion 72 (more specifically, between the facing portion 76 and the ceiling portion 72).

[0025] A plurality of through holes 80 are formed in the ceiling portion 72. Each through hole 80 penetrates the main body portion 42 in the axial direction and communicates with the cooling air flow path 74. The axial direction of the main body portion 42 is the same as the axial direction of the brushless motor 10. Each through hole 80 is formed at a position corresponding to a slot (not shown) between adjacent teeth 38.

[0026] The main body 42 is provided with a connector 82. The connector 82 is configured to include a connector case, connector terminals, etc. The main body 42 is provided with a partition wall 84 that separates the cooling air flow path 74 from the connector 82. The partition wall 84 is formed in a concave shape along the inside of the recess (i.e., the opening of the C) of the ceiling 72, which is C-shaped when viewed in the axial direction of the brushless motor 10.

[0027] The main body 42 has a plurality of openings 86. The plurality of openings 86 are formed on the outer periphery of the main body 42. The plurality of openings 86 communicate with the cooling air flow path 74 and open radially outward from the main body 42. The radial direction of the main body 42 is the same as the radial direction of the brushless motor 10.

[0028] In the brushless motor 10, the mounting angle of the motor holder 22 relative to the center piece 18 is changeable. That is, by selectively connecting any one of the plurality of openings 86 to the guide flow path 66, the mounting angle of the motor holder 22 relative to the center piece 18 can be changed. Depending on the mounting angle of the motor holder 22 relative to the center piece 18, any one of the plurality of openings 86 communicates with the guide flow path 66. The remaining openings 86 of the plurality of openings 86 are blocked by blocking portions 88 provided on the motor holder 22.

[0029] Radial ribs 90 extending radially are formed on the ceiling portion 72. The radial ribs 90 extend from the ceiling portion 72 to one axial side of the brushless motor 10. The ceiling portion 72 is spaced apart from the support portion 44 in the radial direction of the brushless motor 10, and connecting ribs 92 connecting the ceiling portion 72 and the support portion 44 are formed radially between the ceiling portion 72 and the support portion 44 in the radial direction of the brushless motor 10.

[0030] Next, the effects of this embodiment will be described.

[0031] First, to clarify the effects of this embodiment, a comparative example will be described. As shown in Fig. 9, in the first comparative example, the ceiling portion 72 (see Fig. 7, etc.) is omitted from the main body 42 compared to this embodiment. However, when the ceiling portion 72 is omitted, the cooling air W is diffused, and the cooling air W is supplied from the guide flow path 66 to only a portion of the heat sink 26, and there is a risk that the cooling air W will not reach the entire heat sink 26.

[0032] In contrast, in this embodiment, the main body 42 has a ceiling portion 72 that covers the heat sink 26 from the stator 16 side, and the guide flow path 66 guides the cooling air W taken in from the intake 64 to a cooling air flow path 74 between the heat sink 26 and the ceiling portion 72. Therefore, because the ceiling portion 72 can suppress diffusion of the cooling air W, the cooling air W can be distributed throughout the entire heat sink 26 even when the heat sink 26 extends along the periphery of the motor shaft 12.

[0033] Moreover, the heat sink 26 has an opposing portion 76 that faces the ceiling portion 72 in the axial direction of the main body 42, and a plurality of protrusions 78 that protrude from the opposing portion 76 toward the ceiling portion 72 and are disposed in the cooling air flow path 74. Therefore, the cooling air W impinges on the plurality of protrusions 78, thereby improving the cooling performance of the heat sink 26.

[0034] Furthermore, the ceiling portion 72 is formed with a plurality of through holes 80 that communicate with the cooling air flow path 74 and penetrate the main body portion 42 in the axial direction. Therefore, the cooling air W flowing through the cooling air flow path 74 can be discharged to the stator 16 side via the plurality of through holes 80. This allows the stator 16 to be cooled.

[0035] Furthermore, the main body 42 is provided with a partition wall 84 that separates the cooling air flow path 74 from the connector 82. This prevents the cooling air W flowing through the cooling air flow path 74 from leaking into the connector 82.

[0036] The motor holder 22 also has a plurality of openings 86 that can selectively communicate with the guide flow passage 66. Therefore, by selectively connecting any one of the plurality of openings 86 with the guide flow passage 66, the mounting angle of the motor holder 22 with respect to the center piece 18 can be changed.

[0037] 10 , the second comparative example does not include the blocking portion 88. However, when the blocking portion 88 is omitted, the cooling air W flowing through the cooling air flow path 74 leaks out through the remaining opening 86.

[0038] In contrast to this, in the present embodiment, the remaining openings 86 are closed by the closing portions 88. Therefore, it is possible to prevent the cooling air W flowing through the cooling air flow path 74 from leaking through the remaining openings 86.

[0039] Furthermore, radial ribs 90 extending radially are formed on the ceiling portion 72. Therefore, the rigidity of the ceiling portion 72 can be ensured.

[0040] Furthermore, a plurality of connecting ribs 92 are formed between the ceiling portion 72 and the support portion 44, connecting the ceiling portion 72 and the support portion 44. Therefore, the rigidity of the ceiling portion 72 and the support portion 44 can be ensured.

[0041] In a third comparative example shown in Fig. 11 , the wall 68 is omitted from the present embodiment. However, if the wall 68 is omitted, the cooling air W guided by the guide flow path 66 flows into the gap 58 between the cylindrical portion 54 and the rotor housing 28, and the cooling air W leaks to the outside through the gap 58, which may result in a shortage of cooling air W supplied to the objects to be cooled, including the stator 16, the heat sink 26, and the circuit board 20. In particular, as shown in Fig. 12 , if the gap 58 between the cylindrical portion 54 and the rotor housing 28 is large, the amount of cooling air W flowing into the gap 58 between the cylindrical portion 54 and the rotor housing 28 increases.

[0042] In contrast, in the present embodiment, a wall 68 extending radially of the motor holder 22 is provided inside the extension portion 62, and the wall 68 closes the gap between the intake 64 and the rotor housing 28. This prevents the cooling air W guided by the guide flow path 66 from flowing into the gap 58 between the cylindrical portion 54 and the rotor housing 28, thereby ensuring that the cooling air W is supplied to the objects to be cooled, including the stator 16, the heat sink 26, and the circuit board 20. In particular, as shown in FIG. 8 , even when the gap 58 between the cylindrical portion 54 and the rotor housing 28 is large, the cooling air W can be prevented from flowing into the gap 58, which is very effective.

[0043] Furthermore, the wall 68 guides the cooling air W taken in through the intake port 64 to the cooling air flow path 74 between the heat sink 26 and the ceiling portion 72. Therefore, the guide flow path 66 prevents the cooling air W from being guided inside the rotor housing 28, and the cooling air W can be ensured to be supplied from the guide flow path 66 to the heat sink 26.

[0044] Furthermore, an annular portion 56 is located on one axial side of the wall 68 of the motor holder 22 between the intake port 64 and the cylindrical portion 54, and is formed integrally with the extension portion 62. The annular portion 56 extends radially outward from the cylindrical portion 54 of the motor holder 22, and a space 70 is provided between the wall 68 and the annular portion 56 in the axial direction of the motor holder 22. Therefore, compared to when the wall 68 and the annular portion 56 are formed integrally without the space 70, the wall 68 and the annular portion 56 can each be made thinner. This makes it possible to prevent sink marks in the resin on the wall 68 and the annular portion 56 when the motor holder 22 is formed by resin molding.

[0045] 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 modified forms within the scope of the gist of the present disclosure.

[0046] The following are supplementary notes regarding the technology of the present disclosure. (Supplementary Note 1) A rotor (14) having a cylindrical rotor housing (28) with a top, a motor shaft (12) provided at the axial center of the rotor, a stator (16) accommodated inside the rotor housing, a center piece (18) having a main body (42) facing an opening (28A) of the rotor housing and supporting the stator and the motor shaft, a circuit board (20) arranged on the opposite side of the main body from the stator, a heat sink (26) provided on the main body and connected to the circuit board so as to be able to transfer heat, and a motor holder (22) having a cylindrical portion (54) surrounding the rotor housing, wherein the motor holder has an extension portion (62) formed in a duct shape that extends radially outward from the cylindrical portion, and an intake port (64) that opens toward one axial side of the motor holder is formed at the tip of the extension portion and takes in cooling air, a rotor housing having a rotor shaft extending radially from the rotor holder and a rotor housing wall extending radially from the rotor holder and a rotor housing wall covering the rotor housing and configured to guide the cooling air taken in from the intake toward the rotor housing, the rotor shaft having a rotor shaft extending radially from the rotor holder and a rotor housing wall extending radially from the rotor holder and configured to guide the cooling air taken in from the intake toward the rotor housing, the rotor shaft having a rotor shaft extending radially from the rotor holder and configured to guide the cooling air taken in from the intake toward the rotor housing, the rotor housing having a rotor shaft extending radially from the rotor holder and configured to guide the cooling air taken in from the intake toward the rotor housing, the rotor housing having a rotor shaft extending radially from the rotor holder and configured to guide the cooling air taken in from the intake toward the rotor housing, the rotor housing having a rotor shaft extending radially from the rotor holder and configured to (Appendix 3) A brushless motor as described in Appendix 1 or Appendix 2, wherein a ring-shaped portion (56) is formed integrally with the extension portion between the intake port and the cylindrical portion, located on one axial side of the motor holder relative to the wall, and extending radially outward from the cylindrical portion of the motor holder, and a space (70) is provided between the wall and the ring-shaped portion in the axial direction of the motor holder.

Claims

1. A rotor (14) having a cylindrical rotor housing (28) with a top end, a motor shaft (12) provided at the axial center of the rotor, a stator (16) accommodated inside the rotor housing, a center piece (18) having a main body (42) facing an opening (28A) of the rotor housing and supporting the stator and the motor shaft, a circuit board (20) located on the opposite side of the main body from the stator, a heat sink (26) provided on the main body and connected to the circuit board so as to be capable of conducting heat, and a motor holder (22) having a cylindrical portion (54) surrounding the rotor housing, wherein the motor holder has an extension portion (62) formed in a duct shape that extends radially outward from the cylindrical portion, and an intake port (64) that opens toward one axial side of the motor holder is formed at the tip of the extension portion and takes in cooling air, A guide flow path (66) is formed inside the extension portion, extending along the radial direction of the motor holder and guiding the cooling air taken in from the intake toward the main body portion, and a wall (68) is provided inside the extension portion, extending along the radial direction of the motor holder and blocking the space between the intake and the rotor housing.

2. A brushless motor according to claim 1, wherein the heat sink extends along the periphery of the motor shaft, the main body has a ceiling portion (72) that covers the heat sink from the side of the stator, and the wall guides the cooling air taken in from the intake port to a cooling air flow path (74) between the heat sink and the ceiling portion.

3. A brushless motor as set forth in claim 1 or claim 2, wherein a ring portion (56) is formed integrally with the extension portion between the intake port and the cylindrical portion, located on one axial side of the motor holder relative to the wall, and extending from the cylindrical portion radially outward of the motor holder, and a space (70) is provided between the wall and the ring portion in the axial direction of the motor holder.

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