Optical module with imager having damping and heating attachment

Abstract

The invention relates to a light module (6), in particular for a motor vehicle, comprising: an imager (8) having a front surface (8.1), a rear surface (8.2) and a circumferential edge (8.3); means (10) for back-lighting the imager (8), positioned facing the rear surface (8.2) of the imager; a support (12) having an area (12.3, 12.4) for receiving the imager (8) and an area (12.2) for attaching the back-lighting means (10); characterized in that the light module further comprises: at least one strip (16) of flexible electrically heating material, in contact with the circumferential edge (8.3) of the imager (8) and with the area (12.3, 12.4) on the support (12) for receiving the imager. The invention also relates to a method for controlling the temperature of an imager (8) of a light module.

Description

Technical Field

[0001] The present invention relates to the field of luminous signals and lighting, in particular to the field of luminous signals and lighting for motor vehicles. Background Art

[0002] In the field of automotive light signaling, it is currently common practice to incorporate one or more modules in rear lamps that are capable of forming geometrically variable images, such as pictograms for conveying additional information, on the outer lens of the lamp when the lamp is off. This type of module, in a known manner, comprises an imager having a rear surface and a front surface, and a backlighting device positioned facing the rear surface of the imager. The imager is thus illuminated by the backlight, and a light beam modulated by the imager is emitted via its front surface. This light beam illuminates the outer lens of the lamp and forms the light image in question on the outer lens. The imager can be a liquid crystal display. Liquid crystal displays utilize the polarization of light by a polarizing filter and the birefringence of certain liquid crystals in the nematic phase, whose orientation can be varied by an electric field. From an optical point of view, liquid crystal displays are passive devices: they do not emit light, only their transparency varies, and therefore require illumination. Due to the viscosity of the liquid crystals, liquid crystal displays tend to exhibit excessively long response times, or even no response at low temperatures. More specifically, they exhibit excessively long response times at temperatures of -20°C and below, and no response at temperatures of -40°C and below.

[0003] Published patent document CN101510020A discloses a heating device for a liquid crystal display. The device includes a glass substrate having two conductive lateral strips for being powered. A conductive transparent coating based on tin-doped indium oxide, more commonly known as indium tin oxide or ITO, is deposited on the substrate and unevenly, laterally, partially removed from the substrate between the lateral power supply strips to produce a Joule heating effect that is stronger near the two lateral edges than in the center. The device is therefore able to compensate for edge effects and thus ensure a uniform temperature on the liquid crystal display. The device is advantageous due to the performance and fineness of the heating. However, since not all light used to backlight the screen can pass through the heating device, the device has the disadvantages of cost and light loss. This is because the transparent conductive layer actually has a non-zero absorption level. Summary of the Invention

[0004] It is an object of the present invention to alleviate at least one of the above-mentioned disadvantages of the prior art. More specifically, it is an object of the present invention to ensure correct operation of imagers in light modules even at low temperatures, in particular at temperatures below -10°C.

[0005] The subject of the invention is a light module, in particular for a motor vehicle, comprising: an imager having a front surface, a rear surface and a peripheral edge; a backlighting device for backlighting the imager, the backlighting device being positioned facing the rear surface of the device; a support having a receiving area for receiving the imager and an attachment area for attaching the backlighting device; characterised in that the light module further comprises at least one strip of elastic electrically heating material, the strip being in contact with the peripheral edge of the imager and with the imager receiving area of ​​the support.

[0006] The imager is an electrical imager configured to generate an image by the transmission of light. The imager is advantageously a liquid crystal display.

[0007] Preferably, the elastic electric heating material is elastically deformable.

[0008] Preferably, the resilient electric heating material is capable of absorbing or damping vibrations, in particular vibrations present during use of the device.

[0009] Strips made of this material therefore help to attenuate vibrations that may be transferred to the imager from the environment.

[0010] Such strips can also limit the forces applied to the surface of the imager. Too much force could damage or even destroy the imager.

[0011] Such a strip can also absorb manufacturing tolerances of the various components and can eliminate the assembly gaps that would otherwise be required. Components with gaps can generate accompanying noise during use of the device, particularly due to vibrations, and can also lead to damage to the imager.

[0012] According to an advantageous embodiment of the invention, the elastic electric heating material has a hardness lower than 80 Shore A. More particularly, the elastic electric heating material has a hardness lower than 60 Shore A.

[0013] According to an advantageous embodiment of the invention, said at least one strip of elastic electrically heating material has an average thickness greater than 0.1 mm and / or less than 3 mm.

[0014] According to an advantageous embodiment of the invention, the elastic electric heating material is porous.

[0015] According to an advantageous embodiment of the invention, at least one strip of elastic electrical heating material contains metal wires and / or electrically conductive particles.

[0016] According to an advantageous embodiment of the invention, the contact between the at least one strip of elastic electrically heating material and the circumferential edge of the imager is located on at least one, preferably on each, of the front and rear surfaces of the imager.

[0017] According to an advantageous embodiment of the invention, said at least one strip of elastic electrically heating material is configured to be able to maintain an average temperature of the imager above -10°C when said module is subjected to ambient conditions having temperatures ranging from -10°C down to -40°C.

[0018] According to an advantageous embodiment of the invention, the at least one strip of elastic electrically heating material is configured to increase the average temperature of the imager by at least 10°C within one minute when the module is subjected to environmental conditions having a temperature ranging from -10°C down to -40°C.

[0019] According to an advantageous embodiment of the invention, the module further comprises a power supply unit for supplying power to at least one strip of elastic electrically heating material, said unit being configured to maintain the average temperature of the imager above -10°C when the module is subjected to ambient conditions having a temperature ranging from -10°C down to -40°C.

[0020] Another subject of the invention is a method for controlling the temperature of an imager of a light module, characterized in that the light module is a module according to the invention and that at least one strip of elastic electrically heating material is energized so as to heat the imager at an ambient temperature below -10°C.

[0021] The measures implemented by the present invention are advantageous because they allow the imager to function even in cold ambient conditions, and are achieved in a simple, economical, and without any optical interference. The fact that the imager is heated along its circumferential edges is advantageous not only from an optical and volumetric perspective, but also from a thermal perspective, as the imager tends to cool at the edges and exhibit excessively long response times. The fact that the electrical heating function is combined with the damping function also offers advantages in terms of compactness, cost, and ease of assembly.

[0022] Other features and advantages of the present invention will be better understood from the description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a cross section of a light module according to the invention, which is accommodated in a lighting device for a motor vehicle.

[0024] Figure 2 yes Figure 2 Schematic front view of the module.

[0025] Figure 3 yes Figure 2 View of section III-III.

[0026] Figure 4 yes Figure 2 View of section IV-IV. DETAILED DESCRIPTION

[0027] Figure 1 is a schematic diagram of a cross section of a lighting assembly comprising a light module according to the present invention.

[0028] The lighting device 2 mainly includes a housing 4 and at least one light module 6 located in the housing 4. The housing 4 mainly includes a housing 4.1 forming an open cavity and an outer lens 4.2 fixed to the housing 4.1 and closing the relevant opening. The outer lens 4.2 is transparent or translucent.

[0029] The optical module 6 primarily comprises an electronic imager 8 and a backlight 10. The electronic imager 8 is preferably of the liquid crystal type. This imager forms a generally flat screen with a front surface 8.1, a rear surface 8.2, and a peripheral edge 8.3. The screen is constructed from two glass plates, with liquid crystal contained between them. At each interface with the liquid crystal, a grooved layer of polymer provides anchoring for the stationary molecules. In the monochrome case, the two inner surfaces of the glass plates contain an array of transparent electrodes. For color applications, each pixel has three cells, and color filters are used for red, green, and blue patterns. Typically, the color filters are a series of vertical stripes alternating between the three colors. The basic principle is that applying a greater or lesser potential difference between the two electrodes of a pixel causes a change in the molecular orientation, a change in the plane of polarization, and therefore a change in the overall transparency of the device. This screen is passive, as it does not emit light; it requires illumination, in this case, backlighting, to allow light to pass through it.

[0030] To this end, backlighting device 10 is positioned facing rear surface 8.2 of imager 8, so that light emitted by said device passes through the imager and is then projected onto the inner surface of outer lens 4.2 to form a light signal beam. This signal beam displays a possibly changing image on outer lens 4.2, capable of forming a pictogram. To this end, the imager can be electronically controlled to form these pictograms. These pictograms can be configured or selected to display information useful for safety, such as, in particular, the presence of a hazard ahead of the vehicle, the opening of a vehicle door when the vehicle is stationary, the parking of the vehicle, etc. This principle of displaying optical information is known per se to those skilled in the art.

[0031] The backlighting device 10 mainly comprises a mounting board 10.1 and light sources 10.2 arranged and distributed on the mounting board 10.1. The mounting board 10.1 is advantageously a printed circuit board made of glass fiber reinforced epoxy resin, in particular FR-4 (fire resistant 4) epoxy resin. The light sources are advantageously semiconductor-type, preferably light emitting diodes.

[0032] Still refer to Figure 1 , it can be seen that the light module 4 also includes a support 12 to which the backlight 10 and the imager 8 are attached in order to keep these two elements fixed relative to each other. The support includes a wall between the backlight 10 and the imager, said wall forming a housing 12.1 configured to direct light towards the imager 8. To this end, the wall of the housing 12.1 can have a diffuse white light surface.

[0033] The support 12 also includes means 12.2 for positioning and attaching the mounting plate 10.1 of the backlighting device 10. These means may comprise tabs 12.2 extending in continuation of the wall of the housing 12.1 and passing through appropriately shaped openings formed in the mounting plate 10.1 of the backlighting device. A shoulder may be provided at the base of each tab to form an abutment surface for the mounting plate 10.1. These tabs may have, in particular, a clamping surface for snapping onto the edge of the opening in the mounting plate 10.1.

[0034] The support 12 also comprises receiving areas 12.3 and 12.4 for receiving the peripheral edge 8.3 of the imager 8. In this case, these receiving areas 12.3 and 12.4 form a shoulder 12.3 capable of receiving the rear surface 8.2 of the imager, wherein said rear surface is adjacent to the peripheral edge 8.3. One or more retaining members 12.4 are attached to the shoulder 12.3 so as to extend along the peripheral edge 8.3 facing the front surface 8.1 of the imager. Figure 1As can be seen, strips 14 and 16 of elastic material are positioned along the imager's rear and front surfaces, 8.2 and 8.1, respectively, between those surfaces and the corresponding surfaces of the shoulder 12.3 and one or more retaining members 12.4. These strips 14 and 16 of elastic material function to attenuate any vibrations that may be transmitted to the imager 8 from the environment. This is because the imager is essentially composed of two stacked glass plates, which form the front and rear surfaces 8.1 and 8.2. Clamping the imager too tightly at its peripheral edges could damage at least one of the glass plates. It is also undesirable to have play when mounting the imager, as this can easily generate associated noise and potentially damage at least one of the glass plates. The presence of the strips 14 and 16 of elastic material allows these difficulties to be overcome. As described in detail below in conjunction with the accompanying drawings, the elastic material of at least one of the strips 14 and 16 is also electrically heated and connected to a power source, thereby heating the imager 8 in cold conditions, which would otherwise tend to increase its response time. In this particular case, only the strip 16 of elastic material is electrically heated and connected to the power supply, while the other strip 14 of elastic material is not electrically heated. It must be understood that various variations are possible; in particular, strips of elastic heating material may be provided on both surfaces 8.1 and 8.2 of the imager 8, or only on the rear surface 8.2. It is also possible to provide one or more strips of elastic electrically heating material on at least one of the two surfaces 8.1 and 8.2, and only on one or more portions of the circumferential edge, with the remainder of the edge being provided with one or more strips of conventional elastic material, or without any strips of elastic material.

[0035] The elastic material is advantageously a foam-type porous material, in particular a polyurethane foam. Alternatively, the elastic material can be made of a solid material. Advantageously, the elastic material is a polymeric material. Advantageously, the elastic material exhibits a low hardness of less than 80 Shore A, and more advantageously exhibits a low hardness of less than 60 Shore A. The strips 14 and 16 of elastic material can have a thickness greater than 0.1 mm and / or less than 3 mm, preferably greater than 0.2 mm and / or less than 2 mm, more preferably greater than 0.3 mm and / or less than 1 mm. The strips 14 and 16 of elastic material can have a width greater than 2 mm and / or less than 5 mm.

[0036] The elastic electrically heating material also includes electrical conductors so as to form a resistive element along the strip of said material. These electrical conductors may be metal wires, for example made of copper, embedded in the matrix formed by the elastic material, and / or conductive particles dispersed throughout the matrix. Thus, the elastic electrically heating material exhibits a resistance between 0.004 Ωm and 0.024 Ωm (corresponding to the resistance of a section of material of one meter in length and one square meter in cross-section, and expressed in ohm-meters). For a section of material having a length of 4 mm 2 A cross section of 100 mm and a strip length of 50 mm gives a resistance between 50 Ω and 300 Ω. According to the relationship P = RI 2 The resistance of the relevant strip determines the amount of heat generated by the Joule heating effect, where P is the electrothermal power, R is the resistance of the strip of elastic electrically heating material, and I is the current passing through the strip. I is obtained from Ohm's law, that is, I=V / R, where V is the voltage applied to the strip of elastic electrically heating material.

[0037] Figure 2 yes Figure 1 6. One or more retaining members 12.4 of the support 12 can be seen, said retaining members extending along the circumferential edge 8.3 of the imager 8. It can also be seen that a power supply unit 18 for supplying power to the strip 16 of elastic electrically heating material is electrically connected to said strip. In this particular case, the strip 16 of elastic electrically heating material extends along almost the entire circumferential edge 8.3 of the imager (except Figure 2 ) so as to form a single resistive heating element along all four sides of the imager 8. In keeping with the foregoing, it should be understood that it is conceivable to provide multiple strips 16 of resilient electrically heated material, and to do so on the same surface of the imager. In this case, multiple electrical connections to the power supply unit 18 would then be required.

[0038] Figure 3 and Figure 4 yes Figure 2 The views in sections III-III and IV-IV show examples of electrical connections of the strip 16 of elastic electrical heating material.

[0039] exist Figure 3In the drawing, it can be seen that the holder 12.4 made of electrically insulating plastic material comprises an electrode 12.4.1 overmoulded with the plastic material. This electrode forms an outer surface of the holder 12.4 which faces the strip 16 of elastic electrically heating material and which extends a certain distance laterally from the imager so as to form, for example, an electrical contact terminal or plug. In other words, when the holder is assembled towards the imager by a movement substantially perpendicular to the plane of the imager, the contact area of ​​the electrode 12.4.1 facing the strip 16 of elastic electrically heating material will approach said strip until said contact area comes into contact with the strip. If this has the electrical conductivity by being distributed over the entire mass, the simple fact of being in contact with it, in this case via its main face opposite to the imager, will ensure electrical contact. If, on the other hand, the strip 16 of elastic electrically conductive material comprises an electrical conductor 16.1 embedded in a mass of electrically insulating elastic material 16.2, as Figure 3 As shown, the length of the conductor protruding from the end of the electrically insulating elastic material 16.2 needs to be set so that the conductor can be bent 180° against the surface of the elastic conductive material strip 16 opposite to the imager.

[0040] Figure 4 This situation is shown, in which case one can see the electrical conductor 16.1, i.e. the metal wire, which is bent 180° towards the top so as to extend along the surface of the strip 16 of elastic electrically heating material facing the retaining element 12.4 and, more specifically, along the contact area of ​​the electrode 12.4.1 of said element.

[0041] Just combined Figure 3 and Figure 4 The description also applies to Figure 2 The other of the two electrical connections in the Figure 3 and Figure 4 The same applies to the shoulder 12 . 3 , in which case the material of the elastic material strip 14 is also electrically heated.

[0042] Furthermore, it must be understood that other electrical connection techniques are contemplated.

[0043] The one or more strips 16 of resilient electrical heating material and the power supply unit are advantageously dimensioned to be able to raise the average temperature of the imager by at least 10° C. within 60 seconds.

[0044] The power supply unit 18 can be configured to supply power to one or more strips of elastic electrically heated material that regulate the current depending on the imager's temperature. In that case, the power supply unit can be powered and / or controlled in a binary (on / off) manner depending on the ambient temperature. For example, the power supply unit 18 can be powered or controlled to operate as soon as the ambient temperature drops below -10°C. It is also conceivable to provide the power supply 18 with a regulating function. In this case, a thermistor-type temperature sensor can be placed in contact with the imager 8 and independently connected to the power supply unit 18. This sensor can then modulate the supply voltage, and thus the current, depending on the actual temperature of the imager 8. Generally, regardless of the sophistication and complexity of the power supply 18, it is advantageously powered or at least controlled to operate only when the module is activated, i.e., when the backlighting device and the imager are powered.

Claims

1. A light module (6), in particular for use in a motor vehicle, comprising: an imager (8) having a front surface (8.1), a rear surface (8.2) and a peripheral edge (8.3); a backlighting device (10) for backlighting the imager (8) and positioned facing the rear surface (8.2) of the imager; a support (12) having a receiving area (12.3, 12.4) for receiving the imager (8) and an attachment area (12.2) for attaching the backlighting device (10); Characterized in that, the optical module further includes: At least one strip (16) of elastic electrically heating material, said at least one strip being in contact with the peripheral edge (8.3) of the imager (8) and the imager receiving area (12.3, 12.4) of the support (12).

2. The optical module (6) according to claim 1, characterized in that The elastic electric heating material has a hardness lower than 80 Shore A.

3. The optical module (6) according to claim 1, characterized in that The at least one strip (16) of elastic electrically heating material has an average thickness greater than 0.1 mm and / or less than 3 mm.

4. The optical module (6) according to claim 1, characterized in that The elastic electric heating material is porous.

5. The optical module (6) according to one of claims 1 and 2, characterized in that The at least one strip (16) of the elastic electrical heating material comprises metal wires (16.1) and / or electrically conductive particles.

6. The light module (6) according to one of claims 1 and 2, characterized in that Contact between the at least one strip (16) of the elastic electrically heating material and the circumferential edge (8.3) of the imager (8) is located on at least one of the front surface (8.1) and the rear surface (8.2) of the imager, and on each of the front and rear surfaces.

7. The light module (6) according to one of claims 1 and 2, characterized in that The at least one strip (16) of resilient electrically heated material is configured to maintain the imager (8) at an average temperature greater than or equal to -10°C when the module is subjected to ambient conditions having temperatures ranging from -10°C down to -40°C.

8. The light module (6) according to one of claims 1 and 2, characterized in that The at least one strip (16) of resilient electrically heated material is configured to increase the average temperature of the imager (8) by at least 10°C within one minute when the module is subjected to ambient conditions having a temperature ranging from -10°C down to -40°C.

9. The light module (6) according to one of claims 1 and 2, characterized in that The module further comprises a power supply unit (18) for powering the at least one strip (16) of elastic electrically heating material, the unit being configured to maintain an average temperature of the imager above -10°C when the module is subjected to ambient conditions having a temperature ranging from -10°C down to -40°C.

10. A method for controlling the temperature of an imager (8) of an optical module (6), characterized in that The light module (6) is a light module according to one of claims 1 to 9, and the at least one strip (16) of elastic electrically heating material is powered at an ambient temperature below -10°C so as to heat the imager.

Images