Internal-combustion engines – Free piston – Single chamber; one piston
Reexamination Certificate
1998-07-06
2001-01-09
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Free piston
Single chamber; one piston
Reexamination Certificate
active
06170442
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to internal combustion engines, and more particularly relates to improvements in free piston internal combustion engines. The invention frees the internal combustion engine from the constraints of the rigid construction limitations of previously existing internal combustion engines. It does this by uniquely combining features of free pistons, computer control and complete control of valve and valve actuator timing so that the engine can be automatically adjusted to operate under optimum operating conditions for a specific load over a broad range of load conditions. The engine embodying the present invention provides extraordinary freedom of control of all elements or parameters of engine operation so the engine operates at or close to optimum operating conditions for whatever power demand it is currently being presented.
BACKGROUND ART
The internal combustion engine, fueled by liquid petroleum products, has long been the mainstay for supplying mechanical power to a broad variety of mobile and stationary machines. There have been many developments for improving the fuel conversion efficiency of such engines. Although most internal combustion engines which are commercially produced and used today utilize reciprocating pistons which are confined to the motion limits permitted by a crank shaft and interconnected connecting rods, there have also been free piston internal combustion engines. For example, free piston internal combustion engines are shown in U.S. Pat. Nos. 4,873,822; 5,123,245; 5,363,651; 4,530,317; 4,415,313; and 4,205,528. Although most of these engines can be designed and operated to provide a high efficiency at a single selected power output load condition, few engines are called upon to operate under only one load condition. Most internal combustion engines must supply power which varies over a broad range from a low power to a high power.
Three parameters which are important to both the efficiency and the power of an internal combustion engine are stroke or displacement, expansion ratio, and compression ratio. Conventional crank-type internal combustion engines permit no controlled adjustment of any of these parameters. The efficiency of an internal combustion engine is also a function of the ratio of the compression ratio to the expansion ratio. In the conventional internal combustion engine, neither is variable. The power of an internal combustion engine is proportional to the mass flow of air, properly mixed with fuel, through the combustion chamber and therefore is also a function of piston displacement. However, piston displacement is not variable in a crank-type engine.
It is a feature and object of the present invention to provide a free piston internal combustion engine in which not only are all four of these parameters controllably variable, but additionally the expansion ratio and the compression ratio are adjustable independently of each other. This permits the engine to operate with a different expansion ratio than compression ratio and also allows the displacement or stroke of the engine to be controlled. Consequently, upon a low power demand the engine of the present invention can operate with an expansion ratio which is considerably greater than the compression ratio so that it can operate with more nearly full expansion, resulting in a higher proportion of the heat energy of combustion being converted to mechanical output power. For greater power demands, both the engine displacement and the expansion ratio can be varied so as to achieve maximum efficiency for a given power demand.
BRIEF DISCLOSURE OF INVENTION
The invention is an improved free piston, internal combustion engine of the type having at least one piston slidingly and sealingly reciprocatable in a cylinder and preferably having two opposed pistons reciprocating in opposite directions within the cylinder. Each piston has an end face bounding and defining a central combustion chamber. The engine also includes a driver linked to the piston for driving the piston through its compression stroke. The driver is preferably a spring acting upon each piston and storing energy during the expansion stroke of the piston in order to obtain a flywheel effect. The engine also includes a fuel injector, and may also include a spark ignitor for initiating combustion.
The improvement of the invention includes at least one and preferably two combustion chamber valves, each in a passageway extending between the combustion chamber and the earth's atmosphere for controlling the passage of gas between the combustion chamber and the earth's atmosphere. A valve closing actuator is linked to at least one combustion chamber valve. A piston-position sensor is linked to the valve closing actuator and initiates closure of the valve in response to a controllably variable, selected position of the piston in the cylinder. A piston-position responsive, valve opening actuator is also linked to the combustion chamber valve. The two combustion chamber valves open and close essentially in synchronism. Preferably a blower or other air impeller apparatus is connected to the passageways for purging the combustion chamber when the combustion chamber valves are opened and for providing air for supporting combustion.
In operation, the valves are opened to vent the combustion chamber near the desired end of an expansion stroke. Opening the valves terminates the expansion of combustion gas and initiates exhaust and purge of combustion products and, with a sufficient blower, supercharging of the combustion chamber. The valves are closed to terminate the venting and the purge at a controllably, variable piston position, thus terminating the exhaust and initiating the compression.
Under varying load conditions, engine control includes not only varying the quantity of fuel injected into the combustion chamber, but also varying the piston position at which the valves are opened and the piston position at which the valves are closed in order to tailor the engine operation so that it provides the required engine power at the maximum efficiency at which that power can be supplied.
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Dolinar Andrew M.
Foster Frank H.
Huynh Hai
Kremblas, Foster, Millard & Pollick
Sunpower, Inc.
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