| 摘要 |
<p>An automatic transmission for a human powered vehicle having an improved speed sensing mechanism. A rotatable shaft (36) is journalled in a support frame (12, 14, 32, 34) and has a plurality of outwardly extending arms (56, 58) fixed to the shaft. Weights (60, 62) are slideably attached to each of the arms and engage a thrust member (74) which has a surface at an acute angle with the axis of the shaft and is axially slideable along the shaft. Springs (84, 86) urge the thrust member toward the weights and linkage means connects the thrust member to the transmission shift member. The weights are forced outwardly by centrifugal force a distance which is a function of speed. They cause translation of the thrust member 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 (132) at a rate which is a function of vehicle speed. The chamber has a vent (134) with an adjustable orifice and also communicates with a fluid pressure responsive means with an actuator (114, 116) 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. </p> |
