FR2648183A1 - Anti-pollution device for internal combustion engines, exhaust pipe and exhaust pipe accessory including such a device - Google Patents

Abstract

This anti-pollution device consists of a diffuser 1 which is located at the outlet 3 of the exhaust pipe 4 from the internal combustion engine and which acts on the flow of exhaust gases leaving the said pipe to diffuse them and disperse them into the atmosphere as soon as they leave. The diffuser 1 may be produced in the form of a cone 2, preferably flared like the bell of a trumpet, and which is located facing the outlet orifice 3 of the exhaust pipe, with its apex 5 pointing towards the said orifice. The diffuser cone may be mounted so that it is fixed or that it can rotate, and may be equipped with vanes or fins for increasing the turbulence of the flow of exhaust gases.

Description

 The present invention relates to an antipollution device for internal combustion engines, as well as an exhaust pipe and an exhaust pipe accessory comprising such a device.

 On motor vehicles, the ends of exhaust pipes are generally located towards the rear, to the right or left of the vehicle, and often oriented towards the ground and / or laterally to eject exhaust gases if possible outside of the journey of the vehicle in order to inconvenience the driver and the passers of the following vehicle. This has the effect. in urban areas. to send the exhaust gases to the sidewalks, inconvenient pedestrians and animals therein, or to inconvenience drivers and passengers of vehicles traveling in queues adjacent to the emitting vehicles.

 It is the same for air compressors, motor pumps. generator sets. etc. . . entered by internal combustion engines, when temporarily installed in public or private places, for example to carry out civil works on the roads.

 In built-up areas, city centers and suburbs, as well as on highways and motorways & heavy traffic, in traffic jams and in car parks. when idling or when starting the internal combustion engine and more particularly when the choke of the vehicle is operating, there are practically continuous and low layers of exhaust gas which concentrate pollutants such as CC, CC2. NO and unburned gases, which are particularly carcinogenic.

 These gases not only annoy pedestrians. but also the drivers and passengers of the vehicle. Indeed, it is near the ground that practically all the 0 - = air supply systems in the passenger compartments of mobile vehicles come to suck in air (ventilation, heating, air conditioning). Even if the catalytic converters decrease the content of certain pollutants, they generate others and in no case do they decrease the content of C02. Sending air loaded with exhaust gas into the passenger compartments of vehicles forces the driver to breathe air with a reduced oxygen content, which reduces his driving ability and consequently increases the risk of accident. Cec; is well reccnnu, puiscue some high-end cars are now equipped with expensive conditioning systems allowing to recycle the air of the passenger compartment while waiting to have left the area of the sheets of gas with high density of pollutants.

 The present invention aims to remedy the aforementioned drawbacks by reducing the content of exhaust gas in the area where they are released.

 To this end, the anti-pollution device according to the invention is characterized in that it consists of a diffuser which is arranged at the outlet of the exhaust pipe of the internal combustion engine and which acts on the flow of exhaust coming from said pot to diffuse and disperse them as soon as they exit into the atmosphere.

 It is precise that the device of the present invention does not make it possible to reduce the total amount of polluting gases emitted by an exhaust pipe of an internal combustion engine, but insofar as it disperses them more widely in the atmosphere ambient, it reduces their content per ml of ambient air and therefore reduces the amount of pollutants absorbed by the body.

We will now describe, by way of example, various possible embodiments of the present invention with reference to the accompanying drawings in which
Figure 1 shows, very diagrammatically, an anti-pollution device according to the present invention, in the form of a diffusing cone
Figure 2 shows, also very scaematically, another form of the diffuser cone.

 Figure 3 shows a concrete embodiment of the anti-pollution device of the present invention.

the device being shown in side elevation in the lower part of FIG. 3 and in lcr.itudinal section in the upper part of FIG. 3.

 FIG. 4 is a sectional view along the line IV TV of FIG. 3.

 FIG. 5 is a sectional view along the line V-V of FIG. 3.

 FIG. 6 shows, in longitudinal section, an alternative embodiment of the diffuser cone of FIG. 3.

 Figure 7 is a view of the diffuser cone of Figure 6 along arrow F of this figure.

 Figure B shows. partly in side elevation and partly in longitudinal section, another embodiment of a diffuser usable as an anti-pollution device of the invention.

 Figure 9 is a view of the diffuser of Figure 8 along arrow G of this figure.

 Figure 10 is a side elevational view showing the diffuser cone of the invention in an offset position relative to the longitudinal axis of the outlet end of the exhaust pipe.

 Figure 11 is a perspective view showing a diffuser according to the present invention, with blades or fins of different lengths.

 Figure 12 shows, in longitudinal section, a divergent placed at the outlet end of an exhaust pipe, and also shows a compressed air injection nozzle placed in the divergent.

 Figure 13 is a view of the divergent of Figure 12 along arrow H of this figure.

FIG. 14 is a diagram showing the compressed air supply circuit of the injection nozzle of FIGS. 12 and 13,
Figure 15 shows, in long tudinal section, another embodiment of the diffuser of the present invention.

 FIG. 16 is a front view showing the rotor of the diffuser in FIG. 15.

Figure 17 is a sectional view along the line
XVII-XVII of figure 15.

Figure 18 is a sectional view along the line
XVIII-XVIII of figure 12 or figure 15.

 FIG. 19 is a diagram showing the current supply circuit and the compressed air cooling circuit of the electric motor driving the rotary diffuser of FIG. 15.

 The anti-pollution device shown in FIG. 1 essentially comprises a diffuser 1, produced in the form of a cone 2 with a circular section and with a straight generator, which is arranged opposite the outlet orifice 3 of a pot d exhaust 4, the top 5 of the cone 2 being oriented towards the outlet orifice 3.

 As shown in Figure 1, the axis 6 of the cone 2 can be aligned with the axis 7 of the exhaust, but this is however not essential as will be seen later. On the other hand, the diffuser cone 2 must be located at a distance d from the outlet orifice 3 sufficient for the pressure drops in the exhaust pipe 4 not to be modified significantly, and therefore for the diffuser cone 2 does not risk disturbing the operation of the engine and reducing its power.

For the same reason, the half angle at the top of the cone will not exceed about 60. As also shown in FIG. 1, the diameter of the base 8 of the cone 2 can be greater than the outside diameter of the exhaust pipe 4.

 materials used to produce the diffuser cone 2 are chosen so as to be able to withstand the temperatures of the exhaust gases and to resist the corrosion of said gases, such as the exhaust pipes themselves, or by their composition. either grade has a protective coating.

 To ensure more efficient radial diffusion and to reduce both the axial and radial dimensions of the diffusing ozone, its generator can be curved, for example of hyperbolic shape, so as to have a flared shape like the horn of a trumpet as shown in figure 2.

 To facilitate the attachment of the diffuser cone to a support structure as will be described later, the diffuser cone can be extended, on the side of its base 8, by a cylindrical part 9 of circular section, of the same outside diameter as the base 8 of the cone, as also shown in FIG. 2. Preferably, the axial length of the cylindrical part 9 is equal to approximately a quarter of the total length of the diffuser 1 (cone 2 plus cylindrical part 9).

 Figure 3 shows a concrete embodiment of the diffuser cone of Figure 2. The diffuser cone 2 of Figure 3 may for example be constituted by a molded part, for example cast iron, having an internal recess 11 to lighten the weight. As shown in Figure 5, the diffuser clone 2 can between connected to the exhaust 4 by at least one support tab 12, one end of which is fixed to the cylindrical part 9 of the diffuser cone 2 and the other end of which is fixed to the outlet end part of the exhaust pipe 4. For example, as shown in FIG. 4, the cylindrical part 9 of the diffuser cone can have three notches 13 spaced 120 apart in its peripheral surface. Three support tabs 12 are provided.

Each lug 12 can be constituted by a flat iron, for example made of zinc-plated steel, one end of which is engaged in one of the three notches 13 and fixed therein for example by means of a rivet 14.

 CotG muffler 4, there are provided three shims of thickness 15 as shown in Figure 5. Each shim 15 may include a notch 'ongi.zdinale 16 in which is engaged the other end of one of the three flat bars 12. The face 17 of each wedge 15 which is in contact with the exhaust pipe 4 is conformed to conform to the curvature of the external cylindrical surface of said pot. Several sets of shims 15, of different thicknesses, can be provided to allow the anti-pollution device of the invention to be easily adapted to pots whose diameters vary within a given range.

 The flat irons or support lugs 12 can be tightened firmly on the shims 15 and these on the external cylindrical surface of the exhaust pipe 4 by means of a metal strapping band 18 stretched and locked in the stretched state of known manner by a clamp 19, or by means of a clamp of known type with screw clamping device. To prevent any relative displacement between the band or the collar 18 and the support legs 12 in the longitudinal direction of said legs, their end near the exhaust pipe 4 can advantageously be provided with a transverse notch 21 having a depth of approximately lmm and a width equal to that of the band or collar la, as shown in figure 3.

 Preferably, the shims 15 are placed on the outer cylindrical surface of the pot 4 slightly set back relative to the outlet orifice 3, as shown in FIG. 3. Preferably, the shims 15 have rounded edges as shown in Figure 5, to avoid injuring the band or clamp 18.

 When there is no relative movement of the atmosphere - exhaust pipe (this is the case, for example, of a fixed installation or of a stationary vehicle F), the flow of exhaust gases meets the diffusing cone 2 and its kinetic energy is partially absorbed by the deflection of said flowing flow and in which annular vortices are generated as illustrated in FIG. 2. The vortices thus generated ensure an ambient gas-atmospheric mixing and the desired diffusion is thus obtained. The eneration of the vortices is also increased by the presence of the three support legs' 2.

 When there is a relative movement atmosphere-exhaust cycads of a moving motor vehicle), the ambient air which flows along the exhaust 4, outside of it, and which passes between the band or collar 18 and the exhaust pot 4 constitutes a vortex flow which meets the conical wall of the diffuser cone 12 and which, depending on the speed of movement of the vehicle, can constitute a barrier preventing the exit of the gases of exhaust and can therefore disrupt engine operation & internal combustion.

 To avoid this, the diffuser cone 2 can have several openings in its conical wall, for example three large openings 22 as shown in Figures 6 and 7. In this case, the diffuser cone 2 can have an inner cylindrical part 23 connected to the outer cylindrical part 9 by three hollow arms 24, respectively arranged in correspondence with the three support lugs 12. The outer diameter of the inner cylindrical part 23 is smaller than the diameter of the orifice. outlet 3 of the sample pot 4.

 For t. ; use the kinetic energy of the exhaust gases, a general rotation can be imparted to the flow of the exhaust gases to favor the generation of vortices in a given volume or over a given axial distance from the outlet orifice 3 of the exhaust. In this case, the arms 24 of the diffusing cone of FIGS. 6 and 7 can be replaced by arms 25 having the form of fins or propeller blades as shown in FIGS. E and 9. It is better to give a further rotation with the gas flow, there may be provided on the cylindrical part 26 of the diffuser cone 2 a number of other blades or additional propeller blades, for example three blades 27 arranged between the blades 25 as shown in FIG. 9. In again in this case, the cylindrical part 26 preferably has an outside diameter smaller than the diameter of the outlet orifice 3 of the exhaust pipe 4. To avoid the risk of confining the exhaust gases, the external cylindrical part 9 of the diffuser cone of Figures 6 and 7 can be omitted.

In this case, the support legs 12 can be fixed directly to the ends of the blades 25 as also shown in FIGS. 8 and 9. For this purpose, each of the three legs 25 can be extended radially by a lug 28, which is engaged in a mortise provided in the end of the corresponding support tab 12. Preferably, each tenon 28 has a height (measured in the radial direction of the diffuser cone 2) slightly greater than the depth of said mortises. Thus, after having been engaged in the mortise of the corresponding support leg 12, the end of each tenon 28 projects outside, on the other side of the mortise and the support leg 12 may be beech fixed to the corresponding blade 25 by matting of the protruding end of the stud 28. In the case where the cone of the diffuser 2 is realistic in cast iron by molding, said cast iron must be ductile cast iron to allow a mating of the end of the studs 28.

 Although Figures 8 and 9 show a diffuser cone 2 provided with six fins or pays 25 and 27, the number of fins or blades may vary in practice.

This number "depends on the overall rotation effect sought for the flow of exhaust gases. Effect which is also a function of the speed of the vehicle, of the angle of attack of the profiles of the fins or pays (angle of attack which can be constant or variable with the distance from the axis of the diffuser cone), and from the overlap of one fin or blade relative to the next in the circumferential direction.

 In the case of motor vehicles, when the outlet of the exhaust pipe 4 is located close to the ground, as is generally the case for cars and a number of industrial vehicles, it then occurs a "ground effect" well known to automotive specialists. To reduce this effect and send most of the exhaust gases upwards, the axis 6 of the diffuser cone 2 can be offset downwards with respect to the axis 7 of the exhaust pipe as shown schematically on the Figure 10. For this purpose, it is possible to give different thicknesses to the shims 15. In this case, the shim 15 located in the highest region of the outlet end of the exhaust pipe 4 will have a smaller thickness than that of the two other wedges 15 located in the lowest region.

 To obtain the offset of axes 6 and 7, it is also possible to no longer use a diffuser cone having a symmetry around its axis 6, like that of FIGS. 8 and 9, but a diffuser cone 2 whose blades 25 and 27 have different lengths as shown in Figure 11, the diffuser cone nevertheless retaining symmetry with respect to the vertical plane containing the axis 6. The diffuser cone 2 shown in Figure 11 has three blades 25 provided with pins 28 for fixing the cone diffuser with three support legs 12, and two blades 27 each located between the upper blade 25 and one of the two lower blades 25. The upper blade 25 has a length greater than that of the two blades 27, which themselves longer than the two bottom blades 25.

 To make the assembly formed by the outlet section of the exhaust pipe 4 and by the diffuser cone 2 even more effective, the outlet section of the exhaust pipe 4 can be given the shape of a diverging portion 29 as shown in Figure 12, the diffuser cone (not shown in Figure 12) still being arranged in this case outside of the divergent 29 opposite its outlet orifice. The generators of the diverging 29 make with the longitudinal axis 7 of the exhaust 4 preferably an angle at most equal to 6- to avoid detachment of the exhaust gas stream relative to the wall of the diverging. The latter can be an integral part of the exhaust pot 4 as shown in FIG. 12 or, after a possible shortening of the exhaust pot 4, it can be attached and fixed by any known means, for example by welding, at the end of the exhaust pipe 4.

 In the case where the axis 6 of the diffuser cone 2 is offset with respect to the axis 7 of the exhaust pipe 4, for example in the case where a diffuser cone such as that shown in FIG. 11 is used, the outlet of the diverging portion 29 may no longer have a circular shape, but an ovoid shape as shown in FIG. 13.

In this case, the cross section of the divergent 29 evolves from a circular section 3a at its junction with the exhaust pot 4 to an ovoid section 3b at its outlet end.

 To further improve the diffusion of exhaust gases, in particular for fixed installations and for highly polluting industrial vehicles, at least when they are stopped or the engine is idling, the anti-pollution device of the present invention may further include means for providing external energy to the flow of exhaust gases. A first solution for providing this additional energy may consist, for example, of introducing one or more jets of compressed air into the flow of the exhaust gases using one or more injection nozzles located upstream of the diffuser cone 2 and go to it. For example, the compressed air injection nozzle or nozzles can be arranged in the converging element 29 as shown in FIGS. 12 and 13, in which a single nozzle 31 has been shown to simplify the drawing. The nozzle 31 may comprise a nozzle 32 oriented towards the outlet 3b of the diverging portion 29 and carried by a shrouded hollow body 33, itself carried in the diverging portion 29 by a radial arm 34 shrouded as shown in FIG. 18. For its attachment to the wall of the diverging part 29, the arm 34 may comprise a threaded cylindrical part 35, which passes through a hole drilled in the wall of the converging part 29, and on the external part of which is screwed a nut 36. Sealing washers 37 and 38 are provided to guarantee the sealing of the passage of the threaded part 35 through the wall of the diverging part 29.

 A passage 39 pierced longitudinally in the arm 34 and its threaded portion 35 makes it possible to bring compressed air to the nozzle 32. For this purpose, on the external end of the threaded portion 35 can be screwed a connection < not shown) of a pipe 41 (FIG. 14) connecting the nozzle 31 to a source of compressed air comprising for example a reservoir or accumulator of compressed air 42 and a compressor 43, which can be driven in rotation by the motor to combustion internal to the exhaust pipe which is adapted the cone diffuser 2 of the present invention. On industrial vehicles exceeding a certain tonnage, there is now almost always an air compressor and a compressed air accumulator tank, which is normally intended to control, for example, brakes, suspension, etc. , and which can be used in addition, in the present case, as an accumulator 42 and as a compressor 43 to supply the nozzle or nozzles 31 with compressed air. However, since the air compressors usually installed on industrial vehicles produce compressed air only in a relatively limited quantity, it is preferable to use the compressed air produced by the compressor 43 only during the periods when the vehicle is stationary, engine running, or at slow travel speeds to reduce consumption of compressed air admitted to nozzle (s) 31.

For this purpose, an electro-valve 44 can be inserted in the compressed air pipe 41, and means can be provided to control the closing of the electro-valve 44 when the speed of movement of the vehicle becomes greater than a first predetermined value, for example around 40 km / h, and the opening of the solenoid valve 44 when the speed of movement becomes smaller than a second predetermined value smaller than the first value, for example around 20 km / h. For example, the solenoid 45 of the electro-valve 44 can be supplied with current by a battery 46, for example the vehicle battery, through three switches 47, 4R and 49 connected in series as shown in the figure 14. The switch 47 is the switch controlled by the vehicle ignition key. The switch 49 is a switch which opens and closes when the speed of movement of the vehicle becomes respectively greater than 40 km / h and less than 20 km / h.

The purpose of the switch 48 is simply to detect that the internal combustion engine is operating and to authorize the passage of current to the solenoid 45 when the engine is running. Indeed, the ignition key of a motor vehicle generally comprises at least one position in which the switch 47 is closed, without the engine running. As the switch 49 is finished when the vehicle is stopped, it would not be necessary, under these conditions, for the solenoid valve 44 to be open. The switch 48 is therefore designed to be open when the engine is stopped or almost stopped and closed when the engine is idling. For example, for an idle speed set to 750 rpm, switch 48 can be set to close when the engine speed goes above 600 rpm and to open when the engine speed drops below 300 rpm. Thus, the compressed air will only be delivered to the nozzle (s) 31 if the ignition is switched on, if the engine is running and if the vehicle is stopped or is traveling at low speed. For example, if the engine is a diesel engine during a preheating period, the electro-valve 44 will remain closed because, during this period, the switch 48 will remain open.

 The switches 49 and 48 can be inertial hysteresis switches controlled respectively as a function of the speed of rotation of the wheels of the vehicle and as a function of the speed of rotation of the internal combustion engine. However, with the generalization of on-board computers installed in vehicles, switches 48 and 49 may be constituted by electromagnetic contactors actuated by the on-board computer from information. of displacement speed and rotation speed f: o; es & this.

 In some cases where the engine is powerful, operates under normal conditions, therefore delivers a large volume of exhaust gas, with a low or zero translation speed, therefore a large concentration of exhaust gas, a second solution to provide additional energy to the flow of exhaust gases to diffuse said gases more effectively may consist in using no longer a fixed diffuser, but a rotating diffuser, which is mounted to rotate about an axis parallel or coniondu with the axis 7 of the exhaust.

Although. at least in some cases, the diffuser could be mounted freely rotating on its axis and provided with fins to be driven in rotation by the relative wind due to the movement of the vehicle relative to the ambient air, the diffuser is preferably driven in rotation by suitable motor means.

 FIG. 15 shows for example a diffuser cone 2 which can be rotated by an electric motor 51. The motor 51 is fixed by screws 52 to a cover 53 which can be fixed detachably, for example by screws 54; to a cylindrical casing 55 whose bottom wall 56 faces the outlet orifice 3 of the exhaust pipe 4. The interior surface of the casing 55 and its bottom wall 56 is preferably provided with a thermal insulator 57 The output shaft 58 of the motor 51 projects outside the casing 55 through a hole 59 drilled in the center of the wall 56 (FIG. 17). At its outer end, the shaft 58 has a threaded part 58a with a screw pitch opposite to the direction of rotation of the motor 51. The diffuser cone 2 has, in its nose 2a, a tapped hole into which the threaded part 58a is screwed of the shaft 58. On the side of the bottom wall 56, the diffuser cone 2 is supported by a flange 61 mounted on the shaft 58. Otherwise, the conical part and the cylindrical part of the diffuser cone 2 can have a shape and structure similar to that of the diffuser cone of Figures 8 and 9. The fins or blades 62 (see also Figure 16) of the diffuser cone 2 are arranged and oriented in the manner of the blades of the rotor of a fan, but in a direction such that they accelerate the flow of exhaust gases leaving the exhaust 4.

The casing 55 has an outside diameter substantially equal to that of the cylindrical part of the diffuser cone 2 and is provided with two support legs 63 by means of which it can be fixed to the vehicle casings or to any other support structure. As shown in the
on 17, over at least part of their length, the support legs 6 <extend radially from the housing 55, each making an angle of approximately 45 'relative to the vertical plane containing the longitudinal axis of the housing 55. The two support legs 6.3 can be profiled as shown in Figure 18, so as to form fins or fixed blades. Two other blades or fixed fins 64, of the same profile as the blades or fins 63 can be provided on the casing 55 in positions diametrically opposite to those of the blades 63. The blades 63 and 64 constitute a fixed propeller which in combination with the rotor formed by the diffuser cone 2 and its blades 62 ensure the creation of strong vortices and, consequently, an efficient diffusion of the exhaust gases into the atmosphere.

Although the motor 51 is housed in a casing 55 lined internally with a thermal insulator 57, the motor 51 is preferably cooled by a forced circulation of fresh air. To this end, at least one of the two support legs 63, preferably the two legs 63 are hollow so as to have a passage 66, which opens into the housing 55 & through an orifice fi7
(figure 15). In this way, fresh compressed air can be admitted into the casing 55 through one of the two passages 6 and the corresponding orifice 67. In addition, the motor 51 can be equipped with its own fan 68 mounted on the axis 58 inside the housing 55. In this case, the cover 53 can be perforated to allow the cooling air admitted into the housing 55 to escape from it after having cooled the engine 51.

 As shown in Figure 19, the compressed fresh air for cooling the motor 51 can be produced in the housing 55 in exactly the same way as that described in connection with Figure 14, by means of an air compressor 43 , an accumulator 42, an electro-valve 44 and a pipe 41 connected to the passage ofi. However, since the electric motor 51 must preferably be cooled throughout the operating life of the internal combustion engine, the solenoid 45 of the solenoid valve 44 is preferably connected to the junction point between the switches 48 and 49, the switches 47, 48 and 49 in FIG. 19 playing exactly the same role as switches 47, 48 and 49 in FIG. 14, respectively.

 When the anti-pollution device of FIG. 15 is disposed at the outlet end of the exhaust pipe 4 of the internal combustion engine of a motor vehicle, the electric motor 51 is preferably activated only if the vehicle is moving at slow speed or is stopped, engine running, as in the case of the solenoid valve 44 of FIG. 14. This is why, the electric motor 51 is supplied with current through the contact 71 of a relay 72 whose coil 73 can be supplied with current from the battery 46 through the three switches 47, 48 and 49 connected in series.

 Note that the motor power supply cable 51 can arrive inside the casing 55 through the passage 66 from that of the two support legs 63 which is not used to bring the compressed air into the casing 55.

 As shown in the foregoing, the anti-pollution device of the present InventIon can either be integrated into the exhaust during the manufacture thereof, or produced in the form of an accessory which can be adapted to an existing exhaust pipe after having possibly modified the outlet end if necessary.

 It should be understood that the embodiments of the present invention which have been described above have been given by way of purely indicative and in no way limiting example. and cue many modifications can be easily made by those skilled in the art without departing from the scope of the present invention. Thus in particular that instead of using an electric motor, such as the motor 51, to drive the diffuser cone 2 of FIG. 15, any other motor means can be used, such as for example a turbine installed in place of the engine 51 and entered by compressed air produced for example by the compressor 43 of FIG. 14. Finally, the present invention obviously applies to any internal combustion engine (internal combustion engine, diesel engine, turbine with gas ...) with as fuel not only the conventional fuels resulting from the refining of crude oil, but also natural gas, liquefied petroleum gas, synthetic hydrocarbons ..., and generally any solid fuel, liquid or gaseous.

Claims (17)

 1.- Anti-pollution device for internal combustion engines, characterized in that it consists of a diffuser (1), which is arranged at the outlet (3) of the exhaust pipe (4) of the internal combustion engine and which acts on the flow of exhaust gases leaving said pot to diffuse and disperse them as soon as they exit into the atmosphere.  2. Anti-pollution device according to claim 1, characterized in that the diffuser (1) comprises a ctne (2) disposed opposite the outlet orifice (3> of the exhaust pipe (4), the top (5) of the cone being shouted towards said outlet orifice.  3. Anti-pollution device according to claim 2. characterized e that the axis (6) of the diffuser cone (2) is aligned with the axis (7) of the outlet of the exhaust pipe (4).  4. Anti-pollution device according to claim 2, characterized in that the axis (6) of the diffuser cone (2) is parallel and offset downward relative to the axis (7) of the outlet of the pot d '' exhaust (4).  5. Anti-pollution device according to any one of the claims 2 to 4, characterized in that the diffusing cone (2) has a curved generator, so as to have a flared shape like the horn of a trumpet.  6. Anti-pollution device according to any one of claims 2 to 5, characterized in that the diffuser cone (2) is extended. on the side of its base (8), by a cylindrical part (9) of the same outside diameter as the base (8) of the cone.  7. Anti-pollution device according to claim 6, characterized in that the cylindrical part (9) of the diffuser cone (2) has an outside diameter larger than the diameter of the outlet section (3) of the exhaust pipe. (4).  6. Anti-pollution device according to claim 7, characterized in that the diffuser cone (2) has large openings (22) in its conical surface, near the periphery of its base (8).  9.- anti-pollution device according to claim 6, characterized in that the cylindrical part (2fui) of the diffuser cone (2) has an outer diameter smaller than the diameter of the outlet section (3) of the exhaust pipe (4), and in that several blades (27,25v 'extend radially from said cylindrical part (2fui).  10.- anti-pollution device according to any one of claims 1 to 9, characterized in that the diffuser (1) is mounted fixed relative to the exhaust pipe (4).  he. - Anti-pollution device according to Claims 7 and 10, characterized in that the diffuser cone (2) is connected to the exhaust pipe (4) by at least one support tab (12), one end of which is fixed to the cylindrical part (9) of the diffuser cone (2) and the other end of which is fixed to the outlet end part of the exhaust pipe (4).  12.- anti-pollution device according to claims 9 and 10, characterized in that the diffuser cone (2) is connected to the exhaust pipe (4) by at least one support tab (12), one end of which is fixed at the outer end of one (25) of the blades (25,27) of the diffuser cone (2) and the other end of which is fixed to the outlet end part of the exhaust pipe (4).  i3.- Anti-pollution device according to claims 4 and 12, characterized in that, for an exhaust pipe (4) with a substantially horizontal axis, the blades (25,27) have different lengths, the blades located dat- the highest region of the cylindrical part. Dô) of the diffuser cone (2) having a length p greater than those located in the lowest region.  14.- anti-polluticn device according to any one of claims 1 to 13, characterized in that it further comprises, instead of the outlet end portion of the exhaust pipe (4) a divergent ( 29) whose generatrices make with the longitudinal axis t7) of the exhaust pipe (4) an angle at most equal to o-, the diffuser (1) being arranged outside the diverging portion (23) opposite its outlet port (3b).  15.- anti-pollutJon device according to claims 13 and 14, characterized in that said divergent (29) has a cross section which evolves from a circular section (3a) at its junction with the exhaust pipe (4) at an ovoid section (3b) at its exit end.  16.- anti-pollution device according to claim 14 or 15, characterized in that at least one compressed air injection nozzle (31) is disposed in the convergent (29) for injecting therein a jet d air directed towards the outlet (3b) of said convergent.  17. Anti-pollution device according to claim 16, characterized in that, when it is mounted on a motor vehicle, the injection nozzle (31) is connected to a source of compressed air (42,43) & through an electro-valve (44), and in that means (49) are provided for controlling the closing of the electro-valve (44) when the speed of movement of the vehicle becomes greater than a first value predetermined, and the opening of the solenoid valve when said speed of movement becomes smaller than a second predetermined value smaller than the first value.  i8.- anti-pollution device according to any one of claims 1 to 9, characterized in that the diffuser (1) is rotatably mounted about an axis (6) parallel or coincident with that (7) of the part of the exhaust outlet end (4).  19. Anti-pollution device according to claim 18, characterized in that a motor means (51) is provided for rotating the diffuser (1).  20.- Anti-pollution device according to revendicat.cn 19, characterized in that, when it is mounted on a motor vehicle, means (49) are provided for stopping the motor means (51) when the speed of movement of the vehicle becomes larger than a first predetermined value, and to activate the engine inIt <51) when said speed of movement becomes smaller than a second predetermined value smaller than the first value.  21. Anti-pollution device according to claim 20, characterized in that said motor means <51) is an electric motor, disposed in a casing (55) connected to the vehicle trenches, in that means (41-48) are provided for injecting compressed air into said casing (55) to cool the electric motor (51), said compressed air injection means being active in response to the operation of the internal combustion engine of the vehicle and deactivated when said internal combustion engine is stopped.  22.- Exhaust, characterized. in that it comprises, at its outlet, an anti-pollution device according to any one of claims 1 to 21.  23. - Accessory intended to be mounted at the outlet of the exhaust of an internal combustion engine, characterized in that it comprises an anti-pollution device according to any one of the claims l to 21.