Method and device for injecting combustible and/or lubricating fluids in an internal combustion engine

Abstract

 A method and a device are described to effect the injection of a combustible and/or lubricating fluid into one or more cylinders in an internal combustion engine, of the type comprising at least one injector per cylinder, in which means are provided to effect at least two phases of injection in separate times in each cylinder for each engine operating cycle.

Description

[0001] 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.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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".

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Both the auxiliary and the principal injection phases can be effected in this case in the combustion chamber space.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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).

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

Claims

1. Method for effecting the injection of combustible and/or lubricating fluids in an internal combustion engine having one or more cylinders, characterised by comprising at least two injection phases in separate times of one or more of said fluids, or of their mixtures, for each engine operating cycle.

2. A method according to Claim 1, characterised by comprising an auxiliary injection phase of at least one lubricating fluid.

3. A method according to Claim 1, characterised by comprising at least one auxiliary injection phase of a combustible charge inside said engine, said combustible charge having a first predetermined composition.

4. A method according to Claim 1, characterised by comprising at least one principal injection phase of a combustible charge into each of said one or more cylinders, said combustible charge having a second predetermined composition.

5. A method according to Claim 3 or 4, characterised in that the first predetermined composition of the combustible charge injected in said at least one auxiliary injection phase has a mixture strength of fuel less than, or equal to, the second predetermined composition of the charge injected into said at least one principal injection phase.

6. A method according to any of the preceding Claims, characterised in that the first predetermined composition of the combustible charge injected into said at least one auxiliary injection phase comprises a predetermined quantity of a lubricating fluid.

7. A method according to any of the preceding Claims, characterised in that said at least one principal injection phase is effected in the space of the combustion chamber associated with each cylinder.

8. A method according to any of the preceding Claims, characterised in that said at least one principal injection phase is commanded in a period of the engine operating cycle for which it is reduced to a minimum the loss of fuel through the exhaust port inside a cylinder where said at least one principal injection phase is effected.

9. A method according to any of the preceding Claims, characterised in that said at least one principal injection phase is commanded in a period of the engine operating cycle in which it remains substantially closed the exhaust port inside a cylinder where said at least one principal injection phase is effected.

10. A method according to any of the preceding Claims, characterised in that said at least one principal injection phase is commanded in a period of the engine operating cycle in which it is lower than 10 bar the internal pressure into the cylinder where said at least one principal injection phase is effected.

11. A method according to any of the preceding Claims, characterised in that said at least one auxiliary injection phase is effected in the crankcase space.

12. A method according to any of the preceding Claims, characterised in that said at least one auxiliary injection phase is effected in the inlet port of each of said cylinders.

13. A method according to any of the preceding Claims, characterised in that said at least one auxiliary injection phase is effected in the combustion chamber space of each cylinder.

14. A method according to any of the preceding Claims, characterised in that said at least two phases of injection in separate times are effected by a single injector for each cylinder.

15. A method according to any of the Claims from 1 to 13, characterised in that said at least two phases of injection in separate times are effected by two or more separate injectors for each cylinder.

16. Device for effecting the injection of combustible and/or lubricating fluids into an internal combustion engine having one or more cylinders, of the type comprising at least one injector for each of said cylinders, characterised by comprising means for effecting at least two phases of injection in separate times in each cylinder for each engine operating cycle.

17. A device according to Claim 16, characterised in that said internal combustion engine is a two-stroke engine and that said at least one injector is located inside said cylinder in such a position as to effect at least one principal injection phase in the combustion chamber space of each cylinder, and at least one auxiliary injection phase in the crankcase space.

18. A device according to Claim 17, characterised in that said piston has a skirt comprising an access window to the inside wall of the piston oriented towards said at least one injector, said window being so placed as to be brought into correspondence with said injector during said at least one auxiliary injection phase.

19. A device according to Claim 17, characterised in that said piston has a skirt comprising at least one portion of reduced height oriented towards said at least one injector, said portion being so placed as to be brought into correspondence with said injector during said at least one auxiliary injection phase.

20. A device according to Claim 17, characterised in that said piston comprises an access pipe to the inside wall of the piston oriented towards said at least one injector, said pipe being so placed as to be brought into correspondence with said injector during said at least one auxiliary injection phase.

21. A device according to Claim 16, characterised in that said internal combustion engine is a two-stroke engine and that it comprises at least one first injector located inside said cylinder in such a position as to effect at least one principal injection phase in the combustion chamber space of each cylinder, and at least one second injector located in said engine in such a position as to effect at least one auxiliary injection phase in the crankcase space.

22. A device according to Claim 21, characterised in that said at least one second injector is located in such a position as to effect said at least one auxiliary injection phase in one or more intake manifolds.

23. A device according to Claim 21, characterised in that said at least one second injector is located in such a position as to effect said at least one auxiliary injection phase directly into the crankcase of said engine.

24. A device according to any of the Claims from 16 to 23, characterised in that it comprises a third injector in such a position as to effect said at least one principal injection phase in the combustion chamber space of each cylinder.

25. A device according to Claim 16, characterised in that said internal combustion engine is a four-stroke engine and that said at least one injector is located inside said 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 of each cylinder.

26. A device according to Claim 16, characterised in that said internal combustion engine is a four-stroke engine and that it comprises at least one first injector located inside said cylinder in such a position as to effect at least one principal injection phase in the combustion chamber space of each cylinder, and at least one second injector located in said engine in such a position as to effect at least one auxiliary injection phase in the space comprising at least one portion of one or more intake manifolds communicating with the cylinder where said piston runs.

27. Internal combustion engine, characterised by comprising an injection device according to any of the Claims from 16 to 26.

28. An internal combustion engine according to Claim 27, of the type comprising one or more controlled valves associated with each cylinder, characterised in that it comprises at least one first intake conduit that sets the crankcase of said engine in fluid communication with the atmosphere and one or more transfer conduits which set the crankcase space in fluid communication with the combustion chamber space.

29. An internal combustion engine according to Claim 28, characterised in that it comprises an automatic or controlled valve inside said intake conduit.

30. An internal combustion engine according to Claim 28 or 29, characterised in that said one or more controlled valves associated with each cylinder are valves to open and close one or more exhaust ports.

31. An internal combustion engine according to Claim 28 or 29, characterised by being an engine with a two-stroke operating cycle.

32. An internal combustion engine according to Claim 28 or 29, characterised by being an engine with a four-stroke operating cycle.

33. An internal combustion engine according to any of the Claims 28, 29 or 32, characterised in that said one or more controlled valves associated with each cylinder comprises at least one valve to open and close at least one exhaust pipe and at least one valve to open and close a second intake conduit that sets the combustion chamber space in fluid communication with the atmosphere.

Drawing