Pneumatic tires

Abstract

A pneumatic tire is provided with organic fiber reinforcement layers (11, 12) arranged on the outside of a steel reinforcement layer (10) in the tire width direction. The organic fiber reinforcement layers (11, 12) each include a plurality of organic fiber cords aligned in one direction. The organic fiber cords constituting the organic fiber reinforcement layers (11, 12) are oriented in a manner that they intersect with each other between layers. The outer diameter side end (11i) of the organic fiber reinforcement layer (11) is located at a position radially outward of the turned-up end (4e) of the carcass layer (4). The outer diameter side end (12i) of the organic fiber reinforcement layer (12) is located radially inward of the turned-up end (4e) of the carcass layer (4) and radially outward of a line segment (K). The inner diameter side end (11i, 12i) of the organic fiber reinforcement layers (11, 12) is located at a position radially inward of the turned-up end (4e) of the carcass layer (4) and radially outward of the line segment (K). The inner diameter side end (11i, 12i) of the organic fiber reinforcement layers (11, 12) is located at a position radially inward of the line segment (J) in the tire width direction. The cord angle θ of the organic fiber reinforcement layer (11) is A At 20°≤|θ A |≤45° or 70°≤|θ A |≤90°, the cord angle θ of the organic fiber reinforcement layer (12) B At 20°≤|θ B |≤45° or 70°≤|θ B |≤90° range.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire having a structure in which a carcass layer is rolled up from the inside to the outside of the tire around the bead core of each bead portion. More specifically, it relates to a pneumatic tire that can suppress delamination starting from the rolled-up end of the carcass layer and effectively suppress delamination starting from the outer diameter side end of an organic fiber reinforcement layer embedded in the bead portion. Background Art

[0002] Among heavy-duty pneumatic tires used for trucks, buses, and the like, there are pneumatic tires that have a carcass layer stretched between a pair of bead sections. This carcass layer is wound around the bead core of each bead section from the inside to the outside of the tire. A steel reinforcing layer comprising multiple steel cords is arranged in each bead section so as to enclose the carcass layer. In such pneumatic tires, two organic fiber reinforcing layers, comprising multiple organic fiber cords aligned in one direction, are embedded outside the steel reinforcing layer in the tire width direction to prevent delamination originating from the wound-up end of the carcass layer (see, for example, Patent Document 1).

[0003] However, when two organic fiber reinforcing layers are arranged cross-laminated with the tire bead portion, there is a problem in which delamination is easily caused, starting from the outer diameter end portions. More specifically, the two organic fiber reinforcing layers are arranged with their ends offset from each other, so that one organic fiber reinforcing layer becomes a single layer at the outer diameter end portion. Furthermore, when the two cross-laminated organic fiber reinforcing layers are raised radially outward from the tire during the tire forming process, the organic fiber reinforcing layers tend to have a high angle in the single-layer area that deviates from the stacking area. As a result, the tension generated in the organic fiber cords that constitute the organic fiber reinforcing layers increases, making delamination easily caused, starting from the outer diameter end portions.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6554957 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] An object of the present invention is to provide a pneumatic tire capable of suppressing delamination starting from a turned-up end of a carcass layer and effectively suppressing delamination starting from an outer diameter side end of an organic fiber reinforcing layer embedded in a bead portion.

[0009] Means for solving problems

[0010] The pneumatic tire of the present invention for achieving the above-mentioned purpose comprises: a tread portion, which extends in a ring shape along the circumferential direction of the tire; a pair of sidewall portions, which are arranged on both sides of the tread portion; and a pair of bead portions, which are arranged on the inner side of the tire in the outer diameter direction of the sidewall portions, and a carcass layer is stretched between the pair of bead portions, which is wound around the bead core of each bead portion from the inner side to the outer side of the tire, and a steel reinforcing layer containing a plurality of steel cords is arranged in each bead portion in a manner of wrapping the carcass layer, characterized in that

[0011] First and second organic fiber reinforcing layers are disposed on the outer sides of the steel reinforcing layer in the tire width direction. Each of the first and second organic fiber reinforcing layers includes a plurality of organic fiber cords aligned in one direction. The organic fiber cords constituting the first and second organic fiber reinforcing layers are oriented so as to intersect with each other between the layers.

[0012] The outer diameter side end portion of the first organic fiber reinforcing layer is located further outward in the tire radial direction than the turned-up end portion of the carcass layer.

[0013] The outer diameter side end of the second organic fiber reinforcing layer is located inward in the tire radial direction relative to the turned-up end of the carcass layer and outward in the tire radial direction relative to a line segment formed by a horizontal line drawn in the tire width direction from the apex of the bead core that protrudes most radially outward from the tire.

[0014] The inner diameter side ends of the first and second organic fiber reinforcing layers are both located inward in the tire width direction relative to a line segment formed by a normal line drawn from the apex of the bead core most protruding inward in the tire radial direction to the bead base surface.

[0015] The cord angle θ of the first organic fiber reinforcement layer relative to the tire circumferential direction is A At 20°≤|θ A |≤45°or70°≤|θ A |≤90 ° range, the second organic fiber reinforcement layer with respect to the tire circumferential cord angle θ B At 20°≤|θ B |≤45° or 70°≤|θ B |≤90° range.

[0016] Effects of the Invention

[0017] The inventors have conducted intensive research on tire structures in which organic fiber reinforcement layers are arranged in the bead portion. As a result, they found that the cross-laminated organic fiber reinforcement layers suppress the flow of rubber in the bead portion during vulcanization, thereby bringing the carcass layer closer to the balance carcass line, and delamination starting from the rolled-up end of the carcass layer is suppressed. In other words, they found that it is not necessary to cross-laminate the organic fiber reinforcement layers near the rolled-up end of the carcass layer, thereby completing the present invention.

[0018] Specifically, the present invention employs first and second organic fiber reinforcement layers, cross-laminated on the outside of the steel reinforcement layer in the tire width direction. With the line segment defined by a normal drawn from the bead core's most radially inwardly protruding vertex to the bead base surface, both layers extend at least below the bead core. This suppresses rubber flow in the bead area during vulcanization, positions the bead core closer to the bead toe, and allows the carcass layer to approach the balance carcass line. This prevents delamination originating from the turned-up end of the carcass layer. Furthermore, by arranging the outer diameter side end of the first organic fiber reinforcement layer at a position radially outward from the turned-up end of the carcass layer, and on the other hand, arranging the outer diameter side end of the second organic fiber reinforcement layer at a position radially inward from the turned-up end of the carcass layer and radially outward from a line segment formed by a horizontal line drawn along the tire width direction from the apex of the bead core most protruding radially outward, the lifting rate of the cross-laminated first and second organic fiber reinforcement layers when they are lifted radially outward during the tire forming process is reduced, and the first organic fiber reinforcement layer can be prevented from having a high angle near its outer diameter side end. As a result, the cord angle θ of the first organic fiber reinforcement layer with respect to the tire circumferential direction can be reduced. A and the cord angle θ of the second organic fiber reinforcement layer relative to the tire circumferential direction B By setting the tension generated in the organic fiber cords within a range where the tension is reduced, delamination starting from the outer diameter side ends of the first and second organic fiber reinforcing layers can be effectively suppressed.

[0019] In the present invention, when the cord inclination directions of the first and second organic fiber reinforcing layers relative to the tire circumferential direction are opposite, the cord angle θ of the first organic fiber reinforcing layer relative to the tire circumferential direction is A Preferably, it is 20°≤|θ A |≤45°. By making the outer diameter side end portion a single layer, the cord angle θ of the first organic fiber reinforcing layer A Setting the diameter of the first organic fiber reinforcement layer to a small value effectively suppresses delamination starting from the outer diameter side end of the first organic fiber reinforcement layer. In addition, by making the cord inclination directions of the first and second organic fiber reinforcement layers in opposite directions relative to the tire circumferential direction, rubber flow in the bead portion during vulcanization can be effectively suppressed.

[0020] In the present invention, it is preferred that, when the cord inclination directions of the first and second organic fiber reinforcing layers relative to the tire circumferential direction are the same, the cord angle θ of the first organic fiber reinforcing layer relative to the tire circumferential direction is A At 20°≤|θ A |≤45°, the cord angle θ of the second organic fiber reinforcement layer relative to the tire circumferential direction B In |θA |+20≤|θ B By making the outer diameter side end portion a single layer, the cord angle θ of the first organic fiber reinforcing layer A By setting the angle θ to be small, delamination starting from the outer diameter side end of the first organic fiber reinforcement layer can be effectively suppressed. B Cord angle θ relative to the first organic fiber reinforcement layer A The diameter is sufficiently large to effectively suppress the rubber flow in the bead portion during vulcanization.

[0021] Preferably, the distance A from the bead heel apex to the outer diameter side end of the first organic fiber reinforcing layer is h The distance P from the bead heel apex to the turned-up end of the carcass layer h Satisfy A h -P h Thereby, stress concentration at the turned-up end of the carcass layer can be alleviated, and delamination from the turned-up end can be effectively suppressed.

[0022] Preferably, a crack suppression layer is embedded in a position adjacent to the turned-up end of the carcass layer, the outer end of the steel reinforcement layer in the tire width direction, the outer radial end of the first organic fiber reinforcement layer, and the outer radial end of the second organic fiber reinforcement layer, and the 100% modulus Kc of the crack suppression layer is M100 At 4.5MPa≤Kc M100 In the range of ≤10.0MPa, the elongation at break of the crack suppression layer Kc EB At 300% ≤ Kc EB This effectively prevents delamination originating from the turned-up end of the carcass layer, the outer diameter end of the first organic fiber reinforcing layer, and the outer diameter end of the second organic fiber reinforcing layer. It should be noted that the 100% modulus and elongation at break were measured in accordance with JIS-K6251.

[0023] Preferably, one of the first and second organic fiber reinforcing layers is an inner organic fiber reinforcing layer located inward in the tire width direction, and the other of the first and second organic fiber reinforcing layers is an outer organic fiber reinforcing layer located outward in the tire width direction. The outer organic fiber reinforcing layer is arranged so as to cover the inner radial end of the inner organic fiber reinforcing layer. The inner radial end of the outer organic fiber reinforcing layer is spaced at least 5 mm from the inner radial end of the inner organic fiber reinforcing layer and is located radially inward of a line segment formed by a horizontal line drawn along the tire width direction from the outer end of the steel reinforcing layer. In this case, even if the bead toe deforms when the rim is removed, delamination originating from the inner radial end of the outer organic fiber reinforcing layer and the inner radial end of the inner organic fiber reinforcing layer is less likely to occur.

[0024] The fiber structure of the organic fiber cords constituting the first and second organic fiber reinforcing layers preferably ranges from 800 dtex / 2 to 1500 dtex / 2, respectively. By thinning the organic fiber cords constituting the first and second organic fiber reinforcing layers in this manner, the step created when one of the first and second organic fiber reinforcing layers covers the inner diameter end of the other can be reduced. This reduces stress concentration on the step, and suppresses delamination originating from the step of the first or second organic fiber reinforcing layer. Furthermore, by ensuring the minimum necessary thickness of the organic fiber cords constituting the first and second organic fiber reinforcing layers, rubber flow can be suppressed.

[0025] Preferably, the distance A from the bead core's most outwardly protruding apex to the bead heel, measured along a line passing through the bead core's apex and parallel to its longest side, is within the range of 2.5 mm ≤ A ≤ 5.5 mm. By ensuring sufficient distance A, the bead core is positioned closer to the bead toe, increasing the angle formed by the bead toe. As a result, the rigidity of the bead toe is increased, making delamination less likely to occur originating from the inner diameter ends of the first and second organic fiber reinforcing layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a meridian cross-sectional view showing a heavy-load pneumatic tire according to an embodiment of the present invention.

[0027] Figure 2 It shows Figure 1 A cross-sectional view of a bead portion of a pneumatic tire.

[0028] Figure 3 It shows Figure 1 Other cross-sectional views of the bead portion of the pneumatic tire.

[0029] Figure 4 This is a side view showing an extracted portion of an organic fiber reinforcement layer embedded in the bead portion.

[0030] Figure 5 This is a graph showing the relationship between the cord angle and tension of the organic fiber reinforcement layer.

[0031] Figure 6 It is a side view showing a modified example of the organic fiber reinforcement layer embedded in the bead portion.

[0032] Figure 7 It is a cross-sectional view showing another modified example of the organic fiber reinforcement layer embedded in the bead portion.

[0033] Figure 8 It shows Figure 7 Other cross-sectional views of the organic fiber reinforcement layer. DETAILED DESCRIPTION

[0034] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 A heavy-duty pneumatic tire according to an embodiment of the present invention is shown. Figures 2 to 4 Show its main parts.

[0035] like Figure 1 As shown, the pneumatic tire of this embodiment includes: a tread portion 1 extending in a ring shape in the tire circumferential direction; a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1; and a pair of bead portions 3, 3 arranged on the inner side of the sidewall portions 2 in the tire radial direction.

[0036] A carcass layer 4 is provided between a pair of bead portions 3, 3. The carcass layer 4 comprises a plurality of steel cords extending in the tire radial direction and is wound from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. A bead filler 6 composed of a rubber composition having a triangular cross-section is disposed on the outer circumference of the bead core 5.

[0037] Four belt layers 7 are embedded in 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 relative to the tire circumferential direction. These belt layers 7 include two main belt layers 72 and 73 in the center, in which the belt cords intersect each other, and auxiliary belt layers 71 and 74 arranged on the inner and outer diameter sides of these main belt layers 72 and 73. The inclination angle of the belt cords constituting the main belt layers 72 and 73 relative to the tire circumferential direction is set, for example, in the range of 15° to 35°, and the inclination angle of the belt cords constituting the auxiliary belt layers 71 and 74 relative to the tire circumferential direction is set, for example, in the range of 15° to 75°.

[0038] In the pneumatic tire described above, a steel reinforcing layer 10 comprising a plurality of steel cords is disposed in each bead portion 3 so as to enclose a carcass layer 4, a bead core 5, and a bead filler 6. First and second organic fiber reinforcing layers 11 and 12 are disposed on the outer sides of the steel reinforcing layer 10 in the tire width direction. Each of the first and second organic fiber reinforcing layers 11 and 12 comprises a plurality of organic fiber cords aligned in one direction, and the organic fiber cords constituting the first and second organic fiber reinforcing layers 11 and 12 are oriented so as to intersect each other between the layers.

[0039] like Figure 2 As shown, the outer diameter side end 11o of the first organic fiber reinforcing layer 11 is located radially outward from the turned-up end 4e of the carcass layer 4. On the other hand, the outer diameter side end 12o of the second organic fiber reinforcing layer 12 is located radially inward from the turned-up end 4e of the carcass layer 4 and radially outward from a line segment K defined by a horizontal line drawn along the tire width direction from the vertex of the bead core 5 that protrudes most radially outward from the tire. In other words, the first and second organic fiber reinforcing layers 11 and 12 are stacked, but form a single-layer structure near the turned-up end 4e of the carcass layer 4. It should be noted that the horizontal line used to define line segment K is determined when the tire is in its own state and under no load.

[0040] The inner diameter side ends 11i and 12i of the first and second organic fiber reinforcing layers 11 and 12 are both located further inward in the tire width direction than a line segment J formed by a normal drawn from the vertex of the bead core 5, which protrudes most radially inward, to the surface of the bead base 3b. In other words, the first and second organic fiber reinforcing layers 11 and 12 extend below the bead core 5.

[0041] like Figure 4 As shown, the cord angle θ of the first organic fiber reinforcement layer 11 relative to the tire circumferential direction is A Set to 20°≤|θ A |≤45° or 70°≤|θ A |≤90 ° range, the second organic fiber reinforcement layer 12 with respect to the tire circumferential cord angle θ B Set to 20°≤|θ B |≤45° or 70°≤|θ B |≤90° range. Cord angle θ A ,θ B The angle θ of the organic fiber cords measured at the outer diameter side ends 11o and 12o of the first and second organic fiber reinforcing layers 11 and 12 relative to the tire circumferential direction. The inclination direction of the cords of the first and second organic fiber reinforcing layers 11 and 12 relative to the tire circumferential direction may be any direction. For example, the cord angle θ of the first and second organic fiber reinforcing layers 11 and 12 is A ,θ BWhen the organic fiber cords constituting these are inclined toward one side with respect to the tire circumferential direction, the value becomes positive (+), and when the organic fiber cords constituting these are inclined toward the other side with respect to the tire circumferential direction, the value becomes negative (-).

[0042] According to the pneumatic tire described above, first and second organic fiber reinforcing layers 11 and 12 are cross-laminated on the outside of the steel reinforcing layer 10 in the tire width direction. With a line segment J defined by a normal drawn from the vertex of the bead core 5, most protruding inwardly in the tire radial direction, to the surface of the bead base 3b, both first and second organic fiber reinforcing layers 11 and 12 extend at least to below the bead core 5. This suppresses rubber flow in the bead portion 3 during vulcanization, positions the bead core 5 closer to the bead toe 3t, and allows the carcass layer 4 to approach the balance carcass line. This prevents delamination originating from the turned-up end 4e of the carcass layer 4.

[0043] Furthermore, by positioning the outer radial end 11o of the first organic fiber reinforcing layer 11 radially outward relative to the turned-up end 4e of the carcass layer 4, and positioning the outer radial end 12o of the second organic fiber reinforcing layer 12 radially inward relative to the turned-up end 4e of the carcass layer 4 and radially outward relative to a line segment K defined by a horizontal line drawn along the tire width direction, the rate of lift of the cross-laminated first and second organic fiber reinforcing layers 11, 12 radially outward during the tire forming process is reduced, thereby preventing the first organic fiber reinforcing layer 11 from forming a high angle near its outer radial end 11o. It should be noted that since the first organic fiber reinforcing layer 11 extends radially outward relative to the turned-up end 4e of the carcass layer 4, the effect of suppressing rubber flow in the bead portion 3 during vulcanization is fully ensured.

[0044] As described above, since the first organic fiber reinforcement layer 11 can be prevented from having a high angle near its outer diameter side end 11o, the cord angle θ of the first organic fiber reinforcement layer 11 with respect to the tire circumferential direction can be set to A and the cord angle θ of the second organic fiber reinforcement layer relative to the tire circumferential direction B By setting the tension generated in the organic fiber cords to be small, delamination starting from the outer diameter side ends 11 o and 12 o of the first and second organic fiber reinforcing layers 11 and 12 can be effectively suppressed.

[0045] Figure 5 The relationship between the cord angle and tension of the organic fiber reinforcement layer is shown. Figure 5In the figure, "◇" indicates data of the first organic fiber reinforcement layer 11 including a plurality of organic fiber cords aligned in one direction, and "×" indicates data of the second organic fiber reinforcement layer 12 including a plurality of organic fiber cords aligned in one direction. Figure 5 As shown, there is a first organic fiber reinforcement layer 11 with a cord angle θ relative to the tire circumferential direction. A At 20°≤|θ A |≤45° or 70°≤|θ A |≤90 ° range when the tension becomes low, and the second organic fiber reinforcement layer 12 is at a cord angle θ relative to the tire circumferential direction B At 20°≤|θ B |≤45° or 70°≤|θ B |≤90°, the tension tends to be lower. Therefore, by A ,θ B By setting the tension within the above range, it is possible to avoid an increase in tension and suppress delamination starting from the outer diameter side ends 11 o and 12 o of the first and second organic fiber reinforced layers 11 and 12 .

[0046] Here, when the cord angle θ of the first organic fiber reinforcement layer 11 is A At 45°<|θ A |<70°, delamination is likely to occur starting from the outer diameter side end 11o of the first organic fiber reinforcement layer 11. Similarly, when the cord angle θ of the second organic fiber reinforcement layer 12 is B At 45°<|θ B |<70°, delamination is likely to occur starting from the outer diameter side end 12o of the second organic fiber reinforcement layer 12. A |、|θ B When the angle is less than 20°, it is difficult to lift the cross-laminated first and second organic fiber reinforcement layers 11 and 12 outward in the tire radial direction during the tire forming process. In particular, the cord angle θ of the first organic fiber reinforcement layer 11 relative to the tire circumferential direction is A It is preferably set to 25°≤|θ A |≤40° or 75°≤|θ A |≤85 ° range, the second organic fiber reinforcement layer 12 with respect to the tire circumferential cord angle θ B It is preferably set to 25°≤|θ B |≤40°or75°≤|θ B |≤85° range.

[0047] like Figure 4As shown, when the cord inclination directions of the first and second organic fiber reinforcement layers 11 and 12 relative to the tire circumferential direction are opposite, the cord angle θ of the first organic fiber reinforcement layer 11 relative to the tire circumferential direction is A Preferably, it is 20°≤|θ A |≤45°, more preferably 20°≤|θ A |≤35°. By making the outer diameter side end portion 11o a single layer, the cord angle θ of the first organic fiber reinforcing layer 11 A Setting the value to a small value effectively suppresses delamination originating from the outer diameter end 11o of the first organic fiber reinforcing layer 11. Furthermore, since the cord inclination directions of the first and second organic fiber reinforcing layers 11, 12 relative to the tire circumferential direction are opposite, rubber flow in the bead portion during vulcanization can be effectively suppressed. Consequently, balancing of the carcass line can be promoted.

[0048] Figure 6 FIG. 4 shows a modified example of an organic fiber reinforcement layer embedded in the tire bead portion. Figure 6 As shown, the cord inclination directions of the first and second organic fiber reinforcement layers 11 and 12 relative to the tire circumferential direction may also be the same. In this case, the cord angle θ of the first organic fiber reinforcement layer 11 relative to the tire circumferential direction is A Preferably, it is 20°≤|θ A |≤45°, more preferably 20°≤|θ A |≤40 ° range, the second organic fiber reinforcement layer 12 with respect to the tire circumferential cord angle θ B Preferably in |θ A |+20≤|θ B | range. By making the outer diameter side end portion 11o a single layer, the cord angle θ of the first organic fiber reinforcing layer 11 A By setting the cord angle θ to be small, delamination starting from the outer diameter side end 11o of the first organic fiber reinforcement layer 11 can be effectively suppressed. B Cord angle θ relative to the first organic fiber reinforcement layer 11 A The angle θ of the cords of the first and second organic fiber reinforcing layers 11 and 12 is sufficiently large that the rubber flow in the bead portion during vulcanization can be effectively suppressed even if the cords of the first and second organic fiber reinforcing layers 11 and 12 are inclined in the same direction. As a result, the carcass line can be balanced. In addition, since the first and second organic fiber reinforcing layers 11 and 12 are cross-laminated with the same sign, even if the cord angle θ of the second organic fiber reinforcing layer 12 is set to B Cord angle θ relative to the first organic fiber reinforcement layer 11 AWhen the angle is increased by 20° or more, the tension of the second organic fiber reinforced layer 12 is unlikely to increase, and thus delamination starting from the outer diameter side end 12 o of the second organic fiber reinforced layer 12 can be effectively suppressed.

[0049] like Figure 3 As shown, the distance A from the bead heel apex 3h of the bead portion 3 to the outer diameter side end 11o of the first organic fiber reinforcement layer 11 is h and the distance P from the bead heel apex 3h of the bead portion 3 to the turned-up end 4e of the carcass layer 4. h Preferably meet A h -P h ≥5.0mm. That is, the first organic fiber reinforcement layer 11 preferably protrudes sufficiently toward the tire radial direction outside beyond the turned-up end 4e of the carcass layer 4. This can alleviate the stress concentration at the turned-up end 4e of the carcass layer 4 and effectively suppress delamination from the turned-up end 4e. h -P h When the thickness is less than 5.0 mm, the effect of suppressing delamination from the turned-up end 4e of the carcass layer 4 is reduced. In particular, it is preferable to satisfy A h -P h It should be noted that the distance B from the bead heel apex 3h of the bead portion 3 to the outer diameter side end 12o of the second organic fiber reinforcement layer 12 is h and the distance P from the bead heel apex 3h of the bead portion 3 to the turned-up end 4e of the carcass layer 4. h Satisfy P h >B h relationship.

[0050] like Figure 2 As shown, a sidewall rubber layer 13 and a rim cushion rubber layer 14 are disposed in the area extending from the sidewall portion 2 to the bead portion 3, exposed on the outer surface of the tire. Furthermore, in the area surrounded by the bead filler 6, the sidewall rubber layer 13, and the rim cushion rubber layer 14, a crack suppression layer 15 is embedded in a position adjacent to the turned-up end 4e of the carcass layer 4, the outer end 10e of the steel reinforcing layer 10 in the tire width direction, the outer radial end 11o of the first organic fiber reinforcing layer 11, and the outer radial end 12o of the second organic fiber reinforcing layer 12. It should be noted that the turned-up end 4e of the carcass layer 4 and the outer end 10e of the steel reinforcing layer 10 in the tire width direction may also be covered by an edge band. When such an edge band is added, the crack suppression layer 15 is adjacent to the turned-up end 4e of the carcass layer 4 and the outer end 10e of the steel reinforcing layer 10 in the tire width direction, with the edge band interposed therebetween. Preferably, the 100% modulus Kc of the crack suppression layer 15 is 0.001. M100 At 4.5MPa≤Kc M100 In the range of ≤10.0 MPa, the elongation at break Kc of the crack suppression layer 15 is EB300%≤Kc EB Thus, delamination starting from the turned-up end 4e of the carcass layer 4, the outer radial end 11o of the first organic fiber reinforcing layer 11, and the outer radial end 12o of the second organic fiber reinforcing layer 12 can be effectively suppressed.

[0051] Here, when the 100% modulus Kc of the crack suppression layer 15 is M100 If the stress concentration is less than 4.5 MPa, stress concentration may be promoted at the turned-up end 4e of the carcass layer 4, the outer diameter end 11o of the first organic fiber reinforcing layer 11, and the outer diameter end 12o of the second organic fiber reinforcing layer 12, and delamination may occur starting from these ends. M100 When it exceeds 10.0 MPa, it is difficult to increase the elongation at break Kc of the crack suppression layer 15. EB Furthermore, when the elongation at break Kc of the crack suppression layer 15 is EB If the crack suppression layer 15 has a tensile strength of less than 300%, the crack suppression layer 15 has a poor elongation at break. EB The upper limit of % is preferably 500%.

[0052] Figure 7 Another modification of the organic fiber reinforcement layer embedded in the bead portion is shown. Figure 7 In the embodiment, the first organic fiber reinforcing layer 11 is the inner organic fiber reinforcing layer 11 located inward in the tire width direction, and the second organic fiber reinforcing layer 12 is the outer organic fiber reinforcing layer 12 located outward in the tire width direction. The outer organic fiber reinforcing layer 12 is arranged to cover the inner radial end 11i of the inner organic fiber reinforcing layer 11. The inner radial end 12i of the outer organic fiber reinforcing layer 12 is at least 5 mm away from the inner radial end 11i of the inner organic fiber reinforcing layer 11 and is located radially inward of a line segment L defined by a horizontal line drawn along the tire width direction from the outer end 10e of the steel reinforcing layer 10. The separation distance between the inner radial end 12i of the outer organic fiber reinforcing layer 12 and the inner radial end 11i of the inner organic fiber reinforcing layer 11 is measured along the steel reinforcing layer 10.

[0053] With the above-described structure, the inner diameter-side end 11i of the inner organic fiber reinforcing layer 11 is covered by the outer organic fiber reinforcing layer 12. Therefore, no rigid step (stress concentration area) is formed near the bead toe 3t of the bead portion 3. Therefore, even if the bead toe 3t of the bead portion 3 deforms during rim removal, delamination originating from the inner diameter-side end 11i of the inner organic fiber reinforcing layer 11 is less likely to occur. Furthermore, the inner diameter-side end 12i of the outer organic fiber reinforcing layer 12 is positioned appropriately, making delamination originating from the inner diameter-side end 12i of the outer organic fiber reinforcing layer 12 less likely to occur.

[0054] Here, when the distance between the inner radial end 12i of the outer organic fiber reinforcing layer 12 and the inner radial end 11i of the inner organic fiber reinforcing layer 11 is less than 5 mm, the inner radial end 12i of the outer organic fiber reinforcing layer 12 is located near the bead toe 3t of the bead portion 3. Therefore, delamination is likely to occur starting from the inner radial end 12i of the outer organic fiber reinforcing layer 12. Furthermore, the region R radially inward of a line segment L formed by a horizontal line drawn along the tire width direction from the outer end 10e of the steel reinforcing layer 10 in the tire width direction is a region that experiences little movement during tire rolling. However, when the inner radial end 12i of the outer organic fiber reinforcing layer 12 is located radially outward of the line segment L, the movement during tire rolling increases, and delamination is likely to occur from the inner radial end 12i of the outer organic fiber reinforcing layer 12.

[0055] In the above-mentioned pneumatic tire, it is preferable that the fiber structure of the organic fiber cords constituting the first and second organic fiber reinforcing layers 11 and 12 is in the range of 800 dtex / 2 to 1500 dtex / 2. By making the organic fiber cords constituting the first and second organic fiber reinforcing layers 11 and 12 thinner, as shown in FIG. Figure 7 As shown, the step portion generated when the second organic fiber reinforcing layer 12 is arranged so as to cover the inner diameter side end portion 11i of the first organic fiber reinforcing layer 11 can be reduced, stress concentration on the step portion is reduced, and delamination starting from the step portion of the second organic fiber reinforcing layer 12 can be suppressed. In addition, the organic fiber cords constituting the first and second organic fiber reinforcing layers 11 and 12 are kept to the minimum necessary thickness, thereby also achieving the effect of suppressing rubber flow.

[0056] Here, when the fiber structure of the organic fiber cord is less than 800 dtex / 2, the rubber flow in the bead portion 3 cannot be suppressed. Conversely, when it exceeds 1500 dtex / 2, the step portion generated when the first and second organic fiber reinforcing layers 11 and 12 are arranged so that one of the first and second organic fiber reinforcing layers 11 and 12 covers the inner diameter side end portions 11i and 12i of the other of the first and second organic fiber reinforcing layers 11 and 12 becomes larger, and delamination is easily caused due to stress concentration on this step portion.

[0057] In the above-mentioned pneumatic tire, if Figure 8 As shown, the distance A from vertex E, the most outwardly protruding vertex of the bead core 5 in the width direction, to the bead heel, measured along a straight line D passing through vertex E and parallel to the longest side of the bead core 5, is preferably within the range of 2.5 mm ≤ A ≤ 5.5 mm. By ensuring sufficient distance A, the bead core 5 is positioned closer to the bead toe 3t of the bead portion 3, thereby increasing the angle θ formed by the bead toe 3t of the bead portion 3. As a result, the rigidity of the bead toe 3t of the bead portion 3 is increased, making delamination less likely to occur starting from the inner diameter end 11i of the first organic fiber reinforcing layer 11 and the inner diameter end 12i of the second organic fiber reinforcing layer 12.

[0058] It should be noted that the specific method for calculating distance A is as follows. The bead core 5 has a stacked structure obtained by arranging multiple wires in the tire meridian cross-section. Vertex E is the point where a straight line D, which passes through the center of gravity of the wire located at the outermost position of the bead core 5 in the width direction and is parallel to the longest side of the bead core 5, intersects with the outline of the wire located at the outermost position in the width direction. Here, when calculating the imaginary intersection H where a straight line D, which passes through vertex E, which protrudes most outward in the width direction of the bead core 5 and is parallel to the longest side of the bead core 5, intersects with the extension line of the side forming the outline of the bottom surface of the bead and the extension line of the curve forming the outline of the back surface of the bead, a straight line M passing through this imaginary intersection H and being orthogonal to straight line D, and a straight line F passing through vertex E and being orthogonal to straight line D, distance A is the length of the line segment on straight line D that is divided between straight line M and straight line F.

[0059] Here, when the distance A is less than 2.5 mm, the position of the bead core 5 is not sufficiently close to the bead toe 3t side, and the increase in the rigidity of the bead toe 3t is small, so the effect of suppressing delamination is reduced. Conversely, when it exceeds 5.5 mm, it incurs excessive cost increase.

[0060] The pneumatic tire constructed according to the above embodiment preferably has a single-wheel load index of 121 or greater, or a carcass level of 10 PR or greater. Improving the durability of the bead portion in a pneumatic tire having such a load index or carcass level is extremely meaningful.

[0061] Example

[0062] A pneumatic tire with a tire size of 275 / 70R22.5 was produced, which includes a tread portion, a pair of sidewall portions, and a pair of bead portions, wherein a carcass layer composed of a plurality of steel cords is stretched between the pair of bead portions, the carcass layer is wound around the bead core of each bead portion from the inner side to the outer side of the tire, and a steel reinforcing layer composed of a plurality of steel cords is arranged in each bead portion so as to be wrapped in the carcass layer. The first and second organic fiber reinforcing layers are arranged in the bead portion (refer to Figure 2 ) and the tires of Conventional Examples 1 to 2, Comparative Examples 1 to 3, and Examples 1 to 12, with only the bead portion structure being different.

[0063] In the tires of Conventional Examples 1 to 2, Comparative Examples 1 to 3, and Examples 1 to 12, the distance P from the bead heel apex to the turned-up end of the carcass layer was set as shown in Tables 1 and 2. h , the distance A from the bead heel apex to the outer diameter side end of the first organic fiber reinforcement layer h , distance B from the bead heel apex to the outer diameter side end of the second organic fiber reinforcement layer h , the position of the inner diameter side end portion of the first organic fiber reinforced layer, the position of the inner diameter side end portion of the second organic fiber reinforced layer, the cord angle θ of the first organic fiber reinforced layer in the tire A , the cord angle θ of the first organic fiber reinforcement layer during the forming process A ', the cord angle θ of the second organic fiber reinforcement layer in the tire B , the cord angle θ of the second organic fiber reinforcement layer during the forming process B '、|θ B |-|θ A |、A h -P h , 100% modulus Kc of crack suppression layer M100 , elongation at break of crack suppression layer Kc EB The fiber structure of the organic fiber cords constituting the first organic fiber reinforcement layer and the second organic fiber reinforcement layer is 1400 dtex / 2.

[0064] Regarding the positions of the inner diameter side ends of the first organic fiber reinforced layer and the second organic fiber reinforced layer, the inner diameter side ends are positioned inward of the line segment J in the tire width direction as "inside", and the inner diameter side ends are positioned outward of the line segment J in the tire width direction as "outside". h >P h When the outer diameter side end of the first organic fiber reinforcement layer is located at a position closer to the tire radial direction than the turned-up end of the carcass layer, h <P h When the outer diameter side end portion of the second organic fiber reinforcing layer is located further inward in the tire radial direction than the turned-up end portion of the carcass layer.

[0065] For these test tires, delamination resistance (organic fiber reinforcing layer, carcass layer) was evaluated by the following test method, and the results are shown in Tables 1 and 2.

[0066] Delamination resistance (organic fiber reinforcement layer, carcass layer):

[0067] Each test tire was mounted on a JATMA-specified rim and subjected to a running test using a drum tester at 75% of the JATMA-specified air pressure, 1.4 times the JATMA-specified load, and a running speed of 49 km / h. After driving 40,000 km, the test tire was cut along the tire meridian at eight locations equally spaced around the tire circumference. The cross-sectional lengths of cracks originating from the ends of the organic fiber reinforcement layer and the turned-up ends of the carcass layer were measured at the eight cut surfaces on both bead sections (a total of 16 locations). The sum of the cross-sectional lengths of the cracks originating from the ends of the organic fiber reinforcement layer and the turned-up ends of the carcass layer was then calculated. The evaluation results were expressed as indices for the organic fiber reinforcement layer and the carcass layer, using the reciprocal of the measured values as 100 for each of the values in Example 2. A larger index value indicates superior delamination resistance.

[0068] [Table 1]

[0069]

[0070] [Table 2]

[0071]

[0072] As shown in Tables 1 and 2, the tires of Examples 1 to 12 maintain excellent delamination resistance in the carcass layer and significantly improve delamination resistance in the organic fiber reinforcement layer, compared to Conventional Example 2. It should be noted that Conventional Example 1 was unable to produce a tire due to a manufacturing failure. On the other hand, the tires of Comparative Examples 1 to 3 were prone to delamination originating at the outer diameter end of the second organic fiber reinforcement layer due to inappropriate cord angles in the second organic fiber reinforcement layer.

[0073] Next, tires of Examples 13 to 17 were produced, with some modifications to the tire structure of Example 1. In the tires of Examples 13 to 17, the first organic fiber reinforcement layer was the inner organic fiber reinforcement layer, and the second organic fiber reinforcement layer was the outer organic fiber reinforcement layer. Furthermore, the fiber structure of the inner organic fiber reinforcement layer, the position of the inner radial end of the inner fiber reinforcement layer, the fiber structure of the outer organic fiber reinforcement layer, the position of the inner radial end of the outer fiber reinforcement layer, the presence or absence of covering the inner radial end of the inner fiber reinforcement layer by the outer organic fiber reinforcement layer, the distance between the inner radial end of the outer organic fiber reinforcement layer and the inner radial end of the inner organic fiber reinforcement layer, the bead core distance A, and the bead toe angle θ were set as shown in Table 3.

[0074] Regarding the position of the inner diameter side end of the inner organic fiber reinforced layer, the inner diameter side end is located inward in the tire width direction relative to line segment J, and is designated as "inside" when the inner diameter side end is located outward in the tire width direction relative to line segment J. Regarding the position of the inner diameter side end of the outer organic fiber reinforced layer, the inner diameter side end is located inward in the tire radial direction relative to line segment L, and is designated as "lower side" when the inner diameter side end is located outward in the tire radial direction relative to line segment L, and is designated as "upper side" when the inner diameter side end is located outward in the tire radial direction relative to line segment L.

[0075] For these test tires, delamination resistance (organic fiber reinforcement layer) was evaluated by the following test method, and the results are shown in Table 3.

[0076] Delamination resistance (organic fiber reinforcement):

[0077] Each test tire was mounted on a JATMA-specified rim and subjected to a running test using a drum tester at 75% of the JATMA-specified air pressure, 1.4 times the JATMA-specified load, and a running speed of 49 km / h. After traveling 40,000 km, the test tire was cut along the tire meridian at eight locations equally spaced around the tire circumference. The cross-sectional lengths of cracks originating from the ends of the organic fiber-reinforced layer were measured at the eight cut surfaces on both bead sections (a total of 16 locations). The sum of the cross-sectional lengths of the cracks originating from the ends of the organic fiber-reinforced layer was then calculated. The evaluation results were expressed as an index, using the reciprocal of the measured values, with Example 2 as 100. A larger index value indicates greater delamination resistance.

[0078] [Table 3]

[0079]

[0080] As can be seen from Table 3, the tires of Examples 13 to 17, like Examples 1 to 12, had good delamination resistance related to the organic fiber reinforcement layer.

[0081] Description of Reference Numerals

[0082] 1. Tread

[0083] 2 Sidewall

[0084] 3 Bead

[0085] 3t toe

[0086] 3b Bead base

[0087] 3h heel peak

[0088] 4 carcass layers

[0089] 4e Rolled End

[0090] 5 Bead core

[0091] 6 Bead filler

[0092] 7 Belt

[0093] 10 Steel reinforcement layer

[0094] 10e end

[0095] 111st organic fiber reinforcement layer

[0096] 11i Inner diameter end

[0097] 11o outer diameter side end

[0098] 12 Second organic fiber reinforcement layer

[0099] 12i Inner diameter end

[0100] 12o outer diameter side end

[0101] 13 Sidewall rubber layer

[0102] 14 Rim cushion rubber layer

[0103] 15 Crack suppression layer

Claims

1. A pneumatic tire comprising: a tread portion extending in a ring shape along the circumferential direction of the tire; a pair of sidewall portions, the pair of sidewall portions being arranged on both sides of the tread portion; and a pair of bead portions, the pair of bead portions being arranged on the inner side of the sidewall portions in the tire outer diameter direction, a carcass layer being spanned between the pair of bead portions, the carcass layer being wound around the bead core of each bead portion from the inner side to the outer side of the tire, and a steel reinforcing layer including a plurality of steel cords being arranged in each bead portion in a manner of enclosing the carcass layer, characterized in that A first organic fiber reinforcement layer and a second organic fiber reinforcement layer are disposed on the outer side of the steel reinforcement layer in the tire width direction. The first organic fiber reinforcement layer and the second organic fiber reinforcement layer each include a plurality of organic fiber cords aligned in one direction. The organic fiber cords constituting the first organic fiber reinforcement layer and the second organic fiber reinforcement layer are oriented so as to intersect with each other between the layers. The outer diameter side end portion of the first organic fiber reinforcing layer is located further outward in the tire radial direction than the turned-up end portion of the carcass layer. The outer diameter side end of the second organic fiber reinforcing layer is located inward in the tire radial direction relative to the turned-up end of the carcass layer and outward in the tire radial direction relative to a line segment formed by a horizontal line drawn in the tire width direction from the apex of the bead core that protrudes most radially outward from the tire. The inner diameter side ends of the first organic fiber reinforcing layer and the second organic fiber reinforcing layer are both located inward in the tire width direction relative to a line segment formed by a normal line drawn from the vertex of the bead core most protruding inward in the tire radial direction to the bead base surface. The cord angle θ of the first organic fiber reinforcement layer relative to the tire circumferential direction is A At 20°≤|θ A |≤45° or 70°≤|θ A |≤90 ° range, the second organic fiber reinforcement layer with respect to the tire circumferential cord angle θ B At 20°≤|θ B |≤45° or 70°≤|θ B |≤90° range.

2. The pneumatic tire according to claim 1, wherein: The first organic fiber reinforcement layer and the second organic fiber reinforcement layer have their cords inclined in opposite directions relative to the tire circumferential direction. The cord angle θ of the first organic fiber reinforcement layer relative to the tire circumferential direction is A At 20°≤|θ A |≤45° range.

3. The pneumatic tire according to claim 1, wherein: The first organic fiber reinforcement layer and the second organic fiber reinforcement layer have the same inclination direction of the cords relative to the tire circumferential direction. The cord angle θ of the first organic fiber reinforcement layer relative to the tire circumferential direction is A At 20°≤|θ A |≤45°, the cord angle θ of the second organic fiber reinforcing layer relative to the tire circumferential direction B In |θ A |+20≤|θ B |range.

4. The pneumatic tire according to any one of claims 1 to 3, wherein: The distance A from the bead heel apex to the outer diameter side end of the first organic fiber reinforcing layer is h and the distance P from the bead heel apex to the turned-up end of the carcass layer. h Satisfy A h -P h ≥5.0mm.

5. The pneumatic tire according to any one of claims 1 to 4, characterized in that A crack suppression layer is embedded in a position adjacent to the turned-up end of the carcass layer, the outer end of the steel reinforcement layer in the tire width direction, the outer diameter side end of the first organic fiber reinforcement layer, and the outer diameter side end of the second organic fiber reinforcement layer. The 100% modulus Kc of the crack suppression layer is M100 At 4.5MPa≤Kc M100 ≤10.0MPa, the elongation at break Kc of the crack suppression layer EB 300%≤Kc EB range.

6. The pneumatic tire according to any one of claims 1 to 5, characterized in that: One of the first organic fiber reinforced layer and the second organic fiber reinforced layer is an inner organic fiber reinforced layer located inward in the tire width direction, and the other of the first organic fiber reinforced layer and the second organic fiber reinforced layer is an outer organic fiber reinforced layer located outward in the tire width direction. The outer organic fiber reinforcement layer is arranged so as to cover the inner diameter side end portion of the inner organic fiber reinforcement layer, the inner diameter side end portion of the outer organic fiber reinforcement layer being separated from the inner diameter side end portion of the inner organic fiber reinforcement layer by more than 5 mm and being located closer to the tire radial direction than a line segment formed by a horizontal line drawn along the tire width direction from the tire width direction outer end portion of the steel reinforcement layer.

7. The pneumatic tire according to any one of claims 1 to 6, wherein: The fiber structure of the organic fiber cords constituting the first organic fiber reinforcement layer and the second organic fiber reinforcement layer is respectively within a range of 800 dtex / 2 to 1500 dtex / 2.

8. The pneumatic tire according to any one of claims 1 to 7, wherein: A distance A from the apex of the bead core most protruding outward in the width direction to the bead heel position, measured along a straight line passing through the apex of the bead core and parallel to the longest side of the bead core, is in a range of 2.5 mm ≤ A ≤ 5.5 mm.

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