FR2936009A1 - Exhaust gas purifying device for e.g. diesel engine, of motor vehicle, has maintenance unit cooperated with support surfaces of base, where surfaces are supported by lateral face of base and axially recessed in end faces of base - Google Patents

Abstract

The device (10) has an external case (12) defining an exhaust gas passage duct along an axis (A). Gas purifying base (16) e.g. particle filter, is housed inside the case, and has upstream and downstream end faces (33, 34) arranged transversal to the axis. A maintenance unit is cooperated with support surfaces of the base for blocking the base axially with respect to the case, and is constituted of upstream and downstream peripheral joints (18, 20). The surfaces are supported by a lateral face (36) of the base and are axially recessed in the end faces.

Description

The present invention relates to purification devices integrated into exhaust lines for thermal engines, especially for a motor vehicle. More specifically, the invention relates to a device for purifying the exhaust gases of a heat engine, of the type comprising: - an outer envelope defining, along an axis, an exhaust gas passage conduit; a gas purification substrate, housed inside the outer envelope and comprising upstream and downstream end faces disposed substantially transversely to said axis; and, holding means integral with the envelope and capable of cooperating with at least one bearing surface of the substrate for axially locking the substrate relative to the envelope.

The exhaust gases exert longitudinal forces on the substrate. Indeed, the substrate provides resistance to the passage of gases flowing through the purification device. This resistance is sometimes important. Thus, in the case where the substrate is a particulate filter, the soot particles carried by the exhaust gases are trapped by the filter. They can eventually block certain channels of the filter, helping to further increase the filter resistance to the flow of exhaust gas. In addition, for example during a change in engine speed, the purification device may be the seat of significant pressure variations between its upstream side and its downstream side and therefore to significant longitudinal stresses.

In addition, the vibrations of the power unit propellant propagate in the gas purification device and apply additional longitudinal forces on the substrate, catalyst and / or particulate filter. The substrate must therefore be locked longitudinally by holding means adapted to not move relative to the envelope.

It is known to maintain the substrate by layers of fibers arranged at the interface between the substrate and the envelope. The relative dimensions of the substrate and the envelope are adapted to compress the sheet so as to generate sufficient frictional forces on the lateral face of the substrate to block the substrate in position within the envelope. In a highly geometrically constrained exhaust system installation environment, short substrates less than or equal to about 5 cm (2 inches) in length are used. The lateral face of the substrate, opposite the inner face of the envelope, then has a surface that is too small to generate friction forces sufficient to maintain the substrate in the envelope. It is then known to maintain the substrate by peripheral end joints forming blocking wedges.

Thus, the document FR 2 904 658 discloses a device of the aforementioned type comprising two peripheral seals section L. They are respectively arranged around the upstream and downstream end edges of the substrate which connect the lateral face and one of the upstream and downstream end faces of the substrate. An L-shaped joint comprises a wing disposed axially against the lateral face of the substrate, and a wing disposed radially against one of the end faces of the substrate. The upstream and downstream end faces of the substrate thus constitute bearing surfaces with which the L-shaped joints cooperate to lock the substrate longitudinally. The size associated with the implementation of the L-joints penalizes the length of the purification device. Thus, the thickness of the radial flange of a seal being approximately 3 mm, the presence of two joints lengthens the purification device by 3 mm beyond each of the upstream and downstream end faces of the substrate. In addition, the thickness of the envelope must be taken into account because the wall of the envelope is folded radially towards the axis to form flanges at the upstream and downstream ends of the envelope so as to constrain the joints.

The longitudinal size of the purification device may, moreover, interfere with the implantation of probes measuring the efficiency of the purification device. The invention therefore aims to overcome the aforementioned problems. For this purpose, the subject of the invention is an exhaust gas purification device of the abovementioned type, for which the bearing surface is carried by a lateral face of the substrate and is situated axially behind the upstream end faces and downstream of the substrate.

According to particular embodiments of the invention, the exhaust gas purification device comprises one or more of the following characteristics, taken individually or in any technically possible combination: the holding means are adapted to be axially recessed; the upstream and downstream end faces of the substrate, the substrate has a relief projecting radially away from the axis A, the relief bearing an upstream bearing surface and a downstream bearing surface; relief is an insert on a core portion of the substrate, - the relief is of a material similar to that of the core, - it comprises a collar having upstream and downstream transverse faces forming upstream and downstream bearing surfaces, - the lateral face of the substrate has a recess, in depression radially inwardly relative to the lateral face of the substrate, the recess bearing said at least one bearing surface, - the recess st a groove, - the recess is a shoulder on one of the upstream and downstream end faces of the substrate, the radial bottom face of the shoulder defining said bearing surface, - the holding means comprise a seal device having at least one wing bearing against said at least one bearing surface, the seal has an L-shaped profile and comprises a longitudinal wing disposed between the substrate and the casing, and a radial wing bearing against the bearing surface of the shoulder, - the seal has a profile "U" and comprises a bottom forming a longitudinal flange disposed between the substrate and the casing, and two radial wings, respectively upstream and downstream, bearing against bearing surfaces, respectively, upstream and downstream of the collar, - the casing is shaped so as to have a housing for receiving the seal to axially secure with the casing, - the holding means comprise a protuberance carried by the envelope, pheasant projecting radially inwards with respect to an inner face of the envelope, the shape of which is adapted to the geometry of the recess of the substrate, the holding means comprise a protuberance carried by the envelope, projecting radially. outwardly with respect to an inner face of the envelope, whose shape is adapted to the geometry of the relief of the substrate, - the protuberance is a ring fixed on the inner face of the envelope and having a section complementary to that of the groove provided on the substrate, - the protrusion is achieved by a narrowing of the wall of the envelope, - it comprises at least one layer of compressed fibers between the lateral face of the substrate and the envelope, and - the means of maintain cooperate with the support surface of the substrate via the fiber web. The invention also relates to an exhaust line of a heat engine, comprising the exhaust gas purification device shown above. Finally, the invention relates to a vehicle equipped with a heat engine and an exhaust line, the latter comprising the exhaust gas purification device presented above. The invention and its advantages will be better understood on reading the following description given solely by way of example and with reference to the appended drawings, in which: FIG. 1 represents, in longitudinal section, a first embodiment embodiment of the gas purification device according to the invention; and, - Figures 2 to 5 show, respectively, in longitudinal half-section, various alternative embodiments of the invention. An exhaust line of a heat engine vehicle, such as a diesel engine vehicle, comprises, arranged in series, an engine exhaust gas manifold, possibly a turbocharger, a gas purification device and a silencer .

Figure 1 illustrates a first embodiment of the gas purification device. The device 10 comprises an outer casing 12, a gas treatment substrate 16, housed inside the outer casing 12, and at the interface between the substrate 16 and the casing 12, on the one hand, means for holding the substrate 16 inside the casing 12 constituted by two peripheral seals 18 and 20, and, secondly, a sheet of fibers 22. The outer casing 12 delimits a conduit for the passage of gases exhaust system that extends longitudinally along an axis A. In all that follows, the terms upstream and downstream agree with respect to the direction of flow of the exhaust gas in the envelope 12, indicated by the arrows on the FIGS. The envelope 12 is made of a metal material of thickness e substantially constant. It comprises a lateral wall 21, for example cylindrical, of axis A and inner radius D, extending over a length L.

The casing 12 ends longitudinally by upstream end and downstream end flanges 25, arranged transversely to the axis A. The upstream end flange 24 is in the form of a ring between an outer circular edge integral with the side wall 21. and an inner circular edge 26 defining an inlet opening. Similarly, the downstream end flange 25 is crown-shaped between an outer circular edge and an inner circular edge 27 delimiting an exit opening. Substrate 16 is, for example, a catalytic type purification member consisting of a gas-permeable structure coated with catalytic metals promoting the oxidation of the combustion gases and / or the reduction of nitrogen oxides. Alternatively, the substrate is a particulate filter. The substrate is then made of a filtration material consisting of a monolithic ceramic or silicon carbide structure having a porosity sufficient to allow the passage of exhaust gas. The diameter of the pores is chosen to be small enough to ensure retention of the particles, and in particular particles of soot, on an upstream face of the filter. The particulate filter can also be made from a ceramic foam or silicon carbide. It may also consist of a cartridge filter or a sintered metal filter. The particulate filter may comprise for example a set of parallel channels divided into a first group of input channels and a second group of output channels. The input and output channels are staggered. The inlet channels open upstream of the particle filter but are closed downstream of the particulate filter. On the contrary, the outlet channels are closed upstream of the particulate filter and open downstream of the particulate filter. The substrate 16 is a block of cylindrically shaped material capable of being housed inside the outer envelope 12, so that its axis coincides with the axis A. The substrate 16 is delimited, longitudinally, by an upstream end face 33 and a downstream end face 34, and, radially, by a lateral face 36. Once in position inside the casing 12, the end faces 33 and 34 of the substrate are arranged transversely to the axis A. According to the first embodiment shown in Figure 1, an upstream shoulder 38 is machined at the upstream end of the side face 36 of the substrate 16. The upstream shoulder 38 allows to release a axial upstream face 39, cylindrical, of axis A and reduced radius d, and an upstream radial face 40 constituting the bottom of the shoulder 38. The distance separating the upstream radial face 40 and the upstream end face 33 defines the depth h of the shoulder 38, and the difference between the radius D d e the lateral face 36 and the radius d of the upstream axial face 40 defines the width I of the shoulder 38. Similarly, the downstream end of the lateral face 36 is machined so that the substrate 16 is provided with a downstream shoulder 41. The downstream shoulder 41 is delimited by a cylindrical downstream axial face 42, of axis A and of reduced radius d, and a downstream radial face 43.

The downstream shoulder 39 is of depth h and width 1. The radius d of a shoulder 38, 41 is slightly smaller than the radius of the inner edge 26, 27 of the flange 24, 25 located on the same side. The upstream and downstream peripheral seals 18 each comprise one or more non-metallic fibers interwoven in a predetermined pattern, in particular knitted or woven. The seals 18 and 20 consist, for example, of one or more silica fibers with a diameter of between 3 μm and 12 μm, preferably with a diameter of approximately 6 μm. The upstream and downstream seals 20 are annular in shape with an L section. Each seal 18, 20 comprises a longitudinal wing 44 and a radial wing 46. The longitudinal wing 44 is interposed between the lateral face 36 of the substrate 16 and the inner face 48 of the outer casing 12. The radial wing 46 is engaged in the upstream shoulder 38, respectively in the downstream shoulder 39, whose dimensions are adapted for this purpose. The gasket 18 or the gasket 20 is axially constrained, on its upstream side, respectively downstream, by the flange 24, 25, of the envelope 12. Thus secured to the casing 12, the radial flange 46 of the upstream gasket 18 , respectively of the downstream seal 20, is pressed against the upstream radial face 40, respectively the downstream radial face 43. The upstream radial faces 40 and downstream 43 of the substrate 16 thus constitute upstream and downstream bearing surfaces for the holding means. The bearing surfaces are located longitudinally recessed from the upstream end faces 33 and downstream 34 of the substrate 16. The depth h of a shoulder 38, 39, is in fact substantially equal to the sum of the thickness s of the radial flange 46 of a seal 18, 20, and the thickness e of the collar 24, 25, of the casing 12. As a result, the seals 18 and 20 are also set back from the end faces Upstream 33 and downstream 34 of the substrate 16. With this arrangement, the device 10 is made compact because its total length is substantially equal to the distance between the upstream end face and downstream of the substrate.

A web 22 serves for thermal insulation. It is situated, radially, between the lateral face 36 of the substrate 16 and the inner face 48 of the outer casing 12 and, longitudinally, between the longitudinal flanges 44 of the joints 18 and 20. The ply 22 has, for example, a thickness of 12 order of 3 mm to 4 mm, substantially equal to the thickness of the longitudinal wings 46 of the joints 18 and 20. The ply 22 has a generally tubular shape. It can be of intumescent type (XPEAV2 or ISOMATAV AV5 of UNIFRAX, INTERAM 100 or INTERAM 600 NC of 3M for example) or non-intumescent type (ECOFLEX 200 OR FLECN263 for example). The layers of fibers are chosen so as to have good elasticity at high temperature, even after a large number of thermal cycles, that is to say successive heating and cooling of the purification device. This elasticity makes it possible to maintain a clamping pressure of the substrate 16 at a high temperature, despite the differential expansion of the substrate 16 and the outer casing 12 of the device. In an alternative embodiment of this first embodiment, the upstream and downstream annular seals have a rectangular section. One face of the upstream gasket, respectively of the downstream gasket, bears against the upstream and downstream radial face of the substrate. This face of the joint has a length equal to or less than the thickness e. In this variant embodiment, the sheet extends axially from the upstream flange to the downstream flange of the envelope so as to surround both the lateral face of the substrate and each of the faces radially outside the upstream seals. and downstream. The purification device may have multiple alternative embodiments. Four alternative embodiments are shown in Figures 2 to 5. In these figures, an element identical to a constituent element of the first embodiment of Figure 1 is identified by the same reference, and a constituent element similar to a constituent element. of the first embodiment is identified by an increased reference respectively of one, two, three and four hundred (s) with respect to the reference carried by the similar element of the first embodiment. In FIG. 2, the substrate 116 comprises a cylindrical core 117 of axis A. The core 117 has, parallel to the axis A, a lateral face 136, and, perpendicular to the axis A, end faces upstream 133 and downstream 134.

A collar 150 is attached to the lateral face 136 of the core 117 so that the substrate 116 has a protrusion projecting radially outwards towards the envelope 112. The collar 150 has an annular shape of rectangular section . It has an upstream radial face 151, a downstream radial face 152, an inner longitudinal face 153 and an outer longitudinal face 154. The inner longitudinal face 153 has a diameter substantially equal to the diameter of the lateral face 136 to allow the insertion of the collar. 150 around the core 117. The collar 150 is secured, for example by gluing on the core 117. The upstream radial faces 151 151 and downstream 152 are upstream and downstream bearing surfaces for holding means. These comprise, in this second embodiment, a seal 120 whose section "U" is complementary to that of the collar 150. The seal 120 has a bottom portion 144 constituting a wing disposed longitudinally between the outer longitudinal face 154 the collar 150 and the inner face 148 of the casing 112. The seal 120 also has an upstream radial flange 146 and a downstream radial flange 147. The upstream radial wings 146 and downstream 147 of the seal 18, 20 abut against radial faces upstream 151 and downstream 152 of the collar 150.

The side wall 121 of the casing 112 is shaped so as to have a housing 162 on its inner face 148. The shape of the housing 162 is adapted to receive the seal 120 and to constrain it axially and radially, so that it is integral. of the envelope 112.

Finally, an upstream sheet 122 is disposed at the interface between the casing 112 and the substrate 116 upstream of the seal 120, and a downstream sheet 123 is disposed at the interface between the casing 112 and the substrate 116, downstream Preferably, the collar 150 is made of a material identical to that of the core of the substrate 116, but does not undergo the steps of depositing catalyst metals, unlike the core 117 of the substrate 116. Indeed, masking a fraction of the upstream or downstream end face of the substrate, the upstream or downstream L-shaped peripheral seals shield the circulation of the exhaust gases in the channels placed at the periphery of the substrate. These peripheral channels are then of no use for the purification process. However, in the prior art, these channels have been coated with precious metals during the impregnation of the material constituting the substrate. It will be noted that, with identical radial dimensions, ie with identical outer radius, the device according to this second embodiment provides a greater contact area between the substrate and the exhaust gas. Indeed, the diameter of the substrate 116 is here greater. In a variant of this second embodiment, instead of being disposed in the median plane of the substrate, the collar is off-center. It is, for example, disposed in the vicinity of the downstream end face of the substrate. The device advantageously comprises no longer downstream ply and the casing is shaped, downstream side, so as to have a U-shaped joint stress flange. In the third embodiment shown in Figure 3, the substrate 216 comprises a cylindrical core 217 and a ring 250 forming a radial projection, directed towards the casing 212. The ring 250 has a semicircular section. It is preferably attached to the core 217. A diametrical face 251 of the ring 250 is bonded to the lateral face 236 of the core 217. The ring 250 rests in a median transverse plane of the substrate 216, equidistant from the upstream end faces. 233 and downstream 234. The ring 250 is preferably made of a material similar to that of the core 217. The outer face 251, shaped in a circular arc, of the ring 250 defines an upstream bearing surface and a bearing surface. downstream for the substrate holding means. In this third embodiment, the purification device 210 does not include a peripheral seal. The longitudinal retention function of the substrate 216 is performed by a recess 220, annular, of the inner face 248 of the casing 212. The substantially semicircular section of the recess 220 is adapted to receive the ring 250 so as to lock longitudinally the substrate 216. The cooperation between the holding means and the upstream and downstream bearing surfaces defined on the outer face 251 of the ring 250 is performed indirectly via a sheet 222, in the form of a sleeve, disposed at the interface between the 212 and the substrate 216. Once the ring 250 is housed inside the recess 220 and that, moreover, the sheet 222 is compressed against the lateral face 236 of the substrate 216, the latter is maintained at inside the envelope 212.

FIG. 4 shows a fourth embodiment of the purification device according to the invention. The lateral face 336 of the substrate 316 is machined in its middle part, so as to have a groove 350. In FIG. 4, the section of the groove 350 is half-circular. The bottom 351 of the groove 350, in an arc of circle, defines an upstream bearing surface and a downstream bearing surface for holding means of the substrate 316. The holding function is performed by a rod 320, for example made in metal fibers, forming a ring of circular section on the inner face 348 of the casing 312. The rod 320 is secured to the inner face 348 of this casing, for example by welding, so as to form a protrusion protruding radially towards the substrate 416. The diameter of the rod 320 is equal to that of the groove 350 to allow support of the rod 320 in the groove 350 of the substrate 316. The cooperation of the rod 320 and the groove 350 by direct mutual support allows to maintain longitudinally the substrate 316 inside the casing 312.

It will be noted that, on either side of the rod 320, the device 310 comprises an upstream ply 322, disposed longitudinally between the upstream end face 333 of the substrate 316 and the rod 320, and a downstream ply 323, arranged longitudinally between the rod 320 and the downstream end face 334 of the substrate 316.

A fifth embodiment is shown in FIG. 5. The substrate 416 is machined so that its lateral face 436 is provided with a groove 450. This groove is located in a median plane, between the end faces. upstream 433 and downstream 434 of the substrate 416. The groove 450 is annular and of rectangular section. The groove 350 is delimited by a bottom 451, an upstream transverse face 452 and a downstream transverse face 453. The upstream transverse faces 452 and downstream 453 define, respectively, upstream and downstream bearing surfaces for holding means. The outer face 421 of the envelope 412 has a recess 420, so that the inner face 448 of the envelope 412 has a protuberance 420 projecting radially towards the axis A. The projection height of the protuberance 420 is adapted to cooperate with the groove 450 placed vis-à-vis. The purification device 410 comprises a sheet 422 disposed between the envelope 412 and the lateral face 436 of the substrate 416. The sleeve-shaped sheet 422 extends longitudinally from the upstream end face 433 to the downstream end face 434 of the substrate 416. During the assembly of the purification device 410, the substrate 416 is first inserted inside the casing 412. Then, the protuberance 420 is made by crimping the casing. 412 envelope at the throat 450. The sheet 422 is then compressed between the side face 436 of the substrate 416 and the inner face 448 of the casing 412, and in particular between the groove 450 and the protrusion 420. The longitudinal retention of Substrate 416 is thus produced by the support, via the sheet 422, of the protuberance 420 against the upstream radial faces 452 or downstream 453 of the groove 450. Unlike the second and third embodiments, in the fourth and fifth modes of e embodiment, the envelope has no projection on its outer wall. This advantageously makes it possible to reduce the outer radius of the device, in particular with respect to the outer radius of the device according to the first embodiment. Alternatively, while the substrate has been described as having a substantially circular section in a plane transverse to the axis A, it has a rectangular section with rounded, oval corners, or the equivalent.

Claims (21)

CLAIMS1.- A device for purifying the exhaust gases of a heat engine, of the type comprising: - an outer envelope (12; 112; 212; 312; 412) defining, along an axis A, a passage duct exhaust gases; a gas purifying substrate (16; 116; 216; 316; 416) housed within the outer casing and having upstream (33; 133; 233; 433) and downstream (34; 134; 234; 334; 434) disposed substantially transversely to said axis; and, holding means (18, 20; 120; 220; 320; 420) integral with the casing and capable of cooperating with at least one bearing surface of the substrate for axially locking the substrate with respect to the casing; characterized in that said bearing surface (40, 43; 151, 152; 251; 351; 452; 453) is carried by a lateral face (33; 136; 236; 336; 436) of the substrate and is located axially recessed from the upstream and downstream end faces of the substrate. 2.- Device according to claim 1, characterized in that said holding means (18, 20; 120; 220; 320; 420) are adapted to be axially recessed from the upstream and downstream end faces of the substrate. 3.- Device according to claim 1 or claim 2, characterized in that the substrate (116; 216) has a relief (150; 250), projecting radially away from the axis (A), said relief carrying an upstream bearing surface and a downstream bearing surface. 4.- Device according to claim 3, characterized in that the relief (150; 250) is an insert on a core portion (117; 217) of the substrate. 5.- Device according to claim 4, characterized in that said relief (150; 250) is of a material similar to that of said core. 6.- Device according to any one of claims 3 to 5, characterized in that it comprises a collar (150) having transverse faces upstream (151) and downstream (152) forming upstream and downstream bearing surfaces. 7.- Device according to claim 1 or claim 2, characterized in that the lateral face (36; 336; 436) of the substrate (16; 316; 416) has a recess (38,41; 350; depression radially inwardly relative to the side face of the substrate, said recess carrying said at least one bearing surface (40, 43; 351; 452, 453). 8.- Device according to claim 7, characterized in that said recess is a groove (350; 450). 9.- Device according to claim 7, characterized in that said recess is a shoulder (38, 39) on one of the upstream end faces (33) and downstream (34) of the substrate (16), the radial face bottom (40, 41) of the shoulder defining said bearing surface. 10.- Device according to any one of the preceding claims, characterized in that the holding means comprise a peripheral seal (18, 20; 120) having at least one flange (46; 146) bearing on said at least one bearing surface (40, 43; 151; 152). 11.- Device according to claim 9 and claim 10 in combination, characterized in that the seal (18, 20) has an L-shaped profile and comprises a longitudinal flange (44) disposed between the substrate (16) and the envelope (12), and a radial flange (46) bearing against the bearing surface (40, 43) of the shoulder (38, 39). 12.- Device according to claim 6 and claim 10 in combination, characterized in that the seal (120) has a profile "U" and comprises a bottom (144) forming a longitudinal wing disposed between the substrate (116) and the casing (112), and two radial wings (146, 147), respectively upstream and downstream, supporting the support surfaces, respectively upstream (151) and downstream (152) of the collar (150). 13.- Device according to claim 12, characterized in that the casing (112) is shaped so as to have a housing (162) for receiving the seal (120) to axially secure with the casing. 14.- Device according to any one of claims 7 to 9, characterized in that said holding means comprise a protuberance (320; 420) carried by the casing (312; 412), projecting radially inwards by relative to an inner face (348; 448) of the envelope, the shape of which is adapted to the geometry of the recess (350; 450) of the substrate (316; 416). 15.- Device according to any one of claims 7 to 9, characterized in that said holding means comprise a protuberance (220) carried by the casing (212), projecting radially outwardly with respect to a face interior (248) of the envelope, whose shape is adapted to the geometry of the relief (250) of the substrate (216). 16.- Device according to claim 14, characterized in that the protrusion is a rod (320) fixed on the inner face (348) of the casing (312) and having a section complementary to that of the groove (350) provided on the substrate (316). 17.- Device according to claim 14, characterized in that the protuberance (420) is formed by a narrowing of the wall (421) of the casing (412). 18.- Device according to one of the preceding claims, characterized in that it comprises at least one layer of fibers (22; 122; 123; 222; 322; 323; 422) compressed between the side face of the substrate and the envelope. 19- Device according to claim 18, characterized in that the holding means (220; 420) cooperate with said bearing surface (251; 452; 453) of the substrate via the fiber web (222; 422). 20. Exhaust line of a thermal engine comprising an exhaust gas purification device, characterized in that said exhaust gas purification device is a device according to any one of claims 1 to 19. 21. A motor vehicle equipped with a heat engine and an exhaust line, characterized in that said exhaust line includes a gas purification device according to any one of claims 1 to 19.