EP0459848A1 - Improvements in two-stroke internal combustion engine of the reciprocating piston type - Google Patents

Abstract

The two-stroke engine, with distribution by intake and exhaust valves (10, 15), comprises a combustion and sweep prechamber (6) having substantially a shape of revolution around an axis (YY) and provided an intake valve seat (7). Deflector or blading means (17) are arranged inside the intake duct (13), as directly as possible upstream of the seat (7), so as to expel the mass of air inside the combustion chamber (2) in the manner of a slingshot.

Description

The invention relates to reciprocating internal combustion engines, of the two-stroke type, with distribution by intake and exhaust valves, and with combustion and sweep prechamber, whether they are with spark ignition or with spark ignition. compression.

• a) en augmentant la perméabilité du cylindre, c'est-à-dire en laissant passer le débit d'air requis par le moteur, sous une différence de pression entre admission et échappement et/ou avec une durée d'ouverture simultanée des soupapes d'admission et d'échappement qui soient aussi petites que possible ;
• b) en diminuant le court-circuit d'air entre l'admission et l'échappement, grâce à une orientation du courant des particules d'air frais entrant dans le cylindre qui les empêche de passer directement de l'admission à l'échappement, ce qui améliore le rendement de balayage ;
• c) en empêchant autant que possible l'air frais admis au cours d'un cycle dans le cylindre de se mélanger, pendant le balayage, aux gaz brûlés provenant du cycle précédent et quittant le cylindre à travers le ou les orifices d'échappement ; et
• d) pour un moteur à combustion non homogène et à allumage par compression, en créant dans la chambre de combustion d'intenses mouvements d'air bien synchronisés avec l'injection de carburant pour améliorer le mélange entre air et carburant.

In modern engines of this type, efforts are generally made to improve operation.

• a) by increasing the permeability of the cylinder, that is to say by letting pass the air flow required by the engine, under a pressure difference between intake and exhaust and / or with a duration of simultaneous opening of the valves intake and exhaust that are as small as possible;
• b) by reducing the short circuit of air between the intake and the exhaust, thanks to an orientation of the current of the particles of fresh air entering the cylinder which prevents them from passing directly from the intake to the exhaust, which improves the sweeping efficiency;
• c) by preventing as much as possible the fresh air admitted during a cycle into the cylinder from mixing, during the sweeping, with the burnt gases originating from the preceding cycle and leaving the cylinder through the exhaust port (s); and
• d) for a non-homogeneous combustion engine with compression ignition, by creating in the combustion chamber intense air movements well synchronized with the injection of fuel to improve the mixture between air and fuel.

In order to ensure centrifugal stratification of the combustion, it has already been proposed, in document US-A-4,224,905, to organize the circulation of the air admitted into the cylinder in such a way that this air performs at each cycle, inside the cylinder, a helical movement around an axis practically coincident with that of the cylinder but the construction proposed in this document is complicated because it requires to open the prechamber tangentially in the cylinder, so that air is introduced tangentially in the plane of the cylinder head, and to provide a central exhaust valve and an intake valve directly supplying the prechamber, as well as in general two additional intake valves opening in the cylinder and placed on either side of the central exhaust valve.

The invention aims to organize a circulation helical air intake into the cylinder, which simultaneously ensures the reduction of the air short circuit and the formation of a vortex in the combustion chamber. Another object of the invention is to arrange a two-stroke reciprocating engine with valve distribution in such a way that criterion b) defined above is particularly well respected, and this by moving the particles of fresh air introduced into the cylinder, taking into account the orientation of the paths imposed on these particles. The invention also aims to improve the two-stroke engines described in French patent No. 85 19506 of December 31, 1985, which was published under No. 2,592,430 and which will be chosen below to define the state of the art.

• au moins un cylindre dépourvu de lumières latérales;
• une chambre de combustion limitée dans ce cylindre par une culasse fixe par rapport à ce cylindre et par un piston animé d'un mouvement alternatif à l'intérieur de ce cylindre ;
• une préchambre de combustion et de balayage ménagée dans la culasse, munie d'un siège de soupape d'admission et communiquant avec la chambre de combustion par un canal de transfert dont la section droite perpendiculaire à l'axe du cylindre, au débouché dans la chambre de combustion, est une surface oblongue sensiblement tangente intérieurement à la paroi intérieure du cylindre ;
• une soupape d'admission d'axe au moins approximativement orthogonal à l'axe du cylindre et de préférence sécant avec ce dernier axe, disposée de façon telle que la tige de cette soupape soit plus éloignée de ce dernier axe que la tête de celle-ci et que cette tête puisse se déplacer à l'intérieur de ladite préchambre en vue de s'écarter et de se rapprocher du susdit siège de soupape d'admission ;
• un conduit d'admission qui aboutit directement en amont du susdit siège ; et
• au moins une soupape d'échappement disposée de façon telle que son axe soit au moins approximativement parallèle à l'axe du cylindre et qu'elle puisse coopérer, en laissant passer les gaz d'échappement sur la majeure partie au moins de sa périphérie, avec un siège de soupape d'échappement ménagé dans le ciel de la culasse à l'opposé du canal de transfert, ce dernier siège étant de préférence agencé de telle façon que la surface transversale de la tête du piston ne laisse subsister au point mort haut que le jeu de fonctionnement nécessaire avec la soupape d'échappement et le ciel de la culasse,

   caractérisé en ce que la préchambre, en dehors de son raccord avec le canal de transfert, a sensiblement une forme de révolution autour d'un axe parallèle à l'axe de la soupape d'admission, et de préférence pratiquement confondu avec ce dernier axe ou légèrement décalé par rapport à celui-ci ;
   en ce que des moyens déflecteurs, disposés à l'intérieur de la partie terminale du conduit d'admission, c'est-à-dire aussi directement que possible en amont du siège de la soupape d'admission, sont agencés de façon à produire une déflexion dans un seul sens, autour de l'axe de ladite soupape, de la masse d'air qui arrive par ce conduit lorsque cette soupape est ouverte ;
   et en ce que le canal de transfert a une forme telle, d'une part, que la déflexion ainsi produite dans la préchambre par les moyens déflecteurs pendant la phase de balayage engendre un tourbillon sensiblement hélicoïdal dans le cylindre et, d'autre part, que lors de la remontée du piston, ledit tourbillon sensiblement hélicoïdal engendre à son tour dans la préchambre un tourbillon dans le même sens.To this end, the invention relates to a two-stroke internal combustion engine, which comprises:

• at least one cylinder without side lights;
• a combustion chamber limited in this cylinder by a cylinder head fixed relative to this cylinder and by a piston driven by a reciprocating movement inside this cylinder;
• a combustion and sweeping prechamber provided in the cylinder head, fitted with an intake valve seat and communicating with the combustion chamber by a transfer channel whose cross section perpendicular to the axis of the cylinder, at the outlet in the combustion chamber, is a oblong surface substantially tangent internally to the interior wall of the cylinder;
• an inlet valve with an axis at least approximately orthogonal to the axis of the cylinder and preferably intersecting with this latter axis, arranged in such a way that the stem of this valve is more distant from this latter axis than the head thereof. ci and that this head can move inside said prechamber in order to move away and approach the aforesaid intake valve seat;
• an intake duct which terminates directly upstream of the above-mentioned seat; and
• at least one exhaust valve arranged in such a way that its axis is at least approximately parallel to the axis of the cylinder and that it can cooperate, allowing the exhaust gases to pass over at least most of its periphery, with an exhaust valve seat arranged in the headspace of the cylinder head opposite the transfer channel, the latter seat preferably being arranged in such a way that the transverse surface of the piston head does not allow the top dead center to remain that the operating clearance required with the exhaust valve and the headliner,

characterized in that the prechamber, apart from its connection with the transfer channel, has substantially a shape of revolution around an axis parallel to the axis of the intake valve, and preferably practically coincident with the latter axis or slightly offset from it;
in that deflector means, arranged inside the terminal part of the intake duct, that is to say as directly as possible upstream of the seat of the intake valve, are arranged so as to produce a deflection in one direction, around the axis of said valve, of the mass of air which arrives via this duct when this valve is open;
and in that the transfer channel has a shape such, on the one hand, that the deflection thus produced in the prechamber by the deflector means during the scanning phase generates a substantially helical vortex in the cylinder and, on the other hand, that during the raising of the piston, said substantially helical vortex in turn generates in the prechamber a vortex in the same direction.

In other words, it can be said that the vortex induced in the cylinder during scanning generates a vortex in the prechamber during the compression phase. We therefore find ourselves in the presence of a vortex generated in the prechamber for the combustion phase and which does not reverse during expansion, unlike known structures such as the "RICARDO" prechamber.

The aforementioned deflector means, which can be constituted by the actual drawing of the intake duct upstream of the seat but which are preferably constituted by blades, can be linked either to the intake valve being disposed with clearance inside the end part of the intake duct, this intake valve then comprising guide means preventing it from turning on itself, either at the seat of the valve intake by loosely surrounding the stem of this valve.

The prechamber preferably has a height (that is to say a dimension parallel to said axis) which is substantially equal to the stroke of the intake valve. It is advantageous, although not necessary, to give the assembly of the prechamber and the transfer channel a shape which is substantially symmetrical with respect to the plane passing through the axis of the cylinder and through the axis of the intake and give the transfer channel a shape which facilitates the generation of the vortex in the cylinder during scanning as well as the induction of a vortex in the prechamber during compression.

It should be noted that, unlike the above document US-A-4,224,905, the introduction of air into the cylinder is not tangential with a central intake valve but the air particles thus introduced are directed downwards obliquely so as to deflect their trajectory and to move them away from the vicinity of the exhaust.

As will be explained in more detail below with the aid of the drawings, the engine according to the invention does indeed achieve the aims which had been assigned to it.

• les figures 1 à 3 représentent schématiquement un moteur conforme à l'invention dans les positions occupées par le piston et les soupapes lors du balayage, respectivement en perspective et, à plus petite échelle, en coupe par le plan P (figure 3) passant par les axes du cylindre et des soupapes d'admission et d'échappement et par un plan perpendiculaire à ce dernier plan ;
• les figures 4 à 6 sont des vues semblables à celle de la figure 1 mais correspondant respectivement à la compression, à la combustion et à la détente ;
• la figure 7 représente schématiquement la culasse du moteur vue par le dessous de la figure 2 ;
• les figures 8 et 9 représentent schématiquement un système d'alimentation en combustible établi selon une première variante, respectivement par une vue analogue à une partie de la figure 2 et en coupe selon la ligne IX-IX de la figure 8; et
• les figures 10 et 11 représentent schématiquement un système d'alimentation en combustible établi selon une deuxième variante, respectivement par des vues analogues à celles des figures 8 et 9, la figure 11 étant une vue en coupe selon la ligne XI-XI de la figure 10.

The invention will now be described in more detail. using these drawings including:

• Figures 1 to 3 schematically represent an engine according to the invention in the positions occupied by the piston and the valves during scanning, respectively in perspective and, on a smaller scale, in section through the plane P (Figure 3) passing through the axes of the cylinder and of the intake and exhaust valves and by a plane perpendicular to this latter plane;
• Figures 4 to 6 are views similar to that of Figure 1 but corresponding respectively to compression, combustion and expansion;
• FIG. 7 schematically represents the cylinder head of the engine seen from below of FIG. 2;
• Figures 8 and 9 schematically represent a fuel supply system established according to a first variant, respectively by a view similar to a part of Figure 2 and in section along the line IX-IX of Figure 8; and
• Figures 10 and 11 schematically represent a fuel supply system established according to a second variant, respectively by views similar to those of Figures 8 and 9, Figure 11 being a sectional view along line XI-XI of the figure 10.

• au moins un cylindre 1 dépourvu de lumières latérales ;
• une chambre de combustion 2 limitée dans le cylindre 1 par une culasse 3 fixe par rapport au cylindre 1 et par la surface transversale 5 d'un piston 4 animé d'un mouvement alternatif à l'intérieur de ce cylindre 1 ;
• une préchambre de combustion et de balayage 6 ménagée dans la culasse 3, munie d'un siège de soupape d'admission 7 (figure 2) et communiquant avec la chambre de combustion 2 par un canal de transfert 8 dont la section perpendiculaire à l'axe X-X du cylindre 1, au débouché dans la chambre de combustion 2, est une surface oblongue 9 sensiblement tangente intérieurement à la paroi intérieure du cylindre 1 à peu près parallèlement à la grande dimension de cette surface oblongue, comme le montre la figure 7;
• une soupape d'admission 10, d'axe Y-Y au moins approximativement orthogonal à l'axe X-X du cylindre 1 et de préférence sécant avec ce dernier axe X-X, cette soupape d'admission 10 étant disposée de façon telle que sa tige 11 soit plus éloignée de l'axe X-X que la tête 12 de cette soupape 10 et que cette tête 12 puisse se déplacer à l'intérieur de la préchambre 6 en vue de s'écarter et de se rapprocher du susdit siège 7 ;
• un conduit d'admission 13 qui aboutit directement en amont du siège 7,
• au moins une soupape d'échappement 15 disposée de façon telle que son axe Z-Z sont au moins approximativement parallèle à l'axe X-X du cylindre 1 et qu'elle puisse coopérer, en laissant passer les gaz d'échappement sur la majeure partie au moins de sa périphérie, avec un siège 16 ménagé dans le ciel de la culasse 3 à l'opposé du canal de transfert 8, ce dernier siège 16 étant de préférence agencé de telle façon que la surface transversale 5 de la tête du piston 4 ne laisse subsister au point mort haut (figure 5) que le jeu de fonctionnement nécessaire avec la soupape d'échappement 15 et le ciel de la culasse 3, la soupape d'échappement 15 ou l'ensemble des soupapes d'échappement (quand il en existe plus d'une) étant de préférence au moins approximativement symétrique par rapport au plan P (figure 3) passant par l'axe X-X du cylindre 1 et par l'axe Y-Y de la soupape d'admission 10. Il est à noter que ce plan P est confondu avec celui de la figure 2.

The engine shown in Figures 1 to 3 includes:

• at least one cylinder 1 devoid of side lights;
• a combustion chamber 2 limited in the cylinder 1 by a cylinder head 3 fixed relative to cylinder 1 and by the transverse surface 5 of a piston 4 driven by a reciprocating movement inside this cylinder 1;
• a combustion and sweeping prechamber 6 formed in the cylinder head 3, provided with an intake valve seat 7 (FIG. 2) and communicating with the combustion chamber 2 by a transfer channel 8 whose section perpendicular to the axis XX of the cylinder 1, at the outlet in the combustion chamber 2, is an oblong surface 9 substantially tangent internally to the internal wall of the cylinder 1 roughly parallel to the large dimension of this oblong surface, as shown in FIG. 7;
• an intake valve 10, of axis YY at least approximately orthogonal to the axis XX of the cylinder 1 and preferably intersecting with the latter axis XX, this intake valve 10 being arranged so that its stem 11 is more distant from the axis XX that the head 12 of this valve 10 and that this head 12 can move inside the prechamber 6 in order to move away from and approach the above-mentioned seat 7;
• an intake duct 13 which terminates directly upstream of the seat 7,
• at least one exhaust valve 15 arranged so that its axis ZZ are at least approximately parallel to the axis XX of the cylinder 1 and that it can cooperate, allowing the exhaust gases to pass over the at least most of its periphery, with a seat 16 formed in the sky of the cylinder head 3 opposite the transfer channel 8, the latter seat 16 preferably being arranged in such a way that the transverse surface 5 of the head of the piston 4 leaves at top dead center (FIG. 5) only the operating clearance required with the exhaust valve 15 and the head of the cylinder head 3, the exhaust valve 15 or all of the exhaust valves ( when there is more than one) preferably being at least approximately symmetrical with respect to the plane P (FIG. 3) passing through the axis XX of the cylinder 1 and through the axis YY of the intake valve 10. It is it should be noted that this plane P is confused with that of FIG. 2.

An engine as described hitherto with reference to the figures is known from the above-mentioned French patent n ° 85 19506.

However, in accordance with the invention, the prechamber 6 is given, apart from its connection with the transfer channel 8, substantially a form of revolution around an axis parallel to the axis YY of the intake valve. 10 and preferably practically coincident with the latter axis YY or slightly offset with respect thereto and there is arranged inside the terminal part of the intake duct 13, that is to say as directly as possible in upstream of the seat 7, deflector means 17 arranged so as to produce a deflection in one direction, around the axis YY, of the mass of air which arrives via the duct 13 when the inlet valve 10 is open.

In addition, the transfer channel 8 has a shape such, on the one hand, that the deflection thus produced in the prechamber 6 by the deflector means 17 during the scanning phase generates a substantially helical vortex in the cylinder 1 and, on the other hand, that, during the raising of the piston 4, said substantially helical vortex in turn generates in the pre-chamber 6 a vortex in the same direction.

Although they may be constituted by a particular geometry, in particular a helical or "corkscrew" shape, of the intake duct 13, the deflector means 17 are generally constituted by blades and can in this case be linked either to the valve 10 (solution not shown) while being disposed with clearance inside the terminal part of the intake duct 13, in which case the valve 10 comprises guide means preventing it from turning on itself, either at seat 7, with clearance around rod 11 of valve 10 as shown diagrammatically in FIG. 2.

The assembly of the prechamber 6 and the transfer channel 8 preferably has a shape that is substantially symmetrical with respect to a plane parallel to the axis XX of the cylinder 1 and passing through the axis YY of the intake valve 10, preference over plane P.

Preferably, there is associated with cylinder 1 only one exhaust valve 15. Finally, the surface transverse 5 of the piston 4 and the head of the cylinder head 3 are preferably planes (subject to the groove or grooves 20 which will be discussed below) and perpendicular to the axis XX of the cylinder 1.

The lips of the transfer channel 8 are advantageously organized in such a way that the air jet emerging from the prechamber 6 towards the cylinder 1 makes an angle A of the order of 30 ° with the plane parallel to the axis XX of the cylinder 1 and passing through the axis YY of the intake valve 10 (see FIG. 3). This angle A obviously depends on the rate of deflection of the mass of air passing through the seat 7 of the intake valve 10 after having passed the deflector means 17 as well as the shape of the transfer channel 8. This angle will preferably evolve in a opposite direction to that of the stroke / bore ratio. If this angle A is too high, the paths of the air particles do not penetrate far enough into the combustion chamber 2 towards the piston 4 and remain too close to the exhaust port (s), which tends to cause passage direct from the exhaust intake, to the detriment of the quality of the sweep. Conversely, if this angle A is too small, the air particles tend to be returned by the piston 4 to the exhaust port (s), which produces the same harmful effect. The optimal situation is in the vicinity of an angle of 30 ° for a stroke / bore ratio of the order of 1.25.

As shown in Figure 3, the transfer channel 8 has preferably a shape converging towards its outlet in the cylinder 1 and, more preferably, substantially symmetrical with respect to the above-mentioned plane parallel to the axis XX of the cylinder 1 and passing through the axis YY of the intake valve 10, and flourishes at its connection with cylinder 1, thus preferably having a Ω profile.

The geometry of the intake valve 10 prevents it from being put in place by the head of the cylinder head 3. It is therefore advisable, in known manner, to associate with this intake valve 10 a chapel 21 (FIG. 2) allowing it to be put in place with its seat 7 by crossing the cylinder head 3 (that is to say from right to left according to FIG. 2).

As shown in FIG. 7, it is advantageous to provide in the piston 4 or, preferably, in the part of the cylinder head 3 which is external to the outlet (or oblong surface) 9 of the transfer channel 8 and to the seat 16 of the exhaust valve 15, at least one groove 20 which leads to the outlet 9 and the cross section and / or depth of which decrease as one moves away from this outlet 9. This groove (as shown in solid lines) or each of these grooves (as shown in solid lines and broken lines) advantageously has the shape of a semi-crescent.

In the case of a compression-ignition engine, the injection port (s) 18 can be placed in the prechamber 6, either on the side wall thereof, opposite the intake valve 10 and preferably distributed on at least one circle centered on the axis of the prechamber 6, or on the peripheral wall thereof.

According to the first solution, there may be only one annular injection orifice 18 centered on the axis of the prechamber, as shown diagrammatically in FIG. 2, or else a plurality of orifices distributed over a centered circle on the axis of the prechamber and oriented radially towards the periphery thereof, as shown diagrammatically in FIG. 5. But it seems preferable, in order to increase the distance offered to the fuel between the orifice (s) 18 and the wall, as shown in FIGS. 8 and 9, to provide several injection orifices 18, for example eight in number, advantageously distributed along one (as shown) or several circles C preferably centered on the axis of the prechamber 6. These injection orifices are advantageously oriented towards the periphery of the prechamber 6, as appears from FIG. 8 in the manner of one of the families of the generators of a hyperboloid of revolution. In the case (shown) where these orifices 18 are distributed along a single circle C, this circle advantageously has a diameter d of the order of 50% of the diameter D of the prechamber 6 ..

According to the second solution which is illustrated diagrammatically in FIGS. 10 and 11, there is preferably only one injection orifice 18 in the form of a sheet (nipple injector) which is located on the dome of the prechamber 6, it that is to say on the part of the wall peripheral of the latter which is opposite to the transfer channel 8. This injection orifice 18, which flows towards the transfer channel 8, is then oriented so that the jet or sheet of fuel 19 which it discharges is placed in a plane substantially perpendicular to the axis of the prechamber 6.

According to either of these solutions (FIGS. 8 to 11), a better homogeneity of the air / fuel mixture is obtained and, by promoting the initiation of combustion on the periphery of the prechamber 6, formation is avoided. troublesome to a hot area near the injection port.

An engine is thus obtained, the operation of which is as follows, the arrows plotted in FIGS. 1 to 6 diagramming the movements of the fluids inside the cylinder 1 as well as at the inlet and at the outlet thereof. During scanning (Figures 1 to 3), the piston 4 being first in the vicinity of the bottom dead center, then during the first part of its ascent, the air passing through the seat 7 is deflected by the deflector means 17, the valve inlet 10 and the walls of the prechamber 6 so as to enter the cylinder 1 in the form of a jet inclined relative to the axis XX of the cylinder 1 (in the manner of a sling). Because of its cylindrical shape, the paths of the air particles emerging obliquely from the prechamber 6 are wound in a helix inside the cylinder 1, which has the effect of preventing these particles from passing near of the seat 16 of the exhaust valve 15 which is then open. Thanks to the absence of a short circuit, the operating efficiency is high and good thermal uniformity is obtained for the piston 4 and the cylinder 1 (or the jacket thereof).

During compression 1 (Figure 4), the helical rotation movement, induced in the cylinder 1 during the scanning phase, is maintained during the ascent of the piston 4 which tends to reduce the pitch of the propeller.

The air pushed by the ascent of the piston 4 invades the prechamber 6 while keeping the tangential speed induced by the rotation in the cylinder 1, which causes the rotation of the air in the prechamber 6, coaxially with said prechamber and, which is important, without reversing the direction of rotation induced in the prechamber 6 during scanning.

During combustion (Figure 5), almost all of the air trapped in the cylinder 1 is pushed, by the pinching effect of the piston 4 cooperating with the head of the cylinder head 3 and with the exhaust valve 15 resting on its seat 16, inside the prechamber 6 while keeping its rotational movement coaxial with said prechamber. In the preferred case of a diesel engine, the injection orifice (s) 18 spray fuel jets 19 which interfere with the rotational movement of the air and thus facilitate mixing between air and fuel. This is to limit the speed of transfer of gases from the chamber main 2 to the prechamber 6 and vice versa, which advantageously the above-mentioned groove (s) 20 will be arranged, preferably in the cylinder head 3 and not in the piston 4, in particular when the piston 4 has the possibility of turning around its axis in operation (in the case in particular of a spherical articulation of the piston 4 with the connecting rod associated therewith), as shown in FIG. 7.

During expansion (Figure 6), there is a phenomenon opposite to that of compression, the gases leaving the prechamber 6 with an inclination similar to that which had occurred during scanning.

By this mechanism, the rotation of the air and the gases is maintained without reversing the direction both in the cylinder 1 and in the prechamber 6. At each scanning cycle, the rotational movement is reactivated by the deflector means 17 acting on fresh air admitted. We will thus obtain an aerodynamic process generating the minimum losses since there will be re-acceleration at each cycle, without reversing the direction of flow.

In the foregoing, it has been assumed that the engine comprises only one cylinder, but it goes without saying that the explanations which have been given above remain valid in the case where the engine has two or more cylinders. Likewise, although the engine according to the invention has so far been described as comprising a single exhaust valve 15, it could comprise two, or even more. Although Figure 3 shows a prechamber 6 having a shape of revolution around an axis coincident with that YY of the inlet valve 10, the axis of the prechamber 6 could be slightly offset with respect to this axis YY.

The invention applies very particularly advantageously to engines supercharged by turbocharger driven by the exhaust gases.

Claims (18)

Two-stroke internal combustion engine, which includes: - at least one cylinder (1) devoid of lateral lights; - a combustion chamber (2) limited in this cylinder (1) by a cylinder head (3) fixed relative to this cylinder (1) and by a piston (4) driven by a reciprocating movement inside this cylinder (1); - a combustion and sweeping prechamber (6) formed in the cylinder head (3), provided with an intake valve seat (7) and communicating with the combustion chamber (2) by a transfer channel (8) whose cross section perpendicular to the axis (XX) of the cylinder (1), at the outlet in the combustion chamber (2), is an oblong surface (9) substantially tangent internally to the internal wall of the cylinder (1); - an inlet valve (10) of axis (YY) at least approximately orthogonal to the axis (XX) of the cylinder (1) and preferably intersecting with this latter axis (XX), arranged in such a way that the rod (11) of this valve (10) is further from this latter axis (XX) than the head (12) thereof (10) and that this head (12) can move inside said prechamber ( 6) in order to depart and to approach the above-mentioned seat (7) of the intake valve (10); - An intake duct (13) which terminates directly upstream of the above-mentioned seat (7); and - at least one exhaust valve (15) arranged so that its axis (ZZ) is at least approximately parallel to the axis (XX) of the cylinder (1) and that it can cooperate, allowing the gases to pass exhaust over at least most of its periphery, with an exhaust valve seat (16) formed in the head of the cylinder head (3) opposite the transfer channel (8), the latter seat (16 ) preferably being arranged in such a way that the transverse surface (5) of the piston head (4) leaves at top dead center only the operating clearance required with the exhaust valve (15) and the sky of the cylinder head (3), characterized in that the prechamber (6), apart from its connection with the transfer channel (8), has substantially a shape of revolution around an axis parallel to the axis (YY) of the intake valve ( 10) and preferably practically coincident with the latter axis (YY) or slightly offset with respect thereto;
in that deflector means (17), disposed inside the end part of the intake duct (13), that is to say as directly as possible upstream of the seat (7) of the valve d inlet (10), are arranged to produce a deflection in one direction, around the axis (YY) of said valve (10), of the mass of air which arrives via this conduit (13) when this valve (10) is open; and
in that the transfer channel (8) has a shape such, on the one hand, that the deflection thus produced in the prechamber (6) by the deflector means (17) during the scanning phase generates a substantially helical vortex in the cylinder (1) and, on the other hand, that during the raising of the piston (4), said substantially helical vortex in turn generates in the pre-chamber (6) a vortex in the same direction. Engine according to claim 1, characterized in that the deflector means (17) consist of blades around the rod (11) of the intake valve (10). Engine according to claim 2, characterized in that the blades (17) are connected to the intake valve (10) being arranged with clearance inside the end part of the intake duct (13), this valve (10) comprising guide means preventing it from turning on itself. Engine according to claim 2, characterized in that the blades (17) are connected to the seat (7) of the intake valve (10) by playing with clearance the rod (11) of this intake valve (10). Motor according to any one of Claims 1 to 4, characterized in that the pre-chamber (6) has a height which is substantially equal to the stroke of the intake valve (10). Motor according to any one of claims 1 to 5, characterized in that the transfer channel (8) has a shape converging towards its outlet in the cylinder (1), and preferably substantially symmetrical with respect to a plane parallel to the 'axis (XX) of the cylinder (1) and passing through the axis (YY) of the intake valve (10). Motor according to any one of Claims 1 to 6, characterized in that the assembly of the prechamber (6) and the transfer channel (8) 'has a shape which is substantially symmetrical with respect to a plane parallel to the axis ( XX) of the cylinder (1) and passing through the axis (YY) of the intake valve (10). Engine according to any one of claims 1 to 7, characterized in that the cylinder has only one exhaust valve (15). Engine according to any one of claims 1 to 8, supplied by at least one injection orifice (18) opening into the prechamber (6), characterized in that the injection orifice (s) (18) are located in the side wall of the prechamber (6) opposite the inlet valve (10), preferably coaxially therewith. Engine according to claim 9, characterized in that the injection port (s) (18) are oriented towards the periphery of the prechamber (6). Engine according to claim 10, characterized in that it has several injection orifices (18) distributed over at least one circle (C) centered on the axis of the prechamber (6). Engine according to claim 10, characterized in that the injection orifices (18) are distributed over a single circle (C) whose diameter (d) is of the order of 50% of the diameter (D) of the prechamber ( 6). Engine according to any one of Claims 1 to 8, supplied by an injection orifice (18) opening into the prechamber '(6), characterized in that the injection orifice (18) is located on the wall device of the prechamber (6) which is opposite to the transfer channel (8) and is preferably oriented towards the transfer channel (8). Engine according to any one of Claims 1 to 12, characterized in that the transverse surface (5) of the piston (4) and the head of the cylinder head (3) are approximately flat and perpendicular to the axis (XX) of the cylinder (1). Motor according to any one of Claims 1 to 14, characterized in that the lips of the transfer channel (8) are organized in such a way that the jet of air emerging from the prechamber (6) towards the cylinder (1) makes an angle (A) of the order of 30 ° with the plane parallel to the axis (XX) of the cylinder (1) and passing through the axis (YY) of the intake valve (10), when the ratio enter here stroke and the engine bore is about 1.25. Engine according to any one of claims 1 to 15, characterized in that it comprises, in the piston (4) or preferably in the part of the cylinder head (3) which is external to the outlet (9) of the transfer channel (8) and at the seat (16) of the exhaust valve (15), at least one groove (20) which leads to the outlet (9) and whose cross section and / or depth decrease as moves away from this outlet (9). Engine according to any one of claims 1 to 16, characterized in that a chapel (21) is associated with the intake valve (10) and its seat (7). Motor according to any one of claims 1 to 17, characterized in that it is supercharged.

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