JP2013199189A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight pneumatic radial tire without reducing durability.SOLUTION: A pneumatic radial tire includes: a carcass formed of at least one carcass layers formed between a pair of right and left bead cores in a toroidal shape; a tread part arranged outside a crown area of the carcass in a tire radial direction to form a tread portion; and a belt arranged between the tread part and the crown area of the carcass and formed of at least two belt layers. Each of the first and second belt layers of the belt is obtained by embedding steel cords 10 each comprising a core formed by arranging in parallel two core filaments 11 without twisting and N(2≤N≤4) sheath filaments 12 twisted around the core in coating rubber along a belt width direction in parallel. When a diameter of the core filament 11 is d1, and a diameter of the sheath filament 12 is d2, d1>d2 is satisfied.

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 that achieves weight reduction without reducing durability.

  At present, a belt generally used as a reinforcing member for a carcass forming a skeleton of a radial tire for a passenger car, particularly a reinforcing member for a crown portion of a carcass, is mainly a steel cord (hereinafter simply referred to as “ Two or more steel belt layers made of a rubberized layer of “cord” are used, and the steel cords in these belt layers intersect each other.

  In recent years, the importance of environmental performance has increased, and there is an increasing need for weight reduction in rubber articles and tires using steel cords as reinforcing members. One technique for reducing the weight of the tire is to reduce the amount of rubber used in the belt treat and to make the belt thinner. However, if the amount of rubber used is reduced, the distance between the cords of the first belt layer and the second belt layer is shortened, so that the rubber peeling starting from the cord end at the end in the belt width direction easily propagates between the cords. In other words, so-called belt edge separation (BES) is likely to occur, and durability is reduced. As a method for improving this BES, a method of making the rubber at the end of the belt thicker than usual is known, but naturally, it increases the weight, which is contrary to the intended weight reduction of the tire. .

  As a technique for reducing the weight of the tire other than reducing the amount of rubber used in the belt treat, it is conceivable to reduce the amount of steel used, for example, to reduce the number of driven steel cords. However, if the number of steel cords to be driven is reduced, the rigidity of the belt is lowered, which is not preferable. Under such circumstances, many proposals have been made regarding weight reduction and durability improvement of tires. For example, Patent Document 1 proposes a steel cord having an N (N = 2 to 5) + M (M = 1 to 3) structure and the number of filaments N ≧ M for the purpose of reducing the weight of the tire. Patent Document 2 proposes a steel cord having a 2 + 3 structure for the purpose of improving the durability of the belt. Patent Document 3 proposes a steel cord having a 1 × (1 × 2 + N) structure with the same filament diameter for the purpose of improving fatigue resistance.

JP 2001-98480 A Japanese Utility Model Publication No. 3-128689 Japanese Patent Laid-Open No. 5-156581

  However, even with the steel cord described in Patent Document 1, it is difficult to say that the demand for reducing the weight of tires required today is sufficiently satisfied, and a technique for further weight reduction is required. In addition, although the steel cords described in Patent Documents 2 and 3 have improved durability by increasing the permeability of rubber to the steel cord, the weight reduction of tires has not been studied.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire that achieves weight reduction without reducing durability.

  As a result of intensive studies on the structure of the belt in order to solve the above problems, the present inventor has confirmed that the diameter of the core filament and the sheath filament in the steel cord having a 1 × 2 + N structure satisfies a predetermined relationship, thereby It has been found that the weight of the belt treat can be reduced while maintaining the distance, and the present invention has been completed.

That is, the pneumatic radial tire of the present invention is disposed on the outer side in the tire radial direction of the carcass formed of at least one carcass layer straddling a toroidal shape between a pair of left and right bead cores, and in the crown region of the carcass. In a pneumatic radial tire comprising a tread portion forming a portion, and a belt composed of at least two belt layers disposed between the tread portion and the crown region of the carcass to form a reinforcing portion,
The first belt layer of the first layer and the second belt layer of the second layer of the belt both have a core formed by twisting two filaments, and N (2 ≦ N ≦ 4) twisted around the core. ) When a steel cord comprising a sheath filament is juxtaposed in the belt width direction and embedded in a coating rubber, and when the diameter of the core filament is d1 and the diameter of the sheath filament is d2, d1 > D2.

  In the present invention, the number of the sheath filaments is preferably three. In the present invention, it is preferable that the d1 is 0.16 to 0.28 mm, and the d2 is 0.12 to 0.24 mm. Furthermore, in the present invention, the gauge of the rubber layer between the steel cords of the first belt layer and the second belt layer at the end portion of the second belt layer is preferably larger than the gauge at the tire center. Furthermore, in the present invention, the thickness of the belt layer is preferably 0.95 to 1.35 mm.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic radial tire which implement | achieved weight reduction without reducing durability can be provided.

It is a half sectional view of a suitable example of the pneumatic radial tire of the present invention. It is a comparison figure of the diameter of a steel cord, (a) and (b) express the case where d1 = d2, and (c)-(h) express the case where d1> d2. FIG. 3 is an enlarged partial cross-sectional view showing the vicinity of an end portion of a belt layer according to a preferred embodiment of the pneumatic radial tire of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, the one-side sectional view of the suitable example of the pneumatic radial tire of this invention is shown. The illustrated tire includes a tread portion 1 that is disposed in a crown region of the carcass and forms a ground contact portion, and a pair of sidewall portions 2 that extend continuously inward in the tire radial direction on both sides of the tread portion 1; A bead portion 3 is provided on the inner peripheral side of each sidewall portion 2.

  The tread portion 1, the sidewall portion 2, and the bead portion 3 are reinforced by a carcass 4 including a single carcass layer extending in a toroidal shape from one bead portion 3 to the other bead portion 3. The tread portion 1 has at least two layers disposed in the tire radial direction outside of the crown region of the carcass 4, which will be described in detail below, and in the illustrated example, two layers of the first belt layer 5a and the second belt layer 5b. It is reinforced by a belt consisting of Here, a plurality of carcass layers of the carcass 4 may be used, and an organic fiber cord extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 ° can be suitably used.

  In the present invention, the first belt layer 5a and the second belt layer 5b are both a core in which two core filaments are twisted, and N (2 ≦ N ≦ 4) wires twisted around the core, preferably Is a steel cord comprising three sheath filaments juxtaposed in the belt width direction and embedded in the coating rubber, and when the core filament diameter is d1 and the sheath filament diameter is d2, d1> d2 It is. FIGS. 2A to 2H are comparison diagrams of steel cord diameters. FIGS. 2A and 2B show the case of d1 = d2, and FIGS. 2C to 2H show the case of d1> d2. . As shown in the figure, the short diameter of the steel cord 10 having the 1 × 2 + N structure is most affected by the diameter of the sheath filament 12. Therefore, by making the diameter d2 of the sheath filament 12 smaller than the diameter d1 of the core filament 11, the diameter of the steel cord 10 can be efficiently reduced. As a result, the thickness of the belt layer can be reduced while maintaining the distance between the steel cord 10 of the first belt layer and the steel cord 10 of the second belt layer. This makes it possible to reduce the weight of the belt without reducing so-called BES resistance, which is resistance to BES.

  In the present invention, it is preferable that the cords constituting the first belt layer and the second belt layer are cross belts laminated so as to intersect each other with the equator plane interposed therebetween. Further, a belt layer may be provided on the outer side in the tire radial direction of the first belt layer and the second belt layer, and a circumferential belt comprising a rubberized layer of cords arranged substantially parallel to the tire circumferential direction. A layer may be provided. As such a cord, a cord made of organic fiber can be suitably used. For example, a cord made of polyester fiber, nylon fiber, aramid fiber, or polyketone fiber can be suitably used.

  In the present invention, the diameter d1 of the core filament 11 is preferably 0.16 to 0.28 mm, and the diameter d2 of the sheath filament 12 is preferably 0.12 to 0.24 mm. If the filament diameter exceeds the above range, a sufficient light weight effect may not be obtained. On the other hand, if the filament diameter is less than the above range, the belt strength may be insufficient.

FIG. 3 is an enlarged partial cross-sectional view showing the vicinity of the end of the belt layer according to the preferred embodiment of the pneumatic radial tire of the present invention. As illustrated, in the present invention, the gauge H _E of the rubber layer between the steel cord 6 between the first belt layer 5a and the second belt layer 5b in the second belt layer 5b ends, the gauge in the tire center portion H It is preferable that it is larger than _C. Preferably 1.3 to 3.0 times _{H E} is the _{H C} is preferably 1.8 to 2.6 times. By disposing the thick gauge inter-belt rubber 7 at the belt end, the belt durability can be further improved. If this value is less than 1.3 times, such an effect cannot be sufficiently obtained. On the other hand, if it exceeds 3.0 times, the weight of the tire may not be sufficiently reduced.

  Furthermore, in the present invention, from the viewpoint of weight reduction and durability improvement of the tire, the belt layer thicknesses t1 and t2 are preferably 0.95 to 1.35 mm, more preferably 0.95 to 1.5. 25 mm. If the thickness of the belt layer is less than 0.95 mm, sufficient durability may not be obtained. On the other hand, if the thickness of the belt layer is 1.35 mm or more, a sufficient light weight effect cannot be obtained.

  Furthermore, in the present invention, the number of steel cords driven into the belt is preferably 28-57 / 50 mm. When the number of driving is less than the above range, there is a concern of insufficient tensile strength or a decrease in belt rigidity. On the other hand, when the number of driving is larger than the above range, it is difficult to secure the cord interval, it becomes difficult to effectively suppress the BES, and there is a concern that the belt durability is lowered.

In the present invention, it is preferable to use a steel filament having a tensile strength of 2700 N / mm ² or more in order to ensure belt strength. As the steel filament having a high tensile strength, one containing at least 0.72% by mass, particularly at least 0.82% by mass of carbon can be suitably used. In the present invention, the conditions such as the twist direction and twist pitch of the sheath filament are not particularly limited, and can be appropriately configured according to a conventional method.

  In the pneumatic radial tire of the present invention, the specific tire structure other than that is not particularly limited as long as the belt structure satisfies the above requirements. Further, the pneumatic radial tire of the present invention can be suitably used for a passenger car tire. In addition, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples 1-10 and Comparative Examples 1-5>
Tires having a tire size of 195 / 65R15 were manufactured using steel cords having structures shown in Tables 1 to 4 as belt reinforcing materials. The belt was composed of three belt layers, and steel cords shown in Tables 1 to 4 below were applied to the first belt layer and the second belt layer. The steel cord driving angle was ± 26 ° with respect to the tire circumferential direction. Further, as the outermost layer belt layer, a circumferential belt composed of a rubberized layer of organic fiber cords arranged substantially parallel to the tire circumferential direction was disposed. About each obtained tire, durability (BES property) and tire weight were evaluated according to the following procedure.

<Durability>
Each test tire was mounted on a standard rim defined in the JATMA standard, filled with 210 kPa internal pressure and mounted on a passenger car, applied twice the normal load, and traveled on the paved road for 20000 km. Thereafter, the tires were dissected and the separation lengths at the belt ends were compared. Examples 1 to 5 and Comparative Examples 2 and 3 are indexed with Comparative Example 1, Examples 6 and 7 are based on Comparative Example 4, Examples 8 to 10 are indexed with Comparative Example 5 as a reference, and durability The case where the property was superior to the standard tire was evaluated as ◎, the case equivalent to ○ was evaluated as ○, and the case where it was inferior as ×. The results are also shown in Tables 1-4. In addition, this index | exponent is excellent in durability, so that a value is small.

<Tire weight>
The weight per tire was measured. For Examples 1 to 5 and Comparative Examples 2 and 3, tire weight is reduced by 150 g or more based on Comparative Example 1, Examples 6 and 7 are based on Comparative Example 4, and Examples 8 to 10 are based on Comparative Example 5. The evaluation was evaluated as ◎, the case where it was reduced by 50 g or more and less than 150 g as ◯, and the case where it was less than 50 g as △. The results are also shown in Tables 1-4.

<Comprehensive evaluation>
In the evaluation of durability and reduction in tire weight, the case where there was no x was indicated as ◯, and the case where there was an x was indicated as x.

  From Tables 1 to 4, it was confirmed that the pneumatic radial tire of the present invention can reduce the weight of the tire without deteriorating the durability.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5a 1st belt layer 5b 2nd belt layer 6 Steel cord 7 Rubber between belts 10 Steel cord 11 Core filament 12 Sheath filament

Claims (5)

A carcass composed of at least one carcass layer straddling a pair of left and right bead cores in a toroidal shape, a tread portion disposed on the outer side in the tire radial direction of the crown region of the carcass, and a tread portion; In a pneumatic radial tire comprising a belt composed of at least two belt layers, which is disposed between the crown region of the carcass and forms a reinforcing portion,
The first belt layer of the first layer and the second belt layer of the second layer of the belt both have a core formed by twisting two filaments, and N (2 ≦ N ≦ 4) twisted around the core. ) When a steel cord comprising a sheath filament is juxtaposed in the belt width direction and embedded in a coating rubber, and when the diameter of the core filament is d1 and the diameter of the sheath filament is d2, d1 A pneumatic radial tire characterized by being> d2.   The pneumatic radial tire according to claim 1, wherein the number of sheath filaments is three.   The pneumatic radial tire according to claim 1 or 2, wherein the d1 is 0.16 to 0.28 mm and the d2 is 0.12 to 0.24 mm.   The air according to any one of claims 1 to 3, wherein the gauge of the rubber layer between the steel cords of the first belt layer and the second belt layer at the end portion of the second belt layer is larger than the gauge at the tire central portion. Entering radial tire.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the belt layer has a thickness of 0.95 to 1.35 mm.

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