Title of Invention	HIGH-PRESSURE PIPELINE FOR A FUEL INJECTION SYSTEM
Abstract	A high-pressure pipeline is proposed between an injector 1 and a common-rail 114 that completely or partially removes pressure waves that arise as a result of operating the injector 1.

Full Text

Hiah-pressure Pipeline for a Fuel Injection System Prior Art The invention is with regard to a high-pressure pipeline for a fuel injection system of an internal combustion engine. A fuel injection system 102 according to prior art of an internal combustion engine is explained below by means of Figure 8. Reference signs used thereby are also used in the description of the high-pressure pipeline in accordance with the invention. The fuel injection system 102 illustrated in Figure 8 comprises of a fuel tank 104 from which fuel 106 is discharged through an electric or mechanical fuel pump 108. Fuel 106 is fed to a high-pressure fuel pump 111 through a low-pressure fuel pipeline 110. Fuel 106 reaches a common-rail 114 via a high-pressure fuel pipeline 112 from the high-pressure fuel pump 111. Several injectors 1, which inject fuel 106 directly into the combustion chamber 118 of an internal combustion engine that is not illustrated here, are connected to the common-rail 114. The hydraulic connection between common-rail 114 and the injectors 1 takes place per high-pressure pipeline 3. The injector 1 pertaining to the combustion chamber 118 is opened at the start of injection of fuel into the combustion chamber 118. Hence, fuel 106 that is under high pressure, streams from the injector 1 into the combustion chamber 118. Consequently, leaked fuel quantities stream from common-rail 114 towards the injector 1. Since modern injectors 1, particularly piezo-controlled injectors, open and close rapidly, a pressure wave is generated in the high-pressure pipeline 3 when the injectors 1 are operated, that starts from the injector 1 and runs to the common- rail 114. The pressure wave is reflected there and reaches the injector 1 again. The faster the injector 1 opens, the steeper are the flanks of the pressure wave. The steepness of the pressure wave's flanks will hereinafter be designated as gradient dp/dt. Thus, immediately after beginning the injection in the high-pressure pipeline 3 and in the injector 1, the amplitude of the previously described pressure wave is superimposed on the static common-rail pressure. As a result of this, the pressure in injector 1 is not constant and is instead subject to considerable temporal fluctuations. This applies particularly not only during the injection itself but also to the period of time associated with an injection. Since the fuel quantity injected into the combustion chamber 118 is now, among other things, dependent on the pressure prevailing during injection in injector 1, the pressure wave mentioned above has an undesired influence on the injection quantities. This then applies when the injection duration is longer than the transit time of the pressure wave through the high-pressure pipeline, but particularly if a pressure wave that is released through a pre-injection and is reflected at the common-rail 114 takes effect during a subsequent main injection in injector 1. This, thus, also clearly indicates that the quantities that are injected during a main injection depend, to a great degree, on the interval between them and the preceding main injection. Established designs from prior art for the removal of pressure waves in a fuel injection system 102 are described below: A choke (not illustrated) is incorporated in the high-pressure pipeline 3 that does indeed attenuate the pressure wells but, however, also reduces available injection pressure at injector 1, which is undesirable. In addition, a check valve (not illustrated) can be provided parallel to the choke (not illustrated) that opens in the direction of the injector 1. Choke losses can of course be avoided in this case, however the choke is thereby ineffective for as long as fuel streams from common-rail 114 to the injector 1. This means that this design is ineffective during an injection. Further, this type of design that has a check valve per injector is very cost-intensive. DE 100 60 811 A1 has established a design in which an attenuation chamber is provided in injector 1 that is hydraulically connected to the high-pressure pipeline 3 through a choke. The effect of these measures established in prior art for the reduction of compression vibration in the high-pressure pipeline are still in need of improvement, particularly because the problem mentioned above accelerates in the case of increasing injection pressures and injectors that have an ever faster response. Advantages of the Invention The first design of a high-pressure pipeline in accordance with the invention provides for the high-pressure pipeline comprising of a first and second section and that the first section and the second section are connected in parallel. A particularly advantageous design of the invention is characterised by the fact that the first section exhibits an open end and that the second section exhibits a closed end. In accordance with the invention the open end of the first section is connected to the common-rail and the first section and the second section of the high-pressure pipeline merge in the region of contact at the injector. The following effects can be taken advantage of in this set-up: In the case of reflection of a pressure wave at the open end here in the first section of the high-pressure pipeline, at the point where the high-pressure pipeline ends in the common-rail, not just a reflection of a pressure wave takes place but a reversal of the amplitude sign also takes place simultaneously. This means that a pressure increase of the same value results from a reduction of pressure after reflection. In the case of reflection of a pressure wave at a closed end, only the direction in which the pressure wave moves changes but not the amplitude sign. If the first section with its open end and the second section with its closed end are now essentially of the same length, two pressure waves meet in succession at that point where the first section and second section merge, which has the same amplitude whereby the amplitude sign of one pressure wave is positive and of the other negative. The pressure waves are thereby extinguished so that no pressure waves continue to exist behind the merging point of the first section and the section point when seen in the flow direction. In fact, a constant pressure prevails in the injector and therewith constant initial conditions too, for example, for a main injection following an injection and indeed independent of the interval between one another. In another design of the fuel high-pressure pipeline in accordance with the invention, the first section and the second section are hydraulically connected through a choke. This results in a large part of the amplitude of the reflected pressure wave being extinguished even before reaching the merging point, namely the point where a hydraulic connection exists between the first section and the second section through a choke, so that even at the merging point, only very small residual pressure waves come out of the pipeline sections. In another design of the fuel high-pressure pipeline in accordance with the invention, a choke is incorporated in section 2 of the pipeline. This causes a part of the pressure wave to disintegrate in spite of which a sufficient quantity of fuel without any pressure loss worthy of mention, flows from common-rail to the injector through the first section of the high pressure pipeline. The effect of this high-pressure pipeline in accordance with the invention can be improved further by providing a check valve in the second section connected in line with the choke. What is thereby accomplished is that negative pressure waves released by an injection are reflected as before at the closed end, but that the valve however opens in the case of possible incoming excess pressure waves, dismantling the waves through the choke in the rail so that no or almost no reflection occurs. An alternative provision is for the high-pressure pipeline to exhibit a third section and that the first section as well as the second section meets in the third section which stretches between the merging point and the injector. This design ensures that the high-pressure pipeline in accordance with the invention can be connected, without any constructive modification, to common rails and injectors that are already being mass produced. It is of advantage in the case of many designs and applications of the high-pressure pipeline in accordance with the invention, if the length Li of the first section and length L2 of the second section are essentially equal. Similarly, it is of advantage in several application cases, if the hydraulic diameter Di of the first section and the hydraulic diameter D2 of the second section are essentially equal. Lastly, it is also an advantage if the sum of the square of the hydraulic diameter Di of the first section and of the hydraulic diameter D2 of the second section is as large as the square of the hydraulic diameter D3 of the third section. These relations are, however, not a mandatory pre-requisite for the high- pressure pipeline in accordance with the invention. There is a multiplicity of application areas where it would make sense to deviate from these relations. Thus, it can, for example, be required that the reflected pressure wells from Sections 1 and 2 get to the merging point with a specific, temporal offset. In almost the same manner it could, for example, also be undesirable that the diameter Di, D2 and D3 of the service sections be equal. The disadvantage of prior art could also be improved upon by using a one-piece high-pressure pipeline whose one end exhibits an expanded diameter. Through this method, the pressure at the common-rail is not completely reflected at one place but the pressure wave is instead already partially broken up and reflected in the region where the diameter increases in the high-pressure pipeline. As a result of this, the flanks of the reflected pressure wave get flatter which means that the gradient dp/dt increases sharply. Therewith the compression vibration in the region of the nozzle valve seat in the injector minimises, which, for one, markedly reduces the impact of the interval between two injections on the second injection besides resulting in a considerable reduction in wear and tear on the nozzle seat. The expanded diameter of the high-pressure pipeline can be designed either in a conical shape or be tiered. High-pressure pipelines can also be executed from this design in accordance with the invention for which a special connecting piece having an expanded diameter, particularly with a tapered shape or conical diameter expansion, can be fixed at the common-rail. Instead of the conical shape, the diameter can also increase over the length in a non-linear manner which in turn leads to a tapered inner shape that is contorted. As already mentioned the previously described constructive characteristics of the high-pressure pipeline in accordance with the invention can be combined with one another in order to optimise the operating performance of a specific fuel injection system through appropriate selection and dimensioning of the high- pressure pipeline in accordance with the invention. Other advantages and beneficial designs of the invention can be gathered from the subsequent drawings, their description as well as the patent claims. Drawing Figure 1 illustrates a high-pressure pipeline according to prior art. Figures 2-7 are exemplary embodiments of a high-pressure pipeline in accordance with the invention and Figure 8 is a schematic illustration of a fuel injection system. Description of the Exemplary Embodiment Using Figure 1 which illustrates an established high-pressure pipeline 3 from prior art that hydraulically connects a common-rail 114 with an injector 1, the pressure wave that has already been mentioned several times as well as its temporal and local progression in the high-pressure pipeline 3 will be explained in greater detail. An x-p diagram is presented to the left of the high-pressure pipeline 3 for this purpose, whose zero-point lies at the connection between the injector 1 and the high-pressure pipeline 3. The "Y" axis of the diagram that is labelled "p" denotes pressure p (x) in the high-pressure pipeline 3. The high-pressure pipeline 3 has a length L, which means that a pressure wave starting from the injector 1 reaches the common-rail 114 when the location coordinate is x = L and is reflected there. To the left of the high-pressure pipeline 3 is an x-p diagram which illustrates the pressure progression in the high-pressure pipeline 3 when the pressure wave proceeds from the injector 1 in the direction of the common-rail 114. The diagram to the left of the high-pressure pipeline 3 displays a snap-reading method at a particular point in time in which the maximum 5 of the pressure wave takes place between the injector 1 and common-rail 114. The running direction of the pressure wave is indicated by an arrow 7. When observing the p-x diagram illustrated to the left of the high-pressure pipeline 3, it is evident that the pressure wave has the shape of a pressure drop when compared to the static pressure in the high-pressure pipeline 3. This is also immediately obvious when one visualises that through the act of opening the injector 1, particularly opening the same in sudden bursts, fuel gets injected from the injector 1 into the combustion chamber 118 (refer Figure 8) so that a pressure build-up takes place in the injector 1. A pressure wave with negative amplitude (pressure drop) emerges as a result of this, starting from the injector 1 and moving through the high-pressure pipeline 3 in the direction of the common-rail 114. The amplitude of the pressure wave is indicated with "A" in Figure 1. When the pressure wave now reaches the common-rail 114, the common-rail 114 functions as an open end with static pressure, with regard to the pressure wave. The pressure wave is reflected at this open end which means that it changes its running direction and runs henceforth from the common-rail 114 in the direction of the injector 1. At the same time, the sign of the amplitude changes however so that a pressure increase results from a pressure drop which is denoted by the p-x diagram to the right of the high-pressure pipeline 3. The direction of arrow 7 has reversed when compared to the illustration on the left side of the high-pressure pipeline 3. Also, a pressure increase has emerged from the pressure drop as a comparison of pressure waves in the p-x diagrams to the left and right of the high-pressure pipeline 3 shows. When the reflected pressure wave now reaches the injector 1, the pressure in the injector 1 is exposed to considerable fluctuation. Starting from a static pressure Pstat that is marked in the px-diagrams, the pressure in the injector increases at amplitude A. If injection occurs just at that point in time when the pressure wave reaches the injector 1 and the pressure in the injector is therewith temporally subject to strong fluctuations, the same has a direct impact on the injected fuel quantities. As a result of this, the measuring precision of the injector 1 deteriorates and therewith the emission behaviour of the internal combustion engine. The running performance of the internal combustion engine can, likewise, suffer. If, in contrast, the injector 1 is closed at that point in time when the reflected pressure wave reaches it, it then presents its closed end to the pressure wave and the wave, this time while retaining its amplitude, gets reflected again in the direction of the rail. Now a very weak, muted wave finally forms in the pipeline, the pressure in the injector vacillates for a long time after an injection and a considerable impact of the interval between two injections is produced on the second injection. A gradient dp/dt is qualitatively illustrated in the p-x diagram to the left of the high-pressure pipeline 3. This illustration is not completely correct since a temporal progression of pressure "p* is not illustratable; however, due to the constant velocity of propagation of the pressure wave in the high-pressure pipeline 3, there is a direct correlation between the steepness of the flank of the pressure wave as is illustrated in the p-x diagram in accordance with Figure 1 and as is defined in connection with the invention, viz., as a temporal modification of the fuel pressure in the high-pressure pipeline 3, indicated here as gradient dp/dt. Figure 2 presents a first exemplary embodiment of a high-pressure pipeline 3 in accordance with the invention in which the high-pressure pipeline 3 is designed with two parts. It exhibits a first section 3.1 and a second section 3.2 where the first section 3.1 connects the common rail 114 to the injector 1 and has length Li and a hydraulic diameter D^ The second section 3.2 has length L2 and a hydraulic diameter D2. The first section 3.1 and the second section 3.2 meet and merge with one another at that point where they are connected to the injector 1. In contrast to the first section 3.1, the second section 3.2 exhibits a closed end 9. The hydraulic diameters Di and D2 could essentially be equal. In the same manner, it could be an advantage in many applications if the lengths Li and L2 are basically equal. The invention is, however, limited to this dimensioning. A pressure wave occurs if the injector 1 is opened now, as already explained in detail with the help of Figure 1, in the form of a pressure drop that runs through the first section 3.1 as well as through the second section 3.2 of the high- pressure pipeline 3. As already explained using Figure 1, the pressure wave at the open end of the first section 3.1 namely at that point where it ends at the common-rail 114, reflects and thereby changes its sign. This means that a pressure drop changes into a pressure increase. The reflection of the pressure wave at the closed end 9 of the second section 3.2 behaves differently. There the pressure wave changes its running direction only but not the sign of its amplitude. The pressure wave reflected from the closed end 9 of the second section 3.2 continues to be a pressure drop. When the reflected pressure wave of the first section that is henceforth a pressure increase and the reflected pressure wave of the second section 3.2 that continues to be a pressure drop, meet one another at that point where they flow into the injector 1, the reflected pressure waves of the first section 3.1 and of the second section 3.2 get extinguished so that pressure 'p" in the injector remains temporally constant. This means that the pressure wave that emerges in accordance with natural law as a result of opening the injector 1 does not any longer have any negative impact whatsoever on the injected fuel quantities. Figure 3 illustrates another exemplary embodiment of a high-pressure pipeline 1 in accordance with the invention. The essential difference with regard to the exemplary embodiment according to Figure 2 is that a third section 3.3 of the high-pressure pipeline is present between the injector 1 and the first section 3.1 as well as the second section 3.2. The third section 3.3 has a hydraulic diameter D3 and length L3. It can be an advantage if the sum of the squares D12 + D22 of the hydraulic diameter D1 and D2 is equal to the square D32 of the hydraulic diameter D3 of the third section 3.3. The sequence in the first section 3.1 and in the second section 3.2 in this exemplary embodiment correspond to sequences that have already been described with regard to the exemplary embodiment according to Figure 2. The mode of functioning of the second section 3.2 with its closed end 9 is to be clarified once again using this second exemplary embodiment. The p-x diagrams to the right and left of the high-pressure pipeline that are marked with I, show the pressure wave moving from the injector 1 to the common-rail 114 and to the closed end 9 respectively. The p-x diagram to the left of the high-pressure pipeline 3 that is marked with II, shows the reflected pressure wave moving from the common-rail 114 through the first section 3.1 to the injector 1. As already explained in the description of Figure 1, the pressure wave undergoes a sign reversal during reflection at the common-rail 114 so that a pressure increase emerges from a pressure drop. As can be seen from a comparison of the p-x diagrams I and II located to the right of the second section 3.2, no reversal of the amplitude sign takes place during the reflection of the pressure wave at the closed end 9. This means that the pressure drop is only reflected at the closed end 9, which also means that it changes its running direction but not, however, its sign. If the pressure waves according to the p-x diagrams in which they are marked with II in Figure 3, now meet one another at that point where the first section 3.1 and the second section 3.2 flow in to the third section 3.3, the pressure waves get completely extinguished due their various signs so that no pressure wave continues to exist in the third section 3.3 as well as in injector 1. The exemplary embodiment according to Figure 4 corresponds to a large extent to the exemplary embodiment shown in Figure 3, whereby only one choke 11 is provided in the second section 3.2. The injector 1 that is connected to the third section 3.3 is not illustrated in Figures 4, 5, 6 and 7 due to lack of space. The choke 11 causes the pressure wave in the second section 3.2 to get muted so that complete extinguishing of the pressure wave at the branching off from the first section 3.1 and the second section 3.2 does not take place any more. While this seems to be a disadvantage when compared to the exemplary embodiment according to Figure 3, the same can, however, be an advantage in the case of certain exemplary embodiments, particularly when one considers that modern fuel injection systems operate on multiple injection and that such multiple injections are carried out over a very large speed range of the internal combustion engine. Depending on the revolutions per minute of the internal combustion engine, the temporal interval between multiple injections also varies greatly due to the wide speed range of the internal combustion engine. In some cases, as a result of the choke's 11 location in the second section 3.2 in accordance with the invention, the operating performance of the internal combustion engine across the entire speed range and under all load conditions can be improved overall even in cases where complete extinguishing of pressure waves could not possibly be achieved at certain load points and speeds. In the exemplary embodiment according to Figure 5, the choke 11 is not incorporated in section 2 of the pipeline 8 but in fact connects the first section 3.1 and the second section 3.2 to one another. Since the pressure waves that move away in sections 1 and 2 of the pipeline 3 have the same sign, the choke does not exert any impact on these waves - no pressure difference develops at the choke. Waves that are reflected at the rail and at the closed end of section 2 respectively, however, have different signs. When they reach the choke 11, it amounts to a pressure equalisation between sections 1 and 2 as a result of which the reflected waves run towards the merging point in a markedly weakened form but with signs that continue to be opposite to one another. In the exemplary embodiment according to Figure 6, the second section 3.2 too presents a hydraulic connection between the third section 3.3 and the common- rail 114, whereby a choke 11 and a check valve 13 are, however, located in the second section 3.2. The check valve 13 allows the return flow of fuel from the second section 3.2 to the common-rail 114. The check valve 13 functions as a lock in the other direction and remains closed in the case of incoming pressure waves with negative signs, thus continuing to present a closed end to the same with an unaltered function. If, on the other hand, a pressure wave with a positive sign comes in at the check valve, the same opens and the pressure wave interprets the choke 11 to be the termination of the pipeline against which it is either very weakly reflected or not reflected at all. The high-pressure pipeline 3 in the exemplary embodiment according to Figure 7 is again designed as a single piece and exhibits a region 3.4 that has an expanded diameter. In the exemplary embodiment illustrated in Figure 7, this region 3.4 with the expanded diameter is designed as a cone, whereby the end with the larger diameter leads to the common-rail 114. The invention is, however, not limited to conical expansions in diameter but can also be step- shaped or smooth but cannot have linear expansions in diameter. An important effect of this region 3.4 with the expanded diameter is that the incoming pressure waves do not get reflected abruptly at the end of the pipeline but are partially reflected over the entire region 3.4 that has the expanded diameter. The rest of the pressure wave that reaches the common-rail 114 gets reflected there in the manner previously described and changes its sign. This partial reflection of the pressure wave in the region 3.4 with the expanded diameter results in an immediate "smoothening out" of the pressure wave which expresses itself in an amplitude drop of the reflected wave (refer p-x diagrams at the far left in Figure 7) and, particularly, in an essentially flatter flank dp/dt of the reflected pressure wave. The outcome is that the pressure fluctuations within the injector 7 are thus smaller due to the reflected pressure wave and stretches over a longer period. The result is thus that the impact of the interval between two injections on the second injection is markedly reduced and thus increases the precision of measurement of injection quantities. Claims 1. High-pressure pipeline (3) for a fuel injection system for an internal combustion engine, characterised in that the high-pressure pipeline (3) comprises of a first section (3.1) and a second section (3.2) and that the first section (3.1) and the second section (3.2) are connected in parallel. 2. High-pressure pipeline according to Claim 1, characterised in that a choke (11) is provided in the second section (3.2). 3. High-pressure pipeline according to the preceding Claim 2, characterised in that check valve (13) connected in line with the choke (11) is provided in the second section (3.2). 4. High-pressure pipeline according to Claim 3, characterised in that the check valve (13) is fixed with the choke (11) at the end of the second section (3.2) and that the check valve allows fuel to flow out from the second section (3.2). 5. High-pressure pipeline according to one of the preceding claims, characterised in that the first section (3.1) displays an open end and that the second section (3.2) displays a closed end (9). 6. High-pressure pipeline according to one of the preceding claims, characterised in that the first section (3.1) is hydraulically connected to the second section (3.2) by the choke (11). 7. High-pressure pipeline according to one of the preceding claims, characterised in that the high-pressure pipeline (3) has a third section (3.3) and that the first section (3.1) as well as the second section (3.2) end in the third section (3.3). 8. High-pressure pipeline according to one of the preceding claims, characterised in that the length (Li) of the first section (3.1) and the length (l_2) of the second section are essentially equal. 9. High-pressure pipeline according to one of the preceding claims, characterised in that a hydraulic diameter (D-i) of the first section (3.1) and the hydraulic diameter (D2) of the second section (3.2) are essentially equal. 10. High-pressure pipeline according to one of the preceding claims, characterised in that the sums of the hydraulic diameter (D1) of the first section (3.1) and of the hydraulic diameter (D2) of the second section (3.2) are essentially equal to the hydraulic diameter (D3) of the third section (3.3). 11. High-pressure pipeline (3) according to one of the preceding claims, characterised in that one end of the first section (3.1) of the high- pressure pipeline (3) has an expanded diameter (3.4). 12. High-pressure pipeline according to one of the preceding claims, characterised in that the shape of the expanded diameter (3.4) is developed according to one of Claims 14 to 16. 13. High-pressure pipeline (3) for a fuel injection system of an internal combustion engine, characterised in that one end of the high-pressure pipeline (3) exhibits an expanded diameter (3.4). 14. High-pressure pipeline according to Claim 14, characterised in that the diameter of the high-pressure pipeline (3) increases continuously in the region of the expanded diameter (3.4). 15. High-pressure pipeline according to Claim 15, characterised in that the expanded diameter (3.4) is designed with a conical shape. 16. High-pressure pipeline according to Claim 15, characterised in that the diameter of the high-pressure pipeline (3) increases in a cascaded manner in the region of the diameter expansion (3.4). 17. High-pressure pipeline according to one of the preceding claims, characterised in that the high-pressure pipeline (3, 3.1, 3.3) connects a common-rail (114) to an injector (1). 18. High-pressure pipeline according to Claims 18 and 3 or 4, characterised in that the section (3.2) with the check valve (13) and the choke (11) are also connected to the common-rail (114). 19. Fuel injection system (102) for an internal combustion engine with a common-rail (114) and an injector (1) per cylinder of the internal combustion engine and with high-pressure pipeline (3) that is hydraulically connected to a common-rail (114) and an injector (1), characterised in that the high-pressure pipeline (3) is a high-pressure pipeline (3) according to one of the preceding claims. 20. High-Pressure pipeline for a fuel injection system, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

3048-CHENP-2004 AMENDED CLAIMS 27-08-2012.pdf

3048-CHENP-2004 AMENDED PAGES OF SPECIFICATION 27-08-2012.pdf

3048-CHENP-2004 CORRESPONDENCE OTHERS 10-01-2012.pdf

3048-CHENP-2004 EXAMINATION REPORT REPLY RECEIVED 27-08-2012.pdf

3048-CHENP-2004 FORM-1 27-08-2012.pdf

3048-CHENP-2004 FORM-3 27-08-2012.pdf

3048-CHENP-2004 FORM-5 27-08-2012.pdf

3048-CHENP-2004 POWER OF ATTORNEY 27-08-2012.pdf

3048-chenp-2004 abstract.pdf

3048-chenp-2004 claims.pdf

3048-CHENP-2004 CORRESPONDENCE OTHERS 24-02-2012.pdf

3048-chenp-2004 correspondence others.pdf

3048-chenp-2004 correspondence po.pdf

3048-chenp-2004 description (complete).pdf

3048-chenp-2004 drawings.pdf

3048-chenp-2004 form-1.pdf

3048-chenp-2004 form-18.pdf

3048-chenp-2004 form-3.pdf

3048-chenp-2004 form-5.pdf

3048-CHENP-2004 OTHER PATENT DOCUMENT 27-08-2012.pdf