FR2707343A1 - Two-cycle internal combustion engine. - Google Patents

Abstract

Two-stroke cycle internal combustion engine (1) of the pump housing type comprising a housing (2) in which is arranged at least one cylinder (3) defining a combustion chamber, said cylinder (3) having at least one lumen d 'inlet (4) through which the fresh gases enter and at least one exhaust port (7) through which the burnt gases are discharged, said exhaust port (7) communicating with an exhaust line via two separate exhaust ducts (8, 9), characterized in that said exhaust port (7) cooperates with controlled distributor means (10) from the values taken by one or more parameters representative of the operation of said engine (1 ), said distributor means (10) being able to selectively direct the burnt gases towards one or the other of said exhaust ducts (8, 9).

Description

- 1 -

  TWO-CYCLE INTERNAL COMBUSTION ENGINE

TIME

  The present invention relates to an internal combustion engine with two-stroke cycle intended in particular to equip a motor vehicle. -It relates more particularly to an exhaust system making it possible to adapt the characteristics of the exhaust circuit of a two-stroke engine according to the values taken by one or more operating parameters representative of the

engine operation.

  In order to improve the operation of two-cycle internal combustion engines both from the point of view of performance and from the point of view of reducing pollutant emissions, various devices have been developed to adapt the characteristics of the circuit. exhaust of a two-stroke engine according to the

operation of the latter.

  We can thus cite the document EP-A-278181 which discloses an exhaust device adapted to take into account the rise in temperature of the exhaust gases when cold starting a two-stroke engine when the latter is equipped with a catalytic converter. -2- The exhaust device according to document EP-A-278181 comprises in combination: a first pipe connecting a first exhaust port to a catalytic converter, a second pipe connecting a second exhaust port to the catalytic converter. This second

  pipe cooperating with a by- pipe

  catalytic converter pass and with a piloted distribution member positioned at the junction of the

  second pipe with the pipe deé by-

  pass, this distribution member being adapted to selectively distribute the exhaust gases through or outside the catalytic converter; The first pipe can also include a periodic shutter member making it possible to open

  selectively switching to exhaust gases.

  We can also cite the document EP-A-

  338868 which describes an exhaust device having two separate pipes cooperating with specific means for treating exhaust gases and with distribution valves for selectively directing the exhaust gases to

  through one and / or the other of the two pipes.

  If such devices indeed describe variable exhaust systems making it possible to adapt the characteristics of the exhaust circuit of a two-stroke engine according to the operation of the latter and this, in particular to reduce pollutant emissions. It can however be noted that these devices allow a relatively limited adaptation of the exhaust circuit to the engine operating conditions, only the cold start period is for example taken into account in the exhaust device -3- according to the document EP -A-278181, and that on the other hand the proposed systems are

  relatively complex to carry out industrially.

  The object of the present invention is therefore to propose an exhaust system of particularly simple design and which makes it possible to adapt the characteristics of the exhaust circuit of a two-stroke engine over a very wide range of

operation of the latter.

  The present invention therefore aims to

  decrease engine pollution two tempa au-

  beyond the strictest standards and this of a

  particularly simple and economical.

  To this end, the invention relates to an internal combustion engine with two-cycle cycle of the pump housing type comprising a housing in which is arranged at least one cylinder defining a combustion chamber, this cylinder having at least one intake lumen by o penetrate the fresh gases and at least one exhaust port by o are evacuated the burnt gases, the exhaust port communicating with an exhaust line via two separate exhaust ducts. According to the invention, the two-cycle cycle internal combustion engine is characterized in that the exhaust ducts cooperate with distributor means controlled from the values taken by one or more parameters representative of the operation of the engine, the distributor means being able to selectively direct burnt gases to one or the other

of the two exhaust pipes.

  According to another characteristic of the two-cycle internal combustion engine according to the invention, the exhaust light cooperates with shutter means controlled from the values taken by one or more parameters representative of the operation of the engine, the means shutters being able to selectively modify the passage section of the exhaust lumen in the axial direction of the

cylinder.

  l, According to another characteristic of the two-cycle internal combustion engine. According to the invention, at least one of the two conduits cooperates with shutter means controlled from the values taken by one or more parameters representative of the operation of the engine, these shutter means being able to restrict

  selectively the passage section of the duct.

  According to another characteristic of the two-cycle internal combustion engine according to the invention, the distributor means and the various shutter means consist of a single rotary plug driven in rotation by

  corresponding control means.

  According to another characteristic of the two-cycle internal combustion engine according to the invention, the plug journals inside a bore arranged directly in the casing, this bore which extends perpendicular to the axis of the cylinder, communicates directly with the light

  and with the exhaust ducts.

  According to another characteristic of the two-cycle internal combustion engine according to the invention, the parameters representative of the operation of the engine are the load and / or the

  exhaust gas speed and / or temperature.

  According to another characteristic of the two-cycle internal combustion engine according to the invention, at least one of the two exhaust ducts cooperates with means for treating

the exhaust gas.

  According to another characteristic of the internal combustion engine with two-stroke cycle% according to the invention, the means for treating the exhaust gases consist of a priming catalyst. According to another characteristic of the two-cycle cycle internal combustion engine according to the invention, the two exhaust ducts have different acoustic characteristics. The objects, aspects and advantages of the present invention will be better understood from the

  description presented below of a mode of

  embodiment of the invention, given by way of nonlimiting example, with reference to the appended drawing, in which: FIG. 1 is a schematic view in partial vertical section of an engine according to the invention; Figure 2 is a partial detail view of the exhaust system according to the invention; Figures 3 to 5 are views similar to that of Figure 2, specifying the different modes of operation of the exhaust system

according to the invention.

  In accordance with the figures, only the elements necessary for understanding the invention have been shown, and to facilitate the presentation of the invention, the same elements have the same references from one figure to another. 'Referring to Figure 1, the two-cycle cycle internal combustion mgtâr, item 1, is of the pump housing type. It conventionally comprises a casing 2 in which is arranged at least one cylinder 3 defining a combustion chamber. Inside the cylinder 3 is slidably mounted a piston 5 connected by a connecting rod to a crankshaft. The fuel injection is preferably direct and the ignition is obtained by a conventional means: electric system with

spark plug 6.

  The combustion air supply to the combustion chamber is carried out through at least one opening or intake port 4, while the discharge of the burnt gases is carried out through at least one port 7. These orifices are opened in time timely by the back and forth of the piston 5 in

cylinder 3.

  The exhaust port 7 communicates with the exhaust line via two separate exhaust conduits 8, 9. The transfer of the burnt gases from the exhaust light 7 into the conduits is ensured in accordance with the invention -7- by means of a rotary plug 10 driven in rotation by non-illustrated control means controlled from the values taken by one or more parameters representative of the operation of the engine such as the load and / or the rotation speed and / or the temperature of the exhaust gases. The plug 10 journals inside a corresponding bore 11 arranged in the casing 2, the bore 11 which extends perpendicular to the axis of the cylinder 3, communicates directly, .àyVc the exhaust port 7 and with each of the two exhaust ducts 8,9. This plug, the object of which is to form dispensing means but also shutter means intended to restrict the passage section of the burnt gases as detailed below, is formed by a substantially cylindrical part in which is formed a transverse passage adapted. The shape of the passage results from the respective position of the conduits 8, 9 and the exhaust port 7,

as well as their dimensions.

  The operation of the exhaust system according to the invention will now be explained in

see Figures 2 to 5.

  According to these figures, the conduits 8 and 9 are extended outside the casing 2 by an exhaust manifold 14, the conduit 9

  opening into a priming catalytic converter 12.

  If we refer to Figure 2, the plug is positioned so that its passage communicates the exhaust port 7 and the only conduit 8. This arrangement allows -8- maximum permeability for the escape of burnt gases (indicated by the arrows) outside the combustion chamber 3, necessary for a

  full load operation and high revs.

  In accordance with FIG. 3, it can be seen that by rotating the plug 10 it remains possible, while keeping in communication the only conduit 8 and the exhaust port 7, to restrict the section of the latter and, more particularly according to the axiai direction of the cylinder. This results in an increase in the useful displacement while the useful duration of opening to the exhaust decreases. This arrangement allows a significant increase in engine power under the conditions of

  operation at full load and low revs.

  If we refer to Figure 4, we see that the rotation of the plug 10 also allows, while keeping in communication the only conduit 8 and the exhaust port 7, to restrict the passage section of the conduit 8 without affecting the light 7. The restriction of passage through the conduit 8 generates a pressure drop which has the effect of reducing the gas flow velocities inside the cylinder 3 and which makes it possible to operate the internal recirculation of the burnt gases particularly favorable for reducing the emission of pollutants and more particularly nitrogen oxides NOx during operation of the

engine at low load.

  Finally if we refer to Figure 5, we see that the plug 10 can still be positioned so that its passage puts in -9communication the exhaust light 7 and the only conduit 9. This arrangement allows in particular transit, in particular during cold starts of the engine, the exhaust gases through a priming catalyst 12 allowing the treatment of the exhaust gases while the catalyst disposed more downstream ,. on the line

  exhaust is not yet operational ..-

  It can thus be seen that thanks to a particularly simple design and production system, it becomes possible to adapt the characteristics of the exhaust system to the needs of the engine and this in all of the operating ranges of this

latest.

  Of course, the invention is in no way limited to the embodiment described and illustrated

  which was only given as an example.

  On the contrary, the invention includes all the technical equivalents of the means described as well as their combinations if these are carried out

following his spirit.

  Thus it is possible to provide exhaust ducts 8.9 with characteristics

  different acoustics so as to achieve a bi-

acoustic exhaust.

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Claims (1)

CLAIMS [1] Two-cycle cycle internal combustion engine (1) of the pump housing type comprising a housing (2) in which is arranged at least one cylinder (3) defining a combustion chamber, said cylinder (3) having at least one intake slider (4) by o penetrates the fresh gases and at least one exhaust light (7) by o are discharged the burnt gases, said exhaust light (7) communicating with an exhaust line by via two separate exhaust pipes (8,9), characterized in that said exhaust pipes (8,9) cooperate with distributor means controlled (10) from the values taken by one or more representative parameters of the operation of said engine (1), said distributor means (10) being able to selectively direct the burnt gases to one or the other of said exhaust ducts (8, 9). [2] Two-cycle cycle internal combustion engine (1) according to claim 1, characterized in that said exhaust light (7) cooperates with controlled shutter means (10) from the values taken by one or more parameters representative of the operation of said engine (1), said shutter means (10) being capable of selectively modifying the passage section of said exhaust port in the axial direction of said cylinder (3). [3] Two-cycle cycle internal combustion engine (1) according to any one of claims 1 to 2, characterized in that at least one of said conduits (8) cooperates with shutter means controlled (10) from values taken by one or more parameters representative of the operation of said motor (1), said shutter means (10) being capable of selectively restricting the passage section of said duct (8). i [4] Two-cycle cycle internal combustion engine (1) according to any one of claims 2 to 3, characterized in that said distributor means and said shutter means are constituted by a single rotary plug (10) driven by corresponding control means. [5] Two-cycle cycle internal combustion engine (1) according to claim 4, characterized in that said plug (10) journals inside a bore (11) arranged in said casing (2), said bore (11) extending perpendicular to the axis of said cylinder (3) and communicating directly with said exhaust port (7) and with said exhaust ducts (8, 9). [6] Two-cycle cycle internal combustion engine (1) according to any one of claims 1 to 5, characterized in that said parameters representative of the operation of said engine (1) are the load and / or the speed. [7] Two-cycle internal combustion engine (1) according to any one of the claims   1 to 6, characterized in that at least one of said exhaust ducts (9) cooperates with means   (12) to treat exhaust gases.   [8] Two-cycle cycle internal combustion engine (1) according to claim 7, characterized in that said means for treating the exhaust gases consist of a priming catalyst (12).,, [9] Engine internal combustion to cyè1, two-stroke (1) according to any one of claims 1 to 6, characterized in that said exhaust ducts (8,9) have characteristics different acoustics.