FR2944853A1 - LED LIGHTING DEVICE INCORPORATING A SUPPORT FOR THERMAL DISSIPATION. - Google Patents

Abstract

The object of the invention is a lighting device comprising on the one hand a flat plate (14) on which are disposed a plurality of LEDs (16) reported in several longitudinal directions, said plate (14) being attached to a heat-dissipating support (18), and secondly, an optics (20) covering the LEDs (16), characterized in that the support (18) comprises on the one hand an extruded element (62) with sections parallel to the constant plate (14) having an elongate hollow body with a frame-shaped section defining a recess (66) in which is placed an electric power supply (82) for the LEDs and with a plurality of fins on the outside and, on the other hand, a first plate (72) made of a thermal transfer promoting material pressed under the plate (14), the dimensions of which are such that said first plate (72) comes into contact with the upper bearing surface ( 70) of said extrud element (62).

Description

LED LIGHTING DEVICE INCORPORATING A SUPPORT FOR THERMAL DISSIPATION

The present invention relates to an LED lighting device, more particularly intended to equip the lanterns of public lighting systems or roads. Such a device must respect certain characteristics concerning the illuminated zone which must have on the ground the form of a substantially rectangular task of the order of 18 m of length and 9 m of width for a luminous point disposed about 5 m above of the ground. Thus, the light source must also respect a given luminance that must be substantially equal to 10 lux at the level of the illuminated area and a certain homogeneity of the lighting in this area. Preferably, the light should have a warm appearance in yellow-orange tones and not have a whitish color. In known manner, a lighting device may comprise an LED tray fixed on a support and surmounted by a transparent cap subsequently called optical processing LED light beams projected towards the area to be illuminated. LEDs are used to reduce the energy consumption required for lighting. In order to meet the existing needs, the LED lighting device must be compact enough to adapt to existing lanterns and have a lifetime at least equal to existing bulbs and preferably greater.

According to one objective, the invention proposes an LED lighting device comprising an LED support whose design promotes the evacuation of the heat produced by the LEDs in order to substantially increase the lifetime of said lighting device.

For this purpose, the subject of the invention is a lighting device comprising on the one hand a flat plate on which are disposed a plurality of LEDs reported in a plurality of longitudinal directions, said plate being mounted on a support promoting heat dissipation, and on the other hand, an optics covering the LEDs, characterized in that the support comprises on the one hand an extruded element with constant parallel platinum sections comprising an elongated hollow body with a frame-shaped section delimiting a recess in which is placed a power supply of the LEDs and with outside a plurality of fins, and secondly, a first plate made of a material promoting thermal transfer plated under the plate whose dimensions are such that said first plate comes in contact with the upper bearing surface of said extruded member. Other features and advantages will become apparent from the following description of the invention, a description given by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of the lighting device in LED according to the invention, Figure 2 is a sectional view of the lighting device, Figure 3 is a perspective view of an extruded element according to the invention used as a heat sink, Figure 4 is a view illustrating a assembly of several lighting devices according to the invention, - Figure 5 is a top view illustrating the implementation of LEDs and control means on a plate according to the invention, Figure 6 is an electrical diagram illustrating the principle of the different electrical components, FIG. 7 is a perspective view of an optical system according to the invention, FIG. 8 is a section along the line VIII-VIII of FIG. 7 of the optical system of the invention, - the figur e 9 is a section along line IX-IX of FIG. 7 of the optics of the invention, FIG. 10 is a section along the line XX of FIG. 7 of the optics of the invention, FIG. is a perspective view of a portion of the optical surface facing the LEDs, FIG. 12 is a perspective view of a visible optical recovery module in FIG. 7, FIG. Figure 14 is a view illustrating the light rays emitted by an LED in a longitudinal plane, and Figure 15 is a representation of the light intensity of the illuminated area. by the lighting device equipped with an optical system according to Figure 7 mounted in the manner of a lantern of a street lighting. In Figure 1, there is shown at 10 an LED lighting device. The latter is more particularly intended to be incorporated in a lantern of a public lighting. However, the invention is not limited to this application, the lighting device can be used as a projector or for any other lighting. For the application relating to public lighting, the lighting device must make it possible to illuminate a zone 12 that is substantially rectangular, of the order of 18 m in length and 9 m wide for a light point located at about 5 m above the surface. above, as illustrated in Figure 15. For the remainder of the description, the longitudinal direction X corresponds to the width of the substantially rectangular zone and the transverse direction 5 corresponds to the length of the substantially rectangular zone. The lighting device 10 comprises a flat plate 14 on which are disposed a plurality of LEDs 16, said plate 14 being attached to a support 18 promoting heat dissipation. Preferably, the plate 14 comprises LEDs reported along lines, for example thirty LEDs, six lines of five LEDs, the lines being parallel to the longitudinal direction. For the rest of the description, the plane of the plate 14 comprises the longitudinal axis X and the transverse axis Y. A plane orthogonal to the plate 14 and parallel to the longitudinal direction X is called the longitudinal plane and a plane orthogonal to the Platen 14 and parallel to the transverse axis Y is called the transverse plane. The direction Z is perpendicular to the directions X and Y. Preferably, the LEDs 16 used are directive type with a light beam emitted in a cone of the order of 45 °. By way of example, the LEDs 16 used are marketed by CREE under the reference XR. This arrangement of LEDs and their nature combined with a particular optics according to the invention make it possible to obtain a lit area 12 in accordance with the needs. However, the invention is not limited to this arrangement of LEDs and this type of LED, especially when the device is used for other applications. The lighting device 10 includes, for the treatment of the light beams emitted by the LEDs, a substantially transparent cover 20 called optical which covers the LEDs. This optic 20 comprises a front wall disposed between the LEDs 16 and the area to be illuminated 12 with an outer surface facing the area to be illuminated 12 and an inner surface facing the LEDs 16 and a peripheral wall 22 connecting the optical 20 and the support 18 or the plate 14 so as to confine the LEDs in a substantially sealed enclosure. Advantageously, as illustrated in FIGS. 7 to 10, the peripheral wall 22 comprises a flange 24 capable of offering a bearing surface capable of being pressed against the plate 14 or the support 18 and at the level of which a groove can be formed. device 26, visible in particular in Figure 8, adapted to receive a peripheral seal to ensure a better seal. This flange 24 generally comprises screw holes as illustrated in FIG. 7.

According to the invention, the front wall is made of a suitable material and the profiles of its inner and outer surfaces are such that the luminous flux emitted by the LEDs 16 are treated essentially by refraction to obtain an adequate lighting zone. Preferably, the optics are made by injection into polymethylmethacrylate PMMA. For each LED, the inner surface includes an LED-facing boss 28 with a projecting surface 30 near the disk-shaped platen 14 whose center is disposed substantially vertically above the center of the LED. As illustrated in Figure 11, the sides of the boss are slightly convex. This surface 30 concentrically comprises a hollow cupola 32. The distance separating the surface 30 and the LED and the opening diameter of the cupola 32 are adapted so that the surface of said dome is able to receive most of the luminous flux emitted by the LED arranged opposite. In addition, the outer surface of the front wall comprises for each LED two dome portions 34.1 and 34.2 whose junction line 36 is disposed in a transverse plane passing through the center of the corresponding LED. The two domes 34.1 and 34.2 are aligned in the longitudinal direction.

The shapes of the domes 34.1 and 34.2 are such that the light beams of the corresponding LED are distributed over the illuminated zone, as illustrated in FIG. 14. Thus, the illumination of the zone 12 results from the superposition of the light beams emitted by the set of LEDs 16.

As illustrated in FIG. 14, for the spokes 38 emitted with a large angle, the latter can be absorbed by the outer surface of one of the domes of the adjacent LED and reflected by the dome corresponding to this same LED towards the 12. Thus, the domes can orient about 80% of the light beams 10 emitted by each LED towards the area to be illuminated 12. According to the invention, for the remaining 20%, the optical 20 comprises at least one recovery module 40 rectilinear and arranged parallel to the X axis with in a transverse plane a U-shaped section whose opening is oriented towards the plate 14, its function being to guide the greatest number of The optics 20 preferably comprises a recovery module 40 between the lines and two half recovery modules 40 ', one at each end. According to the invention, each recovery module 40 is substantially symmetrical along its median longitudinal plane. According to an embodiment illustrated in FIG. 12, at the outer surface, each recovery module 40 comprises a first panel 42 that is substantially vertical or slightly inclined so as to slightly deviate from the nearest domes while moving away. of the plate 14, a central portion 44 with a curved section so as to constitute a substantially cylindrical shape and a second pan 46 substantially vertical or slightly inclined so as to deviate slightly from the nearest domes away from the platinum 14.

At the inner surface, each recovery module 40 comprises a first panel 48, a second panel 50 forming with the first panel 48 a flared shape in the direction of the plate 14 and a third panel 52 connecting the panels 48 and 50, substantially parallel to the plate 14.

In a variant, the recovery module 40 may comprise two strips separated by an air knife, rectilinear and arranged parallel to the axis X. The two bars may have profiles identical to the branches of the U of the preceding variant, the sections 48 and 50 extending to the outer surface.

According to the two variants, each bar or each branch of the U comprises two refraction / reflection interfaces. It is the same for the half-modules 40 'arranged at each end which comprise only one branch. As illustrated in detail in FIG. 13, the height of the recovery module 40 and more particularly the height of the air gap is greater than or equal to the height of the domes 34.1 and 34.2. Due to the arrangement of the recovery modules 40 near the domes 34.1 and 34.2, some rays 54 refracted by the domes 34.1 and 34.2 penetrate the thickness of the adjacent recovery module 40 where they are refracted and reflected by the two interfaces of the retrieval module 40. The rays concerned are those emitted by the LEDs with a wide angle, as more particularly visible in Figure 13. The recovery module 40 is more refractive than air, there is almost complete reflection on the second interface formed by the pan 50 for the spokes 54 25 which make with the normal angle greater than a threshold angle. These rays 54 are then redirected to the area to be illuminated 12. The redirection of the rays 54 by total reflection is made possible in particular by the height of the module higher than that of the domes 34.1 and 34.2.

By normal is meant each axis locally orthogonal to the interface and passing through the point of intersection of a radius considered with said interface. As illustrated in FIG. 13, for other rays 56 which have a larger angle than the spokes 54, they penetrate the thickness of the adjacent recovery module 40 where they are refracted and reflected by the two interfaces of the recovery module 40 Unlike the spokes 54, the latter are not reflected at the second interface formed by the pan 50 but refracted with an angle sufficient to be oriented towards the area to be illuminated. As illustrated in FIG. 13, only a few light rays 57 which have a larger angle than the rays 56 are not reoriented towards the area to be illuminated 12. However, the luminous flux of these rays 57 is very small. Thus, according to the invention, the recovery modules 40 can direct a greater number of spokes towards the area to be illuminated 12, which increases the efficiency of the lighting device.

Advantageously, the inner optical surface 20 comprises stiffeners 58 parallel to the transverse direction Y disposed between the rows of LEDs, as illustrated in FIG. 11. These stiffeners reinforce the mechanical strength of the optics 20. Preferably, to obtain a In the so-called hot, yellow-orange color, the illumination device comprises LEDs providing a whitish light and LEDs 60 providing a red color. The LEDs 16 providing the whitish light are LEDs marketed by CREE under the name XR-E. The LEDs 60 providing the red color are LEDs marketed by CREE under the name XR-C. In this case, the lighting device comprises thirty LEDs including sixteen red LEDs 60. Preferably, the lighting device comprises from 10 to 60% of red LEDs 60.

Unlike devices of the prior art which provide a colored optics to obtain the hot color which tends to greatly reduce the overall efficiency of the lighting device, the invention proposes a mixture of LEDs of several colors. Given the fact that the illuminated area is obtained by superimposing the luminous flux of all the LEDs, the color is substantially homogeneous over the entire illuminated area. The heat dissipating support 18 comprises an extruded element 62 illustrated in FIG. 3 with parallel sections to the constant plate 14 having an elongated hollow body 64 with a frame-shaped section delimiting a recess 66 and with a A plurality of fins 68 are provided on the outside. The body 64 includes a top bearing surface 70. The support 18 also comprises a first plate 72 made of a heat transfer promoting material placed under the plate 14, the dimensions of which are such that the first plate 72 comes into contact with the upper bearing surface 70 and a second plate 74 made of a material promoting the heat transfer plated under the first plate 72 whose dimensions are such that said second plate 72 is housed in the recess 66. The plates 72 and 74 each have a thickness of about 3 mm to obtain an inertia satisfactory thermal to limit the thermal concentration at the central portion of the plate 14. The plates 72 and 74 promote the thermal transfer of the plate 14 supporting the LEDs towards the extruded element 62. The plate 14 comprises at least one circuit board for powering the LEDs and thermal bridges under each LED 16 to provide thermal transfer of the LEDs 16 to the plates 72 and 74. The extruded member 62 comprises means for securing the optic and the first plate 72. According to one embodiment, the optic 20 comprises at its rim 24 a plurality of passage holes which coincide with passage holes formed at the first plate 72, screws being screwed into housings 76 formed at the extruded element 62 thus maintaining the optics 20 and the first plate 72.

Alternatively, it is possible to envisage a support 18 in two dismountable parts, the first part comprising the plate 14 and the optics 20 and the second part comprising the extruded element 62, the two parts being connected using a connection device described in FIG. FR-0806062. In order to promote heat dissipation, the extruded element 62 comprises fins 68 at the four sides of the hollow and elongate body 64. The extruded element 62 comprises two types of fins 68. Some fins 68.1 have only one heat dissipation function while other fins 68.2 have an additional function ensuring the assembly of several lighting devices 10 as illustrated. in Figure 4.

The fins 68.1 have a section that gradually tapers towards their end and are corrugated in the Z direction in order to increase the surface of the fins and therefore the heat exchange surface. The fins 68.2 have a profile substantially identical to the fins 68.1 with at the end a thickening 78 reducing the spacing with the fin 20 adjacent. The fins 68 are distributed in the following manner on each side of the extruded element 62 in the clockwise direction. The first fin is a fin-type vane 68.2 with an extra thickness 78 oriented towards the second vane, also of the vane type 68.2 with an excess thickness 78 oriented towards the first vane. The last fin is also a blade fin type 68.2 with a thickening 78 oriented in the same way as the first fin. For the long sides of the extruded element 62, all the other fins are blades of the fin type 68.1. For the short sides of the extruded element 62, the third fin is of the fin type 68.2 with an excess thickness 78 oriented in the same way as the first fin, the other fins being blades of the fin type 68.1. In order to increase the exchange surface at the angles of the extruded element 62, the first fin on each side comprises three star-shaped secondary fins 80 whose lengths are adapted to favor the assembly of the lighting devices. As illustrated in FIG. 4, to assemble two lighting devices, the last fin of the first lighting device is disposed between the two first fins of the second lighting device, the last fin of the second lighting device being disposed between the first two fins of the first lighting device. The lighting device comprises a power supply 82 secured to the free face of the second plate 74 and housed in the recess 66. This power supply 82 makes it possible to supply the LEDs preferably in parallel. According to one characteristic of the invention, as illustrated in FIG. 2, the duct formed by the extruded element 62 is closed at one end by the plate of the LEDs 16 or one of the plates 72 and at the other end by of the resin 84, the recess 66 being filled with balls 86 which increase the thermal inertia and promote the heat transfer of the support of the LEDs towards the extruded element 62. To reinforce the seal, a plate with a peripheral seal can be pressed against the bearing surface 88 of the extruded member. Preferably, the amount of balls 86 is sufficient to flood the components of the power supply 82 and that the resin 84 does not touch the components. Advantageously, the balls 86 are ceramic and have a diameter of the order of 5 mm.

According to another characteristic of the invention, the lighting device may comprise control means 90 for controlling the power supply 82. Preferably, these control means 90 are dissociated from the power supply 82 and are implanted at the level of the power supply. platinum 14 on the same side as the LEDs. This arrangement makes it possible to improve the service life of the device insofar as the components of the control means 90 which may be sensitive components are not arranged in an area subjected to a high temperature, such as the zone corresponding to the recess 66.

According to one embodiment, the optic 20 comprises at its peripheral wall a housing 92 in which the control means 90 are arranged. Advantageously, the control means 90 comprise a supply independent of that of the LEDs and comprise at least one photovoltaic cell 94 oriented to be illuminated by certain light rays emitted by the LEDs. This configuration makes it possible to make control means 90 autonomous. This solution makes it possible to rationalize the manufacture of lighting devices that are all identical in terms of power supply 82.

Preferably, the control means 90 comprise first infrared type communication means 96 for transmitting instructions to the power supply equipped with similar communication means 98. In addition, the control means 90 may comprise second control means 100 for receiving at least one instruction from the outside.

Claims (10)

REVENDICATIONS1. Lighting device comprising, on the one hand, a flat plate (14) on which a plurality of LEDs (16) located in a plurality of longitudinal directions are arranged, said plate (14) being attached to a support (18) promoting heat dissipation, and on the other hand, an optics (20) covering the LEDs (16), characterized in that the support (18) comprises on the one hand an extruded element (62) with parallel sections to the constant plate (14) comprising an elongated, hollow body (64) with a frame-shaped section defining a recess (66) in which an LED power supply (82) is placed and with a plurality of fins (68), and on the other hand, a first plate (72) made of a thermal transfer promoting material pressed under the plate (14), the dimensions of which are such that said first plate (72) comes into contact with the upper bearing surface (70) of said extruded element (62). 2. Lighting device according to claim 1, characterized in that it comprises a second plate (74) of a material promoting thermal transfer plated under the first plate (72) whose dimensions are such that said second plate (72) ) is housed in the recess (66). 3. Lighting device according to claim 1 or 2, characterized in that the duct formed by the extruded element (62) is closed at one end by the support of the LEDs (16) and at the other end by a resin (84), the recess (66) being filled with balls (86) which increase the thermal inertia and promote heat transfer of the LED support to the extruded member (62). 4. Lighting device according to claim 3, characterized in that the amount of balls (86) is sufficient to flood the power supply (82) and the resin (84) does not touch the power supply (82) . 5. Lighting device according to claim 3 or 4, characterized in that the balls (74) are ceramic and have a diameter of about 5 mm. 6. Lighting device according to any one of the preceding claims, characterized in that the extruded element (62) comprises fins (68.1) of a first type with a heat dissipation function and fins (68.2) d. a second type with an additional function ensuring the assembly of several lighting devices. 7. Lighting device according to claim 6, characterized in that fins (68.1) of the first type have a section which tapers gradually towards their end and are corrugated in the Z direction to increase the surface of the fins and therefore the heat exchange surface. 8. Lighting device according to claim 6, characterized in that the fins (68.2) of the second type have a profile substantially identical to the fins (68.1) of the first type with at the end an extra thickness (78) reducing the spacing with the adjacent fin. Lighting device according to claims 7 and 8, characterized in that on each side of the extruded element (62) in a clockwise direction, the extruded element (62) comprises a first wing of the second type (68.2). with an oversize (78) oriented towards the second fin of the second type (68.2) with an excess thickness (78) oriented towards the first fin, the last fin being a fin of the second type (68.2) with an oversize (78) oriented of the same way as the first fin. 10. Lighting device according to claim 9, characterized in that for the long sides of the extruded element (62), all the other fins are fins of the first type (68.1) and for the short sides of the élémentextrudé (62), the third fin is of the second type (68.2) with an extra thickness (78) oriented in the same way as the first fin, the other fins being fins of the first type (68.1).