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A lock-up type automatic transmission system includes a torque converter having a lock-up control valve and a lock-up solenoid for controlling the lock-up control valve. In the lock-up state, the lock-up control valve supplies a torque converter operating pressure to an apply chamber of the torque c

A lock-up type automatic transmission system includes a torque converter having a lock-up control valve and a lock-up solenoid for controlling the lock-up control valve. In the lock-up state, the lock-up control valve supplies a torque converter operating pressure to an apply chamber of the torque converter and it connects a release chamber of the torque converter to a drain circuit. In the converter state, the lock-up control valve supplies the operating pressure to the release chamber and connects the apply chamber to the drain circuit. In the lock-up state, when the apply pressure to the apply chamber reaches or exceeds a predetermined level, the lock-up control valve operates as a by-pass valve and directs excess hydraulic fluid, which is directed to the apply chamber, to the drain circuit or an oil cooler interposed in the drain circuit.

대표청구항 ▼

A lock-up type automatic transmission system comprising: a torque converter arranged in a power transmission path of the system and comprising; a lock-up clutch that partitions inside of the torque converter into an apply chamber and a release chamber, wherein input and output elements of the transm

A lock-up type automatic transmission system comprising: a torque converter arranged in a power transmission path of the system and comprising; a lock-up clutch that partitions inside of the torque converter into an apply chamber and a release chamber, wherein input and output elements of the transmission system are engaged with each other when said torque converter assumes a lock-up state, and a lock-up control valve through which a torque converter operating pressure is supplied using hydraulic fluid to said apply chamber and through which said release chamber communicates with a drain circuit to achieve said lock-up state of the torque converter; and a hydraulic fluid cooling device comprising; an oil cooler, and a by-pass valve connected to said apply chamber, said by-pass valve directing a part of the hydraulic fluid, which is directed toward said apply chamber, to said oil cooler only when the pressure in said apply chamber is at or above a predetermined level in said lock-up state.