| 摘要 |
A method is provided for shifting a powershift transmission (16) in a vehicle having an engine (12) controlled by an electronic engine control unit (14) and a powershift transmission (16) controlled by an electronic transmission control unit (24). During a shift the powershift transmission (16) has an off-going clutch and an on-coming clutch. The method includes determining a Predicted Off Slip Pressure for the off-going clutch and determining a Predicted On Slip Pressure for the on-coming clutch, both as a function of engine load. The Predicted Off Slip Pressure is a pressure at which the off-going clutch would start to slip, and the Predicted On Slip Pressure is a pressure at which the on-coming clutch would start to transmit torque. Thereafter, the method includes rapidly reducing off-going clutch pressure (P-off) to a pressure which is slightly higher than the Predicted Off Slip Pressure, and rapidly increasing on-coming clutch pressure (P-on) to a pressure that is slightly lower than the Predicted On Slip Pressure. Then, the method includes gradually decreasing off-going clutch pressure (P-off) and gradually increasing on-coming clutch pressure (P-on) until slipping of the off-going clutch is detected, and gradually and more slowly decreasing off-going clutch pressure (P-off) and gradually more slowly increasing on-coming clutch pressure (P-on) until the oncoming clutch begins to carry torque previously carried by the off-going clutch. Finally, the method includes more rapidly decreasing off-going clutch pressure (P-off) to reservoir pressure, and more rapidly increasing on-coming clutch pressure (P-on) to a full on pressure. |
