LED lamp unit, in particular for automotive lamps

Abstract

An automotive LED lamp unit includes a plate-like mounting member, LED light sources arranged on two opposite sides of the plate-like mounting member, and a heat sink. The heat sink includes cooling fins and a tapered portion facing the LED light sources and being connected to one end of the plate-like mounting member.

Claims

1. An automotive LED lamp unit, comprising: a plate-like mounting member comprising two opposing sides and side edges between the two opposing sides; LED light sources arranged on the two opposing sides of the plate-like mounting member; a heat sink, comprising: a tapered end facing the LED light sources and being connected to one of the side edges at one end of the plate-like mounting member to achieve the emission of the LED light in a large solid angle; a non-tapered end, wherein a thickness of the non-tapered end is more than twice the thickness of the plate-like mounting member; and cooling fins; an electrical connector base, wherein the heat sink is arranged between the electrical connector base and the plate-like mounting member.

2. The LED lamp unit of claim 1, wherein the cooling fins define gaps extending between the tapered end and a backside of the heat sink away from the LED light sources.

3. The LED lamp unit of claim 2, further comprising a fan arranged at the backside of the heat sink.

4. The LED lamp unit of claim 3, wherein the plate-like mounting member, the LED light sources, the heat sink, and the fan together comprise a maximum diameter and a maximum length of a standard automotive bulb.

5. The LED lamp unit of claim 4, wherein the maximum diameter comprises 15 mm and the maximum length comprises 50 mm.

6. The LED lamp unit of claim 1, wherein the plate-like mounting member is formed integrally with the heat sink.

7. The LED lamp unit of claim 1, wherein the plate-like mounting member is mechanically connected to the heat sink.

8. An automotive headlamp comprising the LED lamp unit of claim 1 and a reflector that at least partly surrounds the LED lamp unit.

9. An automotive lamp, comprising: an LED lamp unit, comprising: a plate-like mounting member comprising two opposing sides and side edges between the two opposing sides; LED light sources arranged on the two opposing sides of the plate-like mounting member; a wedge-shaped heat sink, comprising: a tapered end facing the LED light sources and being connected to one longitudinal end of the plate-like mounting member to achieve an emission of LED light in a large solid angle; a non-tapered end, wherein a thickness of the non-tapered end is more than twice the thickness of the plate-like mounting member; and cooling fins; an electrical connector base, wherein the heat sink is arranged between the electrical connector base and the plate-like mounting member; and a reflector that at least partly surrounds the LED lamp unit, wherein the plate-like mounting member, the LED light sources, and the heat sink are completely arranged inside a volume surrounded by the reflector.

10. The automotive headlamp of claim 9, wherein the automotive LED lamp unit further comprises a fan arranged about a backside of the heat sink, the backside being located away from the LED light sources.

11. The automotive headlamp of claim 10, wherein the fan is completely arranged inside the volume surrounded by the reflector.

12. The automotive headlamp of claim 10, wherein the cooling fins define gaps extending between the tapered end and the backside of the heat sink.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment described herein after. In the drawings:

(2) FIG. 1 shows a sectional view of an example of the LED lamp unit according to the invention;

(3) FIG. 2 shows a perspective view of a part of the lamp unit without the fans;

(4) FIG. 3 schematically shows an arrangement of the proposed LED lamp unit in a headlamp lamp;

(5) FIG. 4 shows a view of a halogen lamp which is to be replaced by a LED lamp;

(6) FIG. 5 shows an example of a LED lamp according to the invention replacing the halogen lamp of FIG. 4;

(7) FIG. 6 schematically shows an arrangement of a further embodiment of the proposed LED lamp unit in a headlamp lamp; and

(8) FIG. 7 schematically shows a sectional view of a further example of the LED lamp unit according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) FIG. 1 shows an example of the proposed LED lamp unit in a sectional view. In this example the LED lamp unit 10 comprises two high brightness LED's 2 mounted back to back on a very thin metal plate 1 and emitting in opposite directions or half spaces. A heat sink 3, 4 is mounted perpendicular to the metal plate 1 or LED surfaces on opposite sides at the edges of the metal plate 1. The heat sinks 3, 4 comprise several cooling fins 7 extending between the LED's 2 and the fans 5, 6 mounted at the backsides of the heat sinks 3, 4. The gaps 8 formed between the cooling fins 7 of the heat sinks 3, 4 are opened towards the fans 5, 6 and towards the LED light sources 2. With such an arrangement, a maximum cooling effect can be achieved by blowing air in opposite directions toward the LED's 2.

(10) In the embodiment of FIG. 1, the heat sinks are tapered at their ends facing the LED's 2 in order to achieve the emission of the LED light in a large solid angle. The electrical connections to the LED's and the fans are as well as the electrical connector base are not shown in the figure. These electrical connections may be made by isolated lines attached to the metal plate 1 and the heat sinks 3, 4 or to cooling fins 7 of these heat sinks.

(11) 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, 6including the heat sinks and fansis 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.

(12) FIG. 2 shows a perspective view of an example of such a lamp unit in which the fans 5, 6 are not depicted. In the figure, the heat sinks 3, 4, the metal plate 1 forming the support member as well as one of the LED's 2 can be recognized. The figure schematically also shows the cooling fins 7 and gaps 8 between these cooling fins.

(13) FIG. 3 and FIG. 6 show examples of a headlamp in which such a lamp unit 10 is mounted instead of an halogen bulb. FIG. 3 refers to a lamp unit with two heat sinks, FIG. 6 to a lamp unit with only one heat sink. The headlamp comprises a reflector 11 for reflecting the light emitted by the LED's of lamp unit 10 towards the emission direction 12 of the automotive lamp. The provision of only one heat sink on the emission side of the lamp has the advantage that a light distribution of the emission of the lamp can be achieved which is identical to the light distribution when using a halogen or incandescent bulb. In case of two heat sinks as in FIG. 3, a portion of the LED light might be blocked by the second (inner) heat sink which is necessary to achieve such identical light distribution with the reflector.

(14) 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 FIG. 4 has to be replaced with the designated available space. The white area shown is the available space that can be used for placing LEDs, heat sink and two fans. All these components should not overlap with the hatched area shown by solid parallel lines otherwise it will be an optical barrier. The dimensions indicated in the figure are in millimeters.

(15) The heat sink design for such system is shown in FIG. 5. The two fans 5, 6 are shown at the two ends of the heat sink 3, 4 by rectangles schematically. These fans 5, 6 are located 1 mm away from the heat sink 3, 4. As shown the LEDs 2 are placed on the two opposite sides of the base plate 1 of the heat sink. The total heat dissipation of these LEDs 2 is assumed to be 6 W. The reference plane 13 in FIG. 4 is the separation area between the front and back side of halogen lamp and this is modeled by a separation plane 13 shown in FIG. 5. The heat sink 3, 4 including the base plate 1 is made of copper with thermal conductivity of 400 W/mK. As shown in FIG. 5, these components are placed in an internal air domain 14 with the length, width and depth of 110 mm75 mm40 mm, respectively.

(16) The characteristics of fan 5 are identical to UF3H3-700 which is a sunon fan with the maximum air flow of 16.27 l/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 l/min at zero static pressure. The pressure versus flow rate curves of these fans were taken into account in the simulation.

(17) Obviously, the left side of FIG. 4 is the back side of the car lamp where it is exposed to temperature and flow pattern caused by car engine. The right side of FIG. 4 is exposed to outdoor environment. In order to simulate these external conditions the boundary conditions depicted in FIG. 5 is applied. The simulation was carried out in ANSYS CFX simulation environment using Shear stress transport turbulence model. The surface to surface radiation model was included to account for radiation transport mechanisms.

(18) 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:

(19) 1. Heat removal from the cooling channels of the heat sink to the air

(20) 2. Heat removal from the middle of the heat sink at LED positions

(21) 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.

(22) FIG. 7 shows a further example of the proposed LED lamp unit in a sectional view. In this example two high brightness LED's 2 are mounted on separate support members 15 which are attached in this example at an angle of 120 to one another on a side face or the heat sink 3. This angle is not restricted to 120 and is preferably selected in the range between 20 and 160. The heat sink is connected to the electrical connector base 16. Due to this arrangement the LED's also emit in opposing half spaces (to the upper side and to the lower side in the figure). Such an embodiment is advantageous for the use in a signaling lamp since most of the light emitted by the LED's 2 is directed to the central portion of the reflector (not shown in the figure) and is thus emitted by reflection at the reflector towards the emission direction of the lamp.

(23) 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.

LIST OF REFERENCE SIGNS

(24) 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