1. Field of the Invention
The present invention generally relates to a magnet protection mechanism and a magnet protection method capable of protecting magnet bodies such as permanent magnets, from magnetic powders and dust, placed in a rotor of an inner-rotor type vehicle alternator.
2. Description of the Related Art
There is a conventional technique to increase the magnitude of or to support a magnetic flux of a field current at each claw pole by a magnetic flux of a permanent magnet additionally placed between adjacent claw poles in a Lundell type rotor core of a rotary electric machine such as a vehicle alternator to be driven by an internal combustion engine of a vehicle.
Various prior patent documents, in particularly, following Japanese patent laid open publication documents (1) to (7) have disclosed such a conventional technique:
(1) JP 2004-7958; (2) JP 2002-262530; (3) JP H10-4664;
(4) JP H10-201149; (5) JP H10-4660; (6) JP H10-4662; and
(7) JP H10-4663.
Although the vehicle alternator of the Lundell type rotor core having such a configuration increases its output power by increasing the magnitude of magnetic flux generated by additionally incorporating permanent magnets into the rotor core when compared with a vehicle alternator of a same volume without incorporating any additional permanent magnets, such a configuration deteriorates a magnetic characteristic of and decreases the durability of the magnet components such as the claw poles and the permanent magnets because of the adhesion of magnet powders generated during manufacturing processes of the rotor core onto the surface of the magnet component, in particular, of the permanent magnet.