Brushless motor including thrust bearing
View Patent ↗The present invention provides a low vibration brushless motor for reducing the vibration of the motor in an axial direction. In the brushless motor, a bearing is provided in a bearing boss, a shaft is held by the bearing, an end face of the shaft is contacting a thrust receiving member, and the shaft is rotatably axially supported by the bearing. The brushless motor includes a permanent magnet for attracting the end face of the shaft in the thrust direction with the thrust receiving member therebetween, and a bottom receiving part for supporting the permanent magnet, wherein the bearing boss, bearing, shaft, and bottom receiving part are made of a magnetic material, and a closed magnetic path is formed so that a magnetic flux passes through the permanent magnet, bottom receiving part, bearing boss, bearing, and shaft.
1. A brushless motor in which a bearing is provided in a bearing boss and a shaft is held by the bearing, the shaft having an end face contacting a thrust receiving member and being rotatably axially supported by the bearing, the brushless motor comprising:
a permanent magnet for attracting the end face of the shaft in the thrust direction, with the thrust receiving member therebetween; and
a bottom receiving part for supporting the permanent magnet, wherein
the bearing boss, the bearing, the shaft, and the bottom receiving part are made of a magnetic material, and a closed magnetic path is formed so that a magnetic flux passes through the permanent magnet, the bottom receiving part, the bearing boss, the bearing, and the shaft.
2. The brushless motor as claimed in claim 1 , wherein a space is provided between an outer periphery of the permanent magnet and the bottom receiving part.
3. The brushless motor as claimed in claim 1 , wherein the permanent magnet is formed by being cut out from a block of anisotropic permanent magnet.
4. The brushless motor as claimed in claim 1 , wherein the permanent magnet is shaped to be a triangular or rectangular parallelepiped.
5. The brushless motor as claimed in claim 1 , wherein the shaft is fixed with a pull-out-preventive stopper made of a magnetic material at a tip end portion thereof facing the permanent magnet.
6. A brushless motor comprising:
a magnetic thrust bearing comprising a bearing boss and a shaft held by the bearing, the shaft having an end face contacting a thrust receiving member and being rotatably supported by the bearing,
a receiving part for supporting a permanent magnet;
a permanent magnet being single polarized and magnetized in the axial direction of the shaft, and attracting the shaft;
said permanent magnet being located adjacent the thrust receiving member contacted by the end face of the shaft;
wherein the bearing boss, the bearing, the shaft, and the receiving part comprise a magnetic material so that a closed magnetic path for a magnetic flux passes through the permanent magnet, the receiving part, the bearing boss, the bearing, and the shaft.
7. The brushless motor as claimed in claim 6 , wherein an outer periphery of the permanent magnet and the receiving part are spaced apart.
8. The brushless motor as claimed in claim 6 , wherein the permanent magnet is an anisotropic permanent magnet.
9. The brushless motor as claimed in claim 6 , wherein the permanent magnet is a triangular or rectangular parallelepiped.
10. The brushless motor as claimed in claim 6 , wherein the shaft is fixed in place by a pull-out-preventive stopper comprising a magnetic material at a tip end portion thereof facing the permanent magnet.