US Patent 7041030 Hydraulic control apparatus for hybrid vehicle

A hydraulic control apparatus for a hybrid vehicle, which enables a smooth torque transmission when an engine of the vehicle is started from an idling stop state. The hydraulic control apparatus includes an engine and a motor as power sources, a transmission having a torque converter, a clutch for a starting gear, an engine automatic stop and start device which is associated with the engine, a motor-driven oil pump for supplying oil pressure to the transmission, a brake pedal sensor, an accelerator pedal sensor, an engine revolution rate sensor. The oil pressure applied to the clutch is controlled to a level corresponding to a creeping torque when the engine is automatically stopped. When the brake pedal is released, the engine is automatically started, the accelerator pedal is not depressed, and the engine revolution rate is less than an idling revolution rate, the oil pressure applied to the clutch is maintained to the level corresponding to the creeping torque.