| 摘要 |
PURPOSE:To improve the positioning accuracy by outputting a correcting signal which is varied in according with a time lapse or an environmental temperature variation from a correcting signal generating means, adjusting a ratio of a value of a current flowing to plural phases of a step-motor, and correcting an offset quantity from a target track of a magnetic head. CONSTITUTION:When a magnetic disk 3 is started, an environmental temperature is varied successively by heating, etc. of a rotation driving source, and subsequently, when a step-motor 5 is driven, a magnetic disc 12 is going to offset from a target track by a rise of the environmental temperature. In this case, a correcting signal generating means 18 of a step-motor driving device 16 outputs a correcting offset quantity which is varied in accordance with an environmental temperature detected by a temperature detector 17, as a correcting signal to a current control means 19. Based on said signal, the current control means 19 adjusts a ratio of a value of a current flowing to plural phases of the step-motor 5. Accordingly, a static composition of the step-motor 5 is varied in accordance with the ratio of the current value, and the magnetic head 12 is moved by a correcting offset in the opposite direction of the offset quantity. |
