Variable geometry turbine

Abstract

A variable geometry turbine for a turbocharger has a plurality of vanes disposed in an inlet passageway of a turbine housing outboard of the turbine wheel. The vanes are movable so as to adjust the effective cross-section area of the inlet between a first position in which the area of the inlet is a minimum and a second position in which the area of the inlet is a maximum. The movement of one end of the vanes is supported by a plurality of first guide tracks, such as slots, defined in a guide member. A vane actuator such as, for example a unison ring, effects movement of the vanes. The vane actuator has a plurality of actuation tracks (e.g. slots) for engagement with the vanes and is rotatably disposed in the housing. When it rotates the vane actuator induces sliding translation of the vanes relative to the first guide tracks in a first direction and sliding translation of the vanes relative to the actuation tracks in a second direction so as to adjust the cross-section area of the inlet. The swirl angle changes between the first and second positions.

1 . A variable geometry turbine comprising:
 a housing defining a chamber within which a turbine wheel is mounted for rotation about a turbine axis such that its outer periphery substantially describes a swept circumference;   the chamber having a gas inlet disposed radially outboard of an outer periphery of said turbine wheel;   a plurality of vanes arranged around the turbine axis, each vane having a vane height extending between a first end and a second end in a direction across the inlet in a substantially axial direction and each vane being movable so as to adjust the effective cross-section area of the inlet between a first position in which the area of the inlet is a minimum and a second position in which the area of the inlet is a maximum;   at least one guide member having a plurality of first guide tracks for engagement with the first ends of the vanes;   a vane actuator for effecting translational movement of the plurality of vanes relative to the housing between the first and second positions, the vane actuator having a plurality of actuation tracks for engagement with the plurality of vanes, the vane actuator being rotatably disposed in the housing such that rotation of the vane actuator induces sliding translation of each of the plurality of vanes relative to a respective first guide track in a first direction and sliding translation of each of the plurality of vanes relative to the respective actuation track in a second direction, the second direction being different to the first direction;   wherein in the first position the vanes are disposed such that at a given turbine pressure ratio they direct the gas to the turbine wheel such that it has a first swirl angle at the swept circumference of the turbine wheel and in the second position the vanes are disposed such that at the same turbine press ratio they direct the gas to the turbine wheel such that it has a second swirl angle at the swept circumference, the first swirl angle being greater than the second swirl angle.   
     
     
         2 . A variable geometry turbine according to  claim 1 , wherein the first ends of the plurality of vanes have at least one projection and the plurality of first guide tracks are in the form of first guide slots, the at least one projection of each vane being received in a respective first guide slot. 
     
     
         3 . A variable geometry turbine according to  claim 1 , wherein the plurality of first guide slots extend in a substantially tangential direction. 
     
     
         4 . A variable geometry turbine according to  claim 1 , wherein the plurality of actuation tracks in the vane actuator are in the form of slots. 
     
     
         5 . A variable geometry turbine according to  claim 4 , wherein the actuation tracks extend in a substantially radial direction. 
     
     
         6 . A variable geometry turbine according to  claim 1 , wherein the guide member and the vane actuator are spaced apart in the axial direction, the plurality of vanes being disposed between them. 
     
     
         7 . A variable geometry turbine according to  claim 6 , wherein the second ends of the vanes each have at least one projection and the actuation tracks are in the form of slots, the at least one projection of the second ends being received in a respective slot in the vane actuator. 
     
     
         8 . A variable geometry turbine according to  claim 1 , wherein the guide member and the vane actuator are disposed at the first end of the vanes. 
     
     
         9 . A variable geometry turbine according to  claim 1 , wherein the guide member is defined by a wall of the turbine housing. 
     
     
         10 . A variable geometry turbine according to  claim 1 , wherein the guide member is annular. 
     
     
         11 . A variable geometry turbine according to  claim 1 , wherein there is provided a first guide member having the plurality of first guide tracks and a second guide member spaced apart from the first guide member in an axial direction and having a plurality of second guide tracks for engagement with the second end of the plurality of vanes. 
     
     
         12 . A variable geometry turbine according to  claim 1 , wherein the plurality of vanes have a flange at one or both of the first and second ends. 
     
     
         13 . A variable geometry turbine according to  claim 12 , wherein the vane projections extend from the flanges at each end. 
     
     
         14 . A variable geometry turbine according to  claim 1 , wherein the plurality of vanes each have a pair of projections at a first end for receipt in the first guide tracks. 
     
     
         15 . A variable geometry turbine according to  claim 14 , wherein the pair of guide tracks are substantially identically shaped. 
     
     
         16 . A variable geometry turbine according to  claim 14 , wherein the pair of guide tracks have different profiles. 
     
     
         17 . A variable geometry turbine according to  claim 1 , wherein the vane actuator is a substantially annular unison ring. 
     
     
         18 . A variable geometry turbine according to  claim 1 , wherein the first guide tracks are substantially linear. 
     
     
         19 . A variable geometry turbine according to  claim 11 , wherein the second guide track are substantially linear. 
     
     
         20 . A variable geometry turbine according to  claim 1 , wherein the vanes define trailing edges proximate the turbine wheel and in the first position the trailing edges of the vanes are at a first distance from the turbine wheel swept circumference, in the second position the trailing edges of the vanes are at a second distance from the swept circumference, the first distance being shorter than the second distance. 
     
     
         21 . A variable geometry turbine according to  claim 1 , wherein the plurality of vanes are movable in unison. 
     
     
         22 . A variable geometry turbine according to  claim 1 , wherein the vanes translate without pivoting about a fixed point. 
     
     
         23 . A variable geometry turbine according to  claim 1 , wherein all of the vanes disposed around the turbine axis are movable between the first and second positions. 
     
     
         24 . A turbocharger comprising a compressor driven by an exhaust gas variable geometry turbine according to  claim 1 .