| 摘要 |
An automatic transmission for a human powered vehicle is disclosed having an improved speed sensing mechanism. A rotatable shaft is journalled in a support frame mounted on the vehicle and has a plurality of outwardly extending arms fixed to the shaft. Weights are slideably attached to each of the arms to slide along the arms and engage a thrust member. The thrust member has a surface at an acute angle with the axis of the shaft and is axially slideable along the shaft. A spring urges the thrust member toward the weights and a linkage connects the thrust member to the shift member of the transmission. The weight members are forced outwardly by centrifugal force a distance which is a function of a bicycle speed. The weight members force translation of the thrust member along the axis of the shaft a distance proportional to bicycle speed causing a proportional movement of the shift member. An alternative embodiment of the invention has a fluid pump which is drivingly connected to the vehicle for pumping a fluid into a chamber at a rate which is a function of vehicle speed. The chamber has a vent with an adjustable orifice and also communicates with a fluid pressure responsive means with an actuator linked to the shift member of the transmission. The pressure in the chamber is a function of vehicle speed and causes movement of the actuator and hence shifting of the transmission. |
