Abstract:
A headlight for a motor vehicle designed to fulfil several functions, in particular a dual functions, one of the functions corresponding to a beam with cut-off, comprising: a light source, a main elliptical reflector having a scalloped part and an optical axis; a main lens disposed in front of the main elliptical reflector; a retractable shield able to occupy at least one active position for the cut-off beam and a retracted position for another type of beam; a secondary elliptical reflector coupled to the scalloped part of the main elliptical reflector and having a optical axis inclined with respect to that of the main reflector; and an additional lens disposed in front of the secondary elliptical reflector having an optical axis essentially parallel to that of the main lens.

Description:
FIELD OF INVENTION  
       [0001]     The invention relates to a headlight for motor vehicles designed to fulfil several optical functions. In particular, the invention relates to a dual function headlight with one function at least corresponding to a beam with cut-off. This headlight being of the type which comprises: 
        a reflector of the elliptical type, having for example an internal focus and an external focus on an optical axis,     a light source, preferably placed in the vicinity of the internal focus,     a lens disposed in front of the reflector and preferably having a focus merged with or adjacent to the external focus of the reflector,     and a retractable shield able to occupy at least one active position for a beam with cut-off, and a retracted position for another type of beam, the shield in the active position preferably having a cut-off edge in the vicinity of the focus of the lens.        
 
       BACKGROUND OF THE INVENTION  
       [0006]     Multifunction headlights are known, in particular dual function headlights with a halogen light source, which provide the beam with cut-off, in particular a dipped beam and, when the shield is in the retracted position, another type of beam without cut-off. However, this beam without cut-off is generally too weak to constitute an approved main beam so that it is necessary to provide an additional main-beam headlight which is switched on when the shield is retracted.  
         [0007]     Multifunction headlights are also known, in particular dual function headlights with a halogen light source, approved only for the production of a beam without cut-off, in particular a main beam, but this beam is narrow and not very homogeneous. Dual-function headlights with a xenon source are approved alone with a main beam of satisfactory width, but the homogeneity also requires to be improved.  
       SUMMARY OF THE INVENTION  
       [0008]     The aim of the invention is in particular to provide a multifunction headlight, in particular a dual function headlight, for motor vehicles, which makes it possible to obtain an improved function without cut-off, in particular a main-beam function, which does not require an additional headlight and which provides a sufficient width of the beam, with good homogeneity. It is also desirable for this headlight to remain relatively simple and economical in design.  
         [0009]     According to the invention a headlight for a motor vehicle of the type defined above is characterised in that: 
        the elliptical reflector comprises a scalloped (cut out) part, this scalloped area preferably being provided in an area which is substantially not useful optically for the cut-off beam,     a secondary elliptical reflector is added in the scalloped area of the main reflector, this secondary reflector having an internal focus close to that of the main reflector, the optical axis of the secondary reflector being inclined with respect to that of the main reflector and the external focus of the secondary reflector being distant from the optical axis of the main reflector,     and an additional lens is disposed in front of the secondary reflector with its focus close to the external focus of the secondary reflector, this additional lens having an optical axis essentially parallel to that of the main lens.        
 
         [0013]     The main lens advantageously consists of a convergent lens and the additional lens also consists of an additional convergent lens. The additional lens can constitute a duplication of the central part of the main lens. In a variant, the additional lens is a divergent lens.  
         [0014]     The additional lens can be inserted in a scalloped part of the main lens. The scalloped part of the main lens is situated opposite the scalloped part of the main reflector. Each scalloped part can be situated in the bottom area of the reflector and lens. In a variant, the scalloped part is situated on the right or left of the reflector and main lens. The main lens and the additional lens can be produced in a single moulded piece.  
         [0015]     The shield can be formed by a single plate. The retracted position can be obtained by rotation of the shield about its transverse edge remote from the optical axis of the main reflector. The shield can also pass from an optically active position to a retracted position by other movements, for example by translation, in particular in the plane of the shield/in a substantially vertical plane. The shield can then be arranged so that it has a window in the bottom part: in the “descended” position, the shield is designed so as to allow the light to pass to the main lens and additional lens. “Window” means an opening in the shield of appropriate dimensions and shapes.  
         [0016]     The light source can be a halogen lamp with a single filament. Compared with a dual-filament lamp, this choice requires the use of a moving shield. On the other hand, it is advantageous on an optical level, since dual-filament lamps generally require making a large passage hole at the bottom of the mirror, this type of lamp being appreciably bulkier than a single-filament lamp.  
         [0017]     Provision can be made for the shield to have only one active position and one retracted position, so as to obtain a dual function. However, provision can also be made for the shield to have not only a retracted function but also at least two active positions, making it possible to obtain several beam functions with different cut-offs. Then, for example, a triple function or multifunction is obtained according to the design of the shield.  
         [0018]     According to another possibility, the shield is produced in two parts that can be retracted separately, namely a first part closer to the optical axis of the main reflector, whose retraction makes it possible to obtain a first type of main beam, and a second part, further away from the main optical axis, whose retraction with that of the first part makes it possible to obtain a beam without other cut-off, in particular a stronger main beam.  
         [0019]     Optionally, the shield is associated with an additional optical element disposed between the light source and the shield, the additional optical element being in the vicinity of one of the optically active edges of the shield and having at least one reflective surface able to redirect, above the optically active edge of the shield, light rays emitted by the source in the direction of the shield. This additional element can take the form of a plate whose front edge is pressed against the optically active edge of the shield, which is substantially flat and an upward-turned face of which is reflective. This element can be fixed mechanically to the shield, or can form an integral part of it. This element can be designated by the term “folder component”.  
         [0020]     This folder component is designed so that it returns the rays in a suitable fashion towards the associated lens, rays which, otherwise, would have been lost. This folder component can be associated with one or other of the parts of the shield, in the case where the shield is in several parts, as will be detailed with the help of the example according to  FIG. 11 .  
         [0021]     The beam with cut-off, in particular the dipped beam, is obtained with the two parts of the shield in the active position.  
         [0022]     According to a variant, the second part of the shield has a cross section substantially in the form of an L with two arms at right angles with different lengths and is mounted so as to pivot about a transverse axis passing through the vertex of the angle formed by the L. This second part of the shield can occupy a first angular position in which the long arm of the L is in the active position and cooperates with the first part of the shield in the active position in order to give the beam with cut-off; in a second angular position of the second part, the shorter arm of the L is in the active position when the first part of the shield is also in the active position, a space existing between the facing edges of the two parts and allowing the passage of light rays in order to reinforce a central area of the cut-off beam. It is thus possible to obtain an AFS function which corresponds to a dipped function on a motorway. This variant is particularly advantageous with a light source of the xenon lamp type.  
         [0023]     Another object of the invention is the motor vehicle equipped with at least one headlight described above. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The invention consists, apart from the provisions disclosed above, of a certain number of other provisions which will be dealt with more explicitly below with regard to example embodiments described with reference to the accompanying drawings, but which are in no way limiting. In these drawings:  
         [0025]      FIG. 1  is a schematic vertical section intended to give an understanding of the design of a headlight according to the invention;  
         [0026]      FIG. 2  is a schematic view in exploded perspective of the reflectors and lenses of a headlight according to the invention;  
         [0027]      FIG. 3  is a schematic vertical section of a dual-function headlight according to the invention with halogen light source, the shield being in the active position for the dipped function;  
         [0028]      FIG. 4  is a simplified right-hand view with respect to  FIG. 3  of the lenses;  
         [0029]      FIG. 5  is a schematic representation of the area illuminated by the headlight of  FIG. 3 ;  
         [0030]      FIG. 6  shows, similarly to  FIG. 3 , the same headlight with the shield in the retracted position for a main beam without cut-off;  
         [0031]      FIG. 7  shows, similarly to  FIG. 5 , the area illuminated by the headlight in the position in  FIG. 6 ;  
         [0032]      FIG. 8  is a schematic view, similar to  FIG. 6 , of a variant embodiment with an additional divergent concave lens;  
         [0033]      FIG. 9  is a vertical schematic section of a headlight according to the invention with a xenon source comprising a shield consisting of two independent parts, in the main-beam position;  
         [0034]      FIG. 10  shows the illumination areas obtained with the headlight of  FIG. 9  when the first and second parts of the shield are in the retracted position; and  
         [0035]      FIG. 11  shows, similarly to  FIG. 9 , the headlight in a configuration providing a motorway dipped function (AFS) with the first part of the shield in the active position and the second part in the retracted position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]     Referring to  FIG. 1  of the drawings, a headlight can be seen comprising an elliptical reflector  1   i  having an internal focus Fi and an external focus Fe on an optical axis X-X. A light source S is placed in the vicinity of the internal focus Fi. A lens formed by a convergent lens Lo is disposed in front of the reflector and the focus of the lens is merged with or adjacent to the external focus Fe. A shield M in the active position is essentially orthogonal to the optical axis X-X. The top edge Mh of the shield constitutes a cut-off edge and is in the vicinity of the focus of the lens Lo and of the external focus Fe. The last useful ray Ru for the cut-off beam falls at a point  2  on the reflector  1  such that the reflected ray Ru 1  arrives on the peripheral edge of the lens Lo. Thus, the light rays which form in the area  3  situated in front of the point  2  will give reflected rays which will not be recovered by the lens Lo. The area  3  of the reflector  1  is therefore an area which is not useful optically for the production of the cut-off beam.  
         [0037]     According to the invention, as clearly visible in  FIG. 2 , the reflector  1  comprises a scalloped part  4  in the area  3  that is not useful optically for the cut-off beam. This scalloped part  4  is situated, according to the example in  FIG. 2 , at the bottom part of the reflector and has the shape of a scallop open towards the front, that is to say in the direction of propagation of the light beam.  
         [0038]     A secondary elliptical reflector  5  ( FIGS. 2 and 3 ) is added in the scalloped area  4 . The reflector  5  is formed by a ellipsoid part whose concavity is turned towards the inside of the reflector  1 . The contour of the reflector  5  is connected to the contour of the scallop  4  and opens towards the front. The reflector  5  forms a kind of protrusion with respect to the surface of the reflector  1 .  
         [0039]     The secondary reflector  5  comprises an active front part  5   a  which participates in the production of the light beam, and rear part  5   b  which is not reached by the light rays coming from the source S and which serves for connection with the main reflector  1 . The front part  5   a  is situated on a surface of an ellipsoid whose extension is shown in broken lines in  FIGS. 3 and 6 , which has the same internal focus Fi as the main reflector  1 . The major axis Y-Y of the ellipsoid  6 , which corresponds to the optical axis of the reflector  5 , is inclined with respect to the optical axis X-X of the main reflector  1 . The external focus Fe 5  of the secondary reflector  5  is situated in front of this reflector at a transverse distance towards the bottom of the axis X-X.  
         [0040]     The bottom edge  7  of the shield M is situated at the bottom edge of the reflector  5 . The shield M is mounted so as to rotate about an axis extending along its bottom edge  7  so as to be able to be retracted from the active position illustrated in  FIG. 3  into a retracted position illustrated in  FIG. 6  by a rotation of 90° causing it pass from a vertical position ( FIG. 3 ) to a horizontal position ( FIG. 6 ).  
         [0041]     An additional lens  8  constituting a duplication of the central part  9  of the main lens L is disposed in front of the secondary reflector  5 . The focus of the additional lens  9  is merged with the external focus Fe 5  of the secondary reflector  5  or adjacent to this focus. The optical axis of the additional lens  8  is parallel to the axis X-X. The lens L is advantageously scalloped in a concave part  10  in its bottom part situated facing the secondary reflector  5 . The top part of the additional lens  8  fits within this scallop  10 , whose shape it matches. According to the embodiment in  FIGS. 3 and 6 , a step  11  is formed at the junction of the additional lens  8  and the main lens  9  less thick in the area considered than the lens  8 . It would however be possible to provide a connection of the additional lens and main lens without this step  11 .  
         [0042]     Advantageously, the main lens L and the additional lens  8  can be moulded in a single piece, in particular made from transparent plastics material. Alternatively, the lens can be made from glass. In a variant, the additional lens  8  is attached and fixed, in particular by adhesive bonding, to the main lens L.  
         [0043]     The functioning of the headlight in  FIGS. 3 and 6  is as follows. A first function corresponding to a beam with cut-off, namely a dipped beam, is obtained when the source L is switched on and the shield M is in the active position illustrated in  FIG. 3 , that is to say in the vertical position. The area of illumination on a screen situated in front of the headlight and orthogonal to the axis X-X is illustrated by the hatched area  12  in  FIG. 5 ; this is a simplified representation giving the external contour of the illumination area, without reproducing the isolux curves within this area. The point of maximum illumination is situated substantially halfway across the area, slightly below the top cut-off edge  13  which comprises, in a conventional manner for travelling on the right, a horizontal left-hand part and a right-hand part rising at a given angle of inclination. The edge  13  is an image of the top edge of the shield M.  
         [0044]     When the shield M is folded down in order to provide the second main-beam function, the illumination area, illustrated in  FIG. 7 , comprises, above the area  12 , an area  14  whose isoluxes have not been shown.  
         [0045]     The secondary reflector  5  in combination with the additional lens  8  contributes to the reinforcement of the illumination of the area  14  and avoids the need for a supplementary main-beam headlight when the source S is a halogen source with a single filament. The homogeneity and intensity of the beam are improved whatever the light source.  
         [0046]     The transverse offset between the optical axis of the main lens  9  and the additional lens  8  is only a few centimeters and is not noticeable at a distance of 25 m, at which the illumination checking screen is generally placed.  
         [0047]     Instead of providing the additional lens  8  at the bottom part of the main lens L, it could be provided on the right or left side, with a corresponding scallop in the main lens. However, the light beam would be slightly degraded and in addition the right and left headlights of the same vehicle would be different.  
         [0048]     The example embodiment in FIGS.  3  to  7  have been given with a single additional lens  8 . It would however be possible to provide several hollowed-out parts each associated with an additional lens and a corresponding secondary reflector such as  5 .  
         [0049]      FIG. 8  shows a variant embodiment according to which the additional lens  8   a  is a divergent lens having, for example, a front face concave towards the outside. The external focus Fe 5  of the secondary reflector  5  is situated at the front of the concave face of the lens  8   a , merged with or in the vicinity of the focus of this lens.  
         [0050]     The optical axis Y of the secondary reflector  5  is less inclined to the optical axis X-X because the external focus Fe 5  is situated further forward than in the case where the additional lens  8  is convex. The result is an improvement in efficacy.  
         [0051]     In summary, for the second main-beam function, in the case of a light source of the halogen type, the maximum illumination to be obtained for the main beam does not require any supplementary headlight and results from the combination of the main reflector and an additional optical system implemented with secondary reflector  5  and additional lens  8 .  
         [0052]     By way of non-limiting example, the-maximum illumination area for the main-beam function must reach  63  lux;  47  lux comes from the main reflector and the additional  16  lux comes from the additional system consisting of reflector  5  with lens  8 .  
         [0053]     In this way a dual-function halogen headlight is produced which is approved alone.  
         [0054]     In the solution illustrated in  FIGS. 3 and 5  with the additional lens  8  situated at the bottom part, the performance of the main-beam function will depend on the main lens L depending on whether it is whole or not. The additional lens  8  can be either integrated in the main lens L as illustrated in  FIG. 4  or pressed up against it below.  
         [0055]     FIGS.  9  to  11  illustrate a variant embodiment with a xenon light source Sa that has higher performance than a halogen source. With such a xenon source, an approved dual main-beam and dipped function is obtained without it being necessary to provide an additional system comprising the secondary reflector  5  and a corresponding additional lens.  
         [0056]     However, it is possible to take advantage of the solution of the invention to increase the possibilities offered by the headlight.  
         [0057]     As illustrated in  FIG. 9 , the main reflector I comprises, as in the previous case, a cut-out in the optically non-useful part and the secondary reflector  5  is still connected to the main reflector.  
         [0058]     On the other hand, the shield Ma is produced in two parts respectively  15  and  16 . The first part  15  corresponds to the top part and is articulated about a transverse axis passing through its bottom edge in order to be able to take a retracted horizontal position illustrated in  FIG. 9  or an active vertical position illustrated in  FIG. 11 .  
         [0059]     The bottom part, or second part,  16  of the shield has an L-shaped cross section and is articulated about a horizontal transverse axis passing substantially through the vertex of the right angle formed by the arms  17 ,  18  of the L. In the active position, illustrated in  FIG. 9 , the long arm  17  of the L is vertical whilst the arm  18  is horizontal and turned towards the rear. In the retracted position the long arm  17  is horizontal and the small arm  18  is vertical as illustrated in  FIG. 11 .  
         [0060]     The dual-function headlight Sa with xenon source fulfils the first dipped-beam function when the top part  15  of the shield Ma is in the vertical active position and the bottom part  16  has its long arm  17  vertical. This configuration is not shown in the drawing and can be obtained with partial overlap of the bottom area of the part  15  and the top area of the arm  17 .  
         [0061]     In order to obtain a dipped function, the retraction of the top part  15  is demanded, which passes into the horizontal position as illustrated in  FIG. 9 , while the long arm  17  remains vertical and essentially masks the beam which normally falls on the additional lens  8 .  
         [0062]     The illumination area on a screen situated at a distance from the headlight and orthogonal to the optical axis then corresponds to the representation in  FIG. 7 .  
         [0063]     In order to obtain a main-beam function with stronger illumination, the top part  15  of the shield is kept in the horizontal retracted position and the long arm  17  is made to pass from the vertical position to the retracted horizontal position. There is then obtained, as illustrated in  FIG. 10 , a central illumination area  18  reinforced by virtue of the additional reflector  5 /lens  8  optical system.  
         [0064]      FIG. 11  illustrates a configuration according to which the top part  15  of the shield is in the active position whilst the short arm  18  of the second part of the shield is vertical and the long arm  17  is horizontal, retracted. This configuration makes it possible to obtain an AFS (Advanced Front Lighting System) function which corresponds to a dipped-beam function on the motorway with a reinforced illumination area below the cut-off line. This cut-off line corresponds to the merged image of the top edges of the shields  15  and  18 . When a second cut-off of the dipped-beam type is kept for the top edge of the short arm  18 , when it is vertical, care is taken to align the cut-offs provided by the two top edges of the shields  15  and  18 . The bottom part  16  of the shield makes it possible, when it passes into the retracted position with the horizontal arm  17 , to obtain a supplementary range in dipped or main beam mode.  
         [0065]     The configuration for obtaining a main beam with a strong illumination makes it possible to dispense with the problems of loss of maximum in grained lacquer and to keep homogeneity of illumination when the vehicle turns.  
         [0066]     The invention makes it possible to produce, with a halogen or xenon light source, a dual-function headlight with an improved beam and which does not require a secondary headlight for the main-beam function.  
         [0067]     Compactness of the headlight and a saving in space in the headlight for other functions are obtained.  
         [0068]     Though the example according to the invention concerns a dual function it is clear that the invention applies in a similar fashion to systems with more than two functions, by choosing the configuration and shield movement ad hoc.