Lockup Control

LOCKUP CONTROL

Lockup Operation Conditions:

- By engaging the lockup clutch in the torque converter, the slip in the torque converter is eliminated and power is transmitted more effectively.
- Based on signals from the TCM, the lockup solenoid is controlled in order to let the lockup control valve operate and adjust apply pressure/release pressure, to consequently vary the lockup clutch engagement force.

1. LOCKUP DISENGAGED STATE
When lockup is disengaged, the lockup solenoid causes the lockup control valve to open the clutch disengaging port, and the lockup operating pressure is added to the disengaging circuit. In the meantime, the lockup clutch control valve opens the lockup clutch engaging port and allows the hydraulic fluid in the circuit to flow to the ATF cooler, thus lowering the pressure in the engaging circuit. As a result, the lockup clutch is disengaged due to difference in pressure between both circuits. This operation is performed in all speed gears.

2. LOCKUP ENGAGED STATE
When lockup is engaged, the lockup solenoid puts the lockup control valve in the lockup state and builds up lockup operating pressure.
The lockup control valve then opens the clutch engaging circuit's port that communicates to the torque converter's impeller chamber, allowing high pressure fluid to flow to the lockup clutch and the clutch is engaged.
This operation is performed in all speed gears, and the lockup engages in response to the vehicle speed when the 5th gear is selected in the D range.

3. SMOOTH LOCKUP CONTROL
During the transition period from the lockup (disengaged) state to the lockup engaged state, the TCM controls the current output to the lockup solenoid. By changing the current output to the lockup solenoid and gradually raising the lockup clutch pressure, the lockup clutch piston is first put in a partially engaged state and its pressure is gradually increased to reduce shock.