Automotive turbocharger systems

Abstract

A turbocharger system comprising first and second turbochargers, configured in series, where the turbochargers hand over control from one turbocharger to the other, which incorporates switching adjustment terms at the point of transition to ensure a smooth transition.

1 . A turbocharger system for an automotive engine comprising:
 an air inlet duct;   an exhaust gas duct;   a first turbocharger;   a second turbocharger, the first turbocharger being smaller than the second turbocharger, said first turbocharger and said second turbocharger each including an exhaust turbine situated in the exhaust duct and a blower wheel situated in the inlet duct, said blower wheels being arranged in series along said inlet duct;   a bypass duct, said bypass duct being connected to the exhaust duct on each side of the exhaust turbine of the first turbocharger and having no more than a single inlet port from an exhaust manifold and no more than a single outlet port leading to the second turbo-charger; and   the bypass duct comprising a selectively operable butterfly shut-off valve, said butterfly shut-off valve comprising a valve flap pivotally mounted within a housing, wherein an internal wall of the housing has two oppositely directed semi-annular sealing surfaces extending transversely to the direction of the exhaust gas flow, the valve flap being positionable between an open position in which the bypass duct is substantially unrestricted to gas flow and a closed position in which the valve flap is in sealing engagement with the two oppositely directed semi-annular sealing surfaces.   
   
   
       2 . The system of  claim 1 , wherein the two oppositely directed semi-annular sealing surfaces are offset from one another in the direction of exhaust gas flow through the housing by a distance substantially equal to a thickness of the valve flap. 
   
   
       3 . The system of  claim 1 , wherein the two oppositely directed semi-annular sealing surfaces comprise opposed side surfaces of two semi-annular sealing projections provided on the internal surface of the valve housing. 
   
   
       4 . The system of  claim 1 , wherein the interior surface of the housing is smoothly continuous throughout with the exception of two discontinuities at which the respective two oppositely directed semi-annular sealing surfaces are defined. 
   
   
       5 . A method of controlling a turbo charger system having a controller and first and second turbochargers with respective first and second operational ranges, wherein said first and second turbochargers include respective first and second compressors, said method comprising:
 issuing a control command to open a bypass around said first compressor when a downstream pressure with respect to the first compressor is less than or equal to an upstream pressure with respect to the first compressor; and   comparing one or more engine operating parameters to a threshold and issuing a control command to close said bypass when said comparison indicates that operation of the first compressor is required.   
   
   
       6 . The method of  claim 5 , wherein the set of one or more engine operating parameters that may be compared to a threshold comprises engine speed, engine load, pressure, exhaust gas mass flow, fuelling, and valve position. 
   
   
       7 . The method of  claim 5 , wherein closing the bypass comprises fully or partially closing the bypass. 
   
   
       8 . The method of  claim 5 , wherein the first and second compressors are in a series sequential configuration and the first compressor is in a high pressure location in such configuration. 
   
   
       9 . The method of  claim 5 , further comprising keeping the bypass around the first compressor closed until a control command to re-open the bypass is received. 
   
   
       10 . The method of  claim 9 , wherein keeping the bypass closed comprises preventing issuance of a control command to open the bypass if, after closing the bypass, said downstream pressure becomes less than or equal to said upstream pressure. 
   
   
       11 . A computer-readable medium encoded with a program configured to implement a method of controlling a turbo charger system having a controller and first and second turbochargers with respective first and second operational ranges, wherein said first and second turbochargers include respective first and second compressors, said method comprising:
 issuing a control command to open a bypass around said first compressor when a downstream pressure with respect to the first compressor is less than or equal to an upstream pressure with respect to the first compressor; and   comparing one or more engine operating parameters to a threshold and issuing a control command to close said bypass when said comparison indicates that operation of the first compressor is required.   
   
   
       12 . The computer-readable medium of  claim 11 , further comprising an engine control unit.