| 摘要 |
PURPOSE:To control the speed of revolution of a rotor, by controlling the supply amount of the driving current based on the frequency signal supplied from a magnetized matter and to realize the miniaturization of a rotary driver which uses a brushless motor of a video tape recorder, by adhering a magnetized matter having many magnetic pole surfaces having the magnetization with a prescribed pitch along the entire surface of a rotor, and setting a magnetic detector to a stator to obtain the frequency signal from the magnetized matter and by the revolution of the rotor. CONSTITUTION:A guide drum device is provided with a rotary upper drum 32 and a fixed lower drum 33 which function to wind up a magnetic tape and guides the travelling of the tape to make it touch a rotary magnetic head 31. This guide drum device is connected directly to a driving shaft of a brushless motor in one body. The brushless motor contains a ring-shaped rotor magnet 37 magnetized with 8 poles and a 3-phase stator coil 38 consisting of 6 coils and form a bilateral conduction type motor. A flywheel is attached at the lower surface side of a rotary disk having the magnet 37 via a damper member to prevent the eccentric driving, and a ring-shaped FG magnet 48 is added. |
