Hydraulic pressure control device for automatic transmission for vehicle including reverse stage and lock-up clutch control systems

Claim 1

A hydraulic pressure control device for an automatic transmission for a vehicle, comprising: a manual shift valve for selecting a forward range in which at least one forward speed stage is enabled and a reverse range in which a reverse stage is enabled; a first hydraulic pressure control valve having a first and a second control signal port and controlling switching over of an operation of the automatic transmission according to conversion between supply and non supply of a first and a second signal hydraulic pressure to said first and said second control signal port, respectively, said second signal hydraulic pressure being available in a certain forward speed stage or stages but not available in the reverse stage, said first hydraulic pressure control valve being reactive to the conversion between supply and non supply of said first signal hydraulic pressure when and only when said second signal hydraulic pressure is supplied; a second hydraulic pressure control valve having a third control signal port and selectively interrupting transmission of a third signal hydraulic pressure according to conversion between supply and non supply of said first signal hydraulic pressure to said third control signal port, said third signal hydraulic pressure being available when and only when the manual shift valve is set to the reverse range and serving to set up the reverse stage; and a third hydraulic pressure control valve for controlling the conversion between supply and non supply of said first signal hydraulic pressure so that in the forward speed stage at which said second signal hydraulic pressure is available said operation of the automatic transmission is selectively switched over and in the reverse range the setting up of the reverse stage is selectively interrupted.