JPH0319083B2 - - Google Patents

Abstract

A tyre has a tread reinforcing breaker formed by at least two cross- laid plies 1, 2 of metal reinforcement cables and at least one edge ply, e.g. 3, formed by circumferentially extending reinforcement members. The or each edge ply may have a modulus greater than 5,000 daN/cm and may comprise reinforcement members of aromatic polyamide, or of a material with a large initial elongation under stress. The or each edge ply may be located radially outwardly of the cross-laid plies as shown or between these plies. The tyre may have a radial carcass and an aspect ratio less than 100%. <IMAGE>

Description

[Detailed description of the invention]

FIELD OF INDUSTRIAL APPLICATION This invention relates to pneumatic tires, particularly heavy commercial automotive tires. [Prior art and its problems] Heavy commercial vehicles, especially multi-axle semi-trailers, have an aspect ratio of 3% or less when the aspect ratio is less than 100%.
Pneumatic tires with a radial carcass of low proportions are used. Due to their arrangement, tires of the type described above are subjected to very high transverse loads, which often cause ply separation at the edges of the breakers by causing the tires to rub, leading to premature failure. In order to prevent such ply separation at the edges of the breaker due to cross loads applied to the tire, it is necessary to form the reinforcing members of the breaker from a non-extensible material. however,
In general, when molding tires, the size of the tire installed in the mold is smaller than the size of the mold before vulcanization, from the perspective of insertion into the mold, and when vulcanized, it expands. is pressed against the inner wall surface of the mold,
These are the dimensions of the final product. Therefore, from the viewpoint of tire molding, the reinforcing member must be extensible. In other words, it is desirable for the reinforcing member to be stretchable from the perspective of tire molding, and non-stretchable from the perspective of preventing ply separation, but these requirements are mutually contradictory. Therefore, a tire of a type that can sufficiently prevent ply separation has not been provided in the past. [Problems to be Solved by the Invention] An object of the present invention is to provide a tire that simultaneously satisfies the above-mentioned mutually contradictory requirements, is easily moldable, and can prevent ply separation at the breaker edge. With the goal. [Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a tire having a tread reinforcement breaker, each consisting of parallel reinforcing members made of metal, and these reinforcing members consisting of at least two intersecting plies arranged to extend at an angle to the longitudinal direction of the tire and each reinforcing member parallel to the tire, the reinforcing members extending parallel to the longitudinal direction of the tire; at least two longitudinal plies arranged in such a manner that the longitudinal plies are provided at the lateral edges of the breaker opposite each other with respect to the equatorial plane of the tire and spaced from the equatorial plane. in a tire, whereby a region free from reinforcing members extending parallel to the longitudinal direction is defined in the central region of the breaker between each axially inward edge of each said longitudinal ply. , each of said longitudinal plies,
It has a rapid elongation phase and a subsequent decreased elongation phase, and the modulus in the decreased elongation phase is
It is formed from a reinforcing member with a strength greater than 5000 daN/cm. The modulus M of the ply of wire is the ratio F/
Characterized by dL/L. Here, F is the force required to stretch the corresponding cable of width 1 cm and length L by length dL, and elongation dL/L is the elongation equal to 90% of the elongation at break. For commercial vehicle tires, the modulus M is 5000 daN/cm.
If it exceeds , it is considered high. [Operations and Effects] As described above, a longitudinal ply is formed from a reinforcing member that has a rapid elongation phase and a subsequent reduced elongation phase and has a modulus greater than 5000 daN/cm in the reduced elongation phase. At the same time, by defining a region free from these longitudinal plies in the axial direction between these longitudinal plies, during tire molding, the reinforcing member of the longitudinal ply stretches close to its elongation limit on the inner wall surface of the mold. In addition, when the completed tire is used, the reinforcing members of the longitudinal plies have already been stretched close to their elongation limit, making them essentially non-stretchable. , ply separation can be reliably prevented. [Example] A reinforcing belt that supports lateral forces when a tire is skidding or scraping can be compared to a beam with a load acting on its center. The reinforcing means at the edges of the breaker ply of the present invention provide the ply with a high resistance to bending under such loading conditions. An enlarged section of a reinforcing belt according to the invention is shown in FIG. This reinforcing means consists of two intersecting plies 1, 2 of metal wire, which are known in the art, and a reinforcing element of high modulus, such as a metal wire or cable, preferably with a high initial elongation.
It is composed of two edge plies 3 and 4 extending in the longitudinal direction. Of course, these plies can be made of aromatic polyamide cable or other equivalent high modulus materials. If the tire is being rubbed, arrow A represents the force resulting from the structure of the casing surrounding and supporting the breaker ply, and arrow B is the resultant force of the tire's frictional forces on the ground due to the lateral movement during the rubbing. It represents. FIG. 2 represents a cross section of a tire according to the invention with an aspect ratio of 40%. The illustrated tire includes a radial carcass 5 whose plies surround two bead wires 6 at both ends thereof. The tread 7 is provided with a groove (not shown). The breaker ply, consisting of two crossed plies 1, 2, is reinforced near its edges by two longitudinal plies 3, 4 made of wire, the purpose of which is to prevent belt damage caused by rubbing. The purpose is to increase resistance. The wire used to form the two longitudinal plies 3, 4 has a high modulus M. In other words, for commercial automobile tires, the modulus is 5000 daN/
larger than cm. FIG. 3 is a graph measuring the strength of different types of wire used in tire manufacturing. To make these measurements, increasing tensile forces were applied using a dynamometer until the wire reached its breaking point. During each measurement, the value of the force applied daN
and the corresponding % elongation were recorded. Curve A in Figure 3 represents the case of a metal cable with a size of 7x3x0.20 mm. This elongation at failure is 2.2%, and the force corresponding to 90% (1.98%) of this value is 164 daN. Curve B shows an enlarged view of the elongation due to the force acting on the 3x7x0.22 mm cable in the "high initial elongation" configuration. As can be seen from the figure, although the two cables have very similar structures, curve B
has a different elongation method than curve A. At the beginning of tension, cable B has a much greater elongation than cable A, and then exhibits the same elongation as cable A when the elongation reaches 5 or 6%. The elongation at break is 9.1%, which is 90% (8.2%) of this value.
The corresponding force is 165 daN. Curve C shows the case of a 3x1650 dtex aromatic polyamide cable. This type of cable is sold, for example, by DuPont Nemuth under the trade name Kevlar. This cable is made adhesive to ensure adhesion with the rubber compound. For this cable, the elongation at break is 4%, and the force corresponding to 90% of this value is
It is 42daN. In Figure 3, curve D is for nylon fibers.
The case of 2x1400dtex cable is shown. The elongation at break is 19.6%, which is 90% of this value (17.6
%) is 20 daN. A, B, C,
Type D cables are those currently used in the tire industry. Preferably, the plies are formed by placing closely parallel cables within the rubber mixture. Thus, with F/dL/L defined by the above formula, the elongation coefficient of the ply when dL/L is 90% of the elongation at break can be directly determined from the mechanical properties of the wire and the density within the ply. Can calculate. The following table shows the calculation results for each type of cable calculated as described above.

[Table] As mentioned above, one of the conditions of the present invention is that the modulus M of the cable plies is high, e.g.
It is higher than 5000daN/cm. Under these conditions, only cables A, B, C with sufficient density within the ply will have a sufficiently high modulus. It is desirable that the selected cable have characteristics as represented by curve B, ie, a phase of rapid elongation of 2 to 10% followed by a phase of reduced elongation. This type of cable is called a "high initial elongation cable." 4 to 7 show various embodiments of reinforcing ply arrangements for the intersecting plies forming the breaker ply itself. FIG. 4 shows an example in which longitudinal plies 3, 4 are arranged between crossed plies 1, 2 forming a breaker ply. In FIG. 5, plies 3 and 4 cross ply 8,
It is located above 9 and 10. In this diagram,
The two-ply band of the previous figure has been replaced by three triangular plies 8, 9, 10, with the inner ply 8
for example has metal wires inclined at 68° to the equatorial plane of the tire, the second ply 9 has metal cables arranged at 22° across the cables of the first ply, and the outer ply 10 It has a cable arranged at 22° intersecting the cable of the second ply 9. FIG. 6 shows another variant, in which the longitudinal plies 3, 4 are arranged transversely on the upper cross ply 10 and also intersect one of the plies 9, 8 so as to constitute a reinforcing band as a whole. . In FIG. 7, the longitudinal plies 3, 4 are embedded in the rubber of the tire as in FIG. It is surrounded by ply 11 of the breaker ply. ply 1
1 are overlapped to cover all others as in FIG. 7, but a similar construction without overlap is also possible. Such additional plies 11 can also be used in conjunction with the other variants described above. Longitudinal reinforcing plies are obtained by calendering closely parallel wires or cables with a suitable mixture of rubber compounds. The band thus obtained is then rolled over the edge of the breaker ply at least once. At this time, the edges may or may not be overlapped. Reinforcement plies can also be obtained by winding one or more wires or cables in spiral form, with a rubber composite covering before winding. The longitudinal plies 3, 4 are generally offset inwardly with respect to the second ply of the band, but they can also be overlapped on both sides. The longitudinal ply can be laid flat on the band during its manufacture. The longitudinal ply can also be placed on a pre-bent or shaped band. They can be arranged symmetrically with respect to their width, characteristics, cable density or location. A 315/70R22.5 tire casing was made in accordance with the present invention. The radial casing included a single ply reinforced with metal cables by known processes. The composition of the band is: () The main part is two plies reinforced with 7x4x0.22mm coated metal cables inclined at 22° to the equatorial plane of the tire, closely intersecting and with the inner ply wide 200mm, and the outer ply was 225mm wide. () Additional ply placed in the center above the outer cross ply. Its metal reinforced cable is 7x3x0.20
mm covering structure, oriented in the same direction as the outer cross plies and inclined at 22° to the equatorial plane. () 3x7x0.22mm metal cables of "high initial elongation" type as reinforcing means according to the invention are directed from the edge of the additional ply inwardly from the edge of the outer cross ply to a distance of 55mm, i.e. 52.5mm wide It was wound more than that. The pitch of the winding was 4.5cm. Tests on a rotating road at a speed of 50 km/h and an overload of 60% of the load published by ETRTO have shown that these tire casings have a higher Very good results were also obtained. Even though these tires were subjected to considerable abrasion in very severe on-vehicle testing, they did not experience separation at the edge of the breaker ply prior to complete wear.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the reinforcing belt in the present invention;
Fig. 2 is a cross-sectional view of the tire of the present invention, Fig. 3 is a graph showing the relationship between wire elongation and force, and Figs. 4 to 7 are cross-sectional views showing other embodiments of the tire crown. be. 1, 2: Cross ply, 3, 4: Longitudinal ply.

Claims (1)

[Scope of Claims] 1. A tire having treaded reinforcing breakers, each consisting of parallel reinforcing members made of metal, the reinforcing members being arranged so as to extend at an angle to the longitudinal direction of the tire. At least 2
two intersecting plies 1, 2 and at least two longitudinal plies 3, 4, each consisting of parallel reinforcing members and arranged in such a way that these reinforcing members extend parallel to the longitudinal direction of the tire. The longitudinal plies 3, 4 are arranged at the lateral edges of the breaker opposite each other with respect to the equatorial plane of the tire and spaced from this plane, so that each said longitudinal ply In the central region of the breaker between each axially inner edge of 3, 4 a region free from reinforcing members extending parallel to the longitudinal direction is defined, said respective longitudinal ply 3, 4 comprising: 1. A tire comprising a reinforcing member having a rapid elongation phase and a subsequent reduced elongation phase, the modulus of which is greater than 5000 daN/cm in the reduced elongation phase. 2. Tire according to claim 1, wherein the longitudinal plies 3, 4 are formed of longitudinally extending reinforcing elements embedded in a rubber composite. 3. Tire according to claim 1, wherein the longitudinal plies 3, 4 are made of parallel elements of aromatic polyamide. 4. The reinforcing member of the longitudinal ply is a wire, cable or strand, claim 1.
The tire according to any one of items 3 to 3. 5. Each longitudinal ply 3, 4 is made by winding at least one band formed by an assembly of a plurality of parallel reinforcing elements. Tires listed in any of the sections. 6. A tire according to any one of claims 1 to 5, wherein the longitudinal plies 3, 4 are made by spirally winding reinforcing elements. 7. Tire according to claim 5, wherein the bands forming the longitudinal plies 3, 4 are overlapped at their ends. 8. A tire according to any one of claims 1 to 7, wherein the longitudinal plies 3, 4 are arranged radially outward of the intersecting plies. 9. A tire according to any one of claims 1 to 8, wherein the longitudinal plies 3, 4 are arranged between two intersecting plies forming a reinforcing band. 10. According to claim 5 or 7, the axially inner edges of the longitudinal plies 3, 4 are located between the axially outer edges and the equatorial line of the band. tires. 11. According to claim 5 or 7, the axially outer edges of the longitudinal plies 3, 4 correspond to the axially outer edges of one of the plies 3, 4 of the band. tires.