Conventionally, rotors including a built-in permanent magnet are known for rotary electric machines such as motors and power generators. This type of rotor is also called an “Interior Permanent Magnet (IPM) type rotor”. In such an IPM type rotor, a rotor core formed from a cylindrical magnet body includes a magnet insertion hole which extends in an axial direction near an inner side of an outer circumferential surface of the rotor core. A permanent magnet is inserted inside the magnet insertion hole and adhesively fixed with a resin material.
For example, JP 2011-4529 A (Patent Document 1) discloses an IPM type rotor. In this rotor, a cylindrical rotor core in which electromagnetic steel plates 1 are laminated internally includes an embedded permanent magnet forming magnetic poles. Two end plates are provided at respective ends of the rotor core. The rotor core and the magnet are fixed by the end plates. Each of the end plates is provided with pawl portions which bend at the outer rim. The pawl portions press a part of a side surface of the rotor core. It is described that this rotor can achieve a high-strength structure and effectively suppress leakage flux from the permanent magnet.
JP 2010-183692 A (Patent Document 2) discloses a motor magnet which is inserted in a slot provided in a direction along the axial direction of a rotor. This motor magnet is formed by two or more segment magnets which are stacked in the axial direction of the rotor. An oxide film is formed around each of the segment magnets by the oxidation of the segment magnets.
Further, JP 2005-94845 A (Patent Document 3) discloses a rotor of a permanent magnet type rotary electric machine in which a permanent magnet is inserted and fixed in a magnet insertion hole of a rotor iron core formed by laminating many annular iron core plate members. It is described that the permanent magnet is formed by two or more unit magnets which are aligned in a line in the axial direction and coated with resin to form a bar shape.