JP4693160B2 - Pneumatic tire - Google Patents

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 hydroplaning 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 the ground contact state of the tire during high speed running is observed, the ground contact length (shoulder portion) of the tire is seen to increase in length, and the phenomenon that the contact length of the center portion becomes relatively short occurs. Driving on a road surface on which a water film has been formed in a state where the ground contact shape of the tire is deformed in this way causes a phenomenon that the water film sinks into the tire tread surface, resulting in a sudden possibility of hydroplaning. Will increase. This phenomenon is prominent when high rigidity fibers such as aramid are used as the organic fiber cord of the belt reinforcing layer, rather than a nylon material having a low elastic modulus and large elongation.

As a technique for improving the tire performance during high-speed running 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 calculated in the central region in the tire width direction. A pneumatic radial tire that is smaller than a side region in the tire width direction 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, in order to prevent the deterioration of the hydroplaning performance during high-speed running, the tension acting on the belt reinforcement is appropriately adjusted at the center and shoulders to suppress the deformation of the ground contact shape. Is effective.

  Accordingly, an object of the present invention is to provide a high-performance pneumatic tire in which the tension acting on the center portion and the shoulder portion of the belt reinforcing layer is appropriately adjusted to further improve the hydroplaning performance during high speed running. It is in.

  As a result of intensive studies, the inventor used two or more kinds of organic fiber cords for the belt reinforcement layer, and arranged high-rigidity fibers having a slightly large shrinkage rate in the center portion, thereby the center portion of the belt reinforcement material inside the tire. It has been found that the tension can be increased, thereby increasing the rigidity of the center portion and suppressing the deformation of the ground contact shape 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 ( B), S (A)> S (B) is satisfied,
The organic fiber cord in the tire width direction center portion is made of an aramid / nylon hybrid fiber, and the organic fiber cord in the shoulder portion is made of an aramid fiber.

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 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 hydroplaning performance during high-speed traveling. It became possible to realize a more improved pneumatic tire.

  The pneumatic radial tire described in Patent Document 2 is common with the present invention in that the cord material used in the tire central region has a higher heat shrinkage rate than the cord material used in the shoulder region. However, it is different from the present invention in which a predetermined high rigidity is essential for the organic fiber cord used for the cap in that low-elasticity nylon is used as the cord material in the tire central region.

  In addition, 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 both predetermined tensile elastic moduli 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 when the load is 2.25 g / D exceeds 3.5%, the belt reinforcing layer has insufficient rigidity, and the performance cannot be sufficiently 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 difference in the thermal contraction rate of the belt reinforcing material between the tire width direction center portion 4A and the shoulder portion 4B causes distribution in the initial tension in the tire radial direction, and the tire width direction center portion 4A has a high shrinkage rate. By arranging the rigid fibers, it is possible to suppress the deformation of the ground contact shape of the tire and improve the hydroplaning performance during 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 shoulder portion 4B, a polyketone (PK) is used as the organic fiber cord in the center portion 4A in the tire width direction. ) 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 during running, leading to deterioration of steering stability, while if it exceeds 8.0 MPa, the riding comfort is deteriorated. It is not preferable. Further, when tan δ at 25 ° C. is less than 0.12, fatigue resistance is inferior, while when it exceeds 0.30, rolling resistance is deteriorated, which is not preferable. 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 changed oxygen partial pressure, or 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, Comparative Examples, and Reference 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.

(Hydroplaning generation limit speed)
It entered straight into a pool with a water depth of 10 mm, and the presence or absence of hydroplaning was confirmed. This test was carried out twice. If neither occurred, the speed was increased by 5 km / h and the test was carried out again. This was repeated to determine the rate at which hydroplaning occurred. In the two tests, if hydroplaning occurs even once, it was regarded as the critical generation speed. The results are shown as an index with Comparative Example 1 as 100. The higher the number, the better the result.

＊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 of the central portion of the belt reinforcing layer in the tire width direction, W _B : width of the shoulder portion 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. It was confirmed that the hydroplaning performance was improved as compared with the pneumatic tires of each comparative example using the same organic fiber cord.

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

1 bead core 2 carcass 3 belt layers 4, 14a, 14b belt reinforcing layers 4A, 14A tire width direction center portions 4B, 14B shoulder portions

Claims (6)

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 ( B), S (A)> S (B) is satisfied ,
A pneumatic tire characterized in that the organic fiber cord in the tire width direction center portion is made of an aramid / nylon hybrid fiber, and the organic fiber cord in the shoulder portion is made of an aramid fiber .   2. The pneumatic tire according to claim 1, wherein 0 <WA / (WA + 2WB) <1 is satisfied, where WA is a width of a central portion in the tire width direction of the belt reinforcing layer and WB is a width of a shoulder portion.   The thermal contraction rate S (A) of the organic fiber cord in the tire width direction central portion and the thermal contraction rate 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, satisfying The air according to any one of claims 1 to 3 , 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 4 , wherein the organic fiber cord coating rubber has a 100% modulus in accordance with JIS K6301 within a range of 2.0 to 8.0 MPa. The pneumatic tire according to any one of claims 1 to 5 , 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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