Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1995-03-20
1997-10-21
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
310261, 310 42, 310187, H02K 2112, H02K 1503
Patent
active
056799950
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a permanent magnet rotor of a brushless motor, and particularly to a permanent magnet rotor of a brushless motor which has a yoke made by laminating a large number of steel sheets, an even number of magnetic poles protruding outward on the yoke, and a permanent magnet for a field inserted in each magnetic pole or every other magnetic poles.
BACKGROUND ART
Generally known brushless motors consist of a permanent magnet rotor which has a plurality of permanent magnets for a field inserted in a yoke made by laminating steel sheets and a stator which has magnetic poles opposing to the outer periphery of magnetic poles of the above permanent magnet rotor with a small space therebetween.
FIG. 35 is a sectional view in a direction intersecting at right angles with the rotatable shaft of a brushless motor using a conventional permanent magnet rotor. In this drawing, a conventional brushless motor 51 consists of a stator 52 and a permanent magnet rotor 53. The stator 52 has the permanent magnet rotor 53 rotatably supported therein and many stator magnetic poles 54 protruded inward. The stator magnetic poles 54 have a coil (not shown) wound thereon. Passing a current through the coil excites a prescribed magnetic pole of the stator magnetic poles 54. A magnetic pole face 55 at the end of the stator magnetic poles 54 is positioned above a cylindrical face at an equal distance from the center of a rotatable shaft 56 of the motor.
The permanent magnet rotor 53 consists of a yoke 57 made by laminating many steel sheets and a pair of permanent magnets 58 for a field. The yoke 57 has four magnetic poles 59 protruded externally on its outer periphery, and the permanent magnets 58 for the field are inserted in every other bases of the magnetic poles 59 with N poles opposed to each other. A magnetic pole face 60 at the end of each magnetic pole 59 is formed to have a curved shape at an equal distance from the center of the rotatable shaft 56, and opposed to the magnetic pole face 55 at an equal distance at every point on the face of the rotatable magnetic pole face 60.
In the above permanent magnet rotor 53, the repulsion of the N poles of the permanent magnets 58 for the field causes the magnetic fluxes to get out of the magnetic pole faces 60 without the permanent magnet for the field as shown in the drawing, to pass through the stator, and to enter the yoke 57 from the magnetic pole faces 60 with the permanent magnet for the field. Accordingly, the magnetic poles having the permanent magnet of the permanent magnet rotor 53 become S pole, and those not having the permanent magnet of the permanent magnet rotor 53 become N pole.
As shown in the drawing, the permanent magnet rotor 53 is rotated by exciting the stator magnetic poles 54, which have been slightly deviated in the rotating direction from the center of the magnetic poles 59 of the permanent magnet rotor 53, to N pole. The permanent magnet rotor 53 is rotated by being attracted to the excited stator magnetic poles 54. Then, the stator magnetic poles 54 which are further displaced with respect to the rotated permanent magnet rotor 53 are excited to N pole. The permanent magnet rotor 53 is further rotated by being attracted to the newly excited stator magnetic poles 54. This procedure is repeated to continuously rotate the permanent magnet rotor 53.
The known conventional brushless motor uses a back electromotive force generated by the rotation of the permanent magnet rotor 53 to determine the position of the above permanent magnet rotor. Specifically, the rotation of the permanent magnet rotor 53 causes the magnetic fluxes of the permanent magnets 58 for the field to cross the coils (not shown) wound on the magnetic pole faces 55 of the stator 52 to generate the back electromotive force in the coils of the stator 52. The position of the back electromotive force is detected to detect the position of each permanent magnet for a field of the permanent magnet rotor 53, and the position of the magnetic poles to be excited on th
REFERENCES:
patent: 4922152 (1990-05-01), Gleghorn et al.
patent: 4939398 (1990-07-01), Lloyd
patent: 4973872 (1990-11-01), Dohogne
patent: 5097166 (1992-03-01), Mikulic
patent: 5159220 (1992-10-01), Kliman
patent: 5369325 (1994-11-01), Nagate et al.
Ishiguro Akiyoshi
Nagate Takashi
Yamakoshi Issei
Enad Elvin G.
Seiko Epson Corporation
Stephan Steven L.
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