本文分析了二次喷射现象和等压卸载出油阀的工作原理。指出了两种典型等压卸载出油阀工作原理上的差别和存在问题。提出一种可在中、小型柴油机上应用的等压卸载出油阀结构。 This paper analyzes the phenomenon of secondary injection and the principle of unloading the discharge valve. The differences and existing problems of the working principle of two typical isobaric discharge valves were pointed out. A kind of isobaric discharge valve structure that can be used on medium and small diesel engines is proposed.