TIGHT CONNECTION OF A CONNECTOR TO A COAXIAL TUBE HEAT EXCHANGER

Abstract

A method for sealing a connector (12) to a coaxial tubular heat exchanger (14), particularly for a motor vehicle air conditioning circuit, characterized in that it comprises the following successive steps: a) a free end (14b1) of an external tube of the exchanger is mounted in or on the connector (12), b) the external tube (14b) is secured directly to the connector, c) an internal tube (14a) is inserted into the external tube (14b) until a free end (14a1) of the internal tube is mounted in or on the connector (12), this assembly ensuring a seal between the internal tube and the connector, and d) the internal (14a) and external (14b) tubes are secured directly to each other to prevent relative movement.

Description

Technical field of the invention

[0001] The present invention relates in particular to a method of sealing a connector to a coaxial tubular heat exchanger, as well as a fluid connection device, in particular for an air conditioning circuit of a vehicle. Technical background

[0002] In certain automotive air conditioning systems, particularly those using carbon dioxide or R134a as a refrigerant, heat exchange or transfer is necessary between the fluid in the high-pressure section of the system that is being cooled and the same fluid in the low-pressure section, which acts as a cold source and is heated in exchange, to improve the system's efficiency. This is achieved using an "internal" heat exchanger, as it does not exchange heat with the outside air or the air inside the vehicle.

[0003] In general, a heat exchanger is metallic and is connected to the corresponding pipes of the air conditioning circuit which include in particular flexible hoses, via connectors mounted at each end of the exchanger, which can be for example of the plate type, consisting of a stack of flat tubes and carrying out heat exchange both by convection with the outside air to the exchanger and by conduction, or of the multi-tube type which in its simplest version is of the coaxial counter-flow tubular type, thus carrying out heat exchange without the aforementioned convection.

[0004] In this latter case, the coaxial heat exchanger generally defines at least one internal radial channel, delimited by a sleeve and intended to carry the fluid from the high-pressure portion of the circuit, and at least one external radial channel, located between the sleeve and the heat exchanger shell, intended to carry the fluid from the low-pressure portion of the circuit. The sleeve and the shell are formed as a single piece and connected by longitudinal fins distributed around the circumference of the heat exchanger.

[0005] It is known to use two female connectors for the relevant end of such a coaxial heat exchanger, which are welded or brazed axially separately to both the sleeve and the casing via three weld or braze lines, so that these connectors respectively define passageways for the fluid communicating hermetically with these internal and external channels. For example, document WO-A1-2007 / 1013439 can be cited for a description of these connectors.

[0006] A major drawback of these coaxial internal exchangers equipped with female connectors lies in the mutual proximity of the generated weld or brazing lines which, especially for successive brazings, generate risks of remelting of the previous brazing, and also in the need to carry out these welds or brazings blindly with risks of non-sealing at the junction and / or penetration of the brazing into the corresponding internal or external channel which can therefore lead to pressure losses, pollution or even obstruction of these channels.

[0007] It is also known to use a single connector at the connection end of a coaxial exchanger, as described for example in EP-A1-1 762 806 where the connector is assembled to the outer shell and inner sleeve by brazing via an intermediate fitting, and in EP-A1-1 128 120 (Figures 10 and following) where the connector is brazed directly to the shell and sleeve of the exchanger via two brazing beads.

[0008] A major drawback of the coaxial internal heat exchangers described in these last two documents is that their assembly to a connector requires at least two brazing operations to be performed simultaneously. At least one of these operations, related to the connection between the connector and the internal sleeve, is necessarily performed "blind" or under difficult conditions due to its location inside the connector. This results in significant risks of connection non-conformity and therefore leakage of the transferred fluid. Furthermore, these brazing operations entail relatively high manufacturing costs and a high scrap rate for the resulting connection.

[0009] The Applicant proposed a solution in document EP-A1-2 199 721. This solution consists of assembling the connector to the casing by welding, and to the sleeve by at least one annular sealing gasket mounted on an axial extension of the sleeve relative to the casing. The axial distance between the gasket and the weld line is sufficient to ensure that the gasket is not damaged by the welding. As the heat exchanger is formed from a single piece, the sleeve and the casing are inseparable and are therefore mounted simultaneously in the connector.

[0010] Although this solution is effective, it is not entirely satisfactory because the axial extension of the sleeve results in a significant increase in the size of the exchanger and the connector.

[0011] One aim of the present invention is to offer an alternative to this solution. Summary of the invention

[0012] The present invention proposes a method for the leak-proof connection of a connector to a coaxial tubular heat exchanger, in particular for a motor vehicle air conditioning circuit, this exchanger comprising two coaxial tubes, respectively internal and external, the external tube defining around the internal tube a first annular channel for the circulation of a first fluid, and the internal tube defining a second internal channel for the circulation of a second fluid, the tubes being independent and one of the tubes having projections bearing against the other of the tubes to keep them apart from each other, the connector comprising two fluid passage cavities communicating respectively with the channels of the exchanger, characterized in that it comprises the following successive steps: a) one free end of the outer tube is mounted in or on the connector, b) the outer tube is secured directly to the connector, c) the inner tube is inserted into the outer tube until one free end of the inner tube is mounted in or on the connector, this assembly ensuring a seal between the inner tube and the connector, and d) the inner and outer tubes are secured directly to each other to prevent relative movement.

[0013] Contrary to the instructions in document EP-A1-2 199 721, the inner and outer tubes of the heat exchanger are independent. They are therefore mounted sequentially in or onto the connector. Specifically, the outer tube is mounted in step a) and secured to the connector in step b). This connection can be achieved by welding or brazing if both the outer tube and the connector are metallic. Alternatively, if the outer tube and the connector are made of other materials, they can be joined by bonding, electron beam welding, etc. During this joining step b), the inner tube is not yet inserted into the outer tube and is therefore not at risk of being damaged by the joining process, for example, by the heat generated by welding. The inner tube is then inserted into the outer tube in step c) until it forms a tight seal with the connector.This is generally a blind assembly. There is no direct connection between the inner tube and the connector. They are simply inserted into or stacked on top of each other. The inner tube is indirectly secured to the connector via the outer tube. This securing of the tubes is achieved in step d) and prevents any relative movement between the tubes during operation.

[0014] The process according to the invention may comprise one or more of the following steps or features, taken individually or in combination with each other: step d) is carried out by plastic deformation of at least one of the tubes, and in particular by crimping the outer tube onto the inner tube, or by simultaneous bending of the inner and outer tubes; the process includes, between steps b) and c), a step of mounting at least one annular sealing gasket around the free end of the inner tube; during steps a) and c), the tubes are engaged by male-female push-fitting respectively into two housings of the connector; during steps a) and c), the tubes are guided into the housings by cooperation of their free ends with chamfers of the connector; before step c), the free end of the inner tube is plastically deformed or includes a plastically deformed element, to create at least one annular groove on its outer periphery, and preferably two annular grooves adjacent to its outer periphery;Before step c), the free end of the inner tube is plastically deformed or includes a plastically deformed component to modify its external diameter at at least one end; the inner and outer tubes are made of metallic materials; the inner and outer tubes are made of different materials; the inner tube is metallic and the outer tube is made of plastic or composite material; the outer tube is joined to the connector by welding, brazing, or bonding; the connector is metallic.

[0015] The present invention also relates to a fluid connection device comprising a connector and a coaxial tubular heat exchanger, particularly for a motor vehicle air conditioning circuit, the connector forming two fluid passage cavities communicating respectively with channels of the exchanger, the exchanger comprising two coaxial tubes, respectively internal and external, the external tube defining around the internal tube a first annular circulation channel for a first fluid, and the internal tube defining a second internal circulation channel for a second fluid, the tubes being independent and one of the tubes having projections bearing against the other tube to maintain them at a distance from each other, characterized in that it is obtained by a process as described above and in that: The outer tube includes a free end which is engaged in or on the connector, this outer tube being directly attached to the connector, and the inner tube includes a free end which is mounted in or on the connector, this mounting ensuring a seal between the inner tube and the connector, the inner and outer tubes being directly attached to each other to prevent relative movement.

[0016] Advantageously, the joining of the inner and outer tubes is achieved by crimping the outer tube onto the inner tube, by simultaneously bending the inner and outer tubes, or by welding the ends of the inner and outer tubes opposite the connector. Brief description of the figures

[0017] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the attached drawings in which: [ Fig. 1 ] there figure 1 is a schematic perspective view of a fluidic connection device according to the invention, comprising in particular a heat exchanger and a connector, this device being in a first position prior to a shaping operation, [ Fig. 2 ] there figure 2 is a schematic perspective view of the device of the figure 1 , this device being in a second position following a shaping operation, [ Fig. 3 ] there figure 3 is a schematic perspective view of a coaxial tubular heat exchanger, [ Fig. 4 ] there figure 4 is a larger-scale schematic view of a detail of the device figures 1 and 2, the connector and part of the exchanger being shown in axial section, , Fig. 5 ] there figure 5 is a schematic axial cross-sectional view of the connector of the device figures 1 to 3 , [ Fig. 6 ] there figure 6 is a schematic axial cross-sectional view of a free end of an internal tube of the heat exchanger of the device figures 1 to 3 , [ Fig. 7 ] there figure 7 is a flowchart showing steps in a process according to the invention for the leak-proof connection of a connector to a heat exchanger, and [ Fig. 8 ] there figure 8 is a partial schematic perspective view of an alternative embodiment of the device according to the invention. Detailed description of the invention

[0018] THE figures 1 to 6 illustrate an embodiment of a fluid connection device 10 according to the invention, for an air conditioning circuit of a vehicle, in particular a motor vehicle.

[0019] Device 10 visible in its entirety at figures 1 and 2includes in the example shown a connector 12, here female, and a coaxial tubular type heat exchanger 14.

[0020] The heat exchanger 14 has a generally elongated shape and comprises two coaxial tubes extending one inside the other. The inner tube is referenced 14a and the outer tube is referenced 14b.

[0021] The outer tube 14b defines around the inner tube 14a an annular channel C1 for the circulation of a first fluid, and the inner tube 14a defines a second internal channel C2 for the circulation of a second fluid ( figure 3 To ensure sufficient spacing between the tubes and the formation of channel C1, one of the tubes generally has projections, such as fins, bearing against the other tube to maintain a distance between them. The fins may extend parallel to the longitudinal axis X of the heat exchanger 14 or helically around this axis. They may be continuous or discontinuous.

[0022] It is thus understood that the external tube 14b can include on its internal cylindrical surface surrounding the internal tube 14a internal fins 15 which bear against an external cylindrical surface of the internal tube 14a ( figure 3 ). Alternatively, the inner tube 14a may include on its external cylindrical surface surrounded by the outer tube 14b external fins which bear against an internal cylindrical surface of the outer tube 14b.

[0023] Tubes 14a, 14b can be made of the same or different materials. They can be made of metal alloy(s) or plastic material(s), for example.

[0024] The connector 12 is located at one longitudinal end of the exchanger 14, the opposite longitudinal end of which is connected to another type of connector 16, which is not part of the invention.

[0025] In the figure 1 , the exchanger 14 has a straight shape. In the figure 2 The heat exchanger 14 has a shape with several bends. Heat exchanger 14 of the figure 2 has undergone a forming, shaping, or bending stage, starting from the initial shape of the figure 1 As will be explained below, this shaping can be used to join tubes 14a and 14b together, particularly in areas where the tubes are bent simultaneously and plastically deformed by being clamped against each other. Device 10 of the figure 2 is ready to be fitted into an air conditioning circuit and used.

[0026] There figure 4 is a larger-scale view of connector 12 and its connection to one end of the exchanger 14. Connector 12 is shown alone in the figure 5 .

[0027] As can be seen in the figure 4, the outer tube 14b has a cut end straight (in a plane perpendicular to the longitudinal axis X of the exchanger 14) forming a free end 14b1, this free end 14b1 being engaged in a housing 18 of the connector 12.

[0028] The inner tube 14a has a free end 14a1 which is preferably formed in one piece with the rest of the tube but which can alternatively be formed by attaching and fixing a tubular element 20 onto an end 14a2 of the tube 14a.

[0029] This free end 14a1 or this organ 20 is represented alone at the figure 6The end 14a or the component 20 has undergone a forming or shaping operation. Before this operation, it comprises internal and external cylindrical surfaces and constant internal and external diameters. After this operation, and as illustrated, it has a flared portion 20a connecting to the rest of the internal tube 14a. In the case of using an added component 20, the edge-to-edge connection of the component 20 to the end 14b1 of the tube 14a is as illustrated in the figure 4 This can be achieved by welding or brazing, for example. This section 20a has internal diameters D1 and external diameters D2 that are substantially identical to those of the internal tube 14a.

[0030] The remainder of the end 14a1 or the member 20 has an external cylindrical surface 20c whose external diameter D3 is less than D2, and here greater than D1. At its end 20b opposite the portion 20a, the end 14a1 or the member 20 includes at least one external annular groove 22 for receiving an annular sealing gasket 24.

[0031] In the example shown, the end 14a1 or the component 20 comprises two adjacent grooves 22 and therefore carries two seals 24 ( figure 4 ).

[0032] The 24 seals are preferably made of elastomer. Alternatively, they could be made of metal.

[0033] The end 14a1 or the organ 20 is intended to be engaged in a housing 26 of the connector 12 and the seals 24 are intended to cooperate with a surface, here cylindrical, of this housing 26.

[0034] We now refer to the figure 5 which illustrates connector 12.

[0035] Connector 12 comes in the form of a block of material, for example metallic or plastic.

[0036] The connector 12 has a general parallelepiped shape and includes an upper face 12a, a lower face 12b, and lateral faces 12c.

[0037] Connector 12 includes three ports 28, 30 and 32. Port 28 is located on one of the faces 12c and opens into a bore 34 containing the housings 18 and 26.

[0038] Ports 30, 32 are substantially parallel to each other and perpendicular to port 28 and to the axis of bore 34 which is intended to coincide with the X axis of exchanger 14.

[0039] Ports 30 and 32 are located on the upper face 12a and are spaced apart. They form, for example, female elements configured to cooperate with male elements of a pipe or fitting for fluid communication between this pipe or fitting and the connector 12. Port 30 is located on the side of port 28 and opens into a cavity 36 of the bore 34, and port 32 is located on the opposite side of port 28 and opens into another cavity 38 of the bore 34.

[0040] Furthermore, between ports 30, 32, face 12a of connector 12 includes a threaded hole 40 for receiving a screw to fix connector 12 to an element or another fluid connector of the vehicle.

[0041] In the example shown, the bore 34 is stepped and therefore comprises several successive stages of different diameters and formed in particular by the housings 18, 26 and the cavities 36, 38.

[0042] The bore 24 includes first the housing 18 which is connected to the port 28 and to the face 12c by a first chamfer 42. This housing 18 has an external diameter D4.

[0043] The bore 24 then includes the cavity 36 which extends between the housing 18 and a chamfer 44 connecting to the other housing 26. The cavity 36 has an external diameter D5 and the housing 26 has an external diameter D6, D5 being between D4 and D6.

[0044] Housing 18 is connected to cavity 36 by a cylindrical span 46.

[0045] The bore 34 finally includes the cavity 38 which is connected to the housing 26 by another cylindrical bearing 48 and which ends with a blind hole 50 in the vicinity of the face 12c opposite the port 28.

[0046] Cavity 38 has an external diameter D7, less than D6.

[0047] D4 is substantially the same as or slightly larger than the external diameter Dext of the free end 14b1 of the external tube 14b ( figure 4 ).

[0048] D6 is substantially the same as or slightly larger than the external diameter D3 of the end 20b of the organ 20 or of the free end 14a1 of the inner tube 14a.

[0049] The connection of the heat exchanger 12 to connector 14 will now be described with reference to the figure 7 which illustrates the steps in a connection process.

[0050] The method comprises a first step a) in which the free end 14b1 of the outer tube 14b is engaged in the recess 18 of the connector 12. Insertion of the end 14b1 into the port 28 is facilitated by the chamfer 42 and continued until it abuts against the bearing surface 46. The outer tube 14b forms a male portion engaged in the recess 18, which forms a female portion. The reverse is also possible, however, with the free end 14b1 then forming a female portion engaged on a male portion of the connector 12. This engagement can be performed manually by an operator.

[0051] The process includes a subsequent step b) of directly joining the outer tube 14b to the connector 12. In the case where these two elements are made of metal alloy, this joining can be achieved by welding, for example of the TIG type, an annular weld bead 52 being then formed at the port 28 and the chamfer 42, around the outer tube 14b ( figure 4 ). In the case where the joining was carried out by brazing, the brazing could be almost invisible to the naked eye and, for example, essentially located inside housing 18.

[0052] In the event that tube 14b and connector 12 were made of plastic or composite material, their joining could be ensured by gluing, electron beam welding, etc.

[0053] At the end of step b), the outer tube 14b is fixed to the connector 12 and the inner tube 14a is not yet present in the device 10. The channel C1 is then in fluidic communication with the port 30 via the cavity 36.

[0054] The inner tube 14a is mounted in the next step c). The inner tube 14a is inserted into the outer tube 14b until the free end 14a1 of the inner tube engages in the housing 26 of the connector 12.

[0055] Insertion of the end 14a1 into the housing 26 is facilitated by the chamfer 44 and continued until it abuts against the bearing surface 48. The inner tube 14a also forms a male part engaged in the housing 26, forming a female part. The reverse is also possible, however, with the free end 14a1 then forming a female part engaged on a male portion of the connector 12. This engagement can be performed manually by an operator. It is understood that, since the tubes are relatively rigid, these tubes are preferably straight to facilitate step c).

[0056] The internal tube 14a is mounted in connector 12 in such a way that it alone provides a seal between the internal tube and the connector. Therefore, it is not necessary to provide a direct connection between these elements.

[0057] This sealing can be ensured by a simple cooperation of shapes or a simple support of complementary cylindrical surfaces between the inner tube 14a and the connector 12.

[0058] In the example shown in the drawings, the sealing is ensured by 24 seals whose number and material can be adapted, as mentioned above.

[0059] Channel C2 is then in fluidic communication with port 32 via cavity 38.

[0060] In the case represented and as mentioned above, the process includes two additional optional steps, between steps b) and c), which consist on the one hand of shaping the free end 14a1 of the inner tube 14a, or a member 20 which is then attached to the end of the tube, and then of mounting the seals 24 in the grooves 22 of this free end 14a1.

[0061] The process finally includes a step d) in which the tubes 14a, 14b are joined together to prevent relative displacements between them.

[0062] This reinforcement can be achieved by shaping the interchange 14, and in particular by bending it, as mentioned above in relation to the figure 2 . Tubes 14a, 14b are then plastically deformed and held tightly against each other, thus preventing any relative movement between them.

[0063] The joining can be achieved by plastic deformation of only one of the tubes, and for example the outer tube 14b which is crimped onto the inner tube 14a at a precise location E (cf. figure 8 ). In the example shown, the crimping results in indentations 54 and localized plastic deformations of the outer tube 14b to take support on the inner tube 14a.

[0064] This joining can also be achieved by welding together the ends of tubes 14a, 14b, opposite connector 12 and therefore located on the side of the other connector 16.

[0065] The invention makes it possible to achieve a leak-proof fluid connection between the exchanger 14 and the connector 12, without blind welding while limiting the size of the device 10.

Claims

1. A method for the leak-proof connection of a connector (12) to a coaxial tubular heat exchanger (14), particularly for a motor vehicle air conditioning circuit, this heat exchanger comprising two coaxial tubes, respectively internal (14a) and external (14b), the external tube defining around the internal tube a first annular channel (C1) for the circulation of a first fluid, and the internal tube defining a second internal channel (C2) for the circulation of a second fluid, the tubes being independent and one of the tubes having projections (15) bearing against the other of the tubes to keep them apart from each other, the connector comprising two cavities (36, 38) for the passage of fluids communicating respectively with the channels (C1, C2) of the heat exchanger, characterized in thatIt comprises the following successive steps: a) a free end (14b1) of the outer tube is mounted in or on the connector (12), b) the outer tube (14b) is secured directly to the connector, c) the inner tube (14a) is inserted into the outer tube (14b) until a free end (14a1) of the inner tube is mounted in or on the connector (12), this assembly ensuring a seal between the inner tube and the connector, and d) the inner (14a) and outer (14b) tubes are secured directly to each other to prevent relative movement.

2. A method according to claim 1, wherein step d) is carried out by plastic deformation of at least one of the tubes (14a, 14b), and in particular by crimping the outer tube onto the inner tube, or by simultaneous bending of the inner and outer tubes.

3. Method according to claim 1 or 2, wherein it comprises, between steps b) and c), a step of mounting at least one annular sealing gasket (24) around the free end (14a1) of the inner tube (14a).

4. A method according to any one of the preceding claims, wherein, during steps a) and c), the tubes (14a, 14b) are engaged by male-female interlocking respectively in two housings (18, 26) of the connector.

5. Method according to claim 4, wherein, during steps a) and c), the tubes (14a, 14b) are guided into the housings (18, 26) by cooperation of their free ends (14a1, 14b1) with chamfers (42, 44) of the connector (12).

6. A method according to any one of the preceding claims, wherein, before step c), the free end (14a1) of the inner tube (14) is plastically deformed or comprises a plastically deformed component (20), to produce at least one annular groove (22) at its outer periphery, and preferably two annular grooves (22) adjacent to its outer periphery.

7. A method according to any one of the preceding claims, wherein, before step c), the free end (14a1) of the inner tube (14) is plastically deformed or includes a plastically deformed component (20), to modify its external diameter (D2, D3), at at least one end.

8. A method according to any one of the preceding claims, wherein the inner (14a) and outer (14b) tubes are made of metallic materials.

9. A method according to any one of claims 1 to 7, wherein the inner (14a) and outer (14b) tubes are made of different materials.

10. Method according to the preceding claim, wherein the inner tube (14a) is metallic and the outer tube (14b) is made of plastic or composite material.

11. A method according to any one of the preceding claims, wherein the attachment of the outer tube (14b) to the connector (12) is achieved by welding, brazing or gluing.

12. A method according to any one of the preceding claims, wherein the connector (12) is metallic.

13. Fluid connection device (10) comprising a connector (12) and a coaxial tubular heat exchanger (14), in particular for a motor vehicle air conditioning circuit, the connector forming two fluid passage cavities (18, 26) communicating respectively with channels (C1, C2) of the exchanger, the exchanger comprising two coaxial tubes, respectively internal (14a) and external (14b), the external tube defining around the internal tube a first annular channel (C1) for the circulation of a first fluid, and the internal tube defining a second internal channel (C2) for the circulation of a second fluid, the tubes being independent and one of the tubes having projections (15) bearing against the other of the tubes to maintain them at a distance from each other, characterized in that it is obtained by a process according to one of the preceding claims and in that: the outer tube (14b) includes a free end (14b1) which is engaged in or on the connector (12), this outer tube being directly attached to the connector, and the inner tube (14a) includes a free end (14a1) which is mounted in or on the connector, this mounting ensuring a seal between the inner tube and the connector, the inner (14a) and outer (14b) tubes being directly attached to each other to prevent relative displacements.

14. Device (10) according to the preceding claim, wherein the joining of the inner (14a) and outer (14b) tubes is achieved by crimping the outer tube onto the inner tube, by simultaneously bending the inner and outer tubes, or by welding the ends of the inner and outer tubes opposite the connector.