Internal-combustion engines – Charge forming device – With fuel pump
Patent
1998-05-12
2000-09-12
Miller, Carl S.
Internal-combustion engines
Charge forming device
With fuel pump
123495, F02M 3704
Patent
active
061162205
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection pump with an injection adjusting piston used for adjusting the onset of injection. DE-A-35 32 719 has disclosed an injection pump of this kind in which the control pressure for the injection onset adjustment prevails in the inner pump chamber and this pressure is supplied to the injection adjusting piston and to the control slide valve by way of the central region. The connection between the injection adjusting piston and the cam drive is embodied so that a sliding block is supported centrally in the region of the axis of the injection adjusting piston and the coupling part can engage in the sliding block perpendicular to the rotational movement of the sliding block. The control slide valve is disposed in a region of the injection adjusting piston adjoining the sliding block, to the side of a spring disposed in a bore of the injection adjusting piston and this spring is used as a restoring force and loads an end face of the injection adjusting piston. The pressure chamber defined in this bore by the control slide valve is disposed inside the injection adjusting piston and the control spring is supported so that it is fixed to the housing, parallel to the restoring spring that loads the injection adjusting piston. This embodiment of the injection adjusting piston is symmetrically loaded by the forces engaging it so that no significant tilting moments act on it.
With increased demands on the injection adjuster, it is necessary to accommodate the pressure chamber, which acts on the control slide valve, outside the injection adjusting piston, which is, however, connected with an increased demand for space in the axial direction of the injection adjusting piston. In order to compensate for this problem, the injection adjusting piston must be shorter and the control slide valve must be accommodated in a region of the injection adjusting piston that is simultaneously used to couple the injection adjusting piston to the cam drive. The reaction forces from the cam drive that no longer act on the injection adjusting piston coaxially but rather eccentrically due to this construction, generate tilting moments on the injection adjusting piston, which put a strain on the guidance of the injection adjusting piston in its cylinder. In addition, this construction requires another supply of the control pressure fluid, which must be provided in the central region of the injection adjusting piston and which additionally generates a pressure field on the injection adjusting piston, which in turn radially loads the injection adjusting piston and partially intensifies the radial forces between the injection adjusting piston and the cylinder resulting from the tilting moment.
ADVANTAGES OF THE INVENTION
By means of the fuel injection pump according to the invention, with the features set forth herein, in an injection adjusting piston, which is loaded on one side by reaction forces from the cam drive and additionally has a pressure fluid supply that intensifies the forces resulting from the one-sided loading, a possibility will now be provided in order to compensate for this one-sided loading of the injection adjusting piston and its guidance in such a way that the forces acting perpendicularly on one side, between the injection adjusting piston and the cylinder are reduced.
In an advantageous embodiment, in the recess in the injection adjusting piston, the coupling part encloses a pressure chamber in which a second pressure field is generated, which counteracts the first pressure field generated by the recess that is loaded by the pressure fluid source. On the side opposite from the injection adjusting piston the pressure field is absorbed by the coupling part which belongs to the cam drive and is supported in the housing of the fuel injection pump.
In another advantageous embodiment of the invention is, an additional recess is provided between the jacket face of the injection adjusting piston and the wall of the cylinder and the second pressure field is embodied in the reg
REFERENCES:
patent: 4748958 (1988-06-01), Ash
patent: 5263457 (1993-11-01), Konrath
patent: 5551399 (1996-09-01), Collingborn
patent: 5638794 (1997-06-01), Kubo
Berghaenel Bernd
Fehlmann Wolfgang
Fuchs Wakter
Geiger Wolfgang
Kulder Thomas
Adam Opel AG, a part interest
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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