| 摘要 |
PURPOSE:To accurately detect the position of a pickup by forming a method to grasp the moving of the pickup as a sliding distance generated by extending the said moving through gear device. CONSTITUTION:The pickup 1 moves in a straight and reciprocating movement, and its position is detected by the distance of the movement. As the first rack gear 4 mounted with the pickup 1 moves, the first wheel gear 5 rotates, and a second wheel gear 6 mounted coaxially with the gear 5 are rotated to move the second rack gear 8 engaged with the gear 6. Since the diameter of the gear 6 is made longer than that of the gear 5, the length of the moving of the pickup 1 is represented by the length of the moving of the gear 8 which is the former length extended by the tooth-number ratio between the gears 6 and 5. The sliding length on an electrical resistor 3 of a brush 2 fixed on the gear 8 is longer than the sliding length identical to the distance of the moving of the gear 4. As a result, a detection error due to the ununiformity of a sliding plane and the resistor 3 can be made less.
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