Abstract: A magnet rotor for a synchronous motor includes a yoke formed of a magnetic material. A generally cylindrical permanent magnet is disposed around the yoke magnet and has N and S poles alternately located in the circumferential direction of the permanent magnet. An adhesive is filled in the clearance between the outer peripheral surface of the yoke and the inner peripheral surface of the permanent magnet. The adhesive is hardened at a hardening temperature, which is around a maximum temperature encountered during operation of the motor to accomplish bonding between the yoke and the permanent magnet. The clearance between the yoke and the permanent magnet has a dimension L given by the following formula:L.gtoreq.(E.times..DELTA.L) / .sigma.swhere E is a tensile elastic modulus of the adhesive; .DELTA.L is a change amount of the clearance upon thermal expansion or contraction; and .sigma.s is a tensile stress applied to the adhesive.

Abstract: A rotor comprises a rotor body and a ring-shaped rare earth metal-iron type magnet arranged therearound, in which a low thermal-expansion material is inserted between the rotor body and the magnet.

Abstract: A magnet is formed as a ring magnet and magnetized by radial application of a magnetic field while the intensity of the magnetic field is changed periodically along the circumference of the ring magnet to give a circumferentially sinusoidal waveform distribution of magnetic flux density to the ring magnet in the magnetized state of the magnet.

Abstract: A method for producing an anisotropic rare earth magnet is improved by extruding using a compacted material formed in a shape having difference in level between the center part to be in contact with the end face of a punch and the outer peripheral part to be faced with a molding cavity formed between the punch and a cylindrical die of a mold.

Abstract: A method of forming a cylindrical compact for a cylindrical magnet is improved by moving a core pin and a die of a mold at the same time of pressing magnet materials with a pressing punch in the same direction as that of the pressing punch at travelling speed Vc and Vd indicated by following equation:Vc=m.multidot.Vp(0.5.ltoreq.m.ltoreq.1.0)Vd=n.multidot.Vp(0.5.ltoreq.n.ltoreq.1.0)where Vc is the travelling speed of the core pin, Vd is the travelling speed of the die and Vp is the pressing speed of the pressing punch. It is possible to form the thin-walled elongated cylindrical compact by utilizing the frictional force caused between the mold and the magnet materials for forming the compact very effectively in order to obtain a thin walled elongated cylindrical magnet.

Abstract: A method for producing an anisotropic rare earth magnet is improved by applying compressing stress on a free surface of an compacted material at the time of extruding the compacted material in order to prevent forming cracks, and improved by using a double action punch provided with a core punch and a sleeve punch so as to mold a compacted material and extrude the compacted material into the anisotropic magnet material in a single heat process continuously.