Granted Patent B2

US 7,080,613 · App. 10/981,971 · Granted Jul 25, 2006

Abstract

Claims (16)

1. A method for controlling the air-fuel ratio in a four-stroke direct injection engine operable with controlled auto-ignition combustion and having at least one cylinder containing a piston reciprocably connected with a crank and defining a variable volume combustion chamber including at least one intake valve controlling communication with an air intake and at least one exhaust valve controlling communication with an exhaust outlet, the method comprising:

operating the engine with controlled auto-ignition combustion involving homogeneous charge compression ignition with or without spark ignition assistance, the engine performing two sequential pairs of expansion and contraction strokes during two revolutions of the crank, said two revolutions of the crank defining a combustion cycle;

employing a variable valve actuating system operated with one of an exhaust re-compression valve strategy and an exhaust re-breathing valve strategy controlling cylinder charge ignition temperatures within a self ignition range at ignition of each charge; and

adjusting the flow of air and burned gases entering the combustion chamber to obtain a desired air-fuel ratio for each operating speed and load condition within the self ignition range.

2. The method of claim 1 including the steps of:

providing a flow control valve in the air intake of each cylinder;

operating the engine with the exhaust re-breathing valve strategy wherein portions of the burned combustion gases discharged during the exhaust stroke are readmitted to the cylinder during the intake stroke for heating fresh intake air mixed with the trapped gases and compressed to self-ignition temperature near the end of each compression stroke; and

controlling air-fuel ratio in the cylinder is preformed by adjusting the flow control valve between selected open and closed positions within a predetermined range.

3. The method of claim 1 including the step of:

operating the engine with the exhaust re-compression valve strategy wherein portions of the burned combustion gases are trapped in the cylinders for expansion and re-compression during negative valve overlap between early closing of the exhaust valves and late opening of the intake valves for heating fresh intake air mixed with the trapped gases and compressed to self-ignition temperature near the end of each compression stroke; and

controlling air-fuel ratio in the cylinder is preformed by varying exhaust valve peak lift over a predetermined range.

4. The method of claim 3 wherein the predetermined range is between 1 mm and full lift.

5. The method of claim 1 including the step of:

operating the engine with the exhaust re-breathing valve strategy wherein portions of the burned combustion gases discharged during the exhaust stroke are readmitted to the cylinder during the intake stroke for heating fresh intake air mixed with the trapped gases and compressed to self-ignition temperature near the end of each compression stroke; and

controlling air-fuel ratio in the cylinder is preformed by varying intake valve peak lift over a predetermined range.

6. The method of claim 5 wherein the predetermined range is between 1 mm and full lift.

Assignments (13)