PURPOSE: To ensure a torque doubling capacity irrespective of a pressure state due to a solenoid-operated control valve by unlocking a lockup clutch when the current torque converter speed ratio exceeds the basic unlocking torque converter speed ratio.
CONSTITUTION: An electronic control system performs a desired gearshift on the basis of each signal of various sensors by means of a CPU 405. In addition, the CPU 405 calculates a torque converter speed ratio from the current vehicle speed and the current transmission gear ratio, and finds a torque converter turbine speed through engine speed to be detected by a sensor 413. When the current torque converter speed ratio exceeds the basis unlocking torque converter speed ratio conformed to the desired gear signal, a lockup clutch is unlocked. Thus, the torque doubling capacity of a torque converter is securable irrespective of a state of pressure to be produced by a solenoid-operated control valve.
TOOMASU JIEI GURIIN
BURUUSU JIEI PARANSUKII
