一、前言工程机械高效节能液压系统的研究被列为“九五”期间主要开发内容及关键技术之一。工程机械的一个显著特点就是以内燃机作原动机、工作负荷变化频繁、幅度大、能耗指标重要，相应的技术要求是系统能量转换和利用率要高。为此，工程机械中广泛采用了一种新型节能液压系 I. Introduction The research on high efficiency and energy saving hydraulic system of construction machinery is listed as one of the key development contents and key technologies during the Ninth Five-year Plan period. A notable feature of construction machinery is that the internal combustion engine is the prime mover. The workload changes frequently, the magnitude is large, and the energy consumption index is important. The corresponding technical requirement is that the system energy conversion and utilization rate should be high. To this end, widely used in construction machinery, a new type of energy-saving hydraulic system