Title of Invention

FUEL INJECTOR WITH FORM-MOULDED VALVE SEAT FOR REDUCTION OF ARMATURE STROKE DRIFT

Abstract

The invention is with regard to a process for the manufacture of a fuel injector 1 for an internal combustion engine with a control valve that releases or closes a discharge throttle 20 from a buncher space 18, whereby a closing element 22 is placed in a valve seat 26 to close the discharge throttle 20. The closing seat 26 is designed by form-moulding with a form punch 30. The invention is, furthermore, with regard to a fuel injector that is manufactured using the process. (Figure 3)

Full Text

FUEL INJECTOR WITH FORM-MOULDED VALVE SEAT FOR REDUCTION OF ARMATURE STROKE DRIFT Technical Area In the case of internal combustion engines with fuel injection, fuel is fed to individual combustion chambers of the internal combustion engine via fuel injectors with hydraulically operated jet needles. A valve which, for example, is controlled electro-magnetically or by means of a piezo actuator, is incorporated in the fuel injector for this purpose. A discharge throttle of a buncher space, which is connected to the jet needle, is released or closed by the valve. Prior Art In the case of fuel injectors as are established in prior art, a valve unit is incorporated in the casing of the fuel injector, in which a discharge throttle is designed that is connected to a buncher space. The discharge throttle is released or closed by a closing element. A conical valve seat into which the discharge throttle opens, is designed in this connection in the valve unit. A conical closing element is placed in the conical valve seat in order to close the discharge throttle. In order to achieve high opening and closing speeds of the fuel injector that is required to operate an internal combustion engine, the closing element of the buncher space is placed in its seat or lifted up from the same at a high speed. This constant switching of the closing element results in wear and tear of the valve seat. Armature stroke drift results from this wear and tear. This means the path that the closing element travels in order to close the discharge throttle enlarges due to wear and tear. The enlarged stroke path of the closing element leads to the stroke path of the magnet armature in the case of a magnet-controlled valve and/or of the actuator stroke in the case of a piezo actuator, being enlarged. The resulting longer opening and closing times of the control valve and the therewith longer opening times of the injection port, in turn, results in higher injection quantities. These larger quantities of fuel injected into the combustion chambers of the internal combustion engine result in higher motor emissions and higher combustion noises. Presentation of the Invention In order to reduce wear and tear of the valve seat and therewith to reduce the armature stroke drift, the valve seat is designed by form-moulding with a form punch in the case of the process, in accordance with the invention, for manufacture of a fuel injector for an internal combustion engine with a control valve that releases or closes a discharge throttle from a buncher space and in the case of which a closing element that closes the discharge throttle is placed in a valve seat. That the valve seat wears out during operation of the fuel injector and becomes malleable is, hereby, avoided. In a preferred embodiment, the form punch with which the valve seat is form-moulded, is designed as a closing element. When using a conical closing element that is placed in a conical valve seat, the form punch is preferably designed in the shape of a ball with a truncated cone that emerges tangentially from the same. In an especially preferred embodiment, the truncated cone displays an opening angle that is greater than or equal to the opening angle of the conically designed valve seat. This, thus, prevents the material that is suppressed by moulding, from forming a ridge at that side of the moulding location that faces the discharge throttle. This ridge results in a greater restriction of the fuel flow when the valve is open, which leads to a reduction in the fuel flow rate issuing from the buncher space and, thus, also reduces the opening speed of the injection ports. The form punch is preferably provided with a surface that is composed of a hard metal so that the valve seat and not the form punch is deformed during form-moulding of the valve seat. In a preferred embodiment, the entire form punch is made from a hard metal. Hard metals known to the expert are, for instance, sintered material of tungsten carbide, titanium carbide, tantalum carbide, molybdenum carbide and cobalt. The hard metal preferably has a hardness in the range of 1300-1800 HV30. In the case of the fuel injector designed in accordance with the invention, for an internal combustion engine with a control valve that releases or closes a discharge throttle from a buncher space, whereby a closing element is placed in a valve seat to close the discharge throttle, the valve seat is designed by form-moulding. The valve seat of the control valve is designed to be conical in a preferred embodiment. The preferred closing element for closing or releasing the conically shaped valve seat is designed in the shape of a ball. In another embodiment, the valve seat is designed in one valve unit, which is incorporated in the casing of the fuel injector. Drawing The invention is described in greater detail below with the help of drawings. Figure 1 presents a fuel injector for a high-pressure accumulator system. Figure 1.1 illustrates detail A of Figure 1. Figure 2 presents a conically shaped valve seat upon which a form punch acts. Figure 3 is a contour map of a conically shaped valve seat according to prior art. Figure 4 is a contour map of a conically shaped, form-moulded valve seat in a first embodiment. Figure 5 is a contour map of a conically shaped, form-moulded valve seat in a second embodiment. Embodiment Variants Figure 1 presents a fuel injector for a high-pressure accumulator system. A fuel injector 1 comprises an injector body 2 in which a valve plunger 3 is driven. The valve plunger 3 acts upon a bolt 5 with its front side 4, this bolt 5 being designed at a jet needle 6. At least one injection port 7 is designed in the injector body 2 at that side that faces the combustion chamber and is not illustrated here. When the injection port 7 is closed, the valve plunger 3 exerts a compressive force on the bolt 5 of the jet needle 6 with its front side 4. This places the jet needle 6 in a seat 8 and, in this manner, closes the at least one injection port 7. In addition to the compressive force of the valve plunger 3 on the bolt 5, a spring element 9 that is designed as a compression spring acts upon the jet needle 6. The spring element 9 that is designed as a compression spring is preferably a spiral spring. This encloses the bolt 5 of the jet needle 6 and that part of the valve plunger 3 that faces the jet needle in the embodiment illustrated in Figure 1. The spring element 9 is incorporated in a valve chamber 10 for this purpose. The spring element 9 acts with one side upon a cascade expansion 11 of the jet needle 6 and with the other side against a front side 12 of the valve chamber 10. Fuel supply to the fuel injector 1 takes place via a connecting piece 13 which is connected to a high-pressure accumulator that is not illustrated here. A fuel filter 14, in which fuel is cleaned by particles contained therein, is incorporated in the connecting piece 13 in order to prevent damage from abrasion in the fuel injector 1. A conduit 15 through which fuel reaches a nozzle chamber 16, connects to the fuel filter 14. Fuel flows from the nozzle chamber 16 via an annular gap 17 to the injection port 7. The valve plunger 3 ends in a buncher space 18 at that side that faces away from the jet needle 6. The buncher space 18 is supplied with fuel via an inlet throttle 19. The inlet throttle 19 also connects to the fuel filter 14 so that system pressure also prevails at the upstream flow side of the inlet throttle 19. Fuel from the buncher space 18 reaches the low-pressure side discharge nozzle 21 via a discharge throttle 20, the discharge nozzle 21, for example, being connected to a fuel storage tank that is not illustrated here. The discharge throttle 20 is closed or released by a closing element 22 that is designed in the shape of a ball. System pressure prevails in the buncher space 18, in the valve chamber 10 and in the nozzle chamber 16 when the discharge throttle 20 is closed. As a result of the surface of the front side that borders the buncher space 18 being larger than the surface of the valve plunger 3 facing the opposite direction, compressive force that acts in the direction of the at least one injection nozzle 7 is greater than the compressive force acting in the opposite direction and the jet needle 6 is placed in its seat 8 and thus closes the at least one injection port 7. Pressure in the buncher space 18 sinks the moment the closing element 22 lifts itself from the seat, thus releasing the discharge throttle 20. Thus compressive force acting in the direction of the at least one injection port 7 also reduces as a result. The valve plunger 3 moves in the direction of the discharge throttle 20. The jet needle 6 simultaneously lifts itself from its seat and releases the at least one injection port 7. In the embodiment variant illustrated here, control of the closing element 22 takes place via an electrically controlled solenoid valve 23. A piezo actuator could, however, also be used, if necessary, by interconnecting a hydraulic coupler or a pressure intensifier, in the place of the solenoid valve 23 for the purpose of operating the closing element 22. In order to facilitate manufacture and assembly of the fuel injector 1, a valve unit 24 is inserted in the injector body 2 in which the buncher space 18 is designed together with the inlet throttle 19 and the discharge throttle 20. Furthermore, a bore 25 in which the valve plunger is driven, is designed in the valve unit 24. Figure 1.1 illustrates detail A of Figure 1. Figure 1.1 illustrates the valve plunger 3 in its upper position i.e. when the injection port 7 is open. The discharge throttle 20 has to be closed in order to close the injection port 7. The closing element 22 is placed in a valve seat 26 for this purpose. The valve seat 26 is designed as a conically shaped front side 32 of the valve unit in order to ensure pressure-tight closing of the discharge throttle 20 by the closing element 22. In the embodiment illustrated here, the discharge throttle 20 opens, for this purpose, conically towards the closing element 22. The connection to the low-pressure part of the fuel system is interrupted when the discharge throttle 20 is closed. The buncher space 18 is supplied with fuel which is under system pressure, via the inlet throttle 19 that is connected to the high-pressure accumulator by an annulus collector 27 and a supply conduit 28. Pressure in the buncher space 18 likewise increases again up to system pressure as a result. Due to rising pressure in the buncher space 18, compressive force acting upon the valve plunger 3 increases and the valve plunger 3 is moved in the direction of the at least one injection opening 7. Since the valve plunger 3 is connected by the front side 4 to the bolt 5 of the jet needle 6, the jet needle 6 is likewise moved in the direction of the at least one injection port 7 and closes the same. The closing element 22 is connected by a plunger 29 to the armature of the solenoid valve 23. When using a piezo actuator instead of the solenoid valve 23, the former acts directly on the plunger 29. The valve seat 26 is form-moulded in the fuel injector, in accordance with the invention li order to prevent the valve seat from wearing out due to the high speeds at which the closing element 22 is placed in the same and due to which a larger armature stroke and, therewith, a longer closing time results. The Hertzian surface pressure is reduced by increasing the percentage contact area. This means that the contact surface of the closing element 22 on the valve seat 26 increases by form-moulding. A lower force acts upon the valve seat 26 due to the reduced surface pressure, as a result of which its wear and tear is reduced. Another advantage of form-moulding the valve seat 26 is that the material is strengthened in the moulded region. The rough cone ends that are caused by manufacture are also smoothened. Wear and tear of the seat is forestalled by form-moulding the valve seat 26 and minimised between the valve seat and the closing element 22 during operation. Increase of the pre-injection quantity can be prevented through this due to the increased armature stroke during fuel injector operation. Increasing injection quantities during operation of the internal combustion engine lead to increased emissions of the internal combustion engine and to an increase in combustion noises as well as to a greater load on the entire internal combustion engine. A form punch made from a hard material and which is designed in the shape of a closing element is, for instance, used to form-mould the valve seat 26. Figure 2 illustrates a valve seat in which a form punch is placed. In order to prevent a ridge from forming at that side of the valve seat 26 that faces the discharge throttle 20, the form punch 30 is preferably designed in the shape of a ball with a truncated cone 31 that emerges tangentially from the same in the case of a valve with a spherical closing element 22. The truncated cone 31 prevents the ridge from forming along the ball in that the material is moulded by the shape of the truncated cone 31 along the direction of the valve seat 26 that is also spherical. When this kind of a ridge occurs during form-moulding of the valve seat 26, the cross-section of the stream is reduced when the valve is closed. The valve thus functions as a throttle due to which the fuel flow rate that flows out of the discharge throttle 20 gets reduced. Fuel flow rate that is reduced in this manner leads to a slower pressure drop in the buncher space 18 and, therewith, also to a reduced opening speed of the jet needle 6. This also results in modified injection properties which can negatively influence the combustion process in the combustion chamber of the internal combustion engine. The truncated cone 31 preferably exhibits an opening angle α1 that is larger than the opening angle α2 of the valve seat 26. When the opening angle α1 of the truncated cone 31 and the opening angle α2 of the valve seat 26 is the same, it is possible that a part of the material during form-moulding is pressed in the direction of the discharge throttle 20. A flash gets formed in this case at the transition from the valve seat 26 into the discharge throttle 20 at which the opening angle changes. This flash negatively influences fuel flow. In a preferred embodiment, the opening angle α1 is larger than opening angle α2 of the valve seat 26 by 0 to 10 degrees. A larger opening angle α1 of the truncated cone 31 results in a ridge being formed at the moulding location in the area of the valve seat 26 at the side of the truncated cone 31. Wear and tear at the valve seat 26 can be avoided even in the case of a closing element 22 that is not conical by form-moulding the valve seat 26. In order to prevent a ridge from forming in the area of the valve seat 26 in a conically shaped valve seat 26, the form punch 30 that is designed in the shape of a closing element 22, is preferably provided with a truncated cone 31 even in the case of non-spherical closing element 22, this truncated cone having an opening angle α1 that is larger than the opening angle α2 of the valve seat 26. The closing element 22 can thus, apart from a spherical shape, also be designed in the shape of a for instance, paraboloid or a cylinder in the case of a conically shaped valve seat 26. Besides a truncated cone 31, it is also possible that the form punch 30 ends in the shape of a cone, whose nose angle is larger or the same as the opening angle α2 of the valve seat 26. Any material that is harder than the material from which the valve seat 26 is manufactured, is suitable for the form punch. Materials that are particularly suited for the form punch 30 are, for example, hard metals that are selected from the group of hard metals K 01 - K 40. The hardness of these hard metals ranges from 1300-1800 HV 30, depending upon the composition. Hard metals are, thereby, sintered material of tungsten carbide, titanium carbide, tantalum carbide, molybdenum carbide and cobalt. Apart from hard metals, compression-resistant ceramics that are harder than the material from which the valve seat 26 is manufactured are also suitable. Figure 3 presents a contour map of a conically shaped valve seat according to prior art. At the x co-ordinate 33 of the diagram illustrated in Figure 3, the length of the conically shaped front side 32 of the valve unit 24 is presented in mm, in which the valve seat 26 is designed. Ordinate 34 shows the surface roughness in μm. The line indicated with reference sign 35 shows the surface of the conically shaped front side of the valve unit 24 before the closing element 22 is placed for the first time in the valve seat 26. That the surface of the front side 32 of the valve unit 24 exhibits roughness caused by manufacture can be seen clearly here. The million-fold switching of the closing element 22 results in wear and tear at the valve seat 26. A recess 36 emerges in the region of the valve seat 26 due to the closing element 22. The recess 36 has a depth 37 due to wear and tear that is significantly larger than the central surface roughness of the front side 32 of the valve unit 24. The wear and tear depth 37 results in a considerably elongated closing stroke with which to close the control valve, due to the very small opening stroke and/or closing stroke of the closing element 22. This also results in slower closing of the injection port 7 and therewith to a larger fuel quantity being injected into the combustion chamber. This results in higher motor emissions and greater combustion noise. Figure 4 illustrates a contour map of a conically shaped valve seat in which the valve seat is form-moulded with a conically shaped form punch. It can be gathered from Figure 4 that the surface 35 is markedly smoother before the first closing of the control valve when the valve seat 26 is moulded. The moulding depth to which the valve seat 26 is moulded, is indicated with reference sign 39. The form-moulded valve seat 26 has the cross-section of a segment of a circle due to the spherically shaped form punch. This results in a ridge 40 being formed towards the discharge throttle 20. The ridge 40 results in a reduced cross-section of the stream when the discharge throttle 20 is open. It is for this reason that the valve seat 26 functions as an additional throttle when the discharge throttle 20 is open. The material in the area of the valve seat 26 is strengthened due to moulding of the valve seat 26. This material strengthening as well as the larger contact surface of the closing element 22 in the valve seat 26 result in a recess 36 being formed with only a marginal wear and tear depth 37 when compared with a non-moulded valve seat 26, even after a larger number of opening and closing movements of the closing element 22. Figure 5 presents the front side 32 of the valve unit 24 with a form-moulded valve seat 26 therein, if a spherically shaped form punch is used in the case of which a truncated cone emerges tangentially from the sphere. Even when using this type of a form punch, it can be seen that the roughness of the surface 35 before the first closing of the control valve is less than in the case of a non-moulded valve seat 26. A slight ridge 40 arises at that side of the valve seat 26 that faces the discharge throttle 20 due to the tapered beginning at the form punch 30. Even when using a form punch 30 in the shape of a sphere with a truncated cone 31 emerging tangentially from the same, a recess 36 occurs with only a marginal wear and tear depth 37 after a large number of opening and closing movements of the closing element 22 when compared to a non-moulded valve seat 26. The moulding depth of the form-moulded valve seat 26 is also indicated with reference sign 39 in Figure 5. Reference Sign List Fuel Injector Injector Body Valve Plunger Front Side Bolt Jet Needle Injection Port Seat Spring Element Valve Chamber Cascade Expansion Front Side of the Valve Chamber 10 Connecting Piece Fuel Filter Conduit Nozzle Chamber Annular Gap Buncher Space Inlet Throttle Discharge Throttle Discharge Nozzle Closing Element Solenoid Valve Valve Unit Bore Valve Seat Annulus Collector Supply Conduit Plunger Form Puncl Truncated Cone Front Side X co-ordinates Ordinate Surface before first closing Recess Wear and Tear Depth Seat Breadth Moulding Depth Ridge Opening Angle of the Truncated Cone 31 Opening Angel of the Valve Seat 26 Patent Claims 1. Process for manufacture of a fuel injector (1) for an internal combustion engine with a control valve that releases or closes a discharge throttle (20) from a buncher space (18), whereby a closing element (22) is placed in a valve seat (26) in order to close the discharge throttle (20), characterised in that, the valve seat (26) is formed by form-moulding with a form punch (30). 2. Process according to Claim 1, characterised in that, the form punch (30) is designed in the shape of a closing element (22). 3. Process according to Claim 1, characterised in that, the form punch (30) is designed in the shape of a sphere with a truncated cone (31) emerging tangentially from the same. 4. Process according to Claim 3, characterised in that, the truncated cone (31) has an opening angle (α1) that is larger or equal to the opening angle (α2) of the conically shaped valve seat (26). 5. Process according to one of Claims 1 to 4, characterised in that, the surface of the form punch (30) is made from a hard metal. 6. Fuel injector for an internal combustion engine with a control valve that releases or closes a discharge throttle (20) from a buncher space (18), whereby a closing element (22) is placed in a valve seat (26) to close the discharge throttle (20), characterised in that, the valve seat (26) is formed by form-moulding. 7. Fuel injector according to Claim 6, characterised in that, the valve seat (26) is designed to be spherical. 8. Fuel injector according to Claim 6 or 7, characterised in that, the closing element (22) is designed to be spherical. 9. Fuel injector according to one of Claims 6 to 8, characterised in that the valve seat (26) is designed in a valve unit (24).

Documents:

1435-CHENP-2007 AMENDED PAGES OF SPECIFICATION 17-10-2013.pdf

1435-CHENP-2007 AMENDED CLAIMS 17-10-2013.pdf

1435-CHENP-2007 CORRESPONDENCE OTHERS 03-07-2013.pdf

1435-CHENP-2007 EXAMINATION REPORT REPLY RECEIVED 17-10-2013.pdf

1435-CHENP-2007 FORM-3 17-10-2013.pdf

1435-CHENP-2007 OTHER PATENT DOCUMENT 17-10-2013.pdf

1435-CHENP-2007 POWER OF ATTORNEY 17-10-2013.pdf

1435-chenp-2007-abstract image.jpg

1435-chenp-2007-abstract.pdf

1435-chenp-2007-claims.pdf

1435-chenp-2007-correspondnece-others.pdf

1435-chenp-2007-description(complete).pdf

1435-chenp-2007-drawings.pdf

1435-chenp-2007-form 1.pdf

1435-chenp-2007-form 3.pdf

1435-chenp-2007-form 5.pdf

1435-chenp-2007-pct.pdf