Electrically controlled fuel injection pump for internal combustion engines

摘要

The injection pump has a pump piston driven with a constant stroke which pumps fuel at injection pressure to an injection nozzle so long as an electrically actuated overflow valve blocks the flow of the fuel overflowing via an overflow conduit to a low-pressure chamber. The overflow valve is a needle valve, the valve needle of which, opening inward toward a pressure chamber that can be placed under injection pressure, by means of a conical closing surface radially defining a needle tip controls a valve seat that widens conically toward the pressure chamber. The cone angle of the closing surface is larger than the cone angle of the associated valve seat and the closing surface forms a sealing edge, the diameter of which is equal to or only slightly smaller than the guide diameter of the guide shank on the valve member. In a preferred embodiment, the needle tip of the valve member has an external contour on its end, adjacent to the closing surface, which directs the fuel flow and reinforces the opening movement. The injection pump is particularly suitable for high-pressure injection in Diesel engines, in order to attain an exact electrical control of the supply onset and supply quantity, if a reservoir chamber defined by a deflecting piston is connected to a high-pressure chamber that includes the pump work chamber.