Device for protecting an optical sensor of a vehicle

Abstract

The invention relates to a device (3) for protecting an optical sensor (2) of a vehicle, such as a camera, the protective device (3) comprising a protective casing (4) which is configured to receive the optical sensor (2), the protective casing (4) being mounted so as to be movable about an axis of rotation (I-I) and comprising an optical window (10) which is configured to be arranged in the field of view of the optical sensor (2), and an electric motor (6) coupled to the protective casing (4) in order to rotate it. The protective device (3) further includes an element to reinforce the heat transfer which is configured to improve the heat transfer of the protective casing (4).

Description

Device for protecting an optical sensor of a vehicle Technical field of the invention

[0001] The present invention relates to the field of driving assistance and in particular to driving assistance systems, comprising at least one optical sensor, which can be installed on certain vehicles. More particularly, the invention relates to a device for protecting an optical sensor of a vehicle, such as a camera, and an associated optical device configured to be mounted in a motor vehicle, in particular in an orifice of a vehicle body. Technical background

[0002] Driver assistance systems include, for example, parking assistance systems and lane departure detection systems that use optical sensors installed outside vehicles.

[0003] The optical sensor is highly exposed to projections of mineral or organic dirt that can deposit on its surface. Optical sensors must therefore be protected and cleaned to ensure their proper functioning, and this need is even greater in the case of an autonomous vehicle, in which the vehicle is controlled by means of the information collected by these sensors.

[0004] One solution provides that the optical sensor, and for example a driver assistance system camera, is housed in a rotating protective housing protecting it from the external environment. The protective housing is closed by a transparent optical window arranged opposite the lens of the optical sensor to allow shooting. The protective housing and the optical window are rotated by a motor at a speed sufficient to remove any dirt or water that may be present on the optical window by centrifugal effect.

[0005] However, it may be necessary to provide a system for defrosting the device because water present in the protective device, for example in the form of moisture, may freeze on the components of the device or in the radial operating clearance between the rotating protective housing and the body part, so that the protective housing may be frozen in position.

[0006] It is thus known to provide electric heating elements external to the housing, for example fixed to the grille, close to the housing because it is not possible to place a heating element directly on the housing, and in particular on the optical window, since the housing is rotatable. The heating elements can be powered on demand and in particular in very cold conditions, to ensure that the potentially frosted rotating parts are free to rotate without blocking. However, such an arrangement is bulky and the integration of the system can prove complicated, whether at the level of the packaging of the protection device or the fixing of the heating elements on the grille.

[0007] It is also possible to place a heating element directly at the optical sensor inside the housing. However, this arrangement is limited to the use of the optical sensor of a given vehicle and is not universal.

[0008] We also know a method consisting of heating the engine without rotating it in order to raise the temperature of the casing to break the ice present either within the engine or in the gap between the rotating casing and the grille. A sequence makes it possible to test whether the engine is blocked by the presence of ice and facilitates the breaking of the layer via small rotational jolts. This method effectively makes it possible to raise the temperature of the external surfaces of the casing allowing the system to rotate correctly.

[0009] However, the presence of frost or ice may remain on the optical window, the heating of the motor propagates only very slowly towards the optical window due to the little air circulation and the numerous components interposed between the motor and the optical window. In addition, if the housing is not blocked in rotation due, for example, to little or no icing but the optical window is frosted or iced up preventing good visibility, this presence of ice or frost is not detected. It is however possible to completely defrost the housing by this method, including the optical window, but after a relatively long waiting time.

[0010] The present invention proposes to remedy at least partially the above drawbacks, in particular by making it possible to defrost the surface of the optical window of the protection device.

[0011] To this end, the invention relates to a device for protecting an optical sensor of a vehicle, such as a camera, the protection device comprising: - a protective housing configured to receive the optical sensor, the protective housing being mounted to move about an axis of rotation and comprising an optical window configured to be arranged in the field of vision of the optical sensor, and - an electric motor coupled to the protective housing to drive it in rotation, characterized in that the protection device further comprises a heat transfer reinforcement element configured to improve the heat conduction of the protective housing.

[0012] Thus, during operation, any dirt or water drops are deposited on the optical window rather than on the lens of the optical sensor. The cleaning of the optical window is ensured by centrifugal effect due to the rotation of the protective housing. The heat transfer reinforcement element improves the heat transfer in the protective housing by thermal conduction and therefore the heat transfer from the motor to the optical window, which makes it possible to obtain defrosting of the optical window and the environment of the optical sensor in the event of frost or ice, which is effective, rapid and which helps to avoid diagnostic errors.

[0013] The protective device may further include one or more of the features described below, taken alone or in combination.

[0014] According to an exemplary embodiment, the protective housing comprises a shell closed by the optical window and has a tubular end opposite the optical window, the tubular end being secured to a rotor of the motor to be driven in rotation.

[0015] The heat transfer reinforcement element may be formed by making the shell of the protective housing of a heat-conducting material, such as aluminum or an aluminum-based alloy or a filled plastic and / or by coating the shell with a heat-conducting material.

[0016] For example, the thermally conductive material has a thermal conductivity greater than 150 W / m·K.

[0017] The outer surfaces of the shell made of thermally conductive material can additionally be coated with a thermally insulating material.

[0018] The heat transfer reinforcement element can be formed by a thermally conductive glue interposed between the optical window and the shell.

[0019] The heat transfer reinforcement element may be formed by at least one thermally conductive bridge connecting the shell and the optical window.

[0020] The heat transfer reinforcement element may be formed by a transparent thermally conductive optical coating of all or part of the internal and / or external surface of the optical window or by making the optical window of transparent thermally conductive material.

[0021] The protection device may comprise a control unit configured to generate an alternation of rotation of the protection box making it possible to create heating of the motor for a heating duration greater than the duration allowing the rotation of the protection box to be released.

[0022] The protection device may include an optical monitoring unit configured to perform an optical monitoring via the optical sensor to determine the presence or absence of ice or frost on the optical window.

[0023] The invention also relates to an optical device configured to be mounted in a motor vehicle, in particular in an orifice of a vehicle body, the optical device comprising an optical sensor characterized in that it further comprises a protection device as described previously, the optical sensor being received in the protection housing of the protection device. Brief description of the figures

[0024] Other advantages and characteristics will appear on reading the following description of a particular embodiment of the invention, but in no way limiting, as well as the attached drawing in which:

[0025] This is a cross-sectional view of an optical device. Detailed description

[0026] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments without departing from the scope of the invention, as defined by the claims.

[0027] The invention concerns an optical device 1 configured to be mounted in a motor vehicle, in particular in an orifice of a vehicle body, such as the grille or such as an orifice provided at the rear of the vehicle or on its sides, for example for a vehicle driving assistance system.

[0028] The optical device 1 comprises an optical sensor 2 and a protection device 3 for the optical sensor 2.

[0029] The optical sensor 2 is for example a camera. The camera makes it possible to acquire images of the road scene, which can then be transmitted for example to an electronic card of the vehicle ensuring the management and processing of the images via a rigid power and communication cable 9 called a video cable.

[0030] The protection device 3 comprises, on the one hand, a rotating protection housing 4 in which the optical sensor 2 is received and, on the other hand, a motorization housing 5 and an electric motor 6 received in the motorization housing 5, the rotor 14 of the motor 6 being coupled to the protection housing 4 to drive it in rotation as will be described later in more detail.

[0031] The rigid power and communication cable 9 of the optical sensor 2 passes through a central support rod 8 of the motorization box 5 fixed to the optical sensor 2. The motorization box 5 also receives an electronic card 7 and connectors allowing the power supply and control of the motor 6.

[0032] The protective housing 4 comprises a transparent optical window 10 and a shell 11 closed by the optical window 10 at one end capable of emerging from the bodywork of the vehicle once the optical device 1 is mounted in the latter.

[0033] The optical window 10 is arranged opposite the lens of the optical sensor 2, in the field of vision of the optical sensor 2, to allow images to be taken through the optical window 10. The optical window 10 may be flat or curved, such as being inscribed in a sphere. It is for example made of glass.

[0034] The protective housing 4, i.e. the shell 11 and the optical window 10, is mounted to move about an axis of rotation II. The axis of symmetry of the optical window 10 can be confused with the axis of rotation II.

[0035] The shell 11 is made here in two parts 11a, 11b, front and rear, the front part 11a being on the side of the optical window 10. The two parts 11a, 11b can be assembled and fixed together, for example by screwing, after the insertion of the optical sensor 2 in the rear part 11b. The optical window 10 is for example fixed, for example by gluing, in a circular groove of the front part 11a of the shell 11.

[0036] The shell 11, here the rear part 11b, has a tubular end 12 opposite the optical window 10. The tubular end 12 is crossed by the central support rod 8, itself crossed by the rigid cable 9 of the optical sensor 2. This tubular end 12 of the shell 11 is secured to the rotor 14 of the motor 6 to be driven in rotation by the latter.

[0037] The protection device 3 may further comprise one or more bearings 13, here two, interposed between the tubular end 12 of the shell 11 and the central support rod 8 housing the rigid cable 9 of the optical sensor 2 to allow the protection housing 4 to rotate around the central support rod 8, fixed relative to the protection housing 4.

[0038] Thus, during operation, any dirt or water drops are deposited on the optical window 10 rather than on the lens of the optical sensor 2. The cleaning of the optical window 10 is ensured by centrifugal effect due to the rotation of the protective housing 4.

[0039] The protective device 3 further comprises a heat transfer reinforcement element configured to improve the heat conduction of the protective housing 4. The heat transfer reinforcement element makes it possible to improve the heat transfer in the protective housing 4 by thermal conduction and therefore the heat transfer from the motor 6 to the optical window 10, which makes it possible to obtain defrosting of the optical window 10 and of the environment of the optical sensor 2 in the event of frost or ice, which is effective, rapid and which makes it possible to avoid diagnostic errors.

[0040] The heat transfer reinforcement element may include one or more of the embodiments detailed below.

[0041] The heat transfer reinforcement element can be formed by making the shell 11 of the protective housing 4, here the front and rear parts 11a, 11b, from a heat-conducting material or by coating the shell 11 of the protective housing 4 with a heat-conducting material. The material can be considered to be heat-conducting if its thermal conductivity is greater than 150 W / m·K.

[0042] The thermally conductive material can be aluminum, which has both excellent thermal conductivity and good mechanical properties. It can be pure aluminum (99.99% purity): approximately 237 W / m K, or an aluminum-based alloy, which may have a lower or equivalent conductivity. The thermally conductive coating material can more generally be metallic, such as copper or aluminum.

[0043] The thermally conductive material can also be a filled plastic, such as a polymer composite, which can exhibit enhanced thermal conductivity through the addition of conductive fillers, such as aluminum nanoparticles or graphene. Graphene is a two-dimensional material composed of a single layer of carbon atoms arranged in a hexagonal lattice. Graphene has a very high thermal conductivity, approximately 3000 to 5000 W / m K, making it much more conductive than most traditional materials. When added to polymers, graphene can form a three-dimensional conductive network, facilitating the conduction of heat through the composite material. This allows graphene-filled plastics to have higher thermal conductivity, approaching that of aluminum.

[0044] In another example, the coating material is made of a thin layer of hexagonal boron nitride (hBN). Hexagonal boron nitride has high thermal conductivity and can be deposited in the form of thin layers.

[0045] The shell 11 thus produced or coated makes it possible to improve the heat transfer from the motor 6 to the optical window 10 of the protective housing 4.

[0046] It may also be provided that the outer surfaces of the shell 11 made of thermally conductive material, here of the first and second parts 11a, 11b, are coated with a thermally insulating material. The thermally insulating material may be a polyurethane foam. According to another example, the coating comprises thin layers of reflective or low thermal conductivity materials such as aluminum or ceramic. The layers reflect or absorb radiant heat rather than transferring it. This type of coating may have a small thickness, such as between one and twenty microns. This reduces heat losses to the bodywork opposite or in contact with the outer surfaces of the shell 11 of the protective housing 4.

[0047] The heat transfer reinforcement element may be formed by a heat-conducting adhesive 16 interposed between the optical window 10 and the shell 11, the adhesive 16 making it possible to fix the optical window 10 here in the groove of the front part 11a of the shell 11. The heat-conducting adhesive 16 is for example a synthetic epoxy resin containing metallic and inorganic fillers having for example a thermal conductivity of approximately 1.5 W / m K. The heat-conducting adhesive 16 makes it possible to form a thermal bridge between the optical window 10 and the shell 11 to promote the transfer of heat from the shell 11 to the optical window 10.

[0048] The heat transfer reinforcement element may be formed by at least one heat-conducting bridge 17 connecting the shell 11, here the front part 11a, and the optical window 10. The heat-conducting bridge 17 may be produced by a connecting tab, the heat transfer reinforcement element comprising one or more tabs, or it may be produced by an annular element arranged on the periphery of the optical window 10.

[0049] The thermally conductive bridge 17 may be made of a silicone-based material, having a thermal conductivity of between 0.5 and 5 Watts per meter-kelvin (W / m·K) or may be made of silver oxide or hexagonal boron nitride (hBN), having a higher thermal conductivity, up to approximately 10 W / m·K.

[0050] As an alternative or in addition to the thermally conductive glue 16, the thermally conductive bridge 17 makes it possible to form a thermal bridge between the optical window 10 and the shell 11 to promote the transfer of heat from the shell 11 to the optical window 10.

[0051] The heat transfer reinforcement element may be formed by a transparent thermally conductive optical coating of all or part of the internal and / or external surface of the optical window 10.

[0052] The coating is for example made of indium tin oxide (ITO) which has the advantage of being transparent and thermally conductive. It has for example a thickness of less than 1 µm. The thermal conductivity of indium tin oxide generally varies in a range of 1 to 20 watts per meter-kelvin (W / m K) and is higher than that of glass, generally located in the range of 0.8 to 1.5 W / m K. This improves the conductivity of the optical window 10 made of poorly thermally conductive glass and allows heat transfer to the center of the optical window 10.

[0053] The transparent thermally conductive optical coating of all or part of the internal and / or external surface of the optical window 10 may be produced by a metallic film such as silver or copper deposited in the form of thin layers. These metallic films are generally transparent.

[0054] The coating can be achieved by a nanomaterial-based film. Nanomaterials, such as copper, zinc oxide, or carbon nanoparticles, can be incorporated into transparent polymers to form thin thermal films. These nanomaterials offer higher thermal conductivity than polymers alone, improving heat transfer through the film.

[0055] The coating can be achieved by a composite film. Composite films can be created by incorporating thermally conductive nanoparticles, such as hexagonal boron nitride (hBN) or graphene, into transparent polymers. These composite films exhibit increased thermal conductivity while maintaining the optical transparency of glass.

[0056] The heat transfer reinforcement element may be formed by making the optical window 10 of a transparent heat-conducting material, such as optical glass loaded with conductive nanoparticles of metallic types.

[0057] The protection device 3 may further comprise a control unit, comprising one or more controllers or microcontrollers or processors and a memory, configured on the one hand to control the rotation of the motor 6 and therefore of the protection housing 4 and on the other hand to generate an alternation of rotation of the protection housing 4 making it possible to create a heating of the motor 6, without however making the motor 6 rotate, for a heating duration greater than the duration allowing the unlocking of the rotation of the protection housing 4. The control unit may be mounted on the electronic card 7 received in the motorization housing 5.

[0058] To rotate the rotor 14 of the motor 6, the control module is configured to successively supply the different phases of the motor 6 according to a main supply sequence, in a given order and at a given frequency, for example by controlling relays interposed between each phase and a power supply. This main control instruction makes it possible to create a rotating magnetic field allowing the rotation of the rotor 14.

[0059] To defrost the protective housing 4, for example because the external temperature of the vehicle is negative or when a rotational blockage of the rotor 14 is observed, or at the request of the driver, the control unit generates a secondary power supply sequence, for example by generating an alternating power supply at high frequency, such as greater than or equal to 1 kHz, between two phases of the winding. The alternating power supply of the phases thus generates an alternation of two magnetic fields of opposite directions, which tends to maintain the permanent magnets associated with the rotor 14 in a fixed position, the inertia of the rotor 14 preventing the assembly from rotating before the magnetic field is reversed.The passage of electric currents between the phases at high frequency, and the switching of the switches thus generates a release of heat from the electrical or electronic components concerned, without the rotor 14 being driven into rotation and risking deterioration due to blockage by the layer of frost.

[0060] The rotation alternation makes it possible to test whether the protection device 4 is rotating or blocked and maintaining this secondary control instruction for a sufficient period of time makes it easier to break the glass between the vehicle body and the protection device 4 if necessary.

[0061] Here, the heating time is expected to be longer than the time allowing the protective device 4 to be unlocked after the ice breaks. This heats the motor 6 and therefore the protective housing 4, which allows the optical window 10 to be heated, the heat transfer between the motor 6 and the optical window 10 being promoted by the heat transfer reinforcement element. The alternating rotation during the additional time simultaneously promotes the ejection of ice or frost which begins to soften on the surface of the optical window 10 by centrifugal effect (either in the form of a block or in the form of a drop of melted frost water).

[0062] In another example of the secondary power supply sequence, the control unit generates a reduced frequency power supply to the winding relative to the power supply frequency range generated by the primary control instruction.

[0063] The protection device 3 may further comprise an optical control unit comprising one or more controllers or microcontrollers or processors and a memory, configured to carry out an optical control via the optical sensor 2 to determine the presence or absence of ice or frost on the optical window 10 in order to start and / or stop the alternating rotation of the protection housing 4.

[0064] The optical control unit is for example the same unit as the control unit allowing the control of the motor 6. Once the optical control unit has noted the absence of ice or frost on the optical window 10, the control unit can stop the alternating rotation of the protective housing 4 and control the rotation of the protective housing 4 in a single direction in order to eject any particles, dust or water drops possibly deposited on the optical window 10 by centrifugal effect.

[0065] According to another embodiment, the optical control unit and the control unit are separate from each other and communicate with a central processing unit of the vehicle. The images taken by the optical sensor 2 are sent by the optical control unit to the central processing unit which can accordingly control the engine 6 via the control unit, to heat the protective housing 4 in the event of the presence of frost ice being detected or to control the rotation of the protective housing 4 in a single direction in order to eject the impurities when there is neither frost nor ice.

Claims

Protective device (3) for an optical sensor (2) of a vehicle, such as a camera, the protective device (3) comprising:- a protective housing (4) configured to receive the optical sensor (2), the protective housing (4) being mounted to move about an axis of rotation (II) and comprising an optical window (10) configured to be arranged in the field of vision of the optical sensor (2), and- an electric motor (6) coupled to the protective housing (4) to drive it in rotationcharacterized in that the protective device (3) further comprises a heat transfer reinforcement element configured to improve the heat conduction of the protective housing (4). Protective device (3) according to claim 1, characterized in that the protective housing (4) comprises a shell (11) closed by the optical window (10) and having a tubular end (12) opposite the optical window (10), the tubular end (12) being secured to a rotor (14) of the motor (6) to be driven in rotation. Protective device (3) according to claim 2, characterized in that the heat transfer reinforcement element is formed by making the shell (11) of the protective housing (4) from a heat-conducting material, such as aluminum or an aluminum-based alloy or loaded plastic and / or by coating the shell (11) with a heat-conducting material. Protective device (3) according to claim 3, characterized in that the thermally conductive material has a thermal conductivity greater than 150 W / m·K. Protective device (3) according to one of claims 3 or 4, characterized in that the outer surfaces of the shell (11) made of thermally conductive material are coated with a thermally insulating material. Protective device (3) according to one of claims 2 to 5, characterized in that the heat transfer reinforcement element is formed by a heat-conducting glue (16) interposed between the optical window (10) and the shell (11). Protective device (3) according to one of claims 2 to 6, characterized in that the heat transfer reinforcement element is formed by at least one thermally conductive bridge (17) connecting the shell (11) and the optical window (10). Protective device (3) according to one of the preceding claims, characterized in that the heat transfer reinforcement element is formed by a transparent thermally conductive optical coating of all or part of the internal and / or external surface of the optical window (10) or by making the optical window (10) of transparent thermally conductive material. Protective device (3) according to one of the preceding claims, characterized in that it comprises a control unit configured to generate an alternation of rotation of the protective housing (4) making it possible to create heating of the motor (6) for a heating duration greater than the duration allowing the rotation of the protective housing (4) to be released. Protective device (3) according to one of the preceding claims, characterized in that it comprises an optical control unit configured to carry out an optical control via the optical sensor (2) to determine the presence or absence of ice or frost on the optical window (10). Optical device (1) configured to be mounted in a motor vehicle, in particular in an orifice of a vehicle body, the optical device (1) comprising an optical sensor (2) characterized in that it further comprises a protection device (3) according to one of the preceding claims, the optical sensor (2) being received in the protection housing (4) of the protection device (3).

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