JP2009001228A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which makes the reduction of the weight of a tire and steering stability compatible without reducing riding comfort. <P>SOLUTION: A carcass layer is made to be a single layer structure, and both ends thereof are folded to a position which exceeds a tire maximum width and does not reach a belt layer from the inside of the tire to the outside of the tire in such a way as to sandwich a bead filler 6 around left and right bead cores 4. In the pneumatic tire, the height of the bead filler 6 from a bead heel is 15-30% of a tire cross section height SH, the rubber thickness of a side wall part 2 is 3.5-5.0 mm, and an inner liner 7 is formed of a thermoplastic elastomer composition having a Young's modulus of 5-50 MPa and a thickness of 0.05-0.25 mm and composed of a thermoplastic resin or a thermoplastic resin component and an elastomer component. The side wall part 2 comprises a rubber composition formulated with the natural rubber of 30 wt.% or more and a tread part 1 comprises a rubber composition formulated with the natural rubber of 70 wt.% or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that achieves both weight reduction and steering stability.

  In recent years, it has been required to reduce the weight of pneumatic tires for the purpose of reducing fuel consumption of vehicles. As a method for reducing the weight, for example, measures are taken to reduce the thickness of the rubber layer constituting the tire, reduce the number of carcass layers, or shorten the bead filler. However, when such measures are taken, there is a problem that the steering stability deteriorates because the circumferential rigidity of the tire is greatly reduced.

For this reason, Patent Document 1 proposes to increase the circumferential rigidity by replacing the bead filler with rubber from a thermoplastic resin or a thermoplastic elastomer composition. However, the thermoplastic resin has the characteristics that the specific gravity is smaller than that of rubber and the Young's modulus is large.Thus, this measure reduces the weight and improves the handling stability. There was a problem that the performance decreased.
Japanese Patent Laid-Open No. 9-300924

  An object of the present invention is to provide a pneumatic tire in which the weight reduction of the tire and the steering stability are compatible without causing a decrease in riding comfort.

  The pneumatic tire of the present invention that achieves the above object has a single-layer structure of the carcass layer, and the tire maximum width from the inside to the outside of the carcass layer so that the bead filler is sandwiched between the left and right bead cores. The height from the bead heel of the bead filler is 15 to 30% of the tire cross-section height, the rubber thickness of the sidewall is 3.5 to 5.0 mm, and the carcass layer The inner liner formed on the inner side is composed of a thermoplastic resin having a Young's modulus of 5 to 50 MPa and a thickness of 0.05 to 0.25 mm, or a thermoplastic elastomer composition in which a thermoplastic resin component and an elastomer component are blended. It is characterized by.

  The sidewall portion may be composed of a rubber composition in which 30% by weight or more of natural rubber is blended in the rubber component, and the tread portion may be composed of a rubber composition in which 70% by weight or more of natural rubber is blended in the rubber component.

  The carcass cord constituting the carcass layer is preferably composed of rayon fiber, and the carcass cord may be composed of a twisted cord obtained by twisting 1 to 3 yarns of 400 to 3000 dtex. The driving density is preferably 20 to 30 pieces / 50 mm.

  In the pneumatic tire of the present invention, the carcass layer has a single layer structure, the height of the bead filler is as short as 15 to 30% of the tire cross-sectional height, the side rubber is made as thin as 3.5 to 5 mm, and the inner The liner is formed of a thermoplastic resin or a thermoplastic elastomer composition having a specific gravity smaller than that of rubber, thereby reducing the weight of the tire, while turning the carcass layer to a position exceeding the maximum width of the tire. This thermoplastic resin or thermoplastic elastomer composition has a high Young's modulus compared to a rubber of 5 to 50 MPa, so that the rigidity in the circumferential direction of the tire is increased, so that steering stability can be ensured. Moreover, since the inner liner having a high Young's modulus is made thin with a thickness of 0.05 to 0.25 mm, the ride comfort is not lowered by suppressing the rigidity in the bending direction of the tire.

  FIG. 1 shows an embodiment of the pneumatic tire of the present invention.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, 3 is a bead portion, and 5 is a carcass layer. A belt layer 8 is disposed on the outer periphery of the carcass layer 5, and a belt cover layer 9 is disposed on the outer side. An inner liner 7 is attached inside the carcass layer 5.

  In the tire configuration, the carcass layer 5 has a single-layer structure having only one layer. The single-layer carcass layer 5 is mounted between the pair of left and right bead cores 4 from the tread portion 1 to the bead portion 3 through the left and right sidewall portions 2, and both end portions are bead fillers around the bead core 4. 6 is folded from the inside of the tire to the outside so as to enclose 6. The folding terminal 5a extends to a position exceeding the maximum tire width. The folded terminal 5a may extend to the lower side of the belt layer.

  The bead filler 6 is made of hard rubber and has a low height. The height h from the bead heel is set to 15 to 30% of the tire cross-section height SH. Further, the sidewall portion 2 has a small rubber thickness and is set to 3.5 to 5.0 mm, both of which contribute to weight reduction of the tire.

  Moreover, although the rubber thickness of the side wall part 2 is 3.5-5 mm, Preferably it is 3.5-4.5 mm. If the thickness of the side rubber is less than 3.5 mm, the side cut resistance is insufficient, and if it exceeds 5 mm, the weight of the tire cannot be reduced. Here, the rubber thickness of the sidewall portion refers to the thickness of the rubber layer in the range of 20 to 75% of the tire cross-section height SH, and the surface of the sidewall portion 2 is equally divided into 10 along the radial direction. , The distance perpendicular to the surface of the carcass layer 5 from the midpoint is measured at the midpoint between the respective split points, and the average value of the measured values at the 10 points is measured. Also, the tire cross-section height SH is assembled on a standard rim according to JATMA Yearbook, and the outer diameter and rim diameter of the tire when filled with 5% of the air pressure specified in “5. Tire Measurement Method”. The value is one half of the difference.

  The inner liner 7 has a thickness of 0.05 to 0.25 mm, preferably 0.10 to 0.20 mm, and a Young's modulus of 5 to 50 MPa, preferably 5 to 30 MPa, more preferably 10 to 20 MPa. It is formed of a plastic resin or a thermoplastic elastomer composition. Since the inner liner is lightweight, it does not increase the tire weight, and the rigidity in the circumferential direction of the tire is increased, so that the steering stability is improved. If the thickness of the inner liner 7 is less than 0.05 mm, sufficient air permeation preventive properties cannot be obtained. On the other hand, if the thickness exceeds 0.25 mm, the rigidity in the tire radial direction increases, so that the ride comfort is lowered. Also, if the Young's modulus is less than 5 MPa, the circumferential rigidity of the tire cannot be increased, and steering stability cannot be ensured. If it exceeds 50 MPa, the ride comfort is reduced.

  In the present invention, the thermoplastic resin constituting the inner liner and the thermoplastic resin component in the thermoplastic elastomer composition include, for example, polyamide-based resins [for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46 ), Nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6 / 66), nylon 6/66/610 copolymer (N6) / 66/610), nylon MXD6, nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer], polyester resin [for example, polybutylene terephthalate (PBT), polyethylene Terephthalate (PET), polyethylene isophthalate (PE ), Polybutylene terephthalate / tetramethylene glycol copolymer, PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimidic acid / polybutylene terephthalate copolymer, etc. Aromatic polyester], polynitrile resin [for example, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer Combined], poly (meth) acrylate resin [for example, polymethyl methacrylate (PMMA), polyethyl methacrylate, ethylene ethyl acrylate copolymer (EEA), ethylene acrylic acid copolymer (EAA), Renmethyl acrylate resin (EMA)], polyvinyl resins [eg, vinyl acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC) , Vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer], cellulose resin [for example, cellulose acetate, cellulose acetate butyrate], fluorine resin [for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) ), Polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE)], imide-based resin [for example, aromatic polyimide (PI)] and the like.

  Examples of the elastomer component constituting the thermoplastic elastomer composition include diene rubbers and hydrogenated products thereof [eg, NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis BR), NBR, hydrogen NBR, hydrogenated SBR], olefin rubber [eg ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene propylene rubber (M-EPM)], butyl rubber (IIR), isobutylene and aromatic vinyl or diene monomer Polymer, acrylic rubber (ACM), ionomer, halogen-containing rubber [for example, Br-IIR, Cl-IIR, bromide of isobutylene paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHC, CHR), chlorosulfonated polyethylene ( SM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM)], silicone rubber [eg methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber], sulfur-containing rubber [eg polysulfide rubber] Fluorine rubber [for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber], thermoplastic elastomer [for example, styrene elastomer, olefin elastomer Polyester elastomer, urethane elastomer, polyamide elastomer].

  The composition ratio of the thermoplastic resin component and the elastomer component in the thermoplastic elastomer composition may be appropriately determined depending on the balance of the thickness and flexibility of the inner liner, but the preferred range is 10/90 to 90/10, more preferably 20 / 80 to 85/15 (weight ratio).

  The height h from the bead heel portion of the bead filler 6 to the bead filler top is 15 to 30% of the tire cross-section height SH, and preferably 20 to 30%. If the height h of the bead filler is less than 15% of the tire cross-section height SH, the circumferential rigidity of the tire is insufficient and steering stability cannot be obtained. On the other hand, if it exceeds 30%, the rigidity in the tire bending direction becomes too high, and the riding comfort deteriorates.

  In the present invention, the carcass layer 5 has a single-layer structure, which contributes to reducing the weight of the tire. In addition, since the folded terminal is positioned beyond the maximum tire width, The directional rigidity can be increased, which can contribute to ensuring steering stability. The folded terminal may extend to the inside of the belt layer, but preferably it does not reach the belt layer, so that the ride comfort is not deteriorated.

  The carcass cord is not particularly limited, but it is preferable to use a rayon fiber. Since rayon fibers have a higher elastic modulus than synthetic fibers such as nylon fibers, steering stability can be improved. Further, the carcass cord of the rayon fiber is preferably a twisted cord obtained by twisting 1 to 3 yarns of 400 to 3000 dtex, more preferably 1000 to 2500 dtex, and particularly preferably a double twisted cord. Further, the driving density of the carcass cord is preferably 20 to 30/50 mm. By making the driving density of the carcass cord within such a range, it is possible to compensate for the lack of tire rigidity due to the thin side rubber and the short bead filler.

  The rubber composition constituting the sidewall portion is not particularly limited, but natural rubber may be included as a rubber component. In that case, rolling resistance can be improved by containing 30% by weight or more of natural rubber. At the same time, the ratio of petroleum resources to the tire material can be reduced to make an environmentally friendly tire. The upper limit of the amount of natural rubber is preferably 70% by weight.

  Similarly, the rubber composition constituting the tread portion is preferably 70% by weight or more, more preferably 90 to 100% by weight of natural rubber in the rubber component. By setting the blending amount of the natural rubber in the tread rubber within such a range, the rolling resistance can be further improved. At the same time, the ratio of petroleum resources in the tire material can be reduced and the tire can be made environmentally friendly.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these Examples.

  In the tire structure shown in FIG. 1, the tire size is 195 / 65R15, the inner liner thickness is 0.2 mm, and the inner liner type, side rubber thickness, and bead filler height h are the tire cross-sectional heights. Five types of pneumatic tires (Examples 1 to 3 and Comparative Examples 1 and 2) were manufactured with different ratios to SH as shown in Table 1. The Young's modulus of the thermoplastic elastomer composition used in the inner liners of Examples 1 to 3 and Comparative Example 2 was 20 MPa, and the Young's modulus of the butyl rubber used in Comparative Example 1 was 2 MPa. The five types of pneumatic tires obtained were evaluated for steering stability, riding comfort and rolling resistance by the following test methods, and the results are shown in Table 1.

Steering stability, ride comfort Pneumatic tires are mounted on a rim with a rim size of 15 x 6 JJ, mounted on a domestic 2 liter class test vehicle with an air pressure of 230 kPa, and five trained test drivers go around the test course The feeling of handling stability and ride comfort at the time was scored, and the average value was evaluated. The obtained results were expressed as an index with Comparative Example 1 as 100. The larger the index value, the better the steering stability.

Rolling resistance A pneumatic tire was measured for resistance using a drum testing machine having a drum diameter of 1707 mm under the conditions of air pressure of 230 kPa, load of 4.0 kN, and speed of 80 km / h. The evaluation results are shown as an index with the tire of Comparative Example 1 as 100, using the reciprocal of the measured value. A larger index value means less rolling resistance.

It is meridian direction sectional drawing which shows an example of embodiment of the pneumatic tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass layer 6 Bead filler 7 Inner liner

Claims (4)

  The carcass layer has a single-layer structure, and both ends of the carcass layer are folded back from the tire inner side to the outer side so as to sandwich the bead filler around the left and right bead cores, and the bead filler The height from the bead heel is 15-30% of the tire cross-section height, the rubber thickness of the sidewall is 3.5-5.0 mm, and the inner liner formed inside the carcass layer has a Young's modulus of 5-50 MPa. A pneumatic tire constituted by a thermoplastic elastomer composition having a thickness of 0.05 to 0.25 mm or a blend of a thermoplastic resin component and an elastomer component.   The sidewall portion is composed of a rubber composition in which 30% by weight or more of natural rubber is blended in a rubber component, and the tread portion is composed of a rubber composition in which at least 70% by weight of natural rubber is blended in a rubber component. The pneumatic tire according to 1.   The pneumatic tire according to claim 1 or 2, wherein a carcass cord constituting the carcass layer is made of rayon fibers.   The air according to claim 1, 2 or 3, wherein the carcass cord is constituted by a twisted cord obtained by twisting 1 to 3 yarns of 400 to 3000 dtex, and the driving density of the carcass cord is 20 to 30 cords / 50 mm. Enter tire.

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