FR2777412A1 - Car electric current circulating plastic section - Google Patents

Abstract

The plastic sections form part of the car and circulate battery current.

Description

The invention relates to the production of plastic parts in the field

  vehicles moving on the road, and more particularly

  that of automobile construction.

  More precisely still, it is a question of proposing a part out of plastic material (S) which integrates more easily in an environment o of the electric current of a non negligible intensity must circulate (commonly 60 amps for a 12V battery (Volts) of an automobile,

  or even more if it is a "diesel" or a truck).

  Thus, on a car or truck, a dense network of cables ensures the distribution of current to various locations in the vehicle

  (headlights, nameplate lighting, cabin lighting, etc.).

  However, part of this network passes along plastic parts (bumpers, interior roof or floor lining, door lining,

dashboard...).

  Commonly, cables run behind the parts (non visible side) and are fixed to them by straps, by gluing, or by similar holding techniques. Occasionally, cables can even

  be held in a groove by a gangue of foam (FR-A-2 740 422).

  This nevertheless requires having to manage the use of one or

  several of these electric cables or wires.

  The object of the invention is to propose the creation of current flow zones at the location of a plastic part in order to circulate there a current delivered by a vehicle battery, without having to

  use traditional electric cables or wires for this.

  More specifically, the solution of the invention consists of a plastic part presenting itself either as a rigid molded part, or as a thin flexible plate (or sheet) suitable for being hot formed and / or under pressure, with a mold. , with the characteristics that this part comprises at least one electrically conductive circuit integrated into it and defined by a thin layer of electrically conductive material creating one or more elongated path (s) of current flow compatible (s) with (c (i.e. supporting) a current supplied by a motor vehicle battery and communicating with terminals

  of connection connectable to such an electrical source.

  According to a preferred embodiment, this "integrated circuit" will consist of a surface coating arranged in a predetermined pattern and comprising an electrically conductive substance with a fluid binder

or pasty.

  So that the plastic material of the part is not affected by the heating effect inherent in the flow of current in the circuit thus created, a complementary characteristic of the invention provides that a heat shield can be interposed between the plastic material and the driver circuit. In addition, in order to avoid any unwanted electrical contact along all or part of the circuit created, provision may be made for coating entirely (except of course at the location of the connections) or locally

  this circuit of an electrical insulator.

  In terms of the process for obtaining it, it is a priori advisable to produce the conductive circuit by applying or spraying on the surface of the plastic part already produced, a coating product which can be designated as an "electrically conductive paint", for example deposited at the gun if an appropriate thinner is used, or using some sort of

felt-tip pen or even a brush.

  More generally, the process for obtaining the invention consists in integrating on the surface (or towards the surface) of the plastic of the part at least one electrically conductive circuit forming a thin layer defining the desired paths of circulation of the current To integrate the conductive circuit into the workpiece, an effective method consists in using a mask to "trace" the circuit (that is to say, define its design or contours) and then proceed by surface deposition of the

  conductive layer on the plastic of the part.

  As already indicated, a technique of projecting a

  film-like coating is suitable.

  It will also be noted that if a thermal insulation layer is provided, this will be carried out on the plastic surface, in particular at the

  places intended to receive the circuit, before integrating the latter.

  In practice, it is recalled that two main types of parts are concerned here, the parts being presented as: - a flexible sheet (commonly called "skin") even if it comprises several layers of different materials, (such as a thin non-cellular coating lined with a layer of foam), suitable for being hot formed and / or under pressure, or under tension (in particular thermoforming, thermogainage or thermo-compression in a mold),

  - or a rigid plastic part already molded, constituting in it-

  even a shaped part (shield for example) or else forming the rigid structure (commonly called "insert") of a part not yet finished

  (dashboard insert, door panel ...).

  In the first case ("skin" still to be shaped), this "skin" will first be made as a flexible thin sheet, then the conductive circuit will be integrated on the surface thereof, the circuit of course having a thickness less than that of the "skin". In the second case (rigid structural part), it is advisable to mold the part and, in the mold or after molding, out of the mold, to produce the conductive circuit by integrating for this the circuit with the part produced, in the manner of 'a fine

conductive layer.

  An even more precise description of the invention is presented below.

  after with reference to the accompanying drawings in which: Figure 1 is a schematic perspective view showing a rear bumper of a motor vehicle provided with the integrated circuit of the invention, with a schematic connection to the vehicle battery; Figure 2 is an enlarged local sectional view of the area marked II in Figure 1; Figure 3 shows schematically in enlarged front view of the masking strip (also called "masking") used to define the areas where will be deposited the conductive material of the circuit; Figure 4 shows schematically in perspective a strip of plastic material commonly called "skin" adapted to be hot formed on a plastic insert (known technique of thermoforming or thermogainage), this skin already incorporating the conductive circuit of the invention; and Figure 5 shows schematically a step of

  thermoforming of the skin of Figure 4.

  In FIG. 1 first of all, a shield is therefore seen represented

rear 1 of motor vehicle.

  This shield is a molded piece of rigid plastic (such as

than polypropylene).

  In the central outer part, it has a zone 3 defining

  the location of the police plate (rear license plate).

  In this case, on either side of this plate, there are two lighting strips 5 and 7 (light bulbs). Each strip or each bulb is connected to an electrically conductive circuit 9, 9 '

  integrated into the plastic body 11 of the part 1.

  Each circuit (only circuit 9 appears in FIG. 2) is defined by an electrically conductive deposit, here creating two elongated paths, such as 19 and 29, for the flow of current, each ending in a connection terminal 13, 15 ( or 13 ′, 15 ′ for the two paths of the circuit 9 ′; see FIG. 1), these terminals being connectable to an electrical source constituted by the battery 17 of the vehicle, by the intermediary for example of two traditional cables 21, 23, and other conventional electrical connection means. Electric bridging between the lamps is of course

  also possible, thus avoiding one of the circuits 9 or 9 '.

  For the realization of the conducting circuits, it is advised to resort to a technique of application by a felt-tip pen (even a brush) or of projection by gun, in the manner of a "painting". Moreover, the conductive product used forming the surface coating that can be seen in Figure 2 (paths 19, 29) consists in this case of an electrically conductive substance placed in a fluid or pasty binder. By way of example, BACKERS offers such a product under the name "conductive paint" (reference KJ12 51PC) with a diluent DSll,

  allowing a spray application.

  The conductive substance is frequently silver or

  copper, or other metal that is a good electrical conductor.

  To avoid inappropriate heating of the plastic 11, a heat shield 25 may have been previously placed on the surface (non-visible side) of the plastic body, at least in the environment of the

  area to receive the driver circuit.

  A waterproof protective layer 26 (such as a plastic coating or a varnish) can also cover the conductor (s) for them.

  protect from bad weather, if they are "outside".

  To make the conductive circuits on a rigid plastic part, such as part 11, a masking technique, or even "masking", may prove appropriate, in the event of application by

projection, in particular.

  FIG. 3 shows schematically a masking strip (for example made of flexible plastic) 27 having two elongated slots 31, 33 passing through its entire thickness and corresponding

  "hollow" at the two paths designated above 19, 29.

  Once the part 1 is molded (for example by injection), it will thus be possible to apply the protective mask 27 against a predefined zone (preferably a priori plane). We can then spray the conductive coating (conductive paint, as already mentioned), so that it is deposited in a thin layer on the plastic body 11, passing through slots 31, 33, according to the desired preset pattern (of course, the plastic 11 could have been at least locally pre-coated with

the heat shield 25).

  Thus, depending on the intensity of current to flow in the conductive circuit considered, we will create the paths that constitute it, with a thickness that can range from a few microns (jim) to a few tenths of a millimeter, for a width ranging from a few millimeters at

centimeter, approximately.

  In Figure 4, has been shown schematically the principle of an alternative embodiment which provides for integrating the conductive circuit with a thin plate or flexible plastic sheet adapted to be formed here over a

  more rigid plastic part (see Figure 5).

  This flexible plastic sheet, identified 35 in FIG. 4, thus presents in this figure two electrically conductive paths 39, 49, which have been deposited on the inner face 37 of the sheet, in the form of a "conductive paint" already mentioned. , with the use of a mask thanks

  to which the "negative" drawing of the circuit could have been drawn beforehand (see below

  before). In practice, the thickness of the electrical paths thus produced in

  the surface of the sheet 35 will be of thickness less than that of this sheet.

  Once the sheet locally covered with its conducting circuit, it is shaped on a rigid plastic insert shown at 41 in FIG. 5, where circuits 39 and 49 appear in excess thickness on the side of the

  face 37 for applying the sheet.

  Since it is a thermoforming or thermogainage, (the sheet can then be made of polypropylene), we will first heat it to raise its temperature, soften it and promote its shaping as well

as its adhesion to the insert.

  This softened "skin" 35, which is retained by pinching between the jaws 14a, 14b of a device for holding its ends, 14, is then brought closer to the insert in place on the mold 12 until it come and marry the outline 41a. Traditional air blowing techniques and

  can be used (channels 43, 45).

  Once the part is finished, the conductive circuits are then hidden under the skin 35 (possibly with a heat shield where necessary). In order for them to remain usable, their location has of course been previously identified or they have previously been locally connected to electrical connection terminals (not

  shown) for later connection to the battery (such as 17).

Claims (9)

  1. Plastic part presenting itself as a thin flexible sheet (35) adapted to be shaped hot and / or under pressure, characterized in that it comprises at least one electrically conductive circuit integrated into it and defined by a thin layer of electrically conductive material creating one or more elongated path (s) (39, 49) of current flow supporting a current intensity delivered by a motor vehicle battery and communicating with connectable connection terminals to such an electrical source.   2. Rigid molded plastic part (1) characterized in that it comprises at least one electrically conductive circuit (9, 9 ') integrated into it and defined by a thin layer of electrically conductive material creating one or more path (s) elongated current circulation (s) (19) supporting a current intensity delivered by a battery (17) of a motor vehicle and communicating with connection terminals (13,   , 13 ', 15') connectable to such an electrical source.   3. Part according to claim 1 or claim 2, characterized in that the integrated electrically conductive circuit consists   in a surface coating (9, 9 '; 39, 49) arranged in a pre-   established and comprising an electrically conductive substance with a binder fluid or pasty.   4. Method for obtaining a part according to claim 1, characterized in that: a flexible thin sheet is made of plastic material (s) suitable for being hot formed and / or under pressure, - Then the electrically conductive circuit (s) with a thickness less than that of the sheet are integrated into the surface of this sheet. 5. Method according to claim 4, characterized in that the circuit is integrated by surface deposition, on the plastic, having previously used a mask (27) to trace the circuit 6. Method according to claim 4 or claim 5, characterized in that one projects or is applied on the surface of the plastic of the part a product creating the conductive circuit, in the manner of a painting.   7. Method for obtaining a part according to claim 2, characterized in that: - a rigid plastic part (1) is molded, - and, in the mold or after molding, out of the mold, the path (s) (9, 9 ') of circulation of the electric current, integrating for this, towards the surface of the plastic material (11) of the part, at the   minus an electrically conductive circuit forming a thin layer.   8. Method according to claim 7, characterized in that: - one chooses to integrate the conductive circuit (9, 9 ') after molding, - and once the part thus molded, an electrically deposited substance is deposited on its surface conductive with a binder, following a drawing that   we have previously drawn on this surface.   9. Method according to claim 8, characterized in that the electrically conductive substance and its binder are presented as a   paint that is applied or projected onto the molded part (1).