Mechanically actuated diesel engine fuel injector - has auxiliary return spring to give two different injection speeds

摘要

The fuel injector needle valve (12a) is opened mechanically by a cam, push rod and rocker arm system and closed by a return spring (14). An auxiliary spring (20) whose closing force is considerably less than that of the main spring is in series with the main spring (14). The auxiliary spring (20) is coiled around a tappet (21) which is joined at its lower end to the needle valve actuator piston (12). The upper end of the tappet is formed as a flange (22) able to move axially inside a closed cylinder (23). A gap is formed between the flange (22) and the cylinder cover (24) when the needle valve is in the closed position. the auxiliary spring deforms at a predetermined engine speed to give a direct connection between push rod (27) and actuator piston (12).