JP2006224853A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing generation of inner crack and realizing thin gauge of an inner liner when a conventional rubber composition for inner liner is used for the inner liner. <P>SOLUTION: In the pneumatic tire provided with the inner liner at an inner side in a radial direction of a radial carcass comprising at least one sheet of carcass ply, a terminal end rubber part is arranged at a circumferential joint end of the carcass ply and at a side facing to at least the inner liner. Thereby, a level difference in a carcass ply joint part is gradually reduced and stress concentration to the inner liner in contact with a ply joint part is relaxed to suppress the inner crack. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which a thinner gauge is provided in an inner liner.

Conventionally, an inner liner made of a low gas permeable rubber such as halogenated butyl rubber has been provided on the radially inner side of the carcass of a pneumatic tire in order to prevent air leakage and keep the tire air pressure constant. However, if the content of butyl rubber is increased in order to improve the air permeation resistance, the strength of unvulcanized rubber will decrease, and it will easily cause rubber breakage and sheet holes, especially when the inner liner is made thinner. This causes a problem that the carcass ply cord is easily exposed during tire manufacture. On the other hand, with the recent social demand for energy saving, a method for reducing the gauge of the inner liner has been proposed for the purpose of reducing the weight of the tire for automobiles. For example, Patent Document 1 and Patent Document 2 disclose a method of using nylon film or vinylidene chloride as an inner liner instead of butyl rubber. Patent Document 3 discloses the use of a film of a composition comprising a blend of a thermoplastic resin such as a polyamide resin or a polyester resin and an elastomer. Patent Document 4 discloses a rubber composition for an inner liner that has good air permeation resistance, bending fatigue resistance, and processability, and improved durability at low temperatures.
Japanese Patent Laid-Open No. 7-40702 JP-A-7-81306 JP-A-10-29407 JP 2002-88209 A

  However, when using the inner liner described in Patent Documents 1 to 3, the matrix is a crystalline resin material, even if the weight of the tire can be reduced to some extent. There is a disadvantage that the crack resistance and the bending fatigue resistance at the time of use are inferior to those of the butyl rubber compounding composition that is usually used, and in addition to the usual tire manufacturing process, the treatment for bonding the resin material and the carcass A process is required.

  On the other hand, when the rubber composition for an inner liner described in Patent Document 4 is used, durability at a low temperature is improved as compared with the inner liner described in Patent Documents 1 to 3 above. However, since the butyl rubber content is higher than that of the conventional rubber composition for the inner liner, the unvulcanized rubber strength is reduced as described above, and an inner crack occurs at the carcass ply joint portion of the raw tire. Therefore, there is a problem that the inner liner gauge has to be thicker than before, and a sufficient weight reduction cannot be obtained.

  Under such circumstances, the present invention provides a pneumatic tire that prevents inner cracking when the conventional rubber composition for an inner liner is used for the inner liner and enables the inner liner to have a thinner gauge. It is the purpose.

  As a result of intensive studies to achieve the above object, the present inventors have found that in a pneumatic tire comprising an inner liner on the radial inner side of a radial carcass made of at least one carcass ply, By disposing the end rubber part at the side facing the inner liner at the end of the circumferential joint, the step in the carcass ply joint part is gradually reduced, and the stress concentration on the inner liner in contact with the ply joint part is alleviated. Thus, the inventors have found that the above problem can be solved by suppressing inner cracks, and have completed the present invention.

  That is, the pneumatic tire of the present invention is a pneumatic tire comprising an inner liner on the radial inner side of a radial carcass made of at least one carcass ply, and at least the inner liner at the circumferential joint end of the carcass ply. A terminal rubber portion is disposed on the side facing the surface.

  In a preferred example of the pneumatic radial tire of the present invention, the inner liner is made of a rubber composition containing butyl rubber.

  In a preferred example of the pneumatic radial tire of the present invention, the inner liner is made of a rubber composition containing kaolin clay.

In a preferred example of the pneumatic radial tire of the present invention, the length M (mm) of the end rubber portion in the tire circumferential direction is represented by the following formula (I):
0 <M ≦ 12 / A-0.6 (I)
(In the formula, A is an air permeability coefficient (x10 ⁻¹⁰ cc · cm / cm ² · s · cmHg) of the inner liner at 60 ° C.)
It is characterized by satisfying.

  According to the present invention, when the content of butyl rubber in the rubber composition for an inner liner is increased in order to improve the air permeation resistance, the inner crack is not generated even if the inner liner using the composition is made thinner. Therefore, there is an advantageous effect that the weight of the tire can be reduced by reducing the thickness of the inner liner. Further, it is possible to reduce a gap between the carcass ply joint part and the inner liner caused by a step in the carcass ply joint part, and there is an advantageous effect that it is possible to suppress air entry into the gap.

  Details of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic view showing an example of a carcass ply joint cross section of a tire using a carcass ply by a normal decision, and FIG. 2 is a schematic view showing an example of a carcass ply joint cross section of the tire of the present invention. 1b and 2 show a state where the carcass ply and the inner liner are in contact with each other during molding.

  In the tire using the normal carcass ply 1 shown in FIG. 1, when the inner liner 3 is disposed at the carcass ply joint portion, the gauge of the inner liner 3 is reduced due to a step due to the thickness of the carcass ply 1. As a result, the stress concentrates on the thinned portion, and the inner crack may occur. On the other hand, in the tire of the present invention in which the end rubber portion 4 of FIG. 2 is disposed at the circumferential joint end portion of the carcass ply 1, the step due to the thickness of the carcass ply 1 in the carcass ply joint portion is gradually reduced. The decrease in the gauge of the liner 3 is suppressed, the stress concentration on the inner liner 3 in contact with the carcass ply joint portion is alleviated, and the inner crack can be suppressed. Therefore, it is possible to reduce the thickness of the inner liner gauge that makes the best use of the air permeation performance of the inner liner rubber, leading to weight reduction of the pneumatic tire.

  The terminal rubber portion is a rubber portion or ear rubber protruding from the end of the coating rubber of the carcass ply, and is disposed at least at the joint end of the circumferential joint end of the carcass ply facing the inner liner. Examples of means for disposing the end rubber portion include means for projecting the end portion of the coating rubber of the carcass ply, and means for separately providing ear rubber at the joint end.

The length M (mm) in the tire circumferential direction of the end rubber portion disposed at the joint end is expressed by the following formula (I):
0 <M ≦ 12 / A-0.6 (I)
(In the formula, A is preferably an air permeability coefficient (x10 ⁻¹⁰ cc · cm / cm ² · s · cmHg) of the inner liner at 60 ° C.). Even if the length M (mm) of the end rubber part exceeds (12 / A-0.6), the inner liner can be made thinner, but the amount of rubber increases as the end rubber part length increases. , Hinder weight reduction. Further, as the end rubber portion becomes longer, the end rubber portion is bent, and there is a possibility that problems such as defective joints and poor air entering may occur. In particular, the length M (mm) of the terminal rubber portion is more preferably in the range of 0 <M ≦ 10 / A−0.6.

  In the rubber composition used for the inner liner, butyl rubber containing 40% by weight or more of halogenated butyl rubber is used as the rubber component. Examples of the halogenated butyl rubber include chlorinated butyl rubber, brominated butyl rubber, and modified rubber thereof. For example, there is “EnjayButyl HT10-66” (trademark, manufactured by Enjay Chemical Co., Ltd.) as a chlorinated butyl rubber, and “bromobutyl 2255” (trademark, manufactured by Exxon Corporation) as a brominated butyl rubber. Further, a chlorinated or brominated modified copolymer of a copolymer of isomonoolefin and paramethylstyrene can be used as the modified rubber, and is available as, for example, “Expro 50” (trademark, manufactured by Exxon). . Such a halogenated butyl rubber is excellent in air permeation resistance. In the above rubber composition, the halogenated butyl rubber contains 40% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more. Butyl rubber is used.

  Examples of the conjugated diene rubber that can be blended in the rubber component include natural rubber, isoprene synthetic rubber (IR), cis 1,4-polybutadiene (BR), and syndiotactic-1,2-polybutadiene (1,2BR). , Styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and the like. These may be used alone or in combination of two or more.

  The rubber composition has a ratio of 0 to 100 parts by weight of carbon black, 30 to 180 parts by weight of a layered or plate-like inorganic filler, and 0 to 5 parts by weight of a dispersion improver per 100 parts by weight of the rubber component. And the carbon black and the layered or plate-like inorganic filler can be contained in a total amount of 30 to 200 parts by weight.

The type of the carbon black is not particularly limited, and any one of those conventionally used as a reinforcing filler for rubber can be appropriately selected and used. For example, FEF, SRF, HAF, ISAF, SAF, GPF etc. are mentioned. Among these, those having a nitrogen adsorption specific area (N ₂ SA) of 26 to 170 m ² / g are preferable. N ₂ SA is measured according to ASTM D3037-88.

  The layered or plate-like inorganic filler preferably has an aspect ratio of 5 or more and less than 30. Here, the aspect ratio is obtained as a / b by observing the inorganic filler with an electron microscope, measuring the major axis and minor axis of 50 arbitrary particles, and calculating the average major axis a and the average minor axis b. By adding a layered or plate-like inorganic filler having such an aspect ratio to the rubber component, the air permeation resistance can be improved with a smaller amount than that of ordinary carbon black or inorganic filler. It becomes. As a result, compared to conventional carbon black and inorganic fillers, an increase in hardness at low temperatures can be suppressed, so that durability at low temperatures can be improved. If this aspect ratio is less than 5, the effect of improving the air permeation resistance may not be sufficiently exhibited, and if it is 30 or more, the dispersion into the rubber component tends to be poor, and rather the air permeation resistance tends to be poor. . In this respect, a more preferable aspect ratio is in the range of 7-20. The layered or plate-like inorganic filler having such an aspect ratio may be either a natural product or a synthetic product, and is not particularly limited. For example, a water-containing composite of kaolin, clay, mica, feldspar, silica and alumina. Examples include the body. Of these, kaolin clay is preferred.

  The dispersion improver is used for improving the dispersion of the layered or plate-like inorganic filler or carbon black in the rubber component, and improving the bending fatigue resistance, etc. Examples thereof include a silane coupling agent and dimethyl stearylamine. These may be used singly or in combination of two or more.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples.

  A carcass ply having an end rubber portion having a length shown in Table 1 was prepared by projecting the end portion of the coating rubber at one end of the carcass ply. Carcass ply joints were made so that the end of the carcass ply provided with the end rubber part faces the inner liner, and a test tire equipped with an inner liner having the composition shown in Table 1 was prototyped. The presence or absence of defects such as defects was examined by visual observation and evaluated in three stages: ◎: very good, ◯: good, △: defective. The results are shown in Table 1.

  In the case of setting to the process gauge shown in Table 1 that makes the best use of the inner liner, in Comparative Examples 1 to 3 having no end rubber portion, it was confirmed that an inner crack occurred in the carcass ply joint portion. On the other hand, in Examples 1 to 6 in which the terminal rubber portion was disposed, no inner crack occurred. In Examples 1, 3 and 5 in which the length of the end rubber portion exceeds the range of the above formula (I), the inner liner can be made thinner because no inner crack occurs, but it is used as a whole tire. Since the amount of rubber increases, the tire may not be sufficiently lightened.

FIG. 1 is a schematic diagram showing an example of a cross section of a carcass ply joint of a tire using a carcass ply that is normally determined. FIG. 2 is a schematic view showing an example of a cross section of a carcass ply joint of a tire using the carcass ply of the present invention.

Explanation of symbols

1 Carcass ply 2 Ply cord 3 Inner liner 4 End rubber part

Claims (4)

  In a pneumatic tire comprising an inner liner on the radially inner side of a radial carcass made of at least one carcass ply, a terminal rubber portion is arranged on at least the side facing the inner liner at the circumferential joint end of the carcass ply. The pneumatic tire is characterized by being provided.   The pneumatic tire according to claim 1, wherein the inner liner is made of a rubber composition containing butyl rubber.   The pneumatic tire according to claim 1 or 2, wherein the inner liner is made of a rubber composition containing kaolin clay. The length M (mm) in the tire circumferential direction of the terminal rubber portion is represented by the following formula (I):
0 <M ≦ 12 / A-0.6 (I)
(In the formula, A is an air permeability coefficient (x10 ⁻¹⁰ cc · cm / cm ² · s · cmHg) of the inner liner at 60 ° C.)
The pneumatic tire according to any one of claims 1 to 3, wherein:

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