Hydrostatic retarder pump and motor

A hydrostatic retarder pump and motor apparatus disposed between the transmission and the differential of a vehicle comprising:

• a housing defining an inner channel in fluid communication with a low pressure accumulator;
• and an outer channel in fluid communication with a high pressure accumulator;
• a shaft rotatably supported by the housing, said shaft including a first eccentric portion and a second eccentric portion;
• a plurality of pistons disposed within the housing, said plurality of pistons engageable with said first eccentric portion;
• a plurality of valves disposed within the housing, said plurality of valves engageable with said second eccentric portion, said plurality of valves being configured to selectively connect the plurality of pistons with the low pressure accumulator or the high pressure accumulator;
• wherein shaft rotation may be implemented to drive the plurality of pistons and thereby transfer hydraulic fluid from the low pressure accumulator to the high pressure accumulator such that resistance is applied to the shaft and vehicle output is retarded, and further wherein hydraulic fluid from the high pressure accumulator may be implemented to drive the plurality of pistons and thereby power the vehicle.

A method for improving the efficiency of a vehicle having a transmission and a differential, said method comprising:

• providing a pump disposed mounted to a transmission output shaft between the transmission and the differential, said pump being operatively connected to a low pressure regulator and a high pressure regulator;
• determining if the vehicle is decelerating;
• driving the pump with the rotation of the transmission output shaft if the vehicle is decelerating, wherein the driven pump transfers hydraulic fluid from the low pressure accumulator to the high pressure accumulator such that resistance is applied to the shaft and vehicle output is retarded;
• determining if the vehicle is accelerating;
• and
• driving the pump with hydraulic fluid from the high pressure accumulator if the vehicle is accelerating, wherein the driven pump applies torque to the transmission output shaft to power the vehicle.