EP3581849B1

EP3581849B1 - Cooling device for an automotive lighting device and an automotive lighting device

Info

Publication number: EP3581849B1
Application number: EP18382422.6A
Authority: EP
Inventors: Miguel-Angel LOBATO; Alvaro Andres; Francisco Ruiz
Original assignee: Valeo Iluminacion SA
Current assignee: Valeo Iluminacion SA
Priority date: 2018-06-14
Filing date: 2018-06-14
Publication date: 2022-02-23
Anticipated expiration: 2038-06-14
Also published as: EP3581849A1

Description

TECHNICAL FIELD

This invention is related to the field of heat dissipation in automotive lighting devices.

STATE OF THE ART

Light sources generate a big amount of heat which needs to be dissipated, so that the operation of said light sources is not jeopardized. This issue is even more important when light sources are light emitting diodes (LEDs), since temperature has a big impact on the operational properties of said light sources.
Heat sinks with fins are known to solve this problem. A heat sink is located in thermal contact with the light source, and this heat sink is provided with fins, which dissipate the heat coming from the heat sink, so that air surrounding the fins is heated and then wasted.
Sometimes, a fan is also used to create a forced fluid flow which improves the thermal behaviour of this heat sink. Any improvement in the thermal performance of these elements is crucial, due to the small size of modern automotive lighting devices and the increasing number of individual LEDs which are usually used to achieve the different lighting and signalling functionalities.
Document WO2013/153938 describes an automotive lighting device comprising a heat sink having a plurality of fins.

DESCRIPTION OF THE INVENTION

The invention provides a solution for a heat dissipation arrangement which achieves a great thermal performance by means of an automotive lighting device according to claim 1.
Preferred embodiments of the invention are defined in dependent claims.
Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.
In this text, the term "comprises" and its derivations (such as "comprising", etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.
The invention provides an automotive lighting device comprsing a cooling device comprising a heat sink intended to be in thermal contact with the light source, a plurality of fins in direct thermal contact with the heat sink, at least one light source arranged in thermal contact with the heat sink, wherein the cooling device comprises at least four fins, wherein each fin comprises a base in direct contact with the heat sink, the base comprising first and second sides parallel to a first direction and third and fourth sides shorter than the first and second sides, the third side being oriented according to a second direction forming an angle between 25° and 75° with respect to the first direction, wherein the four fins are arranged so that there is a passage parallel to the first direction between two of the four fins and the other two and there is a passage parallel to the second direction between two of the four fins and the other two.
Due to the fact that there is a third side of the fin which forms such an angle with respect to the first and second sides, a secondary flow may be induced between two rows of fins. This secondary flow improves heat dissipation, since fresh air from exterior channels may access the interior channels.
In some particular embodiments, the fourth side is parallel to the third side. This arrangement allows the secondary flow cross more easily the path created between two adjacent rows of fins.
In some particular embodiments, the length of the first side is between 2 and 5 times the distance between the first and second sides.
In these embodiments, the fins are slim enough so that a predetermined flow direction may be defined, as opposed to the case of pins. However, these fins are not too slim, so that many secondary flows may be created between two adjacent rows of fins, thus improving the cooling behaviour of this device.
In some particular embodiment, the heat sink and the plurality of fins are manufactured as a single piece by an injection moulding process.
There may be a great amount of individual fins, so injection moulding may be a good solution for manufacturing such devices. With this method, the material which is not used, between two longitudinally adjacent fins, is saved.
In some particular embodiments, the distance between the fourth side of the base of a fin and the third side of the base of the nearest fin is comprised between 3 and 10 mm.
In these embodiments, adjacent fins are close enough so that the predetermined flow direction is defined but are not too close, so that the secondary flow is allowed to pass between two adjacent fins belonging to the same row.
In some particular embodiments, the distance between a line which includes the first side of a fin and a line which includes the first side of the nearest fin is comprised between 0 and 5 mm.
In these embodiments, a little offset between two adjacent fins of the same row improves the creation and feeding of the secondary flow.
According to the invention, the cooling device comprises at least four fins, each fin comprising first and second sides parallel to a first direction and third and fourth sides shorter than the first and second sides, the third side being oriented according to a second direction forming an angle between 25º and 75º with respect to the first direction, wherein the four fins are arranged so that there is a passage parallel to the first direction between two of the four fins and the other two and there is a passage parallel to the second direction between two of the four fins and the other two. With such an arrangement, two different flows are more clearly created, and the thermal behaviour of the cooling device improves.
In some particular embodiments, the cooling device further comprises a central continuous rib parallel to the first direction.
This continuous rib is intended to separate the cooling flows when more than one light source is to be cooled.
In some particular embodiments, the cooling device comprises four fins at each side of the central rib, wherein in each group of four fins, each fin comprises a first and second sides parallel to a first direction and a third and fourth sides shorter than the first and second sides, the third side being oriented according to a second direction forming an angle between 25º and 75º with respect to the first direction, wherein the four fins are arranged so that there is a passage parallel to the first direction between two of the four fins and the other two and there is a passage parallel to the second direction between two of the four fins and the other two, and there is a further passage parallel to the first direction between two of the fins and the central continuous rib.
This embodiment combines a good thermal behaviour with the continuous rib, so that the thermal performance of the cooling device may be improved for each light source.
In some particular embodiments, the plurality of fins have a top portion smaller than the base.
This pseudo-conical arrangement is advantageous, since the manufacturing process is easier and more robust.
The at least one light source arranged in thermal contact with the heat sink requires a cooling effect. Heat is dissipated by the heat sink and communicated to the fins, where heat is transferred by convection to the surrounding air. In the lighting device of this invention, more than one light source may be arranged, and their heat may be dissipated by such a cooling device.
In some particular embodiments, the automotive lighting device further comprises a first optical element arranged to receive light from the light source and to shape the light into a light pattern projected outside the lighting device.
An optical element is an element that has some optical properties to receive a light beam and emit it in a certain direction and/or shape, as a person skilled in automotive lighting would construe without any additional burden.
In some particular embodiments, the optical element is at least one of a lens, a light guide, a reflector or a collimator.
These optical elements are useful to manage the light produced by the light source and provide uniform outlet.
In some particular embodiments, the optical element is configured to project light in a projection direction which is substantially perpendicular to the first direction.
The arrangement of such a lighting device has a influence on the heat dissipation. Light is usually projected in a horizontal direction, and when the cooling device is arranged so that this projecting horizontal direction is perpendicular to the first direction, which is the direction of orientation of the main flow, it means that the first direction is vertical. When the cooling device is arranged so that the fins are oriented according to the vertical direction, natural convection helps to improve the thermal behaviour of this device.
In some particular embodiments, the light source is a solid-state light source, and in particular a light emitting diode or LED.
The term "solid state" refers to light emitted by solid-state electroluminescence, which uses semiconductors to convert electricity into light. Compared to incandescent lighting, solid state lighting creates visible light with reduced heat generation and less energy dissipation. The typically small mass of a solid-state electronic lighting device provides for greater resistance to shock and vibration compared to brittle glass tubes/bulbs and long, thin filament wires. They also eliminate filament evaporation, potentially increasing the life span of the illumination device. Some examples of these types of lighting comprise semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma or gas.

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

Figure 1 shows a particular embodiment of a cooling device according to the invention.
Figure 2 shows a more detailed view of such a cooling device.
Figure 3 shows a detail of the fins arrangement of a cooling device according to the invention.
Figure 4 shows the automotive lighting device shown in the previous figures mounted on an automotive vehicle.

DETAILED DESCRIPTION OF THE INVENTION

The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.
Accordingly, while embodiment can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.
Figure 1 shows a perspective front view of a particular embodiment of a cooling device 1 according to the invention. This cooling device 1 is intended to be part of a headlamp and comprises a heat sink 2 which is in thermal contact with a plurality of LEDs (not shown) which provide a light beam functionality.
This headlamp also comprises a lens (not shown), which is intended to receive the light produced by the LEDs and project it according to a projection direction dp.
Figure 2 shows a cut view of such a cooling device 1, so that the elements contained in the cooling device 1 may be seen.
In this particular view, the heat sink 2 is in the background of this figure, and a plurality of fins 3 protrude from this heat sink 2, therefore being in thermal contact with it.
As may be seen in this figure, the fins 3 comprise a base in direct contact with the heat sink. This base comprises a first side 31, a second side 32, a third side 33 and a fourth side 34. In this embodiment, the first side 31 and the second side 32 are parallel to a first direction d1, while the third side 33 and the fourth side 34 are shorter than the first and second ones, and are oriented according to a second direction which forms an angle of substantially 40º with respect to the first direction d1.
The first direction d1 is substantially perpendicular to the projecting direction of the lens, so that this first direction d1 is substantially vertical when the cooling device is installed in a lighting device which is in turn in its operation position in an automotive vehicle. This vertical arrangement is advantageous since natural convection creates the main flow 121.
These plurality of fins 3, despite being bevelled, are substantially oriented according to the first direction d1. The fins are elongated, the length according to the first and second sides is substantially 4 times the distance between these first and second sides so the fins define a main direction for the main cooling air flow 121. But the bevelled shape of the fins 3 induces a further secondary flow 122 according to a second direction d2 to mix with the main flow 121, thus improving the cooling efficiency.
As may be seen in this figure, the cooling device 1 further comprises a central continuous rib 4, which is parallel to the first direction. This central continuous rib 4 divides the cooling flow, which is particularly useful in the event of more than one LED. There are several rows of fins at each side of the rib 4, in such a way that a passage for a main flow is created between rows of fins and the rows of fins and the central continuous rib. Further, a secondary flow 122 is created between groups of fins 3, due to the passage created according to the second direction d2.
The general arrangement of this cooling device makes it easy to be manufactured as a single piece by an injection moulding process.
Figure 3 shows a detail of the fins 3 arrangement of a cooling device according to the invention.
In this embodiment, the distance between the fourth side 34 of the base of a fin and the third side 33' of the base of the nearest fin is comprised between 4 and 5 mm. This distance between two adjacent fins is important to let the secondary flow pass between the adjacent fins.
Further, in this embodiment there is a slight offset between these two adjacent fins. The distance between a line 101 which includes the first side 31 of a fin and a line 102 which includes the first side 31' of the nearest fin of the same row of fins is approximately 2 mm. In other embodiments, both lines 101, 102 may be coincident, and the fins be completely aligned, but this offset is sometimes advantageous to achieve a correct induction of the secondary flow.
Figure 4 shows the automotive lighting device 10 shown in the previous figures mounted on an automotive vehicle 100. This lighting device 10, which provides a low beam functionality, may be equipped with powerful LEDs, the heat generated thereby being dissipated by the cooling device 1.

Claims

An automotive lighting device (10) comprising:
- a cooling device (1) comprising:
a heat sink (2) intended to be in thermal contact with the light source,

a plurality of fins (3) in direct thermal contact with the heat sink (2);

- at least one light source (5) arranged in thermal contact with the heat sink (2); wherein:
- the cooling device comprises at least four fins (3), characterised in that each fin comprises a base in direct contact with the heat sink, the base comprising first (31) and second (32) sides parallel to a first direction (d1) and third (33) and fourth (34) sides shorter than the first (33) and second (32) sides, the third side (33) being oriented according to a second direction (d2) forming an angle between 25º and 75º with respect to the first direction (d1), wherein the four fins are arranged so that there is a passage parallel to the first direction between two of the four fins and the other two and there is a passage parallel to the second direction between two of the four fins and the other two.
Automotive lighting device (10) according to claim 1, wherein the fourth side (34) is parallel to the third side (33).
Automotive lighting device (10) according to any of the preceding claims, wherein the length of the first side (31) is between 2 and 5 times the distance between the first (31) and second (32) sides.
Automotive lighting device (10) according to any of the preceding claims, wherein the heat sink (2) and the plurality of fins (3) are manufactured as a single piece by an injection moulding process.
Automotive lighting device (10) according to any of the preceding claims, wherein the distance between the fourth side of the base of a fin and the third side of the base of the nearest fin is comprised between 3 and 10 mm.
Automotive lighting device (10) according to any of the preceding claims, wherein the distance between a line (101) which includes the first side of a fin and a line (102) which includes the first side of the nearest fin is comprised between 0 and 5 mm.
Automotive lighting device (10) according to any of the preceding claims, wherein the cooling device (1) further comprises a central continuous rib (4) parallel to the first direction (d1).
Automotive lighting device (10) according to claim 7, further comprising four fins at each side of the central rib, wherein in each group of four fins, each fin comprises a first (31) and second (32) sides parallel to a first direction (d1) and a third (33) and fourth (34) sides shorter than the first (33) and second (32) sides, the third side (33) being oriented according to a second direction (d2) forming an angle between 25º and 75º with respect to the first direction (d1), wherein the four fins are arranged so that there is a passage parallel to the first direction between two of the four fins and the other two and there is a passage parallel to the second direction between two of the four fins and the other two, and there is a further passage parallel to the first direction between two of the fins and the central continuous rib.
Automotive lighting device (10) according to any of the preceding claims, wherein the plurality of fins have a top portion smaller than the base.
Automotive lighting device (10) according to any of the preceding claims, further comprising a first optical element arranged to receive light from the light source (5) and to shape the light into a light pattern projected outside the lighting device (10).
Automotive lighting device (10) according to claim 10, wherein the optical element is at least one of a lens, a light guide, a reflector or a collimator.
Automotive lighting device (10) according to any of claims 10 or 11, wherein the optical element is configured to project light in a projection direction (dp) which is substantially perpendicular to the first direction (d1).
Automotive lighting device (10) according to any of claims 9 to 12, wherein the light source (5) is a solid-state light source, and in particular a light emitting diode or LED.