JP4520217B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire. More specifically, the present invention includes a pair of bead cores facing the bead portion in the tire rotation axis direction, and securely holds the carcass ply by sandwiching the end portions of the carcass ply between the bead cores. The present invention relates to a pneumatic radial tire that is locked to and improved the durability of the bead portion.

  The carcass of a pneumatic radial tire has a carcass ply formed by covering a number of parallelly arranged organic fiber cords such as organic fiber cords with topping rubber and cutting them at an angle of approximately 90 ° with respect to the cord direction. The structure shown in FIG. 6 is generally used in which the carcass ply end is wound around the bead core in the bead portion from the inside to the outside of the tire and the carcass ply end is locked to the bead portion.

  In a radial tire having such a conventional winding structure, there is a difference in rigidity in the tire radial direction depending on the presence or absence of the carcass ply at the winding end, and it is easy for the carcass winding end to receive a shear strain due to a load load at the time of rolling the tire, This is the cause of the occurrence of a separation failure with the initiation of adhesive failure at the end of the cord.

In order to solve the problem of the carcass ply winding part, various pneumatic tires having a bead part structure in which the carcass ply end part is sandwiched and locked between a pair of bead cores without winding up the carcass ply are proposed. (For example, Patent Documents 1 and 2).
JP-A-6-171306 JP-A-10-338003

  In the carcass fixing method described in Patent Document 1, the carcass ply does not require a winding part by locking the end of the carcass to the bead core by a shearing force between the bead core and the cord of the carcass ply. However, in the pneumatic tire by the fixing method of the end portion of the carcass ply, since the reciprocating reversal portion of the reciprocating cord is simply sandwiched between the bead cores through the hard rubber, a sufficient carcass ply locking effect cannot be obtained. The carcass cord is likely to be pulled out of the bead core due to the tension during vulcanization molding and the repeated strain during running, and the durability of the bead portion cannot be obtained sufficiently.

  In addition, the bead portion structure based on the technique described in Patent Document 2 has a loop-shaped terminal protruding at the inside of the bead core so as to prevent the carcass end from coming off from the bead core during inflation molding. The cost is increased because equipment and processes for forming a loop-shaped terminal are required. The bead core has a structure in which a flat steel cord having a 1 × N twist structure is wound in a spiral shape in the tire circumferential direction, and the cord has a long diameter side along both ends of the carcass. If only the steel cord is used, the circumscribed circle of the cord cross section is only an ellipse, and even if it is arranged so that the major axis direction of the steel cord is along the surface of the folded portion of the carcass layer, it is sufficient at both ends of the carcass. The locking force cannot be exhibited, the cord may be pulled out during molding, and sufficient bead portion durability cannot be ensured.

  The present invention has been made in view of the above problems of the prior art, and has a bead portion structure in which a carcass ply end portion is sandwiched between a pair of bead cores facing each other in the tire rotation axis direction provided in the bead portion. An object of the present invention is to provide a pneumatic tire excellent in bead portion durability that reliably prevents a cord pull-out phenomenon from a bead core at a carcass ply end portion in a radial tire and eliminates a difference in rigidity and rigidity of the bead portion.

  The pneumatic radial tire of the present invention has a carcass in which carcass plies arranged radially are arranged between a pair of left and right bead portions, and the bead portion includes a pair of bead cores facing in the tire rotation axis direction, and the carcass In a pneumatic radial tire having a ply end sandwiched between the bead cores, the pair of bead cores includes a plurality of bead wires arranged in an innermost layer in a tire radial direction, and the wires are laminated from the inside to the outside to face each other. The surface to be engaged forms an uneven surface, and the end portion of the carcass ply is inserted between the opposing surfaces of the bead core and sandwiched between the uneven surfaces.

In the case of the present invention, the pair of bead cores has N inner wires (N ≧ 2) and outer wires of the innermost core are (N−1), and the outer layers are sequentially arranged. by laminating a bead wire in the N and (N-1) present in the repeating and those configurations.

  As described above, the pair of bead cores provided in the bead portion is an uneven surface in which a plurality of bead wires are arranged on the innermost layer in the tire radial direction and the wires are laminated from the inside to the outside, and the opposing surfaces of the bead cores mesh with each other. As a result, the end of the carcass ply is sandwiched so as to engage in a zigzag manner between the concave and convex surfaces on the opposite surface of the bead core, and the end of the carcass ply is securely locked between the bead cores to form tires and This prevents the displacement of the carcass cord and the pulling phenomenon during the sulfur molding process or traveling, and ensures the strength of the bead portion. Moreover, the problem of the rigidity difference of the bead part which arises by the winding structure of a carcass ply can be eliminated, and bead part durability can be improved.

  The bead core has a plurality of bead wires arranged in the innermost layer in the tire radial direction, the number of wires in the innermost layer of the core is N (N ≧ 2), and the number of wires in the outermost layer of the innermost layer of the core is (N−1) As the outer layer is composed of N and (N-1) repeats sequentially, (N-1) wires fall into the valleys of the N wires to form an uneven surface on the core facing surface. In addition, the core shape can be stabilized and the locking force by the engagement of the end portions of the carcass ply can be increased to improve the effect of preventing the cord drawing phenomenon.

  In the present invention, the bead wire is made of a steel wire subjected to a plating process, a steel cord twisted with a steel element wire, or an organic fiber cord impregnated with a resin to ensure the rigidity of the bead core, and the end of the carcass ply The zigzag engagement of the portions can be facilitated and the locking effect can be improved.

  The bead core is formed by sequentially laminating one bead wire sequentially from the inner side to the outer side in the tire radial direction, thereby facilitating the manufacture of the bead core and improving the manufacturing efficiency and stabilizing the cross-sectional shape. A bead core is obtained.

  According to the pneumatic radial tire of the present invention, the end of the carcass ply is sandwiched between the bead cores facing each other in a zigzag manner, and the end of the carcass ply is locked, thereby securely securing the bead core. It is possible to provide a pneumatic tire excellent in bead portion durability by preventing the cord from being pulled out and eliminating the difference in rigidity between the bead portion and the rolled-up portion.

  Embodiments of the present invention will be described below based on examples shown in the drawings.

  FIG. 1 is a sectional view showing a pneumatic radial tire (hereinafter referred to as a radial tire) T for a passenger car according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a bead portion of the radial tire T shown in FIG. FIG. 3 is a cross-sectional view of the bead core 2.

  A radial tire T according to the present invention includes a tread portion 6, a sidewall portion 7, and a bead portion 1 as shown in the figure, and a carcass ply 3 arranged in a radial code is arranged between a pair of left and right bead portions 1 and 1. A bead core 2 is embedded in the bead portion 1, and a bead filler 5 made of hard rubber is provided on the outer periphery of the bead core 2. Further, on the outer side of the carcass 4 in the tread portion 6, a two-layer belt 8 in which steel cords are arranged is arranged in an annular shape over the tire circumference.

  The carcass ply 3 is made of an organic fiber cord such as polyester, nylon, rayon, or aramid, or a steel cord, and a cord arranged at a predetermined density is covered with a topping rubber, and is cut and used at a predetermined angle. The belt 8 is composed of a belt ply made of a rigid cord such as two steel cords laminated so as to intersect the tire equator C at a small angle (for example, 15 to 35 °), and the carcass 4 is fastened with a tread. The rigidity of the part 6 is increased to ensure steering stability and low rolling resistance.

  The bead core 2 embedded in the bead portion 1 includes a pair of annular bead cores 2a and 2b facing each other in the tire rotation axis direction, and the end portion 3a of the carcass ply 3 is locked between the facing bead cores 2a and 2b. A carcass ply 3 is mounted between the left and right bead portions 1 and 1 to form a carcass 4 of the radial tire T.

  The pair of bead cores 2a and 2b are formed by sequentially laminating bead wires W from the inner side to the outer side in the tire radial direction, and the number of wires in the innermost layer of each of the cores 2a and 2b is N (in the case of the figure). 2), the outermost layer of the core innermost layer is (N-1) (one in the case of the figure), and the outer layer is configured by repeating N and (N-1) sequentially. Yes.

  Due to the configuration of the bead cores 2a and 2b, the N-layers adjacent to the opposite surfaces of the bead cores 2a and 2b by laminating the bead wires W around the entire circumference of the bead cores 2a and 2b (N-1) ) Irregular surfaces 21 and 22 having a plurality of irregularities meshing with each other are formed between the layers.

  Then, the carcass ply end portion 3a is inserted between the bead cores 2a and 2b and sandwiched so as to be engaged between the concave and convex surfaces 21 and 22, so that the carcass ply end portion 3a follows the concave and convex portions of the concave and convex surfaces 21 and 22. The carcass ply end portion 3a is securely locked between the bead cores 2a and 2b so that the carcass cord is displaced or pulled out during the tire molding or vulcanization molding process or running. The phenomenon can be prevented.

  The uneven step (distance between the bottom of the recess and the top of the protrusion) formed on the uneven surfaces 21 and 22 is the thickness of the carcass ply 3 in order to strengthen the locking of the carcass ply end 3a. Although it depends on the flexibility, it is at least 0.3 mm or more, preferably 0.4 mm or more.

  In the pair of bead cores 2a and 2b, a plurality of N bead wires are arranged in the innermost layer in the tire radial direction, and the number of wires in the outermost layer of the innermost layer of the core is (N-1), and the outer layers are sequentially N and (N-1) It is configured by repeating this, that is, by securing the wire volume of the innermost layer that is the foundation of the core, the lamination process of the wires W is stabilized and the core shape is kept good, and at the time of tire molding, Prevents deformation of the bead core in the vulcanization molding process, maintains the locking strength of the carcass ply end portion 3a and the bead portion shape, thereby improving the bead portion durability and improving the fit with the rim. Safety can be ensured.

  In the radial tire of the present invention, since the carcass ply end portion 3a is sandwiched between the left and right bead cores 2a and 2b, the carcass ply 3 can be positioned substantially at the center of the bead portion 1 in the thickness direction. As a result, the carcass ply 3 can be disposed near the center of bending in the bead portion 1, and bending distortion during traveling can be reduced and durability can be further improved.

  In order to sandwich the carcass ply end portion 3a, for example, in the primary molding of the radial tire T, the carcass ply end portion 3a is disposed so as to be sandwiched between the bead cores 2a and 2b, and the bead cores 2a and 2b are crimped together. The carcass ply end portion 3a is tightly locked by being zigzag-engaged and sandwiched between the concave and convex surfaces 21 and 22, and the position of the carcass cord during the green tire expansion or vulcanization process in the secondary molding Deviation and pull-out can be prevented.

  Here, the end portion 3b of the carcass ply securely holds the carcass ply end portion 3a, and the inner peripheral surfaces of the left and right bead cores 2a and 2b in order to prevent air accumulation in the bead core 2 during tire vulcanization. It is preferable to make it protrude more. This protrusion length depends on the tire type and size, but is set to about 0.5 to 5 mm, preferably 1 to 3 mm.

  In the radial tire T of the present invention, as a result of the structure of the bead portion 1 being configured as described above, the opposing bead cores 2a and 2b are sandwiched and engaged firmly so as to engage the carcass ply end portion 3a in a zigzag shape. The resistance to pulling out of the carcass ply 3 is greatly improved, the strength of the bead part 1 is sufficiently secured, and the rigidity difference of the bead part 1 due to the winding of the conventional carcass ply 3 is eliminated, and the adhesive end breakage of the cord end part As a result, it is possible to significantly improve the durability deterioration caused by the above-described problem, and the reinforcing layer 9 (see FIG. 6) for reducing the difference in rigidity that has been conventionally disposed near the carcass ply terminal can be omitted.

  Further, by optimizing the wire configuration of the bead cores 2a and 2b, that is, the N number and the number of laminated layers, the strength ensuring and the rigidity difference required by the bead part 1 can be eliminated, and the durability of the bead part 1 can be improved. The bead structure can be designed more easily, and the bead portion structure suitable for the tire size and application can be easily designed.

  In the present invention, as the bead wires W constituting the bead cores 2a and 2b, steel wires subjected to plating treatment, steel cords obtained by twisting steel strands, or organic fiber cords impregnated with a resin can be used.

  In the case of a steel wire, a bead wire made of a normal hard steel wire having a wire diameter of about 0.8 to 2.0 mm, which has been used in the past, is exemplified, and a wire subjected to bronze plating is exemplified.

  For steel cords, single strand cords such as 1x3-6 structure, 2 + 6, 3 + 8 structure, or 3 + 9 + 15 structure, made by twisting steel wires with a wire diameter of 0.15 to 0.5mm that have been plated with brass Steel cords such as a multi-layer twisted cord.

  Moreover, as the organic fiber cord impregnated with resin, nylon, polyester, and aramid fiber cords having a total fineness of about 3,000 to 10,000 dtex are impregnated with a curable resin having adhesiveness with rubber such as RFL resin. Are illustrated.

  These bead wires W have the advantages of rigidity and high productivity for steel wires, the advantages of steel cords such as easy adjustment of rigidity and elasticity due to the cord structure and improved detachability to the rim, and light weight for organic fiber cords. An advantage of securing the rigidity of the bead core 2 while utilizing the features of each wire such as the merit to the effect and improving the locking effect by the engagement of the carcass ply end portion 3a can be used.

  The bead cores 2a and 2b are preferably formed by a so-called single-strand method in which one bead wire W is sequentially and sequentially laminated from the inner side in the tire radial direction, and the bead cores 2a and 2b are manufactured with increased production efficiency. The bead cores 2a and 2b having a stable cross-sectional shape can be obtained, and the core 2 can be prevented from being deformed during the manufacture of the tire to stabilize the locking strength and the bead portion rigidity of the carcass ply 3, thereby making the bead portion durable. Can be improved.

  Hereinafter, the present invention will be described in more detail based on examples.

  This is a radial ply tire for passenger cars, the size is 175 / 70R13, the overall configuration is in accordance with FIG. 1, the carcass 4 has 1670 dtex / 2 polyester cord (23 piling density at topping / 25 mm), and the belt 8 is 2 + 1. A steel cord having a × 0.27 structure (18 cords / injection density of 25 mm) was standardized for each tire as two plies, a tire was prototyped, the bead portion was evaluated as follows, and the results are shown in Table 1.

  The tire according to the example has a bead portion structure in which a carcass ply end portion 3a is sandwiched between a pair of opposed bead cores 2a and 2b shown in FIG. The bead core 2 is made of a steel wire bead wire having a diameter of 0.96 mm and coated with insulation rubber, and then the wires are laminated in a single-strand method, and the bead core 2a (2 + 1 + 2 + 1 + 2 + 1 + 2) as shown in FIG. It was set as the structure of 2b (2 + 1 + 2 + 1 + 2 + 1).

  The tire of Comparative Example 1 has a bead portion structure similar to that of the example, and has a bead core 2c (1 + 2 + 1 + 2 + 1 + 2 + 1 + 2) and 2d (1 + 2 + 1 + 2 + 1 + 2) shown in FIG. 4 using a steel wire bead wire having a diameter of 0.96 mm.

  The tire of Comparative Example 2 has a bead portion structure in which the carcass ply end portion 3a is simply sandwiched between the flat surfaces of a pair of bead cores 2e. A bead core 2e shown in FIG. It was set as the structure of (2 pieces x 5 layers).

  The conventional tire is a grommet-type bead core 2f (5 × 4 layers) using a steel wire bead wire having a diameter of 0.96 mm, and has a conventional structure shown in FIG. 6 in which the carcass ply end portion 3a is wound up. is there.

[Movement amount at the end of the carcass cord]
The position of the end of the carcass ply cord was compared before and after tire vulcanization, and the amount of movement was measured. The larger the value, the greater the movement amount.

[Bead shape]
After tire vulcanization, 10 places on the circumference of the bead portion were cut, and the cross-sectional shape of the bead core was observed. “○” indicates that there is no shape change in the cross section, and there is a slight shape change in one or two places on the circumference, but “△” indicates that there is no practical problem. “×” was evaluated and shown in the table.

[Tire durability]
The test tire assembled on the standard rim was adjusted to an internal pressure of 180 kPa, and a drum tester (ambient temperature 38 ± 3 ° C.) equipped with a smooth steel drum with a drum diameter of 1700 mm was used, and the speed was kept constant at 80 km / h. Then, 85% of the maximum load specified by JATMA was applied for 4 hours, then 90% of the maximum load was applied for 6 hours, and 100% of the maximum load was applied for 24 hours. The running was continued while increasing the load by 20% every hour, and the vehicle was run until a failure occurred. The total distance traveled until the failure occurred was indicated by an index with the conventional example being 100. The larger the value, the better the durability.

  Clearly from the results shown in Table 1, the tire of the example has a small amount of movement of the carcass ply cord as compared with the conventional winding structure, and has a high locking effect by sandwiching the end portion of the carcass ply in a zigzag shape. It can be seen that separation from the end portion is prevented and the durability is excellent. In other words, it has an advantage that it does not easily lose shape through the tire manufacturing process including the bead core manufacturing process and even during use of the tire.

  On the other hand, in the tire of Comparative Example 1, since the innermost layer of the bead core is made of one wire, the shape stability of the core is lacking, and the bead core shape after vulcanization is greatly deformed. As a result, the effect of meshing the carcass cord is small and the amount of movement of the cord end is large, and the durability is not as good as the embodiment. Since the tire of Comparative Example 2 is simply sandwiched between the flat surfaces of the bead cores, the carcass ply locking effect is inferior, and the amount of movement of the cord ends becomes large, so that the durability is not so improved.

  As described above, the pneumatic radial tire of the present invention can be applied to various sizes of radial tires for passenger cars, trucks and buses, and is particularly suitable for radial tires for passenger cars having a one-ply carcass configuration. is there.

It is sectional drawing of the pneumatic radial tire of embodiment. It is an expanded sectional view of a bead part same as the above. It is sectional drawing of the bead core of embodiment. 6 is an enlarged cross-sectional view of a bead portion of Comparative Example 1. FIG. 10 is an enlarged cross-sectional view of a bead portion of Comparative Example 2. FIG. It is an expanded sectional view of the bead part of a conventional example.

Explanation of symbols

1 …… Bead part 2,2a, 2b …… Bead core 3 …… Carcass ply 3a …… Carcass ply end part 4 …… Carcass 5 …… Bead filler 6 …… Tread part 7 …… Side wall part 21,22 …… Uneven surface W …… Bead wire

Claims (3)

It has a carcass in which carcass plies arranged radially are arranged between a pair of left and right bead portions, and the bead portion includes a pair of bead cores facing each other in the tire rotation axis direction, and the carcass ply end portions are sandwiched between the bead cores. In a pneumatic radial tire
In the pair of bead cores, a plurality of bead wires are arranged in the innermost layer in the tire radial direction, the number of wires in the innermost layer is N (N ≧ 2), and the number of wires in the outermost layer of the innermost layer in the core is (N−1). ) As the book, the outer layer is formed by sequentially laminating the wires from the inside to the outside by repeating N pieces and (N-1) pieces, and forming an uneven surface where the opposing faces of the bead core are engaged with each other,
A pneumatic radial tire characterized in that the end portion of the carcass ply is inserted between opposing surfaces of the bead core and sandwiched between the concave and convex surfaces. 2. The pneumatic radial tire according to claim 1, wherein the bead wire is made of a steel cord that has been subjected to plating treatment, a steel cord in which a steel strand is twisted, or an organic fiber cord impregnated with a resin. The pneumatic radial tire according to claim 1 or 2 , wherein the bead core is formed by sequentially laminating one bead wire sequentially from the inner side to the outer side in the tire radial direction.

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