JP2009001092A - Tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire capable of solving the conventional problem in manufacturing and being efficiently produced in stable quality, with good tire durability, especially a superior wear resistance characteristic. <P>SOLUTION: A crown reinforced layer 13 has a multi-twist-structure constituted by twisting N (N=2 to 8) strands in which a plurality of wires are twisted. When a diameter of the strand, a diameter of a circumscribed circle of a cord and twisting pitch of the cord are defined as d, D and P, respectively, ε<SB>c</SB>is defined by ε<SB>c</SB>=√(-b/2+√(b<SP>2</SP>/4-c))-1 (b shows -1+π<SP>2</SP>(-4R<SP>2</SP>+d<SP>2</SP>)/P<SP>2</SP>, c shows π<SP>2</SP>d<SP>2</SP>k(4π<SP>2</SP>R<SP>2</SP>+P<SP>2</SP>)/P<SP>4</SP>, R shows (D-d)/2, and k shows tan<SP>2</SP>(π/2-π/N) in this formula). This tire is formed by a strip constituted by orienting a rubber-steel-cord composite body made by burying a steel cord satisfying ε<SB>c</SB>≥0.005 in rubber as a whole along a tire peripheral direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tire, and more particularly, to a tire having improved durability by improving a steel cord as a reinforcing material.

  Steel cords are used for the purpose of reinforcing composites by being embedded in a matrix such as rubber. Among them, rubber-steel cord composites in which rubber is reinforced with steel cords are insufficient for rubber products alone. Therefore, it is widely applied to various rubber products such as tires, belts and hoses.

  Usually, a product including such a composite is manufactured through a process of molding in a state where the matrix is fluidized or softened. In such a process, a steel cord used for reinforcement is rigid. For this reason, the flexibility during the molding process is often limited. Therefore, in the conventional steel cord, the strength and rigidity when made into a product are incompatible with the degree of freedom in the manufacturing process.

  In particular, tires are circular and have a curved surface occupying the majority, so flexibility is required in the manufacturing process, and in the vulcanization process, it is usually expanded in a kettle to fit the mold. It is. Above all, the crown part of the tire always receives a tensile input in the circumferential direction due to internal pressure during use, and creeps and extends the circumference due to use, resulting in distortion and deterioration of the durability, or changing the tire cross-sectional shape The wear characteristics may be deteriorated.

  On the other hand, as a technique related to the reinforcement of the tire crown portion, for example, in Patent Document 1, the tread portion around the carcass includes two layers of crossing belts and at least one layer located in the lower layer, and has a waveform. Alternatively, a technique for effectively preventing separation without increasing the weight of the tire by arranging a reinforcing element of a plurality of zigzag-shaped cords (or filaments) and a crown reinforcing layer formed by a strip oriented along the equator as a whole. It is disclosed.

In Patent Document 1, the use of a strip in which corrugated or zigzag cords or filaments as a whole are oriented along the equator is used as the crown reinforcing layer because the elongation during vulcanization can be easily obtained. It is also disclosed that it becomes simple.
JP-A-2-208101 (Claims etc.)

However, in the technique disclosed in Patent Document 1, in order for this steel cord to exhibit sufficient rigidity after becoming a product, the above waveform or zigzag shape is stretched with internal pressure applied to the product. It needs to be almost eliminated. Therefore, in order to match the physical properties of the product tire with the target value, high accuracy is required in the molding process, which has a problem in terms of production efficiency.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tire that can solve conventional manufacturing problems, can be efficiently produced with stable quality, and has good tire durability, in particular, wear resistance.

  In order to solve the above-mentioned problems, the present inventors have intensively studied and found that the above-mentioned problems can be solved by using a steel cord having a specific structure as a reinforcing material, thereby completing the present invention.

That is, the tire of the present invention has at least a pair of carcasses extending in a toroidal shape across at least a pair of bead cores, and has an inclination angle of 20 to 50 ° with respect to the tire equatorial plane on the outer periphery of the carcass. In a tire having at least two layers of crossing belts in which the reinforcing elements are a plurality of cords or filaments that intersect with each other across the equator plane between layers,
At least one crown reinforcing layer is provided between the layers of the at least two layers of crossing belts, and the crown reinforcing layer is formed by twisting N strands (N = 2 to 8) in which a plurality of strands are twisted together. When the strand diameter is d (mm), the circumscribed circle diameter of the cord is D (mm), and the twisting pitch of the cord is P (mm), the following formula:
ε _c = √ (−b / 2 + √ (b ² / 4−c)) − 1
(In the formula, b is −1 + π ² (−4R ² + d ² ) / P ² , c is π ² d ² k (4π ² R ² + P ² ) / P ⁴ , R is (D−d) / 2, k Is a rubber-steel cord composite formed by embedding a steel cord in which ε _c defined by tan ² (π / 2−π / N) satisfies ε _c ≧ 0.005 in rubber as a whole It is formed from a strip oriented along the tire circumferential direction.

In the tire of the present invention, the steel cord preferably satisfies ε _c ≧ 0.015. In the present invention, it is preferable that there is at least one gap between the N strands in the steel cord.

  According to the present invention, by adopting the above-described configuration, it is possible to solve the conventional manufacturing problems, to produce efficiently with stable quality, and to provide a tire having good tire durability, particularly wear resistance. It became possible to realize.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 shows (a) an enlarged cross-sectional view in the vicinity of a tread portion of a tire according to a preferred embodiment of the present invention, and (b) an explanatory diagram of a laminated state of a reinforcing layer. As shown in the figure, the tire 10 of the present invention has at least a pair of carcass 11 extending in a toroid shape between at least a pair of bead cores (not shown) as a skeleton, and has 20 on the outer periphery of the tire equatorial plane. It has at least two layers of crossing belts 12 each having a slant angle of ˜50 ° and having reinforcing elements made of a plurality of cords or filaments intersecting with each other across the equator plane.

  In the tire of the present invention, it is important that at least one crown reinforcing layer 13 using a steel cord having a specific structure shown below is provided between the layers of the cross belt 12 arranged in at least two layers. FIG. 2 shows a cross-sectional view of an example of a steel cord according to the present invention.

As shown in the figure, the steel cord according to the present invention is illustrated with N strands 2 (N = 2 to 8) in which a plurality of strands 1, preferably 5 to 49 strands 1 are twisted together. In the example, it has a double twist structure in which five strands are twisted, the diameter of the strand is d (mm), the circumscribed circle diameter of the cord is D (mm), and the twist pitch of the cord is P (mm), formula,
ε _c = √ (−b / 2 + √ (b ² / 4−c)) − 1
(In the formula, b is −1 + π ² (−4R ² + d ² ) / P ² , c is π ² d ² k (4π ² R ² + P ² ) / P ⁴ , R is (D−d) / 2, k Ε _c defined by tan ² (π / 2−π / N) satisfies ε _c ≧ 0.005. The crown reinforcing layer 13 according to the present invention is formed of a strip formed by orienting a rubber-steel cord composite in which such a steel cord is embedded in rubber along the tire circumferential direction as a whole.

Since ε _c defined by the above equation satisfies ε _c ≧ 0.005, preferably ε _c ≧ 0.015, as shown in the drawing, At least one gap between them, in the illustrated example, a gap of a certain level or more is formed between all the strands 2, and even when this is embedded in a matrix such as rubber, there is a gap between the strands 2. When the matrix is in a soft state, it can easily stretch up to a certain degree of strain against the tensile strain on the cord. As a result, the molding process of the product becomes easy, and the grace period at the time of vulcanization expansion at the time of tire manufacture becomes large, so that there is an advantage that the manufacture is easy.

  On the other hand, if the fluidity of the matrix becomes small like rubber after vulcanization, even if there is a gap between the strands 2 as described above, the steel cord cannot be deformed like a coil spring to make this gap small, The rigidity of steel will be exhibited as if there is no gap. For this reason, the tensile rigidity of the steel cord when it becomes a product is hardly affected by the magnitude of strain applied to the steel cord in the processing step, and always has high rigidity. Further, in the product, a state in which a gap remains between the strands is preferable in terms of fatigue. However, in the cord of the present invention as described above, even when the strands 2 are in close contact with each other, Compared to the above, the tensile rigidity is not greatly reduced.

  Therefore, the steel cord is excellent in molding processability and can exhibit sufficient rigidity as a reinforcing material after becoming a product tire, and the tire of the present invention using this as a rubber reinforcing material Can be efficiently produced with stable quality, and a desired high rigidity can be obtained in the reinforcing layer, thereby providing good durability, particularly wear resistance. In particular, in the present invention, by applying the steel cord having the above specific structure to the crown reinforcing layer 13 made of a strip oriented along the tire circumferential direction, the elongation during vulcanization can be easily obtained, and the manufacturing is simple. In addition, there is little variation in the physical properties of the product with respect to this variation in expansion during vulcanization, and the merit of ensuring stable quality can be obtained.

  In particular, the present invention is useful when applied to a truck / bus (TBR) tire that is used at a high internal pressure and has a high circumferential tension at the crown.

  In the tire of the present invention, only the point that the steel cord having the specific structure is applied as the reinforcing material of the crown reinforcing layer 13 disposed between the layers of the cross belt 12 is important. In addition to the specific cord diameter and twist pitch, the number of reinforcements to be laid in the reinforcing layer, the specific tire structure and material, etc. should be appropriately set according to conventional methods. There is no particular limitation.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example 1>
As shown in FIG. 2, a cord structure 3 + 9 + 15 × 0.23 mm steel cord, which is conventionally used as a reinforcing material for TBR tires, is used as a strand, and five twisted cords are embedded in rubber. An open rubber-steel cord composite with an open structure was prepared. Here, the open structure means a structure in which the strands are twisted together so that there is a gap in which rubber can enter at least one place.

  In a tire having a two-layer cross belt 12 (material: steel cord) that intersects the tire equator plane at an inclination angle of ± 35 ° on the outer periphery of the carcass 11 as shown in FIG. In this embodiment, a single crown reinforcing layer 13 formed of a strip formed by orienting the rubber-steel cord composite as a whole along the tire circumferential direction is provided (FIG. 1 (b)). No. 1 test tire was produced. The tire size was 495 / 45R225.

<Comparative Example 1>
As shown in the plan view in FIG. 3 (b), the steel cord 20 produced with the same cord structure 3 + 9 + 15 × 0.23 mm as the strand in Example 1 has a wave shape (wavelength: λ, amplitude: 2a). The rubber-steel cord composite of Comparative Example 1 was produced by molding the material in parallel and arranging in parallel and embedding in rubber.

  Except for providing a two-layer crown reinforcing layer 13 formed of a strip formed by orienting the rubber-steel cord composite as a whole along the tire circumferential direction on the inner side in the tire radial direction of the two-layered cross belt 12. In the same manner as in Example 1, a test tire of Comparative Example 1 was produced (FIG. 3A).

Each of the test tires was prepared with four pieces, assembled to a rim width of 8.25 and mounted on a commercial truck, and filled with an internal pressure of 900 kPa. Then, with a load of 25480 N (2600 kgf) on average applied, run 100 km on a 30% pavement highway and 70% pavement general road, center groove depth and shoulder groove depth at the end of the run. Were compared, and the amount of wear (uneven wear level difference) from the new article was compared. As a result, although a difference of 2 mm or more occurred in the tire of Comparative Example 1, it was within 1 mm in the tire of Example 1. In addition, if the amount of wear is within 1 mm, it is satisfactory without any problem.
The results are shown in the following Table 1 together with the strand diameter d, the circumscribed circle diameter D of the cord, the twist pitch P of the cord, and the value of ε _c according to the above formula.

As shown in Table 1 above, the conventional cord is used for the tire of Example 1 in which a double twisted cord having a specific structure in which ε _c defined by the above equation satisfies ε _c ≧ 0.005 is applied to the reinforcing material. Compared to the tire of the comparative example, it was confirmed that it was excellent in uneven wear.

(A) is an expanded sectional view which shows the tread part vicinity of the tire of one suitable example of this invention, (b) is explanatory drawing which shows the lamination | stacking state of the reinforcement layer. It is sectional drawing which shows an example of the steel cord which concerns on this invention. (A) is explanatory drawing which shows the lamination | stacking state of the reinforcement layer of the tire of the comparative example 1, (b) is a schematic plan view which shows the rubber-steel cord composite based on the comparative example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Strand 2 Strand 10 Tire 11 Carcass 12 Crossing belt 13 Crown reinforcement layer

Claims (3)

At least a pair of carcasses extending in a toroid shape across at least a pair of bead cores is used as a skeleton, and the outer circumference of the carcass has an inclination angle of 20 to 50 ° with respect to the tire equator plane, and the equator plane is sandwiched between layers. In a tire having at least two layers of crossing belts having a plurality of cords or filaments intersecting with each other as reinforcing elements,
At least one crown reinforcing layer is provided between the layers of the at least two layers of crossing belts, and the crown reinforcing layer is formed by twisting N strands (N = 2 to 8) in which a plurality of strands are twisted together. When the strand diameter is d (mm), the circumscribed circle diameter of the cord is D (mm), and the twisting pitch of the cord is P (mm), the following formula:
ε _c = √ (−b / 2 + √ (b ² / 4−c)) − 1
(In the formula, b is −1 + π ² (−4R ² + d ² ) / P ² , c is π ² d ² k (4π ² R ² + P ² ) / P ⁴ , R is (D−d) / 2, k the ^{tan 2 (π / 2-π} / N) formed by a steel cord epsilon _c defined satisfies epsilon _c ≧ 0.005 embedded in the rubber by a representative) rubber - steel cord composite as a whole A tire formed of a strip oriented along a tire circumferential direction. The tire according to claim 1, wherein the steel cord satisfies ε _c ≧ 0.015.   The tire according to claim 1 or 2, wherein at least one gap exists between the N strands of the steel cord.

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