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 Claim
1.
A four-stroke internal combustion engine having
an intake phase, a compression phase,an expansion phase and an exhaust
phase, said engine including :
- reciprocating pistons [6] [8], provided with
self-ignition or spark ignition means ;
- two crankshafts, the first crankshaft [4] having a long-stroke
crank and the second crankshaft [5] having a crank with a stroke
shorter than that of the first crankshaft, said crankshafts [4]
[5] being coupled at the same rotational speed via a gear train
[19] [20] [21] and a variably timed transmission ;
- a number of cylinders [2] [3], arranged each above one of the
two crankshafts [4] [5], said arrangement including small cylinders
[3] with a displacement smaller than that of the larger cylinders
[2], each larger cylinder communicating with a smaller cylinder
[3] via a clearance space [40], so as to form a group of two cylinders
[3] [4] in communication with each other, so as to enable gases
to flow from one cylinder to the other, irrespective of the position
of the pistons [6] [8] in each of said cylinders [2] [3], each piston
being associated to a connecting rod [9] coacting with a crank of
a crankshaft, the crank of the second crankshaft [5] coacting with
the connecting rod [9] of the piston [8] in the smaller cylinder
[3], and the crank of the first crankshaft [4] coacting with the
connecting rod [7] of the piston [6] in the larger cylinder [2];
- a camshaft in mesh, at half speed, with the first crankshaft [4],
so as to connect periodically groups of two cylinders [2] [3] with
intake and exhaust pipes [11] [12] via intake and exhaust valves
[13] [14], at definite moments of the four-stroke cycle, in which
the variably timed transmission has a control mechanism to vary
the lead angle between the crank of the second crankshaft [5] and
the crank of the first crankshaft [4], by means of a hydraulic force
amplifier having a controlled thrustor acting on the transmission,
said transmission altering at the end of the compression phase of
the piston [6] in the larger cylinder [2], the compression ratio
of the engine between a minimum and a maximum, said minimum and
maximum compression ratios depending on :
a ) the ratio between the displacement of the
larger cylinder [2] and the displacement of the smaller cylinder
[3] , and
b ) the ratio between, on the one hand,
the total volume of the smaller cylinder and the larger cylinder
and between , on the other hand, the volume of the clearance space
[40] and an additional volume created in the smaller cylinder [3]
at the end of the compression phase of the piston [6] in the larger
cylinder [2], the variably timed transmission adjusting the lead
angle between the crank of the second crankshaft [5] and the crank
of the first crankshaft [4], so as to obtain said compression ratios,
said lead angle varying between a maximun so that an angle of at
least 90° is obtained between the connecting rod [9] of the piston
[8] in the smaller cylinder [3] and the crank of the second crankshaft
[5], at the end of the compression phase of the piston [6] in the
larger cylinder [2], in order to define the minimum compression
ratio, and a minimum so that the lead angle corresponds, at the
end of the compression phase of the piston [6] in the larger cylinder
[2], to the appropriate position of the piston [8] in the smaller
cylinder [3] to create the additional volume required to obtain
the maximum compression ratio, the crank of the second crankshaft
[5] forming an angle with the connecting rod [9] of the piston [8]
in the smaller cylinder [3].
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