Internal-combustion engines – Multiple cylinder – Simultaneous compression – distinct pistons – restricted...
Patent
1995-09-19
1997-06-17
Okonsky, David A.
Internal-combustion engines
Multiple cylinder
Simultaneous compression, distinct pistons, restricted...
123 70R, F02B 2508
Patent
active
056387776
DESCRIPTION:
BRIEF SUMMARY
THE PRIOR ART
The supercharging principle of piston engines consists in increasing the air masses without increasing the displacement. For constant compression ratio engines, this results in an increase of the combustion pressure and a higher specific output (with reference to the cylinder volume in liters). However, when the supercharging pressure is increased, the mechanical and thermal stresses increase on the engine members. This main drawback is due to the fact that the compression ratio generated by the combustion chamber and the piston stroke cannot be altered and adapted to pressure and temperature variations of the intake air and to variations in engine speeds and temperatures.
Consequently, engine manufacturers respect certain construction rules by defining, on the one hand, a limit to the amplitude of intake pressure variations and, on the other hand, by achieving an average compression ratio between the atmospheric intake pressure and the supercharging pressure. Since the fact of defining an average compression ratio is a comprise which conciliates at best the different engine loads and speeds, the pressures and temperatures of the atmospheric intake are too low and the supercharging pressures and temperatures are too high.
BRIEF DESCRIPTION OF THE INVENTION
This invention relates to the concept of an engine having a variable compression ratio, which consists in varying the volume of the combustion chamber in function of the intake air density and temperature, the engine speed and the engine temperature, in order to produce a hypersupercharging effect on the engine by means of a single or double supercharging pressure with intercooling.
According to the invention, this new engine has two crankshafts, one with a long-stroke crank and the other with a short-stroke crank. Both crankshafts are coupled at the same rotational speed via a gear train and a variably timed transmission, the coupling gear of which is part of the gear train and may be shifted at an angle with respect to the short-stroke crankshaft, in order to provide an infinite number of lead angles between the two crankshafts without interrupting the coupling of the latter.
According to the invention, the variably timed transmission is designed so that it may be removed from the engine independently of the short-stroke crankshaft, which offers the advantage of easy and fast replacements of defective parts or permits a standard exchange of the variably timed transmission. The cylinders, having different displacements, are respectively arranged above one of the two crankshafts. The crank of the short-stroke crankshaft coacts with the connecting rod of the piston in the smaller cylinder and the crank of the long-stroke crankshaft coacts with the connecting rod of the piston in the larger cylinder. The two cylinders are connected one by one, from one row to the other, through a recess in the cylinder head, so as to form a pair of cylinders in communication with each other, permitting gases to flow from one cylinder to the other, irrespective of the position of the piston in each of the cylinders.
According to the invention, in the case of an engine provided with compression ignition means, the engine comprises at least one fuel injector in the clearance space, the fuel being injected in mesh, at half speed, with the long-stroke crankshaft.
According to the invention, in the case of an engine provided with spark ignition means, the engine comprises at least one spark plug in the clearance space, the ignition being achieved through means known in the art, in synchronism, at half speed, with the long-stroke crankshaft.
According to the invention, engine timing is achieved through at least one camshaft in mesh, at half speed, with the long-stroke crankshaft, so as to connect periodically the pair of cylinders with the intake and exhaust pipes via the intake and exhaust valves, at definite moments of the four-stroke cycle. The expansion phase is effected simultaneously on each piston of the paired cylinders, so as to cause the two crankshaft
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patent: 4211082 (1980-07-01), Bristol
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