-
The present invention relates to methods and devices for effecting
the injection of a combustible fuel in internal combustion engines of
one or more cylinders, be they two-stroke or four-stroke type.
-
Various systems for direct and/or indirect injection of combustible
fluids in internal combustion engines - above all engines with a
four-stroke cycle - have already been known for quite a few years.
Furthermore, various studies have been effected to apply the
systems of direct and/or indirect injection to engines of two-stroke
type, in an attempt of overcome the principal disadvantages of
this type of engine compared to the four-stroke engines.
-
In fact, as is well known, two-stroke engines have very high specific
consumption and emit notably higher levels of polluting substances
(above all carbon oxides and unburned hydrocarbons) compared
to four-stroke engines. On the other hand, two-stroke engines are
simpler in construction and cheaper to produce compared to four-stroke
engines, so much so as to make them suitable and
preferable for certain applications, for instance in the motorcycle
and outboard-motor field.
-
The principal cause of the problems to which two-stroke engines
are subject is the bad "scavenging" of the cylinder. In fact, what
arrives from the transfer ports is not pure air, but a charge of air and
fuel which, while on the one hand it helps to expel the burned
gases from the cylinder, on the other hand mixes with the same
gases and is expelled through the exhaust. Furthermore, it should be
remembered that during normal running of a two-stroke engine,
part of the fuel charge is expelled by passing directly from the
transfer port to the exhaust. Recently, because of more and more
restrictive anti-pollution regulations, the need was felt to develop
two-stroke engines able to limit as much as possible the harmful
emissions of internal combustion engines. For this reason, various
solutions have been experimented, some of which have also been
transferred to production engines, which involve the direct injection
of fuel into the combustion chamber. These solutions, while they
resolve the problems of consumption and emissions, at the same
time require the use of little-tried complicated mechanical
solutions. This has led to two-stroke engines almost as complicated
and expensive as four-stroke engines.
-
In the case of two-stroke engines, the requirement to provide direct
injection clashes with the need to supply lubrication to the moving
parts in contact with each other, above all at the head and the
foot of the connecting-rod. The lubrication is usually effected by
mixing a certain quantity of lubricating oil with the fuel as it is
introduced into the engine. If the combustible charge is injected
directly into the cylinder, there is no possibility of lubricating the
moving parts of the engine by means of oil mixed with the
combustible charge. Auxiliary apparatus must be used for the
lubrication, which considerably complicates the two-stroke engine
and makes it impractical and uneconomic to produce. If on the
other hand, the injection is indirect - through the inlet conduit, for
instance - it is particularly difficult to reduce the consumption and
lower the harmful emissions, which can be achieved only at the
cost of further complications in construction.
-
In some two-stroke engines of recent manufacture, the lubrication is
effected by means of a pump which introduces a pre-determined
quantity of lubricating oil into the crankcase with a fixed frequency,
for instance every 50 turns of the engine. However, the lubrication is
done without regard to the power actually being delivered by the
engine in relation to the rpm. This system of lubrication, while
particularly simple to build, is not very effective in practice and
cannot prevent wear on the mechanical parts in movement and
the consequent breakdown of the engine.
-
In known types of four-stroke engines, induction problems arise to a
lesser extent, due to the presence of controlled valves to keep the
various inlet and exhaust ports open or closed during the engine
operating cycle. However, it should be noted that even in four-stroke
engines, in order to promote the evacuation of the exhaust
gases, the inlet valves are maintained partially open for a short time
together with the exhaust valves, which in this case also causes a
loss of fuel, if somewhat limited, through the engine exhaust.
-
The aim of the present invention is to propose a method and a
device for effecting the injection of fluids in an internal combustion
engine that resolve the above mentioned drawbacks, and in
particular, that drastically reduce the specific consumption of fuel
and the harmful emissions of the same engine.
-
Within the scope of this aim, an object of the present invention is to
propose a method and a device for effecting the injection of fluid
in an internal combustion engine that gives optimum distribution, or
stratification, of the combustible charge in the engine combustion
chamber.
-
Another object of the present invention is to propose a device for
effecting the injection of fluid in an internal combustion engine that
permits maintenance of effective lubrication of the inside parts of
the engine without complicating the structure of the same engine
and without addition of additional parts.
-
Yet another object of the present invention is to propose a device
for effecting the injection of fluid in an internal combustion engine
that permits the injection of all the combustible charge
independently of the conditions of pressure inside the combustion
chambers of the same engine.
-
Yet another object of the present invention is to propose a method
and a device that permits the injection of a complete combustible
charge in each cylinder even with very brief injection times.
-
A further object of the present invention is to furnish the information
to produce an internal combustion engine that is able to work with
a two-stroke cycle or with a four-stroke cycle.
-
Finally, yet a further object of the present invention is to furnish the
information to produce an internal combustion engine, and in
particular an engine with a four-stroke operating cycle, that is
simple in construction and that gives good performance compared
to known four-stroke engines of the same cubic capacity.
-
These objects are achieved by the present invention, which relates
to a method for effecting the injection of combustible and/or
lubricating fluids in an internal combustion engine having one or
more cylinders, characterised by comprising two injection phases at
separate times of one or more fluids, or of their mixtures, for each
engine operating cycle.
-
The method according to the invention provides for at least one
"auxiliary" injection phase of either a lubricating fluid or of a
combustible charge whose initial composition is predetermined and
at least one phase of "principal" injection whose combustible
charge will have a second predetermined composition.
-
In practice, the auxiliary injection phases are timed to occur during
the engine operating cycle in order to produce the scavenging,
with a particularly "lean" charge, i.e. with a particularly low
proportion of fuel. This advantageously reduces to the minimum the
quantity of fuel emitted unburned through the exhaust of the
engine and therefore simultaneously lowers the specific
consumption threshold and the harmful emissions of the same
engine.
-
In particular, the charge introduced during the auxiliary injection
phase could comprise at least one minimum quantity of lubricating
oil, suitably dosed, that would allow the parts of the connecting-rod
and the lower part of the cylinder to be lubricated.
-
The principal injection phases occur during the same operating
cycle and complete the injection with a combustible charge
delivered inside each cylinder with a "richer" mixture. In this case,
the principal injection phases are effected directly into the cylinder.
Preferably, the principal injection phases are timed to occur in a
period of the engine operating cycle in order to cause the least loss
of fuel through the exhaust port of the cylinder where the principal
injection phases are effected.
-
Even more preferably, the principal injection phases occur in a
period of the engine operating cycle in which it is substantially
closed the exhaust port of the cylinder where the charge of these
phases is effected.
-
Beyond the already quoted advantages, it has been noticed that
the method according to the invention also surprisingly gives
optimum stratification of the combustible charge inside the
combustion chamber. Consequently, optimum combustion of all
the fuel occurs in each cycle, so contributing to limit the emission of
unburned hydrocarbons.
-
A distinction will be made between four-stroke engines of the
traditional type currently known and four-stroke engines of the
"non-traditional" type that could be produced applying the
principles of the present invention. By the expression "four-stroke
engines of the non-traditional type" are intended four-stroke
engines with lubrication similar to that of a two-stroke engine - i.e.
with lubrication "by closed crankcase" - i.e. engines without a
lubrication plant comprising a pump, a sump for the recovery of
the oil and a series of pipes that carry the lubricant under pressure
to the bearings of the engine crankshaft. The same expression is
here used also to indicate engines with four-stroke operating cycle
deprived of a pump-type system of lubrication, or however without
recovery of lubricant, i.e. with lost lubricant.
-
In the case of the application of the method according to the
invention to a two-stroke engine and to a four-stroke engine of
"not-traditional" type, the auxiliary injection phase is effected in
what will be referred to below as the "crankcase space", i.e. in a
space comprised between the inside wall of a piston and the inside
wall of the crankcase. The "crankcase space" contains in particular
all the parts of the connecting-rod and the main bearings, and
comprises furthermore at least one portion of one or more conduits
communicating in part with it, as well as with the cylinder in which
the piston tuns, via the respective transfer ports.
-
In this case, the combustible charge injected in the auxiliary
injection phases comprises preferably a predetermined quantity of
a lubricating product - for instance oil - mixed with the fuel before
injection. The mixing of oil and fuel can also be effected before the
admission of the fluid into the injector by means of an automatic
device able to regulate the dosing of oil as a function of the
operating rpm and the power delivered by the engine.
-
Alternatively, the principal injection phases could involve the
admission of fuel alone from one or more injectors, while the
auxiliary injection phases could involve the admission of lubricating
oil and/or fuel. These auxiliary injection phases are preferably
effected by one or more injectors, whose jet is directed into the
crankcase space, which introduce fuel and/or lubricating oil
deriving from separate tanks.
-
In the case of the application of the method according to the
invention to a four-stroke engine of traditional type, the auxiliary
injection phases are to be effected in the inlet conduits of each of
the cylinders.
-
Alternatively, or in combination, the auxiliary injection phases are
effected in what will be referred to below as "combustion chamber
space", i. e. the space included between the inside wall of the
combustion chamber associated with each cylinder, the inside wall
of the cylinder and the head of the piston that runs in the cylinder.
In the case of a four-stroke engine of "non-traditional" type, the
auxiliary injection could be done in the same way as has been
already described for two-stroke engines. In other words, also in
four-stroke engines of "non-traditional" type the lubricating oil is
injected into the crankcase space, so as to produce an opportune
closed circuit through the scavenging conduits that allows the fluid
to flow between the engine crankcase and the upper part of the
cylinder, i.e. between the crankcase space and the combustion
chamber space.
-
Furthermore, the invention concerns a device for effecting the
injection of combustible and/or lubricating fluids in an internal
combustion engine having one or more cylinders, of the type
comprising at least one injector per cylinder, characterised by
comprising means for effecting at separate times at least two
phases of injection in each cylinder for each engine operating
cycle.
-
According to the invention, the auxiliary injection phases and the
principal injection phases in engines -- be they two- or four-stroke --are
effected for each engine operating cycle by means of a
device comprising a single injector for each cylinder.
-
Alternatively, two or more separate injectors can also be used for
each cylinder, for instance at least one injector for the auxiliary
injection phases and at least one injector for the principal injection
phases. In this case, the auxiliary injectors could also inject
lubricating oil only, or a particularly rich mixture of lubricating oil, in
the critical points of the engine. Therefore, the oil arrives at exactly
where it is needed effectively in atomised form and it can be
opportunely dosed at each turn of the engine, under the control of
an electronic apparatus, as a function of the parameters that
influence the system of lubrication at each moment of operation,
parameters that could comprise, for instance, the rpm, the power
delivered by the engine, the temperature, and the like.
-
In particular, in the case in which a sole injector is employed in a
two-stroke engine, the injector is preferably located inside the
cylinder in such position as to effect at least one principal injection
phase into the combustion chamber space, and at least one
auxiliary injection phase into the crankcase space. The position of
the sole injector will be chosen in such a way that the injection jet is
directed to lubricate the critical points of the parts in movement.
-
To allow the auxiliary injection phases to be effected by means of a
sole injector, above all in a two-stroke engine or in a four-stroke
engine of "non-traditional" type, each piston has a skirt comprising
an access window to the inside wall of the piston oriented toward
the injector, in such a way as to bring the window into
correspondence with it during the auxiliary injection phases.
Alternatively, the piston could have a skirt comprising at least one
portion of reduced height oriented toward the injector, or a suitable
channel shaped opportunely, or again a piston could have a skirt
of particular reduced height.
-
In the case in which two or more injectors are used in a two-stroke
engine, at least one first injector is located inside the cylinder so
that it can effect at least one principal injection phase into the
combustion chamber space, and at least one second injector is
located in the engine in such a position as to effect at least one
auxiliary injection phase into the crankcase space. In particular, the
second injector is located in such a position as to effect the auxiliary
injection phases in one or more inlet ports communicating with the
cylinder in which the injection is effected.
-
To improve the lubrication, more injectors can however be
provided, some of which have the jet oriented in such a way as to
make the fluid (lubricating oil or mixture of oil and fuel) arrive in the
particular critical points.
-
In the case in which a sole injector is used for each cylinder in a
four-stroke engine of traditional type, the injector is located inside
the cylinder in such a position as to effect at least one principal
injection phase and at least one auxiliary injection phase in the
combustion chamber space associated with a cylinder.
-
In the case in which two or more injectors are used for each
cylinder in a four-stroke engine, at least one first injector is located
inside the cylinder in such a position as to effect at least one
principal injection phase into the combustion chamber space, and
at least one second injector is located in the engine in such a
position as to effect at least one auxiliary injection phase into one or
more inlet ports communicating with the cylinder in which the
piston runs.
-
The auxiliary injection phase can be effected in the inlet port also in
the "scavenge" phase, i. e. with the exhaust valve still partially
open. This possibly involves a slight loss of fuel into the exhaust pipe
but causes high turbulence and therefore better diffusion of the fuel
in the charge inside the cylinder. The principal injection can
therefore be effected directly into the cylinder when the exhaust
valve is completely closed and the compression phase is about to
begin.
-
In all the cases shown, it is evident that each injector performs the
varied phases of injection in well predetermined times and in phase
with the various positions of the piston during the whole engine
operating cycle, be it two- or four-stroke. The injectors, therefore,
have to be controlled by means of suitable apparatus (electronic,
mechanical or pneumatic) capable of controlling the different
phases of injection as a function of the position of the crankshaft or
of the piston.
-
Further characteristics and advantages of the present invention will
be more evident from the description that follows, which is by way
of illustration and not limiting, with particular reference to the
enclosed schematic sketches in which:
- Figures 1A-1D show some phases of the operating cycle of an
internal combustion engine of two-stroke type, endowed with a
sole injector, to which is applied the method according to the
invention;
- Figures 2A-2D show some phases of the operating cycle of an
internal combustion engine of two-stroke type, comprising two
injectors, to which is applied the method according to the
invention;
- Figures 3 and 4 show an internal combustion engine of two-stroke
type according to other forms of embodiment of the invention that
provide for the employment of at least two separate injectors;
- Figures from 5 to 8 show an internal combustion engine of two-stroke
type according to other forms of embodiment of the
invention that provide for the employment of more than two
separate injectors;
- Figures 9A-9D show some phases of the operating cycle of an
internal combustion engine of the traditional four-stroke type,
endowed with a sole injector, to which is applied the method
according to the invention;
- Figures 10A-10D show some phases of the operating cycle of an
internal combustion engine of the traditional four-stroke type,
comprising two injectors, to which is applied the method according
to the invention;
- Figures 11 and 12 show more in detail the arrangement of the
injectors in the internal combustion engine with traditional type four-stroke
operating cycle shown in Figures 10A-10D;
- Figures 13 and 14 show an internal combustion engine with four-stroke
operating cycle of the traditional type according to another
form of embodiment of the invention that provides for the
employment of at least two separate injectors;
- Figures 15 and 16 show an internal combustion engine with four-stroke
operating cycle of the traditional type according to a further
form of embodiment of the invention that provides for the
employment of at least two separate injectors;
- Figures 17A-17D show some phases of the operating cycle of an
internal combustion engine of the "non-traditional" four-stroke type,
endowed with a sole injector, according to a possible form of
embodiment of the invention;
- Figures 18A-18D show some phases of the operating cycle of an
internal combustion engine of the "non-traditional" four-stroke type,
endowed with a sole injector, according to another possible form of
embodiment of the invention; and
- Figures 19A-19C show some phases of the operating cycle of an
internal combustion engine of the "non-traditional" type, similar in
construction to that shown in Figures 18A-18D, but with a two-stroke
operating cycle.
-
The internal combustion engine shown in Figures 1A-1D is an engine
of two-stroke type, shown for simplicity with a single cylinder, some
phases of whose operating cycle are shown. The engine comprises
an injector 1 that is located in such a position as to be able to
effect at least two separate phases of injection into the cylinder for
each engine operating cycle. Even though it is not expressly shown,
an electronic device is provided to control the injector 1, above all
with regard to the injection times and the quantity of fuel injected
during each phase, as a function of the operating conditions of the
engine.
-
The piston 2 that runs in the cylinder is endowed with a window 3
oriented toward the injector 1 in such a way that the window 3 is in
correspondence with the injector 1 during the movement of the
piston 2 inside the cylinder, allowing the passage of the fluid
injected toward the inside wall of the piston 2.
-
In particular, as shown in Figure 1C, the injector 1 allows at least one
principal injection phase to be effected into the combustion
chamber space, i.e. into that space comprised between the inside
wall 4 of the combustion chamber, the inside wall 5 of the cylinder
and the head 6 of the piston 2.
-
In Figures 1A and 1D the engine is instead shown during some
auxiliary injection phases. In particular, the injector 1 and the
window 3 on the piston 2 allow at least one auxiliary injection phase
to be effected into the crankcase space, i. e. into that space
comprised between the inside wall of the piston 2 and the inside
wall of the crankcase 7. In the space so defined is also included at
least one portion of the intake manifold 8 and, naturally, the space
delimited by the transfer ports 9 which set the inside crankcase
space in fluid communication with the combustion chamber
space.
-
Alternatively, instead of the window 3, the piston 2 could be
endowed with a skirt having a portion of reduced height oriented
toward the injector 1, or the piston could have a skirt of extremely
reduced height, or yet again it could be endowed with a suitable
channel cut into the structure of the piston, in such a way as to
allow the injection of fluid into the crankcase space underlying the
piston 2.
-
In Figure 1A, the piston 2 is shown while it is undergoing the phase of
expansion of the gases immediately following the combustion of
the charge in the cylinder. As it moves downwards, the window 3 of
the piston 2 comes into correspondence with the injector 1, which
can therefore effect a first auxiliary injection phase of the fuel under
pressure via the feedline 12. A very limited quantity of fluid is
preferably injected in this phase, in such a way that the injected
fluid mixes in the crankcase with the air drawn in through the intake
manifold 8 during the induction phase.
-
The charge thus formed in the crankcase is particularly "lean", i.e.
considerably low in fuel -- and therefore not suitable for
combustion, but the charge so formed does allow "scavenging" to
be effected inside the cylinder, thus reducing the maximum fuel
consumption and the emission of pollutants through the exhaust
pipe 10. Furthermore, as is well known, this allows the inside walls 5
of the cylinder, the inside wall 4 of the combustion chamber and
the head 6 of the piston to be cooled.
-
During the auxiliary injection phases, a certain quantity of
lubricating oil mixed with fuel is also preferably injected in such a
way as to permit the lubrication of the parts in movement inside the
engine, such as the connecting-rod bearings, for instance.
-
In Figure 1B, the piston 2 is completing the down-stroke during which
residual gases of combustion are expelled through the exhaust pipe
10. In this phase, the "lean" charge produced by means of the
preceding auxiliary injection is forced up through the transfer ports 9
(Fig. 1A) and occupies the combustion chamber space, thus
effecting the "scavenging".
-
As shown in Figure 1C, the piston 2 is rising again toward T.D.C. (top
dead center) and beginning to compress the combustible charge
present in the cylinder. As soon as the piston has closed the exhaust
port communicating with the exhaust pipe 10, the principal
injection phase begins, consisting substantially of a direct injection
phase, during which a particularly large quantity of combustible
fuel is precisely injected in, thus completing the charge necessary
to give combustion.
-
Independently of the simplification adopted to show the principal
injection phase in Figure 1C, it should be stressed that the principal
injection phase is preferably effected during the period of the
engine operating cycle in which the loss of fuel through the exhaust
port 13 of the exhaust pipe 10 is least. In this case, the principal
injection phase is preferably effected in a period of the engine
operating cycle in which the internal cylinder pressure is lower than
10 bar, in such a way as to allow the employment of simple
injectors of the type generally destined for indirect injection systems.
In Figure 1D, the piston 2 arrives in proximity to T.D.C. bringing the
window 3 into correspondence with the injector 1 again and
allowing at least one second auxiliary injection phase to be
effected. This second auxiliary injection phase, which could be
effected in addition or as an alternative to the first auxiliary injection
phase shown in Figure 1A, also involves the injection of a limited
quantity of fuel - possibly mixed with lubricating oil. The latter could
be mixed with the fuel upstream of injector 1, or could also be
mixed with the fuel in correspondence to injector 1, possibly using a
twin-type injector to which both fuel and oil are delivered under
pressure by separate feedlines.
-
In this case, the electronic injection control device will regulate the
time and the volume of lubricating oil and fuel necessary. In this
way, an auxiliary injection phase of fuel alone, or an auxiliary
injection phase of lubricating oil alone can be effected, further
reducing the polluting emissions.
-
Furthermore, remembering the high rpm that internal combustion
engines can reach - above all in the case of engines with a two-stroke
cycle - it is opportune to underline that the time intervals for
effecting each phase of injection are extremely reduced.
According to the invention, effecting multiple injection phases of
the fuel in each engine operating cycle, the combustible charge in
each cylinder can be completed in an optimum way.
-
Below, for simplicity, those elements already shown in Figures 1A-1D
that are also present in the forms of embodiment shown in other
figures will be identified by the same numerical references.
-
Figures 2A-2D show a two-stroke engine substantially similar to that
already described, to which a second injector 21 supplied via
feedline 22 has been added in such a position as to inject fluid into
the intake manifold 8.
-
The operation of the engine, at least as far as the injection phases
effected by injector 1 are concerned, is substantially similar to that
already described. However, in this case, more auxiliary injection
phases than those already described with reference to Figures 1A-1D
can be fitted into each engine operating cycle.
-
The embodiment shown in Figures 2A-2D gives different
advantages, above all with regard to the execution of the auxiliary
injection phases. For instance, it is possible to further reduce the
opening times of each injector, thus conferring better control of the
dosing of the fuel injected during each single auxiliary injection
phase On the other hand, the possibility of also effecting multiple
auxiliary injection phases in a predetermined time with injector 21
(for instance as in Figures 2A and 2D), allows the optimum charge to
be loaded into the cylinder even in conditions of very high rpm.
-
It should be stressed that each injector control device, and in
particular each electronic control device, also generally allows two
or more injectors to be controlled independently. Therefore, using
more than one injector (for instance, from two to four injectors for
each cylinder) doesn't involve an excessive increase in the overall
cost of injection plant, since the management system is single.
-
Furthermore, when using two or more injectors, there could be
advantages in separating the functions of the same injectors. For
instance, with reference to the form of embodiment shown in
Figures 2A-2D, the injector 1 could be used for effecting principal
injection phases only (Figure 2C), while the injector 21 could be
employed for auxiliary injection phases only (Figures 2A and 2D). In
this case, the auxiliary injection phases of the injector 1 in Figures 2A
and 2D would not need to be effected, so making the presence of
the window 3 provided on the skirt of the piston 2 superfluous.
-
A further possibility for the engine shown in Figures 2A-2D is to
separate feeding of fuel only, effected in particular by injector 1,
from the feeding of lubricating oil only, effected by the injector 21
only.
-
Figures 3 and 4 show different forms of embodiment according to
the invention relating to a two-stroke engine endowed with two
injectors destined respectively to effect auxiliary and principal
injection phases.
-
In particular, the engine shown in Figure 3 is endowed with an
injector 1 located in such a position as to direct the injection jet
through the window 3 of the piston 2, as described for the
corresponding injector 1 already described in Figures 1A-1D and in
Figures 2A-2D. The injector 1 can therefore effect auxiliary injection
phases, possibly injecting a mixture of lubricating oil and fuel, or
principal injection phases. A second injector 31 is instead located in
this case in such a way as to effect at least one principal injection
phase (not shown) whose jet is directed into the combustion
chamber space. Also in this case, the principal injection phase is
effected preferably after the piston 2 has closed exhaust port 13
and before the internal pressure in the combustion chamber rises
above 10 bar.
-
In the form of embodiment shown in Figure 4, a first injector 21 is
located on the intake manifold 8, while a second injector 31 is
located on the cylinder head of the engine - as in the form of
embodiment previously described in Figure 3. In this case, the
injector 21 allows auxiliary injection phases only to be effected
while the injector 31 allows principal injection phases only to be
effected. Compared to forms of embodiment previously described,
the method by which the injection phases are effected remains
substantially unchanged. In the forms of embodiment shown in
Figures 3 and 4, the injector 31 located on the cylinder head of the
engine can also be of the high-pressure type, i. e. an injector even
able to inject at pressures higher than 10 bar. This solution presents
the advantage however of not requiring a window on the skirt of
the piston since the jet of the auxiliary injection phases is directed
into the intake manifold 8 and not under of the skirt of the piston 2.
-
Figures from 5 to 8 shows some forms of embodiment of the
invention in which the employment of three separate located
injectors each in such a position as to guarantee the supply of fuel
and lubrication to the particularly stressed parts.
-
The engine shown in Figure 5 comprises the two injectors 1 and 21 in
particular already shown in Figures 2A-2D and a third injector 41
whose jet is directed directly into the crankcase of the engine. The
jet of the injector 41 is oriented in particular toward the big-end of
the connecting-rod in the moment in which it transits in
correspondence with the injector. This allows effective "aimed"
lubrication of the parts that transit in front of the injector 41 at each
turn of the engine and therefore doses with particular accuracy the
quantity of lubrication oil as a function of the rpm of the engine and
of the power delivered at each instant by the same engine. In this
form of embodiment the injector 1 will effect principal injection
phases as well as auxiliary injection phases, while the injectors 21
and 41 will effect the auxiliary injection phases only. The latter will
involve for instance the injection of a mixture of fuel and lubricating
oil by some of the three injectors, while the principal injection
phases effected by injector 1 preferably involve the injection of fuel
only. In this case, it is however possibly advantageous to divide the
functions of fuel supply and lubrication among the different
injectors, for instance destining injector 41 to the controlled delivery
of lubricating oil only in correspondence with the parts in
movement in the crankcase.
-
The form of embodiment shown in Figure 6 provides for the
employment of the same injectors 1 and 41 already shown in Figure
5 and the employment of an injector 31 with the jet aimed directly
into the engine combustion chamber. In this case the injector 31
effects principal injection phases only, possibly with the support of
the injector 1, to allow completion of the optimum combustible
charge. The injector 1 can therefore effect both auxiliary and
principal injection phases, while the injector 41 could effect auxiliary
injection phases only as already described for the form of
embodiment of Figure 5.
-
Figure 7 shows an engine according to a form of embodiment
substantially similar to that of Figure 4. With regard to the latter form
of embodiment, a third injector 51 is provided, located in the front
part of the engine, whose jet is directed inside the crankcase, as
already described in relation to the injector 41 shown in Figures 5
and 6.
-
The same is true for the form of embodiment shown in Figure 8
where the injector 51 with jet oriented inside the crankcase and the
injectors 1 and 31 already shown in the preceding Figures are all
present.
-
Naturally, the number and the location of the injectors depends on
the demands of supplying the engine with fuel and on the
demands of lubricating the parts in movement in the same engine
while, however, bearing in mind the advantages of the locations
already shown, the limits of encumbrance of each solution, as well
as the possible complexity in construction deriving from these
choices.
-
The internal combustion engine shown in Figures 9A-9D is a four-stroke
engine of the traditional type, shown for simplicity as a single
cylinder; some phases of its operating cycle are shown.
-
The four-stroke engine, as is well known, is endowed with at least
one inlet valve 35 and with at least one exhaust valve 45, both
operated to allow the combustion chamber space to be put in
fluid communication with an inlet port 36 and an exhaust port 46.
-
Similarly to the two-stroke engine shown in Figure 1A-1D, the four-stroke
engine shown in Figures 9A-9D comprises an injector 1 which
is located in such a position as to effect, under the control of an
electronic device, at least two separate injection phases into the
cylinder for each engine operating cycle.
-
Figure 9A shows the piston 2 in the induction phase immediately
following the exhaust and expulsion of the burned gases phases. In
this phase, the inlet valve 35 is completely open and the exhaust
valve 45 still remains partially open for a limited period to allow
"scavenging" of the inside volume of the cylinder.
-
During the down-stroke of the piston 2, the injector 1 effects a first
auxiliary injection phase of the fuel under pressure from the feedline
12. As in the case of the two-stroke engine, a very limited quantity
of fuel is preferably injected in this phase, in such a way as to ensure
that the same fuel is mixed uniformly inside the cylinder with the air
drawn in through the inlet port 36.
-
The air-fuel charge so formed is particularly "lean" i.e. notably low
in fuel, and therefore not suitable for combustion, but allows
"scavenging" to be effected inside the cylinder thus reducing both
the polluting emissions through the exhaust port 46 and the overall
fuel consumption, as well as effectively cooling, as is well known,
the inside walls of the cylinder, the combustion chamber and the
head of the piston 2. In the case of a four-stroke engine the
injection of lubricating mixed oil with the fuel isn't generally
necessary. The lubrication is in fact effected generally by means of
a separate plant that drives lubricating oil under pressure to where
the surfaces are reciprocally in movement.
-
In the phase shown in Figure 9B, the piston 2 is rising again from
B.D.C. (bottom dead center) to effect the phase of compression of
the charge in the cylinder. At this point, both the valves 35 and 45
are closed and the "lean" charge occupies practically all the
combustion chamber space. The injector 1 is then commanded to
begin the principal injection phase, consisting substantially of a
direct injection phase, during which a particularly large quantity of
fuel is precisely injected to complete the charge necessary to give
combustion.
-
The principal injection phase is therefore effected with the exhaust
valve 45 substantially closed and, preferably, in a period of the
engine operating cycle in which the cylinder internal pressure Is
lower than 10 bar, in such a way as to permit the employment of
simple injectors of the type generally destined to the systems of
indirect injection and widely used on four-stroke engines in the auto
field.
-
Both the auxiliary and the principal injection phases can be
effected in this case in the combustion chamber space.
-
In the remaining Figures 9C and 9D, the piston 2 completes the four-stroke
engine operating cycle. Figure 9C shows the combustion of
the charge phase, while Figure 9D, after the expansion phase (not
shown), shows the exhaust phase. At this point, the piston 2 is rising
again toward the top to effect the expulsion of the exhaust gases
phase and then begin the induction phase shown in Figure 9A
again.
-
Figures 10A-10D shows a four-stroke engine substantially similar to
that just described, endowed with a second injector 21, connected
to a feedline 22, in such a position as to inject the fuel into the inlet
port 36.
-
Also in this case, the operation of the engine is substantially similar
to that already described in Figures 9A-9D. But, the presence of a
second injector 21 allows more auxiliary injection phases to be
effected for each engine operating cycle.
-
The embodiment shown in Figures 10A-10D allows the functions of
the two injectors to be separated, destining for instance the injector
1 for effecting the principal injection phases only (Figure 10B) while
the injector 21 could be employed to effect the auxiliary injection
phases only (Figure 10A). Therefore, the auxiliary injection phase of
the injector 1, shown in Figure 10A, would not have to be effected,
since at least one auxiliary injection phase is already effected by
the injector 21.
-
However, both the injectors 1 and 21 can be used to effect other
auxiliary injection phases at different times. The principal injection
phases (Figure 10B) are, however, effected by the injector 1 only.
In this case, since both the injectors 1 and 21 inject fuel only (and
not lubricating oil as well) the feedlines 12 and 22 could be joined
and connected to a sole source of fuel under pressure.
-
Figures 11 and 12 show an internal combustion four-stroke engine of
traditional type in detail, with the injectors 1 and 21 located in the
same positions shown in Figures 10A-10D. In particular, Figure 11
shows the same situation of the operating cycle shown in Figure
10A, i.e. with the inlet valve 35 open and the exhaust valve 45 also
partially open but in the process of closing. In this interval an
auxiliary injection phase is commanded by means of the injector 21
located on the inlet port 36 with a particularly lean charge. That
allows the scavenging of the combustion chamber to be effected
and the exhaust gases to be completely expelled through the
exhaust pipe 46. Figure 12, corresponding to the phase of the cycle
shown in Figure 10B, shows the principal injection phase that is
effected by the injector 1 while maintaining both dams the valves
35 and 45 closed.
-
Figures 13 and 14 show another possible form of embodiment of a
four-stroke engine of traditional type according to the invention, in
which a first injector 61 is located on the cylinder head of the
engine and a second injector 71 is located on the cylinder. Figure
13 shows a particular instant of the induction phase immediately
following the scavenging of the combustion chamber. In this instant
the exhaust valve 45 is already closed while the inlet valve 35 has
opened, allowing the influx of air into the cylinder. Injector 71 then
effects a first auxiliary injection phase of fuel in such a way as to
form a fuel charge that is particularly lean and highly turbulent. The
charge is thereafter completed during the compression phase
(Figure 14) by the injector 61 while the valves 35 and 45 are
completely closed. The layout of the injectors 61 and 71 gives
optimum stratification of the charge, i.e. a charge whose fuel
concentration is highest near the spark-plug and decreases
gradually the further away it is.
-
Figures 15 and 16 show a further form of embodiment of a four-stroke
engine of traditional type endowed with two injectors 21 and
61. The injector 21 is located on the inlet port and allows at least
one auxiliary injection phase to be effected, while the injector 61 is
located on the cylinder head of the engine to allow either auxiliary
and/or principal injection phases to be effected. The phases of the
operating cycle shown in Figures 15 and 16 correspond substantially
to the phases already described with reference to Figures 11 and
12.
-
In this case, as in the forms of embodiment shown in Figures from 13
to 16, the injector 61 located on the cylinder head of the engine
can also be of the high pressure type, i.e. an injector also able to
inject at pressures above 10 bar.
-
According to the present invention, it is possible to produce internal
combustion engines with new particularly advantageous solutions
by exploiting the possibilities of effecting multiple injection phases
for each cycle of the engine.
-
In Figures 17A-17D is shown schematically an internal combustion
engine of the type that is defined in the present description as
"non-traditional", i.e. a four-stroke engine with lost-oil lubrication.
-
In particular, the four-stroke engine of the "non-traditional" type
according to the present invention comprises two or more cylinder
head valves and/or side-valves, in which the operating cycle
makes use of the aforementioned induction and exhaust valves
while the "crankcase" part of the engine which comprises the
space between the crown of the piston, the walls of the cylinder
and the crankcase of the engine doesn't any longer have the
traditional four-stroke engine system of lubrication (in which the
lubricating oil is brought to wet the bearings or washes directly over
the same bearings) but a mixture system of lubrication.
-
According to the present invention, it is in fact also possible to use a
system of lubrication by means of a fuel-oil mixture in four-stroke
engines similar to that already described with reference to two-stroke
engines.
-
As previously stated, the engine shown in Figures 17A- 17D is a four-stroke
engine endowed with an inlet valve 35 and an exhaust valve
45 located in the cylinder head (but they could also be located
sideways) that regulate the opening and the closing of inlet 36 and
exhaust 46 ports respectively, as well as an intake manifold 8 similar
to that already shown in the forms of embodiment for the engines
with two-stroke cycle.
-
The intake manifold 8 communicates with the crankcase 7 and with
the transfer channels that set the crankcase 7 in fluid
communication with the upper part of the cylinder through the
transfer ports 9. The influx of air through the intake port 11 can be
regulated by an automatic-type valve (for instance a rotating
valve or a reed valve) or a controlled valve type that also allows
the induction of air into the low part of the crankcase 7 during the
phases of upward movement of the piston (Figures 17B and 17D),
i.e. during the compression and exhaust phases.
-
The single injector 1 shown in Figures 17A-17D is located in a position
substantially similar to that shown in Figures 1A-1D relative to the
two-stroke engine, i.e. in such a position as to guarantee the best
mixing and lubrication effect, and preferably introduces a mixture
of fuel and lubricating oil. However, it should be clearly understood
that two or more injectors could also be located according to the
forms of embodiment of the engines already described.
-
In the situation shown in Figure 17A, piston 2 begins the downward
stroke of the induction phase, during which the inlet valve 35 is
completely open while the exhaust valve 45 remains partially open
for a limited time to allow "scavenging" of the combustion
chamber. The injector 1 could effect at least one auxiliary injection
phase in this period.
-
Continuing the down-stroke, the piston 2 arrives near to B.D.C. and
the transfer ports 9 open, allowing the combustible charge preformed
in the crankcase 7 to climb toward the top of the cylinder
(Figure 17B). Furthermore, at least one principal injection phase is
effected by the injector 1, thus giving effective mixing of air and
fuel in the cylinder. At the moment in which the piston 2 begins to
rise again, the compression phase begins and the induction 35 and
of exhaust 45 valves are closed.
-
After the ignition of the charge, the expansion phase begins (Figure
17C) and the piston 2 descends again toward the B.D.C. In this
period no fuel injection is effected, so that, when the piston 2 opens
the transfer ports 9 again (Figure 17D) near the B.D.C., only air is
forced into the upper part of the cylinder. The piston 2 then begins
the up-stroke again to effect the exhaust phase during which the
exhaust valve 45 is again open. In this way, only air is substantially
expelled through the exhaust port 46, allowing the consumption of
fuel and the emissions of unburned gas to be limited.
-
A four-stroke engine according to the invention presents different
advantages compared to traditional four-stroke engines. Above all,
the lubrication plant (pump, oil-sump, filter and galleries) is
eliminated with consequent simplification of construction.
Furthermore, pistons without oil-control rings can be used with
consequent drastic reduction of the wear on the cylinder. The oil-control
rings exert considerable radial pressure in fact, greater than
that exerted by the compression rings on the inside walls of the
cylinder.
-
Beyond the obvious reduction in weight and the greater
compactness compared to an equivalent four-stroke engine of
traditional type, a further advantage of the engine produced
according to the invention is the improved performance of the
engine due to the increased supply of air from the crankcase to fill
the cylinder in the compression phase and the "scavenging" of the
high part of the cylinder during the exhaust phase.
-
Figures 18A-18D show another form of embodiment of an internal
combustion engine according to the present invention, in which the
valves located in the cylinder head (or sideways) regulate only the
exhaust phase. Therefore the controlled intake valves of the
traditional four-stroke engines are absent.
-
In this case, all the filling with fresh charge is achieved with the fluid
deriving only from the crankcase 7 through the transfer channels
and the corresponding ports 9.
-
As the piston 2 rises again toward the point therefore T.D.C. (Figures
18B and 18D) it aspirates all the air through the crankcase 7 and the
intake manifold 8 endowed with an automatic or controlled type
valve 11. Also in this case, all the auxiliary injection phases are
effected by the injector 1 (Figure 18A) during the down-stroke of the
piston 2 prior to combustion. Equally, the principal injection phases
(Figure 18B) are effected directly into the cylinder just before the
compression phase or during the same compression phase.
-
During the down-stroke of the piston 2 in the of expansion phase
(Figure 18C some injection phases are performed so that, as the
piston 2 rises to the beginning of the exhaust phase (Figure 18D) only
air is transferred into the upper part of the cylinder. In this case,
there being no controlled intake valves as in the traditional four-stroke
engines, excessive low pressure could be created in the high
part of the cylinder during the induction phase (Figure 18A), since
the exhaust valve 45 is closed. To avoid this drawback, one or both
of the exhaust valves 45 could be commanded to open slightly for
a limited time, in order to reduce the low pressure caused by the
piston 2 in its down-stroke. This condition of the valves 45 is shown by
the broken line in Figure 18A.
-
Also this form of embodiment of the engine according to the
invention presents the same advantages of the four-stroke engine
described with reference to Figures 17A- 17D.
-
A further advantage of this form of embodiment derives by
eliminating the inlet valves in the cylinder head and the
construction of the engine is thus simplified. Furthermore, the
performances could be further improved because there is more
space for the exhaust valves. The latter could therefore have
limited dimensions and limited lifts, with consequent possibility of
raising the maximum rpm of the engine.
-
With the same form of construction, the same engine shown with
four-stroke cycle in Figures 18A-18D could be made to work with a
two-stroke operating cycle. In this case, the sequence of the
phases will end in one revolution of the engine crankshaft and the
phases of injection will be effected in a manner similar to that
explained already for two-stroke engines. Figures 19A-19C show this
particular type of engine, shown for simplicity with a single injector
1, when it is made to work with a two-stroke operating cycle.
-
As shown in Figure 19A, an auxiliary injection phase is performed
when the piston is near top dead center during the expansion
phase immediately following the ignition. When the piston reaches
B.D.C. approximately (Figure 19B) the exhaust valves 45 open and
the piston 2 opens the transfer ports 9 that allow the "lean" air-fuel
charge from the crankcase 7 to rises to the upper part of the
cylinder. In this phase there will be a small loss of fluid through the
exhaust ports 46 which are open.
-
When the piston 2 rises again toward the T.D.C. point, the exhaust
valves 45 are closed (Figure 19C) and there is a principal injection
phase of fuel through the injector 1 prior to a new ignition and a
new expansion phase (Figure 19A).
-
With this form of embodiment an engine can be produced which
will work as either a two-stroke cycle or with four-stroke cycle,
depending on how the correct opening sequence of the valve 45 is
commanded and the correct injection phase sequence is
regulated. This could be done for instance by a device (for instance
a mechanical device) able to change the transmission ratio
between the engine crankshaft and the camshafts and a suitable
adjustment of the central injection control electronics that regulate
the injection sequences and ignition. An engine of this type will be
made to work advantageously with a four-stroke cycle when there
is little application of power and with two-stroke cycle when there is
a demand for the delivery of high power.
-
In the forms of embodiment shown in Figures 17A- 17D, in Figures
18A-18D, and in Figures 19A-19C, the lubrication of the remaining
mechanical parts (for instance camshafts, tappets, valves stems,
etc. ) that are normally included in the lubrication circuit of the
traditional type of four-stroke engine, could be achieved simply by
applying the same principles as the present invention, i. e.
arranging opportunely further injectors in such positions as to direct
a jet of atomised lubricating oil towards the particularly critical
points.
-
Alternatively, or in combination, a small part of the fluid injected
into the crankcase and lubricating oil container could be
circulated by means of opportune conduits or connecting pipes
between the crankcase and the upper part of the head. The
interaction of the pressures or a suitable pump will permit the small
quantity of fluid to be re-circulated.
-
In each case, a small recovery pump can also be provided for the
oil that is deposited on the walls of the crankcase. This small
quantity of oil that has not entered the circle during the phase of
feeding of the mixture (and that has have not therefore been
burned with it in the combustion chamber), could be recovered
and sent to a collection tank to be recycled again.
