JP2006168595A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of obtaining the road noise reducing effect while ensuring excellent steering stability. <P>SOLUTION: In the pneumatic radial tire, carcass layers 4A, 4B are mounted between a pair of bead parts 3, 3, and a plurality of belt layers 7A, 7B are provided on the outer circumferential side of the carcass layers 4A, 4B in a tread part 1. The width W1 of the narrowest belt layer 7B out of the belt layers 7A, 7B is set to be 88-92% of the tread development width TDW, and a belt cover layer 8 consisting of organic fiber cords is arranged outwardly in the tire radial direction of the belt layers 7A, 7B so as to cover the entire surface of the belt layers 7A, 7B. A laminate portion 8a of a three-layer structure is provided on parts corresponding to both edges of the belt layers 7A, 7B in the belt cover layer 8, and the width W2 of each laminate portion 8a is set to be 15-25 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire suitable as a flat tire, and more particularly to a pneumatic radial tire that can obtain a road noise reduction effect while ensuring good steering stability.

  In recent years, pneumatic radial tires are required to have both steering stability and road noise characteristics. On the other hand, as a technique for reducing road noise in the middle frequency range (250 to 315 Hz), a belt cover layer made of an organic fiber cord is disposed so as to cover the edge portion of the belt layer, and the vicinity of the edge portion of the belt layer is arranged. It has been proposed to increase the rigidity (see, for example, Patent Document 1 and Patent Document 2).

However, increasing the stiffness near the edge of the belt layer strengthens the load dependency of the cornering power, especially for flat tires where the stiffness of the belt layer tends to increase, the cornering power of the front wheels that increases the load. And the relative difference between the cornering power of the rear wheel, which has a small load, is a factor that impairs handling stability.
Japanese Patent Laid-Open No. 10-86607 JP 2000-1105 A

  An object of the present invention is to provide a pneumatic radial tire that can obtain an effect of reducing road noise while ensuring good steering stability.

  In order to achieve the above object, a pneumatic radial tire of the present invention is a pneumatic radial tire in which a carcass layer is mounted between a pair of bead portions, and a plurality of belt layers are provided on the outer peripheral side of the carcass layer in a tread portion. A belt made of an organic fiber cord so as to set the width of the narrowest belt layer among the belt layers to 88 to 92% of the tread developed width and to cover the entire surface of the belt layer on the outer side in the tire radial direction of the belt layer. A cover layer is disposed, a laminated portion having a three-layer structure is provided at a portion corresponding to both edge portions of the belt layer in the belt cover layer, and the width of each laminated portion is set to 15 to 25 mm. Is.

  As a result of repeating trial production evaluation of a pneumatic radial tire, the present inventor found that by optimizing the structure of the belt layer and the belt cover layer, both steering stability and road noise characteristics can be achieved, The present invention has been reached.

  That is, according to the present invention, the width of the narrowest belt layer among the belt layers is suppressed to 88 to 92% of the tread developed width, and 3 portions are respectively provided in the belt cover layer corresponding to both edge portions of the belt layer. By providing a layered portion of the layer structure and setting the width of each layered portion to 15 to 25 mm, more preferably 17 to 22 mm, it is possible to avoid the belt from being extremely increased in rigidity near the edge portion of the belt layer. As a result, the effect of reducing road noise can be obtained while ensuring good steering stability.

  In the present invention, the belt cover layer may have a three-layer laminated portion at each of the portions corresponding to both edge portions of the belt layer, and may have a single layer portion between these laminated portions. The method is not particularly limited. For example, the belt cover layer has a structure in which strips made of a plurality of organic fiber cords are spirally wound in the tire circumferential direction, and each laminated portion of the belt cover layer has a structure in which the strips are shifted in the width direction and overlapped. Can be adopted. According to the winding structure, the binding force of the edge portion of the belt layer is increased, and medium frequency road noise can be effectively reduced.

  As the organic fiber cord constituting at least a part of the laminated portion of the belt cover layer, it is preferable to use an organic fiber cord having an intermediate elongation of 5.0% or less at 2.0 cN / dtex. For example, it is preferable to employ a polyethylene terephthalate fiber cord as the organic fiber cord constituting at least a part of the laminated portion of the belt cover layer. When such an organic fiber cord is disposed in the laminated portion of the belt cover layer, the binding force at the edge portion of the belt layer is increased, and medium frequency road noise can be effectively reduced. The intermediate elongation is the elongation when a load of 2.0 cN / dtex is applied to a single cord under the conditions of JIS-L1017.

  Further, a bead filler is arranged on the outer periphery of the bead core embedded in the bead portion, the bead filler is made of a rubber composition having a JIS-A hardness of 90 or more, and the height of the bead filler is set to the tire cross-sectional height. It is preferable to set it as 32 to 42% of. As a result, the casing rigidity can be optimized and better steering stability can be ensured.

  On the other hand, it is preferable that the cap tread rubber layer of the tread portion is composed of a rubber composition having a JIS-A hardness of 68 to 72. As a result, good steering stability can be ensured without deteriorating riding comfort and increasing noise.

  The present invention can be applied to pneumatic radial tires having various flatness ratios, and has a remarkable effect particularly when applied to a pneumatic radial tire having a flatness ratio of 60% or less. .

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Two carcass layers 4 </ b> A and 4 </ b> B are mounted between the pair of bead portions 3 and 3. Each of these carcass layers 4A and 4B is composed of a plurality of organic fiber cords oriented in the tire radial direction. The carcass layer 4 </ b> A located inside the tire is wound up from the inside to the outside so as to wrap the bead core 5 and the bead filler 6 embedded in the bead portion 3. On the other hand, the end portion in the tire width direction of the carcass layer 4B located on the outer side of the tire is disposed on the outer side in the tire width direction with respect to the winding portion of the carcass layer 4A.

  On the outer peripheral side of the carcass layers 4A and 4B in the tread portion 1, two belt layers 7A and 7B are embedded over the entire circumference of the tire. These belt layers 7A and 7B include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. The reinforcing cords of the belt layers 7A and 7B are steel cords. The width of the first belt layer 7A counted from the carcass side is wider than the width of the second belt layer 7B. That is, the belt layer 7B has the narrowest width. The width W1 of the belt layer 7B is set to 88 to 92% of the tread development width TDW. The tread development width TDW is measured along the tread profile when the intersection of the extension of the tread profile and the profile extension of both sidewalls is P in the tire meridian cross section. This is the width between the points P and P. The narrowest belt layer width W1 is the width of the narrowest belt layer measured along the carcass layer in the tire meridian cross section.

  On the outer side in the tire radial direction of the belt layers 7A and 7B, a belt cover layer 8 made of an organic fiber cord extending in the tire circumferential direction is disposed so as to cover the entire surface of the belt layers 7A and 7B. The belt cover layer 8 includes a laminated portion 8a, 8a having a three-layer structure and a single layer portion 8b extending between the laminated portions 8a, 8a at portions corresponding to both edge portions of the belt layers 7A, 7B. I have. In other words, the belt cover layer 8 has a structure in which one full cover and two layer edge covers are laminated. The width W2 of each laminated portion 8a is set to 15 to 25 mm, preferably 17 to 22 mm. The width W2 of the laminated portion is the width of the laminated portion measured along the carcass layer in the tire meridian cross section.

  In the pneumatic radial tire described above, the width W1 of the narrowest belt layer 7B among the belt layers 7A and 7B is suppressed to 88 to 92% of the tread development width TDW, and then the belt layers 7A and 7B in the belt cover layer 8 are reduced. Laminated portions 8a having a three-layer structure are provided at portions corresponding to both edge portions, and the width W2 of each laminated portion 8a is set to 15 to 25 mm. That is, the belt layer 7B made of steel cord is set narrower than usual, and the edge portions of the belt layers 7A and 7B are reinforced intensively by the belt cover layer 8 made of organic fiber cord. For this reason, the binding force at the edge of the belt layer 7A, 7B is increased while avoiding an extreme increase in rigidity near the edge of the belt layer 7A, 7B, and as a result, good steering stability is ensured. In addition, an effect of reducing road noise can be obtained.

  Here, if the width W1 of the belt layer 7B is out of the above range, it becomes difficult to achieve both steering stability and road noise performance. Further, if the width W2 of each laminated portion 8a of the belt cover layer 8 is out of the above range, it becomes difficult to achieve both steering stability and road noise performance.

  In the pneumatic radial tire, an organic fiber cord having an intermediate elongation of 5.0% or less at 2.0 cN / dtex may be used for at least a part of the laminated portion 8 a of the belt cover layer 8. For example, a polyethylene terephthalate (PET) fiber cord may be adopted as such an organic fiber cord. Of course, a nylon fiber cord or the like can be used. When the organic fiber cord having the above physical properties is disposed in the laminated portion 8a of the belt cover layer 8, the binding force of the edge portions of the belt layers 7A and 7B is increased, and the medium frequency road noise can be effectively reduced.

  In the bead portion 3, the bead filler 6 is made of a rubber composition having a JIS-A hardness of 90 or more at 20 ° C., and the height H of the bead filler 6 is set to 32 to 42% of the tire cross-section height SH. Yes. When the JIS-A hardness of the rubber composition constituting the bead filler 6 is less than 90, the steering stability improving effect is insufficient. Further, if the height H of the bead filler 6 is out of the above range, the effect of improving the steering stability becomes insufficient.

  On the other hand, the cap tread rubber layer of the tread portion 1 is composed of a rubber composition having a JIS-A hardness of 68 to 72 at 20 ° C. Higher tread rubber layer hardness is advantageous for achieving high steering stability, but there is an upper limit from the viewpoint of riding comfort and noise.

  FIG. 2 shows a modification of the belt cover layer. In FIG. 2, the belt cover layer 8 has laminated portions 8a each having a three-layer structure at portions corresponding to both edge portions of the belt layers 7A and 7B. Here, the belt cover layer 8 has a structure in which a strip 9 including a plurality of organic fiber cords aligned in the longitudinal direction is spirally wound in the tire circumferential direction. In particular, each laminated portion 8a of the belt cover layer 8 has a structure in which the strips 9 are overlapped with each other shifted by about 3 mm in the width direction. As a result, the belt cover layer 8 gradually changes from the single layer portion 8b to the laminated portion 8a. The width W2 of the laminated portion 8a having the three-layer structure is 15 to 25 mm. When such a winding structure is formed, the binding force of the edge portions of the belt layers 7A and 7B is increased, and the medium frequency road noise can be effectively reduced.

  In a pneumatic radial tire having a belt layer made of steel cord with a tire size of 225 / 50R17, the ratio of the minimum width of the belt layer to the tread development width, the material of the organic fiber cord constituting the belt cover layer, and the lamination of the belt cover layer Comparative Examples 1 to 7 in which the structure, the width of the laminated portion of the belt cover layer, the JIS-A hardness of the bead filler, the ratio of the bead filler height to the tire cross-section height, and the JIS-A hardness of the tread rubber layer were varied. Tires of Examples 1 to 8 were produced.

  Each belt cover layer has a jointless winding structure. Regarding the laminated structure of the belt cover layer, the case where one full cover and one edge cover are laminated is indicated by “JEF”, and the case where one full cover and two edge covers are laminated “ 2JEJF ”.

  About these test tires, road noise characteristics and steering stability were evaluated by the following test methods, and the results are shown in Tables 1 and 2.

Road noise characteristics:
Each test tire is mounted on a wheel with a rim size of 17 x 5.5 JJ, mounted on a 3000 cc domestic FR vehicle, the air pressure is 230 kPa, and the in-vehicle noise is measured while driving on rough roads. Road noise was detected. The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. A larger index value means a greater road noise reduction effect.

Steering stability:
Each test tire was mounted on a wheel with a rim size of 17 × 5.5 JJ, mounted on a 3000 cc domestic FR vehicle, the air pressure was set to 230 kPa, and a sensory evaluation test was conducted at a test course by a professional evaluation driver. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the steering stability.

  As can be seen from these Tables 1 and 2, the tires of Examples 1 to 8 were found to have improved effects on both road noise characteristics and steering stability as compared with Comparative Example 1. On the other hand, in the tires of Comparative Examples 1 to 7, road noise characteristics and steering stability could not be improved at the same time.

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. It is sectional drawing which shows the modification of a belt cover layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4A, 4B Carcass layer 5 Bead core 6 Bead filler 7A, 7B Belt layer 8 Belt cover layer 8a Laminated part 8b Single layer part 9 Strip

Claims (7)

In a pneumatic radial tire in which a carcass layer is mounted between a pair of bead portions and a plurality of belt layers are provided on the outer peripheral side of the carcass layer in the tread portion, the width of the narrowest belt layer among the belt layers is defined as a tread deployment width. A belt cover layer made of an organic fiber cord is disposed on the outer side in the tire radial direction of the belt layer so as to cover the entire surface of the belt layer, and both belt layers in the belt cover layer are disposed. A pneumatic radial tire in which a laminated portion having a three-layer structure is provided at a portion corresponding to the edge portion, and the width of each laminated portion is set to 15 to 25 mm. The pneumatic radial tire according to claim 1, wherein the width of each laminated portion of the belt cover layer is set to 17 to 22 mm. The belt cover layer has a structure in which a strip made of a plurality of organic fiber cords is spirally wound in the tire circumferential direction, and each laminated portion of the belt cover layer has a structure in which the strips are shifted and overlapped in the width direction. The pneumatic radial tire according to claim 1 or claim 2. The pneumatic radial according to any one of claims 1 to 3, wherein an intermediate elongation at 2.0 cN / dtex of the organic fiber cord constituting at least a part of the laminated portion of the belt cover layer is 5.0% or less. tire. The pneumatic radial tire according to any one of claims 1 to 4, wherein the organic fiber cord constituting at least a part of the laminated portion of the belt cover layer is a polyethylene terephthalate fiber cord. A bead filler is disposed on the outer periphery of the bead core embedded in the bead portion, the bead filler is made of a rubber composition having a JIS-A hardness of 90 or more, and the height of the bead filler is set to a tire cross-sectional height of 32. The pneumatic radial tire according to any one of claims 1 to 5, wherein the pneumatic radial tire is -42%. The pneumatic radial tire according to any one of claims 1 to 6, wherein the cap tread rubber layer of the tread portion is made of a rubber composition having a JIS-A hardness of 68 to 72.

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