Patent attributes
A hydraulic circuit for a transmission including a main pump and a sub pump is provided in which when the main pump and the sub pump are driven by an engine after it has been stopped for a long time, due to the internal pressure of a torque converter being low, a sufficient hydraulic pressure cannot be transmitted to a feedback port of a switching valve via a fifth oil passage; communication between a first port and a second port of the switching valve is cut off, and the oil discharged by the sub pump is therefore not supplied to a lubrication system via a sixth oil passage but is supplied via the path: second oil passage→first port of switching valve→fourth oil passage→first port and second port of second pressure regulating valve→torque converter.