JP4373156B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire with reduced road noise.

  Conventionally, examples of pneumatic tires with reduced noise include those disclosed in JP-A-10-109505 and JP-A-6-24214. These have a tire structure and a rubber form of the sidewall portion having a unique configuration and shape to exhibit a noise reduction effect. However, with these methods, when a tire is newly designed, the tire structure and the appearance are restricted in order to pursue noise reduction performance. It is also difficult to apply these methods to existing tires.

  On the other hand, the vibration force which acts on a sidewall part at the time of tire driving | running | working arrange | positions the rubber composition by which loss tangent (tan-delta) was prescribed | regulated to a part of sidewall part which is mentioned in patent document 1. Some of them can absorb the vibration and thereby suppress the vibration. According to this method, it is possible to increase the absorption effect of the excitation force by increasing the tan δ value without restricting the tire structure and appearance, but the durability of the sidewall portion due to heat generation is reduced. Considering this, there is a problem that the tan δ value cannot be increased too much.

  By the way, Patent Document 2 contains a diene elastomer, a polyolefin, and a nylon short fiber in order to achieve both improvement in tire handling stability and improvement in vibration ride comfort and reduction in rolling resistance. It is disclosed that a rubber sheet made of the rubber composition thus formed is inserted into the side wall portion region so that the short fibers are at least in contact with the upper end of the bead filler and the orientation direction is oriented in the tire circumferential direction. However, when nylon short fibers are used as the short fibers in this way, the anisotropy rate, that is, the modulus ratio between the tire circumferential direction and the direction perpendicular thereto cannot be made sufficiently high. There is a problem that it is difficult to obtain a reduction effect.

Patent Document 3 discloses a rubber compounded with short fibers between the bead filler and the carcass layer in order to improve steering stability without deteriorating durability and ride comfort. It is disclosed that the layer is disposed with the orientation direction of the short fibers oriented in the tire circumferential direction. However, in this document, the rubber layer is disposed so as to terminate at a height position on the inner side of the radially outer end of the bead filler. Therefore, a sufficient road noise reduction effect cannot always be obtained. There is a problem.
Japanese Patent Laid-Open No. 7-1924 Japanese Patent Laid-Open No. 2000-142037 JP 2003-146029 A

  The present invention provides steering stability and ride comfort by installing a rubber layer made of anisotropic rubber containing short fibers between the bead filler and the carcass layer so that the direction of short fiber orientation is the tire circumferential direction. An object of the present invention is to provide a pneumatic tire with reduced road noise without sacrificing performance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that an unvulcanized rubber member having anisotropy blended with aramid short fibers is a bead filler so that the short fiber orientation direction is the tire circumferential direction. By applying from the lower part of the tire cross-section lumen side to the vicinity of the maximum tire width position, it has been found that road noise can be reduced by regulating vibrations acting on the sidewalls without sacrificing steering stability and riding comfort. The present invention has been completed.

That is, the pneumatic tire according to the present invention includes a pair of left and right annular bead cores, a carcass layer whose ends are folded back by the bead cores, and a bead filler disposed on a radially outer periphery of the bead core. In the tire, a nylon short fiber composed of 6-nylon short fiber and / or 66-nylon short fiber and an olefin resin are blended between the bead filler and the carcass layer on the inner side in the tire axial direction of the bead filler together with the aramid short fiber. A rubber layer made of the above-mentioned rubber, the rubber layer extending outward from the radially outer end of the bead filler along the carcass layer, and the orientation directions of the aramid short fibers and the nylon short fibers Is installed so as to be in the tire circumferential direction.

According to the present invention, the aramid short fibers and the rubber layer made of an anisotropic rubber blended with nylon short fibers, aramid short fibers and nylon staple fibers in a state of being oriented in the tire circumferential direction, a bead filler as described above Between the carcass layer and beyond the radially outer end of the bead filler, so that it is possible to reduce road noise without sacrificing steering stability and riding comfort. .

  The rubber layer in the present invention is made of anisotropic rubber containing aramid short fibers. The reason for using an aramid short fiber is that the anisotropy rate can be increased, so that the modulus in the tire circumferential direction can be increased while the modulus in the tire radial direction is kept low, and the vibration restraining force of the sidewall portion can be increased. For this reason, the effect of reducing road noise is excellent.

  The aramid short fiber has a fiber diameter of 0.05 to 15 μm, a fiber length of 0.001 to 5 mm, and L / D which is a ratio of the fiber length (L) to the fiber diameter (D) is 50 to 400. preferable. More preferably, the fiber diameter is 0.1 to 10 μm, the fiber length is 0.002 to 4 mm, and L / D is 70 to 250. By using a material within such a range, the anisotropy rate can be effectively increased.

  As the rubber component used for the anisotropic rubber, various diene rubbers such as styrene butadiene rubber, butadiene rubber, natural rubber, and isoprene rubber can be used alone or in combination of two or more.

  The anisotropic rubber is preferably formulated by blending 2 to 15 parts by weight of aramid short fibers with respect to 100 parts by weight of the diene rubber, and more preferably 3 to 10 parts by weight. When the blending amount of the short fibers is less than 2 parts by weight, a sufficient anisotropic ratio cannot be obtained. Conversely, when the blending amount exceeds 15 parts by weight, the ride comfort and the handling stability tend to deteriorate.

The aforementioned anisotropic rubber, with aramid short fibers 6 nylon short fibers and / or 66-nylon short fibers are compounded. By using these nylon short fibers in combination, it is possible to suppress a decrease in the anisotropy rate at the time of high elongation as compared to the case of using aramid short fibers alone. Thus, when using a nylon short fiber together, it is preferable to mix | blend 2-15 weight part with respect to 100 weight part of diene rubbers in total with an aramid short fiber. Moreover, it is preferable that the compounding ratio of an aramid short fiber and a nylon short fiber is aramid short fiber / nylon short fiber = 9/1-1/1 by weight ratio.

  The anisotropic rubber is a master batch obtained by mixing and mixing a relatively large amount of the above short fibers with a diene rubber, and adding this to the remaining diene rubber with other additives. May be prepared. By using such a master batch, good unvulcanized processability and vulcanized rubber properties can be obtained. The content of short fibers in the master batch is preferably 20 to 70% by weight, more preferably 30 to 60% by weight.

  The masterbatch is preferably used for the nylon short fiber, particularly when nylon short fiber is used in combination, and in that case, the masterbatch is preferably further blended with a crystalline resin such as an olefin resin. . Examples of crystalline resins include high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and polypropylene (PP). These may be used alone or in combination of two or more. You can also

  The anisotropic rubber is prepared by blending the above-mentioned short fibers and / or master batch with diene rubber together with various additives and mixing them. Such additives include sulfur, vulcanization accelerators, zinc white, stearic acid, carbon black, softeners, anti-aging agents, organic reinforcing agents such as alkyl fail resins and melamine resin derivatives, and silane coupling agents. The general additive used for the rubber composition for tires is mentioned.

  Next, a pneumatic tire according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a half cross-sectional view of a pneumatic tire 10 according to an embodiment. The tire 10 includes a pair of left and right bead portions 12 and sidewall portions 14, and a tread portion 16 that spans between the sidewall portions 14. Configured.

  The bead portion 12 is provided with an annular bead core 18, and a rubber bead filler 20 is disposed on the outer periphery in the radial direction of the bead core 18. The bead filler 20 has a substantially triangular cross section extending in a tapered shape from the outer surface in the radial direction of the bead core 18 toward the outer side in the tire radial direction. A pair of left and right bead cores 18 is provided with a carcass layer 22 formed of at least one carcass ply formed by extending a large number of cords arranged at right angles to the tire circumferential direction. Then, both end portions of the carcass 22 layer are folded and locked so as to wrap the bead core 18 and the bead filler 20 from the inner side in the tire axial direction to the outer side. A belt 24 is disposed outside the carcass layer 22 in the tread portion 16 in the radial direction. The belt 24 is positioned on the outer surface in the radial direction of the crown portion of the carcass layer 22, and at least two belt plies in which non-extensible cords are inclined at a shallow angle with respect to the tire circumferential direction are overlapped so that the cords intersect each other. It becomes.

  In such a configuration, the rubber layer 30 is disposed between the bead filler 20 and the carcass layer 22 between the bead filler 20 and the carcass layer 22 (not on the folded side) on the inner side in the tire axial direction. The rubber layer 30 is made of the anisotropic rubber described above.

The rubber layer 30 is both the orientation direction of the short aramid fibers and nylon short fibers is disposed such that the tire circumferential direction. Specifically, when the anisotropic rubber is molded using an extruder, the short fibers blended in the rubber composition are arranged in the transport direction, that is, the row direction. If the fiber is disposed at the above position so that the (logical direction) is in the tire circumferential direction, the short fibers can be oriented in the tire circumferential direction. In this case, the orientation direction of the short fibers is preferably within a range of 0 ° ± 20 ° with respect to the tire circumferential direction. When the orientation direction of the short fibers exceeds the above range, the ride comfort is deteriorated.

  Thus, the rubber layer 30 in which the short fibers are oriented in the tire circumferential direction has a 100% modulus in the tire circumferential direction that is more than twice the 100% modulus in the perpendicular direction (the tire radial direction and the tire width direction). Preferably there is. If this modulus ratio (tire circumferential direction / right angle direction) is less than twice, the vibration suppressing effect of the sidewall portion cannot be exhibited.

  The rubber layer 30 extends radially outward from the lower end of the bead filler 20 along the outer surface of the carcass layer 22, and extends further outward beyond the upper end of the bead filler 20, that is, the radially outer end 20o. And is disposed so as to terminate in the vicinity of the tire maximum width position 32.

  More specifically, the radially inner end 30i of the rubber layer 30 is the lower end of the bead filler 20, that is, the height of the radially inner end 20i, and the height of the bead filler 20 from the inner end 20i (the tire radial direction). Dimension) Between 0.6 times the height of h2, that is, the height Hi of the rubber layer inner end 30i from the bead filler inner end 20i is in the range of 0 × h2 to 0.6 × h2. It is preferable to set to. Also, the radially outer end 30o of the rubber layer 30 is between a position 0.4 times and a position 0.8 times the tire cross-section height h1 formed by the base line BL and the center position of the tread surface. That is, the height Ho of the rubber layer outer end 30o from the base line BL is preferably set in the range of 0.4 × h1 to 0.8 × h1.

  More preferably, the rubber layer inner end 30i is positioned 0.1 times the bead filler height h2 from the bead filler inner end 20i, and the bead filler height h2 is 0.4 from the bead filler inner end 20i. That is, the height Hi of the rubber layer inner end 30i from the bead filler inner end 20i is set within a range of 0.1 × h2 to 0.4 × h2. In addition, the rubber layer outer end 30o is at a position between 0.5 times and 0.7 times the tire cross-section height h1, that is, the rubber layer outer end 30o from the base line BL. Is set within a range of 0.5 × h1 to 0.7 × h1.

  By disposing the rubber layer 30 at the position as described above, the modulus of this portion in the tire circumferential direction can be increased to reduce road noise, and the vertical portion of the sidewall portion 14 can be reduced by the anisotropy of the rubber. By maintaining the same modulus in the direction (tire radial direction) as in the past, there is an advantage that the steering stability and ride comfort performance are not impaired.

  The rubber layer 30 preferably has a thickness of 0.5 to 2.0 mm. If it is less than 0.5 mm, it is difficult to obtain the effect of the present invention to reduce road noise. On the other hand, if it exceeds 2.0 mm, road noise performance is excellent, but riding comfort tends to deteriorate.

(Measurement of rubber properties)
According to the formulation shown in Table 1 below, rubber compositions of Formulation Examples 1 and 2 and Comparative Formulation Examples 1 to 4 were prepared.

  In addition, SBR in Table 1 is “SBR1502” manufactured by JSR, natural rubber is RSS No. 1, carbon black is “Seast 6 (N220, ISAF)” manufactured by Tokai Carbon, and oil is “Process X-140” manufactured by Japan Energy Co., Ltd. The anti-aging agent is “Nocrack 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd., the wax is “Sunnock N” manufactured by Ouchi Shinsei Chemical Co., Ltd., and the vulcanization accelerator is “Noxeller CZ-G” manufactured by Ouchi Shinsei Chemical Co., Ltd. The aramid short fiber is “Tauron 1091” manufactured by Teijin Limited, and the fiber length / fiber diameter (L / D) = 1.3 mm / 10 μm = 130. The nylon short fiber is a nylon short fiber masterbatch “HA1060” (natural rubber / high-density polyethylene / 6-nylon = 38/29/33 (weight%)) manufactured by Ube Industries, Ltd. The numerical value indicates the amount of 6-nylon short fibers. The fiber length / fiber diameter (L / D) of the 6-nylon short fiber is 0.020 mm / 0.2 μm = 100.

For each rubber composition, an unvulcanized rubber having a width of 150 mm × thickness of 1.3 mm was prepared using a 12-inch roll, and a mold having a thickness of 1 mm was used under vulcanization conditions of 140 ° C. × 50 minutes. And press vulcanized to prepare a sample. And about this sample, while measuring 100% modulus and breaking strength by the method based on JIS K6251 respectively about two directions, the direction perpendicular to the line direction (extrusion direction) and the line direction, The orientation ratio (anisotropic ratio) in the direction / right angle was determined. The results were displayed as indices with both the 100% modulus and the breaking strength taken as 100 as the value in the line direction of Comparative Formulation Example 1. The results are shown in Table 1.

  As shown in Table 1, in Formulation Example 1 in which an appropriate amount of aramid short fibers is blended, the anisotropic ratio is higher than in Comparative Formulation Examples 1 to 3, and in particular, a blending example in which the same amount of nylon short fibers is blended. Compared to 4, the anisotropy rate was significantly higher. Further, in Formulation Example 2 in which aramid short fibers and nylon short fibers are used in combination, the 100% modulus has a high degree of anisotropy similar to Formulation Example 1, and yet has a different breaking strength at high elongation. The isotropic rate has a value significantly higher than that of Formulation Example 1, and the decrease in the anisotropic rate at the time of high elongation was suppressed.

(Evaluation of tire performance)
Using each of the above rubber compositions, a rubber sheet having a thickness shown in Table 2 below is extruded by an extruder, and this is used as the rubber layer 30 to indicate the position and angle shown in Table 2 (short fiber orientation direction relative to the tire circumferential direction). The pneumatic tire having a tire size of 195 / 65R15 was manufactured. Comparative Example 1 is an example in which no rubber sheet is provided.

The prepared tire was mounted on a 2000 cc passenger car, and this was driven by an evaluation driver to drive the circuit at high speed, and sensory evaluation of road noise, ride comfort, and steering stability was performed. Evaluation is performed by a 10-point method, and the higher the value, the better the performance. In addition, “+” after each score indicates that it is slightly better than that score, and “−” indicates that it is slightly inferior to that score.

As shown in Table 2, in the tires of Examples 1, as compared with Comparative Example 1 without the rubber layer, without deteriorating the riding comfort and steering stability, road noise has been greatly reduced.

  On the other hand, since the short fiber was not mix | blended with the rubber layer in the comparative example 2, the improvement effect was not recognized about any performance. Moreover, in Comparative Example 3, since no rubber layer was provided between the bead filler and the carcass layer, road noise worsened. Furthermore, in the comparative example 4, since the position of the radially outer end of the rubber layer was too high, the riding comfort was deteriorated. Further, in Comparative Example 5, since the radially outer end of the rubber layer did not exceed the upper end of the bead filler, the road noise reduction effect was insufficient.

  Moreover, since the thickness of the rubber layer was too thin in Comparative Example 6, the effect of the rubber layer could not be obtained, and in Comparative Example 7, the rubber layer was too thick, resulting in poor ride comfort. Furthermore, in Comparative Examples 8 and 9, the angle in the orientation direction of the short fibers with respect to the tire circumferential direction was too large, and the riding comfort was impaired.

  Moreover, since comparative example 10 had too little blending amount of aramid short fibers, almost no effect was observed. On the other hand, comparative example 11 had too much blending amount, and the ride comfort and steering stability deteriorated. Moreover, although the comparative example 12 which used the nylon short fiber independently instead of the aramid short fiber has an effect of reducing road noise without affecting other properties, it is more effective than the one using the aramid short fiber. It was small and insufficient.

1 is a half sectional view of a pneumatic tire according to an embodiment of the present invention.

Explanation of symbols

10 …… Pneumatic tire 18 …… Bead core 20 …… Bead filler 20i …… Radial inner end 20o …… Bead filler radial outer end 22 …… Carcass layer 30 …… Rubber layer 30i …… Radial inner end of rubber layer 30o …… Radial outer end of rubber layer h1 …… Tire cross-section height h2 …… Bead filler height

Claims (5)

In a pneumatic tire comprising a pair of left and right annular bead cores, a carcass layer whose ends are folded back by the bead cores, and a bead filler disposed on a radially outer periphery of the bead core,
From rubber blended with olefin resin and nylon short fibers composed of 6-nylon short fibers and / or 66-nylon short fibers together with aramid short fibers between the bead filler and the carcass layer inside the bead filler in the tire axial direction The rubber layer extends along the carcass layer outward from the radially outer end of the bead filler, and the orientation direction of the aramid short fibers and the nylon short fibers is the tire circumference. A pneumatic tire characterized by being installed in a direction. A radially inner end of the rubber layer is located between a radially inner end position of the bead filler and a position 0.6 times the bead filler height (h2) from the inner end,
The pneumatic tire according to claim 1, wherein the radially outer end of the rubber layer is between a position 0.4 times and a position 0.8 times the tire cross-sectional height (h1). .   The pneumatic tire according to claim 1 or 2, wherein a 100% modulus in the tire circumferential direction of the rubber layer is at least twice as large as a 100% modulus in the perpendicular direction. The pneumatic tire according to claim 1, the thickness of the rubber layer is characterized in that it is a 0.5 to 2.0 mm. The rubber layer contains 2 to 15 parts by weight of aramid short fibers and nylon short fibers in total with respect to 100 parts by weight of the diene rubber , and the mixing ratio of the aramid short fibers and the nylon short fibers is an aramid by weight ratio. the pneumatic tire according to claim 1, characterized in that it consists of short fiber / nylon staple fibers = 9 / 1-1 / 1 a is rubber.

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