JP5288543B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire (hereinafter also simply referred to as “tire”), and more particularly to a pneumatic radial tire according to an improvement in a carcass ply structure.

  Conventionally, the carcass of a relatively small pneumatic radial tire for a passenger car is often composed of one layer of carcass ply. However, due to the recent increase in size of tires, the carcass ply may be composed of two layers of carcass plies. It is getting more.

Conventionally, run-flat tires that can safely travel a fixed distance even after puncturing are widely known. As such a run flat tire, for example, a side reinforcing type tire in which a hard rubber layer having a crescent cross-sectional shape is arranged on a tire sidewall portion is known (for example, Patent Document 1). In this type of run-flat tire, when the tire is punctured and becomes zero pressure, a crescent-shaped hard rubber layer disposed on the sidewall portion runs while supporting the load of the vehicle.
Japanese Patent Application Laid-Open No. 2000-309211

  With today's flattening and heightening of tires, the side wall part where the flexible zone has become smaller is the curb of the shoulder of the road, the road fence fixed on the center line of the road or on the pedestrian crossing with bolts or adhesive, There is an increasing number of failures that contact the so-called cat's eye and damage the internal carcass cord, causing it to puncture or generate a pneumatic lobe. In addition, such a failure could not be avoided even in the above-described side reinforcing type run flat tire.

  As a means of solving such problems, there are methods for increasing the total strength of the carcass by increasing the number of cords to be inserted into the carcass ply or increasing the total decitex per cord. Then, the problem that it leads to deterioration of rolling resistance by the increase in cost or the weight of a tire arises.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic radial tire that solves the above problems and has improved side cut resistance without excessively increasing the total carcass strength.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above object can be achieved by improving the ply structure of the carcass, and has completed the present invention.

That is, the pneumatic radial tire of the present invention has a carcass composed of a radial cord layer extending in a toroidal shape across a pair of left and right bead portions as a skeleton, and a belt and a tread are sequentially laminated on the outer side in the radial direction of the crown portion of the carcass. In a pneumatic radial tire in which the carcass is wound up around a bead core provided in the bead portion,
The carcass has a two-layer laminated ply structure, and the value of the product D1 × Ec1 of the total decitex D1 per cord and the number of driven Ec1 per unit width of the cord of the carcass ply inside the crown portion radial direction is A value of (D1 × Ec1) that is greater than the value of the product D2 × Ec2 of the total decitex D2 per cord and the number Ec2 of driving per unit width of the carcass ply cord on the outer side in the crown radial direction Is 1.5 times or more (excluding 1.5 times) the value of (D2 × Ec2).

  In the pneumatic radial tire of the present invention, the cord forming the carcass ply is preferably a polyester fiber, a cellulosic fiber, or a polyketone fiber, and further has a belt reinforcing layer on the outer side in the tire radial direction of the belt. It is preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic radial tire which improved the side cut resistance can be provided, without making carcass total strength excessive.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 is a half sectional view of an example of a pneumatic radial tire of the present invention. A pneumatic radial tire 10 according to the present invention includes a carcass 2 formed of a radial cord layer extending in a toroidal shape across a pair of left and right bead portions 11 as a skeleton, a belt 3 on the outer side in the radial direction of the crown portion 12 of the carcass 2, and its outer side Is provided with a belt reinforcing layer 4 and a tread 5 disposed on the outer side thereof.

  In the present invention, the carcass 2 has a two-layer laminated ply structure composed of carcass plies 2a and 2b, and the total decitex D1 and unit width of the cord of the carcass ply 2a on the inner side in the radial direction of the crown portion 12 The value of the product D1 × Ec1 with the number of hits Ec1 is the product of the total decitex D2 per cord and the number of hits Ec2 per unit width of the cord of the carcass ply 2b on the outer side in the radial direction of the crown 12 It is important that it is greater than the value of Ec2. By satisfying D1 × Ec1> D2 × Ec2, side cut resistance can be improved by improving the strength of the carcass ply 2a that is turned outside the tire after being folded back by the bead core 1. Preferably, the value of D1 × Ec1 is 1.5 times or more the value of D2 × Ec2.

  FIG. 2 is a half sectional view of an example of a pneumatic radial tire according to another embodiment of the present invention. The pneumatic radial tire 20 of the present invention has a carcass 2 made of a radial cord layer extending in a toroidal shape across a pair of left and right bead portions 11 as a skeleton, a belt 3 on the outer side of the crown portion 12 of the carcass 2 in the radial direction, and the outer side thereof. Belt reinforcement layer 4 and a tread 5 arranged on the outer side of the belt reinforcing layer 4, and the meridional section has a crescent shape along the inner surface of the carcass 2 over the entire region of both sidewall portions 13 or substantially the entire region. This is a run flat tire provided with the side reinforcing rubber layer 6. Even in this pneumatic radial tire, particularly a low flat run-flat tire, it is important to satisfy D1 × Ec1> D2 × Ec2. By satisfying the above conditions, side-cut resistance is exhibited at normal internal pressure, and the carcass ply 2a around the bead that increases the strain during run-flat running plays a role in strengthening the run-flat durability. Can be improved.

  In the pneumatic radial tire of the present invention, the cord type forming the carcass ply is not particularly limited, but may be a polyester fiber such as polyethylene terephthalate (PET), a cellulosic fiber such as rayon or lyocell, or a polyketone fiber. preferable.

  In the pneumatic radial tire of the present invention, it is preferable to dispose the belt reinforcing layer 4 on the outer side in the tire radial direction of the belt. In FIGS. 1 and 2, the belt reinforcement layer 4 is disposed so as to cover the entire belt 3, but the belt reinforcement layer 4 may be disposed so as to cover only both end portions of the belt 3. The belt 3 is usually composed of a rubber layer of a cord extending at an inclination with respect to the tire equatorial plane, preferably a rubberized layer of at least one steel cord. The two belt layers in the illustrated example are laminated so that the respective cords constituting the belt layer cross each other to constitute the belt 3.

  The pneumatic radial tire of the present invention relates to an improvement in the carcass ply structure, and other structures and materials are not particularly limited, and known structures and materials may be appropriately employed. it can.

  For example, 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. Further, in the pneumatic tire of the present invention, as the gas filled in the tire, normal or changed oxygen partial pressure, or inert gas such as nitrogen can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Example 1, Reference Example 1-1, Reference Example 1-2, Comparative Example 1, Conventional Example 1)
Test tires were prepared from carcass plies having the tire size of 225 / 45R17 and having the structure shown in FIG. The evaluation method is as follows.

(Side cut resistance)
Side cut resistance is achieved by causing each test tire mounted on an actual vehicle to collide with a specific square steel material (110 mm × 110 mm × 1000 mm) at an approach speed of 10 km / h and an entrance angle of 25 °, and gradually reducing the tire internal pressure. The internal pressure at which air leakage due to the cut occurred was measured, and the index was displayed with the tire of Conventional Example 1 as 100. The index indicates that the larger the value, the better the side cut resistance. The results are shown in Table 1.

(Economic)
The economic efficiency is compared with that of Example 1, Reference Example 1-1, Reference Example 1-2, and Comparative Example 1, based on the total strength of the carcass of Conventional Example 1 (the sum of D1 × Ec1 and D2 × Ec2). The case where it was equal was evaluated as “equivalent”, the case where it was superior as “good”, and the case where it was inferior as “bad”. The results are also shown in Table 1.

(Reference Examples 2-1 to 2-3, Comparative Example 2, Conventional Example 2)
Test tires having a tire size of 225 / 60R17 having the structure shown in FIG. 2 were prepared using carcass plies having specifications shown in Table 2 below, and run-flat durability and economic efficiency were evaluated. The evaluation method is as follows.

(Run flat durability)
Each test tire was fitted with a rim of rim size 7JJ × 17, mounted on the right front wheel of the FR vehicle with an internal pressure of 0 kPa, and traveled at a speed of 80 km / h. Travel distance (km) until the tire was destroyed In comparison, the tire of Conventional Example 2 was displayed as an index with 100 as the tire. The higher the number, the better the result. The load applied to the tire during running was 5.1 kN. The results are shown in Table 2 below.

  From Table 1, it can be seen that the tire of the present invention has improved side cut resistance without excessively increasing the total carcass strength. Further, from Table 2, it was confirmed that the run-flat tire can achieve both run-flat durability and riding comfort at normal internal pressure.

It is a half sectional view of an example of the pneumatic radial tire of the present invention. It is a half sectional view of the other example of the pneumatic radial tire of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 4 Belt reinforcement layer 5 Tread 6 Side reinforcement rubber layer 10 Pneumatic radial tire 11 Bead part 12 Crown part 13 Side wall part 20 Pneumatic radial tire

Claims (3)

As skeleton carcass consisting of radial cord layer toroidally extending over a pair of bead portions, Ri Na are sequentially stacked and a belt and tread crown portion radial direction outer side of the carcass, the carcass the bead portion In the pneumatic radial tire rolled up around the bead core provided in
The carcass has a two-layer laminated ply structure, and the value of the product D1 × Ec1 of the total decitex D1 per cord and the number of driven Ec1 per unit width of the cord of the carcass ply inside the crown portion radial direction is , code of the crown portion radial direction outer side of the carcass ply, than the value of the product D2 × Ec2 the total decitex D2 and implantation number per unit width Ec2 per one cord rather large, and the (D1 × Ec1) A pneumatic radial tire characterized in that the value is 1.5 times or more (excluding 1.5 times) the value of (D2 × Ec2) .   The pneumatic radial tire according to claim 1, wherein the cord forming the carcass ply is a polyester fiber, a cellulosic fiber, or a polyketone fiber.   The pneumatic radial tire according to claim 1 or 2, further comprising a belt reinforcing layer on an outer side in the tire radial direction of the belt.

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