Spark plug with interference-suppression element

Abstract

A spark plug having a spark plug body and an insulator arranged therein, in which insulator a passage is provided in which a center electrode, an ignitor and a glass seal connecting the center electrode to the ignitor and acting as an interference-suppression resistor are arranged. At least one additional interference-suppression element is arranged in the passage of the insulator.

Claims

1. A spark plug having a spark plug body and an insulator arranged therein, the insulator includes a passage in which a center electrode, an ignitor having a shoulder and an end facing the center electrode, and a glass seal connecting the center electrode to the ignitor and acting as an interference-suppression resistor are arranged, wherein a plurality of additional interference-suppression elements are arranged in the passage of the insulator, surround a portion of the ignitor, and at least one of the plurality of additional interference-suppression elements contacts the shoulder of the ignitor, wherein each additional interference-suppression element of the plurality of additional interference-suppression elements are located between the shoulder of the ignitor and the end of the ignitor facing the center electrode.

2. The spark plug according to claim 1, wherein at least one additional interference-suppression element is composed of a ferromagnetic material.

3. The spark plug according to claim 1, wherein at least one additional interference-suppression element is formed annularly and surrounds a portion of the center electrode and/or the glass seal.

4. The spark plug according to claim 3, wherein the plurality of additional interference-suppression elements are annular and are arranged one behind the other in the passage of the insulator in the longitudinal direction of the spark plug.

5. The spark plug according to claim 1, wherein the passage in the insulator is configured as a stepped hole.

6. The spark plug according to claim 5, wherein at least one additional interference-suppression element rests against a step of the stepped hole.

7. The spark plug according to claim 1, wherein at least one additional interference-suppression element is composed of a ferrite having a Curie temperature of more than 250° C.

8. The spark plug according to claim 1, wherein at least one additional interference-suppression element is composed of a nickel-zinc ferrite.

9. The spark plug according to claim 1, wherein at least one additional interference-suppression element is composed of a ferrite having a Curie temperature of more than 500° C.

10. A spark plug having a spark plug body and an insulator arranged therein, the insulator includes a passage in which a center electrode, an ignitor having a shoulder, and a glass seal connecting the center electrode to the ignitor and acting as an interference-suppression resistor are arranged, wherein at least one additional interference-suppression element is arranged in the passage of the insulator, surrounds a portion of the ignitor, and contacts the shoulder of the ignitor, wherein the passage in the insulator is configured as a stepped hole and at least one additional interference-suppression element rests directly against a step of the stepped hole.

Description

DRAWINGS

(1) Further advantages and features may arise from the following description of some exemplary embodiments in connection with the figures. In the figures:

(2) FIG. 1 shows a spark plug in longitudinal section; and

(3) FIG. 2 shows a view similar to FIG. 1 of a variant of a spark plug.

DESCRIPTION

(4) The spark plug 1 illustrated in FIG. 1 includes a sleeve-shaped spark plug body or shell 2 having an external thread 3 for screwing into a combustion chamber. At the front end 4 of the spark plug 1, a ground electrode 5 is fastened to the front side of the spark plug body 2. The spark plug body 2 accommodates an elongated sleeve-shaped insulator 6 in which a passage 7 is provided. The insulator 6 protrudes with its rear end out of the spark plug body 2. A center electrode 8, an ignitor 9, a glass seal 10 and at least one additional interference-suppression element 11 are arranged in the passage 7.

(5) At the front end 4, the center electrode 8 protrudes out of the insulator 6 and the front side of the center electrode, together with the ground electrode 5, forms an air gap route or spark gap 12. In the region of the air gap route 12, the ground electrode 5 and/or the center electrode 8 can be protected against wear by a small precious metal plate. The ignitor 9 protrudes with its connector 13 out of the rear end of the insulator 6. There, a non-illustrated ignition cable can be connected for supplying ignition voltage to the spark plug. At its end facing towards the center electrode 8, the ignitor 9 has a knurling 14. The center electrode 8 and the ignitor 9 are fixedly connected by the glass seal 10. The glass seal 10 is composed of a composite glass, for example a glass-graphite composite, and is electrically conductive. As a result, the glass seal 10 forms an ohmic interference-suppression resistor. Moreover, the glass seal 10 seals the passage 7 of the insulator 6 in a gas-tight manner so that no combustion gases can escape from the combustion chamber of the internal combustion engine through the passage 7.

(6) The passage 7 in the insulator 6 is formed as a stepped hole having a step 15. The ignitor 9 has a shoulder 16 that faces away from the ignitor's connector 13. In FIG. 1, five annular interference-suppression elements 11 are illustrated which are made of ferrite and surround a portion of the ignitor 9. The interference elements 11 are positioned by the step 15 and the shoulder 16 in the longitudinal direction of the spark plug. The number and length of the interference-suppression elements 11 is variable; it is also possible that the spark plug 1 has only one interference-suppression element 11, for example.

(7) During the production of the spark plug 1, the center electrode 8, glass powder for the glass seal 10, the interference-suppression elements 11 and the ignitor 9 are mounted in the insulator 6. Subsequently, the insulator is heated to approximately 900° C. so that the glass of the glass seal 10 melts. Subsequently, the insulator 6 is cooled again. After cooling, the center electrode 8 and the ignitor 9 are fixedly connected by the glass seal 10.

(8) FIG. 2 illustrates a variant of a spark plug 1 in which the interference-suppression elements 11 do not rest against a step 15 in the insulator 6. Apart from this, the spark plug of FIG. 2 corresponds to the spark plug in FIG. 1 so that reference can be made to the description above to avoid repetitions.

REFERENCE LIST

(9) 1 spark plug 2 spark plug body 3 external thread 4 front end 5 ground electrode 6 insulator 7 passage 8 center electrode 9 ignitor 10 glass seal 11 additional interference-suppression element 12 air gap route 13 connector 14 knurling 15 step 16 shoulder