Patent ID: 7748218
Filing Date: 2010-07-06
Classification: F02B,F02D,Y02T

Abstract:
1. A method of exhaust back-pressure control in an internal combustion engine having an intake system for developing charge air for the engine, combustion chambers in which admitted charge air and injected fuel combust to operate the engine, an exhaust system for conveyance of exhaust gas resulting from combustion from the combustion chambers, a two-stage turbocharger comprising an upstream compressor upstream of a downstream compressor in the intake system operated respectively by a downstream turbine downstream of an upstream turbine in the exhaust system, a turbine-shunting bypass valve shunting one of the turbines with which a mechanism for adjusting exhaust back-pressure that the turbocharger is creating on the engine is associated, the downstream compressor and the upstream turbine comprising a high-pressure stage of the turbocharger, with the upstream turbine being the one turbine shunted by the turbine-shunting bypass valve and the downstream compressor being shunted by a compressor-shunting bypass valve, and a control system, comprising a processor, for operating the mechanism and for operating the turbine-shunting bypass valve, the method comprising: executing an algorithm in the processor according to a strategy for selectively causing the control system to be unenabled from operating the turbine-shunting bypass valve when the control system is operating the mechanism to adjust back-pressure within a range of effectiveness for the mechanism to control exhaust back-pressure and to be enabled to operate the turbine-shunting bypass valve when the control system has operated the mechanism to a limit of the range of effectiveness; controlling exhaust back-pressure by selectively positioning adjustable vanes of the upstream turbine when the control system is unenabled; wherein the strategy for selectively causing the control system to be enabled to operate the turbine-shunting bypass valve also causes the control system to be enabled to operate the compressor-shunting bypass valve, and the strategy comprises comparing a data value representing a set-point for desired exhaust back-pressure and a data value representing a set-point defining a maximum that is based on at least one parameter indicative of current engine operation and that needs to be exceeded by the set-point for desired exhaust back-pressure in order to enable the control system to operate the bypass valves, and enabling the control system to operate the bypass valves when the result of the comparing step discloses that the set-point for desired exhaust back-pressure exceeds the defined maximum.