JPH0455104A - Radial tire - Google Patents

Abstract

PURPOSE:To prevent the corrosion of a belt cord and tread separation due to the corrosion while tire performance is kept by adopting a total aromatic polyester fiber cord as the outermost belt cord. CONSTITUTION:A belt layer 9 has a four-layer structure comprising the first, second, third and fourth belt plys 11-14 disposed in order from a carcass 7 towards the tread surface S. The belt ply 14 is formed smaller than the maximum belt width BW and larger than the ply width of the belt ply 13. Accordingly, the other belt plys 11-13 are covered extending over a comparatively wide range. The belt plys 11-13 are formed by a high-tension steel felt cord. The outermost belt ply 14 is formed by a belt cord using a total aromatic polyester fiber. This is a high performance organic fiber having stiffness, the high cut resistance of which can prevent a stab from reaching an inner steel cord. Accordingly, the corrosion of a belt cord by water entering from the stab portion and the tread separation due to the corrosion can be restrained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can effectively prevent separation between the belt and the tread rubber caused by, for example, moisture infiltrating into the tread from a puncture wound. The present invention relates to a radial tire that can be suitably used as a tire for heavy-load vehicles traveling on rough roads.

[Conventional technology]

For example, in the case of radial tires used for heavy-duty vehicles such as trucks and buses, in order to increase tire rigidity and improve running performance, there are multiple layers of steel belt cords arranged on the outside of the carcass, usually 3 to 4 layers. Wrapped with a strong belt layer.

[Problem to be solved by the invention]

However, in such radial tires that use steel cord for the belt layer, sharp crushed stones on the road surface,
When punctures occur on the tread surface due to nails, etc., the outermost steel cords are corroded and damaged by the water, air, etc. that seep in through the punctures, causing the tread rubber to peel off from the belt layer, which greatly shortens its service life. The width decreases. Moreover, this corrosion damage makes it difficult to reuse the tire through tire retreading, etc., and also causes a reduction in the total lifespan.

Therefore, in recent years, in order to prevent this cord corrosion and the accompanying tread peeling, the outermost belt ply has been replaced with a highly strong fully aromatic polyamide fiber cord, so-called para-aramid fiber cord, which has a high modulus of elasticity and excellent corrosion resistance. Some proposals have been made to form it using fiber cord (PPTA). However, as shown in Figure 2, such wholly aromatic polyamide fiber cords have poor moisture and heat aging resistance, with their strength significantly decreasing over time under high temperatures, and thus their running performance gradually decreases. However, it has not been possible to obtain satisfactory performance, sometimes causing cord breakage.

Please note that nylon cords, polyester cords, etc. are not strong enough and have insufficient cut resistance.
It does not prevent puncture wounds from reaching the inner steel cord, which also induces corrosion of the inner steel cord.

The present invention is based on the adoption of a new wholly aromatic polyester fiber cord as the belt cord of the outermost belt ply as a tire cord, and is capable of preventing Bell I cord corrosion and associated tread peeling while maintaining tire performance. The object of the present invention is to provide a radial tire that can prevent such problems and solve the above problems.

[Means to solve the problem]

In order to achieve the above object, the radial tire of the present invention has the following features:
At least a three-layer belt using a carcass that passes from the tread part through the sidewall part and is folded back around the bead core of the bead part, and belt cords arranged radially overlappingly on the outside of the carcass and inside the tread part. At least the belt cord of the outermost belt ply in the radial direction of the belt plies is made of wholly aromatic polyester fiber.

[Effect]

The radial tire constructed in this manner uses a wholly aromatic polyester fiber cord as the belt cord of the outermost belt ply.

Fully aromatic polyester fiber is a rigid, high-performance organic fiber having a molecular structure shown in formula (1), for example, in which an aromatic compound having a benzene ring and a ring in which multiple benzene rings are condensed is ester bonded (-0-Co). It is known as a so-called polyarylate fiber.

Amide fiber has almost the same tensile strength, tensile modulus, and breaking elongation as so-called para-aramid fiber (PPTA), and therefore, together with other belt cords, it has a hoop effect to strongly reinforce tire cases and improves running performance. improve. In addition, when a puncture occurs on the tread, its high cut resistance prevents the puncture from reaching other belt cords on the inside, and prevents corrosion of the belt cord caused by water entering from the puncture. It is possible to suppress the accompanying tread peeling.

The fully aromatic polyester fibers shown in Figure 2 have excellent resistance to moisture and heat aging (7). It is possible to suppress a decrease in strength, increase durability, maintain tire performance over a long period of time, and extend the life of the tire.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In the figure, a radial tire 1 includes a bead portion 3 through which a bead core 2 passes, a sidewall portion 4 that is continuous with the bead portion 3 and extends outward in the tire radial direction, and a tread portion 5 that connects the outer ends of the sidewall portion 4.

Further, between the bead portions 3.3, a toroidal main body portion 7A extending from the tread portion 5 through the sidewall portion 4 to the bead portion 3 is provided at both ends thereof, and is folded around the bead core 2 from the inside of the tire to the outside. The carcass 7 with the folded portion 7B formed thereon is placed on a rack, and the belt layer 9 is wound around the outside of the carcass 7.

The carcass 7 has a radial structure consisting of at least one carcass ply in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator.

In this example, the carcass ply is formed from a single carcass ply made of steel metal fiber cord, but organic fiber cords such as nylon and polyester can also be used as the carcass cord. In such a case, in order to obtain the necessary carcass strength, a plurality of carcass pieces, for example 2 to 3
Preferably, two carcass plies are used and the carcass cords are oriented in different directions so that they cross each other between the plies.

A bead apex 8 is provided between the main body portion 7A and the folded portion 7B of the carcass 7 and has a triangular cross-section and is made of hard rubber and extends radially outward from the bead core 2 with a gradually decreasing thickness. The side wall portion 4 is reinforced from the bead portion 3.

The belt layer 9 includes three or more belt plies 11 each having an array of belt cords, and in this example, first, second, third, and fourth belt plies 11 arranged in order from the carcass 7 toward the tread surface S. It has a four-layer structure consisting of .12, 13, and 14.

Further, the second belt ply 12 is formed to have a larger width in the tire axial direction than the respective widths of the other belt plies 11, 13, and 14, and the maximum belt width BW of the belt layer 9 is larger.
That is, in this example, the second belt ply 12's bris 1↑1 is 0.80 times or more the tread width TW and 0.99
By making the belt layer 9 double or less, the belt layer 9 reinforces the tread portion 5 with a hoop effect over almost the entire iJ. Also the fourth
The belt ply 14 is formed to be smaller than the maximum belt width BW and larger than the ply 1 [J of the third belt ply 13. Therefore, while the fourth belt ply 14 covers the other belt plies 11 to 13 over a relatively wide range,
Each end of radially adjacent belt plies terminates at a different position, thereby relieving the stress concentration acting on the bell I end, especially at the end of the fourth belt ply 14, which is the outermost one. It is possible to suppress the briny edge peeling that progresses starting from this point.

In this example, the belt plies 11, 12, and 13 are formed from high-tensile steel belt cords having an initial elastic modulus of 15 x 10' kgf/cm2 or more, and the first belt ply 11 connects the belt cords to tires. The first, second, and third belt plies 11.12 are arranged at an angle of 40° or more and 70° or less with respect to the equator, approximately 67° in this example, while the first, second, and third belt plies 11.12 each have a belt cord aligned with the tire equator. On the other hand, the angle of 30' or less in this example is about 19 degrees, and the plies are arranged in a direction that intersects with each other. This reduces the difference in rigidity between the belt layer 9 and the carcass 7, while forming a strong truss structure as each cord intersects between the plies.

In the present invention, the outermost belt ply in the radial direction, that is, the fourth belt ply 14, is formed from a belt cord using wholly aromatic polyester fibers, and the wholly aromatic polyester fiber cords are radially adjacent to each other. The steel cords are arranged in the same direction or in different directions with an intersection angle of 10° or less. This allows the fourth belt ply], 4 and the third belt ply 1
This alleviates the shearing force that acts between the two parts and suppresses the peeling between the briars.

Note that when forming a belt ply using a wholly aromatic polyester fiber cord further outside the fourth belt ply 14, the wholly aromatic polyester fiber cord is used as the fourth belt ply.
It is preferable that the fully aromatic polyester fiber cords and the tire equator be arranged at substantially the same inclination angle with respect to the tire equator and in directions that intersect with each other.

Further, the wholly aromatic polyester fiber is, as described above, a rigid, high-performance organic fiber having a molecular structure shown in formula (1), in which an aromatic compound having a benzene ring and a plurality of condensed benzene rings is ester-bonded. Therefore, it is a new fiber material for tire cord, known as so-called BORIALEY 1 fiber.

As shown in Table 1 above, this material has approximately the same tensile strength, tensile modulus, and elongation at break as fully aromatic polyamide fibers, and together with other steel cords, it strongly reinforces tire cases and improves running performance. can be improved. In addition, its high cut resistance prevents puncture wounds from reaching the inner steel cord, and prevents corrosion of the belt cord and associated tread peeling due to water infiltrating from the puncture site.

Moreover, since the wholly aromatic polyester fiber has excellent resistance to moisture and heat aging as shown in FIG. 2, it is possible to prevent a decrease in strength over time, increase durability, maintain tire performance, and extend the life of the tire.

〔Concrete example〕

The tire size with the structure shown in Figure 1 is 10゜00R2.
A 0.14PR tire was prototyped based on the specifications shown in Table 2, and the peeling of the prototype tire from 1 to 3 was compared with a conventional tire through an actual vehicle running test. In the actual vehicle running test, as shown in Fig. 3, tires with punctures K such as nail holes formed in the tread portion 5 reaching the outermost belt ply 14 were mounted on a 2-l-D vehicle. Load capacity 10750
kg.

Under the conditions of internal pressure 8.0 KSC and rim size 7.0 OTX 20, the peeling area between the tread rubber and the belt layer progresses starting from the punctured part K during general driving on a highway, that is, the peeling length shown in FIG. 4. L (cm) and W during peeling (
am) was measured according to the distance traveled. The measurement results are shown in FIG.

〔Effect of the invention〕

No. table 14...Outer belt ply.

Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Masamura Nae As shown in the radial tire of the present invention, the outermost outer belt ply is formed using a novel wholly aromatic polyester fiber cord.
It is possible to effectively prevent the tread from peeling off due to moisture infiltrating through the punctured part while maintaining running performance, and the service life of the tread can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a diagram showing the moisture heat aging resistance of wholly aromatic polyester fiber, and Fig. 3
The figure is a cross-sectional view showing the puncture part K of the tire used in the actual vehicle running test, FIG. 4 is a plan view illustrating the tread peeling area measured in the actual vehicle running test, and FIG. 5 is a diagram showing the test results. 2.--1-bead core, 3-bead portion, 4.
・-Sidewall section, 5...Tread section,
7-, -carcass, 8-apex, 9-, -belt layer, 11.12.13.14. -1- Belt ply, Fig. 3 Fig. 4

Claims (1)

[Claims] 1 A carcass that passes from the tread part through the sidewall part and is folded back around the bead core of the bead part, and at least three layers of belt cords arranged radially outside the carcass and inside the tread part in a radial overlapping manner. A radial tire comprising a belt layer made of belt plies, and a belt cord of at least the outermost belt ply in the radial direction of the belt plies is made of wholly aromatic polyester fiber.