1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine of the type having a high pressure pump and a fuel injector for each cylinder of the engine.
2. Description of the Prior Art
One fuel injection system of the type with which this invention is concerned is known from European Patent Disclosure EP 0 957 261 A1. For each cylinder of the engine, this known fuel injection system has one high-pressure fuel pump and one fuel Injection valve communicating with it. The high-pressure fuel pump has a pump piston, which is driven in a reciprocating motion by the engine and which defines a pump work chamber that communicates with a pressure chamber of the fuel injection valve. The fuel Injection valve has an Injection valve member, by which at least one injection opening is controlled, and which is movable by the pressure prevailing in the pressure chamber in an opening direction counter to a closing force. By means of an electrically controlled control valve, a communication of the pump work chamber with a relief chamber is controlled in order to control the fuel injection. When the pressure in the pump work chamber and thus in the pressure chamber of the fuel injection valve reaches the opening pressure, the injection valve member moves In the opening direction and uncovers the at least one injection opening. The injection cross section that is controlled by the injection valve member in the process is always the same size. This does not enable optimal fuel injection under all engine operating conditions.
The fuel injection system of the invention has the advantage over the prior art that by means of the second injection valve member, an additional injection cross section can be opened or closed with the at least one injection opening as a function of engine operating parameters, so that the injection cross section can be adapted optimally to engine operating conditions.
Various advantageous features and refinements of the fuel injection system of the invention are disclosed. One embodiment makes simple control of the control pressure in the control chamber possible. In another this control can be attained without requiring any additional component. A further embodiment makes it possible upon the supply onset of the pump piston initially to uncover only a slight injection cross section with the at least one injection opening, and upon a greater stroke of the pump piston additionally to uncover a larger injection cross section with the at least one second injection opening. The stroke length of the pump piston beyond which the at least one second injection opening is opened may be varied.
The foregoing and other features of the invention will become apparent from the description contained herein below, taken in conjunction with the drawings, in which:
In
The fuel injection valve 12 has a valve body 26, which can be embodied in multiple parts and in which a first injection valve member 28 is guided longitudinally displaceably in a bore 30. In its end region toward the combustion chamber of the cylinder of the engine, the valve body 26 has at least one first injection opening, and preferably a plurality of first injection openings 32, which are distributed over the circumference of the valve body 26. The first injection valve member 28, in its end region toward the combustion chamber, has a sealing face 34, which for instance is approximately conical, and which cooperates with a valve seat 36 embodied in the end region of the valve body 26 oriented toward the combustion chamber, and from this valve seat or downstream of it, the first injection openings 32 lead away. Between the injection valve member 28 and the bore 30 in the valve body 26, toward the valve seat 36, there is an annular chamber 38, which in its end region remote from the valve seat 36 changes over, by means of a radial widening of the bore 30, into a pressure chamber 40 that surrounds the first injection valve member 28. At the level of the pressure chamber 40, as a result of a cross-sectional reduction, the first injection valve member 28 has a pressure shoulder 42. The end of the first injection valve member 28 remote from the combustion chamber is engaged by a first prestressed closing spring 44, by which the first injection valve member 28 is pressed toward the valve seat 36. The first closing spring 44 is disposed in a first spring chamber 46 of the valve body 26, which chamber adjoins the bore 30.
The first injection valve member 28 of the fuel injection valve 12 is embodied as hollow, and in it, a second injection valve member 128 is guided displaceably in a bore embodied coaxially in the injection valve member 28. By means of the second injection valve member 128, at least one second injection opening 132 in the valve body 26 is controlled. The at least one second injection opening 132 is offset toward the combustion chamber in the direction of the longitudinal axis of the injection valve members 28, 128 from the at least one first injection opening 32. The second injection valve member 128, in its end region toward the combustion chamber, has a sealing face 134, which for instance is approximately conical, and which cooperates with a valve seat 136, embodied in the valve body 26 in its end region toward the combustion chamber, from which or downstream of which valve seat the second injection openings 132 lead away. The second injection valve member 128 can be embodied in two parts and can have one part, toward the combustion chamber, that has the sealing face 134 and one second part, pointing away from the combustion chamber, that adjoins the first part. Near the end toward the combustion chamber of the second injection valve member 128, a pressure face 142 is embodied on the injection valve member, and when the first injection valve member 28 is opened, the pressure prevailing in the pressure chamber 40 acts on this pressure face.
A second spring chamber 146 is embodied in the valve body 26, adjacent to the first spring chamber 46 in the direction away from the combustion chamber, and in this second spring chamber, a second closing spring 144, acting on the second injection valve member 128, is disposed. The first injection valve member 28 protrudes with its end into the first spring chamber 46 and is braced on the first closing spring 44. The first closing spring 44 is braced with its end remote from the first injection valve member 28 on a sleeve 47, which is disposed between the first spring chamber 46 and the second spring chamber 146 and which for instance is press-fitted into the valve body 26. The second injection valve member 128 protrudes through the sleeve 47 into the second spring chamber 146, and it is braced on the second closing spring 144 via a spring plate 147. The second closing spring 144 is braced, by its end remote from the second valve member 128, on the bottom of the second spring chamber 146. By means of the spring plate 147, a control chamber 50 is defined in the second spring chamber 146.
From the pump work chamber 22, a conduit 52 leads through the pump body 14 and the valve body 26 into the pressure chamber 40 of the fuel injection valve 12. By means of an electrically controlled valve 23, a communication of the pump work chamber 22 with a relief chamber is controlled; by way of example, the fuel tank 24 can serve at least indirectly as this relief chamber, or a region in which a pressure that is somewhat elevated compared to the fuel tank 24 is maintained can serve as the relief chamber. As long as no fuel injection is to occur, the control valve 23 is intended to keep the communication of the pump work chamber 22 with the relief chamber open, so that high pressure cannot build up in the pump work chamber 22. When a fuel injection is to occur, the pump work chamber 22 is disconnected from the relief chamber by the control valve 23, so that upon the pumping stroke of the pump piston 18, high pressure can build up in the pump work chamber 22. The control valve 23 can be embodied as a magnet valve or as a piezoelectric valve.
The fuel injection system is shown in a first exemplary embodiment in
Between the camshaft of the engine having the cam 20 and the pump piston 18, an intermediate shaft 70 is disposed, on which a transmission element 71 in the form of a two-armed tilt lever is disposed, which lever rolls with one end over the cam 20, for instance via a roller 72, and is pivotably connected by its other end to the pump piston 18. It is provided that the location of the intermediate shaft 70 having the tilt lever 71 is variable, as a result of which the outset stroke position of the pump piston 18 can be varied. In
An adjustment of the location of the intermediate shaft 70 can be made for instance by means of a hydraulic adjusting device 74, by which the bearing of the intermediate shaft 70 is shifted. Alternatively, the adjusting device 74 can be embodied as an eccentric element, by which the bearing of the intermediate shaft 70 is shifted.
The function of the fuel injection system in the first exemplary embodiment will now be explained. Upon the intake stroke of the pump piston 18, the control valve 23 is opened, so that fuel from the fuel tank 24 reaches the pump work chamber 22. In the pumping stroke of the pump piston 18, the onset of the fuel injection is defined as a result of the fact that the control valve 23 closes, so that the pump work chamber 22 is disconnected from the relief chamber, and high pressure builds up in the pump work chamber 22. As a function of engine operating parameters, the intermediate shaft 70 is adjusted to the requisite position by the adjusting device 74. When the pump piston 18 is in the outset stroke position shown in the right-hand half of
When the pump piston 18 executes its supply stroke further, the conduit 60 in the pump piston 18 moves away from coincidence with the annular groove 62, and so the control chamber 50 is disconnected from the pump work chamber 22. The control chamber 50 preferably communicates with a relief chamber via at least one throttle restriction, so that the pressure in the control chamber 50 decreases. In this case, now only the force of the second closing spring 144, and possibly a slight pressure force, act on the second injection valve member 128, so that the pressure force acting on the second injection valve member 128 via the pressure face 142 as a result of the pressure prevailing in the pressure chamber 40 does suffice to open the second injection valve member 128 as well, so that the at least one second injection opening 132 is uncovered as well. Thus the entire injection cross section of the fuel injection valve 12 is opened, and a larger fuel quantity is injected. The end of the fuel injection is determined by the opening of the control valve 23, as a result of which the pump work chamber 22 communicates with the relief chamber, and high pressure can no longer build up in it.
The pump piston 18 can have one further conduit 65, which upon a maximal stroke of the pump piston 18 into the pump work chamber 22 comes into coincidence with the annular groove 62 and establishes a communication with a relief chamber. At the maximal stroke of the pump piston 18, the control chamber 50 thus communicates with a relief chamber and is pressure-relieved.
It can be provided that the injection cross sections formed by the first injection openings 32 and the second injection openings 132 are at least of approximately equal size, so that when only the first injection valve member 28 is opened, half of the total injection cross section is uncovered. Alternatively, it can be provided that the first injection openings 32 form a larger or smaller injection cross section than the second injection openings 132.
When the pump piston 18 is in its outset stroke position shown in the left half of
The variation in the position of the intermediate shaft 70 and thus in the outset stroke position of the pump piston 19 by the adjusting device 74 is effected as a function of such engine operating parameters as the rpm, load, and temperature, and optionally still other operating parameters. The adjusting device 74 is triggered by an electric control unit 76, by which the control valve 23 is also triggered. If, taking these operating parameters into account, only a slight fuel quantity is to be injected at the onset of the fuel injection, then by means of the control unit 76, the adjusting device 74 is triggered in such a way that the intermediate shaft 70 and thus the pump piston 18 are in the outset stroke position of the pump piston shown in the right half of
In
The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
Number | Date | Country | Kind |
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101 41 679 | Aug 2001 | DE | national |
This application is a 35 USC 371 application of PCT/DE 02/03140 filed on Aug. 23, 2002.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE02/03140 | 8/23/2002 | WO | 00 | 4/26/2004 |
Publishing Document | Publishing Date | Country | Kind |
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WO03/01899 | 3/6/2003 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4306528 | Straubel | Dec 1981 | A |
4538576 | Schneider | Sep 1985 | A |
6378503 | Lambert | Apr 2002 | B1 |
6725838 | Shafer et al. | Apr 2004 | B2 |
6769635 | Stewart et al. | Aug 2004 | B2 |
Number | Date | Country |
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41 23 721 | Jun 1992 | DE |
100 38 054 | Feb 2001 | DE |
100 40 738 | Mar 2001 | DE |
0 972 932 | Jan 2000 | EP |
Number | Date | Country | |
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20040232256 A1 | Nov 2004 | US |