Injector for injecting a gaseous medium
The cap-shaped attachment body with optimized flow control geometry addresses the challenges of gas injector design by enhancing mixture formation and reducing pre-ignition risks, enabling efficient and flexible use in internal combustion engines.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-09-30
- Publication Date
- 2026-06-25
AI Technical Summary
Existing gas injectors for internal combustion engines face challenges in efficiently injecting gaseous fuels due to the large volume of gas requiring increased stroke requirements, which complicates the design of magnetic actuators with standard materials, and there is a risk of pre-ignition from residual gas in the injector.
The injector features a cap-shaped attachment body with a flow control geometry that optimizes gas flow by minimizing losses and guiding the jet into the combustion chamber, using a valve closing element with a disc-shaped end section and a magnetic actuator, allowing for cost-effective material use and reduced back pressure.
This design enhances mixture formation, reduces pre-ignition risks, and allows for flexible use in various combustion chamber geometries, improving efficiency and purging behavior.
Smart Images
Figure EP2025078012_25062026_PF_FP_ABST
Abstract
Description
[0001] R. 417007
[0002] - 1 -
[0003] Description
[0004] title
[0005] Injector for injecting a gaseous medium
[0006] State of the art
[0007] The present invention relates to an injector for injecting a gaseous medium, in particular a gaseous fuel, into a combustion chamber of an internal combustion engine. Specifically, the invention relates to an injector with which hydrogen can be injected directly into the combustion chamber of a mixture-compressing, spark-ignition internal combustion engine.
[0008] Gas injectors are known in various designs from the prior art. Due to cost advantages and improved environmental compatibility, gaseous fuels have become increasingly popular recently. A problem compared to injectors for liquid fuels is that the amount of gas to be injected occupies a much larger volume than an equivalent amount of liquid fuel. This results in an increased stroke requirement for a closing element, which is usually actuated by a magnetic actuator. Designing the magnetic circuit with standard materials is very difficult or sometimes impossible due to the limited installation space. Materials with higher magnetic strength are very expensive and some are hazardous to health (e.g., FeCo). R. 417007
[0009] - 2 -
[0010] From DE 10 2021 206 438 A1, a gas nozzle for a gas valve is already known, comprising a nozzle body that is at least partially hollow and cylindrical, forming a sealing seat over which a gas flow path leads. The gas valve also has a movable valve closing element, partially integrated into the nozzle body, with an end section located outside the nozzle body and having a sealing contour that interacts with the sealing seat. Furthermore, the gas valve has a sleeve surrounding the nozzle body and the end section of the valve closing element, which limits the gas flow path downstream of the sealing seat. The gas flow path downstream of the sealing seat has a cross-sectional constriction to achieve the Venturi effect, in the region of which at least one intake channel opens. The sleeve is designed in the form of a blow-off cap that can be attached to the nozzle body.
[0011] Another injector for injecting a gaseous medium is also known from WO 2023 / 001384 A1. The blowing cap, which can be mounted on a nozzle body, has a sleeve-shaped base with a circumferential outer surface that transitions into a bottom section at the downstream end. The bottom section is designed such that at least one obliquely or asymmetrically blowing outlet opening is provided, and furthermore, the bottom section incorporates a flow-guiding section directed inwards towards the valve closing element, opposite to the flow direction, which deflects the flow of the gas to be blown out.
[0012] Disclosure of the invention
[0013] The injector according to the invention for injecting a gaseous
[0014] Medium, in particular a gaseous fuel in a combustion chamber of an internal combustion engine, with the features of claim 1, R. 417007
[0015] - 3 - in contrast, the advantage is that optimized gas flow in the injector is made possible by the geometric design of a flow control geometry downstream of the sealing seat, so that the internal flow of the gaseous medium is designed to be as loss-free as possible via the inner contour of the cap-shaped attachment body, so that the back pressure below, i.e. downstream of the valve closing element is reduced and at the same time the jet can be introduced into the combustion chamber in a targeted manner.
[0016] Furthermore, the forces acting on the valve closing element are reduced to a minimum in a special way. This reduces the magnetic force of an actuator that must be selected to keep the injector open, thus enabling the use of cost-effective materials in the actuator's magnetic circuit.
[0017] According to the invention, this is achieved by the injector having a valve closing element for opening and closing at least one opening at a sealing seat. The valve closing element is preferably an axially movable valve needle with a disc-shaped end section. Furthermore, an actuator for actuating the
[0018] A valve closing element is provided. The actuator is preferably a magnetic actuator, but can also be, for example, a mechanically or (piezo-)electrically operated actuator. More preferably, the actuator is configured to actively open and hold the valve closing element open by means of a stroke movement, while the valve closing element is closed by a spring force.
[0019] The flow control geometry, which is housed in particular in a cap-shaped attachment body, or in short, a blow cap, is characterized according to the invention in that the attachment body has a hollow cylindrical section in the area of the sealing seat, to which an outflow area with at least one outflow opening R. 417007 having an inner contour is attached.
[0020] - 4 - connects, which opens into an end face facing the combustion chamber, wherein the outflow area downstream of the sealing seat has a trough-like section, to which at least one outflow opening is connected downstream, wherein the trough-like section has a volume V1 and the outflow opening has a volume V2, or in the case of several successive opening sections in the flow direction with different orientations, the outflow opening has several volumes V2, V3, and for the volumes: V1 > V2 and V1 > V3, wherein the axial extent of the at least one outflow opening is at least one third of the total axial extent of the outflow area between the sealing seat and the end face.
[0021] This improves mixture formation and the purging behavior of any remaining residual gas, especially hydrogen, from the exhaust port. This effectively prevents pre-ignition of the hydrogen.
[0022] The dependent claims describe preferred embodiments of the invention.
[0023] The flow control geometry according to the invention is integrated into a relatively open mounting structure following the sealing seat. Such attachment bodies have the advantages of a very simple design and simple, easily reproducible manufacturing. Furthermore, no blocked dead volume is created inside the attachment body, which could adversely lead to premature pre-ignition.
[0024] The concept according to the invention allows for particularly high flexibility in designing the spray pattern. The gas flow can be distributed very evenly throughout the entire combustion chamber, which improves mixture formation and increases efficiency. R. 417007
[0025] - 5 -
[0026] The highly variable internal contour allows for very flexible use of sleeves or attachment bodies on injectors in various combustion chamber geometries of internal combustion engines.
[0027] The present invention is preferably used in injection systems that inject hydrogen directly into a combustion chamber. In particular, the injector is suitable for the direct injection of hydrogen into a combustion chamber of an internal combustion engine.
[0028] drawing
[0029] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawing. The drawing shows:
[0030] Figure 1 shows a schematic sectional view of an injector for injecting a gaseous medium according to the prior art.
[0031] Figure 2 shows a sectional view of a known cap-shaped attachment body for an injector according to Figure 1.
[0032] Figure 3 shows a schematic sectional view of a cap-shaped attachment body for an injector for injecting a gaseous medium according to a first embodiment and
[0033] Figure 4 shows a schematic sectional view of a cap-shaped attachment body for an injector for injecting a gaseous medium according to a second embodiment. R. 417007
[0034] - 6 -
[0035] Preferred embodiments of the invention
[0036] For a better understanding of the invention, the basic structure of an injector for injecting a gaseous medium and a known structure of a flow control geometry downstream of the valve seat are described below with reference to Figures 1 and 2.
[0037] Figure 1 shows a schematic cross-sectional view of the known injector 1 for injecting a gaseous medium. Since the invention relates to the flow control geometry 10, which is downstream of the valve seat 3, only this assembly of the known injector 1 will be described in detail here. For example, a magnetic actuator 21 is provided for actuating the injector 1, allowing the injector 1 to be controlled in a targeted manner.
[0038] The injector 1 also has a nozzle body 2 which, on the injection side, forms a valve seat 3 at its end, for example, a conically shaped one, for an outwardly opening valve closing element 5, i.e., opening towards a combustion chamber 20. The valve closing element 5 is guided axially within the nozzle body 2 by a guide 18. Furthermore, the valve closing element 5 has an end section 6 in the form of a valve disc, which, corresponding to the valve seat 3, forms a sealing seat 7. Both sealing seat components, valve seat 3 and valve closing element 5, are made of metal. The geometric and material design is such that sufficient sealing is ensured during the operation of a hydrogen engine.In the event of a fault, a shut-off system (not shown) installed upstream of injector 1 for safety reasons would interrupt the supply of the gaseous medium, in particular the highly volatile hydrogen. The sealing contour of the end section 6 of the valve closing element 5 R. 417007.
[0039] - 7 - is, for example, rounded, while the valve seat 3 on the nozzle body 2 has a conical shape. However, other contours are also conceivable.
[0040] The nozzle body 2 and the end section 6 of the valve closing element 5 are surrounded by a sleeve 8 for jet shaping. In the following, and particularly with regard to the invention, a flow-control geometry 10 downstream of the sealing seat 7 is generally referred to. This can either be formed directly as a single piece on the nozzle body 2, which, however, requires considerable manufacturing effort, or be integrated into an additional component, which, with reference to the embodiments according to the prior art shown in Figures 1 and 2, is generally referred to as the sleeve 8. The sleeve 8 has a large overlap length with the nozzle body 2 in order to be able to securely and reliably fasten the sleeve 8. However, it can also be described as a cap-shaped attachment body 8, which, with reference to the embodiments according to the invention, is also defined as the blow cap 8.
[0041] The sleeve 8 and the end section 6 of the valve closing element 5 together define a gas flow path 4 into which at least one intake channel 15 formed in the sleeve 8 opens. Air from the environment can be drawn into the gas flow path 4 via one or more intake channels 15.
[0042] If the valve closing element 5 is in an open position lifted from the valve seat 3, the gas flow path 4 then leads via the valve seat 3 into an interior of the sleeve 8, which is characterized by a special shape with an inner contour 9. Starting from a cylindrical section 11 of the sleeve 8 and following the flow direction of the valve closing element 5, a reduction in cross-section occurs at a large axial distance from the valve closing element 5 in a central cylindrical axial region 13 of the flow control geometry 10 of the sleeve 8, whereby the narrowing occurs via a conically extending section 12 in the inner contour 9 of the sleeve 8. R. 417007
[0043] - 8 - is reached. The intake channels 15 open precisely into the inner contour 9 of the sleeve 8 in the central axial area 13.
[0044] The reduction in cross-section within the gas flow path 4 creates the effect that, as the gas flows out through the gas flow path 4 towards an outlet 19, ambient air is drawn into the gas flow path 4 via the intake channels 15 (“Venturi effect”). This means that air is mixed with the gas even before it reaches the outlet 19, thus improving the mixture preparation.
[0045] The reduction in cross-section is reversed by the fact that the central axial area 13 is followed by a conically extending section 1, in this case widening conically in the flow direction, with this section 14 extending to the outlet 19. The reduction in cross-section in the inner contour 9 of the sleeve 8 is thus intended to achieve the Venturi effect, which is optimized together with the air mixture.
[0046] Experience has shown that such a solution, or other known geometries or internal contours of cap-shaped attachment bodies, does not achieve sufficiently good results regarding the introduction of the jets into combustion chamber 20, or their guidance and shaping for optimal combustion. Furthermore, there is a risk of engine pre-ignition due to insufficient
[0047] Rinsing behavior, especially of the hydrogen remaining in the attachment body.
[0048] Therefore, the object of the invention is to provide an inner contour 9 of a cap-shaped attachment body 8 with a flow-influencing geometry 10 downstream of the sealing seat 7, with which optimal combustion results are achieved due to the inventive inner contour design and the resulting flow guidance, wherein an outer contour of the attachment body 8 in conjunction with the R. 417007 defined by the inner contour 9
[0049] - 9 -
[0050] Flow control geometry 10 is intended to achieve improved flushing behavior of hydrogen remaining in the attachment body 8 to avoid pre-ignition.
[0051] Injection systems for the direct injection of a gaseous medium, in particular hydrogen, but also CNG, methane, ammonia, or mixtures of the aforementioned gases, have the task of precisely controlling the metering and the injection direction of the gas jet(s) into the combustion chamber 20 via injection valves or, more generally, injectors 1. For this purpose, corresponding sleeves or injection caps 8 can be used on the injector 1, as previously explained. Furthermore, injection systems for the (hydrogen)-
[0052] Direct injection inherently requires a large stroke of the valve needle with the valve closing element 5. Designing the magnetic circuit (magnetic actuator 21) with standard materials is very difficult, or even impossible, due to the limited installation space. Materials with higher magnetic force and thus better B / H characteristics are very expensive and some are also hazardous to health (e.g., FeCo). Therefore, an improved beam guidance system is also intended to reduce the magnetic force.
[0053] The core of the invention consists in shaping the internal flow of the gaseous medium with as little loss as possible via the inventive inner contour 9 of the cap-shaped attachment body 8, so that the back pressure located below, i.e., downstream of the disc-shaped end section 6 of the valve closing element 5, is reduced and at the same time the jet can be directed precisely into the combustion chamber 20. This defined inner contour 9 is aimed in particular at improved mixture formation. Due to the highly variable contouring of the inner contour 9, a very flexible use of sleeves or attachment bodies 8 on injectors 1 in various combustion chamber geometries of internal combustion engines is possible. R. 417007
[0054] - 10 -
[0055] Overall, the optimized jet-shaping cap geometry allows for improved charge movement with increased purging of residual gas and hydrogen in the internal volume of the attachment body 8. This results in a robustness measure against pre-ignition even with increased seat leakage for the hydrogen injector during engine operation.
[0056] With reference to Figures 3 and 4, injectors 1 with flow-influencing geometries 10 according to the invention, which are downstream of the valve seat 3, are described in detail below according to preferred embodiments of the invention. As already mentioned, these flow-influencing geometries 10 can be formed directly as a single piece on the nozzle body 2 or, as shown in all figures, integrated into an additional component, which can be referred to as a cap-shaped attachment body 8 (or simply blow cap 8). The attachment body 8 will typically have a significantly shorter overlap with the nozzle body 2 than shown in Figure 1. The only essential requirement is a secure and reliable attachment to the nozzle body 2, which enables perfect and axially parallel alignment with the injector 1. Known joining methods such as pressing, welding, brazing, bonding, or combinations thereof can be used.
[0057] Figure 3 shows a first embodiment of a flow-control geometry 10 located downstream of the valve seat 3 in a cap-shaped attachment body 8 and generated by an inner contour 9 according to the invention. The valve closing element 5 with its disc-shaped end section 6 is shown schematically and in a highly simplified cross-section as a chamfered rectangle. However, the end section 6 can also have further chamfers or rounded edges on its outer contour or be completely rectangular. R. 417007
[0058] - 11 -
[0059] The injection-side end with the flow-influencing geometry 10 of the injector 1 is arranged facing the combustion chamber 20 of the internal combustion engine. The flow-influencing geometry 10 generated by the internal contour 9 according to the invention has a key geometric characteristic that primarily deflects the gas flow radially inwards in a downstream direction within the attachment body 8, in order to then discharge the gas to be blown out, in particular hydrogen, into at least one outlet opening 17. In the case of the example shown in Figure 3, the outlet opening 17 extends in two successive opening sections in the flow direction, with a first coaxial section 27 and a second inclined section 28 being provided.
[0060] For the described and illustrated embodiments according to Figures 3 and 4, it generally applies that the attachment body 8 has a hollow cylindrical section in the region of the sealing seat 7, to which an outflow region 16 with at least one outflow opening 17 is connected, which opens into an end face 25 facing the combustion chamber 20. According to the invention, the outflow region 16 has a trough-like section 22 with a volume V1 immediately downstream of the sealing seat 7. Due to the specific internal contour 9, the medium flowing into the attachment body 8 from the sealing seat 7 is guided stably, and the flow velocity is largely maintained up to the inlet cross-section of the outflow opening 17. Such an adaptation in conjunction with different shapes of outflow openings 17 enables targeted shaping of the gas jet as well as optimized mixture formation in the combustion chamber 20.The resulting increased flow rate also reduces the back pressure in the internal volume of the attachment body 8, thus improving flushing and reducing the forces acting on the underside of the end section 6 of the valve closing element 5. R. 417007.
[0061] - 12 -
[0062] The flow control geometry 10 generated by the inner contour 9 has several essential aspects and geometric specifications. Downstream of the valve closing element 5, the inner contour 9 of the attachment body 8 is shaped such that the tapered, in particular conical, section 22 follows, which ensures a significant tapering of the inner contour 9 over a short axial extent, thus advantageously contributing to the desired optimized flow result. The jet guidance from the sealing seat 7 occurs via the inner contour 9 in the conical and overall trough-shaped section 22, which is designed with an inclination angle of 80° > a > 30°, preferably with an inclination angle of > 45°.With this relatively large angle of the conically shaped section 22, a strong radially inward flow component is generated over a very short axial length, so that in this area immediately downstream of the valve closing element 5, flow guidance advantageously occurs in the form of an "S-curve". Instead of the conical shape of section 22, this section 22 can also be slightly concave. The inner contour 9 ensures that a supercritical flow is maintained and that back pressures below the valve closing element 5 are limited.
[0063] The thin-walled sleeve contour of the overlap area for attachment to the nozzle body 2 initially continues largely in the downstream direction, although wall thickness variations along the axial length of the attachment body 8 are conceivable. A significantly greater wall thickness is provided in the axially subsequent outflow area 16.
[0064] Essential in the design of the flow control geometry
[0065] 10 over the inner contour 9 of the attachment body 8 are also the axial R. 417007
[0066] - 13 -
[0067] Extent of the individual sub-areas within the outflow area 16. The volume V1 of the trough-like section 22 is determined accordingly by its axial extent to the inlet plane of the outflow opening 17 and its diameter. A volume V2 is defined in the first coaxial section 27 of the outflow opening 17; a volume V3 is formed in the second inclined section 28 of the outflow opening 17. For optimal flow guidance and minimized stagnation pressure below the end section 6 of the valve closing element 5, the following should apply according to the invention: V1 / V2 = 1.05...3.5, preferably approximately 1.5. Furthermore, the following should apply: V2 / V3 = 0.5...2.2, preferably approximately 1.3. One condition must always be met: V1 > V2 and V1 > V3. The cross-sectional area at the outlet plane of the first coaxial section 27 of the outflow opening 17 is marked A2.The cross-sectional area at the outlet plane of the second inclined section 28 of the outflow opening 17 at the end side 25 of the attachment body 8 is designated A3. The following should be satisfied with regard to the relationship between the two areas: A2 / A3 = 0.8...1.8, preferably approximately 1.2. A dimensionless quantity V1 / A3 of 4.5...11.5, preferably approximately 7, is particularly advantageous. The radius of the inner contour 9, designated R1, in the transition from the trough-like section 22 to the outflow opening 17 also contributes to the optimized flow guidance.
[0068] In contrast to known solutions of blow-off caps with a folded-over thin-walled bottom part, where the axial extent of the outflow opening corresponds only to the thickness of the bottom part and is therefore very small, the axial extent of the at least one outflow opening 17 according to the invention is at least one third of the total axial extent of the outflow area 16 between sealing seat 7 and end side 25.
[0069] Figure 4 shows a schematic sectional view of a cap-shaped attachment body 8 for an injector 1 for injecting a gaseous substance. 417007
[0070] - 14 -
[0071] Medium according to a second embodiment. In the case of the example shown in Figure 4, the outflow opening 17 runs coaxially parallel to the axis, largely cylindrical, or also slightly conically tapered or widening. For optimal flow guidance and minimized back pressure below the end section 6 of the valve closing element 5, the following should apply according to the invention: V1 / V2 = 1.4...9, preferably approximately 4, where V2 is the volume of the outflow opening 17. One condition must always be met: V1 > V2. A dimensionless quantity V1 / V2 advantageously has a value of 4.5...11.5, preferably approximately 7.
[0072] Such attachment bodies 8 have the advantages of a very simple design and simple and easily reproducible manufacturing. Furthermore, no blocked dead volume is created inside the attachment body 8, which could adversely lead to premature pre-ignition.
[0073] In addition to the optimized jet guidance made possible by the attachment body 8 according to the invention, further advantages of the attachment body 8 designed in this way are the increased strength and improved thermal conductivity. By avoiding back pressure downstream of the sealing seat 7, a high degree of pressure independence prevails in this area, so that optimized flushing from the attachment body 8 is possible at all times.
[0074] The concept according to the invention allows for particularly high flexibility in the design of the spray pattern. The gas flow can be distributed very evenly throughout the entire combustion chamber 20, which improves mixture formation and increases efficiency.
Claims
R. 417007 - 15 - Claims 1. Injector (1) for injecting a gaseous medium, in particular a gaseous fuel, preferably hydrogen, into a combustion chamber (20) of an internal combustion engine, comprising an axially movable valve closing element (5) for opening and closing at least one opening on a sealing seat (7), an actuator (21) for actuating the valve closing element (5), and a flow-influencing geometry (10) downstream of the sealing seat (7), wherein the flow-influencing geometry (10) is formed downstream of the sealing seat (7) in an attachment body (8), wherein the attachment body (8) has a hollow cylindrical section in the region of the sealing seat (7), to which an outflow region (16) with at least one outflow opening (17) having an inner contour (9) is connected, which opens into an end face (25) facing the combustion chamber (20), characterized in thatthat the outflow region (16) downstream of the sealing seat (7) has a trough-like section (22) to which at least one outflow opening (17) is connected downstream, wherein the trough-like section (22) has a volume V1 and the outflow opening (17) has a volume V2, or, in the case of several successive opening sections with different orientations in the flow direction, the outflow opening (17) has several volumes V2, V3, and for the volumes V1 > V2 and V1 > V3, wherein the axial extent of the at least one outflow opening (17) is at least one third of the total axial extent of the outflow region (16) between the sealing seat (7) and the end face (25). R. 417007 - 16 - 2. Injector according to claim 1, characterized in that the outflow opening (17) in the outflow area (16) runs axially coaxially, largely cylindrically or also slightly conically tapered or widening.
3. Injector according to claim 2, characterized in that the volumes V1 , V2 of trough-like section (22) and outflow opening (17) are in the ratio of V1 / V2 = 1 ,4...9, preferably approximately 4.
4. Injector according to claim 2 or 3, characterized in that the dimensionless quantity V1 / A2 is a value of 4.5...11 ,5, preferably approximately 7, wherein A2 is the cross-sectional area of the outflow opening (17) at the end side (25).
5. Injector according to claim 1, characterized in that the outflow opening (17) in the outflow area (16) extends with a first coaxial section (27) and a second inclined section (28).
6. Injector according to claim 5, characterized in that a volume V2 is defined in the first coaxial section (27) of the outflow opening 17, while a volume V3 is formed in the second inclined section (28) of the outflow opening (17).
7. Injector according to claim 6, characterized in that the volumes V1, V2 of trough-like section (22) and coaxial section (27) are in the ratio of V1 / V2 = 1.05...3.5, preferably approximately 1.5, and the volumes V2, V3 of coaxial section (27) and inclined section (28) are in the ratio of V2 / V3 = 0.5...2.2, preferably approximately 1.3, and V1 > V3.
8. Injector according to one of claims 5 to 7, characterized in that the dimensionless quantity V1 / A3 is a value of 4.5...11 ,5, preferably approximately 7, where A3 is the cross-sectional area of the outflow opening (17) at the end side (25). R. 417007 - 17 - 9. Injector according to one of the preceding claims, characterized in that the flow control geometry (10) downstream of the sealing seat (7) is realized in a blow cap (8).
10. Injector according to one of the preceding claims, characterized in that the cap-shaped attachment body (8) can be attached to a spray-side end of the injector (1), in particular to a nozzle body (2).
11. Injector according to one of the preceding claims, characterized in that the valve closing element (5) is part of an axially movable valve needle, wherein the valve closing element (5) has an end section (6) which is largely disc-shaped.