Lock-Up Control

Lock Up Control
Lock-up control means that torque converter sliding is eliminated and coupling the lock-up piston in the torque converter raises the power transmission efficiency.
The lock-up solenoid is controlled by a signal from the TCM, the lock-up control valve operation is controlled, and the torque converter lock-up piston is coupled or released.





Lock-up Operation Condition Table

TORQUE CONVERTER CLUTCH CONTROL VALVE CONTROL
- The circuit that supplies operating oil pressure to the lock-up piston chamber is connected to the lock-up control valve. This valve is switched by the lock-up solenoid with signals from the TCM.
- In this way, the circuit that supplies operating oil pressure to the lock-up piston chamber is controlled to the released side or the coupled side.





Lock-up Control System Diagram

Lock-up Released
- In the lock-up released state, the lock-up control valve is set into the un-locked state by the lock-up solenoid and the lock-up apply pressure is drained. In this way, the lock-up piston is not coupled.

Lock-up Applied
- In the lock-up coupled state, the lock-up control valve is set into the locked state by the lock-up solenoid and lock-up apply pressure is generated. In this way, the lock-up piston is pressed and coupled.

SMOOTH LOCK-UP CONTROL
When shifting from the lock-up release state to the lock-up coupled state, the current output to the lock-up solenoid is controlled with the TCM. In this way, when shifting to the lock-up coupled state, the lock-up clutch is temporarily set to the half-clutched state to reduce the shock.

Half Clutched State
- The current output from the TCM to the lock-up solenoid is varied to steadily increase the lock-up solenoid pressure. In this way, the lock-up apply pressure steadily rises and while the lock-up piston is put into half-clutched status, the force pressing on the lock-up piston is increased and the coupling is completed smoothly.

Slip Lock-up Control
- In the slip region, the lock-up solenoid current is controlled with the TCM to put it into the half-clutched state.
This absorbs the engine torque fluctuation and lock-up operates from low speed. This raises the fuel efficiency for 3rd, 4th, and 5th speed at both low speed and when the accelerator has a low degree of opening.