pneumatic tires

Abstract

Provided is a pneumatic tire wherein organic fiber reinforcing layers 11, 12 are disposed on the tire-widthwise outer side of a steel reinforcing layer 10, each of the organic fiber reinforcing layers 11, 12 contains a plurality of organic fiber cords aligned in one direction, the organic fiber cords constituting the organic fiber reinforcing layers 11, 12 are oriented so as to cross each other between layers, an outer-diameter-side end part 11i of the organic fiber reinforcing layer 11 is positioned farther outward along the tire diameter than a wound-up end part 4e of a carcass layer 4, an outer-diameter-side end part 12i of the organic fiber reinforcing layer 12 is positioned farther inward along the tire diameter than the wound-up end part 4e of the carcass layer 4 and farther outward along the tire diameter than a line segment K, inner-diameter-side end parts 11i, 12i of the organic fiber reinforcing layers 11, 12 are both positioned farther inward along the tire width direction than a line segment J, a cord angle θA of the organic fiber reinforcing layer 11 is within the range 20°≤|θA|≤45° or 70°≤|θA|≤90°, and a cord angle θB of the organic fiber reinforcing layer 12 is within the range 20°≤|θB|≤45° or 70°≤|θB|≤90°.

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire having a structure in which a carcass layer is wound up from the inside to the outside of the tire around the bead core of each bead portion, and more specifically to a pneumatic tire that can effectively suppress separation originating from the outer diameter side end of an organic fiber reinforcing layer embedded in the bead portion while suppressing separation originating from the wound-up end of the carcass layer. [Background technology]

[0002] Some heavy-duty pneumatic tires used for trucks, buses, and the like have a carcass layer mounted between a pair of bead portions, the carcass layer wrapped around the bead core of each bead portion from the inside to the outside of the tire, and a steel reinforcing layer containing multiple steel cords arranged in each bead portion so as to encase the carcass layer.In order to prevent separation originating from the wrapped end of the carcass layer in such pneumatic tires, two organic fiber reinforcing layers are embedded on the outer side in the tire width direction of the steel reinforcing layer, the organic fiber cords including multiple organic fiber cords arranged so that these organic fiber cords cross each other between the layers (see, for example, Patent Document 1).

[0003] However, when two cross-laminated organic fiber reinforced layers are arranged in the bead portion, separation starting from the outer diameter side end portion is likely to occur. More specifically, because the two organic fiber reinforced layers are arranged so that their end positions are offset from each other, one of the organic fiber reinforced layers becomes a single layer at the outer diameter side end portion. When the two cross-laminated organic fiber reinforced layers are lifted up radially outward in the tire building process, the organic fiber reinforced layer tends to have a high angle in the single layer region outside the lamination region. As a result, the tension generated in the organic fiber cords constituting the organic fiber reinforced layer increases, making separation starting from the outer diameter side end portion more likely to occur. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent No. 6554957 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pneumatic tire that can effectively suppress separation originating from the outer diameter side end of an organic fiber reinforcement layer embedded in a bead portion while suppressing separation originating from the wound-up end of a carcass layer. [Means for solving the problem]

[0006] In order to achieve the above object, the pneumatic tire of the present invention comprises 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 radially inward of the sidewall portions, wherein a carcass layer is fitted between the pair of bead portions, the carcass layer is wound up around the bead cores of each bead portion from the inside to the outside of the tire, and a steel reinforcing layer including a plurality of steel cords is disposed in each bead portion so as to encase the carcass layer; first and second organic fiber reinforcement layers are disposed on outer sides of the steel reinforcement layer in the tire width direction, each of the first and second organic fiber reinforcement layers includes a plurality of organic fiber cords aligned in one direction, and the organic fiber cords constituting the first and second organic fiber reinforcement layers are oriented so as to cross each other between the layers; an outer diameter side end portion of the first organic fiber reinforcement layer is located radially outward of a turned-up end portion of the carcass layer, an outer diameter side end portion of the second organic fiber reinforcement layer is located radially inward of a turned-up end portion of the carcass layer and radially outward of a line segment formed by a horizontal line drawn in the tire width direction from a vertex that protrudes most radially outward of the bead core, each of the first and second organic fiber reinforcement layers has an inner diameter side end portion located inward in the tire width direction of a line segment formed from a normal line drawn from a vertex of the bead core that protrudes most inward in the tire radial direction to a surface of the bead base; a cord angle θ of the first organic fiber reinforcing layer with respect to the tire circumferential direction; A , 20°≦|θ A |≦45° or 70°≦|θ A ≦90°, and the tie of the second organic fiber reinforced layer Cord angle θ relative to the circumferential direction B , 20°≦|θ B |≦45° or 70°≦|θ B |≦9 It is characterized by being in the range of 0°. [Effects of the Invention]

[0007] As a result of extensive research into tire structures in which organic fiber reinforcement layers are arranged in the bead portions, the inventors have discovered that cross-laminated organic fiber reinforcement layers suppress the flow of rubber in the bead portions during vulcanization, thereby bringing the carcass layer closer to the equilibrium carcass line and suppressing separation originating from the turned-up end of the carcass layer; in other words, they have discovered that there is no need to cross-laminated organic fiber reinforcement layers near the turned-up end of the carcass layer, and have arrived at the present invention.

[0008] In other words, in the present invention, first and second organic fiber reinforcement layers are arranged cross-laminated on the outer side of the steel reinforcement layer in the tire width direction, and both the first and second organic fiber reinforcement layers extend at least to below the bead core, based on a line segment formed by a normal drawn from the apex that protrudes most inward in the tire radial direction of the bead core to the surface of the bead base. This suppresses rubber flow in the bead portion during vulcanization, moves the bead core closer to the toe side, and brings the carcass layer closer to the balanced carcass line. This makes it possible to suppress separation originating from the wrap-up end of the carcass layer. Furthermore, by positioning the outer diameter side end of the first organic fiber reinforcement layer radially outward of the turned-up end of the carcass layer, while positioning the outer diameter side end of the second organic fiber reinforcement layer radially inward of the turned-up end of the carcass layer and radially outward of 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 of the tire, the lift rate when the cross-laminated first and second organic fiber reinforcement layers are lifted up radially outward in the tire building process is reduced, and it is possible to prevent the first organic fiber reinforcement layer 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 is reduced. A and second organic fiber Cord angle θ of the fiber reinforcement layer relative to the tire circumferential direction B The tension generated in the organic fiber cord is It is possible to set the range so that the difference is small, and separation originating from the outer diameter side ends of the first and second organic fiber reinforced layers can be effectively suppressed.

[0009] In the present invention, when the cord inclination directions of the first and second organic fiber reinforced layers with respect to the tire circumferential direction are opposite to each other, the cord angle θ of the first organic fiber reinforced layer with respect to the tire circumferential direction is A teeth , 20°≦|θ A It is preferable that the outer diameter side end is in the range of |≦45°. The cord angle θ of the first organic fiber reinforcing layer is A By setting the value to a small value, the first organic Separation originating from the outer diameter side end of the fiber reinforcement layer can be effectively suppressed. Also, since the cord inclination directions of the first and second organic fiber reinforcement layers with respect to the tire circumferential direction are opposite to each other, rubber flow in the bead portion during vulcanization can be effectively suppressed.

[0010] In the present invention, when the cord inclination directions of the first and second organic fiber reinforced layers with respect to the tire circumferential direction are the same, the cord angle θ of the first organic fiber reinforced layer with respect to the tire circumferential direction is A teeth , 20°≦|θ A ≦45°, and the angle of the second organic fiber reinforcing layer relative to the tire circumferential direction is Cord angle θ B is |θ A |+20≦|θ B It is preferable that the range is in the range of |. Cord angle θ of the first organic fiber reinforcing layer in which the outer diameter side end is a single layer A By setting As a result, separation originating from the outer diameter side end of the first organic fiber reinforced layer can be effectively suppressed. B The first organic fiber reinforced layer Code angle θ A By making it sufficiently large for the rubber of the bead part during vulcanization, The flow can be effectively suppressed.

[0011] Distance A from the bead heel apex to the outer diameter side end of the first organic fiber reinforced layer h and Distance P from the bead heel apex to the wrap-up end of the carcass layer h Toga A h -P h It is preferable that the relationship of ≧5.0 mm is satisfied. This can alleviate stress concentration at the turned-up end of the carcass layer and effectively suppress separation from the turned-up end.

[0012] Crack suppression layers are embedded in positions adjacent to the wound-up end of the carcass layer, the outer end of the steel reinforcing layer in the tire width direction, the outer diameter side end of the first organic fiber reinforcing layer, and the outer diameter side end of the second organic fiber reinforcing layer, and the 100% modulus Kc of the crack suppression layer is M100 is 4.5MPa≦Kc M100 ≦10.0MPa, and the fracture elongation Kc of the crack suppression layer EB is 300%≦Kc EB It is preferable that the modulus is in the range of 100%. This makes it possible to effectively suppress separation originating from the turned-up end of the carcass layer, the outer diameter side end of the first organic fiber reinforced layer, and the outer diameter side end of the second organic fiber reinforced layer. The 100% modulus and breaking elongation are measured in accordance with JIS-K6251.

[0013] Preferably, one of the first and second organic fiber reinforced layers is an inner organic fiber reinforced layer located on the inner side in the tire width direction, and the other of the first and second organic fiber reinforced layers is an outer organic fiber reinforced layer located on the outer side in the tire width direction, the outer organic fiber reinforced layer is arranged to cover the inner diameter side end of the inner organic fiber reinforced layer, the inner diameter side end of the outer organic fiber reinforced layer is 5 mm or more away from the inner diameter side end of the inner organic fiber reinforced layer and is located radially inward in the tire direction of a line segment consisting of a horizontal line drawn in the tire width direction from the outer end of the steel reinforced layer in the tire width direction. In this case, even if the toe of the bead portion is deformed when removing from the rim, separation originating from the inner diameter side end of the outer organic fiber reinforced layer and the inner diameter side end of the inner organic fiber reinforced layer is unlikely to occur.

[0014] The fiber structure of the organic fiber cords constituting the first and second organic fiber reinforced layers is preferably in the range of 800 dtex / 2 to 1500 dtex / 2. By thinning the organic fiber cords constituting the first and second organic fiber reinforced layers in this manner, a step that occurs when one of the first and second organic fiber reinforced layers is arranged to cover the inner diameter side end of the other of the first and second organic fiber reinforced layers is reduced, stress concentration at the step is reduced, and separation originating from the step of the first or second organic fiber reinforced layer can be suppressed. Furthermore, because the organic fiber cords constituting the first and second organic fiber reinforced layers have the minimum necessary thickness, the effect of suppressing rubber flow can also be exhibited.

[0015] It is preferable that the distance A from the apex protruding most outward in the width direction of the bead core to the bead heel position, measured along a straight line parallel to the longest side of the bead core, is in the range of 2.5 mm≦A≦5.5 mm. By ensuring a sufficient distance A, the bead core is positioned 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 is increased, and separation originating from the inner diameter side end of the first organic fiber reinforced layer and the inner diameter side end of the second organic fiber reinforced layer is less likely to occur. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a meridian cross-sectional view showing a heavy-duty pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a bead portion of the pneumatic tire of FIG. [Figure 3] 3 is another cross-sectional view showing the bead portion of the pneumatic tire of FIG. [Figure 4] FIG. 4 is a side view showing the organic fiber reinforcing layer embedded in the bead portion. [Figure 5] FIG. 5 is a diagram showing the relationship between the cord angle and tension of the organic fiber reinforcing layer. [Figure 6]FIG. 6 is a side view showing a modified example of an organic fiber reinforcing layer embedded in a bead portion. [Figure 7] FIG. 7 is a cross-sectional view showing another modified example of an organic fiber reinforcing layer embedded in a bead portion. [Figure 8] FIG. 8 is another cross-sectional view showing the organic fiber reinforced layer of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 shows a heavy-duty pneumatic tire according to an embodiment of the present invention, and Figs. 2 to 4 show its main parts.

[0018] As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially in a ring shape, 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 radially inward of the sidewall portions 2.

[0019] A carcass layer 4 is mounted between the 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 in which the carcass layer 4 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 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0020] 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 include two central main belt layers 72, 73 in which the belt cords intersect with each other, and auxiliary belt layers 71, 74 arranged on the inner diameter side and 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 the range of 15° to 35°, for example, 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 the range of 15° to 75°, for example.

[0021] In the pneumatic tire, a steel reinforcing layer 10 including a plurality of steel cords is disposed in each bead portion 3 so as to encase the carcass layer 4, the bead core 5, and the bead filler 6. First and second organic fiber reinforcing layers 11, 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, 12 includes 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, 12 are oriented so as to cross each other between the layers.

[0022] As shown in Fig. 2, the outer diameter side end 11o of the first organic fiber reinforcement layer 11 is located radially outward of 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 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 formed by a horizontal line drawn in the tire width direction from the apex of the bead core 5 that protrudes most radially outward in the tire direction. In other words, the first and second organic fiber reinforcement layers 11, 12 are laminated, but form a single-layer structure near the turned-up end 4e of the carcass layer 4. The horizontal line used to identify the line segment K is determined for the tire alone when no load is applied.

[0023] The inner diameter side end portions 11i, 12i of the first and second organic fiber reinforced layers 11, 12 are both located on the inner side in the tire width direction of a line segment J formed by a normal line drawn from the vertex that protrudes most inward in the tire radial direction of the bead core 5 to the surface of the bead base 3b. In other words, the first and second organic fiber reinforced layers 11, 12 extend below the bead core 5.

[0024] As shown in FIG. 4, the cord angle θ of the first organic fiber reinforcing layer 11 with respect to the tire circumferential direction is A , 20°≦|θ A |≦45° or 70°≦|θ A 1. The cord angle θ of the second organic fiber reinforcing layer 12 with respect to the tire circumferential direction is set in the range of |≦90°. B , 20°≦|θ B |≦45° or 70°≦|θ B The cord angle θ is set to the range of |≦90°. A ,θ B The first and This is the angle of the organic fiber cord with respect to the tire circumferential direction measured at the outer diameter side ends 11o, 12o of the second organic fiber reinforced layers 11, 12. The cord inclination direction with respect to the tire circumferential direction of the first and second organic fiber reinforced layers 11, 12 may be any. For example, the cord angle θ of the first and second organic fiber reinforced layers 11, 12 A ,θ B is a positive value (+) when the organic fiber cords constituting them are inclined to one side with respect to the tire circumferential direction, and is a negative value (-) when the organic fiber cords constituting them are inclined to the other side with respect to the tire circumferential direction.

[0025] According to the pneumatic tire described above, the first and second organic fiber reinforcement layers 11, 12 are arranged in a cross-laminated configuration on the outer side of the steel reinforcement layer 10 in the tire width direction, and both the first and second organic fiber reinforcement layers 11, 12 extend at least to below the bead core 5, based on a line segment J formed by a normal drawn from the apex that protrudes most inward in the tire radial direction of the bead core 5 to the surface of the bead base 3b. This suppresses rubber flow in the bead portion 3 during vulcanization, moves the bead core 5 closer to the toe 3t side, and brings the carcass layer 4 closer to the balanced carcass line. This suppresses separation originating from the turned-up end 4e of the carcass layer 4.

[0026] Furthermore, by disposing the outer diameter side end 11o of the first organic fiber reinforced layer 11 radially outward of the turned-up end 4e of the carcass layer 4, while disposing the outer diameter side end 12o of the second organic fiber reinforced layer 12 radially inward of the turned-up end 4e of the carcass layer 4 and radially outward of a line segment K formed by a horizontal line drawn in the tire width direction from the apex of the bead core 5 that protrudes most radially outward in the tire direction, the lift rate when the cross-laminated first and second organic fiber reinforced layers 11, 12 are lifted up radially outward in the tire building process is reduced, and it is possible to prevent the first organic fiber reinforced layer 11 from forming a high angle near its outer diameter side end 11o. Note that, because the first organic fiber reinforced layer 11 extends radially outward of the turned-up end 4e of the carcass layer 4, the effect of suppressing rubber flow in the bead portion 3 during vulcanization is sufficiently ensured.

[0027] As described above, the first organic fiber reinforced layer 11 is prevented from having a high angle near its outer diameter side end 11o, so the cord angle θ of the first organic fiber reinforced layer 11 with respect to the tire circumferential direction is A and the cord angle θ of the second organic fiber reinforcing layer with respect to the tire circumferential direction B The organic fiber It is possible to set the tension in the wire to a range that reduces the tension generated in the wire, and separation originating from the outer diameter side ends 11o, 12o of the first and second organic fiber reinforced layers 11, 12 can be effectively suppressed.

[0028] Fig. 5 shows the relationship between the cord angle and tension of the organic fiber reinforced layer. In Fig. 5, "◇" indicates data for the first organic fiber reinforced layer 11 containing a plurality of organic fiber cords aligned in one direction, and "×" indicates data for the second organic fiber reinforced layer 12 containing a plurality of organic fiber cords aligned in one direction. As shown in Fig. 5, the first organic fiber reinforced layer 11 has a cord angle θ A is 20°≦|θ A |≦45° or 70°≦|θ A When the cord angle θ is in the range of |≦90°, the tension is low, and the second organic fiber reinforcing layer 12 has a cord angle θ B is 20°≦|θ B |≦45° or 70°≦|θ B |≦90° Therefore, the tension tends to be low when the cord angle θ A ,θ B By setting the value of the thickness of the first and second organic fiber reinforced layers 11, 12 within the above range, an increase in tension can be avoided, and separation originating from the outer diameter side ends 11o, 12o of the first and second organic fiber reinforced layers 11, 12 can be suppressed.

[0029] Here, the cord angle θ of the first organic fiber reinforcing layer 11 A is 45°<|θ A If the cord angle θ of the second organic fiber reinforced layer 12 is in the range of |<70°, separation starting from the outer diameter side end 11o of the first organic fiber reinforced layer 11 is likely to occur. B is 45°<|θ B If the cord angle |θ is in the range of |<70°, separation starting from the outer diameter side end 12o of the second organic fiber reinforced layer 12 is likely to occur. A |,|θ BIf the cord angle θ of the first organic fiber reinforced layer 11 relative to the tire circumferential direction is less than 20°, it becomes difficult to lift up the cross-laminated first and second organic fiber reinforced layers 11, 12 outward in the tire radial direction during the tire building process. A , 25°≦|θ A |≦40° or 75°≦|θ A | ≦85°, and the cord angle θ of the second organic fiber reinforcing layer 12 with respect to the tire circumferential direction is set in the range B , 25°≦|θ B |≦40° or 75°≦|θ B | Set in the range of ≦85° It is desirable that:

[0030] As shown in FIG. 4, when the cord inclination directions of the first and second organic fiber reinforced layers 11 and 12 with respect to the tire circumferential direction are opposite to each other, the cord angle θ of the first organic fiber reinforced layer 11 with respect to the tire circumferential direction is A , 20°≦|θ A |≦45°, more preferably, 20°≦|θ A |≦35 In this way, the cord angle θ of the first organic fiber reinforcing layer 11, which is a single layer at the outer diameter side end 11o, is preferably in the range of 0°. A By setting the value to be small, the outer diameter side of the first organic fiber reinforced layer 11 Separation originating from the end 11o can be effectively suppressed. In addition, since the cords of the first and second organic fiber reinforced layers 11, 12 are inclined in opposite directions relative to the tire circumferential direction, rubber flow in the bead portion during vulcanization can be effectively suppressed. As a result, the carcass line can be more evenly distributed.

[0031] Fig. 6 shows a modified example of an organic fiber reinforced layer embedded in a bead portion. As shown in Fig. 6, the cord inclination directions of the first and second organic fiber reinforced layers 11 and 12 with respect to the tire circumferential direction may be the same. In this case, the cord angle θ of the first organic fiber reinforced layer 11 with respect to the tire circumferential direction is A , 20°≦|θ A |≦45°, more preferably, 20°≦|θA |≦40° and the cord angle θ of the second organic fiber reinforcing layer 12 with respect to the tire circumferential direction is in the range B is | θ A |+20≦|θ B In this way, the cord angle θ of the first organic fiber reinforcing layer 11, which is a single layer at the outer diameter side end 11o, is preferably in the range of |. A By setting the value to a small value, the first organic fiber It is possible to effectively suppress separation starting from the outer diameter side end 11o of the reinforcing layer 11. In addition, the cord angle θ B The first organic fiber reinforced layer 11 Cord angle θ A By making the thickness of the first and second organic fiber reinforced layers 1 sufficiently large with respect to Even if the cord inclination directions of the first and second organic fiber reinforced layers 11 and 12 are the same, the flow of rubber in the bead portion during vulcanization can be effectively suppressed. As a result, the carcass line can be promoted to be balanced. In addition, since the first and second organic fiber reinforced layers 11 and 12 are cross-laminated with the same cords, the cord angle θ of the second organic fiber reinforced layer 12 can be effectively suppressed. B The cord angle of the first organic fiber reinforcing layer 11 θ A Even if the angle is increased by 20° or more, the tension of the second organic fiber reinforced layer 12 is unlikely to increase. Therefore, separation originating from the outer diameter side end 12o of the second organic fiber reinforced layer 12 can be effectively suppressed.

[0032] As shown in FIG. 3, 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 reinforced layer 11 is h and the bead heel apex 3h of the bead portion 3 to the carcass layer Distance P to the winding end 4e of 4 h What is A h -P h It is good to satisfy the relationship ≧5.0mm That is, it is preferable that the first organic fiber reinforcement layer 11 sufficiently protrudes outward in the tire radial direction beyond the turned-up end 4e of the carcass layer 4. This alleviates stress concentration at the turned-up end 4e of the carcass layer 4, and effectively suppresses separation from the turned-up end 4e. h -P h If the thickness is less than 5.0 mm, the effect of suppressing separation from the turned-up end 4e of the carcass layer 4 decreases. h -P h ≧8.0 mm. 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 reinforced layer 12 is preferably h and bead heel apex 3 of bead part 3 Distance P from h to the turned-up end 4e of the carcass layer 4 h What is P h >B h Satisfied with the relationship do.

[0033] As shown in FIG. 2 , a sidewall rubber layer 13 and a rim cushion rubber layer 14 are disposed in the region extending from the sidewall portion 2 to the bead portion 3, and are exposed on the tire outer surface. In the region 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 at 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 diameter side end 11o of the first organic fiber reinforcing layer 11, and the outer diameter side end 12o of the second organic fiber reinforcing layer 12. The turned-up end 4e of the carcass layer 4 and the outer diameter side end 10e of the steel reinforcing layer 10 in the tire width direction may be covered with edge tape. If such edge tape is attached, the crack suppression layer 15 will be adjacent to the turned-up end 4e of the carcass layer 4 and the outer diameter side end 10e of the steel reinforcing layer 10 via the edge tape. The 100% modulus Kc of the crack suppression layer 15 is M100 is 4.5MPa≦Kc M100 ≦10.0 MPa, and the fracture elongation Kc of the crack suppression layer 15 EB is 300%≦KcEB This makes it possible to effectively suppress separation originating from the turned-up end 4e of the carcass layer 4, the outer diameter side end 11o of the first organic fiber reinforced layer 11, and the outer diameter side end 12o of the second organic fiber reinforced layer 12.

[0034] Here, the 100% modulus Kc of the crack suppression layer 15 M100 If the 100% modulus Kc of the crack suppression layer 15 is less than 4.5 MPa, stress concentration at the turned-up end 4e of the carcass layer 4, the outer diameter side end 11o of the first organic fiber reinforced layer 11, and the outer diameter side end 12o of the second organic fiber reinforced layer 12 will be promoted, and separation may occur starting from these points. M100 If the elongation at break Kc of the crack suppression layer 15 exceeds 10.0 MPa, EB It becomes difficult to make the breaking elongation Kc of the crack suppression layer 15 300% or more. EB If the elongation at break Kc of the crack suppression layer 15 is less than 300%, the effect of suppressing separation originating from the turned-up end 4e of the carcass layer 4, the outer diameter side end 11o of the first organic fiber reinforced layer 11, and the outer diameter side end 12o of the second organic fiber reinforced layer 12 will be reduced. EB The upper limit is preferably 500%.

[0035] FIG. 7 shows another modified example of an organic fiber reinforced layer embedded in a bead portion. In FIG. 7, the first organic fiber reinforced layer 11 is an inner organic fiber reinforced layer 11 located on the inner side in the tire width direction, and the second organic fiber reinforced layer 12 is an outer organic fiber reinforced layer 12 located on the outer side in the tire width direction. The outer organic fiber reinforced layer 12 is disposed so as to cover the inner diameter side end 11i of the inner organic fiber reinforced layer 11, and the inner diameter side end 12i of the outer organic fiber reinforced layer 12 is 5 mm or more away from the inner diameter side end 11i of the inner organic fiber reinforced layer 11 and is located radially inward of a line segment L formed by a horizontal line drawn in the tire width direction from the outer end 10e of the steel reinforced layer 10 in the tire width direction. The distance between the inner diameter side end 12i of the outer organic fiber reinforced layer 12 and the inner diameter side end 11i of the inner organic fiber reinforced layer 11 is measured along the steel reinforced layer 10.

[0036] When the above-described structure is adopted, the inner diameter side end 11i of the inner organic fiber reinforced layer 11 is covered by the outer organic fiber reinforced layer 12, so no rigidity step (stress concentration area) is formed near the toe 3t of the bead portion 3. Therefore, even if the toe 3t of the bead portion 3 is deformed when the tire is removed from the rim, separation originating from the inner diameter side end 11i of the inner organic fiber reinforced layer 11 is unlikely to occur. Furthermore, the inner diameter side end 12i of the outer organic fiber reinforced layer 12 is also positioned appropriately, so separation originating from the inner diameter side end 12i of the outer organic fiber reinforced layer 12 is unlikely to occur.

[0037] Here, if the distance between the inner diameter side end 12i of the outer organic fiber reinforced layer 12 and the inner diameter side end 11i of the inner organic fiber reinforced layer 11 is less than 5 mm, the inner diameter side end 12i of the outer organic fiber reinforced layer 12 is located near the toe 3t of the bead portion 3, and separation starting from the inner diameter side end 12i of the outer organic fiber reinforced layer 12 is likely to occur. Furthermore, a region R radially inward of a line segment L formed by a horizontal line drawn in the tire width direction from the outer end 10e of the steel reinforced layer 10 in the tire width direction is a region that moves little when the tire rolls, but if the inner diameter side end 12i of the outer organic fiber reinforced layer 12 is located radially outward of the line segment L, movement during tire rolling becomes large, and separation is likely to occur from the inner diameter side end 12i of the outer organic fiber reinforced layer 12.

[0038] In the above-described pneumatic tire, the fiber structure of the organic fiber cords constituting the first and second organic fiber reinforced layers 11, 12 preferably ranges from 800 dtex / 2 to 1500 dtex / 2. By thinning the organic fiber cords constituting the first and second organic fiber reinforced layers 11, 12 in this manner, as shown in Fig. 7, a step portion that occurs when the second organic fiber reinforced layer 12 is arranged to cover the inner diameter side end portion 11i of the first organic fiber reinforced layer 11 is reduced in size, stress concentration at the step portion is reduced, and separation originating from the step portion of the second organic fiber reinforced layer 12 can be suppressed. Furthermore, because the organic fiber cords constituting the first and second organic fiber reinforced layers 11, 12 have a minimum necessary thickness, the effect of suppressing rubber flow can also be exhibited.

[0039] Here, if the fiber structure of the organic fiber cord is smaller than 800 dtex / 2, the flow of rubber in the bead portion 3 cannot be suppressed. Conversely, if it is larger than 1500 dtex / 2, a step portion that occurs when one of the first and second organic fiber reinforced layers 11, 12 is arranged so as to cover the inner diameter side end portions 11i, 12i of the other of the first and second organic fiber reinforced layers 11 becomes large, and separation is more likely to be suppressed due to stress concentration at the step portion.

[0040] In the above pneumatic tire, as shown in Fig. 8, the distance A from the vertex E of the bead core 5 that protrudes most outward in the width direction to the bead heel position, measured along a straight line D that passes through the vertex E and is parallel to the longest side of the bead core 5, is preferably in the range of 2.5 mm≦A≦5.5 mm. By ensuring a sufficient distance A in this way, the position of the bead core 5 is closer to the toe 3t 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 is increased, and separation originating from the inner diameter side end 11i of the first organic fiber reinforced layer 11 and the inner diameter side end 12i of the second organic fiber reinforced layer 12 is less likely to occur.

[0041] The specific method for calculating distance A is as follows. The bead core 5 has a laminated structure in which multiple wires are arranged in a tire meridian cross section. Vertex E is the point where a line D, which passes through the center of gravity of the wire located at the outermost side 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 side in the width direction. Here, when a line D passing through the vertex E that protrudes most outward in the width direction of the bead core 5 and is parallel to the longest side of the bead core 5, an imaginary intersection H is obtained where an extension of an edge forming the profile of the bead bottom surface and an extension of a curve forming the profile of the bead back surface intersect, a line M passing through imaginary intersection H and perpendicular to line D, and a line F passing through vertex E and perpendicular to line D are obtained, distance A is the length of the line segment on line D defined between line M and line F.

[0042] Here, if the distance A is less than 2.5 mm, the position of the bead core 5 will not be close enough to the toe 3t side, and the increase in rigidity of the toe 3t will be small, reducing the effect of suppressing separation. Conversely, if the distance A is more than 5.5 mm, it will result in an excessive increase in costs.

[0043] The pneumatic tire according to the above-described embodiment preferably has a single wheel load index of 121 or more or a ply rating of 10PR or more. It is extremely significant to improve the durability of the bead portion of a pneumatic tire having such a load index or ply rating. [Example]

[0044] In a pneumatic tire having a tire size of 275 / 70R22.5 and including a tread portion, a pair of sidewall portions, and a pair of bead portions, a carcass layer including a plurality of steel cords is mounted between the pair of bead portions, the carcass layer is wrapped around the bead core of each bead portion from the inside to the outside of the tire, and a steel reinforcing layer including a plurality of steel cords is disposed in each bead portion so as to encase the carcass layer, first and second organic fiber reinforcing layers (see FIG. 2) are disposed in the bead portions, and tires of Conventional Examples 1 to 2, Comparative Examples 1 to 3, and Examples 1 to 12 were manufactured, which differed only in the structure of the bead portions.

[0045] 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 h , the first organic fiber from the bead heel apex Distance A to the outer diameter end of the fiber reinforcement layer h , outer diameter of the second organic fiber reinforced layer from the bead heel apex Distance to side edge B h , the position of the inner diameter side end of the first organic fiber reinforced layer, Position of inner diameter side end, cord angle θ of the first organic fiber reinforcing layer in the tire A , 1st organic fiber reinforcement Cord angle θ in the layer forming process A ', cord angle θ in the tire of the second organic fiber reinforcement layer B , th 2 Cord angle θ in the molding process of the organic fiber reinforcement layer B ', |θ B |-|θ A |, A h -P h , Kura 100% modulus Kc of the block suppression layer M100 , fracture elongation of crack suppression layer Kc EB were set as shown in Tables 1 and 2. The fiber structure of the organic fiber cords constituting the first organic fiber reinforcing layer and the second organic fiber reinforcing layer was 1400 dtex / 2.

[0046] Regarding the positions of the inner diameter side end portions of the first organic fiber reinforced layer and the second organic fiber reinforced layer, when the inner diameter side end portion is located inside the line segment J in the tire width direction, it is referred to as "inner side", and when the inner diameter side end portion is located outside the line segment J in the tire width direction, it is referred to as "outer side". h >P h When B is set, the outer diameter side end of the first organic fiber reinforcement layer is located radially outward of the turned-up end of the carcass layer, h <P h When this is the case, the outer diameter side end of the second organic fiber reinforcing layer is located radially inward of the turned-up end of the carcass layer in the tire radial direction.

[0047] These test tires were evaluated for separation resistance (organic fiber reinforced layer, carcass layer) by the following test method, and the results are shown in Tables 1 and 2.

[0048] Separation resistance (organic fiber reinforcement layer, carcass layer): Each test tire was mounted on a JATMA-specified rim, and a running test was conducted using a drum testing machine under conditions of 75% of the JATMA-specified air pressure, 1.4 times the JATMA-specified load, and a running speed of 49 km / h. After running 40,000 km, the test tire was cut along the tire meridian at eight equally spaced locations around the tire circumferential direction, and the cross-sectional lengths of cracks originating from the end of the organic fiber reinforcement layer and the turned-up end of the carcass layer were measured at each of the eight cut surfaces (16 locations in total) in both bead portions. The sum of the cross-sectional lengths of cracks originating from the end of the organic fiber reinforcement layer and the turned-up end of the carcass layer was then calculated. The evaluation results were expressed as an index for each of the organic fiber reinforcement layer and the carcass layer using the reciprocal of the measured values, with Conventional Example 2 being assigned a value of 100. A higher index value indicates better separation resistance.

[0049] [Table 1]

[0050] [Table 2]

[0051] As can be seen from Tables 1 and 2, the tires of Examples 1 to 12 were able to significantly improve the separation resistance of the organic fiber reinforced layer while maintaining good separation resistance of the carcass layer, compared to Conventional Example 2. It should be noted that Conventional Example 1 was unable to produce a tire due to a malfunction during production. On the other hand, the tires of Comparative Examples 1 to 3 were prone to separation originating from the outer diameter side end of the second organic fiber reinforced layer because the cord angle of the second organic fiber reinforced layer was inappropriate.

[0052] Next, tires of Examples 13 to 17 were manufactured by partially modifying the tire structure of Example 1. In the tires of Examples 13 to 17, the first organic fiber reinforced layer was an inner organic fiber reinforced layer, and the second organic fiber reinforced layer was an outer organic fiber reinforced layer. The fiber structure of the inner organic fiber reinforced layer, the position of the inner diameter side end of the inner fiber reinforced layer, the fiber structure of the outer organic fiber reinforced layer, the position of the inner diameter side end of the outer fiber reinforced layer, whether the inner diameter side end of the inner fiber reinforced layer was covered by the outer organic fiber reinforced layer, the distance between the inner diameter side end of the outer organic fiber reinforced layer and the inner diameter side end of the inner organic fiber reinforced layer, the bead core distance A, and the toe angle θ were set as shown in Table 3.

[0053] Regarding the position of the inner diameter side end portion of the inner organic fiber reinforced layer, when the inner diameter side end portion is located more inward in the tire width direction than line segment J, it was defined as "inner side," and when the inner diameter side end portion is located more outward in the tire width direction than line segment J, it was defined as "outer side." Regarding the position of the inner diameter side end portion of the outer organic fiber reinforced layer, when the inner diameter side end portion is located more inward in the tire radial direction than line segment L, it was defined as "lower side," and when the inner diameter side end portion is located more outward in the tire radial direction than line segment L, it was defined as "upper side."

[0054] These test tires were evaluated for separation resistance (organic fiber reinforced layer) by the following test method, and the results are shown in Table 3.

[0055] Separation resistance (organic fiber reinforced layer): Each test tire was mounted on a JATMA-specified rim, and a running test was conducted using a drum testing machine under conditions of 75% of the JATMA-specified air pressure, 1.4 times the JATMA-specified load, and a running speed of 49 km / h. After running 40,000 km, the test tire was cut along the tire meridian at eight equally spaced locations around the tire circumferential direction, and the cross-sectional lengths of cracks originating from the ends of the organic fiber reinforced layer were measured at the eight cut surfaces of both bead portions (16 locations in total). The sum of the cross-sectional lengths of 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 Conventional Example 2 being set at 100. A higher index value indicates better separation resistance.

[0056] [Table 3]

[0057] As can be seen from Table 3, the tires of Examples 13 to 17, like Examples 1 to 12, had good separation resistance regarding the organic fiber reinforced layer. [Explanation of symbols]

[0058] 1 Tread section 2 Sidewall 3 Bead section 3t toe 3b bead base 3h Bead heel apex 4 carcass layers 4e Rolled up end 5 bead core 6 Bead filler 7 Belt Layer 10 Steel Reinforcement Layer 10e end 11 First organic fiber reinforcement layer 11i Inner diameter end 11o Outer diameter end 12 Second organic fiber reinforcement layer 12i Inner diameter end 12o Outer diameter end 13 Sidewall rubber layer 14 Rim cushion rubber layer 15 Crack suppression layer

Claims

1. A pneumatic tire comprising a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed radially inward of the sidewall portions, wherein a carcass layer is fitted between the pair of bead portions, the carcass layer is wound up around the bead cores of each bead portion from the inside to the outside of the tire, and a steel reinforcing layer including a plurality of steel cords is disposed in each bead portion so as to encase the carcass layer, first and second organic fiber reinforcing layers are disposed on 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, and the organic fiber cords constituting the first and second organic fiber reinforcing layers are oriented so as to cross each other between the layers; an outer diameter side end portion of the first organic fiber reinforcement layer is located outward in the tire radial direction from a turned-up end portion of the carcass layer, an outer diameter side end portion of the second organic fiber reinforcement layer is located radially inward of a turned-up end portion of the carcass layer and radially outward of a line segment formed by a horizontal line drawn in the tire width direction from a vertex of the bead core that protrudes most radially outward of the tire, each of inner diameter side end portions of the first and second organic fiber reinforcement layers is located inward in the tire width direction of a line segment formed from a normal line drawn from a vertex of the bead core that protrudes most inward in the tire radial direction to a surface of the bead base; a cord angle θ of the first organic fiber reinforcing layer with respect to the tire circumferential direction; A is 20°≦|θ A |≦45° or 70°≦|θ A |≦90°, and the tie of the second organic fiber reinforced layer Cord angle θ relative to the circumferential direction B is 20°≦|θ B |≦45° or 70°≦|θ B |≦9 A pneumatic tire characterized by being in the range of 0°.

2. The cords of the first and second organic fiber reinforced layers are inclined in opposite directions relative to the tire circumferential direction, and the cord angle θ of the first organic fiber reinforced layer relative to the tire circumferential direction is A is 20°≦| θ A 2. The pneumatic tire according to claim 1, wherein the angle is in the range of |≦45°.

3. The cords of the first and second organic fiber reinforced layers are inclined in the same direction relative to the tire circumferential direction, and the cord angle θ of the first organic fiber reinforced layer relative to the tire circumferential direction is A is 20°≦| θ A |≦45°, and the cord of the second organic fiber reinforcement layer with respect to the tire circumferential direction is Angle θ B is |θ A |+20≦|θ B 2. The air space according to claim 1, wherein the air space is in the range of | Favourite tires.

4. The distance A from the bead heel apex of the bead portion to the outer diameter side end of the first organic fiber reinforced layer h and the distance from the bead heel apex of the bead portion to the turned-up end of the carcass layer. P h Toga A h -P h 4. Any one of claims 1 to 3, characterized in that the relationship of ≧5.0 mm is satisfied. The pneumatic tire described above.

5. a crack suppression layer is embedded in a position adjacent to a wound-up end of the carcass layer, an outer end of the steel reinforcing layer in the tire width direction, an outer diameter side end of the first organic fiber reinforcing layer, and an outer diameter side end of the second organic fiber reinforcing layer; and a 100% modulus Kc of the crack suppression layer is M100 is 4.5MPa≦Kc M100 ≦10.0 MPa, and the breaking elongation Kc of the crack suppression layer is in the range EB is 300%≦Kc EB 5. The pneumatic tire according to claim 1, wherein the range is:

6. one of the first and second organic fiber reinforced layers is an inner organic fiber reinforced layer located on an inner side in the tire width direction, and the other of the first and second organic fiber reinforced layers is an outer organic fiber reinforced layer located on an outer side in the tire width direction, 6. The pneumatic tire according to claim 1, wherein the outer organic fiber reinforcement layer is disposed so as to cover an inner diameter side end portion of the inner organic fiber reinforcement layer, and the inner diameter side end portion of the outer organic fiber reinforcement layer is spaced 5 mm or more from the inner diameter side end portion of the inner organic fiber reinforcement layer and is located radially inward of a line segment formed by a horizontal line drawn in the tire width direction from an outer end portion of the steel reinforcement layer in the tire width direction.

7. The pneumatic tire according to any one of claims 1 to 6, characterized in that the fiber structures of the organic fiber cords constituting the first and second organic fiber reinforcing layers are each in the range of 800 dtex / 2 to 1500 dtex / 2.

8. 8. The pneumatic tire according to claim 1, wherein a distance A from the apex of the bead core that protrudes most outward in the width direction to a bead heel position, measured along a straight line that passes through the apex that protrudes most outward in the width direction of the bead core and is 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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