EP2756223A1

EP2756223A1 - Motor vehicle headlamp module for illuminating the road

Info

Publication number: EP2756223A1
Application number: EP12758857.2A
Authority: EP
Inventors: Pierre Albou
Original assignee: Valeo Vision SAS
Current assignee: Valeo Vision SAS
Priority date: 2011-09-13
Filing date: 2012-09-13
Publication date: 2014-07-23
Also published as: US20140321142A1; WO2013037858A1; JP2014527274A; FR2979969B1; FR2979969A1; CN103827574A

Abstract

The present invention relates to a module (210) for a headlamp (102) for a motor vehicle, this module (210) comprising a concave reflector (214), a light source (212) positioned in the concave region of the reflector (214) and an exit lens (216) having a median line on its exit surface forming a space curve (106), characterized in that the exit lens (216) and the reflector (214) are arranged in such a way that a beam of light reflected by the reflector (214) is directly refracted by the exit lens (216) so as to generate a beam of light that illuminates the road.

Description

LUMINOUS PROJECTOR MODULE OF MOTOR VEHICLE

FOR ROAD LIGHTING

The invention relates to a motor vehicle light projector module intended for road lighting, this module comprising a concave reflector, a light source disposed in the concavity of the reflector and a lens directly refracting the light rays reflected by the reflector. .

The evolution of the style of the vehicles leads to projectors with housings provided with ice whose surface has a left curve, varying in three dimensions, hereinafter referred to as average or median line. It is therefore desirable, especially for the style, that the projector lens, disposed in the case behind such ice, follow as far as possible the left curve of the ice.

The patent application EP 1936260 of the company VALEO VISION, published on June 25, 2008, shows a method of manufacturing lighting modules of this type which make it possible, by juxtaposing the ends of the output lenses, to produce a projector whose exit set surface, continuous and smooth, follows a left curve as a median or a mean line. In other words, the average line of the lenses of these projectors extends in three dimensions.

However, this method of determining the shape of the output lenses, which form an overall lens for the projector when they are juxtaposed, is limited in that it requires that each output lens has a same section along the vertical plane. .

In particular, a lens generated according to this method has a torus shape, with a width greater than its height, which may be unsatisfactory for certain body styles.

In other words, the ensemble lens does not completely follow the style curve in the absence of a twisted shape reflecting the variation of this style curve according to the three spatial dimensions.

In addition the lighting modules described in the EP1936260 application require many optical elements, including folders, which make relatively expensive their manufacture.

Finally, such a method is limited to the implementation of code lights, generating a beam cut horizontally through a stigmatic optical system.

The present invention aims to overcome at least one of the problems mentioned above. This is why the invention relates to a light projector module for a motor vehicle, this module comprising a concave reflector, a light source disposed in the concavity of the reflector and an output lens. having a center line on its exit surface forming a left curve, characterized in that the exit lens and the reflector are arranged such that a light beam reflected by the reflector is directly refracted by the exit lens so as to generate a road lighting light beam

Thanks to the invention, a light projector module can be manufactured with a limited number of optical elements, in particular reduced to a light source, a reflector and a lens. Thus, the manufacturing cost of such a projector is reduced compared to a projector according to the prior art which requires additional elements, such as folders.

Moreover the invention makes it possible to manufacture modules provided with exit lenses which follow the shape of a left curve in three dimensions, unlike a lens according to the prior art which was manufactured by translation of the same vertical section.

In one embodiment, the module is characterized in that the output lens and the reflector are arranged such that the light beam directly refracted by the lens forms a cylindrical wave surface.

According to one embodiment, the module is characterized in that the output lens and the reflector are arranged in such a way that the position of the axis of the cylindrical wave surface of the directly refracted light beam determines a height and an opening of said beam bright directly refracted.

According to one embodiment, the reflector and the lens form a system with a focus, the reflector being arranged so that for any given point of the reflector, the optical path to the axis of said cylindrical wave surface corresponding to a ray from said focus passing through that given point of the reflector and emerging at a point of the exit surface of the lens is constant.

In one embodiment, the module is characterized in that the directly refracted light beam is a road-type beam, that is to say a beam intended to illuminate the road.

In one embodiment, the module is characterized in that the output lens has a variable vertical section along the left curve.

In one embodiment, the module is characterized in that the output lens has identical sections in different defined construction planes so that each construction plane, including a point M of the left curve, is perpendicular to a vector tangent to said left curve.

According to one embodiment, the module is characterized in that the reflector and the light source are arranged such that a light beam from the light source is directly reflected by the reflector towards the lens.

The invention also relates to an elementary optical lens capable of being used as an output lens of a module according to one of the preceding embodiments, said lens comprising an exit surface along a left median, sections of the lens at several points of this left median in planes perpendicular to the left median being superimposable by translational movement and / or rotation without deformation.

In one embodiment, the elementary optical lens is characterized in that it forms a stigmatic optical system in the different planes perpendicular to the left median.

According to one embodiment, the elementary optical lens is characterized in that it has a spherical input surface of constant radius in the different planes perpendicular to the left median.

The invention also relates to a module according to one of the preceding embodiments, characterized in that the output lens is an elementary optical lens according to one of the preceding embodiments.

Thus, the beam from a module according to the invention can be used as a road beam, that is to say a beam for illuminating the path of a vehicle.

The invention also relates to an optical lens with portions formed by a plurality of elementary optical lenses in accordance with one of the preceding embodiments. Such an overall lens, formed by output lenses according to the invention, more closely follows the shapes desired by the stylists and has a twisted shape close to the left shape of the style curve.

In one embodiment, the portioned optical lens comprises an overall output face:

formed by exit faces of different elementary optical lenses;

comprising an overall median curve formed by the median curves of the different elementary lenses.

In one embodiment, the portioned optical lens has an overall exit surface that is continuous and smooth.

Other advantages of the invention will emerge in the light of the description of an embodiment of the invention made below, by way of illustration and not limitation, with reference to the attached figures in which:

FIG. 1 is a diagrammatic view of a front left outer edge face of a vehicle equipped with a light projector according to the invention,

FIG. 2 is a perspective view of the optical system implemented by the light projector of FIG. 1;

FIGS. 3 to 7 are representative diagrams of geometrical relations to the surface of a lens or reflector being designed according to the invention, and

- Figures 8 to 1 1 are diagrams showing Isolux curves obtained from a projector according to an embodiment of the invention. In the description below, the elements that are identical or perform a similar function have the same reference in the different figures.

With reference to FIG. 1, the front left end of a vehicle 100 provided with a light projector 102 according to the invention has an overall lens 104 whose shape follows a left curve 106, that is to say say a curve varying in three dimensions relative to a fixed reference (O, x, y, z) relative to the vehicle, in particular defining the vertical (Oz).

This left curve 106 is substantially parallel to a style curve 108 of the projector glass to be consistent with a style of the vehicle body. Referring to Figure 2, the projector 102 is composed of three juxtaposed modules 210, it being understood that a projector 102 according to the invention is not limited to this number of modules juxtaposed. In other words, a projector according to the invention can be formed by n modules 210, n being typically between 1 and 10 and in particular between 2 and 4.

Each module 210 comprises a light source 212 formed by at least one light-emitting diode intended to illuminate towards a reflector 214 so that the latter reflects light rays coming from this source 212 towards an exit lens 216.

The lens and the reflector are arranged such that a light beam reflected by the reflector is directly refracted by the lens, that is to say without being modified by a third optical element. Thus, the number of optical elements to equip the projector 102 is limited to the light source, the reflector and the lens.

Output output lenses 216 are juxtaposed so as to form the assembly lens 104 having a continuous, smooth exit surface capable of generating the driving beam. For this purpose, the design of each module 210 comprises two successive first steps using a local coordinate system imposed by the left curve 106, namely:

a first step of designing each output lens 216, and

a second step of designing the reflector 214 from the exit lens 216 obtained in the first step.

These two steps are detailed below using the expressions "before" or "upstream" and "backward" or "downstream", which are to be understood according to the direction of propagation of the light beam emitted by the light source 212, reflected by the reflector 214 and then refracted by the exit lens 216. Moreover, in these two steps, the left curve 106 of the lens, which corresponds to a median line of the exit surface of the set lens 104, is modeled by a function M (u) such that the coordinates of a point M of the left curve 106 in the reference (O, x, y, z) fixed vis-à-vis the vehicle 100 is:

Where u is a parameter taken in any interval and M (u) is a doubly differentiable function.

In fact, the first and second derivatives of the function M (u) are required to construct the orthonormal local coordinate system, whose orientation at a point M follows the variations of the left curve at this point M, implemented for the design of The lens.

Thus the determination of the shape of the lens in the local coordinate system takes into account the variations of the left curve in the three dimensions at each point M (u). These first or second derivatives are written, for example for the horizontal coordinates XM (U) along the x axis, X'M (U) or X "M (U) with:

In the absence of a known function M (u) to define a left curve, this function M (u) can be obtained by modeling the left curve by a polynomial function, for example according to Bezier curves, using of a plurality of points M whose coordinates are empirically recorded.

First step relating to the design of the lens:

For a given value of the parameter u and, corollary, for a point M, a local coordinate system and the edges of the exit lens 216 are determined using a vector tangent to the left curve M (u). this point M such that:

So that his coordinates are written:

From such a tangent vector it is possible to determine the orthonormal coordinate system

local, located in M (u), comprising said tangent vector and vectors such

than:

the vector defines the first axis of the local coordinate system according to the following vector product:

So that his coordinates are written:

The vector is perpendicular, on the one hand, to the vertical axis z of the fixed reference and, on the other hand, to the tangent vector

the vector defines the second axis of the local coordinate system according to the following vector product:

So that his coordinates are written:

In the local coordinate system, the exit lens 216 is then defined as

a stigmatic optical axis lens having a spherical entry surface

of radius f ", of vertex M (u), of thickness at center E, of draw T and of material of index n, these parameters Ri, E, n, and T being independent of u.

The calculation of the shape of the lens is then performed according to a parameter for scanning the surface of the lens, such as the impact height h on the input face.

With reference to FIG. 3 and considering a radius originating from the focus F, these conditions and the geometrical relations between the incident, refracted, or reflected beams result in the following equalities:

Considering the length of a ray reflected in the lens as a calculation parameter, it appears that a displacement dh along the axis defined by the vector V or dx along the axis defined by the vector is translated by : By writing the equality of two optical paths between two beams:

Where dist (P, (M, V)) is the distance from the point P to a line passing through the point M and collinear to the vector , we then obtain a parametric equation in (u, h) of the input and output faces of the lens:

From where :

From this last equation, it is possible to define l, then dh and dx, as a function of h and E. Therefore, the coordinates of a point P of the lens, and consequently the profile of the latter, are obtained by the following equation:

Second step relating to the reflector design:

In the hypothesis of a point source placed at the point F, the emerging beam of the optical system formed by the reflector and the lens has the shape of a cylindrical wave surface of vertical axis C (z) whose coordinates are :

A modification of the position of this axis C (z) with respect to the exit surface of the lens makes it possible to modify the spreading, or the opening, of the beam and its mean horizontal direction.

By way of example, FIGS. 8, 9 and 10 represent Isolux curves representing the spatial distribution of the light intensity levels of a beam generated by different modules having different openings and average horizontal directions thus obtained.

With such modules, it is then possible to obtain a driving beam combining the properties of these different modules from a projector formed by these three modules (Figure 1 1).

To determine a module, consider two points LP1 and LP2 of the left curve defining the lens 216 as shown in Figure 6. For an average direction H _of v and a horizontal opening H _incpt beam, it appears that:

Where LP ₀ is defined as the middle of the segment [LP1; LP2], this segment modeling the left curve for the calculation.

When the direction v _of H and the horizontal opening _incpt H are fixed, the position of the axis C (z) is determined and the shape of the reflector can also be fixed. We then consider the inverse path of the emitted beam represented by a normal radius to the output wave surface that meets the exit face of the lens at the point P (u, h) (Figure 7).

In this case, the coordinates of the vector are:

The sign function intervenes because, depending on the position of the C (z) axis in

before / upstream of the lens, the considered building radii diverge from or converge towards the axis of the cylinder of the wave surface (for the real rays, respectively convergent or diverging).

The vector product of the vectors derived from the point P (u, h) with respect to u and by ratio to h generates a vector orthogonal to the surface of the lens:

This normal vector can be calculated using the properties of the lens section and functions. With reference to Figure 4, it appears

as well as :

from where:

This equation thus makes it possible to determine the angle η as a function of the height h. We can then calculate the vectors derived from the left curve P (u, h) with respect to u and with respect to h, in particular by considering the angle Θ defined as:

He comes then:

This equation can be developed using vectors considering the writing of their derivatives according to the following formulas:

From the laws of Descartes, it is then possible to determine the direction, according to a vector μ, of the radius refracted at P from an incident ray whose direction is given by the vector j previously determined.

The intersection of the refracted ray (P, μ) with the input face of the lens is then determined in two steps by means of the coordinates of μ established in the local coordinate system. More precisely:

In such a way that:

In a first step, we consider the intersection sought as a point i (u ', h') situated at a distance λ from P, in the plane perpendicular to the style curve in M (u '), which allows us to to establish a function

In such a way that

For a point u corresponding to the section of the input face containing i (u ', h'), the vector (MI) is perpendicular to the left curve so that:

and

that is to say

Which allows to determine the parameter

In a second step, in the construction reference in u ', we consider that belongs to the circle of radius R, and of center located in ER, on the axis , which makes it possible to determine successively

In the local coordinate system, the coordinates of are: Therefore, membership of the indicated circle results in the following equation:

The resolution of this equation makes it possible to define the parameter u of the interface I while the parameter h is given by:

The value of u is determined such that:

Gold From where

A special case arises when the refracted ray is in the plane under construction in u, which results in:

(I being in the construction plan of P.

We then determine from the equation:

Determination of the entrance face of the lens:

If l (u, h) is a point on the input face of the lens, the vector product between the derivatives of the vector with respect to u and h generates a normal vector to the input surface of the lens in reference to FIG. 5, one can then write:

We can therefore write that is the tangent, in I of the plane containing M and

perpendicular to what results in:

From this equation of the normal vector and the previous result, it is possible to propagate the radius through the lens according to the laws of Descartes (Figure 7) and obtain the inverse ray emerging from the lens in the direction of

reflector.

By naming S the point of intersection of the reflector and the distance

from S to i (u ', h'), it appears that the constancy of the optical path K, independent of (u, h) for the path from F to the axis of the output wave area via S , i (u ', h') and P, makes it possible to establish d as a function of u, h and K and thus finally S (u, h, K). More precisely :

Let F be a focal point of the system, it appears that:

From where

And, if we ask:

And

This last equation makes it possible to obtain d and S.

In some cases, ε does not exist as a result of total internal reflection. In this case, it is nevertheless possible to calculate a hypothetical emerging radius, in the limiting direction, in order to complete the mesh of the reflector and to be able to import it more easily in computer-aided design (CAD).

In other words, we use a radius ε perpendicular to and contained in the

plan so that this ray is collinear with the vector from the

vector product:

We can determine K and obtain a parametric equation of the reflector S (u, h) by writing that is a pseudo focal for the reflector

The present invention is capable of numerous variants, for example relating to the light source and its lighting direction. In this description, it is considered that the size of the housing of the projector 102 is limited due to automotive manufacturing requirements. As a result, the light source is relatively close to the ice which may be subjected to too much heating, especially with a transparent plastic ice and a halogen-type light source. To avoid such difficulties, the light source is a light emitting diode but other light sources could be implemented.

In addition, it can be considered in one embodiment that the light source radiates towards a reflector located in a plane below the source, but in other variants, the reflector may be located at different positions with respect to the source. In particular, the method of construction indicated above teaches that the relative position of the source and the reflector depend on the position of the focus F with respect to the lens. For example, if the focus F is located above the lens in front view, the reflector is below the focus F while, if the focus F is located below the lens in front view, the reflector is found above F.

Figure 12 shows the assembly lens 104 of Figure 2, seen from another angle. It is observed that this lens 104 has a curved shape according to different curvatures. Its shape follows a left curve 106. Behind it, there is a set of three reflectors 214 associated with 3 LEDs 212. In this figure are shown two identical sections 104a and 104b (dashed alternating a short line and a long line). These are identical sections in different construction planes defined so that each construction plane, including a point M of the left curve 106, is perpendicular to a vector tangent to said left curve

106, as defined previously, in particular for FIG.

Claims

1. A light projector module (210) for a motor vehicle (100), said module (210) comprising a concave reflector (214), a light source (212) disposed in the concavity of the reflector (214) and an output lens (216) having a center line on its exit surface forming a left curve (106), characterized in that the exit lens (216) and the reflector (214) are arranged such that a light beam reflected by the reflector (214) is directly refracted by the output lens (216) to generate a road illumination light beam.

2. Module (210) according to claim 1 characterized in that the output lens (216) and the reflector (214) are arranged such that the light beam directly refracted by the lens (216) forms a wave surface cylindrical.

3. Module (210) according to claim 1 or 2 characterized in that the output lens (216) and the reflector (214) are arranged such that the position of the axis

(C) of the cylindrical wave surface of the directly refracted light beam determines a height and an opening of said directly refracted light beam.

4. Module (210) according to claim 3, characterized in that the reflector (214) and the lens (216) form a system with a focus (F), said reflector being arranged so that for any given point ( S) of the reflector, the optical path (K) to the axis (C) of said cylindrical wave surface corresponding to a radius from said focus (F) passing through this given point (S) of the reflector and emerging in a point (P) of the exit surface of the lens (216) is constant.

5. Module (210) according to one of the preceding claims characterized in that the directly refracted light beam is a beam of the road type.

6. Module (210) according to one of the preceding claims, characterized in that the output lens (216) has a variable vertical section along the left curve (106).

7. Module (210) according to one of the preceding claims characterized in that the output lens (216) has identical sections in different defined construction planes so that each construction plane, including a point M of the curve left (106), is perpendicular to a tangent vector (t _c ) to said left curve (106).

8. Module (210) according to one of the preceding claims characterized in that the reflector (214) and the light source (212) are arranged such that a light beam from the light source (212) is directly reflected by the reflector (214) to the lens.

9. Elemental optical lens adapted to be used as an output lens (216) of a module (210) according to one of the preceding claims, said lens comprising an exit surface along a left median (106), sections of the lens at several points (M) of this left median in planes perpendicular to the left median (106) being superposable by translation and / or rotation movements without deformation.

10. Elemental optical lens according to claim 9 characterized in that it forms a stigmatic optical system in the different planes perpendicular to the left median (106).

1 1. Elemental optical lens according to claim 9 or 10, characterized in that it (216) has a spherical input surface of constant radius (Ri) in the various planes perpendicular to the left median (106).

12. Module (210) according to one of claims 1 to 8 characterized in that the output lens is an elementary optical lens according to one of claims 9, 10 or 1 1.

13. Optical lens with portions formed by a plurality of elementary optical lenses according to one of claims 9, 10 or 11.

A portioned optical lens according to claim 13 comprising an overall exit face:

formed by exit faces of different elementary optical lenses (216); - comprising an overall median curve (106) formed by the median curves of the different elementary lenses (216).

The portioned optical lens of claim 14 wherein the overall exit surface is continuous and smooth.

16. Projector (102) of a motor vehicle (100) generating a light beam, in particular a road beam, characterized in that it comprises at least two lighting modules (210) according to any one of claims 1 to 8 , juxtaposed so that the overall lens of the projector, formed by the juxtaposition of the output lenses (216) of the modules, follows a left curve (106).

The projector (102) of claim 16 wherein the assembly lens is a portioned optical lens according to one of claims 13 to 15.