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AssigneeRobert Bosch GmbH
InventorsEwald Eblen, Karl Hofmann, Volker Holzgrefe, Jean Pigeroulet, Nestor Rodriguez-Amaya, Nikolaus Simon, Dietrich Trachte, Friedrich Weiss, Ewald Ziegler
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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.
An electrically controlled fuel injection pump for internal combustion engines, in particular a unit fuel injector for a Diesel engine, comprising a housing, at least one pump piston, a pump work chamber adjacent thereto, said pump piston having a supply stroke to pump fuel, which has been delivered at inflow pressure to said pump work chamber to an injection nozzle at injection pressure, an overflow valve provided with a valve member actuated by an electrical adjusting member, said valve member adapted to block the flow of fuel that otherwise overflows from said pump work chamber via an overflow conduit to a low-pressure chamber in proximity to said injection nozzle, said overflow valve further having a pressure chamber arranged to surround said valve member in the vicinity of an end section thereof remote from said electrical adjusting member, a guide shank on said valve member arranged to connect said remote end section of said valve member to said electrical adjusting member, said guide shank further being slidably supported in a guide bore, said remote end section having a conical valve seat, adapted to be closed by a conical surface having a cone angle (.alpha.) on said remote end section at a point of transition which communicates with said low-pressure chamber of said overflow conduit, said overflow valve further being inserted between said first section and a second section which joins said pressure chamber permanently with said pump work chamber of said overflow conduit, said valve member of said overflow valve further including a valve needle arranged to open inwardly toward said pressure chamber, said valve needle having a conical closing surface that radially defines a needle tip, said needle tip further including said surface having said cone angle (.alpha.) which is larger than a cone angle (.beta.) of said conical valve seat that widens toward said pressure chamber, and further that said conical surface, together with an adjoining cylindrical jacket surface on said remote end section of said valve member is adapted to form a sealing edge, said sealing edge having a diameter (d.sub.D) which is equal to or only slightly smaller than the guide diameter (d.sub.F) of said guide shank.
Dependencies are inferred from the claim text.