针对某共轨喷油器小油量工况MAP单调性差，导致喷油稳定性差、油量控制精度低的问题，建立了喷油器AMESim仿真模型，对小油量工况下电磁阀和针阀的运动状态进行分析。通过仿真结果分析得出喷油器小油量工况MAP单调性差的原因：针阀在电磁阀处于完全碰撞状态前开启，随着控制脉宽增加，电磁阀依靠自身惯性与电磁铁碰撞，进而发生速度突变，导致电磁阀和针阀关闭延迟减小，循环喷油量随之下降。从缩短电磁阀开启时间和增大针阀开启延迟两方面对喷油器小油量MAP进行优化，最终选取增大针阀密封锥面直径的方案，在优化小油量喷射特性的同时缩短了标定工况的喷油持续期。

Aiming at the problem of poor injection stability and low precision of quantity control caused by poor monotonicity of MAP for common rail injector under the small fuel quantity condition, an AMESim simulation model of injector was established to analyze the motion state of solenoid valve and needle valve under the small fuel quantity condition. It was concluded that the reason of MAP poor monotonicity was that the needle valve opened before the solenoid valve completed collision with the electromagnet. With the increase of the pulse width, the speed of the solenoid valve changed suddenly when the solenoid valve collided with the electromagnet by its own inertia, which led to the decrease for the closing delay of solenoid valve and needle valve and a consequent decrease in circulating injection volume. Therefore, the MAP of injector with small fuel quantity was optimized by reducing the opening time of solenoid valve and increasing the opening delay of needle valve. Finally, the scheme of increasing the diameter of sealing conical surface from needle valve was used, which not only optimized the injection performance of small fuel quantity condition, but also decreased the injection duration of rated load.