FR2907885A1 - Heat exchanger for exhaust gas recirculation circuit of heat engine of motor vehicle, has definition units of fluid circuit placed on ends of cover, and body including extruded part integrated into central partitions defining channels - Google Patents

Abstract

The exchanger has an aluminum body (3) including a tubular shaped external cover (4) with open ends, and central partitions (5) extending parallel from one of the ends to another end by forming a central channel (7). Definition units of a fluid circuit are placed on the ends of the cover. The body includes an extruded part integrated into the partitions defining a set of channels. The units include a closing element (12) fixed by soldering at an end of the central channel from a side of the ends of the external cover.

Description

The present invention relates to fluid transport circuits such as

  than those used in motor vehicles, in particular to recirculate the exhaust gases of the engines of these vehicles. BACKGROUND OF THE INVENTION An exhaust gas recirculation circuit for the engine of a motor vehicle (commonly known as EGR for "Exhaust Gas Recirculation") extends between the exhaust system of the engine and the engine. intake circuit and generally comprises a heat exchanger for cooling the exhaust gas, an uncooled bypass channel, a bypass valve for selectively directing the gas flow into the heat exchanger or the bypass duct , and a control valve for adjusting the flow rate of the gas stream in the recirculation circuit. According to a first embodiment, the heat exchanger comprises a body comprising tubes received in an outer casing whose ends are connected to flanges for connection to the circuit. Such an exchanger comprises a large number of brazed parts to each other, which makes such a complex exchanger and expensive to manufacture.

  There are also exchangers whose body comprises an outer envelope having end-views of connecting flanges and receiving two molded and contiguous half-shells, provided with internal fins to facilitate heat exchange between, on the one hand the fluid to cool circulating between the fins and, on the other hand, the heat transfer fluid flowing between the outer shell and the half-shells. There are other molded structures having a superposition of channels alternately assigned to transport the fluid to be cooled and the heat transfer fluid. These structures have a reduced number of parts but are expensive to produce. OBJECT OF THE INVENTION An object of the invention is to provide a means for solving at least one of the aforementioned drawbacks. SUMMARY OF THE INVENTION For this purpose, there is provided, according to the invention, a heat exchanger comprising a body having a tubular casing having open ends and internal partitions extending parallel from one end of the casing to the other. by delimiting open channels and on the ends of the body are reported independent fluid circuit defining members in the body, the body having at least one extruded portion incorporating at least some of the partitions defining a plurality of channels. Thus, the body has a structure obtained simply and economically by extrusion. The number of parts constituting the exchanger is thus limited.

Other characteristics and advantages of the invention will emerge on reading the following description of particular non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a heat exchanger associated with a valve assembly in accordance with the invention; FIG. of this heat exchanger in section along the plane II of FIG. 1, the flap being in the position of connection of the valve assembly with the exchanger, and FIG. 3 is a partial view, similar to that of FIG. 2, showing the valve assembly when the flap is in a bypass position, - Figure 4 is a fragmentary perspective exploded view of the heat exchanger equipped with the valve assembly according to FIG. 5 is a partial perspective view of the body of the heat exchanger, FIG. 6 is an end view of the body of the heat exchanger according to a first embodiment, FIG. is a view similar to Figure 6 of the body of the exchanger According to a second embodiment, FIG. 8 is a view similar to that of FIG. 6 of the body of the heat exchanger according to a third embodiment, FIG. 9 is a view similar to that of FIG. FIG. 6 is a view similar to that of FIG. 2, of the heat exchanger according to the fourth embodiment; FIG. 11 is a view of a heat exchanger according to a fourth embodiment; partial cutaway 25 of the body of a heat exchanger with a particular profile of channel separation partition, - Figure 12 is a view similar to that of Figure 6 of a heat exchanger body according to a fifth mode of embodiment, 30 - Figures 13 and 14 are end views of the body of the exchanger according to alternative embodiments, before assembly. DETAILED DESCRIPTION OF THE INVENTION The invention is here described in application to an exhaust gas recirculation circuit of a motor vehicle thermal engine. In a manner known per se, the recirculation circuit is provided with means of its connection on the one hand to the exhaust circuit of the engine and on the other hand to the intake circuit of the engine. The operating principle of such a recirculation circuit is known in itself and will not be detailed below. Referring to Figures 1 to 6, the exhaust gas recirculation circuit comprises a heat exchange device 10 comprising a heat exchanger, generally designated 1, associated with a valve assembly, generally designated 2. The exchanger thermal 1 comprises a body generally designated 3, comprising an outer casing 4, 15 of tubular shape, having open ends 4.1, 4.2. The outer casing 4 here has a parallelepipedal shape and comprises walls 4.3, 4.4, 4.5 and 4.6 parallel and opposite two by two. In the outer casing 4, two central partitions 5 extend parallel to each other and to a longitudinal axis 6 of the outer casing 4. The central partitions 5 have opposite longitudinal edges connected to the walls 4.3, 4. 4 in such a way as to define therewith a central channel 7. The central channel 7 comprises enlarged portions 7.1, 7.2 in the vicinity of the walls 4.3, 4.4 so that the central channel 7 has a cross-section here in the form of an I The portions 7.1, 7.2 communicate outside the outer casing 4 by openings 8.1, 8.2 respectively formed in the walls 4.3, 4.4 in the vicinity of the ends 4.1, 4.2 of the outer casing 4. In the casing 4, peripheral partitions 9 extend parallel to each other and to the longitudinal axis 6. The peripheral partitions 9 35 extend on either side of the central channel 7 and have opposite longitudinal edges connected to each other. respectively to the paro is 4.5, 4.6 and the central partitions 5 so as to define with them peripheral channels 10. The peripheral channels 10 here have a rectangular cross section. The central channel 7 has a section greater than that of the peripheral channels 10. The body 3 is made of aluminum by extrusion so that at the outlet of the extruder, the channels 7 and 10 have open ends. Extrusion manufacturing makes it possible to obtain a one-piece body, which limits assembly operations and minimizes manufacturing costs. The body 3 can also be made of a metal other than aluminum and more generally any material having sufficient thermal conduction properties. On the ends 4.1, 4.2 of the ex-dull envelope 4 are fixed independent fluid circuit defining members.

These members comprise two sealing elements 11, 12 fixed by welding to the ends of the central channel 7, respectively on the end-end 4.1 and end-4.2 side of the outer casing 4. These members also comprise an element of FIG. 25 back 13 which has the shape of a cap having a cylindrical segment bottom wall with an axis perpendicular to the walls 4.5, 4.6 and which is fixed on the end 4.2 of the casing 4. The return element 13 allows to return a stream from some of the peripheral channels 10, in this case those identified 10.a extending in the upper half of the outer envelope 4, to the other peripheral channels 10, i.e. those identified 10.b extending in the lower half of the outer envelope 4 (see more particularly Figures 5 and 6).

These members further comprise a connecting element of the ends of the peripheral channels 10, set on the side of the end 4.1, to fluid supply and discharge conduits. This connecting element is here formed by the valve assembly 2. The valve assembly 2 comprises a valve body 21 having an end portion arranged to form a manifold 22 and an end portion 23 delimiting a first conduit 24 opening into the manifold 22 by 10 a seat 25 for a valve 26 movably mounted in the neck-reader 22 between an extreme position of closure and an extreme opening position of the first conduit 24. The end portion 23 is equipped connecting means of the first conduit 24 to an external pipe. The collector 22 extends the first conduit 24 and here forms a flared end thereof. The valve 26 is connected to the rod of an actuator 27 mounted outside the valve body 21 on the side of its end portion 23. The actuator 27, known per se, is arranged to slide. adjustably adjust the valve 26 between its two positions. The collector 22 also defines a second duct 28 opening into the collector 22 on the side of the wall 4.3 and perpendicular to the longitudinal axis 6.

The second conduit 28 is an inlet conduit for a gas stream in the valve assembly 2 and the first conduit 24 is an outlet conduit for the gas stream of the valve assembly 2. The second conduit 28 is thus intended to be connected to the exhaust system of the heat engine and the first duct 24 is intended to be connected to the intake duct of the heat engine. The collector 22 is fitted between two flanges 31 of a flange, generally designated 30, nested and fixed by welding on the end 4.1 of the outer envelope 4. The flanges 31 are parallel to: K walls 4.5, 4.6 of the outer casing 4 and are provided with bearings pivotally receiving an axis 32 of a double flap, generally designated 33, having two flap portions 33.1, 33.2 extending in the extension of one of the on either side of the axis 32. The flange 30 and the flap 33 define an inlet opening 34 in the exchanger 1 facing the peripheral channels 10.a and an outlet opening 35 of the exchanger 1 opposite the peripheral channels 10.b.

The flap 33 is mounted facing the second duct 28 and the opening 34 and is movable between a bypass position (FIG. 3) in which the flap 33 deflects a gas flow coming from the second duct 28 directly to the first duct 24. without passing through the heat exchanger 1 and a connection position (Figure 2) in which the flap 33 guides the gas flow from the second conduit 24 to the inlet opening 34 and the outlet opening 35 to the first conduit 24.

In the connection position, the side and end edges of the flap portion 33.1 are in sealing engagement respectively against seat surfaces 36, 37 extending into the manifold 22 and belonging to the valve body 21; the side and end edges of the flap portion 33.2 are in sealing engagement respectively against seat surfaces 38, 39 belonging to the flange 30. The surfaces 36, 37 extend from one side of the bearings opposite the surfaces 38 39. The shutter 33 in the connection position thus isolates the portion of the manifold 22 into which the second conduit 28 of the portion of the manifold 23 into which the first conduit 24 opens. In the bypass position, the flap 33 deflects the flow As the inlet and outlet of the exchanger all open into the valve body behind the flap, there is no circulation in the heat exchanger even though it is not insulated in a sealed manner with respect to the conduits 24, 28.

The surface 39 belongs to a crosspiece of the flange 30 which is integral with the shutter element 11 of the central channel 7. Due to the structure of the flange 30 and the distribution of the surfaces 36, 37, 38, 39 forming seat of the flap 33 between the valve body 21 and the flange 30, the flange 30 is compact and makes it possible to obtain a small distance between the valve body 21 and the body 3 of the exchanger 1. The flange 30 is a thermally conductive material and constitutes a thermal bridge between the valve body 21 and the body 3 of the exchanger 1. To improve the heat exchange between the valve body 21 and the body 3 of the heat exchanger 1, the collector 22 is provided with a thermally conductive fin 29 which extends perpendicularly to the axis 32 of the flap 33 and which bears on the body 3 of the exchanger 1, here indirectly via the element shutter 11, made of thermally conductive material. The fin 29 thus promotes thermal conduction between the body 3 of the exchanger 1 and the valve body 21. The return element 13 and the flange 30 comprise end-pieces 14, 15 intended to extend opposite the apertures 8.1, 8.2 to allow the connection of pipes to the central channel 7. These tips 14, 15 are welded to the walls 4.3, 4. 4 and are intended to be connected to pipes for transporting a heat transfer fluid. The central channel 7 thus transports the coolant which will allow the cooling of the exhaust gases that will circulate in the peripheral channels 10. The central partitions 5 are thus in contact with the coolant and the gases to be cooled and allow a direct thermal transfer between these, and the peripheral partitions 9 ensure a heat transfer between the gases to be cooled and the heat-exchange fluid via the central partitions 5. The use of a central channel for the heat transfer fluid and Peripheral channels surrounding the central channel for the fluid to be cooled provides a compact and efficient heat exchanger structure by promoting convective and conductive heat transfer. In addition, a single central channel for the heat transfer fluid limits the lengths to be sealed and minimizes the risk of leakage. It will further be noted that, since the shut-off element 11 is in contact with the coolant, the element promotes the cooling of the fin 29 and therefore of the valve body 21. The components welded to the body 3 of the exchanger are laser welded.

According to a second embodiment, the valve assembly 2 and the return element 13 are arranged in such a way that the channels 10.a extend from one side of the central channel 7 opposite to the channels 10.b. see Figure 7).

According to a third embodiment, as represented in FIG. 8, the body 3 of the exchanger 1 comprises only four main peripheral channels 110 made in the mass of the body 3, each of these peripheral channels 110 being subdivided into a plurality of peripheral sub-channels 111 via a zigzag wall 112 attached to each peripheral channel 110. To create turbulence and increase the efficiency of the heat exchanger, these zigzag walls 112 may have reliefs, for example a gauging, to create turbulence in the gas stream.

Although the invention has been described in relation to a U-shaped heat exchanger, the invention is of course applicable to an I-shaped heat exchanger as in the fourth embodiment shown in FIGS. 9 and 10. the body 203 of the exchanger is then connected to the valve body 221 which defines a single conduit 224 while the opposite end of the body 203 is connected to an outer conduit by a connecting element 252.

In this arrangement, the central channel 207 is identical to the central channel 7 previously described, all the peripheral channels 210 of the body 203 of the exchanger are unidirectional and the body 203 of the exchanger comprises two additional channels, namely a channel of 250 and a heat-insulated isolation channel 251 for thermally isolating the bypass channel 250 of the central channel 207. The valve body 221 of the valve assembly 202 is attached to the body 203 of the the exchanger by a flange 230 having a single flap 233 movable between a connection position of the duct 224 to the peripheral channels 210 and a bypass position in which the duct 224 is connected to the bypass channel 250. It will be noted that the duct isolation 251 is expedient. According to a fifth embodiment, represented in FIG. 12, the body 3 of the heat exchanger comprises two peripheral partitions 300, parallel to the walls 4.5, 4.6, having longitudinal edges connected to the walls 4.3, 4.4 to define with these and with the walls 4.5, 4.6 of the main channels 301 for the passage of the coolant. Between the peripheral partitions 300 extend central partitions 302 delimiting central channels 303 of smaller section than the main channels 301 and intended for the passage of cooling gases 2907885 dir. Of course, the invention is not limited to the embodiments described and variations can be made without departing from the scope of the invention as defined by the claims. In particular, the body of the heat exchanger may have a different structure from that described and result for example from the combination of one or more of the embodiments described or result from an assembly of different parts. The number of channels may be different and the sections of those may not be rectangular. The outer envelope and the central channel may thus have a circular section and the peripheral channels a section into annular segments.

Alternatively, the body may comprise at least one extruded portion incorporating at least some of the partitions delimiting (wholly or in part) a plurality of channels. Thus, as shown in FIGS. 13 and 14, the body 3 of the exchanger can result from the assembly 20 of several extruded parts (the body 3 remains an "extruded body" in the sense of the present description. a first extruded part 3.A forming the envelope 4 and a second part 3.B delimiting the channels 3.B comprises a central portion comprising the two central partitions 5 whose adjacent longitudinal edges are connected by partitions 5 'to delimit the central channel 7 which is open only at its ends before the introduction of the shutter elements 11, 12 (not visible here). 9. Part 3.B is mounted in part 3.A in such a way that the walls 4.3, 4.4, 4.5 and 4.6 delimit the peripheral channels 10 with the peripheral walls 9. It is not necessary to fix the ion- 11 2907885 12 gitudin free of the peripheral partitions 9 to the casing 4, a sealing of the peripheral channels 9 relative to each other is not necessary for the proper operation of the exchanger 1. In contrast, the central channel 5 is longitudinally tight him even before the assembly of part 4.8 in part 4.A, the risk of leakage of the coolant to be avoided. It will be appreciated that ribs 70 project from the peripheral walls to increase the exchange surface area with the gas flow. In FIG. 14, two identical extruded parts can be seen forming half-bodies 3.A ', 3.B' de-limiting each: a longitudinal portion of the walls 4.3 and 4.4; one of the walls 4.5, 4.6; one of the central partitions 5 and peripheral partitions 9. The half-bodies 3.A ', 3.B' are joined to form the central channel 7 and are connected to each other by a longitudinal weld extending along the walls 4.3 and 4.4.

Furthermore, other welding processes than the laser welding mentioned in the description of the previous embodiments may furthermore be used for producing the exchanger. As a variant, the partitions of the body of the exchanger 25 may locally have plastic deformations intended to generate turbulence in the gas flow. These partitions may, for example, be corrugated as shown in FIG. 11. The walls of the envelope 4 may also include local plastic deformations, in particular to take account of the environment of the exchanger and to facilitate its implantation (for example for circumvent a boss ...). The seat surfaces for the flap can be made on the flange only. Seat-forming surfaces may also be provided on the valve body, either for only one of the flap positions, or for both flap positions. In the connection position, the edges of the flap 33 can be spaced apart from the seat surfaces belonging to the valve body 21 and to the flange 30 of a distance less than a minimum clearance clearance. By this is meant that there is no sealed support of the shutter on these surfaces but a space extends between them, this space being of sufficiently small dimensions that the resulting leakage is not detrimental to the operation of the heat exchange device. It is also possible to arrange the valve assembly such that the shutter in the bypass position cooperates with seat surfaces belonging to the valve body and / or the flange. The fin 29 is optional. The flow direction of the gases in the valve assembly and the exchanger can of course be reversed relative to that described.

The second duct may be delimited by the flange.

Claims (16)

  1. Heat exchanger, characterized in that it comprises a body (3) comprising a tubular envelope (4) having open ends and internal partitions (5, 9) extending parallel from one end of the envelope to the other delimiting channels (7, 10) opening and in that on the ends of the body are reported defining members (2, 13, 11, 12) of independent fluid circuits in the body, the body having at least one extruded portion incorporating at least some of the partitions defining a plurality of channels.   2. Heat exchanger according to claim 1, wherein the casing (4) belongs to the extruded part.   3. Heat exchanger according to claim 2, wherein all the partitions (5, 9) and the casing (4) belong to the extruded part.   4. Heat exchanger according to claim 1, wherein the body (3) comprises two identical extruded parts forming half-bodies (3.A ', 3.B') connected to each other by a weld to form the body of the exchanger.   5. Heat exchanger according to claim 1, wherein the body (3) comprises a first portion (3.A) extruded forming the casing (4) and a second portion (3.B) extruded incorporating the partitions (5, 9). ) and extending into the first part.   The heat exchanger according to claim 1, wherein the channels comprise at least one large-section channel (7) and small-section channels (10), and the circuit-defining members comprise closure elements (11, 12) ends of the large section channel and at least one connecting element (2) for connecting adjacent ends of the small section channels (10) to a conduit (24, 28).   7. Heat exchanger according to claim 6, wherein the circuit defining members comprise two connecting elements (2) disposed at each end (41, 42) of the body (3).   8. Heat exchanger according to claim 6, wherein the circuit defining members comprise, opposite the connecting element (2), a return element (13) arranged to send a flow out of a part of the channels of small section (10a) to another part of the channels of small section (10b).   9. Heat exchanger according to claim 6, wherein the channel of large section (7) comprises at least a portion (7.1, 7.2) adjacent the envelope (4) which opens out of the envelope by the least one opening (8.1, 8.2) made therein.   10. Heat exchanger according to claim 9, wherein the circuit defining members comprise tubular connecting piece (14, 15) fixed on the casing (4) opposite the opening (8.1, 8.2). .   11. Heat exchanger according to claim 10, wherein the connection piece (14, 15) is integral with a connecting element (2) fixed on one of the extremities (4.1) of the envelope (4). for connecting adjacent ends of the small section channels (10) to an outer conduit (24, 28).   12. Heat exchanger according to claim 10, wherein the connecting piece (15) is integral with a return element (13) fixed on one end (4.2) of the casing (4) and arranged for sending a gas stream exiting a portion of the small section channels (10a) to another portion of the small section channels (10b). 35   13. Heat exchanger according to claim 6, 2907885 16 wherein the large section channel (7) is disposed in the center of the casing (4) and is surrounded by small section channels (10).   14. Heat exchanger according to claim 6, comprising two large section channels (301) adjacent to two opposite sides of the casing (4) and between which the small section channels (303) extend.   15. Heat exchanger according to claim 1, wherein the partitions (9) comprise local plastic deformations arranged to create turbulence in a fluid flowing in the channels (10).   16. Heat exchanger according to claim 1, wherein the body (1) is aluminum.