JP3058624B2 - Tubeless tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tubeless tire capable of improving the durability of a bead portion.

[0002]

2. Description of the Related Art The present applicant has already proposed Japanese Patent No. 2724291 as a pneumatic tire capable of improving the durability of a bead portion. In this proposal, as shown in FIG. 8, a slim bead portion is formed by shaving the inner surface of the bead portion from a conventional shape indicated by a broken line . Also, the profile shape of the carcass is changed in accordance with this. For example, the ply main body part d2 of the carcass extending between the bead cores c and c (only one is illustrated in FIG. 8 ) has a substantially radially inner end side in the tire radial direction, and the ply folded part d1 of the carcass has Immediately after being turned around the bead core c, a parallel portion g is formed near the ply body portion d2 and extends substantially parallel to the ply body portion d2.

[0003] Such a carcass profile greatly reduces the compressive force on the ply turn-up portion d1 because the ply turn-up portion d1, which is apt to be damaged, approaches the neutral line (neutral axis) side of deformation. It is possible to prevent distortion from being concentrated at a specific position of the bead portion. Also, as a result,
The rubber thickness of the bead portion can be reduced (the bead portion can be made slim), and the heat generation of the bead portion can be greatly reduced, thereby improving the durability and the like.

[0004] In order to further improve the durability of the bead portion, the present inventors have investigated the damage process of the bead portion of the tire having such a structure.

As a result, the outer end e of the ply turn-up portion d1
Since the tire approaches the maximum width position of the tire where the bending is severe, stress tends to be concentrated. Such stress concentration is caused by a small crack of rubber near the outer end e of the ply turn-up portion d1. Was found. Such initial cracks are affected by the repeated deformation of the tire, and the ply body portion d2 and the ply turnover portion d1
It was found that the mixture proceeded to the bead apex rubber b side to reach separation.

[0006] In particular, in a tubeless tire in which the tire lumen is covered with an inner liner rubber layer, the moisture contained in the filling air permeates the inner liner rubber layer together with a small amount of air, and if the carcass cord is made of steel. In the case of organic fibers, corrosion tends to occur, and in the case of organic fibers, water absorption by the cord is caused, and the cord strength and the adhesive strength with rubber tend to decrease. As a result, it was found that the separation was further promoted in combination with the initial cracking.

Here, in order to prevent the initial crack, rubber between the ply body portion d2 and the ply folded portion d1 (hereinafter, sometimes simply referred to as "inter-ply rubber").
Although it is effective to increase the thickness of the ply, the thickness of the rubber between the plies is uniformly increased from the outer end of the bead apex rubber b to the outer end e of the ply turn-up portion d1, so that the deformation during running is relatively small. There is a contradictory problem that a large shearing force and heat are applied to the rubber between the plies at the outer end of the bead apex rubber b, which in turn causes initial cracks at the outer end of the bead apex rubber b.

Accordingly, the present invention reliably prevents a decrease in cord strength and rubber adhesive strength due to moisture permeating the inner liner rubber layer at least in a region around the folded end of the carcass ply, while preventing the outer end of the ply folded portion from being bent. An object of the present invention is to provide a tubeless tire that can effectively suppress initial cracks, which are the starting points of separation, at both the outer ends of the bead apex rubber and can further improve the durability of the bead portion.

[0009]

In order to achieve the above object, the invention according to claim 1 of the present application is directed to a ply main body extending from a tread portion to a side wall portion to a bead core of a bead portion. A carcass having a radially arranged carcass ply integrally provided with a ply turn-up portion that turns from the inside in the tire axial direction to the outside, and an inner liner rubber layer disposed inside the ply body portion of the carcass and forming a tire bore surface The inner liner rubber layer comprises a rubber substrate 1
The ply body is made of a butyl rubber containing 60 parts by weight or more of a halogenated butyl rubber in 00 parts by weight, and a distance K equal to the cross-sectional maximum width BW of the bead core is centered on the radially outer end of the ply turn-up portion. In a region around the folded end radially inward and outward along the inner side, the rubber thickness (Tb) of the inner liner rubber layer is set to be 1.0 to 4.5 times the diameter D of the carcass cord of the carcass ply. The bead portion includes a bead apex rubber tapered and extends outward from the bead core in the tire radial direction, and the ply turnover portion extends outward in the tire radial direction along the outer surface of the bead apex rubber in the tire axial direction. In the vicinity of the outer end of the bead apex rubber, the carcass cord of the ply folded portion and the carcass cord of the ply body portion Inter-cord distance (t) is the minimum value between have become proximity portions (tmin), and the minimum value (tmi
n) is 0.15 to 7.0 of the diameter D of the carcass cord.
In addition, a gradual increase region in which the inter-cord distance (t) gradually increases outward in the tire radial direction is formed outside the proximity portion in the tire radial direction.

[0010] In the invention according to claim 2, the bead portion is at least partly in a range from 0.4 times to 1.0 times the height (h0) of the ply folded portion from the bead base line. A ratio (t / h) between the arbitrary height (h) of the incremental region from the bead baseline and the inter-code distance (t) at the arbitrary height (h), including the incremental region. Is substantially constant, and the value is 0.01 to
It is characterized by being in the range of 0.07.

Further, in the invention according to claim 3, the bead portion is at least partly in a range of 1.1 to 1.5 times the height (ha) of the bead apex rubber from the bead base line. In addition to the above-described proximity portion, the proximity portion has a continuous minimum value (tmin) between the cords (t).
) To form a parallel region in which the carcass cords of the ply main body and the ply turn-up portion extend substantially in parallel.

In the invention described in claim 4, the ply turn-up portion includes an inner portion in which at least the ply portion forming the gradually increasing region is disposed inside the ply portion in the tire axial direction, and a tire shaft of the ply portion. And an outer portion disposed outward in the direction and covered with an insulation rubber different from the sidewall rubber, and the insulation rubber is made of one or two rubber compositions.

According to a fifth aspect of the present invention, in the insulation rubber, the inner portion and the outer portion are integrated at an outer end of the ply turn-up portion and a tire radius is larger than an outer end of the ply turn-up portion. It has a tapered portion extending outward in the direction and terminating in a tapered shape.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tubeless tire 1 of the present invention (hereinafter, sometimes simply referred to as “tire 1”).
1 is formed as a heavy-duty radial tire used for trucks, buses and the like.
1 shows a meridional section in a normal state in which the tire 1 is mounted on a regular rim J (a 15 ° taper deep bottom rim) and filled with a regular internal pressure and no load is applied.

In the present specification, the "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based.
Standard rim for ATMA, "Design R for TRA
im ", or" Measuring Rim "in the case of ETRTO." Normal internal pressure "is the air pressure that is defined for each tire in the standard system including the standard on which the tire is based. If the highest air pressure,
For TRA, see the table "TIRE LOAD LIMITS AT VARIOUSCOLD
The maximum value described in "INFLATION PRESSURES" is "INFLATIONPRESSURE" for ETRTO, but is 180 kPa when the tire is for a passenger car.

In FIG. 1, a tire 1 has a tread 2
A pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3 and seated on the regular rim J.
And

Further, the tire 1 has a ply folding portion which is turned around from the tread portion 2 to the bead core 5 of the bead portion 4 through the side wall portion 3 to the bead core 5 so as to be folded from the inside to the outside in the tire axial direction around the bead core 5. A carcass 6 composed of one or more carcass plies 6A integrally provided with a carcass 6b, and an inner liner rubber layer 9 disposed inside the ply main body 6a of the carcass and forming a tire cavity surface S
With

The carcass ply 6A is formed by AA in FIG.
As shown in FIG. 5, which is a cross section, both sides of a cord array in which carcass cords 6c are radially arranged are topping rubber 6g.
The carcass cord 6c is arranged at an angle of 70 to 90 degrees with respect to the tire equator C. In addition, as 6 g of topping rubber, 10
Those having a 0% modulus of 37 to 47 kgf / cm ² are preferred.

In the present embodiment, a steel cord is used as the carcass cord 6c, but an organic fiber cord such as nylon, rayon, polyester, or aromatic polyamide may be used if necessary and according to the category of the tire. it can. The carcass 6 of the present embodiment is formed from one carcass ply 6A in which steel cords are arranged at an angle of about 90 ° with respect to the tire equator C.

A belt layer 7 is disposed radially outside the carcass 6 and inside the tread portion 2. In this embodiment, the belt layer 7 is made of steel cord and tire equator C
On the other hand, for example, the innermost belt ply 7A inclined at an angle of about 60 ± 10 ° and the belt plies 7B, 7C, and 7D arranged with a steel cord inclined at a small angle of 30 ° or less with respect to the tire equator C. For example, a four-layer structure in which the belt cords are overlapped by providing one or more places where the belt cords cross each other between plies is illustrated. The belt layer 7 can be made of another cord material such as rayon, nylon, aromatic polyamide, and nylon, if necessary.

In the bead portion 4, a bead apex rubber 8 is provided between the ply main portion 6a and the ply turnover portion 6b so as to taper outward from the bead core 5 in the tire radial direction. The height of the bead apex rubber 8, that is, the height (h) from the bead base line BL to the outer end 8t of the bead apex rubber 8
a) is 6 to 31 of the tire section height H (shown in FIG. 1).
%, More preferably 8 to 22%, and still more preferably 8 to 22%.
The height is set to about 11% in this example. Note that the bead base line BL is a tire axial line passing through the rim diameter defined by the above-mentioned standards and the like, and the tire section height H is the outermost position in the tire radial direction from the bead base line BL in the standard state. Up to the height.

In the present embodiment, the bead apex rubber 8 is, as shown in an enlarged view in FIG.
i is formed in a substantially straight line inclined substantially in parallel with the ply body 6a, and the outer surface 8 in the tire axial direction is formed.
o is formed in a circular arc shape that is recessed inward in the tire axial direction. Further, the bead apex rubber 8 is, for example, JI
It is desirable to form the rubber with a SA hardness of 60 to 99 °.

In the present embodiment, the bead core 5 is formed to have a substantially hexagonal cross section by spirally winding a steel wire 5w a predetermined number of times, and the outer peripheral portion is covered with, for example, wrapping rubber. Also, bead core 5
Of the rim J is approximately 15 ° with respect to the tire axial direction, that is, along the inclination of the rim seat surface J1 of the rim J. The bead core 5 may be made of an aromatic polyamide wire material in addition to steel. Further, a bead core of a cable type having a circular cross section may be employed.

The ply turn-up portion 6b has its outer end 6t in the tire radial direction exceeding the outer end 8t of the bead apex rubber 8 in the radially outward direction. In the present example, the outer end 6t is radially inward of the maximum width point M forming the tire maximum width position, and the height h at which the amount of distortion under load is relatively small.
It shows the one terminated so as to be 0.

The height of the ply folded portion 6b, that is, the outer end 6t of the ply folded portion from the bead base line BL.
The height h0 of the tire in the radial direction is larger than the height ha of the bead apex rubber and 15% to 50%, more preferably 20% to 40% of the tire section height H from the bead base line BL. Is preferable, and in this example, about 3
2%.

The ply turn-up portion 6b extends radially outward along the outer surface 8o of the bead apex rubber 8 and extends at the outer end 8 of the bead apex rubber 8.
t, the ply folded portion 6b and the ply body 6
The inter-cord distance t, which is the distance between the carcass cords 6c of a
(Measured as shown in FIG. 5) the proximity X where the minimum value tmin
And the minimum value tmin is equal to the carcass cord 6
It is set to be 0.15 to 7.0 times the diameter D of c.

As described above, by minimizing the inter-cord distance t near the outer end of the bead apex rubber 8, a large shear force and heat are generated on the rubber between plies near the outer end 8t of the bead apex rubber 8. And the initial cracking is suppressed.

If the minimum value tmin is smaller than 0.15 times the diameter D of the carcass cord 6c, the ply body 6
a and the ply folded portion 6b have a too small inter-cord distance, and the rubber tends to have insufficient strength against deformation at this portion. Conversely, if it exceeds 7.0 times, the ply body portion 6a And the distortion and heat generation between the plies due to the shearing force acting on the inter-ply rubber of the ply turnover portion 6b are large,
This part is likely to be the starting point of the separation.

Preferably, the minimum value tmin of the inter-cord distance of the adjacent portion X is, for example, the carcass cord 6c.
0.15 to 5.0 times, more preferably 0.1 times the diameter D of
It is preferably 5 to 4.5 times, more preferably 0.5 to 3.5 times, more preferably 0.8 to 2.5 times.

It is desirable that such a proximity portion X is formed at least partially within a range of 1.1 to 1.5 times the height ha of the bead apex rubber 8 from the bead base line BL. . Further, the proximity portion X may be, for example, local, but the inter-code distance t is the minimum value t.
It is preferable to form a parallel region G in which the carcass cords of the ply main body portion 6a and the ply turn-up portion 6b extend substantially parallel by being continuous while forming a minimum. At this time, at least a part, preferably all, of the parallel region G has a height ha of the bead apex rubber of 1.1 to 1.1.
It is desirable to make the range 1.5 times. However, the parallel region G may exist beyond this range.

In the parallel region G, the ratio (tmin / h) between an arbitrary height h from the bead base line BL and the distance between the cords at this arbitrary height h (in this example, constant at tmin). ) Is also preferably in the range of 0.01 to 0.07. The same units are used for h and t.

As a result of various experiments conducted by the inventors, when the parallel region G formed by the above-described adjacent portion X is formed, the strain and heat generated due to the shear force acting on this portion can be effectively dispersed.
It has been found that the durability of the bead portion can be significantly improved because the effect of suppressing the initial cracks generated near the outer end 8t of the bead apex rubber 8 is further improved.

Further, in the present invention, as shown in an enlarged view in FIG. 2, the ply main body portion 6a of the carcass ply 6A is provided outside the proximity portion X in the tire radial direction (in this example, following the parallel portion G). And the ply turn-up portion 6b forms a gradually increasing region Y in which the inter-cord distance t gradually increases to the outer end 6t of the ply turn-up portion 6b.

By providing such a gradual increase region Y, the thickness of the rubber between the plies between the ply folded portion 6b and the ply main body 6a is reduced at the position of the outer end 6t.
And the outer end 6t of the ply turn-up portion 6b
Can be suppressed over a long period of time. On the other hand, the thickness of the rubber between the plies of the ply main body 6a and the ply turn-up portion 6b gradually decreases in the opposite direction toward the outer end of the bead apex rubber 8, so that the outer end 8t of the bead apex rubber 8 The rubber thickness between the plies in the vicinity position can be made relatively small, and also in this portion, the initial cracking which becomes the starting point of separation can be prevented.

That is, in the present application, by forming such a gradually increasing region Y, it is possible to suppress the initial cracking which becomes the separation starting point at both the outer end 6t of the ply folded portion 6b and the outer end 8t of the bead apex rubber 8. It is.

In the present embodiment, the bead portion 4 gradually increases the height (h0) from the bead base line BL to the outer end of the ply turnover portion 6b by 0.4 to 1.0 times. The most preferable one formed as the region Y is shown. However, for example, the gradual increase region Y is not limited to this range, and is formed in at least a part of this range. For example, the height (h0) of the height from the bead base line BL to the outer end of the ply turn-up portion is determined. The range may be 0.5 times or more and 1.0 times or less, and further may be 0.8 to 1.0 times.

Further, the gradual increase area Y in this example is a ratio (t) between an arbitrary height (h) from the bead base line BL and the inter-code distance (t) at this arbitrary height (h). / H) shows a gradual increase that becomes substantially constant. Thereby, the thickness of the rubber between plies can be increased in a uniform increment according to the height from the bead base line BL toward the vicinity of the outer end 6t of the ply turn-up portion 6b, and a good initial crack preventing effect can be obtained. Can be demonstrated.

At this time, the value of the ratio (t / h) is 0.01 to 0.07, preferably 0.02 to 0.07.
It is desirably in the range of 5.

If the ratio (t / h) is less than 0.01, the effect of increasing the thickness of the rubber between plies may not be sufficiently obtained at the position of the outer end 6t of the ply turn-up portion 6b. The effect of suppressing the initial crack at the outer end 6t of the portion 6b tends to be relatively reduced. On the other hand, if the ratio (t / h) is larger than 0.07, the thickness of the rubber interposed between the plies between the ply body 6a and the ply turn-back portion 6b becomes too large, and the tire is running during running. This portion generates heat due to shear deformation, which may cause deterioration of the rubber.

Here, as an example of the above-mentioned "gradual increase", as described above, the inter-code distance t increases linearly according to the height from the bead base line BL (t / h is substantially constant).
However, in addition to the above, all modes in which the inter-code distance t gradually increases are included, for example, a bead baseline B
This includes at least the case where the inter-code distance increases in accordance with the square of the height h from L (for example, t / h2 = substantially constant). In the above embodiment, the cord-to-cord distance is equal to the ply turnover 6.
Although the most preferable mode of gradually increasing the outer edge 6b to the outer edge 6t of the ply is shown in FIG. 6, as shown in FIG. included. However, in any case, the inter-cord distance t at the position of the outer end 6t is the maximum value tmax.
Becomes Note that this maximum value tmax is usually the minimum value tmax.
is about 1.3 to 3.0 times the min. and 0.5 to 9.0 times, preferably 1.0 to 6.0 times, more preferably 1.5 times the diameter D of the carcass cord 6c. It is good to make it up to 4.5 times.

In this embodiment, as shown in FIGS. 3 and 4, the ply turn-up portion 6b has an inner portion in which at least the ply portion 6b1 forming the gradually increasing region Y is disposed inside the ply portion 6b1 in the tire axial direction. 10a and an outer portion 10b disposed outside the ply portion 6b1 in the tire axial direction.
And is covered with an insulation rubber 10 having a higher modulus than the side wall rubber 11.

The inner portion 10a extends radially outward from the outer end 8t of the bead apex rubber 8 between the ply folded portion 6b and the ply body portion 6a. It is in contact with the main body 6a. In this example, the outer portion 10b has a substantially uniform thickness along the outer surface of the ply turn-up portion 6b in the tire axial direction, and terminates inside the bead core 5 in the tire radial direction.

The insulation rubber 10 of the present embodiment is
The inner portion 10a and the outer portion 10b are integrated at an outer end 6t of the ply turn-up portion 6b, and a taper that extends radially outward from the outer end 6t of the ply turn-up portion 6b and terminates in a tapered shape. Part 10c
Are exemplified. On the outside of the insulation rubber 10 in the tire axial direction, a sidewall rubber 11 which is rich in flexibility and is exposed to the outside at the sidewall portion 3 is connected to the tire radially inside, and the rim J
And a chafer rubber 12 which is in contact with the rubber.

Such an insulation rubber 10 is
Since the outer end 6t of the ply turn-up portion 6b is reliably separated from the sidewall rubber 11, the effect of preventing separation can be further enhanced. In addition, the tapered portion 10c suppresses the separation of the insulation rubber 10 from other rubber bonded thereto. From such a viewpoint, it is desirable that the height of the tapered portion 10c from the outer end 6t of the folded ply portion be 10 mm or more, more preferably 15 mm or more.

The insulation rubber 10 is preferably formed from one or two rubber compositions. FIG. 3 illustrates a case where the insulation rubber 10 is formed of one type of rubber. FIG. 4 shows that the insulation rubber 10 is composed of two types of rubber, that is, the inner part 1.
0a and a tapered portion 10c, a packing rubber portion P1 disposed on the ply body portion 6a side, and an other insulation body portion P2.
An example is shown in which different rubber compositions are used for P2.

Here, in the example of FIG. 4, the packing rubber portion P1 has a crescent shape having a maximum thickness near the outer end 6t, and has a 100% modulus Ma.
Is, for example, 15 to 47 kgf / cm ² . In addition, the insulation body P2 has at least a ply portion 6b1.
Covering the outer surface and the cord end surface at the outer end 6t,
The 100% modulus Mb is 37 to 47 kgf / cm ² and larger than the 100% modulus Ma.
Thereby, the local movement of the outer end 6t of the ply turn-up portion 6b can be more suitably suppressed by the insulation main body P2 having a relatively large modulus of 100%. Further, the movement in which the insulation main body portion P2 and the ply folded portion 6b are integrated can be suitably absorbed by the packing rubber portion P2 having a relatively small modulus of 100%.

At the outer end 6t of the ply turn-up portion 6b,
A cut end surface of a carcass cord having poor adhesion, in this example, a steel cord which has not been plated, appears. By disposing the insulation rubber 10 as described above, the cut end surface has a flexible side wall rubber. 1
1 can be prevented from coming into direct contact, and thus help prevent the rubber between the plies from breaking. In particular, the thickness te of the outer portion 10b of the insulation rubber 10 at the outer end 6t of the ply folded portion 6b is desirably 1 mm or more, and is desirably at least the minimum value tmin.

The sidewall rubber 11 has a 100% modulus Mc of 10 to 20 kgf / cm.
² and for chafer rubber 12
It is desirable to use a rubber composition having a 0% modulus Md of 55 to 71 kgf / cm ² .

Next, the inner liner rubber layer 9 forming the tire inner surface S is provided with a low gas-permeable butyl rubber containing 60 parts by weight or more of halogenated butyl rubber in 100 parts by weight of a rubber base material as a raw rubber. Is adopted. As shown in FIG. 7, such a butyl-based rubber has a reduced gas permeability with an increase in the compounding ratio of the halogenated butyl rubber, and exhibits excellent airtightness (gas-permeation resistance) particularly at 60 parts by weight or more. Therefore, the content of the halogenated butyl rubber is at least 60 parts by weight, preferably at least 90 parts by weight.

Of the raw rubber, natural rubber, butadiene rubber,
A diene rubber such as styrene / butadiene rubber can be used. However, when butyl rubber (regular butyl rubber) is used as the remaining rubber, the co-vulcanization property (adhesion) required for the other rubber member such as the carcass 6 is further improved while maintaining the necessary co-vulcanization property (adhesion property). It is possible to exhibit improved gas permeability resistance. Moreover, since the compounding with the butyl rubber also has an effect of preventing the halogenated butyl rubber from being thermally cured by the heat generation of the tire, it is preferable in suppressing the crack damage of the inner liner rubber layer 9.

The butyl rubber has well-known additives,
For example, a component for improving reinforcing properties such as carbon black; a component for improving processability such as process oil and a vulcanization aid; and acting as a vulcanization retarder such as magnesium oxide and mercaptobenzothiazyl disulfide (MBTS). A retarder for preventing burning of rubber; a vulcanization accelerator such as zinc white; a vulcanizing agent such as sulfur may be appropriately compounded. Table 1 shows examples of the rubber composition that can be used for the inner liner rubber layer 9.

[0052]

[Table 1]

In the tire 1, it is necessary to prevent the decrease in cord strength and rubber adhesive strength caused by the moisture contained in the filling air permeating the inner liner rubber layer 9 from promoting the initial cracking. Therefore, at least in the region Z around the folded end of the carcass ply 6A, the rubber thickness T of the inner liner rubber layer 9 is set.
b is restricted to a predetermined range.

As shown in FIG. 3, the folded end peripheral region Z is defined as a distance K equal to the maximum cross-sectional width BW of the bead core 5 about the outer end 6t of the ply folded portion 6b. 6a means an area separated inward and outward in the radial direction. Further, in the area Z around the folded end, the rubber thickness Tb of the inner liner rubber layer 9 is regulated to a range of 1.0 to 4.5 times the diameter D of the carcass cord 6c.

Thus, it is possible to reliably prevent the permeation of moisture in the region Z around the turning end, and together with the formation of the proximity portion X and the gradually increasing region Y, the generation of the initial cracks and the Can be more effectively suppressed from proceeding to the separation, and the durability of the bead portion 4 can be greatly improved.

If the rubber thickness Tb is less than 1.0 × D, the prevention of water permeation becomes insufficient. Conversely, 4.5
Exceeding × D not only causes an increase in weight and cost, but also causes a decrease in steering stability and fuel efficiency. Therefore, preferably, the rubber thickness Tb is in the range of 1.5 to 3.0 times the diameter D.

In this example, the case where the inner liner rubber layer 9 extends from one end to the other end with the rubber thickness Tb being substantially constant is illustrated, but only the folded end peripheral region Z is formed to be thick in the above range. can do. In order to improve the adhesiveness between the inner liner rubber layer 9 and the carcass 6 and to prevent the inner liner rubber layer 9 from waving during vulcanization molding, in this example, the gap between the inner liner rubber layer 9 and the carcass 6 is set. The inner insulation rubber 15 having a lower modulus than the topping rubber 6g is interposed. The insulation rubber 15 preferably has a 100% modulus of 27 to 45 kgf / cm ² , and the inner liner rubber layer 9 preferably has a 100% modulus of 5 to 20 kgf / cm ² .

As described in detail above, in the present invention, the category of the tire is not limited to the above-mentioned example,
It can be applied to various categories of tubeless tires such as for small trucks, motorcycles, and aircraft.

[0059]

[Example] Tire size is 11R22.5 (14PR)
Prototype of a heavy-duty radial tire according to the specifications in Table 2.
Durability was tested. The test contents are as follows.

(1) Drum Durability Test 1 The test tire was assembled on a rim having a rim size of 8.25 × 22.5, the internal pressure was charged to 1000 kPa, and the tire was run on a drum tester at a speed of 20 km / H and a load of 9000 kgf. ,
The running time until the appearance of the tire was damaged was measured, and the measured running time was indicated by an index with the tire of the conventional structure (conventional example) shown in FIG. The higher the value, the better. Finish 1
0000 km.

(2) Drum Durability Test 2 The test tire is assembled on a rim having a rim size of 8.25 × 22.5, filled with 200 cc of water and filled with an internal pressure of 1000 kPa, and run on the drum under the same conditions as in the above test. At the same time, 200 cc of water was additionally injected every 100 hours, and the running time until the appearance of damage was measured. The higher the value, the better. After running, the tires were disassembled and the presence or absence of rust was compared.

The common specifications of the tires are as follows. <Carcass>-Number of plies: 1-Cord: Steel (3 x 0.2 mm + 7 x 0.23 mm) Diameter D: 0.8 mm-Number of cords to be driven: 38/5 cm (below the bead core)-Cord angle: 90 ° (pair 100% modulus of topping rubber: 42 kgf / cm ² <Belt layer>-Number of plies: 4-Cord: Steel (3 x 0.20 mm + 6 x 0.35 mm)-Number of cords: 26 / 5cm-Cord Angles: + 67 °, + 18 °, -18 °, -18 ° (with respect to the tire equator) <Insulation rubber> ・ 100% modulus Ma: 41 kgf / cm ²

[0063]

[Table 2]

As a result of the test, it was confirmed that in the tire of the example, the durability of the bead portion was further improved.

[0065]

Since the present invention is configured as described above,
Due to the formation of the proximity portion and the gradually increasing region, it is possible to effectively suppress the initial cracking which becomes the starting point of the separation at both the outer end of the ply folded portion and the outer end of the bead apex rubber. In addition, it is possible to reliably prevent a decrease in cord strength and rubber adhesive strength due to moisture passing through the inner liner rubber layer, at least in a region around the folded end of the carcass ply. Properties can be further improved.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view of a rim-assembled tire showing one embodiment of the present invention.

FIG. 2 is a partial sectional view of a bead portion.

FIG. 3 is a partial sectional view showing an example of a rubber distribution in a bead portion.

FIG. 4 is a partial cross-sectional view showing another example of a rubber distribution in a bead portion.

FIG. 5 is a sectional view taken along line AA of FIG. 1;

FIG. 6 is a partial sectional view showing another embodiment of the gradually increasing region.

FIG. 7 is a graph showing the relationship between the substrate transmittance and the content of halogenated butyl rubber.

FIG. 8 is a partial sectional view showing a conventional bead portion.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Ply body part 6b Ply folded part 6t Outer end of ply folded part 8 Bead apex rubber 8t Outer end of bead apex rubber 9 Inner liner rubber layer 10 Inns Ration rubber 10a Inner part 10b Outer part 10c Tip 11 Sidewall rubber S Tire lumen surface X Closer part Y Increasing area Z Folding end peripheral area G Parallel area BL Bead base line

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-10-315718 (JP, A) JP-A-9-11715 (JP, A) JP-A-60-157905 (JP, A) JP-A-5-115 178039 (JP, A) JP-A-2-267012 (JP, A) JP-A-4-185510 (JP, A) JP-A-2-231202 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) B60C 5/14 B60C 9/08 B60C 15/00-15/06

Claims (5)

(57) [Claims] 1. A radially arranged carcass having a ply body portion integrally provided on a ply body portion extending from a tread portion to a bead core of a bead portion through a side wall portion to bend from inside to outside in the tire axial direction around the bead core. A tubeless tire comprising: a carcass having a ply; and an inner liner rubber layer disposed inside the ply body portion of the carcass and forming a tire cavity surface, wherein the inner liner rubber layer is formed of a rubber base material 100. A butyl-based rubber containing 60 parts by weight or more of halogenated butyl rubber in parts by weight, and a distance K equal to the maximum cross-sectional width BW of the bead core around the radially outer end of the folded-back portion of the ply along the ply body. The thickness of the inner liner rubber layer (Tb ) Is 1.0 to 4.5 times the diameter D of the carcass cord of the carcass ply, while the bead portion is provided with a bead apex rubber tapering outward from a bead core in the tire radial direction, The portion extends outward in the tire radial direction along the outer surface of the bead apex rubber in the tire axial direction and near the outer end of the bead apex rubber, the carcass cord of the ply folded portion and the carcass cord of the ply body portion. Is the minimum value (tmi)
n), and the minimum value (tmin) is 0.15 to 7.0 times the diameter D of the carcass cord, and the cord is provided outside the proximity part in the tire radial direction. A tubeless tire, wherein a gradually increasing region in which a distance (t) gradually increases outward in a tire radial direction is formed. 2. The method according to claim 1, wherein the bead portion includes the gradually increasing region in at least a part of a range from 0.4 to 1.0 times a height (h0) of the ply turn-back portion from a bead base line, A ratio (t / h) between an arbitrary height (h) of the gradually increasing region from the bead baseline and the inter-cord distance (t) at the arbitrary height (h) is substantially constant; The tubeless tire according to claim 1, wherein the value is in the range of 0.01 to 0.07. 3. The bead portion includes the proximity portion in at least a part of a range from 1.1 to 1.5 times the height (ha) of the bead apex rubber from a bead base line, The adjacent portion forms a parallel region in which the carcass cords of the ply body portion and the ply turn-up portion extend substantially in parallel when the inter-cord distance (t) continuously becomes the minimum value (tmin). The tubeless tire according to claim 1 or 2, wherein 4. The ply turn-up portion, wherein at least the ply portion forming the gradually increasing region is disposed inside the ply portion in the tire axial direction, and the outer portion is disposed outside the ply portion in the tire axial direction. 4. The insulating rubber according to claim 1, wherein the insulating rubber is covered with an insulation rubber different from the side wall rubber, and the insulation rubber comprises one or two rubber compositions. A tubeless tire according to claim 1. 5. The insulation rubber according to claim 1, wherein the inner portion and the outer portion are integrated at an outer end of the ply turn-up portion, and extend outward in the tire radial direction from the outer end of the ply turn-up portion and have a tapered shape. The tubeless tire according to claim 4, further comprising a tapered portion terminating at the end.