JPH05286304A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To remove the bad workability of a cap band layer cord, tire deformation and the break of the cord and improve high speed durability by making the cap band layer cord and aliphatic polyamide fibre cord whose total denier is of a specific value, making residual tension per width that is expressed by a specific expression, that of a specific value. CONSTITUTION:The cord of the cap band layer 6 of a pneumatic radial tire 1 is made to be an aliphatic polyamide fibre cord whose total denier is 500-3000, and which is of a pair-ply structure and has a low ply number. A ply coefficient NT which is expressed by NT=TX(0.139XD/2X1/rho)<0.5>X10<-3>, is made to be 0.1-0.3, and residual tension F which is expressed by FW=FXEX the number of member sheets, is made to be 85kgf-400kgf. Here, NT is a ply coefficient, T is a ply number (frequency/10cm), D is total denier, and rho is specific gravity. Also, FW is residual tension per cap band layer cord right after picking from a tire center portion, and E is the placed number of cap band layer cords per 5cm in a tire width direction.

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 the cap band layer code of the radial tire, and more particularly to a pneumatic radial tire which improves the high speed durability of the tire.

[0002]

2. Description of the Related Art In recent years, maintenance of highway networks, high output of vehicles,
Due to higher performance, the operating speed of vehicles is becoming ever faster, and along with this, high-speed durability of tires is strongly demanded.

Various attempts have been made to improve the high speed durability of tires. The failure at high speed rotation of the tire is largely due to the tire diameter growth and standing wave due to centrifugal force acting on the tire tread portion at high speed,
In order to suppress this, it is known as one of effective attempts to provide a cap band layer as a reinforcing layer on the outside of the belt layer.

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

[0005]

However, in the method in which a low elongation cord such as aramid fiber is used as the cap band layer code, tire deformation during tire production may cause tire deformation or the cap band. The layer cord may be broken, and if the tire expansion is reduced for that reason, the cord will meander when the tire is vulcanized because the aramid fiber cord has almost no heat shrinkage. Is not preferable.

Further, in the method using polyester fiber such as PET fiber, since the elastic modulus is higher than that of polyamide fiber, the diameter growth of the tire is suppressed, but when used at a high speed, heat-resistant adhesion with the tire member is obtained. Since the performance is poor, separation easily occurs from this portion, which causes a tire failure.

Further, in the method using a single twist cord, there is residual torque in the cord itself, the workability in the weaving and adhesive dipping process is poor, and it easily becomes a hindrance during tire production. Even if the number of twists and the number of impacts are specified, the high-speed durability of the tire cannot be said to be sufficient, and drastic measures have been demanded.

In consideration of the above facts, the present invention takes into consideration the above-mentioned facts that the cap band layer code is defective in workability, the tire is deformed, and the code is broken.
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-resistant adhesion.

[0009]

The present invention according to claim 1 has a tread tread portion having a groove extending in the tire circumferential direction, a pair of side walls and a bead portion, and is substantially parallel to the tire radial direction. And at least one carcass layer composed of cords arranged in a cord, and a belt layer and a cap band layer disposed substantially outwardly of the carcass layer over the width of the tread surface. The layers are composed of cords intersecting each other at a relatively small angle with respect to the tire circumferential direction, and the cap band layer is arranged radially outward of the belt layer and has a width of 25% to 120% of the belt layer. At least one or more spiral strips of rubberized narrow strips containing a plurality of the cap band layer cords are provided 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 ≦
An aliphatic polyamide fiber cord of 3000, which has a twin twist structure and a twist coefficient (N _T ) represented by the following formula 1 is 0.10.
≦ N _T ≦ 0.30, and the residual tension per unit width (F _W ) represented by the following formula 2 is 85 kgf ≦ F _W ≦ 400 kg
It is characterized by being f.

Equation 1: N _T = T × √ (0.139 × D /
2 × 1 / ρ) × 10 ⁻³ N _T ; twist coefficient, T; twist number (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 cord F; Residual tension per cap band layer cord immediately after collecting from tire center part E; Per cap band layer cord per width 5 cm of tire width In order to improve the high-speed durability of the tire, the present inventor paid attention to the cap band layer code, and as a result of intensive studies, as described above, as the cap band layer code, its material, twist structure, By using a novel cord in which factors such as twist coefficient and residual tension of cord in the tire are combined, the pneumatic radial tire of interest has been successfully obtained, and the present invention has been completed.

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

The cap band layer core which is a feature of the present invention
The cap band layer made of rubber has a role of reinforcing the belt layer, and can have various arrangements and structures that match the required performance of the tire. Generally, however, the cap band layer is located radially outward of the belt layer and the belt layer. A narrow rubberized strip having a width of 25% to 120% and containing a plurality of cap band layer cords is placed on the belt layer 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.

Aliphatic polyamide fibers can be mentioned as the cord which is an essential constituent element of the cap band layer of the present invention. An example of an 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, and the like, among which 6,6
-Aliphatic polyamide fibers containing 80% by weight or more of nylon units or 4,6-nylon units are preferable. Further, these polyamide fibers can be usually used by blending a stabilizer comprising a copper salt and an antioxidant in order to impart durability to heat, light, oxygen and the like. When the suitable polyamide fiber is used while satisfying the requirements of the present invention, unlike a conventional fiber cord, there is no deformation of the tire, breakage of the cord, meandering, and heat resistant adhesion to a tire member. It is good.

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

There are various twisting structures of the cap band layer cord, but the twisting structure of the present invention has upper and lower twists in opposite directions, that is, upper twist Z / lower twist S or upper twist S / lower twist Z. A double twist structure is preferably used. Sufficient effects cannot be obtained with other structures. For example, a cord having a single twist structure has residual torque and is not preferable because it has poor workability in the weaving and adhesive dipping process.

In order to improve the high speed durability of the tire,
One of the important features of the present invention is the introduction of a new element called the twist coefficient in the cap band layer cord. The twist coefficient (N _T ) is represented by the above-mentioned Equation 1 and its value is 0.1.
0 ≦ N _T ≦ 0.30, preferably 0.15 ≦ N _T ≦
It is 0.28. The twisting coefficient has a factor of increasing the elastic modulus of the cord, and if it exceeds 0.3, a sufficiently high elastic modulus cannot be obtained, while if it is less than 0.1, fatigue resistance deteriorates. It is not preferable because the cord is likely to break.

Another important feature of the present invention is that the residual tension per width in the tire circumferential direction of the cap band layer cord in a new tire has a great influence on tire deformation during tire production, high-speed durability of the tire, and the like. It is in finding new things to bring. The residual tension per width ( _FW ) of the cap band layer cord is expressed by the above-mentioned formula 2.

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

The residual tension (F _W ) per width is 85 kg
f ≦ F _W ≦ 400 kgf, 100 kgf ≦ F _W ≦
350 kgf is preferable, and 11 is most preferable.
5 kgf ≦ _FW ≦ 300 kgf. The residual tension per width is calculated by the parameter expressed by the equation 2 mentioned above. Generally speaking, it means that the physical properties of the cord, the number of twists, and the tension higher than the conventional tension at the time of dipping the adhesive. And the expansion ratio of the cap band layer before and after vulcanization of the tire which is higher than the conventional one. If the residual tension per width is in this range, the diameter growth during high-speed rotation of the tire is small and the standing wave generation rate is suppressed, which gives a good effect on the high-speed durability of the tire, but this value is 400 kgf. If it exceeds the range, the tire is likely to be deformed during the tire manufacturing and the belt layer is deformed, and the uniformity and flat spot of the tire are adversely affected. On the other hand, if this value is less than 85 kgf, the diameter growth of the tire becomes large, and satisfactory high-speed durability cannot be obtained.

[0020]

EXAMPLES The first to third examples of the pneumatic radial tire of the present invention will be described below.

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

Table 1 shows various parameters relating to the tire size, the cap band layer structure and the cap band layer code of the pneumatic radial tires of the respective examples. Co-
The twist structure of the cord is the double twist structure in the twist direction shown in Table 1.
The twisting coefficient (N _T ) is expressed by the following formula 1: Formula 1: N _T = T × √ (0.139 × D / 2 × 1 /)
ρ) × 10 ⁻³ N _T ; twist coefficient, T; twist number (number of times / 10 cm), D: total denier, ρ; calculated based on specific gravity.

The residual tension (F _W ) per width is expressed by the following equation 2: F _W = F × E × number of members F _W ; residual tension per width of cap band layer cord F; tire center part Was calculated based on the residual tension E per cord of the cap band layer immediately after sampling; E; the number of driving of the cap band layer cord per 5 cm in the tire width direction.

The residual tension (F) per cord of the cap band layer was measured as follows. The tread rubber of the crown center portion of a new unrunning tire is peeled off with a width of about 50 mm until it reaches the band layer code (dotted circle in FIG. 3, shaded portion in FIG. 4). The tires to be tested are round tires that have not been cut on the circumference. Cut tires or tire sections cannot be used due to changes in residual stress. In addition, in order to make accurate measurements, it is important to make sure that the rubber does not remain on the cap band layer code as much as possible when peeling it off, and at the same time pay close attention not to damage the code. is there. Next, from the crown center part to the left and right, 5 for each and 10 cords in total,
Accurately measure a length of 300 mm on the tire, and mark the portion. The code is cut at a point 200 mm or more outside each of the marking points.

Thereafter, each of these cords (black circles 8 in FIG. 4) is taken out, and the residual stress is measured. In this case, the code taken out shrinks immediately due to the release of residual stress, and if left as it is, the code will shrink further due to the influence of humidity in the air.
Within 5 minutes) A code sample (9 in FIG. 5) was set at a chuck (11 in FIG. 5) gap 450 mm of an autograph (S-500) manufactured by Shimadzu Corporation, and contracted at a speed of 10 mm / min. The cord sample was pulled until the mark point (10 in FIG. 5) reached the original 300 mm, the tension at that time was read, and the average value of the ten was measured for the cap band layer cord.
The residual tension (F) per cable is used.

The tires used in each comparative example are Comparative Example 1,
Reference numerals 3 and 6 are the pneumatic radial tires shown in FIG. 1, and Comparative Examples 2, 4 and 5 are the same as those 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 cord is a double twist structure in the twist direction shown in Table 2.
The twist coefficient (N _T ) and the residual tension per width (F _W ) were calculated in the same manner as in the examples. Here, the value of the residual tension (F) per cord was measured in the outer layer in the tire radial direction when the cap band layer was two layers (Comparative Examples 2, 4 and 5).

[Test Example] The tires of the respective examples shown in Table 1 and the tires of the respective comparative examples shown in Table 2 were subjected to a high speed durability evaluation test.

The high speed durability of the tire is evaluated by the American standard FM.
VSS No. According to the test method of 109, the step speed method is performed, that is, the speed is increased every 30 minutes until a failure occurs. The speed (km / hour) at the time of failure and the elapsed time (minutes) at that speed ) 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.

Further, as shown by the results of the comparative example in Table 2,
The values of the number of twists, the number of impacts, etc. of the cap band layer cord are the same as those in the examples, and these are well known in the prior art, but do not satisfy the twist coefficient and / or the residual tension per width which are the features of the present invention. It is understood that the tire after vulcanization is deformed to obtain only one that cannot be used, or even if it is obtained, the high speed durability of the tire is poor.

[0034]

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

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the left half of a pneumatic radial tire having one 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 (dotted line circle portion) of a sample for measuring residual tension of a cap band layer cord.

FIG. 4 is an enlarged view of the sample collection site of FIG.

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

[Explanation of symbols]

 1 Pneumatic radial tire 2 Tread portion 3 Bead portion 4 Carcass 5 Steel belt layer 6 Cap band layer 7 Tread stripping portion (hatched portion) 8 Sampling code (black circle) 9 One code −D 10 Mark point 11 Code chuck

Claims (1)

[Claims] 1. A tread tread portion having a groove extending in the tire circumferential direction, a pair of side walls, and a bead portion,
At least one carcass layer composed of cords arranged substantially parallel to the tire radial direction, and a belt layer and a cap band arranged substantially outwardly of the carcass layer over the width of the tread surface. Layer, the belt layer is composed of cords intersecting each other at a relatively small angle to the tire circumferential direction, and the cap band layer is radially outward of the belt layer and 25% to 25% of the belt layer.
A rubberized narrow strip, which is arranged at a width of 120% and contains a plurality of the cap band layer cords, is made of the cord.
In a pneumatic radial tire formed by spirally winding at least one layer on a belt layer so that the cords are substantially parallel to the tire circumferential direction, the cap band layer cord is the total cord. An denier (D) is an aliphatic polyamide fiber cord of 500≤D≤3000, and it has a twin twist structure and a twist coefficient (N _T ) represented by the following formula 1 is 0.10≤N _T ≤ 0.30, and the residual tension per unit width ( _FW ) represented by the following formula 2 is 85 kg.
A pneumatic radial tire characterized in that f ≦ F _W ≦ 400 kgf. Formula 1: N _T = T × √ (0.139 × D / 2 × 1 /
ρ) × 10 ⁻³ N _T ; twist coefficient, T; twist number (number of times / 10 cm), D; total denier, ρ; specific gravity Formula 2: F _W = F × E × number of members F _W ; cap band layer Residual tension per cord width F; Residual tension per cap band layer cord immediately after sampling from the tire center E; Number of cap band layer cords driven per 5 cm in tire width direction