Outer rotor-type motor

Abstract

A motor 1 has a stator 2 having a stator core 21 in which a cylindrical bearing retaining hole 24 is formed, a rotating shaft 3 arranged in the bearing retaining hole 24, a rotor 6 fixed to the rotating shaft 3, and a pair of bearings 4, 5 arranged axially side by side in the bearing retaining hole 24 and supporting the rotating shaft 3 rotatably relative to the stator core 21. The pair of the bearings each have an inner ring and an outer ring. One of the pair of the bearings has the inner ring fixed to the rotating shaft 3 and the outer ring fixed to the stator core 21. The other of the pair of the bearings has the inner ring fixed to the rotating shaft 3 and the outer ring loosely fitted to the stator core 21, or the inner ring loosely fitted to the rotating shaft and the outer ring fixed to the stator core 21. A biasing member 7 is provided to bias the loosely fitted inner or outer ring in the other of the pair of the bearings against the one of the pair of the bearings. [Selected drawing]

Description

Outer rotor-type motor[Technical Field]

[0001] The present invention relates to an outer rotor-type motor.[Background Art]

[0002] With respect to outer rotor-type motors, a configuration is known in which a bearing is inserted into a laminated core, where no component is used for supporting the bearing (see Patent Literature 1 ). Among outer rotor-type motors, a configuration is known in which a preload is applied using an elastic component such as a spring from the axial outside of two bearings to suppress wear on a surface of a shaft (see Patent Literature 2).[Citation List][Patent Literature]

[0003] [Patent Literature 1] JP 2000-209828 A[Patent Literature 2] JP 2020-048298 A[Summary of Invention][Technical Problem]

[0004] The configuration disclosed in Patent Literature 1 has a problem of causing wear on a non-press-fitted shaft, since a rotor vibrates in an axial direction due to an impact of a gap between the inner ring of the bearing and a surface of the shaft. As a configuration to suppress wear on the shaft, a possible configuration is such that a preload is applied from the axial outside of two bearings as disclosed in Patent Literature 2, for example.

[0005] However, in the motor configuration as disclosed in Patent Literature 2, even if a thin elastic member such as a wave washer were used, an area in which the elastic member is to be arranged would be required on the axial outside, which would hinder the downsizing of the motor.

[0006] The object of the present invention, in response to the above problem for example, is to provide a downsizable motor with suppressed wear on a rotating shaft.[Solution to Problem]

[0007] To achieve the above object, the outer rotor-type motor according to the present invention includes a stator having a stator core in which a cylindrical bearing retaining hole is formed, a rotating shaft arranged in the bearing retaining hole, a rotor fixed to the rotating shaft, and a pair of bearings arranged axially side by side in the bearing retaining hole and supporting the rotating shaft rotatably relative to the stator core, in which the pair of the bearings each have an inner ring and anouter ring. One of the pair of the bearings has the inner ring fixed to the rotating shaft and the outer ring fixed to the stator core. The other of the pair of the bearings has the inner ring fixed to the rotating shaft and the outer ring loosely fitted to the stator core, or the inner ring loosely fitted to the rotating shaft and the outer ring fixed to the stator core. A biasing member is provided to bias the loosely fitted inner ring or outer ring in the other of the pair of the bearings against the one of the pair of the bearings.

[0008] In the outer rotor-type motor according to an embodiment of the present invention, the other of the pair of the bearings has the outer ring interference-fitted to the stator core and the inner ring loosely fitted to the rotating shaft, and the biasing member biases the inner ring of the other of the pair of the bearings against the inner ring of the one of the pair of the bearings.

[0009] In the outer rotor-type motor according to an embodiment of the present invention, the other of the pair of the bearings has the inner ring interference-fitted to the rotating shaft and the outer ring loosely fitted to the stator core, and the biasing member biases the outer ring of the other of the pair of the bearings against the outer ring of the one of the pair of the bearings.

[0010] In the outer rotor-type motor according to an embodiment of the present invention, the inner rings or the outer rings are fixed to the rotating shaft or the stator core with an adhesive.

[0011] In the outer rotor-type motor according to an embodiment of the present invention, the outer ring has a flange and the flange is fixed to the stator core.[Advantageous Effects of Invention]

[0012] The outer rotor-type motor according to the present invention makes it possible to downsize the motor while suppressing wear on the rotating shaft.[Brief Description of Drawings]

[0013] [Fig. 1 ] is a cross-sectional view schematically showing a configuration of an outer rotor-type motor according to a first embodiment of the present invention.[Fig. 2] is an enlarged cross-sectional view of the motor shown in Fig. 1 .[Fig. 3] is a cross-sectional view schematically showing a configuration of an outer rotor-type motor according to a second embodiment of the present invention.[Fig. 4] is an enlarged cross-sectional view of the motor shown in Fig. 3.[Description of Embodiments]

[0014] Outer rotor-type motors according to embodiments of the present invention are described with reference to drawings below.

[0015] [First embodiment]Fig. 1 is a cross-sectional view schematically showing a configuration of an outer rotor-type motor according to a first embodiment of the present invention (hereinafter referred to as “motor 1”). Fig. 2 is an enlarged cross-sectional view of the motor 1 .

[0016] For convenience, in the x-axis direction (hereinafter referred to as “axial direction”), the direction indicated by arrow a is referred to as upper side a, and the direction indicated by arrow b is referred to as lower side b, in the following description. In the radial direction perpendicular to the x-axis, the direction away from the x-axis (namely the direction indicated by arrow c in Figs. 1 and 2) is referred to as an outer circumferential side c, and the direction toward the x-axis (namely the direction indicated by arrow d in Fig. 1 ) is referred to as an inner circumferential side d. For convenience, the direction shown in Fig. 1 is referred to as a profile of the motor 1 in the following description.

[0017] As shown in Fig. 1 , the motor 1 according to the present embodiment has a stator 2 in which a coil 22 is wound around an annular or nearly annular stator core 21 having a cylindrical bearing retaining hole 24 formed in the inner circumference thereof, a rotating shaft 3 arranged in the bearing retaining hole 24, a rotor 6 fixed to the rotating shaft 3 and supporting a permanent magnet 61 in an outer circumference of the stator 2, and a first bearing 4 and a second bearing 5 that are a pair of bearings arranged axially side by side in the bearing retaining hole 24 and supporting the rotating shaft 3 rotatably relative to the stator core 21. In the motor 1 , the pair of the bearings each have an inner ring 41 , 51 and an outer ring 42, 52,respectively. One of the first bearing 4 and the second bearing 5, for example the first bearing 4, has the inner ring 41 fixed to the rotating shaft 3 and the outer ring 42 fixed to the stator core 21 . Specifically, the first bearing 4 has the inner ring 41 and the outer ring 42 fixed to the rotating shaft 3 and the stator core 21 , respectively, by an interference fit, for example. In the motor 1 , the other of the first bearing 4 and the second bearing 5, for example the second bearing 5, has e.g. the fixed outer ring 52 and the inner ring 51 that is fitted to the rotating shaft 3 by a transition fit with an extremely small interference or by a clearance fit (hereinafter referred to as “loose fit”). Specifically, the second bearing 5 has the outer ring 52 fixed to the stator core 21 for example by an interference fit. The motor 1 has a coil spring 7 as a biasing member to bias the loosely fitted inner ring 51 of the second bearing 5. The configuration and operation of the motor 1 are specifically described below.

[0018] [Configuration of Motor]As described above, the motor 1 has the stator 2, the rotating shaft 3, the first bearing 4, the second bearing 5, the rotor 6, and the coil spring 7 as main components.

[0019] The stator 2 has an insulator 23 in addition to the stator core 21 and the coil 22 described above. The stator core 21 is composed of a plurality of laminated annular thin plates of a magnetic material such as a sheet steel. In Figs. 1 and 2, thin plates constituting the stator core 21 are omitted. The stator core 21 has a cylindrical bearing retaining hole 24 formed at the center thereof. The coil 22 is wound around the stator core 21 via the insulator 23. The insulator 23 is aninsulating member attached to the stator core 21. The stator 2 is fixed on a base plate 8. On the base plate 8, an electronic component constituting a control circuit for controlling the operation of the motor 1 may be mounted.

[0020] The rotor 6 has a cylindrical section 62 covering the outer circumferential side of the stator 2 and supporting the permanent magnet 61 on an inner circumference, a disk- or nearly disk-like top face section 63 covering the upper side of the stator 2, and a shaft fitting hole 64 provided at the center of the top face section 63. The rotor 6 is fixed to the rotating shaft 3. Specifically, an end section 31 being the axially upper end of the rotating shaft 3 is fitted to the shaft fitting hole 64 of the rotor 6.

[0021] The rotating shaft 3 is arranged in the bearing retaining hole 24 of the stator core 21 . The first bearing 4 and the second bearing 5 are axially arranged side by side in the bearing retaining hole 24. The first bearing 4 and the second bearing 5 support the rotating shaft 3 rotatably relative to the stator core 21 .

[0022] The first bearing 4 and the second bearing 5 are press-fitted to an inner circumferential surface of the bearing retaining hole 24 of the stator core 21. The first bearing 4 and the second bearing 5 are arranged in the bearing retaining hole 24 so as to be spaced apart from each other in the axial direction of the rotating shaft 3.

[0023] Of the pair of the bearings included in the motor 1 , the first bearing 4 is provided on the upper side in the axial direction of the rotating shaft 3. The firstbearing 4 is a ball bearing having, in addition to the inner ring 41 and the outer ring 42, rolling elements 43 provided between the inner ring 41 and the outer ring 42. In the first bearing 4, the inner circumferential surface 411 of the inner ring 41 is in contact with an outer circumferential surface 32 of the rotating shaft 3, and the inner ring 41 is interference-fitted to the rotating shaft 3. In the first bearing 4, the outer circumferential surface 421 of the outer ring 42 is in contact with an inner circumferential surface of the bearing retaining hole 24 and the outer ring 42 is interference-fitted to the stator core 21 .

[0024] Of the pair of the bearings included in the motor 1 , the second bearing 5 is provided on the lower side in the axial direction of the rotating shaft 3. The second bearing 5 is a ball bearing having, in addition to the inner ring 51 and the outer ring 52, rolling elements 53 provided between the inner ring 51 and the outer ring 52. In the second bearing 5, the inner circumferential surface 511 of the inner ring 51 is in contact with an outer circumferential surface 32 of the rotating shaft 3, and the inner ring 51 is connected to the rotating shaft 3 by a loose fit. In the second bearing 5, the outer circumferential surface 521 of the outer ring 52 is in contact with an inner circumferential surface of the bearing retaining hole 24 and the outer ring 52 is interference-fitted to the stator core 21 .

[0025] The coil spring 7 is provided in an inner circumference of the bearing retaining hole 24 of the stator core 21 , between the first bearing 4 and the second bearing 5. The upper one end of the coil spring 7 is in contact with a downwardly facing lower surface 412 of the inner ring 41 of the upper first bearing 4, and the lower other endof the coil spring 7 is in contact with an upwardly facing upper surface 512 of the inner ring 51 of the lower second bearing 5. The coil spring 7 biases the loosely fitted inner ring 51 of the second bearing 5 from the inner ring 41 of the first bearing 4, connected by an interference fit.

[0026] Next, effects of the motor 1 having the above configuration are described.

[0027] In the motor 1 described above, the first bearing 4 and the second bearing 5 as a pair of bearings have the outer rings 42, 52 fitted to an inner circumference of the stator core 21 . In the motor 1 , the coil spring 7 provided between the first bearing 4 and the second bearing 5 is in contact with the lower surface 412 of the inner ring 41 of the first bearing 4 and the upper surface 512 of the inner ring 51 of the second bearing 5. Thereby the coil spring 7 applies a preload from the interference-fitted inner ring 41 of the first bearing 4 to the loosely fitted inner ring 51 of the second bearing 5.

[0028] In the motor 1 configured as described above, the first bearing 4 and the second bearing 5 are press-fitted to the stator core 21 that is a laminated core. Due to the above configuration, an air gap between the stator 2 and the permanent magnet 61 that constitute a magnetic circuit in the motor 1 is determined simply by positioning the stator 2 and the rotor 6. In contrast, apart from the stator core, when a structure for supporting the bearings on a component such as a base plate is employed in a motor, for example, an air gap between the stator and the rotor isdetermined by positioning the rotating shaft and the stator relative to the above structure and then by positioning the stator relative to the rotor.

[0029] The motor 1 described above does not need to be provided with a structure for supporting the bearing on the base plate for example, and in addition, easy positioning between the stator and the rotor is enabled.

[0030] The motor 1 has a coil spring 7 provided between the first bearing 4 and the second bearing 5 and thereby a preload is applied to the second bearing 5. Thus, an impact of dimensional variation of components during assembly can be reduced in the motor 1 . Moreover, according to the motor 1 , wear on the non-press-fitted rotating shaft 3 can be suppressed, where the wear is caused by the rotor 6 axially vibrating due to an impact of a gap between the loosely fitted inner ring 51 of the second bearing 5 and an outer circumferential surface 32 of the rotating shaft 3.

[0031] In addition, an area in which the coil spring 7 is to be arranged does not exist axially outside, namely does not exist outside the first bearing 4 and the second bearing 5 in a perpendicular direction in the motor 1 , and hence this can contribute to the size reduction of the motor 1 , particularly the reduced dimensions in a perpendicular direction (a height direction).

[0032] Thus, according to the motor 1 described above, noise and vibration can be suppressed by suppressing the wear on the outer circumferential surface 32 of the rotating shaft 3 and the vibration of the rotor 6 during rotation as well, with improvedproductivity. In addition, according to the motor 1 , EMC (Electromagnetic Compatibility) can be improved by applying a preload to the second bearing 5 to bring the rotor 6 and the stator 2 into conduction via the inner ring 51 and the outer ring 52.

[0033] [Second Embodiment]Next, an outer rotor-type motor according to a second embodiment of the present invention is described. In the following description, constituents having functions which are the same as or similar to those of the outer rotor-type motor according to the first embodiment are represented by the same reference numerals with their descriptions omitted, and only different constituents are described.Fig. 3 is a cross-sectional view schematically showing a configuration of an outer rotor-type motor according to the second embodiment of the present invention (hereinafter referred to as “motor 1 B”). Fig. 4 is an enlarged cross-sectional view of the motor 1 B.

[0034] As shown in Figs. 3 and 4, the motor 1 B differs from the previously described motor 1 in that the inner circumferential surface 511 of the inner ring 51 of the second bearing 5 is fixed to the rotating shaft 3 and the outer circumferential surface 521 of the outer ring 52 is loosely fitted to the stator core 21 . Specifically in the motor 1 B, the inner circumferential surface 511 of the inner ring 51 of the second bearing 5 is fixed to the rotating shaft 3 by an interference fit. The motor 1 B differs from the previously described motor 1 in respect of having a coil spring 7B as a biasingmember that biases the loosely fitted outer ring 52 of the second bearing 5 from the first bearing 4.

[0035] As with the coil spring 7, the coil spring 7B is provided in an inner circumference of the bearing retaining hole 24 of the stator core 21 , between the first bearing 4 and the second bearing 5. The upper one end of the coil spring 7B is in contact with a downwardly facing lower surface 422 of the outer ring 42 of the upper first bearing 4 and the lower other end of the coil spring 7B is in contact with an upwardly facing upper surface 522 of the outer ring 52 of the lower second bearing 5. The coil spring 7B biases the loosely fitted outer ring 52 of the second bearing 5 from the interference-fitted outer ring 42 of the first bearing 4.

[0036] In other words, the coil springs 7, 7B may be provided between the first bearing 4 and the second bearing 5 supporting the rotating shaft 3 and being apart from each other in an axial direction, to bias the inner ring 51 or the outer ring 52 of the second bearing 5 that is loosely fitted to the rotating shaft 3 or the bearing retaining hole 24, against the first bearing 4.

[0037] Next, effects of the motor 1 B having the above configuration are described.

[0038] In the motor 1 B described above, the outer rings 42, 52 of the first bearing 4 and the second bearing 5 as a pair of bearings are fitted to an inner circumference of the stator core 21 . In the motor 1 B, the coil spring 7B provided between the first bearing 4 and the second bearing 5 is in contact with the lower surface 422 of theouter ring 42 of the first bearing 4 and the upper surface 522 of the outer ring 52 of the second bearing 5. Thereby a preload is applied from the outer ring 42 that is interference-fitted in the first bearing 4 to the outer ring 52 that is loosely fitted in the second bearing 5.

[0039] In the motor 1 B configured as described above, an air gap between the stator 2 and the permanent magnet 61 that constitute a magnetic circuit is determined simply by positioning the stator 2 and the rotor 6, as with the previously described motor 1. Thus, the motor 1 B does not need to be provided with a structure for supporting the bearings on a component such as the base plate, and in addition, easy positioning of the stator and the rotor is enabled.

[0040] According to the motor 1 B, as with the motor 1 , an impact of dimensional variation of components during assembly can be reduced and the occurrence of wear on the non-press-fitted rotating shaft 3 can be suppressed as well. Moreover, an area in which the coil spring 7B is arranged does not exist axially outside in the motor 1 B as with the motor 1 , and hence this can contribute to the size reduction of the motor 1 B, particularly the reduced dimensions in a perpendicular direction (a height direction).

[0041] Thus, according to the motor 1 B described above, noise and vibration can be suppressed, with improved productivity as with the motor 1 . In addition, according to the motor 1 B, EMC (Electromagnetic Compatibility) can be improved by bringingthe rotor 6 and the stator 2 into conduction via the inner ring 51 and the outer ring 52 as with the motor 1 .

[0042] In addition to the above, the person skilled in the art can appropriately alter the present invention in accordance with conventionally accepted knowledge. The invention altered in such a way is, of course, included in the scope of the present invention as long as it has the configuration of the present invention.

[0043] For example, the motor 1 , 1 B described above uses the coil spring 7, 7B as a biasing member, which may be a different elastic member as long as it can apply a preload to the loosely fitted inner or outer ring provided between the pair of the bearings. Specifically, a biasing member such as a wave washer, a gromet, or a bush may also be used.

[0044] For example, the embodiments in which the first bearing 4 and the second bearing 5 are ball bearings have been described concerning the motors 1 , 1 B, but the present invention is not restricted to such embodiments. That is, the first bearing 4 and the second bearing 5 may be roller bearings such as taper roller bearings.

[0045] For example, the embodiments in which an interference fit is used as a method for fixing the bearings have been described, but the inner or outer ring of the bearings may also be fixed with an adhesive to the rotating shaft or the stator core, namely an object to which it is fixed. For a flanged bearing having an outerring with a flange, the flange may be fixed to the stator core with a screw or an adhesive or by welding for example.[Reference Signs List]

[0046] 1 , 1 B ■ ■ ■ motor, 2 ■ ■ ■ stator, 3 ■ ■ ■ rotating shaft, 4 ■ ■ ■ first bearing, 5 ■ ■ ■ second bearing, 6 ■ ■ ■ rotor, 8 ■ ■ ■ base plate, 21 ■ ■ ■ stator core, 22 ■ ■ ■ coil, 23 ■ ■ ■ insulator, 24 ■ ■ ■ bearing retaining hole, 31 ■ an end section, 32 ■■■ outer circumferential surface, 41, 51 ■■■ inner ring, 42, 52 ■■■ outer ring, 43, 53 ■■■ rolling element, 61 ■■■ permanent magnet, 62 ■ ■ ■ cylindrical section, 63 ■ ■ ■ top face section, 64 ■ ■ ■ shaft fitting hole, 411, 511 ■ ■ ■ inner circumferential surface, 412, 422 ■■■ lower surface, 421, 521 ■■■ outer circumferential surface, 512, 522 ■■■ upper surface.*****

Claims

Claims1 . An outer rotor-type motor comprising a stator having a stator core in which a cylindrical bearing retaining hole is formed, a rotating shaft arranged in the bearing retaining hole, a rotor fixed to the rotating shaft, and a pair of bearings arranged axially side by side in the bearing retaining hole and supporting the rotating shaft rotatably relative to the stator core, wherein the pair of the bearings each have an inner ring and an outer ring, wherein one of the pair of the bearings has the inner ring fixed to the rotating shaft and the outer ring fixed to the stator core, wherein the other of the pair of the bearings has the inner ring fixed to the rotating shaft and the outer ring loosely fitted to the stator core, or the inner ring loosely fitted to the rotating shaft and the outer ring fixed to the stator core, and wherein a biasing member is provided to bias the loosely fitted inner ring or outer ring in the other of the pair of the bearings against the one of the pair of the bearings.

2. The outer rotor-type motor according to claim 1 , wherein the other of the pair of the bearings has the outer ring interference- fitted to the stator core and the inner ring loosely fitted to the rotating shaft, and wherein the biasing member biases the inner ring of the other of the pair of the bearings against the inner ring of the one of the pair of the bearings.

3. The outer rotor-type motor according to claim 1 , wherein the other of the pair of the bearings has the inner ring interference- fitted to the rotating shaft and the outer ring loosely fitted to the stator core, and wherein the biasing member biases the outer ring of the other of the pair of the bearings against the outer ring of the one of the pair of the bearings.

4. The outer rotor-type motor according to claim 1 , wherein the inner rings or the outer rings are fixed to the rotating shaft or the stator core with an adhesive.

5. The outer rotor-type motor according to claim 1 , wherein the outer ring has a flange, and the flange is fixed to the stator core.

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