EP2333472A1 - Internal heat exchanger for a vehicule air conditioning circuit and such circuit - Google Patents

Abstract

The heat exchanger has a spacer unit i.e. spacer insert (30), with thermal conductivity lower than thermal conductivity of metallic radially internal and external tubes (10, 20). The spacer unit is movably mounted in translation between the tubes, and extends over a part of the length of a radially external passage (21). A region of the external passage which is devoid from the spacer unit is intended to be connected to a tapping (40) such as filling valve body or pressure sensor mounting nozzle, by a connecting orifice (23) formed in the external tube at right angle with the region.

Description

The present invention relates to an internal heat exchanger coaxial tubular type for a motor vehicle air conditioning circuit, and such an air conditioning circuit incorporating this exchanger.

In certain air conditioning circuits for motor vehicles, 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 is warmed in exchange, to improve the performance 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.

• à l'intérieur d'un tube interne de l'échangeur, au moins un canal radialement interne destiné à véhiculer le fluide issu de la portion basse pression du circuit, et
• radialement entre ce tube interne et un tube externe formant enveloppe pour l'échangeur, un canal radialement externe usuellement pourvu d'ailettes longitudinales conçues pour optimiser le transfert thermique entre les fluides circulant dans les canaux interne(s) et externe qui sont réparties sur sa circonférence et qui peuvent être solidaires des tubes interne et/ou externe ou encore rapportées entre ces deux tubes, comme illustré par exemple dans le document US-A-6 434 972 .

In the latter case and in particular with fluids such as R134a or R152, this coaxial exchanger generally defines:

• inside an inner tube of the exchanger, at least one radially internal channel intended to convey the fluid coming from the low pressure portion of the circuit, and
• radially between this inner tube and an outer tube forming a shell for the exchanger, a radially outer channel usually provided with longitudinal fins designed to optimize the heat transfer between the fluids circulating in the internal (s) and external channels which are distributed over its circumference and which may be integral with the inner and / or outer tubes or reported between these two tubes, as illustrated for example in the document US-A-6,434,972 .

In this case, at least one metal female connector is generally used for the relevant end of the exchanger, which is welded to or brazed on both the inner and outer tubes of the exchanger so as to define passage ducts for the fluid. communicating in a sealed manner with these internal and external channels.

Patent documents WO-A1-2007 / 013439 and EP-A1-1 762 806 have such internal heat exchangers which are respectively equipped with two female connectors and a single female connector, in these two cases via three lines of solder or solder at the corresponding end of the exchanger.

A major disadvantage of these known coaxial internal exchangers fins is that we must give up making connections on the outer tube to the right of these fins to connect in particular valves or tubes supporting sensors, or while we must before machining the profiles forming the inner and / or outer tubes at the location of the fins they comprise in the exchanger area (usually end) precisely intended to receive these connections, which increases the cost of manufacture exchangers.

Another drawback of known coaxial internal heat exchangers equipped with connectors lies in the relatively high weight of these connectors, which must also be machined precisely and then soldered or brazed to make them integral with the inner and outer tubes of the heat exchangers, which also contributes to increasing the cost of manufacturing and assembly of these.

An object of the present invention is to provide such a coaxial tubular type internal exchanger comprising two low and high pressure portions traversed by a refrigerant, the exchanger defining inside an inner tube at least one radially internal channel. preferably for the low pressure fluid and a radially channel external preferably for the high pressure fluid formed between the inner tube and an outer tube exchanger that can overcome these disadvantages.

For this purpose, an exchanger according to the invention is such that spacing means of thermal conductivity lower than that of the inner and outer tubes are mounted movable at least in translation between these two tubes and extend axially on only a part of the length of the external channel, at least one zone of the latter devoid of these means being intended to be connected to a stitch, such as a valve body or a support tube of a sensor, by a connecting orifice formed in the outer tube to the right of this area.

It should be noted that these spacing means according to the invention which provide a spacer function (ie of spacer) between these tubes thus make it possible, because of their thermal conductivity lower than that of the latter, to avoid a thermal coupling. in the form of thermal bridges between these two inner and outer tubes. By way of example, these spacing means may be made of a metallic material (typically of thermal conductivity lower than that of aluminum in the case of tubes based on this metal) or plastic (eg based on a polyamide) .

According to another characteristic of the invention, these spacing means, which are intended to generate turbulence for the fluid flowing in the external channel so as to optimize the heat transfer between the high and low pressure fluids, can extend axially. in a continuous or discontinuous manner on said portion of the outer channel ending with at least one connecting end of the outer tube.

According to a first exemplary embodiment of the invention, these spacing means are formed by a plurality of longitudinal ribs circumferentially connected between their respective bases by a substantially cylindrical wall adapted to fit the inner tube, so that the total radial height of this wall and each rib is substantially equal to that of the outer channel.

According to a second embodiment of the invention, these spacing means are formed by at least one spiral rib adapted to fit the inner tube extending helically around the latter in a constant or variable pitch.

It will be noted that this mounted and sliding mounting spacing means between the inner and outer tubes allows to position precisely in anticipation of the or each tapping to be performed on the outer tube, by sliding previously axially out of the or each zone of the stitching to provide one or more free space (s) allowing this (s) quilting (s). This completely eliminates the need according to the prior art to use internal or external finned tubes locally machined in the areas intended for taps, which allows to lower the manufacturing cost of the exchanger.

It will also be noted that these connections which are thus facilitated by the adjustable positioning of the spacing means can, for example, enable connection to the body exchanger of refrigerant filling valves, of tubes supporting pressure or temperature sensors or any other tubing or radial connection piece (ie whose axis is perpendicular to the axial direction of the exchanger).

According to another characteristic of the invention, these spacing means can be advantageously mounted in contact with the inner and outer tubes so as to serve as radial spacers between these tubes to ensure their concentricity. Also advantageously, in the case where the exchanger is of the type having at least one bent or curved section, these spacing means are preferably inserted at least at the location of this (s) section (s) and, for even more preferential, over most of the axial length of the external channel.

It will be noted that these spacing means according to the invention thus make it possible to "absorb" the bending and / or curvature radii of the inner and outer tubes of the exchanger along its length, which makes it possible to maintain the passage section for the fluid in the external channel substantially constant and therefore not to hinder the heat exchange in the bent or curved sections.

Advantageously, an exchanger according to the invention may incorporate said tapping in line with said zone of the external channel devoid of these spacing means which is located near an end of the outer tube, this tapping being formed of a connecting pipe. the exchanger for conveying the fluid from or to the external channel.

According to another characteristic of the invention, the heat exchanger may advantageously be devoid of any high pressure / low pressure female connector for connecting the internal (s) and external (s) channels to the air conditioning circuit. In other words, this exchanger is then exclusively made up of the inner tube, the outer tube and said spacing means, which do not oppose a stitch communicating with the external channel and do not have to be machined either. to allow this stitching, as explained above.

It will be noted that this absence of female connector (usually made of aluminum) makes it possible to significantly reduce the mass of the exchanger according to the invention, and in addition its overall manufacturing and assembly cost which in the past was encumbered. by the machining operations of the or each connector.

It will also be noted that the inner and outer tubes of the exchanger according to the invention which no longer have to be machined at the level of the spacing profiles can thus be used directly after their forming.

According to a first embodiment of the invention which is facilitated by the aforementioned sliding assembly of the spacing means, the inner tube has at at least one of its ends a protruding portion which projects axially beyond the corresponding end of the outer tube being integral with the latter end and which forms alone - in place of the aforementioned female connector - another connecting pipe of the exchanger for conveying the fluid from or towards the or each internal channel. In this case, this end of the outer tube can be secured to the inner tube by a simple necking of this end, for example obtained by knurling, followed by a circumferential attachment of this end to this inner tube, for example implemented by welding, brazing, by magnetoforming (preferably in two stages, although only one step is possible) or by gluing.

According to a second embodiment of the invention which is also facilitated by the abovementioned sliding assembly of the spacing means, the outer tube is secured in at least one of its ends to the inner tube by crimping with prior fitting between the respective ends of these tubes at one end of a hose connection to the air conditioning circuit, which pipe is optionally mounted in axial abutment against a flange of the inner tube. It will be noted that this single crimping operation then makes it possible to connect the two inner and outer tubes of the exchanger to the adjacent hose of the air conditioning circuit.

An air conditioning circuit for a motor vehicle according to the invention is such that it comprises an internal heat exchanger as defined above, which is preferably connected to this circuit without high pressure / low pressure female connector.

• l a figure 1 est une vue schématique d'un circuit de climatisation pour véhicule automobile incorporant un échangeur thermique interne selon l'invention,
• l a figure 2 est une vue en perspective d'un insert d'espacement selon un premier exemple de l'invention à insérer dans l'échangeur thermique interne de la figure 1,
• l a figure 3 est une vue partielle, en coupe longitudinale et en partie en perspective, d'une extrémité de raccordement d'un échangeur selon ce premier exemple de l'invention incorporant l'insert de la figure 2,
• l a figure 4 est une vue en perspective d'un insert d'espacement selon un second exemple de l'invention à insérer dans l'échangeur de la figure 1,
• l a figure 5 est une vue partielle, en coupe longitudinale et en partie en perspective, d'une extrémité de raccordement d'un échangeur selon ce second exemple de l'invention incorporant l'insert de la figure 4,
• l a figure 6 est une vue partielle en perspective d'une extrémité de raccordement d'un échangeur thermique interne selon un premier mode de l'invention, notamment en référence aux exemples des figures 3 et 5, et
• l a figure 7 est une vue schématique partielle en demi-coupe longitudinale d'une extrémité de raccordement d'un échangeur thermique interne selon un second mode de l'invention, notamment en référence aux exemples des figures 3 et 5.

Other features, advantages and details of the invention will emerge on reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation, the description being made with reference to the accompanying 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 perspective view of a spacer insert according to a first example of the invention to be inserted into the internal heat exchanger of the figure 1 ,
• the figure 3 is a partial view, in longitudinal section and partly in perspective, of a connecting end of an exchanger according to this first example of the invention incorporating the insert of the figure 2 ,
• the figure 4 is a perspective view of a spacer insert according to a second example of the invention to be inserted into the heat exchanger of the figure 1 ,
• the figure 5 is a partial view, in longitudinal section and partly in perspective, of a connecting end of an exchanger according to this second example of the invention incorporating the insert of the figure 4 ,
• the figure 6 is a partial perspective view of a connection end of an internal heat exchanger according to a first embodiment of the invention, in particular with reference to the examples of figures 3 and 5 , and
• the figure 7 is a partial schematic view in longitudinal half-section of a connecting end of an internal heat exchanger according to a second embodiment of the invention, in particular with reference to the examples of figures 3 and 5 .

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 R134a or R152, without limitation. All these elements are interconnected by rigid or flexible lines consisting of rigid tubular portions and / or flexible, which have at each of their ends sealed connection means.

• une ligne basse pression BP destinée à véhiculer le fluide frigorigène 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 et une sortie s_BP de ce fluide ainsi réchauffé, et
• une ligne haute pression HP destinée à véhiculer ce même fluide en aval du compresseur 2 et du refroidisseur 3 via une entrée e_HP de fluide haute pression à refroidir 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 between the evaporator 4 and the compressor 2, through the exchanger E via a low pressure fluid inlet e _BP to be heated and a _BP output of the fluid thus heated, and
• an HP high pressure line for conveying the same fluid downstream of the compressor 2 and the cooler 3 via an _HP input e high pressure fluid to be cooled and an outlet 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 is of coaxial type against the current, and is intended to cool the fluid from the HP line by conduction in contact with the same fluid from the BP line which is heated in exchange. For this purpose and as illustrated in the example of figure 3 this exchanger E consists of a radially inner metal tube 10 which defines in its internal space an internal channel 11 for the fluid coming from the line BP and which is inserted axially inside a radially external tube 20 also of metal delimiting with the tube 20 an outer channel 21 of annular cross section for the fluid from the line HP.

As illustrated in Figures 2 and 3 a spacer insert 30 forming a spacer according to the first example of the invention, which is intended to optimize the heat transfer between the HP and LP fluids by the generation of turbulence in the external channel 21, is slidably mounted between the tubes 10 and 20 and in contact therewith, being recessed at an adjustable axial distance from the connecting end 22 of the outer tube 20. In this way, the end zone of the outer channel 21 which is completely free of access - because it is devoid of the insert 30 - can be easily connected to a stitching 40, such as a filling valve body or a support tube of a pressure sensor, for example by a connecting orifice 23 formed in the outer tube 20.

The insert 30 is formed by a plurality of ribs 31 circumferentially connected at their respective bases by a cylindrical wall 32 conforming to the wall of the inner tube 10, the total radial height of the wall 32 and each rib 31 being substantially equal to that of the external channel (To the mounting clearance near to allow the sliding of the insert 30).

As visible to Figures 4 and 5 , a spacing insert 130 according to the second example of the invention is formed by a spiral rib conforming to both the inner tube 10 and the outer tube 20 of the exchanger E by extending helically thereabout ( according to a constant step in this embodiment, it being specified that this step could vary in the axial direction and that the spiral could be discontinuous along the outer channel 21).

As indicated above, it will be noted that the insert 30, 130 makes it possible at the same time to improve the heat transfer between HP and BP fluids and to serve as a radial spacer between these tubes to ensure their concentricity, in particular in bent or curved sections of exchanger E.

In the embodiment of the figure 6 , which integrates for example the insert 30, 130 of figures 2 or 4 , the inner tube 10 has a protruding portion 12 which protrudes axially from the end 22 of the tube 20 by being integral therewith and which constitutes the connecting pipe of the internal channel 11 of the exchanger E to the line BP of air conditioning circuit 1. This end 22 of the tube 20 may be secured to the portion 12 of the tube 10 by a necking which is applied to it by knurling, followed by a circumferential attachment of the end 22 thus narrowed on this portion 12 tube of preferably by welding or soldering (it being specified that other methods such as magnetoforming or even gluing are usable).

In the embodiment of the figure 7 , which also integrates for example the insert 30, 130 of figures 2 or 4 , the tube 120 is secured to the tube 110 by crimping with pre-fitting between the respective ends 112 and 122 of the tubes 110 and 120 of an end of a flexible hose 50 for connection to the circuit 1, this hose 50 being in this example mounted in axial abutment against a flange 113 of the tube 110 (schematically the deformations of the respective ends 112 and 122 of the tubes 110 and 120 due to this crimping in contact with the pipe 50).

It will be noted that the two embodiments of the Figures 6 and 7 have the advantage of allowing the connection of the corresponding end of the exchanger E to the rest of the air conditioning circuit 1 without requiring soldering or brazing of one or more female connector (s), whose massive structure and the preliminary machining required are disadvantages known for this connection because of their weight and the overall assembly overhead they represent for the exchanger E.

Claims (12)

Internal heat exchanger (E) of coaxial tubular type for an air conditioning circuit (1) of a motor vehicle comprising two portions of low and high pressure (BP and HP) traversed by a refrigerant, the exchanger defining at least one radially internal channel (11) preferably for the low pressure fluid within an inner tube (10, 110) and a radially outer channel (21) preferably for the high pressure fluid formed between the inner tube and an outer tube (20). , 120), characterized in that spacing means (30, 130) of lower thermal conductivity than the inner and outer tubes are mounted movable at least in translation between these two tubes and extend over only a portion of the the length of the external channel, at least one zone of the latter devoid of these means being intended to be connected to a stitching (40), such as a valve body or a support tube of a sensor, by a connecting orifice; ordement (23) formed in the outer tube to the right of this zone. Heat exchanger (E) according to claim 1, characterized in that said spacing means (30, 130) are mounted in contact with the inner (10, 110) and outer (20, 120) tubes so as to serve as radial spacers between these tubes to ensure their concentricity. Heat exchanger (E) according to claim 2, of the type having at least one bent or curved section, characterized in that said spacing means (30, 130) are inserted at least at the location of this (s) section (s). ). Exchanger (E) according to one of the preceding claims, characterized in that said spacing means (30, 130) extend axially continuously or discontinuously on said portion of the channel outer member (21) terminating at least one end of connection (22, 122) from the outer tube (20, 120), Heat exchanger (E) according to claim 4, characterized in that said spacing means (30) are formed by a plurality of longitudinal ribs (31) circumferentially connected between their respective bases by a substantially cylindrical wall (32) adapted to fit the inner tube (10, 110), so that the total radial height of this wall and each rib is substantially equal to that of the outer channel (21). Exchanger (E) according to claim 4, characterized in that said spacing means (130) are formed by at least one spiral rib adapted to fit the inner tube (10, 110) extending helically around the latter according to a constant or variable step. Heat exchanger (E) according to one of the preceding claims, characterized in that it incorporates said stitching (40) in line with said zone of the external channel (21) devoid of said spacing means (30, 130) which is situated close to one end (22, 122) of the outer tube (20, 120), this tapping being formed of a connecting pipe of the exchanger for conveying the fluid from or towards the external channel. Exchanger (E) according to claim 7, characterized in that the inner tube (10) has at least one of its ends an overflow portion (12) which protrudes axially from the corresponding end (22) of the outer tube. (20) being integral with the latter end and which alone forms another connecting pipe of the exchanger for conveying the fluid from or towards the or each inner channel (11). Heat exchanger (E) according to claim 8, characterized in that said end (22) of the outer tube (20) is secured to the tube internal (10) by a necking of this end for example obtained by knurling, followed by a circumferential attachment of this end on the inner tube for example implemented by welding, brazing, magnetoforming or gluing. Heat exchanger (E) according to claim 7, characterized in that at least one of its ends (122), the outer tube (120) is secured to the inner tube (110) by crimping with pre-fitting between the ends respective ones (112 and 122) of these tubes (110 and 120) of one end of a hose (50) for connection to the air conditioning circuit (1), which hose is optionally mounted in axial abutment against a flange (113) of the inner tube. Exchanger (E) according to one of Claims 7 to 10, characterized in that it does not have any high pressure / low pressure female connectors for connecting the internal (11) and outer (21) channels to the air conditioning circuit (1). Air conditioning circuit (1) for a motor vehicle, characterized in that it comprises an internal heat exchanger (E) as defined in one of the preceding claims, which is preferably connected to this circuit without a high-pressure / low-pressure female connector .

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