JP2000280710A - Pneumatic radial tire - Google Patents

Abstract

(57) [Problem] To provide a pneumatic radial tire in which a belt is reduced in weight and rolling resistance is reduced while maintaining or improving high-speed durability. SOLUTION: A belt 2 is composed of cores 4 and 4 'opposed to both ends in the tire width direction and a shell 8 surrounding and surrounding the cores, and one or more cores 4 and 4' are arranged in parallel. Nylon cord is formed by spirally winding a nylon ribbon 5 coated with rubber on a nylon cord in the circumferential direction of the tire.
One or a plurality of parallel PBO cords are covered with a rubber-coated PBO ribbon 6 from one of the cores 4 toward the other 4 'while being inclined with respect to the tire circumferential direction, bent along the outer edge 7, and spirally wound. Continuous winding until the adjacent ribbons are in parallel with the adjacent ribbons contacting the edges, and the core is formed into a structure in which the core is encapsulated by a shell of a toroidal PBO ribbon. Radial tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire in which a belt is reduced in weight and rolling resistance is reduced without deteriorating high-speed durability.

[0002]

2. Description of the Related Art In a pneumatic radial tire, in order to prevent swelling of a carcass crown portion due to internal pressure and increase rigidity of a tread portion to improve steering stability,
A belt is arranged outside the carcass crown. Most tire belts have a structure in which a large number of steel cords embedded in rubber are overlapped with two to four belt plies which are inclined and parallel to the tire equator. The belts of these tires have a number of brass-plated steel cords arranged in parallel to improve adhesion to rubber. Cut into quadrilaterals, join the cut pieces to each other and join the cords at the edges to form a series of strips, cut this to a predetermined size to produce an annular belt ply that joined the cords at both ends, A plurality of belt plies are overlapped so that the inclination directions of the cords are vertically opposite to each other, and are fitted to the carcass.

[0003] In a tire provided with a belt having the above structure, a cut end of the steel cord, which is not plated with brass, is located at the edge of the belt located at the tire shoulder where the running stress is concentrated. The cut end and the buried rubber are separated, and the separation between the cut end and the buried rubber is initiated and the separation is expanded, so that there is a problem that a failure called belt separation easily occurs. In order to prevent separation of the embedded rubber from the cut end of the steel cord at the edge of the belt, the width is substantially the same as the belt width obtained by spirally winding the cord in a circumferential direction as shown in FIG. There is proposed a belt 12 having no free edge, in which a core 14 having a helical shape is covered by a flat toroidal shell 16 formed by spirally winding a band reinforced with a cord. (JP-A-53-22205)

[0004]

In order to respond to the demands of society for reducing carbon dioxide emissions, fuel efficiency of automobiles has been improved, and tires are required to be lighter and have lower rolling resistance. In a belt having a structure in which a large number of the above-described steel cords are superimposed on a belt ply that is parallel to and inclined with respect to the tire equator, the ends of the cords that are parallel to and inclined with respect to the tire equator of the belt are mechanically besides the embedded rubber. Since the free edge is not restricted by the tire, the distribution in the direction in which the running stress acts when the tire is used, that is, in the width direction of the tensile stiffness in the circumferential direction is not uniform. A falling phenomenon occurs. Even if the stiffness of the belt edge decreases due to shoulder drop, use a highly rigid steel cord so that the required stiffness can be maintained,
Since it is necessary to increase the amount of cord used and increase the rigidity of the entire belt, the weight increases. JP-A-53-222
A belt in which a band is spirally wound around a core having a width substantially the same as the belt width proposed in 05, the center of the belt width where the action of running stress is relatively small is equal to the end where running stress is concentrated. The core is reinforced by the cord, in other words, the central part is excessively reinforced, and there is a problem that the extra material is used and the weight becomes unnecessarily heavy.

An object of the present invention is to provide a pneumatic radial tire in which a belt is reduced in weight and rolling resistance is reduced while maintaining or improving high-speed durability.

[0006]

Means for Solving the Problems A cord made of PBO having a greater modulus per unit weight and strength than a steel cord is used, and one of the cords or one of a plurality of parallel cords is spirally wound with a rubber-coated ribbon. By turning it into a toroidal shape so that free edges do not occur, rigid shoulder drop is eliminated, and one or a plurality of parallel-coated nylon cords are spirally wound in a circumferential direction with a rubber-coated ribbon to form a ring. By arranging and reinforcing the core in the shoulder portion, the separation caused by the running stress concentration of the shoulder portion can be prevented, and at the same time, the separation caused by the belt floating from the carcass due to the centrifugal force when the tire rotates is also prevented.

That is, the present invention relates to a pneumatic tire having a radial structure in which a belt is arranged outside a crown portion of a carcass ply having a large number of cords arranged at right angles to a tire circumferential direction and the outside is covered with tread rubber. The core comprises a core and a shell surrounding and surrounding the core in the width direction of the tire, and the core is formed by spirally winding one or more nylon cords in parallel with a rubber-coated nylon ribbon. The shell is formed by being wound in the tire circumferential direction, and the shell is formed by inclining one or more PBO cords in parallel from one side of the core toward the tire in the rubber circumferential direction. Overturning, bending upward along the outer edge, and spiraling continuously into the opposing core until the adjacent ribbons are in parallel with the adjacent edges touching the edges It continued, the core is a pneumatic radial tire formed in encapsulated structures in Ciel toroidal PBO ribbon.

[0008] Since PBO has a specific gravity of 1.59 and a modulus per unit area and strength greater than that of a steel cord, even if the amount of use is about 1/5 or less of the steel cord by weight, the modulus is equivalent to that of a steel cord. And a belt having high strength can be formed. On the other hand, since the belt of the present invention does not have a free edge where rigid shoulder drop occurs because one PBO ribbon is formed continuously, the amount of cord used is reduced and the rigidity of the entire belt is reduced. Even
The rigidity contributing to steering stability can be made equal to that of conventional tires with cut steel cords in parallel, and there is virtually no cut end with low adhesive strength, so separation is difficult, high-speed durability and steering stability Can be maintained. Furthermore, by replacing the steel cord with a PBO cord, the volume used can be reduced compared to the case using a steel cord, so the cord can be made thinner and the amount of topping rubber used can be reduced, and the weight of the belt can be reduced. Becomes possible.

Nylon cords have a large heat shrinkage unlike other cords used for tires, for example, polyester cords, aramid cords, steel cords, rayon cords, and vinylon cords. By arranging, the core shrinks when vulcanizing the tire and tightens the spirally wound PBO ribbon located below the core, preventing separation caused by lifting of the belt edge due to centrifugal force during running. At the same time, the rigidity of the shoulder portion, which greatly affects high-speed durability, is increased. Core width is 15 to 25 of belt width
% Is preferred. If the width of the core is less than 15% of the belt width, the effect of preventing separation is small. If the width of the core is more than 25%, a portion that does not need to be reinforced by a cord extending in the circumferential direction is reinforced, thereby achieving the object of the present invention. I can't.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a partial perspective view of a pneumatic radial tire according to one embodiment of the present invention, and FIG. 2 is a schematic perspective view illustrating a belt used for the pneumatic radial tire of the present invention. 1 is a carcass ply, 2 is a belt, 3
Is tread rubber. The belt 2 arranged outside the crown portion of the carcass ply 1 is formed by spirally winding a nylon ribbon 5 having a rubber coating around one or a plurality of parallel nylon cords plural times in the circumferential direction, four times in FIG. The two annular cores 4 and 4 'having a width of W1 wound in parallel are opposed to each other in parallel and arranged so that the distance between the outer edges 7, 7' opposite to each other is W. And one or a plurality of parallel-applied PBOs with an adhesion-improving surface treatment
PBO ribbon 6 with a width of Wr covered with rubber around the cord
A of the core 4 located on the left in FIG.
It crosses over to the B position of the core 4 'located to the right from the position, bends inward along the outer edge 7' of the core 4 ', inclines at an angle α with respect to the core, and bends into a U shape in plan view. Return to the inner surface of the left core 4 at the position C, bend upward along the outer edge 7, continuously spiral into the opposing core in a C-shape, and spiral around the core to make one round. At the end of the winding of the eye, the space S required to transfer the ribbon once from the winding start position A is set to the D position of the right core, and the phase is shifted from the D position to the second lap from the first lap. The PBO ribbons 6 that are adjacent to each other at the beginning of the winding, similarly with the winding start shifted in phase
Are wound to form a toroidal shape until they come into contact with each other, so that a pair of cores is covered with a shell formed of the PBO ribbon 6.

The distance W of the outer edge of the core and the inclination angle α of the PBO ribbon with respect to the core greatly affect the tire performance. Therefore, the size is determined first, and the width Wr of the PBO ribbon and the winding width of the PBO ribbon are determined. The number of turns N is determined so as to satisfy the following relational expression. N = 2W cos α / Wr + 1 The above equation was derived as follows. C is the perimeter of the core, W is the distance between the opposite outer edges 7, 7 'of the core,
The width of the PBO ribbon is Wr, and the PBO ribbon is one core 4
The angle with respect to the core circumferential direction when being wound from the core 4 ′ to the other core 4 ′ is α, and the PBO ribbon when wound one turn is wound from the core 4 to the core 4 ′ and bent along the outer edge, The winding pitch length returning to 4 is Pt, the number of winding pitches when making one round of winding (hereinafter, winding is simply called rounding) is F, and the number of winding pitches when the PBO ribbon is turned back once. When the length of the fold is p, and when the adjacent PBO ribbons are in contact with each other, and the number of folds on one core per circumference of the circuit is f, C = Pt · F + p ... ... C = p · f + p... When the adjacent PBO ribbons make a round of N and come into contact with each other, N = Pt / p... The following relationship exists between Pt and W, and between p and Wr. Pt = 2W cotα + p... P = Wr / sinα... Substituting the expression into the expression, the relational expression of N = 2W cosα / Wr + 1 is derived.

[0012]

EXAMPLES A belt was experimentally produced using the cords shown in Table 1 under the conditions shown in Table 1. The weight of the prototype belt was measured. The measurement results are shown in Table 1, and the weight of each prototype belt is indicated by an index, with Comparative Example 1 being 100. Next, the prototype belt was fitted to the crown portion of the carcass, and a size 195 / 65R1591H tire was prototyped. The high-speed durability and rolling resistance of each of the prototype tires were measured by the following methods. The results are shown in Table 1.

[0013]

[Table 1]

High-speed durability test method Air pressure 260 kPa, load 492 k according to ECE-R30
Performed under the conditions of g. Rolling resistance test method Air pressure 240 KPa, load 61 according to ISO-8767
The measurement was performed under the condition of 5 kg, and the results were indicated by an index calculated by the following equation. The smaller the value, the better. (Rolling resistance of each prototype tire) × 100 / (Rolling resistance of Comparative Example 1)

Comparative Example 1 is a conventional tire.
The belt weight is lighter and the rolling resistance has been improved without impairing high-speed durability. Comparative Example 2, which uses the same cord as Comparative Example 1 to form the belt structure of the present invention, has a lighter belt weight, lower rolling resistance, equivalent high-speed durability, and a similar structure to Comparative Example 1. It is shown that by changing this, the weight of the belt can be reduced and the rolling resistance can be reduced while maintaining the durability.However, in order to maintain the required rigidity, the fineness of the aramid cord is larger than that of the PBO cord, and the belt weight is greater than that of the embodiment. It became heavy. Compared with Example 1, Comparative Example 3 made the ratio W of the core width 1 to the belt width W larger than 25%, so that the weight reduction of the belt was small, and Comparative Example 4 reduced the ratio of the core width W1 to the belt width W. Since it was smaller than 15%, high-speed durability was reduced.

[0016]

The belt disposed outside the carcass ply is opposed to a pair of two cores formed by winding a plurality of nylon ribbons, each of which is a nylon cord or a plurality of parallelly arranged nylon ribbons. A structure in which one or a plurality of parallel PBO ribbons are wound around the core in a helical manner to form a N-turn structure, thereby reducing the weight and reducing the rolling resistance without impairing high-speed durability. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a partial perspective view of a pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view illustrating a belt used for the pneumatic radial tire of the present invention.

FIG. 3 is a sectional view of a conventional pneumatic radial tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carcass ply 2 Belt 3 Tread 4 Core 4 'Core 5 Nylon ribbon 6 PBO ribbon 7 Outer edge 7' Outer edge 8 Shell

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B60C 9/22 B60C 9/22 B

Claims (2)

[Claims] 1. A pneumatic tire having a radial structure in which a belt is arranged outside a crown portion of a carcass ply in which a number of cords are arranged at right angles to a tire circumferential direction and the outside is covered with tread rubber. A core and a shell surrounding and surrounding a core disposed at both ends in the width direction. The core is formed of one or more nylon cords and a rubber ribbon coated in parallel in a spiral manner in a tire circumferential direction. And the shell is formed by winding
From one side of the core to the other, one or a plurality of poly-p-phenylene benzobisoxazole (hereinafter, referred to as poly-p-phenylene benzobisoxazole) cords are parallel-coated with a rubber-coated PBO ribbon. Spiral spirally inclining with respect to the circumferential direction of the tire, bending upward along the outer edge, and continuing to wind continuously across the opposing core until adjacent ribbons are in parallel with adjacent edges touching the edges The pneumatic radial tire, wherein the core is formed in a structure covered with a shell of a toroidal PBO ribbon. 2. The pneumatic radial tire according to claim 1, wherein the width of the core is 15 to 25% of the belt width.