FR2731044A1 - Exhaust for multiple cylinder vehicle IC-engine - Google Patents

Abstract

The exhaust has a catalytic converter (4) with a parallelepiped body (41) containing at least one catalytic reactor (42) for the treatment of the burnt gases. The body is formed by the inlet (43) and outlet (44) ends. The inlet end has an integral structure with deflectors for the exhaust gases and absorbers for the engine vibration. The inlet end of the converter can be directly mounted to the outlet of an exhaust manifold by a rigid mounting.

Description

EXHAUST DEVICE FOR INTBRNE COBBU8TION MOTIOR
The present invention relates to a device for exhausting the combustion gases of an internal combustion engine equipping, in particular, a motor vehicle. The present invention relates more particularly to an exhaust device using a device for purifying the flue gases by catalytic conversion.

 In general, standards concerning the pollution of internal combustion engines used in motor vehicles are becoming more and more severe in all the industrialized countries. The automotive industry is now fully mobilized to find technical solutions to meet these constraints and without penalizing neither the performance of engines nor their cost.

To fight against the emission of gaseous pollutants, the automotive industry has adopted the use of exhaust systems that treat the harmful components of flue gases by catalytic conversion. These devices, also called catalytic converters, allow the oxidation of HC unburned hydrocarbons and carbon monoxide.
CO as well as the reduction of nitrogen oxides nuts.

These reactions are indeed all greatly accelerated by the presence of catalysts so that they can be accomplished during the brief passage time of bilge gases through the pot.

 However, the catalytic conversion of the pollutants only starts when the catalysts have reached a certain temperature, generally greater than 300 ° C. As a result, when the engines are started, the temperature of the bilge gases is not sufficient to to initiate the chemical reactions, it then follows a more or less long phase during which the pollutants emitted by the engine are not or insufficiently treated, it can thus be estimated that 80 & 90% of the particles are emitted during the first two minutes of engine operation.

Various solutions have been proposed to overcome this drawback. Exhaust air injection systems can be mentioned to cause the post-combustion of the flue gases and accelerate the temperature rise of the catalytic converter. Mention may also be made of electric or electromagnetic heating or preheating means for catalytic converters as described in patent applications WO-A-90/14507,
WO-A-92/02714 or EP-A-465184.

 The document WO-A-90/02250 provides for the use of a heated catalytic converter, said start, used only as long as the flue gases have not reached a sufficient temperature, means deflectors current directing the flue gases according to their temperature to the starter catalyst or a bypass.

 These various solutions have the disadvantage of involving expensive embodiments and require to operate a more or less significant energy input.

 Another solution for accelerating the rise in temperature of the catalyst is to bring the latter closer to the combustion chambers so as to limit thermal losses and maintain a high temperature for the flue gases entering the catalytic converter. This last solution particularly little story since no additional device is necessary, however proves difficult to implement because of the different elements & put in place between the outlet of the exhaust manifold and the entrance face of the monolith supporting the catalyst.

It is indeed necessary to arrange between the collector and the catalytic monolith a flexible and / or articulated element serving for the axial and lateral decoupling of the vibrations of the engine of the type of joints described in the documents EP-A-575727, WO -A-93/04270 or else FR
A-2642472. Furthermore, it is essential to have a divergent deflection cone at the inlet of the catalytic converter to ensure a substantially homogeneous distribution of the flue gases on the front surface of the monolith and thus to avoid premature and heterogeneous aging of the catalyst due to poor distribution of the bilated gases in the monolith, the dimensions of the divergent are generally imposed.

 The need to dispose, in accordance with known prior art embodiments, between the exhaust manifold and the series catalyst one behind the other a vibratory attenuation section and a deflection section therefore imposes limits. bringing the catalyst closer to the combustion chambers and slowing down the temperature rise of the catalyst.

 The object of the present invention is therefore to overcome the aforementioned disadvantages by allowing the catalyst to approach the combustion chambers by modifying the shape of the catalytic converter so as to reduce the length of the latter upstream of the monolith and this in a particularly simple manner and economic.

 The exhaust device according to the invention for purifying the bilge gases of a combustion engine comprises a catalytic converter of the type comprising an oblong body containing at least one reactor for the catalytic treatment of burnt gases, the elongate body being delimited by adapted entrance and exit ends.

 According to the invention, the exhaust system for an internal combustion engine is characterized in that the inlet end of the catalytic converter has a structure incorporating means for deflecting biled gases and means for absorbing the vibration frequencies. of the motor.

 According to another characteristic of the exhaust system for an internal combustion engine which is the subject of the invention, the inlet end of the catalytic converter is directly mounted at the outlet of an exhaust manifold by a rigid fastening system.

 According to another characteristic of the exhaust system for an internal combustion engine which is the subject of the invention, the inlet end of the catalytic converter comprises, on the one hand, an outer envelope defining a flexible duct element and, on the other hand, an envelope. Coaxially extending inner to the outer casing defining a deflection nozzle & BR through which flows the flow of burnt gases.

 According to another characteristic of the internal combustion engine exhaust device of the invention, the inner casing is secured to the outer casing in the vicinity of its raw gas inlet, while its outlet port opens. freely in front of the front end face of the catalytic reactor.

The aims, aspects and advantages of the present invention will be better understood from the description given below of an embodiment of the invention, chosen as a non-limitative example, with reference to the accompanying drawing on which
Figure 1 is a partial schematic perspective view of an exhaust device according to the present invention.

 The exhaust system according to the invention is more particularly intended to equip a multi-cylinder internal combustion engine such as that of a motor vehicle. Only the elements of the exhaust system which are necessary for the understanding of the invention have been shown in the drawing.

 According to Figure 1, the exhaust device shown is adapted to equip an internal combustion engine & four cylinders in line intended to be mounted for example transversely in the front compartment of a motor vehicle. This exhaust system consists mainly, from upstream to downstream in the direction of flow of the burnt gases, an exhaust manifold 2, a catalytic converter 4 and a line of exhaust.

 The exhaust manifold referenced 2 has four pipes, respectively 2a, 2b, 2c, 2d, able to ensure the evacuation bilge gases from each cylinder of the engine.

 The pipes 2a, 2b, 2c, 2d of the exhaust manifold are directly attached to the engine cylinder head opposite the corresponding exhaust ports via a fastening flange 21. These pipes 2a, 2b, 2c, 2d are, according to the exemplary embodiment shown, arranged to form a collector type 3 Y; two of these are formed by the coupling of the tubes 2a, 2b and 2c, 2d; the arms of the third combine the bodies of the previous to allow the general connection in a single tubular conduit 3.

 The common duct 3 terminating the exhaust manifold 2 is connected directly to the inlet of a reactor or catalytic converter 4 via a rigid flange fastening system 31 integral with the collector 2 and counterflange 46 welded This catalytic converter 4 comprises an oblong cylindrical body 41 of circular or elliptical cross section and inlet end 43 and outlet end 44 respectively of divergent and convergent type.

 The body 41 conventionally defines a central cavity where is housed one (or more) reactor 42 for operating the catalytic conversion of flue gas. This reactor 42 is in the form of a monolith, also known as a honeycomb body, which is conventionally constituted by a cylindrical block of circular or elliptical section substantially corresponding to that of the central cavity of the body 41, inside which is formed a large number of channels whose walls are coated with catalyst and through which the shining gases circulate.

 According to the invention, the inlet end 43 adapted to allow its attachment directly to the outlet of the exhaust manifold 2, has a structure incorporating and in parallel means for deflecting the burnt gases and means for absorbing gases. vibration frequencies of the motor.

 To do this, the inlet end 43 has on the one hand an outer casing 47 defining a flexible duct element, such as a bellows, which provides the sealing connection between the counter-flange 46 and the body 41 of the catalytic converter 4 and on the other hand an inner casing 45 extending coaxially with the outer casing 47, defining a deflection nozzle, of divergent frustoconical type, through which flows the flow of flue gases leaving the exhaust manifold 2 .

 The inner casing 45 is secured, for example by welding, to the outer casing 47 at its inlet of the flue gas extending to the right of the counter-flange 46, while its outlet orifice opens freely in front of the front end face of the catalytic reactor 42.

 Thus, the inlet end 43 of the catalytic converter 4 according to the invention makes it possible, thanks to the outer flexible conduit 47, to break the vibration frequencies and to absorb the movements of the engine relative to the exhaust line, while distributing homogeneously the flue gases over the entire front surface of the catalytic reactor 42 gracie & the inner diffusion nozzle 45.

 This provision therefore eliminates the need for an attenuation section, such as a ball joint held by two springs, commonly interposed according to the prior art between the exhaust manifold and the catalytic converter. This therefore results in a reduction in the distance between the catalytic reactor 42 and the cylinder head of the corresponding internal combustion engine, and therefore a reduction of the heat exchange surfaces capable of cooling the bilge gases before entering the catalytic reactor, which provides an exhaust system with an extremely short catalyst startup time and relatively simple and inexpensive.

 Of course, the invention is not limited to the embodiment described and illustrated which has been given by way of example.

 On the contrary, the invention comprises all the technical equivalents of the means described and their combinations if they are carried out according to its spirit.

 Thus, it is possible to similarly produce the outlet end 44 of the catalytic converter, namely an interior concentration nozzle, convergent frustoconical type, which recovers and directs the burnt gases to the rest of the exhaust line of the catalytic converter. motor and an outer bellows ensuring the connection between the body 41 of the catalytic converter and the exhaust pipe disposed downstream.

Claims (3)

RBV-IDICATIOfl  (1) Exhaust system of an internal combustion engine, comprising a catalytic converter (4) of the type comprising an oblong body (41) containing at least one catalytic reactor (42) for the treatment of burnt gases, said body (41) being delimited by adapted inlet (43) and outlet (44) ends, characterized in that said inlet end (43) has a structure incorporating deflection means (45) for the flue gases and means (47) for absorbing the vibration frequencies of the motor.  (2) Exhaust device for engine & BR <internal combustion according to claim 1, characterized in that said inlet end (43) of the catalytic converter (2) is directly mounted to the outlet of an exhaust manifold (2) by a rigid fastening system (31,46).  (3) Exhaust device for an internal combustion engine according to any one of claims 1 to 2, characterized in that said inlet end (43) comprises firstly an outer casing (47) defining an element of flexible duct and secondly an inner casing (45) extending coaxially to the outer casing (47) by defining a deflection nozzle through which flows the flow of burnt gases.  t4] exhaust system for an internal combustion engine according to claim 3, characterized in that said inner casing (45) is secured to said outer casing (47) at its inlet flue gas, while its outlet orifice opens freely in front of the front end face of the catalytic reactor (42).