AU2012220326A1

AU2012220326A1 - Spark plug having an end part

Info

Publication number: AU2012220326A1
Application number: AU2012220326A
Authority: AU
Inventors: Christian Francesconi
Original assignee: GE Jenbacher GmbH and Co OHG
Current assignee: Innio Jenbacher GmbH and Co OG
Priority date: 2011-02-21
Filing date: 2012-02-20
Publication date: 2013-09-26
Also published as: WO2012113002A1; AT511157A1; ES2611904T5; CA2826807A1; ES2611904T3; FI2678907T4; BR112013021147B1; EP2678907A1; EP2678907B1; EP2678907B2; AT511157B1; BR112013021147A2

Abstract

The present invention relates to a spark plug of an internal combustion engine, preferably for spark-ignition gas engines, comprising a spark plug housing (2) that surrounds an insulating body (1) and comprising a center electrode (3) and at least one ground electrode (4) borne by a ground electrode carrier (6), wherein the ignition surfaces (12) of the center electrode (3) and the ignition surface (26) of the ground electrode (4) are surrounded by a wall (8), which forms a chamber (5) open on the combustion chamber side or a pre-chamber (51) having passage openings (10). According to the invention, an end part (60) is attached to the end area of the spark plug housing (2) on the combustion chamber side, and the ground electrode carrier (6) and the wall (8) are borne by said end part (60).

Description

1 SPARK PLUG WITH END PART This invention relates to a spark plug according to the preamble of patent claim 1. 5 Such spark plugs are known from WO 2009/059339 Al. The object of the invention is to simplify manufacturing of such spark plugs, in particular in view of avoiding complex components which are complicated to make, and the spark plug consisting of parts that are easy to make. This is important in 0 particular for mass production. Moreover, the electrical properties of such spark plugs are to be at least equivalent to those of comparable spark plugs, or even exceed such properties. Consequently, optimal current conduction across the individual ground electrodes has to be provided. Finally, ignition L5 properties are to be improved, preferably by optimizing thermal conductivity and heat dissipation from the ignition surfaces in order to obtain better stability. In a spark plug of the type mentioned in the beginning, these objects are achieved by the features detailed in the 20 characterizing part of claim 1. The end part extends the spark plug housing and allows the electrode arrangement to be of a short and compact design. Heat dissipation from the electrodes, current distribution, resistance to corrosion and ignition reliability are therefore significantly improved. An essential 25 reason for this lies in the shorter overall height or in the proximity of the electrodes to the insulating body. It is advantageous if the ground electrode carrier, as seen perpendicularly to the longitudinal axis of the spark plug, has a smaller distance from the center electrode than the inner 30 surface of the wall of the chamber and carries at least one finger-shaped ground electrode with an ignition surface which lies at the height level of the ignition surface of the center electrode in the chamber, or if the ground electrode carrier, as seen perpendicularly to the longitudinal axis of the spark plug, 35 has a greater distance from the center electrode than the outer 2 surface of the wall of the chamber and supports at least one finger-shaped ground electrode which extends through a recess in the wall into the chamber, wherein the ignition surface of the ground electrode lies at the height level of the ignition 5 surface of the center electrode in the chamber. A compact electrode construction, which can be produced in a simple manner and can be installed on the end part, is thereby achieved. The arrangement of the ground electrodes on a separate carrier ensures a uniform current conduction over the ground 0 electrodes. Since the ground electrode carrier is arranged at a distance from the wall of the chamber, the ground electrodes and the ground electrode carrier represent a system which is independent with regard to the current and heat conduction from the wall of the chamber. This enables a simple readjustment of L5 the ground electrodes and the application-induced electrode consumption can be easily corrected. On account of the possibility of manufacturing the ground electrode carrier and the ground electrodes independently, especially as an integral component, and locating these on the end part, significant 20 production-related advantages ensue. Furthermore, as a result of the fact that the ground electrodes can be manufactured together with the ground electrode carrier as an integral component, and that a gap exists between the ground electrode carrier and the wall of the chamber, improved heat dissipation from the ignition 25 electrodes to the end part and to the spark plug housing is achieved. The special shape of the ground electrodes and their arrangement provide further advantages with regard to an improved ignition performance and screening or flow-through of the chamber, even if the height of the electrodes which are 30 arranged on the end part is smaller than in the case of comparable conventional spark plugs. An especially simple manufacture with a stable construction of the spark plug is achieved as a result of the special shape of the ground electrode carrier. The ground electrode carrier, 35 having a cylinder ring-shaped cross-section, can be adjusted in 3 a simple manner at a circumferentially constant distance from the outer surface of the wall of the chamber so that defined conditions with regard to combustion and current conduction are created. Furthermore, the construction and the installation of 5 the spark plug are simplified since the cylinder ring-shaped ground electrode carrier and also the chamber having a cylinder ring-shaped cross-section can be placed in a simple manner upon the end part and fastened there. This advantageous fastening is achieved if the ground electrode carrier and the wall are [0 supported by the end part which is arranged on the combustion chamber-side end region of the spark plug housing. The ground electrode carrier can be formed with a thread on its inner wall surface or else can have a smooth surface, the same applying to the wall of the chamber. Either the ground electrode carrier or 5 the wall of the chamber are screwed onto the respective projecting end shoulders of the end part and/or are fixed in their position by welding, or these components are slipped onto the end part, with a seating which is accurate as possible, and fixed in their desired position, especially by welding. 20 Provision can be made for the forming of two concentrically disposed cylindrical end shoulders on the end part, of which the inner end shoulder, if applicable, projects beyond the outer end shoulder in the direction of the combustion chamber, wherein the ground electrode carrier, together with the ground electrodes 25 which penetrate the walls, is placed, slipped or screwed on the outer end shoulder and/or fastened by means of spot or seam welding, as applicable, and the wall of the chamber is placed, slipped or screwed on the inner end shoulder and/or fastened by means of spot or seam welding, as applicable, or wherein the 30 wall of the chamber is placed, slipped or screwed on the outer end shoulder and/or fastened by means of spot or seam welding, as applicable, and the ground electrode carrier, which lies at a distance from the inner surface of the wall, is placed, slipped or screwed on the inner end shoulder and/or fastened by means of 35 spot or seam welding, as applicable.

4 It is advantageous if the end part is made integrally with the wall, wherein the ground electrode carrier is placed, slipped or screwed onto the end part and/or fastened by means of spot or seam welding, as applicable, or if the end part is made 5 integrally with the ground electrode carrier, wherein the wall, which encompasses the ground electrode carrier at a distance, is placed, slipped or screwed onto the end part and/or fastened by means of spot or seam welding, as applicable. In this way, the production of the spark plug is simplified L0 and the spark plug housing is extended with the same overall length of the spark plug. With the same overall length of the spark plug, better heat dissipation from the ground electrode and from the wall into the spark plug housing ensues and the risk of spontaneous ignitions is reduced. 5 In principle, the ground electrode carrier could additionally also be fastened on the combustion chamber-side end region of the spark plug housing. Advantages in relation to production ensue if the ground electrode carrier, as seen perpendicularly to the longitudinal 20 axis of the spark plug, has in section at least partially circular cross-section or is formed by a cylinder ring and/or if the at least one ground electrode and the ground electrode carrier are made integrally or are interconnected by welding. With regard to the heat resistance of the spark plug, it is 25 advantageous if through-openings are formed in the wall for passage of the combustion gas. For the function of the spark plug, advantages ensue if the ground electrode carrier supports one, three, or five ground electrodes, and/or if the ground electrodes are arranged on the 30 ground electrode carrier in a distributed manner around the center electrode at equal distances from each other, and/or if each of the ground electrodes, which project from the ground electrode carrier, has a rectangular or cylinder ring segment like cross-section, at least in partial regions of the 35 longitudinal extension thereof and/or if the spark gap is formed 5 between surface areas of the ground electrode and of the center electrode which extend parallel to the longitudinal axis and lie opposite one another. A simple construction ensues if a male thread is formed in 5 each case on the two concentrically disposed end shoulders of the end part and if a female thread, matched to the respective male thread, is formed in each case on the inner wall surface of the wall and/or on the inner wall surface of the ground electrode carrier and/or if the ground electrode carrier and the 0 cylinder ring-shaped wall are arranged concentrically to each other, forming the pre-specified gap and possibly a height offset, and/or if the cylindrical wall and/or the ground electrode carrier is slipped on the respective end shoulder and fastened there by welding. 5 For the construction of the spark plug, especially with regard to current thermal conductivity and heat thermal conductivity or heat dissipation, it is advantageous if a number of preferably parallel extending slots, extending in parallel to the direction of the longitudinal axis of the spark plug, are 20 formed in the wall, through which slots the ground electrodes are guided into the interior of the chamber, wherein the slots, if necessary, extend from the combustion chamber-side end face of the wall up to the level region of the end face of the end part. 25 If the ground electrodes are located outside the wall and project through the longitudinal slots into the chamber which is bounded by the wall, the ground electrodes have a screening effect and a certain desired circulation of the gas can be maintained between the ground electrodes and the adjacent slot 30 surfaces, contributing to the cooling of the electrodes. As a result, an excessive accumulation of heat is avoided and spontaneous combustions are counteracted. In the case of the spark plug according to the invention, it is a special embodiment of a screened spark plug.

6 It is advantageous for ignition and heat dissipation if a ignition surface carrier, which is preferably guided radially through the slot into the interior of the chamber, projects from the portion which extends parallel to, and outside of, the wall 5 and/or if a connecting piece, which preferably extends parallel to the direction of the longitudinal axis of the spark plug, follows the circumferential extent of the wall and partially closes off the slot or is at least partially arranged in the slot space, projects from the ignition surface carrier in the L0 direction of the combustion chamber and, if applicable, terminates there in the same plane with the end face of the wall and/or if the portion of the ground electrode which projects from the ground electrode carrier is located outside the circumferential region of the wall in front of the slot. The L5 wall being thus exposed, it can be better cooled by the gas to be combusted. In a preferred embodiment, provision is made for the center electrode to have a number of radially outwardly projecting, preferably centrally symmetrically formed, electrodes which in 20 their respective end region have an ignition surface, opposite which in each case lies an ignition surface of a ground electrode. A simplified production and exact ignition performance ensue if an encompassing annular groove, which adjoins the insulation-side end of the ignition surfaces of the 25 center electrode, is formed on this center electrode. An advantageous embodiment of the end part provides that the end part, which is placed upon the end region of the spark plug housing, is of a rotationally symmetrical, preferably cylinder ring-shaped, design and is arranged centrally to the 30 longitudinal axis of the spark plug and extends the spark plug housing on the combustion chamber side in form of an intermediate piece and/or that the end part, by its combustion chamber-side end region, encompasses the base portion of the center electrode.

7 A constructionally simpler and operationally more reliable construction ensues if the end part is connected to the spark plug housing by welding and/or screwing, and/or if the end part encompasses the base of the center electrode and the insulating 5 body, forming a gap. Fig. 1 shows a schematic longitudinal section through an embodiment of a spark plug according to the invention. Figs. 2a and 2b shows embodiments of a center electrode. Fig. 3 shows a perspective view of a spark plug according to the invention. L0 Fig. 4a shows a possible embodiment of a spark plug without an end part. Fig. 4b shows an embodiment of a spark plug with a placed attached end part. Fig. 4c shows a spark plug according to the invention with a placed end part which is constructed integrally with the wall of the chamber, wherein the ground L5 electrode carrier is welded on this end part. Figs. 5 and 6 show embodiments of spark plugs in which the ground electrodes or the ground electrode carrier are, or is, located inside the wall on an end part or are connected to the end part integrally. Figs. 7 to 9 show embodiments of spark plugs with an end part which is 20 placed on the spark plug housing and with a pre-chamber encompassing electrodes. Figs. 10 and 11 show a spark plug with an annular sleeve which is arranged between the end part and the pre-chamber. Hereafter, the invention will be explained more in detail 25 by way of example with reference to the drawing. Fig. 1 shows a spark plug for use in an internal combustion engine, especially for a spark ignition gas engine. A spark plug housing 2 is supported by an insulating body 1, wherein a center electrode base 3a is enclosed by, or projects from, the 30 insulating body 1. Placed on this center electrode 3a base of the spark plug is the center electrode 3 which has at least one ignition surface 12. The ignition surfaces 12 lie on discharging projections of the center electrode 3. For the forming of at least one spark gap 12, provision is 35 made for at least one ground electrode 4 which is supported by a 8 ground electrode carrier 6. The ground electrodes 4 are advantageously arranged on the ground electrode carrier 6 in a distributed manner around the center electrode 3 at equal distances from each other. The ground electrode carrier 6 is 5 supported on an end part 60, which is placed upon the spark plug housing 2, or is fastened on this end part. As is apparent from Fig. 1, the ground electrodes 4 project in each case from the ground electrode carrier 6 in the form of a finger with a portion 41 and are fastened, preferably welded, 0 on the carrier 6. The ground electrode 4 and the carrier 6 can be constructed as an integral component, if applicable. The combustion chamber-side end region or the ignition surface 26 of the ground electrode 4 lie on an ignition surface carrier 51 and extend parallel to the longitudinal axis A of the spark plug or L5 parallel to the facing ignition surface 12 of the center electrode 3. The spark gap 13 is formed between the oppositely disposed ignition surfaces 26, 12 of the ground electrode 4 and of the center electrode 3. These ignition surfaces 26, 12 can preferably be coated with noble metal or noble metal alloys in 20 the form of strips or small plates. For the fastening of the ground electrode carrier 6 on the end part 60, provision is made for the end part 60 to have two concentrically located, cylindrical end shoulders 17, 18, of which the inner end shoulder 17 projects beyond the outer end 25 shoulder 18 in the direction of the combustion chamber. The ground electrode carrier 6 is placed, slipped, or screwed on the outer end shoulder 18 and/or, if applicable, fastened by welding, especially spot or seam welding, and a wall 8, which forms a chamber 5 which is open on the combustion chamber side, 30 is placed, slipped or screwed on the inner end shoulder 17 and/or, if applicable, fastened by welding, especially spot or seam welding. The internal dimensions of the wall 8 and of the ground electrode carrier 6 are matched to the respective external dimensions of the end shoulders 17, 18. The wall 8 35 forms a screen or shield or an open chamber and the spark plug 9 according to the invention can also be referred to as a screened spark plug. The ground electrode carrier 6, and especially also the portion 41, of each of the ground electrodes 4 which project 5 from the ground electrode carrier 6 are arranged at a distance from the outer surface 7 of the wall 8 of the chamber 5, possibly offset downwards in the direction of the spark plug housing 2 in relation to the center electrode 3. This distance is provided in order to ensure a defined or uninfluenced current 0 flow in the ground electrode carrier 6. Furthermore, as a result of the distance 21, as already explained above, a distinct or defined heat dissipation from the ground electrodes 4 to the spark plug housing 2 is made possible. Shown in Fig. 1 is a spark plug with a cylinder ring-like 5 wall 8 which circumferentially encompasses the center electrode 3. Variations of the shape of such walls or chambers can also be provided. A simple construction and a simple production of the parts ensue if the wall 8 of the whirl chamber 5, which is open on the 20 combustion chamber side, and the ground electrode carrier 6 have, at least locally, a circular cross-section, or are formed in each case by a cylinder ring. Through-openings 10 can be formed in the wall 8 for passage of the gas. 25 Each finger-shaped ground electrode 4 is advantageously offset from the ground electrode carrier 6 towards the center electrode 3 in the form of an ignition surface carrier 51, forming a portion 41 extending in parallel to the wall 8, and terminates in front of the center electrode 3. To this end, 30 slots 50 are formed in the wall 8. The width of these slots 50 basically corresponds to the width of the portion 41 or slightly exceeds this width. These slots 50 basically extend over the entire height of the wall 8, that is to say they extend especially from a region of the wall 8 which lies approximately 35 at the level of the end face of the end part 60 and terminate on 10 the combustion chamber-side end face of the wall 8. The offset radially extending ignition surface carrier 51 of the ground electrode 4 extends through this slot 50 in the direction of the center electrode 3. A connecting piece 52, which extends 5 parallel to, or in the direction of, the longitudinal axis A of the spark plug, adjoins the ignition surface carrier 51 which extends from the portion 41 radially through the slot 50 into the interior of the chamber 5. The connecting piece 52 follows the circumferential extent of the wall 8 and in this region at L0 least partially closes off the slot 50 or lies preferably inside the slot 50. This connecting piece 52 projects from the ignition surface carrier 51 in the direction of the combustion chamber and terminates with the end face of the wall 8 and contributes to controlled gas circulation. 5 As is apparent from Figs. 2 and 3, the center electrode 3 has three centrally symmetrically arranged ignition surfaces 12, opposite which in each case lies an ignition surface 26 of a ground electrode 4. Adjacent strips 40 consisting of a noble metal alloy can be 20 applied to or fused onto the radially outwardly pointing surface areas 12 of the center electrode 2 and/or onto the surfaces 26 of the respectively opposite ground electrodes 4 which face the center electrode 3. Instead of directly applied or fused on noble metal alloy strips 40 according to Fig. 2a, the noble 25 metal alloy can also be applied to or welded onto or fused onto projecting regions 48 of the cylindrical part of the center electrode 3 in the form of small noble metal plates 40', which regions 48 are formed by projections which are welded on or molded on integrally. Such raised regions 48 can also be formed 30 on or attached to the ground electrodes 4 and to which, or onto which, noble metal alloy, possibly in the form of small noble metal plates, is applied, or welded or fused. On the side of the ignition surfaces 12 which is remote from the combustion chamber or directly beneath the projections 48 of the center electrode 35 3, an encompassing annular groove 61 can be formed. This annular 11 groove 61 represents a defined boundary of the ignition surfaces 12 and makes the welding on and application of small noble metal plates and/or strips 40, 40' easier. The wall 8 of the chamber 5 and/or the ground electrodes 4 5 and/or the ground electrode carrier 6 are manufactured from nickel-based alloy and/or high-temperature high-grade steel and/or hot corrosion resistant metal alloys with good thermal conductivity. The wall 8 can also be manufactured from brass. For the production and the operation of the spark plugs, it 0 has proved to be advantageous if the number of ground electrodes 4 is uneven or if the ground electrodes 4 do not lie opposite each other with regard to the center axis of the center electrode 3. As a result, the application of noble metal alloys upon the ground electrodes 4 which project from the carrier 6 5 becomes possible in a simple manner. The slot 50 which is provided makes necessary maintenance operations or readjustments easier. The ground electrode carrier 6 and the wall 8 of the chamber 5 are connected in an electrically conducting manner to 20 the spark plug housing 2. The center electrode 3 is connected to the center electrode base 3a of the spark plug, preferably by welding. The center electrode base 3a is guided in the insulating body 1 and is electrically insulated towards the spark plug housing 2 by means of the insulating body 1. 25 The ground electrodes 4 are designed in such a way that the portion 41 extends basically in a straight line and parallel to the wall 8 without deflection and preferably has a constant cross-sectional shape over this longitudinal extent. The transition from the ground electrode carrier 6 to the portion 41 30 can extend in a rounded manner. Shown in Fig. 4a is a known spark plug. The length of the spark plug housing 2 is represented by L, wherein on the combustion chamber-side end region of the spark plug 2 the ground electrode carrier 6 and the wall 8 are mounted, or 35 fastened, especially by welding, on corresponding shoulders 17, 12 18 of the spark plug housing 2. In the case of the spark plug according to the invention according to Fig. 4b, the end part 60, in the form of an intermediate ring, is placed, for example slipped or screwed and, if applicable, fastened by means of spot 5 or seam welding, on the combustion chamber-side end region of the spark plug housing 2. This end part 60 serves for extending the spark plug housing 2. This end part 60 supports a shoulder 18 on which the ground electrode carrier 6 is fastened and/or welded and furthermore supports a shoulder 17 which supports the L0 wall 8. Resulting from this, therefore, is a length Li of the spark plug housing 2 and placed end part 60 which is greater that the length L. As a result, the parts which are required for the ignition, specifically the ground electrode 4 and the wall 8, can be of shorter design and the distance B between the wall 5 8 and the stem or portion 41 of the ground electrode can be of longer design. As a result, heat dissipation and ignition reliability are improved. In the case of the embodiment of the spark plug according to Fig. 4c, the wall 8 is made integrally with the end part 60, 20 which is fastened on the combustion chamber-side end region of the spark plug housing 2. A shoulder 64, on which the end part 60 is placed, screwed and, if applicable, fastened by means of seam welding or spot welding, can be formed on the spark plug housing. The ground electrode carrier 6 is placed, especially 25 welded, on the end part 60. The ground electrode carrier 6 can be placed on a shoulder 18 of the end part 60 and fastened there by welding. The dark arrows, which are directed towards the longitudinal axis A of the spark plug, represent possible weld 30 seams or weld spots with which the end part 60 and/or the ground electrode carrier 6 and/or the wall 8 can be welded to the respective components which support them. The spark plug which is shown in Figs. 5 and 6 basically has the same construction as the spark plugs which are shown in 35 the other figures except for the modification that the ground 13 electrodes 4 or the ground electrode carrier 6 are to be located inside the wall 8, in fact at a distance from the inner surface 19 of the wall 8 in the direction of the center electrode 3. A spark plug housing 2 is supported by the insulating body 1, 5 wherein a center electrode base 3a, upon which the center electrode 3 is placed, projects from the insulating body 1. The ground electrodes 4, which are arranged around the center electrode 3, are supported by a ground electrode carrier 6 which is placed on an end shoulder 17 of the end part 60 and, if L0 applicable, is fastened thereto by welding. The wall 8 is placed on a further shoulder 18 and, if applicable, is fastened by welding. The ground electrode carrier 6 and the ground electrodes 4 lie at a distance D away from the inner surface 19 of the wall 8. As a result, a current-wise and heat dissipation 5 wise separation of the ground electrodes 4 from the wall 8 ensues and the heat can be satisfactorily dissipated via the end part 60 or an exact and reliable current conduction can be carried out via the end part 60. As shown in Fig. 6, the ground electrodes 4 can also 20 project from a ground electrode carrier 6 which is made integrally with the end part 60. In this case, the wall 8 is placed upon the end part 60 upon the shoulder 18 and, if necessary, fastened there by welding. Also in the case of this embodiment, an electrode arrangement of shorter construction is 25 achieved, with which the conduction of heat and current is favorably influenced. Also in this case, the end part 60 encompasses the combustion chamber-side end region of the insulating body 1 and/or the base part of the electrode 3 which is remote from the combustion chamber. As a result of the one 30 piece design of the end part 60 and the ground electrode carrier 6, or with the ground electrodes 4, a simplified production of the spark plug ensues since only the wall 8 needs to be placed on and, if applicable, welded onto the one-piece component which is formed by the ground electrodes 4 and the end part 60.

14 It is also possible to provide other types of fastening for the end part 60 on the spark plug housing 2 or for the wall 8 and/or the ground electrode carrier on the end part 60 and/or on the spark plug housing 2, for example by pressing. In any case, 5 the end part 60 is not placed upon the tapering insulating body. The parts are necessarily spaced apart for insulation reasons. The end part 60 encompasses the end region of the insulating body 1 at a distance. By one piece, it is primarily to be understood that the 0 respective component, or components, does not have, or do not have, a welded or soldered connection and is, or are, formed from the same material, or exists, or exist, as a single non assembled part or is, or are, formed from the same component. Spark plugs with open chambers 5 are shown in Figs. 1 to 6. L5 Spark plugs with pre-chambers 5' are shown in Figs. 7 to 9. The number of through-openings 10 which are formed in the chambers 5 and pre-chambers 5' and their shape or position, is selectable or is determined by the application of the spark plug. Shown in Fig. 7 is an embodiment of a spark plug according 20 to the invention, in which the ground electrode carrier 6, as in Fig. 6, is made integrally with the end part 60. The end face of the end part 60 which is remote from the combustion chamber is placed on a shoulder 61 of the spark plug housing 2. In particular, this region of the end part 60, as represented by 55 25 in Fig. 8, can be welded to the spark plug housing 2. On its outer circumference the spark plug housing 2 carries a thread 51 by means of which is can be screwed into an engine block. It is provided that the end part 60 has an annular shape and by the inner surface of its end region which is remote from the 30 combustion chamber and/or by its end face which is remote from the combustion chamber is connected to the spark plug housing 2 or is placed upon this, preferably upon a shoulder 61. Furthermore, it can be provided that the end region of the end part 60 which is remote from the combustion chamber externally 35 encompasses an end region 64 of the spark plug housing 2 which 15 is close to the combustion chamber, or is connected to its outer wall surface, forming a gap 56, if necessary. The annular gap 56 can be formed between the end region 56 of the spark plug housing 2 and the end region of the end part which is remote 5 from the combustion chamber. The insulating body 1, which encompasses the center electrode base 3a and supports the electrode arrangement 3 or the individual electrodes of the center electrode 3, is inserted into the spark plug housing 2 using a seal 52. L0 The end part 60, by means of a shoulder 58, supports the wall 8 of a pre-chamber 5' which covers the electrodes, i.e. the center electrode 3 and the ground electrodes 4 and also the ground electrode carrier 6. Corresponding through-openings 10 are formed in the pre-chamber 5'. 5 A gap 53 is recessed in each case between the ground electrodes 6 which project from the end part 60 and the inner surface of the wall 8 so that the current distribution and heat dissipation are defined. It is furthermore provided that the ground electrode 20 carriers 6 project from the end part 60 in the region, or at the level, in which or at which the end face of the wall 8 which is remote from the combustion chamber is connected to the end part 60 or at which the shoulder 58 lies. The center electrode 3 is designed in such a way that the 25 combustion chamber-side end of the center electrode 3 terminates with the end of the center electrode base 3a or does not project beyond the combustion chamber-side end of the center electrode base 3a or that the electrodes 4 and/or ignition plates 24 which are supported by the center electrode 3 and/or the electrodes 4 30 and/or ignition plates 24 which are supported by the ground electrodes 6 do not project beyond the combustion chamber-side end of the center electrode base 3a on the combustion chamber side. As a result, a short, compact design of the electrodes is achieved, with which the heat transfers and current distribution 35 are advantageously influenced.

16 Shown in an embodiment of a pre-chamber spark plug according to Fig. 8 are weld seams 55 which are to be advantageously applied and with which the spark plug housing 2 can be connected to the end part 60 or with which the end part 5 60 can be connected to the wall 8 of the pre-chamber 5' . Such weld seams 55 can also be used in order to connect the center electrode 3 to the center electrode base 3a. In principle, the gap 53 could even be omitted or the inner surface of the wall 8 could bear against the outwardly 0 orientated surface of the ground electrode carrier 6 or be connected to this. The forming of a gap 53, however, brings defined heat and current conditions. Shown in Fig. 9 is a pre-chamber spark plug in which the chamber 5' has a different shape from the chamber 5' of the L5 spark plugs according to Figs. 7 and 8. In comparison to Fig. 8, the electrode arrangement 3 does not additionally project beyond the electrode base 3a on the combustion chamber side, as is the case with the spark plug according to Fig. 8. It is apparent in the case of the spark plug according to Fig. 8 that 20 the end part 60 has a greater height than the end part 60 of the spark plugs which are shown in Figs. 7 and 9. In Fig. 8, the center electrode 3 projects beyond the center electrode base 3a so that the result is a higher electrode construction or a higher construction of the end part 60 with the ground electrode 25 carriers 6 which are supported by it. Figs. 10 and 11 show a spark plug in which the spark plug housing 2 is extended on the combustion chamber side by a sleeve 70 which supports the pre-chamber 5'. Fig. 10 shows a spark plug in which the pre-chamber 5' is 30 not supported directly by the spark plug housing 2 but supported indirectly by using, or applying, an intermediate piece 70. This intermediate piece 70 is connected to the outer wall of the spark plug housing 2, or is supported by this, and the combustion chamber-side end region of the intermediate piece 70 17 supports the pre-chamber 5', or is connected to the wall 8 of the pre-chamber 5', for example by welding. For the production of such a spark plug, a thread, which possibly exists on the spark plug housing 2, can be turned out 5 and the cylindrical intermediate piece can be fitted onto the thereby prepared spark plug housing 2 and be fastened by welding, especially spot welding or laser welding. As is apparent from Figs. 10 and 11, it is provided that the combustion chamber-side end region of the intermediate piece 70 0 encompasses the electrodes of the spark plug or the center electrode base 3a and also the insulating body 1. It is advantageous in this case if a gap 53 is recessed between the intermediate piece 70 and the ground electrode carrier 6 in order to realize the heat dissipation and the current flow in a L5 defined manner. The seating of the intermediate piece 70 upon the spark plug housing 2 is carried out after installing the electrodes on the center electrode base 3a and after installing the end part 60 together with the ground electrode carrier 6 on the spark plug housing 2. 20 The thread 51 which is formed on the outer wall surface of the intermediate piece 70 is designed in such a way that the spark plug can be screwed into an engine block. The intermediate piece 70 can be placed upon a shoulder 71 of the spark plug housing 2 or located upon this. To this end, a 25 shoulder base 72 is formed on the intermediate piece 70 and can also serve as a carrier for a sealing ring 74 which is provided if necessary. A seal 52 is provided between the spark plug housing 2 and the insulating body 1. Furthermore, seating of the insulating body or of the spark plug housing 2, or the 30 connecting of these two components, is carried out via a socket component 73. The pre-chamber 5' does not project beyond the intermediate piece 70, as seen radially to the longitudinal axis of the spark plug. Furthermore, the wall 8 of the pre-chamber 5' is 35 advantageously free of a thread.

18

Claims

1. A spark plug of an internal combustion engine, preferably for spark-ignition gas engines, having a spark plug 5 housing (2), which encompasses an insulating body (1), and also a center electrode (3) and at least one ground electrode (4) which is supported by a ground electrode carrier (6), wherein the ignition surfaces (12) of the center electrode (3) and the ignition surface (26) of the ground electrode (4) are L0 encompassed by a wall (8) which forms a chamber (5) which is open on the combustion chamber side, or a pre-chamber (5') which has through-openings (10), characterized in that an end part (60) is placed on the combustion chamber-side end region of the spark plug housing (2) and in that the ground electrode carrier L5 (6) and the wall (8) are supported by this end part (60).

2. The spark plug according to claim 1, characterized in that - the ground electrode carrier (6), as seen perpendicularly to the longitudinal axis (A) of the spark plug 20 (2), has a smaller distance from the center electrode (3) than the inner surface (19) of the wall (8) of the chamber (5) or of the pre-chamber (5') and supports at least one finger-shaped ground electrode (4) with an ignition surface (26) which lies preferably at the height level of the ignition surface (12) of 25 the center electrode (3) in the chamber (5) or in the pre chamber, or - in that the ground electrode carrier (6), as seen perpendicularly to the longitudinal axis (A) of the spark plug (2), has a greater distance from the center electrode (3) than 30 the outer surface (7) of the wall (8) of the chamber (5) or of the pre-chamber (5') and supports at least one finger-shaped ground electrode (4) which extends through a recess (50) in the wall (8) into the chamber (5) or into the pre-chamber, wherein the ignition surface (26) of the ground electrode (4) lies 35 preferably at the height level of the ignition surface (12) of 20 the center electrode (3) in the chamber (5) or in the pre chamber (5').

3. The spark plug according to claim 1 or 2, characterized in that two concentrically disposed cylindrical end shoulders 5 (17, 18) are formed on the end part (60), of which the inner end shoulder (17), if applicable, possibly projects beyond the outer end shoulder (18) in the direction of the combustion chamber, wherein the ground electrode carrier (6), with the ground electrodes (4) which penetrate the wall (8), is placed, slipped 0 or screwed on the outer end shoulder (18) and/or fastened by means of spot or seam welding, as applicable, and the wall (8) of the chamber (5) or of the pre-chamber (5') is placed, slipped or screwed on the inner end shoulder (17) and/or fastened by means of spot or seam welding, as applicable, or wherein the L5 wall (8) of the chamber (5) or of the pre-chamber (5') is placed, slipped or screwed on the outer end shoulder (18) and/or fastened by means of spot or seam welding, as applicable, and the ground electrode carrier (6), which lies at a distance from the inner surface (19) of the wall (8), is placed, slipped or 20 screwed on the inner end shoulder (17) and/or fastened by means of spot or seam welding, as applicable.

4. The spark plug according to any of claims 1 to 3, characterized in that the end part (60) is made integrally with the wall (8), wherein the ground electrode carrier (6), which is 25 located outside the wall (8), is placed, slipped or screwed onto the end part (6) and/or fastened by means of spot or seam welding, as applicable, or in that the end part (60) is made integrally with the ground electrode carrier (6), wherein the wall (8) which encompasses the ground electrode carrier (6) at a 30 distance is placed, slipped or screwed onto the end part (60) and/or fastened by means of spot or seam welding, as applicable.

5. The spark plug according to any of claims 1 to 4, characterized in that the base of the wall (8), which lies close to the spark plug housing (2) and is penetrated by the ground 35 electrodes (4), lies closer to the combustion chamber-side end 21 of the spark plug than the ground electrode carrier (6), or in that the base of the ground electrode carrier (6) which faces the spark plug housing (2) lies further from the combustion chamber-side end of the spark plug than the base of the wall (8) 5 which encompasses the ground electrode carrier (6).

6. The spark plug according to any of claims 1 to 5, characterized in that the ground electrode carrier (6) and/or the wall (8), as seen in section perpendicularly to the longitudinal axis (A) of the spark plug, has/have an at least 0 partially circular cross-section or is/are formed by a cylinder ring.

7. The spark plug according to any of claims 1 to 6, characterized in that the at least one ground electrode (4) and the ground electrode carrier (6) are made integrally or are L5 interconnected by welding.

8. The spark plug according to any of claims 1 to 7, characterized in that through-openings (10) are formed in the wall (8) for passage of the combustible gas.

9. The spark plug according to any of claims 1 to 8, 20 characterized in that the ground electrode carrier (6) supports one, three or five ground electrodes (4) and/or in that the ground electrodes (4) are arranged on the ground electrode carrier (6) in a distributed manner around the center electrode (3) at equal distances from each other and/or in that each of 25 the ground electrodes (4) which project from the ground electrode carrier (6) has in one section (41) a rectangular cross-section or cylinder ring segment-like cross-section, at least in partial regions of the longitudinal extension thereof.

10. The spark plug according to any of claims 1 to 9, 30 characterized in that the spark gap (13) is formed between surface areas of the ground electrode (4) and of the center electrode (3) which extend parallel to the longitudinal axis (A), are disposed opposite one another, form the ignition surfaces (12, 26) and, if applicable, have a noble metal or 35 noble metal alloy coating. 22

11. The spark plug according to any of claims 1 to 10, characterized in that a male thread is formed in each case on the two concentrically disposed end shoulders (17, 18) of the end part (60) and a female thread, which is matched to the 5 respective male thread, is formed in each case on the inner wall surface (19) of the wall (8) and on the inner wall surface (20) of the ground electrode carrier (6) and/or in that the ground electrode carrier (6) and the wall (8) are arranged concentrically to each other, forming a pre-specified radial gap L0 (21) and possibly a height offset and/or in that the wall (8) and/or the ground electrode carrier (6) is slipped on the respective end shoulder (17, 18) and fastened there by welding.

12. The spark plug according to any of claims 1 to 11, characterized in that a number of slots (50), which extend L5 parallel to the direction of the longitudinal axis (A) of the spark plug, are formed in the wall (8), through which slots the ground electrodes (4) are guided into the interior of the chamber (5) or of the pre-chamber (5'), wherein the slots (50), if applicable, extend from the combustion chamber-side end face 20 of the wall (8) up to the level region of the end face of the end section (17) or up to the end face level of the end part (60).

13. The spark plug according to any of claims 1 to 12, characterized in that the section (41) of the respective ground 25 electrode (4) which projects from the ground electrode carrier (6) is located outside the circumferential region of the wall (8) in the region which lies in front of the respective slot (50) and/or is orientated parallel to the longitudinal axis (A) of the spark plug. 30

14. The spark plug according to any of claims 1 to 13, characterized in that an ignition surface carrier (51), which leads preferably radially through the slot (50) into the interior of the chamber (5) and supports welded on or fused on small noble metal plates or small noble metal alloy plates, 23 projects from the section (41) of the ground electrode (4) which extends preferably parallel to, and outside of, the wall (8).

15. The spark plug according to any of claims 1 to 14, characterized in that a connecting piece (52), which preferably 5 extends parallel to the direction of the longitudinal axis (A), follows the circumferential extent of the wall (8) and partially closes off the slot (50) or at least partially extends in the slot (50), projects from the section (41), especially from the ignition surface carrier (51), in the direction of the 0 combustion chamber and, if applicable, terminates in the same plane with the end face of the wall (8).

16. The spark plug according to any of claims 1 to 15, characterized in that the center electrode (3) has a number of radially outwardly projecting, preferably centrally 5 symmetrically formed, electrodes which in their respective end region have an ignition surface (12) which in each case lies opposite an ignition surface (26) of a ground electrode (4), wherein the ignition surfaces, if applicable, support welded on or fused on small noble metal plates or small noble metal alloy 20 plates.

17. The spark plug according to claim 16, characterized in that an encompassing annular groove (61), which adjoins the insulated end region of the ignition surfaces (12) of the center electrode (3), is formed in said center electrode (3). 25

18. The spark plug according to any of claims 1 to 17, characterized in that the end part (60), which is placed on the end region of the spark plug housing (2), preferably encompassing this, is designed in the form of a rotationally symmetrical cap or in the form of a cylinder ring and is 30 arranged centrally to the longitudinal axis (A) of the spark plug and extends the spark plug housing (2) on the combustion chamber side in form of an extension piece or intermediate piece.

19. The spark plug according to any of claims 1 to 18, 35 characterized in that the end part (60), by its combustion 24 chamber-side end region, encompasses the base section of the center electrode (3) which is remote from the combustion chamber, forming a gap.

20. The spark plug according to any of claims 1 to 19, 5 characterized in that the end part (60) is connected to the spark plug housing (2) and/or to the wall (8) by welding and/or screwing.

21. The spark plug according to any of claims 1 to 20, characterized in that the end part (60) encompasses the base of 0 the center electrode (3) and/or the combustion chamber-side, preferably tapering, end region of the insulating body (1), forming a gap (63).

22. The spark plug according to any of claims 1 to 21, characterized in that the end part (60) has an annular shape and 5 by the inner surface of its end region which is remote from the combustion chamber and/or by its end face which is remote from the combustion chamber, is connected to the spark plug housing (2) or is placed upon this, preferably upon a shoulder (61).

23. The spark plug according to any of claims 1 to 22, 20 characterized in that the end region of the end part (60) which is remote from the combustion chamber externally encompasses an end region (64) of the spark plug housing (2) which is close to the combustion chamber, forming a gap (56), if applicable, or is connected to its outer wall surface. 25

24. The spark plug according to any of claims 1 to 23, characterized in that the end face of the wall (8) which is remote from the combustion chamber is placed upon the end part (60), preferably upon the shoulder (58), and is connected to this, preferably by welding. 30

25. The spark plug according to any of claims 1 to 24, characterized in that the ground electrode carrier (6) is made integrally with the end part (60) and/or in that the ground electrode carrier (6) projects from the end part (60) in the region of the height or a level at which the end face of the 25 wall (8) which is remote from the combustion chamber is connected to the end part (60).

26. The spark plug according to any of claims 1 to 25, characterized in that the wall (8) encompasses the ground 5 electrode carrier (6) at a distance, forming a gap (53).

27. The spark plug according to any of claims 1 to 26, characterized in that the combustion chamber-side end of the center electrode (3) terminates at the level of the end of the center electrode base (3a) or does not project beyond the 0 combustion chamber-side end of the center electrode base (3a).

28. The spark plug according to any of claims 1 to 27, characterized in that the electrodes (4) and/or small ignition plates (24) which are supported by the center electrode (3) and/or by the ground electrode carrier (6) do not project beyond 5 the combustion chamber-side end of the center electrode base (3a) on the combustion chamber side.

29. The spark plug according to any of claims 1 to 28, characterized in that a sleeve-like intermediate piece (70) is arranged between the pre-chamber (5') and the spark plug housing 20 (2) and is supported by the spark plug housing (2) or is placed upon this and/or connected to this, for example by welding, wherein the intermediate piece (70) supports the pre-chamber (5') or its wall (8), or the pre-chamber (5') is placed by its wall (8) upon the intermediate piece (70) and/or is connected to 25 this, for example by welding.

30. The spark plug according to any of claims 1 to 29, characterized in that the intermediate piece (70) is formed by a cylindrical sleeve which is slipped onto the spark plug housing (2) and fixed in the slipped-on position or fastened on the 30 spark plug housing (2), for example by welding.

31. The spark plug according to any of claims 1 to 30, characterized in that the intermediate piece (70) encompasses at least the combustion chamber-side end region of the spark plug housing (2) and of the insulating body (1) and of the center 35 electrode base (3). 26

32. The spark plug according to any of claims 1 to 31, characterized in that the outer wall of the spark plug housing (2) is thread-free or turned.

33. The spark plug according to any of claims 1 to 32, 5 characterized in that the inner wall surface of the intermediate piece (2) is separated from the ground electrode carrier (6) by means of a gap (53).

34. The spark plug according to any of claims 1 to 33, characterized in that the outer surface of the intermediate L0 piece (70) is provided with a thread (51) by means of which the spark plug can be screwed into an engine block.

35. The spark plug according to any of claims 1 to 34, characterized in that combustion chamber-side end region of the intermediate piece (70) projects beyond the electrodes and also L5 the center electrode (3) and the ground electrodes (4) and the center electrode base (3a) in the direction of the combustion chamber.

36. An intermediate piece according to any of claims 1 to 35, characterized in that the wall (8) of the pre-chamber (5) is 20 connected to the combustion chamber-side end region (54) of the intermediate piece (70), for example by welding.