JP2002178714A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain durability while reducing weight. SOLUTION: Insulation rubber 10 is provided between carcass ply 6A and inner liner rubber 9. The insulation rubber 10 has a thinned changing part 12 in a tread central area. On a normal NS drawn to a carcass from the outside end 7E of a belt layer, the rubber thickness T1s up to the inner liner rubber from a carcess cord is set to 1.5 to 2.0 mm, and on a normal NC drawn on the carcass from the tire equator, the rubber thickness T1c up to the inner liner rubber from the carcass cord is set to 0.7 to 0.9 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire which is particularly suitable for heavy-duty vehicles, and which is lightweight while maintaining durability.

[0002]

2. Description of the Related Art In a so-called tubeless pneumatic tire, a butyl-based air-impermeable material having excellent air-permeability is provided inside a carcass ply in order to keep the internal pressure air tight. Inner liner rubber made of rubber is applied inside.

[0003] However, this butyl-based air-impermeable rubber has a characteristic that it is inferior in rubber physical properties and adhesiveness as compared with a diene-based rubber used for a topping rubber. Therefore, when the coating thickness of the topping rubber on the carcass cord is small, the inner liner rubber and the carcass cord come into contact with each other due to the rubber flow at the time of vulcanization molding, or the inner liner rubber may become loose. It penetrates between the carcass cords and deforms into a wavy shape, causing cracks and the like, resulting in a decrease in durability. In particular, in a heavy-duty tire using a steel cord for the carcass, this tendency becomes stronger as a result of a relatively wide inter-cord distance.

Therefore, conventionally, an insulation rubber having a thickness of about 1 mm is interposed between the carcass ply and the inner liner rubber to prevent contact between the inner liner rubber and the carcass cord, and to prevent the inner liner rubber from waving. ing.

However, this causes a problem that the weight of the tire increases.

Accordingly, the present invention provides an insulation rubber having a thickness-reducing portion in the center region of the tread, and a rubber thickness (insulation) from the carcass cord to the inner liner rubber at the tire equator and the outer edge of the belt layer. (Including rubber and topping rubber) within a predetermined range, while maintaining weight while achieving weight reduction, preventing contact between the inner liner rubber and the carcass cord and preventing the inner liner rubber from waving, etc., and maintaining durability. It is intended to provide a pneumatic tire that can be used.

[0007]

In order to achieve the above object, the invention of claim 1 of the present application relates to a pneumatic tire,
A carcass using a carcass ply extending from the tread portion to the sidewall portion to the bead portion, a belt layer disposed inside the tread portion and outside the carcass, and a tire cavity surface disposed inside the carcass ply. An inner liner rubber having a substantially uniform thickness made of an air-impermeable rubber to be formed, and an insulation rubber interposed between the carcass ply and the inner liner rubber having a changing portion for reducing the thickness, The changing portion is formed in a central region of the tread centered on the tire equator, and has an inner side extending from a side edge of the carcass cord of the carcass ply on the tire lumen side on a normal drawn to the carcass from the outer end of the belt layer. The rubber thickness T1s up to the interface between the liner rubber and the insulation rubber is 1.5 to 2.0 mm, and Rubber of N'narainagomu thickness T2
s is set to 1.5 to 2.0 mm, and from the side edge on the tire lumen side of the carcass cord on the normal drawn to the carcass at the tire equator from the boundary surface between the inner liner rubber and the insulation rubber. The rubber thickness T1c of the inner liner rubber layer from the boundary surface is 0.7 to 0.9 mm, and the rubber thickness T2c of the inner liner rubber layer is 1.5 to 2.0 mm.
mm.

According to the invention of claim 2, the width W1 of the change portion in the tire axial direction is 40 to 40 times the belt width of the belt layer.
60%, and the thickness of the insulation rubber at the change portion is substantially zero.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described together with the illustrated example. FIG. 1 illustrates a meridional section when the pneumatic tire of the present invention is formed as a heavy-duty tire such as for a truck or a bus.

In FIG. 1, a pneumatic tire 1 includes a carcass 6 which is folded from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4 and is locked. 6 and a belt layer 7 disposed outside the belt layer 6. Inside the carcass 6, an inner liner rubber 9 forming the tire inner cavity surface HS and an insulation rubber 10 interposed between the inner liner rubber 9 and the carcass 6 are arranged.

The carcass 6 has at least one carcass having at both ends of a ply body portion 6a extending between the bead cores 5 and 5 a ply turn-up portion 6b which turns around the bead core 5 from inside to outside in the tire axial direction. It is formed from the ply 6A. As the carcass ply 6A, a carcass cord 21... (Shown in FIGS. 3 and 4) arranged at an angle of 70 to 90 ° with respect to the tire equator C is covered with a topping rubber G, as in the past. Is done. In this example, the carcass 6 is formed from a single carcass ply 6A using a steel cord as the carcass cord 21, but the carcass cord 21 is made of an organic material such as nylon, rayon, polyester, or the like. Fiber cords can also be used.

In the case of a heavy duty tire, the belt layer 7 is usually formed of three to four belt plies 11.
In the present example, the first to fourth belt plies 1 in which the belt layer 7 is sequentially stacked from the carcass 6 side toward the radial outside.
An example in which it is formed from 1A to 11D will be described.

In the first belt ply 11A, belt cords are arranged at an angle of, for example, about 60 ± 10 ° with respect to the tire equator C, and the second to fourth belt plies 11B to 11D are 15 to 35 °. The belt cords are arranged at an angle of about. Also, the second and third belt plies 11
The inclination directions of the cords are different between B and 11C, thereby forming a strong truss structure and reinforcing the tread portion 2 with a strong tagging effect. In the case of a tire for heavy loads, a steel cord is suitably used as a belt cord, but if necessary, an organic fiber cord such as nylon, polyester, rayon or aromatic polyamide can be used.

On the inside of the ply body 6a of the carcass 6, an inner liner rubber 9 which forms substantially the whole tire cavity surface HS is disposed via an insulation rubber 10.

The inner liner rubber 9 is made of an air-impermeable rubber such as butyl rubber, and has a substantially uniform rubber thickness T2 and extends continuously between the bead portions 4, 4.

Here, "butyl rubber" means a rubber composition containing butyl rubber or its derivative in a rubber base material in an amount of 20% by weight or more. Butyl rubber (IIR)
Is a copolymer of isobutylene and a small amount of isoprene. As a derivative thereof, halogenated butyl rubber such as chlorinated butyl rubber and brominated butyl rubber obtained by reacting chlorine or bromine with the butyl rubber is used. This butyl rubber is used as a rubber component other than butyl rubber or a derivative thereof, that is, as the remainder of the rubber base, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene / butadiene rubber (SBR), and the like. Is used. A filler such as a reinforcing agent such as carbon black, a vulcanizing agent, a vulcanization accelerator, and a softening agent can be added to the butyl-based rubber produced by these methods, as in the case of ordinary tire rubber.

As the air-impermeable rubber, a halide of isobutylene / paramethylstyrene copolymer can be used in place of the butyl rubber or its derivative. Commercially available halides of isobutylene / paramethylstyrene copolymer include, for example, EXXPRO90-10, EXXPRO89-4, EXX manufactured by Exxon Chemical Co., Ltd.
XPRO93-5 and the like.

The inner liner rubber 9 has a rubber thickness T2 of 1.5 to 1.5 in order to keep the tire cavity airtight.
It is necessary to set the range to 2.0 mm. If the rubber thickness T2 is less than 1.5 mm, air or moisture in the tire lumen leaks and penetrates into the carcass, resulting in not only a decrease in air pressure but also a cord looseness in the carcass, thereby lowering durability. Conversely, if it exceeds 2.0 mm, the weight is unnecessarily increased, and the advantage of weight reduction, which is the subject of the present application, is impaired.

The insulation rubber 10 is interposed between the inner liner rubber 9 and the carcass ply 6A and extends inward and outward in the radial direction, thereby increasing the adhesive strength between the two and also improving the rubber flow during vulcanization molding. caused by,
Contact between the inner liner rubber 9 and the carcass cord 21,
In addition, a waving phenomenon of the inner liner rubber 9 itself is prevented.

For this purpose, the insulation rubber 10 needs to have excellent adhesiveness. In this embodiment, the rubber base material is formed of diene rubber only, and butyl rubber or a derivative thereof is excluded. . In particular, those using natural rubber as the rubber substrate, or carcass ply 6A
It is preferable to use a rubber having the same composition as that of the topping rubber G. The “same composition” means that the rubbers constituting the rubber base material are the same and have different blending ratios.

Here, the conventional insulation rubber has a substantially uniform thickness and is formed uniformly. However, as a result of the study of the present inventor, in the central region of the tread centered on the tire equator, the movement of the carcass topping rubber G is restricted during vulcanization molding because the belt layer 7 is placed outside the carcass 6. Accordingly, it has been found that the inner liner rubber 9 is prevented from coming into contact with the carcass cord 21 or being sucked up between the carcass cords 21 and 21 to form a wavy shape. In addition, since the tread central region has high rigidity and small deformation of the tire during traveling, damage to the carcass 6 and the inner liner rubber 9 is further unlikely to occur.

Therefore, it was found that the insulation rubber did not perform a particularly important function in the central region of the tread.

Therefore, in the pneumatic tire 1 of the present embodiment, as shown in an enlarged view in FIG. 2, in the center region of the tread, the insulation rubber 10 is formed with a change portion 12 having a reduced thickness. Tire weight reduction.

The changing portion 12 is formed around the tire equator C. In the present embodiment, the thickness of the insulation rubber 10 at the changing portion 12 is substantially 0, that is, by removing the insulation rubber 10. This change part 1
2 are formed.

On the other hand, in the outer region including the sidewall portion 3 and the bead portion 4 outside the outer end 7E of the belt layer 7 in the tire axial direction, the movement of the carcass topping rubber G during vulcanization molding is restricted. And tire deformation during running is large. The outer end 7E of the belt layer 7 is
It means the outer end of the widest belt ply among the belt plies 11 constituting the belt layer 7.

Therefore, at least in the outer region, it is necessary to form the insulation rubber 10 with a sufficient thickness to suppress the inner liner rubber 9 from contacting the carcass cord 21 and suppressing the waving.

Therefore, the carcass 6 is connected to the outer end 7E.
Thickness T1s from the side edge of the carcass cord 21 of the carcass ply 6A on the tire lumen side to the boundary surface K between the inner liner rubber 9 and the insulation rubber 10 on the normal line Ns drawn in FIG. 1.5)
2.0 mm. The rubber thickness T1s is the sum of the thickness of the insulation rubber 10 and the coating thickness of the topping rubber G. When the rubber thickness T1s is less than 1.5 mm, the contact of the inner liner rubber 9 with the carcass cord 21 and Rippling cannot be sufficiently suppressed. Also 2.
If it exceeds 0 mm, the weight is unnecessarily increased, and the merit of weight reduction is impaired.

In this example, a preferable case is shown in which the rubber thickness from the carcass cord 21 to the boundary surface K is set substantially equal to the rubber thickness T1s in the entire outer region.

In order to obtain the effect of the changing portion 12, the inner liner rubber 9 and the insulation are mounted on the tire equator C from the side of the carcass cord 21 on the tire lumen side on the normal line Nc drawn to the carcass 6. The rubber thickness T1c (shown in FIG. 4) up to the interface K with the rubber 10 is set to 0.7 to 0.9 mm. If the rubber thickness T1c is less than 0.7 mm, it is not possible to sufficiently suppress the inner liner rubber 9 from coming into contact with the carcass cord 21 and to undulate. If the rubber thickness T1c exceeds 1.0 mm, the weight cannot be sufficiently achieved.

As in the present embodiment, it is preferable to set the rubber thickness from the carcass cord 21 to the boundary surface K substantially equal to the rubber thickness T1c in the entire area of the change portion 12 in order to reduce the weight. preferable.

Here, in order to achieve the maximum weight reduction while ensuring the required durability, the changing portion 12 has a width W1 in the tire axial direction which is determined by the distance between the outer ends 7E of the belt layer 7. 40 to 60% of the belt width WB. If W1 is less than 0.4 × WB, sufficient weight reduction cannot be achieved. Also, on the outer end side of the belt layer 7, since the restraining force of the movement to the carcass stopping rubber G gradually decreases, if the width W1 exceeds 0.6 × WB, the durability decreases on the outer end side of the belt layer 7. Tend to be.

The rubber thickness T2s of the inner liner rubber 9 on the normal line Ns and the rubber thickness T2c of the inner liner rubber 9 on the normal line Nc are 1.5 to 1.5, respectively.
The thickness is in the range of 2.0 mm, and is substantially equal to the rubber thickness T2 because the inner liner rubber 9 has a substantially uniform thickness as described above.

Although a particularly preferred embodiment of the present invention has been described in detail above, for example, the changing portion 12 does not need to have a thickness of 0 if the thickness of the insulation rubber 10 is to be reduced. The present invention is not limited to heavy loads, and may be implemented by being modified into tires of various categories such as passenger cars and commercial vehicles.

[0034]

EXAMPLE A tire having a tire size of 11R22.5 and having a structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the durability and weight of each sample tire were measured.
The results are shown in Table 1.

(1) Durability: Using a drum tester, internal pressure (800 kPa), load (58.52 KN), speed (2
0 km / h), and the running distance (1200 km for a complete run) until tire damage was generated was set to 100 in Comparative Example 1.
It is indicated by an index. The larger the value, the better the durability.

(2) Weight The weight per tire was measured and is indicated by an index with Comparative Example 1 being 100. The smaller the value, the lighter the weight.

[0037]

[Table 1]

[0038]

Since the present invention is configured as described above,
While achieving weight reduction, the contact between the inner liner rubber and the carcass cord, the waving of the inner liner rubber, and the like can be prevented, and the durability can be maintained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the tread portion.

FIG. 3 is a cross-sectional view illustrating a rubber thickness on a normal drawn from an outer end of a belt layer to a carcass.

FIG. 4 is a cross-sectional view illustrating a rubber thickness on a normal drawn from the tire equator to a carcass.

[Explanation of symbols]

 Reference Signs List 2 tread part 3 side wall part 4 bead part 6 carcass 6A carcass ply 7 belt layer 7E outer end of belt layer 9 inner liner rubber 10 insulation rubber 12 changing part 21 carcass cord HS tire inner cavity surface K boundary surface Nc, Ns method line

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[Procedure amendment]

[Submission date] December 12, 2000 (200.12.
12)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Pneumatic tire

Claims (2)

[Claims] 1. A carcass using a carcass ply from a tread portion to a bead portion through a sidewall portion, a belt layer disposed inside the tread portion and outside the carcass, and disposed inside the carcass ply. An inner liner rubber having a substantially uniform thickness made of an air-impermeable rubber forming a tire lumen surface, and an insulator interposed between the carcass ply and the inner liner rubber having a changing portion for reducing the thickness. The changing portion is formed in a central region of the tread centered on the tire equator, and the carcass cord of the carcass ply of the carcass ply on a normal line drawn from the outer end of the belt layer to the carcass. The rubber thickness T1s from the side edge of the rubber to the interface between the inner liner rubber and the insulation rubber is 1.5 to 2.0.
mm and a rubber thickness T2s of the inner liner rubber from the boundary surface is 1.5 to 2.0 mm, and a side edge of the carcass cord on the tire lumen side on a normal drawn to the carcass at the tire equator. And a rubber thickness T1c from 0.7 to 0.9 mm to a boundary between the inner liner rubber and the insulation rubber, and a rubber thickness T2c of the inner liner rubber layer from the boundary to 1.5 to 2 mm. A pneumatic tire having a thickness of 0.0 mm. 2. The width W1 of the change portion in the tire axial direction is 40 to 60% of the belt width of the belt layer, and the thickness of the insulation rubber of the change portion is substantially zero. The pneumatic tire according to claim 1, wherein: