An internal combustion engine having a device for varying the phase of the valves on the camshaft

Abstract

The present invention relates to an internal combustion engine 1, 1B, 1C, 1D for a passenger-seat motor vehicle, comprising at least a first centrifugal device 2, 2B for varying the timing of a first plurality of suction or relief valves 110, 220 relative to a drive shaft 300. The device comprises a driving disc 11, 11B loosely mounted on a first camshaft 10, 20 controlling the plurality of valves, and at least one driven disc 12, 12B integral with the same camshaft 10, 20. A drive element 40 is interposed between the two discs 11, 12 for transmitting motion from the driving disc 11 to the driven disc 12, 12B so as to cause relative rotation of the driven disc 12, 12B with respect to the driving disc 11, 11B when the rotational speed of the two discs exceeds a predetermined threshold. The engine comprises a distribution system 5 mechanically connecting the drive shaft and the driving disc 11, 11B in such a way as to cause the rotation. The engine includes a first gear 15 integral with the drive disc 11, 11B and a second gear 16 attached to the second camshaft 10, 20, the rotation of which directly or indirectly causes rotation of the second shaft. The second gear 16 meshes with the first gear 15, and rotation of the drive disc 11, 11B attached to the first camshaft causes rotation of the second camshaft 10, 20, which is selected to control one or more other relief or suction valves 110, 220 of the engine.

Description

[Technical field]

[0001] The present invention relates to the field of manufacturing vehicles with passenger seats. This term generally means a motorcycle or a motor vehicle with two, three or four wheels, intended primarily for transporting people. The invention particularly relates to an internal combustion engine for a vehicle with passenger seats, comprising a camshaft for controlling a number of (suction or relief) valves and a device for varying the phase of said camshaft, i.e. said valves, relative to the drive shaft. [Background technology]

[0002] As is known, an internal combustion engine for a vehicle having a passenger seat comprises a drive shaft which is rotated by the movement of a piston in a combustion chamber of a cylinder. The engine also comprises one or more suction valves for introducing the mixture into the combustion chamber and one or more relief valves for discharging the burnt gases. The suction and relief valves are controlled by respective camshafts which are mechanically connected to the drive shaft via a distribution system, typically consisting of a gear wheel, a belt or a chain. Thus, the rotational movement of the camshafts through the distribution system is synchronized with the rotational movement of the drive shaft.

[0003] "Timing" usually means the moment when the opening and closing of the suction and relief valves occurs with respect to a given position of the piston. In particular, to define timing, the opening advance (or delay) angle is considered with respect to BDC (bottom dead center) and the closing advance (or delay) angle is considered with respect to UDC (top dead center). Advance is defined as the moment when the valve reaches its fully open / closed position and ends its stroke. The advance value is therefore the moment when the valve starts its opening operation (from a fully closed state) or closing operation (from a fully open state).

[0004] It is also known that in a certain time interval, i.e., a given rotation angle of the drive shaft, the suction valve and the relief valve are open at the same time. This interval is called the "crossing angle" and is the step that induces the intake, which allows the exhaust gas to quickly leave the combustion chamber and increase the intake of fresh gas. Therefore, the timing of the suction valve and the relief valve is the value of the crossing angle.

[0005] It is well known that the value of this crossing angle can produce various effects according to the rotational speed of the drive shaft. Increasing the crossing angle improves performance at high speeds, but reduces engine efficiency at low speeds and also reduces combustion efficiency, resulting in increased exhaust gas. Conversely, if the crossing angle is too small, engine efficiency at high speeds decreases.

[0006] In relation to the above, various technical solutions have been proposed in which the timing of the suction valve and / or the relief valve is changed depending on the rotation speed, i.e. the value of the valve crossing angle is changed.

[0007] One such technical solution is described in patent application WO 2005 / 023363. In particular, patent application WO 2005 / 023363 describes an engine of the DOHC (double overhead camshaft) type, in which the distribution system consists of two camshafts, one intended for controlling the suction valve and the other the relief valve, which are arranged above the engine head. This distribution system comprises three gear wheels: a driving wheel integrated with the drive shaft and two driven wheels, each mounted idle on the end of one of the two camshafts. The three (driving and driven) wheels are connected by a drive belt.

[0008] A device for changing the timing of the corresponding valve is provided on each of the camshafts. Such a device comprises a drive element that coincides with a driven wheel of the distribution system. The device further comprises a guide element that is keyed to said end of the camshaft via a grooved profile coupling so as to take a position adjacent to the drive element, whereby one side of the drive element faces one side of the guide element. Between the driven wheel and the guide element is interposed a drive element of ball-shaped movement. Each drive element is partially housed in a groove defined in a side of the drive element and also partially housed in a corresponding groove defined in a side of the guide element. The grooves of the drive element have an inclination evaluated in a plane perpendicular to the rotation axis of the camshaft, which inclination is different from the grooves of the guide element. Each drive element is therefore housed between two grooves that are only partially facing each other. Furthermore, the associated grooves of both components (drive element and guide element) have a curved profile evaluated in a radial sectional plane.

[0009] The device described in the patent document 1 further comprises thrust means acting on the guide element and forcing it axially against the driven wheel. The rotation of the drive shaft is transmitted via the distribution system described above to a corresponding drive element attached to the corresponding camshaft. The rotational movement of the drive element is transmitted by the drive element to the camshaft. When the rotation speed increases, centrifugal forces push the drive element outwards along the groove, i.e. away from the axis of rotation of the camshaft. Due to the effect of the shape of the groove, the guide element moves axially and at the same time rotates relative to the drive element. This rotation causes the camshaft to rotate relative to the drive element (in phase with the drive shaft) and therefore the timing of the corresponding valve is modified.

[0010] As mentioned above, the distribution system in the technical solution described in the patent document 1 provides for mounting a driven wheel on each of the camshafts. This configuration of the distribution system, on the one hand, facilitates a phase change of one of the suction valves and the relief valve, but on the other hand, is not always feasible in the past for reasons of space and cost.

[0011] When only the discharge port is provided with a phase difference, the distribution system is simplified as shown in the attached figures 1 to 3. In particular, a first shaft (701) controlling a suction valve (711) and a second shaft (702) controlling a relief valve (712) are identified. The distribution system (500) comprises a first drive wheel (801) integral with a drive shaft (not shown), a second drive wheel (802) rigidly keyed to the end of the first shaft (701) and a flexible element (803). Also keyed to the first shaft (701) is a further gear wheel (850), which always rotates in phase with the same first shaft (701).

[0012] A centrifugal phase changer device is associated with the second shaft (702) to provide a phase change during discharge. Such a device can also be attributed in function and structure to that described in US Pat. In any case, since a phase changer device is involved, a toothed disk (901) is provided which is loosely mounted on the second shaft (702) and a guide element (902) which is integral with the second camshaft (702). Between the toothed disk (901) and the guide element (902) a drive element can be arranged according to the same principle or which is attributed to that described in US Pat.

[0013] The toothed disk (901) of the phase changer meshes with the gear wheel (850) that is integral with the first camshaft (701). As a result, the rotation of the gear wheel (850), which always rotates in phase with the drive shaft, is transmitted to the second camshaft (702) via the toothed disk (901) that forms the phase changer.

[0014] Thus, with respect to the solution described in the patent application WO 2005 / 023336, the distribution system in the solution shown in figures 1 to 3 has a simpler construction, since the drive shaft is operatively connected only to one of the camshafts. The latter therefore always remains in phase with the drive shaft and supports a gear wheel (850) which causes the rotation of the other camshaft. While the solution shown in figures 1 and 3 simplifies the distribution system in terms of volume and manufacturing costs, such a solution remains applicable in any case only if a phase change is provided for only one type of valve (traditionally a relief valve). In fact, in the known solutions (figures 1 to 3), it is necessary that one of the two camshafts is always in phase with the drive shaft.

[0015] Another limitation of the solution shown in figures 1 to 3 is identified in the location of the components that transmit the motion from one camshaft to the other, namely the wheel (850) and the phase changer (200). Such components occupy an intermediate position, i.e. far from both ends of the corresponding camshafts (701, 702). This intermediate position is a key point in designing the cylinder head and the associated fusion of the engine. In fact, the cylinder head provides an adequate expansion in the area where the two drive elements (850-200) are located. At the same time, the intermediate position is certainly disadvantageous in terms of manufacturing costs, since it requires a longer and more demanding machining.

[0016] In relation to the above considerations, a need appears to arrange for new technical solutions which on the one hand make it possible to use simple distribution systems and at the same time are usable both in cases where a phase change is required only on exhalation or on inhalation and in cases where a phase change is required on exhalation and on inhalation. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] U.S. Patent No. 9,719,381 Summary of the Invention [Problem to be solved by the invention]

[0018] The main object of the present invention is therefore to provide an internal combustion engine for vehicles with passenger seats, which is able to overcome the above-mentioned drawbacks. Within this object, a first object of the present invention is to provide an engine in which the distribution system has a simple configuration in terms of number of parts and volume. A second object related to the first object is to provide an engine in which the transmission of the rotary motion to one of the two camshafts is performed via parts attached to the other shaft, such transmission being versatile in relation to the type of phase change required (at the discharge and / or at the intake). It is another object to provide an engine in which the configuration of the distribution system, the camshafts and the parts for transmitting the rotation makes it easy to design and manufacture the cylinder head of the engine. Yet another object of the present invention is to provide an engine which is reliable, easy to manufacture and cost-competitive. [Means for solving the problem]

[0019] The applicant has ascertained that the above-mentioned problems and objects can be achieved by connecting a distribution system to a drive element of a phase change device mounted on one of the camshafts and transmitting the rotation of the same drive element to the other camshaft via two gear wheels. More specifically, the above problems and objects are achieved through an internal combustion engine for a motor vehicle having passenger seats, the engine comprising a drive shaft, a first camshaft controlling a number of suction valves and a second camshaft controlling a number of relief valves. The engine comprises at least a first centrifugal device for changing the timing of one of said valves relative to said drive shaft. Such a device comprises: a drive disk loosely mounted on one of the camshafts controlling said one of the plurality of valves, the drive disk rotating about an axis of rotation of said one of the camshafts; at least one driven disc integral with said one of said camshafts; - a drive element for transmitting motion between the driving disc and the driven disc, the disc and the drive element being configured to cause relative rotation of the driven disc with respect to the driving disc when the rotational speed of the disc exceeds a predetermined threshold value; Equipped with.

[0020] The engine according to the present invention further comprises a distribution system mechanically connecting said drive shaft and said drive disc to effect rotation thereof.

[0021] The engine according to the present invention is also characterized in that it comprises a first gear integral with the drive disc and a second gear attached to the other of the camshafts, the rotation of which directly or indirectly causes the rotation of the other of the camshafts. According to the present invention, the second gear directly meshes with the first gear such that the rotation of the drive disc causes the rotation of the other of the camshafts selected to control the other of the plurality of valves. Thus, the two gear wheels are in contact with each other.

[0022] Therefore, the present invention provides that the rotation of the driving disk of the phase change device is used to rotate not only the camshaft on which the same driving disk is installed, but also the other camshaft through two gears. Therefore, the distribution system has the task of synchronizing the rotation of the drive shaft only with the driving disk, so that the number of parts is small and the configuration is relatively simple. At the same time, the driving disk and the two gears involved in the distribution can be installed near the corresponding ends of the two camshafts, so that the design and manufacture of the engine cylinder head are simplified.

[0023] According to a possible embodiment, the distribution system comprises a first distribution wheel keyed to the drive shaft, a second distribution wheel integral with the first disk, and a flexible drive element connecting the distribution wheels such that the rotation of the drive shaft is transmitted to the drive disk. The distribution system advantageously requires only one distribution wheel, and not two distribution wheels as provided in many conventional solutions.

[0024] The engine preferably comprises a sleeve body in integral rotation with the driving disc, the driving disc being arranged at a first end of the sleeve body, the sleeve body comprising a flange portion defined at a second end opposite the first end, the second distribution wheel being connected to the flange portion of the sleeve body. The sleeve body advantageously facilitates the assembly of the phase change device and its connection to the distribution system. Also, possible inspection and / or maintenance operations of the engine are simplified.

[0025] According to a possible embodiment, the first gear is made integral with said driving disc in the form of a gear wheel.

[0026] According to a further possible embodiment, the second gear is made integral with said other one of said camshafts.

[0027] In a possible embodiment, the first gear is mounted idle on the first camshaft and the second gear is mounted idle on the second camshaft, so that in this embodiment, a change in the phase of the suction valve can be actuated while the relief valve always remains in the same phase as the drive shaft.

[0028] In an alternative embodiment, the drive disc is loosely mounted on the second camshaft and the second gear is mounted on the first camshaft. In this embodiment, the relief valve can be operated with different phases, but the suction valve always remains in phase with the drive shaft.

[0029] According to a further possible embodiment, the engine comprises a further centrifugal device for varying the timing of the phase of the valve controlled by the other of the camshafts, the further centrifugal device comprising: a further driving disc loosely mounted on the other of the camshafts and adapted to rotate about an axis of rotation of the other of the camshafts; a driven disc integral with the other of the camshafts; - a further drive element for transmitting motion between the further driving disc and the further driven disc, the further disc and the further drive element being configured to cause relative rotation of the further second disc with respect to the further first disc when the rotational speed of the further disc exceeds a predetermined threshold value; Equipped with.

[0030] The second gear is integral with the further driving disc such that rotation of the driving disc mounted on the one of the camshafts is transmitted to the further driving disc mounted on the other of the camshafts. Advantageously, the engine may provide phase changes with the same configuration of the distribution system both at intake and at discharge.

[0031] Further features and advantages of the present invention will become more apparent from the consideration of the following detailed description of some preferred, but not exclusive, embodiments of an engine according to the invention, given as non-limiting examples with the aid of the attached drawings, in which: [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram of an engine as known from the prior art. [Diagram 2] FIG. 2 is a schematic diagram of an engine as known from the prior art. [Diagram 3] FIG. 3 is a schematic diagram of an engine as known from the prior art. [Figure 4] FIG. 4 is a schematic diagram relating to a possible embodiment of an engine according to the invention. [Diagram 5] FIG. 5 is a further view of the engine of FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a further view of the engine of FIG. [Figure 9] FIG. 9 is an enlarged view of detail IX-IX shown in FIG. [Figure 10] FIG. 10 is a schematic diagram relating to a possible embodiment of an engine according to the invention. [Figure 11] FIG. 11 is a schematic diagram relating to a possible embodiment of an engine according to the invention. [Figure 12] FIG. 12 is a schematic diagram relating to a possible embodiment of an engine according to the invention. [Figure 13] FIG. 13 is a schematic diagram relating to a possible embodiment of an engine according to the invention.

[0033] Like numbers and reference characters in the figures indicate like elements or components. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] The present invention relates to a combustion engine for a vehicle with passenger seats (this term generally means a motorcycle or a car with two, three or four wheels, intended primarily for transporting people).

[0035] The engine 1 according to the invention comprises a first camshaft 10 rotating about a first axis of rotation 101 and a second camshaft 20 rotating about a second axis of rotation 102 for controlling a plurality of suction valves 110 and a plurality of suction valves 210, respectively. The engine 1 also comprises at least a first device 2 for varying the timing of the valves 110, 210 of one of the two camshafts 10, 20 relative to a drive shaft.

[0036] In the embodiment shown in Figures 9 to 13, the device 2 is applied to the first camshaft 10 to change the phase of the suction valve 110 relative to the drive shaft 300. However, as shown in the schematic diagram of Figure 11, the device 2 may be operatively associated with the second camshaft 20 to change the phase of the relief valve 220. Thus, although the invention has been described primarily with reference to an engine in which a phase change is provided on the intake side (i.e. for the suction valve), the technical solution may also be applied, mutatis mutandis, to an engine in which a phase change is provided on the discharge side (i.e. for the relief valve). In summary, the following description of the first and second camshafts of an engine configured with a phase change on the intake side is considered to be valid for the second and first camshafts, respectively, in the case of an engine configured with a phase change on the discharge side.

[0037] Some of the attached figures (FIGS. 4 to 9) show only certain parts of an internal combustion engine 1 according to the invention, while other parts that are not essential for understanding the invention are not shown for reasons of increasing illustrative clarity. The other attached figures are merely schematic representations of possible embodiments of the engine according to the invention, which are in any case understandable to the skilled person.

[0038] The drive shaft is not shown in the accompanying figures, but rather is shown diagrammatically with an axis having the reference numeral 300. The device 2 is also referred to by the terms "phase changer 2" or "phase changer device 2" in the remainder of the description. When referring to components of the phase changer 2, the terms "axial" and "axially" refer to a distance, thickness, and / or location evaluated along the axis of rotation 101, 102 of the first camshaft 10 with which the phase changer is operatively associated.

[0039] According to the invention, the phase change device 2 employed is of centrifugal type and therefore operates according to principles known per se. The device 2 comprises a driving disk 11 (or first disk 11), a driven disk 12 (or second disk 12) and a number of driving elements 40, each of which is interposed between the two disks 11, 12 indicated above. The driving element 40 and the disks 11, 12 are configured to rotate the second disk 12 relative to the first disk 11 when the rotational speed exceeds a predefined threshold value.

[0040] For this purpose, according to principles known per se, the driving disc 11 is mounted idle on the first camshaft 10, such that the two components (first camshaft 10 and first disc 11) rotate about the same axis of rotation 101. The first disc 11 is "idle" in the sense that it retains freedom of rotation with respect to the first camshaft 10 on which it is mounted, and vice versa.

[0041] The driven discs 12 are connected to the same first camshaft 10, but are connected to rotate together, i.e. about the same axis of rotation 101, 102. The two discs 11, 12 therefore rotate about the first axis of rotation 101. In this respect, the driven discs 12 may be made in one piece with the first camshaft 10 (as shown) or alternatively may be made separately and rigidly keyed thereto (e.g. via a keyed connection or a connection by a grooved profile).

[0042] According to what is conventional for centrifugal phase changers, a first groove 31 is defined in the side surface 111 of the driving disc 11, which partially faces a second groove 32 defined in the side surface 122 of the driving disc 12. Each of the driving elements 40 is partially housed in one of said first grooves 31 and partially housed in one of said second grooves 32. When the centrifugal force increases due to an increase in the rotation speed, each of the driving elements 40 moves along the two grooves 31, 32 between a first position closest to the rotation axis 101 of the two discs 11, 12 and a second position furthest from the same rotation axis. In some cases, the first groove 31 is oriented and / or shaped in a different way than the second groove 32, so that reaching said second position involves a relative rotation of the second disc 12 with respect to the first disc 11. Such a translation results in a change in the phase of the valve with respect to the drive shaft 300.

[0043] 9, one can refer to possible, and therefore non-exclusive, embodiments of the phase changer 2 according to the invention. In the particular embodiment shown, the phase changer 2 comprises preloading means 70 arranged to oppose an axial movement of the first disc 11 relative to the second disc 12 and thus to maintain the drive element 40 between the two discs 11, 12, in the two grooves (first groove 31 and corresponding groove 32) in which it is respectively housed.

[0044] In a possible non-exclusive embodiment shown in Fig. 9, the preloading means 70 comprises a Belleville spring 71 acting on the flange portion 61 of the sleeve body 62 to press the latter towards the second disc 12. The Belleville spring 71 is interposed between the flange portion 61 and an adjusting screw 72 which is coaxially threaded into the end of the camshaft 10 on which the flange portion 61 is located. Closure of the screw 72 compresses the Belleville spring 71 and thus generates an axial force opposing the movement of the first disc 11 away from the second disc 12.

[0045] The axial preloading means 70 can therefore be configured to prevent relative movement of the first disc 11 with respect to the second disc 12, as occurs in the device described in the above-mentioned patent document 1, or can be configured only to oppose such movement.

[0046] The phase changer 2 shown in Fig. 9 further comprises means 6 for holding the driving element 40 interposed between the first disk 11 and the second disk 12. Such holding means 6 apply a force to each of the driving elements 40 tending to press the driving elements 40 towards the first position shown above (i.e. towards the rotation axis 101). The adoption of the holding means 6 makes it possible to recover the clearance between the driving element 40 and the grooves 31, 32, thus making the transmission more efficient and at the same time simplifying the shape of the device components themselves.

[0047] It is again pointed out that the shape of the device 2 shown in detail in Figure 9 is not essential to the invention, the novel and inventive features of which are described below, and in this respect the device 2 may have the configuration described in the above-referenced patent application WO 2005 / 023366.

[0048] In any event, according to the invention, the engine 1 comprises a distribution system 5 mechanically connecting the drive shaft 300 to the drive disc 11 to effect its rotation about its axis of rotation 101 .

[0049] Again, according to the invention, the driving disc 11 is integral with the first gear 15. Such a first gear 15 is preferably made in one piece with the driving disc 11 so that the driving disc 11 assumes the configuration of a wheel. In effect, in this configuration, the driving disc 11 is provided with an outer ring gear which defines the first gear 15.

[0050] The engine 1 according to the invention is arranged such that a second gear 16 is mounted on the second camshaft 20, the rotation of which directly or indirectly causes the rotation of the second camshaft 20. According to the invention, the second gear 16 is meshed with the first gear 15, such that the rotation of a first disk 11 mounted on the first shaft 10 is transmitted, via the second gear 16, to the second camshaft 20. Advantageously, the rotation of the second camshaft 20 is thus caused by the drive disk 11 of a phase change device 2 provided for changing the timing of the valves controlled by the first camshaft 10.

[0051] As will be better explained below, the term "directly" refers to a possible embodiment in which the second gear 16 is keyed onto the second camshaft 20 so as to rotate integrally therewith. Alternatively, the term "indirectly" refers to a possible embodiment in which phase modification is provided on both intake and exhaust. In this hypothesis, the second gear 16 is integral with a driving disk 11B of a further phase modifying device 2B operatively associated with the second camshaft 20 to modify the timing of the relief valve (see Figures 12 and 13).

[0052] According to a possible embodiment shown in Figures 5 to 9, the distribution system 5 comprises a first distribution wheel 51 keyed to the drive shaft 300 (shown in dashed lines in Figure 2), a second distribution wheel 52 integral with the first disc 11, and a flexible drive element 53 (in the form of a chain or belt) connecting the two distribution wheels 51, 52 so that the rotation of the drive shaft 300 is transmitted to the first disc 11 of the phase changer 2.

[0053] According to an embodiment, which is also shown in figures 4 to 9, the second distribution wheel 52 is connected to a flange portion 61 of a sleeve body 62 made in one piece with the driving disc 11. In particular, the driving disc 11 is defined in a first end of the sleeve body 62, opposite to a second end defining the flange portion 61. The second distribution wheel 52 is preferably connected to the flange portion 61 via a threaded connection means 66 (see figures 4 and 6). With reference to figures 6 to 9, the sleeve body 62 is preferably mounted on the end 10A of the camshaft 10 in such a way that the first disc 11 faces the second disc 12, for the purposes already indicated above.

[0054] Figures 10 to 13 are schematic diagrams of four possible embodiments of an engine according to the invention (designated with the reference numerals 1, 1B, 1C, 1D). The embodiment shown diagrammatically in Figure 10 corresponds substantially to the one shown in Figures 4 to 9.

[0055] The embodiment shown in FIG. 11 refers to an engine 1B according to the invention, in which a phase change in the discharge is provided, and therefore a phase change device (designated with reference numeral 2B) is operatively associated with the second shaft 20. As a result, a driving disk (designated with 11B) is mounted idle on the second camshaft 20, while a driven disk (designated with 12B) is integral with the same second camshaft 20. Instead, a second gear 16, which meshes with a first gear 15, which is integral with the driving disk 11B, is keyed to the first camshaft 10. According to the principles of the invention, the distribution system 5 is configured in any case to cause the rotation of the driving disk 11B. Thus, a second distribution wheel 52 and a sleeve 62, in which the same driving disk 11B is integrated, are mounted on the end of the second camshaft 20.

[0056] It is noteworthy in the embodiment shown in Fig. 11 that the suction valve 110 always keeps the same timing with respect to the drive shaft 300. In fact, the rotation of the first camshaft 10 caused by the distribution system is transmitted via a transmission defined by a first gear 15 (integral with the drive disc 11B) and a second gear 16. The second camshaft 20 is therefore excluded from such transmission, and this second camshaft remains free to change its angular position with respect to the drive disc 11B in order to cause a phase change of the relief valve 220.

[0057] Figure 12 relates to a possible embodiment (already described above) where the engine comprises a first device 2 operatively associated with the first camshaft 10 for varying the timing of the suction valve 110, and a second device (shown as 2B) associated with the second camshaft 20 for varying the phasing of the relief valve 220. That is, in the arrangement of Figure 12, a phasing change is provided for both the intake and the exhaust.

[0058] Thus, the driving disk 11 of the first device 2A is mounted idle on the first camshaft 10, while the associated driven disk 12 is rotationally integrated with the same first camshaft 10. In exactly the same way, the driving disk (designated 11B) of the second device 2B is mounted idle on the second camshaft 20, while the associated driven disk (designated 12B) is rotationally integrated with the second camshaft 20. The distribution system is configured to cause the rotation of the driving disk 11 of the first device 2. Thus, the sleeve 62 connected to the second distribution wheel 52 is keyed idle to the end of the first camshaft 10.

[0059] 12, the second gear 16 is integral with the first disk 11B of a second device 2B provided for varying the timing of the relief valve 220. In this embodiment, the second gear 16 is idle mounted on the second camshaft 20 and transmits motion to the second camshaft 20 indirectly via the second device 2B.

[0060] 12 embodiment, in the entire assembly of components formed by the sleeve 62, the driving disc 11 of the first unit 2, the first gear 15, the second gear 16 and the driving disc 11B of the second unit 2B always rotate in phase with the drive shaft 300. The two camshafts 10, 20 and therefore the associated valves 110, 220 may alternatively change their timing angles relative to the drive shaft 300.

[0061] The embodiment shown in Fig. 13 differs from that of Fig. 12 exclusively in that the distribution system is arranged to cause the rotation of the drive disk 11B of the second device 2B. Here, the sleeve 62 connected to the second distribution wheel 52 is therefore keyed idle to the end of the second camshaft 20. The first gear 15 is therefore integral with the drive disk 11B of the second device 2B and the second gear 16 is integral with the drive disk 11 of the first device 2. The operating positions of the two gears 15, 16 are therefore reversed with respect to the embodiment shown in Fig. 12. In any case, for both discussed embodiments (FIGS. 12 and 13), the rotation imparted to the driving disk (11 or 11B) connected to the distribution system 5 is used not only to rotate the camshaft (10 or 20) on which the same driving disk (11 or 11B) is mounted idle, but also to rotate the other camshaft (20 or 10) (via the two gears 15, 16). This solution allows to maintain a simple configuration of the distribution system in any case, since only one distribution wheel is provided, which is associated with one of the camshafts. That is to say, the same distribution system can be used both for providing a phase change only for one type of valve (intake or discharge) and for providing a phase change for two types of valve (intake and discharge).

Claims

1. An internal combustion engine (1, 1B, 1C, 1D) for a motorcycle, the engine (1, 1B) comprising a drive shaft (300), a first camshaft (10) controlling a plurality of suction valves (110), and a second camshaft (20) controlling a plurality of relief valves (220), the engine (1, 1B, 1C, 1D) comprising at least a first centrifugal device (2, 2B) for varying the timing of one of the plurality of suction valves (110) and the plurality of relief valves (220) relative to the drive shaft (300), the first centrifugal device (2, 2B) comprising: a driving disk (11, 11B) loosely mounted on one of the first camshaft (10) and the second camshaft (20) for controlling the one of the plurality of suction valves (110) and the plurality of relief valves (220), the driving disk (11, 11B) rotating about a rotation axis (101 or 102) of the one of the first camshaft (10) and the second camshaft (20); at least one driven disc (12, 12B) integral with said one of said first camshaft (10) and said second camshaft (20); - a drive element (40) for transmitting motion between said driving disc (11, 11B) and said driven disc (12, 12B), said driving element (40) being configured to cause relative rotation of said driven disc (12, 12B) with respect to said driving disc (11, 11B) when the rotational speed of said driving disc (11, 11B) and said driven disc (12, 12B) exceeds a predefined threshold value; a distribution system (5) that mechanically connects said drive shaft (300) and said driving discs (11, 11B) and causes their rotation; Equipped with the engine (1) comprises a first gear (15) integral with the drive disk (11, 11B); and a second gear (16) attached to the other of the first camshaft (10) and the second camshaft (20), wherein rotation of the second gear (16) directly or indirectly causes rotation of the other of the first camshaft (10) and the second camshaft (20), the second gear (16) directly meshing with the first gear (15), and rotation of the drive disk (11, 11B) causes rotation of the other of the first camshaft (10) and the second camshaft (20) that controls the other of the plurality of suction valves (110) and the plurality of relief valves (220); said distribution system (5) comprising a first distribution wheel (51) keyed to said drive shaft (300), a second distribution wheel (52) integral with said drive discs (11, 11B), and a flexible drive element (53) connecting between said distribution wheels (51, 52) such that the rotation of said drive shaft (300) is transmitted to said drive discs (11, 11B), Motorcycle internal combustion engines (1, 1B, 1C, 1D).

2. 2. The engine (1, 1B, 1C, 1D) according to claim 1, comprising a sleeve body (62) which is integral in rotation with the driving disc (11, 11B), the driving disc (11) being arranged at a first end of the sleeve body (62), the sleeve body having a flange portion (61) defined at a second end opposite the first end, and the second distribution wheel (52) being connected to the flange portion (61) of the sleeve body (62).

3. 3. The engine (1, 1B, 1C, 1D) according to claim 2, comprising axial preload means (70) acting on the driving disc (11, 11B) by opposing its axial translation relative to the driven disc (12, 12B) along a direction parallel to a rotation axis (101 or 102) of the one of the first and second camshafts (10) and (20).

4. An engine (1, 1B) according to any one of claims 1 to 3, wherein said first gear (15) is made integral with said driving disc (11, 11B) in the form of a gear wheel.

5. The engine (1, 1B) according to any one of claims 1 to 4, wherein the second gear (16) is made integral with the other of the first camshaft (10) and the second camshaft (20).

6. The engine (1) according to any one of claims 1 to 5, wherein the first gear (15) is loosely attached to the first camshaft (10), and the second gear (16) is attached to the second camshaft (20).

7. The engine (1B) according to any one of claims 1 to 5, wherein the driving disk (11B) is loosely attached to the second camshaft (20), and the second gear (16) is attached to the first camshaft (10).

8. The engine comprises a further centrifugal device (2, 2B) for varying the timing of the other of the plurality of suction valves (110) and the plurality of relief valves (220) controlled by the other of the first camshaft (10) and the second camshaft (20), the further centrifugal device (2A, 2B) comprising: a further driving disc (11, 11B) loosely mounted on the other of the first camshaft (10) and the second camshaft (20), the further driving disc (11, 11B) rotating about the axis of rotation (101 or 102) of the other of the first camshaft (10) and the second camshaft (20); a further driven disc (12, 12B) integral with the other of said first camshaft (10) and said second camshaft (20); a further drive element (40) for transmitting motion between said further driving disc (11, 11B) and said further driven disc (12, 12B), said further driving disc (11, 11B) and said further driven disc (12, 12B) and said further driving element (40) being configured to cause a relative rotation of said further second disc (12B) with respect to said further first disc (11B) when the rotational speed of said further driving disc (11, 11B) and said further driven disc (12, 12B) exceeds a predefined threshold value; Equipped with The engine (1C, 1D) according to any one of claims 1 to 5, wherein the second gear (16) is integral with the further driving disc (11, 11B), and rotation of the driving disc (11) attached to the one of the first camshaft (10) and the second camshaft (20) is transmitted to the further driving disc (11B) attached to the other of the first camshaft (10) and the second camshaft (20).

Images