ARRANGEMENT OF AN ELECTRONICS CARD AND A HEAT SUN AND MOTOR FAN UNIT WITH SUCH ARRANGEMENT

Description

Technical field

[0001] The invention relates to an assembly of an electronic card and a heat sink for a motor-fan unit of a motor vehicle. The invention also relates to such a motor-fan unit and to a ventilation device for a motor vehicle comprising such a motor-fan unit. Prior art

[0002] A motor-fan unit equips a ventilation, heating and / or air conditioning device of a motor vehicle, which ensures the regulation of the temperature of an air flow intended to supply the passenger compartment of the vehicle.

[0003] The fan motor assembly allows the airflow to enter and circulate in the ventilation, heating and / or air conditioning system to outlet vents, where the air enters the passenger compartment.

[0004] The motor-fan unit comprises, in a known manner, an electric motor, for example with brushes, on which is mounted a wheel to set the air in motion, a device for controlling the electric motor, the device for controlling the electric motor comprising an electronic card and electronic components, as well as a heat sink.

[0005] In the motor-fan unit, the heat sink serves to cool the electronic board and the electronic components controlling the motor, particularly high-power components. Typically, the heat sink is in the form of a plate with studs protruding from the plate, the plate and studs being made of a thermally conductive material.

[0006] This solution has the disadvantage of being bulky, due to the presence of the pads. In addition, the cooling efficiency is not always satisfactory. The weight of this type of heat sink is also relatively high.

[0007] Additionally, a heat sink with pads is typically made by molding. This manufacturing process is particularly expensive, which increases the total cost of the heat sink.

[0008] An aim of the invention is to provide an assembly of an electronic card and a heat sink which does not have at least some of the drawbacks of the prior art.

[0009] Furthermore, unpublished application FR1901364 discloses a heat sink for an electronic card of a motor vehicle fan unit, comprising a surface intended to exchange heat with an air flow set in motion by the motor fan unit, called the exchange surface, said exchange surface comprising a flat portion arranged so that, in a position installed in the motor fan unit, the air flow set in motion by the motor fan unit flows substantially parallel to said flat portion, the exchange surface also comprising a set of non-through cavities flush with said flat portion. Another assembly of an electronic card and a heat sink for a motor vehicle fan unit is known from document FR2921446. Summary

[0010] The present description proposes an assembly of an electronic card and a heat sink, in particular for a motor vehicle fan unit, according to claim 1.

[0011] It is thus possible to manufacture the heat sink by extrusion and cutting. Alternatively, the heat sink can be manufactured by punching a metal plate. Each of these manufacturing processes is more economical than a molding process, which helps reduce the cost of the heat sink.

[0012] Additionally, this configuration unexpectedly improves air convection against the surface of the heat sink plate, making the heat sink more efficient in cooling. This configuration ensures the reduction of the heat sink footprint, which also improves aeraulic and acoustic performance by reducing pressure losses. In fact, the heat sink offers less resistance in the airflow.

[0013] Furthermore, the heat sink thus produced is lighter than those known from the prior art.

[0014] The circuit board and heat sink assembly may have one or more of the following characteristics: the thermal paste, placed between the electronic card and the plate, is waterproof and / or sticky; the thermal paste, placed between the electronic card and the plate, has a thermal conductivity of between 1 W / mK and 50 W / mK; the thermal paste is an epoxy or silicone resin; the thermal paste forms a layer, with a thickness of between 25 µm and 450 µm, between the electronic card and the plate; the layer of thermal paste has at least one relief extending into a through opening of the plate; each through opening of the plate has a polygonal section, in particular hexagonal or rectangular, or circular; the through openings of the plate are of polygonal section, a ratio between the thickness of the plate and the length of one side of the polygonal section being between 0.005 and 0.5; each through opening has a section of between 10 mm 2< and 500 mm 2<;the through openings are arranged in a grid of quadrilaterals, for example rectangular and / or staggered, or in a honeycomb grid; the electronic component preferably has at least two fixing lugs, each fixing lug being received in a through opening; an electronic component has at least two fixing lugs, each fixing lug being received in a through opening; an electronic component has at least two fixing lugs, each fixing lug being received in a respective through opening, the respective through openings preferably being adjacent; the plate and / or the electronic card is / are devoid of holes for fixing by a screw or rivet; the plate comprises at least one hole for fixing by a screw or rivet, the plate preferably being devoid of a through opening in the vicinity of the fixing hole;and the plate is made of an aluminum alloy, for example AlSi12, Al9Cu or AlSi10. ;

[0015] According to another aspect, there is also described a motor-fan unit for a motor vehicle, comprising a motor, a wheel for setting in motion an air flow configured to be driven by the motor, a device for controlling the motor, the control device comprising an assembly of an electronic card and a heat sink as described above in all its combinations.

[0016] According to another aspect, there is also described a ventilation device for a motor vehicle, comprising: a motor-fan unit as described above in all its combinations, a duct, the wheel of the motor-fan unit being received in the duct, the plate being received in the duct, the plate forming in particular at least a portion of a wall of the duct.

[0017] According to yet another aspect, there is also described a method of manufacturing an assembly of an electronic card and a heat sink as described above in all its combinations, comprising the steps of: providing the plate, in which the step of providing the plate preferably comprises a sub-step of extruding a profile whose section corresponds to the section of the plate, then a sub-step of cutting a plate from the profile; applying the thermal paste to the electronic card and / or to the plate; and fixing the plate to the electronic card.

[0018] The step of providing the plate may also include a sub-step of providing a solid plate, then a sub-step of punching the solid plate.

[0019] The step of fixing the plate to the electronic card may also include a sub-step of air polymerization of the thermal paste.

[0020] The step of fixing the plate on the electronic card can also include a sub-step of polymerization by heating the thermal paste. Brief description of the drawings

[0021] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which: [ Fig. 1 ] illustrates a partial sectional view of a detail of a vehicle ventilation device comprising a motor-fan unit. [ Fig. 2 ] illustrates a perspective view of a first example of an assembly of an electronic card and a heat sink that can be implemented in the motor-fan unit of the Figure 1 . [ Fig. 3 ] illustrates a top view of the first example assembly of an electronic board and a heat sink of the Figure 2 . [ Fig. 4] illustrates a detail of a longitudinal section of the first example of an assembly of an electronic card and a heat sink of the Figure 2 . [ Fig. 5 ] illustrates another detail of a longitudinal section of the entire electronic board and heat sink of the Figure 2 . [ Fig. 6 ] illustrates a front view of a second example of an assembly of an electronic card and a heat sink, which can be implemented in the motor-fan unit of the Figure 1 . [ Fig. 7 ] illustrates a front view of a third example of an electronic card and heat sink assembly, which can be implemented in the motor-fan unit of the Figure 1 . [ Fig. 8 ] illustrates a flowchart of a manufacturing process for obtaining an assembly of an electronic card and a heat sink according to one of the Figures 2 , 6 Or 7 . Description of the embodiments

[0022] A ventilation device for a motor vehicle, a detail of which is illustrated in the Figure 1 is described below with reference to the drawings.

[0023] The ventilation device 8 incorporates a motor-fan unit 10. The motor-fan unit 10 comprises a fan 14. The fan 14 here comprises an electric motor 12 and a wheel 15 configured to be driven by the motor 12 in rotation around an axis of rotation A1 common to the motor 14 and to the wheel 15. The wheel 15 is here received in a duct 16 of the ventilation device 8. Thus, the fan 14 generates an air flow in the duct 16.

[0024] The motor-fan unit 10 also comprises a device 18 for controlling the electric motor 12. The control device 18 includes an electronic card 22 and electronic components 20 fixed on the electronic card 22 (not visible on the figure 1). The control device 18 makes it possible to control the electric motor 12 of the fan 14.

[0025] The motor-fan unit 10 also comprises a heat sink 24 capable of cooling the control device 18. As illustrated in the Figure 1 , the heat sink 24 is received in the duct 16 in which the wheel 15 of the fan 14 is received. Alternatively, the heat sink 24 can be arranged so as to form a portion of a wall of the duct 16. These configurations allow the heat sink 24 to exchange heat with the air flow generated by the fan 14, in particular by convection.

[0026] As illustrated in the figure 2, the heat sink 24 comprises a plate 28 and a thermal paste 26. The heat sink 24 is fixed to the electronic card 22. The thermal paste 26 is arranged between the plate 28 and the electronic card 22. Thus, the motor-fan unit 10 comprises an assembly 11 composed of the electronic card 22 and the heat sink 24.

[0027] The plate 28 of the heat sink 24 has a surface, in a plane parallel to the extension plane of the electronic card 22, having through openings 30. The through openings 30 allow the air flow generated by the fan 14 to penetrate inside these through openings 30 while creating turbulence in the air flow in the vicinity of the plate 28. In addition, the through openings 30 make it possible to limit the weight of the plate 28 and, in doing so, the weight of the heat sink 24.

[0028] The plate 28 is preferably made of a material having good thermal conductivity. For example, the plate 28 may be made of an aluminum alloy, in particular AlSi 12 , Al 9 Cu or AlSi 10 . These alloys have the advantage of having good thermal conductivity while being relatively light.

[0029] As illustrated on the Figures 2 And 3 , the through openings 30 in the plate 28 may be of polygonal S section. Such a polygonal S section is relatively easy to produce. In the example illustrated, the S section is hexagonal. Preferably, the S section has the shape of a regular polygon, in particular a regular hexagon.

[0030] The through openings 30 are of substantially constant section across the plate 28. In other words, the through openings 30 are substantially cylindrical, here of polygonal section. Alternatively, however, the through openings 30 may be frustoconical. In other words, the cross section of the through openings 30 may be reduced on one face of the plate 28 relative to the other face of the plate 28. This may in particular be the case when the through openings 30 are produced by punching.

[0031] The area A of the section S of the through openings 30 is for example between 10 mm 2 and 500 mm 2. The area A is understood to be the maximum area of ​​the section S, if applicable.

[0032] The plate 28 has a length L, a width l and a thickness e. The length L of the plate 28 corresponds to its largest dimension. For example, the length of the plate 28 is between 50 mm and 200 mm. The width l corresponds to the second largest dimension of the plate 28, which may possibly be equal to the largest dimension of the plate 28. The width l of the plate 28 is for example between 25 mm and 180 mm. Here, the length L and the width l of the plate 28 are measured in a plane parallel to the extension plane of the electronic card 22. Finally, the thickness e1 of the plate 28 is the smallest dimension of the plate 28. Here, the thickness e1 is measured in a direction normal to the extension plane of the electronic card 22. The thickness e1 of the plate 28 is for example between 0.5 mm and 5 mm. The thickness e1 of the plate 28 is advantageously of reduced dimension compared to the length L and the width l of the plate 28.For example, the thickness e1 of the plate 28 is at least ten times smaller than the length L and the width l of the plate 28, preferably at least fifty times smaller than the length L and the width l of the plate 28. The through openings 30 are oriented in the direction of the thickness of the plate 28.

[0033] A ratio e1 / L between the thickness e1 of the plate 28 and the length L of one side of the polygonal section S is for example between 0.005 and 0.5. Such a ratio ensures good circulation of the air flow generated by the fan 14 in the through openings 30.

[0034] A ratio between a length LS of one side of the polygonal section S and a distance d between two centers C1, C2 of two adjacent openings 30, illustrated in the Figure 3, is for example between 0.1 and 0.5. Such values ​​of the ratio LS / d ensure a satisfactory occupancy rate of the through openings 30 on the surface of the plate 28.

[0035] As illustrated in the Figure 3 , the distance d between the centers C1, C2 of two adjacent openings 30 is the same over the entire plate 28. The distribution of the through openings 30 on the plate 28 is then regular, making it possible to obtain regular cooling thanks to the plate 28. The rigidity of the plate 28 can thus also be the same over the area of ​​the plate 28 where through openings 30 are made. In addition, this can facilitate the manufacture of the plate 28, in particular by punching.

[0036] Alternatively, the plate 28 may comprise areas without through openings 30. Thus, these areas have greater rigidity than the rest of the plate 28. Advantageously, manufacturing by punching makes it possible to avoid areas requiring greater rigidity.

[0037] As illustrated in the Figure 3 , the through openings 30 are arranged according to a mesh. By mesh, we mean here a regular or irregular division of the plane of the plate 28, by one or more patterns, which are repeated. In this case, the mesh is regular which is composed of a pattern M repeating in two directions u , v linearly independent. A distribution of the through openings 30 according to such a regular mesh makes it possible to obtain regular cooling over the entire surface of the plate 28. In addition, a satisfactory compromise is thus obtained between the rigidity and the weight of the plate 28.

[0038] For example, on the Figure 3 , a pattern M is a parallelogram formed by the centers C3, C4, C5, C6, of four neighboring through openings 30. Such a pattern M makes it possible to optimize the occupancy rate of the through openings 30 on the plate 28, while maintaining satisfactory rigidity of the plate 28.

[0039] The mesh M illustrated in the Figure 3 can however be described as a honeycomb mesh, in that the hexagonal through openings 30 here form a honeycomb. Thus, in this mesh, each side of a through opening 30 extends parallel and opposite one side of a neighboring through opening 30. This type of mesh advantageously makes it possible to maximize the number of through openings 30 on the plate 28 while maintaining the rigidity of the plate 28.

[0040] The pattern M is distributed over substantially the entire main surface of the plate 28. In fact, the edge of the plate 28 is here devoid of through openings 30.

[0041] As visible on the Figure 4 , the heat sink 24 comprises thermal paste 26, arranged between the electronic card 22 and the plate 28. The thermal paste 26 thus fills microcavities present between the plate 28 and the electronic card 22. The microcavities present between the plate 28 and the electronic card 22 would be likely to trap air, which has a high thermal resistance. Thus, it is preferable to fill the microcavities using the thermal paste 26, to improve the thermal transfers between the electronic card 22 and the plate 28.

[0042] For example, the thermal paste 26 has a thermal conductivity of between 1 W / mK and 50 W / mK. The thermal conductivity of the thermal paste 26 is preferably greater than that of air.

[0043] The thermal paste 26 forms for example a layer between the electronic card 22 and the plate 28. The thickness e2 of the layer, measured between the plate 28 and the electronic card 22, is for example between 25 µm and 450 µm. The thickness e2 is thus sufficient to fill the microcavities between the electronic card 22 and the plate 28. Nevertheless, the thermal paste may have a lower thermal conductivity than the plate 28. Thus, it is preferable to limit the thickness e2 of the thermal paste 26 for better heat transfer from the electronic card 22 to the air flow of the fan 24.

[0044] The thermal paste 26 may be sticky. In this case, the thermal paste 26 may allow the plate 28 to be fixed to the electronic card 22. Such a sticky thermal paste 26 is, for example, Silicone SEMICOSIL ®< 9712.

[0045] When the thermal paste 26 is sticky, the plate 28 and / or the electronic card 22 may be devoid of holes for fixing screws or rivets. Indeed, in this case, the fixing of the plate 28 with the electronic card 22 can be carried out by means of the thermal paste 26 alone, preferably without using any fixing screws. A hole for fixing by a screw or rivet is distinguished from a through opening 30, in particular by its circular shape, possibly tapped, and / or by the area of ​​its section, less than the area A of the section S of a through hole 30.

[0046] The thermal paste 26 may also be waterproof. By waterproof is meant waterproof. In this case, the thermal paste 26 makes it possible to protect the electronic card 22 and the electronic components 20 against the humidity present in the air flow generated by the fan 14. Such a waterproof thermal paste 26 is for example Silicone SEMICOSIL ®< 9712.

[0047] The thermal paste 26 may also be both sticky and waterproof. Such a thermal paste 26, which is both sticky and waterproof, is for example Silicone SEMICOSIL ®< 9712.

[0048] If the thermal paste 26 does not provide a seal at the periphery of the plate 28, a seal may be arranged at the periphery of the plate 28 to provide this seal. The seal prevents the air flowing along the plate 28 from coming into contact with the electronic components 20 located on the face of the electronic card 22 opposite the face fixed to the plate 28. The presence of the seal makes it possible, for example, to use a non-sealed thermal paste 26.

[0049] The thermal paste layer 26 may form a protruding relief 32, inside the through openings 30, as illustrated in the Figure 4 The relief 32 can be formed under the effect of the weight of the plate 28 on the thermal paste 26.

[0050] On the Figure 5, two electronic components 20a, 20b fixed on the electronic card 22 are illustrated. Each electronic component 20a, 20b comprises, as illustrated, a body 34 and, here, two fixing tabs 36. Each fixing tab 36 extends here, from the body 34 of the associated electronic component 20a, 20b, towards the plate 28, passing through the electronic card 22. Here, each fixing tab 36 extends from the body 34 of the associated electronic component 20a, 20b, to a free end 38 of the fixing tab 36 considered. Each free end 38 is here received in a through opening 30. This makes it possible to avoid contact between the plate 28 and an electronic component 20a, 20b. Furthermore, the free ends 36 of the different fixing tabs 36 do not protrude from the plate 28.

[0051] In the example of the Figure 5, the portion of the fixing lugs 36 between the electronic card 28 and the free end 38 of the fixing lugs 36 does not protrude from the layer of thermal paste 26. Thus, the free end 38 of the fixing lugs 36, in particular, is covered with thermal paste 26. Thus, the free end 38 of the fixing lugs 36 is not in direct contact with the surrounding environment. This makes it possible, for example, to protect the electronic components 20a, 20b from the humidity of the air flow generated by the fan 14, in particular when the thermal paste 26 is waterproof.

[0052] As illustrated in the Figure 5, the first electronic component 20a has two fixing lugs 36 such that the distance between the two fixing lugs 36 is less than the diameter of a through hole. By “diameter” is meant here, in the broad sense, the greatest distance measured between two points of the section S of the through hole 30. In this case, advantageously, the two fixing lugs 36 of the electronic component 20a can be received in the same through hole 30.

[0053] Alternatively, the distance between the fixing lugs 36 of an electronic component 20b is preferably chosen such that the fixing lugs 36 are received in separate through openings 30. This limits the risks of contact between the fixing lugs 36. In particular, as illustrated in Figure 5, the distance between the fixing lugs 36 of an electronic component 20b is chosen so that the fixing lugs 36 are received in adjacent through openings 30. To do this, for example, electronic components 20 are chosen whose distance between the fixing lugs 36 is substantially equal to the distance d between the center C1, C2 of two adjacent through openings 30.

[0054] There Figure 6 illustrates a second example of plate 28, on which the through openings 30 define a second example of mesh. The distributed pattern M2 is formed by the centers C3, C4, C5, C6 of four neighboring through openings 30. The pattern M2 thus defined is a rectangle, which is repeated over substantially the entire surface of the plate 28, by translation in two directions u , v perpendicular. We thus define a mesh of quadrilaterals, by repeating a quadrilateral-shaped pattern.

[0055] There Figure 7 illustrates a third example of plate 28, on which the through openings 30 define a third example of mesh. The through openings 30 here define a pattern M3 of centers of through openings 30 in staggered rows. By staggered rows, it is meant here that the pattern M3 is defined by a group of five neighboring through openings 30, such that the centers C3, C4, C5, C6 of four of them define a rectangle, in particular a square, and that the center C7 of the fifth through opening 30 is located substantially in the center of the rectangle C3C4C5C6. The pattern M3 thus defined is rectangular, which is repeated over substantially the entire surface of the plate 28, by translation in two directions u , vperpendicular. The mesh thus produced can be described as a mesh of staggered quadrilaterals. This type of mesh allows a compromise between the occupancy rate of the through openings 30 on the plate 28 and the rigidity of the plate 28.

[0056] We will now describe, with regard to the Figure 8 , an example of a method 100 for manufacturing an assembly 11 of an electronic card 22 and a heat sink 24 as described above.

[0057] As illustrated, the manufacturing method 100 comprises a first step 102 of providing the plate 28.

[0058] Step 102 of providing the plate may comprise a first sub-step of extruding a profile. The profile may then have as many longitudinal conduits as the plate 28 has through openings 30. The profile may in particular have a cross-section substantially identical to the cross-section of the plate 28. Step 102 of providing the plate 28 may then comprise a second sub-step of cutting the profile obtained in the first sub-step, to obtain a plate 28 of desired thickness e1. Advantageously, step 102 of providing the plate 28 is then devoid of any other consecutive sub-step.

[0059] Alternatively, the step 102 of providing the plate 28 may comprise a first sub-step of providing a plate of solid section, followed by a second sub-step of producing the through openings 30. In this case, the through openings 30 may in particular be produced by punching.

[0060] The manufacturing method 100 then comprises a second step 104 of applying the thermal paste 26 to the electronic card 22 and / or to the plate 28.

[0061] The manufacturing method 100 continues with a third step 106 of fixing the plate 28 on the electronic card 22. The fixing step 106 may comprise a sub-step of air polymerization of the thermal paste 26. Alternatively, the fixing step 106 may comprise a sub-step of polymerization by heating of the thermal paste 26. Advantageously, the fixing step 106 does not comprise a sub-step of fixing by screwing the plate 28 on the electronic card 22 nor of riveting the plate 28 on the electronic card 22.

[0062] The invention is not limited to the examples described above but is susceptible to numerous variants accessible to those skilled in the art.

[0063] In the examples described, the through openings 30 are of polygonal S section. The through openings 30 may however be of circular section. Openings of circular section can in fact be more easily produced, in particular by drilling or punching.

[0064] The through openings 30 may not all have the same section S across the entire plate 28. For example, some through openings 30 may have a first polygonal section, and other through openings 30 may have a second polygonal section or a circular section.

[0065] The through openings 30 can be distributed according to other types of mesh than those described previously.

[0066] In particular, a mesh is possible which consists of a pattern reproduced in an irregular pattern on the plate 28 or substantially the entire plate 28 ("irregular mesh"). Alternatively, a mesh is possible, which consists of the regular or irregular reproduction of two or more patterns.

[0067] Through openings 30 may not be present over the entire surface of the plate 28, in particular to locally stiffen the plate. In particular, when the plate has a hole for fixing by a screw or rivet, it may be preferred that the plate 28 be devoid of through openings 30 in the vicinity of this hole for fixing by a screw or rivet.

Claims

1. Assembly (11) comprising an electronic board (22) and a heat sink (24), in particular for a motor-fan unit (10) in a motor vehicle, comprising: - an electronic board (22); - a heat sink (24) comprising a plate (28) fixed to the electronic board (22), the surface of which has through-openings (30), and a thermal paste (26) disposed between the electronic board (22) and the plate (28), said assembly (11) comprising at least one electronic component (20a; 20b) with an electronic component body (34) and at least one fastening tab (36) passing through the electronic board (22) from the electronic component body (34) to the plate (28), the fastening tab (36) extending at least to a through opening (30) in the plate (28), a portion of the fastening tab (36) between the electronic board (22) and a free end (38) being covered by the thermal paste (26).

2. Assembly according to claim 1, wherein the thermal paste (26) is waterproof and / or adhesive.

3. Assembly according to claim 1 or 2, wherein each through opening (30) in the plate (28) has a polygonal, in particular hexagonal or rectangular, or circular cross-section (S).

4. Assembly according to one of the preceding claims, in which the through openings (30) in the plate (28) have a polygonal cross-section, with a ratio between the thickness (e1) of the plate (28) and the length (Ls) of one side of the polygonal cross-section (S) being between 0.005 and 0.5.

5. Assembly according to any of the preceding claims, in which the through openings (30) are arranged in a grid of quadrilaterals, for example rectangular and / or staggered, or in a honeycomb grid.

6. Assembly acccording to any of the preceding claims, wherein the electronic component (20a; 20b) has at least two mounting tabs (36), each fastening tab (36) being received in a through opening (30).

7. Assembly according to any of the preceding claims, wherein the plate (28) and / or the electronic board (22) is / are devoid of screw mounting holes.

8. Assembly according to any of claims 1 to 6, wherein the plate (28) comprises at least one screw or stud fastening hole, the plate (28) preferably having no through opening (30) in the vicinity of the at least one fastening hole.

9. Motor fan unit (10) for a motor vehicle, comprising a motor (12), an impeller (15) for moving an air flow configured to be driven by the motor (12), a device (18) for controlling the motor (12), the control device (18) comprising an assembly (11) of an electronic board (22) and a heat sink (24), according to any of the preceding claims.

10. Method for manufacturing an assembly (11) of an electronic board (22) and a heat sink (24) according to any of claims 1 to 8 , comprising the steps of: i) providing the plate (28), the step of providing the plate preferably comprising a sub-step of extruding a profile whose cross-section corresponds to the cross-section of the plate (28), then a sub-step of cutting a plate (28) from the profile; ii) applying the thermal paste (26) to the electronic board (22) and / or to the plate (28); and iii) fixing the plate (28) to the electronic board (22).