FR2797029A1 - ELLIPTICAL PROJECTOR FOR A MOTOR VEHICLE, CAPABLE OF GENERATING A TWO-FUNCTIONAL LIGHT BEAM - Google Patents

Abstract

A motor vehicle headlamp comprises in combination two light sources (10a, 10b), a mirror (20) and a lens (40). The sources occupy a first focal region (F1a, F1b) of the mirror, and the lens (40) has a focal line (LF) occupying a second focal region of the mirror and extending on either side of an axis ( XL). The lens projects onto the road an image of a light spot formed by the mirror in its second focal region. The mirror (20) comprises a first zone (21) forming with one (10a) of the sources a light spot having a concentration zone located in the vicinity of the focal line (LF) and offset laterally relative to the optical axis (XL) of the lens, and a second zone (22) forming with the other source (10b) a spreading zone distributed laterally in the vicinity of said focal line (LF) .Application in particular to bend / fog lights.

Description

The present invention relates generally to lighting

  automotive, and more particularly the additional headlamps capable of enriching a dipped beam laterally, called cornering headlights, which can take the place of fog lights or dipped headlights at the same time, by

example.

  There has already been proposed in the prior art a headlamp comprising a light source mounted in a mirror which is capable of selectively switching between a first position, in which the headlamp generates a beam capable of laterally extending a passing beam - generated in parallel by a dedicated headlamp -, and a second position, in which the headlamp generates a suitable beam

for the fog light function.

  However, for reasons notably of cost price and reliability, it is generally preferred to design projectors the mirror or mirrors of which occupy a fixed position (besides of course the possibilities of beam adjustment in elevation or in azimuth, during mounting or in operation to compensate for variations

vehicle trim).

  It is understood, however, that the use of such a fixed mirror is incompatible with the solutions known in

  cornering / fog light material.

  In addition, in the aforementioned tilting mirror headlamps, provided with a common lens, it can be difficult to design the mirror so that it generates both a satisfactory turning beam and a beam

satisfactory fog light.

  The object of the present invention is to produce headlamps for left and right turns which on the one hand make it possible to effectively enrich a given beam such as a passing beam in a given lateral direction, and which on the other hand can give rise to to another type of beam conforming to certain regulations, such as an anti-fog beam, without having to move an optical component (typically the mirror) of the projector, and by having recourse to two light sources belonging to the same lamp such as preferably a standard lamp

"H4".

  Another object of the present invention is to be able to achieve this objective with a projector produced in elliptical technology, known per se for its qualities of compactness and good recovery of the flux emitted by the

lamp, among others.

  Thus, the present invention provides a motor vehicle headlamp, in particular a bend / fog headlamp, characterized in that it comprises in combination two light sources, a mirror and a lens, the sources being placed in a first focal region of the mirror, and the lens having a focal line placed in a second focal region of the mirror and extending on either side of an optical axis of the lens, so that the lens projects onto the road an image of a light spot formed by the mirror in its second focal region from the radiation emitted by at least one of the sources, and in that the mirror comprises a first zone capable of forming, in cooperation with one of the sources, a light spot having a concentration zone located in the vicinity of the focal line and offset laterally relative to the optical axis of the lens, and a second zone capable of forming, in cooperation with the other sou rce, a spreading area distributed laterally in the vicinity of said focal line. Preferred, but not limiting, aspects of the headlight according to the invention are the following: - the mirror is constituted by a succession of generally elliptical vertical sections each having a point of vertical convergence, while a first lateral zone of the mirror has the general shape of a piece of ellipsoid of revolution of which a first focal point receives the first light source and of which all the sections share the same vertical point of convergence, constituted by its second focal point, which is offset laterally on the focal line and which allows to form said concentration zone, and that a second lateral zone of the mirror has a plurality of vertical convergence points distributed in the vicinity of the focal line and on which the light reflected from a first focal point different from the first focal point is concentrated of the piece of ellipsoid and receiving the

second light source.

  - said vertical convergence points of the plurality are distributed substantially between two vertical convergence points located on either side of the axis

lens optics.

  the extent of the piece of ellipsoid in an axial horizontal plane is determined by a pair of extreme light rays capable, in this plane, of reaching the useful entry surface of the lens from the

  shared vertical point of convergence.

  - the major axis of the ellipsoid is inclined by

  relative to the optical axis of the lens.

  - the major axis of the ellipsoid is horizontal.

  - the sources are offset laterally relative to the optical axis of the lens. the vertical convergence points of said plurality have a dimension, measured transversely to the optical axis of the lens, which varies monotonically as a function of the angle of a plane containing the considered section of the second region of the mirror by compared to a

  vertical plane containing the optical axis of the mirror.

  the vertical convergence points of said plurality vary between two extrema located symmetrically on either side of the optical axis of the

lens.

  - at least some of the vertical convergence points of said plurality are offset forward or backward relative to the focal line of the lens, so as to thicken the beam portion

corresponding.

  the projector also comprises a screen located in the vicinity of the focal line of the lens and intended to form an upper cut in the projected beam

by the lens.

  - the position of the light spot's concentration zone is such that it is projected by the lens about 30 to 40 to the side with respect to

the optical axis of the lens.

  - the first source is associated with a concealment means such that the second area of the mirror is not substantially exposed to the light produced by said

first source.

  the projector has a first operating mode in which only the second source is switched on, and a second operating mode in which

both sources are on.

  The present invention also provides a pair of left and right headlamps for a motor vehicle, in particular cornering / fog headlamps, characterized in that it comprises two headlamps as defined above, the mirror of the right headlamp being identical to that of the headlamp left at a

reversal to the nearest 180.

  Advantageously, the light concentration zone of the left headlamp is projected towards the left of the road and the light concentration zone of the

  right headlight is projected to the right of the road.

  Other aspects, aims and advantages of the present invention will appear better on reading the

  following detailed description of embodiments

  preferred thereof, given by way of nonlimiting example and made with reference to the accompanying drawings, in which: FIG. 1 is a view in axial horizontal section illustrating the principle of construction of a projector mirror according to the invention , FIG. 2 is a view in axial vertical section of the parts of the projector illustrated in FIG. 1, FIG. 3 is a graph illustrating a law of evolution of points of vertical concentration used in the construction of the projector of FIGS. 1 and 2, FIG. 4 illustrates a variant of the invention in terms of the focal points of the mirror, FIG. 5 is a top view showing the volume of the mirror by surface lines, FIG. 6 is a view similar to FIG. 5, in back view, Figure 7 is a view similar to Figures 5 and 6, in side view, Figure 8 is a view similar to Figures 5 to 7, in perspective view, Figure 9 illustrates by a set of curves isocandela the shape of the beam in generated by a projector according to the invention, with one of the sources on and in the absence of a screen, and FIG. 10 illustrates by a set of isocandela curves the shape of the beam generated by the projector according to the invention, with both sources

  on and always in the absence of a screen.

  Referring firstly to Figures 1 and 2, there is partially shown a projector which comprises two light sources 0la and 0lb, such as the two filaments of an incandescent lamp (for example of

  standard type "H4" or similar).

  These two sources 10, shown diagrammatically in the form of cylinders, are oriented axially in a mirror 20 capable of forming one of two concentration spots in the vicinity of a screen or blackout 30, the light image formed by the spot partially obscured by l blackout 30 being projected onto the road by a

lens 40.

  The foremost filament 10a is partially surrounded by a concealment cup 11, traditionally provided in an H4 lamp, the lamp being oriented in the mirror so that the filament 10a emits light laterally, here towards the side left, substantially in a demarcated half-space

by an axial vertical plane.

  For the sake of simplicity, the other components of the projector have not been shown in the figures, such as the housing, closing glass, adjustment devices, connectors, etc. The mirror 20 has a first zone 21 exposed to most of the radiation from the filament 10a not obscured by the cup 11 and intended to form in the vicinity of the screen 30 a spot of relatively small concentration, in a position such that this spot is projected towards the road offset laterally with respect to the axis of the road, typically from 30 to 40, in this case to the right, to fulfill a lighting function when cornering when the vehicle is turning to the right. The second zone 22 of the mirror is intended to spread the light on either side of the axis of the road, to form an illumination

anti-fog.

  We will now describe the construction of the zone 21. First, the focal line LF, or line of the paraxial focal points, of the lens 40 is determined, which is formed by the intersection of the surface of the paraxial focal points of the lens with the axial horizontal plane, which has a curved shape symmetrical with respect to

to the optical axis XL of the lens.

  Next, a desired lateral inclination is determined for a light concentration zone corresponding to the turning function of the headlight. As indicated, a satisfactory turning beam is generally obtained with a concentration point offset by about 35 to 40 on the outside of the vehicle by

relative to the axis of the road.

  This inclination 0v corresponds to a point Fv on the focal line LF. A desired depth P2 is then determined for the left part 21 of the mirror 20, as well as the maximum acceptable distance P1 between a first base focus Fla of the area 21 of the mirror and the bottom of the latter, this distance being generally imposed. by the distance of the filament 10a of the lamp from its base. In connection with this depth and this distance, the imposed horizontal lines L0, Li and L2 have been drawn in FIG. 1, the mirror having to extend between the lines L0 and L2 and the focal point Fla having to be located on the line L1. Then, with respect to the angular extent of the useful part of the entry face 41 of the lens 40 seen from the point Fv, the extreme reflected rays Rg and Rd are determined which delimit this angular extent, as illustrated. The radius Rd crosses the line L2 at a well-determined point, named Xd, while the radius Rg crosses the

  line L0 at another well-defined point, named Xg.

  The position of the focal point Fla along the line L1 is then determined from these various data, by solving the following equation: FvXd + FlaXd = FlaFv + 2FlaXg which expresses the equality between the paths traveled by a ray passing through the extreme reflection point Xd and by a ray passing through the extreme reflection point Xg, and which makes it possible to determine the place where must be

find the Fla home.

  A reflective surface 21 of the mirror 20 is then constructed, which is constituted by a piece of ellipsoid of revolution whose major axis GA passes through the points Fla and Fv and whose two foci are located at these points, and one places the lamp so that the

  filament 10a is substantially centered at point Fl.

  In this way, the reflecting surface 21 will well concentrate the light coming from the source in the vicinity of the point Fv, and so that, downstream of this point, the angular coverage of the light corresponds substantially to the angular extent occupied by the part

  useful of the input face 41 of the lens 40.

  Thanks to this concentration of light provided by the zone 21 of the mirror, a substantially concentrated light spot is produced, projected towards the road laterally at a predetermined angle relative to the axis of the road, to fulfill the lighting function.

cornering.

  It is observed here that, in the precise example as illustrated, the above approach has resulted in a focal point Fla which is offset laterally to the left relative to the optical axis XL of the lens, and to a large axis GA of the ellipsoid 21 which is inclined to the left with respect to this same axis. The axis of the mirror, which constitutes

  the lamp mounting axis is indicated in XM.

  Depending on the parameters involved, and mainly as a function of the useful diameter and the focal length of the lens 40 and of the values chosen for the distances Pi and P2, it is possible to obtain very diverse configurations in terms of the position of the focal point Fla, d inclination of the major axis GA and of the edges Xd and Xg of the piece

ellipsoid 21.

  According to a concrete example, if we use a lens with a diameter of 40 mm and a focal length of 30 mm, and if we set P1 = 20 mm and P2 = 95 mm, we end up with an offset side of the Fla hearth about 10

  mm to the left with respect to the XL axis.

  Zone 22 of the mirror, extending to the right from point Xg, is exposed mainly to radiation from the rear filament 10b and used to ensure, in cooperation with this filament, a spread of light in a substantially symmetrical manner and

on the other side of the optical axis XL.

  Preferably, this area is produced by following the approach described in document FR-A-2 704 044 in the name of the Applicant, so that the points of vertical convergence of the light coming from the filament lOb and reflected by the area 22 of the mirror, starting from the vertical section of the mirror passing through the point Xg to the right up to the right edge of the mirror, gradually vary from a point Fag to a point Fad preferably located symmetrically from the point Fag with respect to

the optical axis XL of the lens.

  The point Fag is here slightly offset inwards with respect to the point Fv used to determine the zone 21 of the mirror, its position being determined as a function of the desired width for the beam formed

with the filament lOb.

  Thanks to this distribution of light provided by the zone 22 of the mirror, a light spot has been produced which has a certain spread in width, with good homogeneity. The whole of this spot is partially obscured by the screen 30, which here has an upper edge located in the axial horizontal plane and whose profile matches the focal line LF, as illustrated in FIG. 1, so as to ensure good sharpness of cut, so to obtain after projection a beam delimited by a

horizontal cut.

  Figure 3 shows, for zone 22, the shape of the evolution of the position (abscissa y measured perpendicular to XM, the origin being on XM) of the vertical concentration points along the line LF as a function of l angle Gold of a vertical plane containing the rays emitted by the source towards a section of the zone 22 also contained in this plane, with respect to a reference constituted by a vertical plane passing through

the XM axis.

  In this example, the separation between zones 21 and 22 takes place on slightly negative Gold (other configurations can lead to separations at different angles). Starting from this slightly negative value of Gold towards the positive values, which corresponds to the angular coverage of the zone 22, the value y gradually increases from the value corresponding to Fag up to the value, positive and here of the same value.

  absolute, corresponding to the point Fad.

  It will be noted here that the cooperation of the lit filament b with the zone 21 of the mirror, which is not specifically designed to cooperate with this filament, can give rise to stray light in the beam formed. However, and as will be seen in detail below, this stray light will be greatly separated laterally from the axis of the road, and will not in practice be inconvenient for the driver. It is also possible to increase this spacing if a shorter focal length is used for the zone 21 (that is to say if one goes upwards in FIG. 1 the line L0). One can also, to attenuate or completely eliminate this stray light, design the cover 30 so that it eliminates any inclined radiation, after projection by the lens, beyond a given angle (by

  example close to 50) with respect to the axis of the road.

  It will also be noted that the cooperation between the filament 10a and the part of the zone 22 located, in FIG. 1, to the left of the axis XM and therefore exposed to the radiation of this filament, also gives rise to stray light. However, this light is relatively weak (taking into account the limited surface of the part concerned of zone 22) and diffuse, and does not prove to be annoying. In addition, in the preferred case o, as will be seen in detail below, the filament 10b remains lit when the filament 10a is lit, this

  stray light is even more imperceptible.

  Returning now to FIG. 1, with regard to the fog beam generated by the area 22 of the mirror, it is understood that with the construction described, the right part of this beam, generated by the light directed by the area 22 towards the region of the point Fag, will have a greater thickness than its part on the left, generated by the light directed by the zone 22 towards the region of the point Fad. Indeed, the images of the source 10 generated by the background region of the mirror have a size substantially larger than the images of the source generated by the lateral regions of said mirror, which are substantially more

  distant from the source as said background region.

  To compensate for this lack of homogeneity of the part of the fog beam, it is advantageous to modify the position of the line of displacement of the vertical convergence points of the area 22 of the mirror with respect to the focal line LF of the lens 40. Thus , with reference to FIG. 4, the focal line LF has been represented, which is the same as in FIG. 1 for an identical lens, and a line of points of vertical convergence LCV has also been represented which progressively deviates of the LF line. In this way, the vertical convergence of the light being obtained not on the LF line, but at a distance therefrom, the light emitted by the mirror is thickened towards the region on the right

of the said LF line.

  Thus, by an appropriate adjustment of the difference between the LF and LCV lines, it is possible to ensure that the beam portion corresponding to the fog function has a thickness that is substantially

constant over its entire extent.

  Figures 5 to 8 illustrate the shape in more detail

  of the mirror 20 of a projector according to the present invention.

  We observe the clearly dissymmetrical character of the mirror with respect to an axial vertical plane, and the discontinuity between the reflecting surfaces 21 and 22 due in particular to the offset between their respective first focal points Fla and Flb, while it is symmetrical with respect to a plane

horizontal axial.

  The projector described above is advantageously used in one of the following two modes: - fog mode: only the filament lo0b is on; FIG. 9 illustrates by a set of isocandela curves on a projection screen graduated in degrees, the shape of the beam projected on the road with the only filament 10b lit, without the thickness compensation described with reference to FIG. 4, and without the intervention of the screen 30; we observe the stray light stray strongly shifted to the right and created by the zone 21, as mentioned above; - fog + turn mode: the filaments 10a and 10b are both on; FIG. 10 illustrates the shape of the beam projected under these conditions; we observe that the beam has a spot of concentration marked at about 37 to the right

  (cornering function), superimposed on the beam in Figure 9.

  Of course, it is also possible to produce a headlamp with fog beam or turning spot, depending on whether only the filament 10b or only the filament 10a

is on.

  It will be observed here that, because of the aforementioned symmetry of the mirror with respect to an axial horizontal plane, one can use in the left and right headlights of the vehicle the same mirror, which will simply be turned 180 on itself to pass to the side right (example described above) to the left side. The lamp is

also returned to 180.

  The cornering / fog lights according to the invention are typically controlled from the dashboard of the vehicle as follows: fog mode: the filaments 10b of the two headlights are on, with their nominal power; - cornering mode: the two filaments lOa and lOb of the left headlamp or of the right headlamp are switched on, in addition to the vehicle's low beam headlamps, depending on the turns taken by it (thanks for example to appropriate sensors provided at the steering column); this ignition can be carried out either all or nothing, or with progressive power depending on the more or less pronounced character of the turn taken by the vehicle, and if necessary with different power developments at the level of

filaments 10a and 10b.

  Of course, the present invention is in no way limited to the embodiments described and shown, but a person skilled in the art will be able to provide it.

  many variations or modifications.

  In particular, it is understood that by playing on the profile of the upper edge 31 of the cover and on the law of distribution of the points of vertical convergence (cf. FIG. 3), according to the principles described in FRA-2 704 044, one can produce a headlamp capable of generating a concentrated turning beam and different types of beams, and in particular a passing beam.

Claims (16)

  1. Motor vehicle headlamp, in particular bend / fog headlamp, characterized in that it comprises in combination two light sources (10a, b), a mirror (20) and a lens (40), the sources being placed in a first focal region (Fla, Flb) of the mirror, and the lens (40) having a focal line (LF) placed in a second focal region of the mirror and extending on either side of an optical axis (XL) of the lens, so that the lens projects onto the road an image of a light spot formed by the mirror in its second focal region from the radiation emitted by at least one of the sources (10b, 10a, 10b), and in that the mirror (20) comprises a first zone (21) capable of forming, in cooperation with one (10a) of the sources, a light spot having a concentration zone located in the vicinity of the focal line (LF) and offset laterally with respect to the optical axis (XL) of the lens, and a second area e (22) capable of forming, in cooperation with the other source (10b), a spreading zone distributed laterally in the vicinity of said focal line (LF).   2. Projector according to claim 1, characterized in that the mirror (20) consists of a succession of generally elliptical vertical sections each having a vertical point of convergence (Fv, Fag, Fad), in that a first lateral zone (21) of the mirror has the general shape of a piece of ellipsoid of revolution, a first focus (Fla) of which receives the first light source (10a) and all of whose sections share the same vertical point of convergence (Fv), consisting by its second focal point, which is offset laterally on the focal line (LF) and which makes it possible to form said concentration zone, and in that a second lateral zone (22) of the mirror has a plurality of vertical convergence points (Fag , ..., Fad) distributed in the vicinity of the focal line (LF) and on which the light reflected from a first focus (Flb) different from the first focus of the piece of ellipsoid is focused and receiving the second light source (0lb).   3. Projector according to claim 2, characterized in that said vertical convergence points (Fag, ..., Fad) of the plurality are distributed substantially between two vertical convergence points (Fad) located on either side of the optical axis (XL) of The lens.   4. Projector according to one of claims 2 and   3, characterized in that the extent of the piece of ellipsoid in an axial horizontal plane is determined by a pair of extreme light rays (Rg, Rd) capable, in this plane, of reaching the useful entry surface (41 ) of the lens from the point of   shared vertical convergence (Fv).   5. Projector according to claim 4, characterized in that the major axis (GA) of the ellipsoid is inclined relative to the optical axis (XL) of the lens. 6. Projector according to claim 5, characterized in that the major axis (GA) of the ellipsoid is horizontal.   7. Projector according to one of claims 1 to   6, characterized in that the sources (10a, 0lb) are offset laterally with respect to the optical axis (XL) of The lens.   8. Projector according to one of claims 2 to 6   or claim 7 taken in dependence on the latter, characterized in that the vertical points of convergence (Fag, ..., Fad) of said plurality have a dimension (y), measured transversely to the optical axis (XL) of the lens, which varies monotonically as a function of the angle (Gold) of a plane containing the considered section of the second zone (22) of the mirror with respect to a vertical plane containing the optical axis (XM) from the mirror.   9. Projector according to claim 8, characterized in that the vertical points of convergence (Fag, ..., Fad) of said plurality vary between two extrema (Fag, Fad) located symmetrically on the side and   on the other side of the optical axis (XL) of the lens.   10. Projector according to one of claims 8 and   9, characterized in that at least some of the vertical convergence points (Fag, ..., Fad) of said plurality are offset forward or backward relative to the focal line (LF) of the lens , in a way to   thicken the corresponding beam part.   11. Projector according to one of claims 1 to   , characterized in that it further comprises a screen (30) located in the vicinity of the focal line of the lens and intended to form an upper cut in the   beam projected by the lens (40).   12. Projector according to one of claims 1 to   11, characterized in that the position of the area of concentration of the light spot is such that it is projected by the lens (40) at about 30 to 40 towards   the side with respect to the optical axis (XL) of the lens.   13. Projector according to one of claims 1 to   12, characterized in that the first source (10a) is associated with a concealment means (11) such that the second zone (22) of the mirror is not substantially exposed to the   light produced by said first source (0la).   14. Projector according to claim 13, characterized in that it has a first operating mode in which only the second source (10b) is on, and a second operating mode in   which both sources (10a, lOb) are on.   15. Pair of left and right headlights for motor vehicle, in particular cornering / fog lights, characterized in that it   comprises two projectors according to one of claims   1 to 13, the mirror (20) of the right headlamp being identical to that of the left headlamp when turned over to within 180.   16. Pair of projectors according to claim 15, characterized in that the concentration zone of   light from the left headlamp is projected to the left5 of the road and the light concentration area of the right headlamp is projected to the right of the road.