FR3135429A1 - Part for a vehicle intended to be placed opposite an emission cone of a radar sensor of the vehicle and comprising a defrosting system provided with several heat conduction elements - Google Patents

Abstract

The invention relates to a part (2) for a vehicle intended to be arranged opposite an emission cone of a radar sensor (4), the radar sensor (4) being configured to emit an electromagnetic wave (6), said part (2) comprising at least one electronic component capable of emitting heat when an electric current passes through it, said part (2) having on one of its faces (10) a system (12) for defrosting the part (2). According to the invention, the defrosting system (12) comprises a set (13) of heat conduction elements (14), each heat conduction element (14) being made of a thermally conductive material and being in contact with said at least one heat-emitting electronic component, to bring heat from the heat-emitting electronic component to said face (10) of the part (2) by thermal conduction. FIG. 1 [Fig 1] [Fig 2]

Description

Part for a vehicle intended to be placed opposite an emission cone of a radar sensor of the vehicle and comprising a defrosting system provided with several heat conduction elements

The present invention belongs to the field of the integration of radar sensors within motor vehicles, and in particular to the field of defrosting systems for motor vehicles making it possible to maintain reliability of detection by such radar sensors. The invention relates in particular to a part for a vehicle intended to be placed opposite an emission cone of a radar sensor of the vehicle, and comprising such a defrosting system.

State of the art

Autonomous or partially autonomous driving vehicles need a large amount of sensors that are responsible for receiving redundant data from the vehicle's surroundings, to avoid collisions and ensure that the vehicle arrives at its destination safely. These sensors, many of which are radar sensors, are placed in predetermined locations on the vehicle so that the data covers as much information as possible. The vehicle's lighting devices (headlight, taillight, etc.) are generally advantageous locations for such radar sensors, although other locations on the vehicle are also possible.

The electromagnetic wave emitted by such radar sensors is generally linearly polarized. By convention, the polarization of the electromagnetic wave describes the vibration of the electric field. When the wave is linearly polarized, this electric field oscillates in only one direction, this is the main polarization direction, classically a horizontal or vertical polarization direction.

A problem linked to the integration of such a radar sensor in a motor vehicle lies in the need for the sensor to be able to detect external objects whatever the weather conditions in which the vehicle is operating. However, for temperatures below the 0°C threshold, a layer of frost is likely to form on the transmission/reception location(s) of the radar sensor on the vehicle. Such a layer of frost then reflects and absorbs a very large part of the radar waves emitted, due to the very high refractive index of water. The range of the radar may then be significantly reduced, and the detection functionality of the radar sensor may no longer be operational within the vehicle.

In order to respond to this problem it is known to use, at the reception location of the radar sensor on the vehicle, a defrosting system making it possible to maintain the detection functionalities of the sensor.

The published patent document WO 2020/239380 A1 discloses for example such a defrosting system for a vehicle component subject to the problem of icing (such as a radar sensor for example). The defrosting system is located outside the emission cone of the radar sensor, on the edges of the sensor reception housing. The heat for defrosting is transmitted into the system through the use of an electrically conductive elastomeric material. Electricity applied to the elastomeric material produces the heat necessary for defrosting.

However, such a defrosting system cannot be placed inside the emission cone of the radar sensor without altering the electromagnetic wave emitted by the sensor. As a result, the space available for the defrosting system on the radar sensor reception housing on the vehicle is relatively limited, because it is limited to the edges of the housing. This imposes a sizing constraint on the defrost system, which substantially limits the defrost speed. In addition, this defrosting speed is dependent on the electrical conductivity of the elastomeric material used. Finally, such a defrosting system has the disadvantage of resulting in high energy consumption to allow defrosting by heat emission.

The present invention improves the situation.

An objective of the invention is to propose a part for a vehicle intended to be placed opposite an emission cone of a radar sensor of the vehicle, and comprising a defrosting system having an increased defrosting speed and energy consumption. scaled down.

To this end, a first aspect of the invention relates to a part for a vehicle intended to be placed opposite an emission cone of a radar sensor of the vehicle, the radar sensor being configured to emit an electromagnetic wave in the cone of the vehicle. emission, the electromagnetic wave propagating in a main propagation direction, said part comprising at least one electronic component capable of emitting heat when passed through by an electric current, said part having on one of its faces a defrosting system the room. The emission cone of the radar sensor corresponds to the angular zone in which the sensor transmits. This angular zone has a main direction which corresponds to the main propagation direction of the wave for which the amplitude of the wave is maximum.

According to the invention, the defrosting system comprises a set of heat conduction elements, each heat conduction element being made of a thermally conductive material and being in contact with said at least one heat-emitting electronic component, to bringing heat from the heat-emitting electronic component to said face of the part by thermal conduction. Each heat conduction element thus forms a sort of heat conduit.

Due to the fact that the face of the part carrying the heat conduction elements is arranged facing the emission cone of the vehicle's radar sensor, a relatively high number of heat conduction elements can be used for the defrosting system, thus increasing the defrosting speed. In addition, by varying the number and density of heat conduction elements, the defrosting speed is further increased compared to prior art systems. Furthermore, the particular configuration of the heat conduction elements (which are in contact with the heat-emitting electronic component) makes it possible to recover the heat emitted by this component to bring it towards the face of the part, without requiring any additional input. of specific external energy (such as an injection of electric current for heating, for example). This makes it possible to advantageously reduce the energy consumption of the defrosting system. Indeed, the heat emitted by the heat-emitting electronic component when an electric current passes through it is residual heat constituting a collateral side effect of the main function of this electronic component (in other words, an electric current is applied in in all cases to the electronic component so that it performs a main function other than that of emitting heat). Finally, such a “passive” heating defrosting system plays the role of a heat sink for the heat-emitting electronic component. Such a defrosting system benefits from the natural air convection movement acting on the front of the room, and facilitating heat dissipation. This makes it possible to reduce the size of a conventional heat sink, usually attached to the electronic component to allow the evacuation and dissipation of heat, or even to eliminate the need to use such a conventional heat sink.

According to a preferred embodiment of the invention, the electric field of the electromagnetic wave emitted by the radar sensor comprises a component oscillating in a direction of interest, in which the heat conduction elements are elongated elements, and in which at least one subset of said set of heat conduction elements is located in the emission cone of the radar sensor when the part is placed facing the radar sensor and is configured so that each heat conduction element of said subassembly is arranged on the part so as to extend in a direction substantially perpendicular to the direction of interest of the electric field of the electromagnetic wave emitted by the radar sensor when the part is placed facing the radar sensor. The direction of interest of the electric field of the electromagnetic wave corresponds to a preferred direction, perpendicular to the direction of main propagation of the wave. The electric field of the electromagnetic wave emitted by the radar sensor can be non-polarized, or linearly polarized (typically in a vertical or horizontal direction, or in any rectilinear direction other than the vertical or horizontal direction). When the radar sensor is linearly polarized according to a main polarization direction (for example horizontal or vertical), the direction of interest corresponds to this main polarization direction. In this case, the electric field of the wave only includes its component of interest. Due to the orientation of the elongated heat conduction elements located in the emission cone of the radar sensor, which are arranged on the part so as to extend in a direction substantially perpendicular to the direction of interest of the electric field of the electromagnetic wave emitted by the radar sensor, the defrosting system allows the component of interest of the electromagnetic wave to pass. This component of interest is almost not reflected by the slender heat conduction elements and is almost entirely transmitted to the other side of the defrosting system. The room defrosting system according to the invention can thus be placed inside the emission cone of the radar sensor without altering the electromagnetic wave emitted by the sensor and therefore without harming the effectiveness of the latter.

According to one embodiment of the invention, the heat conduction elements extend in the same plane, said plane extending perpendicular to the direction of main propagation of the electromagnetic wave emitted by the radar sensor.

According to one embodiment of the invention, the heat conduction elements extend parallel to each other in said plane, all of the heat conduction elements forming a grid wave polarizer.

According to a first embodiment of the invention, the heat conduction elements are arranged so that the distance separating two adjacent heat conduction elements is constant.

According to one embodiment of the invention, the distance separating two adjacent heat conduction elements is less than the wavelength of the electromagnetic wave emitted by the radar sensor.

According to one embodiment of the invention, the distance separating two adjacent heat conduction elements is less than 5 mm, preferably between 1 mm and 5 mm, more preferably between 2 mm and 4 mm.

According to one embodiment of the invention, the ratio between the width of each heat conduction element and the wavelength of the electromagnetic wave emitted by the radar sensor is less than 1/10.

According to one embodiment of the invention, the width of each heat conduction element is less than 0.5 mm, preferably substantially equal to 0.4 mm.

According to a second embodiment of the invention, a first sub-assembly of heat conduction elements is located in the emission cone of the radar sensor when the part is placed facing the radar sensor, and a second sub-assembly set of heat conduction elements is located outside the emission cone of the radar sensor when the part is placed facing the radar sensor, the heat conduction elements of the first and second subassemblies being arranged so that, considering a direction of travel going from the second sub-assembly towards the first sub-assembly perpendicular to the direction of main propagation of the electromagnetic wave emitted by the radar sensor, and from the outside of the emission cone of the sensor radar towards the center of said emission cone, the distance separating two heat conduction elements is non-constant and follows an increasing distance profile function. This second embodiment of the invention makes it possible to further increase the defrosting speed compared to the first embodiment of the invention in which the heat conduction elements extend parallel to each other forming a wave polarizer grid, and with a constant distance between two adjacent heat conduction elements. Indeed, in this second embodiment, the density of the heat conduction elements of the second subassembly is maximized outside the emission cone of the radar sensor, in order to maximize the electrical conductivity and therefore the defrosting speed. . Conversely, inside the emission cone of the radar sensor, the distance between two adjacent heat conduction elements of the first subassembly is greater than the distance between two adjacent heat conduction elements of the second subassembly. -together. This makes it possible to minimize the attenuation of the signal coming from the radar sensor, whatever the component of the electromagnetic wave considered. According to a first variant of this second embodiment, inside the emission cone of the radar sensor, the heat conduction elements of the first sub-assembly are arranged so that the closer we get transversely to the center of the cone, the more the distance between two adjacent heat conduction elements increases. According to another variant of this second embodiment, the distance separating two adjacent heat conduction elements of the first subassembly is constant.

According to one embodiment of the invention, said increasing distance profile function is a linear function, or a piecewise linear function, for example a step function.

According to one embodiment of the invention, the minimum distance separating two adjacent heat conduction elements of the first subset of heat conduction elements is greater than 2 mm, preferably greater than 3 mm.

According to one embodiment of the invention, the width of each heat conduction element of the first subset of heat conduction elements is less than 0.5 mm.

According to one embodiment of the invention, the defrosting system further comprises a plastic film on which the heat conduction elements are printed, in particular by screen printing, each heat conduction element forming a heat conductive track on said film plastic.

According to one embodiment of the invention, the thermally conductive material constituting each heat conduction element is copper, silver or even graphite.

According to a third embodiment of the invention, the defrosting system further comprises a set of elongated heating elements, at least one subset of said set of elongated heating elements being located in the emission cone of the radar sensor when the part is arranged facing the radar sensor and being configured so that each elongated heating element of said subassembly is arranged on the part so as to extend in a direction substantially perpendicular to the direction of interest of the electric field of the electromagnetic wave emitted by the radar sensor when the part is placed facing the radar sensor. This makes it possible to form a hybrid defrosting system, particularly suited to situations where the heat emitted by the heat-emitting electronic component is not sufficient to ensure complete and/or rapid defrosting of the room.

According to one embodiment of the invention, the elongated heating elements are heating wires or metal strips, or heating tracks printed on a support, in particular by screen printing. The wires, metal strips or heating tracks are for example powered by a common electrical power supply unit configured to circulate an electric current within each of the wires or metal strips. Heat used for defrosting (in addition to the heat emitted by the heat conduction elements) is then produced by the Joule effect in the heating wires, the heating metal strips or in the heating tracks. The electrical power supply unit is for example connected to the wires, metal strips or heating tracks via one or more electrical connection elements (such as for example electrical current distribution strips, electrical cables and /or an electrical supply cable). These electrical connection elements, which are generally made of a non-transparent electrically conductive material, are arranged in the room outside the emission cone of the radar sensor.

According to one embodiment of the invention, each heating wire or metal strip is coated with a layer of a dielectric material or is arranged in a dielectric protection and insulation element.

According to one embodiment of the invention, the dielectric material has a refractive index and a thickness which is between 0.8 times and 1.2 times an ideal thickness, the ideal thickness being equal to a natural number multiplied by the wavelength of the electromagnetic wave emitted by the radar sensor and divided by two times the refractive index of the dielectric material, for a zero angle of incidence of the electromagnetic wave (normal electromagnetic wave). This ideal thickness is such that the electromagnetic waves reflected by the heating wires or metal strips undergo destructive interference, thus minimizing or even eliminating any attenuation of the signal from the radar sensor. The transmission of the signal through the wires or metal strips is thus maximized, whatever the component of the electromagnetic wave considered. In some special cases, the thickness of the dielectric material is between 0.8 times and 1.2 times the wavelength divided by twice the refractive index. This thickness, which corresponds to the minimum possible for this embodiment of the invention, makes it possible to avoid other interferences.

According to one embodiment of the invention, at least one of the heat conduction elements is connected to at least one of the elongated heating elements via a thermal junction. This makes it possible to homogenize the distribution of heat on the face of the part, allowing better transmission of heat from the electronic component to the face of the part, and thus homogenization of the heat over the entire surface of the part. .

According to one embodiment of the invention, said at least one heat-emitting electronic component is chosen from the group consisting of: an electronic circuit, a printed circuit board on which at least one light source is mounted, and an electronic device controlling at least one light source. In particular, the vehicle part may be provided with an illumination function when the heat-emitting electronic component is for example a printed circuit board on which at least one light source of the light-emitting diode type is mounted.

According to one embodiment of the invention, the part further comprises a temperature sensor configured to measure the temperature of said face of the part. This prevents the defrosting system from running out of control if the control carried out by a vehicle temperature sensor (external to the room) is faulty (in the event of snow accumulation for example) and/or raises a temperature in the vehicle erroneous (too high or low) compared to the “real” temperature measured in the area where the radar sensor is installed. The presence of such a sensor thus allows precise regulation and control of the temperature on the face of the part carrying the defrosting system, and also protects this part against any possible overheating.

According to one embodiment of the invention, each of the heat conduction elements has a thermal conductivity greater than 50 W/(m·K), preferably between 50 W/(m·K) and 500 W/(m ·K).

According to one embodiment of the invention, the vehicle part is a stylish part intended to mask the radar sensor.

For example, the style piece can be a logo.

According to one embodiment of the invention, the vehicle part is a closing window of a lighting and/or signaling element in which the radar sensor is integrated.

Another object of the invention relates to an assembly comprising a vehicle radar sensor and a vehicle part according to the invention, in which the radar sensor is configured to emit an electromagnetic wave in an emission cone, the electromagnetic wave is propagating in a main propagation direction, the vehicle part being arranged facing the emission cone of the radar sensor.

According to one embodiment of the invention, the electric field of the electromagnetic wave emitted by the radar sensor comprises a component oscillating in a direction of interest.

According to one embodiment of the invention, the radar sensor is a millimeter radar sensor polarized in a horizontal or vertical polarization direction. The oscillation of the electric field of the electromagnetic wave then extends in the horizontal or vertical direction. The wavelength of the radar sensor is typically between 3.70 mm and 3.94 mm. This type of radar sensor is typically suited to autonomous driving applications, and such a wavelength is advantageously suited to detecting objects without excessive power consumption or response delay.

According to one embodiment of the invention, the radar sensor has an operating frequency of between 76 GHz and 81 GHz.

According to one embodiment of the invention, the assembly is a lighting and/or signaling element of a vehicle, in particular a vehicle headlight. For example, the vehicle part may be a closing window of said lighting and/or signaling element, said window constituting one face of said element. Such a lighting and/or signaling element can then house the radar sensor.

Here, the term “vehicle” means any type of vehicle such as a motor vehicle, a moped, a motorcycle, a storage robot in a warehouse, or any other vehicle capable of carrying at least one passenger or intended for the transport of people. or objects.

The term “electric cable” means one or more elongated electrically conductive element(s) surrounded by at least one electrically insulating layer, the electrically insulating layer being able to be directly in physical contact with the element(s). elongated electrically conductive(s).

The term “electrical power supply sheet” also means an electrical power supply element whose thickness is small in relation to its length and width. It can be curved and have a given curve. Thus the sheet has two extended faces separated by a periphery, this periphery defining a thickness of the sheet, which can be variable, for example decreasing from one end to the other.

“Track” also means a flat element whose thickness is small compared to its length and width.

Other characteristics and advantages of the invention will appear on examination of the detailed description below, and the appended drawings in which:

is a schematic representation, in perspective view, of an assembly comprising a radar sensor and a vehicle part according to a first embodiment of the invention;

is a schematic representation, in front view, of the vehicle part of the ;

is a schematic representation, in side view, of the vehicle part of the ;

is a schematic representation, in front view, of a vehicle part according to a second embodiment of the invention;

is a schematic representation of an electrical circuit equivalent to the configuration of the ;

is a schematic representation, in front view, of a vehicle part according to a third embodiment of the invention;

is a schematic representation, in front view, of a vehicle part according to a first variant of the third embodiment of the invention; And

is a schematic representation, in front view, of a vehicle part according to a second variant of the third embodiment of the invention.

In this document, unless otherwise indicated, the terms "upstream" and "downstream" refer to the direction of propagation of the electromagnetic beam in the object to which it refers and also to the direction of emission of the electromagnetic wave outside said object. .

Furthermore, everything called “rear” is on the upstream side while everything called “front” is on the downstream side.

The terms “horizontal”, “vertical” or “transverse”, “lower”, “upper”, “top”, “bottom”, “side” are defined in relation to the orientation of the part 2 according to the invention, intended to be mounted in the vehicle. In particular, in this application, the term “vertical” designates an orientation perpendicular to the horizon while the term “horizontal” designates an orientation parallel to the horizon.

In Figures 1 to 4, and 6 to 8, there is shown an orthogonal marker associated with part 2 for a vehicle. This reference is composed of three axes X, Y and Z being called, here, respectively longitudinal axis X, transverse axis Y and vertical axis Z.

detailed description

There is a schematic representation, in perspective view, of an assembly 1 comprising part 2 for a vehicle according to the invention, and of its operating principle. The assembly 1 further comprises a radar sensor 4. Only part of the part 2 is shown in the figures for reasons of clarity. Without this being limiting in the context of the present invention, the assembly 1 is for example a lighting and/or signaling element of a vehicle, in particular a vehicle headlight. In this case, part 2 is typically a closing glass of the lighting and/or signaling element 1. Glass 2 then constitutes one face of this element 1. Alternatively, part 2 can be a part of style intended to mask the radar sensor 4, such as for example a logo. In this case, assembly 1 may be a vehicle lighting and/or signaling element, or any other element of the vehicle.

The radar sensor 4 is configured to emit an electromagnetic wave 6 in an emission cone 7 (such an emission cone 7 is not shown on the but is visible in Figures 2, 4, and 6 to 8). The electric field of the electromagnetic wave 6 emitted by the radar sensor 4 includes a component E1 oscillating in a direction of interest P1. More precisely, this means that this component E1 of the electric field of the electromagnetic wave 6 extends, in projection in the plane S defined by the emission surface of the radar sensor 4, along the direction of interest P1. The direction of interest P1 of the electric field of the electromagnetic wave 6 corresponds to a preferred direction, perpendicular to the main propagation direction D1 of the wave 6, and according to which the component of interest E1 of the electric field of the wave 6 oscillates. When the radar sensor 4 is linearly polarized in a main polarization direction (for example horizontal or vertical), the direction of interest P1 corresponds to this main polarization direction. In the exemplary embodiment illustrated on the , the direction of interest of the wave 6 is the vertical direction, corresponding to the vertical axis Z. According to this embodiment, the electric field of the electromagnetic wave 6 emitted by the radar sensor 4 is non-polarized. As a variant not shown, the electric field of the electromagnetic wave emitted by the radar sensor can be polarized vertically or horizontally, or in any rectilinear direction other than the vertical or horizontal direction.

The electromagnetic wave 6 propagates along a main propagation direction D1. The emission cone 7 of the radar sensor 4 corresponds to the angular zone in which the sensor 4 transmits. This angular zone has a main direction which corresponds to the main propagation direction D1 of wave 6 for which the amplitude of the wave is maximum. Here, the main propagation direction D1 corresponds to the optical axis of the radar sensor 4. In the illustrated embodiment, the main propagation direction D1 is the longitudinal direction, corresponding to the longitudinal axis X in the figures.

The radar sensor 4 is typically a millimeter radar sensor, with frequency modulated continuous wave, whose operating frequency is typically between 76 GHz and 81 GHz. The radar sensor 4 is for example a long-range radar sensor (therefore with a low field of vision) or a medium-range radar sensor (therefore with a medium field of vision). The wavelength of the radar sensor 4 is typically between 3.70 mm and 3.94 mm. This type of radar sensor is typically suited to autonomous driving applications, and such a wavelength is advantageously suited to detecting objects without excessive power consumption or response delay.

As illustrated in Figures 1, 2, 4, and 6 to 8, part 2 is arranged opposite the emission cone 7 of the radar sensor 4, at the front of it. The part 2 has on one of its faces 10 a system 12 for defrosting the part 2. The part 2 further comprises at least one electronic component 11 capable of emitting heat when passed through by an electric current, such an electronic component 11 being visible in Figures 2 and 6 to 8.

The defrosting system 12 comprises a set 13 of heat conduction elements 14. Preferably, as illustrated in Figures 2 and 6 to 8, the defrosting system 12 also comprises a plastic film 15. Each heat conduction element 14 is made of a thermally conductive material, such as for example copper, silver or even graphite. Each heat conduction element 14 is in contact with the heat-emitting electronic component 11, to bring heat from the heat-emitting electronic component 11 to the face 10 of the part 2, by thermal conduction. Each heat conduction element 14 thus forms a sort of heat conduit, bringing heat (from the electronic component 11) to the face 10 of the part and dissipating the heat on this face 10 to allow defrosting of the latter. Preferably, as illustrated in Figures 1, 2, 4, and 6 to 8, the heat conduction elements 14 are elongated elements. More preferably, each of the heat conduction elements 14 has a thermal conductivity greater than 50 W/(m·K), preferably between 50 W/(m·K) and 500 W/(m·K). The heat conduction elements 14 are for example printed on the plastic film 15, in particular by screen printing (in the form of an ink deposit). Each heat conduction element 14 then forms a heat conductive track on the plastic film 15. A thermal interface (such as for example an adhesive or a thermal paste) can be added between the plastic film 15 and the heat emitting electronic component. 11 in order to guarantee good heat exchange. This makes it possible to reduce costs by simplifying assembly by reducing the number of operations.

All or part of the heat conduction elements 14 is located in the emission cone 7 of the radar sensor 4, as will be described in more detail later. When the heat conduction elements 14 are elongated elements, each heat conduction element 14 located in the emission cone 7 of the radar sensor 4 is arranged on the part 2 so as to extend in a direction substantially perpendicular to the direction of interest P1 of the electric field of the electromagnetic wave 6 emitted by the radar sensor 4. In the illustrated embodiment, this direction of extension of the elongated heat conduction elements 14 is the transverse direction, corresponding to the longitudinal axis Y in the figures. In this way, the component of interest E1 of the electromagnetic wave 6, which extends perpendicular to the direction of extension of the elongated heat conduction elements 14, is almost not reflected by these elements 14 and is almost fully transmitted to the other side of the defrosting system 12. In addition to its component of interest E1, the electric field of the electromagnetic wave 6 emitted by the radar sensor 4 of the comprises other components 9a, 9b, 9c which each extend respectively, in projection in the plane S defined by the emission surface of the radar sensor 4, along a respective direction other than the direction of interest P1 . As illustrated on the , these other components 9a, 9b, 9c of the electromagnetic wave 6 are reflected by the elongated heat conduction elements 14 and are not transmitted to the other side of the defrosting system 12. In a variant not shown, when the sensor radar is linearly polarized, the electric field of the electromagnetic wave 6 emitted by the radar sensor 4 is made up of the component E1.

As illustrated in Figures 1 to 4 and 6 to 8, the elongated heat conduction elements 14 extend in the same plane T. This plane T extends perpendicular to the main propagation direction D1 of the electromagnetic wave 6 emitted by the radar sensor 4. In other words, the plane T in which the elongated heat conduction elements 14 are arranged extends substantially parallel to the plane S defined by the emission surface of the radar sensor 4, at the front of this plane S. In the particular embodiment shown in Figures 1 to 4 and 6 to 8, the elongated heat conduction elements 14 extend parallel to each other in the plane T. The set 13 of the elongated elements of heat conduction 14 then forms a grid wave polarizer.

In the particular embodiments illustrated in Figures 2 and 6 to 8, the electronic component 11 capable of emitting heat when an electric current passes through it is for example a printed circuit board (or PCB – of the English “Printed Circuit Board”), on which at least one light source of the light-emitting diode type is mounted (not visible in the figures). In the embodiment shown on the , the heat-emitting electronic component is also present in part 2, although not shown. The printed circuit board 11 is for example fixed to the rear of the face 10 of the part 2. The part 2 for vehicle is then provided with an illumination function, in particular when this part 2 is a stylish part logo type. As a variant not shown, the heat-emitting electronic component 11 can be an electronic device for controlling at least one light source of the light-emitting diode type, or any other electronic circuit capable of emitting heat when a current passes through it. electric.

According to a first embodiment of the invention, shown in Figures 1 to 3, the set 13 of the elongated heat conduction elements 14 is located in the emission cone 7 of the radar sensor 4. The elongated conduction elements heat conduction elements 14 are arranged so that the distance d2 separating two adjacent elongated heat conduction elements 14 is constant (such a distance d2 being visible on the and being here measured in the vertical direction of the Z axis).

Preferably, the distance d2 separating two adjacent elongated heat conduction elements 14 is less than the wavelength of the electromagnetic wave 6 emitted by the radar sensor 4. The distance d2 separating two adjacent elongated heat conduction elements 14 is typically less than 4 mm, preferably between 2 mm and 4 mm.

More preferably, the ratio between the width of each elongated heat conduction element 14 and the wavelength of the electromagnetic wave 6 emitted by the radar sensor 4 is less than 1/10, preferably substantially equal to 1/ 10 (the width here being measured in the vertical direction of the Z axis). The width of each elongated heat conduction element 14 is typically less than 0.5 mm, preferably substantially equal to 0.4 mm. It should be noted that on the , the distance d2 and the width of the elements 14 are not represented to scale.

According to a second embodiment of the invention, represented on the , a first subset 16 of elongated heat conduction elements 14 is located in the emission cone 7 of the radar sensor 4, and a second subset 18 of elongated heat conduction elements 14 is located at the exterior of the emission cone 7 of the radar sensor 4. The elongated heat conduction elements 14 of the second subassembly 18 then extend to the periphery of the emission cone 7 of the radar sensor 4. The elongated heat conduction elements heat 14 of the first and second sub-assemblies 16, 18 are arranged so that, considering a direction of travel going from the second sub-assembly 18 towards the first sub-assembly 16 perpendicular to the main propagation direction D1 of the electromagnetic wave 6 emitted by the radar sensor 4 (therefore inside the plane YZ), and from the outside of the emission cone 7 of the radar sensor 4 towards the center of the emission cone 7, the distance separating two elements adjacent elongated heat conduction lines 14 is non-constant and follows an increasing distance profile function. This increasing distance profile function is for example a linear function, or a piecewise linear function, for example a step function. According to a first variant of this second embodiment of the invention, inside the emission cone 7 of the radar sensor 4, the elongated heat conduction elements 14 of the first subassembly 16 are arranged so that more we approach the center of the cone transversely, the more the distance between two adjacent elongated heat conduction elements 14 increases. According to another variant of this second embodiment, which is illustrated on the , the distance separating two adjacent elongated heat conduction elements 14 of the first subassembly 16 is constant inside the emission cone 7 of the radar sensor 4.

Preferably, the minimum distance separating two adjacent elongated heat conduction elements 14 of the first subassembly 16 is greater than 2 mm, preferably greater than 3 mm (the distance here being measured in the vertical direction of the Z axis) .

More preferably, the maximum distance separating two adjacent elongated heat conduction elements 14 of the first subassembly 16 is less than the wavelength of the electromagnetic wave 6 emitted by the radar sensor 4.

More preferably, the width of each elongated heat conduction element 14 of the first subassembly 16 is less than 0.5 mm (the width here being measured in the vertical direction of the Z axis). This width can be variable for each of the adjacent elongated heat conduction elements of the first subassembly 16. It should be noted that on the , the distance separating two adjacent elongated heat conduction elements 14 and the width of each elongated heat conduction element 14 are not shown to scale.

In the two embodiments of part 2 described above, the distance between two adjacent elongated heat conduction elements and the width of each elongated heat conduction element are calculated so as to minimize the reflection of the wave 6 on the elements, and therefore to maximize the transmission of this wave 6 to the other side of the elements. The calculation of these two parameters depends on the type of polarization and the wavelength of the radar sensor 4, and the angle of incidence of the wave 6, as will be detailed later.

More precisely, the configuration of room 2 illustrated on the is schematized on the by an equivalent electrical circuit. In this equivalent electrical circuit, in which the radar sensor 4 is polarized vertically in the direction P1 which is perpendicular to the direction of extension of the elongated heat conduction elements 14, the parameters Y ₀ and B are given by the equation ( 1) following: (1);
with ; <<1;
d the distance between two adjacent elongated heat conduction elements 14;
has the sum of the width of a slender heat conduction element 14 and the distance d;
λ the wavelength of the radar sensor 4;
θ the angle of incidence of the electromagnetic wave 6 emitted by the radar sensor 4.

When the angle of incidence θ of the electromagnetic wave 6 is 0 degrees, equation (1) becomes: (1);

Based on the electrical diagram of the , the reflection coefficient R _v of wave 6, which is a complex number, is then given by the following equation (2): (2);

The distance d between two adjacent elongated heat conduction elements 14 and the width ad of each elongated heat conduction element 14 are then calculated so as to minimize the modulus of this reflection coefficient R _v .

According to a third embodiment of the invention, represented on the , the defrosting system 12 further comprises a set 20 of elongated heating elements 22. The defrosting system 12 further comprises an electrical power supply unit (not shown), connected to the elongated heating elements 22 via one or more heating elements. electrical connection (such as for example electrical current distribution strips, electrical cables and/or an electrical power supply). These electrical connection elements, which are generally made of a non-transparent electrically conductive material, are arranged in the part 2 outside the emission cone 7 of the radar sensor 4. The electrical supply unit is configured to circulating an electric current within each of the elongated heating elements 22. Each elongated heating element 22 is typically a heating wire or metal strip, or even a heating track printed on a support (for example a plastic support) , notably by screen printing. The additional heat provided by the heating elements 22 (and used for defrosting) is then produced by the Joule effect in the wires, the metal strips or the heating tracks 22. As illustrated in the , the set 13 of heat conduction elements 14 and the set 20 of elongated heating elements 22 are for example intertwined.

Preferably, each elongated heating element 22 is coated with a layer of a dielectric material or is arranged in a protective and insulating dielectric element (such a material or dielectric element not being shown in the figures for reasons clarity). The dielectric material has a refractive index and thickness. The thickness of the dielectric material is advantageously between 0.8 times and 1.2 times an ideal thickness, the ideal thickness being equal to a natural number multiplied by the wavelength of the electromagnetic wave 6 emitted by the sensor radar 4 and divided by two times the refractive index of the dielectric material, for a zero angle of incidence of the electromagnetic wave 6 (normal electromagnetic wave). According to a particular embodiment, the thickness of the dielectric material is between 0.8 times and 1.2 times the wavelength divided by twice the refractive index. This thickness, which corresponds to the minimum possible for this particular characteristic of the invention, makes it possible to avoid other interferences.

All or part of the elongated heating elements 22 is located in the emission cone 7 of the radar sensor 4. Each elongated heating element 22 located in the emission cone 7 of the radar sensor 4 is arranged on the part 2 so as to to extend in a direction substantially perpendicular to the direction of interest P1 of the electric field of the electromagnetic wave 6 emitted by the radar sensor 4. In this way, the component of interest E1 of the electromagnetic wave 6, which extends perpendicularly to the direction of extension of the elongated heating elements 22, is almost not reflected by these elements 22 and is almost entirely transmitted to the other side of the defrosting system 12. The other possible components 9a, 9b, 9c of the electromagnetic wave 6 are reflected by the elongated heating elements 22 and are not transmitted to the other side of the defrosting system 12.

As illustrated on the , the elongated heating elements 22 extend in the same plane T. In the particular embodiment shown on the , the elongated heating elements 22 extend parallel to each other in the plane T. The set 20 of the elongated heating elements 22 then forms a grid wave polarizer.

The set 20 of the elongated heating elements 22 is for example located in the emission cone 7 of the radar sensor 4, as shown in the . The elongated heating elements 22 are arranged in such a way that the distance d3 separating two adjacent elongated heating elements 22 is constant (such a distance d3 being visible on the and being here measured in the vertical direction of the Z axis).

Preferably, the distance d3 separating two adjacent elongated heating elements 22 is less than the wavelength of the electromagnetic wave 6 emitted by the radar sensor 4. The distance d3 separating two adjacent elongated heating elements 22 is typically less than 4 mm , preferably between 2 mm and 4 mm.

More preferably, the ratio between the width of each elongated heating element 22 and the wavelength of the electromagnetic wave 6 emitted by the radar sensor 4 is less than 1/10, preferably substantially equal to 1/10 (the width being here measured in the vertical direction of the Z axis). The width of each elongated heating element 22 is typically less than 0.5 mm, preferably substantially equal to 0.4 mm. It should be noted that on the , the distance d3 and the width of the elements 22 are not represented to scale.

As a variant not shown, a first subset of elongated heating elements 22 is located in the emission cone 7 of the radar sensor 4, and a second subset of elongated heating elements 22 is located outside the cone emission 7 of the radar sensor 4. The elongated heating elements 22 of the second sub-assembly then extend to the periphery of the emission cone 7 of the radar sensor 4.

This third embodiment of the invention corresponds to a hybrid defrosting system 12, adapted in particular to situations for which the heat emitted by the heat-emitting electronic component 11 is not sufficient to ensure complete and/or rapid defrosting of part 2. Such an embodiment makes it possible to reduce the energy consumption and the weight of the defrosting system 12 compared to a defrosting system of the prior art consisting solely of elongated heating elements 22 (with equal defrosting performance).

According to a first variant of the third embodiment of the invention, represented on the , the part 2 further comprises a temperature sensor 24 configured to measure the temperature of the face 10 of the part 2. Such a temperature sensor 24, which is typically printed on the plastic film 15, is for example connected to a unit data processing unit (not shown in the figures) which is installed within the vehicle. This makes it possible to avoid a runaway defrosting system 12 if the control carried out by a vehicle temperature sensor (external to the room) is faulty (in the event of snow accumulation for example) and/or goes back to the vehicle once erroneous temperature (too high or low) compared to the “real” temperature measured in the area where the radar sensor 4 is installed. The presence of such a temperature sensor 24 thus allows precise regulation and control of the temperature on face 10 of part 2, as a function of the temperature measured on this face 10, and also protects part 2 against any possible overheating. Program code instructions can be implemented in the vehicle data processing unit connected to the temperature sensor 24, to regulate the temperature on the face 10 of the part 2 depending for example on the outside temperature and the speed driving of the vehicle.

It should be noted that the addition of a temperature sensor 24 within part 2 is also possible for the embodiments illustrated in Figures 2, 4 and 8, without departing from the scope of the present invention.

According to a second variant of the third embodiment of the invention, represented on the , each heat conduction element 14 is connected to two elongated heating elements 22 via a thermal junction 26. This alternative embodiment makes it possible to homogenize the distribution of heat on the face 10 of the part 2, allowing better transmission of the heat from the electronic component 11 towards the face 10 of the part 2, and thus a homogenization of the heat over the entire surface of the part 2. In a variant not shown, at least one of the heat conduction elements 14 can be connected to one or more elongated heating element(s) 22 via a thermal junction 26.

The present invention is not limited to the embodiments described above by way of examples; it extends to other variants.

Claims (30)

Part (2) for a vehicle intended to be arranged facing an emission cone (7) of a radar sensor (4) of the vehicle, the radar sensor (4) being configured to emit an electromagnetic wave (6) in the emission cone (7), the electromagnetic wave (6) propagating in a main propagation direction (D1), said part (2) comprising at least one electronic component (11) capable of emitting heat when crossed by an electric current, said part (2) having on one of its faces (10) a system (12) for defrosting the part (2);
characterized in that the defrosting system (12) comprises a set (13) of heat conduction elements (14), each heat conduction element (14) being made of a thermally conductive material and being in contact with said at least one heat-emitting electronic component (11), for bringing heat from the heat-emitting electronic component (11) to said face (10) of the part (2) by thermal conduction. Part (2) for a vehicle according to claim 1, in which the electric field of the electromagnetic wave (6) emitted by the radar sensor (4) comprises a component (E1) oscillating in a direction of interest (P1), in in which the heat conduction elements (14) are elongated elements, and in which at least one subassembly (16) of said set (13) of heat conduction elements (14) is located in the emission cone (7) of the radar sensor (4) when the part (2) is arranged facing the radar sensor (4) and is configured so that each heat conduction element (14) of said subassembly (16) is arranged on the part (2) so as to extend in a direction substantially perpendicular to the direction of interest (P1) of the electric field of the electromagnetic wave (6) emitted by the radar sensor (4) when the part (2) is arranged opposite the radar sensor (4). Part (2) for a vehicle according to claim 1 or 2, in which the heat conduction elements (14) extend in the same plane (T), said plane (T) extending perpendicular to the main propagation direction (D1) of the electromagnetic wave (6) emitted by the radar sensor (4). Part (2) for a vehicle according to claim 3 when it depends on claim 2, in which the heat conduction elements (14) extend parallel to each other in said plane (T), the set (13) of heat conduction elements (14) forming a gate wave polarizer. Vehicle part (2) according to claim 4, in which the heat conduction elements (14) are arranged in such a way that the distance (d2) separating two adjacent heat conduction elements (14) is constant. Vehicle part (2) according to claim 5, in which the distance (d2) separating two adjacent heat conduction elements (14) is less than the wavelength of the electromagnetic wave (6) emitted by the radar sensor (4). Part (2) for a vehicle according to claim 5 or 6, in which the distance (d2) separating two adjacent heat conduction elements (14) is less than 5 mm, preferably between 1 mm and 5 mm, more preferably between 2 mm and 4 mm. Part (2) for a vehicle according to one of claims 4 to 7, in which the ratio between the width of each heat conduction element (14) and the wavelength of the electromagnetic wave (6) emitted by the radar sensor (4) is less than 1/10. Part (2) for a vehicle according to the preceding claim, in which the width of each heat conduction element (14) is less than 0.5 mm, preferably substantially equal to 0.4 mm. Part (2) for a vehicle according to claim 3 or 4 when dependent on claim 2, in which a first subassembly (16) of heat conduction elements (14) is located in the emission cone ( 7) of the radar sensor (4) when the part (2) is arranged facing the radar sensor (4), and a second sub-assembly (18) of heat conduction elements (14) is located outside of the emission cone (7) of the radar sensor (4) when the part (2) is arranged facing the radar sensor (4), the heat conduction elements (14) of the first and second sub-assemblies (16, 18) being arranged so that, considering a direction of travel going from the second sub-assembly (18) towards the first sub-assembly (16) perpendicular to the main propagation direction (D1) of the electromagnetic wave (6) emitted by the radar sensor (4), and from the outside of the emission cone (7) of the radar sensor (4) towards the center of said emission cone (7), the distance separating two heat conduction elements ( 14) is non-constant and follows an increasing distance profile function. Part (2) for a vehicle according to the preceding claim, in which said increasing distance profile function is a linear function, or a piecewise linear function, for example a step function. Part (2) for a vehicle according to claim 10 or 11, in which the minimum distance separating two heat conduction elements (14) of the first subassembly (16) of heat conduction elements (14) is greater than 2 mm, preferably greater than 3 mm. Part (2) for a vehicle according to one of claims 10 to 12, in which the width of each heat conduction element (14) of the first subassembly (16) of heat conduction elements (14) is less than to 0.5 mm. Part (2) for a vehicle according to one of the preceding claims, in which the defrosting system (12) further comprises a plastic film (15) on which the heat conduction elements (14) are printed, in particular by screen printing, each heat conduction element (14) forming a heat conductive track on said plastic film (15). Part (2) for a vehicle according to one of the preceding claims, in which the thermally conductive material constituting each heat conduction element (14) is copper, silver or graphite. Part (2) for a vehicle according to one of the preceding claims, in which the defrosting system (12) further comprises a set (20) of elongated heating elements (22), at least one sub-assembly of said set (20). ) of elongated heating elements (22) being located in the emission cone (7) of the radar sensor (4) when the part (2) is arranged facing the radar sensor (4) and being configured so that each element elongated heating element (22) of said subassembly is arranged on the part (2) so as to extend in a direction substantially perpendicular to the direction of interest (P1) of the electric field of the electromagnetic wave (6) emitted by the radar sensor (4) when the part (2) is placed opposite the radar sensor (4). Part (2) for a vehicle according to the preceding claim, in which the elongated heating elements (22) are heating wires or metal strips, or else heating tracks printed on a support, in particular by screen printing. Part (2) for a vehicle according to claim 16 or 17, in which at least one of the heat conduction elements (14) is connected to at least one of the elongated heating elements (22) via a thermal junction (26). Part (2) for a vehicle according to one of the preceding claims, in which said at least one heat-emitting electronic component (11) is chosen from the group consisting of: an electronic circuit, a printed circuit board on which is mounted at at least one light source, and an electronic device for controlling at least one light source. Part (2) for a vehicle according to one of the preceding claims, in which the part (2) further comprises a temperature sensor (24) configured to measure the temperature of said face (10) of the part (2). Part (2) for a vehicle according to one of the preceding claims, in which each of the heat conduction elements (14) has a thermal conductivity greater than 50 W/(m·K), preferably between 50 W/(m ·K) and 500 W/(m·K). Part (2) for a vehicle according to one of the preceding claims, in which the part (2) for a vehicle is a stylish part intended to mask the radar sensor (4). Part (2) for a vehicle according to the preceding claim, in which the style part is a logo. Part (2) for a vehicle according to one of claims 1 to 21, in which the part (2) for a vehicle is a closing window of a lighting and/or signaling element (1) in which the radar sensor (4). Assembly (1) comprising a vehicle radar sensor (4) and a vehicle part (2) according to one of the preceding claims, in which the radar sensor (4) is configured to emit an electromagnetic wave (6) in a cone emission (7), the electromagnetic wave (6) propagating in a main propagation direction (D1), the vehicle part (2) being arranged facing the emission cone (7) of the radar sensor (4 ). Assembly (1) according to the preceding claim when the vehicle part (2) is according to claim 2 or one of claims 3 to 24 in combination with claim 2, in which the electric field of the electromagnetic wave (6) emitted by the radar sensor (4) comprises a component (E1) oscillating in a direction of interest (P1). Assembly (1) according to claim 25 or 26, in which the radar sensor (4) is a millimeter radar sensor polarized in a horizontal or vertical polarization direction. Assembly (1) according to the preceding claim, in which the radar sensor (4) has an operating frequency of between 76 GHz and 81 GHz. Assembly (1) according to one of claims 25 to 28, in which the assembly (1) is a lighting and/or signaling element of a vehicle, in particular a vehicle headlight. Assembly (1) according to the preceding claim, in which the vehicle part (2) is a closing window of said lighting and/or signaling element (1), said window constituting one face of said element (1).