Pneumatic tire

Abstract

To provide a pneumatic tire capable of effectively suppressing toe chipping in a bead part.SOLUTION: An inside organic fiber reinforcement layer 11 and an outside organic fiber reinforcement layer 12 are arranged outside in a tire width direction of a steel reinforcement layer 10; an inner diameter side end part 11i of the inside organic fiber reinforcement layer 11 is located inside in the tire width direction of a line segment J formed of a normal line drawn from the most projecting vertex inside in a tire radial direction of a bead core 5 to a bead base surface; the outside organic fiber reinforcement layer 12 is arranged so as to cover the inner diameter side end part 11i of the inside organic fiber reinforcement layer 11; and an inner diameter side end part 12i of the outside organic fiber reinforcement layer 12 is separated from the inner diameter side end part 11i of the inside organic fiber reinforcement layer 11 by 5 mm or more, and is located inside in the tire radial direction of a line segment L formed of a horizontal line drawn in the tire width direction from an end part 10e outside in the tire width direction of the steel reinforcement layer 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pneumatic tire suitable for heavy loads used in trucks, buses, etc., and more particularly to a pneumatic tire capable of effectively suppressing toe chipping in the bead portion.

Background Art

[0002] In a pneumatic tire for heavy loads used in trucks, buses, etc., a carcass layer is mounted between a pair of bead portions, and the carcass layer is wound from the inside to the outside of the tire around the bead core of each bead portion, and a steel reinforcing layer including a plurality of steel cords is disposed in each bead portion so as to wrap the carcass layer. In this type of pneumatic tire, there is a problem that the frequency of toe chipping occurring in the bead portion during tire replacement is relatively high.

[0003] In the pneumatic tire configured as described above, when a plurality of organic fiber reinforcing layers are disposed outside the tire width direction of the steel reinforcing layer and these organic fiber reinforcing layers are cross-laminated even under the bead core (for example, see Patent Document 1), since the rubber flow from the bead heel during vulcanization is suppressed, it becomes possible to dispose the bead core on the toe side and to blunt the angle formed by the toe. Therefore, in the structure in which an organic fiber reinforcing layer is added to the bead portion, the problem of toe chipping is reduced. However, even in the structure in which an organic fiber reinforcing layer is added to the bead portion, toe chipping may still occur, and further improvement is required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a pneumatic tire capable of effectively suppressing toe chipping in the bead portion.

Means for Solving the Problems

[0006] The pneumatic tire of the present invention for achieving the above object includes a tread portion extending in the tire circumferential direction and having an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire outer diameter direction of these sidewall portions. A carcass layer is mounted between the pair of bead portions, and the carcass layer is wound upward from the inner side to the outer side around the bead core of each bead portion. In the pneumatic tire in which a steel reinforcing layer including a plurality of steel cords is disposed so as to wrap the carcass layer, Two layers of organic fiber reinforcing layers are disposed on the outer side in the tire width direction of the steel reinforcing layer. The two layers of organic fiber reinforcing layers include an inner organic fiber reinforcing layer adjacent to the steel reinforcing layer and an outer organic fiber reinforcing layer located on the outer side in the tire width direction than the inner organic fiber reinforcing layer. The inner diameter side end portion of the inner organic fiber reinforcing layer is located on the inner side in the tire width direction than a line segment formed by a normal line drawn from the apex most protruding inward in the tire diameter direction of the bead core to the bead base surface. The outer organic fiber reinforcing layer is disposed so as to cover the inner diameter side end portion of the inner organic fiber reinforcing layer. The inner diameter side end portion of the outer organic fiber reinforcing layer is separated from the inner diameter side end portion of the inner organic fiber reinforcing layer by 5 mm or more, and is located on the inner side in the tire diameter direction than a line segment formed by a horizontal line drawn in the tire width direction from the outer end portion in the tire width direction of the steel reinforcing layer. together with the inner organic fiber reinforcing layer includes a plain weave material composed of warp and weft, and the fiber structures of the warp and weft of the plain weave material are each in the range of 200 dtex / 1 to 1000 dtex / 1 It is characterized by the above.

Effects of the Invention

[0007] As a result of intensive research on a tire structure in which an organic fiber reinforcing layer is disposed in the bead portion, the inventor has found that most of the cracks caused by toe chipping propagate to the end of the organic fiber reinforcing layer, and such a phenomenon is caused by the end of the organic fiber reinforcing layer being in contact with rubber without being covered by another reinforcing layer in a region close to the toe of the bead portion, leading to the present invention.

[0008] That is, in the present invention, with respect to a line segment formed by a normal line drawn from the vertex most protruding radially inward of the tire diameter of the bead core to the bead base surface as a reference, both the inner organic fiber reinforcing layer and the outer organic fiber reinforcing layer extend at least to below the bead core. Therefore, the rubber flow in the bead portion during vulcanization is suppressed, the position of the bead core moves closer to the toe side, the angle formed by the toe of the bead portion increases, and thus, it can be blunt. As a result, the rigidity of the toe of the bead portion increases, and toe chipping is less likely to occur. Further, the outer organic fiber reinforcing layer is disposed so as to cover the inner diameter side end portion of the inner organic fiber reinforcing layer, and the inner diameter side end portion of the outer organic fiber reinforcing layer is separated from the inner diameter side end portion of the inner organic fiber reinforcing layer by 5 mm or more. Therefore, even when the toe of the bead portion is deformed during demounting, cracks starting from the inner diameter side end portion of the outer organic fiber reinforcing layer and the inner diameter side end portion of the inner organic fiber reinforcing layer are less likely to occur. As a result, the toe chipping resistance can be significantly improved.

[0010] In the present invention, The inner organic fiber reinforcing layer preferably includes a plain weave material composed of warp and weft, and the fiber structures of the warp and weft of the plain weave material are each in the range of 200 dtex / 1 to 1000 dtex / 1. By making the warp and weft of the plain weave material constituting the inner organic fiber reinforcing layer thinner in this way, the step portion generated when the outer organic fiber reinforcing layer is disposed so as to cover the inner diameter side end portion of the inner organic fiber reinforcing layer can be reduced, the stress concentration on the step portion can be reduced, and toe chipping can be effectively suppressed. Further, since the minimum necessary thickness is ensured for the warp and weft of the plain weave material constituting the inner organic fiber reinforcing layer, the effect of suppressing rubber flow can also be exhibited.

[0011] The distance measured along a straight line parallel to the longest side of the bead core passing through the vertex that most protrudes outward in the width direction of the bead core, where the distance A from the vertex to the bead heel position is preferably in the range of 2.5 mm to 5.5 mm. By ensuring such a sufficient distance A, the position of the bead core can be closer to the toe side, and the angle formed by the toe of the bead portion can be increased. As a result, the rigidity of the toe of the bead portion increases, and it becomes difficult for toe chipping to occur.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire for heavy loads according to an embodiment of the present invention, and FIGS. 2 to 3 show the main parts thereof.

[0014] As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and forms an annular shape, a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3, 3 disposed on the inner side in the tire radial direction of these sidewall portions 2.

[0015] A carcass layer 4 is mounted between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of steel cords extending in the tire radial direction, and has a structure wound from the inner side to the outer side of the tire around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0016] Four belt layers 7 are embedded on the outer diameter side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of belt cords (steel cords) inclined with respect to the tire circumferential direction. These belt layers 7 have two main belt layers 72, 73 in the center where the belt cords cross each other, and auxiliary belt layers 71, 74 disposed on the inner diameter side and the outer diameter side of these main belt layers 72, 73. The inclination angle of the belt cords constituting the main belt layers 72, 73 with respect to the tire circumferential direction is set in a range of, for example, 15° to 35°, and the inclination angle of the belt cords constituting the auxiliary belt layers 71, 74 with respect to the tire circumferential direction is set in a range of, for example, 15° to 75°.

[0017] In the pneumatic tire, in each bead portion 3, a steel reinforcing layer 10 including a plurality of steel cords is disposed so as to wrap the carcass layer 4, the bead core 5, and the bead filler 6. Two organic fiber reinforcing layers 11, 12 are disposed on the outer side in the tire width direction of the steel reinforcing layer 10. The inner organic fiber reinforcing layer 11 is adjacent to the steel reinforcing layer 10, and the outer organic fiber reinforcing layer 12 is located on the outer side in the tire width direction than the inner organic fiber reinforcing layer 11. Each of these organic fiber reinforcing layers 11, 12 may include a plurality of organic fiber cords aligned in one direction, or may include a plain woven material.

[0018] As shown in FIG. 2, the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 is located on the inner side in the tire width direction with respect to a line segment J formed by a normal line drawn from the vertex most protruding inward in the tire diameter direction of the bead core 5 to the surface of the bead base 3b. That is, the inner organic fiber reinforcing layer 11 extends to below the bead core 5. The inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 is located in the vicinity of the toe 3t formed at the tip of the bead portion 3.

[0019] On the other hand, the outer organic fiber reinforcing layer 12 is disposed so as to cover the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11. That is, the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 is located on the inner side in the tire width direction with respect to the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11. And the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 is separated from the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 by 5 mm or more, and is located on the inner side in the tire diameter direction with respect to a line segment L formed by a horizontal line drawn in the tire width direction from the end portion 10e on the outer side in the tire width direction of the steel reinforcing layer 10. The separation distance between the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 and the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 is a distance measured along the steel reinforcing layer 10. Further, the horizontal line for specifying the line segment L is specified when the tire is unloaded.

[0020] According to the pneumatic tire described above, with reference to the line segment J formed by the normal line drawn from the vertex most protruding inward in the tire diameter direction of the bead core 5 to the surface of the bead base 3b, both the inner organic fiber reinforcing layer 11 and the outer organic fiber reinforcing layer 12 extend at least below the bead core 5. Therefore, the rubber flow of the bead portion 3 during vulcanization is suppressed, the position of the bead core 5 moves closer to the toe 3t side, the angle θ formed by the toe 3t of the bead portion 3 increases, and as a result, the toe 3t can be blunted. As a result, the rigidity of the toe 3t of the bead portion 3 increases, and it becomes difficult for toe chipping to occur.

[0021] Further, the outer organic fiber reinforcing layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11. Since the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 is separated from the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 by 5 mm or more, even if the toe 3t of the bead portion 3 is deformed when the rim is removed, cracks starting from the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 and the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 are less likely to occur. As a result, the toe chipping resistance can be significantly improved.

[0022] Here, if the separation distance between the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 and the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 is less than 5 mm, the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 is located near the toe 3t of the bead portion 3. Therefore, cracks starting from the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 are likely to occur, and toe chipping is likely to occur. Also, although the region R radially inside the tire of the line segment L formed by a horizontal line drawn in the tire width direction from the end portion 10e on the outer side in the tire width direction of the steel reinforcing layer 10 is a region with little movement during tire rolling, if the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 is located radially outside the line segment L, the movement during tire rolling becomes large, so separation is likely to occur from the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12.

[0023] In the pneumatic tire described above, the inner organic fiber reinforcing layer 11 preferably includes a plurality of organic fiber cords aligned in one direction, and the fiber structure of the organic fiber cords is in the range of 800 dtex / 2 to 1500 dtex / 2. By making the organic fiber cords constituting the inner organic fiber reinforcing layer 11 thinner in this way, the step portion generated when the outer organic fiber reinforcing layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 can be reduced, the stress concentration on the step portion can be reduced, and toe chipping can be effectively suppressed. Also, since the minimum necessary thickness of the organic fiber cords constituting the inner organic fiber reinforcing layer 11 is ensured, the effect of suppressing the rubber flow can also be exerted.

[0024] Here, if the fiber structure of the organic fiber cord is smaller than 800 dtex / 2, the rubber flow in the bead portion 3 cannot be suppressed. Conversely, if it is larger than 1500 dtex / 2, when the outer organic fiber reinforcing layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11, the step portion generated becomes large, and the effect of suppressing toe chipping due to stress concentration at the step portion decreases. When the inner organic fiber reinforcing layer 11 includes a reinforcing material composed of a plurality of organic fiber cords aligned in one direction, the reinforcing material of the outer organic fiber reinforcing layer 12 may be a plurality of organic fiber cords aligned in one direction, or may be a plain woven material composed of warp and weft.

[0025] In the pneumatic tire described above, as another aspect, it is preferable that the inner organic fiber reinforcing layer 11 includes a plain woven material composed of warp and weft, and the fiber structures of the warp and weft of the plain woven material are each in the range of 200 dtex / 1 to 1000 dtex / 1. By making the warp and weft of the plain woven material constituting the inner organic fiber reinforcing layer 11 thinner in this way, the step portion generated when the outer organic fiber reinforcing layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11 can be made smaller, stress concentration at the step portion can be reduced, and toe chipping can be effectively suppressed. In addition, since the minimum necessary thickness is ensured for the warp and weft of the plain woven material constituting the inner organic fiber reinforcing layer 11, the effect of suppressing rubber flow can also be exhibited.

[0026] Here, if the fiber structure of the warp and weft of the plain woven material is smaller than 200 dtex / 1, the rubber flow in the bead portion 3 cannot be suppressed. Conversely, if it is larger than 1000 dtex / 1, when the outer organic fiber reinforcing layer 12 is arranged to cover the inner diameter side end portion 11i of the inner organic fiber reinforcing layer 11, the step portion generated becomes large, and the effect of suppressing toe chipping due to stress concentration at the step portion decreases. When the inner organic fiber reinforcing layer 11 includes a reinforcing material composed of a plain woven material including warp and weft, the reinforcing material of the outer organic fiber reinforcing layer 12 may be a plurality of organic fiber cords aligned in one direction, or may be a plain woven material composed of warp and weft.

[0027] In the above pneumatic tire, as shown in FIG. 3, it is preferable that the distance A from the apex E, which is the most protruding apex in the width direction outside of the bead core 5, to the bead heel position along the straight line D parallel to the longest side of the bead core 5 is in the range of 2.5 mm to 5.5 mm. By ensuring such a sufficient distance A, the position of the bead core 5 can be closer to the toe 3t side of the bead portion 3, and the angle θ formed by the toe 3t of the bead portion 3 can be increased. As a result, the rigidity of the toe 3t of the bead portion 3 increases, and it becomes difficult for toe chipping to occur.

[0028] The specific method for obtaining the distance A is as follows. The bead core 5 has a laminated structure in which a plurality of wires are arranged in the tire meridian cross-section. The apex E is the point where the straight line D parallel to the longest side of the bead core 5 passes through the center of gravity of the wire located most outside in the width direction of the bead core 5 and intersects the contour of the wire located most outside in the width direction. Here, when the straight line D parallel to the longest side of the bead core 5 passing through the apex E, which is the most protruding apex in the width direction outside of the bead core 5, the extension line of the side forming the profile of the bead bottom surface, and the extension line of the curve forming the profile of the bead back surface intersect at a virtual intersection point H, a straight line M perpendicular to the straight line D passing through the virtual intersection point H, and a straight line F perpendicular to the straight line D passing through the apex E are obtained, the distance A is the length of the line segment on the straight line D partitioned between the straight line M and the straight line F.

[0029] Here, if the distance A is less than 2.5 mm, the position of the bead core 5 does not sufficiently approach the toe 3t side, and since the increase in the rigidity of the toe 3t is small, the effect of suppressing toe chipping is reduced. Conversely, if it exceeds 5.5 mm, an excessive cost increase will occur.

[0030] FIG. 4 shows the bead portion of a conventional pneumatic tire (without an organic fiber reinforcing layer), and FIG. 5 shows the bead portion of another conventional pneumatic tire (with an organic fiber reinforcing layer). As shown in FIG. 4, when the organic fiber reinforcing layers 11 and 12 are not arranged in the bead portion 3, rubber flow occurs in the bead portion 3 during vulcanization, and since the bead core 5 is located on the bead heel side, the angle θ formed by the toe 3t of the bead portion 3 becomes small. Therefore, toe chipping is likely to occur in the bead portion 3. On the other hand, as shown in FIG. 5, although the organic fiber reinforcing layers 11 and 12 are arranged in the bead portion 3, when the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 is located near the toe 3t of the bead portion 3 and the inner diameter side end portion 12i is not covered by other reinforcing layers, cracks starting from the inner diameter side end portion 12i of the outer organic fiber reinforcing layer 12 are less likely to occur, and the toe chipping resistance cannot be sufficiently improved. According to the pneumatic tire comprising the above-described embodiment of the present invention, these problems can be solved, and toe chipping in the bead portion can be effectively suppressed.

[0031] The pneumatic tire comprising the above-described embodiment preferably has a load index of 121 or more in a single wheel, or a ply rating of 10PR or more. A pneumatic tire having such a load index or ply rating is generally a heavy-duty tire. The present invention can be expected to have a remarkable effect in heavy-duty pneumatic tires.

Example

[0032] Tires of Conventional Examples 1 to 4, Comparative Examples 1 to 2, and Examples 1 to 7 were manufactured, which had a tire size of 275 / 70R22.5, included a carcass layer containing a plurality of steel cords between the pair of bead portions, the carcass layer was wound upward from the inner side to the outer side of the tire around the bead core of each bead portion, and a steel reinforcing layer containing a plurality of steel cords was arranged in each bead portion so as to wrap the carcass layer, with only the structure of the bead portion being different. Note that in this specification, Examples 1, 2, 4 to 7 are reference examples.

[0033] In these tires of Conventional Examples 1 to 4, Comparative Examples 1 and 2, and Examples 1 to 7, the presence or absence of the organic fiber reinforcing layer, the type of the inner organic fiber reinforcing layer, the fiber structure of the inner organic fiber reinforcing layer, the position of the inner diameter side end of the inner fiber reinforcing layer, the type of the outer organic fiber reinforcing layer, the fiber structure of the outer organic fiber reinforcing layer, the position of the inner diameter side end of the outer fiber reinforcing layer, the presence or absence of covering of the inner diameter side end of the inner fiber reinforcing layer by the outer organic fiber reinforcing layer, the distance between the inner diameter side end of the outer organic fiber reinforcing layer and the inner diameter side end of the inner organic fiber reinforcing layer, the distance A of the bead core, and the angle θ of the toe were set as shown in Table 1.

[0034] Regarding the types of the inner organic fiber reinforcing layer and the outer organic fiber reinforcing layer, when the reinforcing material is a plurality of organic fiber cords aligned in one direction, it is referred to as "curtain weave", and when the reinforcing material is a plain weave material composed of warp and weft, it is referred to as "plain weave". Regarding the position of the inner diameter side end of the inner organic fiber reinforcing layer, when the inner diameter side end is located inside the tire width direction from the line segment J, it is referred to as "inner", and when the inner diameter side end is located outside the tire width direction from the line segment J, it is referred to as "outer". Regarding the position of the inner diameter side end of the outer organic fiber reinforcing layer, when the inner diameter side end is located inside the tire diameter direction from the line segment L, it is referred to as "lower side", and when the inner diameter side end is located outside the tire diameter direction from the line segment L, it is referred to as "upper side".

[0035] For these test tires, the separation resistance (organic fiber reinforcing layer, carcass layer) and the toe chipping resistance were evaluated by the following test methods, and the results are also shown in Table 1.

[0036] Separation resistance (organic fiber reinforcing layer, carcass layer): Each test tire was mounted on the specified rim of JATMA, with the air pressure set at 75% of the specified air pressure of JATMA, a load of 1.4 times the specified load of JATMA was applied, and a running test was conducted on a drum tester under the condition of a running speed of 49 km / h. After running 40,000 km, the test tire was cut along the tire meridian at 8 equally spaced locations in the tire circumferential direction, and the cross-sectional direction lengths of the cracks starting from the inner diameter side ends of the outer organic fiber reinforcing layer and the rolled-up ends of the carcass layer were measured at 8 cut surfaces (a total of 16 locations) in both bead parts. Then, the total sum of the cross-sectional direction lengths of the cracks starting from the inner diameter side ends of the outer organic fiber reinforcing layer and the rolled-up ends of the carcass layer was determined respectively. The evaluation results were shown in terms of an index with the conventional example 3 set to 100 for each of the organic fiber reinforcing layer and the carcass layer, using the reciprocal of the measured value. The larger this index value, the better the separation resistance.

[0037] Resistance to toe chipping: Each test tire was mounted on the specified rim of JATMA, with the air pressure set at 75% of the specified air pressure of JATMA, a load of 1.4 times the specified load of JATMA was applied, and a running test was conducted on a drum tester under the condition of a running speed of 49 km / h. After running 40,000 km, the test tire was repeatedly removed from and mounted on the rim, and the number of attachment and detachment times when toe chipping first occurred was measured. The evaluation results were shown in terms of an index with the number of attachment and detachment times when toe chipping occurred in the conventional example 1 set to 100. The larger this index value, the better the resistance to toe chipping.

[0038]

Table 1

[0039] As can be seen from Table 1, the tires of Examples 1 to 7 had significantly improved resistance to toe chipping compared to those of Conventional Examples 1 to 4, and moreover, sufficient separation resistance was ensured. Since the tire of Conventional Example 1 did not have an organic fiber reinforcing layer, the balance of the carcass line was not achieved due to the rubber flow during vulcanization, and as a result, cracks were likely to occur at the rolled-up ends of the carcass layer. In the tire of Comparative Example 1, the distance between the inner diameter side end of the outer organic fiber reinforcing layer and the inner diameter side end of the inner organic fiber reinforcing layer was too small, so the improvement effect of resistance to toe chipping was insufficient. In the tire of Comparative Example 2, since the inner diameter side end of the outer organic fiber reinforcing layer was located outside the tire diameter direction from the line segment L, cracks starting from the inner diameter side end of the outer organic fiber reinforcing layer were likely to occur.

Explanation of symbols

[0040] 1 Tread part 2 Sidewall part 3 Bead part 3t Toe 3b Bead base 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 10 Steel reinforcing layer 10e End part 11 Inner organic fiber reinforcing layer 11i Inner diameter side end 12 Outer organic fiber reinforcing layer 12i Inner diameter side end

Claims

1. A pneumatic tire comprising a tread portion extending in the circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the outer diameter direction of the tire of these sidewall portions, a carcass layer being mounted between the pair of bead portions, the carcass layer being wound up from the inner side to the outer side around the bead core of each bead portion, and a steel reinforcing layer including a plurality of steel cords being disposed so as to wrap the carcass layer in the pneumatic tire, two organic fiber reinforcing layers are disposed on the outer side in the tire width direction of the steel reinforcing layer, the two organic fiber reinforcing layers including an inner organic fiber reinforcing layer adjacent to the steel reinforcing layer and an outer organic fiber reinforcing layer located on the outer side in the tire width direction than the inner organic fiber reinforcing layer, the inner diameter side end portion of the inner organic fiber reinforcing layer is located on the inner side in the tire width direction than a line segment formed by a normal line drawn from the apex most protruding inward in the tire diameter direction of the bead core to the bead base surface, the outer organic fiber reinforcing layer is disposed so as to cover the inner diameter side end portion of the inner organic fiber reinforcing layer, the inner diameter side end portion of the outer organic fiber reinforcing layer is separated from the inner diameter side end portion of the inner organic fiber reinforcing layer by 5 mm or more, and is located on the inner side in the tire diameter direction than a line segment formed by a horizontal line drawn in the tire width direction from the outer end portion in the tire width direction of the steel reinforcing layer, and the inner organic fiber reinforcing layer includes a plain weave material composed of warp and weft, and the fiber structures of the warp and weft of the plain weave material are each in the range of 200 dtex / 1 to 1000 dtex / 1. A pneumatic tire characterized by this.

2. A pneumatic tire according to claim 1, characterized in that a distance A from the apex to the bead heel position, which is a distance measured along a straight line parallel to the longest side of the bead core passing through the apex most protruding outward in the width direction of the bead core, is in the range of 2.5 mm to 5.5 mm.

Images