Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-11-05
2001-08-07
Solis, Erick (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S298000, C123S301000, C123S305000
Reexamination Certificate
active
06269790
ABSTRACT:
TECHNICAL FIELD
This invention relates to stratified-charge combustion systems for direct-injection spark-ignited engines.
BACKGROUND
Internal combustion engines are known which utilize spark-ignited direct in-cylinder fuel injection systems. The fuel injection mechanisms spray a fuel mist directly into each cylinder and inlet air is directed into the cylinder from one or more inlet ports to produce an appropriate air-fuel mixture in the combustion chamber. The air-fuel mixture is ignited by a spark plug during each cycle of the piston in the cylinder bore. Various piston bowl and combustion chamber configurations have been devised in order to provide appropriate air-fuel mixing and to direct the mixtures toward the spark plug for ignition, particularly in low load operation of the engines. It is an object of these systems to provide an overall lean but ignitable gas mixture and to reduce undesirable emissions in order to meet appropriate standards of fuel economy and emissions.
One object of these systems is to achieve charge stratification through direct fuel injection into the combustion chamber with minimum wall wetting by the fuel and with an overall lean but locally burnable fuel-air mixture directed to the spark plug.
Several attempts have been made to accomplish this by reorganizing the combustion chamber configuration, modifying the in-cylinder air flow, and optimizing fuel injection with respect to timing, location and spray characteristics. For example, U.S. Pat. No. 5,711,269 discusses a reverse tumble combustion system with a spherical bowl in the top of the piston near the intake valve side and with a fuel injector in the intake valve side. Also, U.S. Pat. No. 5,259,348 shows a stratified-charge combustion system with a swirl air flow and a bowl in the piston at the intake valve side. Although these systems have appeared to work well in practice, they still have relatively high hydrocarbon emissions and soot formation, some of which may result from an undesirable amount of wetting of the piston wall by the fuel spray.
It is thus desirable to provide a combustion chamber design which minimizes wetting of the piston bowl wall by the fuel injector and which further reduces hydrocarbon emissions and soot formation.
SUMMARY OF THE INVENTION
The present invention provides a unique combustion chamber design and system which minimizes wall wetting and provides an overall lean air-fuel mixture at an optimum position in the combustion chamber in order to secure improved fuel economy and reduced emissions. The inventive system utilizes a piston with a spherical or nearly spherical bowl configuration located near or adjacent to the exhaust valve side of the combustion chamber. The intake port design provides a normal tumble flow of intake air. The injector is located on the intake valve side of the combustion chamber and a small recess can be provided at the edge of the piston bowl in order to avoid contact with the injector and/or avoid impingement of the fuel spray outside the bowl.
The distance for penetration of the fuel spray is increased due to the positioning of the piston bowl. The spray droplets have more time to evaporate before they can contact the far wall of the piston bowl. Also, due to the normal tumble flow of inlet air, the direction of the fuel spray is in opposition to the direction of the tumble inlet air flow at certain points in the combustion cycle. This further slows the fuel droplet movement and allows more time for evaporation. Further, the in-cylinder tumble air flow moves the vapor and fuel cloud in the direction of the spark plug located adjacent the center of the cylinder head. Moreover, with the inventive system, a lower fuel spray penetration rate can be utilized.
Due to the unique combustion chamber and bowl design combined with the inlet air flow, the present invention minimizes wall wetting and overly rich fuel regions. This reduces soot formation and reduces the amount of unburned hydrocarbons. Also, the invention provides improved ignitability of the injected fuel and reduces cycle-by-cycle variations and misfirings.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiments when taken in conjunction with the attached drawings and appended claims.
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Anderson Richard Walter
Yang Jialin
Yi Jianwen
Drouillard, Esq Jerome R.
Ford Global Technologies Inc.
Solis Erick
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