JP3105632B2 - Pneumatic radial tire - Google Patents

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 and, more particularly, to an improvement in a cap band layer code of the radial tire, and more particularly to a pneumatic radial tire having improved high-speed durability of the tire.

[0002]

2. Description of the Related Art In recent years, maintenance of a highway network, high output of vehicles,
As the performance becomes higher, the operating speed of vehicles increases more and more, and accordingly, high-speed durability of tires is also strongly required.

Various attempts have been made to improve the high-speed durability of tires. Failure at the time of high-speed rotation of the tire is a major factor due to tire diameter growth and standing wave due to centrifugal force acting on the tire tread at high speed,
In order to suppress this, it is known that providing a cap band layer as a reinforcing layer outside the belt layer is one of the effective attempts.

[0004] It is known that the cord of the cap band layer enhances its elastic modulus in order to achieve the above-mentioned object, one of which is aromatic polyamide (aramid) fiber,
A method using a high elastic modulus material such as polyethylene terephthalate (PET) fiber, and other methods use a polyamide fiber, a polyester fiber, a rayon fiber, particularly a polyamide fiber, and use a single twist and a twist number of 10 to 40 times. / 10 cm, and a method using a number of shots of 60 to 300/10 cm (Japanese Patent Publication No. 59-1601) has been proposed.

[0005]

However, in the method of using a low elongation cord such as aramid fiber as a cap band layer code, tire deformation occurs due to tire expansion during tire manufacturing, or the cap band is not used. The layer code may be broken, and if the tire expansion is reduced, the code may meander during vulcanization of the tire because the heat shrinkage of the aramid fiber code hardly occurs. Is not preferred.

[0006] In the method using polyester fiber such as PET fiber, since the modulus of elasticity is higher than that of polyamide fiber, the diameter growth of the tire is suppressed. Poor performance, separation is likely to occur from this part, causing tire failure.

Further, in the method using the single twist cord, the cord itself has a residual torque, and the workability in the weaving and the adhesive dipping process is poor, which is likely to hinder the tire production. Even if the number of twists and the number of strikes are specified, the high-speed durability of the tire cannot be said to be sufficient, and drastic measures have been desired.

In view of the above facts, the present invention takes into account the poor work of the cap band layer cord, deformation of the tire, breakage of the cord,
It is an object of the present invention to provide a pneumatic radial tire that can improve high-speed durability without problems of meandering and heat resistance.

[0009]

The present invention according to claim 1 has a tread tread portion having a groove extending in a tire circumferential direction, a pair of side walls and a bead portion, and is substantially parallel to the tire radial direction. At least one carcass layer composed of a cord disposed at a position substantially the same as the belt layer and the cap band layer disposed substantially over the entire width of the tread tread on a radially outer side of the carcass layer. The layers comprise cords which intersect each other at a relatively small angle to the tire circumferential direction, and the cap band layer is disposed radially outward of the belt layer and has a width of 25% to 120% of the belt layer. And a rubberized narrow strip including a plurality of the cap band layer cords is provided on at least one or more spiral layers on the belt layer so that the cords are substantially parallel to the tire circumferential direction. A pneumatic radial tire formed by winding the Jo, the cap band layer co - de is co - total denier of de - Le (D) is 500 ≦ D ≦
It is a 3,000 aliphatic polyamide fiber cord having a twin twist structure and a twist coefficient ( _NT ) of 0.10 represented by the following formula 1.
≦ _NT ≦ 0.30, and the residual tension per width (F _W ) represented by the following equation 2 is 85 kgf ≦ F _W ≦ 400 kg
f.

Equation 1: N _T = T × √ (0.139 × D /
2 × 1 / ρ) × 10 ⁻³ N _T ; Twisting coefficient, T: Number of twists (number of times / 10 cm), D: Total denier, ρ; Specific gravity Formula 2: F _W = F × E × Number of members F _W Residual tension per width of cap band layer code F; Residual tension per cap band layer code immediately after collection from tire center E: Per 5 cm width of cap band layer code per tire width direction In order to improve the high-speed durability of the tire, the present inventors focused on the cap band layer code, and as a result of intensive studies, as described above, as the cap band layer code, the material, twist structure, By using a new cord that combines factors such as twisting coefficient and residual tension of the cord in the tire, the intended pneumatic radial tire was successfully obtained, and the present invention was completed.

The tread surface, side wall, bead, carcass layer and belt layer of the tire used in the present invention may be of ordinary materials, shapes and arrangements.

A cap band layer core which is a feature of the present invention.
The cap band layer made of a rubber layer has a role of reinforcing the belt layer, and can have various arrangements and structures that match the required performance of the tire, but is generally radially outward of the belt layer and of the belt layer. A rubberized narrow strip, comprising a plurality of cap band layer cords, arranged on a belt layer with a width of 25% to 120%, such that the cords are substantially parallel to the tire circumferential direction. It is formed by spirally winding at least one layer (structure). The structure of the cap band layer described here usually employs one or two layers.

The code which is an essential component of the cap band layer of the present invention includes aliphatic polyamide fibers. An example of aliphatic polyamide fiber is 6-
Nylon, 6T-nylon, 6,6-nylon, 4,6
-Nylon, a copolymer of a combination of these units, or a fiber of a mixture thereof;
-Aliphatic polyamide fibers in which the ratio of nylon units or 4,6-nylon units is 80% by weight or more is preferred. In addition, these polyamide fibers can usually be used in combination with a stabilizer comprising a copper salt and an antioxidant in order to impart durability to heat, light, oxygen and the like. If the preferred polyamide fiber is used while satisfying the requirements of the present invention, unlike conventional fiber cords, there is no tire deformation, code breakage, meandering, and heat resistance to tire members. Good.

The cap band layer code of the present invention has a total denier (D) of 500 ≦ D ≦ 3000, preferably 1000 ≦ D ≦ 2000. Total Deni
If the diameter exceeds 3,000, the cord is too thick to generate heat, the amount of rubber between the cords also increases, and the gage and weight of the cap band layer increase. If the total denier is smaller than 500, the total elastic modulus in the tire circumferential direction becomes small even if the number of cords is increased as much as possible, which is not preferable because sufficient rigidity cannot be obtained.

There are various types of twisted structures of the cap band layer code, but the twisted structure of the present invention has the upper and lower twists in opposite directions, ie, the upper twist Z / first twist S or the first twist S / first twist Z. A twin twist structure is preferably used. In other structures, a sufficient effect cannot be obtained. For example, a cord having a single twist structure has a residual torque, and the workability in the weaving and the adhesive dipping process is poor, which is not preferable.

In order to improve the high-speed durability of the tire,
One of the important features of the present invention is that a twist factor is newly introduced into the cap band layer code. The twist coefficient ( _NT ) is represented by the above-mentioned equation 1, and its value is 0.1
0 ≦ _NT ≦ 0.30, preferably 0.15 ≦ _NT ≦
0.28. The twist modulus takes into account the factor of increasing the modulus of the cord. If it exceeds 0.3, a sufficiently high modulus cannot be obtained, while if it is less than 0.1, the fatigue resistance deteriorates. It is not preferable because the cord is easily broken.

Another important feature of the present invention is that the residual tension per width in the circumferential direction of the tire in the cap band layer code in a new tire has a great effect on tire deformation during tire manufacturing, high-speed durability of the tire, and the like. I have found something new. The residual tension per width (F _W ) of the cap band layer code is represented by the above-mentioned equation (2).

Here, the value of the residual tension (F) per cord is a value measured in the outer layer in the tire radial direction when the cap band layer is two layers, and a value in the inner layer in the tire radial direction when the cap band layer is two layers. Or the average of both.

The residual tension per width (F _W ) is 85 kg
f ≦ F _W ≦ 400 kgf, and 100 kgf ≦ F _W ≦
350 kgf is preferred, and most preferably 11 kgf.
5 kgf ≦ F _W ≦ 300 kgf. The residual tension per width is calculated by the parameter expressed by the above-mentioned equation 2, which generally indicates the physical properties of the cord, the number of twists, and a higher tension than before when the adhesive is dipped. And the expansion ratio of the cap band layer before and after vulcanization of the tire is selected higher than before. If the value of the residual tension per width is within this range, the diameter growth during high-speed rotation of the tire is small and the standing wave generation speed is also suppressed, giving a good effect on the high-speed durability of the tire, but this value is 400 kgf. Exceeding the range tends to cause deformation of the tire and deformation of the belt layer during tire production, and adversely affects the uniformity and flat spot of the tire. On the other hand, if this value is less than 85 kgf, the diameter of the tire grows larger and satisfactory high-speed durability cannot be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments of the pneumatic radial tire according to the present invention will be described below.

As shown in FIG. 1, the pneumatic radial tire 1 of the present embodiment mainly comprises a tread portion 2, a bead portion 3, a carcass 4, two steel belt layers 5, and a cap band layer 6. .

Table 1 shows the tire size, cap band layer structure, and various parameters relating to the cap band layer code of the pneumatic radial tire of each embodiment. Co
The twist structure of the dough is a twin twist structure in the twist direction shown in Table 1.
The twist coefficient (N _T ) is given by the following equation 1: Equation 1: N _T = T × √ (0.139 × D / 2 × 1 /
ρ) × 10 ⁻³ N _T ; Twist coefficient, T: Number of twists (number of times / 10 cm), D: Total denier, ρ: Specific gravity.

The residual tension per width (F _W ) is given by the following equation 2: Equation 2: F _W = F × E × number of members F _W ; Residual tension per width of cap band layer code F; Tire center From the sample, the residual tension E per cap band layer code immediately after collection; calculated based on the number of hits of the cap band layer code per 5 cm in the tire width direction.

The residual tension (F) per cap band layer code was measured as follows. The tread rubber of the crown center portion of the unrunnable new tire is peeled off at a width of about 50 mm until it reaches around the band layer code (circled portion in FIG. 3 and shaded portion 7 in FIG. 4). The tires used for the test shall be round tires that are not cut on the circumference. Cut tires or tire sections cannot be used because of residual stress changes. In addition, in order to perform accurate measurement, it is important to take care not to leave rubber on the cap band layer cord as much as possible when peeling it off, and at the same time, to be careful not to damage the cord. is there. Next, for a total of 10 codes, 5 on each side from the crown center,
A length of 300 mm is accurately measured on a tire, and the portion is marked. The code is cut at points 200 mm or more outside the marking point.

Thereafter, this code is taken out one by one (black circle 8 in FIG. 4) and the residual stress is measured. In this case, the taken-out code shrinks immediately after the residual stress is released, and if left as it is, the code shrinks further due to the influence of the humidity in the air.
Within minutes) A code sample (9 in FIG. 5) was set at a 450 mm interval between chucks (11 in FIG. 5) of an autograph (S-500) manufactured by Shimadzu Corporation and contracted at a speed of 10 mm / min. Pull the mark of the code sample (10 in FIG. 5) to the original 300 mm, read the tension at that time, and calculate the average value of the 10 wires to determine the cap band layer code.
It is defined as the residual tension per rod (F).

The tire used in each comparative example was Comparative Example 1,
3 and 6 are pneumatic radial tires shown in FIG. 1 and Comparative Examples 2, 4 and 5 are pneumatic radial tires shown in FIG. 2 (the same as FIG. 1 except for the two cap band layers 6).

Table 2 shows various parameters relating to the tire size, cap band layer structure, and cap band layer code of the tires of these comparative examples. In addition,
The twist structure of the coil is a twin twist structure in the twist direction shown in Table 2.
The twist coefficient ( _NT ) and the residual tension per width ( _FW ) were calculated in the same manner as in the examples. Here, the value of the residual tension (F) per cord was measured for the outer layer in the tire radial direction when there were two cap band layers (Comparative Examples 2, 4 and 5).

[Test Examples] An evaluation test of high-speed durability was performed on the tires of the examples shown in Table 1 and the tires of the comparative examples shown in Table 2.

The evaluation of the high-speed durability of the tire is based on the US standard FM.
VSS No. The test was performed in a step speed manner in accordance with the test method of No. 109, that is, the speed was increased every 30 minutes until a failure occurred, and the speed at the time of failure (km / h) and the elapsed time at that speed (minutes) ) Was measured, and the results are shown in Tables 1 and 2.

[0030]

[Table 1]

[0031]

[Table 2]

As is clear from Table 1 and Comparative Example Table 2,
It can be seen that the high-speed durability of the pneumatic radial tire according to the present invention is extremely excellent.

As shown in the results of the comparative examples in Table 2,
The values such as the number of twists and the number of drivings of the cap band layer code are the same as those of the embodiment. These are conventionally known, but do not satisfy the twisting coefficient and / or the residual tension per width, which are features of the present invention. It can be seen that the tire after vulcanization was deformed and could only withstand use, or that the tire was inferior in high-speed durability.

[0034]

Since the pneumatic radial tire of the present invention has the above-described structure, there is no problem of defective work of the cap band layer cord, deformation of the tire, breakage of the cord, meandering, heat-resistant adhesion, and high speed. It has an excellent effect that durability can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the left half of a pneumatic radial tire having a single cap band layer.

FIG. 2 is a cross-sectional view of the left half of a pneumatic radial tire having two cap band layers.

FIG. 3 is a tire cross-sectional view showing a portion (circled portion with a dotted line) of a sample for measuring a residual tension of a cap band layer code.

FIG. 4 is an enlarged view of a sample collection site in FIG. 3;

FIG. 5 is a view showing a state in which a sample immediately after collection from a tire is set in an autograph for measuring residual tension per cap band layer code.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pneumatic radial tire 2 tread portion 3 bead portion 4 carcass 5 steel belt layer 6 cap band layer 7 stripped portion of tread (hatched portion) 8 code for sampling (black circle) 9 single core -D 10 Mark point 11 Code chuck part

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 9/00-9/22 D02G 3/48

Claims (1)

(57) [Claims] 1. A tread tread portion having a groove extending in a tire circumferential direction, a pair of side walls and a bead portion,
At least one carcass layer consisting of cords arranged substantially parallel to the tire radial direction, and a belt layer and a cap band arranged substantially radially outside the carcass layer over the entire width of the tread tread surface. A belt layer comprising cords crossing each other at a relatively small angle with respect to the tire circumferential direction, wherein the cap band layer is radially outward of the belt layer and 25% of the belt layer.
A rubberized narrow strip comprising a plurality of said cap band layer codes arranged at a width of 120%.
In a pneumatic radial tire formed by spirally winding at least one layer on a belt layer so that the cord is substantially parallel to the tire circumferential direction, the cap band layer code is a total of the code. An aliphatic polyamide fiber code having a denier (D) of 500 ≦ D ≦ 3000, a twin-twist structure, and a twist coefficient (N _T ) represented by the following formula 1 of 0.10 ≦ _NT ≦≦ 0.30, and the residual tension per width (F _W ) represented by the following equation 2 is 85 kg
A pneumatic radial tire, wherein f ≦ F _W ≦ 400 kgf. Equation 1: _NT = T × √ (0.139 × D / 2 × 1 /
ρ) × 10 ⁻³ N _T ; twist coefficient, T: number of twists (number of times / 10 cm), D: total denier, ρ: specific gravity Formula 2: F _W = F × E × number of members F _W ; Residual tension per cord width F: Residual tension per cap band layer cord immediately after sampling from tire center E: Number of hits per 5 cm width of cap band layer cord per tire width direction