JP2007050726A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire with high performance ensuring performance in high speed traveling to a high degree by suitably adjusting tension applied to a center part and a shoulder part of a belt reinforcement layer. <P>SOLUTION: The pneumatic tire has a carcass 2 troidally extending between a pair of bead cores 1; a belt layer 3 arranged in a radial direction of a crown part; and the belt reinforcement layer 4 arranged at an outer side in a tire radial direction. The belt reinforcement layer 4 comprises two kinds or more of organic fiber cords having elongation of 3.5% or lower inloading a load of 2.25 g/D and the organic fiber cord constituting the belt reinforcement layer has different materials and/or twisting at a central part 4A in a tire width direction and a shoulder part 4B. When a thermal shrinkage percentage of the organic fiber cord at the central part in the tire width direction is represented by S(A) and a thermal shrinkage percentage of the organic fiber cord at the shoulder part is represented by S(B), S(A)<S(B) is satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic tire in which high-speed running performance is improved by improving a belt reinforcing layer.

  Conventionally, on the outer periphery of a belt layer of a pneumatic tire, a twisted cord of an organic fiber such as nylon (polyamide) is substantially disposed in the tire circumferential direction in order to prevent separation of the belt layer (separation between the cord and the covering rubber). It is practiced to dispose a belt reinforcing layer that is spirally wound around the belt.

  Here, the circumferential tension acting on the belt reinforcing member when the vehicle is running is not uniform and largely differs depending on the position in the tire radial direction. In particular, when observing the ground contact state of the tire during high-speed driving or cornering, the contact length of the ground contact edge (near the shoulder) extends more than the center part. The change is considered to be greater at the shoulder than at the center. For this reason, due to the change in the tensile tension, steering stability, rolling resistance, wear resistance, and the like during high speed traveling are deteriorated. Such a phenomenon is conspicuous when high-strength fibers such as aramid are used as the organic fiber cords of the belt reinforcing layer, rather than nylon having a large elongation, that is, relatively low rigidity.

As a technique for improving high-speed durability by improving the physical properties of the belt reinforcing material, for example, in Patent Document 1, the thermal contraction rate of the organic fiber cord constituting the belt reinforcing layer is determined in the tire width direction in the tire width direction central region. A pneumatic radial tire smaller than the side area is described. In Patent Document 2, the cord material used for the belt reinforcing layer is changed between the tire central region and the shoulder region, the cord material in the tire central region is nylon, and the cord material in the shoulder region is a specific polyketone (PK). A pneumatic radial tire is described. Further, Patent Document 3 discloses an organic fiber in which at least a cord in the center portion in the width direction of the belt reinforcing layer is made of polyethylene-2,6-naphthalate (PEN) cord, and cords at both ends in the belt width direction have a predetermined tensile elastic modulus. A radial tire consisting of a cord is described.
JP 2002-370507 A (Claims etc.) JP 2004-306634 A (Claims etc.) JP 2000-203212 A (Claims etc.)

  As described above, it is effective to appropriately adjust the tension acting on the belt reinforcing material between the center portion and the shoulder portion in order to prevent deterioration in performance during high-speed running. As shown in the above-mentioned patent documents 1 to 3, various studies have been made on this point, and a certain effect has been obtained, but with the recent technological development, the performance during high-speed traveling has been secured to a higher degree. Realization of pneumatic tires is required.

  Accordingly, an object of the present invention is to provide a high-performance pneumatic tire that appropriately adjusts the tension acting on the center portion and the shoulder portion of the belt reinforcing layer to ensure higher performance during high-speed running. It is in.

  As a result of intensive studies, the present inventor uses two or more types of organic fiber cords for the belt reinforcement layer, and arranges high-rigidity fibers having a slightly large shrinkage rate in the shoulder portion. The present inventors have found that the tension can be increased, and that it is possible to suppress a decrease in performance during high-speed traveling, and the present invention has been completed.

That is, the pneumatic tire according to the present invention includes a carcass composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores, and two sheets arranged in the radial direction of the crown portion of the carcass and in which cords cross each other. Pneumatic having a belt layer composed of the above belt ply and at least one belt reinforcing layer disposed outside the belt layer in the tire radial direction and having an organic fiber cord wound substantially in the tire circumferential direction In the tire,
The belt reinforcing layer is composed of two or more organic fiber cords having an elongation of 3.5% or less at a load of 2.25 g / D, and the organic fiber cord constituting the belt reinforcing layer is a tire width direction center. The portion and the shoulder portion have different materials and / or twists, and the heat shrinkage rate of the organic fiber cord in the center portion in the tire width direction is S (A), and the heat shrinkage rate of the organic fiber cord in the shoulder portion is S ( When B), S (A) <S (B) is satisfied.

In the present invention, when the width of the central portion in the tire width direction of the belt reinforcing layer is W _A and the width of the shoulder portion is W _B , 0 <W _A / (W _A + 2W _B ) <1 is satisfied. Is preferred. Further, the heat shrinkage rate S (A) of the organic fiber cord in the center portion in the tire width direction and the heat shrinkage rate S (B) of the organic fiber cord in the shoulder portion are S (B) −S (A) ≧ 1. It is also preferable to satisfy 0.0.

  Further, in the pneumatic tire of the present invention, the organic fiber cord in the tire width direction center portion is made of aramid fiber, and the organic fiber cord in the shoulder portion is made of polyethylene naphthalate fiber, aramid / nylon hybrid fiber or It is preferable that the belt reinforcing layer is made of polyketone fiber, and the belt reinforcing layer may be composed of one or more sheets disposed so as to cover the entire width of the belt layer and one or more sheets disposed only on the shoulder portion. Good. The organic fiber cord coating rubber has a 100% modulus in accordance with JIS K6301 in the range of 2.0 to 8.0 MPa, and a tan δ at 25 ° C. in the range of 0.12 to 0.30. Those within are preferred.

  According to the present invention, with the above-described configuration, the tension acting on the belt reinforcing member during traveling can be appropriately adjusted between the center portion and the shoulder portion, thereby improving the performance during high-speed traveling conventionally. Compared to this, it is possible to realize a pneumatic tire with a higher level of security.

  In addition, the pneumatic radial tire described in Patent Document 1 is different in that the thermal contraction rate of the organic fiber cord constituting the belt reinforcing layer is smaller in the center region in the tire width direction than in the tire width direction side region. Although common to the invention, in Patent Document 1, the low-elasticity nylon is always used as one of the two types of organic fibers, and the present invention requires a predetermined high rigidity for the organic fiber cord used for the cap. Is different in this respect. Further, in the pneumatic radial tire described in Patent Document 2, nylon is used as the cord material in the tire central region of the belt reinforcing layer, and a specific polyketone (PK) is used as the cord material in the shoulder region. Unlike the invention, the nylon used in the tire center region has a higher heat shrinkage rate than the PK used in the shoulder region.

  Furthermore, the radial tire of Patent Document 3 is made of polyethylene-2,6-naphthalate cord at the belt reinforcing layer width direction center portion, and organic fiber cord having a predetermined tensile elastic modulus at both belt width direction ends. In the present invention, it is essential that all the organic fiber cords constituting the cap have a predetermined high rigidity. In this respect, the technique described in Patent Document 3 is different from the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In FIG. 1, the schematic sectional drawing of the pneumatic tire of this invention is shown. As shown in the drawing, the tire of the present invention includes a carcass 2 composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores 1 and a crown portion 2 arranged in the radial direction of the crown portion, and cords intersect with each other. The belt layer 3 includes at least one belt ply and at least one belt reinforcing layer 4 that is disposed on the outer side in the tire radial direction and in which an organic fiber cord is wound substantially in the tire circumferential direction.

  In the present invention, the belt reinforcing layer 4 has two or more organic fibers having an elongation of 3.5% or less, preferably 1.0 to 3.4% when a load of 2.25 g / D (denier) is applied. Consists of code. If the elongation of the organic fiber cord under a load of 2.25 g / D exceeds 3.5%, the belt reinforcing layer has insufficient rigidity, and there is a problem that sufficient performance cannot be exhibited.

  Further, in the tire of the present invention, the organic fiber cord constituting the belt reinforcing layer 4 has different materials and / or twists in the tire width direction central portion 4A and the shoulder portion 4B. The direction center portion 4A and the shoulder portion 4B have different heat shrinkage rates. Specifically, when the thermal contraction rate of the organic fiber cord in the tire width direction central portion 4A is S (A) and the thermal contraction rate of the organic fiber cord in the shoulder portion 4B is S (B), S (A) < S (B), preferably, S (B) −S (A) ≧ 1.0 is satisfied.

  That is, the shoulder portion of the belt reinforcing layer 4 is formed by providing the shoulder portion 4B with high-rigidity fibers having a high shrinkage rate by providing a difference in the heat shrinkage rate of the belt reinforcing material between the central portion 4A and the shoulder portion 4B in the tire width direction. The part tension can be increased as compared with the center part tension, thereby suppressing the protrusion of the shoulder part at the time of high speed running and ensuring the performance at the time of high speed running.

  As a specific material of the belt reinforcing material that satisfies the above conditions, for example, when an aramid fiber is used for the organic fiber cord in the tire width direction central portion 4A, polyketone (PK) is used as the organic fiber cord in the shoulder portion 4B. ) Fibers, polyethylene naphthalate (PEN) fibers, or aramid / nylon hybrid fibers can be preferably used.

  By cording the organic fiber cord such as the PK fiber, a cord / rubber composite used for the belt reinforcing layer can be obtained. Here, the coating rubber of the organic fiber cord is not particularly limited, and various compounded rubbers conventionally used for the belt reinforcing layer can be used. In particular, the 100% modulus in accordance with JIS K6301 is 2. A compounded rubber having a range of 0 to 8.0 MPa, preferably 2.3 to 5.5 MPa, and a tan δ at 25 ° C. of 0.12 to 0.30 can be suitably used. If the 100% modulus of the coating rubber is less than 2.0 MPa, the movement in the width direction of the cord increases and the steering stability is deteriorated. On the other hand, if it exceeds 8.0 MPa, the riding comfort is deteriorated. . On the other hand, if tan δ at 25 ° C. is less than 0.12, the fatigue property is inferior, while if it exceeds 0.30, the rolling resistance is deteriorated. Prior to rubberizing the organic fiber cord, an adhesive treatment may be applied to the PK fiber cord to improve the adhesion to the coating rubber. The number of organic fiber cords other than the PK fibers can be determined as appropriate, but is usually in the range of 10 to 50/50 mm.

In the present invention, arrangement width in the tire width of the belt reinforcing layer 4 direction central portion 4A and the shoulder portion 4B is not particularly limited, width W _A of the respective tire width direction center portion, the width of the shoulder portion when was a _{W B, 0 <W a /} (W a + 2W B) <1, preferably, be set to satisfy the _{0.25 <W a / (W a} + 2W B) <0.75 it can.

  Further, it is necessary to provide at least one belt reinforcing layer 4 as shown in FIG. 1, but it covers the entire width of the belt layer 3 as shown in FIGS. 2 (a) and 2 (b). It is also preferable to include one or more belt reinforcing layers 14a arranged and one or more belt reinforcing layers 14b arranged only on the shoulder portion. Also in this case, for each of the two belt reinforcing layers 14a and 14b, it is necessary to determine the material and the like of the organic fiber cord to be used so that the center portion 14A and the shoulder portion 14B in the tire width direction satisfy the above conditions. It is.

  In the pneumatic tire of the present invention, the belt reinforcing layer 4 is not particularly limited except that the belt reinforcing layer 4 is provided so as to satisfy the above conditions for each of the tire width direction center portion 4A and the shoulder portion 4B. For example, although not shown, an inner liner is usually disposed in the innermost layer of the tire, and a tread pattern is appropriately formed on the tread surface. Further, in the pneumatic tire of the present invention, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  The tire of the present invention is manufactured by a conventional method by applying a cord / rubber composite formed by rubberizing different organic fiber cords satisfying the above conditions to each of the central portion and the shoulder portion of the belt reinforcing layer in the tire width direction. can do. In this case, in particular, a ribbon-like sheet obtained by rubberizing one or more reinforcing elements having a width smaller than the width of the belt reinforcing layer 4 is spirally wound a plurality of times in the tire width direction until a predetermined width dimension is reached. A method of forming the belt reinforcing layer 4 by turning it can be preferably used. By forming the reinforcing layer 4 by continuously spirally winding the ribbon-like sheet, a joint portion does not occur in the tire circumferential direction, and the belt layer 3 can be uniformly reinforced.

Hereinafter, the present invention will be described in more detail with reference to examples.
With the structure shown in FIG. 1, pneumatic tires of Examples and Comparative Examples were manufactured according to the conditions shown in Tables 1 and 2 below at a tire size of 245 / 40R18. The results of the following measurements for each test tire are shown in Table 1 below together with the 100% modulus (M100) of the coating rubber used in the organic fiber cord of the belt reinforcing layer according to JIS K6301 and the value of tan δ at 25 ° C. , 2 together. In addition, the measurement of tan δ uses a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Toyo Seiki Co., Ltd. for a coating rubber composition vulcanized under a vulcanization condition of 160 ° C. × 14 minutes, an initial load of 160 g, frequency It is the result measured at 52 Hz, 1% strain, and a measurement temperature of 25 ° C.

(Measurement of heat shrinkage)
An initial load of 0.01782 (g / D) was applied to each organic fiber cord, and heat shrinkage was performed in a 177 ° C. constant temperature bath for 30 minutes, and the heat shrinkage rate was measured.

(Maneuvering stability test)
An actual vehicle feeling test was carried out at a speed of 60 to 200 km / h, and a score of 1 to 10 was given for four items: (i) straight running stability, (ii) turning stability, (iii) rigidity, and (iv) handling. Each item was averaged to give an actual vehicle handling stability score, and comparative evaluation was performed using an index with Comparative Example 1 being 100. The higher the number, the better the result. Two drivers were appointed as the driver, and the average of the scores of the two was determined. The standard of the score is as follows.
0 to 2 points: Unusable, 2 to 4 points: Bad 4 to 6 points: Normal, 6 to 8 points: Good, 8 to 10 points: Very good

＊１）Ｋ＝Ｗ_A／（Ｗ_A＋２Ｗ_B）（Ｗ_A：ベルト補強層のタイヤ幅方向中央部の幅、Ｗ_B：ベルト補強層のショルダー部の幅）
＊２）アラミド：荷重２．２５ｇ／Ｄ負荷時における伸び１．３％
＊３）ＰＥＮ：荷重２．２５ｇ／Ｄ負荷時における伸び２．８％

* 1) K = W _A / (W _A + 2W _B ) (W _A : width at the center of the belt reinforcing layer in the tire width direction, W _B : width of the shoulder of the belt reinforcing layer)
* 2) Aramid: 1.3% elongation at a load of 2.25 g / D
* 3) PEN: Elongation at a load of 2.25g / D 2.8%

＊４）アラミド／ナイロンハイブリッド：荷重２．２５ｇ／Ｄ負荷時における伸び２．５％
＊５）ＰＫ：荷重２．２５ｇ／Ｄ負荷時における伸び２．８％

* 4) Aramid / nylon hybrid: 2.5% elongation at a load of 2.25 g / D
* 5) PK: Elongation 2.8% at a load of 2.25 g / D

  As can be seen from the results in Tables 1 and 2 above, in the pneumatic tire of each example in which the material of the organic fiber cord is changed at the center portion and the shoulder portion in the tire width direction of the belt reinforcing layer and the heat shrinkage rate is set to a predetermined value. Compared to the pneumatic tires of the comparative examples using the same organic fiber cord, it was confirmed that the steering stability was improved.

1 is a schematic cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. (A), (b) is a schematic explanatory drawing which shows the other example of arrangement | positioning of the belt reinforcement layer which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt layer 4, 14a, 14b Belt reinforcement layer 4A, 14A Tire width direction center part 4B, 14B Shoulder part

Claims (9)

A carcass composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores, and a belt layer composed of two or more belt plies arranged in the radial direction of the crown portion of the carcass and in which cords cross each other; In a pneumatic tire having at least one belt reinforcing layer that is disposed on the outer side in the tire radial direction of the belt layer and in which an organic fiber cord is wound substantially in the tire circumferential direction,
The belt reinforcing layer is composed of two or more organic fiber cords having an elongation of 3.5% or less at a load of 2.25 g / D, and the organic fiber cord constituting the belt reinforcing layer is a tire width direction center. The portion and the shoulder portion have different materials and / or twists, and the heat shrinkage rate of the organic fiber cord in the center portion in the tire width direction is S (A), and the heat shrinkage rate of the organic fiber cord in the shoulder portion is S ( A pneumatic tire characterized by satisfying S (A) <S (B) when B). 2. The air according to claim 1, wherein the belt reinforcing layer satisfies the following condition: 0 <W _A / (W _A + 2W _B ) <1, where W _{A is} the width in the center in the tire width direction and W _B is the width of the shoulder. Enter tire.   The heat shrinkage S (A) of the organic fiber cord in the tire width direction center portion and the heat shrinkage S (B) of the organic fiber cord in the shoulder portion are S (B) −S (A) ≧ 1.0. The pneumatic tire according to claim 1 or 2, which satisfies:   The pneumatic tire according to any one of claims 1 to 3, wherein the organic fiber cord in the center portion in the tire width direction is made of an aramid fiber, and the organic fiber cord in the shoulder portion is made of a polyketone fiber.   The pneumatic tire according to any one of claims 1 to 3, wherein the organic fiber cord in the center portion in the tire width direction is made of an aramid fiber, and the organic fiber cord in the shoulder portion is made of a polyethylene naphthalate fiber.   The pneumatic tire according to any one of claims 1 to 3, wherein the organic fiber cord in the center portion in the tire width direction is made of an aramid fiber, and the organic fiber cord in the shoulder portion is made of an aramid / nylon hybrid fiber.   The air according to any one of claims 1 to 6, wherein the belt reinforcing layer includes one or more sheets disposed so as to cover the entire width of the belt layer and one or more sheets disposed only on the shoulder portion. Enter tire.   The pneumatic tire according to any one of claims 1 to 7, wherein a 100% modulus in accordance with JIS K6301 of the coating rubber of the organic fiber cord is in a range of 2.0 to 8.0 MPa.   The pneumatic tire according to claim 1, wherein tan δ at 25 ° C. of the coating rubber of the organic fiber cord is in a range of 0.12 to 0.30.

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