JP5543100B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that is excellent in adhesion of a carcass ply and that can adjust high-speed durability and steering stability.

  In order for a tire to exhibit sufficient durability and performance, it is necessary to reinforce the tire with various organic fiber cords and steel cords. In particular, the carcass ply constituting the carcass of a tire has, for example, rayon, nylon, or polyester to ensure or improve the strength for maintaining the internal pressure and the fatigue resistance for maintaining the strength as basic characteristics. Various organic fibers such as are used as the cord material.

  When the tire carcass is composed of a plurality of carcass plies, organic fiber cords made of the same material are generally used as the organic fiber cords for the carcass ply, and in particular, the viewpoint of improving the durability of the tire Therefore, many polyester cords are used. However, polyester cords have room for improvement in terms of adhesion to rubber and high-temperature stability during high-speed rolling.

  In contrast, JP-A-64-32902 (Patent Document 1) discloses a tire having a carcass made of a plurality of carcass plies, using a nylon cord for the carcass ply inside the tire, A technique for improving high load durability and interlayer adhesion by using a polyester cord for a carcass ply is disclosed. However, in the combination of organic fiber cords disclosed in Japanese Patent Application Laid-Open No. 64-32902, the thermal contraction of nylon cords is too large, and there is a possibility of causing thermal degradation during high-speed rolling.

  By the way, in order to improve the high-speed durability of the tire compared to the case where a polyester cord is used for the carcass ply, it is conceivable to use a rayon cord. However, the rayon cord is likely to have high rigidity and driving performance. Tended to become peaky and tend to lower the handling stability, and further, there was a problem that the cost was high.

JP-A-64-32902

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire that solves the above-described problems of the prior art, is excellent in adhesion of a carcass ply, and can adjust high-speed durability and steering stability.

As a result of intensive studies to achieve the above object, the present inventor, as a result, in a carcass composed of two or more carcass plies using different fiber cords, at least the innermost layer of the carcass ply having a rewinding portion wound around the bead core. Cellulosic fiber cords are used for the products, and fiber cords other than the cellulose fibers used for other carcass plies are selected as appropriate, improving the adhesion of the carcass ply and adjusting the high-speed durability and handling stability. The present inventors have found that the present invention can be accomplished and have completed the present invention.

That is, the pneumatic tire of the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extends in a toroidal shape between the pair of bead portions. In a pneumatic tire comprising a carcass composed of at least one carcass ply and a belt disposed on the outer side in the tire radial direction of the crown portion of the carcass, at least one of the carcass plies is embedded in the bead portion. A first carcass ply having a main body portion extending in a toroidal shape between the bead cores and a rewinding portion wound around the bead core, and at least the innermost layer of the first carcass ply has a plurality of cellulosic fiber cords A carcass ply made of a cellulosic fiber cord Other carcass ply Ri Do carcass ply coated with fibers code other than the plurality of cellulosic fibers with a coating rubber, fiber cords other than the cellulosic fibers, characterized in Rukoto a polyethylene terephthalate or polyethylene naphthalate .

  In a preferred example of the pneumatic tire of the present invention, the fiber cord other than the cellulosic fiber is smaller than the elastic modulus of the cellulosic fiber cord. In this case, the rigidity of the entire fiber cord is lowered while maintaining high-speed durability, and steering stability can be improved.

  In another preferred embodiment of the pneumatic tire of the present invention, the cellulosic fiber cord is a rayon cord or a lyocell cord.

  In another preferable example of the pneumatic tire according to the present invention, the pneumatic tire further includes a pair of side reinforcing rubber layers disposed inside the carcass of the sidewall portion. In this case, the rigidity of the sidewall portion can be improved without increasing the rigidity of the fiber cord.

According to the present invention, in a carcass composed of two or more carcass plies using different fiber cords , a cellulosic fiber cord is used for at least the innermost layer of the carcass ply having a turn-up portion wound around the bead core. Providing a pneumatic tire that is excellent in adhesion of a carcass ply and can adjust high-speed durability and steering stability by appropriately selecting a fiber cord other than the cellulosic fibers used for other carcass plies. it can.

  Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the pneumatic tire of the present invention, FIG. 2 is a cross-sectional view of another example of the pneumatic tire of the present invention, and FIG. 3 is another example of the pneumatic tire of the present invention. It is sectional drawing of the example of. 1-3, the same code | symbol shows that it is the same member.

  The tire shown in FIG. 1 has a pair of bead portions 1 and a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions 2, and extends in a toroidal shape between the pair of bead portions 1. Further, a radial carcass 5 composed of two or more carcass plies 4 and a belt 6 positioned on the outer side in the tire radial direction of the crown portion of the carcass 5 are provided.

  In the illustrated tire, the carcass 5 includes two carcass plies 4, and the carcass ply 4 includes a main body portion extending in a toroid shape between the bead cores 7 embedded in the bead portion 1, and the carcass ply 4. A first carcass ply 4a having a rewinding portion wound around the bead core 7 from the inner side to the outer side in the tire width direction; And a second carcass ply 4b. In the pneumatic tire of the present invention, the number of carcass plies is at least two, and at least one of the carcass plies has a main body portion extending in a toroid shape between bead cores embedded in the bead portions, and the carcass ply. A first carcass ply having a rewinding portion wound around the bead core may be used, and the number and structure of the carcass plies are not limited to the carcass ply shown in FIG. For example, the tire shown in FIG. 2 includes a radial carcass 5 including two first carcass plies 4a, and the tire shown in FIG. 3 includes one first carcass ply 4a and two second carcass plies. A radial carcass 5 consisting of 4b is provided.

Here, in the pneumatic tire of the present invention, at least the innermost layer of the first carcass ply 4a is composed of a carcass ply in which a plurality of cellulosic fiber cords are coated with a coating rubber, and the cellulosic fiber cords are used. The carcass ply other than the carcass ply includes a carcass ply in which a fiber cord other than a plurality of cellulosic fibers is coated with a coating rubber. In general, the first carcass ply 4a has a large distortion in the vicinity of the end portion of the winding portion located in the bead portion and the vicinity thereof due to the deformation of the bead portion that occurs during traveling. May occur, separation may occur, and durability of the carcass ply end may be reduced. However, in the pneumatic tire of the present invention, the coating rubber at the end of the rolled-up portion is applied to at least the innermost layer of the first carcass ply 4a by applying a cellulosic fiber cord excellent in adhesion to rubber and heat resistance. Can be prevented, and a decrease in elastic modulus at high temperature can be suppressed. For this reason, the pneumatic tire of the present invention has improved adhesion and heat resistance of the carcass ply 4 and can improve high-speed durability.

  Further, the carcass 5 of the pneumatic tire of the present invention does not use any cellulosic fiber cords for the entire carcass ply 4 and has at least one carcass ply using fiber cords other than cellulosic fibers. . For this reason, it is possible to improve the problems of rigidity, steering stability, and cost, which are observed when a cellulosic fiber cord such as rayon cord is used. The structure of the carcass ply other than the carcass ply using the cellulose fiber cord is not particularly limited, and is not limited to the structure of the first carcass ply 4a and the second carcass ply 4b.

  In order to achieve the object of the present invention, means for applying a composite cord composed of a cellulosic fiber and a fiber other than the cellulosic fiber to the carcass ply 4 is also conceivable. The effect of improving the property is not sufficient, and the effect of improving the high-speed durability of the carcass ply is low. In the carcass 5, the coating rubber constituting the carcass ply 4 is not particularly limited, and a normal rubber composition for coating rubber can be used.

  In the illustrated tire, the belt 6 includes two belt layers. However, in the tire of the present invention, the number of belt layers constituting the belt is not limited thereto. The belt layer is formed by coating a plurality of cords with a coating rubber. For the cord constituting the belt layer, for example, an organic fiber cord or a steel cord is preferably used, and the coating rubber constituting the belt layer is used. Is not particularly limited, and a normal rubber composition for coating rubber can be used.

  In addition, the pneumatic tire of this invention can further provide a well-known tire member as needed. For example, as shown in FIG. 1, the pneumatic tire of the present invention can include a pair of side reinforcing rubber layers 8 disposed inside the carcass 5 located in the sidewall portion 2. In this case, the rigidity of the sidewall portion can be improved without increasing the rigidity of the fiber cord. In addition, as shown in FIG. 1, the pneumatic tire of the present invention has a belt reinforcing layer 9 made of a rubberized layer of cords arranged substantially parallel to the tire circumferential direction on the outer side in the tire radial direction of the belt 5. An interlayer rubber (not shown) may be further provided between the end portion of the belt 5 and the belt reinforcing layer.

In the carcass 5 of the pneumatic tire of the present invention, a cellulose fiber cord is used at least for the first carcass ply 4a of the innermost layer . Cellulosic fiber cords are cords made from cellulosic fibers as raw materials. In addition to rayon cords or lyocell cords, cellulose fiber cords are chemically esterified or etherified with cellulose, which is a natural polymer. Also included is a cord produced using a cellulose derivative obtained by converting into a raw material.

Further, the carcass ply 4 constituting the carcass 5 includes at least one carcass ply using a fiber cord other than the cellulose fiber, in addition to the first carcass ply 4a using the cellulose fiber cord. Thus, by using fiber cords other than cellulosic fibers, the problems seen when using only cellulosic fiber cords can be improved, and the type of fiber cord other than cellulosic fibers can be appropriately selected. Thus, high-speed durability and steering stability can be easily adjusted. Examples of the fiber cords other than the cellulose fibers include nylon cords, polyester cords, aromatic polyamide (aramid) cords, polyketone fiber cords, carbon fiber cords, glass fiber cords, steel cords, and the like. and require that from the viewpoint of improving the steering stability, a polyester cord comprising a port triethylene terephthalate or polyethylene naphthalate.

  In the pneumatic tire of this invention, it is preferable that fiber cords other than the said cellulose fiber are smaller than the elastic modulus of the said cellulose fiber cord. By combining the cellulosic fiber cord with a fiber cord having a smaller elastic modulus than that of the cellulosic fiber cord, the rigidity of the entire fiber cord can be reliably reduced and the steering stability can be improved. Further, the higher the elastic modulus of the fiber cord, the smaller the dimensional change under the same load and the better the form stability. Therefore, the fiber cord used for the carcass ply 4 has an elastic modulus of the raw yarn of 40 to 2500 cN / It is preferably dtex, more preferably 100 to 450 cN / dtex. If the elastic modulus of the yarn of carcass ply fiber cords (including cellulosic fiber cords and fiber cords other than cellulosic fibers, the same applies below) is less than 40 cN / dtex, the tire stiffness is too low and steering stability is sufficient. I can't meet. On the other hand, if it exceeds 2500 cN / dtex, the stiffness of the fiber cord becomes too high, and the steering stability may be lowered. The elastic modulus (cN / dtex) of the fiber cord raw yarn is an elastic modulus at a load of 49 N at 25 ° C., and is a value calculated from a tangent at 49 N of the SS curve by a JIS cord tension test.

  The carcass ply fiber cord preferably has a tensile strength of 3.0 to 40 cN / dtex in order to enable use in a field where strength is required or to reduce the amount of fiber cord used. More preferably, it is 4.0-25 cN / dtex. If the tensile strength of the yarn of the carcass ply fiber cord is less than 3.0 cN / dtex, sufficient rigidity may not be secured for the carcass ply cord, whereas if it exceeds 40 cN / dtex, the fiber cord The rigidity of the vehicle may become too high, and the steering stability may be reduced. The tensile strength (cN / dtex) of the fiber cord raw yarn is a value calculated by a JIS cord tension test at 25 ° C.

  In the pneumatic tire of the present invention, the fiber cord for carcass ply preferably has a total fineness in the range of 500 to 6000 dtex. If the total fineness of the fiber cord for carcass ply is less than 500 dtex, the rigidity of the carcass ply 4 may be insufficient. On the other hand, if it exceeds 6000 dtex, the amount of coating rubber decreases and the adhesion of the carcass ply decreases. Sometimes.

  The above-mentioned fiber cord for carcass ply may have a single twist structure in which one filament bundle of fibers is twisted, and two or more filament bundles of fibers subjected to a lower twist are combined and subjected to an upper twist. You may have a twin twist structure. Here, the number of twists and the twist structure imparted to the cord during the lower twist and the upper twist are determined in consideration of the strength, convergence and other physical properties of the cord. In the present invention, the fiber for the carcass ply is used. The number of twists of the cord is preferably in the range of 10 times / 10 cm to 50 times / 10 cm for both the lower twist and the upper twist. The fiber cord for carcass ply used in the pneumatic tire of the present invention needs to use at least a cellulosic fiber cord. If the number of twists of the fiber cord is within the above specified range, Appropriate rigidity is imparted, and steering stability can be improved.

  In addition, as above-mentioned, as a coating rubber which comprises the carcass ply 4, a normal rubber composition for coating rubbers can be used. For example, the rubber component used in the rubber composition for the coating rubber is not particularly limited. In addition to natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber ( BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), etc. can be used. These rubber components are used alone. You may use, and you may blend and use 2 or more types. The rubber composition for coating rubber includes, in addition to the rubber component, for example, filler, softener, anti-aging agent, vulcanizing agent, vulcanization accelerator, scorch preventing agent, zinc white, stearic acid, silane coupling. A compounding agent usually used in the rubber industry such as an agent can be appropriately selected and compounded within a range not impairing the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition for a coating rubber can be produced by blending a rubber component with various compounding agents appropriately selected as necessary, kneading, heating, extruding, and the like.

  The pneumatic tire of the present invention uses at least one first carcass ply 4a in which the above-described cellulose fiber cord is coated with a coating rubber on the carcass 5, and further covers a fiber cord other than the above-described cellulose fiber with a coating rubber. By using at least one carcass ply, it can be manufactured by a conventional method. Prior to rubberizing the cord, the cord may be treated with an adhesive to improve the adhesion to the coating rubber. In addition, as gas with which the pneumatic tire of this invention is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  Next, a plurality of fiber cords listed in Tables 1 and 2 were drawn together as warp yarns, and a thin fiber cord into which thin and weak weft yarns were roughly applied was coated with a coating rubber to produce a rubber-coated cord. The obtained rubber-coated cords were used in carcass plies in the combinations shown in Tables 1 and 2 to produce a tire having a carcass structure shown in Tables 1 and 2 and a tire size of 215 / 45ZR17. The tires of Conventional Example 1, Example 1, Example 3, Example 5, and Comparative Example 1 do not include the side reinforcing rubber layer 8. The tire was evaluated for the adhesion at the end of the rewinding portion, high-speed durability, and steering stability by the following methods. The results are shown in Tables 1-2.

(1) Adhesiveness at the end of the rolled-up portion The twisted cord or dip-treated cord is embedded in an unvulcanized rubber composition and vulcanized under pressure of 20 kg / cm ² at 160 ° C for 20 minutes. The cord was dug up from the article, the cord was peeled off from the vulcanizate at a rate of 30 cm / min, the peel resistance at 25 ° C. was measured, and this was defined as the adhesive strength (kg / one cord). For tires having no side reinforcing rubber layer, the index of adhesion of the tire of Conventional Example 1 is indicated as 100, and for tires having the side reinforcing rubber layer, the index of adhesiveness of the tire of Conventional Example 2 is indicated as 100. . It shows that it is excellent in the adhesiveness of a winding-up part edge part, so that an index value is large.

(2) High-speed durability The test tire was assembled on a rotating drum and run at a speed of 150 km / h for 30 minutes. If there was no failure, the speed was increased by 6 km / h, and the durability time until the failure occurred was measured. . For tires having no side reinforcing rubber layer, the durability of the tire of Conventional Example 1 is indicated as an index, and for tires having a side reinforcing rubber layer, the durability of the tire of Conventional Example 2 is indicated as 100. . A larger index value indicates a longer durability time and better high-speed durability.

(3) Steering stability The test stability was evaluated based on an actual vehicle sensory test with a specialized driver wearing the test tire. For tires without side reinforcing rubber layers, the steering stability of the tire of Conventional Example 1 is indicated as an index, and for tires with side reinforcing rubber layers, the steering stability of the tire of Conventional Example 2 is indicated as 100. displayed. The larger the index value, the better the steering stability.

* 1 PET is an abbreviation for polyethylene terephthalate, and PEN is an abbreviation for polyethylene naphthalate.
* 2 The elastic modulus at 25 ° C calculated from the tangent at 49N of the SS curve in the JIS cord tension test.
* 3 Tensile strength at 25 ° C calculated by JIS cord tension test.
* 4 4a is a first carcass ply having a main body portion and a winding portion, and 4b is a second carcass ply covering the winding portion of the first carcass ply.

From the comparison between the conventional example and the examples, it is composed of two or more carcass plies using fiber cords having different carcass, using a cellulosic fiber cord for at least the innermost layer of the first carcass ply, and for other carcass plies. It can be seen that by using a fiber cord other than the cellulosic fiber, the adhesion of the carcass ply is improved and the high-speed durability can be improved. Moreover, the tire of an Example uses polyester cords, such as PET cord or PEN cord, as fiber cords other than a cellulosic fiber, and it turns out that high-speed durability and steering stability can be improved significantly. In addition, it is clear from the comparison between the conventional example and the examples that the effect of improving the high-speed durability and the handling stability appears remarkably by using the cellulosic fiber cord and the polyester cord together.

  From the comparison between the examples and the comparative examples, it can be seen that when the fiber cords for carcass ply are all made of cellulosic fiber cords, the stiffness of the fiber cords becomes too high and the steering stability is lowered. Further, it can be seen that, when a cellulosic fiber cord is used for a carcass ply other than the first carcass ply, the effect of improving the adhesion of the carcass ply cannot be obtained, so that the high-speed durability cannot be improved.

It is sectional drawing of an example of the pneumatic tire of this invention. It is sectional drawing of the other example of the pneumatic tire of this invention. It is sectional drawing of the other example of the pneumatic tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass ply 4a 1st carcass ply 4b 2nd carcass ply 5 Carcass 6 Belt 7 Bead core 8 Side reinforcement rubber layer 9 Belt reinforcement layer

Claims (4)

A carcass composed of two or more carcass plies having a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extending in a toroidal shape between the pair of bead portions; In a pneumatic tire comprising a belt arranged on the outer side in the tire radial direction of the crown portion of the carcass,
At least one of the carcass plies is composed of a first carcass ply having a main body portion extending in a toroid shape between bead cores embedded in the bead portions and a rewinding portion wound around the bead core,
At least the innermost layer of the first carcass ply comprises a carcass ply in which a plurality of cellulosic fiber cords are coated with a coating rubber, and a carcass ply other than the carcass ply using the cellulosic fiber cords is other than a plurality of cellulosic fibers. Ri Do from fiber cords coated with the coating rubber carcass ply,
A pneumatic tire, wherein a fiber cord other than the cellulosic fibers is made of polyethylene terephthalate or polyethylene naphthalate .   The pneumatic tire according to claim 1, wherein a fiber cord other than the cellulosic fiber is smaller in elastic modulus than the cellulosic fiber cord.   The pneumatic tire according to claim 1, wherein the cellulosic fiber cord is a rayon cord or a lyocell cord.   The pneumatic tire according to claim 1, further comprising a pair of side reinforcing rubber layers disposed inside the carcass of the sidewall portion.

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