Brushless motor

• US 7,839,039 B2
• Filed: 06/26/2007
• Issued: 11/23/2010
• Est. Priority Date: 06/27/2006
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: Horie, Tetsuo, Kitabayashi, Minoru, Takahashi, Tomofumi, Matsubara, Ken
• Primary Examiner(s): Mullins; Burton
• Assistant Examiner(s): Kim; John K
• Application Number:
  US11/819,280
• Publication Number:
  US 20080174191A1
• Time in Patent Office: 1,246 Days
• Field of Search: 310/89, 310/90, 310/216, 310/218, 310/91
• US Class Current: 310/90
• CPC Class Codes: F16C 19/06 with a single row or balls
• CPC Class Codes: F16C 19/54 Systems consisting of a plurality of bearings with rolling friction spindle bearings F16C35/08
• CPC Class Codes: F16C 25/083 with resilient means acting axially on a race ring to preload the bearing
• CPC Class Codes: H02K 5/1732 radially supporting the rotary shaft at both ends of the rotor H02K5/1737 takes precedence

Abstract

A rotary shaft of a rotor including a magnet with a plurality of magnetic poles arranged at equal intervals on an outer circumference is supported at both ends by bearings. By externally fitting the inner ring of one bearing to the rotary shaft and holding it to be immovable in an axial direction and loosely fitting the outer ring of the bearing into the support hole and positioning it with belleville springs which are in contact resiliently with both sides, the rotary shaft and the rotor are supported so that they are movable in an axial direction within a movement amount of not greater than 2 mm according to a movement of the bearing caused against spring forces of the belleville springs.

Claims

1. A brushless motor comprising:

a rotor including a magnet and rotatably supported by a rotary shaft, said magnet having magnetic poles to the number of p arranged at equal intervals on an outer circumference;

a stator stationarily mounted to surround an outside of said rotor, said stator including slots to the number of n arranged at equal intervals in an inner circumference;

two bearings supporting said rotor at both ends thereof, and an outer ring of at least one of said bearings being loosely fitted to a housing; and

a resilient body disposed on both sides of the outer ring, the resilient body resiliently contacting the outer ring,

wherein the ratio n/p of n to p is set between 1.2 and 1.5,

an axial length of said rotor is substantially equal to an axial length of said stator, and

said rotor is supported so that said rotor is movable in an axial direction within a movement amount ranging from 1 mm to 2 mm by the outer ring resiliently contacting the resilient body, thereby reducing cogging torque based on a magnetic flux change due to a positional displacement in both ends in the axial direction of the rotor and the stator and reducing friction due to rotation of the rotor.

2. The brushless motor according to claim 1, wherein said bearings are two deep-groove ball bearings to which no pre-load is applied.

3. The brushless motor according to claim 2, further comprising said housing for storing said rotor and said stator,

wherein an inner ring of said one deep-groove ball bearing is externally fitted to the rotary shaft of said rotor.