FR3083301A1 - HEATER BLOCK ASSEMBLED BY BRAZING - Google Patents

Abstract

Electric heating block (1) comprising at least one dissipator (10) intended to be traversed by a fluid and at least one tube (20) accommodating one or more electric heating elements (50), said tube (20) having two large walls (21), said dissipator (10) being fixed to one and / or the other of the large walls (21) of the tube (20) by brazing.

Description

The present invention relates to an electric heating block, such as a heating block intended for a motor vehicle.

The invention also relates to a method of manufacturing such a heating block.

Electric heating blocks are known, comprising tubes intended to accommodate heating elements. Such heating elements include, for example, PTC effect resistors (for positive temperature coefficient). Such heating blocks also include dissipators, such as for example fins, in thermal contact relationship with the heating elements. The tubes serve to electrically insulate the heating elements from the outside while allowing thermal conduction between the heating elements and the heatsinks.

Conventionally, the tubes are assembled to the heatsinks by gluing. This bonding step can be carried out before or after the introduction of the heating elements into the tubes. Bonding, however, has a number of drawbacks. First, the bonding assembly is not particularly resistant to high temperatures, which can be problematic when the heating elements heat up. In addition, the adhesive does not have good thermal conductivity, which decreases the heat exchanges between the heating elements and the heatsinks and therefore the performance of the heating block.

The invention aims to at least partially overcome the drawbacks mentioned above and for this purpose provides an electric heating block comprising at least one dissipator intended to be traversed by a fluid and at least one tube accommodating one or more heating elements. electrical, said tube having two large walls, said dissipator being fixed to one and / or the other of the large walls of the tube by brazing.

The brazing of the dissipator (s) on the tube makes it possible to improve the heat exchanges between the heating elements and the dissipators. Such a heating block therefore has improved performance. In addition, once the tube has undergone a brazing operation, the tube material, for example aluminum, will be more malleable and more easily deformable than before brazing, even after it has dropped to room temperature. This state of matter guarantees a tight contact between the tube and the heating elements and therefore a better heat exchange. Brazing also ensures a better life for the tube because it will be less sensitive to temperature and relaxation variations during the life of the heating block.

The invention may also include any of the following characteristics, taken individually or in any technically possible combination:

- the dissipator includes a fin,

- the fins have a wavy shape,

- the fins have a succession of folds connected by vertices,

- the fins are brazed to the large walls at the level of said folds,

- the fins include louvers intended to promote heat exchange,

the tube comprises side walls, said heating elements being held in said tube by compression between said large walls thanks to an operation of deformation of the side walls towards the inside of the tube,

the side walls have an external face and an internal face, the external faces of the side walls of the tube having a central groove so as to facilitate the deformation of said tube in the event of lateral compression,

the external faces of the side walls of the tube have two substantially straight sections and defining between them an angle forming the central groove at their junction,

the internal faces of the side walls of the tube are configured so as to limit the deformation of said tube in the event of vertical compression,

the internal faces of the side walls of the tube have a substantially vertical profile,

the internal faces of the side walls of the tube are configured so as to have a thickness as regular as possible and the minimum of material at the level of the central groove, given the geometry of the external faces,

the internal faces of the side walls of the tube have a substantially rounded profile,

- the large walls and the side walls of the tube meet at connection edges,

- the tube has an internal groove, at the connection edges, the internal groove acting as a hinge,

- the large walls have an external surface compatible with the geometry of the fin (s),

- the large walls have a flat external surface between the connection edges,

the edges have an external face with a square profile and an internal face with a hollowed profile with respect to an internal face of the large walls and the internal face of the side walls, so that the internal face of the connection edge defines said groove,

- The surface of the internal face of the large wall is substantially equal to the surface of the external face of said large wall so that the heat exchange surface between the electric heating elements and the fins is optimal.

The invention also relates to a method of manufacturing an electric heating block comprising a step of assembling at least one dissipator intended to be traversed by a fluid and at least one tube, said tube being intended to accommodate electric heating elements and having two large walls and two side walls, so as to fix the dissipator on one and / or the other of the large walls of the tube, the assembly being carried out by brazing.

The method according to the invention can also include any of the following characteristics, taken individually or in any technically possible combination:

- the dissipator includes a flexible fin,

the method also includes a step of introducing the heating elements into the tube,

the method also comprises a step of deformation of the tube so as to fix the heating elements in said tube,

- the assembly step is carried out simultaneously for all the tubes and dissipators of the heating block,

- the assembly step, the introduction step and the deformation step follow each other in this order,

the deformation step is carried out by deformation of the side walls of the tube so as to fix the heating elements in the tube,

the deformation step is carried out by applying pressure to the external faces of the side walls of the tube along an axis substantially orthogonal to said side walls, the pressure being applied by a pressure tool,

- the pressure tool comes into contact with the side walls of the tube at a central groove so that the deformation of the side walls of the tube is controlled,

- The application of pressure during the deformation step is carried out simultaneously for the two side walls of the same tube and successively for each of the tubes of the heating block.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

FIG. 1 partially illustrates schematically in cross-sectional view an electric heating block according to the invention before the introduction of the heating elements,

FIG. 2 partially illustrates schematically in cross-sectional view an electric heating block according to the invention after the introduction of the heating elements and before the deformation step,

FIG. 3 partially illustrates schematically in cross-sectional view an electric heating block according to the invention,

FIG. 4 is a perspective view of a tube according to the invention, before deformation,

- Figure 5 is a schematic illustration of the different steps of the method according to the invention.

As illustrated in FIG. 3, the invention relates to an electric heating block 1. Said heating block 1 is intended to be supplied with electric current to heat an air flow F passing through said block 1.

Said electric heating block 1 advantageously has a substantially parallelepiped configuration, extending on the surface. It is intended to be positioned transversely to the air flow F. More precisely, said air flow F is intended to be oriented perpendicular to said block 1.

The heating block comprises at least one dissipator 10, intended to be traversed by a fluid, in particular the air fluid F, and at least one tube 20 receiving one or more electric heating elements 50.

The heating block here comprises several tubes 20 and several dissipators 10 stacked alternately in a vertical stacking direction in the figure. The tubes 20 are positioned parallel to each other in a direction perpendicular to the plane of the figure.

Said tubes 20 make it possible to electrically isolate and protect the said heating element (s) 50 from the outside.

The heatsinks 10 increase the surface area for exchange with the fluid.

The heating elements 50 are, for example, PTC effect resistors (for positive temperature coefficient). Advantageously, each tube 20 comprises several heating elements 50 located one after the other in a direction perpendicular to the plane of FIGS. 1 to 3. Said heating elements 50 are advantageously distributed regularly along the tubes 20.

The tubes 20 form with the heating elements 50 heating units. Preferably, said heating units are selectively supplied with current. By this is meant that the heating elements 50 of each heating unit are supplied with current independently of the heating elements 50 of the other heating units and can therefore be traversed by a different current, in particular by its intensity, from the current flowing through the other heating units. heated.

The heating units further include here electrodes 52, located on either side of the heating elements 50 for their supply of electric current. Said heating units also comprise layers of material 54, electrically insulating and thermally conductive, said layers 54 being located between one of the electrodes 52 and a large wall 21 of the tube 20. In this way, the tube 20 is electrically isolated from the electrodes 52 and heating elements 50 but thermally in contact with them.

Preferably, in each of the heating units, said heating elements 50 are electrically connected in parallel, in particular using the electrodes 52.

If one refers to FIGS. 1 to 3, it can be seen that the heatsinks 10 are in thermal contact relation with the tubes 20. Said heatsinks 10 are positioned between said tubes 20, in particular between the large walls 21 of said tubes 20.

The tubes 20 have two side walls 24 connecting the large walls 21. The large walls 21 each have an external face 22 on which the dissipator 10 is fixed and an internal face 23 intended to come into thermal contact with the heating elements 50. A thermal contact involves a heat exchange between the elements, even if these elements are not directly in physical contact with each other. The large walls 21 have the function of transmitting the heat generated by the electric heating elements 50 to the dissipators 10. The tube 20 can be of any material suitable for use in an electric heating block 1. In particular, the tube 20 is made of aluminum and / or aluminum alloy.

Advantageously, the heating elements 50 are held in the tube 20 by deformation of the tube 20 so as to compress the large walls 21 in the direction of said heating elements 50.

In an electric heating block 1 according to the invention, the dissipator 10 is fixed to one and / or the other of the large walls 21 of the tube 20 by brazing.

This technique for fixing the dissipators 10 has several advantages. First of all, the brazing of the dissipators 10 on the tube 20 makes it possible to improve the heat exchanges between the heating elements 50 and the dissipators 10. Furthermore, once the tube 20 has undergone a brazing operation, the material of the tube 20, for example aluminum, will be more malleable and more easily deformable than before the brazing step, even after having dropped to room temperature. This decreases the elastic relaxation that the material could have after deformation. In addition, this state of matter guarantees tight contact between the tube 20 and the heating elements 50 and therefore better heat exchange. Brazing also ensures a better life for the tube 20 because it will be less sensitive to variations in temperature and relaxation during the life of the heating block 1. Finally, a brazing step prior to the deformation of the tube makes it possible to reduce the force necessary for the deformation.

Advantageously, the dissipator 10 comprises a fin 10. Such a fin 10 makes it possible to maximize the heat exchange surfaces between the air flow F and the dissipator 10 and thus to improve the efficiency of the heating block 1.

Advantageously also, the fins 10 have a wavy shape. Likewise, such a corrugated structure makes it possible to maximize the heat exchange surfaces between the air flow F and the dissipator 10. Preferably, the fins 10 have a succession of folds connected by vertices.

Advantageously, the fins 10 are directly brazed to the tubes. In particular, the fins 10 are brazed to the large walls 21 of the tube 20 at the folds. This configuration improves the heat exchange between the heating elements 50 and the fins 10 and thus improves the efficiency of the heating block 1.

Advantageously also, the fins 10 include louvers intended to promote heat exchanges with the fluid.

The compression of the large walls 21 in the direction of the heating elements 50 can result from the application of pressure on the large walls 21 and / or on the side walls 24 of the tube 20.

Advantageously, the compression of the large walls 21 results from a deformation operation of the side walls 24 towards the inside of the tube 20. When the side walls 24 deform towards the inside of the tube 20, the large walls 21 approach the one from the other and thus compress the heating elements 50 located in the tube 20. Following their deformation, the side walls 24 have a configuration curved towards the inside of the tube 20.

The deformation of the side walls 24 of the tube 20 allows the displacement of the large walls 21 in the direction of the heating elements 50 without having to crush the heating block 1 in a direction perpendicular to the large walls 21 of the tubes 20 and therefore without risk of damaging the fins 10. The displacement of the large walls 21 of the tube 20 causes compression of the heating elements 50. Thus, the fins 10 can be fixed to one and / or the other of the large walls 21 before the tubes 20 are deformed in order to maintain the heating elements 50. In fact, the fins 10 fixed to one and / or the other of the large walls 21 do not undergo compression and are not liable to be damaged. Consequently, a heating block 1 according to the invention makes it possible to use fins 10 which are less resistant and more thermally efficient than in a conventional heating block. In addition, the fact of being able to fix the fins 10 to the tubes 20 makes it easier to handle the block 10 during its manufacture.

FIG. 4 illustrates a tube 20 advantageously intended for a heating block 1 according to the invention. Such a tube 20 has not yet undergone deformation. However, all of the elements and characteristics of the tube 20 before deformation are found on this same tube 20 after deformation, once integrated into the heating block 1. A tube 20 after deformation is notably illustrated in FIG. 3.

The side walls 24 of the tube 20 each have an external face 25 and an internal face 28. The deformation of the side walls 24 is produced by the application of pressure at the level of the external faces 25 along an axis substantially orthogonal to said side walls 24 The application of pressure to the side walls 24 can be carried out by a pressure tool.

Advantageously, the external faces 25 have a shape curved towards the inside of the tube and a central groove 26. The presence of a central groove 26 associated with a side wall 24 having a curved configuration makes it possible to precisely control the deformation of the tube 20 in the event of lateral compression. Indeed, the inwardly curved shape of the tube makes it possible to reduce the lateral force necessary to deform the tube 20 and the groove 26 ensures that the side walls 24 deform at the level of said groove 26.

Advantageously, the internal faces 28 of the side walls 24 of the tube 20 have a substantially vertical profile, if necessary slightly rounded. Such a profile makes it possible to limit the deformation in compression of the side walls 24 in the event of vertical compression of said tube 20, once integrated in the block 1. In addition, such a profile also allows the side walls 24 to have a thickness as regular as possible and the minimum of material at the level of the central groove 26, given the geometry of the external faces 25. Finally, such a profile facilitates the flexural deformation of the side walls 24 in the event of lateral compression.

Advantageously also, the external faces 25 of the side walls 24 have two substantially straight sections 27. These straight sections 27 define between them an angle forming the central groove 26. When a pressure tool is used to deform the side walls 24, the sections 27 act as a guide and facilitate the positioning of the pressure tool at the groove 26. When a pressure tool is used to deform the side walls 24, the pressure tool is housed at the level of the groove 26. Thus, the presence of sections 27 further facilitates the control of the deformation of the side wall 24.

The large walls 21 and the side walls 24 of the tube 20 meet at the connection edges 30. The edges 30 are, like the large walls 21 and the side walls 24, made of material from the tube 20. Even if several parts are defined, the tube is a single piece.

The tube 20 has an internal groove 35, at the level of said connection edges 30. The large walls 21 have an external face 22 compatible with the geometry of the dissipator 10 so as to maximize their contact surface. Advantageously, the large walls 21 have a planar external face 22 between said connection edges 30.

By providing said grooves 35, the lateral walls 24 are allowed to be deformed while keeping the large walls 21 flat, the planar nature of said large walls 21 allowing better contact with the fins and therefore better heat exchange.

Advantageously, the dissipator 10 does not extend over the entire surface of the external face 22 of the large wall 21 so as to leave a gripping area. This gripping zone extends over a distance of between 0.1 and 2 mm starting from the connection stops 30. Said gripping zone allows the use of a gripping tool in order to manipulate the block 1 at the level of the tube 20 and in particular during the deformation of said tube 20.

Advantageously, the connection edges 30 have an external face 32 of substantially square profile and an internal face 34 of hollowed out profile with respect to the internal face 23 of the large walls 21 and the internal face 28 of the side walls 24, so that the face internal 34 of the connection edge 30 defines the groove 35. By substantially square is meant forming a right angle or having a very small radius of curvature.

When the side walls 24 are deformed towards the inside of the tube 20, material from said side walls 24 bears against material from the large walls 21 at the edges 30. This compression results in resistance to the deformation of the walls lateral 24. The presence of the groove 35 acts as a hinge which makes it possible to avoid excessive compression and therefore limits the resistance to deformation. Thus, the particular shape of the edges and, in particular, the presence of a groove, makes it possible to facilitate the deformation of the side walls.

Conventionally, when the side walls of a tube are deformed, the horizontal walls are deformed in turn, in particular towards the outside of the tube. This parasitic deformation is called buckling. This buckling thus prevents optimal thermal contact between the heating elements and the horizontal heat exchange walls. The conventional solution to the problem of buckling is to increase the thickness of the walls of the tube, in particular of the heat exchange walls.

In a heating block 1 according to the invention, the dissipators 10, by their mere presence and without having to present any particular mechanical resistance, reinforce the rigidity of the large walls 21 of the tube 20 and help them to remain straight during the operation of deformation of the side walls 24. In this way, in a tube 20 of a heating block 1 according to this aspect of the invention, the large walls 21 are not necessarily thicker compared to the side walls 24 of the same tube 20.

Thus, the tube 20 of a heating block 1 according to the invention is even more stable against buckling than a single more rigid tube of the same thickness. This makes it possible to reduce the thickness of the walls of the tube 20 in order to optimize their weight and their cost since they do not need to be particularly thick to avoid buckling.

As specified above, a heating block 1 according to this aspect of the invention makes it possible to use fins 10 which are less resistant and more thermally efficient than in a conventional heating block. Advantageously, the fins 10 of the heating block 1 are flexible before assembly. As already said, it could be wavy fins.

FIG. 4 illustrates a tube 20 as such. The tube 20 shown in FIG. 4 is advantageously a tube intended for a heating block 1 according to the invention which has not yet undergone a deformation operation. It is identical to the tube 20 of the heating block 1 shown in Figures 1 and 2 which has not yet undergone a deformation operation.

It is the particular shape of the tube 20 which allows a deformation of the tube and the maintenance of the heating elements 50. As specified above, all of the elements and characteristics of the tube 20 before deformation are found on this same tube 20 after deformation, once integrated into heating block 1.

Thus, the tube 20 intended for the heating block 1 as described above has two large walls 21 and two side walls 24, each of the large walls 21 having an external face 22 intended to come into contact with a dissipator 10 and a face internal 23 intended to come into thermal contact with electric heating elements 50. The large walls 21 are advantageously substantially parallel to one another.

The tube 20 illustrated in FIG. 4 also comprises side walls 24 having two substantially straight sections 27 and defining between them an angle forming a central groove 26. The side walls 24 have a pre-configuration curved towards the inside of the tube 20. This curvature is accentuated by the operation of deformation of the side walls 24. Said tube 20 also includes edges 30 for connection between the side walls 24 and the large walls. 21. Said edges 30 having an external face 32 of substantially square profile and an internal face 34 of hollowed out profile with respect to the internal face 23 of the large walls 21 and the internal face 28 of the side walls 24, so that the internal face 34 of the connection edge 30 defines a groove 35.

Advantageously, the surface of the internal face 23 of the large wall 21 of the tube 20 is substantially equal to the surface of the external face 22 of said large wall 21. Thus, the heat exchange surface between the electric heating elements 50 and the fins 10 is maximum, after assembly.

As illustrated in FIG. 5, another aspect of the invention relates to a method for manufacturing a heating block 1 as described above. Such a method comprises a step (El) of assembling at least one dissipator 10 and at least one tube 20. The dissipator 10 is intended to be traversed by a fluid. The tube 20 is intended to accommodate electric heating elements 50 and has two large walls 21 and two side walls 24. The assembly step (El) makes it possible to fix the dissipator 10 on one and / or the other of the large walls 21 of the tube 20. According to the invention, the assembly step (El) is carried out by brazing.

This assembly technique makes it possible, among other things, to give a tight contact and to improve the heat exchanges between the heating elements 50 and the dissipators. Another advantage of soldering is the ease of implementation and the low cost of this technique.

Preferably, the dissipator comprises a flexible fin 10.

Advantageously, the method also includes a step (E2) of introducing the heating elements 50 into the tube 20.

Advantageously still, the method comprises a step (E3) of deformation of the tube 20 so as to fix the heating elements 50 in the tube 20. Said step (E3) of deformation is advantageously carried out by deformation of the side walls 24 of the tube 20 so fixing the heating elements 50 in the tube 20.

Such a method makes it possible to produce an electric heating block 1 as described above.

Advantageously, the step (E1) of assembly by brazing is carried out simultaneously for all the tubes 20 and the dissipators 10 of the heating block.

Advantageously also, the assembly step (E1), the introduction step (E2) and the deformation step (E3) are consecutive and follow each other in this order.

A step (E1) of assembly prior to the step (E3) of deformation and produced by brazing makes it possible to reduce the force necessary for the deformation of the tube 20.

FIG. 1 illustrates a heating block 1 according to the invention, after the assembly step (E1) and before the steps (E2) and (E3). The dissipators 10 are then fixed on the large walls 21 of the tube 20. FIG. 2 illustrates a heating block 1 according to the invention during step (E2) of introduction of the heating elements 50 and before the deformation step (E3). The heating elements 50 are here introduced into the tube 20 but they are not yet maintained in position by compression of the large walls 21. FIG. 3 illustrates a heating block 1 according to the invention after step (E3) deformation. The side walls 24 have here been deformed towards the inside of the tube 20, said deformation then causing the large walls 21 to move towards one another, which makes it possible to maintain the heating elements 50 by compression in the tube 20.

The fact of starting by assembling at least one dissipator 10 on one and / or the other of the large walls 21 of the tube 20 makes it possible to stiffen said large walls 21. Thus, during the deformation step (E3), when the side walls 24 of the tube 20 are deformed so as to fix the heating elements 50 in the tube 20, the dissipators 10 help the large walls 21 to remain straight and prevent the phenomenon of buckling.

Advantageously also, the deformation step (E3) is carried out by the application of pressure at the level of the external faces 25 of the side walls 24 of the tube 20 along an axis substantially orthogonal to said side walls 24. The pressure exerted can in particular be applied by a pressure tool.

Advantageously also, during the deformation step (E3), the pressure tool comes into contact with the side walls 24 of the tube 20 at a central groove 26. As mentioned above, the presence of a groove 26 makes it possible to precisely control the deformation of the tube 20. In fact, by applying the pressure necessary for the deformation of the tube 20 at the level of the groove 26, said groove 26 acts as a preform and the side walls 24 fold along said groove 26.

The application of pressure during the deformation step (E3) is carried out simultaneously for the two side walls 24 of the same tube 20. Thus, the large walls 21 of the tube 20 remain substantially parallel during the deformation, which prevents any dissociation of the dissipators 10 and the tube 20.

In addition, the application of pressure during the deformation step (E3) is carried out successively for each of the tubes 20 of the heating block 1. In fact, if this deformation step were to be carried out simultaneously for a plurality of tubes 20 of the same block, the simultaneous bringing together of a plurality of large walls 21, two by two, would lead to dissociation of the dissipators 10 and the tubes 20.

Claims (15)

1. Electric heating block (1) comprising at least one dissipator (10) intended to be traversed by a fluid and at least one tube (20) accommodating one or more electric heating elements (50), said tube (20) having two large walls (21), said dissipator (10) being fixed to one and / or the other of the large walls (21) of the tube (20) by brazing. 2. Heating block (1) according to the preceding claim, in which the dissipator (10) comprises a fin (10). 3. Heating block (1) according to the preceding claim, wherein the fins (10) have a wavy shape. 4. Heating block (1) according to the preceding claim, wherein the one or more fins (10) have a succession of folds connected by vertices. 5. Heating block (1) according to the preceding claim, wherein the fins (10) are brazed to the large walls (21) at said folds. 6. Electric heating block (1) according to one of the preceding claims, in which the tube (20) comprises side walls (24), said heating elements (50) being held in said tube (20) by compression between said large walls (21) by an operation of deformation of the side walls (24) towards the inside of the tube (20). 7. Heating block (1) according to claim 6, in which the large walls (21) and the side walls (24) of the tube (20) meet at the level of connection stops (30), said tube having a internal groove (35), at the level of said connection stops (30), said large walls (21) having an external face (22) planar between said connection stops (30). 8. A method of manufacturing an electric heating block comprising a step (El) of assembling at least one dissipator (10) intended to be traversed by a fluid and at least one tube (20), said tube (20) being intended to receive electric heating elements (50) and having two large walls (21) and two side walls (24), so as to fix the dissipator (10) on one and / or the other of the large walls (21) of the tube (20), the assembly being carried out by brazing. 9. The method of claim 8, wherein the sink (10) comprises a flexible fin (10). 10. Method according to one of claims 8 to 9, also comprising: a step (E2) of introducing the heating elements (50) into the tube (20), - A step (E3) of deformation of the tube (20) so as to fix the heating elements (50) in said tube (20). 11. The method of claim 10, wherein the assembly step (El) is carried out simultaneously for all of the tubes (20) and dissipators (10) of the heating block (1). 12. Method according to one of claims 10 to 11, wherein the step (E1) of assembly, the step (E2) of introduction and the step (E3) of deformation follow each other in this order. 13. Method according to one of claims 10 to 12, wherein the deformation step (E3) is carried out by deformation of the side walls (24) of the tube (20) so as to fix the heating elements (50) in the tube (20). 14. Method according to one of claims 10 to 13, in which the deformation step (E3) is carried out by the application of pressure at the level of external faces (25) of the side walls (24) of the tube ( 20) along an axis substantially orthogonal to said side walls (24), the pressure being applied by a pressure tool. 15. Method according to one of claims 10 to 14, wherein the application of pressure during the deformation step (E3) is carried out simultaneously for the two side walls (24) of the same tube (20 ) and successively for each of the tubes (20) of the heating block (1).