Internal-combustion engines – Adjustable combustion chamber – Piston in head adjusted
Reexamination Certificate
1998-11-16
2001-07-17
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Adjustable combustion chamber
Piston in head adjusted
C123S0480AA, C123S0780AA
Reexamination Certificate
active
06260520
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a homogeneous charge compression ignition internal combustion engine (HCCI) in which a premixed charge fires without the need of a sparkplug.
BACKGROUND DISCLOSURE INFORMATION
The HCCI engine offers tantalizing potential for low hydrocarbon emissions and low NOx emissions coupled with significant fuel economy improvement. Unlike its better known compression ignition cousin, the diesel engine, the HCCI engine may be operated soot free and also with low NOx emissions because there is no locally rich zone of combustion. Rather, ignition occurs spontaneously and concurrently at many points in the combustion chamber. A problem heretofore, however, has resided in the lack of capability to precisely control the onset of the ignition event. The present invention solves this problem.
Another problem with previous HCCI engines was the apparent inability to operate satisfactorily on fuels having a wide range of cetane or octane ratings. An engine according to this present invention has adaptable timing capability which will allow fuel quality to be accurately and adequately handled.
SUMMARY OF THE INVENTION
An HCCI engine includes a cylinder block having a cylinder formed therein, a cylinder head mounted upon the cylinder block for closing the cylinder, and a piston slidably contained within the cylinder. A combustion chamber is defined by the cylinder head, the cylinder and the piston. The piston is attached to a crankshaft by means of a connecting rod. A fuel system, which may comprise either a carburetor or direct cylinder injection system or port fuel injection system, introduces fuel to the combustion chamber.
A boost piston initiates timed combustion of fuel within the combustion chamber. The boost piston is housed within a wall of the combustion chamber, such as the cylinder head, so that when the piston moves from a base position to an extended position, the effective compression ratio of the cylinder increases. A driver moves the boost piston from the base position to the extended position during successive cycles of the engine so as to cause fuel within the combustion chamber to burn in response to movement of the boost piston to the extended position. In essence, when the boost piston moves from the base position to the extended position, during each compression stroke of the engine, the concomitant increase of heat within the combustion chamber is sufficient to initiate combustion.
The driver which moves the boost piston from its base position to the extended position may comprise a camshaft powered by the engine's crankshaft, with the camshaft being mounted within the cylinder head and having at least one lobe for contacting an upper surface of the boost piston. The phase relationship between the camshaft and crankshaft may be variable, which allows the timing of the movement of the boost piston to be varied by a controller which senses a plurality of engine operating parameters and determines an appropriate time for the boost piston to be moved. In this manner, the controller will minimize unwanted variations in pressure within the combustion chamber. This will allow adaptability of the present engine to changes in the octane or cetane rating of fuel being burned by the engine.
According to another aspect of the present invention, the present engine may further comprise a spark plug having electrodes extending within the combustion chamber such that cold starting and also misfire avoidance may be provided by the spark plug.
The controller will operate the driver so as to produce a relatively lower compression ratio in the event that the fuel has a lower octane rating and a relatively higher compression ratio in the event that the fuel has a higher octane rating. This is accomplished by varying the amount by which the boost piston moves into the combustion chamber as the boost piston moves from its base position to its extended position. Also, the controller will operate the driver so that the timing of the onset of combustion is advanced when the fuel has a higher octane rating and retarded when the fuel has a lower octane rating.
It is an advantage of the present invention that an engine equipped with the present system will offer lower hydrocarbon emissions, lower emissions of NOx, and lower emissions of CO
2
.
It is a further advantage of the present invention that an engine according to this invention will operate with low smoke emissions and no knocking because combustion duration is reduced.
It is a further advantage of the present invention that an engine according to this invention will operate with much better fuel economy, as compared with premixed charge engines. This results at least in part from the ability of the present engine to operate without air throttling.
Other advantages as well as objects and features of the present invention will become apparent to the reader of this specification.
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Benton Jason
Ford Global Technologies
Ford Global Technologies
Wolfe Willis R.
LandOfFree
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