JP2009166781A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lighten the weight of a tire while capable of suppressing the occurrence of a belt separation failure resulting from the deterioration of coating rubber at a belt ply end. <P>SOLUTION: A third belt ply 18C narrower than a first belt ply 18A and a second belt ply 18B is disposed between the first belt ply 18A and a carcass 14 on the side of a width end of the first belt ply 18A forming a main crossing layer, so that the coating rubber 22A at the width end (the ply end of the first belt ply 18A) of the innermost belt ply of the main crossing layer is sufficiently spaced away from a tire inner surface, thereby capable of suppressing the oxigen-deterioration of the coating rubber 22A caused by oxygen in the tire. In addition, the third belt ply 18C secures rigidity in the vicinity of the end of the main crossing layer and lighten tire weight while suppressing belt separation resulting from the oxygen-deterioration of the coating rubber 22A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire capable of improving the durability of a belt.

Among pneumatic radial tires, in pneumatic radial tires for light trucks, the internal pressure is set higher (about twice) compared to passenger car tires. In many cases, the coating rubber at the end of the innermost belt ply forming the main crossing layer is easily deteriorated, which is one factor of belt separation failure with the deteriorated coating rubber portion as a core.
That is, since the coating rubber becomes brittle when it deteriorates, the coating rubber is liable to crack, and a large stress acts on the belt ply end of the main crossing layer (stress concentration) during running, causing cracks with the belt ply end as the core. It progresses along the surface, leading to a belt separation failure.
In recent years, the demand for light weight and low fuel consumption for tires has become increasingly severe due to global environmental problems.

  Radial tires include tires with a main crossing layer consisting of two steel belts and tires with a main crossing layer consisting of three or more steel belts, but tires using three or more steel belts are: There is a problem of weight compared to a tire using a two-layer steel belt. On the other hand, a tire using a two-layer steel belt is lighter than a tire using a three-layer or more steel belt, but because the rigidity near the belt end is low and the movement is large, There is a problem that a large stress is likely to act on the rubber near the belt end and the above-described belt separation is likely to occur.

In addition, although there exists a thing of patent document 1 as a technique which suppresses deterioration of the coating rubber of a ply end, it is the structure which arrange | positions a polymer film between a carcass and an inner liner, and a main crossing layer is two layers. The rigidity in the vicinity of the belt end is insufficient.
JP-A-9-48209

  The present invention has been made to solve the above-described problem, and provides a pneumatic radial tire capable of suppressing the occurrence of a belt separation failure due to deterioration of the coating rubber at the belt ply end and reducing the weight of the tire. The purpose is to provide.

  The pneumatic radial tire according to claim 1 includes a carcass straddling in a toroidal shape between one bead portion and the other bead portion, and a belt disposed on the outer side in the tire radial direction of the carcass, The belt is continuously arranged from one tread end side to the other tread end side on the outer side in the tire radial direction of the carcass, and a plurality of first cords inclined with respect to the tire equatorial plane are covered with a coating rubber. The first belt ply and the first belt ply are continuously disposed on the outer side in the tire radial direction of the first belt ply from one tread end side to the other tread end side, and the first cord is relative to a tire equatorial plane. A second belt ply formed by coating a plurality of second cords inclined in opposite directions with a coating rubber and paired with the first belt ply to form a main crossing layer; One belt ply is disposed between the first belt ply and the carcass on the width direction end side, and is formed to be narrower than the first belt ply and the second belt ply. The third belt ply includes a third belt ply in which the third cord is coated with a coating rubber. The width of the third belt ply is the width of the first belt ply. It is characterized by being set within a range of 10 to 20%.

Next, the operation of the pneumatic radial tire according to claim 1 will be described.
In the pneumatic radial tire according to claim 1, a main crossing layer is formed by the first belt ply and the second belt ply having different cord directions, and the crown portion of the carcass is reinforced. Further, between the first belt ply and the carcass, the first belt ply and the third belt ply narrower than the second belt ply on the widthwise end side of the first belt ply. Is secured, the rigidity in the vicinity of the end portion of the main crossing layer is ensured.

Here, in a conventional tire in which a main crossing layer is formed by a plurality of belt plies arranged continuously from one tread end side to the other tread end side, the innermost belt ply in the tire width direction The coating rubber at the end is close to the inner surface of the tire, and the coating rubber is easily deteriorated by oxygen from inside the tire. In the present invention, the innermost first belt ply forming the main crossing layer is the belt Since the third belt layer is disposed between the end and the carcass, the end of the innermost first belt ply constituting the main crossing layer is compared with the conventional tire inner peripheral surface. Is separated by the thickness of the third belt layer, making it difficult for oxygen in the tire to reach the coating rubber at the end of the first belt ply constituting the main crossing layer. Oxygen inferiority of rubber It is possible to suppress the conventional contrast.
In the pneumatic radial tire of the present invention, the belt has a three-layer structure in the vicinity of the end portion, and the rigidity in the vicinity of the belt end is increased in comparison with the tire in which the main crossing layer is formed by only two belt plies. The stress acting on the rubber can be reduced by suppressing the movement near the end, and the belt separation occurs with cracks as the core due to the deterioration of the coating rubber at the ply end of the innermost first belt ply constituting the main crossing layer. Can be suppressed.

  Since the third belt ply is not continuously arranged from one tread end side to the other tread end side, the three belts continuous from one tread end side to the other tread end side are arranged. The belt of the present invention is lighter than the conventional belt in which the main crossing layer is formed of the ply.

  If the width of the third belt ply is less than 10% of the width of the first belt ply, the rigidity in the vicinity of the end in the width direction of the main crossing layer is not sufficient, and the width of the third belt ply is the first width. If it exceeds 20% of the width of the belt ply, the effect of securing the rigidity in the vicinity of the end portion in the width direction of the main crossing layer will reach its peak, resulting in wasted material and the advantage of reducing the tire weight. Therefore, the width of the third belt ply is set within a range of 10 to 20% of the width of the first belt ply.

  According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, the outer end in the tire width direction of the third belt ply is the first radial width when viewed in a cross section along the tire rotation axis. The belt ply is arranged within a range of 15 mm from the outer end in the tire width direction toward the inner side in the tire width direction and up to 5 mm toward the outer side in the tire width direction.

Next, the operation of the pneumatic radial tire according to claim 2 will be described.
When the outer end in the tire width direction of the third belt ply is located at a position exceeding 15 mm inward in the tire width direction with respect to the outer end in the tire width direction of the first belt ply, the third belt ply is Even if it is arranged between the belt ply and the carcass, the outer end in the tire width direction of the first belt ply is bent toward the carcass, that is, the inner surface of the tire during vulcanization molding, and the completed pneumatic radial tire In this case, oxygen in the tire is likely to reach the coating rubber at the outer end in the tire width direction of the first belt ply.

  On the other hand, when the outer end in the tire width direction of the third belt ply is located at a position exceeding 5 mm outward in the tire width direction of the first belt ply with respect to the outer end in the tire width direction of the first belt ply, The effect reaches its peak against suppression of deterioration of the coating rubber at the end of one belt ply and reinforcement in the vicinity of the end of the main crossing layer in the width direction, and further improvement of the effect cannot be expected. Therefore, the material is wasted and the merit of reducing the weight of the tire is reduced.

  According to a third aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the thickness of the third belt ply is 80 to 120% with respect to the thickness of the first belt ply. It is set within the range of.

Next, the operation of the pneumatic radial tire according to claim 3 will be described.
If the thickness of the third belt ply is less than 80% of the thickness of the first belt ply, the effect of suppressing the deterioration of the coating rubber at the end of the first belt ply is not sufficient.
On the other hand, when the thickness of the third belt ply exceeds 120% with respect to the thickness of the first belt ply, the merit of weight reduction becomes small.
Therefore, it is preferable to set the thickness of the third belt ply within a range of 80 to 120% with respect to the thickness of the first belt ply.

  A fourth aspect of the present invention is the pneumatic radial tire according to any one of the first to third aspects, wherein the pneumatic radial tire is a small truck tire.

Next, the operation of the pneumatic radial tire according to claim 4 will be described.
The pneumatic radial tire according to claim 4 is a tire for a light truck, and can function as a tire to the maximum by being mounted on a light truck.
Also, light truck tires have higher internal pressure than passenger car tires, and the coating rubber at the end of the belt ply is likely to deteriorate, but the structure of the present invention suppresses the deterioration of the coating rubber. Can do.

  As described above, since the pneumatic radial tire of the present invention has the above-described configuration, it is possible to suppress the occurrence of a belt separation failure due to deterioration of the coating rubber at the belt ply end, and to reduce the weight of the tire. It has an excellent effect.

One embodiment of a pneumatic radial tire of the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the pneumatic radial tire 10 of the present embodiment is a small truck tire, and includes a carcass 14 straddling a toroid between one bead portion 12 and the other bead portion 12. Both ends of the carcass 14 are folded around the bead core 16 from the tire inner side to the outer side.

As shown in FIGS. 1 and 2, a belt 18 is disposed outside the carcass 14 in the tire radial direction.
The belt 18 of the present embodiment is continuously arranged on the outer side in the tire radial direction of the carcass 14 from one tread end side to the other tread end side, and a plurality of first cords inclined with respect to the tire equatorial plane CL. A first belt ply 18A in which 20A is coated with a coating rubber 22A; and a first cord ply 18A continuously disposed on the outer side in the tire radial direction of the first belt ply 18A from one tread end side to the other tread end side. Is formed by covering a plurality of second cords 20B inclined in the opposite direction with respect to the tire equatorial plane CL with a coating rubber 22B, and forming a main crossing layer in pairs with the first belt ply 18A. The second belt ply 18B is disposed between the first belt ply 18A and the carcass 14 on the width direction end portion side of the first belt ply 18A, and the first belt ply 1 A and a belt belt that is formed to be narrower than the second belt ply 18B, and includes only a total of three types of belt plies, including a third belt ply 18C in which a plurality of third cords 20C are covered with a coating rubber 22C. Has been.

In this belt 18, the first belt ply 18A is the widest belt ply.
The first cord 20A, the second cord 20B, and the third cord 20C of the present embodiment are steel cords.

Here, the width W3 of the third belt ply 18C is preferably set within a range of 10 to 20% of the width W1 of the first belt ply.
The position of the outer end in the tire width direction of the third belt ply 18C is within a range of 15 mm toward the inner side in the tire width direction and up to 5 mm toward the outer side in the tire width direction with respect to the outer end in the tire width direction of the first belt ply 18A. It is preferable to arrange in the inside.
As shown in FIG. 3, the thickness t3 of the third belt ply 18C is preferably set within a range of 80 to 120% with respect to the thickness t1 of the first belt ply 18A.
As shown in FIG. 1, in the present embodiment, the third belt ply 18C is disposed closer to the tire equatorial plane than the outer end in the tire width direction of the first belt ply 18A.
An inner liner 24 is provided on the inner side of the carcass 14 as usual, and a tread rubber 26 is provided on the outer side in the radial direction of the belt 18.

(Function)
Next, the operation of the pneumatic radial tire 10 of this embodiment will be described.
In the pneumatic radial tire 10 of the present embodiment, the third belt ply 18C is disposed between the end portion in the width direction of the main crossing layer, that is, the ply end of the innermost first belt ply 18A and the carcass 14. Since the distance from the tire inner peripheral surface is sufficiently separated, the oxygen in the tire hardly reaches the coating rubber 22A at the ply end of the first belt ply 18A constituting the main crossing layer. Oxygen deterioration of the coating rubber 22A at the ply end of the first belt ply 18A constituting the crossing layer can be suppressed.

  Light truck tires have a higher internal pressure than passenger car tires, and oxygen in the air filled in the tires can easily permeate the rubber. By applying the present invention to light truck tires, The effect of suppressing the deterioration of the coating rubber 22A at the end portion in the width direction of the innermost first belt ply 18A in the layer can be particularly exhibited.

  In the pneumatic radial tire 10 of the present embodiment, a main crossing layer is formed by the first belt ply 18A and the second belt ply 18B having different cord directions, and the main crossing layer forms a crown portion of the carcass 14. It is reinforced. Further, between the first belt ply 18A and the carcass 14, the first belt ply 18A and the second belt ply 18B are narrower than the first belt ply 18A and the second belt ply 18B. Since the third belt ply 18C is arranged, the rigidity in the vicinity of the width direction end of the main crossing layer, that is, the rigidity in the vicinity of the belt end is improved.

  The pneumatic radial tire 10 of the present embodiment has higher rigidity near the belt end compared to a tire in which a main crossing layer is formed by only two belt plies, and therefore the movement near the end of the belt 18 during traveling is increased. The stress acting on the rubber can be reduced by suppressing the belt, and the belt separation with the crack caused by the deterioration of the coating rubber 22A at the innermost belt ply of the main crossing layer, that is, the ply end of the first belt ply 18A as a core. Can be suppressed.

  Since the third belt ply 18C is not continuous from one tread end side to the other tread end side like the first belt ply 18A and the second belt ply 18B, The weight is reduced as compared with a conventional belt in which a main crossing layer is formed by three belt plies continuous from the end side toward the other tread end side.

  Here, if the width W3 of the third belt ply 18C is less than 10% of the width of the main crossing layer, that is, the width W1 of the first belt ply 18A, the rigidity in the vicinity of the end of the main crossing layer in the width direction is sufficient. If the width W3 of the third belt ply 18C exceeds 20% of the width W1 of the first belt ply 18A, the effect of securing the rigidity in the vicinity of the end of the main crossing layer in the width direction has reached its peak. This wastes money and reduces the benefits of tire weight reduction.

Further, the outer end in the tire width direction of the third belt ply 18C exceeds 15 mm inward in the tire width direction with respect to the end in the width direction of the main crossing layer, that is, the outer end in the width direction of the first belt ply 18A. In the position, even if the third belt ply is disposed between the first belt ply and the carcass, the outer end in the tire width direction of the first belt ply 18A is the carcass side, that is, the tire during vulcanization molding. As a result, the oxygen in the tire tends to reach the coating rubber 22A at the outer end in the tire width direction of the first belt ply 18A.
On the other hand, when the outer end in the tire width direction of the third belt ply 18C is located at a position exceeding 5 mm outward in the tire width direction of the first belt ply 18A, the coating rubber 22A of the ply end of the first belt ply 18A The effect reaches its peak against suppression of deterioration and reinforcement in the vicinity of the end in the width direction of the main crossing layer, and further improvement of the effect cannot be expected.

  Furthermore, if the thickness t3 of the third belt ply 18C is less than 80% of the thickness t1 of the first belt ply 18A, the effect of suppressing the deterioration of the coating rubber 22A at the ply end of the first belt ply 18A is sufficient. Not. On the other hand, when the thickness t3 of the third belt ply 18C exceeds 120% with respect to the thickness t1 of the first belt ply 18A, the merit of weight reduction becomes small.

[Other Embodiments]
The first cord 20A, the second cord 20B, and the third cord 20C of the above embodiment are steel cords having the same thickness. However, the present invention is not limited to this, and each cord is aromatic polyamide or the like. Organic fiber cords may be used.

[Test example]
In order to confirm the effect of the present invention, two types of conventional tires and one type of tire according to the present invention were prepared, and the belt durability performance was compared.
In the test, a tire (LT 205 / 65R16) is mounted on a rim (16 × 5.5 JJ), and the tire is filled with oxygen (internal pressure 600 kPa) and left in a constant temperature chamber at 60 ° C. for 2 weeks. Oxygen was removed and air was filled (internal pressure 600 kPa), and a drum test was performed with an indoor drum tester.
The drum test was performed under the condition of a load of 1030 kg and a speed of 100 km, and the travel distance when the tire failed (belt separation) was examined. The evaluation is an index display in which the traveling distance of Conventional Example 1 is 100, and the larger the index, the better the belt durability.

The test tire is described below.
Conventional Example 1: The belt has a three-layer structure, and the width and thickness (index) are as described in Table 1 below.
Conventional Example 2: The belt has a two-layer structure, and the width and thickness (index) are as described in Table 1 below.
Example: The belt is the structure of the present invention described in the embodiment, and the width and thickness (index) are as described in Table 1 below.

試験の結果から、本発明の適用された実施例のタイヤは、従来例１と同等のベルト耐久性を確保しつつ、軽量化が図られていることが分かる。

From the test results, it can be seen that the tire of the example to which the present invention is applied is lighter while ensuring the belt durability equivalent to that of the conventional example 1.

1 is a cross-sectional view of a pneumatic radial tire according to an embodiment of the present invention. It is a top view of a belt and a carcass. It is sectional drawing of a tread part (3-3 line cross section of FIG. 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic radial tire 12 Bead part 14 Carcass 16 Bead core 18 Belt 18A 1st belt ply 18B 2nd belt ply 18C 3rd belt ply 20A 1st cord 20B 2nd cord 20C 3rd cord 22A Coating rubber 22B Coated rubber 22C Coated rubber CL Tire equator

Claims (4)

A carcass straddling a toroid between one bead portion and the other bead portion, and a belt disposed on the outer side in the tire radial direction of the carcass,
The belt is continuously arranged on the outer side in the tire radial direction of the carcass from one tread end side to the other tread end side, and a plurality of first cords inclined with respect to the tire equatorial plane are covered with a coating rubber. The first belt ply and the first belt ply are continuously disposed on the outer side in the tire radial direction of the first belt ply from one tread end side to the other tread end side, and the first cord is a tire equatorial plane. A second belt ply formed by coating a plurality of second cords inclined in opposite directions with a coating rubber and forming a main crossing layer in pairs with the first belt ply; The belt ply is disposed between the first belt ply and the carcass on the width direction end side, and is formed to be narrower than the first belt ply and the second belt ply. 3 of the code and the third belt ply coated with coating rubber, is composed only of a total of three kinds of the belt ply,
The pneumatic radial tire according to claim 1, wherein a width of the third belt ply is set in a range of 10 to 20% of a width of the first belt ply.   When viewed in a cross-section along the tire rotation axis, the outer end in the tire width direction of the third belt ply is 15 mm from the outer end in the tire width direction of the first belt ply to the inner side in the tire width direction. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is arranged in a range of up to 5 mm outward.   The air according to claim 1 or 2, wherein a thickness of the third belt ply is set in a range of 80 to 120% with respect to a thickness of the first belt ply. Entering radial tire.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the pneumatic radial tire is a light truck tire.

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