Internal-combustion engines – Two-cycle – Pump compression
Patent
1982-06-11
1983-12-06
Burns, Wendell E.
Internal-combustion engines
Two-cycle
Pump compression
123 39, 123431, F02B 108, F02B 3300, F02B 7500
Patent
active
044186576
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to internal combustion engines in which compression is performed in compression cylinders maintained cold and combustion takes place in firing cylinders maintained hot, the compression and firing cylinders being physically separated. Compression pistons and power pistons reciprocate respectively within the compression and firing cylinders, all of the pistons being connected to a common crankshaft. Each firing cylinder has minimal working clearance between the crown of the power piston and the cylinder head, which, together with recesses for the valves and the spark plug, define the combustion chamber. The unswept portion of the combustion chamber is accordingly of very small capacity. The pressures reached within the combustion chambers are greater than those reached in engines operating on the Otto or diesel cycles. The engines of the above described construction are referred to hereinafter as "split cycle engines".
BACKGROUND ART
Split cycle engines have been described in my U.S. Pat. Nos. 3,408,811 and 4,186,561. It has been found in practical experience with engines of the construction described in U.S. Pat. No. 3,408,811 that the high gas pressures in the combustion chamber during ignition require higher electrical potentials to be applied to spark plugs than in conventional internal combustion engines, with the result that the working life of the spark plugs is shortened.
U.S. Pat. No. 4,186,561 was directed to avoiding this difficulty by using ignition means other than spark plugs. Spark plugs, however, permit the timing of ignition in a particularly convenient manner, and equipment for use with them is already available on the market.
DISCLOSURE OF THE INVENTION
It is accordingly the principal object of the present invention to provide a split cycle engine wherein combustion is initiated by conventional spark plugs operating at electrical potentials sufficiently low to ensure a spark plug life comparable with the life of the spark plugs used in conventional Otto cycle spark ignition engines. This requires a gas pressure at the time the spark passes of less than 2000 kPa.
In order to achieve this principal object, the present invention provides a spark ignition internal combustion engine comprising a firing cylinder and a compression cylinder having reciprocating therein respectively a power piston and a compression piston connected to a common crankshaft, a combustion chamber defined by the firing cylinder head, at least one recess containing valve heads and spark plug electrodes, and the crown of the moving power piston, characterised by means directing into the combustion chamber in advance of the spark as the power piston approaches or reaches top dead centre a pilot charge composed of spark-ignitable fuel mixed with compressed air at a pressure below 2000 kPa, means producing a spark across the electrodes at or near top dead centre, and means directing into the combustion chamber after the spark and while the piston is moving away from the cylinder head on the first part of the power stroke a second charge composed of fuel and air compressed to a pressure greater than 2000 kPa.
The unique characteristics of split cycle engines can be exploited to assist deceleration of the engine when by diverting the compressed air supplied by the compression cylinder away from the power cylinder, thereby reducing the pressure in the combustion chamber. The compressed air so diverted may conveniently be stored in a compressed air receiver, which to save weight and space may consist of a honeycomb arrangement of hexagonal tubes joined together side by side to form structural members of a frame of a vehicle or other structure associated with the engine.
The means directing compressed air into the combustion chamber may comprise at least one poppet valve closed by a compression spring bearing against a movable stop urged in the direction to close the valve by the pressure of the compressed air. The force required from the mechanism opening the valve is then less than
REFERENCES:
patent: 1163671 (1915-12-01), Kraus
patent: 1296686 (1919-03-01), Neff
patent: 2799258 (1957-07-01), Black
patent: 2873574 (1959-02-01), Webb
patent: 3148668 (1964-09-01), Bianchi
patent: 3408811 (1968-11-01), Wishart
patent: 4230075 (1980-10-01), Lowther
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