Rotor of electric motor and method for manufacturing the same

Abstract

Between a permanent magnet formed in a ring shape and a rotating shaft arranged at the center of the permanent magnet, a cushioning member made of rubber material is vulcanized and molded, and the permanent magnet and the rotating shaft are integrally coupled through the cushioning member, whereby vibration isolation, eccentricity and the like of a rotor are realized with a small number of components to manufacture an electric motor at low cost.

1 . A rotor of an electric motor to be arranged inside a stator for generating a revolving magnetic field, comprising: a permanent magnet formed in a ring shape; a rotating shaft arranged at a center of said permanent magnet; and a cushioning member made of rubber material having predetermined hardness, vulcanized and molded between said permanent magnet and said rotating shaft, characterized in that said permanent magnet and said rotating shaft are integrally coupled through said cushioning member.  
     
     
         2 . The rotor of an electric motor according to    claim 1   , characterized in that on an inner peripheral surface of said permanent magnet, there is formed a protruded portion which enters said cushioning member as an anchor.  
     
     
         3 . The rotor of an electric motor according to    claim 2   , characterized in that said plurality of protruded portions are provided at predetermined intervals circumferentially on an inner peripheral surface of said permanent magnet.  
     
     
         4 . The rotor of an electric motor according to    claim 2   , characterized in that said protruded portions are formed in a series of flange shape circumferentially on an inner peripheral surface of said permanent magnet.  
     
     
         5 . The rotor of an electric motor according to any of    claims 1    to    4   , characterized in that joining of said permanent magnet and said rotating shaft to said cushioning member is further reinforced with adhesive.  
     
     
         6 . The rotor of an electric motor according to any of    claims 1    to    4   , characterized in that joining of said rotating shaft and said cushioning member is further reinforced by baking means.  
     
     
         7 . The rotor of an electric motor according to any of    claims 1    to    6   , characterized in that said cushioning member is provided with displacement absorbing means for absorbing displacement of said cushioning member.  
     
     
         8 . The rotor of an electric motor according to    claim 7   , characterized in that said displacement absorbing means consists of a plurality of through-holes formed in said cushioning member in parallel to said rotating shaft.  
     
     
         9 . The rotor of an electric motor according to    claim 7   , characterized in that said displacement absorbing means consists of a plurality of recesses formed on both surfaces of said cushioning member.  
     
     
         10 . The rotor of an electric motor according to any of    claims 1    to    10   , characterized in that said cushioning member is chloroprene rubber.  
     
     
         11 . A method for manufacturing a rotor of an electric motor to be arranged inside a stator for generating a revolving magnetic field, comprising the steps of: after a permanent magnet formed in a ring-shape in advance and a rotating shaft are concentrically arranged within a metal mold, pouring rubber material in fluid state into space between said permanent magnet and said rotating shaft to vulcanize and mold a cushioning member having predetermined hardness, and integrally coupling said permanent magnet and said rotating shaft through said cushioning member.  
     
     
         12 . The method for manufacturing a rotor of an electric motor according to    claim 11   , characterized in that said permanent magnet is made of plastic magnet, and when said cushioning member is vulcanized and molded within space between said permanent magnet and said rotating shaft, the molding temperature is controlled to be equal to or less than temperature at which said plastic magnet does not become deformed.  
     
     
         13 . The method for manufacturing a rotor of an electric motor according to    claim 11    or    12   , characterized in that prior to vulcanizing and molding of said cushioning member, both an inner peripheral surface of said permanent magnet and said rotating shaft, or either of them is coated with adhesive.  
     
     
         14 . The method for manufacturing a rotor of an electric motor according to    claim 11   ,    12    or  13 , characterized in that after vulcanizing and molding of said cushioning member, a joined portion between said rotating shaft and said cushioning member is further baked.