SPARK PLUG ELECTRODE AND SPARK PLUG WITH THE SPARK PLUG ELECTRODE AND MANUFACTURING METHOD FOR THE SPARK PLUG ELECTRODE

Description

State of the art

[0001] An electrode for a spark plug according to the preamble of the independent claim is known, for example, from DE 10 2014 225 402 A1. Furthermore, a method for its production is known from this prior art.

[0002] The production of the electrode and the connection of the base body to the wear part according to the state of the art require the use of strong laser beams at flat angles to the workpiece surface and are therefore comparatively complex.

[0003] Spark plugs are known from DE 11 2016 005813 T5, DE 10 2018 120985 A1, DE 10 2018 110571 A1 and US 2018 / 331508 A2. Disclosure of the invention

[0004] The electrode according to the invention, however, can be produced comparatively simply and robustly using the method according to the invention.

[0005] Because this results in a positive connection between the base body and the wear part in addition to a weld between the base body and the wear part, the connection is strengthened overall, or the requirements placed on the welded connection as such are reduced, although the electrode is still able to reliably withstand all loads occurring during operation and testing.

[0006] The wear part can have the shape of a truncated cone, i.e., the shape of a body created by connecting all points of a flat base in a straight line to a vertex, and then removing the region of the vertex by cutting along a plane parallel to the base. The base can be circular, in which case it is a truncated circular cylinder. Furthermore, the line connecting the center of the circle of the base to the vertex can be perpendicular to the base, in which case it is a straight truncated circular cylinder, which is particularly preferred within the scope of the invention.

[0007] The base body may have an undercut recess, i.e. a recess that widens in the direction from the surface into the interior of the base body.

[0008] The positive connection between the wearing part and the base body can result in particular from the fact that a part of the wearing part comprising the base surface of the truncated cone is arranged in the undercut recess and a part of the truncated cone comprising the cutting surface of the truncated cone protrudes, wherein the truncated cone completely fills the undercut recess.

[0009] In a further development, the base body can be welded to the wearing part on parts of the edge surface of the recess or on the entire edge surface of the recess.

[0010] It can further be provided that the truncated cone originates from a right circular cone, so that it has an axis that is perpendicular to the base surface and the cutting surface of the truncated cone, and has a base surface radius rg and a cutting surface radius rs and has a height h. It can be provided that the base body has a flat surface laterally next to the recess, which is parallel to the base surface and the cutting surface of the truncated cone, and that the base surface is spaced from the surface in the axial direction by a melting length lin, i.e. lies below this surface by the melting length lin. The wearing part is then in particular accommodated in the base body or melted into the base body.

[0011] Of the following relations: a) h < rs, in particular h<1 / 2 rs, b) rs < 0.9 rg, in particular rs<0.85 rg, c) lin < 1 / 2 h, in particular lin<1 / 3 h, one, two or all relations can be realized, in particular the following relations: a; b; c; a and b; a and c; b and c; a, b and c.

[0012] The half cone angle α (aperture angle) of the cone underlying the truncated cone is, with these notations, α = arctan ((rg-rs) / h) and can preferably be between 10° and 40°, in particular between 15° and 35°. For example, 3 mm ≥ rg ≥ 2 mm can be selected.

[0013] For example, 1 mm ≥ h ≥ 0.2 mm can be selected.

[0014] According to the invention, it is provided that the base body has a circumferential welding bead between the recess and the flat surface, which lies laterally against the lateral surface of the wearing part, which increases the contact surface between the wearing part and the base electrode and thus improves the material bond.

[0015] The nickel-based alloy contains predominantly nickel by weight. It can be NiAlxSiy or NiAlxSiyY, each with 4 ≥ x+y ≥ 1, e.g., NiAl1Si1. The iridium-based alloy contains predominantly iridium by weight. It can, for example, consist entirely of precious metals. It can be IrRhzReu with 16 ≥ z+u ≥ 3, e.g., IrRh8Re3.

[0016] The invention also relates to a spark plug having at least one such electrode. This can be a center electrode and / or a ground electrode. The ground electrode can be a top electrode, side electrode, and / or a bracket electrode.

[0017] Such electrodes or spark plugs can be manufactured using the following process steps: Providing a pre-base body with a flat surface made of a nickel-based alloy; providing a truncated cone-shaped pre-wear part made of an iridium-based alloy; applying the base side of the pre-truncated cone to the flat surface of the pre-base body; electrically contacting the pre-wear part and the pre-base body; introducing an electric current that flows between the pre-wear part and the pre-base body so that the pre-wear part melts in the area where the pre-wear part rests; and simultaneously introducing a mechanical force that acts between the pre-wear part and the pre-base body, resulting in: penetration of the pre-wear part into the pre-base body, wherein the material of the pre-base body displaced by the penetration is at least partially deposited on the peripheral surface of the pre-wear body, whereby the pre-wear part subsequently forms the wear part and the pre-base body forms the base body.

[0018] The process can be carried out in such a way that the electric current causes a heating that is always lower than the melting temperature of the iridium-based alloy, for example, always lower than 1600°C. Then, the shape of the pre-wear part is transformed unchanged into the shape of the wear part, and a particularly strong positive connection between the base electrode and the wear part can be achieved.

[0019] If the quotient of the mechanical force and the base area of the pre-base body is selected such that it corresponds to a mechanical pressure of between 40 and 300 N / mm2, the pre-wear part penetrates quickly into the pre-base body and the manufacturing process can be carried out in a short time. drawing

[0020] Figure 1 shows an example of a spark plug. Figure 2 shows an example of an electrode according to the invention. Figure 3 shows an example of the production of a center electrode according to the invention. Description of the embodiment

[0021] Figure 1 shows a schematic representation of a spark plug 1. The spark plug 1 has a metallic housing 2 with a thread 3 for mounting the spark plug 1 in an engine block. An insulator 4 is arranged within the housing 2. A center electrode 5 and a connecting bolt 7 are arranged within the insulator 4 and are electrically connected via a resistance element (not shown here). In the example, the center electrode 5 projects beyond the combustion chamber side of the insulator 4.

[0022] A ground electrode 6 is arranged at the combustion chamber end of the housing 2. Together with the center electrode 5, it forms an ignition gap. The ground electrode 6 can be designed as a roof electrode, a side electrode, or a bracket electrode. The bracket electrode has two limbs, each of which is welded to the housing 2 by its leg 16. The limbs are at an angle of 30° to 180° to one another. The bracket electrode can be constructed in one piece or in multiple parts. In a multi-part construction, the individual parts are connected to one another by a material bond, such as welding.

[0023] In Figure 2a is a perspective view and in the Figure 2b a side view (left) and a section (right) of an electrode 5, 6 according to the invention is shown. Figure 2c shows a separate view of the wearing part 10.

[0024] The electrode 5, 6 comprises a base body 8 made of a nickel-based alloy and a wear part 10 made of an iridium-based alloy. The wear part 10 is arranged on the base body 8 in such a way that, together with the opposite electrode 6, 5 or a second wear part arranged on the opposite electrode 6, 5, it forms the ignition gap.

[0025] In the example, the wear part 10 has the shape of a straight truncated cone with a height of h. The radius of the base surface g is rg and the radius of the cutting surface s is rs.

[0026] The base electrode 8 has an undercut recess 9, ie the recess 9 tapers towards the outer surface 13 of the base electrode 8 (in the Figure 2bupwards). In the recess 9, a part (Ti) of the wear part 10 is arranged, which encompasses the base area g of the truncated cone, and from the recess 9, a part (Tv) of the truncated cone, which encompasses the cutting surface s of the truncated cone (in the Figure 2b outwards / upwards). The truncated cone completely fills the undercut recess 9 and the base body 8 is welded to the wear part 10 at the edge surface of the recess 9.

[0027] The outer surface 13 of the base body 8 is formed laterally adjacent to the recess 9 as a flat surface that is parallel to the base surface g and the sectional surface s of the truncated cone. The base surface g is spaced axially from the flat surface by the melting length lin.

[0028] In the example: rg=1.2 mm; rs=1 mm, h=0.4 mm, lin=0.1 mm or lin=0.05 mm. In the example, the base body 8 is made of NiAl1Si1Y, and the wear body 10 is made of IrRh8Re3.

[0029] From the Figure 2b It can be seen that the base body 8 has a circumferential welding bead 11 between the recess 9 and the flat surface 13, which laterally rests against the lateral surface m of the wear part 10. In the example, the material of the welding bead 11 is the material of the base body 8, which was displaced into the base body 8 during the manufacture of the electrode 5, 6, when the recess 9 was created by inmelting the wear part 10.

[0030] The electrode 5, 6 described in this example can be manufactured as follows: Step V1: Providing a pre-base body with a flat surface made of a nickel-based alloy; Step V2: Providing a frustoconical pre-wear part made of an iridium-based alloy; Step V3: Applying the base side of the pre-truncated cone to the flat surface of the pre-base body (V3); Step V4: Electrically contacting the pre-wear part and the pre-base body; Step V5: Introducing an electric current that flows between the pre-wear part and the pre-base body so that the pre-base body heats up (for example, maximum 1400°C) and melts in the area where the pre-wear part rests;and at the same time introducing a mechanical force which acts between the pre-wear part and the pre-base body (step V6), for example 500 Newton, resulting from this: step V7: penetration of the pre-wear part into the pre-base body, whereby the material of the pre-base body displaced by the penetration is at least partially deposited on the circumferential surface of the pre-wear body as a welding bead, ; whereby the pre-wear part subsequently forms the wear part 10 and the pre-base body forms the base body 8.

[0031] The process steps V1 to V7 are in the Figure 3 shown.

Claims

1. Electrode for a spark plug (1), comprising a main body (8) composed of a nickel-based alloy and a wear part (10) composed of an iridium-based alloy, wherein the main body (8) has a recess (9) which is laterally surrounded by a planar surface (13) of the main body (8), wherein the wear part (10) is arranged in the recess (9), wherein the wear part (10) is both welded and connected in a form-fitting manner to the main body (8), characterized in that the main body has an encircling welding bead (11) between the recess (9) and the planar surface (13), the welding bead bearing laterally against a casing surface (m) of the wear part (10).

2. Electrode according to Claim 1, characterized in that the wear part (10) is in the shape of a truncated cone and the main body (8) has an undercut recess (9) in which a part (Ti) of the wear part (10) that comprises the base surface (g) of the truncated cone is arranged and from which a part (Tv) of the truncated cone that comprises the sectional surface (s) of the truncated cone protrudes, wherein the truncated cone completely fills the undercut recess (9) and wherein the main body (8) is welded to the wear part (10) at the edge surface of the recess (9).

3. Electrode according to Claim 2, characterized in that the truncated cone originates from a right circular cone, so that it has an axis (100) which is perpendicular to the base surface (g) and the sectional surface (a) of the truncated cone, and has a base surface radius (rg) and has a sectional surface radius (rs) and has a height (h), in that the main body (8) has a planar surface (13) laterally next to the recess (9), the planar surface being parallel to the base surface (g) and / or the sectional surface (s) of the truncated cone, and the base surface (g) is spaced apart from the surface (13) by a melting length (lin) in the axial direction (100).

4. Electrode according to Claim 3, characterized in that one, several or all of the following relationships are realized: a) h < rs, in particular h < 1 / 2rs b) rs < 0.9rg, in particular rs < 0.85rg c) lin < 1 / 2h, in particular lin < 1 / 3h; where h is the height (h) of the truncated cone, rs is the radius (rs) of the sectional surface (s), rg is the radius (rg) of the base surface (g) and lin is the melting depth (lin).

5. Electrode according to any of the preceding claims, characterized in that the nickel-based alloy is NiAlxSiy or NiAlxSiyY, where 4 ≥ x+y ≥ 1 in both cases; and the iridium-based alloy is IrRhzReu, where 16 ≥ z+u ≥ 3.

6. Spark plug, characterized in that the spark plug (1) has at least one electrode (5, 6) according to any of the preceding claims.

7. Method for producing an electrode according to any of Claims 1 to 5 or a spark plug according to Claim 6, characterized by the following method steps - providing a preliminary main body having a planar surface composed of a nickel-based alloy (V1) - providing a truncated cone-shaped preliminary wear part composed of an iridium-based alloy (V2) - placing the base side of the preliminary truncated cone onto the planar surface of the preliminary main body (V3) - electrically contact-connecting the preliminary wear part and the preliminary main body (V4) - introducing an electric current, which flows between the preliminary wear part and the preliminary main body (V5), so that the preliminary main body melts in the region of support of the preliminary wear part; and at the same time introducing a mechanical force, which acts between the preliminary wear part and the preliminary main body (V6), this resulting in: - the preliminary wear part entering the preliminary main body, wherein the material of the preliminary main body displaced by the entry at least partially accumulates on the circumferential surface of the preliminary wear body (V7), wherein subsequently the preliminary wear part forms the wear part (10) and the preliminary main body forms the main body (8).

8. Method according to Claim 7, characterized in that the electric current causes heating which is always lower than the melting point of the iridium-based alloy, for example always lower than 1600°C.

9. Method according to Claim 7 or 8, characterized in that the quotient of the mechanical force and the base surface of the preliminary main body corresponds to a mechanical pressure of between 40 and 300 N / mm2.