Title of Invention

FUEL INJECTOR WITH A DIRECT CONTROLLED INJECTION VALVE MEMBER

Abstract

The invention is with regard to a fuel injector for injection of fuel into a combustion chamber (30) of an internal combustion engine, with an injector body (2) and a fuel-injector mount (3) in which an injection valve element (5) that can be moved is incorporated, which has a seat (28) that releases or closes injection apertures (29) and a piezo actuator (9) that operates the injection valve element (5), characterised in that the piezo actuator (9) operates a first transmission piston (11) in which a second transmission piston (9) that is linked to an injection valve element (5) is guided.

Full Text

FUEL INJECTOR WITH DIRECTLY CONTROLLED INJECTION VALVE ELEMENT Technical Field Today, direct injection systems (common rail systems) that enable speed and load independent calibration, are being increasingly used in internal combustion engines. In the case of common rail systems, pressure creation and the injection procedure are de-linked chronologically as well as spatially. Injection pressure is created by a separate high-pressure pump. It is not mandatory that the high-pressure pump be actuated synchronous to the injections. Pressure can be calibrated independent of speed and injection quantities. Electrically operated injectors, with which the actuation time and actuation duration, the beginning of injection and the injection quantities can be determined, are used in common rail systems in the place of pressure controlled injection valves. This type of injection system offers a great deal of liberty with regard to the structuring of multiple injections or separated injections. Prior Art Fuel injectors for direct injection systems (common rail systems) are usually actuated by magnet valves or piezo actuators. Decompression of a buncher space takes place by means of the magnet valve and the piezo actuator respectively. For this purpose, the buncher space has a discharge channel in which the discharge throttle is usually located. Filling in of the buncher space for operating an injection valve element usually takes place via an inlet from the high-pressure side, in which an inlet throttle element is inserted. A valve closing element which closes the discharge channel, is operated by means of the magnet valve that is allocated to the buncher space or the piezo actuator that is allocated to the buncher space When the magnet valve and the piezo actuator respectively are in operation, the valve closing element, which could, for example, be spherical or a cone, releases the discharge channel so that a control volume is able to flow out of the buncher space. Pressure in the buncher space thus reduces and an injection valve element, that is usually needle-shaped and that is impacted upon by the buncher space, ascends in a vertical direction. As a result of the ascending movement of the injection valve element, injection apertures are released at that end of the injector that faces the combustion chamber, so that fuel can be injected into the combustion chamber of an internal combustion engine. Fuel injectors that are established according to prior art and that can be operated by magnet valves or by piezo actuators respectively usually include an injector body that is designed to be compression-proof and pressure-tight. The magnet valve and the piezo actuator respectively are contained outside this injector body. The pressure level in the buncher space is reduced through these by releasing the discharge channel. In accordance with this principle, operation of the needle-shaped injection valve element takes place in an indirect manner. A hydraulic transformation device is usually allocated to the piezo actuator that is located outside the valve body, so that its stroke path can be extended since piezo crystals that are arranged in a stacked manner exhibit only marginal longitudinal changes during current feed. If the fuel injector is instead operated by a magnet valve then the exact calibration of its residual air gap and its armature stroke path is required in order to correspondingly precisely actuate the valve closing element that closes the discharge channel of the buncher space, particularly in the high speed range of an internal combustion engine. Due to the actuation device i.e., a magnet valve and a piezo actuator respectively, that is located outside the injector body, fuel injectors that are established in prior art are built relatively high and, as a result, have a higher installation area requirement in the cylinder head region of an internal combustion engine. The trend in modern internal combustion engines, however, runs towards increasingly less installation space being available in the cylinder head region. This is linked to the fact that internal combustion engines with a high power output per litre per cubic capacity require complex cooling of the cylinder head region. This usually takes place through channels that run through the cylinder head of the internal combustion engine and exhibit particular characteristics for thermal reasons as well as for reasons of heat conductibility. Installation space required for the installation of fuel injectors thereby reduces, with the result that other solutions have to be developed. Description of the Invention Through the solution proposed in accordance with the invention, an especially compactly built fuel injector is made available with which direct operation of a needle-shaped injection valve element is achieved. For this purpose, an actuator that has a piezo crystal stack is incorporated in a pressure chamber that is filled with system pressure. A front face is connected to a first transmission piston, which encloses a second transmission piston. The second transmission piston is designed at the injection valve element. The first transmission piston and the second transmission piston are guided one into the other, which enables further guiding of the injection valve element in addition to a guide section of the same within the fuel-injector mount. Other guide sections of the injection valve element can, thus, be dispensed with. The first transmission piston is enclosed by a buncher space sleeve that is placed, loaded by spring pressure, at an end face of the fuel-injector mount. The biting flange of the buncher space sleeve is held in continuous contact with the end face of the fuel-injector mount combination by the pressure spring, which ensures that the buncher space is sealed. Fuel flows from the pressure chamber that is subject to system pressure via a nozzle chamber supply to the nozzle chamber that surrounds the injection valve element and from the nozzle chamber via an annular gap towards the seat of the injection valve element. Using the solution proposed in accordance with the invention, the current feed time of the piezo actuator can be decreased since the same holds the injection valve element in its closed position not when it is being fed with current but when it is not being fed current. When the actuator is fed with current, a pressure increase takes place in the buncher space that causes the second transmission piston, which is connected to the injection valve element, to open. The injection valve element, thereupon, releases the injection aperture at the combustion chamber side. If, on the other hand, the actuator is not fed with current, then the injection valve element is pressed into its closed position by a pressure spring that is located between a first transmission piston and a second transmission piston. The proposed pressure intensifier thus acts as a pressure intensifier with a direction reversal for a fuel injector, this pressure intensifier causing the injection valve element to open when the actuator is fed with current and to close when it is not fed with current. Drawing The invention is described below in greater detail by means a drawing. The single illustration is a section running through a fuel injector, proposed in accordance with the invention, with a directly controlled injection valve element. Design Variants The drawing illustrates a fuel injector 1 that includes an injector body 2. The injector body 2 is connected to a fuel-injector mount 3 by a nozzle clamping nut 4. This design is termed the fuel-injector mount combination. An external screw thread section 34 is provided at the injector body to connect the injector body 2 and the fuel-injector mount 3 at which the nozzle clamping nut 4, provided with an internal screw thread 35, is wound with a pre-determined torque. The nozzle clamping nut 4 encloses the fuel-injector mount with a circular contact surface. A high-pressure supply 6 is provided in the injector body 2 that is connected to a high-pressure storage volume (common rail) that is not illustrated in the drawing. The high-pressure storage volume (common rail) is loaded by a high-pressure pump that is not illustrated in the drawing. The pressure level (system pressure) that prevails in the high-pressure storage volume lies in the range of between 1400 bar and 1600 bar. A pressure chamber 7 that is designed in the injector body 2 is loaded through a high-pressure supply 6 by fuel 8 that is under system pressure. A nozzle chamber supply 24, through which fuel that is under system pressure is supplied to a nozzle chamber 25 in the fuel-injector mount 3, branches off from the pressure chamber 7 within the injector body 2. An actuator 9 that is preferably designed as a piezo actuator and has a piezo crystal stack 10, is incorporated within the pressure chamber 7 that serves as a hydraulic additional volume with which compressional vibrations can be attenuated and/or completely removed. When feeding the piezo crystal stack 10 with current via contacts that are not illustrated in the drawing, the piezo crystals that are located in a stacked manner undergo a change in length which can be used to operate an injection valve element. The piezo actuator 9 lies at the front face 12 of a first transmission piston 11. The wall of the first transmission piston 11 is provided with a balance hole 13 through which the pressure chamber 7 is connected to a hydraulic chamber 41. The first transmission piston 11 surrounds a second transmission piston 19 that is incorporated at the injection valve element 5. Over and above this, the second transmission piston 19 has a recess 32 in which a spring element 17 is embedded, which supports itself at a contact surface 37 in the interior of the first transmission piston 11. The second transmission piston 19 and the injection valve element 5 are connected firmly to one another. A first ring surface 38 of the second transmission piston 19 borders the hydraulic chamber 41, while a second ring surface 39 borders a buncher space 18 at the lower surface of the second transmission piston 19. This buncher space 18 is, likewise, bordered by a ring surface 20 at the lower surface of the first transmission piston 11 and, in addition, bordered by the interior of a buncher space sleeve 21 as well as a circular end face section 23 of the fuel-injector mount 3 lying next to the injector body 2. A supporting ring 14 is incorporated at the shell surface of the first transmission piston 11 at which a contact ring 15 supports itself. The contact ring 15 forms a contact surface for a pressure spring 16 that engages the buncher space sleeve 21 at the end face 23 of the fuel-injector mount 3. The buncher space sleeve 21 that surrounds the first transmission piston 11 has a biting flange 22. When impacting the buncher space sleeve 21 with pressure by means of the pressure spring 16, the biting flange 22 engages at the upper side of the end face 23 of the fuel-injector mount 3 in a sealing fashion. The buncher space 18, in which pressure is required with which to operate the injection valve element 5 that is different from the system pressure within the pressure chamber 7, is thus effectively sealed against the pressure chamber 7 that is impacted upon by fuel 8 which is under system pressure. The injection valve element 5 is incorporated in the fuel-injector mount 3 within a guide section 31. Nozzle chamber 25 is found below the guide section 31 and is impacted upon through the already mentioned nozzle chamber supply 24 from the pressure chamber 7 by fuel 8 that is under system pressure. The annular gap 27 extends from the nozzle chamber 25 up to the seat 28 of the injection valve element 5 at that end of the fuel-injector mount 3 that faces the combustion chamber. If the injection valve element 5 is placed in the seat 28 then the injection apertures 29 in the combustion chamber of the internal combustion engine will be closed; if the seat 28 is, in contrast, open, then fuel can be injected through the nozzle chamber supply 24, the nozzle chamber 25, the annular gap 27 and the subsequently opened injection apertures 29 into the combustion chamber 30 of the injection combustion engine. In order to secure pressurisation of the buncher space sleeve 21, the same has a contact surface for the pressure spring 16 at its side that faces the pressure spring 16. The front face of the injector body 2 and the end face 23 of the fuel-injector mount 3 together form a butt joint 36 that, enclosed by the nozzle clamping nut 4, presents a pressure-tight sealing of the buncher space 18 when screwing the injector body 2 and the fuel-injector mount 3. The mode of operation of the fuel injector presented in the drawing is described below - The first transmission piston 11 remains in its rest position when the piezo crystal stack 10 of the actuator 9 is not being fed with current due to the pressure balance between the pressure chamber 7 and the hydraulic chamber 41 through the inlet port 13. The spring element 17 that lies against the contact surface 37 loads the second transmission piston 19 in the closing direction so that the injection valve element 5, which is firmly connected to the second transmission piston 19, is positioned in its seat 28. Injection apertures 29 at the combustion side end of the fuel-injector mount 3 are thereby closed. No fuel can reach the combustion chamber 30 of the internal combustion engine. The spring element 17 is designed in such a manner that it creates a higher forward force when it is in the closed position. This force exceeds the hydraulic opening force acting in the opening direction and created at the compression stage 26 in the nozzle chamber 25 when the same is impacted upon by pressure. If, on the other hand, the piezo crystal stack 10 of actuator 9 is fed with current, then the individual piezo crystals of the piezo crystal stack 10 increase in length so that a force is created at the front face 12 of the first transmission piston 11, which regulates the same downwards in a vertical direction. The ring surface 20 of the first transmission piston 11 that thereby moves into the buncher space 18 effects a pressure increase in the same. The pressure increase is transmitted to the second ring surface 39 at the lower side of the second transmission piston 19. Hydraulic pressure acting at the second ring surface 39 of the second transmission piston 19 as well as hydraulic pressure acting at the compression stage 26 in the nozzle chamber 25 exceed the forward force created by the spring element 17 so that the injection valve element 5 together with the second transmission piston 19 moves into the hydraulic chamber 41. Fuel volumes that are thereby disposed from the same, stream via the port 13 into the pressure chamber 7. The opening injection valve element 4 moves out from its seat 28 at that end of the fuel-injector mount 3 that faces the combustion chamber so that the injection apertures 29 get released and fuel that is under system pressure flows out from the nozzle chamber 25 via the annular gap 27 towards the injection apertures 29 and can then be injected into the combustion chamber 30. If current feed to the piezo crystal stack 10 of the actuator 9 is neutralised instead, then the first transmission piston 11 moves into its rest position as a result of which pressure prevailing in the buncher space 18 decreases. Hydraulic force at the second ring surface 39 acting in the opening direction at the lower side of the second transmission piston 19 sinks due to pressure decrease in the buncher space 18 so that the closing movement takes place through the spring element 17 incorporated in the hydraulic chamber 41, while force acting in the closing direction exceeds hydraulic force acting at the compression stage 26. The injection valve element 5 that is firmly connected to the second transmission piston 19 is thereby positioned in its seat 28 which faces the combustion chamber. The injection apertures 29 are closed as a result and fuel can no longer be injected into the combustion chamber 30 of the internal combustion engine. The first transmission piston 11 and the second transmission piston 19 present a pressure intensifier with reversal of direction. In this case, the injection valve element is opened when the actuator is fed with current while the injection valve element is driven into its closed position when the actuator is not fed with current. The transmission pistons 11 and 19 that are guided into one another form a further guide for the injection valve element that does not have to be designed in a casing. It is an advantage that the injection valve element 5 can be moved only within a guide section 31 in the fuel-injector mount 3. Since the actuator 9 is located within the pressure chamber 7 that is impacted upon by system pressure, the design of the proposed fuel injector is very compact. The assembly of the transmission pistons 11 and 19 as well as of the buncher space sleeve 21 incorporated at the shell surface of the first transmission piston 11 advantageously enables a simple equalisation of load tolerance of the injector body 2 as well as of the buncher space sleeve 21 relative to the end face 23 of the fuel-injector mount 3. Another advantage of the proposed design of the fuel injector 1 in accordance with the invention is that the current-feed time of the actuator 9 can be reduced, which favourably increases its lifespan. List of Reference Signs 1 Fuel injector 2 Injector body 3 Fuel-injector mount 4 Nozzle clamping nut 5 Injection valve element 6 High-pressure supply 7 Pressure chamber 8 Fuel under system pressure 9 Actuator 10 Piezo crystal stack 11 First transmission piston 12 Front face 13 Balance hole 14 Supporting ring 15 Contact rings 16 Pressure spring 17 Spring element 18 Buncher space 19 Second transmission piston 20 Ring surface of first transmission piston 11 21 Buncher space sleeve 22 Biting flange 23 End face of fuel-injector mount 3 24 Nozzle chamber supply 25 Nozzle chamber 26 Compression stage 27 Annular gap 28 Seat 29 Injection aperture 30 Combustion chamber 31 Guide section 32 Recess in second transmission piston 19 33 Ring surface of buncher space sleeve 21 34 External screw thread section 35 Internal screw thread section 36 Butt joint 37 Contact surface spring element 17 38 First ring surface of second transmission piston 19 39 Second ring surface of second transmission piston 19 40 Interior of the buncher space sleeve 41 Hydraulic chamber Patent Claims 1. Fuel injector for injection of fuel into a combustion chamber (30) 2. of an internal combustion engine with an injector body (2) and a 3. fuel-injector mount (3), in which an injection valve element (5) 4. that can be moved is incorporated, which has a seat (28) that 5. releases or closes injection apertures (29) and the injection 6. valve element (5) can be operated by a piezo actuator (9), 7. characterised in that, the piezo actuator (9) directly operates a 8. first transmission piston (11) into which a second transmission 9. piston (19) that is connected to the injection valve element (5) is 10. guided in order to change pressure within a buncher space (18). 11. Fuel injector in accordance with Claim 1, characterised in that, 12. the piezo actuator (9) is incorporated within a pressure chamber 13. (7) built in the injector body (2). The pressure chamber (7) is 14. impacted upon through a high-pressure supply (6) by fuel (8) 15. that is under system pressure. 16. Fuel injector in accordance with Claim 2, characterised in that, 17. the buncher space (18) is bordered by a buncher space sleeve 18. (21), a ring surface (20) of the first transmission piston (11), a 19. ring surface (39) of the second transmission piston (19) as well 20. as an end face (23) of the fuel-injector mount (3). 21. Fuel injector in accordance with Claim 3, characterised in that 22. the buncher space sleeve (21) is guided at the first transmission 23. piston (11) and impacted upon through a pressure spring (16). 24. Fuel injector in accordance with Claim 3, characterised in that 25. the buncher space (18) is sealed against the pressure chamber 26. (7) through a biting flange (22) that works together with the end 27. face (23) of the fuel-injector mount (3). 28. Fuel injector in accordance with Claim 1, characterised in that, a 29. hydraulic chamber (41) is built between the first transmission 30. piston (11) and the second transmission piston (19) and is 31. hydraulically connected through a balance hole (13) to a 32. pressure chamber (7) within the injector body (2). 33. Fuel injector in accordance with Claim 6, characterised in that a 34. spring element (17) that lies against a contact surface (37) is 35. incorporated within the hydraulic chamber (41) and impacts 36. upon the injection valve element (5) in the closing direction. 37. Fuel injector in accordance with Claim 1, characterised in that, a 38. nozzle chamber supply (24) that connects the pressure 39. chamber (7) to the nozzle chamber (25), branches off from the 40. pressure chamber (7). 41. Fuel injector in accordance with Claim 1, characterised in that 42. guiding of the injection valve element (5) within the fuel-injector 43. mount (3) takes place in a guide section (31) and guiding within 44. the injector body (2) takes place through the transmission 45. pistons (11, 19). 10. Fuel injector in accordance with Claim 1, characterised in that the hydraulic chamber (41) that is connected to a pressure chamber (7) via a balance hole (13) has a contact surface (37) for the spring element (17) which supports itself in a recess (32) of the second transmission piston (19), which has a first ring surface (38) that borders a hydraulic chamber (41).

Documents:

2848-CHENP-2006 AMENDED CLAIMS 09-08-2012.pdf

2848-CHENP-2006 CORRESPONDENCE OTHERS 10-10-2011.pdf

2848-CHENP-2006 EXAMINATION REPORT REPLY RECEIVED 09-08-2012.pdf

2848-CHENP-2006 FORM-3 09-08-2012.pdf

2848-CHENP-2006 OTHER PATENT DOCUMENT 09-08-2012.pdf

2848-CHENP-2006 POWER OF ATTORNEY 09-08-2012.pdf

2848-chenp-2006-abstract.pdf

2848-chenp-2006-claims.pdf

2848-chenp-2006-correspondnece-others.pdf

2848-chenp-2006-description(complete).pdf

2848-chenp-2006-drawings.pdf

2848-chenp-2006-form 1.pdf

2848-chenp-2006-form 26.pdf

2848-chenp-2006-form 3.pdf

2848-chenp-2006-form 5.pdf

2848-chenp-2006-pct.pdf