Compressor diffuser

Abstract

A compressor diffuser for a vehicle engine turbocharger, the diffuser comprising: a diffuser housing having a gas flow path having a side wall connecting a gas inlet to a gas outlet; a plurality of pivotally mounted diffuser vanes arranged in the flow path to control gas flow, and a vane angle control device for adjusting the angle of each of the plurality of vanes in the flow path; the control device comprising a unison ring coupled to the plurality of vanes in such a way that rotation of the unison ring pivots each of the vanes by interaction of a cam surface with a respective cam follower.

1 . A compressor for a turbocharger comprising: 
 a diffuser assembly comprising a diffuser housing defining a gas inlet and a gas outlet pneumatically connected by a gas flow path, a plurality of pivotally mounted diffuser vanes arranged in the flow path, and a vane angle control device for adjusting the angle of the diffuser vanes wherein the vane control device further comprises a unison ring coupled to the diffuser vanes in such a way that rotation of the unison ring pivots each of the diffuser vanes by interaction of a cam surface with a respective cam follower; and,    an impeller assembly positioned adjacent the diffuser assembly, the impeller assembly comprising an impeller wheel having a plurality of impeller blades adjoined thereto, a shroud wall extending circumferentially around the impeller blades, a venting chamber defined by the shroud wall and removed from the impeller wheel, wherein the shroud wall comprises at least one vent pneumatically connecting the impeller wheel to said venting chamber.    
   
   
       2 . A compressor according to  claim 1  further comprising means for controlling the airflow through each vent.  
   
   
       3 . A compressor according to  claim 2  wherein the means for controlling the airflow through the or each vent comprises a sliding cover.  
   
   
       4 . A compressor according to  claim 2  wherein the means for controlling the airflow through the or each vent comprises a rotatable cover.  
   
   
       5 . A compressor according to  claim 2  wherein the airflow through the or each vent is independently controllable.  
   
   
       6 . A compressor according to  claim 1  wherein a portion of the plurality of impeller blades comprise splitter blades and the remainder of plurality of impeller blade comprise full blades, wherein said full blades extend greater axial distance from the impeller wheel than the splitter blades.  
   
   
       7 . A compressor according to  claim 1  wherein all of said plurality of impeller blades are full blades.  
   
   
       8 . A compressor according to  claim 1  wherein the unison ring is mounted for rotation in a recess in the diffuser housing such that the side of the unison ring exposed to the gas flow in the gas path is generally flush with the remainder of the diffuser housing making up a side wall of the flow path, so that the exterior circumferential edge of the ring is not in the flow path.  
   
   
       9 . A compressor according to  claim 8  wherein the impeller wheel has a diameter and the unison ring has a thickness about 5% of the impeller wheel diameter.  
   
   
       10 . A compressor according to  claim 1  wherein each diffuser vane comprises a leading end and a trailing end and each is pivotally mounted about a pivot point adjacent the leading end.  
   
   
       11 . A compressor according to  claim 1  wherein the cam follower has a generally elongate oval shape in cross section to engage the cam surface over a contact surface.  
   
   
       12 . A compressor according to  claim 1  wherein the cam follower is formed as a tab on each vane and the respective cam surfaces are formed on the unison ring.  
   
   
       13 . A compressor diffuser according to  claim 1  wherein each cam surface is formed as an internal surface of an elongate slot in the unison ring, and wherein the slot has an arcuate form.  
   
   
       14 . A compressor according to  claim 11  wherein the elongate oval shape of the cam follower comprises a central generally rectangular region and two curved end regions.  
   
   
       15 . A compressor according to  claim 14  wherein the elongate oval shape of the cam follower further comprises a region having a trapezium cross-section formed between the rectangular region and each curved end section, so as to present at least three generally planar sides on each side of the cam follower.  
   
   
       16 . A compressor according to  claim 11  wherein the cam surface is contoured to be complementary to the engaging surface of the cam follower so as to maximize the area of the contact surface between the cam and the cam follower.  
   
   
       17 . A compressor according to  claim 1  wherein each vane has an elongate isosceles triangle shape with the apex of the triangle forming said one end, and the angle subtended at the apex of the triangle is between about 5 degrees and 15 degrees.  
   
   
       18 . A compressor according to  claim 1  wherein at least one side of each vane is curved.  
   
   
       19 . A compressor according to  claim 1  wherein the vane angle control device further comprises a rack and pinion driven crank shaft.  
   
   
       20 . A compressor according to  claim 19  wherein the vane angle control device further comprises a spring biased variable current solenoid.  
   
   
       21 . A compressor according to  claim 20  wherein the crank shaft is coupled to the solenoid via a cam on the crank shaft to provide direct position feedback to the solenoid.  
   
   
       22 . A compressor according to  claim 1  wherein each vane is pivotally mounted by means of a pivot pin on the vane which engages with a hole in the diffuser housing, and wherein the pivot pin and the cam follower are mounted on the same side of the vane and the pivot pin extends beyond the tab.  
   
   
       23 . A turbocharger comprising a compressor according to  claim 1 .  
   
   
       24 . A turbocharger according to  claim 23  further comprising means for controlling the airflow through the or each vent.  
   
   
       25 . A compressor for a turbocharger, comprising a diffuser assembly adjoined to an impeller assembly, 
 the diffuser comprising: 
 a diffuser housing defining a gas flow path having a side wall connecting a gas inlet to a gas outlet and a plurality of diffuser vanes arranged in the flow path to control gas flow; and, the impeller assembly comprising: 
 an impeller wheel having a plurality of impeller blades attached thereto, a venting chamber and a compressor housing shroud wall extending around the impeller blades and separating the impeller wheel from said venting chamber, wherein the shroud wall comprises at least one vent pneumatically connecting the impeller wheel to said venting chamber.  
 
   
   
   
       26 . A compressor according to  claim 25  wherein all of said plurality of impeller blades are full blades extending from the impeller wheel to a similar axial position.  
   
   
       27 . A compressor according to  claim 26  wherein the diffuser vanes are pivotally mounted such that their angle relative to the flow path can be adjusted.