Patent ID: 8056336

Claim:
A variable nozzle for a turbocharger, comprising: a generally annular nozzle ring defining a plurality of circumferentially spaced bearing apertures extending axially through an axially facing face of the nozzle ring; a nozzle wall defining a face axially spaced from and opposing the face of the nozzle ring, a nozzle flow path being defined between the opposing faces of the nozzle ring and nozzle wall; and a plurality of circumferentially spaced vanes disposed in the nozzle flow path, each vane comprising a shaft defining a pivot axis for the vane, the shafts of the vanes being respectively received in the bearing apertures of the nozzle ring and being rotatable therein about the respective pivot axes such that the vanes are adjustable in setting angle between a closed position and an open position, each vane including an aerodynamic airfoil portion having an outer airfoil surface, each airfoil portion being joined to the respective shaft and extending along the pivot axis from a first end to an opposite second end, the first and second ends of each airfoil portion respectively defining first and second end faces that are substantially perpendicular to the pivot axis, clearances existing between the first end faces of the airfoil portions and the face of the nozzle ring and between the second end faces of the airfoil portions and the face of the nozzle wall, wherein each airfoil portion has a suction side and an opposite pressure side and has a leading edge and a trailing edge, and the airfoil surfaces of each vane have a length in a flow direction from the leading edge to the trailing edge, the pivot axis of each vane being located intermediate the leading and trailing edges; wherein at least the face of the nozzle ring includes at least one step defining sealing surfaces that are positioned to be substantially abutted by the airfoil surfaces in the closed position of the vanes and to be spaced from the airfoil surfaces in positions other than the closed position, and wherein the at least one step includes leading-edge step portions positioned to be substantially abutted by leading-edge portions of the airfoil surfaces on the pressure sides of the airfoil portions, and trailing-edge step portions positioned to be substantially abutted by trailing-edge portions of the airfoil surfaces on the suction sides of the airfoil portions; wherein each vane has a bearing portion disposed between the first end of the airfoil portion and the shaft, the bearing portion having a substantially circular outer peripheral surface of larger diameter than the shaft, and wherein the at least one step in the face of the nozzle ring includes medial step portions defining sealing surfaces in substantial abutment with the outer peripheral surfaces of the bearing portions.