Electric motor

Patent metadata

Field	Value
Publication number	US-9831728-B2
Application number	US-201214400635-A
Country	US
Kind code	B2
Filing date	May 25, 2012
Priority date	May 25, 2012
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

An electric motor includes a yoke having a cylindrical section, two pairs of permanent magnets disposed at an inner circumferential surface of the cylindrical section to oppose each other, and an armature rotatably supported further inside in a radial direction than the permanent magnets, wherein at least a pair of first flat sections opposing each other in the radial direction are formed at the cylindrical section, and the permanent magnets are disposed at positions distant from the first flat sections.

First claim

The invention claimed is:

1. An electric motor comprising:
a yoke having a cylindrical section about an axial direction;
two pairs of permanent magnets fixed to an inner circumferential surface of the cylindrical section and arranged such that magnetic N poles and S poles are alternately disposed in a circumferential direction;
an armature rotatably supported about the axial direction further inside in a radial direction than the permanent magnets;
brushes configured to supply electricity to the armature; and
a brush holder formed to hold the brushes and having an outer shape circumferentially about the axial direction, the brush holder has a longitudinal direction and lateral direction along the radial direction, the lateral direction is orthogonal to the longitudinal direction, one length in the longitudinal direction of the outer shape is greater than the other lengths in the radial direction of the outer shape,
wherein the cylindrical section has first flat sections and arc-shaped sections, each of the arc-shaped sections being configured to connect two of the first flat sections in the circumferential direction,
the permanent magnets are disposed at positions corresponding to the arc-shaped sections, respectively, in the circumferential direction,
a width of the opposite first flat sections in the radial direction is represented as L 1 and a width of the opposite arc-shaped sections in the radial direction is represented as R 1 , the width L 1 of the first flat sections and the width R 1 of the arc-shaped sections are set to satisfy L 1 <R 1 ,
in the cross-sectional view of the axial direction, the opposite first flat sections are aligned along the lateral direction of the outer shape of the brush holder,
each of the first flat sections of the cylindrical section is disposed between two of the permanent magnets in the circumferential direction,
each of the arc-shaped sections of the cylindrical section has a portion that is disposed between two of the permanent magnets in the circumferential direction, and
the portions of the arc-shaped sections and the first flat sections are alternately disposed in the circumferential direction.

2. The electric motor according to claim 1 , wherein a brush holder-receiving section, which is configured to receive the brush holder, is integrally formed with the cylindrical section of the yoke at an opening section of the cylindrical section.

3. The electric motor according to claim 2 , wherein the outer shape of the brush holder has substantially oval shape in the cross-sectional view, the brush holder-receiving section has a circumferential wall that has a substantially oval shape in the cross-sectional view so as to substantially correspond to the outer shape of the brush holder, the circumferential wall of the brush holder-receiving section has flat walls and arc-shaped walls, each of the arc-shaped walls being configured to connect two of the flat walls in the circumferential direction, and the flat walls of the brush holder-receiving section are formed to be flush with the first flat sections of the yoke.

4. The electric motor according to claim 3 , further comprising two brushes configured to supply electricity to the armature,
wherein the two brushes are disposed at mechanical angle at a 90° interval in a circumferential direction,
a heat protection element configured to cut the supply of electricity to the armature upon overheating is disposed at an opposite side of the two brushes with a rotary shaft of the armature sandwiched therebetween, and
a choke coil is disposed inside the flat walls of the brush holder-receiving section.

5. The electric motor according to claim 4 , further comprising an armature core constituted by a plurality of core plates, which are stacked, each having a core main body fitted and fixed onto the rotary shaft and ten teeth protruding from the core main body outward in the radial direction, and on which a winding is wound between two of the teeth neighboring the circumferential direction,
wherein the teeth comprise two tooth groups, each constituted by five deformed teeth neighboring the circumferential direction,
the two tooth groups are disposed to be point-symmetrical to each other about the rotary shaft,
the five deformed teeth are constituted by:
a first deformed tooth having a distal end formed to be tilted toward an opposite side of the winding direction of the winding with respect to a virtual standard tooth extending in the radial direction; and
four second deformed teeth formed in the circumferential direction at the winding direction side of the first deformed tooth and having distal ends formed to be tilted in the winding direction with respect to the virtual standard tooth,
a first deformed slot is formed between the second deformed teeth and the first deformed tooth of the other tooth group adjacent to the second deformed teeth at the winding direction side of the second deformed teeth,
a second deformed slot is formed between the first deformed tooth and the second deformed teeth adjacent to the first deformed tooth one of the second deformed teeth closest to the first deformed tooth at the winding direction side of the first deformed tooth, and three third deformed slots are formed between the second deformed teeth neighboring each other in the circumferential direction, and the first deformed slot, the second deformed slot, and the third deformed slots are sequentially formed in the winding direction.

6. The electric motor according to claim 5 , further comprising a commutator installed at the rotary shaft adjacent to the armature core,
wherein the winding is wound at each of the teeth and having a 5-phase structure is formed in the circumferential direction through a distributed winding method to straddle the two neighboring teeth, in the circumferential direction in sequence of a U1 phase, a V1 phase, a W1 phase, an X1 phase, a Y1 phase, a U2 phase, a V2 phase, a W2 phase, an X2 phase and a Y2 phase,
the commutator has a total of the ten segments disposed in the circumferential direction such that two segments having the same electric potential corresponding to each phase are disposed to oppose each other about the rotary shaft, and the segments having the same electric potential are constituted in four poles, ten slots and ten segments by short-circuiting the winding,
the winding is connected to the two segments as a coil of the U1 phase, the coil of the U1 phase is wound between the first deformed slot and the third deformed slot disposed at a rear side in the winding direction of the first deformed slot, the winding is connected to the two segments as a coil of the V1 phase, the coil of the V1 phase is wound between the second deformed slot and the third deformed slot disposed at a rear side in the winding direction of the second deformed slot, the winding is connected to the two segments as a coil of the W1 phase, the coil of the W1 phase is wound in two third deformed slots disposed at both sides with a middle third deformed slot interposed therebetween in the three third deformed slots, the winding is connected to the two segments as a coil of the X1 phase, the coil of the X1 phase is wound between the first deformed slot of the other tooth group and the middle third deformed slot disposed at a rear side in the winding direction of the first deformed slot of the other tooth group, the winding is connected to the two segments as a coil of the Y1 phase, and then the coil of the Y1 phase is wound between the second deformed slot of the other tooth group and the last third deformed slot in the winding direction of the current tooth group,
further, simultaneously with the formation of the coils of the U1 phase, the V1 phase, the W1 phase, the X1 phase and the Y1 phase, the winding is

Assignees

• Kawashima Yoshichika
• Tokizaki Teppei
• Kojima Naoki
• Mitsuba Corp

Inventors

• Kawashima Yoshichika
• Tokizaki Teppei
• Kojima Naoki

Classifications

• H02K1/17 Primary

  Stator cores with permanent magnets · CPC title

• H02K23/32

  having wave or undulating windings · CPC title

• H02K5/148

  Slidably supported brushes · CPC title

• H02K1/265

  Shape, form or location of the slots · CPC title

• H02K11/25

  Devices for sensing temperature, or actuated thereby · CPC title