motor

Abstract

Provided is a motor capable of suppressing temperature rise in a bearing.　The motor (1) comprises: a rotor (40) having a cylinder (12), a shaft (20), an annular space (CR) formed between the inner peripheral surface (13if) of the cylinder (12) and the outer peripheral surface (20op) of the shaft (20), a first bearing (21), a second bearing (22), a stator (30) fixed to the cylinder (12), an inner peripheral section (42a) fixed to the shaft (20) and equipped with a protrusion (42ap) facing the second bearing (22), an outer peripheral section (43) surrounding the stator (30), and a magnet (44) fixed to the outer peripheral section (43); and a substrate (15) fixed to a part of the cylinder (12) between the stator (30) and the first bearing (21) in the longitudinal direction of the shaft (20). The motor (1) additionally comprises a flow path (FP) in which a fluid flows between an inner ring (21in) of the first bearing (21) and a rolling element (21re), between the annular space (CR), an inner ring (22in) of the second bearing (22), and a rolling element (22re), and between the surface (42apf) of the protrusion (42ap) and the second bearing (22) in this order, then flows out to the exterior.

Description

Motor

[0001] The present invention relates to a motor.

[0002] 2. Description of the Related Art Some motors, such as the motor described in Patent Document 1, include a shaft and a bearing that supports the shaft so that the shaft can rotate.

[0003] JP 2019-75890 A

[0004] However, if the temperature of the bearings rises during motor operation, there is a risk that the durability of the bearings will be affected, for example, by volatilizing the grease provided in the bearings. Therefore, in motors, it is necessary to suppress the temperature rise of the bearings.

[0005] Therefore, one object of the present invention is to provide a motor that can suppress temperature rise in the bearings.

[0006] (1): A motor according to the present invention comprises a cylinder, a shaft, an annular space formed between the inner circumferential surface of the cylinder and the outer circumferential surface of the shaft, a first bearing having an inner ring, rolling elements, and an outer ring fixed to the shaft, a second bearing having the inner ring, rolling elements, and an outer ring fixed to the shaft, a stator fixed to the cylinder, a rotor having a protrusion facing the second bearing and having an inner circumferential portion fixed to the shaft, an outer circumferential portion surrounding the stator, and a magnet fixed to the outer circumferential portion, and a substrate fixed to a portion of the cylinder between the stator and the first bearing in the longitudinal direction of the shaft. The motor according to the present invention further comprises flow paths through which a fluid flows in the following order: between the inner ring of the first bearing and the rolling elements of the first bearing, in the annular space, between the inner ring of the second bearing and the rolling elements of the second bearing, and between the surface of the protrusion of the rotor and the second bearing, before flowing out to the outside.

[0007] (2): In (1), the first bearing may have a larger outer diameter than the second bearing in the radial direction, and the inner surface of the outer ring of the second bearing may be located on the shaft side relative to the inner surface of the outer ring of the first bearing in the radial direction.

[0008] (3) In (1) or (2), the inner peripheral surface of the cylinder may be located on the shaft side relative to the inner surface of the outer ring of the first bearing in the radial direction.

[0009] (4): In any of (1) to (3), the second bearing may have a cover that covers the rolling elements of the second bearing, and a gap through which the fluid passes may be formed between the cover of the second bearing and the inner ring of the second bearing in the radial direction, and the internal space of the second bearing may be open toward the surface of the protruding portion of the rotor through the gap.

[0010] (5) In (4), the gap may be located on the shaft side relative to the inner circumferential surface of the cylinder in the radial direction.

[0011] (6) In any one of (1) to (5), the dimension of the inner surface of the outer ring of the second bearing may be larger than the center dimension of the first bearing.

[0012] (7): In any of (1) to (6), the fluid may flow out to the outside by passing between the outer wall of the insulator of the stator and the inner surface of the magnet, and between the end of the magnet on the first bearing side and the substrate.

[0013] (8) In any one of (1) to (7), the fluid may pass through a through-hole of the rotor and flow out to the outside.

[0014] Fig. 4 is a perspective view of a motor according to an embodiment of the present invention, as seen from one side in the longitudinal direction of the shaft. Fig. 5 is a perspective view of the motor shown in Fig. 1, as seen from the other side in the longitudinal direction of the shaft. Fig. 6 is a cross-sectional view of the motor shown in Fig. 1 along the longitudinal direction of the shaft. Fig. 7 is an enlarged view of a first bearing and its vicinity shown in Fig. 3. Fig. 8 is an enlarged view of a second bearing and its vicinity shown in Fig. 3. Fig. 9 is an enlarged view of a magnet and its vicinity shown in Fig. 3. Fig. 10 is a cross-sectional view showing a modified example of the motor shown in Fig. 3. Fig. 11 is a cross-sectional view showing another modified example of the motor shown in Fig. 3.

[0015] Below, embodiments of a motor according to the present invention will be illustrated with reference to the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention can be modified or improved from the following embodiments without departing from the spirit of the present invention. In addition, in the accompanying drawings, the dimensions of each component may be exaggerated or reduced, and hatching may be omitted, in order to facilitate understanding.

[0016] Fig. 1 is a perspective view of a motor according to an embodiment, seen from one side in the longitudinal direction of a shaft (hereinafter simply referred to as the "longitudinal direction"). Fig. 2 is a perspective view of the motor shown in Fig. 1, seen from the other side in the longitudinal direction. Fig. 3 is a cross-sectional view of the motor shown in Fig. 1 along the longitudinal direction (which in this embodiment corresponds to the direction of the rotation axis).

[0017] As shown in Figures 1 to 3, the motor 1 according to this embodiment has a tubular (cylindrical) outer shape and mainly comprises a shaft 20, a bearing holder 12, a first bearing 21, a second bearing 22, a stator 30, and a rotor 40. The shaft 20 passes through the center of the motor 1 and has one end 20a and the other end 20b. That is, Figure 1 is a view of the shaft 20 as seen from the one end 20a side, and Figure 2 is a view of the shaft 20 as seen from the other end 20b side. In the longitudinal direction, the first bearing 21 is located on the other end 20b side, and the second bearing 22 is located on the one end 20a side.

[0018] The bearing holder 12 is a tubular member located in the center of the motor 1, and in this embodiment is a cylindrical member. Therefore, the bearing holder 12 can also be referred to as a cylinder 12. As shown in Fig. 3, the bearing holder 12 includes a first portion 16, a second portion 14, and a third portion 13. In the longitudinal direction, the first portion 16, the second portion 14, and the third portion 13 are arranged in this order from the other end 20b side toward the one end 20a side. The shaft 20 is located in the center of the internal space of the bearing holder 12.

[0019] The first portion 16 of the bearing holder 12 has the largest outer shape among the first portion 16, the second portion 14, and the third portion 13 in the radial direction perpendicular to the longitudinal direction. Specifically, it has a cylindrical shape with the largest inner and outer diameters. Note that in the radial direction, the side relatively closer to the shaft 20 may be referred to as the "inner" side, and the side relatively farther from the shaft 20 may be referred to as the "outer" side. In this embodiment, the first portion 16 has a length of approximately one-quarter of the entire length of the bearing holder 12 in the longitudinal direction, but is not limited to this. The upper end surface 16uf of the first portion 16 (the surface on the side of one end 20a in the longitudinal direction) is flat in the radial direction and connects to the outer peripheral surface 13of of the third portion 13 approximately perpendicularly.

[0020] The third portion 13 of the bearing holder 12 has a cylindrical outer shape and is smaller in the radial direction than the first portion 16. Specifically, the outer diameter of the third portion 13 is smaller than the outer diameter of the first portion 16, and the inner diameter of the third portion 13 is smaller than the inner diameter of the first portion 16. In this embodiment, the third portion 13 has a length that is approximately half of the entire length of the bearing holder 12 in the longitudinal direction, but is not limited to this. The portion of the outer surface 13of of the third portion 13 on the side of one end 20a in the longitudinal direction is located more inward (closer to the shaft 20) than the portion on the side of the other end 20b. In other words, the boundary between the portion of the outer surface 13of of the third portion 13 on the side of one end 20a and the portion on the side of the other end 20b forms a stepped surface 13sf that is flat in the radial direction. The outer peripheral surface 20op of the shaft 20 passing through the internal space of the bearing holder 12 and the inner peripheral surface 13if of the third portion 13 are spaced apart in the radial direction. That is, an annular space CR is formed between the inner peripheral surface 13if of the cylinder 12 and the outer peripheral surface 20op of the shaft 20.

[0021] 4 is an enlarged view of the first bearing 21 and its vicinity. As shown in FIG. 4, a lower end surface 13df (the surface on the other longitudinal end 20b side) of the third portion 13 of the bearing holder 12 is formed flat in the radial direction. The lower end surface 13df of the third portion 13 is connected to the inner circumferential surface 16if of the first portion 16 substantially perpendicularly.

[0022] 3, the second portion 14 of the bearing holder 12 has an outer diameter that is the same as the outer diameter of the portion of the third portion 13 that is closer to one end 20a than the stepped surface 13sf, and an inner diameter that is larger than the inner diameter of the third portion 13. Therefore, in this embodiment, the outer peripheral surface of the second portion 14 is formed flush with the portion of the outer peripheral surface 13of of the third portion 13 that is closer to one end 20a than the stepped surface 13sf. In this embodiment, the second portion 14 has a length that is approximately one-quarter of the entire length of the bearing holder 12 in the longitudinal direction, but this is not limited to this.

[0023] 5 is an enlarged view of the second bearing 22 and its vicinity. As shown in Fig. 5, the inner circumferential surface 14if of the second portion 14 of the bearing holder 12 is connected substantially perpendicularly to the upper end surface 13uf of the third portion 13, which is flat in the radial direction (the surface on the side of one end 20a in the longitudinal direction).

[0024] As shown in FIGS. 3 and 4 , the first bearing 21 is a ball bearing including an inner ring 21in, multiple rolling elements 21re, and an outer ring 21ou. The multiple rolling elements 21re are located radially between the inner ring 21in and the outer ring 21ou. The first bearing 21 has a larger outer diameter than the second bearing 22 in the radial direction. Most of the first bearing 21 is housed inside the first portion 16 of the bearing holder 12. Specifically, most of the first bearing 21 is located within a space surrounded by the inner circumferential surface 16if of the first portion 16 of the bearing holder 12, the lower end surface 13df of the third portion 13 of the bearing holder 12, and the outer circumferential surface 20op of the shaft 20. In the radial direction, the outer surface of the outer ring 21ou faces and is close to the inner circumferential surface 16if of the first portion 16 of the bearing holder 12. In the longitudinal direction, there is a gap between the first bearing 21 and the lower end surface 13df of the third portion 13 of the bearing holder 12, and a ring-shaped spring member 17 is disposed in this gap. The outer ring 21ou is supported by the lower end surface 13df of the third portion 13 of the bearing holder 12 via this spring member 17. In the radial direction, the inner circumferential surface 13if of the third portion 13 of the bearing holder 12 (cylinder 12) is located inside (on the shaft 20 side) with respect to the inner surface 21ouf of the outer ring 21ou.

[0025] The lower end of the first bearing 21 (the end on the other end 20b side in the longitudinal direction) and a portion nearby protrude from the bearing holder 12 toward the other end 20b and are exposed to the external space of the motor 1. The shaft 20 is provided with a protrusion 18 that protrudes radially outward (opposite the shaft 20) from the outer circumferential surface 20op of the shaft 20. The protrusion 18 is not particularly limited, and may be, for example, a C-ring or an O-ring. The lower end of the inner ring 21in of the first bearing 21 is supported by contact with the protrusion 18 in the rotational axis direction (longitudinal direction), thereby positioning the inner ring 21in in the longitudinal direction. The inner ring 21in is attached to the shaft 20 by, for example, a clearance fit.

[0026] In this embodiment, the first bearing 21 is supported by the bearing holder 12 in the above manner. Specifically, the outer ring 21ou is supported so as not to rotate relative to the bearing holder 12, and the inner ring 21in is supported so as to be rotatable relative to the bearing holder 12 and the outer ring 21ou in conjunction with the rotation of the shaft 20. Note that the means for supporting the first bearing 21 by the bearing holder 12 is not limited to the above. For example, the protrusion 18 may not be provided, and the inner ring 21in may be attached to the shaft 20 by an interference fit.

[0027] At the lower end of the first bearing 21 (the end closer to the other end 20b of the first bearing 21 in the longitudinal direction), a ring-shaped cover 21dc extends radially inward (toward the shaft 20) from the inner surface 21ouf of the outer ring 21ou. This cover 21dc covers the rolling elements 21re on the other end 20b side in the longitudinal direction. The end of the cover 21dc faces the outer surface 21inf of the inner ring 21in in the radial direction, and a gap 21dcg through which air, a fluid, can pass, is formed between the inner ring 21in of the first bearing 21 and the cover 21dc. The external space of the motor 1 and the internal space of the first bearing 21 are in communication via the gap 21dcg. The internal space of the first bearing 21 includes the gap between the inner ring 21in and the rolling elements 21re and the gap between the outer ring 21ou and the rolling elements 21re.

[0028] Furthermore, at the upper end of the first bearing 21 (the end closer to one end 20a of the first bearing 21 in the longitudinal direction), a ring-shaped cover 21uc extends radially inward from the inner surface 21ouf of the outer ring 21ou. This cover 21uc covers the rolling elements 21re on the side closer to one end 20a in the longitudinal direction. The end of the cover 21uc faces the outer surface 21inf of the inner ring 21in in the radial direction, and a gap 21ucg through which air, a fluid, can pass is formed between the inner ring 21in of the first bearing 21 and the cover 21uc. The internal space of the first bearing 21 and the annular space CR are in communication via the gap 21ucg. In this embodiment, the outer surface 21inf of the inner ring 21in of the first bearing 21 is located radially inward (closer to the shaft 20) with respect to the inner circumferential surface 13if of the third portion 13 of the bearing holder 12. Therefore, the area directly above the gap 21ucg is not covered by the lower end surface 13df of the third portion 13 of the bearing holder 12, and the gap 21ucg directly communicates with the annular space CR.

[0029] As shown in Figures 3 and 5, the second bearing 22 is a ball bearing including an inner ring 22in, multiple rolling elements 22re, and an outer ring 22ou. The multiple rolling elements 22re are located radially between the inner ring 22in and the outer ring 22ou. The second bearing 22 has a smaller outer diameter than the first bearing 21 in the radial direction. The inner surface 22ouf of the outer ring 22ou of the second bearing 22 is located inside (closer to the shaft 20) than the inner surface 21ouf of the outer ring 21ou of the first bearing 21. Here, the "center dimension" is defined as the sum of the inner diameter and outer diameter of the bearing divided by 2. In Figure 3, a line CD extending in the rotational axis direction (longitudinal direction) of the portion corresponding to the center dimension of the first bearing 21 is indicated by a dashed line. As shown in FIG. 3 , in this embodiment, the dimension of the inner surface 22 ouf of the outer ring 22 ou of the second bearing 22 is larger than the center dimension of the first bearing 21 .

[0030] The second bearing 22 is housed inside the second portion 14 of the bearing holder 12. Specifically, the second bearing 22 is located in a space surrounded by the inner circumferential surface 14if of the second portion 14 of the bearing holder 12, the upper end surface 13uf of the third portion 13 of the bearing holder 12, and the outer circumferential surface 20op of the shaft 20. In the radial direction, the outer surface of the outer ring 22ou faces and is close to the inner circumferential surface 14if of the second portion 14 of the bearing holder 12. The lower end surface of the outer ring 22ou (the surface on the side of the other end 20b in the longitudinal direction) is placed on the upper end surface 13uf of the third portion 13 of the bearing holder 12. The outer ring 22ou may be fixed to the bearing holder 12, for example, by bonding its outer surface to the inner circumferential surface 14if of the second part 14 of the bearing holder 12 and by bonding its lower end surface to the upper end surface 13uf of the third part 13 of the bearing holder 12. On the other hand, the inner ring 22in is attached to the shaft 20 by, for example, a clearance fit.

[0031] In this embodiment, the second bearing 22 is supported by the bearing holder 12 in the above manner. Specifically, the outer ring 22ou is supported so as not to rotate relative to the bearing holder 12, and the inner ring 22in is supported so as to be rotatable relative to the bearing holder 12 and the outer ring 22ou in response to rotation of the shaft 20. Note that the means for supporting the second bearing 22 by the bearing holder 12 is not limited to the above.

[0032] At the lower end of the second bearing 22 (the end closer to the other end 20b of the second bearing 22 in the longitudinal direction), a ring-shaped cover 22dc extends radially inward (toward the shaft 20) from the inner surface 22ouf of the outer ring 22ou. This cover 22dc covers the rolling elements 22re on the side closer to the other end 20b in the longitudinal direction. The end of the cover 22dc faces the outer surface 22inf of the inner ring 22in in the radial direction, and a gap 22dcg through which air, a fluid, can pass, is formed between the inner ring 22in of the second bearing 22 and the cover 22dc. The annular space CR and the internal space of the second bearing 22 are in communication via the gap 22dcg. The internal space of the second bearing 22 includes the gap between the inner ring 22in and the rolling elements 22re and the gap between the outer ring 22ou and the rolling elements 22re.

[0033] At the upper end of the second bearing 22 (the end on the side of one end 20a of the second bearing 22 in the longitudinal direction), a ring-shaped cover 22uc extends radially inward from the inner surface 22ouf of the outer ring 22ou. This cover 22uc covers the rolling elements 22re on the side of one end 20a in the longitudinal direction. In the radial direction, the end of the cover 22uc faces the outer surface 22inf of the inner ring 22in, and a gap 22ucg through which air, which is a fluid, can pass is formed between the inner ring 22in of the second bearing 22 and the cover 22uc.

[0034] In the radial direction, the gaps 22dcg and 22ucg are located on the inner side (shaft 20 side) of the inner circumferential surface 13if of the third portion 13 of the bearing holder 12 (cylinder 12).

[0035] As shown in FIG. 3 , the rotor 40 includes a holder 41 and a magnet 44. The holder 41 is made of a magnetic material and includes a cylindrical (cylindrical) tubular portion 43 and an annular portion 42 integrally formed with the tubular portion 43. The tubular portion 43 is the outer peripheral portion of the rotor 40 and is the outer periphery of the rotor 40. The tubular portion 43 (outer peripheral portion 43) surrounds the stator 30 in the radial direction. The annular portion 42 is annular when viewed in the longitudinal direction and extends radially inward (toward the shaft 20) from an end portion of the tubular portion 43 on the side of one end 20 a in the longitudinal direction. One end 20 a of the shaft 20 is fixed to the inner peripheral portion 42 a of the annular portion 42 by, for example, press-fitting. Therefore, the holder 41 and the shaft 20 rotate integrally. In the longitudinal direction, the annular portion 42 is located on the side of one end 20a relative to the second bearing 22, the bearing holder 12, the magnet 44, and the stator 30. In the longitudinal direction, a space G1 that extends radially is formed between the annular portion 42 and the second bearing 22, the bearing holder 12, the magnet 44, and the stator 30.

[0036] The inner circumferential portion 42a of the annular portion 42 has a protruding portion 42ap that protrudes in the longitudinal direction toward the second bearing 22 (the other end 20b side). In the longitudinal direction, the protruding portion 42ap is located on the one end 20a side of the second bearing 22 and faces the second bearing 22. The shaft 20 is fixed to the inner circumferential surface of the protruding portion 42ap.

[0037] As shown in Fig. 5, the protruding portion 42ap of the inner circumferential portion 42a of the rotor 40 includes a surface (opposing surface 42apf) that faces the upper end surface of the second bearing 22. More specifically, the opposing surface 42apf faces the cover 22uc of the second bearing 22 at a predetermined distance in the longitudinal direction, forming a space G12, and the space G12 communicates with the gap 22ucg. In other words, the internal space of the second bearing 22 is open toward the opposing surface 42apf of the protruding portion 42ap of the rotor 40 via the gap 22ucg of the second bearing 22. The space G1 communicates with the space G12 between the opposing surface 42apf and the second bearing 22.

[0038] FIG. 6 is an enlarged view of the magnet and its vicinity. As shown in FIGS. 3 and 6 , the cylindrical portion 43 (outer peripheral portion 43) extends from the outer end of the annular portion 42 toward the other end 20b in the longitudinal direction. The magnet 44 has an annular shape and is fixed to the inner peripheral surface of the cylindrical portion 43 (outer peripheral portion 43). Furthermore, the magnet 44 has a plurality of different magnetic poles (N poles and S poles) alternately formed along the circumferential direction. In the radial direction, the inner peripheral surface 44if of the magnet 44 faces the stator 30 via an air gap G2. The magnet 44 is disposed spaced apart from the annular portion 42 in the longitudinal direction. Furthermore, in the longitudinal direction, the end 44de of the magnet 44 (the end on the side of the other end 20b in the longitudinal direction) is located on the other end 20b side relative to the lower end surface of the cylindrical portion 43.

[0039] 3, the stator 30 is formed in a cylindrical shape and is formed in a ring shape when viewed in the longitudinal direction. An inner peripheral portion 30ip of the stator 30 is adjacent to the outer peripheral surface 13of of the third portion 13 of the bearing holder 12, and a lower end portion 30ipd of the inner peripheral portion 30ip of the stator 30 is placed on and supported by a stepped surface 13sf of the outer peripheral surface 13of. The stator 30 is fixed to the bearing holder 12 by, for example, bonding the inner peripheral portion 30ip to the outer peripheral surface 13of of the third portion 13 of the bearing holder 12 and the stepped surface 13sf of the outer peripheral surface 13of.

[0040] The stator 30 includes a stator core 37 formed by stacking a plurality of magnetic materials, such as electromagnetic steel sheets, in the longitudinal direction, an insulator 34 surrounding the stator core 37, and a plurality of coils 33 wound around the insulator 34. The stator core 37 includes an annular portion (core) 31 concentric with the shaft 20, and a plurality of teeth (magnetic pole portions) 32 formed to extend radially outward from the annular portion 31. At least a portion of the annular portion 31 and the teeth 32 is covered by the insulator 34. The plurality of coils 33 is wound around the insulator 34, which covers each of the plurality of teeth 32. In this way, the stator core 37 and the plurality of coils 33 are insulated from each other.

[0041] In this embodiment, the insulator 34 includes a main body portion 34a extending radially and around which the coil 33 is wound, a first convex portion 34b protruding from the outer periphery of the main body portion 34a toward one end 20a in the longitudinal direction, a second convex portion 34c protruding from the inner periphery of the main body portion 34a toward one end 20a in the longitudinal direction, a third convex portion 34d protruding from the outer periphery of the main body portion 34a toward the other end 20b in the longitudinal direction, and a fourth convex portion 34e protruding from the inner periphery of the main body portion 34a toward the other end 20b in the longitudinal direction.

[0042] The insulator 34 does not necessarily have to be provided with the first convex portion 34b, the second convex portion 34c, the third convex portion 34d, and the fourth convex portion 34e. Alternatively, the insulator 34 may be provided with one, two, or three of the first convex portion 34b, the second convex portion 34c, the third convex portion 34d, and the fourth convex portion 34e. However, for reasons described below, it is preferable to provide at least one of the first convex portion 34b and the third convex portion 34d.

[0043] As shown in FIG. 6 , the outer peripheral wall 34ow of the insulator 34 is located radially inward (toward the shaft 20) of the magnet 44 and faces the inner peripheral surface 44if of the magnet 44 across an air gap G2. The outer peripheral wall 34ow includes the outer peripheral wall of the first protrusion 34b and the outer peripheral wall of the third protrusion 34d. Openings are formed in the outer peripheral wall 34ow, and the outer peripheral portions of the teeth 32 of the stator core 37 are exposed through these openings. That is, the outer peripheral portions of the teeth 32 face the inner peripheral surface 44if of the magnet 44 across the air gap G2. In this embodiment, the outer peripheral wall 34ow of the insulator 34 and the outer peripheral portions of the teeth 32 exposed from the outer peripheral wall 34ow of the insulator 34 are generally flush with each other, but this is not limited to this.

[0044] As shown in Figures 2 and 3, the substrate 15 is formed in a disk shape. The inner peripheral portion 15ip ​​of the substrate 15 is placed on the upper end surface 16uf of the first portion 16 of the bearing holder 12 and is adjacent to the outer peripheral surface 13of of the third portion 13 of the bearing holder 12, and is fixed to the bearing holder 12. As shown in Figure 6, the substrate 15 extends radially outward beyond the cylindrical portion 43 of the holder 41. The substrate 15 and the holder 41 generally define the internal space of the motor 1, and the entire stator 30 is housed within the internal space of the motor 1. In the longitudinal direction, the substrate 15 and the end 44de of the magnet 44 face each other in the rotational axis direction (longitudinal direction), forming a gap G3, which connects the internal space of the motor 1 with the external space of the motor 1. For example, a connector (not shown) is connected to a lower surface 15df (see FIG. 2 ) (the surface on the other longitudinal end 20b side) of the substrate 15. Electric power may be supplied to the substrate 15 and the plurality of coils 33 via this connector.

[0045] As shown in FIGS. 1 and 2, the shaft 20 passes through the base plate 15 and the first portion 16 of the bearing holder 12 , and the other end 20 b of the shaft 20 is exposed to the external space of the motor 1 .

[0046] When current is supplied to the coil 33 of the motor 1 having this configuration, magnetic interaction occurs between the coil 33 and the magnet 44, generating a force that tries to rotate the rotor 40 relative to the stator 30 and bearing holder 12. The rotor 40 is fixed to the shaft 20. The shaft 20 is rotatably supported by the bearings 21 and 22. Therefore, the force that tries to rotate the rotor 40 relative to the stator 30 and bearing holder 12 causes the rotor 40 and the shaft 20 to rotate relative to the stator 30 and bearing holder 12. In this way, the motor 1 of this embodiment is configured as an outer rotor type motor.

[0047] When the shaft 20, rotor 40, etc. (which may be collectively referred to as the "rotating body") rotate relative to the stator 30, bearing holder 12, etc. (which may be collectively referred to as the "stationary body") as described above, a fluid flow (in this embodiment, an air flow) is generated by the centrifugal force caused by the rotation of the rotating body. This fluid flow (air flow) tends to be stronger on the side closer to the rotating body. Note that in this embodiment, the rotating body includes the shaft 20, rotor 40, inner ring 21in of the first bearing 21, and inner ring 22in of the second bearing 22, and the stationary body includes the stator 30, bearing holder 12, outer ring 21ou of the first bearing 21, and outer ring 22ou of the second bearing 22.

[0048] When the rotating body, shaft 20, rotates, centrifugal force of shaft 20 generates an airflow (fluid flow) that flows in the longitudinal direction around the other end 20b of shaft 20 that is exposed to the external space of motor 1. That is, air outside motor 1 flows in the longitudinal direction near shaft 20 toward first bearing 21. This airflow is indicated by dashed lines in Figures 3 to 6. Note that the dashed lines in Figures 3 to 6 schematically represent the flow rate of the airflow in the internal space of motor 1 and do not limit the area through which the airflow flows.

[0049] As described above and as shown in FIG. 4 , a gap 21dcg is formed between the inner ring 21in of the first bearing 21 and the cover 21dc. That is, in this embodiment, the gap 21dcg, which serves as an entrance to the internal space of the first bearing 21, is formed near the shaft 20, which is a rotating body, and the inner ring 21in. Therefore, the airflow from outside the motor 1 can flow into the internal space of the first bearing 21 through this gap 21dcg. Furthermore, because the gap 21dcg is formed near the rotating body, this airflow is more likely to flow into the internal space of the first bearing 21 than if, for example, the gap were formed between the outer ring 21ou and the cover 21dc of the first bearing 21 (i.e., on the side farther from the rotating body or closer to the stationary body). The air flow that flows into the internal space of the first bearing 21 flows mainly in the vicinity of the inner ring 21in, which is a rotating body, where the centrifugal force of the inner ring 21in is likely to affect, i.e., between the inner ring 21in and the multiple rolling bodies 21re, toward the cover 21uc.

[0050] As described above and as shown in FIG. 4 , a gap 21ucg is formed between the inner ring 21in of the first bearing 21 and the cover 21uc. That is, in this embodiment, the gap 21ucg, which serves as an outlet from the first bearing 21, is formed near the inner ring 21in, which is a rotating body. Therefore, the air flow that has flowed through the internal space of the first bearing 21 can flow into this gap 21ucg. Furthermore, because the gap 21ucg is formed near the rotating body, this air flow is more likely to flow out of the internal space of the first bearing 21 than when, for example, a gap is formed between the outer ring 21ou and the cover 21dc of the first bearing 21 (i.e., on the side farther from the rotating body or closer to the stationary body). As described above, in this embodiment, the area directly above the gap 21ucg is not covered by the lower end surface 13df of the third portion 13 of the bearing holder 12. In other words, the inner circumferential surface 13if and the gap 21ucg are spaced apart in the radial direction, so the gap 21ucg directly communicates with the annular space CR in the rotational axis direction (longitudinal direction). Therefore, the air flow that has flowed through the internal space of the first bearing 21 can easily flow out of the gap 21ucg into the annular space CR.

[0051] As shown in Figure 3, the air flow that flows into the annular space CR from the gap 21ucg mainly flows in the vicinity of the shaft 20, which is a rotating body, where the centrifugal force of the shaft 20 is likely to affect, along the longitudinal direction toward the second bearing 22.

[0052] As described above and as shown in FIG. 5 , a gap 22dcg is formed between the inner ring 22in and the cover 22dc of the second bearing 22. That is, in this embodiment, the gap 22dcg, which serves as an entrance to the internal space of the second bearing 22, is formed near the shaft 20, which is a rotating body, and the inner ring 22in. Therefore, the air flow that has flowed through the annular space CR can flow into the internal space of the second bearing 22 through this gap 22dcg. Furthermore, because the gap 22dcg is formed near the rotating body, this air flow is more likely to flow into the internal space of the second bearing 22 than, for example, when the gap is formed between the outer ring 22ou and the cover 22dc of the second bearing 22 (i.e., on the side farther from the rotating body or closer to the stationary body). The air flow that flows into the internal space of the second bearing 22 flows mainly in the vicinity of the inner ring 22in, which is a rotating body, where the centrifugal force of the inner ring 22in is likely to affect, i.e., between the inner ring 22in and the multiple rolling bodies 22re, toward the cover 22uc.

[0053] As described above and shown in FIG. 5 , a gap 22ucg is formed between the inner ring 22in of the second bearing 22 and the cover 22uc. That is, in this embodiment, the gap 22ucg, which serves as an outlet from the second bearing 22, is formed near the inner ring 22in, which is the rotating body. Therefore, the airflow that flows through the internal space of the second bearing 22 can flow into this gap 22ucg. Furthermore, because the gap 22ucg is formed near the rotating body, this airflow is more likely to flow out of the internal space of the second bearing 22 than if a gap were formed, for example, between the outer ring 22ou and the cover 22dc of the second bearing 22 (i.e., on the side farther from the rotating body or closer to the stationary body). Also, as described above, in this embodiment, the internal space of the second bearing 22 is open through the gap 22ucg toward the surface of the protruding portion 42ap of the rotor 40 (the opposing surface 42apf). Therefore, the air flow that has flowed through the internal space of the second bearing 22 can flow out from the gap 22ucg through the space G12 between the opposing surface 42apf and the second bearing 22 into the space G1.

[0054] 3 and 5 , the airflow that has flowed out into the space G1 flows mainly through an area of ​​the space G1 where the centrifugal force of the rotor 40, which is a rotating body, is likely to affect (i.e., near the rotating body). Specifically, this airflow flows radially outward between the opposing surface 42apf of the protruding portion 42ap of the rotor 40 and the second bearing 22, then flows roughly longitudinally toward one end 20a near the side surface 42aps of the protruding portion 42ap of the rotor 40, then flows radially outward near the inner surface 41if of the holder 41 of the rotor 40, and finally flows roughly longitudinally toward the other end 20b near the inner surface 41if of the holder 41 and near the inner circumferential surface 44if of the magnet 44 of the rotor 40.

[0055] As described above, the insulator 34 includes a first protrusion 34b that protrudes from the outer periphery of the main body 34a toward the one end 20a in the longitudinal direction. Therefore, the airflow that flows along the longitudinal direction near the inner periphery 44if of the magnet 44 toward the other end 20b is guided by the first protrusion 34b and directed to the air gap G2 between the insulator 34 and the inner periphery 44if of the magnet 44, as shown in FIG. 6 . Thus, the airflow that flows through the space G1 flows through the air gap G2 along the longitudinal direction toward the other end 20b. Furthermore, as described above, the insulator 34 includes a third protrusion 34d that protrudes from the outer periphery of the main body 34a toward the other end 20b in the longitudinal direction. As a result, the air flow that has flowed through the air gap G2 is guided by the third protrusion 34d, exits the air gap G2, and then flows along the inner circumferential surface 44if of the magnet 44 toward the substrate 15. As described above and as shown in FIG. 6 , a gap G3 is formed between the end 44de of the magnet 44 and the substrate 15, and this gap G3 connects the interior space of the motor 1 with the exterior space of the motor 1. Therefore, the air flow that has flowed out of the air gap G2 and along the inner circumferential surface 44if of the magnet 44 flows radially outward within the gap G3 due to centrifugal force generated by the rotation of the magnet 44, which is a rotating body, and then flows out to the outside of the motor 1.

[0056] As shown in FIG. 3 , the motor 1 further includes a flow path FP through which fluid flows in the following order: between the inner ring 21in of the first bearing 21 and the rolling elements 21re of the first bearing 21 (gap 21dcg, gap 21ucg); the annular space CR; between the inner ring 22in of the second bearing 22 and the rolling elements 22re of the second bearing 22 (gap 22dcg, gap 22ucg); and between the opposing surface 42apf of the protrusion 42ap of the rotor 40 and the second bearing 22, before flowing out to the outside. More specifically, the flow path FP includes an air gap G2 and a gap G3. Therefore, the airflow (fluid) flowing through the motor 1 passes between the outer peripheral wall 34ow of the insulator 34 of the stator 30 and the inner peripheral surface 44if of the magnet 44, and between the end 44de of the magnet 44 on the first bearing 21 side and the substrate 15, before flowing out to the outside. 6, the radially outer surface of the stator 30 is exposed and not covered by the insulator 34. Therefore, air also flows between the radially outer surface of the stator 30 and the inner circumferential surface 44if of the magnet 44, thereby suppressing a rise in temperature of the stator 30.

[0057] As described above, the motor 1 according to this embodiment includes the cylinder 12 (bearing holder), the shaft 20, an annular space CR formed between the inner peripheral surface 13if of the cylinder 12 and the outer peripheral surface 20op of the shaft 20, a first bearing 21 having an inner ring 21in, rolling elements 21re, and an outer ring 21ou fixed to the shaft 20, a second bearing 22 having an inner ring 22in, rolling elements 22re, and an outer ring 22ou fixed to the shaft 20, a stator 30 fixed to the cylinder 12, a rotor 40 having a protrusion 42ap facing the second bearing 22 and having an inner peripheral portion 42a fixed to the shaft 20, an outer peripheral portion 43 surrounding the stator 30, and a magnet 44 fixed to the outer peripheral portion 43, and a substrate 15 fixed to a portion of the cylinder 12 between the stator 30 and the first bearing 21 in the longitudinal direction of the shaft 20. In addition, the motor 1 further includes a flow path FP through which fluid (air) flows in the following order: between the inner ring 21in of the first bearing 21 and the rolling element 21re of the first bearing 21 (gap 21dcg, gap 21ucg), the annular space CR, between the inner ring 22in of the second bearing 22 and the rolling element 22re of the second bearing 22 (gap 22dcg, gap 22ucg), and between the opposing surface 42apf of the protrusion 42ap of the rotor 40 and the second bearing 22, and then flows out to the outside.

[0058] The motor 1 having the above configuration includes the fluid flow path FP as described above, so that when the rotating body rotates, the fluid (air) outside the motor 1 flows through the internal space of the first bearing 21 and then the internal space of the second bearing 22, and then flows out to the outside. Therefore, the motor 1 can cool the first bearing 21 and the second bearing 22 with the fluid (air), making it possible to suppress an increase in the temperature of the bearings. As a result, the motor 1 suppresses the evaporation of grease inside the bearings, thereby extending the life of the bearings and, ultimately, the life of the motor.

[0059] Furthermore, in the motor 1, the first bearing 21 located outside the holder 41 of the rotor 40 has a larger outer diameter in the radial direction than the second bearing 22 located inside the holder 41. This makes it possible to ensure a wide coil winding area while ensuring rotational stability.

[0060] Although the present invention has been described above using the above embodiment as an example, the present invention is not limited to this.

[0061] For example, a motor 1A as shown in FIG. 7 may be configured as a modification of the motor 1 according to the embodiment. In this modification, instead of the insulator 34 of the motor 1 according to the embodiment, an insulating resin film 134 is provided on the surface of the stator core 37 to insulate the stator core 37 from the coils 33. The other configurations of the motor 1A are the same as those of the motor 1. This motor 1A can reduce the number of components constituting the motor. On the other hand, when the insulator 34 according to the embodiment is used, the first protrusion 34b guides the airflow to the air gap G2, as described above, making the airflow more likely to be guided to the air gap G2. Furthermore, the third protrusion 34d guides the airflow toward the substrate 15, making the airflow more likely to be guided to the gap G3, which is the outlet from the motor 1.

[0062] As another modification of the motor 1 according to the above embodiment, a motor 1B as shown in FIG. 8 may be configured. In this modification, a through-hole 42Bh is formed in the holder 41 of the rotor 40. This through-hole 42Bh penetrates the annular portion 42B of the holder 41 in the longitudinal direction. In other words, in the motor 1B, the holder 41 of the rotor 40 includes the annular portion 42B in which the through-hole 42Bh is formed. The rest of the configuration of the motor 1B is similar to that of the motor 1. As shown by the dashed lines in FIG. 8 , a flow path FPB is formed inside the motor 1B, including a flow path through which the airflow (fluid) passes through the gap G3 and flows out to the outside of the motor 1B, and a flow path through which the airflow (fluid) passes through the through-hole 42Bh of the rotor 40 and flows out to the outside of the motor 1B. Note that the dashed lines in FIG. 8 schematically represent the flow rate of the airflow in the internal space of the motor 1B and do not limit the area through which the airflow flows.

[0063] In addition, in the above-described embodiment and each modified example, the first bearing 21 is provided with the cover 21dc and the cover 21uc, but at least one of the cover 21dc and the cover 21uc may be omitted. Even in this case, the centrifugal force generated by the rotation of the motor allows the outside air to flow into the inside of the first bearing 21, mainly through the gap between the inner ring 21in and the rolling element 21re, and into the annular space CR.

[0064] In addition, in the above-described embodiment and each modified example, the second bearing 22 is provided with the cover 22dc and the cover 22uc, but at least one of the cover 22dc and the cover 22uc may be omitted. Even in this case, the air flowing through the annular space CR due to the centrifugal force caused by the rotation of the motor can flow into the second bearing 22, mainly through the space between the inner ring 22in and the rolling elements 22re, and then out into the space between the second bearing 22 and the opposing surface 42apf of the protrusion 42ap of the rotor 40.

[0065] Furthermore, in the above-described embodiment and each of the modifications, an outer rotor type motor has been described as an example, but the present invention can also be applied to an inner rotor type motor.

[0066] In addition, those skilled in the art can appropriately modify the motor of the present invention in accordance with conventionally known knowledge. As long as such modifications still comprise the configuration of the present invention, they are of course included in the scope of the present invention.

[0067] DESCRIPTION OF SYMBOLS 1, 1A, 1B...motor, 12...bearing holder (cylinder), 13if...inner peripheral surface, 15...substrate, 20...shaft, 20op...outer peripheral surface, 21...first bearing, 21in...inner ring, 21ou...outer ring, 21ouf...inner surface, 21re...rolling element, 22...second bearing, 22dc...cover, 22in...inner ring, 22ou...outer ring, 22ouf...inner surface, 22re...rolling element, 22uc...cover, 30...stator, 34...insulator, 34ow...outer peripheral wall, 40...rotor, 42a...inner peripheral portion, 42ap...protrusion, 42apf...opposing surface (surface), 42Bh...through hole, 43...outer peripheral portion, 44...magnet, 44de...end, 44if...inner peripheral surface, CR...annular space, FP, FPB...flow path

Claims

1. A motor comprising: a cylinder; a shaft; an annular space formed between an inner surface of the cylinder and an outer surface of the shaft; a first bearing having an inner ring, rolling elements, and an outer ring fixed to the shaft; a second bearing having an inner ring, rolling elements, and an outer ring fixed to the shaft; a stator fixed to the cylinder; a rotor having an inner peripheral portion fixed to the shaft and with a protrusion facing the second bearing, an outer peripheral portion surrounding the stator, and a magnet fixed to the outer peripheral portion; and a substrate fixed to a portion of the cylinder between the stator and the first bearing in the longitudinal direction of the shaft, and further comprising flow paths through which a fluid flows in the following order: between the inner ring of the first bearing and the rolling elements of the first bearing, in the annular space, between the inner ring of the second bearing and the rolling elements of the second bearing, and between the surface of the protrusion of the rotor and the second bearing, before flowing out to the outside.

2. The motor according to claim 1, wherein the first bearing has an outer diameter larger than that of the second bearing in the radial direction, and the inner surface of the outer ring of the second bearing is on the shaft side in the radial direction relative to the inner surface of the outer ring of the first bearing.

3. The motor according to claim 2, wherein, in the radial direction, the inner peripheral surface of the cylinder is on the shaft side relative to the inner surface of the outer ring of the first bearing.

4. The motor described in claim 3, wherein the second bearing is provided with a cover which covers the rolling elements of the second bearing, a gap through which the fluid passes is formed between the cover of the second bearing and the inner ring of the second bearing in the radial direction, and the internal space of the second bearing is open towards the surface of the protruding portion of the rotor via the gap.

5. The motor according to claim 4, wherein the gap is located on the shaft side relative to the inner peripheral surface of the cylinder in the radial direction.

6. The motor according to any one of claims 1 to 5, wherein the dimension of the inner surface of the outer ring of said second bearing is larger than the center dimension of said first bearing.

7. The motor according to claim 1, wherein the fluid flows out to the outside through a gap between the outer peripheral wall of the stator insulator and the inner peripheral surface of the magnet, and between the end of the magnet on the first bearing side and the substrate.

8. The motor according to claim 1, wherein the fluid passes through a through hole in the rotor and flows out to the outside.

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