Patent ID: 8621858

Claim:
A regenerative drive system for a motor vehicle, said drive system including: a main accumulator; a pump/motor to deliver and receive hydraulic fluid to/from the main accumulator, said pump/motor having a variable capacity, a mechanism to change said capacity, and a control hydraulic circuit to provide control hydraulic fluid under pressure to be used in controlling the mechanism, the circuit including: a first hydraulic line connected to the pump/motor to deliver the control hydraulic fluid under pressure to said mechanism; a control accumulator to receive hydraulic fluid under pressure and connected to said line to provide said control hydraulic fluid under pressure for delivery to the pump/motor; a control pump connected to the control accumulator to deliver hydraulic fluid under pressure thereto; a control motor drivingly connected to the control pump to drive the control pump to produce the hydraulic fluid under pressure; a switch operatively associated with the motor to activate the motor when said system is operative and pressure in said line falls below a predetermined pressure; and wherein said system further includes: a second hydraulic line connecting the main accumulator and pump/motor, and communicating with said first line so that pressure from said second line can be delivered to said first line; and a one-way valve preventing hydraulic fluid flowing from said first line to said second line.