WO2003093032A1

WO2003093032A1 - Tyre with bead comprising a micro-deformable anchor zone

Info

Publication number: WO2003093032A1
Application number: PCT/EP2003/004417
Authority: WO
Inventors: Pascal Auxerre
Original assignee: Societe De Technologie Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2002-04-29
Filing date: 2003-04-28
Publication date: 2003-11-13
Also published as: AU2003233193A1

Abstract

The invention relates to a tyre for the wheel of a vehicle, comprising: two sidewalls; beads which are disposed radially inside each of the sidewalls, each bead comprising a seat and an outer flange which are intended to come into contact with a suitable rim; and a reinforcing structure (2) which extends in an essentially radial manner from each of the beads along the sidewalls towards the crown. According to the invention, at least one of the aforementioned beads comprises a zone (30) for anchoring the reinforcing structure in said bead, consisting of a substantially radial arrangement of circumferential wires (12) which are disposed essentially adjacent to a portion of the reinforcing structure, said anchor zone being at least partially formed by a matrix comprising a plurality of micro-deformable zones (80) which can facilitate the steps involving the mounting/removal of the tyre on/from a rim adapted therefor. The above-mentioned micro-deformable zones contain particles which are immiscible in the matrix, such as, preferably metal, beads, microbeads or rods.

Description

PNEUMATIC TIRE WITH MICRODEFORMABLE ANCHORING AREA

The present invention relates to a tire whose "mountability / dismountability" characteristics are optimized, thanks to judiciously arranged "microdeformable" zones.

The presence of at least one of these zones, for example within the anchoring zone of the reinforcing structure, promotes the deformability of the tire. This results in better rim mountability. The assembly / disassembly difficulties are lessened and the qualities of the product linked to durability are improved. These different aspects are particularly advantageous for tires in which at least one of the beads has a seat with a generator whose axially inner end is on a circle with a diameter greater than the diameter of the circle on which the axially outer end is located. This type of design is particularly suitable for new generations of tires which can be used, within certain limits, under conditions of low pressure, or even zero or almost zero pressure, with an elimination of the risk of the tire becoming detached from the rim on which it is mounted. This concept is often referred to as "extended mobility".

For a long time, tire manufacturers have been trying to develop a tire that does not create any source of risk or potential danger during an abnormal lowering or even a total loss of pressure. One of the difficulties encountered relates to running flat or at very low pressure. In fact, when running at very low pressure, or even at zero pressure with conventional tires, the beads are very likely to become detached from the periphery of the rim against which they were held by the pressure.

Many solutions have been tested in order to overcome these drawbacks. Often these solutions cause additional difficulties in mounting and dismounting the tire on the rim. Furthermore, the function of tightening the tire on the rim is an essential function for ensuring the qualities of the tire in operation. Indeed, it acts directly or indirectly on multiple aspects such as mounting (sometimes called "clipping") or fixing the tire, sealing the tire, rotation on the rim, etc. These functions are all critical and require specific characteristics and rigorous manufacturing of the products, in particular if high quality standards are sought. However, rims and tires often have slightly different dimensions for the same code, mainly due to manufacturing tolerances. These dimensional variations complicate compliance with the various functions previously listed.

To fulfill these functions, two main types of solutions are used industrially. First of all, for traditional tires, the bead wire performs all of these functions simultaneously.

More recently, for several types of products manufactured by the applicant, the conventional rod is replaced by an anchoring zone comprising in particular arrangements of circumferential wires cooperating with the carcass-type reinforcement structure via an anchoring or binding mixture. Again, the anchoring area provides all of the functions presented above.

In these two cases, it is however difficult to optimize certain parameters, because very often, the improvement of one, is done to the detriment of another. This game of compromise between gain on one side and penalization on the other, therefore has certain limits, since it is often difficult to tolerate poorer performance for certain aspects.

Document EP 0 582 196 presents a tire comprising a tread extended by two sidewalls and two beads as well as a carcass anchored in the two beads with an annular reinforcement. The carcass is made up of wires arranged adjacent to each other, circumferentially aligned and in contact with at least one layer of bonding rubber of very high elastic modulus in the attachment zone of the bead comprising the reinforcement. annular. In this tire, the annular reinforcement of the bead attachment zone consists of stacks of circumferential cords with interposition between the reinforcing cords of the carcass and these stacks of a layer of bonding rubber of very high elasticity modulus . This embodiment is intended for tires of the conventional type, with retention of the beads against the rim hook due to the inflation pressure of the tire. We find in this type of arrangement a predominance of lateral or axial type forces, inducing significant compressive forces acting substantially axially from the walls towards the center of said bead. These forces increase as a function of the inflation pressure. The increase in pressure tends to slide the bead against the hook, radially outward. The forces induced radially inwards against the seat of the rim decrease with increasing pressure, or with any increase in tension in the carcass-type reinforcing structure.

Note also that the stacks of son are aligned in a direction substantially parallel to the orientation of the profile of the rim hook against which the bead is supported. The profile of the bead of this type of tire is relatively narrow and elongated; the anchor is distributed over most of the height and width of the bead. The passage of the carcass in the bead is generally substantially central with respect to the walls of said bead. Furthermore, in the case of a relatively narrow bead subject to predominantly axial forces, neither the inflation pressure nor the tension induced in the carcass allow the generation of significant moments or couples, tending to rotate or rotate the bead on itself.

With such a type of tire, if the pressure drops and rolling continues, the maintenance of the tire on the rim is no longer ensured, and in most cases, there is a backlash.

Document EP 0 673 324 describes a rolling assembly comprising at least one tire with a radial carcass reinforcement anchored in each bead and a rim of particular shape. This rim has a first seat with a generator such that the axially outer end of said generator is distant from the axis of rotation by a length less than the distance separating its axially inner end and is delimited axially on the outside by a rim projection or rim. The tire includes bead seats suitable for mounting on this rim. The type of pneumatic / rim interface proposed in this document has many advantages compared to already known solutions, in particular in terms of ease of assembly / disassembly while allowing a certain distance to be traveled despite a pressure drop.

The document EP 0 748 287 describes a solution allowing a first optimization of the basic technology described in the document EP 0 673 324 previously cited. It is a tire of which at least one bead has a structure making it possible to modify the tightening of said bead as a function of the tension of the carcass reinforcement and in particular a reinforcement thereof when the inflation pressure increases. up to its nominal value. The document thus proposes the use of a bead with anchoring of the end of the carcass by turning it around the base of the rod, by the axially and radially inner sides with respect to the rod. The bead also comprises, adjacent to the rod and axially outside of the latter, a rubber mixture profile of relatively high hardness against which the rod can come to exert a compressive force during an increase in tension of the carcass reinforcement. This compressive force creates a self-tightening of the tip of the bead on the mounting rim. The tension of the carcass therefore causes the rod to move outward, so that the latter generates said compressive force. In such a configuration, the presence of a rod of the conventional type and the inversion of the carcass under the latter are presented as being essential, in order to generate the compression force. This limits the possibilities of considering other types of arrangement.

On the other hand, document EP 0 922 592 describes two embodiments with anchoring of the carcass by turning it axially outward.

The first mode proposes an anchoring of the carcass in the bead by turning radially outward from the end of the carcass. The upturn is surrounded on either side by two radially superposed layers of metal wires arranged axially side by side and covering substantially the entire axial portion along the seat of the bead. The layers are arranged so as to be parallel to the seat. The types of wires and the corresponding dimensions are very precise. The second solution proposed in this document relates to bead seats with different diameters. The carcass is also stowed differently than the first solution. First of all, the carcass is subdivided into two radially separated portions at the level of the bead. Each portion is joined by a layer of wires arranged radially, each layer being disposed radially outwardly against each of the carcass portions. The radially outer carcass portion and the layer of wires radially inside are separated by an elastomer type insert of high hardness provided in the bead. This insert axially lines the central portion of the bead and rises radially outwards and axially inwards, beyond the radial limit of presence of the metallic wires.

The two examples of solutions in document EP 0 922 592 have several drawbacks. Thus, the stowage of the carcass proposed in this document requires the presence of an axially outward turning of the end portion of the carcass. On the other hand, the superimposed layers of son are arranged radially near the seat of the bead, for the most part in a radial position closer to the axis of rotation than the upper portion of the rim on which the bead rests. Unless highly extensible cords are used, mounting / dismounting of the tire is difficult to perform, due to the unfavorable radial position of the cords. We also note that the stacks are oriented substantially parallel to the profile of the seat against which the bead presses. According to the second solution, the carcass is subdivided into two portions and a high hardness insert is necessary to separate on the one hand the layers of wires and on the other hand the two carcass portions. However, the carcass is not anchored in the insert. The shape of the insert described is limiting. The present invention therefore proposes to overcome the various drawbacks inherent in the solutions set out above.

To do this, it provides a tire for a vehicle wheel, comprising

-two sides spaced axially from one another, joined to their radially outer portions by a crown zone provided on its radially outer portion with a circumferential tread;

-beads, arranged radially inside each of the sidewalls, each bead comprising a seat and an external flange intended to come into contact with a suitable rim;

a reinforcing structure extending substantially radially from each of the beads, along the flanks, towards the crown area;

at least one of said beads comprising:

a zone for anchoring the reinforcing structure in said bead, comprising a substantially radial arrangement of circumferential wires disposed substantially adjacent to a portion of the reinforcing structure, said anchoring zone being at least partially made up of a matrix comprising a plurality of microdeformable zones.

The presence of these zones is likely to favor the stages of mounting / dismounting the tire on a rim adapted for the latter. The “deformability” of the tire is increased, the effort required is less and the risk of deterioration of the product due to repeated cycles is thereby minimized.

According to an advantageous exemplary embodiment, the microdeformable zones contain particles immiscible in the matrix.

These particles can take the form, for example of beads or micro-beads, of rods or plates, integrated in the matrix. These various elements are adapted to allow micro-creep of the matrix favoring the mounting / dismounting of the tire.

Advantageously, the material of the particles is non-elastomeric and preferably metallic.

According to an advantageous embodiment of the invention, the microdeformable zones correspond substantially to the interface zones between the matrix of rubber material and the circumferential wires. As in the previous examples, the presence of wires, arranged in the matrix, and immiscible in the latter, promotes the deformability of the product. This results in easy mounting / dismounting on the rim.

The present invention is particularly advantageous with a tire in which the bead also comprises a bead seat comprising a generator whose axially inner end is on a circle with a diameter greater than the diameter of the circle on which the axially outer end is located.

According to an advantageous embodiment, the arrangement of circumferential wires of the anchoring zone comprises at least two piles distributed on either side of the reinforcement structure, a connection mixture being arranged between the circumferential wires and the structure reinforcement.

Here are still other advantages which the invention also makes it possible to benefit from.

The anchoring zone does not comprise a rod, in particular a rod of the traditional type, such as for example a rod r ultifilaire against which a carcass ply is turned over, so that the zone of cooperation between the inverted portion of ply and the rod provides support for the carcass.

Advantageously, the carcass-type reinforcement structure extends substantially radially from each of the beads, along the sides, towards the summit area. Said structure can thus be unitary and extend from one bead to another, or even be divided into two half-structures, each extending along a single flank.

The number of stacks as well as the number of windings or turns of each of the stacks is advantageously established as a function of the characteristics sought for the tire, for example its operating pressure. For example, a higher number of stacks may be desired in order to increase the rigidity at the bead area.

The carcass-type structure preferably consists of a wire winding going back and forth between the two beads, forming loops in each of the beads. Furthermore, the wire winding preferably consists of a single wire.

According to another advantageous variant, the internal bead intended to be disposed on the internal side of the wheel and the external bead intended to be installed on the external side of the wheel, are arranged asymmetrically. So for example, the number of stacks or the number of turns of each of the stacks can be different, for example so that the number of stacks of threads in the inner bead is different from the number of stacks of threads in the bead exterior side.

According to another aspect, the symmetry concerns the arrangements of the anchoring, intermediate and support zones. Each of the beads can have different architectures where, for example, the shapes, the arrangements, the dimensions of one or more of the zones can vary. One can also vary the constituent materials, the mechanical characteristics, such as for example the hardness, just as one can vary the number of zones.

Other characteristics and advantages of the invention will appear on reading the exemplary embodiments of the tire according to the invention, given without limitation and with reference to the appended FIGS. 1 to 3, in which: FIG. 1 illustrates, in cross section, a tire according to the invention;

FIG. 2 illustrates, in enlarged cross-section, a bead of a first variant of a tire according to the invention;

FIG. 3 illustrates, in enlarged cross-section, another variant of beads, where the different zones of the bead are arranged in an advantageous manner.

The reinforcement or reinforcement of tires is currently - and most often - constituted by stacking one or more plies conventionally designated “carcass plies”, “crown plies”, etc. This way of designating the reinforcing reinforcements comes from the manufacturing process, consisting in producing a series of semi-finished products in the form of plies, provided with wire reinforcements often longitudinal, which are then assembled or stacked in order to make a blank of pneumatic. The sheets are made flat, with large dimensions, and are then cut according to the dimensions of a given product. The plies are also assembled, initially, substantially flat. The blank thus produced is then shaped to adopt the toroidal profile typical of tires. The semi-finished products called "finishing" are then applied to the blank, to obtain a product ready for vulcanization.

Such a “conventional” method involves, in particular for the manufacturing phase of the tire blank, the use of an anchoring element (generally a bead wire), used to anchor or maintain the carcass reinforcement in the area of the tire beads. Thus, for this type of process, a portion of all the plies making up the carcass reinforcement (or a portion only) is turned around a bead wire disposed in the bead of the tire. This creates an anchoring of the carcass reinforcement in the bead.

The generalization in the industry of this type of conventional process, despite many variations in the way of making the sheets and the assemblies, has leads those skilled in the art to use a vocabulary modeled on the process; hence the generally accepted terminology, including in particular the terms "plies", "carcass", "rod", "conformation" to designate the transition from a flat profile to a toroidal profile, etc.

However, today there are tires which do not, strictly speaking, have “plies” or “bead wires” according to the preceding definitions. For example, document EP 0 582 196 describes tires produced without the aid of semi-finished products in the form of plies. For example, the threads of the various reinforcement structures are applied directly to the adjacent layers of rubber mixtures, the whole being applied in successive layers to a toroidal core whose shape allows a profile to be obtained directly similar to the final profile of the tire. during manufacture. Thus, in this case, there are no more "semi-finished", nor "tablecloths", nor "rod". The products of. base such as rubber mixes and reinforcements in the form of threads or filaments, are directly applied to the core. This core being of toroidal shape, we no longer have to form the blank to pass from a flat profile to a profile in the form of a torus.

Furthermore, the tires described in this document do not have the "traditional" reversal of the carcass ply around a bead wire. This type of anchoring is replaced by an arrangement in which there is disposed adjacent to said flank reinforcement structure of the circumferential filaments, the whole being embedded in a rubber mixture of anchoring or binding.

There are also assembly processes on a toroidal core using semi-finished products specially adapted for rapid, efficient and simple installation on a central core. Finally, it is also possible to use a composite comprising both certain semi-finished products to produce certain architectural aspects (such as tablecloths, rods, etc.), while others are produced from direct application. mixtures and / or reinforcements in the form of filaments. In this document, in order to take account of recent technological developments both in the field of manufacturing and for product design, the conventional terms such as "tablecloths", "rods", etc., are advantageously replaced by neutral terms or independent of the type of process used. Thus, the term “carcass-type reinforcement” or “sidewall reinforcement” is valid for designating the reinforcing threads of a carcass ply in the conventional process, and the corresponding threads, generally applied at the flanks, of a tire produced using a semi-finished process. The term “anchoring zone” for its part, can designate the “traditional” turning of the carcass ply around a rod of a conventional process just as much as the assembly formed by the circumferential filaments, the rubber mixture and the adjacent flank reinforcement portions of a lower zone produced with a method with application to a toroidal core.

In the present description, the term "thread" generally designates both monofilaments and multifilaments or assemblies such as cables, twists or any other equivalent type of assembly, regardless of the material and the treatment. of these sons. It may for example be surface treatments, coating or pre-sizing to promote adhesion to the rubber.

On the other hand, by radial structure is meant an arrangement at 90 degrees, but also, depending on usage, at an angle close to 90 °.

We know that, in a traditional way, the carcass ply (s) are turned around around a rod. The rod then fulfills a function of anchoring the carcass. Thus, in particular, it supports the tension developing in the carcass wires, for example under the effect of the inflation pressure. The arrangement described in this document ensures a similar anchoring function. It is also known to use the rod of the traditional type to ensure a function of tightening the bead on a rim. The arrangement described in this document also ensures a similar tightening role.

In the present description, the term “gum” or “binding” mixture is understood to mean the rubber mixture possibly in contact with the reinforcing wires, adhering to them and capable of filling the interstices between adjacent wires.

The term "contact" between a wire and a layer of bonding rubber means that at least part of the outer circumference of the wire is in intimate contact with the rubber mixture constituting the bonding rubber.

The sidewalls are the portions of the tire most often of low bending stiffness located between the crown and the beads. “Sidewall mixes” are rubber mixes located axially outwardly relative to the wires of the carcass reinforcement structure and to their bonding rubber. These mixtures usually have a low modulus of elasticity.

The portion of the tire adjacent radially inside the sidewall is called "bead".

FIGS. 1 to 3 illustrate a tire 1 according to the invention. This tire comprises a first sidewall 5 adjacent to a first bead 3 preferably corresponding to the inner bead. Similarly, the opposite portion of the tire comprises a second sidewall 6 adjacent to a second bead 4. A crown 7, on which a tread 8 is provided, provides the junction between the sidewalls. The top preferably includes at least one reinforcing belt.

The tire comprises a carcass-type reinforcement structure 2, provided with reinforcements advantageously configured in a substantially radial arrangement. This structure can be arranged continuously from one bead to the other, passing through the sides and the top, or it can comprise two or more parts, arranged for example along the sides, without covering the entire Mountain peak.

The end portions of the reinforcing structure 2 cooperate with the beads in an anchoring zone 30. This creates an anchoring of these portions in the said beads so as to ensure the integrity of the tire. The reinforcing structure 2 can be produced by winding a single wire going back and forth between the two beads, forming loops in each of the beads. These loops, coated in the rubber mixture, contribute to the mechanical connection between the reinforcement structure 2 and the bead, in particular the piles 13. By the presence of loops between the "outward" course and the "return" of the wire, we see that the reinforcement is of the monofilament type. Of course, the carcass might not be made continuously from a single wire, and there might not be loops, but for example cut ends.

Circumferential wires 12, preferably arranged in the form of batteries 13, form an arrangement of wires 11. These wires are preferably metallic. Part or all of the threads can also be made of textile or other materials.

At least one wire 12 from one of the stacks 13 is preferably placed in the immediate vicinity of a portion 21 of the reinforcing structure 2. The stacks can also be arranged so that a portion 21 is interposed between stacks 13.

The space between the wires 12 and the reinforcement structure 2 is occupied by a rubber bonding mixture14. It is also possible to provide for the use of several mixtures having different characteristics, delimiting several zones, the combinations of mixtures and the resulting arrangements being almost unlimited. According to an advantageous variant, provision is made for the presence of a mixture of rubber with a substantially high modulus of elasticity in the area of intersection between the arrangement of wires 11 and the reinforcement structure 2, by way of nonlimiting example, the elastic modulus of such an eraser can reach 10 to 20 and even exceed 40 Mpa.

The anchoring zone 30 is at least partially made up of a matrix comprising a plurality of microdeformable zones 80 capable of promoting the stages of mounting / dismounting the tire on a rim adapted for the latter. The microdeformable zones contain immiscible particles in the matrix. The particles may be beads or micro-beads, adapted to allow creep of the matrix favoring mounting / dismounting in said matrix. According to another example of embodiment, the microdeformable zones contain rods or plates integrated in the matrix. The material of the particles is non-elastomeric and preferably metallic. According to another exemplary embodiment, the microdeformable zones correspond substantially to the interface zones between the matrix of rubber material and the circumferential wires.

The bead, with its anchoring zone according to the invention, is particularly suitable for a tire with extended mobility, such as for example, a tire whose bead also comprises a bead seat comprising a generator whose axially inner end is on a circle with a diameter greater than the diameter of the circle on which the axially outer end is located.

The wire arrangements 11 can be arranged and manufactured differently. For example, a battery 13 can advantageously consist of a single wire 12, wound (substantially at zero degrees) in a spiral, preferably from the smallest diameter to the largest diameter. A pile can also consist of several concentric wires laid one inside the other.

Surprisingly, it has been found that the anchoring of the reinforcing structure in the bead can be achieved by the type of interface described, despite the fact that in the tire with extended mobility according to the invention, the forces induced at the level of the bead differ from those of a conventional bead. For example, with the tire according to the invention, an increase in pressure causes an increase in the radial thrust of the radially outer portion of the seat of the bead against the seat of the rim.

Figures 2 and 3 illustrate an example of arrangement of the other zones of the bead. Radially inside the anchoring zone, or more particularly in the radially internal portion of the bead, in the zone of the seat, a support area 50 is provided. This area acts as an interface between the rest of the bead and the seat of the rim. Significant efforts of the radial and axial type are therefore transmitted through this zone. A high modulus rubber mixture contributes to the transfer of these forces by ensuring good retention of the bead against the rim.

Between these first two zones, an intermediate zone 40 is advantageously provided, so as to ensure mechanical continuity. The forces can thus be transmitted from the anchoring zone 30 to the support zone 50, via the intermediate zone 40.

The tire according to the invention is particularly suitable for use on a rim of the type described in document EP 0 673 324. Such a rim comprises a seat and preferably a raising or rim located axially and radially outward.

The various examples of embodiments described and / or illustrated can advantageously be carried out with devices of the type of those described in document EP 0 580 055.

For example, it is very advantageous to make the tire on a central core imposing the shape of its internal cavity. All the constituents of the tire are applied to this core, preferably in the order required by the final architecture, which are arranged directly in their final place, according to a substantially final profile. In this case, such a tire can be molded and vulcanized as described in document US 4,895,692.

Claims

1. Tire for vehicle wheel, comprising:

at least one of said beads comprising:

2. A tire for a vehicle wheel according to claim 1, in which the microdeformable zones contain immiscible particles in the matrix.

3. A tire for a vehicle wheel according to claim 2, in which the particles are beads or micro-beads.

4. Tire for vehicle wheel according to one of claims 1 or 2, wherein the microdeformable areas contain rods or pads.

5. Tire for vehicle wheel according to one of claims 2 to 4, in which the material of the particles is non-elastomeric and preferably metallic.

6. Tire for vehicle wheel according to one of the preceding claims, in which the microdeformable zones correspond substantially to the interface zones between the matrix of rubber material and the circumferential cords.

7. A tire for a vehicle wheel according to claim 1, in which the bead also comprises a bead seat comprising a generator whose axially inner end is on a circle with a diameter greater than the diameter of the circle on which the tire is located. axially outer end.

8. Tire for vehicle wheel according to one of the preceding claims, in which said arrangement of circumferential wires of the anchoring zone comprises at least two piles distributed on either side of the reinforcement structure, a connection mixture being disposed between the circumferential wires and the reinforcing structure.