DE102021117156A1 - LIGHT GUIDE FOR VEHICLES WITH PROTECTIVE SHEATH - Google Patents

Abstract

According to the invention, a light guide 1 for vehicles is created, which is protected by a partial or complete sheath 4. The casing 4 is held on the light guide 1 via spacers 3 and protects the light guide 1 from damage both before and during assembly and in the installed state. In addition, the casing can also assume sealing functions. In addition, a method of manufacturing the optical fiber 1 and the cladding 4 will be explained.

Description

The invention is based on light guides, particularly in vehicles, which are intended to emit light evenly over a certain length for design purposes.

In the past, (signal) lighting on the vehicle - apart from dashboards and "map reading lights" or similar useful lighting in the interior - was relatively limited to the headlights / lights themselves. Recently, the design aspect has been growing, so that light also migrates into body parts. Typically, lights are installed behind the body parts for this purpose. Examples include the Peugeot 208 (2020 model) with a kind of "saber tooth" as a vertical extension of the signature in the main headlight or the VW Golf GTI (2020 model) with luminous elements running horizontally below the bonnet.

The design of the light function of such a line-shaped "design lamp" can take place via LEDs arranged in a band, but is often implemented more cost-effectively as light guides. For this purpose, a plastic rod (usually made of PC, polycarbonate, or PMMA, polymethyl methacrylate, also commonly known as “Plexiglas”) is illuminated from one side by a light source (usually an LED). The rod deflects the light via decoupling structures on its back (in the direction of travel) or couples it out (towards the front).

Light guides require a transparent material (if possible without imperfections) and a medium with a lower refractive index surrounding them for their ideal light-guiding function, so that total reflection occurs at the transition (which can also be gradual / staged, e.g. when light-guiding in gradient fibers) due to the difference in refractive index ( so-called TIR - total internal reflection). Of course, one could also coat the interface with a “mirror”. However, such a reflection does not have a 100% degree of reflection, but - at least in the case of large-scale industrially economical production processes - typically just 80% - 90%. This means that light has shrunk to 10% of its original intensity after 10 interface contacts (or a path length of a few centimeters or millimeters, depending on the geometry), and to just over 1% after 20 contacts. A light guide is not effectively possible.

Typical light (wave) conductors in communication technology, for example glass fibers, are therefore made from two transparent glasses and/or plastics with different refractive indices. In the course of the outer layer (“cladding”), the light decays towards the outside (“evanescent waves”), so that no energy arrives on the outside. In this case, the glass fibers are typically additionally coated with a non-transparent protective layer.

In the automotive sector, in contrast to data transmission, high amounts of light are important. Conversely, only shorter distances are relevant. Therefore, higher refractive differences are helpful there. A high difference in refractive index is easier (easier) to achieve if the surrounding material has a refractive index that is as small as possible, such as air (n-1). However, the light guide must then be protected from external environmental influences by a housing. Such a typical light guide from the prior art (in a straight design for the sake of simplicity) is 1 to see.

Light is coupled in, for example, by an LED (not shown) at one end (here on the left or in the foreground) of the light guide 1 . Special decoupling structures 2 (here prism-shaped on the underside) deflect the light guided in the light guide (here upwards) so that targeted decoupling occurs. The top can also be shaped accordingly in order to direct the light in the appropriate directions in a more targeted manner. Here, the surface is configured like a cylindrical lens, for example. Due to the individually shaped (generally increasing) decoupling structures 2 (here on the underside), a uniform luminance is achieved on the decoupling side (here at the top).

the DE 10 2018 000 304 A1 discloses, by way of example, a lighting arrangement for illuminating the outside of a motor vehicle, albeit not a light guide as proposed here. She proposes inserting a lamp into a molded part (as a lamp housing) which then emits the light from the lamp on its outside (and the outside of the vehicle).

A disadvantage of such arrangements in the vehicle sector is that they each require their own lights, i.e. in particular light housings, in order to protect the light guides from external influences such as dirt. This is relatively complicated and expensive.

The configuration presented below reduces the outlay for a lamp housing, thus saving parts and costs and reducing the necessary installation space (and thus the costs again). Of course, this configuration can also be used (in whole or in part) within luminaires and is not limited to pure design elements.

The object of the present invention is to reduce the outlay for a lamp housing by saving parts and costs and reducing the installation space required (which also causes costs) and the weight. Of course, this configuration as in the DE 10 2018 000 304 A1 (fully or partially) used within luminaires.

This object is achieved by a system of light guide and sheathing having the features listed in claim 1 and a method for producing the system having the features listed in claim 12.

Particularly advantageous configurations can be found in the dependent claims.

The invention relates to a system made up of an optical fiber and a protective sheath. On a base body of the light guide, in which light can be transmitted by total reflection, a distinction is made between at least one coupling side, on which light can be coupled into the light guide, an upper side that is capable of emitting light, and a rear side, on which coupling structures are provided, to direct light to the top. Structures that are formed in one piece and are not part of the base body are provided on the light guide (hereinafter usually referred to as “spacers” for short), which serve as spacers between the base body of the light guide and the protective sheathing and to which the protective sheathing can be attached. Light is coupled into the light guide on the in-coupling side and either emitted as far as possible on the upper side or partially emitted on a light transmission side to a next light guide or a comparable element. Of course, it is also possible to couple and transmit light at more than one location, for example by means of a "Y"-shaped structure with two (or more) coupling and/or light transmission locations. In addition, it is not absolutely necessary to transmit light passing through to a “light transmission side”; the light can also be “consumed” completely or for the most part in the light guide or emitted via the decoupling structures and the top. In addition, small portions of unused "residual light" can escape at any location where the appearance is not disturbed, or they are absorbed (e.g. by corresponding dark areas). Here, for the sake of simplicity, reference is made below to (each) a coupling location and a light transmission location. The spacers keep the protective sheathing away from the free surfaces of the light guide, so that total reflection can occur on these free surfaces.

The spacers are preferably provided between the top and the rear of the base body. Normally, light should exit at the top, and structures such as prisms are therefore provided on the opposite rear side, as mentioned in the explanation of the prior art, which redirect the light to the top. Spacers can inevitably only be provided to a limited extent on the upper side, since they impede the decoupling and/or radiation or cannot fit into the concept in terms of design. Likewise, spacers on the back impair the deflection of the light.

The profile of the light guide is preferably circular, elliptical, polygonal or a keyhole profile. In other words, the profile can be largely freely selected, ie it can also have a so-called free form. It can also change in the course of the light guide. However, in order to obtain good light conduction by means of total reflection and to enable economical production, for example by extruding a plastic light guide, the profile types listed are to be preferred.

The decoupling structures on the back of the light guide include, for example, structures made of prisms, spherical caps and/or a roughened surface. The spherical caps are designed in such a way that they deflect incident light rays. These decoupling structures are used to guide light impinging on them through total reflection and/or scattering to the upper side in such a way that it exits there and is no longer reflected. For this purpose, the incident light beams must ideally be deflected approximately at a right angle to the direction of coupling (plus/minus a few tens of angular degrees; strictly speaking, the deflected light beam must impinge on the exit surface at an angle to the normal that is more acute than the critical angle of total reflection at this area is). This can be achieved with the means mentioned.

The spacers are further preferably formed continuously on the light guide. With such a configuration, the light guide with the molded spacers can be manufactured very economically, e.g. by extrusion, and then shortened to the desired length, and further processing steps such as bending etc. can then be carried out in order to achieve the desired shape of the light guide.

Alternatively, the spacers can be formed on the light guide in a periodically alternating manner. This configuration only allows extrusion as a step in the production of the light guide, which is followed by a further subtractive (cutting away) or additive step (for example gluing, welding, etc. of the structures formed). but has the advantage that less light is lost at the transition between the light guide and the structures that serve as spacers, i.e. less light is coupled out of the light guide at undesired points.

The system set out above can further preferably have a sheathing of the light guide which rests on or can be fastened to the structures which serve as spacers. The casing can preferably be fastened to the spacers, for example by means of clips, or glued to the spacers or extruded directly onto them. The cladding can leave the top free, ie it can only be provided on the back of the light guide.

The cladding may be at least partially transparent and wrap around the entire light guide. Such a cladding either protects the light guide “only” on the back towards the installation space or envelops or encases it completely. The front side of the light guide is typically significantly less susceptible to environmental influences (since it is not so filigreely shaped) and/or is often protected by a cover pane anyway. However, instead of or in addition to the cover plate, a complete casing can also be provided which is partially (in front of the surface) transparent.

The casing or its transparent part can be made at least partially from appropriate plastics such as PMMA or PC (polycarbonate), COC/COP (cycloolefin copolymers or cycloolefin polymers), Durabio, SAN (styrene-acrylonitrile copolymers), silicone or glass consist. With a "soft" complete jacket, the assembly of the light guide as well as the transport and storage prior to assembly can also be simplified, since such a jacket protects the actual light guide against scratches and the like, provided that it is produced directly after or during the manufacture of the light guide . Even if the casing is harder and could therefore also have scratches or the like, those on sides other than the top through which light is intended to exit the casing are irrelevant, so that simple protection of this top is sufficient. A non-transparent part of the sheathing can consist of suitable plastics such as PC, PMMA, ABS, PA, PBT or combinations thereof, also with fiber materials or other plastics. The wide range of materials that can be used makes it possible to find an optimal combination depending on the application. The non-transparent part can be colored accordingly (e.g. white) in order to "recycle" any scattered light on the back and/or to adapt the color appearance of the light guide, which is usually transparent, in the unlit/illuminated state.

The system according to the invention can also include optics on the in-coupling and light transmission sides for the in-coupling and transmission of light at the entry and/or exit surface of the light guide. Light is typically coupled laterally into such a light guide. In certain designs, it may be desirable to fabricate the light guides in a particular configuration from multiple pieces to facilitate assembly. Several coupling surfaces and light transmission surfaces can also be provided between such pieces, for example on the sides.

In order to manufacture a light guide as described above, according to the invention a plastic profile can be extruded as a light guide and at the same time a plastic profile can be extruded on as a sheath. Alternatively, light guide and plastic profile are extruded separately, for example cut to the required lengths and then either assembled and prepared for further assembly, or brought together individually for assembly and only assembled during or shortly before installation.

• 1 einen typischen Lichtwellenleiter aus dem Stand der Technik;
• 2 einen erfindungsgemäßen Lichtwellenleiter nach einer ersten Ausführungsform;
• 3 den erfindungsgemäßen Lichtwellenleiter nach der ersten Ausführungsform mit einer Ummantelung nur an der Rückseite;
• 4a und 4b den erfindungsgemäßen Lichtwellenleiter mit einer kompletten Ummantelung, die teilweise bzw. vollständig transparent ist;
• 5 den erfindungsgemäßen Lichtwellenleiter nach einer anderen Ausführungsform;
• 6 den erfindungsgemäßen Lichtwellenleiter in einer Draufsicht nach einer noch anderen Ausführungsform;
• 7a und 7b eine weitere bevorzugte Ausführungsform in perspektivischer Darstellung und in Draufsicht; und
• 8a und 8b eine Variante der in 7a und 7b gezeigten Ausführungsform in perspektivischer Darstellung und in Draufsicht.

The invention will be explained in more detail below using exemplary embodiments. The figures show:

• 1 a typical prior art optical fiber;
• 2 an optical waveguide according to the invention according to a first embodiment;
• 3 the optical waveguide according to the invention according to the first embodiment with a cladding only on the back;
• 4a and 4b the optical waveguide according to the invention with a complete cladding that is partially or completely transparent;
• 5 the optical waveguide according to the invention according to another embodiment;
• 6 the optical waveguide according to the invention in a plan view according to yet another embodiment;
• 7a and 7b a further preferred embodiment in a perspective view and in a plan view; and
• 8a and 8b a variant of the in 7a and 7b embodiment shown in a perspective view and in plan view.

1 shows a conventional optical fiber 1 from the prior art. As already explained in the explanation of the prior art, light coupled in “at the front” in the figure is largely reflected by the light waveguide 1 sent. The part of the light that hits the prismatic structures 2 on the underside is reflected in the prismatic structures 2 at an angle of around 90° plus/minus approx. 40° to its light-guiding direction at the current location or to a direction of a neutral fiber of the light guide deflected. As explained above, it is permissible to deviate from the "90°" mentioned so far that the deflected beam hits the exit surface at an angle at which it can exit the light guide, instead of being totally reflected at the interface of the light guide, and that the beam to be deflected is previously reflected on the prism surface due to the TIR condition, the condition for total internal reflection.

As a result, this part of the light falls at a steep angle (eg approximately perpendicular) onto the cylindrical surface here, so that the critical angle of total reflection (to the perpendicular on this surface) is not reached and the light emerges. Since this happens evenly distributed on the surface depending on the coupling angles of the incident light, which is promoted by the corresponding design of the prismatic structures 2 (as mentioned above, the structures become larger in the course of the light path), on the coupling-out side (above in 1 ) achieves a uniform luminance.

2 shows compared to 1 an optical waveguide according to a first embodiment of the invention. The prismatic structures 2 on the underside and the structure on the upper side of the light guide 1 are largely identical to the corresponding structures from the prior art, as a result of which a comparable technical effect is also achieved.

However, in contrast to the idealized light guide, real light guides have 1 other geometries for coupling (as mentioned not shown in the figures), attachment and referencing or alignment. Such extensions lead to light losses at the place where they are arranged, because the total reflection is eliminated, i.e. they “cost” light, but they are necessary. Ideally, such additional structures are arranged neither on the decoupling side (essentially “in front” or on the “top” in the figure) nor on the side of the prismatic structures 2 (“rear”), since otherwise in both cases they lead to undesired light exits lead and/or prevent light decoupling. As in 2 is shown, the additional structures, namely spacers 3, are therefore preferably arranged on the side of the light guide 1. In 2 projections (“pins”) 5 are also drawn in for referencing, which are provided on the spacers 3 and can be used to align the light guide 1 with other components.

These spacers 3 with the projections 5 can be used to attach the light guide 1 during assembly. For example, the projections 5 can be used as holders to which a circuit board with an LED for coupling in light can be fastened (or at least aligned).

Since the spacers 3 are at a height between the top and the prismatic structures 2, they hardly impede the outcoupling of the light, since they do not act in the outcoupling direction (nor in the light transmission direction) and are therefore not directly visible. Independent of the structures according to the invention, the majority of the coupled-in light is further deflected after a few reflections on the underside and coupled out on the upper side.

The spacers 3 provided according to the invention on the light guide 1 are particularly preferably used in order to attach a sheathing to them. Examples show the 3 , 4a and 4b .

In 3 the light guide 1 according to the first embodiment is as in FIG 2 pictured; only the projections 5 used to align LEDs 2 were omitted because they do not contribute to the effect of the spacers 3, which is essential here. On the spacers 3 is in 3 a rear protective casing (hereinafter abbreviated: casing) 4 is provided. As already explained above, the upper side of the light guide is usually more resistant to environmental influences than, for example, the back with the relatively filigree prismatic structures, and also often protected by a downstream cover pane (or by hardening, coating or painting) when installed. The casing 4 is therefore in the exemplary embodiment 3 on the corner areas of the prismatic structures 2 and is hooked into the correspondingly designed spacers 3 .

4a and 4b show another embodiment of the light guide 1 with a sheath. As can be seen in both figures, the spacers 3 are shaped in such a way that they enclose the light guide 1 in an “H” shape, which means that they have as little “contact surface” as possible with the actual light guide profile, and can still be manufactured easily, for example by extrusion.

The casing 4 includes in the case of 4a a non-transparent part 41 and a transparent part 42, which together enclose the light guide 1 like a tube. This achieves very good all-round protection for the light guide. Although this is not shown, the non-transparent part 41 can, for example, be mirrored on the inside (or with be coated with a reflective paint, eg white, or made of reflective material (specular/reflecting or diffusely scattering) in order to further increase the light output of the system.

In 4b the entire casing consists of a transparent part 42. Otherwise, this variant with the in 4a shown variant identical. A completely transparent sheathing can make assembly easier because you don't have to pay attention to the alignment of the sheathing to the light guide.

the 5 and 6 show alternative embodiments of the light guide 1 according to the invention, in particular the spacers 3 and the decoupling structures 2.

As in 5 as can be seen, the spacers 3 are designed here as individual, periodically alternating shapes protruding from the base body of the light guide 1 . In this way, the transition area between light guide 1 and spacers 3 is reduced, so that less light is undesirably coupled out. In addition, in 5 - Regardless of the changed shape of the spacers 3 - a different shape of the prisms used as decoupling structures 2 for the deflection is also shown. Here the prisms are molded into the light guide 1 as “prism holes” instead of being attached to the outside as in the figures shown so far. This design of the prisms can be used as an alternative to the design with external prisms, for example for the purpose of reducing space requirements. Other alternatives, not shown, for sending the coupled-in light to the exit surface are spherical caps (these too can preferably be shaped as a hole), or a (periodically, irregularly or continuously) roughened surface.

In 6 1 is a plan view (or a sectional view) of yet another modification of a light guide according to the invention. How out 6 is recognizable, according to the in 6 The variant shown has four spacers 3 and protruding prisms as decoupling structures 2 (as in Figs 1 until 4b shown) provided on a light guide 1. Since the spacers 3 are shown without a transition to the light guide 1, all the spacers 3 shown are exposed—in contrast to the exemplary embodiment 5 - at a height. The spacers preferably run continuously along the light guide 1 . Such a design has - similar to the design according to the 2 until 4b - the advantage that it is easy to produce in the extrusion process.

7a and 7b reveal another variant. In this case, the protective sheathing 4 is produced via a plastic profile extruded directly onto the light guide 1 . This can be done in a combined manufacturing process ("in the same factory") or completely independently of each other (e.g. manufacturing the light guide in the first location and e.g. winding it onto a roll; in the second location the light guide is then pulled from the roll through an extrusion machine , provided with the sheathing 4 and wound back onto a roll. Only in a third location is the optical fiber 1 with the sheathing 4, for example, fully assembled ("cut to length") and installed). Alternatively, a fiber optic cable that cannot be coiled can be cut to length at the first location and then fed into the extrusion process (sheathing) as bar stock.

The sheathing can not only as in the 7a and 7b shown can be done by a half-shell, but also as in the 8a and 8b shown as a full jacket 4.

Due to the extrusion process and the choice of material, both the half-shell and the full casing can contain (additional) geometries at low cost, which enable attachment and at the same time sealing (e.g. using material with a lower Shore hardness for extruded sealing lips 43) in an associated assembly.

By using different components (2K/3K/...), the extrusion process also makes it possible to produce the area under the light decoupling structures in a different color than the area covering the front of the light guide. For example, a full encapsulation can be produced with a white lower shell and a diffuse or clear upper shell at the same time, similar to in 4a shown.

Reference List

1

light guide

2

decoupling structures

3

spacers

4

sheathing

5

Protrusions (referencing)

41

Non-transparent part of the casing

42

Transparent part of the sheath

43

sealing lip

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018000304 A1 [0008, 0011]

Claims (14)

System consisting of a light guide (1) and a protective sheathing (4), the light guide (1) on a base body in which light can be transmitted by total reflection, - at least one coupling side on which light can be coupled into the light guide (1); - a translucent top; and - has a rear side on which coupling-out structures (2) are provided in order to direct light to the upper side; characterized by structures (3) formed in one piece on the light guide (1) and not part of the base body, to which a casing (4) can be attached and/or which serve as spacers between the base body of the light guide (1) and the casing (4). system after claim 1 , wherein the structures (3), which serve as spacers, are provided between the top and the back of the base body. system after claim 1 or 2 , wherein the profile of the light guide (1) is circular, elliptical, polygonal or a keyhole profile. System according to one of the preceding claims, in which the decoupling structures (2) on the back comprise prisms, spherical caps and/or a roughened surface. System according to one of the preceding claims, in which the structures (3) which serve as spacers are continuously formed on the light guide (1). system according to one of the Claims 1 until 4 , wherein the structures (3), which serve as spacers, are formed periodically or periodically alternating on the light guide (1). System according to one of the preceding claims, further with a casing (4) which rests on the structures (3) which serve as spacers or can be attached thereto, in particular can be glued or clipped on. system after claim 7 , wherein the sheathing (4) is at least partially transparent and runs around the entire light guide (1). system after claim 7 or 8th , wherein the casing (4) consists at least partially of PMMA, PC, COC/COP (cycloolefin copolymers or cycloolefin polymers), SAN (styrene-acrylonitrile copolymers), Durabio, silicone or glass. system according to one of the Claims 7 until 9 , wherein a non-transparent part of the casing (4) consists of PC, PMMA, ABS, PA, PBT or combinations thereof, also with fiber materials. System according to one of the preceding claims, further with optics for the transmission of light on the coupling side and/or light transmission side and/or the upper side of the light guide (1). Method for producing a light guide (1) according to one of the preceding claims with the steps: - Extruding a plastic profile as a light guide (1) and - An extruding of a plastic profile as sheathing (4). procedure after claim 12 , wherein the step of extruding the casing (4) comprises extruding a plurality of components. procedure after claim 12 or 13 , wherein the step of extruding the casing (4) comprises a step of extruding a sealing lip (43).

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