EP2199721B1 - Internal heat exchanger for an automobile air conditioning circuit, such circuit and method of connecting a connector to this exchanger - Google Patents

Description

The present invention relates to an internal heat exchanger coaxial tubular type in particular for a motor vehicle air conditioning circuit according to the preamble of claim 1, such an air conditioning circuit incorporating this exchanger and a method of connecting a female connector high and low pressure at least one of the ends of this exchanger. Such an exchanger is known from the document EP-A1 128 120 .

In certain air conditioning circuits for motor vehicles, especially those using carbon dioxide or R134a as a refrigerant, it is necessary to perform an exchange or heat transfer between the fluid of the high pressure portion of the circuit that is to be cooled and the same fluid from the low pressure portion of this circuit which serves as a cold source and which is heated in exchange, to improve the efficiency of the circuit. To this end, an internal heat exchanger is used, because it does not seek an exchange with the outside air of the vehicle or with the air of the passenger compartment.

In known manner, a heat exchanger is of metal type and is connected to the corresponding pipes of the air conditioning circuit which comprise in particular hoses, via connectors mounted at each end of the exchanger, which may be for example of plate type , consisting of a stack of flat tubes and carrying out the heat exchange both by convection with the air outside the exchanger and by conduction, or of multitube type which in its simplest version is of the coaxial tubular type against the current, then realizing the heat exchange without the aforementioned convection.

In the latter case, this coaxial exchanger generally defines at least one radially internal channel defined by a sleeve and intended to convey the fluid from the high pressure portion of the circuit, and at least one radially outer channel between the sleeve and the envelope. of the exchanger and intended to convey the fluid from the portion low pressure circuit, this sleeve being usually provided with longitudinal fins distributed over its circumference.

It is known to use two female connectors for the end concerned of such a coaxial exchanger, which is welded or brazed axially separated both on the sleeve and on the envelope via three lines of solder or solder , such that these connectors respectively define passage ducts for the fluid communicating in a sealed manner with these internal and external channels. For example, the document WO-A-20071013439 for the description of these connectors.

A major disadvantage of these coaxial internal exchangers equipped with female connectors resides in the mutual proximity of the generated solder or solder lines which, in particular for successive solders, generate risks of reflow of the anterior solder, and also in the need to achieve these welds or brazing blind with risks of non-sealing at the junction and / or penetration of the solder in the corresponding internal or external channel may thereby cause pressure losses, pollution or plugging of these channels.

It is also known to use a single connector at the connection end of a coaxial exchanger, as for example described in the document EP-A-1 762 806 where the connector is assembled to the outer shell and the inner sleeve by brazing via an intermediate fitting, and in the document EP-A-1,128,120 (Figure 10 and following) where the connector is brazed directly on the casing and on the sleeve of the exchanger via two solder cords.

A major disadvantage of the coaxial internal exchangers presented in these two documents is that their assembly to a female connector requires at least two soldering operations to be performed at the same time and at least one of which relates to the connection to be made between the connector. and the inner sleeve, is necessarily "blind" or in difficult conditions because of its location inside the connector. This results in significant risks of non-compliance of the connectors and thus leakage of the transferred fluid. In addition, these brazing involve a relatively high manufacturing cost and scrap rate for the connection obtained.

An object of the present invention is to provide an internal heat exchanger coaxial tubular type in particular for a motor vehicle air conditioning circuit having two portions of high and low pressure respectively traversed by a refrigerant, which overcomes the aforementioned drawbacks, this exchanger defining at least one radially internal channel for the fluid issuing from the low pressure portion and, for that issuing from the high pressure portion, at least one radially outer channel formed between a tubular sleeve surrounding the internal channel (s) (s) ) and a tubular casing surrounding the external channel (s), the sleeve extending axially beyond the end of the casing by an axial length passing zone L, at least one both ends of the exchanger being equipped with a female metal connector which is sealingly assembled on and around the envelope and the sleeve and which form two fluid passageways respectively communicating with the or each internal channel and with the or each external channel.

For this purpose, an exchanger according to the invention defined in claim 1 is such that the connector is assembled to the casing by a circumferential weld line for example to the arc located outside the connector and the envelope , and to the sleeve by at least one annular seal which is mounted on said protruding zone being coaxial with the weld line and which seals under an inner axial surface of the connector, the gasket or the gasket - or proximal seal - which is closest to this weld line being separated by an axial distance D preferably at least equal to 1 cm, so as not to be impaired by welding.

By the term "circumferential weld line" is meant generally in the present description an annular weld zone of variable axial thickness and which may be continuous or not, for example a "multiline" type zone such as a doubled line.

As regards the material that can be used to produce this exchanger, it may for example be, in the case where the refrigerant used is carbon dioxide, R134a or the like, a metal material made of an aluminum base alloy or steel or well, in the case of the use of another refrigerant, a suitable plastic material.

It will be noted that the assembly according to the invention, which may advantageously comprise only two lines of high and low pressure sealed connector / heat exchanger respectively formed, on the one hand, from the internal seal to the connector sealingly separating the high and low pressure fluids and, on the other hand, the external welding line separating these fluids from the outside atmosphere, is thus achieved in a single welding operation, which represents an assembly cost and a scrap rate. more reduced than in the prior art where two or even three welding / soldering operations were required.

Note also that in this assembly according to the invention, the interior of the connector is devoid of any permanent junction with the sleeve made by heat input, such as welding or brazing, because the only welding performed l 'is outside the connector. As a result, the precision of welding for the operator is increased, which minimizes the risk of non-compliance of the welding and therefore leakage of the refrigerant. The weld line of the assembly according to the invention may advantageously join an outer radial edge of the connector to the axial outer face of the envelope.

It will further be noted that the preferred use according to the invention of an arc welding (ie carried out by fusion, the heat being produced by at least one electric arc springing between one or more electrodes and the parts to be welded, or between electrodes), preferably a MIG (for "Metal Inert Gas" in English, made under protection of inert gas with a fuse-wire electrode which contributes to fill the weld) or TIG (for " Tungsten Inert Gas "in English, also in an internal atmosphere but with a tungsten electrode), makes it possible to minimize the propagation of the heat thus brought into the connector. Indeed, this Arc welding can advantageously be carried out at a relatively reduced temperature (below 650 ° C.) and with a very brief welding cycle (less than 10 seconds), which allows the prior positioning of a seal, such as an elastomeric O-ring, near the location chosen for this welding.

Advantageously, said axial distance D between this weld line and the proximal seal may be between 1.5 cm and 5 cm, preferably being greater than the length L of said overflow zone.

According to another characteristic of the invention, said or each seal can be housed in a groove of said sleeve by being compressed by said inner axial surface of the connector. Preferably, a single seal is interposed radially between the inner surface of the connector and this groove, which is formed at said end of the sleeve.

Advantageously, the inner surface of the connector may comprise a first axial portion mounted in contact with the casing and a second axial portion mounted in contact with said overflow zone of the sleeve, said conduit of the connector which communicates with the or each external channel opening through preferably obliquely at the end of the envelope while the other conduit can coaxially extend the sleeve.

It will be noted that the exchanger according to the invention may be provided on its circumference with longitudinal fins which extend radially inside the envelope and axially behind the end of the latter, so that the the space of the external channel axially between these fins and the envelope end forms, in connection with said high pressure conduit, an annular chamber collecting the flow of the fluid. For the choice of the shape and the arrangement of these fins, it will be possible for example to refer to the documents US-A-2,551,710 and U.S.-B1-6,434,972 , without limitation.

The invention also comprises an air conditioning circuit according to claim 10. This air conditioning circuit for a motor vehicle according to the invention comprises an internal heat exchanger as defined above.

In general, it will be noted that the air conditioning circuit according to the invention can operate in the usual ranges of temperature and pressure relative to the refrigerant used, ie for example at pressures ranging from several tens of bars to approximately 150 bars. for carbon dioxide or R134a.

1. a) on met en place au moins une garniture annulaire d'étanchéité autour de ladite zone de dépassement du manchon,
2. b) on monte le connecteur autour de ladite extrémité de l'échangeur de manière qu'il soit en contact, d'une part, avec une zone d'extrémité de la face radialement externe de l'enveloppe et, d'autre part, avec la ou chaque garniture et une partie de ladite zone de dépassement adjacente, puis
3. c) on soude, de préférence à l'arc et à une température inférieure à 650° C et pendant un temps de cycle inférieur à 10 secondes, le connecteur ainsi monté sur cette zone d'extrémité de l'enveloppe, en une ligne circonférentielle de soudure qui joint la surface externe du connecteur à cette zone de l'enveloppe et qui suffisamment éloignée de ladite garniture ou garniture proximale, de préférence d'une distance axiale D au moins égale à 1 cm, pour éviter son altération par ce soudage.

The invention also comprises a method according to claim 11. This sealed connection method according to the invention of a female metal connector to at least one of the two ends of an internal heat exchanger according to the invention as described herein. above, this connector forming two fluid passage conduits communicating respectively with the or each internal channel and with the or each external channel of the exchanger, comprises the following successive steps:

1. a) at least one annular seal is placed around said overflow zone of the sleeve,
2. b) the connector is mounted around said end of the exchanger so that it is in contact, on the one hand, with an end zone of the radially outer face of the envelope and, on the other hand, with the or each trim and a portion of said adjacent overrun area, and
3. c) the connector thus mounted on this end zone of the envelope, in a circumferential line, is welded, preferably to an arc and at a temperature below 650 ° C. and for a cycle time of less than 10 seconds. weld which joins the outer surface of the connector to this zone of the envelope and which is sufficiently remote from said proximal seal or lining, preferably of an axial distance D of at least 1 cm, to prevent its alteration by this welding.

As indicated above, this welding is carried out exclusively on the outer periphery of the connector and the exchanger, for example by joining an outer radial edge of the connector to the axial outer face of the envelope.

Advantageously, MIG or TIG welding is used in step c), the welding temperature preferably being between 600 and 640 ° C.

It will be noted that the arc welding that can be used in the invention allows a shorter welding cycle than other modes of joining by thermal input, such as soldering, and that this external arc welding makes it possible, in addition to to improve the reliability of the connector / exchanger junction, to minimize the propagation of heat in the mass of the connector and therefore towards the or each gasket, in combination with the choice of a connector having a high thermal inertia. For this purpose, the connector is advantageously based on a metal or metal alloy of high heat capacity, such as an aluminum-based material.

• la figure 1 est une vue schématique d'un circuit de climatisation pour véhicule automobile incorporant un échangeur thermique interne selon l'invention,
• la figure 2 est une vue schématique partielle, en coupe longitudinale et en partie en perspective, d'un échangeur thermique interne équipé selon l'invention d'un connecteur femelle à l'une de ses extrémités, et
• la figure 3 est une vue schématique partielle en coupe longitudinale d'un échangeur thermique interne équipé selon l'invention d'un connecteur femelle selon une variante de la figure 2.

The features of the present invention will emerge on reading the following description of an exemplary embodiment of the invention, given by way of nonlimiting illustration, the description being made with reference to the attached drawings, among which:

• the figure 1 is a schematic view of an air conditioning circuit for a motor vehicle incorporating an internal heat exchanger according to the invention,
• the figure 2 is a partial schematic view, in longitudinal section and partly in perspective, of an internal heat exchanger equipped according to the invention with a female connector at one of its ends, and
• the figure 3 is a partial schematic view in longitudinal section of an internal heat exchanger equipped according to the invention with a female connector according to a variant of the figure 2 .

The air conditioning circuit 1 illustrated in the figure 1 is in known manner a closed circuit or "loop" which comprises, in addition to an internal heat exchanger E, several elements distributed inside the engine compartment of the vehicle, in particular a compressor 2, a cooler or condenser 3 and an evaporator 4, and wherein circulates a refrigerant under pressure, such as carbon dioxide or R134a, without limitation. All these elements are interconnected by rigid or flexible lines constituted by rigid and / or flexible tubular portions, which have at each of their ends sealed connection means.

• une ligne basse pression BP destinée à véhiculer le fluide frigorigène (tel que du CO₂ à l'état gazeux, du R134a ou équivalent) entre le l'évaporateur 4 et le compresseur 2, à travers l'échangeur E via une entrée e_BP de fluide basse pression à réchauffer (par exemple de 30 à 40° C pour le CO₂) et une sortie S_BP de ce fluide ainsi réchauffé, et
• une ligne haute pression HP destinée à véhiculer ce même fluide (à l'état supercritique pour du CO₂) en aval du compresseur 2 et du refroidisseur 3 via une entrée e_HP de fluide haute pression à refroidir (par exemple de 13 à 16° C pour le CO₂) et une sortie S_HP de ce fluide ainsi refroidi, une valve de détente 5 étant agencée en aval de cette sortie S_HP et en amont de l'évaporateur 4.

More specifically, the circuit 1 comprises:

• a low-pressure line BP for conveying the refrigerant (such as CO ₂ in the gaseous state, R134a or equivalent) between the evaporator 4 and the compressor 2, through the exchanger E via a _BP input e low pressure fluid to be heated (for example 30 to 40 ° C for CO ₂ ) and a S _LP output of the fluid thus heated, and
• a high pressure line HP for conveying the same fluid (in the supercritical state for CO ₂ ) downstream of the compressor 2 and the cooler 3 via an inlet e _HP of high pressure fluid to be cooled (for example 13 to 16 °) C for CO ₂ ) and an output S _HP of this fluid thus cooled, an expansion valve 5 being arranged downstream of this outlet S _HP and upstream of the evaporator 4.

The exchanger E, E 'according to the exemplary embodiments of the invention illustrated in FIGS. figures 2 and 3 is of coaxial type against the current, and is intended to cool the fluid from the line HP by conduction in contact with the same fluid from the BP line which is heated in exchange. For this purpose, this exchanger E, E 'is in this example constituted by a radially inner metal sleeve 10, 110 which delimits in its internal space an internal channel 11, 111 for the fluid coming from the line BP and which is inserted axially inside a radially outer envelope 20, 120 also metal delimiting with the sleeve 10, 110 an external channel 21, 121 of annular cross section for the fluid from the line HP. This sleeve 10, 110 extends axially beyond the end of the casing 20, 120 by a protruding zone 13, 113 of axial length L terminating in a circumferential groove 14, 114, into which a liner is inserted. elastomeric sealing ring 15, 115 and whose outer rim forms the substantially radial end of the casing 20, 120.

In addition, the sleeve 10, 110 is provided on its circumference with a plurality of longitudinal fins 12 (visible at the figure 2 in perspective, and in section only for the lower fin 12) which extend radially inside the casing 20, 120 and terminate axially recessed from the end of the latter, so that the space of the external channel 21, 121 axially between the fins 12 and this end of the 20, 120 envelope forms a collector annular chamber of the flow of the refrigerant.

In at least one of the ends E1, E'1 of the exchanger E, E 'which is illustrated in FIG. figure 2 is assembled a female connector 30, 130 which defines two passage ducts 31, 131 and 32, 132 for the refrigerant communicating in a sealed manner with the internal channel 11, 111 and the external channel 21, 121, respectively (this duct 32, 132 has an oblique section 32a, 132a opening on the outer channel 21, 121 and extending by an axial section 32b, 132b opening out of the connector 30, 130).

• de la garniture d'étanchéité 15, 115, préalablement positionnée dans la gorge 14, 114 du manchon 10, 110 puis comprimée radialement par une portion axiale 34, 134 de la surface interne du connecteur 30, 130 de sorte à appuyer de manière étanche sur ce dernier, et
• d'une unique ligne circonférentielle de soudure par exemple à l'arc 40, 140 qui est intégralement localisée à l'extérieur du connecteur 30, 130 et de l'enveloppe 20, 120 du fait qu'elle joint un bord radial extérieur 33, 133 du connecteur 30, 130 et la face externe axiale de l'enveloppe 20, 120, cette ligne de soudure 40, 140 étant coaxiale à la garniture 15, 115 mais en étant séparée de celle-ci d'une distance axiale D choisie suffisante pour que la garniture 15, 115 ne soit pas altérée par le soudage adjacent.

The connector 30, 130 according to these examples of the invention is assembled to the envelope by two sealing lines formed:

• of the seal 15, 115, previously positioned in the groove 14, 114 of the sleeve 10, 110 and then compressed radially by an axial portion 34, 134 of the inner surface of the connector 30, 130 so as to press tightly on the latter, and
• a single circumferential welding line, for example arc 40, 140 which is entirely located outside the connector 30, 130 and the envelope 20, 120 because it joins an outer radial edge 33, 133 of the connector 30, 130 and the axial outer face of the casing 20, 120, this weld line 40, 140 being coaxial with the lining 15, 115 but separated therefrom by an axial distance D chosen sufficiently so that the liner 15, 115 is not affected by the adjacent welding.

We also see on these figures 2 and 3 that the connector 30, 130 is mounted in contact with the radially outer face of the casing 20, 120 by another axial portion 35, 135 of its inner surface which makes a right angle with the outer edge 33, 133 of the connector weld 30, 130.

This arc welding is preferably carried out using the MIG technique, it being specified that TIG welding can also be used. This produces a reliable weld 15, 115 (the resulting line can for example extend over an axial width of between 6 mm and 8 mm), while being performed at a sufficiently low temperature (advantageously of the order of 620 ° C.) and for a sufficiently short cycle time (less than 10 seconds) for not deteriorating the elastomeric material of the liner 15, 115. These reduced temperature and cycle time conditions for the arc welding used, combined with the use of a connector 30, 130 having a thermal inertia or high heat capacity (Based on a metallic material of high thermal conductivity, such as aluminum, for example) allow this welding to be carried out in the immediate vicinity of the lining 15, 115, while preserving its properties of resilience and thus of sealing. This proximity, measured by the distance D above, may be equal to or greater than 1 cm and is preferably between 1.5 cm and 5 cm, being for example about 2 cm.

Claims (13)

1. Internal heat exchanger (E, E') of the coaxial tube type, in particular for an air conditioning circuit (1) of an automotive vehicle, comprising two high pressure (HP) and low pressure (LP) portions respectively, through which a refrigerant circulates, the exchanger defining at least one radially inner passage (11, 111) for the fluid leaving the low pressure portion and, for the fluid leaving the high pressure portion, at least one radially outer passage (21, 121) which is formed between a tubular sleeve (10, 110) surrounding the inner passage(s) and a tubular casing (20, 120) surrounding the outer passage(s), the sleeve extending axially beyond the end of the casing by means of an extended zone (13, 113) with an axial length L, at least one of the two ends (E1, E'1) of the exchanger being fitted with a metal female connector (30, 130) which is assembled in a sealed manner on and around the casing and sleeve and which forms two fluid passage conduits (31, 131 and 32, 132) communicating respectively with the or each inner passage and with the or each outer passage, wherein the connector is assembled with the casing by means of a circumferential, for example arc-welded, weld line (40, 140) disposed on the exterior of the connector and casing, and characterised in that the connector is assembled with the sleeve by means of at least one annular seal fitting (15, 115) which is fitted on said extended zone coaxially with the welded line and which presses in a sealed manner underneath an axially inner surface (34, 134) of the connector,
   the fitting or the one of the fittings which is closest to this welded line being spaced therefrom by an axial distance D which is preferably at least equal to 1 cm so that it is not damaged by the welding.
2. Internal heat exchanger (E, E') as claimed in claim 1, characterised in that said welded line (40, 140) joins an external radial edge (33, 133) of the connector (30, 130) to the axial external face of the casing (20, 120).
3. Internal heat exchanger (E, E') as claimed in claim 2, characterised in that the interior of the connector (30, 130) does not have any permanent joint with said sleeve (10, 110) that is produced by applying heat.
4. Internal heat exchanger (E, E') as claimed in claim 1 or 2, characterised in that said distance D is between 1.5 cm and 5 cm, preferably being longer than the length L of the extended zone (13, 113).
5. Internal heat exchanger (E, E') as claimed in one of the preceding claims, characterised in that said welded line (40, 140) is produced by arc welding at a temperature of less than 650° and for a cycle time of less than 10 seconds.
6. Internal heat exchanger (E, E') as claimed in claim 5, characterised in that said welded line (40, 140) is produced by metal inert gas or tungsten inert gas welding so as to minimise propagation of the applied heat to the connector (30, 130), which preferably made from a metal or metal alloy with a high thermal inertia, such as aluminium.
7. Internal heat exchanger (E, E') as claimed in one of the preceding claims, characterised in that said or each seal fitting (15, 115), such as an elastomer toroidal sealing ring, is fitted in a groove (14, 114) of said sleeve (10, 110), where it is compressed by said internal axial surface (34, 134) of the connector (30, 130).
8. Internal heat exchanger (E, E') as claimed in claim 7, characterised in that a single seal fitting (15, 115) is radially inserted between said internal surface (34, 134) of the connector (30, 130) and said groove (14, 114) formed on said end of the said sleeve (10, 110).
9. Internal heat exchanger (E, E') as claimed in one of the preceding claims, characterised in that said internal surface of the connector comprises a first axial portion (35, 135) mounted in contact with the casing (20, 120) and a second axial portion (34, 134) mounted in contact with said extended zone (13, 113) of the sleeve (10, 110), said conduit (32, 132) of the connector (30, 130) communicating with the or each outer passage (21, 121) opening in an oblique arrangement at the end of the casing, whereas the other conduit (31, 131) coaxially extends the sleeve.
10. Air conditioning circuit (1) for an automotive vehicle, characterised in that it has an internal heat exchanger (E. E') as claimed in one of the preceding claims.
11. Method of providing a sealed connection for a female metal connector (30, 130) to at least one of the two ends (E1, E'1) of an internal heat exchanger (E, E') of the coaxial tube type, in particular for an air conditioning circuit (1) of an automotive vehicle, comprising two high pressure (HP) and low pressure (LP) portions respectively, through which a refrigerant circulates, the exchanger defining at least one radially inner passage (11, 111) for the fluid leaving the low pressure portion and, for the fluid leaving the high pressure portion, at least one radially outer passage (21, 121) which is formed between a tubular sleeve (10, 110) surrounding the inner passage(s) and a tubular casing (20, 120) surrounding the outer passage(s), the sleeve extending axially beyond the end of the casing by means of an extended zone (13, 113) with an axial length L, the connector forming two fluid passage conduits (31, 131 and 32, 132) communicating respectively with the or each inner passage and with the or each outer passage, characterised in that it comprises the following successive steps:

    a) at least one annular seal fitting (15, 115) is placed around said extended zone of the sleeve,

    b) the connector is fitted on said end of the exchanger so that it is in contact on the one hand with an end zone of the radially external face of the tubular casing (20, 120) and on the other hand with the or each fitting and a part of said adjacent extended zone, then

    c) the connector thus mounted (20, 120) is welded on this end zone of the tubular casing, preferably by arc welding and at a temperature of less than 650°C and for a cycle time of less than 10 seconds, by means of a circumferential line of weld which joins the external surface of the connector to this zone of the tubular casing (20, 120) and is sufficiently spaced apart from said fitting or proximal fitting, preferably by an axial distance D of at least 1 cm, to prevent it from being damaged by this welding.
12. Method of producing a sealed connection as claimed in claim 11, characterised in that the weld applied in step c) is applied exclusively to the outer periphery of the connector (30, 130) and of the exchanger (E, E'), by joining an external radial edge (33, 133) of the connector to the axial external face of the tubular casing (20, 120).
13. Method of producing a sealed connection as claimed in claim 12, characterised in that metal inert gas or tungsten inert gas welding is used in step c), the welding temperature preferably being between 600°C and 640°C.

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