JP2013039851A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that has improved durability while preventing riding comfort from being deteriorated even with a fillerless bead structure.SOLUTION: The pneumatic tire T includes: a right and left pair of beads 1; and a carcass ply 41 disposed between the beads, and whose end 41a is wound from the inside to the outside in the width direction of the tire without a bead filler provided around a bead 1a. In the pneumatic tire, a reinforcing layer 8 formed of a central area 8b for covering the end 41a, an outer region 8a than the central area 8b in the radial direction of the tire, and an inner region 8c than the central area 8b in the radial direction of the tire is provided outside the carcass ply 41 in the width direction of the tire, wherein each of the outer area 8b and the inner area 8c has smaller longitudinal rigidity than that of the central area 8b.

Description

  The present invention includes a pair of left and right bead portions, and a carcass ply that is disposed between the bead portions and has an end portion wound up from the inner side to the outer side in the tire width direction without arranging a bead filler around the bead. The present invention relates to a pneumatic tire provided.

  Conventionally, in a pneumatic tire, an annular bead and a bead filler are provided in a bead portion, and a carcass ply is folded back on the inner peripheral side of the bead and wound up from the inner side to the outer side in the tire width direction. However, since the bead filler has problems such as an increase in weight and cost, a filler-less bead portion structure in which the bead filler is omitted has been proposed (for example, Patent Document 1). However, in the filler-less bead portion structure, the durability is reduced unless the thickness of the sidewall portion is equal to or larger than that of the conventional one, so that the weight cannot be sufficiently reduced.

  Therefore, in Patent Document 2, for the purpose of enabling the tire weight reduction without filler without reducing the durability, a resin film is provided on the winding end of the carcass ply so as to straddle the tire radial direction inside and outside. A laminated pneumatic tire is described. By laminating such resin films, it is possible to prevent stress from concentrating on the winding end of the carcass ply, to prevent separation at the winding end, and to improve durability.

  However, since the pneumatic tire of Patent Document 2 extends the resin film uniformly along the tire radial direction, the longitudinal rigidity of the sidewall portion becomes too large, and the ride comfort may deteriorate. There was found.

Japanese Patent Laid-Open No. 2-11406 Japanese Patent Laid-Open No. 10-35231

  The present invention has been made in view of the above circumstances, and the object thereof is to provide a pneumatic tire with improved durability while suppressing deterioration in riding comfort even when the fillerless bead structure is adopted. There is to do.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is arranged between a pair of right and left bead portions and the bead portions, and the end portion is directed from the inner side to the outer side in the tire width direction without arranging a bead filler around the bead. In a pneumatic tire including a carcass ply that is wound up, on the outer side in the tire width direction of the carcass ply, a central region that covers the end, an outer region on the outer side in the tire radial direction than the central region, and the central region And a reinforcing layer in which the longitudinal rigidity of the outer region and the inner region is smaller than the longitudinal rigidity of the central region.

  The pneumatic tire of the present invention has a filler-less bead portion structure in which no bead filler is disposed outside the bead in the tire radial direction. According to the present invention, since the end portion of the carcass ply is reinforced by the reinforcing layer, separation at the end portion can be prevented and durability can be improved. Furthermore, since the longitudinal rigidity of the outer region and the inner region of the reinforcing layer of the present invention is smaller than that of the central region, the vertical rigidity of the sidewall portion is higher than when the longitudinal stiffness is uniform. It does not become too large, and deterioration of ride comfort can be suppressed. The longitudinal rigidity of the present invention refers to the longitudinal rigidity of the tire.

  In the pneumatic tire of the present invention, the reinforcing layer is configured by juxtaposing cords extending in the tire circumferential direction along the tire radial direction, and per unit length in the tire radial direction of the outer region and the inner region. The number of cords is preferably smaller than the number of cords per unit length in the tire radial direction of the central region.

  Generally, the tightening force by the cord extending in the tire circumferential direction increases the longitudinal rigidity. However, as the number of cords increases, the tightening force also increases and the longitudinal rigidity increases. For this reason, the number of cords per unit length in the tire radial direction in the outer region and the inner region is smaller than the number of cords per unit length in the tire radial direction in the central region, respectively. Are smaller than the tightening force in the central region. Thereby, since the vertical rigidity of the outer region and the inner region can be made smaller than the vertical rigidity of the central region, it is possible to provide a pneumatic tire with improved durability while suppressing deterioration in riding comfort.

  In the pneumatic tire of the present invention, the reinforcing layer is configured by juxtaposing cords extending in the tire circumferential direction along the tire radial direction, and the Young's modulus of the cords in the outer region and the inner region is It is preferable that the Young's modulus of the cord in the central region is smaller than each other.

  Generally, the tightening force by the cord extending in the tire circumferential direction increases the longitudinal rigidity. However, as the Young's modulus of the cord increases, the tightening force increases and the longitudinal rigidity further increases. Therefore, by making the Young's modulus of the cord in the outer region and the inner region smaller than the Young's modulus of the cord in the central region, the tightening force in the outer region and the inner region is smaller than the tightening force in the central region, respectively. Become. Thereby, since the vertical rigidity of the outer region and the inner region can be made smaller than the vertical rigidity of the central region, it is possible to provide a pneumatic tire with improved durability while suppressing deterioration in riding comfort.

  In the pneumatic tire of the present invention, the reinforcing layer is configured by arranging cords extending in the tire radial direction side by side in the tire circumferential direction, and the tires in the tire radial direction of the cords in the outer region and the inner region. It is preferable that the angle is larger than the angle formed with the tire radial direction of the cord in the central region.

  In general, the cord extending along the tire radial direction increases the longitudinal rigidity. However, the smaller the angle between the cord and the tire radial direction, the more the vertical rigidity increases. Therefore, the longitudinal rigidity of the outer region and the inner region is increased by increasing the angle formed between the cords of the outer region and the inner region with respect to the tire radial direction of the cords of the central region. Since each can be smaller than the rigidity, it is possible to provide a pneumatic tire with improved durability while suppressing deterioration in ride comfort.

  In the pneumatic tire of the present invention, it is preferable that the longitudinal rigidity of the outer region is equal to or less than the longitudinal rigidity of the inner region. According to this configuration, it is possible to effectively suppress the increase in the longitudinal rigidity in the vicinity of the center of the sidewall portion, so that it is possible to further suppress the deterioration in riding comfort.

Tire meridian cross-sectional view schematically showing an example of a pneumatic tire according to the present invention Enlarged view showing the periphery of the end of the carcass ply The enlarged view which shows the edge part periphery of the carcass ply which concerns on another embodiment The enlarged view which shows the edge part periphery of the carcass ply which concerns on another embodiment The enlarged view which shows the edge part periphery of the carcass ply which concerns on Example 2. FIG. The enlarged view which shows the edge part periphery of the carcass ply which concerns on the comparative example 2 The enlarged view which shows the edge part periphery of the carcass ply which concerns on the comparative example 3

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A pneumatic tire T shown in FIG. 1 includes a pair of left and right bead portions 1, sidewall portions 2 extending outward in the tire radial direction from each of the bead portions 1, and tire radial outer sides of the sidewall portions 2. And a tread portion 3 connected to the end. The bead portion 1 is provided with an annular bead 1a formed by covering a convergent body such as a steel wire with rubber. In the present invention, a bead filler having a substantially triangular cross section is not disposed outside the bead 1a in the tire radial direction, and a so-called filler-less bead portion structure is formed.

  A toroidal carcass layer 4 is disposed between the pair of left and right bead portions 1. The carcass layer 4 is constituted by at least one carcass ply 41, and the carcass ply 41 is formed by covering a cord extending at an angle of approximately 90 ° with respect to the tire equator CL with a topping rubber. The carcass ply 41 is locked in a state where the end portion 41a is wound up from the inner side to the outer side in the tire width direction without disposing a bead filler around the bead 1a. On the inner periphery of the carcass layer 4, an inner liner rubber 5 for maintaining air pressure is disposed. A sidewall rubber 6 is disposed on the outer periphery of the sidewall portion 2 of the carcass layer 4.

  On the outer periphery of the tread portion 3 of the carcass layer 4, a belt layer 7 composed of a plurality of (two in this embodiment) belt plies is disposed. Each belt ply is formed by covering a cord extending obliquely with respect to the tire equator CL with a topping rubber, and the cords are laminated so as to cross each other in opposite directions. On the outer periphery of the belt layer 7, a belt reinforcing layer (not shown) formed by covering a cord extending substantially in the tire circumferential direction with a topping rubber may be disposed. The belt reinforcing layer is disposed so as to cover at least both end portions of the belt layer 7, and can prevent the belt layer 7 from being lifted by a centrifugal force during high-speed running, thereby improving high-speed durability.

  In the pneumatic tire T of the present invention, the reinforcing layer 8 is provided outside the carcass ply 41 in the tire width direction. The reinforcing layer 8 includes a central region 8b covering the end portion 41a, an outer region 8a on the outer side in the tire radial direction than the central region 8b, and an inner region 8c on the inner side in the tire radial direction from the central region 8b. In this embodiment, the ratio of the height ha of the outer region 8a in the tire radial direction, the height hb of the central region 8b in the tire radial direction, and the height hc of the inner region 8c in the tire radial direction is 1: 1: 1. Yes.

  The height h in the tire radial direction of the reinforcing layer 8 is preferably in the range of 15 to 45% of the tire cross-section height H. The upper end 81 of the reinforcing layer 8 (the outer end in the tire radial direction of the outer region 8a) is at a position 35 to 45% of the tire cross-section height H from the rim base line BL. On the other hand, the lower end 84 (the inner end in the tire radial direction of the inner region 8c) of the reinforcing layer 8 is a position separated by 3 mm or more outward in the tire radial direction from the ply bending position positioned at the upper end of the bead 1a.

  The outer end 82 in the tire radial direction of the central region 8b (the inner end in the tire radial direction of the outer region 8a) is preferably positioned 3 to 7% of the tire cross-section height H from the end 41a to the outer side in the tire radial direction. Further, the inner end 83 in the tire radial direction of the central region 8b (the outer end in the tire radial direction of the inner region 8c) is set at a position 3 to 7% of the tire cross-section height H from the end 41a to the inner side in the tire radial direction. preferable. As will be described later, by disposing the central region 8b having a large vertical rigidity in the above range with respect to the end portion 41a, separation at the end portion 41a can be effectively prevented and durability can be improved.

  In the reinforcing layer 8, the longitudinal stiffness Ka and Kc of the outer region 8a and the inner region 8c are made smaller than the longitudinal stiffness Kb of the central region 8b. That is, Kb> Ka and Kb> Kc. Thereby, the reinforcement layer 8 can suppress that the vertical rigidity of the side wall part 2 increases excessively, fully reinforcing the edge part 41a of the carcass ply 41. FIG.

  In addition, it is preferable that the longitudinal rigidity Ka of the outer region 8a is equal to or less than the longitudinal rigidity Kc of the inner region 8c. That is, Ka, Kb, and Kc preferably satisfy the relationship of Kb> Kc ≧ Ka. Thereby, since it can suppress effectively that the longitudinal rigidity of the center part vicinity of the sidewall part 2 increases, the deterioration of riding comfort can further be suppressed.

  The reinforcing layer 8 of the present embodiment is configured by arranging cords 9 extending in the tire circumferential direction side by side along the tire radial direction, and the number of cords per unit length in the tire radial direction of the outer region 8a and the inner region 8c. Is less than the number of cords per unit length in the tire radial direction of the central region 8b. That is, the cords 9 of the outer region 8a and the inner region 8c are roughly arranged in parallel, and the cords 9 of the central region 8b are arranged closely. Thereby, the vertical rigidity Ka of the outer area | region 8a and the inner area | region 8c can be made smaller than the vertical rigidity Kb of the center area | region 8b, respectively. As the material of the cord 9, organic fiber cords such as polyester, rayon, nylon, and aramid can be used.

Examples of Ka are 1200 to 4500 N / mm ² , Kb is 8000 to 15000 N / mm ² , and Kc is 2400 to 12000 N / mm ² . Further, Ka, it is preferably at least 3500 N / mm ² smaller than Kb, Kc is preferably at least 3000N / mm ² smaller than Kb.

  When an organic fiber cord is used as the material of the cord 9, for example, 5 to 8 cords 9 per inch are arranged in the outer region 8a, and 22 to 28 cords 9 per inch are arranged in the central region 8b. In the inner region 8c, 15 to 18 cords 9 are arranged per inch. Thereby, the longitudinal rigidity Ka, Kb, Kc of each area | region can satisfy | fill the relationship of Kb> Kc> = Ka. When the number of cords 9 in each region is the above number, if the Young's modulus in the tire circumferential direction of the central region 8b is 100%, the Young's modulus in the tire circumferential direction of the outer region 8a is 15 to 30%, and the inner region 8c. The Young's modulus in the tire circumferential direction is about 30 to 80%.

  The reinforcing layer 8 of the present embodiment is formed, for example, by covering a cord 9 spirally wound in the tire circumferential direction with a topping rubber. When the cords 9 are spirally wound, the number of cords per unit length in the tire radial direction can be easily set by making the intervals between the cords 9 different in the outer region 8a, the central region 8b, and the inner region 8c. .

<Another embodiment>
(1) The reinforcing layer 8 is configured by arranging the cords 9 extending in the tire circumferential direction side by side along the tire radial direction. The Young's modulus of the cords 9 in the outer region 8a and the inner region 8c is set to be equal to that in the central region 8b. Each may be smaller than the Young's modulus of the cord 9. When the number of cords per unit length in the tire radial direction of the outer region 8a, the central region 8b, and the inner region 8c is the same, for example, the cord 9 of the outer region 8a is made of nylon 6, and the cord 9 of the central region 8b Can be made of rayon, and the cord 9 in the inner region 8c can be made of polyester. When the Young's modulus of rayon is 100%, the material of the cord 9 is selected so that the Young's modulus of nylon 6 is about 15% and the Young's modulus of polyester is about 80%. , Kb, Kc can satisfy the relationship of Kb> Kc ≧ Ka. The Young's modulus of the cords in each region may be varied, and the number of cords per unit length in the tire radial direction of each region may be varied. Thereby, it is easy to set the longitudinal rigidity of each region to a desired size.

  (2) The reinforcing layer 8 is configured by arranging the cords 9 extending along the tire radial direction side by side in the tire circumferential direction, and an angle between the outer region 8a and the inner region 8c of the cord 9 in the tire radial direction, Each may be larger than the angle formed with the tire radial direction of the cord 9 in the central region 8b. FIG. 3 is a view of the cord 9 as seen from the tire width direction, and the vertical direction is the tire radial direction. For example, when the angle B formed with the tire radial direction of the cord 9 in the central region 8b is set, the angle A formed with the tire radial direction of the cord 9 in the outer region 8a is larger by 10 to 20 ° than the angle B, and the inner region 8c By making the angle C of the cord 9 made with the tire radial direction larger by 5 to 15 ° than the angle B, the longitudinal rigidity Ka, Kb, Kc of each region can satisfy the relationship of Kb> Kc ≧ Ka. The cord 9 in the central region 8b may be parallel to the tire radial direction, but is preferably inclined with respect to the tire radial direction. Specifically, the angle B is preferably 10 to 20 °. As the cord 9 in this embodiment, a steel cord is preferable.

  (3) The reinforcing layer 8 may have a laminated structure as shown in FIG. 4 in order to increase the longitudinal rigidity of the central region 8b. In this example, the first reinforcing layer 85 configured using a cord having a high Young's modulus is disposed in the central region 8b and the inner region 8c, and a cord having a low Young's modulus is used in the outer region 8a and the central region 8b. The second reinforcing layer 86 configured as described above is disposed, and the first reinforcing layer 85 and the second reinforcing layer 86 are laminated in the central region 8b. Thereby, the vertical rigidity of the outer region 8a and the inner region 8c can be easily made smaller than the vertical rigidity of the central region 8b. Further, the longitudinal rigidity of the outer region 8a can be made smaller than that of the inner region 8c.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows. The size of the tire subjected to the test was 195 / 65R15, and was mounted on a rim having a rim size specified by JATMA.

(1) Durability Using an indoor drum testing machine equipped with a drum with a diameter of 1.7m, air pressure is 180kPa, speed is 80km / h, tire load load starts from 85% of maximum load specified by JATMA, specified time Each time the load was increased and the vehicle was finally run at 140%, and a 15000 km running test was conducted. After the running test, the tire was disassembled and the separation at the winding end of the carcass ply was examined. The case where there was no separation was evaluated as “◯”, and the case where separation occurred was evaluated as “×”.

(2) Ride comfort Four panelists comprehensively evaluated the ride comfort on the test course. The result of Comparative Example 1 was evaluated as an index with the value of 100, and the larger the index, the better the ride comfort.

(3) Low rolling resistance The rolling resistance was measured with a drum running tester and evaluated based on the reciprocal of the measured value. The running conditions are a drum diameter of 1.7 m, a camber angle of 0 °, an air pressure of 210 kPa, a speed of 80 km / h, and a load of 4300 N. The result of Comparative Example 1 was evaluated as an index with the value of 100, and the larger the index, the better the low rolling resistance.

(4) Steering stability Four panelists conducted a comprehensive sensory evaluation on starting, turning and braking on the test course. The result of Comparative Example 1 was evaluated as an index with the value 100, and the larger the index, the better the steering stability.

Example 1
As shown in FIG. 2, cords extending in the tire circumferential direction are arranged side by side along the tire radial direction, and the number of cords per unit length in the tire radial direction of the outer region and the inner region is set as the tire diameter in the central region. A pneumatic tire provided with a reinforcing layer that was less than the number of cords per directional unit length was defined as Example 1. All cord materials were rayon. Table 1 shows the measurement results of the evaluation items.

Example 2
As shown in FIG. 5, Example 2 is the same as Example 1 except that the number of cords per unit length in the tire radial direction in the outer region and the inner region is gradually increased toward the central region. did. Table 1 shows the measurement results of the evaluation items.

Example 3
Air comprising a reinforcing layer that is formed by arranging cords extending in the tire circumferential direction side by side along the tire radial direction, and in which the Young's modulus of the cord in the outer region and the inner region is smaller than the Young's modulus of the cord in the central region, respectively. Example 3 was used as the entering tire. The outer region cord material is nylon 66, the central region cord material is rayon, and the inner region cord material is polyester. The number of cords per unit length in the tire radial direction in each region was the same. Table 1 shows the measurement results of the evaluation items.

Example 4
Reinforcement with cords extending in the tire circumferential direction arranged side by side along the tire radial direction, with different numbers of cords per unit length in the tire radial direction in each region, and different Young's modulus of the cords in each region A pneumatic tire provided with a layer was defined as Example 4. Table 1 shows the measurement results of the evaluation items.

Example 5
The cords extending along the tire radial direction are arranged side by side in the tire circumferential direction, and the angle between the outer region and the inner region of the cord in the tire radial direction is greater than the angle between the central region of the cord and the tire radial direction. A pneumatic tire provided with the enlarged reinforcing layer was defined as Example 5. The cord was a steel cord. Table 1 shows the measurement results of the evaluation items.

Comparative Example 1
A pneumatic tire not provided with the reinforcing layer according to the present invention was set as Comparative Example 1. Table 1 shows the measurement results of the evaluation items.

Comparative Example 2
Instead of the reinforcing layer according to the present invention, Comparative Example 2 was obtained by arranging a fastening member 10 as shown in FIG. 6 around a bead 1a of a pneumatic tire. The fastening member 10 extends from the inside in the tire radial direction and the tire width direction of the bead 1 a to a position outside the bead 1 a in the tire radial direction and beyond the winding end 41 a of the carcass ply 41. Table 1 shows the measurement results of the evaluation items.

Comparative Example 3
As shown in FIG. 7, Comparative Example 3 was used in which the number of cords per unit length in the tire radial direction in the inner region was the same as the number of cords per unit length in the tire radial direction in the central region. Table 1 shows the measurement results of the evaluation items.

  Since the pneumatic tire of Comparative Example 1 has a filler-less bead structure, it is necessary to increase the thickness of the sidewall portion to improve durability, and the ride comfort is worse than when a bead filler is disposed. There is a tendency. Further, since the reinforcing layer was not provided, separation of the carcass ply winding end portion occurred. Compared to the comparative example 1, the durability of the examples 1 to 5 is improved while suppressing deterioration in ride comfort. Further, in Comparative Example 2, durability was improved by arranging a fastening member around the bead, but the riding comfort was equivalent to Comparative Example 1. Although the comparative example 3 is provided with the reinforcing layer, the durability is improved, but the longitudinal rigidity of the inner region is approximately the same as the longitudinal rigidity of the central region, and thus the deterioration in riding comfort cannot be sufficiently suppressed. .

  Moreover, although a rigidity difference arises in the winding end part of a carcass ply and distortion becomes high, Examples 1-5 can reduce distortion with a reinforcement layer. Furthermore, if a reinforcing layer is provided, a difference in rigidity may occur at both ends in the tire radial direction and distortion may be increased, but as in Examples 1 to 5, the vertical rigidity of the outer region and the inner region is more than the vertical rigidity of the central region. Also, by reducing each of them, the difference in rigidity at both ends can be suppressed and distortion can be reduced. By reducing the strain in this way, the rolling resistance of Examples 1 to 5 is smaller than that of Comparative Example 1.

  Moreover, unlike Example 1-4, Example 5 improved steering stability by improving lateral rigidity in order to reinforce with a steel cord. However, the ride comfort decreased because the longitudinal rigidity increased.

DESCRIPTION OF SYMBOLS 1 Bead part 1a Bead 2 Side wall part 3 Tread part 4 Carcass layer 8 Reinforcement layer 8a Outer area 8b Center area 8c Inner area 9 Cord 41 Carcass ply 41a End part T Pneumatic tire

Claims (5)

A pneumatic tire provided with a pair of left and right bead portions and a carcass ply that is disposed between the bead portions and whose end portions are wound from the inner side to the outer side in the tire width direction without arranging a bead filler around the bead. In
The outer region in the tire width direction of the carcass ply is configured by a central region that covers the end portion, an outer region in the tire radial direction outside the central region, and an inner region in the tire radial direction from the central region, A pneumatic tire is provided with a reinforcing layer in which the longitudinal stiffness of the outer region and the inner region is smaller than that of the central region. The reinforcing layer is configured by arranging the cords extending in the tire circumferential direction along the tire radial direction,
The pneumatic tire according to claim 1, wherein the number of cords per unit length in the tire radial direction of the outer region and the inner region is smaller than the number of cords per unit length in the tire radial direction of the central region. The reinforcing layer is configured by arranging the cords extending in the tire circumferential direction along the tire radial direction,
The pneumatic tire according to claim 1, wherein Young's modulus of the cords in the outer region and the inner region is smaller than Young's modulus of the cords in the central region. The reinforcing layer is configured by juxtaposing cords extending in the tire radial direction in the tire circumferential direction,
2. The pneumatic tire according to claim 1, wherein an angle formed between the outer region and the inner region of the cord in the tire radial direction is larger than an angle formed between the central region of the cord and the tire radial direction. The pneumatic tire according to any one of claims 1 to 4, wherein a longitudinal rigidity of the outer region is equal to or less than a longitudinal rigidity of the inner region.

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