Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1999-10-01
2001-01-23
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C417S273000, C184S006600
Reexamination Certificate
active
06176223
ABSTRACT:
PRIOR ART
The invention relates to a radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines, particularly in a common rail injection system, with a drive shaft that is supported in a pump housing and has an eccentrically embodied shaft section upon which a ring is supported in sliding fashion by means of a bearing bush, the ring cooperates preferably with a number of pistons that are disposed radially with regard to the drive shaft, each in a respective cylinder chamber. The eccentric shaft section and the ring are fixed in the axial direction by means of stop faces and a bearing gap is provided between the bearing bush and the eccentric shaft section, into which lubricant can travel from the inside of the pump housing.
An object of the invention is to improve the supply of lubricant to the bearing gap in order to assure a lubricating film with a full bearing capacity.
A radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines, particularly in a common rail injection system. The piston pump has a drive shaft that is supported in a pump housing and has an eccentrically embodied shaft section upon which a ring is supported in sliding fashion by means of a bearing bush. The ring cooperates preferably with a number of pistons that are disposed radially with regard to the drive shaft, each in a respective cylinder chamber. The the eccentric shaft section and the ring are fixed in the axial direction by means of stop faces and a bearing gap is provided between the bearing bush and the eccentric shaft section, into which lubricant can travel from the inside of the pump housing. An object of the invention is attained by virtue of the fact that the hub end faces of the pump housing are embodied as conical so that a wedge-shaped gap is produced which narrows in the direction of the bearing gap. As a result, the connection between the inner chamber of the pump housing and the bearing gap is enlarged and the entry of lubricant into the bearing gap is encouraged.
One particular embodiment of the invention is characterized in that the hub end faces on the back side of the stop collar are embodied by axial bearings. When the drive shaft is driven by the engine, for example by way of diagonally toothed gears, this results in the fact that forces are exerted on the shaft in the axial direction. In this instance, it is advisable to install an axial slide bearing which absorbs the axial forces. In an axial slide bearing of this kind, the back side of the stop collar of the flange bush can, for example, be inclined in order to produce a wedge-shaped gap. As a result, the supply of lubricant to the bearing gap is improved.
Another particular embodiment of the invention is characterized in that the hub end faces have at least one blade which is aligned on one side so that the lubricant is fed from the pump housing to the bearing gap. The delivery of lubricant is counteracted by centrifugal force, which interferes with the lubricant supply. If only one blade is attached to the stop face, it must be precisely positioned so that the lubricant is delivered to the correct location in the bearing gap. Providing a number of blades is in fact more expensive in the manufacturing, but offers the advantage that mounting them in a position-oriented fashion is not required.
Another particular embodiment of the invention is characterized in that the blade is embodied as symmetrical with regard to a radial. The symmetrical design of the blade has the advantage that the feeding action is produced independent of the rotational direction of the drive shaft.
Another particular embodiment of the invention is characterized in that the blade surface is embodied as flat. The flat blades have the advantage that they are simple and inexpensive to produce.
Another particular embodiment of the invention is characterized in that the blade surface is embodied as curved. With the curved blades, more lubricant can be fed into the bearing gap, because this form is more favorable from a technical flow standpoint.
Other advantages, features, and details of the invention ensue from the description below, in which various exemplary embodiments are described in detail with reference to the drawings. In this connection, the features mentioned hereinafter in the description can be essential to the invention by themselves or in arbitrary combinations with one another.
REFERENCES:
patent: 4671743 (1987-06-01), Frey
patent: 5382140 (1995-01-01), Eisenbacher et al.
patent: 5967123 (1999-10-01), Rouff et al.
patent: 5979297 (1999-11-01), Ricco
Kuhn Uwe
Schwarz Thomas
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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