SCOPE

[0001 ] The present invention concerns an improved intake system for an internal combustion engine, an internal combustion engine comprising said intake system and a motor vehicle thereof.

STATE OF THE ART

[0002] As is well known, multi-cylinder internal combustion engines have problems in terms of filling efficiency of the cylinders, which significantly reduce the volumetric efficiency.

[0003] In effect, intake systems typically have a box (called an airbox) that collects the intake air and conveys it into the various intake ducts of the cylinders (trumpets). The fluid dynamics of the intake is extremely complex since the cylinders, in order to regulate the torque output, and thus the engine operation, as much as possible, do not work in phase. In other words, the combustion cycles (whether Diesel cycles or Otto cycle) of the various cylinders are out of phase.

[0004] Therefore, during the intake phase of one cylinder, the combustion phase of another cylinder may occur and so on.

[0005] The intake cycles of the various cylinders may thus mutually disturb each other, reducing the overall volumetric efficiency of the engine, right inside the filter box.

[0006] Moreover, the operating range, i.e. the speed range of internal combustion engines, may vary considerably, triggering at certain speeds resonance phenomena of the intake air masses that may improve or worsen the overall volumetric efficiency.

[0007] These phenomena are even more difficult to handle in the case of engines with a very wide speed range, such as for example in applications for motorcycles.

[0008] In order to improve the fluid dynamics of the intake, several solutions have been devised that substantially modify the length of the intake ducts according to the engine speed: in this way one may attempt to exploit the resonance phenomena to aid in filling the cylinders.

[0009] These solutions do not manage to optimize engine operation since they do not take into account the specific operating characteristics of each cylinder, mainly (but not exclusively) due to the engine architecture itself, i.e. the arrangement of the cylinders with respect to the airbox. PRESENTATION OF THE INVENTION

[0010] The need is therefore felt to resolve the drawbacks and limitations cited with reference to the known art.

[001 1 ] Such requirement is met by an internal combustion engine intake system according to claim 1 , by an internal combustion engine according to claim 20 and by a motor vehicle according to claim 21 .

DESCRIPTION OF THE DRAWINGS

[0012] Further features and advantages of the present invention will become more apparent from the following description of the preferred and non-limiting examples of embodiment thereof, wherein:

[0013] figure 1 shows an enlarged schematic view of an internal combustion system according to an embodiment of the present invention.

[0014] The elements or parts of elements in common between the embodiments described hereinafter will be indicated at the same numerical references.

DETAILED DESCRIPTION

[0015] With reference to the aforesaid figures, a collective schematic view of an intake system for an internal combustion engine 8 according to the present invention is collectively indicated at 4.

[0016] For the purposes of the present invention, it should be specified that the term “internal combustion engine” should be considered in a broad sense, comprising any engine type or architecture, comprising in said category Otto cycle and Diesel cycle endothermic engines, as well as rotary engines (Wankel).

[0017] Moreover, the engine type is in no way linked to the type of vehicle whereon the engine may be mounted.

[0018] As mentioned, the present invention results in particular benefits to motorcycles, which are characterized by significant constraints in terms of size, weight and aesthetics, but it may also be applied to automobiles, industrial vehicles and motor vehicles in general.

[0019] The term“motorcycle” means is a motorized cycle with at least two wheels, i.e. a front wheel and a rear wheel. Such definition includes, therefore, also motorcycles having three wheels, including, for example, two paired steering wheels on the forecarriage and one drive wheel on the rear axle, but also motorcycles comprising a single steering wheel on the forecarriage and two drive wheels on the rear axle. Finally, so-called quadricycles are also included in the definition of a motorcycle, which have two wheels on the forecarriage and two wheels on the rear axle.

[0020] The intake system 4 for an internal combustion engine 8 comprises an air conveyance duct 12 extending from an air inlet opening 16 to an air outlet opening 20 delimiting a conveying volume.

[0021 ] Typically, upstream of the air inlet opening 16, the intake system 4 comprises at least one air filter 24; said air filter 24 may also be placed inside the air conveyance duct 12, or even downstream of the air outlet opening 20. In any case, the air filter 24 may also be omitted.

[0022] The intake system 4 further comprises‘n’ intake trumpets 28, separated from each other, and facing said air outlet opening 20, with‘n’ >2.

[0023] The intake trumpets 28, in a known way, preferably have a frusto-conical shape that tapers from the air outlet opening 20 toward the associated cylinder of the internal combustion engine 8. In other words, the trumpets have a smaller diameter mouth facing the respective cylinder. Preferably, each intake trumpet 28 is associated with a corresponding cylinder of the internal combustion engine 8, so as to feed the same. As seen, the number‘n’ of intake trumpets 28, and thus the number of cylinders of the internal combustion engine 8, is greater than or equal to 2. This means that the intake system 4 of the present invention applies to any internal combustion engine 8 of the multi-cylinder type.

[0024] Advantageously, the air conveyance duct 12 comprises at least one internal partition wall 32 extending continuously along the air conveyance duct 12, so as to divide it internally into‘n’ channels 36 which are fluidly separated from each other.

[0025] In other words, the internal partition wall 32 preferably extends along the entire section between the air inlet opening 16 and the air outlet opening 20; in this way the ‘n’ channels 36 do not communicate and do not influence each other inside the air conveyance duct 12. The air and/or pressure wave exchanges between the ‘n’ channels may thus take place upstream of the air inlet opening 16 and/or downstream of the air outlet opening 20, at which each of the said‘n’ channels 36 ends up facing a corresponding intake trumpet 28.

[0026] In particular, as better described hereinafter, the air/wave pressure exchanges between the‘n’ ducts downstream of the air outlet opening 20 allow the intake flows in the various cylinders to be‘equalized’, optimizing the overall volumetric efficiency of the internal combustion engine 8.

[0027] According to one embodiment, said‘n’ channels 36 are delimited by at least one internal partition wall 32 and by the inside, i.e. the inner side wall, of said air conveyance duct 12.

[0028] As seen, preferably the at least one internal partition wall 32 divides the conveying volume into‘n’ volumes of the channels 36.

[0029] Preferably, the internal combustion engine 8 comprises a number‘n’ of cylinders equal to the number ‘n’ of channels, wherein each cylinder is equipped with its respective intake trumpet 28 and is fluidically fed by a respective channel 36.

[0030] According to one embodiment, the intake system 4 comprises an airbox 30 arranged so as to contain at least a part of the intake trumpets 28, at least a part of the air conveyance duct 12 and its partition wall(s) 32 in such a way that the air inlet opening 16 is positioned outside the same airbox 30. Substantially, the airbox 30 has a box shape wherein merges the air outlet opening 20, i.e. the air outlet mouth 20. Such outlet mouth 20 faces towards the mouth 40 of the trumpets 28 with larger diameter.

[0031 ] According to one embodiment, the air conveyance duct 12 and the at least one internal partition wall 32 are shaped in such a way that a gap 44 is defined between the air outlet opening 20 of the channels 36 and an air inlet edge 40 of the corresponding intake trumpets 28.

[0032] The air inlet edge 40 delimits the inlet section or mouth, inside each inlet trumpet 28, of the air flow coming from a corresponding channel 36 facing thereto.

[0033] Preferably, the intake trumpets 28 have an overall tapered shape, e.g. frusto- conical, moving from the side of the air outlet opening 20 towards the corresponding intake duct of the internal combustion engine 8.

[0034] The overall tapered shape does not necessarily have a circular cross-section, relative to a cross-section plane perpendicular to a predominant extension axis of the intake trumpets 28, but may also have different types of cross-section, comprising, for example, an elliptical-type geometry.

[0035] Moreover, it is also possible to provide intake trumpets 28 that have a geometry with a substantially constant cross-section, i.e. substantially free of tapered parts.

[0036] According to a possible embodiment, said gap 44 has a width comprised between 30% and 70% of the diameter 48 of the air inlet edge 40 of the corresponding intake trumpets 28. The diameter 48 must be understood in relation to a cross-section plane perpendicular to a predominant extension axis of the intake trumpets 28. In particular, the gap 44 is measured in height with respect to the inlet of the trumpets, or with respect to their inlet edge. The gap 44 can also be determined according to a radial direction, that is, as a diametrical difference between the mouth of the respective conveying duct and the mouth of the corresponding trumpet.

[0037] According to a possible embodiment, the intake trumpets 28 are connected to moving means, not illustrated, adapted to vary said gap 44 appropriately.

[0038] The variation of said gap 44 is preferably obtained as a function of the variation of the operating parameters of the internal combustion engine 8. Typically, the variation of said gap 44 varies according to the speed of the internal combustion engine 8, in order to optimize, by resonance phenomena of the intake air flows, the volumetric filling of the various cylinders of the same engine.

[0039] For example, the moving means are configured to eliminate substantially said gap 44, bringing the air inlet edge 40 into contact with said air outlet opening 20. By elimination it is also meant the achievement to few millimeters or tenths of millimeters, which substantially cancels the external dispersion in the passage of the air flow. If the gap 44 is eliminated, the air intake flows of adjacent channels 36 are prevented from affecting each other even after flowing out of the air outlet opening 20. The gap 44 may be substantially eliminated, for example, by bringing the air inlet edge 40 of the intake trumpets 28 in contact with a part of each corresponding channel 36 at the air outlet opening 20. Preferably, the contact between the components is damped by the interposition of at least one gasket which, in addition to reducing vibrations and noise, would also allow the air flow to be sealed.

[0040] It is also possible to configure the moving means in such a way as to eliminate said gap 44, bringing the air inlet edge 40 at least partially inside the channels 36.

[0041 ] According to a possible embodiment, the movement of said intake trumpets 28 is independent, so as to vary the‘n’ gaps independently.

[0042] In other words, it is possible to vary the distance between each intake trumpet 28 and the corresponding channel 36 independently and separately. In this way it is possible to optimize the volumetric filling of each cylinder according to the specific and contingent operating conditions of the same cylinder, also taking into account parameters of a geometric nature, linked, for example, to the architecture and thus to the positioning of the duct inside the intake system 4. For example, it is possible to increase or decrease the gap 44 of a cylinder arranged on the forward -facing side and, conversely, to decrease or increase the gap 44 of a corresponding cylinder arranged on the opposite side, in an engine with a‘V’ architecture. [0043] According to a possible embodiment, at least one internal partition wall 32 divides the conveying volume into ‘n’ volumes of the channels 36, which are substantially identical to each other.

[0044] For example, it is possible to increase an air passage section of the channels 36 having smaller extension and decrease the air passage section of the channels having larger extension, said extension being the average length traveled in each channel 36 to pass from the air inlet opening 16 to the air outlet opening 20.

[0045] According to a possible embodiment, said at least one internal partition wall 32 comprises at least one moving element (not illustrated) connected to motor means (not illustrated) capable of modifying the volume of at least one of said‘n’ channels 36.

[0046] The arrangement of the channels 36 is highly variable, and typically, but not exclusively, depends on the architecture of the internal combustion engine 8, i.e. the arrangement of the relevant cylinders.

[0047] For example, at least two of said channels 36 may be provided positioned side by side in a transverse direction T, perpendicular to a direction of flow X, i.e. the inlet direction, of the air through the air inlet opening 16.

[0048] It is also possible to provide for at least two of said channels 36 being positioned side by side in a longitudinal direction L, perpendicular to a direction of flow, i.e. incoming, of the air through the air inlet opening and in a longitudinal direction L.

[0049] For example (figure 1 ), the air conveyance duct 12 may be provided comprising four channels 36 arranged according to a square matrix scheme, along said transversal T and longitudinal L directions.

[0050] It is possible to provide for the channels 36 to convey only intake air or a mixture of air and fuel appropriately injected by fuel injection devices 52.

[0051 ] According to one embodiment, within each of said ‘n’ channels 36, a fuel injection device 52 is at least partially housed.

[0052] For the purposes of the present invention, the specific type of fuel injection device 52 which may, for example, be electronic, piezo-electric or similar, is not relevant.

[0053] Preferably, a fuel injection point P of the fuel injection devices 52 is arranged, within each channel 36, at a distance D from the air outlet opening 20 of not less than 20% of a diameter K of a cross-section of the channel 36 at the air outlet opening 20.

[0054] According to a possible embodiment, each fuel injection device 52 penetrates at least one channel 36. [0055] For example, in the case wherein the channels 36 are at least partially overlapping, e.g. along said longitudinal direction L, each fuel injection device may pass through at least two channels 36, also overlapping along the same longitudinal direction L.

[0056] Fuel injection devices 52 may be arranged or better oriented in different ways within the respective channel 36; depending on a possible embodiment, fuel injection devices 52 are arranged in a direction substantially perpendicular to the air outlet opening 20 of each channel 36.

[0057] As may be appreciated from the foregoing, the present invention allows the drawbacks of the prior art to be overcome.

[0058] In particular, the subdivision of the duct into‘n’ channels along the entire length of the same duct (i.e. from the air inlet opening to the air outlet opening) allows each channel to be calibrated according to the specific intake trumpet (and thus the relative cylinder) that supplies it, without the individual intake flows being able to affect each other, as long as the air does not escape from the outlet opening.

[0059] Thus, the presence of gaps allows a pressure exchange to be obtained at the inlet edges of adjacent trumpets that “equalizes” the intake flows in the various cylinders, optimizing the collective volumetric efficiency.

[0060] Due to the division between the various ducts, in the entire section between the air inlet opening and the air outlet opening, the premixing between the air and the fuel inside each of the ducts is not affected by the adjacent ducts.

[0061 ] The equalization and thus the recall of the intake to the trumpets is influenced and optimized by the resonances of the various ducts only after having passed the air outlet opening.

[0062] If necessary, under particular operating conditions, it is also possible to occlude the gaps so as to prevent interference between at least one duct and those adjacent thereto.

[0063] The arrangement of the injectors inside the fluidly separated ducts allows the injection spray to be better isolated and the mixing, and thus the titer, of the gas conveyed by each trumpet towards the respective cylinder to be controlled in an extremely precise way.

[0064] A person skilled in the art, in the object of satisfying contingent and specific requirements, may make numerous modifications and variations to the intake systems and to the engines described above, all of which are contained within the scope of the invention as defined by the following claims.