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

1. 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 annular chamber extending circumferentially about the bore, and a turbine wheel disposed within the turbine housing and arranged for receiving exhaust gas from the annular 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 annular chamber 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;

a gas pressure-responsive member that is arranged to be axially movable relative to the vanes, the gas pressure-responsive member comprising a pipe having a tubular portion that extends axially and an annular flange portion that extends radially outwardly from one end of the tubular portion, the flange portion forming the second wall of the turbine nozzle, the pipe forming said contour;

an elastic member affixed to the pipe and disposed between the pipe and a portion of the turbine housing such that a dead-headed space is created between a back side of the flange portion and the turbine housing, in which said dead-headed space the exhaust gas from the annular chamber is substantially stagnated such that a static pressure in said dead-headed space is higher than a static pressure of the exhaust gas flowing through the turbine nozzle on an opposite front side of the flange portion so as to urge the pipe axially toward the nozzle ring, and wherein one side of the elastic member is exposed to said static pressure in said dead-headed space to increase a contact force between the elastic member and the portion of the turbine housing, wherein the elastic member is annular having a radially outer edge and a radially inner edge, and wherein one end of the elastic member defined by the radially inner edge is affixed to the pipe and an opposite end of the elastic member defined by the radially outer edge engages the portion of the turbine housing; and

a first stop positioned so that the flange portion of the pipe which is urged axially toward the nozzle ring is stopped by the first stop from contacting the second ends of the vanes, so that there is a non-zero first value for a clearance between the second ends of the vanes and the flange portion.

2. The turbocharger of claim 1 , wherein the elastic member is affixed to the tubular portion of the pipe.

3. The turbocharger of claim 2 , wherein the elastic member is press-fit onto the tubular portion.

4. The turbocharger of claim 1 , wherein the elastic member is a resilient metal part.

5. The turbocharger of claim 1 , wherein the elastic member is pre-compressed between the turbine housing and the pipe so as to urge the pipe toward the first stop in the absence of differential gas pressure on the pipe.

6. The turbocharger of claim 1 , wherein the first stop is provided by spacers rigidly affixed to the nozzle ring and extending axially from the nozzle ring toward the flange portion of the pipe.

7. The turbocharger of claim 6 , wherein each spacer extends through an opening in the flange portion of the pipe.

8. The turbocharger of claim 7 , wherein the spacers define a second stop for the flange portion, the flange portion being limited in axial movement away from the first stop by abutment against the second stop.

9. The turbocharger of claim 1 , wherein the pipe is substantially rigid.

10. The turbocharger of claim 1 , wherein the pipe is a stamped sheet metal part.