FIELD OF THE INVENTION

The present invention relates to an automotive light bulb comprising a carrier arrangement comprising a first main surface and a second main surface opposite the first main surface, a first plurality of solid state lighting elements on the first main surface and a second plurality of solid state lighting elements on the second main surface.

The present invention further relates to a luminaire including such an automotive light bulb.

BACKGROUND OF THE INVENTION

In many lighting applications, traditional incandescent light bulbs are replaced by more energy-efficient alternatives, in particular by solid state lighting (SSL) elements such as semiconductor light emitting diode (LED) devices. Apart from being more energy-efficient, such SSL element-based devices tend to have a superior lifetime compared to incandescent light bulbs, with lifetime improvements by a factor of about 10 being achievable. In addition, the colour temperature of SSL element-based devices can be easily tuned to a colour temperature of 4,000K or above, which gives the device a desirable cool colour.

These characteristics of SSL element-based devices for instance make such devices particularly attractive for automotive lighting applications. However, automotive light bulbs must produce homologated light outputs, i.e. light outputs that comply with required safety standards. This is a far from trivial exercise, as the output characteristics of SSL elements are completely different to the output characteristics of incandescent light bulb filaments.

For instance, in order to mimic the output intensity of an incandescent light bulb filament, a SSL-based device typically must contain a large number of SSL elements as the output intensity of a single SSL element is much smaller than that of an incandescent light bulb filament. Also, SSL elements produce a beam angle of 180° whereas filaments tend to generate omnidirectional light, i.e. emit light over the full 360° range. In addition, because incandescent light bulbs are mounted in a glass housing, beam shaping elements, e.g. for glare-reducing purposes such as the light-blocking cap on automotive light bulbs such as H7, H8, Hl l, H16, HB4 sized light bulbs and so on can be easily mounted on the glass housing. This is not as straightforward for SSL-based devices where encapsulation of the SSL elements may be undesirable for cooling purposes. Overheating of the SSL elements may cause an unwanted change in the colour temperature of the light bulb and may reduce its lifetime.

CN 2026918423 U discloses an automotive light bulb comprising LEDs on opposite sides of a heat sink plate. This light bulb does not produce a homologated light output such that additional beam shaping measures have to be taken in the luminaire, e.g. the vehicle lens unit in which the light bulb is placed. This is undesirable as it is costly and makes the lens unit suitable for a particular type of automotive light bulb only, thus hampering the replacement of the automotive light bulb in case of a light bulb failure.

SUMMARY OF THE INVENTION

The present invention seeks to provide an SSL element-based automotive light bulb capable of producing a homologated light output.

The present invention further seeks to provide a luminaire including such a light bulb.

According to an aspect, there is provided an automotive light bulb comprising a main body; a carrier arrangement extending from said main body, the carrier arrangement comprising a first main surface and a second main surface opposite the first main surface; a first plurality of solid state lighting elements on the first main surface; a second plurality of solid state lighting elements on the second main surface; and a glare -reducing light shielding arrangement on a distal end of the carrier arrangement and arranged to block a part of the luminous output of the solid state elements.

Such a light bulb is capable of producing an omnidirectional luminous output of high intensity due to the presence of a plurality of SSL elements on opposite carrier surfaces whilst at the same time producing a homologated output due to the glare-reducing light shielding arrangement, which mimics the light blocking cap of automotive light bulbs such as H7, H8, HI 1, HI 6, HB4 sized light bulbs and the like.

The light shielding arrangement may form part of the carrier arrangement. In an embodiment, the glare -reducing light shielding arrangement comprises a glare-reducing light shielding member mounted on the distal end of carrier arrangement.

Alternatively, the light shielding arrangement may be separate to the carrier arrangement. In an embodiment, the automotive light bulb further comprises a heat sink portion extending from the main body and enveloping the carrier arrangement, the heat sink portion comprising a first recess exposing the first plurality of solid state lighting elements and a second recess exposing the second plurality of solid state lighting elements, wherein each of the first recess and the second recess comprises a side wall at a distal end of the heat sink portion, wherein said side walls define the glare-reducing light shielding arrangement. This obviates the need for a separate lighting shielding member and ensures a highly efficient cooling of the SSL elements.

The glare -reducing light shielding arrangement preferably is arranged to block luminous output generated at an angle in the range of 0° to at least 20° with the first main surface and second main surface respectively to ensure that the light output of the automotive light bulb is homologated. More preferably, light generated under an angle of up to 35° with the first main surface and second main surface respectively is blocked by the glare -reducing light shielding arrangement.

Preferably, the main body forms part of a heat sink arrangement, which may further include the heat sink portion. This further improves the cooling of the SSL elements of the automotive light bulb.

The carrier arrangement may comprise a single printed circuit board comprising the first main surface and the second main surface opposite the first main surface. This yields a very compact automotive light bulb.

Alternatively, the carrier arrangement may comprise a first printed circuit board comprising the first main surface and a second printed circuit board comprising the second main surface opposite the first main surface for the sake of manufacturing simplicity. A heat sink plate extending from the main body may also be present, wherein the first printed circuit board and the second printed circuit board are mounted on opposite sides of the heat sink plate to further improve heat transfer from the SSL elements.

Each printed circuit board preferably has a thickness of 3 mm or less in order to mimic the diameter of a traditional incandescent or halogen automotive light bulb filament, which ensures that a similar beam pattern is produced.

In an embodiment, the main body is dimensioned such that it does not block the luminous output of the first plurality of solid state lighting elements and the second plurality of solid state lighting elements that is generated under a further angle of at least 30° with a plane perpendicular to the first main surface and the second main surface respectively. This ensures that main body reflects or absorbs a small part of the luminous output of the automotive light bulb only, which ensures that the automotive light bulb closely mimics the emissive characteristics of a filament of an incandescent light bulb.

The main body may house a driver circuit for driving the solid state lighting elements. This obviates the need for a separate driver circuit and contributes to the compactness of the overall automotive lighting arrangement.

Each of the solid state lighting elements preferably has a luminous area having a width not exceeding 4 mm such that sufficient solid state lighting elements can be placed along a length that is similar to the length of a traditional incandescent or halogen automotive light bulb filament, which ensures that a similar beam pattern is produced.

The first plurality of solid state lighting elements preferably is placed along a first length of the first main surface and the second plurality of solid state lighting elements preferably is placed along a second length of the second main surface, said first length and said second length not exceeding 7 mm to ensure that a luminous output profile closely mimicking that of a filament of an incandescent or halogen light bulb is obtained.

According to another aspect, an automotive luminaire comprising the automotive light bulb according to an embodiment of the present invention is provided. Such a luminaire may for instance be a vehicle lens unit.

The automotive luminaire may comprise a fitting into which the automotive light bulb is fitted and a light exit window opposite said fitting, wherein the automotive light bulb is fitted into said fitting such that the light shielding arrangement is proximal to said light exit window to ensure the appropriate homologated luminous output.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail and by way of non-limiting examples with reference to the accompanying drawings, wherein:

FIG. 1 schematically depicts a cross-section of an automotive light bulb according to an embodiment of the present invention;

FIG. 2 schematically depicts an aspect of an automotive light bulb according to embodiments of the present invention;

FIG. 3 schematically depicts a cross-section of an automotive light bulb according to another embodiment of the present invention;

FIG. 4 schematically depicts a cross-section of an automotive light bulb according to yet another embodiment of the present invention;

FIG. 5 schematically depicts a cross-section of an automotive light bulb according to yet an embodiment of the present invention;

FIG. 6 schematically depicts a top view of the automotive light bulb of FIG. 5; and

FIG. 7 schematically depicts a cross-section of an automotive luminaire according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

FIG. 1 schematically depicts a cross-section of an automotive light bulb 1 according to an embodiment of the present invention. The automotive light bulb 1 comprises a main body 30, which for instance may be a metal or metal alloy body acting as a heat sink. In an embodiment, the main body 30 comprises aluminium or an aluminium alloy. A fitting member 35 may be attached to the main body 30 for fitting the automotive light bulb 1 into a luminaire, as is known per se. A carrier 10 extends from the main body 30 and in particular from a protrusion 32 of the main body 30. The carrier 10 may have a thickness of 3 mm or less and may be any suitable type of carrier, e.g. a printed circuit board (PCB) such as a double-sided metal core PCB. The protrusion 32 typically acts as a heat sink portion for the carrier 10 and the solid state lighting elements on the carrier 10 as will be explained in more detail below. The carrier 10 may be mounted in the protrusion 32 in any suitable manner, e.g. using fixing members such as screws, or instead the protrusion 32 may be molded around the carrier 10 to create an intimate fit between the carrier 10 and the protrusion 32. The carrier 10 comprises a first main surface 12 and a second main surface 12'. The first main surface 12 and a second main surface 12' are typically arranged on opposite sides of the carrier 10, i.e. are opposite surfaces of the carrier 10.

The first main surface 12 carries a first plurality of solid state lighting elements 20 and the second main surface 12' carries a second plurality of solid state lighting elements 20'. In an embodiment, the solid state lighting elements 20 are light emitting diodes (LEDs), e.g. inorganic or organic semiconductor LEDs. The first main surface 12 and the second main surface 12' preferably carry the same number of solid state lighting elements 20 and 20' respectively, with the solid state lighting elements 20 and 20' preferably being located in the same location on the first main surface 12 and the second main surface 12' respectively to ensure a symmetrical luminous distribution by the automotive light bulb 1. In case a non-symmetrical luminous distribution is required, the solid state light elements 20 may be placed in a different location on the first main surface 12 compared to the locations of the solid state light elements 20' on the second main surface 12' and/or a different number of the solid state light elements 20 may be placed on the first main surface 12 compared to the number of solid state light elements 20' on the second main surface 12'.

The automotive light bulb 1 further comprises a light shielding portion 40 mounted on a distal end of the carrier 10, i.e. the end of the carrier 10 opposite the protrusion 32 of the main body 30. The light shielding portion may be made of any suitable light absorbing or reflecting material. In an embodiment, the light shielding portion 40 is made of aluminium. The light shielding portion 40 is dimensioned such that light generated by the solid state lighting elements 20 under an angle a or less with the first main surface 12 and the light generated by the solid state lighting elements 20 under an angle a' or less with the second main surface 12' is blocked by the light shielding portion 40. This ensures that the automotive light bulb 1 does not generate direct light under shallow angles along its central axis, as such direct can cause glare and can potentially blind road users travelling towards a vehicle including the automotive light bulb 1, e.g. road users travelling in an opposite direction on another lane of a road used by the vehicle including the automotive light bulb 1.

The values of angles a and a' may be individually optimized depending on the desired light distribution pattern of the automotive light bulb 1. In an embodiment, the angles a and a' have the same (absolute) value. For instance, a and a' are individually chosen to have a value of at least 20°, 30° or about 35° depending on the desired beam pattern of the automotive light bulb 1. Other values of a and a' may of course be contemplated. The light shielding portion 40 may have any suitable shape, e.g. a circular shape or an oval shape.

The protrusion 32 is preferably shaped such that light produced by the solid state elements 20 under an angle β or less and light produced by the solid state elements 20' under an angle β' or less with a plane perpendicular to the first main surface 12 and the second main surface 12' is not blocked by the protrusion 32 to ensure that the automotive light bulb 1 produces a homologated luminous output. The angles β and β' may be the same or different. In an embodiment, the angles β and β' are the same and are at least 40°. Again, it should be understood that other values of β and β' of course may be contemplated depending on the desired beam pattern to be produced by the automotive light bulb 1.

FIG. 2 schematically depicts a particular advantageous arrangement of the solid state lighting elements 20 on the first main surface 12 of the carrier 10. Although not explicitly shown, it should be understood that the same arrangement is preferably chosen for the solid state lighting elements 20' on the second main surface 12' of the carrier 10. Each of the solid state lighting elements 20 has a luminous surface with a width (or diameter) w, with w < 4.0 mm. The solid state lighting elements 20 are preferably spaced along the central axis of the carrier 10 over a distance f, which distance is typically chosen to mimic the length of a filament of a corresponding incandescent or halogen automotive light bulb. In an embodiment, the distance is chosen as f < 7.0 mm. The solid state lighting elements 20 may be placed on the central axis or displaced relative to the central axis by an amount not exceeding 2.0 mm. For instance, in an embodiment, the first main surface 12 and the second main surface 12' each carry three solid state lighting elements 20 and 20' respectively having a luminous surface with a width w of 1.2 mm and spaced over a total length f of 4.5 mm on a double-sided metal core PCB having a thickness of 0.8 mm. It has been found that when this arrangement is chosen in combination with the light shield portion 40 and an appropriately shaped protrusion 32, an SSL element-based automotive light bulb 1 is obtained that closely mimics the (homologated) luminous characteristics, e.g. beam patterns, of traditional counterparts such as corresponding incandescent or halogen automotive light bulbs.

FIG. 3 schematically depicts a cross-section of an automotive light bulb 1 according to an alternative embodiment. The automotive light bulb 1 of FIG. 3 is identical to the automotive light bulb 1 of FIG. 3 apart from the replacement of the single carrier 10 by a carrier arrangement including back-to-back carriers 10 and 10', with the solid state lighting elements 20 placed on the first main surface 12 of the first carrier 10 and the solid state lighting elements 20' placed on the second main surface 12' of the second carrier 10'. The first carrier 10 and the second carrier 10' may be any suitable carrier, e.g. any suitable PCB. The light shielding portion 40 is mounted on the distal end of the carrier arrangement, i.e. on the end opposite the protrusion 32 of the main body 30 in which the carrier arrangement is mounted. Each carrier 10 and 10' may have a thickness of 3 mm or less. In an embodiment, the carrier arrangement has a combined thickness of 3 mm or less.

FIG. 4 shows yet another embodiment of the automotive light bulb 1. The automotive light bulb 1 of FIG. 4 is identical to the automotive light bulb 1 of FIG. 3 apart from the presence of a heat sink plate 34 extending from the main body 30 in between the first carrier 10 and the second carrier 10', such that the first carrier 10 and the second carrier 10' are mounted on opposite sides of the heat sink plate 34. In this embodiment, the protrusion 32 of the main body 30 may be omitted, although it should be understood that alternatively the protrusion 32 may still be present. This embodiment may for instance be used in combination with high power solid state lighting elements 20 and 20' where the heat transfer capabilities of the single carrier 10 as shown in FIG. 1 or the carrier arrangement shown in FIG. 3 are insufficient to prevent overheating of the solid state lighting elements 20 and 20'. The heat sink plate 34 may be made of any suitable thermally conductive material, e.g. a metal such as aluminium or a metal alloy such as an aluminium-based alloy. In an embodiment, the combined thickness of the first carrier 10, the heat sink plate 34 and the second carrier 10' is 3 mm or less.

In the above embodiments, a light shielding portion 40 at a distal end of the carrier arrangement is used to reduce the risk of glare and to produce a homologated light output with the automotive light bulb 1. However, it should be understood that such a homologated luminous output may also be produced using alternative measures at the distal end of the carrier arrangement. A cross-section of such an example alternative embodiment is shown in FIG. 5, with FIG. 6 showing a top view of this arrangement. The automotive light bulb 1 of FIG. 5 is identical to the automotive light bulb of FIG. 1 apart from the omission of the light shielding portion 40 at the distal end of the carrier 10. Instead, the protrusion 32 envelopes the carrier 10 and comprises a first recess 36 for exposing the solid state lighting elements 20 on the first main surface 12 and a second recess 36' for exposing the solid state lighting elements 20' on the second main surface 12. The first recess 36 typically comprises a first side wall 37 proximal to the main body 30 and a second side wall 38 distal to the main body 30, i.e. the first side wall 37 is opposite the second side wall 38. The second recess 36' typically comprises a first side wall 37' proximal to the main body 30 and a second side wall 38' distal to the main body 30, i.e. the first side wall 37' is opposite the second side wall 38'.

The respective second side walls 38 and 38' are typically shaped to perform the function of the light shielding portion 40, i.e. to block the light generated under angles a and a' or less by the solid state lighting elements 20 and 20' respectively as explained in more detail in the detailed description of FIG. 1.

The respective first side walls 37 and 37' are typically shaped to ensure that light produced by the solid state elements 20 under an angle β or less and light produced by the solid state elements 20' under an angle β' or less with a plane perpendicular to the first main surface 12 and the second main surface 12' is not blocked as explained in more detail in the detailed description of FIG. 1.

The dimensions of the respective first side walls 37 and 37' and the respective second side walls 38 and 38' may be individually optimized to deliver the desired luminous output characteristics of the automotive light bulb 1. In case of a symmetrical luminous distribution the first side wall 37 and the first side wall 37' typically have the same dimension. Also, the second side wall 38 and the second side wall 38' typically have the same dimension. In case of a desired asymmetrical luminous distribution, the first side wall 37, the first side wall 37', the second side wall 38 and the second side wall 38' all may have different dimensions.

In FIG. 5, the respective side walls of the first recess 36 and the second recess 36' are shown as slanted side walls by way of non-limiting example. It should be understood that it is equally feasible for the first recess 36 and the second recess 36' to have vertical or upright side walls. It should furthermore be understood that the single carrier 10 in FIG. 5 may be replaced by the carrier arrangement shown in FIG. 3 or FIG. 4 without departing from the present invention.

The automotive light bulb 1 may be a H7, H8, Hl l, H16, HB4 sized light bulb or any other size automotive light bulb requiring a glare reducing member to obtain a homologated light output, e.g. head light bulbs, fog light bulbs and the like.

The inventor have made a comparison between the homologated luminous distribution of a prior art HI 1 halogen fog light bulb (top pane) and a HI 1 automotive light bulb according to an embodiment of the present invention (bottom pane). It can be immediately recognized that the automotive light bulb 1 of the present invention is capable of producing a homologated luminous output that closely resembles the luminous output of a prior art HI 1 halogen fog light bulb.

FIG. 7 schematically depicts a luminaire 100 comprising an automotive light bulb 1 according to an embodiment. The luminaire 100 comprises a fitting 120 engaging with the fitting member 35 of the automotive light bulb 1. The luminaire further comprises a housing with a light exit window 130 and a reflector 110 for directing light generated by the automotive light bulb 1 towards the light exit window 130. The light exit window 130 may comprise additional optics, e.g. may act as a lens to produce a light beam with the desired light beam characteristics. The light exit window 130 may be realized in any suitable material, e.g. glass or an optical grade transparent polymer material. Similarly, the reflector 110 may be realized in any suitable material, e.g. a reflective metal such as silver or aluminium.

In an embodiment, the glare reducing member at the distal end of the carrier arrangement of the automotive light bulb 1, i.e. the light shielding portion 40 or the distal side walls 38, 38', are arranged opposite the light exit window 130 such that light produced by the solid state lighting elements 20, 20' under a shallow angle with the carrier surfaces 12 and 12' respectively cannot directly escape the luminaire 100 through the light exit window 130, thereby reducing the risk of an opposing road user suffering from glare produced by the luminaire 100.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. 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.