Internal-combustion engines – Particular piston and enclosing cylinder construction – Piston
Reexamination Certificate
1999-12-23
2002-03-26
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Piston
Reexamination Certificate
active
06360709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a piston design, and more particularly, to a piston having a sloped crown.
2. Description of Related Art
In a combustion engine, a combustion chamber is formed by a cylinder head, cylinder bore wall and piston crown. The piston crown, which is the surface of the piston exposed to an air/fuel mixture, may be flat, concave, convex, or shaped so as to promote turbulence or control combustion in the combustion chamber. Conventional piston crowns are shaped to achieve a desired compression ratio, as well as to accommodate the intake and exhaust valves located within the cylinder head. But, conventional pistons do not optimally distribute the air/fuel mixture in the combustion motion of the piston's compression stroke. As a result, the combustion charge is not homogeneous, and the charge in some regions of the combustion chamber has a greater volatility than other regions. Uneven, or unpredictable, combustion occurs, resulting in poor emissions, spark knock problems, idle instability, and exhaust gas recirculation intolerance.
SUMMARY OF THE INVENTION
The piston according to the invention more evenly distributes the air/fuel mixture in the combustion chamber and provides a more homogeneous air/fuel mixture near the spark plug, resulting in an improved combustion charge that reduces emissions, promotes idle stability, and improves exhaust gas recirculation tolerance. The piston generally includes a sloped crown supported by a cylindrical body. The sloped crown includes a pair of slopes converging toward a raised peak, which is disposed offset from a longitudinal center axis of the piston cylindrical body and toward an exhaust side of the combustion chamber. As the piston moves through the compression stroke, the sloped crown alters the combustion motion, or velocity and flow direction, of the air/fuel mixture. The resulting combustion motion is directed toward the exhaust side of the combustion chamber, thereby causing a less localized air/fuel ratio distribution and a more homogeneous air/fuel ratio near the spark plug.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4300499 (1981-11-01), Nakanishi et al.
patent: 5305720 (1994-04-01), Ando et al.
patent: 5309879 (1994-05-01), Regueiro
patent: 5363820 (1994-11-01), Neitz
patent: 5738057 (1998-04-01), Vallejos
patent: 6019079 (2000-02-01), Sakurahara et al.
Anderson Jeffrey W
DeGroot Kenneth P
Jenkins Joseph
Keller Philip S
Soltis Dennis A
DaimlerChrysler Corporation
Maclean Kenneth H.
McMahon Marguerite
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