US-12627192-B2 - Permanent magnet electric motor

Abstract

There is provided a permanent magnet electric motor that can be downsized in a rotation axis direction and can also suppress a leakage flux. The permanent magnet electric motor includes: a columnar rotor including a permanent magnet portion annularly disposed; a shaft disposed along a rotation axis of the rotor; a cylindrical stator core disposed on an outer circumferential side of the rotor; a main body including a shell integrally formed with the stator core; a bracket attached to one end side of the main body; and a bearing that rotatably supports the shaft. The bracket includes a bearing house portion that stores the bearing, and a non-magnetic portion that is connected to the bearing house portion. The bearing house portion is disposed on an inner diameter side relative to the permanent magnet portion as viewed from an axis direction of the rotation axis, and an edge portion of the bearing house portion on an outer diameter side is covered with the non-magnetic portion.

Inventors

• Yoichi Tanabe
• Tomonori Kojima
• Yosuke Matsui
• Rei OMATA
• Hiroo Kojima

Assignees

• FUJITSU GENERAL LIMITED

Dates

Publication Date

20260512

Application Date

20210324

Priority Date

20200331

Claims (8)

1. 1 . An inner rotor permanent magnet electric motor, comprising: a columnar rotor including a permanent magnet portion annularly disposed; a shaft fixed to the rotor along a rotation axis of the rotor; a cylindrical stator core disposed on an outer circumferential side of the rotor; a main body including a shell integrally formed with the stator core; a bracket attached to one end side of the main body and formed having a gap between the bracket and the rotor in an axial direction of the rotation axis; and a bearing that rotatably supports the shaft, wherein the bracket includes a magnetic bearing house portion that stores the bearing, and a non-magnetic portion that is connected to the bearing house portion, the bearing house portion includes a tubular portion and a flange portion extending outward in a radial direction from one end side of the tubular portion, an outer circumferential edge portion of the flange portion of the bearing house portion is disposed on an inner diameter side relative to the permanent magnet portion as viewed from an axis direction of the rotation axis, and is covered with the non-magnetic portion, and the tubular portion of the bearing house portion and the non-magnetic portion of the bracket are disposed opposite each other in a radial direction perpendicular to the axial direction, and a clearance portion is formed between the tubular portion and the non-magnetic portion.
2. 2 . The inner rotor permanent magnet electric motor according to claim 1 , wherein the bearing includes a first bearing fixed to one end side of the shaft and a second bearing fixed to an other end side of the shaft, the bearing house portion includes a first bearing house portion that stores the first bearing and a second bearing house portion that stores the second bearing, the bracket includes the first bearing house portion, and a non-magnetic portion that is connected to the first bearing house portion, an outer circumferential edge portion of the flange portion of the first bearing house portion is disposed on an inner diameter side relative to the permanent magnet portion as viewed from an axis direction of the rotation axis, and is covered with the non-magnetic portion, the tubular portion of the first bearing house portion and the non-magnetic portion of the bracket are disposed opposite each other in a radial direction perpendicular to the axial direction, and a clearance portion is formed between the tubular portion and the non-magnetic portion, the main body includes an annular portion integrally formed with the stator core, and an end surface portion formed of a non-magnetic substance is connected to an end portion of the annular portion and expands inward in the radial direction from the annular portion, the end surface portion includes a connection portion connected to the second bearing house portion, an outer circumferential edge portion of a second flange portion of the second bearing house portion is disposed on an inner diameter side relative to the permanent magnet portion as viewed from an axis direction of the rotation axis, and is covered with the non-magnetic portion, and the tubular portion of the second bearing house portion and the non-magnetic portion of the bracket are disposed opposite each other in a radial direction perpendicular to the axial direction, and a clearance portion is formed between the tubular portion and the non-magnetic portion.
3. 3 . The inner rotor permanent magnet electric motor according to claim 2 , wherein the permanent magnet portion of the rotor faces the stator core in the radial direction, the rotor further includes a coupling portion that couples the permanent magnet portion and the shaft to each other, the coupling portion includes an annular recess that is disposed on an inner diameter side of the permanent magnet portion and is recessed toward a center of the coupling portion in the axis direction, and the flange portion of the bearing house portion is disposed to overlap with the recess in the axis direction.
4. 4 . The inner rotor permanent magnet electric motor according to claim 3 , wherein the permanent magnet portion is a bonded magnet.
5. 5 . The inner rotor permanent magnet electric motor according to claim 2 , wherein the permanent magnet portion is a bonded magnet.
6. 6 . The inner rotor permanent magnet electric motor according to claim 1 , wherein the permanent magnet portion is a bonded magnet.
7. 7 . The inner rotor permanent magnet electric motor according to claim 1 , wherein the bearing includes a first bearing fixed to one end side of the shaft and a second bearing fixed to an other end side of the shaft, the bearing house portion includes a first bearing house portion that stores the first bearing and a second bearing house portion that stores the second bearing, the inner rotor permanent magnet electric motor further includes an electrically conductive member for electrical conduction between the first bearing and the second bearing, and at least one end of the conductive member is disposed in a clearance portion.
8. 8 . The inner rotor permanent magnet electric motor according to claim 7 , wherein the permanent magnet portion is a bonded magnet.

Description

CROSS REFERENCE TO PRIOR APPLICATION This application is a National Stage Patent Application of PCT International Patent Application No. PCT/JP2021/012247 (filed on Mar. 24, 2021) under 35 U.S.C. § 371, which claims priority to Japanese Patent Application No. 2020-063644 (filed on Mar. 31, 2020), which are all hereby incorporated by reference in their entirety. TECHNICAL FIELD The present invention relates to an inner-rotor permanent magnet electric motor including a rotor disposed coaxially with a cylindrical stator on the inner diameter side of the stator. BACKGROUND ART As an electric motor, an inner-rotor permanent magnet electric motor has been conventionally known, in which a columnar rotor including a permanent magnet portion is disposed coaxially with a cylindrical stator, which generates a rotating magnetic field, on the inner diameter side of the cylindrical stator. This type of permanent magnet electric motor includes a permanent magnet electric motor including: a rotor including an annular permanent magnet portion facing a stator in a radial direction; and a coupling portion (yoke) that couples the permanent magnet portion to a shaft. In the permanent magnet electric motor of Patent Literature 1, a bearing house portion (bearing bracket) that holds a bearing is disposed close to the rotor in the axis direction of the stator, so that the electric motor is downsized in the axis direction. CITATION LIST Patent Literature Patent Literature 1: Japanese Patent Application Laid-open No. 2011-109861 DISCLOSURE OF INVENTION Technical Problem However, there has been a problem that, if the bearing house portion (bearing bracket) formed of a magnetic substance is disposed close to the permanent magnet portion of the rotor, the magnetic flux flowing from the permanent magnet portion of the rotor to the yoke (coupling portion) side of the stator also flows to the bearing house portion side, and a leakage flux increases, so that the output of the permanent magnet electric motor is lowered. Advantageous Effects of Invention In this regard, it is an object of the present invention to provide a permanent magnet electric motor that can be downsized in an axis direction and can suppress a leakage flux. Solution to Problem According to an aspect of the present invention, there is provided a permanent magnet electric motor including: a columnar rotor including a permanent magnet portion annularly disposed; a shaft disposed along a rotation axis of the rotor; a cylindrical stator core disposed on an outer circumferential side of the rotor; a main body including a shell integrally formed with the stator core; a bracket attached to one end side of the main body; and a bearing that rotatably supports the shaft. The bracket includes a bearing house portion that stores the bearing, and a non-magnetic portion that is connected to the bearing house portion. The bearing house portion is disposed on an inner diameter side relative to the permanent magnet portion as viewed from an axis direction of the rotation axis. An edge portion of the bearing house portion on an outer diameter side is covered with the non-magnetic portion. According to the present invention, it is possible to downsize an electric motor in an axis direction of a rotation axis and to suppress a leakage flux flowing from a permanent magnet portion of a rotor to a bearing house portion side. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an overall perspective view of a permanent magnet electric motor according to the present invention. FIG. 2 is a transverse cross-sectional view of the permanent magnet electric motor according to the present invention. FIG. 3 is a perspective view of a bracket of the permanent magnet electric motor according to the present invention. FIG. 4 is an overall perspective view of the permanent magnet electric motor according to the present invention, showing a state in which the bracket of FIG. 3 is removed. FIG. 5 is a cross-sectional view of a cross-section taken along a slitted groove shown in FIG. 1. MODE(S) FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to the drawings. In the following description about the drawings, the same or similar portions will be denoted by the same or similar reference symbols. It should be noted that the drawings are schematic and may differ from reality. Therefore, specific constituent parts should be determined by referring to the following description. Further, the embodiment to be described below exemplifies apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the shape, structure, arrangement, and the like of the constituent parts to those described below. Various modifications can be made to the technical idea of the present invention within the technical scope defined by the claims. Hereinafter, an electric motor according to an embodiment of the