WO2015058940A1

WO2015058940A1 - Lighting device for a motor vehicle, comprising a multifunctional luminaire

Info

Publication number: WO2015058940A1
Application number: PCT/EP2014/071118
Authority: WO
Inventors: Matthias Brendle
Original assignee: Automotive Lighting Reutlingen Gmbh
Priority date: 2013-10-25
Filing date: 2014-10-02
Publication date: 2015-04-30
Also published as: DE102013221743A1

Abstract

The invention relates to a lighting device (10) for a motor vehicle, comprising a first light source (16) which generates light of a first color, at least one second light source (18) which generates light of a second color, and an optical system (26) which generates a first regulation-compliant distribution of light when only light of the first light source is supplied into the optical system and which generates a second regulation-compliant distribution of white light when light of the second light source is supplied into the optical system. The lighting device is characterized in that a location (8) of the first color in a CIE color diagram lies on a first side of an ECE white field (5), a location (9) of the second color in the CIE color diagram lies on a second side of the ECE white field, and a straight line (7) connecting the two locations passes through the ECE white field.

Description

Lighting device for a motor vehicle with a multi-function light

The present invention relates to a lighting device for a motor vehicle according to the preamble of claim 1.

Such a lighting device is known per se and has a first light source, a second light source and an optical system. The first light source generates light of a first light color. The second light source generates light of a second light color. In each case the light from at least one of said light sources is fed into the optical system. The optical system is configured to generate a first light distribution conforming to the rules when only light of the first light source is fed into the optical system, and is adapted to generate a second white light color compliant second light distribution when the light from the second light source enters the optical system optical system is fed.

In the prior art, the first light color is the yellow of a flashing light distribution and the second light color is the white of a daytime running light distribution.

In recent years, more and more lighting functions such as daytime running lights, flashing lights, dynamic cornering lights, cornering lights or anti-glare high beams have been integrated into automotive lighting systems. Due to the large number of structures required for this purpose, such as light sources, light guides, reflectors, lenses and the like, the available installation space in the illumination device is becoming increasingly scarce.

As a light source LEDs are increasingly used. This applies both to signal light functions and to headlight functions such as low beam and high beam. The achievable with light-emitting diodes are usually smaller than achievable with gas discharge lamps luminance. In order to generate luminous flux with light-emitting diodes which are comparable to the high luminous fluxes of gas-discharge lamps, larger optical surfaces are required. Examples of optical surfaces are the coupling surface of a light guide, the surface of a luminaire reflector or the surface of a lens. The widespread use of LEDs thus exacerbates the problem of shrinking installation space.

In this context, it is also known to use in the lighting device multi-function light modules, which are characterized in that the same optical surfaces for different light functions and thus used multiple times.

With regard to light modules for signal light functions, it is above all position light, daytime running light and flashing light that can be combined in such a way that the same optical surfaces are used for generating the associated light distributions.

This possibility results from the similarity of the shape of each light distribution to be generated.

Due to the different light colors yellow for flashing light and white for daytime running lights and position light, however, different bulbs are needed. When using light-emitting diodes, these are thus yellow light-emitting light-emitting diodes and white light-generating light-emitting diodes. In the following, light-emitting diodes are also designated by the color of the light generated by them, that is to say, for example, as white, yellow, blue or red light-emitting diodes.

The yellow as the white light is usually generated with blue emitters, the blue light is converted to yellow LEDs by a comparatively thick phosphor converter layer in yellow light. For white light-emitting diodes, a comparatively thinner phosphorus converter layer is used, which converts only part of the blue light into yellow light. The initially remaining blue portion then gives, together with the proportion converted into yellow light, the white light color.

In the known illumination device, a light module is used, in which the first light source is formed by a plurality of yellow light emitting diodes and the second light source by a plurality of white light emitting diodes. In order to couple the luminous fluxes of both light sources, for example, into one and the same optical waveguide in order to use this multiple times, a correspondingly large optical surface in the form of the light entry surface of the optical waveguide is required. In general, the optical fiber cross sections must be almost doubled compared to cross sections where they are only needed to fulfill a lighting function. This entails long process times in the manufacture of the light guide and other disadvantages (weight, space).

Against this background, the object of the invention is to specify an illumination device of the type mentioned above, in which optical surfaces of an optical system used to generate a plurality of light distributions are smaller than in the prior art. An example of such an optical surface is the coupling surface of a light guide required for coupling in the differently colored light of several light sources

This object is achieved with the features of claim 1.

The invention is characterized in that a color locus of the first light color in a CIE color diagram lies on a first side of an ECE white field, a color locus of the second light color in the CIE color diagram lies on a second side of the ECS white field opposite the first side, and a connecting line of the two color loci passes through or at least touches the ECE white field. The letters CIE are an abbreviation for Commission Internationale de l'Éclairage, ie for the International Commission on Illumination. ECE homologation is a supranational system for the registration of vehicles and vehicle parts.

Also known as a standard color chart, the CIE color chart is used to metrologically characterize colors. Each color is characterized by a pair of numbers.

Blending light of a color location of the first color of light located in the CIE color chart on a first side of an ECE white field with light of a color location of a second color of light located in the CIE color chart on a first side opposite second side of the ECS white field , a mixed color can be generated, which lies on the connecting line of the two color loci. When this straight line passes through the ECE white field, in particular white light can be generated.

By way of illustration and without limitation of generality, it is assumed below that the first light color is yellow and the second light color is blue. With the yellow light alone, a flashing light function can be realized. By adding blue light matching color location and appropriate luminous flux results in white light with which a position light distribution and / or a daytime running light distribution can be generated.

The light-emitting diodes and light sources, which generate light of a certain color, are referred to below with this color. Yellow light-emitting LEDs are therefore referred to as yellow LEDs, blue light-emitting LEDs as blue LEDs.

In the invention, at least individual yellow LEDs are used several times, in which they are turned on both for the generation of the flashing light distribution as well as for the generation of a light distribution of white light color.

By this multiple use of the yellow light source, it is sufficient if the second light source generates only a smaller luminous flux than in the prior art, in which the second light source must generate the required for the white light distribution luminous flux alone.

As an example, again a yellow flashing light distribution and a white light distribution, in particular a daytime running light distribution is considered. Both light distributions require about the same amount of luminous flux, which are generated in the example considered each of n light-emitting diodes.

In the prior art, n yellow light-emitting diodes are required as the first light source and n white light-emitting diodes as the second light source. The light entry surface of a light guide, which forms the optical system or forms part of it, must be correspondingly large. The optical system may also include, for example, a cover plate provided with scattering structures. In particular, the light entry surface must be at least as large as the sum of all the light exit surfaces of the 2n light emitting diodes.

In contrast, in the considered example in which a light distribution with n light-emitting diodes is generated, the invention has fewer total light-emitting diodes. If all the LEDs provide the same luminous flux with each other, the invention comes with n yellow and n / 2 blue LEDs. The daytime running light distribution is then generated by operating n / 2 yellow light-emitting diodes with n / 2 blue light-emitting diodes together. The light entry surface of the light guide, which here represents an example of an optical surface of the optical system, must therefore only be as large as 3/2 n light exit surfaces of a single light-emitting diode in the example considered. Here it was assumed that the LEDs are the same size and generate the same luminous flux. The advantage of a reduced number of light-emitting diodes required and a reduced total area of their light-emitting surfaces, however, also results from this particular example.

A preferred embodiment is characterized in that the first light color is yellow and the second light color is blue.

It is also preferable that the yellow has a color locus in an ECE range for turn signals.

It is also preferred that the second light color is a blue having a wavelength which lies in the wavelength range between 470 nm and 505 nm, in particular between 480 nm and 500 nm.

It is also preferable that the yellow light-emitting light-emitting diodes are based on the same blue-emitting emitters as the blue light-emitting light-emitting diodes.

It is also preferable that the yellow light-emitting LEDs have a phosphor converter layer resting on the blue light emitting emitters.

It is also preferable that the first light color is red and the second light color is blue.

It is also preferable that the first light source has n light-emitting diodes and the second light source has light-emitting diodes, m being less than n.

It is also preferred that the LEDs of the first light source and the second light source are arranged in common on a one-piece circuit board, which is mounted on a heat sink.

It is also preferred that the light exit surfaces of the LEDs are opposite to an optical surface of an optical system.

It is also preferred that the optical surface is a light entry surface of the optical system, so that the light emitted by the light emitting diodes enters the optical system via the light entry surface.

It is also preferred that the optical system has one or more light guides and / or one or more concave mirror reflectors and / or one or more lenses.

It is also preferable that the first light distribution is a flashing light distribution and the second light distribution is a daytime running light distribution or a position light distribution.

It is also preferred that the first light source consists of a first group of light-emitting diodes and a second group of light-emitting diodes, the first group being switched on and off by a first switch of the lighting device, and the second group being switched on and off by a second switch of the lighting device switched off and the second light source is switched on and off by a third switch of the lighting device.

Further advantages will become apparent from the following description, the drawings and the dependent claims. It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

Show, in schematic form:

Figure 1 is a standard color chart with different color fields;

Figure 2 shows an embodiment of a motor vehicle lighting device according to the invention;

FIG. 3 shows a shape of rule-compliant light distributions; and

Figure 4 is an electrical circuit diagram of a lighting device according to the invention

In this case, the same reference numerals in different figures denote the same or at least functionally comparable elements.

FIG. 1 shows a CIE color diagram, also referred to as a standard color chart, for the metrological characterization of colors. Each color has a red X, a green Y and a blue Z. For the standard color chart, the reds are plotted on the abscissa and the green on the ordinate. The blue component results in each case mathematically by subtracting the sum of red component and blue component of the value 1 and therefore lacks in the two-dimensional representation.

Each point of the horseshoe-shaped surface 1 represents a color location. The curved line 2 delimiting the horseshoe-shaped surface is called the spectral color line. On it lie the monochromatic colors, that is, the colors of light, which only has wavelengths from a narrow range. On line 2, bottom left, are the light colors with short wavelengths. The lower left end point 3 corresponds to the blue-violet end of the spectrum of visible light. If you go through the spectral color line clockwise, the wavelengths are getting longer. The right end point 4 corresponds to the red end of the spectrum of visible light.

Within the horseshoe-shaped area are the color locations of mixed colors. In the center of the horseshoe-shaped surface arises as a mixed color white. In the color diagram there is an ECE white field 5 for the daytime running light functions and position light functions as well as the yellow field 6 for the flashing light function.

Blending light of a color location of the first color of light located in the CIE color chart on a first side of the ECE white field with light of a color location of a second color of light located in the CIE color chart on a second side of the ECS white field opposite the first page , a mixed color can be generated, which lies on the connecting line of the two color loci. When this straight line passes through the ECE white field, in particular white light can be generated.

In the examples shown in FIG. 1, the color loci of the first light color lie in the ECE yellow field 6, respectively, and the color loci of the second light color lie on the spectral color line in the range of blue to blue-green colors, ie in the range from 470 nm to 505 nm, in particular in the range of 480 nm to 500 nm.

The intersection of the connecting lines 7 of the

color loci

8 and 9 with the ECE white field 5 provides the set of all color loci in the ECE white field, which can be mixed with light from the

color loci

8 and 9. The location of the resulting color locus on the straight line 7 depends on the luminous fluxes. Increasing the luminous flux of the color locus 9 causes a shift to the left, while increasing the luminous flux of the color locus 8 causes a shift to the right.

The color location of the white mixed color on the connecting line between the color loci of the blue and the yellow LEDs is determined by the ratio of the electrical currents with which the blue and the yellow LEDs are operated. This applies because the luminous flux depends on this operating current. If the electrical operating currents of the respective light-emitting diodes are adapted to the actual color locations of the light-emitting diodes, which is possible by a color location measurement, large tolerances can be permitted, in particular when choosing the color location of the blue light source.

A theoretically also possible additive color mixtures from the three primary colors red (R), green (G) and blue (B), which would theoretically be possible by an arrangement of RGB light emitting diodes and because of the dissemination of this method would be closer than the solution presented here , is difficult to realize. This is because the ECE yellow area is at the edge of the horseshoe-shaped area. Another disadvantage is that RGB LEDs have chips that are based on different technologies, so that the technology that allows the weakest luminous flux correspondingly limits the total luminous flux of the RGB LED. Another disadvantage is that the different LED chips have a different temperature behavior from each other. As a result, the color location of the mixed color then varies as a function of temperature, which of course is undesirable.

In principle, the color diagram can be used to determine which color loci can be set with two predefined light sources. These are all color locations that lie on the connecting line between these two points. Due to the color tolerances of the individual light sources, in particular the green light source, the adjustment of the color yellow from red and green becomes difficult or even impossible, because the connecting line may not intersect the yellow field.

The color tolerances of the individual light sources results overall in a very sensitive system. The white area is well covered by the RGB system, but the difficulties with yellow predominate, so that especially flashing light distribution compliant with the rules is difficult to set with RGB systems.

2 shows a cross section of a lighting device 10 according to the invention in a highly schematic form. The lighting device has a housing 12 with a light exit opening, which is covered by a transparent cover 14. The illumination device has a first light source 16 which generates light of a first light color. The first light source has n = 2 light-emitting diodes, where n can also be a number deviating from 2.

In addition, the illumination device has a second light source 18 which generates light of a second light color. The second light source has here n / 2 equal to a light emitting diode, where n can also be a different number of 2. The second light source can also have m light emitting diodes, where m is not equal to n / 2. It is decisive in each case that the sum of the light exit surfaces of the light emitting diodes m is smaller than in the prior art, in which the white light is generated solely by the second light source and without participation of the differently colored first light source. As a rule, m will be less than n.

The first light color is particularly preferably yellow or red, where yellow is a color from the ECE yellow range for turn signals and red is a color from an ECE red range for tail lights. The second light color is preferably blue, with blue in particular being light from the wavelength range between 470 nm and 505 nm, in particular between 480 nm and 500 nm.

In a preferred embodiment, in which blue light-emitting diodes and yellow light-emitting diodes are used, the yellow light-emitting diodes are based on the same semiconductor chips as the blue light-emitting diodes. The yellow light-emitting diodes thereby arise from blue light-emitting diodes through a yellow conversion layer, which rests on the blue-emitting emitters of the semiconductor chips. As is known, this layer absorbs the blue light with sufficient thickness and releases the excitation energy resulting from the absorption in the form of yellow light. This means that one can use electrically identical or very similar light-emitting diodes for the generation of the yellow light and the blue light, which differ only by a conversion layer or the thickness of a conversion layer. With regard to the control, one therefore only has to deal with blue, electrically identical or similar emitters, which makes possible simpler control devices and which reduces an undesired variation of the color location of the mixed color as a function of the temperature.

The light-emitting diodes of the first light source and the second light source are preferably arranged in common on a one-piece circuit board 20, which is fastened on a heat sink 22, so that waste heat of the light-emitting diode chips flows via the circuit board into the heat sink. On the board are printed conductors for supplying the light emitting diodes with electrical energy and optionally electronic components that serve to control the light emitting diodes arranged.

The light exit surfaces of the light emitting diodes are opposite to an optical surface 24 of an optical system 26. Here, the optical surface is a light entry surface of the optical system, so that the light emitted by the light emitting diodes enters the optical system via the light entry surface. The optical system comprises, for example, one or more light guides and / or one or more concave mirror reflectors and / or one or more lenses. Lenses differ from optical fibers in that light deflections in the case of lenses only occur when passing through interfaces, while with optical fibers additionally deflecting reflections occur on lateral transport surfaces.

The optical system is set up to generate rule-compliant light distributions from the coupled-in light. How this goes in detail, is known from the series use and has to do only insofar with the invention, as this allows a reduction of the optical surfaces of the optical system, in particular a reduction of the light entrance surface of a light guide of the optical system.

The center of such a light distribution lies on an optical axis 28 of the optical system and is in the figure. 3 shown. The plane shown in Figure 3 is oriented perpendicular to the optical axis. The crossing point of the vertical V and the horizontal H represents the penetration point of the optical axis through this plane. In this crossing point results in rule-compliant signal light distributions, a maximum brightness of the light emanating from the illumination device. From this center, the brightness along the horizontal direction H and the vertical direction V continues to decrease as the distance from the center increases, and within the rimmed area between -20 ° and + 20 ° on the horizontal and -10 ° and + 10 ° on the vertical, predetermined luminance values proportional to the maximum brightness in the center must not be fallen below.

The invention is particularly suitable for the production of light distributions, both of which have the same shape, because then one and the same optical system can be used several times. This is the case, for example, in the flashing light distribution and the daytime running light distribution as well as the position light distribution, all of which have the shape shown in FIG.

FIG. 4 shows a circuit diagram which, in addition to the first light source 16 and the second light source 18, has a current source 19, switches 30, 32, 34 and a control unit 36 as well as

signal generators

38 and 40 providing input signals for the control unit. The first light source consists of a first group 16.1 of light-emitting diodes and a second group 16.2 of light-emitting diodes. The first group 16.1 is switched on and off by a first switch 30. The second group is turned on and off by a second switch 32. The second light source is turned on and off by a third switch 34.

The

switches

30, 32 and 34 are actuated by a control unit 36, which in turn receives input signals from a flashing signal request generator 38 and a daytime running light request transmitter 40. If a flashing light distribution is requested with the transmitter 38, the control unit closes and opens the two switches of the two groups 16.1 and 16.2 of light emitting diodes of the first light source, intermittently, wherein it preferably simultaneously opens and closes the two switches simultaneously. Thus, the yellow LEDs are alternately turned on and off as a closed group to produce a flashing light distribution with a proportional to the number of simultaneously switched LEDs brightness.

By switching on and off is here meant an operation of the switch at intervals, in which the human sense of sight perceives the change between lit and off non-luminous LEDs as a flashing signal. The switching frequency is of the order of one Hz.

This should be distinguished from a higher-frequency switching on and off, for example, with a fixed frequency of more than 100 Hz and variable duty cycle, to adjust the average brightness. Such a rapid change is perceived by the human visual sense not as a change of light and dark, but only as medium brightness.

With the concept of simultaneity used above, it is meant that the human sense of sight perceives an average brightness which results as the sum of the individual brightnesses of both groups. The individual switches can optionally be clocked independently of each other with the higher frequency.

Such a higher-frequency clocking is also suitable for dimming the light source. In an alternative embodiment, the luminous flux of the yellow light is not reduced by switching off individual LEDs or a group of LEDs, but by dimming all yellow light sources.

In order to produce a white daytime running light distribution, in one embodiment only one of the two groups of light emitting diodes of the first light source is permanently switched on, and at the same time the second light source is permanently switched on. Here too, the concept of simultaneity is to be understood as meaning that the human sense of sight perceives not the individual light colors blue and yellow, but their mixed color white. The individual switches can optionally be clocked independently of each other with the higher frequency.

Since approximately the same intensity values are required for flashing light distributions and daytime running light distributions, the yellow luminous flux in the generation of the daytime running light distribution compared to the generation of the flashing light distribution can be significantly reduced. He is about halved. This happens depending on the configuration by dimming or by switching off individual LEDs.

In one embodiment, when a flashing light distribution is generated, a group of the yellow light-emitting diodes is alternately switched off at the same time as the second light source is switched on and switched on at the same time as the second light source is switched off. Then there is a change between the switch-on phases of the yellow flashing light distribution and the white daytime running light distribution.

The invention can in principle also be realized with red LEDs and blue LEDs. This is the result of the standard color chart. If one connects a color locus lying close to the red end 4 with a color locus lying at 500 nm on the blue side, for example, the connecting line intersects the white field. This combination of red and blue LEDs can be used in the taillight area to create a red light function such as taillight or brake light through the same optical system as a white reversing light.

Claims

A lighting device (10) for a motor vehicle, comprising a first light source (16) producing light of a first light color and at least a second light source (18) producing light of a second light color and an optical system (26) into which the light is input from at least one of said light sources and is arranged to generate a first light distribution conforming to the rule when only light from the first light source is fed into the optical system and configured to generate a second white light compliant second light distribution when the light of the second light source is fed into the optical system, characterized in that a color location (8) of the first light color in a CIE color diagram lies on a first side of an ECE white field (5), one color location (9) of the second Light color is in the CIE color diagram on a first side opposite the second side of the ECE white field and a e connecting line (7) of the two color loci passes through or at least touches the ECE white field.
Lighting device (10) according to claim 1, characterized in that the first light color is yellow and the second light color is blue.
Lighting device (10) according to claim 2, characterized in that the yellow has a color locus in an ECE area (6) for flashing lights.
Lighting device (10) according to any one of the preceding claims, characterized in that the second light color is a blue having a wavelength which is in the wavelength range between 470 nm and 505 nm, in particular between 480 nm and 500 nm.
Lighting device (10) according to one of the preceding claims, characterized in that the yellow light-emitting light emitting diodes based on the same blue light emitting emitters as the blue light emitting LEDs.
Lighting device (10) according to claim 5, characterized in that the yellow light-emitting LEDs have a resting on the blue light emitting emitter phosphorus converter layer.
Lighting device (10) according to claim 1, characterized in that the first light color is red and the second light color is blue.
Lighting device (10) according to claim 7, characterized in that the red has a color locus in a ECE red area for rear lights.
Lighting device (10) according to one of the preceding claims, characterized in that the first light source has n light-emitting diodes and the second light source has m light-emitting diodes, wherein m is smaller than n.
Lighting device (10) according to any one of the preceding claims, characterized in that the light-emitting diodes of the first light source and the second light source are arranged in common on a one-piece board (20) which is mounted on a heat sink (22).
Lighting device (10) according to one of the preceding claims, characterized in that the light exit surfaces of the light emitting diodes of an optical surface (24) of an optical system (26) are opposite.
Lighting device (10) according to claim 11, characterized in that the optical surface is a light entry surface of the optical system, so that the light emanating from the light emitting diodes enters the optical system via the light entry surface.
Lighting device (10) according to one of the preceding claims, characterized in that the optical system comprises one or more light guides and / or one or more concave mirror reflectors and / or one or more lenses.
Lighting device (10) according to one of the preceding claims, characterized in that the first light distribution is a flashing light distribution and the second light distribution is a daytime running light distribution or a position light distribution.
Lighting device (10) according to one of the preceding claims, characterized in that the first light source consists of a first group (16.1) of light-emitting diodes and a second group (16.2) of light-emitting diodes, wherein the first group of a first switch (30) of the illumination device is turned on and off, the second group of a second switch (32) of the lighting device switched on and off and the second light source of a third switch (34) of the lighting device is turned on and off.