Internal-combustion engines – Valved piston – Charge passes from crankcase through valve in piston
Patent
1992-03-07
1993-11-16
Okonsky, David A.
Internal-combustion engines
Valved piston
Charge passes from crankcase through valve in piston
123 59BS, F01L 1100
Patent
active
052613585
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an internal combustion engine.
The invention has been devised particularly, although not solely, for use as an internal combustion engine operating on a two-stroke cycle.
BACKGROUND ART
With a reciprocating piston engine operating on a two stroke cycle, part of the compression and expansion strokes are used for the purpose of exhaust and induction. It is common for the piston itself to be used to open and close inlet and exhaust ports. On upward movement of the piston, the crankcase is decompressed and a charge of air or combustible mixture is admitted into the crankcase through a self-acting valve. During the expansion stroke the charge of air or combustible mixture in the crankcase is compressed, and near the end of this stroke the exhaust port is uncovered to allow the combustion products to discharge from the combustion chamber. Further movement of the piston uncovers the inlet port and the compressed charge from the crankcase flows into the combustion chamber. The exhaust and inlet ports are open simultaneously for a short period so that the incoming charge can assist in clearing the combustion chamber of combustion products. The cycle is completed by compression and subsequent ignition of the charge trapped in the combustion chamber.
A deficiency of this common arrangement in two-stroke engines is that the process of clearing the combustion products from the combustion chamber and recharging it is restricted, owing to the little time available for induction and exhaust and the fact that for a portion of this time the inlet and exhaust ports are both open, with the result that some incoming charge escapes with the exhausting combustion products.
DISCLOSURE OF INVENTION
The present invention when applied as a two-stroke engine seeks to provide an engine having an improved process of clearing combustion products from the combustion chamber in comparison to the common arrangement described hereinbefore.
In one form the invention resides in an internal combustion engine comprising a cylinder and a piston mounted for reciprocation in the cylinder, the piston and the cylinder co-operating to define a combustion chamber and a pumping chamber each of which varies in volume upon reciprocation of the piston in the cylinder, an inlet means to admit fluid into the pumping chamber, a transfer chamber defined within the piston for receiving and containing fluid from the pumping chamber, and a control means for controlling discharge of the fluid from the transfer chamber into the combustion chamber.
Preferably, the piston includes a transfer passage controlled by a non-return valve to allow delivery of fluid from the pumping chamber to the transfer chamber upon volume reduction of the pumping chamber.
The control means may be of any suitable form such as a discharge passage including a discharge port opening onto the combustion chamber and a valve means for controlling flow through the discharge passage. The valve means may comprise a self-acting valve or valve operable under external control to open and close the discharge port. Where the valve is self-acting valve, it may for example be arranged to operate in response to a predetermined difference in pressure between the combustion and transfer chambers. Where the valve is operable under external control, a control mechanism may for example be provided to operate the valve according to the relative position of the piston in the cylinder. Such a control mechanism may comprise a push-rod for operating the valve, the push rod being operatively connected to a cam on a crankshaft to which the piston is operatively connected.
In a preferred construction of the invention:
(a) the cylinder comprises two cylinder portions being a cylinder Working portion and a cylinder pumping portion, the cylinder pumping portion being larger in cross-sectional area than the cylinder working portion, the cylinder working portion having a wall at one of its ends and opening onto the cylinder pumping portion at the other of its ends, and a fu
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patent: 2215793 (1940-09-01), Mayes
patent: 2952252 (1960-09-01), Geatty
patent: 3177853 (1965-04-01), Herdershot
patent: 3301234 (1967-01-01), Reilly
Aardvark Pty Ltd.
Okonsky David A.
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