FR2760068A1 - MOTOR VEHICLE HEADLIGHT WITH MIRROR WITH LATERALLY JUXTAPOSED ZONES, AND METHOD FOR MANUFACTURING SUCH A MIRROR - Google Patents

Abstract

A headlamp for a motor vehicle comprises a light source (10), a mirror (20) and a lens. According to the invention, the mirror comprises a plurality of zones (Z) juxtaposed laterally to each other and delimited by transition lines. at break in slope, at least some of the zones (Z1, Z2) each consisting of a part of a base surface (SB1, SB2) with parabolic horizontal generator (P1, P2) on which a stripe is formed by geometric projection (S1, S2) with essentially circular horizontal profile; said horizontal generators share a common axis (OY) and a common focus (F); and the focal lengths (f1, f2) of the parabolic generators are different between at least one of the zones and an adjacent zone. The invention also provides a method of manufacturing the mirror of such a projector.

Description

The present invention relates generally to

  motor vehicle headlamps.

  More specifically, it relates to a new projector capable of generating, without the intervention of the glass, an appropriate light distribution beam. Headlights are already known which are capable of generating beams by themselves such as passing beams or anti-fog beams, delimited in their upper part by a well cut profile.

determined.

  Mention will be made in particular of documents FR-A-2 536 502 and FR-A-2 536 503 in the name of the Applicant. With these known projectors, the required width of the beam is obtained using prisms and ridges formed on the lens of the projector, the design of these deflecting elements being generally made as judged ", step by step, so as to what the beam finally presents a satisfactory photometry. The Applicant then developed reflectors whose reflecting surfaces were designed to give the beam, upstream of the ice, a certain width, the ice then being slightly deflecting or smooth, which was desirable on the one hand in terms of style, and on the other hand from an optical point of view, the inclination of the lenses of modern projectors making the work of horizontal light spreading relatively delicate by

  these. Documents FR-A-2 609 146, FR-A-2 609 148, FR-

  A-2 639 888 and FR-A-2 664 677 illustrate this state of the art. To better control the lateral spreading given to the beam, specific streaks have been designed, affixed directly to the reflecting surface of the mirror, such as

as described in FR-A-2 732 446.

  However, the production of these projectors on an industrial scale poses certain difficulties. More precisely, as the horizontal spread of the beam was better and better controlled, the lateral edges of the beam adopt excessively sharp delimitations, the light disappearing relatively suddenly beyond a certain angle of deflection to the left and to the right. In addition, the various manufacturing defects, particularly in terms of varnish deposition on surfaces, give the beam to the

  these edges look like a comb.

  These two defects are all the more noticeable as they occur near the limit of vision

peripheral of the human eye.

  In addition, mirrors with a smooth surface and mirrors with an irregularly ridged surface are not always desirable for stylists, who are now looking for projector mirrors with more original aspects, while being able, without the intervention of glass. , generate

  photometrically satisfactory beams.

  The present invention aims to overcome these drawbacks

  and limitations of the state of the art.

  Thus, the present invention relates according to a first aspect to a motor vehicle headlamp, comprising a light source, a mirror and a lens, characterized in that the mirror comprises a plurality of zones juxtaposed laterally to each other and delimited by transition lines at break in slope, at least some of the zones each consisting of a part of a base surface with parabolic horizontal generator on which is formed by geometrical projection a streak with essentially circular horizontal profile, in that said horizontal generators share an axis common and a common focus, and in that the focal lengths of the parabolic generators are different between at least

  one of the zones and an adjacent zone.

  Certain preferred, but not limiting, aspects of the headlamp according to the invention are as follows: the streaks of the different zones are subdivided into sub-streaks which are essentially vertically aligned and which, before projection, each have radii of curvature which vary monotonously between their upper end and their lower end. the sub-streaks, before projection, have reference levels which vary monotonously between their ends

  upper and their lower end.

  - the radius of curvature and the level at the bottom of a first sub-streak are identical to the radius of curvature and at the level at the top of a second sub-streak located

  immediately below the first.

  - The base surface of at least one of the zones is a surface capable of bringing all the images of the light source below and essentially flush with a horizontal cut. - the streak projected on the base surface of the said

  at least one area has a vertical axis.

  - the mirror comprises at least one other zone juxtaposed laterally to said certain zones and whose base surface is capable of bringing all the images of the light source below and essentially flush with another

  cut offset from said horizontal cut.

  - Said other cut is angularly offset.

  - Said other cut is offset in height.

  - The streak projected on the base surface of said other zone has an axis inclined relative to the vertical. - the base surface of at least one of the zones is a

  part of a paraboloid of revolution.

  - the radii of curvature of the streaks projected on the different zones are all the greater as said

  areas are distant from the mirror axis.

  According to a second aspect, the invention provides a method of manufacturing a motor vehicle headlamp mirror, characterized in that it comprises the following steps: defining a plurality of base surfaces with parabolic horizontal generator, said generators sharing a common axis and a common focus, apply a streak with a circular horizontal profile to each of the base surfaces, to obtain a reflecting surface, adjust the focal length of each of said horizontal generatrices so that said zones intersect along lines of intersection connecting an upper edge and a lower edge of the mirror, machining a mold comprising in a juxtaposed horizontally zones constituted respectively by the parts of said reflecting surfaces which are delimited by said lines of intersection, and

  mold the mirror using this mold.

  Preferably, the step of applying a streak consists in applying a plurality of sub-streaks aligned vertically with one another and having

  different radius of curvature and level settings.

  Advantageously, the step of adjusting the focal lengths is implemented as a function of the desired position, in the lateral direction, of the transition lines.

between the different zones.

  Optionally, the adjustment step further comprises

  the adjustment of at least one parameter of each sub-streak.

  Other aspects, purposes and advantages of this

  invention will appear better on reading the description

  following detailed of preferred embodiments thereof, given by way of example and made with reference to the accompanying drawings, in which: Figure 1 is a perspective view illustrating the construction of a projector mirror according to the present invention , Figure 2 is an axial horizontal sectional view illustrating a part of the mirror obtained, Figure 3 is a back view of a mirror according to a first concrete embodiment of the present invention, Figure 4a is a plan view illustrating the optical behavior of a central area of the mirror of Figure 3, Figure 4b is a perspective view illustrating the optical behavior of three central areas of the mirror of Figure 3, Figures Sa to 5e illustrate by a set of curves isocandela on a projection screen the optical behavior of five different areas of the mirror of figure 3, without the intervention of the glass, figure 6 illustrates by a set of isocand curves the shape of the beam generated by the assembly of the mirror of FIG. 3, without the intervention of the glass, FIG. 7 is a back view of a mirror according to a second concrete embodiment of the present invention, Figures 8a to 8g illustrate by a set of isocandela curves on a projection screen the optical behavior of the seven different areas of the mirror of Figure 7, without the intervention of the glass, and Figure 9 illustrates by a set of isocandela curves the appearance of the beam generated by the entire

  mirror of Figure 7, without the intervention of the glass.

  Referring first to FIG. 1, an orthonormal reference frame has been illustrated, Ox being horizontal and perpendicular to the optical axis, 0Y being the optical axis and

OZ being vertical.

  A mirror according to the invention is produced by individually defining a plurality of reflective zones, juxtaposed laterally to each other, that is to say bounded by border lines extending between the

  upper and lower edges of the mirror.

  An area n of this mirror is defined by first defining at this area a base surface SBn having a horizontal parabolic generator, or very

close to a parable.

  This base surface can be of different types, depending on the beam that one seeks to achieve. In particular, to produce a headlamp, preferably using a base surface constituted by a portion of a paraboloid of revolution, the focal point F of which is positioned correctly relative to the source 10, constituted in this case by a glowing filament. On the other hand, to produce a cut-off beam, such as a passing beam or a fog beam, a surface is advantageously used as described in FR-A-2 536 502 or FR-A-2 536 503, such a surface being able to bring all the images of the source below and flush with a horizontal or inclined cut. In this case also, the reference focal point of the surface is suitably positioned with respect to the source,

  preferably as described in the two aforementioned documents.

  On this base surface is projected by projection along the 0Y axis a convex streak Sn, which is subdivided into

  a plurality of Sni sub-streaks, in this case four sub-

  streaks Sn1 to Sn4, superimposed vertically on each other. Each of these sub-streaks is characterized by four parameters, namely its radius of curvature at its upper end, respectively Rhl to Rh4, its radius of curvature at its lower end, respectively Rbl to Rb4, its level at its upper end, respectively Nhl to Nh4, and finally its level at its lower end, respectively Nbl to Nb4. The levels in question consist of

  shifts in support of the streak along the OY axis.

  Each Sni sub-streak has a continuous and smooth surface, and is characterized by a radius of curvature which varies monotonously, for example linearly, between its high and low end values Rhi and Rbi, and by a level which varies from monotonously, for example linearly, between its high and low end values

Nhi and Nbi.

  Such a sub-streak allows, by the variable nature of the radius of curvature, to ensure a spread of the light in which no abrupt limit is encountered, knowing that the maximum lateral deflection of the radiation varies regularly as we moves vertically along the sub-streak. In addition, the variation in the level of the sub-streak, which amounts to superimposing it on a prism, makes it possible to shift all of the projected radiation towards the

  up or (in this case) down.

  The whole of the streak defined by the sub-streaks Snl to Sn4 tooth the parameters are indicated above present

  also a continuous and smooth surface.

  This is achieved by choosing, as illustrated, the following equalities: Rbl = Rh2 and Nbl = Nh2 Rb2 = Rh3 and Nb2 = Nh3

Rb3 = Rh4 and Nb3 = Nh4.

  We will observe here, as we will see in detail below, that we can choose in some cases an invariable radius of curvature along the streak, that is to say from Rhl to Rb4, without you might as well create a sudden stop of light at the side edges of the beam. In addition, if no vertical shift of the light is sought, advantageously a zero level is chosen all the time.

along the streak, between Nhl and Nb4.

  It will also be observed, for a good understanding of the invention, that the contours of the streak Sn projected onto the base surface SBn in no way correspond to the contours

  of the area under construction.

  More specifically, the construction of a mirror according to the invention is carried out in successive stages. We start by defining one of the areas of the mirror, as explained above. Preferably, this is the area occupying the bottom of the mirror, and the parameters (focal length of the horizontal generator, and values of Rhi, Rbi, Nhi, Nbi of the different Sni sub-streaks) are defined mainly as a function of mirror size and photometry

  sought for the wide part of the beam.

  Then, according to an essential aspect of the invention, the adjacent areas, to the left and to the right of the background area, are defined with their own parameters (here again the focal length of the horizontal generator of the base surface, and values of Rhi, Rbi, Nhi, Nbi of the different sub-streaks Sni), on the one hand as a function of the desired positioning of the light projected by these zones, and on the other hand and above all so that the reflecting surface of these adjacent zones intersects the reflective surface of the background area along a transition line that extends from top to bottom between the edges

upper and lower of the mirror.

  Thus, FIG. 2 illustrates the case where a bottom zone Zl of the mirror 20 was initially defined, the base surface SB1 of which rests on a parabolic generator Pi of focal length fl and focal point F, on which has been projected a streak S1 having the parameters Rhl to Rh4, Rbl to

  Rb4, Nhl to Nh4 and Nbl to Nb4 desired.

  A zone Z2 is then defined, its base surface SB2 resting on a parabolic generator P2 having a focal length f2 different from fl, but the same focal point F, a streak S2 of parameters Rhl 'to Rh4', Rbl 'to Rb4 ', Nhl' to Nh4 'and Nbl' to Nb4 'having been projected onto this surface of

based.

  We understand that by playing in particular on the value of f2, we can ensure that, in the XOY plane, the two zones intersect at a point with a well-defined dimension X12. Insofar as the other parameters of the zone z2 remain within reasonable limits, the two zones will in fact intersect along a transition line LT12 passing through the dimension X12 at the level of the cutting plane X0Y and following a trajectory more or less curved and sinuous, according to the values of the parameters of the different sub-streaks located on either side, between the upper edge and

bottom of the mirror.

  It will thus be observed that the desired positioning of the transition line LT12 following OX can also be obtained by varying the level parameters, and the

  if necessary, the parameters of the radii of curvature.

  However, the preferred procedure consists in choosing the values of Rhl 'to Rh4', Rbl 'to Rb4', Nhl 'to Nh4' and Nbl 'to Nb4' according to the lateral spread and the vertical offset required for the zone Z2 , then adjust the value of f2 so that the transition line LT12 is placed at the place

desired in lateral direction.

  It will also be observed that, the transition LT12 being produced by the intersection of two generally non-tangent surfaces to one another, it does not create zero order discontinuity between the reflecting surfaces of the two zones, but there exists at its level an elbow which, when the spotlight is off, allows the observer to clearly differentiate the different zones, this

  which is interesting aesthetically.

  We also note that the transition line LT12 between zones Zl and Z2 will generally follow a more or less curved and sinuous trajectory which is not confused with a line of lateral isodeviation of zone zl, nor with a lateral isodeviation line of zone Z2. It follows that, for each of these two zones, the maximum lateral spread provided at the level of the transition line LT12 will vary when one moves along this line, and this even when the radius of curvature does not does not evolve along the streak, so much so that the phenomenon of sudden stopping of the beam part generated by

each of these areas is avoided.

  Finally, it will be noted that by playing on the position of the transition lines which delimit a given area, one can easily favor the spreading of the light either to the left or to the right, the spreading towards a given side being of as much less important than the transition line

  concerned is close to the top of the projected streak.

  The construction of the mirror is continued by defining, in the same way as above, a zone Z3 adjacent to the zone Z2 and configured so as to obtain a bent transition line LT23 extending at the dimension in

X wanted in the X0Y plane.

  These steps can be repeated for as many areas

  as necessary, in the left and right parts of the mirror.

  The invention thus makes it possible to produce a mirror in which different zones juxtaposed laterally can be configured so as to generate parts of different beams with great flexibility, to facilitate the modeling of the final beam, while obtaining a reflective surface without discontinuities of zero order, which in a well known manner creates optical anomalies, and by obtaining a surface with left streaks and

  broad aesthetically interesting.

  Preferably, all of the modeling of the beam being carried out at the level of the mirror, the lens for closing the projector (not shown), can be entirely smooth, or only comprise elements of style optically

inactive or practically inactive.

  Furthermore, in order to adapt as best as possible to the geometry of the environment of the projector (lateral cheeks capable of obscuring a too broad beam, foot of ice likely to create optical anomalies, etc.), provision is advantageously made. that the central zones of the mirror have small radii of curvature, so as to ensure the width of the beam using large images of the source, while the lateral zones of the mirror have greater radii of curvature, in order to ensuring the central beam concentration spot using smaller images of the filament, the intermediate zones providing intermediate lateral spreading. FIG. 3 illustrates a mirror of a European passing beam for right-hand traffic produced

  in accordance with the present invention.

  It includes six zones designed as described above, namely, from left to right: - a left edge zone Za whose base surface is defined by the equation indicated on page 9, line 7, of FR- A-2 536 502, capable of aligning the images of the source below and flush with a cut inclined at 15 above the horizontal, to which has been applied a groove with a circular guide of offset axis , in correspondence, of 15 with respect to the vertical, - a first intermediate zone Zb, a bottom zone Zf, - a second intermediate zone Zc,

- two edge zones Zd and Ze.

  Zones Zb to zf are designed with surfaces of

  base as defined on page 9, line 3, of document FR-A-

  2,536,502, the values of the reference focal length f0

  being adjusted as described above.

  In this embodiment, the radii of curvature of the projected striations of the different zones are all the greater the more the zone is laterally distant from the axis.

optical.

  The lateral spreading provided by the zone Zf is illustrated in FIG. 4a, while the lateral spreading provided by

  zones Zb, Zf and zc is illustrated in FIG. 4b.

  The shape of the beam portions generated by the zones Za to Ze is illustrated in FIGS. 5a to 5e, respectively. The numerical indications which appear there

  express the horizontal and vertical deviations in degrees.

  It is observed that each of the beam parts, for the reasons explained above, has fuzzy lateral edges, which ensures a homogeneous mixture of these different

  beam parts in the overall beam.

  The shape of this overall beam is illustrated in FIG. 6. It can be seen there that the beam has at the same time a large concentration in the axis, a large width and a great homogeneity. We also note that, by the design of the zone Zf as described above, the lateral edges of the beam are blurred, which avoids disturbances in the field of peripheral vision of

the human eye.

  We also observe that the part of the beam located along the half-cut inclined at 15 upwards does not

  not extend excessively far along this half

  cut-off, which allows to properly illuminate the side of the road without dazzling vehicle drivers

  exceeded via the exterior mirrors of these vehicles.

  It will be understood that the invention makes it possible to produce beams with cut-off adapted to the different applications, mainly crossing and fog lights) and to the different regulations by simply adapting the base surfaces and the streak parameters used. Thus it is advantageous to design a mirror having a central zone Zf identical for all the projectors, only the intermediate zones and the edge zones being adapted

  to set the desired cutoff.

  FIG. 7 represents a mirror of a spotlight

  route carried out in accordance with the present invention.

  In this case, the base surfaces of the different zones Za 'to Zg' are paraboloids of suitable focal lengths. Here again, the radii of curvature of the various projected streaks are all the more important as the zones

  considered are laterally distant from the optical axis.

  Figures 8a to 8g illustrate the shape of the beam parts generated by the different zones, while Figure 9 illustrates the whole of the beam obtained. Here again we see a great width, a great homogeneity and a spot of concentration of significant level, at the same time as an essentially constant beam thickness,

  also advantageous in terms of visual comfort.

  Thus the present invention makes it possible to produce projectors which, while generating beams which are entirely different from each other, will all be able to present the same appearance when they are switched off, which is

  particularly advantageous in terms of style.

  Of course, the present invention is in no way limited to the embodiments described and shown, but those skilled in the art will be able to make any variant or

  modification according to his spirit.

  In particular, we can use instead of

  outlined convex streaks, concave streaks.

Claims (16)

  1. Motor vehicle headlamp, comprising a light source (10), a mirror (20) and a lens, characterized in that the mirror comprises a plurality of zones (Z) juxtaposed laterally to each other and delimited by lines of transition at break in slope, at least some of the zones (Zl, Z2) each consisting of a part of a base surface (SB1, SB2) with parabolic horizontal generator (P1, P2) on which is formed by geometric projection a streak (S1, S2) with essentially circular horizontal profile, in that said horizontal generatrices share a common axis (0Y) and a common focal point (F), and in that the focal lengths (fl, f2) of the parabolic generators are different between at least one of the zones and an adjacent zone. 2. Projector according to claim 1, characterized in that the ridges (S) of the different zones are subdivided into sub-ridges essentially vertically aligned and which, before projection, each have radii of curvature (Rh, Rb) which vary so monotonous between their upper end and their end lower.   3. Projector according to claim 2, characterized in that the streaks (S), before projection, have reference levels (Nh, Nb) which vary monotonously between their upper end and their lower end.   4. Projector according to one of claims 2 and 3,   characterized in that the radius of curvature (Rbi) and the level (Nbi) at the bottom of a first sub-streak are identical to the radius of curvature (Rhi + l) and at the level (Nhi + l)   at the top of a second sub-streak located immediately above below the first.   5. Projector according to one of claims 1 to 4,   characterized in that the base surface (SB) of at least one of the zones (Zb-Zf) is a surface capable of bringing all the images of the light source below and   essentially flush with a horizontal cut.   6. Projector according to claim 5, characterized in that the groove (S) projected on the base surface of   said zone at least has a vertical axis.   7. Projector according to one of claims 4 and 5,   characterized in that the mirror comprises at least one other zone (Za) juxtaposed laterally to said certain zones (Zb-Zf) and the base surface of which is capable of bringing all the images of the light source below and essentially flush with '' another cut offset by   with respect to said horizontal cut.   8. Projector according to claim 7, characterized   in that said other cut is angularly offset.   9. Projector according to claim 7, characterized   in that said other cut is offset in height.   10. Projector according to claim 8, characterized in that the groove projected on the base surface of said other zone (Za) has an axis inclined relative to the vertical.   11. Projector according to one of claims 1 to 4,   characterized in that the base surface of at least one of the zones (Za'-Zg ') is a part of a paraboloid of revolution.   12. Projector according to one of claims 1 to 11,   characterized in that the radii of curvature (Rhi, Rbi) of the streaks projected on the different zones (Z) are all the greater as said zones are distant from the axis of the mirror. 13. Method for manufacturing a motor vehicle headlamp mirror (20), characterized in that it comprises the following steps: defining a plurality of base surfaces (SB) with parabolic horizontal generator (P), said generators sharing a common axis (0Y) and a common focus (F), apply on each of the base surfaces a streak (Sn) with circular horizontal profile, to obtain a reflective surface (20), adjust the focal length (f) of each of said horizontal generators in such a way that said zones intersect along lines of intersection (LT) connecting an upper edge and a lower edge of the mirror, machining a mold comprising in a juxtaposed horizontally zones constituted respectively by the parts of said reflecting surfaces which are delimited by the said intersection lines, and   mold the mirror using this mold.   14. The method of claim 13, characterized in that the step of applying a streak (Sn) consists in applying a plurality of sub-streaks (Sni) aligned vertically with each other and having   different radius of curvature and level settings.   15. Method according to one of claims 13 and 14,   characterized in that the step of adjusting the focal lengths is carried out as a function of the desired position, in the lateral direction (Ox), of the transition lines (LT) between the different zones.   16. Method according to claims 13 and 14 taken   in combination, characterized in that the adjustment step further comprises the adjustment of at least one parameter (Rhi,   Rbi, Nhi, Nbi) of each sub-streak.