Brushless D.C. motor having alternating wider and narrower pole shoes
First Claim
1. A self-starting brushless DC motor comprising a rotor rotatable about an axis of rotation and including a permanent magnet magnetized to have circumferentially alternately opposite rotor poles;
- a stator provided with projecting poles corresponding in number to said rotor poles;
coils wound on said projecting poles, said projecting poles each including a generally radially extending base means and a circumferentially extending shoe means extending circumferentially from a free end of said base means, said base means of said projecting poles being spaced apart circumferentially equidistantly, said circumferentially extending shoe means of said projecting poles being of alternately wider and narrower circumferential width and formed of magnetizable material, said coils being connected to alternately excite the wider and narrower shoe means in opposite polarities;
a Hall effect element opposed to said rotor for detecting the polarity of one of the rotor poles at a predetermined position and providing a control signal dependent on said polarity detected; and
means responsive to said control signal for supplying a direct current of a predetermined direction to the coils for said excitation;
said narrower shoe means extending in only one circumferential direction from said free end of its associated base portion to enable the rotor to self-start in one direction with an enhanced starting torque.
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Accused Products
Abstract
A brushless D.C. motor wherein one of projected stator poles positioned to be mutually equally spaced in mechanical angle is made sufficiently smaller than the other as partly cut off at circumferentially expanding pole tooth part, the stator poles being respectively polarized depending on controllably varied direction of direct current to coils on the poles by means of a rotor position detecting Hall element which detects the polarity at a predetermined position of the rotor, for allowing the rotor to self-start constantly in one direction with a remarkably increased starting torque.
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Citations
5 Claims
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1. A self-starting brushless DC motor comprising a rotor rotatable about an axis of rotation and including a permanent magnet magnetized to have circumferentially alternately opposite rotor poles;
- a stator provided with projecting poles corresponding in number to said rotor poles;
coils wound on said projecting poles, said projecting poles each including a generally radially extending base means and a circumferentially extending shoe means extending circumferentially from a free end of said base means, said base means of said projecting poles being spaced apart circumferentially equidistantly, said circumferentially extending shoe means of said projecting poles being of alternately wider and narrower circumferential width and formed of magnetizable material, said coils being connected to alternately excite the wider and narrower shoe means in opposite polarities;
a Hall effect element opposed to said rotor for detecting the polarity of one of the rotor poles at a predetermined position and providing a control signal dependent on said polarity detected; and
means responsive to said control signal for supplying a direct current of a predetermined direction to the coils for said excitation;
said narrower shoe means extending in only one circumferential direction from said free end of its associated base portion to enable the rotor to self-start in one direction with an enhanced starting torque. - View Dependent Claims (2, 3, 4, 5)
- a stator provided with projecting poles corresponding in number to said rotor poles;
Specification