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US 4,891,567 AGranted
Brushless DC motor having an outer rotor
AssigneeMinebea Co., Ltd.
InventorsSakae Fujitani, Yuzuru Suzuki, Masanao Okuda, Hitoshi Takahashi, Junichiro Fukazawa
Life of this patent
Estimating the term…
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.
Claims20
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.
5 more elements
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.
5 more elements
Dependencies are inferred from the claim text.