ES2821656T3 - Spark plug for an internal combustion engine - Google Patents

Abstract

A spark plug (30) for an internal combustion engine (1), wherein the spark plug (30) comprises: a central electrode (68) extending along a longitudinal direction (L); an insulator (70) disposed around the center electrode (68); a housing (50) mounted on the insulator (70), the housing (50) being in thermal contact with the insulator (70) at a first contact interface (80) and having an opening (54) at one end (51) in the longitudinal direction (L) through which the central electrode (68) is exposed; a mounting portion (56) provided on an outer surface of the housing (50) and configured to removably mount the spark plug (30) in a spark plug hole (44) of the internal combustion engine (1); a sealing portion (58) provided on the outer surface of the housing (50) and configured to hermetically engage an inner surface of the spark plug hole (44) at a second contact interface (82) when the spark plug (30) is mounted in the spark plug hole (44), wherein the sealing part (58) is arranged between the mounting part (56) and the opening (54) in the longitudinal direction (L); characterized in that it also comprises a protective element (98) that covers, at least in part, a front surface (53) of the casing (50) at the end (51) thereof, where the protective element (98) is made of a material that has a lower thermal conductivity than the material that forms the housing (50), for example, Inconel and / or ceramic materials.

Description

DESCRIPTION

Spark plug for an internal combustion engine

Technical field

The present description refers generally to an internal combustion engine, and more especially, to a spark plug for an internal combustion engine.

Background

Internal combustion engines, eg, gaseous fuel internal combustion engines fed with a mixture of gaseous fuel and air, may comprise one spark plug per cylinder for ignition. In particular, large diameter gaseous fuel internal combustion engines can benefit from a spark plug arranged in a pre-combustion chamber (also called a pre-chamber), as it is otherwise difficult to consistently achieve complete and exhaustive combustion of the engines. gaseous fuel / air mixtures.

Typically, said pre-chamber is fluidly connected to a main combustion chamber of a respective cylinder through a riser channel and a plurality of flow transfer channels. The flow transfer channels and the riser channel allow the flow of the gaseous fuel and air mixture from the main combustion chamber to the pre-chamber during a compression stroke. The enrichment of the mixture in the pre-chamber can be effected by supplying a small amount of fuel (gaseous) to the pre-chamber through a separate fuel supply conduit, for example, during the intake stroke. The enriched mixture is ignited in the prechamber by the spark plug. The ignition of the enriched mixture causes a flame front of hot gases that propagates, from the pre-chamber through the flow transfer channels, to the main combustion chamber. Therefore, the mixture in the main combustion chamber ignites and burns and thus expands against a movable piston that drives a crankshaft.

US-2008/0061670 A1 describes a spark plug that includes a center electrode, an insulator, and a metallic coating. The metal liner includes a mounting part, a cylindrical part, a sealing part, a crimp part, and a clasp part. The length in the axial direction of an external thread formed on the mounting part is less than the length of the cylindrical part in the axial direction.

JP 2000003777 A describes a spark plug and a spark plug assembly.

US-5 186132 A describes a spark plug for an internal combustion engine.

GB 2 541 880 A describes a protective arrangement to allow safe starting of positive-ignition lean-burn engines.

US-2017/0167358 A1 describes a pre-chamber body for an internal combustion engine.

The present disclosure is intended, at least in part, to improve or exceed one or more aspects of the prior art systems.

Brief description of the invention

In one aspect, the present description refers to a spark plug for an internal combustion engine. The spark plug comprises a center electrode extending along a longitudinal direction, an insulator disposed around the center electrode, and a housing mounted on the insulator. The housing is in thermal contact with the insulator at a first contact interface and has an opening at one end in the longitudinal direction through which the center electrode is exposed. A mounting portion is provided on an outer surface of the housing and configured to removably mount the spark plug in a spark plug hole of the internal combustion engine. A sealing portion is provided on the outer surface of the housing and is configured to seal an inner surface of the plug hole at a second contact interface when the plug is mounted in the plug hole. The sealing part is arranged between the mounting part and the opening in the longitudinal direction. A protective element covers at least in part a front surface of the housing at the end thereof. The protective element is made of a material that has a lower thermal conductivity than the material that forms the housing, for example Inconel and / or ceramic materials.

According to another aspect, the present description refers to a pre-chamber assembly for an internal combustion engine. The pre-chamber assembly comprises a pre-chamber body that defines a pre-chamber and a spark plug which, according to the above aspect, is mounted in a spark plug hole formed in the pre-chamber body so that the sealing portion of the spark plug is tightly engaged. to the inner surface of the spark plug hole at the second contact interface.

Other features and aspects of this description will become apparent from the description that follows and the accompanying drawings.

Brief description of the drawings

The accompanying drawings, which are incorporated herein and made a part of the specification, illustrate illustrative embodiments of the description and, together with the description, serve to explain the principles of the description. In the drawings:

Fig. 1 shows a schematic cross-sectional view of a part of an internal combustion engine equipped with a pre-chamber assembly according to the present disclosure;

Fig. 2 shows a schematic cross-sectional view of a pre-chamber body including a spark plug according to the present disclosure; Y

Fig. 3 shows a partial cross-sectional view of a spark plug according to the present invention.

Detailed description

The following is a detailed description of illustrative embodiments of the present disclosure. The illustrative embodiments described in the present disclosure and illustrated in the drawings are intended to teach the principles of the present disclosure, allowing one skilled in the art to apply and use the present disclosure in many different settings and for many different applications. Therefore, the illustrative embodiments are not intended to be and should not be construed as a limiting description of the scope of patent protection. Rather, the scope of patent protection will be defined by the appended claims.

The present description is based in part on the understanding that a known spark plug design has the disadvantage that the heat flow from the spark plug electrodes takes place over long distances and therefore the electrodes can reach become very hot and subject to considerable wear and tear. This is especially true when using high pressures and rich combustion. Furthermore, even using materials such as iridium, platinum and rhodium, this effect can only be reduced, but the problem cannot be solved.

With the foregoing in mind, it has been understood that a new spark plug design is needed that can significantly reduce the heat transfer distances from the electrodes to the part of the engine where the spark plug is mounted. In this way, the temperature of the electrodes can be significantly reduced, and oxidation of the electrode material can also be reduced.

The present disclosure is also based in part on understanding that providing additional insulation to the combustion chamber spark plug can further reduce the heat transferred from the combustion chamber, also improving heat transfer from the electrodes. In particular, it has been understood that materials having low thermal conductivity, such as Inconel or ceramic materials, can be advantageously employed.

Referring now to the drawings, Fig. 1 represents a piston 2 arranged in a cylinder 4 of a part of an internal combustion engine 1 (not shown in more detail). The cylinder 4 is covered by a cylinder head 6. The piston 2, the cylinder 4 and the cylinder head 6 together define a main combustion chamber 8 of the internal combustion engine 1. The piston 2 is arranged alternately to the cylinder 4 to move between a top dead center (TDC) and a bottom dead center (PMI) during the operation of the internal combustion engine 1.

For the purpose of describing illustrative embodiments of the present disclosure, the internal combustion engine 1 is considered a stationary or marine four-stroke internal combustion engine that operates, at least in part, on gaseous fuel, for example, a fuel engine. gas or a dual fuel engine. However, one skilled in the art will appreciate that the internal combustion engine can be any type of engine (turbine, gas, diesel, natural gas, propane, two-stroke, etc.) that would utilize the pre-chamber assembly as described in herein, or may not have the prechamber assembly. Furthermore, the internal combustion engine can be of any size, with any number of cylinders, and have any configuration (V-type, in-line, radial, etc.). Moreover, the internal combustion engine can be used to power any machine or other device, including locomotion applications, trucks or road vehicles, trucks or off-road machines, earth-moving machinery, generators, aerospace applications, marine applications, pumps , stationary equipment or other motor-driven applications.

The cylinder head 6 includes at least one inlet valve 10, for example a poppet valve. The inlet valve 10 is housed in an opening of the inlet channel 12 in a piston side face 14 of the cylinder head 6 to supply a mixture of gaseous fuel and air to the main combustion chamber 8. Similarly, at least one outlet valve 16, for example also a poppet valve, is housed in an outlet channel 18 of the cylinder head 6 to guide the exhaust gas out of the main combustion chamber 8.

The cylinder head 6 further comprises a pre-chamber assembly 20. A plurality of flow transfer channels 22 fluidly connects the main combustion chamber 8 with an interior of the prechamber assembly 20.

The pre-chamber assembly 20 is installed in the cylinder head 6 through a mounting body 24 as shown in Fig. 1. Alternatively, the pre-chamber assembly 20 may be installed in the cylinder head 6 of any another suitable way.

In Fig. 2, an illustrative embodiment of a pre-chamber assembly 20 is shown in a schematic cross-sectional view.

The pre-chamber assembly 20 includes a first pre-chamber body 26, a second pre-chamber body 28, a spark plug 30, and a fuel supply device 32. The first pre-chamber body 26 and the second pre-chamber body 28 are connected to each other. Spark plug 30 and fuel supply device 32 are housed in second pre-chamber body 28.

The first pre-chamber body 26 includes and defines a pre-chamber 34, an upstream channel 38, and flow transfer channels 22. In an assembled state, the flow transfer channels 22 fluidly connect an interior of the pre-chamber body 26 (the pre-chamber 34 and the riser channel 38) and the main combustion chamber 8 (Fig. 1). As can be seen in Fig. 2, the diameter of the prechamber 34 is greater than the diameter of the riser channel 38, which in turn is greater than the diameter of the flow transfer channels 22.

Prechamber 34 extends along a longitudinal axis A of first prechamber body 26 which is funnel-shaped and tapers toward rising channel 38. Alternatively, prechamber 34 may have any other shape, such as a cylindrical, a pyramidal shape, a conical shape, and combinations thereof. For example, the pre-chamber 34 may have a volume in the range 0.1% to 10% of the compression volume of the cylinder 4 (see Fig. 1).

A lower section of the pre-chamber 34 smoothly passes into the riser channel 38. The riser channel 38 extends longitudinally in the first body 26 of the pre-chamber and opens with one end in the pre-chamber 34. In the configuration shown in Fig. 2, the ascending channel 38 is aligned with the longitudinal axis A of the prechamber. Alternatively, the riser channel 38 may run parallel to the longitudinal axis A of the prechamber, or it may circumscribe an angle with the longitudinal axis A of the prechamber. Riser channel 38 fluidly connects pre-chamber 34 and flow transfer channels 22.

To fluidly connect a lower section of riser channel 38 and an upper section of main combustion chamber 8 (see Fig. 1), flow transfer channels 22 are provided. The flow transfer channels 22 extend through a tip portion 43 of the first chamber body 26. In some embodiments, the flow transfer channels 22 may be opened directly into the pre-chamber 34. In other words, a fluidly interconnected riser channel between the pre-chamber and the flow transfer channels may be omitted.

Spark plug 30 is installed in pre-chamber assembly 20 so that spark plug 30 is functionally coupled to pre-chamber 34.

As used herein "functionally coupled" means that the spark plug 30 is configured and arranged to ignite a flammable mixture in the pre-chamber 34. For example, the plug 30 may extend into the pre-chamber 34. Specifically, the electrodes of the spark plug 30 may reach into the pre-chamber 34 such that a spark between the electrodes ignites a mixture in the pre-chamber 34. The spark plug 30 may be mounted in a spark plug hole 44 formed in the first and / or second pre-chamber body 26, 28.

The fuel supply device 32 is mounted in a fuel supply port 46 which extends through the second pre-chamber body 28. Alternatively, the fuel supply device 32 may be mounted on the first pre-chamber body 26. The fuel supply device 32 is configured to supply a fuel, for example, a gaseous fuel, or a rich mixture of fuel and air to the pre-chamber 34 for enrichment.

As shown in Fig. 2, the spark plug 30 comprises a center electrode 68 that extends along a longitudinal direction L. An insulator 70 is disposed around the center electrode 68 and is in thermal contact therewith. In addition, a housing 50 is mounted on the insulator 70. The housing 50 is a substantially cylindrical body that surrounds the insulator 70 and is in thermal contact with the insulator 70 at a first contact interface 80. As used herein, the term "contact interface" generally designates an interface between two elements that are directly or indirectly in contact with each other, in particular, in thermal contact with each other. Therefore, as used herein, the term "contact interface" includes a direct contact between the surfaces of two elements or an indirect contact between the two elements through an intermediate element. In particular, as used herein, the term "contact interface" designates an interface through which heat transfer occurs between two elements. The first contact interface 80 will be described in more detail below.

The housing 50 of the spark plug 30 further has an opening 54 at one end 51 in the longitudinal direction A. The center electrode 68 is exposed through the opening 54. In the example shown in Fig. 2, the center electrode 68 protrudes from aperture 54 to pre-chamber 34. However, in other embodiments, center electrode 68 may not protrude from aperture 54 and may be disposed in a cavity formed in end 51 of housing 50. Thus, as stated As used herein, the term "exposed" is used to designate the accessibility of the center electrode 68 from the side of the pre-chamber 34 through the opening 54 formed in the housing 50.

As shown in Fig. 2, in an illustrative embodiment, spark plug 30 further includes at least one grounding electrode 94 mounted to end 51 of housing 50. In particular, grounding electrode 94, which It may be a J-gap electrode, it is arranged to face the center electrode 68 so that a spark can be generated between the center electrode 68 and the grounding electrode 94 in a known manner. As will be described in more detail below, the at least one grounding electrode 94 is configured to be in thermal contact with the inner surface of spark plug hole 44 through housing 50 and a second contact interface 82, which also it will be described in more detail below.

A mounting portion 56, configured to removably mount the spark plug 30 in the plug hole 44, is provided on an outer surface of the housing 50. In particular, as shown in Fig. 2, the mounting portion 56 includes a shoulder 88 formed on the outer surface of housing 50. Shoulder 88 is formed, for example, as a substantially annular edge on housing 50.

Furthermore, as shown in FIG. 2, in the illustrative embodiment, the mounting portion 56 further comprises a mounting sleeve 90 configured to mount on the outer surface of the housing 50 to engage the shoulder 88 and urging the housing 50 toward the end 51 of the housing 50 in the longitudinal direction L. In particular, the mounting sleeve 90 includes a male threaded portion 92 configured to engage a corresponding female threaded portion formed on the inner surface of the spark plug hole 44. Thus, the spark plug 30 is mounted in the spark plug hole 44 by squeezing the mounting sleeve 90 to press the housing 50 of the spark plug 30 against the pre-chamber body 26, 28, which will be described in greater detail later.

A sealing portion 58 is provided on the outer surface of the housing 50 and is configured to seal an inner surface of the plug hole 44 at the second contact interface 82 when the plug 30 is mounted in the plug hole 44 as previously described.

With the above configuration, heat that is transferred to the center electrode 68 and grounding electrode 94 due to combustion in the pre-chamber 34 can be transferred to the pre-chamber body 26, 28 through the first contact interface 80 and the second contact interface 82. In particular, heat is transferred from the grounding electrode 94 to the housing 50, in particular, the end 51 thereof where the grounding electrode 94 is connected to the housing 50, and from the end 51 from the housing 50 to the second prechamber body 28 through the second contact interface 82 where the housing 50 is pressed against the inner surface of the spark plug hole 44. In addition, heat is transferred from the center electrode 68 to the second body 28 of the prechamber through the insulator 70, the first contact interface 80, and the second contact interface 82.

According to the present description, the sealing portion 58 of the spark plug 30 is disposed between the mounting portion 56 and the aperture 54 at the end 51 of the housing 50 in the longitudinal direction L. As shown in Fig. 2, this has the effect that the heat transfer from the housing 50 to the second pre-chamber body 28 occurs very close to the end 51, where the center electrode 68 and grounding electrode 94 become hot due to combustion in the pre-chamber 34. This in contrast to known designs in which the corresponding sealing part is arranged further from the end of the spark plug than the corresponding mounting part, so that the heat transfer occurs at a significantly greater distance, ie , results in significantly less effective cooling of the exposed portions of the center electrode 68 and grounding electrode 94.

Fig. 3 shows in more detail an illustrative configuration of a spark plug 30 according to the present invention.

As shown in Fig. 3, the sealing portion 58 includes a conical sealing surface 84 formed on the outer surface of the housing 50 and configured to tightly engage a contact sealing surface of the spark plug hole 44 (see Fig. . two). However, it will be readily appreciated that the conical sealing surface 84 is only one example of the sealing portion 58 of the present disclosure and other suitable configurations may be used. For example, instead of a conical sealing surface, a shoulder or step may be formed on the outer surface of housing 50, as long as an extended sealing surface is provided that can be pressed against a contact seal surface of bore 44 of spark plug when spark plug 30 is mounted on it. In addition, in other embodiments, the heat transfer between the housing 50 and the spark plug hole 44 can be done by providing an intermediate member therebetween, for example, an annular seal mounted on the outer surface of the housing 50 and configured to tightly mate. the inner surface of the spark plug hole 44.

Furthermore, although FIG. 3 shows an illustrative configuration in which the mounting portion 56 includes the shoulder 88 formed on the outer surface of the housing 50 and the mounting sleeve 90 described above, it is It will be readily appreciated that in other embodiments the mounting portion may be configured as a male threaded portion that is formed on the housing 50 and engages a female threaded portion formed on the interior surface of the spark plug hole to mount the spark plug therein. so that the sealing portion 58 is tightly coupled to the inner surface of the plug hole 44 at the second contact interface 82. Obviously, in any of the aforementioned configurations, the heat transfer path from the center electrode 68 and grounding electrode 94 to the pre-chamber body 26, 28 or any other part of the engine in which the spark plug is mounted 30 may be shortened because the sealing portion 58 is arranged closer to the end 51 of the housing 50 than the mounting portion 56.

As shown in Fig. 3, in the illustrative embodiment, the first contact interface 80 is formed between a conical outer surface of the insulator 70 and a corresponding conical inner surface of the housing 50 between which a seal 87 is disposed. the spark plug 30 is assembled, the heat transfer between the insulator 70 and the housing 50 occurs mainly between the two aforementioned conical surfaces through the seal 87. Thus, the heat transfer from the center electrode 68 to the housing 50 also occurs primarily through the first contact interface 80. The heat that is transferred from the center electrode 68 to the housing 50 through the first contact interface 80 is then transferred to the second body 28 of the pre-chamber through the second contact interface 82 (see FIG. 2). The corresponding heat transfer path from the center electrode 68 is shown by a dashed line in Fig. 3.

Similarly, heat from grounding electrode 94 is also transferred to second prechamber body 28 from housing 50 through second contact interface 82, in particular through conical sealing surface 84 which is in thermal contact with a contact surface of the spark plug hole 44.

As shown in Fig. 3, in one embodiment, the at least one grounding electrode 94 may be configured as a plurality of linear electrodes 96 protruding from the housing 50 with respect to the longitudinal axis L, for example, at an angle between 0 ° and 15 °. Furthermore, in some embodiments, the plurality of linear electrodes 96, for example, three of said linear electrodes, may be arranged at equal intervals in the circumferential direction. The heat transfer path from the linear electrodes 96 to the second contact interface 82 is also shown by a dashed line in FIG. 3.

It will be appreciated that the configurations of grounding electrode 94 shown in the drawings are illustrative only and that any suitable configuration can be used for such grounding electrodes. Also, in some embodiments, the grounding electrodes 94 may be omitted. In particular, in some cases the housing 50 itself can serve as a "grounding electrode" to generate the spark to ignite the combustion in the pre-chamber 34. Obviously, in this case also the advantageous effect described above of the short trajectory can be obtained. heat transfer from the housing 50 to the second pre-chamber body 28 or to a corresponding part of the engine.

Fig. 3 also shows that, to increase the thermal insulation of the casing 50 from combustion within the pre-chamber 34, a protective element 98 may be provided which covers at least in part a front surface 53 of the casing 50 at the end 51 Of the same. In particular, the protective element 98 may be formed as a cover that covers the front surface 53 of the housing 50, for example, a plug-like element that is attached to the end 51 of the housing 50 so that the plurality of electrodes lines 96 and the center electrode 68 protrude therefrom. In accordance with the present invention, the shield element 98 is made of a material that has a lower thermal conductivity than the material that forms the housing 50. For example, the shield element 98 can be made of a material such as Inconel or ceramics to reduce additionally the amount of heat that is transferred from the side of the pre-chamber 34 to the housing 50. This further increases the amount of heat that can be transferred from the center electrode 68 and the plurality of linear electrodes 96 to the housing 50 and to the pre-chamber body 26, 28. On the other hand, the housing 50 can be formed of a material with a high thermal conductivity, for example, aluminum alloy and / or copper alloy.

According to some illustrative embodiments, the second contact interface 82 is disposed closer to the opening 54 than the first contact interface 80 or at substantially the same position along the longitudinal direction L. Thus, heat transfer from the housing 50 to the part of the engine in which the spark plug 30 is mounted can take place as close as possible to the end 51 of the housing 50 to minimize the length of the heat transfer path from the center electrode 68 and the at least a grounding electrode 94 to the part of the engine in which the spark plug 30 is mounted.

With the spark plug 30 according to the present disclosure, the heat transfer distances for at least the center electrode 68 and, if any, the grounding electrode 94, can be shortened to efficiently cool the electrodes. Furthermore, the mounting portion 56 of the housing 50 is isolated from the side of the pre-chamber 34 by the sealing portion 58 disposed therebetween. In particular, if a male threaded portion is formed on an outer surface of the housing 50 or the mounting sleeve 90, it will not be subjected to the heat generated by combustion in the pre-chamber 34. Furthermore, the housing 50 itself may be thermally insulated from pre-chamber 34 by providing shield element 98 to further enhance heat transfer from the electrodes.

Industrial applicability

Spark plug 30, as illustratively depicted herein, is particularly applicable to gaseous fuel internal combustion engines operating on a mixture of gaseous fuel and air. However, as one skilled in the art will appreciate, spark plug 30, as described herein, can also be used in other types and configurations of engines.

Generally, a gaseous fuel internal combustion engine for use with the teachings of the present disclosure comprises a plurality of cylinders and a plurality of pre-chamber assemblies. Each pre-chamber assembly comprises a pre-chamber body defining a pre-chamber, a fuel supply device housed in the pre-chamber body and configured to supply gaseous fuel to the pre-chamber, and a spark plug according to the present disclosure mounted in the hole formed in the pre-chamber. pre-chamber body and configured to ignite the gaseous fuel in the pre-chamber. The plurality of pre-chamber assemblies configured as described above are respectively mounted on the cylinder heads of the plurality of cylinders of the gaseous fuel internal combustion engine.

It should be mentioned that, although the embodiments have been described with respect to a spark plug provided in a pre-chamber assembly, in other embodiments the spark plug may also be incorporated into an engine that does not have a pre-chamber assembly. That is, the spark plug described herein can be mounted in a cylinder head of an internal combustion engine and can be arranged in a main combustion chamber of the engine. Furthermore, although the present embodiments have been described with respect to the combustion of gaseous fuel, it will be appreciated that different types of fuel may be used in some embodiments, for example liquid fuels and / or a mixture of gaseous fuel and / or liquid fuel.

Terms such as "about", "about", or "substantially" as used herein when referring to a measurable value such as a parameter, an amount, a time duration, and the like, are intended to encompass variations in ± 10% or less, preferably ± 5% or less, more preferably ± 1% or less, and still more preferably ± 0.1% or less of the specified value, insofar as such variations are suitable in the disclosed invention. It should be understood that the value referred to by the modifier "about" is preferably also concretely described. Specifying numeric ranges using extreme values includes all numbers and fractions included in the respective ranges, as well as the specified extreme values.

Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without leaving the scope of the claims that follow.

Claims (13)

i A spark plug (30) for an internal combustion engine (1), where the spark plug (30) comprises: a central electrode (68) extending along a longitudinal direction (L); an insulator (70) disposed around the center electrode (68); a housing (50) mounted on the insulator (70), the housing (50) being in thermal contact with the insulator (70) at a first contact interface (80) and having an opening (54) at one end (51) in the longitudinal direction (L) through which the central electrode (68) is exposed; a mounting portion (56) provided on an outer surface of the housing (50) and configured to removably mount the spark plug (30) in a spark plug hole (44) of the internal combustion engine (1); a sealing portion (58) provided on the outer surface of the housing (50) and configured to hermetically engage an inner surface of the spark plug hole (44) at a second contact interface (82) when the spark plug (30) is mounted in the spark plug hole (44), wherein the sealing part (58) is arranged between the mounting part (56) and the opening (54) in the longitudinal direction (L); characterized in that it also comprises a protective element (98) that covers, at least in part, a front surface (53) of the casing (50) at the end (51) thereof, wherein the protective element (98) is made of a material that has a lower thermal conductivity than the material that forms the housing (50), for example, Inconel and / or ceramic materials. The spark plug of claim 1, wherein the sealing portion (58) includes a conical sealing surface (84) configured to hermetically engage a contact sealing surface of the spark plug hole (44). The spark plug of claim 1 or 2, wherein the sealing portion (58) includes an annular seal mounted to the outer surface of the housing (50) and configured to tightly engage the inner surface of the hole (44) of the spark plug. The spark plug of any of claims 1 to 3, wherein the mounting portion (56) includes a shoulder (88) formed on the outer surface of the housing (50). The spark plug of claim 4, wherein the shoulder (88) is formed as a substantially annular edge on the housing (50). The spark plug of claim 4 or 5, further comprising a mounting sleeve (90) configured for mounting on the outer surface of the housing (50) to engage the shoulder (88) and biasing the housing (50) toward the end (51) in the longitudinal direction (L). The spark plug of claim 6, wherein the mounting sleeve (90) includes a male threaded portion (92) configured to mate with a female threaded portion formed on the inside surface of the spark plug hole (44) to mount the plug. spark plug (30) into the spark plug hole (44). The spark plug of any one of claims 1 to 3, wherein the mounting portion (56) includes a male threaded portion formed on the housing (50) and configured to engage a female threaded portion formed on the inner surface of the Spark plug hole (44) for mounting the spark plug (30) into the spark plug hole (44) so that the sealing portion (58) tightly engages the inner surface of the spark plug hole (44) at the second interface (82) contact. The spark plug of any preceding claim further comprising at least one grounding electrode (94) mounted to the end (51) of the housing (50) and arranged to face the center electrode (68), the at least one grounding electrode being configured to be in thermal contact with the inner surface of the spark plug hole (44) through the housing (50) and the second contact interface (82). The spark plug of claim 9, wherein the at least one grounding electrode (94) includes a plurality of linear electrodes (96) protruding from the housing (50) at an angle relative to the longitudinal direction ( L), for example, at an angle between 0 ° and 15 °. The spark plug of claim 10, wherein the plurality of linear electrodes (96), eg, three linear electrodes, are arranged at equal intervals in the circumferential direction. The spark plug of any one of the preceding claims, wherein the second contact interface (82) is disposed closer to the opening (54) than the first contact interface (80), or in substantially the same position as the first contact interface (80) in the longitudinal direction (L). 13. A pre-chamber unit (20) for an internal combustion engine (1) comprising: a pre-chamber body (26, 28) defining a pre-chamber (34); Y A spark plug (30) according to any of claims 1 to 12 mounted in a spark plug hole (44) formed in the pre-chamber body (26, 28) so that the sealing portion (58) of the spark plug (30) hermetically engages the inner surface of the spark plug hole (44) at the second contact interface (82).