Internal-combustion engines – Charge forming device – With fuel pump
Patent
1991-11-22
1993-11-09
Miller, Carl S.
Internal-combustion engines
Charge forming device
With fuel pump
123501, 123447, F02M 3704
Patent
active
052593517
DESCRIPTION:
BRIEF SUMMARY
RELATED PATENT APPLICATION
This invention relates to PCT/DE 91/00184 filed Mar. 1, 1991.
The invention relates to a fuel injection device for -injected internal combustion engines, in particular a unit fuel injector, in which the control of the onset and end of supply is effected by means of a magnet valve incorporated between a low-pressure circuit and a work chamber of the pump piston; a scavenging line that can be connected to the work chamber is provided and communicates with a low-pressure chamber or the tank, and a delivery line for delivering the fuel from the magnet valve to the work chamber of the pump piston via a connecting bore intersects the guide bore of the pump piston. In the known injection pumps of this type (European Patent Application A 0 207 652), the scavenging bore is embodied by a separate auxiliary bore, which discharges with circumferential offset with respect to the delivery bore into the guide bore of the pump piston and is opened, in the region of bottom dead center, by the end-face edge of the pump piston. An additional bore of this type is expensive.
The object of the invention is to simplify the construction and to reduce the production cost.
The invention therefore substantially resides in the fact that the portion of the delivery bore remote from the magnet valve and located downstream of the intersection with the guide bore of the piston is utilized as a scavenging bore of the scavenging line. The part of the delivery bore remote from the magnet valve and located downstream of the intersection with the guide bore of the pump piston serves in the known injection pump merely to make it possible to produce the bore. In the known injection pumps, this part of the delivery bore, which is closed at one end, is an idle part. This previously idle part of the delivery bore is now utilized as a scavenging bore, and the product cost for the injection pump is reduced by the elimination of a separate scavenging bore or line.
In the known injection pumps, the delivery bore extends obliquely in the direction of top dead center. This has the advantage that the bore can be made more easily. With this kind of oblique disposition of the delivery bore, it is now advantageously possible, in accordance with a further feature of the invention, for the obliquity to be dimensioned so that one end-face edge of the piston opens the mouth of the scavenging bore, or this otherwise idle part of the delivery bore, in the vicinity of bottom dead center. This makes scavenging of the work chamber at bottom dead center possible.
However, the invention also makes scavenging in the top dead center position of the piston possible. The arrangement is suitably such, that the portion of the delivery bore located downstream of the intersection and utilized as a scavenging bore can be made to communicate via a recess or annular groove of the piston, in the region of top dead center of the piston, with the part of the delivery line, originating at the magnet valve, that communicates permanently with the work chamber of the pump piston via the connecting bore. The communication of the work chamber of the piston with the low-pressure chamber or the tank is now established at top dead center.
A check valve opening in the direction of the low-pressure chamber may be disposed in a branch line of the scavenging line joining this scavenging bore, or the idle part of the delivery bore, to the low-pressure chamber.
The invention is explained schematically in the drawing in terms of the exemplary embodiments.
FIGS. 1 and 2 are details of an embodiment belonging to the prior art, with FIG. 1 being a section taken along the line I--I of FIG. 2 and FIG. 2 being a section taken along the line II--II of FIG. 1. FIGS. 3 and 4 are longitudinal sections through an embodiment which makes scavenging at bottom dead center possible, with FIG. 3 showing the piston at bottom dead center and FIG. 4 showing the piston just before it reaches top dead center. FIG. 5 is a detail of FIG. 3 for a slightly modified embodiment. FIGS. 6 and 7, in
REFERENCES:
patent: 4448169 (1984-05-01), Badgley
patent: 4467772 (1984-08-01), Williamson
patent: 4653455 (1987-03-01), Eblen
patent: 4811899 (1989-03-01), Egler
patent: 5040511 (1991-08-01), Eckert
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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