ACTUATION OF SPEED CHANGE GEAR

摘要

PURPOSE: To prevent heat-related damage to the torque transmitting devices of a transmission by limiting the number of shifts. CONSTITUTION: An improved method for scheduling of a gear ratio shifting in the transmission 14 of a vehicle 10 adaptively adjusts a normal shift schedule to avoid shift-related overheating of the torque transmitting devices 28-34 of the transmission 14. In normal operation, the shift of the transmission 14 is scheduled by comparing the measurements of vehicle speed and engine throttle position 16 with predefined load data. In the background, a transmission controller 270 determines cumulative thermal energy stored in the torque transmitting devices. If excessive energy is indicated the normal shift schedule is modified to allow extended operation in the lower speed ratios. When the cumulative energy indication returns to a normal value, normal shift scheduling is resumed.