Lock-Up Control

LOCK-UP CONTROL
Lock-up control is to enhance delivery efficiency by preventing the torque converter from slipping, engaging the lock-up piston into the torque converter.
It operates lock-up solenoid control in response to a signal from A/T control unit (TCM) and lock-up control valve behavior control, engages or releases the lock up piston of the torque converter.





LOCK-UP OPERATING CONDITION TABLE
Lock-up control valve control
^ In the lock-up control valve, there is operating fluid pressure circuit linked into the lock-up piston and lock-up solenoid operates valve shift in response to a signal from the A/T control unit.
^ Operating fluid pressure circuit that is applied to the lock-up piston chamber is controlled with the release or apply sides.





LOCK-UP CONTROL SYSTEM DIAGRAM
Lock-up released
^ In the lock-up control valve, there is operating fluid pressure circuit connected into the lock-up piston and lock-up solenoid operates valve shift in response to a signal from the A/T control unit. Therefore, the lock-up piston is not coupled.

Lock-up applied
^ During the lock-up applied status, lock-up apply pressure is generated having the lock-up control valve to L/U by the lock-up solenoid.
Therefore, press the lock-up piston to be coupled.

Smooth lock-up control
^ A/T control unit (TCM) controls current value that is output to the lock-up solenoid when shifting lock-up applied state from lock-up released state.
Therefore the lock-up clutch is temporarily set to half-clutched state when shifting the lock-up applied state to reduce the shock.

Half-clutched state
^ Changes current value that is output to the lock-up solenoid from A/T control unit (TCM) to gradually increase lock-up solenoid pressure.
In this way, the lock up apply pressure gradually rises and while the lock-up piston is put into half-clutched status, the lock-up piston operating pressure is increased and the coupling is completed smoothly.

Slip lock-up control
^ In the slip region, A/T control unit controls current value of the lock-up solenoid to half-clutched status.
Therefore lock-up operates from low speed absorbing torque fluctuation of engine.
Thereby fuel consumption was increased during low accelerator opening with 4th, and 5th gears at low speed.

ENGINE BRAKE CONTROL
^ The forward one-way clutch delivers driving force from the engine to the rear wheel but reverse driving from the wheel drive is not delivered since the one-way clutch is idling.
Therefore low coast brake solenoid is operated to prevent the forward one-way clutch from idling so that the engine brake is operated in the same as before.





ENGINE BRAKE CONTROL SYSTEM DIAGRAM
^ The operation of the low coast brake solenoid switches the low coast brake switch valve and controls the coupling and releasing of the low coast brake.
The low coast brake reducing valve controls the low coast brake coupling force.