Prechamber spark plug, ignition electrode for a prechamber spark plug and method for producing an ignition electrode

Abstract

A prechamber spark plug having a housing, which at its front end comprises a prechamber with an ignition electrode arranged therein, wherein the ignition electrode comprises a base and electrode legs protruding from the base, wherein the ignition electrode is machined from a sheet made of an iridium alloy and the legs are bent out of the plane of the base to form a basket shape, characterized in that the ignition electrode, in particular the electrode legs, is/are separated out of the sheet metal by means of laser cutting. Furthermore, a corresponding ignition electrode and a method for producing such an ignition electrode are claimed.

Claims

1. A prechamber spark plug having a housing, which at its front end comprises a prechamber having an ignition electrode arranged therein, wherein the ignition electrode comprises a base and electrode legs protruding from the base, wherein the ignition electrode is machined from a sheet made of an iridium alloy and the legs are bent out of the plane of the base to form a basket shape, the ignition electrode separated out of the sheet metal by means of laser cutting, wherein the electrode legs have a thickness in a range from 0.2 mm to 0.5 mm and a width in a range from 0.3 mm to 0.6 mm, which gives a ratio of thickness/width in a range of 0.33 to 1.67.

2. The prechamber spark plug according to claim 1, the legs being bent approximately orthogonally out of the plane of the base.

3. The prechamber spark plug according to claim 1, the legs being bent out of the plane of the base at an angle <90°, preferably 81° to 89°.

4. The prechamber spark plug according to claim 1, the electrode legs being bent into their basket shape by means of hot bending.

5. The prechamber spark plug according to claim 1, the ignition electrode consists of one of a group including IrRh5, IrRh10 and IrRh3Nb1.

6. The prechamber spark plug according to claim 1, the electrode comprises four, six or eight electrode legs.

7. The prechamber spark plug according to claim 1, the ignition electrode comprises an arrangement of two individual electrodes one above the other or one behind the other, wherein the number of the respective electrode legs are identical or different from one another.

8. The prechamber spark plug according to claim 7, the ignition electrodes are welded to one another with or without a spacing from one another.

9. The prechamber spark plug according to claim 7, the arrangement of two ignition electrodes comprises a total of eight or twelve electrode legs.

10. The prechamber spark plug according to claim 7, the individual electrodes with their electrode legs are twisted relative to one another, so that the electrode legs are not aligned and complement each other in the bent state to form the basket shape.

11. The prechamber spark plug according to claim 1, the electrode legs are approximately square in cross section.

12. The prechamber spark plug according to claim 1, the electrode legs have a thickness in the range from 0.2 mm to 0.5 mm and a width in the range from 0.3 mm to 0.6 mm, which gives a ratio of thickness/width in the range of 0.33 to 1.67 with a range of 0.4 (slightly rectangular) to 1.0 (square).

13. An ignition electrode for a prechamber spark plug, which is arranged in a housing comprising a prechamber, wherein the ignition electrode comprises a base and electrode legs protruding from the base and is machined from a sheet made of an iridium alloy and the legs are bent away approximately orthogonally to the base to form a basket shape the ignition electrode is separated out of the sheet metal by means of laser cutting, wherein the electrode legs have a thickness in a range from 0.2 mm to 0.5 mm and a width in a range from 0.3 mm to 0.6 mm, which gives a ratio of thickness/width in a range of 0.33 to 1.67.

14. A method for producing an ignition electrode for a prechamber spark plug comprising a base and electrode legs protruding from the base, wherein the ignition electrode is cut out of a sheet made of an iridium alloy and the legs are subsequently bent approximately orthogonally to the base to form a basket shape, the ignition electrode is cut out of the sheet metal by means of laser cutting, and wherein the electrode legs have a thickness in a range from 0.2 mm to 0.5 mm and a width in a range from 0.3 mm to 0.6 mm, which (lives a ratio of thickness/width in a ramie of 0.33 to 1.67.

15. The prechamber spark plug of claim 1, wherein the ratio of thickness/width is in the range of 0.4 to 1.0.

16. The ignition electrode of claim 13, wherein the ratio of thickness/width is in the range of 0.4 to 1.0.

17. The method of claim 14, wherein in cutting the ignition electrode, the ratio of thickness/width is in the range of 0.4 to 1.0.

Description

(1) There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, reference is made on the one hand to the claims dependent on claim 1 and on the other hand to the following explanation of preferred embodiments of the invention with reference to the drawings. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawings, generally preferred embodiments and developments of the teaching are also explained. In the drawings:

(2) FIG. 1 is a schematic view, partially in section, of an embodiment of a prechamber spark plug,

(3) FIG. 2 is a schematic view, partially broken away, of a view into the prechamber of the prechamber spark plug,

(4) FIG. 3 is a schematic top view of the blank of an ignition electrode having four electrode legs produced by means of laser cutting,

(5) FIG. 4 is a schematic side view of the object from FIG. 3,

(6) FIG. 5 is a schematic view of an ignition electrode comprising four electrode legs, with electrode legs bent into a basket and with an approximately square cross-section,

(7) FIG. 6 is a schematic view of an ignition electrode comprising four electrode legs, with electrode legs bent into a basket and having an approximately rectangular cross-section,

(8) FIG. 7 is a schematic view of an ignition electrode comprising six electrode legs, with electrode legs bent into a basket and with an approximately rectangular cross-section,

(9) FIG. 8 is a schematic view of the combination of two electrodes, each having four electrode legs, and

(10) FIG. 9 is a schematic view of the combination of two electrodes, each having six electrode legs.

(11) FIG. 1 shows the basic structure of a prechamber spark plug, wherein the present invention only deals with the prechamber 1 and the ignition electrode 2 arranged therein.

(12) The prechamber 1 is essentially formed by the end cap 3, which is equipped with overflow bores. The cap 3 is welded to a housing 4. In addition, a ground electrode 5 is formed by the inner wall of the cap 3. For the function of the prechamber spark plug, reference is made to the prior art mentioned in the introduction to the description.

(13) FIG. 2 shows a view into the prechamber 1, wherein the cap 3 with the ground electrode 5 can be seen. The ignition electrode 2 is seated in the interior of the prechamber 1 and, in the embodiment shown in FIG. 2 as ignition electrode 2 having a total of six electrode legs 6. The electrode legs 6 are bent away from their base 7 in a basket shape.

(14) FIG. 3 shows, in a schematic plan view, the blank cut out from a sheet metal by laser cutting, wherein the sheet metal is made of an iridium alloy. It is a blank, from the base 7 from which a total of four electrode legs 6 extend away. The electrode legs 6 are arranged in pairs and may be aligned with one another at an angle of 20 degrees to 70 degrees. The electrode legs 6 can have a length between 6 mm and 16 mm and a thickness or width of 0.3 mm to 0.6 mm.

(15) FIG. 4 shows the object from FIG. 3 in a side view, according to which the electrode legs 6 extend outward from the base 7, in the still unbent state.

(16) FIG. 5 shows a schematic view of an ignition electrode 2 which is bent from the blank according to FIGS. 3 and 4. The electrode legs 6 are bent by hot bending until the electrode legs 6 define the basket shape and are bent more or less orthogonally from the base 7 toward the free end. According to FIG. 5, the cross section of the electrode legs 6 is approximately square.

(17) The ignition electrode 2 according to FIG. 6 differs from the ignition electrode 2 from FIG. 5 in that the electrode legs 6 are made somewhat wider than they are thick. The cross section is roughly rectangular.

(18) FIG. 7 shows an ignition electrode 2 having a total of six electrode legs 6, wherein three of the electrode legs 6 are formed close to one another and in two groups of three opposite one another. As in the embodiment according to FIG. 6, the cross section is rather rectangular.

(19) FIG. 8 shows an ignition electrode 2, which consists of a combination of two individual electrodes 8, each having four electrode legs 6. The individual electrodes 8 are permanently and directly welded to one another and complement one another to form an ignition electrode 2 having a total of eight electrode legs 6.

(20) FIG. 9 shows the combination of two individual electrodes 8, wherein each individual electrode 8 has six electrode legs 6. Overall, the combination of the two individual electrodes 8 results in an ignition electrode 2 having twelve electrode legs 6.

(21) With an increased number of electrodes, there is a considerable wear reserve, which increases the service life of the ignition electrode 2.

(22) In relation to FIGS. 1 and 5 to 9, it should be noted with regard to the alignment of the electrode legs 6 that they are bent out of the plane of the base 2 at an angle <90°, wherein the angle preferably is in the range between 81° and 89°, so that in the installed state according to FIGS. 1 and 2, the electrode legs 6 approach the ground electrode 5 or the inner wall of the cap 3 toward the free end. The “basket” formed in this way widens toward the free end of the electrode legs 6.

(23) With regard to further advantageous embodiments of the teaching according to the invention, reference is made to avoid repetition to the general part of the description and to the appended claims.

(24) Finally, it should be expressly noted that the above-described embodiments of the teaching according to the invention are merely used for the purpose of discussing the claimed teaching, but not limited to the embodiments.

LIST OF REFERENCE SIGNS

(25) 1 Prechamber

(26) 2 Ignition electrode (center electrode or base with electrode legs)

(27) 3 Cap

(28) 4 Housing

(29) 5 Ground electrode (inner wall of the cap)

(30) 6 Electrode legs (the ignition electrode)

(31) 7 Base (center electrode of ignition electrode)

(32) 8 Single electrode (for combination with a second single electrode)