Fuel injection device

Abstract

Fuel injection device (100) for an internal combustion engine, in particular of a motor vehicle, comprising a fuel pressure accumulator (10), an injector (12) with an injection nozzle (14) which is adjustable from a closed position to an injection position and vice versa, and a pressure booster (20) with a pressure booster piston (22) for increasing the injection pressure that can be generated by the injection nozzle (14), and a two-stage valve with a main valve (40) controlled via a pilot valve (30) for activating the pressure booster (20), wherein - the upstream valve (30) is a 3 / 2-way servo valve and the main valve (40) is a hydraulic valve, wherein the outflowing fluid of the upstream valve (30) is used as the hydraulic control fluid to control the main valve (40), - the main valve (40) has a control chamber (42) in fluid communication with a fluid outlet (34) of the pilot valve (30) and a control element (44), wherein the control chamber (42) is connected to the fuel pressure accumulator (10), wherein the main valve (40) has a pressure chamber (47) which is continuously connected to the fuel pressure accumulator (10), - the control element (44) is forced into a closed position in a first switching position (I), in which the control chamber (42) of the main valve (40) is pressurized, so that a passage between the fuel pressure accumulator (10) and the pressure booster (20) is closed, wherein the control element (44) is adjustable via a pressure change in the control chamber (42), and - the control element (44) of the main valve (40) is forced towards the control chamber (42) by actuation of the pilot valve (30) depending on a pressure ratio between the control chamber (42) and the pressure chamber (47) of the main valve (40), and the pressure booster piston (22) of the pressure booster (20) is activated in a second switching position (II) by actuation of the main valve (40), wherein in the second switching position (II) the control chamber (42) of the main valve (40) is depressurized, so that the control element (42) of the main valve (40) is forced into the second switching position (II), in which the passage between the fuel pressure accumulator (10) and the pressure booster (20) is open.

Description

[0001] The invention relates to a fuel injection device for an internal combustion engine, in particular of a motor vehicle, comprising a fuel pressure accumulator (common rail), an injector with an injection nozzle and a pressure booster with a pressure booster piston (plunger) for increasing the injection pressure that can be generated by the injection nozzle.

[0002] In common-rail fuel injection systems, which are particularly suitable for internal combustion engines such as diesel and gasoline engines, the fuel is pressurized by a high-pressure pump and held under pressure in the fuel accumulator during engine operation. The injectors are connected to the fuel accumulator via valves to supply the combustion engine's cylinders with fuel from the accumulator.

[0003] For this purpose, the injectors can have axially displaceable injection pistons or injection needles, each separating a control chamber of the injector from a pressure chamber of the injector, whereby by switching the valves the pressure ratio between control chamber and pressure chamber can be adjusted so that the injection piston moves and the injection nozzle is thereby opened or closed.

[0004] High injection pressures may be desirable or even necessary, especially in diesel engines. To avoid having to maintain such high pressures throughout the entire fuel pressure reservoir, pressure boosters are used. These boosters increase the fuel pressure at the injector at the injection point above the pressure in the common rail. Higher injection pressures are also increasingly desired in gasoline engines. Furthermore, high injection pressures can help reduce particulate emissions within the engine.

[0005] From the publication DE 10 2008 015 857 A1, a fuel injection device for an internal combustion engine is known in which fuel can be injected into a working cylinder by means of an injection nozzle, wherein a stationary pressure adjusting valve is provided to connect an inlet of the injection nozzle to a fuel return line depending on a switching pressure.

[0006] From EP 1 892 409 B1, a fuel injection device for an internal combustion engine is known, comprising an injector and a pressure booster with a pressure booster piston for increasing the injection pressure of the injector nozzle. This allows comparatively high injection pressures to be achieved despite a comparatively low fuel pressure in the fuel pressure accumulator. An intermediate storage tank is provided in a fuel return line to increase efficiency.

[0007] From EP 2 057 372 B1, a fuel injection device with an injector and a pressure booster is also known. The pressure booster can be activated by means of a 4 / 2-way valve, which in a first switching position connects an amplifier chamber and a spring chamber of the pressure booster and isolates them from the fuel pressure accumulator, and in a second switching position connects the spring chamber of the pressure booster to a leakage line and the amplifier chamber of the pressure booster to the fuel pressure accumulator.

[0008] Despite these measures, the resulting injection pressure does not always lead to optimal fuel atomization. Mixture formation, or fuel droplet production, can be optimized, among other things, by adjusting the fuel pressure. Furthermore, there is still room for optimization regarding the setting of a specific pressure profile or a specific modulation of the injection rate. A specific injection pressure profile may be necessary to comply with prescribed emissions standards and to achieve a specific combustion behavior in the cylinder.

[0009] German patent DE 26 02 280 A1 discloses a high-pressure fuel injection device for diesel engines with a hydraulically driven pump nozzle per working cylinder, the pump piston of which is driven by a servo piston with a larger diameter, and which is connected to a pressure source that supplies fuel to both the pump working chamber via an inlet valve and the servo pressure chamber bounded by an end face of the servo piston, and in which a switching valve, electromagnetically controlled by a control device in sync with the machine, connects the pressure source to the servo pressure chamber in its first switching position and the servo pressure chamber to a return line in its second switching position, and whose injection nozzle has a valve needle loaded by a valve spring, opening against the flow direction of the fuel.The plan is that shortly before the end of the injection stroke, fuel under increased pressure is fed into the spring chamber located at the rear of the valve needle, which receives the valve spring, and that after the end of the injection and before the start of the subsequent injection stroke, the increased pressure in the spring chamber is eliminated.

[0010] Document US 2007 / 0007362A1 discloses fuel injectors and methods for fuel injection, wherein one of the fuel injectors incorporates a pressure booster of a fuel injection device which is controlled via a pilot valve.

[0011] The publication EP 0 286 467 A1 also describes a fuel injection system that includes an injection unit for each cylinder of the engine, comprising a metering and injection chamber and a pump chamber, each capable of holding a specific quantity of fuel, as well as a piston for compressing the fuel present in the metering and injection chamber to inject it using the pressure of the fuel in the pump chamber. The two chambers are connected to pumps that generate fuel pressure via a metering line and a pump line, operating at different pressures. A distributor element is connected to the pump line and a pressure-controlled pressure outlet line, which in turn is connected to the metering line via a check valve that prevents the pressurized fuel from escaping the metering line.The distributor element includes a closure that is movable between a first position, in which the metering and injection chamber is filled with fuel, and a second position, in which the pump chamber of the injection unit is connected to the pump line to effect the fuel injection process.

[0012] Further state of the art is represented by the publications DE 10 2005 003 659 A1 and US 7 293 547 B2.

[0013] In view of the problems described, the object of the present invention is to further develop common-rail injection devices with pressure boosters in such a way that high injection pressures can be set as precisely as possible and while adhering to a predetermined pressure profile.

[0014] This problem is solved according to the invention by a fuel injection device of the type mentioned above with the features characterized in claim 1. Advantageous embodiments of the invention are described in the dependent claims.

[0015] The fuel injection device according to the invention for an internal combustion engine, in particular of a motor vehicle, comprises a fuel pressure accumulator, an injector with an injection nozzle which is adjustable from a closed position to an injection position and vice versa, and a pressure amplifier with a pressure amplifier piston for increasing the injection pressure that can be generated by the injection nozzle.

[0016] The fuel injection device also features a two-stage valve with a main valve, controllable via a pilot valve, for activating the pressure booster. In other words, unlike conventional injection devices, the pressure booster is not activated by a simple 3 / 2- or 4 / 2-way valve, but rather the injection device has a pilot valve for adjusting a control element of a main valve, which in turn activates the pressure booster.

[0017] The provision is that the upstream valve is a 3 / 2-way servo valve and the main valve is a hydraulic valve, wherein the outflowing fluid of the upstream valve is used as the hydraulic control fluid to control the main valve, wherein the main valve has a control chamber in fluid communication with a fluid outlet of the upstream valve and a control element, wherein the control chamber is connected to the fuel pressure accumulator, and wherein the main valve has a pressure chamber that is continuously connected to the fuel pressure accumulator.

[0018] It is further provided that the control element is forced into a closed position in a first switching position, in which the control chamber of the main valve is under pressure, so that a passage between the fuel pressure accumulator and the pressure booster is closed, whereby the control element can be adjusted via a pressure change in the control chamber.

[0019] Furthermore, it is provided that the control element of the main valve is forced towards the control chamber by actuating the pilot valve depending on a pressure ratio between the control chamber and the pressure chamber of the main valve, and that the pressure booster piston of the pressure booster is activated in a second switching position by actuating the main valve, wherein in the second switching position the control chamber of the main valve is depressurized, so that the control element of the main valve is forced into the second switching position in which the passage between the fuel pressure accumulator and the pressure booster is open.

[0020] The invention is based on the finding that the pressure intensifier can be controlled with particular precision by means of such an internal pressure intensifier, resulting in an optimal pressure profile in the high-pressure chamber of the pressure intensifier. This is because the pre-valve can be used with a fast response to control signals, since the pre-valve does not need to be designed to allow the flow of all the fuel to be pressurized, but only the flow of the control fluid for controlling the main valve. Furthermore, the additional stage in the form of the pre-valve allows for a higher overall pressure in the high-pressure chamber of the pressure intensifier and thus a higher injection pressure, so that the high-pressure pump of the fuel accumulator can be designed to generate a lower fuel pressure in the common rail.Furthermore, the volumetric efficiency is better and the high pressure is only present directly at the injector and not in the common rail as a whole.

[0021] For rapid activation and precise adjustability of the pre-valve, it has proven advantageous for the pre-valve to be electromagnetically or electrically actuated, for example, by means of a coil or a piezoelectric element. A valve actuated by a piezoelectric element allows for the application of particularly high forces within a very short time.

[0022] With regard to a compact design of the two-stage valve, it has proven advantageous for the main valve to be a medium-operated valve, i.e., as mentioned above, a hydraulic valve, for example a medium-operated proportional valve.

[0023] The main valve is preferably connected directly behind the upstream valve, whereby the outflowing fluid of the upstream valve can be used as the hydraulic control fluid to control the main valve.

[0024] With a view to a rapid response of the main valve to an adjustment of the pilot valve, it has proven advantageous that the control element of the main valve is axially adjustable via the control chamber which is in fluid communication with a fluid outlet of the pilot valve.

[0025] In other words, the pre-valve and the main valve are cascaded. Actuating the pre-valve moves the control element of the main valve, while actuating the main valve activates the pressure booster piston.

[0026] To provide efficient pressure amplification, it has proven advantageous for the main valve, which is connected directly behind the pre-valve, to be designed to open and close the passage between the fuel pressure accumulator and a fluid inlet of the pressure booster.

[0027] Releasing the fluid connection between the fuel pressure accumulator and the fluid inlet of the pressure booster causes the pressure booster piston of the pressure booster to pressurize the fuel in a high-pressure chamber of the pressure booster, so that injection can take place at a higher pressure than the rail pressure.

[0028] After the passage is closed, the high-pressure chamber and / or a spring chamber of the pressure booster are supplied with fuel from a fuel reservoir, such as a low-pressure chamber, whereupon a new pressure cycle can be initiated. For this purpose, the fluid inlet of the pressure booster, the high-pressure chamber of the pressure booster, and / or the spring chamber of the pressure booster can be connected to the low-pressure chamber via the main valve after the pressure boosting has taken place.

[0029] With regard to a particularly good sealing of the main valve in the closed position, it has proven advantageous that the main valve has a closing element preferably connected to the control element with a substantially spherical sealing surface.

[0030] In particular, the closing element features a preferably vapor-deposited or coated closing ball. The closing ball can be configured to close the passage between the fuel pressure accumulator and the fluid inlet of the pressure booster in the closed position of the main valve. Alternatively or additionally, the closing ball, or a further closing ball, can be provided to tightly seal a passage between the fluid inlet of the pressure booster and the low-pressure chamber in a second operating position of the main valve.

[0031] A spherical sealing surface provides a particularly good and reliable seal, even with potential dimensional tolerances in the passages to be sealed. The tightness of the main valve can be further improved by coating or vapor-depositing the sealing surface with a sealing material.

[0032] Typically, the fuel in the rail is under a pressure of approximately 200 bar. With regard to effective pressure amplification by the pressure booster, it has proven advantageous that the geometric area ratio between an inflow and an outflow side of the pressure booster piston is arranged such that the pressure booster results in a pressure increase compared to the pressure in the fuel pressure accumulator by a factor of 3 or more, in particular 5 or more.

[0033] In other words, with a suitable geometric design of the pressure booster piston, pressures of 600 bar or more, and in particular 1000 bar or more, can be achieved. When using high-pressure pumps with a higher output pressure (for example, approximately 350 bar to approximately 400 bar), injection pressures of significantly more than 2000 bar, and in particular 3000 bar or more, are even possible, as may be desirable especially for diesel injectors, without having to address the issue of the rail and line strength.

[0034] Preferably, the fluid outlet of the pre-valve can be connected to the fuel pressure accumulator or to a low-pressure chamber as required, with the fluid outlet of the pre-valve being in fluid communication with the control chamber of the main valve.

[0035] As mentioned, the upstream valve is a 3 / 2-way servo valve. A servo valve allows for a smooth transition between switching positions, so the fluid flow through the valve can be continuously adjusted. A servo valve reacts particularly quickly to switching signals and enables very precise pressure control.

[0036] With regard to efficient pressure control, it has proven advantageous that in the first switching position the pilot valve connects a control chamber of the main valve to the fuel pressure accumulator and in the second switching position connects the control chamber of the main valve to the low-pressure chamber, such as a return line and / or a leakage chamber.

[0037] Consequently, in the first switching position, the control chamber of the main valve is under pressure, so that a control element of the main valve is forced into a closed position, in which a passage between the fuel pressure accumulator and the pressure booster is closed.

[0038] Furthermore, in the second switching position, the control chamber of the main valve is depressurized, so that the control element of the main valve can be forced into a position in which the passage between the fuel pressure accumulator and the pressure booster is open.

[0039] The control element of the main valve is axially movable between the control chamber and a pressure chamber of the main valve. The area of ​​the control element's inflow surface facing the control chamber can differ from that facing the pressure chamber, so that a resultant force acts on the control element at the same fluid pressure on both sides. The pressure chamber of the main valve can be permanently connected to the fuel pressure accumulator. Depending on the pressure ratio between the control chamber and the pressure chamber of the main valve, the control element moves towards the control chamber or towards the pressure chamber, thereby activating or deactivating the pressure booster.

[0040] In other words, the fuel in the fuel pressure accumulator is used both to control the main valve's control element and as a working fluid.

[0041] This eliminates the need for an additional pressure pump and a separate fluid chamber for a control fluid to control the main valve.

[0042] Furthermore, with regard to effective pressure amplification and efficient fuel supply to the pressure booster, it has proven advantageous for the main valve to connect the fluid inlet of the pressure booster to a fuel reservoir in the low-pressure chamber in the first switching position of the pre-valve, and to connect the fluid inlet of the pressure booster to the fuel pressure chamber in the second switching position of the pre-valve.

[0043] With regard to independent control of the injector and the pressure booster, it has proven advantageous to provide a further valve controlled by a coil, such as a 3 / 2-way valve, for adjusting the injector from the closed position to the injection position and vice versa, wherein in the injection position the further valve connects a low-pressure chamber with a control chamber of the injector and in the closed position connects the control chamber of the injector with the fuel pressure accumulator, wherein a pressure chamber of the injector is connected to the fuel pressure accumulator.

[0044] The additional valve can be electrically or electromagnetically controlled. For example, the additional valve can be controlled by means of a coil or a piezoelectric element.

[0045] The additional valve makes it possible to operate the injector using only the fuel pressure in the fuel pressure accumulator, without using the pressure booster.

[0046] For this purpose, the other valve is adjusted to the injection position using the piezo element and / or the coil.

[0047] However, if a higher injection pressure is required, the pressure booster is used. The maximum adjustable injection pressure depends on the pressure in the common rail and the geometric area ratio of the pressure booster piston. To activate the pressure booster, the pilot valve is actuated. This reduces the pressure in the control chamber of the main valve, opening the passage between the fuel pressure accumulator and the pressure booster. The pump pressure from the high-pressure pump is now applied to the pressure booster, resulting in pressure amplification. Depending on the timing of the valves, the injection rate and / or the injection profile can be set and modulated with exceptional precision and repeatability.

[0048] The invention will be explained in more detail below with reference to the drawing. This shows in Fig. 1 a schematic circuit diagram of a preferred embodiment of a fuel injection device according to the invention, Fig. 2 a two-stage valve with pre-valve and main valve of the fuel injection device according to the invention in a schematic sectional view, Fig. 3 the pre-valve of the two-stage valve from Fig. 2 in an enlarged sectional view, Fig. 4 the main valve of the two-stage valve from Fig. 2 in an enlarged sectional view, Fig. 5a the fuel injection device according to the invention made of Fig. 1 in a perspective view, Fig. 5b the fuel injection device according to the invention made of Fig. 1 in a sectional view, Fig. 6 a diagram in which the injection pressure generated by means of the fuel injection device according to the invention is plotted against time.

[0049] The in Fig. A schematically illustrated, preferred embodiment of a fuel injection device 100 according to the invention for an internal combustion engine (for example, a diesel engine or a gasoline engine) comprises a high-pressure source 11 such as a high-pressure fuel pump, a fuel pressure accumulator 10, a low-pressure chamber 50 such as a leakage line or a return line, an injector 12 with an injection nozzle 14, a pressure booster 20, and a two-stage valve consisting of a pre-valve 30 and a main valve 40 for activating the pressure booster 20.

[0050] In the injector 12, an injection piston or a nozzle needle can be arranged to be axially displaceable, which closes injection ports in a closed position of the injector 12. The injection piston can be adjusted from the closed position to an injection position and vice versa via a further valve 60, in particular a 3 / 2-way valve. In the injection position, the further valve 60 connects the low-pressure chamber 50 to a control chamber 15 of the injector 12, and in the closed position, the valve 60 connects the control chamber 15 of the injector 12 to the fuel pressure accumulator 10, or vice versa. A pressure chamber 17 of the injector 12 is connected to the fuel pressure accumulator 10.

[0051] The other valve 60 is a directly driven 3 / 2-way valve. It can be controlled by means of a coil 62 or by means of a piezoelectric element.

[0052] Documents DE 10 2008 015 857 A1, EP 1 892 409 B1 and EP 2 057 372 B1 describe details of the features of the injector 12 and its connection options to the fuel pressure accumulator 10, which are hereby incorporated into the present disclosure by express reference.

[0053] The pressure intensifier 20 has an axially displaceable pressure intensifier piston 22, which separates a fluid inlet 24, a spring chamber 23, and a high-pressure chamber 26 of the pressure intensifier 20. A return spring is arranged in the spring chamber 23. The pressure intensifier 20 serves to increase the injection pressure generated by the injection piston. The pressure intensifier piston 22 (plunger) achievable is freely selectable via the geometric design of the plunger. For example, the pressure can be increased by a factor of 5. With a fuel pressure in the fuel pressure accumulator 10 of approximately 200 bar, a pressure increase to approximately 1000 bar or more is possible by the pressure intensifier 20.

[0054] For diesel injectors, even higher injection pressures of more than 3000 bar may be desired. For this purpose, the plunger design can be adapted accordingly and / or a more powerful high-pressure pump can be used as the high-pressure source 11.

[0055] Details concerning the features and operation of the pressure intensifier are also explained in the publications DE 10 2008 015 857 A1, EP 1 892 409 B1 and EP 2 057 372 B1 and are incorporated into the present disclosure by reference.

[0056] The following section will discuss the activation of the pressure amplifier 20 via a two-stage valve, which is of particular importance for the present invention.

[0057] The pre-valve 30 is a 3 / 2-way valve electromagnetically actuated by means of a coil 32, and the main valve 40 is a hydraulic valve. The fluid outlet 34 of the pre-valve 30 is connected to a control chamber 42 of the main valve 40, resulting in a cascaded valve arrangement. In other words, the pressure in the control chamber 42 of the main valve 40 can be adjusted by actuating the pre-valve 30.

[0058] In the Fig. In the first switching position I shown in Figure 1, the pilot valve 30 connects the fuel pressure accumulator 10 to the control chamber 42 of the main valve 40. This pushes a control element 44 of the main valve 40 axially away from the control chamber 42 and closes a passage between the fuel pressure accumulator 10 and the fluid inlet 24 of the pressure booster 20 (see Figure 1). Fig. 2 and Fig. 4) At the same time, the main valve 40 can open a passage between the low-pressure accumulator 50 and the fluid inlet 24 of the pressure booster 20.

[0059] In the Fig. In the second switching position II shown in Figure 2, the pilot valve 30 connects the control chamber 42 of the main valve 40 to the low-pressure chamber 50, thus depressurizing the control chamber 42. This results in a force acting on the control element 44 of the main valve 40, which forces the control element 44 towards the control chamber 42. This opens the passage between the fuel pressure accumulator 10 and the fluid inlet 24 of the pressure booster 20, thereby activating the pressure booster 20. Simultaneously, the passage between the low-pressure accumulator 50 and the fluid inlet 24 of the pressure booster 20 can be closed.

[0060] The pressure chamber 47 of the main valve 40 can be continuously connected to the fuel pressure accumulator 10. In this case, the resulting force pushing the control element 44 towards the control chamber 42 in the second switching position II is due to the geometric design of the control element 44.

[0061] Furthermore, a fluid connection can be provided between the spring chamber 23 of the pressure booster 20 and the low-pressure chamber 50 (see Fig. 2).

[0062] At least one closing element 46 in the form of a closing ball is arranged on the control element 44 of the main valve 40. In the first switching position I, the closing ball seals the passage between the fuel pressure accumulator 10 and the fluid inlet 24 of the main valve 40 by contacting a sealing surface of the main valve 40. Alternatively or additionally, in the second switching position II, the closing ball or another closing ball seals the passage between the fluid inlet 24 of the main valve 40 and the low-pressure chamber 50 by contacting another sealing surface of the main valve 40. The use of a ball offers certain advantages with regard to tolerances and sealing. Furthermore, the ball can be vapor-deposited or coated to achieve even better sealing.

[0063] The pre-valve 30 is designed as a servo valve, enabling particularly precise and essentially linear pressure adjustment across its entire switching range. The main valve 40 can be a medium-controlled proportional valve or a medium-controlled servo valve.

[0064] Further details of the pre-valve 30 and the main valve 40 are described in the Fig. 3 respectively Fig. Figure 4 shows the pre-valve 30. This pre-valve 30 is a servo valve with a spring as a return element, which holds the pre-valve 30 in the second switching position II when the coil 32 is not activated to activate the pre-valve 30.

[0065] A shut-off valve is arranged between the fluid inlet 24 and the high-pressure chamber 26 of the pressure booster 20, and a shut-off valve is arranged between the high-pressure chamber 26 and the injector 12, also in the direction of the high-pressure chamber 26.

[0066] In Fig. Figure 5a shows the fuel injection device 100 according to the invention in a perspective view, and in Fig. Figure 5b shows a sectional view of the fuel injection device 100 according to the invention. At its lower end, the fuel injection device 100 has the injector 12 with the injection nozzle 14. This is adjusted from a closed position to an injection position and vice versa via the further valve 60. The injection pressure is increased by activating the pressure amplifier 20, which includes the pressure amplifier piston 24.

[0067] The pressure profile of the resulting injection pressure is in Fig.Figure 6 is shown against time. It is clearly evident that the injection pressure increases by approximately a factor of five compared to the fuel pressure in the rail during the time window between approximately 5 ms and 11 ms in which the pressure booster 20 is activated. This allows maximum injection pressures of more than 3000 bar to be achieved. Furthermore, the pressure slopes are very steep and the increased pressure is very constant. Reference symbol list 10 Fuel pressure accumulators (common rail) 11 High-pressure source 12 injectors 14 Injector nozzle 15 Injector control chamber 17 Pressure chamber of the injector 20 pressure boosters 22 pressure booster pistons 23 Spring chamber of the pressure booster 24 Fluid inlet of the pressure booster 26 High-pressure chamber of the pressure intensifier 30 Pre-valve 32 coil 34 Fluid outlet of the pre-valve 40 Main valve 42 Control chamber of the main valve 44 Control element 46 Locking element 47 Pressure chamber of the main valve 50 Low-pressure room 60 more valve 62 Coil 100 Fuel injection device I first switching position II second switching position

Claims

Fuel injection device (100) for an internal combustion engine, in particular of a motor vehicle, comprising a fuel pressure accumulator (10), an injector (12) with an injection nozzle (14) which is adjustable from a closed position to an injection position and vice versa, and a pressure booster (20) with a pressure booster piston (22) for increasing the injection pressure that can be generated by the injection nozzle (14), and a two-stage valve with a main valve (40) controlled via a pilot valve (30) for activating the pressure booster (20), wherein the pilot valve (30) is a 3 / 2-way servo valve and the main valve (40) is a hydraulic valve, wherein the outflowing fluid of the pilot valve (30) is used as the hydraulic control fluid for controlling the main valve (40), and the main valve (40) has a control chamber (42) in fluid communication with a fluid outlet (34) of the pilot valve (30) and a control element. (44) exhibitswherein the control chamber (42) is connected to the fuel pressure accumulator (10), wherein the main valve (40) has a pressure chamber (47) which is continuously connected to the fuel pressure accumulator (10),- the control element (44) is forced into a closed position in a first switching position (I) in which the control chamber (42) of the main valve (40) is pressurized, so that a passage between the fuel pressure accumulator (10) and the pressure booster (20) is closed, wherein the control element (44) is adjustable via a pressure change in the control chamber (42), and- the control element (44) of the main valve (40) is forced towards the control chamber (42) by actuating the pilot valve (30) depending on a pressure ratio between the control chamber (42) and the pressure chamber (47) of the main valve (40), and by actuating the main valve (40) the pressure booster piston (22) of the pressure booster (20) in a second Switch position (II) is activated,wherein in the second switching position (II) the control chamber (42) of the main valve (40) is depressurized, so that the control element (42) of the main valve (40) is forced into the second switching position (II) in which the passage between the fuel pressure accumulator (10) and the pressure booster (20) is open. Fuel injection device (100) according to claim 1, wherein the pre-valve (30) is a valve that can be actuated electromagnetically or electrically, in particular by means of a coil (32) or by means of a piezoelectric element. Fuel injection device (100) according to claim 1 or 2, wherein the control element (44) of the main valve (40) is axially adjustable via the control chamber (42) which is in fluid communication with the fluid outlet (34) of the pilot valve (30). Fuel injection device (100) according to at least one of the preceding claims, wherein the main valve (40) is connected directly behind the pre-valve (30) and is configured to open and close the passage between the fuel pressure accumulator (10) and a fluid inlet (24) of the pressure booster (20). Fuel injection device (100) according to claim 3 or 4, wherein the main valve (40) has a closing element (46) connected to the control element (44) with a substantially spherical sealing surface for closing the passage. Fuel injection device (100) according to claim 5, wherein the closing element (46) has a vapor-deposited or coated closing ball. Fuel injection device (100) according to at least one of the preceding claims, wherein a geometric area ratio between an inflow and outflow side of the pressure booster piston (22) is arranged such that the pressure booster (20) provides a pressure increase compared to the pressure in the fuel pressure accumulator (10) by a factor of 3 or more. Fuel injection device (100) according to at least one of the preceding claims, wherein the pilot valve (30) in the first switching position (I) connects the control chamber (42) of the main valve (40) to the fuel pressure accumulator (10) and in the second switching position (II) connects the control chamber (42) of the main valve (40) to the low-pressure chamber (50), such as a return line and / or a leakage chamber. Fuel injection device (100) according to claim 8, wherein the main valve (40) in the first switching position (I) of the pre-valve (30) connects the fluid inlet (24) of the pressure booster (20) to the low-pressure chamber (50) and in the second switching position (II) of the pre-valve (30) connects the fluid inlet (24) of the pressure booster (20) to the fuel pressure chamber (10). Fuel injection device (100) according to one of the preceding claims, comprising a further valve (60) controlled by a coil (62), such as a 3 / 2-way valve, for adjusting the injection nozzle (14) from the closed position to the injection position and vice versa, wherein the further valve (60) in the injection position connects a low-pressure chamber (50) with a control chamber (15) of the injector (12) and in the closed position connects the control chamber (15) of the injector (12) with the fuel pressure accumulator (10), wherein a pressure chamber (17) of the injector (12) is connected to the fuel pressure accumulator (10).

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