Title of Invention

FUEL-INJECTION VALVE

Abstract

The invention relates to a fuel-injection valve, in particular, a fuel-injection valve which projects directly into the combustion chamber of an internal combustion engine, comprising a fuel inlet, an excitable actuating element which can displace a valve closing element, a fixed valve seat which interacts with the valve closing member to open and close the valve and comprising a fuel outlet which is configured in a valve end that is located downstream. The fuel outlet is formed from at least one exit opening which is located downstream of the valve seat. The valve-seat element which has at least one exit opening has a coating at least in the mouth area of the exit opening on its downstream face which prevents coke deposits in this area.

Full Text

The invention proceeds from a fuel injection valve, in particular a fuel injection valve which projects directly into the combustion chamber of an internal combustion engine. In engine operation the problem occurs, generally with direct injection of a fuel into the combustion chamber of an internal combustion engine, particularly in the case of direct petrol injection or the injection of diesel fuel, that the downstream tip of the injection valve projecting into the combustion chamber is subject to coking due to fuel deposits and/or that soot particles formed in the flame front accumulate on the valve tip. In hitherto known valves that project into the combustion chamber there is therefore a risk, over the life of the valve, of a negative effect on the spray parameters (for example, static flow rate, spray dispersal angle, droplet size, stranding), which can lead to uneven running of the internal combustion engine or even to a failure of the injection valve. Advantages of the invention The fuel injection valve according to the invention having the characteristic features of the main claim has the advantage that the abovementioned negative effects of coking (soot deposits) on the valve tip projecting into the combustion chamber are mitigated or eliminated. The application, according to the invention, of coatings to the downstream valve end, primarily around the orifice areas of the outlet openings, reduces or prevents the coking and formation of deposits (soot) at the valve end, which generally have a negative effect on the spray parameters and the valve function. The measures described in the subordinate claims permit advantageous developments and enhancements of the fuel injection valve specified in the main claim. It is advantageous to apply coatings to the valve end, which either give rise to a catalytic conversion (combustion) of the deposits or which reduce the surface energy and/or the surface roughness of the component to be coated, thereby modifying the wetting characteristics or preventing the formation of a reactive layer. Drawing An exemplary embodiment of the invention is represented in the drawing and described in more detail in the following description. Figure 1 shows a fuel injection valve inserted into a seating bore of a cylinder head, Figure 2 shows a longitudinal section through a fuel injection valve, Figure 3 shows a first exemplary embodiment of a valve end coated according to the invention, Figure 4 shows a second exemplary embodiment of a valve end coated cording to the invention, Figure 5 shows an alternative guide and seating area at the discharge end of the valve, Figure 6 shows a longitudinal section through a fuel injection valve for an internal combustion engine with compression ignition and Figure 7 shows the combustion chamber end of the fuel injection valve according to Figure 6. Description of exemplary embodiments Figure 1 represents a section through part of a cylinder head 1 of an internal combustion engine, especially a mixture-compressing internal combustion engine with spark ignition. A stepped seating bore 2, which extends symmetrically along a longitudinal axis 4 to a combustion chamber 3, is formed in the cylinder head 1. A fuel injection valve 5 according to the invention is inserted into the seating bore 2 of the cylinder head 1. The fuel injection valve 5 serves for the direct injection of fuel, especially petrol, but also diesel fuel, for example as shown with reference to Figures 6 and 7, into the combustion chamber 3 of the internal combustion engine. The fuel injection valve 5 can preferably be solenoid operated by way of an electrical connecting lead 6. The fuel is delivered to the fuel injection valve 5 by way of an inlet connection 7. The fuel injection valve 5 represented in Figure 1 is a so-called top-feed injection valve, in which the fuel from the inlet connection 1 is fed through the entire injection valve 5 in an axial direction, being discharged into the combustion chamber 3 at the discharge end 8 situated opposite the inlet end. In order to protect the fuel injection valve 5 in proximity to the combustion chamber 3 against overheating, the injection valve 5 is at least partially enclosed, for example by a thermal insulation sleeve 9 likewise inserted in the seating bore 2, although such a sleeve can, however, also be dispensed with. Figure 2 shows an exemplary embodiment of a fuel injection valve 5 according to the invention in a sectional representation. This is a solenoid-operated valve having a tubular, largely hollow-cylindrical core 11, at least partially surrounded by a solenoid 10 and serving as inner pole of a magnetic circuit. A stepped coil core 13 made of plastic, for example, accommodates a winding of the solenoid 10 and in conjunction with the core 11 and a non-magnetic intermediate part 14, partially surrounded by the solenoid 1, permits an especially compact and short construction of the injection valve in the area of the solenoid 1. Instead of the solenoid operating element, the fuel injection valve 5 may be operated by piezoelectric or magnetostrictive means. A continuous longitudinal opening 15, which extends along a valve longitudinal axis that coincides with the longitudinal axis 4 of the seating bore 2, is provided through the core 11. The core 11 of the magnetic circuit also serves as inlet connection 7. Fixed to the core 11 above the solenoid 1 is an outer metal (e.g. ferritic) housing part 16, which as outer pole or outer conductive element closes the magnetic circuit and completely surrounds the solenoid 1 at least in a circumferential direction. A fuel filter 17, which ensures that those fuel constituents, which owing to their size might cause blockages in or damage to the injection valve, is provided in the longitudinal opening 15 of the core 11 on the inlet side. A bottom tubular housing part 18, which encloses or accommodates an axially moveable valve part, for example, comprising an armature 19 and a rod-shaped valve needle 20 and an elongate valve seat carrier 21, is firmly and tightly connected to the upper housing part 16. The two housing parts 16 and 18 are firmly joined together by a circumferential weld seam, for example. The sealing between the housing part 18 and the valve seat carrier 21 is achieved, for example, by means of a sealing ring 22. The valve seat carrier 21 has an inner through-opening 24 passing through its entire axial extent, which runs concentrically with the valve longitudinal axis. At its bottom end, which at the same time also represents the downstream termination of the entire fuel injection valve 5, the valve seat carrier 21 encloses a disc-shaped valve seat element 26 fitted in the through-opening 24 with a valve seat face 27 tapering with a truncated cone shape in a downstream direction. The valve needle 20, which has a valve closing section 28 at its downstream end, is arranged in the through-opening 24. The said valve closing section 28, which may be spherical, partially spherical or conically tapering, for example, interacts in a known manner with the valve seat face 27 provided in the valve seat element 26. Downstream of the valve seat face 27 at least one outlet opening 32 for the fuel is incorporated in the valve seat element 26. A guide opening 34 provided in the valve seat carrier 21 at the end facing the armature 19 on the one hand, and a disc-shaped guide element 35 having a guide opening 36 true to size and arranged upstream of the valve seat element 26 on the other, serve for guiding the valve needle 20 during its axial movement with the armature 19 along the valve longitudinal axis. The lift of the valve needle 20 is predetermined by the fitted position of the valve seat element 26. One limit position of the valve needle 20 is fixed by the valve closing section 20 bearing on the valve seat face 27 of the valve seat element 26 when the solenoid 1 is unenergized, whilst the other limit position of the valve needle 20 is produced by the armature 19 bearing on the dos end face of the core 11 when the solenoid is energized. The surfaces of the components in the aforementioned stop area are, for example, chromium-plated. The electrical contacting of the solenoid 1 and hence its energization occurs by way of contact elements 43, which outside the coil former 13 are provided with a plastic coating 44. The plastic coating 44 may also extend over other components (housing parts 16 and 18, for example) of the fuel injection valve 5. The electrical connecting lead 6 supplying current to the solenoid 1 runs out of the plastic coating 44. The guide and seat area provided in the discharge end of the valve seat carrier 21 in the through-opening 24 thereof is formed by three disc-shaped, functionally separated elements in axial succession to another succeeding one another in the downstream direction are the guide element 35, a swirl element 47 and the valve seat element 26. A compression spring 50 surrounding the valve needle 20 braces the three elements 35. 47 and 26 in the valve seat carrier 21. The swirl element 47 may be cost- effectively manufactured, for example by stamping, wire spark erosion, laser cutting, etching or other known processes, from a metal sheet or by electrodeposition. An inner swirl chamber and a number of swirl ducts opening into the swirl chamber are provided in the swirl element 47. In this way, upstream of the valve seat 27 a swirl component is superimposed on the fuel to be discharged, so that the flow enters the outlet opening 32 having had a swirl imparted to it, so that a finely swirled and well-atomized spray is delivered into the combustion chamber 3. In engine operation the problem occurs, generally with direct injection of a fuel into the combustion chamber of an internal combustion engine, that the downstream tip of the injection valve projecting into the combustion chamber is subject to coking due to fuel deposits, and/or that soot particles formed in the flame front accumulate on the valve tip. In hitherto known valves that project into the combustion chamber there is therefore a risk, over the life of the valve, of a negative effect on the spray parameters (for example static flow rate, spray-dispersal angle, droplet size, stranding), which can lead to uneven running of the internal combustion engine or even to a failure of the injection valve. According to the invention the aforementioned problems are mitigated or eliminated by the application of coatings to the valve end 8. In so doing different effects are obtained by means of different coatings on the surface 54 of the component to be coated, such as on the valve seat element 26 composed of chromium steel, but the aim of all measures is to reduce or prevent coking and/or the formation of deposits (soot) on the valve end 8, which generally have a negative effect on the spray parameters and the valve function. Individual coating possibilities are described in more detail below. Coating having a catalytic effect constitute a first group of coatings. The electrolytically applied layers ensure a catalytic conversion (combustion) of the deposited soot particles or prevent the deposition of carbon particles from the outset. Suitable materials for such a coating to prevent coking are cobalt and nickel oxides and oxides of alloys of the said metal. The noble metals Ru, Rh, Pd, Os5 Ir and Pt and alloys of these metals with one another or with other metals exhibit catalytic activity. The required layers are produced for example, by electrochemical metal deposition or deposition without the supply of external current. In the case of Ni, Co or alloys of these metals, oxide formation in air or an additional oxidation stage (wet chemical, plasma) may also be used. The coatings that modify the wetting characteristics on the corresponding surface 54 form a second major group. With these, the coatings serve to reduce the surface energy and/or the surface roughness of the critical areas at the valve end 8. The interfacial energy between the surface 54 and the fuel is thereby reduced, as a result of which the wetting is impaired. This allows the fuel droplets to bead on the areas coated according to the invention where they are entrained by the surrounding flow at the valve end 8. Permanent wetting of the valve end 8 no longer occurs. Possible coatings of this type include ceramic coatings, carbon coatings, which may or may not contain metals, or coatings containing fluorine. Such coatings containing fluorine include, for example, heat-resistant PTFE-like coatings cr, in particular, organic ceramic coatings or so-called Ormocer® coatings of fluorosilicate (FAS). Such coatings containing fluorine are applied, for example, by spraying or dipping. Sapphire coatings are also conceivable. Those coatings which can serve to prevent a reactive layer form a third group. These include, for example, nitrite coatings (TiN, CrN) or oxide coatings (tanatalum oxide, titanium oxide). With these coatings, particles are accumulated on the surfaces 54 to be coated by vapour deposition in a vacuum furnace in a process akin to sputtering. At the valve end 8, those areas which immediately surround the orifice area 55 of at least one outlet opening 32 are in particular need of coating. This is because an accumulation of soot particles in the outlet opening 32 or on its immediate boundary edge in particular leads to the abovementioned detrimental effect on the spray parameters (for example, static flow rate, spray-dispersal angle, droplet size, stranding). A coating should therefore always be applied to the downstream end (orifice area 55) of each individual outlet opening 32, regardless of which component of the fuel injection valve 5 the outlet openings 32 are formed on. Figures 3 and 4 represent two exemplary embodiments of valve ends 8 coated according to the invention, viewed from beneath, which differ in that in one case the entire downstream component surface 54 of the component having the outlet opening 32, in this case the valve seat element 26, is coated (Figure 3), whereas in the other only an annular section of the downstream component surface 54 is coated around the minimum of one outlet opening 32 (Figure 4). The dotted areas are intended to illustrate the coated areas. In Figures 3 and 4 the orifice areas 55 of the outlet openings 32 are situated in the plane of projection. It should be emphasized that the coatings can also extend slightly into the outlet opening 32. In each of the exemplary embodiments shown the valve seat element 26 is that component of the fuel injection valve 5 which forms the downstream end 8 and has the outlet opening 32, so that the coating must be applied to the downstream end face 54 of the valve seat element 26. The application of a coating according to the invention is, however, not confined to a valve seat element. Other valve components, which form the downstream valve end 5 and therefore project into the combustion chamber 3, may have such a coating. In the case of such components arranged downstream of the valve seat 27 (see discharge member 67 in Figure 5), it is again necessary to coat at least those areas immediately adjacent to the outlet openings 32, so that the actual discharge area is protected against coking. Figure 5 shows an alternative guide and seat area at the discharge end of the valve 8, in order to illustrate that the statements regarding the coating according to the invention also relate to valve developments of different design. In this exemplary embodiment a further disc-shaped discharge member 67 is arranged downstream of the valve seat element 26. In this case the discharge member 67 has the outlet opening 32. The outlet opening 32 is inclined at an angle to the valve longitudinal axis, ending downstream in a convexly curved discharge area 66. The discharge member 67 and the valve seat element 26 are, for example, joined to one another by a weld seam 68 obtained by means of laser welding, the welding having been undertaken in an annular, circumferential depression 69. The discharge member 67 is also joined to the valve seat carrier 21 by a weld seam 61. The coating is applied, for example, either over the entire curved discharge area 66 or directly in an annular pattern around the orifice area 55 of the outlet opening 32, so that the coating applied to a curved surface 54 is eccentric in relation to the valve longitudinal axis. Figure 6 represents a longitudinal section through a fuel injection valve for internal combustion engines with compression ignition, especially diesel engines, showing only that part facing the combustion chamber. Figure 7 represents an enlargement of the combustion chamber end of the fuel injection valve 5 shown in Figure 6. A component designed as valve body 72 is clamped against a valve retaining body 73 by means of a clamping nut 75. A bore 84, in which the piston-shaped valve needle 20 is arranged so that it can move axially against a closing force, is formed in the valve body 72. The bore 84 is designed as a blind hole, the closed end facing the combustion chamber 3 forming a valve seat 27, which is of an essentially truncated cone shape. A blind hole 92, in the wall of which at least one outlet opening 90 is arranged connecting the blind ho 92 to the combustion chamber 3, is formed by an indentation of the combustion chamber end of the valve seat face 27. The valve needle 20 is divided into a larger-diameter section remote from the combustion chamber 3, this section being guided in the bore 84, and a smaller diameter section, between which and the wall of the bore 84 a pressure chamber 86 is formed, which can be filled with highly pressurized fuel by way of an inlet duct 80 formed in the valve retaining body 73 and in the valve body 72. The stepping of the outside diameter of the valve needle 20 forms an exposed annular area 82 thereon, which is arranged inside the pressure chamber 86. The fuel pressure in the pressure chamber 86 generates a force acting on the exposed annular area 82, the component of which acting in an axial direction is opposed to the closing force acting on the valve needle 20 and, given a corresponding fuel pressure, is thus capable of moving the valve needle 20 against the closing force. A valve seal face 88 forming the valve closing section 28 is formed on the valve needle 20 at the combustion chamber end, this seal face interacting with the valve seat face 27 in such a way that the minimum of one outlet opening 90 is sealed off from the pressure chamber 86 by the valve seal face 88 bearing on the valve seat face 27. The inwardly directed opening movement away from the combustion chamber 3 causes the valve seal face 88 to lift off from the valve seat face 27, thereby connecting the pressure chamber 86 to the outlet opening 90. The catalytically active coating is applied, for example, over the entire end face of the valve body 72 facing the combustion chamber 3. It is also possible to provide just the curved outer face 96 of the blind hole wall 93 defining the blind hole 92, in which the minimum of one outlet opening 90 is formed, with a coating. Provision may also be made to extend the coating into the outlet opening 90. WE CLAIM: 1. A fuel injection valve (5), in particular fuel injection valve (5) which projects directly into a combustion chamber (3) of an internal combustion engine, having a fuel inlet (7), having a moveable valve closure member (28), having a fixed valve seat (27), with which the valve closure member (28) interacts to open and close the valve, and having a fuel outlet formed in a downstream valve end (8), the fuel outlet being formed by at least one exit opening (32, 90) which is arranged downstream of the valve seat (27), and the component (26, 67, 72) which comprises the at least one exit opening (32, 90), at least in the region (55) where the exit opening (32, 90) opens out, having a coating around this exit opening, characterized in that the coating is in the form of a fluorine-containing layer, the fluorine-containing layer being a layer of fluorosilicate (FAS). 2. The fuel injection valve according to claim 1, wherein the fuel injection valve projects into the combustion chamber (3) of a spark-ignition internal combustion engine. 3. The fuel injection valve according to claim 1, wherein the fuel injection valve projects into the combustion chamber (3) of a compression-ignition internal combustion engine 4. The fuel injection valve according to any one of the preceding claims, wherein the coating is provided in the form of a ring around the exit opening (32, 90) of the downstream surface (54, 96) of the component (26, 67, 72). 5. The fuel injection valve according to any one of claims 1 to 3, wherein the coating is provided over the whole of the downstream surface (54, 96) of the component (26, 67, 72). 6. The fuel injection valve according to either of claims 4 and 5, wherein the coating, in addition to the coating of the surface (54, 96) of the component (26, 67, 72), also extends into the exit opening (32, 90). 7. The fuel injection valve according to any one of the preceding claims, wherein the fluorine-containing layer can be applied by means of spraying. 8. The fuel injection valve according to any one of claims 1 to 6, wherein the fluorine- containing layer can be applied by means of dipcoating.

Documents:

abs-in-pct-2002-003-che.jpg

in-pct-2002-003-che-abstract.pdf

in-pct-2002-003-che-claims filed.pdf

in-pct-2002-003-che-claims granted.pdf

in-pct-2002-003-che-correspondnece-others.pdf

in-pct-2002-003-che-correspondnece-po.pdf

in-pct-2002-003-che-description(complete)filed.pdf

in-pct-2002-003-che-description(complete)granted.pdf

in-pct-2002-003-che-drawings.pdf

in-pct-2002-003-che-form 1.pdf

in-pct-2002-003-che-form 26.pdf

in-pct-2002-003-che-form 3.pdf

in-pct-2002-003-che-form 5.pdf

in-pct-2002-003-che-other documents.pdf

in-pct-2002-003-che-pct.pdf