Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-11-03
2002-07-02
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S495000
Reexamination Certificate
active
06412474
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a radial piston pump for producing high fuel pressure in fuel injection systems of internal combustion engines, particularly in a common rail injection system, with a drive shaft supported in a pump housing, which shaft is embodied eccentrically or has cam-like projections in the circumference direction, and preferably with a number of pistons, each in its own cylinder chamber, arranged radially with regard to the drive shaft, and with a plate attached to the ends of these cylinders oriented toward the drive shaft, which plate has a blind hole in its center which receives the end of the associated piston, and on its circumference, the piston has a groove into which a snap ring is inserted in order to fasten a plate retainer to the piston, which holds the plate on the piston.
With a partial filling of the cylinder chambers, the components of the radial piston pump that are exposed to high pressure undergo an extremely high amount of stress.
SUMMARY OF THE INVENTION
In accordance with the present invention a radial piston pump provided which can withstand the pressures of up to 2000 bar that occur with a partial filling of the cylinder chambers and nevertheless can be easily and inexpensively manufactured.
In a radial piston pump for producing high fuel pressure in fuel injection systems of internal combustion engines, in particular in a common rail injection system, with a drive shaft supported in a pump housing, which shaft is embodied eccentrically or has cam-like projections in the circumference direction, and preferably with a number of pistons, each in its own cylinder chamber, arranged radially with regard to the drive shaft, and with a plate attached to the ends of these cylinders oriented toward the drive shaft, which plate has a blind hole in its center for receiving the end of the associated piston, and on its circumference, the piston has a groove into which a snap ring is inserted in order to fasten a plate retainer to the piston, which holds the plate on the a piston, the object of the invention is attained by virtue of the fact that at the rim of the blind hole in the plate, a cylindrical recess is produced, where the play between the snap ring and the circumference of the cylindrical recess is smaller than the depth of the groove. The cylindrical recess is used to contain the snap ring, or more precisely stated, to contain the part of the snap ring which protrudes from the groove. The dimensioning of the cylindrical recess according to the invention achieves the fact that the snap ring is contained in captive fashion in its space. As a result, greater forces can be transmitted than in conventional radial piston pumps.
One particular embodiment of the invention is characterized in that the radius of the groove is greater than the radius of the snap ring. This dimensioning of the groove and of the snap ring produces the advantage that the snap ring always rests against the bottom of the groove and not against the edges of the groove. As a result, damage to the seat is prevented and the initial stress of the snap ring can be optimally utilized. The initial stress of the snap ring can be increased by increasing the thickness and diameter of the snap ring as well as the diameter of the groove.
Another particular embodiment of the invention is characterized in that the region of the plate retainer that rests against the snap ring expands radial to the piston and is embodied as flat. As a result, the snap ring can be seen better before the plate is inserted into the plate retainer. This results in the fact that installation is simplified and errors are prevented in the assembly of the radial piston pump according to the invention. Consequently, valuable time can be saved and the goal of zero errors can be better attained.
Another particular embodiment of the invention is characterized in that a step is embodied on the plate retainer. The step is advantageously used to center a spring which is used to prestress the plate toward the drive shaft.
Another particular embodiment of the invention is characterized in that on its circumference, the plate has a groove which contains a securing ring which rests against the plate retainer. The elastic securing ring produces a frictional and consequently play-free connection between the plate retainer and the plate. This assures that the piston base remains in contact with the plate during operation. During insertion of the plate into the plate retainer, the securing ring flexes so that the plate retainer can be embodied as rigid.
Another particular embodiment of the invention is characterized in that snap segments are embodied on the plate retainer, which rest against the circumference of the plate. In comparison to the claws known from the prior art, the snap segments have the advantage that they are more stable as a result of their size. Furthermore, the snap segments of one plate retainer do not interlock as easily with the snap segments of other plate retainers during storage. This facilitates the installation of the plate retainers.
Another particular embodiment of the invention is characterized in that the ends of the snap segments are each bent slightly outwards. As a result, the installation of the plate is advantageously simplified because during insertion of the plate into the plate retainer, the snap segments that are bent slightly outwards automatically spread out.
Another particular embodiment of the invention is characterized in that the ends of the snap segments each have a bevel. This produces the same effect as the snap segments that are bent slightly outwards. The installation of the plate is simplified.
Another particular embodiment of the invention is characterized in that a polygonal or cylindrical ring is disposed between the drive shaft and the plate. The ring is used to transmit forces from the eccentrically embodied drive shaft onto the plate. The ring is advantageously supported against the drive shaft in a sliding fashion. The ring can be embodied either cylindrically or with flattened places.
In general, the current invention has the advantage that the basic concept of this invention can easily be used on existing radial piston pumps. Generally, the component strength is increased, particularly at a zero delivery in the intake stroke, without increasing the space of the radial piston pump.
REFERENCES:
patent: 3857642 (1974-12-01), Miller
patent: 5364234 (1994-11-01), Eickmann
patent: 5983863 (1999-11-01), Cavanagh et al.
patent: 6176223 (2001-01-01), Kuhn et al.
patent: 6311674 (2001-11-01), Igashira et al.
patent: 6345609 (2002-02-01), Djordjevic
Guentert Josef
Simon Hans-Juergen
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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