Electric-motor-driven oil pump control system

An electric-motor-driven oil pump control system with automatic engine-stop system interaction, comprising:

• an electric-motor-driven oil pump used for supplying working oil through a sub-working-oil passage to a transmission of an automotive vehicle employing an automatic engine-stop system configured to automatically stop an engine, and driven by an electric motor for hydraulic pressure supply from the sub-working-oil passage through a check valve to the transmission, at least when hydraulic pressure supplied to the transmission is dropping under a stopped state of a mechanical oil pump driven by the engine;
• a motor current detector for detecting a motor current flowing through the electric motor;
• and
• a controller configured to temporarily execute a preliminary operation of the electric-motor-driven oil pump when a length of time, elapsed from a point of time when the electric motor becomes stopped, exceeds a predetermined time length and a vehicle speed becomes less than a given vehicle-speed threshold value, the controller further configured to output an enabling signal to the automatic engine-stop system for permitting a mode shift to an automatic engine-stop mode when a motor current value, detected by the motor current detector during the preliminary operation, rises from zero to a high current value once and then turns to a drop, and thereafter rises again, and the controller still further configured to output an inhibiting signal to the automatic engine-stop system for inhibiting a mode shift to an automatic engine-stop mode when the motor current value, detected by the motor current detector during the preliminary operation, is continuously kept high or continuously kept low.