FR3139617A1 - Lighting device for motor vehicle - Google Patents

Abstract

The invention relates to a lighting device for a motor vehicle, comprising a transparent body (10) adapted to form a light guide, said transparent body extending between a first end (12) adapted to receive a light generator (32) and an opposite second end (14) having a free surface (34), said second end (14) being adapted to receive rays of light produced by said light generator (32) at said first end (12), while said rays of light refract at said free surface (34); and said transparent body (10) is bent defining a convex zone (16), said convex zone having a flat surface portion (24) to form inside said transparent body an internal reflection surface (25) adapted to reflect towards said second end (14), said rays of light produced by said light generator (32). Figure to be published with the abstract: Fig. 1

Description

Lighting device for motor vehicle

The present invention relates to a lighting device for a motor vehicle.

One envisaged field of application of the invention is in particular, but not exclusively, that of light distribution modules located at the front of the vehicle and including high beam and/or low beam lights.

The light devices according to the invention can also be used at the rear of vehicles as signaling lights. They can also be used as flashing lights.

Known light distribution modules include a parabolic mirror and a light producing device adjusted substantially to the focus of the parabolic mirror.

The light producing device can be an incandescent lamp or more energy efficient light emitting diodes.

Such light distribution modules can be relatively bulky, whereas we are looking for the most compact devices possible.

Furthermore, their luminous efficiency may appear to be modest in view of the constraints imposed on manufacturers to optimize the energy consumption of motor vehicles.

Also, it could be imagined to insert different optical elements, for example lenses, in order to improve the compactness of the light distribution modules.

Such optical elements have the disadvantage, not only of reducing the luminous efficiency, but also of increasing the cost of the luminous devices, both because of the implementation of additional parts, and also because of the costs of additional labor.

Furthermore, the lighting devices thus developed may have an unfavorable aesthetic appearance.

Also, a problem which arises and which the present invention aims to solve is to provide a lighting device which not only has good luminous efficiency, but also which is aesthetic and inexpensive.

In order to solve this problem, a motor vehicle lighting device is proposed, comprising a transparent body adapted to form a light guide, said transparent body extending between a first end adapted to receive a light generator and a second opposite end having a free surface, said second end being adapted to receive rays of light produced by said light generator at said first end, while said rays of light are refracted at said free surface; and in that said transparent body is bent by defining a convex zone, said convex zone presenting a portion of flat surface to form inside said transparent body an internal reflection surface adapted to reflect towards said second end, said rays of light produced by said light generator.

Thus, a characteristic of the invention lies in the implementation of an angled transparent body allowing the guidance of light rays, from a light source or light generator, without light loss. The light generator is installed at the first end of the transparent body, while the second end of the transparent body opens into the exterior surface of the motor vehicle. At the very least, the free surface of the second end of the transparent body comes flush with the exterior surface of the motor vehicle.

In this way, the light rays emitted at the light generator are guided into the angled transparent body without attenuation and are refracted onto the free surface. As will be explained in more detail below, the bent transparent body makes it possible to juxtapose a plurality of transparent bodies and thus to produce a light device capable of guiding several light beams of different types or different colors.

According to a particularly advantageous embodiment of the invention, said light generator is arranged at said first end of said transparent body so that said rays of light extend in the same direction of collimation inclined by a first angle less than 50° relative to said internal reflection surface.

In other words, the collimation direction is tilted relative to the normal to the internal reflection surface by an angle greater than 40°. This angle varies depending on the nature of the material and more precisely its refractive index. The transparent body is preferably made of polycarbonate or polymethyl methacrylate whose refractive indices are respectively 1.52 and 1.48. Therefore, to achieve total reflection of the rays of light on the internal reflection surface, the collimation direction must be inclined with respect to the internal reflection surface by an angle less than 48° and 45' respectively by an angle lower than 47° and 9'. These values result directly from the Snell-Descartes laws of refraction, which are established in relation to the normal to the reflection surface. In other words, to obtain a total reflection, the direction of collimation must be inclined, relative to the normal to the internal reflection surface, by an angle greater than 41° and 15' and respectively by an angle greater than 42° and 51'.

Thus, since the light rays are completely reflected and there is no loss by refraction, the light energy is entirely transmitted towards the second end and its free surface.

Furthermore, the rays of light reflected by said internal reflection surface are able to extend towards said second end in the same direction of reflection inclined relative to said internal reflection surface at a second angle identical to said first angle. In other words, the reflected rays of light are in a direction inclined relative to the normal to the internal reflection surface, at an identical angle formed by the incident ray with the same normal.

Also, said first end of said transparent body has a first parabolic surface of revolution of a first axis of revolution.

Preferably, said direction of collimation is substantially parallel to said first axis of revolution. Therefore, by placing a light source at the focus of the parabolic surface, which is located inside the first end of the transparent body, we obtain a collimator from which the rays of light are oriented parallel to each other in the direction of collimation .

Also, advantageously, said first end has an axial cavity adapted to receive said light generator. And preferably, the axial cavity is arranged so as to open axially outside the first end of the transparent body and it extends to the focus of the parabolic surface in order to carry the light source there.

Advantageously, a light-emitting diode is inserted inside the axial cavity as a light generator.

In addition, said free surface of said second end of said transparent body advantageously presents a second parabolic surface of revolution of a second axis of revolution. Furthermore, said direction of reflection is preferably substantially parallel to said second axis of revolution. In this way, the rays of light refracted at the free surface converge towards the external focus of the second end of the transparent body.

According to another embodiment, the second end of the transparent body has a second cylindrical surface.

According to yet another embodiment, said second surface is spherical. It can also be aspherical.

According to another embodiment, said free surface of said second end of said transparent body is flat. And preferably, said direction of reflection is substantially perpendicular to said free surface.

In this way, the reflected rays of light extend perpendicular to the free surface and thus do not undergo any diffraction.

Other particularities and advantages of the invention will emerge on reading the description given below of particular embodiments of the invention, given for information but not limitation, with reference to the appended drawings in which:

is a schematic view in axial section of the object of the invention according to a first mode of implementation; And,

is a schematic view in axial section of the object of the invention according to a second mode of implementation.

There shows a transparent body 10 extending from a first end 12 to a second end 14. It is bent and has a convex zone 16 opposite a concave zone 18.

Also, the transparent body 10 illustrated on the has a first part 20 of generally cylindrical shape and of rectangular cross section. The first part 20 extends longitudinally along a first axis A, from the first end 12 to the convex 16 and concave 18 zones. The first axis A is defined by the crossing points of the diagonals of the straight sections of the first part 20 .

The transparent body 10 has a second part 22 also of generally cylindrical shape of rectangular cross section, and extending longitudinally along a second axis B of the convex 16 and concave 18 zones up to the second end 14. The second axis B is also defined by the crossing points of the diagonals of the straight sections of the second part 22.

It will be observed that the first axis of symmetry A of the first part 20 and the second axis of symmetry B of the second part 22 intersect and together form an angle substantially equal to 120°.

The transparent body 10 is produced, according to the implementation example presented here, by molding a transparent polymer material and in this case polymethyl methacrylate. This material is easily moldable and has a refractive index of 1.48.

Furthermore, and this is a particularity of the invention, in the convex zone 16 the transparent body 10 has a portion of flat surface 24 which delimits in a whistle both the first part 20 and the second part 22.

The flat portion 24 defines an internal reflection surface 25 and a plane P, on which the first A and second B axes of symmetry meet at a point C.

Furthermore, the flat surface portion 24 is defined so that the first axis of symmetry A is inclined by a first angle â with the plane P less than 48° and 45', and so that the second axis of symmetry B is inclined by a second angle û, substantially equal to the first angle â. The first angle â, of the example illustrated on the measures 30°.

We will explain, in the remainder of the description, the interest of such a flat surface 24.

Furthermore, the first end 12 of the transparent body 10 has a first parabolic external surface 26 with an axis of revolution S1 coinciding with the first axis of symmetry A.

Also, the first end 12 has an opening axial cavity 28 and extending along the axis of revolution S1 at least as far as the focus 30 of the parabolic external surface 26.

The transparent body 10 is then equipped with a light-emitting diode 32 housed inside the cavity 28 in the vicinity of the focus 30.

In contrast, the second end 14 has a free surface forming a second cylindrical external surface 34, for example, parabolic cylindrical.

Thus, the transparent body 10 can be installed in a lighting device capable of being mounted in a motor vehicle so that the second cylindrical external surface 34 of the second end 14 opens into the wall of the motor vehicle, for example at the rear, while the first end 12 equipped with its powered light-emitting diode 32 is hidden. Furthermore, the transparent body 10 is arranged so that the second axis of symmetry B extends substantially perpendicular to the wall portion of the vehicle into which the second end 14 opens.

According to another mode of implementation, not shown, the second external surface is planar and it is perpendicular to the second axis of symmetry B.

We will now describe the operation of the light device when the light-emitting diode 32 is powered.

Thus, when the light-emitting diode 32 emits light radiation, the rays are emitted in all directions inside the first end 12. The rays emitted in the axis of the cavity 28 are refracted and collimated along the first axis of symmetry A. The rays emitted against the side walls of the cavity 28 are not collimated but they are reflected on the parabolic surface 26 and are reflected parallel to each other parallel to the first axis of symmetry A of the first part 20.

Thus, the first part 20 equipped with the light-emitting diode 32 constitutes a collimator, the light rays which it produces then constitute incident rays 35 parallel to each other and forming an angle close to the first angle â, with the reflection surface 25 formed by the flat portion 24 of the transparent body 10.

Also, each of the incident rays 35 forms an angle of 90° - â with a straight line parallel to the normal N to the internal reflection surface 25. And each of the incident rays 35 is reflected entirely at said reflection surface 25, forming a reflected ray 36. And each of the reflected rays 36 forms an angle of 90°- û equal to 90°- â with a straight line parallel to the normal N.

Consequently, we obtain a plurality of reflected rays 36 extending generally in the same direction, which propagate in the second part 22 and refract at the parabolic external surface 34. The reflected rays 36 extend with dispersion angles relative to the second axis of symmetry B making it possible to distribute the light.

It will be observed that the normal line N to the reflection surface 25 is a bisector of the angle formed by the first A and second B axes of symmetry.

And thanks to the geometry of the free surface, and starting from the parabolic cylindrical external surface 34, the refracted light rays 38 converge at a point F’.

Furthermore, taking into account the angle of the incident rays 35 with the internal reflection surface 25, the latter constitutes a perfect mirror and none of the incident rays 35 is refracted. In other words, all of the incident rays 35 are reflected.

In this way, a coherent light distribution is obtained, without attenuation and with high luminous efficiency.

We will now refer to the , illustrating the invention according to a second mode of implementation. Elements identical to the subject of the figure will present the same references assigned a prime sign: “'”.

There shows another transparent body 10' extending from a first end 12' to a second end 14'. It is also angled, with a greater amplitude than the transparent body 10 of the and it has a convex zone 16' opposite a concave zone 18'.

It has a first part 20' of generally cylindrical shape of rectangular cross section and first axis A', extending longitudinally from the first end 12' to the convex 16' and concave 18' zones. Also, it has a second part 22' also of generally rectangular cylindrical shape with a second axis B', and extending longitudinally from the convex 16' and concave 18' zones to the second end 14'.

In this second mode of implementation, the first axis of symmetry A' and the second axis of symmetry B' intersect, together forming an angle greater than or equal to twice the critical angle of total internal reflection depending on the material.

The 10' transparent body is made by molding in Polycarbonate. Therefore, the aforementioned angle is greater than twice 41°15’.

It presents, in the convex zone 16', a portion of flat surface 24' which delimits in a whistle both the first part 20' and the second part 22'.

The plane portion 24' defines an internal reflection surface 25' and a plane P', on which the first A' and second B' axes of symmetry meet at a point C'.

Also, the flat surface portion 24' is defined so that the first axis of symmetry A' is inclined by a first angle â' with the plane P' less than 48° and 45', and so that that the second axis of symmetry B' is inclined by a second angle û', substantially equal to the first angle â'. The first angle â', of the example illustrated on the measures 47°.

Furthermore, the first end 12' of the transparent body 10' has a first parabolic external surface 26' with an axis of revolution S1' coinciding with the first axis of symmetry A'.

Also, the first end 12' has an opening axial cavity 28' and extending along the axis of revolution S1 at least as far as the focus 30' of the parabolic external surface 26'.

The transparent body 10' is capable of receiving a light-emitting diode housed inside the cavity 28' in the vicinity of the focus 30'.

In contrast, the second end 14' has a free surface forming a second external surface cylindrical 34’.

In the same way, the transparent body 10' can be installed in a lighting device capable of being mounted in a motor vehicle so that the second parabolic external surface 34' of the second end 14' opens into the wall of the motor vehicle, while the first end 12' equipped with its light-emitting diode, is masked.

Thus, when light radiation is emitted by a light-emitting diode inside the axial cavity 28', thanks to the first parabolic surface 26', the light rays are essentially reflected parallel to each other and also parallel to the first axis of symmetry A' of the first part 20'.

Thus, the light rays produced constitute incident rays 35' parallel to each other and forming an angle close to the first angle â', with the reflection surface 25' formed by the plane portion 24' of the transparent body 10'.

Also, each of the incident rays 35' forms an angle of 90° - â with a straight line parallel to the normal N' to the internal reflection surface 25'. And each of the incident rays 35' is reflected entirely on said reflection surface 25, forming a reflected ray 36'. And each of the reflected rays 36’ forms an angle of 90°- û equal to 90°- â with a straight line parallel to the normal N’.

Therefore, we obtain a plurality of reflected rays 36’ oriented in the same direction and which propagate in the second part 22' and refract on the parabolic external surface 34'.

Taking into account the angle of the incident rays 35' with the internal reflection surface 25', the latter also constitutes a perfect mirror and none of the incident rays 35' is refracted. In other words, all of the 35’ incident rays are reflected.

In this way, a coherent light distribution is obtained, without attenuation and with high luminous efficiency.

Other configurations are considered and also, with other materials whose refractive indices are significantly different. In all cases, we will ensure that the angle of the incident rays with the internal reflection surface respects the laws of Snell-Descartes to be able to constitute a perfect mirror.

Claims (10)

Lighting device for a motor vehicle, characterized in that it comprises a transparent body (10) adapted to form a light guide, said transparent body extending between a first end (12) adapted to receive a light generator (32) and an opposite second end (14) having a free surface (34), said second end (14) being adapted to receive rays of light produced by said light generator (32) at said first end (12), while said rays of light refract at said free surface (34); and in that said transparent body (10) is bent by defining a convex zone (16), said convex zone having a flat surface portion (24) to form inside said transparent body an internal reflection surface (25) adapted to reflect towards said second end (14), said rays of light produced by said light generator (32). Light device according to claim 1, characterized in that said light generator (32) is arranged at said first end (12) of said transparent body (10) so that said rays of light extend in the same direction of inclined collimation of a first angle (â) less than 50° relative to said internal reflection surface (25). Light device according to claim 2, characterized in that the rays of light reflected (36) by said internal reflection surface (25) are capable of extending towards said second end (14) in the same direction of reflection inclined relative to to said internal reflection surface (25) of a second angle (û) identical to said first angle (â). Lighting device according to any one of claims 1 to 3, characterized in that said first end (12) of said transparent body (10) has a first parabolic surface (26) of revolution of a first axis of revolution S1. Light device according to claims 2 or 3 and 4, characterized in that said direction of collimation is substantially parallel to said first axis of revolution S1. Light device according to claim 5, characterized in that said first end has an axial cavity adapted to receive said light generator. Lighting device according to any one of claims 1 to 6, characterized in that said free surface (34) of said second end (14) of said transparent body (10) has a second parabolic surface of revolution of a second axis of revolution S2. Lighting device according to claims 3 and 7, characterized in that said direction of reflection is substantially parallel to said second axis of revolution S2. Light device according to any one of claims 1 to 6, characterized in that said free surface of said second end of said transparent body (10) is planar. Lighting device according to claims 3 and 9, characterized in that said direction of reflection is substantially perpendicular to said free surface.