Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Reexamination Certificate
1999-03-10
2001-05-29
Tyler, Cheryl J. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
C417S454000
Reexamination Certificate
active
06238189
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a radial piston pump for high-pressure fuel supply in fuel injection systems of internal combustion engines, in particular in a fuel injection system, having a drive shaft. The pump piston is supported in a pump housing and embodied eccentrically or has a plurality of camlike protuberances in the circumferential direction. Preferably a plurality of pistons are disposed radially with respect to the drive shaft in a given cylinder chamber, which upon rotation of the drive shaft the pistons are movable radially back and forth in the cylinder chamber. Each of the face ends remote from the drive shaft define a suction or compressor chamber, and have check valves on the intake side and the high-pressure side.
A radial piston pump of this type is sold by Applicant under the brand name CP1. In such a previously known pump, the mounting forces are initiated via a plurality of components braced against one another. For sealing, a number of elastomer sealing elements are used.
OBJECTS AND SUMMARY OF THE INVENTION
With this as the point of departure, it is an object of the present invention to create a radial piston pump that is high-pressure proof up to 2000 bar, with little idle volume and correspondingly high efficiency, in which the components are acted upon by high pressure and their sealing points are decoupled from one another and are defined statically exactly.
In the radial piston pump of the type described at the outset, this object is attained according to the invention in that for each piston, one metal insert part forming the respective cylinder chamber is provided inside the housing and radially to the drive shaft. The metal insert and communicates with the intake side and with the high-pressure side, and that the respective insert part, in the direction of the drive shaft between two flangelike metal housing parts with bearing faces extending perpendicular to the drive shaft rests on these faces. The respective insert part has a fuel delivery opening and a fuel discharge opening, which discharge in the region of the bearing faces and are aligned with a further respective delivery and discharge opening in the housing parts. The flangelike housing parts are tightened against one another, with the interposition of the insert parts, in such a way that the bearing faces of the respective insert part and housing parts effect a high-pressure sealing without the interposition of sealing elements.
While in previously known radial piston pumps the high-pressure sealing has also been attained via elastomeric, more or less deforming sealing elements and the mounting of the components defining the high-pressure side included—as noted at the outset—a flow of force via a plurality of components, which led to a static indefiniteness, with the invention it is proposed that the sealing be attained via metal sealing faces of the insert part and of the flangelike housing parts that extend at right angles to the drive shaft. To that end, the fuel delivery and discharge during the pumping stroke of the pump pistons are effected via fuel delivery openings and fuel discharge openings, which discharge at one end in the intake or compressor chamber and on the other in the sealing faces on both sides. The insert part now rests in a statically precisely determined way against the two flangelike housing parts, without the interposition of any sealing elements of any kind. When the housing parts are tightened against one another, a so-called hard sealing is effected by means of the metal bearing faces of the insert part and of the flangelike housing parts on both sides.
Preferably, all the sealing points, acted upon by high pressure, of metal components tightened against one another are formed without the interposition of additional sealing elements, that is, so-called hard seals.
The metal components resting sealingly against one another preferably have lapped bearing faces. By means of the lapping operation, a desired surface roughness is created while maintaining the dimensional accuracy.
From the standpoint of production technology, it is proved to be especially advantageous if the respective insert part is positioned relative to the housing parts via pins extending parallel to the drive shaft.
If the check valve on the intake side and on the high-pressure side, respectively, is integrated with the respective housing part; and the downstream side of the check valve on the high-pressure side extends as far as a high-pressure connection stub entirely inside the housing part, then the high-pressure side is sealed off securely by the hard (only) seal between the insert part and the housing part.
The aforementioned high-pressure connection stub is preferably tightened with one face end against a step, forming a direct metal-to-metal seal. The metal seal is advantageously embodied such that the sealing faces resting on one another of the metal components have a sharp-edged or beadlike protuberance, which when the components are tightened against one another leads to a sealing plastic deformation along the protuberance. This is known as a biting edge seal. In the case of the high-pressure connection stub, this biting edge is preferably provided extending all the way around on the face end.
The insert part extending radially to the drive shaft could have a blind bore to form the cylinder chamber. However, to enable machining the wall of the cylinder chamber in a suitable way, for instance by lapping, it proves to be advantageous if the insert part has a through opening, extending radially to the drive shaft and forming the cylinder chamber, which opening is closed radially on the outside by a metal closing element that is screwed into the through opening.
To form a high-pressure seal, the metal closing element is tightened with its face end against an axial step in the through opening in such a way that high-pressure sealing is brought about. To that end, the face end of the closing element may have an encompassing biting edge, which when the closing element is tightened forms a sealing plastic deformation with the axial step face.
REFERENCES:
patent: 4952121 (1990-08-01), De Matthaeis et al.
patent: 4957416 (1990-09-01), Miller et al.
patent: 5382140 (1995-01-01), Eisenbacher et al.
patent: 5395219 (1995-03-01), Hosoya et al.
patent: 6162022 (2000-12-01), Anderson et al.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Tyler Cheryl J.
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