Injection system having at least one valve for metering a fluid

Abstract

The present invention relates to an injection system having at least one valve (2) for metering a fluid, in particular a fuel injection valve for injecting a gaseous fuel into a combustion chamber (3) of an internal combustion engine. The valve (2) has an inflow-side valve end (5) that forms the inflow-side inlet for the fluid. The valve (2) additionally has an outflow-side valve end (6) facing a combustion chamber (3), wherein the valve (2) can be installed in a longitudinal bore (35) of a cylinder head (10), and a first upper bearing region of the valve (2) is provided at its inflow-side valve end (5) and a second lower bearing region of the valve (2) is provided at its outflow-side valve end (6) in the longitudinal bore (35), wherein the upper bearing region of the valve (2) comprises at least one spherical bearing and there is no axial support for the valve (2) in the longitudinal bore (35). The valve (2) 'freely suspended' in this way has a clamping claw (11) in the upper bearing region, which has spherically formed contact sections (41) with hold-down arms (27) to form a spherical bearing, which correspond with the valve (2) at its inflow-side valve end (5).

Description

[0001] Description

[0002] title

[0003] Injection or blowing system with at least one valve for metering a fluid

[0004] State of the art

[0005] The present invention relates to an injection or injection system with at least one valve for metering a fluid, in particular a fuel injection valve for injecting a gaseous fuel into a combustion chamber of an internal combustion engine. Specifically, the invention relates to an injection system with which hydrogen can be injected directly into the combustion chamber of a mixture-compressing, spark-ignition internal combustion engine.

[0006] A holder for a fuel injection system is known from DE 10 2014 200 597 A1. This holder serves to hold a fuel injector at a connection point of a fuel-carrying component. A connecting piece of the fuel injector has a partially spherical sealing surface that bears against a conical sealing surface of the component. The connecting piece is subjected to a preload force against the conical sealing surface. The preload force is applied by a clamping screw and transmitted via guide parts.

[0007] Furthermore, DE 10 2015 205 980 A1 discloses a hydraulic connection via which a fuel injector can be connected to a fuel-carrying component. This arrangement has a retaining bridge, which in turn has a support surface. A connecting piece of a fuel injector is provided, which can be supported on the support surface of the retaining bridge. Furthermore, a connecting body is provided, wherein a hydraulic connection is formed between the connecting piece of the fuel injector and the connecting body. For this purpose, a spherically convexly curved support surface is provided on the connecting body, and a conically extending support surface is formed on the connecting piece of the fuel injector. To form the hydraulic connection, contact is established between the connecting piece of the fuel injector and the connecting body at the convexly curved support surface and the support surface.The support surface of the connecting piece is axially symmetrical with respect to a longitudinal axis. In this respect, the mating area is a familiar metallic ball / cone seal.

[0008] Fuel injectors are known in various designs according to the state of the art. In high-pressure injection systems for liquid fuels, as the aforementioned prior art documents demonstrate, a metal-to-metal connection is increasingly being implemented between a fuel rail and an injector in the connection area. However, these metal-to-metal connections require relatively high forces, with which the sealing components must be pressed together with their surfaces to ensure sufficient sealing.

[0009] In the course of the search for alternative fuels to reduce or avoid harmful emissions, the aim is in particular to provide an optimized solution for connecting or suspending a fuel injection valve for directly injecting a gaseous fuel, in particular hydrogen, into a combustion chamber of an internal combustion engine.

[0010] Tests on engine test benches have shown that a simple transfer of the known connections or suspensions of direct-injection fuel injectors for liquid fuels to a connection or suspension of direct-injection fuel injectors for gaseous fuels is not possible. The higher the transverse force introduced by the hold-down, the more the service life of the fuel injector, during which full functionality is guaranteed, is reduced due to the high stress. The present invention aims to eliminate this disadvantage for a "suspended" fuel injector.

[0011] Disclosure of the invention

[0012] The injection or blow-in system according to the invention with at least one valve for metering a fluid with the features of claim 1 has the advantage that an optimal mounting of the valve is achieved and a maximum of many degrees of freedom are available when mounting the valve in a longitudinal bore of a cylinder head, which simplify the installation of the valve and protect the valve from damage.

[0013] A particular advantage of the solution according to the invention is that, despite the radial play of the valve in the longitudinal bore, due to the special bearing, no harmful movement of the valve within the longitudinal bore occurs when a screw is tightened to hold the valve down and the valve is not exposed to any dangerous load (e.g. transverse force). The solution according to the invention offers further advantages, such as the following. With the clamping claw as a spherically mounted hold-down device, the installation space can be significantly reduced. The small number of components enables a particularly simple assembly process. In addition, the clamping claw as a hold-down device can also provide clear orientation, e.g. via a connector plug or via flattened areas for a jet alignment that is defined on the valve.

[0014] The subclaims describe preferred developments of the invention.

[0015] The metal-to-metal seal or bearing is preferably a metallic ball / cone seal or a ball / ball seal.

[0016] While the clamping claw and a sleeve body protruding from the cylinder head form a multiple spherical bearing in the upper bearing area for the valve, a second bearing point for the valve is formed at a lower valve end facing the combustion chamber in the area of ​​a sealing ring, which is typically made of PTFE. The two bearing points are separated by a maximum distance in the axial direction. The valve is supported by the sealing ring on the wall of the longitudinal bore of the cylinder head.

[0017] To avoid a large damage volume in the longitudinal bore, an annular gap is advantageously formed between the wall of the longitudinal bore and the blow-off side valve end, the radial extent of which is only approximately 50 to 100 pm. In this respect, the outer diameter of the valve end and the inner diameter of the longitudinal bore in the cylinder head differ only very slightly. The valve is aligned with the wall of the longitudinal bore via the bearing point on the sealing ring at the valve end. The upper bearing area of ​​the valve provides the necessary degree of freedom. The valve can "hang" freely, which can be described as a "suspended design" so that the bearing is provided exclusively by the lower sealing ring and the upper bearing area.

[0018] It is particularly advantageous to provide four spherical bearing points in the upper bearing area of ​​the valve, namely in the valve / clamping claw area, in the valve / sleeve body area, in the clamping claw / screw area with a spherical washer or a spherically shaped screw head and in the clamping claw / bearing journal area of ​​the cylinder head.

[0019] When the clamping claw is firmly connected to the cylinder head or a corresponding attachment body by means of a screw and the screw is tightened, the valve is finally held down firmly and securely and largely free of transverse forces.

[0020] The valve can have an "arched shape" for structural reasons without introducing any transverse force into the valve, as this is avoided by the hold-down device according to the invention. Furthermore, the design according to the invention enables a high manufacturing tolerance with regard to coaxiality and angular errors between the upper bearing area and the longitudinal bore of the cylinder head. The "suspended" design of the valve suspension in combination with the multiple spherical bearings in the upper bearing area always enables optimal sealing and the transverse force-free installation of several valves on one and the same cylinder head, even with larger deviations in coaxiality, position, and manufacturing-related angular errors. The present invention is preferably used in injection systems that inject directly into a combustion chamber. In particular, the system is suitable for directly injecting hydrogen into the combustion chamber of an internal combustion engine.

[0021] drawing

[0022] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0023] Figure 1 is a schematic sectional view of an injection system with two bearing points of the valve in an upper bearing area and a lower bearing area in the cylinder head,

[0024] Figure 2 is a detailed view of the upper bearing area of ​​the valve in the injection system with a clamping claw according to section II in Figure 1,

[0025] Figure 3 is a perspective view of the detailed view of Figure 2 of the upper bearing area of ​​the valve in the injection system with a clamping claw according to section II in Figure 1,

[0026] Figure 4 is a plan view of the injection system, in particular the valve with clamping claw according to the first embodiment shown in Figures 1 to 3,

[0027] Figure 5 is a perspective view of the upper bearing area of ​​the valve in the injection system with a clamping claw in a section similar to section II in Figure 1 according to a second embodiment,

[0028] Figure 6 is a schematic sectional view of an injection system with two bearing points of the valve in an upper bearing area and a lower (not shown) bearing area in the cylinder head according to the second embodiment,

[0029] Figure 7 is a perspective view of the clamping claw as a single component for holding down the valve in the first bearing area according to the second embodiment and

[0030] Figure 8 is a perspective view of the upper bearing area of ​​the valve in the injection system with a clamping claw and an additional holding element in a section similar to section II in Figure 1 according to a third embodiment.

[0031] Preferred embodiments of the invention

[0032] An injection system 1 according to preferred embodiments of the invention is described in detail below with reference to Figures 1 to 8. Preferably, this is an injection system 1 for injecting a gaseous fuel, in particular hydrogen, into a combustion chamber 3 of an internal combustion engine.

[0033] In principle, the system designed according to the invention can alternatively also be used as an injection system 1 for injecting a liquid fuel into a combustion chamber 3 of an internal combustion engine, whereby from now on only reference will be made to an injection system 1. Alternative exemplary embodiments not shown in the figures will also be mentioned below. The injection system 1 comprises at least one valve 2 for metering a fluid, in particular a gaseous fuel such as hydrogen, but also CNG, methane, ammonia, etc. The valve 2 is designed as an injection valve 2 that blows directly into the combustion chamber 3. The gas to be injected flows through the valve 2. The gas enters the valve 2, which can also be referred to as an injector, via an upstream valve end 5, while the metering, jet shaping, and processing of the gaseous medium takes place at a downstream valve end 6 facing the combustion chamber 3.The valve end 5 of the valve 2 can, for example, be designed to allow a line or hose connection. Via such a line (not shown), for example, the gas coming from a fluid distributor can be supplied to the valve 2.

[0034] The injection system 1 has two bearing points for the valve 2, with an upper bearing area for the valve 2 being provided on the one hand, and a lower bearing area for the valve 2 being provided in a cylinder head 10 on the other. Figure 1 shows a schematic sectional view of such an injection system 1 with the two bearing points for the valve 2.

[0035] In the upper bearing area of ​​the valve 2, a metal-to-metal seal is possible due to the design as a spherical bearing between a hold-down device, in particular a clamping claw 11 fastened to the cylinder head 10, and the valve 2.

[0036] As will be described later with reference to the following Figures 2 to 8, according to the invention there is a multiple spherical bearing in the upper bearing area, which is created via the clamping claw 11, the valve 2, a screw 13 for fastening the clamping claw 11 to the cylinder head 10 or to an attachment part of the cylinder head 10 and a sleeve body 12 in the cylinder head 10 and ensures an optimized installation and hold-down situation of the valve 2, in which maximum degrees of freedom of the radial compensation of the valve 2 in the installed state or when clamping the valve 2 in a longitudinal bore 35 of the cylinder head 10 can be achieved.

[0037] In addition to the bearing of the valve 2, a sealing of the longitudinal bore 35 of the cylinder head 10 against oil or water ingress, e.g. due to humidity, rainwater or cleaning, is also made possible.

[0038] At its valve end 6 facing the combustion chamber 3, the valve 2 has a circumferential sealing ring 33 on the outer circumference, which represents the second bearing point for the valve 2. Ideally, this is a PTFE sealing ring that is dimensioned or inserted into an annular groove on the valve 2 in such a way that a spherical bearing is preferably also produced, since the sealing ring 33 bulges slightly radially outwards when the valve 2 is installed, so that under compression pressure there is only an approximately linear bearing of the sealing ring 33 on the wall of the longitudinal bore 35 in the cylinder head 10 for receiving the valve 2. Advantageously, the diameter of the valve 2 at its valve end 6 and the diameter of the longitudinal bore 35 differ only slightly. For optimum support, the annular gap formed between the wall of the longitudinal bore 35 and the valve end 6 can only be approximately 50 to 100 pm in its radial extent.In a particularly advantageous manner, the damage volume is kept very small so close to the combustion chamber 3 in the longitudinal bore 35 of the cylinder head 10.

[0039] The valve 2 is aligned via the bearing point on the sealing ring 33 on the

[0040] Valve end 6 of valve 2 extends relative to the wall of the longitudinal bore 35. The multiple spherical bearings in the upper bearing area provide the necessary degree of freedom. The valve must not be pressed axially onto the cylinder head; rather, it must "hang" freely, which can be described as a "suspended design," so that the bearings are provided exclusively by the lower sealing ring and the upper bearing area.

[0041] With the above-described mounting of valve 2, the two bearing points are located as far apart as possible. Depending on the construction, valve 2 may even have a certain "arched shape" without introducing a transverse force into valve 2 due to the described hold-down.

[0042] The arrows 18 in Figure 1 symbolically indicate the two bearing points of the valve 2, at which the valve 2 can be aligned at any time, even during assembly, and at which radial compensation is possible. The arrows 19, on the other hand, symbolically indicate the axial force introduction in two spherical bearing areas on the clamping claw 11, valve 2 and sleeve body 12, which are essential for the invention. A particular advantage of the solution according to the invention is that, despite the radial play of the valve 2 in the longitudinal bore 35, due to the special bearing when the screw 13 for holding down the valve 2, no harmful movement of the valve 2 occurs within the longitudinal bore 35 and the valve 2 is not exposed to any dangerous load.

[0043] The inventive solution offers further advantages, such as the following. With the clamping claw 11 as a spherically mounted hold-down device, the installation space can be significantly reduced. The small number of components enables a particularly simple assembly process. As will be explained later, the clamping claw 11 as a hold-down device can also provide clear orientation, for example, via a connector 50 or other geometric features such as flattened portions for a jet alignment defined on the valve 2.

[0044] The positioning of valve 2 is determined by the geometry of the valve 2 and the longitudinal bore 35 of the cylinder head 10. This eliminates the need for additional alignment or positioning of the valve 2 to avoid transverse forces. Ultimately, the valve 2 aligns itself after it has been inserted into the longitudinal bore 35. The hold-down device cannot introduce any additional transverse forces into the system.

[0045] Figure 2 shows a detailed view of the upper bearing area of ​​the valve 2 in the injection system 1 with the clamping claw 11 engaging the valve 2 according to section II in Figure 1, on the basis of which the four spherical bearing points of the upper bearing area are to be explained in more detail.

[0046] The basic contour of the clamping claw 11 has a geometry known per se. The clamping claw 11 is a flat metal component having a base section 26 from which two hold-down arms 27 protrude in a clasp-like manner. The two hold-down arms 27 enclose the valve 2 at its inflow-side valve end 5 by a good 180°. To prevent rotation and ensure clear geometric alignment of the clamping claw 11, the valve 2 has two molded-on flattened areas 28 spaced 180° apart, which positively accommodate the two hold-down arms 27 of the clamping claw 11 in a radial direction. In the axial direction, the two hold-down arms 27 each have spherically designed contact sections 41 for resting on an annular collar 40 of the valve 2 and thus for holding the valve 2 down. The annular collar 40 has a flat, level support surface 43 facing the hold-down arms 27.

[0047] In the downstream direction, i.e. facing the combustion chamber 3, the annular collar 40 or another comparable shoulder or another collar of the valve 2 has a spherically shaped contact surface 42 which interacts with the upper end face of the sleeve body 12 to form a further spherical bearing. The sleeve body 12 is a thin-walled component which is pressed into the cylinder head 10, for example, or fitted in some other way, and which protrudes from the cylinder head 10 away from the combustion chamber 3. The upper end face of the sleeve body 12 for supporting the valve 2 is conical, specifically tapering radially inwards as seen in the direction of flow, with the total angle being approximately 90° on average, so that a tight ball / cone connection is present in this area.

[0048] Instead of the sleeve body 12, a geometrically different support for the valve 2 can alternatively be provided, which is additionally mounted on the cylinder head 10 or protrudes directly from the cylinder head 10 and has a conical shape, which also creates a tight ball / cone connection.

[0049] A particularly advantageous feature is that, thanks to this tight cone / ball connection between sleeve body 12 and valve 2, no additional components are required on valve 2, which typically serve to seal valve 2 against the wall of the longitudinal bore 35 in cylinder head 10, such as sealing rings, compensating rings, and retaining rings. The tight mounting prevents oil or water from entering the longitudinal bore 35 of cylinder head 10. Water buildup, e.g., due to humidity, rain, or cleaning, can also be largely prevented, thus increasing the corrosion resistance of valve 2.

[0050] A third spherical bearing in the upper bearing area of ​​the valve 2 occurs in the area of ​​the base section 26 of the clamping claw 11 at its end opposite the hold-down arms 27, wherein a spherically shaped, nose-like projection 46 is provided on the clamping claw 11 for this purpose, which engages in a conical recess 47 on the cylinder head 10 or an attachment part of the cylinder head 10 for bearing purposes.

[0051] The base section 26 of the clamping claw 11 also has a longitudinal opening 48 (see Figure 6), through which the screw 13 required to tighten the clamping claw 11 relative to the valve 2 passes. The longitudinal opening 48 has a conical chamfer on its upper end face facing the screw head of the screw 13. A spherical washer 49 interacts with this conical section 45 of the longitudinal opening 48 to form a fourth spherical bearing. The spherical washer 49 is pushed onto the screw 13 before it is inserted into the longitudinal opening 48 of the clamping claw 11, so that it is positioned directly below the screw head of the screw 13. As an alternative to the spherical washer 49, the screw head of the screw 13 can also be provided with an integrated spherical section facing the clamping claw 11, which then interacts with the conical section 45 of the longitudinal opening 48.As an alternative to the conical section 45 of the longitudinal opening 48 on the upper side of the clamping claw 11, the longitudinal opening 48 can also be spherically curved there, so that together with the spherical washer 49 or a spherical section of the screw head of the screw 13, a ball / ball bearing is then present.

[0052] Figure 3 shows a perspective view of the detailed view of Figure 2 of the upper bearing area of ​​the valve 2 in the injection system 1 with a clamping claw 11 according to section II in Figure 1. Figure 4 shows a plan view of the injection system 1, in particular the valve 2 with the clamping claw 11 according to the first exemplary embodiment shown in Figures 1 to 3. These two figures are intended to illustrate in particular that a defined installation position of the valve 2 in the longitudinal bore 35 of the cylinder head 10 is guaranteed via the flattened portions 28 on the valve end 5 of the valve 2 and the corresponding hold-down arms 27 of the clamping claw 11, for example in relation to an electrical connection plug 50 of the valve 2, which protrudes 90° from the extension of the clamping claw 11, for example.

[0053] Figure 5 shows a perspective view of the upper bearing area of ​​the valve 2 in the injection system 1 with a clamping claw 11 in a section similar to section II in Figure 1 according to a second embodiment. The contour of the clamping claw 11 is shown only symbolically. Thus, the clamping claw 11 can also taper or be rounded towards the end of the base section 26. Of particular importance are the three spherical bearings of the clamping claw 11 with the valve 2, with the screw

[0054] 13 and with the cylinder head 10. As a key difference to the embodiment shown in Figures 1 to 4, the third-mentioned bearing is now designed with a reversed geometry, so that the conical recess 47 (Figure 7) is now provided in the base section 26 of the clamping claw 11. The projection 46 of the clamping claw 11, on the other hand, is adequately implemented as a bearing journal 51 on the side of the cylinder head 10. The bearing journal 51 projects into the conical recess 47 of the clamping claw 11 for spherical support and is either an inserted, pressed-in, or otherwise fitted component in the cylinder head 10, which projects out of it towards the clamping claw 11, or a journal section formed directly on the cylinder head 10. In all cases, the bearing pin 51, which can also be referred to as a fixation pin, has a spherically curved bearing surface 52.

[0055] Figure 6 shows a schematic sectional view of an injection system 1 with two bearing points for the valve 2 in an upper bearing area and a lower (not shown) bearing area in the cylinder head 10 according to the second exemplary embodiment. As can be seen from Figure 6, the bearing journal 51 can be fitted into an opening in the cylinder head 10. The screw 13 engages, by means of a screw connection, in a threaded bore 53 of the cylinder head 10 to securely hold the valve 2 in the cylinder head 10 via the clamping claw 11. Figure 6 shows the four spherical bearing points of the upper bearing area of ​​the valve 2 in the area of ​​the valve 2 / clamping claw 11 (indicated by dashed lines), in the area of ​​the valve 2 / sleeve body 12, in the area of ​​the clamping claw 11 / screw 13 with the spherical washer 49, and in the area of ​​the clamping claw 11 / bearing journal 51 of the cylinder head 10.

[0056] Figure 7 shows a perspective view of the clamping claw 11 as an individual component for holding down the valve 2 in the first bearing area according to the second exemplary embodiment. Particularly in the area of ​​the base section 26, the clamping claw 11 is shown only in a very simplified and symbolic manner in its external contour. The external contour can differ considerably in all dimensions from the illustration in Figure 7. The bearing areas at the contact sections 41 of the hold-down arms 27 and at the conical recess 47 are essential to the invention. The conical section 45 of the longitudinal opening 48 for the further spherical bearing with the spherical disk 49 is not visible, as it is formed on the upper side of the clamping claw 11.

[0057] Figure 8 shows a perspective view of the upper bearing area of ​​the valve 2 in the injection system 1 with a clamping claw 11 and an additional holding element 55 in a section similar to section II in Figure 1 according to a third exemplary embodiment. The holding element 55 is designed, similar to the clamping claw 11, in a clip-like manner with two holding arms 56 that at least partially encompass the valve 2; however, a closed design is also conceivable. The holding arms 56 or a closed holding ring (not shown) are positioned such that they clamp the valve 2 in the area of ​​the annular collar 40 against the holding arms 56 or a holding ring in a spherically mounted manner. The holding arms 56 engage, for example, in a groove 57 on the valve 2. The screw 13 for fastening the clamping claw 11 to the cylinder head 10 also passes through the holding element 55 in a longitudinal bore.In contrast to the disc-like clamping claw 11, the holding element 55, for example, has a significantly larger axial extension. In the fully assembled and clamped state, the clamping claw 11 rests with its base section 26 against an upper end face 58 of the holding element 55.

[0058] A spherical bearing is understood to be a bearing that is either a ball / cone bearing or is designed similarly to a rod end or a ball joint with two spherically curved corresponding bearing surfaces.

[0059] Sealing concepts using ball / cone connections, cone / cone connections, and radially sealing O-rings are already known in existing combustion engines, as are clamping claws 11 for holding down injectors, particularly diesel injectors. However, a combination of such sealing concepts with the addition of a "suspended" design, together with a clamping claw 11 spherically mounted on valve 2, represents a particularly advantageous and previously unknown solution.

Claims

Claims 1. An injection or injection system comprising at least one valve (2) for metering a fluid, in particular a fuel injection valve for injecting a gaseous fuel into a combustion chamber (3) of an internal combustion engine, wherein the valve (2) has an inlet-side valve end (5) forming the inlet-side inlet for the fluid, and an outflow-side valve end (6) facing a combustion chamber (3), wherein the valve (2) is installable in a longitudinal bore (35) of a cylinder head (10), and a first upper bearing region of the valve (2) is provided at its inlet-side valve end (5) and a second lower bearing region of the valve (2) is provided at its outflow-side valve end (6) in the longitudinal bore (35), wherein the upper bearing region of the valve (2) comprises at least one spherical bearing, characterized in that a clamping claw (11) is provided in the upper bearing region,which has hold-down arms (27) having spherically designed contact sections (41) to form a spherical bearing, which arms correspond to the valve (2) at its inlet-side valve end (5).

2. System according to claim 1, characterized in that the lower bearing area of the valve (2) is provided at its downstream valve end (6) in the area of a sealing ring (33) in the longitudinal bore (35), without the valve (2) being axially supported in the longitudinal bore (35).

3. System according to claim 1 or 2, characterized in that the upper bearing area of the valve (2) has more than one spherical bearing point, in particular two to four spherical bearing points.

4. System according to claim 3, characterized in that in addition to the spherical bearing by means of the hold-down arms (27) of the clamping claw (11), a further spherical bearing point is provided between the valve (2) and a sleeve body (12) introduced into the longitudinal bore (35) and protruding from the cylinder head (10) on the inflow side.

5. System according to claim 4, characterized in that an annular collar (40) is formed on the inlet-side valve end (5) of the valve (2), the flat upper support surface (43) of which forms the spherical bearing point with the hold-down arms (27) of the clamping claw (11) and the lower spherically formed contact surface (42) of which forms the spherical bearing point with the sleeve body (12).

6. System according to claim 4 or 5, characterized in that the sleeve body (12) has a conical upper end face.

7. System according to one of claims 3 to 6, characterized in that the clamping claw (11) forms a further bearing point with the cylinder head (10) or an attachment part of the cylinder head (10), wherein for this purpose the clamping claw (10) has on a base section (26) opposite the hold-down arms (27) either a spherically curved projection (46) which interacts with a conical recess (47) of the cylinder head (10) or the cylinder head (10) has a projecting bearing journal (51) with a spherically curved bearing surface (52) which interacts with a conical recess (47) of the clamping claw (11).

8. System according to one of claims 3 to 7, characterized in that the clamping claw (11) forms a further bearing point with a screw (13) serving for fastening to the cylinder head (10), wherein a spherical disk (49) is provided which is either pushed onto the screw (13) or a spherical section is integrated into the screw head and which cooperates with a conical or spherically curved section (45) of a longitudinal opening (48) in the clamping claw (11).

9. System according to one of the preceding claims, characterized in that the clamping claw (11) comprises two hold-down arms (27) which at least partially encompass the valve (2) in its upper bearing area in the manner of a clamp.

10. System according to claim 9, characterized in that the valve (2) has two flattened portions (28) formed 180° opposite each other in its upper bearing area, which receive the two hold-down arms (27) of the clamping claw (11) in a form-fitting manner in the radial direction, ensuring anti-twist protection and clear orientation of the valve (2). 11 . System according to one of the preceding claims, characterized in that the valve (2) is mounted in the lower bearing area of the sealing ring (33) on the wall of the longitudinal bore (35) and the annular gap formed between the wall of the longitudinal bore (35) and the valve end (6) is only approximately 50 to 100 pm in its radial extent.

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