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

Abstract

The invention relates to a fuel injection device for an internal combustion engine comprising at least one central rail which is in fluid communication with at least one primary fuel tank, characterized in that at least one auxiliary fuel pressure accumulator is provided, the internal volume of which is in communication with the central rail via at least one control valve in order to temporarily provide a simultaneous fuel supply to the central rail from the auxiliary fuel pressure accumulator and the primary fuel tank.

Claims

1. Fuel injection device for an internal combustion engine, comprising at least one central rail (10) in fluid communication with at least one primary fuel tank, 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) to temporarily provide a simultaneous fuel supply to the central rail (10) from the additional fuel pressure accumulator (20) and the primary fuel tank.

2. Fuel injection device according to claim 1, wherein 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 (1) an internal combustion engine after any necessary preparation by means of the fuel injection device.

3. Fuel injection device according to claim 1, wherein the auxiliary fuel pressure accumulator (20) is a preloaded pressure accumulator, preferably a bladder accumulator.

4. Fuel injection device according to claim 1, wherein the auxiliary fuel pressure accumulator (20) is directly connected to the central rail (10) via the control valve (13).

5. Fuel injection device according to claim 1, wherein the auxiliary 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 auxiliary fuel pressure accumulator (20).

6. Fuel injection device according to claim 1, wherein the auxiliary fuel pressure accumulator (20) is in fluid connection only with the central rail (10), in particular charging and/or discharging of the auxiliary fuel pressure accumulator (20) is possible only via the central rail (10).

7. Fuel injection device according to claim 1, wherein the control valve (13) is a directional control valve, in particular a 2/2 directional control valve.

8. Fuel injection device according to claim 1, wherein the control valve (13) can be actuated via an actuator, in particular by an electromagnet (14), and the actuator is arranged spatially separate from and/or partitioned off from the control valve (13).

9. Fuel injection device according to claim 1, wherein 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 auxiliary fuel pressure accumulator (20), to protect the pressure sensor from a pressure wave when the fluid connection between the central rail (10) and the auxiliary fuel pressure accumulator (20) is open.

10. Fuel injection device according to claim 1, wherein a pressure sensor is arranged inside the auxiliary fuel pressure accumulator (20).

11. Fuel injection device according to claim 1, wherein a control system is provided and configured to keep the control valve (13) closed during normal operation of the internal combustion engine and to open, in particular alternately open and close, the control valve (13) in the event the increase in the requested fuel quantity is above a threshold value.

12. Fuel injection device according to claim 11, wherein the control is further configured to open the control valve (13) under the condition the pressure in the central rail (10) is greater than the pressure in the auxiliary fuel pressure accumulator (20), in particular the pressure difference exceeds a defined value, and the internal combustion engine is operated in normal mode.

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

14. Fuel injection device according to claim 11, wherein the controller 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 claim 11, wherein the controller is configured, optionally in conjunction with at least one further external controller, 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 claim 1.

17. Fuel injection device according to claim 2, wherein the auxiliary fuel pressure accumulator (20) is a preloaded pressure accumulator, preferably a bladder accumulator.

18. Fuel injection device according to claim 17, wherein the auxiliary fuel pressure accumulator (20) is directly connected to the central rail (10) via the control valve (13).

19. Fuel injection device according to claim 3, wherein the auxiliary fuel pressure accumulator (20) is directly connected to the central rail (10) via the control valve (13).

20. Fuel injection device according to claim 2, wherein the auxiliary fuel pressure accumulator (20) is directly connected to the central rail (10) via the control valve (13).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further advantages and features of the invention will be explained in more detail below with reference to an exemplary embodiment shown in the figures. The figures show in:

[0028] FIG. 1: a schematic representation of the fuel injection device according to the invention for direct injection into an internal combustion engine,

[0029] FIG. 2: a schematic diagram of the fuel injection device according to the invention for the case of intake manifold injection,

[0030] FIG. 3: a perspective view of the underside of an air distributor with attached central rail and auxiliary fuel pressure accumulator,

[0031] FIG. 4: a rear view of the air distributor according to FIG. 3,

[0032] FIG. 5: a sectional view with angled cross-section through the internal combustion engine with attached air distributor according to FIGS. 3, 4 and

[0033] FIG. 6, 7: an enlarged detail view of the sectional view according to FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] FIG. 1 shows 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, the engine is a gas engine which is operated with hydrogen as fuel. For this purpose, an injector 2 is provided, via which the required quantity of fuel is injected into the combustion chamber 1 of the internal combustion engine. The supply to the injector 2 or to 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 gas path 6 and drives the compressor 4 to compress the charge air in the charge air path 8. An electric motor 7 can be provided as a back-up in order to be able to supply additional drive power to the compressor 4 if a rapid increase in the available charge air volume is required.

[0035] The idea according to the invention is that the fuel is supplied to the central valve 10 exclusively via the primary fuel path 12 during normal operation, but that in the event of a certain rate of increase in the required target fuel quantity for the combustion chamber 1, an additional fuel quantity can be provided from a separate auxiliary 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 directional control valve, whereby an additional fuel quantity can be provided within a short reaction time over the shortest possible line path. The control valve 13 is actuated by an electromagnet 14, which acts on the control valve 13 via a plunger.

[0036] Provided that the auxiliary fuel pressure accumulator 20 has a certain amount of fuel, i.e. a certain pressure level is present therein, opening of the control valve 13 is provided when a sharp increase in the target output of the internal combustion engine occurs. As a result, a higher fuel supply rate is temporarily available, which can be made available to the combustion chambers 1 immediately in terms of time. If the fuel supply in the auxiliary fuel pressure accumulator 20 is sufficiently high, the occurrence of a fuel deficit can be compensated for until the device for supplying fuel from the primary fuel tank located in the primary fuel path 12 has adapted to the required higher fuel supply rate and the occurrence of a fuel deficit has therefore become unnecessary.

[0037] In order to keep the expense of the device according to the invention as low as possible, there is preferably no separate unit for filling the auxiliary fuel pressure accumulator 20. The auxiliary fuel pressure accumulator 20 is then filled exclusively via the central rail 10 with the control valve 13 open. The control valve 13 remains closed during normal operation and is only opened if fuel is to be supplied to the auxiliary fuel pressure accumulator 20 via the central rail 10 or if fuel is to be supplied from the auxiliary fuel pressure accumulator 20 to the central rail 10 or if the auxiliary fuel pressure accumulator 20 is to be discharged via the control valve 13 for safety reasons. The control valve 13 should have as high a dynamic response as possible and produce as low a pressure loss as possible in the open state. 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 solenoid 14 is activated.

[0038] Deviating from the configuration of FIG. 1, the fuel injection device shown can also be used for an internal combustion engine with intake manifold injection, as shown in FIG. 2. In contrast to the embodiment of FIG. 1, the fuel here is injected by the injector 2 into a common intake manifold 15 of a plurality of combustion chambers 1 or an inlet duct of the combustion chamber 1. In the intake manifold 15 or the inlet duct, the fuel/air mixture is generated and supplied to the combustion chamber 1.

[0039] FIG. 3 shows 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 version shown, supplies six combustion chambers 1 of the internal combustion engine as an example. The charge air flows in the area around the cylinder-specific fuel supply tubes 32 from the air distributor 30 into a respective inlet duct 52a of the internal combustion engine or of the cylinder head 52, which is marked here with the reference character 33a.

[0040] The individual supply tubes 32 each serve to supply fuel into an inlet duct 52a from the central rail 10 attached directly to the air distributor 30. The gas connection or fuel connection of the central rail 10 to the primary fuel path 12 is indicated by the reference character 17. The indicated fuel outlet from a supply tube 32 is exemplarily shown with an arrow 34. The cylinder-individual supply tubes 32 each extend, starting from the end of the injector 2 projecting into the central rail 10, through the air distributor 30 and extend into the inlet duct 52a. In FIG. 3, the installation position of the injector 2 is only partially visible, because the component ends of the injector 2 located outside the central rail 10 are concealed by the auxiliary fuel pressure accumulator 20 in this view. 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 are used for the screw connection between the air distributor 30 and the central rail 10. The reference character 17 indicates the gas connection of the central rail 10 to the primary fuel path 12.

[0041] Mounted behind the central rail 10 is the auxiliary fuel pressure accumulator 20 according to the invention. It can be seen here that fluid communication between these two internal volumes extends along correspondingly aligned openings in the housing walls. The illustration of FIG. 4 shows a view of the air manifold 30 facing away from the internal combustion engine with respect to an attached air manifold 30. In the illustration, only five injectors 2 have so far been installed in the corresponding mounting openings of the central rail 10, with the second injector from the left merely placed in an installation location but not yet fixed. The direct attachment of the auxiliary fuel pressure accumulator 20 to the central rail 10 reduces the required fluid paths between the central rail 10 and auxiliary fuel pressure accumulator 20 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 auxiliary fuel pressure accumulator 20 within a very short period of time.

[0042] FIGS. 5 to 7 are sectional views of the exemplary embodiment, showing the arrangement and some of the fluid connections of the components of particular focus. These include the central rail 10, the auxiliary fuel pressure accumulator 20, the air distributor 30 and a fuel injector 2, as well as its reaching into the recess present in the cylinder head 52, which forms the inlet duct 52a there. FIG. 5 here shows a section through the internal combustion engine, wherein parts which are not essential to the invention are shown only schematically. However, FIG. 5 serves to visualize the embodiment example with respect to the installation position of the air distributor 30, the central rail 10 and the auxiliary fuel pressure accumulator 20 on the internal combustion engine. FIGS. 6, 7 are respective enlargements of the relevant interface area.

[0043] The engine block 51 accommodates the liner 53, which in turn accommodates the piston 57. Above the cylinder head 52 is the cylinder head cover 58. 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 duct 52a to the combustion chamber is opened and closed in a defined manner, respectively. In the enlarged illustrations, the fluid connection between the inner volume of the central rail 10 and the injector 2 can still be seen. In the region of the rail opening 18, the injector 2 has a circumferential annular groove with a row of radial bores, which can be seen in FIG. 7, through which the fuel from the central rail 10 can enter the injector 2 and be injected into the inlet duct 52a via the supply tube 32.

[0044] The operation of the invention is explained below with reference to the possible situations of use:

Normal Mode:

[0045] In normal mode, the internal combustion engine operates at low dynamics, whereby the increases in fuel demand that occur in this case can be covered by the fuel supply available in the central rail 10. If the rail pressure is higher (by a certain amount) than the internal pressure in the auxiliary fuel pressure accumulator 20, the control valve 13 should preferably be opened and closed in stutter mode until the rail pressure has reached its setpoint and there is a balance between the internal pressures prevailing in the central rail 10 and in the auxiliary fuel pressure accumulator 20. As soon as this condition is met, the control valve 13 remains closed.

Transition to Special Case:

[0046] The initial situation is normal operation, in which the internal combustion engine operates under a certain load and with limited dynamics, whereby the increases in fuel demand that occur in this case can be covered by the compressor 4 and the fuel supply available in the central rail 10. Furthermore, the gas pressure in the auxiliary fuel pressure accumulator 20 has a value above the rail pressure. From this initial situation, a transient increase in the target delivery power occurs:

[0047] In order to prevent a drop in the actual rail pressure value as far as possible in the event of a transient load increase, or even to enable an increase in the direction of the new rail pressure setpoint value, fuel is to flow from the auxiliary fuel pressure accumulator 20 into the central rail 10 by opening the control valve 13. Preferably, the control valve 13 performs opening and closing movements in immediate succession.

[0048] Precise coordination of these opening and closing interval times of the control valve 13 is implemented by an actuator system, with the corresponding coordination preferably being performed by a control unit which can be specified by a corresponding actuator system with knowledge of certain engine parameters and operating variables. Examples of such possible operating variables are the instantaneous rail pressure actual value, the crankshaft actual speed, the setpoint value 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 provided) the switching timing of the control valve 13, etc. Optionally, the control unit or another control unit networked with it assumes coordination with the operating state of the air path by detecting certain operating variables of the air path (e.g. the air mass flow) and/or by influencing certain actuators in the air path (e.g. the activation of a throttle valve, if present, or an activation of the electric motor 7 to increase the speed of the compressor 4, whereupon an increase in the charge air mass flow occurs).

[0049] Equipped with appropriate software, the control unit can use the degrees of freedom of the internal combustion engine under the given instantaneous conditions—by way of example, the actual and set operating point of the speed-torque trajectory, the actual and set values of the rail pressure, the actual pressure in the auxiliary fuel pressure accumulator 20, the operating state of the air path—to achieve the best possible utilization of the fuel quantity available in the auxiliary fuel pressure accumulator 20.

[0050] Insofar as, after the internal combustion engine has been switched on, the auxiliary fuel pressure accumulator 20 contains only very little fuel—i.e. there is a comparatively low level of fuel in it—or the auxiliary fuel pressure accumulator 20 contains only ambient air because the safety concept provides for purging with air, 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 functional capability of the invention, is only present through temporary high-load operation, which need only be of very short duration.

[0051] The system according to the invention is preferably suitable for the use of 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 working machines, etc.

[0052] The use of a system according to the invention is therefore particularly advantageous for hydrogen engines because gaseous hydrogen has a very particularly low volumetric energy density compared with all other fuels. A corresponding increase in the internal volume of the rail or central rail is in turn disadvantageous because, if the mechanical output power demanded by the hydrogen engine decreases and thus the rail pressure is lowered, the quantity of hydrogen to be taken from the rail becomes correspondingly larger, which, however, unlike in the case of diesel fuel, a diesel-like fuel, etc., cannot simply be fed back into the primary fuel tank.

[0053] The advantages of the invention can be briefly summarized again as follows: [0054] The extension according to the invention has a high potential for a rapid increase in the output power at comparatively low [0055] additional equipment costs [0056] additional weight [0057] additional installation space requirements [0058] additional energy consumption [0059] The extension can be easily added to existing fuel supply systems, favoring a common parts strategy (for internal combustion engines with and without this additional equipment. [0060] A modification of other components and an addition of other components remote from the internal combustion engine is not required. (Only an electrical wiring and/or a hydraulic connection to effect an actuation of that control valve 13 which can block and release the fluid connection between the central rail 10 and the auxiliary fuel pressure accumulator 20). [0061] The invention can be applied regardless of the form in which the fuel is stored in the primary tank (e.g., in liquid or in gas form, or in a chemically bonded form) and the manner in which it is provided as fuel (e.g., by an evaporation or a reformation).

TABLE-US-00001 List of reference characters Combustion chamber  1 Injector  2 Turbine  3 Compressor  4 Exhaust gas 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 Suction tube 15 Gas connection 17 Rail opening 18 Auxiliary fuel pressure accumulator 20 Air distributor 30 Internal volume of the air distributor 30a Leadership 30b Mounting wall air distributor 31 Supply tube 32 Charge air (before entering the air collector) 33 Charge air (when flowing into the cylinder head) 33a Fuel 34 Engine block 51 Cylinder head 52 Inlet duct 52a Liner 53 Inlet valve 55 Spark plug 56 Piston 57 Cylinder head cover 58