JP2011240867A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which improves a uniformity and is superior in its resistance for partial abrasion.SOLUTION: The pneumatic tire has as a skeleton a carcass 5 extending in a toroidal form between a pair of right and left bead parts 1 and includes sequentially two complex belt layers 6a and 6b and an auxiliary belt layer 7 in the radial direction of the tire of the carcass 5. A cord of the auxiliary belt layer 7 is a dipped cord formed with an organic fiber having a dry heat shrinkage percentage of 10 to 15% during a thermal treatment at 160°C×30 minutes. The auxiliary belt layer 7 includes a warp intersecting the cord and the size of the warp is 350 dtex or more and driving number is 3.0/5 cm or above.

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic tire with improved uniformity and excellent uneven wear resistance.

  Currently, the belt commonly used as the reinforcing member of the carcass that forms the skeleton of the radial tire for passenger cars, especially the reinforcing member of the crown portion of the carcass, is mainly made of a rubberized layer of a steel cord that is inclined with respect to the equator plane of the tire. Two or more steel belt layers are used, and the steel cords in these belt layers intersect each other.

  In addition, the stability of the tire during running of the tire, particularly the stability during high speed running, and further the peeling of the belt layer during high speed running, particularly the peeling that occurs remarkably at the end of the belt layer, prevents the durability of the tire. In order to improve performance, a belt protective layer formed by rubberizing a nylon cord or the like in the tire circumferential direction may be disposed on the outer side in the tire radial direction of the belt. As the structure of such a belt protective layer, a so-called cap structure or layer structure is known.

  Furthermore, conventionally, as a technique for improving the performance of a pneumatic tire, a floating belt structure including an auxiliary belt layer using a cord disposed substantially at 90 ° with respect to the circumferential direction of the tire as a reinforcing material is known. (For example, refer to Patent Document 1). This structure has a bending behavior that follows the shear input generated between the road surface and the belt, and it is possible to equalize the widthwise distribution of slip and tangential force between the outer surface of the tire tread and the road surface. And it is possible to improve uneven wear resistance. For this reason, this floating belt structure is disposed along the radially inner belt layer as an auxiliary belt layer. At this time, in order to perform an ideal 90 ° arrangement, an organic fiber cord having a woven fabric structure using wefts as the diameter yarn is often used for the belt reinforcing layer.

JP 2007-331424 A

  In such a vulcanization process during the manufacturing process of the tire, the tire shrinks in the width direction due to thermal shrinkage, but if the shrinkage rate of the auxiliary belt layer is smaller than the shrinkage rate of the tire, the tire follows the shrinkage of the tire. You can't do that, and the code may wave. Therefore, the arrangement becomes non-uniform or sagging occurs at the belt end. As a result, a decrease in rigidity against shear input and a deterioration in uniformity caused by disorder of the arrangement are caused, and uneven wear tends to occur.

  In response to such problems, by using an auxiliary belt layer using a cord having a thermal contraction rate of 10 to 15%, it is possible to follow the shrinkage of the auxiliary belt layer to the shrinkage of the tire, and to prevent uneven wear resistance. It is also possible to improve. However, in order to obtain a heat shrinkage rate in the above range, it is necessary to set the dip tension at the time of the dip treatment of the cord, and at that time, the driving of the diameter yarn is greatly disturbed, and the uniformity is deteriorated. . Therefore, there has been a problem that uneven wear resistance, which is a characteristic of the floating belt structure, is impaired.

  Accordingly, an object of the present invention is to provide a pneumatic tire with improved uniformity and excellent uneven wear resistance.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by defining the thickness and the number of driven yarns of the woven fabric structure constituting the auxiliary belt layer. The invention has been completed.

That is, the pneumatic tire of the present invention has a carcass extending in a toroidal shape between a pair of left and right bead portions as a skeleton, and two intersecting belt layers and an auxiliary belt layer are formed on the outer side in the tire radial direction of the carcass. In pneumatic tires that are sequentially laminated,
The cord of the auxiliary belt layer includes, as a dip-treated cord, an organic fiber having a dry heat shrinkage rate of 10 to 15% during heat treatment at 160 ° C. for 30 minutes, and the auxiliary belt layer includes a weft that intersects the cord. The weft yarn has a fineness of 350 dtex or more, and the number of driven yarns is 3.0 / 5 cm or more.

  In the present invention, the cord angle of the auxiliary belt layer is preferably 80 to 90 ° with respect to the tire circumferential direction. Moreover, it is preferable to have a belt protective layer made of a cord wound spirally in the tire circumferential direction, covering both ends of the auxiliary belt layer. Further, the weft is preferably a cellulosic fiber or a vinylon fiber, and the weft is preferably a spun yarn.

  According to the present invention, it is possible to provide a pneumatic tire with improved uniformity and excellent uneven wear resistance.

It is sectional drawing which shows the pneumatic tire which concerns on one embodiment of this invention. (A) is a top view which shows the lamination | stacking state of the crossing belt layer which concerns on one embodiment of this invention, an auxiliary | assistant belt layer, and a belt protective layer, (b) is typical sectional drawing which shows the same lamination | stacking state FIG.

Preferred embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 shows a schematic cross-sectional view of an example of a pneumatic tire according to an embodiment of the present invention. The illustrated tire 10 includes a tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction from both ends thereof, and a pair of bead portions 3 positioned at the inner ends thereof, and includes at least one carcass. A carcass layer 5 composed of a ply (one sheet in the illustrated example) is extended toroidally between a pair of bead cores 4 embedded in the bead portion 3.

  In the tire 10, as shown in FIG. 2, a belt 6 including two intersecting belt layers 6 a and 6 b and an auxiliary belt layer 7 are sequentially arranged on the outer side in the crown portion tire radial direction of the carcass layer 5. Yes. As will be described later, in the present invention, as shown in the illustrated example, a belt protective layer 8 made of a cord wound spirally in the tire circumferential direction is disposed at both ends of the auxiliary belt layer 7 on the outer side in the tire radial direction. May be.

  In the present invention, the cord of the auxiliary belt layer 7 is an organic fiber having a dip-treated cord and a dry heat shrinkage rate during heat treatment at 160 ° C. for 30 minutes (hereinafter also simply referred to as “heat shrinkage rate”) of 10 to 15%. The auxiliary belt layer 7 includes a weft that intersects with the cord, and it is important that the weft has a fineness of 350 dtex or more and a driving number of 3.0 / 5 cm or more.

When the heat shrinkage rate of the cord of the belt auxiliary layer 7 is less than 10%, the auxiliary belt layer 7 cannot shrink following the tire shrinkage during vulcanization. On the other hand, when the thermal shrinkage rate exceeds 15%, the turbulence of the diameter yarn cannot be suppressed, such as undulation in the auxiliary belt layer 7 due to the thermal shrinkage of the cord itself. The heat shrinkage rate is preferably 12 to 13%. Note that the heat shrinkage during heat treatment at 160 ° C. for 30 minutes in the present invention means that the cord of the auxiliary belt layer 7 before vulcanization subjected to general dipping treatment is 160 ° C. for 30 minutes in the oven. It is a value obtained by the following equation by performing dry heat treatment and measuring the fiber length before and after the heat treatment with a load of 50 g.
Thermal contraction rate (%) = (Lb−La) / Lb × 100
However, Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment.

  In addition, by setting the weft fineness to 350 dtex or more, the frictional force between the weft and the diameter yarn can be increased, so that the deformation of the entire cord due to the tensile strain generated when tension is applied to the cord during dipping is suppressed. can do. When the fineness of the weft is less than 350 dtex, a disturbance in driving of the diameter yarn occurs. Moreover, the tensile strain generated in the auxiliary belt layer 7 cannot be suppressed. In addition, when the fineness of the weft is 700 dtex or more, the weft becomes thick, the weight of the woven fabric becomes large, and the weaving reaction becomes thick. Preferably it is 350-450 dtex.

  Furthermore, by setting the number of driven wefts to 3.0 / 5cm or more, it is possible to increase the frictional force between the wefts and the diameter yarns. Therefore, due to the tensile strain generated when the cord tension is applied during the dipping process. Deformation of the entire code can be suppressed. When the number of wefts driven is less than 3.0 / 5 cm, the radial yarns are disturbed, and the tensile strain generated in the auxiliary belt layer 7 cannot be suppressed. When the number of wefts driven is 7.0 / 5cm or more, the number of wefts increases, so the weight of the woven fabric increases, and it is necessary to weave more wefts more closely, so the weaving time is excessive. It is not preferable because it becomes longer. Preferably it is 3.5-4.5 / 5cm.

  In the present invention, the cord angle of the auxiliary belt layer 7 is preferably 80 to 90 ° C. with respect to the tire circumferential direction. If the cord angle of the reinforcing belt layer 7 is out of the above range with respect to the tire circumferential direction, the shrinkage in the shrinkage direction occurs with respect to the shrinkage in the tire width direction during vulcanization, which may lead to deterioration in uniformity. is there. In addition, the vertical spring becomes high, which may cause a deterioration in ride comfort.

  Moreover, in this invention, it is preferable to provide the belt protective layer 8 which consists of the cord wound in the tire circumferential direction spirally so that the both ends of the auxiliary | assistant belt layer 7 may be covered as mentioned above. With such a structure, the tightening effect is enhanced, and the gap between the auxiliary belt layer 7 and the belt protective layer 8 is reduced, and the separation property is improved.

  As shown in the figure, the belt protective layer 8 has a so-called layer structure disposed on both ends of the auxiliary belt layer 7. The belt protective layer 8 is formed by spirally winding a thin ribbon-like sheet obtained by rubberizing two or more reinforcing elements having a width smaller than the arrangement width until the arrangement width is reached. Preferably formed. By forming the belt protective layer 8 by continuously spirally winding the ribbon-like sheet, a joint portion does not occur in the tire circumferential direction, and the belt 6 and the auxiliary belt layer 7 can be uniformly reinforced. Become.

  In the present invention, the wefts in the auxiliary belt layer 7 are preferably cellulosic fibers or vinylon fibers, and in particular, the wefts are preferably spun yarns. Cellulose fibers and vinylon fibers have a high elastic modulus and do not follow the tensile strain, so that deformation of the cord can be satisfactorily suppressed. Preferable examples include lyocell and polynosic.

  In the present invention, the cord type, the inclination angle, and the number of driving of the cords of the two layers of crossing belt layers 6a and 6b can be appropriately selected from a known range, and are particularly limited as long as a desired tag effect is obtained. Should not be done.

  In the present invention, as long as the auxiliary belt layer 7 has the above structure, the other tire structures and materials are not particularly limited, and can be appropriately set according to a conventional method. For example, the carcass 5 includes one carcass ply in the illustrated example, but two or more carcass may be provided. Although not shown, an inner liner is usually disposed in the innermost layer of the tire, and a tread pattern is appropriately formed on the tread surface. In the pneumatic tire of the present invention, 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.

Hereinafter, the present invention will be specifically described based on examples.
(Examples 1 to 6, conventional example and comparative examples 1 to 3)
A tire in which two crossing belt layers and an auxiliary belt layer were sequentially laminated on the outer side in the tire radial direction of the carcass was manufactured with a tire size of 215 / 45ZR17. The cord structure of the auxiliary belt layer is as shown in Tables 1 and 2 below. The angle of the intersecting belt layer with respect to the tire circumferential direction was ± 40 °. In addition, the thermal shrinkage rate in the table was changed by changing the dip treatment conditions of the fiber cord. For each of the obtained tires, the yarn yarn disorder index, uneven wear resistance, and uniformity were evaluated according to the following procedures.

(Diameter yarn disorder index)
The number of driving per 10 cm of the dip counter is measured in the width direction, and the minimum value of the driving number per 10 cm at that time is A, the maximum value is B, and the radial yarn disturbance index C is expressed by the following formula:
C = B / A × 100
Calculated based on It shows that the smaller the value of C, the less the disturbance of the diameter yarn and the better. The results obtained are also shown in Tables 1 and 2.

(Uneven wear resistance)
All the test tires were mounted on an actual vehicle under the same conditions, and the amount of uneven wear after traveling 10,000 km was measured. The evaluation was performed by index display with the reciprocal of the uneven wear amount of the conventional example being 100. The larger the value, the better the uneven wear resistance. The results obtained are also shown in Tables 1 and 2.

(Uniformity)
RFV (Radial Force Variation) and LFV (Lateral Force Variation) of a test tire filled with an internal pressure of 230 kPa were measured, and the value of the tire of the conventional example was represented as an index as 100. The smaller the index value, the better the uniformity. The results obtained are also shown in Tables 1 and 2.

※１：ディップ処理を施した加硫前のコードに対して、オーブン中で１６０℃、３０分の乾熱処理を行ない、熱処理前後の繊維長を、５０ｇの荷重をかけて計測して下式により求められる値である。
熱収縮率（％）＝（Ｌｂ−Ｌａ）／Ｌｂ×１００
但し、Ｌｂは熱処理前の繊維長、Ｌａは熱処理後の繊維長である。
※２：６６ナイロン

* 1: Dip-treated cord is subjected to dry heat treatment at 160 ° C for 30 minutes in an oven, and the fiber length before and after heat treatment is measured under a load of 50 g. This is the required value.
Thermal contraction rate (%) = (Lb−La) / Lb × 100
However, Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment.
* 2: 66 nylon

  As can be seen from the evaluation results of the tire performance shown in Tables 1 and 2, the tires of the examples are less disturbed in the diameter yarns and are excellent in uniformity and uneven wear properties than the tires of the conventional example and the comparative example. .

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass 6 Belt 7 Auxiliary belt layer 8 Belt protective layer 10 Pneumatic tire

Claims (5)

In a pneumatic tire in which a carcass extending in a toroid shape between a pair of left and right bead portions is used as a skeleton, and two crossing belt layers and an auxiliary belt layer are sequentially laminated on the outer side in the tire radial direction of the carcass.
The cord of the auxiliary belt layer includes, as a dip-treated cord, an organic fiber having a dry heat shrinkage rate of 10 to 15% during heat treatment at 160 ° C. for 30 minutes, and the auxiliary belt layer includes a weft that intersects the cord. A pneumatic tire characterized in that the fineness of the weft is 350 dtex or more and the number of driving is 3.0 / 5 cm or more.   The pneumatic tire according to claim 1, wherein a cord angle of the auxiliary belt layer is 80 to 90 ° with respect to a tire circumferential direction.   The pneumatic tire according to claim 1 or 2, further comprising a belt protective layer made of a cord wound in a spiral shape in the tire circumferential direction, covering both ends of the auxiliary belt layer.   The pneumatic tire according to any one of claims 1 to 3, wherein the weft is a cellulosic fiber or a vinylon fiber.   The pneumatic tire according to any one of claims 1 to 4, wherein the weft is a spun yarn.

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