Gap geometry in a cohesively joined cooling-channel piston

1. A cooling-channel piston for an internal combustion engine, having an upper part and a lower part, wherein the upper part and the lower part are connected to one another by way of a cohesive joint in a form of a weld seam and the upper part and the lower part form an annular circumferential cooling channel that is located behind a ring belt, wherein a gap geometry is provided between a lower edge of the ring belt and an upper edge of the lower part, wherein the gap geometry has at least one sliding surface that is arranged on a lower edge of the ring belt of the cooling-channel piston and/or on the corresponding upper edge of a lower part of the cooling-channel piston.

2. The cooling-channel piston from claim 1 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis.

3. The cooling-channel piston from claim 1 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path.

4. The cooling-channel piston from claim 1 , wherein a projection is provided on a side of the ring belt facing the cooling channel.

5. The cooling-channel piston from claim 4 , wherein the projection follows a curvilinear path.

6. The cooling-channel piston from claim 4 , wherein the projection forms a contoured guide for a cooling medium.

7. The cooling-channel piston from claim 4 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis.

8. The cooling-channel piston from claim 4 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path.

9. The cooling-channel piston from claim 4 , having a gap within the gap geometry that separates the upper part and the lower part, wherein a separation between the upper part and the lower part is greater at an upper end of the gap than at a lower end of the gap.

10. The cooling-channel piston from claim 1 , having a gap within the gap geometry that separates the upper part and the lower part, wherein a separation between the upper part and the lower part is greater at an upper end of the gap than at a lower end of the gap.

11. The cooling-channel piston from claim 10 , wherein at least one section of the gap separating the upper part and the lower part is parallel to a piston stroke axis.

12. The cooling-channel piston from claim 10 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis.

13. The cooling-channel piston from claim 10 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path.

14. A method for operating the cooling-channel piston for internal combustion engines in accordance with claim 1 , wherein the gap geometry has a contoured guide that guides a cooling medium around the gap geometry.

15. The method from claim 14 , wherein a projection is provided on a side of the ring belt facing the cooling channel.

16. The method from claim 15 , wherein the projection is configured as a contoured guide for the cooling medium, wherein a defined direction of flow for the cooling medium during upward motion of the cooling-channel piston and another defined direction of flow for the cooling medium during downward motion of the cooling-channel piston is achieved.

17. A method for operating a cooling-channel piston for internal combustion engines in accordance with claim 1 , wherein in the event of contact between the upper part and the lower part of the cooling-channel piston, at least one sliding surface arranged on the upper part and/or lower part enables the upper part and the lower part to slide relative to one another.

18. The method from claim 17 , wherein the upper part and the lower part slide along a curvilinear sliding surface.

19. The cooling-channel piston from claim 1 , wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a diagonal path with respect to a piston stroke axis;

wherein the lower edge of the ring belt of the cooling-channel piston and/or the corresponding upper edge of the lower part of the cooling-channel piston follows a curvilinear path;

wherein a projection is provided on a side of the ring belt facing the cooling channel; and

wherein a gap within the gap geometry that separates the upper part and the lower part has an upper gap dimension that is greater than a lower gap dimension.

20. The cooling channel piston from claim 1 wherein the at least one sliding surface allows at least one of the upper part or the lower part to slide along the at least one sliding surface towards a piston stroke axis or opposite to the piston stroke axis.