EP1180199B1 - Valve device for two-stroke engine - Google Patents

Abstract

The invention concerns a valve device for a two-stroke engine, designed to be mounted between a carburettor and an induction unit, and comprising an inner diffusion cavity, having at least an inlet (6), for receiving gases coming from the carburettor, and at least an outlet, enabling said gases to flow towards the induction unit; and at least a valve, selectively closing said at least outlet so as to allow through the gases in the direction from the carburettor towards induction unit, and prevent the gases flowing through in the opposite direction. The invention is characterised in that said inner cavity has at least three outlets (7 to 10), allowing said gases to flow in at least three separate and non-parallel directions (13, 13', 15, 16) in pairs. Moreover, each of said three outlets is selectively closed by at least one valve.

Description

The field of the invention is that of two-stroke engines, used in particular, but not exclusively, in all-terrain vehicles, motorcycles motocross, snowmobiles, U.L.M., etc.

More precisely. the invention relates to a valve device for an engine in two stages. Remember that such a device is intended to be mounted between a carburetor and an intake block, to allow the flow of gases in the carburetor direction to intake block, while preventing gas passage In the opposite way. By intake block, we generally mean cylinders or the low engine.

Examples of such devices are described in particular in documents US-A-3 412 754 and DE-A-43 04 892.

Traditionally, we use a valve device "V", qualified aisni because of its profile (see fig. 2A). It is now described briefly, in relation with FIGS. 1A, 2A, 3A and 4A, which show views from above, from the side, of front and back respectively.

This "V" device has a substantially prism-based form triangular, with two lateral faces 21 and 22 of triangular shape, one face front 23 rectangular, and two upper rear faces 24 and lower 25, also of rectangular shape. A flange 26 surrounds the front face 23 all around, so that the valve device can be attached to the carburetor (not shown), directly or via a mounting part intermediate. This fixing is generally carried out by screws, thanks to openings 27 provided for this purpose in the collar 26.

The interior of the prism constitutes an internal gas diffusion cavity, having an inlet port 28 and four outlet ports 29 to 32. The port inlet 28 is formed on the front face 23. It corresponds substantially to all of the surface of it. It receives gases from the carburetor. Among the orifices there are two upper outlet ports 29 and 30, and two ports lower outlet 31 and 32. They are formed on the upper rear faces 24 and lower 25 respectively. They allow the flow of gases to the block of admission (not shown).

Each of the outlet ports 29 to 32 is selectively closed by a valve 33 to 36. The valves are held on one of their sides by flaps 39 and 40, themselves fixed to the upper rear 24 and lower 25 faces by screws 41. In operation, the gases from the carburetor pass through the internal cavity and lift the valves (see arrows referenced 37 and 38). So they flow to the intake block in high and low axial directions (see arrows referenced 44 to 46) parallel to plane 43 of right-left symmetry of the "V" device. On the other hand, in the opposite direction, the gases coming from the block intake, which cannot lift the valves, remain blocked without being able flow to the carburetor.

Furthermore, as appears in the front view of Figure 3A (at through the inlet orifice corresponding substantially to the front face 28), the cavity internal has a plurality of internal walls 42. The latter have the form angular and define four separate flow paths, each connecting the inlet port 28 to one of the four outlet ports 29 to 32.

It turns out that the "V" valve device, which has just been described above, has many disadvantages.

First of all, it does not allow good diffusion of the gases leaving the valve device.

Indeed, with the valve device "V", the gas flow is done only in high and low axial directions. Indeed, the flow gas is carried forward on the one hand from above (via the two orifices adjacent upper exit 29 and 30) and secondly from below (via the two adjacent lower outlet ports 31 and 32).

However, in the intake block, part of the gases must be directed to the sides, via lateral transfer elements.

Therefore, the flow received by the intake block, according to the directions high and low axial gas outlet of the device "V", must be divided into a central flow and at least two lateral flows. Such a division of the flow unfortunately causes turbulence in the intake block (gases swirl at the output of the device "in V"), and therefore a loss of power of the engine. This loss of power becomes all the more important in motorized competitions. where the slightest gain in engine power can be a decisive advantage for competitors.

In addition, the rotation of the crankshaft (located, within the engine, downstream) disturbs the gases directed according to the central flow and therefore increases the vortex effect at the output of the "V" device. The flow division at the inlet of the intake block is even worse, and therefore the loss of engine power is even bigger.

Furthermore, due to the angular shape of the internal walls of the cavity of diffusion of the device "in V", points of turbulence appear along flow paths defined by these walls.

We also know a valve device "W", obtained by superposition of two "V" valve devices. This "W" device presents the same drawbacks as that "in V" described above, since the flow gas is only done in high and low, parallel axial directions to the right-left plane of symmetry of the "V" device. It will therefore not be described in detail here.

The invention particularly aims to overcome these different disadvantages of the state of the art.

More specifically, one of the objectives of the present invention is to provide a valve device for a two-stroke engine, making it possible to improve the gas flow between the carburetor and the intake block. and so increase the engine power output.

The invention also aims to provide such a device does not showing no turbulence along the gas flow paths defined within its internal cavity.

Another object of the invention is to provide such a device allowing to reduce the friction effects of the valves.

• une cavité interne de diffusion, présentant au moins un orifice d'entrée. recevant des gaz provenant du carburateur. et au moins un orifice de sortie, permettant l'écoulement desdits gaz vers le bloc d'admission ;
• au moins un clapet, permettant l'obturation sélective dudit au moins un orifice de sortie, de façon à permettre le passage des gaz dans le sens carburateur vers bloc d'admission de gaz, et empêcher le passage des gaz dans le sens inverse.

These various objectives, as well as others which will appear subsequently, are achieved according to the invention using a valve device for a two-stroke engine, of the type intended to be mounted between a carburetor and a block of admission, including:

• an internal diffusion cavity, having at least one inlet orifice. receiving gas from the carburetor. and at least one outlet, allowing the flow of said gases to the intake block;
• at least one valve, allowing the selective closure of said at least one outlet orifice, so as to allow the passage of gases in the carburetor direction to gas intake block, and prevent the passage of gases in the opposite direction.

According to the invention. said internal cavity has at least three outlet orifices, allowing said gases to flow in at least three directions of flow distinct and not parallel to each other two by two. In addition, each of said at at least three outlet orifices is selectively closed by at least one valve.

The general principle of the invention therefore consists in increasing the number gas flow directions, at the outlet of the valve device. In a manner generally, these gas flow directions can be arbitrary. Through example. the valve device according to the invention may have, in addition to the top and bottom axial directions, one or more additional directions lateral (s), allowing to pre-direct part of the gas flow. In this way, we improves the circulation of gases at the inlet and within the intake block, and thereby even the efficiency of the engine. In particular, the rotation effect of the crankshaft on the part of the gas flow pre-directed in separate directions axial directions.

Advantageously, said internal cavity comprises a plurality of internal walls, defining at least three distinct flow paths, connecting each said at least one inlet port to one of said at least three inlet ports exit.

Advantageously, said internal walls have shapes rounded. In this way, the formation of turbulence points is avoided as well as the friction effects of the valves. The yield of the engine.

Preferably, said device has a shape that is substantially pyramidal, with: on the one hand, a polygonal base, having at least three sides, and on which said at least one inlet orifice is formed; And on the other hand, at least three faces from said base, and on each of which is formed one said at least three outlet ports.

It is understood that the total number of directions of flow is equal in this case to the number of sides of the polygonal base, and therefore also to the number of faces from this base.

In a preferred embodiment of the invention, said device has a substantially pyramidal shape, with a rectangular base, on which is formed said at least one inlet, and four faces, from said base and on each of which is formed one of four outlet orifices. Thus, there are four distinct directions of flow, such as by example two axial directions. high and low respectively, and two directions lateral, left and right respectively. The two lateral directions allow pre-directing the gases, at the outlet of the valve device. towards lateral transfer elements of the intake block.

Preferably, said pyramidal shape is truncated and has an H-shaped apex, with a central bar, corresponding to the junction upper edges of two faces from two opposite first sides of said rectangular base, and two side bars, each corresponding to the edge upper of one of the two faces from two opposite second sides of said rectangular base. So. in this particular embodiment, the device to valves according to the present invention can be seen, for simplification, as the complex combination of a first "V" valve device and two halves a second valve device "V", obtained by cutting the latter according to its plane of symmetry up-down: each of the two halves being affixed, by its new face resulting from the cut (i.e. after a quarter turn rotation around the front-rear plane of symmetry), at one of the side faces (shaped triangular) of the first "V" device.

Advantageously, the number of outlet openings is equal to the number separate flow directions, and each of said at least three orifices of outlet allows the flow of said gases in one of said directions flow.

Advantageously, the number of valves is equal to the number of orifices of outlet, and each of said at least three outlet ports is selectively closed by only one of said valves.

In this way, the number of outlet openings and the number of valves, and the turbulence at the outlet of the valve device is therefore further reduced, as well as the effects of friction of the valves.

Preferably, said internal cavity has outlet orifices axial and lateral outlet openings, and the size of said outlet openings lateral is greater than that of said axial outlet orifices. In this way, we takes into account that most of the gases (typically around 90 %) flow into the side transfer elements of the intake block.

Preferentially. the valves closing said axial outlet orifices have a thickness greater than that of the valves closing said orifices of side outlet. In this way, it is taken into account that the valves do not undergo not all the same pressure.

• les figures 1A, 2A, 3A et 4A présentent différentes vues. respectivement de dessus, de côté, de devant et de derrière, d'un dispositif à clapets "en V" selon l'art antérieur ;
• les figures 1B, 2B, 3B et 4B présentent différentes vues, respectivement de dessus, de côté, de devant et de derrière, d'un mode de réalisation particulier d'un dispositif à clapets selon la présente invention.

Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of non-limiting example, and the accompanying drawings, in which:

• Figures 1A, 2A, 3A and 4A show different views. respectively from above, from the side, from the front and from behind, of a "V" valve device according to the prior art;
• Figures 1B, 2B, 3B and 4B show different views, respectively from above, from the side, from the front and from behind, of a particular embodiment of a valve device according to the present invention.

The invention therefore relates to a valve device for two-engine time.

In the particular embodiment illustrated in FIGS. 1B, 2B, 3B and 4B, this device has substantially the shape of a truncated pyramid. This pyramid has a rectangular base (or front face) 1, on which is formed an inlet 6, and four rear faces (upper 2, lower 3, left 4 and right 5 respectively), from base 1 and on which are formed four outlet ports (upper 7, lower 8, left 9 and right 10 respectively). Note that in the front view of Figure 3B, there are partially, through the inlet 6, the four outlet 7 to 10.

A flange 11 surrounds the front face 1 around its entire periphery (or made integral part thereof), so as to allow the attachment of the device to valves on the carburetor (not shown), directly or via a piece of intermediate mounting. This fixing is generally carried out by screws, thanks to openings 12 provided for this purpose in the collar.

The pyramid includes an internal gas diffusion cavity. connecting the inlet 6 to the four outlet ports 7 to 10. The inlet receives the gas from the carburetor. The outlet ports allow the flow of gas to the intake block (not shown).

• d'une part des directions axiales haute et basse (cf flèches référencées 15 et 16, fig.1B et 2B), parallèles au plan de symétrie droite-gauche 14 (cf fig.1B) du dispositif "en V" ; d'autre part des directions radiales gauche et droite (cf flèches référencées 13 et 13', fig.1B), parallèles au plan de symétrie haut-bas 17 (cf fig.2B) du dispositif "en V".

Each of the outlet openings 7 to 10 is selectively closed by a valve (not shown, for the sake of simplification of the figures). Conventionally, the valves are held on one of their sides by flaps (not shown) (or any other fixing means), themselves fixed to the rear faces 2 to 5. In operation, the gases coming from the carburetor pass through the internal cavity and lift the valves. Thus, the gases flow to the intake block, according to:

• on the one hand, the upper and lower axial directions (see arrows referenced 15 and 16, fig.1B and 2B), parallel to the right-left plane of symmetry 14 (see fig.1B) of the "V"device; on the other hand, left and right radial directions (see arrows referenced 13 and 13 ', fig.1B), parallel to the up-down plane of symmetry 17 (see fig.2B) of the "V" device.

On the other hand, in the opposite direction, the gases coming from the intake block, which cannot lift the valves, remain blocked without being able to flow towards the carburetor.

The top of the pyramid is H-shaped (see fig.4B). The central bar 18 du H corresponds to the junction of the upper edges of the two rear faces upper 2 and lower 3. The two side bars 19 and 20 of the H each correspond to the upper edge of one of the two left rear faces 4 and right 5.

Furthermore, as appears in particular in full line on the view of in front of Figure 3B (through the inlet) and dotted on the views of above and from the side of FIGS. 2B and 1B, the internal cavity comprises a plurality of internal walls 50. The latter have rounded shapes and define four separate flow paths, each connecting the inlet to one of the four outlet ports.

Optionally, the two upper 7 and lower 8 outlet ports (or axial) are smaller than that of the two left outlet ports 9 and right 10 (or lateral).

Also optionally, the valves (not shown) closing the upper outlet 7 and lower outlet 8 have a thickness (for example equal to 0.42 mm) greater than that (for example equal to 0.38 mm) of the valves closing the left 9 and right 10 outlet ports.

The valve device according to the present invention is for example manufactured as a single piece. The material used is for example quality aluminum, meeting international standard 6060 or 6061, so as to have sufficient resistance to deformation and marking caused by the valves. It is clear, however, that other materials can also be used, such as for example baked or molded resins.

In order to perfect the sealing of the valves and reduce the effect of vibrations, the different inlet and / or outlet orifices can be fitted with stops (not shown), rubber or other material.

It is clear that many other embodiments of the invention can be considered. One can in particular provide a form other than pyramidal and outflow directions other than front, rear, left and right. We can also provide shapes and / or numbers different from inlet and / or outlet and / or valves.

Claims (7)

1. Flap valve device for a two-stroke engine, of the type which is designed to be fitted between a carburettor and an intake unit, and comprising:

   an internal diffusion cavity, which has at least one intake opening (6) which receives gases obtained from the carburettor, and at least one outlet opening, which permits the flow of the said gases to the intake unit;

   at least one flap valve, which permits selective shutting of the said at least one outlet opening, such as to permit passage of the gases in the direction from the carburettor to the gas intake unit, and to prevent passage of the gases in the inverse direction,

   the said internal cavity having at least three outlet openings (7 to 10) which permit flow of the said gases in at least three distinct directions of flow (13, 13', 15, 16) which are not parallel to one another in pairs, each of the said at least three outlet openings being shut selectively by at least one flap valve, the said flap valve device having a substantially pyramid form with a rectangular base (1), in which the said at least one intake opening (6) is provided, and four surfaces (2 to 5) obtained from the said base, and in each of which one of four outlet openings is provided (7 to 10),
   characterised in that the said pyramid form is truncated, and has a summit in the form of an "H", with:

   a central bar (18) which corresponds to the junction of the upper edges of two surfaces (2,3) obtained from two first opposite sides of the said rectangular base (1);

   two lateral bars (19,20), each of which corresponds to the upper edge of one of the two surfaces (4,5) obtained from two second opposite sides of the said rectangular base (1).
2. Flap valve device according to claim 1, characterised in that the said internal cavity comprises a plurality of internal walls (50) which define at least three distinct flow paths, each of which connects the said at least one intake opening (6) to one of the said at least three outlet openings (7 to 10).
3. Flap valve device according to claim 2, characterised in that the said internal walls (50) have rounded forms.
4. Flap valve device according to any one of claims 1 to 3, characterised in that the number of outlet openings is equal to the number of distinct directions of flow, and in that each of the said at least three outlet openings permits the flow of the said gases in one of the said directions of flow.
5. Flap valve device according to any one of claims 1 to 4, characterised in that the number of flap valves is equal to the number of outlet openings, and in that each of the said at least three outlet openings is shut selectively by a single one of the said flap valves.
6. Flap valve device according to any one of claims 1 to 5, characterised in that the said internal cavity has axial outlet openings (7,8) and lateral outlet openings (9,10), and in that the size of the said lateral outlet openings is greater than that of the said axial outlet openings.
7. Flap valve device according to claim 6,
   characterised in that the flap valves which close the said axial outlet openings (7,8) have a thickness which is greater than that of the flap valves which close the said lateral outlet openings (9,10).

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