JP2002166710A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire to be lightened, or more specifically, an air-filled tire for a heavy load, lightened without deteriorating other performances. SOLUTION: The tire has a carcass 2 and a bead reinforcing layer 7. In addition, the tire also has a rubber chafer 4 made of hard rubber comprising a base part 4c located inside the bead core 8 in the radial direction of the tire, an outer raised part 4a connected to the base part 4c at the bead toe part inside the inner surface of the tire, and an outer raised part 4b connected to the base part 4c at the bead heel part extending on the outer surface of the tire. The relation on the regular condition among the height h4a of the inner raised part 4a from the bead base line BL, the height h7a of a rolled-in part 7a of the bead reinforcing layer 7, and the height h8 of the outermost end of the bead core 8 is as follows; h8-5 mm<=h7a<=h8+5 mm, h7a<=h4a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire that can be reduced in weight, and more particularly to a pneumatic tire for heavy load that is reduced in weight without impairing other performances.

[0002]

2. Description of the Related Art Pneumatic tires, particularly heavy duty pneumatic tires used for heavy vehicles such as trucks and buses,
The bead portion is required to have high durability because it is used under a high internal pressure and under a large load, and is used for rehabilitation. For this reason, it is common practice to cover a carcass wound and locked around a bead core with a bead reinforcing layer. Also, in some passenger car tires,
Such a bead reinforcing layer is arranged for the purpose of improving structural durability and steering stability.

The bead reinforcing layer is made of a non-metallic cord such as an organic fiber cord or a cord ply in which a number of metal cords are arranged in parallel. Particularly in a heavy-duty pneumatic tire, a cord ply made of a metal cord is usually used. Is used.

[0004] Further, the cord reinforcing layer conventionally has a winding portion that passes through the inside of the bead core in the radial direction and rises inside the carcass in the tire axial direction, and a winding portion that is located outside of the carcass in the tire radial direction. The winding portion and the hoisting portion extend outwardly in the tire radial direction beyond the bead core to the center of the bead apex or higher. Thereby, the compressive stress acting on the winding portion based on the bending moment due to the large load acting on the bead portion, and the tensile stress acting on the winding portion, against the bending moment by being borne by the cord of the cord of the bead reinforcing layer. It is intended to suppress bending deformation of the bead portion and improve bead durability. The resistance can be increased by forming the bead reinforcing layer with a metal cord.

On the other hand, with the recent improvement in material technology and the evolution of the carcass shape of tires, the volume of tires has been reduced in order to reduce bead reinforcement layers while maintaining bead durability, to reduce tire weight, to save resources, and to improve fuel efficiency. Japanese Unexamined Patent Application Publication No. 10-1 has disclosed a bead reinforcing layer having no beveled portion, that is, a pneumatic radial tire for heavy load having a bead reinforcing layer that is interrupted at a radially inward position of a bead core without providing a wound portion inward in the tire axial direction.
No. 47117.

[0006]

However, the heavy duty pneumatic tire having the bead reinforcing layer without the winding portion proposed by the above-mentioned proposal is a tubeless type tire whose proposal is mainly applied as a result of a production test. That is, when adopted as a tube type tire mounted on a 5 ° taper rim having a different bead shape from a tubeless type tire in which the bead base is mounted on a 15 ° taper rim inclined at 15 ° with respect to the tire axis, Then, the position of the bead reinforcement layer may lack stability,
It has also been found that this may cause a case where the rubber thickness of the bead core inside the tire axial direction is insufficient.

FIG. 2 shows a bead portion of a tube-type tire mounted on a 5 ° taper rim. As shown in FIG. When the bead core b is located inward of the tire radial direction in the tire radial direction, the pressing force acting on the tire cavity surface s at the time of vulcanization molding causes rubber movement and the bead reinforcing layer c tends to be displaced outward in the tire axial direction. It is estimated that the position becomes unstable.

That is, the bead bottom surface d is inclined at an angle of 5 degrees and the thickness increases toward the inside in the tire axial direction. With the displacement of the layer c to the outside in the tire axial direction, rubber shrinkage occurs in the tire axially inward portion of the bead core b, and the rubber thickness t at this portion decreases, and water or moisture in the air (hereinafter referred to as moisture) ) Easily enters from the tire inner surface s.

In particular, since a heavy-duty pneumatic tire is used at a high internal pressure, moisture easily penetrates, and a metal cord is usually used for the carcass cord. And the carcass cord itself is easily corroded and broken, and the displacement of the bead reinforcing layer c tends to have a bad influence on the uniformity of the tire.

An object of the present invention is to provide a heavy-duty pneumatic tire having a bead structure capable of solving such a problem and achieving a reduction in weight of the tire without impairing tire durability.

[0011]

According to the first aspect of the present invention,
A carcass 2 that is folded back and locked by a bead core 8 of a bead portion from a tread portion through a sidewall portion, and a winding portion 7a that passes through the bead core 8 in the tire radial direction and rises inside the carcass 2 in the tire axial direction. And a hoisting portion 7b that rises outside the carcass 2 in the tire axial direction.
And a bead reinforcing layer 7 made of a cord ply having a base portion 4c which is located inside the bead core 8 in the tire radial direction and forms a bead bottom surface.
A rising portion 4a connected to the base portion 4c at a bead toe portion and extending radially outward from the tire cavity surface; and an outer rising portion connected to the base portion 4c at a bead heel portion and extending radially outward from the tire outer surface side. In a standard state in which a rubber chafer 4 made of hard rubber having an inner portion 4b and a normal internal pressure is charged into a normal rim J, a height h4a of the inner rising portion 4a from the bead base line BL is provided.
And a height h7a of a winding portion 7a of the bead reinforcing layer 7.
And a height h8 of the outermost end of the bead core 8 has the following relationship. h8-5 mm ≦ h7a ≦ h8 + 5 mm h7a ≦ h4a

Further, in the invention according to claim 2, the rubber chafer 4 comprises 20 to 80 parts by weight of natural rubber and 80 to 80 parts by weight of butyl rubber.
20% by weight and a rubber polymer having a rubber hardness of 75 to 95 degrees. The invention according to claim 3, wherein the carcass 2 is a non-air An insulation rubber 5 having excellent adhesion is disposed between the inner liner 3 and a rubber having high permeability and low air permeability, and the inner rising portion 4a of the rubber chafer 4 is provided on the inner surface of the tire cavity. The insulation rubber 5 without contacting the inner liner 3
The invention is characterized in that the insulation rubber 5 is made of natural rubber.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows, for example, trucks, buses,
In addition, a heavy-duty pneumatic tire (hereinafter referred to as a tire) 1 used for these similar vehicles,
t is a meridional section of the bead portion B in a standard state where the bead portion B is mounted on a deep 5 ° taper rim J inclined at an angle α of 5 ° with respect to the tire axial direction and filled with normal internal pressure. In this embodiment, the tire 1 is configured as a tube type using a tube TB.

In this specification, the "regular rim" is a standard rim defined by JATMA and defined by TRA.
"Design Rim" or "Measur" specified by ETRTO
ing Rim ", and" normal internal pressure "is the maximum air pressure specified in JATMA, TRA table" TI
RE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE
S "or" INF specified by ETRTO "
LATION PRESSURE ".

In the present embodiment, the tire 1 includes a carcass main body portion 2a passing through the bead core 8 in the tire axial direction from the tread portion through the sidewall portion (both not shown), and the bead core 8 The carcass 2 includes a carcass turn-over portion 2b which is continuous with the carcass main body portion 2a through a radially inner portion of the bead core 8 and is turned back outward in the tire axial direction of the bead core 8.

The carcass 2 has a radial structure in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire equator. In this embodiment, the carcass 2 is composed of one carcass ply using a steel cord. A non-metallic cord such as an organic fiber cord such as nylon, rayon, polyester, or aromatic polyamide may be used, and a steel cord or the like (not shown) may be provided inside the tread portion and outside the carcass 2 in the radial direction. A plurality of well-known belt plies are arranged to strongly reinforce the tread portion. In this example, the bead core 8 has a substantially hexagonal cross section formed by spirally winding a steel wire in multiple stages, and a radially outermost substantially horizontal outermost side 8f is formed into an innermost innermost side 8d. The width is larger than that.

A space between the carcass main body portion 2 and the carcass turn-over portion 2b is filled with a bead apex 6 which extends in a radially outward direction from the surface of the bead core 8 toward the tire radial direction. Bead Apex 6 has a rubber hardness of 65 to 98 °, more preferably 70 to 98 °.
A high hardness apex portion 6a using a rubber of ~ 95 °,
Rubber hardness of 30 to 70 °, more preferably 40 to 60 °
And a low hardness apex portion 6b using rubber. In this specification, "rubber hardness" is defined as JIS
-Means durometer A hardness measured by durometer type A based on K6253.

As described above, the high hardness apex portion 6a extends from the surface facing the outside of the bead core 8, and in the present embodiment, the outermost end 8 which is the horizontal outermost side 8f.
The outer surface in the tire axial direction is bent starting from the vicinity of the height position of f1 and has a vertically long triangular cross section in which the thickness gradually decreases outward in the tire radial direction. The low hardness apex portion 6b extends radially outward from the starting point in contact with the tire axial direction outer surface of the high hardness apex portion 6a at the tire radial outer end of the high hardness apex portion 6b. The cross section has a substantially crescent shape having a lower portion having a maximum thickness and an upper portion connected to the lower portion and extending outward in the tire radial direction while gradually reducing the thickness, and the bead apex 6 has a tapered triangular shape as a whole. Take the form of a shape.

In the bead portion B of the tire 1, a bead reinforcing layer 7 using a steel cord ply located outside the carcass 2 and passing inward in the radial direction of the bead core 8 is disposed inside the carcass body portion 2a. An inner liner 3, which forms a lumen surface s, an insulation rubber 5 interposed between the inner liner 3 and the carcass body 2a, and a chafer 4 are arranged.

The inner liner 3 is made of a non-air-permeable or low-air-permeable rubber such as butyl rubber, halogenated butyl rubber, brominated butyl rubber, chlorinated butyl rubber, and the like. Bead toe T of bead part 1 through sidewall part
Is formed in a toroidal shape that forms the tire inner cavity surface s up to the innermost end 3e in the tire radial direction.

The bead reinforcing layer 7 can employ a steel cord having a cord size substantially equal to that of the carcass cord, and is inclined at an angle of 15 to 45 degrees, preferably 20 to 35 degrees with respect to the tire radial direction. And the number of shots per 5 cm is 15 to 50, preferably 20 to 40
A steel ply with a certain degree is used. Further, a winding portion 7a which rises inward in the tire axial direction along the carcass main body portion 2a along the tire radial direction inside of the bead core 8 and a winding portion 7b which rises outward in the tire axial direction of the carcass folded portion 2b. And covers the outside of the carcass 2 in that range.

In this embodiment, the height h7b of the upper end of the winding portion 7b of the bead reinforcing layer 7 from the bead base line BL.
Is not more than the height h2b of the upper end of the carcass folded portion 2b and larger than the height hj of the rim flange JS, and the height h2b of the upper end of the carcass folded portion 2b is usually larger than the height of the tire maximum width position. Small. In addition, the bead base line BL is a straight line extending in parallel with the tire axis used when defining the rim diameter in each standard, passes through the intersection Q of the inner surface line of the rim flange Js and each extension line of the rim sheet Jt, This is a straight line drawn parallel to the tire axis.

The height h7a of the upper end 7e of the winding portion 7a of the bead reinforcing layer 7 from the bead base line BL is set to ± 5 mm of the height h8 of the outermost end 8f1 of the bead core 8.
Set to the range. That is, (h8-5mm) ≦ h7a ≦
(H8 + 5 mm) is satisfied. In addition, the winding part 7
a height h7a is 5 mm from the h8 of the bead core 8.
Is smaller (h7a <h8-5 mm), that is, the upper end (7) of the winding portion 7a of the bead reinforcing layer 7 is smaller.
e) is located more inward in the tire radial direction than the above requirements, it is difficult to ensure the rubber thickness of the portion for the above reasons, and the position of the bead reinforcing layer 7 during molding and vulcanization as described above Easy to become unstable. H7a> h8 + 5
mm is unnecessary, and the weight reduction effect is reduced. Therefore, by adopting the above-described configuration, the winding portion 7a of the bead reinforcing layer 7 is arranged in a suitable region inside the bead core 8 in the tire axial direction. As a result, displacement can be prevented by pressing during vulcanization molding, and the shortage of the thickness can be suppressed by arranging the winding portion 7a which is arranged in the tire axially inner portion of the bead core 2 where the rubber thickness is most likely to decrease. .

The insulation rubber 5 is interposed between the inner liner 3 and the carcass main body 2a to prevent direct contact with the carcass main body 2a, thereby improving the bonding of the inner liner 3 and preventing peeling. In addition, the insulation rubber 5 has a required thickness, and the insulation rubber 5 extends beyond the inner end 3e of the inner liner 3 inward in the radial direction and extends to a middle position of the bead core 8 in the tire axial direction. By this, the bead reinforcing layer 7 is covered in a range up to the center of the winding portion 7a and the bead core 8. The insulation rubber 5 is preferably a natural rubber which has excellent adhesion to adjacent rubbers such as the inner liner 3 and the rubber chafer 4 and reduces peeling. Carbon black, oil and resin are used for 100 parts by weight of the natural rubber. And a rubber composition to which other necessary compounding agents are added.

The rubber chafer 4 is disposed inside the bead core 8 in the tire radial direction and has a base 4 c forming a bead bottom surface.
A rising portion 4a connected to the base portion 4c at a bead toe portion on the inner side in the tire axial direction and extending radially outward while forming a tire lumen surface s; and a bead heel portion on the outer side in the axial direction of the base portion 4c, and An outer rising portion 4b is formed, and the extension portion 5A of the insulation rubber 5 is covered on the tire toe portion side, so that the inner rising portion 4a is installed between the tire and the bead reinforcing layer 7. The extension 5A of the ration rubber 5 is interposed. As described above, the rubber chafer 4 made of hard rubber and the bead reinforcing layer 4 generally having poor adhesiveness are not directly contacted with each other, and the peeling at the interface of the rubber chafer 4 is suppressed by interposing the insulation rubber 5. be able to.

The rubber chafer 4 is made of, for example, 20 to 80 parts by weight of natural rubber and 80% by weight of butyl rubber 80 in order to reduce air permeability while suppressing wear caused by contact with the rim J.
A rubber composition in which a compounding agent such as carbon black, an antioxidant, and zinc white is blended with 100 parts by weight of a rubber polymer blended with about 20 parts by weight can be preferably used. The rubber hardness of the rubber chafer 4 is 75 to 95 in order to prevent rubber chipping and large deformation of the bead portion.
Degrees, more preferably 75 to 83 degrees.

The inner rising portion 4a is a relatively thin triangular rubber piece having a reduced thickness and extending radially outward, and has a height h4a of the upper end 4ae from the bead base line BL, The height of the upper end 7e of the winding portion 7a of the bead reinforcing layer 7 from the bead base line BL is equal to or greater than h7a (h4a ≧ h7a). Still more preferably, h4ah
7a.gtoreq.5 mm, and since the rising portion 4a of the rubber chafer 4 is located inward of the upper end 7e of the winding portion 7a of the bead reinforcing layer 7 in the tire axial direction, the rubber thickness of this portion is further increased. Is easily secured.

Further, the height h of the inner rising portion 4a
4a is a rubber chafer 4 made of hard rubber, having a height h3 or less of the inner end 3e of the inner liner 3,
Prevents contact with the inner liner 3 made of butyl rubber, which is usually poor in rubber adhesion, and suppresses rubber peeling that tends to occur at the boundary surface when the rubber chafer 4 and the inner liner 3 come into contact. The height difference (h3−h4a) is set to be larger than 0 and about 5 mm or less to reduce the length of the insulation rubber 5 exposed on the tire inner surface s. Note that the inner rising portion 4a and the inner liner 3 may be separated from each other such that the inner liner 3 and the inner liner 3 are overlapped in the tire axial direction with the insulation rubber 5 interposed therebetween.

On the other hand, a rising portion 4 outside the rubber chafer 4
b is, in the standard state, an exposed point P0 on the radially outer side from a separation point P1 separated from the rim flange Js.
Exposure in the range. Thereby, it is possible to reinforce the bead portion 1 and effectively prevent wear due to contact with the flange due to the fall of the bead portion 1 during use. On the radially outer side of the exposure point P0, the outer rising portion 4b is reduced in thickness on the outer side in the tire axial direction of the carcass folded portion 2b and extends outward in the tire radial direction,
A sidewall rubber 10 having a rubber hardness smaller than that of the rubber chafer 4 is arranged outside the rubber chafer 4.

In the tire 1, for example, the outer portion extending beyond the upper end of the bead apex 6 between the outer winding portion 7 b of the bead reinforcing layer 7 and the rising portion 4 b outside the rubber chafer 4. Buffer rubber 12, intermediate buffer rubber 13 extending between the wound portion 7b of the bead reinforcing layer 7 and the carcass folded portion 2b and covering the upper end of the wound portion 7b, the carcass folded portion 2b and the bead apex 6 A suitable rubber layer capable of reducing the stress concentration at each ply end, reducing the difference in rubber hardness between adjacent rubbers, and reducing the shearing force, such as the buffer rubber 14 located between and extending upward, A ply layer can also be provided. Further, the tire of the present invention can be adopted for passenger cars, light trucks, and the like, and can also be used as a tire for a 15-degree taper rim.

[0031]

EXAMPLES Five types including the present invention were experimentally manufactured, and the rubber thickness near the bead core and the durability were evaluated. Table 1 shows the results.

[0032]

[Table 1]

In Table 1, the cord density means the number of cords within 5 cm in the direction of the ply plane perpendicular to the cords, the carcass cord density is a measured value on the tire equatorial plane, and the cord density of the bead reinforcing layer is And measured values at the lower part of the bead core.

The conditions of the indoor durability test are as follows. Internal pressure: 700 KPa Load: 29.59 KN Speed: 20 km / h Evaluation method of the results: For each tire in Table 1, the rubber compounded in Table 2 was used. Comparative Example 5 is a conventional tire.

[0035]

[Table 2]

As is clear from the test results, the tires of the examples maintain the thickness of the rubber inside the bead core in the tire axial direction while achieving weight reduction. Therefore, in the indoor durability test for evaluating the durability of the bead portion, the same durability as Comparative Example 5 showing the conventional product was exhibited.

[0037]

As described above, the tire of the present invention can be reduced in weight without decreasing the durability of the bead by reducing the decrease in the rubber thickness of the bead core inside the tire in the axial direction.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a bead portion of a heavy-duty pneumatic tire according to an embodiment of the present invention in an enlarged manner.

FIG. 2 is an enlarged sectional view showing the vicinity of a bead portion of a conventional tire in an enlarged manner.

[Explanation of symbols]

 B Bead portion 2 Carcass 3 Inner liner 4 Rubber chafer 4a Rising portion inside 4b Rising portion outside 4c Base 5 Insulation rubber 6 Bead apex 7 Bead reinforcement layer 7a Roll-in portion 7b Roll-up portion 8 Bead core

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 15/06 B60C 15/06 G

Claims (4)

[Claims] 1. A carcass (2) which is folded back from a tread portion via a sidewall portion and is locked by a bead core (8) of a bead portion, and a carcass (2) passing radially inside of the bead core (8) in a tire radial direction. ) And a bead reinforcing layer (7) made of a cord ply having a winding portion (7a) rising up inward in the tire axial direction and a winding portion (7b) rising up outward in the tire axial direction of the carcass (2). And a base (4c) located on the bead core (8) radially inward of the bead core (8) and forming a bead bottom surface,
A rising portion (4a) which is connected to the base portion (4c) at a bead toe portion and extends radially outward from the tire cavity surface, and an outer portion which is connected to the base portion (4c) at a bead heel portion and extends radially outward on the tire outer surface side. In a standard state in which a rubber chafer (4) made of hard rubber having a rising portion (4b) having a predetermined internal pressure is incorporated into a normal rim J and filled with a normal internal pressure, the inner rising portion from the bead baseline BL ( 4a) height h4a and the bead reinforcing layer (7)
The height h7a of the winding portion (7a) and the height h8 of the outermost end of the bead core (8) have the following relationship. h8-5 mm ≦ h7a ≦ h8 + 5 mm h7a ≦ h4a 2. The rubber chafer (4) comprises a natural rubber 2
A rubber polymer blended with 0 to 80 parts by weight and 80 to 20 parts by weight of butyl rubber, and having a rubber hardness of 75 to 95.
2. The pneumatic tire according to claim 1, wherein the degree is a degree. 3. An insulation excellent in adhesion between the carcass (2) and an inner liner (3) made of a non-air-permeable, low-air-permeable rubber disposed on the inner surface of the tire cavity. A rubber (5) is arranged, and the inner rising portion (4a) of the rubber chafer (4) is arranged.
The pneumatic device according to claim 1 or 2, wherein the pneumatic tire is adjacent to the inner liner (3) via the insulation rubber (5) without contacting the inner liner (3) disposed on the inner surface of the tire. tire. 4. The pneumatic tire according to claim 3, wherein said insulation rubber (5) is made of natural rubber.