Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Reexamination Certificate
1999-07-29
2001-05-01
Freay, Charles G. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
C417S454000, C137S454400, C137S541000
Reexamination Certificate
active
06224350
ABSTRACT:
SPECIFICATION
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. The pump includes a drive shaft that is supported in a pump housing and is embodied as eccentric or has a number of cam-like projections in the circumference direction. A number of pistons that are disposed radially with regard to the drive shaft, each in a respective cylinder chamber, and can be set into a reciprocating motion in the cylinder chamber upon rotation of the drive shaft. An intake side check valve and a high-pressure side check valve, includes a component which has a through opening that constitutes the cylinder chamber and into whose radially outer end, a sealing element is inserted, wherein the intake side check valve is integrated into the sealing element.
A radial piston pump of this kind has been disclosed by Mannesmann Rexroth GmbH. The component that constitutes the cylinder chamber is provided inside a housing flange, i.e. is embodied as a component on the inside of the housing. The fuel supply to the intake side check valve takes place from the end of the sealing element remote from the piston, i.e. from the radial outside—with regard to the drive shaft—of the component that contains the pistons. A radially external intake chamber must therefore be provided there, which is encompassed by the housing flange.
Based on this, an object of the current invention is to disclose a more compact design of the radial piston pump.
In a radial piston pump of the type mentioned at the beginning, this object is attained according to the invention by virtue of the fact that the sealing element is sealed in a pressure-tight fashion toward the outside in the longitudinal direction of the through opening that constitutes the cylinder chamber, and the fuel supply to the intake side check valve takes place by way of a fuel supply opening that is disposed in the component and is disposed essentially radial to the longitudinal direction.
Since the sealing element constitutes a pressure-tight closure of the intake or compression unit in the longitudinal direction of the cylinder chamber or in the radial direction to the drive shaft and since the intake side fuel supply takes place transversely in relation to the longitudinal direction of the cylinder chamber through the component that defines the cylinder chamber, both the intake chamber that is on the radial outside (in relation to the drive shaft) and the additional external housing wall that is required for this can be omitted.
The sealing element can be an easy-to-install screw plug which is screwed into an internal thread that is provided on the radially outer end of the component.
It has turned out to be advantageous if the through opening in the component is embodied as offset or stepped and the sealing element is pressed with a sealing flange, in particular an annular collar-like one, in a sealed fashion against a step of the through opening and the intake valve is disposed centrally inside the sealing flange. To seal the sealing element on the radially outer end, a sealing means can be provided, for example in the form of an elastomer sealing ring, while the seal in relation to the cylinder chamber is produced by pressing the sealing flange against the step. For this purpose, it turns out to be advantageous if the sealing element can be tightened against the step like a screw plug.
In another embodiment of the invention, an annular chamber is provided opposite the sealing flange of the sealing element, between the sealing element and the wall of the component that defines the through opening, and the fuel supply opening feeds into this annular chamber. This annular chamber thus constitutes an intake chamber inside the component. The fuel supply to the component takes place by way of a metering device that is not shown.
Leading from the annular chamber, an oblique bore can be provided, which extends at a diagonal to the longitudinal direction of the through bore, into the interior of the sealing element, and to the intake side check valve, in order to produce a flow connection between the intake side of the check valve and the annular chamber.
On its end oriented toward the piston, the sealing element can have a cup-shaped recess which contains the intake side check valve.
The above-mentioned oblique bore then feeds into the cup-shaped recess. The intake side check valve, which can preferably be embodied in the manner described below, can be detached from the component that comprises the cylinder chamber and be mounted on the sealing element outside the pump housing. An element that constitutes a valve seat can be inserted in a sealed fashion into the cup-shaped recess and has a central opening through which a tappet of a valve body extends. The valve body has valve disk that is attached to the tappet and can be placed in a sealed fashion against the end face encompassing the tappet opening, i.e. against the end of the element oriented toward the piston. This brings with it the advantage that in the compression stroke of the piston, the piston end face oriented toward the sealing element can extend almost to the sealingly contacting valve disk, so that a small dead volume and thereby an optimal efficiency of the pump can be achieved.
From a technical manufacturing standpoint, it has turned out to be advantageous that the tappet can reach with play through the opening of the element that constitutes the valve seat, without this impairing the opening and closing function of the check valve.
If the valve seat and the valve body that cooperates with it have conically extending sealing faces, then the valve plate automatically centers itself when the check valve closes.
The valve is preferably embodied so that a spring which pre-stresses the valve body in the closing direction is provided on the end of the element, which is inserted into the cup-shaped recess, remote from the pump piston. The spring can be supported on one end against the element and on the other end, against a counter support that is attached to the tappet, so that the tappet is pre-stressed in the closing direction, i.e. toward the bottom of the cup-shaped recess, and is placed in a sealed fashion against the sealing seat embodied on the end of the element oriented toward the piston.
The counter support on the tappet could be embodied in an intrinsically arbitrary manner. For technical manufacturing reasons, it turns out to be particularly advantageous if the counter support is constituted by a collar bushing element, which is slid with its bushing section onto the tappet and is attached to the tappet there in a fundamentally arbitrary manner, but preferably in a positively engaging fashion, in particular by means of a crimping work cycle or a by means of a laser weld.
In another embodiment of the invention, it is quite particularly significant that the counter support is fixed to the tappet in such a position that a desired, pre-selected opening pressure of the check valve is produced. For this purpose, in the assembly of the check valve, the valve body is guided with its tappet through the tappet opening in the insertion element described above. The valve body is then placed in a sealed fashion against the sealing seat and the counter support is slid onto the tappet from the other end, with the interposition of the spring. The further the counter support is slid onto the tappet in opposition to the spring force, the greater the force that defines the opening pressure of the valve. In order to be able to predetermine a desired pressure in a lasting manner, the counter support is fixed at this position on the tappet when the desired opposing pressure is achieved.
The subassembly described above is than inserted in a sealed fashion into the cup-shaped recess of the sealing element. For this purpose, the element can be advantageously screwed into the cup-shaped recess and simultaneously glued in. A reliable and favorably sealing fixed position can be achieved in
Guentert Josef
Haegele Ralf
Freay Charles G.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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