METHOD FOR PRODUCING A SPARK PLUG, AND SPARK PLUG

Abstract

A method for producing a spark plug including a spark plug electrode assembly having a center electrode and a ground electrode surrounding the center electrode. The spark plug electrode assembly is formed from a one-piece spark plug electrode base body made of spark plug electrode material, and the ground electrodeand the center electrode are connected to one another by a connecting region, wherein the center electrode and an inner surface of the ground electrode are polygonal. The method includes: a) connecting the spark plug electrode assembly to a spark plug base body, and b) removing the connecting region between the ground electrode and the center electrode.

Claims

1-13. (canceled)

14. A method for producing a spark plug, the spark plug including a spark plug electrode assembly having a center electrode and a ground electrode surrounding the center electrode, the method comprising the following steps: forming the spark plug electrode assembly from a one-piece spark plug electrode base body made of spark plug electrode material, and the ground electrode and the center electrode being connected to one another by a connecting region, and wherein the center electrode and an inner surface of the ground electrode are polygonal; connecting the spark plug electrode assembly to a spark plug base body; and removing the connecting region between the ground electrode and the center electrode.

15. The method according to claim 14, wherein the center electrode and the inner surface of the ground electrode are at least triangular.

16. The method according to claim 14, wherein the center electrode and the inner surface of the ground electrode are respectively triangular or respectively quadrangular.

17. The method according to claim 14, further comprising: attaching small noble metal plates to connection surfaces between two corners of the center electrode and the ground electrode so that the small noble metal plates on the center electrode are opposite the small noble metal plates on the ground electrode at least in portions.

18. The method according to claim 17, wherein the small noble metal plates of the center electrode have the same geometric shape as the small noble metal plates of the ground electrode.

19. The method according to claim 17, wherein the small noble metal plates are arranged such that they substantially completely cover the connection surfaces between the two corners.

20. A spark plug, comprising: a ground electrode; a center electrode, wherein the ground electrode surrounds the center electrode, and wherein the center electrode and an inner surface of the ground electrode are polygonal; and small noble metal plates arranged on connection surfaces of the between two corners of the ground electrode and the center electrode, wherein a spark gap is formed between a small noble metal plate of the ground electrode and a small noble metal plate of the center electrode; wherein the corners of the center electrode include small noble metal plate-free regions.

21. The spark plug according to claim 20, wherein the center electrode and the inner surface of the ground electrode are respectively triangular or respectively quadrangular.

22. The spark plug according to claim 20, wherein the small noble metal plates of the center electrode have the same geometric shape as the small noble metal plates of the ground electrode.

23. The spark plug according to claim 20, wherein the center electrode is triangular and includes a respective small noble metal plate on each of its three side surfaces, wherein the inner surface of the ground electrode is hexagonal and includes a respective small noble metal plate on each of three side surfaces so that the small noble metal plates of the center electrode are opposite the small noble metal plates of the ground electrode, wherein further three side surfaces of the ground electrode are substantially small noble metal plate-free regions.

24. The spark plug according to claim 20, wherein the center electrode is quadrangular and includes a respective small noble metal plate on each of its four side surfaces, wherein the inner surface of the ground electrode is octagonal and includes a respective small noble metal plate on each of four side surfaces so that the small noble metal plates of the center electrode are opposite the small noble metal plates of the ground electrode, wherein further four side surfaces of the ground electrode are substantially small noble metal plate-free regions.

25. The spark plug according to claim 20, wherein each of the small noble metal plates include iridium, wherein a content of the iridium is at least 60 mass %, based on a total mass of the small noble metal plate.

26. The spark plug according to claim 25, wherein the small noble metal plates further include rhodium and/or rhenium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Exemplary embodiments of the present invention are described in detail below with reference to the figures.

[0043] FIG. 1 is a partial sectional view of a spark plug according to a first example embodiment of the present invention.

[0044] FIG. 2 is a partial view of a spark plug before initial operation, according to a second example embodiment of the present invention in section.

[0045] FIG. 3 is a partial view of the spark plug of FIG. 2 during initial operation, in section.

[0046] FIG. 4 is a partial view of a spark plug before initial operation, according to a third example embodiment of the present invention in section.

[0047] FIG. 5 is a partial view of the spark plug of FIG. 4 during initial operation, in section.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0048] Only the main details of the present invention are shown in the figures. All other details are omitted for the sake of clarity. In addition, identical reference signs refer to identical components.

[0049] As can be seen in FIG. 1, the spark plug 1 comprises a ground electrode 2, a center electrode 3, and an insulator 4. A housing 5 at least partially surrounds the insulator 4. A thread 6, which is designed for fastening the spark plug 1 in a cylinder head 7, is arranged on the housing 5. In order to generate an ignition spark, the center electrode 3 is connected to an electrical connection 8.

[0050] In the spark plug 1 of FIG. 1, the ground electrode 2 and the center electrode 3 are formed from the same material, namely, in such a way that the ground electrode 2 and the center electrode 3 were initially formed, connected to one another by a connecting region, from a one-piece spark plug electrode base body made of spark plug electrode material, for example by deep-drawing of the spark plug electrode base body.

[0051] Small noble metal plates were arranged on the polygonal ground electrode 2 and on the likewise polygonal center electrode 3, wherein a spark gap F is formed between the small noble metal plates of the ground electrode 2 and the small noble metal plates of the center electrode 3.

[0052] In a further step, the spark plug electrode base body was connected to a spark plug base body 9, which, as shown here, comprises the housing 5, the insulator 4, and the electrical connection 8.

[0053] As shown here, the ground electrode 2 is preferably connected to the housing 5 by a first welded connection S1, and the center electrode 3 is advantageously connected to the electrical connection 8 by a second welded connection S2. The connecting region, which was initially formed between the ground electrode 2 and the center electrode 3, was removed for the initial operation of the spark plug 1.

[0054] Due to the fact that the ground electrode 2 and the center electrode 3 and the small noble metal plates correspondingly arranged thereon were produced by forming a connecting region between the ground electrode 2 and the center electrode 3, the electrode distance between the small noble metal plates of the ground electrode 2 and the small noble metal plates of the center electrode 3 is permanently stable and very precisely adjusted to a predetermined distance in the spark plug 1 shown in FIG. 1. In addition, due to the polygonal design of the ground electrode 2 and the center electrode 3, the wear surfaces are increased. The spark plug 1 is consequently characterized by a high power density and a low spark-erosion wear with a simple and cost-effective production method.

[0055] FIG. 2 shows a partial view of a spark plug 1 having a spark plug electrode assembly 10 before initial operation, according to a second embodiment in section.

[0056] The spark plug 1 comprises a ground electrode 2 and a center electrode 3, both of which are polygonal. The ground electrode 2 surrounds the center electrode 3 on all sides.

[0057] The center electrode 3 is quadrangular and, on its four side surfaces 11, comprises a respective small noble metal plate 12. A side surface 11 represents a connection surface between two corners 17. Since the center electrode 3 comprises four side surfaces 11, the center electrode 3 also has four small noble metal plates 12 and four corners 17. The small noble metal plates 12 are identical in shape and dimension.

[0058] The inner surface of the ground electrode 2 is octagonal, having eight side surfaces 13, 16 and eight corners 14. The side surfaces 13, 16 serve as connection surfaces between two corners 14. Small noble metal plates 15 are arranged on four of the eight side surfaces 13, 16 so that, twice in the octagon, two small noble metal plates 15 are opposite one another. The small noble metal plates 12 of the center electrode 3 are also opposite the small noble metal plates 15 of the ground electrode 2. The presence of corners 14 (and also corners 17) has the advantage that field enhancements are present in the electric field at the corners 14 (17) so that the ignition voltage requirement for the ignition spark formation is reduced.

[0059] All small noble metal plates 12, 15 used not only have the same geometry and dimension but are also formed from the same material, namely, they comprise iridium, wherein the content of iridium is at least 60 mass %, based on the total mass of a small noble metal plate. In addition, rhodium and/or rhenium can be contained as alloying elements. Rectangular small noble metal plates, as shown in this embodiment, can very well be produced having high mechanical stability from the corrosion-stable iridium and installed.

[0060] The further four side surfaces 16 of the ground electrode 2, which do not comprise small noble metal plates 15, are substantially small noble metal plate-free regions. The small noble metal plate-free regions, i.e., the four side surfaces 16 of the ground electrode 2, are opposite the four corners 17 of the center electrode 3.

[0061] In the spark plug electrode assembly 10, the noble metal-free regions of the ground electrode 2 are connected to the corners 17 of the center electrode by connecting regions 18. The connecting regions 18 result from the one-piece production of a spark plug electrode assembly 10 used for the production of the spark plug 1. As a result, a precise defined electrode distance is already adjusted during the production of the electrodes 2, 3, which results in a uniform spark gap after the small noble metal plates 12, 15 have been arranged. This improves the service life of the spark plug 1 at high power density.

[0062] In the embodiment shown here, all small noble metal plates are of identical design, thus have the same geometry and dimension. A permanently good spark generation can thus take place with low spark-erosion wear of the electrodes. In addition, the production of the spark plug is thereby facilitated.

[0063] Due to the design of the ground electrode 2 having an octagonal inner surface and of the center electrode 3 having a quadrilateral shape, very good flow properties are achieved in the combustion chamber between the electrodes 2, 3, and the fuel gases are brought to combustion particularly uniformly, which further improves the service life of the spark plug 1.

[0064] FIG. 3 shows the same partial view of the spark plug 1 according to the second embodiment as shown in FIG. 2, but now during initial operation of the spark plug 1. This means that the previously present connecting region 18, consisting of webs, between the ground electrode 2 and the center electrode 3 was removed in order to electrically separate the electrodes. The small noble metal plate-free corners 17 of the quadrilateral center electrode 3 are exposed and opposite the small noble metal plate-free side surfaces 16 of the octagonal ground electrode 2. The fuel gases can now pass uniformly into a region between the electrodes 2, 3 so that particularly uniform ignition spark formation is promoted. In addition, the corners 14 and also corners 17 are exposed so that field enhancements are present in the electric field at the corners 14, 17 and the ignition voltage requirement for the ignition spark formation is reduced.

[0065] FIG. 4 shows a partial view of a spark plug 1 having a spark plug electrode assembly 10 before initial operation, according to a third embodiment in section.

[0066] The spark plug 1 shown in FIG. 4 differs from that of FIG. 2 in that the center electrode 3 is triangular, i.e., is formed having three side surfaces 11 and three corners 17. The inner surface of the ground electrode 2 is hexagonal, having six side surfaces 13, 16 and six corners 14.

[0067] Three side surfaces 13 of the six side surfaces 13, 16 of the ground electrode 2 comprise small noble metal plates 15, which are arranged on side surfaces 13, which connect two corners 14 of the inner surface of the ground electrode 2. The three side surfaces 16 of the inner surface of the ground electrode 2 do not comprise any small noble metal plates and are substantially small noble metal plate-free regions. These substantially small noble metal plate-free regions of the inner surface of the ground electrode 2 in turn are opposite the corners 17 of the center electrode 3.

[0068] The spark plug 1 is not yet configured for start of operation, since the electrodes 2, 3 are still electrically connected to one another by a connecting region 18 in the form of three webs.

[0069] Reference sign 19 denotes openings, more precisely gas exchange openings or overflow bores, which make purposeful flushing of the so-called breathing space of the spark plug 1 possible so that combusted waste gases are flushed out and fresh fuel gas is introduced into the breathing space and into the spark gap F, which improves the ignition properties of the spark plug 1.

[0070] The embodiment shown here is characterized by particularly good fuel gas flow conditions. The fuel gases pass into the spark gap F on all sides around the center electrode 3 in order to generate an ignition spark and ignite the fuel. The spark plug 1 is characterized by very large wear surfaces of the electrodes so that the service life of the spark plug 1 is increased with very simple and cost-effective producibility. Since the spark plug 1 in this embodiment was also produced using a one-piece spark plug electrode assembly, the electrode distance 2, 3 is already predetermined at the time of the electrode production and is particularly precise so that the spark gap F is uniform in all regions after attaching the small noble metal plates.

[0071] FIG. 5 shows the same partial view of the spark plug 1 according to the third embodiment as shown in FIG. 4, but now during initial operation of the spark plug 1. This means that the previously present connecting region 18, consisting of webs, between the ground electrode 2 and the center electrode 3 was removed in order to electrically separate the electrodes. The small noble metal plate-free corners 17 of the triangular center electrode 3 are exposed and opposite the small noble metal plate-free side surfaces 16 of the hexagonal ground electrode 2. Here, the fuel gases can pass particularly uniformly into a region between the electrodes 2, 3 so that particularly good ignition spark formation is promoted.