Gas injector, in particular for high combustion chamber pressures

Abstract

The present invention relates to a gas injector for injecting a gaseous medium, said gas injector comprising: an outwardly open valve needle (2); a valve body (3); a sealing seat (4) on the valve body (3), against which sealing seat the valve needle (2) forms a seal when the gas injector is in the closed state, the valve body (3) being hollow-cylindrical with a combustion-chamber-side end face (30), an outer lateral region (31), and an inner lateral region (32), the sealing seat (4) being arranged on the end surface (30) of the valve body (3), the valve body (3) having a combustion-chamber-side end region (33) on the outer lateral region (31), and a first recess (5) being formed in the outer lateral region (31) of the combustion-chamber-side end region (33) so that a wall thickness of the valve body (3) in the region of the first recess (5) is reduced to a first wall thickness (W1) which is the smallest wall thickness of the combustion-chamber-side end region (33).

Description

[0001] Description

[0002] title

[0003] Gas injector, especially for high combustion chamber pressures

[0004] State of the art

[0005] The present invention relates to a gas injector for injecting a gaseous medium, such as hydrogen, natural gas, methane, LPG, ammonia or the like, into a combustion chamber of an internal combustion engine.

[0006] Gas injectors are known in various designs from the prior art. Compared to injectors for liquid fuels, gas injectors require significantly larger flow cross-sections because the volume of the gaseous medium is significantly larger than with liquid fuels for the same energy content. This larger volume therefore actually requires larger diameters at the combustion chamber end of the gas injector, but this is difficult due to efforts to downsize internal combustion engines. In conventional internal combustion engines, at least two intake and two exhaust valves, as well as possibly an ignition source, are arranged in the combustion chamber, which means that the installation space for the gas injector is very small. It should also be noted that in turbocharged internal combustion engines, compression is high during the injection period, so the injection period is relatively short.The high pressures in the combustion chamber can also lead to geometric deformations on a valve body or a valve needle of the gas injector during operation, which can lead to undesirable sliding contacts between the valve needle and the valve body, particularly during the closing process of the gas injector, which can lead to undesirable disruption or wear with possible subsequent leaks.

[0007] Disclosure of the Invention The gas injector according to the invention for injecting a gaseous medium with the features of claim 1 has the advantage that wear, particularly on a sealing seat between a valve needle and a valve body of the gas injector, is significantly reduced. This can be achieved even at very high combustion chamber pressures, for example in turbocharged internal combustion engines. Furthermore, a predetermined, precise closing time can be reliably maintained during operation. This is achieved according to the invention in that the gas injector has an outwardly opening valve needle and a valve body. A sealing seat is formed on the valve body, against which the valve needle seals when the gas injector is closed. Furthermore, the valve body is hollow-cylindrical with an end face on the combustion chamber side. The sealing seat is arranged on the combustion chamber side end face.Furthermore, the valve body has an inner and an outer jacket region, wherein a combustion chamber-side end region is formed on the outer jacket region, which is designed to be connected to the combustion chamber when the gas injector is mounted in a cylinder head or the like. Thus, the combustion chamber-side end region of the outer jacket region of the valve body is exposed to the combustion chamber gases and the high combustion chamber pressure. Furthermore, the combustion chamber-side end region is designed such that during a closing process of the gas injector, no or at most a minimal tangential force, preferably a maximum of 5 N, in particular a maximum of 2 N, occurs between the valve body and the valve needle. This tangential force is defined as a thrust force in the valve seat plane that is perpendicular to the axial axis of the gas injector. Thus, no sliding occurs between the valve needle and the valve body during the closing process.This results in less disruption and reduced wear at this point.

[0008] The gas injector according to the invention for injecting a gaseous medium with the features of claim 3 has the advantage that wear, in particular on a sealing seat between a valve needle and a valve body of the gas injector, is significantly reduced. This can be achieved even at very high combustion chamber pressures, for example in turbocharged internal combustion engines. Furthermore, a predetermined, precise closing time can be reliably maintained during operation. This is achieved according to the invention in that the gas injector has an outwardly opening valve needle and a valve body. A sealing seat is formed on the valve body, against which the valve needle seals when the gas injector is closed. Furthermore, the valve body is hollow-cylindrical with an end face facing the combustion chamber. The sealing seat is arranged on the end face facing the combustion chamber.Furthermore, the valve body has an inner and an outer jacket region, wherein a combustion chamber-side end region is formed on the outer jacket region, which is designed to be connected to the combustion chamber when the gas injector is mounted in a cylinder head or the like. Thus, the combustion chamber-side end region of the outer jacket region of the valve body is exposed to the combustion chamber gases and the high combustion chamber pressure. Furthermore, the combustion chamber-side end region of the valve body has a first recess on the outer jacket region, so that a wall thickness of the combustion chamber-side end region of the valve body is reduced to a first wall thickness in the region of the first recess. The first wall thickness is the smallest wall thickness of the combustion chamber-side end region. The wall thickness is measured perpendicular to the center axis of the gas injector.The first recess at the combustion chamber end area enlarges the surface of the outer jacket area facing the combustion chamber. Furthermore, the first recess at the outer jacket area increases the elasticity of the valve body at the combustion chamber end area when the valve needle is pressed into the seat area at the sealing seat of the valve body during the closing process of the gas injector.

[0009] This results in a certain degree of compliance of the valve body at the end facing the combustion chamber, which improves seat tightness during operation. Any existing out-of-roundness or unevenness that may result from the manufacturing process and / or wear during operation can also be bridged by the compliance of the sealing seat when the valve needle is pressed into the sealing seat.

[0010] Furthermore, the first recess ensures that almost no tangential force occurs between the valve needle and the valve body during the closing process. Tangential force here refers to a thrust force in a valve seat plane, where the valve seat plane is perpendicular to a center axis of the gas injector through the sealing seat. This is especially important at very high combustion chamber pressures, for example, 170 x 10 5 Pa up to 200 x 10 5 Pa. The lack of tangential force between the valve needle and the valve body during the closing process ensures that no sliding occurs between the valve needle and the valve body. This can significantly reduce wear on the sealing seat.

[0011] The subclaims show preferred developments of the invention.

[0012] Preferably, the first recess is a first circumferential groove in the outer casing area of ​​the valve body. The first circumferential groove can preferably be arcuate or rectangular in cross-section. The first circumferential groove preferably has a constant depth. The depth of the first circumferential groove is naturally selected such that no strength problems arise at the combustion chamber-side end area of ​​the valve body during operation.

[0013] Further preferably, the combustion chamber-side end region of the valve body is provided such that an outer and an inner partial region are provided. The outer partial region is arranged closer to the combustion chamber than the inner partial region. The first recess is arranged in the outer partial region of the combustion chamber-side end region of the valve body.

[0014] Further preferably, the inner shell area of ​​the valve body is cylindrical. This has particular manufacturing advantages.

[0015] The valve needle preferably has a shaft and a valve plate, with the valve plate sealing against the sealing seat on the valve body when the gas injector is closed. The valve plate is preferably disc-shaped.

[0016] According to a further preferred embodiment of the invention, the valve plate of the valve needle has a second recess on a surface facing the combustion chamber. The second recess on the valve plate supports the flexibility during the closing process between the valve needle and the valve body, thus enabling a secure closing process without tangential forces on the sealing seat.

[0017] The second recess is preferably a second circumferential groove in the valve disk. Alternatively or additionally, the second recess comprises a central depression, the center point of which preferably lies in the center axis of the gas injector. The central depression is preferably partially spherical. The sealing seat on the valve body further preferably has a seat angle α, which lies in a range from 90° to 130°, in particular 100° to 120°, more particularly 105° to 117°, in particular 110° to 112°, and more particularly 111°. Thus, the combustion chamber-side end surface of the valve body is conical with the seat angle α.

[0018] The valve needle preferably has an arcuate surface with a radius R1 on the valve plate, with the arcuate surface of the valve needle sealing against the sealing seat on the valve body when closed. This creates a ball-and-cone sealing seat between the valve body and the valve needle. It should be noted that the ball-and-cone sealing seat can also be provided such that the cone is provided on the valve needle and the arcuate surface is provided on the valve body.

[0019] According to a further preferred embodiment of the invention, the valve needle on the valve plate has an inner surface facing away from the combustion chamber, which is designed such that, when the gas injector is closed, at least a portion of the inner surface is arranged closer to the combustion chamber than the valve seat plane, which is perpendicular to the center axis of the gas injector and runs through the sealing seat. A free space is thus formed between the valve seat plane and the inner surface of the valve plate. In section, this preferably results in a substantially arrow-shaped tip of the valve needle. This free space, in conjunction with the first recess in the outer jacket region of the valve body, further increases compliance during the closing process of the gas injector, so that a tangential force between the valve needle and the valve body can be reduced practically to zero.A maximum depth of the free space in the axial direction of the gas injector is preferably equal to or greater than a maximum stroke of the valve needle.

[0020] Preferably, the first wall thickness (W1) satisfies the following equation:

[0021] - 0.5 x W2 < W1 < 0.75 x W2,

[0022] - where W2 is a constant, second wall thickness of the valve body at an outer portion (33a) in which the first recess (5) is formed. Furthermore, the present invention relates to a gas internal combustion engine with a gas injector according to the invention.

[0023] Short description of the drawings

[0024] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0025] Figure 1 is a schematic partial sectional view of a gas injector according to a first embodiment of the invention,

[0026] Figure 2 is an enlarged partial sectional view of a combustion chamber side

[0027] End area of ​​the gas injector of Figure 1 in the closed state,

[0028] Figure 3 is a schematic partial sectional view of an end region of a

[0029] Gas injector in the closed state according to a second embodiment of the invention,

[0030] Figure 4 is a schematic partial sectional view of an end region of a

[0031] Gas injector in the closed state according to a third embodiment of the invention, and

[0032] Figure 5 is a schematic partial sectional view of an end region of a

[0033] Gas injector according to a fourth embodiment of the invention.

[0034] Preferred embodiments of the invention

[0035] A gas injector 1 according to a first preferred embodiment of the invention will be described in detail below with reference to Figures 1 and 2.

[0036] Figure 1 shows a cross-section of a gas injector 1. The gas injector 1 has a magnetic actuator 9 for actuating a valve needle 2. The gas injector 1 is an outward-opening injector, in which the valve needle 2 opens toward a combustion chamber 10. In the closed state of the gas injector 1 shown in Figure 1, the valve needle 2 closes against a sealing seat 4 on a valve body 3. The valve body 3 is a substantially hollow-cylindrical component.

[0037] In this embodiment, the valve needle 2 is designed in two parts and comprises a needle 20 with a valve plate 20a and an anchor bolt 21 loosely attached to the needle 20.

[0038] Actuator 9 comprises an armature 90, a coil 91, and an inner pole 92. The armature 90 is fixed to the armature bolt 21. Reference numeral 93 denotes an armature stroke, which the armature 90 travels during the opening process in the axial direction XX of the gas injector for a full stroke.

[0039] The needle 20 has a first guide 22 and a second guide 23 and is guided along an inner jacket region 32 of the valve body 3. Corresponding openings are provided in the first and second guides for the gas to flow through when the gas injector is open.

[0040] The armature 90 is further arranged in a lubricant chamber 12, which is only shown schematically in Figure 1. The lubricant chamber 12 is sealed from the gas-conducting region of the gas injector 1 by means of a bellows 13, which is fixed to the needle 20. The lubricant chamber 12 is filled with a lubricant, for example oil or the like, and lubricates the armature, allowing easy movement of the gas injector during the opening and closing process. A return element 11, in this embodiment a cylindrical spring, is also provided in the lubricant chamber 12, which holds the gas injector in the closed state when the magnetic actuator 9 is de-energized and, after opening, returns the valve needle to the closed state.

[0041] As can be seen from Figure 1, the valve body 3 also has an outer jacket region 31. A seal 6 is arranged on the outer jacket region 31. When the gas injector is installed, the seal 6 seals a gap between the gas injector and an installed component, for example, a cylinder head 14. Thus, a combustion chamber-side end region 33 is present on the valve body 3, which comes into contact with the combustion chamber gases and the combustion chamber pressures in the combustion chamber 10 during operation of a gas internal combustion engine.

[0042] The combustion chamber-side end region 33 is, as can be seen from Figures 1 and 2, divided into an outer subregion 33a and an inner subregion 33b. The outer subregion 33a is located closer to the combustion chamber 10 than the inner subregion 33b. The valve body 3 further has an end surface 30 directed toward the combustion chamber 10, which in this embodiment is a conical surface. The sealing seat 4 is formed on the end surface 30.

[0043] As can be seen in particular from Figure 2, the end surface 30 with the sealing seat 4 thus forms a conical region with a seat angle a of approximately 111°.

[0044] Furthermore, a recess 5 is formed in the outer shell region 31 at the outer subregion 33a of the combustion chamber-side end region 33. The recess 5 is formed closer to the end surface 30 than to the inner subregion 33b.

[0045] The recess 5 is a circumferential groove and, in this embodiment, has a semicircular cross-section. However, it should be noted that the recess 5 can also have other cross-sections.

[0046] The recess 5 reduces a maximum wall thickness in the region of the outer partial region 33a to a first wall thickness W1. The remaining region of the outer partial region 33a has a constant, second wall thickness W2, which is greater than the first wall thickness W1. The second wall thickness W2 is approximately twice as large as the first wall thickness W1.

[0047] The first recess 5 thus enlarges a surface of the outer shell area and is not filled with a seal or the like.

[0048] At the inner portion 33b of the combustion chamber-side end portion 33, the valve body 3 has a third wall thickness W3. The third wall thickness W3 is greater than the second wall thickness W2. The third wall thickness W3 is approximately twice as large as the second wall thickness W2. A transition 38 between the second wall thickness W2 and the third wall thickness W3 is formed at the inner portion 33b and is conical in this embodiment.

[0049] As can be seen in detail in Figure 2, the outer section 33a and the inner section 33b are exposed to the combustion chamber pressures and combustion chamber gases when assembled. Only the seal 6 on the outer jacket area 31 of the valve body 3 seals the gas injector from the cylinder head 14.

[0050] As shown in Figure 2, the needle 20 is formed with the valve plate 20a, which, when closed, seals against the sealing seat 4 on the valve body 3. The valve plate 20a has an arcuate cross-sectional profile with a radius R1 on its radially outer circumference. This creates a cone-ball sealing seat between the valve needle 2 and the valve body 3, enabling a linear seal at the sealing seat 4.

[0051] Thus, the gas injector 1 in the area close to the seat is designed in such a way that even at very high combustion chamber pressures of up to 200 x 10 5 Pa between the valve needle 2 and the valve body 3, no tangential forces arise. The tangential forces here are thrust forces that would occur in a valve seat plane E during a closing process of the gas injector. The valve seat plane E is perpendicular to the axial axis XX and runs through the linear sealing seat 4.

[0052] Thanks to the recess 5 in the valve body 3, no sliding occurs between the valve needle 2 and the valve body 3, even when high combustion chamber pressure presses the valve needle 2 into the sealing seat. Due to the absence of sliding and thus the absence of tangential forces between the valve body 3 and the valve needle 2, there is significantly less disruption of the sealing seat and less wear during operation. This significantly increases the service life of the gas injector and ensures a leak-free seal even after many hours of operation.

[0053] It should be noted that during operation, minimal tangential forces in the valve seat plane E may be tolerated, which do not lead to damage to the sealing seat or to the sealing surfaces on the valve needle 2 and the valve body 3. In this exemplary embodiment, the selection of the seat angle a in the range of 111° supports a sliding closing process between the valve needle 2 and the valve body 3 during the closing process.

[0054] If the seat angle a is selected too small, for example, 80°, two elastic deformations can occur at the end region 33 of the valve body 3 during the closing process due to the high closing forces on the valve needle 2. Since the valve body 3 may be pushed back towards its undeflected initial position by the combustion chamber pressures acting on the valve body 3 with external support, the described undesirable sliding processes occur, which produce the disadvantages described above.

[0055] If the seat angle a is selected to be too large, in the extreme case 180°, which would be a so-called flat seat, no radial forces of the valve needle 2 on the valve body 3 occur during the closing process. However, with such a flat seat, the valve body 3 deforms radially inwards in the area of ​​the end area 33 due to the high combustion chamber pressures, so that sliding processes also occur here between the valve needle 2 and the valve body 3 during the closing process, which lead to the wear phenomena explained above.

[0056] According to the invention, however, the provision of the recess 5 on the outer circumference of the combustion chamber-side end region 33 can counteract the undesired deformation of the end region 33 of the valve body 3 during the closing process. The targeted weakening by means of the recess 5 in the end region 33 results in any deformations that may occur near the minimum first wall area W1. Thus, no sliding occurs between the valve needle 2 and the valve body 3 during the closing process, so that even during continuous operation or very long operation, no wear occurs on the sealing seat 4. This significantly improves the sealing performance of the gas injector 1.

[0057] Particularly good results are achieved when the seat angle a is in the range from 105° to 117°, a cone-ball sealing seat 4 is present and the first wall thickness W1 in particular satisfies the equation 0.5 x W2 < W1 < 0.75 x W2 and the constant second wall thickness W2 in particular satisfies the equation 0.4 x W3 < W2 < 0.6 x W3.

[0058] Figure 3 shows a combustion chamber-side end region 33 of a gas injector according to a second exemplary embodiment of the invention. Identical or functionally identical parts are designated by the same reference numerals as in the first exemplary embodiment.

[0059] In contrast to the first exemplary embodiment, the gas injector of the second exemplary embodiment has, in addition to a first recess 5 in the valve body 3 corresponding to the first exemplary embodiment, a second recess 15 in the valve needle 2. As can be seen from Figure 3, the valve needle 2 is again formed with a valve plate 20a, wherein the second recess 15 is formed on a surface of the valve plate 20a directed towards the combustion chamber 10. In this exemplary embodiment, the second recess 15 is a circumferential groove which has an arcuate cross-section (cf. Figure 3). It should be noted, however, that other cross-sections are also possible here. The circumferential groove has a center point which lies in the center axis of the gas injector in the axial direction XX.The second recess 15 in the valve needle 2 on the side facing the combustion chamber thus makes it possible for the valve needle 2 to also have increased flexibility, whereby sliding processes between the valve needle 2 and the valve body 3 during the closing process can be further reduced or prevented. Otherwise, this embodiment corresponds to the first embodiment, so reference can be made to the description given there.

[0060] Figure 4 shows an end region 33 of a gas injector according to a third exemplary embodiment of the invention. The third exemplary embodiment essentially corresponds to the second exemplary embodiment, wherein a central depression with an arcuate cross-section is provided as the second recess 15 in the valve needle 2. As can be seen from Figure 4, the second recess 15 here is a partial sphere. It should be noted that it would also be possible, for example, to provide several separate recesses in the surface of the valve plate 20a facing the combustion chamber, for example similar to recesses on a golf ball. Figure 5 shows a valve needle 2 and a valve body 3 of a gas injector 1 according to a fourth exemplary embodiment of the invention. As can be seen from Figure 5, the valve needle 2 of the fourth exemplary embodiment has a different design. In the fourth exemplary embodiment, a valve plate 20a of the valve needle 2 is conical.This results in an end region of the valve needle 2 that is arrow-shaped in section and directed towards the combustion chamber. As can be seen directly from Figure 5, the valve plate 20a thus has an inner hollow cone region 50 and an outer cone 51 approximately parallel to the inner contour. The seat angle a is approximately 105°. The recess 5 is formed, as in the previous exemplary embodiments, on the outer jacket region 31 of the valve body 3. The somewhat smaller seat angle a compared to the previous exemplary embodiments has the advantage that the valve needle 2 is pressed more easily and with less wear into the conical sealing seat 4 on the valve body 3 during a closing process. This also improves sealing in the closed state of the gas injector, in particular.As can be seen from Figure 5, the arrow-shaped valve needle 2 is designed such that, when the gas injector is closed, a clearance 8 is created between the valve plate 20a and the valve seat plane E. The clearance 8 ensures that the conical valve plate 20a has a certain degree of flexibility during the closing process, thus preventing sliding between the valve needle 2 and the valve body 3 during the closing process. In conjunction with the recess 5, this prevents the undesirable tangential force effects that can cause damage to the sealing seat 4.

[0061] It should be noted that in the fourth embodiment, a second recess, as described above, may also be provided on a side of the valve plate 20a facing the combustion chamber.

Claims

Claims 1. Gas injector for injecting a gaseous medium, comprising: - an outward opening valve needle (2), - a valve body (3), - a sealing seat (4) on the valve body (3), against which the valve needle (2) seals when the gas injector is closed, - wherein the valve body (3) is hollow-cylindrical with a combustion chamber-side end surface (30), an outer jacket region (31) and an inner jacket region (32), - wherein the sealing seat (4) is arranged on the end face (30) of the valve body (3), - wherein the valve body (3) has an end region (33) on the combustion chamber side, and - wherein the combustion chamber-side end region (33) is designed such that no or at most a minimal tangential force occurs between the valve body (3) and the valve needle (2) during a closing process of the gas injector.

2. Gas injector according to claim 1, wherein the valve body (3) has a first recess (5) in the outer jacket region (31), so that a wall thickness of the valve body (3) in the region of the first recess (5) is reduced to a first wall thickness (W1), which is the smallest wall thickness of the combustion chamber-side end region (33).

3. Gas injector for injecting a gaseous medium, comprising: - an outward opening valve needle (2), - a valve body (3), - a sealing seat (4) on the valve body (3), against which the valve needle (2) seals when the gas injector is closed, - wherein the valve body (3) is hollow-cylindrical with a combustion chamber-side end surface (30), an outer jacket region (31) and an inner jacket region (32), - wherein the sealing seat (4) is arranged on the end face (30) of the valve body (3), - wherein the valve body (3) has a combustion chamber-side end region (33) on the outer jacket region (31), and - wherein a first recess (5) is formed in the outer jacket region (31) of the combustion chamber-side end region (33), so that a wall thickness of the valve body (3) in the region of the first recess (5) is reduced to a first wall thickness (W1), which is the smallest wall thickness of the combustion chamber-side end region (33).

4. Gas injector according to claim 2 or 3, wherein the first recess (5) is a circumferential groove, in particular with a constant depth.

5. Gas injector according to one of the preceding claims, wherein the combustion chamber-side end region (33) has an outer partial region (33a) and an inner partial region (33b), wherein the outer partial region (33a) forms an end of the valve body (3) directed towards the combustion chamber, wherein the first recess (5) is formed in the outer partial region (33a).

6. Gas injector according to one of the preceding claims, wherein the inner jacket region (32) is cylindrical.

7. Gas injector according to one of the preceding claims, wherein the valve needle (2) has a needle (20) with a valve plate (20a), wherein the valve plate (20a) seals against the sealing seat (4) of the valve body (3) when the gas injector is in the closed state.

8. Gas injector according to claim 7, wherein the valve plate (20a) has a second recess (50) on a combustion chamber side of the valve plate (20a).

9. Gas injector according to claim 8, wherein the second recess (50) is a circumferential groove and / or a central depression whose center lies in a central axis of the gas injector.

10. Gas injector according to one of the preceding claims, wherein the end surface (30) of the valve body (3), on which the sealing seat (4) is formed, is conical with a seat angle (a) in a range of 90° to 130°, in particular 100° to 120°, further in particular 105° to 117°, further in particular 110° to 112° and further in particular 111°.

11. Gas injector according to one of claims 7 to 10, wherein the valve plate (20a) is formed on an outer circumference in an arcuate section with a radius (R1), so that in the closed state of the gas injector a cone-ball seal is produced at the sealing seat.

12. Gas injector according to one of claims 7 to 11, wherein the valve needle (2) has a conical valve plate (20a), wherein the conical valve plate (20a) is designed such that in the closed state of the gas injector there is a free space (8) between an inner side of the valve plate (20a) facing away from the combustion chamber and a valve seat plane (E), wherein the valve seat plane (E) is perpendicular to an axial direction XX and the sealing seat (4) is arranged in the valve seat plane.

13. Gas injector according to one of the preceding claims, wherein the first wall thickness (W1) satisfies the following equation: - 0.5 x W2 < W1 < 0.75 x W2, - wherein W2 is a constant, second wall thickness of the valve body at an outer portion (33a) in which the first recess (5) is formed.

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