Patent ID: 10012310

Abstract:
A hydraulic control unit for an automatic transmission has a mechanically-operated oil pump (6), an electrically-operated oil pump (106) actuated while an engine (2) is automatically shut down, and a hydraulic pressure circuit (100) which controls supply of hydraulic pressure to a frictional engagement element (40, 60) to be engaged, in the automatic transmission, at a vehicle's start. In the hydraulic pressure circuit, discharge oil from the electrically-operated oil pump is drained from a predetermined drain portion (154) when a selector valve (120) is in the first state (in which the mechanically-operated oil pump is a source of the supply of the hydraulic pressure to the frictional engagement element), whereas less discharge oil is drained from the drain portion, compared to the first state, when the selector valve (120) is in the second state (in which the electrically-operated oil pump is the source of the supply of the hydraulic pressure).