Abstract:
The invention proposes a motor-vehicle headlamp ( 10 ), of the type including a main optical system ( 23 ) which comprises, arranged from back to front overall along a main optical axis (A—A), a main light source ( 16 ), a main reflector ( 14 ) of the elliptical type, and a converging main lens ( 18 ), 
     characterised in that it includes a secondary optical system ( 36 ) comprising: 
     a secondary light source ( 48 ) which is arranged behind the main lens ( 18 ) and off the path of the light rays emitted by the main light source ( 16 ); 
     and an optical distribution element ( 42 ) which is interposed between the secondary light source ( 48 ) and the exit surface ( 19 ) of the main lens ( 18 ), in such a way as to form, at the exit from the main lens ( 18 ), a secondary regulatory beam for indicating.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a motor-vehicle headlamp. 
     BACKGROUND OF THE INVENTION 
     The present invention relates more particularly to a motor-vehicle headlamp which is intended to produce at least one regulatory light beam, especially of the main-beam or of the dipped-beam type, of the type including a main optical system which comprises, arranged from rear to front overall along a main optical axis, a main light source, a main reflector of the elliptical type a first focus of which is situated in the vicinity of the source, and a converging main lens a focal plane of which passes close to a second focus of the main reflector. 
     In the motor-vehicle headlamps which include at least one main light source arranged within a reflector of generally parabolic shape or a reflector of the complex-surface type, it is known to arrange a secondary light source in a region of the reflecting wall of the reflector which is not essential to the forming of the regulatory light beam associated with the headlamp. This secondary source makes it possible to form a regulatory indicator beam of the position-light type. 
     According to the regulations in force, the position-light regulatory indicator beam, also called sidelight or sidelamp, has to shed light overall in all directions situated to the front of the headlamp with a relatively low luminous intensity compared to a main lighting beam such as a dipped beam or a main beam. 
     However, the arranging of a secondary light source in a reflecting wall of a main reflector cannot be envisaged for a headlamp equipped with a reflector of the elliptical type and with a lens. 
     This is because, since the main light source is arranged at the focus of the ellipse formed by the reflector, then the secondary light source absolutely must be arranged in a region which is very “defocused” and very much offset radially with respect to the main optical axis. 
     Consequently, the light beam produced by the secondary source at the exit from the lens is oriented mainly in a single direction very much inclined with respect to the optical axis. The luminous intensity is therefore not sufficient in the other directions, especially in the axial direction, to fulfil the regulatory requirements associated with a position-light beam. 
     Moreover, the headlamps with an elliptical reflector generally include a partial-shading device or mask, which is interposed axially between the reflector and the lens, with a view to shading some of the light rays emitted by the main light source so as to produce the corresponding regulatory light beam. 
     In the case of a headlamp forming a dipped beam, the mask is intended to shade mainly the light rays which would be directed upwards at the exit from the optical system. The mask is therefore arranged in front of the lower half of the outlet aperture of the elliptical reflector. 
     In this case, only the region of the reflecting wall of the elliptical reflector which is situated at the bottom, behind the mask, is not essential to implementing the main function and can therefore accommodate a secondary light source. 
     The light rays emitted by the secondary source then undergo the same shading effect as the main source. The light beam at the lens exit is therefore not correctly distributed in all directions, which does not allow it to satisfy the regulatory requirements. 
     Generally, when the main headlamps are of the elliptical-reflector type, it is then necessary to arrange the secondary light source outside the main headlamps, which is penalising especially in terms of costs and of bulk. 
     Moreover, the regulations of certain countries makes provision to oblige motor manufacturers to equip their vehicles with headlamps which produce a specific indicator beam, called “Day Running Light” or “daytime light”, and which are intended to be lit permanently when driving by day. 
     Currently, this new indicating function requires a specific headlamp to be produced, dedicated to producing this regulatory daytime light beam. 
     There therefore exists a requirement for the design of a headlamp making it possible, in addition to at least one main function such as a dipped-beam function or main-beam function, to perform a secondary indicating function such as a position-light or daytime light function. 
     SUMMARY OF THE INVENTION 
     The invention aims to remedy the above-mentioned drawbacks, by proposing a headlamp of the elliptical type which is simple and economical, and which makes it possible to produce an indicator beam, in addition to at least one main lighting function such as a dipped beam or a main beam. 
     To that end, the invention proposes a motor-vehicle headlamp which is intended to produce at least one regulatory light beam, especially of the main-beam or dipped-beam type, of the type including a main optical system which comprises, arranged from back to front overall along a main optical axis, a main light source, a main reflector of the elliptical type a first focus of which is situated in the vicinity of the source, and a converging main lens a focal plane of which passes close to a second focus of the main reflector, characterised in that it includes a secondary optical system comprising: 
     a secondary light source which is arranged behind the main lens and off the path of the light rays emitted by the main light source; 
     and an optical distribution element which is interposed between the secondary light source and the exit surface of the main lens, which receives the light rays emitted by the secondary source on its entry surface and which distributes them over its exit surface, in such a way as to form, at the exit from the main lens, a secondary regulatory beam for indicating, especially of the position-light type or of the daytime-light type. 
     According to other characteristics of the invention: 
     the exit surface of the optical distribution element is adjacent to a portion of the entry surface of the main lens; 
     the optical distribution element is formed in a peripheral portion of the main lens; 
     the optical distribution element is a secondary lens; 
     the secondary light source and the optical distribution element are aligned generally along a secondary optical axis which is substantially parallel to the main optical axis; 
     the secondary optical system includes means designed to concentrate the light rays emitted by the secondary source onto the entry surface of the optical distribution element; 
     the secondary light source is arranged within a secondary reflector of generally parabolic or elliptical shape; 
     the structure of the secondary reflector is formed by moulding in a single piece with the structure of the main reflector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics and advantages of the invention will become apparent on reading the detailed description which follows, for an understanding of which reference will be made to the attached drawings, among which: 
     FIG. 1 is a view in axial section, which diagrammatically represents a main-beam headlamp of the elliptical type equipped with a secondary optical system in accordance with the teachings of the invention; 
     FIG. 2 is a view in perspective which diagrammatically represents the secondary optical system of FIG. 1; 
     FIG. 3 is a view similar to that of FIG. 1 which represents a variant embodiment of the invention in which a secondary lens is formed in a portion of the main lens. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First of all, it will be noted that, from one figure to the other, the elements which are identical or similar are referenced as far as possible by the same reference marks. 
     In FIG. 1, a headlamp  10  for a motor vehicle has been represented, which is produced in accordance with the teachings of the invention. 
     In a conventional way, the headlamp  10  includes a main light bulb  12  mounted in the back of a main reflector  14  of the elliptical type, in such a way that the filament  16  of the main light bulb  12  lies close to a first focus of the main reflector  14 . 
     In the remainder of the description, an orientation from back to front will be used in a non-limiting way, along the main optical axis A—A of the headlamp  10 , which corresponds to an orientation from left to right when considering FIG.  1 . The main optical axis A—A is generally parallel to the longitudinal axis of the vehicle which the headlamp  10  equips. 
     The main optical axis A—A is substantially horizontal here, and it can be defined, for example, by the two foci of the main reflector  14 . 
     An orientation from top to bottom will also be used, in a non-limiting way, along a vertical axis when considering FIG.  1 . 
     The headlamp  10  includes a converging lens  18  which is mounted, at the front, in a framework element  20  of the headlamp  10  which is fixed onto a front transverse surface  22  of the main reflector  14 . 
     The focal plane of the lens  18  passes close to the second focus of the main reflector  14 . 
     The main light bulb  12 , the main reflector  14  and the lens  18  together form a main optical system  23  the exit surface  19  of which is the front surface of the lens  18 . 
     In the embodiment represented here, the main optical system  23  is intended to carry out a main-beam function, and, to that end, it includes a shading device, or mask  24 , which is interposed axially between the front transverse surface  22  of the main reflector  14  and the rear transverse surface  26  of the framework element  20 . The mask  24  is arranged substantially in the focal plane of the main lens  18 . 
     The mask  24  is produced, for example, in accordance with the teachings contained in the French application No. 00.08903 filed on Jul. 7, 2000. Here it has the shape of a metal plate, oriented transversely overall with respect to the main optical axis A—A, which includes a shading part  28  in the upper half of the exit aperture  30  of the main reflector  14 , and which delimits a window  32  in the lower half of the exit aperture  30  of the main reflector  14 . 
     The mask  24  here aims to form an obstacle to the light rays emitted by the main light bulb  12  towards the upper part of the reflecting wall  34  of the main reflector  14 , with a view to diminishing the luminous intensity emitted by the headlamp  10 , in main-beam mode, in a region close to the front of the vehicle. 
     In accordance with the teachings of the invention, the headlamp  10  includes a secondary optical system  36  comprising a secondary light bulb  48 , a secondary reflector  40  and an optical distribution element  42 . 
     The secondary optical system  36  is intended here to perform a regulatory service of the position-light type. It is therefore necessary for the secondary light bulb  48  to produce a light beam at the exit from the main lens  18  which is spread out in all directions to the front of the vehicle, especially on the sides, downwards and upwards, as well as in the axis of the vehicle, as the regulations envisage. 
     The secondary optical system  36  here defines a secondary optical axis B—B which is substantially parallel to the main optical axis A—A and which is arranged here below the latter. 
     The secondary reflector  40  is adjacent to the lower part of the reflecting wall  34  of the main reflector  14 . Here it has a generally parabolic shape. It includes, to the front, an exit aperture  44  and, to the rear, a hole  46  allowing fitting of the secondary light bulb  38 , in such a way that its filament  48  is arranged generally at the focus of the parabola. 
     It will be noted that the mask  24  includes a window  50  facing the exit aperture  44  of the secondary reflector  40 , so as to let through all the light rays emitted by the secondary light bulb  38 . 
     In FIG. 2, the secondary reflector  40 , the secondary light bulb  38 , the optical distribution element  42 , as well as the entry surface  56  of the main lens  18  have been represented diagrammatically in perspective. 
     The optical distribution element  42  here is a piece, made of glass for example, forming a converging secondary lens. 
     The secondary lens  42  therefore includes, at the rear, an entry surface  52  of overall concave hemispherical shape, which is inclined forwards and downwards, and, at the front, a flat exit surface  54  which is oriented transversely with respect to the secondary optical axis B—B. 
     Advantageously, the exit surface  54  of the secondary lens is adjacent to a peripheral portion of the rear entry surface  56  of the main lens  18 . 
     It will be noted that, if the secondary lens  42  were not present, as the filament  48  of the secondary light bulb  48  is not arranged at the focus of the main lens  18 , the major part of its light rays would be directed along directions substantially parallel to the secondary optical axis B—B over the peripheral portion face-to-face with the entry surface  56  of the main lens  18 . The major part of these light rays would then be diverted upwards at the exit from the main lens  18 , because of its convergence properties. 
     The secondary lens  42  therefore makes it possible to correct the angle of incidence of the light rays emitted by the secondary light bulb  38  onto the entry surface  56  of the main lens  18 , in such a way that these light rays leave the main lens  18  while being distributed in all the directions to the front of the headlamp  10 , which makes it possible to form the regulatory position-light beam. 
     In order to form the secondary lens  42 , the conventional properties of the field of optics are used. It is possible, for example, to determine the optical characteristics of the secondary lens  42  which make it possible, at the exit from the main lens  18 , to obtain light rays seeming to originate from the focus of the main lens  18 , that is to say which make it possible to place the virtual image of the secondary filament  48  at the focus of the main lens  18 . 
     Advantageously, the structure  58  of the secondary reflector  40  is formed by injection and moulding in a single piece with the structure  60  of the main reflector  14 . 
     Structure  58 ,  60 , here is intended to mean the body of each reflector  14 ,  40 , as well as the means  62 ,  64  for support of each light bulb  12 ,  38 . 
     The structure  58 ,  60  of the reflectors  14 ,  40  is produced, for example, by injection and moulding from metal, such as an alloy of magnesium or of aluminium. The reflecting surfaces of the reflectors  14 ,  40  are produced, for example, by depositing a layer of aluminium or of aluminium alloy. 
     As the main and secondary optical axes A—A and B—B are substantially parallel, the two light bulbs  12 ,  38  can be mounted in their respective reflectors  14 ,  40  according to the same principle, that is to say axially from rear to front, inside corresponding holes. This makes it possible to facilitate the operations of fitting and removal of the light bulbs  12 ,  38  in the headlamp  10 , especially when changing the light bulbs  12 ,  38 . 
     For preference, the headlamp  10  according to the invention is a main-beam headlamp, since the light beam from it is less demanding in terms of photometry, which makes it possible not to take account of the degradation of the light beam originating from the main light bulb  12  due to the presence of the secondary lens  42 . 
     However, the headlamp  10  according to the invention can also be used to form a dipped beam, or to perform several different functions, in the case in which the headlamp  10  includes several movable masks  24 , for example, which are associated with several different lighting functions. 
     According to one embodiment variant, which is represented in FIG. 3, the secondary lens  32  is formed directly in the main lens  18 . 
     As can be seen in this figure, a lower peripheral portion of the main lens  18  forms a secondary lens  42  which is arranged axially (B—B) face-to-face with the secondary light bulb  38 . 
     Advantageously, the entry surface  52  of the secondary lens  42  is flat and it is situated in the same transverse plane as the entry surface of the main lens  18 . 
     The exit surface  54  of the secondary lens  42  is of substantially hemispherical and convex shape here. 
     According to this embodiment, the secondary reflector  40  is preferably of the elliptical type, and it includes a first focus close to the secondary source  48  and a second focus close to the focal plane of the secondary lens  42 . 
     The main lens  18  is currently produced by moulding. Consequently, in order to integrate the secondary lens  42  into the main lens  18 , it is sufficient to modify the shape of the mould of the side with the exit surface. 
     Advantageously, the headlamp  10  according to the invention can be used in the context of a main light beam using infrared light. The document FR-A-2.756.237 describes an example of a headlamp capable of producing an infrared-light beam. 
     In fact, in this type of headlamp, it is sought to eliminate the “red leakages”, that is to say the red-coloured light rays which leave the headlamp, despite the presence of a filter designed to let through only the infrared rays. 
     By virtue of the secondary light bulb  38 , which shares its exit surface  19  of the headlamp  10  with the exit surface  19  of the main light bulb  12 , it is possible to drown the red-coloured light rays originating from the main light bulb  12  with the substantially white-coloured light rays originating from the secondary light bulb  38 . 
     Needless to say, the headlamp  10  according to the invention can be used in every case which requires an indicator beam, in particular to form a regulatory light beam for driving by day, or daytime light. 
     According to one embodiment variant, not represented, the optical distribution element  42  may be a mirror or a prism of appropriate shape. 
     In the embodiments described above, a secondary reflector  40  has been used to concentrate the light rays originating from the secondary light bulb  38  onto the entry surface  52  of the secondary lens  42 . According to embodiment variants (not represented) of the invention, it is possible to use other means of concentrating the light rays, such as light guides, bundles of optical fibres, Fresnel-lens (or graded-lens) concentrating devices, etc, for example. 
     As Fresnel-lens concentrating device, it is possible to use a device such as a “cap” which is used in certain vehicle rear indicator lights to concentrate the light rays emitted by a light bulb without a reflector into parallel directions. 
     The cap generally includes a tubular fixing portion and a hemispherical portion which “envelops” the associated light bulb and which forms a Fresnel lens focused on the filament of the light bulb. The cap is generally produced from a plastic which can easily be tinted, which may be advantageous in the case of a main light beam using infrared light, with a view to eliminating the “red leakages” by the addition of slightly coloured light. 
     It will be noted that, when the main light bulb  12  is lit, it produces a substantial quantity of heat which is transmitted by convection, to a large extent to the upper part of the main reflector  14 . However, for reasons of cost, the light bulbs  38  used to form the secondary source generally have plastic lamp bases which are sensitive to heat. 
     Consequently, the secondary reflector  40  and its light bulb  38  are preferably arranged below or beside the main reflector  14 , so as to reduce the heating of the secondary light bulb  38  when the main light bulb  12  is lit.