Fuel injection device for engines

A fuel injection device for engines comprising:

• a device body including nozzle holes at a front end thereof for injecting fuel;
• a control sleeve fixed in a hollow portion of the device body;
• a valve assembly having an end thereof inserted into a hole in the control sleeve, the end comprising a pressure receiving surface, the valve assembly including a needle valve reciprocally movable in the hollow portion of the device body and adapted to open and close the nozzle holes;
• a balance chamber formed by the hole of the control sleeve and the pressure receiving surface of the valve assembly to control a lift of the valve assembly;
• a supply passage formed in the control sleeve to supply a fuel pressure to the balance chamber;
• an exhaust passage formed in the control sleeve to release the fuel pressure from the balance chamber;
• and
• a control means to open and close the exhaust passage;
• wherein the control means includes a solenoid valve comprising a solenoid producing an electromagnetic force to open an exhaust port of the exhaust passage and a return spring mechanism having springs to apply spring forces to the solenoid valve to close the exhaust port;
• wherein an effective opening area of the exhaust port of the exhaust passage opened by the solenoid valve is set smaller than a minimum cross-sectional area of the exhaust passage;
• and
• wherein the return spring mechanism comprises a first plate spring, a first spring retainer coupled to the first plate spring, a second plate spring spaced from the first plate spring in an axial direction of the needle valve, and a second spring retainer coupled to the second plate spring, and
• wherein the second spring retainer is disposed between the first plate spring and the second plate spring.