Exhaust gas turbocharger

1. An exhaust gas turbocharger, comprising:

a turbine casing ( 4 );

a turbine wheel ( 10 ) which is rotatably arranged relative to an axis of rotation ( 1 ) within the turbine casing ( 4 );

a guide vane ring ( 22 ) which is non-rotatably arranged within the turbine casing ( 4 ); and

variable guide vanes ( 44 ) which are arranged upstream of the turbine wheel ( 10 ) with respect to an exhaust gas flow, the variable guide vanes ( 44 ) being a part of the guide vane ring ( 22 ),

wherein the guide vane ring ( 22 ) is centered by a matched pair of two contact surfaces ( 24 , 26 ) pressed against each other with respect to the turbine casing ( 4 ), of which at least one contact surface ( 24 or 26 , respectively) is conical, and

wherein the at least one conical contact surface ( 26 ) is disposed at a radial outer zone ( 61 ) of the guide vane ring ( 22 ).

2. The exhaust gas turbocharger according to claim 1 ,

wherein the matched pair of two contact surfaces ( 24 , 26 ) forms a seal which essentially separates a space ( 14 ) within the exhaust gas flow from a holding space ( 60 ), and

wherein a connection mechanism ( 58 ) is arranged in the holding space ( 60 ), and

wherein the connection mechanism ( 58 ) connects swivel shafts ( 42 ) for varying the variable guide vanes ( 44 ) to an actuating device ( 66 ) for rotating the swivel shafts ( 42 ).

3. The exhaust gas turbocharger according to claim 1 ,

wherein the at least one conical contact surface ( 26 ) is arranged directly at the guide vane ring ( 22 ), and

wherein on the at least one conical contact surface ( 26 ) a cone angle (α) is formed whose vertex ( 65 ) lies on the axis of rotation ( 1 ) in a direction which axially faces an exhaust gas outlet ( 36 ).

4. The exhaust gas turbocharger according to claim 3 ,

wherein the cone angle (α) is in a range from 120° to 150°.

5. The exhaust gas turbocharger according to claim 1 ,

wherein a further one of the two contact surfaces ( 24 ) is conical and is arranged directly at the turbine casing ( 4 ), and

wherein on the further conical contact surface ( 24 ) a cone angle (α) is formed whose vertex ( 65 ) lies on the axis of rotation ( 1 ) in a direction which axially faces an exhaust gas outlet ( 36 ).

6. The exhaust gas turbocharger according to claim 5 ,

wherein the cone angle (α) is in a range from 120° to 150°.

7. The exhaust gas turbocharger according to claim 1 ,

wherein the two contact surfaces ( 24 , 26 ) are both formed conically and

wherein their matched materials and their cone angles (α) ensure that no self-locking can occur at the conical centering in a direction of the axis of rotation ( 1 ).

8. The exhaust gas turbocharger according to claim 1 ,

wherein the two contact surfaces ( 24 , 26 ) contact each other in a direction of the axis of rotation ( 1 ) under preload of a spring ( 20 ).

9. The exhaust gas turbocharger according to claim 8 ,

wherein the spring is a disc spring.

10. The exhaust gas turbocharger according to claim 8 ,

wherein the two contact surfaces ( 24 , 26 ) are essentially disposed in an axial area of the spring ( 20 ) and of a heat shielding plate ( 16 ) which is axially arranged between the spring ( 20 ) and the turbine wheel ( 10 ).

11. The exhaust gas turbocharger according to claim 10 ,

wherein the heat shielding plate ( 16 ) has a radial clearance relative to the guide vane ring ( 22 ) or a bearing housing ( 6 ), which is large enough to ensure centering by the two contact surfaces ( 24 , 26 ).

12. The exhaust gas turbocharger according to claim 3 ,

wherein the two contact surfaces ( 24 , 26 ) are formed conically and have an identical cone angle (α), which ensures that a reduction of a preload due to thermal expansions of components of the exhaust gas turbocharger ( 2 ) during its operation is compensated.

13. The exhaust gas turbocharger according to claim 1 ,

wherein the variable guide vanes ( 44 ) are pivotably mounted on a base ring ( 38 ) of the guide vane ring ( 22 ), which comprises a radially projecting annular collar ( 64 ) at which the one conical contact surface ( 26 ) is arranged which contacts the other conical contact surface ( 24 ) which is arranged at a radially inward extending shoulder ( 62 ) of the turbine casing ( 4 ) and

wherein the other conical contact surface ( 24 ) is arranged at a side of the shoulder ( 62 ) facing away from a turbine spiral channel ( 14 ), while the side of the shoulder ( 62 ) facing the turbine spiral channel ( 14 ) is formed as part of an inner wall ( 63 ) of the turbine spiral channel ( 14 ).

14. The exhaust gas turbocharger according to claim 1 ,

wherein the two contact surfaces ( 24 , 26 ) are configured conically and without protrusions so that the guide vane ring ( 22 ) may be steplessly fixed at the turbine wheel ( 10 ) in various angular positions about the axis of rotation ( 1 ).