HEAD DRUM OF VIDEO TAPE RECORDER

摘要

PURPOSE:To drive a rotary head correctly and to obtain a precise signal by using magnetized frequency detecting magnetic poles for a magnetic field magnet and forming a comb-like conductive patterns for detecting rotation speed on a part opposed to the magnetic poles. CONSTITUTION:Driving magnetic poles 10a' of the magnetic field magnet 10 are magnetized to form 8 magnetic poles consisting of N and S magnetic poles alternately, and frequency detecting magnetic poles 10b' consisting of about 180 rotor rotation speed detecting poles are magnetized around the peripheral part. The frequency detecting magnetic poles 10b' from strong N-magnetized parts and weak N'-magnetized parts alternately with a fine pitch in the driving N- magnetic poles 10a' and strong S-magnetized parts and weak S'-magnetized parts alternately with a fine pitch in the driving S-magnetic poles 10a'. The comb-like conductive patterns 18 are formed on a part of the surface of a printed substrate 17 which is opposed to the frequency detecting magnetic poles 10b' of the magnetic field magnet 10' to generate electromotive force corresponding to the rotation speed of the frequency detecting magnetic poles 10b' in the same direction.