| 摘要 |
An automatic transmission system for a vehicle comprises a transmission clutch 16, a transmission brake 70, an electronic control unit 34, means for sensing transmission brake actuation, means for sensing engine torque, means 50 for sensing vehicle speed, means 48 for sensing gear downshift requests or operation and means 60, 62, 64 for sensing operating brake 52, 54, 56 application. The control unit 34 controls the transmission brake 70 to apply a braking torque to the transmission when engine torque is negative, vehicle speed is above a predetermined value, a gear downshift is in progress or has been requested and the operating brake 52, 54, 56 is not applied. The transmission brake 70 may be used to prevent unwanted acceleration, caused by a loss of engine braking force, when down shifting while travelling down an incline. The transmission brake 70 may also be used to hold the vehicle when starting from rest on an incline. |
