US4891567A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Brushless DC motor having an outer rotor
Assignee: Minebea Co Ltd
•
Filing: 1988-07-12
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Granted: 1990-01-02
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Expires: 2008-07-12
Abstract
Abstract Herein disclosed is a brushless DC motor of high performance, which has its construction simplified and feasible made by sandwiching an annular coil between two stator yokes having a plurality of magnetic elements in the circumferential direction, by magnetically shorting the two stator yokes through a shorting member, and by providing a magnetic pole detector for detecting the positions of the magnetic poles of a rotor.
Inventors
- 👤 Sakae Fujitani
- 👤 Yuzuru Suzuki
- 👤 Masanao Okuda
- 👤 Hitoshi Takahashi
- 👤 Junichiro Fukazawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 04:42
CPC Classifications
H; H02; H02K; H02K21/00; H02K21/12; H02K21/22; H02K21/227; H02K29/00; H02K29/06; H02K29/08; H02K2201/00; H02K2201/12
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
228 words
A brushless DC motor having an outer rotor comprising: a plurality of magnetic poles disposed in the rotating direction on an inner surface of the rotor, said rotor being mounted rotatably in a bearing housing, a stator disposed coaxially with the rotor and inside of the magnetic poles so as to maintain an even air gap between the stator and the magnetic poles for generating a magnetic field which drives the magnetic poles of the rotor when an electric current is fed to an annular coil of the stator; and a magnetic pole detector for detecting the positions of the magnetic poles of said rotor to control the electric current to be fed to said stator, wherein said stator includes: a bobbin provided coaxially with the rotor and wound with the annular coil for passing the electric current therethrough; and two stator yokes made of a magnetic material, each having magnetic elements, made by bending magnetic metal plates, in a number half as many as that of the magnetic poles of said rotor, said stator yokes being arranged to face each other at their magnetic element forming sides through said annular coil, said magnetic elements being so combined with each other as to establish a magnetic unbalance in said air gap with respect to the magnetic poles of said rotor and being magnetically shorted through a shorting member.
Claim 2
Dependent Claim
228 words
A brushless DC motor having an outer rotor comprising: a plurality of magnetic poles disposed in the rotating direction on an inner surface of the rotor, said rotor being mounted rotatably in a bearing housing, a stator disposed coaxially with the rotor and inside of the magnetic poles so as to maintain an even air gap between the stator and the magnetic poles for generating a magnetic field which drives the magnetic poles of the rotor when an electric current is fed to an annular coil of the stator; and a magnetic pole detector for detecting the positions of the magnetic poles of said rotor to control the electric current to be fed to said stator, wherein said stator includes: a bobbin provided coaxially with the rotor and wound with the annular coil for passing the electric current therethrough; and two stator yokes made of a magnetic material, each having magnetic elements, made by bending magnetic metal plates, in a number half as many as that of the magnetic poles of said rotor, said stator yokes being arranged to face each other at their magnetic element forming sides through said annular coil, said magnetic elements being so combined with each other as to establish a magnetic unbalance in said air gap with respect to the magnetic poles of said rotor and being magnetically shorted through a shorting member.
Claim 3
Dependent Claim
18 words
A brushless DC motor according to claim 1, wherein said stator yokes are made of a ferromagnetic material.
Claim 4
Dependent Claim
19 words
A brushless DC motor according to claim 1, wherein said stator yokes are made of a soft, magnetic material.
Claim 5
Dependent Claim
16 words
A brushless DC motor according to claim 1, wherein said shorting member is a cylindrical member.
Claim 6
Dependent Claim
24 words
A brushless DC motor according to claim 4, wherein said cylindrical member is formed with notches, slits or holes for suppressing an eddy current.
Claim 7
Dependent Claim
19 words
A brushless DC motor according to claim 4, wherein said cylindrical member is made of a soft, magnetic material.
Claim 8
Dependent Claim
32 words
A brushless DC motor according to claim 1, wherein said shorting member is a cylindrical member, and said cylindrical member and said stator yokes are monolithically made of a soft, magnetic material.
Claim 9
Dependent Claim
20 words
A brushless DC motor according to claim 7, wherein said soft, magnetic material is a resin containing soft, magnetic powder.
Claim 10
Dependent Claim
30 words
A brushless DC motor according to claim 1, wherein the bobbin of said annular coil and the bearing housing of said rotor are monolithically made of a soft, magnetic material.
Claim 11
Dependent Claim
20 words
A brushless DC motor according to claim 9, wherein said soft, magnetic material is a resin containing soft, magnetic powder.
Claim 12
Dependent Claim
21 words
A brushless DC motor according to claim 1, wherein the bobbin of said annular coil is made of a synthetic resin.
Claim 13
Dependent Claim
31 words
A brushless DC motor according to claim 1, wherein said stator yokes and the bobbin of said annular coil are formed with holes and projections which can engage with each other.
Claim 14
Dependent Claim
20 words
A brushless DC motor according to claim 1, wherein said shorting member is a plurality of soft, magnetic shorting rods.
Claim 15
Dependent Claim
25 words
A brushless DC motor according to claim 13, wherein said soft, magnetic shorting rods are monolithically insert molded with the bobbin of said annular coil.
Claim 16
Dependent Claim
21 words
A brushless DC motor according to claim 1, wherein said stator yokes are formed with notches for suppressing an eddy current.
Claim 17
Dependent Claim
21 words
A brushless DC motor according to claim 1, wherein said stator yokes are formed with slits for suppressing an eddy current.
Claim 18
Dependent Claim
34 words
A brushless DC motor according to claim 1, wherein said shorting member is a cylindrical member, and said cylindrical member and the bearing housing of said rot monolithically made of a soft, magnetic material.
Claim 19
Dependent Claim
20 words
A brushless DC motor according to claim 17, wherein said soft, magnetic material is a resin containing soft, magnetic powder.
Claim 20
Dependent Claim
21 words
A brushless DC motor according to claim 1, wherein said stator yokes are formed with holes for suppressing an eddy current.
Claim 21
Dependent Claim
222 words
A brushless DC motor having an outer rotor comprising: a plurality of magnetic poles disposed in the rotating direction on an inner surface of the rotor, said rotor being mounted rotatably in a bearing housing, a stator disposed coaxially with the rotor and inside of the magnetic poles so as to maintain an even air gap between the stator and the magnetic poles for generating a magnetic field which drives the magnetic poles of the rotor when an electric current is fed to an annular coil of the stator; and a magnetic pole detector for detecting the positions of the magnetic poles of said rotor to control the electric current to be fed to said stator, wherein said stator includes: a bobbin provided coaxially with the rotor and wound with the annular coil for passing the electric current therethrough; and two stator yokes made of a magnetic material, each having magnetic elements in a number half as many as that of the magnetic poles of said rotor, said stator yokes being arranged to face each other at their magnetic element forming sides through said annular coil, said magnetic elements being so combined with each other as to establish a magnetic unbalance in said air gap with respect to the magnetic poles of said rotor and being magnetically shorted through a shorting member.
Claim 22
Dependent Claim
222 words
A brushless DC motor having an outer rotor comprising: a plurality of magnetic poles disposed in the rotating direction on an inner surface of the rotor, said rotor being mounted rotatably in a bearing housing, a stator disposed coaxially with the rotor and inside of the magnetic poles so as to maintain an even air gap between the stator and the magnetic poles for generating a magnetic field which drives the magnetic poles of the rotor when an electric current is fed to an annular coil of the stator; and a magnetic pole detector for detecting the positions of the magnetic poles of said rotor to control the electric current to be fed to said stator, wherein said stator includes: a bobbin provided coaxially with the rotor and wound with the annular coil for passing the electric current therethrough; and two stator yokes made of a magnetic material, each having magnetic elements in a number half as many as that of the magnetic poles of said rotor, said stator yokes being arranged to face each other at their magnetic element forming sides through said annular coil, said magnetic elements being so combined with each other as to establish a magnetic unbalance in said air gap with respect to the magnetic poles of said rotor and being magnetically shorted through a shorting member.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-01-01 | 1993-07-03 | 1994-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-01 | 1997-07-03 | 1998-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-01 | 2001-07-03 | 2002-01-02 | $7700.00 | Window Closed / Lapsed |