Abstract: Fuel injection nozzle for internal combustion engines includes a nozzle element having a front cusp formed with a conical valve seat face. At least one injection hole is provided in the front cusp. The outer wall area of the front cusp which is disposed opposite to the valve seat face has a lower hardness than that of the inner wall area forming the valve seat face. When the injection hole extends from a pocket hole, preferably the outer wall area of the front cusp encompassing the picket hole has a lower hardness than that of the opposite disposed inner wall area. The intermediary center wall area preferably has a still lower hardness than the outer wall area. Thus, it is achieved that the front cusp of the nozzle element has a higher rigidity than in a known embodiment, without the valve seat face losing any hardness or that the protection of the outer wall area of the front cusp being unduly severly reduced against abrasive wear.

Abstract: The invention relates to a fuel injection system with a device for controlling the preliminary and principal injections wherein control is effected by intermediate relief of the injection pressure which includes a slide valve for exerting the control which is braked during its reverse movement before interrupting the connection between the pressure chamber of the injection nozzle and the delivery line leading to the injection pump to thereby make possible the relief of the pressure chamber toward the injection pump, i.e. to avoid dribbling.

Abstract: A fuel injection nozzle for preliminary and primary fuel injection, wherein the preliminary injection of fuel is effected by temporarily relieving the feed or delivery pressure. Control is accomplished by means of a control slide valve preferably arranged around the valve needle, at least a portion of the preliminary injection quantity being displaced by way of this control slide valve.