Patent ID: 6973781

Claim:
A hydraulic pressure reserve system for a vehicle hydraulic system including a primary hydraulic circuit including a hydraulic pump and a hydraulic sump and providing hydraulic pressure to at least a hydraulically actuated transmission, the hydraulic pressure reserve system comprising: an accumulator tank connected from the primary hydraulic circuit for storing a reserve of hydraulic fluid at an accumulator pressure, and an accumulator control valve for controlling a flow of hydraulic fluid between the primary hydraulic circuit and the accumulator tank, and an accumulator controller responsive to a primary hydraulic circuit pressure and to the accumulator pressure for controlling the accumulator control valve, wherein the accumulator controller actuates the accumulator control valve to allow a flow of the hydraulic fluid from the primary hydraulic circuit and into the accumulator tank when the primary hydraulic circuit pressure is greater than the accumulator pressure, and the accumulator controller actuates the accumulator control valve to allow a flow of the hydraulic fluid from the accumulator tank to the primary hydraulic circuit when the primary hydraulic circuit pressure is lower than a desired minimum primary hydraulic circuit pressure, thereby raising the primary hydraulic circuit pressure towards the desired primary hydraulic circuit pressure.