JP2010208524A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire that suppresses air leakage from the inside of the tire and improves durability by suppressing the oxidation degradation of rubber in folding end parts of a carcass layer. <P>SOLUTION: A pneumatic tire 1 is arranged with at least one carcass layer 4 and at least two belt layers 6, 6 formed of steel cords. The innermost carcass layer 4 located on the innermost side of the tire among the carcass layer(s) 4, is horizontally split into two parts on an inner side of the belt layers 6, and a height H of each of wound-up ends 4a of the innermost carcass layer 4 is 25% or less of a tire cross-sectional height SH. The pneumatic tire 1 includes air permeation preventing layers 7 arranged on an outer side of the wound-up ends 4a of the innermost carcass layer 4 in a tire width direction, respectively. The air permeation preventing layer 7 has an air permeation factor of (1-100)×10<SP>-12</SP>cc*cm/cm<SP>2</SP>*sec*cmHg. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that suppresses air leakage from the inside of the tire and improves durability by suppressing oxidative deterioration of rubber at a folded end portion of a carcass layer. .

  Carcass cords made by twisting organic fibers and metal fibers used as the carcass layer of pneumatic tires are hard to penetrate completely into the inside of the cord, so a gap is formed along the longitudinal direction inside the cord. In addition, the air permeability in the longitudinal direction of the cord is high. For this reason, in the air-filled tire, with the passage of time, the air that has passed through the inner liner layer reaches the carcass layer, and this air flows through the carcass cord as a bypass to reach the folded end, and from the folded terminal to the surrounding rubber The phenomenon of diffusing and leaking outside occurs. The air diffused from the folded terminal of the carcass layer has a problem that the surrounding rubber is oxidized and deteriorated, and the durability of the bead portion and the sidewall portion is lowered.

  As a factor causing such air leakage, there is a non-uniformity of the thickness of the inner liner layer as the air permeation preventive layer. In other words, the inner liner layer is formed with a thinner crown than other parts in the expansion process during tire vulcanization molding, so the air permeation speed from the inside of the tire is high, and the carcass cord in the crown Air that has entered early is swept to the folded end on the sidewall side and diffused from the folded terminal, which causes oxidative degradation of the surrounding rubber and reduces the durability of the beads and sidewalls. It was.

  Therefore, the folded end portion of the carcass layer terminates in a thin region of the rubber layer in the bead portion or the sidewall portion as the folded height increases, so that the oxidation deterioration of the surrounding rubber increases as the folded height of the carcass layer increases. As a result, the durability of the bead portion and the sidewall portion is reduced, and at the same time, air leakage to the outside is increased.

  In order to solve the above-described problems, the present inventor has determined that the carcass layer serving as an air bypass should be reduced as much as possible in the range where the pressure resistance of the tire is not inhibited at the crown portion of the tire, and further, the folded end of the carcass layer. On the part side, paying attention to reducing the folding height of the carcass layer as much as possible and providing a new means for suppressing air permeation in the vicinity of the folding terminal within the range not impairing the tire performance. The present invention has been completed.

  Conventionally, there has been a proposal (for example, see Patent Document 1) in which the carcass layer in the crown portion of the tire has a hollow structure and the folding height of the carcass layer is lowered in order to reduce in-vehicle noise. . However, although these proposals can be expected to some extent to reduce air leakage and prevent oxidative deterioration of the rubber layer, they can still be sufficiently satisfactory as measures to suppress the decrease in durability at the folded end of the carcass layer. It was not a thing.

Japanese Patent Laid-Open No. 2001-187511

  The present invention solves the above-described problems, and suppresses air leakage from the inside of the tire and suppresses oxidation deterioration of rubber at the folded end portion of the carcass layer to improve durability. To provide tires.

In order to achieve the above object, a pneumatic tire according to the present invention includes at least one carcass layer wound around a bead core embedded in a pair of left and right bead portions from the inside to the outside of the tire, and an outer peripheral side of the carcass layer. The innermost carcass layer located on the innermost side of the carcass layer is disposed on the inner side of the belt layer. In the region inside the tire from both ends, a left and right part is formed to form a separation portion, the height of the winding terminal of the innermost carcass layer is 25% or less of the tire cross-sectional height, and the winding terminal of the carcass layer was placed an air permeability coefficient (1~100) × 10 ^-12 air permeation preventive layer of ^{cc · cm / cm 2 · sec} · cmHg in the tire width direction outside of the To feature the door.

  Furthermore, in the structure mentioned above, it is preferable to comprise as described in (1)-(4) below.

(1) The separation width in the separation portion is set to 50 to 95% of the maximum belt width.
(2) A rubber-coated fiber cord layer or an air permeation preventive layer having an air permeability coefficient of (1 to 100) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg is disposed in the spacing portion.
(3) The air permeability coefficient is (1 to 100) × 10 ⁻¹² cc · cm / in the tire inner side of the innermost carcass layer and at least in the region from both ends of the belt layer to 50% of the tire cross-section height. An air permeation preventive layer of cm ² · sec · cmHg is disposed.
(4) A rim protect bar extending in the tire circumferential direction is formed on the outer wall of the bead portion, and the air permeability coefficient of the rim protect bar is (1-100) × 10 ⁻¹² cc · cm / cm ² · sec · Set to cmHg.

  According to the present invention, the innermost carcass layer located on the innermost side of the tire among the carcass layers is divided into left and right in the region inside the tire from both ends of the belt layer, so that the air that has permeated the inner liner layer in the crown portion. Can reduce the amount of intrusion into the innermost carcass layer and suppress air leakage from the inside of the tire.

Further, the height of the winding terminal of the innermost carcass layer is set to 25% or less of the tire cross-section height, and the air permeability coefficient is (1-100) × 10 ⁻¹² cc · cm on the outer side in the tire width direction of the winding terminal. Since the air permeation preventive layer of / cm ² · sec · cmHg is arranged, the permeated air diffusing from the winding terminal to the surrounding rubber layer is suppressed, and the decrease in durability at the winding end of the innermost carcass layer is suppressed. be able to.

It is sectional drawing which shows the principal part of the pneumatic tire by embodiment of this invention. It is a partial cross section figure which shows embodiment in the terminal of the carcass cord of the tire of FIG. It is a partial cross section figure showing the tread part of the pneumatic tire by other embodiments of the present invention. FIG. 4 is a partial cross-sectional view corresponding to FIG. 3 according to still another embodiment of the present invention. FIG. 6 is a half cross-sectional view showing a pneumatic tire according to still another embodiment of the present invention. FIG. 6 is a half cross-sectional view showing a pneumatic tire according to still another embodiment of the present invention.

  In FIG. 1, a pneumatic tire 1 according to the present invention includes at least one layer of carcass wound around the bead cores 3 and 3 embedded in a pair of left and right bead portions 2 and 2 from the inside of the tire toward the outside. The belt layer 6 and the belt layers 6 and 6 composed of at least two layers (two layers in the drawing) in which the cord directions cross each other are arranged on the outer peripheral side of the carcass layer 4 in the tread portion 5. ing. In the figure, 8 indicates a sidewall portion, and 9 indicates a bead filler.

In the present invention, the innermost carcass layer 4 located on the innermost side of the tire among the carcass layers 4 is divided into left and right sides in the region inside the tire with respect to both end portions 6a and 6a of the belt layer 6 to form a separation portion R. In addition, the height H of the winding terminal 4a is set to 25% or less, preferably 3 to 20% of the tire cross-section height SH, and the air permeability coefficient is (1) on the outer side in the tire width direction of the winding terminal 4a of the carcass layer 4. ˜100) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg, preferably (1-50) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg, an air permeation preventive layer 7 is disposed. .

  As described above, the innermost carcass layer 4 is divided into left and right inside the tire of the belt layer 6, so that the weight of the tire can be reduced by partially reducing the carcass layer 4 in the crown portion, and at the same time, the inner liner layer in the crown portion can be reduced. The amount of permeated air entering the innermost carcass layer 4 can be reduced, and air leakage from the inside of the tire can be suppressed.

Further, the height H of the winding terminal 4a of the innermost carcass layer 4 is set to 25% or less of the tire cross-section height SH, and the air permeability coefficient is (1 to 100) × 10 on the outer side in the tire width direction of the winding terminal 4a. ^Since the air permeation preventive layer 7 of ⁻¹² cc · cm / cm ² · sec · cmHg is arranged, the permeation air diffusing from the winding terminal 4a to the surrounding rubber layer is suppressed, and the winding end of the innermost carcass layer 4 It is possible to suppress a decrease in durability.

  Here, when the height H of the winding terminal 4a exceeds 25% of the tire cross-section height SH, the winding terminal 4a terminates in the region of the sidewall portion 8 where the thickness of the rubber is thin. The air that has passed through oxidizes and degrades the rubber in the thin sidewall portion 8 at an early stage, thereby destroying the sidewall portion 8 at an early stage. In addition, the lower limit value of the height H of the winding terminal 4a is not particularly limited, but the effect of locking the carcass layer 4 by the bead core 3 is not deteriorated so as not to adversely affect the motion performance of the tire. The tire cross-section height SH should be set to about 5%.

Further, if the air permeation coefficient of the air permeation preventive layer 7 is less than 1 × 10 ⁻¹² cc · cm / cm ² · sec · cmHg, the flexibility is insufficient and the durability is deteriorated due to the decrease in flexural fatigue. If it ^exceeds 100 × 10 ⁻¹² cc · cm / cm ² · sec · cmHg, the air permeation preventing effect cannot be sufficiently exhibited.

  The thickness of the air permeation preventive layer 7 and the width in the tire radial direction are not particularly limited, but the thickness is 0.05 to 1.0 mm, preferably 0.05 to 0.5 mm. The overlapping width of the innermost carcass layer 4 with the winding portion is adjusted to be 25 to 100%, preferably 25 to 50% of the height H of the winding terminal 4a. If the thickness of the air permeation preventive layer 7 is less than 0.05 mm, the air permeation preventive function cannot be sufficiently obtained, and if it exceeds 1.0 mm, the tire weight increases. Further, when the overlapping width of the innermost carcass layer 4 with the winding portion is less than 25% of the height H of the winding terminal 4a, the air permeation preventing function cannot be sufficiently obtained, and when it exceeds 100%, the inner carcass layer 4 The difference in rigidity from the air permeation prevention layer 7 becomes too large, and the concentration of stress accompanying the rigidity step in the vicinity of the terminal 4a of the innermost carcass layer 4 causes a decrease in durability.

  Although the material which comprises the air permeation | blocking prevention layer 7 mentioned above is not specifically limited, Butyl rubber, a thermoplastic resin, a thermoplastic elastomer, an ethylene vinyl alcohol copolymer, etc. are used preferably.

  Examples of thermoplastic resins include polyamide resins, alkoxyalkylated products or methoxymethylated products thereof, polyester resins, polynitrile resins, polymethacrylate resins, polyvinyl resins, cellulose resins, fluorine resins, imide resins, and the like. Are preferably used.

  Further, the thermoplastic elastomer composition may be constituted by blending the above-described thermoplastic resin and elastomer. As the elastomer constituting the thermoplastic elastomer composition, for example, a diene rubber or a hydrogenated product thereof, an olefin rubber, a halogen-containing rubber, a silicon rubber, a sulfur-containing rubber, a fluorine rubber, a thermoplastic elastomer, or the like is preferably used.

  In the thermoplastic elastomer composition described above, the composition ratio of the thermoplastic resin to the elastomer is not particularly limited, but when the elastomer is dispersed as a discontinuous phase in the thermoplastic resin matrix. Good. In this case, the weight ratio of the thermoplastic resin to the elastomer is preferably 90/10 to 30/70.

  The ethylene vinyl alcohol copolymer can be produced, for example, by hydrolyzing (saponifying) an ethylene-vinyl acetate copolymer (EVA) obtained by radical polymerization of ethylene and vinyl acetate. In the present invention, commercially available products such as Eval L171B (ethylene composition ratio 2.6 mol%, manufactured by Kuraray) and Evar H171B (ethylene composition ratio 3.8 mol%, manufactured by Kuraray) are used alone or in any mixture as the ethylene vinyl alcohol copolymer. Can be used as

  In the present invention, more preferably, as illustrated in FIG. 2, the air permeation described above is applied to the winding terminal 4 a of the innermost carcass layer 4 and / or the terminal 4 b of the carcass layer 4 in the separated portion R of the innermost carcass layer 4. The thin film 10 having a thickness equivalent to that of the prevention layer 7 and having a thickness of about 5 to 150 μm may be covered. Thereby, the leakage of air from the terminals 4a and 4b of the innermost carcass layer 4 can be effectively suppressed.

  In the present invention, the separation width A in the separation portion R of the innermost carcass layer 4 may be 50 to 95%, preferably 60 to 90% of the belt maximum width BW. As a result, the amount of air that has permeated through the inner liner layer in the crown portion and enters the innermost carcass layer 4 can be reliably reduced. If the separation width A is less than 50% of the belt maximum width BW, the amount of permeated air entering the innermost carcass layer 4 cannot be effectively suppressed, and if it exceeds 95%, the durability of the tire may be reduced. .

More preferably, as shown in FIG. 3 or 4, the rubber-coated fiber cord layer 11 or the air permeability coefficient is (1 to 100) × 10 ⁻¹² cc · cm / An air permeation preventive layer 12 of cm ² · sec · cmHg may be disposed. Here, when the fiber-coated fiber cord layer 11 is disposed, the distance x between the terminal 4b of the innermost carcass layer 4 and the terminal 11z of the fiber cord layer 11 may be set to 2 mm or more. If the distance x is less than 2 mm, the interlaminar shear force may increase and the durability may decrease.

  For the fiber cord layer 11 described above, a fiber cord equivalent to the carcass layer 4 is used, and this is coated with rubber having low air permeability, so that the angle of the fiber cord is 0 to 90 ° with respect to the tire circumferential direction. Preferably, it may be arranged at 0 to 40 °. Accordingly, it is possible to secure the rigidity in the separation portion R while suppressing the diffusion of the permeated air and suppress the deterioration of the tire performance.

More preferably, as illustrated in FIG. 5, the innermost carcass layer 4 is at the inner side of the tire and at least from both ends 6a, 6a of the belt layer 6 to 50%, preferably 30% of the tire cross-section height SH. The air permeation preventive layer 13 having an air permeation coefficient (1 to 100) × 10 ⁻¹² cc · cm / cm ² · sec · cm Hg having characteristics equivalent to those of the air permeation preventive layer 7 described above is provided in the region Q up to P. It is good to arrange. In this case, the air permeation preventive layer 13 described above is preferably arranged so that the upper end thereof partially overlaps the belt layer 6. Thereby, the amount of permeated air that enters the innermost carcass layer 4 can be more efficiently suppressed.

As illustrated in FIG. 6, the pneumatic tire 1 of the present invention may form a rim protect bar 14 that extends in the tire circumferential direction on the outer wall of the bead portion 2. In this case, the rim protect bar 14 may be made of a material having an air permeability coefficient of (1 to 100) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg. Thereby, the permeated air diffused from the winding terminal 4a of the carcass layer 4 can be blocked more efficiently, and air leakage from the inside of the tire can be reliably suppressed.

  As described above, the pneumatic tire according to the present invention divides the innermost carcass layer located on the innermost side of the carcass layer into the left and right sides in the region inside the tire from both ends of the belt layer, and the innermost carcass. The height of the winding end of the layer is 25% or less of the tire cross-section height, and an air permeation prevention layer having a predetermined air permeability coefficient is arranged outside the winding end, thereby suppressing air leakage from inside the tire. In addition, it suppresses a decrease in durability at the winding end of the carcass layer, and can be preferably applied to a pneumatic tire for a passenger car made of a relatively thin rubber layer.

  The tire size is 225 / 45R18, the basic structure of the tire (BW = 200 mm) is shown in FIG. 1, and the separation width ratio (A / BW) and the carcass winding height ratio (H / SH) in the separation portion are shown in Table 1. The conventional tire (conventional example) and the comparative tire (comparative example 1) in which the air permeation preventive layer is not arranged outside the winding end of the carcass layer and the air permeation prevention outside the winding end of the carcass layer The tires of the present invention (Examples 1 to 5) and comparative tires (Comparative Example 2) in which the layers were arranged were prepared.

In Examples 1 to 5 and Comparative Example 2, the air permeation preventive layer disposed outside the winding end of the carcass layer is nylon having an air permeation coefficient of 20 × 10 ⁻¹² cc · cm / cm ² · sec · cm Hg, respectively. 6/66 and a bromide of isobutylene paramethyl styrene copolymer were blended with a thermoplastic elastomer (thickness: 0.1 mm), and the fiber cord layer disposed in the separated portion of the carcass layer in Example 4 Thermoplastic elastomer equivalent to the air permeation preventive layer comprising the steel cord disposed at 30 ° with respect to the direction and having the air permeation preventive layer disposed in the separated portion of the carcass layer in Example 5 disposed outside the winding end. (Thickness 0.1 mm).

  These eight types of tires were evaluated for internal pressure retention performance, durability performance and steering stability performance by the following test methods, and the results are also shown in Table 1.

[Internal pressure retention performance]
Each tire was fitted to a rim (size: 18 × 8J), filled with air pressure of 250 kPa, and allowed to stand at room temperature of 21 ° C. under no load conditions for 3 months. Evaluation of internal pressure retention performance was made based on the rate of decrease. The results are shown in Table 1 using an index with the conventional example being 100. The smaller the value, the better the internal pressure retention performance.

[Durability]
Each tire was fitted to a rim (size: 18 × 8 J), filled with an air pressure of 350 kPa, left in an oven at 70 ° C. under no load conditions for 2 weeks, and then adjusted to an air pressure of 200 kPa. A maximum load (6.03 kN) specified by JATMA was applied, and the vehicle was run on the drum at a speed of 80 km / h, and continued to run until damage was confirmed near the folded end of the carcass layer by visual inspection. The run was terminated when the occurrence of the problem was confirmed. The travel distance was used as an evaluation of durability, and the results are shown in Table 1 using an index with the conventional example as 100. The larger the value, the better the durability performance.

[Maneuvering stability]
Each tire is fitted to a rim (size: 18 × 8J), filled with air pressure of 250 kPa, mounted on the front and rear wheels of a test vehicle with a displacement of 2400 cc, and a test course consisting of asphalt road surface at an average speed of 90 km / h It was run and sensory evaluation was performed by a skilled test driver. And this result was published in Table 1 by the 10-point method which made the conventional example 5. The larger the value, the better the steering stability performance.

  From Table 1, it can be seen that the tire of the present invention improves the internal pressure retention performance and the durability performance without substantially impairing the steering stability as compared with the conventional tire. In Comparative Example 1, since the winding height of the carcass layer was too high and no air permeation preventing layer was disposed outside the winding end, the internal pressure holding performance was extremely lowered. Further, in Comparative Example 2, since no separation portion was formed in the carcass layer, the permeated air diffused from the winding end portion was damaged early in the vicinity of the winding end portion (bead portion) of the carcass layer, resulting in a decrease in durability. Was.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Bead core 4 Carcass layer 6 Belt layer 7, 12, 13 Air permeation prevention layer 11 Fiber cord layer 13 Rim protect bar R Spacing part A Spacing width of innermost carcass layer BW Maximum belt width H Carcass layer Winding terminal height SH Tire cross-section height

Claims (7)

At least one carcass layer wound around the bead core embedded in the pair of right and left bead portions from the inside to the outside of the tire, and at least two steel layers in which the cord directions intersect each other on the outer peripheral side of the carcass layer In a pneumatic tire with a belt layer made of cord,
The innermost carcass layer located on the innermost side of the tire among the carcass layers is divided into left and right sides in the region on the inner side of the tire from both ends of the belt layer to form a separation portion, and the winding terminal of the innermost carcass layer And the air permeability coefficient is (1-100) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg on the outer side in the tire width direction of the winding end of the carcass layer. A pneumatic tire with an air permeation preventive layer.   The pneumatic tire according to claim 1, wherein a separation width in the separation portion is 50 to 95% of a maximum belt width.   The pneumatic tire according to claim 1 or 2, wherein a fiber cord layer covered with rubber is disposed in the spaced-apart portion.   The pneumatic tire according to claim 3, wherein an interval between the end of the innermost carcass layer and the end of the fiber cord layer in the separation portion is 2 mm or more. 3. The pneumatic tire according to claim 1, wherein an air permeation prevention layer having an air permeability coefficient of (1 to 100) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg is disposed in the spaced-apart portion. The air permeability coefficient is (1 to 100) × 10 ⁻¹² cc · cm ² · cm ² · inside the tire of the innermost carcass layer and at least in the region from both ends of the belt layer to 50% of the tire cross-section height. The pneumatic tire according to any one of claims 1 to 5, wherein a sec.cmHg air permeation preventive layer is disposed. A rim protect bar extending in the tire circumferential direction was formed on the outer wall of the bead portion, and the air permeability coefficient of the rim protect bar was (1-100) × 10 ⁻¹² cc · cm / cm ² · sec · cmHg. The pneumatic tire according to any one of claims 1 to 6.

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