Hydraulic Regeneration System and Method for a Material Handling Vehicle

摘要

A hydraulic system has a cylinder and ram assembly that raises and lowers a load carrying carriage on a material handling vehicle. The fluid exhausting from the cylinder, while the carriage is lowering, is controlled to recover energy from that fluid. A first path routes the exhausting fluid to drive the pump as a hydraulic motor. A second path routes the exhausting fluid to a reservoir, bypassing the pump. In a first lowering mode, the second path is closed and the first path is opened. In a second lowering mode, both the first and second paths are open and the flow through each one is proportionally controlled. In a third lowering mode, only the second path is opened. The mode to use is selected based on the desired lowering speed of the carriage.

主权项

1. A hydraulic system for a material handling vehicle that has body and a carriage for carrying a load being transported, said hydraulic system comprising:
a hydraulic cylinder and ram assembly operatively connected to raise and lower the carriage with respect to the body and having a cylinder port; a reservoir; a pump operatively connected to draw fluid from the reservoir and provide the fluid under pressure to an pump outlet; a proportional first valve that is electrically operated and that selectively controls a first path through which fluid flows between the pump outlet and the cylinder port; a proportional return valve that is electrically operated and that selectively controls a second path through which fluid flows between the cylinder port and the reservoir bypassing the pump; wherein the hydraulic system operates in a plurality of modes to lower the carriage comprising: (a) first mode in which the return valve is closed and the first valve is open to direct fluid to flow from the cylinder port into the pump outlet, thereby operating the pump as a hydraulic motor; and (b) a second mode in which the return valve is open to direct fluid to flow through the second path from the cylinder port to the reservoir, and in which the first valve is open to direct fluid to flow from the cylinder port into the pump outlet, thereby operating the pump as a hydraulic motor.