COOLING DEVICE FOR A HEAT SOURCE
A cooling element for a heat source, especially LED modules with many components, includes a base body in thermal and mechanical contact with a body of the heat source, at least one heat pipe having an end section inserted into the base body in a form-fitting and thermoconducting manner, and at least one cooling body having cooling body lamellae on the other end section of the heat pipe. The heat pipes extend over the entire length of the base body such that a hot zone of the heat source lies on a contact surface of the base body, the heat pipes extend parallel to each other and to the contact surface of the heat source. The base body is fixed to the body of the heat source, base body lamellae being provided on the outer side of the base body, formed as a single component thereon or connected thereto.
The invention concerns a cooling element for the cooling of a heat source, for example an LED module in accordance with the first part of claim 1, as they are used, for example, as LED lights to illuminate interior spaces and in some outdoor areas (e.g. tunnels, gardens, building illumination).
LEDs (light emitting diodes) are often used as light sources. LEDs are electronic semi-conductor components. If electricity flows through the diode in the direction of the outlet, light is emitted. Light diodes possess an exponentially increasing current-voltage-characteristic (I-V curve) which, among other things, depends on temperature. The luminous flux is nearly proportional to the operating current. The forward voltage adjusts itself due to constant current through operation, possesses tolerances and is temperature-dependant—it sinks with increasing temperature as with all semiconductor diodes. High temperatures (usually due to high currents) shorten the life span of LED's dramatically.
Typically, multiple light emitting diodes together on one carrier are arranged to one unit colloquially referred to as an “LED” light, which is now also subsequently referred to as an LED. The brightness of an LED grows with power consumption. At a constant semiconductor temperature the increase is roughly proportional. The level of efficiency drops with increasing temperature, and it is for this reason that the light yield drops at the limit of performance depending on the type of cooling. LED's generally have bad thermal stability which is why they must be cooled off for long-time use, so that their lifespan is not dramatically shortened. Heavily populated LED modules, meaning modules which are furnished with many light-emitting diodes, like, for example, the Fortimo DLM Line by Philips, or XLM by Xicato, or BOA by Bridgelux, and others, are particularly heat sensitive.
The heat produced by the operating current as thermal power loss may not heat up the module above 65° C. at the housing measuring point defined in order to be able to ensure the predetermined lumen output (luminous flux unit ->luminosity) and the required lifespan (min. 50,000 operating hours).
In order to achieve this various precautions have already been taken.
Attempts were made to cool using free convection on the LED's extensive housing, or with these thermally connected arrangements with cooling elements (passive cooling), i.e. using diverse lamellae arrangements. Apart from the fact that a lot of space is required for this these relatively heavy metal elements form inefficient cooling elements, particularly in the assembly of a larger number of LEDs in the module or lamp body (DE 10 2007 030 186 B1, DE 20 2008 906 325 U1).
Further, using actively moved elements for cooling (active cooling) is known, for which, in connection with convection elements, motor driven fans, or a oscillating membrane, are used, see “Application guide, Philips Fortimo LED downlight module system (DLM)”. Page 18, Abb.: SynJet cooling System von Nuventix: Apart from the fact that these elements also require additional energy to function, they produce very disruptive noises (over 20 db), which can lead to very high resonances, particularly with the arrangements of many lights of this kind on suspended ceilings of larger rooms, in addition vibrations and echo effects occur which can build up to extremely distracting background noise, up to five times amplification. In addition the side lamellae cooling elements provided are not suited for, and also not intended, to enable the necessary reduction in temperature. They only serve to spread the heat. For this reason these lights could only be used to a limited extent until now.
Finally, it is known to use arrangements with heat pipes for heat dissipation. For example, cooling elements with heat pipes, with which one end of the heat pipes is thermally connected with a heat source, while their external sections are equipped with a lamellae-equipped, or lamellae-like, cooling element, are known from DE 10 2007 038 909 A1 and DE 10 2006 045 701 A1. Apart from the fact that this concerns systems that are practically useful only in outdoor applications in motor vehicles and not for lights to be used indoors, therefore not for indoor applications, this concerns cooling threads shaped directly on the pipe casing and ineffective cooling elements, or a lamella package which is applied on heat pipes with various contents and purposes. These cooling elements are not suitable for cooling lights in building spaces. Cooling elements in accordance with the category are known from EP 1903278 A1 and DE 20 2009008456U1, which are, however, not satisfactorily manufacturable and/or sufficiently efficient and space saving—particularly for application in lighting elements. Therefore, the problem of the invention is to create a space-saving cooling element, in accordance with the category, for effective, silent cooling of lights with a high number of LEDs.
The problem is solved by a cooling element with the characterizing features of claim 1. Advantageous embodiments may be taken from the dependent claims.
The basic elements in a cooling element according to the invention are: at least one, preferably two, three, or more heat pipes which extend on a common level and for each of which one (first) end section is embedded in one of the base bodies to be connected to the heat source, while on the other (second) end section a cooling body is attached consisting of multiple lamellae. The heat pipes are arranged across the entire length of the base body so that the heat source, or the LED module, lies on the base area of the base body. In doing so, the heat pipes run parallel to each other and to the metal contact surfaces, parallel to the heat source with the hottest zone (hot spot). The lamellae are provided integrally with these on the exterior of the base body. Consequently, one end of the tubes runs very close along the hot base of the LED module across its entire length, so that a very good thermal conduction from the heat source to the heat pipes is ensured. In addition, the lamellae are already being cooled in the area of the base body and the heat source above the base body at the same time, thereby, on the whole, significantly contributing to the heat dissipation.
It is beneficial that the base body lamellae, which can be designed differently, are arranged on the base body in a transverse or longitudinal direction. For the primarily U-shaped base body, surrounding the U-shaped metal housing of the rectangular-shaped LED modules at least partially, offers, to also arrange the lamellae in a U-shape in transverse axial succession. However, it simpler if the cooling ribs or lamellae are arranged lengthwise or axially for manufacture. Therefore the base body is, as a whole, manufacturable as one piece using extrusion or extrusion moulding.
It can be advantageous if two or three or more heat pipes always running through one common level are used for one cooling element. In this way three heat pipes can be used together, which, for example, have a pipe diameter of 5 mm, whereby the arrangement of the heat pipes is selected in such as way that their first end section is embedded in a form-fitting, and thermally conductive manner, in the base body in the corresponding opening and in the corresponding axially parallel distance to one another, while they are continued in various forms after their exit from the base body. In this way, for example, a central
heat pipe is extends axially in a straight direction while both side heat pipes extend on their separate ways, and the distance between the heat pipes increases across a relatively short distance, for better heat dissipation, after which they continue even axially parallel in the cooling body so that, overall, a forked arrangement of the heat pipes exists.
The cooling body, which consists primarily of many parallel, distanced lamellae, stretches across the entire second end section of the heat pipes. The lamellae are advantageously designed so that through-holes for the passage of the heat pipes are shaped so that the heat pipes, in press fit, or shrink fit, are firmly in tight, thermally conducting, form-fitting contact with the lamellae, whereby optimum thermally conducting contacts between the heat pipes and the lamellae are ensured.
In order to simply maintain a constant distance between the lamellae various spacers can be used. These, for example, can, in each case, be simple spacer rings on both of the exterior heat pipes. They have spacers rising vertically out of the lamellae, which can be directly cut in, in a tongue-like manner, and vertically bent out by the punching manufacturer.
With an embodiment with only two heat pipes they are similarly shaped as the two external heat pipes of the above-described embodiment with three heat pipes. The first end sections of the heat pipes in the interior of the base body also run parallel to each other, then after exiting the base body diverging and upon entry into the cooling body again parallel to one another so that the shape is roughly like a tuning fork. Here it can be useful to select heat pipes with a somewhat thicker diameter, i.e. with 6 mm, so that overall similar thermal and strength conditions exist as in the embodiment with three pipes with a diameter of 5 mm.
The heat pipes can, in a first embodiment, be embedded, form-locking, in axial or longitudinal holes, in the base body base section, along its entire length, whereby they have no physical contact with the hot zone of the LED module. Through the good conductivity of the base body, particularly the base section, in which the heat pipes are embedded, the heat absorbed by the base body through its close contact with the hot zone of the module to be cooled off, can be easily transferred to the pipes and active vaporization of the fluid medium found in the heat pipes under absorption of the latent warmth, and with that the dissipation in the following cool zone with condensation and release of the latent warmth takes place.
Usually the heat pipes extend through the thermal absorption plates. However, for some applications it is advantageous if the heat pipes are each placed in a groove which is open to the contact surface of the base body-base element. In doing so, the cross section of the grooves can be designed essentially U-shaped for maximum contact and form fit, with the same groove-base diameter as those of the heat pipes and a groove height according to the thickness of the heat pipes. As a result, full surface contact with the LED module in the base body occurs concurrently with direct contact between the heat pipes and the hot base surface of the LED modules. Therefore a particularly good thermal contact is obtained so that the evaporization of the medium of the heat pipes and with it most efficient heat dissipation can occur.
According to the invention, the base body can have various embodiments. It can be designed as a simple plate, upon or to which, an LED module can be fastened, with good contacts, accordingly. Then the plate comprises vertically extending lamellae on its flat exterior accordingly, which can run lengthwise or crosswise for the course of the heat pipes arranged therein.
However, the base body can also be designed so that it can, at least, partially laterally encompass the heat source, or the LED Module, in a U shape, therefore itself have a U-shape. Therefore, the base body comprises a base body floor section wherein the heat pipes extend partially in corresponding holes, or grooves, as well as two sides vertically thereto. The distance between the base body sides is to be designed so that their inner flanks have a good contact area and therefore lie on the metal flanks of the LED module so that they are thermally conductive. In order to establish this contact the base body sides can also be attached on the side using fasteners on the flanks of the LED module.
Further, the base body sidewalls along the flank of the LED can run shorter or longer. So, for example, a base body side length of only 0.5 to 15 mm, preferably 8 mm, is conceivable which only serves as a fastening aid. The short base body side design form has the significant advantage that more leeway remains for mounting a light housing to be used, which then encroaches upon or is fastened to the lower part of the LED module.
In a further embodiment the base body, or at least its base body floor section, is relatively thin. The thickness of the base body floor section is less than the diameter of the heat pipes. At the same time grooves with an opening directed to the contact surface for simple insertion of the heat pipes are provided, while the thin material of the base body is guided around these grooves in an arched shape. In addition, the lamellae provided on the front side of the base body protrude vertically from the exterior of the base body floor section so that optimal heat dissipation, with economic material use, exists.
With long U-shaped encompassing base body side walls, and axially extending lamellae, side lamellae can also be provided in addition to the lamellae protruding outward from the base body floor section. For reasons of space these can then also be at least partially angled upwards. Only with very short side walls should side lamellae not be provided, because only a little heat can be absorbed in the short stub base body sides, and therefore dissipated.
Because here the heat source to be cooled, here the LED module, has multiple fastening devices, i.e. holes, in a special arrangement, these should also be provided in the base body floor section. The Fortimo module, for example, provides three anchor holes, arranged in the shape of an isosceles triangle.
It is particularly advantageous if, in addition to the customary three holes (two in the front, one in the centre rear) an additional three holes are provided, which are arranged in a mirror image of the first three, namely a centre hole on the front outer edge and two holes spaced apart from each other on the inside edge of the base body. So the base body can simply be turned by 180° on an LED module and fastened so that the LED module can either be mounted with its electrical connection side facing outward, or inward, across from the entire element. This is particularly the case when using the cooling element not only for the rectangular Fortimo LED modules for example, but also for the Lexel modules by Philips having the same width, however, approx. double the length. The base body can be placed on the module so that it locks with the outer end of the LED module on the front side, whereby then, for example, the power-connection side of the LED module protrudes over the inner edge of the base body far inwards, in the direction of the cooling body. In this arrangement, the hot zone is found in the module zone facing the electric connection end. With a changed application of the module, with the power connection part facing outward, the thermal conducting base body of the cooling element sits on the then inner zone so that the front side of the base body is flush with the corresponding front side of the LED module.
With an arrangement with an internal power connection of the LED module it is important to ensure that a corresponding inner distance between the base body and the cooling body exists. This can be achieved, among other things, by using the heat pipes reversed, namely with the Crimp-end, unusable for a form-locking contact with the lamellae not protruding far out of the last lamella, but instead with this and laid into the groove of the base housing. In this way the entire lamellae package of the cooling body can be fastened very close to the now outward facing flat end.
With a further embodiment at least one, preferably two support sheets spaced apart from each other provided for the vertical support of the cooling body. As a result, the entire cooling lamellae package of the cooling body is carried through only three heat pipes protruding from the base body. The heat pipes are mostly manufactured out of relatively soft material with good thermal conductivity, like aluminum, or copper, and bend very easily under the weight of the lamellae package, or through improper handling, and are therefore easily damaged.
The support sheets can simply lie flat or linear on the underside, or bottom edge, of the lamellae for support. However, they can also, in a particularly advantageous manner, join in a form-fit corresponding vertical slits in the lamella, so that not only a vertical, but also a good lateral support exists. The support sheet can be designed in various ways, particular its length, whereby its first end can be attached to the sides of the module of the base body, while a second console-type protruding longer end should at least extend across the majority of the length of the cooling body.
It is advantageous if the support sheets are on the top side designed in the length of the corresponding contact facing the lamellae and are angled toward the top, with slope, or incline. There even a slight incline of preferably 5°, or at most 18°, is already extremely effective, because the entire lamellae package with heat pipes then runs angled toward the top directed towards the cooling end, whereby the condensate transport is supported by gravitational force. Using only a slight slope of the heat pipes a significantly faster return of the cooled medium takes place within the heat pipes to the first, hot vaporization end. Thereby, through an extremely simple measure, a remarkably better cooling effect can be achieved, paired with increased strength and safety. For example, for the their application on non-square heat sources, with larger length measurements and reverse layout, i.e. with the electrical power connections of the heat source, or the light housing not facing out, but instead facing in facing the lamellae cooling body, the distance between the base body and the lamellae cooling body can be designed at least 10 mm larger than for square LED modules.
Finally, it is advantageous if at least the lamellae or even all parts of the cooling element are executed in black because black surfaces radiate more heat than white, or bare metal surfaces.
In the following, the invention is explained using embodiments with reference to the drawing, to which it is in no way limited. Therein show:
In
Further it is shown that the cooling element 1 has a relatively long cooling body of cooling body lamellae 20 on its other end. Here, the cooling body lamellae 20 are simple squares and are lined up at spaced at a constant distance from one another on the heat pipes 5, 6.
The heat pipes 4, 5, and 6 are guided across the entire length, parallel to each other, with relatively small space in between in the base body, base body floor section 7 and exit from the inner side of the base body 2 with corresponding distance. Concurrently therewith the middle heat pipe 4 runs in the centre, straight and axially, while both of the outer heat pipes 5 and 6 are first angled diagonally outward, then again run parallel to one another at a corresponding larger distance from one another, so that the shape of a fork with three teeth is achieved. The cooling body lamellae 20 of the cooling body 3 are lined up on the fork teeth section.
In
As a particularity it should be understood that three heat pipes are no longer provided, but instead only two, namely heat pipes 5 and 6, which correspond to the shape and arrangement of this in
In addition, two slits 30 are introduced vertically from the bottom to the top on the cooling body lamellae 20, whereby here only one of the two slits is shown. The vertical insertion slots each serve to include a support sheet, as seen in
In cooling body 3 two backwards bent spacers 32 can be seen, each of which appear as only an axial line, so that an optical illusion of a line, which could represent a continuous plate, exists.
The front view of the cooling element 25 in
The rear view of the cooling body 3 from
Further, the arrangement here of the threaded holes 19 is identified, which serves for the attachment to the LED module. Here, not only are just the three threaded holes 19 planned in a triangle arrangement, but instead, in addition, a mirror image duplication of this arrangement, i.e. six holes. This has the advantage that the LED module can be mounted to the base body in any way, i.e. rotated by 180°, meaning that a choice exists whether the power connection will face outward, or inward.
The particular arrangement of the threaded holes can also be identified in
The power connection 41 of the LED module 12 points backwards, whereby a cable 42 leads to a connection box 43 of a LED generator 44. Through the slight angulation of the lamellae package some more lower space results, so that the corresponding connections can be formed to the back more easily and without disturbance.
In
Especially suited are adhesives including admixed heat-conducive metals. Through the adhesive layer ring around the heat pipe made in this way, the mechanical and thermal connection of the heat pipe on the lamellae 20 is improved.
In
In
Even though the invention was explained in detail with a preferred embodiment, it is in no way limited to this design but is only determined by the protection of the accompanying claims.
REFERENCE LIST
- 1. Cooling element, first design.
- 2. Base body
- 3. Cooling body
- 4. Heat pipe
- 5. Heat pipe
- 6. Heat pipe
- 7. Floor section
- 8. Base body side
- 9. Hole
- 10. Lamellae (base body-)
- 11. Fastening hole, side
- 12. LED-Module (heat source)
- 13. Metal housing part
- 14. Plastic housing part
- 15. Floor section—contact surface
- 16. Hot zone (hot-spot)
- 17. Metal housing part—base body side
- 18. Fastening hole
- 19. Threaded hole
- 20. Lamellae (cooling body)
- 21. Floor section contact surface
- 22. Base body contact surface
- 24. Light zone (-floor)
- 25. Cooling element, second design
- 26. Groove
- 27. Arch
- 28. Side lamellae
- 29. Punched hole
- 30. Slit
- 32. Spacer
- 33. Crimp-End of 4, 5
- 34. Smooth end of 4, 5
- 35. Cooling element, third design
- 36. Support sheet
- 37. Support sheet
- 38. Hole
- 39. Lamp housing
- 40. Power connection
- 41. Fastening screw
- 42. Cable
- 43. Connection box
- 44. LED generator
- a Angle
Claims
1-17. (canceled)
18. A cooling element for a heat source, particularly for highly equipped LED modules, comprising:
- one base body that is in thermal and mechanical contact with a body of the heat source;
- at least one heat pipe, whose end is received in a form-fitting and thermally conducting manner in the base body; and
- at least one cooling element with cooling body lamellae on the other end of the heat pipe,
- wherein:
- the heat pipes run over an entire length of the base body so that the heat source is in contact with a hot zone on a contact surface of the base body, whereby the heat pipes run parallel to each other spaced from another and parallel to a contact surface of the heat source with the hot zone, and the base body is fastened to the body of the heat source,
- lamellae which are connected with the base body are provided on an exterior of the base body and are integrally formed therewith, and
- the heat pipes run in an angle increasing outward in an end direction of the cooling element, whereby a positive angle of a warm side to a cold side is present.
19. The cooling element according to claim 18, wherein at least two heat pipes are provided that, outside of the base body, lead away from each other in a pitchfork-like manner, and thereafter run parallel to one another with a larger distance between them, whereby the cooling body is formed by an outer sec of the heatpipes having greater distance therebetween with cooling body lamellae provided thereto.
20. The cooling element according to claim 18, wherein three thermoconducting pipes are provided, whereby a straight central heat pipe runs in the middle between two outer, pitchfork-shaped, heat pipes that are bent outwardly in a three-pronged-fork-like manner, whereby the cooling body is formed through a part thereof with parallel section areas of the heat pipes having cooling body lamellae.
21. The cooling element according to claim 18, wherein that the heat pipes are received in holes along a whole length of the base body or are set in a groove that is open to the contact surface between the base body and the heat source, so that there is good contact between the heat pipes and the contact surface of the heat source.
22. The cooling element according to claim 18, wherein the base body is a plate with exterior base body lamellae extending from the contact surface.
23. The cooling element according to claim 22, wherein the plate of the base body is thinner than a diameter of the heat pipe and is arched around the heat pipe through grooves.
24. The cooling element according to claim 21, wherein the base body with a base body section and base body sides at least partially wraps around the heat source in a U-form, whereby the base body sides provide support.
25. The cooling element according to claim 21, wherein the base body lamellae run perpendicular or parallel to the base body.
26. The cooling element according to claim 24, wherein on the base body sides axially aligned base body lamellae are provided in addition to the lamellae extending upwards from a floor of the base body, as side lamellae.
27. The Cooling element according to claim 26, wherein in the base body floor section thread holes are provided to fasten to the heat source that correspond with holes in the heat source, whereby optionally additional fastening holes are provided in the base body which mirror said threaded holes so that turning the entire cooling element by 180 degrees to the heating source is possible.
28. The cooling element according to claim 18, wherein the cooling body lamellae are rectangular, with arch-shaped and wing-shaped sections, oval or cloud-like notches in an oval or cloud-like fashion, round or other metal cuttings, in order to ensure a minimal visible surface of the cooling body.
29. The cooling element according to claim 18, wherein the cooling lamellae of the cooling body are press- or shrink-fit on the heat pipes at a predetermined distance from one another, whereby spacers are provided between the cooling lamellae.
30. The cooling element according to claim 29, wherein the spacers are punched out from lamellae sheet tongues, bent away from a lamella main level.
31. The cooling element according to claim wherein on a lower side of the cooling body lamellae, at least one slit running from top to bottom or leading inside is provided to accommodate vertical support sheets.
32. The cooling element according to claim 18, wherein the cooling element is configured above the base body, whereby the heat pipes on the cooling element connected to the thermal conducting tubes are bent upwards in a U-shape.
33. The cooling element according to claim 18, wherein openings for the heat pipes of the cooling body cooling lamellae comprise a step-like deep drawn area in their circumference, so that after passing through the heat pipe, adhesives can collect in a groove formed between the heat pipe and the cooling body lamella.
34. The cooling element according to claim 27, wherein the cooling body lamellae are rectangular, with arch-shaped and wing-shaped sections, oval or cloud-like notches in an oval or cloud-like fashion, round or other metal cuttings, in order to ensure a minimal visible surface of the cooling body.
35. The cooling element according to claim 19, wherein on a lower side of the cooling body lamellae, at least one slit running from top to bottom or leading inside is provided to accommodate vertical support sheets.
36. The cooling element according to claim 20, wherein on a lower side of the cooling body lamellae, at least one slit running from top to bottom or leading inside is provided to accommodate vertical support sheets.
37. The cooling element according to claim 21, wherein on a lower side of the cooling body lamellae, at least one slit running from top to bottom or leading inside is provided to accommodate vertical support sheets.
Type: Application
Filed: Sep 9, 2010
Publication Date: Aug 23, 2012
Inventors: Hans Kunstwadl (Markt Schwaben), Abdallah Haddad (Munchen), Song Lin (Cheilaston), Jamie Donaldson (Badlington)
Application Number: 13/496,808
International Classification: F28D 15/02 (20060101);