JPH03136904A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve maneuvering stability during a high speed travel by forming a carcass layer having a crown part end number specified with the predetermined diameter of nylon cords, and covering the carcass layer with a rubber composition having specific loss tangent, hardness and modulus. CONSTITUTION:A carcass layer 4 is so constituted that nylon cords sized to 840 D/2 are arranged in such a way as to give the end number of 65 to 75/50mm at a crown part 3, and covered with a rubber. This covering rubber has 0.18 to 0.30 loss tangent at 20 deg.C, hardness of 68 or more as per JIs, and 300% modulus of 150kg/cm<2> or less. According to the aforesaid construction, maneuvering stability at a high speed can be enhanced without any loss of high sped durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire (hereinafter abbreviated as radial tire), and particularly to a radial tire that exhibits excellent handling stability for high-speed running.

[Conventional technology]

In order to maintain the handling stability of radial tires, which are used under harsh driving conditions such as rapid acceleration/deceleration and sharp turns/turns when driving at high speeds, like competition radial tires, it is necessary to It is necessary to maintain stable ground contact at all times, even on uneven surfaces.

In order for conventional competition radial tires to be able to track even minute irregularities under such harsh driving conditions, it is generally important to balance the rigidity of the area from the bead to the sidewall. Various proposals have been made for reinforcing structures in the above areas.

However, with recent advances in automobile technology, radial tires used in vehicles are becoming faster and faster.
An increasingly high degree of maneuverability is required. On the other hand, as long as the size of the tire is specified within certain conditions by the standard,
It has been difficult to satisfy the requirement for high handling stability only by balancing the rigidity.

The present inventors have focused on the fact that the handling stability of a radial tire for high-speed running used under the above-mentioned severe driving conditions is closely related to the vibration damping performance of this radial tire during high-speed running, The present invention has been accomplished through extensive research.

[Problem to be solved by the invention]

An object of the present invention is to provide a radial tire that can improve steering stability without impairing high-speed durability even when used under particularly severe driving conditions as described above. be.

[Means to solve the problem]

The object of the present invention is to use an 840 D/2 nylon cord as a carcass cord of a radial tire, arrange this nylon cord so that the number of ends at the crown part is 65 to 7515 (lam), and , loss tangent (hereinafter referred to as tan δ) at 20″C is 0.18 to 0.30, JIS hardness is 68 or more, 3
This can be achieved by embedding it in a coating rubber composition whose 00% modulus is 150 Kg/c+a'' or less.

As shown in the figure, the radial tire of the present invention includes a pair of left and right bead portions 1, a pair of left and right sidewall portions 2 continuous between the bead portions, a crown portion 3 continuous between the sidewall portions, and the above-described components. a carcass layer 4 consisting of a carcass cord folded back from the inside of the tire to the outside of the bead core la of the bead portion 1 and arranged substantially in the cross-sectional direction of the tire;
It is comprised of at least two belt layers 5 disposed on the carcass layer of the crown portion. In addition, 6,7
is a bead filler and R is a rim.

The radial tire of the present invention uses a nylon cord represented by nylon 6, nylon 66, etc. as a carcass cord for reinforcing the carcass layer, and two fiber bundles having a total denier (D) of 840D are twisted together. This uses fine denier cord. Here, the reason why nylon cord is used as the carcass cord is that nylon has low heat generation, good bending fatigue resistance and adhesion to rubber, and relatively high tensile strength, and is used to reinforce the carcass of competition tires. This is because it has well-balanced physical properties.

If the cord is thicker than 8400/2, such as 12600/2, it is not possible to simultaneously improve handling stability and high-speed durability when used in a radial tire for high-speed running.

Further, in the present invention, the density of the carcass layer is important, and it is necessary that the number of ends of the 840 D/2 nylon cord is 65 to 75 per 50-width at the crown portion. This number of ends is 65 150 sn
If it is smaller than , the effect of improving high-speed durability will be insufficient, and if it exceeds 75 150 sus, it will not be possible to sufficiently improve handling stability.

What is more important in the present invention is that the rubber covering the carcass cord has a tan δ of 0 at 20°C.
．． 18~0.3G, JIS hardness 68 or higher, 300%
It is made of a rubber composition with a modulus of 150 Kg/cm" or less. Even if the carcass cord of the present invention described above is embedded in a rubber composition that does not satisfy the above physical properties, it will maintain stable handling and high-speed durability. Even if it is possible to improve either one of them, it is not possible to improve both at the same time.

That is, the carcass layer of the radial tire of the present invention has the above-mentioned fine denier nylon cords arranged at a relatively high density, and the nylon cords are arranged in accordance with JIS hardness and t
Since the anδ is relatively high and the 300% modulus is relatively small, the vibration damping properties of the tire are improved by coating the tire with a rubber composition that has high vibration damping properties and has well-balanced rubber physical properties. Synergistically improve
Reduce heat generation. Therefore, even when running at ultra-high speeds of 300 km/hr or more, the tires of the present invention are excellent because they immediately damp and converge the vibrations that occur when riding over minute irregularities, and adhere closely to and follow the road surface. It exhibits excellent handling stability, and its low heat generation improves high-speed durability.

The tan δ specified in the present invention, JIS hardness, 3
As a specific example of a rubber composition satisfying 00% modulus, for example, natural rubber (hereinafter abbreviated as NR) and synthetic polyisoprene rubber (hereinafter abbreviated as ■R) are essential rubber components, and the nitrogen adsorption specific surface area ( Hereinafter abbreviated as N and SA) is 7
0 to 90ml/g, dibutyl phthalate oil absorption (hereinafter abbreviated as DBP oil absorption) is 90m/! Examples include rubber compositions containing carbon black with a small particle size of /100g or less and a low structure.

By blending carbon black with such a low structure, it is possible to increase the hardness and tan δ of the rubber composition, and reduce the modulus by 300%. The amount of carbon black to be blended is preferably within the range of 55 to 80 parts by weight per 100 parts of the raw material rubber. If the amount of carbon black is less than 40 parts by weight, the tan δ will not increase, and if it exceeds 80 parts by weight, the modulus will become too high and the vibration damping property will not improve.

In addition to the above-mentioned essential rubber components and carbon black, the coated rubber composition of the present invention includes various rubber compounding chemicals such as styrene-butadiene copolymer rubber (SBR) and polybutadiene rubber (BR) as rubber components. For example, sulfur, a vulcanization accelerator, a vulcanization accelerator, an anti-aging agent, an aromatic oil, zinc white, stearic acid, etc., a metacresol resin, and a tall oil rosin maleate can be appropriately blended.

Among these, meta-cresol resin has high rubber hardness and ta
It is effective to increase nδ, and if tall oil rosin maleate is used in combination with metacresol resin, the rubber hardness, tanδ, and 300% specified in the present invention can be improved.
It becomes easy to prepare a rubber composition that satisfies the modulus,
It's advantageous.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Three types of rubber compositions having compounding compositions A, B and C shown in Table 1 were prepared. These three types of rubber compositions were vulcanized according to a conventional method, and the resulting vulcanized rubber was
JIS hardness, 300% modulus, and loss tangent tan δ at 20'C were measured, respectively. The measurement results are shown in Table 1.

The following four types of cords made of nylon 6 were produced as carcass cords.

Code I: 1260 D/2. Number of ends = 54 1
50m Code II: 1260 D/2. Number of ends = 64 150mm: 2-)'III: 840
D/2. x number of counts = 70 pieces 150as + code IV
: 840 D/2. Number of ends = 56 150mm
.

(The number of ends means the number at the crown portion.) These four types of carcass cords and the three types of coating rubber compositions were combined as shown in Table 2 to produce 10 types of radial tires.

The damping rate, high-speed durability, and handling stability of these 10 types of radial tires were evaluated. The results are shown in Table 2.

In addition, J of the vulcanized coating rubber composition at 20°C
The IS hardness, 300% modulus, tan δ, and damping rate of the radial tire, high-speed durability, and steering stability were each determined by the following measurement methods.

JIS and 300! : [-juice: JIS
Measured according to the method specified in -K 6301.

tan δ: Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho ■,
Length between chucks 20m1, width 5mm+, thickness 2+am
, a strip-shaped sample with a length of 20III11 was heated at a frequency of 20Hz,
Measurement was performed under the conditions of an elongation rate of 10%, a dynamic strain of ±2χ, and a temperature of 20°C.

Keshuo: Measure the time waveform of the vertical protrusion impact force, consider this as a damping waveform of one degree of freedom system, calculate the logarithmic damping rate, and calculate the index value with the measurement result of Comparative Example 1 tire as 100. It was expressed as The larger the index value is, the better the vibration damping property is.

1.200 by attaching tires to the two-indoor high-speed drum testing machine! m
/hr, in the speed range of 200-240Km+/hr, 10 minutes each for every 20Km/hr, 240Km/h
At speeds above r, every 10km/hr for 20 minutes.
As you step up, the speed at which the tire breaks (
Km/hr) was defined as durability. The larger this value is, the better the high-speed durability is.

Longitudinal stability: Laps were measured every lap on a circuit with a length of 4.41 Km, and the best lap times were measured five times, and the best lap times were expressed as an index value, with the best lap of Comparative Example 1 tire being 100. The smaller the index value, the better the lap and the better the steering stability.

(Margins below this page) In Table 1, ') indicates RSS #4. 2) is “NIPOL” 1502.3 manufactured by Nippon Zeon ■
is “NIPOL” BR1220, 4, manufactured by Nippon Zeon ■
is N-(1,3-dimethylbutyl)-N゛-phenyl-
P-phenylenediamine, 5) is “Sumikanol” 61O manufactured by Sumitomo Chemical Co., Ltd.
1-) is “Noritak AQ-9” manufactured by Harima Chemical Industry ■
OA,? ) is Nz5A= 28+/! /g, DBP
Oil absorption = 89ml/100g, S) is Nz5A
=82+aj! /gSDBP oil absorption = 72mL'1
00g.

9) is 20x oil-extended insoluble sulfur, +01 is N-t-butyl-2-benzothiazolylsulfenamide.

(Margins below on this page) The measurement results shown in Table 2 will be described below with reference to the results of the tire of Comparative Example 1.

Comparative Example 2 is an example in which the same large 1260 D/2 nylon cord as in Comparative Example 1 was used, but a rubber composition with a different composition was used. In this case, although the damping rate and steering stability are slightly improved, the high-speed durability is reduced because the tan δ of the rubber composition is large.

Comparative Example 3 is an example in which a rubber composition (jan δ large) having a different composition from Comparative Examples 1 and 2 was used. In this case as well, the damping rate and steering stability are slightly improved, but tan δ is even larger than in Comparative Example 2, so the high-speed durability is also significantly reduced.

Comparative Example 4 is the same as Comparative Example 1, but the type of nylon cord (
This is an example of changing the number of ends).

Although the high-speed durability is improved compared to Comparative Example 1, the damping rate is decreased and the steering stability is decreased.

Comparative Example 5 is the same as Comparative Example 3, but the nylon cord type M
This is an example of changing (increasing the number of ends). The damping rate, handling stability, and high-speed durability are substantially the same as those of Comparative Example 1 tire.

Comparative Example 6 Tire is an example of Comparative Examples 1 and 4 in which the type of nylon cord (which satisfies the regulations of the present invention) is changed. In this case, the high-speed durability is improved, but the damping rate and steering stability are unchanged from Comparative Example 1.

Furthermore, in Comparative Examples 7 and 8, the nylon cord of the present invention (
However, the number of ends is small), and the former does not satisfy the provisions of the present invention, while the latter does. In the case of Comparative Example 7, the damping rate and steering stability are the same as those of Comparative Example 1, but the high-speed durability is lower. Furthermore, although the tire of Comparative Example 8 has improved damping rate and handling stability, its high-speed durability has significantly decreased.

On the other hand, Examples 1 and 2 are examples in which the same nylon cord was used, but the physical properties of the rubber composition were changed. The tire of Example 1 has improved damping rate, steering stability, and high-speed durability compared to the tire of Comparative Example 1. Further, although the tire of Example 2 has the same high-speed durability as the tire of Comparative Example 1, the damping rate and steering stability are significantly improved.

〔Effect of the invention〕

As explained above, according to the present invention, a thin nylon cord is used as the carcass layer of a radial tire, and this cord is driven in a specific number of ends, and rubber having specific physical properties is used as the carcass layer of a radial tire. The placement of the carcass layer embedded in the composition provides high vibration damping properties. Therefore, it is possible to maintain a stable ground contact state even under severe high-speed driving conditions, improving handling stability and at the same time improving high-speed durability.

[Brief explanation of the drawing]

The figure is a half sectional view showing an example of a radial tire. 1...Bead part, 2...Side wall part, 4...
・Carcass layer, R...rim.

Claims (1)

[Claims] A carcass layer is constructed by arranging nylon cords having a thickness of 840D/2 so that the number of ends at the crown portion thereof is 65 to 75/50mm, and the coating rubber of the nylon cord has a loss tangent at 20°C. 0.18
~0.30, a pneumatic radial tire made of a rubber composition having a JIS hardness of 68 or more and a 300% modulus of 150 Kg/cm^2 or less.