Dual fuel injector

Abstract

A dual-fuel injector for injecting two separate fuels into the combustion chamber of an internal combustion engine comprises a nozzle body housing a dual-needle valve configuration. The valve configuration comprises first and second fuel needle valves, the first fuel needle valve defining a first needle valve shaft. The injector comprises a first fuel control chamber defined by the upper surface of the upper end of the first fuel needle valve, thereby changing the first pressure in the first fuel control chamber, which in turn changes the force on the upper end of the first fuel needle valve. The first fuel needle valve comprises a bore extending from a hole defined on its upper surface through the upper end of the first fuel needle valve. The second fuel needle valve is slidably received in the bore extending through the upper end of the first fuel needle valve, i.e., within the first fuel needle valve bore. The second fuel needle valve protrudes from the hole, thereby the upper end of the second fuel needle valve extending above the upper end of the first fuel needle valve.

Description

Technical Field

[0001] The present invention generally relates to a fuel injector, and more specifically to a dual fuel injector for an internal combustion engine.

Background Art

[0002] Internal combustion (IC) engines are typically powered by burning a fuel such as petroleum (gasoline) or diesel in a combustion chamber. New technologies are being developed to increase fuel efficiency and reduce the exhaust gases of IC engines. One such development involves the combustion of two separate fuels within the combustion chamber of a dual fuel engine. For example, a first fuel such as methane gas or hydrogen gas can be supplied to the combustion chamber due to its advantageous combustion characteristics or exhaust gas characteristics. A second fuel such as petroleum or diesel can be supplied to the combustion chamber to improve the reliability and timing of the combustion of the first fuel.

[0003] In a dual fuel engine, the first fuel and the second fuel can be supplied to the combustion chamber in several different ways. Some examples include mixing the two fuels with air in the intake manifold and then supplying the fuel / air mixture to the combustion chamber through the intake valve, supplying air and the first fuel through the intake valve and then injecting the second fuel into the combustion chamber, or injecting each fuel into the combustion chamber using separate fuel injectors. However, each of these methods has drawbacks in terms of the efficiency and / or packaging of the engine components.

[0004] To overcome these shortcomings, dual-fuel injectors, i.e., a single injector that injects both the first and second fuels into the combustion chamber, have been developed. However, significant problems remain. For example, dual-fuel injectors may require more auxiliary components, such as control valves packaged in a packing envelope similar to or identical to that of an equivalent single-fuel injector. A longer and more complex hydraulic system may be required to control the needle valves that regulate the delivery of each fuel. This can lead to wave activity and delays in the hydraulic control of the needle valves, increasing response time and reducing the consistency and reliability of fuel delivery. Consequently, the problematic packaging constraints ultimately result in undesirable combustion performance.

[0005] It is against this background that the present invention was conceived. [Overview of the project] [Means for solving the problem]

[0006] The present invention provides a dual fuel injector for injecting two separate fuels into the combustion chamber of an internal combustion engine. The dual fuel injector comprises a nozzle body housing a dual needle valve configuration. The dual needle valve configuration comprises a first fuel needle valve and a second fuel needle valve, the first fuel needle valve defining a first needle valve shaft. The dual fuel injector further comprises a first fuel control chamber at least partially defined by the upper surface of the upper end of the first fuel needle valve, thereby changing the first pressure in the first fuel control chamber, which changes the force on the upper end of the first fuel needle valve. The first fuel needle valve comprises a bore extending from a hole defined on its upper surface through the upper end of the first fuel needle valve. Furthermore, the second fuel needle valve is slidably received in the bore extending through the upper end of the first fuel needle valve, i.e., in the first fuel needle valve bore. The second fuel needle valve protrudes from the hole, and thereby the upper end of the second fuel needle valve extends above the upper end of the first fuel needle valve.

[0007] The second fuel needle valve is preferably slidably received within the first fuel needle valve bore using a matching clearance fit. The matching clearance fit, i.e., matching diameter, between the first fuel needle valve bore and the second fuel needle valve is preferably defined between the inner diameter of the first fuel needle valve bore and the outer diameter of the second fuel needle valve. For example, the diameter clearance in the matching clearance fit of the first fuel needle valve bore and the second fuel needle valve is preferably 2 μm to 4 μm.

[0008] In some embodiments, the operation of the first fuel needle valve can be hydraulically controlled by a first fuel control valve. For example, the first fuel control valve may define a first switching volume, through which the first fuel control chamber can be selectively fluid-coupled to either a high-pressure fluid source or a low-pressure fluid drain. Thus, the first switching volume can provide a fluid passage between the first fuel control chamber and the high-pressure fluid source, and a fluid passage between the first fuel control chamber and the low-pressure fluid drain. Selective fluid coupling of the first fuel control chamber to the high-pressure fluid source or the low-pressure fluid drain can change the pressure within the first fuel control chamber, and thus actuate the first fuel needle valve. The first fuel control chamber can be fluid-coupled to the first fuel control valve, i.e., the first switching volume, via a first control conduit. The first fuel control chamber and the first control conduit can define a first fuel control volume.

[0009] In some embodiments, a second fuel needle valve may extend through the first fuel control chamber. Therefore, the upper end of the second fuel needle valve preferably extends through the first fuel control chamber.

[0010] In some embodiments, the first fuel control chamber can be at least partially defined by the outer surface of the second fuel needle valve. Thus, the fluid within the first fuel control chamber can come into contact with the outer surface of the second fuel needle valve. Therefore, the first fuel control chamber can be manufactured as a hollow open space, and the second fuel needle valve can extend through the open space. Advantageously, such a configuration can facilitate the relatively simple manufacture of the first fuel control chamber.

[0011] Furthermore, in some embodiments, the first fuel control chamber may have a first central axis coaxial with the first needle valve shaft. Positioning the first control chamber coaxial with the first needle valve is advantageous in that the distance between the first fuel control valve and the first fuel control chamber can be minimized. Thus, the first control volume can be minimized. This reduces the risk of wave activity in the first control volume, decreases the delay in the hydraulic control of the first fuel needle valve, thereby shortening the valve response time and improving the consistency and reliability of the first fuel delivery to the combustion chamber.

[0012] In some preferred embodiments, the second fuel needle valve may be coaxial with the first fuel needle valve. For example, the second fuel needle valve may define a second needle valve shaft, which may be coaxial with the first needle valve shaft. It will be understood that the first needle valve shaft and / or the second needle valve shaft are preferably the longitudinal axes of the respective needle valves.

[0013] In some preferred embodiments, the first fuel control chamber may define a substantially circular outer circumference. For example, the first fuel control chamber may include a rotational stroke volume about a first central axis. Thus, in some preferred embodiments, it will be understood that the first central axis defines the geometric center of the first fuel control chamber. In some embodiments, the first fuel control chamber may form an annulus extending around a portion of the second fuel needle valve.

[0014] In some preferred embodiments, the nozzle body may comprise different parts, each configured to perform a distinct function. For example, the nozzle body may comprise a lower section configured to extend into the combustion chamber. Thus, the lower section of the nozzle body may be formed of a material capable of withstanding the high temperatures and pressures within the combustion chamber. The nozzle body may comprise an upper section comprising hydraulic conduits that supply fuel and hydraulic control fluid around the injector. In some embodiments, the upper section of the nozzle body may also provide mounting positions for attaching auxiliary components, such as control valves, to the injector.

[0015] In some embodiments, the nozzle body may define a needle guide. For example, the upper part of the nozzle body may define a needle guide. The upper end of the first fuel needle valve may be slidably received within the needle guide. In some preferred embodiments, the upper end of the first fuel needle valve may be received within the needle guide using a coincident clearance fit. The coincident clearance fit, i.e., coincident diameter, between the upper end of the first fuel needle valve and the needle guide is preferably defined between the outer diameter of the upper end of the first fuel needle valve and the inner diameter of the needle guide. For example, the needle guide and the upper end of the first fuel needle valve preferably have a diameter clearance of 2 μm to 3.5 μm.

[0016] In some embodiments, the first fuel control chamber may be defined at least partially by the ceiling surface of the needle guide. For example, the first control chamber may be defined between the upper end of the first fuel needle valve and the ceiling surface of the needle guide.

[0017] In some embodiments, the nozzle body may comprise a bore extending from a hole defined in the ceiling surface of the needle guide. The upper end of the second fuel needle valve may be received within the bore extending from the hole in the ceiling surface of the needle guide. In some preferred embodiments, the upper end of the second fuel needle valve may be received within the bore using a matching clearance fit. The matching clearance fit, i.e., matching diameter, between the upper end of the second fuel needle valve and the bore of the nozzle body is preferably defined between the outer diameter of the upper end of the second fuel needle valve and the inner diameter of the bore of the nozzle body. For example, the upper end of the second fuel needle valve and the bore preferably have a diameter clearance of 1.5 μm to 2.5 μm.

[0018] In some embodiments, the dual fuel injector may further comprise a second fuel control chamber. The second fuel control chamber may be at least partially defined by the upper surface of the upper end of the second fuel needle valve, thereby changing the second pressure within the second fuel control chamber, which changes the force on the upper end of the second fuel needle valve. In some embodiments, the second fuel control chamber may be at least partially defined by the nozzle body. For example, in some embodiments, the second fuel control chamber may be defined by a bore extending from a hole defined in the ceiling surface of the needle guide portion of the nozzle body.

[0019] In some embodiments, the operation of a second fuel needle valve can be hydraulically controlled by a second fuel control valve. For example, the second fuel control valve may define a second switching volume, through which the second fuel control chamber can be selectively fluid-coupled to either a high-pressure fluid source or a low-pressure fluid drain. Thus, the second switching volume can provide a fluid passage between the second fuel control chamber and the high-pressure fluid source, and a fluid passage between the second fuel control chamber and the low-pressure fluid drain. Selective fluid coupling of the second fuel control chamber to the high-pressure fluid source or the low-pressure fluid drain can change the pressure within the second fuel control chamber, and thus actuate the second fuel needle valve. The second fuel control chamber can be fluid-coupled to a second fuel control valve, i.e., a second switching volume, via a second control conduit. The second fuel control chamber and the second control conduit can define a second fuel control volume.

[0020] As described above, the second fuel needle valve protrudes from the hole of the first fuel needle valve, thereby the upper end of the second fuel needle valve extends above the upper end of the first fuel needle valve. In some embodiments, particularly when the second fuel control chamber is at least partially defined by the upper surface of the upper end of the second fuel needle, the configuration of the protruding second fuel needle valve advantageously minimizes the distance between the second fuel control valve and the second fuel control chamber. Thus, in such a configuration, the second control volume is minimized. This reduces the risk of wave activity in the second control volume, reduces the delay in the hydraulic control of the second fuel needle valve, thereby shortening the valve response time and improving the consistency and reliability of the supply of the first fuel to the combustion chamber.

[0021] In some preferred embodiments, the second fuel control chamber may have a second central axis coaxial with the first needle valve shaft. Furthermore, in some preferred embodiments, the second fuel control chamber may define a substantially circular outer circumference. For example, the second fuel control chamber may include a rotational stroke volume centered on the second central axis. Thus, in preferred embodiments, it will be understood that the second central axis defines the geometric center of the second fuel control chamber. Such configurations and arrangements are further advantageous in manufacturing a dual fuel injector and minimizing the second control volume.

[0022] In some preferred embodiments, the first central axis and / or the second central axis may be coaxial with the second needle valve axis. Thus, in some preferred embodiments, the first needle valve axis and the second needle valve axis, as well as the first central axis and the second central axis, may all be coaxial with each other. Such a configuration may be advantageous for manufacturing and assembly, as well as for loading and wear of components during use. Additionally, such a configuration may further promote a reduction in the respective control volume by shortening the distance between the control valve and the control chamber.

[0023] In some preferred embodiments, a second fuel needle valve and associated second fuel control chamber may hydraulically dampen the opening speed of the first fuel needle valve. For example, as will be described in more detail later, a second pressure in the second fuel control chamber may apply a closing force to the second fuel needle valve, thereby holding the valve in the closed position relative to the second fuel valve seat of the first fuel needle valve. Thus, the second pressure may apply a force to the first fuel needle valve through the second fuel needle valve and the second fuel valve seat. For example, if the second pressure in the second fuel control chamber is maintained when the first fuel needle valve is opened by reducing the first pressure in the first fuel control chamber, i.e., when the first fuel needle valve is lifted, this may provide a counterforce acting against the opening of the first fuel needle valve (i.e., the closing force referred to above). Thus, this may slow down the opening speed of the first fuel needle valve.

[0024] Furthermore, the counterforce provided by the second pressure and the second fuel needle valve may act in the same direction as the force from the first pressure in the first fuel control chamber that acts to close the first fuel needle valve. Thus, this configuration can accelerate the closing of the first fuel needle valve. Both damping the opening of the first fuel needle valve and accelerating its closing are advantageous for combustion in the engine's combustion chamber. These advantages are primarily driven by the configuration of the second fuel needle valve, which protrudes from the first fuel needle valve such that its upper end extends above the upper end of the first fuel needle valve, thereby allowing the first and second fuel needle valves to move substantially independently.

[0025] In some embodiments, the nozzle body may define a first fuel valve seat. For example, the lower part of the nozzle body may be configured to extend into the combustion chamber and define a first valve seat. The dual fuel injector may further include a first biasing means configured to bias a first fuel needle valve to engage with the first fuel valve seat.

[0026] In some embodiments, the nozzle body may at least partially define a first fuel accumulator volume and one or more first fuel injection ports in fluid communication with the first fuel accumulator volume for injecting first fuel from the first fuel accumulator volume into the combustion chamber. For example, the first fuel accumulator volume may be at least partially defined between the first fuel needle valve and the inner surface of the nozzle body. Further, the first fuel valve seat may define the first fuel injection port or each first fuel injection port. Thus, the first biasing means may bias the first fuel needle valve to close the first fuel injection port or each first fuel injection port and interrupt the fluid communication between the first fuel accumulator volume and the combustion chamber. Similarly, increasing the pressure in the first fuel control chamber pushes the first fuel needle valve into engagement with the first fuel valve seat, thereby closing the first fuel injection port or each first fuel injection port may be closed. The first biasing means may advantageously accelerate the closing of the first fuel needle valve at the end of the first fuel injection. This can be beneficial for combustion and fuel efficiency.

[0027] In some embodiments, the first biasing means may be disposed around the first fuel needle valve. In some preferred embodiments, the first biasing means comprises a coil spring extending around the outer surface of the first fuel needle valve. Further, in some embodiments, the first biasing means may be located within the first fuel accumulator volume. For example, the first biasing means may be located between the first fuel needle valve and the internal bore of the nozzle body. Thus, the first biasing means may be located in a completely separate part of the injector compared to the first fuel control chamber. This means that there is no need to dimension the first fuel control chamber to accommodate the first biasing means, and as described above, the first fuel control chamber, and by extension, the first fuel control volume can be minimized, thereby improving fuel delivery and combustion performance.

[0028] In some embodiments, the first fuel needle valve may include a shoulder portion, and the first biasing means may abut or engage with the shoulder portion of the first fuel needle valve. Advantageously, the first biasing means may be configured to bias the first fuel needle valve along the first needle valve axis without necessarily relying on the upper end of the first fuel needle valve. Accordingly, the volume of the first fuel control chamber can be minimized, which is advantageous for the reasons described above.

[0029] In some embodiments, the dual fuel injector may further include a collar coupled to the first fuel needle valve. For example, the collar may define a shoulder portion. The first biasing means may engage with the collar and a portion of the nozzle body to bias the first fuel needle valve to engage with the first fuel valve seat. For example, the nozzle body may include a seat configured to engage with the first biasing means. The first biasing means is preferably compressed and held between the collar and the nozzle body seat to bias the first fuel needle valve. In some embodiments, the collar may be press-fitted onto the outer surface of the first fuel needle valve, i.e., the first fuel needle valve. Including a collar for engaging the first biasing means may be advantageous for facilitating manufacturing and assembly.

[0030] As described above, in some embodiments, the first fuel needle valve may define a second fuel valve seat. The dual fuel injector may further include a second biasing means configured to bias the second fuel needle valve to engage with the second fuel valve seat. Further, in some embodiments, the second biasing means may be disposed within a second fuel accumulator volume within the first fuel needle valve.

[0031] In some embodiments, the first fuel needle valve may define one or more second fuel injectors that are in fluid communication with the second fuel accumulator volume to inject the second fuel from the second fuel accumulator volume into the combustion chamber. In some embodiments, the second fuel valve seat may define the second fuel injectors or each of the second fuel injectors. Thus, the second biasing means may bias the second fuel needle valve to close the second fuel injectors or each of the second fuel injectors, thereby interrupting the fluid communication between the second fuel accumulator volume and the combustion chamber. Similarly, increasing the pressure in the second fuel control chamber may push the second fuel needle valve in and engage with the second fuel valve seat, thereby closing the second fuel injectors or each of the second fuel injectors.

[0032] In some preferred embodiments, a second biasing means may be disposed around a second fuel needle valve within a second fuel accumulator volume. For example, the second biasing means may comprise a coil spring extending around the outer surface of the second fuel needle valve. In some embodiments, the second fuel needle valve may comprise a shoulder portion, or a collar may be coupled to the second fuel needle valve. The second biasing means may engage with the shoulder portion or collar and the ceiling surface of the second fuel accumulator volume to bias the second fuel needle valve into engaging with the second fuel valve seat. For example, the second biasing means may be compressed and held between the shoulder portion or collar of the second fuel needle valve and the ceiling surface of the second fuel accumulator volume.

[0033] In particular, in a preferred embodiment, the second biasing means may be disposed within the second fuel accumulator volume in the first fuel needle valve, while the second fuel control chamber may be at least partially defined by the upper surface of the upper end of the second fuel needle valve extending above the upper end of the first fuel needle valve. Thus, in a preferred embodiment, the second biasing means may be located completely separate from the second fuel control chamber. Consequently, the second fuel control chamber does not need to be dimensioned to accommodate the second biasing means, and therefore the volume of the second fuel control chamber can be minimized.

[0034] In some preferred embodiments, the first fuel may be a gaseous fuel. For example, the first fuel may be methane gas or hydrogen gas. As an addition or alternative, the second fuel may be a liquid fuel. For example, the second fuel may be petroleum (gasoline) or diesel.

[0035] In some embodiments, the dual fuel injector may further comprise an annular hydraulic sealing gallery extending around the outer surface of the first fuel needle valve. The annular hydraulic sealing gallery may be fluid-coupled to a high-pressure fluid source. In some embodiments, the annular hydraulic sealing gallery may be fluid-coupled to at least one of a first switching volume and / or a second switching volume, thereby fluid-coupled to a high-pressure fluid source via the sealing gallery. Thus, in some embodiments, a control chamber or each control chamber may receive a supply via the sealing gallery.

[0036] In some embodiments, the first fuel control valve may be a three-way valve. The first switching volume may have a diameter of less than 5 mm, preferably less than 3 mm, and most preferably less than 1.5 mm. In addition or alternatively, in some embodiments, the second fuel control valve may be a three-way valve. The second switching volume may have a diameter of less than 5 mm, preferably less than 3 mm, and most preferably less than 1.5 mm.

[0037] In some embodiments, the first fuel control valve may include a first plunger configured to move along a first control valve shaft to selectively fluid-couple the first fuel control chamber to a high-pressure fluid source or a low-pressure fluid drain. Thus, the first plunger may be located within a first switching volume. The first fuel control valve is preferably configured such that the first plunger is selectively movable along the first control valve shaft between a first position and a second position. The first fuel control valve is preferably configured such that the first plunger facilitates either a) fluid-coupling the first fuel control chamber to a high-pressure fluid source and fluid-separating the first fuel control chamber from the low-pressure fluid drain (i.e., blocking fluid communication between the first fuel control chamber and the low-pressure fluid drain), or b) fluid-coupling the first fuel control chamber to the low-pressure fluid drain and fluid-separating the first fuel control chamber from the high-pressure fluid source. Preferably, the first fuel control valve is configured such that, in a second position, the first plunger facilitates either a) fluid coupling the first fuel control chamber to a high-pressure fluid source and fluidly separating the first fuel control chamber from a low-pressure fluid drain, or b) fluid coupling the first fuel control chamber to a low-pressure fluid drain and fluidly separating the first fuel control chamber from a high-pressure fluid source.

[0038] The second fuel control valve may include a second plunger configured to move along a second control valve shaft to selectively fluid-couple the second fuel control chamber to a high-pressure fluid source or a low-pressure fluid drain. Thus, the second plunger may be located within a second switching volume. The second fuel control valve is preferably configured such that the second plunger is selectively movable along the second control valve shaft between a first position and a second position. The second fuel control valve is preferably configured such that the second plunger facilitates either a) fluid-coupling the second fuel control chamber to a high-pressure fluid source and fluid-separating the second fuel control chamber from the low-pressure fluid drain (i.e., blocking fluid communication between the second fuel control chamber and the low-pressure fluid drain), or b) fluid-coupling the second fuel control chamber to the low-pressure fluid drain and fluid-separating the second fuel control chamber from the high-pressure fluid source. The second fuel control valve is preferably configured such that the second plunger facilitates, in a second position, either a) fluid coupling the second fuel control chamber to a high-pressure fluid source and fluidly separating the second fuel control chamber from a low-pressure fluid drain, or b) fluid coupling the second fuel control chamber to a low-pressure fluid drain and fluidly separating the second fuel control chamber from a high-pressure fluid source.

[0039] The first fuel control valve and the second fuel control valve are arranged side by side such that the first control valve shaft extends parallel to the second control valve shaft. In some preferred embodiments, both the first and second control valve shafts may extend parallel to the first needle valve shaft, and both the first and second control valve shafts may be offset from the first needle valve shaft, so that neither control valve shaft is coaxial with the first needle valve shaft. In some embodiments, the first and second control valve shafts may each be offset by the same distance from the first needle valve shaft. Thus, in advantageous embodiments, neither control valve is preferred over the other; instead, both control conduits are optimized with respect to reducing the distance to their respective control chambers, thereby reducing their respective control volumes.

[0040] Placing the first and second fuel control valves side-by-side can help reduce the overall size of the dual fuel injector and improve combustion in the combustion chamber during use by enabling improved valve movement control. For example, arranging the first and second fuel control valves side-by-side such that their respective valve shafts are parallel to but not concentric with the first needle valve shaft means that both control valves can be located close to their respective control chambers. Reducing the distance between the control valves, i.e., reducing the switching volume of the control valves and their respective control chambers, shortens the length of the control conduits, and thereby reduces each control volume. This minimizes switching losses or control volume losses, allows for faster needle valve response (i.e., valve opening and closing speeds), reduces hydraulic wave activity in each control volume, and thereby delivers fuel more accurately and consistently into the combustion chamber.

[0041] In some embodiments, a dual fuel injector may include a first control orifice through which a first fuel control chamber is fluidly connected to a first control conduit. Thus, the flow area of ​​the first control orifice, or the diameter of the first control orifice, may affect the inflow and outflow velocities to the first fuel control chamber. Consequently, the flow area or diameter of the first control orifice may affect the opening and closing velocities of the first fuel needle valve. For example, the first control orifice may be configured to fluidly connect the first fuel control chamber to a low-pressure fluid drain, thereby attenuating, i.e., decelerating, the opening velocities of the first fuel needle valve when the first control valve is operated so that the fluid in the first fuel control chamber is discharged to the low-pressure fluid drain through the first control orifice. Thus, the flow area of ​​the first control orifice, or the diameter of the first control orifice, may be smaller than the flow area or diameter of the first control conduit.

[0042] In some embodiments, a dual fuel injector may include a second control orifice through which a second fuel control chamber is fluidly connected to a second control conduit. Therefore, the flow area or diameter of the second control orifice affects the inflow and outflow velocities to the second fuel control chamber. Thus, the flow area or diameter of the second control orifice may affect the opening and closing velocities of the second fuel needle valve. For example, the second control orifice may be configured to fluidly connect the second fuel control chamber to a low-pressure fluid drain, thereby attenuating, i.e., decelerating, the opening speed of the second fuel needle valve when the second control valve is operated so that the fluid in the second fuel control chamber is discharged through the second control orifice to the low-pressure fluid drain. Therefore, the flow area or diameter of the second control orifice may be smaller than the flow area or diameter of the second control conduit.

[0043] In some embodiments, the nozzle body may comprise an assembly of multiple nozzle body sections. For example, the nozzle body may comprise a separate nozzle body section that at least partially defines the aforementioned portion of the nozzle body. For example, the nozzle body may comprise a tip section that defines at least a portion of the lower part of the nozzle body and thus extends into the combustion chamber. The tip section of the nozzle body may comprise a different material from the other nozzle body sections or each other nozzle body section in order to withstand the high temperature and pressure in the combustion chamber. For example, the tip section of the nozzle body may define a first fuel valve seat, and thus the tip section may also define a first fuel injector or each first fuel injector. As an addition or alternative, in some embodiments, the tip section of the nozzle body may define at least a portion of the first fuel accumulator volume.

[0044] To inject a quantity of first fuel into the combustion chamber, the dual fuel injector can be operated such that a first fuel control valve is fluidly connected to a low-pressure fluid drain of the first fuel control chamber, resulting in a decrease in the first pressure within the first fuel control chamber, thereby weakening the force on the upper end of the first fuel needle valve. Thus, the pressure of the first fuel in the first fuel accumulator volume can overcome the remaining closing force that holds the first fuel needle valve in contact with the first fuel valve seat, thereby lifting the first fuel needle valve and allowing the first fuel to flow out of the first fuel accumulator volume and into the combustion chamber.

[0045] Under typical operating conditions, a certain amount of second fuel may be injected into the combustion chamber during or after the injection of first fuel. Thus, a second pressure is maintained in the second fuel control chamber, and the second fuel needle valve can be held in the closed position relative to the second fuel valve seat of the first fuel needle valve while the first fuel needle valve is open, i.e., while it is lifting. Therefore, the second fuel needle valve can act substantially independently of the first fuel needle valve when closed, and thus can exert force on the first fuel needle valve. Thus, in some embodiments, the second fuel needle valve can attenuate, i.e., decelerate, the opening speed of the first fuel needle valve. Furthermore, the additional force exerted by the second fuel needle valve can accelerate the closing speed of the first fuel needle valve. Both of these effects are beneficial to combustion.

[0046] In some embodiments, the first fuel is a gaseous fuel. For example, the first fuel may be a gas such as methane or hydrogen gas. Additionally or alternatively, the second fuel may be a liquid fuel. For example, in some embodiments, the second fuel may be a liquid such as liquid diesel or liquefied petroleum (gasoline). In some other embodiments, the first and second fuels may be fuels of the same type. For example, in some embodiments, both the first and second fuels may be liquid fuels, or alternatively, in other embodiments, both the first and second fuels may be gaseous fuels.

[0047] In some preferred embodiments, each of the matching diameters referenced herein is preferably concentric within a range of 0.5 μm from the first needle valve shaft.

[0048] Next, embodiments of the present invention will be described with reference to the attached figures, but only through non-limiting embodiments. [Brief explanation of the drawing]

[0049] [Figure 1] This is a schematic cross-sectional view of a dual fuel injector. [Figure 2] This is an enlarged view of the cross-section shown in Figure 1. [Figure 3] This is a schematic perspective view of the internal volume defined by the first and second control chambers of the dual fuel injector. [Modes for carrying out the invention]

[0050] Figure 1 shows a schematic cross-sectional view of a dual-fuel injector 10 for injecting two separate fuels into the combustion chamber 12 of an internal combustion engine. For example, the injector 10 may be configured to inject a first fuel in gaseous form, such as methane or hydrogen, and a second fuel in liquid form, such as petroleum (gasoline) or diesel. As already explained in the background, the first fuel may be selected for its favorable combustion or exhaust gas characteristics, and the second fuel supplied to the combustion chamber 12 may help improve the reliability and timing of the combustion of the first fuel.

[0051] The dual fuel injector 10 includes a nozzle body 14 that houses a dual needle valve configuration 16 for regulating the supply of a first fuel and a second fuel to the combustion chamber 12. Thus, the dual needle valve configuration 16 includes a first fuel needle valve 18 and a second fuel needle valve 20. The injector 10 also includes a first fuel control chamber 22. The first fuel control chamber 22 is preferably configured to hydraulically control the movement of the first fuel needle valve 18. For example, the first fuel control chamber 22 is at least partially defined by the upper surface 24 of the upper end 26 of the first fuel needle valve 18. Thus, changing the first pressure in the first fuel control chamber 22 changes the force on the upper end 26 of the first fuel needle valve 18. Thus, the movement of the first fuel needle valve 18 can be controlled by controlling the pressure in the first fuel control chamber 22.

[0052] In addition, referring to Figure 2, which shows an enlarged view of the cross-sectional view of Figure 1 for ease of reference, in some preferred embodiments, the upper end 26 of the first fuel needle valve 18 may be slidably received within a needle guide 28 defined by the nozzle body 14. Thus, as shown in the embodiment of Figure 2, the first fuel control chamber 22 may be at least partially defined by the ceiling surface 30 of the needle guide 28. The first fuel needle valve 18 may be received within the needle guide 28 using a matching clearance fit to facilitate the movement of the first fuel needle valve 18 relative to the nozzle body 14. It will be understood that the first fuel needle valve 18 defines the first needle valve shaft 32, and the needle guide 28 is preferably configured to restrict the first fuel needle valve 18 to move linearly along the first needle valve shaft 32.

[0053] Continuing to refer to Figures 1 and 2, as previously stated, the dual needle valve configuration 16 includes a second fuel needle valve 20 for regulating the supply of a second fuel to the combustion chamber 12. The second fuel needle valve 20 is slidable relative to the first fuel needle valve 18 and, as will be described in more detail later, can advantageously move substantially independently of the first fuel needle valve 18. As is most clearly shown in Figure 2, the first fuel needle valve 18 includes a bore 34 extending from a hole 36 defined in its upper surface 24 through the upper end 26 of the first fuel needle valve 18. The second fuel needle valve 20 is slidably received within its first fuel needle valve bore 34.

[0054] In particular, the upper end 38 of the second fuel needle valve 20 extends above the upper end 26 of the first fuel needle valve 18, since the second fuel needle valve 20 protrudes from the hole 36 in the upper surface 24 of the upper end 26 of the first fuel needle valve 18. It will be understood that this configuration facilitates separate control and movement of the second fuel needle valve 20, independently of the first fuel needle valve 18. For example, as is most clearly shown in Figure 2, the movement of the second fuel needle valve 20 can be controlled by changing the second pressure in the second fuel control chamber 40, which is at least partially defined by the upper surface 42 of the upper end 38 of the second fuel needle valve 20.

[0055] Furthermore, since the second fuel control chamber 40 may be provided in a portion of the injector 10 that is completely separated from the first fuel needle valve 18, independent control of the second fuel needle valve 20 is facilitated, at least partially. For example, continuing to refer to Figure 2, the nozzle body 14 may have a hole 44 in the ceiling surface 30 of the needle guide portion 28. The upper end 38 of the second fuel needle valve 20 may be received in a bore 46 extending from the hole 44. Thus, the second fuel control chamber 40 can be defined at least partially by the upper end 38 of the second fuel needle valve 20 and at least partially by the nozzle body 14.

[0056] As shown in Figures 1 and 2, in some preferred embodiments, the second fuel needle valve 20 may extend through the first fuel control chamber 22. Thus, the first fuel control chamber 22 may be at least partially defined by the outer surface 48 of the second fuel needle valve 20. Additionally, referring to Figure 3, the internal volumes defined by the first fuel control chamber 22 and the second fuel control chamber 40 are shown separately, and in some embodiments, the first fuel control chamber 22 may form an annulus extending around a portion of the second fuel needle valve 20. For advantageous load distribution in packaging and use, the dual fuel injector 10 may be configured such that the central axis 50 of the first fuel control chamber 22 is coaxial with the first needle valve axis 32. For the same reason, the central axis 52 of the second fuel control chamber 40 may be coaxial with the axis 54 defined by the second needle valve 20. The first fuel needle valve 18 and the second fuel needle valve 20 may be coaxial, and therefore, in some embodiments, each of the needle valves 18, 20 and the control chambers 22, 40 may be coaxial with each other for advantageous load distribution during use.

[0057] Referring again to Figures 1 and 2, in some embodiments, the nozzle body 14 may define one or more first fuel injectors 56. The first fuel injectors 56, or each first fuel injector 56, may be defined by a first fuel valve seat 58 of the nozzle body 14. The first fuel injectors 56, or each first fuel injector 56, may be configured to promote fluid communication between the first fuel accumulator volume 60 and the combustion chamber 12. Therefore, the first fuel needle valve 18 is preferably configured to selectively block or allow fluid communication between the first fuel accumulator volume 60 and the combustion chamber 12 through the first fuel injectors 56. For example, high pressure in the first fuel control chamber 22 may provide a closing force applied to the upper end 26 of the first fuel needle valve 18, so that the needle valve 18 engages with the first fuel valve seat 58, thereby blocking the first fuel injectors 56. In order to inject the first fuel into the combustion chamber 12, the first pressure in the first fuel control chamber 22 may be reduced, resulting in the pressure in the first fuel accumulator volume 60 becoming higher than the first pressure in the first fuel control chamber 22, thereby causing the first fuel needle valve 18 to move away from the first fuel valve seat 58 and promoting fluid communication between the first fuel accumulator volume 60 and the combustion chamber 12 via the first fuel injector 56.

[0058] The dual fuel injector 10 may also include a first biasing means 62 configured to bias a first fuel needle valve 18 to engage with a first fuel valve seat 58. This additional biasing force may help accelerate the closing speed of the first fuel needle valve 18. As shown in Figures 1 and 2, in some embodiments, the first biasing means 62 may be arranged around the first fuel needle valve 18. For example, the first biasing means 62 may be located within the first fuel accumulator volume 60. It should be noted, in particular, in advantageous embodiments, the first biasing means 62 may be located in a completely isolated area of ​​the injector 10 compared to the first fuel control chamber 22. Therefore, the first fuel control chamber 22 does not need to be sized to accommodate the first biasing means 62, but can instead be minimized to improve the response of the first fuel needle valve 18 to pressure changes within the first fuel control chamber 22 when the first fuel needle valve 18 is actuated during use.

[0059] The first biasing means 62 preferably engages with a portion of the nozzle body 14 to bias the first fuel needle valve 18 to engage with the first fuel valve seat 58. To improve ease of manufacture, the injector 10 may include a collar 64 coupled to the first fuel needle valve 18, and the first biasing means 62 may engage with the collar 64 and a portion of the nozzle body 14.

[0060] Continuing to refer to Figures 1 and 2, as previously stated, the movement of the second fuel needle valve 20 can be controlled by changing the second pressure in the second fuel control chamber 40. This changes the force on the upper end 38 of the second fuel needle valve 20, causing the second fuel needle valve 20 to actuate. As in the description relating to the first fuel needle valve 18, it will be understood that when the second fuel needle valve 20 is actuated, either shutting off or opening occurs for one or more second fuel injectors 66. The second fuel injectors 66, or each second fuel injector 66, may be defined by the second fuel valve seat 68 of the first fuel needle valve 18. The second fuel injectors 66, or each second fuel injector 66, may promote fluid communication between the second fuel accumulator volume 70 and the combustion chamber 12. Therefore, when in use, the second fuel needle valve 20 is held in contact with the second fuel valve seat 68, and for example, when the second pressure in the second fuel control chamber 40 is higher than the pressure in the second fuel accumulator volume 70, fluid communication between the second fuel accumulator volume 70 and the combustion chamber 12 is cut off.

[0061] The dual fuel injector 10 may also include a second biasing means 72 configured to bias a second fuel needle valve 20 to engage with a second fuel valve seat 68. The additional biasing force provided by the second biasing means 72 may help accelerate the closing speed of the second fuel needle valve 20. As shown in Figures 1 and 2, in some preferred embodiments, the second biasing means 72 may be disposed within a second fuel accumulator volume 70. As in the preceding description with reference to the first fuel control chamber 22 and the first biasing means 62, positioning the second biasing means 72 in a completely separate area of ​​the injector 10 compared to the second fuel control chamber 40 means that the second fuel control chamber 40 does not need to have a size to accommodate the second biasing means 72. Therefore, instead, the volume of the second fuel control chamber 40 can be minimized in order to improve the response of the second fuel needle valve 20 to pressure changes in the second fuel control chamber 40 during use.

[0062] Finally, as shown in Figure 1 and more clearly in Figure 2, in some embodiments the injector 10 may additionally include an annular sealing gallery 74 extending around the outer surface 76 of the first fuel needle valve 18. As previously stated, the first fuel needle valve 18 is preferably slidably received within the needle guide portion 28 of the nozzle body 14. Therefore, a small gap may exist between the needle guide portion 28 and the first fuel needle valve 18 due to a clearance fit to allow for a sliding relationship. Thus, including the sealing gallery 74 may be advantageous for sealing between the first fuel needle valve 18 and the needle guide portion 28 of the nozzle body 14.

[0063] For example, a sealed gallery 74 may be located between the first fuel control chamber 22 and the first fuel accumulator volume 60. The sealed gallery 74 may be in fluid communication with a high-pressure fluid source, and therefore, in a preferred embodiment, the sealed gallery 74 may be maintained at a higher pressure than the first fuel in the first fuel accumulator volume 60. Thus, a differential pressure may exist between the sealed gallery 74 and the first fuel accumulator volume 60, preventing any movement of the first fuel from the first fuel accumulator volume 60 toward the sealed gallery 74 and / or the first fuel control chamber 22.

[0064] Although not shown in the cross-sectional view of the attached figure, in some preferred embodiments, the sealing gallery 74 may perform additional functions in addition to its primary sealing function. For example, a multifunctional sealing gallery 74 may achieve both sealing between the first fuel needle valve 18 and the needle guide 28 and supplying control fluid to one or both of the control chambers 22, 40. In such embodiments, the control fluid is preferably supplied to one or both of the control chambers 22, 40 via their respective control valves 78, 80, which are configured to change the pressure within the control chambers 22, 40, thereby acting on the first fuel needle valve 18 and the second fuel needle valve 20. Thus, the sealing gallery 74 may be in fluid communication with at least one of the first fuel control chamber 22 and / or the second fuel control chamber 40. Such fluid communication is preferably via control valves 78, 80 for regulating the supply of fluid to the respective chambers 22, 40 to control the first fuel needle valve 18 and / or the second fuel needle valve 20.

[0065] It will be understood that the above description serves to demonstrate possible embodiments of the present invention. Features described in reference to any of the above embodiments can be readily combined with any other features described in reference to different embodiments without departing from the scope of the present invention as defined in the appended claims. [Explanation of Symbols]

[0066] 10 Dual Fuel Injectors 12 Combustion Chamber 14 Nozzle body 16 Dual needle valve configuration 18. First fuel needle valve 20. Second fuel needle valve 22 First fuel control chamber 24 Top 26 Top 30 Ceiling surface 32 First needle valve shaft 34 Bore 36 holes 38 Top 40 Second fuel control chamber 42 Top surface 44 holes 46 Bore 48 Exterior 50 center axis 52 Center axis 54 axes 56 First fuel injector 58 First fuel valve seat section 60 First fuel accumulator volume 62 First biasing means 64 Colors 66 Second fuel injector 68 Second fuel valve seat section 70 Second fuel accumulator volume 72 Second biasing means 74 Circular Sealed Gallery 76 Exterior 78, 80 Control valves

Claims

1. A dual fuel injector (10) for injecting two separate fuels into the combustion chamber (12) of an internal combustion engine, wherein the dual fuel injector (10) A nozzle body (14) housing a dual needle valve configuration (16), the dual needle valve configuration comprising a first fuel needle valve (18) and a second fuel needle valve (20), wherein the first fuel needle valve (18) defines a first needle valve shaft (32) and the nozzle body (14), A first fuel control chamber (22) is defined at least partially by the upper surface (24) and upper end (26) of the first fuel needle valve (18), thereby changing the first pressure within the first fuel control chamber (22), which changes the force on the upper end (26) of the first fuel needle valve (18), Equipped with, The first fuel needle valve (18) includes a bore (34) extending from a hole (36) defined in the upper surface (14) through the upper end (26) of the first fuel needle valve (18), The second fuel needle valve (20) is slidably received within the first fuel needle valve bore (34). Dual fuel injector (10), wherein the second fuel needle valve (20) protrudes from the hole (36), and thereby the upper end (38) of the second fuel needle valve (20) extends above the upper end (26) of the first fuel needle valve (18).

2. The dual fuel injector (10) according to claim 1, wherein the second fuel needle valve (20) extends through the first fuel control chamber (22).

3. The dual fuel injector (10) according to claim 1 or claim 2, wherein the first fuel control chamber (22) is at least partially defined by the outer surface (48) of the second fuel needle valve (20).

4. The dual fuel injector (10) according to any one of claims 1 to 3, wherein the first fuel control chamber (22) comprises a first central axis (50) coaxial with the first needle valve shaft (32).

5. The dual fuel injector (10) according to any one of claims 1 to 4, wherein the first fuel control chamber (22) forms an annulus extending around a portion of the second fuel needle valve (20).

6. The dual fuel injector (10) according to any one of claims 1 to 5, wherein the nozzle body (14) defines a needle guide portion (28), and the upper end (26) of the first fuel needle valve (18) is slidably received within the needle guide portion (28).

7. The dual fuel injector (10) according to claim 6, wherein the first fuel control chamber (22) is at least partially defined by the ceiling surface (30) of the needle guide portion (28).

8. The dual fuel injector (10) according to claim 7, wherein the nozzle body (14) comprises a bore (46) extending from a hole (44) defined in the ceiling surface (30) of the needle guide portion (28), and the upper end (38) of the second fuel needle valve (20) is received within the bore (46).

9. A dual fuel injector (10) according to any one of claims 1 to 8, further comprising a second fuel control chamber (40) which is at least partially defined by the upper surface (42) of the upper end (38) of the second fuel needle valve (20), thereby changing the second pressure in the second fuel control chamber (40) which changes the force on the upper end (38) of the second fuel needle valve (20).

10. The dual fuel injector (10) according to claim 9, wherein the second fuel control chamber (40) is at least partially defined by the nozzle body (14).

11. The dual fuel injector (10) according to claim 9 or 10, wherein the first fuel control valve comprises a first plunger configured to move along a first control valve shaft to selectively fluid-couple the first fuel control chamber (22) to a high-pressure fluid source or a low-pressure fluid drain, and the dual fuel injector further comprises a second fuel control valve comprising a second plunger (46) configured to move along a second control valve shaft (48) to selectively fluid-couple the second fuel control chamber (40) to a high-pressure fluid source or a low-pressure fluid drain, wherein the first fuel control valve and the second fuel control valve are arranged side by side such that the first control valve shaft extends parallel to the second control valve shaft, both the first and second control valve shafts extend parallel to the first needle valve shaft, and both the first and second control valve shafts are offset from the first needle valve shaft, so that neither control valve shaft is coaxial with the first needle valve shaft.

12. The dual fuel injector (10) according to any one of claims 1 to 11, wherein the nozzle body (14) defines a first fuel valve seat portion (58), and the dual fuel injector (10) further comprises a first biasing means (62) configured to bias the first fuel needle valve (18) to engage with the first fuel valve seat portion (58).

13. The dual fuel injector (10) according to claim 12, wherein the first biasing means (62) is disposed around the first fuel needle valve (18).

14. The dual fuel injector (10) according to claim 12 or 13, further comprising a collar (64) coupled to the first fuel needle valve (18), wherein the first biasing means (62) engages with the collar (64) and a portion of the nozzle body (14) to bias the first fuel needle valve (18) and engage with the fuel valve seat (58).

15. The dual fuel injector (10) according to any one of claims 1 to 14, wherein the first fuel needle valve (18) defines a second fuel valve seat (68), and the dual fuel injector (10) further comprises a second biasing means (72) configured to bias the second fuel needle valve (20) to engage with the second fuel valve seat (68).

16. The dual fuel injector (10) according to claim 15, wherein the second biasing means (72) is disposed within the second fuel accumulator volume (70) in the first fuel needle valve (18).

17. A dual fuel injector (10) according to any one of claims 1 to 16, further comprising an annular sealing gallery (74) extending around the outer surface (76) of the first fuel needle valve (18), wherein the sealing gallery (74) is in fluid communication with a high-pressure fluid source.

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