The present invention relates to a LED lamp unit comprising at least two LED light sources arranged at two opposing sides of the lamp unit to emit in opposed half spaces, as well as a headlamp or signaling lamp (=automotive lamps), wherein the LED lamp unit is completely arranged inside a volume at least partly surrounded by a reflector of the automotive lamp such that light emitted from the LED light sources is directed by said reflector towards a light emission direction of said lamp.
Halogen, xenon and incandescent bulbs used for automotive headlamp applications have high brightness filaments with precise geometry. On the other hand the energy efficiency as well as the lifetime is significantly lower compared to other light source technologies, especially LED technology.
Incandescent bulbs that are used for automotive signaling lamps have less brightness and the tolerances of the geometry are less critical. However due to the limited lifetime, it is of interest to make used of LED technology for signaling lamps.
Currently LED's are available with brightness levels comparable or even significantly higher compared to automotive halogen and incandescent bulbs. While LED's emit only in one half of the sphere, the coil of an halogen and incandescent bulb emits in the complete hemisphere. Thus the headlamp optic developed for filament bulbs does not fit to the emission pattern of a single LED. Multiple high brightness LED's have to be arranged in such geometry that the emission pattern as well as the geometry resembles the corresponding emission pattern and geometry of a filament bulb and makes efficient use of the existing automotive optical components.
U.S. 2010/0244649 A1 discloses a LED lamp unit for automotive lamps in which two LED's are mounted at two opposing sides of a common mounting plate to emit in opposed half spaces. The mounting plate is thermally connected at one side to a heat sink comprising several cooling fins. A fan is arranged at the backside of the heat sink to generate a forced air cooling of the heat sink. In the proposed automotive lamp, the two LED's are arranged inside of the volume surrounded by the reflector of the lamp whereas the large heat sink and the fan are arranged outside. Such a lamp unit requires a different construction of the lamp compared with the known constructions using halogen and incandescent bulbs.
It is an object of the present invention to provide a lamp unit which can simply replace known halogen and incandescent bulbs in automotive lamps without changing the construction of such a lamp.
The object is achieved with the LED lamp unit according to claim 1. Claim 12 relates to an automotive lamp which can be a signaling or headlamp including the LED lamp unit according to claim 1. Advantageous embodiments of the LED lamp unit and headlamp or signaling lamp are subject matter of the dependent claims or are disclosed in the subsequent portions of the description and preferred embodiment.
The proposed LED lamp unit comprises at least two LED light sources, an electrical connector base for electrical connecting the LED light sources and a heat sink in thermal contact with the support member(s) of the LED light sources. The LED light sources are arranged between the electrical connector base and at least a portion of the heat sink at two opposing sides of the lamp unit to emit in opposed half spaces. Optionally, an electrically operated fan for forced air cooling of the heat sink can be arranged at the heat sink in order to increase the cooling power.
In an advantageous embodiment the at least two LED light sources are arranged on two opposing sides of a common plate-like support member, in particular a mounting plate, to emit in opposed half spaces or directions. The electrical connector base and the heat sink in thermal contact with the support member are arranged on opposing side edges of the support member.
When the proposed LED lamp is mounted in a headlamp or signaling lamp, at least a portion of the heat sink is thus arranged between the LEDs and the light emission side of the headlamp, blocking part of the light emitted by the LEDs directly towards this light emission side. This has the advantage that the dazzling effect of the lamp is reduced.
With such a construction of the LED lamp unit an illumination into both opposing half spheres is achieved similar to the illumination of a halogen and incandescent bulb. The arrangement of at least part of the heat sink on the side opposite to the electrical connection base allows an elongated shape an dimensions similar to those of known halogen and incandescent bulbs for automotive lamps. The LED lamp can thus simply replace known halogen and incandescent bulbs in automotive lamps without changing the construction of such a lamp.
In a preferred embodiment two separate heat sinks are arranged at two opposing edges of the plate-like support member in thermal contact with the support member. One of these heat sinks is thus arranged between the electrical connector base and the support member. The heat sinks may comprise several cooling fins. In order to improve the cooling power, an electrically operated fan is arranged at one or both of the heat sinks such that the fan generates a flow of cooling gas, in particular cooling air, through gaps between the cooling fins of the heat sink towards the LED light sources.
With this arrangement of two heat sinks at both opposing edges of the common plate-like support member an elongated shape of the LED lamp unit can also be achieved similar to the elongated shape of a halogen or incandescent bulb. The use of fans at both opposing ends of the heat sinks provides an effective cooling of the whole LED lamp unit. Due to this construction and effective cooling such a LED lamp unit can be designed with small dimensions similar to those of known halogen and incandescent bulbs for automotive lamps even if operated with high power and can thus replace such lamps without any further modification of the optical system and construction of the lamp.
In a preferred embodiment, the two heat sinks are formed such that the gaps between the cooling fins are opened towards the support member/LED light sources and towards the fans. These gaps thus form continuous cooling channels extending between the fan and the LED light sources. With such an arrangement the cooling gas or cooling air is forced from two opposing sides through the heat sinks towards the LED light sources and also directly cools these LED light sources. The counter flow of the cooling gas or cooling air from both sides results in a further improved cooling of the lamp unit. Due to this efficient cooling the heat sinks can be dimensioned in an even compacter form and/or the lamp can be driven with higher electrical power.
Preferably the whole LED lamp unit even if including the two fans, the two heat sinks and the intermediate support member with the LED light sources has a dimension in a longitudinal direction, i.e. the direction between the axes of the two fans, of less than 80 mm, more preferably of ≤50 mm, and a diameter perpendicular to this longitudinal direction of less than 20 mm, more preferably ≤15 mm. The diameter in this context refers to the direction of longest extension of the lamp unit perpendicular to the above longitudinal direction.
The support member is preferably formed integrally with the heat sink(s) but may also be mechanically connected in any other way to the heat sink(s). The support member is made of a thermally high conductive material, preferably of a metal plate.
The proposed LED lamp unit may replace for example commonly used H7 bulbs in automotive headlamps or in future even Xenon high intensity discharge bulbs. Nevertheless, the LED lamp unit may also be used in other lamps, in particular in cornering light or fog light reflectors.
A proposed headlamp or signaling lamp comprises at least a reflector and the proposed LED lamp unit. In such a headlamp or signaling lamp the LED lamp unit is completely arranged inside of the volume surrounded by the reflector, such that light emitted by the LED light sources is directed by said reflector towards the light emission direction of the lamp.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment described herein after. In the drawings:
In the embodiment of
The whole lamp unit 10 is designed to have a dimension which fits in every state of the art automotive low beam, high beam, cornering light or fog light reflector. Considering a H7 retrofit for example, the maximum diameter D of the heat sink 3, 4 plus fan 5, 6 is 15 mm. The maximum length L of the LED lamp unit measured along the longitudinal direction connecting the axes 9 of the fans 5, 6—including the heat sinks and fans—is 50 mm. When introducing such a LED lamp unit in a H7 headlamp a sharp cut offline can be achieved and a legal low beam pattern is possible at a fraction of the power consumption of the corresponding halogen or incandescent light source.
In the following section, the feasibility of the proposed solution is shown by means of a case study performed in the simulation environment ANSYS. Assuming the H7 lamp of
The heat sink design for such system is shown in
The characteristics of fan 5 are identical to UF3H3-700 which is a sunon fan with the maximum air flow of 16.27 1/min at zero static pressure. Fan 6 is chosen to be UF3F3-700 from the same fan supplier with the maximum air flow of 8.75 1/min at zero static pressure. The pressure versus flow rate curves of these fans were taken into account in the simulation.
Obviously, the left side of
As a result of the simulation a maximum temperature of 140° C. could be reached at the LED positions that could be easily handled by LUXEON F LEDs. The heat removal from the heat sink to the air occurs in two steps:
The first heat transfer mechanism is enhanced through fans operating towards each other, leading to “boundary layer thinning” which improves the heat transfer coefficient on the surface of the cooling channels. The second heat transfer mechanism is again enhanced through the fans operating in this unique configuration. Two main air flow streams meet each other at high speed in the middle of the heat sink where LEDs are positioned, leading to “boundary layer removal” at the hottest point of the system which highly increases the heat transfer rate. This phenomenon is similar to jet cooling of hot spots where the boundary layer is removed through impinging air flow on a perpendicular surface. In this invention, the perpendicular surface is created or mimicked by a fan operating in an opposing direction.
While the invention has been illustrated and described in detail in the drawings and forgoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. The heat sinks may also be formed different than in the figures. The gaps formed between the cooling fins may extend parallel to one another and parallel to the longitudinal direction of the lamp unit. Nevertheless, these gaps may also be inclined to one another and to this longitudinal direction. Although the figures only show two opposing LED light sources, there may also be arranged more than 2 LED's. In the claims, the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In particular, the features of claims 7 to 11 can be freely combined with the features of all preceding claims. Any reference signs in the claims should not be construed as limiting the scope of the claims.
1 metal plate
2 LED
3 heat sink
4 heat sink
5 fan
6 fan
7 cooling fin
8 gap
9 fan axis
10 LED lamp unit
11 reflector
12 emission direction
13 reference/separation plane
14 internal air domain
15 support member
16 electrical connector base
This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/IB13/054568, filed on Jun. 03, 2013, which claims the benefit of U.S. Provisional Patent Application No. 61/655,001, filed on Jun. 04, 2012. These applications are hereby incorporated by reference herein.
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WO2013/182973 | 12/12/2013 | WO | A |
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