Note: Descriptions are shown in the official language in which they were submitted.
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HIGH-PRESSURE SPARK-IGNITION AND STRATIFICATION DEVICE FOR
AN INTERNAL COMBUSTION ENGINE
The present invention relates to a high-pressure spark-ignition and
stratification
device for a reciprocating internal combustion engine with a highly diluted
charge using means for recirculating previously cooled exhaust gases, known
as "external cooled EGR" means.
The thermodynamic efficiency of reciprocating internal combustion heat engines
depends on a number of factors including, firstly, the duration and phasing of
the combustion intended to raise the temperature of the gases trapped in the
combustion chamber after they have been compressed; secondly, the heat
losses of said gases in contact with the internal walls of said engine; and,
thirdly, the rate of expansion of said gases, said expansion allowing said
gases
to exert a thrust on the piston of said engine so as to convert the heat
energy
released by said combustion into mechanical work.
However, the positive work produced by the thrust of said gases on said piston
in their expansion is partially lost before it can be used at the output shaft
of the
heat engine. This is due to the negative, or resistive, work created by the
pumping and transfer of said gases in the various intake and exhaust conduits
and circuits of the heat engine, by the mechanical friction between the parts
of
said engine, and by the driving of the accessories and auxiliary equipment of
said engine.
Thus, for a given quantity of fuel consumed, the efficiency of a reciprocating
internal combustion heat engine rises with an increase in the positive work
done
on the piston of said engine by the gas compression-expansion cycle, and with
a simultaneous decrease in the negative, or resistive, work produced by the
entry and exit of said gases into and from said engine and the work produced
by the mechanism of said engine and its accessories.
In order to convert the heat released by combustion into mechanical work as
efficiently as possible, it is preferable for the fuel-air mixture introduced
into the
cylinder of the heat engine to burn rapidly, near the top dead center of the
piston of said engine, in other words at quasi-constant volume. This remains
true as long as the gas temperature does not reach such a high level that the
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heat exchange between said gases and the internal walls of the combustion
chamber of the engine becomes excessive. It also remains true as long as the
pressure gradient created by the combustion does not result in excessive noise
and is not caused by pinging.
Pinging is a spontaneous gas combustion which occurs after a certain period,
under the combined effect of pressure and temperature, and which produces
very large pressure waves which also tend to increase the heat exchange
between said gases and said walls, notably by detaching the layer of
insulating
air covering the surface of said walls. Thus pinging is an undesirable
phenomenon, which reduces the efficiency of the heat engine and which also
tends to damage the internal members of the engine by thermal and mechanical
overload.
Among the main methods of initiating combustion in the combustion chamber of
reciprocating internal combustion heat engines, it is possible to distinguish
between spark ignition, spontaneous ignition of the fuel on the injection
front
which is characteristic of diesel engines, and compression ignition using
methods known by the abbreviations CAI (for Controlled Auto
Ignition) or HCCI (for Homogeneous Charge Compression Ignition).
The combustion rate of controlled ignition engines depends primarily on the
air/fuel ratio and the content of residual burnt gases in the fuel-air mixture
introduced into the combustion chamber of said engines, on the distance that
must be covered by the flame in order to burn all said mixture, and on the
microturbulence within said mixture, the flame propagation speed being
approximately proportional to said turbulence.
In the diesel cycle, the combustion rate is mainly determined by the diesel
fuel
injection quality, and by the ketane number of said diesel fuel. In CAI or
HCCI,
the compression ratio, the initial temperature of the fuel-air mixture and its
content of burnt gases, the characteristics of the fuel used and the
homogeneity
of the charge are factors which determine the initiation and rate of
combustion.
Regardless of the methods of initiating combustion, the rate of said
combustion
determines the rate of energy release, usually expressed in degrees of
rotation
of the crankshaft between the start and end of combustion, following a curve
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showing the cumulative fraction of burnt fuel as a function of the angular
position of the crankshaft, one degree at a time.
Regardless of the combustion mode of the reciprocating internal combustion
heat engines, in practice their efficiency is always higher when the heat
exchange between the hot gases and the internal walls of said engines is
minimal.
It should be noted that said heat exchange decreases if there is a small
temperature difference between said gases and said walls, if there is little
or no
turbulent convection increasing the power of said exchange above that which is
due to simple thermal conduction and radiation, and if the mass per unit
volume
of said gases is low.
In order to reduce the temperature difference between the hot gases and the
internal walls of a reciprocating internal combustion heat engine, the
temperature of said walls can be raised, and/or the temperature of said gases
can be lowered. However, these two arrangements rapidly reach their limits in
the improvement of the efficiency of controlled ignition reciprocating
internal
combustion heat engines.
This is because increasing the temperature of the internal walls of the
combustion chamber of a reciprocating internal combustion heat engine has the
disadvantage of reducing its filling capacity: the cold air or gas mixture
coming
into contact with said hot walls expands instantaneously, thereby reducing the
volumetric efficiency of said engine in the intake phase, and consequently
reducing its overall efficiency. Furthermore, the cold air or gas mixture
overheated in this way makes the engine more liable to pinging, which must be
compensated for, by providing a lower compression/expansion ratio and/or by
providing delayed ignition, although both of these arrangements also reduce
the
efficiency of said engine. Various tests have been conducted in order to raise
the temperature of the internal walls of the combustion chamber, as in the
case
of the so-called "adiabatic" engine with a ceramic combustion chamber and
cylinders, made by Toyota. This engine offers very limited advantages in terms
of efficiency, notably because, in the final analysis, the excessively high
wall
temperature tends to increase the heat loss of the gases on said walls, by
comparison with other engines in which the cooler walls are more favorable to
the maintenance and efficacy of the fine layer of insulating air which covers
the
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internal walls of all reciprocating internal combustion heat engines. For
these
reasons, "adiabatic" engines have not progressed beyond the experimental
stage.
As an alternative to raising the temperature of the internal walls of the
combustion chamber, it is possible to reduce the temperature of the gases by
diluting them either with added air or with exhaust gases which may or may not
be previously cooled, these exhaust gases being obtained from the preceding
cycle or cycles. By diluting the fuel-air charge introduced into the
combustion
chamber of a reciprocating internal combustion heat engine with a gas which
does not participate in the combustion, it is possible to increase the total
heat
capacity of said charge in order to reduce its mean temperature for a given
amount of energy released by said combustion.
Furthermore, regardless of the diluting gas used, it contributes to the
conversion
of the heat released by combustion into mechanical work. However, in the case
of controlled spark ignition engines, the propagation of the flame in a
mixture
which is excessively lean in fuel or lean in oxygen is either too slow or is
impossible. This results in reduced thermodynamic efficiency, because the
combustion takes place to an excessive degree at non-constant volume, as well
as highly unstable combustion and ignition failures.
In order to dilute the charge introduced into the cylinder of a controlled
ignition
reciprocating internal combustion heat engine without suffering excessively
from
the last-mentioned drawbacks, there is an alternative approach in which said
charge is stratified; in other words, a pocket of combustible fuel-air mixture
centered around the ignition point of said engine is created, said pocket
being
surrounded with a mixture lean in fuel, highly diluted with cold air and/or
exhaust gases in such proportions that said lean mixture is still mostly
combustible.
Said pocket is formed, notably, by the movements of the gases within the
combustion chamber of said engine, said movements being caused, notably, by
the geometry of the intake conduits of said engine and of the walls of said
chamber, as well as by the dynamics and shape of the fuel jet injected
directly
into said chamber.
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This method, known as the "stratified charge" method, usually requires the use
of direct fuel injection and results in a charge which is rich in fuel around
the
ignition point, lean in fuel in the remaining area, and rich in oxygen
throughout,
giving rise to various problems in modern engines, notably in view of the
5 regulations on pollution emissions.
This is because said charge stratified in this way must contain sufficient
oxygen
to ensure good initiation of combustion in the part of the charge around the
ignition point, and sufficient oxygen in its remaining part to ensure good
development of said combustion and its propagation throughout the volume of
the combustion chamber of the engine, including the areas lean in fuel.
The excess oxygen which is characteristic of the operation of stratified
charge
engines according to the prior art makes it impossible to decrease nitrogen
oxides by the three-way catalysis which is normally used for post-treatment of
exhaust gases from controlled ignition engines.
In order to compensate for this problem which affects both stratified charge
engines and engines with a lean mixture operating with excess oxygen,
systems of post-treatment of nitrogen oxides in an oxidizing medium must be
used, such as NOx traps or SCR (selective catalytic reduction), but said
systems are particularly costly and sensitive to the quality and sulfur
content of
fuels, as well as being heavy and bulky.
It should be noted that the problems associated with stratified charges
include
the delayed direct injection of the fuel required for forming a fuel-rich
pocket
centered around the ignition point, said delayed injection resulting in a
considerable production of fine particles which are health hazards.
Another problem associated with the stratified charge method is its operating
range which is too limited at low loads, thus limiting its efficacy in
reducing fuel
consumption in currently used motor vehicles, particularly those having
engines
with a small cylinder capacity relative to their weight.
The latter problem which is related to the post-treatment of nitrogen oxides
in an
oxidizing medium can be avoided by providing compression ignition of the
charge, as proposed in the CAI and HCCI methods, instead of spark ignition.
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These ignition methods lead to low-temperature combustion which produces
practically no nitrogen oxides, and therefore enables the charge to be highly
diluted with excess oxygen and/or the burnt gases initially produced in the
preceding cycle or cycles, without the need to post-treat said oxides. Since
it is
not initiated by a spark, CAI or HCCI combustion avoids the constraints
imposed by flame propagation from a single ignition point, as the combustion
is
initiated spontaneously at many points. However, CAI and HCCI are particularly
sensitive to any variation in one or more of the parameters which enable it to
operate, including, for example, the initial temperature of the charge, the
effective compression ratio to which it is subjected, the quality of fuel
contained
in it, and its content of burnt gases. CAI or HCCI combustion also generates a
high pressure gradient, because it is extremely fast, and therefore produces
disagreeable acoustic emissions.
Furthermore, like the stratified charge method, CAI and HCCI only operate at
relatively low loads, thus limiting its efficacy in reducing fuel consumption
in
currently used motor vehicles, particularly those having engines with a small
cylinder capacity relative to their weight.
An alternative to the use of a stratified charge or a homogeneous lean mixture
with excess oxygen would be to replace the excess oxygen introduced into the
charge with the recirculated burnt gases from the preceding cycle or cycles,
using the method known to those skilled in the art as EGR (standing for
exhaust
gas recirculation). The problem with EGR is that, if cooling is not used
(internal
EGR), it increases the sensitivity of the heat engine to pinging, which
adversely
affects the efficiency of the engine, while if said EGR is previously cooled
in a
heat exchanger (external cooled EGR) the initiation and propagation of the
flame become random and unstable. In all cases, it is difficult to combine EGR
with stratification, where the lean areas would become incombustible.
As mentioned above, it is preferable for the fuel-air mixture introduced into
the
cylinder of any reciprocating internal combustion heat engine to burn rapidly,
near the top dead center of the piston of said engine, in other words at quasi-
constant volume, and with the lowest possible heat loss at the walls.
In the case of controlled ignition engines, fast burning of said charge
conflicts
with the aim of diluting the charge with a gas which does not participate in
its
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combustion, in order to reduce the heat losses on the internal walls of said
engines, because a gas of this type tends to reduce the propagation speed of
the flame in the volume containing said charge.
In order to restore a higher flame propagation speed, the internal turbulence
of
the fuel-air mixture can be increased, but said turbulence must not
excessively
increase the convective exchange, which magnifies the heat loss at the walls,
thus counteracting the desired effect of charge dilution.
Another method of restoring said propagation speed may be to increase the
compression ratio of the internal combustion heat engine with the aim of
increasing the density and enthalpy of the charge, both of which factors are
favorable to said propagation speed.
However, this method is difficult to use in engines with a fixed compression
ratio, in which providing a markedly high compression ratio would limit the
torque at low engine speed, thus increasing the mean fuel consumption of the
motor vehicles.
In this context, internal combustion heat engines with a variable compression
ratio have the decisive advantage of allowing their compression ratio to be
increased in a controlled way when the charge introduced into their
cylinder(s)
is highly diluted, particularly if said engines operate with partial charges,
while
allowing said ratio to be reduced when the charge is higher and/or less
diluted.
Accordingly, said variable compression engines allow the combustion of
charges which are highly diluted with exhaust gases having low coefficients of
cyclic variation, in other words small differences in combustion rate from one
cycle to another and from one cylinder to another.
However, it should be noted that a high compression ratio is unfavorable to
the
conversion of the macroscopic movements of the charge into fine turbulence at
the top dead center of the piston of said engine, said turbulence being
favorable
to the fast propagation of the flame in the fuel-air mixture.
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In order to overcome this problem, a combustion chamber of what is known as
the "squish" type can be provided, this chamber producing high turbulence
when the piston reaches the vicinity of its top dead center.
However, the problem with squish chambers is that the piston has to be brought
very close to the cylinder head, entailing a risk of collision between said
piston
and said cylinder head, while the desired squish effect is provided only in
the
vicinity of the top dead center, in other words relatively late with respect
to the
moment of the spark-initiated ignition of the charge.
Another drawback of squish chambers is that they strongly promote heat
exchange between the gases and the internal walls of the combustion chamber.
In view of the above, it would clearly be advantageous to be able to provide
fast
combustion of stoichiometric charges highly diluted with external cooled EGR,
in such a way that the polluting products could be post-treated with a three-
way
catalytic converter, without any excess turbulence which would counteract the
reduction of the heat losses at the walls which is the desired effect of the
dilution of said charge by said EGR. It would also be clearly advantageous to
arrange for the combustion of the highly diluted stoichiometric charges over
the
widest possible operating range of the heat engine.
It is in order to meet this objective, to overcome the various aforementioned
problems encountered in the prior art regarding internal combustion engines,
and to enable these engines to be used in an economical, clean and fuel-saving
manner that the high-pressure spark-ignition and stratification device for a
reciprocating internal combustion engine with a highly diluted charge
proposes,
according to the invention and according to a particular embodiment:
= To create a pocket of stoichiometric fuel-air gas mixture forming what is
called a "pilot" charge of small volume and mass, with a low content of
EGR, which is centered, as far as possible, around the ignition point, is
locally turbulent even in operation at a high compression ratio, is
produced at the most suitable moment during the compression phase,
and is then ignited by an electric arc struck between the electrodes of a
spark plug.
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This has the purpose of:
= Using the combustion of said pilot charge to provide, over a wide
operating range of reciprocating internal combustion engines, ignition
and combustion of a stoichiometric charge called the "main" charge,
prepared in advance in the intake and/or compression phase and highly
diluted with external cooled EGR supplied by an exhaust gas tapping
device interacting with a cooler.
This has the effect of:
= Generating a locally high turbulence in the pilot charge surrounding the
ignition point and at the interface between said pilot charge and the main
charge, so as to promote the rapid development of a wide flame front in
the three-dimensional space of the combustion chamber, while retaining
a globally moderate turbulence within said main charge in order to limit
the convective heat exchange between the hot gases of said main
charge and the internal wall of said chamber;
And has the following results:
= Allowing the combustion of stoichiometric charges with a very high
content of external cooled EGR;
= Promoting fast, regular combustion of said stoichiometric charges close
to the isochore;
= Benefiting from the high energy efficiency of the stratified charge used
in
excess air, but by means of the stratification of stoichiometric charges
which are highly diluted with external cooled EGR, so as to allow the
post-treatment of pollutants produced by the combustion using a simple
three-way catalytic converter and thus avoiding the use of costly, heavy
and bulky NOx traps or selective catalytic reduction (SCR) devices;
= Greatly extending the range of operating loads and positive effects on
the efficiency of the stratification, from the lowest loads to relatively high
or very high loads;
= Significantly reducing the fuel consumption of all motor vehicles,
including low powered vehicles and thermal-electric hybrid vehicles in
which methods such as the reduction of cylinder capacity, known as
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"downsizing", or the inactivation of cylinders have little or no positive
effect on energy performance, said reduction in consumption being
achieved, according to the invention, not by the repositioning of the
engine operation in its speed-load ranges offering the best energy
5 efficiency, but by increasing the energy efficiency over almost the
whole
operating range of said engine;
= Making the high levels of downsizing of engines less necessary for
reducing the mean consumption of motor vehicles, said high levels of
downsizing significantly increasing the production cost of said vehicles,
10 notably because of the high-performance supercharger systems which
are required in these cases;
= Allowing the production of engines having very low cylinder capacity with
high energy efficiency, notably by reducing the unfavorable effect on their
thermodynamic efficiency of the high surface/volume ratio of their
combustion chambers which leads to high heat losses, this being
achieved according to the invention by a significant reduction in the
mean charge temperature of said engines due to the high dilution of said
charge with external cooled EGR, said dilution naturally reducing said
heat losses of said engines;
= Enabling the engines to operate at a high compression ratio in order to
increase the thermodynamic efficiency, this being made possible, on the
one hand, by a high resistance to pinging of the principal charge because
of its high degree of dilution with external cooled EGR, and, on the other
hand, by a high resistance to pinging of the pilot charge because of its
proximity to the ignition point and its consequent fast combustion;
= Naturally reducing the pumping losses of the engines, since the large-
scale introduction of external cooled EGR into their cylinder(s) has the
effect of increasing the intake pressure of said engines and thus opening
their butterfly valves wider for a given operating point, said natural
reduction of the pumping losses making it less necessary to use complex
and costly devices for variable lifting of the intake valves to reduce said
losses;
= Avoiding the delayed gasoline injection during the compression phase
that is characteristic of the operation of stratified charge engines
operating in excess air, thereby avoiding the large-scale production of
fine particles during combustion and thus avoiding the use of a costly
and bulky particle filter for the post-treatment of said fine particles;
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= Enabling the charge to be stratified with a multi-point gasoline
injection
system as an alternative to the direct gasoline injection normally used to
stratify the charge, the latter form of injection being more complicated
and costly;
5 =
Providing freedom from the internal geometric constraints of the
combustion chamber and of the intake conduit(s) and/or freedom from
the constraints on the positioning and shape of the injector jet imposed
by the use of the stratified charge according to the prior art, said
constraints arising from the need to provide a combustible pocket which
10 is
approximately centered around the ignition point and leading to various
aerodynamic arrangements within the combustion chamber and within
the intake conduit(s), mainly known under the terms "wall-guided", "air-
guided" and "spray-guided", whereas these constraints are virtually
dispensed with by using the ignition device according to the invention
15 which
offers greater freedom in the design of said chamber and said
conduits;
= Allowing the stratification of charges highly diluted with external
cooled
EGR in engines of low unitary cylinder capacity, in which, firstly, the
small bore is poorly compatible or even incompatible with direct injection
20 which
requires a minimum distance between the source of the injection
jet and the walls of the combustion chamber, and, secondly, the mean
charge currently used is potentially too high for sufficient benefit to be
obtained from the advantages of the stratified charge operating with
excess oxygen where operation is too limited at low loads, or in which,
25
thirdly, the overall production cost of said stratified charge and of the
associated post-treatment devices is too high relative to the category of
vehicles for which said engines are intended;
= Providing a fast temperature rise in the engines, notably because of the
cooling of the recirculated exhaust gases via an air/water heat exchanger
30 heated
by the cooling water of said engines, this fast temperature rise
making it possible, notably, to reduce the viscosity of the lubricating oil of
said engines and the associated frictional losses, this resulting in a lower
fuel consumption of the motor vehicles when they are used on short
journeys beginning with a cold start of said engines, said fast
= 35
temperature rise also having the advantage of improving the passenger
comfort of said vehicles because of the faster temperature rise of the
passenger compartments of said vehicles in the winter period;
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= Greatly reducing the consumption of gasoline and the associated carbon
dioxide emissions of all motor vehicles at a limited production cost.
It should be noted that the ignition device according to the invention can
also be
used in non-stoichiometric engines operating with excess oxygen.
It should also be noted that the ignition device according to the invention
can be
applied to any reciprocating internal combustion engine with a fixed or
variable
compression ratio and/or cylinder capacity, but that it offers more optimal
operation when it is used in an engine having at least a variable compression
ratio, since this type of engine makes it possible to benefit from a high
level of
downsizing, owing to excellent efficiency at very high loads and owing to a
distinctive capacity to handle said very high loads even without external
cooled
EGR using a temporarily low compression ratio, and also to benefit from a very
high rate of external cooled EGR at low and intermediate loads where
combustion is made possible by a temporarily high compression ratio. Without
excluding any other application, the ignition device according to the
invention is
particularly suitable for reciprocating internal combustion engines used to
power
motor vehicles.
The high-pressure spark-ignition and stratification device for an internal
combustion engine according to the present invention comprises:
= at least one stratification valve housed in the cylinder head of the
internal
combustion engine, said valve being kept in contact with a seat by at least
one spring and said valve closing a first end of at least one stratification
conduit which opens into a stratification prechamber while a second end that
said conduit comprises opens into a stratification chamber, the latter being
connected by at least one stratification injection conduit to the combustion
chamber of the internal combustion engine, said injection conduit opening
into said combustion chamber near protruding electrodes of a spark plug
fixed in the cylinder head of the internal combustion engine, said electrodes
being positioned in the combustion chamber of said engine;
= at least one stratification actuator controlled by the ECU computer of the
internal combustion engine, said actuator being responsible for lifting the
stratification valve off its seat, keeping it open and returning it to its
seat;
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= at least one stratification line connecting the stratification prechamber
to the
outlet of a stratification compressor the inlet of which is connected directly
or
indirectly to an atmospheric stratification air supply conduit, said supply
conduit, said compressor and the inlet and outlet thereof, said line, said
prechamber and the stratification conduit forming in combination an
atmospheric air supply circuit for the stratification chamber, and said
chamber itself forming an integral part of said circuit;
= at least one stratification fuel injector controlled by the ECU computer of
the
internal combustion engine, said injector being capable of producing a jet of
fuel either within the atmospheric air supply circuit for the stratification
chamber at any point in said circuit, or within the stratification injection
conduit, or within said circuit and said conduit;
= at least means of recirculating previously cooled exhaust gases, called
"external cooled EGR" means, controlled by the ECU computer of the
internal combustion engine, said means making it possible to tap exhaust
gases from the exhaust conduit of said engine and then reintroduce said
gases to the intake side of said engine after said gases have previously
been cooled by means of at least one cooler.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a seat of the stratification valve which has a face
oriented
toward the outside of the stratification prechamber in such a way that the
stratification actuator can lift said valve of said seat only by moving said
valve
away from said prechamber.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a seat of the stratification valve which has a seat which
is
oriented toward the inside of the stratification prechamber so that the
stratification
actuator can lift said valve of said seat only by moving said valve closer
toward
said prechamber.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification actuator which consists of at least one
coil of
conductive wire secured to the cylinder head of the internal combustion
engine,
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said coil attracting a magnetic core or blade when an electric current flows
through
said coil, so that said one core or blade moves in longitudinal translation
the
stratification valve to which it is connected by coil pushing or pulling
means.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification actuator which consists of at least one
stack of
piezoelectric layers the thickness of which varies when said layers are
subjected
to the passage of an electric current, in such a way that said stack moves in
longitudinal translation the stratification valve to which it is connected by
stack
pushing or pulling means.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stack of piezoelectric layers which is connected to the
stratification valve by means of at least one lever which multiplies the
displacement imparted by said stack to said valve.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification actuator which consists of a pneumatic
stratification actuating cylinder comprising a pneumatic stratification
receiving
chamber and a pneumatic stratification receiving piston, said piston being
secured
to the stratification valve or being connected thereto by pneumatic piston
pushing
or pulling means, whereas said pneumatic chamber can be placed in
communication either with a high-pressure reserve of air or the open air or
with a
low-pressure reserve of air by at least one solenoid valve.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification actuator which consists of a hydraulic
stratification actuating cylinder comprising a hydraulic stratification
receiving
chamber and a hydraulic stratification receiving piston, said piston being
secured
to the stratification valve or being connected to the latter by hydraulic
piston pulling
or pushing means.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a hydraulic stratification receiving chamber which may be
connected either to a high-pressure hydraulic control fluid reservoir or to a
low-pressure hydraulic control fluid reservoir by at least one high-pressure
solenoid valve and/or by at least one low-pressure solenoid valve.
CA 02863474 2014-07-31
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a high-pressure hydraulic control fluid reservoir which is
pressurized by a hydraulic control pump, said pump transferring hydraulic
fluid
5 tapped from the low-pressure hydraulic control fluid reservoir so that it
can be
transferred to said high-pressure hydraulic control fluid reservoir.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification fuel injector which is connected to a
reservoir
10 of pressurized combustible gas.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises an atmospheric air supply circuit for the stratification
chamber
which comprises a homogenization circulator, said circulator being placed at
any
15 point of said circuit and aggregating atmospheric air or a gaseous
mixture
contained in said circuit by causing said air or said mixture to circulate
through
said circuit.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises an atmospheric air supply circuit for the stratification
chamber
which comprises an air-to-air heat exchanger for heating the supply circuit
which
heats atmospheric air or gaseous mixture contained in said circuit by
extracting
heat from the exhaust gases of the internal combustion engine, said air or
gaseous mixture and said exhaust gases passing simultaneously through said
exchanger without mixing with one another.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises an atmospheric air supply circuit for the stratification
chamber
which comprises at least one electrical resistance for heating the supply
circuit
which heats atmospheric air or gaseous mixture contained in said circuit.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises an internal surface of the atmospheric air supply circuit
of the
stratification chamber which is wholly or partially covered with a thermal
insulation
material.
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The high-pressure spark-ignition and stratification device according to the
present
invention comprises an atmospheric air supply circuit for the stratification
chamber
which comprises an air-to-cooling water heat exchanger for cooling the supply
circuit which cools atmospheric air or gaseous mixture contained in said
circuit by
surrendering heat from said atmospheric air or gaseous mixture to a heat-
transfer
fluid contained in the cooling circuit of the internal combustion engine.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises stratification chamber which comprises at least one inlet
and/or at least one outlet which is/are tangential.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises an atmospheric air supply circuit for the stratification
chamber
which comprises at least one agitation chamber which imparts a turbulent
motion
to a gaseous mixture which is moving in said circuit or which causes the
gaseous
mixture to undergo rapid pressure variations.
The high-pressure spark and stratification ignition device according to the
present
invention comprises a stratification line which comprises at least one
discharge
valve which opens over a particular pressure prevailing in said line.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification line and/or an outlet of the
stratification
compressor and/or a stratification prechamber which comprises at least one
discharge solenoid valve the outlet of which opens into the intake side of the
internal combustion engine, or into a canister, or into a storage reservoir.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises an outlet of the stratification compressor which is
connected
to a pressure accumulator which stores atmospheric air or a gaseous mixture
previously pressurized by said compressor, said accumulator also communicating
directly or indirectly with the stratification line and the stratification
prechamber so
as to keep said line and said prechamber under pressure.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises means for recirculating previously cooled exhaust gases,
called "external cooled EGR" means, which consist of at least one proportional-
lift
CA 02863474 2014-07-31
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EGR tapping valve or of at least one proportional-rotation EGR tapping flap
valve
or of at least one proportional-rotation EGR tapping sleeve valve positioned
on the
exhaust manifold of the internal combustion engine, said valve or said flap
valve or
said sleeve valve being capable of placing said manifold in communication with
an
external EGR supply conduit of which the opposite end to the end that opens
into
said manifold opens into the intake plenum of the internal combustion engine.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a proportional-lift EGR tapping valve or a proportional-
rotation
EGR tapping flap valve or a proportional-rotation EGR tapping sleeve valve
positioned on the exhaust manifold which collaborates with at least one
proportional-lift exhaust back-pressure valve or with a proportional-rotation
exhaust back-pressure flap valve or with a proportional-rotation exhaust back-
pressure sleeve valve that at least one of the outlets of said manifold
comprises.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification EGR cooler which is a high-temperature
air-to-water exchanger in the external EGR supply conduit which cools the
exhaust
gases tapped from the exhaust conduit of the internal combustion engine, said
exhaust gases surrendering some of their heat to a heat-transfer fluid
contained in
the cooling circuit of said internal combustion engine.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification EGR cooler which is a low-temperature
air-to-water exchanger in the external FOR supply conduit which cools the
exhaust
gases tapped from the exhaust conduit of the internal combustion engine, said
exhaust gases surrendering some of their heat to a heat-transfer fluid
contained in
an independent cold water circuit that said internal combustion engine
comprises.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification chamber which consists of an annular
cavity
formed in a cylindrical hole in which a cylindrical sealing tip that the spark
plug
comprises is engaged, said hole opening into the combustion chamber of the
internal combustion engine.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification injection conduit which consists of at
least one
CA 02863474 2014-07-31
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stratification injection channel a first end of which communicates with the
stratification chamber and a second end of which opens between the inside of
the
cylindrical sealing tip and a central insulating cone that the spark plug
comprises.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification injection conduit which consists of at
least one
stratification injection capillary formed inside a central electrode that the
spark plug
comprises so that the first end of said capillary communicates with the
stratification
chamber and the second end of said capillary opens at the end of said central
electrode.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification injection conduit which consists of at
least one
peripheral stratification nozzle a first end of which communicates with the
stratification chamber and a second end of which opens at the periphery of the
spark plug, said second end being directed approximately toward the electrodes
that said spark plug comprises.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises at least the stratification valve, the seat, the spring,
or all part
of the stratification conduit, the stratification prechamber and the
stratification
actuator which are incorporated in combination into at least one cartridge
fixed or
screwed into the cylinder head of the internal combustion engine.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a stratification line and/or an outlet of the
stratification
compressor and/or a stratification prechamber which comprises at least one
valve
or injector of air-fuel mixture making it possible to keep the pollutant
post-treatment catalytic converter at temperature, said type of valve or
injector
being capable of transferring an air-fuel mixture from said line or from said
outlet
or from said prechamber to the exhaust conduit of the internal combustion
engine,
said mixture being introduced into said conduit by said type of valve or
injector at
any point of said conduit positioned between the exhaust valve of said engine
and
said catalytic converter of said engine.
The high-pressure spark-ignition and stratification device according to the
present
invention comprises a valve or injector for an air-fuel mixture for keeping
the
CA 02863474 2014-07-31
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catalytic converter at temperature which is connected to the exhaust conduit
of the
internal combustion engine by a catalytic converter temperature maintaining
air-fuel mixture conduit.
The following description which refers to the appended drawings, provided by
way
of non-limiting examples, will assist in the understanding of the invention,
its
features and the advantages it can provide:
Figure 1 is a schematic view of the high-pressure spark-ignition and
stratification
device according to the invention mounted on a reciprocating internal
combustion
engine.
Figures 2 and 3 are schematic sectional views of the high-pressure spark-
ignition
and stratification device according to the invention, with the stratification
valve
respectively in the closed and then open position, it being possible for said
valve to
be lifted off its seat by a stratification actuator consisting of a coil of
conductive
wire capable of attracting a magnetic core connected to said valve by coil
pushing
or pulling means.
Figure 4 is a schematic sectional view of the high-pressure spark-ignition and
stratification device according to the invention in which the stratification
valve can
be lifted off its seat by a stratification actuator consisting of a stack of
piezoelectric
layers which is connected to said valve by stack pushing or pulling means.
Figure 5 is a schematic sectional view of the high-pressure spark-ignition and
stratification device according to the invention the stratification valve of
which can
be lifted off its seat by a stratification actuator consisting of a hydraulic
stratification
actuating cylinder the hydraulic stratification receiving piston of which is
connected
to said valve by hydraulic piston pushing or pulling means.
Figure 6 illustrates a first variant arrangement of the various components of
the
high-pressure spark-ignition and stratification device according to the
invention,
said device being applied to a reciprocating internal combustion engine with
four
in-line cylinders supercharged by a turbocharger, and said variant notably
comprising a homogenization circulator, a proportional-lift EGR tapping valve
and
a proportional-lift exhaust back-pressure valve.
CA 02863474 2014-07-31
Figure 7 illustrates a second variant arrangement of the various components of
the
high-pressure spark-ignition and stratification device according to the
invention,
said device being applied to a reciprocating internal combustion engine with
four
in-line cylinders supercharged by a turbocharger and said variant notably
5 comprising a pressure accumulator which stores atmospheric air or the
gaseous
mixture pressurized by the stratification compressor, a stratification fuel
injector
connected to a reservoir of pressurized combustible gas, a proportional-lift
EGR
tapping flap valve and a proportional-lift exhaust back-pressure flap valve.
10 Figure 8 shows a third variant arrangement of the various components of
the high-
pressure spark-ignition and stratification device according to the invention,
said
device being applied to a reciprocating internal combustion engine with four
in-line
cylinders supercharged by a turbocharger and said variant comprising notably
an
air-to-air heat exchanger for heating the atmospheric air supply circuit, a
15 proportional-lift EGR tapping sleeve valve and a proportional-lift
exhaust back-
pressure sleeve valve.
Description of the Invention
20 Figure 1 shows an internal combustion engine 1 comprising a high-
pressure
spark-ignition and stratification device 2 according to the present invention.
The internal combustion engine 1 comprises an engine block or crankcase 3
which
contains at least one combustion cylinder 4 closed by a cylinder head 8 and in
which a combustion piston 5 moves.
The combustion piston 5 is mounted articulated on a connecting rod 6 connected
to a crankshaft 7, said connecting rod 6 transmitting the movement of said
combustion piston 5 to said crankshaft 7 when said piston 5 moves inside the
combustion cylinder 4.
The cylinder head 8 of the internal combustion engine 1 comprises a combustion
chamber 9 into which there open, on the one hand, an intake conduit 11 which
may or may not be closed off by an intake valve 13 and which communicates with
an intake plenum 19 and, on the other hand, an exhaust conduit 10 which may or
may not be closed off by an exhaust valve 12 and which communicates with an
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exhaust manifold 18 and with a catalytic converter 75 for the post-treatment
of the
pollutants.
The internal combustion engine 1 further comprises a cooling circuit 17 and a
computer ECU.
Figures 1 to 8 show the high-pressure spark ignition and stratification device
2
according to the present invention.
The high-pressure spark-ignition and stratification device 2 comprises at
least one
stratification valve 20 housed in the cylinder head 8 of the internal
combustion
engine.
Said valve is kept in contact with a seat 21 by at least one spring 22, said
valve
closing a first end of at least one stratification conduit 23 which opens into
a
stratification prechamber 79, whereas a second end that said conduit comprises
opens into a stratification chamber 24.
The stratification chamber 24 is connected by at least one stratification
injection
conduit 39 to the combustion chamber 9 of the internal combustion engine 1,
said
injection conduit 39 opening into said combustion chamber 9 near protruding
electrodes 26 of a spark plug 25 fixed into the cylinder head 8 of the
internal
combustion engine 1, said electrodes being positioned in the combustion
chamber
9 of said engine 1.
According to one particular embodiment of the high-pressure spark-ignition and
stratification device 2 according to the invention, said spark plug 25 may be
identical to or similar to those fitted to controlled-ignition internal
combustion
engines such as known to those skilled in the art.
It will be noted that the spring 22 may act directly or indirectly by means of
a solid
or of a fluid on the stratification valve 20, whereas it may be mechanical
whatever
the material, may operate in flexion, torsion or traction, and may be, for
example, a
"Belleville" spring washer, a helical or leaf spring, a corrugated spring
washer or a
spring washer having any other geometry and may be of any type known to those
skilled in the art.
CA 02863474 2014-07-31
22
In a particular embodiment, said spring 22 may also be pneumatic, using the
properties of compressibility of a gas, or hydraulic, using the properties of
compressibility of a fluid.
It will be noted that the high-pressure spark-ignition and stratification
device 2
comprises at least one stratification actuator 27 controlled by the computer
ECU of
the internal combustion engine 1, said actuator being responsible for lifting
the
stratification valve 20 of its seat 21, keeping it open and returning it to
its seat.
The high-pressure spark-ignition and stratification device 2 also comprises at
least
one stratification line 28 connecting the stratification prechamber 79 to the
outlet of
a stratification compressor 29 the inlet of which is connected directly or
indirectly
to a stratification atmospheric air supply conduit 30.
Said supply conduit, said compressor and the inlet and outlet thereof, said
line,
said prechamber and the stratification conduit 23 in combination form an
atmospheric air supply circuit 31 for the stratification chamber 24, and said
chamber itself forms an integral part of said circuit.
It will be noted that the stratification compressor 29 may be of any type
known to
those skilled in the art, said compressor be of fixed or variable cylinder
capacity,
have piston(s), vanes, screws with or without lubrication, may be single-
stage,
two-stage or multi-stage and may or may not have intermediate cooling.
Depending on the chosen way of embodying the high-pressure spark-ignition and
stratification device 2 according to the invention, said stratification
compressor 29
may notably be fixed directly or indirectly to the internal combustion engine
1 and
be mechanically driven by the crankshaft 7 that said engine comprises via at
least
one pinion or via at least one chain or via at least one belt 32 via a
transmission
having fixed or variable transmission ratio, or electrically via an alternator
driven by
said crankshaft which produces the current required by an electric motor
driving
said compressor, in which case the electrical energy produced by said
alternator
may or may not be stored in advance in a battery.
The high-pressure spark-ignition and stratification device 2 further comprises
at
least one stratification fuel injector 33 controlled by the ECU computer of
the
internal combustion engine 1, it being possible for said injector to produce a
jet of
CA 02863474 2014-07-31
23
fuel either within the atmospheric air supply circuit 31 for the
stratification chamber
24 at any point in said circuit or within the stratification injection conduit
39, or
within said circuit and said conduit.
According to one particular embodiment of the device according to the
invention,
said stratification fuel injector 33 may inject a liquid or gaseous fuel and
may be a
single-stage or multiple-stage injector of the solenoid or piezoelectric type
or, in
general, of any type known to those skilled in the art.
As has been shown in figures 6, 7 and 8, the high-pressure spark-ignition and
stratification device 2 comprises at least means for recirculating previously
cooled
exhaust gases 40, called "external cooled EGR" means, controlled by the ECU
computer, these previously cooled exhaust gas recirculation means 40 making it
possible to tap exhaust gases from the exhaust conduit 10 of the internal
combustion engine 1 and then reintroduce said gases into the intake side of
said
engine after said gases have been cooled by means of at least one cooler 41.
In a certain embodiment, the high-pressure spark-ignition and stratification
device
2 comprises a stratification valve 20 the seat 21 of which has a face which is
oriented toward the outside of the stratification prechamber 79 so that the
stratification actuator 27 can lift said valve of said seat only by moving
said valve
away from said prechamber (figures 2 to 5).
According to another embodiment, the high-pressure spark-ignition and
stratification device 2 comprises a stratification valve 20 the seat 21 of
which has a
face which is oriented towards the inside of the stratification prechamber 79
so
that the stratification actuator 27 can lift said valve of said seat only by
moving said
valve toward said prechamber.
As has been shown in figures 2 and 3, the stratification actuator 27 may
consist of
at least one coil of conductive wire 50 secured to the cylinder head 8 of the
internal combustion engine 1, said coil attracting a magnetic core or blade 51
when an electric current flows through said coil, so that said one core or
blade
moves in longitudinal translation the stratification valve 20 to which it is
connected
by coil pushing or pulling means 42.
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24
Figure 4 shows that the stratification actuator 27 may consist of at least one
stack
of piezoelectric layers 52 the thickness of which varies when said layers are
subjected to a flow of electric current, so that said stack moves in
longitudinal
translation the stratification valve 20 to which it is connected by stack
pushing or
pulling means 80.
According to a variant of the device according to the invention, the stack of
piezoelectric layers 52 may be connected to the stratification valve 20 via at
least
one lever (not depicted) which multiplies the displacement imparted by said
stack
to said valve.
Said lever may for example consist of a washer itself made up of a succession
of
small levers joined together in a circle, each small lever resting against the
top of
the stack of piezoelectric layers 52 on the one hand, and against the
stratification
valve 20 on the other, either directly or via stack pushing or pulling means
80.
According to another embodiment, the high-pressure spark-ignition and
stratification device 2, the stratification actuator 27 may consist of a
stratification
pneumatic actuating cylinder (not depicted) comprising a stratification
pneumatic
receiving chamber and a stratification pneumatic receiving piston, said piston
being secured to the stratification valve 20 or connected thereto by pneumatic
piston pushing or pulling means, whereas said pneumatic chamber can be placed
in communication either with a reserve of high-pressure air or with the open
air or
with a reserve of low-pressure air by at least one solenoid valve.
According to another variant depicted in figure 5, the high-pressure spark-
ignition
and stratification device 2 may comprise a stratification actuator 27
consisting of a
stratification hydraulic actuating cylinder 36 and comprising a stratification
hydraulic receiving chamber 37 and a stratification hydraulic receiving piston
38,
said piston being secured to the stratification valve 20 or connected thereto
by
hydraulic piston pushing or pulling means 53.
Said hydraulic stratification receiving piston 38 may comprise seals to seal
against
a cylinder with which it interacts, and the hydraulic stratification receiving
chamber
37 may be connected either to a high-pressure hydraulic control fluid
reservoir or
to a low-pressure hydraulic control fluid reservoir by at least one high-
pressure
solenoid valve and/or by at least one low-pressure solenoid valve.
CA 02863474 2014-07-31
The high-pressure spark-ignition and stratification device 2 may comprise a
high-pressure hydraulic control fluid reservoir, not depicted, which is
pressurized
by a hydraulic control pump, said pump transferring a hydraulic fluid tapped
from
According to one particular embodiment, the high-pressure spark-ignition and
stratification device 2 comprises a stratification fuel injector 33 which may
be
comprises a homogenization circulator 56 placed at any point of said circuit
and
which agitates atmospheric air or a gaseous mixture contained in said circuit
by
causing said air or said mixture to circulate through said circuit.
chamber 24 which comprises an air-to-air heat exchanger 57 for heating said
circuit 31 which heats atmospheric air or a gaseous mixture contained in said
circuit 31 by extracting heat from the exhaust gases of the internal
combustion
engine 1, said air or gaseous mixture and said exhaust gases passing
According to one particular embodiment of the high-pressure spark-ignition and
stratification device 2, the atmospheric air supply circuit 31 for the
stratification
chamber 24 comprises at least one electrical resistance for heating the supply
It will be noted that, possibly, the internal surface of the atmospheric air
supply
circuit 31 of the stratification chamber 24 may wholly or partially be covered
with a
CA 02863474 2014-07-31
26
Said internal surface may also be covered with a non-stick material such as
Teflon
for example, or any other coating known to those skilled in the art and that
makes
it possible to avoid any products derived from the polymerization of the fuel
circulating in said supply circuit 31 from adhering to said surface.
Figure 7 shows the atmospheric air supply circuit 31 for the stratification
chamber
24 which comprises an air-to-cooling water heat exchanger for cooling the
supply
circuit 58 which cools atmospheric air or a gaseous mixture contained in said
circuit by surrendering heat from said atmospheric air or gaseous mixture to a
heat-transfer fluid contained in the cooling circuit 17 of the internal
combustion
engine 1.
According to one embodiment, not depicted, the stratification chamber 24
comprises at least one inlet and/or at least one outlet which is/are
tangential, so
that said inlet and/or outlet are able to impart a swirling movement to the
atmospheric air or to the gaseous mixture coming from the stratification line
28
when said air or mixture is introduced into said chamber.
The atmospheric air supply circuit 31 for the stratification chamber 24 may
also
comprise at least one agitation chamber, not depicted, which imparts a
turbulent
motion to a gaseous mixture which is moving in said circuit or which causes
said
gaseous mixture to undergo rapid pressure variations, said agitation chamber
being able for example to create a venturi effect so as to encourage the
evaporation of the fuel contained in said mixture on the one hand, and the
aggregation of said mixture on the other hand.
According to one particular embodiment, the high-pressure spark-ignition and
stratification device 2 comprises a stratification line 28 which may comprise
at
least one discharge valve 59 which opens over a particular pressure prevailing
in
said line, it being possible for the outlet from said discharge valve 59 to
open ¨
according to one particular embodiment of the device according to the
invention ¨
into the intake plenum 19 or into the exhaust circuit 10 of the internal
combustion
engine 1, or to the open air (figure 8) .
The stratification line 28 and/or the outlet of the stratification compressor
29 and/or
the stratification prechamber 79 may also comprise at least one discharge
solenoid valve the outlet of which opens into the intake side of the internal
CA 02863474 2014-07-31
27
combustion engine, or into a canister not depicted, or into a storage
reservoir
likewise not depicted.
It may be noted that said solenoid valve may be actuated so as to open when
the
internal combustion engine 1 stops, in such a way that said canister or said
reservoir stores most of the hydrocarbon vapors contained in said
stratification line
28 and/or said outlet of the stratification compressor 29 and/or said
stratification
prechamber 79, said vapors then being burnt when said engine is subsequently
restarted, or in such a way that said vapors are burnt immediately by said
engine
when they are expelled to the intake side of said engine by said solenoid
valve.
Figure 7 shows that the outlet of the stratification compressor 29 may be
connected to a pressure accumulator 60 which stores atmospheric air or a
gaseous mixture previously pressurized by said compressor, said accumulator
also communicating directly or indirectly with the stratification line 28 and
the
stratification prechamber 79 so as to keep said line and said prechamber under
pressure.
Said pressure accumulator 60 serves notably to stabilize the pressure
established
in these members in the case in which, for example, the stratification
compressor
29 includes a single piston rotating at low speed, this configuration
generating
high-amplitude pressure waves within said members.
The high-pressure spark-ignition and stratification device 2 comprises means
40
for recirculating previously cooled exhaust gases, called "external cooled
EGR"
means, which consist of at least one proportional-lift EGR tapping valve 63
(figure
6) or of at least one proportional-rotation EGR tapping flap valve 64 (figure
7) or of
at least one proportional-rotation EGR tapping sleeve valve 65 (figure 8)
positioned on the exhaust manifold 18 of the internal combustion engine 1,
said
valve or said flap valve or said sleeve valve being capable of placing said
manifold
in communication with an external EGR supply conduit 66 of which the opposite
end to the end that opens into said manifold opens into the intake plenum 19
of
the internal combustion engine.
The proportional-lift EGR tapping valve 63 or the proportional-rotation EGR
tapping flap valve 64 or the proportional-rotation EGR tapping sleeve valve 65
positioned on the exhaust manifold 18 collaborates with at least one
CA 02863474 2014-07-31
28
proportional-lift exhaust back-pressure valve 67 (figure 6) or with a
proportional-rotation exhaust back-pressure flap valve 68 (figure 7) or with a
proportional-rotation exhaust back-pressure sleeve valve 69 (figure 8) that at
least
one of the outlets of said manifold comprises.
Figures 6 to 8 show a stratification EGR cooler 41 which is a high-temperature
air-to-water exchanger in the external EGR supply conduit which cools the
exhaust
gases tapped from the exhaust conduit 10 of the internal combustion engine 1,
said exhaust gases surrendering some of their heat to a heat-transfer fluid
contained in the cooling circuit 17 of said internal combustion engine.
Figures 6 to 8 also show a stratification EGR cooler 41 which is a low-
temperature
air-to-water exchanger in the external EGR supply conduit which cools the
exhaust
gases tapped from the exhaust conduit 10 of the internal combustion engine 1,
said exhaust gases surrendering some of their heat to a heat-transfer fluid
contained in an independent cold water circuit that said internal combustion
engine
comprises. It will be noted that said cold water circuit may be that of the
charge air
cooler that said engine comprises, such a circuit being known to those skilled
in
the art.
Figures 3 to 5 illustrate that the stratification chamber 24 consists of an
annular
cavity 45 formed in a cylindrical hole 46 in which a cylindrical sealing tip
44 that
the spark plug 25 comprises is engaged, said hole 46 opening into the
combustion
chamber 9 of the internal combustion engine 1.
As depicted in figures 2 and 3, the stratification injection conduit 39 may
consist of
at least one stratification injection canal 15 a first end of which
communicates with
the stratification chamber 24 and a second end of which opens between the
inside
of the cylindrical sealing tip 44 and a central insulating cone 43 that the
spark plug
25 comprises.
However, figure 4 shows that the stratification injection conduit 39 consists
of at
least one stratification injection capillary 16 formed inside a central
electrode 47
that the spark plug 25 comprises so that the first end of said capillary
communicates with the stratification chamber 24 and the second end of said
capillary opens at the end of said central electrode 47.
CA 02863474 2014-07-31
29
Figure 5 illustrates that the high-pressure spark-ignition and stratification
device 2
comprises a stratification injection conduit 39 which consists of at least one
peripheral stratification nozzle 48 a first end of which communicates with the
stratification chamber 24 and a second end of which opens at the periphery of
the
spark plug 25, said second end being directed approximately toward the
electrodes 26 that said spark plug comprises.
It should be noted that at least the stratification valve, the seat 21, the
spring 22,
all or part of the stratification conduit 23, the stratification prechamber 79
and the
stratification actuator 27 may be incorporated in combination into at least
one
cartridge fixed or screwed into the cylinder head 8 of the internal combustion
engine 1.
Figure 8 shows that the stratification line 28 and/or the outlet of the
stratification
compressor 29 and/or the stratification prechamber 79 may comprise at least
one
valve or injector 76 of air-fuel mixture making it possible to keep the
pollutant
post-treatment catalytic converter 75 at temperature.
Said valve or injector 76 may transfer an air-fuel mixture from said line 28
or from
said outlet or from said prechamber 79 to the exhaust conduit 10 of the
internal
combustion engine 1, said mixture being introduced into said conduit 10 by
said
type of valve or injector 76 at any point of said conduit positioned between
the
exhaust valve 12 of said engine and said catalytic converter 75 of said engine
1.
Said mixture may thus and if necessary be introduced into said exhaust conduit
10
once said catalytic converter 75 for post-treating the pollutants has reached
an
operating temperature at which it can operate with at least adequate
efficiency, in
order to ensure that said mixture is burnt in said catalytic converter 75 in
such a
way that the latter is kept at a sufficient temperature to enable it to
maintain a high
pollutant to non-pollutant gas conversion efficiency.
In this case, the valve or injector 76 for introducing an air-fuel mixture for
keeping
the catalytic converter 75 at temperature may be connected to the exhaust
conduit
10 of the internal combustion engine 1 by a catalytic converter temperature
maintaining air-fuel mixture conduit 77, it also being possible for said
mixing
conduit 77 to comprise an insulating tube or flange 78 which prevents said
conduit
77 from reaching an excessively high temperature.
CA 02863474 2014-07-31
Operation of the invention
The ignition device according to the invention operates in at least the
following
5 modes:
= Combustion of a stoichiometric pilot charge only, the main charge not
containing, in practice, either oxygen or fuel, but solely external cooled
EGR and/or internal hot EGR.
= Combustion of a stoichiometric pilot charge which then ignites a
10
stoichiometric main charge which is highly diluted with external cooled
EGR and/or internal hot EGR.
= Combustion of a stoichiometric pilot charge which then ignites a
stoichiometric main charge which is undiluted or only slightly diluted with
external cooled EGR and/or internal hot EGR.
15 =
Combustion of a stoichiometric pilot charge only which is highly diluted,
undiluted or only slightly diluted with external cooled EGR and/or internal
hot EGR.
In a particular embodiment and use, the ignition device according to the
invention
20 operates
as follows, for example when used in a four-cylinder reciprocating
internal combustion heat engine as shown in Figures 6 to 8:
Phase of pressurization of the stratification line 28: the engine 1 is started
in the
same way as a prior art engine with multipoint injection, the ignition device
2
25 according
to the invention not being used at this stage, except as regards the
spark plug 25 included in the device.
Being directly driven by the crankshaft 7 of the engine according to this
example,
the stratification compressor 29 is put into operation at the same time as
said
30
crankshaft and draws in its own air tapped from the outlet of the air filter
housing
70 of said engine.
In this particular embodiment, an injector 33 sprays fuel into the intake of
said
stratification compressor 29 in such proportions that a stoichiometric fuel-
air
mixture is delivered at the outlet of said compressor, directly into the
stratification
line 28.
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31
In parallel with the action of the stratification compressor 29, the
homogenization
circulator 56 causes the stoichiometric fuel-air mixture to flow subsequently
through the stratification line 28, through the various stratification
prechambers 79
incorporated in each combustion cylinder 4 of the internal combustion engine 1
as
specified by the invention, and then through the homogenization return conduit
71
so as to return to said circulator and start out again on the same circuit as
long as
said line 28 is pressurized and the internal combustion engine remains in
operation.
The agitation created by the homogenization circulator 56 serves to reduce the
condensation of the gasoline contained in the stoichiometric fuel-air mixture
on the
internal walls of the stratification line 28 and of the stratification
chambers 24, said
mixture being under pressure and therefore unfavorable to the maintenance of
the
vapor state of the gasoline.
This agitation also serves to force the stoichiometric fuel-air mixture to
remain
homogeneous and at a temperature close to that of said walls, said temperature
being below the spontaneous ignition point of said mixture, and to clean said
walls,
notably by rediluting any gasoline residues adhering to said walls as a result
of
previous use of the ignition device according to the invention.
Under the action of the stratification compressor 29, the pressure of the
stratification line 28 rises to a level greater than the pressure established
in the
combustion chamber 9 of the internal combustion engine 1 when the piston 5 of
the latter reaches the end of its compression stroke, immediately before the
ignition of the charge contained in said chamber. When said line has been
pressurized, the ignition device according to the invention is ready to
stratify the
charge of said engine, which takes place as follows:
Phase of initial stratification:
A few degrees of rotation of the crankshaft 7 of the engine before the
initiation of
the spark ignition of the main stoichiometric charge contained in the
combustion
chamber 9 of said engine by means of the spark plug 25, an electric current is
sent
to the terminals of the coil 50 of the electric stratification actuator 27
(Figure 3).
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The magnetic core 51 of said actuator is then attracted by said coil and moves
toward the latter, pulling on the coil push or pull means 42 which connect it
to the
stratification valve 20, so as to lift said valve off its seat 21 and so that
a fraction of
the pressurized carburetted mixture contained in the stratification line 28
and,
more specifically, in the stratification prechamber 79, escapes toward the
combustion chamber 9 of the engine 1 via the stratification chamber 24 and the
stratification injection conduit 39 respectively.
While escaping via the stratification injection conduit 39, said mixture
enters at
high speed the space between the cylindrical sealing tip 44 of the spark plug
25
and the central insulating cone 43 of said spark plug. In so doing, said
mixture is
agitated with a turbulent motion while remaining confined in a small volume
centered around the electrodes 26 of the spark plug 25, said mixture thus
constituting the stoichiometric pilot charge (figure 3).
Once the desired quantity of mixture has been transferred from the
stratification
line 28 to the combustion chamber 9 to form the pilot charge, the coil 50 of
the
stratification actuator 27 ceases to be supplied with electric current by the
ECU of
the internal combustion engine 1, the magnetic core 51 of said actuator
returns to
its initial position, pushed back by the spring 22 of the stratification valve
20 which
at the same time is returned to its seat 21, i.e. the closed position.
The pilot charge is then ignited, a high-voltage current being applied to the
terminals of the spark plug 25 so as to form an electric arc between the
electrodes
26 of said spark plug. Since the pilot charge is stoichiometric and has a
strong
turbulent motion, it is ignited rapidly, and then forms a substantially
spherical hot
volume which expands rapidly under the effect of heat to form a substantially
truncated spherical flame front with a large surface area in contact with the
main
charge, which is also rapidly ignited, because the distance which the flame
still has
to cover in order to burn the whole of said main charge is short. When this
mode of
combustion by pilot charge and main charge has been established, the
previously
cooled exhaust gas recirculation means 40, called "external cooled EGR" means,
come into operation as follows:
Phase of dilution of the charge with external cooled EGR:
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In order to recirculate the exhaust gases, the previously cooled exhaust gas
recirculation means 40 according to the invention and according to the present
exemplary embodiment may include a proportional-lift EGR tapping valve 63
positioned on an exhaust manifold 18 which links the exhaust outlets of the
cylinders A and B of the internal combustion engine 1 to one another and which
is
incorporated in said engine, said tapping valve 63 interacting with a
proportional-
lift exhaust back-pressure valve 67 positioned at the outlet of said manifold
18.
When the EGR tapping valve 63 is fully open and said exhaust back-pressure
valve 67 is fully closed, all the exhaust gases from cylinders A and B are
reintroduced into the intake plenum 19 of the internal combustion engine 1 via
the
tapping valve 63 and the external EGR supply conduit 66, the latter including
an
external EGR air-to-water cooler of the hot air type 72, in other words a
cooler in
which the water is that used to cool said engine itself, into which said gases
flow to
undergo a first temperature reduction, after which they flow into an air-to-
water
cooler of the cold water type 73 contained in the intake plenum 19 to undergo
a
second temperature reduction, the latter cooler also serving to cool the
supercharging air of said engine when the engine is supercharged by its
turbocompressor 74 (Figure 6).
With this configuration and this setting, the air admitted at the intake of
the engine
1 contains approximately fifty percent EGR and is at a temperature only a few
degrees higher than that of the ambient air.
It can easily be deduced from this arrangement that the engine can be made to
operate at between zero and fifty percent of external cooled EGR by varying
the
respective lift of the EGR tapping valves 63 and the exhaust back-pressure
valves
67 incorporated in the exhaust manifold 18 of the exhaust outlets of cylinders
A
and B, the appropriate level of EGR being set at all times by the engine
operating
computer ECU according to a criterion of better energy efficiency and
stability
limits on the combustion of said engine.
It should be noted that, when the turbocompressor 74 of the engine 1 is used
to
supercharge the latter, the EGR tapping valve 63 and the exhaust back-pressure
valve 67 are set in such a way that enough energy remains in the exhaust gases
to allow the turbocompressor turbine to drive the centrifugal compressor
incorporated in said turbocompressor in the desired conditions.
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This requirement to reduce the EGR level in order to prioritize the energy
available
for said turbine has a smaller negative effect on the final efficiency of the
engine
when the engine has a variable compression ratio because in such instances
said
engine requires little or no external cooled EGR at full load in order to
overcome
pinging and/or to deliver high energy efficiency.
It should be noted that, when the engine 1 operates with high levels of
external
cooled EGR, combustion which is normally difficult or even impossible to
initiate in
the absence of the ignition device 2 according to the invention is made
possible by
said device in good conditions.
This is because the initiation of combustion of the stoichiometric main charge
which is highly diluted with external cooled EGR is provided by the flame
front with
a large surface area developed on the periphery of the pilot charge and
brought
into contact with said main charge.
In this context, said main charge burns rapidly as a result, firstly, of the
compression created by the combustion of the pilot charge, said compression
increasing the enthalpy of said main charge which is as yet unburnt; secondly,
of
the large contact surface exposed to the flame; and thirdly, of the small
distance
still to be covered by said flame in order to burn all of said charge.
Since it is highly diluted with external cooled EGR, the mean temperature of
the
charge during combustion is lowered considerably, simultaneously reducing the
sensitivity of the engine to pinging and the heat losses at the walls. It is
then
possible to initiate the combustion of the charge at the optimal moment
according
to a criterion of maximum efficiency, and to increase the compression ratio of
the
engine, which may be fixed or variable, in order to increase the thermodynamic
efficiency of the gas expansion.
It should be noted that, in the case of an engine with a variable compression
ratio,
the mean external cold EGR content of the charge may advantageously be
increased in parallel with the compression ratio, the increase of this being
simultaneously favorable to the stability of combustion with a high level of
external
cooled EGR and to the thermodynamic efficiency of the gas expansion.
CA 02863474 2014-07-31
It should be noted that, on completion of the phase of pressurizing the
stratification
line 28, the phases of stratification and subsequent dilution of the charge
with
external cooled EGR may be delayed in time so as to allow the fuel stored in
said
line at the time of the last use of the internal combustion engine 1 to return
to the
5 vapor state as a result of the rise in temperature of the internal walls
of said line
and the agitation provided by the homogenization circulator 56.
This delay also enables all the energy contained in the exhaust gases of the
engine to be reserved temporarily for the heating of the three-way catalytic
10 converter of said engine before the charge of said engine is diluted
with external
cooled EGR.
It should be noted that the ignition device 2 according to the invention may
enable
combustion to be initiated in a single engine cycle in two different modes,
the first
15 mode being controlled spark ignition and used for the pilot charge,
while the
second mode is ignition initiated by compression according to the principles
of CAI
and HCCI and is used for the main charge.
According to this method of using the ignition device 2 according to the
invention,
20 the external cooled EGR may be entirely or partially replaced by
internal hot EGR,
so that the conditions of temperature, pressure and composition required for
the
correct initiation of combustion by CAI or HCCI can be provided for the main
charge.
25 It should be noted that said initiation of combustion in said two
different modes in
the same engine cycle is easier to control if it is used in a variable
compression
ratio engine.
In a particular mode of use of the ignition device 2 according to the
invention, the
30 internal combustion engine may advantageously have a device for
controlling the
opening and/or closing and/or lifting of its intake valves 13 and/or its
exhaust
valves 12, in addition to or instead of a variable compression ratio.
This particular embodiment may be used, notably, to advance the closing of the
35 intake valve 13 during the intake stroke of the combustion piston 5 of
said engine
1, in order to reduce its residual pumping losses at low loads.
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The last-mentioned method may be used, for example, to provide a very high
volumetric ratio for said engine 1, in which the very high rate of expansion
of the
gases is favorable to high thermodynamic efficiency.
It is to be understood that the above description is provided purely by way of
example, and does not in any way limit the scope of the invention, from which
there would be no departure if the details of embodiment which have been
described were to be replaced by any other equivalents.
