Fuel injector for internal combustion engines

Abstract

A fuel injector for internal combustion engines comprises a nozzle body, having at one end a hollow nozzle tip and a pintle which is axially movable in the nozzle body. The inside surface of the hollow nozzle tip constitutes a conical valve seat which cooperates with a conical valve surface of the pintle to form a valve that is spring-urged closed. The nozzle tip is formed with at least one discharge bore along its inside surface. The inside surface of the nozzle tip terminates in a first sharp edge leading into a blind bore. The conical valve surface of the pintle is terminated adjacent to the blind bore by a second sharp edge. To improve the atomization of fuel delivered by the fuel injector, the distance from the center of an entrance opening of the discharge bore to the nearer of the first and second sharp edges is not in excess of one and one-half times the diameter of the entrance opening, while the distance to the other sharp edge is equal to or greater than one and one-half times the diameter of the entrance opening. If two or more discharge bores are provided, the distance between the centers of the entrance openings, measured along the surface of the valve seat, is not in excess of three and one-half times the diameter of the entrance opening. In a preferred embodiment, movement of the pintle is opposed by two springs acting in series, so that the pintle is moved away from the nozzle tip in two lifting phases.