Electric motor and production method for the electric motor

Patent metadata

Field	Value
Publication number	US-9515527-B2
Application number	US-201313919392-A
Country	US
Kind code	B2
Filing date	Jun 17, 2013
Priority date	Jun 29, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A plurality of lamination steel sheets that form a rotor core are stacked so that the lamination steel sheets are angularly shifted from each other, and a plurality of cavities are formed. Permanent magnets are molded and disposed in the cavities by injection molding. Each permanent magnet has a uniform plate thickness, and is bent with respect to an axial direction so as to have a triangular wave shape or an S shape. The permanent magnets are magnetized after being disposed in the cavities. The paired magnet pieces have poles of the same polarity, which face each other in the circumferential direction of a rotor, and each of the magnet pieces is magnetized in directions of normals to a surface of the magnet piece, the surface having a linear sectional shape.

First claim

What is claimed is:

1. An electric motor comprising:
a rotor provided on a rotary shaft; and
a stator fixed outside an outer peripheral surface of the rotor,
the rotor including:
a rotor core fixed to the rotary shaft so as to be rotatable together with the rotary shaft; and
a plurality of permanent magnets embedded and fixed in the rotor core,
wherein the permanent magnets extend in radial directions of the rotor and are spaced from each other in a circumferential direction of the rotor and each of the permanent magnets have a magnetic-pole facing portion with a flat plate shape that extends radially and a proximity portion that extends from a radially inner end portion of the magnetic-pole facing portion toward the magnetic-pole facing portion of an adjacent permanent magnet so that the proximity portion of permanent magnets adjacent to each other face each other, and each of the permanent magnets (i) is magnetized in directions normal to a surface of the permanent magnet so that poles of the same polarity face each other in the circumferential direction, (ii) has a uniform thickness and (iii) is bent from one end portion of the rotor to the other end portion of the rotor with respect to a direction of the rotary shaft of the rotor so that the permanent magnet has a triangular wave shape in which a plurality of linear portions are sequentially connected, and
wherein the magnetic-pole facing portion of each of the adjacent permanent magnets is substantially longer than the proximity portion such that the magnetic-pole facing portions extend generally along a straight line to the proximity portion, the proximity portions defining a curved shaped end of each of the adjacent permanent magnets.

2. The electric motor according to claim 1 , wherein,
each of the permanent magnets further (i) has a thickness in a magnetization direction that increases from a distal end portion to a radially outer end portion and (ii) has a uniform thickness in an axial direction.

3. The electric motor according to claim 1 , wherein,
in an inner peripheral surface of the rotor core, the magnets of the plurality of permanent magnets are arranged in pairs, and each of the pairs of magnets has pole-facing portions with the same polarity that face each other in the circumferential direction.

4. The electric motor according to claim 1 , wherein,
in an inner peripheral surface of the rotor core, the magnets of the plurality of permanent magnets are arranged in pairs, and each of the pairs of magnets has pole-facing portions that are magnetized to have a magnetization direction of each of the pole-facing portions coinciding with a circumferential direction of the rotor.

5. The electric motor according to claim 1 , wherein,
the magnets of the plurality of permanent magnets are arranged in pairs, each magnet of the pairs of magnets has a corresponding proximity portion that extends from a radially inner portion of the magnetic pole-facing portion toward the other magnet in the pair of magnets, and the magnetization direction of each of the proximity portions gradually changes from the circumferential direction to the radial direction toward a distal end of the proximity portion such that each of the magnets is magnetized in a direction that substantially coincides with a direction of a thickness of the magnets.

6. The electric motor according to claim 1 , wherein,
each of the permanent magnets is not only magnetized in the circumferential direction.

7. An electric motor comprising:
a rotor provided on a rotary shaft; and
a stator fixed outside an outer peripheral surface of the rotor,
the rotor including:
a rotor core fixed to the rotary shaft so as to be rotatable together with the rotary shaft; and
a plurality of permanent magnets embedded and fixed in the rotor core,
wherein the permanent magnets extend in radial directions of the rotor and are spaced from each other in a circumferential direction of the rotor and each of the permanent magnets have a magnetic-pole facing portion with a flat plate shape that extends radially and a proximity portion that extends from a radially inner end portion of the magnetic-pole facing portion toward the magnetic-pole facing portion of an adjacent permanent magnet so that the proximity portion of the permanent magnets adjacent to each other face each other, and each of the permanent magnets (i) is magnetized in directions normal to a surface of the permanent magnet so that poles of the same polarity face each other in the circumferential direction, (ii) has a uniform thickness and (iii) is tortuous from one end portion of the rotor to the other end portion of the rotor with respect to a direction of the rotary shaft of the rotor so that the permanent magnet has a generally S shape in which a plurality of curved portions are sequentially connected, and
wherein the magnetic-pole facing portion of each of the adjacent permanent magnets is substantially longer than the proximity portion such that the magnetic-pole facing portions extend generally along a straight line to the proximity portion, the proximity portions defining a curved shaped end of each of the adjacent permanent magnets.

8. The electric motor according to claim 7 , wherein,
each of the permanent magnets further (i) has a thickness in a magnetization direction that increases from a distal end portion to a radially outer end portion and (ii) has a uniform thickness in an axial direction.

9. A production method for an electric motor that includes:
a rotor provided on a rotary shaft; and
a stator fixed outside an outer peripheral surface of the rotor,
the rotor including:
a rotor core fixed to the rotary shaft so as to be rotatable together with the rotary shaft; and
a plurality of permanent magnets embedded and fixed in the rotor core and each of the permanent magnets have a magnetic-pole facing portion with a flat plate shape that extends radially and a proximity portion that extends from a radially inner end portion of the magnetic-pole facing portion toward the magnetic-pole facing portion of an adjacent permanent magnet so that the proximity portion of permanent magnets adjacent to each other face each other, wherein each of the permanent magnets is magnetized in directions normal to a surface of the permanent magnet so that poles of the same polarity face each other in the circumferential direction, the magnetic-pole facing portion of each of adjacent permanent magnets being substantially longer than the proximity portion such that the magnetic-pole facing portions extend generally along a straight line to the proximity portion, the proximity portions defining a curved shaped end of each of the adjacent permanent magnets, the production method comprising:
a stacking step of forming the rotor core by stacking a plurality of lamination steel sheets so that the lamination steel sheets are angularly shifted from each other and cavities are formed, each of the cavities being bent or curved with respect to a direction of the rotary shaft of the rotor; and
a molding step of molding and disposing the permanent magnets in the cavities by injection molding.

Assignees

• Jtekt Corp

Inventors

• Shibata Yoshiyuki

Classifications

• H02K1/2773 Primary

  consisting of tangentially magnetized radial magnets · CPC title

• H02K2201/06

  Magnetic cores, or permanent magnets characterised by their skew · CPC title

• Y10T29/49012

  Rotor · CPC title

• H02K15/03

  having permanent magnets · CPC title