Hydraulic pressure control apparatus for use in automatic transmission

Claim 1

A hydraulic pressure control apparatus for use in an automobile transmission, comprising: a throttle pressure valve (140) having a first port (142) to be supplied with a line pressure, a second port (146) to provide a throttle pressure, a spool (148) for controlling magnitude of connection between said first and said second ports, a first spring for biasing said spool in a first direction to decrease said magnitude of connection between said first and said second ports, a third port for receiving said throttle pressure to apply said throttle pressure to said spool so as to drive said spool in said first direction, a plug (154) disposed in axial alignment with said spool to be selectively driven by an external control force from a stop end position thereof toward said spool in a second direction opposite to said first direction when said throttle pressure is to be increased, a second spring (152) mounted between said spool and said plug for biasing said spool and said plug away from one another, a fourth port (339) to be supplied with a control source pressure, and a fifth port (338) to provide a control signal pressure, said plug controlling connection between said fourth and said fifth ports so as to connect said fourth port to said fifth port to provide said control signal pressure when and only when said plug is at said stop end position; and a relay valve (422) having a sixth port (428) to be supplied with said control signal pressure and adapted to control supply of a lock-up clutch actuating hydraulic pressure to a lock-up clutch (400) so as to disengage the lock-up clutch when said control signal pressure is supplied to said sixth port.