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Paragraph 1 : Crankcase
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The
crankcase [1] comprises two crankshafts [4] and [5] arranged parallel
to one another, one with a long-stroke crank [4], the other with
a short-stroke crank [5]; the two cylinders [2] and [3], provided
respectively with pistons [6] and [8] and connecting rods [7] and
[9], are respectively arranged above one of the two crankshafts
[4] and [5].
The crank of the short-stroke crankshaft [5]
coacts with the connecting rod [9] of the piston [8] in the smaller
cylinder [3] and the crank of long-stroke crankshaft [4] coacts
with the connecting rod [7] of the piston [6] in the larger cylinder
[2].
The two cylinders [2] and [3] are connected
one by one, from one row to the other, through a recess in the cylinder
head [10], so as to form a pair of cylinders [2] and [3] in communication
with each other.
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Paragraph
2 : Applications |
In
the case of an engine provided with compression ignition means,
the engine comprises at least one fuel injector (not shown) in the
clearance space. The fuel is injected through means known in the
art (not shown) in mesh, at half speed, with the long-stroke crankshaft
[4].
In the case of an engine provided with spark
ignition means, the engine comprises at least one spark plug (not
shown) in the clearance space [40]. The ignition is achieved through
means known in the art (not shown) in synchronism, at half speed,
with the long-stroke crankshaft [4]. Engine timing is achieved by
means of at least one camshaft (not shown) in mesh, at half speed,
with the long-stroke crankshaft [4].
The section of the cylinder head [10] overhanging
the larger cylinder [2] comprises the intake and exhaust valves
[13] and [14], which connect periodically the pair of cylinders
[2] and [3] with the intake and exhaust pipes [11] and [12] at definite
moments of the four-stroke process.
In the case of an engine with an extremely
high displacement, a second camshaft (not shown) in mesh, at half
speed, with the long-stroke crankshaft [4] may be arranged in the
section of the cylinder head [10] overhanging the smaller cylinder
[3], so as to provide a second periodic opening and closing of the
intake and exhaust at the same time as the opening and closing of
the intake and exhaust valves of the larger cylinder [2].
The ratio between the paired cylinders [2]
and [3] is at least between 2.5 and 5, so as to permit engine accom-modation
to supercharging pressure ratios ranging from 1 to 7.
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Paragraph
3 : Variably timed transmission (part 1) |
The variably timed transmission comprises three superposed concentric
members :
the first member is the drive shaft [17] located
in the inner section,
the second member is the sleeve [28] of gear
[20] located in the outer section and
the third member is the sliding tube [32]
located in the intermediate section between the two aforesaid members.
Said sleeve [28] is held in a bearing plate
[15] by means of a suitable double-row angular contact bearing [16]
mounted between the bearing plate [15] and sleeve [28].
Said bearing plate [15] is secured to the engine
unit [1] so that the variably timed transmission forms a separate
assembly with respect to the shaft [18] of the short-stroke crankshaft
[5].
For this purpose , the variably timed transmission
and the short-stroke crankshaft [5] are designed each with their
own shaft [17] and [18].
The abuting ends of shaft [17] of the variably
timed transmission and of shaft [18] of the short-stroke crankshaft
[5] are provided with straight male splines and corresponding female
splines, so as to permit their coupling within the engine unit [1]
through an axial slide movement when the bearing plate [15] in engaged
in an opening of the engine unit [1].
The bearing place [15] is centred with respect
to shaft [18] of the short-stroke crankshaft [5], so as to permit
sel-centering of shaft [17] with respect to shaft [18] , the latter
also acting as a free bearing for shaft [17] when the bearing plate
[15] is applied against the engine unit [1] ; such means permits
the variably timed transmission to be removed from the engine unit
[1] without having to remove the short-stroke crankshaft [5].
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Paragraph
4 : Variably timed
transmission (part 2) |
Drive
shaft [17] and sleeve [28] are advantageously held concentrically
and axially with respect to each other by means of a bearing housing
[22] rigidly connected to shaft [17].
The bearing housing [22] is provided with an
axial and radial thrust bearing [23], so as to permit free rotation
of shaft [17] independently of sleeve [28].
The bearing housing [22] is an integral part
of shaft [17] at the boundary of the straight splines of the abuting
ends which serve to couple shaft [17] to shaft [18] of the short-stroke
crankshaft [5].
The bearing housing [22] and sleeve [28] are
located inside the engine unit [1].
The bearing housing [22] is shaped as a disk
which also serves as a flywheel.
The periphery of said flywheel is regularly
pierced with holes [24], so as to permit a ring [25] to be bolted
onto the surface of the flywheel opposite the side where the boundary
of the straight splines is located.
The mounting of ring [25] on the flywheel of
the bearing housing [22] serves to form a recess, so as to permit
the mounting of the outer ring [26] of the axial and radial thrust
bearing [23].
The inner ring [27] of bearing [23] is mounted
on the sleeve [28] against a ring-shaped spacer [29] encircling
sleeve [28].
The spacer [29] serves to take up the space
between the inner ring [27] of bearing [23] and the inner ring of
the angular contact bearing [16], the latter being held axially
against a shoulder of sleeve [28] through the securing of all above
parts, by means of a single nut [30] on sleeve [28].
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Paragraph
5 : Variably
timed transmission (part 3) |
Gear
[20] of sleeve [28] is located outside the engine unit [1] and is
coupled, at the same rotational speed, to the long-stroke crankshaft
[4] by means of a gear [19] rigidly mounted on the latter and an
intermediate gear [21] located between both aforesaid gears [19]
and [20].
The drive shaft [17] comprises, on the side
of the bearing housing [22] facing the bearing plate [15], helical
splines [31] onto which the sliding tube [32] is engaged.
The inner surface of said sliding tube [32]
comprises splines [33] mated to the helical splines [31], so as
to permit the sliding tube [32] to travel helically along drive
shaft [17] and provide an angular displacement between said first
and third members.
The outer surface of the sliding tube [32]
also comprises helical splines [34], the helix of which is contrary
to that of the splines [33] on the inner surface of the sliding
tube [32].
The inner surface of sleeve [28] comprises
helical splines [35] mated to the outer helical splines [34] of
the sliding tube [32], so as to permit the latte to travel helically
in sleeve [28] and provide an angular displacement between said
second and third members, at the same time as the helical travel
of the sliding tube [32] along drive shaft [17].
The sleeve [28] rotates again with shaft [17]
when the sliding tube [32] no longer travels axially.
The length of the sliding tube [32] is established
inside sleeve [28] when the end of said sliding tube [32] is located
at the stop point defined by the surface of the bearing housing
[22], the other end of the sliding tube [32] is free outside sleeve
[28], passes through gear [20] and emerges from the engine unit
[1], so as to permit, through appropriate means, the inner ring
of the double-row angular contact bearing [36] to be mounted and
secured.
Said inner ring of bearing [36] rotates with
the sliding tube [32], whereas the outer ring of bearing [36] does
not rotate and is rigidly connected to the holding member [37].
A decision-making memory of the compression
ratio programme, acting by means of a hydraulic control system,
permits the holding member [37] and the sliding tube [32] to be
shifted, so as to alter the lead angle between the two crankshafts
[4] and [5].
The start-of-travel of the variably timed transmission
is arranged so that the sliding tube [32] is at the travel-out stop
position ( not shown ) of sleeve [28] ( low torque ), which corresponds
to the minimum lead angle between the crank of the short-stroke
crankshaft [5] and the crank of the long-stroke crankshaft [4].
The end-of-travel of the variably timed transmission
is arranged so that the sliding tube [32] is at the travel-in stop
position ( not shown ) of sleeve [28] ( high torque ), which corresponds
to the maximum lead angle between the crank of the short-stroke
crankshaft [5] and the crank of the long-stroke crankshaft [4].
According to the invention, to define and facilitate
the coupling of both crankshafts [4] and [5] between the variably
timed transmission, the number of teeth of gear [20] is even when
the number of mated splines [34] and [35] of sliding tube [32] and
sleeve [28] respectively, of mated splines [31] and [33] of shaft
[17] and sliding tube [32] respectively, and of abuting splines
between both shafts [17] and [18] is uneven and vice versa.
According to an alternative embodiment of the
invention, the shaft [17] of the variably timed transmission comprises,
on the side of the bearing housing [22] facing the bearing plate
[15], straight splines [38] instead of helical splines [31], onto
which the sliding tube [32] is engaged, and the inner surface of
the sliding tube [32] comprises straight splines [39] instead of
helical splines [33], mated to the straight splines [38] of shaft
[17].
According to the invention, the minimum and
maximum compression ratios selected for the type of engine to be
designed, are determined based on the dimensions of the different
engine members, i.e. on the one hand, the ratio between the displacements
of the paired cylinders [2] and [3] and, on the other hand, the
ratio between the total displacement of these cylinders [2] and
[3] and the clearance space [40], these ratios being defined so
that the maximum lead angle between the crank of the short-stroke
crankshaft [5] and the crank of the long-stroke crankshaft [4],
defined by the end-of-travel position of the variably timed transmission,
determines at the end of the compression phase ( top dead center
of piston [6] ), the position of piston [8] with respect to the
additional volume required for the clearance space [40] to define
said minimum compression ratio of the engine, with an angle of at
least 90° between the connecting rod [9] and the crank of the short-stroke
crankshaft [5].
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Paragraph
6 : Adjustment of angle |
The
adjustment of the angle between both crankshafts, in the end-of-travel
position of the variably timed transmission, in function of the
appropriate dimensions of the different engine menbers, allow the
engie to operate :
- in the expansion phase, with the combustion
gases on the piston [8] associated at least from the maximum instantaneous
torque on the crank of the short-stroke crankshaft [5] ;
- in the expansion phase, by limiting the rise of piston [8] prior
to the opening of the exhaust valve [14], a source of combustion
gas back pressure on said piston [8];
- at the end of the intake phase, by limiting the rise of piston
[8], a cause of loss of filling volume within the cylinder [3].
This offers the advantage of maintaining the
maximum specific output of the engine at full load.
The maximum compression ratio selected is
achieved with the same data basis of dimensional values defined
for the minimum compression ratio so that the minimum lead angle
between the crank of the short-stroke crankshaft [5] and the crank
of the long-stroke crankshaft [4], defined by the start-of-travel
position of the variably timed transmission, determines at the end
of the compression phase ( top dead center of piston [6] ), the
position of piston [8] with respect to the additional volume required
for the clearance space [40] to define said maximum compression
ratio of the engine, with the connecting rod [9] of the crank of
the short-stroke crankshaft [5] away from its top dead center, so
that said connecting rod [9] forms an angle with the crank of the
short-stroke crankshaft [5].
The adjustment of the angle between both crankshafts,
in the start-of-travel position of the variably timed transmission,
in function of the appropriate dimensions of the different engine
members, allows the engine to operate :
- at the end of the compression phase, by providing
a greater translational motion to piston [8] per unit degree of
angular displacement between the cranks of the two crankshafts [4]
and [5].
This offers the advantage of speeding up the
modification process of the compression ratio of the engine at low
load.
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Paragraph
7 : Compression ratio formulation |
p = compression ratio
V1 = displacement of the larger cylinder
of the paired cylinders.
V2 = displacement of the smaller cylinder
of the paired cylinders.
V1/V2 =ratio betwwen the displacements
on the paired cynlinders
α = lead angle of the crank of
the short-stroke crankshaft
ve = clearance space of the paired cylinders
required for gas transfer without excessive lamination.
(α minimun) = lead angle of the crank
of the short-stroke crankshaft, at the start- of-travel of the variably
timed transmission.
(α maximun) = lead angle of the crank
of the short-stroke cranskshaft, at the end-of-travel of the variably
timed transmission.
Va (α minimun) = additional volume added
to the clearance space, at the start-of-travel of the variably timed
transmission, defined by the minimum lead angle of the crank of
the short-stroke crankshaft, when the crank of the long-stroke crankshaft
is located at its top dead center, at the end of the compression
phase.
Va (α maximun) = additional volume added
to the clearance space, at the end-of-travel of the variably timed
transmission, defined by the maximum lead angle of the crank of
the short-stroke crankshaft, when the crank of the long-stroke crankshaft
is located at its top dead center, at the end of the compression
phase.
Vr (α minimun) = compressed air volume
at the start-of-travel of the variably timed transmission, defined
by the minimum lead angle of the crank of the short-stroke crankshaft,
when the crank of the long-stroke crankshaft is located at its bottom
dead center, at the end of the intake phase.
Vr (α maximun) = compressed air volume
at the end-of-travel of the variably timed transmission, defined
by the maximum lead angle of the crank of the short-stroke crankshaft,
when the crank of the long-stroke crankshaft is located at its bottom
dead center, at the end of the intake phase. Compression ratio characteristics
and formulas of the variable volume combustion chamber engine.
( V1 + V2 ) x number of pairs of cylinders
= engine displacement.
V1 + [ V2 - Vr (α) ] x number of pairs of
cylinders = displacement of the engine defined by the lead angle
of the variably timed transmission.
V1 + [ V2 - Vr (α)
] + ve
ve + Va (α) |
= P.theoretic |
theoretic compression characteristic of the
engine after definition of the compression ratios established by
the lead angle of the variably timed transmission.
V1 + [ V2 - Vr (α
minimum) ] + ve
ve + Va (α minimum)
|
= P maximum |
definition of the maximum compression ratio
at the start-of-travel of the variably timed transmission. In practice,
Vr (α minimum) should not be deducted from V2 as it
is too negligible.
V1 + [ V2 - Vr (α
maximum) ] + ve
ve + Va (α maximum)
|
= P minimum |
definition of the minimum compression ratio
at the end-of-travel of the variably timed transmission. In practice,
Vr (α maximum) should not be deducted from V2 since
the air mass admitted in V1 and V2 depends on the
stored calibration at the maximum supercharging pressure.
A simplified formula of the compression ratio
may be assumed depending on whether Va(α) is located at any
angular position between the start-of-travel and the end-of-travel
of the variably timed transmission, which is :
V1 + V2 + ve
ve + Va (α)
|
= P |
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Paragraph
8 : Minimum & Maximum compression ratios |
According to the invention,
the minimum compression ratio selected may be achieved between
two end-of-travel limits of the variably timed transmission.
The first limit is achieved with a maximum lead angle between
the crank of the short-stroke crankshaft [5] and the crank of
the long-stroke crankshaft [4], so as to determine at the end
of the compression phase ( top dead centre of piston [6] ) the
position of piston [8] with respect to the additional volume
required for the clearance space [40] to define said minimum
compression ratio with an angle of at least 90° between the
connecting rod and the crank of the short-stroke crankshaft
[5], the second limit is achieved with a smaller lead angle
between the crank of the short-stroke crankshaft [5] and the
crank of the long-stroke crankshaft [4], proportionally to the
reduction of the displacement ratio of the two cylinders [2]
and [3], up to the tolerance limit generated by the working
area of the two crankshafts [4] and [5], defined by the parallel
and close positions of the paired cylinders [2] and [3], according
to the following minimum compression ratio formula : |

|
V1 + [ V2 - Vr (α
maximum) ] + ve
ve + Va (α maximum)
|
= P minimum |
It is possible to define a higher compression
ratio between the displacements of the paired cylinders, so as to
reduce the stresses on the variably timed transmission mounted on
engines having lower displacements and inversely, it is possible
to define a smaller compression ratio between the displacements
of the paired cylinders [2] and [3], so as to increase the speed
of engines having higher displacements. In practice, Vr (α maximum)
should not be deducted from V2, since the mass of air admitted in
V1 and V2 depends on the stored calibration between the compression
ratio and the supercharging pressure. The maximum compression ratio
selected is achieved on the basis of the dimensional values defined
for the minimum compression ratio, so that at the start-of-travel
of the variably timed transmission, the minimum lead angle between
the crank of the short-stroke crankshaft [5] and the crank of the
long-stroke crankshaft [4] determines, at the end of the compression
phase ( top dead centre of piston [6] ), the position of piston
[8] with respect to the additional volume required for the clearance
space [10] to define a maximum compression ratio, with the connecting
rod [9] of the crank of the short-stroke crankshaft [5] away from
its top dead centre, so that said connecting rod [9] forms an angle
with the crank of the short-stroke crankshaft [9]. The maximum compression
ratio may thus be defined by means of the following formula :
V1 + [ V2 - Vr (α
minimum) ] + ve
ve + Va (α minimum)
|
= P maximum |
In practice, Vr (α minimum) should not be deducted
from V2, since the mass of air admitted in V1 and V2 depends on
the stored calibration between the compression ratio and the atmospheric
depression in the intake pipe.
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Paragraph
9 : Volume Formulation |

The
diagrams of figures 10 and 11 are based
on the above formula where:
a = top dead center of smaller cylinder [3]
b = summit of smaller piston [8]
s = surface of smaller piston [8]
l = length of smaller connecting rod [9]
r = length of smaller crankshaft [5]
A = top dead center of larger cylinder [2]
B = summit of larger piston [6]
S = surface of larger piston [6]
L = length of larger connecting rod [7]
R = length of larger crankshaft [4]
Vm = clearance space [40]
α = angular rotation (0° at top dead center ) ( counterclockwise
)
φ = lead angle of smaller crankshaft [5] with respect to
the larger crankshaft [4].
Example to make the engine functional and
performant according to one of the numerous applications:
The above formula stored in a computer computation
sheet allows generation and selection of the dimensional values
of the different engine members, i.e. the compression ratios between
the displacements of the paired cylinders [2] and [3] and the ratio
between the total volume of these cylinders [2] and [3] and the
clearance space [40]; the computation sheet is defined so that the
values reckoned for the maximum and minimum compression ratios of
the engine coincide with the corresponding degrees of the minimum
and maximum lead angles between the crank of the short-stroke crankshaft
and the crank of the long-stroke crankshaft, respectively at the
start-of-travel and at the end-of-travel of the variably timed transmission.
The diagrams of figures 10 and 11 show examples of variation curves
of the compression ratio and of the volumetric efficiency of the
paired cylinders [2] [3] over 360° of angular rotation of the crank
of the long-stroke crankshaft [4].
According to a particular embodiment of the
invention, in the case of a high-capacity power unit, the two crankshafts
[4] and [5] are each mechanically connected to a generator and the
electrical circuits of the two generators are connected in parallel.
The capacity of each generator is defined in function of the actual
output of the corresponding crankshaft at cruise speed of the engine,
so that the variably timed transmission and the corresponding couplings
of the two crankshafts [4] and [5] are limited to torque compensating
loads.
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Paragraph
10 : Advantages |
Advantages for a four-stroke engine with compression
ignition means.
- higher volumetric efficiency ;
- higher specific output ;
- lower losses
due to mechanical friction ;
- engine accommodation
to the cetane number ;
- accurate
definition of an ideal temperature at the end of the compression
phase, so to provide suitable self-ignition of the fuel in all circumstances
( from cold starting to high supercharging pressures ) ;
- better engine
performance at high altitudes ;
- lower emissions
of hydrocarbons and nitrogen oxide in the exhaust gases.
Advantages for a four-stroke engine with spark
ignition means.
-
higher volumetric efficiency ;
- higher specific
output ;
- lower losses
due to mechanical friction and pumping ;
- higher partial-load
effeciency of the engine, due to a higher compression ratio proportionally
to the depression in the intake pipe (closing of the throttle valve)
;
- engine accomodation
to the octane number ;
- better engine
performance at high altitudes ;
- better air-fuel
mixture homogeneity ;
- lower emmissions
of carbon monoxide, nitrogen oxides and hydrocarbons in the exhaust
gases.
Advantages and conditions of use of the four-stroke
engine with compression ignition means and high supercharging pressure
levels, mounted in road haulage tractors.
The reduction of the displacement of each cylinder
of the engine, based on the mean piston speed, permits an increase
in the speed of the engine and a consistent decrease in low frequencies.
A higher gear reduction on the gearbox - output shaft assembly should
howewer be provided up to the second engine-drive reduction. Since
the mechanical friction is proportional to the displacement and
less load-sensitive, the efficiency is higher. The engine brake
may be kept whilst increasing the power of the engine, supported
by a speed limiter on the vehicle.
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Paragraph
11 : Claim 1 |
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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Paragraph
12 : Claim 2 |

Claim 2.
A four-stroke internal combustion engine according
to claim 1, for which the crank of the first crankshaft [4] passes
through a top dead center and a bottom dead center during its rotation,
in which the paired cylinders [2] [3] with parallel and close positions
and the two crankshafts [4] [5] are arranged to define a minimum
working space of the two crankshafts, so that a minimum compression
ratio between the paired cylinders [2] [3] is obtained, and in which
the variably timed transmission travels between a start-of-travel
position and an end-of-travel position, the minimum compression
ratio of the paired cylinders [2] [3] being obtained at the end-of-travel
of the variably timed transmission and calculated according to thefollowing
forrmula :
(V1 + [ V2
- Vr (α maximum) ] + ve)
(ve + Va (α maximum)) |
= P minimum in which |
V1 |
= displacement of the larger
cylinder [2] of the paired cylinders [2] [3]. |
V2 |
= displacement
of the smaller cylinder [3] of the paired cylinders [2] [3]. |
ve |
= volume of the clearance
space [40] of the paired cylinders [2] [3] required for gas
transfer between the cylinders [2] [3], without excessive lamination.
|
(α maximum) |
= lead angle of the crank
of the second crankshaft [5], at the end-of-travel of the variably
timed transmission. |
Vr (α maximum) |
= compressed air volume at
the end-of-travel of the variably timed transmission, defined
by the lead angle of the crank of the second crankshft [5],
when the crank of the first crankshaft [4] is located at its
bottom dead center, at the end of the intake phase. |
Va (α maximum) |
= additional volume added
to the clearance space volume [40], at the end-of-travel of
the variably timed transmission, defined by the lead angle of
the crank of the second crankshaft [5], when the crank of the
first crankshaft [4] is located at its top dead center, at the
end of the compression phase. |
|
Paragraph
13 : Claim 3 |
Claim
3.
A four-stroke internal combustion engine according
to claim 1 or 2, in which the variably timed transmission includes
three superposed concentric members, i.e. an inner member constituted
by a drive shaft [17], an outer member constituted by a sleeve [28]
supporting a gear [20] for coupling the two crankshafts [4] [5],
and an intermediate member located between said inner and outer
members and constituted by a tube [32] which slides with respect
to said inner and outer members, the sleeve [28] being held in a
bearing plate [15] by means of a double-row angular contact bearing
[16], in which the shaft [18] of the second crankshaft [5] has one
end which abutes one end of the drive shaft [17], said ends having
straight male splines and corresponding female splines, so as to
enable their coupling and self-centering of the three members with
respect to the shaft [18] of the second crankshaft [5] when the
bearing plate [15] is engaged in an opening of the engine unit,
and enable the transmission to be removed without having to remove
the second crankshaft [5], in which a bearing [22] has a mounting
ring [25] which forms the housing of the outer ring [26] of a bearing
[23], the inner ring [27] of which is mounted on the sleeve [28]
so as to hold the drive shaft [17], in which a spacer [29] extends
between the inner ring [27] of the bearing [23] and the inner ring
of the angular contact bearing [16], said spacer serving to take
up the space between said rings and holding axially the ring of
the angular contact bearing [16] against a shoulder of the sleeve
[28], in which a single nut [30] holds the inner rings of the bearing
[23] and of the angular contact bearing [16] and the spacer [29]
on the sleeve [28], in which the drive shaft [17] has, on the side
of the mounting ring [25] , helical or straight splines [31] onto
which the sliding tube [32] is engaged, the inner surface of which
has helical or straight splines [33] so as to enable said tube [32]
to travel helically or linearly along the drive shaft [17], in which
the inner surface of the sleeve [28] has helical splines [35], the
helix of which is contrary to that of the splines of the drive shaft
when the latter are helical, in which the sliding tube [32] has
one end permanently free outside the sleeve [28], said end being
held by an inner ring of a double-row angular contact bearing [36],
the outer ring of said bearing [36] being rigidly connected to a
holding member [37] of the thrustor, and in which the helical splines
are arranged so that when the sliding tube [32] travels out of the
sleeve, said tube reduces the lead angle between the crank of the
second crankshaft [5] and the crank of the first crankshaft [4].
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Paragraph
14 : Claim 4 |
Claim
4.
A four-stroke internal combustion engine according
to any claim 1 to 3, in which the spark ignition means includes
at least one spark plug in the clearance space [40], the ignition
being effected in sychronism, at half speed, with the first crankshaft
[4].
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Paragraph
15 : Claim 5 |
Claim
5.
A four-stroke internal combustion engine according
to any claim 1 to 4, in which the ratio between the displacements
of the paired cylinders [2] [3] is between 2.5 and 5.
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Paragraph
16 : Claim 6 |
Claim
6.
A four-stroke internal combustion engine according
to claim 3, in which the gear [20] supported by the sleeve [28]
has respectively an even or uneven number of teeth when the number
of teeth of the splines between the drive shaft [17] and the sliding
tube [32] and the number of teeth of the splines at the abuting
ends of the drive shaft [17] and of the shaft [18] of the second
crankshaft [5] are respectively uneven or even.
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