JP2015196472A - tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which can achieve both tire weight reduction and high durability by establishing a technology capable of securing a sufficient prevention effect against a diameter growth even in the case of reducing the quantity of steel used in a belt layer.SOLUTION: There is provided a tire including: two or more crossing belt layers 4 including a rubberized layer made of steel cords extending with an inclination of an angle of 10° to 30° with regard to a tire equator surface, which is arranged between at least some of the layers in such a manner that the cord directions intersect each other; and a large angle belt layer 3 including a rubberized layer made of steel cords extending with an inclination of a larger angle than that of the crossing belt layers by 5° or more. The tensile modulus of elasticity of the coating rubber of the large angle belt layer measured according to JIS K6251 is larger than that of the coating rubber of the crossing belt layers measured according to JIS K6251.

Description

  The present invention relates to a tire, and more particularly, to a tire according to an improvement in a reinforcing structure of a tread portion.

  In general, tires, particularly heavy-duty tires used in heavy-duty vehicles such as trucks and buses, are provided with a plurality of belt layers for suppressing diameter growth due to internal pressure and for protecting the tread portion. Have a structure.

  As a conventional technique related to the reinforcing structure of the tread portion, for example, two crossing belt layers are arranged so that the cords intersect with each other at an inclination angle of 10 to 30 ° with respect to the tire equator plane, and further, A technique is known in which a high-angle belt layer is arranged at a cord angle that is at least 5 ° higher than the cord angle of the crossing belt layer (see Patent Document 1). In such a laminated belt structure, when tension is applied to the crossing belt layer in the tire circumferential direction, the cord movement of the crossing belt layer is suppressed by the cord of the high-angle belt layer, so that the tire width of the crossing belt layer is reduced. By suppressing the shrinkage in the direction, the circumferential rigidity of the belt can be improved and the effect of suppressing the diameter growth can be obtained.

JP-A-8-244407

  In recent years, there has been an increasing demand for environmental load reduction, and from the viewpoint of reducing the weight of tires, reduction of the amount of tire constituent materials has become an important issue. Therefore, it is important that the improvement of the belt structure is compatible with the demand for weight reduction of the tire. However, the technique described in Patent Document 1 cannot sufficiently satisfy recent demands for weight reduction.

  It is also conceivable to reduce the weight of the tire by reducing the amount of steel used for the high-angle belt layer than that of the crossing belt layer, but the tire tends to grow in diameter due to the decrease in the amount of steel. Therefore, it is necessary to prevent the diameter growth and improve the tire durability while reducing the weight of the tire.

  Therefore, an object of the present invention is to provide a tire that can achieve both weight reduction and high durability by establishing a technology capable of ensuring a sufficient diameter growth preventing effect even when the amount of steel used in the belt layer is reduced. There is to do.

  The high-angle belt layer enhances tire circumferential rigidity by preventing shrinkage (Poisson deformation) of the crossing belt layer in the tire width direction. As a result of intensive investigations focusing on this point, the present inventor has suppressed the shrinkage of the cross belt layer even when the steel amount of the high angle belt layer is reduced by increasing the rigidity of the coating rubber of the high angle belt layer. The inventors have found that an effect can be obtained and have completed the present invention.

That is, according to the present invention, the rubberized layers of steel cords extending at an angle of 10 ° to 30 ° with respect to the tire equatorial plane are arranged so that the cord directions intersect each other at least between some layers. A tire comprising: a cross belt layer of layers or more; and a high-angle belt layer made of a rubberized layer of a steel cord extending inclined at an angle of 5 ° or more larger than the cross belt layer,
The tensile elastic modulus measured according to JIS K6251 of the coating rubber of the high-angle belt layer is larger than the tensile elastic modulus measured according to JIS K6251 of the coating rubber of the crossed belt layer. Is.

  In the present invention, the mass of the steel cord per unit area included in the high-angle belt layer is preferably 80% or less of the mass of the steel cord per unit area included in the crossing belt layer.

  According to the present invention, even when the amount of steel used in the belt layer is reduced, it is possible to establish a technology capable of ensuring a sufficient diameter growth preventing effect, and realize a tire that can achieve both weight reduction and high durability. It became possible to do.

It is a width direction sectional view showing an example of 1 composition of a tire of the present invention. It is a schematic sectional drawing which shows the structure of the steel cord used in the Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction showing one structural example of the tire of the present invention. The illustrated tire 10 includes a pair of bead cores 11, a pair of side wall portions 12 connected to the bead portion 11, and a tread portion 13 straddling the both side wall portions 12. A carcass ply 2 that extends in a toroidal shape across 1 is used as a skeleton.

  In the present invention, the high-angle belt layer 3 and the crossing belt layer 4 are disposed outside the crown portion of the carcass ply 2 in the tire radial direction. Of these, the crossing belt layer 4 is composed of two or more rubberized layers of steel cord extending at an angle of 10 ° to 30 ° with respect to the tire equator plane, and can be provided with, for example, 2 to 4 layers, In the illustrated example, it is provided with two layers. The crossing belt layer 4 is arranged so that the cord directions intersect each other at least between some layers. On the other hand, the high-angle belt layer 3 is made of a rubberized layer of steel cord extending at an angle larger than the crossing belt layer 4 by 5 ° or more, for example, 40 ° to 80 ° with respect to the tire equatorial plane.

  In the present invention, it is important that the tensile elastic modulus of the coating rubber of the high-angle belt layer 3 is larger than the tensile elastic modulus of the coating rubber of the crossing belt layer 4. The high-angle belt layer 3 is made of a coating rubber having a larger tensile elastic modulus than that of the crossing belt layer 4, so that even if the amount of steel used for the high-angle belt layer 3 is reduced to reduce the weight, By the increase, the effect of suppressing the movement of the cords of the crossing belt layer 4 can be supplemented, and as a result, the effect of preventing the diameter growth can be ensured. That is, when an input due to the tire internal pressure is input to the belt layer, the surrounding coating rubber is also deformed by compression or bending deformation of the steel cord of the high-angle belt layer 3, but the elasticity of the coating rubber is increased. It is considered that the effect of preventing the diameter growth due to the tire internal pressure can be obtained by suppressing the deformation. A means to increase the elastic modulus of the coating rubber of the crossing belt layer is also conceivable, but in this case, since the stress applied to the rubber at the belt end of the crossing belt layer increases, belt edge separation is likely to occur and durability is improved. It will cause a decline.

  Here, the value measured based on JIS K6251 is used as the tensile elastic modulus of the coating rubber in the present invention. Specifically, the tensile stress at 200% elongation of the coating rubber measured according to JIS K6251 is defined as the tensile elastic modulus in the present invention. In the present invention, the tensile elastic modulus of the coating rubber of the high-angle belt layer 3 needs to be larger than 100%, preferably 105 to 200% of the tensile elastic modulus of the coating rubber of the cross belt layer 4. Preferably it is 110 to 150%. If the tensile elastic modulus of the coating rubber of the high-angle belt layer 3 is too large compared to the coating rubber of the crossing belt layer 4, the stress applied to the coating rubber of the high-angle belt layer 3 increases, There is a risk that belt edge separation is likely to occur. In the present invention, the specific value of the tensile elastic modulus of the coating rubber of the high-angle belt layer 3 and the crossing belt layer 4 is not particularly limited, and is appropriately set according to the tire size and the like according to a conventional method. be able to. Further, the specific rubber compounding of the coating rubber used for the high-angle belt layer 3 and the crossing belt layer 4 is not particularly limited, and is appropriately selected according to a conventional method within a range in which a desired elastic modulus value can be obtained for each layer. can do.

  In the present invention, the mass of the steel cord per unit area included in the high-angle belt layer 3 is 80% or less, particularly 70 to 78% of the mass of the steel cord per unit area included in the crossing belt layer 4. It is preferable that By reducing the amount of steel contained in the high-angle belt layer 3 to the above range, it is possible to effectively reduce the weight of the tire. On the other hand, in the present invention, even if the amount of steel contained in the high-angle belt layer 3 is reduced to the above range, a sufficient diameter growth preventing effect can be ensured by the combination with the coating rubber rigidity. A tire having durability can be obtained. If the mass of the steel cord contained in the high-angle belt layer 3 is made too small compared to the cross belt layer 4, the effect of suppressing the shrinkage of the cross belt layer cannot be sufficiently exerted, and sufficient durability is obtained. There is a risk of disappearing.

  In the present invention, the specific mass of the steel cord per unit area included in the high-angle belt layer 3 and the crossing belt layer 4 is not particularly limited. The steel amount can be controlled by appropriately selecting the structure of the steel cord used for each layer (the filament wire diameter, the number of filaments, etc.) and the number of drivings. Specifically, for example, using a steel cord having the same code structure for each layer, changing the number of driving, using the same number of driving for each layer, using a steel cord with a different code structure, or having a different code structure for each layer A method of changing the number of shots using a steel cord is also included.

  In the illustrated example, the high-angle belt layer 3 and the crossing belt layer 4 are stacked in this order from the inner side in the tire radial direction. However, in the present invention, the high-angle belt layer 3 and the crossing belt layer 4 are arranged. The order is not limited to this.

  In the tire of the present invention, the coating rubber of the high-angle belt layer 3 and the crossing belt layer 4, particularly the steel amount, may satisfy the above condition, and thereby the desired effect of the present invention can be obtained. Can be obtained. In the present invention, the tire structure other than the high-angle belt layer 3 and the crossing belt layer 4 and the material of each component are not particularly limited, and can be appropriately selected from conventionally known ones.

  For example, the carcass ply 2 is formed by covering a steel cord with rubber, and it is necessary to arrange at least one piece, but two or more pieces may be arranged. Both ends of the carcass ply 2 in the tire width direction are usually folded and locked around the bead core 1 from the inside to the outside of the tire as illustrated.

  In the illustrated tire, a tread pattern is appropriately formed on the surface of the tread portion 13, and an inner liner (not shown) is formed in the innermost layer. Further, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used. The tire of the present invention is particularly suitable as a heavy duty pneumatic tire applied to heavy duty vehicles such as trucks and buses.

Hereinafter, the present invention will be described in more detail with reference to examples.
Heavy duty tires of each of the examples and comparative examples were manufactured at a tire size of 11R22.5. The carcass ply crown portion on the outer side in the tire radial direction is a high-angle belt layer with a cord angle of 50 ° to the right and 20 ° to the left, 20 ° to the left, and 20 ° to the left sequentially from the inner layer side to the tire equatorial plane. Three crossing belt layers having a cord angle of 5 were arranged. The high-angle belt layer and the crossing belt layer are both 3 × 0.20 mm + 6 × 0.35 mm (see FIG. 2) steel cord, and are included in each layer as shown in the following table by changing the number of driving. The mass of the steel cord per unit area is adjusted. Moreover, about the coating rubber of each layer, what has the physical property shown in the following table | surface was used.

<Evaluation of diameter growth after running>
Each of the obtained test tires was filled with an internal pressure of 900 kPa, and the circumference of the tire after running at 50,000 km at a speed of 60 km / h was measured with a drum testing machine. For each tire, the percentage of elongation was calculated from the circumference when the internal pressure before running the drum was 100 kPa, and the index was shown as an index of 100 for the conventional example. The smaller the numerical value, the smaller the formation length after running and the better.

<Evaluation of tire durability>
Each obtained tire was filled with an internal pressure of 600 kPa, a load of 2725 N was applied, a slip angle of 5 ° was applied, and the drum was run at a speed of 60 km / h, and a crack appeared on the surface from the belt end. The distance traveled was measured. The travel distance of each tire is indicated by an index with the travel distance of the conventional example as 100. The larger the value, the longer the travel distance and the better the durability.

  These results are shown in the table below.

＊１）各層のコーティングゴムについて、ＪＩＳ Ｋ６２５１に準拠して、２００％伸び時の引張応力を求め、引張弾性率とした。

* 1) About the coating rubber of each layer, based on JIS K6251, the tensile stress at the time of 200% elongation was calculated | required, and it was set as the tensile elasticity modulus.

  As can be seen from the results in Table 1 above, even when the tire weight is reduced by reducing the amount of steel used for the belt layer by increasing the rigidity of the coating rubber of the high-angle belt layer compared to the cross belt layer, the diameter growth It was confirmed that the tire durability can be secured by suppressing the above.

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass ply 3 High angle belt layer 4 Crossing belt layer 10 Tire 11 Bead part 12 Side wall part 13 Tread part

Claims (2)

Two or more crossing belt layers in which rubberized layers of steel cords extending at an angle of 10 ° to 30 ° with respect to the tire equatorial plane are arranged so that the cord directions intersect each other at least between some layers. And a high-angle belt layer comprising a rubberized layer of steel cord extending at an angle of 5 ° or more larger than the crossing belt layer,
The tensile elastic modulus measured according to JIS K6251 of the coating rubber of the high-angle belt layer is larger than the tensile elastic modulus measured according to JIS K6251 of the coating rubber of the crossed belt layer. tire.   The tire according to claim 1, wherein the mass of the steel cord per unit area included in the high-angle belt layer is 80% or less of the mass of the steel cord per unit area included in the crossing belt layer.

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