BRUSHLESS DC MOTOR DEVICE AND PERMANENT MAGNET THEREOF

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PROBLEM TO BE SOLVED : To significantly reduce the size, maintain and enhance the high torque characteristics and high efficiency, and further enhance the cogging torque of a brushless DC motor. SOLUTION : The brushless DC motor is comprised of : a stator made of an electromagnet; and a rotor that is disposed at the central part thereof and has a magnetic core and a permanent magnet on the outer circumferential surface thereof. The permanent magnet is an anisotropic rare-earth bonded magnet whose maximum magnetic energy product is not less than 143 kJ/m3 and not more than 279 kJ/m3 and which is in the shape of a thin integrated ring magnetized in 14 poles. The stator has 12-pole teeth. If the radius of the rotor is rm, the radius of the magnetic core is rc, the radial thickness of the anisotropic rare-earth bonded magnet is d, and the radius of the motor is R, the motor is so constructed that the following relation holds : the ratio of the magnet thickness to the motor radius d/R is not less than 0.025 and not more than 0.045; and the ratio of the magnetic core radius to the motor radius rc/R is not less than 0.55 and not more than 0.72. COPYRIGHT : (C)2007, JPO&INPIT