求翻译：当ECU发出喷油脉冲时，三通阀使单向孔板上面的空腔与回油管连通，燃油流到回油管去，充满在这个空腔里的高压燃油压力立刻下降到大气压力。由于单向孔板节流，其下面控制腔中的压力只能缓慢地下降，喷油器针阀逐渐地升起，造成所谓的德尔塔型（三角型）喷油规律，这种喷油规律对气缸内的燃烧十分有利。是什么意思？

When when ecu issued injector pulse, three-way valve so that the cavity of the one-way orifice above connected with the return pipe, the fuel flow to the return pipe, filled with high-pressure fuel pressure in the cavity immediately dropped to atmospheric pressure. One-way orifice, the pressure cont