Pumps – Expansible chamber type – Pumping member position controlled port
Reexamination Certificate
2000-06-05
2001-12-25
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Pumping member position controlled port
C137S539500
Reexamination Certificate
active
06332761
ABSTRACT:
PRIOR ART
The invention relates to a radial piston pump for high pressure fuel delivery in fuel injection systems of internal combustion engines, in particular in a common rail injection system, having a drive shaft that is supported in a pump housing and is eccentrically embodied or has cam-like projections in the circumference direction. The piston pump and preferably has a number of pistons which are arranged radially in relation to the drive shaft, each in a respective cylinder chamber, and can be moved in a reciprocating fashion in the cylinder chamber when the drive shaft rotates. The piston pump has a spring-preloaded check valve respectively on the intake side and on the high pressure side, and has a component with a through opening that constitutes the respective cylinder chamber. A high-pressure delivery opening leads away from the cylinder chamber and in the sealing seat of the high pressure side check valve, opens out into a mounting opening of this component which opening contains the valve components.
OBJECTS AND ADVANTAGES OF THE INVENTION
A radial piston pump of this kind has been disclosed by Mannesmann-Rexroth GmbH. The assembly of the high-pressure side check valve is complicated since this valve includes a number of components which have to be inserted into the mounting opening of the component that constitutes the respective cylinder chamber. The check valve is not accessible since the valve components are covered by a flange plate which holds the valve components in the mounting opening. The high-pressure seal is produced by using elastomer seals.
Based on this, the object of the current invention is to improve a radial piston pump of the type mentioned above so that in the vicinity of the high-pressure side check valve, a simplified assembly and more reasonably priced manufacture are achieved.
This object is attained according to the invention with a radial piston pump of this generic type by virtue of the fact that with the exception of a valve body which can be placed against the sealing seat, the high-pressure side check valve can be inserted into the mounting opening as a preassembled unit and can be tightened against the component to form a high-pressure seal.
In order to assemble the high-pressure side check valve, therefore, the preferably ball-shaped valve body is first inserted into the mounting opening. Through a preferably conical embodiment of the mounting opening in the vicinity of the sealing seat, the valve body can be assured of assuming its proper position during assembly. Then the preassembled valve unit is inserted and tightened against the component. For this purpose, the preassembled valve unit preferably has a sealing element of with an external thread which can be screwed into an internal thread of the mounting opening.
The high-pressure seal is preferably produced by virtue of the fact that the sealing element rests with an axial shoulder or end face against an axial step of the mounting opening.
In a very particularly advantageous embodiment of the invention, the sealing surface pair of the sealing element and the axial step in the mounting opening has a flat sealing surface on the one part and a preferably sharp-edged, closed circumferential projection on the other part, which when the components are tightened against each other, produce a high pressure seal. In this connection, when the components are tightened against each other, a sealing plastic deformation takes place along the contact line of the flat and the sharp-edged sealing surfaces. Therefore no elastomer sealing elements, which are susceptible to aging, have to be used, which also almost always prevent a definite, mutually decoupled contact of the components against each other. A high pressure seal can be achieved by virtue of the fact that the valve unit, which can be preassembled, is tightened against the metallic component which constitutes the mounting opening and also the cylinder chamber(s).
In a preferred embodiment of the high-pressure side check valve, the valve unit includes a cup-shaped loading element, which is pre-stressed in the closing direction and can move in a limited fashion in the closing or opening direction, and which, with the outside of its cup bottom forming a spring plate, forces the valve body into contact with the sealing seat. If the valve body is embodied as ball-shaped in a preferred manner, then the outside of the cup bottom of the loading element preferably has an arc shape that corresponds to the ball shape.
The cup-shaped loading element in this connection is dimensioned, pre-stressed, and embodied in its axial mobility in such a way that during the assembly of the valve unit, the valve unit can be placed with the outside of its cup bottom against the valve body and then can be moved back slightly in the direction toward the sealing element until this element has reached its sealing end position.
The preassembled valve unit preferably includes a pin-shaped projection, which engages in the cup-shaped loading element from the side remote from the cup bottom of and guides the loading element radially in its axial movement in the closing or opening direction. The cup-shaped loading element could, for example, be pre-stressed in the closing direction, i.e. in the direction toward the sealing seat of the mounting opening, by means of a spiral spring provided around the pin-shaped projection. The spiral spring in this connection could, for example, be supported against the sealing element. Meanwhile, it has turned out to be advantageous if a spring is provided on the interior of the cup-shaped loading element and is supported on one end against the inside of the cup bottom and is supported on the other end against an end face of the pin-shaped projection. This results in a compact design of the preassembled valve unit.
In order to prevent the cup-shaped loading element from becoming detached from the valve unit due to the initial stress of the spring, the cup-shaped loading element is locked by means of an axial stopping means. According to a preferred embodiment of the preassembled valve unit, the pin-shaped projection has a diametrically reduced axial section which is preferably embodied by an annular recess and the cup-shaped loading element engages with a projection in this axial section. Contact of the projection against an axial step of the projection, which defines the diametrically reduced axial section, prevents the cup-shaped loading element from becoming detached from the pin-shaped projection.
According to a preferred improvement of the concept of the invention, the projection is constituted by a crimping of the edge of the cup-shaped loading element oriented toward the sealing element. The crimping can be embodied as continuous in the circumference direction. However, it turns out to be advantageous if only one or a number of partial sections in the circumference direction of the edge are crimped so that an uncrimped edge section of the cup-shaped loading element can be placed against an axial stop face in order to embody a stroke limitation. The axial stop face can preferably be embodied by an end face of the sealing element.
Other features, details, and advantages of the invention ensue from the graphic depiction and the following description of a preferred embodiment of the radial piston pump according to the invention.
REFERENCES:
patent: 4277229 (1981-07-01), Pacht
patent: 5382140 (1995-01-01), Eisenbacher et al.
patent: 6238189 (2001-05-01), Guentert
Frey Hansjoerg
Guentert Josef
Freay Charles G.
Greigg Ronald E.
Robert & Bosch GmbH
Rodriguez William H.
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