Multi-layer motor vehicle exterior part comprising a heating element

Abstract

Motor vehicle exterior part comprising: a wall comprising a face intended to be visible from outside the vehicle, the face being coated with a first layer; a second layer covering the first layer; and a heating element arranged between the two layers on the first layer, the first layer comprising an area of increased thickness and the heating element being arranged only on the area of increased thickness of the first layer.

Claims

1. A method of manufacturing an exterior part, comprising the following steps executed sequentially: producing a wall comprising a face; coating said face with a first layer; forming an area of increased thickness in the first layer; depositing a heating element only on the area of increased thickness in the first layer; and coating the first layer and the heating element with a second layer, wherein the exterior part includes the wall, wherein the face of the wall is intended to be visible from outside of a vehicle, wherein the exterior part further includes the second layer covering the first layer, wherein the exterior part further includes the heating element arranged between the first layer and the second layer, wherein the heating element is arranged only on the area of increased thickness of the first layer, wherein the heating element is a heating filament.

2. The method according to claim 1, wherein the wall comprising the face is produced by molding of a plastic material.

3. The method according to claim 1, wherein the wall comprising the face is coated with the first layer by injection molding of a polymer or of a mixture of polymers in a mold, wherein a molding chamber for the injection molding has a shape adapted for formation of the area of increased thickness in the first layer.

4. The method according to claim 1, wherein the first layer and the heating element are coated with the second layer by injection molding of a polymer or a mixture of polymers.

5. The method according to claim 1, wherein the wall comprising the face is composed of a mixture of acrylonitrile butadiene styrene polymer and polycarbonate.

6. The method according to claim 3, wherein the polymer or the mixture of polymers injected to form the first layer is polyurethane.

7. The method according to claim 4, wherein the polymer or the mixture of polymers injected to form the second layer is polyurethane.

8. The method according to claim 1, wherein the area of increased thickness in the first layer extends outward from a rest of the first layer.

9. The method according to claim 1, wherein an exterior face of the second layer, not in contact with the heating element, is substantially planar.

10. The method according to claim 1, wherein the first layer and the second layer are substantially transparent to electromagnetic waves at frequencies used by radars.

11. The method according to claim 1, wherein the first layer and the second layer are substantially transparent to electromagnetic waves at frequencies of visible light.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings in which:

(2) FIG. 1 is a perspective view of a motor vehicle exterior part according to one embodiment of the invention.

(3) FIG. 2 is a perspective view of the exterior part of FIG. 1 at an intermediate stage of its manufacturing method, i.e., before coating with the second layer.

(4) FIG. 3 is a side section of the exterior part of FIG. 1.

(5) FIG. 4 is a side section of the exterior part of FIG. 1, taken in a section perpendicular to that of FIG. 3.

DETAILED DESCRIPTION

(6) FIGS. 1 to 4 show a motor vehicle exterior part according to a first embodiment, designated by general reference 1.

(7) The motor vehicle exterior part 1 is intended to protect sensors placed in a bumper or in other bodywork elements of a motor vehicle. These sensors can be of any type, and some of them may no longer function in the presence of frost, snow or ice on the exterior part 1, knowing that icing may occur once the outside temperature drops below 10 C., due to the movement speed of the vehicle. It is therefore necessary for the exterior part 1, in addition to its function of protection against external aggressions, to have a de-icing function with respect to the sensor that it protects and which is located on the interior side of the vehicle relative to the exterior part. The motor vehicle exterior part 1 will be described with reference to FIGS. 1 to 4.

(8) The exterior part 1 comprises a wall comprising a face 10 which is intended to be visible from the outside of the vehicle and coated with a first layer 12. The layer 12 at least partially covers said face 10. The first layer 12 is in turn covered with a second layer 16. The exterior part 1 is shown flat in the figures, but it is understood that it can be placed vertically when it is installed on the motor vehicle. Thus, the face 10 is positioned on the interior side of the vehicle, and the second layer 16 is positioned toward the exterior of the vehicle when the exterior part 1 is installed on the vehicle.

(9) A heating element 14 is positioned on the layer 12. The heating element 14 comprises electrical connection parts 18 which are intended to be connected to a power supply. Generally, the heating element 14 converts electrical energy into thermal energy, by the Joule effect. The heating element 14 is thus used to de-ice the exterior part in the portion facing a sensor placed toward the interior of the vehicle relative to the exterior part 1

(10) In an advantageous embodiment, the first layer 12 comprises a so-called area of increased thickness 124, which is thicker than the rest of the layer 122. As illustrated in FIG. 3, the heating element 14 is positioned only on the area of increased thickness 124 of the layer 12. In addition, the area of increased thickness 124 extends outwardly from the rest of the first layer 12. In this way, the distance between the area of increased thickness 124, therefore the heating element 14 arranged thereon, and the outer surface of the second layer, is further reduced. In other words, the heating element 14 is close to the outer surface of the layer 16; the term close is understood here to mean a distance substantially equal to or less than 0.1 mm from the outer surface of the layer 16.

(11) In one embodiment, the heating element 14 is a heating filament. Such filaments are traditionally used on parts of vehicles which need to be de-iced by heating, such as the rear windows of vehicles or the rearview mirrors, for example. In the case where the sensor located opposite the heating element 14 is a radar sensor or a lidar sensor, the filament is arranged in such a way that it does not disturb the passage of the electromagnetic waves which are necessary for the operation of the sensor.

(12) In another embodiment, the heating element 14 is a heating film. Such heating films are already used in applications for heating and defrosting vehicle parts such as rearview mirrors. In the case where the sensor located opposite the heating element 14 is a radar sensor or a lidar sensor, the heating film is chosen from films not disturbing the passage of the electromagnetic waves which are necessary for the operation of the sensor.

(13) The second layer 16 at least partially covers the first layer 12, at least over the area of increased thickness 124 of the first layer 12. In this way, the second layer 16 also covers the heating element 14. In other words, the heating element 14 is arranged between the first layer 12 and the second layer 16, or is sandwiched between the two layers 12 and 16. Thus, the element 14 is protected from external aggressions.

(14) In addition, the heating element 14 is placed only on the area of increased thickness 124. Consequently, when the outer surface of the layer 16 is substantially flat, which is the most frequent case, the thickness of the layer 16 in the portion 164 facing the heating element 14 placed on the area of increased thickness 124 is small, which implies that the heating element is close to the outer surface of the layer 16. This allows the heating of the outer surface of the layer 16 to be more efficient, and therefore the de-icing to be fast and complete. Thus, the sensors placed toward the interior of the vehicle relative to the part 1 can function correctly.

(15) The wall comprising a face 10 may be the outer wall of a bumper or other plastic bodywork element. The wall can also be the outer surface of an element attached to a bumper or of another bodywork element.

(16) In a preferred embodiment, the first layer 12 has a thickness of about 3.2 mm in the area of increased thickness 124 and has a thickness of about 2.5 mm in the portion 122 outside of the area of increased thickness.

(17) In a preferred embodiment, the second layer 16 has a thickness of about 3 mm in its thickest section 162 and has a thickness of about 0.7 mm in its thinnest section 164 located opposite the area of increased thickness 124 comprising the heating element 14.

(18) Advantageously, the heating element 14 has a small thickness compared to the thicknesses of the layers 12 and 16. This makes it possible in particular to limit the total thickness of the exterior part 1, which is preferable for reasons of esthetics and weight.

(19) Advantageously, but non-limitingly, the surface 10 is composed of a polymer material consisting of a mixture of Acrylonitrile Butadiene Styrene polymer and of polycarbonate, and often referred to as ABS-PC. Such a material indeed has characteristics that are well suited to the manufacture of motor vehicle exterior parts, and in particular good transformability or processability, good impact resistance, and good heat resistance, as well as good performance over time.

(20) Advantageously, the first and the second layer 12, 16 are composed of polyurethane. Polyurethane is suitable because it has good transformability or processability and good mechanical properties, and it is further transparent to electromagnetic waves in the frequencies used by radar sensors. On the other hand, polyurethane has good adhesion capacity on ABS/PC, which is an additional advantage.

(21) Additionally, polyurethane can also be transparent to visible light, which is useful if the sensors are lidar-type sensors. The transparency of the layers 12, 16 to visible light further has the advantage that the heating element 14 is visible from outside of the vehicle. This is all the more advantageous in the case where the heating element 14 is placed on the area of increased thickness 124 of the first layer 12 because a depth effect is then obtained which gives a person looking at the exterior part the impression that the heating element is not in contact with the part, or is not part of this part, which is aesthetically appealing.

(22) It is understood that the polymer materials mentioned above are illustrative and non-limiting, and that other materials may be suitable.

(23) The motor vehicle exterior part 1 can be manufactured according to the following method: a wall comprising a face 10 which is intended to be visible from the outside of the vehicle is produced, said face 10 is coated with a first layer 12, a heating element 14 is deposited on the layer 12, the first layer 12 and the heating element 14 are coated with a second layer 16.

(24) Preferably, the layers 12 and 16 are formed by injection molding.

(25) Preferably, an area of increased thickness 124 is formed on the layer 12 and the heating element 14 is deposited on this area of increased thickness. If the layer 12 is formed by injection molding, the molding chamber has a shape so as to allow the formation of an area of increased thickness 124 in the layer 12.

(26) Advantageously, in this method, the wall comprising a face 10 is composed of ABS-PC (mixture of acrylonitrile butadiene styrene and polycarbonate), and the first layer 12 and second layer 16 are composed of polyurethane.

(27) This manufacturing method is simple to implement, and comprises a relatively small number of steps, which also allows rapid manufacturing. In particular, the heating element 14 is simply deposited on the area of increased thickness 124 of the first layer 12, and is then held in place by the overmolding of the second layer 16.