Turbocharger with variable-vane turbine nozzle having a gas pressure-responsive vane clearance control member

A turbocharger, comprising:

• a compressor comprising a compressor housing and a compressor wheel disposed in the compressor housing;
• a turbine housing defining a bore extending axially through the turbine housing and defining an exhaust gas inlet and an annular chamber that receives exhaust gas via the exhaust gas inlet, the chamber extending circumferentially about the bore, and a turbine wheel disposed within the turbine housing and arranged for receiving exhaust gas from the chamber and expanding the exhaust gas and discharging the exhaust gas into the bore, the compressor wheel and the turbine wheel being affixed to opposite ends of a shaft;
• a turbine nozzle extending from the chamber generally radially inwardly to the turbine wheel, the turbine nozzle being defined between a first wall and a second wall axially spaced wall from the first wall, and a contour adjacent a radially outer periphery of the turbine wheel and transitioning from the turbine nozzle into the bore;
• a variable-vane assembly comprising a fixed nozzle ring and a plurality of circumferentially spaced vanes rotatably mounted on the nozzle ring such that the vanes are each rotatable about respective vane pivot axes, the nozzle ring defining the first wall of the turbine nozzle, the vanes being disposed in the turbine nozzle, each vane having a first end adjacent the first wall and a second end adjacent the second wall;
• wherein the second wall of the turbine nozzle is formed by a gas pressure-responsive member that is arranged to be axially movable relative to the vanes;
• a first stop positioned so that the gas pressure-responsive member is urged axially against the first stop by a differential gas pressure between a side of the gas pressure-responsive member adjacent the vanes and an opposite side of the gas pressure-responsive member, so that there is a non-zero first value for a clearance between the second ends of the vanes and the second wall of the turbine nozzle.