JP4458942B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire. More specifically, the present invention includes a plurality of bead cores facing the bead portion in the tire rotation axis direction, and a plurality of carcass plies are sandwiched between the bead cores so as to be engaged with each other. The present invention relates to a pneumatic radial tire in which the bead portion is securely locked to improve the durability of the bead portion.

  The bead portion of the pneumatic radial tire has a carcass ply arranged in a radial direction between the pair of left and right bead portions, and the carcass ply end portion is wound around the bead core in the bead portion from the inside to the outside of the carcass ply. When the carcass is composed of a plurality of carcass plies, the structure in which the end portion is locked to the bead portion is common. For example, in a two-ply tire, the first ply on the inner layer side and the second ply on the outer layer side as shown in FIG. The bead core is rolled up and locked.

  In a radial tire having such a conventional winding structure, there is a difference in stiffness in the tire radial direction due to the presence or absence of the carcass ply at the winding end, and the shear strain due to the load applied during rolling of the tire is received by the carcass winding end. This may cause separation failure with the initiation of adhesive fracture on the cut end face.In particular, high-performance tires for high-speed running and large-ply tires with a large load have large rigidity differences in the radial direction and bead volume. Increasing the load on the bead part and causing a failure due to high heat generation are likely to occur.

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

  In the carcass fixing method described in the above-mentioned document 1, the carcass ply does not require a winding portion 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 Document 2 is provided with a protruding loop-shaped end on the inside of the bead core and locked in order to prevent the carcass end from coming out of the bead core during inflation molding. Therefore, equipment and processes for forming a loop-shaped terminal are required, resulting in an increase in cost. 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.

  Further, the bead portion structure disclosed conventionally as in the above-mentioned documents 1 and 2 relates to a tire that assumes a one-ply configuration, and no proposal has been made for a tire having a multi-ply carcass configuration. .

  The present invention has been made in view of the above-described problems of the prior art, and in a pneumatic radial tire having a multi-ply carcass configuration, the carcass ply end portion is sandwiched between bead cores provided in the bead portion, and the carcass ply end It is an object of the present invention to provide a pneumatic radial tire excellent in bead portion durability in which the cord pull-out phenomenon from the bead core is reliably prevented and the strength of the bead portion is secured and the rigidity difference is eliminated.

  The pneumatic radial tire of the present invention has a carcass in which a plurality of carcass plies arranged in a radial manner are arranged between a pair of left and right bead portions, and the bead portions include a plurality of bead cores facing each other in the tire rotation axis direction. In the pneumatic radial tire in which the end portion of the carcass ply is sandwiched between the plurality of bead cores, the plurality of bead cores includes a plurality of bead wires arranged in a tire radial innermost layer and an outermost layer, and the bead core It is formed by laminating wires from the inside to the outside while forming uneven surfaces where the opposing surfaces mesh with each other, and at least one ply end portion of the plurality of carcass plies is disposed between the opposing uneven surfaces of the bead core. The pneumatic radial tire is characterized by being inserted and clamped.

  As described above, the plurality of bead cores provided in the bead portion provide a plurality of bead wires in the innermost layer and the outermost layer in the tire radial direction, thereby improving the stability of the core shape at the time of core manufacture and tire molding. By forming concave and convex surfaces that mesh with each other on the opposing surfaces, and inserting and engaging the carcass ply ends between the concave and convex surfaces, the carcass ply ends are sandwiched in a zigzag manner between the concave and convex surfaces, and the ply ends are bead cores. It can be securely locked between the tires, the vulcanization molding process, or the carcass cord position displacement and pulling phenomenon during running can be prevented to ensure the strength of the bead portion, and also caused by the carcass ply winding structure The problem of the difference in rigidity of the bead portion can be solved and the bead portion durability can be improved.

  In the pneumatic radial tire of the present invention, the bead filler is inserted between the carcass plies by arranging the bead filler having a substantially triangular cross section along the outer periphery of the plurality of bead cores, so that the carcass ply is locally disposed. Therefore, the carcass cord can be maintained in good fatigue resistance, the rigidity of the bead portion can be ensured, and the flexibility can be gradually improved toward the sidewall portion.

  In the pneumatic radial tire of the present invention, the bead core has N (N ≧ 2) wires in the innermost layer in the tire radial direction, and (N−1) wires in the outermost layer of the innermost layer. Further, it is preferable that the outer layer is formed by alternately repeating N and (N-1) wires, and the number of wires constituting the outermost layer is N, and the gap between the N wires (N-1 ) The wire falls and forms an uneven surface on the core facing surface, stabilizes the core shape, increases the locking force by meshing the end of the carcass ply and improves the effect of preventing the cord pulling phenomenon, Moreover, the arrangement of the bead filler having a substantially triangular cross section can be stabilized by setting the number of wires in the outermost layer to N.

  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 portion of the carcass ply The zigzag engagement can be facilitated and the locking effect can be improved.

  In addition, 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 carcass ply end portion is sandwiched so that the end portions of at least one of the plurality of carcass plies constituting the carcass are engaged in a zigzag manner between the bead cores facing each other in the bead portion. By locking, the carcass ply is securely held in the bead part, the cord pull-out phenomenon is prevented, the strength of the bead part is secured, and the rigidity difference of the rolled-up part is eliminated. A pneumatic radial tire having the configuration can be provided.

  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.

  As shown in the figure, the radial tire T of the present invention includes a tread portion 6, a sidewall portion 7, and a bead portion 1. A pair of left and right bead portions includes two carcass plies 3 a and 3 b that are radially arranged. 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-ply belt 8 in which steel cords are arranged is annularly arranged on the tire circumference, and the outer circumference of the belt 8 is spirally corded almost in parallel with the tire circumferential direction. A belt reinforcing layer 9 is wound around the belt.

  The carcass ply 3 is made of an organic fiber cord such as polyester, nylon, rayon, or aramid, or a steel cord. A cord arranged at a predetermined density is covered with a topping rubber, and a predetermined angle of approximately 90 ° with respect to the cord direction. It is cut at an angle of and used. 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 belt reinforcement layer 9 tightens the belt 8 in the tire circumferential direction to suppress the growth of the belt 8 during high-speed running and the belt end rise and improve the high-speed durability.

  The bead core 2 embedded in the bead portion 1 includes three annular bead cores 2a, 2b, and 2c that face each other in the tire rotation axis direction, and the end of the first ply 3a on the inner layer side and the end of the 2nd ply 3b on the outer side. The carcass plies 3a and 3b are mounted between the left and right bead parts 1 and 1, and the carcass 4 of the radial tire T is formed by locking the parts between the bead cores 2a and 2b and 2b and 2c facing each other.

  In the bead portion 1, bead fillers 5a, 5b, and 5c having a substantially triangular cross section made of hard rubber are disposed along the outer peripheries of the bead cores 2a, 2b, and 2c. As shown in the figure, the bead fillers 5a, 5b, 5c are arranged between the carcass plies 3a, 3b and on both sides of the bead portion so that the carcass plies 3a, 3b are locally within the bead portion 1. Arranged without bending, maintaining good fatigue resistance of the cord, ensuring the rigidity of the bead part 1 and gradually improving the flexibility toward the side wall part 7 to cause a radial rigidity difference Therefore, the flexibility of the sidewall portion 7 can be ensured.

  As shown in FIG. 3, the three bead cores 2a, 2b, 2c are formed by sequentially laminating bead wires W from the inner side to the outer side in the tire radial direction, and each of the bead cores 2a, 2b, 2c. The number of wires in the innermost layer in the tire radial direction is set to two, the number of wires in the outermost layer of the innermost layer is set to one, and the outer layer is configured by alternately repeating two and one in order. The number of wires is terminated as two, and in the case of the figure, a (2 + 1 + 2 + 1 + 2) laminated core is formed.

  Due to the configuration of the bead core, the bead cores 2a, 2b, and 2c are stacked with one upper and lower wires W falling between the valleys of the two wires W as shown in the figure, so that the core periphery is placed on both sides of the core. Convex / concave surfaces 21, 22, 23 having concavities and convexities meshing with each other between two adjacent layers and one layer on the opposing surfaces of bead cores 2 a, 2 b, 2 c by laminating bead wires W on the entire circumference in the direction , 24 are formed and are arranged so that the irregularities thereof mesh with each other.

  That is, the bead cores 2a, 2b, 2c have a plurality of N bead wires arranged in the innermost layer in the tire radial direction, the number of wires in the outermost layer of the core innermost layer is (N-1), and the outer layers are sequentially N By repetitively configuring the book and (N-1) book, the wire volume of the innermost layer that is the foundation of the core is secured, the lamination process of the wire W is stabilized, the core shape is kept good, and the tire is molded. The bead core is prevented from being deformed in the vulcanization molding process, and the bead portion durability is improved by maintaining the locking strength and the bead portion shape of the end portions of the carcass plies 3a and 3b, and the fitting property with the rim is improved. To ensure safety.

  Further, the bead cores 2a, 2b, 2c are arranged so that the bottom surfaces of the bead fillers 5a, 5b, 5c having a substantially triangular cross section are in contact with the wires W at the upper end of the core by setting the number of wires in the outermost layer of the core to N. By doing so, the position of each filler can be accurately stabilized, and the fatigue resistance of the carcass plies 3a and 3b and the rigidity of the bead portion 1 can be ensured.

  The N cores constituting the bead cores 2a, 2b, and 2c are not particularly limited as long as they are two or more, and the number of stacked layers is not limited, and can be appropriately designed depending on the tire size and application, and the core 2a , 2b, and 2c, the N number may be changed.

  The uneven step formed on the uneven surfaces 21, 22, 23, 24 (the distance between the bottom of the recess and the top of the protrusion) is to strengthen the locking of the ends of the carcass plies 3a, 3b. Depending on the thickness and stiffness of the carcass plies 3a and 3b, it is at least 0.3 mm or more, preferably 0.4 mm or more.

  Then, by inserting the end portions of the carcass plies 3a, 3b between the bead cores 2a, 2b and 2b, 2c, and sandwiching them between the concave and convex surfaces 21, 22 and 23, 24, the carcass plies The end portions of the plies 3a and 3b are sandwiched so as to engage in a zigzag manner along the unevenness of the uneven surfaces 21, 22 and 23, 24, and the carcass plies 3a and 3b are sandwiched between the bead cores 2a and 2b and 2b and 2c. By securely engaging, it is possible to prevent misalignment or pull-out phenomenon of the carcass cord during the tire molding, vulcanization molding process, or traveling.

  In the present invention, at least one ply end of the plurality of carcass plies may be sandwiched between the bead cores. For example, as shown in FIG. 4, only the 1st ply 3a on the tire inner layer side may be sandwiched between the bead cores 2a and 2b, and the end of the 2nd ply 3b on the outer layer side may be disposed outside the bead core 2 '. Although not shown, two carcass ply end portions may be integrally sandwiched between a pair of bead cores. In any case, it is sufficient if the bead core can sufficiently secure the locking force of the end portion of the carcass ply.

  In order to sandwich the end portions of the carcass plies 3a and 3b, for example, in the primary molding of the radial tire T, the end portions of the carcass plies 3a and 3b are sandwiched between the bead cores 2a and 2b and 2b and 2c, respectively. By arranging and crimping the bead cores 2a, 2b and 2b, 2c, the end portions of the carcass plies 3a, 3b are meshed in a zigzag manner between the concave and convex surfaces 21, 22 and 23, 24 and are firmly held. The carcass cord can be prevented from being displaced or pulled out during expansion of the green tire in the secondary molding or in the vulcanization process.

  Here, the end portions 3d and 3e of the carcass ply securely hold the end portions of the carcass plies 3a and 3b, and in order to prevent air accumulation in the bead core 2 during tire vulcanization, It is preferable to protrude from the inner peripheral surfaces of 2b and 2c. 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, the structure of the bead portion 1 is configured as described above, so that the opposite bead cores 2a, 2b and 2b, 2c are sandwiched so that the ends of the carcass plies 3a, 3b are engaged in a zigzag shape. By firmly locking, the pulling resistance force of the carcass plies 3a, 3b is greatly improved, the strength of the bead portion 1 is sufficiently secured, and the rigidity difference of the bead portion 1 due to the winding of the conventional carcass ply 3 is reduced. The bead portion reinforcing layer 10 (see FIG. 8) is used to eliminate the rigidity difference caused by the breakage of the cord end portion and to relieve the rigidity difference which has been conventionally arranged near the carcass ply terminal. ) Can be omitted.

  Further, by optimizing the wire configuration of the bead cores 2a, 2b, and 2c, 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 eliminated. Improvement can be further ensured, and a bead portion structure suitable for the tire size and application can be easily designed.

  As described above, the radial tire T of the present invention can form a carcass by firmly locking the end portions of a plurality of carcass plies between bead cores, thereby improving the bead portion durability of a tire having two or more plies. Therefore, it is suitable as a high-performance tire for high-speed traveling, an RV vehicle with a large load, an electric vehicle, or a light truck tire.

  In the present invention, as the bead wires W constituting the bead cores 2a, 2b and 2c, 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 And steel cords such as layer twist cords.

  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. It is possible to use the one that secures the rigidity of the bead core 2 while utilizing the features of each wire such as the merit to the effect and improves the locking effect by engaging the ends of the carcass plies 3a and 3b.

  The bead cores 2a, 2b, and 2c 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 production efficiency of the bead cores 2a, 2b, and 2c is improved. The bead cores 2a, 2b, 2c having a stable cross-sectional shape can be obtained while enhancing the manufacturing process, and the core 2 can be prevented from being deformed during the manufacture of the tire, and the locking strength and bead rigidity of the carcass plies 3a, 3b can be obtained. The durability of the bead portion 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 215 / 45ZR17, the overall configuration is in accordance with FIG. 1, the carcass 4 has a polyester cord of 1670 dtex / 2 (23 piling density at topping / 25 mm) and 2 plies, and the belt 8 is 2 + 1 × 0.27 steel cord (18 cords / 25mm driven density) 2 plies, belt reinforcement layer 9 is 940 dtex / 2 nylon 66 cords with a density of 30 cords / 25 mm and spiral wound around the belt. The tires were prototyped in unison for each tire, and the bead portion was evaluated according to the following method. The results are shown in Table 1.

  The tire according to the example has a bead portion structure in which the end portions of the carcass plies 3a and 3b are sandwiched between the bead cores 2a and 2b and between the bead cores 2a and 2c shown in FIG. The bead core 2 is coated with insulation rubber using a bead wire W made of steel wire having a bronze plating with a diameter of 1.20 mm (the same wire is used in the following comparative examples and conventional examples), and then a single strand. As shown in the figure, the wires W are laminated by the method, and the bead cores 2a, 2b, 2c are all configured as (2 + 1 + 2 + 1 + 2), and the ends of the carcass plies 3a, 3b are sandwiched between the cores 2a, 2b and 2b, 2c, Bead fillers 5a, 5b, and 5c were arranged on the outer periphery of each bead core.

  The tire of Comparative Example 1 uses the bead cores 2d, 2e, and 2f shown in FIG. 5 as the (1 + 2 + 1 + 2 + 1 + 2) configuration, and the end portions of the carcass plies 3a and 3b are connected between the bead cores 2d and 2e and 2e, as in the example. The bead fillers 5a, 5b, and 5c having the same shape as that of the example were arranged on the outer periphery of each bead core.

  As shown in FIG. 6, the tire of Comparative Example 2 has a structure in which the end portions of the carcass plies 3a and 3b are sandwiched in the same manner as in the example by using the bead cores 2a, 2b, and 2c (2 + 1 + 2 + 1 + 2) having the same configuration as the example. There is a bead portion structure in which an integral bead filler 5d is arranged on the outer periphery of the bead core.

  As shown in FIG. 7, the tire of Comparative Example 3 uses bead cores 2g, 2g, and 2g (2 + 2 + 2 configuration) having the same configuration in which two wires W are stacked in parallel, and end portions of the carcass plies 3a and 3b are used as the tires. It is a bead portion structure that is simply sandwiched between opposed flat core surfaces. As the bead filler, bead fillers 5a, 5b and 5c having the same shape as in the example were arranged.

  The tire of the conventional example uses a bead core 2h in which a bead wire W having a diameter of 1.20 mm is laminated in a (5 + 5 + 5 + 5 + 4) configuration by a conventional single strand method, and an integrated bead filler 5e in which carcass plies 3a and 3b are wound around the bead core 2h. It is the tire of the conventional structure shown in FIG.

[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. The tire of Comparative Example 2 has the same structure as that of the example in which the end portion of the carcass ply is sandwiched, but the durability of the carcass cord is reduced because the bead filler is an integral part and the carcass cord is bent excessively on the bead core. The improvement of power was not obtained. The tire of Comparative Example 3 is inferior in the locking effect of the carcass ply because it is simply sandwiched between the flat surfaces of the bead cores, and the movement amount of the cord end portion is increased, so that the durability is not improved so much.

  As described above, the pneumatic radial tire of the present invention can be applied to radial tires of various sizes and applications including those for passenger cars, particularly high performance tires for high speed running and RV vehicles with a large load. Suitable for electric vehicles and the like.

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. It is an expanded sectional view of the bead part which shows one example of an 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. 10 is an enlarged cross-sectional view of a bead portion of Comparative Example 3. FIG. It is an expanded sectional view of the bead part of a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bead part 2, 2a, 2b, 2c ... Bead core 3a, 3b ... Carcass ply 4 ... Carcass 5, 5a, 5b, 5c ... Bead filler 6 ... Tread part 7 ... Side wall part 21, 22, 23, 24 ... Uneven surface T ... Pneumatic radial tire W ... Bead wire

Claims (5)

A carcass in which a plurality of carcass plies arranged in a radial manner are arranged between a pair of left and right bead portions, the bead portion includes a plurality of bead cores facing each other in the tire rotation axis direction, and an end portion of the carcass ply is disposed on the end portion of the carcass ply. In a pneumatic radial tire sandwiched between a plurality of bead cores,
The plurality of bead cores are formed by arranging a plurality of bead wires in the innermost and outermost layers in the tire radial direction, and by laminating the wires from the inside to the outside while forming an uneven surface where the opposing surfaces of the bead cores mesh with each other. Being
A pneumatic radial tire characterized in that at least one ply end portion of the plurality of carcass plies is inserted and sandwiched between the opposing concave and convex surfaces of the bead core. The pneumatic radial tire according to claim 1, wherein a bead filler having a substantially triangular cross section is disposed on the periphery of the bead portion along the outer periphery of the plurality of bead cores. In the bead core, the number of wires in the innermost layer in the tire radial direction is set to N (N ≧ 2), the number of wires in the outermost layer of the innermost layer is set to (N−1), and the outer layer is set to N (N -1) The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is configured by alternately repeating the wires, and the number of wires constituting the outermost layer is N. The air according to any one of claims 1 to 3, wherein the bead wire is made of a steel wire subjected to plating treatment, a steel cord obtained by twisting steel strands, or an organic fiber cord impregnated with a resin. Entering radial tire. The pneumatic radial tire according to any one of claims 1 to 4, wherein the bead core is formed by sequentially and sequentially laminating one bead wire from the inner side to the outer side in the tire radial direction.

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