JP6131514B2 - Manufacturing method of two-layer multi-strand metal cord - Google Patents

Description

  The present invention relates to a method for producing a multi-strand cord that can be used to reinforce tires, particularly tires for heavy industrial vehicles.

  A tire having a radial carcass reinforcement includes a tread, a non-extendable bead, two sidewalls connecting the bead to the tread, and a belt or crown disposed circumferentially between the carcass reinforcement and the tread. And a reinforcing material. The belt optionally has a plurality of rubber plies reinforced with reinforcing elements or reinforcements of the metal or textile (textile) type, for example cords or monofilaments.

  Tire belts are generally formed of at least two superimposed belt plies, sometimes referred to as “working” plies or “cross” plies, and the generally metal reinforcement cords of the belts are effectively within the plies. Parallel to each other, however, there is a crossing relationship between one ply and the other ply, i.e., symmetric or asymmetric, whether or not with respect to the intermediate circumferential plane The tires are arranged so as to be inclined at an angle of 10 ° to 45 ° as a whole according to the tire type. These cross plies may be supplemented with various other auxiliary rubber plies or layers, the width of these other auxiliary rubber plies or layers may vary from case to case, and these other auxiliary rubber plies or layers may be It may or may not have a reinforcer or reinforcing element. As an example of a simple rubber cushion, it is located radially outward or radially inward with respect to a “protective” ply or cross-ply that serves to protect the rest of the belt from external attack and drilling. Regardless of whether it is, there is a “hooping” ply (ply called a “zero-degree ply”) that includes a reinforcer oriented substantially circumferentially.

  In particular, construction plant type heavy industrial vehicle tires are subject to numerous attacks. More specifically, this type of tire usually travels on uneven road surfaces, and in some cases results in holes in the tread. These perforations allow the entry of corrosive agents, such as air and water, which oxidize the metal reinforcements of the crown reinforcement and significantly shorten the useful life of the tire.

  Cords for protective plies for heavy industrial vehicle tires are known from the prior art. The cord has a 4 × (1 + 5) type structure, and the cord includes an inner layer composed of one wire and five wires wound spirally around the wires of the inner layer. It consists of four strands with an outer layer composed of

  This prior art cord has acceptable corrosion resistance and elasticity, but the force at break is relatively limited, and such a force at break is satisfactory for some uses, It is not sufficient for cords for specific uses, especially for heavy industrial vehicle tires.

  Thus, an object of the present invention is to provide a multi-strand cord that is corrosion resistant and has a high force at break.

For this purpose, the gist of the present invention is a method for producing a two-layer multistrand metal cord,
-The N wires constituting the outer layer of the strand are spirally wound around the two wires constituting the inner layer of the strand to form a strand;
The pre-formed L (L is 2 or more) outer strands constituting the unsaturated outer layer of the metal cord, and the pre-formed K (K is 2 or more) constituting the inner layer of the metal cord. ) Spirally wound around the inner strand of the book,
-Perform over twisting of the wound cord,
-Perform the over-twisted cord balancing step to zero residual torque in the cord,
The method is characterized in that the untwisting step of the balanced over-twisted cord is carried out.

  Multi-strand cord (K + L) x (2 + N) series of over-twisting (over twisting: twisting more than specified), balancing and untwisting steps, ventilated (ventilated) To obtain a cord characterized in that the wire is separated in the axial direction (direction perpendicular to the axial direction of the strand) and the strand is separated in the axial direction (direction perpendicular to the axial direction of the cord) Can do. Specifically, the strands constituting the wires and the strands constituting the strands are plastically deformed during the overtwisting step, thus comparing the initial curvature of the cord before the overtwisting step and before the overtwisting step. And excessive curvature. This relatively large excess curvature causes the wires that make up the strands and the strands that make up the cords to axially separate when the cord is at rest, especially when the cord is not subjected to tensile forces. This curvature is determined by both the helix diameter and helix pitch of each layer of wire or strand, or indeed the helix angle (measured from the axis of the cord) of each layer of wire or strand.

  The cord produced in this way is of the “HE” type, i.e. has a high elasticity and a high penetration. In addition to making the cords elastic, the separation of the strands and the respective wires and strands with respect to the cord axis allows the rubber to pass between the wires of each strand and between different strands. Thus, the corrosion resistance is improved.

  By definition, an unsaturated layer of strands has enough room in this layer to add to this layer at least one (L + 1) th strand having the same diameter as the L strands of this layer. It is possible that a plurality of strands are in contact with each other. In contrast, this layer has enough room in this layer to add at least one (L + 1) th strand having the same diameter as the L strands in this layer. It is called saturated when it does not exist.

  The cord has a high corrosion resistance. Specifically, the unsaturation of the outer layer of the cord can create at least one passage opening for the rubber between the two outer strands so that the rubber can be used during vulcanization of the tire. Will be able to invade effectively. The 2 + N structure of each strand enhances rubber passage. Specifically, each strand has an envelope with an elongated profile, which helps keep adjacent strands from contacting each other, thus facilitating the passage of rubber.

  Furthermore, the cord has significant strength properties. The strength of the cord can be measured by its force value at break, which characterizes its ability of structural strength to force.

  The multi-strand structure (K + L) × (2 + N) of the cord gives excellent mechanical strength of the cord, particularly high force at break.

  With this structure of the cord, it is possible to produce a protective crown ply having a relatively high linear density, for example a working ply or a cross ply. Thus, the strength of the tire is greatly improved.

  When the cord is used in the protective ply, the protective ply has a high elasticity and a high corrosion resistance due to its high penetration and high elasticity, and due to its high penetration, the rubber makes the cord corrosive. It can be protected from the agent, and due to its high elasticity, the cord can be easily deformed independently of the road surface.

  When the cord is used in a working ply or cross ply, the cord is notable because of its high mechanical strength, in particular its compressive fatigue strength, especially of the cross ply in the shoulder region of the tire, which is called “cleavage”. High durability with respect to edge separation / cracking phenomenon.

  The expression “metal cord” is understood by definition to mean a cord made of wires, which are mostly (ie more than 50% of these wires) or wholly (100% of wires). Made of metal material. The present invention is preferably a steel cord, more preferably pearlite (or ferrite-pearlite) carbon steel or stainless steel, hereinafter referred to as “carbon steel” (by definition, steel is at least 11% chromium and at least 50%. Implemented with a cord made of (including% iron). However, it will be appreciated that other steels or other alloys can be used.

  When carbon steel is used, its carbon content (% by weight of steel) is preferably 0.4 to 1.2%, in particular 0.5% to 1.1%, It represents a good compromise between the required mechanical properties and the feasibility of the wire. It should be noted that steels with a carbon content of 0.5% to 0.6% can ultimately be cost-effective. This is because such steel is easy to pull out. Also, in another advantageous embodiment of the invention, depending on the intended use, in particular in view of low cost and high pullability, a low carbon content, for example 0.2% to 0.5% carbon content. Steel with a quantity is used.

  The metal or steel used, in particular whether it is carbon steel or stainless steel, can itself be coated with a metal layer, which can be, for example, a metal cord and / or ) Improving the workability or cord of the component and / or the service properties of the tire itself, such as adhesion, corrosion resistance or aging resistance.

  According to a preferred embodiment, the steel used is covered with a layer of brass (Zn-Cu alloy) or zinc. Recall that during the wire manufacturing process, the brass or zinc coating facilitates the drawing of the wire as well as the attachment of the wire to the rubber. However, the wires are, for example, a thin metal layer other than brass or zinc, which has the function of improving the corrosion resistance of these wires and / or the adhesion of the wires to rubber, for example, Co, Ni, Al or metals such as Cu, Zn , Al, Ni, Co, Sn may be covered with a thin layer of two or more alloys.

  A person skilled in the art will adjust the steel composition and the final work hardening degree of these wires according to their specific special requirements, and for example certain additional elements such as Cr, Ni, Co, V or various Knows how to make steel wires with such properties by using microalloyed carbon steels containing other known elements (for example, ("Micro-alloyed steel, “Micro-alloyed steel cord constructions for tires”, Research Disclosure 34984, May 1993; “High Tensile Strength Steel Cord Constructions For Tires (High tensile strength steel cord constructions for tires) ", Research De Scan closure (Research Disclosure) 34054, see the August 1992).

  Preferably, K inner strands are spirally wound.

Preferably, in the following order:
-Forming each inner and outer strand,
-Spirally wound pre-formed K inner strands,
-Pre-formed L outer strands are spirally wound around K previously wound spiral inner strands.

  Advantageously, the outer layer of each strand is unsaturated.

  By definition, an unsaturated layer of wire has enough room in this layer to add to this layer at least one (N + 1) th wire having the same diameter as the N wires of this layer. As such, multiple wires can be in contact with each other. Conversely, this layer has enough room in this layer to add at least one (N + 1) th wire having the same diameter as the N wires in this layer to this layer. It is called saturated when it does not exist.

  The degree of protection of the cord from corrosion is improved for reasons similar to those described for the unsaturation of the outer layer of the cord. In particular, the rubber will penetrate to the central channel defined by the strands of the inner layer of the cord. Thus, in such cords, rubber penetrates within each strand and between strands.

  Preferably, the breaking force of the metal cord is 4000 N or more, preferably 5000 N or more, more preferably 6000 N or more.

  Preferably, the total elongation At at break of the metal cord, that is, the total of its structural elongation rate, elastic elongation rate and plastic elongation rate (At = As + Ae + Ap) is 4.5% or more, preferably 5% or more, more preferably Is 5.5% or more.

  The structural elongation As is determined by the configuration of the multi-strand cord and / or its element strand (elementary wire) and the actual ventilation state and, if applicable, one or more of these element strands and / or wires. This inherent elasticity results from the preforming performed on the substrate.

  The elastic elongation Ae occurs as a result of the actual elasticity of the metal of the metal wire taken individually (Hooke's law).

  The plastic elongation Ap occurs as a result of the metal elasticity (irreversible deformation beyond the yield point) of these metal wires taken individually.

  These various elongations and their meanings (which are well known to those skilled in the art) are described in US Pat. No. 5,845,583, WO 2005/014925, and 2007/090603. Yes.

  Advantageously, the metal cord has a structural elongation As of 1% or more, preferably 1.5% or more, more preferably 2% or more.

  Advantageously, K = 3 or K = 4.

  Preferably, L = 8 or L = 9.

  Advantageously, N = 2, N = 3, or N = 4.

  Preferred codes are structures (3 + 8) × (2 + 2), (3 + 8) × (2 + 3), (3 + 8) × (2 + 4), (4 + 8) × (2 + 2), (4 + 8) × (2 + 3), (4 + 8) × ( 2 + 4), (4 + 9) × (2 + 2), (4 + 9) × (2 + 3), and (4 + 9) × (2 + 4) codes.

  As will be recalled here, as is known, the pitch represents a length measured parallel to the axis of the cord, after which the wire with this pitch makes a full rotation around this axis of the cord. To do.

According to optional features,
-The inner wire of each of the K inner strands is spirally wound at a pitch of 3.6 to 16 mm (including values at both ends), preferably 4 to 12.8 mm (including values at both ends).
The diameter of the inner wire of each of the K inner strands is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends).
-The ratio of the pitch and diameter of the inner wires of each of the K inner strands is 20-40 (including the values at both ends).
-Spirally wound the outer wire of each of the K inner strands at a pitch of 3.1 to 8.4 mm (including values at both ends), preferably 3.4 to 6.7 mm (including values at both ends) .
-The diameter of the outer wire of each of the K inner strands is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends).
-The ratio of the pitch and diameter of the outer wire of each of the K inner strands is 17-21 (including values at both ends).

  Thus, at a constant diameter, the outer wire preferably has a shorter pitch than the pitch of the inner wire. The elasticity of each of the K strands is improved.

  Preferably, the inner layer and the outer layer of each of the K inner strands are wound in the same twisting direction. In addition to promoting the elasticity of the cord, winding the inner and outer layers in the same direction minimizes the frictional force between the two layers, thus minimizing wear on the wires that make up these layers. Can be suppressed.

According to other optional features,
-The inner wire of each of the L outer strands is spirally wound at a pitch of 7.2 to 32 mm (including values at both ends), preferably 8 to 25.6 mm (including values at both ends).
The diameter of the inner wire of each of the L outer strands is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends).
-The ratio of the pitch and diameter of the inner wire of each of the L outer strands is 40-80 (including the values at both ends).
-Spirally wrap the outer wire of each of the L outer strands at a pitch of 4.1 to 13.2 mm (including values at both ends), preferably 4.6 mm to 10.6 mm (including values at both ends) .
The diameter of the outer wire of each of the L outer strands is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends).

  The ratio of the pitch and diameter of the outer wire of each of the L outer strands is 23 to 33 (including values at both ends).

  Thus, at a constant diameter, the outer wire preferably has a shorter pitch than the pitch of the inner wire. The elasticity of each of the L strands is improved.

  Preferably, the inner layer and the outer layer of each of the L outer strands are wound in the same twisting direction. Thus, the elasticity and wear resistance of the cord is improved in the same way as the inner strand.

According to yet another optional feature:
-The inner strand is spirally wound at a pitch of 3.6 to 16 mm (including values at both ends), preferably 4 to 12.8 mm (including values at both ends).
The ratio of the pitch of each inner strand to the diameter of the wire of each inner strand is 20 to 40 (including values at both ends). Thus, all of the wires of each inner strand have the same diameter.
-The outer strands are spirally wound at a pitch of 7.2 to 32 mm (including values at both ends), preferably 8 to 25.6 mm (including values at both ends).
The ratio of the pitch of the outer strands to the diameter of the wire of each outer strand is 40 to 80 (including the values at both ends). Thus, all of the wires of each outer strand have the same diameter.

  Thus, at a constant diameter, the outer strands preferably have a pitch that is greater than the pitch of the inner strands.

  Preferably, the inner layer and the outer layer of the metal cord are wound in the same twisting direction. This winding minimizes the frictional force between the two layers, thus minimizing wear on the wires that make up these layers.

  Advantageously, all the wires and strands are wound in the same twisting direction. Thereby, the elasticity of the cord is increased.

  In order to obtain an optimized compromise between strength and structural stretch or elasticity capability and durability and flexibility, all the diameters of the outer and inner wires of each strand (the wires are identical) It is preferably 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends).

  For each strand, the inner and outer wires may have the same or different diameters from one layer to the other. Preferably, wires having the same diameter between one layer and the other are used. The inner wire of each strand is preferably made of steel, more preferably carbon steel. Separately and independently, the outer wire of each strand is preferably made of steel, more preferably carbon steel.

  The code is a tire for industrial vehicles selected from heavy vehicles, i.e. subway vehicles, buses, road transport vehicles (lorries, tractors, trailers), off-road vehicles, agricultural or construction plant machinery and other transport or handling vehicles. It is further intended to be used as a reinforcing element for other crown reinforcements.

  Preferably, as described above, the tire has a carcass reinforcing member anchored in two beads and having a crown reinforcing member placed on the radial direction, and a tread is placed on the crown reinforcing member itself. The tread is joined to the bead by two sidewalls and the crown reinforcement has a cord.

  Advantageously, the cord is intended to be used as a reinforcing element for the protective ply. As a variant, the cord is intended to be used as a reinforcing element for the working ply.

  The cord can also be used in other embodiments to reinforce other portions of tires for other types of vehicles.

  Thus, for example, it can be assumed that the cord is used as a reinforcing element for the hanging ply. According to various embodiments, such a hanging ply can be between one or more carcass plies and one or more working plies, between working plies, or one or more working plies. And one or a plurality of protective plies are preferably arranged radially.

  The invention will be better understood when the following description, given by way of example only, is read with reference to the drawings, in which:

FIG. 4 is a cross-sectional view perpendicular to the axis of the cord obtained by the method of the present invention, which is assumed to be straight and resting. A small size of the strand of the cord of FIG. It is sectional drawing perpendicular | vertical to the circumferential direction of the tire which has a code | cord | chord of FIG. FIG. 2 is a cross-sectional view similar to the cross-sectional view of FIG. 1 of a prior art code.

Code obtained by the method according to the invention

  FIG. 1 shows an example of a metal cord denoted as a whole by the reference numeral 10. The cord 10 is of the multi-strand type with two cylindrical layers. Thus, as will be appreciated, there are two layers of strands that are the constituent material of the cord 10. The layers of strands are adjacent to each other and concentric. The cord 10 has no rubber when the cord is not incorporated into the tire.

  The cord 10 has an inner layer C1 of the cord 10, which is composed of K inner strands TI, preferably in this case K = 3 or K = 4, in which case K = 3. Layer C1 has a substantially tubular envelope that gives layer C1 its cylindrical contour E1.

  The inner strand TI is spirally wound at a pitch pI of 3.6 to 16 mm (including values at both ends), preferably 4 to 12.8 mm (including values at both ends). In this case, pI = 7.5 mm.

  The cord further comprises an outer layer C2 of cord 10, this outer layer C2 being composed of L outer strands TE, in this case preferably L = 8 or L = 9, in this case L = 8. Layer C2 has a substantially tubular envelope that gives layer C2 its cylindrical contour E2.

  The outer strand TE is in a juxtaposed state, which corresponds to a mechanically balanced position, and at least two outer strands TE are separated from each other by a passage opening 14 for rubber. Inner layer C2 is unsaturated, i.e. to add at least one (L + 1) th strand in layer C2 having the same diameter as the L strands of layer C2 to this layer C2. There is sufficient room, and thus multiple strands can be in contact with each other. Thus, the outer strand TE is arranged such that the layer C2 allows the rubber to pass radially through the opening 14 between the outer side and the inner side of the layer C2.

  The outer strand TE is spirally wound around the inner layer C1 at a pitch pE of 7.2 to 32 mm (including values at both ends), preferably 8 to 25.6 mm (including values at both ends). In this case, pE = 15 mm.

  The strands TI, TE are advantageously of the same twisting direction, ie either in the S direction (“S / S” arrangement) or in the Z direction (“Z / Z” arrangement), in this case S / S It is wound in an array state.

  FIG. 2 shows the strands TI and TE. Such a strand is called an element strand.

  Each strand TI, TE has an extended envelope that gives each strand TI, TE its elongated contour E3. Each strand TI, TE has an inner layer 12 composed of two inner wires F1 and an outer layer 16 composed of N outer wires F2, where N = 2, N = 3, or N = 4, in this case N = 3.

  The outer wire F2 is generally juxtaposed when the cord is at rest, which corresponds to a mechanical equilibrium position, and at least two outer wires F2 have a passage opening 18 for rubber. Separated from each other by Layer 16 is in an unsaturated state, i.e. at least one (N + 1) th outer wire F2 having the same diameter as the N outer wires F2 of layer 16 is added to this layer. There seems to be enough room for it. Thus, the outer wire F2 of the layer 16 is arranged such that the layer 16 allows rubber to pass radially through the opening 18 between the outside and the inside of the layer 16.

  Each wire F1, F2 is preferably made of carbon steel coated with brass. The carbon steel wire is prepared in a known manner, for example from machine wire (diameter 5-6 mm), which is first work hardened by rolling and / or drawing to an intermediate diameter of about 1 mm. To do. The steel used for Code 10 is NT (representing “Normal Tensile”) type carbon steel with a carbon content of 0.7%, the balance being iron and steel production Consists of normal unavoidable impurities associated with the process. As a variant, SHT (“Super High Tensile”) carbon steel is used, and the carbon content of such SHT carbon steel is about 0.92%, which is about 0.002%. Contains 2% chromium.

  Intermediate diameter wires are subjected to degreasing and pickling treatments, which are then converted. After the brass coating is applied to these intermediate wires, it is called the “final” work hardening operation by cold drawing in a wet medium, for example using a drawing lubricant in the form of an aqueous suspension or dispersion. The operation being performed is performed on each wire (ie, after the final patenting heat treatment). The brass coating surrounding the wire has a very small thickness and is much smaller than 1 micron, for example about 0.15 to 0.30 μm, which is negligible compared to the diameter of the steel wire it can. Of course, the steel composition of the wire is the same as the steel composition of the starting wire with respect to its various elements (eg, C, Cr, Mn).

  The inner wires F1 of each of the K inner strands TI are spirally wound at a pitch p1, i of 3.6 to 16 mm (including values at both ends), preferably 4 to 12.8 mm (including values at both ends). .

  The diameter D1, i of the inner wire F1 of each of the K inner strands TI is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends). It is. Preferably, all of the inner wires F1 of the K inner strands TI have the same diameter.

  The inner wire F1 of each inner strand TI is wound so that the ratio R1, i between the pitches p1, i of the inner wire F1 and the diameters D1, i is 20 to 40 (including values at both ends). In this case, p1, i = 7.5 mm, D1, i = 0.26 mm, and R1, i = 28.8.

  The outer wires F2 of each of the K inner strands TI are pitches p2 and i of 3.1 to 8.4 mm (including values at both ends), preferably 3.4 to 6.7 mm (including values at both ends). Wind spirally.

  The diameter D2, i of the outer wire F2 of each of the K inner strands TI is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends). It is. Preferably, all of the outer wires F2 of the K inner strands TI have the same diameter.

  The inner layer such that the outer wire F2 of each inner strand TI has a ratio R2, i of the pitches p2, i of the outer wires F2 of each inner strand TI and the diameters D2, i of 17 to 21 (including values at both ends). Wind around 12 in a spiral. In this case, p2, i = 5 mm, D2, i = 0.2 mm, R2, i = 19.2.

  The inner wire F1 of each of the L outer strands TE is wound at a pitch p1, e of 7.2 to 32 mm (including values at both ends), preferably 8 to 25.6 mm (including values at both ends).

  The diameters D1 and e of the inner wires F1 of each of the L outer strands TE are 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends). It is. Preferably, all of the inner wires F1 of the L outer strands TE have the same diameter.

  The inner wire F1 of each outer strand TE is wound so that the ratio R1, e between the pitches p1, e of the inner wire F1 and the diameters D1, e is 40 to 80 (including values at both ends). In this case, p1, e = 15 mm, D1, e = 0.26 mm, R1, e = 57.7.

  The outer wires F2 of each of the L outer strands TE are pitches p2 and e of 4.1 to 13.2 mm (including values at both ends), preferably 4.6 mm to 10.6 mm (including values at both ends). Roll it up.

  The diameter D2, e of the outer wire F2 of each of the L outer strands TE is 0.18 mm to 0.40 mm (including values at both ends), preferably 0.20 mm to 0.32 mm (including values at both ends). It is. Preferably, all of the outer wires F2 of the L outer strands TE have the same diameter.

  Inner layer so that outer wire F2 of each outer strand TE has a ratio R2, e of pitches p2, e and diameters D2, e of outer wires F2 of each outer strand TE to 23 to 33 (including values at both ends). Wind around 12 in a spiral. In this case, p2, e = 7.5 mm, D2, e = 0.26 mm, R2, e = 28.8.

  Preferably, all of the wires F1, F2 have the same diameter.

  The inner strand TI is spirally wound so that the ratio RI between the pitch pI of the inner strand TI and the diameters D1, i, D2, i of the wires F1, F2 of each inner strand TI is 20 to 40 (including values at both ends). . In this case, RI = 28.8.

  Around the inner layer C1, the outer strand TE has a pitch RE of the outer strand TE and a diameter RE, e, D2, e of the wires F1, F2 of each outer strand TE and a ratio RE of 40 to 80 (including values at both ends). Wound in a spiral. In this case, RE = 57.7.

  The wires F1, F2 of each strand TI, TE are advantageously of the same twisting direction, ie either in the S direction (“S / S” arrangement) or in the Z direction (“Z / Z” arrangement), In this case, it is wound in the S / S arrangement state.

  Thus, all of the wires F1, F2 and all of the strands TI, TE are wound in the same twisting direction S. As a modification, all of them are wound in the same twisting direction Z.

  FIG. 4 shows a prior art code indicated generally by the reference numeral 100.

  The cord 100 has a 4 × (1 + 5) type structure, and the cord is spirally wound around the inner layer 102 and the wires 104 of the inner layer 102 each composed of one wire 104. It has four strands T with an outer layer 106 made up of five wires 108. The strand T defines a central channel 110.

  Next, the method of the present invention for manufacturing the cord 10 will be described.

It will be recalled that there are two possible techniques for assembling (assembling) metal wires or strands beforehand.
-By cabling. In such a case, the wires or strands do not twist about their own axis in view of the synchronous rotation before and after the assembly point.
-Or by twisting or twisting. In such a case, the wires or strands produce both a batch of twists and individual twists about their own axis, thereby creating an untwisting torque applied to each of the wires or strands.

Assembly (assembly) of each strand TI, TE

  First, the element strands TI and TE are formed as follows.

  During the twist assembly step, the N inner wires F1 constituting the outer layer 16 are spirally wound around the two inner wires F1 constituting the inner layer 12 in the S direction at an intermediate pitch equal to 15 mm. During the execution of this step, the inner wires F1 are parallel to each other and thus have an infinite intermediate pitch.

Assembly of code 10 (assembly)

  Next, the code 10 is assembled as follows.

  During the twisting assembly step, the K inner strands TI formed earlier during the step of forming the strands TI and constituting the inner layer C1 are called the initial pitch equal to 7.5 mm in the S direction. Wind spirally at the pitch.

Next, during another twisting assembly step that is performed or not performed in line with the previous twisting step, it is composed of the L outer strands TE previously formed during the step of forming the strand TE The outer layer C2 is spirally wound around the inner layer C1 of the K inner strands previously spirally wound in the S direction at a pitch called initial pitch equal to 15 mm. The strands TI, TE and the wires F1, F2 of the layers C1, C2 thus have the initial pitch described in Table 1. As a variant, these have other initial pitches.
Table 1

  Next, the step of overtwisting the cord 10 is performed. Thus, the previously wound wires F1 and F2 and the strands TE and TI are excessively twisted, that is, the cord 10 is further twisted in the S direction. During this over-twisting step, the initial pitch of each of the wires F1, F2 and the strands TI, TE is reduced to obtain an intermediate pitch that is smaller than the corresponding initial pitch.

  Next, the step of balancing the over-twisted cord 10 is performed to reduce the residual torque in the cord 10 to zero. For this purpose, the cord is passed through a rotary balancing means. The term “balance” is used herein to refer to the residual load applied to both the wires of the cord in the twisted state and the strands of the cord in the twisted state in a manner known to those skilled in the art. It should be understood to mean canceling the twisting torque (or untwisting springback). Balancing means are known to those skilled in the twisting art. These balancing means may consist, for example, of a twister having, for example, one, two or four pulleys, in which the cord runs in a single plane.

  Next, a step of untwisting the over-twisted and balanced cord is performed. Thus, the wires F1 and F2 and the strands TE and TI of the cord 10 previously balanced are untwisted, that is, the cord 10 is twisted in the Z direction. Thus, the intermediate pitch of the wires F1, F2 and the strands TE, TI is increased to obtain the initial pitch. At the end of this untwisting step, the pitch of the wires F1, F2 and the strands TI, TE is thus again the pitch of Table 1.

  Finally, the cord 10 is preferably wound around a storage spool.

  The code 10 described above can be obtained by the method described above.

Tire having a cord obtained by the method of the present invention

  FIG. 3 shows a tire generally designated 20.

  The tire 20 includes a crown 22 reinforced by a crown reinforcement member 24, two sidewalls 26, and two beads 28, each of which is reinforced with a bead wire 30. A tread (not shown in this diagram) rests on the crown 22. A carcass reinforcement 32 is wound around each of the two bead wires 30 within each bead 28, and this carcass reinforcement is arranged near the outside of the tire 20, shown here attached to the wheel rim 36. A folded portion (also referred to as a “winding portion”) 34 is provided. The carcass reinforcement 32 is made of at least one ply reinforced in a manner known per se by a cord called a “radial” cord, which means that these cords extend substantially parallel to each other. And extends from one bead to the other bead at an angle of 80 ° to 90 ° with the circumferential midplane (this circumferential midplane is perpendicular to the tire's axis of rotation and Located in the middle of each other and passing through the middle of the crown reinforcement 24).

  The crown reinforcement member 24 has at least one crown ply, and the reinforcement cord of the crown ply is the metal cord 10 as described above. In this crown reinforcement 24 shown in a very simple manner in FIG. 3, as will be appreciated, the cord can, for example, reinforce all or some of the working crown plies. Alternatively, if a triangular structure forming crown ply (or ply half) or protective crown ply is used, such triangular structure forming crown ply (or half ply) and / or protective crown ply can be reinforced. Apart from the working ply and the triangular structure forming ply and / or the protective ply, the crown reinforcement 24 of the tire 20 has, of course, other crown plies, for example one or more straddle crown plies. Is good.

  Of course, the tire 20 further comprises, in a known manner, an inner layer of rubber or elastomer (commonly referred to as an “inner liner”), which is the radially inner side of the tire. It constitutes a face and protects the carcass ply from the diffusion of air originating in the space inside the tire. Advantageously, particularly in the case of tires for heavy vehicles, the tire is arranged between the carcass ply and the inner layer and is adapted to reinforce the inner layer and consequently the carcass layer, It may further comprise an intermediate reinforcing elastomer layer adapted to partially delocalize the force applied.

  In this belt ply, the density of the cord 10 is preferably 15 to 80 cords (including values at both ends) per dm (decimeter) of the belt ply, more preferably 35 to 65 per dm of the belt ply. A cord (including values at both ends), and a distance between two adjacent cords (distance between axes) is preferably about 1.2 to 6.5 mm (including values at both ends), and more preferably Is approximately 1.5 to 3.0 mm (including values at both ends).

  The cord 10 is preferably arranged so that the width of the rubber bridge between two adjacent cords (denoted L) is 0.5 to 2.0 mm (including values at both ends). . As is well known, the width L represents the difference between the rolling pitch (pitch in which the cord is laid in the rubber fabric) and the diameter of the cord. Below the indicated minimum, a rubber bridge that is too narrow creates a risk of mechanical degradation when the ply is running, especially during deformation that occurs in its own plane under elongation or shear. . Exceeding the indicated maximum value can cause objects to penetrate between the cords by drilling. More preferably, for these same reasons, the width L is selected to be between 0.8 and 1.6 mm (including values at both ends).

  Preferably, the rubber composition used for the fabric of the belt ply is 5 to 25 MPa (including values at both ends), more preferably 5 to 20 MPa (including values at both ends) in a vulcanized state (that is, after vulcanization). ), Especially when the fabric is intended to form a belt ply, such as a protective ply, having a secant modulus E10 during elongation of 7-15 MPa (including values at both ends). It is in this modulus range that a compromise on the best durability between the cord 10 on the one hand and the fabric reinforced by these cords on the other hand is found.

  Next, a method for manufacturing the tire 20 will be described.

  The cord 10 is incorporated into a composite fabric formed from a known composition mainly composed of natural rubber and carbon black as a reinforcing filler conventionally used for producing a crown reinforcement for radial tires by rolling. . This composition essentially consists of an elastomer and a reinforcing filler (carbon black) plus an anti-aging agent, stearic acid, extender oil, cobalt naphthenate as an adhesion promoter, and finally a vulcanizing system ( Sulfur, vulcanization accelerator, and ZnO).

  The composite fabric reinforced by these cords has a rubber matrix made of two thin rubber layers, which are superimposed on each side of the cord, 0.5 mm to 0.8 mm (both ends) Thickness). The rolling pitch (pitch for laying the cord in the rubber fabric) is 1.3 mm to 2.8 mm (including values at both ends).

  These composite fabrics are then used as protective plies in these reinforcements during the implementation of the tire manufacturing method, and the steps of the tire manufacturing method are otherwise known to those skilled in the art.

Measurement and comparison test

  Code 10 was compared with prior art code 100 of structure 4 × (1 + 5).

  The diameter of each wire 104, 108 of the cord 100 is equal to 0.26 mm. The pitch P of the strands 106 is equal to 8 mm, and the pitch p of the wires 108 around the wires 104 is equal to 5 mm.

Dynamometric measurement

  With respect to a metal cord, the breaking force indicated by Fm (maximum load represented by N) is measured under tension according to the standard ISO6892 (1984). Measurements of total elongation at break (At) and structural elongation or elongation capacity (As) (elongation in%) are well known to those skilled in the art and are described, for example, in US Patent Application Publication No. 2009/2009. (See FIG. 1 and the description relating thereto).

Table 2 below shows the results obtained for the force at break Fm and the structural elongation.
Table 2

  The cord 10 has a total elongation at break At of 4.5% or more, preferably 5% or more, more preferably 5.5% or more.

  The cord 10 has a structural elongation As of 1% or more, preferably 1.5% or more. In a modification not shown, the structural elongation As is 2% or more.

  The breaking force of the cord 10 is 4000 N or more, preferably 5000 N or more, more preferably 6000 N or more.

  The cord 10 has a breaking force 2.3 times that of the cord 100 while maintaining its structural elongation characteristics and thus its elasticity. This elasticity represents the air permeability of the cord as described above, which is advantageous for the high penetration of the cord by rubber.

Air permeability test

  This test allows the longitudinal permeability of the tested cord to air to be determined by measuring the amount (volume) of air that has passed through the specimen under a given pressure at a given time. The principle of such a test, well known to those skilled in the art, is to demonstrate the effectiveness of the processing of the cord so that the cord is impermeable to air, and this principle is for example the standard ASTM D2692-98. It is described in.

  This test is now carried out either on cords taken from tires or on those cords that have been reinforced and thus have already been coated from the outside with the rubber in a cured state or cords that have just been produced. .

  In the latter case, the cord just manufactured needs to be coated from the outside in advance with a rubber called coated rubber. For this purpose, a series of ten cords laid parallel to each other (the distance between the cords is 20 mm) is converted into two layers or “skims” of raw diene rubber compound (80 × 200 mm Placed between each other, each skim has a thickness of 3.5 mm, then all of this is immobilized in the mold, each of the cords being placed in the mold When the cords are kept straight, they are kept under sufficient tension (eg 2 daN) using a clamping module and then each cord is kept at a temperature of 140 ° C. and a pressure of 15 bar over 40 minutes. Vulcanize (harden) (80 × 200 mm rectangular piston). The whole is then removed from the mold and the 10 specimens of the cord thus coated are cut into a 7 × 7 × 20 mm parallelepiped shape for characterization.

  The compound used as the coating rubber is composed mainly of natural (peptide-modified) rubber and carbon black N330 (65 phr), and includes the following usual additives: sulfur (7 phr), sulfenamide vulcanization accelerator (1 phr) ZnO (8 phr), stearic acid (0.7 phr), anti-aging agent (1.5 phr), cobalt naphthenate (1.5 phr) (phr means parts by weight per 100 parts of elastomer) Further, it is a diene rubber compound used in a conventional tire including the above, and the E10 modulus of the coated rubber is about 10 MPa.

The test was carried out on a 2 cm long cord, which was thus coated in its cured state with its surrounding rubber composition (or coated rubber) as follows and air was applied to the cord inlet under a pressure of 1 bar: The volume of air at the feed and outlet is measured by the use of a flow meter (the flow meter is calibrated to, for example, 0-500 cm ³ / min). During measurement, a sample of cord is immobilized in a compression-tight seal (eg, a seal made of high density foam or rubber) and along its longitudinal axis from one end to the other along the cord. Only the amount of air passed is put into the cord by measurement and the airtightness of the hermetic seal itself is pre-checked using a solid rubber specimen, ie a rubber specimen without a cord.

The higher the longitudinal impermeability of the cord, the lower the measured average air flow (averaged over 10 specimens). Since the measurement is carried out with an accuracy of ^{± 0.2cm 3 / min, 0.2cm 3} / min following measurements are assumed to be zero, these measurements along the axis (i.e., in the longitudinal direction) airtight Corresponds to a code that can be described as (completely airtight).

The air permeability test described above was carried out by measuring the amount of air (in cm ³ ) that passed through the cord 10 per minute (averaged over 10 measurements).

The average air flow measured for code 10 is zero, which means that for each specimen, the measured air flow is 0.2 cm ³ / min or less.

  The cord 10 thus has a very low permeability to air since the air permeability is virtually zero (zero average air flow) and therefore has a high penetration by rubber. Thus, the cord 10 has particularly improved corrosion resistance.

  Of course, the present invention is not limited to the exemplary embodiments described above.

  For example, some of the wires may have non-circular, eg plastically deformed cross-sections, in particular oval or polygonal, eg triangular, square or rectangular cross-sections.

  Wires with or without a circular cross section, such as corrugated wires, may be twisted or contoured into a spiral or zigzag shape. In such a case, it should be understood that the diameter of the wire represents the diameter of the imaginary rotating cylinder surrounding the wire (envelope diameter), and the diameter of the core wire itself (or any other if its cross section is not circular) It is to be understood that the lateral dimensions of

  For reasons of industrial ease, cost and overall performance, the present invention is preferably implemented with a straight wire, ie, a straight wire having a conventional circular cross section.

  It may also be possible to combine the features of the various embodiments described above or planned above. However, they must be compatible with each other.

Claims (13)

In a method for producing a two-layer multi-strand metal cord (10),
-N wires (F2) constituting the outer layer (16) of the strand (TI, TE) are routed around the two wires (F1) constituting the inner layer (12) of the strand (TI, TE). Spirally wound to form the strands (TI, TE),
The preformed L outer strands (TE) constituting the unsaturated outer layer (C2) of the metal cord (10) are connected to the inner layer of the metal cord (10) ( Spirally wound around pre-formed K (K is 2 or more) inner strands (TI) constituting C1)
-Over twisting the wound cord (TI, TE),
-Performing a balancing step of the over-twisted cord (10) to zero residual torque in the cord (10);
-A method of carrying out the untwisting step of said balanced over-twisted cord (10).   The method of claim 1, wherein the K inner strands are spirally wound. -Forming each inner and outer strand,
-Spirally winding the previously formed K inner strands,
3. A method according to claim 1 or 2, wherein the preformed L outer strands are spirally wound around the K inner strands previously spiraled.   The method according to any one of claims 1 to 3, wherein the outer layer (16) of each strand (TI, TE) is brought into an unsaturated state. It said metal cord (10) has at least 1% structural elongation of (As), The method according to any one of claims 1-4. The method according to any one of claims 1 to 5, wherein the metal cord (10) has a structural elongation (As) of 1.5% or more. The method according to any one of the preceding claims, wherein the metal cord (10) has a structural elongation (As) of 2% or more. The method according to any one of claims 1 to 7 , wherein the metal cord (10) has a total elongation at break (At) of 4.5% or more. The method according to claim 1, wherein the metal cord has a total elongation at break (At) of 5% or more. The method according to any one of claims 1 to 9, wherein the metal cord (10) has a total elongation at break (At) of 5.5% or more. K = 3 or K = 4, the method according to any one of claims 1-10. L = 8 or L = 9, The method according to any one of claims 1 to 11. N = 2, N = 3, or N = a 4 A method according to any one of claims 1 to 12.

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