Fuel injector and internal combustion engine having a fuel injector

Abstract

The present invention relates to a fuel injector for an internal combustion engine. The fuel injector comprises a hydraulically actuable first supply system for a first fuel which can be supplied to the internal combustion engine via a first fuel supply path, and a second supply system for a liquid second fuel, with a second fuel supply path, a control fluid path and a blocking fluid path. The second supply system is designed to supply the second fuel to the internal combustion engine via the second fuel supply path, as control fluid for actuating the first supply system via the control fluid path, and as blocking fluid via the blocking fluid path to prevent leakage of the first fuel from the first fuel supply path into the control fluid path. The blocking fluid path branches off from the control fluid path at a first branch. A first pressure control valve is arranged at the first branch or downstream of the first branch.

Description

[0001] Fuel injector and internal combustion engine with fuel injector

[0002] The present invention relates to a fuel injector for an internal combustion engine and to the internal combustion engine provided with the fuel injector.

[0003] The present disclosure relates to fuel injectors (fuel injection valves) that are configured to operate with two fuels (for example, so-called dual-fuel injectors).

[0004] For example, in such a fuel injector, the supply of one fuel into the cylinder of the internal combustion engine can be carried out by a hydraulic control using the other fuel.

[0005] For example, in the described fuel injectors, the main energy input into the internal combustion engine can be provided by a first fuel, which can be under high pressure (up to a maximum of 60 MPa, preferably even more). Furthermore, the second fuel can also serve as the main fuel (when the operating mode of the internal combustion engine changes). Furthermore, the second fuel can serve not only as a control fluid for metering the first fuel, but also as a barrier fluid, which ensures a separation of the first fuel and the control fluid. In particular, the barrier fluid can form a barrier fluid seal (fluid seal), which ensures that the high-pressure first fuel does not penetrate into the area of ​​the fuel injector where the control fluid is located and mix with it.

[0006] If the second fuel is used as both a control and a barrier fluid, the barrier fluid path can be supplied via the control fluid path to simplify the fuel supply design. This option results from the pressure gradient between these two fluid circuits (barrier fluid pressure < control fluid pressure). To avoid impairing the combustion characteristics of the first fuel, it is also desirable to keep the uncontrolled fluid entry (as leakage fuel) of the second fuel from the barrier fluid circuit as low as possible. In addition to manufacturing factors (such as the selection of appropriate fits), this can be achieved by keeping the barrier fluid pressure as low as possible.

[0007] The two fuels can therefore be at very different pressures. In this case, maintaining pressure differences is essential for the function of the fuel injector due to its hydraulic control.

[0008] Due to the operation of the fuel injector, running-in or wear scenarios can occur which, without compensation, can significantly change the function of the fuel injector because they can affect the pressure differences.

[0009] The functional impairment of the fuel injector due to running-in or wear can lead to overloading of the fuel injector and damage to the internal combustion engine.

[0010] As a countermeasure, safeguarding or monitoring functions are conceivable that detect functional impairment of the fuel injector using measurement signals. These measurement signals are processed in the internal combustion engine's control unit, and the impairment of the fuel injector is compensated, for example, by extending the injection duration. This results in altered combustion, which must be taken into account during combustion design through appropriately robust and tolerance-based design. However, this type of design leads to reduced combustion efficiency. The components and processes required to monitor fuel injector function also adversely affect the complexity of the fuel injector and the internal combustion engine.

[0011] In order to achieve the structure of a fuel injector described above and the desired effects, and to eliminate or at least minimize the associated disadvantages, the invention provides for the installation of a pressure regulating valve in the transition from the control fluid circuit to the barrier fluid circuit. In the new or original condition of the fuel injector (which also includes a repaired or completely overhauled fuel injector), the pressure buildup in the barrier fluid circuit occurs subordinately or subordinately via the manufacturing-related leaks and essentially via the pressure regulating valve, which is arranged in the transition from the control fluid circuit to the barrier fluid circuit. The ratio of the supply components can vary from fuel injector to fuel injector due to manufacturing reasons and can be adjusted accordingly via the setting or control of the pressure regulating valve.

[0012] As the fuel injector's operating life increases, the proportion of pressure buildup in the fluid seal due to mating-related leaks (nozzle needle to nozzle needle guide) will increase (increasing clearance fit). In return, the supply of the second fuel via the pressure control valve can be reduced to keep the barrier fluid pressure essentially constant.

[0013] Preferably, a second pressure control valve can be arranged in a drain or outlet (drain line) of the blocking fluid path, for example to the leakage fuel line of the fuel injector.

[0014] From a predetermined degree of wear of the pairing of nozzle needle and its guide, it may also be advantageous to use the second optional pressure control valve to increase the discharge of the barrier fluid from the barrier fluid circuit or from the fluid seal.

[0015] From the activation rate of the first pressure control valve and / or the second optional pressure control valve, or from the ratio of the activation of both pressure control valves, conclusions can be drawn about the condition of the fuel injector and its wear behavior. Preferably, the feedback of the signals can be displayed (e.g., visualized) via the on-board diagnostics.

[0016] The fuel injector according to the invention, including preferred embodiments, can also be implemented if the barrier fluid supply is provided at reduced pressure via a pilot fuel supply. For example, the control fluid can be branched off from the pilot fuel circuit, and the barrier fluid, in turn, can be branched off from the control fluid circuit.

[0017] Preferably, the first pressure control valve and / or the second optional pressure control valve can additionally be functionally connected to an optional third pressure control valve installed in the fuel supply path of the first fuel.

[0018] The fuel injector described here can deliver constant operating values ​​throughout the TBO (Time Between Overhaul; corresponds to the period between two overhauls or repairs of the fuel injector or from commissioning until the first overhaul or repair of the fuel injector). Furthermore, the fuel injector can reduce the entry of leakage fluid from the barrier fluid circuit into the fuel supply path of the first fuel to a minimum or can be specifically varied towards the end of the TBO to maintain internal combustion engine operation. Furthermore, the fuel injector can prevent the first fuel from penetrating the control fluid path. Overall, the fuel injector can ensure more stable, reliable, and safer operation of the internal combustion engine. An internal combustion engine equipped with the fuel injector can therefore be operated more stable, reliably, and safely.

[0019] The effects and advantages described above are achieved by a fuel injector and an internal combustion engine having the features of the independent claims. Advantageous developments of the present invention are the subject of the dependent claims.

[0020] The fuel injector according to the invention comprises a hydraulically actuated first supply system for a first fuel, which can be supplied to the internal combustion engine via a first fuel supply path, and a second supply system for a liquid second fuel, having a second fuel supply path, a control fluid path, and a blocking fluid path. The second supply system is configured to supply the second fuel to the internal combustion engine via the second fuel supply path, as control fluid for actuating the first supply system via the control fluid path, and as blocking fluid via the blocking fluid path to prevent leakage of the first fuel from the first fuel supply path into the control fluid path. The blocking fluid path branches off from the control fluid path at a first branch. A first pressure control valve is arranged at the first branch or downstream of the first branch (in the flow direction of the second fuel).

[0021] Preferably, in the presently disclosed fuel injector, a valve member and a valve housing with a clearance fit are provided in the first supply system. The valve member can reciprocate within the valve housing to open and close a valve nozzle opening (for example, in the axial direction of the valve member and / or the valve housing). The opening and closing of the valve nozzle opening enables a controlled supply of the first fuel into the combustion chamber of the internal combustion engine.

[0022] Preferably, in the presently disclosed fuel injector, a control unit is connected to the first pressure regulating valve. The control unit is configured to control the first pressure regulating valve such that, as the fit (e.g., clearance fit) between the valve member and the valve housing increases over the operating time of the fuel injector, it reduces a pressure downstream of the first pressure regulating valve in response to the increasing fit. The pressure of the barrier fluid in the fluid seal is built up, on the one hand, by the barrier fluid path, which supplies the second fuel as barrier fluid to the fluid seal, and, on the other hand, by manufacturing- and operation-related leaks from the control fluid circuit. With increasing operating time of the fuel injector, the leaks can increase (e.g., due to increasing fits), thereby increasing the pressure in the fluid seal.To compensate for this continuous pressure increase and thus keep the barrier fluid pressure in the fluid seal constant throughout the operating life of the fuel injector, the control unit can control the pressure control valve in such a way that the barrier fluid pressure from the barrier fluid path decreases, thereby keeping the total pressure in the fluid seal constant. The individual pressure components as well as the total pressure can be measured using sensors or predicted or estimated, for example, using simulations, calculations, and / or empirical values ​​stored in characteristic maps. A mixture of measured and predicted or estimated values ​​can also be used.

[0023] In general, the terms “control” or “control” also include “regulation” or “regulation” (ie, a closed control circuit).

[0024] Preferably, in the presently disclosed fuel injector, a second pressure regulating valve is arranged in an outlet (drain, drain line) of the blocking fluid path. Even more preferably, the control unit is additionally connected to the second pressure regulating valve (or alternatively to the embodiment described above, in which the control unit is connected to the first pressure regulating valve). In this case, the control unit is configured to control the second pressure regulating valve such that, as the fit (e.g., clearance fit) between the valve member and the valve housing increases over the operating time of the fuel injector, it reduces a pressure upstream of the second pressure regulating valve in response to the increasing fit.The above-described control of the total pressure by reducing the pressure component generated by supplying the barrier fluid via the barrier fluid path can be achieved analogously, alternatively or additionally, by discharging the barrier fluid (instead of or in addition to the inlet) via the second pressure control valve. The principle remains the same: the increasing pressure component generated by the leak is compensated for via the regular outlet or inlet, so that the total pressure in the fluid seal remains constant.

[0025] Even more preferably, the control unit is configured to draw conclusions about the size of the fit (for example the clearance fit) between the valve member and the valve housing from a control signal of the first pressure control valve and / or the second pressure control valve or from a ratio of the control signals of the first pressure control valve and the second pressure control valve. This can be done, for example, using the aforementioned characteristic maps, which are created by simulations, calculations and / or empirical values. Even more preferably, the control unit is configured to adapt (extend or shorten) the period until maintenance or replacement of the fuel injector (i.e., the TBO) based on the conclusions about the size of the fit, and even more preferably to shorten it.

[0026] Through the aforementioned measures, the pressure of the barrier fluid in the fluid seal can be maintained at a desired level. Otherwise, the barrier fluid (second fuel) could enter the first fuel supply path of the first fuel (if the pressure in the fluid seal were too high), or the first fuel could enter the control fluid circuit (if the pressure in the fluid seal were too low). Both scenarios are undesirable and should be avoided.

[0027] Preferably, in the presently disclosed fuel injector, a third pressure control valve is arranged upstream of a nozzle chamber in the first fuel supply path. The nozzle chamber is a chamber in the valve housing that is arranged upstream of the valve nozzle opening in the flow direction of the first fuel and in which the first fuel, which is to be ejected through the valve nozzle opening into the combustion chamber of the internal combustion engine, can collect.

[0028] Even more preferably, the control unit is connected to the third pressure control valve in addition to the connection to the first and / or second pressure control valve. In this case, the control unit is configured to control the pressure in the nozzle chamber by means of the third pressure control valve. This allows the pressure ratio between the first fluid in the nozzle chamber and the barrier fluid to be adjusted.

[0029] Even more preferably, the control unit is configured to control each combination of the first, second, and third pressure regulating valves based on the size of the fit (e.g., the clearance fit) between the valve member and the valve housing. Preferably, in the presently disclosed fuel injector, the control fluid path branches off from the second fuel supply path at a second branch. The second branch is arranged upstream of the first branch in the flow direction of the second fuel in the second supply system. This makes it possible to simplify the design of the injector or the fuel supply for the second fuel, since, for example, components can be saved. For example, only one fuel reservoir (reservoir, fuel tank) and only one delivery means (such as a pump) for the second fuel are required.By means of these components, the second fuel is fed into the injector provided for injecting the second fuel into the combustion chamber. From this fuel supply path, the control fluid path then branches off at the second branch (possibly with a pressure reduction), which supplies the second fuel as control fluid to the fuel injector to control the supply of the first fuel. From the control fluid path, the blocking fluid path then branches off at the first branch (possibly with a pressure reduction), which supplies the second fuel as a blocking fluid for the fluid seal into the fuel injector. In this way, components specifically provided for the control fluid path and / or blocking fluid path, such as fuel reservoirs or conveying means, can be omitted (but do not have to be).

[0030] More preferably, a throttling means (a throttle, which may be fixed or variable) is arranged downstream of the second branch. In this way, the second fuel, which is supplied under high pressure in the second fuel supply path for injection into the combustion chamber, can be easily regulated (pressure-reduced) to the pressure required to control the supply of the first fuel into the combustion chamber.

[0031] More preferably, the throttling means is provided upstream of the first branch. In other words, the throttling means is preferably arranged between the first and second branches in the flow direction of the second fuel.

[0032] Alternatively or additionally, in the presently disclosed fuel injector, the pressure in the barrier fluid seal, which is supplied with the barrier fluid (and also with the leakage fluid), is adjustable within a range of 0.5 to 5 MPa above the pressure in the nozzle chamber, which is supplied with the first fuel. More preferably, the pressure in the barrier fluid seal is adjustable within a range of 1 to 3 MPa above the pressure in the nozzle chamber.

[0033] Preferably, in the presently disclosed fuel injector, a first control chamber and a second control chamber for actuating the valve member for supplying the first fuel into the combustion chamber of the internal combustion engine are provided in the control fluid path.

[0034] More preferably, a switching valve is arranged upstream of the first and second control chambers in the control fluid path. The switching valve is configured to alternately pressurize the first control chamber and the second control chamber using the second fuel as the control fluid. In this way, a simple and effective control of the supply of the first fuel to the combustion chamber of the internal combustion engine can be achieved.

[0035] More preferably, the switching valve is a four-port, two-position valve, such as a 4 / 2-way spool valve. Alternatively, the switching valve is a three-port, two-position valve, such as a 3 / 2-way spool valve.

[0036] Preferably, in the presently disclosed fuel injector, the first fuel is a liquid or gaseous fuel, such as liquefied petroleum gas or natural gas.

[0037] Alternatively or additionally, the second fuel is a fuel that is liquid at room temperature (approximately 21 degrees Celsius), such as diesel similar to DIN EN 590.

[0038] Preferably, in the presently disclosed fuel injector, the first fuel can be supplied to the internal combustion engine as the main fuel via the first fuel supply path in a first operating mode (for example, a gas drive mode). The second fuel can be supplied to the internal combustion engine as the pilot fuel in the first operating mode. The pilot fuel can be supplied to the combustion chamber of the internal combustion engine via a dedicated (or more than one) injector to ignite the first fuel. The injector for the pilot fuel can also be integrated with the fuel injector according to the invention. In a second operating mode (for example, in a diesel mode), the second fuel can be supplied to the internal combustion engine as the main fuel via the second fuel supply path.This supply can again be effected either via one (or more) specifically provided injectors or via one (or more) injectors integrated into the fuel injector according to the invention. This can be the same (integrated or separate) injector provided for the pilot fuel, or an injector specifically provided for supplying the second fuel as the main fuel, different from the pilot fuel injector. Preferably, in the second operating mode, the supply of the first fuel to the combustion chamber of the internal combustion engine is stopped (e.g., pure diesel operation).

[0039] Additionally or alternatively, the first supply system and the second supply system are designed downstream as two concentric nozzle needles. In the case of concentric nozzle needles, the nozzle needle for the first fuel is arranged on the outside, for example. This nozzle needle forms a first sealing seat with the injector housing. The nozzle needle for the second fuel is arranged, for example, inside the nozzle needle for the first fuel. The nozzle needle for the second fuel forms a second sealing seat with an inner side of the nozzle needle for the first fuel. This arrangement achieves a compact design. Because the nozzle needle for the first fuel is arranged on the outside in the concentric arrangement, a larger supply quantity of the first fuel can generally be provided. This arrangement is advantageous when the first operating mode is the primarily used or desired operating mode.However, if the second operating mode is the primarily used or desired operating mode, the arrangement of the concentric nozzle needles can be reversed so that the outer nozzle needle is used to supply the second fuel and the inner nozzle needle is used to supply the first fuel.

[0040] Alternatively, the first supply system and the second supply system are arranged in their downstream sections as two independent (non-concentrically arranged) nozzle needles in an injector housing. The independent nozzle needles each form their own sealing seat with the injector housing. Preferably, the nozzle needle for the first fuel is a plurality of nozzle needles arranged around the nozzle needle for the second fuel. Even more preferably, the nozzle needles for the first fuel are also hydraulically actuated via the control fluid path. This arrangement has the advantage that the first fuel, as the main fuel, can be distributed well and evenly in the combustion chamber of the internal combustion engine, thus optimizing the combustion process.The central arrangement of the nozzle needle for the second (pilot) fuel ensures uniform ignition of the main fuel in the combustion chamber, which further optimizes the combustion process.

[0041] Preferably, in the presently disclosed fuel injector, a further throttling means (e.g., a fixed or variable throttle) is provided in an outlet (outlet, outlet line) of the control fluid path. The outlet of the blocking fluid path opens into (ends in) the outlet of the control fluid path downstream of the further throttling means.

[0042] Alternatively, the drain (drain, drain line) of the control fluid path flows into the drain (drain, drain line) of the barrier fluid path.

[0043] In this way, the two paths that carry the second fuel at different pressures, namely the control fluid path and the barrier fluid path, can share common components, such as lines or a fuel storage device (reservoir, fuel tank).

[0044] The fuel injector described above comprises the first supply system for the first fuel and the second supply system for the second fuel, wherein the second supply system in turn comprises the second fuel supply path, the control fluid path, and the blocking fluid path. In this context, "comprises" refers to both structural (physical) and functional inclusion. This means that, on the one hand, the fuel injector according to the invention can structurally comprise the first and second supply systems, including all components, i.e., the two supply systems are arranged in the fuel injector. On the other hand, this also means that parts or components of the first and / or second supply systems can also be arranged (spatially / structurally) outside the (housing) of the fuel injector, but are assigned to the fuel injector according to their function.For example, any or all components from the group of fuel storage (reservoirs, fuel tanks) of the two fuels, the delivery means (pumps) for the fuels, the described throttling means, the described first to third pressure control valves, the described switching valve, corresponding fuel lines, the control unit, etc., can be arranged outside the fuel injector, but functionally be part of the fuel injector.

[0045] According to the invention, an internal combustion engine is also provided which comprises the fuel injector described above in all the described embodiments.

[0046] All fuel injector designs described above and below, or individual components or functions of the described designs, can be combined with each other, unless this is technically impossible. The same applies to all described internal combustion engine designs.

[0047] An exemplary embodiment of the fuel injector according to the invention is described below with reference to Fig. 1.

[0048] Fig. 1 shows schematically an embodiment of the fuel injector.

[0049] As already described, the components shown in Fig. 1 are not necessarily a structural component of the fuel injector according to the invention. However, if the individual components are described as belonging to the fuel injector, they are in any case a functional component of the fuel injector.

[0050] In Fig. 1, the fuel injector 1 is shown only schematically.

[0051] In the exemplary embodiment shown, the first fuel is the main fuel and can be, for example, liquefied petroleum gas or natural gas, which is supplied and combusted in either liquid or gaseous form during normal operation of the internal combustion engine. The second fuel is used as a pilot fuel in the embodiment shown and can be, for example, diesel. A first supply system 20 serves to supply the first fuel to the internal combustion engine for combustion. In the embodiment shown in Fig. 1, the first supply system 20 comprises a first fuel supply path 21, a first valve housing 22, 23, a valve member (a nozzle needle) 24, a nozzle chamber 25, at least one valve nozzle opening 26, a (first) fuel line 27, a (first) delivery means (first fuel pump) 28, and a (first) fuel reservoir (first fuel tank) 29.

[0052] The valve housing 22, 23 is constructed in two parts. In the present embodiment, a lower valve housing part 23 accommodates the valve nozzle opening 26, the nozzle chamber 25, a lower part of the nozzle needle 24, and a fluid seal 65 together with parts of a barrier fluid line 63, a drain line 64 for the barrier fluid, and the fuel line 27. An upper valve housing part 22 accommodates an upper part of the nozzle needle 24, a first and second control chamber 54, 55, a spring 81, and parts of a control fluid line 51 and a drain line 53 for the control fluid. The two valve housing parts are assembled in one piece and form the valve housing 22, 23. The valve housing can also be constructed from one or more than two housing parts.

[0053] In this case, the nozzle needle 24 is hydraulically movable back and forth within the valve housing 22, 23. The nozzle needle 24 is guided through the valve housing 22, 23.

[0054] Accordingly, there is a clearance fit between the nozzle needle 24 and the valve housing 22, 23, which becomes increasingly larger due to wear with increasing operating time. The clearance fit results in gaps (e.g. annular gaps) between the nozzle needle 24 and the valve housing 22, 23, so that an (undesired) fluidic connection (fluid path) exists between the nozzle chamber 25, the fluid seal 65 and the first and second control chambers 54, 55. The cross-section or the capacity of the fluid path between the nozzle needle 24 and the valve housing 22, 23 becomes increasingly larger as the clearance fit between the nozzle needle 24 and the valve housing 22, 23 increases, and the undesired fluid exchange between the nozzle chamber 25, the fluid seal 65 and the first and second control chambers 54, 55 therefore increases with increasing operating time of the fuel injector 1. In the (in Fig.1 exemplary upper part) the nozzle-remote part of the nozzle needle 24 has a control section (shown in the figure as a section with an enlarged diameter).

[0055] In the first fuel supply path 21, the first fuel is pumped under high pressure from the first fuel tank 29 through the first fuel line 27 into the nozzle chamber 25 by the first fuel pump 28. The first fuel collects in the nozzle chamber 25. As soon as the nozzle needle 24 is hydraulically lifted by the control fluid (as described below), it releases the valve nozzle opening 26. The first fuel is ejected under high pressure into the combustion chamber of the engine (not shown) for combustion.

[0056] In the present embodiment, a (third) pressure control valve 82 is arranged between the first fuel pump 28 and the nozzle chamber 25 on the first fuel line 27.

[0057] The fuel injector 1 also includes a second supply system 30. The second supply system 30 serves to supply the second fuel to the internal combustion engine for combustion. In the embodiment shown in Fig. 1, the second supply system 30 includes a second fuel supply path 40, a control fluid path 50, and a blocking fluid path 60. The second supply system 30 also includes a (second) delivery means (second fuel pump) 31, a (second) fuel reservoir (second fuel tank) 32, a (second) fuel line 33, and the valve housing 22, 23.

[0058] In the embodiment shown here, the second fuel supply path 40 comprises a (third) fuel line 41 and at least one pilot injector 42.

[0059] In the second fuel supply path 40, the second fuel is pumped under high pressure from the second fuel tank 32 through the fuel line 41 into the pilot injector 42 by means of the second fuel pump 31, and is expelled by the latter under high pressure into the combustion chamber of the engine (not shown) for combustion or igniting the first fuel. In another operating mode, in which the second fuel is the main fuel, the at least one pilot injector serves to inject the second fuel (not as pilot fuel but) as the main fuel for combustion in the internal combustion engine. Preferably, no first fuel is supplied to the internal combustion engine in the other operating mode (for example, pure diesel operation).

[0060] The control fluid line 51 branches off from the fuel line 33 at a second branch 72, which in this case is arranged downstream of the second fuel pump 31 and upstream of the pilot injector 42.

[0061] In the embodiment shown here, the control fluid path 50 comprises the control fluid line 51, a switching valve 52, the drain line 53 of the control fluid, the first control chamber 54 and the second control chamber 55.

[0062] In the present embodiment, a throttling means (a throttle) 56 is arranged downstream of the second branch 72 in the flow direction of the second fuel. A first branch 71 is arranged downstream of the throttle 56 in the flow direction of the second fuel, at which the blocking fluid path 60 branches off from the control fluid path 50.

[0063] The second fuel that does not flow into the pilot injector 42 via the fuel line 41, i.e., a portion of the second fuel, flows into the control fluid line 51 at the second branch 72 as control fluid. The pressure of the control fluid is reduced in the throttle 56. The portion of the second fuel that does not flow into the blocking fluid path 60 at the first branch 71, i.e., a portion of the second fuel, flows further toward the switching valve 52 as control fluid.

[0064] As indicated in Fig. 1, when the switching valve 52 is not activated or energized, it is preloaded (first switching position) such that the control fluid coming from the second fuel tank 32 flows into the first control chamber 54. In cooperation with the (optional) spring 81 arranged in the first control chamber 54, the control fluid preloads the nozzle needle 24 into the closed position, in which the at least one valve nozzle opening 26 is closed, so that the first fuel cannot flow from the nozzle chamber 25 into the combustion chamber of the engine. On the opposite side (near the valve nozzle opening 26) of the control section (far from the valve nozzle opening 26) of the nozzle needle 24, the second control chamber 55 is connected to the drain line 53 of the control fluid in the first switching position of the switching valve 52, so that the control fluid can drain into the second fuel tank 32 via the switching valve 52.In other words, in the first switching position of the switching valve 52, the first control chamber 54 is pressurized, and the pressure in the second control chamber 55 is reduced. In still other words, in the first switching position of the switching valve 52, the nozzle needle 24 opens at least one valve nozzle opening 26.

[0065] Only when the switching valve 52 is activated or energized does it, in the embodiment shown here, move against its preload into a second switching position, in which the control fluid coming from the second fuel tank 32 flows into the second control chamber 55. In addition, in the second switching position of the switching valve 52, the first control chamber 54 is connected to the control fluid drain line 53, so that the control fluid can drain via the switching valve 52 into the second fuel tank 32. In other words, in the second switching position of the switching valve 52, the second control chamber 55 is pressurized, and the pressure in the first control chamber 54 is reduced. As a result, the nozzle needle 24 is moved away from the valve seat, which it forms with the lower valve housing part 23, and opens the valve nozzle opening.In the second switching position of the switching valve 52, the first fuel can be injected from the nozzle chamber 25 via the valve nozzle opening 26 into the combustion chamber of the internal combustion engine for combustion. In other words, in the second switching position of the switching valve 52, the second control chamber 55 is pressurized, and the pressure in the first control chamber 54 is reduced. In still other words, in the second switching position of the switching valve 52, the nozzle needle 24 closes the at least one valve nozzle opening 26.

[0066] In this way, the nozzle needle 24 is hydraulically actuated essentially by means of the switching valve 52 and the first and second control chambers 54, 55, which are located on opposite sides of the control section of the nozzle needle 24. The second fuel serves as the control fluid. In the embodiment shown here, the blocking fluid path 60 comprises the blocking fluid line 63, the (first) pressure regulating valve 61, which is arranged on the blocking fluid line 63, the blocking fluid seal 65, and the drain line 64. The pressure regulating valve 61 can be arranged downstream of the first branch 71 in the flow direction of the blocking fluid. Alternatively, it can be arranged directly at the first branch 71. In a preferred embodiment, the pressure regulating valve 61 represents or comprises the first branch. Preferably, the barrier fluid path 60 comprises a (second) pressure control valve 62 arranged on the drain line 64.

[0067] At the first branch 71, the blocking fluid path 60 branches off from the control fluid path 50. The second fuel that does not flow via the control fluid line 51 to the switching valve 52, i.e., a portion of the second fuel, flows into the blocking fluid line 63. There, the second fuel flows as blocking fluid via the pressure control valve 61 into the blocking fluid seal 65.

[0068] The blocking fluid then flows into the second fuel tank 32 via the drain line 64 and - if present - the pressure control valve 62.

[0069] A further throttling means (throttle), for example, downstream of the switching valve 52, can be arranged in the outlet line 53 of the control fluid path 50. The outlet line 64 of the blocking fluid path 60 can open into the outlet line 53 of the control fluid path 50 downstream of the further throttle, so that the blocking fluid flows into the pressure-reduced control fluid.

[0070] Alternatively, for example downstream of the switching valve 52, the drain line 53 of the control fluid path 50 can open into the drain line 64 of the blocking fluid path 60.

[0071] By combining the downstream parts of the drain lines 53 and 64, the structure of the fuel injector 1 is simplified and / or components and / or installation space are saved.

[0072] A control unit (not shown in the present embodiment) can be connected to at least one or any combination of the three pressure control valves 61, 62, and 82 and can control the pressure control valves (the pressure control valve) to adjust the pressure(s) in the barrier fluid seal 55 and / or in the nozzle chamber. In particular, the control unit can ensure that the pressure changes in the barrier fluid seal 55 and / or in the nozzle chamber, which result from leaks due to the increasingly large fit between the nozzle needle 24 and the valve housing 22, 23 with increasing operating time, are compensated by the pressure control valves (the pressure control valve).

[0073] The control unit can be configured to evaluate the control signals to the pressure control valves (the pressure control valve) and to calculate or estimate the size of the fit or the change in the fit between the nozzle needle 24 and the valve housing 22, 23 from this. Preferably, the control unit can use the results to adjust the TBO. Adjusting involves shortening the TBO if the fit exceeds a predetermined threshold or falls within a predetermined range, or lengthening the TBO if the fit falls below a predetermined threshold or falls within a predetermined range. Alternating between shortening and lengthening is also possible as a result of repeated evaluation of the control signals.

Claims

Claims 1. Fuel injector (1) for an internal combustion engine, comprising a hydraulically actuated first supply system (20) for a first fuel, which can be supplied to the internal combustion engine via a first fuel supply path (21); and a second supply system (30) for a liquid second fuel, with a second fuel supply path (40), a control fluid path (50) and a blocking fluid path (60); wherein the second supply system (30) is designed to supply the second fuel to the internal combustion engine via the second fuel supply path (40), as control fluid for actuating the first supply system (20) via the Control fluid path (50), and as a barrier fluid via the barrier fluid path (60) to prevent leakage of the first fuel from the first fuel supply path (21) into the control fluid path (50); the barrier fluid path (60) branches off from the control fluid path (50) at a first branch (71); and a first pressure control valve (61) is arranged at or downstream of the first branch (71).

2. Fuel injector (1) according to claim 1, wherein in the first supply system (20) a valve member (24) and a valve housing (22) are provided with a clearance fit, so that the valve member (24) can move back and forth in the valve housing (22) to open and close a valve nozzle opening (26); and preferably a control unit is connected to the first pressure regulating valve (61) and configured to control the first pressure regulating valve (61) to reduce a pressure downstream of the first pressure regulating valve (61) in response to the increasing clearance fit as the clearance fit increases over the operating time of the fuel injector (1).

3. Fuel injector (1) according to claim 2, wherein a second pressure regulating valve (62) is arranged in an outlet (64) of the blocking fluid path (60); and preferably the control unit is additionally connected to the second pressure regulating valve (62) and is configured to control the second pressure regulating valve (62) to reduce a pressure upstream of the second pressure regulating valve (62) in response to the increasing clearance fit as the clearance fit increases over the operating time of the fuel injector (1).

4. Fuel injector (1) according to claim 2 or 3, wherein the control unit is configured to draw conclusions about a size of the clearance fit from a control signal of the first pressure control valve (61) and / or the second pressure control valve (62) or from a ratio of the control signals of the first pressure control valve (61) and the second pressure control valve (62) and, preferably, to adapt the period until maintenance or replacement of the fuel injector (1) on the basis of the conclusions, and even more preferably to shorten it.

5. Fuel injector (1) according to one of claims 2 to 4, wherein a third pressure regulating valve (82) is arranged upstream of a nozzle chamber (25) in the first fuel supply path (21); and preferably the control unit is additionally connected to the third pressure regulating valve (82) and is configured to control the pressure in the nozzle chamber (25) by means of the third pressure regulating valve (82); and even more preferably the control unit is configured to control the first, second and third pressure regulating valves (61, 62, 82) based on the size of the clearance fit.

6. Fuel injector (1) according to one of the preceding claims, wherein the control fluid path (50) branches off from the second fuel supply path (40) at a second branch (72) arranged upstream of the first branch (71) in the second supply system (30), and preferably a throttling means (56) is provided downstream of the second branch (72), and more preferably upstream of the first branch (71); and / or a pressure in a barrier fluid seal (65) that can be supplied with the barrier fluid is adjustable in a range of 0.5 to 5 MPa above the pressure in the nozzle chamber (25) that can be supplied with the first fuel, and more preferably in a range of 1 to 3 MPa above.

7. Fuel injector (1) according to one of the preceding claims, wherein a first control chamber (54) and a second control chamber (55) for actuating the valve member (24) are provided in the control fluid path (50); wherein a switching valve (52) is preferably arranged upstream of the first and second control chambers (54, 55) in the control fluid path (50) and is configured to alternately pressurize the first control chamber (54) and the second control chamber (55); wherein even more preferably the switching valve (52) is a valve with four ports and two positions, such as a 4 / 2-way slide valve, or a valve with three ports and two positions, such as a 3 / 2-way slide valve.

8. Fuel injector (1) according to one of the preceding claims, wherein the first fuel is a liquid or gaseous fuel, such as liquefied petroleum gas or natural gas; and / or the first fuel can be supplied to the internal combustion engine as the main fuel via the first fuel supply path (21) in a first operating mode, and the second fuel can be supplied to the internal combustion engine as the pilot fuel in the first operating mode or as the main fuel in a second operating mode via the second fuel supply path (40);and / or the first supply system (20) and the second supply system (30) are designed downstream as two concentric nozzle needles, in which the nozzle needle for the first fuel is arranged on the outside and forms a first sealing seat with an injector housing and the nozzle needle for the second fuel is arranged in the nozzle needle for the first fuel and forms a second sealing seat with an inside of the nozzle needle for the first fuel; or the first supply system (20) and the second supply system (30) are arranged downstream as two mutually independent nozzle needles in an injector housing and each form a sealing seat with the injector housing, wherein preferably the nozzle needle for the; first fuel is a plurality of nozzle needles arranged around the nozzle needle for the second fuel, wherein preferably the nozzle needles for the first fuel are also hydraulically actuatable via the control fluid path (50).

9. Fuel injector (1) according to one of the preceding claims, wherein a further throttling means is provided in an outlet (53) of the control fluid path (50), and the outlet (64) of the blocking fluid path (60) opens into the outlet (53) of the control fluid path (50) downstream of the further throttling means; or the outlet (53) of the control fluid path (50) opens into the outlet (64) of the blocking fluid path (60).

10. Internal combustion engine with the fuel injector (1) according to one of the preceding claims.

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