WO2006071230A1

WO2006071230A1 - Extended-mobility tire comprising an insert having two zones with substantially different sizes

Info

Publication number: WO2006071230A1
Application number: PCT/US2004/043958
Authority: WO
Inventors: Walter Lee Willard
Original assignee: Michelin Recherche et Technique SA Switzerland
Current assignee: Michelin Recherche et Technique SA Switzerland
Priority date: 2004-12-29
Filing date: 2004-12-29
Publication date: 2006-07-06
Anticipated expiration: 2007-06-29

Abstract

A tire adapted for continued mobility in a substantially deflated condition comprises a carcass structure (5)anchored in each side of the tire in a bead (1) and runflat inserts (9) provided in the axially inner portion of the sidewalls (13), at least one of inserts (9) comprising two zones, an axially outer zone (11), having a volume Vo, occupied by an outer zone elastomeric material, and an axially inner zone (10), having a volume Vi, occupied by an inner zone elastomeric material, the inner zone elastomeric material having a lower modulus of extension ME10 than the outer zone elastomeric material, wherein the inner zone volume Vi is substantially smaller than the outer zone volume Vo such that the volume ratio between Vi and Vo is substantially between 1/15 and 1/25.

Description

EXTENDED-MOBILITY TIRE COMPRISING AN INSERT HAVING TWO ZONES WITH SUBSTANTIALLY DIFFERENT SIZES

BACKGROUND OF THE INVENTION

The invention relates to a tire, more specifically to a pneumatic tire capable of continued mobility in a deflated condition.

For some years, tire manufacturers have been devoting considerable effort to developing original solutions to a problem dating back to the very first time use was made of wheels fitted with tires of the inflated type, namely how to allow the vehicle to continue on its journey despite a considerable or total loss of pressure in one or more tires. For decades, the spare wheel was considered to be the sole, universal solution. Then, more recently, the considerable advantages linked to the possible elimination thereof have become apparent. The concept of "extended mobility" is being developed. The associated techniques allow travel to continue with the same tire, within certain limits, after a puncture or a drop in pressure. This allows the driver to travel to a repair point, for example, without having to stop, in frequently dangerous circumstances, to fit the spare wheel.

Two major types of extended-mobility technology are currently available on the automobile market. On the one hand, there are tires of the self-supporting type (often known by their English abbreviation ZP, standing for "zero pressure"). Self- supporting tires are capable of bearing a load under reduced pressure, or indeed without pressure, thanks to sidewalls which are reinforced, most frequently by means of inserts of rubber material, provided in the sidewalls.

On the other hand, wheels are available which are equipped with supports capable of supporting the inside of the tread of a tire in the event of sagging of the sidewalls following a drop in pressure. This solution is advantageously combined with a tire comprising a bottom zone capable of minimising the risk of the tire sliding out of the rim. This solution is advantageous since it makes it possible to keep substantially intact the characteristics of travel under normal conditions. On the other hand, it has the drawback of requiring an additional component, the support, for each of the wheels of the vehicle.

Corning back to self-supporting tires, the extended mobility requirements are such that it is in general difficult to provide tires with comfort and driving characteristics that are comparable to standard tires. To support the vehicle load under low pressure conditions, the sidewall inserts are provided with high modulus materials, which generally have reduced comfort characteristics.

BRIEF SUMMARY OF THE INVENTION

In order to avoid these drawbacks, the invention provides a tire comprising a carcass structure anchored in each side of the tire in a bead, each bead having a base which is intended to be mounted on the tire's design mounting rim, each bead being extended radially upward by a sidewall portion, a reinforced summit, the sidewall portions joining said summit, said bead further comprising an anchoring zone for anchoring said carcass structure in said bead, said tire being adapted for continued mobility in a substantially deflated condition and comprising runflat inserts provided in the axially inner portion of the sidewalls, at least one of said inserts comprising two zones, an axially outer zone, having a volume Vo, occupied by an outer portion elastomeric material, and an axially inner zone, having a volume Vi, occupied by an inner portion elastomeric material, the elastomeric material of said axially inner zone having a lower Modulus of extension ME10 than the elastomeric material of said axially outer zone, wherein the volume Vi of said inner zone is substantially smaller than the volume Vo of said axially outer zone such that the volume ratio between the volume Vi of said axially inner zone and the volume Vo of s aid a xially o uter zone i s s ubstantially between 1/15 and 1/25.

These characteristics provide an extended mobility tire having a longer range under reduced or no pressure conditions and increase the comfort level. According to a preferred embodiment, most of the volume of said inner zone is provided below the larger portion of the tire (portion in which the distance between the sidewalls outer portions is maximum).

According to a preferred embodiment, the elastomeric material of said inner zone has a Modulus of extension ME10 comprised between 2 to 5 Mpa, and most preferably comprised between 3 to 4 Mpa.

According to another preferred embodiment, the elastomeric material of said outer zone has a Modulus of extension ME10 comprised between 4 to 9 Mpa, and most preferably comprised between 5 to 6 Mpa.

In a variant, said runflat insert is in direct contact with the cords of said carcass structure.

In another variant, said axially inner zone extends at least partially along the carcass structure.

According to still another preferred embodiment, said at least one insert is provided on the inner sidewall of the tire. The inner sidewall corresponds to the sidewall on the inner side of the vehicle when said tire is mounted under standard operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

All the details of embodiment are given in the following description, supplemented by Figures 1 , 2 and 3, in which:

Figure 1 illustrates a first example of a runflat tire according to the invention, taken along a meridian plane through the axis of rotation;

Figure 2 illustrates a second example of a runflat tire according to the invention, taken along a meridian plane through the axis of rotation; Figure 3 illustrates a third example of a runflat tire according to the invention, taken along a meridian plane through the axis of rotation, having two carcass structures.

DETAILED DESCRIPTION OF THE INVENTION

"Axial" and "axially" mean the lines or directions that are parallel to the axis of rotation of the tire.

"Radial" and "radially" mean directions radially toward or away the axis of rotation of the tire.

"Angle defined with respect to an axial direction" means an angle measured axially and radially outwardly from the innerside of the tire; such an angle is between 0 and 180 degrees.

The reinforcement armature or reinforcement of the tires is currently - and most frequently - constituted by stacking one or more plies conventionally referred to as "carcass plies", "crown plies", etc. This manner of designating the reinforcement armatures is derived from the manufacturing process, which consists of producing a series of semi-finished products in the form of plies, provided with cord reinforcing threads which are frequently longitudinal, which products are then assembled or stacked in order to build a tire blank. The plies are produced flat, with large dimensions, and are subsequently cut according to the dimensions of a given p roduct. T he p lies a re a lso a ssembled, i n a first p hase, substantially flat. The blank thus produced is then shaped to adopt the toroidal profile typical of tires. The semi-finished products referred to as "finishing" products are then applied to the blank, so as to obtain a product ready to be vulcanised.

Such a type of "conventional" process involves, in particular for the phase of manufacture of the blank of the tire, the use of an anchoring element (generally a bead wire), used for anchoring or holding the carcass reinforcement in the zone of the beads of the tire. Thus, in this type of process, a portion of all the plies constituting the carcass reinforcement (or only a part thereof) is turned up around a bead wire arranged in the tire bead. In this manner, the carcass reinforcement is anchored in the bead.

The general adoption of this type of conventional process in the industry, despite the numerous different ways of producing the plies and assemblies, has led the person skilled in the art to use a vocabulary which reflects this process; hence the generally accepted terminology, comprising in particular the terms "plies", "carcass", "bead wire", "shaping" to designate the change from a flat profile to a toroidal profile, etc.

However, there are nowadays tires which do not, properly speaking, comprise "plies" or "bead wires" in accordance with the preceding definitions. For example, document EP 0 582 196 describes tires manufactured without the aid of semifinished products in the form of plies. For example, the cords of the different reinforcement structures are applied directly to the adjacent layers of rubber mixes, the whole being applied in successive layers on a toroidal core having a shape which makes it possible to obtain directly a profile similar to the final profile of the tire being manufactured. Thus, in this case, there are no longer any "semifinished products", nor "plies", nor "bead wires". The base products, such as the rubber mixes and reinforcing threads in the form of cords or filaments, are applied directly to the core. As this core is of toroidal form, the blank no longer has to be shaped in order to change from a flat profile to a profile in the form of a torus.

Furthermore, some of the examples of embodiment of tires described in this document do not have the "conventional" upturn of the carcass ply around a bead wire. In these examples, this type of anchoring is replaced by an arrangement in which circumferential filaments are arranged adjacent to said sidewall reinforcement structure, the whole being embedded in an anchoring or bonding rubber composition.

There are also processes for assembly on a toroidal core using semi-finished products specially adapted for quick, effective and simple laying on a central core. Finally, it is also possible to use a mixture comprising both certain semi-finished products to produce certain architectural aspects (such as plies, bead wires, etc.), whereas others are produced from the direct application of mixes and/or reinforcing threads in the form of filaments or strips.

In the present document, in order to take into account recent technological developments both in the field of manufacture and in the design of products, the conventional terms such as "plies", "bead wires", etc., are advantageously replaced by neutral terms or terms which are independent of the type of process used. Thus, the term "carcass structure" is valid as a designation for the reinforcement cords of a carcass ply in the conventional process, and the corresponding cords, generally applied at the level of the beads, sidewalls and summit of a tire produced in accordance with a process without semi-finished products. The term "anchoring zone", for its part, may equally well designate the "traditional" upturn of a carcass ply around a bead wire of a conventional process or the assembly formed by the circumferential filaments, the rubber composition and the adjacent sidewall reinforcement portions of a bottom zone produced with a process with application to a toroidal core.

In the present description, the term "cord" very generally designates both monofilaments and multifilaments or assemblies such as cables, plied yarns or alternatively any equivalent type of assembly, whatever the material and the treatment of these cords. This may, for example, involve surface treatments, coating or pre-sizing in order to promote adhesion to the rubber. The expression "unitary cord" designates a cord formed of a single element, without assembling. The term "multifilament", in contrast, designates an assembly of at least two unitary elements to form a cable, plied yam etc.

"Characteristics of the cord" is understood to mean, for example, its dimensions, its composition, its characteristics and mechanical properties (in particular the modulus), its chemical characteristics and properties, etc.

In the present description, "contact" between a cord and a layer of bonding rubber is understood to mean the fact that at least part of the outer circumference of the cord is in intimate contact with the rubber composition constituting the b onding rubber.

It is known that, conventionally, the carcass ply or plies is/are turned up about a bead wire. The bead wire then performs a carcass anchoring function. Thus, in particular, it withstands the tension which develops in the carcass cords for example under the action of the inflation pressure. Some arrangements described in the present document makes it possible to provide a similar anchoring function. It is also known to use the bead wire of conventional type to perform the function of clamping the bead on a rim. According to the invention, any type of anchoring may be used.

"Sidewalls" refers to the portions of the tire, most frequently of low flexural strength, located between the crown and the beads. "Sidewall mix" refers to the rubber mixes located axially to the outside relative to the cords of the reinforcement structure of the carcass and to their bonding rubber. These mixes usually have a low elasticity modulus.

"Bead" refers to the portion of the tire adjacent radially internally to the sidewall.

"Modulus of extension ME10" of a rubber composition is understood to mean an apparent secant modulus of extension obtained at a uniaxial deformation of extension of the order of 10% measured at 23⁰C in accordance with Standard ASTM D 412.

As a reminder, "radially upwards" or "radially upper" or "radially externally" means towards the largest radii.

A reinforcement or reinforcing structure or carcass structure will be said to be radial when its cords are arranged at 90°, but also, according to the terminology in use, at an angle close to 90°. The tire of the invention comprises a bead 1 provided with a seat 12, specially adapted to fit on the tire mounting rim. The bead extends substantially radially to the sidewall 13. The summit 14 comprises reinforcement layers of known type.

The tire comprises a carcass structure 5, extending from bead to bead or leaving a gap between two half structures, for instance in the substantially median portion of the summit. The radially inwardmost extent of the carcass structure 5 terminates in an anchoring zone 2 of the bead 1. In the example illustrated in figure 1 , the carcass structure is not turned up around bead cores or other bead reinforcement. That is to say, each axial coordinate defining the profile of the carcass structure has a unique radial position for each radial position less than that of the tire equator. The carcass structure is anchored in the bead portion by a bead reinforcement 3. A preferred embodiment of such a reinforcement comprises a cord arrangement 4 provided with at least one substantially circumferentially oriented cord laterally bordering the carcass structure on at least one side. In this instance "anchored" in the bead portion means that the cord arrangement resist the tension developed in the carcass structure during inflated or deflated use of the tire by the adherence of the carcass reinforcing structure laterally with the cord arrangement rather than being wound around a traditional bead core.

The mechanical properties of the anchoring zone 4 may be optimized in using an elastomeric bead filler having preferably a relatively high elasticity modulus.

In the example illustrated in figure 2, the carcass ply is conventionnally turned up about a bead wire to form the anchoring zone 4 The bead wire then performs a carcass anchoring function.

The tire of the invention preferably comprises a runflat insert 9 p rovided i n t he axially inner portion of each sidewall. At least one of said inserts comprisies two zones or portions, an axially outer zone or portion 11 , having a volume Vo, and an axially inner zone or portion 10 having a volume Vi substantially smaller than said volume of said axially outer zone. The elastomeric material of said axially inner zone has a lower Modulus of extension ME10, than the elastomeric material of said axially outer zone. For instance, the Modulus of portion 1 0 m ay b e b etween 2 t o 5 M pa, w hereas t he Modulus of the portion 11 may be between 4 to 9 Mpa. The volume ratio between the volume Vi of said axially inner zone and the volume Vo of said axially outer zone is such that Vi/Vo is substantially between 1/15 and 1/25.

The inner portion 10 is advantageously of a crescent shape. As illustrated in figure 1 , it is preferably positioned in the lower portion of the runflat insert.

Figure 3 illustrates another variant of the tire of the invention, provided with two carcass structures 5. In the illustrated example, the two carcass structures are axially separated along the sidewalls, and are substantially coplanar in the summit zone. In another variant, they are separated from one bead to the other, including the summit zone. Such a dual arrangement provides increased rigidity and may contribute to extend the reduced pressure rolling possibilities.

In the case where only one insert is provided with two zones, this insert is provided on the inner sidewall of the tire.

In order to position the reinforcement cords as precisely as possible, it is very advantageous to build the tire on a rigid support, for instance a rigid core imposing the shape of its inner cavity. All the components of the tire, which are disposed directly in their final place, are applied onto this core in the order required by the final architecture, without undergoing shaping at any moment of the building. In this case, the tire can be molded and vulcanized in the manner explained in US 4,895,692.

While the invention has been described in combination with embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing teachings. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.

Claims

1. A tire comprising a carcass structure anchored in each side of the tire in a bead, each bead having a base which is intended to be mounted on the tire's design mounting rim, each bead being extended radially upward by a sidewall portion, a reinforced summit, the sidewall portions joining said summit, said bead further comprising an anchoring zone for anchoring said carcass structure in said bead, said tire being adapted for continued mobility in a substantially deflated condition and comprising runflat inserts provided in the axially inner portion of the sidewalls, at least one of said inserts comprising two zones, an axially outer zone, having a volume Vo, occupied by an outer portion elastomeric material, and an axially inner zone, having a volume Vi, occupied by an inner portion elastomeric material, the elastomeric material of said axially inner z one h aving a l ower M odulus of extension ME10 than the elastomeric material of said axially outer zone, wherein the volume Vi of said inner zone is substantially smaller than the volume Vo of said axially outer zone such that the volume ratio between the volume Vi of said axially inner zone and the volume Vo of said axially outer zone is substantially between 1/15 and 1/25.

2. The tire of claim 1 , wherein most of the volume of said inner zone is provided below the larger portion of the tire.

3. The tire of claim 1 , wherein the elastomeric material of said inner zone has a Modulus of extension ME10 comprised between 2 to 5 Mpa, and most preferably comprised between 3 to 4 Mpa.

4. The tire of claim 1 , wherein the elastomeric material of said outer zone has a Modulus of extension ME10 comprised between 4 to 9 Mpa, and most preferably comprised between 5 to 6 Mpa.

5. The tire of claim 1 , wherein said runflat insert is in direct contact with the cords of said carcass structure.

6. The tire of claim 1 , wherein said axially inner zone extends at least partially along the carcass structure.

7. The tire of claim 1 , wherein said at least one insert is provided on the inner sidewall of the tire.