Torque Converter: Description and Operation

A: CONSTRUCTION AND FUNCTION





This system causes the impeller and turbine to be coupled directly without the aid of oil when the engine rpm reaches a certain level. This direct coupling eliminates torque converter clutch slip and thus leads to a reduction in engine rpm, which in turn results in less fuel consumption and less noise.
The single plate type lock-up clutch is used, and the transition hydraulic oil pressure is controlled for reducing the lock-up shock of the clutch thereby achieving smooth lock-up operation.
The lock-up clutch is fitted with torsional dampers which are adopted for reducing the vibration and noise in the driving system.

B.: LOCK-UP OPERATION





The Transmission Control Module (TCM) sends output signal to the duty solenoid B (lock-up). Since the duty solenoid B (lock-up) 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.

C: NON-LOCK-UP OPERATION





The transmission control module (TCM) sends output signals to the duty solenoid B (lock-up). This causes the amount of ATE drained from the duty solenoid B (lock-up) 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.

D: SMOOTH CONTROL
When the lock-up clutch activates, the clutch partially engages. Lock-up apply pressure increases smoothly to engage the lock-up clutch.

E: NON-LOCK-UP OPERATION DURING "1ST, 2ND AND 3RD SPEED", "N", "R" AND "P" POSITION
In this mode of operation, pilot pressure is generated, and the lock-up control valve is pushed upward where lock-up is inoperative.