Turbine housing insert in sliding variable-geometry turbocharger

Abstract

A turbocharger includes a thin-walled insert installed in the bore of the turbine housing. The insert is generally ring-shaped and is radially resilient. The insert can be made of sheet metal formed into a ring shape, and in some embodiments is a split ring. A piston is axially slidable in the bore for varying the size of the turbine nozzle. The outer surface of the piston slides against the inner surface of the insert, and in preferred embodiments a piston ring that encircles the piston engages the inner surface of the insert to substantially seal the interface between the insert and the piston.

1 . A turbocharger comprising:
 a compressor wheel affixed to one end of a shaft and disposed in a compressor housing;   a center housing having one side coupled to the compressor housing, the shaft passing through the center housing;   a turbine wheel affixed to an opposite end of the shaft and disposed in a bore of a turbine housing that is coupled to an opposite side of the center housing, the turbine housing defining a chamber surrounding the turbine wheel for receiving exhaust gas, and a nozzle through which the exhaust gas is directed into the turbine wheel;   an insert formed separately from the turbine housing and disposed in the bore of the turbine housing with a radially outer surface of the insert engaging an inner surface of the bore, the insert having a generally cylindrical inner surface, wherein the insert comprises a radially resilient ring formed of sheet metal; and   a tubular piston disposed in the bore such that the piston is slidable along an axial direction substantially parallel to a rotational axis of the turbine wheel for varying an effective size of the nozzle, wherein a radially outer surface of the piston slides against the inner surface of the insert.   
   
   
       2 . The turbocharger of  claim 1 , wherein the inner surface of the bore in the turbine housing defines a circumferential groove, and at least part of the insert is disposed in the groove such that the insert is restrained by the groove against axial movement of the insert. 
   
   
       3 . The turbocharger of  claim 2 , wherein the insert defines a flange that projects radially outwardly from one axial end of the insert, the flange being received in the groove while the remainder of the insert is outside the groove. 
   
   
       4 . The turbocharger of  claim 3 , wherein an opposite axial end of the insert defines a radially inwardly projecting flange, the two flanges serving to enhance hoop stiffness of the insert. 
   
   
       5 . The turbocharger of  claim 2 , wherein the groove has an axial length sufficient to receive a full axial length of the insert in the groove. 
   
   
       6 . The turbocharger of  claim 2 , wherein the insert comprises a split ring having opposite ends that are proximate to and circumferentially spaced from each other, the split ring being radially inwardly compressed by the turbine housing such that a restoring spring force of the split ring urges the split ring radially outwardly against a surface of the turbine housing. 
   
   
       7 . The turbocharger of  claim 6 , wherein the groove has a first end wall at one axial end of the groove and a second end wall at an opposite axial end of the groove, and wherein the insert is retained between the first and second end walls. 
   
   
       8 . The turbocharger of  claim 7 , wherein in a relaxed condition of the split ring the opposite ends thereof are axially offset relative to each other such that an axial length of the split ring exceeds an axial length of the groove, and such that the split ring is axially compressed between the first and second end walls of the groove. 
   
   
       9 . The turbocharger of  claim 6 , wherein the split ring has a split oriented substantially parallel to the axial direction. 
   
   
       10 . The turbocharger of  claim 6 , wherein the split ring has a split oriented at an acute angle to the axial direction. 
   
   
       11 . The turbocharger of  claim 6 , wherein the split ring has a split that is crenellated. 
   
   
       12 . The turbocharger of  claim 6 , wherein the split ring has a split that is wavy. 
   
   
       13 . The turbocharger of  claim 1 , wherein the piston includes a sealing ring encircling the outer surface of the piston and retained in a groove formed in the outer surface, the piston ring contacting the inner surface of the insert for substantially sealing an interface between the piston and the insert.