초록 ▼

The invention comprises a strategy and method for phase shifting intake and exhaust valve timing relative to crankshaft position as a function of engine operating variables, whereby valve overlap is delayed to obtain improved fuel economy resulting from a late intake valve closing to reduce pumping

The invention comprises a strategy and method for phase shifting intake and exhaust valve timing relative to crankshaft position as a function of engine operating variables, whereby valve overlap is delayed to obtain improved fuel economy resulting from a late intake valve closing to reduce pumping work during the intake stroke. The exhaust gases are drawn into the combustion cylinder of the engine during the intake stroke, which reduces oxides of nitrogen in the exhaust gas and reduces unburned hydrocarbons. Improved thermal efficiency and reductions in oxides of nitrogen are achieved as the combustion charge is diluted at higher loads by an external exhaust gas recirculation system, thereby combining the effects of exhaust gas recirculation and dual equal variable camshaft timing to obtain fuel economy benefits that cannot be achieved with either a conventional EGR system acting alone or dual equal variable camshaft timing acting alone.

대표청구항 ▼

[ What is claimed is:] [1.]1. A method for phase shifting the valve timing of an internal combustion engine with a four-stroke combustion cycle, an air/fuel combustion chamber, an intake valve, an external air exhaust gas recirculation flow passage, an exhaust valve in the combustion chamber, and a

[ What is claimed is:] [1.]1. A method for phase shifting the valve timing of an internal combustion engine with a four-stroke combustion cycle, an air/fuel combustion chamber, an intake valve, an external air exhaust gas recirculation flow passage, an exhaust valve in the combustion chamber, and a camshaft having valve operating cams for opening and closing the intake and exhaust valves during a four-stroke combustion cycle, the method comprising the steps of:advancing the timing of the opening of the intake valve and the closing of the exhaust valve as a function of engine load whereby the opening event of the intake valve and the closing of the exhaust valve occur after the instant of the top dead center position of the piston;providing sufficient overlap in the opening event for the intake valve and the closing event for the exhaust valve to effect internal exhaust gas recirculation in the combustion chamber during the engine intake stroke whereby the internal exhaust gas recirculation is added to the exhaust gases recirculated through the external exhaust gas recirculation flow passage; andinitiating external exhaust gas recirculation when the engine load is in the range of 25% to 45% of maximum engine load.