FR2844386A1 - Electrical wire for making connections to batteries and similar applications on vehicles, comprises bundled strands of which only some have coating of electrically conducting material such as tin - Google Patents

Abstract

The spade connector (2) has a crimped portion (19) with an internal electrically conducting layer (25) which encloses bundled conductor strands (7). Alternate layers of the strands are individually covered with electrically conducting coating (27). The electrically conducting material is typically tin which on crimping prevents the ingress of air and/or water and retards corrosion Independent claims are also included for the following : 1) Electrical connector which uses the conductor which has only some strands coated with an electrically conducting material such as tin 2) Vehicle which uses the conductor which has only some strands coated with an electrically conducting material such as tin

Description

The invention relates to a wire of the type comprising an electrically sheath

  insulating and an electrically conductive core disposed in the sheath, the core comprising several electrically conductive strands

  which have coatings of an electrically conductive material.

  The invention applies in particular to motor vehicles, for example to the battery connection wires or to the wires used in the

  airbag systems.

  Generally, these wires are fixed to contact elements, such as lugs, which allow their electrical connection to devices.

  1 0 electrical such as batteries.

  The electrical connection between the strands of a wire and a lug is effected, for example, by crimping on the lug of the strands one end of the wire,

  the insulating sheath has been removed beforehand.

  Generally, the strands and the terminal are made of copper. All

  1.5 the strands and the terminal are coated with tin to improve the electrical connection.

  Indeed, since tin is softer than copper, it deforms under the forces resulting from crimping by enlarging the contact area between

each strand and the terminal.

  More precisely, this deformation of the tin forms

  2 0 beads on the edges of each contact zone.

  These beads protect the contact areas from oxidation by

  external agents, mainly oxygen and humidity. This makes it possible to limit over time the increase in the electrical resistance of the electrical connection between the wire and the terminal, which could result from the presence of electrically insulating copper oxides.

  In addition, the increase in the surfaces of the contact zones by the deformation of the tin makes it possible to reduce the current density and therefore to achieve a low electrical resistance in the electrical connection between the

wire and thimble.

  If the tinning of the strands makes it possible to obtain a good electrical connection and to guarantee its durability, such treatment of the strands turns out to be expensive. An object of the invention is to solve this problem by providing a wire of the aforementioned type which makes it possible to establish a satisfactory electrical connection.

  with a contact element and which is of reduced cost.

  To this end, the invention relates to a wire of the aforementioned type, characterized in that only some of the strands have coatings of said material.

  According to particular embodiments, the wire can comprise one or more of the following characteristics, taken alone or according to all technically possible combinations: - strands of a radially inner region of the core do not have any coating of said material, - none of the strands of the radially inner region has a coating of said material, - the radially outer region has a radial thickness of a single strand, - the strands of the core are ordered in concentric layers, and the layers are alternately layers consisting of strands having a coating of said material and layers consisting of strands do not

  having no coating of said material, and said material comprises tin.

  The invention further relates to an electrical connection assembly comprising a contact element and a wire fixed to the element

  contact, characterized in that the wire is a wire as defined above.

  The invention also relates to a motor vehicle, characterized in that it comprises at least one wire as defined above.

  The invention will be better understood on reading the description which

  will follow, given solely by way of example and made with reference to the appended drawings, in which: - Figure 1 is a partial schematic view from above of an electrical connection assembly according to a first embodiment of the invention, - Figure 2 is a partial section taken along line 11-Il of Figure 1 and illustrating the connection between the terminal and the end of the wire of the assembly of Figure 1, - Figure 3 is an enlarged schematic section illustrating the contact between a strand of the wire and the terminal of the assembly of FIG. 1, and - FIG. 4 is a view similar to FIG. 2 illustrating another

  embodiment of the invention.

  Figure 1 illustrates an electrical connection assembly 1 used

  in a motor vehicle, for example to connect its battery to the rest 10 of its electrical circuit.

  The assembly 1 comprises a contact element 2 in the form of a

lug and wire 3.

  Conventionally, the wire 3 comprises an outer sheath 4

  electrically insulating and an electrically conductive core 5 disposed in the sheath 4.

  The core 5 comprises several electrically conductive strands 7.

  The strands 7 are for example wound in successive concentric layers, only some of which, identified by the references 9 to 13, have

  have been shown in Figure 2.

  In the embodiment of Figures 1 and 2, the strands 7 of a

  same layer are joined so that the strands 7 constitute a strand.

  The sheath 4 has been removed from one end 17 of the wire 3 to expose the strands 7. These exposed strands 7 are mechanically fixed to the terminal 2 by

  crimping of two lugs 19 of the terminal 2.

  Thus, the legs 19 and the base 21 of the terminal 2 enclose the strands

  7 by exerting radial forces on them.

  The sheath 4 is also crimped onto the terminal 2 by two tabs 23.

  The strands 7 and the terminal 2 are conventionally made of copper.

  The terminal 2 is provided, on its face opposite the strands 7, with a coating 25 of tin visible in FIG. 2.

  As also illustrated by FIG. 2, some of the strands 7 are provided with an external coating 27 of tin while others do not. More specifically, the strands 7 of one layer out of two are provided

  of a coating 27. Thus, the strands 7 of the most radially outer layer 9 do not have a coating 27, all the strands 7 of the layer 10 have such coatings 27, the strands 7 of the layer 11 do not have no coating 27, all the strands 7 of the layer 12 have coatings 27 and the strands 7 of the layer 13 do not have any.

  In FIG. 2, the strands 7 and the coverings 25 and 27 have been

shown undeformed.

  In reality, the mechanical forces resulting from crimping 10 lead to deformations of the strands 7 and of the coatings 25 and 27.

  FIG. 3 illustrates the deformation of the coating 25 between a strand 7 of the layer 9 and a tab 19 of the terminal 2. As can be seen in this figure, the coating 25 is deformed by creating beads 29 on either side of the zone 31 of contact between the strand 7 and the covering 25. It will be noted that in FIG. 3, the strand 7 has been drawn undeformed and the tab 19 has

  been drawn flat to facilitate representation.

  As indicated above, the beads 29 contribute to increasing the surface of the area 31 and to protecting it against oxidation. Similarly, the coverings 27 of the strands 7 will deform in

  2 0 the core 5 under the forces resulting from the crimping.

  The strands 7 of a layer on two having coatings 27,

  there will always be a coating 27 of tin between two adjacent strands 7.

  Furthermore, the strands 7 of layer 9, even if they are not

  tinned, are in contact with the terminal 2 thanks to the coating 25 of the terminal 25 2.

  Thus, the electrical connection between the terminal 2 and the wire 3 is satisfactory and has a low electrical resistance. In addition, she is

  protected against oxidation thanks to coatings 25 and 27.

  However, the cost of the wire 3 and therefore of the assembly 1 is reduced, since only some of the strands 7 have been tinned.

  FIG. 4 illustrates a second embodiment in which

  only the strands 7 of the layer 9 have coatings 27 of tin.

  In this embodiment, the zones 31 of

  contact between the terminal 2 and the radially outer strands 7.

  It is in fact these contact zones 31 which are highly stressed on the one hand mechanically during the bending of the wire 3 near the terminal 2, and on the other hand chemically due to the oxidation which the condensation phenomena and the air flows charged with

  corrosive dust in the vicinity of terminal 2.

  Furthermore, it has been found that components of the materials used to form the insulating sheath 4 could, in the absence of coating 10 27, locally oxidize the surface of the strands 7 of the outer layer 9. The coatings 27 of the strands 7 of this outer layer 9 make it possible to avoid such oxidation and therefore to ensure a satisfactory electrical connection between

terminal 2 and wire 3.

  In other variants not shown, the strands 7 of the same layer may have coatings 27 and other strands of the same

diaper don't have one.

  Thus, one strand 7 out of two or three, for example, can have

  a coating 27 within the same layer or within the entire core 5.

  The above principles can be applied to wires 3 whose 20 strands 7 do not constitute a strand but constitute a twist, that is to say

  that the strands 7 are not joined within the same layer.

  More generally, these principles can also

  apply to strands 7 ordered differently.

  The wires 3 described above can be used to electrically connect other electrical devices than batteries. They may, for example, be electrical devices of airbag systems for which the embodiment of FIG. 4 will be

particularly well suited.

  Other contact elements than the terminals can be fixed 3 o to the wires 3, using other fixing methods than crimping. We will note

  that these contact elements are not necessarily tinned, in particular in the case where the most radially outer strands 7 are.

  More generally, other materials improving the electrical connections than tin can be used to constitute the

  coatings 25 and 27. One can thus use for example silver.

Claims (8)

  1. Wire (3) of the type comprising an electrically insulating sheath (4) and an electrically conductive core (5) disposed in the sheath (4), the core (5) comprising several electrically conductive strands (7) which have 5 coatings (27) of an electrically conductive material, characterized in that only some of the strands (7) have coatings (27) of said material. 2. Wire according to claim 1, characterized in that the strands (7) of a radially outer region (9) of the core (5) have coatings (27) of said material, and in that strands ( 7) of a radially inner region (10 to 13) of the core (5) do not have coating of said material.   3. Wire according to claim 2, characterized in that none of the strands   (7) of the radially inner region (10, 11, 12, 13) does not have a coating (27) of said material.   4. Wire according to claim 2 or 3, characterized in that the region   radially outer (9) has a radial thickness of a single strand (7).   5. Wire according to one of the preceding claims, characterized in that   that the strands (7) of the core (5) are ordered in concentric layers (9 to 20 13), and in that the layers are alternately layers made up   strands (7) having a coating (27) of said material and layers consisting of strands (7) having no coating (27) of said material.   6. Wire according to one of the preceding claims, characterized in that   that said material comprises tin.   7. Electrical connection assembly comprising a contact element (2) and a wire (3) fixed to the contact element (2), characterized in that the   wire is a wire according to one of the preceding claims.   8. Motor vehicle, characterized in that it comprises at least one   wire according to one of claims 1 to 6.