WO2013056939A1

WO2013056939A1 - Led light source module for head lamp

Info

Publication number: WO2013056939A1
Application number: PCT/EP2012/068668
Authority: WO
Inventors: Hisashi Honda; Nobutaka Itagaki; Akihiro Oki; Toshio Ota
Original assignee: Osram Gmbh
Priority date: 2011-10-17
Filing date: 2012-09-21
Publication date: 2013-04-25
Also published as: JP2013089425A

Abstract

It is the object of the invention to provide a replaceable LED light source module for a head lamp with a low-cost configuration. To achieve this object, the invention offers an LED light source module (1) for a head lamp, integrally comprising an LED part (2) having at least one LED chip; a driver part (6) driving the LED part; a heat sink part (3) thermally connected to the LED part (2); an active cooling part (4) force-cooling the heat sink part (3); a module housing (5) for arranging the LED part (2) at a predetermined location within a headlight main body (10), the module housing (5) being detachably fixed to the headlight main body (10); and a power plug (7) for providing the driver part (6) and the active cooling part (4) with electric power.

Description

LED light source module for head lamp [Technical Field]

[0001] This invention relates to lighting fixtures for vehi^¬ cles, in particular to an LED light source module to be re- placeably mounted to a head lamp of a vehicle. [Background Art]

[0002] Head lamps using an LED (light emitting diode) as light source (LED head lamps) are used in some hybrid cars and electric cars. Since LED head lamps have low power con^¬ sumption and great variability with regard to design, it is possible that they will be used in many types of cars if their costs decrease from now as a result of mass production.

[0003] However, at present such LED head lamps for vehicles are designed separately in their entirety - including their light source part - for each type of car. This is one of the reasons for the high costs of LED head lamps, and it keeps them from becoming more popular.

[0004] Main reasons for why it is currently necessary to de- sign LED head lamps separately for each type of car are:

(1) compared to the light source parts of halogen lamps and metal halide lamps, greater positional precision (especially the positional precision in relation to the reflector) is necessary in LEDs , and

(2) since defects such as decrease in luminous flux, color change of the emitted light, decrease in luminance, shorten^¬ ing of lifespan, etc. occur when the internal temperature of an LED approaches its maximum junction temperature due to self-heating, it is necessary to cool LEDs to their maximum junction temperature or below.

In other words, since it is currently difficult to simultane^¬ ously cope with the high positional precision required in LEDs and the necessity for strict heat management, it has been necessary to designing LEDs separately for each type of vehicle .

[0005] One example of a conventional LED head lamp is an LED head lamp in which a heat sink is attached to the carrier of the LED, an electric fan is arranged so as to face the heat sink, and the air is forcedly circulated by the electric fan such that the diffusion of the heat from the heat sink is fa^¬ cilitated and thus the LED is force-cooled (see Patent Docu- ment 1 and Patent Document 2) . In addition, some compara^¬ tively low-light output lighting fixtures for vehicles, such as fog lamps, have a replaceable light bulb using an LED as light source (Patent Document 3) . [Prior Art Documents]

[Patent Documents]

[0006]

[Patent Document 1] JP Patent Appl. Publ . No. 2007-103365

[Patent Document 2] JP Patent Appl. Publ. No. 2010-262903

[Patent Document 3] JP Patent Appl. Publ. No. 2006-324217

[Summary of the Invention]

[Problem to be solved by Invention]

[0007] Now, in the conventional LED headlamps disclosed in Patent Documents 1 and 2, a light source part using an LED is integrated into the lamp main body, so that whenever the light source part needs to be replaced, the LED headlamp as a whole must be replaced. Also, the light bulb disclosed in Patent Document 1 uses a low-luminance LED as light source, so that it cannot be used as light source part for a head lamp. The use of a high-luminance LED, which would provide sufficient light output for a head lamp, as light source in such a light bulb poses the above-described problem concern- ing heat management.

[0008] The problem to be solved by the present invention is to realize an LED light source module that is replaceably mounted to a head lamp of a vehicle and has a low-cost con- figuration.

[Means for Solving the Problem]

[0009] For solving said problem, this invention offers an LED light source module for a head lamp, integrally comprising an LED part having at least one LED chip, a driver part driving the LED part, a heat sink part thermally connected to the LED part, an active cooling part force-cooling the heat sink part, a base for arranging the LED part at a predetermined location within a headlight main body, the base being detach- ably fixed to the headlight main body, and a power plug for providing the driver part and the active cooling part with electric power.

[0010] Such an LED light source module for a head lamp has a simple configuration and can therefore be provided at low cost. Also, in case it needs to be replaced, such an LED light source module for a head lamp can be replaced by itself without the headlight main body having to be replaced, as has conventionally been the case.

[0011] Preferably, in the LED light source module for a head lamp, the heat sink part comprises a heat sink main body in^¬ tegrally linked to the base, and a heat transmission part protruding in the shape of a rod from the heat sink main „

body, and the LED part is attached to the tip section of the heat transmission part.

In such a configuration, the base is fixed to the headlight main body, so that the heat sink main body is fixed to the headlight main body via the base. At the same time, the LED part attached to the tip section of the heat transmission part of the heat sink is arranged at a predetermined location within the headlight main body.

[0012] Further, the LED light source module for a head lamp preferably comprises a control circuit keeping the junction temperature of the LED part at or under a standard tempera^¬ ture (predetermined temperature lower than the maximum junc^¬ tion temperature) by comparing the forward voltage of the LED chip with a reference voltage and driving the active cooling part such that these voltages become identical.

In this configuration, the forward voltage of the LED chip is fed back to the control circuit, and the active cooling part is driven such that the difference to a reference voltage is minimized. Thus, unnecessary power consumption due to the cooling process can be prevented and the LED part can be force-cooled efficiently with a minimum of electric power.

[Effect of Invention]

[0013] With the present invention, a replaceable LED light source module for a head lamp can be realized with a low-cost configuration .

[Short Explanation of Drawings]

[0014]

Fig. 1 is a conceptual view showing an LED light source mod^¬ ule for a head lamp according to the present invention in a state where it is mounted to the headlight main body. Fig. 2 is a front view showing an example of an embodiment of an LED light source module for a head lamp according to the present invention.

Fig. 3 is a conceptual view showing an LED light source mod- ule for a head lamp according to the present invention in a state where it is mounted to the headlight main body.

Fig. 4 is a conceptual view showing an LED light source mod^¬ ule for a head lamp according to the present invention in a state where it is mounted to the headlight main body.

[Embodiments ]

[ 0015 ] Hereinafter, embodiments of the present invention will be described with the help of the drawings. [First Embodiment]

Now, a first embodiment of a LED light source module for a head lamp (hereinafter simply called "LED light source module") according to the present invention as shown in Figs. 1 and 2 is described.

The headlight main body 10 shown in Fig. 1 is configured such that most of it is a reflector 11. The reflector 11 has a light emission opening 11a, which is a large opening at the front end of the reflector 11. A lens 12 is mounted to the light emission opening 11a. The entire inner face of the re- flector 11 is a reflective face. The rear end section of the reflector 11 is curved in a dome-shape in such a manner that the light emitted from the LED light source module 1 towards the rear is reflected on the reflective face lib of this curved section and directed towards the front.

[0016] The bottom 11c of the reflector 11 is provided with a fixing hole lid for mounting the LED light source module 1. The bottom 11c is plane. The fixing hole lid is provided at a location toward the rear end of the bottom 11c. In the pe- ,

b riphery of the fixing hole lid, a fitting part, which is not shown in the drawings, for freely detachably mounting the LED light source module 1 is formed. [0017] As shown in Figs. 1 and 2, the LED light source module 1 comprises an LED part 2; a heat sink part 3 thermally con^¬ nected to the LED part 2; an active cooling part 4 force- cooling the heat sink part 3; a base 5 (hereinafter called "module housing") for arranging the LED part 2 at a predeter- mined location within a headlight main body 10, the base 5 being detachably fixed to the headlight main body 10; a driver part 6 driving the LED part 2 ; and a power plug 7 for providing the active cooling part 4 and the driver part 6 with electric power.

[0018] The LED part 2 comprises at least one LED chip 2a and an LED carrier 2b carrying the at least one LED chip 2a. The LED part 2 has a radiation performance of at least 1000 lu^¬ men. Further, the radiation performance is preferably 2000 lumen at most.

[0019] The heat sink part 3 comprises a circular, planar heat sink main body 3a which is integrated into the lower end sec^¬ tion of the module housing 5, and a cylindrical heat slug (heat transmission part) 3b which protrudes upwards from the center section of the heat sink main body 3a. The heat slug 3b has a cross-sectional area of 100 to 400 mm². An LED mounting face 3c is formed on the tip (upper end) section of the heat slug 3b, and the LED part 2 is fixed to the center section of the LED mounting face 3c. In this embodiment, the end face of the heat slug 3b is the LED mounting face 3c. The LED carrier 2b of the LED part 2 is formed as one piece with the LED mounting face 3c of the heat slug 3b, so that good heat conduction between them is maintained. The carrying an- gle Θ at which the LED chip 2a is carried on the LED carrier 2b (the angle between the light emission face of the LED chip 2a and the plane S which is orthogonal to the axis of the heat slug 3b) is selected depending on the configuration of the reflector 11 of the headlight main body 10.

[0020] The heat sink main body 3a is fitted and fixed to a lower end opening 5a of the module housing 5. A cylindrical protrusion 3d, which is formed to be coaxial to the heat slug 3b, and a multitude of heat-dissipating fins 3e are formed on the lower end section of the heat sink main body 3a. Also, a housing 4b of the active cooling part 4 is fixed to the pro^¬ trusion 3d so as to face the heat-dissipating fins 3e. [0021] The active cooling part 4 houses an electric fan 4a inside its housing 4b. The air flow of the electric fan 4a is selected based on the results of the measurement of the heat sink's thermal resistance, etc. The active cooling part 4 is provided with a space sufficient in volume to enable the air intake and air blowing of the electric fan 4a.

[0022] The lower end opening 5a of the module housing 5 is hermetically sealed by the heat sink main body 3a. The driver part 6 is accommodated inside the module housing 5 in a state where it is fixed to the upper face of the heat sink main body 3a.

An annular flange part 5b is formed in the vicinity of the upper end of the module housing 5. By inserting the LED part 2 side into the headlight main body 10 and fitting said flange part 5b to the fitting part of the headlight main body 10, the LED light source module 1 is detachably mounted to the headlight main body 10. With a diameter of 50 mm or less, the module housing 5 is the element with the largest diameter of all the essential elements of the LED light source module 1.

[0023] The length dimension of the heat slug 3b (the protru- sion length from the heat sink 3) is selected such that when the LED light source module 1 is mounted to the headlight main body 10, the LED part 2 is arranged with great posi^¬ tional precision with respect to the reflecting face lib of the reflector 11.

[0024] As described above, the LED light source module 1 is configured to integrally comprise its essential elements: the LED part 2, the heat sink part 3, the active cooling part 4, the module housing 5, the driver part 6, and the power plug 7. In addition, it is configured so as to be freely attach^¬ able to and detachable from the headlight main body 10. Therefore, when it needs to be replaced, it is possible to replace the LED light source module 1 by itself without the headlight main body 10 having to be replaced, as has conven- tionally been the case. Further, this LED light source module 1 has a simple configuration and can therefore be provided at low cost.

[0025] It follows that by using this LED light source module 1 as light source part in an LED head lamp, the costs for the LED head lamp itself can be greatly decreased compared to conventional LED head lamps in which the light source part using an LED could not be replaced by itself. Further, since the light source part can now be dismounted, maintainability of the LED head lamp is greatly improved. This LED light source module 1 can be distributed not only by selling it as part of vehicles with installed LED head lamps, but also by selling it as a spare part for already purchased vehicles. Also, it can also be used not only in head lamps for four- wheeled vehicles, but also in head lamps for two-wheeled ve^¬ hicles .

[0026] In addition, since this LED light source module 1 com- prises - as means for force-cooling the LED part 2 - the heat sink 3, which draws the heat from the LED part 2, and the ac^¬ tive cooling part 4, which cools the heat sink 3, there is no need for a separate heat-dissipation system. The active cool^¬ ing part 4 is provided with an electric fan 4a that cools the heat sink 3 through air blowing, and it can keep the junction temperature of the LED part 2, which has a radiation performance of 1000 lumen, at or under a standard temperature (about 150°C) at which a stable operation of the LED part 2 is pos^¬ sible. It follows that besides being replaceable, the LED light source module 1 also puts forth the radiation perform^¬ ance of 1000 lumen required in cases when the head lamp is designed comprising one module.

[0027] With such an LED light source module 1, the light out- put required for head lamps of vehicles, i.e. at least 1000 lumen per lamp, can be achieved with one light source module.

Therefore, it is not necessary to design a head lamp with a combination of a plurality of light source modules in order to achieve the required light output. By using this LED light source module 1 as general purpose light source in head lamps, it becomes unnecessary to design a different head lamp for each type of vehicle.

[Second Embodiment]

[0028] ext, a second embodiment is described with the help of Fig. 3. Components corresponding to Fig. 1 will be given the same numerals as in Fig. 1 and their explanation will be omitted . [0029] The reflector 21 of the head lamp main body 20 shown in Fig. 3 has a light emission opening 21a, which is a large opening at the front end of the reflector 21, and also com^¬ prises on its rear end a fixing hole 21d for mounting the LED light source module 1. A lens 22 is mounted to the light emission opening 21a. On the fixing hole 21d, a fitting part, which is not shown in the drawings, for freely detachably mounting the LED light source module 1 from behind is formed. The LED light source module 1 is attached to the head lamp main body 20 such that the axis of the heat slug 3b carrying the LED part 2 coincides with the optical axis of the lens 22. An LED part 2 with a carrying angle Θ different from that of the LED chip 2 shown in Fig. 1 is attached to the LED mounting face 3c of the heat slug 3b. The carrying angle Θ of the LED chip 2a in this LED light source module 1 is approxi^¬ mately 0 degrees. In other words, the light emission face of the LED chip 2a is orthogonal to the optical axis of the re^¬ flector 21. In this configuration, the greater part of the light emitted from the LED part 2 can be directly emitted to- wards the front through the lens 12 without being reflected by the reflector 21. Now, in case of such a configuration, a screen plate (light distribution control plate) , which is not shown in the drawings, may be placed between the LED part 2 and the lens 22 in order to control the light distribution pattern on the road surface.

[Third Embodiment]

[0030] ext, a third embodiment is described with the help of Fig. 4. Components corresponding to Fig. 1 will be given the same numerals as in Fig. 1 and their explanation will be omitted .

The LED light source module 1 in this embodiment comprises a control circuit 8 that keeps the junction temperature of the LED part 2 at or under a standard temperature (predetermined temperature lower than the maximum junction temperature) by comparing the forward voltage of the LED chip 2a with the reference voltage V_ref and driving the active cooling part 4 such that these voltages become identical.

A control program based on the voltage-temperature character^¬ istic of the LED part 2 is incorporated into the control cir^¬ cuit 8.

Since diodes - including LEDs - have the characteristic that their forward voltage V_d decreases when the temperature T rises, the forward voltage V_d of the LED chip 2a is fed back to the control circuit, and the active cooling part 4 is driven such that the difference to the reference voltage V_ref is minimized. Thus, unnecessary power consumption due to the cooling process can be prevented and the LED part 2 can effi- ciently be force-cooled with a minimum of electric power.

[0031] The present invention is not limited to the above em^¬ bodiments. Rather, the shape and dimensions of each part as well as the specific configuration of each element can be changed as necessary.

For example, while in the above embodiments, the active cool^¬ ing part 4 uses the electric fan 4a as cooling means, a ther^¬ moelectric element can also be used as cooling means instead of the electric fan 4a. The electric fan 4a and the thermoe- lectric element can also be used in combination.

[0032] Further, while in the above embodiments, the carrying angle Θ of the LED chip 2a is changed by changing the LED carrier 2b, it is also possible to change the carrying angle Θ of the LED chip 2a by changing the angle of the LED mount^¬ ing face 3c of the heat slug 3b (angle with respect to the axis of the heat slug 3b) . [0033] Also, it is not necessary for the heat sink part 3 and the module housing 5 to have a cylindrical outer shape; they can also be rectangular or have any other shape.

[Explanation of Reference Numerals]

[0034]

1 LED light source module for head lamp

2 LED part

2a LED chip

2b LED carrier

3 heat sink part

3a heat sink main body

3b heat slug (heat transmission part) 4 active cooling part

4a electric fan

5 module housing (base)

5b flange part

6 driver part

7 power plug

8 control circuit

10, 20 headlight main body

11, 21 reflector

lib reflective face

lid, 21d fixing hole

12, 22 lens

Claims

1. LED light source module for head lamp, integrally compris^¬ ing :

an LED part having at least one LED chip,

a driver part driving the LED part,

a heat sink part thermally connected to the LED part, an active cooling part force-cooling the heat sink part, a base for arranging the LED part at a predetermined location within a headlight main body, the base being detachably fixed to the headlight main body, and

a power plug for providing the driver part and the active cooling part with electric power.

2. The LED light source module for head lamp according to claim 1, wherein

the heat sink part comprises a heat sink main body integrally linked to the base, and a heat transmission part protruding in the shape of a rod from the heat sink main body, and the LED part is attached to the tip section of the heat transmission part.

3. The LED light source module for head lamp according to claim 1 or 2, comprising a control circuit keeping the junc- tion temperature of the LED part at or under a standard tem^¬ perature by comparing the forward voltage of the LED chip with a reference voltage and driving the active cooling part such that the difference between these voltages disappears.