Patent ID: 7107767

Claim:
A hydraulic energy storage system for use in a vehicle comprising a high pressure accumulator, a first low pressure accumulator and a second low pressure accumulator connected in parallel, a pump/motor in fluid communication with the high pressure accumulator and with the first and second low pressure accumulators for pumping a fluid from the first and second low pressure accumulators to the high pressure accumulator when the pump/motor is driven in a pump mode and for returning fluid to the first and second low pressure accumulators when the pump/motor is in a motor mode, said pump/motor having a case for circulating fluid there through, a first check valve in series between the pump/motor and the second low pressure accumulator when the pump/motor is in the motor mode for unidirectional flow of a portion of fluid from the pump/motor to the second low pressure accumulator, a cooler in fluid communication in series between the case of the pump/motor, the second low pressure accumulator, and the pump/motor, and a second check valve in series between the second low pressure accumulator and the pump/motor case for unidirectional flow of fluid from the second low pressure accumulator through pump/motor case and the cooler to the pump/motor for cooling of said portion of the fluid when the pump/motor is in the pump mode.