Spark plug for an internal combustion engine

1. A spark plug for an internal combustion engine, comprising

a center electrode;

a ground electrode arranged in radial direction around the center electrode; and

an annular spark gap is formed between the center electrode and the ground electrode for igniting a fuel mixture by an electric ignition spark between the center electrode and the ground electrode,

wherein the ground electrode is contoured such that particles reaching a region of the ground electrode can be removed from the annular spark gap under an influence of gravitational force,

wherein the ground electrode has a first portion extending in axial direction of the center electrode and a second portion extending in radial direction toward the center electrode,

through-holes for the fuel mixture arranged circumferentially in the first portion that penetrate the ground electrode viewed in radial direction of the center electrode, whereby the particles reaching the region of the ground electrode are removed via the through-holes,

wherein the annular spark gap is formed between the center electrode and the second portion of the ground electrode, and

wherein the ground electrode is contoured at an upper surface of the second portion extending in radial direction of the center electrode such that the upper surface extends downward in a ramp-like manner with an increasing distance from the annular spark gap, and

wherein a valley is formed at an upper surface of the second portion extending in radial direction of the center electrode,

wherein a lower surface of the second portion opposite the upper portion is substantially planar and substantially perpendicular to the first portion,

wherein the valley is formed adjacent to the through-holes for the fuel mixture that penetrate the ground electrode viewed in radial direction of the center electrode, between the through-holes and the annular spark gap at a radial distance from the through-holes and at radial distance from the annular spark gap, and

wherein the radial distance from the through-holes is smaller than the radial distance from the annular spark gap.

2. The spark plug according to claim 1 , wherein the valley extends annularly around the annular spark gap at a radial distance.

3. The spark plug according to claim 2 , wherein the valley is formed in a transition area between the first portion of the ground electrode and the second portion of the ground electrode.

4. An internal combustion engine, configured to burn a fuel mixture comprising gaseous fuel and air, having at least one spark plug comprising

a center electrode; and

a ground electrode arranged in radial direction around the center electrode,

wherein an annular spark gap is formed between the center electrode and the ground electrode for igniting the fuel mixture by an electric ignition spark developing between the center electrode and the ground electrode, and

wherein the ground electrode is contoured such that particles reaching a region of the ground electrode can be removed from the annular spark gap under an influence of gravitational force,

wherein the ground electrode has a first portion extending in axial direction of the center electrode and a second portion extending in radial direction toward the center electrode,

through-holes for the fuel mixture arranged circumferentially in the first portion that penetrate the ground electrode viewed in radial direction of the center electrode, whereby the particles reaching the region of the ground electrode are removed via the through-holes,

wherein the annular spark gap is formed between the center electrode and the second portion of the ground electrode, and

wherein the ground electrode is contoured at an upper surface of the second portion extending in radial direction of the center electrode such that the upper surface extends downward in a ramp-like manner with an increasing distance from the annular spark gap, and

wherein a valley is formed at an upper surface of the second portion extending in radial direction of the center electrode,

wherein a lower surface of the second portion opposite the upper portion is substantially planar and substantially perpendicular to the first portion,

wherein the valley is formed adjacent to the through-holes for the fuel mixture that penetrate the ground electrode viewed in radial direction of the center electrode, between the through-holes and the annular spark gap at a radial distance from the through-holes and at radial distance from the annular spark gap, and

wherein the radial distance from the through-holes is smaller than the radial distance from the annular spark gap.

5. The spark plug according to claim 1 , wherein a valley is formed at an upper surface of the second portion extending in radial direction of the center electrode.

6. The spark plug according to claim 5 , wherein the valley is formed in a transition area between the first portion of the ground electrode and the second portion of the ground electrode.

7. The internal combustion engine according to claim 4 , wherein the internal combustion engine is an Otto gas engine.