JP2012201352A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire superior in lightweightness, and improving bad road travel performance, while maintaining tire various performances.SOLUTION: This pneumatic tire includes a carcass constituted of at least one carcass layer, a tread part arranged outside in the tire radial direction of a crown area of the carcass, a belt constituted of at least two belt layers, and a belt reinforcing layer formed by spirally winding an organic fiber cord in the circumferential direction on the outside in the tire radial direction of the belt. A reinforcing material of the belt layers is a bundle 7 of arranging two cords in a pair, and when assuming a diameter of a filament 8 for constituting the cords as a (mm), an interval between mutual adjacent bundles 6 increases by a/4 (mm) or more as an expected value than an interval expressed by using a circumscribed circle 9 of the cords, and tensile strength F (N) at 5% elongation time of one organic fiber cord taken out of a tire central part of the belt reinforcing layer and the driving number N (a piece/5 cm) per a 5 cm width of the tire central part, satisfy F×N>2,500.

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic tire that is excellent in light weight while maintaining various tire performances and improved in rough road performance.

  Currently, a belt generally used as a reinforcing member of a carcass forming a skeleton of a tire for a passenger car, in particular, a reinforcing member of a crown portion of a carcass, is mainly composed of a rubberized layer of a steel cord inclined and arranged 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 are configured to cross 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 the improvement in performance of automobiles, higher performance is required for various tire performances. In addition, weight reduction of tires has become an important issue in order to improve automobile fuel efficiency. Under such circumstances, the belt structures described in Patent Documents 1 and 2 are not necessarily sufficient. Furthermore, more advanced countermeasures are required for the destruction of the tread portion when stepping on convex objects such as stones and curbs on the road.

  Accordingly, an object of the present invention is to provide a pneumatic tire that is excellent in light weight while maintaining various tire performances and improved in rough road performance.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by controlling the breakdown energy of the belt configuration and the belt reinforcing layer, and have completed the present invention. .

That is, the pneumatic tire of the present invention is disposed on the outer side in the tire radial direction of a carcass layer including at least one carcass layer straddling a toroidal shape between a pair of left and right bead cores, and a crown region of the carcass. 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, and an organic fiber on the outer side in the tire radial direction of the belt In a pneumatic tire provided with a belt reinforcing layer formed by spirally winding a cord in the circumferential direction,
The belt has at least one inclined belt layer, and the reinforcing material constituting the inclined belt layer is a bundle in which two cords are aligned without being twisted, and all filaments constituting the cord When the diameter is a (mm), the distance between adjacent bundles is a / 6 (mm) as an expected value than the distance expressed using the circumscribed circle of the cord. More than
Tensile strength F (N) at the time of 5% elongation of one organic fiber cord taken out from the tire central portion of the belt reinforcing layer, and the number N of driving (5/5 cm) per 5 cm width of the tire central portion, Is the following formula,
F × N> 2500
It is characterized by satisfying the relationship represented by Here, the tensile strength is a value obtained by a tensile test according to JIS L 1017, and the tire central portion refers to a region of 2.5 cm from the midpoint in the width direction of the inclined belt toward both ends. .

  In the present invention, the organic fiber cord is preferably a cord comprising at least one fiber selected from the group consisting of nylon, polyester, aramid, rayon, lyocell and polyketone. Moreover, in this invention, it is preferable that the tensile strength at the time of 5% elongation of the said organic fiber cord is 30 N or more. Furthermore, in the present invention, the cut elongation of one organic fiber cord is preferably 10% or more. Furthermore, in the present invention, it is preferable that the interval between the adjacent bundles is increased by a / 4 (mm) or more as an expected value, compared to the interval expressed using the circumscribed circle of the cord. The above configuration is suitable for a pneumatic tire having a flatness ratio of 45 or less. Here, the elongation at break is a value obtained by measurement according to JIS L 1013.

  According to the present invention, it is possible to provide a pneumatic tire that is excellent in light weight while maintaining various tire performances and improved in rough road performance.

It is sectional drawing which shows the pneumatic tire of one suitable example of this 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.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 shows a cross-sectional view of a pneumatic 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; And a bead portion 3 continuous 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. A belt 5 composed of at least two belt layers is disposed outside the crown region of the carcass 4 in the tire radial direction, and the belt 5 has at least one layer in which the reinforcing material is inclined with respect to the tire circumferential direction. Then, it has two layers of the first belt layer 5a and the second belt layer 5b. A belt reinforcing layer 6 formed by spirally winding an organic fiber cord in the circumferential direction is disposed over the entire width of the belt 5 on the outer side in the tire radial direction. 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 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 a bundle of two cords, the interval between the reinforcing materials in the belt layer becomes wider than when the cords are not bundled, and BES 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 more than a / 6 (mm), preferably more than a / 4, more preferably more than 4a / 11 (mm). 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 a cord bundle when two cords are used as a bundle 17. First, a change in the cord diameter will be described with reference to FIGS.

  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 bundle 18 in the horizontal direction is smaller than the circumscribed circle 19.

  The tire of the present invention uses a bundle of cords as a belt reinforcing material. However, as described above, when the cord diameter changes in the belt width direction, the distance between adjacent bundles is also the cord diameter. To change, it will change continuously. That is, a wide part and a narrow part appear in the interval between adjacent bundles. BES can be more effectively suppressed by the presence of a portion where the distance between the bundles is wide. 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.

  A belt in which the expected value of the increase amount of the bundle interval calculated by the above formula is increased by a / 6 or more, preferably a / 4 (mm) or more, more preferably 4a / 11 (mm) or more as two bundles. By using as a reinforcing material, a pneumatic 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 reinforcements to be driven into the belt is 35 to 65 pieces / 50 mm, and more preferably 40 to 59 pieces / 50 mm. If the number of implantations is less than the above range, the tensile strength may not be ensured. On the other hand, when the number of implantations is larger than the above range, it is difficult to secure the bundle interval, it becomes difficult to effectively suppress BES, and durability may be lowered.

  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. If the thickness of the belt layer is 0.70 mm or less, sufficient durability may not be obtained. On the other hand, if the thickness of the belt layer is 1.20 mm or more, a sufficient light weight effect may not be obtained. More preferably, it is 0.80 to 1.10 mm.

  In the present invention, the filament diameter of the filament constituting the cord is preferably 0.23 to 0.30 mm. If the filament diameter is less than 0.23, sufficient strength may not be exhibited. On the other hand, if the filament diameter is larger than 0.30, the belt becomes thick and a sufficient light weight effect may not be obtained.

In the present invention, the conditions such as the twisting direction and twisting pitch of each 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.

Further, in the pneumatic tire of the present invention, the tensile strength F (N) at the time of 5% elongation of one organic fiber cord taken out from the tire central portion of the belt reinforcing layer 6 and the width per 5 cm of the tire central portion. The driving number N (lines / 5 cm) is the following formula:
F × N> 2500
It is also important to satisfy the relationship expressed by One of the indicators of the tire's fracture durability is the fracture energy (energy until the tread part breaks) when the tire rides over the projections that are uneven on the road surface, and this value is the tensile strength and elongation of the organic fiber cord It can be estimated from the area value of the stress-strain curve. This value represents the toughness of the organic fiber cord itself, and the total strength of the belt reinforcing layer can be obtained by multiplying this by the number of driving. Thereby, the breaking energy of the belt reinforcing layer can be controlled. In the present invention, F × N> 2500. However, as long as this relationship is satisfied, it is possible to sufficiently ensure durability against road hazards regardless of the tire size. Although there is no restriction | limiting in particular about the upper limit of FxN, Preferably it is 2500-13000. Such an effect can be satisfactorily obtained in a tire having a flatness ratio of 45 or less.

  In the present invention, any organic fiber cord can be used as long as it satisfies the above relationship. For example, the cord is made of nylon, polyester, aramid, rayon, lyocell, and polyketone, or two or more of these. The composite cord can be used satisfactorily. Further, the cord structure and the number of twists of these cords are not particularly limited as long as the above relational expression is satisfied.

  Moreover, in this invention, it is preferable that the tensile strength F at the time of 5% elongation of one organic fiber cord is 30N or more. When the tensile strength F at 5% elongation of one organic fiber cord is less than 30 N, the number N of organic fiber cords to be driven increases in order to satisfy the relationship of F × N> 2500, which is not preferable. On the other hand, the upper limit of the tensile strength F at 5% elongation is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 30 to 400N, more preferably 100 to 400N.

  Furthermore, in this invention, it is preferable that the cutting elongation of one organic fiber cord is 10% or more. By setting the cutting elongation of one organic fiber cord to 10% or more, the risk of damage to the belt reinforcing layer due to the hazard on the road surface can be greatly improved. Although there is no restriction | limiting in particular about the upper limit of the cutting elongation of one organic fiber cord, A 10-20% thing can be used suitably.

  The structure of the belt and the belt reinforcing layer that have been described in detail so far is suitable for an extra road tire, particularly a low-flat tire having a flatness ratio of 45 or less. As long as the structure of the belt and the belt reinforcing layer satisfies the above requirements, the tire of the present invention is not particularly limited with respect to the other specific tire structures. 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 1-5>
A steel cord having the structure shown in Tables 1 and 2 below is used as a belt reinforcing material, an organic fiber cord having the structure shown in the same table is used as a reinforcing material in a belt reinforcing layer, and a tire of the type shown in FIG. Prepared with 45R17XL. The driving angle of the belt reinforcing material was set to ± 26 ° with respect to the tire circumferential direction, and the organic fiber cord as the reinforcing material of the belt reinforcing layer was spirally wound along the circumferential direction. About each obtained tire, according to the following procedure, abrasion resistance (rigidity), durability, tire weight, and fracture energy were evaluated.

<Conventional example>
A steel cord having the structure shown in Table 2 below is used as a belt reinforcing material, an organic fiber cord having the structure shown in the same table is used as a reinforcing material for the belt reinforcing layer, and a tire of the type shown in FIG. 1 is obtained at tire size 215 / 45R17XL. Produced. The driving angle of the belt reinforcing material was set to ± 26 ° with respect to the tire circumferential direction, and the organic fiber cord as the reinforcing material of the belt reinforcing layer was spirally wound along the circumferential direction. About each obtained tire, according to the following procedure, abrasion resistance (rigidity), durability, tire weight, and fracture energy were evaluated.

<Comparative Examples 1-3>
A steel cord having the structure shown in Table 2 below is used as a belt reinforcing material, and an organic fiber cord having the structure shown in the same table is used as a reinforcing material for a belt reinforcing layer, and the tire shown in FIG. 1 is changed to a tire size 215 / 45R17XL. Made. The driving angle of the belt reinforcing material was set to ± 26 ° with respect to the tire circumferential direction, and the organic fiber cord as the reinforcing material of the belt reinforcing layer was spirally wound along the circumferential direction. About each obtained tire, according to the following procedure, abrasion resistance (rigidity), durability, tire weight, and fracture energy were evaluated.

<Abrasion resistance>
After assembling each test tire on a 7J × 17 rim, the remaining tire groove depth (center rib groove) after endurance running (running the existing circuit of 3.5km per lap for 20 laps in the limit running mode) Measurements were made and index evaluation was performed with a conventional tire as 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 mounted on a 7J × 17 rim, filled with internal pressure corresponding to the maximum load capacity in JATMA YEAR BOOK, and mounted on 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 the tire of the conventional example was marked with ○, and the case where it was inferior was marked with ×. The results are shown together in 1 and 2.

<Tire weight>
The weight of each test tire was measured, and index evaluation was performed with the conventional tire 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 together in 1 and 2.

<Destruction energy>
Each test tire was assembled on a 7J × 17 rim and then filled with an internal pressure of 200 kPa. Thereafter, a circular protrusion (φ20 mm) was pushed into the center block of each test tire, and the energy required for the tread portion to break was calculated. The obtained value was expressed as an index with the tire of Comparative Example 1 as 100. The larger this value, the better the bad road performance. The case where this value was larger than 100 was marked with ◯, and the case where the value was 100 or smaller was marked with ×. The results are shown in Tables 1 and 2.

  From Tables 1 and 2, it was confirmed that the tire of the present invention was excellent in lightness while maintaining various performances of the tire and improved in rough road performance.

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 layers 7, 17 Bundles 8, 18 Filaments 9, 19 circumscribed circle

Claims (6)

A carcass formed 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 to form a ground contact portion, and the 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 an organic fiber cord spirally wound in the circumferential direction on the outer side in the tire radial direction of the belt In a pneumatic tire comprising a belt reinforcement layer,
The belt has at least one inclined belt layer, and the reinforcing material constituting the inclined belt layer is a bundle in which two cords are aligned without being twisted, and all filaments constituting the cord When the diameter is a (mm), the distance between adjacent bundles is a / 6 (mm) as an expected value than the distance expressed using the circumscribed circle of the cord. More than
Tensile strength F (N) at the time of 5% elongation of one organic fiber cord taken out from the tire central portion of the belt reinforcing layer, and the number N of driving (5/5 cm) per 5 cm width of the tire central portion, Is the following formula,
F × N> 2500
A pneumatic tire characterized by satisfying the relationship represented by:   The pneumatic tire according to claim 1, wherein the organic fiber cord is a cord made of at least one fiber selected from the group consisting of nylon, polyester, aramid, rayon, lyocell, and polyketone.   The pneumatic tire according to claim 1 or 2, wherein the tensile strength at 5% elongation of the one organic fiber cord is 30 N or more.   The pneumatic tire according to any one of claims 1 to 3, wherein a cut elongation of the one organic fiber cord is 10% or more.   The pneumatic tire according to any one of claims 1 to 4, wherein the flatness is 45 or less.   The pneumatic tire according to any one of claims 1 to 5, wherein an interval between the adjacent bundles is increased by a / 4 (mm) or more as an expected value from an interval expressed using a circumscribed circle of the cord. .

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