Compressor wheel

Abstract

Compressor wheel ( 16 ) and techniques for manufacturing such a wheel are provided. The wheel may include a hub ( 21 ) with a counterbore ( 36 ) internally treated to impart residual compressive stresses, for enhanced endurance to stress-induced fatigue. The surface treatment allows extending the counterbore relatively closer to a plane ( 30 ) of typical maximum stress of the wheel. This design flexibility advantageously allows avoiding or reducing overhang of the compressor wheel, thereby improving rotor dynamics and reducing the axial length of the hub, and the overall foot print of the compressor wheel.

1 . A compressor wheel, the compressor wheel having an axis of rotation and comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein at least a portion of the backface is provided with a layer of residual compressive stress extending to a depth below the surface of the backface.  
   
   
       2 . A compressor wheel according to  claim 1 , wherein said backface portion is annular.  
   
   
       3 . A compressor wheel according to  claim 2 , wherein said backface portion extends radially from the axis of the compressor wheel.  
   
   
       4 . A compressor wheel according to  claim 1 , wherein said portion of the surface of the backface is a substantial portion of the surface of the backface.  
   
   
       5 . A compressor wheel according to  claim 4 , wherein the entire surface of the backface is provided with said layer of residual compressive stress.  
   
   
       6 . A compressor wheel according to  claim 1 , wherein the layer of residual compressive stress has a maximum depth of at least 300 μm.  
   
   
       7 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a minimum depth of 300 μm.  
   
   
       8 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a maximum depth of at least 500 μm.  
   
   
       9 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a minimum depth of at least 500 μm.  
   
   
       10 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a maximum depth of at least 800 μm.  
   
   
       11 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a minimum depth of at least 800 μm.  
   
   
       12 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a maximum depth of at least 1 mm.  
   
   
       13 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress has a minimum depth of at least 1 mm.  
   
   
       14 . A compressor wheel according to  claim 1 , wherein the depth of the layer of residual compressive stress varies across said portion of the surface of the backface.  
   
   
       15 . A compressor wheel according to  claim 14 , wherein said depth is minimised in regions of said portion of the backface susceptible to deformation under compressive forces required to produce said layer of compressive stress.  
   
   
       16 . A compressor wheel according to  claim 1 , wherein said layer of residual compressive stress is induced by applying a cold working technique to said portion of the backface.  
   
   
       17 . A compressor wheel according to  claim 16 , wherein said cold working technique comprises roller burnishing.  
   
   
       18 . A compressor wheel assembly comprising: 
 a compressor wheel having an axis of rotation and comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein at least a portion of the backface is provided with a layer of residual compressive stress extending to a depth below the surface of the backface.    
   
   
       19 . A compressor wheel assembly according to  claim 18 , wherein a second member is mounted to the shaft for rotation therewith in abutment with a region of the wheel backface, and wherein said portion of the wheel comprising said layer of residual compressive stress includes at least said region.  
   
   
       20 . A compressor wheel assembly according to  claim 19 , wherein said second member comprises an oil control device such as an oil slinger.  
   
   
       21 . A compressor wheel assembly according to  claim 19 , wherein said second member comprises a component of a thrust bearing assembly mounted on said shaft.  
   
   
       22 . A compressor wheel assembly according to  claim 18 , wherein the compressor wheel is welded to said shaft, a transition region being formed between the backface and shaft in the region of said weld, said transition region being provided with said layer of compressive residual stress.  
   
   
       23 . A compressor wheel assembly according to  claim 22 , wherein said transition region comprises a fillet radii.  
   
   
       24 . A compressor wheel assembly, comprising a compressor wheel welded to a shaft for rotation about an axis, the compressor wheel comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein a transition region is defined between the backface and shaft in the region of said weld, said transition region being provided with a layer of residual compressive stress extending the depth below the surface of the backface.  
   
   
       25 . A turbocharger comprising a compressor wheel having an axis of rotation and comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein at least a portion of the backface is provided with a layer of residual compressive stress extending to a depth below the surface of the backface.  
   
   
       26 . A method of manufacturing a compressor wheel to provide increased resistance to critical failure, the compressor wheel having an axis of rotation and comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein at least a portion of the backface is treated to form a layer of residual compressive stress extending to a depth below the surface of the backface.  
   
   
       27 . A method according to  claim 26 , wherein said treatment comprises applying a cold working technique to said portion of the backface.  
   
   
       28 . A method according to  claim 27 , wherein said cold working technique comprises roller burnishing.  
   
   
       29 . (canceled)  
   
   
       30 . A turbocharger comprising a compressor wheel welded to a shaft for rotation about an axis, the compressor wheel comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein a transition region is defined between the backface and shaft in the region of said weld, said transition region being provided with a layer of residual compressive stress extending the depth below the surface of the backface.  
   
   
       31 . A method of manufacturing a compressor wheel assembly comprising: 
 welding a compressor wheel to a shaft for rotation about an axis, the compressor wheel comprising a plurality of blades extending generally radially away from said axis and generally axially from one face of a disc-like support, the opposite face of the support defining a wheel backface, wherein a transition region is defined between the backface and shaft in the region of said weld; and    treating said transition region to form a layer of residual compressive stress extending the depth below the surface of the backface.