INJECTOR FOR INJECTING FUEL

Abstract

The invention relates to an injector for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprising a fuel supply line for introducing a highly pressurized gaseous fuel, an active valve which can be actively shut off and which is designed to close or release at least one passage on a first face of a valve plate in order to selectively release or interrupt a fluidic connection between the fuel supply line and a region which is downstream of the first face of the valve plate, and a passive valve which is arranged downstream of the valve plate and can be passively switched to a closing or releasing state as a result of different pressure ratios upstream and downstream of the passive valve.

Claims

1. Injector for injecting fuel, comprising: a fuel supply line for introducing gaseous fuel, an active valve which is actively switchable and is designed to close or release at least one passage on a first side of a valve plate, in order to selectively release or interrupt a flow connection from the fuel supply line to a region downstream of the first side of the valve plate, and a passive valve which is arranged downstream of the valve plate and is switchable passively into a closing or releasing state by different pressure ratios prevailing upstream and downstream of the passive valve, wherein the passive valve is designed to close or release the at least one passage on a second side of the valve plate facing away from the first side with a tappet, in order to selectively release or interrupt a flow connection between the second side of the valve plate and a region downstream of the passive valve.

2. Injector according to claim 1, wherein in a closed state of the passive valve the tappet of the passive valve, which is movable back and forth, is in contact with the second side of the valve plate, in order to seal the at least one passage of the valve plate.

3. Injector according to claim 2, wherein in a closed state of the passive valve the tappet is directly in contact with the second side of the valve plate or indirectly in contact therewith via an intermediate element.

4. Injector according to claim 1, wherein in a closed state of the active valve an armature of the active valve that is movable back and forth is in contact with the first side of the valve plate, in order to seal the at least one passage of the valve plate.

5. Injector according to claim 4, wherein in a closed state of the active valve the armature is directly in contact with the first side of the valve plate or is indirectly in contact therewith via an intermediate element [(25)].

6. Injector according to claim 1, wherein the stop of the tappet that contacts the valve plate is designed, together with the second side of the valve plate, as a flat seal, a conical seal and/or a spherical seal.

7. Injector according to claim 1, further comprising a pushing device which is designed to push the tappet of the passive valve towards the valve plate, into the closed position.

8. Injector according to claim 7, wherein the pushing device comprises a spring element.

9. Injector according to claim 1, wherein an intermediate element is arranged between the tappet and the valve plate, which element, in a closed position of the passive valve, is contacted on one side by the tappet and on a side opposite thereto by the valve plate.

10. Injector according to claim 9, wherein the intermediate element is made of a flexible material in order to reduce bouncing of the tappet in the case of an impact on the valve plate.

11. Injector according to claim 9, wherein the intermediate element is made of a flexible material that comprises a ceramic or is made of a ceramic.

12. Injector according to claim 9, wherein the intermediate element comprises or is a coating arranged on the end face of the tappet facing the valve plate, and/or comprises or is a coating arranged on the end face of the valve plate facing the tappet.

13. Injector according to claim 9, wherein the intermediate element is fastened on the tappet and/or the valve plate, or is arranged so as to be freely movable between the tappet and the valve plate.

14. Injector according to claim 1, wherein a counter stop that limits the maximum stroke of the tappet from the valve plate is provided.

15. Internal combustion engine having fuel injection, having direct gas injection, comprising an injector according to claim 1.

16. Injector according to claim 4, wherein the injector further comprises a coil which is designed to move the armature out of its closed position by means of magnetic force.

17. Injector according to claim 14, wherein the counter stop is provided with at least one damping element, in order to damp an impact of the tappet and reduce bouncing.

Description

[0049] Further features, details and advantages of the invention will become clear on the basis of the following description of the figures, in which:

[0050] FIG. 1: is a schematic sectional view of an injector according to the prior art,

[0051] FIG. 2: shows various states of components and pressures in an injector;

[0052] FIG. 3: is a schematic partial sectional view of an injector according to the invention in the region of the valve plate,

[0053] FIG. 4a-b: are schematic sectional views of the injector according to the invention in a closed and an open state,

[0054] FIG. 5: is a schematic partial sectional view of an injector according to the invention, according to a second embodiment, in a closed state,

[0055] FIG. 6: is a schematic partial sectional view of the injector according to the invention, according to a third embodiment, in a closed state, and

[0056] FIG. 7: is a schematic partial sectional view of the injector according to the invention, according to a fourth embodiment, in a closed state.

[0057] The following detailed figure description of FIG. 1 is explained on the basis of an injector for blowing in a gaseous fuel, wherein it is clear to a person skilled in the art, however, that the invention also comprises an injector for injecting another fuel.

[0058] In this case, FIG. 1 is a longitudinal sectional view of an injector 1 for blowing a gaseous fuel, for example hydrogen, into a combustion chamber. In this case, the injector 1 has an injector housing in which different components of the injector 1 are located. On the connection side, a fuel supply line 2 for introducing a fuel into the injector 1 is provided. Initially, in this case, the fuel or another combustible fluid (for example a hydrogen) is conducted through a drilled hole of a cover 16, extending approximately centrally in the injector housing, and subsequently through a fluid channel of an armature mating piece 19, a through-opening of the armature base 23, and a hollow interior of the armature 7, which is sometimes also referred to as a hollow needle or simply just needle, to the end of the armature 7 remote from the connection side.

[0059] Depending on the position of the armature 7 relative to the valve plate 5, the openings A1 penetrating the valve pate 5 are closed or released. In the state shown in FIG. 1, the passages A1 are close by pressing the armature 7 against the valve plate 5, since the end face of the armature 7 covers the opening contours of the passages A1. In order to improve the tightness, sealing elements 25 can be provided, which extend around the opening contours of the passages A1 and, in a sealed state, contact the end face of the armature 7. If the passages A1 are closed by the end face of the armature 7, the fluid flow of the fuel is stopped at this point of the injector 1, and there is no downstream flow of fuel on the other side of the valve plate 5.

[0060] If, in contrast, the passages A1 are released, which is implemented by raising the armature 7 away from the valve plate 5, the fuel, introduced into the injector 1 at a certain pressure, flows out and escapes on the side of the valve plate 5 spaced apart from the armature 7, via the plurality of passages A1. After flowing through a passive valve 4, which is provided in the injector 1, the pressurized fuel flows out of the injector, through the blow-in cap 28. After flowing through the blow-in cap 28, the fuel output via the injector 1 is then typically located outside the injector 1, in a combustion chamber. Furthermore, compression of the fuel typically takes place in the combustion chamber 16, where the fuel then ignites or is ignited.

[0061] The passive valve 4, which is located on the side of the valve plate 5 remote from the armature 7, serves to keep a very high pressure, prevailing in the combustion chamber, away from the armature 7. Otherwise, it could be the case that the very high pressure prevailing in the combustion chamber acts on the armature 7 and moves it away, out of its position closing the at least one passage A1. In the following work step of the injector 1, the fuel required for the combustion would then no longer be introduced into the combustion chamber, but rather a mixture that is already combusted at least in part, which can lead to an interruption of the combustion process or, at best, to a lower power of the combustion process.

[0062] In this case, the passive valve 4 comprises a valve tappet 6, a valve guide 27, and a valve spring 10 which pushes the valve tappet 6 into a closed position, such that an outflow of fuel via the opening contour A2 of the passive valve 4 occurs only when a pressure prevails on the side of the passive valve 4 facing the valve plate 5 which is greater, at least by the restoring force of the valve tappet 6 exerted by the valve spring 10, than the pressure prevailing on the side facing away from the passive valve 4 towards the valve plate 5. An inflow of a fluid from the side of the passive valve 4 facing the combustion chamber is thereby prevented.

[0063] Deviating from the illustrative drawings, it can be provided that the opening contour is implemented by a single drilled hole, preferably a single central drilled hole, through which the flow of the gaseous fuel is guided the passive valve. Providing just one drilled hole in the passive valve can be advantageous with respect to the necessary production costs of the passive valve and any occurring turbulence during flow guidance.

[0064] The armature 7 is movable back and forth in the longitudinal direction of the injector 1. In this case, the movement of the armature 7, which can be formed in one piece or can consist of an armature base 23 and an armature tip (also referred to as needle or hollow needle), is controlled via an active valve 3, which, in the present illustration of FIG. 1, is a solenoid valve. In this case, the armature 7 is designed such that it reacts to the magnetic force generated by a coil 8. In this case, current can selectively flow through the coil 8, such that the magnetic force resulting in the process moves the armature 7 in the direction of the fuel connection 2. This movement results in the armature 7 being raised relative to the valve plate 5. As a result, the passages A1 in the valve plate 5 are released, such that fuel can flow through the valve plate 5.

[0065] For precise guidance of the armature 7 along the longitudinal axis of the injector or an armature guide 24 can be provided, which peripherally surrounds an outside of the armature 7.

[0066] An air gap 22 is provided between the armature 7 and the armature mating piece 19, which gap is closed or reduced when the coil 8 is energized.

[0067] In order to improve the magnetic flux 12 when the active valve 3 is implemented as a solenoid valve, the coil 8 can be surrounded, on its peripheral outside, by a magnetic yoke 21, in which the magnetic field can propagate particularly well. The situation is similar in the case of the housing component that directly surrounds the armature element 5 and the armature mating piece 27, which housing component likewise preferably consists of a magnetizable material. It may thus be advantageous if the pole tube 18, which is a component of the injector housing 2, is also made of iron or another ferromagnetic material. The same also applies of the armature mating piece 19 which advantageously also consists of a magnetizable material.

[0068] A visualized illustration of the magnetic field lines 12 is illustrated in each case by a dotted, closed line, which extends around the coil in a circular manner. The magnetic force pulls the armature element 7 (together with the armature base 23) towards the armature mating piece 19 and thus is raised from the valve plate 5 or from the passages A1 penetrating the valve plate 5, such that an inflow of fuel to the passive valve can occur, from where fuel is ultimately introduced into the combustion chamber, via the blow-in cap 28.

[0069] FIG. 2 shows the fundamental behavior of the injector 1 during blowing in. In the starting position, at the timepoint to at the lower dead center (UT) of the cylinder piston, the armature 7 and valve tappet 6 are pushed into their respective stop by the pretensioned armature spring 17 or passive valve spring 10 and close the throttle points A1 and A2 which connect the needle space with the valve space, and the valve space with the blow-in chamber, respectively, in the open state of the armature 7 or valve tappet 6. The pressure in the injector 1 corresponds to the pressure in the supply line, and the pressure in the combustion chamber and in the blow-in chamber corresponds to the boost pressure during the suction phase of the cylinder piston, in which fresh air is suctioned into the combustion chamber via the inlet valves. The pressure in the valve space corresponds approximately to the combustion chamber pressure, and depends inter alia on the armature spring 17, the pressure in the combustion chamber during the phase of emission of the hot combustion gases via the outlet valves of the combustion chamber, and possibly preceding blowing-in. The functional representation below is simplified and does not take into account the load alternation by opening and closing the inlet and outlet valves of the combustion chamber.

[0070] At the timepoint t.sub.1, the actuator device applies a voltage signal to the coil 8 of the actuator via the electrical contacts, such that the current F1 in the electrical circuit rises to a defined final level. The coil 8 through which current flows induces a magnetic field 12 in the actuator, the magnetic field lines of which propagate toroidally around the coil (see FIG. 1). The magnetic field 12 builds up a magnetic force F2 in the air gap between the armature 7 and the armature mating piece 19, as a result of which, at the timepoint 12, the armature 7 is drawn to the armature mating piece 19, as soon as the magnetic force F2 exceeds the closing force (sum of the preload force of the armature spring 17 and the compressive forces on the armature 7). In this case, the building up of the magnetic field, and thus the magnetic force F2, is delayed by eddy currents in the iron parts of the magnetic circuit. The armature 7 is integrally or rigidly connected to the armature base 23, such that the armature 7 moves uniformly with the armature stroke (or also: needle stroke) F3. As soon as the sealing element 25 on the valve plate 5 at the timepoint 13 is no longer in contact with the end face of the armature 7, the connection between the needle space and the valve space is released, such that the fuel flows from the needle space into the valve space. As a result, the pressure in the valve space increases. As soon as the pressure difference between the valve space and the blow-in chamber corresponds to a force difference on the valve tappet 6 of the same magnitude as the preload force of the valve spring 10, the passive valve 4 opens, i.e. the valve tappet 6 moves away from the seat along a valve tappet stroke F4 and releases the connection between the valve space and the blow-in chamber, such that fuel flows from the valve space into the blow-in chamber. This results in a pressure increase in the blow-in chamber (cf. F8: pressure in the blow-in chamber). The fuel flows further, downstream, through the opening(s) A3 in the blow-in cap 28 into the combustion chamber. In this case the blow-in cap 28 is designed such that the flow can be introduced into the combustion chamber in a defined state (jet orientation, inflow momentum, jet pattern, etc.). The open state of the armature 7 and valve tappet 6 is maintained during the entire remaining energization phase. The current level can be reduced (e.g. by a PWM voltage signal) as soon as the armature 7 is fully open and possible bouncing does not lead to closing of the armature 7. During blowing in, the cylinder of the engine is in the compression phase, such that the combustion chamber pressure F5 rises continually.

[0071] In order to end the blow-in procedure, the voltage supply is ended by the controller, such that the current F1 through the coil 8 is reduced to zero (timepoint t.sub.4). On account of the eddy currents the magnetic force F2 also reduces, in a temporally delayed manner. As soon as the magnetic force F2 is lower than the sum of the closing force of the armature spring 17 and the hydraulic forces on the armature 7, the armature 7 begins to close uniformly (timepoint t.sub.5); cf. also F3, F4. If the end face of the armature 7 strikes the sealing element 25 of the valve plate 5, then the connection between the needle space and the valve space is separated and the fuel flow from the needle space into the valve space is interrupted (timepoint t.sub.6). As a result, the pressure in the valve space F7 reduces. When the pressure difference between the valve space F7 and the blow-in chamber F8 corresponds to a force difference on the valve tappet 6 of the same magnitude as the valve spring force, the valve tappet 6 moves back into its closed position on the valve seat 27 and is pressed against the seat 27 by the increasing pressure F5 in the combustion chamber and thus in the blow-in chamber, such that the fuel connection between the valve space and the blow-in chamber (optionally after a phase of bouncing of the tappet on the valve seat 27) is interrupted (timepoints t.sub.6-t.sub.7). The blow-in procedure is thus concluded. During the further compression phase of the combustion chamber, up to the upper dead center (OT) in the time period t.sub.7-t.sub.8, the air/fuel mixture is compressed in the blow-in chamber, while it relaxes in the subsequent expansion phase (time period t.sub.8-t.sub.9), wherein the further interim increase in the combustion chamber pressure F5 on account of combustion is not shown here, for the sake of simplicity. If the pressure in the combustion chamber drops to such an extent that the difference between compressive forces on the valve tappet 6 corresponds to the preload force of the armature spring 17 (timepoint t.sub.9), then the valve tappet 6 opens again briefly, such that a portion of the fuel present in the valve space escapes into the combustion chamber. This procedure is dependent on the spring fore and can occur repeatedly (time period t.sub.9-t.sub.10).

[0072] In this case, the respective mass flow of the fuel via the passages A1 of the valve plate 5, the passages A2 of the tappet 6, and the and the passages A3 of the blow-in cap 28 is indicated by F9, F10 and F11, respectively.

[0073] FIG. 3 is a partial sectional view of an injector 1 according to the present invention, focusing on the passive valve 4 and the valve plate 5. It can be seen that the tappet 6 of the passive valve 4 is provided on an underside of the valve plate 5 and seals the passages A1 provided in the valve plate 5 by direct contact. In this case, on the other side of the valve plate 5, depending on the position of the armature 7 (or also: armature needle or simply needle) the at least one passage A1 is also selectively closed or released by the valve plate 5. Since the valve plate 5 can into contact from two sides with respective valve inserts, specifically the tappet 6 and the armature 7, a two-sided valve is disclosed which is opened only when both valve inserts (tappet 6 and armature 7) are in the open position. It can thus be seen that one end of the at least one passage A1 can be closed by the armature 7, and the other end of the at least one passage A1 can be closed by the tappet 6. In this case, the closing forces of the two valve inserts act antiparallel to one another, such that a force for raising a respective valve insert (armature 7 and tappet 6) must in each case be directed away from the valve plate 5.

[0074] In this case, the tappet 6 is pushed into its closed position by a spring element 10, wherein the spring element 10 is supported on a mating stop arranged downstream, which is rigidly arranged in the injector 1. It can furthermore be seen that the seal, implemented by the tappet 6, on the underside of the valve plate 5 is a flat seal or a flat seat 13.

[0075] The armature 7 is also pushed towards the valve plate 5 with a certain force, which is typically exerted via an armature spring 17. In this case, the force exerted by the armature spring 17 on the armature 7 acts in the opposite direction from the force which is exerted by the spring element for pushing the tappet 6 into its closed position.

[0076] In this case, the configuration shown, having direct sealing on the underside of the valve plate 5, is very space-saving and allows for injectors 1 that are very short in the longitudinal direction.

[0077] In this case, FIG. 4a and FIG. 4b show a closed state (FIG. 4a) and an open state (FIG. 4b) of the injector. In this case, FIG. 4b shows, by means of arrows, the flow of the fuel proceeding from the fuel supply line to the blow-in cap. Furthermore, the necessary movement of the components out of their respective closed position, which is required for establishing the fluid connection between the fuel supply line and the blow-in cap, is highlighted by arrows. It can be seen that the armature is raised out of its closed position on account of energization of the coil, which results in the fuel, which is under high pressure, pushing the tappet of the passive valve out of its closed position. If a corresponding movement of the components has taken place, the fuel, which is under high pressure, can flow out of the injector 1, from the fuel supply line to the blow-in cap.

[0078] FIG. 5 is a schematic partial sectional view of an injector according to the invention, according to a second embodiment, in a closed state. Corresponding shaping of the tappet 6 and the underside of the valve plate 5 is visible, such that the seal, produced by pushing the tappet 6 onto the underside of the valve plate 5, is implemented by a conical sealing seat or a spherical sealing seat. An advantage of this is that these types of sealing seats allow for reliable sealing and are low-wear.

[0079] FIG. 6 shows a further embodiment of the present invention, in which an intermediate element 11 is arranged in the intermediate region between the tappet 6 and the valve plate 5, which intermediate element preferably covers or surrounds a contour of the at least one passage A1 of the valve plate 5 that faces towards the tappet 6. In this case, it can be provided that the intermediate element 11 is made of a flexible material, in order to damp an impact of the tappet 6 in the case of a movement in the direction of the valve plate 5. In this case, an elastomer lends itself as an implementation, by way of example, for the flexible material, which elastomer has very good damping properties.

[0080] Alternatively, or in addition to the embodiment as flexible material, it can also be provided that the intermediate element 11 has a thermally insulating property or comprises a thermally insulating material or consists of said material. Furthermore, the intermediate element can also be a coating that is applied to the tappet 6 and/or the valve plate 5, wherein alternatively thereto, however, it is also possible for the intermediate element 11 to be arranged so as to be freely movable in the intermediate space, between the tappet 6 and the valve plate 5.

[0081] Providing the intermediate element 11 is advantageous in particular with respect to the fatigue strength of the sealing connection between the tappet 6 and the valve plate 5 and protects the components which are typically subjected to high load in the case of impact between the tappet 6 and the valve plate 5.

[0082] FIG. 7 shows a further modification of the concept according to the invention, in which the mating stop 9, which defines the maximum stroke of the tappet 6 away from the valve plate 5, comprises a damping element 15. Said damping element 15 is arranged on the mating stop 9 in such a way that a tappet 6 moving towards the mating stop 9 is damped by the damping element 15 before its movement is completely stopped. This reduces the bouncing of the tappet 6 when opening the passive valve 4, wherein furthermore the high material loading, associated with the bouncing, are also reduced on account of the damping element 15.

[0083] It is clear to a person skilled in the art that the various embodiments of the present invention explained in the figures can be combined with one another in part or completely.

LIST OF REFERENCE CHARACTERS

[0084] 1 injector [0085] 2 fuel supply line [0086] 3 active valve [0087] 4 passive valve [0088] 5 valve plate [0089] 6 tappet/valve insert [0090] 7 armature [0091] 8 coil [0092] 9 mating stop [0093] 10 spring element [0094] 11 intermediate element [0095] 12 magnetic field lines [0096] 13 flat seal/flat seat [0097] 14 conical sealing seat/spherical sealing seat [0098] 15 damping element [0099] 16 housing cover [0100] 17 armature spring [0101] 18 pole tube [0102] 19 armature mating piece [0103] 20 bypass [0104] 21 magnetic yoke [0105] 22 air gap [0106] 23 armature base [0107] 24 armature guide/needle guide [0108] 25 sealing element [0109] 26 blow-in pipe [0110] 27 valve guide [0111] 28 blow-in cap [0112] A1 passage of the valve plate [0113] A2 passage of the tappet [0114] A3 passage of the blow-in cap