Patent Application
20090229577
The invention is based on a fuel injection system for an internal combustion engine as generically defined by the preamble to claim 1.
One such fuel injection system is known from German Patent Disclosure DE 101 23 994 A1. This fuel injection system has two electrically actuated control valves for controlling the fuel injection. The two control valves are each connected to an electric control unit via electric lines. The electrical contacting of the two control valves is complicated; typically, a separate terminal for each control valve must be present, with which a respective terminal element, for instance a plug element, must be joined together. This makes for complicated production and assembly of the fuel injection system. with many individual parts. Moreover, under some circumstances, the installation space required for the fuel injection system is greater, and enough free space in the surroundings of the fuel injection system in the engine must be provided, to enable attaching and detaching the plug elements. An electrical connection beginning at a common electrical terminal for both control valves and extending inside the fuel injection system could also be provided, but once again that would lead to increased production effort and expense, and in terms of its accommodation within the fuel injection system and the requisite sealing off from the fuel, this would be problematic.
The fuel injection system according to the invention, having the characteristics of claim 1, has the advantage over the prior art that the electrical terminals of the two control valves are disposed on a single structural element, so that only at a single point in the fuel injection system is enough free space required for mounting and detaching one or more terminal elements. Because of the integration of the at least one connecting line to the second control valve with the structural element, it is moreover unnecessary to lay electric lines inside the fuel injection system.
Advantageous embodiments and refinements of the fuel injection system of the invention are disclosed in the dependent claims. In the embodiment according to claims 4 and 5, the structural element is jointly used for the construction of the first control valve, so that no further components, or only a few further components, are needed for the purpose. The embodiment of claims 6 and 7 makes it possible to compensate for tolerances and thermal expansions and thus makes a durable, secure contacting of the second control valve possible. The embodiment according to claim 8 makes simple contacting of the second control valve possible.
One exemplary embodiment of the invention is shown in the drawings and described in further detail in the ensuing description.
In
The invention will be described below in terms of use in a unit fuel injector, but it can be adopted to the aforementioned other versions of fuel injection systems as well. The high-pressure fuel pump 10 has a pump piston 20, which is guided tightly in a cylinder bore 16 of a pump body 18 and which defines a pump work chamber 22 in the cylinder bore 16. The pump piston 20 is driven at least indirectly, for instance via a tilt lever, in a reciprocating motion counter to the force of a restoring spring 26 by a cam 24 of a camshaft of the engine. In the intake stroke of the pump piston 20, fuel from a fuel tank 28 is delivered to the pump work chamber 22, for instance by means of a feed pump 29.
The fuel injection valve 12 has a valve body 30, which is connected to the pump body 18 and may be embodied in multiple parts, and in the valve body, in a bore 32, an injection valve member 34 is guided tightly and longitudinally displaceably. Between the valve body 30 and the pump body 18, an intermediate body 36 may be disposed. The valve body 30, in its end region toward the combustion chamber of the cylinder of the engine, has at least one and preferably a plurality of injection openings 38. In its end region toward the combustion chamber, the injection valve member 34 has a sealing face 40, which for instance is approximately conical and which cooperates with a valve seat 41, embodied in the end region of the valve body 30 toward the combustion chamber, from or downstream of which seat the injection openings 32 lead away. In the valve body 30, between the injection valve member 34 and the bore 32 toward the valve seat 41, there is an annular chamber 42, which in its end region, remote from the valve seat 41, changes over by way of a radial widening of the bore 32 into a pressure chamber 44 that surrounds the injection valve member 34. At the level of the pressure chamber 44, by means of a cross-sectional change, the injection valve member 34 has a pressure shoulder 46 oriented toward the valve seat 41. The end of the injection valve member 34 remote from the combustion chamber is engaged by a prestressed closing spring 48, by which the injection valve member 34 is pressed toward the valve seat 41. The closing spring 48 is disposed in a spring chamber 49 which is located in the valve body 30 or the intermediate body 36 and adjoins the bore 32.
The spring chamber 49 is adjoined, on its end remote from the pressure chamber 44, by a bore 50 of smaller diameter. A control piston 51 is tightly guided in the bore 50 and defines a control pressure chamber 52 in the bore 50. The control piston 51 is braced on the injection valve member 34, but it may also be embodied in one piece with the injection valve member 34, and depending on the pressure prevailing in the control pressure chamber 52, it generates a force in the closing direction on the injection valve member 34 that reinforces the closing spring 48. From the pump work chamber 22, a conduit 54 leads through the pump body 18, the intermediate body 36, and the valve body 30 into the pressure chamber 44 of the fuel injection valve 12. From the conduit 54, a communication 55 leads away to the feed pump 29 and to the fuel tank 28. The communication 55 is controlled by a first electrically actuated control valve 56, which is embodied as a 2/2-way valve. The control valve 56 may be embodied as a magnet valve with an electromagnetic actuator and is controlled by an electric control unit 57 and will be described in further detail hereinafter. From the conduit 54, a further conduit 58 leads away into the control pressure chamber 52, and the control pressure chamber 52 has a communication 59 with a relief region, such as a return line to the fuel tank 28. The communication 59 of the control pressure chamber 52 with the relief region is controlled by a second electrically actuated control valve 60, which is likewise triggered by the control unit 57. The second control valve 60 may likewise be embodied as a magnet valve, with an electromagnetic actuator. Alternatively, the first control valve 56 and/or the second control valve 60 may have a piezoelectric actuator. The pressure buildup in the pump work chamber 22 of the high-pressure fuel pump 10 is controlled by the first control valve 56, and the pressure in the control pressure chamber 52, and as a result, regardless of the pressure buildup in the pump work chamber 22, the opening motion of the injection valve member 34 of the fuel injection valve 12 are controlled by the second control valve 60. If because of the pressure prevailing in the control pressure chamber 54 when the second control valve 60 is closed and the closing spring 48 generates a greater force on the injection valve member 34 in the closing direction than the force generated in the opening direction via the pressure shoulder 46 as a result of the pressure prevailing in the pressure chamber 44, then the injection valve member 34 remains in its closing position or is moved into its closing position. If the pressure prevailing in the pressure chamber 44 exerts a greater force on the injection valve member 34, via the pressure shoulder 46, than the closing spring 48 and the pressure prevailing in the control pressure chamber 52 when the second control valve 60 is open, then the injection valve member 34 moves in the opening direction 35 and uncovers the injection openings 38.
The first control valve 56 has a control valve member 62, by which, in cooperation with a valve seat 63, the communication 55 of the pump work chamber 22 with the relief region is opened in a first position and closed in a second position. The control valve member 62 is displaceable between its two positions by the actuator 64, counter to the force of a restoring spring 65. The control valve member 62 is disposed for instance such that it is guided displaceably transversely, preferably perpendicular to the direction of motion of the injection valve member 34, in a bore 19 in the pump body 18. The actuator 64 embodied as an electromagnet is disposed on the outer circumference of the pump body 18. The actuator 64 has a magnet coil 66, a magnet cup 67, and a magnet armature 68, and the magnet armature 68 acts on the control valve member 62.
The second control valve 60 has a control valve member 72, by which, in cooperation with a valve seat 73, the communication 59 of the control pressure chamber 54 with the relief region is opened in a first position and closed in a second position. The control valve member 72 is displaceable between its two positions by the actuator 74, counter to the force of a restoring spring 75. The control valve member 72 is disposed for instance such that it is displaceable approximately parallel to the direction of motion of the injection valve member 34. The actuator 74 embodied as an electromagnet is disposed in the intermediate body 36 or in the valve body 30 and has a magnet coil 76, a magnet cup 77, and a magnet armature 78, and the magnet armature 78 acts on the control valve member 72. For electrical contacting of the magnet coil 76, at least one electrical terminal 79 on the second control valve 60 is provided, which is embodied for instance as part of a plug-in connection. For instance, three electrical terminals 79 are provided, which are embodied as plug prongs. The plug prongs 79 are for instance disposed approximately parallel to the direction of motion of the control valve member 72.
In the pump body 18, a conduit 80 is provided, which is formed by a bore in the pump body 18 and extends transversely, preferably at least approximately perpendicular to the direction of motion of the injection valve member 34, and discharges on one end on the outer circumference of the pump body 18. Two bores 81 discharge into the conduit 80, near its closed end that is located inside the pump body 18. The bores 81 extend at least approximately perpendicular to the conduit 80 and discharge at the face end of the pump body 18 oriented toward the intermediate body 36.
In the region of the actuator 64 of the first control valve 56, a structural element 82 that can be secured to the pump body 18 is provided, on which electrical terminals 83 for the first control valve 56 and electrical terminals 84 for the second control valve 60 are disposed. The electrical terminals 83, 84 are preferably embodied as plug prongs with which corresponding plug bushes can be joined that are disposed in a plug or in separate plugs disposed in turn on the electric lines leading to the control unit 57. Preferably, only a single plug is provided, with which all the plug terminals 83, 84 are contacted.
At least one electric connecting line 85 leading from the terminals 84 to the second control valve 60 is integrated with the structural element 82. The structural element 82 has a central region 86, secured to the pump body 18, and a finger 87, which protrudes from the central region into the conduit 80 and in which the connecting lines 85 extend. The connecting lines 85 are embodied for instance as conductor tracks or contact tracks. The structural element 82 is preferably of plastic and is produced by injection molding, and the connecting lines 85 are spray-coated with the plastic material. The finger 87 of the structural element 82 is preferably embodied as elastically deformable in at least a portion of its longitudinal extent. Elastic deformability of the finger 87 can be attained for instance by means of a spring-bellows-like portion 88. In the portion 88, the finger 87 is elastically deformable in both the longitudinal direction and the transverse direction. The end region, protruding into the conduit 80, of the finger 87 is embodied cylindrically, and disposed in this end region are electric terminal elements 89, which are open toward the outerjacket of the finger 87 and are preferably embodied as plug bushes. The finger 87 of the structural element 82 can be thrust into the conduit until it contacts a defined stop, and in the end position of the finger 87, the plug bushes 89 are aligned with the bores 81. When the pump body 18 is joined to the intermediate body 36 in the direction of the longitudinal axis 17 of the cylinder bore 16, the plug prongs 79 of the second control valve 60 pass through the bores 81 and enter the plug bushes 89 of the finger 87 of the structural element 82, so that the actuator of the second control valve 60 is electrically contacted with the connecting lines 85. Instead of an elastic deformability of the finger 87 of the structural element 82, it may be provided that the plug prongs 79 of the second control valve 60 and/or the plug bushes 89 of the structural element 82 are elastically deformable, to enable compensating for production tolerances and/or thermal expansions.
The central region 86 of the structural element 82 can be secured to the pump body 18 by means of one or more screws 90, for instance. A plug housing 91 is integrally formed onto the central region 86 of the structural element 82, and the plug prongs 83, 84 are disposed in this housing and with it one or more plugs can be put together with the electric lines that lead to the control unit 27. At least one component of the first control valve 56 is preferably disposed in the central region 86 of the structural element 82. The magnet cup 67 and/or the magnet coil 66 is preferably disposed in the central region 86. By means of the structural element 82, not only is the joint electrical contacting of the two control valves 56, 60 made possible, but also the first control valve 56 is in part formed by it, so that for the first control valve, only a few further individual components are needed, essentially only the magnet armature 68. The magnet cup 67 and/or the magnet coil 66 can be integrated with the structural element 82 in the production of the structural element 82 in an injection mold, or can be joined to the structural element 82 after the production of the structural element 82, for instance by means of press-fitted connections or in some other way. The magnet coil 66 is connected to the plug terminals 83 via connecting elements extending inside the structural element 82.
Upon securing of the structural element 82 to the pump housing 18, the magnet coil 66 and/or the magnet cup 67 disposed on the housing is introduced into a corresponding receptacle on the pump housing 18 that is embodied for instance as a bore 92. Moreover, the finger 87 of the structural element 82 is introduced in the process into the conduit 80, and the bore 92 and the conduit 80 extend at least approximately parallel to one another. In the end position of the structural element 82, its central region 86 comes to rest on the pump housing 18, and its finger 87 comes into contact with its stop, and the bores 81 are aligned with the plug bushes 89 in the finger 87. Because of the elastically deformable portion 88 of the finger 87, compensation for production tolerances is made possible, as is compensation for various thermal expansions. By means of the finger 87, the conduit 80 is sealed off, and at least one elastic sealing ring 96 may additionally be provided between the finger 87 and the conduit 80.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102004061799.6 | Dec 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/56149 | 11/22/2005 | WO | 00 | 6/8/2007 |
