EP1180199A1

EP1180199A1 - Valve device for two-stroke engine

Info

Publication number: EP1180199A1
Application number: EP00910972A
Authority: EP
Inventors: Alain Freret
Original assignee: Celtic Sport Developpement
Current assignee: Celtic Sport Developpement
Priority date: 1999-03-16
Filing date: 2000-03-16
Publication date: 2002-02-20
Anticipated expiration: 2020-03-16
Also published as: ATE276433T1; WO2000055479A1; EP1180199B1; FR2791086B1; FR2791086A1; AU3299500A; DE60013809D1

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

Valve device for two-stroke engine.

The field of the invention is that of two-stroke engines, used in particular, but not exclusively, in all-terrain vehicles, motocross motorcycles, snowmobiles. ULMs, etc. More specifically, ^the invention relates to a valve device for two-stroke engine. It is recalled that such a device is intended to be mounted between a carburetor and an intake block, in order to allow the flow of gases in the carburetor direction to intake block, while preventing the passage of gases in the direction reverse. By intake block, we generally mean the cylinders or the engine.

Traditionally, a "V" valve device has been used. qualified aisni due to its profile (see fig.2A). It is now described briefly, in relation to FIGS. 1A. 2A, 3A and 4A. which present views from above, from the side, from the front and from behind respectively. This "V" -shaped device has a substantially triangular prism shape, with two lateral faces 21 and 22 of triangular shape, a front face 23 of rectangular shape, and two upper rear faces 24 and lower 25, also of rectangular shape. A flange 26 surrounds the front face 23 over its entire periphery, so as to allow the fixing of the valve device to the carburetor (not shown), directly or via an intermediate mounting part. This fixing is generally carried out by screws, thanks to openings 27 provided for this purpose in the flange 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 inlet port 28 is formed on the front face 23. It corresponds substantially to any the surface of it. It receives gases from the carburetor. Among the outlet openings, there are two upper outlet openings 29 and 30. and two lower outlet openings 31 and 32. They are formed on the upper rear 24 and lower 25 faces respectively. They allow the flow of gases to the intake block (not shown). Each of the outlet orifices 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). Thus, they flow towards the intake block, in high and low axial directions (see arrows referenced 44 to 46) parallel to the plane 43 of right-left symmetry of the device "in V". 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.

Furthermore, as appears in the front view of FIG. 3A (through the inlet orifice corresponding substantially to the front face 28), the internal cavity has a plurality of internal walls 42. These latter are of angular shape 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 valve device "V", which has just been described above, has many drawbacks.

First of all, it does not allow good diffusion of the gases at the outlet of the valve device. Indeed, with the valve device "V", the flow of gases is done only in high and low axial directions. Indeed, the gas flow takes place forward on the one hand from the top (via the two adjacent upper outlet orifices 29 and 30) and on the other hand from the bottom (via the two adjacent orifices of lower outlets 31 and 32). However, in the intake block, part of the gas must be directed to the sides, via lateral transfer elements.

Consequently, the flow received by the inlet block, along the upper and lower axial directions of gas outlet of the device "in 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 (the gases swirl at the outlet of the device "in V"), and therefore a loss of power 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 inlet flow division of the intake block is even worse, and therefore the loss of engine power is even greater.

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

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

The invention is especially to overcome these different drawbacks of ^the prior art. Specifically, one of ^the objectives of the present invention is to provide a valve device for two-stroke engine, to improve the flow of gases between the carburetor and the intake block, and thus increase the yield in engine power.

The ^invention also aims to provide such a device having no point of turbulence along the gas flow paths defined within the internal cavity.

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

These various objectives, as well as others which will appear subsequently, are achieved according to the invention using a valve device for two-engine time, of the type intended to be mounted between a carburetor and an intake block, and comprising: an internal diffusion cavity, having at least one inlet port, receiving gases from the carburetor, and at least one outlet port , 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 intake block of prevent the passage of gases in the opposite direction.

According to the invention, said internal cavity has at least three outlet orifices, allowing the flow of said gases in at least three distinct directions of flow which are not parallel to each other in pairs. In addition, each of said 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 of gas flow directions. at the outlet of the valve device. In general, these directions of gas flow can be arbitrary. For example, the valve device according to the invention may have, in addition to the high and low axial directions, one or more additional lateral directions, making it possible to predigive part of the gas flow. In this way, the circulation of gases at the inlet and within the intake block is improved, and thereby the efficiency of the engine. In particular, the effect of rotation of the crankshaft on the part of the gas flow predirided in directions distinct from the axial directions is eliminated. Advantageously, said internal cavity comprises a plurality of internal walls, defining at least three separate flow paths, each connecting said at least one inlet orifice to one of said at least three outlet orifices.

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

Preferably. said device has a substantially pyramidal shape, 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 of said at least three outlet orifices.

We understand 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 said at least one inlet orifice is formed, and four faces, coming from said base and on each of which is formed one of four outlet ports. Thus, there are four separate flow directions, such as for example two axial directions, high and low respectively, and two lateral directions, left and right respectively. The two lateral directions make it possible to pre-direct 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 top, with a central bar, corresponding to the junction of the upper edges of two faces from two opposite first sides of said rectangular base, and two lateral bars, corresponding each at the upper edge of one of the two faces from two opposite second sides of said rectangular base. Thus, in this particular embodiment, the valve device according to the present invention can be seen, for simplicity, as the complex combination of a first valve device "V" and two halves of a second valve device "in V", obtained by cutting the latter according to its top-bottom plane of symmetry: each of the two halves being affixed, by its new face resulting from the cut (that is to say after rotation of a quarter of tower around the front-rear plane of symmetry), to one of the lateral faces (of triangular shape) of the first "V-shaped" device.

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

Advantageously, the number of valves is equal to the number of outlet orifices, and each of said at least three outlet orifices is selectively closed by only one of said valves. In this way, the number of outlet orifices and the number of valves are limited, and the turbulence at the outlet of the valve device is thus further reduced, as well as the friction effects of the valves.

Preferably, said internal cavity has axial outlet openings and lateral outlet openings, and the size of said lateral outlet openings is greater than that of said axial outlet openings. In this way, account is taken of the fact that most of the gases (conventionally around 90

%) flow into the side transfer elements of the intake block.

Preferably. the valves closing said axial outlet orifices have a thickness greater than that of the valves closing said lateral outlet orifices. In this way, account is taken of the fact that the valves are not all subjected to the same pressure.

^Other features and advantages of the ^invention will appear on reading the following description of a preferential embodiment of the invention, given by way ^of example and non-restrictively, and the appended 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 present different views. respectively from above, from the side, from the front and from behind, particular embodiment of a valve device according to the present invention. The invention therefore relates to a valve device for a two-stroke engine. In the particular embodiment illustrated in Figures 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 an inlet orifice 6 is formed, and four rear faces (upper 2, lower 3, left 4 and right 5 respectively), coming from base 1 and on which are formed four outlet openings (upper 7, lower 8, left 9 and right 10 respectively). Note that in the front view of Figure 3B. there are partially distinguished, through the inlet orifice 6, the four outlet orifices 7 to 10.

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

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

Each of the outlet ports 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 towards the intake block, according to: on the one hand, the high and low 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" -shaped device; on the other hand, left and right radial directions (see arrows referenced 13 and 13 ', fig. 1B), parallel to the top-bottom plane of symmetry 17 (see fιg.2B) of the "V" -shaped 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 upper 2 and lower rear faces 3. The two side bars 19 and 20 of H each correspond to the upper edge of one of the two left 4 and right 5 rear faces.

Furthermore, as appears in particular in solid lines in the front view of FIG. 3B (through the inlet orifice) and in dotted lines in the top and side views 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 orifice to one of the four outlet orifices.

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

Also optionally, the valves (not shown) closing the upper 7 and lower 8 outlet openings 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 openings left outlet 9 and right 10. The valve device according to the present invention is for example manufactured in the form of a single piece. The material used is for example a 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 to attenuate the effect of vibrations, the various inlet and / or outlet orifices can be fitted with stops (not shown), in rubber or other material.

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

Claims

1. A valve device for a two-stroke engine, of the type intended to be mounted between a carburetor and an intake block, and comprising: an internal diffusion cavity, having at least one inlet orifice (6), 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 towards the gas intake block, and prevent the passage of gases in the opposite direction, characterized in that said internal cavity has at least three outlet orifices (7 to 10), allowing the flow of said gases in at least three separate flow directions (13, 13 ', 15, 16) and not parallel to each other two, and in that each of said at least three outlet orifices is selectively closed by at least one valve.

2. Valve device according to claim 1, characterized in that said internal cavity comprises a plurality of internal walls (50). defining at least three separate flow paths, each connecting said at least one inlet orifice (6) to one of said at least three outlet orifices (7 to 10).

3. Valve device according to claim 2, characterized in that said internal walls (50) have rounded shapes.

4. Valve device according to any one of claims 1 to 3. characterized in that it has a substantially pyramidal shape, with: a polygonal base (1) having at least three sides, and on which said at least is formed an inlet port; at least three faces (2 to 5) from said base, and on each of which is formed one of said at least three outlet orifices.

5. Valve device according to claim 4, characterized in that it has a substantially pyramidal shape, with: a rectangular base (1) on which said at least one inlet orifice (6) is formed; four faces (2 to 5) from said base, and on each of which is formed one of four outlet orifices (7 to 10).

6. Valve device according to any one of claims 4 and 5, characterized in that said pyramidal shape is truncated and has an H-shaped top, with: a central bar (18), corresponding to the junction of the upper edges from two faces (2, 3) from two first opposite sides of said rectangular base (1); two side bars (19, 20), each corresponding to the upper edge of one of the two faces (4, 5) from two opposite second sides of said rectangular base (1).

7. valve device according to any one of claims 1 to 6, characterized in that the number of outlet openings is equal to the number of separate flow directions, and in that each of said at least three outlet openings allows the flow of said gases in one of said directions of flow.

8. Valve device according to any one of claims 1 to 7, characterized in that the number of valves is equal to the number of outlet ports, and in that each of said at least three outlet ports is selectively closed by only one of said valves.

9. Valve device according to any one of claims 1 to 8, characterized in that said internal cavity has axial outlet openings (7, 8) and lateral outlet openings (9, 10), and in that the size of said lateral outlet openings is greater than that of said axial outlet openings.

10. Valve device according to claim 9, characterized in that the valves closing said axial outlet openings (7, 8) have a thickness greater than that of the valves closing said lateral outlet openings (9, 10).