Hybrid Hydraulic System

A hybrid hydraulic system is a hydraulic system that contains one or more accumulators which are used to store a significant amount of energy in the form a compressed gas. Gas in an accumulator is compressed by pumping hydraulic fluid into the accumulator. Energy is released from an accumulator by allowing the gas to expand and push out some of the hydraulic fluid. A hybrid hydraulic vehicle (HHV) is one that typically uses a relatively small internal combustion engine in a hybrid hydraulic system to propel the vehicle.

The two main functions of the accumulator in a HHV are 1: To store energy provided by a small engine which drives a hydraulic pump so that a larger amount of power than can be produced by the engine alone can be produced for moderate amounts of time. and 2: To store vehicle kinetic energy which is reclaimed during the braking process. Both of these functions allow for very high fuel economy to be achieved by a HHV.

The accumulator typically has the form of a pressure tank with a bladder inside which separates the gas and the hydraulic fluid. To be continued...