We developed a new injector for direct injection gasoline engines that reduce the exhaust emissions and help to reduce fuel consumption. The newly developed actuator in this injector has two features. One is a bounceless valve closing mechanism, and the second is quick response moving parts. The first feature, the bounceless valve closing mechanism, can prevent ejecting a coarse droplet, which causes unburned gas emission. The new actuation mechanism realizes the bounceless valve closing. We analyzed the valve motion and injection behavior. The second feature, the quick-response actuator, achieves a smaller minimum injection quantity. This feature assists in reducing the fuel consumption under low load engine conditions. The closing delay time of the needle valve is the dominant factor of the minimum injection quantity because the injection quantity is controlled by the duration time of the valve opening. The new actuator movements can be operated with a shorter closing delay time. The closing delay time is caused by a magnetic delay and kinematic delay. A compact magnetic circuit of the actuator reduces the closing delay time by 26%. In addition, the kinematic delay was improved when the hydraulic resistance was reduced by 9%. As a result, the new injector realizes reduction of the minimum injection quantity by 25% compared to a conventional injector.

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