Patent Publication Number: US-6986594-B2

Title: Lighting device for motor vehicles

Description:
The present invention relates to a lighting device for motor vehicles and in particular to a lighting device that can be used as a motor vehicle lamp. 
     Motor vehicle lamps essentially serve to render the outlines of the vehicle visible even in the dark and to indicate the manoeuvring intentions of the vehicle driver to other road users. Such lamps may be side lamps and parking lamps, rear lamps, turn-signal indicators or brake lights and usually comprise a light source together with an end cover composed of a suitable material such as glass or plastic, for example. In modern motor vehicles, however, use is increasingly being made of lamps which have an end cover comprising multiple sections. The various sections of the end cover can then have different optical characteristics, colours and design shapes. 
     In such lamps having an end cover comprising multiple sections it may be desirable, not only on aesthetic but also on functional grounds, for example, to concentrate the light from the light source on to specific sections of the end cover instead of shining it uniformly on to the end cover. 
     The object of the present invention, therefore, is to provide a lighting device for motor vehicles having an end cover made up of multiple sections, in which such a concentration of the light beams emitted from the light source on to specific sections of the end cover is possible. 
     According to the invention this object is achieved by a lighting device which comprises a light source and an end cover having at least a first section and a second section. The light source may be an R5W bulb, for example, or some other bulb or another means of illumination, such as LED&#39;s for example. The lighting device further comprises a first reflector, which directs light emitted by the light source on to the end cover. A first optically active element, which deflects the light rays emitted by the light source so that the deflected rays strike the first reflector at an angle of incidence, the associated angle of reflection of which causes the rays from the first reflector to be directed at least substantially on to the second section of the end cover, is arranged in the ray path between the light source and the reflector. In other words, the first optically active element deflects the light rays in such a way that the rays only strike those areas of the first reflector which transmit the light on to the second section of the end cover. The arrangement according to the invention therefore allows the light emitted by the light source to be concentrated on to a defined section of the end cover. 
     The first section of the end cover preferably has a lower light transmission than the second section of the end cover. Here the first section may either still have a certain light transmission or it may be completely non-transparent. The arrangement according to the invention means that in such a lighting device the light losses due to the emission of light on to the less transparent first section of the end cover are minimised, thereby permitting optimum utilisation of the light emitted by the light source. 
     The first section of the end cover may be arranged in a central area of the end cover and enclosed by the second section of the end cover. The first section is preferably circular and the second section of annular design shape. The first optically active element then directs the light rays emitted by the light source at an angle of incidence to the first reflector, the associated angle of reflection of which causes the rays from the first reflector to be directed on to the annular second section of the end cover enclosing the first section. In this way a circular lamp can be provided which creates an especially attractive aesthetic impression. 
     The first section of the end cover is preferably designed as reflex reflector and reflects light incident upon its outer surface remote from the light source. The reflex reflector is only slightly transparent, if at all, for light shone by the light source on to its inner surface facing the light source. A lighting device of such a type is particularly suited to use as a vehicle tail light, for example as a rear lamp or brake light. The concentration of the light rays emitted by the light source on to the second section of the end cover means that a high luminous efficiency can be achieved despite the low light transmission of the reflex reflector. 
     The light source is advantageously arranged behind the first section of the end cover designed as reflex reflector. This makes it impossible to discern the light source, for example a bulb, from outside, thereby creating an especially attractive aesthetic impression. 
     The light source may be a bulb, the filament of which is arranged at the focal point of the first reflector. 
     The first optically active element is preferably hemispherical. This ensures that all the light emitted by the light source passes through the first optically active element. The centre of the hemispherical first optically active element preferably coincides with the focal point of the first reflector. 
     The first optically active element may be provided with an annular prism and cylindrical lens. The prism lens produces a deflection or a total reflection of the incident light rays, whilst the cylindrical lens causes a dispersion. The first optically active element furthermore contains non-optical surfaces. The term “non-optical surfaces” is here used to refer to surfaces having no optical function, through which the light is directed straight on to the first reflector without being deflected or reflected. 
     In a preferred embodiment of the lighting device according to the invention a second reflector, which reflects light not shone directly from the light source on to the first optically active element on to the first optically active element, is provided adjacent to the first reflector. The second reflector may be hemispherical and may enclose the light source on a side remote from the end cover. The light source may extend into the second reflector through an aperture, a cylindrical continuation of the second reflector surrounding a socket holder for the light source. The second reflector also permits the utilisation of light that has not been shone directly on to the first optically active element, thereby further increasing the luminous efficiency of the lighting device. 
     The second reflector is preferably provided with at least one ventilation opening in order to prevent heat accumulation inside the light device. 
     In a first preferred embodiment of the lighting device according to the invention the first reflector is a parabolic reflector, so that the light rays directed on to the first reflector by the first optical element are directed essentially parallel to one another on to the second section of the end cover. Alternatively the first reflector may also, however, be designed as free-form reflector. 
     The second section of the end cover may be of light-dispersing design, the dispersion of the light directed on to the second section of the end cover being produced by a plurality of lenses. This ensures a uniform distribution of the light emitted by the lighting device. 
     Alternatively, in a second preferred embodiment of the lighting device according to the invention the first reflector may also be provided with a plurality of second optically active elements, which disperse light rays incident upon the first reflector so that they are directed as diffused radiation on to the second section of the end cover. In this embodiment of the lighting device the light directed on to the first reflector by the first optically active element is already dispersed by the second optically active elements, so that a uniform light distribution is obtained. A dispersion lens formed in the second section of the end cover is therefore not required in this embodiment. 
    
    
     
       Two examples of embodiments of the lighting device according to the invention are explained below with reference to the schematic drawings attached, of which 
         FIG. 1  shows a longitudinal section through a first example of an embodiment of the lighting device according to the invention, 
         FIG. 2  shows a perspective view of the first example of an embodiment of the lighting device according to the invention represented in  FIG. 1 , 
         FIG. 3  shows a perspective view of a second example of an embodiment of the lighting device according to the invention, and 
         FIG. 4  shows a perspective view of the second example of an embodiment of the lighting device according to the invention represented in FIG.  3 . 
     
    
    
     In the figures attached a lamp that can be used in a motor vehicle is generally denoted by  10 . The lamp  10  comprises a bulb  12  serving as light source, a first reflector  14  and an end cover  16 . The end cover  16  of circular design shape has a circular first section  18  arranged around a centre point M of the end cover  16 , together with an annular second section  20  enclosing the first section  18 . The first section  18  is designed as reflex reflector and reflects light incident upon outer surface  22  thereof remote from the bulb  12 . It is only slightly transparent for the light which the bulb  12  shines on to its inner surface  24  facing the bulb  12 . By contrast, the annular second section  20  of the end cover  16  has a high light transmission. 
     The bulb  12  arranged behind the circular first section  18  of the end cover extends partially into the first reflector  14  and on its front side facing the end cover  16  is enclosed by a first hemispherical optically active element  26 . A filament  27  of the bulb  12  is arranged at a focal point B of the first reflector  14  coinciding with the centre point of the first hemispherical optically active element  26 . As is shown in  FIGS. 1 and 3 , the light emitted by the bulb  12  first passes through the first optically active element  26  and then strikes the first reflector  14 . 
     The first optically active element  26  is provided with an annular prism and cylindrical lens, not shown in the figure, and non-optical surfaces. The prism lens produces a deflection or a total reflection of the incident light rays, whilst the cylindrical lens causes a dispersion. Through the non-optical surfaces the light is directed straight on to the first reflector  14  without being deflected or reflected. 
     The first optically active element  26  produces a deflection of the light rays emitted by the bulb  12 , so that they strike the first reflector  14  at an angle of incidence, the associated angle of reflection of which causes the rays from the first reflector  14  to be directed on to the second section  20  of the end cover  16 . 
     A hemispherical second reflector  28  is arranged on the rear side of the bulb  12  remote from the end cover  16 . The hemispherical second reflector  28  is arranged over an aperture  29  formed in the first reflector  14  and through which the bulb  12  extends into the first reflector  14 . The second reflector  28  likewise has an aperture  30 , through which the bulb  12  extends into the second reflector  14 . A cylindrical continuation  32  of the second reflector  28  encloses a socket holder  34  of the bulb  12 . Light rays that are not shone directly from the bulb  12  towards the first optically active element  26  are reflected by the second reflector  28 , so that the reflected rays also pass through the first optically active element  26 . The second reflector  28  has a ventilation opening  36 , which prevents the lamp  10  overheating. 
     In the embodiment of the lamp  10  represented in  FIGS. 1 and 2 , the first reflector  14  is designed as parabolic reflector, whilst the second section of the end cover  16  is designed to disperse light. The light dispersion in the second section  20  of the end cover  16  is produced by a plurality of lenses  38 . As shown in  FIG. 1 , the parabolic reflector causes the light rays deflected by the first optically active element  26  to be reflected essentially parallel to one another on to the second section  20  of the end cover  16 . There they are dispersed by the lenses  38 , thereby ensuring a uniform distribution of the light passing through the second section  20 . 
     In the alternative embodiment of the lamp  10  represented in  FIGS. 3 and 4  the first reflector  14  is provided with a plurality of second optically active elements  40 . As is shown in  FIG. 3 , the second optically active elements  40  produce a dispersion of the light rays incident upon the first reflector  14 . The dispersed light rays are then deflected on to the second section  20  of the end cover  16 . A dispersion lens formed in the second section  20 , as has already been described in connection with the example of an embodiment represented in  FIGS. 1 and 2 , is not necessary in this embodiment of the lamp  10 , since the uniform distribution of the light emitted by the light source is already ensured by the dispersion effect of the second optically active elements  40 .