| 摘要 |
<p>A transmission for a vehicle which is frequently reversed comprises a torque convertor (12) to be driven by an internal combustion engine, and planetary change speed gearing (1, 2, 3, 4) having an input (10) driven by the output of the torque converter and an output (14) connected to the driving wheels (15) of the vehicle. The individual speed ratios in both the forward and the reverse directions of drive are each selectively engaged by the engagement of associated friction elements IBR) to provide a plurality of speed ratios in the forward direction and at least one speed ratio in the reverse direction. In response to movement of the control element from a first position corresponding to the prevailing direction of drive to a second position corresponding to the opposite direction of drive, the following operations are caused to occur in sequence:</p><p>release of the friction element (BR3) determining the ratio engaged in the prevailing direction of drive, engagement of the friction element (K1, K2) associated with a high speed ratio in the opposite direction of drive and initiation of engagement of the friction element (BR2) associated with a lower speed ratio in the said opposite direction of drive, followed by release of the friction element (K2) associated with the said high ratio in the said opposite direction after a period of retardation of the vehicle but preferably before its speed has been reduced to zero in the said prevailing direction.</p> |
