Outer rotor-type motor

Abstract

To realize miniaturization while suppressing abrasion of a rotating shaft.SOLUTION: A motor 1 comprises: a stator 2 that has a stator core 21 in which a cylindrical bearing retaining hole 24 is formed; a rotating shaft 3 that is arranged in the bearing retaining hole 24; a rotor 6 that is fixed to the rotating shaft 3; and a pair of bearings 4 and 5 that is arranged axially side by side in the bearing retaining hole 24, and supports 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 outer ring fixed to the rotating shaft 3 and the inner ring loosely fitted to the stator core 21, or the outer ring loosely fitted to the rotating shaft and the inner 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: Figure 1

Description

[Technical field]

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

[0002] In an outer rotor motor, a structure is known in which bearings are inserted into a laminated core without using parts to support the bearings (see Patent Document 1).In an outer rotor motor, a structure is known in which wear on the shaft surface is suppressed by applying preload from the axial outside of the two bearings using elastic parts such as springs (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-209828 A [Patent Document 2] JP 2020-48298 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the structure disclosed in Patent Document 1 has a problem in that the rotor vibrates in the axial direction due to the effect of the gap between the inner ring of the bearing and the surface of the shaft, causing wear of the non-press-fitted shaft. As a structure for suppressing shaft wear, for example, a structure in which preload is applied from the outside in the axial direction of the two bearings as in Patent Document 2 can be considered.

[0005] However, in the case of a motor structure such as that of Patent Document 2, even if a thin elastic member such as a wave washer is used, an area for arranging the elastic member is required on the outside in the axial direction, which is an obstacle to miniaturizing the motor.

[0006] The present invention addresses the above-mentioned problem by way of example, and has an object to provide a motor that can be made smaller while suppressing wear on the rotating shaft. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, an outer rotor type motor of the present invention comprises 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 side by side in the axial direction within the bearing retaining hole, supporting the rotating shaft rotatably relative to the stator core, each of the pair of bearings having an inner ring and an outer ring, one of the pair of bearings having the inner ring fixed to the rotating shaft and the outer ring fixed to the stator core, and the other of the pair of bearings having the inner ring fixed to the rotating shaft and the outer ring loosely fitted in the stator core, or having the inner ring loosely fitted on the rotating shaft and the outer ring fixed to the stator core, and comprising a biasing member that biases the inner ring or the outer ring, which is loosely fitted, against one of the pair of bearings.

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

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

[0010] In an outer rotor type motor according to one aspect of the present invention, the inner ring or the outer ring is fixed to the rotating shaft or the stator core by an adhesive.

[0011] In an outer rotor motor according to one aspect of the present invention, the outer ring has a flange, and the flange is fixed to the stator core. Effect of the Invention

[0012] According to the outer rotor motor of the present invention, it is possible to reduce the size of the motor while suppressing wear on the rotating shaft. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an outer rotor motor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the motor shown in FIG. [Diagram 3] FIG. 11 is a cross-sectional view illustrating a schematic configuration of an outer rotor type motor according to a second embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the motor shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An outer rotor type motor according to an embodiment of the present invention will now be described with reference to the drawings.

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

[0016] In the following description, for convenience, the direction of arrow a in the direction of axis x (hereinafter referred to as the "axial direction") is defined as the upper side a, and the direction of arrow b is defined as the lower side b. In addition, in the radial direction perpendicular to axis x, the direction away from axis x (the direction of arrow c in Figs. 1 and 2) is defined as the outer circumferential side c, and the direction toward axis x (the direction of arrow d in Fig. 1) is defined as the inner circumferential side d. In the following description, for convenience, the direction shown in Fig. 1 is defined as the side of motor 1.

[0017] As shown in Fig. 1, the motor 1 according to the present embodiment includes a stator 2 having a coil 22 wound around an annular or substantially annular stator core 21 having a cylindrical bearing retaining hole 24 formed in its inner circumference, 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 on the outer circumference of the stator 2, and a pair of bearings arranged side by side in the axial direction in the bearing retaining hole 24, a first bearing 4 and a second bearing 5 supporting the rotating shaft 3 rotatably relative to the stator core 21. In the motor 1, the pair of bearings each have an inner ring 41, 51 and an outer ring 42, 52, and one of the first bearing 4 and the second bearing 5, for example, the first bearing 4, is fixed such that the inner ring 41 is fixed to the rotating shaft 3 and the outer ring 42 is fixed to the stator core 21. Specifically, the first bearing 4 is fixed such that the inner ring 41 is fixed to the rotating shaft 3 and the outer ring 42 is fixed to the stator core 21 by, for example, an interference fit. In the motor 1, the other of the first bearing 4 and the second bearing 5, for example, the second bearing 5, has, for example, an outer ring 52 fixed, and an inner ring 51 fitted on the rotating shaft 3 with a very small interference or with a clearance fit (referred to as a "loose fit" in this specification). Specifically, the second bearing 5 has, for example, the outer ring 52 fitted and fixed to the stator core 21 with an interference fit. The motor 1 includes a coil spring 7 as a biasing member that biases the inner ring 51, which is loosely fitted in the second bearing 5. The configuration and operation of the motor 1 will be specifically described below.

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

[0019] The stator 2 includes the above-mentioned stator core 21 and coil 22, as well as an insulator 23. The stator core 21 is formed by laminating a plurality of thin plates of annular magnetic material, such as steel plates. The thin plates that constitute the stator core 21 are not shown in Figs. 1 and 2. The stator core 21 has a cylindrical bearing retaining hole 24 formed in the center. The coil 22 is wound around the stator core 21 via the insulator 23. The insulator 23 is an insulating member that is attached to the stator core 21. The stator 2 is fixed to a base plate 8. The base plate 8 may be equipped with electronic components that constitute a control circuit that controls the operation of the motor 1.

[0020] The rotor 6 includes a cylindrical portion 62 that covers the outer periphery of the stator 2 and supports a permanent magnet 61 on its inner periphery, a disk-shaped or approximately disk-shaped top surface portion 63 that covers the upper side of the stator 2, and a shaft mounting hole 64 provided in the center of the top surface portion 63. The rotor 6 is fixed to the rotating shaft 3. Specifically, one end portion 31 of the axial upper end of the rotating shaft 3 is mounted in the shaft mounting hole 64 of the rotor 6.

[0021] The rotating shaft 3 is disposed in a bearing retaining hole 24 of the stator core 21. The first bearing 4 and the second bearing 5 are disposed side by side in the axial direction in the bearing retaining hole 24. The first bearing 4 and the second bearing 5 support the rotating shaft 3 rotatably with respect to the stator core 21.

[0022] The first bearing 4 and the second bearing 5 are press-fitted into the 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 while being spaced apart from each other in the axial direction of the rotating shaft 3.

[0023] The first bearing 4 is one of a pair of bearings provided in the motor 1 and is provided on the upper side in the axial direction of the rotating shaft 3. The first bearing 4 is a ball bearing including an inner ring 41, an outer ring 42, and rolling elements 43 provided between the inner ring 41 and the outer ring 42. An inner peripheral surface 411 of the inner ring 41 of the first bearing 4 contacts the outer peripheral surface 32 of the rotating shaft 3, and the inner ring 41 of the first bearing 4 is fitted into the rotating shaft 3 with an interference fit. In addition, an outer peripheral surface 421 of the outer ring 42 of the first bearing 4 contacts the inner peripheral surface of the bearing retaining hole 24, and the outer ring 42 of the first bearing 4 is fitted into the stator core 21 with an interference fit.

[0024] The second bearing 5 is one of a pair of bearings provided in the motor 1, and is provided below the rotating shaft 3 in the axial direction. The second bearing 5 is a ball bearing including an inner ring 51, an outer ring 52, and rolling elements 53 provided between the inner ring 51 and the outer ring 52. An inner circumferential surface 511 of the inner ring 51 of the second bearing 5 contacts the outer circumferential surface 32 of the rotating shaft 3, and the inner ring 51 of the second bearing 5 is coupled to the rotating shaft 3 by a loose fit. An outer circumferential surface 521 of the outer ring 52 of the second bearing 5 contacts the inner circumferential surface of the bearing retaining hole 24, and the outer ring 52 of the second bearing 5 is fitted into the stator core 21 by an interference fit.

[0025] The coil spring 7 is provided between the first bearing 4 and the second bearing 5 on the inner periphery of the bearing retaining hole 24 of the stator core 21. One upper end of the coil spring 7 abuts against a lower surface 412 facing downward of the inner ring 41 of the upper first bearing 4, and the other lower end abuts against an upper surface 512 facing upward of the inner ring 51 of the lower second bearing 5. The coil spring 7 biases the inner ring 51, which is fitted loosely in the second bearing 5, from the inner ring 41, which is connected with an interference fit in the first bearing 4.

[0026] Next, the operation of the motor 1 having the above-described configuration will be described.

[0027] In the motor 1 described above, the first bearing 4 and the second bearing 5 serving as a pair of bearings have their outer rings 42, 52 fitted into the inner periphery of the stator core 21. Also, in the motor 1, the coil spring 7 provided between the first bearing 4 and the second bearing 5 abuts against the lower side 412 of the inner ring 41 of the first bearing 4 and the upper side 512 of the inner ring 51 of the second bearing 5, thereby applying a preload from the inner ring 41, which is fitted with an interference fit in the first bearing 4, to the inner ring 51, which is fitted with a loose fit in the second bearing 5.

[0028] In the motor 1 configured as above, the first bearing 4 and the second bearing 5 are press-fitted into the stator core 21, which is a laminated core. With this configuration, in the motor 1, the air gap between the stator 2 and the permanent magnet 61 that configure the magnetic circuit is determined only by positioning the stator 2 and the rotor 6. On the other hand, in the case where the motor employs a structure that supports the bearings on, for example, a base plate, in addition to the stator core, the air gap between the stator and the rotor is determined by first positioning the rotating shaft and the stator with respect to the above structure, and then positioning the rotor.

[0029] According to the motor 1 described above, it is not necessary to provide a structure for supporting the bearings on a base plate or the like, and in addition, the positioning of the stator and rotor can be easily performed.

[0030] In the motor 1, a preload is applied to the second bearing 5 by providing a coil spring 7 between the first bearing 4 and the second bearing. Therefore, the motor 1 can reduce the influence of dimensional variations of parts due to assembly. In addition, the motor 1 can suppress wear of the non-press-fitted rotating shaft 3 caused by the rotor 6 swinging in the axial direction due to the influence of a gap between the inner ring 51 of the second bearing 5, which is loosely fitted, and the outer circumferential surface 32 of the rotating shaft 3.

[0031] In addition, in motor 1, the area for arranging coil spring 7 is not located axially outward, that is, vertically outward of the first bearing 4 and the second bearing 5, which can contribute to miniaturization of motor 1, particularly in the vertical (height) dimensions.

[0032] Therefore, according to the motor 1 described above, it is possible to suppress wear on the outer circumferential surface 32 of the rotating shaft 3 and vibration of the rotor 6 during rotation, thereby suppressing noise and vibration and improving productivity. Also, according to the motor 1, by applying a preload to the second bearing 5, the rotor 6 and the stator 2 are electrically connected via the inner ring 51 and the outer ring 52, thereby improving EMC (Electromagnetic Compatibility).

[0033] [Second embodiment] Next, an outer rotor type motor according to a second embodiment of the present invention will be described. Below, components having the same or similar functions as those in the outer rotor type motor according to the first embodiment described above will be given the same reference numerals and their description will be omitted, and only the different components will be described. Fig. 3 is a cross-sectional view showing a schematic configuration of an outer rotor type motor (hereinafter referred to as "motor 1B") according to a second embodiment of the present invention. Fig. 4 is an enlarged cross-sectional view of motor 1B.

[0034] 3 and 4, the motor 1B differs from the motor 1 described above in that an inner circumferential surface 511 of an inner ring 51 of the second bearing 5 is fixed to the rotating shaft 3, and an outer circumferential surface 521 of an outer ring 52 is fitted into the stator core 21 by a loose fit. Specifically, the motor 1B is fitted and fixed to the rotating shaft 3 by an inner circumferential surface 511 of the inner ring 51 of the second bearing 5 by an interference fit. The motor 1B also differs from the motor 1 described above in that the motor 1B includes a coil spring 7B as a biasing member that biases the outer ring 52, which is loosely fitted into the second bearing 5, from the first bearing 4.

[0035] Similar to the coil spring 7, the coil spring 7B is provided on the inner circumference of the bearing retaining hole 24 of the stator core 21, between the first bearing 4 and the second bearing 5. One upper end of the coil spring 7B abuts against a lower surface 422 facing downward of the outer ring 42 of the upper first bearing 4, and the other lower end abuts against an upper surface 522 facing upward of the outer ring 52 of the lower second bearing 5. The coil spring 7B biases the outer ring 52, which is fitted loosely in the second bearing 5, from the outer ring 42, which is fitted tightly in the first bearing 4.

[0036] In other words, the coil springs 7, 7B are provided between the first bearing 4 and the second bearing 5 which are spaced apart in the axial direction and support the rotating shaft 3, and bias the inner ring 51 or the outer ring 52 of the second bearing 5 which is loosely fitted into the rotating shaft 3 or the bearing retaining hole 24, against the first bearing 4.

[0037] Next, the operation of the motor 1B having the above-described configuration will be described.

[0038] In the motor 1B described above, the first bearing 4 and the second bearing 5 serving as a pair of bearings have their outer rings 42, 52 fitted into the inner periphery of the stator core 21. Also, in the motor 1, the coil spring 7B provided between the first bearing 4 and the second bearing 5 abuts against the lower side 422 of the outer ring 42 of the first bearing 4 and the upper side 522 of the outer ring 52 of the second bearing 5, thereby applying a preload from the outer ring 42, which is fitted with an interference fit in the first bearing 4, to the outer ring 52, which is fitted with a loose fit in the second bearing 5.

[0039] In motor 1B configured as above, similarly to motor 1 described above, the air gap between stator 2 and permanent magnet 61 that constitute a magnetic circuit is determined only by the positioning of stator 2 and rotor 6. Therefore, motor 1B does not require a structure for supporting bearings on a base plate or the like, and can easily position the stator and rotor.

[0040] Furthermore, similar to motor 1, motor 1B can reduce the effects of dimensional variations in parts due to assembly and suppress wear of the non-press-fitted rotating shaft 3. Also, similar to motor 1, motor 1B does not have an area for arranging coil spring 7B on the outside in the axial direction, which can contribute to miniaturization of motor 1B, particularly in the vertical (height) dimension.

[0041] Therefore, according to the motor 1B described above, it is possible to improve productivity while suppressing noise and vibration, similar to the motor 1. Furthermore, according to the motor 1B, like the motor 1, it is possible to improve EMC (Electromagnetic Compatibility) by electrically connecting the rotor 6 and the stator 2 via the inner ring 51 and the outer ring 52.

[0042] In addition, those skilled in the art can appropriately modify the present invention in accordance with conventionally known knowledge. As long as the configuration of the present invention is still provided even after such modifications, the modifications are of course included in the scope of the present invention.

[0043] For example, the motors 1 and 1B described above both use coil springs 7 and 7B as the biasing members, but the biasing members may be other elastic members as long as they can apply preload to the inner or outer ring that is loosely fitted between a pair of bearings. Specifically, the biasing members may be, for example, wave washers, grommets, bushes, etc.

[0044] For example, in the motors 1 and 1B described above, the first bearing 4 and the second bearing 5 are both ball bearings, but the present invention is not limited to this. That is, the first bearing 4 and the second bearing 5 may be rolling bearings such as tapered roller bearings.

[0045] For example, although an example has been described in which an interference fit is used as a method for fixing a bearing, the inner and outer rings of the bearing may also be fixed to the rotating shaft or stator core, which are the objects to be fixed, with an adhesive, or in the case of a flanged bearing, the outer ring has a flange, and so the flange may be fixed to the stator core with screws, welding, adhesive, etc. [Explanation of symbols]

[0046] Reference Signs List 1, 1B...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...one end, 32...outer peripheral surface, 41, 51...inner ring, 42, 52...outer ring, 43, 53...rolling element, 61...permanent magnet, 62...tubular portion, 63...top surface, 64...shaft mounting hole, 411, 511...inner peripheral surface, 412, 422...lower surface, 421, 521...outer peripheral surface, 512, 522...upper surface

Claims

1. A stator having a stator core with cylindrical bearing retention holes, A rotating shaft positioned within the bearing holding hole, A rotor fixed to the aforementioned rotating shaft, A pair of bearings are arranged axially within the bearing holding hole and rotatably support the rotating shaft relative to the stator core, Equipped with, The pair of bearings each have an inner ring and an outer ring, One of the pair of bearings has its inner ring fixed to the rotating shaft and its outer ring fixed to the stator core. The other of the pair of bearings has an inner ring fixed to the rotating shaft and an 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. An outer rotor type motor comprising a biasing member that biases the inner ring or outer ring, which is loosely fitted in the other of the pair of bearings, relative to one of the pair of bearings.

2. The other of the pair of bearings has an outer ring fitted into the stator core by an interference fit, and an inner ring fitted onto the rotating shaft by a loose fit. The biasing member biases the inner ring of the other of the pair of bearings relative to the inner ring of one of the pair of bearings. The outer rotor type motor according to claim 1.

3. The other of the pair of bearings has an inner ring fitted to the rotating shaft by an interference fit and an outer ring fitted to the stator core by a loose fit. The biasing member biases the outer ring of the other of the pair of bearings relative to the outer ring of one of the pair of bearings. The outer rotor type motor according to claim 1.

4. The inner ring or the outer ring is fixed to the rotating shaft or the stator core with adhesive. The outer rotor type motor according to claim 1.

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

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