the external dimension of the motor is large because the case 103, the bobbin 101, the stator coil 105 and the stator yoke 106 are arranged concentrically about the outer periphery of the rotor. This step motor has another drawback of low output, for, as shown in FIG. 19, the flux of magnetic force generated upon energization of the stator coil 105 mainly passes between an end face 106a1 of the stator tooth 106a and an end face 106b1 of the stator tooth 106b and does not act on the rotor magnet 111 effectively.
The step motor shown in FIG. 20 is also ineffective in making the flux of magnetic force that is generated upon energization of the coil act on the magnet because the flux of magnetic forcerotor. The second coil excites a second outer magnetic pole that faces the outer peripheral surface of the rotor as well as a second inner magnetic pole that faces the inner peripheral surface of the rotor. The rotation axis that is the rotor shaft is taken out the interior of the cylindrical permanent magnet.
The motor structured as above has a high output and a small motor external dimension, but there is room to improve it in facilitating joining of the rotor shaft to the permanent magnet. If a thin magnet is used in the structure above, the distance between the first outer magnetic pole and the first inner magnetic pole as well as the distance between the second outer magnetic pole and the second inner magnetic pole can