JP2002103907A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability in an inner linerless structure. SOLUTION: At least an inner part of the topping rubber of a carcass ply is made of a low air permeable rubber composition including 100 pts.wt. of a rubber base material composed of 1-50 wt.% of bromide of butyl rubber halide or isobutylene paramethyl styrene copolymer, and 45-60 pts.wt. of carbon black. The carbon black has the iodine adsorption amount of 80-125 mg/g or the nitrogen adsorption specific surface area of 80-120 m2/g, and further has the DBP absorption amount of 70-100 ml/100 g, or the compressed DBP absorption amount of 70-90 ml/100 g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic pneumatic pump in which the innermost carcass ply is provided with a pneumatic holding force, thereby substantially eliminating the conventional inner liner and achieving weight reduction while maintaining durability. Regarding tires.

[0002]

2. Description of the Related Art In a tubeless pneumatic tire, an inner liner made of a low-air-permeable rubber composition is usually adhered to the inside of a carcass in order to keep the internal pressure air tight. However, even with such tires, further reduction in weight has been demanded in response to recent demands for low fuel consumption.

For this purpose, for example, Japanese Patent Application Laid-Open No. 6-15600
No. 7, JP-A-8-113007 and the like, by forming a topping rubber of the innermost carcass ply with the low air-permeable rubber composition and giving the carcass ply an air holding power. A tire having an inner linerless structure in which the inner liner is eliminated has been proposed.

[0004]

However, in the tire having this structure, the inner liner is eliminated, and the innermost carcass ply is exposed as the inner surface of the tire. In some cases, the topping rubber flows greatly, and the thickness of the rubber from the inner edge of the carcass cord to the inner surface of the tire may be significantly reduced. The decrease in rubber thickness causes damage such as cracks on the inner surface of the tire, and causes a decrease in air pressure retention and durability.

[0005] Accordingly, the present invention is based on specifying the type and amount of carbon black to be compounded in a low air permeable rubber composition and suppressing the rubber flow during vulcanization of the rubber composition, based on the fact that the inner edge of the carcass cord is reduced. The aim is to provide a pneumatic tire that can stably secure the rubber thickness up to the tire lumen surface and achieve excellent durability and pneumatic holding power while achieving the weight reduction of the inner linerless structure. .

[0006]

In order to achieve the above object, the invention of a pneumatic tire according to claim 1 of the present invention is directed to a primary ply in which a cord array in which carcass cords are arranged in parallel is covered with topping rubber. The secondary ply formed by diagonally cutting and primary joining is formed to have a circumferential length of one ply or a secondary ply formed by attaching a cover rubber sheet to one surface of the joining sheet, and the secondary ply is formed at both ends in the circumferential direction. By surrounding the tire lumen by joining, or by joining the joining sheet to one circumferential length and attaching it to a cover rubber sheet wound in advance on a forming drum and joining at both ends in the circumferential direction. One or more carcass plies to be bridged between the bead cores are formed, and the innermost carcass ply is an inner portion of the topping rubber facing the tire cavity side. Alternatively, the tire inner cavity surface is formed by the cover rubber sheet, and at least the inner part and the cover rubber sheet of the inner part and the opposite outer part of the topping rubber of the innermost carcass ply are formed by diene. 50 to 90% by weight of rubber
And 10 to 50% by weight of brominated halogenated butyl rubber or isobutylene / paramethylstyrene copolymer
And a low air permeable rubber composition containing 45 to 60 parts by weight of carbon black, and the carbon black has an iodine adsorption amount of 80 to 125 mg / g or a nitrogen adsorption ratio. 8 surface area
0 to 120 m ² / g, and the DBP absorption is 70 to 10
0ml / 100g or compressed DBP absorption 70-90m
1/100 g.

Further, in the invention according to claim 2, the innermost carcass ply is such that the outer portion is the same as the inner portion,
Alternatively, it is characterized by being formed of a low air-permeable rubber composition of the same composition or a rubber composition different from the inner portion containing a diene rubber.

In the invention according to claim 3, the innermost carcass ply is characterized in that the rubber thickness from the inner edge of the carcass cord to the inner surface of the tire cavity is 0.2 to 0.7 mm.

The above "Iodine adsorption amount", "Nitrogen adsorption specific surface area", "DBP absorption amount" and "Compressed DBP absorption amount" are JIS K6217, item 6 "Iodine adsorption amount" and item 7 "Nitrogen adsorption amount", respectively. It is a value measured based on “specific surface area”, section 9 “DBP absorption”, section 10 “DBP absorption of compressed sample”.

[0010]

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 shows a meridional section when the pneumatic tire of the present invention is a passenger car tire.

In the figure, a pneumatic tire 1 has a tread portion 2, sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead core 5 located at an inner end of each sidewall portion 3. And a bead portion 4 having the above configuration. Further, a carcass 6 is bridged between the bead cores 5 and 5 on the tire 1, and a tough belt layer 7 is disposed radially outside the carcass 6 and inside the tread portion 2.

The belt layer 7 is composed of two or more belt plies 7 in which high elastic belt cords are arranged at an angle of, for example, 10 ° to 35 ° with respect to the tire circumferential direction.
A and 7B are exemplified. The belt plies 7A and 7B are arranged in different directions so that the belt cords intersect each other between the plies, thereby increasing the belt rigidity by a triangle structure of the cords, and having a tag effect with substantially the entire width of the tread portion 2. And reinforce.

The carcass 6 is, as shown in FIG.
The carcass cord 10 is, for example, 75
It is formed from one or more carcass plies 9 arranged at an angle α of up to 90 degrees, in this example one carcass ply 9. The carcass ply 9 includes a ply body 6A extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, and in the present example, the ply body portion 6A is connected to the ply body portion 6A and the bead core 5 is rotated around the tire. It has a so-called 1-0 structure having a ply turnup portion 6B that is turned inward from the outside in the axial direction. In addition, what is called a 2-0 structure using two carcass plies 9 and 9 or what is called a 1-1 structure can also be suitably employ | adopted by request.

As shown in FIG. 3, the carcass ply 9 is a long primary carcass cord 10 formed by covering a cord array 11 in which carcass cords 10 are aligned in parallel along a longitudinal direction with a topping rubber 12. The ply D is formed as a raw material. The primary ply D is cut into cut pieces D1... At the angle α with respect to the length direction and at a length La corresponding to the width of the carcass ply 9, and thereafter, the non-cut side of each cut piece D1 is cut. Are sequentially connected (primary joint J1) between the end portions De, and the joint sheet 16 of the cut piece D1 is formed.

In this embodiment, FIG.
As shown in (A) and (B), a secondary ply F is formed only by the joining sheet 16, and the secondary ply F is
An example is shown in which the innermost carcass ply 9A is formed by cutting at a circumferential length and then connecting (secondary joint J2) between both ends Fe in the circumferential direction.

In the tire 1 of the present invention, FIG.
As shown in (B), the innermost carcass ply 9A
The conventional inner liner is substantially eliminated by imparting a pneumatic holding force to the inner liner. That is, the innermost carcass ply 9A is formed on the tire cavity surface HSi by the inner portion 12i of the topping rubber 12 facing the tire cavity H side.
Is formed.

In order to provide the air pressure holding force, at least the inner portion 12i of the inner portion 12i of the topping rubber 12 and the opposite outer portion 12o are replaced with a low air permeable rubber composition 13 It is formed by.

In this embodiment, a case where a non-low air-permeable rubber composition 14 containing more than 90% by weight of a diene rubber as a rubber base material is used for the outer portion 12o. Natural rubber, butadiene rubber, styrene / butadiene rubber, isoprene rubber,
Chloroprene rubber, acrylonitrile butadiene rubber and the like can be used alone or in combination.

The low air permeable rubber composition 13 is used as a rubber base material in an amount of 50 to 90% by weight of the diene rubber.
And 10 to 50% by weight of brominated halogenated butyl rubber or isobutylene / paramethylstyrene copolymer
And the one containing This achieves both low air permeability and adhesion to other rubber members and the carcass cord 10. (Hereinafter, a halogenated butyl rubber and a halide of an isobutylene / paramethylstyrene copolymer may be referred to as a low air-permeable rubber.) From the viewpoint of adhesiveness, the content of the diene rubber is within the above range. Preferably, the amount is 65% by weight or more, and the content of the low air permeable rubber is 35% by weight or less.

As the halogenated butyl rubber, chlorinated butyl rubber and brominated butyl rubber can be used.

The brominated isobutylene / paramethylstyrene copolymer is not particularly limited. From the viewpoint of adhesion, the isobutylene content is 89 to 97% by weight, preferably 89 to 95% by weight. Particularly preferably 8
It is preferably from 9 to 93% by weight. Examples of commercially available halides of isobutylene / paramethylstyrene copolymer include, for example, EXXPRO90-1 manufactured by Exxon Chemical Company.
0, EXXPRO 89-1, EXXPRO93-5,
EXXPRO96-4 and the like.

In the present invention, in the low air permeable rubber composition 13, 100 parts by weight of the rubber base is used.
45 to 60 parts by weight of carbon black is blended, and the carbon black has an iodine adsorption amount of 80%.
１２５125 mg / g or nitrogen adsorption specific surface area is 80１２０120
m ² / g and DBP absorption of 70-100 ml / 1
00g or compressed DBP absorption 70-90ml / 100
There is a great feature in using g.

Here, the "amount of iodine adsorbed" and the "specific surface area of nitrogen adsorbed" are, as is well known, a measure of the specific surface area of carbon black. The higher the respective values, the smaller the particle diameter is. The contact area with rubber molecules increases.

The "DBP absorption amount" and the "compressed DB"
As is well known, the "P absorption amount" is a measure for measuring the degree of the structure (aggregation state of particles) of carbon black, and the higher the value, the longer the continuation of particles.

Then, the iodine adsorption amount is set to 80 to 125
mg / g or nitrogen adsorption specific surface area of 80 to 120 m ² /
g, and the DBP absorption amount is 70 to 100 ml / 100.
g or the compressed DBP absorption amount is 70 to 90 ml / 100 g, so that the blending amount of carbon black is
Even in the case where it is controlled within the range of ~ 60 parts by weight, a sufficient reinforcing effect is obtained, and in the vulcanized rubber, the flexibility is kept high, and the tensile stress and the tensile strength etc. are improved while exhibiting excellent flex cracking properties. Can improve. In the unvulcanized rubber, the viscosity (Mooney viscosity) increases, and the rubber flow during vulcanization is suppressed. As a result, the thickness variation of the low air permeable rubber composition 13 before and after vulcanization can be suppressed to a low level. It becomes possible.

As a result, as shown in this example, the carcass cord 1
Even when the rubber thickness T2 from the inner edge of 0 to the tire cavity surface HS is set in the range of 0.2 to 0.7 mm, the rubber thickness T2 can be stably secured, and the inner linerless structure has It can exhibit excellent durability and pneumatic holding power while achieving weight reduction. If the rubber thickness T2 is less than 0.2 mm, the air leak resistance is greatly reduced and the necessary air pressure holding force cannot be secured, and the carcass cord 10 is exposed from the tire cavity surface HS due to bending deformation or the like. Damages such as cracks. On the other hand, if the thickness exceeds 0.7 mm, the weight is unnecessarily increased, and the advantage of weight reduction by the inner linerless structure is impaired.

The iodine adsorption amount is less than 80 mg / g.
Full or nitrogen adsorption specific surface area is 80m ^Two/ G or less,
For unvulcanized rubber, viscosity may decrease and fluidity may increase.
And the rubber residue deteriorates and secures the gauge under the cord.
And vulcanized rubber, tensile strength and tear strength
There is an inconvenience that the degree and the like decrease. Conversely, iodine adsorption amount
Is greater than 125 mg / g, or the nitrogen adsorption specific surface area is 1
20m^Two/ G is larger than the hardness of the obtained rubber composition.
The inconvenience that the ride comfort deteriorates because it rises more than necessary
There is a case.

The DBP absorption amount is 70 ml / 100 g.
If the compression DBP absorption is less than 70 ml / 100 g, the tensile strength is insufficient, and if carbon is increased to compensate for this, the heat generation may be too high. Conversely, if the DBP absorption is more than 100 ml / 100 g or the compressed DBP absorption is more than 90 ml / 100 g, the viscosity becomes high with the unvulcanized rubber, the processability becomes poor, and the elongation of the obtained rubber composition increases. And the bending fatigue resistance is insufficient.

In addition to specifying the type of carbon black as described above, the viscosity of the unvulcanized rubber may also be increased by increasing the compounding amount beyond 60 parts by weight or by reducing the amount of a plasticizer such as process oil. Can be increased. However, in such a case, after vulcanization, the flexibility of the low air permeable rubber composition 13 is impaired, and the effect of improving durability, such as a marked decrease in flex cracking properties, cannot be obtained.

The primary joint J1 and the secondary joint J2
As shown in FIG. 5B, between ends De, De,
This is performed by overlapping and crimping the ends Fe and Fe to each other, thereby forming the lap joints 20 and 21.

In the spliced portions 20, 21, the joining lines 20A, 21A are exposed on the tire cavity surface HS. Therefore, when the release agent is applied to the tire cavity surface HS by a spray gun or the like, The release agent is bitten, for example, a part of it enters from the exposed portion, and tends to be a starting point of a crack.

Therefore, in this embodiment, the tire 1 is formed by vulcanization molding without applying a mold release agent to the tire cavity surface HS side.

At this time, in order to prevent bridging between the tire cavity surface HS and the bladder, in this embodiment, a release agent is applied to the bladder side. The release agent for bladder is not particularly limited. For example, a composition obtained by dissolving an amide compound and silicon in an organic solvent such as gasoline can be used. After the composition is applied to the bladder surface, it is naturally dried in an explosion-proof room. A release coating is formed by volatilizing the gasoline. Examples of the release agent for bladder include, for example, JP-A-59-10
Various compositions proposed in JP-A-6948, JP-A-6-134769, JP-A-8-323773 and the like can be preferably used.

Next, another example of the innermost carcass ply 9A is shown in FIGS. 6 (A) and 6 (B). In this example, the case where the secondary ply F is formed by the joining sheet 16 and the thin cover rubber sheet 17 stuck on one surface thereof is illustrated. That is, the innermost carcass ply 9A forms the tire cavity surface HS by the cover rubber sheet 17 facing the tire cavity H side.

In such a structure, as shown in FIG. 7A, the exposed portion of the joining line 20A generated in the joining sheet 16 is
Since it can be covered and protected by the cover rubber sheet 17, it is expected that the release agent is prevented from being caught from the exposed portion.

However, the cover rubber sheet 17
In order to suppress an increase in weight due to the thickness, the inner portion 12i is formed thinner by an amount corresponding to the thickness, and the rubber thickness T from the inner edge of the carcass cord 10 to the tire cavity surface HS is reduced.
It is important to keep 2 within the same range of 0.2 to 0.7 mm as described above. As a result, even in this coating structure, when the rubber thickness T2 is regulated to a low value in the range of 0.2 to 0.7 mm, a new bite of the release agent is caused due to the rubber flow during vulcanization. There is a risk of inducing.

Therefore, also in this example, the tire inner surface H
It is preferable to carry out vulcanization molding without applying a release agent to the S side.

In order to stably obtain the rubber thickness T2 within the above range, the cover rubber sheet 17 must also be formed of the low air permeable rubber composition 13. At this time, the cover rubber sheet 17 and the inner portion 12i are completely integrated without substantially forming the boundary line P, and an effect that excellent bonding strength can be maintained can be expected. This makes it unclear whether the cover rubber sheet 17 is stuck on the contrary.
The presence or absence of the cover rubber sheet 17 can be determined by comparing the thicknesses TA and TB of the reference numeral 21.

The cover rubber sheet 17 secures a rubber volume in the spliced portion 21 at the spliced portion 21 as shown in FIG. 7B. As a result, the joining strength in the joining line 21A can be increased, and the occurrence of cracks due to the secondary joint can be suppressed. But,
In order to more reliably suppress the occurrence of cracks, the tire lumen surface HS is covered with the joining line 21A,
It is preferable to add a rubber strip layer 22 extending in the direction between the bead cores 5 and 5.

In this embodiment, the rubber strip layer 22
The thickness T1 is 0.1 to 0.5 mm and the width W1 is 5 to 80.
By forming and protecting the exposed portion of the joining line 21A in the shape of a thin strip of mm, the occurrence of cracks is suppressed. Note that the thickness T1 is less than 0.1 mm and the width W1 is 5
If the thickness is less than 0.5 mm, the suppression effect is reduced, and conversely, the thickness T1 is not more than 0.1 mm.
If the width is more than 5 mm and the width W1 is more than 80 mm, the weight is unnecessarily increased, and not only does the advantage of weight reduction by the inner linerless structure be impaired, but also the tire uniformity is adversely affected. Therefore, the width W1 is 25
About 50 mm is more preferable.

The rubber strip layer 22 can be a low air permeable rubber composition having the same or the same composition as the inner portion 12i, or a rubber composition having a different composition. Here, the “homogeneous composition” means the same kind of rubber constituting the rubber base material and the compounding ratio thereof is different, and the “heterogeneous composition” means the type of rubber constituting the rubber base material It means something different in itself.

In this embodiment, as described above, the outer portion 1
Although the case where the non-low air permeability rubber composition 14 is used in 2o is exemplified, the low air permeability rubber composition having the same or the same composition as the inside portion 12i, or the low air permeability rubber composition having a different composition is used. It may be formed by an object.

When the outer portion 12o is formed of the non-low air permeability rubber composition 14, the inner portion 1o
The boundary line K between 2i and the outer portion 12o may be located outside the inner edge of the carcass cord 10 as in this example.
Although preferred from the viewpoint of weight reduction and air leak resistance, when the outer portion 12o is formed of a low air permeable rubber composition, the boundary line K may be located inside the inner edge of the carcass cord 10. Good.

In the primary joint J1, for example, as shown in FIG. 8, there is a case where the end portions De are joined to each other in a zipper shape with their end faces attached to each other. It is preferable that a cover rubber sheet 17 is stuck on one surface to cover the joint portion 24.

Next, still another example of the innermost carcass ply 9A is shown in FIG. In the present embodiment, the carcass ply 9A is wound first by winding the cover rubber sheet 17 around a forming drum, and attaching both ends of the cover sheet 16 to the outer peripheral surface thereof, while attaching both ends thereof secondarily. Is formed.

In this structure, the cover rubber sheet 17
As a result, the tire lumen surface HS is formed, and both the joining lines 20A and 21A are covered and protected.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0048]

Example 1 Rubber composition A1 preferred as inner portion of topping rubber and cover rubber sheet according to the present invention
A10 and comparative rubber compositions B1 to B10 were prototyped based on the specifications in Tables 1 and 2, and their rubber properties (Moony viscosity, air permeability, flex cracking properties, and adhesion) were measured. The basic characteristics of each type of carbon black are shown in Table 3.

(1) Mooney viscosity: The Mooney viscosity (ML1 + 4, 130 ° C) of the unvulcanized rubber of each rubber composition at 130 ° C was measured according to JIS K6300, and the value of the comparative rubber composition B1 was 100 It was indicated by an index.
The higher the value, the higher the viscosity.

(2) Air permeability; vulcanization pressure (9.8 MPa), vulcanization temperature (170 MPa) of each rubber composition using a hydraulic press
C), and a sample obtained by vulcanization under the conditions of vulcanization time (12 minutes) was subjected to a gas permeability measurement device M-C1 manufactured by Toyo Seiki Co., Ltd. in accordance with the test method of ASTM-D1434-75M.
Was used to measure the air permeability coefficient. The smaller the value, the lower the air permeability.

(3) Bending cracking property: According to JIS K6260, bending was performed 1 million times at 50% strain and 300,000 times at 70% strain, and the length of the generated crack was measured.
The number of bends per 1 mm of the crack length is shown. The larger the value, the better the flex cracking property.

(4-1) Adhesion 1 (adhesion between rubber compositions A and B and cord);
5cm polyester cord (1670dtex / 2)
Two plies obtained by coating the above-mentioned cord arrangement body with the rubber compositions A and B are superimposed so that the cord directions are perpendicular to each other. The mixture was vulcanized and bonded at a pressure of 9.8 MPa for one minute. A peel test was performed on the obtained sample for measuring adhesive strength at a test speed of 50 mm / min using a tensile tester, and the adhesive (peel) strength (N / 25 mm) was measured. There is no problem if it is 300 N / 25 mm or more.

(4-2) Adhesion 2 (adhesion between rubber compositions A and B and sidewall rubber);
B rubber sheet (thickness 2 mm, width 80 mm, length 150
mm). Next, a sidewall rubber sheet having the same size was obtained using a representative rubber composition C1 (Table 4) as the sidewall rubber. Then, the rubber sheet and the side wall rubber are cured at a vulcanization pressure of 2 MPa and a vulcanization temperature of 15 MPa.
The sample was vulcanized and bonded at 0 ° C. for a vulcanization time of 30 minutes, and the obtained bonding strength measurement sample was measured for bonding strength (kgf / 25 mm) in the same manner as described above. The results are shown in Table 2 as Adhesion 2. There is no problem if it is 50 kgf / 25 mm or more.

(4-3) Adhesion 3 (adhesion between rubber compositions A and B as inner parts of topping rubber and the following rubber composition and cord as outer parts); Book / 5cm polyester cord (16
70 dtex / 2), a rubber sheet forming an inner portion made of the rubber compositions A and B, and a rubber sheet forming an outer portion using a typical rubber composition C2 (Table 4) as a topping rubber. The ply covered with
Created. Then, the two plies are overlapped so that the cords are oriented at right angles to each other, and the rubber sheet forming the inner portion and the rubber sheet forming the outer portion face each other. Vulcanization bonding was carried out at a pressure of 9.8 MPa at 30 ° C. for 30 minutes. The obtained adhesive strength measurement sample was measured for adhesive strength (N / 25 mm) in the same manner as described above. 300N / 25
There is no problem if it is not less than mm.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

Example 2 Using a carcass ply having the rubber composition shown in Tables 1 and 2 as a topping rubber, a tire having a structure shown in FIG. 1 and a tire size of 185 / 65R14 was prepared.
In addition to trial production based on the specifications in Tables 5 and 6, the tire weight, air leak resistance (air pressure retention),
Each was tested for durability.

(1) Tire weight: The weight per tire was measured and is indicated by an index with Comparative Example 1 being 100. Smaller values are lighter.

(2) Air leak resistance (air pressure retention): After mounting the test tire on the rim (5.5 J × 14) and filling it with the internal pressure (300 kPa), the internal pressure drops when left naturally for 90 days. Rate was measured, and Comparative Example 1 was 1
It is indicated by an index of 00. The larger the value, the smaller the decrease rate and the better.

(3) Durability The test tire was mounted on a rim (5.5 J × 14), filled with an internal pressure (190 kPa), and loaded on a drum (5.0 kN) and speed (80 km / h). 20,000k
m (durability 1). If there is no abnormality in the test of durability 1, the tire is satisfactory in durability if used normally, but has passed the durability 1 since the wear resistance of the recent tire has been improved. The tire thus continued to travel further up to 40,000 km under the same conditions (durability 2). Also, from the viewpoint of recent environmental problems, in consideration of weight reduction and long-term use of the vehicle, recycling of tires, etc., it is necessary to drive a longer mileage. For another 60000k
m (durability 3). When there was no abnormality after each run, "走 行" was given, and when there was an abnormality, "x" was given. The number in parentheses is the index of the mileage at the time of the occurrence of an abnormality. (If the test ends up to 15000 km and there is an abnormality at the time of testing up to 20000 km, the index is 75.)
Shown.

[0063]

[Table 5]

[0064]

[Table 6]

As shown in Tables 5 and 6, it can be confirmed that in the tires of the examples, the durability can be greatly improved while taking advantage of the inner linerless structure.

[0066]

As described above, in the present invention, the type and amount of carbon black to be compounded in the low air permeable rubber composition are specified. By increasing the amount and suppressing the rubber flow during vulcanization, the rubber thickness from the inner edge of the carcass cord to the inner surface of the tire cavity can be stably secured. Further, after vulcanization, flexibility is maintained high, and tensile stress and tensile strength can be improved while exhibiting excellent flex cracking properties. As a result, excellent durability and pneumatic pressure retention can be exhibited while achieving the weight reduction of the inner linerless structure.

[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 a perspective view showing a secondary joint of the carcass ply.

FIG. 3 is a diagram illustrating a primary ply and a joining sheet.

FIGS. 4A and 4B are diagrams illustrating an example of a secondary ply and a carcass ply formed by the secondary ply.

FIGS. 5A and 5B are cross-sectional views showing a primary joint and a secondary joint in the carcass ply in an enlarged manner.

FIGS. 6A and 6B are diagrams illustrating another example of a carcass ply. FIGS.

FIGS. 7A and 7B are cross-sectional views showing a primary joint and a secondary joint in the carcass ply in an enlarged manner.

FIG. 8 is a sectional view showing another example of the primary joint.

FIG. 9 is a diagram illustrating still another example of the carcass ply.

[Explanation of symbols]

 Reference Signs List 5 bead core 9 carcass ply 9A innermost carcass ply 10 carcass cord 11 cord array 12 topping rubber 12i inner part 12o outer part 13 low air-permeable rubber composition 16 joint sheet 17 cover rubber sheet 20, 21 overlap joint D1 Next ply F Secondary ply J1 Primary joint J2 Secondary joint HS Tire bore surface

[Procedure amendment]

[Submission date] October 11, 2000 (2000.10.
11)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

Claims (3)

[Claims] At least the inner portion and the cover rubber sheet of the inner portion and the opposite outer portion of the topping rubber of the innermost carcass ply,
Rubber substrate 1 comprising 50 to 90% by weight of diene rubber and 10 to 50% by weight of brominated halogenated butyl rubber or isobutylene / paramethylstyrene copolymer
The carbon black has a low air permeability rubber composition containing 00 parts by weight and 45 to 60 parts by weight of carbon black, and the carbon black has an iodine adsorption amount of 80 to 125.
mg / g or nitrogen adsorption specific surface area of 80 to 120 m ² /
g, and the DBP absorption is 70-100ml / 100g
Alternatively, a pneumatic tire having a compressed DBP absorption of 70 to 90 ml / 100 g. 2. The innermost carcass ply is made of a low air-permeable rubber composition whose outer portion is the same as or similar to the inner portion, or a rubber composition different from the inner portion containing a diene rubber. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed. 3. The innermost carcass ply has a rubber thickness of 0.2 from the inner edge of the carcass cord to the inner surface of the tire cavity.
The pneumatic tire according to claim 1 or 2, wherein the diameter is 0.7 mm.