JP2020196337A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of improving durability of a bead part.SOLUTION: A pneumatic tire which has such a structure that a carcass layer 4 including a steel cord is curled up from a tire inside to an outside around a bead core 5 of each bead part 3 is such that: a curled up end 4e of the carcass layer 4 is covered by a first organic fiber reinforcement layer 12A and a second organic fiber reinforcement layer 12B at both sides in a tire width direction; the first organic fiber reinforcement layer 12A and the second organic fiber reinforcement layer 12B contact with each other in an area from the curled up end 4e of the carcass layer 4 to a tire radial direction outside; an organic fiber cord comprising the first organic fiber reinforcement layer 12A, and an organic fiber cord comprising the second organic fiber reinforcement layer 12B have the same inclination direction with respect to a tire circumferential direction; and an end 12e of a tire radial direction inside of at least one of the first organic fiber reinforcement layer 12A and the second organic fiber reinforcement layer 12B is positioned in an area X.SELECTED DRAWING: Figure 3

Description

The present invention relates to a pneumatic tire having a structure in which a carcass layer including a steel cord is wound around the bead core of each bead portion from the inside to the outside of the tire, and more specifically, it is possible to improve the durability of the bead portion. Regarding pneumatic tires.

In pneumatic tires for heavy loads used for trucks, buses, etc., a carcass layer containing a plurality of aligned steel cords is mounted between a pair of bead portions, and the carcass layer is the bead core of each bead portion. Some tires have a structure that is rolled up from the inside to the outside of the tire. At least one organic fiber reinforcing layer including a plurality of aligned organic fiber cords may be arranged on the outer side of each bead portion in the width direction for the purpose of improving the durability of the bead portion. (See, for example, Patent Document 1).

However, in a pneumatic tire having such a configuration, since the carcass layer is made of a steel cord, the rigidity step at the winding end portion of the carcass layer becomes very large, and separation starting from the end portion is likely to occur. This is a factor that reduces the durability of the bead portion.

Japanese Unexamined Patent Publication No. 63-110006

An object of the present invention is to provide a pneumatic tire capable of improving the durability of a bead portion.

In order to achieve the above object, the pneumatic tire of the present invention includes a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions. It is provided with a pair of bead portions arranged inside in the radial direction of the tire, and a carcass layer containing a plurality of steel cords is mounted between the pair of bead portions, and the carcass layer is placed around the bead core of each bead portion. In a pneumatic tire having a structure wound from the inside to the outside, a bead filler is arranged on the outer periphery of the bead core of each bead portion, and a plurality of organic fiber cords are placed on the outer side of the bead filler in the tire width direction at each bead portion. An organic fiber reinforcing layer including the tire is arranged, and the organic fiber reinforcing layer is a tire width of a first organic fiber reinforcing layer and the first organic fiber reinforcing layer arranged inside in the tire width direction at the winding end of the carcass layer. It has a second organic fiber reinforcing layer arranged on the outer side in the direction, and the winding ends of the carcass layer are formed on both sides in the tire width direction by the first organic fiber reinforcing layer and the second organic fiber reinforcing layer. The first organic fiber reinforcing layer and the second organic fiber reinforcing layer are in contact with each other in a region that is covered and laterally outward in the tire radial direction from the winding end of the carcass layer, and the first organic fiber reinforcing layer is formed. The organic fiber cord formed and the organic fiber cord forming the second organic fiber reinforcing layer have the same inclination direction with respect to the tire circumferential direction, and are located on the innermost side in the tire radial direction among the plurality of strands constituting the bead core. When the region X is defined as the region where the shortest distance from the line segment J is -8 mm to 8 mm with respect to the direction perpendicular to the line segment J connecting the center of the wire to be formed and the bead toe of the bead portion, the first It is characterized in that at least one end of the one organic fiber reinforcing layer and the second organic fiber reinforcing layer on the inner side in the tire radial direction is located in the region X.

In the present invention, a bead filler is arranged on the outer periphery of the bead core of each bead portion, and an organic fiber reinforcing layer containing a plurality of organic fiber cords is arranged outside the bead filler in the tire width direction in each bead portion to reinforce the organic fiber. The layers consist of a first organic fiber reinforcing layer arranged inside the winding end of the carcass layer in the tire width direction and a second organic fiber reinforcing layer arranged outside the tire width direction of the first organic fiber reinforcing layer. Since it has, the rigidity step can be reduced and the stress concentration can be relaxed at the winding end portion of the carcass layer. As a result, the separation from the winding end portion of the carcass layer can be suppressed, and the durability of the bead portion can be improved. In particular, the winding ends of the carcass layer are covered on both sides in the tire width direction by the first organic fiber reinforcing layer and the second organic fiber reinforcing layer, and the first in the region outside the tire radial direction from the winding ends of the carcass layer. Since the organic fiber reinforcing layer and the second organic fiber reinforcing layer are in contact with each other, it contributes to the relaxation of stress concentration at the winding end of the carcass layer.

Further, since the organic fiber cord forming the first organic fiber reinforcing layer and the organic fiber cord forming the second organic fiber reinforcing layer have the same inclination direction with respect to the tire circumferential direction, these organic fiber reinforcing layers are integrally formed. Since it moves and acts flexibly against deformation, the rigidity of the organic fiber reinforcing layer is not excessively increased, and voids that are likely to occur in the region surrounded by the carcass layer and the organic fiber reinforcing layer can be suppressed. As a result, the separation from the winding end portion of the carcass layer can be suppressed, and the durability of the bead portion is improved. Further, since at least one end of the first organic fiber reinforcing layer and the second organic fiber reinforcing layer on the inner side in the tire radial direction is located in the region X, the winding end of the carcass layer and the organic fiber reinforcing layer It is possible to suppress the difference in strain in the tire radial direction at the end of the tire. As a result, the stress concentration at the winding end of the carcass layer is relaxed, and the separation from the winding end of the carcass layer can be suppressed, so that the durability of the bead portion is improved.

In the present invention, the length L in which the first organic fiber reinforcing layer and the second organic fiber reinforcing layer are in contact with each other is preferably 5 mm to 30 mm. As a result, the separation from the winding end of the carcass layer can be effectively suppressed.

The number of organic fiber cords that form the first organic fiber reinforcement layer N _A , the number of organic fiber cords that form the second organic fiber reinforcement layer N _B, and the number of steel cords that form the carcass layer N _M. Preferably satisfies the relationship of N _A / N _M <0.8 and N _B / N _M <0.8. As a result, the rigidity of the two organic fiber reinforcing layers is not excessively increased, so that the formation of voids can be suppressed in the region surrounded by the carcass layer and the organic fiber reinforcing layer. As a result, the separation from the winding end portion of the carcass layer can be suppressed, so that the durability of the bead portion can be improved.

The inclination angle φ _A of the organic fiber cord forming the first organic fiber reinforcing layer with respect to the tire circumferential direction is 10 ° to 45 °, and the inclination angle φ _A of the organic fiber cord forming the second organic fiber reinforcing layer with respect to the tire circumferential direction is _B is preferably 10 ° to 45 °. As a result, the separation from the winding end of the carcass layer can be effectively suppressed.

Absolute value of the angle difference between the inclination angle φ _A of the organic fiber cord forming the first organic fiber reinforcing layer with respect to the tire circumferential direction and the inclination angle φ _B of the organic fiber cord forming the second organic fiber reinforcing layer with respect to the tire circumferential direction. It is preferable that | φ _{A −} φ _B | is 5 ° to 35 °. As a result, the separation from the end of the organic fiber reinforcing layer can be effectively suppressed.

Absolute value of the difference between the height H _A of the tire radial outer edge in the first organic fiber reinforcing layer and the height H _B of the tire radial outer edge in the second organic fiber reinforcing layer | _HA −H _B | is preferably 5 mm or more. As a result, the separation from the end of the organic fiber reinforcing layer can be effectively suppressed.

The distance from the winding end of the carcass layer to the contact start point of the first organic fiber reinforcing layer and the second organic fiber reinforcing layer is preferably 8 mm or less. As a result, the separation from the end portion of the organic fiber reinforcing layer can be effectively suppressed.

It is a meridian cross-sectional view which shows the pneumatic tire for heavy load which concerns on embodiment of this invention. It is sectional drawing which shows the bead part of the pneumatic tire of FIG. It is another cross-sectional view which shows the bead part of the pneumatic tire of FIG. It is a side view which shows by extracting the organic fiber reinforcing layer embedded in the bead part. It is sectional drawing which shows the modification of the bead part. It is sectional drawing which shows the other modification of the bead part.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire for heavy load according to the embodiment of the present invention, and FIGS. 2 to 4 show a main part thereof.

As shown in FIG. 1, the pneumatic tire of the present embodiment has a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2 and 2 arranged on both sides of the tread portion 1. And a pair of bead portions 3 and 3 arranged inside the sidewall portions 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The 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 around the bead core 5 arranged in each bead portion 3 from the inside to the outside of the tire. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

A four-layer belt layer 7 is 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) that are inclined with respect to the tire circumferential direction. These belt layers 7 include main belt layers 72 and 73 of two central layers in which belt cords intersect with each other, and auxiliary belt layers 71 and 74 arranged on the inner diameter side and the outer diameter side of these main belt layers 72 and 73. Have. The inclination angle of the belt cords constituting the main belt layers 72 and 73 with respect to the tire circumferential direction is set in the range of, for example, 15 ° to 35 °, and the inclination angle of the belt cords forming the auxiliary belt layers 71 and 74 with respect to the tire circumferential direction is set. For example, it is set in the range of 15 ° to 75 °.

In the pneumatic tire, as shown in FIG. 2, the winding end portion 4e of the carcass layer 4 is arranged on the inner diameter side of the outer diameter side end portion 6e of the bead filler 6. That is, the winding end portion 4e of the carcass layer 4 is terminated at the middle portion of the bead filler 6. In each bead portion 3, a steel reinforcing layer 11 including a plurality of steel cords is arranged so as to wrap the carcass layer 4, the bead core 5, and the bead filler 6.

Further, in each bead portion 3, an organic fiber reinforcing layer 12 including a plurality of organic fiber cords is arranged on the outer side of the bead filler 6 in the tire width direction. The organic fiber reinforcing layer 12 is arranged on the inside of the winding end portion 4e of the carcass layer 4 in the tire width direction, and on the outside of the first organic fiber reinforcing layer 12A in the tire width direction. It also has a second organic fiber reinforcing layer 12B.

The first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are arranged so as to cover the winding end portion 4e of the carcass layer 4. Specifically, in the tire meridian cross section, the portion of the carcass layer 4 extending from the winding end portion 4e toward the bead core 5 is covered with the first organic fiber reinforcing layer 12A on the inner side surface in the tire width direction. The outer side surface in the tire width direction is covered with the second organic fiber reinforcing layer 12B.

Here, "coating" means that each end portion 12e of the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B on the inner side in the tire radial direction is adjacent to the carcass layer 4, and the first organic fiber reinforcing layer is reinforced. The layer 12A and the second organic fiber reinforcing layer 12B are adjacent to each other in the vicinity of the winding end portion 4e of the carcass layer 4, and the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are further attached to the carcass layer 4. It means that it extends outward in the radial direction of the tire from the winding end portion 4e. At this time, in the region outside the winding end portion 4e of the carcass layer 4 in the bead portion 3 in the tire radial direction, the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are in contact with each other. There is. Further, the above-mentioned "adjacent" means the distance between the cords of the organic fiber cords constituting the organic fiber reinforcing layer 12 and the carcass cords constituting the carcass layer 4, or constitutes the first organic fiber reinforcing layer 12A. This means that the distance between the organic fiber cord and the organic fiber cord constituting the second organic fiber reinforcing layer 12B is 0.2 mm to 2.0 mm.

On the other hand, in the region extending from the sidewall portion 2 to the bead portion 3, the sidewall rubber layer 13 exposed on the outer surface of the tire is arranged. A rim cushion rubber layer 14 is arranged between the bead filler 6 and the sidewall rubber layer 13. The rim cushion rubber layer 14 extends from the side position of the bead filler 6 toward the inner diameter side. That is, it is arranged in a region extending from the position on the inner diameter side of the outer diameter side end portion 6e of the bead filler 6 to the position on the inner diameter side of the bead core 5. The rim cushion rubber layer 14 is arranged so as to cover the winding end portion 4e of the carcass layer 4, the winding end portion 11e of the steel reinforcing layer 11, and the organic fiber reinforcing layer 12.

Between the bead filler 6 and the sidewall rubber layer 13, the crack suppressing layer 15 is a rolled-up end portion 11e of the steel reinforcing layer 11, the first organic fiber reinforcing layer 12A, the outer end portion 12e in the tire radial direction, and the second. It is arranged so as to cover the organic fiber reinforcing layer 12B of. The crack suppressing layer 15 is arranged in a region extending from a position on the inner diameter side of the bead filler 6 to a position near the end portion 11e of the steel reinforcing layer 11.

The winding end portion 4e of the carcass layer 4 and the winding end portion 11e of the steel reinforcing layer 11 may be covered with rubber edge tapes, respectively. Edge tape is not always necessary, but it is effective from the viewpoint of preventing separation.

As shown in FIG. 3, a line segment connecting the center of the wire I located on the innermost side in the tire radial direction and the bead toe 3t of the bead portion 3 among the plurality of wires constituting the bead core 5 is defined as a line segment J. A region (a region surrounded by a single point chain line in the figure) in which the shortest distance from the line segment J is −8 mm to 8 mm with respect to the direction perpendicular to the line segment J is defined as a region X. At this time, at least one end portion 12e of the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B on the inner side in the tire radial direction is arranged in the region X. The region X is a region inside the tire width direction (left side in the figure) from the line segment J when the shortest distance is a positive value, and outside the tire width direction from the line segment J when the shortest distance is a negative value (FIG. The area on the right side of).

In the above-described embodiment, only the inner end portion 12e in the tire radial direction in the first organic fiber reinforcing layer 12A is arranged in the region X, but as a more preferable embodiment, the first organic fiber The tire radial inner end 12e of both the reinforcing layer 12A and the second organic fiber reinforcing layer 12B may be arranged in the region X (see FIG. 6).

As shown in FIG. 4, both the organic fiber cord forming the first organic fiber reinforcing layer 12A and the organic fiber cord forming the second organic fiber reinforcing layer 12B are inclined with respect to the tire circumferential direction. The organic fiber cord forming the first organic fiber reinforcing layer 12A and the organic fiber cord forming the second organic fiber reinforcing layer 12B have the same inclination direction with respect to the tire circumferential direction.

In the above-mentioned pneumatic tire, the bead filler 6 is arranged on the outer periphery of the bead core 5 of each bead portion 3, and the bead filler 6 is reinforced with organic fibers including a plurality of organic fiber cords on the outer side of the bead filler 6 in the tire width direction. The layer 12 is arranged, and the organic fiber reinforcing layer 12 is the tire width direction of the first organic fiber reinforcing layer 12A and the first organic fiber reinforcing layer 12A arranged inside the winding end portion 4e of the carcass layer 4 in the tire width direction. Since it has the second organic fiber reinforcing layer 12B arranged on the outside, the rigidity step can be reduced and the stress concentration can be relaxed at the winding end portion 4e of the carcass layer 4. As a result, the separation of the carcass layer 4 from the winding end portion 4e can be suppressed, and the durability of the bead portion 3 can be improved. In particular, the winding end 4e of the carcass layer 4 is covered on both sides in the tire width direction by the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B, and the winding end 4e of the carcass layer 4 is in the tire radial direction. Since the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are in contact with each other in the outer region, it contributes to the relaxation of stress concentration at the winding end portion 4e of the carcass layer 4.

Further, in the above-mentioned pneumatic tire, the organic fiber cord forming the first organic fiber reinforcing layer 12A and the organic fiber cord forming the second organic fiber reinforcing layer 12B have the same inclination direction with respect to the tire circumferential direction. Since these organic fiber reinforcing layers 12 move integrally and act flexibly against deformation, the rigidity of the organic fiber reinforcing layer 12 is not excessively increased and is surrounded by the carcass layer 4 and the organic fiber reinforcing layer 12. It is possible to suppress voids that are likely to occur in the region. As a result, the separation of the carcass layer 4 from the winding end portion 4e can be suppressed, and the durability of the bead portion 3 is improved.

On the other hand, in the conventional structure, two organic fiber reinforcing layers are embedded in the bead portion, and the inclination directions of the organic fiber cords forming each of the organic fiber reinforcing layers with respect to the tire circumferential direction are different. However, in this case, since the organic fiber cords forming the two organic fiber reinforcing layers are present so as to intersect each other, they cannot act flexibly against deformation, increase the rigidity of the organic fiber reinforcing layer, and carry out carcass. Voids are likely to occur in the region surrounded by the layer and the organic fiber reinforcing layer. In this respect, according to the configuration according to the present invention, it is possible to prevent an adverse effect on the bead portion.

Further, in the above-mentioned pneumatic tire, at least one end portion 12e of the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B on the inner side in the tire radial direction is located in the region X, so that the carcass layer It is possible to suppress the difference in strain in the tire radial direction between the winding end portion 4e of 4 and the end portion 12e of the organic fiber reinforcing layer 12. As a result, the stress concentration at the winding end portion 4e of the carcass layer 4 is relaxed, and the separation from the winding end portion 4e of the carcass layer 4 can be suppressed, so that the durability of the bead portion 3 is improved.

Here, when the shortest distance from the line segment J is less than -8 mm, the end portion 12e on the inner side in the tire radial direction of the organic fiber reinforcing layer 12 is arranged in a region where contact with the rim is severe, and thus the end portion thereof. There is concern about the occurrence of separation from 12e. On the other hand, when the shortest distance from the line segment J exceeds 8 mm, the end portion 12e of the organic fiber reinforcing layer 12 on the inner side in the tire radial direction is arranged in a region having an effect of suppressing the difference in strain in the tire radial direction. This is not preferable because it causes an excessive increase in cost.

In the pneumatic tire, the length L (see FIG. 3) in which the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are in contact with each other is preferably 5 mm to 30 mm, preferably 8 mm to 25 mm. Is more preferable. By appropriately setting the length L in this way, the separation from the winding end portion 4e of the carcass layer 4 can be effectively suppressed. In FIG. 3, the contact start point P is a point at which the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B start contacting each other.

Here, when the length L is less than 5 mm, the amount of reduction in the rigidity step at the winding end 4e of the carcass layer 4 is small, and the stress is not dispersed at the winding end 4e of the carcass layer 4, so that the carcass layer 4 is wound. There is concern about the occurrence of separation from the end 4e. On the other hand, when the length L exceeds 30 mm, the end portion 12e on the outer side in the tire radial direction of the organic fiber reinforcing layer 12 is arranged in a region where the deformation in the bead portion 3 is large, so that the outer side in the tire radial direction of the organic fiber reinforcing layer 12 There is a concern that separation may occur from the end 12e of the tire.

Further, the height _HA of the outer end portion 12e in the tire radial direction in the first organic fiber reinforcing layer 12A (see FIG. 3) and the height of the outer end portion 12e in the tire radial direction in the second organic fiber reinforcing layer 12B. The absolute value | _HA −H _B | of the difference from H _B (see FIG. 3) is preferably 5 mm or more. The height H _B of the height H _A and the second organic fiber reinforced layer 12B of the first organic fiber reinforced layer 12A may be on the inner diameter side than both the outer diameter side end portion 6e of the bead filler 6 Is preferable. Further, it is more preferable that the height H _A of the first organic fiber reinforcing layer 12A is higher than the height H _{B of} the second organic fiber reinforcing layer. The heights H _A and H _B are both distances [mm] from the apex 3h of the bead heel.

Absolute value as described above | H _A -H _B | a By setting appropriately, it is possible to effectively suppress the separation from the end 12e of the organic fiber reinforcing layer 12. Here, the absolute value | H _A -H _B | if is less than 5 mm, the rigidity step is increased in the vicinity of the tire radial direction outer end 12e of the organic fiber reinforcing layer 12, the tire diameter of the organic fiber reinforcing layer 12 There is a concern that separation may occur from the end portion 12e on the outer side of the direction.

In the pneumatic tire, the number of organic fiber cords driven into the first organic fiber reinforcing layer 12A N _A , the number of organic fiber cords driven into the second organic fiber reinforcing layer 12B N _B, and the carcass layer 4 are provided. The number of steel cords to be driven N _M preferably satisfies the relationship of N _A / N _M <0.8 and N _B / N _M <0.8, and N _A / N _M <0.6 and N _B. / N _M <it is more preferable to satisfy 0.6 relationships. Further, it is preferable that the number of driven organic fiber cords N _A forming the first organic fiber reinforcing layer 12A and the number of driven organic fiber cords N _B forming the second organic fiber reinforcing layer 12B are the same. The number of steel cords driven into the carcass layer 4 N _M [lines / 50 mm] is the number of threads measured at the center of the tread portion 1, and the number of organic fiber cords driven N _A , N _B [lines / [50 mm] is the number of driving lines measured at the winding end portion 4e of the carcass layer 4.

As described above, the rigidity of the two organic fiber reinforcing layers 12 is excessively increased by setting the number of driven organic fiber reinforcing layers N _A and N _B smaller than the number of driving N _M of the carcass layer 4. Instead, the formation of voids can be suppressed in the region surrounded by the carcass layer 4 and the organic fiber reinforcing layer 12. As a result, the separation of the carcass layer 4 from the winding end portion 4e can be suppressed, so that the durability of the bead portion 3 can be improved.

In the pneumatic tire, the inclination angle φ _A (see FIG. 4) of the organic fiber cord forming the first organic fiber reinforcing layer 12A with respect to the tire circumferential direction is 10 ° to 45 °, and the second organic fiber reinforcing layer 12B The inclination angle φ _B (see FIG. 4) of the organic fiber cord forming the tire with respect to the tire circumferential direction is preferably 10 ° to 45 °. Further, it is more preferable that the inclination angle φ _B of the organic fiber cord forming the second organic fiber reinforcing layer 12B is larger than the inclination angle φ _A of the organic fiber cord forming the first organic fiber reinforcing layer 12A. By setting the inclination angles φ _A and φ _B appropriately in this way, the separation from the winding end portion 4e of the carcass layer 4 can be effectively suppressed.

Here, when the inclination angles φ _A and φ _B are less than 10 °, the amount of reduction in the rigidity step at the winding end 4e of the carcass layer 4 is small, and the stress is not dispersed at the winding end 4e of the carcass layer 4. There is a concern that separation may occur from the winding end 4e of the carcass layer 4. On the other hand, when the inclination angles φ _A and φ _B exceed 45 °, the tension acting on the organic fiber reinforcing layer 12 becomes excessively large, so that there is a concern that the strain at the end portion 12e of the organic fiber reinforcing layer 12 increases.

In particular, at the inclination angle φ _A of the organic fiber cord forming the first organic fiber reinforcing layer 12A and the inclination angle φ _B of the organic fiber cord forming the second organic fiber reinforcing layer 12B, the absolute value of the angle difference between the two | φ _A −φ _B | is preferably 5 ° to 35 °. By appropriately setting the absolute value | φ _{A −} φ _B | of the angle difference between the inclination angles φ _A and φ _B in this way, the separation from the end portion 12e of the organic fiber reinforcing layer 12 can be effectively suppressed. Can be done.

Here, when the absolute value | φ _{A −} φ _B | is less than 5 °, the rigidity is strengthened in only one direction, so that the winding end portion 4e of the carcass layer 4 is strengthened in the direction in which the rigidity is not strengthened. The amount of reduction in the rigidity step is small, the stress is not dispersed at the winding end 4e of the carcass layer 4, and there is a concern that separation may occur from the winding end 4e of the carcass layer 4. On the other hand, when the absolute value | φ _{A −} φ _B | exceeds 35 °, the stress is not dispersed at the winding end 4e of the carcass layer 4, and there is a concern that separation may occur from the winding end 4e of the carcass layer 4. ..

FIG. 5 shows another modified example of the bead portion. As shown in FIG. 5, the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are in contact with each other in a region R within a radius of 8 mm centered on the winding end portion 4e of the carcass layer 4. In other words, the distance from the winding end portion 4e of the carcass layer 4 to the contact start point P of the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B is 8 mm or less.

In FIG. 5, there are voids in the region outside the tire radial direction of the winding end portion 4e of the carcass layer 4 where the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B are not in contact with each other. It is in a state where the rubber 16 is filled. The rubber 16 is composed of a coated rubber or other rubber that coats the organic fiber reinforcing layer 12.

In the above-mentioned pneumatic tire, the distance from the winding end portion 4e of the carcass layer 4 to the contact start point P of the first organic fiber reinforcing layer 12A and the second organic fiber reinforcing layer 12B is 8 mm or less, so that the organic fiber The separation from the end portion 12e of the reinforcing layer 12 can be effectively suppressed.

Here, when the distance from the winding end portion 4e of the carcass layer 4 to the contact start point P exceeds 8 mm, the amount of reduction in the rigidity step at the winding end portion 4e of the carcass layer 4 is small, and the winding end portion 4e of the carcass layer 4 In, the stress is not dispersed, and there is a concern that separation may occur from the winding end portion 4e of the carcass layer 4.

With a tire size of 275 / 70R22.5, a tread portion, a pair of sidewall portions, and a pair of bead portions are provided, and a carcass layer containing a plurality of steel cords is mounted between the pair of bead portions. Manufactured tires of Conventional Examples 1 and 2 and Examples 1 to 11 in which only the structure of the bead portion was different in a pneumatic tire having a structure in which the tire was wound from the inside to the outside around the bead core of each bead portion. ..

In the tires of Conventional Examples 1 and 2 and Examples 1 to 11, whether or not the carcass end is coated, whether or not the organic fiber reinforcing layers are in contact with each other, the direction of inclination of the organic fiber cord, and among the first organic fiber reinforcing layers end position, the inner end position of the second organic fiber reinforced layer, the contact length L of the organic fiber reinforcing layer, the number implantation for end count N _M N _a, number implantation for end count N _M N _B, the inclination of the organic fiber cord Set the angle φ _A , the inclination angle φ _B of the organic fiber cord, the difference between the inclination angle φ _A and the inclination angle φ _B , the difference between the height H _A and the height H _B , and the distance to the contact start point as shown in Table 1. did.

In Table 1, the "inner end position of the first organic fiber reinforcing layer" and the "inner end position of the second organic fiber reinforcing layer" are the inner ends of the respective organic fiber reinforcing layers in the radial direction of the tire. It is the distance from the line segment J.

For these test tires, the durability of the bead portion was evaluated by the following test method, and the results are also shown in Table 1.

Durability of bead part:
Each test tire is mounted on the specified rim of JATTA, set to 75% of the specified air pressure of JATTA, loaded 1.4 times the specified load of JATTA, and subjected to the drum test under the conditions of running speed 49 km / h and mileage. A running test was conducted. After traveling 40,000 km, the test tire was cut along the tire meridian at eight points at equal intervals in the tire circumferential direction, and the winding end of the carcass layer and the winding end of the carcass layer at eight cut surfaces (16 points in total) of both bead parts. The length of the crack in the cross-sectional direction starting from each end of the organic fiber reinforcing layer was measured. The evaluation result is shown by an index with Conventional Example 1 as 100 using the reciprocal of the measured value. The larger the index value, the better the durability of the bead portion.

As can be seen from Table 1, the tires of Examples 1 to 11 had improved durability of the bead portion as compared with the conventional example 1.

In the tire of Conventional Example 2, the organic fiber cord forming the first organic fiber reinforcing layer and the organic fiber cord forming the second organic fiber reinforcing layer are inclined in different directions with respect to the tire circumferential direction, and the first organic fiber reinforcement is performed. Since the distance from the line segment J at the inner end in the tire radial direction in the layer and the second organic fiber reinforced layer is set outside the range specified in the present invention, it is possible to obtain a sufficient improvement effect in the durability of the bead portion. could not.

1 Tread part 2 sidewall part 3 bead part 4 carcass layer 5 bead core 6 bead filler 12 organic fiber reinforcing layer 12A first organic fiber reinforcing layer 12B second organic fiber reinforcing layer 12e end

Claims (7)

A tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged inside the tire radial direction of these sidewall portions. In a pneumatic tire having a structure in which a carcass layer containing a plurality of steel cords is mounted between the pair of bead portions, and the carcass layer is wound around the bead core of each bead portion from the inside to the outside of the tire. ,
A bead filler is arranged on the outer periphery of the bead core of each bead portion, and an organic fiber reinforcing layer containing a plurality of organic fiber cords is arranged on the outer side of the bead filler in the tire width direction in each bead portion. The first organic fiber reinforcing layer arranged inside the winding end of the carcass layer in the tire width direction and the second organic fiber reinforcing layer arranged outside the tire width direction of the first organic fiber reinforcing layer. The winding end portion of the carcass layer is covered on both sides in the tire width direction by the first organic fiber reinforcing layer and the second organic fiber reinforcing layer.
The first organic fiber reinforcing layer and the second organic fiber reinforcing layer are in contact with each other in a region outside the tire radial direction from the winding end of the carcass layer.
The organic fiber cord forming the first organic fiber reinforcing layer and the organic fiber cord forming the second organic fiber reinforcing layer have the same inclination direction with respect to the tire circumferential direction.
From the line segment J in the direction perpendicular to the line segment J connecting the center of the wire located on the innermost side in the tire radial direction and the bead toe of the bead portion among the plurality of wire wires constituting the bead core. When the region where the shortest distance is -8 mm to 8 mm is defined as the region X, at least one end of the first organic fiber reinforcing layer and the second organic fiber reinforcing layer on the inner side in the tire radial direction is defined as the region X. Pneumatic tires characterized by being located. The pneumatic tire according to claim 1, wherein the length L in which the first organic fiber reinforcing layer and the second organic fiber reinforcing layer are in contact with each other is 5 mm to 30 mm. The number of organic fiber cords that form the first organic fiber reinforcing layer N _A , the number of organic fiber cords that form the second organic fiber reinforcing layer N _B, and the number of steel cords that form the carcass layer. the pneumatic tire according to claim 1 or 2 and N _M is characterized by satisfying the relation of N _a / N _M <0.8 and N _B / N _M <0.8. The inclination angle φ _{A of the} organic fiber cord forming the first organic fiber reinforcing layer with respect to the tire circumferential direction is 10 ° to 45 °, and the inclination of the organic fiber cord forming the second organic fiber reinforcing layer with respect to the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 3, wherein the angle φ _B is 10 ° to 45 °. The angle difference between the inclination angle φ _{A of the} organic fiber cord forming the first organic fiber reinforcing layer with respect to the tire circumferential direction and the inclination angle φ _B of the organic fiber cord forming the second organic fiber reinforcing layer with respect to the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 4, wherein the absolute value | φ _{A −} φ _B | is 5 ° to 35 °. Absolute value of the difference between the height H _A of the tire radial outer end in the first organic fiber reinforcing layer and the height H _B of the tire radial outer end in the second organic fiber reinforcing layer | The pneumatic tire according to any one of claims 1 to 5, wherein H _A- H _B | is 5 mm or more. Any of claims 1 to 6, wherein the distance from the winding end of the carcass layer to the contact start point of the first organic fiber reinforcing layer and the second organic fiber reinforcing layer is 8 mm or less. Pneumatic tires described in.

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