| 摘要 |
PURPOSE:To eliminate the need for tack magnets and to decrease magnetic noises by detecting the magnetic fields by the polarized magnetic charges of a rotor magnet and obtaining the rotating position signals of a video head. CONSTITUTION:A cylinder motor detects the rotating position of a rotor magnet 1 by using three pieces of magnetic field detecting elements 4, 4', 4''. The elements 4-4'' are inserted into the small holes provided within the plane of a stator yoke 3 and the preceding ends of the elements 4-4'' face the magnetic pole surface of the magnet 1, and detect the positions by the magnetic fields right under said magnetic pole surface. The magnetic charges on the magnetic pole surface of the magnet 1 are polarized and appear at the preceding end of the magnetic material piece fixed on the magnetic pole surface of the magnet 1. Thus, the magnetic field intensity of the electromagnetic gap between said surface and the surface of the yoke 3 is increased locally by the part of the magnetic mateial piece 7, and the detected signal thereof is a tack signal. |
