JPH0796712A - Pneumatic radial tire for two-wheeled vehicle - Google Patents

Abstract

PURPOSE:To provide a tire for a two-wheeled vehicle considerably reduced in the stretch-out of the tread face at the time of high speed rotation and excellent in durability without sacrificing excellent rectilinear stability in the tire having a belt layer formed by spirally winding a strip ply. CONSTITUTION:With a carcass 2, formed of a radial aray cord ply extended toroidally between a pair of beads, as a skeleton, a strip ply with one or plural cords covered with rubber is spirally wound around at least a part of the crown part of the carcass 2 to form a belt layer 3. In a pneumatic radial tire for a two-wheeled vehicle provided with such a belt layer 3, the belt layer 3 is constituted of a steel cord formed by twisting a sheath, formed of one to four steel filaments, around a core formed of one or two steel filaments so that the elongation under the load of 5kg is 0.8-4%. In this steel cord, the sheath filaments are arranged close along the peripheral surface of the cord in the cross section orthogonal to the longitudinal direction of the cord.

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 for a two-wheeled vehicle which is excellent in straight running stability and durability.

[0002]

2. Description of the Related Art In a pneumatic radial tire for a two-wheeled vehicle, a belt having at least one layer is formed by spirally winding a belt-shaped ply formed by covering a carcass crown portion with a plurality of cords covered with rubber. Tires having improved straight running stability have been developed by reinforcing the layers.

It is customary to use organic fibers such as polyamide for the cords constituting the belt layer. Therefore, in a tire having such a belt layer, the cord ply is made up of two steel cords and the cords are vertically arranged. Compared to the conventional belt structure, which is laminated in a crossed arrangement, the tread surface is not sufficiently suppressed from being pushed out due to centrifugal force generated by high-speed rotation, and wear and uneven wear caused by this pushing out occur. It left an easy problem.

On the other hand, in Japanese Patent Application Laid-Open No. 4-362402, N ×
A tire for a two-wheeled vehicle is disclosed in which a steel cord having an M structure is applied to a belt layer in which the band-shaped ply is spirally wound. In this tire, by applying a steel cord to the belt layer, it is possible to prevent the tread surface from sticking out due to high speed rotation.

[0005]

However, the steel cord has a modulus of elasticity comparable to that of an aromatic polyamide in order to control the penetration of rubber between the filaments and the control of cord elongation, so that the steel cord shown in FIG. As shown in Fig. 3, each filament is given a proper habit to reduce the elastic modulus, but due to the habit, the number of point contacts between filaments increases and fretting wear easily occurs. Fatigue resistance deteriorates and the problem remains where the tire durability is poor. Especially, since excessive input is repeatedly applied near the bottom of the tread groove during cornering, fretting wear progresses early and cord breakage occurs. The cracks that form the core easily progress, resulting in a tire failure.

Therefore, an object of the present invention is to prevent the tread surface from sticking out at a high speed without sacrificing the excellent straight running stability in a tire having a belt layer formed by spirally winding a belt-shaped ply. It is intended to provide a tire for a two-wheeled vehicle, which has extremely few and excellent durability.

[0007]

According to the present invention, a carcass composed of a ply of radial array cords extending in a toroidal shape between a pair of bead portions is used as a skeleton, and one carcass is provided in at least both side regions of the crown portion of the carcass. A pneumatic radial tire for a two-wheeled vehicle, comprising a belt layer formed by spirally winding a band-shaped ply having a plurality of cords covered with rubber, the belt layer being a core composed of one or two steel filaments. A sheath made of 1 to 4 steel filaments is twisted around
It is composed of steel cords having an elongation under load of 5 kg of 0.8 to 4%, and the steel cords are arranged such that the sheath filaments are arranged closely along the peripheral surface of the cord in a cross section orthogonal to the longitudinal direction of the cord. Is a pneumatic radial tire for a two-wheeled vehicle.

Now, FIG. 1 shows a cross section of a pneumatic radial tire for a two-wheeled vehicle according to the present invention. In the figure, 1
Is a pair of bead cores, and a carcass 2 made of a ply of radial arrangement cords extending in a toroidal shape is arranged between these bead cores 1. Further, a belt layer 3 and a tread are provided outside a crown portion of the carcass 2 in the tire radial direction. 4 are arranged in order. The belt layer 3 includes one or a plurality of belt cords, in the example shown in FIG. 2, two steel cords that are aligned and covered with rubber. The belt-shaped ply 5 is spirally formed on the circumference of the crown portion of the carcass 2. It is wound and laminated on the carcass 2 as shown in FIG. The belt layer 3 may be installed on at least a part of the crown portion of the carcass 2 as shown in FIG. 4A or 4B, and further, as shown in FIG. It is also possible to arrange two layers on both sides of the.

Next, the steel cord applied to the belt layer 3 will be described with reference to FIG. In the figure, reference numeral 6 denotes a core filament, which is formed by applying a wavy shape to the core filament 6 and then twisting sheath filaments 7 to 10 having the same diameter around the core filament 6. The cord whose cross section is shown in FIG. 7 is an example having two core filaments 6.

The sheath filaments 7 to 7 of these cords
It is important that 10 be arranged closely side by side along the circumferential surface of the cord in any of the cross sections orthogonal to the longitudinal direction of the cord. That is, the four sheath filaments 7 to 10 are arranged along the peripheral surface of the cord with a slight gap or no gap, and a large gap is formed on the peripheral surface of the remaining cord. When the molding is performed, the phases between the sheath filaments become substantially the same, and the cord breaking resistance is improved. Here, the habit imparted to the core filament is not limited to the above-mentioned wave shape, and may be a spiral shape, or the habit may be omitted.

Further, as a code used in the present invention,
It is important that the elongation under a load of 5 kg is 0.8 to 4%. If the elongation is less than 0.8%, fretting may occur between filaments and the cord may be worn out, leading to cord breakage. On the other hand, if the elongation exceeds 4%, the rigidity of the steel cord itself may increase. This is because it becomes difficult to suppress the protrusion of the tread surface at the time of high rotation.

The diameter of the core filament is 1/3 to 2 times the diameter of the sheath filament, and more preferably 1/2.
It is preferably about 2 to 7/4 times in order to improve the tensile rigidity of the cord and to avoid the belt end separation. In particular, it is preferable to use a filament in the range of 0.08 to 0.18 mm in order to avoid fretting and ensure the rigidity of the steel cord. Further, the twist pitch of the sheath filament is economically disadvantageous if it is less than 6.0 mm, while the cord rupture resistance deteriorates if it exceeds 28 mm, so it is desirable to set it to 9.0 to 24 mm. Further, as long as the cord structure is the 1 + N structure, the cord breaking resistance is similarly obtained regardless of whether it is the closed type or the open type having the core as the center.

Here, in manufacturing the steel cord of the present invention, a required amount of mold is applied by a preformer, and four sheath filaments are made to have substantially the same phase, and the core filament is made. It may be twisted around the core filament, or may be produced by applying a predetermined amount of mold to a bundle of four wires with a preformer and twisting around the core filament.

[0014]

In the cord applied to the tire for a two-wheeled vehicle according to the present invention, the sheath filaments are arranged in close proximity along the peripheral surface of the cord in the cross section for the following reason. N × such as the conventional 1 × 4 or 3 × 3 structure
Steel cord of M twist structure, that is, the above-mentioned Japanese Patent Laid-Open No.
In the steel cord disclosed in Japanese Patent Laid-Open No. 362402, when there is a compressive bending input, as shown in FIG. 8, a compressive buckling phenomenon occurs at a critical point where a large bending deformation occurs, whereas in FIG. In the case of the code used in this invention,
As shown in FIG. 8, no buckling phenomenon is observed.

This is because the arrangement of the sheath filaments shown in FIG. 6 makes the phases of the respective sheath filaments substantially the same, so that even if there is a compression bending input in the cord, four sheath filaments Since the input can be absorbed without causing buckling, it is considered that the buckling phenomenon does not occur. In particular, in the cord in which the core filament has a habit, the core filament can follow the deformation of the sheath filament, and therefore the core filament can absorb the compressive bending input without buckling.

[0016]

EXAMPLE A steel cord shown in FIG. 6 and FIGS.
The steel cords shown in Table 1 and the steel cords shown in FIGS. 15 to 17 for comparison were used in the following tests. That is, size 170 /
In the belt layer of 60ZR 17 radial tires for motorcycles,
It was applied under the specifications shown in Tables 1 and 2, respectively. Then, a tire with an internal pressure of about 1/2 of the specified value was mounted on a two-wheeled vehicle with a displacement of 750 cc, and after running for about 5000 km, the tire was disassembled and examined for the presence of break codes in the belt layer.

Then, a similar tire is filled with a specified internal pressure,
Set this tire on the drum to gradually increase the running speed on the drum, take a picture of the tread tread in each speed range with a TV camera, measure the amount of protrusion, and measure the approach in each speed range. A comprehensive evaluation of the degree of squeeze was made by comparing the amount of squeeze. In this case, the result of Comparative Example 2 is shown as an index when set to 100, and the larger the number, the better the result.

Further, the driver is attached to the rear wheels of the above-mentioned two-wheeled vehicle, and the grip force during normal traveling at the time of turning and traveling immediately after passing over the gap and how the vehicle body sway due to disturbance during straight traveling is suppressed (straightness) Was evaluated for feeling, and after being normally run on an ordinary road for 3000 km, the wear amount was calculated by measuring the groove depth of the tread, and the wear amount was calculated as an index when the result of Comparative Example 3 is 100. The larger the number, the better the result. The evaluation results are also shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

According to the present invention, since the durability against the compressive deformation applied to the cord is improved, the durability of the two-wheeled vehicle tire having high straight running stability can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a tire of the present invention.

FIG. 2 is a perspective view of a strip ply.

FIG. 3 is an explanatory view showing the arrangement of belt layers.

FIG. 4 is a sectional view of a tire of the present invention.

FIG. 5 is a sectional view of a tire of the present invention.

FIG. 6 is an explanatory diagram of a steel cord according to the present invention.

FIG. 7 is a sectional view of a steel cord according to the present invention.

FIG. 8 is a graph showing the relationship between compressive strain (%) and compressive stress (kgf) of a cord.

FIG. 9 is a sectional view of a steel cord according to the present invention.

FIG. 10 is a sectional view of a steel cord according to the present invention.

FIG. 11 is a sectional view of a steel cord according to the present invention.

FIG. 12 is a sectional view of a steel cord according to the present invention.

FIG. 13 is a sectional view of a steel cord according to the present invention.

FIG. 14 is a sectional view of a steel cord according to the present invention.

FIG. 15 is a sectional view of a steel cord.

FIG. 16 is a sectional view of a steel cord.

FIG. 17 is a sectional view of a steel cord.

[Explanation of symbols]

 1 bead core 2 carcass 3 belt layer 4 tread 5 strip ply 6 core filament 7 sheath filament 8 sheath filament 9 sheath filament 10 sheath filament

Claims (1)

[Claims] 1. A carcass composed of a ply of radial array cords extending in a toroidal shape between a pair of bead parts has a skeleton as a skeleton, and at least a part of a crown part of the carcass,
A pneumatic radial tire for a two-wheeled vehicle, comprising a belt layer formed by spirally winding one or more cord-coated cord-shaped plies, the belt layer comprising:
Stretched with 1 to 4 steel filaments around a core consisting of 1 or 2 steel filaments, and the elongation under load of 5 kg is 0.8 to 4%.
The steel cord is a pneumatic cord for a two-wheeled vehicle, characterized in that in a cross section orthogonal to the longitudinal direction of the cord, the sheath filaments are arranged closely adjacent to each other along the peripheral surface of the cord. Radial tires.