Motor with permanent magnet

• US 6,583,531 B1
• Filed: 04/08/2002
• Issued: 06/24/2003
• Est. Priority Date: 05/21/1999
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kiriyama, Hiroyuki, Tamamura, Toshiyuki, Sawahata, Takao, Kurahayashi, Takahisa, Asano, Yoshinari, Honda, Yukio
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): PHAM, LEDA T
• Application Number:
  US09/979,516
• Time in Patent Office: 442 Days
• Field of Search: 310/254, 310/257, 310/258
• US Class Current: 310/429
• CPC Class Codes: H02K 1/08 Salient poles
• CPC Class Codes: H02K 1/146 consisting of a generally annular yoke with salient poles
• CPC Class Codes: H02K 1/148 Sectional cores H02K1/141 takes precedence
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems

Abstract

A motor has a stator having a plurality of teeth for receiving windings, a yoke connected to each tooth, and a rotor having permanent magnets facing the stator. An inner wall surface of each tooth faces the rotor with an air-gap therebetween. Each tooth is separated from an adjacent tooth by a slot-open-section extending between a tailing end of the tooth and a leading end of the adjacent tooth. The inner wall surface of each tooth has an arc extending from a center of the slot-open-section toward the tailing end. The air-gap at the tailing end of each tooth is greater than the air-gap at the leading end of each tooth. The inner wall surface of each tooth includes a straight-line tailing section extending from the center of the slot-open-section toward the leading end. The straight-line tailing section extends tangentially from the arc.

Claims

1. A motor of an inner-rotor type comprising:

a stator including a plurality of teeth for receiving windings, and a yoke connected to each tooth; and

a rotor having permanent magnets facing said stator;

wherein an inner wall surface of each tooth faces said rotor with an air-gap therebetween,

wherein each tooth is separated from an adjacent tooth by a slot-open-section extending between a tailing end of the tooth and a leading end of the adjacent tooth,

wherein the inner wall surface of each tooth has an arc extending 90/N degrees from a center of the slot-open-section toward the tailing end, N representing an integer not less than 1,

wherein the air-gap at the tailing end of each tooth is greater than the air-gap at the leading end of each tooth,

wherein the inner wall surface of each tooth includes a straight-line tailing section extending 30/N degrees from the center of the slot-open-section toward the leading end, and

wherein the straight-line tailing section extends tangentially from the arc.

2. The motor according to claim 1, wherein the number of teeth is 3N and the number of polarities of said rotor is 2N.

3. The motor according to claim 2, wherein the air-gap at the straight-line tailing section is greater than the air-gap at the arc.

4. The motor according to one of claims 1-3, wherein the rotor has a rotor core, and the permanent magnets are disposed on a wall of the rotor core.

5. The motor according to one of claims 1-3, wherein said stator is formed by piecing together a plurality of divisional cores, each divisional core comprising a tooth and a yoke connected to the tooth and by coupling a teeth section and a yoke section.

6. The motor according to claim 5, wherein the slot-open-section has a gap between the leading and tailing ends of adjacent teeth, the gap being closely spaced.

7. The motor according to claim 6, wherein the gap between the leading and tailing ends is not greater than a smallest width of the air-gap.

8. The motor according to claim 4, wherein said stator is formed by piecing together a plurality of divisional cores, each divisional core comprising a tooth and at yoke connected to the tooth and by coupling a teeth section and a yoke section.

9. The motor according to claim 8, wherein the slot-open-section has a gap between the leading and tailing ends of adjacent teeth, the gap being closely spaced.

10. The motor according to claim 9, wherein the gap between the leading and tailing ends is not greater than a smallest width of the air-gap.