JP5945140B2 - 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 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. In addition to these, Patent Documents 3 to 7 propose steel cords having a 2 + 3 structure for the purpose of improving various physical properties and workability required as tire reinforcing materials.

JP 2001-98480 A Japanese Utility Model Publication No. 3-128689 JP-A-6-306784 Japanese Patent Laid-Open No. 7-126992 JP 2001-98460 A JP 2006-328557 A JP 2007-63706 A

  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. Moreover, although the steel cord of patent document 2 is improving durability by improving the permeability | transmittance of the rubber with respect to a steel cord, the weight reduction of a tire is not examined. Furthermore, even in the steel cords described in Patent Documents 3 to 7, the current situation is that the study on weight reduction of tires is not always satisfactory.

  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-mentioned problems, the present inventors have confirmed that the diameter of the core filament and the sheath filament satisfies a predetermined relationship in the steel cord having the 2 + N structure, and the average molding of the sheath filament is performed. It has been found that by setting the rate within a predetermined range, the weight of the belt treat can be reduced while maintaining the distance between the cords of the belt, 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 that forms a portion; and a belt that is disposed between the tread portion and the crown region of the carcass and forms a reinforcing portion, and a belt composed of at least two belt layers.
The first belt layer of the first layer and the second belt layer of the second layer of the belt both have a core in which two filaments are arranged in parallel without being twisted, and N is twisted around the core. (2 ≦ N ≦ 4) a steel cord comprising sheath filaments and juxtaposed in the belt width direction and embedded in the coating rubber,
When the diameter of the core filament is d1 and the diameter of the sheath filament is d2, d1> d2 and the average rate (%) of the sheath filament is 30 or more and 55 or less. It is.

  In the present invention, the average molding rate (%) is preferably 40 to 55. In the present invention, it is preferable that the d1 is 0.16 to 0.32 mm, and the d2 is 0.12 to 0.29 mm. Furthermore, in the present invention, the number of sheath filaments is preferably three. 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 of the second belt layer is preferably larger than the gauge at the tire center. In the present invention, the belt layer preferably has a thickness of 0.85 to 1.65 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 short diameter of a steel cord, (a) shows the case where d1 = d2, and (b), (c), and (d) show the case of d1> d2. It is explanatory drawing which shows the shaping | molding amount of a sheath filament. It is sectional drawing of the steel cord which shows the relationship between the average molding rate of a sheath filament, and a code | cord | interval, (a) is a case where an average molding rate is 50%, (b) is a case where an average molding rate is 100%. . 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, both the first belt layer 5a and the second belt layer 5b are arranged in parallel without twisting two core filaments, and N (2 ≦ N ≦) twisted around the core. 4) A steel cord comprising three, preferably three sheath filaments, is embedded in the coating rubber in parallel with the belt width direction so that the long diameter of the steel cord 10 is in the belt width direction; and When the core filament diameter is d1 and the sheath filament diameter is d2, d1> d2. FIGS. 2A to 2D are comparative diagrams of the short diameters of the steel cords. FIG. 2A shows a case where d1 = d2, and FIGS. 2B to 4D show cases where d1> d2. As shown in the figure, the short diameter of the steel cord 10 having the 2 + N structure is governed by the diameter of the sheath filament 12. Accordingly, by making the diameter d2 of the sheath filament 12 smaller than the diameter d1 of the core filament 11, the short diameter of the steel cord 10 can be reduced. As a result, the thickness of the belt layer can be reduced while maintaining the distance between the steel cord of the first belt layer and the steel cord 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.

Moreover, in this invention, the average shaping | molding rate (%) of the sheath filament 12 is 30-75, Preferably it is 40-72. Here, the average molding rate (%) of the sheath filament 12 is the average of the amount A of the sheath filament 12 Aave. When the following formula,
Average molding rate (%) = Aave. / (2 × d1 + d2) × 100
Defined by Aave., Which is the average of the amount of typing. Means the average of the maximum value A1 and the minimum value A2 after measuring the amount of molding in the sheath filament after the steel cord is unwound. Note that FIG. 3 is an explanatory view showing the amount of sheath filament molding.

  FIG. 4 is a cross-sectional view of the steel cord 10 showing the relationship between the average molding rate (%) of the sheath filament 12 and the cord interval w, (a) is the case where the average molding rate (%) is 50%, b) is the case where the average molding rate (%) is 100%. As shown in FIG. 4B, when the average molding rate (%) of the sheath filament 12 is much higher than 75%, a gap is formed between the core filament 11 and the sheath filament 12. Compared with the case where the average molding rate (%) is 30 to 75% (see FIG. 4A), the major axis of the cord 10 becomes large. As a result, even if the number of implantations is the same, if the average molding rate (%) of the sheath filament 12 is much higher than 75, the cord interval w becomes narrow and there is a concern that the BES property is deteriorated. Further, if a gap is formed between the core filament 11 and the sheath filament 12, there is a concern that the rigidity of the cord 10 is lowered. On the other hand, when the average molding rate (%) of the sheath filament 12 is less than 30, the shape stability of the steel cord 10 is lowered. As a result, the cords are broken when the tire is manufactured, and workability is impaired.

  If the average mold rate (%) of the sheath filament 12 is less than 70, the shape stability of the steel cord 10 is deteriorated when d1 = d2. However, when the relationship of d1> d2 is satisfied as in the steel cord 10 of the present invention, the contact area between the core filament 11 and the sheath filament 12 is smaller than in the case of d1 = d2, and therefore the core filament 11 And the contact stress of the sheath filament 12 increases, and the shape of the steel cord 10 is stabilized. In order to obtain the effect of the present invention satisfactorily, the ratio of d1 and d2, and the range of d1 / d2 is preferably 1.1 to 2.5.

  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 0.32 mm, and the diameter d2 of the sheath filament 12 is preferably 0.12 to 0.29 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. 5 is an enlarged partial cross-sectional view showing the vicinity of the end portion 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 0.85 to 1.65 mm, and more preferably 0.95 to 1.5 mm. 10 mm. If the thickness of the belt layer is less than 0.85 mm, sufficient durability may not be obtained. On the other hand, if the thickness of the belt layer is 1.65 mm or more, sufficient light weight effect may not be obtained. is there.

  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 1-6, Reference Examples 1 and 2 and Comparative Examples 1-8>
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.

<Reference Examples 3 and 4 and Comparative Examples 9 and 10>
Tires having a tire size of 265 / 70R16 were manufactured using steel cords having the structures shown in Table 5 below as belt reinforcing materials. The belt was composed of three belt layers, and steel cords shown in Table 5 below were applied to the first belt layer and the second belt layer. The steel cord driving angle was ± 24 ° 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 and 2, Reference Examples 1 and 2 and Comparative Examples 2 to 6 are Comparative Example 1, Examples 3 and 4 are based on Comparative Example 7, Examples 5 and 6 are based on Comparative Example 8, and Reference Examples 3 and 4 and Comparative Example 10 were indexed using Comparative Example 9 as a reference, and in addition, ◎ if the durability was 100 or less compared to the reference tire, ◯ if more than 100 and less than 110, The case of 110 or more was evaluated as x. The results are also shown in Tables 1-5. In addition, this index | exponent is excellent in durability, so that a value is small.

<Tire weight>
The weight per tire was measured. Examples 1 and 2, Reference Examples 1 and 2 and Comparative Examples 2 to 6 are Comparative Example 1, Examples 3 and 4 are based on Comparative Example 7, Examples 5 and 6 are based on Comparative Example 8, and For Reference Examples 3, 4 and Comparative Example 10, the case where the tire weight was reduced by 200 g or more based on Comparative Example 9 was evaluated as ◎, the case where the tire weight was reduced from 100 g or more but less than 200 g was evaluated as ◯, and the case where it was less than 100 g was evaluated as ×. did. The results are also shown in Tables 1-5.

<Cord shape stability>
Examples 1 and 2, Reference Examples 1 and 2 and Comparative Examples 2 to 6 are Comparative Example 1, Examples 3 and 4 are based on Comparative Example 7, Examples 5 and 6 are based on Comparative Example 8, and For Reference Examples 3, 4 and Comparative Example 10, with reference to Comparative Example 9, ◎ when workability is good, ◯ when workability is slightly good, △ when workability is slightly deteriorated, work The case where the property greatly deteriorated was marked with “x”.

<Comprehensive evaluation>
In the evaluation of durability, tire weight reduction, and cord shape stability, “の み” is given when only “◎”, “○” is given when only “○” and “○”, and “△” is given when there is no “◎”.

  From Tables 1 to 5, it was confirmed that the pneumatic radial tire of the present invention was able to 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 (6)

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; 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 in which two filaments are arranged in parallel without being twisted, and N is twisted around the core. (2 ≦ N ≦ 4) a steel cord comprising sheath filaments and juxtaposed in the belt width direction and embedded in the coating rubber,
D1> d2 when the diameter of the core filament is d1 and the diameter of the sheath filament is d2, and the average forming rate (%) of the sheath filament is 30 or more and 55 or less. Entering radial tire. The pneumatic radial tire according to claim 1, wherein the average molding rate (%) is 40 to 55 .   The pneumatic radial tire according to claim 1 or 2, wherein the d1 is 0.16 to 0.32 mm, and the d2 is 0.12 to 0.29 mm.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the number of sheath filaments is three.   The air according to any one of claims 1 to 4, wherein the gauge of the rubber layer between the steel cords of the first belt layer and the second belt layer at the end of the second belt layer is larger than the gauge at the center of the tire. Entering radial tire.   The pneumatic radial tire according to any one of claims 1 to 5, wherein the belt layer has a thickness of 0.85 to 1.65 mm.

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