초록 ▼

An internal combustion engine valve control system for improving automotive cold-starts. A "negative" valve-overlap (NVO) time period is created during a first part of each piston's intake stroke wherein, with the intake and exhaust valves closed, a high vacuum is produced in its associated cylinder

An internal combustion engine valve control system for improving automotive cold-starts. A "negative" valve-overlap (NVO) time period is created during a first part of each piston's intake stroke wherein, with the intake and exhaust valves closed, a high vacuum is produced in its associated cylinder. As the intake valve starts to open at the end of the period an initial small low-lift valve gap creates a high-pressure differential across the gap increasing the velocity of the air/fuel charge being injected through the gap. The added velocity elevates turbulent mixing intensity in the cylinder enhancing atomization and vaporization of the charge, improving distribution in the combustion chamber for charge stability. This allows additional spark retard and a leaner air/fuel ratio, achieving rapid catalyst warm-up, while promoting converter efficiency and reducing exhaust-gas emissions.

대표청구항 ▼

1. A valve control system for an internal combustion spark ignition engine having its exhaust coupled to a catalytic converter and at least one cylinder having a reciprocal piston together with at least one pair of intake and exhaust valves, an engine valve timing system for cold-starts comprising:

1. A valve control system for an internal combustion spark ignition engine having its exhaust coupled to a catalytic converter and at least one cylinder having a reciprocal piston together with at least one pair of intake and exhaust valves, an engine valve timing system for cold-starts comprising: means for initiating the cold-start control system by virtue of the intake valve opening after the exhaust valve closes in the piston intake stroke region, resulting in a NVO period defined by both inlet and exhaust valves being in their closed mode simultaneously in the region for a predetermined crank-angle movement, thereby creating a high-vacuum in the cylinder; and upon completion of the NVO period the intake valve defining an initial small valve-lift gap during its opening resulting in a high-pressure differential across the gap, causing a high-velocity in-flow of the air/fuel charge through the gap, such that the in-flow enhances turbulent intensity and mixing of the charge in the cylinder so as to improve its combustion stability, enabling an increase in spark retard together with a leaner air/fuel ratio, thereby achieving rapid catalyst warm-up and improved converter efficiency reducing exhaust-gas emissions.