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Rotor for electric motor
| Details |
Inventors: Shiga, Tsuyoshi; Hayashi, Kinya; Endou, Masami;
Assignee: Kabushiki Kaisha Toshiba (Kawasaki, JP)
Primary Examiner: Ramirez; Nestor
Assistant Examiner: Waks; Joseph
Attorney, Agent or Firm: Pillsbury Madison & Sutro LLP
A rotor for an electric motor includes a frame made of a resin and having a cylindrical yoke mounting portion, a base covering one end side of the yoke mounting portion, and a shaft supporting portion located at the center of rotation of the base, all of which are formed integrally with the frame, a rotor yoke mounted on the yoke mounting portion and substantially divided into a plurality of unit yokes, and a plurality of rotor magnets mounted on the yoke mounting portion along the rotor yoke. |
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DETAILED DESCRIPTION Therefore, an object of the present invention is to provide a rotor for electric motors, in which occurrence of cracks can be prevented from being produced in the frame body and the dimensional accuracy of the shaft supporting portion can be rendered stable.
The present invention provides a rotor for an electric motor, comprising a frame made of a resin and having a cylindrical yoke mounting portion, a base covering one end side of the yoke mounting portion, and a shaft supporting portion located at the center of rotation of the base, the yoke mounting portion, the base and the shaft supporting portion being formed integrally with the frame, a rotor yoke provided on the yoke mounting portion and substantially divided into a plurality of unit yokes, and a plurality of rotor magnets provided on the yoke mounting portion along the rotor yoke.
According to the above-described rotor, the rotor yoke is divided into a plurality of the unit yokes completely or incompletely, for example, by slits.
Accordingly, expansion and shrinkage of the rotor yoke are circumferentially dispersed at divided portions when the frame is molded from the resin.
Since this reduces an amount of stress exerted on the base of the frame, occurrence of cracks due to the residual stress is prevented in the base.
Further, since the shaft supporting portion is prevented from displacement, the dimensional accuracy of the shaft supporting portion can be rendered stable.
The number of the unit yokes is preferably equal to that of divisors obtained by dividing the number of teeth of a stator by the number of phases of stator coils, the divisors excluding 1.
In this construction, spaces between the adjacent ends of all the unit yokes are simultaneously opposed to the teeth of the stator or to slots defined between the teeth during rotation of the rotor.
Consequently, since the rotor magnets develop uniform torque, nonuniformity in the rotation of the rotor can be reduced.
Each unit yoke preferably has two circumferential ends each of which is adjacent to each one circumferential end of the neighboring unit yokes with a space therebetween, and the rotor magnets preferably include those each of which has a circumferential central portion opposed to the space between the adjacent ends of the unit yokes
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Generators or Motors 
