Importance

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Abstract

A two-stroke cycle engine is provided with valveless exhaust and inlet ports in a cylinder wall. A piston is mounted for reciprocal movement in the cylinder. A precombustion chamber is formed in the piston, which communicates with the combustion chamber above the piston by a relatively large aperture adapted to receive the end of a spark plug. When the piston is at the bottom of its stroke, pressurized fresh air is supplied through the inlet ports for purposes of scavenging the combustion chamber and filling it with fresh air. There is also provided means for forcing a charge of rich fuel-air mixture into the precombustion chamber. The aperture providing communication between the precombustion chamber and the combustion chamber is sufficiently large that a desired amount of fuel can be ejected into the combustion chamber. During the compression stroke of the piston, the fuel-air mixtures in the precombustion chamber and in the combustion chamber are compressed. Very early in the compression stroke, the exhaust and inlet ports in the cylinder wall and the port used for charging the precombustion chamber are sealed by the piston wall. As the piston nears the end of its compression stroke, a spark plug, projecting downwardly from the top of the cylinder, enters the precombustion chamber through the aperture providing communication between the precombustion chamber and the combustion chamber. The flow of fuel-air mixture from the combustion chamber into the precombustion chamber near the end of the compression strokes generates high turbulence within the precombustion chamber, ensuring good mixture of the fuel-air mixture within the precombustion chamber. The combustion chamber is shaped such that it extends from the ejection gap formed between the edge of the aperture of the precombustion chamber and the spark plug radially with respect to the spark plug axis and away from the precombustion chamber in a direction opposite to that of the entering spark plug. It is thus shaped to conform to the direction of the flame ejected from the precombustion chamber through the ejection gap. When the spark plug is shallowly inserted in the precombustion chamber, the flames travel from the ejection opening near conical surfaces of the combustion chamber. As the spark plug projects more deeply into the precombustion chamber, the sheet of the flame is moved away from the conical surfaces and toward the top surface of the piston. Finally, at top dead center position, the flame is deflected by planar, annular surfaces into a direction along a surface perpendicular to the spark plug axis. The flame is thereby made to scan through the combustion chamber providing thorough ignition in every part of the combustion chamber.

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First Claim