Patent ID: 8480539

Claim:
A hydraulic pressure control method for an automatic transmission that comprises a first hydraulic pump having a first motor and generating a low pressure, a second hydraulic pump having a second motor and generating a high pressure, a first regulating valve having a first valve spool and regulating the low pressure received from the first hydraulic pump as a first operating pressure to supply the first operating pressure to a torque converter, a second regulating valve having a second valve spool and regulating the high pressure received from the second hydraulic pump as a second operating pressure to supply the second operating pressure to a powertrain, a variable control solenoid valve changing a target hydraulic pressure of the first and second regulating valves, a control unit controlling the first and second motors and the variable control solenoid valve, and first and second switches respectively transmitting information on the hydraulic pressure of the first and second regulating valves, the method comprising: determining whether both of the first and second switches are in ON positions; determining whether a control pressure of the variable control solenoid valve is decreased when both of the first and second switches are in their respective ON positions; controlling an RPM of the second motor to be an optimal RPM when the control pressure of the variable control solenoid valve is decreased; and controlling an RPM of the first motor to be an optimal RPM when the control of the second motor is completed.