Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2000-04-17
2001-09-11
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S568120, C123S568210
Reexamination Certificate
active
06286489
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to an internal combustion engine and specifically to a method of controlling an exhaust gas recirculation system.
BACKGROUND ART
Future regulations on emissions require significantly reduced production of pollutants from an internal combustion engine. Engine manufacturers have responded by developing a number of methods and systems directed at reducing pollutants. Exhaust gas recirculation (EGR) is a scheme to reduce the formation of NOx, an uncertain mixture of oxides of nitrogen. In an exhaust gas recirculation system, exhaust gas is introduced into the inlet air stream. The exhaust gas replaces a portion of oxygen that would normally occupy a combustion chamber. Reducing oxygen in the combustion chamber slows the combustion process. Slowing the combustion process reduces a peak gas temperature in the combustion chamber. High peak gas temperatures in the combustion chamber are generally associated with the formation of NOx.
Many current exhaust gas control schemes attempt to control a mass of oxygen available for combustion. These systems typically focus on manners of measuring mass flow in the inlet stream and mass flow of recirculated gas. These systems further use control valves to vary the mass flow of recirculated gas using a pressure differential between the inlet air stream and the exhaust gas. Relying on the pressure differential limits the effectiveness of these systems. As inlet air stream pressures increase with increasing loads, less exhaust gas recirculates into the inlet stream. To achieve greatly reduced emissions envisioned by future regulations, exhaust gas must be recirculated over a wider operating range, especially in the high load high speed range where NOx production increases rapidly.
In U.S. Pat. No. 4,426,848 issued to Stachowicz on Jan. 24, 1984, a venturi nozzle expands the operating range of the exhaust gas recirculation system. The venturi nozzle creates a reduced pressure area in the inlet stream where the exhaust gas may be introduced. However, these systems reduce the effectiveness of a pressure charging device and ultimately reduce engine performance. In U.S. Pat. No. 5,517,976 issued to Bachle on May 21, 1996, a single piston or group of pistons forces exhaust gas into the inlet stream wherein the pistons act as positive displacement pumps. This system provides a fixed volumetric percentage of recirculated exhaust gas. In a low load condition at low speeds, the air to fuel ratio may be so low that using the fixed volumetric percentage of exhaust gas may prevent proper combustion. The present invention is directed at overcoming one or more of the problems set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a method of controlling an exhaust gas recirculation system in an internal combustion engine improves operation over a broad engine range. The method involves determining an operating condition of the engine. Based on the engine operating condition, a controller determines a total mass of fuel for the determined operating condition. The controller than distributes the total mass of fuel to the combustion chambers and recirculation combustion chamber in non-equal proportions according to the operating condition with the recirculation combustion chamber receiving a larger proportion of the total mass of fuel where the engine operates in a predetermined upper range. The recirculation combustion chamber receives an equal proportion of the total mass of fuel where the engine operates in a predetermined middle range. In a lower operating range, the recirculation combustion chamber receives a smaller proportion of the total.
In another aspect of the present invention, a system improves control of exhaust gas recirculation in an internal combustion engine. The system comprises a plurality of combustion chambers. An exhaust system and an inlet system fluidly connect with the combustion chambers. A recirculation combustion chamber fluidly connects with the inlet system. An engine operating condition sensing device connects to the engine. The engine operating sensing device is adapted to sense an engine operating condition. A fuel deliver device is fluidly connected with the combustion chambers and the recirculation combustion chamber. A controller connects to the fuel delivery device. The controller determines a total mass of fuel according to a sensed engine operating condition. The controller determines an equal proportion of the total mass of fuel to be delivered to each of the combustion chambers and the recirculation combustion chamber. The controller adjusts the equal proportion of the total mass to be delivered to the combustion chambers inversely with said sensed operating condition. The controller adjusts the equal proportion of the total mass of fuel to be delivered to the recirculation combustion chamber in direct relation with the sensed operating condition.
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patent: 4131095 (1978-12-01), Ouchi
patent: 5178119 (1993-01-01), Gale
patent: 5517976 (1996-05-01), Bachle et al.
patent: 5802846 (1998-09-01), Bailey
patent: 5894726 (1999-04-01), Monnier
patent: 6209530 (2001-04-01), Faletti et al.
Caterpillar Inc.
Roberson Keith P.
Wolfe Willis R.
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