| 摘要 |
A chain drive transmission has a variable diameter sprocket. The sprocket has a number of sectors which can be moved radially relative to a hub of the sprocket. The sectors are biased outwardly but can be pulled inwardly by flexible members which wind around a spool. The spool is, in turn connected to an axially movable shifting member. The gear ratio of the transmission can be changed by either allowing the shifting member to move axially outwardly, in which case the effective diameter of the variable diameter sprocket increases, or by momentarily braking rotation of the shifting member, in which case the flexible members are wound onto the spool thereby reducing the effective diameter of the variable sprocket. Shifting between gear ratios may be done with a simple rugged mechanism. Shifting between gear ratios requires little force and can be controlled with an electromechanical actuator. Both driving and driven sprockets in a power transmission may be variable diameter sprockets.
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