JP2006248440A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing driving stability and ground followability while maintaining rolling resistance by devising a structure of a carcass layer. <P>SOLUTION: The pneumatic tire is structured so that a carcass layer 4 formed by covering a plurality of carcass cords with carcass compound is laid between a right and a left bead portions 3, 3, includes a half radial structure in which the carcass cord is inclined in a tire radial direction, wherein the storage modulus of elasticity E'(MPa) at 20°C of the carcass compound is 15≤E'≤18 and the loss tangent tanδ at 20°C is 0.10≤tanδ≤0.25. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire in which a carcass layer is mounted between a pair of left and right bead portions. More specifically, the configuration of the carcass layer is devised to improve steering stability and road surface followability while maintaining rolling resistance. The present invention relates to a pneumatic tire that is improved.

  A pneumatic radial tire generally has a structure in which a carcass layer is mounted between a pair of left and right bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion. In such pneumatic radial tires, it has been proposed to improve steering stability by defining the compound physical properties of the tread portion and the cord physical properties of the belt layer (see, for example, Patent Document 1).

However, in recent years, there has been a demand for further improvements in handling stability as the vehicle speeds up and upgrades, and improvement in handling stability is required simply by improving the compound physical properties of the tread and the cord properties of the belt layer. It has become difficult to respond to.
JP 2001-180225 A

  An object of the present invention is to provide a pneumatic tire that can improve steering stability and road surface followability while maintaining rolling resistance by devising a configuration of a carcass layer.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire in which a carcass layer is formed by covering a plurality of carcass cords with a carcass compound between a pair of left and right bead portions. The carcass compound has a half radial structure inclined with respect to the tire radial direction, the storage modulus E ′ (MPa) at 20 ° C. of the carcass compound is 15 ≦ E ′ ≦ 18, and the loss tangent tan δ at 20 ° C. is 0.10. ≦ tan δ ≦ 0.25. The half radial structure is a structure in which the angle of the carcass cord with respect to the tire circumferential direction is 50 ° to 85 °.

  As a result of earnest research on the influence of the configuration of the carcass layer on the steering stability and road surface followability, the present inventor adopted a half radial structure, and by defining the physical properties of the carcass compound and the twisted structure of the carcass cord, It has been found that steering stability and road surface followability are remarkably improved while maintaining rolling resistance, and the present invention has been achieved.

  In other words, in addition to adopting a half radial structure, by setting the storage elastic modulus E ′ of the carcass compound to a high level within the above range, it is possible to significantly improve the steering stability and the road surface followability. Further, by setting the loss tangent tan δ of the carcass compound within the above range, the rolling resistance can be maintained even when the half radial structure is adopted. Here, the steering stability is the stability of the vehicle with respect to the steering, and the road surface followability is the ability of the tire to be flexibly deformed according to the road surface shape to transmit the driving force to the road surface.

  The carcass cord is composed of a twisted yarn in which a base yarn of an organic heat-shrinkable fiber is subjected to a lower twist to obtain a lower twisted yarn, and then a plurality of the lower twisted yarns are aligned and the upper twist is applied in the opposite direction to the lower twist. The twist coefficient obtained from the ratio of the number of lower twists T1 and the number of upper twists T2 (T1 / T2) is 1.75 ≦ T1 / T2 ≦ 4.0, and the twist number T2 and the total display decitex D (T2 × √D) is preferably 1000 ≦ T2 × √D ≦ 4700. When the carcass compound is applied to a carcass cord having such a twisted structure, the effect of improving the steering stability becomes remarkable.

  In the present invention, when the loss tangent tan δ of the tread compound is lowered in order to further improve the rolling resistance, the handling stability improved by devising the configuration of the carcass layer is lowered. Therefore, silica is preferably added to the tread compound in order to reduce the loss tangent tan δ of the tread compound. That is, the tread compound used in the tread portion contains 10 to 120 parts by weight of silica with respect to 100 parts by weight of the vulcanizable rubber component, and the loss tangent tan δ at 60 ° C. is 0.10 ≦ tan δ ≦ 0.30. It is preferable that In this case, steering stability, road surface followability, and rolling resistance can be achieved at a high level.

  In the present invention, the storage elastic modulus E ′ and the loss tangent tan δ are measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho under the conditions of an initial strain of 10%, a dynamic strain of ± 2%, and a frequency of 20 Hz.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside to the outside of the tire. The carcass layer 4 is formed by covering a plurality of aligned carcass cords with a carcass compound, and the carcass cords are inclined with respect to the tire radial direction. In the carcass layer 4 having a half radial structure, the angle of the carcass cord measured at the center position in the tread width direction with respect to the tire circumferential direction is set to 50 ° to 85 °. On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a belt layer 6 is disposed over the entire tire circumference. These belt layers 6 include reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords cross each other between the layers.

In the pneumatic tire having the half radial structure, the storage elastic modulus E ′ (MPa) at 20 ° C. of the carcass compound used for the carcass layer 4 is 15 ≦ E ′ ≦ 18, and the loss tangent tan δ at 20 ° C. is 0.8. 10 ≦ tan δ ≦ 0.25. These storage elastic modulus E ′ and loss tangent tan δ can be appropriately adjusted based on the types and blending amounts of rubber components and additives. If the storage elastic modulus E ′ of the carcass compound is too small, the effect of improving the steering stability cannot be obtained. On the other hand, if the storage modulus E ′ is too large, the compound viscosity before vulcanization becomes too high, making it difficult to manufacture the tire. Further, if the loss tangent tan δ of the carcass compound is too small, the effect of improving the road surface followability cannot be obtained. Manufacturing becomes difficult.

Here, Table 1 shows a blending example of the carcass compound.

  As shown in FIG. 2, the carcass cord used for the carcass layer 4 is obtained by applying a lower twist to an organic heat-shrinkable fiber yarn to form a lower twisted yarn 10, and then drawing a plurality of the lower twisted yarns 10 together. And a twisted yarn 11 having an upper twist in the opposite direction. As the carcass cord, a nylon cord or a polyester cord may be used.

  The ratio (T1 / T2) between the number of twists T1 and the number of twists T2 (T1 / T2) of the twisted yarn 11 is set in the range of 1.75 ≦ T1 / T2 ≦ 4.0. The number of lower twists T1 and the number of upper twists T2 are the number of twists per 10 cm of yarn length (times / 10 cm). Thus, when the number of lower twists T1 is larger than the number of upper twists T2, the heat shrinkage force of the carcass cord made of organic heat-shrinkable fibers is effectively increased due to the lower twist remaining after the completion of the upper twist. Can do. Accordingly, the tension of the carcass cord in a state where the tire generates heat when the vehicle travels increases, which contributes to improvement in steering stability. And since tension | tensile_strength is raised using the thermal contraction of the code | cord | chord which made the lower twist number T1 larger than the upper twist number T2 without using a high elastic modulus cord, it does not cause deterioration of durability. However, if the ratio (T1 / T2) between the number of lower twists T1 and the number of upper twists T2 is less than 1.75, the effect of improving the steering stability becomes insufficient, and conversely, if the ratio exceeds 4.0, the upper twist It is necessary to significantly reduce the number T2, and as a result, the durability is lowered.

  The twist coefficient (T2 × √D) obtained from the number T2 of the twisted yarns 11 and the total display decitex D is set to 1000 ≦ T2 × √D ≦ 4700. If the twist coefficient (T2 × √D) is less than 1000, the durability is lowered. Conversely, if it exceeds 4700, it is difficult to apply the upper twist, and it is difficult to manufacture the above-described twisted yarn 11.

  In the pneumatic tire, a cap tread rubber layer 21 is disposed on the tread portion 1. The tread compound used for the cap tread rubber layer 21 contains 10 to 120 parts by weight of silica with respect to 100 parts by weight of the vulcanizable rubber component, and the loss tangent tan δ at 60 ° C. is 0.10 ≦ tan δ ≦ 0. .30. The rolling resistance can be improved by reducing the loss tangent tan δ of the tread compound. Moreover, the tread compound containing silica has the same loss tangent tan δ and has a higher gripping force than that containing no silica, so it can reduce rolling resistance without impairing improved handling stability. it can.

As the vulcanizable rubber component, natural rubber (NR), butadiene rubber (BR), nitrile rubber (NBR), styrene butadiene rubber (SBR), or other general rubber used for tires may be used. it can. If the compounding amount of silica is less than 10 parts by weight with respect to 100 parts by weight of the rubber component, the effect of improving the handling stability becomes insufficient. In addition to silica, general additives used for tires such as a vulcanizing agent, a vulcanization accelerator, and an anti-aging agent can be appropriately blended with these rubber components. On the other hand, if the loss tangent tan δ of the tread compound is less than 0.10, the gripping force is reduced. Conversely, if the loss tangent tan δ exceeds 0.30, the effect of improving the rolling resistance becomes insufficient.

Here, Table 2 shows a blending example of the tread compound.

  In a pneumatic tire using a nylon 66 cord (1400 dtex / 2) as a carcass cord, the storage elastic modulus E ′ and loss tangent tan δ of the carcass compound, the ratio of the number T1 and the number of upper twists T2 of the carcass cord (T1 / Four types of test tires (conventional examples, comparative examples 1 and 2 and examples) were manufactured with different T2), twist coefficient (T2 × √D), and the angle of the carcass cord with respect to the tire circumferential direction. For each test tire, a tire size 205 / 55R16 front wheel and a tire size 225 / 50R16 rear wheel were prepared.

  For these test tires, steering stability, road surface followability, and rolling resistance were evaluated by the following test methods, and the results are shown in Table 3.

Steering stability:
The test tire was mounted on a rear-wheel drive vehicle with a displacement of 3200 cc under the condition of an air pressure of 200 kPa, and a feeling evaluation by a test driver was performed on a test course. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

Road following ability:
The test tire was mounted on a rear-wheel drive vehicle with a displacement of 3200 cc under the condition of an air pressure of 200 kPa, and a feeling evaluation by a test driver was performed on a test course. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the road surface followability.

Rolling resistance:
The rolling resistance of the test tire was measured using an indoor drum type testing machine having a drum diameter of 1707 mm. The evaluation results are shown as an index with the conventional example being 100. It means that rolling resistance is so small that this index value is small.

  As shown in Table 3, in the tire of Comparative Example 1, in addition to the storage elastic modulus E ′ and loss tangent tan δ of the carcass compound, the ratio (T1 / T2) of the number of lower twists T1 and the number of upper twists T2 of the carcass cord ) Was changed from the conventional example, and an improvement effect of steering stability and road surface followability could be obtained, and rolling resistance could be maintained by adding silica to the tread compound. Here, the tire of Comparative Example 2 adopting the same structure as Comparative Example 1 except that the carcass cord is inclined with respect to the tire radial direction is improved in steering stability and road surface followability based on the half radial structure. Although the effect increased, on the other hand, the rolling resistance was increased. In contrast, the tire of the example adopting the same structure as that of Comparative Example 1 except that the carcass cord is inclined with respect to the tire radial direction and the storage elastic modulus E ′ and loss tangent tan δ of the carcass compound are changed. Was able to further improve steering stability and road surface followability while maintaining rolling resistance.

  As a result of repeating such experiments, in a pneumatic tire having a half radial structure, the storage elastic modulus E ′ at 20 ° C. of the carcass compound is 15 to 18 MPa, and the loss tangent tan δ at 20 ° C. is 0.10 to 0. In the case of .25, it has been found that steering stability and road surface followability can be improved at a high level while maintaining rolling resistance.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which shows an example of the carcass cord used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 10 Lower twist thread 11 Twist thread 21 Tread rubber layer

Claims (4)

A pneumatic tire having a carcass layer formed by covering a plurality of carcass cords with a carcass compound between a pair of left and right bead portions, and having a half radial structure in which the carcass cord is inclined with respect to the tire radial direction. The storage modulus E ′ (MPa) at 20 ° C. of the carcass compound is 15 ≦ E ′ ≦ 18, and the loss tangent tan δ at 20 ° C. is 0.10 ≦ tan δ ≦ 0.25. tire. The pneumatic tire according to claim 1, wherein an angle of the carcass cord with respect to a tire circumferential direction is 50 ° to 85 °. The carcass cord is composed of a twisted yarn obtained by applying a lower twist to an organic heat-shrinkable fiber yarn to obtain a lower twisted yarn, and then arranging a plurality of the lower twisted yarns and applying an upper twist in a direction opposite to the lower twist. The twist coefficient obtained from the ratio of the number of lower twists T1 and the number of upper twists T2 (T1 / T2) is 1.75 ≦ T1 / T2 ≦ 4.0, and the twist number T2 and the total display decitex D The pneumatic tire according to claim 1, wherein (T2 × √D) is 1000 ≦ T2 × √D ≦ 4700. The tread compound used for the tread part contains 10 to 120 parts by weight of silica with respect to 100 parts by weight of the vulcanizable rubber component, and the loss tangent tan δ at 60 ° C. is 0.10 ≦ tan δ ≦ 0.30. The pneumatic tire according to any one of claims 1 to 3.

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