WO2007054554A1

WO2007054554A1 - Crimping method and crimped wire

Info

Publication number: WO2007054554A1
Application number: PCT/EP2006/068320
Authority: WO
Inventors: Roel Hellemans
Original assignee: Rh Innovation
Priority date: 2005-11-09
Filing date: 2006-11-09
Publication date: 2007-05-18
Also published as: FR2893193A1; FR2893193B1

Abstract

The invention relates to a crimping method in which a preformed barrel is deformed in such a way that the transverse cross section of the barrel (3) obtained has, at right angles to an axis (36) of compression of the barrel, a dimension, termed the obtained width (29), that is greater than or equal to 1.05 times the dimension, termed the initial width, that the transverse cross section of the preformed barrel has at right angles to the axis (36) of compression.

Description

CRIMPING METHOD AND SERTI WIRE

The invention relates to a crimping method in which a bundle of conductive strands is crimped onto a connecting piece by deforming a barrel of the connecting piece on the conductive strands by compression so as to obtain a barrel electrically connected to the conductive strands. .

The invention also relates to a crimped wire as obtained according to said crimping method.

Standards and certifications are known which lay down strict requirements as to the quality of crimping of crimped wires, in particular concerning crimped wires intended for on-board wiring, such as wiring of automobiles or aircraft. In particular, there are known such certifications or standards defining criteria of minimum quality of the electrical connection, made between the conductive strands of the electrical wire and a barrel of the connection piece, in particular under thermal stress.

Answering these criteria of crimp quality is a problem that arises particularly for producers of large volumes of small crimped threads, especially producers of crimped threads used in automobile wiring.

In this regard, automobiles are known whose wiring comprises up to 15,000 son crimped copper conductive strands and copper lugs. A slight change in the cost price of such crimped threads results in a significant change in large-scale production costs. In particular, it is, while meeting the criteria (standards, certifications) of the quality of the electrical connection crimped son products, to obtain a high rate of production son crimped from preformed pods having a small thickness, therefore presenting a low cost in terms of material (s) first (s). It should be noted that the thickness of the barrel should be interpreted, here as in what follows, as the smallest distance between the inner wall of the barrel in contact with the strands of the multi-stranded conductor and an outer wall of the barrel opposite to the internal wall. Crimping presses used for the production of son crimped copper conductive strands and copper lugs are known, in particular, such presses are known operating by compression of a preformed lug between a crimping anvil and a crimping die. .

In particular, known anvils and dies, according to the type of lug used, or at least according to the type of preformed lug used, to deform the preformed lug so that it has a crimping barrel having a section transverse straight having dimensions recommended by each manufacturer of lugs. This recommended conformation would indeed provide a mechanical connection and an electrical connection of optimal quality with respect to the amount of raw material used and the cost of performing the corresponding crimping process.

Lugs, presses, crimping dies and crimping anvils used together to produce crimped yarns at a high crimp rate are known. The invention aims at the production of crimped son quality in accordance with the requirements of industrial applications when the son implement a conductive material whose thermal expansion coefficient is greater than the coefficient of thermal expansion of the material crimped elements.

In particular, the invention aims to reduce a portion of the cost of crimped son attributable to the cost of a conductive material constituting at least partly crimped son. In particular, the invention aims to use a more economical conductive material, and without any unacceptable increase in the cost related to the execution of crimping in the factory.

In particular, the invention aims to provide such crimped son without requiring crippling modifications of existing production facilities. Furthermore, the invention aims to provide such crimped son without decreasing the crimping rate of existing production facilities. In particular, the invention aims to reduce the cost price of these electrical son without decreasing the quality and durability of the electrical connection of these electrical son with devices to provide wiring, including existing electromechanical devices and embedded electronics. In particular, the invention aims at providing such crimped threads whose crimping quality continues to meet the requirements, for example of normative requirements or certifications, specific to the industrial use to which the crimped wire is intended, such as for example automobile wiring. In particular, the invention aims to provide such crimped son having a durable quality crimp face heat stress under a temperature range of normal use crimped son.

To achieve this result, the invention proposes a crimping method in which:

- A bundle of conductive strands is inserted into a barrel of a connecting piece, the strands being substantially parallel to a longitudinal axis of the barrel;

- The connecting piece consists essentially of a first conductive material; the conductive strands consist essentially of a second conductive material having a coefficient of thermal expansion greater than that of the first material; the barrel is plastically deformed by compression along an axis on the conductive strands to maintain the bundle of conductive strands and provide electrical continuity between said bundle of strands and said barrel, and; the barrel is deformed so that a cross section of the barrel, perpendicular to the longitudinal axis of said barrel, has a dimension perpendicular to the compression axis, called the obtained width, between 1.75 times and 2.40 times a dimension in the direction of the compression axis, said obtained height. Preferably to obtain crimped wires closer to an optimum in terms of electrical characteristics, the width obtained after crimping according to the section of the wire used is between 1.85 times and 2.30 times the height obtained. In order to achieve implementation of the process without questioning the currently used methods or tools implemented with these current methods, the barrel is: a. preformed so that it has a dimension before compression, in a direction perpendicular to the longitudinal axis to the barrel and perpendicular to the compression axis, said initial width of the preformed barrel, corresponding to an inner dimension of the barrel along said width initial substantially equal to the average diameter of the bundle of conductive strands, then; b. deformed by compression, according to at least one imprint of a matrix in which the barrel is placed, said fingerprint comprising two walls disposed facing one another and separated by a spacing distance, along the initial width of the is preformed, greater than 1, 05 times and preferably less than 1.30 times the initial width of the preformed drum, and; vs. deformed by compression at least to a compression such that walls of the compressed barrel come into contact with the walls of the impression of the matrix.

The invention thus makes it possible to use conductive strands consisting of a second material whose cost price is lower than the cost price of the first material. The invention makes it possible to use such conductive strands without this producing a drastic reduction in the quality of crimping performed and the reliability of this crimping in the face of heat stress.

In particular, the invention makes it possible to prevent plastic deformation of the drum from occurring, under normal conditions of use of the electrical wire under a constraint resulting from the difference in expansion between this shaft and the conductive strands, following an increase in the temperature of the crimped wire. Such deformation is indeed likely to result in a decrease in the quality of the electrical contact between the conductive strands and the drum after the cooling of the first and second materials. In particular, the electrical wire can be obtained by means of a known model of preformed connection piece or, at least, of a known type of preformed connection piece made of the first material. Thus, the manufacture of an electrical wire according to the invention is capable of being able to at a high rate of production by means of crimping presses traditionally used for the model or known type of preformed connection piece.

Advantageously and according to the invention, the first material is mainly made of copper.

Advantageously and according to the invention, the second material is mainly made of aluminum.

Advantageously and according to the invention, the preformed drum has a thickness of less than 450 microns. Advantageously and according to the invention, the preformed barrel is an open type barrel having a transverse cross-sectional profile comprising:

- a curved and convex soul,

- Two fins disposed on either side of the core and extending from the core, substantially parallel and facing one another. Advantageously and according to the invention, the process is characterized in that:

the preformed barrel has a thickness of less than 250 μm,

the conductive strand bundle has more than 8 conductive strands each having a diameter of at least 200 μm. Advantageously and according to the invention, the connecting piece is a terminal.

Advantageously and according to the invention:

the preformed drum is inserted into the impression defined by the die before being deformed by compression against this impression, when it is inserted into the impression, the preformed drum is interposed, in the width dimension of its cross-section transverse, between said two walls of the footprint.

Advantageously and according to the invention:

the preformed drum is deformed by compression between the impression of said matrix, called the first matrix, and a cavity defined in a second matrix,

the imprint of the second matrix has a dimension, in the direction of the initial width of the preformed barrel, equal to a clearance close to the distance spacing the walls facing the impression of the first matrix so as to be able to engage between the walls of the impression of the first matrix.

The invention also relates to a process characterized in combination by all or part of the characteristics mentioned above or below and a crimped wire having such characteristics.

Other characteristics, objects and advantages of the invention will appear on reading the following description which refers to the appended figures in which: FIG. 1 is a schematic perspective view of an electrical wire according to a preferred embodiment of the invention,

FIG. 2 is a diagrammatic perspective view of a section of conductive wire with insulating sheath and of a preformed lug used for the production of an electric wire according to the preferred embodiment of the invention, FIG. is a diagrammatic cross-sectional view, before a pressing operation, of a crimping anvil defining an indentation in which conductive strands of the conductor wire section of FIG. 2 and a preformed barrel of the preformed lug of FIG. arranged,

FIG. 4 is a diagrammatic cross-sectional view of the anvil, of the conductive strands of FIG. 3 and of the barrel obtained following a deformation of the preformed barrel of FIG. 3 resulting from a compression of this pre-formed barrel between the anvil and a matrix,

FIG. 5 is a table comparing the main dimensional characteristics of lugs after their crimping on electrical wires of a first gauge,

FIG. 6 is a table comparing the main dimensional characteristics of lugs after their crimping on electrical wires of a second gauge.

FIG. 7 is a graphic illustration of crimping tests presented in the table of FIG. 5,

Fig. 8 is a graphical illustration of crimping tests shown in the table of Fig. 6. It should be noted that, for the sake of clarity, scale and proportions are not respected in Figures 1, 2, 3 and 4.

In a preferred embodiment of an electrical wire according to the invention, the electrical wire is formed of a section 11 of insulating sheath wire 9 and a tinned copper lug 2 mounted at one stripped end of section 11. of conductive wire.

The electrical wire of this preferred embodiment of the invention is particularly suitable for the production of automobile wiring.

In this embodiment, the tinned copper lug 2 forms a preformed connection piece according to the invention. In addition, tinned copper forms a first material according to the invention.

In the preferred embodiment of the invention, the section 11 of conductive wire comprises a bundle 13 strands 6 conductive aluminum alloy optionally plated with a layer of a protective material such as a copper layer. For example, the strands may be made of an aluminum alloy marketed by the company PECHINEY (Paris, France) under the name CONDUCTAL ALUFLEX 131050 Al Fe Mg. In the preferred embodiment of the invention, this aluminum alloy forms a second material according to the invention. The conductive wire may also comprise other strands such as for example one or more steel strands for mechanical reasons.

Preferably, this alloy of conductive strands 6 is an annealed alloy.

It should be noted that the conductive strands according to the invention may be formed of any other suitable electrically conductive material, the method being applicable when said material has a coefficient of thermal expansion greater than the first material. In particular, the second material may be a multilayer material, an alloy, a composite material or the like. For example, the conductive strands may be strands (not shown) of copper-clad aluminum, so-called CCA strands. In this case, the combination of aluminum and copper forms a second material according to the invention.

In the preferred embodiment of the invention, the conductive section of the bundle 13 of strands 6 is greater than 0.2 mm ² . For example, a stretch 11, said section of 0.5 gauge, conductive wire having a nominal conductor section of 0.5 mm ² is used. In another example, a section 11, said section 11 of 0.35 caliber, insulating conductor wire having a nominal conductor section of 0.35 mm ² is used. The section 11 of caliber 0.5 and the section 11 of caliber 0.35 comprise in these examples respectively 12 and 9 strands 6 conductors each having a nominal diameter of 200 microns.

In general, the invention relates to electrical wires of small conductive sections, that is to say less than or equal to about 1 mm ² , and comprising several conductive strands whose cross section is between 150 and 600 μm.

In a preferred embodiment of the invention, the electric wire is obtained by crimping the bundle 13 of conductive strands and a preformed lug 4 forming, following a crimping process in which the preformed barrel 5 is deformed on the strands. conductors 6 by compression, the terminal 2 of the electric wire.

In another mode, not described, of implementation of the method, the connection piece 2 and in particular the part 3 to be crimped on the strand bundle 13, is not or is only partially preformed and undergoes a preforming step during the crimping operation.

The preformed lug 4 has a core 12 extending in a longitudinal direction 31 of the lug 4 preformed. The core 12 has a profile, in a cross section of the lug 4 preformed curved shape. The profile of the core 12 is regular in the longitudinal direction of the lug 4 preformed.

The preformed lug 4 has a connection termination of the preformed lug 4 located at a first longitudinal end of the lug 4 preformed. This connection termination is formed by two tabs 10 extending one opposite the other and whose profiles in a cross section (not shown) of the lug 4 preformed, each extend one end of the curved profile of the 12 core at the termination connection. The preformed lug 4 further has a branching termination 14 located at a second longitudinal end of the preformed lug 4.

Preferably, the termination 14 of connection already has a definitive functional form. In particular, the termination 14 of the branch may be in the form of a cylindrical sleeve, of annular shape, in the form of a rectangular plug or the like. Moreover, nothing prevents the termination 14 is provided with means (such as lugs, punches etc.) to maintain this termination 14 in a branch position. The lug 3 is of the type 14 terminating branch in the form of cylindrical sleeve.

Obviously, nothing prevents the final shape of the branch termination from being formed by means of a suitable forming process that can be carried out previously, simultaneously or subsequently, with the crimping process described hereinafter. In addition, the preformed lug 4 of the preferred embodiment of the invention comprises, disposed between the termination 14 and the connection termination, two fins 15 extending opposite one another. The profiles of these fins 15 along the transverse cross section of the preformed lug 4 each extend one end of the curved profile of the core 12.

These fins 15 form, with the core 12 of the lug 4 preformed, a preformed barrel 5 of the preformed lug 4 disposed between the connection termination and the termination 14 and extending in the longitudinal direction 31 of the lug 4 preformed. In practice, the tinned copper pre-formed lug 4 of the preferred embodiment of the invention may be a prefabricated commercial lug ready to be crimped.

Crimping is traditionally performed with this type of lug preformed by compression of the barrel 5 preformed along a compression axis 36 extending substantially parallel, or at least generally parallel to the fins 15 of the lug 4 preformed before deformation.

An electric wire obtained by means of such a pre-formed lug 4 is particularly adapted to the economic and technical constraints related to the realization of automobile wiring, application for which the use of this type of preformed lug 4 is already known. In particular, the use of a tinned copper pre-formed lug 4 makes it possible to ensure the compatibility of the electric wire obtained with the tin connection terminals, which are provided with known electronic and electromechanical equipment, embedded on board automobiles. In particular, it makes it possible to avoid galvanic corrosion at the contact of a tin terminal with the lug 2 of the electric wire obtained.

In addition, the use of a known lug saves the design of a new specific preformed lug, and facilitates the supply at lower cost and in large quantities of these lugs preformed.

In the preferred embodiment of the invention, the crimping is performed during a pressing of the preformed lug 4 described below.

During the pressing described below, the tongues 10 are bent around one end of the insulating sheath 9 to form clamping flanges of the sheath 9 so as to hold the lug 2 securely on the section 11.

In the preferred embodiment of the invention, a device (not shown) for supplying sections 11 of conductive wires and a crimping press (not shown) are used for pressing the identical preformed lugs 4 connected together and which are adjacent to each other by forming a rosary (not shown) of preformed pods 4.

The crimping press preferably comprises a tool holder (not shown) adapted to be able to carry a crimping die 20. Preferably, this tool holder comprises means for removably attaching crimping dies adapted to allow such a removable attachment.

In addition, the press comprises a sole (not shown) rigidly attached to a frame of the press. This sole comprises removable attachment means, crimping anvils adapted to allow such a removable attachment to this sole.

In addition, the press includes:

automatic means (not shown) for driving the chain of pods 4 preformed, adapted to successively dispose of the lugs 4 preformed of the rosary one by one on an impression of the crimping anvil carried by the sole,

- means (not shown) for driving the tool holder adapted to repeatedly drive the tool holder and the crimping die towards the anvil and the sole so as to:

. to successively deform by compression one by one between the anvil and the die, the lugs 4 preformed arranged to rest on the impression of the crimping anvil,

. to dissolve the rosary successively one by one these lugs 4 preformed.

In addition, the feeder 11 of sections of conductive son is adapted to automatically cut, at predetermined length, the sections 11 of conductive son from a coil of conductive wire. This feed device is further adapted to automatically strip one end of each section 11 of conductive wire.

Moreover, the device for supplying sections 11 of conducting wires is adapted, in synchronization with the drive means of the tool holder of the press, to arrange successively one by one each of the stripped ends 13 of the sections 11 of conducting wire. longitudinally in the preformed barrel 5 of the preformed lug 4 disposed on the impression of the anvil so as to crimp, under the repeated drive of the tool holder, each of these ends 13 stripped with a lug.

The press, excluding the matrix 20 and the anvil 21, and the device for supplying sections 11 of conducting wires may be known traditional devices.

In practice, a machine marketed under the name "GAMMA 255" by KOMX AG (Dierikon - Switzerland) can produce the crimping press and the feed device in sections of conductive son described above. In the preferred embodiment of the invention, an anvil 21 is used comprising:

a housing (not shown) adapted to receive the connection termination of the preformed lug 4, a housing (not shown) adapted to receive the termination 14 of connection of the preformed lug 4,

a housing of the preformed barrel 5 located between the housing of the connection termination and the housing of the termination terminal 14.

The anvil 21 forms a first matrix according to the invention. The walls of the housing of the preformed barrel 5 define a crimping recess according to the invention.

The transverse cross section of the impression of the anvil 21 at the housing of the barrel 5 is illustrated in FIG.

In the preferred embodiment of the invention, the housing of the preformed barrel 5 forms a groove of regular cross section. This housing is delimited by two walls 25 extending substantially parallel to each other on either side of a bottom of the groove. The bottom of the housing of the preformed barrel 5 has, in the preferred embodiment of the invention, a groove 37 extending longitudinally in an axial direction (not shown) of the groove. The core 12 of the level of the preformed drum 5 rests in this groove 37 following the insertion of the preformed lug 4 into the impression of the anvil 21. This groove 37 facilitates an arrangement of the preformed barrel of the lug 4 preformed in the impression of the anvil 21 according to which the fins 15 are arranged generally parallel to the walls 25 of the impression of the anvil 21.

The anvil 21 forms a first matrix according to the invention. It should be noted that the first matrix according to the invention can be made by means of a machined part, or of several machined parts then assembled, defining a footprint having a spacing distance according to the invention.

In the preferred embodiment of the invention, a matrix 20 is used comprising a portion, called the impression portion, defining a crimping impression intended to print a compressive force on the preformed drum 5 by engaging in the housing. preformed drum 5 under the drive towards the bottom of the groove, the die 20 by the tool holder.

The matrix 20 forms a second matrix according to the invention. This imprint portion has a regular cross section in the axial direction of the groove in the form of two arches 26 joined side by side. The crimping impression of the matrix 21 is thus shaped so as to bend the fins 15 of each preformed lug 4 disposed in the cavity of the anvil 21, towards the inside of the preformed barrel 5 of the preformed lug 4.

This matrix 20 may further comprise a portion (not shown) of form conjugated to that of the housing of the connection termination so as to curl the tabs 10 on the sheath 9 of the section. In addition, this matrix 20 may comprise a portion (not shown) of shape conjugate to the housing of the branch termination to carry out, if necessary, the forming of this termination.

In the preferred embodiment of the invention, the matrix 20 is brought closer, during the crimping operation, to the anvil 21 along an axis 36, orthogonal to an axial direction of the groove and substantially parallel to the walls 25 of the groove. the impression of the anvil 21 so as to exert compression of the barrel 5 preformed along this axis 36. During this compression, the preformed barrel 5 deforms to come into contact with the conductive strands 6 by gripping the strands 6 conductors. Furthermore, during this compression, the transverse cross section, that is to say in a plane substantially perpendicular to the longitudinal axis 31, of the preformed drum 5 is deformed in a direction perpendicular to the axis 36 so that the barrel 3 obtained, following compression, extends in this direction perpendicular to the axis 36, said direction in width, from one of the walls 25 opposite to the other wall 25 opposite. In the preferred embodiment of the invention, the facing walls 25 are spaced apart from each other by a spacing distance 27 adapted so that the barrel 3 obtained has a dimension in the width direction, said width 29 obtained, at least 1, 05 times the size, called initial width 17, of the drum 5 preformed in the width direction before compression deformation.

In the preferred embodiment of the invention, an adjustment of the stroke in which the tool holder brings the matrix 20 closer to the anvil 21, to print a compressive force on the preformed lug 4, is realized in order to achieve a crimping providing an optimal quality of mechanical connection and electrical connection between the barrel 3 obtained and the strands 6 conductors. This adjustment of the travel of the tool holder can be achieved in a known manner according to a control method in which the length of a drive arm (not shown) of the tool holder, actuated by a flywheel (not shown) is modulated. by means of shims (not shown) interposed between the drive arm and a stop of the tool holder so as to change the penetration depth of the die 20 in the cavity of the anvil 21 during crimping. In practice, several crimping tests are carried out and the adjustment, ie the thickness of the shim, making it possible to obtain crimped wires whose mechanical connection by crimping has a maximum tensile strength, that is to say when the curve tensile strength function of the thickness of the shim passes through a maximum, is retained.

The invention makes it possible to obtain an electrical wire comprising at least one connection by crimping a bundle of conductive strands of the electric wire with a barrel of a connecting part of the electric wire, the barrel being constituted by a first conducting material and the crimped connection providing an electrical connection between the conductive strand bundle and the barrel, in the electrical wire according to the invention: the conductive strands consist of a second conductive material having a coefficient of thermal expansion greater than that of the first material,

- The barrel has a cross sectional profile having a width to height ratio greater than 1.75 and less than 2.4 and preferably greater than 1.85 and less than 2.2.

Preferably, in the electrical wire obtained by means of the invention, the barrel has an average thickness of less than 450 μm.

Preferably, in the electrical wire obtained by means of the invention, the barrel has an open cross-sectional profile having two curved lateral portions forming two fins extending generally symmetrical with respect to each other since a portion median, called soul, of the profile. Preferably, in the electrical wire obtained by means of the invention, the barrel has an average thickness of less than 250 μm and contains more than 8 conductive strands each having a diameter of at least 200 μm.

Comparative tests of the quality of the electrical connection of crimped wires obtained from lugs 4 preformed pod model of the exemplary preferred embodiment of the invention and having pods having different widths obtained after crimping, allowed to note an improved quality of the electrical connection for the electric son with drums 3 whose width is greater than the initial width of the barrel 5 preformed, width recommended by the manufacturers of lugs as to be the width of the barrel after crimping.

In the example used to describe a preferred embodiment of the invention, the initial width 17 of the preformed barrel 5 is 1.44 mm and the width 29 obtained from the barrel 3 obtained is 1.64 mm for an electric wire. 0.5-gauge section, or 1.57 mm for 0.35 gauge wire. To do this, the spacing distance 27 may be 1.64 mm in the case where the electrical wire is 0.5 gauge section. In addition, the spacing distance 27 may be 1.57 mm in the case of a 0.35 gauge wire.

The standard issued by the Deutsche Institut fur Normung (Berlin, Germany) under the reference DIN 60068-2-14 of the automotive industry defines a test, called durability test against heat stress, to verify the durability of an electrical connection set against repeated temperature variations. This test involves performing a thermal stress test of 144 cycles each composed of a heating phase of 30 minutes, during which the crimped wire is gradually heated from -40 degrees Celsius up to 125 degrees Celsius, then a 30-minute phase, during which the electric wire is gradually cooled from 125 degrees Celsius to -40 degrees Celsius.

Crimped wire tests durability test against thermal stress if electrical resistance of crimped wire after heat stress test has not increased by more than 0.5 mOhms compared to a value measured before the stress test thermal. Indeed, a loss of the conductivity of the electric wire results most often from a decrease in the quality and the electrical connection at the crimping. Such a reduction in the quality of the electrical connection may occur due to a plastic deformation of the terminal resulting from a too large difference between the thermal expansion of the bundle 8 of conductive strands 6 and that of the terminal 2. FIG. is a summary table of an evaluation of the quality of the crimping of 0.35 gauge electrical wires 11 and a preformed lug 4 of the model of the preferred embodiment of the invention.

This table makes it possible to make a comparison of the quality of the crimping of electrical wires, according to different spacing distances 27, each being obtained by means of:

a set, said set A, of an anvil and a matrix conjugate,

one of several sets, called sets B, C, D and E, of an conjugate matrix and anvil according to the preferred embodiment of the invention.

The anvil and the matrix of the assembly A are similar to those of the preferred embodiment of the invention except, in particular, in that the crimping impression of the anvil of the assembly A has two walls in viewed spaced apart by a spacing distance equal to a clearance close to the initial width of the preformed barrel 5 so as to be able to interpose the preformed barrel 5 between these two walls. This set A corresponds to the case of crimping according to the prior art and according to the recommendations of suppliers of crimp connection parts.

The crimping recess of the anvil of the assembly B has a spacing distance equal to 1.1 times the initial width 17 of the preformed barrel.

The crimping indentation of the anvil of the assembly C has a spacing distance equal to 1, 15 times the initial width 17 of the preformed barrel. The crimping recess of the anvil of the assembly D has a spacing distance equal to 1.2 times the initial width 17 of the preformed barrel.

The crimping recess of the anvil of the assembly E has a spacing distance equal to 1.3 times the initial width 17 of the preformed barrel. This comparative test is carried out by means of the same crimping press set for each of the sets A, B, C, D and E according to the previously mentioned adjustment method.

In this table: a column 101 comprises, for each set A, B, C, D and E, the spacing distance of the anvil expressed as a multiplicative factor of the initial width 17 of the preformed drum,

a column 102 comprises, for each set A, B, C, D and E, the width obtained of the transverse straight sections of the drums obtained; a column 103 comprises, for each set A, B, C, D and E, measured height of the transverse straight sections of the casks obtained,

- A column 104 comprises for each set A, B, C, D and E, the width-to-height ratio of cross sections of the barrels obtained. Fig. 6 is a summary table similar to that of Fig. 5 for an evaluation of the crimping quality of electrical wires obtained using the same anvil and die assemblies A, B, C, D, E of Fig. 5 as well as from sections 11 of 0.5-gauge conductive wires and preformed lugs 4 of the preferred embodiment of the invention. In this table :

a column 201 comprises, for each set A, B, C, D and E, the spacing distance of the anvil expressed in the form of a multiplicative factor of the initial width 17 of the preformed drum,

a column 202 comprises, for each set A, B, C, D and E, the width obtained of the transverse straight sections of the drums obtained,

a column 203 comprises, for each set A, B, C, D and E, the measured height of the transverse straight sections of the drums obtained,

a column 204 comprises, for each set A, B, C, D and E, the width-to-height ratio of the transverse straight sections of the drums obtained.

The results of the tests corresponding to the tables of FIGS. 5 and 6 are presented generally in FIGS. 7 and 8 respectively. FIG. 7 illustrates the test results for the configurations of the table of FIG. 5 for the wires of 0.35 mm 2 of conducting section. It shows on the ordinates of the graph the minimum and maximum values of the variation of the electrical resistance ΔΩ (in milliOhm) of the crimped wire measured before and after the complete thermal cycle recommended by the DIN standard mentioned above.

The values of variation of electrical resistances are measured for

20 test samples, each comprising two crimps, for each crimping configuration, ie for each set A, B, C, D, E, for copper-copper lug pairs, marked Cu in the figure, and for the pairs aluminum wire - copper lug, marked Al in the figure.

The results are presented with the values of column 104 of the table of FIG. 5 on the abscissa scale, that is to say the value of the ratio between the width and the height of the barrel after crimping.

FIG. 8 illustrates the results of the tests in the same manner for the configurations of the table of FIG. 6 corresponding to the wire of 0.5 mm 2 of conductive section.

All 0.35-gauge electrical wires obtained from Sets B and C meet the DIN 60068-2-14 test criterion.

Virtually all of the 0.35-gauge electrical wires obtained by means of the D package meet the DIN 60068-2-14 test criterion, except for a few electrical wires with a resistance increase of approximately 1 mOhm. beyond the threshold of 0.5 mOhms.

On the contrary, about half of the electrical wires obtained from assembly A in accordance with current recommendations do not meet the DIN 60048-2-14 standard test.

It is also noted that the quality of the electrical son is degraded for crimping made with the assembly E.

Thus, as illustrated in FIGS. 7 and 8, it is possible, for example by reading the interpolation curves between the values tested, to determine extreme values 105, 106, 205, 206, respectively, of the width-to-width ratio. crimped post height for which the crimped wires meet the conditions required by the standard when said ratio is between 107 and 207 between the said extreme values and for which the quality with regard to the conditions required by the standard is uncertain when said ratio is not in the range 107, 207 respectively.

Thus, for the wire of 0.35 mm 2, the extreme values of the ratio width 29 to height 30 of the barrel after crimping are:

- 1.80 for the lower value 105 and - 2.10 for the higher value 106.

For the 0.50 mm2 wire, the extreme values 205 and 206 are respectively 2 and 2.4.

For the area of the small sections considered, ie less than or equal to 1 mm2, the optimum value of deformation of the barrel varies slightly with the section of the wire considered. The ratios of the width of the barrel after crimping, substantially equal to the spacing distance 27 of the walls 25 of the cavity of the first matrix 21, to the initial width 17 of the barrel 5 before crimping, ie the ratios corresponding to the values of columns 101 and 201 of the tables of FIGS. 5 and 6 to be retained are therefore substantially:

- 1, 05 for the lower value and - 1, 30 for the higher value.

In the preferred embodiment, the drum 3 obtained comprises, after crimping, advantageously a transverse cross section having a width-to-height ratio of 1.93 for an electric wire with a gauge size.

0.5 or a width-to-height ratio of 1.85 for 0.35 gauge electrical wire.

In the preferred embodiment of the invention, the width 29 of the barrel obtained for a 0.5 gauge section electrical wire corresponds substantially to 1, 14 times the initial width 17 of the barrel.

In addition, the width 29 of the barrel obtained for a section electric wire, 0.35 caliber corresponds substantially to 1, 09 times the initial width 17 of the barrel. In this example, the bottom of the housing of the preformed barrel of the sets A, B, C, D and E comprises, disposed on either side of the groove 37, two flat portions extending the bottom of the barrel between each wall 25 and the flute 37 from the bottom of the barrel housing. Each of these flat portions 39 forms with the corresponding wall 25 a clearance space in which extends, until occupying the space at the end of pressing, a lateral portion of the barrel 5 preformed.

In the case of the traditional assembly A, each of these two clearance spaces is delimited by the corresponding flat portion 39 and an outer surface of the core of the preformed barrel extending opposite the flat portion and the wall 25. corresponding.

Preferably, for a known type or design of preformed lugs, the flat portions of the housing of the preformed barrel of anvils according to the invention may be of the same size, in a transverse cross section, as a similar conventional matrix adapted for this purpose. preformed pod. In addition, the groove preferably has the same depth as that of the traditional matrix. To do this, the curvature of the cross section of the flute 37 may be slightly flared to obtain an anvil according to the preferred embodiment of the invention. In a variant, nothing prevents the curvature of the groove 37 from being preserved by modifying the transverse dimension of the flat portions 39 and / or by modifying the depth of the groove 37.

Alternatively (not shown), the die carried by the tool holder may be provided with two facing walls, functionally similar to the walls of the anvil of the preferred embodiment of the invention, separated from one another. other in the direction of the initial width of the preformed drum at a nominal distance greater than or equal to 1.05 times the initial width 17 of the preformed drum 5 and preferably less than or equal to 1.30 times the initial width 17 of the preformed drum . In this case, the preformed barrel 5 may be deposited on the impression of a conjugate anvil of the matrix, this impression possibly comprising a groove and flat portions similar to those of the anvil 21 of the preferred embodiment of the invention. invention, but be devoid of opposite walls, functionally similar to those of the anvil 21 of the preferred embodiment of the invention.

It should be noted that the spacing distance 27 must then be interpreted as the distance separating, in the direction of the initial width 17 from the preformed drum 5 as defined before the compression of the preformed drum 5, the two walls facing each other. the imprint of the matrix when the matrix has reached the end of its course bringing it closer to the anvil.

Such a matrix forms a first matrix according to the invention while the conjugate anvil of this matrix forms a second matrix according to the invention.

Such an anvil and such a matrix are particularly suitable for a high rate of production using known presses.

It should be noted that, in addition to the aforementioned advantages, the invention makes it possible to use the same set of matrix and anvil to produce alternately, without changing the setting of the press, and from the same preformed pod model mainly. made of copper, electrical son according to the method of the invention and electrical son comprising, such as in traditional crimped electrical son, strands mainly made of copper. Indeed, observations have been able to demonstrate that the copper strand electrical wires thus obtained have, like the electrical wires obtained according to the method of the invention, a satisfactory electrical connection quality. In particular, these electrical strands with copper strands, like the electrical wires obtained according to the method of the invention, meet the criterion of the standard DIN 60068-2-14 described above. Alternatively (not shown), an electric wire according to the invention may comprise a connection piece other than a thimble 3 open. In particular, the electric wire can be obtained by means of a cylindrical preformed barrel lug of circular cross section. In this case, the initial width of the preformed lug 5 corresponds to the diameter of an outer wall of the cross section of the preformed barrel. The width obtained is also interpreted as the largest dimension of the cross section of the barrel obtained after crimping. The height is interpreted as the dimension of the straight section of the barrel obtained in the direction perpendicular to the width obtained. In addition, the connecting piece may be other than a terminal, or any type of room for establishing an electrical connection with a conductor wire by means of a mechanical connection by crimping the conductive wire. By way of example, the connection piece may be a connection terminal integral with an electrical, electronic or electromechanical device, the electrical connection of which is achieved by crimping a bundle of conductive strands in a crimping barrel of this terminal.

Claims

Crimping method in which: - a bundle of strands (6) conductors is inserted into a barrel (5) of a connecting piece, the strands (6) being substantially parallel to a longitudinal axis (31) of the barrel (5) ; - The connecting piece consists essentially of a first conductive material; - the strands (16) conductors consist essentially of a second conductive material having a coefficient of thermal expansion greater than that of the first material; the barrel (5) is plastically deformed by compression along an axis (36) on the conductive strands (6) to maintain the bundle of conductive strands (6) and provide electrical continuity between said bundle of strands and said barrel; characterized in that the barrel (5) is deformed so that a cross section of the barrel (3), perpendicular to the longitudinal axis (31) of said barrel, has a dimension perpendicular to the compression axis (36), so-called obtained width (29), between 1.75 times and 2.40 times a dimension in the direction of the axis (36) of compression, said obtained height (30). The method of claim 1 wherein the resulting width (29) is from 1.85 times to 2.20 times the obtained height (30). The method of claim 1 or claim 2 wherein the shank (5) is: d. preformed so that it has a dimension before compression, in a direction perpendicular to the longitudinal axis (31) to the barrel (5) and perpendicular to the axis (36) of compression, said initial width (17) of the barrel preformed, corresponding to an inner dimension of the barrel (5) along said initial width substantially equal to the average diameter of the bundle of conductive strands (6), then; e. deformed by compression, according to at least one imprint of a matrix (21) in which is placed the barrel (5), said imprint comprising two walls (25) arranged opposite one another and separated by a distance spacing (27), according to the initial width (17) of the preformed drum, between 1.05 times and 1.30 times the initial width (17) of the preformed drum, and; f. deformed by compression at least up to a compression such that walls (15) of the compressed barrel (5) come into contact with the walls (25) of the cavity of the matrix (21). -Procédé according to one of claims 1 to 3, wherein the shaft (5) is a preformed barrel of open type having a cross sectional cross section comprising: a. a curved and convex core (12), b. two fins (15) disposed on either side of the core (12) and extending from the core (12), substantially parallel and facing one another. Method according to one of the preceding claims wherein the barrel (5) is made of a first material mainly made of copper. Method according to one of the preceding claims wherein the strands (6) are made with a second material mainly made of aluminum. Method according to one of the preceding claims wherein the shaft (5) is made with a thickness (16) less than 450 microns. Method according to one of the preceding claims, wherein: a. the barrel (5) is made with a thickness (16) of less than 250 μm; b. the bundle (13) of conductive strands (6) comprises more than 8 conductor strands (6) each having a diameter of at least 200 μm. Method according to one of the preceding claims wherein the piece (2) of connection is formed into a lug (14). Crimped wire having a bundle (13) of conductive strands (6) based on a first electrically conductive material having a conductive section equal to or less than 1 mm2 and at least one connecting piece (2), made of a second electrically conductive material having a coefficient of thermal expansion less than the coefficient of thermal expansion of the first conductor, crimped by compression of a shank (5) of said connection piece on the bundle (13) of strands (6) characterized in that the barrel (5) after compression has a dimension (30) in a direction (36) of compression, said height of the crimped barrel, and a dimension (29) in a direction perpendicular to the direction of compression (36). ) and perpendicular to a direction (31) substantially along a longitudinal axis of the shank (5), called the width of the crimped barrel, such that the ratio of the width (29) of the barrel crimped by the height (30) of the crimped barrel is included between 1.75 and 2.40. The crimped wire of claim 10 wherein the ratio of the width (29) of the crimped barrel by the height (30) of the crimped barrel is between 1.85 and 2.20. A crimped wire according to claim 10 or claim 11 wherein the first material of the conductive strands (6) consists essentially of an aluminum alloy. Crimped wire according to one of claims 10 to 12 wherein the second material of the connecting piece (2) consists essentially in the region of the barrel (5) by a copper-based alloy. Crimped wire according to one of claims 10 to 13 wherein the bundle (13) of strands (6) comprises at least 8 strands having a diameter of 150 to 400 micrometers.