Spark plug assembly with a seating of a tapered shape

Abstract

The present invention pertains to a spark plug assembly (10) for a gas engine, comprising a spark plug (16) and a spark plug sleeve (18), wherein a seating (26) between the spark plug (16) and the spark plug sleeve (18) has a tapered shape.

Description

[0001] Description

[0002] SPARK PLUG ASSEMBLY WITH A SEATING OF A TAPERED SHAPE

[0003] Technical Field

[0004] The present invention relates to internal combustion engines running on gaseous fuel which are equipped with spark plug assemblies.

[0005] Technological Background

[0006] To achieve favorable combustion conditions during operation of a gas engine, it is known to employ pre-combustion chambers within cylinders of the engine. This particular applies to large-bore engines and engines which combust lean fuel air mixtures. Typically, in such a configuration, an air fuel mixture enters the pre-combustion chamber during a compression stroke of an associated cylinder which is then ignited by a spark plug. By doing so, a flame front is generated which propagates from the pre-combustion chamber via flow transfer channels into a main combustion chamber of the associated cylinder, thereby enabling to consistently burn the air fuel mixture present in the main combustion chamber.

[0007] For such gas engine configurations, the use of components referred to as “pre-chamber spark plugs” is known in which the function of a prechamber and a spark plug are combined in a single unit. Typically, such prechamber spark plugs are arranged at a cylinder head of an engine such that a tip forming a pre-chamber projects into and is fluid-communicatively connected to a main combustion chamber of an associated cylinder.

[0008] Further, for mounting the pre-chamber spark plugs to the cylinder head, the use of spark plug sleeves, also referred to as mounting sleeves, is known. These sleeves, which preferably are made of a metal material, may ensure proper installation and may serve to remove heat from the pre-chambers spark plugs during operation of the engine. In the context of the present disclosure, an assembly comprising a spark plug and a spark plug sleeve is referred to as a “spark plug assembly”. Further, an assembly comprising a spark plug sleeve and a pre-chamber spark plug or a spark plug and a separate pre-chamber is referred to as a “pre-chamber spark plug assembly”.

[0009] Typically, a requirement for such pre-chamber spark plug assemblies is to ensure tightness and proper heat conduction between the prechamber spark plug and the spark plug sleeve during operation.

[0010] Summary of the Invention

[0011] Starting from the prior art, it is an objective to provide an improved spark plug assembly for a gas engine, which comprises a spark plug and a spark plug sleeve and which in particular improves tightness and heat conduction between its components during operation of the gas engine. Further, it is an objective to provide a spark plug and a spark plug sleeve for use in such a spark plug assembly.

[0012] The spark plug assembly may comprise a pre-chamber spark plug and / or a spark plug without a pre-chamber and / or a separate pre-chamber.

[0013] These objectives are solved by the subject matter of the independent claims. Preferred embodiments are set forth in the present specification, the Figures as well as the dependent claims.

[0014] Accordingly, a spark plug assembly, in particular a pre-chamber spark plug assembly, for a gas engine is provided, comprising a spark plug, in particular a pre-chamber spark plug, and a spark plug sleeve, wherein a seating between the spark plug and the spark plug sleeve has a tapered shape.

[0015] Further, a spark plug, in particular a pre-chamber spark plug, for use in such a spark plug assembly, in particular a pre-chamber spark plug assembly, is provided, comprising a seating surface configured to abut on a further seating surface of the spark plug sleeve to form the seating between the pre-chamber spark plug and the spark plug sleeve, wherein the seating surface has a tapered shape.

[0016] Still further, a spark plug sleeve for use in such a spark plug assembly, in particular in such a pre-chamber spark plug assembly, is provided, comprising a seating surface configured to abut on a further seating surface of the spark plug, in particular of the pre-chamber spark plug, to form the seating between the pre-chamber spark plug and the spark plug sleeve, wherein the seating surface has a tapered shape.

[0017] As the spark plug and the spark plug sleeve are intended to be used in the above described spark plug assembly, technical features described hereinafter in the context with the spark plug assembly thus may also refer and be applied to, i.e. are to be considered as disclosed for, the spark plug and the spark plug sleeve, and vice versa.

[0018] Brief Description of the Drawings

[0019] The present disclosure will be more readily appreciated by reference to the following detailed description when being considered in connection with the accompanying drawings in which:

[0020] Fig. 1 depicts a longitudinal view of a spark plug assembly according to a first embodiment;

[0021] Fig. 2 depicts an enlarged view of the spark plug assembly in a disengaged state of its components;

[0022] Fig. 3 depicts a spark plug assembly according to a second embodiment; and

[0023] Fig. 4 depicts a spark plug assembly according to a third embodiment.

[0024] Detailed Description of Preferred Embodiments

[0025] In the following, the invention will be explained in more detail with reference to the accompanying Figures. In the Figures, like elements are denoted by identical reference numerals and repeated description thereof may be omitted in order to avoid redundancies.

[0026] Figure 1 depicts a spark plug assembly in the form of a prechamber spark plug assembly 10, which is referred to as the “pre-chamber assembly” in the following. The pre-chamber assembly 10 is, at least partly, received in and mounted to a cylinder head 12 of an internal combustion engine, also referred to as "the engine" in the following. The engine preferably is a gas engine. In the context of the present disclosure, the term “gas engine” generally refers to any internal combustion engine which runs on gaseous fuel, such as natural gas, biogas, etc. The use of the suggested pre-chamber assembly 10 is not limited to engines of a specific application, but rather may be applied among different technical fields, such as gas engines used in power plants or vehicles as a main or auxiliary engine or the like.

[0027] The engine, which employs the suggested pre-chamber assembly 10, preferably comprises a plurality of cylinders, e.g., four, eight, twelve or eighteen cylinders. The cylinders may be provided in an engine block and are delimited from above by at least one cylinder head 12. In general, the cylinder head 12 refers to a component of the engine which preferably is fixed to the engine block and which partly delimits one or more combustion chambers 14, also referred to as “main combustion chambers” in the following, provided in the cylinders of the engine.

[0028] Preferably, the engine is equipped with a plurality of pre-chamber assemblies 10, each of which is associated to a different one of the plurality of cylinders. In other words, one pre-chamber assembly 10 is provided per cylinder of the engine.

[0029] In the following, the structural and function configuration of the pre-chamber assembly 10 is described with reference to the embodiment depicted in Fig. 1 which may apply to one or more, preferably to all, of the plurality of pre-chamber assemblies 10 employed in the engine.

[0030] The pre-chamber assembly 10 comprises a pre-chamber spark plug 16 and a spark plug sleeve 18, also referred to as the “sleeve” hereinafter. The pre-chamber spark plug 16 is, at least partly, received within the sleeve 18 and is fixed or attached thereto, inter alia, by at least one threaded connection 20. Specifically, the pre-chamber spark plug 16 is received within the sleeve 18 such that a first seating surface 22 of the pre-chamber spark plug 16 abuts on a second seating surface 24 of the sleeve 18. By this configuration, the first seating surface 22 and the second seating surface 24 form a seating 26 between the pre- chamber spark plug 16 and the sleeve 18. The sleeve 18, in turn, is fixed to the cylinder head 12 by a further threaded connection 28.

[0031] The pre-chamber spark plug 16 and the sleeve 18 extend along a longitudinal axis L of the pre-chamber assembly 10. The longitudinal axis L of the pre-chamber assembly 10 coincides with a middle longitudinal axis of the spark plug 16 and the sleeve 18.

[0032] As can be gathered from Fig. 1, the threaded connection 20, via which the pre-chamber spark plug 16 is fixed to the sleeve 18, and the further threaded connection 28, via which the sleeve 18 is fixed to the cylinder head 12, overlap in a direction along the longitudinal axis L. In other words, the threaded connection 20 and the further threaded connection 28 are arranged, at least partly, at the same height or level with regard to the longitudinal axis L.

[0033] This arrangement is achieved by providing the sleeve 18 with a hollow-cylindrical shape at its bottom portion, i.e. the portion of the sleeve 18 facing the main combustion chamber 14, which is provided with an internal thread and an external thread. As can be gathered from Fig. 1, the internal thread, hereinafter also referred to as first thread, is configured to engage with a correspondingly designed thread, hereinafter also referred to as second thread, provided at an outer surface of the pre-chamber spark plug 16 which together form the first threaded connection 20. The external thread at the sleeve 18 is configured to engage with a further thread provided at an inner surface of a receiving aperture of the cylinder head 12 which together form the second threaded connection 28.

[0034] Generally, in the context of the present disclosure, the terms “lower”, “bottom”, etc., refer to a location or section which faces or is arranged adjacent to or in the vicinity of the associated cylinder or main combustion chamber 14 of the engine. Accordingly, the term “below” is used hereinafter to denote a direction pointing towards the associated cylinder or main combustion chamber 14 of the engine, whereas the term “above” or “upward” refer to an opposite direction. More specifically, the sleeve 18 is designed such that its inner thread and its external thread extend from a bottom end of the sleeve 18 in an upward direction along the longitudinal axis, i.e. in a direction along the longitudinal axis L which faces away from the main combustion chamber 14. In the shown configuration, the inner thread extends beyond the external thread in the upward direction.

[0035] The pre-chamber spark plug 16 is provided to combine the function of a pre-combustion chamber and the function of an ignition element, in particular a spark plug, in a single unit, which may be assembled from several parts. As such, the pre-chamber spark plug 16 includes a pre-combustion chamber and a spark plug (not shown). The pre-combustion chamber is formed by a pre-chamber cap 30 provided at a tip end of the pre-chamber spark plug 16. In the mounted state of the pre-chamber spark plug assembly 10, as depicted in Fig. 1, the pre-chamber cap 30 protrudes into the main combustion chamber 14 and is fluid-communicatively connected to the main combustion chamber 14 via a plurality of flow transfer channels 32. By this configuration, during operation of the engine, an air fuel mixture may enter the pre-combustion chamber within the pre-chamber cap 30 via the flow transfer channels 32, in particular during a compression stroke, which then may be ignited by a spark generated by the ignition element of the pre-chamber spark plug 16. By doing so, a flame front may propagate from the pre-combustion chamber via the flow transfer channels 32 into the main combustion chamber 14, thereby combusting the air fuel mixture present in the main combustion chamber 14.

[0036] According to one configuration, the pre-chamber spark plug 16 may be designed such that the air fuel mixture soaked into the pre-combustion chamber during the intake stroke is enriched by supplying gaseous fuel into the pre-combustion chamber via a separate fuel feed passage. According to an alternative configuration, such a separate fuel feed passage may be omitted such that the air fuel mixture soaked into the pre-combustion chamber is ignited without being enriched by additional fuel. The pre-chamber spark plug 16 may comprise different portions, which may subdivide the pre-chamber spark plug 16 into different sections, in particular along the longitudinal axis L. For example, in the shown configuration, the pre-chamber spark plug 16 may be subdivided into a tip portion 34 and a rear portion (not shown). The tip portion 34 is arranged in a lower section or lower half of the pre-chamber spark plug 16 facing the main combustion chamber 14. As can be gathered from Fig. 1, the tip portion 34 comprises the pre-chamber cap 30, the second thread forming the threaded connection 20 and the seating 26. As such, the tip portion 34 comprises the pre-combustion chamber.

[0037] The pre-chamber spark plug 16 and the sleeve 18 may be made of the same material. For example, the pre-chamber spark plug 16 and the sleeve 18 may be made of a ferrous material, in particular of steel, such as cast iron or gray cast iron.

[0038] The basic structural and functional configuration of such a prechamber assembly 10, in particular of its pre-chamber spark plug 16 and sleeve 18, are well known to a person skilled in the art and are thus not further described in the present disclosure. Rather, technical features relating to the seating 26 and its underlying function are specified in the following which are interlinked with the present invention. Although not further described hereinafter, the skilled person understands that the pre-chamber spark plug 16 may comprise additional components, such as, insulators, electrodes, fuel supply passages, etc.

[0039] The seating 26 serves for proper installation of the pre-chamber spark plug 16 within the sleeve 18. As such, the seating 26 may have, inter alia, the function of a sealing to establish tightness between the components of the prechamber assembly 10. Accordingly, the seating 26 may also be referred to as a sealing or sealing seat. Further, the seating 26 preferably serves to transfer heat between the components during operation of the engine, e.g. to protect the prechamber spark plug from overheating.

[0040] As can be gathered from Fig. 1, the threaded connection 20 is arranged in the area of the seating 26, in particular in the vicinity of the seating 26. This is achieved by arranging the threaded connection 20 and the seating 26 at or within the tip portion 34 of the pre-chamber spark plug 16. As such, the threaded connection 20 and the seating 26 are arranged in the same half of the pre-chamber assembly 10, i.e. in its bottom half. In other words, the seating 26 and the threaded connection 20 are arranged within a tip half, which may also be referred to as bottom half, of the pre-chamber spark plug 16 or the prechamber assembly 10 which faces and at least partly protrudes into the main combustion chamber 14. The tip half may extend along half of a total length of the pre-chamber spark plug 16 or the pre-chamber assembly 10 along its longitudinal axis L. More specifically, the threaded connection 20 is arranged at a distance d, in particular a minimal distance d, from the seating 26, wherein the distance d is smaller than 0.1 to 3 times a diameter D of the pre-chamber spark plug 16 at the seating 26. As can be gathered from Fig. 1, the diameter D extends perpendicular to the longitudinal axis L. Specifically, the distance d may be 0.1 to 3 times the diameter D. Alternatively or additional, the distance d may be smaller than the diameter D.

[0041] Compared to configurations of a pre-chamber spark plug assembly, in which a threaded connection is merely provided at a rear end or rear portion of the pre-chamber spark plug assembly, but not in the vicinity of a seating, it has been found that the suggested arrangement may improve pressure distribution at the seating 26 and thus tightness and heat conduction characteristics of the suggested assembly.

[0042] In the shown configuration, the pre-chamber assembly 10 is designed such that, along a longitudinal direction, i.e. a direction along the longitudinal axis L, pointing from a rear end to the pre-chamber cap 30 of the pre-chamber spark plug 16, the threaded connection 20 is arranged behind, i.e. after, the seating 26. In other words, the threaded connection 20 is arranged below the seating 26. In an alternative embodiment, as specified below in connection with the configuration depicted in Fig. 4, the threaded connection 20 may be arranged before, i.e. in front of, the seating 26 along the longitudinal direction. In a further alternative embodiment, the threaded connection 20 may comprise a first section arranged before, i.e. above, and a second section arranged behind, i.e. below, the seating 26 along the longitudinal direction.

[0043] In the following, the structural configuration of the seating 26 is further specified with reference to Fig. 2.

[0044] As can be gathered from Fig. 2 , the seating 26 has a tapered shape. In other words, the seating 26 has a shape that narrows along the longitudinal axis L of the pre-chamber spark plug 16. Specifically, the seating 26 narrows, i.e. its diameter decreases, along the longitudinal direction pointing from the rear end to the pre-chamber cap 30 of the pre-chamber spark plug 16.

[0045] More specifically, in the shown configuration, the seating 26 has a conical shape. In the context of the present disclosure, the term “conical shape” refers to a shape that follows or represents at least a part of a shell surface of a cone. As such, the conical shape may refer to a shape that follows or mimics the shell surface of a cone or truncated cone. However, according to the suggested configuration, the seating may not be limited to a conical shape, but rather may comprise any suitable tapered shape. The tapered shape may be a continuously narrowing shape, e.g. having a curved shape or shell surface, or a gradually narrowing shape, e.g. having a stepped shape or shell surface.

[0046] In the shown configuration, the seating 26 may have a cone angle y, which may also be referred to as angle of taper, between substantially 75° to substantially 105°, in particular between 79° and 102 °. For example, the cone angle y of the seating 26 may be 80° or substantially 80° as indicated in Fig. 1. Compared to smaller cone angles, the proposed cone angle may affect, in particular decrease a minimum release torque required to disengage the prechamber spark plug 16 from the sleeve 18. Accordingly, by this configuration, assembly or disassembly operations for an installer may be improved.

[0047] As set forth above, the seating 26 is formed by at least the first seating surface 22 of the pre-chamber spark plug 16 and the second seating surface 24 of the sleeve 18. The first seating surface 22 is provided at an outer or shell surface of the pre-chamber spark plug 16. Specifically, the first seating surface 22 is provided circumferentially around the longitudinal axis and circumferentially along the outer or shell surface of the pre-chamber spark plug 16. The second seating surface 22 is provided at an inner surface of the spark plug sleeve 18, in particular circumferentially around its longitudinal axis and circumferentially along the inner surface of the spark plug sleeve 18. In the shown configuration, each one of the first seating surface 22 and the second seating surface 24 has a conical shape as depicted in Fig. 2.

[0048] Fig. 2 shows a disengaged state of the pre-chamber assembly 10 in which the pre-chamber spark plug 16 and the spark plug sleeve 18 are not fully engaged such that the first seating surface 22 and the second seating surface 24 are disengaged, i.e. spaced apart from one another. In this state, the first seating surface 20 is inclined relative to a longitudinal axis of the pre-chamber spark plug 16 about a first inclination angle a and the second seating surface 24 is inclined relative to the longitudinal axis of the spark plug sleeve 18 about a second inclination angle 0. In the shown state, the longitudinal axis of the prechamber spark plug 16 and the longitudinal axis of the spark plug sleeve 18 coincide.

[0049] The first inclination angle a of the first seating surface 22 is smaller than the second inclination angle 0 of the second seating surface 24. By this configuration, pressure distribution at the seating may adapted such that at a radially inner area of the seating 26 seating pressure is higher compared to a radially outer area. In this way, the suggested arrangement may ensure improved tightness between the components of the pre-chamber spark plug assembly 10.

[0050] Specifically, a difference between the first inclination angle a of the first seating surface 22 and the second inclination angle 0 of the second seating surface 24 is greater than a tolerance, in particular a manufacturing or component tolerance, of at least one of the first inclination angle a and the second inclination angle 0. More specifically, the difference between the first inclination angle a of the first seating surface 22 and the second inclination angle 0 of the second seating surface 24 is greater than a sum of the tolerance, in particular a manufacturing or component tolerance, of the first inclination angle a and the tolerance of the second inclination angle 0.

[0051] More specifically, the difference between the first inclination angle a of the first seating surface 22 and the second inclination angle 0 of the second seating surface 24 is at least 10’ or at least 20’ or at least 30’ or at least 40’.

[0052] Fig. 3 shows a further embodiment of the pre-chamber assembly 10. Compared to the configuration depicted in Fig. 1 and Fig. 2, the seating 26 of the pre-chamber spark plug assembly 10 is additionally provided with a circumferential groove 36, which may also be referred to as a sealing groove. By providing the seating 26 with the groove 36, it has been found that tightness of the seating 26 may be improved.

[0053] More specifically, in the shown configuration, the first seating surface 22 is provided with the groove 36. Alternatively or additionally, the second seating surface 24 may be provided with such a circumferential groove. Accordingly, the technical features of the groove 36 of the first seating surface 22 described in the following may apply correspondingly to a groove provided in the second seating surface and are thus to be regarded as disclosed.

[0054] The groove 36 extends along the first seating surface 22 circumferentially around the longitudinal axis L. In the shown configuration, the groove 36 is arranged within a middle area of the first seating surface 22. That is, along the longitudinal axis L, the groove 36 is arranged spaced apart from end sections or border edges of the first seating surface 22. In other words, the groove 36 divides the first seating surface 22 into two sections, i.e. into an upper section 22a and a lower section 22b, as can be gathered from Fig. 3. Alternatively, the groove 36 may be arranged in the vicinity of or adjacent to one of the border edges of the first seating surface 22.

[0055] In the shown configuration, the first seating surface 22 is provide with a single groove 26. In a further development, the first seating surface 22 may be provided with more than one groove 26, e.g. with two separate grooves. Optionally, a sealing element 38 is accommodated within the groove 36. The sealing element 38 may be made of a metal or rubber material. For example, the sealing element 38 may be an O-ring or a sealing tape. Alternatively or additionally, a heat conducting paste or heat conducting component may be provided in the groove 36.

[0056] Fig. 4 shows a further embodiment of the pre-chamber assembly 10. Compared to the configuration depicted in Fig. 1 and Fig. 2, the threaded connection 20 is arranged before, i.e. in front of, the seating 26 along the longitudinal direction of the pre-chamber spark plug assembly 10.

[0057] Also in the shown configuration, the threaded connection 20 is arranged at or within the tip portion 34 of the pre-chamber spark plug 16. Specifically, the threaded connection 20 is arranged at a distance d’, in particular a minimal distance d’, from the seating 26, wherein the distance d’ is smaller than 0.1 to 3 times a diameter D of the pre-chamber spark plug 16 at the seating 26. Specifically, the distance d’ may be 0.1 to 3 times the diameter D. Alternatively or additional, the distance d’ may be smaller than the diameter D.

[0058] By this configuration, i.e. by interposing the seating 26 between the threaded connection 20 and the combustion chamber 14, the threaded connection may be prevented from being subjected to combustion products. Further, it has been found that, by arranging the threaded connection 20 above the seating 26, the threaded connection 20 may be arranged closer to cooling channels provided in or adjacent to the pre-chamber assembly 10 and thereby may improve heat transfer from the pre-chamber spark plug assembly 10.

[0059] Further, by this structural configuration, a tip end gap 40 is provided which extends from the seating 26 between the sleeve 18 and the tip end portion 34 and opens into the combustion chamber 14. The gap 40 extends circumferentially around the tip portion 34 and has a width, i.e. along a radial direction, between 0 mm to 1 mm, for example 0.5 mm. Alternatively or additionally, the gap 40 may have a width that is or between 0 % to 5 % of the diameter D, for example 3,5 % of the diameter D. Specifically, the gap 40 may have a width that is between 0 % to 1 % of the diameter D. By arranging the threaded connection 20 above the seating 26, the shown configuration may be provided with the gap 40, the width of which may be smaller compared to configurations in which the threaded connection is arranged below the seating 26. The shown structural configuration thus may allow to provide pre-chamber assemblies of smaller diameters, which may thus contribute to an improved space utilization.

[0060] It will be obvious for a person skilled in the art that these embodiments and items only depict examples of a plurality of possibilities. Hence, the embodiments shown here should not be understood to form a limitation of these features and configurations. Any possible combination and configuration of the described features can be chosen according to the scope of the invention. This is in particular the case with respect to the following optional features which may be combined with some or all embodiments, items and / or features mentioned before in any technically feasible combination.

[0061] Specifically, a spark plug assembly for a gas engine may be provided.

[0062] The spark plug assembly may be a pre-chamber spark plug assembly. As such, the spark plug assembly may comprise a pre-chamber spark plug and / or a spark plug without a pre-chamber and / or a separate pre-chamber. As such the suggested spark plug assembly is not limited to pre-chamber spark plug assemblies.

[0063] The spark plug assembly, in particular the pre-chamber spark plug assembly, may comprise a spark plug, in particular a pre-chamber spark plug, and a spark plug sleeve, wherein a seating between the spark plug and the spark plug sleeve has a tapered shape.

[0064] The spark plug may be within the spark plug sleeve and may be fixed thereto by at least one threaded connection. Further, the spark plug sleeve may be configured to be fixed to or mounted at a cylinder head of the gas engine by a further threaded connection, wherein in particular the threaded connection and the further threaded connection overlap in a direction along a longitudinal axis of the spark plug assembly. Further, the threaded connection may be arranged in the area of the seating. For example, the seating and the threaded connection may be arranged at a tip portion of the spark plug. The tip portion may comprise a precombustion chamber. Specifically, the threaded connection may be arranged within a distance from the seating, wherein the distance may be 0.1 to 3 times a diameter of the spark plug at the seating, in particular smaller than the diameter. Alternatively or additionally, the spark plug assembly may be designed such that, in a direction along a longitudinal axis of the assembly pointing form a rear end to the tip portion of the spark plug, the threaded connection is arranged behind and / or before the seating.

[0065] Alternatively or additionally, the seating may have a conical shape. The seating may have a cone angle between 75° to 105°, in particular of 80° or substantially 80°. In a further development, the seating may be formed by at least a first seating surface of the spark plug and a second seating surface of the spark plug sleeve. Optionally, the spark plug assembly may be designed such that, in a disengaged state of the seating in which the first seating surface and the second seating surface are disengaged, i.e. are spaced apart from one another, the first seating surface is inclined relative to a longitudinal axis of the spark plug about a first inclination angle that is smaller than a second inclination angle about which the second seating surface is inclined relative to a longitudinal axis of the spark plug sleeve. In a further development, a difference between the first inclination angle and the second inclination angle may be greater than a sum of a tolerance of the first inclination angle and a tolerance of the second inclination angle.

[0066] For example, the difference between the first inclination angle and the second inclination angle may be at least 10', i.e. 10 minutes of arc, or at least 20', i.e. 20 minutes of arc.

[0067] Alternatively or additionally, at least one of the first seating surface and the second seating surface may be provided with a circumferential groove. In a further development the at least one circumferential groove may divide the first seating surface and / or the second seating surface into two sections. Further, at least one of the at least one circumferential groove may accommodate a sealing element, e.g. an O-ring and / or sealing tape and / or a heat conducting element, such as a heat conducting paste.

[0068] Furthermore, a spark plug, in particular a pre-chamber spark plug, may be provided for use in a spark plug assembly, in particular a pre-chamber spark plug assembly, as described above, comprising a seating surface configured to abut on a further seating surface of the spark plug sleeve to form the seating between the spark plug and the spark plug sleeve, wherein the seating surface has a tapered shape. The seating surface of the spark plug may be a circumferential seating surface of a tapered shape, in particular of a conical shape. For example, the seating surface may have a cone angle between 75° to 105°, in particular of 80° or substantially 80°. Further, the spark plug may comprise a thread configured to engage with a further thread of the sleeve. The thread may be arranged in the area or vicinity of the seating surface. In a direction along a longitudinal axis of the spark plug pointing towards a tip portion thereof, the thread may be arranged before or behind the seating surface.

[0069] Alternatively or additionally, the thread may be arranged within a distance from the seating surface, wherein the distance may be less or may be 0.1 to 3 times a diameter of the spark plug at the seating, in particular smaller than the diameter.

[0070] Alternatively or additionally, is the seating surface may be provided with a circumferential groove, in particular as described above.

[0071] Furthermore, a spark plug sleeve may be provided for use in a spark plug assembly as described above, comprising a seating surface configured to abut on a further seating surface of the spark plug to form the seating between the spark plug and the spark plug sleeve, wherein the seating surface has a tapered shape. The seating surface of the sleeve may be a circumferential seating surface of a tapered shape, in particular of a conical shape. For example, the seating surface may have a cone angle between 75° to 105°, in particular of 80° or substantially 80°. Further, the sleeve may comprise a thread configured to engage with a further thread of the sleeve. The thread may be arranged in the area or vicinity of the seating surface. In a direction along a longitudinal axis of the sleeve pointing form a rear end of a first diameter towards a tip portion of a smaller second diameter, the thread may be arranged before or behind the seating surface. Alternatively or additionally, the seating surface may be a circumferential seating surface of a tapered shape, in particular of a conical shape, which may be provided with a circumferential groove, in particular as described above.

[0072] Industrial Applicability With reference to the Figures, a spark plug assembly for a gas engine is suggested. The spark plug assembly as mentioned above is applicable in any suitable internal combustion engine. The suggested spark plug assembly may replace conventional spark plug assemblies and may serve as a replacement or retrofit part.

Claims

Claims1. Spark plug assembly (10), in particular for a gas engine, comprising a spark plug (16) and a spark plug sleeve (18), wherein a seating (26) between the spark plug (16) and the spark plug sleeve (18) has a tapered shape.

2. Spark plug assembly according to claim 1, wherein the spark plug (16) is received within the spark plug sleeve (18) and is fixed thereto by at least one threaded connection (20), in particular arranged in the area of the seating (26).

3. Spark plug assembly according to claim 2, wherein the seating (26) and the threaded connection (20) are arranged at a tip portion (34) of the spark plug (16), wherein in particular the tip portion (34) comprises a precombustion chamber.

4. Spark plug assembly according to claim 2 or 3, wherein in a direction along a longitudinal axis (L) pointing form a rear end to the tip portion (34) of the spark plug (16), the threaded connection (20) is arranged behind or before the seating (26).

5. Spark plug assembly according to any one of claims 2 to 4, wherein the threaded connection (20) is arranged within a distance (d; d’) from the seating (26), wherein the distance (d; d’) is 0.1 to 3 times a diameter (D) of the spark plug (16) at the seating (26), in particular is smaller than the diameter (D).

6. Spark plug assembly according to any one of claims 1 to 5, wherein the seating (26) has a conical shape.

7. Spark plug assembly according to claim 6, wherein the seating (26) has a cone angle (y) between 75° to 105°, in particular of substantially 80°.

8. Spark plug assembly according to claim 6 or 7, wherein the seating (26) is formed by a first seating surface (22) of the spark plug (16) and a second seating surface (24) of the spark plug sleeve (18), and wherein the spark plug assembly (10) is designed such that, in a disengaged state of the seating (26) in which the first seating surface (22) and the second seating surface (24) are disengaged, the first seating surface (22) is inclined relative to a longitudinal axis (L) of the spark plug (16) about a first inclination angle (a) that is smaller than a second inclination angle (0) about which the second seating surface (24) is inclined relative to a longitudinal axis (L) of the spark plug sleeve (18).

9. Spark plug assembly according to claim 8, wherein a difference between the first inclination angle (a) and the second inclination angle (0) is greater than a sum of a tolerance of the first inclination angle (a) and a tolerance of the second inclination angle (0).

10. Spark plug assembly according to any one of claims 8 or 9, wherein the difference between the first inclination angle (a) and the second inclination angle (0) is at least 10' or 20'.

11. Spark plug assembly according to any one of claims 1 to 10, wherein the first seating surface (22) or the second seating surface (24) is provided with a circumferential groove (36).

12. Spark plug assembly according to claim 11, wherein the circumferential groove (36) divides the first seating surface (22) or the second seating surface (24) into two sections (22a, 22b).

13. Spark plug assembly according to claim 11 or 12, wherein a sealing element (38) is accommodated in the circumferential groove (36).

14. Spark plug (16) for use in a spark plug assembly (10) according to any one of claims 1 to 13, comprising a seating surface (22) configured to abut on a further seating surface (24) of the spark plug sleeve (18) to form the seating (26) between the spark plug (16) and the spark plug sleeve (18), wherein the seating surface (22) has a tapered shape.

15. Spark plug sleeve (18) for use in a spark plug assembly (10) according to any one of claims 1 to 13, comprising a seating surface (24) configured to abut on a further seating surface (22) of the spark plug (16) to form the seating (26) between the spark plug (16) and the spark plug sleeve (18), wherein the seating surface (24) has a tapered shape.

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