The invention is based on a high-pressure pump for a fuel injection system of an internal combustion engine as generically defined by the preamble to claim 1.
One such high-pressure pump is known from German Patent Disclosure 197 29 790 A1. This high-pressure pump has at least one pump element, with a pump piston guided displaceably in a cylinder bore of a housing part of the high-pressure pump and driven in a reciprocating motion. In the cylinder bore, the pump piston defines a pump work chamber, into which the pump piston, in its intake stroke, aspirates fuel via an inlet valve, and from which the pump piston in its pumping stroke positively displaces fuel. The inlet valve has a pistonlike valve member, which is guided displaceably in a valve housing communicating with the housing part of the high-pressure pump. The valve member has a sealing face, with which it cooperates with a valve seat, embodied on the valve housing for controlling a communication of the pump work chamber with a fuel inlet. The valve member is urged in the closing direction toward the valve seat by a closing spring, disposed in the valve housing, and by the pressure prevailing in the pump work chamber, and is urged in the opening direction by the pressure prevailing in the fuel inlet. The fuel inlet discharges in the valve housing, and the valve housing together with the valve member and the closing spring forms a preassembled structural unit, which is inserted into the housing part of the high-pressure pump. Because of the separate valve housing, the high-pressure pump is complicated and thus expensive to manufacture and produce. Moreover, the valve housing covers the pump work chamber, so that between the housing part of the high-pressure pump and the valve housing, complicated sealing off from the high pressure in the pump work chamber is necessary.
The high-pressure pump of the invention having the characteristics of claim 1 has the advantage over the prior art that no separate valve housing for the inlet valve and thus no sealing off from the high pressure in the pump work chamber are necessary. For the housing part, the only additional part that must be made is the valve seat, which can be machined in a simple way from the inside of the cylinder bore. The valve member is introduced from the inside of the cylinder bore, with its shaft leading, and the closing spring is mounted from the outside of the housing part, diametrically opposite the cylinder bore, and joined to the shaft of the valve member.
In the dependent claims, advantageous features and refinements of the high-pressure pump of the invention are recited. The version of claim 2 makes an easily manufactured course of the fuel delivery possible. The embodiment of claim 4 enables guidance of the valve member and thus a secure sealing action of the inlet valve as well as low wear to the sealing face and the valve seat possible. The embodiment of claim 5, even without guidance of the valve member, makes a secure sealing action of the inlet valve possible.
Two exemplary embodiments of the invention are shown in the drawing and described in further detail in the ensuing description.
In
In a region located between the two bearing points, the drive shaft 12 has at least one portion 16, or cam, that is eccentric to its pivot axis 13; the cam 16 may also be embodied as a multiple cam. The high-pressure pump has at least one, or more, pump elements 18 disposed in the pump housing 10, each with a pump piston 20 that is driven in a reciprocating motion by the eccentric portion 16 or cam of the drive shaft 12, in a direction that is at least approximately radial to the pivot axis 13 of the drive shaft 12. In the region of each pump element 18, one housing part 22 connected to the basic body 14 is provided, which is embodied as a cylinder head. The housing part 22 has a flange 24, resting on an outside of the basic body 14, and an approximately cylindrical extension 26, of lesser diameter than the flange 24, protruding toward the drive shaft 12 through an opening 15 in the basic body 14.
The pump piston 20 is guided tightly displaceably in a cylinder bore 28 that is embodied in the housing part 22, and with its face end remote from the drive shaft 12, the pump piston defines a pump work chamber 30 in the cylinder bore 28. The pump work chamber 30 is disposed in the region of the flange 24 of the housing part 22, and the cylinder bore 28 extends as far as the end, toward the drive shaft 12, of the extension 26 of the housing part 22. Via a fuel delivery conduit 32 extending in the pump housing 10, the pump work chamber 30 has a communication with a fuel delivery means, such as a feed pump. At the mouth of the fuel delivery conduit 32 into the pump work chamber 30, there is an inlet valve 34 which opens into the pump work chamber 30. Via a fuel outflow conduit 306 extending in the pump housing 10, the pump work chamber 30 also has a communication with an outlet, which for instance communicates with a high-pressure reservoir 110. One or preferably more injectors 120 disposed at the cylinders of the engine communicate with the high-pressure reservoir 110, and through them fuel is injected into the cylinders of the engine. At the mouth of the fuel outflow conduit 36 into the pump work chamber 30, there is an outlet valve 38 that opens out of the pump work chamber 30. The housing part 22 comprises a high-strength material, since in the pump work chamber 30, high pressure prevails during the pumping stroke of the pump piston 20. The housing part 22 may for instance comprise steel or gray cast iron.
Between the pump piston 20 and the eccentric portion 16 or cam of the drive shaft 12, a support element may be disposed, in the form of a tappet 40, by way of which the pump piston 20 is braced at least indirectly on the cam 16. The pump piston 20 is coupled to the tappet 40 in a manner not shown in detail in the direction of its longitudinal axis 21. The tappet 34 may be braced directly on the eccentric portion 16 or cam. A ring 42 on which the tappet 40 rests may be rotatably supported on the portion 16 of the drive shaft 12. For each pump element 18, the ring 42 has one flat face 44 on which the tappet 40 rests. In the rotary motion of the drive shaft 12 about its pivot axis 13, the pump piston 20 is driven in a reciprocating motion via the ring 42 and the tappet 40, but the ring 42 does not rotate with the drive shaft 12; it is instead stationary. The tappet 40 is displaceably supported in the base body 14 of the pump housing 10 or on the housing part 22 and absorbs transverse forces that occur upon the conversion of the rotary motion of the drive shaft 12 into the reciprocating motion of the pump piston 20, so that these forces do not act on the pump piston 20. The tappet 40 is engaged by a prestressed restoring spring 48, by which the tappet 40 and the pump piston 20 connected to it are pressed toward the portion 16.
The inlet valve 34 in a first exemplary embodiment will now be described in further detail, referring to
The further bore 54 is tightly closed off toward the outside of the housing part 22 by means of a closure element 68, which is inserted into the bore 54. The closure element 68 may for instance, as shown in
The bores 50, 54 and the valve seat 52 can be easily manufactured in the housing part 22, since before the housing part 22 and the basic body 14 are put together, the valve seat 52 is accessible for machining purposes from the inside of the cylinder bore 28. Before the housing part 22 and the basic body 14 are put together, the valve member 56 is introduced from the inside of the cylinder bore 28 with its shaft 62 leading, so that this shaft protrudes outward through the bore 50; next, the closing spring 64 and the spring plate 66 are installed, and finally the closure element 68 is inserted.
In the intake stroke of the pump piston 20, in which the pump piston together with the tappet 40 is moved radially inward by the restoring spring 48, a low pressure prevails in the pump work chamber 30, and thus the inlet valve 34 opens in that its valve member 56, with its sealing face 60, lifts from the valve seat 52, since because of the pressure prevailing in the fuel delivery conduit 32, a greater force is generated in the opening direction than the total of the force of the closing spring 64 and of the force generated by the pressure prevailing in the pump work chamber 3-. From the chamber 72, when the inlet valve 34 is open, fuel flows through the annular gap 63 into the pump work chamber 30. At low pressure in the pump work chamber 30 during its filling, the outlet valve 38 is closed. In the pumping stroke of the pump piston 20, in which the pump piston together with the tappet 40 moves radially outward, fuel in the pump work chamber 30 is compressed by the pump piston 20, so that because of the increased pressure in the pump work chamber 24, the inlet valve 34 closes, while fuel at high pressure is pumped through the fuel outflow conduit 36, with the outlet valve 38 open, to the high-pressure reservoir 110. The valve member 56 of the inlet valve 34 is not guided; because of its convex sealing face 60 and the frustoconical valve seat 52, centering is brought about upon the closing motion of the valve member 56, so that the sealing face 60 securely seals off the valve seat 52, and the pump work chamber 30 is disconnected from the fuel delivery conduit 32.
In
The indentation 76 is tightly closed off from the outside by means of a closure element 68, and the closure element 68 may be screwed together, pressed on, or welded to the housing part 22. By means of the closure element 68, a chamber 72 is defined in the indentation 76, and the fuel delivery conduit 32 discharges into this chamber; the chamber 72 communicates with the annular gap 63 surrounding the shaft 62 of the valve member 56 via the bores 78. When the inlet valve 34 is open, fuel flows out of the indentation 76 via the bores 78 into the annular gap 63 and from it into the pump work chamber 30. In its opening and closing motion, the valve member 56 is guided with its shaft 62 in the second bore portion 250.
Number | Date | Country | Kind |
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10 2004 013 244.5 | Mar 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/50193 | 1/18/2005 | WO | 9/18/2006 |