| 摘要 |
PROBLEM TO BE SOLVED: To materialize a structure having excellent transmission efficiency and sufficient durability as an actuator for adjusting a space between the fixed side pulley piece and the displacement side pulley piece. SOLUTION: A ball screw type actuator 20 comprises a fixed male ball screw cylinder 22 in which male ball screw grooves 25 are formed on the outer peripheral surface, a female ball screw cylinder 26 in which female ball screw grooves 31 are formed on the inner peripheral surface and which is rotated and driven by an electric motor, and a plurality of balls 34 and 34. The first and second dust-proof members 40 and 41 eliminate incorporation of foreign matters into installation parts of respective balls 34 and 34, which prevents degradation of durability caused by foreign matters.
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