EP3277520A1

EP3277520A1 - Tyre comprising a carcass structure equipped with strips

Info

Publication number: EP3277520A1
Application number: EP16716901.0A
Authority: EP
Inventors: Bertrand BOISDON; Sébastien RIGO; Bastien LIMOZIN
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2015-03-30
Filing date: 2016-03-24
Publication date: 2018-02-07
Also published as: FR3034352A1; CN107995895A; FR3034352B1; WO2016156960A1

Abstract

The invention relates to a tyre (6) comprising two sidewalls (7) connected at a tyre crown zone (8), and a bead zone, each bead comprising a circumferential reinforcing element (9), a carcass-type reinforcing arrangement (1) being disposed from one bead (9) to another, passing through the sidewalls (7) and the crown (8), as well as comprising a plurality of substantially flat strips (3) of average width "L", disposed axially in at least two radially stacked rows arranged with a pitch of between L and 2L, said rows being separated from one another by a layer (4) of elastomer composition and offset by a distance of between 0.2 and 0.5 times the pitch, said strips (3) having a nitrogen permeability of between 0.001 and 10 cm3.mm/m2/day/atm.

Description

PNEUMATIC COMPRISING A CARCASS STRUCTURE

WITH STRIPES

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a tire comprising two sidewalls joined by a tire crown area, beads, provided in the radially inner extension of the sidewalls and a carcass-type reinforcement arrangement arranged from one bead to the other in passing by the flanks and the summit.

STATE OF THE PRIOR ART

Conventionally, the sealing function of the tires is implemented using a layer of elastomeric material having a substantially high airtightness ratio. This layer is conventionally arranged radially internally and at the same time forms a protective layer with respect to the tire cavity.

More specifically, the tire is conventionally defined on the basis of three zones:

a radially outer zone and in contact with the ambient air. This zone consists essentially of the tread and the outer zone of the tire sidewalls;

a radially inner zone in contact with the inflation gas. This zone is generally constituted by the inflation gas-tight layer. It is sometimes referred to as the "inner liner". This area is described in more detail below.

- The inner area of the tire, that is to say that between the outer and inner zones. This area includes layers or webs that are referred to herein as "inner layers of tires". These are by for example, the carcass ply, the tread sub-layers, the tire belt plies, or any other layer that is not in contact with the ambient air or the inflation gas of the tire.

In a conventional tire of the "tubeless" type (that is to say without an air chamber), the radially inner face has an airtight layer (or more generally any inflation gas) which allows inflation and maintenance under pressure of the tire. Its sealing properties enable it to guarantee a relatively low rate of pressure loss, making it possible to keep the inflated tire in a normal operating state for a sufficient duration, normally of several weeks or several months. It also serves to protect the carcass reinforcement structure and more generally the rest of the tire of a risk of oxidation due to the diffusion of air from the interior of the tire. This layer is called "waterproof layer". It covers the entire inner wall of the tire, extending from one side to the other, at least up to the level of the rim hook when the tire is in the mounted position.

This sealed layer defines the radially inner face of the tire and has a sealing coefficient such that the layer may be described as sealed relative to the other layers of the tire. Usually, this waterproof layer is at least three times less permeable, that is to say at least three times more impervious than the inner layers.

[0006] The document WO2008 / 145277 of the Applicants proposes a tire provided with a layer which is impervious to inflation gases. This layer is designed from an elastomeric composition comprising at least one thermoplastic copolymer elastomer with polystyrene and polyisobutylene blocks and a polybutene oil. In this architecture, the "inner liner" function is fulfilled by compositions based on butyl rubber (isobutylene and isoprene copolymer), which have long been recognized for their excellent sealing properties, or based on thermoplastic elastomer copolymer block polystyrene and polyisobutylene.

[0007] It is known that the performance of the tires is optimal for a defined inflation pressure. This inflation pressure must be checked regularly by users to enable them to obtain the best performance of their tires. It is therefore desirable to further improve the overall tire tightness in order to improve the tire performance stability over time while extending the time intervals between which users must check the inflation pressure of their tires.

[0008] FIG. 1 illustrates an example of an architectural tire 10 with such a sealing layer, identified by the reference numeral 11. This type of solution is well known since it makes it possible to produce tires having improved properties. particularly advantageous sealing. By cons, the implementation of the solution requires the preparation of an additional layer, provided only for this function, with significant costs of preparation and installation.

[0009] Also conventionally, in tire architectures, the carcass plays an important role in all the characteristics of the tire, namely its mechanical characteristics, its behavior, its performance, and so on. In addition, the other architectural elements depend directly on the design of the carcass. Conventionally, the carcass is made from a ply (the carcass ply), consisting of an elastomeric matrix in which longitudinal reinforcements are arranged, as shown in Figure 1 (reference numeral 12). The carcass ply is conventionally made over long lengths, and subsequently cut into a plurality of sections for producing as many tires. There are also various cases of tires built on the basis of a carcass made from strips. For example, the document FR2721553 describes a tire comprising a carcass reinforcement consisting entirely of a single strip wound circumferentially with a covering between two turns, so as to ensure the continuity of the carcass. The strip is oriented in the circumferential direction and does not perform any function in relation to the seal.

US3356553 discloses a tire provided with a carcass consisting of a single strip placed continuously with a slight angle. The strip is arranged in two layers having a variable overlap decreasing from the lower zone to the top.

These two documents are related to architectures using a single strip, and not related to sealing functions.

EP2205452 discloses a tire comprising a sealed envelope of elastomer composition and a reinforcing structure essentially formed of a plurality of fibers embedded in the elastomeric composition and arranged in layers. This reinforcement structure comprises at least one carcass layer and a crown layer. The fibers of these layers are bonded to each other and oriented, relative to the median plane (P) of the tire, at respective angles of the order of 90 degrees and 0 degrees, each of these fibers also having a cross section related and flattened form. The fibers are arranged without overlap between them.

The application EP1397262 discloses a radial tire comprising a crown, two beads extended by flanks comprising a radial carcass reinforcement. This carcass reinforcement extends into the crown and is anchored in each bead to at least one inextensible element in the circumferential direction. The tire comprises, in at least one sidewall, a additional reinforcement frame consisting of an elastomeric composition of reinforcements inclined relative to the circumferential direction.

The reinforcement additional reinforcement comprises at least one group of at least two strips extending in the circumferential direction. Each band of width Li is substantially equal to or greater than the total width Lt of the armature divided by the total number of bands in the group considered. Each band is formed of an elastomeric composition reinforced by a plurality of cables or wires inclined at an angle of between 30 ° and 90 °, in the same group, each circumferential band being partially superimposed with a neighboring band. In this architecture, the strips are arranged circumferentially.

It is noted that none of the above documents describes a tire having an optimized architecture so as to reduce the weight, while ensuring a high level of tightness.

To overcome these disadvantages, the invention provides different technical means.

SUMMARY OF THE INVENTION

First, a first object of the invention is to provide a tire whose mass is substantially reduced, without affecting the other characteristics of the tire.

Another object of the invention is to provide a tire whose mass is substantially reduced, while maintaining a good level of tightness.

Another object of the invention is to provide a tire with a simplified architecture. Yet another object of the invention is to provide a simple tire and inexpensive to manufacture.

To do this, the invention provides a tire comprising two sides joined by a tire crown area, a bead area each comprising a circumferential reinforcing element, provided in the radially inner extension of the flanks, a reinforcing arrangement. carcass type arranged from one bead to the other through the flanks and the top, and comprising a plurality of substantially flat strips and average width "L" arranged axially in at least two rows superimposed radially, each row comprising a plurality of strips arranged with a pitch of between L and 2L, the rows being separated from each other by a layer of elastomeric composition (decoupling) and offset with a phase shift of between 0.2 times said pitch and 0.5 times said pitch, the strips having a permeability to nitrogen of between 0.001 and 10 cm3. mm / m 2 / day / hour.

Advantageously, the reinforcing arrangement is covered with a layer of elastomeric mixture on each of the faces.

According to an advantageous embodiment, the pitch is between 1.1 L and 1.4 L in the bead zone.

According to another advantageous embodiment, the phase difference between the two rows is between 0.35 times said step and 0.5 times said step.

Advantageously, the strips have an average width of between 1 and 12 mm and preferably between 3 and 7 mm.

The strips preferably have a thickness of between 0.05 and 0.35 mm and preferably between 0.05 and 0.15 mm. The thickness of the elastomeric mixing layer (decoupling) is advantageously between 0.1 and 0.35 mm.

According to another embodiment, the elastomer composition comprises at least one compound chosen from compounds having a Young's modulus of between 0.1 and 10 MPa, and preferably between 0.1 and 3 MPa.

The strips preferably have a permeability to nitrogen of between 0.001 and 10 cm3. Mm / m 2 / day / hour and more preferably between 0.01 and 1 cm 3 mm / m 2 / day / hour.

Advantageously, the layer of elastomeric decoupling composition has a permeability of between 10 and 2000 cm3.mm/m2/day/atm, and more preferably between 200 and 1000 cm3.mm/m2/jour/atm.

The strips may be mono-material, preferably selected from PET, PEN, aluminum, polyamides and steel.

Alternatively, the strips are made of composite material with PET matrix, PEN, PA or epoxy resin.

[0034] Advantageously, the composite material comprises matrix-based fiber materials, and arranged substantially unidirectionally. A predetermined rate of fibers is preferably provided to achieve the desired tensile strength characteristics.

The composite material may comprise PET or PEN fibers and a polyamide-based matrix. DESCRIPTION OF THE FIGURES

All the details of implementation are given in the description which follows, supplemented by FIGS. 1 to 10, presented solely for purposes of non-limiting examples, and in which:

- Figure 1 is a sectional view of a tire of known type comprising a substantially sealed inner layer;

FIG. 2 is a section of a cross section of a carcass ply of a tire of known type such as that of FIG. 1;

FIG. 3A is a section in the lower zone of a carcass ply according to the invention;

FIG. 3B is a section in the shoulder zone of a carcass ply according to the invention;

- Figure 4 is a section of a carcass ply according to the invention with the indications for identifying the relative dimensions of the various elements;

FIG. 5 is a perspective view of a carcass ply according to the invention shaped for integration into a tire according to the invention;

- Figure 6 is an elevational view of a carcass ply according to the invention;

FIG. 7 illustrates a succession of sections of three strips adjacent to a carcass according to the invention in order to show the reduction of the overlap between the two rows of strips from the lower zone (with stronger overlap) towards the zone of shoulder and crown (overlap less important) of the tire, following the arrow indicating a radial position further and further away from the center of rotation;

FIG. 8 is a sectional view of a tire according to the invention comprising a carcass ply according to the invention, this tire being devoid of a tight inner layer;

FIG. 9 is a graph illustrating the permeability ratio as a function of the width of the strips, in relation to a reference tire of the prior art; FIG. 10 is a column diagram showing the loss of pressure in mb for different embodiments with different widths of strips.

DETAILED DESCRIPTION OF THE INVENTION

In the present document, the term "carcass ply" is understood to mean a reinforcement structure for a tire in the form of a layer consisting of a matrix made of elastomeric material in which generally textile filaments or yarns are arranged according to a substantially parallel and longitudinal alignment. The carcass ply is advantageously manufactured flat, in great length, then cut to the appropriate dimensions for the manufacture of a tire for which the carcass ply is adapted.

By "decoupling layer" means an elastomeric layer whose mechanical properties allow a relative re-arrangement of the strips together when the carcass ply is put into toroidal form, such as at the time of integration of the carcass ply to an assembly intended to constitute a tire (operation referred to as "conformation" in this document).

"Calender layer" means a layer intended to cover a surface, for example for protection purposes. In this document, the calender layer is intended to cover the strips.

An element is said "radially inward" with respect to another element, when its radial distance measured from the axis of rotation of the tire is shorter than that of the other element.

"Radial direction" means the direction intersecting the axis of rotation of the tire and perpendicular thereto. By "longitudinal direction" or "circumferential direction" means a direction which corresponds to the periphery of the tire and which is defined by the rolling direction of the tire.

By "unconformed profile" is meant a substantially flat or cylindrical profile.

By "shaped profile" means a torus-shaped profile. In the case of a "shaped profile" carcass ply, the various points of the carcass ply do not have the same radius.

By "conformation" is meant the phase or operation in which the passage of a substantially flat or cylindrical profile to a toroidal profile is performed. This phase is generally a step in the tire manufacturing process in which the carcass ply is disposed on a core or on a deformable membrane (for example by inflation) adopting the toric profile of a tire. During this step, the central sector corresponding to the tread adopts a radial position more and more distant from the center and the flanks adopt a substantially radial alignment. This step generates a significant difference in the radial positioning of the tire zones. In the flanks, the further one moves away from the beads, the greater the spacing between the radial reinforcements (including those of the carcass) becomes important. The implementation of this phase is possible if the materials are provided so as to allow the rearrangement of the architectural elements relative to each other without damage to the product.

[0046] Figure 1 illustrates an example of a carcass ply performed in conventional manner. A plurality of longitudinal reinforcements are thus encompassed in a layer of elastomeric composition. Figure 2 schematically illustrates the path ZZ to be made by the inflation gas to pass through the layer corresponding to a conventional carcass ply 12. It is observed that this course is substantially rectilinear since the elastomer mixture used does not form significant obstacle against the progression of the inflation gas. In such an architecture, the sealed inner layer 11 (Figure 1) is provided to slow the progression of the inflation gas as soon as this gas comes into contact with the inner wall.

FIGS. 3A and 3B schematically show the relative provisions of the constituent elements for embodiments of carcass plies 1 according to the invention, when the ply is flat in FIG. 3A, and in FIG. web is shaped on a core so as to adopt the toroidal shape corresponding to the tire to be produced.

In Figure 3A, two rows of strips 3 arranged to create a lateral offset or phase shift are separated from one another by a layer 4 of elastomeric decoupling composition. On both sides of the strips 3, the sheet is covered by a layer 5 of calendering.

In this example, the arrow Y-Y illustrates the path to be made by air to get through the carcass ply. It is observed that the Y-Y path of FIG. 3A is substantially larger than the Z-Z path of FIG. 2, where the crossing of the material takes place perpendicularly to the wall of the layer. The additional distance to be traveled by the inflation gas molecules serves to slow or retard the flow of air to the outside, thus reducing the loss of inflation gas.

However, in practice, as seen in Figure 5, the carcass ply, when arranged in a tire, adopts a toric profile corresponding to that of the tire. When moving from a flat profile to a toric profile (during the "conformation" phase), depending on the position in the profile of the tire, the strips deviate from each other, to form the final profile. For example, in the shoulder area of the tire (example of FIG. 3B), the overlap between the successive rows of strips 3 is reduced, and the diffusion path DD is also shortened. So the profile toric tire has the effect that the overlap between the strips varies depending on the radial position, as described below in connection with Figures 5 to 7.

The proposed carcass ply 1 architecture makes it possible to obtain a level of tightness sufficient for the tire which incorporates this carcass ply to have a good level of sealing without having to use an inner layer such as that described with reference to FIG. figure 1.

FIG. 4 illustrates some geometrical details of the carcass ply 1 according to the invention:

the dimension L corresponds to the width of the strip: advantageously between 1 and 12 mm and preferably between 3 and 7 mm;

- The dimension P corresponds to the pitch: advantageously between L and 2L, and preferably between 1.1 L and 1.4L;

the dimension E corresponds to the thickness of a strip: advantageously between 0.05 and 0.35 mm and preferably between 0.05 and 0.15 mm;

the dimension D corresponds to the thickness of the decoupling layer: advantageously between 0.1 and 0.35 mm;

- Dimension C corresponds to the thickness of the calender layer: advantageously between 0.1 and 0.5 mm and preferably around 0.3 mm.

Figures 5 to 7 illustrate, from different complementary views, the progression of the overlap between the two rows of strips according to the decrease of the radius due to the toric form of the tire. FIG. 5 illustrates a schematic representation in perspective of the arrangement of the strips 3 to form a carcass-type reinforcement arrangement 2. FIG. 6 shows a side view of the reinforcing arrangement 2. FIG. 7 shows a succession of sections of three adjacent strips presented in relation to FIG. 6, so that the strips at the bottom of the Figure 7 correspond to the area of the bead of the tire. At this position, recovery is the most important. The higher the radius increases, according to the arrow of Figure 7, the more the recovery is reduced.

The applicants have nevertheless found, surprisingly, that despite the fact that the recovery decreases as a function of the radius, the carcass ply 1 according to the invention provides a particularly high level of tightness, and sufficient to allow to design a tire without internal sealing layer. Such a tire 6 has a sealing level comparable to a conventional tire using a tight inner layer, as in the example of Figure 1.

An example of such a tire 6 is shown in Figure 8. It comprises a carcass 1 as previously described. This carcass 1 extends from one bead 9 to the other, through the sidewalls 7 and the crown 8 of the tire 6. The tire 6 does not have a tight inner layer (comparable to the layer 11 of the tire reference of FIG. 1).

EXAMPLE 1 (FIG. 9): Permeability ratio between the reference tire and the inner layer of permeability and the tire according to the invention.

The graph of Figure 9 comprises, as abscissa, the values of widths of strips expressed in mm. On the ordinate, the graph presents permeability ratio values between the reference tire having an inner layer of permeability and the tire according to the invention. Curve A shows the values obtained with a configuration in which the decoupling layer between the strips is 0.1 mm. For curve B, this thickness is 0.3 mm. Curve C shows the results for a decoupling thickness of 0.5 mm. Curve D shows the results with a decoupling layer of 0.7 mm. The line E illustrates the limit under which the values represented constitute an improvement with respect to the reference tire. Values above this line are less favorable than for the reference tire. The curves of Figure 9 illustrate the results obtained with a carcass ply and a tire according to the invention. These tests made it possible to obtain particularly conclusive results with respect to the sealing gains. The tests were carried out in comparison with a reference tire of known type such as that of FIG. 1, which comprises an internal layer designed to confer the sealing properties. For the reference tire, the measured pressure loss was 45 mb / month (millibars / month). Various embodiments of tires according to the invention have been measured. The various embodiments further involved several strip widths and several thicknesses of the decoupling layer. For a strip width of 6 mm, the measured pressure loss was 39 mb / month (point c1 of curve C). For a strip width of 8 mm, the measured pressure loss was 14 mb / month (point c2 of curve C). For a strip width of 10 mm, the measured pressure loss was only 9 mb / month (point c3 of curve C). These last three measurements are decoupling isocouples with a thickness of 0.5 mm. It is observed that all the pressure loss values for the tires according to the invention provided with strips at least 7 mm wide allow gains relative to the reference tire. The gains are particularly advantageous for the largest widths of strips and the thinnest decoupling layers, in particular for 0.1 and 0.3 mm (curves A and B).

EXAMPLE 2 (FIG. 10): Pressure loss measurements as a function of the thickness of the strips for a 165 / 70R16 tire.

The column diagram of FIG. 10 confirms the results expressed in the graph of FIG. 9. This diagram illustrates the pressure loss values, expressed in mb, for various variants of embodiment of tires according to the invention with different widths. strips. On the left of the table, column F indicates the value obtained for the tire used as a reference (tire 165 / 70R16 with internal sealing layer as described in connection with the tire of FIG. 1), ie 45 mb. Column G indicates the pressure loss value for a tire according to the invention with strips with a width of 6 mm. The pressure loss value is 39 mb. Column H indicates a value of 14 mb, corresponding to the pressure loss for one embodiment with 8 mm strips. Finally, column I shows the result obtained with strips of 10 mm, 9mb.

The measurements carried out during these tests have thus made it possible to confirm, on the one hand, that the permeability decreases with the increase in the width of the strips, and on the other hand that the permeability decreases with the reduction in the thickness of the strips. calendering between two rows of strips.

Moreover, it has been observed that the strips allow to obtain drift rigidity gains, as well as weight gains due to the rigidity provided by the strips.

Reference numbers used in the figures

Carcass tablecloth

Reinforcement arrangement

strips

Decoupling layer

Calender layer

Pneumatic

flanks

Mountain peak

beads

Pneumatic according to the prior art

Internal waterproof layer according to the prior art

Carcass according to the prior art

Claims

A tire (6) comprising two sidewalls (7) joined by a tire crown zone (8), a bead zone each comprising a circumferential reinforcing element (9), provided in the radially inner extension of the flanks, an arrangement carcass-type reinforcement (1) arranged from one bead (9) to the other through the flanks (7) and the top (8) and comprising a plurality of strips (3) substantially flat and of medium width " L "arranged axially in at least two radially superposed rows, each row comprising a plurality of strips (3) arranged with a pitch of between L and 2L, the rows being separated from each other by a layer (4) of elastomer composition and staggered with a phase shift between 0.2 times said step and 0.5 times said pitch, the strips (3) having a permeability to nitrogen of between 0.001 and 10 cm3.mm/m2/day/atm.

2. A tire according to claim 1, wherein the strips (3) have an average width of between 1 and 12 mm and preferably between 3 and 7 mm.

3. A tire according to one of the preceding claims, wherein the strips (3) have a thickness of between 0.05 and 0.35 mm and preferably between 0.05 and 0.15 mm.

4. A tire according to one of the preceding claims, wherein the thickness of the elastomeric mixture layer (4) is between 0.1 and 0.35 mm.

5. A tire according to one of the preceding claims, wherein the elastomeric composition (4) comprises at least one compound selected from compounds having a Young's modulus of between 0.1 and 10 MPa, and preferably between 0.1 and 3 MPa.

6. A tire according to one of claims 1 to 5, wherein the strips (3) are mono-material.

7. A tire according to claim 6, wherein the mono-material is selected from PET, PEN, aluminum, steel or polyamides.

8. A tire according to one of claims 1 to 5, wherein the strips (3) are made of composite material, with a matrix of PET, PEN, PA or epoxy resin.

The tire of claim 8, wherein the composite material comprises matrix-based fiber materials, said fibers being arranged in a substantially unidirectional arrangement.

The tire of claim 8, wherein the composite material comprises PET or PEN fibers and a polyamide-based matrix.

11. Tire according to one of the preceding claims, wherein the pitch is between 1.1xL and 1.4xL in the bead zone.

12. A tire according to one of the preceding claims, wherein the phase difference between the two rows is between 0.35 times said step and 0.5 times said step.