The invention is based on a fuel injection apparatus for an internal combustion engine as generically defined by the preamble to claim 1.
A fuel injection apparatus of this kind is known from the literature, for example from Diesel Motor Management, Verlag Vieweg, 2nd edition, 1998, p. 246. This fuel injection apparatus has a solenoid valve for controlling the fuel injection. The solenoid valve is inserted into a housing part and has a solenoid assembly with a magnetic coil and a magnet armature. The housing part has a cover piece attached to it that holds the solenoid assembly of the solenoid valve in the housing part. With the insertion of the solenoid assembly into the housing part, the problem arises that the solenoid assembly is only fixed in place when the cover piece is attached to the housing part so that before attachment of the cover piece, the solenoid assembly can fall back out of the housing part. In order to avoid unnecessary assembly steps, the cover piece should preferably be attached to the housing part only after the function of the solenoid assembly has been tested, but there is the danger that the solenoid assembly will fall out during the function testing. Furthermore, in this known fuel injection apparatus, it is not possible to compensate for different lengths of the solenoid assembly so that in some cases, it is not fixed securely in the housing part.
The fuel injection apparatus according to the invention, with the characterizing features of claim 1, has the advantage over the prior art that the solenoid assembly is fixed in the housing part before the attachment of the cover piece. In addition, the spring element makes it possible to compensate for the length of the solenoid assembly and therefore permits it to be securely fixed. The embodiment of the at least one securing element so that it is of one piece with the spring element means that only one additional component is required.
Advantageous embodiments and modifications of the fuel injection apparatus according to the invention are disclosed in the dependent claims. With the embodiment of the spring element in the form of a disc spring according to claim 2, it requires only a small amount of space. The embodiment according to claim 3 and 4 permits a secure fixing of the spring element and therefore also of the solenoid assembly.
Several exemplary embodiments of the invention are shown in the drawings and will be explained in detail in the subsequent description.
The invention will be explained below in conjunction with its use in a unit injector, but it can also be transferred to the above-mentioned other embodiments of fuel injection apparatuses. The high-pressure fuel pump 10 has a pump piston 20, which is guided in a sealed fashion in a cylinder bore 16 of a pump body 18 and defines a pump working chamber 22 in the cylinder bore 16. A cam 24 of a camshaft of the engine sets the pump piston 20 into a stroke motion at least indirectly, for example via a rocker, counter to the force of a return spring 26. A fuel-supply pump 29, for example, supplies fuel from a fuel tank 28 to the pump working chamber 22 during the intake stroke of the pump piston 20.
The fuel injection valve 12 has a valve body 30, which is connected to the pump body 18, can be composed of a number of parts, and contains a bore 32 in which an injection valve element 34 is guided so that it can slide longitudinally in a sealed fashion. An intermediate body 36 is disposed between the valve body 30 and the pump body 18. In its end region oriented toward the combustion chamber of the engine cylinder, the valve body 30 has at least one, preferably several injection openings 38. The injection valve element 34, in its end region oriented toward the combustion chamber, has a for example conical sealing surface 42 that cooperates with a valve seat 41 embodied in the end region of the valve body 30 oriented toward the combustion chamber; the injection openings 32 branch off from this valve seat 41 or branch off downstream of it. Between the injection valve element 34 and the bore 32 leading to the valve seat 41, the valve body 30 contains an annular chamber 42, whose end region oriented away from the valve seat 41, by means of a radial expansion of the bore 32, transitions into a pressure chamber 44 encompassing the injection valve element 34. At the same level as a pressure chamber 44, the injection valve element 34 has a pressure shoulder 46, which is oriented toward the valve seat 41 and is formed by a cross-sectional change. A prestressed closing spring 48 engages the end of the injection valve element 34 oriented away from the combustion chamber and pushes the injection valve element 34 toward the valve seat 41. The closing spring 48 is disposed in a spring chamber 49 that is contained in the valve body 30 or in the intermediate body 36 and adjoins the bore 30.
The end of the spring chamber 49 oriented away from the pressure chamber 44 adjoins a bore 50 with a smaller diameter. A control piston 51 is guided in a sealed fashion in the bore 50 and delimits a control pressure chamber 52 in the bore 50. The control piston 51 rests against the injection valve element 34 and, depending on the pressure prevailing in the control pressure chamber 52, generates a force in the closing direction on the injection valve element 34 that boosts the action of the closing spring 48. From the pump working chamber 22, a conduit 54 leads through the pump body 16, 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 connection 55 leads to the fuel-supply pump 29 and to the fuel tank 28. A first solenoid valve 56 embodied as a 2/2-way valve controls the connection 55. An electronic control unit 57 that will be described in more detail below triggers the solenoid valve 56. Another conduit 58 leads from the conduit 54 into the control pressure chamber 52 and the control pressure chamber 52 has a connection 59 to a discharge region, for example a return into the fuel tank 28. The control unit 57 also triggers a second solenoid valve 60 that controls the connection 59 of the control pressure chamber 52 to the discharge region. The first solenoid valve 56 controls the pressure buildup in the pump working chamber 22 of the high-pressure fuel pump 10 and the second solenoid valve 60 controls the pressure in the control pressure chamber 52 and therefore controls the opening of the fuel injection valve 12. The second solenoid valve 60 and the control pressure chamber 52 can also be omitted, in which case the closing spring 48 alone determines the opening of the fuel injection valve 12. If the pressure prevailing in the pressure chamber 44 and acting on the pressure shoulder 46 exerts a greater force on the injection valve element 34 than the closing spring 48 and the pressure prevailing in the control pressure chamber 52, then the injection valve element 34 moves in the opening direction 35 and unblocks the injection openings 38.
In a first exemplary embodiment shown in FIGS. 2 to 4, the solenoid assemblies 62 of the two solenoid valves 56, 60 are each secured in the recesses 61 by a respective spring element 70. A spring element 70 embodied in the form of a round disc spring is provided for each solenoid assembly 62 and, via the respective pressure piece 65, clamps the solenoid assembly 62 in the recess 61 in an axial direction, i.e. in the direction of the longitudinal axis of the recess 61 and of the solenoid assembly 62. The two spring elements 70 here are embodied as being of one piece with each other and are connected to each other via a bridge piece 71 shown in
When the spring elements 70 are inserted into the recesses 61, the hook 72 encompasses the pin 74 or is press-fitted onto the pin 74 and the lugs 75 embrace the pin 76, thus producing a clamped connection between the spring elements 70 and the pins 74, 76 so that the spring elements can no longer fall out of the intermediate body 36. The spring elements 70 consequently fix the solenoid assemblies 62 of the solenoid valves 56, 60 in the intermediate body 36 so that they cannot fall out. It is therefore possible to test the function of the solenoid assemblies 62 of the solenoid valves 56, 60 inserted into the recesses 61 of the intermediate body 36, without the danger of the solenoid assemblies 62 falling out. The spring elements 70 also prevent the solenoid assemblies 62 inserted into the intermediate body 36 from falling out during subsequent transport before final assembly of the fuel injection apparatus. During subsequent assembly of the fuel injection apparatus, the pump body 16 and the valve body 30 are fitted together with the intermediate body 36; the pump body 16 constitutes a cover piece that axially compresses the spring elements 70 and by means of them, clamps the solenoid assemblies 62 into the recesses 61 of the intermediate body 36, consequently fixing them without play.
Number | Date | Country | Kind |
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103 04 742.5 | Feb 2003 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE03/03415 | 10/14/2003 | WO | 8/5/2005 |