Internal-combustion engines – Precombustion and main combustion chambers in series – Precombustion chamber assembly inserted in spark plug hole
Reexamination Certificate
1999-02-02
2001-04-10
Kwon, John (Department: 3747)
Internal-combustion engines
Precombustion and main combustion chambers in series
Precombustion chamber assembly inserted in spark plug hole
C123S273000
Reexamination Certificate
active
06213085
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to spark plugs of the type that provide torch jet-assisted spark ignition of an air/fuel mixture within a main combustion chamber of an internal combustion engine. In particular, this invention is directed to a torch jet spark plug having a nozzle disposed at an angle to the axis of the plug, which enables flame propagation from the plug to be directed to a specific location within the combustion chamber.
BACKGROUND OF THE INVENTION
Spark ignition of an air/fuel mixture within a combustion chamber of an internal combustion engine typically involves igniting the air/fuel mixture with an electric spark jumped between an electrode and a ground electrode of a spark plug. An alternative to spark ignition known in the art is torch jet-assisted spark ignition which, as taught by U.S. Pat. Nos. 3,921,605 to Wyczalek, 4,924,829 to Cheng et al., 5,405,280 to Polikarpus et al., and 5,421,300 to Durling et al., offers several advantages over spark ignition approaches. As the name suggests, torch jet-assisted spark ignition utilizes a jet of burning gases that are propelled into the combustion chamber in order to enhance the burning rate within the combustion chamber by providing increased turbulence as well as presenting a larger flame front area. As a result of a faster burning rate, lower cyclic variation in cylinder pressure is achieved, which enables a higher engine efficiency with a higher compression ratio.
In a torch jet-assisted spark ignition system, the jet typically emanates from a combustion prechamber within the spark plug, passing through an orifice into the main combustion chamber. The axis of the orifice is parallel and often coaxial with the combustion prechamber. Though an air/fuel mixture can be introduced directly into the prechamber through a separate intake valve or fuel injector, it is generally preferable that the air/fuel mixture originates from the main chamber in order to simplify the construction of the engine and its ignition system. Combustion of the air/fuel mixture within the prechamber can be initiated from within by a separate igniter, or initiated by the flame front within the main chamber. With either approach, combustion typically proceeds relatively simultaneously in both the prechamber and the main chamber. However, because of the small relative volume of the prechamber, a high pressure is developed in the prechamber while the pressure is still relatively low in the main chamber. As a result, a jet of burning gases shoots from the prechamber far into the main chamber, significantly increasing the combustion rate in the main chamber.
Engine testing of torch jet spark plugs has verified that torch jet-assisted ignition results in faster burn rates than conventional spark ignition techniques, which produce a fixed flame “kernel” and relies on engine design to achieve suitable flame propagation within the main chamber. Torch jet-assisted ignition also relies on engine design considerations, which include tailoring swirl, turbulence and valve design to control the fuel/air charge for more complete and faster burns. Even with optimal engine design, there are typically regions within a main chamber in which the fuel/air mixture does not burn well, resulting in lower combustion efficiency. Accordingly, further enhancements in combustion efficiency using torch jet-assisted ignition would be desirable, the result of which would provide increased power, reduced emissions and better fuel economy for a given engine design.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a torch jet spark plug for use in a spark ignition system of an internal combustion engine. As with prior art torch jet spark plugs, the spark plug of this invention provides for the ignition of an air/fuel mixture within a combustion prechamber within the plug, and then propels the resulting burning gases through an orifice and into the engine main combustion chamber to increase the burning rate of the air/fuel mixture within the combustion chamber. However, the spark plug of this invention further promotes combustion efficiency by enabling the jet of burning gases to be selectively directed to any desired region within a combustion chamber, such as a region within the chamber that would not otherwise burn well compared to other regions of the chamber.
The spark plug of this invention generally includes a body having an interior chamber (“prechamber”) and an orifice in fluidic communication with the chamber for venting the chamber to the exterior of the body. Contrary to prior art torch jet spark plugs, the orifice is oriented in the body so that its axis is not parallel or coaxial with the longitudinal axis of the body, i.e., an angle of greater than zero from the longitudinal axis of the body. The orifice provides the only vent between the chamber and the exterior of the body, and may be disposed at an angle of up to about 30 degrees from the axis of the body.
The torch jet spark plug of this invention is capable of being used as a production plug or adapted for engine design and development. As a production plug, the body includes means for establishing the rotational orientation of the plug in a spark plug well, so that the orifice will be properly oriented to optimize the benefits gained by selectively directing the torch jet into the combustion chamber. In this embodiment, the position of the torch jet spark ignition device is preferably limited to a single orientation within its corresponding well. For design and development purposes, the body is used in conjunction with means that enables the orientation of the body to be selectively varied within a spark plug well, so that combustion conditions can be evaluated with the torch jet directed into different areas of a combustion chamber. In this embodiment, the torch jet spark ignition device is configured to be positively secured in any one of a plurality of orientations in the well.
In accordance with the above, the spark plug of this invention can be used to compensate in part for conventional engine design considerations, such as swirl, turbulence and valve design, to control the fuel/air charge for more complete and faster burns. Specifically, the spark plug can be oriented to promote combustion within a region of a combustion chamber in which a fuel/air mixture would not otherwise burn well, resulting in higher combustion efficiency. Simultaneously, jet velocities can be altered by tailoring the chamber and orifice sizes to achieve burn rates and intensities that are compatible with, and possibly augment the effects of, a particular burn direction. Accordingly, this invention enables significant enhancements in combustion efficiency using torch jet-assisted ignition, the result of which is increased power, reduced emissions and better fuel economy for a given engine design.
The spark plug of this invention also promotes engine design flexibility by permitting spark plug location to be determined by considerations other than spark location. Specifically, the angled orifice employed by this invention permits the selective “placement” of the torch jet in regions of the combustion chamber other than directly below the spark plug. As a result, spark location within the combustion chamber does not dictate spark plug placement at the expense of other considerations, such as accessibility for service, availability of cooling passages in the cylinder head, and avoidance of engine valves and head bolts. Accordingly, engine packaging and combustion performance can both be improved with the spark plug of this invention.
Another significant advantage of this invention is that the plug can be used during engine development and testing to generate combustion data for different flame propagation directions and rates within an engine without necessitating modifications to engine hardware. A particularly notable aspect of this capability is that the plug can assist in efforts to evaluate emission levels and knock-limited power levels, which depend in part on f
Durling Harold E.
Ralph Joseph G.
Delphi Technologies Inc.
Kwon John
McBain Scott A.
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