JP2889455B2 - 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 capable of reducing the weight of a tire while improving the cut resistance of a sidewall portion.

[0002]

2. Description of the Related Art In recent years, it has become important to reduce tire weight in order to save resources and improve high-speed running performance. In order to reduce the weight of the tire, it has been conventionally proposed to reduce the thickness of the sidewall rubber forming the sidewall portion.

[0003]

However, when the thickness of the sidewall rubber is reduced, the weight of the tire is reduced, but the cut resistance of the sidewall portion is reduced, and rough roads such as gravel roads are reduced. By traveling
There is a problem that a so-called road hazard occurs in which foreign matter collides with the outer side surface of the sidewall portion and damages the tire.

According to the present invention, the cut resistance and road hazard resistance of the sidewall rubber are based on forming a sidewall rubber from an inner layer and an outer layer and mixing short fibers made of organic fibers into the inner layer. It is an object of the present invention to provide a pneumatic radial tire that can reduce the weight of a tire while improving it and can solve the above problems.

[0005]

According to the present invention, an organic fiber cord is disposed radially from an inner side to an outer side in a tire axial direction around a bead core of a bead portion from a tread portion to a sidewall portion. A pneumatic radial tire comprising a carcass comprising a carcass ply and a belt layer comprising two belt plies disposed inside the tread portion and above the carcass and crossing steel cords. The sidewall rubber disposed outside the carcass of the sidewall portion in the tire axial direction includes an inner layer adjacent to the carcass, and an outer layer forming an outer wall surface outside the inner layer, and the inner layer includes a rubber component. Carbon black having an iodine adsorption amount of 35 to 90 mgr / gr based on 100 parts by weight
0 and parts, Ri Do from the short fibers made of an organic fiber rubber composition containing 10 to 40 parts by weight, and the short fibers are straight
Diameter D is 0.3-0.5μm, length L is 300-500μ
m and an angle of 0 to 45 ° with respect to the tire circumferential direction.
Pneumatic radial tie characterized by degrees of orientation
Ya.

[0006]

Further, the thickness t of the inner layer is 0.3 to 0.8 times the total thickness T of the sidewall rubber, and the thickness t is 1 mm or more, and the total thickness T is 2 mm or more and 10 mm It is preferable to set the following.

[0008]

The sidewall rubber is formed of an inner layer and an outer layer, and the inner layer is composed of 20 to 50 parts by weight of carbon black and 10 to 40 parts by weight of short fibers composed of organic fibers with respect to 100 parts by weight of the rubber component. And

Therefore, it is possible to increase the strength of the inner layer while reducing the total thickness T of the sidewall rubber, to improve the cut resistance and the road hazard resistance of the sidewall portion, and to reduce the carcass in the sidewall portion. The durability can be increased, and the weight of the tire can be reduced.

If the amount of carbon black and short fibers is less than the lower limit of each of the above-mentioned numerical values, the strength of the inner layer is reduced, so that the cut resistance cannot be improved. If the value exceeds the upper limit of the numerical value, the heat generation due to the repetitive deformation of the inner layer increases, and the heat is likely to cause peeling of the carcass from the sidewall rubber, and conversely, the strength may decrease.

The inner layer regulates the compounding ratio of carbon black and short fibers in the rubber component and regulates the iodine adsorption amount of the carbon black itself.

The specific surface area of carbon black per unit weight of the carbon black can be determined by measuring the amount of iodine adsorbed. As a characteristic of carbon black, the bond between particles tends to increase as the specific surface area increases, that is, as the iodine adsorption amount increases. The measurement of the iodine adsorption amount is performed according to JIS K6221.

In the present invention, by controlling the amount of iodine adsorbed on carbon black to 35 to 90 mgr / gr,
The aim is to optimize the bonding between the particles of the carbon black. Examples of types of carbon black satisfying the regulation of the iodine adsorption amount include, for example, GPF, FEF, and HA.
F and ISAF.

When the short fibers are oriented at an angle of 0 to 45 ° with respect to the circumferential direction of the tire, the short fibers intersect with the radially arranged carcass cords, and the cut resistance (load hazard resistance) of the sidewall portion. Can be further improved.

The thickness t of the inner layer is 0.3 to 0.8 times the total thickness of the side wall rubber, and the thickness t is 1
When the total thickness T is 2 mm or more and 10 mm or less, the thickness of the outer layer can be reduced, and the weight of the tire can be reduced.

If the thickness t is less than 0.3 times the total thickness T or less than 1 mm, the strength of the inner layer is reduced, and the improvement in cut resistance cannot be sufficiently achieved. Conversely, if the thickness t is larger than 0.8 times the total thickness T, the strength of the sidewall portion becomes excessively high, which adversely affects the riding comfort.

Further, by not mixing short fibers in the outer layer, the thickness of the outer layer can be reduced, and the weight of the tire can be further reduced.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. In the figure, a pneumatic radial tire 1 according to the present invention comprises:
Bead section 4 from tread section 2 through sidewall section 3
And a belt layer 7 disposed inside the tread portion 2 and above the carcass 6, ie, radially outward, around the bead core 5 from the inside toward the outside in the tire axial direction.

The tread portion 2 has a tread surface formed by a tread rubber TR disposed radially outside the belt layer 7 and a main body of the carcass 6 radially outside the bead core 5 of the bead portion 4. A bead apex 9 having a triangular cross-section and rising from the folded portion and made of hard rubber is provided.

The carcass 6 is composed of at least one carcass ply in which a radially arranged carcass cord inclined at an angle of 75 to 90 ° with respect to the tire equator C is covered with a case topping rubber CR, in this embodiment, one carcass ply. Organic fiber cords such as nylon, rayon, polyester, and aromatic polyamide are used as carcass cords.

The belt layer 7 has a thickness of 15 with respect to the tire equator C.
Two belt plies 7 in which a steel cord inclined at an angle of ~ 85 ° is covered with a belt topping rubber BR.
The tread portion 2 is formed by laminating the steel cords a and 7b with the steel cords intersecting each other, thereby increasing the rigidity of the tread portion 2.

The sidewall rubber SR disposed outside the carcass 6 of the side wall portion 3 in the tire axial direction includes an inner layer 10 adjacent to the carcass and an outer wall surface provided by being disposed outside the inner layer 10 in the tire axial direction. Outer layer 11 forming
Consists of

The total thickness T of the sidewall rubber SR is 2
mm or more and 10 mm or less, and the thickness t of the inner layer 10
Is 0.3 to 0.8 times the total thickness T and 1 mm or more.

If the total thickness T is smaller than 2 mm, the strength of the side wall portion 3 is excessively reduced and the cut resistance is impaired. On the other hand, if the total thickness T is larger than 10 mm, reduction of the tire weight cannot be achieved. .

Therefore, in order to reduce the tire weight and improve the cut resistance, the total thickness T is set to 2 mm or more and 10 mm or less, and the thickness t of the inner layer 10 is restricted to the above range.

The inner layer 10 contains 20 to 50 parts by weight of carbon black having an iodine adsorption amount in the range of 35 to 90 mgr / gr and 1 short fiber for 100 parts by weight of the rubber component.
From 0 to 40 parts by weight.

The short fibers are made of organic fibers such as nylon and polyester, and have a diameter D of 0.3 to 0.5 μm, a length L of 300 to 500 μm, and an aspect ratio L / D.
Is an ultra-fine and short-sized fibrous body of about 1,000. The short fibers are oriented at an angle of 0 to 45 ° with respect to the tire circumferential direction. The angle of the orientation is such that 70% of the short fibers out of all the short fibers contained therein should be oriented at the angle.

The strength of the inner layer 10 is increased by the short fibers and the carbon black, and the cut resistance of the sidewall portion 3 can be improved.

The outer layer 11 is a thin rubber body not containing the short fibers, and contributes to the weight reduction of the tire.

An example of the rubber composition of the inner layer 10 is shown in Table 1.
Table 2 shows an example of the rubber composition of each part forming the tire.

[0031]

[Table 1]

[0032]

[Table 2]

In FIG. 1, HE indicates the height of the tire section from the bead base line BL, HC indicates the turning height of the carcass 6, and HB indicates the tip height of the bead apex 9.

[0034]

[Specific Examples] Tires ( Examples 1 to 3 ) having a tire size of 215 / 80R16 and having the structure shown in FIG. 1 were prototyped according to the specifications shown in Table 3, and their performance was tested. In addition, the conventional tire without the inner layer 10 (Comparative Example 1) and the tires other than the configuration of the present invention (Comparative Examples 2 to 2)
7) was also tested and the performance was compared.

The test method is as follows. 1) Cut resistance (road hazard resistance) A controlled rough road was provided on the test course, and after running 15,000 km on this rough road, the total damage (length × depth) on the tire side was compared with Comparative Example 1. 100
It is indicated by an index. The higher the numerical value, the better, and 160 or more is a pass level.

2) High-speed durability A prototype tire having a tire internal pressure of 2.00 kgf / cm ² and a load of 600 kg was started at an initial speed of 150 km / H.
A high-speed endurance test was performed by a step-up method in which the speed was increased by 10 km / H every 0 minutes, and the speed at which damage occurred was indicated by an index with Comparative Example 1 being 100. The larger the numerical value, the better, and 80 or more is a pass level.

3) Tire Weight The weight per tire was indicated by an index with Comparative Example 1 being 100. The smaller the numerical value, the better, and 100 or less is a pass level.

4) Ride Comfort The test tire was mounted on a fixed shaft of a commercially available bump-over vibration tester, and the load was 1.510 kg, the internal pressure was 7 kg / cm ² , and the speed was 6
The axial load fluctuation at the time of moving over the protrusion was measured at 0 to 100 km / H, and the index was indicated by an index with Comparative Example 1 being 100. The larger the numerical value, the better, and 90 or more is a pass level. Table 3 shows the test results.

[0039]

[Table 3]

As a result of the test, the example of the present invention achieves cut resistance (road hazard resistance) while achieving reduction in tire weight.
Was improved.

[0041]

As described above, in the pneumatic radial tire of the present invention, the sidewall rubber is formed from an inner layer and an outer layer, and the inner layer is reinforced by mixing short fibers into the inner layer. Cut resistance and road hazard resistance can be improved while reducing the weight.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Description of Signs] 2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 10 Inner layer 11 Outer layer SR Sidewall rubber

Claims (3)

(57) [Claims] 1. A carcass comprising a carcass ply formed by folding a bead core of a bead portion from an inner side to an outer side in a tire axial direction from a tread portion through a sidewall portion to an outer side and arranging an organic fiber cord in a radial direction, A pneumatic radial tire comprising a belt layer comprising two belt plies disposed inside a tread portion and above a carcass and intersecting steel cords, wherein the carcass of the sidewall portion has The sidewall rubber disposed on the outer side in the tire axial direction includes an inner layer adjacent to the carcass and an outer layer forming an outer wall surface outside the inner layer, and the inner layer absorbs iodine with respect to 100 parts by weight of the rubber component. Amount of carbon black having an amount of 35 to 90 mgr / gr
５０50 parts by weight and 10-40 staple fibers composed of organic fibers
Ri Do the rubber composition and a weight portion, and the short fibers, the diameter D is 0.3 to 0.5 [mu] m, length
L is 300-500 μm, and in the tire circumferential direction
A pneumatic radial tire, wherein the tire is oriented at an angle of 0 to 45 degrees . 2. The method according to claim 1, wherein the thickness t of the inner layer is a side wall rubber.
0.3 to 0.8 times the total thickness T, and the thickness t
The pneumatic radial tire according to claim 1 , wherein a total thickness T is 2 mm or more and 10 mm or less . Wherein the outer layer, the pneumatic radial tire according to claim 1 or 2, wherein the free of the short fibers.