FR2829183A1 - Depollution device in vehicle exhaust comprises inlet deflector which controls area of device in use to increase as temperature of exhaust gases increases - Google Patents

Abstract

An exhaust gas deflector (8) in the inlet (4a) of a depollution device (4) can be controlled to direct the exhaust gases to a reduced section of the inlet face of the porous body when the exhaust gases are at a low temperature and to an increasing section of the porous body as the temperature of the exhaust gases rises The exhaust pipe of a vehicle connected to the exhaust from a vehicle engine (1) with a device (4) for depolluting the exhaust gases comprising a porous body (5) in a cylindrical envelope, filling the whole cross section of the envelope. The depollution device (4) is connected directly to the exhaust pipe (2) via a pipe (7) opening into the inlet (4a) of the depollution device and therefore the inlet face (5a) of the porous body (5). The inlet into the catalytic device (5) is conical with a small section end connected to the exhaust gas inlet pipe (7). The deflector is a deformable leaf, fixed at one of its longitudinal ends to the conical inlet at the level of its small section inlet and with a free end inside the conical inlet. The deflector comprises two metal plates positioned and fixed one on top of the other and with different thermal expansion coefficients. The depollution device is positioned so the cylindrical envelope is vertical at the front of the vehicle engine and is a catalytic converter or a particle filter for a petrol or diesel engine.

Description

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 The invention relates to an exhaust line of a motor vehicle connected to an exhaust part of the engine of the motor vehicle and comprising a device for cleaning up exhaust gases with thermal adjustment.

 The exhaust lines of motor vehicle engines most often include pollution control devices which are used to remove the pollutants present in the exhaust gases at the outlet of the engine cylinders.

 The pollutants present in the exhaust gases of motor vehicle engines can consist, for example, of carbon monoxide CO, nitrogen oxides or even unburnt hydrocarbons.

 The exhaust gas depollution devices inserted on the exhaust line of a motor vehicle generally consist of a porous catalyst body disposed in an envelope of cylindrical overall shape whose catalyst body occupies the entire cross section. The pollutants contained in the high temperature exhaust gases which pass through the catalyst body of the pollution control device, inside channels coated with catalytic materials, for example of precious metals, are transformed into non-polluting species such as gas. carbon dioxide and water vapor.

 The exhaust gases of motor vehicles at the outlet of the exhaust line contain high proportions of pollutants, just after the engine of the motor vehicle is started, and in particular in the first seconds after starting, because the catalysts installed on the exhaust line are not yet at a temperature to make them active in contact with gases from the exhaust part of the engine of the motor vehicle.

 In order for the catalysts to be primed so as to ensure treatment of the pollutants, it is necessary to reach a certain temperature at the inlet to the catalyst, this temperature being called the "light-off" temperature. As long as the exhaust are not able to raise the temperature of the catalyst to the 'light off' temperature, it is

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 inoperative to treat pollutants. It is therefore necessary to ensure very rapid heating of the catalyst, immediately after starting the engine, so as to make it capable of cleaning up the exhaust gases.

 Since the volumes of the catalyst bodies are quite large, it is necessary to supply a large amount of thermal energy to the catalyst, from the start of the engine. In addition, the amount of pollutants increasing over time, the entire volume of the catalyst is not necessary from the start of the engine. However, no simple device is known which makes it possible to take advantage of these operating characteristics of the catalyst, to optimize its operation, in particular at the time of starting the engine.

 The object of the invention is therefore to propose an exhaust line of a motor vehicle connected to an exhaust part of the engine of the motor vehicle, comprising a device for depolluting exhaust gases constituted by a porous body disposed in an envelope of cylindrical overall shape, throughout the cross section of the envelope, which makes it possible to obtain satisfactory operation of the pollution control device from the start of the engine and during the subsequent phases of operation.

 For this purpose, the pollution control device is connected directly to the exhaust part of the engine, by a pipe opening into an inlet part of the pollution control device, facing an inlet face of the body. porous and the pollution control device comprises an exhaust gas deflector disposed in the inlet part of the device, adjustable so as to direct the exhaust gases to a portion of reduced section of the inlet face of the porous body, when the exhaust gases are at low temperature, and towards a part of increasing section of the inlet face, when the temperature of the exhaust gases increases.

 In order to clearly understand the invention, a description will be given, with reference to the appended figures, of an embodiment of an exhaust line according to the invention comprising a catalytic pollution control device with thermal adjustment.

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 Figures 1 and 2 are schematic elevational views of an engine and an exhaust line according to the invention, of a motor vehicle, during two operating phases of the engine and the motor vehicle.

 FIG. 3 is an elevation view of the inlet part of a catalytic depollution device for the exhaust line shown in FIGS. 1 and 2.

 Figure 4 is a perspective view of the inlet part of the pollution control device seen from inside the pollution control device.

 Figure 5 is a perspective view of an adjustable deflector of the pollution control device in two functional positions.

 Figure 6 is a conventional representation of the deflector in two functional positions.

 In Figures 1 and 2, we see an engine 1 of a motor vehicle comprising an exhaust part 2 such as a manifold or a set of pipes and an exhaust line 3 on which is disposed a catalytic pollution control device 4 placed at the front of the engine in a vertical arrangement.

 The catalytic pollution control device 4 comprises an outer casing of generally cylindrical shape containing a porous catalyst body 5, crossed by generally axial direction channels.

 The walls of the porosities or channels of the catalyst body 5 are covered with a catalytic material such as a precious metal in contact with which the pollutants of the exhaust gases from the engine at high temperature are treated to be transformed into non-polluting substances.

 The metal casing of the catalytic pollution control device 4 comprises, at its ends, inlet and outlet connection pieces 4a and 4b making it possible to connect the catalytic pollution control device to two conduits of the exhaust line.

 The connecting piece 4a located at the inlet of the catalytic pollution control device 4, in the direction of circulation of the exhaust gases (arrow 6), can be constituted for example by an inlet cone with curved generators visible in particular on Figure 3 and for connecting a

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 upstream pipe 7 of the exhaust line at one end of the inlet cone 4 having a small section. The second opposite end of the inlet cone 4a has substantially the cross section of the cylindrical body of the catalyst 4 to which it is connected.

 The interior volume of the inlet cone 4a of the catalytic pollution control device 4 constitutes the inlet portion of the catalyst into which the pipe 7 for the arrival of the exhaust gases opens and which is delimited by an end face, or face inlet 5a, from the catalyst body 5.

 According to the invention, the inlet part of the catalytic depollution device delimited by the inlet cone 4a and the inlet face 5a of the porous body 5 is connected directly to the exhaust part 2 of the engine 1, for example - full to the exhaust pipes of the engine, no other component of the exhaust line being interposed between the exhaust part 2 of the engine 1 and the inlet part of the catalytic depollution device 4.

 According to the invention also, a deflector 8 is arranged in the inlet part of the catalytic pollution control device 4, so as to direct the flow of exhaust gas 6 ′ coming from the duct 7 towards only part of the section of the inlet face 5a of the catalyst body, when the deflector 8 is in its position shown in FIG. 1. The deflector is in this first position shown in FIG. 1, when the exhaust gases are at a low temperature, by example in the first seconds after starting engine 1.

 In this case, the exhaust gases constituting the flow 6 ′ only come into contact with a part of reduced section of the inlet face of the catalyst and circulate only in a part of the volume of the catalyst, so that the heating of this part of the catalyst under the effect of the circulation of the exhaust gases is substantially faster than in the case where the exhaust gases come into contact, as soon as the engine is started, with the entire section from the inlet side of the catalyst.

 In addition, the exhaust gases containing a smaller quantity of pollutants, in the start-up phase than in later engine operating phases, the fraction of the catalyst used for

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 the depollution is sufficient to ensure effective depollution of the exhaust gases.

 In a later phase of engine operation, as shown in FIG. 2, the deflector 8 is deformed by bending under the effect of a rise in temperature due to the contact of the exhaust gases and the flow of exhaust 6 "entering the inlet part of the catalytic device 4 comes into contact with a larger part of the section of the inlet face 5a of the catalyst body 5.

 The catalyst which had been activated by heating in its part of reduced section just after starting the engine gradually heats up, in a larger part of its volume, because the movement of the deflector allows the exhaust gases to '' coming into contact with a larger section of the inlet surface 5a of the catalyst body.

 The outlet part of the catalytic pollution control device consists of a manifold 4b for recovering the gases treated in the pollution control device which is connected to the downstream part 9 of the engine exhaust line generally arranged in the longitudinal direction of the motor vehicle.

 In the case of a catalytic pollution control device whose envelope is placed in a vertical arrangement at the front of the engine 1, the downstream part 9 of the exhaust line passes under the engine 1 then under the floor of the motor vehicle to extend in the longitudinal direction of the vehicle. Catalyst devices and exhaust pipes can be placed on the downstream part 9 of the exhaust line.

 The pollution control device produced according to the invention and comprising the deflector 8 which is connected directly to the exhaust part of the engine 1 could also be placed horizontally on a part of the exhaust line, in a longitudinal direction of the motor vehicle.

 The deflector 8 can be constituted by two metal plates having different coefficients of thermal expansion fixed to one another, in a superposed position, by riveting, welding or gluing. Because the two plates expand differently, the deflector 8 is deformed by bending to pass for example from its first configuration 8 ′ to

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 a second configuration 8 "shown in FIG. 4 which shows the internal surface of the inlet cone 4a of the envelope of the pollution control device seen from inside the pollution control device and in FIG. 5 which shows the deflector alone.

 The deflector 8 constituted for example in the form of a bimetallic strip, as described above, is fixed, by one of its ends, for example by welding, to the connection part 4a with small cross section of the inlet cone to the exhaust gas inlet pipe 7. The second end of the deflector is free to move inside the inlet part 4a of the pollution control device.

 As can be seen in FIG. 4, the deflector 8 has, in its configuration 8 ′, when the exhaust gases are at low temperature, after starting the engine, a curvature directed towards the wall of the inlet cone opposite to the wall on which the end of the blade is fixed at the entry end. This curvature makes it possible to direct the gases towards a reduced part of the cross section of the inlet face 5a of the catalyst body 5.

 The contact of the deflector constituted by a bimetallic strip with the exhaust gases at increasing temperature, during the phases following the starting of the engine, allows the deflector 8 to progressively pass from its configuration 8 ′ to its configuration 8 ″ in which the curvature of the bimetallic strip is inverted and practically conforms to the curvature of the interior surface of the inlet cone 4a In this latter configuration which corresponds to exhaust gases at a maximum equilibrium temperature during the running of the motor vehicle, the exhaust are guided only by the wall of the inlet cone 4a and are distributed along the entire section of the inlet face 5a of the catalyst body 5.

 In Figure 6, there is shown schematically the deformation of a deflector formed in the form of a bimetallic strip and comprising two superposed plates, in a first configuration 8a substantially planar and in a second configuration 8b in the curved deformed state , the two configurations corresponding to the contact of the deflector with exhaust gases at first and second temperatures having between

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they a difference AT. By designating by a the specific thermal bending coefficient of the plates (a is of the order of 14. 10-6OK-1), by e the thickness of the two plates and by L the length of the plates between their edge fixed on the wall of the inlet cone 4a of the depollution device and their edge not fixed, one can calculate the deflection f or thermal deflection characterizing the deformation of the plates by differential expansion by the formula:

When the temperature of the engine exhaust gases increases from a low temperature corresponding to the starting of the engine, and an equilibrium temperature of the engine exhaust gases in operation, the superimposed plates constituting the deflector 8 pass from the first configuration 8 'to the second 8 "configuration.

 We can determine the different characteristics of the plates constituting the deflector 8, to adapt the deflector 8 to the shape of the inlet cone of the pollution control device, the plates can be flat or curved, in their first and in their second configurations, depending on the cone shape.

 The plates can also have any other shape desired by the shape of the inlet part of the catalytic pollution control device.

 To obtain the desired deformation of the deflector between its first and second configurations, one can play on at least one of the following parameters: coefficient of thermal expansion of the components of the bimetallic strip, thickness of the plates, material constituting the plates, length of the plates between their fixing point and their free end, curvature of the plates or any other parameter allowing to act on the deformation as given by the formula mentioned above.

 The invention is not limited to a motor vehicle exhaust line comprising a catalytic depollution device as described above.

 The invention can be applied both in the case of petrol engines and of turbocharged or uncompressed diesel engines, the exhaust line depollution device, located immediately downstream of the par-

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 engine exhaust tie, which may comprise a porous catalyst body of any type or be constituted in the form of a pollution control element comprising a porous filtration body, such as a particle filter.

 The invention applies to any type of motor vehicle.

Claims (1)

 CLAIMS 1.-Exhaust line of a motor vehicle connected to an exhaust part (2) of the engine (1) of the motor vehicle, comprising a device for cleaning up exhaust gases (4) constituted by a porous body (5) disposed in an overall cylindrical envelope, along the entire cross section of the envelope, characterized in that the pollution control device (4) is connected directly to the exhaust part (2) of the engine (1 ) by a pipe (7) opening into an inlet part (4a) of the pollution control device (4), facing an inlet face (5a) of the porous body (5) and that the pollution control device (4) comprises an exhaust deflector (8), arranged in the inlet part (4a) of the pollution control device (4), adjustable so as to direct the exhaust gases to a portion of reduced section of the inlet face (5a) of the porous body (5), when the exhaust gases are at ba sse temperature, and towards a portion of increasing section of the inlet face (5a), when the temperature of the exhaust gas increases.  2.-exhaust line according to claim 1, characterized in that the envelope of the catalytic device (5) comprises an inlet portion (4a) having the shape of a cone connected by an end portion d entry to the exhaust gas inlet pipe (7) with a small cross-section, and that the deflector (6) is formed in the form of a deformable blade fixed, at one of its longitudinal ends, in the inlet cone (4a) of the pollution control device (4), at its inlet end with a small section and having a free end inside the inlet cone (4a).  3.-exhaust line according to any one of claims 1 and 2, characterized in that the deflector is constituted by two metal plates reported and fixed one on the other in superimposed position and having coefficients of expansion different thermal.  4.-exhaust line according to any one of claims 1 to 3, characterized in that the pollution control device (4) is arranged so that its cylindrical envelope is vertical, in front of the engine (1) of the motor vehicle. <Desc / Clms Page number 10>  5.-exhaust line according to any one of claims 1 to 4, characterized in that the pollution control device is one of the following devices: catalytic pollution control device, particle filter, for a gasoline engine or a diesel engine.