Patent ID: 8056666

Claim:
A vehicle powertrain comprising: an engine capable of being selectively turned on and turned off; a transmission operatively connected to the engine; and a hydraulic control system including: a pump arranged relative to the transmission in fluid communication with the transmission via a structure forming a fluid passage, the pump operatively connected to the engine for supplying fluid to the transmission when the engine is on, wherein the pump is idle when the engine is off; an accumulator arranged relative to the transmission in fluid communication with the fluid passage and controlled to accumulate fluid when the engine is on, to retain the fluid when the engine is turned off, and to discharge the fluid to the fluid passage when the engine is restarted; and a device arranged in fluid communication with the fluid passage downstream of the accumulator to discharge fluid from the accumulator; and an electronic controller arranged to govern the device such that the accumulator accumulates the fluid when the engine is on, the fluid is retained by the accumulator when the engine is turned off, and the fluid is discharged by the accumulator to the fluid passage when the engine is restarted to afford full transmission operation substantially without delay.