JP2001047813A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for heavy load having inhibited growth of an outer periphery of the tire and improved durability. SOLUTION: This pneumatic radial tire for heavy load has at least three belt layers. The cross belt layers 3b, 3c are adjacent belt layers 3 having reinforcing cords 4 arranged so as to cross each other with a tire equator line being between them, and their respective reinforcing cord covering rubbers each have a dynamic modulus of elasticity ranging from 10 to 30 MPa. The reinforcing cord covering rubber of the belt layer 3a other than the cross belt layers 3b, 3c has a dynamic modulus of elasticity set at 40 to 80% of the dynamic modulus of elasticity of each of the cross belt layers 3b, 3c.

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 for heavy loads, and more particularly to a tire for suppressing peripheral growth and improving durability while maintaining performance such as steering stability and cut resistance. Heavy duty pneumatic radial tire.

[0002]

2. Description of the Related Art In recent years, flattening of heavy-duty pneumatic radial tires used for heavy vehicles such as trucks and buses and light trucks has been progressing. However, as the tire becomes flatter, the internal pressure sharing ratio to the tire belt increases, and the tire outer peripheral growth occurs, thereby causing a problem that the durability of the tire is significantly reduced.

In order to suppress the growth of the outer periphery of the tire, there has been proposed a tire in which an organic fiber reinforcing layer in which highly elastic organic fibers are arranged is arranged on the outer periphery of the belt layer (Japanese Patent Application Laid-Open No. 9-193610). JP-A-9-240213). However, since it is necessary to arrange a reinforcing layer using a special fiber on the outer periphery of the belt portion, the number of tire manufacturing steps increases, and the tire weight increases,
There has been a demand for a tire capable of suppressing the growth of the outer periphery of the tire without changing the reinforcing cord structure of the tire and without increasing the number of tire members.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress the outer circumferential growth of a tire while maintaining performance such as steering stability and cut resistance without changing the cord reinforcing structure of the tire. An object of the present invention is to provide a pneumatic radial tire for heavy loads with improved durability.

[0005]

According to the present invention, in a heavy-duty pneumatic radial tire having at least three belt layers in which reinforcing cords are arranged outside a carcass layer of a tread portion, the reinforcing cord is connected to the tire equator. The dynamic elastic modulus of the reinforcing cord-coated rubber of the crossed belt layer, which is the adjacent belt layer arranged so as to intersect with each other across the line, is 10 to 30 MPa, and the reinforcing cord coating of the belt layers other than the crossed belt layer is performed. A pneumatic radial tire for heavy loads is provided in which the dynamic elastic modulus of rubber is 40 to 80% of the dynamic elastic modulus of the cross belt layer.

[0006]

FIG. 1 shows a partial cross section in the meridian direction of an example of a pneumatic radial tire for heavy load according to the present invention, and FIG. 2 shows a belt structure of the pneumatic radial tire viewed from the outer peripheral direction of the belt. . In FIGS. 1 and 2, four belt layers 3 on which reinforcing cords 4 are arranged are arranged outside the carcass layer 2 of the tread portion 1. 2 of these
The third and third belt layers 3b and 3c are adjacent cross belt layers in which the reinforcing cords 4 are arranged so as to cross each other with the tire equator line CL interposed therebetween. The first belt layer 3a and the fourth belt layer 3d adjacent to the carcass layer 2 are the same as the reinforcing cords 4 of the adjacent cross belt layers described above.
Are the belt layers in which the reinforcing cords 4 are not arranged so as to intersect each other with the equator line CL interposed therebetween, and the reinforcing cords 4 are arranged in substantially the same direction as the reinforcing cords 4 of the adjacent crossed belt layers.

According to the present invention, the dynamic elastic modulus of the reinforcing cord-coated rubber of the crossed belt layers (belt layers 3b, 3c) is set to 10 to 30 MPa, and the belt layers other than the crossed belt layers (belt layers 3a, 3d). By setting the dynamic elastic modulus of the rubber covered with the reinforcing cord to be 40 to 80% of the dynamic elastic modulus of the cross belt layer, it is possible to suppress tire outer peripheral growth.

[0008] The growth of the outer periphery of the tire is caused by the fact that the rubber covering between the reinforcing cords embedded in the cross belt layer which plays the role of the hoop effect is stretched by the tension in the circumferential direction of the tire, and the rubber deteriorates for a long period of time. This causes the circumference of the entire belt layer to grow.

Therefore, in the present invention, as described above, the dynamic elastic modulus of the reinforcing cord-coated rubber of the cross belt layer is increased, and the dynamic elastic modulus of the reinforcing cord-coated rubber other than the cross belt layer is reduced. The configuration was such that the growth of the circumference of the crossed belt layer itself was suppressed.

[0010] The dynamic elastic modulus of the reinforcing cord-coated rubber of the cross belt layer of the present invention is 10 to 30 MPa, preferably 1 to 30 MPa.
If it is less than 10 MPa, the rubber is too soft and the effect of suppressing the peripheral growth is small.
If it exceeds Pa, the rubber is too hard and is apt to be subjected to stress concentration on the belt layer, which causes separation of the belt layer.

The dynamic elastic modulus of the reinforcing cord-coated rubber of the belt layers other than the cross belt layer may be 40 to 80%, preferably 50 to 75% of the dynamic elastic modulus of the cross belt layer. . When the dynamic elastic modulus of the belt layer between the cross belt layer and the carcass layer, in FIG. 1, the first belt layer 3a is less than 40% of the dynamic elastic modulus of the cross belt layer,
The movement of the cross belt layer during tire running becomes too large,
Driving stability deteriorates, and conversely if it exceeds 80%,
Stress tends to be concentrated between the carcass layer 2 and the belt layer 3 and tread separation is likely to occur. When the dynamic elastic modulus of the belt layer disposed on the outer periphery of the cross belt layer, that is, the fourth belt layer 3d in FIG. The movement of the tread becomes too large, resulting in inferior abrasion resistance and tread separation resistance. Conversely, if it exceeds 80%, the belt layer is inferior in cut protection resistance.

The cord angle of the reinforcing cord 4 of the above-mentioned cross belt layer is not particularly limited.
The angle may be up to 35 °.

[0013]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples.

The test tires used in each of the following examples were manufactured as follows. Preparation of test tires Rubbers A to E having the compounding composition (parts by weight) shown in Table 1 below
The reinforcing cord (steel cord) covering rubber of each belt layer is constituted by a combination as shown in Table 2 below, and FIG.
A pneumatic radial tire for heavy load having a tire size of 11R22.5 as shown in was manufactured and subjected to the following tests.

Dynamic Elastic Modulus E '(MPa) Measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho at a static strain of 10%, a dynamic strain of ± 2%, and a frequency of 20 Hz. Outer diameter growth (%) For vehicles equipped with each tire, 47 test courses
The outer diameter growth of the tire after traveling 2 km was measured.

Indoor mileage (index) JATMA YEARBOOK Installed on the standard rim described in the 1999 edition,
Air pressure for maximum load (single wheel), drum diameter 1707mm
Speed 45km, slip angle ± 2 °
The load is changed from 115% of the maximum load to 5% every 24 hours.
The running distance until the breakage was increased by one by one was evaluated by an index value with the conventional example being 100. Uneven wear resistance (index) After traveling 50,000 km on a paved general road, the amount of uneven wear generated on the ribs of the shoulder portion was measured, and the result was evaluated by an index value with the conventional example being 100. The larger the value, the better the uneven wear resistance.

Cut resistance (index) After traveling 50,000 km on a general road including unpaved roads, the number and extent of cuts on the tread are visually evaluated, and the result is expressed as an index value with the conventional example being 100. displayed. The higher the value, the better the cut resistance. Driving stability (index) The feeling of each tire by a test driver was scored on a dry road surface, and the index was expressed as an index with the conventional example being 100. The larger the value, the better the steering stability.

[0018]

[Table 1]

The following ingredients were used. NR: RSS # 3 Carbon black: N326 grade carbon black Zinc flower: Zinc flower R, Ginrei Stearic acid: Tung grade, Nippon Oil & Fat Co. Antioxidant: N-phenyl-N '-(1,3-dimethylbutyl)- p-
Phenylenediamine and poly (2,2,4-trimethyl-1,
2-Dihydroquinoline Plasticizer: Aroma oil, Desolex # 3, manufactured by Showa Shell Sekiyu KK Sulfur: Insoluble sulfur (20% oil added product) Vulcanization accelerator: N-N'-dicyclohexyl-2-benzothiazol sulfenamide Resin 1: Condensate of m-cresol and formaldehyde Resin 2: Hexamethoxymethylmelamine

[0020]

[Table 2]

[0021]

[Table 3]

As shown in Table 2, as compared with Comparative Example 1 in which the reinforcing rubber layer was conventionally blended and Comparative Examples 1 to 7 in which the ratio of the dynamic elastic modulus of the reinforcing rubber layer was set outside the range of the present invention. ,
In the tires of Examples 1 to 8 of the present invention, good results were obtained in all of the carcass edge separation resistance.

[0023]

According to the present invention, the dynamic elastic modulus of the reinforcing cord coating rubber of the cross belt layer in the pneumatic tire for heavy load is 10 to 30 MPa, and the dynamic elastic modulus of the reinforcing cord coating rubber of the belt layers other than the cross belt layer is dynamic. The dynamic elastic modulus of the cross belt layer is set to 40 to 80% of the dynamic elastic modulus of the cross belt layer, thereby maintaining the performance such as steering stability and cut resistance without changing the cord reinforcement structure of the tire. It is possible to obtain a pneumatic radial tire for heavy load in which peripheral growth is suppressed and durability is improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view in the meridian direction of a heavy-duty pneumatic tire of the present invention.

FIG. 2 is a plan view of a belt layer.

[Explanation of symbols]

 Reference Signs List 1 tread 2 carcass layer 3 belt layer 3a first belt layer 3b second belt layer 3c third belt layer 3d fourth belt layer 4 reinforcing cord

Claims (1)

[Claims] 1. A heavy-duty pneumatic radial tire having at least three belt layers in which reinforcing cords are arranged outside a carcass layer of a tread portion, wherein the reinforcing cords are arranged so as to intersect with each other across a tire equator line. The dynamic elastic modulus of the reinforcing cord-coated rubber of the cross belt layer, which is the adjacent belt layer, is 10 to 30 MPa, and the dynamic elastic modulus of the reinforcing cord-coated rubber of the belt layer other than the cross belt layer is determined by the cross belt. 40-80% of the dynamic modulus of the layer
A pneumatic radial tire for heavy loads, characterized in that: