US20190186324A1 - Heat recovery device and corresponding manufacturing process - Google Patents

Abstract

A heat recovery device comprises a body inwardly delimiting an exhaust gas circulation passage and a heat exchanger. The heat exchanger includes a casing, a plurality of exhaust gas circulation tubes and at least one grate arranged in the proximal opening of the casing. The grate comprises a wall in which orifices are arranged for receiving tubes. The grate also has an upright edge protruding toward an inside of the heat exchanger, the upright edge being rigidly attached to the casing. The wall of the grate has, around the orifices, a planar surface turned toward the body. The body has an opening delimited by a flat edge pressed against the planar surface. The planar surface and the flat edge are rigidly attached to one another to be tight with respect to exhaust gases.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a U.S. non-provisional application claiming the benefit of French Application No. 1762294, filed on Dec. 15, 2017, which is incorporated herein by herein in its entirety.
FIELD OF INVENTION
• The invention generally relates to heat recovery devices for exhaust lines.
BACKGROUND OF THE INVENTION
• Motor vehicle exhaust lines may include heat exchangers of the type shown inFIG. 1. Such a heat exchanger1 comprises a plurality of exhaustgas circulation tubes3. Thesetubes3 are held at each of their longitudinal ends by agrate5. Acasing7 is placed around thetubes3 and grates5. Thetubes3, thegrates5, and thecasing7 are attached to one another by brazing in a furnace.
• Eachgrate5 includes anupright edge9 oriented toward an outside of the heat exchanger1, to be attached on abody11, shown inFIG. 2. Thebody11 is, for example, integrated into a three-way valve making it possible to orient the exhaust gases selectively either toward the heat exchanger1 or toward a bypass pipe of the heat exchanger1. Anend rim13 of theupright edge9 must be far enough away from the junction between thegrate5 and thecasing7 so as not to cause the braze securing thegrate5 to thecasing7 to melt during the welding of thegrate5 on thebody11.
• Thegrate5 has a generally rectangular shape. It may be formed from a flat metal sheet, the sides of which are folded down to give it a basin shape, and thus to create theupright edge9. The metal sheet is next pierced to create orifices for receiving thetubes3.
• During the shaping of the flat metal sheet, the material is compressed at each corner of theupright edge9. The surface condition inside the four corners is not good. Folds can be seen both inside and outside the basin.
• Thus, the shaping of thegrate5 does not make it possible to have a good surface condition, or good dimensional allowances, in each corner of theupright edge9.
• Furthermore, it is difficult to obtain good flatness of each of the sides of theupright edge9. This is due to the resilient return of the material in the four corners.
• Furthermore, as visible inFIG. 2, the exchanger1 can be attached to abarrel stretcher15 arranged in thebody11. Theupright edge9 is inserted inside thebarrel stretcher15.
• Although the barrel stretching is obtained by an elongation of the material and not by compression, the edges of thebarrel stretcher15 are absolutely not planar, due to the resilient return of the material during the shaping. The edges of thebarrel stretcher15 are not perpendicular to the plane of the opening delimited in thebody11, the undercut angle being approximately 2°.
• Thus, the play between theupright edge9 of thegrate5 and thebarrel stretcher15 is not constant, and may be greater than 0.5 mm on average.
• It is possible to consider butt welding theupright edge9 and thebarrel stretcher15, in the configuration shown inFIG. 2.
• In the exhaust field, the welding method traditionally used is MAG (Metal Active Gas). With such a welding method, the significant play between theupright edge9 and thebarrel stretcher15 may generate defects, or even holes.
• For lap welding, it would be necessary to have theupright edge9 and thebarrel stretcher15 go past one another. Yet the length of theupright edge9 is limited by the fact that the compression of the material in the corners becomes impossible past a certain limit.
• Likewise, thebarrel stretcher15 has a maximum length, related to the acceptable maximum elongation of the material.
• Furthermore, the MAG method has certain known flaws, the most significant of which is deforming the parts to be welded, because these parts are heated to a high temperature, and locally.
• This flaw is particularly critical when the heat exchanger1 must be rigidly attached to a valve body, which must have a good final geometry in order for the axis of the flap to be able to rotate without interference with the valve body, and for the valve to have a good sealing level.
• In this context, the invention aims to propose a heat recovery device that does not have the above flaws.
SUMMARY OF THE INVENTION
• The invention relates to a heat recovery device for an exhaust line, the device comprising a body inwardly delimiting an exhaust gas circulation passage, and a heat exchanger, the heat exchanger comprising:
• a casing having a proximal edge delimiting a proximal opening;
• a plurality of exhaust gas circulation tubes, extending inside the casing;
• at least one grate arranged in the proximal opening, the at least one grate comprising a wall in which orifices are arranged, each exhaust gas circulation tube having a proximal end engaged in one of the orifices and attached to the at least one grate, the at least one grate further having an upright edge extending around the wall and protruding from the wall toward an inside of the heat exchanger, the upright edge being rigidly attached to the casing;
• the wall of the at least one grate having, around the orifices, a planar surface turned toward the body;
• the body having a body opening delimited by a flat edge pressed against the planar surface; and
• the planar surface and the flat edge being rigidly attached to one another to be tight with respect to exhaust gases.
• Thus, in the invention, the at least one grate is turned in a direction oppositeFIG. 1. This makes it possible to make the connection between the body and the grate at the planar surface of the grate surrounding the receiving orifices of the tubes. It is therefore no longer necessary to perform barrel stretching around the opening of the body, the connection between the body and the grate being done at two planar surfaces that are parallel to one another.
• This advantageously makes it possible to secure the at least one grate and the body through either a brazing method or a laser welding method.
• These methods are advantageous, since they do not require considerable heating of the parts, and therefore minimize the risk of deformation of the body.
• Obtaining good flatness of the planar surface of the at least one grate and the flat edge of the body is easier than monitoring the geometry of the barrel stretching or the upright edge on the device ofFIGS. 1 and 2.
• Furthermore, the height of the upright edge is less significant than inFIGS. 1 and 2, since it is not necessary to extend the latter to the free edge of the barrel stretcher. It is only necessary to provide the junction with the casing of the heat exchanger. The manufacture of the at least one grate is easier, and the deformations are less pronounced.
• The heat recovery device may also have one or more of the features below, considered individually or according to all technically possible combinations:
• the planar surface and the flat edge are rigidly attached to one another by laser welding or by brazing;
• the upright edge of the at least one grate is rigidly attached to the proximal edge of the casing, the wall of the at least one grate being offset toward an outside of the casing;
• the planar surface has a closed contour and has a width of at least two millimeters;
• the casing includes a central tubular part having a first straight section, the proximal opening having a second section greater than the first straight section;
• the proximal edge of the casing is connected to the central tubular part by a tubular segment that flares from the central tubular part, the tubular segment delimiting a heat transfer fluid circulation channel along the at least one grate;
• the casing has a heat transfer fluid inlet and a heat transfer fluid outlet, the heat transfer fluid inlet being arranged in the central tubular part, the central tubular part having a zone protruding toward the outside of the casing extending from the heat transfer fluid inlet to the heat transfer fluid circulation channel along the at least one grate;
• the exhaust gas circulation tubes have protuberances forming spacers maintaining a determined spacing between the exhaust gas circulation tubes, and between the exhaust gas circulation tubes and the casing, the protuberances in contact with the casing all being located outside the heat transfer fluid circulation channel along the grate;
• the planar surface extends in a first plane, the orifices being surrounded by a ridge adjacent to the planar surface, the ridge extending in a second plane parallel to the first plane and offset toward the inside of the heat exchanger relative to the first plane.
• According to a second aspect, the invention relates to a method for manufacturing a heat recovery device having the above features,
• assembling the casing, the exhaust gas circulation tubes and the at least one grate to one another by brazing; and
• attaching the planar surface of the at least one grate and the flat edge of the body to one another by laser welding or by brazing.
BRIEF DESCRIPTION OF THE DRAWINGS
• Other features and advantages of the invention will emerge from the detailed description thereof provided below, for information and non-limitingly, in which:
• FIG. 1 is a cross-sectional view of a heat exchanger not according to the invention;
• FIG. 2 is a sectional view of one end of the heat exchanger ofFIG. 1, attached on a body;
• FIG. 3 is an exploded view of heat exchanger of a heat recovery device according to the invention;
• FIG. 4 is a longitudinal sectional view of the heat exchanger ofFIG. 3, in the assembled state;
• FIG. 5 is a sectional view of one end of the heat exchanger ofFIGS. 3 and 4, attached on a body;
• FIG. 6 is a perspective view of the heat exchanger ofFIGS. 3 to 5;
• FIG. 7 is a bottom view of the heat exchanger, for an alternative embodiment;
• FIG. 8 is an enlarged sectional view of part of one of the grates of the heat exchanger ofFIGS. 3 and 4; and
• FIG. 9 is a perspective view of the grate ofFIG. 8.
DETAILED DESCRIPTION
• Theheat recovery device17 is provided to be integrated into an exhaust line, typically an exhaust line of a vehicle equipped with a heat engine. The vehicle is, for example, a motor vehicle, typically a car or truck.
• Theheat recovery device17 is provided to recover part of the heat energy from the exhaust gases circulating in the exhaust line. The heat energy thus recovered is used on board the vehicle, for example to accelerate the temperature increase of the heat engine, or to heat the passenger cab.
• Theheat recovery device17 shown inFIGS. 3 to 5 comprises a body19 (FIG. 5) inwardly delimiting an exhaustgas circulation passage21, and aheat exchanger23.
• Thebody19 has anopening25, through which thecirculation passage21 communicates with theheat exchanger23.
• Thebody19 is, for example, a valve body. In this case, the valve is typically a three-way valve, thebody19 having at least one exhaust gas inlet and two outlets, all communicating fluidly with thecirculation passage21. The inlet is in fluid communication with a collector capturing the exhaust gases at the outlet of the combustion chambers of the heat engine. One of the outlets constitutes theopening25 and communicates with the exhaust gas circulation side of theheat exchanger23. The other outlet emerges in a bypass pipe of the heat exchanger. InFIG. 5, only oneopening25 has been shown.
• Alternatively, thebody19 is an exhaust gas circulation pipe, the heat exchanger being mounted in a bypass on said pipe.
• As illustrated inFIGS. 3 to 5, theheat exchanger23 comprises acasing27, and a plurality of exhaustgas circulation tubes29, extending inside thecasing27.
• Thetubes29 communicate fluidly with thecirculation passage21 through theopening25.
• Thecasing27 has aproximal edge31, delimiting aproximal opening33.
• It also includes adistal edge35, delimiting adistal opening37. Theproximal edge31 and thedistal edge35 have closed contours.
• Theheat exchanger23 also includes at least onegrate39, arranged in theproximal opening33. Thegrate39 comprises awall41 in whichorifices43 are arranged.
• Eachtube29 has aproximal end45, arranged in one of theorifices43 and attached to thegrate39.
• Advantageously, theheat exchanger23 comprises anothergrate47 arranged in thedistal opening37. Theother grate47 comprises awall49 in whichorifices51 are arranged. Eachtube29 has adistal end53 engaged in one of theorifices51 and attached to theother grate47.
• Typically, thegrate39 and theother grate47 are identical in all points. Only thegrate39 will therefore be described below in detail.
• Preferably, thetubes29 are rectilinear, and extend longitudinally from theproximal end45 to thedistal end53.
• For example, thetubes29 have, in a transverse plane perpendicular to the longitudinal direction, a substantially rectangular section, constant over the entire longitudinal length of thetube29. The section is elongated along a transverse direction T. The longitudinal L and transverse T directions are shown inFIG. 3.
• Eachtube29 therefore has twolarge faces55,57, opposite one another, and connected to one another by shearededges59. The large faces55,57 extend substantially in planes containing the longitudinal L and transverse T directions. These planes are perpendicular to an elevation direction E, embodied inFIG. 3.
• Advantageously, thetubes29 are all stacked along the elevation direction. In other words, theheat exchanger23 in a transverse plane comprises no more than a single tube.
• Eachtube29 therefore extends practically over the entire transverse width of theheat exchanger23. Thetubes29 are stacked such that thelarge base55 of a given tube is placed across from thelarge base57 of the tube immediately below it in the stack along the elevation direction.
• Fins62 are placed inside eachtube29 to promote heat exchanges on the gas side. Thefins62 are, for example, made in the form of a metal sheet folded in an accordion and inserted inside thetube29.
• Theorifices43 and51 of thegrates39 and47 have a shape conjugated with that of thetubes29. They therefore have a transversely elongated shape and extend over practically the entire width of the grate. They are arranged in a single column.
• Thegrate39 comprises anupright edge60, extending around thewall41 and protruding from thewall41 toward the inside of theheat exchanger23.
• In the illustrated example, thewall41 is substantially rectangular, with rounded corners. As a result, theupright edge60 includes twosegments61 that are substantially parallel to one another and extend along the transverse direction T, and twosegments63 that are substantially parallel to one another and extend along the elevation direction E. Preferably, the twosegments61 are parallel to one another and extend along the transverse direction T. Preferably, the twosegments63 are parallel to one another and extend along the elevation direction E. Thesegments61 and63 are connected to one another by curved portions.
• Theupright edge60 protrudes along the longitudinal direction L. As shown inFIG. 4, theupright edge60 is engaged in said theproximal edge31 of thecasing27, theproximal edge31 being pressed against an outer surface of theupright edge60. Theupright edge60 is rigidly attached to thecasing27. More specifically, theproximal edge31 is brazed on theupright edge60.
• Thewall41 of thegrate39 is offset toward the outside of thecasing27. Thewall41 is offset along the longitudinal direction L. This means that thewall41 is not located inside thecasing27, but is located longitudinally past theproximal end31 of thecasing27.
• Thewall41 of thegrate39 has, around theorifices43, aplanar surface65 turned toward thebody19.
• Typically, theplanar surface65 extends in a determined plane. This plane is perpendicular to the longitudinal direction L and therefore contains the transverse direction T and the elevation direction E.
• Theplanar surface65 extends all around theorifices43. Theplanar surface65 therefore has a closed contour.
• It has a width of at least 2 mm, for example of between 2 and 5 mm. This width is taken along a direction perpendicular to ajunction line67 between theupright edge60 and thewall41. In other words, this width is taken along the elevation direction E along thesegment61 of theupright edge60, and along the transverse direction T along thesegment63 of theupright edge60.
• Theplanar surface65 extends, in the illustrated example, up to thejunction line67 between theupright edge60 and thewall41, i.e., up to the outer edge of thewall41.
• Theopening25 is cut out in a wall of thebody19.
• Typically, it is cut out in a substantiallyplanar zone68 of the wall, preferably with a flatness of less than 0.3. Thisplanar zone68 delimits, on one side, the inside of thecirculation passage21, and is therefore in direct contact with the exhaust gases. On the opposite side, it is in contact with thegrate39 of the heat exchanger.
• Theopening25 of thebody19 is delimited by aflat edge69, pressed against theplanar surface65.
• Theflat edge69 is therefore in contact on one side with theplanar surface65, and on the opposite side of theplanar surface65, with the exhaust gases circulating in thebody19.
• Theplanar surface65 and theflat edge69 are rigidly attached to one another to be tight with respect to the exhaust gases.
• Theplanar surface65 and theflat edge69 are directly attached to one another.
• Theplanar surface65 and theflat edge69 are rigidly attached to one another by laser welding or by brazing.
• Theplanar zone68 does not bear any relief around theflat edge69, which makes it possible to adjust the position of thegrate39 relative to thebody19.
• It should be noted that theother grate47 is also mounted on a planar zone, such that it is possible to adjust the positions of both ends of the heat exchanger relative to one another.
• Theflat edge69 has, toward theheat exchanger23, a planarouter surface71, pressed against theplanar surface65.
• This planarouter surface71 extends in a plane, said plane being perpendicular to the longitudinal direction L in the illustrated example.
• Theedge69 has a closed contour and extends all the way around theopening25.
• Theopening25 has a size and shape such that all of theorifices43 are located in line with saidopening25. The proximal ends45 of thetubes29 protrude past thegrate39, and penetrate slightly inside theopening25, as illustrated inFIG. 5.
• Theheat exchanger23 also includes a reinforcinggrate73, arranged to reinforce the connection between thetubes29 and thegrate39. It advantageously includes another reinforcinggrate75, arranged to reinforce the connection between thetubes29 and theother grate47. Thegrate73 and thegrate75 are identical, only thegrate73 therefore being described below.
• The reinforcinggrate73 is a plate in which apertures77 have been arranged. Theapertures77 are delimited by necks79 (FIG. 5) and are each passed through by theproximal end45 of one of thetubes29. Theapertures77 are each placed across from one of theorifices43. Thenecks79 are brazed on thetubes29. Theperipheral edge81 of the reinforcing plate, and thefields83 located between theapertures77, are brazed on the inner surface of thewall41.
• In the illustrated example, theproximal edge31 and thedistal edge35 of thecasing27 are located at the two opposite longitudinal ends thereof.
• Thecasing27 is made in two half-shells85,87. The half-shells85,87 are secured to one another by brazing, along two longitudinal lines89 (FIG. 6).
• Each half-shell85,87 has a U-shaped section in a plane perpendicular to the longitudinal direction L.
• Thecasing27 includes a centraltubular part91 having a first straight section, theproximal opening33 having a second section greater than the first section (FIG. 4). Likewise, thedistal opening37 has a section greater than the first section, and typically equal to the second section.
• To that end, theproximal edge31 of thecasing27 is connected to the centraltubular part91 by atubular segment93 that flares from the centraltubular part91.
• Likewise, thedistal edge35 of thecasing27 is connected to the centraltubular part91 by anothertubular segment95 that flares from the centraltubular part91.
• Thetubular segment93 delimits a heat transferfluid circulation channel97 along thegrate39. Likewise, thetubular segment95 delimits a heat transferfluid circulation channel98 in contact with theother grate47.
• The passage section offered to the heat transfer fluid by thecirculation channel97, and also by thecirculation channel98, is significantly greater than in the heat exchanger shown inFIG. 1.
• This results from several constructive arrangements of the heat exchanger.
• First of all, theplanar surface65 of thewall41 is significantly wider in the invention than in the heat exchanger ofFIG. 1. Indeed, thisplanar surface65 is deliberately made wider in the invention, to allow good quality tight attachment of theflat edge69 on theplanar surface65.
• Furthermore, as previously stressed, in the invention, thewall41 is offset toward the outside of thecasing27. In the heat exchanger ofFIG. 1, the wall in which the receiving orifices of the tubes are arranged is placed inside thecasing7.
• This large passage section of thecirculation channel97 is particularly advantageous, since it is thus possible to increase the heat transfer fluid flow rate in contact with thegrate39. Thegrate39 is typically located at the exhaust gas inlet inside the heat exchanger. Yet the heat exchangers used in exhaust lines must never come to a boil. The most critical zone with respect to boiling is always located on the exhaust gas inlet side, i.e., in the zone where the exhaust gases are hottest. In case of boiling, the heat transfer fluid turns to vapor, such that the heat exchanges at the inlet of the heat exchanger are gas-gas locally. As a result, the skin temperature of the exchanger increases quickly, and may approach the temperature of the exhaust gases (for example, around 850° C.). This risks locally creating a thermal shock and temperature gradients causing breaks, and therefore leaks, at the brazes securing the various components of the heat exchanger to one another.
• It is therefore critical for a heat exchanger of this type for the heat transfer fluid flow rate in thegrate39 to be high enough to prevent any risk of boiling.
• Thecasing27 has a heattransfer fluid inlet99 and a heat transfer fluid outlet101 (FIGS. 3 and 6).
• In the illustrated example, the heattransfer fluid inlet99 andoutlet101 are arranged in the half-shell87. The heattransfer fluid inlet99 andoutlet101 are arranged side by side, and offset longitudinally relative to one another. Theinlet99 is located on the side of thegrate39, and theoutlet101 on the side of thegrate47. In other words, the heattransfer fluid inlet99 is located toward the exhaust gas inlet and the heattransfer fluid outlet101 toward the exhaust gas outlet.
• The heattransfer fluid inlet99 is located in the centraltubular part91 of thecasing27. Advantageously, and as illustrated inFIG. 7, the centraltubular part91 has azone103 protruding toward the outside of thecasing27, extending from the heattransfer fluid inlet99 to the heat transferfluid circulation channel97, along thegrate39.
• Thezone103 is not shown inFIGS. 3 to 5.
• More specifically, thecasing27 has twolarge faces105 and107, which are substantially perpendicular to the elevation direction E, and two side faces109, which are substantially perpendicular to the transverse direction T, and connecting thefaces105 and107 to one another. The heattransfer fluid inlet99, and typically the heattransfer fluid outlet101, are arranged in one of the side faces109. The protrudingzone103 is advantageously arranged on thelarge face107. It has a generally triangular shape, as shown inFIG. 7. It extends transversely from the heattransfer fluid inlet99 to theside face109 opposite the heattransfer fluid inlet99. Its width, taken along the longitudinal direction, decreases from the heattransfer fluid inlet99 toward theside face109 opposite the heattransfer fluid inlet99.
• Advantageously, the protrudingzone103 protrudes relative to acentral zone111 of the centraltubular part91 over a height substantially equal to that of theproximal end31.
• The protrudingzone103 makes it possible to collect the heat transfer fluid at the heattransfer fluid inlet99, and to steer it preferentially toward thecirculation channel97. This promotes the cooling at the inlet of the heat exchanger and limits the risk of boiling.
• Advantageously, thecasing27 also includes another protrudingzone112, extending from the heattransfer fluid outlet101 to the heat transferfluid circulation channel98 along the other grate47 (FIG. 7).
• The protrudingzone112 is symmetrical with the protrudingzone103 relative to the median plane of the heat exchanger perpendicular to the longitudinal direction L.
• Thetubes29 haveprotuberances113 forming spacers maintaining a determined spacing between thetubes29, and between thetubes29 and thecasing27. Theseprotuberances113 are distributed on the large faces55 and57 of the tubes.
• In the illustrated example, each of the large faces55,57 has around tenprotuberances113.
• Theprotuberances113 protrude toward the outside of thetubes29. They are obtained by deformation of the metal making up thetube29.
• Theprotuberances113 in contact with thecasing27 are all located outside the heat transferfluid circulation channel97 along thegrate39, and typically also outside the heat transferfluid circulation channel98 along theother grate47.
• This is favorable to the mechanical strength between thecasing27 and theprotuberances113.
• Preferably, these protuberances are also located outside the protrudingzone103 and outside the protrudingzone112.
• Typically, theprotuberances113 formed on the large faces55 of atube29 are located across from theprotuberances113 formed on the large faces57 of saidsame tube29. “Across from” means opposite one another along the elevation direction E. Likewise, theprotuberances113 formed on a giventube29 are located in the extension of theprotuberances113 of theother tubes29 along the elevation direction E, as illustrated inFIG. 4. In other words, all of thetubes29 haveprotuberances113 having the same arrangement on their two opposite large faces55,57, such that saidprotuberances113 form stacks in a column, along the elevation direction E. This is favorable to increasing the rigidity of theheat exchanger23.
• According to another advantageous aspect of the invention, theplanar surface65 of thegrate39 extends in a first plane P1, theorifices43 being surrounded by aridge115 adjacent to theplanar surface65, theridge115 extending in a second plane P2 parallel to the first plane P1 and offset toward the inside of theheat exchanger23 relative to the first plane P1. This is illustrated inFIG. 8.
• Theridge115 extends over the entire perimeter of theorifices43. It has a closed contour, and is inwardly adjacent to theplanar surface65. It is separated from theplanar surface65 by a step.
• Thus, during the brazing of theheat exchanger23, the brazing material cannot spread over theplanar surface65. It is retained by the step separating theridge115 from theplanar surface65.
• According to another aspect, the invention relates to the process for manufacturing theheat recovery device17 described above.
• This manufacturing process comprises the following steps:
• assembly by brazing thecasing27,tubes29 and grate39 to one another;
• attaching theplanar surface65 of thegrate39 and theflat edge69 of thebody19 to one another by laser welding or by brazing.
• Typically, in the assembly step, theother grate47 is assembled by brazing to thecasing27 and thetubes29.
• Furthermore, the reinforcinggrates73,75 are advantageously assembled by brazing to thetubes29 and thegrates39,47, in the same step.
• The assembly step also makes it possible to secure the half-shells85,87 of thecasing27 to one another.
• As described above, thecasing27 is assembled to thegrate39 by brazing of theproximal edge31 on theupright edge60.
• Thetubes29 are assembled to one another by brazing, said brazing preferably being done at theprotuberances113.
• Thetubes29 are assembled to thecasing27 by brazing of theprotuberances113 on thecasing27, and more specifically on the centraltubular part91 of thecasing27.
• The brazing step is advantageously done in a furnace.
• When the attachment of theplanar surface65 on theflat edge69 is done by laser welding, this welding is done by transparency, through theflat edge69. The weld line has a closed contour, and extends over the entire perimeter of theopening25.
• When the attachment is done by brazing, brazing paste is deposited between theflat edge69 and theplanar surface65. The brazing paste is melted, for example, by placing thebody19 and theheat exchanger23 in a furnace. In this case, the brazing of theplanar surface65 and theflat edge69 can be done at the same time as the assembly by brazing of the different elements of the heat exchanger to one another.
• Theheat recovery device17, and the corresponding manufacturing process, can assume multiple variants.
• Thegrate47 arranged in thedistal opening37 of thecasing27 could be of a different type from that arranged in theproximal opening33.
• Thetubes29 do not necessarily have the shape described above. They could a circular section, an oval section, or any other appropriate section. These tubes are not necessarily rectilinear, but alternatively are curved. In this case, thedistal opening37 of thecasing27 is not necessarily placed longitudinally across from theproximal opening33.
• The heat transfer fluid is typically a liquid. Alternatively, it is another type of fluid.
• Theheat exchanger23 is not necessarily symmetrical relative to a median transverse plane of the heat exchanger. It may not include acirculation channel98 of the heat transfer fluid in contact with theother grate47 and/or not include a protrudingzone112.
• Thewall41 of thegrate39 may have all types of shapes. It is not necessarily rectangular. Alternatively, thewall41 is circular, or elliptical, or has any other appropriate shape.
• In this case, theopening25 arranged in thebody19 also does not have a rectangular shape. It typically has a shape corresponding to the shape of thegrate39, and more particularly to the shape of thewall41.
• To attach thegrate39 to thecasing27, theupright edge60 is not necessarily engaged inside theproximal edge31 of thecasing27. Alternatively, it is theproximal edge31 of thecasing27 that is engaged in theupright edge60 of thegrate39.
• Thecasing27 is not necessarily made up of two half-shells85,87 assembled to one another. It could be obtained by rolling a metal sheet around the longitudinal axis, or by deforming a tube segment.
• Thetubes29 may be arranged in all types of different ways inside theheat exchanger23. In particular, it is possible to placeseveral tubes29 next to one another transversely and not just one as described above.
• Theplanar surface65 does not necessarily extend in a single plane. It may include several planar zones, arranged in several planes parallel to one another or tilted relative to one another. In these cases, theflat edge69 has substantially the same shape as theplanar surface65. In any case, theflat edge69 and theplanar surface65 are in contact with one another over a zone with a closed contour surrounding theopening25 and surrounding all of theorifices43,51. This zone is wide enough to allow the attachment of theplanar surface65 and theflat edge69 to one another, preferably by laser welding or by brazing.
• Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.

Claims (11)

1. A heat recovery device for an exhaust line, the device comprising:

a body inwardly delimiting an exhaust gas circulation passage; and

a heat exchanger comprising:

a casing having a proximal edge delimiting a proximal opening;

a plurality of exhaust gas circulation tubes extending inside the casing;

at least one grate arranged in the proximal opening, the at least one grate comprising a wall in which orifices are arranged, each exhaust gas circulation tube having a proximal end engaged in one of the orifices and attached to the at least one grate, the at least one grate further having an upright edge extending around the wall and protruding from the wall toward an inside of the heat exchanger, the upright edge being rigidly attached to the casing;

the wall of the at least one grate having, around the orifices, a planar surface turned toward the body;

the body having a body opening delimited by a flat edge pressed against the planar surface; and

the planar surface and the flat edge being rigidly attached to one another to be tight with respect to exhaust gases.

2. The device according toclaim 1, wherein the planar surface and the flat edge are rigidly attached to one another by laser welding or by brazing.

3. The device according toclaim 1, wherein the upright edge of the at least one grate is rigidly attached to the proximal edge of the casing, the wall of the at least one grate being offset toward an outside of the casing.

4. The device according toclaim 1, wherein the planar surface has a closed contour and has a width of at least two millimeters.

5. The device according toclaim 1, wherein the casing includes a central tubular part having a first straight section, the proximal opening having a second section greater than the first straight section.

6. The device according toclaim 5, wherein the proximal edge of the casing is connected to the central tubular part by a tubular segment that flares from the central tubular part, the tubular segment delimiting a heat transfer fluid circulation channel along the at least one grate.

7. The device according toclaim 6, wherein the casing has a heat transfer fluid inlet and a heat transfer fluid outlet, the heat transfer fluid inlet being arranged in the central tubular part, the central tubular part having a zone protruding toward an outside of the casing extending from the heat transfer fluid inlet to the heat transfer fluid circulation channel along the at least one grate.

8. The device according toclaim 6, wherein the plurality of exhaust gas circulation tubes have protuberances forming spacers maintaining a determined spacing between the plurality of exhaust gas circulation tubes, and between the plurality of exhaust gas circulation tubes and the casing, the protuberances in contact with the casing all being located outside the heat transfer fluid circulation channel along the at least one grate.

9. The device according toclaim 1, wherein the planar surface extends in a first plane, the orifices being surrounded by a ridge adjacent to the planar surface, the ridge extending in a second plane parallel to the first plane and offset toward the inside of the heat exchanger relative to the first plane.

10. The device according toclaim 1, wherein the body opening is cut out in a wall of the body.

11. A process for manufacturing a heat recovery device for an exhaust line, the process comprising the following steps:

providing a body inwardly delimiting an exhaust gas circulation passage and a heat exchanger that includes

a casing having a proximal edge delimiting a proximal opening, a plurality of exhaust gas circulation tubes extending inside the casing, at least one grate arranged in the proximal opening, the at least one grate comprising a wall in which orifices are arranged, each exhaust gas circulation tube having a proximal end engaged in one of the orifices and attached to the at least one grate, the at least one grate further having an upright edge extending around the wall and protruding from the wall toward an inside of the heat exchanger, the upright edge being rigidly attached to the casing;

the wall of the at least one grate having, around the orifices, a planar surface turned toward the body;

the body having a body opening delimited by a flat edge pressed against the planar surface;

assembling the casing, the plurality of exhaust gas circulation tubes and the at least one grate to one another by brazing; and

attaching the planar surface of the at least one grate and the flat edge of the body to one another by laser welding or by brazing to be tight with respect to exhaust gases.

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