FR2940404A1 - IMPROVED LIGHTING MODULE FOR MOTOR VEHICLE. - Google Patents

Abstract

A lighting module providing a cut-off light beam, having a concave reflector (2), at least one light source (S) disposed in the concavity of the reflector, and a lens (3) located in front of the reflector which is associated with a folder (4) whose upper face is reflective. Said folder has a front end edge (5) adapted to form the cut in the lighting beam; the front edge (5) of the folder is formed by a plane curve with variable curvature, the curvature at a point (M) being a continuous function of the lateral coordinate (x) of this point. The reflector (2) is determined to transform the wave surface from the source into a wave surface that is reduced to the variable curvature curve of the edge (5) of the folder, and the lens (3) is determined to give a point (M) of the edge (5) of the folder an image to infinity.

Description

The invention relates to a lighting module for a motor vehicle headlamp, giving a cut-off light beam, of the kind of those comprising a concave reflector, at least one light source arranged in the light-emitting diode. concavity of the reflector to illuminate in particular at least upwards, and a lens located in front of the reflector and the light source, the reflector being associated with a folder, especially horizontal, whose upper surface is reflective to fold the beam from the reflector said bender having a front end edge adapted to form the ~ o cut in the lighting beam. By the term "folding" is meant a substantially flat and reflective plate. A lighting module of the kind defined above is known from patent EP-A-1 610 057. Such a module makes it possible to obtain a very wide illumination beam with a sharp cut across the entire width of the beam. This kind of module is well suited for lighting systems combining several modules with different optical axes and curvatures. A fog lamp generally uses two or three of these modules to give a light beam with a satisfactory distribution of illumination 20 over the entire angular extent of the beam, in particular towards the angular limits of the beam. It is however desirable to reduce the number of modules to be used to obtain a satisfactory beam, in particular fog. The object of the invention is, above all, to propose a module of the kind defined above which makes it possible to obtain a beam in which the distribution of the light is improved in order to increase the illumination of the angular extreme zones, in particular those situated at around 35 ° C. ° on either side of the optical axis, without reducing the illumination of the central zone located substantially between + 10 ° and -10 ° on either side of the optical axis. Another object of the invention is to provide a sufficiently improved lighting module to constitute in itself a fog lamp meeting the requirements imposed. According to the invention, a lighting module of the kind defined above is such that the front edge of the folder is formed by a plane curve with variable curvature, the curvature at a point being a continuous function of the distance from this point to the optical axis, or lateral coordinate of this point, the reflector is determined for transforming the wave surface coming from the source into a wave surface that is reduced to the curve with variable curvature of the front edge of the folder; and in that the lens is determined to give a point (especially any point) of the front edge of the folder, for all the rays contained in the plane perpendicular to the front edge of said folder at the point considered, an image at the infinite, especially in a direction inclined relative to the plane of the folder of a continuous function angle of the distance from this point to the optical axis (or lateral coordinate of this point). ~ o The curvature of the front edge of the folder has, in particular, at least a maximum located angularly between the optical axis of the module and an angular limit of the beam. Preferably, the curvature of the front edge of the folder has a maximum on each side of the optical axis. Usually, the front edge of the folder is symmetrical with respect to this optical axis. Preferably, the curvature of the front edge of the folder has a secondary maximum located on or substantially on the optical axis. Generally, the wave surface coming from the source is comparable to a spherical wave surface. The maximum curvature of the front edge of the folder is chosen so that the illumination of the extreme angular zones of the beam, in particular in directions greater than or equal to 35 ° on both sides of the optical axis, is reinforced, without reducing the illumination of the central zone. The surface of the reflector is such that light rays coming from the source and falling at points situated on the intersection of this surface and a vertical plane normal to the front edge of the folder, but separated from the source, are reflected. in this vertical plane so as to converge at a point located at the intersection of the vertical plane and the edge of the folder. Advantageously, the lighting module is provided so that the illumination in the central zone between -10 ° and + 10 ° on the one hand and 3o of the other on the optical axis is maintained with respect to a base module whose bending machine would have a circular front edge of radius equal to the mean radius of curvature of the front edge, while the zones located at -35 ° and + 35 ° on either side of the optical axis, and corresponding to lines listed 9-1 and 9-2 according to R19-3, have a higher illumination than that obtained with said basic module. Advantageously, the cut-off beam obtained is flat-cut, in particular being chosen between an anti-fog beam and a flat-cut code beam portion.

The invention also relates to a projector comprising at least one module as defined above. The invention consists, apart from the arrangements set out above, in a number of other arrangements which will be more explicitly discussed below with respect to an embodiment described with reference to the accompanying drawings, but which is in no way limiting. In these drawings: 1 is a simplified schematic perspective view of a module according to a first variant of the invention. ~ o Fig. 2 is a diagram in perspective from another angle, with part cut or torn off, on a larger scale, of a vertical section of the module according to the previous figure, with representation of light rays. Fig.3 is a diagram of a partial section of the lens according to the preceding figures for the calculation. Fig. 4 is a schematic view from above, on a larger scale, of the front edge of the bender of the module according to the preceding figures. Fig. 5 is a diagram showing the variation of the bending radius of the bender of the module according to the preceding figures with the abscissa the lateral distance to the optical axis and the ordinate the radius of curvature at a point of the curve, and Fig. . 6 is a diagram of the light distribution, on a screen, of the beam produced by the module of the module according to the preceding figures of the invention. 7 to 9 relate to a second variant of the invention. Referring to FIG. 1 of the drawings, it is possible to see a lighting module 1 for a motor vehicle headlamp, schematically represented, this module being adapted to give a light beam cut. The module 1 comprises a concave reflector 2, at least one light source S arranged in the concavity of the reflector to illuminate at least upwards, and a lens 3 situated in front of the source S and the reflector 2, in the direction of propagation of the light beam. The reflector 2 is associated with a folder 4, consisting of a flat reflecting plate, horizontal as shown in FIG. 1. The folder 4, at least the upper surface of which is reflective, has a front end edge 5 suitable for forming the cut-off 35 in the lighting beam. When the folder 4 is horizontal, the cutting of the beam is horizontal and the illuminated area is located below a horizontal line. By tilting the plane of the bender 4 around the horizontal optical axis of the module, it is possible to tilt the cut-off line of the beam.

The light source S is advantageously substantially punctual, in particular formed by a light-emitting diode enveloped by a globe or a hemispherical capsule, this diode having a light-scattering axis substantially orthogonal to the folder 4, and illuminating upwards. According to the invention, in order to transfer the light beam towards the external angular zones from intermediate angular zones without penalizing the central zone, the front edge of the folder is given the shape of a plane curve with variable curvature. , whose curvature at a point is a continuous function of the distance x, or lateral coordinate, from this point to the optical axis Y, for the point considered. As shown in Fig. 1, 2 and 4, in the central zone 5a of the edge the curvature is constant on either side of the optical axis; this part 5a corresponds to a circular arc of constant radius, centered on the optical axis Y. The ends of the arc 5a are connected, respectively, to an arc 5b1, 5b2 having a higher curvature. The radius of curvature (inverse of the curvature) of the arcs 5b1, 5b2 is smaller than that of the central part 5a. A portion 5c1, 5c2 provides the connection between the ends of the high-curvature zones 5b1, 5b2 with forward convex end arches 5d1, 5d2 having a curvature less than or equal to that of the central portion 5a. The intermediate zones 5c1, 5c2 are of variable convexity with respect to the adjacent zones. The set of these zones backward with respect to the circle of radius Ra as represented in FIG. 5. The zones of high curvature 5b1, 5b2 make it possible to spread the beam 25 laterally and to reinforce the illumination in the extreme angular zones, for example at 35 ° on either side of the optical axis Y, by decreasing the intensities in the intermediate zones, and without affecting the central part of the beam whose illumination depends mainly on the central zone 5a of the curve. Indeed, the area of the curve corresponding to the angles of the lines 8 according to FIG. 6 detailed later (the zones 5b) are of small size, the angles evolve rapidly as a function of x, because of the strong curvature, so that there is more room for the zones 5d, where the angles are varied more slowly as a function of x. The central portion of the bundle generally corresponds to an angle of 10 ° on either side of the optical axis and the angular extent of the central portion 5a of the folder is sufficient to provide the desired intensity in the range 10 °. °. It should be noted that if the front edge of the folder was formed by a circular arc, centered on the optical axis, it would be possible by reducing the radius of this arc, and thus increasing the curvature on the entire edge , to improve the illumination of the extreme angular areas, but this improvement would be accompanied by a decrease in illumination in the central zone 10 ° on either side of the optical axis, which the invention allows avoid. Figure 4 shows the position of the centers of curvature for the different areas shown in Figure 5. C is the circle of radius Ra. O is the center of curvature for area 5a of radius Ra. 01 is the center of curvature for zone 5d2 of radius Rd. 02 is the center of curvature for the point oo of minimum radius of curvature (Rb), point located at the end of zone 5b2. When traversing the zone 5b2 of the zone 5a towards the zone 5c2, the center of curvature of the plane curve 5 moves from O to 02. When one passes the zone 5c2 of the zone 5b2 to the zone 5d2, the center curvature moves from 02 to 01. FIG. 5 illustrates the variation of the radius of curvature R at a point of the curve 5, as a function of its lateral distance, that is to say its distance x to the optical axis, carried as abscissa. The radius R, carried on the ordinate, corresponds to the inverse of the curvature. It appears that the radius R passes through two minimum values Rb, on either side of the optical axis, corresponding to the points of greatest curvature 20 of parts 5b1, 5b2. The central portion has a radius of curvature Ra constant in the example and the end parts a higher radius of curvature Rd also constant. The reflector 2 is determined to transform a spherical wave surface from the light source S into a wave surface that returns to the curve of the edge of the folder. Folder edge 5 is a solution of a differential equation involving radius of curvature R (x) as discussed further, which solution can be found numerically by choosing an arbitrary point of edge 5. Preferably, the position from the source S being known, we take the point My 30 (FIG. 2) of the edge belonging to the optical axis Y of the module, which axis passes through the center of the source; this reduces the choice of the point of passage to that of a simple real parameter, similar to the distance between foci in an ellipsoid. With conventional numerical methods (eg Runge-Kutta) the position (x, f (x), 0) of a current point M (Fig. 2) can be calculated with the desired accuracy (with the necessary computation time). ) of abscissa x along the axis X, ordinate f (x) along the optical axis Y and zero altitude along the vertical axis Z. It is also possible to calculate the tangent Tau edge 5 at this point M, by determining the director vector of component 1, f '(x), 0 of this tangent T. We deduce the normal plane Em at the edge 5 at the point M considered. This normal plane is a vertical plane whose trace on the plane of the edge 5 is the normal water edge 5 at the point M. The reflector 2 is determined by a family of curves 2m, each curve 2m corresponding to the intersection of the reflector with a Em normal plane at the edge 5 at a current point M. Each curve 2m is located in a plane Em. The family of curves 2m is obtained by moving the plane Em perpendicular to the edge 5. A curve 2m must have the following property. We consider light rays i, he, coming from the focus O center of the source S, and reaching the reflector 2 at current points P, P1 belonging to the plane Em. The points P, P1 are located on the curve 2m, which is such that the rays i, they are reflected along r r1 r1 rays pointing to the point M edge 5. The rays reflected r, r1 are contained in the plane Em. This property, and the choice of an arbitrary point for example the point Py intersection of the reflector and the optical axis Y, completely define the reflector 2, the curve 5 having been previously defined, by writing the constancy of the optical path from the source S to the edge 5 of the folder. The value of the optical path results from the choice of arbitrary points My and Py. The more detailed calculation is given later in this description. The reflector 2 can thus be calculated as a parametric surface in x (dimension of a point M on the bending edge 5, along the X axis) and according to the angle (1), this angle being that formed between a radius as r1, returned by the reflector 2 and falling on the edge 5 at the point M, and the plane of the folder (see Fig. 2). The height of the folder is zero, z = 0. The lens 3 can be determined as follows. The section, or intersection, 3Em of the lens 3 with the plane Em defined above, corresponds to the section of a stigmatic lens between the point M of the folding edge 5 of the folder and the infinite, this plane containing the axis of the stigmatic lens. This section 3Em is delimited by two dioptres: a diopter of entry 3Eme, and a dioptre of exit 3Ems. The material, glass or transparent plastic, of the section 3Em is between these two diopters.

One can choose arbitrarily one of the two dioptres of the lens. Generally one chooses the diopter of entry 3Eme. In the calculation example given below, this input diopter is constituted by an arc of circle in the plane Em, convex towards the rear, of center f2 (FIG. 3) situated in the plane of the folder 5. The output diopter 3Ems is calculated so that a light ray u1, emerging from the lens 3 and coming from an incident ray q1 coming from the point M, is parallel to the horizontal plane of the folder 5. The lens 3 could be parameterized by the same way as the reflector, but a mesh in (x, h), h being the height of the points on the input face of the lens (see Fig. 2 and 3) allows a simpler calculation. The lens 3 is not revolution, especially around a vertical axis. Fig. 6 schematically illustrates the network of isolux curves obtained on a screen, generally at a distance of 25 m, with a module according to ~ o the invention. The illumination in the central zone between -10 ° and + 10 ° on either side of the optical axis is not decreased compared to a module whose folder would have a circular front edge of radius equal to the radius means of curvature of the edge 5 according to the invention. On the other hand, the zones situated approximately at -35 ° and + 35 ° on either side of the optical axis, and corresponding to lines labeled 9-1 and 9-2 according to the R19-3 standard, exhibit an illumination higher than that of a module with a folding machine in an arc. Areas in which light has been taken to be transferred to lines 9-1 and 9-2 correspond substantially to intermediate lines 8-1 and 8-2 between the central zone and the end zones. The invention thus allows optimization, in particular by the choice of R (x) from which the curve f (x) describing the front edge 5 of the folder is deduced, and offers greater flexibility. The optimization can result from comparative calculations made with different equations f (x) for the curve 5. It becomes possible to make a fog lamp with a single module, while producing a beam that meets the regulatory requirements. A module according to the invention can also serve as a basic module for a code projector. Examples of calculation are given below for the determination of the reflector 2 and the lens 3, with reference to Figs. 2 and 3. Example of the calculation of the reflector 2 Let R (x) be the radius of curvature of the edge of the bender at a point M, with abscissa x, 35 located on curve 5 of equation y = f (x). The center of curvature at the point M is in the plane z = o. The radius of curvature R (x) is given by the formula: R (x) (1+ f '(x)') - differential equation in f, with initial conditions at the point My: f (0) = Yo f '(0) = 0 soluble in the form Y' = F (x, Y), where Y_ (x) _ '. (X) Y, 1 Vector tangent to the point M: f' (x) 0 (1) + Y, 'F _ R (x) / = T 1 20 25 Normal vector (in the direction of the center of curvature): 15 at point M

Suppose the source placed in O:

For all x, and for every v orthogonal to Tm (x),

there is a current point P of the reflector such that: PM (x) + PO = K = optical path with M (x) P collinear to v

x and M (x) = f (x) (current point of curve 5). K is an arbitrary constant. where P = M + Δv where v coscpn + sincpz From the optical equation we draw: OP = K-MP = OP2 = K2 + MP2u2 KMP -0 .-- OM2 + A2 + 2ΔOM.v = K2 + A2û2KMP 35 a2À ( OM v + K) = K2-OM2 When K2 = OM2 a limit point is reached for the calculation of the reflector. Example of Calculation for the Lens 3 Let I (FIG. 3) be a current point of altitude h of the input diopter 3E, of radius of curvature R 1. Let Q be the distance from the point M of the curve 5 to the point of the input diopter situated in the horizontal plane of the curve 5. The angle a designates the angle between MI and the horizontal. Q denotes the center of the arc of ~ o circle forming the input diopter 3Eme, Q being located in the plane of the folder. The angle between 01 and the horizontal is denoted by R.sub.h sin (3 = ## EQU1 ## where: nt. = Refractive index of the material of the lens 3 angle of incidence: a + R refraction angle: p nL sin p = sin (a + R) Y = pUR 25 By designating by p the distance, in the lens 3, between the entry point I of a beam and the point W of output on the diopter of output 3Ems, one obtains for coordinates of the point W

Wry, +, ucosy +, usin y 30 Let eL be the thickness of lens 3 in the center, we put: yo = Q + eL and KI = Q + nL eL Optical path = h + nL p + Yo û Yw sin a

= h + (YoYi) + p (nL ûcosy) = K1 5 sin a

from where we draw p (h), and thus y (h) and W (h)

Conjugated surfaces 10 Two points depending on x and h

Input: M - yn + hie Output: M û yw n, + zW z According to another variant of the invention, it is sought to make a light beam with a descending cut in its most lateral zones, as represented in FIG. As explained in FIG. 9, which represents the evolution of the value of rj (x) as a function of x, we see that we use a function rj (x) which is increasing or constant as a function of Ix1 (absolute value of x): - according to the curve C2, for x xo and for x <_ xi, where xo> _ 0, and xi <_ 0, the planes normal to the curve 5 in xo and xi form an angle greater than 5 °, preferably greater than or equal to 10 °, with respect to the optical axis. For x belonging to the segment [x, _ xo], r (x) is zero. By comparison, the first variant of the invention, with the light beam according to FIG. 6, corresponds in this FIG. 7 to the curve C1, where it (x) is constantly zero. FIG. 10, which represents the curve 5 in plan view, represents the trace of the plane normal to the points M of coordinates x, and xo 30 Si rj (x) remains low (in particular less than 3.5 °), the beam is improved. without compromising compliance with standards, including fog lamps. By improved beam, it is understood here that it is possible to increase the amount of light close to the vehicle at the high lateral angles, a light more useful to the driver than distant light. What distinguishes this variant of the preceding variant relates to the construction of the lens: in this variant, the lens 3 `can be determined as follows: The section, or intersection 3'Em of the lens 3 'with the plane Em defined below. above, corresponds to the section of a stigmatic lens between the point M of the edge 5 of the folder and infinity, this plane containing the axis of the stigmatic lens, axis inclined by an angle n, continuous function of x, relative to the projection of the optical axis of the module in the plane considered. Here, the output diopter 3Ems' is calculated so that the lo light ray u1 'coming out of the lens 3' and coming from an incident ray q1 coming from the point M makes an angle rj (x) with the horizontal plane of the The calculation example for the lens 3 'has the following modifications with respect to the example according to the first variant detailed above: as for the previous example, the point I is a current point which is in a plane 15 perpendicular to the curve 5 passing through any point M 'of it of lateral coordinate x. The optical path is modified as follows:

Optical path = h + n ~ p + pi sin a 20 = h + (yoûy ') cosri + hsinrl + p (nL û cosycosil + 5m y 5m ri) = Ki sin ci The inclined plane of an angle rj (x) relative to the vertical and perpendicular to the plane of the construction whose trace is the line rr constitutes an exit wave surface by the section of the lens considered. If we put il (x) = 0, we find the example according to the previous variant. In summary, for this second variant, the lighting module is such that, for any plane perpendicular to the edge of the folder 5 at a point M, the intersection of the lens 3 with said plane is the section of a stigmatic lens between the point M and the infinite, the direction of emerging rays making an angle ri with the plane of the folder, continuous function angle of the lateral coordinate (x) of said point M. Preferably, the function rj (x) is constant or increasing as a function of the lateral coordinate (x) of the point M. And, in particular, the function r (x) is constant and zero between the lateral coordinates of the points of the edges of the folder situated on either side of a vertical plane containing the optical axis (Y) of the module, preferably with the angle of the normal planes at the edge of the folder passing through these points with said axis (Y) being greater than or equal to 5 °, in particular greater than or equal to 10 °. 35

Claims (15)

REVENDICATIONS1. Lighting module for a motor vehicle headlamp, giving a cut-off light beam, comprising a concave reflector (2), at least one light source (S) disposed in the concavity of the reflector for illuminating, in particular at least upwards, and a lens (3) located in front of the reflector and the light source, the reflector being associated with a folder (4), in particular horizontal, whose upper surface is reflective for folding the beam coming from the reflector, said folder having an edge ( 5) of the front end suitable for forming the cut in the lighting beam, characterized in that: - the front edge (5) of the folder is formed by a plane curve with variable curvature, the curvature at a point (M ) being a continuous function of the lateral coordinate (x) of this point, - the reflector (2) is determined to transform the wave surface from the source into a wave surface that is reduced to the curvature curve variable of the edge (5) of the folder, and the lens (3) is determined to give a point (M) of the edge (5) of the folder, especially for all the rays contained in the plane perpendicular to the edge before said folder at the point considered, an image to infinity. 2. Lighting module according to the preceding claim, characterized in that the lens (3) is determined to give a point (M) of the edge (5) of the folder an image at infinity in a direction inclined by relative to the plane of the folder 25 of a continuous function angle of the distance from this point to the optical axis. 3. Lighting module according to claim 1, characterized in that the curvature of the front edge (5) of the folder has at least a maximum (5b1, 5b2) located angularly between the optical axis (Y) of the module and a angular limit of the beam. 4. Lighting module according to one of the preceding claims, characterized in that the curvature of the front edge (5) of the folder has a secondary maximum located on or substantially on the optical axis. 5. Lighting module according to claim 3 or 4, characterized in that the curvature of the front edge (5) of the folder has a maximum (5b1, 5b2) on each side of the optical axis. 6. Lighting module according to the preceding claim, characterized in that the front edge (5) of the folder is symmetrical with respect to the optical axis. 7. Lighting module according to any one of the preceding claims, characterized in that the maximum curvature (5b1, 5b2) of the front edge of the folder is chosen so that the illumination of the extreme angular zones of the beam is reinforced, without reducing the illumination of the central area. 8. Lighting module according to any one of the preceding claims, characterized in that the extreme angular regions of the beam extend in directions greater than or equal to 35 ° on either side of the optical axis. 9. Lighting module according to one of the preceding claims, characterized in that, for any plane perpendicular to the edge of the folder 5 at a point M, the intersection of the lens (3) with said plane is the cut of a stigmatic lens between the point M and the infinite, the direction of the emergent rays making an angle n with the plane of the folder, angle continuous function of the lateral coordinate (x) of said point M. 10. Lighting module according to one of the preceding claims, characterized in that the function rj (x) is constant or increasing as a function of the absolute value of the lateral coordinate (x) of the point M. 11. Lighting module according to one of the preceding claims, characterized in that the function ri (x) is constant and zero between the lateral coordinates of the points of the edges of the folder located on either side of a plane vertical axis containing the optical axis (Y) of the module, preferably with the angle of the normal planes to the edge of the folder passing through these points with said axis (Y) being greater than or equal to 5 °, in particular greater than or equal to 10 °. 12. Lighting module according to any one of the preceding claims, characterized in that the surface of the reflector (2) is such that light rays (i, i1) from the source and falling at points (P, P1). ) located on the intersection (2m) of this surface and a vertical plane (Em) passing through the center of curvature, but separated from the source, are reflected in this vertical plane so as to converge at a point (M) located at the intersection of the vertical plane and the edge of the folder. 15 13. Lighting module according to any one of the preceding claims, characterized in that the illumination in the central zone between -10 ° and + 10 ° on either side of the optical axis is maintained relative to to a basic module whose folder would have a circular front edge of radius equal to the average radius of curvature of the front edge (5), while the areas located at -35 ° and + 35 ° on either side of the optical axis, and corresponding to the lines listed 9-1 and 9-2 according to the R19-3 standard, have a higher illumination than that obtained with said basic module. 14. Lighting module according to any one of the preceding claims, characterized in that the cut-off beam obtained is flat cut, being chosen in particular between an anti-fog beam and a flat cut code beam portion. 15. Motor vehicle headlight, characterized in that it comprises at least one module according to any one of the preceding claims.