HEAT EXCHANGE DEVICE, IN PARTICULAR FOR MOTOR VEHICLE

In particular, a device to heat exchange.

By said US 6,397 450 patent a heat exchanger for cooling electronic modules power using a metal foam. The foam is compressed, prior to use, to achieve a certain alignment of the ligaments in order to promote the flow air exchanges of heat in a particular direction.

Are also known by WO 2008/119696 a porous structure attached to a holder by sintering (' sintering ' english).

In particular, the heat exchange by convection, for heating or cooling, by means of a foam metal.

Communication considered in the invention can be embodied in forced convection and/or natural indifferently. The foams relevant metal herein are open cell, the latter permitting a flow of fluid of a cell to neighbouring cells.

In usual manner, a metal foam may include an array of metal ligaments forming numerous cells allowing air movable from a cell to another.

These metal foams allow a very good heat exchange by convection foam to a heat transfer fluid (air for example and without limitation), across the contact surfaces and the high air movement more or less chaotic (non-rectilinear).

A equal exchange performance in the air, the volume of foam kit may be about 30% lower than in finned technology.

The aim is to improve the exchange of heat between a thermal member and a metal foam.

A heat exchange device, in particular for a motor vehicle, said device comprising:

-at least a metal foam,

-a thermal member in direct contact with the metal foam for heat exchange between the thermal member (which in particular forms a source of calories or frigories) and the metal foam.

Optionally, the device uses no cooling fluid other than air, passing through the cells of the foam.

At direction of the present invention, in particular a direct contact is contact without interposition of additional material for the contact between the foam and the thermal member.

Preferably, the metal foam is deformed before or during assembly, in particular being locally compressed to the areas of contact, at the junction with the thermal member. This offers the advantage of increasing the contact area between the thermal member.

The local compression of the fiber/foam ligaments can be used to increase the contact surface between the foam and the thermal member. A larger surface makes it possible to limit losses in temperature at the interface, because the latter are proportional to the surface.

The present invention can be greater, thermally, with respect to, for example, a solution using a bonding or welding, solution which results in a thermal interface which is not optimum because non-heat conducting sufficiently efficiently and in a contact with the foam which is restricted.

Preferably, the thermal member and the metal foam are assembled together, in particular force, only mechanical, in particular without welding or brazing.

A solution of bonding or welding has the disadvantage that its additional process step and may involve limitations in the style of the finished product and a higher cost.

May also be provided, if necessary, local tack welding, for example and without limitation, with a laser, to provide the proper mechanical strength of the foam with the constraints that it might otherwise (heat shock, stress relaxation...).

In this case, the weld is local and without the addition of material and participating in that very little heat transfer surface because of the low (less than 10% of the contact surface foam thermal member).

In one embodiment of the invention, the metal foam is locally deformed, particularly locally compressed, merging with the thermal member.

If desired, the metal foam has, at least locally, in particular in a region remote from the junction with the thermal member, isotropic distribution of the cells of the foam.

Within the region of the foam, the coefficient of thermal diffusion is preferably the same in any direction.

For example, the thermal member and the metal foam are secured together by a force attachment.

Advantageously the thermal member is attached to the metal foam by locally deforming the foam, at least in the contact area between the thermal member and the metal foam.

In one embodiment of the invention, the metal foam comprises at least one through passage arranged to permit insertion, especially by force, a portion of the thermal member in the passage.

To perform the mounting force, the surface of the insertion passage is partially or completely contained in the surface of the portion of the thermal member fitting in the metal foam.

The passage may for example be made by cutting and/or drilling of the foam.

The insertion passage of the foam can be formed by a port, for example, in a cylindrical configuration, said hole being optionally penetrating or not.

Alternatively, the passage is formed by a slot, for example rectangular cross-section.

The section of the passage is preferably lower than that of the portion of the heat will be inserted therein.

If desired, the foam has a plurality of insertion passages, in particular arranged substantially parallel.

This arrangement has the advantage of facilitating placement during assembly.

Alternatively, the foam comprises a single insertion passage.

In one embodiment of the invention, the thermal member has a plurality of portions fitting each into a passage of insertion of the foam, the plurality of portions of the thermal member may be substantially parallel.

For example, the portion of the thermal member is inserted in the insertion passage of the foam includes a fin or a point.

The invention can thus eliminate gluing and provide for attachment by compressing the foam between two fins of the thermal member.

If desired, the foam is pierced for forcefully inserting the fins.

This may require have a bore of the foam with a smaller cross section than that of the fin to ensure that the foam comes in contact with the fin.

The invention also greatly reduce manufacturing costs.

Furthermore, the contact between the fins or pins and the foam is increased.

Indeed, during the compression of the foam, the fibers (or ligaments) of the foam is compress on the thermal member and the part in contact increases, which ensures an improved heat conducting fins or pins to the fibers of the foam.

If desired, the thermal member comprises a rod or a heat-conducting pipe (heat pipe) and the portion of the thermal member which is inserted into the passage of insertion of the foam is a portion of the rod or pipe.

If desired, the thermal member comprises a tube in circulating a first heat transfer fluid associated with the source of calories or frigories. The tube embeds in foam which exchange with a second heat transfer medium.

In one embodiment of the invention, the thermal member has a portion in the plate advantageously in contact with an outer surface of the foam.

Optionally, the thermal member includes a plurality of fins and a plate portion, each of the fins adjoining plate portion for example by means of an elbow.

The thermal member may be joined to a single metal foam.

Alternatively, the thermal member is assembled with at least two metal foams, spaced apart or in contact with each other, with different thermal properties or identical.

In one embodiment of the invention, the insertion passage of the foam is initially, prior to insertion of the corresponding portion of the thermal member, to a preform of a passage.

Alternatively, the insertion passage to the foam is formed concomitantly for insertion into the foam of the corresponding portion of the thermal member. In this case, the passageway is not preformed.

If desired, upon insertion into the foam of the corresponding portion of the thermal member, this portion causes a deformation of the foam compresses the foam and in particular in the vicinity of the through passage.

The portion of the thermal member adapted to be inserted into a insertion passage of the foam may for example pass through the foam right through.

In one embodiment of the invention, the thermal member including at least two fingers/stubs (or fins having a dimension at least 5 times larger than the other two). The fingers/stubs are in contact with the foam and provides the thermal contact. The fingers/pins can be bent at one or more locations.

The thermal member can be obtained by one of the following processes:

sheet metal stamping, injection, extrusion, weld connection...

In an example implementation of the invention, insertion passages are not required in the metal foam.

The metal foam comes to rest between the fingers/pins. In the case of a foam in the shape of a rectangle, the foam is compressed by its two opposing sides by at least one face of the thermal member on one side and at least one face of the thermal member in the other side.

Alternatively of the invention, at least two fingers/stubs positioned in a first plane and at least one finger/pin in a direction substantially parallel to the first plane are used to provide the contact with the foam.

Alternatively, one of the contact faces is carried out by a plate that can be used to support the source of calories or frigories. The other faces is formed by fingers/stubs, bent at least once, so as to be substantially parallel to the plate.

In an exemplary application, the fingers are traversing of the foam. Obtaining the parallelism is performed two times (before and after insertion of the foam).

In another case of application, the fingers extend to cover the foam. The parallelism is obtained before insertion of the foam. May be provided a further time come bending the fingers so as to block any outlet of the foam.

In one embodiment of the invention, the assembly of the foam and the thermal member can be obtained by the interior of the foam and by contact by outside of the foam.

In one embodiment of the invention, the thermal member carries at least one light source, in particular a LED (the thermal member serves as a carrier LED), and in particular an electric circuit of the LED.

Preferably, the device is arranged into the illumination device and/or signalling device for a motor vehicle.

The invention also relates to a method for assembling a thermal member with a metal foam, the method comprising the step of:

-assembling the thermal member with the foam directly, in particular without the addition of material, and without sintering.

The method can include the step of:

-inserting a portion of the thermal member in a passage of insertion of the foam.

Advantageously the metal foam is at least locally compressed upon assembly of the thermal member and the metal foam.

The invention also relates to, independently or in combination with the above, a heat exchange device, in particular for a motor vehicle, said device comprising:

-at least a metal foam,

-a thermal member in contact with the metal foam for heat exchange between the thermal member and the metal foam, the thermal member is bonded to the metal foam by a link from the formation of at least one of the metal foam and the thermal member.

The invention makes it possible in particular to ensure a good thermal connection of the thermal member, which supports the LED may contain one or more or a heat source, to the foam, which effectively dissipating the heat.

This greatly reduces heat losses at the interface between the thermal member and the foam.

The invention also makes it possible to prevent a potential problem of flatness of the foam before it is fixed onto the thermal member.

The invention can also be used for carrying out a thermal member with a complex shape.

Advantageously the metal foam and the thermal member are a monolithic piece, in other words in particular integrally.

In one embodiment of the invention, the metal foam and the thermal member are made of a same material. Alternatively, the foam and the metal member are made of different materials.

If desired, the thermal member extends substantially over the whole of one face of the metal foam, in particular enable increase the contact area between these elements and thus the heat exchange.

The thermal member may have a shape substantially plate or alternatively, a more complex shape.

Optionally, the thermal member has at least one cooling fin, in particular a plurality of cooling fins.

The thermal member may include at least one fastening element for attachment, for example by screwing, on a separate part.

In one embodiment of the invention, the thermal member comprises at least one hollow cylindrical member, in particular extending between two opposed sides of the metal foam.

Advantageously, the thermal member is arranged to participate in a photometric function (for example the lighting function code and/or route) of the device, the thermal member comprising at least one reflecting face, for example a reflective face into a portion of an ellipsoid or paraboloid or complex surface, or in the alternative the thermal member at least partially forms a mask of the device or a light shield for blanking a portion of the stray rays.

The device is preferably arranged into the illumination device and/or signalling device for a motor vehicle, for example a lighting projector.

The invention also relates to a method for forming a thermal member assembly with a metal foam, comprising the following step:

-forming at least one of the metal foam and the thermal member in contact with the other of the foam and the thermal member.

The method can include the step of:

-forming the metal foam and the thermal member at the same time. In one embodiment of the invention, the method comprises the step of:

-forming the metal foam and the thermal member at the same time, using a mold, in particular ceramic or plaster, arranged to allow simultaneous formation of the metal foam and the thermal member by casting a liquid material, in particular a liquid metal, in contact with the mold.

The mold is in particular a single-use mold, preferably made of one or more models (models lost e.g. wax or polystyrene) which, when brought together, form the shape of the foam and/or of the thermal member to manufacture.

Advantageously the mold (models lost), in particular ceramic or plaster, is placed inside an enclosure and the thermal member is formed between the mold and an inner wall of the enclosure, in a free space of predetermined shape between the mold and the wall of the enclosure.

If desired, the mold, in particular ceramic, defines both the shape of the foam and that of the thermal member. That is the mold occupies substantially the entire volume of the enclosure, without leaving free space of predetermined shape between the mold and the walls of the enclosure.

In another application of the invention, the method comprises the step of:

-successively forming the metal foam and the thermal member. The method can include the following steps:

-first forming the metal foam,

-then dipping the metallic foam in a bath of melt, in particular molten metal, to form the thermal member from the melt.

If desired, the method comprises the following steps:

-first forming the metal foam,

-melting the foam surface to form the thermal member, locally in particular by subjecting the metallic foam to a heat source or a induction field.

The method may, optionally, include the following steps:

-first forming the thermal member, or the plurality of thermal members,

-then form the foam by casting melt in contact with the thermal member.

Advantageously the model of the thermal member is created as polystyrene, or any other material disappearing under an external action, for example on exposure to an elevated temperature. The model of radiator is then contacted against the model of the metal foam before making the mould to single use, such as ceramic.

It is also possible, in model contact the foam, a radiator in the final material. Thus provide a piece multiple material.

Unlike the metal foam, the thermal member is a solid piece, non-voided.

In one embodiment of the invention, the thermal member comprises a portion forming a reflector and/or an optical surface.

It will be better understood by reading the detailed description which will follow, of examples of implementation non-limiting embodiments of the invention, and for the examination of the attached drawing, on which:

-figure 1 represents, schematically and partially, perspective, a mesh metal foam,

-figure 2 represents, schematically and partially, perspective, a heat exchange device according to an example implementation of the invention, prior to assembly of the thermal member with the metal foam,

-figure 3 is a plan view of the device of Figure 2, after assembly,

-figure 4 represents, schematically and partially, perspective, a heat exchange device according to another example implementation of the invention, prior to assembly of the thermal member with the metal foam,

-figures 5 and 6 represent, schematically and partially, perspective, a heat exchange device according to another example implementation of the invention, respectively before and after connection,

-figures 7 to 10 represent, schematically and partially, perspective, a heat exchange device according to other examples for practicing the invention, and

-figures 11 to 15 represent, schematically and partially, heat exchange devices according to other examples for practicing the invention.

The Figure 1 a metal foam 1 comprising a network of metal ligaments forming open cells 2 3 to have a porosity.

The Figure 2 a heat exchange device 10, for a motor vehicle, the device 10 comprising:

-a metal foam 1,

-a thermal member 11 in direct contact with the metal foam 1 for heat exchange between the thermal member 11 and the metal foam 1.

In the example described, the device 10 uses no cooling fluid other than air (heat transfer fluid), passing through the cells 3 of the foam 1.

The thermal member 11 and the metal foam 1 are assembled together only mechanical, in particular without welding or brazing between these elements.

For example, the metal foam 1 is locally deformed at the junction 13 with the thermal member 11 (see Figure 2 for example).

In the example described, the metal foam 1 has, in a region 14 remote from the junction 13 with the thermal member 11, a distribution isotropic 3 cells of the foam.

Within the region 14 of the foam, the coefficient of thermal diffusion is preferably the same in any direction.

The thermal member 11 is attached to the metal foam 1 by locally deforming the foam, at least in a connecting area 13 between the thermal member 11 and the metal foam 1.

In the example described, the metal foam 1 has a plurality of insertion passages 15 arranged to allow each insertion force, a portion 16 of the thermal member 11 in the passage 15.

These passages 15 are for example made by piercing the foam 1.

Each insertion passage 15 of the foam is a cylindrical shape, the orifice 15 is through-opening so as to emerge on two opposed and parallel faces 17 of the foam 1. The faces 17 may be planar.

Alternatively, as shown in Figure 4, the passages may be formed by slots 19, for example of rectangular section, these slots extending for example along the thickness "e" of the foam 1.

In the examples of Figures 2 to 4, the portions 16 of the thermal member 11 fitting into the insertion passages 15 or 19 of the foam 1 are each formed by a fin.

The fins 16 are parallel to each other.

Each fin 16 has at its free end a bevel 18 to assist in the insertion of said vane 16 in the corresponding port 15.

The boom F (see Figure 2) denotes the direction of insertion of the foam 1 on the thermal member 11.

Each port 15 of the foam may have a smaller cross section than that of the fin 16 to ensure that the foam 1 comes in contact with the fin 16.

The contact between the fins 16 and the foam 1 is increased.

Indeed, during the compression of the foam 1, the fibers (or ligaments) of the foam is compress on the fins 16 and the contact increases, which ensures an improved heat conducting fins 16 to the fibers of the foam 1.

Each fin 16 of the thermal member 11 is inserted in the insertion passage of the foam 15 projecting out of the fluid passage 15, at the end of the insertion (see Figure 3).

In the example of Figures 2 and 3, the thermal member 11 includes a plate portion 20 having an electric circuit incorporating a LED 21 22.

In this example, the plate 20 is cantilevered relative to the foam block 1.

Alternatively, as shown in Figures 5 and 6, the plate 20 of the thermal member 11 is in contact with an outer face 25 of the foam 1.

In this example, a plurality of fins 16 connect the plate portion 20, each of the fins 16 adjoining plate portion 20 by means of an elbow 26, in particular a U-shaped bend.

The foam 1 is thus trapped between the plate portion 20 and the fins 16, as shown in Figure 6.

In the examples described above, the foam 1 is formed substantially in a tile.

In another example implementation of the invention shown in Figure 7, the thermal member 11 has a portion in the plate 20 with tabs 29 provided by cutting and folding of the plate portion 20, thereby revealing holes 30 in the plate portion 20.

Each tab 29 passes through the thickness of the foam 1 and is folded at its free end to hold the foam integral with the thermal member 11.

In another example implementation of the invention shown in Figure 8, the thermal member 11 comprises a portion with plate 20, alternately, from an edge 33, straight fins and curved fins 16a 16.

The fins 16 straight into a foam block 1, and the fins bent 16a enter another block of foam 1a.

In this example, the device 1 uses two foam blocks.

In another example implementation of the invention shown in Figure 9, the thermal member 11 includes a plate portion 20 with both of the straight vanes 16 such as those described in reference to Figure 2, and tabs 29 as described in Figure 7.

The fins 16 and these tabs 29 are perpendicular to each other, and are respectively associated with a block of foam 1 and 1a.

In another example implementation of the invention shown in Figure 10, the thermal member 11 comprises a rod or a heat-conducting pipe 40 (heat pipe) and the portion of the thermal member which is inserted into the passage 41 insertion (cylindrical) of the foam 1 corresponds to a portion 40a of this rod or line.

The device 1 is arranged into the illumination device and/or signalling device for a motor vehicle, for example a projector for providing illumination and/or road crossing.

In applications press-fit, it may be necessary to ensure that the metal foam remains attached to the metal member.

The advantage can be avoid the participating in the game in the time, the production of dust and the loss of the contact function in time.

This can be obtained by blocking at the ends for example, by folding a portion of the metal member, or by local squeezing one end of non-participant cooling foam.

Another solution could be to perform local welding points operable to only the mechanical holding.

Finally a last solution would be adding an element additional a screw or more screws, to maintain the metal member and the foam integrally.

One will now describe with reference to Figures 11 to 15 other examples for practicing the invention.

In these examples, the heat exchange device 10 includes:

-at least a metal foam 1,

-a thermal member 11 in contact with the metal foam 1 for heat exchange between the thermal member and the metal foam, the thermal member is bonded to the metal foam by a link from the formation of at least one of the metal foam and the thermal member.

1 The metal foam and the thermal member 11 form a single piece, in other words in particular integrally.

Example for practicing the invention with reference to Figures 11 and 12

In this example, the metal foam 1 and the thermal member 11 are made of a same material, e.g. aluminium.

The foam 1 has a pad shape.

The thermal member 11 has a shape substantially in a plate.

The thermal member 11 extends over the whole face of the metal foam 40 1, in particular enable increase the contact area between these elements and thus the heat exchange.

The device 10 is manufactured by a method which comprises the following step:

-1 form the metal foam and the thermal member 11 at the same time, using a mold 41 to single use, in particular ceramic, arranged to allow simultaneous formation of the metal foam and 1 of the thermal member 11 by casting a liquid material, in particular a liquid metal, in contact with the mold 41, as shown in Figure 12.

The mold 41 is placed in an enclosure 42 and the thermal member 11 is formed between the mold 41 and an inner wall 43 of the enclosure 42, in a free space 44 beneath the mould 41. That is, the metal member 11 is formed only partially by contact with the mould 41. The foam 1 is formed, it, by the mould 41.

The steps of the method are, in the example described, as follows:

Step 1 : making a wax model or polystyrene, if necessary by assembling several pieces of model,

Step 2 : soaking the wax model or polystyrene in a ceramic bath, to providing a mold,

Step 3 : remove material from the model, for example the wax, by heating, to obtain the ceramic mold 41,

Step 4 : position the mold 41 in an enclosure 42,

Step 5 : casting molten aluminium contact with the mould 41, and cooling aluminum,

Step 6 : removing the ceramic for example by vibration, pressure water jets... to obtain the metal foam 1 and optionally the thermal member 11.

Optionally the thermal member 11 is finally machined to achieve the desired mechanical tolerances.

If desired, it is possible to cast the finished material (for example aluminium) in the mold always comprising the model. The finished material, due to its temperature, allows removal by sublimation of the material of the model.

Alternatively for practicing the invention, the method comprises the following steps:

-first forming the metal foam 1,

-then dipping the metallic foam in a bath of molten material, in particular of metal (tin, magnesium or aluminum for instance) molten, to form the thermal member 11 from the melt.

In embodiment, the method comprises the following steps:

-first forming the metal foam 1,

-melting the foam surface to form the thermal member 11, in particular by subjecting locally the metal foam, in particular one of its faces, to a source of heat, or induction field.

The shape of the melted portion can be rectangular or of more complex shape.

By melt the surface foam provides a satisfactory mechanical and thermal bonding between the foam and the thermal member.

Example for practicing the invention with reference to the drawing 13

In this example, the thermal member 11 comprises a plurality of cooling fins 48, arranged in two parallel rows and connecting to a central core 49 bent.

Each row of blades 48 is integral with a metal foam 1.

The thermal member 11 is therefore secured to two blocks of metal foam.

The thermal member 11 comprises two lugs 50 for securing the member 11 to a separate part.

The device 10 is manufactured by the following steps:

-first forming the thermal member 11,

-then form the foam blocks 1 by casting melt in contact with the thermal member 11 and preforms.

The device 10 thus produced is provided with solid portions (core fins 48 and 49) for the conduction of heat and mechanical strength, and foam in the proper location to an excellent convective heat transfer.

In this example, the thermal member 11 comprises a plurality of mounting members 51 for attachment, for example by screwing, on a separate part.

Each fastener 51 comprises at least one hollow cylindrical member 52, extending between two opposite faces 53 and 54 of the metal foam 1.

In this example, the thermal member 11 is arranged to participate in a photometric function (such as the function code and/or route) of the device 1 by forming an optical surface, the thermal member 11, in the form of a portion of shell, having a reflective face 55, for example a reflective face into a portion of an ellipsoid.

55 The reflecting face to reflect light from the light source 22.

The foam 1 is on the outside of the thermal member 11, and the reflecting surface 55 on the inside.

This makes it possible to use one or more optical surfaces to dissipate heat generated by the light source.