JP2001233013A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance air pressure holding performance. SOLUTION: This pneumatic tire is provided with a carcass 2 and an inner finer 3 equipped with a main part 3a which has a coated part 10 extending from a side wall part 4 to a bead part 1 and forming a tire cavity surface (i) and extends radially to the inside of the tire. A rolled-up part 3b which continues to the main part 3a, axially bends outside and turns toward the inside of a bead core 6 is formed at the inner end of the main part 3a. The outer end 3e of the rolled-up part 3b is terminated outside a first area AT parted in and out from a radial center fine Y passing through the axial tire center of the opposite side 5a of the bead core 5 almost paralleling to and facing the bottom surface 1a of the bead by a distance K which is 25% of the length W of the opposite side 5a, and outside a second area A2 parted radially outside by 20 mm from a separating point P1 where the external surface of the bead part 1 is separated from the rim flange JF of a normal rim J. The rubber thickness of the rolled-up part 3b is set for 0.5 mm or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubeless type pneumatic tire having excellent air pressure retention.

[0002]

2. Description of the Related Art A pneumatic tire, such as a tubeless type heavy duty tire used for heavy vehicles such as trucks and buses, has a carcass a and a cord reinforcing layer b as shown in FIG. An inner liner c made of rubber having excellent air impermeability is disposed on the inner surface side of the tire to maintain the air pressure of the tire. Further, the conventional inner liner c generally has a bead toe e forming the toe of the bead portion d or a terminal end before the bead toe e.

[0003] The inventors examined the contribution of each part of the tire to the decrease in tire air pressure and found that air leakage was about 20% at the lower side of the bead portion d. When the cause was investigated in more detail, as shown in FIGS. 7A and 7B, when the tire was continuously used, as shown in FIGS.
Strain during running of the tire repeatedly acts on the bead toe, causing deterioration of the chafer rubber f and the like in contact with the rim j, and the bead toe e is permanently deformed starting from the inner end position k of the bead core g in the tire axial direction. It turned out to be floating from j. In particular, in the case of a heavy-duty pneumatic tire using a steel cord for the carcass a, such a bead toe e is easily raised. In the bead portion d in which such deformation has occurred, the bead bottom surface m not covered with the inner liner c is exposed to the tire lumen side, and the air pressure retention performance is lowered such that leakage occurs due to the permeation of air therefrom. Turned out to be.

The present invention has been devised in view of such a situation. The present invention forms a wrap portion which is bent outward in the tire axial direction in the inner liner and extends inward in the radial direction of the bead core. The purpose of the present invention is to provide a pneumatic tire capable of improving the air pressure retention performance and effectively preventing damage to an inner liner having a low adhesive force, in particular, a pneumatic tire for heavy loads by appropriately regulating the pneumatic tire. And

[0005]

According to a first aspect of the present invention, there is provided a side wall made of a carcass extending from a tread portion to a bead core of a bead portion via a side wall portion and a rubber having excellent air impermeability. An inner liner having a main portion extending inward in the tire radial direction having a covering portion extending from the portion to the bead portion and forming a tire lumen surface, and a radially inner end of the main portion. A tire shaft in a normal state in a no-load normal state in which a winding portion is formed to be bent outward in the tire axial direction continuously to the main portion and directed radially inward of the bead core, assembled to a normal rim and filled with a normal internal pressure. In the tire meridian section including, from the radial center line passing through the center in the tire axial direction of the opposite side of the bead core substantially parallel and facing the bead bottom, the tire of the opposite side Outside the first region, which is separated by 25% of the length in the direction from the inside to the outside, and outside the second region, which is separated by 20 mm radially outward from the separation point where the outer surface of the bead portion and the rim flange of the regular rim are separated from each other. The outer end of the entangled portion is terminated, and the rubber thickness of the entangled portion is set to 0.
It is characterized in that it is 5 mm or more.

Here, the "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, and TRA is "Design rim". Rim "or ETR
If it is TO, it will be "Measuring Rim". The “normal internal pressure” is the air pressure defined for each tire in the standard system including the standard on which the tire is based.
"TIRE LOAD LIMITS AT VARIOUS COLD INFLATIONPRESSU
RES ", EINFTO" INFLATION
PRESSURE ", but if the tire is for a passenger car, the pressure is 180 KPa.

Further, it is preferable that the winding portion terminates before reaching the first region, or terminates between the first region and the second region. Further, the bead portion includes a bead structure including a bead core, the carcass, and a reinforcing ply for reinforcing a bead portion curved along the bead core, and the winding portion extends outside the bead structure. It is desirable to pass.

A toe region surrounded by a first straight line passing through the cross-sectional center of gravity of the bead core and parallel to the opposite side of the bead core, a second straight line passing through the cross-sectional center of gravity and perpendicular to the first straight line, and a bead toe surface. In the above, the ratio (Si / St) of the total area St of the rubber included in the toe region to the total area Si of the inner liner included in the toe region is 0.2 to 0.2.
0.9 is desirable.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a tubeless type pneumatic tire, in which a heavy-duty tire used for trucks, buses, and similar vehicles is mounted on a 15 ° deep rim J serving as a normal rim and filled with a normal internal pressure. FIG. 2 shows a meridional section of the bead portion 1 in a normal state of load, and FIG. 2 shows a free state before assembling the rim.
The pneumatic tire (not shown) of the present embodiment includes a carcass 2 forming a tire frame and an inner liner 3. Needless to say, pneumatic tires include not only heavy-duty tires but also various tires for passenger cars and light trucks.

In the present embodiment, the carcass 2 has a bead portion 1 from a tread portion (not shown) via a sidewall portion 4.
The carcass ply 2A includes a main body 2a reaching the bead core 5 and a folded portion 2b connected to the main body 2a and turned around from the inside in the tire axial direction to the outside around the bead core 5. This carcass ply 2
A is formed, for example, using a ply in which carcass cords arranged in parallel are covered with topping rubber, and the carcass cords adopt a so-called radial structure arranged at an angle of 70 to 90 ° with respect to the tire equator. . In this example, the carcass 2 is constituted by one carcass ply 2A. The carcass cord is made of a steel cord, but an organic fiber cord such as nylon, rayon, polyester, or aromatic polyamide can be used as necessary or according to the type of tire.

In the present embodiment, the bead core 5 is formed by spirally winding a steel wire a predetermined number of times to form a horizontally long cross section having a substantially hexagonal shape. The bead core 5 has opposite sides 5a which are substantially parallel to and face the bead bottom surface 1a in the normal state. That is, the opposite side 5a is configured to substantially extend at about 15 ° with respect to the tire axial line, that is, along the inclination of the rim seat surface Ja of the rim J. The bead core 5 can use an aromatic polyamide cord or the like in addition to the steel wire.

The bead portion 1 has a carcass ply 2A.
A bead apex 6 (shown in FIG. 2) extending in a tapered shape from the bead core 5 to the outside in the tire radial direction is disposed between the main body portion 2a and the folded portion 2b. The bead apex 6 has a JIS durometer A hardness of 65, for example.
It is made of rubber having an angle of up to 98 degrees, more preferably 70 to 95 degrees, and serves to increase the bending rigidity and the like of the bead portion 1. Further, a reinforcing ply 7 for reinforcing the bead portion, which is curved in a substantially U-shaped cross section along the bead core 5, is disposed in the bead portion 1 of this embodiment. This reinforcing ply 7
, For example, in this example, is constituted by plies in which steel cords are arranged in parallel. Thus, a bead structure 9 including the carcass 2, the bead core 5, and the reinforcing ply is formed in the bead portion 1 of the present embodiment.

The inner liner 3 is made of rubber having excellent air impermeability, and has a covering portion 10 extending from the side wall portion 4 to the bead portion 1 and forming a tire cavity surface i and extends inward in the tire radial direction. It has a main part 3a. The inner liner 3 can prevent the air in the tire cavity from permeating to the outside and maintain the air pressure of the tire. The rubber having excellent air impermeability includes, for example, butyl rubber, halogenated butyl rubber, brominated butyl rubber, chlorinated butyl rubber, and rubbers equivalent thereto, and those rubbers mainly (for example, 100 parts by weight of a rubber base material). Rubber having a property of hardly permeating air, such as a rubber material containing 50 parts by weight of the rubber.

Further, the inner liner 3 is integrally provided at the radially inner end of the main portion 3a with a winding portion 3b which is bent outward in the tire axial direction continuously from the main portion 3a toward the radially inner side of the bead core 5. . The entangled portion 3b of the present embodiment exemplifies a portion that goes outside the bead structure 9, that is, the inside of the bead core 5 in the tire radial direction through the outside of the reinforcing ply 7. Such an inner liner 3 includes not only the main portion 3a but also a winding portion 3b directed inward in the radial direction of the bead core 5,
As shown in FIG. 3, even when the bead toe 1b undergoes permanent deformation accompanied by lifting, the bead toe 1b can be interposed in the raised portion including the bead bottom surface 1a and the like, and can suppress the transmission of air from the raised portion. Therefore, permeation of air from the bead portion 1 can be reduced as compared with the related art, and a decrease in tire air pressure can be prevented for a longer period.

Here, it is desirable that the rubber thickness t of the entangled portion 3b of the inner liner 3 be 0.5 mm or more, more preferably 1 mm or more, in order to reliably prevent air from permeating. The upper limit of the rubber thickness of the entangled portion 3b is not particularly limited, and is appropriately set according to the structural requirements of the bead portion 1 of the tire. In addition, the entangled portion 3b
When the outer end 3e has a tapered shape that terminates by gradually reducing its thickness, the thickness of the terminal end is not particularly limited to 0.5 mm.

[0016] Rubber having excellent air impermeability, such as butyl rubber, tends to have low adhesive strength to other rubbers. For this reason, when the outer end 3e of the entangled portion 3b of the inner liner 3 is arranged in a region where distortion is large or a region where rubber cracks or the like are likely to occur, the outer end 3e of this entangled portion 3b is
There is a possibility that adhesion peeling or the like occurs in e, and the durability of the bead portion 1 is reduced. Therefore, in the present invention, by arranging the outer end 3e of the entangled portion 3b outside the region where the distortion or the like is large, that is, outside the region, it is possible to appropriately prevent the durability of the heed portion 1 from being lowered. .

Here, the first region A1 is an example of a region where rubber cracks and the like easily occur in the bead portion 1.
As shown in FIG. 1, the first area A1 is a tire on the opposite side 5a of the bead core 5 in a tire meridian section including a tire shaft in a normal state in a no-load state where the tire is assembled to a normal rim J and filled with a normal internal pressure. From the radial center line Y passing through the center in the axial direction, the tire axial length W of the opposite side 5a is 25
% Distance k, k is defined as a region separating the inside and outside in the tire axial direction. In the first area A1, the carcass ply 2A, the reinforcing ply 7 and the like are bent around the bead core 5 and are bent at a substantially constant curvature. 5 is a region where the amount of rubber between the opposite side 5a of the bead core 5 and the bead bottom surface 1a is small. For this reason, when the outer end of the entangled portion 3b having a low adhesive force is arranged in such a first area A1, the outer end 3e of the entangled portion 3b is located.
May come into direct contact with the cord of the ply rubber crack,
Damage such as adhesive breakage is relatively likely to occur. When the bead core 5 has, for example, a substantially circular cross section, the opposite side 5
a can be defined as a radially inner semicircular portion facing the bead bottom surface 1a.

As a region having large distortion, a second region A
2 is mentioned. The second region A2 is a region from the separation point P1 at which the outer surface of the bead portion 1 and the rim flange JF of the normal rim J are separated from each other in the normal state to a position P2 that separates a distance S of 20 mm radially outward from the separation point P1. Is set. The second area A2 is an area where the bending distortion due to the running of the tire is the largest, and if the outer end 3e of the entangled portion 3b of the inner liner 3 is terminated in such an area, the adhesive peeling or the like may occur early. The resulting bead portion 1 will have reduced durability. By arranging the outer end 3e of the entangled portion 3b of the inner liner 3 outside the first area A1 and the second area A2 in this manner, the entangled part 3
Damage to the outer end 3e of b can be suppressed. Note that the second area A2
Is a tire normal N1 passing through the separation point P1 and the position P2,
It is an area sandwiched by N2.

Further, the winding part 3b of this embodiment has an outer end 3
e terminates between the first area A1 and the second area A2. Further, in this example, the outer end 3e terminates at a position separating a small distance r from the separation point P1 inward in the tire radial direction. This distance r is desirably, for example, 3 mm or more, more preferably 5 mm or more.

Further, as shown in FIG. 2, a rubber chafer 12 is arranged in the bead portion 1 of the present embodiment. The rubber chafer 12 is made of hard rubber, and is disposed inside the entangled portion 3b of the inner liner 3 in the tire radial direction and exposed to the bead bottom surface 1a;
The bead toe 1 extends inward in the axial direction of the base 12A.
a rising portion 12B extending radially outward from the tire inner surface i side from b; and an rising portion extending axially outward from the base portion 12A and extending radially outward from the bead heel 1c to the outside surface of the bead portion. 12C. Such a rubber chafer 12 can prevent direct contact between the inner liner 3 and the rim J, increase rigidity of the bead bottom surface 1a and the like, and reduce abrasion caused by contact with the rim J.

The rubber chafer 12 is composed of, for example, 20 to 60 parts by weight of natural rubber and 80 to 40 parts by weight of butadiene rubber blended with 100 parts by weight of a rubber polymer, and a compounding agent such as carbon black, an antioxidant, and zinc white. Can be preferably employed. Also,
The rubber chafer 12 has a JISA hardness of 70 to 90 in order to prevent chipping of rubber and large deformation of the bead portion 1.
Degrees, more preferably 75 to 83 degrees (79 degrees in this example). The complex elastic modulus of the rubber chafer 12 is about 10 to 15 M in consideration of rim assembly and durability.
It is desirable to set it to Pa. The complex elastic modulus was determined by cutting a strip sample of 4 mm width × 30 mm length × 1.5 mm thickness and using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. at a temperature of 70 ° C., a frequency of 10 Hz and a dynamic strain of ± The value is measured under the condition of 2%. Further, the rising portion 12C outside the rubber chafer 12 is exposed to the outer surface of the bead portion, and is positioned and terminated beyond the separation point P1 outward in the radial direction so as to be in contact with the rim flange JF. Thereby, the outer surface of the bead portion 1 can be suitably reinforced, and damage due to contact with the flange can be prevented. It should be noted that instead of such a rubber chafer 12, or together with the rubber chafer 12, a canvas chafer having a cloth rubberized can be used.

FIG. 4 shows another embodiment of the present invention. The outer end 3e of the entangled portion 3b of the present example is illustrated as being terminated axially outside the inner end 5i of the bead core 5 in the tire axial direction and before reaching the first region A1. In this example, the reinforcing ply 7 has an inner end in the tire axial direction terminated inside the bead core 5. Further, the reinforcing ply 7 can be omitted.

In each of the embodiments shown in FIGS. 1 and 4, the inner liner 3 includes a first straight line L1 which passes through the center of gravity G of the cross section of the bead core 5 and is parallel to the opposite side 5a of the bead core 5, as shown in FIG. A toe region At (first straight line L1, second straight line L1, second straight line L2) surrounded by a second straight line L2 passing through the sectional center of gravity G and perpendicular to the first straight line L1 and a bead toe surface which is the surface of the toe portion including the bead toe 1b. , The straight line L2, the tire inner surface i and the bead bottom surface 1a).
The total area St of the rubber included in the toe area At and the total area S of the inner liner 3 included in the toe area At
The ratio (Si / St) to i is set to 0.2 to 0.9. In a conventional tire of this type, the ratio (Si / S
The value of t) is less than 0.2, and the toe area At hardly contains the inner liner 3 rubber. For this reason, there is a problem that air pressure leaks in this portion, and that the rigidity is too high to be easily assembled on the rim and that the rubber rim is easily deformed due to excessive deformation when the rim is assembled.

Therefore, in the present embodiment, the above-described toe area At
In addition, since more inner liners 3 are included as compared with the related art, leakage of air can be further prevented. Further, since the inner liner 3 has a lower rubber hardness than the rubber chafer 12 or the like, such rubber is applied to the toe region At.
By arranging more, the toe area A when the rim is assembled
It is particularly preferable in that t can be appropriately deformed and problems such as rubber chipping can be prevented. The ratio (Si / S
When t) is less than 0.2, there is not much difference from the conventional art, and the improvement of the air pressure holding performance and the rim assembling property cannot be improved.
If it exceeds 9, the amount of the rubber chafer 12 is reduced, and the rigidity is apt to be significantly reduced. From such a viewpoint, the ratio (Si / St) is particularly preferably about 0.3 to 0.7. The total area St of the rubber included in the toe region At is for the rubber outside the bead structure (that is, outside the reinforcing ply 7 in this example), and does not include the rubber 14 inside the carcass 2. .

[0025]

EXAMPLE A pneumatic radial tire for heavy load according to the present invention having a tire size of 295 / 80R22.5 and having a bead structure shown in FIGS. And so on. For comparison, a test was also performed on a conventional tire having the same tire size (comparative example) shown in FIG. 6 to compare the performance. The test method is as follows.

<Air Pressure Retaining Performance> The tires are assembled into a regular rim (9.00 × 22.5) and the regular internal pressure (850).
kPa), the tire is mounted on a 2-2 · D type test vehicle, traveled 10 km, filled with the normal internal pressure again, and left in an oven at 80 ° C. for 10 days. Was measured. The reciprocal of the internal pressure drop rate was indicated by an index with the comparative example being 100. The larger the value, the better the air permeation resistance.

<Durability> A test tire was mounted on the regular rim, filled with an internal pressure of 850 kPa, and loaded with a load of 104 kN.
(3 times the maximum load of JATMA standard), speed 20km /
The vehicle was run on the drum at h, and when the damage was visually confirmed, the running was terminated, and the damage was evaluated by the percentage of the damage occurrence distance L1 and the complete running distance L0 (10000 km). The higher the value, the better.

<Rim assemblability> The reciprocal of the time required to assemble the test tire into the regular rim by hand assembly is shown as a comparative example.
The evaluation was made using an index of 00. The larger the value, the better the rim assemblability. Table 1 shows the test results.

[0029]

[Table 1]

[0030]

As described above, according to the first to third aspects of the present invention, the inner liner is provided at the radially inner end of the main portion covering the tire cavity surface, continuously to the main portion, in the tire axial direction. By having a winding portion having a predetermined rubber thickness directed inward in the radial direction of the bead core, even if the bead toe is lifted and deformed during traveling, the winding portion is interposed in the rising portion, so that the rising portion is formed. Permeation of air from the air can be suppressed. Therefore, permeation of air from the bead portion can be reduced as compared with the related art, and a decrease in tire air pressure can be prevented for a longer period.

According to the present invention, a first straight line passing through the center of gravity of the cross section of the bead core and parallel to the opposite side of the bead core; a second straight line passing through the center of gravity of the cross section and perpendicular to the first straight line; In the toe area surrounded by the surface,
The ratio of the total area St of the rubber included in the toe area to the total area Si of the inner liner included in the toe area (S
By restricting (i / St) to a certain range, air leakage from the toe area can be further prevented, and the toe area at the time of assembling the rim can be ensured to be deformable, thereby preventing defects such as rubber chipping.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a bead portion according to an embodiment of the present invention in a normal state.

FIG. 2 is a sectional view of the free state.

FIG. 3 is a cross-sectional view illustrating the operation of the present invention.

FIG. 4 is an enlarged sectional view of a bead portion in a normal state according to another embodiment.

FIG. 5 is an enlarged sectional view of a bead toe.

FIG. 6 is an enlarged sectional view of a conventional bead portion.

FIG. 7A is a cross-sectional view of a bead portion after traveling, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass 2a Main part 2b Folding part 3 Inner liner 4 Rubber chafer 5 Adhesion improving rubber 6 Bead apex

Claims (4)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a covering portion made of rubber having excellent air impermeability and extending from the sidewall portion to the bead portion and forming a tire cavity surface. A pneumatic tire having an inner liner having a main portion extending inward in the tire radial direction, the bead core being bent outward in the tire axial direction at the radially inner end of the main portion and continuously with the main portion. The bead core is substantially parallel to and opposed to the bead bottom surface in a tire meridian section including a tire shaft in a normal state under no load filled with a regular rim and filled with a regular internal pressure. A first area which is spaced inward and outward by a distance of 25% of the length of the opposite side in the tire axial direction from a radial centerline passing through the center of the opposite side in the tire axial direction Terminating the outer end of the entangled portion outside a second region separated by 20 mm radially outward from a separation point where the outer surface of the bead portion and the rim flange of the regular rim are separated from each other; Pneumatic tire characterized by having a diameter of 0.5 mm or more. 2. The air according to claim 1, wherein the convoluted portion terminates before reaching the first region, or terminates between the first region and the second region. Containing tires. 3. The bead portion includes a bead structure including a bead core, the carcass, and a reinforcing ply curving along the bead core for reinforcing a bead portion, and the winding portion includes a bead structure. The pneumatic tire according to claim 1, wherein the pneumatic tire passes outside the body. 4. A first straight line passing through the cross-sectional center of gravity of the bead core and parallel to the opposite side of the bead core, a second straight line passing through the cross-sectional center of gravity and perpendicular to the first straight line, and a bead toe surface. In the toe region, the ratio (S) of the total area St of the rubber included in the toe region to the total area Si of the inner liner included in the toe region
The pneumatic tire according to any one of claims 1 to 3, wherein i / St) is 0.2 to 0.9.