| 摘要 |
A circular-plate permanent magnet, with its one side being magnetized as N-pole while the other as S-pole, which is sandwiched between two rotor yokes made of a magnetic circular plate, is mounted on a rotor shaft as one unit, and this unit makes up the rotor. The stator, which is arranged in a position where its inner surface opposes the outer periphery of the aforesaid rotor across a small air gap, is firmly held between a front cover and a rear cover. Around the outer periphery of the aforesaid rotor yokes, toothed-wheel-like jags which provide the permeance variations are installed. By letting DC current flow stepwise through the stator coils which are wound around the aforesaid stator, the rotor rotates stepwise. With D1 and D2 being the outside diameter and the inside diameter respectively of the cylindrical part on the inside diameter side of the front cover and rear cover, D0 being the outside diameter of the rotor yokes, L being the shaftwise length of the rotor shaft, Gl being the dimension of the air gap between the outer periphery of the rotor yokes and the inner surface of the stator, Dl being the distance between the end surface of the cylindrical part on the inside diameter side of the front and rear covers, and n being any optional natural number, then by satisfying the expression of Dl/Gl>nx(D12-D22)/(4DoxL) the magnetic flux leaking outside the motor can be minimized to less than 1/n of the effective magnetic flux of the motor.
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