INJECTOR FOR FUEL INJECTION

Description

[0001] The present invention relates to an injector for injecting fuel, in particular for injecting a gas, preferably for directly injecting hydrogen. The injector can be designed to inject fuel into a combustion chamber of an internal combustion engine.

[0002] As emissions standards become increasingly stringent worldwide and ambitious climate protection goals are set, the environmental requirements for internal combustion engines are steadily increasing. The goal in the foreseeable future is low-emission or even zero-emission drive technologies that meet even the most stringent emissions standards and make a significant contribution to achieving climate protection goals. For technologies that rely on combustion, these goals can only be achieved through the use of climate-neutral, renewably produced fuels that produce no emissions along the entire value chain (so-called "zero-emission" fuels).

[0003] With current conventional gasoline, diesel and gas engines, the requirements for emission-free combustion cannot be met - even when using so-called e-fuels, e.g. a synthetically produced OME fuel, the production of which requires only renewable energy - because the emission of harmful exhaust gases such as nitrogen oxides (NO x ), unburned hydrocarbons (UHC) and soot cannot be completely reduced with current technologies.

[0004] In principle, battery-powered drives comply with the zero-emissions directive during operation and are gaining ground, especially in the passenger car sector. However, if the entire value chain is considered, the production of (lithium) batteries is very energy-intensive and problematic from an environmental perspective, as significant environmental damage occurs, particularly during raw material extraction, and the extraction of the raw materials required for batteries is not sustainable. Furthermore, the power-to-weight ratio of batteries that can be achieved today does not allow their use in machines with high (peak) power requirements.

[0005] Fuel cell-powered engines powered by renewably produced hydrogen meet the specified climate protection targets and are already in use to a very limited extent. However, this concept also has some disadvantages, such as low peak power and low economic efficiency compared to current diesel engines.

[0006] The focus has therefore shifted to hydrogen combustion engines, which represent a promising alternative propulsion system. However, to date, these exist almost exclusively in very small numbers or as demonstrators with a low level of maturity. Hydrogen produced from renewable energies would meet all the requirements of "zero emissions" because it can be burned without emissions.

[0007] In the passenger car sector, for example, hydrogen engines with external mixture formation (PFI = port fuel injection) are found, in which the fuel is thoroughly mixed with air in sufficient time before entering the combustion chamber. Hydrogen engines with direct injection of the fuel into the combustion chamber (internal mixture formation, DI = direct injection) play virtually no role today, but compared to the PFI concept, they offer, among other things, higher efficiency, more stable combustion, and eliminate the risk of backfiring in the intake tract.

[0008] In direct-injection hydrogen engines, a distinction is typically still made regarding the maximum injection pressure in the injector (< 60 bar: low pressure, > 60 bar: high pressure), although the limits are not clearly defined and the transitions are fluid. Higher pressures offer the potential for shortened injection duration in a later compression phase at higher combustion chamber pressures, resulting in increased efficiency and improved combustion stability. However, overall efficiency decreases if compression of the hydrogen is required beforehand.

[0009] If the hydrogen is produced 100% from renewable energy sources, hydrogen combustion engines can operate virtually climate-neutrally. In addition, there are numerous other advantages: Use of known technologies with a high degree of maturity and existing production facilities Unlimited availability of hydrogen through water electrolysis Use of the existing filling station system possible (after appropriate conversion) with fast refueling times (almost) emission-free conversion of hydrogen during combustion possible, as it is CO2-neutral, only minimal CO, UHC, particle and soot emissions (only caused by lubricants in the feed system, below the measuring limit) and only minimal NOx emissions through a suitable combustion process (if necessary with exhaust gas recirculation, SCR catalyst) Significantly lower requirements for hydrogen purity compared to fuel cell drives No need for platinum for production as with fuel cells

[0010] In addition to these numerous advantages over other drive concepts, there are also some challenges that need to be overcome in the development of hydrogen combustion engines: Low molecular weight of hydrogen, resulting in a low density associated with a low volumetric energy density (with a high mass-specific energy density); see Table 1 Provision of a correspondingly high volume flow when injecting hydrogen Corresponding provision of large flow cross-sections in the injector and thus required significantly larger strokes of the actuator than with conventional drive types Accompanying development of a significantly stronger actuator unit with simultaneously limited installation space Tightness of the entire system / prevention of external leaks, especiallyWith regard to safety aspects (risk of fire and explosion due to hydrogen escaping from the system) increased risk of wear on guides of moving components due to the practically non-existent lubricating effect of hydrogen significantly greater tendency of moving components to bounce on mechanical stops in gas injectors compared to injectors with liquid fuels due to low damping effect during gas compression material resistance to hydrogen necessary with regard to the risk of hydrogen embrittlement in mechanically stressed / pressurized components (reduced strength) or due to chemical reaction of the hydrogen with the oxygen present in the copper coil of the actuator (hydrogen disease of the copper) mixture preparation in the combustion chamber / influence on the injection jet / ignition behavior with very small quantities of injection. Table 1: Mass and volume specific calorific value of diesel and hydrogen Diesel Hydrogen (at 25 °C) Calorific value in MJ / kg 43.0 120.0 Calorific value in MJ / m 3 35'819 9.8 at 1 bar 287.7 at 30 bar 2464.4 at 300 bar

[0011] DE 10 2014 224341 A1 shows an injector used in hydrogen combustion engines.

[0012] The aim of the present invention is to at least partially overcome or mitigate the disadvantages listed above. In particular, the aim is to create a fuel injector that exhibits particularly low wear and thus offers improved robustness and durability. Furthermore, it is desirable to create an injector in which the mass flow of the dispensed fuel is easily predictable and not subject to fluctuations, thus achieving a smooth injection rate or injection rate (e.g., by reducing valve bounce).

[0013] At least some or all of the aforementioned objects are achieved with an injector for injecting fuel having all the features of claim 1. Advantageous embodiments of the injector are specified in the dependent claims.

[0014] An injector according to the invention for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprises a fuel supply line for introducing a gaseous fuel under high pressure, an active valve which is actively switchable and is designed to close or open at least one passage in order to selectively open or interrupt a flow connection from the fuel supply line to a region downstream of the active valve, and a passive valve which is arranged downstream of the active valve and is passively switchable into a closing or opening state by different pressure conditions upstream and downstream of the passive valve in order to selectively open or interrupt a flow connection from upstream of the passive valve to a region downstream of the passive valve.The injector is characterized in that a reciprocating plunger (or valve insert) of the passive valve comprises or is a permanent magnet, and a plunger guide is provided for guiding the reciprocating movement of the plunger, which is electrically conductive and non-magnetizable or only weakly magnetizable. Within the scope of the invention, the materials of which the plunger and plunger guide are made can also be interchanged, as recited in claim 1.

[0015] Due to the design with a permanent magnetic tappet and non- / weakly magnetizable, electrically conductive tappet guide, eddy currents are induced in the tappet guide when the valve opens and closes, which in turn induce a magnetic field that counteracts the original magnetic field of the tappet (according to Lenz's law). As a result - in accordance with the principle of the eddy current brake - a magnetic force acts on the tappet during the opening and closing process, opposing the movement, which slows down the movement. This braking force is proportional to the speed at which the tappet moves, i.e. the more it is accelerated by pressure forces and / or spring force, the more the movement is dampened by the induced eddy currents. At the beginning of the movement during opening or closing, the speed is very low, so that there is initially no negative influence on the dynamics of the fuel delivery.With increasing speed and / or increasing distance from the respective stop, the magnetic damping effect increases. This reduces the impact speed of the tappet against a counter-stop. This reduces wear and increases the robustness of the design, as the forces acting on the tappet during impact are reduced. Furthermore, a smooth injection or blow-in rate progression is achieved (due to tappet bouncing in the stroke range, where dethrottlement has not yet taken place, otherwise drops in the discharged fuel rate progression would occur).

[0016] The basic idea of ​​the present invention is therefore to limit the dynamic movement of the tappet of the passive valve by utilizing the magnetic force generated when a permanent magnet is moved in an electrically conductive element. This creates a magnetic force that opposes the movement of the magnet, which can be advantageously used in the injector for injecting fuel.

[0017] According to an advantageous modification of the present invention, it can be provided that in a closed state of the passive valve, the reciprocating tappet of the passive valve is in contact with a stop element in order to seal at least one passage of the stop element.

[0018] The stop element defines at least one opening which, when the tappet is lifted, has a fluid connection to the fuel supply line of the injector, so that the fuel flows through the passive valve. This at least one opening is closed when the tappet rests against the stop element, which can be a valve plate of an injector, for example, thus preventing the flow connection. In order to determine the maximum stroke of the tappet, a counter-stop can also be provided, against which the tappet strikes when it is at its maximum distance from the stop element. The stop element therefore has an opening that can be sealed by the tappet, so that in cooperation with the tappet the valve can be brought into its closed position. The tappet can therefore only move back and forth in a linear movement between the stop and the counter-stop.

[0019] In this case, it can advantageously be provided that the stop element is a valve plate of the injector, wherein the valve plate can preferably be contacted by an armature of the active valve from a first of its flat sides and by the tappet of the passive valve from the opposite second flat side. Typically, an injector has an actively actuated armature, which can be lifted from a closed position, for example, using a coil.

[0020] For example, it can be provided that the armature acts on the valve plate from one side and the tappet acts on the valve plate from the other side in the opposite direction. In this way, at least one passage running through the valve plate can be sealed on both sides, which enables a particularly space-saving design of the injector. The use of the passive valve is advantageous because a very high pressure originating from the discharge opening of the injector (for example generated by a combustion process in a combustion chamber) is not able to lift an armature from a closed position against its closing direction. Such a pressure is prevented by the passive valve because the valve then changes to its closed position or is forced into the closed position by such pressure emanating from the combustion chamber.

[0021] Advantageously, according to the invention, the stop surface of the tappet contacting the stop element, in particular the valve plate, can be designed as a flat seal, conical seal, and / or ball seal. It will be clear to those skilled in the art that a variety of possible contact pairings can lead to a desired sealing effect. However, the flat seal is particularly advantageous because, during an opening process in which the tappet is pushed away from the valve plate or stop element from a closing position, the fuel flow originating from the fuel supply line impinges directly on a flat plate, creating a high back pressure and exerting large pressure forces that open the tappet quickly and reliably.

[0022] According to an optional development of the present invention, it can be provided that the tappet is a permanent magnet or has a permanent magnet whose magnetic poles are arranged offset in the longitudinal direction of the injector.

[0023] The arrangement of the different poles of the permanent magnet offset from the direction of movement of the tappet creates magnetic field lines that largely run parallel to the direction of movement of the tappet (and thus also to the longitudinal direction of the injector). This is necessary to generate corresponding eddy currents in the tappet guide, which—due to the resulting magnetic fields—provide the desired braking effect of the tappet movement.

[0024] According to an optional modification of the present invention, it can be provided that the tappet has the shape of a circular ring in cross section, so that in an open position of the passive valve, a flow of fuel can be carried out in its central recess.

[0025] In a closed position, a face of the tappet, for example, a contour of a circular ring, seals at least one passage of a stop element. The at least one passage is thus covered by the face (contour of the circular ring) and, in the event of direct contact, prevents fuel from flowing downstream of the passive valve.

[0026] Furthermore, according to the present invention, the tappet guide can be provided to surround the tappet circumferentially and preferably extend along the entire maximum possible stroke of the tappet. Preferably, the tappet guide also extends beyond the length of the maximum stroke of the tappet, for example, by more than 5%, more than 10%, or more than 15% of the total stroke length.

[0027] Arranging the plunger guide over the entire maximum possible stroke of the plunger ensures that the desired braking effect occurs precisely in the stop areas of the plunger. It will be clear to those skilled in the art that a two-part or multi-part design of the plunger guide can also be provided, in which, for example, a central area of ​​the plunger guide, viewed in the longitudinal direction, has an interruption so that no braking effect acts on the plunger there.

[0028] Furthermore, according to the invention, the tappet guide can be made of a different material than the injector housing. Thus, the injector housing can have a recess to accommodate the tappet guide. However, it can also be provided that the entire injector housing is made of an electrically conductive material that is not, or only weakly, magnetizable. A separate insertion of a tappet guide into the housing or the relevant housing section can then be omitted.

[0029] According to an advantageous development of the present invention, the tappet guide can be in the form of a sleeve, preferably with the inner diameter of the sleeve corresponding to the outer diameter of the tappet or being no more than 10%, preferably 5%, and more preferably 2% larger than the outer diameter of the tappet. The coordinated dimensions of the inner diameter of the tappet guide and the outer diameter of the tappet (which has or consists of the permanent magnet) ensure that the magnetic field lines emanating from the permanent magnet have to overcome the smallest possible air gap when passing into the tappet guide, which counteracts the magnetic force induced in the tappet guide.

[0030] According to a further advantageous modification of the present invention, it can be provided that the plunger is arranged slidingly in the plunger guide and / or the different poles of the plunger provided with the permanent magnet or of the plunger designed as a permanent magnet are arranged offset from one another in the sliding direction.

[0031] Furthermore, according to the invention, it can be provided that the stop element with which the tappet is in contact in a closed position of the passive valve is made of a non-magnetizable or only weakly magnetizable material.

[0032] The stop element, which can particularly be the injector's valve plate, cannot then be magnetized by the tappet, regardless of the magnetization strength. This is particularly advantageous when the tappet has direct contact with the stop element (the valve plate) in the closed position, so that "sticking" due to magnetic attraction between the valve tappet and the valve plate cannot occur.

[0033] According to a further, optional development of the present invention, a spacer element can be provided between a stop element for the closed position, in particular a valve plate, and the tappet in order to adjust a maximum magnetic force between the stop element and the tappet. Preferably, the spacer element is a disc, a film, or a coating applied to the stop element and / or the tappet. The spacer element is made of a non-magnetic or only weakly magnetic material, in particular a plastic, e.g., polyamide.

[0034] This is particularly advantageous when the stop element, for example the valve plate, is made of a ferromagnetic material that itself becomes magnetic when exposed to a high magnetic field. In order to avoid very high magnetic forces, which typically occur when there is direct contact between the permanent magnet and the stop element, a spacer element is provided that maintains a minimum distance between the permanent magnet and the stop element. The material used to implement the spacer element can typically be a plastic, in particular a polyimide. The tappet and / or the valve plate can also be provided with a corresponding coating. This prevents undesirably high magnetic forces from occurring, which could lead to a magnet being impressed into the ferromagnetic material of the stop element.The spacer element can therefore regulate the maximum permissible magnetic force that may act on the stop element, in particular the valve plate, by ensuring that a minimum distance between the permanent magnet and the stop element is not undercut.

[0035] According to a further advantageous embodiment of the present invention, it can be provided that the tappet guide and the tappet are arranged coaxially to one another, preferably with the tappet guide surrounding the tappet circumferentially.

[0036] Furthermore, according to the invention, the tappet guide and the tappet can each be rotationally symmetrical and have a common axis of rotation or axis of rotation. The common axis of rotation or axis of rotation can run parallel to the longitudinal direction of the injector or be identical to it. Rotationally symmetrical or rotationally symmetrical components are easier to install and simpler to manufacture.

[0037] The invention further relates to an internal combustion engine with a fuel injection, in particular with a gas direct injection, in particular with a hydrogen direct injection, comprising an injector according to one of the variants discussed above.

[0038] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show: Fig. 1: a schematic sectional view of an injector according to the prior art, Fig. 2: a representation of various states of components and pressures in an injector, Fig. 3: a schematic partial sectional view of an injector in the region of the passive valve, Fig. 4a-b: a schematic sectional view of the injector in a closed and an open state, Fig. 5: a schematic partial sectional view of an injector according to the invention in a closed state, Fig. 6: a schematic partial sectional view of the injector according to the invention according to a second embodiment in a closed state, and Fig. 7: a sketchy representation to explain the underlying operating principle of the present invention.

[0039] The following detailed description of the figures of the Fig. 1is explained using an injector for injecting a gaseous fuel, although it will be clear to the person skilled in the art that the invention also includes an injector for injecting another fuel.

[0040] Fig. 1shows a longitudinal section through an injector 1 for injecting a gaseous fuel, for example hydrogen, into a combustion chamber. The injector 1 has an injector housing in which various components of the injector 1 are located. On the connection side, a fuel supply line 2 is provided for introducing a fuel into the injector 1. First, the fuel or another flammable fluid (for example hydrogen) is guided through a bore in a cover 16 running approximately centrally in the injector housing and then through a fluid channel of an armature counterpart 19, a through opening in the armature base 23 and the hollow interior of the armature 7, which is sometimes also called a hollow needle or simply a needle, to the end of the armature 7 remote from the connection side.

[0041] Depending on the position of the armature 7 relative to the valve plate 5, the openings A1 penetrating the valve plate 5 are closed or opened. Fig. 1 In the illustrated state, the passages A1 are closed by the pressing of the armature 7 against the valve plate 5, since the end face of the armature 7 covers the opening contours of the passages A1. To improve the tightness, sealing elements 25 can be provided that run around the opening contours of the passages A1 and contact the end face of the armature 7 in a sealed state. 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 in the injector 1, and there is no downstream flow of fuel beyond the valve plate 5.

[0042] If, however, the passages A1 are opened, which is implemented by the armature 7 being lifted away from the valve plate 5, the fuel introduced into the injector 1 at a certain pressure flows out and exits via the multiple passages A1 on the side of the valve plate 5 spaced apart from the armature 7. After flowing through a passive valve 4 provided in the injector 1, the pressurized fuel flows out of the injector through the injection cap 28. After flowing through the injection cap 28, the fuel delivered by the injector 1 is then typically located outside the injector 1 in a combustion chamber. In addition, a compression of the fuel typically takes place in the combustion chamber 16, where the fuel is then ignited or is ignited.

[0043] The passive valve 4, which is located on the side of the valve plate 5 facing away from the armature 7, serves to keep the very high pressure prevailing in the combustion chamber away from the armature 7. Otherwise, the very high pressure prevailing in the combustion chamber could act on the armature 7 and move it away from its position closing at least one passage A1. In a subsequent operating step of the injector 1, the fuel required for combustion would then no longer be introduced into the combustion chamber, but rather a mixture that has already been at least partially combusted, which could lead to an interruption of the combustion process or, at best, to a reduced performance of the combustion process.

[0044] The passive valve 4 has a valve tappet 6, a valve guide 27, and a valve spring 10, which urges the valve tappet 6 in a closing direction, so that an outflow of fuel via the opening contour A2 of the passive valve 4 only occurs when a pressure prevails on the side of the passive valve 4 facing the valve plate 9 that is greater than the pressure prevailing on the side facing away from the passive valve 4 and the valve plate 5 by at least the restoring force of the valve tappet 6 exerted by the valve spring 10. This prevents fluid from flowing in from the side of the passive valve 4 facing the combustion chamber.

[0045] The armature 7 is movable back and forth in the longitudinal direction of the injector 1. The movement of the armature 7, which can be made in one piece or can consist of an armature base 23 and an armature tip (also called a needle or hollow needle), is controlled by an active valve 3, which in the present illustration is the Fig. 1a solenoid valve. The armature 7 is designed such that it reacts to the magnetic force generated by a coil 8. The coil 8 can optionally be energized in such a way that the resulting magnetic force moves the armature 7 toward the fuel connection 2. This movement causes the armature 7 to be lifted relative to the valve plate 5. This opens the passages A1 in the valve plate 5, allowing fuel to flow through the valve plate 5.

[0046] For precise guidance of the armature 7 along the longitudinal axis of the injector, an armature guide 24 may be provided which circumferentially encloses an outer side of the armature 7.

[0047] An air gap 22 is provided between the armature 7 and the armature counterpart 19, which is closed or reduced when the coil 8 is energized.

[0048] To improve the magnetic flux when implementing the active valve 3 as a solenoid valve, the coil 8 can be surrounded on its outer circumferential side by an iron yoke 21, in which the magnetic field can propagate particularly well. A similar situation applies to the housing component directly surrounding the armature element 5 and the armature counterpart 27, which is also preferably made of a magnetizable material. Thus, it can 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 applies to the armature counterpart 19, which is advantageously also made of a magnetizable material.

[0049] A visual representation of the magnetic field lines is illustrated by the dotted, closed line that runs in a circle around the coil. The magnetic force pulls the armature element 7 (together with the armature base 23) toward the armature counterpart 19, thus lifting it from the valve plate 5 or from the passages A1 penetrating the valve plate 5, allowing fuel to flow toward the passive valve, from where it is ultimately introduced into the combustion chamber via the injection cap 28.

[0050] Fig. 2 shows the basic behavior of injector 1 during injection. In initial position at the time t0 at bottom dead center (BDC) of the cylinder piston, armature 7 and valve tappet 6 are pressed into their respective stops by the pre-tensioned armature spring 17 and passive valve spring 10 respectively, and close the throttle points A1 and A2, which connect the needle chamber with the valve chamber and the valve chamber with the injection chamber when armature 7 and valve tappet 6 are open. The pressure in injector 1 corresponds to the pressure in the supply line, the pressure in the combustion chamber and in the injection chamber corresponds to the boost pressure during the intake phase of the cylinder piston, in which fresh air is sucked into the combustion chamber via the intake valves. The pressure in the valve chamber roughly corresponds to the combustion chamber pressure and depends, among other things, on the armature spring 17, the pressure in the combustion chamber during the phase in which the hot combustion gases are expelled via the exhaust valves of the combustion chamber and, if applicable, preceding injections.The functional representation is simplified below and does not take into account the charge exchange through opening and closing of the intake and exhaust valves of the combustion chamber.

[0051] At the time t 1, a voltage signal is applied by the control unit to the coil 8 of the actuator via the electrical contacts, so that the current F1 in the electrical circuit increases to a defined final level. The current-carrying coil 8 induces a magnetic field in the actuator, whose magnetic field lines spread torus-shaped around the coil (see Fig. 1 ). The magnetic field creates a magnetic force F2 in the air gap between armature 7 and armature counterpart 19, which at the time t2 the armature 7 is attracted to the armature counterpart 19 as soon as the magnetic force F2 exceeds the closing force (sum of the preload force of the armature spring 17 and the pressure forces on the armature 7). The build-up of the magnetic field and thus of the magnetic force F2 is delayed by eddy currents in the iron parts of the magnetic circuit. The armature 7 is integrally or firmly connected to the armature base 23, so that the armature 7 moves uniformly with the armature stroke (or needle stroke) F3. As soon as the sealing element 25 on the valve plate 5 at the time t3 is no longer in contact with the end face of the armature 7, the connection between the needle chamber and the valve chamber is released, allowing fuel to flow from the needle chamber into the valve chamber. This increases the pressure in the valve chamber. As soon as the pressure difference between the valve chamber and the injection chamber corresponds to a force difference on the valve tappet 6 equal to 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 chamber and the injection chamber, allowing fuel to flow from the valve chamber into the injection chamber. This causes a pressure increase in the injection chamber (cf. F8: Pressure in the injection chamber). The fuel flows downstream through the opening(s) A3 in the injection cap 28 into the combustion chamber. The injection cap 28 is designed so that the flow remains in a defined state (spray orientation, entry pulse, spray pattern, etc.) into the combustion chamber. The open state of armature 7 and valve tappet 6 is maintained throughout the remaining current application phase. The current level can be reduced (e.g., by a PWM voltage signal) once armature 7 is fully open and possible bouncing does not cause armature 7 to close. During injection, the engine cylinder is in the compression phase, so the combustion chamber pressure F5 increases steadily.

[0052] To stop the blowing process, the power supply is stopped by the control unit so that the current F1 through the coil 8 is reduced to zero (time t 4 ). Due to the eddy currents, the magnetic force F2 also decreases with a time delay. As soon as the magnetic force F2 is less 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 (time t5 ); see also F3, F4. If the front side of the armature 7 hits the sealing element 25 of the valve plate 5, the connection between the needle chamber and the valve chamber is severed and the fuel flow from the needle chamber into the valve chamber is interrupted (time t 6 ). This causes the pressure in the valve chamber F7 to drop. If the pressure difference between the valve chamber F7 and the injection chamber F8 corresponds to a force difference on the valve tappet 6 equal to the valve spring force, the valve tappet 6 moves back to 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 injection chamber, so that the fuel connection between the valve chamber and the injection chamber is interrupted (possibly after a phase of bouncing of the tappet on the valve seat 27) (times t 6 - t 7 ) .The injection process is now complete. During the further compression phase of the combustion chamber up to top dead center (TDC) in the period t 7 - t 8, the air-fuel mixture is compressed in the injection chamber, while it is expanded in the subsequent expansion phase (period t 8 - t 9 ), whereby the further intermediate increase in the combustion chamber pressure F5 due to combustion is not shown here for the sake of simplicity. If the pressure in the combustion chamber drops so far that the difference between the pressure forces on the valve tappet 6 corresponds to the preload force of the armature spring 17 (time t 9 ), the valve tappet 6 opens again briefly, so that part of the fuel in the valve chamber escapes into the combustion chamber. This process depends on the spring force and can occur repeatedly (period t 9 - t 10 ).

[0053] 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 passages A3 of the injection cap 28 is indicated by F9, F10 and F11 respectively.

[0054] Fig. 3 shows a partial sectional view of an injector 1 with focus on the passive valve 4. 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.

[0055] The tappet 6 is urged into its closed position by a spring element 10, with the spring element 10 being supported on a counter-stop arranged downstream. It can also be seen that the seal created by the tappet 6 on the underside of the valve plate 5 is a flat seal or flat seat. The illustrated configuration with a direct seal on the underside of the valve plate 5 is very space-saving and enables very short injectors 1 in the longitudinal direction.

[0056] Fig. 4a and Fig. 4b show a closed state ( Fig. 4a ) and an open state ( Fig. 4b ) of the injector. In Fig. 4bThe flow of fuel from the fuel supply line to the injection cap is shown with arrows. Furthermore, the movement of the components from their respective closed positions, which is necessary to create the fluid connection between the fuel supply line and the injection cap, is also highlighted by arrows. It can be seen that the armature has been lifted from its closed position due to energization of the coil, which causes the high-pressure fuel to force the tappet of the passive valve out of its closed position. Once the components have moved accordingly, the high-pressure fuel can flow out of injector 1 from the fuel supply line to the injection cap.

[0057] Fig. 5shows a first embodiment of the present invention, wherein the movable plunger 6 is also urged into its closed position by means of a spring element 10. It should be noted that other implementations of the urging element, which in this case is designed by means of a spring element, are also possible. As can be seen, the plunger 6 is implemented by a permanent magnet 11, whose magnetic poles 13, 14 are arranged offset along the direction of movement. The south pole 13 is therefore arranged, for example, on the side spaced from the stop element 5, whereas the north pole 14 is provided on the side of the plunger 6 facing the stop element 5. The magnetic field lines 12 formed by the permanent magnet 11 are in Fig. 5represented by a dotted, closed circle. If the tappet 6 is moved along its direction of movement, i.e. lifted from the valve plate 5 or moved in the direction thereof, the magnetic field emanating from the tappet 6 generates eddy currents in the tappet guide 9. These eddy currents, in turn, generate a magnetic force that opposes the direction of movement of the tappet 6, so that the tappet is decelerated. This particularly reduces the bouncing of the tappet 6 when it contacts the valve plate 5 or the counter-stop, which leads to better predictability and a more uniform output of the fuel rate delivered by the injector. The ripple in the fuel rate generated by the bouncing, as can be seen, for example, in Fig. 2 is evident (cf. F9 and F10) therefore no longer arises.

[0058] The plunger 6, designed as a permanent magnet, is enclosed on the circumference by the plunger guide 9, wherein the plunger guide 9 has the shape of a sleeve. The sleeve 9 can be designed such that it completely encloses the plunger 6 on the circumference. Furthermore, the plunger guide 9 is arranged continuously over the entire length of the two stop points of the plunger 6, which are spaced apart from one another in the longitudinal direction, and preferably extends beyond them. Thus, on the counter-stop, the plunger guide 9 is also provided in a more distant region in the longitudinal direction, which can never come into direct contact with the plunger 6, although this is intentional because the magnetic field emanating from the plunger 6 can also extend into more distant sections. Accordingly, according to the invention, it can be provided that the plunger guide extends not only within the stroke range of the plunger 6, but also beyond this.

[0059] Fig. 6shows a schematic partial sectional view of the injector according to the invention according to a second embodiment in a closed state. The depicted illustration is comparable to that of Fig. 5similar, but now in the intermediate area between the tappet 6 and the valve plate 5 (stop element) a spacer element 15 is provided, which regulates the magnetic force of the tappet 6 acting on the valve plate 5. If the valve plate 5 is made of a ferromagnetic material, a magnetic field can be impressed into the ferromagnetic material upon continuous and repeated physical contact with a permanent magnet, so that an increased magnetic force is generated, which prevents the tappet 6 from opening from its closed position. In the worst case scenario, the magnetic field thus impressed can then cause the tappet 6 to adhere to the valve plate 5 during an actual opening process, so that the desired opening of the valve can no longer be achieved.To prevent such sticking, a spacer element 15 made of a non-magnetizable or only weakly magnetizable material can be arranged between the tappet 6 and the valve plate 5. The spacer element can be disc-shaped or implemented via a coating or film on an end face of the valve plate 5 or the tappet 6. Plastic, such as polyimide, is particularly suitable as a material for the spacer element.

[0060] Fig. 7is a sketch to explain the underlying operating principle of the eddy current brake used for the present invention. It shows the tappet guide 9 and the permanent magnet 11 arranged therein, which represents the tappet 6. If the permanent magnet 11 is now moved, the magnetic field 12 of the permanent magnet 11 causes eddy currents 29 to be induced in the valve guide 9. These eddy currents 29, in turn—like any movement of a charged particle—create a corresponding magnetic field 30 that opposes the magnetic field of the moving permanent magnet 11, so that the movement of the permanent magnet 11 (represented by the thick black arrow) is braked. This effect is utilized during the movement of the tappet 6 in the passive valve to prevent the tappet 6 from traveling at high speed when it strikes a stop or counter-stop, thereby reducing bounce.This also prevents excessive mechanical stress on the plunger 6 caused by unbraked impact. Reducing the high impact speed results in the plunger having a longer service life and improved fatigue strength, making the overall system more robust. List of reference symbols:

[0061] 1 Injector 2 Fuel supply line 3 Active valve 4 Passive valve 5 Valve plate 6 Tappet / valve insert 7 Armature 8 Coil 9 Tappet guide / valve insert guide 10 Spring element 11 Permanent magnet 12 Magnetic field lines 13 Magnetic south pole 14 Magnetic north pole 15 Spacer element 16 Housing cover 17 Armature spring 18 Pole tube 19 Armature counterpart 20 Bypass 21 Iron return 22 Air gap 23 Armature base 24 Armature guide / needle guide 25 Sealing element 26 Injection tube 27 Valve guide 28 Injection cap A1 Valve plate passage A2 Tappet passage A3 Injection cap passage

Claims

1. Injector (1) for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprising: a fuel feed line (2) for introducing a fuel, in particular a gaseous fuel, under high pressure, an active valve (3) which can be actively switched and is configured to close or open at least one passage (A1) in order to selectively open or interrupt a flow connection from the fuel feed line (2) to an area downstream of the active valve (3), and a passive valve (4) which is arranged downstream of the active valve (3) and can be passively switched into a closing state or releasing state by different pressure ratios applied upstream and downstream of the passive valve (4) in order to optionally release or interrupt a flow connection from upstream of the passive valve (4) to an area downstream of the passive valve (4), characterized in that a reciprocating tappet (6) of the passive valve (4) comprises a permanent magnet or is a permanent magnet, and a tappet guide (9) is provided for guiding the reciprocating movement of the tappet (6), which is electrically conductive and non-magnetizable or only weakly magnetizable, or a reciprocating tappet (6) of the passive valve (4) is electrically conductive and non-magnetizable or only weakly magnetizable, and a tappet guide (9) is provided for guiding the reciprocating movement of the tappet (6), which comprises a permanent magnet or is a permanent magnet.

2. Injector (1) according to the preceding claim 1, wherein in a closed state of the passive valve (4) the reciprocating tappet (6) of the passive valve (4) is in contact with a stop element in order to seal off at least one passage (A1) of the stop element.

3. Injector (1) according to the preceding claim 2, wherein the stop element is a valve plate (5), wherein the valve plate (5) can preferably be contacted from one of its flat sides by an armature of the active valve (3) and from the opposite flat side by the tappet (6) of the passive valve (4).

4. Injector (1) according to any one of the preceding claims 2 or 3, wherein the stop surface of the tappet (6) contacting the stop element, in particular the valve plate (5), is configured as a flat seal, cone seal and / or ball seal.

5. Injector (1) according to any one of the preceding claims, wherein the tappet (6) is a permanent magnet or comprises a permanent magnet whose magnetic poles are arranged offset in the longitudinal direction of the injector (1).

6. Injector (1) according to any one of the preceding claims, wherein the tappet (6) has the shape of a circular ring in cross-section, so that in an open position of the passive valve (4) a flow of fuel can be passed through in its central recess.

7. Injector (1) according to any one of the preceding claims, wherein the tappet guide (9) surrounds the tappet (6) on the circumferential side and preferably extends along the entire maximum possible stroke of the tappet (6).

8. Injector (1) according to any one of the preceding claims, wherein the tappet guide (9) is made of a different material than the housing of the injector (1).

9. Injector (1) according to any one of the preceding claims, wherein the tappet guide (9) has the shape of a sleeve, preferably wherein the inner diameter of the sleeve corresponds to the outer diameter of the tappet (6) or is not more than 10 %, preferably 5 %, more preferably 2 % larger than the outer diameter of the tappet (6).

10. Injector (1) according to any one of the preceding claims, wherein the tappet (6) is arranged slidingly in the tappet device (9) and / or the different poles of the tappet (6) provided with the permanent magnet or of the tappet (6) configured as a permanent magnet are arranged offset with respect to one another in the sliding direction.

11. Injector (1) according to any one of the preceding claims, wherein the stop element, with which the tappet (6) is in contact in a closed position of the passive valve (4), is made of a non-magnetizable or only weakly magnetizable material.

12. Injector (1) according to any one of the preceding claims, wherein a spacer element (15) is provided between a stop element for the closed position, in particular a valve plate (5), and the tappet (6), in order to set a maximum magnetic force between the stop element and the tappet (6), wherein preferably the spacer element (15) is a disk, a foil or a coating attached to the stop element and / or the tappet (6), which is made of a non-magnetic or only weakly magnetic material, in particular a plastic, for example polyimide.

13. Injector (1) according to any one of the preceding claims, wherein the tappet guide (9) and the tappet (6) are arranged coaxially to each other.

14. Injector (1) according to any one of the preceding claims, wherein the tappet guide (9) and the tappet (6) are each configured to be rotationally symmetrical and have a common axis of rotation.

15. Internal combustion engine with a fuel injection system, in particular with a gas direct injection system, in particular with a hydrogen direct injection system, comprising an injector (1) according to any one of the preceding claims 1-14.