HEADLIGHT WITH AN LED LIGHT SOURCE

Abstract

This invention relates to a headlight with an LED light source which contains at least one light-emitting diode arranged on a circuit board and is arranged in a housing enclosing the LED light source, which includes at least one light exit surface through which the light emitted by the LED light source exits. According to the invention it is provided that the housing encloses the LED light source in a liquid- or gas-tight way and includes at least one coolant inlet and one coolant outlet for a liquid or gaseous coolant.

Claims

1. A headlight with an LED light source comprising: at least one light-emitting diode arranged on a circuit board; a housing enclosing the LED light source, wherein the housing: includes at least one light exit surface through which the light emitted by the LED light source exits; and: encloses the LED light source in a liquid- or gas-tight way and includes at least one coolant inlet and one coolant outlet for a liquid or gaseous coolant.

2. The headlight according to claim 1, wherein the housing encloses the LED light source and a cooling element connected with the circuit board, which in particular consists of cooling ribs.

3. The headlight according to claim 1, wherein the light exit surface is formed as optical element or optical window.

4. The headlight according to claim 1, wherein the optical element or optical window is connected with the housing in a liquid- or gas-tight way.

5. The headlight according to claim 1, wherein the optical element or optical window consists of a transparent, optical plastic material or glass.

6. The headlight according to claim 1, wherein the optical element or optical window consists of a plane-parallel glass or plastic plate.

7. The headlight according to claim 1, wherein the optical element or optical window is optically active for beam formation and/or color mixing.

8. The headlight according to claim 1, wherein the optical element or optical window includes curved or stepped optical surfaces for light guidance.

9. The headlight according to claim 8, wherein the optical element or optical window consists of a lens, a lens array, a scattering plate or of a light mixing rod.

10. The headlight according to claim 8, wherein the optical element or optical window is coated with a luminescent material.

11. The headlight according to claim 1, wherein the distance and/or the orientation of the optical element, optical window or the housing with respect to the position of the LED light source is variable for the dynamic beam formation of the light emitted by the at least one LED of the LED light source.

12. The headlight according to claim 1, wherein the refractive index and the spectral transmission and reflection of the optical element or optical window, the surface of the LED light source, a primary lens of the LED light source as well as the coolant are adjusted to achieve a specified lighting result, in particular a specified radiation angle or a specified light output.

13. The headlight according to claim 1, wherein within the housing or on a wall surface of the housing further optical elements such as reflectors or lenses are arranged.

14. The headlight according to claim 1, wherein the circuit board is formed as cooling plate or is connected with a cooler.

15. The headlight according to claim 13, wherein the coolant flows through the circuit board formed as cooling plate and/or through the cooler and/or the housing.

16. The headlight according to claim 1, characterized by a cooling system containing the coolant, which cools the coolant down to a specified service temperature.

17. The headlight according to claim 15, wherein the cooling system is arranged within the headlight.

18. The headlight according to claim 1, wherein the cooling system is arranged outside the headlight.

19. The headlight according to claim 1, wherein the LED light source and/or the cooler are traversed by a coolant which is movable by a cooling system distributed over several systems or appliances and can be cooled down to service temperature.

20. The headlight according to claim 1, wherein the LED light source is arranged in a secondary cooling circuit and the cooling plate is arranged in a primary cooling circuit and that the primary and secondary cooling circuits are thermally coupled via a heat exchanger.

21. The headlight according to claim 1, wherein the cooling system includes a coolant reservoir, a coolant pump, a heat sink, cooling fins or cooling ribs and a fan.

22. The headlight according to claim 1, wherein the cooling system consists of a heat-absorbing exchangeable cold pack.

23. The headlight according to claim 1, wherein the cooling system is connected to a central cooling device with a coolant distribution via a specified standardized coolant port.

24. The headlight according to claim 22, wherein the standardized coolant port includes an interface for an electrical connection and/or a control bus for controlling and regulating the LED light source.

25. The headlight according to claim 22, wherein the standardized coolant port is connectable with a hybrid cable which includes the interfaces for an electrical connection, electrical control signals, a supply voltage and the cooling liquid.

26. The headlight according to claim 1, wherein a central cooling system dissipates the heat emitted by the coolant and that the headlight includes a pump for the coolant.

27. The headlight according to claim 1, wherein the cooling system consists of a central cooling unit with central coolant distribution and coolant regulation of a generator vehicle for the power supply of several cooling devices connected to the generator vehicle.

28. The headlight according to claim 1, wherein the at least one LED of the LED light source consists of a light-emitting diode in a ceramic or plastic housing which is mounted on the circuit board.

29. The headlight according to claim 28, wherein the LED of the LED light source arranged in a ceramic or plastic housing is covered with an optically active or inactive material.

30. The headlight according to claim 1, wherein the at least one LED consists of an LED chip which is mounted on the circuit board in chip-on-board technology.

31. The headlight according to claim 1, wherein the color locus of the LEDs of the LED light source can be regulated and stabilized electronically in dependence on the temperature of the LEDs.

32. The headlight according to claim 1, wherein the color locus of the LEDs of the LED light source can be stabilized by regulating the coolant temperature, the coolant flow or the rotational speed of the fan at the heat exchanger.

33. The headlight according to claim 30, wherein in a mixed operation the color locus of the LEDs of the LED light source can be regulated and stabilized both in dependence on the temperature of the LEDs and in dependence on the coolant temperature, the coolant flow or the rotational speed of the fan at the heat exchanger.

34. The headlight according to claim 32, wherein in a normal operation the color locus of the LEDs of the LED light source can be stabilized up to a specifiable ambient temperature by regulating the coolant temperature, the coolant flow or the rotational speed of the fan at the heat exchanger and upon exceedance of the specified ambient temperature can be stabilized in an intensive operation by electronic regulation of the LED light source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] With reference to exemplary embodiments illustrated in the drawing the idea underlying the invention will be explained in detail. In the drawing:

[0049] FIGS. 1 to 3 show a side view, isometric view and top view of an LED light source with LEDs mounted on a cooled circuit board, surrounded by a liquid-tight housing and flowed around by an inert coolant;

[0050] FIGS. 4 to 6 show various optical windows in the housing surrounding the LEDs in a section along line A-A according to FIG. 3;

[0051] FIGS. 7 to 9 show a side view, isometric view and top view of an LED light source with a housing surrounding a circuit board with LEDs mounted thereon and a cooling plate, which is traversed by a coolant flowing in a cooling circuit;

[0052] FIG. 10 shows a longitudinal section through the LED light source along line B-B according to FIG. 9;

[0053] FIGS. 11 to 15 show a schematic representation of a cooling circuit of an inert coolant flowing through a cooling plate, which is thermally coupled with a circuit board with LEDs mounted thereon, and/or flowing around the LEDs and recooled in a recooling device;

[0054] FIG. 16 shows a schematic representation of a primary cooling circuit flowing through the cooling plate, which is thermally coupled with the circuit board accommodating the LEDs, and of a secondary cooling circuit connected with the primary cooling circuit via a heat exchanger, which flows around the LEDs mounted on the circuit board; and

[0055] FIGS. 17 to 20 show a schematic representation of a cooling system according to the prior art with a cooling plate traversed by a coolant, which is thermally coupled with a circuit board accommodating the LEDs.

DETAILED DESCRIPTION

[0056] The first embodiment shown in FIGS. 1 to 6 in various views and in a longitudinal section to represent a direct cooling of an LED light source 1 mounted on a circuit board 2 includes a cooler 3 thermally closely coupled with the circuit board 2, which is traversed by a coolant which is guided in a first coolant line 81 which is coupled with the cooler 3 via a first coolant inlet 31 and a first coolant outlet 32. According to FIGS. 11 to 15 the heat absorbed by the coolant is emitted to the environment or to a heat-absorbing device by means of a cooling system 7a to 7e, so that in operation of the LED light source 1 a substantially constant temperature can be adjusted at the circuit board 2 with the LEDs mounted thereon.

[0057] The LEDs of the LED light source 1, which are mounted on the circuit board 2 as finished light-emitting diodes in a ceramic or plastic housing or alternatively are mounted on the circuit board 2 as LED chips without housing by means of a chip-on-board technology, are surrounded by a preferably flat, generally cuboid or circular housing 4 adapted to the shape of the LED light source 1, which via a second coolant inlet 41 and a second coolant outlet 42 is connected with a second coolant line 82 of a cooling system 7a to 7d according to FIGS. 11 to 14, so that the cooling liquid guided in the first coolant line 81 directly flows around the LEDs of the LED light source 1. Via the cooling system 7a to 7d the heat absorbed by the coolant is emitted to the environment or to a heat-absorbing device. Alternatively, a heat-absorbing device in the form of a cold pack 300 corresponding to the schematic representation in FIG. 15 also can directly by flange-mounted to the LED light source 1.

[0058] For radiating the light emitted by the LEDs of the LED light source 1 the surface of the wall of the housing 4 surrounding the LED light source 1, which faces the LED light source 1, includes an optical window 5 which can have different optical properties and according to FIG. 4 can consist of a plane-parallel glass or plastic plate 50 or of a structure with curved or stepped surfaces such as e.g. a lens 51 according to FIG. 5, a lens array, a scattering plate 52 according to FIG. 6, or of a light mixing rod, in order to perform a beam formation and/or color mixing already at the optical window 5. In addition, a dynamic beam formation can be achieved by an optical window arranged in front of the LED light source 1 in a fluid-tight, but movable way.

[0059] The second exemplary embodiment of an LED light source 1 as shown in FIGS. 7 to 10 in various views and in a longitudinal section differs from the first exemplary embodiment described above with reference to FIGS. 1 to 6 as well as 11 and 12 to the effect that the housing 40 not only surrounds the LED light source 1 mounted on a circuit board 2, but also a cooling element 30 consisting of cooling ribs, cooling pins or the like, so that the coolant guided in a first coolant line 81 and entering the housing 40 via the coolant inlet 41 and leaving the housing 40 via the coolant outlet 42 flows around both the LED light source 1 and the cooling element 30 and emits the absorbed heat to the environment or to a heat-absorbing device via a cooling system 7.

[0060] Analogous to the representations of FIGS. 4 to 6 the optical window 5 arranged in front of the LEDs 1 in emission direction of the LEDs can be formed as plane-parallel plate or as lens, lens array or light mixing rod, in order to perform a beam formation and/or color mixing. In this embodiment, too, a dynamic beam formation can be achieved by an optical window 5 arranged in front of the LED light source 1 in a fluid-tight, but movable way. It can be coated with luminescent material and thus fulfill the function of a remote-phosphor light source.

[0061] The LEDs 1 mounted on the circuit board 2 are connected with a power supply cable 14 which is connected to an electronic controller, a mains unit or ballast 12. The control unit, mains unit or ballast 12 is connected with a voltage source via a mains cable 13.

[0062] With reference to the schematic representations of FIGS. 11 to 16 various cooling systems 7a to 7e will be explained, wherein the type of cooling and recooling however is not limited to the illustrated systems.

[0063] The circulating air cooling system 7a as shown in FIG. 11 contains a heat sink 71 thermally coupled with the coolant lines 81, 82, a fan 70 for producing a stream of cooling air directed to the heat sink 71, and a coolant reservoir or a tank 72 for the coolant as well as a coolant pump 73 for producing a circulating stream of coolant.

[0064] FIG. 12 shows a schematic representation of a cooling system formed as recooling system 7b with primary coolant circuit and secondary refrigerant circuit with a mechanical cooling device consisting of an evaporator 74 formed as heat exchanger with primary-side connection to the coolant lines 81, 82 and secondary-side connection to a refrigerant line 77 which connects the evaporator 74 with a condenser 75 via a compressor 76. In this exemplary embodiment, analogous to the arrangement according to FIG. 11, the condenser 75 includes a fan 70 and a heat sink 71 which emits the heat quantity transported via the refrigerant line 77 to the environment. The primary-side connection of the evaporator 74 corresponds to the arrangement according to FIG. 11 with a coolant reservoir or tank 72 and a coolant pump 73 to produce a circulating stream of coolant.

[0065] In the recooling system 7b as shown in FIG. 12 the coolant is cooled by the refrigerant, when it passes through the evaporator 74. The refrigerant absorbs the thermal energy, evaporates and is liquefied again by means of the compressor 76 and the condenser 75, wherein during the condensation the heat is emitted to the ambient air by means of the fan 70 and the heat sink 71.

[0066] In the embodiment according to FIG. 13 the cooling system consists of a water exchange system 7c with a heat exchanger 78 which on the primary side is connected to the coolant lines 81, 82, to the coolant reservoir 72 for the coolant and to the coolant pump 73 for producing a circulating stream of coolant, while on the secondary side the heat exchanger 78 is connected to process water lines 84, 85. In this water exchange system 7c the coolant is passed from the primary circuit through the heat exchanger 78, where it is cooled by the colder process water supplied from outside.

[0067] FIG. 14 shows a schematic representation of the use of a heat-absorbing device formed as cold pack 300 in an indirect cold pack system 7d, in which the cold pack 300 is flange-mounted to the coolant lines 81, 82. For this purpose, a heat exchanger 79 on the primary side is connected to the coolant circuit consisting of the coolant lines 81, 82, the coolant reservoir 72 for the coolant and the coolant pump 73 for producing the circulating stream of coolant, and on the secondary side is provided with a corresponding device for accommodating the cold pack 300 or for flange-mounting the cold pack 300.

[0068] FIG. 15 shows a schematic representation of the formation of a cooling system as heat-absorbing direct cold pack system 7e with a cold pack 300, which is directly flange-mounted to the housing 4, 40 accommodating the LED light source 1 or to the coolant line. The cold pack 300 absorbs the thermal energy emitted by the LED light source 1 for a limited period of time and upon reaching a specified temperature is then replaced by a second cold pack 300 prepared for absorbing thermal energy.

[0069] In an alternative arrangement according to the schematic representation of FIG. 12 the coolant flowing around the LED light source 1 is guided in a coolant line 83 which forms a secondary circuit and via a heat exchanger 9 is thermally coupled with a primary cooling circuit which includes a coolant line 81 which via the first coolant inlet 31 and the first coolant outlet 32 is connected with the cooling plate 3 and a cooling system 7. The secondary cooling circuit includes a reservoir 10 for taking up cooling liquid and a coolant pump 11 for the transport of the coolant through the secondary circuit. The cooling system 7 can be formed analogous to the cooling systems 7a to 7c described above with reference to FIGS. 11 to 13.

LIST OF REFERENCE NUMERALS

[0070] 1 LED light source [0071] 2 circuit board [0072] 3 cooler [0073] 3 cooling plate [0074] 4 housing [0075] 5 optical window [0076] 7; 7a-7e cooling system [0077] 8 coolant line [0078] 9 heat exchanger [0079] 10 reservoir [0080] 11 coolant pump [0081] 12 mains unit or ballast [0082] 13 mains cable [0083] 14 power supply cable [0084] 30 cooling element (cooling ribs, cooling pins) [0085] 31, 41 coolant inlet [0086] 32, 42 coolant outlet [0087] 40 housing [0088] 50 plane-parallel glass or plastic plate [0089] 51 lens [0090] 52 scattering plate [0091] 70 fan [0092] 71 heat sink, cooling fins or cooling ribs [0093] 72 coolant reservoir [0094] 73 coolant pump [0095] 74 evaporator [0096] 75 condenser [0097] 76 compressor [0098] 77 refrigerant line [0099] 78, 79 heat exchanger [0100] 81-83 coolant lines [0101] 84, 85 process water lines [0102] 300 cold pack