Magnet protection mechanism for magnet body in rotor and magnet protection method

Abstract

A magnet covering member made of a soft steel plate covers an outer surface of a magnetized permanent magnet placed in a rotor core of a rotor. The magnet covering member is detached from the permanent magnet when the rotor is incorporated into a stator of an alternator during an alternator assembling process. Because of a soft magnetic characteristic of the magnet covering member, an outer magnetic field generated by the permanent magnet placed between adjacent claw poles of the rotor core makes a magnetic short-circuit, and a magnetic attracting phenomenon caused by such a magnetic field is thereby reduced. The soft magnetic characteristic of the magnet covering member also serves to support the rotor.

1 . A magnet protection mechanism capable of protecting magnet bodies mounted on a rotor, comprising: 
 a magnet covering member, covering at least an outer exposed surface of each magnet body, including a magnetized magnet, at an outer peripheral side thereof, and the magnet covering member being detachably supported by a rotor with the magnet bodies.    
     
     
         2 . The magnet protection mechanism according to  claim 1 , wherein 
 the magnet body is placed in a gap between adjacent claw poles of a Lundell type rotor core in the rotor and is positioned radially inward of the rotor rather than an outer peripheral surface of the claw pole, and    the magnet covering member is made of a soft magnetic metal sheet and placed radially inward than the outer peripheral surface of the claw pole of the Lundell type rotor core.    
     
     
         3 . The magnet protection mechanism according to  claim 2 , wherein 
 a sectional shape of the magnet covering member is an approximate “U” shape, and the magnet covering member is placed in the gap between the adjacent claw poles, the magnet covering member comprises: 
 an outer surface part configured to cover the outer exposed surface of the magnet body; and  
 a pair of side parts extended from both ends of an axis direction of the outer surface part of the magnet covering member toward the inside of the radial direction, covering the side surfaces of the magnet body.  
   
     
     
         4 . The magnet protection mechanism according to  claim 3 , wherein 
 a front part of each side part of the magnet covering member has a sealing projection part that is bent toward the magnet body side and detachable in the radial direction from the magnet body.    
     
     
         5 . The magnet protection mechanism according to  claim 2 , wherein 
 the magnet covering member is attached onto the magnet body at a predetermined distance determined by the gap, between the adjacent claw poles, against the outer exposed surface of the magnet body at the outer peripheral side.    
     
     
         6 . The magnet protection mechanism according to  claim 1 , wherein 
 the magnet body is placed in a gap between adjacent claw poles of a Lundell type rotor core in the rotor and is positioned radially inward of the rotor rather than an outer peripheral surface of the claw pole, and    the magnet covering member has a cylindrical shape and attached to the outer peripheral surface of a Lundell type rotor core of the rotor in which each magnet body is placed at a gap between adjacent claw poles of the Lundell type rotor core.    
     
     
         7 . The magnet protection mechanism according to  claim 6 , wherein 
 the magnet covering member of a cylindrical shape is divided into two parts, and each part has a bottom part having a semicircular hole formed at a center of the bottom part through which a rotary shaft of the rotor is inserted.    
     
     
         8 . The magnet protection mechanism according to  claim 3 , wherein 
 the outer surface part of the magnet covering member covering the outer exposed surface of the magnet body is coated with a resin film.    
     
     
         9 . The magnet protection mechanism according to  claim 1 , wherein 
 the magnet covering member is made of an adhesion tape, and one surface of which is coated with an adhesion material to be attached onto the exposed surface of the magnet body.    
     
     
         10 . A magnet protection method of protecting magnet bodies being magnetized placed and fixed to a rotor core in a rotor in which an outer surface of each magnet body being placed radially inward than an outer peripheral surface of the rotor core, comprising steps of: 
 attaching a magnet covering member, before cutting and grinding processes of the outer peripheral surface of the rotor core, onto at least the outer surface of the magnet body at an outside position of the radial direction than the outer surface of the magnet body and radially inward of the outer surface of the rotor core; and    detaching the magnet covering member from the magnet body after completion of the cutting and grinding process and before assembling process of incorporating the rotor into a stator of an alternator.    
     
     
         11 . The magnet protection mechanism according to  claim 6 , wherein the magnet covering member diameter is smaller than the stator inner diameter.  
     
     
         12 . The magnet protection mechanism according to  claim 1 , wherein the magnet covering member being detachably supported by a rotor with the magnet bodies before incorporated into a stator in an alternator.