JP2014040183A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an overcrowded state of steel cords in a steel reinforcing layer, on the inside in a tire diametrical direction of a bead core.SOLUTION: A steel reinforcing layer 30 is provided, which is folded from the inside to the outside in a tire width direction around a bead core 11 on the outside of a carcass layer 20 and continuously arranged in a tire circumferential direction, and has a plurality of steel cords intersecting carcass cords. A shock absorbing layer 40 is provided, which is folded from the inside to the outside in the tire width direction around the bead core between the carcass layer and the steel reinforcing layer and continuously arranged in the tire circumferential direction; has a tire width direction inside end portion 41 positioned on tire diametrical direction outer side than a tire width direction inside end portion 31 of the steel reinforcing layer, and a tire width direction inside end portion 42 positioned on the tire diametrical direction outer side than tire width direction outside end portions 22 and 32 of the carcass layer and the steel reinforcing layer; and has hardness after vulcanization higher than coating materials for coating the carcass layer and the steel reinforcing layer by 5 or more.

Description

  The present invention relates to a heavy duty pneumatic tire, and more particularly to a heavy duty pneumatic tire including a steel reinforcing layer around a bead core.

  Conventionally, for example, a heavy-duty pneumatic tire (pneumatic tire) described in Patent Document 1 includes a steel reinforcing layer around the bead core and outside the carcass layer in which carcass cords are arranged along the radial direction. An organic fiber reinforcing layer is provided between the carcass layer and the steel reinforcing layer. The steel reinforcing layer is formed of a steel cord having an angle with respect to the radial direction, and is folded back from the inner side to the outer side in the tire width direction around the bead core along the carcass layer. The organic fiber reinforcing layer is formed of an organic fiber cord having an angle smaller than that of the steel cord with respect to the radial direction, and is at least between the inner side in the tire radial direction of the bead core and the end portion on the outer side in the tire width direction of the steel reinforcing layer. It is arranged.

JP 2008-222161 A

  In a heavy duty pneumatic tire having a steel reinforcing layer, the rigidity of the bead portion can be effectively increased. On the other hand, since the steel cord has an angle with respect to the carcass cord along the radial direction, there is a risk of producing defects. Specifically, during tire molding and vulcanization, the gap between the bead portions narrows inward in the tire width direction, and the carcass cord is pulled in the radial direction due to the diameter expansion of the tire. There is a phenomenon in which the tire is pulled in close to the inside in the tire radial direction. This overcrowding of the steel cord is uneven in the tire circumferential direction, and may cause a defect in uniformity and a rim shift due to a decrease in durability.

  The heavy-duty pneumatic tire described in Patent Document 1 includes an organic fiber reinforcing layer between a carcass layer and a steel reinforcing layer. However, the organic fiber reinforcing layer of Patent Document 1 is disposed so that both ends of the organic fiber reinforcing layer are disposed between the carcass layer and the steel reinforcing layer, so that the ends of the steel cord overlap in the vicinity of the carcass cord. For this reason, when the carcass cord is pulled in the radial direction, an effect of suppressing the phenomenon that the steel cord is drawn so as to be overcrowded inside the bead core in the tire radial direction cannot be expected.

  The present invention has been made in view of the above, and an object of the present invention is to provide a heavy duty pneumatic tire capable of suppressing a situation in which a steel cord in a steel reinforcing layer becomes overcrowded on the inner side in the tire radial direction of a bead core. And

  In order to solve the above-described problems and achieve the object, the heavy-duty pneumatic tire of the first invention includes a bead core disposed on each of the bead portions on both sides in the tire width direction, and one bead portion to the other. The carcass cord is disposed around the bead core and folded around the bead core from the inner side to the outer side in the tire width direction and continuously arranged in the tire circumferential direction. A plurality of carcass layers arranged side by side in a direction, and are continuously disposed in the tire circumferential direction by folding back from the inner side to the outer side in the tire width direction around the bead core on the outer side of the carcass layer. A steel reinforcing layer having a plurality of steel cords intersecting with each other, and a heavy duty pneumatic tire comprising the above, Between the cusp layer and the steel reinforcing layer, the bead core is folded back from the inner side to the outer side in the tire width direction and continuously disposed in the tire circumferential direction. The outer end of the tire tire in the tire width direction is located on the outer side in the tire radial direction of the layer, and the outer end of the tire width direction is on the outer side in the tire radial direction of the outer end of the carcass layer and the steel reinforcing layer in the tire width direction. And a buffer layer having a hardness after vulcanization that is 5 or more higher than that of the respective covering materials covering the cords of the carcass layer and the steel reinforcing layer.

  According to this heavy duty pneumatic tire, the rigidity of the bead portion can be increased by providing the steel reinforcing layer having a plurality of steel cords intersecting the carcass cord around the bead core. Moreover, around the bead core, the inner side in the tire width direction is longer than the steel reinforcing layer on the outer side in the tire radial direction, and the outer side in the tire width direction is longer on the outer side in the tire radial direction than the carcass layer and the steel reinforcing layer. A buffer layer having a hardness after vulcanization of 5 or more than the respective covering materials covering the cord of the steel reinforcing layer is provided. For this reason, even when the bead portion is narrowed inward in the tire width direction or the carcass cord is pulled in the radial direction due to the diameter expansion of the tire during molding and vulcanization of the tire, the buffer layer and the carcass layer The contact with the steel reinforcing layer is prevented, and the deviation of the steel cord is suppressed by the hardness of the buffer layer. As a result, since the steel cord in the steel reinforcing layer is suppressed from being pulled in, it is possible to suppress a situation in which the steel cord becomes overcrowded inside the bead core in the tire radial direction. Thereby, uniformity can be improved and durability of a bead part can be maintained or improved.

  The heavy duty pneumatic tire of the second invention is the heavy duty pneumatic tire according to the first invention, wherein the buffer layer has a hardness after vulcanization of 75 or more and 90 or less and a modulus at 100 [%] elongation of 10 [MPa]. It is characterized by being made of a rubber material having a thickness of 13 [MPa] or less and a thickness of 1 [mm] or more and 2 [mm] or less.

  Rubber material having a hardness after vulcanization of 75 to 90, a modulus at 100 [%] elongation of 10 [MPa] to 13 [MPa], and a thickness of 1 [mm] to 2 [mm] The buffer layer made of has sufficient rigidity to prevent the steel cord in the steel reinforcing layer from being pulled. For this reason, according to this heavy-duty pneumatic tire, the effect of suppressing the deviation of the steel cord and suppressing the situation where the steel cord becomes overcrowded inside the tire core in the tire radial direction can be obtained.

  In the heavy duty pneumatic tire of the third invention, in the first invention, the buffer layer has an organic fiber cord covered with a rubber material, and the number of ends of the organic fiber cord with the carcass cord is The difference is -1 [lines / 50 mm] or more and +1 [lines / 50 mm] or less, the angle difference of the organic fiber cord with respect to the carcass cord is -3 [°] or more and +3 [°] or less, and the organic fiber cord The thickness including the rubber material is 1 [mm] or more and 2 [mm] or less.

  The organic fiber cord is coated with a rubber material, and the difference in the number of ends of the organic fiber cord from the carcass cord is set to -1 [lines / 50 mm] or more and +1 [lines / 50 mm] or less, and the angle difference between the organic fiber cord and the carcass cord -3 [°] or more and +3 [°] or less, the organic fiber cord is arranged in the same manner as the carcass cord, and the thickness including the organic fiber cord and the rubber material is 1 [mm] or more and 2 [mm] or less. Has sufficient rigidity to prevent the steel cord in the steel reinforcing layer from being pulled in, and the organic fiber cord is arranged in the same manner as the carcass cord, making it difficult to inhibit the pulling of the carcass cord (slippery ) To suppress the influence on the steel cord. For this reason, according to this heavy-duty pneumatic tire, the effect of suppressing the deviation of the steel cord and suppressing the situation where the steel cord becomes overcrowded inside the tire core in the tire radial direction can be obtained.

  The heavy duty pneumatic tire according to a fourth aspect of the present invention is the tire according to any one of the first to third aspects, from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the steel reinforcing layer. Tire radial direction dimension A, tire radial direction dimension B from the tire radial direction innermost position of the bead core to the outer end of the carcass layer in the tire width direction, and buffering from the tire radial direction innermost position of the bead core. The relationship with the tire radial direction dimension C to the outer end in the tire width direction of the layer satisfies 5 [mm] ≦ B−A ≦ 15 [mm], 5 [mm] ≦ C−B ≦ 15 [mm]. It is characterized by that.

  According to this heavy-duty pneumatic tire, on the outer side in the tire width direction of the bead portion, the end portion on the outer side in the tire width direction of the buffer layer is located on the outermost side in the tire radial direction, and then on the outer side in the tire width direction of the carcass layer. The end portion is located, the position of the end portion of the steel reinforcing layer on the outer side in the tire width direction is located on the innermost side in the tire radial direction, and 5 [mm] ≦ B−A ≦ 15 [mm], 5 [mm ] ≦ C−B ≦ 15 [mm]. With such a configuration, even when the carcass layer is narrowed inward in the width direction of the tire or the carcass cord is pulled in the radial direction due to the diameter of the tire during molding and vulcanization of the tire, the carcass layer and Prevents contact with the steel reinforcement layer and effectively suppresses the deviation of the steel cord. As a result, it is possible to effectively suppress the steel cord from being drawn in the steel reinforcing layer, and to significantly obtain the effect of suppressing the situation where the steel cord becomes overcrowded inside the bead core in the tire radial direction. Thereby, a uniformity can be improved and durability of a bead part can be improved.

  Further, a heavy duty pneumatic tire according to a fifth invention is the tire according to the fourth invention, wherein the tire radial dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer; The tire radial direction dimension D from the innermost position in the tire radial direction of the bead core to the inner end in the tire width direction of the steel reinforcing layer, and the inner side in the tire width direction of the buffer layer from the innermost position in the tire radial direction of the bead core. The relationship with the tire radial direction dimension E to the end satisfies 5 [mm] ≦ DC ≦ 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm].

  According to this heavy-duty pneumatic tire, on the outer side in the tire width direction of the bead portion, the end portion on the outer side in the tire width direction of the buffer layer is located on the outermost side in the tire radial direction, and then on the outer side in the tire width direction of the carcass layer. The end portion is located, the position of the end portion of the steel reinforcing layer on the outer side in the tire width direction is located on the innermost side in the tire radial direction, and 5 [mm] ≦ B−A ≦ 15 [mm], 5 [mm ] ≦ C−B ≦ 15 [mm]. Further, at the inner side of the bead portion in the tire width direction, the end portion of the buffer layer on the inner side in the tire width direction and the end portion of the steel reinforcing layer on the inner side of the tire width direction are smaller than the end portion of the buffer layer on the outer side in the tire width direction. The end of the buffer layer on the inner side in the tire width direction is located on the outer side in the tire radial direction of the end of the steel reinforcing layer in the tire width direction, and 5 [mm] ≦ D− C ≦ 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm]. With such a configuration, even when the carcass layer is narrowed inward in the width direction of the tire or the carcass cord is pulled in the radial direction due to the diameter of the tire during molding and vulcanization of the tire, the carcass layer and Prevents contact with the steel reinforcement layer and effectively suppresses the deviation of the steel cord. As a result, it is possible to effectively suppress the steel cord from being drawn in the steel reinforcing layer, and to significantly obtain the effect of suppressing the situation where the steel cord becomes overcrowded inside the bead core in the tire radial direction. Thereby, a uniformity can be improved and the durability of a bead part can further be improved.

  The pneumatic tire which concerns on this invention can suppress the situation where the steel cord in a steel reinforcement layer becomes overcrowded inside the tire radial direction of a bead core.

FIG. 1 is a meridional sectional view showing a bead portion of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 2 is a development view of the bead portion of the heavy duty pneumatic tire according to the embodiment of the present invention. FIG. 3 is a development view of a bead portion of another example of the heavy duty pneumatic tire according to the embodiment of the present invention. FIG. 4 is a chart showing results of performance tests of heavy duty pneumatic tires according to examples of the present invention. FIG. 5 is a chart showing results of performance tests of heavy duty pneumatic tires according to examples of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a meridional sectional view showing a bead portion of a heavy duty pneumatic tire according to the present embodiment, and FIG. 2 is a development view of the bead portion of the heavy duty pneumatic tire according to the present embodiment.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the heavy-duty pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire diameter The direction outer side means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction refers to a direction parallel to the rotation axis, the inner side in the tire width direction is the side toward the tire equatorial plane (not shown) in the tire width direction, and the outer side in the tire width direction is in the tire width direction. The side away from the tire equator. Further, the radial direction is a direction including the tire radial direction and the tire width direction along the meridian direction orthogonal to the tire equatorial plane. The tire equator plane is a plane that is orthogonal to the rotation axis of the heavy duty pneumatic tire 1 and passes through the center of the tire width of the heavy duty pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane in the tire width direction.

  As shown in FIG. 1, the heavy-duty pneumatic tire 1 is a predetermined inner portion in the tire radial direction from an end portion in the tire width direction of a tread portion (not shown) formed in the outermost portion in the tire radial direction. The side wall part 5 is provided up to the position. That is, the sidewall portions 5 are provided at two locations of the heavy duty pneumatic tire 1 and are provided at symmetrical positions with respect to the tire equatorial plane on both outer sides in the tire width direction. Further, the heavy load pneumatic tire 1 is provided with a bead portion 10 on the inner side in the tire radial direction of each sidewall portion 5. The bead part 10 is provided in two places of the heavy-duty pneumatic tire 1 similarly to the sidewall part 5, and is provided at symmetrical positions with respect to the tire equatorial plane on both outer sides in the tire width direction.

  The bead unit 10 has a bead core 11. The bead core 11 is formed by winding a bead wire, which is a steel wire, in a ring shape along the tire circumferential direction. Also, the bead portion 10 is formed as a bead base 12 on the inner side in the tire radial direction. The bead base 12 is a portion located on the inner side in the tire radial direction of the bead core 11 and in contact with a rim (not shown). In the bead portion 10, a bead filler 13 is disposed outside the bead core 11 in the tire radial direction. The bead filler 13 includes a lower bead filler 13a near the bead core 11 and an upper bead filler 13b on the outer side in the tire radial direction.

  In the heavy duty pneumatic tire 1, a carcass layer 20 is provided on the tread portion, the sidewall portion 5, and the bead portion 10. The carcass layer 20 is continuously disposed in the tire circumferential direction, and, as shown in FIG. 2, a carcass cord 23 that extends along the radial direction and is arranged in the tire circumferential direction is covered with a rubber material. It is covered with a material 24. The carcass layer 20 is disposed from one bead portion 10 to the other bead portion 10 among the bead portions 10 provided on both sides in the tire width direction. Further, the carcass layer 20 has a turn-up structure in which the bead portion 10 is folded around the bead core 11 from the inner side to the outer side in the tire width direction of the bead core 11.

  That is, as shown in FIG. 1, the carcass layer 20 is directed from the sidewall portion 5 to the bead portion 10, passes from the inner side in the tire width direction of the bead core 11 to the inner side in the tire radial direction of the bead core 11, and further in the tire width direction of the bead core 11. It passes outside. In the carcass layer 20, a portion located outside the bead core 11 in the tire width direction is a turn-up portion 21, and an end portion of the turn-up portion 21 on the outer side in the tire radial direction is an end portion of the carcass layer 20. A carcass layer end 22 is formed. The end portion 22 of the carcass layer is located on the outer side in the tire radial direction than the bead core 11, and is located on the outer side in the tire width direction of the upper bead filler 13b in the present embodiment.

  In the heavy duty pneumatic tire 1, a steel reinforcing layer 30 is provided on the bead portion 10. The steel reinforcing layer 30 is disposed on the outer side of the carcass layer 20 so as to be overlapped with the carcass layer 20, and is folded around the bead core 11 from the inner side to the outer side in the tire width direction and continuously disposed in the tire circumferential direction. As shown in FIG. 2, the steel reinforcing layer 30 is formed by covering a plurality of steel cords 33 intersecting the carcass cord 23 with a covering material 34 made of a rubber material. For example, the steel cord 33 is disposed at an inner side in the tire radial direction of the bead core 11 with an angle of −70 [°] or +70 [°] with respect to the radial direction along which the carcass cord 23 extends.

  As shown in FIG. 1, the steel reinforcing layer 30 is located inside the carcass layer 20 in the tire width direction in the bead portion 10 where the carcass layer 20 is located inside the bead core 11 in the tire width direction. ing. Further, the steel reinforcing layer 30 is located on the inner side in the tire radial direction of the carcass layer 20 in a portion where the carcass layer 20 is located on the inner side in the tire radial direction from the bead core 11. Further, the steel reinforcing layer 30 is located on the outer side in the tire width direction of the carcass layer 20 in a portion where the carcass layer 20 is located on the outer side in the tire width direction with respect to the bead core 11.

  Further, in the steel reinforcing layer 30, the end portion on the tire radial direction outer side of the portion located on the inner side in the tire width direction than the bead core 11 is the steel reinforcing layer inner end portion 31, and the steel width in the tire width direction than the bead core 11. An end portion on the outer side in the tire radial direction of the portion located on the outer side is a steel reinforcing layer outer end portion 32. In other words, the steel reinforcing layer inner end portion 31 is an end portion on the inner side in the tire width direction of the steel reinforcing layer 30, and the steel reinforcing layer outer end portion 32 is an end portion on the outer side in the tire width direction of the steel reinforcing layer 30. . The steel reinforcing layer inner end 31 and the steel reinforcing layer outer end 32 are both positioned on the outer side in the tire radial direction from the bead core 11. Further, the steel reinforcing layer inner end portion 31 is positioned on the outer side in the tire radial direction from the position of the carcass layer end portion 22, and the steel reinforcing layer outer end portion 32 is on the inner side in the tire radial direction from the position of the carcass layer end portion 22. Is located.

  In the heavy duty pneumatic tire 1, a buffer layer 40 is provided on the bead portion 10. The buffer layer 40 is folded around the bead core 11 from the inner side to the outer side in the tire width direction and continuously disposed in the tire circumferential direction between the carcass layer 20 and the steel reinforcing layer 30.

  The buffer layer 40 is located on the inner side in the tire width direction of the carcass layer 20 in the bead portion 10 where the carcass layer 20 is located on the inner side in the tire width direction than the bead core 11. Located on the outside in the tire width direction. Further, the buffer layer 40 is located on the inner side in the tire radial direction of the carcass layer 20 in the portion where the carcass layer 20 is located on the inner side in the tire radial direction from the bead core 11, and the outer side in the tire radial direction of the steel reinforcing layer 30. Is located. Further, the buffer layer 40 is located on the outer side in the tire width direction of the carcass layer 20 in the portion where the carcass layer 20 is located on the outer side in the tire width direction than the bead core 11, and the inner side in the tire width direction of the steel reinforcing layer 30. Is located.

  Further, in the buffer layer 40, the end portion on the tire radial direction outer side of the portion located on the inner side in the tire width direction from the bead core 11 is the buffer layer inner end portion 41, and the outer side in the tire width direction than the bead core 11. The end portion on the outer side in the tire radial direction of the positioned portion is the buffer layer outer end portion 42. In other words, the buffer layer inner end portion 41 is an end portion on the inner side in the tire width direction of the buffer layer 40, and the buffer layer outer end portion 42 is an end portion on the outer side in the tire width direction of the buffer layer 40. . Further, both the buffer layer inner end 41 and the buffer layer outer end 42 are located on the outer side in the tire radial direction than the bead core 11. Further, the buffer layer inner end portion 41 is located on the outer side in the tire radial direction from the position of the carcass layer end portion 22, and is located on the outer side in the tire radial direction from the steel reinforcing layer inner end portion 31. Further, the buffer layer outer end portion 42 is positioned on the outer side in the tire radial direction from the position of the carcass layer end portion 22, and is positioned on the outer side in the tire radial direction from the steel reinforcing layer outer end portion 32.

  The buffer layer 40 is formed so that the hardness after vulcanization is 5 or more higher than the covering material 24 of the carcass layer 20 and the covering material 34 of the steel reinforcing layer 30.

  Thus, the heavy-duty pneumatic tire 1 of the present embodiment is disposed from the bead cores 11 disposed on the bead portions 10 on both sides in the tire width direction, and from one bead portion 10 to the other bead portion 10. In addition, a plurality of carcass cords 23 are arranged around the bead core 11 so as to be folded back from the inner side to the outer side in the tire width direction and continuously arranged in the tire circumferential direction, and extend along the radial direction. The carcass layer 20 and a plurality of outer sides of the carcass layer 20 that are folded back from the inner side to the outer side in the tire width direction around the bead core 11 and are continuously disposed in the tire circumferential direction. And a steel reinforcing layer 30 having a steel cord 33. And between the carcass layer 20 and the steel reinforcement layer 30, it is turned around the bead core 11 from the inner side to the outer side in the tire width direction and continuously arranged in the tire circumferential direction. The buffer layer inner end portion 41) is located on the outer side in the tire radial direction of the steel reinforcing layer 30 on the inner side in the tire width direction (steel reinforcing layer inner end portion 31), and the outer end portion on the tire width direction (buffer layer). The outer end portion 42) has a tire diameter that is larger than the end portion of the carcass layer 20 on the outer side in the tire width direction (carcass layer end portion 22) and the end portion of the steel reinforcing layer 30 on the outer side in the tire width direction (steel reinforcing layer outer end portion 32). A buffer layer 40 is provided which is located on the outside in the direction and has a hardness after vulcanization of 5 or more than the covering materials 24 and 34 covering the cords 23 and 33 of the carcass layer 20 and the steel reinforcing layer 30.

  According to the heavy-duty pneumatic tire 1, the rigidity of the bead portion 10 can be increased by providing the steel reinforcing layer 30 having the plurality of steel cords 33 intersecting the carcass cord 23 around the bead core 11. It becomes possible. Moreover, it is formed around the bead core 11 so as to be longer on the outer side in the tire width direction than the steel reinforcing layer 30 on the outer side in the tire width direction and longer on the outer side in the tire radial direction than the carcass layer 20 and the steel reinforcing layer 30 on the outer side in the tire width direction. In addition, a buffer layer 40 having a vulcanized hardness of 5 or more higher than the covering materials 24 and 34 covering the cords 23 and 33 of the carcass layer 20 and the steel reinforcing layer 30 is provided. For this reason, even when the carcass cord 23 is drawn in the radial direction due to the diameter of the tire being narrowed between the bead portions 10 when the tire is molded and vulcanized, Contact between the carcass layer 20 and the steel reinforcing layer 30 is prevented, and the deviation of the steel cord 33 is suppressed by the hardness of the buffer layer 40. As a result, since the steel cord 33 in the steel reinforcing layer 30 is suppressed from being pulled in, it is possible to suppress a situation in which the steel cord 33 becomes overcrowded inside the bead core 11 in the tire radial direction. Thereby, the uniformity can be improved and the durability of the bead portion 10 can be maintained or improved.

  In the heavy-duty pneumatic tire 1 of the present embodiment, the buffer layer 40 has a hardness after vulcanization of 75 to 90 and a modulus at 100 [%] elongation of 10 [MPa] to 13 [MPa]. It is preferable that the rubber material 44 has a thickness of 1 [mm] to 2 [mm].

  Rubber material having a hardness after vulcanization of 75 to 90, a modulus at 100 [%] elongation of 10 [MPa] to 13 [MPa], and a thickness of 1 [mm] to 2 [mm] The buffer layer 40 made of 44 has sufficient rigidity to prevent the steel cord 33 in the steel reinforcing layer 30 from being pulled. For this reason, according to this heavy-duty pneumatic tire 1, it is possible to remarkably obtain the effect of suppressing the deviation of the steel cord 33 and suppressing the situation where the steel cord 33 becomes overcrowded inside the bead core 11 in the tire radial direction. become. The hardness after vulcanization of the coating material 24 of the carcass layer 20 and the coating material 34 of the steel reinforcing layer 30 is, for example, about 60 to 65, and the hardness after vulcanization of the buffer layer 40 is higher than this. Hard enough.

  In the heavy-duty pneumatic tire 1 of the present embodiment, as shown in FIG. 3, the buffer layer 40 has an organic fiber cord 43 covered with a rubber material 44, and the organic fiber cord 43 is connected to the carcass cord 23. The difference in the number of ends is −1 [lines / 50 mm] or more and +1 [lines / 50 mm] or less, and the angle difference between the organic fiber cord 43 and the carcass cord 23 is −3 [°] or more and +3 [°] or less. The thickness including the fiber cord 43 and the rubber material 44 is preferably 1 [mm] or more and 2 [mm] or less.

  The organic fiber cord 43 is covered with a rubber material 44, and the difference in the number of ends of the organic fiber cord 43 from the carcass cord 23 is set to -1 [piece / 50 mm] or more and +1 [piece / 50 mm] or less. The difference between the angle with respect to the cord 23 is −3 [°] or more and +3 [°] or less, the organic fiber cord 43 is disposed in the same manner as the carcass cord 23, and the thickness including the organic fiber cord 43 and the rubber material 44 is 1 [mm]. The buffer layer 40 having a size of 2 mm or less has sufficient rigidity to prevent the steel cord 33 in the steel reinforcing layer 30 from being drawn, and the organic fiber cord 43 is disposed in the same manner as the carcass cord 23. Therefore, it is difficult to inhibit the pulling of the carcass cord 23 (easiness to slip), and has a buffer property to suppress the influence on the steel cord 33. For this reason, according to this heavy-duty pneumatic tire 1, it is possible to remarkably obtain the effect of suppressing the deviation of the steel cord 33 and suppressing the situation where the steel cord 33 becomes overcrowded inside the bead core 11 in the tire radial direction. become. The organic fiber cord 43 is preferably made of nylon, but may be other than nylon as long as it is an organic fiber. In this case, for example, aramid, polyester, aromatic polyamide, high-tensile vinylon, and the like are preferable.

  Further, as shown in FIG. 1, the heavy load pneumatic tire 1 of the present embodiment has an end portion (outer end portion of the steel reinforcing layer) of the steel reinforcing layer 30 from the innermost position in the tire radial direction of the bead core 11. 32), the tire radial dimension B from the innermost position in the tire radial direction of the bead core 11 to the outer end (carcass layer end 22) in the tire width direction of the carcass layer 20, and the bead core 11. The relationship with the tire radial direction dimension C from the innermost position in the tire radial direction to the outer end in the tire width direction of the buffer layer 40 (buffer layer outer end 42) is 5 [mm] ≦ B−A ≦ 15 [ mm], 5 [mm] ≦ CB ≦ 15 [mm] is preferably satisfied.

  According to the heavy load pneumatic tire 1, the outer end in the tire width direction of the buffer layer 40 (the outer end 42 of the buffer layer) is located on the outermost side in the tire radial direction on the outer side in the tire width direction of the bead portion 10. Next, the end of the carcass layer 20 on the outer side in the tire width direction (carcass layer end 22) is located, and the end of the steel reinforcing layer 30 on the outer side in the tire width direction (steel reinforcing layer outer end 32) is the most. 5 [mm] ≦ BA ≦ 15 [mm], 5 [mm] ≦ CB ≦ 15 [mm], and 10 [mm] ≦ CA ≦ 30 [mm]. With such a configuration, even when the carcass cord 23 is narrowed inward in the tire width direction or the carcass cord 23 is pulled in the radial direction due to the diameter of the tire during molding and vulcanization of the tire, The contact between the layer 20 and the steel reinforcing layer 30 is prevented, and the deviation of the steel cord 33 is effectively suppressed. As a result, the steel cord 33 in the steel reinforcing layer 30 can be effectively suppressed from being pulled in, and the effect of suppressing the situation in which the steel cord 33 becomes overcrowded inside the bead core 11 in the tire radial direction can be significantly obtained. Become. Thereby, uniformity can be improved and durability of bead part 10 can be improved.

  In addition to the relationship between the tire radial dimensions A, B, and C, the heavy load pneumatic tire 1 according to the present embodiment has a buffer layer 40 that extends from the innermost radial position of the bead core 11 as shown in FIG. The tire radial direction dimension C to the outer end in the tire width direction (buffer layer outer end 42) and the inner end in the tire width direction of the steel reinforcing layer 30 (steel reinforcing layer) from the tire radial innermost position of the bead core 11 Tire radial dimension D to the inner end 31) and tire radial dimension E from the innermost position of the bead core 11 in the tire radial direction to the inner end of the buffer layer 40 in the tire width direction (buffer layer inner end 41). Is preferably 5 [mm] ≦ D−C ≦ 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm].

  According to the heavy load pneumatic tire 1, the outer end in the tire width direction of the buffer layer 40 (the outer end 42 of the buffer layer) is located on the outermost side in the tire radial direction on the outer side in the tire width direction of the bead portion 10. Next, the end of the carcass layer 20 on the outer side in the tire width direction (carcass layer end 22) is located, and the end of the steel reinforcing layer 30 on the outer side in the tire width direction (steel reinforcing layer outer end 32) is the most. 5 [mm] ≦ BA ≦ 15 [mm], 5 [mm] ≦ CB ≦ 15 [mm], and 10 [mm] ≦ CA ≦ 30 [mm]. Further, on the inner side in the tire width direction of the bead portion 10, an end portion on the inner side in the tire width direction of the buffer layer 40 (buffer layer inner end portion 41), and an end portion on the inner side in the tire width direction of the steel reinforcing layer 30 (inside the steel reinforcing layer) The end portion 31) is located on the outer side in the tire radial direction of the buffer layer 40 on the outer side in the tire width direction (buffer layer outer end portion 42), and the end portion on the inner side in the tire width direction of the buffer layer 40 (inner side of the buffer layer) The end portion 41) is positioned on the outer side in the tire radial direction of the end portion in the tire width direction of the steel reinforcing layer 30 (the steel reinforcing layer inner end portion 31), and 5 [mm] ≦ D−C ≦. 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm], and 10 [mm] ≦ E−C ≦ 30 [mm]. With such a configuration, even when the carcass cord 23 is narrowed inward in the tire width direction or the carcass cord 23 is pulled in the radial direction due to the diameter of the tire during molding and vulcanization of the tire, The contact between the layer 20 and the steel reinforcing layer 30 is prevented, and the deviation of the steel cord 33 is effectively suppressed. As a result, the steel cord 33 in the steel reinforcing layer 30 can be effectively suppressed from being pulled in, and the effect of suppressing the situation in which the steel cord 33 becomes overcrowded inside the bead core 11 in the tire radial direction can be significantly obtained. Become. Thereby, the uniformity can be improved and the durability of the bead portion 10 can be further improved.

  In the present example, performance tests regarding uniformity (RFV: Radial Force Variation) and durability of the bead portion were performed on a plurality of types of pneumatic tires having different conditions (see FIGS. 4 and 5).

  Uniformity (RFV) performance test was conducted by using a heavy load pneumatic tire with a tire size of 295 / 75R22.5, assembled with a regular rim, filled with regular internal pressure, applied with regular load, Radial force variation (RFV) based on the standard of C607 “Automotive Tire Uniformity Test Method” is measured. Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is more preferable as the numerical value is smaller, particularly as 95 or less.

  The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, a maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  The durability performance test of the bead part was performed by assembling a heavy-duty pneumatic tire with a tire size of 295 / 75R22.5 on a regular rim, filling the regular internal pressure, adding 200% of the regular load, Performed by a low-pressure endurance test using a drum tester. And the running time until a tire (bead part) fails is measured with the running speed of 50 [km / h]. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases.

  4 and 5, the conventional heavy-duty pneumatic tire has a steel reinforcing layer but does not have a buffer layer. Moreover, although the heavy duty pneumatic tire of the comparative example has a steel reinforcing layer and a buffer layer (rubber material), the arrangement of the buffer layer is outside the specified range.

  On the other hand, in FIG. 4, the heavy-duty pneumatic tires of Examples 1 to 14 have a steel reinforcing layer and a buffer layer (made of a rubber material), the arrangement of the buffer layer is within a specified range, and The hardness of the buffer layer is 5 or more higher than that of the covering material (60) covering the cord of the steel reinforcing layer. In the heavy duty pneumatic tires of Examples 5 to 14, the hardness of the buffer layer is 75 or more and 90 or less, and the modulus when the buffer layer is stretched 100% is 10 [MPa] or more and 13 [MPa] or less. The thickness of the buffer layer is 1 [mm] or more and 2 [mm] or less. The pneumatic tires for heavy loads of Examples 9 to 14 include the tire radial direction dimension A from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the steel reinforcing layer, and the tire radial direction outermost position of the bead core. A tire radial dimension B from the inner position to the outer end in the tire width direction of the carcass layer, and a tire radial dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer. The relationship satisfies 5 [mm] ≦ B−A ≦ 15 [mm], 5 [mm] ≦ CB ≦ 15 [mm]. The heavy-duty pneumatic tires of Examples 12 to 14 include the tire radial dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer, and the innermost radial direction of the bead core. A tire radial direction dimension D from the position to the inner end of the steel reinforcing layer in the tire width direction, and a tire radial dimension E from the innermost position of the bead core in the tire radial direction to the inner end of the buffer layer in the tire width direction. The relationship satisfies 5 [mm] ≦ D−C ≦ 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm].

  In FIG. 5, the heavy-duty pneumatic tires of Examples 15 to 29 have a steel reinforcing layer and a buffer layer (organic fiber cords covered with a rubber material), and the arrangement of the buffer layer is defined. And the hardness of the buffer layer is 5 or more higher than that of the covering material (60) covering the cord of the steel reinforcing layer. In the heavy duty pneumatic tires of Examples 18 to 29, the difference in the number of ends from the carcass cord of the organic fiber cord is -1 [piece / 50 mm] or more and +1 [piece / 50 mm] or less, and the organic fiber cord carcass The difference in angle with respect to the cord is -3 [°] or more and +3 [°] or less, and the thickness including the organic fiber cord and the rubber material is 1 [mm] or more and 2 [mm] or less. The pneumatic tires for heavy loads of Examples 24 to 29 are the tire radial dimension A from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the steel reinforcing layer, and the tire radial direction innermost of the bead core. A tire radial dimension B from the inner position to the outer end in the tire width direction of the carcass layer, and a tire radial dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer. The relationship satisfies 5 [mm] ≦ B−A ≦ 15 [mm], 5 [mm] ≦ CB ≦ 15 [mm]. Furthermore, the heavy-duty pneumatic tires of Examples 27 to 29 are the tire radial direction dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer, and the tire radial direction of the bead core. A tire radial dimension D from the innermost position to the inner end in the tire width direction of the steel reinforcing layer, and a tire radial dimension E from the innermost position in the tire radial direction of the bead core to the inner end in the tire width direction of the buffer layer And 5 [mm] ≦ D−C ≦ 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm].

  As shown in the test results of FIGS. 4 and 5, the heavy duty pneumatic tires of Examples 1 to 29 have improved uniformity (RFV) and maintained or improved durability of the bead portion. I understand that.

DESCRIPTION OF SYMBOLS 1 Heavy duty pneumatic tire 10 Bead part 11 Bead core 12 Bead base 13 Bead filler 20 Carcass layer 21 Turn-up part 22 Carcass layer edge part 23 Carcass cord 24 Coating | covering material 30 Steel reinforcement layer 31 Steel reinforcement layer inner edge part 32 Steel reinforcement layer Outer end portion 33 Steel cord 34 Coating material 40 Buffer layer 41 Buffer layer inner end portion 42 Buffer layer outer end portion 43 Organic fiber cord 44 Rubber material

Claims (5)

A bead core disposed on each of the bead portions on both sides in the tire width direction; and disposed around from the one bead portion to the other bead portion and folded around the bead core from the inner side to the outer side in the tire width direction. A carcass layer arranged continuously in the direction and extending in the radial direction and arranged in the tire circumferential direction, and a tire width direction around the bead core outside the carcass layer In a heavy-duty pneumatic tire comprising a steel reinforcing layer having a plurality of steel cords that are folded back from the inside to the outside and continuously disposed in the tire circumferential direction and intersecting the carcass cord,
Between the carcass layer and the steel reinforcing layer, the bead core is folded back from the inner side to the outer side in the tire width direction and continuously disposed in the tire circumferential direction. The reinforcing layer is positioned on the outer side in the tire radial direction from the inner end in the tire width direction of the reinforcing layer, and the outer end in the tire width direction is positioned in the tire radial direction from the outer end in the tire width direction of the carcass layer and the steel reinforcing layer. A heavy-duty pneumatic tire, comprising a buffer layer positioned on the outside and having a hardness after vulcanization of 5 or more higher than each covering material covering the cords of the carcass layer and the steel reinforcing layer.   The buffer layer has a hardness after vulcanization of 75 or more and 90 or less, a modulus at 100 [%] elongation of 10 [MPa] or more and 13 [MPa] or less, and a thickness of 1 [mm] or more and 2 [mm]. The heavy duty pneumatic tire according to claim 1, comprising the following rubber material.   In the buffer layer, an organic fiber cord is covered with a rubber material, and the difference in the number of ends of the organic fiber cord from the carcass cord is -1 [/ 50 mm] or more and +1 [/ 50 mm] or less, The difference in angle between the organic fiber cord and the carcass cord is -3 [°] or more and +3 [°] or less, and the thickness including the organic fiber cord and the rubber material is 1 [mm] or more and 2 [mm] or less. The heavy duty pneumatic tire according to claim 1, wherein the pneumatic tire is heavy.   A tire radial direction dimension A from the innermost position in the tire radial direction of the bead core to an end portion on the outer side in the tire width direction of the steel reinforcing layer, and an outer side in the tire width direction of the carcass layer from the innermost position in the tire radial direction of the bead core. The relationship between the tire radial dimension B to the end and the tire radial dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer is 5 [mm] ≦ B The heavy tire for a heavy load according to any one of claims 1 to 3, wherein -A≤15 [mm], 5 [mm] ≤CB≤15 [mm] is satisfied.   The tire radial direction dimension C from the innermost position in the tire radial direction of the bead core to the outer end in the tire width direction of the buffer layer, and the inner side in the tire width direction of the steel reinforcing layer from the innermost position in the tire radial direction of the bead core. The relationship between the tire radial dimension D to the end and the tire radial dimension E from the innermost position in the tire radial direction of the bead core to the inner end in the tire width direction of the buffer layer is 5 [mm] ≦ D The heavy-duty pneumatic tire according to claim 4, wherein −C ≦ 15 [mm], 5 [mm] ≦ ED ≦ 15 [mm] is satisfied.

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