FR3060489A1 - HEATING DEVICE FOR PROTECTING A MOTOR VEHICLE RADAR - Google Patents

Abstract

- The invention relates to a device (10) for protecting a radar (20) of a motor vehicle, comprising at least one current generator (30) and a cache (40), the cache (40) comprising at least one zone transmission unit (50) capable of being traversed by waves (60) of said radar (20), characterized in that the transmission zone (50) comprises a coating (70) constituting an electrical resistance, and in that the generator of current (30) is able to generate a current in said coating (70).

Description

(57). The invention relates to a device (10) for protecting a radar (20) of a motor vehicle, comprising at least one current generator (30) and a cover (40), the cover (40) comprising at least one area for transmission (50) capable of being traversed by waves (60) of said radar (20), characterized in that the transmission zone (50) comprises a coating (70) constituting an electrical resistance, and in that the current generator (30) is capable of generating a current in said coating (70).

The present invention relates to the field of motor vehicles equipped with radar, and more particularly, the field of devices for deicing such a radar.

The device according to the invention applies in particular to radars placed at the front of vehicles, for example of the ACC type.

For safety reasons in particular, it is known to equip motor vehicles with radars, for example of the ACC type, according to the Anglo-Saxon expression "Adaptive Cruise Control". Such a radar is used in particular to regulate the speed of vehicles as a function of traffic and / or obstacles on the road. The radar detects the speed and distance of the object in front of the carrier vehicle, so as to maintain a safety distance between the vehicles in particular

ACC radars are mounted on the front of vehicles, generally between the bars of the cooling grid.

To hide these radars for aesthetic reasons, and / or to protect them from external aggressions (rain, ice, frost, mud, insects, leaves ...), it is known to use a protective part comprising a plastic cover positioned in front of the sensor.

Such a plastic cover lets the radar waves through with as little attenuation as possible so as not to disturb the operation of the radar itself.

A common problem is the formation of ice or frost on the ACC radar or on the protective part. This ice or frost disrupts the transmission and reception of radar waves and makes the system unreliable, even unusable.

By default it is then possible and preferable to disconnect the ACC function when the outside temperature is below 3 ° C, provided that the driver is informed of this deactivation. However, this approach degrades the safety of the occupants of the vehicle even though they are warned.

A better solution is to equip the protective part with a heating system, allowing a defrosting function to be carried out. Heating of the protective part can be carried out using electrically conductive tracks deposited on the surface of the part to be heated.

Therefore the cover can be heated, in order to melt the ice or the frost or the snow. After defrosting, the ACC function can therefore be used. This solution therefore makes it possible not to deactivate the ACC function.

However, the use of a conductive surface surface makes the deicing system of the protective part fragile. Indeed, external elements can damage the tracks, and thus cut the electrical circuit, and therefore, the heating mechanism.

There is also a solution consisting in drowning (integrating) the conductive wires traversed by a current within the protective part.

However, wherever they are located, the major drawback of these deicing systems is that they require the use of electrically conductive materials in order to produce the heating tracks. This causes disturbances and weakening of the radar signal due to the presence of metallic conductive elements in front of the radar.

The invention aims to remedy these drawbacks by providing a robust protection device capable of being traversed by heat without affecting the transmission of radar waves.

Thus, the object of the invention relates to a device for protecting a motor vehicle radar, comprising at least one current generator and a mask, the mask comprising at least one transmission zone capable of being traversed by waves of said wave. radar. The transmission zone comprises a coating constituting an electrical resistance, and the current generator is able to generate a current in said coating.

The device according to the invention thus has the advantage of allowing the use of the ACC function at temperatures below 3 ° C., while offering increased robustness to the external elements compared to known devices and maximum transmission of radar waves. .

The device can also include one or more of the following characteristics, taken alone or in combination:

the coating has a resistivity capable of giving off, by the Joule effect, sufficient heat to raise the temperature of the transmission zone beyond zero degrees Celsius when it is traversed by the current of the current generator.

the coating has a resistance of less than 20kQ to 300K, and preferably less than 5kQ, and more preferably less than 3kQ.

the coating is an automobile body paint enriched with electrically conductive charges.

the conductive filler is chosen alone or in combination from the following filler group: graphite, metals, such as copper, silver, iron, indium, graphite and metal alloy.

the paint comprises more than 10% by weight of filler, preferably between 20% and 60% by weight.

the coating has a thickness of between 10 and 30 microns.

the device comprises at least one electrode capable of transmitting to said coating, a current generated by the current generator.

the cover is made of glass or plastic resin, such as a polypropylene-based resin.

the current generator is positioned outside the transmission area.

at least one of the electrically conductive elements is a metal insert overmolded during the shaping of the cover.

the overmolded metal insert is an eyelet, a plate or a braid.

at least one of the electrically conductive elements is an insert and fixed to the cover after it has been shaped.

the insert is a conductive adhesive strip forming a conductive adhesive film.

the insert is a superconductive coating layer.

The invention also relates to a set of a radar, such as an ACC type radar, and a device according to the invention.

Finally, the invention also relates to a motor vehicle equipped with an assembly according to the invention.

The invention will be better understood on reading the appended figures, which are provided by way of examples and have no limiting character, in which:

- Figure 1 illustrates an embodiment of the device according to the invention;

FIG. 2 illustrates the positioning of the device according to the invention with respect to the radar;

FIG. 3 illustrates an example of positioning of the electrodes.

Referring now to FIG. 1. The protection device 10 of a radar 20 of a motor vehicle, according to the invention, comprises at least one current generator 30 and a cover 40.

As illustrated in FIG. 2, the cover 40 is intended to be placed in front of the radar 20. The cover 40 can be made of glass or plastic.

The cover 40 comprises at least one transmission zone 50 capable of being traversed by the waves 60 of the radar 20. According to one embodiment, the material constituting the transmission zone 50 is a plastic resin, advantageously based on polypropylene.

The current generator 30 is of course positioned outside of the transmission zone, that is to say that it is not located in the path of the radar waves, so as not to disturb the radar waves.

The transmission zone 50 comprises a coating 70 capable of constituting an electrical resistance, the heat emitted by the Joule effect is sufficient to raise the temperature of the transmission zone beyond zero degrees Celsius (melting temperature of the ice).

The electrical resistance translates the property of a component to oppose the passage of an electric current. Resistance is responsible for dissipating energy in the form of heat (Joule effect). Thus, the term resistance designates the ability of a conductive material to heat during the passage of an electric current.

According to the invention, the electric current is generated by the current generator 30, and it is transmitted to the coating 70 of the transmission zone 50 by means of electrodes 80.

Coating 70

Properties

In the description, all the resistance values are values measured using an ITW Ransburg resistivity meter, using electrodes 25mm apart and positioned in the center of a rectangular plate of 200mm by 600mm. These measurements are carried out for coatings having a thickness of between 10 and 30 microns, at a temperature of 300K.

A primer conventionally used in an automotive bodywork paint chain has a resistance greater than 30kQ and less than 1ΜΩ.

Due to its high resistance, such a coating cannot be crossed by a current not exceeding 15V (current generally used industrially for safety reasons).

This is why, according to the invention, a coating 70 is used having a resistance of less than 20kQ, preferably less than 5kQ, still more preferably less than 3kQ, so that the coating can be traversed by a current even if it does not exceed 15V. However, its resistance allows a release of heat by Joule effect sufficient for the desired application.

Formulation

The formulation of the coating 70 according to the invention also has the following properties:

its formulation is adapted to body parts; it must in particular have good adhesion to the material of the part, for example on a treated polypropylene;

its formulation is sufficiently transparent to radar waves to allow radar to operate;

its formulation is compatible with the material of the cover 40.

According to one embodiment, the coating 70 is an automobile body paint enriched with electrically conductive pigments.

The quantity of pigments is defined as a function of the resistivity of the pigment used, therefore as a function of the nature of the pigment, and as a function of the quantity of heat desired. One can for example use powdered graphite pigments.

According to an exemplary embodiment, the coating 70 comprises: a paint, for example polyurethane;

a solvent, for example water, xylene or butyl acetate glycol a binder, for example isocyanate or polyol;

loads of conductive pigments; such fillers can be chosen alone or in combination from the following group of fillers: graphite in its different forms (tube, nanotubes, powders), metals such as copper, silver, iron, indium, etc. in different forms (tube, powder, wire), an alloy of graphite and metal;

optionally a rheology agent, for example an anti-sagging agent;

optionally a thickening agent, for example talc;

optionally traditional additives and adjuvants, for example an adhesion promoter.

In general, the paint comprises more than 10% by weight of pigments, preferably between 20% and 60% by weight.

The particle size of the pigments is preferably less than 25 micrometers. Such a particle size also makes it possible to obtain better dispersibility and to increase the distribution of the graphite pigments in the resin.

According to another embodiment, a paint is used as described in patent application FR2967271. The coating 70 then comprises:

a paint, for example: vinyl, acrylic, epoxy, polyurethane, glycerophthalic;

a solvent, for example water or of the aromatic (xylene, toluene, etc.), aliphatic, alcoholic (isopropyl alcohol, methoxylopropyl alcohol, ethanol) ... type; a binder, for example based on modified acrylic resin;

fillers of graphite pigments;

optionally a rheology agent, for example an anti-sagging agent.

Thickness

In order to provide the heat necessary for defrosting the cover 40, while letting the radar waves pass, the coating 70 has a thickness of between 10 and 30 microns.

The current generator 30 and the electrodes 80

The electrodes 80 constitute electrically conductive elements attached to the device 10, so as to connect the current generator 30 to the coating 70. They are preferably positioned outside of the transmission zone 50, that is to say that they are not located on the path of the radar waves 60, so as not to disturb the radar waves.

These electrically conductive elements 80 are distributed over the surface of the cover 40 in such a way that the current circulates in a surface of the covering 70 large enough to produce sufficient heat in the transmission zone 50. In fact, it is not necessarily necessary as the entire coating heats up, the important thing is that the quantity of heat released allows defrosting of the transmission zone 50.

Obviously, according to one embodiment, the electrically conductive elements 80 are distributed over the surface of the cover 40 so that the current flows over the entire surface of the coating 70, and therefore over the entire surface of the transmission zone 50, thus allowing optimal defrosting.

It will thus be possible to use two electrodes 80, positioned on opposite edges of the cover 40, or diametrically opposite if the cover is circular.

It will be possible to add electrodes on the edge or edges of the cover 40, in order to increase the current circulation area, and therefore the thermal efficiency.

FIG. 3 illustrates an example of positioning the electrodes 80 on a device 10, in which the device 10 comprises 2 diametrically opposite electrodes 80.

According to a variant, an electrode 80 may consist of a conductive sticky strip which forms an adhesive film on the cover 40, between the generator and the transmission zone 50.

In a variant, an electrode 80 may consist of an insert, preferably metallic, overmolded during the molding of the cover 40. Such an insert can be chosen from the following list: eyelet; plate; braided. Such an insert can in particular be made of copper or silver.

In another variant, an electrode 80 can consist of a local application of a superconductive coating, which has a resistance of less than 20kQ for a thickness of between 10 and 30 microns, with a distance between the electrodes of 25mm. Compared to a conventional coating which has a resistance greater than 30kQ under the same conditions, this superconductive coating thus ensures better conductivity at the surface of the device 10, between the generator and the transmission zone 50.

According to one example, the current generator 30 is positioned near the transmission zone 50.

The cover 40 is suitable for being fixed on a motor vehicle bumper, in front of the radar.

The invention also relates to an assembly of a radar 20, in particular of the ACC type, and of a device 10 according to the invention, as well as a motor vehicle equipped with such an assembly.

Example of realization

Using a graphite-based coating as described above, and using a 15v, 0.1 amp current generator, a temperature of 30 ° C is obtained on the coating, or 30 ° C using a 15v current generator, 0.2 amp,

List of references

10: 20: protective device radar 5 30: power generator 40: hidden 50: transmission area 60: waves 70: coating 10 80: electrodes

Claims (18)

1. Device (10) for protecting a radar (20) of a motor vehicle, comprising at least one current generator (30) and a cover (40), the cover (40) comprising at least one transmission zone (50 ) capable of being traversed by waves (60) of said radar (20), characterized in that the transmission zone (50) comprises a coating (70) constituting an electrical resistance, and in that the current generator (30) is able to generate a current in said coating (70). 2. Device (10) according to claim 1, wherein the coating (70) has a resistivity capable of giving off, by Joule effect, sufficient heat to raise the temperature of the transmission zone (50) beyond zero degrees Celsius when the current of the current generator (30) flows through it. 3. Device (10) according to one of the preceding claims, in which the coating (70) has a resistance of less than 20kQ at 300K, preferably less than 5kQ, and more preferably less than 3kQ. 4. Device (10) according to one of the preceding claims, in which the coating (70) is an automobile body paint enriched with electrically conductive charges. 5. Device (10) according to the preceding claim, wherein the conductive filler is chosen alone or in combination from the following filler group: graphite, metals, such as copper, silver, iron, indium, alloy of graphite and metal. 6. Device (10) according to one of claims 4 and 5, wherein the paint comprises more than 10% by weight of filler, preferably between 20% and 60% by weight. 7. Device (10) according to one of the preceding claims, in which the coating (70) has a thickness of between 10 and 30 microns. 8. Device (10) according to one of the preceding claims, comprising at least one electrode (80) capable of transmitting to said coating (70), a current generated by the current generator (30). 9. Device according to one of the preceding claims, in which the cover (40) is made of glass or plastic resin, such as a polypropylene-based resin. 10. Device according to one of the preceding claims, in which the current generator (30) is positioned outside the transmission zone (50). 11. Device according to one of the preceding claims, in which at least one of the electrically conductive elements (80) is a metal insert overmolded during the shaping of the cover (40). 12. Device according to the preceding claim, wherein the overmolded metal insert is an eyelet, a plate or a braid. 13. Device according to one of claims 1 to 10, wherein at least one of the electrically conductive elements (80) is an insert and fixed on the cover (40) after its shaping. 5 14. Device according to the preceding claim, wherein the attached element is a conductive adhesive strip forming a conductive adhesive film. 15. Device according to the preceding claim, wherein the added element is a superconductive coating layer. 16. Set of a radar (20) and a device (10) according to one of the preceding claims 10. 17. The assembly of claim 16, wherein the radar (20) is an ACC type radar. 18. Motor vehicle equipped with an assembly according to one of claims 16 and 17. 3060 1/2