Fuel injector unit for assembly to cylinder head of piston internal combustion engine and piston internal combustion engine provided with fuel injector unit

Abstract

The invention relates to a fuel injector unit (10) for assembly to a cylinder head of a piston internal combustion engine (12), the fuel injector unit (10) being adapted to inject a first fuel and a second fuel into a combustion chamber of the piston internal combustion engine, the fuel injector unit (10) comprising in its housing (16):-a first fuel inlet (101) and a second fuel inlet (102); -a first fuel supply section (100) comprising a hydraulically operated first valve control section (110), and a sealing fluid chamber (118) is arranged between the first fuel passage (106) and the first valve control section (110) of the first fuel injection valve (102); -a first fuel supply (200) comprising a hydraulically operated second valve control (210) wherein each of the first valve control (110), the second valve control (210) and the sealing fluid chamber (118) is in continuous flow connection with a second fuel inlet (102) for pressurized fuel, and wherein the second valve control (210) and the sealing fluid chamber (118) are in continuous flow connection with the second fuel inlet (102) for pressurized fuel. The second fuel is used as a hydraulic fluid in the control portion (110, 210) and as a sealing fluid in the sealing fluid chamber (118).

Description

Technical Field

[0001] The invention relates to a fuel injector unit according to the preamble of claim 1. The invention also relates to a piston internal combustion engine provided with such a fuel injector unit. Background Art

[0002] Reciprocating internal combustion engines are typically equipped with fuel injection systems in which the means for pressurizing the fuel and the means for controlling the timing and duration of injection are functionally separate. Fuel is supplied to a so-called pressure accumulator (e.g., a fuel rail or accumulator chamber) by means of at least one high-pressure fuel pump. From this accumulator, the fuel is directed via separate channels to the injectors or injection valves of each cylinder. These systems are often referred to as common rail fuel injection systems. It is also known to provide fuel injection systems with injector-type pressure accumulators. In practice, the operation of the fuel injectors is electronically controlled, for example, by means of a hydraulic control system with solenoids or piezoelectric valves, to achieve sufficiently short and precise injection control.

[0003] It is also known in the prior art to operate a piston engine by using different or several fuels. Typically, a gaseous fuel such as natural gas is used as the main fuel, and a liquid fuel such as LFO or diesel fuel oil is used as the pilot fuel in order to ignite the mixture of air and gaseous fuel present in the combustion chamber of the engine.

[0004] WO2017162902A1 discloses a fuel injector unit, which includes two fuel supply parts for injecting a first fuel and a second fuel into the cylinder of a piston internal combustion engine. The publication discloses that a unique mixture of multiple fuels with a concept can be used, and the multiple fuels are, for example, fuels with ultra-low viscosity, liquefied gas, liquid alcohol (such as methanol, MeOH) or light fuel oil (LFO). All liquefied gases, toxic fuels or fuels that are easily evaporated that are not desired to leak from the fuel injector or more specifically from the first fuel injection valve are available. In the second fuel supply part, the injection is controlled by utilizing the second fuel, while in the first fuel supply part, the injection is controlled by a separate control fluid. Therefore, this solution is somewhat complicated. WO2017162902A1 discloses a sealed fluid chamber in the first injection valve, which is located between the control part and the fuel passage of the injection valve, and the second fuel is arranged to serve as a sealing fluid, thereby minimizing the flow of the first fuel from the first fuel passage to the first control part. Even though the fuel supply device shown in WO2017162902A1 is so advantageous, its structure is somewhat complicated.

[0005] An object of the present invention is to provide a fuel injector which is simpler in structure and more reliable in operation. Summary of the Invention

[0006] The objects of the invention may be substantially met as disclosed in the independent claim and the other claims describing more details of different embodiments of the invention.

[0007] A fuel injector unit for assembly to a cylinder head of a piston internal combustion engine, the fuel injector unit being adapted to inject a first fuel and a second fuel into a combustion chamber of the piston internal combustion engine, the fuel injector unit comprising a first fuel inlet and a second fuel inlet, a first fuel supply portion and a second fuel supply portion in its housing.

[0008] In the fuel injector unit, the first fuel supply portion includes:

[0009] o at least one first fuel injection valve for, in use, administering a first fuel into the piston internal combustion engine;

[0010] ○First fuel injection valve needle;

[0011] o a first fuel passage; and

[0012] o A hydraulically operated first valve control portion, the first valve control portion being arranged at an end of a first fuel injection valve needle opposite to the needle end, wherein a first fuel passage is provided with one or more injection orifices which are opened or closed in response to a position of the first fuel injection valve needle, wherein the first fuel passage is connected to a first fuel inlet, and a sealed fluid chamber is arranged between the first fuel passage and the first valve control portion of the first fuel injection valve.

[0013] In the fuel injector unit, the second fuel supply portion includes:

[0014] a second fuel injection valve for, in use, administering a second fuel to the piston internal combustion engine;

[0015] o a second fuel injection valve needle; and

[0016] o a second fuel passage; and

[0017] o A hydraulically operated second valve control portion arranged at an end of the second fuel injection needle opposite the needle end, wherein the second fuel passage is connected to the second fuel inlet.

[0018] In the fuel injector unit according to the invention, each of the first valve control portion, the second valve control portion and the sealing fluid chamber is in continuous flow connection with the second fuel inlet so that the second fuel serves as hydraulic fluid in the control portion and as sealing fluid in the sealing fluid chamber.

[0019] In this way, the hydraulic control of the valve unit can be operated solely with fuel, and no additional hydraulic system is required. Furthermore, the valve unit provides a safety measure that prevents both fuel injection valves from operating in the event of a fault in the second fuel system. In other words, the first fuel injection valve is arranged to operate dependently on the second fuel injection valve. When the second fuel is arranged to serve as the control fluid for the first injection valve, if a fault occurs in the second fuel system, the first fuel cannot be injected. This prevents a situation in which the first fuel would be injected into the combustion chamber (if controlled independently of the second fuel system), but would not be injected due to such a fault in the second fuel system.

[0020] The combustion is also better controllable because only two different fuel materials are combusted: the first fuel via the first fuel injection valve and a minor portion of the second fuel (leaking sealing fluid) and the second fuel via the second fuel injection valve.

[0021] According to an embodiment of the invention, the second valve control portion and the sealing fluid chamber are in continuous flow connection with the second fuel inlet via a fuel accumulator in the second fuel supply.

[0022] This provides uniform fuel pressure to the second valve control portion and the sealing fluid chamber, and thus provides trouble-free control of the first fuel injector and provides sealing between the fuel passage and the control chamber.

[0023] According to an embodiment of the invention, the first fuel supply is further provided with a first fuel accumulator space arranged in the fuel injector unit between the first inlet for pressurized fuel and the first fuel passage.

[0024] In this way, the injection pressure of the first fuel injector can be maintained at a sufficient level during the injection.

[0025] According to an embodiment of the present invention, the first fuel supply portion is further provided with a flow cutoff valve in the fuel injector unit between the first fuel accumulator space and the first fuel passage.

[0026] In the event that the pressure differential increases beyond a predetermined level (eg, due to leakage from the valve needle), the flow fuse will close the flow connection between the accumulator and the fuel passage.

[0027] According to an embodiment of the invention, the housing of the fuel injection unit comprises a cylindrical guide section for the first fuel injection needle, and the sealing fluid chamber comprises an annular space arranged to enclose the first fuel injection needle in the guide section.

[0028] In this way, the sealing effect is uniform over the circumference of the needle at the location of the annular space.

[0029] According to an embodiment of the invention, the flow connection between the second fuel inlet and the first valve control is arranged to extend via the sealing fluid chamber.

[0030] This provides the effect of interconnecting the control and sealing operations and thus ensures that the seal is effective when the first injection valve is operable (which involves hydraulic control).

[0031] According to an embodiment of the invention, the flow connection between the second fuel inlet for pressurized fuel and the sealing fluid chamber is arranged to extend via the first valve control.

[0032] This also provides the effect of interconnecting the control and sealing operations and thus ensures that the seal is effective when the first injection valve is operable (which involves hydraulic control).

[0033] According to an embodiment of the invention, the first valve control portion is in continuous flow connection with the second fuel inlet for pressurized fuel via a constriction.

[0034] This provides the effect of minimizing possible pressure fluctuations in the second fuel inlet.

[0035] According to an embodiment of the present invention, the housing of the fuel injection unit includes a cylindrical guide section for a first fuel injection valve needle, and the sealed fluid chamber includes an annular space, which is arranged to surround the first fuel injection valve needle in the guide section, and the first fuel injection valve needle is provided with a flow path, such as a bore, which connects the side wall of the valve needle at a longitudinal position of the annular space to the end of the needle at the first valve control portion.

[0036] This provides the effect of interconnecting the control and sealing operations and thus ensures that the seal is effective when the first injection valve is operable (which involves hydraulic control).

[0037] According to an embodiment of the present invention, the annular flow path between the first fuel injection needle and the cylindrical guide section forms a flow path connecting the sealing fluid chamber with the first valve control portion.

[0038] Thus, there is no need to provide a flow passage for the valve needle, which simplifies the structure.

[0039] According to an embodiment of the invention, the first fuel injection needle comprises a longitudinal groove or a bore, which forms a flow path connecting the annular space with the first valve control.

[0040] According to an embodiment of the invention, the first fuel injection valve needle is biased towards its closing direction by a mechanical spring which is arranged at the end of the valve control portion of the needle.

[0041] According to an embodiment of the invention, the first fuel injection needle is biased towards its closing direction by a mechanical spring which is at least partially arranged in the fuel passage of the first fuel supply.

[0042] According to an embodiment of the present invention, the second fuel supply is configured to administer fuel by one injection so as to provide maximum energy equal to energy contained in the fuel administered by one injection of the first fuel supply.

[0043] It can be said that according to this particular embodiment, the second fuel supply is configured to deliver up to 100% of the maximum fuel injection amount of the first fuel supply. In this way, even in the event of a failure of the first fuel supply, the engine can continue to run at a feasible load.

[0044] According to an embodiment of the present invention, the first fuel injection valve needle includes a piston portion at the end of the valve control part of the needle, the diameter of the piston portion is larger than the diameter of the valve needle, and the housing of the fuel injection unit includes a cylindrical guide section, the cylindrical guide section having a first section arranged to guide the valve needle and a second section arranged to guide the piston portion, wherein the piston portion includes a flow path from its annular surface to its end face.

[0045] According to an embodiment of the present invention, the housing of the injector unit is a multi-part assembly, wherein the intersection position of the first fuel supply channel of the first fuel supply part at the boundary between the parts in the multi-part assembly includes a hydraulic leakage barrier surrounding the supply channel, and the sealed space of the hydraulic leakage barrier is directly connected to the second accumulator space through a sealing fluid channel, and the sealed fluid channel is fluidly connected to the second fuel passage through a connecting channel at its end opposite to the end connected to the second accumulator space, so that the connecting channel and the sealing fluid channel form a parallel flow path with the second fuel supply channel from the second accumulator space to the second fuel passage.

[0046] The present invention also provides a piston-type internal combustion engine comprising the fuel injector unit according to the present invention.

[0047] According to an embodiment of the invention, the body of the injector unit is a multi-part assembly, wherein the first fuel supply channel of the first fuel supply section comprises a hydraulic leakage barrier surrounding the supply channel at an intersection at a boundary between parts in the multi-part assembly.

[0048] The exemplary embodiments of the invention presented in this patent application should not be interpreted as limiting the applicability of the appended claims. The verb "comprise" is used in this patent application as an open limitation that does not exclude the presence of unrecited features. Unless expressly stated otherwise, the features recited in the dependent claims may be freely combined with each other. Novel features considered as characteristic of the present invention are particularly set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In the following, the present invention will be described with reference to the accompanying exemplary schematic drawings, in which:

[0050] Figure 1 shows a fuel injector unit according to an embodiment of the present invention;

[0051] Figure 2 shows a fuel injector unit according to another embodiment of the present invention; and

[0052] Figures 3 to 9 Alternative embodiments of a first fuel injection valve that can be used in a first fuel supply of an injector according to an embodiment of the present invention are disclosed. DETAILED DESCRIPTION

[0053] Figure 1 A fuel injector unit 10 is schematically depicted, which is configured for assembly into a piston type internal combustion engine ( Figure 1 The fuel injector unit 10 is adapted to independently controllably inject a first fuel and a second fuel into a piston-type internal combustion engine. This is achieved by the fuel injector unit 10 comprising a first fuel supply 100 and a second fuel supply 200, both of which are arranged within the housing 16 of the injector unit 10.

[0054] The fuel injector unit 10 includes a first fuel inlet 101 and a second fuel inlet 201. When assembled to the engine, the first fuel inlet 101 and the second fuel inlet 201 are connected to the source of the first fuel source and the second fuel source. The source of the first fuel is configured to deliver fuel at a predetermined pressure to the injector unit 10. The first fuel that can be used in the fuel injector unit 10 is preferably one of the following or an applicable mixture: liquefied natural gas (LNG), liquefied petroleum gas (LPG), ammonia, hydrogen, bio- or synthetic fuels, or carbon-neutral methane and methanol. Depending on the fuel and the actual setting, the first fuel can be injected into the engine in liquid or gaseous phase. In particular, a unique mixture of multiple fuels can be used in one unit, such as a fuel with ultra-low viscosity, liquefied gas, liquid alcohol (e.g., methanol, MeOH), or light fuel oil (LFO). The present invention provides benefits for all liquefied gases, toxic fuels, or easily evaporated fuels that are not desired to leak from the fuel injector or, more specifically, from the first fuel injection valve. Typically, the first fuel is such that it will not ignite on its own in the engine, and therefore the first fuel can also be referred to as a less reactive fuel. The second fuel is preferably one of the following, or a suitable mixture thereof: light fuel oil (LFO), biodiesel, marine diesel oil (MDO), or a corresponding synthetic liquid fuel. The second fuel is used to ignite the first fuel, and the second fuel causes compression ignition, so the second fuel is a fuel that can autoignite at the design compression pressure / temperature of the engine. Therefore, the second fuel can also be referred to as a more reactive fuel.

[0055] The first fuel supply 100 in the fuel injector unit 10 is configured to inject the main fuel of the engine. Typically, the main fuel produces at least 90% of the engine power. Figure 1In the embodiment, the first fuel supply unit 100 includes a first fuel injection valve 102 for delivering a first fuel into the combustion chamber of the engine. Also located within the first fuel injection valve is a first fuel injection needle 104, coaxially arranged within the cylindrical space provided for needle 104. Furthermore, a first fuel passage 106 is disposed within the space provided for needle 104, and an injection orifice 108 is provided in the injector housing. Injection orifice 108 opens or closes in response to the position of first fuel injection needle 104. First fuel passage 106 is fluidically connected to the first fuel inlet 101 via a first fuel supply passage 112. The first fuel supply passage is provided with a first accumulator space 114 and a flow cutoff valve 116, with flow cutoff valve 116 disposed between accumulator 114 and first fuel passage 106. Thus, first fuel passage 106 is fluidically connected to the first fuel inlet 101 via the first accumulator space and flow cutoff valve 115. The flow cutoff valve 116 limits and eventually prevents fuel from flowing from the first accumulator space to the fuel passage in the event of an injector malfunction (e.g., when the valve needle fails to close properly) based on the pressure difference between the fuel passage and the first accumulator space. The first accumulator space 114 and the flow cutoff valve 116 are also arranged within the housing 16 of the injector unit 10.

[0056] There is also a hydraulically operated first valve control 110 which is arranged at the end of the first fuel injection valve needle 104 opposite the needle end. On top of the first needle 104 there is a first control space 120 into which a pressurized control fluid enters to control the position of the needle. In this case, a second fuel is used as the control fluid, which will be explained later. The pressure of the fluid produces a closing force on the needle, while the fuel pressure in the passage 106 together with the biasing spring 122 produces an opening force on the needle. In the closed position in which the needle 104 closes the orifice 108, the closing force is greater than the opening force. When the orifice 108 is to be opened, the pressure in the control space 120 is released, which changes the force balance so that the needle 104 moves away from the orifice 108, in Figure 1 There is a first return channel 124 extending from the control space 120 to a first control valve 126. The first control valve 126 is an on-off solenoid valve that operates to either maintain pressure or release pressure from the control space 120. The return channel 124 further extends to the fuel outlet 103 of the injector unit 10.

[0057] Furthermore, a sealing fluid chamber 118 is provided, connected to the first valve needle 104. Sealing fluid chamber 118 is arranged around valve needle 104, completely enclosing the valve needle longitudinally (axially) between the first fuel passage 106 and the first valve control portion 110 of the first fuel injection valve 102. More specifically, the fuel injection unit's housing 16 includes a cylindrical guide section for the first fuel injection needle 104, wherein sealing fluid chamber 118 comprises an annular annular space arranged to enclose the first fuel injection needle 104 within the guide section. Sealing fluid chamber 118 is separated from the first fuel passage 108 to the extent practical. Sealing fluid chamber 118 is in continuous flow connection with the second fuel inlet 201 of the injector unit 10. A flow connection is also provided between sealing fluid chamber 118 and control space 120, allowing, in use, the second fuel to flow from the sealing fluid chamber to control space 120 for use as a pressurized control fluid for needle 104, as described above. The flow connection includes a flow channel 105 arranged to connect to the needle 104 and to the needle's end face. Flow channel 105 is formed so that the first fuel injection valve needle 104 is provided with a borehole that connects the sidewall of the valve needle at a longitudinal location within a sealing fluid chamber 118 (such as an annular space) to the needle's end at the first valve control space 120. The sealing fluid chamber provides a more reliable seal between the fuel passage 106 and the first control space 120. The pressure in the second fuel supply 200 is maintained higher than the fuel pressure in the first fuel supply 100 to ensure that the sealed fluid system operates as intended. The pressure differential can be, for example, 5 MPa to 20 MPa.

[0058] The continuous flow connection between the sealed fluid chamber 118 and the second fuel inlet 201 can also be understood as a direct flow connection, in the sense that there is no device, such as a shutoff valve, between the sealed fluid chamber 118 and the fuel inlet 201 that can completely close the flow connection in the direction of flow toward the sealed fluid chamber. However, one or more throttle valves, etc., for reducing and / or regulating pressure may still be present. The operation of the sealed fluid chamber allows the second fuel to enter the chamber, and a predetermined pressure of the second fuel is maintained substantially constant in the sealed fluid chamber. The pressure in the sealed fluid chamber is equal to or higher than the injection pressure of the first fuel, which prevents the first fuel from flowing from the first fuel passage to the first control space. Any small amount of leakage of the second fuel into the first fuel passage 106 that may occur is burned in the engine along with the first fuel.

[0059] The second fuel supply 200 is configured to inject the so-called pilot fuel of the engine at least during normal operation. Typically, the pilot fuel is in such an amount that it ensures ignition of the main fuel. Figure 1In the embodiment, the second fuel supply unit 200 includes a second fuel injection valve 202 for delivering a second fuel into the engine's combustion chamber. The second fuel injection valve also includes a second fuel injection needle 204, coaxially arranged within the cylindrical space provided for needle 204. Furthermore, a second fuel passage 206 is arranged within the space provided for needle 204, and an injection orifice 208 is provided in the injector housing. Injection orifice 208 opens and closes in response to the position of second fuel injection needle 204. Second fuel passage 206 is fluidically connected to second fuel inlet 201 via a second fuel supply passage 212. A second accumulator space 214 is provided between second fuel passage 212 and second fuel inlet 201. Therefore, second fuel passage 206 is fluidically connected to second fuel inlet 201 via second pressure accumulation space 214. Second accumulator space 214 is also located within the housing 16 of the injector unit 10. Fuel injector unit 10 also includes a hydraulically operated second valve control 210, located at the end of second fuel injection needle 204 opposite the needle end. A second control space 220 is located atop second needle 204, allowing pressurized control fluid to enter from a second fuel passage 206 in this embodiment. A flow connection is provided from second fuel passage 206 to control space 220, allowing a secondary fuel to flow into control space 220 during use, serving as the pressurized control fluid for needle 204. The flow connection includes a flow channel 205, such as a bore, arranged in needle 204, which opens into the needle's end surface. The secondary fuel supply can be designed to deliver fuel to the engine's combustion chamber in an amount representing even 70-100% of the energy required for the engine to operate at its design load. However, the secondary fuel's most important function is to facilitate or provide ignition of the primary fuel.

[0060] Moreover, in this embodiment, the second fuel is used as the control fluid of the second valve 202. In other words, the second fuel supply 200 also utilizes the second fuel as the control fluid of the valve. The pressure of the second fuel in the second control space 220, together with the biasing spring 222 of the valve needle 204, generates a closing force on the valve needle 204, while the fuel pressure in the second fuel passage 206 generates an opening force on the valve needle. In the closed position where the needle 204 closes the orifice 208, the closing force is greater than the opening force. When the orifice 208 is to be opened, the pressure in the control space 220 is released, which changes the force balance so that the needle 204 moves away from the orifice 208. Figure 120 and opens the orifice 208. There is a second return passage 224 extending from the second control space 220 to a second control valve 226. The second control valve 226 is an on-off solenoid valve that operates to either maintain pressure or release pressure from the control space 220. The return passage 224 further extends to the fuel outlet 103 of the injector unit 10. More specifically, in Figure 1 In the embodiment of FIG. 5 , the first return channel 124 and the second return channel 224 are combined within the valve unit 10 , and the combined return channel 224 ′ connects the first return channel 124 and the second return channel 224 to the fuel outlet 103 .

[0061] The sealed fluid chamber 118 in the first fuel supply is in continuous flow connection with the second fuel inlet 201 via a sealed fluid supply passage 128. The sealed fluid supply passage 128 extends between the sealed fluid chamber 118 and the second fuel accumulator 214. In other words, the sealed fluid chamber 118 is in continuous flow connection with the second fuel inlet 201 in the second fuel supply and the second accumulator 214. This ensures that the pressure in the sealed fluid chamber is substantially uniform, so that pulses generated by operation of the second valve needle 204 are not transmitted to the sealed fluid chamber 118, at least not to the extent that they would interfere with the proper operation of the sealed fluid chamber. The check valve 130 is arranged to allow the second fuel to flow only in a direction toward the sealed fluid chamber 118 and prevent pressure pulses from being transmitted from the first fuel supply 100 to the second fuel supply 200. The check valve 130 also prevents fuel from flowing back from the sealed fluid chamber 118 into the second accumulator 214 when the second needle 204 is opening and / or is open, and the pressure in the second accumulator 214 may temporarily decrease. During the closing movement of the needle, the first control space 120 is filled with the second fuel which flows from the sealing fluid chamber 118 via the flow channel 105 in the needle to the control space 120 and the pressure in the first control chamber increases significantly to the pressure level of the second accumulator 214 .

[0062] As in Figure 1 As is clear from the figure, the first fuel injection valve needle 104 includes a piston portion 107 at the end of the valve control section of the first valve needle 104. The piston portion includes a cylindrical portion, the diameter of which is greater than the diameter of the valve needle, so that it delimits the sealing fluid chamber from the first control space 120. The housing 16 of the fuel injection unit includes a cylindrical guide section for accommodating the piston portion therein and arranged to guide the valve needle. The piston portion 107 includes a flow path 105 from its annular surface to its end face. In this way, the flow connection between the second fuel inlet 201 for pressurized fuel and the first valve control part 110 (more precisely, the first control space 120) is arranged to extend or run via the sealing fluid chamber 118.

[0063] Figure 2 Publicly published similar Figure 1 The first fuel supply 100 and the second fuel supply 200 are shown, along with certain additional preferred features of the fuel injector unit 10. The injector unit 10 is configured for assembly to a cylinder head of a piston internal combustion engine 12. The housing of the injector unit 10 is an assembly of individual housing parts 16.1-16.N. That is, a multi-part assembly. Therefore, the passages extending within the housing 16 extend from one housing part to another, and the intersections between the housing parts are sealed. As shown in Figure 2As is apparent from the figure, at least the first fuel supply channel 112, the second fuel supply channel 212, the first fuel return channel 124, and the second fuel return channel 224 extend through more than one housing part 16.1-16.N, thus presenting more than one intersection. The intersection of the first fuel supply channel 112 of the first fuel supply unit 100 at the boundary between the housing parts 16.1-16.N in the multi-part assembly includes a hydraulic leakage barrier 302 surrounding the supply channel. In practice, this means that the first fuel supply channel section, which is substantially at injection pressure during use, is sealed at the intersection with the hydraulic leakage barrier 302. Hydraulic leakage barrier 302 comprises a sealing space 304 arranged around the fuel supply channel. This sealing space 304 radially surrounds the fuel supply channel at a distance from the sealing system of channel 112, resulting in a land area between channel 112 and seal 302. In this land area, the housing parts preferably contact one another. Sealing space 304 is preferably annular and is formed, for example, by providing one or more grooves in the facing housing parts. Hydraulic leakage barrier 302 is filled with pressurized (when in use) second fuel, resulting in a sealed fluid passage 306 connecting second fuel system 200 with hydraulic leakage barrier 302 at the high-pressure section of second fuel system 200 (i.e., the section where the fuel is at injection pressure when in use). Preferably, sealed fluid passage 306 directly connects sealed space 304 with second accumulator space 214 using a constant diameter passage. This minimizes pressure fluctuations in sealed space 304. Where housing parts 16.1-16.N come into direct (metal-to-metal) contact with each other at the intersection, sealed fluid passage 306 is provided with a mechanical seal 402. Sealed fluid passage 306 is fluidically connected to each of second accumulator space 214 and sealed space 304. When sealed space 304 is connected in series to sealed fluid passage 306, sealed fluid passage 306 is preferably fluidically connected to second fuel passage 206 at its end opposite the end connected to second accumulator space 214 via connecting passage 306'. The connecting passage 306′ and the sealing fluid passage 306 form a parallel flow path with the second fuel supply passage 212 from the second accumulator space 214 to the second fuel passage 206. In this way, the second fuel can be supplied from both ends of the array of serially coupled sealed spaces 304 to serve as the sealing fluid in the sealed spaces 304. This has the effect of providing a more uniform pressure in the sealed spaces 304.

[0064] Regarding the second fuel supply passage 211 (which also extends from one housing part to another), the seals at the intersections include mechanical seals 402, such as O-rings compressed between the housing parts. Furthermore, the first and second return passages 124, 224', 224' are each provided with corresponding mechanical seals at their intersections. Preferably, only the intersection of the first fuel supply passage 112 is provided with hydraulic leak barriers 302, while mechanical seals are provided at all other intersections.

[0065] Figures 3 to 9 Alternative embodiments of a first fuel injection valve 102 are disclosed, which are suitable for use in a first fuel supply 100 of an injector unit 10. All of these embodiments of the first fuel injection valve 102 include a sealing fluid chamber 118 connected to a first valve needle 104. The sealing fluid chamber 118 is arranged around the valve needle 104 so as to completely surround the valve needle in the longitudinal direction (in the axial direction) between the first fuel passage 106 and the first valve control portion 110 of the first fuel injection valve 102. More specifically, the housing 16 of the fuel injection unit includes a cylindrical guide section for the first fuel injection valve needle 104, wherein the sealing fluid chamber 118 includes an annular space that is arranged to surround the first fuel injection valve needle 104 in the guide section. The sealing fluid chamber 118 is arranged to be in fluid communication with the second accumulator space 214 of the second fuel supply 200 and is also in fluid communication with the first control space 120. In this way, the second fuel supply

[0066] exist Figure 3 In the embodiment of FIG. 1 , sealing fluid chamber 118 is arranged to receive sealing fluid, i.e., the second fuel, from first control space 120 via a gap or annular flow path between the needle and its housing. In other words, the flow connection between the second fuel inlet for pressurized fuel and the sealing fluid chamber is arranged to extend via the first valve control portion. The distance between the needle and its housing in the area between sealing fluid chamber 118 and the first control space is greater than the distance between the needle and its housing in the area between sealing fluid chamber 118 and fuel passage 106.

[0067] exist Figure 4 In the embodiment of FIG. 1 , the sealing fluid chamber 118 is arranged to receive the second fuel via a sealing fluid supply channel 128 having a branch line 128 ′ connected to the first control space 120. In the branch, a local flow constriction is arranged in the flow region, for example an orifice in the branch line or another local reduction in the cross-sectional area.

[0068] exist Figure 5In the embodiment of FIG. 1 , the sealing fluid chamber 118 is arranged to receive the second fuel via a sealing fluid supply passage 128. The first control space 120 is connected to the sealing fluid chamber via a flow passage 105 arranged to the needle 104, the flow passage leading to the end face of the needle. The flow passage 105 is formed such that the first fuel injection valve needle 104 is provided with a borehole that connects the side wall of the valve needle at a longitudinal position of the sealing fluid chamber 118 (such as an annular space) to the end of the needle at the first valve control space 120.

[0069] Figure 6 A fuel injection valve is disclosed which is similar in other respects to the fuel injection valve of FIG. 1 except that the spring 122 is arranged in the control space 120 instead of the fuel passage 106. Figure 5 The fuel injection valve shown in .

[0070] In addition, Figures 3 to 5 In FIG. 1 , a mechanical spring is shown arranged in the fuel passage of the injection valve, while in FIG. Figures 6 to 9 In the exemplary embodiment of FIG. 1 , the mechanical spring is arranged in the control space 120 of the injection valve.

[0071] In addition, Figures 7 to 9 In the illustrated embodiment, the first fuel injection valve needle includes a piston portion 140 at the control space end of the needle, the diameter of the piston portion 140 being greater than the diameter of the valve, and the housing of the fuel injection unit includes a cylindrical guide section having a first section 142 arranged to guide the valve needle and a second section 144 arranged to guide the piston portion 140.

[0072] exist Figure 7 In FIG, the piston portion includes an axial flow path 105 extending from its lower annular surface in the figure to its end surface at its upper end in the figure. The flow path is provided with a constriction that allows the pressure in the control space to be appropriately reduced when the first control valve 126 is opened. The sealed fluid chamber 118 is in direct communication with the second accumulator 214. A branch line 128" connects the space below the piston portion 140, defined by the lower annular surface, to the second accumulator 214.

[0073] In this way, a flow connection between the second fuel inlet 201 for pressurized fuel and the first control space 120 is arranged to extend or run via the flow path 105 .

[0074] Figure 8 The embodiment in is otherwise similar to Figure 7, but here the second pressure accumulator 214 is directly connected to the space below the piston part 140, which is delimited by the lower annular surface, while the sealing fluid chamber 118 is connected to said space via a flow channel 105' arranged to the valve needle 104, which opens at a position in the vicinity of the annular surface of the piston part 140 and at an axial position of the sealing fluid chamber 118. The flow channel 105' is preferably an oblique bore through the needle.

[0075] Figure 9 The embodiment in is otherwise similar to Figure 8 , but here the sealing fluid chamber 118 is connected to the second pressure accumulator 214 via an annular flow path between the first fuel injection needle 104 and the cylindrical guide section of the injection unit and the space defined by the lower annular surface below the piston part 140.

[0076] Although the present invention has been described herein by combining examples of what are currently considered to be the most preferred embodiments, it will be apparent to those skilled in the art that, as technology advances, the basic concept of the present invention can be implemented in a variety of ways. Therefore, the present invention and its embodiments are not limited to the examples and specimens described above, but rather may vary within the scope of the patent claims and their legal equivalents. Details mentioned in connection with any of the above embodiments may be combined with another embodiment when such a combination is technically feasible.

Claims

1. A fuel injector unit (10) for assembly to a cylinder head of a piston internal combustion engine (12), the fuel injector unit (10) being adapted to inject a first fuel and a second fuel into a combustion chamber of the piston internal combustion engine, the fuel injector unit (10) comprising in its housing (16): - a first fuel inlet (101) and a second fuel inlet (201); - a first fuel supply unit (100), the first fuel supply unit (100) comprising: o at least one first fuel injection valve (102) for administering a first fuel into the piston internal combustion engine in use; ○ A first fuel injection valve needle (104); o a first fuel passage (106); and a hydraulically operated first valve control portion (110) arranged at an end of the first fuel injection valve needle (104) opposite the needle end, wherein the first fuel passage (106) is provided with one or more injection orifices (108) that open or close in response to a position of the first fuel injection valve needle (104), and wherein the first fuel passage (106) is connected to the first fuel inlet (101), and wherein a sealing fluid chamber (118) is arranged between the first fuel passage (106) and the first valve control portion (110) of the first fuel injection valve (102); - a second fuel supply unit (200), the second fuel supply unit (200) comprising: a second fuel injection valve (202) for injecting a second fuel into the piston internal combustion engine (12) when in use; ○ Second fuel injection valve needle (204); ○ Second fuel passage (206); a hydraulically operated second valve control portion (210), the second valve control portion (210) being arranged at an end of the second fuel injection valve needle (204) opposite the needle end, wherein the second fuel passage (206) is connected to the second fuel inlet (102), Characterized in that each of the first valve control portion (110), the second valve control portion (210) and the sealing fluid chamber (118) is connected in continuous flow with the second fuel inlet (201), so that the second fuel serves as a hydraulic fluid in the control portion (110, 210) and as a sealing fluid in the sealing fluid chamber (118).

2. The fuel injector unit (10) according to claim 1, characterized in that The second valve control portion (210) and the sealed fluid chamber (118) are in continuous flow connection with the second fuel inlet (102) via a second accumulator (214) in the second fuel supply (200).

3. The fuel injector unit (10) according to claim 1, characterized in that The first fuel supply (100) is further provided with a first fuel accumulator space (114) arranged in the fuel injector unit (10) between the first inlet for pressurized fuel and the first fuel passage (106).

4. The fuel injector unit (10) according to claim 3, characterized in that The first fuel supply portion (100) is further provided with a flow cutoff valve (126) in the fuel injector unit (10) between the first fuel accumulator space (114) and the first fuel passage (106).

5. The fuel injector unit (10) according to any one of the preceding claims, characterized in that The housing (16) of the fuel injection unit (10) comprises a cylindrical guide section for the first fuel injection valve needle (104), and the sealing fluid chamber (118) comprises an annular space arranged to enclose the first fuel injection valve needle (104) in the guide section.

6. The fuel injector unit (10) according to any one of the preceding claims 1 to 5, characterized in that A flow connection between the second fuel inlet and the first valve control portion (110) is arranged to extend via the sealed fluid chamber (118).

7. The fuel injector unit (10) according to any one of the preceding claims 1 to 5, characterized in that A flow connection between the second fuel inlet (201) for pressurized fuel and the sealing fluid chamber (118) is arranged to extend via the first valve control portion (110).

8. The fuel injector unit (10) according to any one of the preceding claims 1 to 5, characterized in that The first valve control portion (110) is in continuous flow connection with the second fuel inlet (201) for pressurized fuel via a constriction.

9. The fuel injector unit (10) according to claim 6 or 7, characterized in that The first fuel injection valve needle (104) is provided with a flow path, such as a bore, connecting a side wall of the valve needle at a longitudinal position of the sealing fluid chamber (118) to an end of the needle at the first valve control portion (110).

10. The fuel injector unit (10) according to claim 6 or 7, characterized in that An annular flow path between the first fuel injection needle (104) and the cylindrical guide section forms a flow path connecting the sealed fluid chamber (118) with the first valve control portion (110).

11. The fuel injector unit (10) according to claim 6 or 7, characterized in that The first fuel injection valve needle (104) includes a longitudinal groove forming a flow path connecting the sealed fluid chamber (118) and the first valve control portion (110).

12. The fuel injector unit (10) according to any one of the preceding claims, characterized in that The first fuel injection valve needle (104) is biased towards its closing direction by a mechanical spring arranged at the end of a valve control portion of the needle.

13. The fuel injector unit (10) according to any one of the preceding claims 1 to 11, characterized in that The first fuel injection valve needle (104) is biased toward its closing direction by a mechanical spring, which is at least partially arranged in a fuel passage of the first fuel supply.

14. The fuel injector unit (10) according to any one of the preceding claims, characterized in that The second fuel supply portion (200) is configured to administer fuel through one injection so as to provide maximum energy equal to energy contained in the fuel administered through one injection of the first fuel supply portion.

15. The fuel injector unit (10) according to any one of the preceding claims, characterized in that A first fuel injection valve needle (104) includes a piston portion at the end of a valve control portion of the needle, the diameter of the piston portion being larger than the diameter of the valve needle, and a housing (16) of the fuel injection unit (10) includes a cylindrical guide section having a first section arranged to guide the valve needle and a second section arranged to guide the piston portion, wherein the piston portion includes a flow path from its annular surface to its end surface.

16. The fuel injector unit (10) according to claim 2, characterized in that The housing (16) of the injector unit (10) is a multi-part assembly, wherein the first fuel supply channel of the first fuel supply part (100) includes a hydraulic leakage barrier (302) surrounding the supply channel (112) at an intersection position at a boundary between the parts (16.1, 16.2, 16.N) in the multi-part assembly, and the sealed space (304) of the hydraulic leakage barrier (302) is directly connected to the second accumulator space (214) via a sealed fluid channel (306), and the sealed fluid channel (306) is fluidically connected to the second fuel passage (206) at its end opposite to the end connected to the second accumulator space (214) via a connecting channel (306'), so that the connecting channel (306') and the sealing fluid channel (306) form a parallel flow path with the second fuel supply channel from the second accumulator space (214) to the second fuel passage (206).

17. A piston internal combustion engine (12) comprising a fuel injector unit (10) according to any one of the preceding claims.

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