Variable valve timing operated engine

Claim 1

A method of operating an automotive-type internal combustion engine to control the emission of unburned hydrocarbons and nitrogen oxides while providing efficient engine operation, stable idle, and increased torque and power output, consisting of: independently varying the openings and closings of the engine intake and exhaust valves from fixed valve lift and duration valve event timing schedules to provide the most efficient speed and torque operation accompanied by optimum fuel economy; and comprising the steps of: for engine idle speed operation, providing a small overlap between the opening of the intake valve during the piston exhaust stroke and the closing of the exhaust valve during the piston intake stroke to minimize the amount of residual gas in the engine combustion chamber to increase fuel economy while concurrently providing a minimal backflow of gas into the intake manifold to promote mixing of the air/fuel charge for better combustion stability; and, for part load and moderate engine accelerating operating conditions, shifting the intake and exhaust valve timing events by significantly delaying the intake valve opening and the exhaust valve closing from their normal timing schedules and also to provide a greater overlap between the opening of the intake valve and the closing of the exhaust valve than at idle to provide a greater volume of internal exhaust gas recirculation (EGR) into the cylinder and intake port to reduce NOx and HC emissions, the crank angle degree and timing of overlap varying as a function of the load, the gas backflow into the cylinder and the intake port reducing engine pumping losses by reducing the manifold vacuum levels; and for engine wide open throttle (WOT) operating conditions, shifting the valve event timing schedules back towards the idle speed position but with a large valve overlap that decreases as a function of increasing the speed.

Claim 2

A method of operating an automotive-type internal combustion engine to control the emission of unburned hydrocarbons and nitrogen oxides while providing efficient engine operation, stable idle, and increased torque and power output, consisting of: independently varying the openings and closings of the engine intake and exhaust valves from fixed valve lift and duration valve event timing schedules to provide the most efficient speed and torque operation accompanied by optimum fuel economy; and comprising the steps of: for engine idle speed operation, providing a small overlap between the opening of the intake valve during the piston exhaust stroke and the closing of the exhaust valve during the piston intake stroke to minimize the amount of residual gas in the engine combustion chamber to increase fuel economy while concurrently providing a minimal backflow of gas into the intake manifold to promote mixing of the air/fuel charge for better combustion stability; and, for part load and moderate engine accelerating operating conditions, shifting the intake and exhaust valve timing events by significantly delaying the intake valve opening and the exhaust valve closing from their normal timing schedules and also to provide a greater overlap between the opening of the intake valve and the closing of the exhaust valve than at idle to provide a greater volume of internal exhaust gas recirculation (EGR) into the cylinder and intake port to reduce NOx and HC emissions, the crank angle degree and timing of overlap varying as a function of the load, the gas backflow into the cylinder and the intake port reducing engine pumping losses by reducing the manifold vacuum levels; and for engine wide open throttle (WOT) operating conditions, shifting the valve event timing schedules back towards the idle speed position but with a large valve overlap that decreases as a function of increasing the speed.