| 摘要 |
The derailleur is provided with a base member; a linkage mechanism including a support member, a pair of linkage members, and a movable member; and a chain guide having a guide sprocket and a tension sprocket. The support member is supported swingably relative to the base member through a first horizontal shaft, and the chain guide is supported swingably relative to the movable member through a second horizontal shaft. Also, first and second springs are provided between the base member and the linkage mechanism, and the movable member and the chain guide. The first and second springs balance with each other to set the position of the guide sprocket with respect to a selected particular rear chain gear. The spring force of at least one of the first and second springs is changed with respect to the other by the swinging motion of at least one of the linkage mechanism and the chain guide in excess of a predetermined angle, thereby yielding an optimum distance between the guide sprocket and the rear chain gear.
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