Abstract:
An illumination device for producing a light strip along a predetermined distance includes light sources and light conductors, wherein light of a first one of the light sources is distributable along a first section of the distance by a first one of the light conductors up to an end region of the first light conductor, wherein light of a second one of the light sources is distributable along a second section of the distance by a second one of the light conductors up to an end region of the second light conductor, and wherein the end region of the first light conductor and the end region of the second light conductor are arranged adjacent one another along the distance.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of German Patent Application, Serial No. 10 2011 112 321.4, filed Sep. 2, 2011, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to an illumination device for generating a light strip along a predetermined distance on a component 
         [0003]    The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention. 
         [0004]    In order to allow a person to orient themselves also inside the motor vehicle in darkness individual components for example a cup holder or a loudspeaker can be illuminated from their interior with a light source. The person can then recognize where the functional element is located in the interior without the entire interior having to be illuminated. The above mentioned illumination device allows to distribute the light of a light source along a contour of the respective functional element so that the contour is recognizable in the dark as bright strip. Typically such an illumination device is used for a circumferential illumination, i.e. in this case the strip has the shape of a closed band. 
         [0005]    In order to generate a circumferential light strip, a ring shaped light conductor made of Polymethylmethacrylate (PMMA, Plexiglas) can be used into which light is coupled on both ends. The light conductor has the shape of the contour to be represented and can for example by means of a latching engagement be fixed on the component or about the component. The light emitting diodes can each be mounted in an element for coupling-in which an electric switch is located for operating the light emitting diode and by which light of the light emitting diode is focused and directed onto a coupling surface of the light conductor. 
         [0006]    Along its longitudinal extension in the direction of extension of the contour, the light conductor has scattering centers i.e., for example indents on its outer walling or reflecting particles in its inside by which a portion of the light is respectively deflected and exits the light conductor. By this, the light of the light diodes is distributed along the distance, thereby causing the light conductor to appear evenly bright along the contour. By means of such light conductors a surface of up to 200 mm×150 mm can typically be surrounded by an evenly bright sight strip. 
         [0007]    When a larger area is to be surrounded with a circumferential light strip, the light strip has to have an according length. This poses the problem that thermally caused changes in length of the light conductor can cause mechanical tensions in its material which can lead to hairline cracks in the material or even destruction of the light conductor. In particular, in a motor vehicle temperatures of between −40° C. to 80° C. can occur. 
         [0008]    It would therefore be desirable and advantageous to provide an improved illumination device by means of which an evenly bright light strip can be produced along the contour of a large-surface-area functional element. 
       SUMMARY OF THE INVENTION 
       [0009]    The illumination device according to the invention allows producing a light strip along a predetermined distance. For this, light is distributed along different sections of this distance by a respective light conductor. Two of these light conductors cross over at their ends along a course of the distance. 
         [0010]    According to one aspect of the present invention an illumination device for producing a light strip along a predetermined distance, includes first and second light sources, and first and second light conductors, wherein light of the first light source is distributable along a first section of the distance by the first light conductor up to an end region of the first light conductor, wherein light of the second light source is distributable along a second section of the distance by the second light conductor up to an end region of the second light conductor, and wherein the end region of the first light conductor and the end region of the second light conductor are arranged adjacent one another along the distance. The illumination device according to the invention has the advantage that a continuous light strip can also be produced along a relatively long distance, i.e. an edge of a dash board or on an encasing for a sunroof. A continuous light strip means a strip-shaped region of a surface which is evenly brightly illuminated from inside along the distance. An evenly bright light strip means that differences of brightness values of the light strip along the distance are so small that the differences in brightness are imperceptible for a person. 
         [0011]    Arranging the two light conductors offset to one another instead of arranging them to abut one another with respective front sides, avoids that the two light conductors exert mechanical pressure on each other when they expand as a result of high temperature. This also avoids that the light strip is interrupted in case of contraction of the light conductors at very low temperature so that their respective overall length is smaller than at room temperature. Another advantage is that the two light conductors can be manufactured with greater tolerances with regard to their longitudinal dimensions, thus allowing decreasing manufacturing costs for the illumination device. 
         [0012]    According to another advantageous feature of the invention, the two end regions of the light conductors can be supported for movement relative to one another in a direction of extension of the distance. This avoids that a mechanical stress along the distance in the respective light conductors exceeds a predetermined value in case of a thermally caused change in length. 
         [0013]    According to another advantageous feature of the invention, the light of the two light sources is guidable in the light conductors in opposite directions of extension of the distance. In other words, the end regions of the light conductors which are arranged adjacent one another are located between the two light sources in a region which is relatively far from the two light sources. While this may cause the amount of emitted light to be smaller in the end region of the individual light conductors compared to a region which is close to the respective light source, the adjacently arranged end regions of the two light conductors together also allow to achieve the same brightness in the end regions as in the remaining sections of the distance by overlapping of the light that is emitted in the two end regions. 
         [0014]    According to another advantageous feature of the invention both light conductors are arranged in an at least partially transparent receiving device which extends along the two sections. This allows a relative movement of the light conductors with regard to the receiving device. The walls of the light conductors can also slide along the inner walling of the receiving device in the direction of extension of the distance. The receiving device allows providing a closed surface which extends along the distance i.e. along a contour and is evenly brightly illuminated from the inside. The receiving device can be made of a material which has a smaller coefficient of thermal extension compared to the material of which the light conductors are made. This allows ensuring that gap sizes between the receiving device and surrounding components do not exceed a predetermined threshold value. The smaller light conductivity of the material which is oftentimes associated with a smaller coefficient of thermal extension does not play a significant role here because the light conduction from the light sources to the individual light-exiting site occurs mostly via the light conductors. The latter can expand freely due to the described support. 
         [0015]    In order to be able to arrange the light conductors adjacent one another in a simple manner one of the light conductors preferably has an offset end region. In this way the two end regions can be arranged behind one another relative to a viewing direction from which an observer views the light strip. This results in an evenly broad light strip. For this purpose the two light conductors can also be inserted into one another in their end regions. 
         [0016]    According to another advantageous feature of the invention at least the first light conductor is configured L-shaped. A coupling-in region for the light of the first light source into the first light conductor is arranged in the bend of the L-shape. This embodiment has the advantage that an evenly bright light strip can be generated for a rectangular contour. Preferably both light conductors are configured L-shape as described. The arrangement of the coupling-in region in the bend of the L-shape has the advantage that the light strip does not appear brighter in the coupling-in region. 
         [0017]    In another embodiment, more than one light source is used in at least the first light conductor. The light of the further light sources can be distributed along a third section of the distance by means of the first light conductor up to a further end region of the first light conductor. This allows the light conductor to have a strongly curved or bent region which still appears evenly bright. The sections of the distance which can be illuminated by means of the first light conductor are preferably straight while the light sources are arranged in the curved or bent region. 
         [0018]    According to another aspect of the present invention a motor vehicle has at least one illumination device which corresponds to an embodiment of the illumination device according to the invention. This motor vehicle has the advantage that contours of large functional elements for example a control panel of a dash board, an access opening for a clove compartment or a handle for a door, can also be made recognizable in the dark by means of an evenly bright light strip. The at least one illumination device can be exposed to great temperature fluctuations without damage to the light conductors, or without a gap forming between the illumination device and a component by which the illumination device is encased due to deformation of the illumination device. 
         [0019]    In particular, in the motor vehicle according to the invention a closable opening can be surrounded by the at least one illumination device. For example, a door frame can be illuminated which allows a passenger avoiding bumping her head when entering or exiting. Preferably the at least one illumination device is arranged in a frame of a sunroof. 
         [0020]    In the motor vehicle according to the invention, an evenly bright illumination can be provided along an angular contour in a particularly simple manner, in that the light sources of the at least one illumination device are arranged in a respective corner region of the distance to be illuminated and the end regions are arranged in a straight section of the distance. This has the advantage that the light sources and the coupling-in regions of the light conductors can be arranged fixed in the motor vehicle which allows a particularly simple design of the at lest one illumination device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0021]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0022]      FIG. 1  shows a schematic representation of an illumination device for a sunroof of a motor vehicle which represents an embodiment of the motor vehicle according to the invention; 
           [0023]      FIG. 2  shows an enlarged section from the representation of  FIG. 1 ; and 
           [0024]      FIG. 3  shows a schematic representation of a cross section of one of the illumination devices of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]    Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0026]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown a frame  10  which surrounds a roof opening  12  in a roof of a (not further shown) motor vehicle. The roof opening  12  can be closed by a sunroof (not shown).  FIG. 1  shows the frame  10  from the inside of the motor vehicle in viewing direction upwards, which means in the vertical direction of the motor vehicle. The frame  10  is surrounded by a roof liner  14 . A bright strip extends along a surface of the frame  10  which allows a person located in the motor vehicle to recognize a contour of the roof opening  12  in the dark. The light strip surrounds the roof opening  12  completely and its brightness along its extension varies to such a small degree that a person is not able to recognize this variation. 
         [0027]    In order to produce the light strip, four light conductors  16 ,  18 ,  20 ,  22  are located inside the frame  10 . The light conductors  16  to  18  are each configured L-shaped. The Light conductors  16  to  18  have the same construction. For reasons of simplicity only the light conductor  16  is described in the following. 
         [0028]    The light conductor  16  has two coupling-in regions  26 ,  28  in a corner of its L-shape, each of which coupling region  26 ,  28  is inserted into a coupling-in element  30 ,  32 . Each of the coupling-in elements  30 ,  32  has illumination means in its interior whose light enters the light conductor  16  in the coupling-in region  26  or  28 . The coupling-in regions can for example each have one or multiple light emitting diodes as illumination means. The light generated in the coupling-in element  30  propagates in the light conductor  16  predominantly along a leg  34  of the L-shape and the light of the coupling element  32  correspondingly along a leg  36  of the L-shape. In a curved region  38  of the light conductor  16 , the light of both coupling-in elements  30 ,  32  overlaps. 
         [0029]    Along the legs  34 ,  36  and in the curved region  38 , portions of the light exit from the light conductor  16  and enter the inner space of the motor vehicle. The scattering centers are configured so that the amount of light exiting per section of the distance along the leg  34  and  36  until a respective end region  40 ,  42  of the legs  34  or  36  is almost the same. As a result, leg  34  illuminates a section  44  of the contour of the roof opening  12  and leg  36  illuminates a section  46  of the contour. 
         [0030]    Leg  48  of the light conductor  18  illuminates a further section  50  of the contour with light which is generated in a coupling-in element  52 . The end region  42  of the leg  36  and the end region  56  of the leg  48  overlap along a direction of extension K of the contour in a transition region  54 . For better illustration the transition region  54  is shown again enlarged in  FIG. 2 . Although the end region  42  represents the portion of the leg  36  which is farthest away from the coupling-in element  32  and correspondingly the end region  56  also represents the portion of the leg  48  which is farthest away from the coupling-in element  52 , a person does not perceive a difference in brightness of the light strip in the end regions  46 ,  50  on one hand, and in the transition region  54  on the other hand. As a result of the overlap of the end regions  42  and  56 , the light exiting from these end regions is superimposed which results in an overall brightness of the light strip in the transition region  54  which corresponds to the brightness of the light strip in the sections  46  and  50 . 
         [0031]    The end regions  42  and  56  overlap so that they are spaced apart at a distance A in the direction of extension K. The distance A can for example be 20 mm at a temperature of 20° C. 
         [0032]    When the legs  36  and  48  are heated to a temperature above 20 C the distance A is reduced. At a temperature of the legs  36  and  48  below 20° C. the distance A is correspondingly greater. 
         [0033]    The legs  36  and  48  are arranged coaxial relative to one another. The overlap of the end regions  42  and  56 , i.e. the arrangement of the two end regions  42  and  56  adjacent one another is enabled by bent shape of the end region  56 . The end region  56  has two curvatures  58 ,  60  which result in an axially parallel offset between the leg  48  and an end piece  62 . The end piece  62  is located in the direction of extension K adjacent the end piece  42 . 
         [0034]    In case of a change in length of the legs  34  and  36  of the light conductor  16  a position of the coupling-in regions  26  and  28  and the coupling-in elements  30  and  32  relative to the frame  10  remains constant. For this, the light conductor  16  is fixedly connected with the frame  10  in the region of its bend  24 . The end regions  40  and  42  on the other hand are movable along the direction of extension of the contour. 
         [0035]    This floating bearing of the legs  34  and  36  of the light conductor  16  in the frame  10  is explained in more detail by way of  FIG. 3 , which shows a sectional view of the frame  10  along a cut line indicated in  FIG. 1 . The light conductor  16  is supported in a transparent scatter body  64 . The scatter body  64  has a rectangular basic shape which corresponds to the shape of the frame  10 . The scatter body  64  surrounds the roof opening  12  completely. It can be built one-piece. 
         [0036]    The light conductor  16  is held in the scatter body  64  by a snap connection which is enabled by a latching region R of the scatter body  64 , which latching region R engages in a corresponding recess R′ of the light conductor  16 . As a result of the engagement of the latching region R in the recess R′ and an overall irregular cross section of the leg  36 , the leg  36  cannot rotate about its longitudinal axis relative to the scatter body  64 . This causes the scatter centers to always remain oriented in the same position in the scatter body. Along the direction of extension K of the contour the leg is not fixed. 
         [0037]    The scatter body  64  is mounted between a strip  66  of the frame  10  and a clamping element  68  of the frame  10 . The strip  66  can be a crown strip which can be made for example of hard rubber or a metal alloy. The clamping element holds a decorative fabric  70  of the ceiling  14 . The scatter body  64  can be connected with the strip  66  and with the clamping element  68  for example by a bonding connection. The clamping element  68  can be made for example of plastic or particle board. A gap size Z 1  between a projection  72  of the scatter body  64  via which light which enters the scattering body  64  from the light conductor, reaches the interior of the motor vehicle, and the strip  66  changes due to temperature only to a degree which is imperceptible by a user of the motor vehicle. The same applies to a gap size Z 2  between the projection  72  and the clamping element  68 . The small change of the gap sizes Z 1  and Z 2  results from a correspondingly small coefficient of thermal expansion of the material of which the scattering body  64  is made. In the example, the strip  66  is held by a connection element  74  by means of a clip connection on a metal plate of the roof  14 . A clamp  76  fixes the strip  66  relative to the connection element  74 . 
         [0038]    The light conductor  16  which is supported in the scatter body  64  has a greater light conductivity than the scatter body  64 . For this, the light conductor  16  is made of a corresponding material. The light conductor  16  can be made of Polymethylmethacrylate (PMMA) or a Polycarbonate (PC). The material of the light conductor  16  can have a greater thermal coefficient than the material of the scatter body  64 . When the light conductor  16  changes its position due to a change of the room temperature, the leg  36  slides in the scatter body  64  along the direction of extension K. 
         [0039]    Due to the similar construction, the above explanations apply also to the other light conductors  18 ,  20  and  22 . In addition to the transition region  54 , three further transition regions result from the four L-shaped light conductors  16  to  22 . The transition regions  54 ,  72  are each arranged in a center of a straight edge of the rectangular contour of the roof opening  12 . The end regions of the respective legs of the light conductors are also arranged pair wise adjacent one another in the direction of extension of the contour. In addition to the already mentioned coupling-in elements  30 ,  32  and  52 , light is fed into the light conductors by further coupling elements  74 . 
         [0040]    The example shows how the invention enables a circumferential illumination of a large surface area component, here a sunroof, without visible interruption. Four light conductors are used which are illuminated cross-wise with light emitting diodes at the corners of the sunroof. The corners of the sunroof section in the ceiling form the fixed bearings of the light conductors. The floating bearings form the overlapping ends of the light conductors which allow compensation of tolerances. The light conductors are made of customary, light-conducting material and extend in a circumferential scatter body. The scatter body is held by a strip of the frame of the sunroof. The scatter body includes the surface which is visible for the persons in the interior of the motor vehicle and can thus be mechanically decoupled from the ceiling only to a limited degree because no division is possible. In the invention the material of the scattering body can be chosen so that it has a better thermal coefficient of expansion than the light conductor located inside the scattering body. When the light conductors expand due to the heat they can move along the scattering body. The coupling-in elements can also be supported floatingly. 
         [0041]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0042]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: