JP4842628B2 - Heavy duty pneumatic radial tire - Google Patents

Description

  The present invention relates to a heavy-duty pneumatic radial tire for construction machinery and industrial vehicles, and more particularly to a heavy-duty pneumatic radial tire with improved durability around a bead portion.

In conventional heavy-duty pneumatic radial tires used in construction machinery and industrial vehicles, wire chafers and organic fiber chafers are placed along the outside of the carcass at the bead to improve the durability of the bead. (For example, refer to Patent Document 1).
JP 2001-225618 A

  However, since the outer end of the wire chafer in the tire axial direction and the outer end of the organic fiber chafer in the axial direction of the tire were near the rim line, the vehicle weight increased due to the improvement in vehicle performance and the use in the market expanded. Crack failure occurs with the outer end of the wire chafer in the tire axial direction and the outer end of the organic fiber chafer in the tire axial direction as nuclei.

This is because the outer end of the wire chafer in the tire axial direction and the outer end of the organic fiber chafer in the axial direction of the tire are located in the vicinity of the rim line where distortion increases during use.
As a countermeasure, in the heavy-duty pneumatic radial tire 100, as shown in FIG. 3, the height of the tire axial direction outer end portion 106A of the wire chafer 106 and the tire axial direction outer end portion 108A of the organic fiber chafer 108 is set. When lower than the rim line P (at the tire center side), the failure rate at the tire axial direction outer end portion 106A of the wire chafer 106 and the organic fiber chafer 108 at the tire axial direction outer end portion 108A was reduced.
In FIG. 3, reference numeral 102 denotes a bead portion, 104 denotes a carcass, 110 denotes a rim, and 112 denotes a bead core.

However, when the application of such heavy-duty pneumatic radial tires has been expanded to industrial vehicles that are used under more severe load conditions, the outer end of the wire chafer in the axial direction of the tire can be used even if the above measures are taken. The problem that crack failure occurred as a nucleus occurred.
In the market, it is expected that a heavy-duty pneumatic radial tire that can sufficiently suppress the occurrence of a crack failure around the bead even when used in an industrial vehicle having a more severe load condition.

  An object of the present invention is to provide a heavy-duty pneumatic radial tire excellent in durability around the bead portion in consideration of the above facts.

In order to achieve the above object, a heavy-duty pneumatic radial tire according to claim 1 of the present invention straddles a pair of bead portions in a toroidal shape, and surrounds a bead core disposed in the bead portion from the inner side in the tire axial direction. One or more carcass plies formed by covering a plurality of ply cords with a coating rubber, and the height h3 of the outer end portion in the tire axial direction is arranged outside the wire chafer. A first organic fiber chafer formed by coating a plurality of organic fiber cords with a coating rubber, the height being lower than a height h2 of the outer end portion in the tire axial direction of the wire chafer, and the wire chafer and the first The bead core extends from the tire center side to the tire inner side, and the height of the inner end in the tire axial direction is the height of the bead core. higher than h1, characterized in that it comprises a second organic fibers chafer formed by coating the organic fiber cords of the plurality of in coating rubber, the.

In this specification, the regular rim is a rim defined by the JATMA (Japan Automobile Tire Association) Year Book 2005 version, and the normal internal pressure is the maximum load capacity of the JATMA (Japan Automobile Tire Association) Year Book 2005 version. The normal load is a load corresponding to the maximum load capacity when a single wheel of Year Book 2005 version of JATMA (Japan Automobile Tire Association) is applied.
Outside Japan, the load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the following standard, and the internal pressure is the maximum load (maximum load) of a single wheel described in the following standard. The rim is a regular rim (or “Approved Rim”, “Recommended Rim”) in the applicable size described in the following standards.

  The standards are determined by industry standards that are valid in the region where the tire is produced or used. For example, “Year Book of The Tire and Rim Association Inc.” in the United States, “Standards Manual of The European Tire and Rim Technical Organization” in Europe.

Further, the height of each end portion in the tire axial direction described above is the height in the tire radial direction with reference to a reference line parallel to the tire axial direction for measuring the tire cross-sectional height, and the flange height is also Similarly, it is the height outward in the tire radial direction with reference to the reference line for measuring the tire cross-section height described above.
Further, the rim width measurement reference line is a reference line parallel to the tire equatorial plane for measuring the rim width of the rim described above.
In addition, a rim line extending in the tire circumferential direction is often provided at a position 1.18 times as high as the flange height of the rim, and serves as a measure of whether or not the tire and rim shaft centers are properly combined when the rim is assembled. As described above, there is a large distortion when using the tire.

Next, the function and effect of the heavy duty pneumatic radial tire according to claim 1 will be described. Crack failure occurred at the core end of the wire chafer in the tire axial direction by making the height h2 of the outer end in the tire axial direction of the wire chafer lower than 1.18 times the flange height h of the rim. Can be suppressed.
In addition, the height h2 is lower than 1.18 times the height h in order to prevent the occurrence of crack failure with the outer end of the wire chafer in the axial direction of the tire as the core, so that the strength of the bead portion is increased. Although the height decreases, the height h1 of the inner end portion in the tire axial direction of the wire chafer is made higher than 1.18 times the height h, so that a decrease in the strength of the bead portion can be compensated.
Further, the height h3 of the outer end portion in the tire axial direction of the first organic fiber chafer is made lower than the height h2, so that the crack having the outer end portion in the tire axial direction of the first organic fiber chafer as a nucleus is formed. The occurrence of failure can be prevented.
And the rubber gauge between the wire cord and the ply cord measured at the outer end in the tire axial direction of the wire chafer is measured at the other portion inside the tire radial direction from the outer end in the tire axial direction of the wire chafer. By making it wider than the rubber gauge, the strain generated at the outer end of the wire chafer in the tire axial direction can be reduced.

From the above, the outer end in the tire axial direction of the wire chafer and the outer end in the tire axial direction of the first organic fiber chafer are arranged at appropriate positions, so that each outer end in the tire axial direction is the core. The occurrence of crack failure can be suppressed or prevented, and the inner end of the wire chafer in the tire axial direction is arranged at an appropriate position, so that the strength of the bead portion is secured, and the outer end of the wire chafer in the axial direction of the tire is secured. By making the rubber gauge wider than the rubber gauge of other parts, it is possible to reduce the strain generated at the outer end of the wire chafer in the tire axial direction. Therefore, the heavy-duty pneumatic radial tire of the present invention is excellent in durability around the bead portion.

  The heavy-duty pneumatic radial tire according to claim 2 of the present invention is the heavy-duty pneumatic radial tire according to claim 1, wherein the wire cord measured at the outer end in the tire axial direction of the wire chafer When the rubber gauge between the ply cord and the ply cord is t1, and the rubber gauge between the wire cord and the ply cord measured on the inner side in the tire radial direction of the bead core is t2, t1 / t2 = 1.72-3. 46 is satisfied.

  Next, functions and effects of the heavy duty pneumatic radial tire according to claim 2 will be described. When the relationship between the rubber gauge t1 and the rubber gauge t2 is t1 / t2 <1.72, the effect of reducing the strain generated at the outer end of the wire chafer in the tire axial direction is not sufficient, and when t1 / t2> 3.46. Further, the volume of the rubber becomes too large, and the heat generation becomes large, which may adversely affect the durability of the bead portion. Therefore, it is preferable to satisfy t1 / t2 = 1.72 to 3.46.

  The heavy-duty pneumatic radial tire according to claim 3 of the present invention is the heavy-duty pneumatic radial tire according to claim 1 or 2, wherein the wire cord is measured at a tire axially outer end of the wire chafer. The rubber gauge t1 between the wire cord and the ply cord is 2.75 to 5.52 times the cord diameter of the wire cord.

  Next, functions and effects of the heavy duty pneumatic radial tire according to claim 3 will be described. If the rubber gauge t1 is less than 2.75 times the cord diameter of the wire cord, the effect of reducing the strain generated at the outer end of the wire chafer in the tire axial direction is not sufficient, and if it exceeds 5.52 times, There is a possibility that the volume will increase too much and the heat generation will increase and adversely affect the durability of the bead portion. Accordingly, the rubber gauge t1 is preferably 2.75 to 5.52 times the wire diameter of the wire cord.

  The heavy-duty pneumatic radial tire according to claim 4 of the present invention is the heavy-duty pneumatic radial tire according to any one of claims 1 to 3, wherein the height h1 is 1. 44 to 1.86 times.

  Next, functions and effects of the heavy duty pneumatic radial tire according to claim 4 will be described. If the height h1 of the wire chafer inner end in the tire axial direction is less than 1.44 times the flange height h of the rim, the height h2 of the outer end in the tire axial direction of the wire chafer is reduced. It cannot compensate for the strength reduction of the bead portion. Further, when the height h1 exceeds 1.86 times the height h, the distortion of the inner end portion in the tire axial direction of the wire chafer increases, and the possibility of failure due to the occurrence and progress of cracks increases. Therefore, the height h1 preferably satisfies 1.44 to 1.86 times the height h.

  A heavy-duty pneumatic radial tire according to a fifth aspect of the present invention is the heavy-duty pneumatic radial tire according to any one of the first to fourth aspects, wherein the height h2 is a height of 0.0. It is 6 to 0.97 times.

  Next, the function and effect of the heavy duty pneumatic radial tire according to claim 5 will be described. If the height h2 of the outer end portion in the tire axial direction of the wire chafer is less than 0.6 times the flange height h of the rim, the reinforcement effect of the bead portion is significantly reduced. If it exceeds 0.97 times, the outer end of the wire chafer in the axial direction of the tire approaches 1.18 times the flange height of the rim, so that the distortion becomes large, and the failure due to the occurrence and development of cracks The possibility increases. Therefore, the height h2 preferably satisfies 0.6 to 0.97 times the height h.

  A heavy-duty pneumatic radial tire according to a sixth aspect of the present invention is the heavy-duty pneumatic radial tire according to any one of the first to fifth aspects, wherein the height h3 is a height of 0.02 of the height h2. It is 6 to 0.84 times.

Next, the function and effect of the heavy duty pneumatic radial tire according to claim 6 will be described. If the height h3 of the outer end portion in the tire axial direction of the first organic fiber chafer is less than 0.6 times the height h2 of the outer end portion in the tire axial direction of the wire chafer, the tire of the wire chafer is manufactured at the time of manufacture. The axially outer end portion moves around the bead base as a fixed end and is easily exposed on the tire surface. Also, if h3 exceeds 0.84 times h2, the outer end of the first organic fiber chafer in the axial direction of the tire approaches 1.18 times the flange height, resulting in increased strain and cracking. The possibility of failure due to occurrence and progress increases. Therefore, the height h3 preferably satisfies 0.6 to 0.84 times the height h2.

  A heavy-duty pneumatic radial tire according to a seventh aspect of the present invention is the heavy-duty pneumatic radial tire according to any one of the first to sixth aspects, wherein the bead core is measured in parallel to the tire axial direction. When the distance measured in parallel to the tire axial direction from the rim width measurement reference line to the bead toe in a no-load state in which the distance is a bead core width b1 and attached to the normal rim and filled with the normal internal pressure is the bead width bp, b1 / bp = 0.45 to 0.61 is satisfied.

  Next, the function and effect of the heavy duty pneumatic radial tire according to claim 7 will be described. If the relationship between the bead core width b1 and the bead width bp is b1 / bp <0.45, the effect of suppressing the falling deformation of the bead portion is not sufficient, and if b1 / bp> 0.61, the falling deformation of the bead portion is not achieved. Can be suppressed, but the tire weight increases, which is not realistic. Therefore, the bead core width b1 preferably satisfies 0.45 to 0.61 times the bead width bp.

  As described above, the heavy-duty pneumatic radial tire of the present invention is excellent in durability around the bead portion.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. A heavy-duty pneumatic radial tire 10 (hereinafter simply referred to as a tire 10) according to the present embodiment includes a carcass 12, a wire chafer 14, organic fiber chafers 16 and 26 in FIG. It has. Other configurations are the same as those of a general pneumatic radial tire.

(Carcass)
The carcass 12 includes a carcass ply 36 formed by embedding a plurality of ply cords 32 arranged in parallel with each other in a coating rubber 34.
As shown in FIG. 1A, the carcass ply 36 is wound from the inner side to the outer side in the tire width direction around the body portion 36A straddling the toroidal shape between the pair of bead portions 18 and the bead core 20 disposed on the bead portion 18. It has a folded portion 36B formed by being returned. (In FIG. 1A, only one side of the bead portion 18 is shown.)
In addition, although the carcass 12 of the present embodiment is composed of one carcass ply 36, it may be composed of two or more carcass plies.

  In order to ensure the rigidity of the bead portion 18, a bead filler 28 that tapers outward in the tire radial direction is disposed between the main body portion 36 </ b> A and the folded portion 36 </ b> B of the carcass ply 36.

(Wire chafer)
The wire chafer 14 is disposed in close contact along the outer peripheral surface of the carcass ply 36 in the bead portion 18. The wire chafer 14 is formed by embedding a plurality of wire cords 38 arranged in parallel with each other in a coating rubber 40.
In addition, although the wire chafer 14 of this embodiment is a structure which arrange | positions only one layer, the structure which arrange | positions two or more layers may be sufficient.
The height h1 of the tire axial direction inner end portion 14B (hereinafter referred to as the inner end portion 14B) of the wire chafer 14 is higher than 1.18 times the flange height h of the rim 24 for the tire 10, The height h2 of the tire axial direction outer end portion 14A (hereinafter referred to as the outer end portion 14A) is disposed lower than 1.18 times the height h.
Further, as shown in FIG. 1B, the rubber gauge t1 between the wire cord 38 and the ply cord 32 measured at the outer end portion 14A of the wire chafer 14 is on the inner side in the tire radial direction from the outer end portion 14A. It is set wider than the rubber gauge measured in other parts.
In this embodiment, except for the vicinity of the outer end portion 14A of the wire chafer 14, the rubber gauge between the wire cord 38 and the ply cord 32 is constant, and the outer end in the tire axial direction of the organic fiber chafer 16 to be described later The rubber gauge gradually spreads from the vicinity of the position of the height h3 of the portion 16A toward the outer end portion 14A.
In addition, each rubber gauge is measured along a normal line standing on the ply cord 32 of the carcass ply 36.
Moreover, the rubber gauge measured in the vicinity of the outer end portion 14A of the wire chafer 14 is measured along the above-described normal line passing through the outermost wire cord 38E.
Here, when there are two or more wire chafers and two or more carcass plies, the rubber gauge is measured with the outer end of the wire chafer in the tire axial direction and the carcass ply located on the outermost side. To do.

(Organic fiber chafer)
Organic fiber chafers 16 and 26 are disposed outside the wire chafer 14. In the configuration of this embodiment, two layers of organic fiber chafers are disposed, but it is sufficient that one or more layers are disposed.
The organic fiber chafer 16 is formed by embedding a plurality of organic fiber cords (for example, aliphatic polyamide fibers (nylon: trade name)) arranged in parallel with each other in a coating rubber. The organic fiber chafer 26 is formed by embedding a plurality of organic fiber cords (for example, aliphatic polyamide fibers (nylon: trade name)) arranged in parallel with each other in a coating rubber.
As shown in FIG. 1A, the inner organic fiber chafer 26 extends from the lower side of the bead core 20 (the tire center side) to the tire inner side, and is described as a tire axial inner end portion 26B (hereinafter referred to as an inner end portion 26B). Is disposed higher than the height h1 of the inner end portion 14B of the wire chafer 14.
An inner end 16B in the tire axial direction of the outer organic fiber chafer 16 (hereinafter referred to as an inner end 16B) is disposed lower than the inner end 26B of the organic fiber chafer 26. Further, the outer end 16A in the tire axial direction of the organic fiber chafer 16 (hereinafter referred to as the outer end 16A) is disposed lower than the height h1 of the outer end 14A of the wire chafer 14.

Note that the height of each end in the tire axial direction in the present embodiment is the height of the outer side in the tire radial direction with reference to a reference line RDL parallel to the tire axial direction for measuring the tire cross-section height. Similarly, the flange height is also the height outward in the tire radial direction with reference to the reference line RDL.
In this embodiment, the rim line P (height hp = 1.18 × h) is provided at a position 1.18 times the flange height of the rim. The rim line P is a line in the tire circumferential direction that serves as an indication of whether or not the tire and rim shaft centers are properly combined during rim assembly.

The rubber gauge between the wire cord 38 and the ply cord 32 measured at the outer end portion 14A of the wire chafer 14 is t1, and between the wire cord 38 and the ply cord 32 measured at the inside of the bead core 20 in the tire radial direction. When the rubber gauge is t2 (see FIG. 1C), it is preferable to satisfy t1 / t2 = 1.72 to 3.46.
The rubber gauge t1 is preferably 2.75 to 5.52 times the cord diameter of the wire cord 38.

The height h1 of the inner end portion 14B of the wire chafer 14 preferably satisfies 1.44 to 1.86 times the flange height h of the rim 24.
The height h2 of the outer end portion 14A of the wire chafer 14 preferably satisfies 0.6 to 0.97 times the height h.
The height h3 of the outer end portion 16A of the organic fiber chafer 16 preferably satisfies 0.6 to 0.84 times the height h2.
The bead core width b1 of the bead core 20 preferably satisfies 0.45 to 0.61 times the bead width bp of the bead portion 18.

  The bead core width b1 of the bead core 20 indicates the longest distance measured in parallel with the tire axial direction of the bead core 20, and the bead width bp of the bead portion 18 is filled with the normal internal pressure by attaching the tire 10 to the rim 24. The distance measured in parallel to the tire axial direction from the bead toe 18T of the bead portion 18 in the unloaded state to the reference line RWL parallel to the tire equatorial plane for measuring the rim width. Further, the bead toe 18T indicates an innermost end portion of the tire in a contact surface between the bead portion 18 and the rim 24.

(Function)
In the tire 10 of the present embodiment, the height h2 of the outer end portion 14A of the wire chafer 14 is lower than 1.18 times the flange height h of the rim 24, so that the outer end portion 14A of the wire chafer 14 is reduced. The occurrence of crack failure with the core can be suppressed.
In addition, the strength of the bead portion 18 is reduced by reducing the height h2 to be lower than 1.18 times the height h in order to prevent the occurrence of crack failure with the outer end portion 14A as a core described above. By making the height h1 of the inner end portion 14B of the wire chafer 14 higher than 1.18 times the height h, the strength reduction of the bead portion 18 can be compensated.
Furthermore, by making the height h3 of the outer end portion 16A of the organic fiber chafer 16 lower than the height h2, it is possible to prevent the occurrence of crack failure with the outer end portion 16A of the organic fiber chafer 16 as a core.
The rubber gauge t1 between the wire cord 38 and the ply cord 32 measured at the outer end portion 14A of the wire chafer 14 is more than the rubber gauge measured at the other portion inside the tire radial direction from the outer end portion 14A. By widening, the distortion generated in the outer end portion 14A can be reduced.
Therefore, the heavy-duty pneumatic radial tire 10 of the present invention is excellent in durability around the bead portion 18.

  Further, if the relationship between the rubber gauge t1 and the rubber gauge t2 is t1 / t2 <1.72, the effect of reducing the strain generated in the outer end portion 14A is not sufficient, and if t1 / t2> 3.46, the rubber volume As the amount of heat increases, the heat generation increases and the durability of the bead portion 18 may be adversely affected. Therefore, it is preferable to satisfy t1 / t2 = 1.72 to 3.46.

  If the rubber gauge t1 is less than 2.75 times that of the wire cord 38, the effect of reducing the distortion generated in the outer end portion 14A is not sufficient, and if it exceeds 5.52 times, the volume of the rubber becomes too large and heat is generated. There is a possibility that it becomes large and adversely affects the durability of the bead portion. Therefore, the rubber gauge t1 is preferably 2.75 to 5.52 times the cord diameter of the wire cord 38.

  If the height h1 is less than 1.44 times the height h, it is impossible to compensate for the strength reduction of the bead portion 18 due to the reduction in the height h2. Further, when the height h1 exceeds 1.86 times the height h, the distortion of the inner end portion 14B increases, and the possibility of failure due to the occurrence and development of cracks increases. Therefore, the height h1 preferably satisfies 1.44 to 1.86 times the height h.

  If the height h2 is less than 0.6 times the height h, the reinforcement effect of the bead part 18 will be remarkably reduced. On the other hand, if it exceeds 0.97 times, the outer end portion 14A approaches the rim line P, so that the distortion becomes large, and the possibility of failure due to the occurrence and development of cracks increases. Therefore, the height h2 preferably satisfies 0.6 to 0.97 times the height h.

  If the height h3 is less than 0.6 times the height h2, the outer end portion in the tire axial direction of the wire chafer moves with the vicinity of the bead base as a fixed end at the time of manufacture, and is easily exposed to the tire surface. Further, if h3 exceeds 0.84 times h2, the outer end portion 16A approaches the rim line P, so that the distortion increases, and the possibility of failure due to the occurrence and development of cracks increases. Therefore, the height h3 preferably satisfies 0.6 to 0.84 times the height h2.

  When the relationship between the bead core width b1 and the bead width bp is b1 / bp <0.45, the effect of suppressing the collapse deformation of the bead portion 18 is not sufficient, and when b1 / bp> 0.61, the bead portion 18 Although the falling deformation can be suppressed, the tire weight increases, which is not realistic. Therefore, the bead core width b1 preferably satisfies 0.45 to 0.61 times the bead width bp.

(Test example)
For tires having a tire size of 16.00R25, tires according to the conventional example, the present invention, and a comparative example were manufactured under the conditions shown in Table 1, and the distortion of the outer end portion in the tire axial direction of the wire chafer, the tire of the organic fiber chafer Evaluation was made on the distortion at the outer end in the axial direction and the amount of tire collapse. The results are shown in Table 1.

  The evaluation of the strain was performed by assembling the tire on the 11.25 / 2.0 rim, setting the internal pressure to 1000 kPa, and applying a load of 15.7 t (153.86 kN) on the drum testing machine to achieve a speed of 20 km / After running 5800 km at h, the tire was cut and dissected and the average crack length at the chafer end in the tire axial direction was measured. The evaluation value is indicated by an index with the comparative example being 100, and the smaller the value, the better the result. In the comparative example, the height h1 is smaller and the heights h2 and h3 are larger than the conventional example.

  In addition, the evaluation of the tire collapse amount is based on the position of the rim line P (a point of 1.18 times the rim flange height h) in the no-load state by assembling the tire on the rim and filling the normal internal pressure. Thus, the amount of displacement of the rim line P in the tire axial direction when a normal load was applied was measured as the amount of tire collapse.

According to this test example (Table 1 and FIG. 2), the distortion of the outer end portion in the tire axial direction of the wire chafer is the least in the case of the present invention, and compared with any of the conventional example and the comparative example, It can be seen that there is a significant decrease.
Further, the amount of tire collapse is the smallest in the present invention, and it can be seen that increasing the bead core width with respect to the bead width improved the strength around the bead portion.

  The present invention is most favorable for the distortion of the outer end portion in the tire axial direction of the organic fiber chafer. This is because in the tire of the present invention, the height h3 of the outer end portion in the tire axial direction of the organic fiber chafer is set lower than the height h2 of the outer end portion in the tire axial direction of the wire chafer. Since the outer end portion is not covered with the organic fiber chafer, the strain tends to be slightly increased because the strain is reduced by the rubber gauge t1, so that the tire of the present invention has less strain than the conventional tire. It is thought that it became.

(A) It is sectional drawing which shows the bead part of the pneumatic radial tire for heavy loads which concerns on this Embodiment. FIG. 2B is an enlarged cross-sectional view of the wire chafer shown in FIG. However, organic fiber chafers are not shown. FIG. 2C is an enlarged cross-sectional view of the bead core of the wire chafer shown in FIG. However, organic fiber chafers are not shown. It is a figure which shows the distortion of the tire axial direction outer side edge part of a wire chafer by the index | exponent which set the comparative example to 100. FIG. It is sectional drawing which shows the bead part of the pneumatic radial tire for heavy loads which concerns on a prior art example.

Explanation of symbols

10 Heavy load pneumatic radial tire 12 Carcass 14 Wire chafer 14A Tire axial outer end 14B Tire axial inner end 16 Organic fiber chafer 16A Tire axial outer end 18 Bead 18T Bead to 20 Bead core 24 Rim rim)
32 Ply cord 34 Coated rubber 36 Carcass ply 38 Wire cord 40 Coated rubber RWL Rim width measurement reference line

Claims (7)

One or more sheets formed by straddling between a pair of bead parts in a toroidal manner, winding around the bead core disposed in the bead part from the inner side to the outer side in the tire axial direction, and covering a plurality of ply cords with a coating rubber Carcass ply
The bead portion is disposed along the outer side of the carcass ply, and the height h1 of the inner end portion in the tire axial direction is higher than 1.18 times the flange height h of the regular rim, and the height of the outer end portion in the tire axial direction. h2 is lower than 1.18 times the height h, and is formed by coating a plurality of wire cords with a coating rubber and between the wire cord and the ply cord measured at the outer end in the tire axial direction. At least one layer of wire chafer that is wider than the rubber gauge measured at the other portion inside the tire radial direction than the outer end portion in the tire axial direction,
It is arranged outside the wire chafer, the height h3 of the outer end in the tire axial direction is lower than the height h2 of the outer end in the tire axial direction of the wire chafer, and a plurality of organic fiber cords are coated with coating rubber A first organic fiber chafer formed
It is arranged between the wire chafer and the first organic fiber chafer, extends from the tire center side of the bead core to the tire inner side, and the height of the inner end in the tire axial direction is higher than the height h1. A second organic fiber chafer formed by coating a plurality of organic fiber cords with a coating rubber;
A pneumatic radial tire for heavy loads, comprising:   A rubber gauge between the wire cord and the ply cord measured at the outer end in the tire axial direction of the wire chafer is t1, and the wire cord and the ply cord measured at the inner side in the tire radial direction of the bead core. 2. The heavy-duty pneumatic radial tire according to claim 1, wherein t1 / t2 = 1.72 to 3.46 is satisfied when a rubber gauge between them is t2.   A rubber gauge t1 between the wire cord and the ply cord measured at the outer end in the tire axial direction of the wire chafer is 2.75 to 5.52 times the cord diameter of the wire cord. The pneumatic radial tire for heavy loads according to claim 1 or 2.   The heavy-duty pneumatic radial tire according to any one of claims 1 to 3, wherein the height h1 is 1.44 to 1.86 times the height h.   The heavy-duty pneumatic radial tire according to any one of claims 1 to 4, wherein the height h2 is 0.6 to 0.97 times the height h.   The heavy radial pneumatic tire according to any one of claims 1 to 5, wherein the height h3 is 0.6 to 0.84 times the height h2.   The distance measured when the bead core is measured parallel to the tire axial direction is the bead core width b1 and the tire axial direction from the rim width measurement reference line to the bead toe in a no-load state in which the normal rim is mounted and the normal internal pressure is filled. 7. The heavy-duty pneumatic radial tire according to claim 1, wherein b1 / bp = 0.45 to 0.61 is satisfied when a distance measured in parallel is a bead width bp. .

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