Injection nozzle for a fuel injector and fuel injector

Abstract

The present invention relates to an injection nozzle for a fuel injector. The injection nozzle comprises a nozzle housing, a valve needle, and a vortex generator. The nozzle housing has a valve seat and a fuel injection port. The fuel injection port is located at a downstream end of the valve seat, oriented in the direction of fuel flow. The valve needle is designed to move axially back and forth, thereby opening and closing the fuel injection port in conjunction with the valve seat. The vortex generator is positioned axially upstream of the fuel injection port and radially between the valve needle and the nozzle housing. The vortex generator has a main passage and a helical fuel passage. The main passage guides the valve needle axially. The fuel passage directs fuel to the fuel injection port and has a cross-sectional area that narrows along the direction of fuel flow.

Description

[0001] The present invention relates to an injection nozzle for a fuel injector and a fuel injector provided with the injection nozzle.

[0002] In internal combustion engines powered by liquid fuel (e.g., methanol), the combustion characteristics are significantly influenced by the supply and distribution of the fuel into and within the combustion chamber (so-called spray patterns). These combustion characteristics include the engine's fuel consumption, efficiency, and pollutant emissions.

[0003] The spray patterns (flow rate, spray angle, droplet size, etc.) are significantly influenced by the fuel injectors, which inject the fuel either directly into the combustion chamber (direct injection) or into the intake manifold (port-to-port injection). To achieve the desired spray patterns, the fuel injectors are therefore designed and further developed.

[0004] One development goal with regard to improved combustion characteristics is to distribute the fuel as finely as possible within the combustion chamber before combustion. To achieve this, the fuel should not simply be injected as a straight jet, but rather spread or disperse laterally in the shape of a cone or fan.

[0005] The object underlying the invention is to provide a fuel injector that generates spray patterns that promote the distribution of the fuel in the combustion chamber.

[0006] In addition to injection parameters, such as injection pressure or flow rate, or the arrangement and number of fuel injection openings in the fuel injector, the spray pattern can also be influenced by the design of the fuel injector's injection nozzle.

[0007] The present invention relates to an injection nozzle for a fuel injector. The injection nozzle according to the invention is intended to improve the spray pattern and thus the combustion characteristics. The injection nozzle comprises a nozzle housing, a valve needle, and a vortex generator. The nozzle housing has a valve seat and at least one fuel injection opening. The fuel injection opening is arranged at a downstream end in a fuel flow direction of the nozzle housing. In particular, the fuel injection opening is located downstream of the valve seat in the fuel flow direction through the fuel injector or is formed at the downstream end of the valve seat in the fuel flow direction. In other words, the fuel injection opening is located downstream of the valve seat or at its downstream end.The valve needle is configured to reciprocate in the axial direction and thereby, in cooperation with the valve seat, open and close the fuel injection opening. The vortex generator is positioned upstream of the valve seat in the axial direction and between the valve needle and the nozzle housing in the radial direction of the nozzle housing. In other words, the vortex generator is located in the fuel injector upstream of the valve seat. The vortex generator has a main passage and a helical fuel passage. The main passage serves to guide the valve needle in the axial direction. In other words, the fuel injector encloses the valve needle. The valve needle reciprocates in the main passage to open and close the fuel injection opening.The fuel passage guides a fuel to the fuel injection port and has a cross-sectional area (flow area) that narrows along a fuel flow direction.

[0008] In the present disclosure, the terms “downstream” and “upstream” refer to the direction of flow of fuel through the fuel injector.

[0009] By reducing the cross-sectional area or flow cross-section in the downstream direction of the fuel (along the fuel flow path), the exit area at the downstream end of the vortex generator is only slightly larger than the cross-sectional area of ​​the valve seat or the flow cross-section at the valve seat. Thus, the fuel flow between the exit of the vortex generator and the valve seat no longer needs to be significantly accelerated, and in particular, the axial component of the acceleration will not increase significantly. In other words, because the flow cross-section does not need to narrow significantly due to the similarly sized areas between the downstream end of the vortex generator and the valve seat, the fuel flow velocity downstream of the vortex generator does not increase significantly, particularly in the axial direction of the fuel injector.

[0010] This ensures that the circumferential velocity of the fuel flow at the valve seat is relatively high compared to the axial velocity of the fuel flow. This leads to a high swirl of the fuel flow downstream of the valve seat. The high swirl, in turn, promotes a distribution of the fuel in the radial direction of the fuel injector after exiting the fuel injection port. This, in turn, promotes the distribution of the fuel in the combustion chamber and thus beneficially influences the combustion characteristics.

[0011] Preferably, the valve needle resting on the valve seat defines a (preferably annular) sealing seat, and the helical fuel passage has a flow cross-section at its downstream end in the fuel flow direction that is at most twice, and preferably 1.3 times, the (upstream) flow cross-section of the sealing seat. In other words, the ratio of the cross-sectional area or flow cross-section at the outlet of the vortex generator to the cross-sectional area or flow cross-section at the valve seat is in a range from 2 to 1.3. In this way, on the one hand, a slight acceleration of the fuel in the axial direction downstream of the vortex generator is achieved, which leads to a satisfactory range of the fuel jet after it exits the fuel injection opening. On the other hand, in this range of the ratio of the cross-sectional areas orFlow cross-sections achieve a relatively high ratio of circumferential speed to axial speed of the fuel, which favors the distribution of the fuel.

[0012] The injector nozzle represents the downstream part of the fuel injector. The nozzle housing, which is the housing of the injector, can either be a separate, downstream part of the fuel injector housing or a downstream section of a one-piece fuel injector housing.

[0013] In the unactuated (e.g. not energized) state, the valve needle can either open or close the fuel injection opening.

[0014] The type of actuation of the valve needle includes common types of actuation, in particular electromagnetic, hydraulic and pneumatic actuation.

[0015] Preferably, the helical fuel passage is formed directly around the main passage of the vortex generator in such a way that the valve needle penetrating the vortex generator in the axial direction forms an inner surface of the helical fuel passage in the radial direction. Even more preferably, the valve needle forms the entire inner surface of the helical fuel passage in the radial direction. In other words, in this preferred embodiment, the main passage and the fuel passage are completely or partially (fluidically) connected to one another. This means that in the vortex generator there is at least partially no separation between the main passage and the fuel passage. This can be advantageous, for example, during manufacture of the vortex generator, since both passages can be formed together, orthe first formed main passage in the form of an axial breakthrough (e.g. a bore) through the vortex generator can be used as a starting point for the production of the helical fuel passage.

[0016] Alternatively, the helical fuel passage is preferably formed around the main passage of the vortex generator such that a radial inner wall of the vortex generator forms an inner surface of the helical fuel passage in the radial direction. Thus, in this configuration, the main passage and the fuel passage are separated from each other. This means they are not (fluidically) connected to each other. This is advantageous, for example, in that the fuel within the vortex generator cannot leak from the fuel passage into the gap between the valve needle and the radial inner surface of the main passage.

[0017] Preferably, the cross-sectional area of ​​the helical fuel passage narrows continuously (i.e., continuously and preferably without interruption of the area reduction) from its upstream end to its downstream end in the fuel flow direction. This minimizes the flow resistance of the fuel through the vortex generator, as well as flow separation at the wall of the vortex generator and associated fuel turbulence.

[0018] Preferably, more than one helical fuel passage in the vortex generator is configured in the manner of a two- or multi-start thread. In other words, just as the individual threads do not meet (cross) in two- or multi-start threads, the two or more fuel passages in the preferred vortex generator also do not meet (cross). This means that the two or more fuel passages only cross in projection. In other words, the fuel streams of the two or more fuel passages do not mix with each other. They represent independent streams.This design has the advantage that the total flow cross-section of the fuel is increased by the vortex generator, but the individual partial fuel streams can be guided more effectively than in a single fuel passage with the same total flow cross-section, allowing the swirl component to be applied to the partial fuel streams more easily and quickly. This allows, for example, the axial length of the vortex generator and thus of the injection nozzle or fuel injector to be shortened.

[0019] The vortex generator is preferably formed in one piece, more preferably monolithic, with an inner wall of the nozzle housing. In this context, “one piece” means that the vortex generator is not loosely inserted into the central bore of the fuel injector or merely axially fixed, but is also secured against rotation about the longitudinal axis of the fuel injector by means of a positive or non-positive fit. In other words, the vortex generator and the inner wall of the nozzle housing form a single unit. In this context, “monolithic” means that the vortex generator and the inner wall of the nozzle housing are manufactured as a single unit without being subsequently assembled. In other words, the vortex generator and the inner wall of the nozzle housing are, for example, manufactured from one piece of material, injection-molded or compression-molded as a (seamless) component.Cast or manufactured seamlessly using an additive manufacturing process, such as three-dimensional printing. In other words, monolithic means that the vortex generator and the inner wall of the nozzle housing have no connection or joining points. They are connected seamlessly.

[0020] This structure of the injector nozzle enables easy manufacturing using one of the methods described above, increases the mechanical strength of the fuel injector, and ensures that no fuel can leak between the vortex generator and the inner wall of the nozzle housing.

[0021] The injection nozzle preferably has a modular design, with the nozzle housing, valve seat, and vortex generator being separate components of the injection nozzle that can be removed and thus interchangeably assembled. The modular design makes it possible to replace standardized components intended for mass production with other standardized components, thus adapting the fuel injector to desired configurations without having to replace the entire fuel injector. The multi-part, modular design of the injection nozzle makes it possible to achieve various spray patterns, particularly in the form of a swirl atomizer nozzle (so-called hollow cone nozzle). This makes the fuel injector suitable for mass production.

[0022] Even more preferably, in the modular design of the injection nozzle, the nozzle housing has a cup-shaped recess at one axial end, which has a bottom surface and is open towards the axial end. In other words, the recess is a substantially bottomed, cylindrical recess, wherein the open end is oriented downstream in the axial direction and the bottom of the cylinder is oriented upstream. Furthermore, in this configuration, the valve seat is cup-shaped. Furthermore, the valve seat has the fuel injection opening in a bottom surface. This means that the valve seat also has a bottomed, cylindrical configuration. Furthermore, the valve seat can be inserted into the recess. The valve seat can be inserted with its opening towards the bottom of the recess.In other words, when the valve seat is inserted into the recess, the bottom surface of the recess and the valve seat opening face each other upstream, while the bottom of the valve seat is enclosed by the recess opening downstream. This means that the valve seat and the recess form a substantially closed cylinder. In this state, the vortex generator is inserted into the interior of the cylinder. The vortex generator is inserted into the recess, and then the valve seat is inserted into the recess as a kind of cover over the vortex generator. In this assembled state, the vortex generator is fixed in the axial direction by the bottom surfaces of the recess and the valve seat, and in the radial direction by the (radially inner) cup-shaped valve seat.The valve seat can preferably be fixed in the recess (in the axial direction) by means of a detachably mountable (e.g. screw-on) cap.

[0023] The design as a swirl atomizer nozzle (so-called hollow cone nozzle) can also be used without the modular structure described above.

[0024] According to the invention, a fuel injector with an injection nozzle designed as described above is also provided. Preferably, the fuel injector is an injector for a liquid fuel. Even more preferably, the fuel injector is an injector for methanol. Alternatively or additionally, the fuel injector is an injector for injecting fuel into the intake manifold or into the combustion chamber of an internal combustion engine.

[0025] Further details of the present invention will become apparent from the following detailed description of preferred embodiments. Fig. 1 shows a longitudinal section through a general fuel injector. Fig. 2 is a scaled image of a fuel injection through the fuel injector according to the invention with a swirl atomizer nozzle. Fig. 3 shows a longitudinal section through the injection nozzle according to the invention. Fig. 4 shows a further longitudinal section through the injection nozzle according to the invention.

[0026] In the following detailed description, the same parts are designated by the same reference numerals.

[0027] Fig. 1 shows a general structure of a fuel injector 1. The injection nozzle 15 according to the invention can be used in a fuel injector 1 as shown in Fig. 1 is shown.

[0028] The exemplary fuel injector 1 shown in the Fig. 1 is, for example, an electromagnetically actuated injector.

[0029] The fuel injector 1 comprises, among other things, a fuel inlet 2 with a filter (not shown), an electrical connection 3 for controlling the actuating mechanism, a spring 4, an electromagnetic coil (not shown), a valve housing 6, a valve needle 7 with a magnet armature, a valve seat 8 and at least one valve outlet channel 9 which has a fuel injection opening 10.

[0030] The Fig. The fuel injector 1 shown in Figure 1 is an injector that is closed when not actuated. The valve needle 7 is biased toward the valve seat 8 by the spring 4. Only when the coil is energized is the magnet armature and thus the valve needle 7 moved against the force of the spring 4 and thus away from the valve seat 8, thereby releasing the valve outlet channel 9 including the fuel injection opening 10.

[0031] The valve seat 8 can be mounted separately from the valve housing 6 as an independent component (as in Fig. 1) or can be formed integrally with the valve housing 6.

[0032] In the valve seat 8 or the valve housing 6 (which forms the nozzle housing or in combination with the valve seat forms the nozzle housing) the vortex generator 11, which will be described below, is accommodated.

[0033] Fig. Figure 2 shows the fuel, for example, methanol, injected into the internal combustion engine from the fuel injector 1. The injection nozzle 15 used for the image acquisition is a swirl atomizer nozzle whose spray pattern is characterized by producing small to medium-sized droplets in a hollow conical pattern over a wide range of flow rates and pressures.

[0034] Fig. 3 shows a preferred embodiment of the injection nozzle 15 according to the invention. The valve seat 8 and the valve housing 6 are designed here as separate parts, by way of example.

[0035] The valve seat 8 is cup-shaped and inserted into a cup-shaped recess at the axial end of the valve housing 6. The valve seat 8 is axially secured upstream by the bottom surface 17 of the recess and downstream by a cap 13. The cap 13 is, for example, screwed onto the valve housing 6. Other (detachable) connections are also conceivable. Furthermore, the cap 13 can, for example, be screwed into the valve housing 6. The cap 13 has an opening that is fluidically connected to the fuel injection opening 10 or the valve outlet channel 9. The valve seat 8 is radially secured by the valve housing 6.

[0036] The fuel injection port 10 and the valve outlet channel 9 are formed in the bottom surface of the valve seat 8. At the upstream end of the valve outlet channel 9 is the sealing seat 14, which is formed by the valve needle 7 resting on the valve seat 8.

[0037] In the exemplary embodiment shown, the vortex generator 11 is inserted into the cup-shaped valve seat 8. However, the vortex generator 11 could also be arranged, for example, upstream in the valve housing 6. The vortex generator 11 is designed as a separate part in the exemplary embodiment shown. However, it can also be formed monolithically with the valve seat 8 and / or the valve housing 6 (as in Fig. 4 is shown).

[0038] The vortex generator 11 has a main passage 16 and at least one fuel passage 12. The main passage 16 is formed centrally in the vortex generator 11 and axially penetrating the latter in order to guide the valve needle 7 during its movement in the axial direction. The at least one fuel passage 12 is formed partially or completely and helically around the main passage 16. In the exemplary embodiment shown, the valve needle 7 inserted into the main passage 16 forms the radial inner wall of the at least one fuel passage 12, so that without the valve needle 7, the main passage 16 and the fuel passage 12 are fluidically connected to one another. However, there are also embodiments in which the main passage 16 and the fuel passage 12 are separated from one another by a wall that is different from the valve needle 7.

[0039] The at least one fuel passage 12 is arranged helically around the main passage 16. The flow cross-section of the fuel passage 12 narrows continuously downstream, ie, in the direction of the fuel injection opening 10 along the fuel flow direction (the flow thread) in the injection nozzle 15. In the sectional drawing of the Fig. 3 shows, for example, two fuel passages 12 in the form of a double thread.

[0040] Fig. Figure 4 shows a further preferred embodiment of the injection nozzle 15 according to the invention. The valve seat 8 and the valve housing 6 are, for example, monolithic in this case. Likewise, the vortex generator 11 is formed with the monolithic valve seat 8 and valve housing 6, which together form the nozzle housing.

[0041] The vortex generator 11 in the exemplary embodiment has a main passage 16 and a fuel passage 12.

Claims

[1] Injection nozzle (15) for a fuel injector (1), with a nozzle housing (6, 8) having a valve seat (8) and a fuel injection opening (10) at a downstream end in a fuel flow direction; a valve needle (7) which is arranged to move back and forth in the axial direction and thereby, in cooperation with the valve seat (8), to open and close the fuel injection opening (10); and a vortex generator (11) which is arranged upstream of the fuel injection opening (10) in the axial direction and is arranged between the valve needle (7) and the nozzle housing (6, 8) in the radial direction of the nozzle housing (6, 8), wherein the vortex generator (11) a main passage (16) for guiding the valve needle (7) in the axial direction and a helical fuel passage (12) that guides a fuel to the fuel injection port (10) and has a cross-sectional area that narrows along the fuel flow direction. [2] Injector (15) according to claim 1, wherein the helical fuel passage (12) is formed immediately around the main passage (16) of the vortex generator (11) such that the valve needle (7) penetrating the vortex generator (11) in the axial direction forms an inner surface of the helical fuel passage (12) in the radial direction, wherein preferably the valve needle (7) forms the entire inner surface. [3] The injection nozzle (15) according to claim 1, wherein the helical fuel passage (12) is formed around the main passage (16) of the vortex generator (11) such that a radial inner wall of the vortex generator (11) forms an inner surface of the helical fuel passage (12) in the radial direction. [4] Injection nozzle (15) according to one of the preceding claims, wherein the valve needle (7) resting on the valve seat (8) defines an annular sealing seat (14) and the helical fuel passage (12) has at its downstream end in the fuel flow direction a flow cross-section which is at most twice and preferably 1.3 times as large as a flow cross-section of the sealing seat (14). [5] An injector (15) according to any preceding claim, wherein the cross-sectional area of ​​the helical fuel passage (12) narrows continuously from its upstream end to its downstream end in the fuel flow direction. [6] Injector (15) according to one of the preceding claims, wherein more than one helical fuel passage (12) in the vortex generator (11) is formed in the manner of a two- or multi-start thread. [7] Injection nozzle (15) according to one of the preceding claims, wherein the vortex generator (11) is formed integrally, preferably monolithically, with an inner wall of the nozzle housing (6, 8). [8] Injection nozzle (15) according to one of claims 1 to 6, wherein the injection nozzle (15) is of modular construction in that the nozzle housing (6), the valve seat (8) and the vortex generator (11) are detachably and thus interchangeably mountable with one another as separate components of the injection nozzle (15). [9] Injection nozzle (15) according to claim 8, wherein the nozzle housing (6) has a cup-shaped recess at one axial end, which has a bottom surface (17) and is open towards the axial end; and the valve seat (8) is cup-shaped, has the fuel injection opening (10) in a bottom surface, and can be inserted into the recess such that the vortex generator (11) can be fixed in the axial direction by the bottom surfaces of the recess and the valve seat (8) and in the radial direction by the cup-shaped valve seat (8), wherein the valve seat (8) can preferably be fixed in the recess by means of a detachably mountable cap (13). [10] Fuel injector (1), with an injection nozzle (15) according to one of the preceding claims, wherein the fuel injector (1) is preferably an injector for a liquid fuel and more preferably for methanol, and / or an injector for injecting fuel into the intake manifold or combustion chamber of an internal combustion engine.

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