Title of Invention	FUEL-INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE
Abstract	Abstract FUEL INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE A fuel injection device (18) for an internal combustion engine comprises a housing (22) and a valve element (32) which is arranged in the housing (22). Said valve element (32) interacts, in the region of a fuel outlet opening (42), with a valve seat. It is proposed that at least one first part (34) and one second part (36) of the valve element (32) are coupled to one another by means of a hydraulic coupler (92) which has a coupling space (94) which is delimited at least in regions by means of a sleeve (88) which is guided on the first part (34), and that said sleeve comprises a guide element (70) which guides a coupler-side end region of the first part (34) of the valve element (32).

Title of Invention

FUEL-INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE

Abstract

Abstract FUEL INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE A fuel injection device (18) for an internal combustion engine comprises a housing (22) and a valve element (32) which is arranged in the housing (22). Said valve element (32) interacts, in the region of a fuel outlet opening (42), with a valve seat. It is proposed that at least one first part (34) and one second part (36) of the valve element (32) are coupled to one another by means of a hydraulic coupler (92) which has a coupling space (94) which is delimited at least in regions by means of a sleeve (88) which is guided on the first part (34), and that said sleeve comprises a guide element (70) which guides a coupler-side end region of the first part (34) of the valve element (32).

Full Text	TITLE FUEL-INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE DESCRIPTION The invention is with regard to a fuel-injection device for an internal combustion according to the preamble of Claim 1. A fuel-injection device with which fuel can be injected directly into a combustion chamber of the internal combustion engine allocated to it, is established in the market. A valve element is located in a casing for this purpose, said valve element exhibiting a pressure surface in the region of a fuel discharge outlet that, on the whole, acts in the opening direction of the valve element. A control surface which acts in a closing direction and which is located at the opposite end of the valve element is present, said control surface bordering a buncher space. The control surface that acts in the closing direction is, on the whole, larger than the pressure surface acting in the opening direction when the valve element is open. A higher fuel pressure is present in the region of the pressure surface acting in the opening direction and in the region of the control surface acting in the closing direction when the fuel-injection device is closed than would be present were it to be made available by a fuel collecting pipe (rail), for example. In order to open the valve element, pressure present at the control surface is dropped till the resulting hydraulic force acting in the opening direction exceeds force acting in the closing direction at the pressure surface. The valve element is opened in this manner. A pre-requisite for the functioning of this fuel-injection device is the sealing between that region in which the comparably small pressure surface acting in the opening direction is present and that region of the valve element in which the comparably larger control surface acting in the closing direction is present. Leakage fluid is, in the case of the established fuel-injection device, diverted from the region of the sealing via a leakage pipe. The objective of the present invention is to further develop a fuel-injection device of the type mentioned initially, so that it can be built as simply and cost-effectively as possible and can be used at very high operating pressure. The fuel-injection device should, apart from this, also function in a reliable manner in the presence of manufacturing tolerances. DISCLOSURE OF THE INVENTION The objective is met by a fuel-injection device with the characteristics of Claim 1. Advantageous improvements of the invention are specified in the sub claims. Other characteristics essential to the invention are listed in the subsequent description and in the Figures, whereby these characteristics could also essential to the invention in completely different combinations without the same having to be explicitly mentioned. ADVANTAGES OF THE INVENTION Liberty with regard to the layout design of the fuel-injection device is considerably increased in the case of the fuel-injection device, in accordance with the invention, due to the hydraulic coupling of two separate parts of the valve element because the respective parts of the valve element could each be optimally aligned to the location within the fuel-injection device. For example, the elastic characteristics of the valve element could be optimally aligned to the designated application area by a corresponding selection of materials used and of the dimensions. Over and above this, the manufacture of the valve element is, on the whole, simplified considerably since even parts with a constant diameter are used. This allows for a design of the fuel-injection device with simple parts, which, facilitates manufacture on the one hand while rendering a small design possible. Over and above this, numerous components of the present devices can be used further In order to implement the present invention. Another advantage of the hydraulic coupler is the equalisation of tolerances, which simplifies manufacture and assembly. Furthermore, coupling of two parts of the valve element by means of a hydraulic coupler permits implementation of a certain damping of movement. The hydraulic coupler can be implemented simply and necessary casing-sided operations simplified, due to the sleeve provided in accordance with the invention. Over and above a guide element provided separate from the casing, in accordance with the invention, a misalignment error of the sleeve with regard to a casing-sided sealing surface that works with the sleeve, is minimised. This is of significance when the first part of the valve element is particularly long and when the sleeve is guided particularly closely on the first part of the valve element. Leakages at the interaction space are minimised throughout or are even prevented completely. A complex and cost-intensive calibration process can, therefore, be avoided. A wear and tear-related change in the functioning characteristics of the fuel-injection device in accordance with the invention is reduced. Manufacturing tolerances are compensated by using guide elements for guiding which ensures reliable functioning of the injector. The fuel-injection device is particularly simple structurally when the sleeve supports itself at the guide element. In this case, a sealing surface at the guide element at which the sleeve supports itself can be designed at a precise right angle to the guiding axis of the guide element so that misalignment of the sleeve guided on the first part vis-a-vis the sealing surface at the guide element is, in particular, minimised considerably. In a further development to this, it is proposed that a fluid passage leading from one side to the other side of the guide element be present in at least one part of a guide region of the guide element or of a complementary region of the first part of the valve element. A clear separation of functions occurs as a result, in that, the guide region of the guide element exhibits pure guide functions and the sleeve exhibits a pure sealing function. This type of separation of functions allows for respective optimal layout design. In a concrete further development, the fluid passage can be formed by a guide clearance between the guide element and the first part of the valve element. This is particularly easy to implement technically. Furthermore, in an advantageous improvement of the fuel-injection device in accordance with the invention, it is proposed that the guide element comprise a stroke stopper for the second part of the valve element. This is, above all, an advantage in the case of those types of fuel-injection devices with which comparably large fuel quantities are to be injected as, for example, in the case of commercial vehicles. This type of fuel-injection device could experience strong stroke turbulence due to manufacture tolerances in the linear dimensions as a result of its multi-part design. This has, till now, been reduced by calibrating the setting element. In doing so, each relevant installation dimension had to be measured with influence on stroke tolerance before assembling the individual parts of the fuel-injection device. The correct stroke value can be set from these measurement values through a selection group of setting elements. This type of method can be avoided by using the stroke stopper integrated in the guide element for the second part of the valve element, which simplifies assembly. Should, however, adjustability of the stroke of the second part of the valve element be necessary due other requirements, the same can furthermore take place by locating this stroke setting element between the second part of the valve element and the stroke stopper, in or at the guide element. Manufacture of the fuel-injection device is again simplified if the guide element comprises a through hole, preferably with a flow restrictor that connects a pressure chamber in the region of the valve seat to a high-pressure chamber. In order to ensure optimal sealing of the interaction space as well as of the high-pressure chamber or of a fluid channel, the guide element can be clamped between two casing bodies of the fuel-injection device, whereby its contact surfaces with the casing body are designed in such a manner that their centre lies at least approximately at the centre line of a guide region of the guide element. It is also proposed that the sleeve be loaded by a spring that supports itself at a shoulder that is designed at the first part of the valve element. This allows implementation of a pre-assembled unit that comprises at least the first part of the valve element, the sleeve and the spring and, if necessary, the guide element. Apart from saving of time at the final assembly of the fuel-injection device, damage due to the high-precision guiding between the sleeve and the first part of the valve element is, hereby, avoided at the final assembly. The otherwise required lose-proof intermediate layer of the sleeve can, moreover, be done away with during assembly and during the calibration process of the spring. The danger of contamination or of damage or even of the loss of the sleeve arising from this type of intermediate layer is eliminated. In addition, the casing and, consequently, its manufacture is simplified, since only a smooth through bore without tiers can be provided for incorporation of the valve element in the casing. High-pressure resistance of the fuel-injection device also improves for this reason and its larger storage volumes (chamber between valve element and through bore in casing) results in a reduction of compressional vibration. An alternative to this consists of loading the sleeve by a first spring that supports itself on a shoulder which is designed on a side of a ring element, said ring element being loaded on the other side by a second spring which supports itself at least indirectly at the casing and which is coupled to the valve element in its closing direction via a coupling element. The guide element can exhibit a central section, preferably a central band that centres the guide element vis-a-vis a casing. The valve element and other regions of the casing that lie away from the coupler are hereby also, at least indirectly, centred to one another. DRAWINGS Particularly preferred embodiments of the present invention are explained in greater detail below with reference to the enclosed drawings. Figure 1 is a schematic illustration of an internal combustion engine with a fuel-injection device; Figure 2 is a schematic and partial sectional illustration of a first embodiment of the fuel-injection device from Figure 1; Figure 3 is a detailed illustration of an area of the fuel-injection device of Figure 2; Figure 4 is a top view of a guide element of the fuel-injection device of Figure 3; Figure 5 presents a section along line V-V in Figure 4; Figure 6 is an illustration of an area of the second embodiment of a fuel-injection device similar to that in Figure 2; Figure 7 is an illustration of an area of the third embodiment of a fuel-injection device similar to that in Figure 2; Figure 8 presents a fourth embodiment that is similar to Figure 2 and Figure 9 presents a fifth embodiment that is similar to Figure 2. DESCRIPTION OF THE EXEMPLARY EMBODIMENTS The internal combustion engine, which, in the present case, serves to drive a motor vehicle that is not illustrated, is on the whole assigned reference sign 10 in Figure 1. A high-pressure conveyor 12 supplies fuel from a fuel storage tank 14 to a fuel pressure accumulator 16 ("rail"). Pressurised fuel, for example diesel or petrol, is stored in the pressure accumulator. Several fuel-injection devices 18 that inject fuel directly into the combustion chamber allocated to it, are connected to rail 16 by means of a high-pressure connector 17 respectively. The fuel-injection devices 18 also respectively exhibit a low-pressure connector 21 through which they are connected to the low-pressure region i.e. to the fuel storage tank 14 in the present case. In a first embodiment, fuel-injection devices 18 could be designed corresponding to Figures 2 and 3: In the present embodiment, fuel-injection device 18 illustrated there comprises a casing 22 with a nozzle body 24, a main body 26 and an end body 28. A single piece design of the main body 26 and end body 28 is also possible. A tiered recess 30, in which a needle-type of valve element 32 is incorporated, is present in the longitudinal direction of casing 22. This valve element 32 has two parts comprising a control piston 34 and jet needle 36. Jet needle 36 has pressure surfaces 38 that are adjacent to a pressure chamber 40 and whose resulting hydraulic force is demonstrated in the opening direction of the jet needle 36. At its lower end in Figure 2, jet needle 36 functions with a casing-sided valve seat (no reference number) in a manner that is not illustrated in greater detail. Fuel discharge outlets 42 can be separated from or connected to pressure chamber 40 in this manner. Jet needle 36 exhibits section 44 that has a smaller diameter and section 46 that has a larger diameter. Jet needle 36 is guided in the longitudinal direction in nozzle body 24 using section 46. Control piston 34 is incorporated in main body 26. An upper end region 48 of control piston is executed as a guide in Figure 2 that is incorporated and guided in a sleeve-type of appendage of end body 28. Spring 50 supports itself at a shoulder at control piston 34 formed by an annular collar 52, said spring loading control piston 34 in the closing direction. The upper, axial end surface of control piston 34 in Figure 2 forms a hydraulic control surface 54 acting in the closing direction of valve element 32 which, together with the end body 28, forms a buncher space 56. Buncher space 56 is connected through an inlet throttle 58, which is present in the sleeve-type appendage of end body 28, to an annulus collector 60 located in the present case between the sleeve-type appendage of end body 28 and the main body 26, said annulus collector 60 being, in turn, connected to the high-pressure connector 17. Annulus collector 60 is formed in the main body 26 by recesses 30 incorporated in the same. Buncher space 56 is, moreover, connected by a discharge throttle 64 that is present in end body 28, to a 2/2 switch-over valve 66. Depending upon the switching position, the switch-over valve 66 connects or blocks this discharge throttle 64 to the low-pressure connector 21. Annulus collector 60 is, furthermore, connected by at least one channel to pressure chamber 40. Guide element 70 is clamped between the nozzle body 24 and main body 26 and its precise design can be seen in Figures 4 and 5: Accordingly, guide element 70 comprises a base plate 72 and a cylindrical appendage 74 placed at the same that forms a guiding collar exhibiting a centring function. Guiding bore 76 that forms a guide region is present in the guide element 70, concentric to appendage 74. In the installation position illustrated in Figures 2 and 3, this guiding bore works together with a guide at the lower end region 77 of control piston 34 in Figures 2 and 3. The upper and lower sides of base plate 72 are designed as high-pressure sealing surfaces 78 which, in the installation position, ensure reliable sealing of casing 22, particularly of annulus collector 60 and of the chambers lying within guide element 70, vis-a-vis the surrounding of the fuel-injection device 18. The position of the centre to the central axis also plays a part in good sealing action. This is achieved by a corresponding shaping of the outer contour of base plate 72 in such a manner, in fact, that the centre lies at least approximately at the central axis (not illustrated) of the guiding bore 76. Bore attachment piece 80 that is concentric to the guide bore 76 and has a diameter that is larger than the latter's, is worked into the underside of base plate 72. The diameter of the bore attachment piece 80 is also larger than the diameter of section 46 of jet needle 36. Bore attachment piece 80 thus forms a stroke stopper for jet needle 36 in a manner that is yet to be presented. An eccentric through hole or bore 82 that is a part of channel 68 in the installation position, is also incorporated in base plate 72 of guide element 70. In some cases of fuel-injection device 18 application at the internal combustion engine 10, through hole 82 must comprise a flow restrictor, as indicated in Figure 2. A front side 85 of appendage 74, acting as a sealing surface, is very precisely at right angles to the axis of guide bore 76. In the installation position presented in Figures 2 and 3, a sleeve 88 supports itself at a sealing edge 86, said sleeve being guided with very little clearance on the control piston 34. Sleeve 88 is loaded by spring 90 against guide element 70, said spring in turn supporting itself at the main body 26. Sleeve 88 belongs to a hydraulic coupler 92 through which the first part of valve element 32, viz., the control piston 34, is coupled to the second part of valve element 32, viz., the jet needle 36. For this purpose, hydraulic coupler 92 comprises a hydraulic interaction space 94 with sub spaces 94a and 94b that is formed between sleeve 88, the guide element 70, the lower end region of control piston 34 in Figures 2 and 3 and the upper end region of jet needle 36 in Figures 2 and 3. Volumes formed by the guide clearance between guide bore 76 and guide 77 at control piston 34 are dimensioned in such a manner that the sub spaces 94a and 94b of interaction space 94 form interrelated control volumes without hydraulic influence. Aforesaid volumes thus form a fluid passage from one side to the other of guide element 70. Alternatively or in addition, the fluid passage could also comprise at least one groove in guide bore 76 and/or at least one flat portion at control piston 34. Fuel-injection device 18 presented in Figures 2 and 3 functions in the following manner: In the initial state when the switch-over valve 66 is not fed with current, buncher space 56 is separated from the low-pressure connector 21 and is connected by inlet throttle 58 to the high-pressure connector 17 and therewith to rail 16. Consequently, the same pressure prevails in buncher space 56 as in the annulus collector 60 and prevails in pressure chamber 40 too via channel 68. This pressure also prevails in interaction space 94 as a result of certain unavoidable leakages due to guiding of jet needle 36 in the nozzle body 24 and sleeve 88 on control piston 34. On the whole, a force acting in the closing direction of valve element 32 ensues from this set-up and presses valve element 32 against the valve seat in the region of the fuel discharge outlets 42 and is exerted through spring 50 on control piston 34. Fuel can thus not emerge from the fuel discharge outlets 42. Discharge throttle 64 will be connected to the low-pressure connector 21 when the switch-over valve 66 is fed with current, whereby pressure in buncher space 56 sinks. On the whole, a force now ensues, acting in the opening direction of control piston 34, which now begins to move upwards against the force of spring 50 in Figures 2 and 3, whereby pressure in the interaction space 94 sinks due to volume increase. Jet needle 36 in Figures 2 and 3 now also moves upwards i.e., it moves from its valve seat in the region of the fuel discharge outlets 42 due to the pressure and/or force difference that has now set itself between an end surface 96 of jet needle 36 bordering the interaction space 94 and the pressure surfaces 38. Fuel from rail 16 can thus be injected via the high-pressure connector 17, the annulus collector 60, channel 68, pressure chamber 40 and via the fuel discharge outlets 42 into the combustion chamber 20. Valve element 32 and/or control piston 34 is held in position vis-a-vis sealing surface 86 by guide element 70. Tilting of sleeve 88 against the sealing surface 85 is prevented in this manner. This type of tilting would have resulted in a leakage between the annulus collector 60 and interaction space 94 and, therewith, to erroneous functioning of the fuel-injection device 18. The stroke of jet needle 36 is restricted by stroke stopper 80. The stroke of jet needle 36 can, as illustrated in Figures 2 to 5, be implemented by machining the bore attachment piece 80 or even by machining the shoulder at end surface 96 of jet needle 36. In this case, sealing surface 78 simultaneously forms a stroke stopper for the end surface 96 of jet needle 36 (refer Figure 6). Control piston 34 proceeds with its stroke movement. Free lift of control piston 34 must, therefore, always be greater than the maximum stroke of jet needle 36. Due to the narrow guide clearance between sleeve 88 and control piston 34 and the resulting low leakage into interaction space 94, control piston 34 is, however, so strongly decelerated that it can only execute a minor additional movement. In the alternate embodiment illustrated in Figure 7, a stroke setting element 97 through which an additional setting of a desired stroke of jet needle 36 is possible, is located between end surface 96 and the stroke stopper 80. In order to terminate an injection, the switch-over valve 66 is brought to its closed position again in which the connection from the buncher space 56 to the low-pressure connector 21 is blocked. Pressure in buncher space 56 increases continuously via inlet throttle 58, as a result of which, control piston 34 is moved again in the closing direction since pressure in the interaction space is initially less than in buncher space 56. Pressure consequently increases in interaction space 94 due to volume reduction which results in a closing movement of jet needle 36. An alternate embodiment of a fuel-injection device 18 is presented in Figure 8, whereby it applies, not just here but as a matter of principle, that such elements and regions that have functions equivalent to elements and regions described before, have the same reference numbers and are not explained again in detail. For the sake of simplicity, only those reference signs have essentially been entered that are required to explain the difference with regard to a previous embodiment. In contrast to the embodiment illustrated in Figures 2 and 3, spring 90 which loads the sleeve 88 surrounding interaction space 94 against guide element 70, supports itself not at main body 26 but at the annular collar 52 and/or the shoulder that is formed by the same. Both springs 90 and 50 thus act at the same annular collar 52 of control piston 34. When designing spring 50, force components of spring 90 acting in the opening direction have, therefore, to be taken into account. Another difference with regard to the embodiment in Figures 2 and 3 lies in the two-part end body 28. This has been divided in such a manner that discharge throttle 64 lies in the remaining end body 28 and inlet throttle 58 in the now separate sleeve 99. Spring 50 thus presses sleeve 99 through its sealing surface or sealing edge (no reference number) against end body 28 and creates a sufficient separation of the annulus collector 60 from the buncher space 56. The advantage of the fuel-injection device 18 illustrated in Figure 8, when compared to those of Figures 2 and 3, is that control piston 34 can form a pre-assembled unit with sleeve 99, spring 50, spring 90 and sleeve 88 so that, in the case of later assembly of all components of fuel-injection device 18, the sleeves 99 and 88 no longer have to be separated from control piston 34. Apart from this, recess 30 can be executed as a smooth through bore in main body 26 of casing 22, which facilitates the setting up of a comparably large annulus collector 60 and a correspondingly large storage volume for fuel. A similar variant is present by Figure 9 wherein a circumferential groove 100, in which a ring-shaped coupling element 102 is inserted, is present instead of an annular collar 52 in control piston 34, an annular element 104 supporting itself, in turn, at the coupling element 102 but only in the closing direction of valve element 32. Spring 90 acts upon annular element 104 on one side, while spring 50 acts upon the same on the other side. Control piston 34 with sleeve 99, spring 50, sleeve 88 and spring 90 as well as coupling element 102 and annular element 104 can form a pre-assembled unit here too, which can be mounted as the same and, in the case of final assembly, can be inserted in recess 30 in main body 26 of casing 22. CLAIMS 1. Fuel-injection device (18) for an internal combustion engine (10), with a casing (22) and a valve element (32) located in casing (22), said valve element working together with a valve seat lying in the region of a fuel discharge outlet (42), characterised in that, at least a first part (34) and a second part (36) of valve element (32) are coupled to one another via a hydraulic coupler (92) which has an interaction space (94) that is bordered, at least in certain areas, by a sleeve (88) that is guided on the first part (34) and that the sleeve comprises a guide element (70) which guides a coupler-sided end region (77) of the first part (34) of valve element (32). 2. Fuel-injection device (18) according to Claim 1, characterised in that, sleeve (88) supports itself at the guide element (70). 3. Fuel-injection device (18) according to Claim 2, characterised in that, a fluid passage (77) that extends from one side to the other side of guide element (70) is present in at least one part of guiding region (76) of the guide element (70) or in a complementary region of the first part of valve element (32). 4. Fuel-injection device (18) according to one of the preceding claims, characterised in that, guide element (70) comprises a stroke stopper (80) for the second part (36) of valve element (32). 5. Fuel-injection device (18) according to Claim 4, characterised in that, a stroke setting element (97) is located between the second part (36) of valve element (32) and the stroke stopper (80). 6. Fuel-injection device (18) according to one of the preceding claims, characterised in that, guide element comprises a fluid channel (68) with a through hole (82) that at least indirectly connects a pressure chamber (40) in the region of the valve seat to a high-pressure connector (17). 7. Fuel-injection device (18) according to Claim 6, characterised in that, the through hole (82) comprises a flow restrictor. 8. Fuel-injection device (18) according to one of the preceding claims, characterised in that, guide element (70) is clamped between two casing bodies (24, 26) and its contact surfaces (78) with the casing bodies (24, 26) are designed in such a manner that their centres lie at least approximately at a central axis of a guide region (76) of the guide element (70). 9. Fuel-injection device (18) according to one of the preceding claims, characterised in that, sleeve (88) is loaded by spring (90) that supports itself at a shoulder (52) which is designed at the first part (34) of valve element (32). 10. Fuel-injection device (18) according to one of Claims 1 to 8, characterised in that, sleeve (88) is loaded by a first spring (90) that supports itself at a shoulder, said shoulder being designed at one side of annular element (104) which is loaded at the other side by a second spring (50) which supports itself at least indirectly at casing (22) and which is coupled to the valve element (32) in its closing direction via a coupling element (102). 11. Fuel-injection device (18) according to one of the preceding claims, characterised in that, guide element (70) exhibits a centring section, preferably a centring collar, which centres guide element (70) vis-a-vis a casing body (26).

Full Text

TITLE
FUEL-INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE
DESCRIPTION
The invention is with regard to a fuel-injection device for an internal combustion according to the preamble of Claim 1.
A fuel-injection device with which fuel can be injected directly into a combustion chamber of the internal combustion engine allocated to it, is established in the market. A valve element is located in a casing for this purpose, said valve element exhibiting a pressure surface in the region of a fuel discharge outlet that, on the whole, acts in the opening direction of the valve element. A control surface which acts in a closing direction and which is located at the opposite end of the valve element is present, said control surface bordering a buncher space. The control surface that acts in the closing direction is, on the whole, larger than the pressure surface acting in the opening direction when the valve element is open.
A higher fuel pressure is present in the region of the pressure surface acting in the opening direction and in the region of the control surface acting in the closing direction when the fuel-injection device is closed than would be present were it to be made available by a fuel collecting pipe (rail), for example. In order to open the valve element, pressure present at the control surface is dropped till the resulting hydraulic force acting in the opening direction exceeds

force acting in the closing direction at the pressure surface. The valve element is opened in this manner.
A pre-requisite for the functioning of this fuel-injection device is the sealing between that region in which the comparably small pressure surface acting in the opening direction is present and that region of the valve element in which the comparably larger control surface acting in the closing direction is present. Leakage fluid is, in the case of the established fuel-injection device, diverted from the region of the sealing via a leakage pipe.
The objective of the present invention is to further develop a fuel-injection device of the type mentioned initially, so that it can be built as simply and cost-effectively as possible and can be used at very high operating pressure. The fuel-injection device should, apart from this, also function in a reliable manner in the presence of manufacturing tolerances.
DISCLOSURE OF THE INVENTION
The objective is met by a fuel-injection device with the characteristics of Claim 1. Advantageous improvements of the invention are specified in the sub claims. Other characteristics essential to the invention are listed in the subsequent description and in the Figures, whereby these characteristics could also essential to the invention in completely different combinations without the same having to be explicitly mentioned.

ADVANTAGES OF THE INVENTION
Liberty with regard to the layout design of the fuel-injection device is considerably increased in the case of the fuel-injection device, in accordance with the invention, due to the hydraulic coupling of two separate parts of the valve element because the respective parts of the valve element could each be optimally aligned to the location within the fuel-injection device. For example, the elastic characteristics of the valve element could be optimally aligned to the designated application area by a corresponding selection of materials used and of the dimensions. Over and above this, the manufacture of the valve element is, on the whole, simplified considerably since even parts with a constant diameter are used. This allows for a design of the fuel-injection device with simple parts, which, facilitates manufacture on the one hand while rendering a small design possible. Over and above this, numerous components of the present devices can be used further In order to implement the present invention.
Another advantage of the hydraulic coupler is the equalisation of tolerances, which simplifies manufacture and assembly. Furthermore, coupling of two parts of the valve element by means of a hydraulic coupler permits implementation of a certain damping of movement.
The hydraulic coupler can be implemented simply and necessary casing-sided operations simplified, due to the sleeve provided in accordance with the invention. Over and above a guide element provided separate from the casing, in accordance with the invention, a misalignment error of the sleeve with regard to a casing-sided sealing surface that works with the sleeve, is minimised. This is of significance when the first part of the valve element is particularly long and when the sleeve is guided particularly closely on the first part of the valve

element. Leakages at the interaction space are minimised throughout or are even prevented completely. A complex and cost-intensive calibration process can, therefore, be avoided. A wear and tear-related change in the functioning characteristics of the fuel-injection device in accordance with the invention is reduced. Manufacturing tolerances are compensated by using guide elements for guiding which ensures reliable functioning of the injector.
The fuel-injection device is particularly simple structurally when the sleeve supports itself at the guide element. In this case, a sealing surface at the guide element at which the sleeve supports itself can be designed at a precise right angle to the guiding axis of the guide element so that misalignment of the sleeve guided on the first part vis-a-vis the sealing surface at the guide element is, in particular, minimised considerably.
In a further development to this, it is proposed that a fluid passage leading from
one side to the other side of the guide element be present in at least one part
of a guide region of the guide element or of a complementary region of the first
part of the valve element. A clear separation of functions occurs as a result, in
that, the guide region of the guide element exhibits pure guide functions and
the sleeve exhibits a pure sealing function. This type of separation of functions
allows for respective optimal layout design. In a concrete further
development, the fluid passage can be formed by a guide clearance between the guide element and the first part of the valve element. This is particularly easy to implement technically.
Furthermore, in an advantageous improvement of the fuel-injection device in accordance with the invention, it is proposed that the guide element comprise a stroke stopper for the second part of the valve element. This is, above all, an advantage in the case of those types of fuel-injection devices with which

comparably large fuel quantities are to be injected as, for example, in the case of commercial vehicles. This type of fuel-injection device could experience strong stroke turbulence due to manufacture tolerances in the linear dimensions as a result of its multi-part design. This has, till now, been reduced by calibrating the setting element. In doing so, each relevant installation dimension had to be measured with influence on stroke tolerance before assembling the individual parts of the fuel-injection device. The correct stroke value can be set from these measurement values through a selection group of setting elements.
This type of method can be avoided by using the stroke stopper integrated in the guide element for the second part of the valve element, which simplifies assembly. Should, however, adjustability of the stroke of the second part of the valve element be necessary due other requirements, the same can furthermore take place by locating this stroke setting element between the second part of the valve element and the stroke stopper, in or at the guide element.
Manufacture of the fuel-injection device is again simplified if the guide element comprises a through hole, preferably with a flow restrictor that connects a pressure chamber in the region of the valve seat to a high-pressure chamber.
In order to ensure optimal sealing of the interaction space as well as of the high-pressure chamber or of a fluid channel, the guide element can be clamped between two casing bodies of the fuel-injection device, whereby its contact surfaces with the casing body are designed in such a manner that their centre lies at least approximately at the centre line of a guide region of the guide element.

It is also proposed that the sleeve be loaded by a spring that supports itself at a shoulder that is designed at the first part of the valve element. This allows implementation of a pre-assembled unit that comprises at least the first part of the valve element, the sleeve and the spring and, if necessary, the guide element. Apart from saving of time at the final assembly of the fuel-injection device, damage due to the high-precision guiding between the sleeve and the first part of the valve element is, hereby, avoided at the final assembly. The otherwise required lose-proof intermediate layer of the sleeve can, moreover, be done away with during assembly and during the calibration process of the spring. The danger of contamination or of damage or even of the loss of the sleeve arising from this type of intermediate layer is eliminated. In addition, the casing and, consequently, its manufacture is simplified, since only a smooth through bore without tiers can be provided for incorporation of the valve element in the casing. High-pressure resistance of the fuel-injection device also improves for this reason and its larger storage volumes (chamber between valve element and through bore in casing) results in a reduction of compressional vibration.
An alternative to this consists of loading the sleeve by a first spring that supports itself on a shoulder which is designed on a side of a ring element, said ring element being loaded on the other side by a second spring which supports itself at least indirectly at the casing and which is coupled to the valve element in its closing direction via a coupling element.
The guide element can exhibit a central section, preferably a central band that centres the guide element vis-a-vis a casing. The valve element and other regions of the casing that lie away from the coupler are hereby also, at least indirectly, centred to one another.

DRAWINGS
Particularly preferred embodiments of the present invention are explained in greater detail below with reference to the enclosed drawings.
Figure 1 is a schematic illustration of an internal combustion engine with a fuel-injection device;
Figure 2 is a schematic and partial sectional illustration of a first embodiment of the fuel-injection device from Figure 1;
Figure 3 is a detailed illustration of an area of the fuel-injection device of Figure 2;
Figure 4 is a top view of a guide element of the fuel-injection device of Figure 3;
Figure 5 presents a section along line V-V in Figure 4;
Figure 6 is an illustration of an area of the second embodiment of a fuel-injection device similar to that in Figure 2;
Figure 7 is an illustration of an area of the third embodiment of a fuel-injection device similar to that in Figure 2;
Figure 8 presents a fourth embodiment that is similar to Figure 2 and
Figure 9 presents a fifth embodiment that is similar to Figure 2.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
The internal combustion engine, which, in the present case, serves to drive a motor vehicle that is not illustrated, is on the whole assigned reference sign 10 in Figure 1. A high-pressure conveyor 12 supplies fuel from a fuel storage tank 14 to a fuel pressure accumulator 16 ("rail"). Pressurised fuel, for example diesel or petrol, is stored in the pressure accumulator. Several fuel-injection devices 18 that inject fuel directly into the combustion chamber allocated to it, are connected to rail 16 by means of a high-pressure connector 17 respectively. The fuel-injection devices 18 also respectively exhibit a low-pressure connector 21 through which they are connected to the low-pressure region i.e. to the fuel storage tank 14 in the present case.
In a first embodiment, fuel-injection devices 18 could be designed corresponding to Figures 2 and 3: In the present embodiment, fuel-injection device 18 illustrated there comprises a casing 22 with a nozzle body 24, a main body 26 and an end body 28. A single piece design of the main body 26 and end body 28 is also possible. A tiered recess 30, in which a needle-type of valve element 32 is incorporated, is present in the longitudinal direction of casing 22. This valve element 32 has two parts comprising a control piston 34 and jet needle 36.
Jet needle 36 has pressure surfaces 38 that are adjacent to a pressure chamber 40 and whose resulting hydraulic force is demonstrated in the opening direction of the jet needle 36. At its lower end in Figure 2, jet needle 36 functions with a casing-sided valve seat (no reference number) in a manner that is not illustrated in greater detail. Fuel discharge outlets 42 can be separated from or connected to pressure chamber 40 in this manner. Jet needle 36 exhibits section 44 that has a smaller diameter and section 46 that

has a larger diameter. Jet needle 36 is guided in the longitudinal direction in nozzle body 24 using section 46.
Control piston 34 is incorporated in main body 26. An upper end region 48 of control piston is executed as a guide in Figure 2 that is incorporated and guided in a sleeve-type of appendage of end body 28. Spring 50 supports itself at a shoulder at control piston 34 formed by an annular collar 52, said spring loading control piston 34 in the closing direction. The upper, axial end surface of control piston 34 in Figure 2 forms a hydraulic control surface 54 acting in the closing direction of valve element 32 which, together with the end body 28, forms a buncher space 56.
Buncher space 56 is connected through an inlet throttle 58, which is present in the sleeve-type appendage of end body 28, to an annulus collector 60 located in the present case between the sleeve-type appendage of end body 28 and the main body 26, said annulus collector 60 being, in turn, connected to the high-pressure connector 17. Annulus collector 60 is formed in the main body 26 by recesses 30 incorporated in the same. Buncher space 56 is, moreover, connected by a discharge throttle 64 that is present in end body 28, to a 2/2 switch-over valve 66. Depending upon the switching position, the switch-over valve 66 connects or blocks this discharge throttle 64 to the low-pressure connector 21. Annulus collector 60 is, furthermore, connected by at least one channel to pressure chamber 40.
Guide element 70 is clamped between the nozzle body 24 and main body 26 and its precise design can be seen in Figures 4 and 5: Accordingly, guide element 70 comprises a base plate 72 and a cylindrical appendage 74 placed at the same that forms a guiding collar exhibiting a centring function. Guiding bore 76 that forms a guide region is present in the guide element 70,

concentric to appendage 74. In the installation position illustrated in Figures 2 and 3, this guiding bore works together with a guide at the lower end region 77 of control piston 34 in Figures 2 and 3. The upper and lower sides of base plate 72 are designed as high-pressure sealing surfaces 78 which, in the installation position, ensure reliable sealing of casing 22, particularly of annulus collector 60 and of the chambers lying within guide element 70, vis-a-vis the surrounding of the fuel-injection device 18. The position of the centre to the central axis also plays a part in good sealing action. This is achieved by a corresponding shaping of the outer contour of base plate 72 in such a manner, in fact, that the centre lies at least approximately at the central axis (not illustrated) of the guiding bore 76.
Bore attachment piece 80 that is concentric to the guide bore 76 and has a diameter that is larger than the latter's, is worked into the underside of base plate 72. The diameter of the bore attachment piece 80 is also larger than the diameter of section 46 of jet needle 36. Bore attachment piece 80 thus forms a stroke stopper for jet needle 36 in a manner that is yet to be presented. An eccentric through hole or bore 82 that is a part of channel 68 in the installation position, is also incorporated in base plate 72 of guide element 70. In some cases of fuel-injection device 18 application at the internal combustion engine 10, through hole 82 must comprise a flow restrictor, as indicated in Figure 2.
A front side 85 of appendage 74, acting as a sealing surface, is very precisely at right angles to the axis of guide bore 76. In the installation position presented in Figures 2 and 3, a sleeve 88 supports itself at a sealing edge 86, said sleeve being guided with very little clearance on the control piston 34. Sleeve 88 is loaded by spring 90 against guide element 70, said spring in turn supporting itself at the main body 26. Sleeve 88 belongs to a hydraulic coupler 92 through which the first part of valve element 32, viz., the control piston 34, is coupled to the second part of valve element 32, viz., the jet needle 36. For this

purpose, hydraulic coupler 92 comprises a hydraulic interaction space 94 with sub spaces 94a and 94b that is formed between sleeve 88, the guide element 70, the lower end region of control piston 34 in Figures 2 and 3 and the upper end region of jet needle 36 in Figures 2 and 3. Volumes formed by the guide clearance between guide bore 76 and guide 77 at control piston 34 are dimensioned in such a manner that the sub spaces 94a and 94b of interaction space 94 form interrelated control volumes without hydraulic influence. Aforesaid volumes thus form a fluid passage from one side to the other of guide element 70. Alternatively or in addition, the fluid passage could also comprise at least one groove in guide bore 76 and/or at least one flat portion at control piston 34.
Fuel-injection device 18 presented in Figures 2 and 3 functions in the following manner: In the initial state when the switch-over valve 66 is not fed with current, buncher space 56 is separated from the low-pressure connector 21 and is connected by inlet throttle 58 to the high-pressure connector 17 and therewith to rail 16. Consequently, the same pressure prevails in buncher space 56 as in the annulus collector 60 and prevails in pressure chamber 40 too via channel 68. This pressure also prevails in interaction space 94 as a result of certain unavoidable leakages due to guiding of jet needle 36 in the nozzle body 24 and sleeve 88 on control piston 34. On the whole, a force acting in the closing direction of valve element 32 ensues from this set-up and presses valve element 32 against the valve seat in the region of the fuel discharge outlets 42 and is exerted through spring 50 on control piston 34. Fuel can thus not emerge from the fuel discharge outlets 42.
Discharge throttle 64 will be connected to the low-pressure connector 21 when the switch-over valve 66 is fed with current, whereby pressure in buncher space 56 sinks. On the whole, a force now ensues, acting in the opening direction of control piston 34, which now begins to move upwards against the

force of spring 50 in Figures 2 and 3, whereby pressure in the interaction space 94 sinks due to volume increase. Jet needle 36 in Figures 2 and 3 now also moves upwards i.e., it moves from its valve seat in the region of the fuel discharge outlets 42 due to the pressure and/or force difference that has now set itself between an end surface 96 of jet needle 36 bordering the interaction space 94 and the pressure surfaces 38. Fuel from rail 16 can thus be injected via the high-pressure connector 17, the annulus collector 60, channel 68, pressure chamber 40 and via the fuel discharge outlets 42 into the combustion chamber 20.
Valve element 32 and/or control piston 34 is held in position vis-a-vis sealing surface 86 by guide element 70. Tilting of sleeve 88 against the sealing surface 85 is prevented in this manner. This type of tilting would have resulted in a leakage between the annulus collector 60 and interaction space 94 and, therewith, to erroneous functioning of the fuel-injection device 18. The stroke of jet needle 36 is restricted by stroke stopper 80. The stroke of jet needle 36 can, as illustrated in Figures 2 to 5, be implemented by machining the bore attachment piece 80 or even by machining the shoulder at end surface 96 of jet needle 36. In this case, sealing surface 78 simultaneously forms a stroke stopper for the end surface 96 of jet needle 36 (refer Figure 6).
Control piston 34 proceeds with its stroke movement. Free lift of control piston 34 must, therefore, always be greater than the maximum stroke of jet needle 36. Due to the narrow guide clearance between sleeve 88 and control piston 34 and the resulting low leakage into interaction space 94, control piston 34 is, however, so strongly decelerated that it can only execute a minor additional movement.

In the alternate embodiment illustrated in Figure 7, a stroke setting element 97 through which an additional setting of a desired stroke of jet needle 36 is possible, is located between end surface 96 and the stroke stopper 80.
In order to terminate an injection, the switch-over valve 66 is brought to its closed position again in which the connection from the buncher space 56 to the low-pressure connector 21 is blocked. Pressure in buncher space 56 increases continuously via inlet throttle 58, as a result of which, control piston 34 is moved again in the closing direction since pressure in the interaction space is initially less than in buncher space 56. Pressure consequently increases in interaction space 94 due to volume reduction which results in a closing movement of jet needle 36.
An alternate embodiment of a fuel-injection device 18 is presented in Figure 8, whereby it applies, not just here but as a matter of principle, that such elements and regions that have functions equivalent to elements and regions described before, have the same reference numbers and are not explained again in detail. For the sake of simplicity, only those reference signs have essentially been entered that are required to explain the difference with regard to a previous embodiment.
In contrast to the embodiment illustrated in Figures 2 and 3, spring 90 which loads the sleeve 88 surrounding interaction space 94 against guide element 70, supports itself not at main body 26 but at the annular collar 52 and/or the shoulder that is formed by the same. Both springs 90 and 50 thus act at the same annular collar 52 of control piston 34. When designing spring 50, force components of spring 90 acting in the opening direction have, therefore, to be taken into account. Another difference with regard to the embodiment in Figures 2 and 3 lies in the two-part end body 28. This has been divided in

such a manner that discharge throttle 64 lies in the remaining end body 28 and inlet throttle 58 in the now separate sleeve 99. Spring 50 thus presses sleeve 99 through its sealing surface or sealing edge (no reference number) against end body 28 and creates a sufficient separation of the annulus collector 60 from the buncher space 56.
The advantage of the fuel-injection device 18 illustrated in Figure 8, when compared to those of Figures 2 and 3, is that control piston 34 can form a pre-assembled unit with sleeve 99, spring 50, spring 90 and sleeve 88 so that, in the case of later assembly of all components of fuel-injection device 18, the sleeves 99 and 88 no longer have to be separated from control piston 34. Apart from this, recess 30 can be executed as a smooth through bore in main body 26 of casing 22, which facilitates the setting up of a comparably large annulus collector 60 and a correspondingly large storage volume for fuel.
A similar variant is present by Figure 9 wherein a circumferential groove 100, in which a ring-shaped coupling element 102 is inserted, is present instead of an annular collar 52 in control piston 34, an annular element 104 supporting itself, in turn, at the coupling element 102 but only in the closing direction of valve element 32. Spring 90 acts upon annular element 104 on one side, while spring 50 acts upon the same on the other side. Control piston 34 with sleeve 99, spring 50, sleeve 88 and spring 90 as well as coupling element 102 and annular element 104 can form a pre-assembled unit here too, which can be mounted as the same and, in the case of final assembly, can be inserted in recess 30 in main body 26 of casing 22.

CLAIMS
1. Fuel-injection device (18) for an internal combustion engine (10), with a casing (22) and a valve element (32) located in casing (22), said valve element working together with a valve seat lying in the region of a fuel discharge outlet (42), characterised in that, at least a first part (34) and a second part (36) of valve element (32) are coupled to one another via a hydraulic coupler (92) which has an interaction space (94) that is bordered, at least in certain areas, by a sleeve (88) that is guided on the first part (34) and that the sleeve comprises a guide element (70) which guides a coupler-sided end region (77) of the first part (34) of valve element (32).
2. Fuel-injection device (18) according to Claim 1, characterised in that, sleeve (88) supports itself at the guide element (70).
3. Fuel-injection device (18) according to Claim 2, characterised in that, a fluid passage (77) that extends from one side to the other side of guide element (70) is present in at least one part of guiding region (76) of the guide element (70) or in a complementary region of the first part of valve element (32).
4. Fuel-injection device (18) according to one of the preceding claims, characterised in that, guide element (70) comprises a stroke stopper (80) for the second part (36) of valve element (32).
5. Fuel-injection device (18) according to Claim 4, characterised in that, a stroke setting element (97) is located between the second part (36) of valve element (32) and the stroke stopper (80).
6. Fuel-injection device (18) according to one of the preceding claims, characterised in that, guide element comprises a fluid channel (68) with a through hole (82) that at least indirectly connects a pressure chamber (40) in the region of the valve seat to a high-pressure connector (17).

7. Fuel-injection device (18) according to Claim 6, characterised in that, the
through hole (82) comprises a flow restrictor.
8. Fuel-injection device (18) according to one of the preceding claims,
characterised in that, guide element (70) is clamped between two casing
bodies (24, 26) and its contact surfaces (78) with the casing bodies (24,
26) are designed in such a manner that their centres lie at least
approximately at a central axis of a guide region (76) of the guide
element (70).
9. Fuel-injection device (18) according to one of the preceding claims,
characterised in that, sleeve (88) is loaded by spring (90) that supports
itself at a shoulder (52) which is designed at the first part (34) of valve
element (32).
10. Fuel-injection device (18) according to one of Claims 1 to 8,
characterised in that, sleeve (88) is loaded by a first spring (90) that
supports itself at a shoulder, said shoulder being designed at one side of
annular element (104) which is loaded at the other side by a second
spring (50) which supports itself at least indirectly at casing (22) and
which is coupled to the valve element (32) in its closing direction via a
coupling element (102).
11. Fuel-injection device (18) according to one of the preceding claims,
characterised in that, guide element (70) exhibits a centring section,
preferably a centring collar, which centres guide element (70) vis-a-vis a
casing body (26).

Documents:

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Patent Number

269797

Indian Patent Application Number

4356/CHENP/2008

PG Journal Number

46/2015

Publication Date

13-Nov-2015

Grant Date

06-Nov-2015

Date of Filing

19-Aug-2008

Name of Patentee

Robert Bosch GmbH

Applicant Address

Post fach30 02 20, 70442 STUTTGART,Germany

Inventors:

#	Inventor's Name	Inventor's Address
1	BRAUN, WOLFGANG;	DITZENBRUNNERSTRASSE 108, 71254 DITZINGEN,
2	VAHLE, DIRK,	HAUFFSTRASSE 10, 71679 ASPERG,
3	KATZ, MARTIN,	WERNER-HAAS-WEG 5, 70469 STUTTGART
4	WERNAU, ALEXANDER,	IM BURGSTALL 33, 74572 BLAUFELDEN,

PCT International Classification Number

F02M63/00

PCT International Application Number

PCT/EP07/50300

PCT International Filing date

2007-01-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	102006008648.1	2006-02-24	Germany