JP2006069435A - Radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial tire with excellent turning performance, making ground-contact pressure distribution and ground-contact shape proper and stabilizing behavior of the tire near a cornering limit point. <P>SOLUTION: The radial tire is provided with a radial carcass 4 comprising one sheet or more of carcass ply; and a belt 5 comprising two layers of steel belt layers 5a, 5b arranged on an outer periphery side of a crown part of the radial carcass 4. A ratio of a steel code amount per unit width of the steel belt layer 5a of first layer and the steel belt layer 5b of second layer (embedding number of steel code×steel code cross section) is 100:85-85:100 and a ratio of volume fraction of the steel code (cross section of steel code/whole cross section of steel code and coating rubber) is 100:85-85:100. Flexural rigidity of any one of the steel belt layer is lower than flexural rigidity of the other steel belt layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radial tire. More specifically, the present invention relates to a radial tire that improves the contact pressure distribution and the contact shape by improving the steel belt layer, stabilizes the behavior of the tire near the cornering limit point, and has excellent turning performance. .

  In general, high-performance radial tires of a type that require excellent turning performance are arranged with the steel cords crossing each other on the outer side of the carcass layer in the radial direction of the tire and arranged substantially over the entire tread width. A two-layer belt layer and an additional layer in which cords made of organic fibers are arranged substantially parallel to the tire circumferential direction on the outer side in the radial direction are provided to improve high-speed durability. Here, as the additional layer, for example, it is disposed over the entire width of the belt layer, and is disposed to reinforce an additional reinforcing layer referred to as a so-called cap layer and both side areas of the belt layer, and is referred to as a so-called layer. Additional auxiliary layers and the like are known, and these are general belt structures for high-performance radial tires.

  In conventional radial tires using steel cords in the belt layer, a so-called buckling phenomenon occurs in the vicinity of the high-speed traveling handling or cornering limit point where a heavy load is applied, and the contact pressure distribution of the tire becomes uneven. There was a problem. In particular, in the vicinity of the cornering limit point, the belt layer was bent in the in-plane direction, and there was a problem of occurrence of contact pressure drop on the side where the lateral force entered.

  In order to suppress the occurrence of such a buckling phenomenon, the present applicant has previously proposed in Japanese Patent Application Laid-Open No. H11-228707 to apply a textile cord having a specific initial tensile modulus as a belt layer.

In addition, in the patent document 2, the present applicant secures steering stability by making the bending rigidity of the second steel belt layer lower than the bending rigidity of the first steel belt layer of the second steel belt layer. Has also proposed.
JP-A-7-257110 JP-A-8-164704

  However, the radial tires proposed so far are no longer fully satisfactory today, and there is room for improvement. That is, in the radial tire described in Patent Document 1, the necessary belt rigidity cannot be sufficiently secured, and it is no longer satisfactory in terms of handling stability such as response.

  Further, as in Example 1 and Example 2 described in Patent Document 2, the steel amount of the first steel belt layer and the second steel belt layer (= steel cord driving number × steel cord cross-sectional area) and For radial tires with belt layers that change the volume fraction (cross section of steel cord / total cross section of steel cord and rubber), the asymmetry of the belt layer increases and steering stability such as straight running stability performance There is a problem that it is difficult to ensure a good quality.

  Therefore, the object of the present invention is to improve the above-mentioned drawbacks of conventional high-performance radial tires, optimize the contact pressure distribution and contact shape, stabilize the tire behavior near the cornering limit point, and turn The object is to provide a radial tire with excellent performance.

In order to solve the above-described problems, a radial tire according to the present invention includes a radial carcass including one or more carcass plies, and a belt including two steel belt layers disposed on the outer peripheral side of the crown portion of the radial carcass. In radial tires with
The ratio of the amount of steel cord per unit width of the first steel belt layer and the second steel belt layer (the number of steel cords to be driven × steel cord cross-sectional area) is 100: 85 to 85: 100, and The ratio of volume fraction of steel cord (cross-sectional area of steel cord / total cross-sectional area of steel cord and coated rubber) is 100: 85 to 85: 100,
One of the steel belt layers has a bending rigidity lower than that of the other steel belt layer.

  In a high-performance radial tire including a belt composed of two steel belt layers, the two steel belt layers are subjected to a large in-plane bending deformation in the vicinity of the cornering limit point. Due to this deformation, the belt layer is subjected to a large compressive deformation inside the bending deformation, which causes the occurrence of buckling in the conventional radial tire, but in the present invention, the bending rigidity of the two-layer steel belt layer is totally reduced. As a result, the out-of-plane deformation pressure accompanying the compression deformation is reduced, and buckling deformation can be suppressed by the tire internal pressure. Thereby, the drop of the ground pressure is suppressed, and the ground pressure becomes uniform. In addition, since the bending spring constant and rebound resilience of the cord are small, smooth behavior can be obtained even under high speed conditions.

  According to the present invention, the above-mentioned drawbacks of conventional high-performance radial tires are eliminated, the contact pressure distribution and the contact shape are optimized, the tire behavior near the cornering limit point is stable, and the turning performance is excellent. Has an effect.

An embodiment of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a radial tire according to an embodiment of the present invention.
The illustrated radial tire includes a tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction continuously on both sides of the tread portion 1, and a bead continuous on the inner peripheral side of each sidewall portion 2. Part 3.

  The tread portion 1, the sidewall portion 2, and the bead portion 3 are reinforced by a radial carcass 4 including a single carcass ply extending from one bead portion 3 to the other bead portion 3 in a toroidal shape. Further, the tread portion 1 is reinforced by two steel belt layers 5a and 5b disposed on the outer peripheral side of the crown portion of the radial carcass 4 described in detail below.

  Here, the carcass ply of the radial carcass 4 may be plural, 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 preferably used.

  The steel belt layers 5a and 5b, which are the belt layers on the radial carcass 4 side, have a cord driving angle of preferably 10 ° to 30 ° with respect to the tire circumferential direction, and the belt layers 5a and 5b cross each other.

  In the present invention, the ratio of the steel cord amount per unit width between the first steel belt layer 5a and the second steel belt layer 5b and the ratio of the volume fraction are both 100: 85 to 85: 100. That is, these ratios are substantially equal between the steel belt layer 5a and the steel belt layer 5b, and the bending rigidity of one steel belt layer is lower than the bending rigidity of the other steel belt layer. It is important that This makes it possible to optimize the ground pressure distribution and the ground shape without increasing the asymmetry of the two steel belt layers. As a result, in addition to steering stability such as straight running stability performance, the behavior of the tire near the cornering limit point is stabilized, and excellent turning performance is exhibited.

  In the radial tire of the present invention, as long as the steel cord amount and volume fraction of the first steel belt layer 5a and the second steel belt layer 5b are equal, the bending rigidity of the first steel belt layer 5a is Even if the bending rigidity of the second steel belt layer 5b is lower, or the bending rigidity of the second steel belt layer 5b is lower than the bending rigidity of the first steel belt layer 5a. In any case, the intended purpose of the present invention can be achieved.

  When the bending rigidity of the steel belt layer 5a is lower than the bending rigidity of the steel belt layer 5b, the ratio between the bending rigidity of the steel belt layer 5a and the bending rigidity of the steel belt layer 5b is preferably 10 to 90: 100. More preferably, it is 20-50: 100. When the bending rigidity of the steel belt layer 5b is lower than the bending rigidity of the steel belt layer 5a, the ratio between the bending rigidity of the steel belt layer 5b and the bending rigidity of the steel belt layer 5a is preferably 10. ~ 90: 100, more preferably 20-50: 100. When the ratio between the bending rigidity of the steel belt layer 5a and the bending rigidity of the steel belt layer 5b is within the above preferred range, buckling deformation can be satisfactorily suppressed.

  When the bending rigidity of the steel belt layer 5a is lower than that of the steel belt layer 5b, or when the bending rigidity of the steel belt layer 5b is lower than that of the steel belt layer 5a, both The total bending stiffness of the belt is preferably 1.76 to 10.58 N / mm (180 to 1080 g / mm). When this value is less than 1.76 N / mm, the rigidity of the entire belt 5 is lowered and the entire belt is easily broken. On the other hand, when it exceeds 10.58 N / mm, the steering stability is deteriorated. Absent.

  Examples of cords made of steel fibers that can be applied to the steel belt layers 5a and 5b include steel cords that are usually used for reinforcement of tires and belt members, and are not particularly limited. In order to obtain a particularly high tensile strength, a steel fiber cord containing at least 0.7% by mass, preferably at least 0.8% by mass of carbon is desirable.

  The radial tire of the present invention relates to an improvement in the belt structure, and other structures and materials are not particularly limited, and known structures and materials can be adopted.

Hereinafter, the present invention will be described based on examples, comparative examples, and conventional examples.
Cord structure, number of driving, steel belt layer (treat) bending of first steel belt layer (1B) and second steel belt layer (2B) (corresponding to belt layers 5a and 5b in FIG. 1) shown in Table 1 below Size 185 / 70R14 with stiffness, total belt bending stiffness, steel cord amount (steel cord drive count x steel cord cross section) and volume fraction (steel cord cross section / total cross section of steel cord and coated rubber) Each radial tire was prototyped. The two crossed steel belt layers 5a and 5b are laminated at 22 ° to the right and 22 ° to the left with respect to the tire circumferential direction.

  Treat bending stiffness was measured as follows. First, as shown in FIG. 2A, when a cord with rubber taken out from a tire is hung between three-point pulleys (pulley diameter 10 mmφ, distance between pulleys 50 mm), and the middle pulley is moved in the direction of the arrow, An SS curve can be drawn as shown in 2 (b). Then, when the moving distance becomes 10 mm, the original direction is restored. Next, move the middle pulley again in the direction of the arrow to draw a graph. The inclination θ obtained in this way is the bending rigidity to be obtained, and is expressed by the bending rigidity of the treat = θ × the number of driving (per 50 mm). The evaluation was expressed as an index with the tire of Comparative Example 1 as 100. It shows that bending rigidity is so high that a numerical value is large.

  The prototype tire was mounted on a rim 5.5J, an indoor drum test was performed at an air pressure of 230 kPa, and the maximum value (CFmax) of the cornering force when the slip angle was gradually increased was measured. This value is a substitute value for the steering stability felt by the driver during the high-speed driving handling operation. The evaluation was expressed as an index with the tire of Comparative Example 1 as 100. The larger the value, the better the result. In addition, the test tire was mounted on an actual vehicle, an actual vehicle running test was performed at a load of 3800 N, and the behavior of the tire in the vicinity of the response and cornering limit (limit behavior) was evaluated by the driver's feeling. The obtained results are shown in Table 1 below.

１）１２ＣＣは１×１２のコンパクト撚り構造を意味する。

1) 12CC means 1 × 12 compact twist structure.

  From the results shown in Table 1, the tires of the examples according to the present invention have a steering stability that is an indoor test result and response and limit behavior that are a feeling test result by an actual vehicle, as compared with Comparative Example 1 that is a conventional tire. It turns out that it is excellent in any.

  In the radial tire of the present invention, since the bending rigidity of the belt layer is made softer than the conventional one, the out-of-plane deformation pressure accompanying the belt layer compression is small, and the buckling phenomenon is suppressed. Even if a buckling phenomenon occurs, the belt cord has a small bending spring constant and rebound resilience, so that the behavior becomes gentle and smooth even under high-speed running conditions. As a result, a significant difference appears in the handling stability feeling felt by the driver during high-speed traveling handling operation.

1 is a partial cross-sectional view of a radial tire according to an embodiment of the present invention. (A) And (b) is explanatory drawing which shows the measuring method of the bending rigidity of a steel belt layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Radial carcass 5 Belt 5a 1st steel belt layer 5b 2nd steel belt layer

Claims (9)

In a radial tire comprising a radial carcass composed of one or more carcass plies, and a belt composed of two steel belt layers disposed on the outer peripheral side of the crown portion of the radial carcass,
The ratio of the amount of steel cord per unit width of the first steel belt layer and the second steel belt layer (the number of steel cords to be driven × steel cord cross-sectional area) is 100: 85 to 85: 100, and The ratio of volume fraction of steel cord (cross-sectional area of steel cord / total cross-sectional area of steel cord and coated rubber) is 100: 85 to 85: 100,
A radial tire characterized in that the bending rigidity of one of the steel belt layers is lower than the bending rigidity of the other steel belt layer.   The radial tire according to claim 1, wherein the bending rigidity of the first steel belt layer is lower than the bending rigidity of the second steel belt layer.   The radial tire according to claim 1, wherein a bending rigidity of the second steel belt layer is lower than a bending rigidity of the first steel belt layer.   The radial tire according to claim 2, wherein a ratio of a bending rigidity of the first steel belt layer to a bending rigidity of the second steel belt layer is 10 to 90: 100.   The radial tire according to claim 3, wherein a ratio of a bending rigidity of the second steel belt layer to a bending rigidity of the first steel belt layer is 10 to 90: 100.   The radial tire according to claim 4, wherein a ratio of a bending rigidity of the first steel belt layer to a bending rigidity of the second steel belt layer is 20 to 50: 100.   The radial tire according to claim 5, wherein a ratio of a bending rigidity of the second steel belt layer to a bending rigidity of the first steel belt layer is 20 to 50: 100.   The radial tire according to claim 2, 4 or 6, wherein the total bending rigidity of the belt is 1.76 to 10.58 N / mm.   The radial tire according to claim 3, 5 or 7, wherein the belt has a total bending rigidity of 1.76 to 10.58 N / mm.

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