Fuel injector

Abstract

According to one aspect of the invention, a fuel injector (1) for delivering gaseous fuel to a fuel injection system of an internal combustion engine is provided. The fuel injector (1) comprises: an injector nozzle (10) having a valve needle (18) movable within a bore (20) of the injector nozzle (10) for controlling the delivery of gaseous fuel to an internal combustion engine; a needle control valve (12) for controlling the movement of the valve needle (18) by controlling the pressure of a control fluid in a control chamber (32) of the needle control valve (12); a first fluid supply network (44) for delivering control fluid from the first injector inlet (40) to the inlet (29) of the needle control valve (12); a second fluid supply network (46) for delivering gaseous fuel from the second injector inlet (42) to a delivery chamber (24) for injection into the internal combustion engine, the delivery chamber being defined in the bore (20) of the injector nozzle (10) around the valve needle (18); and one or more sealant chambers (60a-e) for sealing respective leakage paths of the second fluid supply network (46), each leakage path extending between respective adjacent bodies (15, 16, 36) of the fuel injector (1) and a respective sealant chamber (60a-e) defined at an abutment surface of those bodies (15, 16, 36) closing the leakage path, wherein each sealant chamber (60a-e) is connected to the first fluid supply network (44) such that, in use, a control fluid is supplied from the first fluid supply network (44) to each sealant chamber (60a-e) at a higher pressure than the fuel supply in the second fluid supply network (46), thereby substantially inhibiting leakage from the second fluid supply network (46) via the respective leakage path.

Description

Technical Field

[0001] The present invention relates to a fuel injector for a fuel injection system for an internal combustion engine. Aspects of the present invention relate to a fuel injector and a fuel injection system for an internal combustion engine. Background Art

[0002] Fuel injectors are provided in a fuel injection system to inject high pressure fuel into an associated combustion cylinder. Each fuel injector includes an injector nozzle having a valve needle that is typically operated by an actuator to move toward and away from a valve seat. In this way, the valve needle can be moved to control fuel delivery into the combustion cylinder through one or more injection holes or nozzle outlets at the end of the injector nozzle.

[0003] However, when using gaseous fuels such as hydrogen, high flow rates are required to deliver enough gas into the combustion cylinder within the available time. In part, this is because the available injection pressure can vary depending on the residual pressure in the fuel tank, which decreases as more fuel is used. Therefore, large valve seats are usually required to provide sufficient flow rates into the combustion cylinder.

[0004] However, increasing the flow rate in this way results in an increased reaction force on the nozzle return spring, which must therefore be sized appropriately. Thus, a typical direct-acting injector does not have the magnetic force required to lift the valve needle and open the nozzle against the force of the return spring.

[0005] It is against this background that the present invention has been devised. Summary of the invention

[0006] According to one aspect of the present invention, a fuel injector for a fuel injection system for delivering gaseous fuel to an internal combustion engine is provided. The fuel injector comprises: an injector nozzle having a valve needle that can move within a hole of the injector nozzle for controlling the delivery of gaseous fuel to the internal combustion engine; a needle control valve for controlling the movement of the valve needle by controlling the pressure of a control fluid in a control chamber of the needle control valve; a first fluid supply network for delivering a control fluid from a first injector inlet to an inlet of the needle control valve; a second fluid supply network for delivering gaseous fuel from a second injector inlet to a delivery chamber for injection into the internal combustion engine, the delivery chamber being located at the inlet of the injector nozzle. The fuel injector is provided with a plurality of sealant chambers, each of which is connected to the first fluid supply network and is defined around the valve needle in the hole; and one or more sealant chambers for sealing corresponding leakage paths of the second fluid supply network, each leakage path extending between corresponding adjacent bodies of the fuel injector, and the corresponding sealant chambers are defined at the docking surfaces of those bodies to close the leakage paths, wherein each sealant chamber is connected to the first fluid supply network so that in use, a control fluid is supplied to each sealant chamber from the first fluid supply network at a pressure higher than the fuel supply in the second fluid supply network, thereby substantially suppressing leakage from the second fluid supply network via the corresponding leakage paths.

[0007] Thus, in use, the fuel injector is configured to receive a control fluid for controlling the closing force on the valve needle and separately receive gaseous fuel for injection into the internal combustion engine. The needle control valve is operable to control the control fluid pressure in the control chamber, thereby controlling the closing force acting on the valve needle independently of the control fluid pressure in the rest of the first fluid supply network. Advantageously, when the control fluid and the fuel are separated in the fuel injector and received in the respective supply networks, a pressure difference can be maintained between the supply networks, and a sealant chamber connected to the first fluid supply network can be used to substantially inhibit leakage of gaseous fuel from the second fluid supply network by means of the pressure difference. Thus, the present invention facilitates lifting of the valve needle, while the fuel injector is able to function over a wider range of gaseous fuel pressures without leaking gaseous fuel.

[0008] Optionally, at least one of the leakage paths of the second fluid supply network can be defined between the docking surface of the valve needle and the hole of the injector nozzle. That is, the leakage path between the fuel delivery chamber and the control chamber is generated due to the gap between the docking surface of the valve needle and the hole of the injector nozzle to allow the relative movement of the valve needle. Optionally, the corresponding sealant chamber can be at least partially defined by a recess in the hole of the injector nozzle at this interface. In this way, the sealant chamber can substantially inhibit the leakage of gas fuel from the delivery chamber. Optionally, the sealant chamber can be configured so that the lubricating flow of the control fluid leaks from the sealant chamber to the delivery chamber during use. In this way, the control fluid can lubricate the surface and reduce wear. In the example, the lubricating flow of the control fluid leaks from the sealant chamber to the delivery chamber, thereby lubricating the downstream interface between the valve needle and the injector hole, including at the valve seat. In the example, the lubricating flow of the control fluid can additionally lubricate any additional guiding structure provided for the valve needle in the injector hole. In this regard, the lubricating flow of the control fluid advantageously lubricates the interface between the end of the valve needle and the valve seat, generating a high contact pressure at the interface. This is important because, in some examples, the gaseous fuel in the delivery chamber may provide limited lubrication. Therefore, the lubricating flow of the control fluid significantly reduces wear and damage to the valve needle and / or injector nozzle.

[0009] In one example, the valve needle is matched with the hole of the injector nozzle, or vice versa, such that a gap between the abutting surface of the valve needle and the hole of the injector nozzle provides or controls the lubrication flow of the control fluid from the sealant chamber to the delivery chamber. For example, the valve needle can be matched with the hole such that the gap is less than or equal to 2 microns. For example, the valve needle can be matched with the hole of the injector nozzle by finishing at least one of the valve needle and the hole using a matching grinding process.

[0010] Optionally, at least one of the leakage paths of the second fluid supply network is defined between abutment surfaces of axially adjacent first and second bodies of the fuel injector, for example in a connection region between respective conduits of the second fluid supply network in the first and second bodies. A respective sealant chamber may be at least partially defined by a recess in abutment surface of at least one of the first and second bodies, for example around the connection region, to seal the leakage path in use.

[0011] In an example, the one or more sealant chambers include a plurality of sealant chambers. For example, the plurality of sealant chambers may be configured to seal a corresponding leakage path of the second fluid supply network at each mating surface or controlled gap of the fuel injector.

[0012] Optionally, at least one of the sealant chambers comprises an annular chamber surrounding the respective leakage path. In other examples, the sealant chamber may take any suitable form surrounding the respective leakage path.

[0013] The gaseous fuel may be hydrogen, for example. In this case, the invention is particularly advantageous due to the need for a large valve seat for sufficient hydrogen flow rate.

[0014] Optionally, in use, the control fluid is delivered in the first fluid supply network as a liquid fluid. Optionally, the control fluid is a hydraulic fluid or a diesel fuel.

[0015] In one example, the fuel injector further includes a return spring that urges the valve needle against a valve seat of the injector nozzle.

[0016] Optionally, the second fluid supply network includes a first high pressure line and a second high pressure line, each of which extends from the second injector inlet to the delivery chamber. Thus, each of the first high pressure line and the second high pressure line extends through the fuel delivery portion and the corresponding body of the needle control valve, and extends into the nozzle body.

[0017] Optionally, the first fluid supply network comprises: a first high pressure line extending from the first injector inlet to the inlet of the needle control valve; and a corresponding branch extending from the first high pressure line to each sealant chamber. In this way, the control fluid is supplied to each sealant chamber at the delivery pressure. Therefore, the pressure of each sealant chamber is independent of the operation of the needle control valve.

[0018] In one example, the needle control valve comprises one or more solenoid valves operable to selectively connect an inlet of the needle control valve and / or an outlet of the needle control valve to a control chamber, thereby controlling the pressure of the control chamber in use.

[0019] Optionally, the one or more solenoid valves include a three-way valve that selectively connects the control chamber to the inlet in a closed state of the fuel injector or connects the control chamber to the outlet in an open state of the fuel injector.

[0020] The control chamber may for example be arranged such that the control fluid in the control chamber acts on a distal surface of the valve needle.The distal surface may have a diameter that is larger than a diameter of a valve seat of the injector nozzle.

[0021] According to another aspect of the invention, there is provided a fuel injection system for delivering a gaseous fuel to an internal combustion engine, comprising a fuel injector as described in the previous aspects of the invention. For example, the internal combustion engine may be a hydrogen engine. The fuel injection system may include a first fluid delivery system for delivering a control fluid to the fuel injector and a second fluid delivery system for delivering fuel to the fuel injector.

[0022] According to another aspect of the present invention, there is provided a method for controlling fuel injection from a fuel injection system, the fuel injection system comprising: a fuel injector as described in the previous aspect of the present invention; a first fluid delivery system for delivering a control fluid to the fuel injector; and a second fluid delivery system for delivering fuel to the fuel injector. The method comprises: supplying a control fluid from the first fluid delivery system to a first fluid supply network; supplying fuel from the second fluid delivery system to a second fluid supply network; and controlling the fuel injection from the fuel injector by: operating a needle control valve to reduce the pressure of the control fluid in a control chamber of the needle control valve, thereby starting fuel injection; subsequently operating the needle control valve to increase the pressure of the control fluid in the control chamber, thereby shutting off fuel injection; and controlling at least one of the first fluid delivery system and the second fluid delivery system to provide a pressure difference between the first fluid supply network and the second fluid supply network during fuel injection, so that each sealant chamber is supplied with a control fluid from the first fluid supply network, the pressure of which is higher than the fuel supply in the second fluid supply network, thereby substantially inhibiting leakage from the second fluid supply network via the corresponding leakage path.

[0023] Optionally, at least one of the first fluid delivery system and the second fluid delivery system is controlled to provide a pressure differential between the first fluid supply network and the second fluid supply network, the pressure differential generating a lubrication flow of the control fluid from a sealant chamber at least partially defined by a recess in the bore of the injector nozzle to the delivery chamber.

[0024] It should be understood that the various features of each aspect of the invention are also applicable to other aspects of the invention, either alone or in appropriate combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order that the invention may be more readily understood, preferred non-limiting embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which like features are assigned like reference numerals, and in which:

[0026] Figure 1 is an isometric view of an example fuel injector showing a wireframe body in accordance with an embodiment of the present invention; and

[0027] Figure 2 yes Figure 1 An enlarged isometric view of a portion of a fuel injector is shown;

[0028] Figure 3 yes Figure 1 A schematic diagram of an injection portion of an example fuel injector shown in ; and

[0029] Figures 4 to 7 Schematic diagram showing the various phases of the injection cycle Figure 3 The injection portion of a fuel injector is shown.

[0030] In the following description, directions or relative references such as "upper", "lower", "above" and "below" refer to the orientation of features as shown in the accompanying drawings, but such references are not considered limiting. Those skilled in the art will understand that a fuel injector according to an embodiment of the present invention may be oriented differently than depicted in the actual drawings. DETAILED DESCRIPTION

[0031] Embodiments of the present invention relate to a gas fuel injector for an internal combustion engine. As is conventional, the fuel injector includes an injector nozzle having an orifice and a valve needle that is movable within the orifice to control the delivery of gaseous fuel to the internal combustion engine. The fuel injector also includes a needle control valve for controlling the movement of the valve needle by controlling the pressure of a control fluid in a control chamber of the needle control valve. Therefore, the fuel injector includes separate fluid supply networks for delivering respective supplies of control fluid and fuel. A first fluid supply network extends through the fuel injector to deliver the control fluid from a first injector inlet to an inlet of the needle control valve, and a second fluid supply network extends through the fuel injector to deliver the fuel from a second injector inlet to a delivery chamber that is defined around the valve needle in the orifice of the injector nozzle.

[0032] The needle control valve is operated to control the pressure of the control fluid in the control chamber, thereby allowing the valve needle to be lifted away from the valve seat of the injector nozzle, so that fuel is injected from the delivery chamber into the combustion chamber of the internal combustion engine.

[0033] Advantageously, embodiments of the present invention also include one or more sealant chambers for sealing the corresponding leakage paths of the second fluid supply network. In particular, the leakage paths of the second fluid supply network exist at the interface of adjacent bodies of the fuel injector, such as where axially adjacent bodies are connected together and / or where the corresponding bodies of the fuel injector are designed to move relative to each other, such as at the interface between the valve needle and the hole of the injector nozzle. Each sealant chamber is defined at the docking surface of such a body to close the leakage path, and each sealant chamber is connected to the first fluid supply network so that in use, each sealant chamber is filled with a control fluid at a higher pressure than the fuel in the second fluid supply network. In this way, the sealant chamber substantially inhibits leakage from the second fluid supply network via the corresponding leakage path. For example, such a sealant chamber can be defined at the docking surface of the valve needle and the hole of the injector nozzle. Therefore, due to the pressure difference between the control fluid and the gaseous fuel, the gaseous fuel is substantially prevented from passing through the sealant chamber. However, a small amount of control fluid can be allowed to leak from the sealant chamber into the fuel delivery chamber, which is used to lubricate the interface and reduce wear.

[0034] It is contemplated that the fuel injector will thus substantially suppress leakage of gaseous fuel, while the needle control valve provides increased needle response and precise control of injection, particularly near peak cylinder pressure.

[0035] Now refer to Figures 1 to 3 The illustrated example embodiment discusses the fuel injector in greater detail.

[0036] Figure 1 An exemplary fuel injector 1 according to an embodiment of the present invention is shown extending along a longitudinal axis 2 from a tip 4 at a proximal end 6 to an opposing distal end 8 connected to various fluid delivery systems (not shown).

[0037] The fuel injector 1 is made up of a series of sub-assemblies including an injector nozzle 10 and a needle control valve 12 for controlling the supply of gaseous fuel (eg hydrogen) to an internal combustion engine (not shown).

[0038] The injector nozzle 10 comprises a nozzle body 16 and a generally cylindrical valve needle 18. The nozzle body 16 extends along a longitudinal axis 2 from a distal end 4 at a proximal end 6 to an opposite distal end 14 of a body 15 connected to a needle control valve 12. The valve needle 18 is slidable in a cylindrical blind bore 20 provided in the nozzle body 16. The bore 20 extends along the longitudinal axis 2 from the distal end 14 of the nozzle body 16 to the distal end 4 at the proximal end 6. The bore 20 is shaped to define a delivery chamber 24 between the valve needle 18 and the bore 20, and in use, fuel is delivered from a fuel supply line ( Figure 1 The valve needle 18 can be axially moved to engage with the valve seat ( Figure 1 In this way, the valve needle 18 moves toward and away from the valve seat to control the flow of gas into the combustion chamber ( Figure 1 In order to deliver fuel to the combustion chamber (not shown), the fuel injector 1 protrudes into the combustion chamber during use.

[0039] The movement of the valve needle 18 towards and away from the valve seat is controlled by the needle control valve 12, and a return spring 28 is used to push the valve needle 18 against the valve seat to close the injection.

[0040] In this example, the needle control valve 12 is a hydraulically controlled electromagnetic control valve actuator, which is supplied with control fluid from a supply network arranged in the fuel injector 1 .

[0041] The fuel injector 1 therefore comprises separate fluid supply networks for delivering the control fluid to the needle control valve 12 and for delivering the gaseous fuel, for example hydrogen, to the delivery chamber 24 .

[0042] To this end, the fuel injector 1 further comprises a fluid delivery body 36 connected to the distal end 17 of the needle control valve body 15. The fluid delivery body 36 comprises: a first injector inlet 40 for connecting to a first fluid delivery system (not shown) to provide a supply of control fluid; and a second injector inlet 42 for connecting to a second fluid delivery system (not shown) to provide a supply of fuel, which may be a gaseous fuel. For example, the second injector inlet 42 may be connected to a high pressure common rail or a hydrogen tank to provide a supply of pressurized gaseous fuel.

[0043] It is important that the control fluid is provided to the first injector inlet 40 at a higher delivery pressure than the fuel supplied to the second injector inlet 42, for example with a pressure differential of at least 10 bar, preferably at least 15 bar, relative to the gaseous fuel. In the example, the first fluid delivery system can therefore be controlled to maintain the pressure differential when the amount of gaseous fuel in the supply tank decreases, thereby reducing the pressure of the gaseous fuel supply. In other words, the delivery pressure of the control fluid provided by the first fluid delivery system can be varied depending on the delivery pressure of the gaseous fuel, for example maintaining a pressure differential of 10 to 15 bar.

[0044] The fuel injector 1 further comprises a first fluid supply network 44 for delivering control fluid from the first injector inlet 40 to the needle control valve 12 and a second fluid supply network 46 for delivering gaseous fuel from the second injector inlet 42 to the delivery chamber 24 .

[0045] like Figure 1 As shown, the first fluid supply network 44 includes a high pressure line 48 extending from the first injector inlet 40 through the fluid delivery body 36 to the inlet 29 of the needle control valve 12 defined in the needle control valve body 15 .

[0046] The second fluid supply network 46 includes first and second high pressure lines 50 , 52 , each extending from the second injector inlet 42 , through the fluid delivery body 36 and the needle control valve body 15 , to the delivery chamber 24 defined in the bore 20 of the nozzle body 16 .

[0047] Thus, the second fluid supply network 46 extends through a series of bodies of the fuel injector 1 and delivers a gaseous fuel, such as hydrogen, in use. Thus, the continuous conduits of each of the first high-pressure line 50 and the second high-pressure line 52 meet and connect at the interface of the axially adjacent bodies 15, 16, 36 of the fuel injector 1. Typically, there is a risk of gaseous fuel leaking from the second fluid supply network 46 along the corresponding leakage paths defined between the adjacent bodies 15, 16, 36. For example, the leakage path may extend between the abutment surfaces of the adjacent bodies 15, 16, 36 around the connection of the continuous conduit. It should be understood that the term "leakage path" is used herein to refer to an unexpected leakage from the first high-pressure line 50 and the second high-pressure line 52.

[0048] Advantageously, the fuel injector 1 according to the invention comprises a respective sealant chamber 60a-d arranged between such interfaces to close and seal such leakage paths. In particular, each sealant chamber 60a-d is connected to the first fluid supply network 44 via a respective branch 62a-d, so that in use, the sealant chamber 60a-d is filled with a control fluid at a higher pressure than the gaseous fuel in the second fluid supply network 46. In this way, the pressure difference ensures that in the event of separation at the interface or other causes of leakage, the gaseous fuel does not escape the second fluid supply network 46. On the contrary, the pressure difference ensures that any leakage occurs in the direction of the control fluid entering the second fluid supply network 46. Therefore, when the control fluid may enter the second fluid supply network 46 in the event of a leakage, the control fluid is preferably a combustible fuel, such as diesel fuel, because the leaking control fluid can be injected into the internal combustion engine.

[0049] As will now be described in more detail, Figure 2 , exemplary sealant chambers 60a-d are shown in more detail in . In this example, the fuel injector 1 is shown to include first, second, third and fourth sealant chambers 60a-d for sealing the corresponding leakage paths of the second fluid supply network 46 at the mating interface of the fuel injector 1. The first sealant chamber 60a is defined at the interface of the fluid delivery body 36 and the needle control valve body 15. In particular, the first sealant chamber 60a is defined by complementary recessed structures in the mating surfaces of the fluid delivery body 36 and the needle control valve body 15, which meet in assembly to define the first sealant chamber 60a at the interface. In this example, the first sealant chamber 60a is shown to take the form of an annular chamber. The annular chamber surrounds the corresponding opening of the connecting conduit of the first high-pressure pipeline 50 at the interface. In this way, in the case where the gaseous fuel may leak from the conduit along the leakage path between the mating surfaces, the first sealant chamber 60a completely surrounds such a leakage path.

[0050] In a corresponding manner, the second sealant chamber 60 is also provided in the form of an annular chamber which seals off the connection of the second high pressure line 52 at the interface between the fluid delivery body 36 and the needle control valve body 15. Figure 2 As shown, each of the first sealant chamber 60a and the second sealant chamber 60b is connected to the first fluid supply network 44 by a respective branch 62a, b extending from the high pressure line 48, so that in use, the first sealant chamber 60a and the second sealant chamber 60b are filled with the control fluid, and thus the pressure of such sealant chambers 60a, 60b is controlled by the first fluid delivery system attached to the first injector inlet 40. In other examples, it should be understood that each of the first sealant chamber 60a and the second sealant chamber 60 may be provided in other forms surrounding the connection portion of the first high pressure line 50 and the second high pressure line 52 at the interface.

[0051] The third and fourth sealant chambers 60c, 60d operate in a corresponding manner at the interface between the needle control valve body 15 and the nozzle body 16. Specifically, the third and fourth sealant chambers 60c, 60d form corresponding annular chambers around the connection of the first high pressure line 50 and the second high pressure line 52 of the second fluid supply network 46 at the interface between the needle control valve body 15 and the nozzle body 16. The third and fourth sealant chambers 60c, 60d are similarly supplied with control fluid by corresponding branches 62c, d of the high pressure line 48 from the first fluid supply network 44, so that each of the third and fourth sealant chambers 60c, 60d is filled with control fluid and maintained at the pressure of the high pressure line 48.

[0052] In this manner, leakage of gaseous fuel into the first fluid supply network 44 at each mating interface is substantially eliminated.

[0053] In an embodiment, the fuel injector 1 may further include a sealant chamber 60e arranged at the interface between the valve needle 18 and the hole 20, such as Figure 2As shown, there is a clearance fit to allow the valve needle 18 to move along the hole 20. In particular, the clearance fit provides a potential leakage path for the second fluid supply network 46 extending from the delivery chamber 24 between the abutting surfaces of the valve needle 18 and the hole 20. In order to suppress such leakage, the additional sealant chamber 60e can be defined by a recessed structure in the wall of the hole 20, thereby forming an annular chamber defined around the valve needle 18. The control fluid can be similarly supplied to the annular sealant chamber from the first fluid supply network 44 via another branch 62e originating from the high-pressure pipeline 48, so that the annular sealant chamber 60e is maintained at a higher pressure than the gas fuel in the delivery chamber 24 during use. In this way, the pressure difference substantially suppresses the leakage of the gas fuel from the delivery chamber 24 to the needle control valve 12. However, in the example, a small amount of control fluid can be allowed to leak from the sealant chamber 60e into the fuel delivery chamber 24, which is used to lubricate the interface and reduce wear. In order to control such leakage, the gap between the valve needle 18 and the hole 20 can be strictly controlled during manufacturing. In particular, the valve needle 18 may be matched with the hole 20 of the injector nozzle 10, or vice versa, such that a clearance between the abutting surface of the valve needle 18 and the hole 20 of the injector nozzle 10 controls the lubrication flow of the control fluid from the sealant chamber 60 e to the delivery chamber 24. For example, the valve needle 18 may be matched with the hole 20 such that the clearance is less than or equal to 2 microns, or even less than or equal to 1.5 microns.

[0054] To this end, one of the valve needle 18 and the hole 20 can be refined by a matching grinding process to match the other of the valve needle 18 and the hole 20. For example, the matching grinding process can involve measuring, grinding and calibrating the two components to match each other with a gap of less than or equal to 2 microns, preferably less than or equal to 1.5 microns. In this way, when the first fluid delivery system and / or the second fluid delivery system are operated to provide or maintain a pressure difference between the first fluid supply network 44 and the second fluid supply network 46 in use, a controlled leakage of the control fluid is generated from the sealant chamber 60e to the delivery chamber 24. Therefore, the control fluid travels toward the end 4 of the fuel injector 1 and lubricates the docking surface arranged on the proximal side of the sealant chamber 60e. This can include any additional guiding structure (not shown) arranged around the valve needle 18 for guiding the valve needle 18 in the hole 20 of the injector nozzle 10. Importantly, the controlled leakage further lubricates the valve seat of the injector nozzle 10, and the valve needle 18 repeatedly engages and disengages the valve seat. This is important because, in some examples, the gaseous fuel in the delivery chamber 24 may provide insufficient lubrication at the valve seat. Thus, the lubricating flow of the control fluid significantly reduces wear and damage to the valve needle 18 and / or the injector nozzle 10.

[0055] Figure 3 A schematic diagram of the first and second fluid supply networks 44, 46 and the corresponding connections to the needle control valve 12, the sealant chambers 60a-e, and the delivery chamber 24 is provided.

[0056] like Figure 3 As shown, the first fluid supply network 44 is connected to the inlet 29 of the needle control valve 12, so that the inlet 29 is supplied with a control fluid at a delivery pressure (i.e., at the pressure of the high-pressure supply line 48). The needle control valve 12 also includes a control chamber 32 arranged at the distal end of the valve needle 18, and the control fluid is supplied from the inlet 29 to the control chamber 32 to exert pressure on the valve needle 18, thereby pushing the valve needle 18 toward the valve seat 35. The needle control valve 12 also includes an outlet 31 connected to the low-pressure return line 33 and a solenoid control valve 30 for selectively connecting the inlet 29 and / or the outlet 31 to the control chamber 32. In this way, the solenoid control valve 30 controls the pressure of the control fluid in the control chamber 32. For example, the solenoid control valve 30 can take the form of a three-way valve, such as Figure 3 As shown, it is used to selectively connect: (i) the inlet 29 to the control chamber 32 to provide a supply of high-pressure control fluid to the control chamber 32; and / or (ii) connect the control chamber 32 to the outlet 31 to reduce the pressure of the control fluid in the control chamber 32, as will be described in more detail. The control fluid in the control chamber 32 acts on the distal surface 37 of the valve needle 18 and generates a force for pushing the valve needle 18 against the valve seat 35, thereby closing the nozzle outlet at the end of the hole 20 and cutting off the injection. In the example, such a distal surface 37 can be provided, for example, by the distal end of the valve needle 18 or the distal end of the command piston (not shown), which in turn is used to displace the valve needle 18 within the hole 20. It is worth noting that in the example, the distal surface 37 has a larger diameter than the valve seat 35, so that when the solenoid valve 30 connects the control chamber 32 to the first fluid supply network 44 (such as Figure 3 ), the valve needle 18 engages the valve seat 35 and the nozzle remains closed.

[0057] Figure 3 Also schematically shown is a connection between the first fluid supply network 44 and each sealant chamber 60a-e, such that control fluid is provided to each sealant chamber 60a-e at a delivery pressure from the high pressure line 48. In this manner, high pressure control fluid is provided to the sealant chambers 60a-e from the supply line 48, and the pressure of the sealant chambers 60a-e is substantially independent of the operation of the needle control valve 12.

[0058] The second fluid supply network 46 is also Figure 31 and connected to the fuel delivery chamber 24 so that the fuel delivery chamber 24 is supplied with pressurized gaseous fuel. In this way, the gaseous fuel in the delivery chamber 24 acts on the proximal surface of the valve needle 18 to generate a lifting force that acts against the closing force of the return spring 28 and the pressurized control chamber 32. Therefore, when the needle control valve 12 reduces the pressure in the control chamber 32, the gaseous fuel can lift the valve needle 18 and open the nozzle outlet to inject fuel into the combustion chamber.

[0059] It should be understood that the needle control valve 12 is therefore operated to regulate the pressure in the control chamber 32 and thereby control the closing force applied to the valve needle 18 to allow the opening and closing of the fuel injector 1. Therefore, the needle control valve 12 may include a control system for regulating the position of the solenoid control valve 30 and thereby controlling the pressure of the control fluid in the control chamber 32. Alternatively or additionally, the needle control valve 12 may receive a command signal from an external control system (such as an engine control unit). Various methods for controlling the solenoid needle control valve in this manner are known in the art and will not be described in detail here to avoid obscuring the present invention. By way of example only, the control system may be configured to control the position of the solenoid valve 30 based on one or more inputs, including but not limited to the injection cycle programmed for the fuel injector 1, the fuel pressure in the delivery chamber 24, and / or the amount of fuel in the storage tank of the fuel delivery system.

[0060] Now refer to Figures 3 to 7 Describe the manner in which the fuel injector 1 is operated, Figures 3 to 7 The fuel injector 1 is shown schematically during various phases of an injection cycle.

[0061] like Figure 3 As shown, the needle control valve 12 is first operated to connect the inlet 29 to the control chamber 32 and close the path to the outlet 31. The control chamber 32 is thus provided with control fluid at the delivery pressure, which generates a closing force on the valve needle 18 and pushes the valve needle 18 against the valve seat 35, thereby preventing injection.

[0062] Subsequently, when fuel injection is required, the electromagnetic needle control valve 30 is operated to connect the control chamber 32 to the outlet 31 and cut off the supply from the inlet 29, thereby reducing the pressure in the control chamber 32. Figure 4 As shown, the pressure in the control chamber 32 is thus reduced to below the pressure of the gaseous fuel, thereby allowing the valve needle 18 to lift away from the valve seat 35 (against the spring return force) for fuel injection. While the needle control valve 12 is maintained in this open state, the valve needle 18 moves further away from the valve seat 35 to the fully open position, as shown in FIG. Figure 5As shown, the maximum rate of fuel injection is allowed. Subsequently, to cut off the fuel injection, the solenoid valve 30 is actuated to the closed position to connect the inlet 29 to the control chamber 32 again and seal the outlet 31. As a result, the pressure in the control chamber 32 quickly returns to the delivery pressure, and the valve needle 18 is pushed back towards the valve seat 35, as shown. Figure 6 As shown, until the fuel injector 1 is closed again, as shown Figure 7 As shown, the valve needle 18 engages the valve seat 35 .

[0063] Thus, the present invention facilitates lifting of the valve needle 18 while providing a large valve seat for high flow rates of gaseous fuel. In addition, since the sealant chambers 60a-e can be maintained at the delivery pressure independently of the operation of the needle control valve 12, a pressure differential is maintained between the sealant chambers 60a-e and the closed leak path, thereby substantially inhibiting leakage of gaseous fuel from the second fluid supply network 46.

[0064] It will be appreciated that as the supply of gaseous fuel decreases, the pressure in the delivery chamber 24 will also decrease. Therefore, the first fluid delivery system (not shown) may be controlled accordingly to reduce the pressure of the control fluid in the first fluid supply network 44 and maintain a pressure differential of approximately 10 to 15 bar between the sealant chambers 60a-e and the gaseous fuel in the second fluid supply network 46.

[0065] In this way, the fuel injector 1 is able to function over a wide range of gaseous fuel pressures, allowing, for example, injection pressures between 50 bar and 300 bar. It is also envisaged that the fuel injector 1 of the present invention will therefore provide increased needle response and precise control of injection without the risk of harmful leakage of gaseous fuel into the needle control valve 12.

[0066] It will be appreciated by those skilled in the art that the present invention may be modified to assume many alternative forms to those described herein without departing from the scope of the appended claims.

[0067] Reference numerals used:

[0068] 1- Fuel Injector

[0069] 2 - Longitudinal axis (of the fuel injector)

[0070] 4-end (of the fuel injector)

[0071] 6-Proximal end (of fuel injector)

[0072] 8 - Distal end (of fuel injector)

[0073] 10-Injector Nozzle

[0074] 12-needle control valve

[0075] 14 - Distal end (of nozzle body)

[0076] 15-Needle Control Valve Body

[0077] 16-Nozzle body

[0078] 17- Distal end (of needle control valve body)

[0079] 18-Valve needle

[0080] 20-hole

[0081] 24-Conveyor Room

[0082] 28-Return spring

[0083] 29-Inlet (of needle control valve)

[0084] 30-Solenoid control valve

[0085] 31-(needle control valve) outlet

[0086] 32-Control Room

[0087] 33-Return line

[0088] 34-Piston

[0089] 35-valve seat

[0090] 36-Fluid transport body

[0091] 37-distal surface

[0092] 40-First Entrance

[0093] 42-Second Entrance

[0094] 44-First fluid supply network

[0095] 46- Second fluid supply network

[0096] 48-High-pressure pipeline (of the first fluid supply network)

[0097] 50 - first high pressure pipeline (of the second fluid supply network)

[0098] 52 - Second high pressure pipeline (of the second fluid supply network)

[0099] 60a-e - Sealant chamber

[0100] 62a-e - Branches to the first fluid supply network

Claims

1. A fuel injector (1) of a fuel injection system, the fuel injection system being used to deliver gaseous fuel to an internal combustion engine, the fuel injector (1) comprising: an injector nozzle (10) having a valve needle (18) movable within a bore (20) of the injector nozzle (10) for controlling delivery of the gaseous fuel to the internal combustion engine; A needle control valve (12) for controlling the movement of the valve needle (18) by controlling the pressure of a control fluid in a control chamber (32) of the needle control valve (12); a first fluid supply network (44) for conveying the control fluid from the first injector inlet (40) to the inlet (29) of the needle control valve (12); a second fluid supply network (46) for delivering the gaseous fuel from a second injector inlet (42) to a delivery chamber (24) for injection into the internal combustion engine, the delivery chamber being defined around the valve needle (18) in the bore (20) of the injector nozzle (10); as well as One or more sealant chambers (60a-e) for sealing respective leakage paths of the second fluid supply network (46), each leakage path extending between respective adjacent bodies (15, 16, 36) of the fuel injector (1), and respective sealant chambers (60a-e) being defined at abutting surfaces of those bodies (15, 16, 36) to close the leakage paths, wherein each sealant chamber (60a-e) is connected to the first fluid supply network (44) so ​​that, in use, a control fluid is supplied to each sealant chamber (60a-e) from the first fluid supply network (44) at a higher pressure than the fuel supply in the second fluid supply network (46), thereby substantially suppressing leakage from the second fluid supply network (46) via the respective leakage paths.

2. The fuel injector (1) according to claim 1, wherein: At least one of the leakage paths of the second fluid supply network (46) is defined between a mating surface of the valve needle (18) and the bore (20) of the injector nozzle (10), and a corresponding sealant chamber (60e) is at least partially defined at the interface by a recess in the bore (20) of the injector nozzle (10).

3. The fuel injector (1) according to claim 2, wherein: The valve needle (18) is matched with the hole (20) of the injector nozzle (10) so that a gap between the mating surface of the valve needle (18) and the hole (20) of the injector nozzle (10) provides a lubrication flow of the control fluid from the sealant chamber (60e) at least partially defined by the recess in the hole (20) of the injector nozzle (10) to the delivery chamber (24), optionally wherein the gap between the mating surface of the valve needle (18) and the hole (20) of the injector nozzle (10) is less than or equal to 2 microns, and / or the valve needle (18) is matched with the hole (20) of the injector nozzle (10) by refining at least one of the valve needle (18) and the hole (20) using a matching grinding process.

4. A fuel injector (1) according to any one of the preceding claims, wherein: In the first and second bodies (15, 16, 36) and in the connection area between the corresponding conduits of the second fluid supply network (46), at least one of the leakage paths of the second fluid supply network (46) is defined between the abutment surfaces of the axially adjacent first and second bodies (15, 16, 36) of the fuel injector (1), and wherein, in use, the corresponding sealant chamber (60a-d) is at least partially defined by a recess in the abutment surface of at least one of the first and second bodies (15, 16, 36) surrounding the connection area to seal the leakage path.

5. A fuel injector (1) according to any one of the preceding claims, wherein: The one or more sealant chambers (60a-d) include a plurality of sealant chambers (60a-e), optionally wherein one or more of the plurality of sealant chambers (60a-e) are configured to seal a corresponding leakage path of the second fluid supply network (46) at each mating surface or controlled gap of the fuel injector (1).

6. A fuel injector (1) according to any one of the preceding claims, wherein: At least one of the sealant chambers (60a-e) comprises an annular chamber that closes a corresponding leakage path.

7. A fuel injector (1) according to any one of the preceding claims, wherein: The gaseous fuel is hydrogen.

8. A fuel injector (1) according to any one of the preceding claims, wherein: In use, the control fluid is delivered as a liquid fluid in the first fluid supply network (44), optionally wherein the control fluid is a hydraulic fluid or diesel fuel.

9. A fuel injector (1) according to any one of the preceding claims, further comprising a return spring which pushes the valve needle (18) against a valve seat (35) of the injector nozzle (10).

10. A fuel injector (1) according to any one of the preceding claims, wherein: The second fluid supply network (46) includes a first high pressure line (50) and a second high pressure line (52), each extending from the second injector inlet (42) to the delivery chamber (24).

11. A fuel injector (1) according to any one of the preceding claims, wherein: The first fluid supply network (44) includes: a first high-pressure pipeline (48) extending from the first injector inlet (42) to the inlet (29) of the needle control valve (12); and a corresponding branch (62a-e) extending from the first high-pressure pipeline (48) to each sealant chamber (60a-e).

12. A fuel injector (1) according to any one of the preceding claims, wherein: The needle control valve (12) includes one or more solenoid valves, which are capable of being operated to selectively connect the inlet (29) of the needle control valve (12) and / or the outlet of the needle control valve (12) to the control chamber (32), and thereby control the pressure of the control chamber (32) during use, optionally wherein the one or more solenoid valves include a three-way valve, which selectively connects the control chamber (32) to the inlet (29) when the fuel injector (1) is in a closed state or connects the control chamber (32) to the outlet (31) when the fuel injector (1) is in an open state.

13. A fuel injector (1) according to any one of the preceding claims, wherein: The control fluid in the control chamber (32) acts on a distal surface of the valve needle (18), and wherein the diameter of the distal surface is greater than the diameter of the valve seat (35) of the injector nozzle (10).

14. A fuel injection system for delivering gaseous fuel to an internal combustion engine, the fuel injection system comprising a fuel injector (1) according to any one of the preceding claims, optionally wherein: The internal combustion engine is a hydrogen engine.

15. A method of controlling fuel injection from a fuel injection system, the fuel injection system comprising: A fuel injector (1) according to any one of the preceding claims; a first fluid delivery system for delivering a control fluid to the fuel injector (1); and a second fluid delivery system for delivering fuel to the fuel injector (1); the method comprising: supplying a first fluid supply network (44) with control fluid from the first fluid delivery system; supplying a second fluid supply network (46) with fuel from the second fluid delivery system; and The fuel injection from the fuel injector (1) is controlled by: Operate the needle control valve (12) to: reducing the pressure of the control fluid in the control chamber (32) of the needle control valve (12), thereby initiating fuel injection; and subsequently increasing the pressure of the control fluid in the control chamber (32) to cut off fuel injection; and At least one of the first fluid delivery system and the second fluid delivery system is controlled to provide a pressure differential between the first fluid supply network (44) and the second fluid supply network (46) during fuel injection, so that the control fluid is supplied from the first fluid supply network (44) to each sealant chamber (60a-e) at a higher pressure than the fuel supply in the second fluid supply network (46), thereby substantially suppressing leakage from the second fluid supply network (46) via the corresponding leakage path.

16. A method according to claim 15, when dependent on claim 2, wherein: At least one of the first fluid delivery system and the second fluid delivery system is controlled to provide a pressure differential between the first fluid supply network (44) and the second fluid supply network (46), the pressure differential generating a lubricating flow of a control fluid from the sealant chamber (60e) at least partially defined by the recess in the bore (20) of the injector nozzle (10) to the delivery chamber (24).

Images