Patent Application
20200300434
This application claims the priority benefit of Czech Patent Application Serial No. PV 2019-176 entitled “A lighting unit for a light device of a motor vehicle and a light device with the lighting unit,” filed Mar. 22, 2019, the entire disclosure of which is incorporated herein by reference.
The invention relates to a lighting unit for a light device of a motor vehicle and a light device with the lighting unit.
New vehicle lighting systems do not only focus on the optical output increasing the driving comfort and traffic safety, but it is also the appearance that is important for modern light devices of motor vehicles as headlights or signal lamps of a motor vehicle. Modern point and planar light sources, especially LED and OLED sources, have opened a new chapter for new stylistic options of car designers.
Using a planar light source, especially OLED—Organic Light Emitting Diodes—brings not only an extension of designer possibilities of the emitted light function, but it is also characterized by certain technical benefits including e.g. compact installation dimensions, low heat production, low energy consumption etc. Unfortunately, there are still some limitations of the OLED technology preventing widespread deployment of this technology in the serial production of car lighting. E.g. service life, penetration of moisture, low luminance for power functions, limitation to planar surfaces only and last, but not least, a high price. Another drawback of the OLED technology is the fact that a lamp of a motor vehicle must be adapted do detect an error status of the light source. With conventional LED's, this condition can be detected relatively well because in most cases, a short circuit or diode disconnection occurs, which results in a change of an electric quantity that can be relatively easily electronically detected. The situation of planar sources is more complicated because OLED's comprise organic layers that emit light after connection of electric voltage/current.
In the patent references U.S. Pat. Nos. 9,335,460, 7,651,241, 5,791,757, US20160356942, US20160349570, US20150331169, US20140268873, US20130033895, US20110249939, US20110170315, US20100309677, US20080186726, GB2537088, KR2008111786, there are many solutions that use a planarly shaped lighting unit equipped with an exit area for the output of light rays without using organic substances such as OLED. The disadvantage of the above-mentioned design solutions is that these lighting units are not intended to be used as external lighting equipment for motor vehicles, for which a variety of technical specifications and regulatory requirements must be followed and fulfilled. There is also a requirement for low manufacturing and assembly costs of such devices. For example, chemically cured cover glass that is used in the manufacturing process of screens is unsuitable for use as a cover glass of motor vehicle headlights as its manufacturing costs are too high.
To achieve the highest possible efficiency of light devices, efficient binding of light rays to light-guiding components must be ensured. Individual optical elements as a system of refractive and reflective surfaces and interfaces of optical environments must be arranged in such a way to prevent light losses to the highest possible extent, and at the same time to create an output light trace with the required light characteristic, i.e. the required light intensity and homogeneous appearance with constant luminance all over the exit surface.
Car lighting has certain specific features as it is not only the appearance and the total luminance of the lighting function that is concerned. Individual lighting functions must conform to locally valid legislative regulations (e.g. ECE, SAE, CCC etc.). Each function has different requirements for the minimal and maximal luminous intensity values at certain angles. This means that the purpose is not only to emit a certain amount of light from lighting elements. It is also necessary to emit light having certain luminous intensity at individual angles specified by the legislation. This luminous intensity is based on the minimum and maximum values in individual regulations for individual angles. A lighting function should be preferably designed in such a way to meet requirements of as many regulations as possible. So there is a certain overlap of the intervals of the specified minimum and maximum values for individual angles. In this case, a lamp or headlight can be used for more markets at the same time without changes. However, there are cases when the requirements of all regulations cannot be met with the use of a single design of a lighting function. In that case, the lighting function must be adapted to the requirements of individual markets, which results in a unique product for the particular market.
The requirements for the luminous intensity at individual angles are based on traffic safety requirements. This is because the primary task of signal lights is to make sure that a vehicle that emits a signal can be seen from angles that are critical for the particular function. All the signal functions (except the lateral ones) must emit light with the highest possible luminous intensity in the vehicle axis direction. The requirements for individual luminous intensity values at individual angles then decrease with the increasing angle of deflection from this axis. This decrease is gradual and does not approximate Lambert's distribution (cosine emitter). Thus, it is not desirable to strive to achieve this (Lambertian) distribution, which is close to the distribution that OLED lights or some displays work with. Concerning displays and TV screens, the aim is to ensure as constant luminance as possible from the widest possible viewing angles, which is a principal difference from the requirements for angular luminous intensities that light devices of motor vehicles, i.e. also the light device of a motor vehicle according to the present invention, are subject to.
As indicated above, fading at large viewing angles is rather considered as a defect in the case of displays and TV screens. On the other hand, signal lights of motor vehicles are subject to specifications what luminous intensities must be achieved at what angles to ensure safe visibility of a vehicle emitting a signal. In most cases, a light cone must be produced having the highest luminous intensity within the angle of +/−10° horizontally and +/−5° vertically from the longitudinal axis of the vehicle. Lower luminous intensities are then required up to the angles of +/−20° horizontally and +/−10° vertically from the vehicle axis. These angles are required for the main beam, the luminous intensity of the main beam being several times higher than the required luminous intensity at the other angles. At the other angles, visibility is the relevant parameter. I.e. a requirement for the signal to be visible from a large range of angles. E.g. for the stop function, visibility is required in the angular range of +/−45° horizontally and +/−15° vertically. However, for the tail light and the turn indicator function the visibility angle out of the vehicle has been extended up to 80°. With regard to the production tolerances it is then important to design the light function in such a way as to always meet the required luminous intensity value at the particular angle. Therefore, the minimal and maximal values are designed with a certain angular and value margin. This e.g. means that if a minimal luminous intensity is required up to a certain angle, the function is mostly designed in such a way for this minimal value to exceed the given angular direction by at least 1.5°.
The above-mentioned description implies that to efficiently meet the legislative regulations, the light must be directed specifically at individual angles.
Unlike displays and TV screens, in the automotive industry, the required shape of the output surface must further be considered. This is because in most cases, the use of a simple square or rectangular surface is not acceptable from a designer point of view. Today, the style of a car is a very important parameter and at the same time a limit for meeting technical and legislative requirements. Therefore, style must be combined with technological features to achieve the desired result. For this reason, within the design of the light-conductive core, the distribution and size of unbinding elements must be optimized.
The references CZ2017480 and CZ20180107 describe light devices for motor vehicles that comprise a panel-shaped shaped lighting unit with an exit area of light rays. The lighting unit is powered by spot light sources, in particular by LED, and it is equipped with optical elements to create signal light functions while the panel-shaped shaped lighting unit offers stylistic advantages comparable to the OLED technology. It is ensured that all technical specifications and legal requirements for use of lighting equipment in the automotive industry are fulfilled. The light device comprises a light-conductive core from an optically transparent material with an associated light unit situated against the entry area of the light-conductive core. The lighting unit further comprises a functional layer arranged between the light-conductive core and the translucent cover and configured to focus the beams of light rays that exit its surface averted from the light-conductive core in a predetermined direction, and a technological layer (situated in contact with the top surface of the light-conductive core and configured for total reflection of light rays). The lighting unit further comprises separators situated on the top surface of the light conductive core to delimit the required thickness of the technological layer. A disadvantage of these designs is the fact that the light rays are diffused with a relatively large lateral dispersion. This assembly achieves a lateral dispersion for the required luminous intensity of approx. 60°. Within the dispersion region of 60°, an almost homogeneous distribution of light is achieved on the display area whereas in the field of automotive lighting equipment it is desirable to emit a large amount of light especially in the vehicle axis direction and to diffuse a certain amount of light. Another drawback of the above-mentioned designs is the entire structural arrangement of the optical parts, which does not enable their variable configuration based on designer requirements, e.g. if it is necessary to direct the light beam in a certain manner, or if a spatial shape of an optical element is to be achieved.
The object of the invention is to disclose a new design of a light device of a motor vehicle that comprises a panel-shaped lighting unit with an exit area of light rays that will offer designer advantages comparable to the OLED technology and at the same time ensure that all technical specifications and legal requirements for use of lighting equipment in the automotive industry are fulfilled at acceptable manufacturing costs.
The above-mentioned object of the invention is fulfilled by a lighting unit according to the invention, intended for a light device of a motor vehicle, comprising a light guide to lead light rays from at least one light source. The light guide comprises a front surface and an apposite rear surface. The front surface comprises exit areas for the output of light rays from the light guide and intermediate areas situated between the exit areas and configured for total reflection of light rays passing along the light guide. The lighting unit further includes a light assembly situated against the front surface of the light guide and comprising optical elements containing a bearing area through which the optical elements are connected with the opposite exit areas directly or indirectly in such a way that between the exit areas and bearing areas transitional layers are arranged. The optical elements are configured to bind light rays falling onto the exit areas and to emit them from the exit surface of the optical elements, averted from the light guide, in a predetermined direction or directions.
In one of preferred embodiments, the rear surface of the light guide is smooth and without unbinding elements so that the light guide is virtually configured for the exit of light rays out of the light guide through the exit areas only.
In another one of preferred embodiments, the rear surface of the light guide is fitted with unbinding elements configured to direct light rays towards the exit areas and/or intermediate areas and to ensure their exit through the exit areas and/or intermediate areas out of the light guide.
The light assembly may preferably comprise a carrier carrying optical elements.
In another one of preferred embodiments, the optical element comprises a functional element and an emitting element, which are directly or indirectly connected to each other, the functional element comprising a bearing area and at least one reflective area to reflect light rays that have left the light guide through the exit area and entered the functional element through the bearing area, and to direct them to the emitting element comprising an exit surface for the exit of light rays out of the functional element.
In another one of preferred embodiments, the functional elements protrude from the rear surface of the carrier facing the front surface of the light guide and the emitting elements protrude from the front surface of the carrier averted from the front surface of the light guide.
The optical elements may preferably be integral bodies embedded in the carrier.
In another one of preferred embodiment, the functional elements and the emitting elements are separated from each other by the carrier.
The said transitional layers may preferably be part of a monolithic layer.
In one of preferred embodiments, the light guide is longitudinally shaped or panel-shaped. The carrier may be advantageously panel-shaped or longitudinally shaped as well.
In another one of preferred embodiments, the emitting elements have the form of ball-shaped lenses with a convex shape of the exit area and the functional element has the shape of a truncated cone whose base is the bearing area.
In another one of preferred embodiments, the emitting elements have an elongated shape, especially the shape of cylindrical lenses.
In another one of preferred embodiments, at least two of the emitting elements differ from each other with their shape and/or size.
In another one of preferred embodiments, the lighting unit includes a filter located behind the light guide to influence the color background when the lighting unit is viewed in its inactive state.
In another one of preferred embodiments, the lighting unit comprises a filter, especially homogenizer adapted for homogenization—diffusion of light rays, the filter being situated at a distance in front of the optical assembly and comprising a superficial or internal volume structure to influence the flow direction of the light rays, or the filter being colored or metal-plated in a semi-permeable way.
The thickness of the lighting unit is preferably from 0.1 mm to 14 mm.
The invention also relates to a light device comprising the lighting unit described above, situated to emit light rays from the exit areas of the optical elements out of the light device.
The light device may advantageously comprise multiple lighting units to serve one or more light functions of the light device.
The present invention will be further clarified in more detail with the use of its embodiment examples referring to the enclosed drawings wherein:
b show embodiment examples of the lighting unit 3 according to the invention.
The lighting unit 3 comprises a light guide 15 made of an optically transparent material, with an associated light unit 7 comprising light sources 11 situated on a carrier 12. The light guide 15 can e.g. be of a plate-like shape (a panel-shaped light guide) and have a constant or variable thickness, or be of an elongated shape (rod light guide), it may be straight, bent, undulated or spatially shaped. The light sources 11 are situated at the entry area 9 of the light guide 15 and are designed to emit light rays 10 into the light guide 15. These light rays 10 pass along the light guide 15 using the total reflection principle, which occurs on the rear surface 18 and front surface 17 of the light guide 15 which form interfaces between the light guide 15 and the surroundings of the light guide 15 with a low refractive index with respect to the refractive index of the light guide 15 material, except the exit areas 30 designed specifically for the exit of light rays 10 out of the light guide 15 as described in detail below. The front surface 17 of the light guide 15 comprises exit areas 30 and intermediate areas 19 that separate the exit areas 30 from each other.
The rear surface 18 of the light guide 15 can be (see the embodiments of
The lighting unit 3 further comprises an optical assembly 23 situated against at least a part of the front surface 17 of the light guide 15 in such a way that the optical assembly 23 virtually follows the shape of the opposite front surface 17. The optical assembly 23 always comprises optical elements 26. Each optical element 26 contains an emitting element 26a and a functional element 26b. The optical assembly 23 can further comprise a carrier 15 (it is the case of the embodiments shown in
The emitting elements 26a and functional elements 26b are preferably arranged in mutual alignment opposite each other as in the case of the presented preferred embodiments. Each pair of an emitting element 26a and functional element 26b is part of one optical element 26. However, the invention also envisages embodiments wherein the emitting element 26a and functional element 26b from which light rays 10 proceed to the emitting element 26a assigned to this functional element 26b are situated at a distance from each other, to which, however, the geometry and shape of these elements must be adapted, to achieve the desired propagation of light rays 10 from the functional element 26b to the emitting element 26a. In this case, the functional element 26b and the emitting element 26a assigned to it are considered as parts of one optical element 26.
The said carrier 25 may be e.g. foil.
The optical element 26 comprising a functional element 26b and an emitting element 26a assigned to it can be an integral optical element 26 that is embedded in the carrier 25 as shown in
The shape of the functional elements 26b is configured to direct light rays 10 in predetermined directions to push the light rays 10 to the emitting elements 26a from where they are emitted out of the lighting unit 3. The functional elements 26b are further configured to bind light rays 10 from the exit areas 30 through the bearing area 14 into the functional elements 26b. The emitting element 26a is configured to emit a beam or beams of light rays 10 in a predetermined direction of directions and/or in a predetermined angular range. The functional elements 26b and emitting elements 26a usually have a size on the order of nanometers, micrometers to millimeters, e.g. in the range from 10 μm to 2000 μm.
The optical elements 26 are attached directly or indirectly to the exit areas 30 of the light guide 15 with their bearing areas 14. As direct attachment (see e.g.
The transitional layer 24 can be of the same size and positionally aligned with the exit surface 30 and bearing area 14 so that the bearing area 14, transitional layer 24 and exit area 30 are arranged on each other in a precise alignment (see e.g.
The transitional layer 24 in the sense of this invention is a layer configured to eliminate the air gap between the exit surfaces 30 of the light guide 15 and the opposite bearing surfaces 14 of the functional elements 26, as the purpose is to prevent total reflection of light rays 10 on their incidence on the exit surfaces 30, and conversely to enable transition of these rays 10 through the transitional layers 24 into the functional elements 26b.
Note that the production process of the light unit 3 preferably comprises the step of using a light guide 15 whose entire front surface 17 is adapted for total reflection of light rays 10 passing along the light guide, i.e. the front surface is completely uniform in this sense. Thus, before connection to the optical assembly 23, the front surface 17 does not comprise any exit areas 30 because they will only be produced by attachment of the optical assembly 23 to the light guide 15. The exit areas 30 are created because in places where the bearing areas 14 are attached to the front surface of the light guide 15, either directly or via a transitional layer 24, the surface of the light guide will no longer form an interface between materials with a significantly different refractive index, and therefore light rays 10 will (with no or small refraction depending on whether the refractive indexes of the material of the light guide 15 and transitional layer 24 or light guide 15 and the functional element 26a are the same or slightly different) transit from the light guide 15 into the functional elements 26a.
In embodiments that comprise a carrier 25 (embodiments of
The emitting elements 26a shown in
The emitting elements 26a shown in
As shown in
The thickness of the lighting unit 3 is preferably from 0.1 mm to 14 mm.
A relatively simplest configuration is such when the front surface 25a of the carrier 25 is situated approximately perpendicularly to the longitudinal axis of the vehicle and is approximately planar. However, this configuration is not always suitable for the style of the vehicle. Therefore, the optical assembly 23 or combination of optical assemblies 23 is adapted to redirect the main axis of the final light beam exiting from the optical assemblies 23. If there is an additional requirement that the optical assemblies 23 should be shaped and curved on the basis of designer requirements, optical analyses should be carried out and their results used to optimize the optical assemblies 23 or individual optical elements 26 to meet the legislative requirements for the particular function.
At present, motor vehicles are equipped with signal lamps designed to emit various light beams. Such signal lamps can be integrated in the body as separate lighting elements or they can be an integral part of headlights and tail lights in the form of a partial lighting unit.
Such functions are considered as signal functions that do not directly illuminate the space in front of the vehicle, but enhance road traffic safety by helping to improve visibility of the respective vehicle for the other road traffic participants. This mainly relates to the following functions:
DRL—Daytime running light, of white color
Turn indicator, of amber or red color
Front position light, of white color
Front parking light, of white color
Tail light, of red color
Stop light, of red color
High mount stop light (HMSL), of red color
Side marker, of white, amber or red color
Besides the required color of the light beam, each of the signal functions is characterized by visibility, which is based on the required directions and propagation angles of the light beam both on the horizontal and vertical plane as well as photometric requirements where in various angular areas in front of/behind the vehicle there are various areas with various required luminous intensity values.
1—housing
2—chamber
3—lighting unit
4—layer
5—coating
7—light unit
8—connecting element
9—entry area
10—light ray
11—light source
12—carrier
13—spacing element
14—bearing area
15—light guide
16—rear face
17—front surface
18—rear surface
19—intermediate area
20, 21—filter
22—exit surface
23—optical system
24—transitional layer
25—carrier
25
a—front surface
25
b—rear surface
26—optical element
26
a—emitting element
26
b—functional element
27—reflective surface
28—unbinding element
29—exit area
30—exit area
| Number | Date | Country | Kind |
|---|---|---|---|
| PV 2019-176 | Mar 2019 | CZ | national |
