EP4375491A1

EP4375491A1 - Valve drive

Info

Publication number: EP4375491A1
Application number: EP22208873.4A
Authority: EP
Inventors: Umberto Borile
Original assignee: Marik Srl
Current assignee: Marik Srl
Priority date: 2022-11-22
Filing date: 2022-11-22
Publication date: 2024-05-29

Abstract

A distribution apparatus (12) for an engine comprises at least one intake valve (14, 16) and at least one exhaust valve (18, 20). The apparatus comprises movement means (22) for the at least one intake valve (14, 16) and for the at least one exhaust valve (18, 20). The movement means (22) comprise a first crossbow element (24) and a second crossbow element (26) to which the at least one intake valve (14, 16) and the at least one exhaust valve (18, 20) are connected, respectively. The first crossbow element (24) and the second crossbow element (26) are connected at each end (242, 244; 262, 264) with respective distribution rod heads (302, 282, 322, 342). The distribution rods (28, 30, 32, 34) are arranged in correspondence with a foot (282, 302, 322, 342) thereof, opposite the head (284, 304, 324, 344) with a bearing (36, 38, 40, 42). Each of the bearings (36, 38) is in connection with respective cam means (40, 42, 44, 46) suitable for being put into rotation by a drive shaft (48) for moving the at least one intake valve (14, 16) and the at least one exhaust valve (18, 20) .

Description

FIELD OF APPLICATION

The present invention relates to a distribution apparatus for engines, and an engine comprising such a distribution apparatus.

PRIOR ART

As is known, two-stroke or four-stroke engines are equipped with a cylinder head that, together with the piston and the cylinder, creates the combustion chamber. The intake and exhaust valves, necessary for the completion of the phases of the engine cycle, are housed in the cylinder head.
The valves are driven by camshafts, which push them down towards the combustion chamber. In turn, the camshafts may be moved by means of rods, a chain, a toothed belt or gears, typically a cascade of gears, or else using a shaft and two bevel wheels.
The step of raising the valves into the seats thereof is performed by springs, which may be made of steel, titanium, or be pneumatic.
As is known, the descent movement of the valves must overcome the force that is applied by the relative spring, which is precisely loaded by virtue of the descent of the valve. However, part of the work performed in moving the valve and therefore loading the spring is however lost (about 30-35% of the total work).
One type of distribution with a higher efficiency is the so-called desmodromic distribution, which does not use return springs for the movement of the valves. In fact, the desmodromic distribution uses rocker arms for both opening and closing the valves, and a small spring to ensure the closure of the valve.
However, even in this case, which is similar to the previous cases, there are working losses due to the tensioners of the chain or toothed belt used for the movement of the rocker arms. In addition to this, the rocker arms need to be pivoted in order to ensure the alternating movement. Therefore, even in this case, friction is generated that may be reduced by using bearings, to the detriment of the weight and size of the distribution.
Also known is a technical solution wherein the rocker arms are replaced with a double camshaft that uses the cam directly above the valve head together with the intersection of a cup with a calibrated pad. In this solution, it is necessary to lubricate the area where the cam rubs against the pad in order to reduce the sliding friction that is generated, and it is also necessary to dispose of the heat generated using special radiators.
Therefore, the prior art, whilst widely used and appreciated, is not without drawbacks.

DISCLOSURE OF THE INVENTION

The need to solve the drawbacks and limitations mentioned with reference to the prior art is therefore felt.
The need is therefore felt to provide a distribution apparatus wherein part of the work produced by the combustion engine is not wasted in the movement of the valves and the loading of the relative spring.
Furthermore, there is a need to further improve the desmodromic distribution, both with regard to the chain tensioners or toothed belt, and with regard to friction.
These requirements are met at least partially by a distribution apparatus for engines according to claim 1, and by an engine comprising such a distribution apparatus according to claim 17.
In particular, these needs are met at least partially by a distribution apparatus for an engine comprising at least one intake valve and at least one exhaust valve; said apparatus comprising movement means for said at least one intake valve and for said at least one exhaust valve; characterized in that said movement means comprise a first crossbow element and a second crossbow element to which said at least one intake valve and said at least one exhaust valve are respectively connected, arranged in a direction substantially perpendicular to said at least one intake valve and to said at least one exhaust valve; said first crossbow element and said second crossbow element being connected at each end with respective heads of distribution rods; said distribution rods being arranged in correspondence with a foot thereof, opposite to said head with at least one bearing; each of said bearings being in connection with respective cam means suitable for being put into rotation by a drive shaft for the movement of said at least one said inlet valve and said at least one exhaust valve.

DESCRIPTION OF THE DRAWINGS

Further features and advantages of this invention will become more apparent from the following detailed description of preferred, non-limiting embodiments thereof, wherein:

Figure 1 shows in schematic form a front view of the distribution apparatus according to one embodiment of the present invention, with some components of a related engine;
Figure 2 shows in schematic form a side view of the distribution apparatus according to one embodiment of the present invention, with some components of a related engine;
Figure 3 shows in schematic form a plan view from above of the distribution apparatus according to one embodiment of the present invention, with some components of a related engine;
Figure 4 shows in schematic form a prospective view of the distribution apparatus according to one embodiment of the present invention, with some components of a related engine;
Figure 5 shows in schematic form a portion of the distribution apparatus according to one embodiment of the present invention;
Figure 6 shows in schematic form an alternative embodiment of the distribution apparatus according to the present invention;
Figure 7 shows the distribution apparatus of Figure 6, in which other components have been shown;
Figure 8 shows in schematic form a perspective view of an alternative embodiment of a component of the distribution apparatus according to the present invention; and
Figure 10 represents in schematic form the perspective view of Figure 8, in which a component has been removed in order to make a portion more visible.

It is specified herein that elements of different embodiments described below may be combined together in order to provide further embodiments without limitation whilst respecting the technical concept of the invention, as the average person skilled in the art will effortlessly understand from that described and claimed hereinafter.
The present disclosure further refers to the prior art for the implementation thereof, with respect to those detailed characteristics which are not described, such as, for example, elements of minor importance that are usually used in the prior art in solutions of the same type.
When introducing an element, it is always to be understood that it may be "at least one" or "one or more" unless otherwise explicitly indicated.
When a list of elements or characteristics is listed in this description, it is understood that the invention according to this description "comprises" or alternatively "is composed of" such elements.
In the accompanying figures, identical or similar elements will be indicated using the same numerical references.

DETAILED DESCRIPTION

A distribution apparatus for engines according to the present invention is shown in Figure 1 with the reference 12.
The distribution apparatus 12 comprises at least one intake valve 14, 16, at least one exhaust valve 18, 20, and movement means 22 for the at least one intake valve 14, 16 and for the at least one exhaust valve 18, 20.
The movement means 22 comprise a first crossbow element 24 and a second crossbow element 26 to which the at least one intake valve 14, 16 and the at least one exhaust valve 18, 20 are connected, respectively, and which are arranged in a direction substantially perpendicular to the at least one intake valve 14, 16 and to the at least one exhaust valve 18, 20.
The first crossbow element 24 and the second crossbow element 26 are connected at each end 242, 244; 262, 264 with respective heads 282, 302, 322, 342 of distribution rods 28, 30, 32, 34.
The distribution rods 28, 30, 32, 34 are arranged in correspondence with a foot 282, 302, 322, 342 thereof, opposite the relevant head 284, 304, 324, 344 with at least one bearing 36, 38.
Each of the bearings 36, 38 is in connection with respective cam means 40, 42, 44, 46 suitable for being put into rotation by a drive shaft 48 for moving the at least one intake valve 14, 16 and the at least one exhaust valve 18, 20.
As may be seen in the accompanying figures, and in particular in Figure 3, the engine may be of the type comprising at least one cylinder on which two intake valves 14, 16 and two exhaust valves 18, 20 are arranged. Advantageously, this is a single-cylinder engine for a motorcycle.
In any case, as will be apparent to a person skilled in the art, this reference is given for descriptive and non-limiting purposes in relation to the different applications that may be the subject of the distribution apparatus according to the present invention.
In fact, the principles of the present invention may also be applied, for example, to multi-cylinder engines facing forward or with a V-shaped arrangement.
According to a possible embodiment, the at least one intake valve 14, 16 and the at least one exhaust valve 18, 20 are respectively arranged on the first crossbow element 24 and on the second crossbow element 26 by means of forks 142, 162, 182, 202.
As seen for example in Figure 4, the fork 142, 162, 182, 202 may be fixed to the relevant crossbow element whilst the valve may be rotatably fixed between the ends of the fork.
According to a possible embodiment, the at least one intake valve 14, 16 and the at least one exhaust valve 18, 20 are substantially parallel with respect to the respective distribution rods 28, 30, 32, 34.
Insofar as they are already known to a person skilled in the art, the inlet valves 14, 16 and the exhaust valves 18, 20 will not be described in further detail.
The first crossbow element 24 and the second crossbow element 26 may have a diameter of between 4 and 6 mm, preferably around 5 mm.
As seen in Figure 4, the ends 242, 244; 262, 264 of the first crossbow element 24 and the second crossbow element 26 may be made using a tube, into which the distribution rod 28, 30, 32, 34 is engaged. The ends 242, 244; 262, 264 of the first crossbow element 24 and the second crossbow element 26 may be locked relative to the relevant distribution rod 28, 30, 32, 34 in a manner known to a person skilled in the art.
According to a possible embodiment, the first crossbow element 24 and the second crossbow element 26 may be made of harmonic titanium. In alternative embodiments, the first crossbow element 24 and the second crossbow element 26 may be made of a different metal of harmonic type.
According to a possible alternative embodiment, each crossbow element 24, 26 may be implemented by means of two crossbow element rods 241, 243 which are side by side and substantially parallel to one another.
As may be seen in Figure 11, in which only the crossbow element 24 is shown, the latter may be made by using two crossbow element rods 241, 243 which are side by side and substantially parallel. The two crossbow element rods may be made with the same features as the single crossbow element indicated above. In particular, the two crossbow element rods 241, 243 may be made of harmonic titanium.
In this way, it is possible to use a perforated insert 181 that allows for the insertion of the valve 18 and the adjustment of the same. Advantageously, the valve 18 may be arranged with a threaded head suitable for being connected to an upper fork 182 and a lower fork 183 for adjusting the valve 18 itself, leaving the rotation thereof free.
According to a possible embodiment, damping elements suitable for damping the vibrations of the crossbow rods 241, 243 may be arranged between the two crossbow element rods 241, 243.
The distribution rods 28, 30, 32, 34 may be made using a tube. By way of example, the distribution rods 28, 30, 32, 34 may be made using a tube having an outer diameter of around 10 mm, and an inner diameter of around 8 mm. These dimensions are clearly given for explanatory and non-limiting purposes only.
According to a possible embodiment, the distribution rods 28, 30, 32, 34 may be made of harmonic titanium. In alternative embodiments, they may be made of a different metal.
The use of distribution rods 28, 30, 32, 34 is advantageous at least in that:

there are no rockers to be moved, but instead valves, directly, that are pivoted on the rods; and
the inner diameter and outer diameter may be greater, even double, in relation to those used in the prior art, by virtue of the use of lighter materials, such as titanium.

The distribution rods 28, 30, 32, 34 are suitable for moving in an alternating rectilinear motion, and may be guided by a pair of opposite concave bearings 90.
According to a possible embodiment, the cam means 40, 42, 44, 46 may comprise, for each bearing 36, 38, an opening cam 402, 422 adapted to interact with the relevant bearing 36, 38 to open the at least one intake valve 14, 16 or the at least one exhaust valve 18, 20, and a closing cam 404, 424 adapted to interact with the relevant bearing 36, 38 to close the at least one intake valve 14, 16 or the at least one exhaust valve 18, 20.
As shown in the example of Figure 5, each bearing 36, 38 may be interposed between two respective cams 402, 404 and 422, 424. As seen for example in Figure 5, the bearing 36, 38 may be interposed between an opening cam 402, 422 adapted to push the bearing 36, 38 towards the engine crankcase, so as to move the valve inside the combustion chamber, and a closing cam 404, 424 adapted to push the bearing 36, 38 in the opposite direction with respect to the engine crankcase, so that the valve moves in contact with the seat, so that it may close.
As seen in Figure 5, the opening cam 402, 422 may be provided with a radial protrusion 410, while the closing cam 404, 424 may be provided with a radial recess 412.
According to a possible embodiment, the opening cam 402, 422 and the closing cam 404, 424 are adapted to always be in contact with the relevant bearing 36, 38 during the movement thereof.
As seen in the accompanying figures, each opening cam 402, 422 and each closing cam 404, 424 may be keyed to a relevant shaft 403, 423, 405, 425, on which a relevant cam toothed wheel 406, 407, 426, 427 is also keyed.
The function of the cam toothed wheels 406, 407, 426, 427 is to receive motion and rotate the respective cams.
In accordance with a possible embodiment of the present invention, a central toothed wheel 58 adapted for receiving motion directly or indirectly from the drive shaft may be provided, wherein the central toothed wheel 58 engages simultaneously with the four cam toothed wheels 406, 407, 426, 427.
In this way, the rotation of the cams may be synchronized according to specific needs, by modifying the engagement between the central toothed wheel 58 and the toothed wheels 406, 407, 426, 427 of the cams.
In any case, the transmission ratio between the cam and the drive shaft will be 2:1.
As seen in Figure 4, the opening cams 402, 422 and the closing cams 404 may be contained within respective box elements 60, 62, 64, 66 which, in addition to at least partially containing the cams 402, 422, 404, 424 during the movement thereof, may be suitable for creating support surfaces for the cam shafts 403, 423, 405, 425.
According to a possible embodiment, the foot 282, 302, 322, 342 of the distribution rods 28, 30, 32, 34 may be shaped like a fork so that the bearing 36, 38 may be supported between the prongs of the forks. Advantageously, slotted openings 68 may be made on the side profile of the fork to allow the fork to slide with respect to the shafts on which the opening cams are arranged.
In Figures 6-9, an alternative embodiment of the cam means 40, 42, 44, 46 is shown.
As may be seen in the embodiment shown in Figure 7, the distribution rods 28, 30, 32, 34 may be arranged at the foot 282, 302, 322, 342 thereof with two bearings 36, 361; 38, 381 which are side by side and arranged on the same axis.
In particular, the foot 282, 302, 322, 342 of the distribution rods may be shaped like a fork so that a first bearing 36 is connected to one prong of the fork, and a second bearing 361 is connected to a second prong of the fork.
In this case, the embodiment will be described with reference to a portion of the distribution apparatus, it being understood that the opposite part, i.e. the part connected to the two feet of the distribution rod, which is not described, will be substantially the same.
According to a possible embodiment, the cam means 42 may comprise a double cam element 70, 72 for each distribution rod 28, 30, 32, 34.
As may be seen for example in Figure 7, the double cam element 70, 72 may have a rotational axis that is substantially parallel to the rotational axis of the drive shaft 48.
The double cam element 70, 72 is arranged with a substantially cylindrical body having an opening cam 702, 722 and a closing cam 704, 724 side by side. In particular, the double cam element 70, 72 is arranged on one side with an external abutment surface for a bearing defining the opening cam 702, 722 and on the opposite side with an internal abutment surface defining the closing cam 704, 724.
In this case, the rotation of the double cam element 70, 72, together with the sliding of the relevant bearing 36, 361: 38, 381, causes the reciprocating motion of the relative distribution rod 30, 34, thus causing the closure or opening of the relative valve.
Figures 8 and 9 show a detail of the sliding of the bearing with respect to the profile of the closing cam 724.
According to a possible alternative embodiment, only one bearing suitable for sliding in a track between an inner cam and an outer cam may be arranged at the foot of the distribution rod.
According to a possible embodiment, on the external surface of at least one double cam element 70, 72, a double cam element toothed wheel 730 may be implemented that is suitable for engaging with a corresponding shaft toothed wheel 735 arranged on the drive shaft 48 or by means of gears.
The advantages that may be achieved with a distribution apparatus according to the present invention are now apparent.
The distribution apparatus according to the present invention is affected by lower working losses compared to the distribution apparatus of the prior art.
This is due in particular to the fact that the friction involved is only of the rolling and not the sliding type.
Furthermore, the distribution apparatus according to the present invention may have a contained head height, going from about 150 mm of a normal head to about 80 mm.
Furthermore, the distribution apparatus according to the present invention is more balanced than the distribution apparatus of the prior art, since there are no weight components or rotations of elements in the vicinity of the cylinder head. In fact, all of the rotations are arranged at the base of the cylinder.
Furthermore, the distribution apparatus according to the present invention does not use belts or chains and, above all, does not use rocker arms. Consequently, the periodic replacement of a belt or chain need not be performed.
Those skilled in the art will be able to make modifications to the embodiments described above or substitute described elements with equivalent elements, in order to satisfy particular requirements, without departing from the scope of the accompanying claims.

Claims

Distribution apparatus (12) for an engine comprising at least one intake valve (14, 16) and at least one exhaust valve (18, 20); said apparatus comprising movement means (22) for said at least one intake valve (14, 16) and for said at least one exhaust valve (18, 20);
characterized in that said movement means (22) comprise a first crossbow element (24) and a second crossbow element (26) to which said at least one intake valve (14, 16) and said at least one exhaust valve (18, 20) are connected, respectively, arranged in a direction substantially perpendicular to said at least one intake valve (14, 16) and said at least one exhaust valve (18, 20);

said first crossbow element (24) and said second crossbow element (26) being connected at each end (242, 244; 262, 264) with respective heads (282, 302, 322, 342) of distribution rods (28, 30, 32, 34);

said distribution rods (28, 30, 32, 34) being arranged in correspondence with a foot thereof (282, 302, 322, 342), opposite said head (284, 304, 324, 344) with at least one bearing (36, 38);

each of said bearings (36, 38) being in connection with respective cam means (40, 42, 44, 46) suitable to be put into rotation by a drive shaft (48) for moving said at least one intake valve (14, 16) and said at least one exhaust valve (18, 20).
Distribution apparatus (12) according to claim 1, characterized in that it comprises two intake valves (14, 16) and two exhaust valves (18, 20).
Distribution apparatus (12) according to any of the claims 1-2, characterized in that said at least one intake valve (14, 16) and said at least one exhaust valve (18, 20) are arranged on said first crossbow element (24) and said second crossbow element (26) respectively by means of forks (142, 162, 182, 202).
Distribution apparatus (12) according to any of the claims 1-3, characterized in that said at least one intake valve (14, 16) and said at least one exhaust valve (18, 20) are substantially parallel to the respective distribution rods (28, 30, 32, 34).
Distribution apparatus (12) according to any of the claims 1-4, characterized in that said first crossbow element (24) and said second crossbow element (26) have a diameter of between 4 and 6 mm, preferably around 5 mm.
Distribution apparatus (12) according to any of the claims 1-5, characterized in that said first crossbow element (24) and said second crossbow element (26) are made of harmonic titanium.
Distribution apparatus (12) according to any of the claims 1-6, characterized in that said distribution rods (28, 30, 32, 34) are made of a tube.
Distribution apparatus (12) according to claim 7, characterized in that said distribution rods (28, 30, 32, 34) are made of a tube having an outer diameter in the region of 10 mm, and an inner diameter in the region of 8 mm.
Distribution apparatus (12) according to any of the claims 1-8, characterized in that said distribution rods (28, 30, 32, 34) are made of titanium.
Distribution apparatus (12) according to any of the claims 1-9, characterized in that said distribution rods (28, 30, 32, 34) are suitable for moving in alternating rectilinear motion, said rods being guided by a pair of opposite concave bearings (90).
Distribution apparatus (12) according to any of the claims 1-10, characterized in that said cam means (40, 42, 44, 46) comprise, for each bearing (36, 38), an opening cam (402, 422) adapted to interact with the respective bearing (36, 38) to open said at least one intake valve (14, 16) or said at least one exhaust valve (18, 20), and a closing cam (404, 424) adapted to interact with the respective bearing (36, 38) to close said at least one intake valve (14, 16) or said at least one exhaust valve (18, 20).
Distribution apparatus (12) according to claim 11, characterized in that the bearing (36, 38) is interposed between an opening cam (402, 422) adapted to push the bearing (36, 38) towards the engine crankcase, so as to move the valve inside the combustion chamber, and a closing cam (404, 424) adapted to push the bearing (36, 38) in the opposite direction with respect to the engine crankcase, so that it can close.
Distribution apparatus (12) according to any of the claims 11-12, characterized in that said opening cam (402, 422) is provided with a radial protuberance (410), while the closing cam (404, 424) is provided with a radial recess (412) .
Distribution apparatus (12) according to any of the claims 11-13, characterized in that said opening cam (402, 422) and said closing cam (404, 424) are adapted to always be in contact with the respective bearing (36, 38) during the movement thereof.
Distribution apparatus (12) according to any of the claims 11-14, characterized in that each opening cam (402, 422) and each closing cam (404, 424) is keyed to a respective shaft (403, 423, 405, 425), on which a respective cam toothed wheel (406, 407, 426, 427) is also keyed, said distribution apparatus (12) further comprising a central toothed wheel (58) adapted for receiving rotational motion directly or indirectly from the drive shaft (48), said central toothed wheel (58) engaging simultaneously with the four cam toothed wheels (406, 407, 426, 427).
Distribution apparatus (12) according to claim 15, characterized in that the foot (282, 302, 322, 342) of the distribution rods (28, 30, 32, 34) is shaped like a fork so that the bearing (36, 38) can be supported between the prongs of the fork, slotted openings (68) being made on the side profile of the fork suitable to allow the fork to slide with respect to the shafts (403, 423) on which the opening cams (402, 422) are arranged.
Distribution apparatus (12) according to any of the claims 1-10, characterized in that the cam means (42) comprise a double cam element (70, 72) for each distribution rod (28, 30, 32, 34), said double cam element (70, 72) having a rotation axis substantially parallel to the rotation axis of the crankshaft (48), said double cam element (70, 72) being arranged with a substantially cylindrical body having an opening cam (702, 722) and a closing cam (704, 724) side by side; said double cam element (70, 72) being provided on one side with an external abutment surface for a bearing defining the opening cam (702, 722) and on the opposite side with an internal abutment surface defining the closing cam (704, 724) .
Engine comprising a distribution apparatus (12) according to any of the claims 1-17.