Coordinating variable valve actuation and turbocharger operation in an internal combustion engine
View Patent ↗An engine control system coordinates control of a pressure regulating mechanism associated with a turbocharger turbine and control of a variable valve actuating (VVA) mechanism for expanding the range of possible exhaust gas recirculation rates over a large portion of an engine operating map to provide EGR rates which are greater than typical present-day levels while mitigating engine pumping losses by causing the turbocharger to operate with better efficiency in some regions of the map where it otherwise would not. Turbocharger efficiency is improved by controlling the VVA mechanism to set the timing of operation of its respective cylinder valves in accordance with a predetermined correlation of operating efficiencies of a compressor to timing of operation of respective engine cylinder valves, causing the compressor to operate at points of better efficiency than it otherwise would without use of VVA.
1. A method for changing pressure in an exhaust manifold of an internal combustion engine, comprising:
providing engine structure comprising engine cylinders within which fuel is combusted to operate the engine,
providing a turbocharger comprising at least one turbine for operating at least one compressor,
providing an exhaust system through which engine exhaust created in the engine cylinders is conveyed from the engine cylinders, the exhaust system comprising an exhaust manifold through which engine exhaust leaves the engine cylinders, at least one of the turbines of the turbocharger being in downstream flow relation to the exhaust manifold and operated by engine exhaust, and a variable valve pressure control element which is operable to different settings of interaction with the at least one turbine to control pressure in the exhaust manifold,
providing cylinder exhaust valves for controlling admission of engine exhaust from the engine cylinders into the exhaust manifold,
providing an intake system comprising an intake manifold through which a mixture having an air component for supporting combustion of fuel and an engine exhaust component enters the engine cylinders,
providing cylinder intake valves for controlling admission of the mixture from the intake manifold into the engine cylinders,
further providing the intake system with an air inlet through which the air component enters the intake system, and the at least one compressor of the turbocharger being in downstream flow relation to the air inlet and operated by the turbine with which the variable valve pressure control element interacts for causing pressure of the mixture in the intake manifold to be superatmospheric,
providing an exhaust gas recirculation (EGR) system for conveying the engine exhaust component of the mixture from the exhaust system to the intake system,
controlling the opening and closing movement of the cylinder intake valves, and controlling the opening and closing of the cylinder exhaust valves such that at least one of the valves is controllable to change the timing of its operation, and
during engine operation;
changing the timing of operation of at least one of the cylinder intake valves without changing an existing setting of the variable valve pressure control element, and when changing the timing of operation of at least one of the cylinder intake valves without changing an existing setting of the variable valve pressure control element is by itself unable to change the existing pressure in the exhaust manifold to a different pressure, changing the existing setting of the variable valve pressure control element to a different setting to change the existing pressure in the exhaust manifold to the different pressure.
2. The method set forth in claim 1 in which the variable valve pressure control element comprises a selectively operable valve shunting the turbine with which the variable valve pressure control element interacts.
3. A method for changing pressure in an exhaust manifold of an internal combustion engine, the method comprising:
providing an engine structure comprising engine cylinders within which fuel is combusted to operate the engine,
providing an exhaust system through which engine exhaust created in the engine cylinders is conveyed from the engine cylinders, the exhaust system comprising an exhaust manifold through which engine exhaust leaves the engine cylinders, a turbine in downstream flow relation to the exhaust manifold and operated by engine exhaust, and a variable valve-pressure control element which is operable to different settings of interaction with the turbine to control pressure in the exhaust manifold,
providing cylinder exhaust valves for controlling admission of engine exhaust from the engine cylinders into the exhaust manifold,
providing an intake system comprising an intake manifold through which a mixture having an air component for supporting combustion of fuel and an engine exhaust component enters the engine cylinders,
providing cylinder intake valves for controlling admission of the mixture from the intake manifold into the engine cylinders,
further providing the intake system with an air inlet through which the air component enters the intake system, and also a compressor in downstream flow relation to the air inlet and operated by the turbine for causing pressure of the mixture in the intake manifold to be superatmospheric,
providing an exhaust gas recirculation (EGR) system for conveying the engine exhaust component of the mixture from the exhaust system to the intake system,
providing an intake valve operating mechanism for operating the cylinder intake valves,
at least one of the cylinder intake valves being operable to change timing of its opening and closing operation, and
during engine operation;
operating at least one of the cylinder intake valves to set the timing of its operation in accordance with a predetermined correlation of compressor operating efficiency at each of various combinations of engine speed and engine load to timing of operation of the respective cylinder valves, which correlation, for each of at least some of the combinations, places the corresponding correlated compressor operating efficiency at a location of greater efficiency on a predetermined compressor operating efficiency diagram than the location for the corresponding combination on a predetermined compressor operating efficiency diagram representing compressor operating efficiency when the respective cylinder valves are operated at a fixed baseline timing.