JP4950592B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy-duty tire capable of suppressing chafer rubber peeling damage at a bead toe portion when a rim is attached or detached while suppressing poor air entry in the bead portion.

  In heavy-duty tires for trucks and buses used under severe conditions such as high loads and high internal pressures, large repeated deformations act on the bead part, so that damage tends to concentrate on the bead part. Therefore, conventionally, as shown in FIG. 3, the bead portion a is provided with a bead reinforcement layer d made of a steel cord ply that wraps around the bead core b in a U shape via a carcass c, thereby reinforcing the bead portion a. ing.

  Reference numeral e in the figure denotes a chafer rubber for preventing rim displacement, and a rising portion e2 extending radially outward from the bead toe portion is slightly increased on the tire cavity surface side of the base portion e1 exposed at the bottom surface of the bead. That's it! The rising portion e2 covers and protects the radially inner portion of the inner liner f made of air-impermeable rubber, and prevents the inner liner f from being damaged by rubbing against the rim flange when the rim is attached or detached. .

JP 2001-10312 A

  However, in the conventional bead structure, since the bead reinforcement layer d is formed of a steel cord ply having a high bending rigidity, a strong bending return force is generated in the bead reinforcement layer d bent in a U shape. Therefore, there is a problem in that when the raw tire is formed, the inner piece d1 of the bead reinforcing layer d on the inner side in the tire axial direction is separated from the carcass c and a defective air is generated in this portion. Since the outer piece d2 of the bead reinforcing layer d is covered and restrained by the rising portion e3 outside the chafer rubber e having a large rubber thickness, the outer piece d2 is covered with the inner piece d1 covered by the thin inner liner f. Separation occurs.

  In view of such a situation, as a result of the study by the present inventor, it is possible to reduce the bending return force by deleting the inner piece d1 and making the bead reinforcement layer d L-shaped. It was found that it can be suppressed. However, as a result of further research by the present inventor, when the inner piece d1 is deleted, the deformation of the bead toe portion at the time when the bead toe portion at the rim flange is caught when the rim is attached / detached becomes large. As a result, it has been found that when the rim is attached / detached, a new problem arises that the rising portion e2 of the chafer rubber e is likely to fall off from the inner liner f having poor adhesion and to be easily peeled off. This peeling becomes more conspicuous as the chafer rubber hardens with running.

  Therefore, the present invention eliminates the inner piece portion of the bead reinforcement layer, and forms the rising portion in the chafer rubber higher than the conventional one, and suppresses poor air entry in the bead portion, while removing and attaching the rim. It is an object of the present invention to provide a heavy duty tire that can suppress peeling damage from the inner liner of the chafer rubber at the bead toe portion.

In order to achieve the above-mentioned object, the invention of claim 1 of the present application relates to a main body part extending from a tread part through a sidewall part to a bead core of a bead part, and a turn-up part that turns around the bead core from the inner side to the outer side in the tire axial direction. A bead apex rubber 8 having a substantially triangular cross section extending radially outward from the bead core, and a tire that is made of air-impermeable rubber and between the carcass provided in series and the main body portion and the folded portion. A heavy-duty tire comprising an inner liner disposed on a lumen surface and a chafer rubber for preventing rim displacement, and a bottom piece along the folded portion passing through a radially inner side of the bead core on the bead portion; And an outer piece portion which is continuous with the bottom piece portion and extends radially outward along the outer side surface of the folded portion in the tire axial direction. The chafer rubber is made of a hard rubber having a rubber hardness Hs1 of 70 to 85, and is located on the radially inner side of the bottom piece and exposed at the bottom of the bead, and is connected to the base. An outer rising portion extending radially outward from the bead heel portion to the tire outer surface side, and extending from the bead toe portion to the tire lumen surface radially outward from the bead toe portion and covering the radially inner portion of the inner liner And a radial height Hp from the bead base line at the radially outer end of the inner rising portion is 0.4 to 2.2 times the flange height Hf of the rim. In the chafer rubber, the radially outer portion of the outer raised portion is the same as the radially inner portion of the sidewall rubber that forms the outer surface of the sidewall portion. It is adjacent to the outer side in the tire axial direction of the wall rubber, the rubber hardness Hs2 of the side wall rubber is set to 50 to 60, and exceeds the outer end in the tire radial direction of the folded portion between the sidewall rubber and the folded portion. An outer cushioning rubber extending outward and having an inner cushioning rubber extending outwardly beyond the outer end in the tire radial direction of the folded portion between the folded portion and the apex rubber. The rubber and the buffer rubber therein are made of softer rubber than the side wall rubber and the apex rubber .

In the invention of claim 2, the bead reinforcing layer is characterized in that the distance Ls in the tire axial direction between the inner end in the tire axial direction and the bead toe end of the bottom piece is in the range of 3 to 10 mm. The

  In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified when the bead part is held in accordance with the rim width defined by the tire size in a non-rim assembled state. . The “bead baseline” is defined as a tire axial line passing through a rim diameter position determined by a standard based on a tire. The rubber hardness Hs is a durometer A hardness measured with a durometer type A based on JIS-K6253.

  In the present invention, as described above, the bead reinforcement layer is formed of a bottom piece and an outer piece, and is formed in an L shape in which a conventional inner piece is omitted. Therefore, the bending return force of the bead reinforcing layer can be reduced, and poor air entry in the bead portion can be suppressed. Further, in the chafer rubber, the height in the radial direction of the rising portion is set to 0.4 to 2.2 times the flange height Hf of the rim, which is higher than the conventional one. As a result, it is possible to increase the bonding area itself with the inner liner, prevent friction between the outer end of the inner rising portion and the rim flange, and prevent peeling damage of the inner rising portion when the rim is attached / detached. Become.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a heavy load tire according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing a bead portion thereof.
As shown in FIG. 1, the heavy load tire 1 of the present embodiment is composed of a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4 and an air-impermeable rubber, and inside the tire. An inner liner 10 disposed on the cavity surface and a chafer rubber 12 made of hard rubber and disposed on the bead portion 4 for preventing rim displacement are provided.

  The carcass 6 is provided with one or more, in this example, one sheet of folded-back portions 6b that fold around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the body part 6a straddling the bead cores 5 and 5. It is formed from the carcass ply 6A. The carcass ply 6A has a so-called radial structure in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction, and the carcass cord is an organic fiber cord such as nylon, rayon, polyester, aromatic polyamide, or the like. A steel cord is preferably used.

  A belt layer 7 made of two or more belt plies using steel cords as belt cords is disposed outside the main body portion 6a of the carcass 6 and inside the tread portion 2. As this belt layer 7, in this example, the innermost belt ply 7A in which belt cords are arranged at an angle of, for example, about 60 ± 10 ° with respect to the tire circumferential direction, and a small angle of 30 ° or less with respect to the tire circumferential direction. The belt plies 7B, 7C, and 7D arranged in (4) are illustrated as an example. The belt layer 7 enhances the belt rigidity by providing one or more locations where the belt cords cross each other between the plies, and strongly reinforces almost the entire width of the tread portion 2.

  A bead apex rubber 8 having a substantially triangular cross section extending radially outward from the bead core 5 is disposed between the main body portion 6a and the folded portion 6b of the carcass 6, and the bead portion 4 includes: A bead reinforcing layer 9 having a substantially L-shaped cross section is provided to cover the folded portion 6b. The bead core 5 has, for example, a ring shape formed by winding a bead wire made of steel. In this example, the bead core 5 has a flat hexagonal shape with a horizontally long cross section, and its radially inner surface extends along the bead bottom surface 4S. This increases the fitting force with the rim over a wide range.

  The bead apex rubber 8 includes a radially inward apex portion 8a having a small triangular shape with a slope S1 inclined inward in the tire axial direction outward in the tire radial direction, and outward in the tire radial direction from the slope S1. It has a two-layer structure consisting of a radially outward apex portion 8b. The inner apex portion 8a is made of a hard rubber having a rubber hardness Hs of 80 to 95, and the outer apex portion 8b is made of a soft rubber having a rubber hardness of 50 to 70. And by setting the radial height Ha from the bead base line BL of the inner apex portion 8a to be in the range of 40 to 60% of the total height H0 of the bead apex rubber 8, the ride comfort and the handling stability can be improved. Higher order is compatible. Also, when the tire is deformed, the compressive stress acting on the outer end of the folded portion 6b of the carcass 6 is relaxed by the soft outer apex portion 8b to suppress damage.

  The bead reinforcing layer 9 is made of a steel cord ply in which reinforcing cords, which are steel cords, are arranged at an angle of, for example, 15 to 60 ° with respect to the tire circumferential direction, and the bead portion 4 is formed in cooperation with the bead apex rubber 8. Reinforce and improve bead durability and handling stability. As shown in FIG. 2, the bead reinforcing layer 9 includes a bottom piece 9A passing through the inner side in the radial direction of the bead core 5 and along the carcass folded portion 6b, and a tire shaft of the carcass folded portion 6b connected to the bottom piece 9A. It is formed in a substantially L shape comprising an outer piece portion 9B extending radially outward along the outer side surface in the direction. In the bead reinforcement layer 9, when the rim is assembled, the bottom piece 9A is sandwiched between the bead core 5 and the rim sheet Rs (shown in FIG. 1), thereby ensuring a high fitting force with the rim R. Therefore, in this example, the case where the bottom piece 9 </ b> A has a linear shape substantially parallel to the inner surface in the radial direction of the bead core 5 is illustrated. Further, in the bead reinforcement layer 9, the bottom piece 9A has an L-shaped cross-section cut off under the bead core, so that the bending return force of the bead reinforcement layer 9 can be reduced, and poor air entry during tire formation can be prevented. Can do.

  Here, the radial height h1 of the outer piece portion 9B from the bead base line BL is preferably smaller than the radial height h2 of the carcass folded portion 6b and in a range of 15 to 40 mm. If this range is exceeded, the compressive stress acting on the outer end of the outer piece portion 9B becomes large when the tire is deformed, and damage starting from this outer end is likely to occur. On the other hand, below the above range, the reinforcing effect by the bead reinforcing layer 9 becomes insufficient. Further, it is preferable to secure the difference h2-h1 between the heights h1 and h2 to be 5 mm or more, more preferably 8 mm or more in order to alleviate the stress concentration.

  Next, an inner liner 10 that forms substantially the entire tire cavity surface is disposed on the inner side of the main body 6 a of the carcass 6 via a second insulation rubber layer 11.

  The inner liner 10 is made of air impermeable rubber such as butyl rubber in which 80 parts by mass or more of butyl rubber (or a derivative thereof) is blended in 100 parts by mass of a rubber component, for example, 1.0 to 2.0 mm. It has a rubber thickness and extends between the bead portions 4 and 4 continuously. In butyl rubber, diene rubber such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene / butadiene rubber (SBR) is used as the remaining rubber other than butyl rubber (or its derivative). Examples of butyl rubber derivatives include halogenated butyl rubbers such as chlorinated butyl rubber and brominated butyl rubber. As the air-impermeable rubber, a halide of isobutylene / paramethylstyrene copolymer may be used instead of the butyl rubber (or a derivative thereof).

  In the inner liner 10, the radially inner portion terminates radially inward from the bead base line BL. As a result, moisture and the like contained in the filling air in the tire lumen are prevented from entering the bead portion 4.

  The second insulation rubber layer 11 is interposed between the inner liner 10 and the carcass 6 to increase the adhesive force between the two to prevent delamination and to prevent the rubber flow during vulcanization molding. The resulting contact between the inner liner 10 and the carcass cord is suppressed. Therefore, it is important for the second insulation rubber layer 11 to have excellent adhesiveness. In this example, for example, 70 parts by mass or more of natural rubber (NR) is blended in 100 parts by mass of the rubber component. NR rubber is used. Note that isoprene rubber (IR) or butadiene rubber (BR) can be suitably used as the remaining rubber.

  The second insulation rubber layer 11 extends inward and outward in the radial direction in contact with the inner liner 10 over the entire length of the inner liner 10, and the radially inner end thereof is a bottom piece in the bead reinforcing layer 9. It terminates at a substantially linear lower surface 11S connected to the inner end of the portion 9A in the tire axial direction. In this example, the lower surface 11S is substantially parallel to the inner surface in the radial direction of the bead core 5.

  Next, the chafer rubber 12 is located on the inner side in the radial direction of the bottom piece 9A and exposed at the bead bottom surface 4S, and extends from the bead heel portion Bh to the tire outer surface side radially outward from the base portion 12A. It has an outer rising portion 12B, and an inner rising portion 12C that extends from the bead toe portion Bt and extends radially outward in the radial direction from the bead toe portion Bt.

  The outer rising portion 12B is exposed to the outer surface of the tire at least in a flange contact area that contacts the rim flange, and cooperates with the base portion 12A exposed on the entire surface of the bead bottom surface 4S to prevent rim displacement during running. To do.

  The inner rising portion 12C covers the radially inner portion of the inner liner 10, and prevents the inner radial portion of the inner liner 10 from being directly rubbed and damaged when the rim is attached or detached. . Here, the chafer rubber 12 is formed of a hard rubber having a rubber hardness Hs in the range of 70 to 90 in order to prevent rubber chipping, rubber crushing due to compression, wear damage, and the like. At this time, as a rubber component, a blend rubber in which 20 to 60 parts by mass of natural rubber (NR) and 80 to 40 parts by mass of butadiene rubber (BR) are blended in 100 parts by mass of the rubber component is wear resistant. From the viewpoints of impact resilience, aging resistance, etc., it can be suitably employed.

  However, when the bottom piece 9A of the bead reinforcing layer 9 is interrupted under the bead core, the rigidity of the bead toe portion Bt is reduced. Therefore, when the bead toe portion Bt is caught on the rim flange Rf when the rim is attached or detached, the bead toe portion Bt is deformed. Becomes larger. Therefore, there arises a problem that the rising portion 12C of the chafer rubber 12 is easily peeled off from the inner liner 10 having poor adhesion.

  Therefore, in the heavy load tire 1 of the present embodiment, the radial height Hp from the bead base line BL at the radially outer end of the inner rising portion 12C is set to 0.4 to 2.2 of the rim flange height Hf. The range is doubled. As a result, the bonding area between the inner rising portion 12C and the inner liner 10 is increased, and the outer end position of the inner rising portion 12C is increased to reduce friction with the rim flange at the outer end. It becomes possible to prevent peeling damage. When the ratio Hp / Hf between the height Hp and the rim flange height Hf is less than 0.4, the peeling suppressing effect is insufficient. On the other hand, if it exceeds 2.2, the edge of the chafer rubber 12 becomes a region having a large deflection, and there is a problem that the chafer rubber 12 is peeled off. Therefore, the lower limit of the ratio Hp / Hf is preferably 0.5 or more, more preferably 0.7 or more, and the upper limit is preferably 1.8 or less, more preferably 1.5 or less.

  When the bottom piece 9A of the bead reinforcing layer 9 is cut off under the bead core, the inner liner 10 extends downwardly beyond the bead base line BL in the radial direction, but the filled air in the tire lumen is filled. There is also a possibility that moisture or the like contained in the water enters from the inner end in the tire axial direction of the bottom piece 9A and causes corrosion of the reinforcing cord or damage such as cord loose. Therefore, in this example, the distance Ls in the tire axial direction between the inner end in the tire axial direction of the bottom piece 9A and the bead toe end is restricted to a range of 3 to 10 mm. If it is less than 3 mm, the corrosion damage of the reinforcing cord cannot be sufficiently suppressed. On the other hand, if it exceeds 10 mm, moisture or the like may enter the carcass 6 to cause corrosion damage of the carcass cord, and the fitting force with the rim R may be reduced.

  When the bottom piece 9A of the bead reinforcement layer 9 is interrupted under the bead core, the bead rigidity is lower than that of a U-shaped conventional bead reinforcement layer. Therefore, the stress acting on each outer end of the bottom piece portion 9A in the carcass folded portion 6b and the bead reinforcing layer 9 is increased, and there is a tendency to cause damage.

  Therefore, in this example, the sidewall rubber 3G forming the outer surface of the sidewall portion 3 is a soft rubber having a rubber hardness Hs of 50 to 60, and the radially outer portion 12Be of the outer rising portion 12B is The sidewall rubber 3G is adjacent to the radially inner portion 3Ge on the outer side in the tire axial direction. That is, contrary to the prior art, the inner portion 3Ge of the sidewall rubber 3G is disposed on the inner side in the tire axial direction of the boundary surface S2, and the outer portion 12Be of the chafer rubber 12 is disposed on the outer side in the tire axial direction of the boundary surface S2. It is arranged. For convenience, this structure is called chafer rubber over sidewall rubber (COS), and the conventional structure is called sidewall rubber over chafer rubber (SOC). In this COS structure, the radially inner end point of the boundary surface S2 is positioned on the outer piece portion 9B of the bead reinforcing layer 9. Accordingly, the outer ends of the carcass folded portion 6b and the outer piece portion 9B can be covered with the soft sidewall rubber 3G, respectively, and the stress acting on each outer end can be relaxed and the damage can be suppressed. .

In the present invention, between the side wall rubber 3G and the carcass folding portion 6b, the outer buffer rubber 23 extending beyond the outer end of the carcass folding portion 6b, and the carcass folding portion 6b and the outer apex portion 8b. Between the two, a shock absorbing rubber 24 that extends beyond the outer end of the carcass folding portion 6b is disposed. The buffer rubbers 23 and 24 are made of a softer rubber than the side wall rubber 3G and the outer apex portion 8b, and cover and protect the outer end of the carcass folded portion 6b to prevent the damage.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A heavy duty tire having a tire size of 10R22.5 having the tire structure shown in FIG. 1 is manufactured according to the specifications shown in Table 1, bead durability of each sample tire, chafer rubber peelability when the rim is attached and detached, and a bead portion when the tire is formed. The rate of occurrence of defective air entry was measured and compared with each other. In each sample tire, the tire cross-section height is 223 mm, the rim flange height Hf is 12.7 mm, the chafer rubber has a rubber hardness of 75, and the side wall rubber has a rubber hardness of 53, which are substantially the same.

(1) Bead durability:
Using a drum testing machine, running on the drum at a speed of 20 km / h under the conditions of a rim (22.5 × 7.50), internal pressure (725 kPa), and longitudinal load (47.4 kN: twice the standard load) The running time until the bead portion was damaged was measured. The evaluation was expressed as an index with the traveling time of Comparative Example 1 as 100. The larger the value, the better.

(2) Separability of chafer rubber when rim is attached / detached:
For tires after running 15,000 km on a drum at a speed of 80 km / h under the conditions of rim (22.5 × 7.50), internal pressure (725 kPa), and longitudinal load (23.7 kN) A rim removal test was conducted using a hydraulic tire changer to inspect the chafe rubber at the bead toe portion.

(3) Air entry failure:
The rate of occurrence of poor air entry at the bead portion during tire formation was displayed as an index with Comparative Example 1 taken as 100. The smaller the value, the fewer defects and the better.

It is sectional drawing of the tire of one Example of this invention. It is sectional drawing which expands and shows the bead part. It is sectional drawing which expands and shows the conventional bead structure.

Explanation of symbols

2 Tread portion 3 Side wall portion 3G Side wall rubber 4 Bead portion 4S Bead bottom surface 5 Bead core 6 Carcass 6a Main body portion 6b Folded portion 9 Bead reinforcement layer 9A Bottom piece portion 9B Outer piece portion 10 Inner liner 12 Chafer rubber 12A Base portion 12B Standing outside Raised part 12h in raised part Bh Bead heel part Bt Bead toe part BL Bead base line

Claims (2)

A carcass provided with a series of turn-up portions that turn back the bead core from the inner side to the outer side in the tire axial direction on the main body portion extending from the tread portion through the sidewall portion to the bead core of the bead portion,
A bead apex rubber having a substantially triangular cross section extending radially outward from the bead core between the main body portion and the folded portion;
An inner liner made of air-impermeable rubber and disposed on the tire inner surface;
A heavy duty tire comprising a chafer rubber for preventing rim displacement,
From the bead portion, a bottom piece portion that passes along the radially inner side of the bead core and extends along the folded portion, and an outer piece portion that continues to the bottom piece portion and extends radially outward along the outer surface in the tire axial direction of the folded portion. And bead reinforcement layer using steel cord,
The chafer rubber is made of a hard rubber having a rubber hardness Hs1 of 70 to 85. The base portion is located on the radially inner side of the bottom piece portion and exposed at the bottom surface of the bead, and is connected to the base portion from the bead heel portion to the tire outer surface side. An outer rising portion that extends radially outward, and an inner rising portion that extends from the bead toe portion to the tire lumen surface radially outward and covers the radially inner portion of the inner liner. And having
The radial height Hp from the bead base line at the radially outer end of the rising portion is 0.4 to 2.2 times the rim flange height Hf ,
In the chafer rubber, the radially outer portion of the outer rising portion is adjacent to the radially inner portion of the sidewall rubber forming the outer surface of the sidewall portion on the outer side in the tire axial direction of the sidewall rubber. With
The rubber hardness Hs2 of the sidewall rubber is 50-60,
Between the sidewall rubber and the folded portion, comprising an outer shock absorbing rubber extending outward beyond the outer end in the tire radial direction of the folded portion,
And, between the folded portion and the apex rubber, comprising an inner cushion rubber that extends outward beyond the outer end in the tire radial direction of the folded portion,
The outer shock-absorbing rubber and the inner shock-absorbing rubber are made of a softer rubber than the sidewall rubber and the apex rubber . The bead reinforcing layer, the tire axial distance Ls between the axially inner end and the bead toe end of the bottom piece, heavy duty tire according to claim 1, characterized in that a range of 3~10mm .

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