JP2002103906A - 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 an innermost carcass ply 9A is made of a specific low air permeable rubber composition 13, and a rubber thickness T2 from an inner edge of a carcass cord 10 to a tire inner cavity face HS is 0.2-0.7 mm. The tire inner cavity face side is vulcanized without coated with a mold releasing agent.

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.

On the other hand, a carcass ply a is conventionally
As shown in (A), a long primary ply d formed by covering a cord array b in which carcass cords are aligned in parallel in the longitudinal direction with a topping rubber c is used as a raw material. Specifically, the primary ply d is set at a desired angle α with respect to the length direction (for example, 75 to 9 in a radial tire).
0 °) and the length La corresponding to the width of the carcass ply a
Is cut into pieces d1..., While the non-cut side ends de of the cut pieces d1 are sequentially connected (primary joint j1), so that the carcass cord has the angle with respect to the longitudinal direction. A long spliced sheet h arranged in α is formed as a secondary ply f. Then, as shown in FIG. 10 (B), the secondary ply f is cut at one circumferential length, and both ends fe and fe in the circumferential direction are connected (secondary joint j2) to thereby form the carcass ply f. a is formed.

At this time, the primary joint j1 and the secondary joint j2 usually have an end d as shown in FIG.
By overlapping and crimping between e and de and between the end portions fe and fe, a lap joint portion g is formed. Therefore, in the tire having the inner linerless structure described above, the joining line g1 of the plurality of lap joints g is exposed on the tire inner cavity surface.

[0006]

However, in the case of pneumatic tires, when vulcanizing, the green tire is pressed against the mold surface by pressing the inner surface of the tire with a bladder, and the vulcanizing is performed. In order to prevent bridging between the bladder and the green tire, a mold release agent is applied to the inner surface of the tire in advance. This release agent (so-called inside paint) is in the form of a paint dissolved or dispersed by a solvent, and is usually sprayed and applied using a spray gun or the like.

Accordingly, like the inner linerless structure,
When a plurality of joining lines g1 are exposed on the inner surface of the tire, the release agent is easily bitten at the joining lines g1. As a result, cracks tend to occur starting from the joining line g1, and there is a problem that air pressure retention and durability are significantly reduced.

Therefore, as shown in FIG. 11 (B), the present inventor made one of the joint sheets h as the secondary ply f.
A cover rubber sheet i is stuck on the surface, and a lap spliced portion g by primary splicing is used in advance, or a cover rubber sheet i is wound around a forming drum in advance, and a splice sheet h is stuck thereon. It has been proposed to cover and protect the lap joint g by the primary joint and the secondary joint. However, even in such a case, when the coating thickness t on the carcass cord was small, it was found that the release agent was bitten by the rubber flow during vulcanization, and similarly, there was a possibility that cracks might occur. .

Therefore, the present invention is based on vulcanization without applying a release agent to the tire cavity surface side, and can effectively suppress the occurrence of cracks and the like due to biting of the release agent, It is an object of the present invention to provide a pneumatic tire capable of securing excellent durability and pneumatic holding force while achieving a weight reduction comparable to a conventional inner linerless structure.

[0010]

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. Or, while forming the tire inner cavity surface by the cover rubber sheet, at least the inner portion of the inner portion of the topping rubber of the innermost carcass ply and the outer portion opposite thereto, the diene rubber of 50 to The innermost carcass ply comprises a low-air-permeability rubber composition containing 90% by weight and 10 to 50% by weight of a halogenated butyl rubber or a halide of isobutylene / paramethylstyrene copolymer, and the innermost carcass ply comprises:
The rubber thickness from the inner edge of the carcass cord to the tire cavity surface is set to 0.2 to 0.7 mm, and vulcanization is performed without applying a release agent to the tire cavity surface.

In the invention according to claim 2, the innermost carcass ply has an outer portion which 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.

According to a third aspect of the present invention, the cover rubber sheet is formed by using a low air permeable rubber composition.

[0013]

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 embedded 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 highly 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, 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.

Here, as shown in FIG. 3, the carcass ply 9 is formed by covering a cord array 11 in which carcass cords 10 are arranged in parallel along the 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 and the opposite outer portion 12o of the topping rubber 12 is provided with a low air-permeable rubber composition 13 It is formed by.

In this example, 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 a halogenated butyl rubber or a halogenated isobutylene / paramethylstyrene copolymer. 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 halide of the isobutylene / paramethylstyrene copolymer is not particularly limited.
From the viewpoint of adhesiveness, the isobutylene content is 89 to 97.
%, Preferably 89 to 95% by weight, particularly preferably 89 to 93% by weight. Examples of commercially available halides of isobutylene / paramethylstyrene copolymer include, for example, EXXPRO90- manufactured by Exxon Chemical Co., Ltd.
10, EXXPRO89-4 and EXXPRO93-5.

In this example, in order to ensure higher adhesiveness in the low air-permeable rubber composition 13, a tackifier is added and the use of a plasticizer is excluded. Examples of the tackifier include a coumarone resin, a phenol resin, a terpene resin, a petroleum hydrocarbon resin, a rosin derivative, and the like.
1 to 10 parts by weight, further 3 to 10% by weight, further 3
It is preferable to mix -8% by weight from the viewpoint of adhesiveness. Also, as the plasticizer, mineral oil-based softeners such as mineral oil and aroma oil, plant-based softeners, phthalic acid derivatives and the like are known, and are usually added for improving the processability and flexibility of rubber. However, in this example, it is not used because it tends to reduce the adhesiveness.

In the innermost carcass ply 9A,
The rubber thickness T2 from the inner edge of the carcass cord 10 to the tire cavity surface HS needs to be 0.2 to 0.7 mm, and if it is less than 0.2 mm, the air pressure resistance required to greatly decrease the air leak resistance is required. You will not be able to secure power. If it exceeds 0.7 mm, the weight will increase unnecessarily,
The advantage of lighter weight due to the inner linerless structure is impaired.

Next, the primary joint J1 and the secondary joint J
2 are end portions De, De as shown in FIG.
This is performed by overlapping and crimping between the ends and between the ends Fe and Fe, whereby the overlapped joints 20, 2
1 is formed.

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 the present invention, the tire 1 is formed by vulcanization molding without applying a release agent to the tire cavity surface HS side.

At this time, in order to prevent cross-linking between the tire cavity surface HS and the bladder, in the present embodiment, a release agent is applied to the bladder side. Although not particularly limited in the present application, a composition in which an amide compound and silicon are dissolved in an organic solvent such as gasoline can be used as the release agent for bladder. After the composition is applied to the bladder surface, it is naturally used in an explosion-proof room. By drying (gasoline is volatilized), a release coating is formed. In addition, as a release agent for bladder, for example,
Various compositions proposed in JP-A-9-106948, JP-A-6-134767, JP-A-8-323773 and the like can be suitably 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 necessary to carry out vulcanization molding without applying a release agent to the S side.

In order to secure sufficient air leak resistance even when the inside portion 12i is made thinner, the cover rubber sheet 17 is used as the low air permeable rubber composition 13
It is preferable to use a good low air permeability rubber composition in which the amount of the low air permeability rubber is the same as or higher than that.

In the case of the same composition, the cover rubber sheet 17 and the inner portion 12i are completely integrated without substantially forming the boundary line P, and excellent bonding strength can be maintained. This makes it unclear whether or not the cover rubber sheet 17 is stuck. However, by comparing the respective thicknesses TA and TB of the lap joints 20 and 21, the cover rubber sheet 17 is The presence or absence can be determined. In the case of a good low air permeability rubber composition, the boundary line P
Furthermore, the presence or absence of the cover rubber sheet 17 can be determined by comparing the thicknesses TA and TB.

As shown in FIG. 7B, the cover rubber sheet 17 increases the rubber volume in the spliced portion 21 as shown in FIG. 7 (B), and promotes the flow of rubber during vulcanization. As a result, the joining strength at the joining line 21A is increased, and the occurrence of cracks due to the secondary joint can be suppressed. However, in order to more reliably suppress the occurrence of cracks, it is preferable that a rubber strip layer 22 extending in the direction between the bead cores 5 and 5 is provided on the tire cavity surface HS so as to cover the joining line 21A. preferable.

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.
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 is preferably formed of a low air permeable rubber composition from the viewpoint of air leak resistance. At this time, a low air permeable rubber composition having the same or the same composition as the inner portion 12i is used. Or a low air permeable rubber composition of 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. The rubber strip layer 22 may be formed of a non-low air-permeable rubber composition.

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 permeable rubber composition 14, the inner portion 1
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, the ends De, De may be 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.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG.
/ 65R15 tires were prototyped based on the specifications in Table 1, and the tire weight, air leak resistance (air pressure retention), and durability of each test tire were measured, and the results were compared with those of conventional tires. It describes in. Table 2 shows the composition of the rubber composition used in Table 1.

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

(2) Air leak resistance (air pressure retention): A sample tire was mounted on a rim (15 × 6JJ),
In addition, after filling the internal pressure (300 kPa), the rate of decrease in the internal pressure when allowed to stand naturally for 90 days is indicated by an index with the conventional tire being 100. The smaller the value, the better.

(3) Durability The sample tire was mounted on a rim (15 × 6JJ), filled with an internal pressure (190 kPa), and loaded on a drum (6.
The tire was run at a speed of 96 km / h and at a speed of 70 km / h, and the running distance until the outer surface of the tire was damaged was represented by an index when the conventional tire was set to 100. The larger the index, the better.

[0050]

[Table 1]

[0051]

[Table 2]

As shown in Table 1, in the tire of the embodiment,
It can be confirmed that the durability can be greatly improved while taking advantage of the inner linerless structure.

[0053]

As described above, the present invention is constituted,
It is possible to effectively suppress the occurrence of cracks and the like due to the bite of the release agent, and achieve excellent durability and air pressure holding force while achieving weight reduction comparable to a conventional 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.

FIGS. 10A and 10B are diagrams illustrating a process of forming a carcass ply.

FIGS. 11A and 11B are cross-sectional views of an overlapping portion of a carcass ply for explaining a conventional problem.

[Description of Signs] 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 Spread sheet 17 Cover rubber sheet 20, 21 Lap joint D Primary ply F Secondary ply J1 Primary ply J2 Secondary ply H Tire bore HS tire bore

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // B29K 9:00 B29K 9:00 23:00 23:00 (72) Inventor Masayuki Sakamoto Kobe City, Hyogo Prefecture 3-6-9 Wakihama-cho, Chuo-ku Sumitomo Rubber Industries Co., Ltd. (72) Inventor Atsushi Yamakage 3-6-9, Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo F-term (reference) 4F203 AA12 AA14 AA46 AH20 DA11 DB01 DK05 4F212 AA12 AA14 AA46 AH20 VA02 VC32 VD10 VD18 VK02

Claims (3)

[Claims] 1. A cover rubber sheet formed by diagonally cutting and priming a primary ply in which a cord arrangement body in which carcass cords are arranged in parallel and covered with topping rubber and primary-splicing the primary ply. The secondary ply formed by laminating is made to have one circumferential length, and is further seamed at both ends in the circumferential direction, or the joining sheet is made to have one circumferential length, and the cover rubber is previously wound around a forming drum. The two or more carcass plies are formed around the tire cavity by being secondarily spliced at both ends in the circumferential direction while being attached on the sheet, and one or more carcass plies are bridged between the bead cores. Forming an inner surface of the tire with the inner portion of the topping rubber or the cover rubber sheet facing the inner side of the tire; At least the inner portion of the inner portion of the topping rubber and the opposite outer portion of the top ply of 50-90% by weight of the diene rubber and the halide of butyl rubber or isobutylene / paramethylstyrene copolymer And the innermost carcass ply has a rubber thickness from the inner edge of the carcass cord to the inner surface of the tire of 0.2 to 0.7% by weight.
mm, and vulcanized without applying a release agent on the inner surface of the tire. 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 pneumatic tire according to claim 1, wherein the cover rubber sheet is formed using a low air permeable rubber composition.