Spark plug electrode with precious metal-containing ignition element

Abstract

Spark plug electrode (4, 5) comprising an electrode base (41, 51) and an ignition element (42, 52) arranged on the electrode base (41, 51), wherein the ignition element (42, 52) consists of a noble metal-containing material and has a first side (420, 520) facing the electrode base (41, 51) and a second side (422, 522) facing away from the electrode base (41, 51), wherein the ignition element (42, 52) has a recess (421, 521) on its first side (420, 520), wherein the recess (421, 521) on the first side (420, 520) of the ignition element (42, 52) along the circumference of the recess (421, 521) is made of material of the ignition element (42, 52) is surrounded.

Description

State of the art

[0001] The invention relates to a spark plug electrode and a spark plug with such an electrode.

[0002] Today's spark plug electrodes consist of an electrode base and an ignition element. The electrode base, for example, is made of a nickel alloy, and the ignition element is made of a material containing precious metals. The use of precious metal-containing ignition elements extends the service life of the spark plug electrode and thus the entire spark plug, as precious metal-containing materials exhibit lower wear than nickel alloys.

[0003] For example, spark plugs with such spark plug electrodes are known from DE 10 2004 032 723 B4.

[0004] However, precious metals and precious metal-containing materials are expensive and continue to rise in price. Accordingly, it is a constant effort to use as few precious metal-containing materials as possible in spark plug electrodes and to use the precious metal-containing materials used as efficiently as possible.

[0005] It is an object of the present invention to provide a spark plug electrode in which the use of materials containing precious metals is reduced. Disclosure of the invention

[0006] Accordingly, it is an object of the present invention to improve a spark plug electrode and a spark plug with such a spark plug electrode of the type mentioned at the outset in such a way that the above disadvantages are eliminated or minimized.

[0007] This object is achieved according to the invention in the spark plug electrode of the type mentioned at the outset in that the ignition element has a recess on its first side, wherein the recess on the first side of the ignition element is surrounded by material of the ignition element along the circumference of the recess.

[0008] The spark plug electrode according to the invention comprises an electrode base and an ignition element arranged on the electrode base. The ignition element is made of a noble metal-containing material and has a first side facing the electrode base and a second side facing away from the electrode base. The ignition element has a recess on its first side, wherein the recess on the first side of the ignition element is surrounded by material of the ignition element along the circumference of the recess.

[0009] Investigations by the applicant have shown that the side of the ignition element facing the electrode base is not worn over the lifetime of the spark plug. Thus, there is potential for savings in the use of the precious metal-containing material of the ignition element, while maintaining the robustness and service life of the ignition element.

[0010] According to the invention, the ignition element has a recess on its first side, wherein the recess on the first side of the ignition element is surrounded by material of the ignition element along the circumference of the recess. This recess is arranged on the side of the ignition element facing the electrode base, precisely in the area of ​​the ignition element that is not worn away during the sparking of the ignition element during the intended use of the spark plug electrode in a spark plug. By forming the recess on the first side of the ignition element, expensive material containing precious metals can be saved, on the one hand, and on the other hand, the robustness and longevity of the spark plug electrode are maintained.

[0011] Further advantageous embodiments are the subject of the subclaims.

[0012] In an advantageous embodiment of the spark plug electrode, the recess extends from the first side of the ignition element to the second side of the ignition element through the ignition element, so that the ignition element also has the recess on its second side. The ignition element then has the shape of a ring, whereby the ignition element deliberately does not contain any material containing precious metals along the central axis of the ignition element, which extends from the first side to the second side. This ring-shaped ignition element is used, for example, in ground electrodes. Studies have shown that material removal in ground electrode ignition elements usually occurs in a ring shape and that the material in the center of the ignition element is hardly removed. This is particularly the case when the opposite center electrode has an ignition element with a smaller diameter than the ignition element of the ground electrode.The ring-shaped ignition element thus allows further savings in precious metal-containing material.

[0013] In an alternative embodiment of the spark plug electrode, the recess extends from the first side of the ignition element into the interior of the ignition element and ends inside the ignition element. The ignition element is shaped like a cap. A cap-shaped ignition element has the advantage that the electrode base and its material are covered in the direction of the ignition gap. The material of the electrode base is generally not as robust as the precious metal-containing material of the ignition element.

[0014] In a cap-shaped ignition element, there is a distance D between the end of the recess inside the ignition element and the second side of the ignition element, which is measured parallel to the center axis of the ignition element. It is advantageous if the distance D is not less than 0.2 mm and not greater than 0.5 mm, in particular 0.25 mm - 0.45 mm and especially 0.3 mm - 0.4 mm. Studies have shown that the distance D should be within this range to ensure, on the one hand, that there is enough material on the second side of the ignition element for the wear expected over the service life of the spark plug electrode and, on the other hand, that there is not too much unused material containing precious metals remaining at the end of the ignition electrode's service life.

[0015] For example, the recess can have a cylindrical shape. Alternatively, the recess can also have a conical or tapered shape or even a truncated cone shape. It is also possible for the recess to have a cylindrical and a conical or truncated cone-shaped section. For example, starting from the first side, the recess can initially have a section with a cylindrical shape, followed by a section with a conical shape. Alternatively, starting from the first side, the recess can initially have a section with a cylindrical shape, followed by a section with a truncated cone shape. In a further possibility, the recess can initially have a section with a cylindrical shape, starting from the first side, followed by a section with a truncated cone shape and then a section with a conical shape.Preferably, the different shapes for the recess each have a circular base.

[0016] In an advantageous further development, the electrode base has a section that is at least partially arranged within the recess. The ignition element, for example, is plugged onto this section of the electrode base with its recess.

[0017] In the case of the cap-shaped ignition element, it is conceivable, for example, that the section of the electrode base has a complementary shape to the recess and, for example, completely fills it, so that no cavity remains within the cap-shaped ignition element.

[0018] The invention also relates to a spark plug having a housing, an insulator arranged in the housing, a ground electrode arranged on the housing and a center electrode arranged in the insulator, wherein the ground electrode is a spark plug electrode according to the invention and / or the center electrode is a spark plug electrode according to the invention.

[0019] This spark plug has the advantage that the service life of the spark plug is maintained and at the same time the precious metal-containing material of the ignition element is used optimally.

[0020] In a further development of the spark plug, the ground electrode is designed as a roof electrode, so that an axial ignition gap is formed between the ignition element of the ground electrode and the ignition element of the center electrode.

[0021] It has been found to be advantageous if the outer diameter of the ignition element of the ground electrode is larger than the outer diameter of the ignition element of the center electrode.

[0022] For example, the ignition element of the ground electrode is designed as a ring with a recess that extends from the first side of the ignition element to the second side of the ignition element. This ring-shaped ignition element has an outer diameter D Ma of at least D Mi +0.6mm and an inner diameter d Ma of maximum D Mi -0.6 mm, where D Mi the diameter of the ignition element of the central electrode and, in particular, the centers of the outer diameter and the inner diameter coincide, so that the ring has a uniform width of at least 0.6 mm. drawing Fig. 1 shows an example of a spark plug electrode according to the invention Fig. 2 shows a first embodiment of the spark plug electrode according to the invention Fig. 3 shows a second embodiment of the spark plug electrode according to the invention Fig. 4 shows a third embodiment of the spark plug electrode according to the invention Fig. 5 shows an example of a spark plug Description of the embodiment

[0023] Fig. 1 shows a first example of a spark plug electrode 4 according to the invention in section. The spark plug electrode 4 has an electrode base 41 and an ignition element 42. The ignition element 42 has a recess 421 on its first side 420 facing the electrode base 41, wherein the recess 421 is surrounded along its circumference by material of the ignition element 42. The recess 421 has a conical shape and ends within the ignition element 42. The electrode base 41 has a section 411 arranged within the recess 421. In this example, the section 411 of the electrode base 41 has a shape complementary to the recess 421 and completely fills the recess 421.

[0024] In Fig. 2 is the first embodiment according to Fig. 1. This corresponds to Fig. 2a of the Fig. 1. In Fig. 2b, the ignition element 42 is shown individually, whereby the perspective view clearly shows the shape of the recess 421. In Fig. Figure 2c shows the electrode base 41 in isolation, with the perspective view clearly showing the shape of section 411. Section 411 of the electrode base 41 has the shape of a cone. Accordingly, the recess 421 in the ignition element 42 also has the shape of a cone.

[0025] Fig. Figure 3 shows a second embodiment of a spark plug electrode 4 according to the invention. The first and second embodiments differ in that the recess 421 in the ignition element 42 and the section 411 of the electrode base 41 have a different shape. In the second embodiment, the shape of the recess 421 and the electrode base section 411 is composed of a cylindrical section and a conical section.

[0026] The spark plug electrode 4 according to the first or second embodiment may be a center electrode or a ground electrode.

[0027] In Fig. Figure 4 shows a third embodiment of the spark plug electrode 5 according to the invention. The ignition element 52 has the shape of a ring. The recess 521 extends through the entire ignition element 52 from the first side 520 to the second side 522. The outer diameter D Ma of the ignition element 52 is larger than an outer diameter D Mi a counter electrode 4. The diameter d Ma the recess 522 on the second side 522 of the ignition element 52 is smaller than the outer diameter D Mi the counter electrode

[0028] Fig.5 shows a spark plug 1. The spark plug 1 comprises a housing 2. An insulator 3 is inserted into the housing 2. A center electrode 4 is inserted into the insulator 3. Furthermore, a connecting bolt 8 extends into the insulator 3, via which the spark plug 1 can be electrically contacted with a voltage source (not shown here).

[0029] A ground electrode 5 is arranged in an electrically conductive manner on the combustion chamber-side end face of the housing 2. The ground electrode 5 and the center electrode 4 are arranged relative to one another in such a way that an ignition gap forms between them, where the ignition spark is generated.

[0030] The housing 2 has a shaft. A polygon 21, a shrink recess, and a thread 22 are formed on this shaft. The thread 22 serves to screw the spark plug 1 into an internal combustion engine. An outer sealing element 6 is arranged between the thread 22 and the polygon 21. In this exemplary embodiment, the outer sealing element 6 is designed as a folded seal. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2004 032 723 B4

[0003]

Claims

[1] Spark plug electrode (4, 5) comprising an electrode base (41, 51) and an ignition element (42, 52) arranged on the electrode base (41, 51), wherein the ignition element (42, 52) consists of a noble metal-containing material and has a first side (420, 520) facing the electrode base (41, 51) and a second side (422, 522) facing away from the electrode base (41, 51), characterized by that the ignition element (42, 52) has a recess (421, 521) on its first side (420, 520), wherein the recess (421, 521) on the first side (420, 520) of the ignition element (42, 52) is surrounded by material of the ignition element (42, 52) along the circumference of the recess (421, 521). [2] Spark plug electrode (4, 5) according to claim 1, characterized bythat the recess (421, 521) extends from the first side (420, 520) of the ignition element (42, 52) to the second side (422, 522) of the ignition element (42, 52) through the ignition element, so that the ignition element (42, 52) also has the recess (421, 521) on its second side (422, 522). [3] Spark plug electrode (4, 5) according to claim 1, characterized by that the recess (421, 521) extends from the first side (420, 520) of the ignition element (42, 52) into the interior of the ignition element (42, 52) and ends in the interior of the ignition element (42, 52). [4] Spark plug electrode (4, 5) according to claim 3, characterized by that the end of the recess (421, 521) inside the ignition element (42, 52) has a distance D to the second side (422, 522) of the ignition element (42, 52), wherein the distance D is not less than 0.2 mm and not greater than 0.5 mm, in particular 0.25-0.45 mm, in particular 0.3-0.4 mm [5] Spark plug electrode (4, 5) according to one of the preceding claims, characterized by that the recess (421, 521) has a cylindrical and / or a conical shape. [6] Spark plug electrode (4, 5) according to one of the preceding claims, characterized by that a portion of the electrode base (41, 51) is arranged at least partially within the recess (421, 521). [7] Spark plug electrode (4, 5) according to claim 3 and claim 6, characterized by that the section of the electrode base (41, 51) has a complementary shape to the recess (421, 521) and in particular completely fills it. [8] Spark plug (1) with a housing (2), an insulator (3) arranged in the housing (2), a ground electrode (5) arranged on the housing (2) and a center electrode (4) arranged in the insulator (3), characterized bythat the ground electrode (5) is a spark plug electrode according to one of claims 1 to 7 and / or the center electrode (4) is a spark plug electrode according to one of claims 1 to 7. [9] Spark plug (1) according to claim 8, characterized by that the ground electrode (5) is a roof electrode, so that an axial ignition gap is formed between the ignition element (52) of the ground electrode (5) and the ignition element (42) of the center electrode (4). [10] Spark plug (1) according to claim 9, characterized by that the outer diameter (D Ma ) of the ignition element (52) of the ground electrode (5) is larger than the outer diameter (D Mi ) of the ignition element (42) of the center electrode (4).

Images