EP2137477B1 - Heat exchanger for gas - Google Patents

Description

The present invention relates to a heat exchanger for gas.

The invention finds particular application in the exhaust gas recirculation exchangers (EGRC) of an engine.

BACKGROUND OF THE INVENTION

In some heat exchangers used to cool gases, for example those used in exhaust gas recirculation systems to the inlet of an internal combustion engine, the two heat exchange media are separated by a wall.

The heat exchanger itself can have several different configurations: for example, it can be composed of a carcass inside which are arranged a series of parallel ducts for the passage of gases, the refrigerant circulating in the carcass outside the ducts; in another embodiment, the exchanger has a series of parallel plates forming the heat exchange surfaces, the exhaust gas and the refrigerant flowing between two plates, in alternating layers.

In the case of ductwork heat exchangers, the junction between the ducts and the casing may be of different types. In general, the ducts are fixed at their ends between two support plates coupled to each end of the carcass, the two support plates having a plurality of orifices for the introduction of the ducts. respectively. Said support plates are themselves attached to connection means to the recirculation line.

Said connecting means may consist of a V-shaped connection or of a peripheral flange of connection or flange, depending on the configuration of the recirculation line to which the exchanger is connected.

When using a peripheral flange or flange, two different designs are possible. The peripheral rim may be connected to a gas reservoir, so that the gas reservoir is an intermediate piece between the carcass and the rim. In addition, the flange can also be directly connected to the carcass. This latter design is common when the exchanger is directly joined to an EGR valve.

In some EGR applications, it is necessary to cool the EGR valve. In this case, the most common design comprises a bypass duct which conducts the refrigerant fluid, which flows in the EGR exchanger, to or from the EGR valve. If the EGR exchanger is connected to the EGR circuit by means of a peripheral flange, the refrigerant by-pass duct must be manufactured through said peripheral flange. According to another embodiment, the bypass duct is external and connects the carcass to the valve.

Similarly, the gas circuit may be of linear type in which the inlet and the outlet of the gases are arranged at opposite ends; or may be in the form of a "U" in which the gas inlet and outlet occupy adjacent positions at the same open end, the opposite end being closed, and defining a forward passage and a return passage. In the latter case, the closed end for the return of gases is generally consists of a closed gas tank.

In practice, EGR heat exchangers are metal and usually made of stainless steel. All the components of the ductwork heat exchangers, like those of the stacked plate heat exchangers, are metallic, so that the exchangers are assembled by mechanical means and then welded in the oven to ensure an adequate level of sealing for this application.

One action to reduce the cost of the EGR heat exchanger is to replace the stainless steel casing with another material, whether this material has a low cost or that it allows to integrate other functions, such as the integration of the refrigerant conduits or fixing brackets to a surface to which the exchanger will be fixed.
There are EGR duct heat exchangers whose carcass is made of aluminum rather than stainless steel. In this case, since the exchanger as a whole can not be immediately welded to the oven, a mechanical connection is provided between the carcass and other components, such as a gas tank, support plates or support edges.

The patent WO 2005/052346 relates to a heat exchanger comprising a plastic carcass inside which is housed a metal core formed of a bundle of parallel conduits joined at their ends to two support plates, said plates being joined to connections with the line of recirculation of gases. A plastic seal is further provided between the corresponding end of the carcass and the support plate to provide the required level of sealing. Plastic carcasses have the advantage of reducing the cost of production to the extent where they allow the integration of refrigerant circuit conduits and fixing brackets. In general, the junction between the metal support plate and the plastic casing is made by a mechanical assembly.

Licences US 6,269,870 , WO 2004/001203 and US 2003/0079869 relate to type heat exchangers which comprise a bundle of conduits, the support plates of which incorporate an outwardly oriented peripheral wall which extends beyond the ends of the conduits, so that each peripheral wall is joined on the internal surface of a metal casing and in a position adjacent to a diffuser, by arc welding. The junction between the conduits and the support plates is performed by laser welding.

Licences JP 2004177058 , JP 2004028469 and JP 2004263616 relate to heat exchangers of the type which comprise a bundle of conduits, whose metal carcass is formed of two parts joined together by laser welding, and which use an oven weld for the junctions between the conduits and the support plates.

The patent US 6,311,678 relates to a heat exchanger of the type which comprises a core having a bundle of parallel conduits joined at their ends to two support plates, said plates being joined to connections with the gas recirculation line. Once mounted, the core is inserted into a cast aluminum block to form a metal carcass.

However, the manufacturing process of the various heat exchangers mentioned is generally complex, insofar as, in the cases where it uses a baking process, it requires the use of support elements for immobilizing the various components when the exchanger is inside the oven. This greatly complicates the manufacturing process of the exchanger, and also increases the time and cost of production.

It should be emphasized that the manufacturing process is also complex when it combines different types of welding, such as arc welding, laser welding or furnace, to join the various components of the exchanger. In addition, in most cases, these components are structurally complex because they require additional surfaces or flanges to ensure proper junction.

According to another aspect, in the exchangers with a U-shaped configuration, the open-side junction generally comprises a seal to prevent any leakage of the coolant to the outside, while the junction of the closed side does not require any sealing function, because on this side, the only need is to support the metal body in the plastic carcass. The patent WO 2007/048603 describes a heat exchanger of this type, wherein the junction means of the closed side comprise a support integral with the plastic carcass, said support being provided with a slot for receiving a projection integral with the closed gas reservoir.

The document DE102006031606 discloses a gas heat exchanger according to the preamble of claim 1.

However, the known exchangers of this type have a series of disadvantages insofar as the attachment of the metal body of the exchanger to the plastic casing is very confrontational and requires taking into account the following considerations in terms of design:

1) The contact area:

The working temperatures of the plastic casing and the body of the exchanger are different. The metal body can reach high temperatures insofar as it is in contact with the gas, the temperature of which varies from 750 ºC input to 500 ºC output; while the plastic casing supports relatively low temperatures because it is immersed in the refrigerant whose temperature is between 70 ºC and 90 ºC.

The contact zone between the body of the exchanger and the plastic casing must be very well cooled by the refrigerant.

In other words, on the one hand, the flow of refrigerant in this zone must be sufficiently large, the coolant passage being therefore preferential; and, on the other hand, the contact zone must be very small to maintain the temperature in the contact zone of the plastic material at values close to the temperature of the refrigerant. Similarly, the contact zone must be large enough to support the metal body.

2) Thermal expansion:

Because of the temperature difference between the metal body and the plastic frame, the thermal expansion of the two components will be different, and will also depend on the coefficient of thermal expansion.

This has the disadvantage of producing undesirable movements between the components, preferably in the longitudinal direction, due to their own expansion.

3) Distance between the metal body and the carcass:

As mentioned previously, the contact zone between the plastic carcass and the metal body, generally the gas tank, must be well cooled by the refrigerant, which means that the refrigerant in this zone must be preferential. To improve the flow of refrigerant in this area, the design requirements are very important.

In this sense, it is very important to define the distance between the metal body and the plastic carcass. The choice of this value depends on the minimum cross section of the coolant in the heat exchanger. For example, if the gas tubes of a tubular heat exchanger are separated by a distance of 1.3 mm, it is advisable to have a distance of 2.6 mm, on both opposite sides, between the tank of gas and plastic carcass.

4) Position of the refrigerant inlet connection:

It is very important to position the coolant inlet fitting close to the contact area to ensure a minimum flow of coolant.

5) Position of the mounting brackets on a surface of the engine environment:

It is advisable to have at least one mounting bracket for the motor in the support zone of the duct bundle at the level of the heat exchanger casing, in order to obtain a better resistance of the metal body to the vibrations of the motor.

6) Design of the means for joining the metal body to the carcass:

A good design of the body junction metal to the plastic casing is necessary to be able to absorb the play due to the tolerances of the components.

According to another aspect, in the exchangers with a plastic casing, one of the main points of this development is the maximum temperature that the plastic must withstand. This type of exchanger generally comprises a metal flange attached to the support plate and in direct contact with the plastic carcass, the EGR or bypass valve being connectable to this rim directly or by means of a connecting body. intermediate. As a result, the elevated temperature can be transferred from the walls of the valve or intermediate coupling body to the flange and, therefore, to the plastic. This involves using a plastic material for the carcass that withstands a high temperature, which limits the range of plastics that can be used and assumes a considerable increase in cost.

In order to guarantee the tightness of the gas flow between the valve and the exchanger, a seal is inserted between the metal flange and the valve or the intermediate coupling body. This seal is generally metallic, for example steel, for EGRC applications. Said metal seal also has a high heat conductivity, so that the heat transferred from the material in contact with the gas does not decrease.

In another aspect, generally, the applications that EGR circuits corresponding to high pressure (HP) configurations in which the EGR exchanger is located in the EGR gas recirculation line, mounted directly on the engine. In addition, WCAC exchangers are generally air-cooled and located at the front of the vehicle.

• Les échangeurs WCAC sont refroidis par le liquide réfrigérant, et il existe déjà des applications en série du fait de leur bonne intégration et compacité.
• Les circuits LP EGR sont développés par les principaux fabricants de moteurs, et leur usage peut être étendu aux générations suivantes d'échangeurs.
• Il existe de nouvelles conceptions d'échangeurs EGR avec carcasse en plastique. Les carcasses en plastique ont l'avantage de réduire le poids et le coût de production dans la mesure où elles permettent l'intégration des conduits du circuit du fluide réfrigérant et des supports de fixation à une surface de l'environnement moteur.

There are at present various developments of this type of exchangers as indicated below:

• The WCAC exchangers are cooled by the coolant, and there are already serial applications because of their good integration and compactness.
• LP EGR circuits are developed by major engine manufacturers, and their use can be extended to subsequent generations of heat exchangers.
• There are new designs of EGR exchangers with plastic carcass. The plastic carcasses have the advantage of reducing the weight and cost of production insofar as they allow the integration of the refrigerant circuit conduits and the attachment brackets to a surface of the engine environment.

In this context, it is important to develop the technology of the EGR exchanger to be able to assemble it in new engine environments. In addition, integration possibilities in this new environment need to be assessed. Generally, the low pressure (LP) EGRs have a configuration in which the EGR is located outside the engine block, and therefore this component could be integrated with other nearby components. The integration would be more profitable if the EGR exchanger could be integrated with another exchanger also cooled by the refrigerant or a similar technology exchanger.

The heat exchange means (for example, a bundle of parallel conduits) of the EGRC and WCAC exchangers may be similar, since the function of these two exchangers is to cool a gas. The outer carcass may also be similar; in practice, there are known applications of WCAC exchangers with plastic casings, and new developments have been launched for the use of a plastic casing for EGR exchangers.

However, at present there is no known exchanger incorporating in the same plastic frame an EGR exchanger and a WCAC exchanger.

DE102006031606 discloses a heat exchanger according to the preamble of claim 1.

DESCRIPTION OF THE INVENTION

The present invention relates to a heat exchanger for gas to overcome the disadvantages of exchangers known in the art, ensuring a reduction in the number of components and a reduction in manufacturing costs.

The gas heat exchanger which is the subject of the present invention is of the type which comprises a metal core comprising a set of parallel ducts intended for the circulation of gases with heat exchange with a refrigerant, at least one support plate joined by welding laser to at least one end of said set of parallel conduits, and at least one gas reservoir or connecting member, and is characterized in that said gas reservoir or connecting member is joined directly to said support plate by laser welding or arc welding.

In this way, it is possible to obtain a structurally simpler core, without the need for a carcass, inasmuch as the gas reservoir or the connecting element is directly attached to the support plate. instead of being attached to a carcass, as was the case in the state of the art.

Furthermore, joining processes between the core components are carried out quickly and efficiently, without the need for soldering in the oven and without the need for additional surfaces or edges to ensure proper junction, as was the case in the state of the art. It is also possible to obtain a reduction in the volume and cost of said heat exchanger.

Moreover, the simplicity of use of the laser or arc welding makes it possible to give the gas circuit to cool any configuration or orientation.

It is also possible to manufacture a single unit, without intermediate stocks, which reduces quality defects. The core is placed in a carcass connected to the refrigerant circuit.

In this way, the laser-welded or arc-welded components that form the core remain stationary when they are introduced into the carcass and joined to the carcass, whether by welding in the oven or by any other type of junction.

1. a) obtenir un coeur comprenant un ensemble de conduits parallèles, au moins une plaque de support métallique, et au moins un réservoir de gaz ou élément de raccord ;
2. b) joindre ladite plaque de support par soudure au laser à au moins l'une des extrémités dudit ensemble de conduits parallèles ;
3. c) joindre ledit réservoir de gaz ou élément de raccord directement à ladite plaque de support par soudure au laser ou soudure à l'arc ;
4. d) introduire le coeur dans une carcasse raccordée au circuit du fluide réfrigérant ; et
5. e) joindre le coeur à ladite carcasse pour compléter l'échangeur.

In addition, the configuration of the core is independent of the material of manufacture of the carcass, whether it is plastic, metal or a composite material. The heat exchanger is of the "U" shaped type in which the inlet and the outlet of the fluid to be cooled occupy adjacent positions at the same open end of the set of parallel ducts, the opposite end being closed, and defining a go and a return pass. The core includes a first support plate disposed at the open end and having a rim for joining a carcass, and a second support plate disposed at the closed end and joined to a reservoir. closed gas. The manufacturing method applied to the heat exchanger of the invention implements the following steps:

1. a) obtaining a core comprising a set of parallel conduits, at least one metal support plate, and at least one gas reservoir or connecting element;
2. b) attaching said support plate by laser welding to at least one end of said set of parallel conduits;
3. c) joining said gas reservoir or connecting member directly to said support plate by laser welding or arc welding;
4. d) introducing the core into a carcass connected to the refrigerant circuit; and
5. e) attach the core to said carcass to complete the exchanger.

It is thus possible to obtain a simpler manufacturing process and a reduction in the volume and manufacturing costs of the heat exchanger.

Advantageously, the junction of the core to the carcass according to step e) is performed by welding, bonding or mechanical assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

• La figure 1 est une vue en perspective d'un coeur métallique soudé au laser ;
• la figure 2 est une vue en perspective d'un échangeur de chaleur du type en forme de "U", illustrant le coeur de la figure 1 joint à une carcasse en plastique par soudure ;
• la figure 3 est une vue partielle d'une coupe longitudinale de l'échangeur de la figure 2, illustrant la zone de jonction entre le coeur et la carcasse ;
• la figure 4 est une vue en perspective et éclatée d'un échangeur de chaleur du type en forme de "U", illustrant un coeur métallique soudé au laser avant d'être joint à une carcasse en plastique par assemblage mécanique ;
• la figure 5 est une vue en perspective et éclatée d'un échangeur de chaleur pour gaz, selon un premier mode de réalisation de l'invention ;
• la figure 6 est une vue en coupe longitudinale de l'échangeur monté de la figure 5 ;
• les figures 7, 8 et 9 sont des vues en coupe transversale de l'échangeur, selon la ligne VII-VII de la figure 6, illustrant les moyens de jonction avec six, quatre et deux nervures respectivement, selon différentes variantes ;
• la figure 10 est une vue partielle d'une section longitudinale, illustrant les nervures longitudinales ;
• les figures 11 et 12 sont des vues en coupe transversale de l'échangeur, illustrant les moyens de jonction avec deux nervures ramifiées comprenant deux et trois branches respectivement, selon différentes variantes ;
• les figures 13 et 14 sont des vues en coupe transversale de l'échangeur, illustrant les moyens de jonction avec six nervures à deux branches avec différents angles respectivement, selon différentes variantes ;
• la figure 15 est une vue en coupe transversale de l'échangeur, illustrant une vue agrandie d'une nervure longitudinale pourvue d'une pluralité de protubérances ;
• la figure 16 est une vue en perspective et éclatée d'un échangeur de chaleur pour gaz, selon un deuxième mode de réalisation de l'invention ;
• la figure 17 est une vue de dessus du joint d'étanchéité en matériau thermo-isolant de l'échangeur de la figure 16 ;
• la figure 18 est une vue en perspective d'un échangeur de chaleur pour gaz ; et
• la figure 19 est une vue en coupe transversale et en perspective de l'échangeur de la figure 18.

In order to facilitate the description of what has been explained above, drawings which show, in schematic form and by way of non-limiting example only, five practical examples of a gas heat exchanger. In these drawings:

• The figure 1 is a perspective view of a laser welded metal core;
• the figure 2 is a perspective view of a "U" shaped heat exchanger, illustrating the heart of the figure 1 attached to a plastic carcass by welding;
• the figure 3 is a partial view of a longitudinal section of the heat exchanger of the figure 2 , illustrating the zone of junction between the heart and the carcass;
• the figure 4 is an exploded perspective view of a "U" -shaped heat exchanger illustrating a laser-welded metal core before being joined to a plastic carcass by mechanical assembly;
• the figure 5 is a perspective and exploded view of a heat exchanger for gas, according to a first embodiment of the invention;
• the figure 6 is a longitudinal sectional view of the mounted exchanger of the figure 5 ;
• the Figures 7, 8 and 9 are cross-sectional views of the exchanger along line VII-VII of the figure 6 , illustrating the means of joining with six, four and two ribs respectively, according to different variants;
• the figure 10 is a partial view of a longitudinal section, illustrating the longitudinal ribs;
• the Figures 11 and 12 are sectional views cross section of the exchanger, illustrating the junction means with two branched ribs comprising two and three branches respectively, according to different variants;
• the Figures 13 and 14 are cross-sectional views of the exchanger, illustrating the means of joining with six ribs with two branches with different angles respectively, according to different variants;
• the figure 15 is a cross-sectional view of the exchanger, illustrating an enlarged view of a longitudinal rib provided with a plurality of protuberances;
• the figure 16 is a perspective and exploded view of a gas heat exchanger, according to a second embodiment of the invention;
• the figure 17 is a top view of the seal of heat-insulating material of the heat exchanger of the figure 16 ;
• the figure 18 is a perspective view of a gas heat exchanger; and
• the figure 19 is a cross-sectional perspective view of the exchanger of the figure 18 .

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Figures 1 to 3 illustrate a first heat exchanger.

The heat exchanger 1 for gas comprises a metal core 2 comprising a set of parallel ducts 3, which, in this example, are planar and of rectangular section, intended for the circulation of gases with heat exchange with a refrigerant.

In this embodiment, the exchanger is of the "U" -shaped type, namely the inlet 4 and the outlet 5 of the gases to be cooled occupy positions adjacent to the level of the same open end 6 of the set of parallel conduits 3, the opposite end 7 being closed, and defining a go and a return passage, as illustrated by the arrows of the figure 1 .

The two ends 6 and 7 of the bundle of ducts 3 are fixed to two support plates 8 and 9, which have a plurality of orifices 10 in which the respective ducts 3 are inserted.

In this example, the support plate 8 fixed at the free end 6 has a peripheral flange 11 intended to be coupled to a carcass, as will be explained later, while the support plate 9 fixed at the level the closed end 7 is joined to a gas reservoir 12. The junction between the plate 9 and the gas reservoir 12 is preferably made without using a peripheral flange so as to obtain a stronger junction and reduced cross section.

The junction between the ends of the duct assembly 3 and the support plates 8, 9 is made by laser welding, whereas the junction between the plate 9 and the gas reservoir 12 may be made by laser welding or by arc welding.

With reference to the figure 2 , the core 2 may be housed inside a carcass 13 of plastic incorporating the inlet ducts 14 and the outlet 15 of the refrigerant. The carcass 13 comprises at its free end a peripheral flange 13a facing outwardly of said carcass 13, and substantially perpendicular to its axis. Said peripheral flange 13a is intended to be joined to the connecting means corresponding to the gas recirculation duct (not shown).

In this embodiment, as illustrated by figure 3 , the junction of the heart 2 to the carcass in plastic 13 is made using a metal insert 16 overmolded at the open end of the plastic carcass 13, specifically on the peripheral rim 13a of said carcass 13. The metal core 2 is then introduced to the inside the carcass until the peripheral rim 11 of the support plate 8 partially bears against the metal insert 16. Thereafter, said junction is preferably laser welded, although it can also be arc welded or glued with a suitable adhesive.

The appropriate choice of the geometry and distances between the metal components, namely between the metal insert 16 and the corresponding metal support plate 8, makes it possible to perform the laser welding between these two components without risk of damaging the carcass. in plastic. This is possible thanks to laser technology, in which the temperature rise associated with the weld is much more localized.

Similarly, since the plastic seals used in the state of the art are removed, product reliability is ensured as the plastic seals complicate assembly and also have durability problems.

The figure 4 illustrates a second heat exchanger.

The heat exchanger comprises the same elements bearing the references 2 to 15 of the first embodiment. The difference lies in the fact that the junction between the support plate 8a and the plastic casing 13 is made by mechanical assembly. To this end, the support plate 8a has a peripheral rim 11a with tabs intended to be folded and fixed against the contour of the plastic casing 13. It further comprises a plastic seal 17 to also ensure the compressive force.

Since the components of the metal core are joined by laser or arc welding, it is thus possible to obtain a simpler manufacturing process and a reduction in the volume and manufacturing costs of the heat exchanger. heat.

Although the gas circuit described in this second embodiment is in the form of a "U" (the inlet and the outlet of the gases are arranged at the same end), it can also be of the linear type (the inlet and the gas outlet are disposed at opposite ends).

The carcass may be plastic, as described, aluminum or other metallic material, or a composite material. In addition, it should be emphasized that instead of being introduced into a carcass, the core may be housed in a chamber forming part of the refrigerant circuit of the engine.

The Figures 5 to 15 illustrate a first embodiment of the invention.

The heat exchanger 1b comprises the same elements bearing the references 2 to 15 and 17 of the first and second embodiments. In this case, the inlet 4 of the gases should be arranged close to the passage of the cooling fluid, whether at the inlet or at the outlet. In the embodiment illustrated on the figure 5 , the inlet 4 of the gas is located near the inlet 14 of the refrigerant.

The duct bundle 3 is fixed at its free end to the metal support plate 8b, and at its closed end to the storage tank. gas 12.

In this case, said support plate 8b is fixed at the open end of the plastic casing 13 by means of screws. A plastic seal 17 is further provided between the open end of the carcass 13 and the support plate 8b to provide the required level of sealing.

The plastic casing 13 is fixed at its closed end to said metal gas reservoir 12 by means of joining which comprise a plurality of longitudinal ribs 18 with a small contact surface, integral with the plastic casing 13 and capable of being nested in corresponding orifices 19 formed in the gas reservoir 12, as shown for example by the Figures 7 to 9 .

In this example, the orifices 19 are formed in said gas tank by stamping.

The longitudinal ribs 18 make it possible to solve the problem of having both an area sufficiently small to maintain the temperature in the contact zone of the plastic material at values close to the temperature of the coolant, and a sufficiently large contact zone. to be able to support the metal body.

In addition, this solution makes it possible to obtain an abundant flow of the coolant to cool the contact zone which is at an elevated temperature.

Furthermore, the establishment of the body of the heat exchanger inside the plastic carcass during the mounting operation is facilitated.

Generally, between two and eight longitudinal ribs 18 distributed in a relatively equidistant manner are used to obtain a correct distribution of the weight of the metal body on the carcass. plastic, thus guaranteeing a good stability of the whole.

According to a variant illustrated on the figure 7 , the connecting means comprise six longitudinal ribs 18 symmetrically distributed, so that each large side of said rectangular cross section comprises two ribs and each small side comprises a rib.

According to another variant illustrated on the figure 8 , the connecting means comprise four longitudinal ribs 18 distributed symmetrically, so that each large side of said rectangular cross section comprises two ribs.

According to another variant illustrated on the figure 9 , the joining means comprise two longitudinal ribs 18 distributed symmetrically, so that each long side of said rectangular cross section comprises a rib.

Similarly, the longitudinal ribs 18 have a minimum longitudinal dimension to allow the displacements due to the different thermal expansion between the metal gas tank 12 and the plastic casing 13, thus ensuring proper operation of the exchanger. The arrow with two points shown on the figure 10 indicates the direction of these longitudinal displacements.

A minimum distance between the gas tank 12 and the plastic casing 13 is also provided, depending on the minimum cross-sectional area of the refrigerant flow in the exchanger 1b. This ensures an abundant flow of refrigerant.

This minimum distance between the gas reservoir 12 and the plastic casing 13, measured on each opposite side of the gas reservoir 12, is twice the distance between the gas conduits 3. A safety distance is also provided, equal to between 1.5 and 2.5 times the minimum cross section of the refrigerant flow.

The outlet fitting 15 of the refrigerant fluid is located near the contact zone of the junction between the carcass 13 and the gas reservoir 12, as shown by FIGS. figures 6 and 10 . This guarantees a minimum refrigerant flow.

The exchanger 1b comprises mounting brackets 20 to a surface of the engine environment, which are located close to said contact zone of the junction between the carcass 13 and the gas reservoir 12, as shown in FIG. figure 5 . In this way, a better resistance of the metal body to the vibrations due to the motor is obtained.

The longitudinal ribs 18 comprise a suitable configuration to absorb the clearance due to the tolerances of the gas reservoir 12 and the plastic casing 13.

The shape of the longitudinal ribs 18 will admit a minor deformation of the plastic material if the interference of assembly between the two components exceeds the allowable interference, that is to say if the gas tank has the greatest permissible tolerance and that the distance between the longitudinal ribs is as small as possible. In this case, the longitudinal ribs 18 may comprise a branched configuration, as shown by the Figures 11 to 14 .

According to a variant illustrated on the figure 11 , the longitudinal ribs 18 comprise two diverging branches which form a suitable angle chosen as a function of the plastics material used.

We can observe on Figures 13 and 14 , respectively, different values of the angle formed by the branches of the longitudinal ribs 18. The greater the angle defined between the branches, the lower the mounting force is.

According to another variant illustrated on the figure 12 the longitudinal ribs 18 comprise three diverging branches. In this case, the addition of an additional central branch makes it possible to improve the stability.

The longitudinal ribs 18 may comprise a plurality of small protuberances 21 on their outer surface, as shown in FIG. figure 15 . The volume of plastic to be deformed is thus less, in the event of interference of assembly, and, consequently, the mounting procedure is facilitated.

Although a parallel tube bundle exchanger has been described in this third embodiment, the invention can also be applied to stacked plate heat exchangers. Similarly, in both cases, the gas circuit may be of the "U" -shaped type (the gas inlet and outlet are arranged at the same end) or of the linear type (the inlet and the outlet gases are arranged at opposite ends).

The Figures 16 and 17 illustrate a second embodiment of the invention.

The heat exchanger 1c comprises the same elements bearing the references 2 to 15 and 17 of the previous embodiments. In this case, the support plate 8c is joined to a metal flange 22, which is coupled in direct contact with the open end of the plastic casing 13 by means of screws and a plastic seal 17 to secure the sealing of the refrigerant.

The establishment of an EGR valve or bypass (not shown) connected to said metal flange 22 is also provided.

In addition, to ensure the sealing of the gas flow between the valve and the exchanger 1c, a seal 23 is provided between the metal flange 22 and the valve.

Said seal 23 is made of a heat-insulating material, preferably of mica, thus reducing the heat transfer from the valve to the plastic casing 13. Furthermore, said seal 23 has a shape that coincides with the shape of the rim 22, as shown in figure 16 .

The seal 23 is able to withstand a high temperature up to about 950 ºC, which allows the temperature in contact with the plastic casing 13 to be reduced to about 50ºC.

In this way, the seal 23 reduces the temperature level, thus ensuring the durability of the EGR exchanger, and, more importantly, it increases the range of plastics that can be used with the carcass . In addition, the cost of production is reduced.

Although a parallel tube bundle exchanger has been described in this fourth embodiment, the invention can also be applied to stacked plate heat exchangers. Similarly, in both cases, the gas circuit may be of the "U" -shaped type (the gas inlet and outlet are arranged at the same end) or of the linear type (the inlet and the outlet gases are arranged at opposite ends).

The Figures 18 and 19 illustrate another heat exchanger.

The heat exchanger 1d comprises the same elements bearing the references 2 to 15 of the previous embodiments. With reference to Figures 18 and 19 , the heat exchanger 1d consists of a carcass in plastic 13 which comprises in its interior a first circuit 3 EGR type provided with a bundle of conduits for cooling the engine exhaust gas, and a second circuit 3a of the type WCAC (Water Charge Air Coolers) provided with a conduit bundle for cooling the intake air of the engine, the two circuits 3, 3a being arranged adjacent. Each circuit 3, 3a is located on the figure 19 by means of a circle.

The plastic casing 13 may have a free shape adapted to the environment, and the two circuits EGR 3 and WCAC 3a may be arranged relative to each other in different arrangements, for example in parallel, as shown in FIG. figure 1d , or in series, "L" shaped, "T" shaped, etc.

Inside the plastic casing 13, outside the EGR circuits 3 and WCAC 3a, circulates a refrigerant fluid, from a single inlet 14 to a single outlet 15, thus sharing the same cooling circuit for the two EGR circuits 3 and WCAC 3a.

It should be emphasized that other configurations may exist; for example there may be two inputs and two outputs of the refrigerant respectively for each EGR circuit 3 and WCAC 3a, sharing the same cooling circuit or with two independent cooling circuits.

As shown in figure 18 , the exchanger 1d is of linear type, that is to say that the inlet and the outlet of the gases are arranged at opposite ends.

In this embodiment, the inputs 4, 4a of each EGR circuit 3 and WCAC 3a are disposed at the same end of the carcass 13, while the outputs 5, 5a are disposed at the opposite end.

There may also be others provisions; for example the input of an EGR circuit 3 or WCAC 3a and the output of the other circuit can be arranged at the same end of the carcass 13.

The exchanger 1d comprises two support plates 8d, each of which is coupled to one end of the two circuits EGR 3 and WCAC 3a.

In the same way, the exchanger 1d also comprises two gas reservoirs 12, each of them being coupled to one end of the plastic casing 13.

In this example, each gas tank 12 is manufactured in one piece integrating the inputs or outputs of each EGR circuit 3 and WCAC 3a. Specifically, one of the gas tanks 12 comprises the respective inputs 4, 4a for each EGR circuit 3 and WCAC 3a; while the other gas tank 12 comprises the respective outlets 5, 5a for each EGR circuit 3 and WCAC 3a. The direction of the gas flow at the inlet and the outlet of the two circuits EGR 3 and WCAC 3a is indicated by arrows on the figure 19 .

In this way, it is possible to integrate an EGR exchanger and a WCAC exchanger in the same plastic casing, which makes it possible to obtain an appropriate integration and compactness.

It should be emphasized that other provisions may exist; for example the gas tank 12 can be divided into two parts, each of them being associated with an inlet or an outlet of each EGR circuit 3 and WCAC 3a.

The ducts of each EGR circuit 3 and WCAC 3a may be similar, and may also have different dimensions to better meet the requirements in terms of heat efficiency.

The two beams EGR ducts 3 and WCAC 3a can be fixed together to the carcass 13 or using independent means to obtain a certain durability, for example to meet the requirements of thermal shock.

Claims (1)

1. Heat exchanger (1b, 1c) for gas, comprising a metal core (2) comprising a collection of parallel ducts (3) intended for the circulation of the gases with exchange of heat with a refrigerant fluid, of the U-shaped type in which the inlet (4) and the outlet (5) for the fluid that is to be cooled occupy adjacent positions at the one same open end (6) of the collection of parallel ducts (3), the opposite end (7) being closed, and defining an outbound passage and a return passage, the core (2) comprising a first support plate (8b, 8c) arranged at the open end (6) and provided with a rim (11b, 22) intended to connect to a shell, and a second support plate (9) positioned at the closed end (7) and joined to a sealed metal gas reservoir (12), each support plate (8b, 8c, 9) joined by laser welding to at least one of the ends of the said collection of parallel ducts (3), the said gas reservoir (12) being joined directly to the said support plate (9), the core (2) being housed inside a shell (13) made of plastic and connected to the refrigerant fluid circuit, characterized in that the shell (13) is fixed at its closed end to the said metal gas reservoir (12) by joining means comprising a plurality of longitudinal ribs (18) with a small contact area, which are secured to the shell (13) and fit into corresponding orifices (19) made in the gas reservoir (12), and in that the gas reservoir (12) is joined to the said support plate (9) by laser welding or arc welding.

Images