FUEL INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE, IN PARTICULAR FOR A HYDROGEN COMBUSTION ENGINE

Description

[0001] The invention relates to a fuel injection device for an internal combustion engine comprising at least one rail which is a component of two fuel paths.

[0002] Due to well-known advantages, fuel is often supplied to the intake manifold or combustion chambers in internal combustion engines under greatly increased pressure. If the engine design allows for this, the internal combustion engine often has a pressure accumulator called a rail, to which the fuel is initially supplied. Typically, a common rail, referred to as the central rail, is used for a group of several or all combustion chambers of the internal combustion engine.

[0003] If the target output of the internal combustion engine increases, the opening duration of the specific injector through which the current fuel supply to the respective combustion chamber is to take place is extended. In the case of an internal combustion engine that uses liquid fuel, the resulting drop in rail pressure remains within certain limits, even with an extended injection duration and thus an increased fuel delivery rate from the rail, which allows for compensation with regard to the fuel supply rate.

[0004] In order to achieve more precise adherence to the desired fuel metering, this additional opening duration of the injector can in turn include the period that includes the decrease in fuel mass flow caused by the drop in rail pressure. After a certain period of time, the rail pump delivers a higher amount of fuel, which leads to the rail pressure setpoint being reached again, even if the increased fuel consumption persists. Typically, a rail pump in delivery mode always delivers a quantity of fuel to the rail that is at least slightly greater than the instantaneous fuel consumption of the internal combustion engine. If the rail pressure has reached or already exceeded its setpoint, the excess fuel is diverted from the rail and usually returned to the primary fuel tank.

[0005] Since liquids can be compressed much more easily than gases to a pressure level of a few tens of bar up to many hundreds of bar, at the same time they have a significantly higher volumetric density than gases and the widely used liquid fuels (diesel and diesel-like fuels, petrol, LPG, etc.) can be practically stored at atmospheric or slightly higher pressure at normal ambient temperatures in a primary fuel tank that is simple in design and handling, the above-mentioned measures are technically still relatively easy to implement with regard to the possibility of quickly increasing the fuel supply rate for the aforementioned fuels. In other words: Under the assumption of an existing orWith the mandatory high-pressure fuel injection, the additional effort required to increase the supply of liquid fuel within a short period of time is comparatively low.

[0006] A rapid increase in the mechanical power output of an internal combustion engine also requires a correspondingly dynamic increase in the air flow rate. If the request for a transient power increase occurs during an initial situation in which the current air supply to the combustion chambers is limited by throttling in the air path and / or the addition of exhaust gas, at least a certain increase in the air supply is possible relatively quickly. Furthermore, certain aids are known with which the air supply can be increased significantly and relatively quickly, e.g., by means of an electrically driven compressor integrated into the air path.

[0007] In an internal combustion engine powered by one of the liquid fuels mentioned above, its dynamic performance is essentially attributable to the limited rate of increase in the air supply. In contrast, a limited rate of increase in the fuel supply can also be decisive for the dynamic performance of a gas engine. In other words: if a gas engine is required to achieve high performance dynamics, it is not enough to simply focus on the air path. Once a certain level of dynamics has to be achieved, it is no longer sufficient to simply equip the air path with aids that enable a high rate of increase in the air supply; rather, suitable measures must also be taken in the fuel path to enable a high rate of increase in the fuel supply. The latter becomes all the more important the lower the density of the gaseous fuel.

[0008] If a gaseous fuel is not stored in the primary tank in gaseous form, but for example in liquid form or in a chemical bond, an excess amount of fuel in the rail can no longer be returned to the primary tank or a return would be very complex and / or impractical.

[0009] When a gas engine experiences a significant increase in the target power output, extending the respective injector opening times is only possible to a limited extent, at least temporarily, because an "unexpectedly" long opening of the injectors would lead to a significant drop in rail pressure. If the opening time of an injector were to be excessively extended in order to approximately or completely meet the fuel quantity requirement of the current injection event, the rail pressure would drop significantly, causing the fuel delivery rate to decrease for the subsequent injection event(s), even though this rate would clearly increase with a required power increase.

[0010] If the primary tank for the gaseous fuel is designed as a pressure reservoir and the gas pressure therein exceeds the rail pressure setpoint by a certain minimum, a rapid increase in the rail pressure is easily possible. However, if no additional means for increasing the rail pressure are provided, a comparatively high proportion of the gaseous fuel in the primary tank cannot be used if the setpoint is sufficiently high.

[0011] If the gaseous fuel has a very low boiling point and is stored as liquefied gas, conditioning the fuel requires significant heating. In such a case, an increase in fuel demand—i.e., an increase in compressed gaseous fuel, both in terms of the required pressure level and quantity—entails the need for a temporally and spatially coordinated increase in the heat input into the fuel supply path. Examples of such fuels are liquid hydrogen and liquefied natural gas.

[0012] If the gaseous fuel in the primary tank is stored chemically bound rather than in its molecular form, increasing the fuel supply in terms of pressure and quantity involves all process steps along a multi-stage conditioning path. For example, if the fuel in the primary tank is hydrogen, which in turn is stored in a liquid organic hydrogen carrier (LOHC), this carrier fluid must first be conditioned for a reformation process and undergo this conditioning process.The resulting molecular hydrogen is then already in gaseous form and must then be compressed (again) if the pressure level required in the rail is higher than the corresponding pressure level under which the liquid organic hydrogen carrier can be fed into the reformation process in order to obtain the hydrogen compressed to a corresponding extent.

[0013] WO 2015 / 169684 A1 already discloses an injection system that includes an additional fuel reservoir for reducing the pressure in the injection system when the engine is at a standstill. WO 2019 / 048134 A1 discloses an injection system for liquefied petroleum gas that also relies on an additional gas reservoir. During a cold start, fuel is to be drawn exclusively from the additional gas reservoir as long as the pump for gas preparation is not yet ready for operation. EP 3 741 984 A1 discloses a system that provides different fuel reservoirs for supplying fuel to a manifold injection system and the injector of a pre-chamber. WO 2018 / 072839 A1 discloses a possibility for recuperating unburned gases in an additional fuel reservoir. Another device for supplying a gaseous fuel to an engine is known from EP 3 885 640 A2.Gaseous fuel can be pumped directly from a primary tank to a rail. If the pressure in the primary tank drops below a threshold, the fuel pressure is increased via a compressor and fed into a gas buffer, which then ensures supply to the rail.

[0014] The object of the present invention is to provide a modified fuel injection device which is characterized by a simple construction and offers an energy-efficient possibility for quickly increasing the fuel supply rate up to the intended maximum rate in the combustion chambers.

[0015] This object is achieved by a fuel injection device according to the features of claim 1. Advantageous embodiments of the fuel injection device are the subject of the dependent claims.

[0016] According to the invention, it is proposed to supplement the injection device with at least one additional fuel pressure accumulator, the internal volume of which is connected to the at least one rail via at least one control valve. If the internal combustion engine has a plurality of combustion chambers, there is preferably a so-called central rail over which the fuel path extends to supply several or all of the combustion chambers. The valve control enables the fluid connection between the additional fuel pressure accumulator and the central rail to be opened and closed as required. This makes it possible to make a higher quantity of fuel available to the central rail at short notice, i.e. almost instantaneously, for a limited period of time. When the control valve is open, the central rail is supplied with a certain quantity of fuel from the additional fuel pressure accumulator in addition to the regular fuel path from the primary fuel tank.Such a parallel supply from the primary fuel tank and the auxiliary fuel pressure accumulator is particularly useful in the case of a comparatively high increase in the desired fuel metering rate. The additional supply of fuel from the auxiliary fuel pressure accumulator can prevent or reduce a pressure drop in the central rail, which would otherwise occur due to the extended opening times of the injectors or would be significantly greater. With a sufficiently high fuel supply in the auxiliary fuel pressure accumulator, a possible fuel deficit can be compensated until the regular fuel path from the primary fuel tank to the central rail has been adapted to the higher fuel supply.

[0017] The invention eliminates the problems mentioned above that occur in gas engines. Due to the particularly low volumetric energy density of gaseous hydrogen and the high technical complexity of hydrogen compression, the application of the invention in hydrogen engines results in particularly high benefits. An injection device according to the invention therefore offers great benefits for supplying such internal combustion engines that are operated with a gaseous fuel. The primary fuel tank is suitable for providing the fuel, in particular hydrogen, wherein the fuel can be stored in the primary tank in liquid or gaseous form. In hydrogen engines, the hydrogen can be in (i) molecular form or (i) alternatively as a gas admixed in molecular form to another fuel gas, e.g.It can be methane or (iii) alternatively, it can be stored in a chemically bound form that enables so-called hydrogen reformation in the system, e.g., a vehicle, in which the hydrogen engine is operated, with practical effort. If the hydrogen is admixed in molecular form with another fuel or another fuel component, the weight fraction of hydrogen is at least 20%, preferably at least 40%, and most preferably at least 60%.

[0018] A pre-loaded pressure accumulator is preferred as an additional fuel pressure accumulator. A bladder accumulator is also conceivable.

[0019] In an advantageous embodiment, the additional fuel pressure accumulator is connected to the central rail only via the control valve and is otherwise directly connected. In particular, the fluid connection should be kept as short as possible to ensure the shortest possible reaction time. This is crucial in order to be able to compensate for or even prevent any fuel deficit, which could be caused by a sharp increase in the target delivery quantity, as quickly as possible and thus to minimize or ideally avoid a pressure drop in the central rail. A particularly short line path between the central rail and the additional fuel pressure accumulator results if the additional fuel pressure accumulator is arranged directly on the central rail or at least in the immediate vicinity of the central rail.In an advantageous embodiment, the fluid connection between the central rail and the auxiliary fuel pressure accumulator extends only along aligned openings in the housing walls of the central rail and the auxiliary fuel pressure accumulator. The control valve and any sealing elements can be partially or completely integrated into a housing of the auxiliary fuel pressure accumulator or the central rail.

[0020] In one embodiment, all gas paths leading to and from the auxiliary fuel pressure accumulator extend exclusively via the central rail. Obviously, in this case, the fuel is supplied to the auxiliary fuel pressure accumulator via the central rail. Preferably, there is a single fluid connection between the central rail and the auxiliary fuel pressure accumulator, via which, when the control valve is open, fuel can flow from the central rail into the auxiliary fuel pressure accumulator, and, when the pressure conditions change accordingly, fuel can flow from the auxiliary fuel pressure accumulator into the central rail.Ideally, the auxiliary fuel pressure accumulator is charged up to a predetermined gas pressure. This charging is initiated by opening the control valve only when the current consumption required to meet the engine's target power can be met by drawing fuel from the primary tank alone. Once pressure equalization has been achieved between the two fuel quantities inside the central rail and the auxiliary fuel pressure accumulator, the control valve can be or will be closed again.

[0021] Clearly, the charging of the additional fuel pressure accumulator can also be carried out in portions if no fuel is drawn from the additional fuel pressure accumulator between two or more consecutive charging processes, as can be demonstrated by a simple example:

[0022] Within a certain period of time, there is an operating phase in which the internal combustion engine is operating at, for example, approximately 50% full load and the current fuel supply can already be completely covered by simultaneous fuel withdrawal from the primary tank. If the internal pressure in the additional fuel pressure accumulator is lower than the rail pressure, the corresponding control valve is actuated accordingly, so that after a certain time the pressure prevailing in the additional fuel pressure accumulator has the same value as the rail pressure. In the subsequent period of time in the example, the output power required by the internal combustion engine increases, whereby this required increase is correspondingly slow, whereby this increase in power can be covered without gas withdrawal from the additional fuel pressure accumulator.Once the engine's power output has increased to a certain level, the rail pressure increases, causing the control valve in question to open, thereby supplying a certain amount of fuel to the additional fuel pressure reservoir.

[0023] In one possible implementation of the invention, a simple and cost-effective design of the control valve as a simple directional control valve is sufficient, which has only two switching states and therefore does not allow for continuous flow rate changes. The valve can be actuated by an actuator based, for example, on an electromagnet. The operating environment requires spatial separation and / or insulation of the actuator, particularly the electrical part, from fluid-carrying, i.e., fuel-carrying, components, particularly the valve part.

[0024] The central rail can be equipped with at least one internal pressure sensor integrated into or within it to monitor the current rail pressure and / or be part of a rail pressure control system. It is advisable to position the rail pressure sensor within the central rail, as protected as possible from a potential pressure wave, to ensure the acquisition of representative measured values. In particular, the pressure sensor should be positioned on the central rail at a sufficient distance from the inlet passage of the fluid connection of the auxiliary fuel pressure accumulator.

[0025] Optionally, the additional fuel pressure accumulator can be equipped with its own physical internal pressure sensor. Alternatively or additionally, the status of the additional fuel pressure accumulator can also be monitored by evaluating the measured values ​​of the rail pressure sensor. In the simplest case, if the control valve is open, the currently measured pressure value of the rail pressure sensor can be selected as a substitute value for the internal pressure in the additional fuel pressure accumulator. Whereas if the control valve is closed, the respective final value of the rail pressure sensor at the time immediately before the control valve was last closed is used as a substitute value for the internal pressure of the additional fuel pressure accumulator. Preferably, a software-supported evaluation of several raw data samples is used in order to obtain a rail pressure value deemed relevant in each case, which can then be used for all further processes, including, if applicable.existing subsequent calculations that are to be influenced by the actual rail pressure value. Alternatively or additionally, such an approach is suitable for the raw measured values ​​obtained from a pressure sensor and / or temperature sensor, etc., which may be installed inside the additional fuel pressure accumulator.

[0026] According to the invention, the fuel injection device is equipped with a controller that is configured to keep the control valve closed during normal operation of the internal combustion engine. The controller is further configured to open the control valve once the required target fuel metering has increased, i.e., when the associated increase rate is above a certain threshold value in relation to the currently available fuel supply quantity. After the control valve has been opened, it can be kept open for a certain period of time and / or depending on certain parameters - e.g., the fuel quantity to be substituted, the pressure difference in the rail and the additional fuel pressure accumulator, etc. It may be better not to keep the control valve open continuously, but to open and close it alternately depending on the aforementioned and other criteria, i.e.,The control valve is switched according to a fixed and preferably variably definable cycle. The switching cycle can preferably be determined dynamically, in particular based on one or more engine operating parameters and / or operating variables of the internal combustion engine. Relevant in this context may be the current rail pressure and / or the current engine speed or crankshaft speed and / or the setpoint of the currently feasible fuel metering and / or the desired value for the current fuel metering.

[0027] The control system can also optionally include coordination for charging the auxiliary fuel pressure accumulator via the central rail. In particular, the control system takes into account the current internal pressures of the auxiliary fuel pressure accumulator and the central rail, as well as the currently possible fuel delivery rate into the central rail. If the internal pressure in the auxiliary fuel pressure accumulator is lower than the internal pressure in the central rail, the control valve can be opened to equalize the pressure between the auxiliary fuel pressure accumulator and the central rail. This is logically coordinated depending on the current load or currently requested fuel quantity, taking into account the currently possible fuel delivery rate, so that a momentary charging of the auxiliary fuel pressure accumulator does not impair the current fuel supply to the internal combustion engine.The control system causes the control valve to close at the latest when pressure equalization has occurred between the two accumulators.

[0028] The fuel injection device according to the invention enables dynamic control of the available fuel supply rate from a central rail. In addition, influencing the air path of the internal combustion engine can also be considered to optimize engine operation. For example, it is conceivable that the control system that coordinates the opening and closing of the control valve controls the control valve and / or one or more actuators in the air path, such as a throttle valve or a switchable device by means of which an increase in charge air compression can be achieved, possibly in an expanded coordination with air path monitoring and intervention options.

[0029] Further advantages and features of the invention will be explained in more detail below using an exemplary embodiment illustrated in the figures. They show: Figure 1: a schematic representation of the fuel injection device according to the invention for direct injection into an internal combustion engine, Figure 2: a schematic representation of the fuel injection device according to the invention for the case of intake manifold injection, Figure 3: a perspective view of the underside of an air distributor with attached central rail and additional fuel pressure accumulator, Figure 4: a rear view of the air distributor according to Figure 3 , Figure 5: a sectional view with angled section through the internal combustion engine with attached air distributor according to Figures 3 , 4 and Figures 6, 7: enlarged detail view of the sectional view according to Figure 5 .

[0030] Figure 1shows a first exemplary embodiment of the invention with the injection device according to the invention for direct injection into the combustion chamber 1 of an internal combustion engine. In the present case, this is a gas engine that is operated with hydrogen as fuel. For this purpose, there is an injector 2 through which the required amount of fuel is injected into the combustion chamber 1 of the internal combustion engine. The supply to the injector 2 or all injectors of the internal combustion engine is provided from a central rail 10, which is connected to the primary fuel tank (not shown) via a primary fuel path 12 provided with the rail pressure control valve 11. In addition to the fuel, the amount of air required for combustion is made available to the internal combustion engine via the charge air path 8. This is a supercharged internal combustion engine.The turbine 3 is driven by the exhaust gas volume flow in the exhaust path 6 and drives the compressor 4 to compress the charge air in the charge air path 8. An electric machine 7 can be provided as support in order to be able to supply additional drive power to the compressor 4 if a rapid increase in the available charge air quantity is required.

[0031] The inventive concept provides that, during normal operation, the fuel is supplied to the central rail 10 exclusively via the primary fuel path 12. However, in the event of a certain rate of increase in the requested target fuel quantity for the combustion chamber 1, an additional fuel quantity can be provided from a separate additional fuel pressure accumulator 20. The additional fuel pressure accumulator 20, designed here as a preloaded pressure accumulator, is fluidically connected directly to the central rail 10 via a control valve 13 designed as a 2 / 2-way valve, whereby an additional fuel quantity can be provided over the shortest possible line path within a short response time. The control valve 13 is actuated by an electromagnet 14, which acts on the control valve 13 via a tappet.

[0032] Provided that the additional fuel pressure accumulator 20 has a certain amount of fuel, i.e., a certain pressure level is present therein, the control valve 13 is provided to open when a sharp increase in the target output of the internal combustion engine occurs. This temporarily provides a higher fuel supply rate, which can be made available immediately to the combustion chambers 1. With a sufficiently high fuel supply in the additional fuel pressure accumulator 20, the occurrence of a fuel deficit can be compensated for until the device located in the primary fuel path 12 for providing fuel from the primary fuel tank has adjusted to the required higher fuel supply rate, thus eliminating the need for a fuel deficit.

[0033] In order to keep the complexity of the device according to the invention as low as possible, there is preferably no separate unit for filling the additional fuel pressure accumulator 20. The additional fuel pressure accumulator 20 is then filled exclusively via the central rail 10 when the control valve 13 is open. The control valve 13 remains closed during normal operation and is only opened if fuel is to be supplied to the additional fuel pressure accumulator 20 via the central rail 10 or if fuel is to be fed from the additional fuel pressure accumulator 20 into the central rail 10 or if the additional fuel pressure accumulator 20 is to be discharged via the control valve 13 for safety reasons. The control valve 13 should have the highest possible dynamic response and generate the lowest possible pressure loss when open.Since the control valve 13 is predominantly closed during operation of the internal combustion engine, it is energetically advantageous if it is open when the electromagnet 14 is activated.

[0034] Deviating from the execution of the Figure 1 The fuel injection device shown can also be used for an internal combustion engine with intake manifold injection, as shown in Figure 2 In contrast to the execution of the Figure 1 Here, the fuel is injected by the injector 2 into a common intake manifold 15 of several combustion chambers 1 or an intake port of the combustion chamber 1. The fuel / air mixture is generated in the intake manifold 15 or the intake port and supplied to the combustion chamber 1.

[0035] Figure 3shows a bottom view of an air distributor 30 for an internal combustion engine. The air distributor 30 shown here is mounted with its side 31 on the internal combustion engine or on the cylinder head 52 and, in the embodiment shown, supplies six combustion chambers 1 of the internal combustion engine. The charge air flows in the area around the cylinder-specific fuel supply tubes 32 from the air distributor 30 into a respective intake duct 52a of the internal combustion engine or cylinder head 52, which is designated here by reference numeral 33a.

[0036] The individual supply tubes 32 serve to supply fuel to an inlet channel 52a from the central rail 10, which is directly attached to the air distributor 30. The gas connection or the fuel connection of the central rail 10 to the primary fuel path 12 is indicated by reference numeral 17. The indicated fuel outlet from a supply tube 32 is shown as an example with an arrow 34. The cylinder-specific supply tubes 32 each extend from the end of the injector 2 projecting into the central rail 10, through the air distributor 30, and into the inlet channel 52a. Figure 3The installation position of the injectors 2 is only partially visible, because the component ends of the injectors 2 located outside the central rail 10 are concealed in this view by the additional fuel pressure accumulator 20. The central rail 10 is attached to the housing wall of the air distributor 30 opposite the wall 31. Cast-on bushings on the central rail 10 serve for the screw connection between the air distributor 30 and the central rail 10. The gas connection of the central rail 10 to the primary fuel path 12 is indicated by reference number 17.

[0037] The additional fuel pressure accumulator 20 according to the invention is mounted behind the central rail 10. It can be seen here that the fluid connection between these two internal volumes extends along correspondingly aligned openings in the housing walls. The illustration of the Figure 4shows a view of the air distributor 30, which is turned away from the internal combustion engine with respect to an attached air distributor 30. In the illustration, only five injectors 2 have been installed in the corresponding mounting openings of the central rail 10, with the second injector from the left merely positioned at an installation location but not yet fixed. By directly attaching the additional fuel pressure accumulator 20 to the central rail 10, the required fluid paths between the central rail 10 and the additional fuel pressure accumulator 20 are reduced to a minimum, so that in the event of a highly dynamic increase in the required fuel supply quantity to the combustion chambers 1, an additional quantity of fuel can be provided from the additional fuel pressure accumulator 20 within a very short period of time.

[0038] Both Figures 5 to 7These are sectional views of the exemplary embodiment, showing the arrangement and some of the fluid connections of the components in particular focus. These include the central rail 10, the additional fuel pressure accumulator 20, the air distributor 30, and a fuel injector 2, as well as its extension into the recess in the cylinder head 52, which forms the intake port 52a there. Figure 5 shows a section through the internal combustion engine, whereby parts not essential to the invention are shown only schematically. Figure 5 However, it serves to visualize the exemplary embodiment with regard to the installation position of the air distributor 30, the central rail 10 and the additional fuel pressure accumulator 20 on the internal combustion engine. Figures 6 , 7 are respective enlargements of the relevant interface area.

[0039] The engine block 51 houses the cylinder liner 53, which in turn houses the piston 57. The cylinder head cover 58 is located above the cylinder head 52. Apart from the indicated spark plug 56 and a valve tappet 55, the components located below the cylinder head cover are not shown because they are not the focus of the invention. By means of the valve tappet 55, the flow path of the air-fuel mixture along the inlet channel 52a to the combustion chamber is opened and closed in a defined manner. The enlarged illustrations also show the fluid connection between the internal volume of the central rail 10 and the injector 2. The injector 2 has, in the area of ​​the rail opening 18, a circumferential annular groove with a series of radial bores, which are arranged in the Figure 7can be seen through which the fuel from the central rail 10 can penetrate into the injector 2 and can be injected via the feed tube 32 into the inlet channel 52a.

[0040] The operation of the invention is explained below based on possible application situations: Normal mode:

[0041] In normal mode, the internal combustion engine operates at low dynamics, whereby the resulting increases in fuel demand can be covered by the fuel supply available in the central rail 10. If the rail pressure is (by a certain amount) higher than the internal pressure in the auxiliary fuel pressure accumulator 20, the control valve 13 should be opened and closed, preferably in stuttering mode, until the rail pressure reaches its target value and the internal pressures prevailing in the central rail 10 and the auxiliary fuel pressure accumulator 20 are equalized. As soon as this condition is met, the control valve 13 remains closed. Transition to the special case:

[0042] The initial situation is normal operation, in which the internal combustion engine operates under a certain load and with limited dynamics, whereby the resulting increases in fuel demand can be covered by the compressor 4 and the fuel supply available in the central rail 10. Furthermore, the gas pressure in the additional fuel pressure accumulator 20 has a value above the rail pressure. This initial situation results in a transient increase in the target output: In order to prevent a drop in the actual rail pressure value in the event of a transient load increase, or even to allow an increase towards the new rail pressure target value, fuel should flow from the additional fuel pressure accumulator 20 into the central rail 10 by opening the control valve 13. The control valve 13 preferably performs directly consecutive opening and closing movements.

[0043] A precise coordination of these opening and closing interval times of the control valve 13 is implemented by an actuator, whereby the corresponding coordination is preferably carried out by a control unit, which can be specified by a corresponding actuator with knowledge of certain engine parameters and operating variables. Examples of such possible operating variables are the current rail pressure actual value, the crankshaft actual speed, the setpoint of the actually feasible fuel injection, the desired value of the fuel injection (i.e. the fuel quantity under whose availability and usability in the combustion chamber the requested output power could be achieved), the switching timing of the control valve 13, etc. Optionally, the control unit or another control unit networked with it takes over coordination with the operating state of the air gap by recording certain operating variables of the air gap (e.g.the air mass flow) and / or by influencing certain actuators in the air path (e.g. the control of a throttle valve, if present, or the activation of the electric motor 7 to increase the speed of the compressor 4, whereupon an increase in the charge air mass flow occurs).

[0044] Equipped with appropriate software, the control unit can utilize the degrees of freedom of the internal combustion engine under the given instantaneous conditions - examples of which include the actual and target operating point of the speed-torque trajectory, the actual and target value of the rail pressure, the actual pressure in the additional fuel pressure accumulator 20, and the operating state of the air path - in order to achieve the best possible utilization of the amount of fuel available in the additional fuel pressure accumulator 20.

[0045] If, after the internal combustion engine is switched on, the auxiliary fuel pressure accumulator 20 contains only very little fuel—i.e., the fuel level therein is comparatively low—or if the auxiliary fuel pressure accumulator 20 contains only ambient air because the safety concept provides for air purging, the invention clearly cannot yet be used. In this case, it could be provided that the user is informed that the boost function, i.e., the functionality of the invention, is only achieved through temporary high-load operation, which need only be of a very short duration.

[0046] The system according to the invention is preferably suitable for use with dynamically operated gas engines, and particularly preferably for hydrogen engines. Alternatively or additionally, the system according to the invention is particularly preferably suitable for gas engines used in mobile applications, e.g., road vehicles, mobile work machines, etc.

[0047] The use of a system according to the invention is particularly advantageous for hydrogen engines because gaseous hydrogen has a particularly low volumetric energy density compared to all other fuels. A corresponding increase in the internal volume of the rail or central rail is disadvantageous because, with a decrease in the mechanical output required by the hydrogen engine and thus a reduction in the rail pressure, the amount of hydrogen to be extracted from the rail increases accordingly. However, unlike diesel fuel, a diesel-like fuel, etc., this amount of hydrogen cannot simply be returned to the primary fuel tank.

[0048] The advantages of the invention can be briefly summarized as follows: The extension according to the invention has a high potential for a rapid increase in output power with a comparatively low additional expenditure on equipment. Additional weight, additional installation space requirement, additional energy consumption. The extension can be easily attached to existing fuel supply systems, which favors a common parts strategy (for internal combustion engines with and without this additional equipment). Modification of other components and addition of other components that are located far away from the internal combustion engine are not required. (Only an electrical wiring and / or a hydraulic connection in order to effect an actuation of the control valve 13, which can block and release the fluid connection between the central rail 10 and the additional fuel pressure accumulator 20.) The invention can be used regardless of the form in which the fuel is stored in the primary tank (e.g.in liquid or gaseous form or in a chemically bound form) and how it is made available as a fuel (e.g. by evaporation or reformation). List of reference symbols: combustion chamber 1 Injector 2 turbine 3 compressor 4 Exhaust path 6 electric motor 7 Charge air path 8 Central Rail 10 Rail pressure control valve 11 primary fuel path 12 control valve 13 electromagnet 14 intake manifold 15 Gas connection 17 Rail opening 18 Additional fuel pressure accumulator 20 Air distributor 30 Internal volume of the air distributor 30a guide 30b Mounting wall air distributor 31 Feed tube 32 Charge air (before flowing into the air collector) 33 Charge air (flowing into the cylinder head) 33a fuel 34 Engine block 51 cylinder head 52 Inlet channel 52a cylinder liner 53 Inlet valve 55 spark plug 56 Pistons 57 cylinder head cover 58

Claims

1. Fuel injection device for supplying gaseous fuel to an internal combustion engine, comprising at least one central rail (10) in fluid communication with at least one primary fuel tank via a primary fuel path, wherein at least one additional fuel pressure accumulator (20) is provided, the internal volume of which is connected to the central rail (10) via at least one control valve (13) in order to temporarily provide a simultaneous fuel supply to the central rail (10) from the additional fuel pressure accumulator (20) and the primary fuel tank, wherein a control system is provided and configured to keep the control valve (13) closed in a normal operation of the internal combustion engine so that the fuel is supplied to the central rail (10) exclusively via the primary fuel path, characterized in that the control system is further configured to open the control valve (13) in the event that of the requested target fuel addition with respect to the fuel supply amount applied currently in the normal operation is above a threshold so that the central rail is supplied with fuel parallelly from the primary fuel tank and the additional fuel pressure accumulator (20).

2. Fuel injection device according to claim 1, characterized in that the fuel primary tank is used for storing molecular hydrogen or a fuel which has at least a weight proportion of molecular hydrogen of at least 20%, preferably of at least 40% and very preferably of at least 60%, or a liquid hydrogen carrier, and the fuel can be injected into the at least one combustion chamber of the an internal combustion engine (1) after any necessary preparation by means of the fuel injection device.

3. Fuel injection device according to claim 1 or 2, characterized in that the additional fuel pressure accumulator (20) is a preloaded pressure accumulator, preferably a bladder accumulator.

4. Fuel injection device according to any one of the preceding claims, characterized in that the additional fuel pressure accumulator (20) is directly connected to the central rail (10) via the control valve (13).

5. Fuel injection device according to any one of the preceding claims, characterized in that the additional fuel pressure accumulator (20) is arranged on the central rail (10) and / or the control valve (13) is an integral part of the central rail (10) and / or the additional fuel pressure accumulator (20).

6. Fuel injection device according to any one of the preceding claims, characterized in that the additional fuel pressure accumulator (20) is in fluid connection only with the central rail (10), in particular charging and / or discharging of the additional fuel pressure accumulator (20) is possible only via the central rail (10).

7. Fuel injection device according to any one of the preceding claims, characterized in that the control valve (13) is a directional control valve, in particular a 2 / 2 directional control valve.

8. Fuel injection device according to any one of the preceding claims, characterized in that the control valve (13) can be actuated via an actuator, in particular by means of an electromagnet (14), wherein the actuator is arranged spatially separate from and / or partitioned off from the control valve (13).

9. Fuel injection device according to any one of the preceding claims, characterized in that the central rail (10) comprises at least one integral pressure sensor, preferably spaced apart from the fluid connection of the central rail (10) with the additional fuel pressure accumulator (20), to protect the pressure sensor from a pressure wave when the fluid connection between the central rail (10) and the additional fuel pressure accumulator (20) is open.

10. Fuel injection device according to any one of the preceding claims, characterized in that a pressure sensor is arranged inside the additional fuel pressure accumulator (20).

11. Fuel injection device according to any one of the preceding claims, characterized in that the control system is further configured to open the control valve (13) in the event that the increase in the requested fuel quantity is above a certain threshold, in particular to alternately open and close the control valve (13), and / or open the control valve only under the additional condition that the additional fuel pressure accumulator (20) has a defined fuel quantity, in particular a pressure level defined therein prevails.

12. Fuel injection device according to any one of the preceding claims, characterized in that the control system is further configured to open the control valve (13) under the condition that the pressure in the central rail (10) is greater than the pressure in the additional fuel pressure accumulator (20), in particular the pressure difference exceeds a defined value, and the internal combustion engine is operated in the normal operation.

13. Fuel injection device of claim 12, characterized in that the control system is configured to close the control valve (13) when pressure equalization within the additional fuel pressure accumulator (20) and within the central rail (10) has occurred in the presence of a boost operation of the additional fuel pressure accumulator (20).

14. Fuel injection device according to any one of the preceding claims, characterized in that the control system is configured to take into account one or more engine parameters and / or operating variables of the internal combustion engine, for example the rail pressure actual value and / or the crankshaft speed and / or the setpoint value of the fuel injection which can actually be carried out and / or the desired value of the fuel injection, for actuating the control valve (13).

15. Fuel injection device according to any one of the preceding claims, characterized in that the control system is configured, optionally in conjunction with at least one further external control system, to monitor the operating state of the air path of the internal combustion engine and optionally to control one or more actuators of the air path, for example a throttle valve, taking into account one or more operating variables of the air path and / or the fuel path.

16. Internal combustion engine comprising a fuel injection device according to any one of the preceding claims.