WO2006032479A1

WO2006032479A1 - Tyre comprising a running tread with continuously variable characteristics

Info

Publication number: WO2006032479A1
Application number: PCT/EP2005/010204
Authority: WO
Inventors: Yves Potin
Original assignee: Societe De Technologie Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2004-09-24
Filing date: 2005-09-21
Publication date: 2006-03-30

Abstract

The invention concerns a tyre comprising a crown reinforcement, including a cord (11) arranged circumferentially so as to form a plurality of coils wherein the circumferential tension is capable of varying based on the axial position of the cord to form at least two lateral tension varying zones (21) wherein the tension varies inversely, starting from a minimum tension value (Tb) at the edge of the crown towards a higher value in the axial direction towards the center, the two lateral zones (21) being separated by a median zone (22) wherein the median tension (Tm) is substantially constant over a plurality of coils, the median tension (Tm) corresponding to a maximum tension of the cord.

Description

TIRE COMPRISING A TREAD WITH VARIABLE CHARACTERISTICS CONTINUOUSLY

The present invention relates to a tire comprising a tread with circumferential reinforcements, the tension of which varies progressively over at least a portion of the width of the crown of the tire. This type of crown reinforcement thread configuration provides substantial gains for important tire characteristics such as wear, wet behavior, noise, comfort in general.

The circumferential reinforcing threads of the crown zone are generally directly applied to a tire blank near the end of the assembly process of the various components. This type of assembly process is widely used in the tire industry and has many advantages, for example in terms of productivity, particularly for products of large or very large series. This type of process generally involves long cable lengths stored in coils or rollers, and ready to be unrolled on the tire blank during manufacture.

To lay the wire, it is guided to its location and the wire is unrolled and applied, while gradually adjusting the axial position of laying, so as to cover the whole of the planned crown area. Such a wire is laid without tension, or slightly pre-tensioned, but has the same tension over the entire laying width.

According to certain embodiments, one or more characteristics such as the nature of the wires varies according to the axial position on which one is located. For example, the diameters may vary depending on the position. It is also possible to use wires of different materials. Finally, certain arrangements are also known comprising wires arranged with a spacing or not which varies according to the axial position. Document US 6,766,840 provides such an arrangement, with a larger pitch in the sensitive areas of edges of ground tips. US 5,902,425 also shows a tire with a variable pitch, the latter varying so as to become larger and larger towards the center of the summit. This particular embodiment is however intended for tires for two-wheeled vehicles. Finally, US Pat. No. 5,032,198 describes a method of laying circumferential reinforcements by providing that the laying tension varies between the edges and the central region of the crown. The wire is thus laid with a tension of higher and higher, as one gets closer to the edges.

Thanks to these different manufacturing tips, it is possible to produce products with interesting features, and developers have many degrees of freedom.

However, some constraints remain, partly due to the manufacturing process used. For example, a circumferential son laid without tension is likely to end up in excess length after cooking. Indeed, during molding, the rubber materials component of the tire are strongly constrained and thus crushed. They can occupy a smaller volume after molding, than during installation. However, the circumferential threads do not necessarily undergo a shrinkage that would completely compensate for this loss of volume. This may result in a longer wire length than that required for a voltage-free situation, ie an excess length.

Finally, it is customary for developers who wish to vary the characteristics of the vertex reinforcement son according to the axial position, either to apply additional layers in certain places, or to use locally materials or steps. different. However, the implementation of these features can be expensive, or involve additional weight. On the other hand, these means do not always achieve the desired performance for certain types of product for which the technical requirements are high. It would therefore be useful for developers wishing to optimize certain geometric features to have other means of adjustments. In order to overcome these various drawbacks, the invention proposes a tire comprising at least one carcass-type reinforcement structure anchored on each side of said tire in a bead whose base is intended to be mounted on a rim seat, each of said beads being extending substantially radially externally in the form of flanks, the flanks joining radially outwardly a tread, the carcass-type reinforcing structure extending circumferentially from the bead towards said sidewall, a crown reinforcement, each of the beads comprising in addition, an anchoring zone allowing the reinforcement structure to be maintained, said crown reinforcement comprising a single wire arranged circumferentially so as to form a plurality of turns in which the circumferential tension is likely to vary as a function of the axial position of the wire so as to form at least two extreme lateral zones s of voltage variations in which the voltage varies inversely, starting from a boundary voltage value Tb at the edge of the vertex to a higher value while moving axially centrally, the two extreme lateral zones being separated by a median zone in which the median tension Tm is substantially constant over a plurality of turns (at least four turns - and according to an advantageous example over a peak width of approximately 45 mm), the median tension Tm corresponding to a maximum tension of the thread .

Such a tire possesses qualities of behavior and endurance superior to a tire with reinforced top of known type. In addition, there is an increase in the area of the contact area on the sides of the tire, which allows in particular to extend the life of the tire.

Advantageously, the tire comprises a single circumferential wire on which the voltage variation profile is applied. The speed of laying a single wire provides significant benefits in terms of productivity and cost. This type of tire can be achieved for example by a control or substantially continuous control of the laying tension of the circumferential wire.

In addition, by laying the circumferential wire with a certain pretension, one can avoid the situation in which such a wire is found in excess length after baking the tire.

According to an advantageous exemplary embodiment, the median zone is disposed substantially axially centrally.

Preferably, the circumferential tension of the wire varies substantially symmetrically on each side of the median zone of the tire.

According to an advantageous example, the tension of the thread in the lateral zones of the edge of the apex is substantially zero. According to another embodiment, it increases gradually approaching the middle portion.

According to another embodiment, the circumferential tension of the voltage variation zones varies substantially linearly over at least a portion of the zone.

The central zone advantageously comprises a central portion consisting of a plurality of turns in which the voltage Tpc is lower than that of the central zone. According to an exemplary embodiment, the value of the voltage Tpc of said central portion is substantially zero. These embodiments allow for example to reduce rolling noise.

Advantageously, the pitch of the wire is substantially the same in a given area. According to another exemplary embodiment, the pitch is not identical in all the zones. Preferably, the voltage varies inversely and substantially symmetrically (with respect to the median section of the tire).

Advantageously, the tire according to the invention comprises a single circumferential wire on which the voltage variation profile is applied. This provides advantages in terms of installation time, adjustments and adjustments, which are optimized, compared to a laying with several son arranged side by side. The voltage profile is also better controlled.

The median tension Tm preferably corresponds to a maximum tension of the thread.

In the present description, the term "wire" refers in general to both monofilaments and rnultifilaments or assemblies such as cables, twisted or any type of equivalent assembly, and this, whatever the material and treatment of these sons. It may be for example surface treatments, coating or pre-sizing to promote adhesion to the rubber. The term "unitary wire" refers to a single-component wire, without assembly. On the contrary, the term "malifilaments" refers to an assembly of at least two unitary elements to form a cable, a twist, and so on.

The term "circumferential threads" means son arranged substantially at zero degrees with respect to the direction of rotation of the tire.

"Wire characteristics" means, for example, its dimensions, its composition, its characteristics and mechanical properties (in particular the modulus), its characteristics and chemical properties, etc.

As a reminder, "radially upwards", or "radially upper" or "radially outward" means towards the largest radii. All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 to 7 in which:

FIG. 1 shows a profile of a section of a crown of a tire in which the circumferential threads are seen, this section being related to a graph illustrating a profile of tension of application of a circumferential thread;

FIG. 2 shows a laying voltage profile of the example of FIG. 1;

FIG. 3 shows a variant of the laying voltage profile of the example of FIG. 1 comprising a central portion with a voltage whose value is less than that of the central zone;

FIG. 4 shows another variant of the laying voltage profile of the example of FIG. 1, comprising a central portion with a voltage whose value is substantially zero;

FIG. 5 shows another variant of the laying voltage profile of the example of FIG. 1 comprising a central portion with a voltage whose value is greater than that of the central zone;

FIG. 6 shows a variant of the laying voltage profile of the example of FIG. 1, comprising a central portion with a voltage whose value is less than both that of the median zone and that of the edges;

FIG. 7 shows a variant of the laying voltage profile of the example of FIG. 1, the lateral zones of variation of voltage of which are not linear.

FIG. 1 illustrates an example of axial distribution of the circumferential threads at the crown of a tire. The bottom portion of the figure shows an exemplary embodiment of an area of the crown of a tire, with two layers of reinforcements vertex, a radially outer crown reinforcing layer 12 and a radially inner crown reinforcing layer 13 and a series of circumferential reinforcements 11 radially arranged externally to these two layers 12 and 13. The graph situated above this portion of the tire presents a example of the value or the profile of the laying voltage of the wire as a function of its axial position along the top. In more detail, we find on the abscissa the axial position of the wire for each turn, and on the ordinate, an example of tension applied during the laying, also for each turn, in Newtons. The axial position is given by a numbering of each of turns made by the wire, the first tower to the left of the figure, until the ^190th turn, right of FIG. In this example, the total number of turns is 190. In other exemplary embodiments, this total number of turns, as well as the pitch, can vary according to a quasi-infinity of possibility, without going beyond the scope of the present invention.

According to this example, the first turns are laid virtually without tension, or with no noticeable tension, and then, in a lateral zone 21 of variation of tension, the laying tension increases gradually, turn by turn, as the we move towards the portion or median area 22 of the tire. In this example, the voltage varies substantially linearly. To 7O ^lap, the central region 20 is reached, and son are placed on several turns with substantially the same voltage arises. In this example, about 50 turns make up the middle portion. The voltage level of this zone is around 30 Newtons.

Continuing the study of this same figure, we see that on the right side of the median zone, the laying tension of the circumferential wire decreases, from the value of the median tension, ie about 30 N, towards a value more and more weak, according to a substantially linear regression. In the area of the shoulder, the laying tension is substantially zero. The laying tension profile of the wire thus forms a kind of "n".

In this example, the voltage profile is substantially symmetrical with respect to the central section of the tire. According to various variants, one or more parameters may vary, such as: the pitch, the rate of change of the voltage, the relative width of the various porti ons, namely the lateral zones of variation of tension and the median zone, the maximum and minimum values of voltage, etc. Developers therefore have a design tool with great flexibility, to adapt to many types of products, and to optimize different parameters of the product.

FIG. 2 illustrates a representation of the voltage profile of a circumferential wire for the embodiment of FIG. 1. FIGS. 3 to 5 show variants of this example, in which the central zone comprises a central portion 30, a width of a few turns, in which the laying voltage Tpc is substantially different from the voltage value of the central zone. For example, in FIG. 3, the value of Tpc is substantially less than the value of Tm (approximately 10N), but greater than zero N. In FIG. 4, Tpc is substantially zero. In FIG. 5, Tpc is substantially greater than Tm (approximately 35 N with respect to 30N).

In the embodiment of Figure 6, the value of Tpc is less than Tb, the edge voltage. Indeed, in this example, the crown edges comprise portions in which the laying tension is greater than 0 N, 5 N in this example, over a width of a few turns.

The embodiment of FIG. 7 differs in that the rate of variation of voltage of at least one of the lateral zones 21 between the borders and the median zone 22 is not linear. In the example shown, it forms a concave profile. According to one variant, this profile results in a convex shape. Finally, various combinations of combinations are possible with concave and convex portions of the same side of the medial portion, or a concave side and the other convex side.

In the example illustrated in FIG. 1, a crown reinforcement consists for example of two layers of reinforcing threads 12 and 13 arranged at substantially equal but opposite angles. Of course, other types of arrangements can be used without departing from the scope of the present invention. Thus, the number of layers, the angles used as well as the types of son can be different.

The industrial manufacture of a tire according to the invention can be carried out according to several types of processes. Advantageously, a principle of laying on a central core is used allowing either the individual laying of the constituent elements such as rubber mixes and reinforcements (son) or the laying of semi-finished products such as rubber reinforced lamellae.

Claims

A tire comprising at least one carcass-type reinforcing structure anchored on each side of said tire in a bead whose base is intended to be mounted on a rim seat, each of said beads extending substantially radially externally in the form of flanks. , the flanks joining radially outwardly a tread, the carcass-type reinforcing structure extending circumferentially from the bead towards said sidewall, a crown reinforcement, each of the beads also comprising an anchor zone allowing the maintaining the reinforcing structure, said crown reinforcement having a circumferentially disposed wire so as to form a plurality of turns in which the circumferential tension is likely to vary turn by turn, depending on the axial position of the wire so as to form the minus two lateral zones of voltage variations in which the voltage varies inverse direction, starting from a minimum edge tension value Tb at the edge of the vertex to a higher value while moving axially centrally, the two lateral zones being separated by at least one median zone in which the median tension Tm is substantially constant on a plurality of turns.

2. A tire according to claim 1, wherein the crown reinforcement comprises at least one zone of several turns in which the circumferential tension varies turn by turn.

3. The tire according to one of claims 1 or 2, wherein the central zone is disposed substantially axially centrally.

4. A tire according to one of the preceding claims, wherein the circumferential tension of the wire varies substantially symmetrically on each side of the median zone of the tire.

5. A tire according to one of the preceding claims, wherein the tension of the yarn in the side edge areas of the crown is substantially zero.

Tire according to one of the preceding claims, wherein the circumferential tension of the voltage variation zones varies substantially linearly over at least a portion of the zone.

7. A tire according to one of the preceding claims, wherein the central zone comprises a central portion consisting of a plurality of turns in which the voltage Tpc is lower than that of the central zone.

8. A tire according to claim 7, wherein the value of the voltage Tpc of said central portion is substantially zero.

9. A tire according to one of the preceding claims, wherein the voltage varies inversely and substantially symmetrically.

10. A tire according to one of the preceding claims, comprising a single circumferential wire on which the voltage variation profile is applied.

11. A tire according to one of the preceding claims, wherein the median tension Tm corresponding to a maximum tension of the yarn.