短語詞組短語valve type piston 閥式活塞valve operating piston 閥動(dòng)活塞release valve lower piston 緩解閥下活塞valve balancing piston 閥平衡活塞release valve upper piston 緩解閥上活塞main valve lower piston 主閥下活塞valve type piston pu 閥形活塞泵valve type piston pump 閥形活塞泵main valve upper piston 主閥上活塞 返回 valve piston