JP2013022968A - Tire, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a bead part and a driving stability while suppressing the weight of a tire from increasing in comparison with a bead part where a reinforcement member is arranged.SOLUTION: A bead filler 60 includes an outside bead filler 60A which constitutes a tread-width-direction outside surface of the bead filler 60, and an inside bead filler 60B which is arranged on the tread-width-direction inside with respect to the outside bead filler 60A. When the distortion factors of the outside and inside bead fillers 60A and 60B are identical to each other and 50% or less, the modulus of elasticity of the inside bead filler 60B is higher than that of the outside bead filler 60A.

Description

  The present invention relates to a tire including a pair of bead cores, a carcass, and a pair of bead fillers, and a tire manufacturing method.

  Generally, when the rigidity of the bead portion is improved, the bead portion is less likely to be deformed, so that durability of the bead portion is improved and steering stability is improved.

  Conventionally, in order to improve the rigidity of a bead part, the tire by which the reinforcement member was arranged at the bead part is known (for example, refer to patent documents 1). In the tire of Patent Document 1, a reinforcing member having a predetermined hardness is disposed in the bead portion on the outer side in the tread width direction of the carcass main body portion straddling between the pair of bead cores. Since the reinforcing member has higher rigidity than the rubber member generally used for the bead portion, the rigidity of the bead portion is improved in the tire in which the reinforcing member is disposed.

Japanese Patent Laid-Open No. 11-20424

  In recent years, there has been a demand for reducing rolling resistance of tires due to increasing environmental considerations. The rolling resistance increases as the tire weight increases. Since the reinforcing member is added to the tire in which the reinforcing member is disposed in the bead portion, the weight of the tire increases. For this reason, the tire in which the reinforcing member is disposed has a problem that the rolling resistance generally increases.

  Accordingly, the present invention has been made in view of such a situation, and the durability of the bead portion is suppressed while suppressing an increase in the weight of the tire as compared with a tire in which a reinforcing member is disposed in the bead portion. It is another object of the present invention to provide a tire and a tire manufacturing method with improved steering stability.

  In order to solve the above-described problems, the present invention has the following features. A feature of the present invention is that it includes a pair of bead cores, a carcass, and a pair of bead fillers, and the carcass is folded back outwardly in the tread width direction from the carcass main body between the pair of bead cores. The bead filler is located between the carcass body portion and the carcass folded portion in the tread width direction, and is disposed on the outer side in the tire radial direction of the bead core, The bead filler has an outer bead filler constituting an outer surface in the tread width direction of the bead filler, and an inner bead filler disposed on the inner side in the tread width direction than the outer bead filler, and the distortion rate of the outer bead filler and the inner bead filler is The inner bead filler in the same and less than 50% Modulus and gist larger than the elastic modulus of the outer bead filler.

  According to the characteristics of the present invention, the elastic modulus of the inner bead filler is larger than the elastic modulus of the outer bead filler when the distortion rate of the bead filler is the same and equal to or less than 50% (that is, the distortion rate of the bead filler generated during normal running). . Since the bead filler is less likely to be deformed as the elastic modulus is larger, the bead filler has the inner bead filler, whereby the rigidity of the bead portion is improved. Thereby, durability and handling stability of a bead part improve.

  Generally, when the elastic modulus of the bead filler is increased, the rigidity of the bead filler is improved, so that a large difference in rigidity (so-called rigidity step) is generated between the end of the carcass folded portion and the bead filler. When an external force is applied to the bead portion during normal traveling, the carcass is distorted in accordance with the external force, whereas the bead filler having a high rigidity generates a distortion smaller than the distortion generated in the carcass. For this reason, the force generated by the distortion is concentrated on the end portion of the carcass folded portion. As a result, separation in which the end portion of the carcass folded portion is peeled off from the surrounding rubber member is likely to occur.

  In the tire according to the present invention, the outer bead filler constitutes the outer surface in the tread width direction of the bead filler, and therefore, the outer bead filler is located on the carcass folded portion side. Since the outer bead filler has a lower elastic modulus than the inner bead filler, the difference in rigidity between the end portion of the carcass folded portion and the outer bead filler is small. For this reason, since it is suppressed that the force produced by distortion concentrates on the edge part of a carcass folding | turning part, it becomes difficult to generate a separation. Therefore, even if the tire according to the present invention has a bead filler having a large elastic modulus, a decrease in durability of the bead portion based on the separation can be suppressed.

  According to the characteristic of this invention, in order to improve the rigidity of a bead part, the reinforcement member is not added. For this reason, it can suppress that the weight of a tire increases compared with the tire which added the reinforcement member.

  Further, when the strain rate of the outer bead filler and the inner bead filler is 50%, the increase rate of the elastic modulus of the inner bead filler with respect to the strain rate may be smaller than the increase rate of the elastic modulus of the outer bead filler with respect to the strain rate. Good.

  Further, when the strain rate of the outer bead filler and the inner bead filler is 150%, the elastic modulus of the inner bead filler may be smaller than the elastic modulus of the outer bead filler.

  The bead filler may be composed of only the outer bead filler and the inner bead filler.

  ADVANTAGE OF THE INVENTION According to this invention, manufacture of the tire and tire which improved durability and steering stability of the bead part, suppressing the increase in the weight of a tire compared with the tire by which the reinforcement member was arrange | positioned in the bead part. Can provide a method.

FIG. 1 is a partial cross-sectional view along the tread width direction and the tire radial direction of the tire 1 according to the present embodiment. FIG. 2 is a cross-sectional view along the red width direction and the tire radial direction of the bead portion 100 of the tire according to the present embodiment. FIG. 3 is a graph showing the relationship between the strain rate and the elastic modulus of the outer bead filler 60A and the inner bead filler 60B. FIG. 4 is a cross-sectional view showing the outer rubber member 62A and the inner rubber member 62B before vulcanization. FIG. 5 is a cross-sectional view along the red width direction and the tire radial direction of a bead portion 100 of a tire according to another embodiment.

  An example of a tire according to the present invention will be described with reference to the drawings. Specifically, (1) this embodiment, (2) other embodiments, and (3) comparative evaluation will be described.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. It should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. It goes without saying that the drawings include parts having different dimensional relationships and ratios.

  In the description of the present invention, the elastic modulus is obtained by adding a predetermined strain rate (for example, 5% strain) to a rubber sample with a temperature of 50 ° C., a frequency of 15 Hz, and measuring the reaction force at that time. It is a measured value. Specifically, for example, the elastic modulus can be measured using a viscoelasticity measuring device manufactured by Rheometrics.

(1) This Embodiment (1.1) Schematic Configuration of Tire 1 A schematic configuration of the tire 1 according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a partial cross-sectional view along the tread width direction and the tire radial direction of the tire 1 according to the present embodiment. FIG. 2 is a cross-sectional view along the red width direction and the tire radial direction of the bead portion 100 of the tire according to the present embodiment. That is, FIG. 2 is a partially enlarged view of FIG.

  The tire according to this embodiment includes a pair of bead cores 20, a carcass 40, a pair of bead fillers 60, and a belt layer 80.

  The bead core 20 is disposed in the bead unit 100. The bead core 20 is configured by a bead wire.

  The carcass 40 is arranged from the tread part 200 through the sidewall part 300 to the bead part 100. The carcass 40 spans between the pair of bead cores 20 and is folded back outward in the tread width direction so as to wind the bead cores. The carcass 40 includes a carcass main body 43 and a carcass folding portion 45. The carcass main body 43 straddles between the pair of bead cores 20. The carcass folding portion 45 is a portion that is folded from the carcass main body portion 43 outward in the tread width direction. The carcass folded portion 45 has a folded end portion 45a that is an end portion on the outer side in the tire radial direction. In the present embodiment, the folded end 45a is adjacent to the bead filler 60 in the tread width direction.

  The bead filler 60 is disposed outside the bead core 20 in the tire radial direction. The bead filler 60 is located between the carcass main body 43 and the carcass folding portion 45 in the tread width direction. The bead filler 60 has an outer end portion 65a that is an end portion on the outer side in the tire radial direction and an inner end portion 65b that is an end portion on the inner side in the tire radial direction. In the present embodiment, the outer end portion 65a is located on the outer side in the tire radial direction than the folded end portion 45a. That is, the structure of the carcass 40 is a so-called low turnup structure. The inner end portion 65 b is adjacent to the bead core 20.

  The belt layer 80 is disposed on the tread portion 200. The belt layer 80 is located on the outer side in the tire radial direction than the carcass main body 43. In the present embodiment, the belt layer 80 includes a plurality of belts.

(1.2) Schematic Configuration of Bead Part 100 A schematic configuration of the bead part 100 of the tire 1 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 3 is a graph showing the relationship between the strain rate and the elastic modulus of the outer bead filler 60A and the inner bead filler 60B.

  The bead filler 60 includes an outer bead filler 60A and an inner bead filler 60B. In the present embodiment, the bead filler 60 includes only the outer bead filler 60A and the inner bead filler 60B. That is, the bead filler 60 has a two-layer structure of an outer bead filler 60A and an inner bead filler 60B.

  The outer bead filler 60 </ b> A constitutes the outer surface in the tread width direction of the bead filler 60. That is, the outer bead filler 60A is adjacent to the folded end 45a in the tread width direction. The inner bead filler 60B is arranged on the inner side in the tread width direction than the outer bead filler. In the present embodiment, the inner bead filler 60B is in contact with the outer bead filler 60A in the tread width direction. In the present embodiment, the carcass 40 and the bead filler 60 are arranged in the order of the carcass folded portion 45, the outer bead filler 60A, the inner bead filler 60B, and the carcass main body 43 from the outer side in the tread width direction to the inner side.

  The elastic modulus of the outer bead filler 60A and the elastic modulus of the inner bead filler 60B differ depending on the strain rate. Specifically, as shown in FIG. 3, when the strain rate of the outer bead filler 60A and the inner bead filler 60B is the same and 50% or less, the elastic modulus of the inner bead filler 60B is higher than the elastic modulus of the outer bead filler 60A. large. That is, the elastic modulus of the inner bead filler 60B is smaller than the elastic modulus of the outer bead filler 60A in a low strain region where the distortion rate is 50% or less (the distortion rate of the bead filler generated during normal running).

  Further, when the strain rate of the outer bead filler 60A and the inner bead filler 60B is 50%, the increase rate of the elastic modulus of the inner bead filler 60B with respect to the strain rate may be smaller than the increase rate of the elastic modulus of the outer bead filler 60A with respect to the strain rate. preferable. In this case, the elastic modulus of the inner bead filler 60B becomes equal to the elastic modulus of the outer bead filler 60A when the strain rate of the outer bead filler 60A and the inner bead filler 60B is greater than 50%. As shown in FIG. 3, the elastic modulus of the inner bead filler 60B is equal to that of the outer bead filler 60A when the distortion rate is greater than 100%. When the strain rate of the outer bead filler 60A and the inner bead filler 60B is 150%, the elastic modulus of the inner bead filler 60B is smaller than that of the outer bead filler 60A. In addition, when the strain rate of the inner bead filler 60B is 50%, the increase rate of the elastic modulus of the inner bead filler 60B with respect to the strain rate is preferably in the range of 100% to 150%. When the strain rate of the outer bead filler 60A is 50%, the increase rate of the elastic modulus of the outer bead filler 60A with respect to the strain rate is preferably in the range of 75% to 100%. In the inner bead filler 60B shown in FIG. 3, the increase rate of the elastic modulus of the inner bead filler 60B with respect to the strain rate is decreased in the region of the strain rate of 50% to 100%. The increase rate of the elastic modulus of the inner bead filler 60B with respect to the strain rate is represented by (elastic modulus / strain rate of the inner bead filler 60B) × 100. The increase rate of the elastic modulus of the outer bead filler 60A with respect to the strain rate is represented by (elastic modulus / strain rate of the outer bead filler 60A) × 100.

  The outer bead filler 60A preferably has an elastic modulus generally used when the strain rate is 50% or less so that the difference in rigidity from the folded end portion 45a is small. Specifically, the elastic modulus of the outer bead filler 60A is preferably 8 MPa or less. If the elastic modulus of the outer bead filler 60A is 8 MPa or less, the difference in rigidity between the folded end 45a and the outer bead filler 60A is small, so that the occurrence of separation can be suppressed.

  In order to improve the rigidity of the bead part 100, the inner bead filler 60B is preferably 4 MPa or more when the strain rate is 50% or less. Thereby, since it becomes difficult for the bead part 100 to deform | transform, durability of the bead part 100 and steering stability can be improved.

  As shown in FIG. 2, in the thickness direction of the bead filler 60 orthogonal to the extending direction of the bead filler 60, the width of the outer bead filler 60A is the width Wa, and the width of the inner bead filler 60B is the width Wb. The width Wa is preferably in the range of 50% to 150% of the width Wb. If the width Wa is 50% or more of the width Wb, the influence of the rigidity of the inner bead filler 60B can be further suppressed, so that separation is less likely to occur. If the width Wa is 100% or less of the width Wb, the ratio of the inner bead filler 60B is large, so that the rigidity of the bead filler 60 can be further ensured. As a result, durability and handling stability of the bead portion can be improved.

  In the thickness direction of the bead filler 60, the maximum width of the bead filler 60 is defined as the maximum width Wf, and the width of the bead portion 100 at the maximum width Wf is defined as the bead width W. The maximum width Wf is preferably 60% or less with respect to the bead width W. If the maximum width Wf is 60% or less with respect to the bead width W, an increase in the weight of the tire due to the weight of the bead filler 60 can be suppressed, and therefore an increase in rolling resistance can be further suppressed.

  Note that the width of the bead filler 60 in the thickness direction of the bead filler 60 becomes narrower toward the outer side in the tire radial direction. That is, the bead filler 60 has a substantially triangular shape.

(1.3) Manufacturing Method of Tire 1 A manufacturing method of the tire 1 according to the present embodiment will be described with reference to FIG. FIG. 4 is a cross-sectional view showing the outer rubber member 62A and the inner rubber member 62B before vulcanization.

  First, members constituting the tire 1 such as the bead core 20, the carcass 40, the bead filler 60, and the belt layer 80 are prepared. Members such as the bead core 20, the carcass 40, and the belt layer 80 are prepared using a generally known method. The bead filler 60 is prepared using the following method.

  A ribbon-shaped rubber strip 62a and a rubber strip 62b are prepared. The ribbon-shaped rubber strip 62a and the rubber strip 62b are manufactured by extruding with an extruder, for example. As the ribbon-shaped rubber strip 62a and the rubber strip 62b, for example, those having a width of 10 mm and a thickness of 3 mm are manufactured. The rubber strip 62a and the rubber strip 62b are unvulcanized rubber members. Since the rubber strip 62a and the rubber strip 62b constitute the outer bead filler 60A and the inner bead filler 60B by vulcanization, respectively, the materials of the rubber strip 62a and the rubber strip 62b are made to have a predetermined elastic modulus corresponding to the strain rate. Adjust as appropriate.

  Considering the diameter of the annular bead core 20, the prepared rubber strip 62b is wound in a circular shape a plurality of times to form an inner rubber member 62B having the same shape as the inner bead filler 60B. That is, a ribbon-shaped rubber strip 62b is spirally wound and laminated to form an annular laminated body (inner rubber member 62B). In FIG. 4, the inner rubber member 62 </ b> B is formed by overlapping the end portions in the width direction of the rubber strip 62 b, but this is not necessarily limited thereto. You may form the inner side rubber member 62B laminated | stacked several dozen layers so that the inner side bead filler 60B of a desired magnitude | size may be formed. In this way, an inner rubber member having the same shape as the inner bead filler 60B is prepared.

  Similarly to the preparation of the inner rubber member 62B, the prepared rubber strip 62a is wound in a circular shape a plurality of times to form the outer rubber member 62A having the same shape as the outer bead filler 60A. That is, a ribbon-shaped rubber strip 62a is spirally wound and laminated to form an annular laminated body (outer rubber member 62A).

  The bead filler 60 is prepared by the above method. In addition to the method described above, as is conventionally known, an annular outer rubber member and an inner rubber member that are integrally formed may be prepared using an extruder. That is, the outer rubber member 62A and the inner rubber member 62B having the cross section shown in FIG. 1 may be prepared without having the cross section shown in FIG. Note that at least the inner rubber member 62B is preferably formed by winding and laminating a ribbon-shaped rubber strip 62b a plurality of times as described above.

  Next, the members constituting the prepared tire 1 are assembled into a tire shape using a molding machine. The outer rubber member 62A and the inner rubber member 62B are adjacent to each other (see FIG. 4). The outer rubber member 62A and the inner rubber member 62B are arranged in the bead portion 100 so that the outer rubber member 62A is located on the outer side in the tread width direction than the inner rubber member 62B. Other members are arranged in the same manner as in general tire molding. Thereby, a green tire in which the outer rubber member 62A and the inner rubber member 62B are arranged is prepared. The green tire is vulcanized by placing the green tire in a mold and increasing the temperature and pressure. Thereby, the tire 1 is manufactured.

(1.4) Operational Effect According to the tire 1 according to the present embodiment, the bead filler 60 includes the outer bead filler 60A and the inner bead filler 60B, and the distortion rates of the outer bead filler 60A and the inner bead filler 60B are the same and 50% or less. In the case of (that is, the strain rate of the bead filler generated during normal traveling), the elastic modulus of the inner bead filler 60B is larger than the elastic modulus of the outer bead filler 60A. Since the bead filler 60 is less likely to be deformed as the elastic modulus is larger, the bead filler 60 has the inner bead filler 60B, whereby the rigidity of the bead portion 100 is improved. Thereby, durability and handling stability of bead part 100 improve.

  In general, when the elastic modulus of the bead filler 60 is increased, the rigidity of the bead filler 60 is improved, so that a large difference in rigidity (so-called rigidity step) occurs between the folded end 45a and the bead filler 60. When an external force is applied to the bead unit 100 during normal traveling, the carcass 40 is distorted in accordance with the external force, whereas the bead filler 60 having high rigidity is distorted smaller than the carcass 40. For this reason, the force generated by the distortion concentrates on the folded end 45a. As a result, the separation at which the folded end 45a is peeled off from the surrounding rubber member (for example, the bead filler 60) is likely to occur.

  According to the tire 1 according to the present embodiment, the outer bead filler 60A constitutes the outer surface in the tread width direction of the bead filler 60, and thus the outer bead filler 60A is located on the carcass folded portion 45 side. Since the outer bead filler 60A has a lower elastic modulus than the inner bead filler 60B, the difference in rigidity between the folded end 45a and the outer bead filler 60A is small. That is, the outer bead filler 60A functions as a buffer rubber between the inner bead filler 60B and the folded end 45a. For this reason, since it is suppressed that the force produced by distortion concentrates on the return | turnback edge part 45a, it becomes difficult to generate a separation. Therefore, even if the tire 1 has the bead filler 60 (inner bead filler 60B) having a large elastic modulus, it is possible to suppress a decrease in durability of the bead portion 100 based on the separation.

  In this embodiment, in order to improve the rigidity of the bead part 100, it is not necessary to add a reinforcing member. For this reason, it can suppress that the weight of the tire 1 increases compared with the tire which added the reinforcement member. As a result, it is possible to improve the durability and steering stability of the bead part while suppressing an increase in the weight of the tire as compared with the bead part in which the reinforcing member is disposed.

  The bead portion 100 is deformed when a strong external force is applied to the bead portion 100 due to sudden start, sudden braking, cornering at high speed, or the like (that is, when the distortion rate of the bead filler 60 is 100% or more). The bead filler 60 is greatly distorted. In general, the bead filler 60 has an elastic modulus that increases as the strain rate increases. For this reason, when a strong external force is applied to the bead part 100, the rigidity of the bead filler 60 is increased, so that the bead filler 60 is less likely to follow the deformation of the bead part 100. As a result, the bead filler 60 tends to damage the rubber member that forms the periphery of the bead filler 60.

  In the present embodiment, when the strain rate of the outer bead filler 60A and the inner bead filler 60B is 50%, the increase rate of the elastic modulus of the inner bead filler 60B with respect to the strain rate is higher than the increase rate of the elastic modulus of the outer bead filler 60A with respect to the strain rate. small. When the strain rate of the outer bead filler 60A and the inner bead filler 60B is 150%, the elastic modulus of the inner bead filler 60B is smaller than that of the outer bead filler 60A. Thereby, even if a strong external force is applied to the bead part 100 and the distortion rate of the bead filler 60 is increased, the elastic modulus of the inner bead filler 60B is not significantly increased. As a result, the bead filler 60 can easily follow the deformation of the bead portion 100, so that the bead filler 60 is less likely to damage the rubber member that forms the periphery of the bead filler 60. For this reason, durability of bead part 100 improves.

  In the present embodiment, the bead filler 60 includes only an outer bead filler 60A and an inner bead filler 60B. For this reason, since it becomes easy to ensure the magnitude | size of the inner bead filler 60B with a large elasticity modulus in a low-strain area | region, durability and handling stability of the bead part 100 can be improved more. Moreover, since the thickness of the bead filler 60 can be easily reduced as compared with the bead filler 60 having a multilayer structure, an increase in the weight of the tire can be suppressed.

  In the present embodiment, the inner rubber member 62B having the same shape as the inner bead filler 60B is prepared by winding a ribbon-shaped rubber strip 62b a plurality of times in a circular shape. Since the inner bead filler 60B has a large elastic modulus in a low strain region, it takes time to push out the integrally formed inner rubber member 62B having a large cross-sectional area by the extruder. The ribbon-shaped rubber strip 62b can be easily pushed out as compared with the integrally formed inner rubber member 62B. Therefore, when the tire 1 is manufactured by winding the ribbon-shaped rubber strip 62b a plurality of times in a circle and preparing the inner rubber member 62B having the same shape as the inner bead filler 60B, the productivity of the tire 1 can be improved.

(2) Other Embodiments Although the contents of the present invention have been disclosed through the embodiments of the present invention, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. The present invention includes various embodiments not described herein.

  For example, in the tire 1 according to the above-described embodiment, the bead filler 60 includes only the outer bead filler 60A and the inner bead filler 60B, but is not limited thereto. As shown in FIG. 5, the bead filler 60 may include an outer bead filler 60A, an inner bead filler 60B, and an innermost bead filler 60C. That is, the bead filler 60 has a three-layer structure. The outer bead filler 60A and the innermost bead filler 60C may be manufactured from the same rubber member, and the inner bead filler 60B may be manufactured from another rubber member. In this case, when the strain rates of the outer bead filler 60A, the inner bead filler 60B, and the innermost bead filler 60C are the same and 50% or less, the elastic modulus of the inner bead filler 60B is larger than the elastic modulus of the outer bead filler 60A and the innermost bead filler 60C. Therefore, since the rigidity step between the carcass main body 43 and the innermost bead filler 60C is reduced, the separation between the carcass main body 43 and the innermost bead filler 60C can be suppressed. As a result, the durability of the bead portion can be further improved.

  In addition, the outer bead filler 60A and the inner bead filler 60B may be manufactured from the same rubber member, and the innermost bead filler 60C may be manufactured from another rubber member. In this case, when the strain rates of the outer bead filler 60A, the inner bead filler 60B, and the innermost bead filler 60C are the same and 50% or less, the elastic modulus of the innermost bead filler 60C is larger than the elastic modulus of the outer bead filler 60A and the inner bead filler 60B.

  Further, the bead filler 60 may have a multilayer structure of four or more layers instead of the three-layer structure. As described above, since the elastic modulus of the bead filler 60 can be appropriately adjusted by adopting a multilayer structure, the durability and steering stability of the bead unit 100 can be improved according to the required performance.

  The tire 1 according to the above-described embodiment does not have the reinforcing member, but it is not always necessary. In order to obtain various performances, a reinforcing member may be provided. According to the present invention, the rigidity of the bead portion can be ensured even when a reinforcing member having a thickness smaller than that of a conventional reinforcing member is used. Therefore, since the amount of the reinforcing member to be used can be reduced, an increase in the weight of the tire can be suppressed.

  The tire according to the present invention may be a pneumatic tire or a tire filled with rubber. Moreover, a gas-filled tire other than air containing a rare gas such as argon may be used.

  As described above, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the description of the present specification.

(3) Comparative evaluation In order to confirm the effect of the tire according to the present invention, durability (separation resistance) and steering stability of the bead portion were evaluated. In addition, this invention is not limited to a following example.

  In the evaluation of separation resistance and steering stability, tires according to examples and comparative examples shown in Table 1 were used. A tire size of 175 / 65R15 was used. For each tire, the elastic modulus of the outer bead filler and the inner bead filler was measured in the low strain region (when the strain rate was 50%). Using the elastic modulus of the outer bead filler and the elastic modulus of the inner bead filler of Comparative Example 1 as a reference (100), the elastic modulus of the other outer bead filler and the elastic modulus of the inner bead filler were indicated by an index. The other structures are the same in all tires.

  In Comparative Example 1, Comparative Example 2, Comparative Example 4 and Comparative Example 5, the bead filler has a single-layer structure. In Comparative Example 2 and Example 1, the bead filler has a two-layer structure (see FIG. 2). In Example 2, the bead filler has a three-layer structure (see FIG. 5).

  In Comparative Example 4, a steel wire insert was disposed as a reinforcing member between the bead filler and the carcass folded portion in the tread width direction. In Comparative Example 5, an NY insert made of organic fiber was disposed as a reinforcing member between the bead filler and the carcass folded portion in the tread width direction.

  In Comparative Example 2, the elastic modulus of the outer bead filler and the inner bead filler are 150. In Comparative Example 3, the elastic modulus of the outer bead filler is 100, and the elastic modulus of the inner bead filler is 75. In Comparative Example 4 and Comparative Example 5, the elastic modulus of the outer bead filler and the elastic modulus of the inner bead filler are 100. In Example 1, the elastic modulus of the outer bead filler is 100, and the elastic modulus of the inner bead filler is 150. In Example 2, the elastic modulus of the outer bead filler is 100, and the elastic modulus of the inner bead filler is 150. Furthermore, in Example 2, the elastic modulus of the innermost bead filler is the same as the elastic modulus of the outer bead filler. That is, the elastic modulus of the innermost bead filler is 100 (index indication).

  Steering stability: Each rim assembled on a rim having a rim size of 5J × 17 was mounted on an FF vehicle (displacement 1300 cc). The internal pressure of the tire is 230 kPa. The FF vehicle was run on the test course (dry road surface). The driving stability during driving was scored by a 10-point method based on the sensory evaluation of the driver. The results are shown in Table 1. The larger the value, the better the steering stability.

  Separation resistance: Each tire assembled on a rim having a rim size of 5J × 15 was set on a drum having a diameter of 1.7 m. The vehicle was run for 10,000 km under conditions of an internal pressure of 300 kPa and a load of 1000 kg. About each tire after driving | running | working, the separation amount of the folding | turning edge part of a carcass folding | turning part was measured six places. The separation amount of Comparative Example 1 was used as a reference (100), and the separation amounts of other tires were displayed as indexes. The results are shown in Table 1. The larger the value, the better the separation resistance.

  Mass: The mass of each tire was measured. The results are shown in Table 1.

  As shown in Table 1, in Example 1 and Example 2, an inner bead filler having a large elastic modulus is used. As a result, it can be seen that the steering stability is better than that of Comparative Example 1. In Comparative Example 2, the rigidity of the entire bead filler is improved. In this case, it was found that although the steering stability is improved, the separation resistance is lowered. In Example 1 and Example 2, the separation resistance is maintained. By improving the rigidity of the bead portion, the durability of the bead portion is improved as much as the deformation of the bead portion is suppressed. Therefore, compared with the comparative example 1, in Example 1 and Example 2, durability of a bead part is improving.

  Moreover, as Table 1 showed, in Example 1 and Example 2, it turned out that the mass of a tire is light compared with the comparative example 4 and the comparative example 5 with which the reinforcement member was arrange | positioned.

  Therefore, according to the tires according to Example 1 and Example 2, the durability and handling stability of the bead part are suppressed while suppressing an increase in the weight of the tire as compared with the tire in which the reinforcing member is arranged in the bead part. It was found that can be improved.

  DESCRIPTION OF SYMBOLS 1 ... Tire, 20 ... Bead core, 40 ... Carcass, 43 ... Carcass main-body part, 45 ... Carcass folding | turning part, 45a ... Folding end part, 60 ... Bead filler, 60A ... Outer bead filler, 60B ... Inner bead filler, 60C ... Inner side bead filler, 62A ... outer rubber member, 62B ... inner rubber member, 62a, 62b ... rubber strip, 65a ... outer end portion, 65b ... inner end portion, 80 ... belt layer, 100 ... bead portion, 200 ... tread portion, 300 ... side wall Part

Claims (5)

A pair of bead cores, a carcass, and a pair of bead fillers are provided,
The carcass has a carcass body portion straddling between the pair of bead cores, and a carcass folded portion folded back from the carcass body portion toward the tread width direction,
The bead filler is a tire that is located between the carcass main body portion and the carcass folded-back portion in the tread width direction, and is disposed outside the bead core in the tire radial direction,
The bead filler has an outer bead filler constituting an outer surface in the tread width direction of the bead filler, and an inner bead filler disposed on the inner side in the tread width direction than the outer bead filler,
In the case where the strain rate of the outer bead filler and the inner bead filler is the same and 50% or less, the elastic modulus of the inner bead filler is larger than the elastic modulus of the outer bead filler.   2. The increase rate of the elastic modulus of the inner bead filler with respect to the strain rate is smaller than the increase rate of the elastic modulus of the outer bead filler with respect to the strain rate when the strain rate of the outer bead filler and the inner bead filler is 50%. The described tire.   3. The tire according to claim 1, wherein an elastic modulus of the inner bead filler is smaller than an elastic modulus of the outer bead filler when a strain rate of the outer bead filler and the inner bead filler is 150%.   The tire according to any one of claims 1 to 3, wherein the bead filler includes only the outer bead filler and the inner bead filler. A pair of bead cores, a carcass, and a pair of bead fillers are provided,
The carcass has a carcass body portion straddling between the pair of bead cores, and a carcass folded portion folded back so as to wind the bead core,
The bead filler is located between the carcass main body portion and the carcass folded portion, and is disposed on the tire radial direction outer side of the bead core,
The bead filler is a method for manufacturing a tire having an outer bead filler constituting an outer surface in the red width direction of the bead filler, and an inner bead filler disposed on the inner side in the tread width direction than the outer bead filler,
The tire manufacturing method includes:
Preparing an outer rubber member having the same shape as the outer bead filler;
Winding a ribbon-shaped rubber strip a plurality of times in a circle, and preparing an inner rubber member having the same shape as the inner bead filler;
The outer rubber member and the inner rubber member are arranged so that the outer rubber member constitutes an outer surface in the tread width direction of the bead filler, and the inner rubber member is located on the inner side in the tread width direction than the outer rubber member. Process,
Vulcanizing a raw tire in which the outer rubber member and the inner rubber member are arranged, and
A tire manufacturing method in which the elastic modulus of the inner bead filler is larger than the elastic modulus of the outer bead filler when the distortion rate of the outer bead filler and the inner bead filler is the same and 50% or less.

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