D: Lock-Up Control

D: LOCK-UP CONTROL

The lock-up engaging and disengaging conditions are set for 4th gear shift range, gear position and shift pattern and correspond to the throttle position and vehicle speed, and the duty solenoid electronically controlled by TCM controls the lock-up clutch. The lock-up clutch engagement and disengagement are controlled by the lock-up control valve.



The lock-up control valve engages and disengages the lock-up clutch by adjusting the hydraulic pressure.

Non-Lock-Up Operation

The Transmission Control Module (TCM) sends output signals to the lock-up duty solenoid. This causes the amount of ATF drained from the lock-up duty solenoid valve to be reduced, which increases the lock-up duty pressure.

The increased lock-up duty pressure moves the lock-up control valve upwards, connecting the torque converter regulator valve to the torque converter control valve release port.
Therefore, the oil pressure from the torque converter regulator valve flows through the lock-up control valve release port to the torque converter clutch and the torque converter apply circuit. As a result, the lock-up piston is forced to separate from the impeller cover, and power is transmitted from impeller to turbine to input shaft, as with an ordinary torque converter clutch coupling.

Lock-Up Operation

The Transmission Control Module (TCM) sends output signal to the lock-up duty solenoid. Since the lock-up duty solenoid operates in proportion to the duty ratio, the amount of ATF drained from there is increased, thus lock-up duty pressure being reduced.

As a result, the lock-up control valve moves downward, which connects the torque converter regulator valve and the lock-up control valve apply port to each other.

In this condition, the oil pressure from the torque converter valve flows through the lock-up control valve apply port to the torque converter and the torque converter clutch. This causes a pressure differential across the lock-up piston. The piston is then forced against the impeller cover and turned as an integral unit with the cover. Thus, power from the engine is directly transmitted to the transmission input shaft. That is, the transmission is directly coupled to the engine.



The lock-up duty solenoid is controlled by the TOM and controls the operation of the lock-up control valve. Because the lock-up operating pressure is controlled by the lock-up control valve, the force applied to the lock-up clutch is controlled for smooth clutch operation.

When locking up, the clutch is set in the half-engaged state beforehand. After this, the lock-up operating pressure is gradually increased to achieve smooth locking up.