| 摘要 |
PURPOSE:To improve the positioning accuracy of a cam body by exerting a bias force toward a magnetic sensor to the cam body by a compression spring or the like and arranging a guide member between a magnet ring provided to the cam and a reference chassis so as to make the air gap constant. CONSTITUTION:A compression spring 5 acts like biasing a cam 3 toward the magnetic sensor 9. Moreover, the guide member 8 is arranged to three positions of the reference chassis 6 at a location escaping the magnetic sensor 9. The guide member 8 guides slidably the magnet ring 7 with the magnetic ring 7 and the reference chassis 6 to keep the air gap between the both constant and the biasing force of the compression spring 5 may be a weak force to a degree giving a sufficient force to the cam 3 so as to keep the air gap between the magnetic sensor 9 and the magnetic ring 7 constant. Thus, the information representing the location of the magnetic head is read accurately without level fluctuation.
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