Valve for an exhaust gas line of an internal combustion engine

1. A valve for an exhaust gas line of an internal combustion engine, comprising:

a housing with an inlet opening and an outlet opening and a duct for directing exhaust gases from the inlet opening to the outlet opening;

a closure body arranged in the duct and positioned in a torque-proof manner in a recess of a shaft, the closure body being pivotable about a rotation axis of the shaft and having a closed position in which the closure body separates upstream and downstream sections of the duct;

the closure body having first and second sides, wherein in the closed position of the closure body the first side faces the upstream section of the duct and the second side faces the downstream section of the duct;

the closure body having a circumferential surface arranged between the first and second sides, the circumferential surface having sections with different external dimensions;

a first external dimension of the circumferential surface in a first section being smaller than the smallest internal dimension between two end regions of the recess, wherein all said dimensions are measured parallel to one another along the rotation axis of the shaft;

a second external dimension of the circumferential surface in a second section being greater than the smallest internal dimension between the two end regions; and

the circumferential surface contacting the shaft in each of the two end regions of the recess.

2. The valve according to claim 1 , wherein the contact between the circumferential surface of the closure body and the shaft is formed by a line contact lying within the recess of the shaft.

3. The valve according to claim 2 , wherein the line contact forms a straight line.

4. The valve according to claim 1 , wherein the circumferential surface of the closure body has at least one stop shoulder, which in one of the two end regions of the recess lies against the shaft.

5. The valve according to claim 1 , wherein the circumferential surface of the closure body has two stop shoulders, each of which lies against the shaft in one of the two end regions of the recess.

6. The valve according to claim 1 , further comprising:

two projections arranged on an inner wall of the duct in a region of the closure body, the projections extending in a circumferential direction of the duct, one of the projections being situated in an upstream section of the duct and the other projection being situated in a downstream section of the duct;

each of the projections having a valve seat pointing in the longitudinal direction of the duct, the two valve seats pointing in opposite directions; and

the closure body having two sealing surfaces arranged on opposite sides thereof, wherein each sealing surface in the closed position of the closure body lies against one of the valve seats and, by pivoting the closure body from its closed position, the sealing surfaces are raised from their respective valve seats.

7. The valve according to claim 6 , further comprising:

a polymer seal arranged on the valve seats, wherein in the closed position of the closure body, the polymer seal is contacted in a sealing manner by the associated sealing surface of the closure body;

a cylindrical surface formed on the shaft in the end regions; and

the polymer seal contacting in a sealing manner at least a region of the cylindrical surface facing the upstream section of the duct.

8. The valve according to claim 7 , wherein the polymer seal surrounds and seals the entire circumference of the shaft.

9. The valve according to claim 6 , wherein the seal has a sealing lip extending in an axial direction of the shaft, the sealing lip contacting in a sealing manner the cylindrical surface of the shaft and on pivoting of the closure body slides over the shaft.

10. The valve according to claim 1 , wherein the recess of the shaft has at least one slot passing radially through the shaft in which the closure body is placed.