Patent Publication Number: US-10317038-B2

Title: Cooler of a light source

Description:
FIELD OF THE INVENTION 
     The invention relates to a cooler of a light source, especially a planar light source of a motor vehicle lamp, mounted in the holder of the light source, arranged in a heat conductive cooling monobloc, fitted with cooling elements for dissipation of heat. 
     BACKGROUND OF THE INVENTION 
     Lamps of motor vehicles produced at present use powerful light emitting diodes (LED&#39;s), which however heat up strongly during operation and issue high amounts of heat. The high temperature of LED&#39;s has a negative influence of the properties of semiconductors, which form the principal components of LED&#39;s. A higher working temperature reduces both the instantaneous luminous intensity of LED&#39;s and their service life. Therefore, intensive cooling of LED&#39;s is essential for proper functioning of light sources of the above mentioned type. What also needs to be provided is reliable mounting in the cooling monobloc and ingress protection of electric components. To reduce the temperature of LED&#39;s, coolers are used that are fixed to the structure of the lamp or the entire lamp body is used as a cooler. A commonly used material for a LED light source coolers is aluminum because it features high thermal conductivity, which ensures quick dissipation of heat from the heated part to other, colder parts. 
     Some designs are also known from, the prior art when the cooler of a light source is made of a thermally conductive plastic material. Thermal conductivity of a plastic material is substantially lower than that of an aluminum, cooler and the need to dissipate excessive heat is more urgent in the case of plastic material. Excessive heat is also dissipated from the light source by transfer to the ambient air. Due to high demand of the cooling media the cooling system must be equipped with a powerful cooling media source, e.g. a fan. On the other hand, plastic-based materials make it possible to produce complex components by compression moulding with good dimensional tolerances and very good surface finish. Another advantageous property is their design flexibility, which eliminates the need of final treatment of the surface and many assembly operations. 
     The document EP2187121 discloses a cooler of the light sources of optical modules of lighting devices of motor vehicles arranged next to each other, comprising optical modules arranged next to each other, each of them comprising a plate holder with a planar light source. The plate holders of the optical modules arranged next to each other are mutually connected with thermally conductive bridges for better temperature distribution and the thermally conductive bridges are equipped with cooling fins for heat dissipation. The plate holders of the planar light sources and the cooling fins form cooling monoblocs. The cooling fins are cooled by the ambient air. A disadvantage is a complex design of the cooler and insufficient dissipation of heat from the light source. A disadvantage of this design is also the fact that it uses a material with high thermal conductivity, which is associated with high financial demands. Also, the possibilities of the metal working technology are limited. The limited possibilities of the technology of machining of highly thermally conductive materials have a significant impact on the final shape and structural arrangement of the cooler. It is often necessary to adapt, the other components of the lighting device to the shape and dimensions of the cooler. 
     The document FR2996905 discloses a light device for motor vehicles with flat LED light sources mounted for heat distribution on a thermally conductive plate made of a plastic material with higher thermal conductivity than 1 W m−1° K.−1. To improve cooling of the thermally conductive plate the plate is fitted with a row of cooling fins arranged next to each other on the side that is averted from the light source. However, the efficiency of heat dissipation is very low as the light sources are cooled by mere blowing of air over the light sources and the other side of the thermally conductive plate is not exposed to streaming air. 
     The goal of the invention is a cooler of a planar light source that will have higher efficiency of heat transfer from the light source to the cooling media, and that will dissipate more heat from the light source on the whole. The goal of the invention is further such an arrangement of the cooler of the planar light source that will enable an easy replacement of the light source, easy association of the lamp reflector and cooling media source, and that will have a cooling monobloc with an integral and compact design. Also, the goal of the invention is to improve concentration of the streaming cooling media around the light source. Finally, the final goal of the invention is to achieve a simple design of the cooler of the planar source and shape flexibility of its parts during production. 
     SUMMARY OF THE INVENTION 
     The disadvantages of the prior devices are substantially eliminated and the goal of the invention is fulfilled by a cooler of a light source, especially a planar light source of a motor vehicle lamp, mounted in the holder of the light source, and arranged in a thermally conductive cooling monobloc. This cooling monobloc is fitted with cooling elements for heat dissipation according to the invention, the principle of which is that the cooling monobloc is equipped with channels for supply of the cooling media from the cooling media source to the cooling first side of the holder of a flat shape on the other opposite side of which the light source is mounted, while the main channel is arranged with the cooling media flow direction in parallel to longitudinal axis of cooling monobloc, and at least one secondary channel leads into the main channel under the first side of the light source holder. 
     Two secondary channels can preferably lead under the first side of the light source holder, arranged against each other or next to each other. The secondary channels can preferably lead into the main channel at the angle β, δ=30°-90° with respect to the streaming direction of the cooling media through the main channel. The inner cooling fins of the cooling monobloc can preferably reach into the secondary channel between the source of the cooling media and the outlet of the secondary channel. The secondary channels can preferably at least partly comprise removable covers fitted with inner guiding and cooling fins or outer cooling fins. The cooling media source can be preferably mounted on the cooling monobloc fitted with a distribution partition to supply the cooling media separately to the main channel and separately to the secondary channel. The light source holder can be preferably inclined in the streaming direction of the cooling media at the angle φ=0°-60° with respect to the horizontal plane. 
     The light source cooler according to the invention exhibits higher transfer of neat from the light source to the cooling media and a significant improvement of cooling of the light source. The cooling media flows through the secondary channels where the inner fins of the cooling monobloc and the inner fins of the outer cover are arranged. The inner fins of the cooling monobloc dissipate heat from the streaming cooling media to the cooling monobloc, from which heat is further dissipated by the outer fins of the cooling monobloc by heat transfer to the ambient internal environment of the lamp. The inner fins arranged on the outer cover of the secondary channels dissipate heat into the outer cover and its outer fins from which heat is transferred to the ambient internal environment of the lamp. Thanks to the arrangement of the main channel and the secondary channels according to the invention, a greater quantity of cooling media is supplied to the cooled holder of the light source, at the opposite side of the holder with regard to the light source intensive turbulence of the cooling media occurs, resulting in better dissipation of heat from the light source. The arrangement of the cooling monobloc according to the invention makes the light source easy to replace. The source of cooling media according to the invention forms an integral part of the light source cooler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The light source cooler according to the invention is clarified with the use of drawings where: 
         FIG. 1  shows a light source cooler in accordance with the present invention in a perspective view, 
         FIG. 2  shows covers of secondary channels in accordance with the present invention in a perspective view, 
         FIG. 3  shows a diagram of lateral secondary channels of the present invention, 
         FIG. 4  shows a diagram of a bottom secondary channel of the present invention, and 
         FIG. 5  shows a diagram of a bottom secondary channel of the present invention with the varying Holder inclination angle (φ). 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a light source cooler in a perspective view with a plastic cooling monobloc  11  made of a thermally conductive material with low thermal conductivity, up to 50 W m −1  ° K −1 . The cooling monobloc  11  is equipped with outer fins  13  for heat transfer into the ambient environment, which is the enclosed internal space of the motor vehicle lamp. On the rear, elevated part of the cooling monobloc  11  the cooling media source  21  is mounted, which is preferably a fan. The source  21  blows cooling media into the cooling monobloc  11 , where the cooling media stream is divided by a partition, which is not shown here, into two directions, namely the inlet part  15  of the main channel  14  the media flow being in the direction indicated by S 15 , and into the secondary channels  17 ,  18  through the inner cooling fins  12 , which are part of the cooling monobloc  11 . The inner cooling fins  12  of the cooling monobloc  11  reach into the secondary channels  17 ,  18  between the source  21  of cooling media and the outlet of the secondary channels  17 ,  18  into the main channel  14 . The main channel  14  is arranged, with the cooling media flow direction, in parallel to longitudinal axis of cooling monobloc. Over the main channel  14 , in the horizontal wall of the cooling monobloc, a recess  20  is created from the top, where a holder  2  of a flat plate-like shape is mounted. Reference  20  in  FIG. 1  points to just a half of the recess  20 , since the other half of the recess  20  is covered by a half of the holder  2  being depicted on the opposite side. As shown in  FIG. 5 , the holder  2  of the light source  1  can be inclined in the streaming direction of the cooling media at the angle φ=0°-60° with respect to the horizontal plane. In the place of the recess  20 , the horizontal wall of the cooling monobloc  11  is interrupted and the bottom, first side  3  of the plate holder  2  thus encloses the main channel  14  from the top and is in contact with the cooling media, streaming through the main channel  14 . On the other, top side  4  of the holder  2  the LED light source  1  is mounted. The secondary channels  17 ,  18  are routed out of the cooling monobloc  11  laterally with regard to the longitudinal axis x of the cooling monobloc  11 , and then, following a break (see angle α in  FIG. 3 ), they are directed and connected to the main channel  14  under the bottom, first side  3  of the plate holder  2 , on the top, other side  4  of which the LED light source  1  is mounted. The two secondary channels  17 ,  18  lead into the area under the first side  3  of the holder  2  of the light source  1  laterally against each other, but they can lead there from the bottom, arranged next to each other. The secondary channels  17 ,  18  partly comprise removable covers  22  fitted with inner guiding and cooling fins  23 ,  24 . The removable covers  22  can also or alternatively be fitted with outer cooling fins. The cooling media source  21  is mounted on the cooling monobloc  11 , which is fitted with a distribution partition to supply the cooling media separately to the main channel  14  and separately to each secondary channel  17 ,  18 . 
       FIG. 2  shows the covers  22  of the secondary channels  17 ,  16  in a perspective view, arranged on the cooling monobloc  11 . The covers  22  are fitted with inner guiding and cooling fins  23 ,  24  that guide the streaming cooling media on the one hand and dissipate heat from the streaming cooling media and cool it on the other hand. The cooling media flows through the secondary channels  17 ,  18  in the indicated directions S 17 , S 18 , leading perpendicularly from sides into the main channel  14  in the place under the plate holder  2  of the LED light source  1 , which is not shown here. After mixing of the cooling media streams from the secondary channels  17 ,  18  with the cooling media stream in the main channel  14 , the cooling media flows through the outlet part  16  of the main channel  14  in the flow direction indicated by S 16 . 
       FIG. 3  presents a diagram of the lateral secondary channels  17 ,  18 , which are arranged in a break along the sides of the main channel  14 . The lateral channels  17 ,  18  first lead from the side walls of the cooling media source  21 , are broken at the angle α=0°-90° and lead into the main channel  14  from the lateral sides between the inlet part  15  and the outlet part  16  at the angle β=30°-90° with respect to the direction S 14  of the cooling media flow through the main channel  14 . 
       FIG. 4  presents a diagram of a bottom secondary channel  19 , which is arranged under the main channel  14 . The source  21  of cooling media supplies cooling media partly to the main channel  14  and partly to the secondary channel  19 . The bottom secondary channel  19  leads from the cooling media source  21 , and is broken at the angle γ=10°-80°. In the flow direction indicated by S 19 , the cooling media flows through the secondary channel  10  and its outlet into the horizontally arranged main channel  14 . The secondary channel  19  is connected to the main channel e.g. at the angle δ=90° with regard to the direction S 14  of the cooling media flow through the main channel  14 . The angle   can be in the range δ=30°-90°. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Light source 
           2  Holder 
           3  First side 
           4  Second (opposite) side 
           11  Cooling monobloc 
           12  Inner cooling fin 
           13  Outer cooling fin 
           14  Main channel 
           15  Inlet part 
           16  Outlet part 
           17  Secondary channel 
           18  Secondary channel 
           19  Bottom secondary channel 
           20  Recess 
           21  Cooling media source 
           22  Cover 
           23  Guiding and cooling fin 
           24  Guiding and cooling fin 
         S 14  Flow direction through the main channel  14   
         S 15  Flow direction through the inlet part 
         S 16  Flow direction through the outlet part 
         S 17  Flow direction through the secondary channel  17   
         S 18  Flow direction through the secondary channel  17   
         S 19  Flow direction through the bottom secondary channel  17   
         Longitudinal axis X of the cooling monoblock  11   
         α Break angle of the secondary channel 
         β Outlet angle of the secondary channel 
         γ Inclination angle of the secondary channel 
         δ Outlet angle of the secondary channel 
         φ Holder inclination angle