FR3097939A1 - LUMINOUS MODULE WITH HEATING SHOCK ABSORBER IMAGER - Google Patents

Abstract

LIGHT MODULE WITH IMAGER WITH DAMPING AND HEATING FIXING The invention relates to a light module (6) in particular for a motor vehicle, comprising an imager (8) with a front face (8.1), a rear face (8.2) and a peripheral edge (8.3); a backlighting device (10) of the imager (8), arranged opposite the rear face (8.2) of said imager; a support (12) with a reception area (12.3, 12.4) of the imager (8) and an attachment area (12.2) of the backlighting device (10); characterized in that the light module further comprises, at least one strip of flexible material and electrically heating (16) in contact with the peripheral edge (8.3) of the imager (8) and the reception zone (12.3, 12.4) of said imager on the support (12). The invention also relates to a method for controlling the temperature of the imager (8) of the light module. (Figure to be published with the abstract: Figure 1)

Description

LIGHT MODULE WITH IMAGER WITH DAMPING AND HEATED MOUNTING

The invention relates to the field of light signaling and lighting, in particular for motor vehicles.

It is currently common in the field of automobile light signaling to provide, in a rear light, one or more modules capable of forming on the glass closing the light images with variable geometry, such as pictograms intended to transmit additional information. . This type of module comprises, in known manner, an imager with a rear face and a front face, and a backlighting device arranged opposite the rear face of the imager. The imager is thus backlit and emits from its front face a light beam modulated by the imager, this beam illuminating the glass of the light by forming the light image in question there. The imager may be a liquid crystal display. Liquid crystal screens use the polarization of light by polarizing filters and the birefringence of certain liquid crystals in the nematic phase, the orientation of which can be varied according to the electric field. From the optical point of view, the liquid crystal screen is a passive device: it does not emit light, only its transparency varies, and it must therefore have lighting. Due to the viscous nature of liquid crystals, a liquid crystal display is susceptible to excessive response time, or even no response, at low temperatures. More specifically, a liquid crystal display has too long a response time at temperatures below or equal to -20°C and no response from -40°C.

Published patent document CN 101510020 A discloses a heating device for a liquid crystal display. This device comprises a glass substrate with two conductive side strips intended to be electrically supplied. An electrically conductive and transparent coating, based on indium-tin oxide (or indium oxide doped with tin or ITO for the English name: Indium tin oxide), is deposited on the substrate and is partially removed in a non-homogeneous manner transversely between the electrical supply side strips, so as to produce heat by the Joule effect, and this more close to the two side edges than in the central part. This device thus makes it possible to compensate for edge effects and thus ensure a uniform temperature of the liquid crystal screen. This device is interesting by the performance and fineness of heating. However, it has a cost disadvantage as well as light loss since all of the screen backlight light has to pass through the heater. The electrically conductive and transparent layer indeed has a non-zero absorption rate.

The aim of the invention is to overcome at least one of the drawbacks of the aforementioned state of the art. More particularly, the aim of the invention is to ensure proper operation of an imager in a light module, even at low temperature, in particular below -10°C.

The subject of the invention is a light module, in particular for a motor vehicle, comprising an imager with a front face, a rear face and a peripheral edge; a device for backlighting the imager, arranged opposite the rear face of said device; a support with an area for receiving the imager and an area for attaching the backlight device; remarkable in that the light module further comprises at least one strip of flexible and electrically heated material in contact with the peripheral edge of the imager and the zone for receiving said imager on the support.

The Imager is an electrical imager configured to produce an image by transmission of light. The imager is advantageously a liquid crystal screen.

According to an advantageous embodiment of the invention, the flexible and electrically heated material has a hardness of less than 80° Shore A. More advantageously, the flexible and electrically heated material has a hardness of less than 60° Shore A.

According to an advantageous embodiment of the invention, the at least one strip of flexible and electrically heating material has an average thickness greater than 0.1mm and/or less than 3mm.

According to an advantageous embodiment of the invention, the flexible and electrically heating material is honeycombed.

According to an advantageous embodiment of the invention, the at least one strip of flexible and electrically heating material comprises metal wires and/or conductive particles.

According to an advantageous embodiment of the invention, the contact of the at least one strip of flexible material and electrically heating with the peripheral edge of the imager is on at least one, preferably each, of the front and rear faces of said imager.

According to an advantageous embodiment of the invention, the at least one strip of flexible material and electrically heating is configured to be able to maintain the imager at an average temperature greater than -10° C. when said module is subjected to ambient conditions with a temperature ranging from -10°C to -40°C.

According to an advantageous embodiment of the invention, the at least one strip of flexible and electrically heated material is configured to be able to increase an average temperature of the imager by at least 10° C. in one minute, when said module is subjected to ambient conditions with temperature ranging from -10°C to -40°C.

According to an advantageous embodiment of the invention, said module further comprises a power supply unit for the at least one strip of flexible and electrically heated material, said unit being configured to maintain an average temperature of the higher imager at -10°C when said module is subjected to ambient conditions with a temperature ranging from -10°C to -40°C.

The invention also relates to a method for controlling the temperature of an imager of a light module, noteworthy in that said light module is according to the invention, and in that the at least one strip of flexible material and electrically heated is electrically powered to heat the imager provided that the ambient temperature is below -10°C.

The measurements of the invention are interesting in that they make it possible to ensure functionality of the imager in cold ambient conditions in a simple and economical manner, without any optical disturbance. The fact of heating the imager along its peripheral edge is not only interesting from an optical point of view and size but also from a thermal point of view, because it is indeed at the level of the edges that the imager tends to cool down and show too long a response time. Combining the electric heating function with the damping function also has advantages of compactness, cost and ease of assembly.

Other features and advantages of the present invention will be better understood from the description and the drawings.

is a schematic sectional view of a light module according to the invention, housed in a light device for a motor vehicle.

is a schematic front view of the module of Figure 2.

is a III-III sectional view of Figure 2.

is a sectional view IV-IV of Figure 2.

detailed description

Figure 1 is a schematic cross-section of a light device containing a light module according to the invention.

The light device 2 essentially comprises an envelope 4 and at least one light module 6 arranged inside the envelope 4. The latter essentially comprises a housing 4.1 forming an open cavity, and a glass 4.2 fixed to the housing 4.1 and closing the opening in question. Ice 4.2 is transparent or translucent.

The light module 6 essentially comprises an electronic imager 8, preferably of the liquid crystal type, and a backlight device 10. Such an imager forms a generally flat screen with a front face 8.1, a rear face 8.2 and a peripheral edge 8.3. It consists of two glass plates between which are housed liquid crystals. At each of the interfaces with the liquid crystals, a grooved polymer layer anchors the molecules at rest. The two internal faces of the glass plates include a matrix of transparent electrodes for black and white. For color applications, there are three cells per pixel and a color filter of red, green and blue patterns. Generally the filter is a succession of vertical bands alternating the three colors. The basic principle is that the application of a higher or lower potential difference between the two electrodes of a pixel leads to a change in the orientation of the molecules, a variation in the plane of polarization, and therefore a variation in transparency. of the whole device. Such a screen is passive in that it does not emit light; it requires lighting, in this case a backlight in order to be traversed by light.

To this end, the backlighting device 10 is arranged opposite the rear face 8.2 of the imager 8, so that the light emitted by said device is passed through and transmitted by the imager and is then projected onto the inner face of the glass 4.2 with a view to forming a signaling light beam displaying on the glass 4.2 a potentially changing image, which may form a pictogram. For this purpose, the imager can be controlled electronically in order to form these pictograms. These pictograms can be configured or selected to display useful safety information such as the presence of a hazard in front of the vehicle, the opening of the door of the vehicle when stationary, the parking status of the vehicle, etc. This principle of displaying light information is known per se to those skilled in the art.

The backlighting device 10 essentially comprises a plate 10.1 and light sources 10.2 arranged and distributed on the plate 10.1. The plate 10.1 is advantageously a printed circuit plate, made of epoxy resin reinforced with glass fibers, such as in particular FR-4 (abbreviation for “Flame Resistant 4”). The light sources are advantageously of the semiconductor type, preferably electroluminescence diodes.

Still with reference to FIG. 1, it can be seen that the light module 4 also comprises a support 12 on which the backlighting device 10 and the imager 8 are fixed, so as to keep these two elements fixed relative to each other. the other. The support comprises, between the backlight device 10 and the imager, walls forming a box 12.1 configured to channel the light towards the imager 8. For this purpose, the walls of the box 12.1 may have diffusing white surfaces.

The support 12 also comprises means 12.2 for positioning and fixing the plate 10.1 of the backlight device 10. These means may comprise tongues 12.2 extending in the extension of the walls of the case 12.1 and passing through holes of suitable shapes. performed in the plate 10.1 of the backlighting device. A shoulder at the base of each tab can be provided to form a support surface for plate 10.1. These tabs may have a hooking surface with an edge of the holes in the plate 10.1, in particular of the clipping type.

The support 12 also comprises reception zones 12.3 and 12.4 of the peripheral edge 8.3 of the imager 8. These reception zones 12.3 and 12.4 in this case form a shoulder 12.3 capable of receiving the rear face 8.2 of the imager, adjacent at the peripheral edge 8.3. One or more retaining pieces 12.4 are fixed to the shoulders 12.3 so as to extend opposite the front face 8.1 of the imager, along the peripheral edge 8.3. As can be seen in FIG. 1, strips of flexible material 14 and 16 are arranged on the rear 8.2 and front 8.1 faces, respectively, of the imager, between these said faces and the corresponding surfaces of the shoulders 12.3 and the corresponding surfaces of the retainer(s) 12.4. These strips of flexible material 14 and 16 have the function of ensuring damping of the vibrations likely to be transmitted by the environment to the imager 8. The latter in fact essentially consists of two superposed glass plates, these plates forming the front 8.1 and rear 8.2 faces. Too much tightening of the imager at its peripheral edge is likely to break at least one of the glass plates. An assembly with play is also undesirable because it is likely to generate parasitic noises and possibly also the breakage of at least one of the glass plates. The presence of strips of flexible material 14 and 16 overcomes these difficulties. As will be detailed below, in relation to the following figures, the flexible material of at least one of the strips 14 and 16 is also electrically heated and connected to an electrical power supply, in order to ensure heating of the imager 8 in cold conditions otherwise likely to increase the response time of the imager 8. In this case, only the strip of flexible material 16 is electrically heated and connected to a power supply, the other 14 not being. not. It is understood that various variations are possible; it is in particular possible to provide strips of flexible and heating material on the two faces 8.1 and 8.2 of the imager 8, or only on the rear face 8.2. It is also possible to provide on at least one of the two faces 8.1 and 8.2, one or more strips of flexible material and electrically heating on one or more portions of the peripheral edge, the rest of said edge being provided with strip(s) of flexible material conventional or even free of strip of flexible material.

The flexible material is advantageously a cellular material of the foam type, in particular polyurethane. Alternatively, it can be made of solid material. The flexible material is advantageously of the polymer type. It advantageously has a reduced hardness of less than 80° Shore A, more advantageously less than 60° Shore A. The strip(s) of flexible material 14 and 16 may have a thickness greater than 0.1 mm and/or less than 3 mm, preferably greater than 0.2mm and/or less than 2mm, more preferably still greater than 0.3mm and/or less than 1mm. The strip(s) of flexible material 14 and 16 may have a width greater than 2mm and/or less than 5mm.

The flexible and electrically heating material further comprises electrical conductors to form electrical resistance along the strip of said material. These electrical conductors can be metal wires, for example copper, embedded in the matrix formed by the flexible material, and/or conductive particles distributed in the matrix. The flexible and electrically heating material then has a resistivity (corresponding to the resistance of a section of material one meter in length and one square meter in section and is expressed in ohm-meters) of between 0.004 and 0.024 Ωm. For a strip with a section of 4mm ² and a length of 50mm, this gives a resistance of between 50 and 300 Ω. The resistance of the strip in question determines the heat produced by the Joule effect according to the relationship P=RI ² where P is the electrical and thermal power, R the resistance of the strip of flexible and electrically heated material, and I is the current flowing through said strip. The latter is obtained by Ohm's law, namely I=V/R , where V is the electric voltage applied to the strip of flexible and electrically heated material.

FIG. 2 is a front view of the module 6 of FIG. 1. One can observe the retaining part or parts 12.4 of the support 12, extending along the peripheral edge 8.3 of the imager 8. One can also observe that an electrical supply unit 18 of the strip of flexible and electrically heating material 16 is electrically connected to said strip. In this case, the strip of flexible material and electrically heating 16 extends continuously over almost all (with the exception of the area of the lower left corner in Figure 2) of the peripheral edge 8.3 of the imager , so as to form a single heating resistor along the four sides of the imager 8. Echoing what was mentioned above, it is understood that it is possible to provide several strips of flexible material and electrically heating 16, and this on the same face of the imager. In this case, it is then necessary to provide several electrical connections with the power supply unit 18.

Figures 3 and 4, which are sectional views III-III and IV-IV in Figure 2, illustrate an example of electrical connection of the strip of flexible material and electrically heating 16.

In Figure 3, it can be seen that the retainer 12.4, made of electrically insulating plastic material, comprises an electrode 12.4.1 overmolded by the plastic material. This electrode forms the outer surface of the retaining part 12.4 facing the strip of flexible material and electrically heating 16, and extending transversely at a distance from the imager so as to form, by way of example , a plug or an electrical contact terminal. In other words, when the retaining piece is put in place, by a movement essentially perpendicular to the plane of the imager, in the direction of the imager, the contact zone of the electrode 12.4.1, in vis-à-vis the strip of flexible material and electrically heating 16 will approach said strip until contact. If the latter has an electrical conductivity distributed in its mass, the simple fact of contacting it, in this case on its main face opposite the imager, will ensure electrical contact. If, on the other hand, the strip of flexible and electrically heating material 16 comprises electrical conductors 16.1 embedded in a mass of electrically insulating flexible material 16.2, as shown in FIG. 3, it is then advisable to provide a length of said conductors exceeding the end of the flexible electrically insulating material 16.2, in order to fold them back by 180° against the face of the strip of flexible material and electrically heating 16, opposite to the imager.

Figure 4 illustrates this situation where one can observe the electrical conductors 16.1, namely the metal son, bent 180 ° upwards so as to extend over the face of the strip of flexible material and electrically heating 16 which screws -à-vis the retained part 12.4, more particularly the contact zone of the electrode 12.4.1 of said part.

What has just been described in relation to FIGS. 3 and 4 also applies to the other of the two electrical connections in FIG. 2. What has just been described in relation to FIGS. 3 and 4 applies also to the shoulder 12.3 when the material of the strip of flexible material 14 is also electrically heated.

Also, it is understood that other electrical connection techniques may be considered.

The strip or strips of flexible and electrically heating material 16 and the power supply unit are advantageously sized to be able to increase the average temperature of the imager by at least 10° C. in less than 60 seconds.

The power supply unit 18 can be configured to supply the strip or strips of flexible and electrically heating material, the latter ensuring the regulation of the current as a function of the temperature of the imager. In this context, the power supply unit can be powered and/or binary controlled (on/off) depending on the ambient temperature. For example, it can be powered or controlled to operate as soon as the ambient temperature is below -10°C. It is also possible to provide a power supply unit 18 with a regulation function. In this case, a temperature sensor of the thermistor type can be arranged in contact with the imager 8 and be connected independently to the electrical power supply unit 18. The latter can then modulate the supply voltage and hence , the current, as a function of the effective temperature of the imager 8. In general, independently of the level of sophistication and complexity of the power supply 18, the latter will advantageously only be powered or at least controlled to operate only when the module is active, that is to say when the backlighting device and the imager are electrically powered.

Claims (10)

Light module (6) in particular for a motor vehicle, comprising:
- an imager (8) with a front face (8.1), a rear face (8.2) and a peripheral edge (8.3);
- a backlight device (10) of the imager (8), arranged opposite the rear face (8.2) of said imager;
- a support (12) with a reception area (12.3, 12.4) of the imager (8) and an attachment area (12.2) of the backlight device (10);
characterized in that the light module further comprises:
- at least one strip of flexible and electrically heated material (16) in contact with the peripheral edge (8.3) of the imager (8) and the reception zone (12.3, 12.4) of said imager on the support (12). Light module (6) according to Claim 1, characterized in that the flexible and electrically heating material has a hardness of less than 80° Shore A. Light module (6) according to one of Claims 1 and 2, characterized in that the at least one strip of flexible and electrically heating material (16) has an average thickness greater than 0.1mm and/or less than 3mm. Light module (6) according to one of Claims 1 to 3, characterized in that the flexible and electrically heating material is honeycombed. Light module (6) according to one of Claims 1 to 4, characterized in that the at least one strip of flexible and electrically heating material (16) comprises metal wires (16.1) and/or conductive particles. Light module (6) according to one of Claims 1 to 5, characterized in that the contact of the at least one strip of flexible and electrically heating material (16) with the peripheral edge (8.3) of the imager (8 ) is on at least one, preferably each, of the front (8.1) and rear (8.2) faces of said imager. Light module (6) according to one of Claims 1 to 6, characterized in that the at least one strip of flexible and electrically heating material (16) is configured to be able to maintain the imager (8) at a higher average temperature or equal to -10°C when said module is subjected to ambient conditions with a temperature ranging from -10°C to -40°C. Light module (6) according to one of Claims 1 to 7, characterized in that the at least one strip of flexible and electrically heating material (16) is configured to be able to increase an average temperature of the imager (8) by at least 10°C in one minute, when said module is subjected to ambient conditions with a temperature ranging from -10°C to -40°C. Luminous module (6) according to one of Claims 1 to 8, characterized in that the said module further comprises an electrical supply unit (18) for the at least one strip of flexible and electrically heating material (16 ), said unit being configured to maintain an average temperature of the imager greater than -10°C when said module is subjected to ambient conditions with a temperature ranging from -10°C to -40°C. Method for controlling the temperature of an imager (8) of a light module (6), characterized in that the said light module (6) is according to one of Claims 1 to 9 and in that the at least one strip of flexible material and electrically heating (16) is electrically powered so as to heat the imager on the condition that the ambient temperature is below -10°C.