JP2012171364A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire, which does not degrade rigidity, has superior durability and is lightweight, and is improved in rolling resistance.SOLUTION: The pneumatic radial tire includes a belt 5 constituted of two belt layers, and a belt reinforcing layer 6 made of rubber cloth of the organic fiber cord at the outside in the tire radial direction of the belt 5. The reinforcement material of the belt layer is a bundle of two cords arranged without twisting, and when diameters of all filaments constituting the cord are defined as a (mm), an interval between adjacent bundles is increased by ≥a/6(mm), as an expected value, compared with an interval expressed by using the circumscribing circle of the cord, an initial tensile resistance degree per one organic fiber cord of the belt reinforcing layer 6 is ≤20 GPa, and an apparent treat initial tensile resistance degree in all regions of the belt reinforcing layer 6 is ≤400 GPa/cm.

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 is excellent in durability and light weight without deteriorating rigidity and improved in rolling resistance.

  Currently, the belt commonly used as the reinforcing member of the carcass that forms the skeleton of the radial tire for passenger cars, especially the reinforcing member of the crown portion of the carcass, is mainly made of a rubberized layer of a steel cord that is inclined with respect to the equator plane of the tire. Two or more steel belt layers are used, and the steel cords in these belt layers intersect each other.

  Conventionally, various studies have been made on improvement of the belt layer. For example, Patent Document 1 discloses a technique for improving the durability of a belt by forming a bundle of reinforcing elements within several bundles and driving the bundle with constant dispersion. Further, in Patent Document 2, by using a steel cord having a (1 × 2) structure as a belt reinforcing material, separation (BES) generated at the belt end can be suppressed, and the weight of the tire can be reduced. That is disclosed.

JP-A-5-213007 Japanese Patent Laid-Open No. 62-234922

  In recent years, with higher performance of automobiles, higher performance is required for tires. In addition, weight reduction of tires has become an important issue for improving the fuel efficiency of automobiles. Under such circumstances, the belt structures described in Patent Documents 1 and 2 are not necessarily sufficient in terms of tire durability and light weight. In addition, it is necessary to ensure high rigidity of the belt in terms of performance such as ride comfort and handling stability.Furthermore, in order to improve fuel efficiency, it is necessary to consider not only weight reduction of tires but also rolling resistance. Become.

  Accordingly, an object of the present invention is to provide a pneumatic radial tire that is excellent in durability and light weight without deteriorating rigidity and improved in rolling resistance.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by setting the belt layer and the belt reinforcing layer to have a predetermined structure, and the present invention is completed. It came to.

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. A tread portion forming a portion, a belt comprising at least two belt layers disposed between the tread portion and the crown region of the carcass to form a reinforcing portion, and a tire radially outward of the belt In a pneumatic radial tire provided with a belt reinforcing layer made of rubberized cloth of organic fiber cords arranged substantially parallel to the circumferential direction,
The reinforcing material constituting the belt layer is a bundle in which two cords are aligned without twisting, and the diameters of all the filaments constituting the cord are the same, and the diameter is a (mm) Then, the interval between the adjacent bundles is increased by a / 6 (mm) or more as an expected value from the interval expressed using the circumcircle of the cord,
An organic fiber cord having an initial tensile resistance per organic fiber cord of 20 GPa or less and an initial tensile resistance per organic fiber cord per unit width in the entire region of the belt reinforcing layer. The apparent treat initial tensile resistance multiplied by the number is 400 GPa / cm or less. Here, the initial tensile resistance is a value determined in accordance with JIS L 1017.

  In the present invention, the initial tensile resistance per one organic fiber cord is preferably 7 GPa or more, and in the present invention, the apparent treat initial tensile resistance is 150 GPa / cm or less. Preferably, in the present invention, the belt reinforcing layer is arranged in a range from the inner side in the width direction to the end of the belt layer having the maximum belt width from the end of the belt layer having the minimum belt width. It is preferable to be provided.

  According to the present invention, it is possible to provide a pneumatic radial tire that is excellent in durability and light weight without deteriorating rigidity and improved in rolling resistance.

1 is a cross-sectional view showing a pneumatic radial tire according to a preferred example of the present invention. It is sectional drawing which shows the example of a change of the cross section of a bundle at the time of making two cords of (1 * 2) structure into a bundle. It is sectional drawing which shows the example of the change of the cross section of a bundle at the time of making two cords of the (1 + 1) structure into a bundle. It is explanatory drawing for calculating the expected value of the increase amount of a bundle | flux space | interval at the time of making two cords of (1x2) structure into a bundle. It is explanatory drawing for calculating the expected value of the increase amount of a bundle | flux space | interval at the time of making two cords of (1x2) structure into a bundle. It is a fragmentary sectional view of the belt layer and belt reinforcement layer of the pneumatic radial tire of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a sectional view of a pneumatic radial tire according to a preferred embodiment of the present invention. 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 A belt reinforcing layer 6 made of an organic fiber cord rubberized cloth arranged substantially parallel to the tire circumferential direction is disposed over the entire width of the belt 5. 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.

First, the belt layer 5 of the pneumatic radial tire of the present invention will be described.
In the present invention, the reinforcing material constituting the first belt layer 5a and the second belt layer 5b is a bundle in which two cords are aligned without being twisted. By making the reinforcing material into a bundle of two cords, the spacing between the reinforcing materials in the belt layer becomes wider than when the cords are not bundled, and the rubber peeling starting from the end of the cord in the belt width direction is started. BES that easily propagates between adjacent codes can be suppressed. Thereby, the durability of the belt can be improved. In the present invention, when the diameters of all the filaments constituting the cord are the same diameter and the diameter is a (mm), the distance between adjacent bundles is the distance expressed using the circumscribed circle of the cord. The expected value increases by a / 6 (mm) or more, preferably 4a / 11 (mm) or more. FIGS. 2A to 2C show a case where two cords having a (1 × 2) structure are used as a bundle 7 as a reinforcing material for the belt layer, and FIGS. 3A to 3C show a (1 + 1) structure. FIG. 6 is a cross-sectional view showing an example of a change in the cross section of the cord bundle when two cords are used as a bundle 17. Hereinafter, the change in the cord diameter will be described with reference to FIGS. 2 and 3.

  Usually, the cord diameter Dc is represented by the diameter of the circumscribed circle 9 of the filament 8 as shown in FIG. However, since the cord having the (1 × 2) structure is a cord obtained by twisting two filaments 8, the position of the filament 8 continuously changes in the cord (inside the circumscribed circle 9). For example, when the position of the filament 8 changes by 45 ° as shown in FIGS. 2B and 2C, the actual cord diameter in the horizontal direction decreases from the circumscribed circle 9. The same applies to the cord of the (1 + 1) structure, and as shown in FIGS. 3A to 3C, when the position of the filament 18 changes by 45 ° as shown in FIGS. 3B and 3C, The actual diameter of the cord 17 in the horizontal direction is smaller than the circumscribed circle 19.

  The pneumatic radial tire of the present invention is used as a bundle of two cords as a belt reinforcing material, but as described above, when the cord diameter changes in the belt width direction, the interval between adjacent bundles is also As the cord diameter changes, it will change continuously. That is, a wide part and a narrow part appear in the interval between adjacent bundles. The presence of a portion having a wide space between the bundles can more effectively suppress BES that easily propagates between adjacent cords, with rubber peeling starting from the cord end of the belt width direction end. . As a result, the durability of the belt is further improved. In addition, since there is a portion where the distance between the bundles is narrow, the rigidity of the belt can be maintained.

Next, a method for calculating the expected value of the increase amount of the bundle interval will be described. 4 and 5 are explanatory diagrams for calculating an expected value of the increase amount of the bundle interval when two cords having a (1 × 2) structure are bundled. First, as shown in FIG. 4A, one of the adjacent codes of adjacent bundles 7 is a code X, the other is a code Y, and the distance between the circumscribed circles of the code X and the code Y is W. . Next, in the horizontal direction, a state where the distance between the circumscribed circles of the cord X and the cord Y and the distance between the filaments of the cord X and the cord Y are equal is a basic state of the cord X and the cord Y (FIG. 4A). And FIGS. 4A to 4H show cross-sectional shapes when the code X is rotated by 360 ° at a pitch and the code X is rotated 45 ° from the basic state, respectively, as an example. Referring to FIG. 4B, by rotating the code X by 45 ° from the basic state, the actual distance between the code X and the code Y increases by xz ₂ from W. Further, when the code X is rotated by 45 ° (FIGS. 4C to 4H), the actual amount of increase in the distance between the code X and the code Y changes by xz _{3 to} xz ₈ . Note that xz ₁ and xz ₅ in the basic state (FIG. 4A) and the state rotated 180 ° from the basic state (FIG. 4E) are 0.

Similarly, for the code Y, when the code Y rotates 360 ° at one pitch, the cross-sectional shapes when the code Y is rotated by 45 ° are shown as FIGS. 5A to 5H, respectively. As shown in the figure, by rotating the code Y by 45 ° from the basic state (FIG. 5A) (FIG. 5B), the actual distance between the code X and the code Y increases by yz ₂ from W. . Further, when the rotation is performed by 45 ° (FIGS. 5C to 5H), the actual amount of increase in the distance between the code X and the code Y changes by yz _{3 to} yz ₈ .

により、束間隔の増加量の期待値を算出する。なお、コード構造が（１×２）構造を例として説明したが、他の構造のコードについても同様の手順で算出することができる。 Up to this point, the case where the code X and the code Y are rotated by 45 ° has been described as an example of the calculation method of the increase amount of the bundle interval. However, in the present invention, the code is calculated based on the same concept. When X and code Y rotate 360 ° at one pitch, code X and code Y are rotated by 1 ° from the basic state, and xz _{1 to} xz ₃₆₀ and yz _{1 to} yz ₃₆₀ are obtained. Based on the obtained value, the following formula:

Thus, an expected value of the increase amount of the bundle interval is calculated. The code structure has been described by taking the (1 × 2) structure as an example, but codes of other structures can be calculated in the same procedure.

  By using a cord in which the expected value of the increase amount of the bundle interval calculated by the above formula increases by a / 6 (mm) or more, preferably 4a / 11 (mm) or more, as a bundle of belts as a bundle of two A pneumatic radial tire excellent in durability and light weight can be obtained without deteriorating rigidity. Examples of the code structure that satisfies the above relationship include a (1 × 2) structure and a (1 + 1) structure.

  In the present invention, it is preferable that the number of the reinforcing material driven into the belt layer is 35 to 65/50 mm. By setting the number of drivings within the above range, both belt strength and BES suppression can be achieved at a high level. More preferably, it is 40-59 pieces / 50 mm.

  In the present invention, the thickness of the belt layer is preferably greater than 0.70 mm and less than 1.20 mm from the viewpoint of weight reduction and durability improvement of the tire. By setting the thickness of the belt layer within the above range, durability and lightness can be favorably obtained. More preferably, it is 0.80 to 1.10 mm.

  Furthermore, in the present invention, the filament diameter of the filament constituting the belt reinforcing cord is preferably 0.23 to 0.30 mm. By setting the filament diameter in the above range, the belt strength and light weight can be obtained satisfactorily.

In the present invention, the conditions such as the twist direction and the twist pitch of the filament are not particularly limited, and can be appropriately configured according to a conventional method depending on the application. Moreover, there is no restriction | limiting in particular about the material of a filament, However, A steel filament is suitable. As the steel filament, a tensile strength of 2700 N / mm ² or more can be suitably used. As the monofilament cord 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.

Next, the belt reinforcing layer 6 of the pneumatic radial tire of the present invention will be described.
In general, it is known that the provision of the belt reinforcing layer 6 can improve the durability (market durability) against high-speed durability, wear resistance, rust caused by moisture entering from trauma caused by tread cuts, and the like. Yes. It is also known that the higher the rigidity of the belt reinforcing layer 6, the better the road noise reduction and the high-speed durability, and the lower the rigidity, the better the rolling resistance. However, the belt reinforcing layer 6 has a problem in that shearing strain is generated between the belt layer 5b and the belt reinforcing layer 6 during traveling, causing a separation nucleus and causing early failure.

  In the pneumatic radial tire of the present invention, a cord having an expected value of an increase in the bundle interval of a / 6 (mm) or more is used as a reinforcing material for the belt layer 5. In such a cord, the cord diameter does not change only in the width direction, and the cord diameter similarly changes in the tire radial direction. Accordingly, in the tire having the belt reinforcing layer 6, as shown in FIG. 6, for example, when a cord having a 1 × 2 structure is used as the belt reinforcing cord, the cord bundle 27 of the belt layer 5b and the belt reinforcing layer 6 There are portions where the actual distance from the organic fiber cord 10 is locally wide and narrow. If there is a narrow portion of the interlayer gauge, the local strain between the layers becomes large, and the above-mentioned separation problem becomes significant.

  Since the shear strain between the belt layer and the belt reinforcing layer increases as the cord rigidity of the belt reinforcing layer and the cord layer increases, the smaller one is preferable. Therefore, in the present invention, the initial tensile resistance per one organic fiber cord 10 constituting the belt reinforcing layer 6 is set to 20 GPa or less, and one organic fiber cord 10 is formed in the entire region of the belt reinforcing layer 6. The apparent initial tensile resistance obtained by multiplying the initial initial tensile resistance by the number of organic fiber cords present per unit width is 400 GPa / cm or less.

  By setting the initial tensile resistance per one organic fiber cord 10 to 20 GPa or less, it is possible to improve rolling resistance while reducing shear strain generated between the belt layer 5b and the belt reinforcing layer 6. In addition, if the initial tensile resistance of one organic fiber cord is greater than 20 GPa, the restraint force on the belt during vulcanization of the tire is high, so the distance between the belt reinforcing layer reinforcing cord and the belt reinforcing cord is shortened, and the separation occurs. Become a nucleus. It is preferably 3 to 7 GPa. In addition, when the apparent initial tensile resistance is greater than 400 GPa / cm, the number of organic fiber cords to be driven increases, the distance between the cords becomes small, and separation easily occurs. Preferably, it is 100-150 GPa. In general, the separation phenomenon occurs near the belt end. Therefore, in the present invention, as shown in FIG. 1, the belt reinforcing layer 6 may have a structure that covers the entire width of the belt 5 (so-called cap structure), but the belt reinforcing layer 6 covers the end of the belt 5. It is good (so-called layer structure). In this case, the belt reinforcing layer 6 is preferably arranged in a range from the inner side in the width direction to the end of the belt layer having the minimum belt width and the outer side in the width direction from the end of the belt layer having the maximum belt width.

  As the organic fiber cord, a cord made of nylon fiber or a cord made of polyethylene terephthalate (PET) can be suitably used, and a composite cord of these may be used. The organic fiber cord is not particularly limited with respect to the cord diameter, the cord structure, the number of twists and the like as long as the above physical properties are satisfied. The belt reinforcement layer 6 is preferably formed by spirally winding a ribbon-like sheet having a width smaller than the arrangement width thereof and rubberized one or more reinforcement cords a plurality of times. Can do.

  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. Moreover, 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 1-3 and Comparative Examples 1-4>
A tire of the same type as the tire shown in FIG. 1 was produced with a tire size of 205 / 55R16. The belt layer was produced using a belt reinforcing material in which two steel cords having the structures shown in Tables 1 and 2 below were bundled. The belt reinforcing layer was produced using an organic fiber cord having the structure shown in the table as a reinforcing material. The belt has a laminated structure of two belt layers, and the belt angle is ± 30 ° with respect to the tire circumferential direction. The belt reinforcing layer was arranged substantially parallel to the circumferential direction so as to cover the entire belt surface. About each obtained tire, according to the following procedure, abrasion resistance (rigidity), durability, tire weight, market durability, and rolling resistance were evaluated.

<Abrasion resistance>
The tire remaining groove depth (center rib groove) after actual vehicle durability running (running an existing circuit of 3.5 km per lap for 20 laps in the limit running mode) was measured, and index evaluation was performed with the tire of Comparative Example 1 being 100. When this value is 100 ± 2, it is equivalent to the conventional product, and Δ is greater than 102, and x is smaller than 98. The results are shown in Tables 1 and 2. Note that the low wear resistance means that the tread contact area is small and is a criterion for judging the rigidity of the belt.

<Durability>
Each test tire was attached to a 6.5 J × 16 rim, filled with a specified internal pressure, and attached to a passenger car. After traveling 40,000 km on the paved road, the tires were dissected and the separation length of the belt end was examined. A result shows a favorable result, so that a value is small. Moreover, the case where it was equal to or more than that of the tire of Comparative Example 1 was marked with ◯, and the case where it was inferior was marked with ×. The results are shown in Tables 1 and 2.

<Tire weight>
The weight per tire was measured, and index evaluation was performed with the tire of Comparative Example 1 as 100. The case where this value was less than 100 was marked with ◯, and the case where it was 100 or more was marked with ×. The results are shown in Tables 1 and 2.

<Market durability>
Four obtained tires were attached to a 6.5 J × 16 rim, filled with a specified internal pressure, and attached to a four-wheeled vehicle. After running on the actual road for 50,000 km, the four wheels were rotated with a drum at 120 km / h, the time until failure was measured, and the average value of four tires was calculated. The obtained numerical value was taken as an index with Comparative Example 1 as 100. The larger this value, the better the market durability. The obtained results are shown in Tables 1 and 2.

<Rolling resistance>
Using a rotating drum having a steel smooth surface with an outer diameter of 1707.6 mm and a width of 350 mm, the measurement was performed by the coasting method when rotating at a speed of 80 km / h under the action of a load of 4500 N (460 kg). About the obtained value, it represented with the index which makes Comparative Example 1 100. It shows that it is excellent in rolling resistance, so that this value is small. The obtained results are shown in Tables 1 and 2.

※１：有機繊維コード１本の初期引張抵抗度
※２：見かけのトリート初期引張抵抗度
※３：ポリエチレンナフタレート

* 1: Initial tensile resistance of one organic fiber cord * 2: Apparent treat initial tensile resistance * 3: Polyethylene naphthalate

※１：有機繊維コード１本の初期引張抵抗度
※２：見かけのトリート初期引張抵抗度
※４：ポリエチレンテレフタレート

* 1: Initial tensile resistance of one organic fiber cord * 2: Apparent treat initial tensile resistance * 4: Polyethylene terephthalate

  From Tables 1 and 2, it was confirmed that the pneumatic radial tire of the present invention was excellent in durability and light weight without deteriorating rigidity and improved in rolling resistance.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5a 1st belt layer 5b 2nd belt layer 6 Belt reinforcement layer 7,17 Bundle 8,18 Filament 9,19 circumscribed circle 10 Organic fiber cord

Claims (4)

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; And a belt composed of at least two belt layers disposed between the crown region of the carcass and forming a reinforcing portion, and arranged substantially parallel to the tire circumferential direction on the outer side in the tire radial direction of the belt. In a pneumatic radial tire provided with a belt reinforcing layer made of a rubberized cloth of organic fiber cord,
The reinforcing material constituting the belt layer is a bundle in which two cords are aligned without twisting, and the diameters of all the filaments constituting the steel cord are the same, and the diameter is a (mm ), The interval between the adjacent bundles is increased by a / 6 (mm) or more as an expected value from the interval expressed using the circumscribed circle of the cord,
An organic fiber cord having an initial tensile resistance per organic fiber cord of 20 GPa or less and an initial tensile resistance per organic fiber cord per unit width in the entire region of the belt reinforcing layer. A pneumatic radial tire characterized by an apparent treat initial tensile resistance of 400 GPa / cm or less multiplied by the number.   The pneumatic radial tire according to claim 1, wherein an initial tensile resistance per one organic fiber cord is 7 GPa or more.   The pneumatic radial tire according to claim 1 or 2, wherein the apparent initial initial tensile resistance is 150 GPa / cm or less.   The belt reinforcing layer is disposed in a range from the inner side in the width direction from the end of the belt layer having the minimum belt width to the outer side in the width direction from the end of the belt layer having the maximum belt width. A pneumatic radial tire according to any one of the above.

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