JP5718086B2 - 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 that is more productive and lighter than conventional ones while improving durability.

  In recent years, the importance of environmental performance has increased, and there is an increasing need for weight reduction in rubber articles and tires using steel cords as reinforcing members. To reduce the weight of the tire, it is effective to reduce the thickness of the belt made of steel cord. To that end, it is necessary to make the cross section of the steel cord flat and to reduce the diameter (minor axis) of the steel cord. It is effective.

  Normally, when a steel cord having a (1 × N) structure is flattened using a jig such as a press roller, the initial elongation occurs when a tensile force is applied to the steel cord, so that the effect as a reinforcing member is reduced. . Thus, for example, Patent Documents 1 to 4 have been proposed as a cord structure having a flat shape without impairing the tensile rigidity of the steel cord. The steel cord described in Patent Document 1 has a 2 + 6 structure, and a technique for infiltrating rubber between filaments by providing a gap between sheath filaments has been proposed. Moreover, the steel cord described in Patent Document 2 attempts to solve the above problem by defining the core filament diameter and the sheath filament diameter. Furthermore, the steel cord described in Patent Document 3 discloses a technique for improving the permeability of rubber into the steel cord by defining the ratio between the core filament diameter and the sheath filament diameter. Furthermore, Patent Document 4 discloses a technique for ensuring rubber permeability by adopting a single twist structure or a layer twist structure of 6 to 10 steel filaments.

Japanese Patent Laid-Open No. 9-158066 JP 2005-120491 A JP 2007-63724 A JP 2007-90937 A

  However, although Patent Documents 1 to 4 have been studied from the viewpoint of rubber permeability, that is, durability, it cannot be said that the productivity of the steel cord has been sufficiently studied and is necessary between the sheath filaments. When the above gap is left, the sheath filaments are not evenly distributed around the core filaments, resulting in a problem of poor productivity. That is, when the entire steel cord is bent, the tension on each filament is likely to be non-uniform, causing a phenomenon in which some filaments are stretched out. In addition, since the tension is not evenly distributed to the filament when the steel cord is pulled, there is a problem that the strength is reduced.

  In addition, light truck tires are often used at higher internal pressures and higher loads than passenger car tires, and as a result, many structures having a belt reinforcing layer made of a non-metallic cord have been proposed. Today, there is a demand for further improvement in durability of the belt portion.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire that is more productive and has a reduced weight while improving durability compared to the prior art.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above-described problems can be solved by adopting the following configuration, and has completed the present invention.

That is, the pneumatic tire of the present invention has a pair of bead portions, a pair of sidewall portions that are continuous to the outside in the tire radial direction of both bead portions, and a tread portion that is continuous between both sidewall portions. A belt comprising at least one carcass ply extending in a toroidal shape between bead parts and reinforcing these parts, and at least one belt layer disposed on the outer side in the tire radial direction of the crown part of the carcass. In pneumatic tires with
The steel cord constituting the belt layer is a steel cord comprising a core arranged in parallel without twisting two core filaments, and six sheath filaments twisted around the core, When the diameter of the core filament is dc, the diameter of the sheath filament is ds, and the twist pitch of the sheath filament is p (mm), the following formula (I),
D = [L-6ds {1+ (L / p) 2} 1/2] / 6 (I)
(Wherein L = (π + 2) dc + πds), the average sheath filament spacing D is 25-80 μm, and
A cap layer comprising a rubberized layer of a non-metallic cord disposed outside the belt layer in the tire radial direction over the entire width of the belt layer and arranged substantially parallel to the tire circumferential direction; and / or Layer layers composed of rubberized layers of non-metallic cords arranged in both end regions of the belt layer and arranged substantially parallel to the tire circumferential direction are arranged,
The dc and the ds are represented by the following formulas (II) to (IV),
dc <ds (II)
0.20 ≦ dc ≦ 0.32 (III)
0.27 ≦ ds ≦ 0.43 (IV)
It is characterized by satisfying the relationship represented by

In the present invention, the belt layer preferably has a thickness of 1.30 mm to 1.65 mm, and the sheath filament preferably has a twist pitch of 18 mm or less, and is coated with rubber cut out from a tire. The steel cord has a tensile modulus of 19
0 GPa or more is preferable, and the steel cord has a minor axis of 0.85.
The distance between adjacent steel cords in the inclined belt layer is preferably 0.50 mm to 1.40 mm.

  According to the present invention, it is possible to provide a pneumatic tire that is more productive and has a lighter weight while improving durability than the conventional one.

It is a half sectional view showing a preferred embodiment of the pneumatic tire of the present invention. It is explanatory drawing of the structure of the steel cord which concerns on the pneumatic tire of this invention. It is sectional drawing of the steel cord in case D is less than 25 micrometers. It is sectional drawing of the steel cord in case D is larger than 80 micrometers.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 is a half sectional view showing a preferred embodiment of the pneumatic tire of the present invention. The tire shown in FIG. 1 has a pair of bead portions 1, a pair of sidewall portions 2 that are continuous to the outside in the tire radial direction of both bead portions, and a tread portion 3 that is continuous to both sidewall portions 2. A carcass 4 composed of at least one carcass ply (two in the illustrated example) that extends in a toroidal shape between the bead parts 1 and reinforces the parts 1, 2, and 3, and a tire radius of a crown part of the carcass 4 The belt 5 is composed of at least one (two in the illustrated example) belt layers 5a and 5b disposed on the outer side in the direction. In the illustrated example, on the outer side in the tire radial direction of the belt layers 5a and 5b, 5b, and a layer layer 7 arranged in both end regions of the belt.

  The carcass 4 in the illustrated example is composed of two folded carcass plies. The folded carcass ply includes a main body portion extending in a toroidal shape between a pair of bead cores 8 embedded in the bead portion 1, and each bead core 8. Although it is composed of a folded portion wound around radially outward from the inside in the tire width direction to the outside, the number of plies and the structure of the carcass 4 are not limited to this. The belt 5 is preferably a crossing belt in which steel cords are laminated so as to intersect with each other across the tire equator plane.

In the present invention, the steel cord constituting the belt layer is a steel cord composed of a core in which two core filaments are arranged in parallel without being twisted, and six sheath filaments twisted around the core. When the core filament diameter is dc, the sheath filament diameter is ds, and the sheath filament twist pitch is p (mm), the following formula (I):
D = [L-6ds {1+ (L / p) ² } ^1/2 ] / 6 (I)
An average sheath filament interval D represented by (here, L = (π + 2) dc + πds) is 25 to 80 μm. By using a flat steel cord having such a structure as a belt reinforcing material, the weight of the tire can be reduced without deteriorating durability and productivity. Hereinafter, the steel cord will be described.

  FIG. 2 is an explanatory diagram of the structure of a steel cord according to the pneumatic tire of the present invention. As shown in the figure, the core includes two core filaments 11 arranged in parallel without being twisted, and six sheath filaments 12 twisted around the core. By using such a flat steel cord, the thickness of the belt layer can be reduced, and the weight of the tire can be reduced. The reason why the number of the core filaments 11 is two is that when the number of the core filaments 11 is three or more, it is difficult to arrange them in parallel without being twisted. Moreover, the rubber permeability to the center part of the steel cord 10 required for ensuring durability can be efficiently ensured by using six sheath filaments 12. When the number of sheath filaments is 5 or less, the rubber permeability is good, but the dispersibility of the sheath filament is deteriorated and the strength is insufficient. On the other hand, when the number of sheath filaments is seven or more, it becomes impossible to secure a sufficient gap for rubber penetration, and durability is lowered.

In the present invention, when the diameter of the core filament 11 is dc, the diameter of the sheath filament 12 is ds, and the twist pitch of the sheath filament is p (mm), the following formula (I):
D = [L-6ds {1+ (L / p) ² } ^1/2 ] / 6 (I)
It is important that the average sheath filament interval D represented by (L = (π + 2) dc + πds) satisfies 25 to 80 μm. By combining the diameter dc of the core filament 11 and the diameter ds of the sheath filament 12 so as to satisfy the formula (I), sufficient penetration of the rubber into the gap of the sheath filament 12 can be ensured and no extra gap is left. In addition, deterioration of steel cord productivity and strength reduction due to filament tension during bending of steel cord can be suppressed.

  When D is smaller than 25 μm, for example, as shown in FIG. 3, the rubber cannot sufficiently penetrate into the gap between the sheath filaments 12, and when the belt is cut, moisture penetrates and propagates, so-called cut separation occurs. Will occur. On the other hand, when D is larger than 80 μm, for example, as shown in FIG. 4, the sheath filament 12 is not evenly distributed around the core filament 11, so that the productivity is inferior and rubber is sufficiently applied to the portion where the sheath filament 12 is biased. Cannot penetrate. In addition, there is a concern that the filament may be stretched or the strength may be reduced. Preferably, the thickness is 30 to 70 μm, more preferably 50 to 60 μm. By setting the value of D within this range, the rubber permeability and the dispersibility of the sheath filament 12 are optimally balanced.

In the present invention, the diameter dc of the core filament 11 and the diameter ds of the sheath filament 12 are the following formulas (II) to (IV),
dc <ds (II)
0.20 ≦ dc ≦ 0.32 (III)
0.27 ≦ ds ≦ 0.43 (IV)
It is preferable to satisfy the relationship represented by these. That is, the diameter dc of the core filament 11 and the diameter ds of the sheath filament 12 are different combinations. In particular, the diameter dc of the core filament 11 should be smaller than the diameter ds of the sheath filament 12. Thereby, the short diameter of the flat-shaped steel cord obtained can be made smaller with respect to the case where filaments having the same diameter are combined. Further, by satisfying the above (III) and (IV), the steel cord can obtain higher strength. Preferably 0.23 ≦ dc ≦ 0.27 and 0.30 ≦ ds ≦ 0.35, more preferably 0.24 ≦ dc ≦ 0.26 and 0.32 ≦ ds ≦ 0.34. By setting the core filament diameter dc and the sheath filament diameter ds in this range, weight reduction of the tire can be realized in a balanced manner while maintaining rubber permeability and steel cord strength.

  In the present invention, the rubber layers of the non-metallic cord are arranged on the outer side in the tire radial direction of the belt layers 5a and 5b over the entire width of the belt layers 5a and 5b and arranged substantially parallel to the tire circumferential direction. A layer layer 7 composed of a rubberized layer of a non-metallic cord disposed in both end regions of the cap layer 6 and / or the belt layers 5a and 5b and arranged substantially parallel to the tire circumferential direction. Arranged as layers (see FIG. 1). By arranging the belt reinforcing layer in the circumferential direction, it can sufficiently withstand use under high internal pressure and high load.

  As non-metallic cords, for example, polyamides such as nylon and aramid, polyesters such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and twisted cords made of organic fibers such as rayon, polyketone and vinylon are preferably used. Can do. Note that the number of driven-in wires can be appropriately determined in consideration of the combination with the configuration of the belt cord.

  In the present invention, the thickness of the belt layer is preferably 1.30 mm to 1.65 mm. If the thickness of the belt layer is less than 1.30 mm, sufficient durability may not be obtained, which is not preferable. On the other hand, if the thickness of the belt layer exceeds 1.65 mm, the tire weight reduction effect may not be obtained, which is not preferable. From the viewpoint of reducing the weight of the tire, it is preferably 1.40 mm or more and 1.55 mm or less.

  In the present invention, the twist pitch of the sheath filament 12 is preferably 18 mm or less. When the twist pitch of the sheath filament 12 is larger than 18 mm, the dispersibility of the sheath filament 12 tends to deteriorate, which is not preferable. On the other hand, when the twist pitch of the sheath filament 12 is set to 18 mm or less, the productivity can be further improved. In order to obtain the above effect satisfactorily, the thickness is preferably 16 mm or less. A twist pitch of less than 1 mm is not preferable because it is difficult to manufacture a steel cord.

  Furthermore, in the present invention, it is preferable that the tensile elastic modulus of the rubber-coated steel cord cut out from the tire after the tire vulcanization molding is 190 GPa or more. In particular, light truck tires are often used at a higher internal pressure than passenger car tires, and steel cords preferably have a higher tensile elastic modulus. By setting the tensile modulus of the rubber-coated steel cord cut out from the tire to 190 GPa or more, the in-plane rigidity (rigidity in the tire ground contact surface) of the belt can be improved, and the belt durability can be improved satisfactorily. . Moreover, since belt rigidity improves, the tension | tensile_strength burden concerning the belt reinforcement layer using a nonmetallic cord can be reduced, and the failure starting from a nonmetallic cord can be prevented. On the other hand, if it is less than 190 GPa, the in-plane rigidity of the belt may not be sufficiently exhibited, and the steering stability may be deteriorated.

  Furthermore, in the present invention, it is preferable that the short diameter of the steel cord is 0.85 mm to 1.05 mm. By making the short diameter of the steel cord 1.05 mm or less, the belt can be effectively thinned. When the minor axis is 1.00 mm or less, the effect of weight reduction is increased, which is more preferable. However, if the minor axis is less than 0.85 mm, the amount of steel is greatly reduced, and thus the strength required for the belt may not be ensured.

  Moreover, in this invention, it is preferable that the space | interval of adjacent steel cords is 0.50 mm-1.40 mm. If the distance between the steel cords is less than 0.50 mm, the peeling of the belt layer due to the development of cracks generated from the ends of the steel cords, so-called belt edge separation, may be significantly deteriorated. Preferably they are 0.70 mm or more and 1.20 mm or less. On the other hand, if the distance between the steel cords is greater than 1.40 mm, the number of steel cords to be driven is too small, so that sufficient strength as a tire may not be obtained.

  There is no restriction | limiting in particular as a raw material of the steel filament used for this invention, What is used conventionally can be used, However, It is a high carbon steel whose carbon component is 0.80 mass% or more. Is preferred. The effect of the present invention can be obtained satisfactorily by making the filament material a high carbon steel having a high hardness carbon component of 0.80% by mass or more. On the other hand, if the carbon component exceeds 1.5% by mass, the ductility is lowered and the fatigue resistance is inferior.

  The steel cord of the present invention is preferably plated on the cord surface. The composition of the cord surface plating is not particularly limited, but is preferably brass plating composed of copper and zinc, and more preferably the copper content is 60% by mass or more. Thereby, the adhesiveness of a steel filament and rubber can be improved.

  The material of the coating rubber used in the present invention is not particularly limited, and a known rubber can be used, but those having a Mooney viscosity of 50 or more and 110 or less are preferable. If the Mooney viscosity is less than 50, the tire performance is degraded, and if it is greater than 110, a portion where the rubber does not sufficiently permeate locally occurs between the sheath filaments. Here, the Mooney viscosity is a value obtained by measurement according to JIS-K6300.

  As described above, the pneumatic tire of the present invention is particularly suitable as a light truck tire and truck / bus tire because it is lightweight and excellent in durability. 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.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples 1 to 13, Comparative Examples 1 to 8 and Conventional Examples 1 and 2>
Steel cords and non-metallic cords shown in Tables 1 to 4 below were applied to the belt layer and the belt reinforcing layer, respectively, to produce tires having a tire size of 205 / 65R16. The belt was composed of three belt layers, and steel cords shown in Tables 1 to 4 were applied as reinforcing materials for all belt layers. The angles of the belt layers were + 50 °, + 20 °, and −20 °, respectively, from the inner side in the tire radial direction. The steel cord was arranged so that the major axis direction was along the belt width direction. In addition, a 1400 dtex double-twisted nylon was used for the reinforcing cord of the belt reinforcing layer, and the cord was arranged so as to be parallel to the tire circumferential direction so that the number of driving per 50 mm was 48. The obtained test tires were evaluated for rubber permeability, high speed durability test, diameter growth and belt weight according to the following procedures. The steel cord productivity and cord tensile modulus were also evaluated. The tensile modulus of rubber-coated steel cord cut out from the tire was calculated according to the following procedure.

<Cord tensile modulus>
After the steel cords of the tires of Examples, Comparative Examples, and Conventional Examples were dissected from the tire and removed, excess rubber on the surface of the steel cord at the grip portion was removed, and a tensile test was performed with a cord tensile tester. At that time, the tensile strain was measured by a video extensometer. The distance between the gauge points in the measurement is 100 mm, and the tensile test speed is 10 mm / min. In the obtained stress-strain curve, the slope between two points of the stress at a tensile strain of 0.1% and the stress of 0.5% was calculated, and the cord tensile modulus was calculated. The results are also shown in Tables 1-4. The cross-sectional area of the cord in the stress calculation was calculated by π × (dc ² × 2 + ds ² × 6) / 4.

<Rubber permeability>
The steel cords of the tires of Examples, Comparative Examples, and Conventional Examples were dissected out of the tire and taken out, and then immersed in a NaOH-10% aqueous solution and allowed to stand for 24 hours. Then, the “rubber peel length” was measured. . If rubber penetrates into the steel cord, the rubber will not peel off. The case where the rubber peeling length was equal to or less than that of the steel cord of the conventional example was rated as “◯”, and the case where it was inferior as “X”. The results are also shown in Tables 1-4.

<High speed durability>
After the obtained tire was incorporated into a 6J rim, a high-speed durability drum test was performed in which the internal pressure was filled up to 600 kPa, the load was applied to 8.9 kN, and the speed was increased by 8 km / h every 30 minutes. In the evaluation, the time until the tire broke down starting from the belt portion was measured, and compared with the tire of the conventional example, the case where it was equal to or higher was evaluated as ◯ and the case where it was inferior was evaluated as ×. The results are also shown in Tables 1-4.

<Diameter growth>
After assembling each test tire on a 6J rim, the diameter growth when the internal pressure was filled from 50 kPa to 600 kPa was measured at the center of the belt. The diameter growth amount was suppressed as compared with the belt of the conventional example. The results are also shown in Tables 1-4.

<Belt weight>
Each test tire was dissected and the crossing layer at the center in the width direction was sized in the width direction of 100 mm × circumferential length of 500 mm, and in the thickness direction between the belt layers (the first belt layer and the second belt). Cut out along the rubber at the center of the thickness between the belt layers of the layers and between the belt layers of the second belt layer and the third belt layer), and the weight was measured. The belts that were substantially lighter than the conventional belts were marked with ◯, and the others were marked with ×. The results are also shown in Tables 1-4.

<Code productivity>
The steel cords of the tires of the examples, comparative examples, and conventional examples were bent and deformed, and visually evaluated for filament tension. Further, the steel cord was cut with pliers, and it was visually evaluated whether the filament breakage (so-called flare property) had deteriorated. In those evaluations, those that were not deteriorated from the conventional examples were marked with ◯, and others that were marked with x. The results are also shown in Tables 1-4.

※タイヤから切出したゴム被覆コードの引張弾性率

* Tensile modulus of rubber-coated cord cut from tire

※タイヤから切出したゴム被覆コードの引張弾性率

* Tensile modulus of rubber-coated cord cut from tire

※タイヤから切出したゴム被覆コードの引張弾性率

* Tensile modulus of rubber-coated cord cut from tire

※タイヤから切出したゴム被覆コードの引張弾性率

* Tensile modulus of rubber-coated cord cut from tire

  From the said Tables 1-4, it was confirmed that the pneumatic tire of this invention can obtain the pneumatic tire which was excellent in productivity and implement | achieved weight reduction, improving durability rather than before.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass 5a, 5b Belt layer 6 Cap layer 7 Layer layer 8 Bead core 10 Steel cord 11 Core filament 12 Sheath filament

Claims (6)

It has a pair of bead portions, a pair of sidewall portions that are continuous to the outside in the tire radial direction of both bead portions, and a tread portion that is continuous between both sidewall portions, and extends in a toroidal shape between the pair of bead portions. A pneumatic tire comprising a carcass made of at least one carcass ply for reinforcing each of these parts, and a belt made of at least one belt layer disposed on the outer side in the tire radial direction of the crown part of the carcass.
The steel cord constituting the belt layer is a steel cord comprising a core arranged in parallel without twisting two core filaments, and six sheath filaments twisted around the core, When the diameter of the core filament is dc, the diameter of the sheath filament is ds, and the twist pitch of the sheath filament is p (mm), the following formula (I),
D = [L-6ds {1+ (L / p) 2} 1/2] / 6 (I)
(Wherein L = (π + 2) dc + πds), the average sheath filament spacing D is 25-80 μm, and
A cap layer comprising a rubberized layer of a non-metallic cord disposed outside the belt layer in the tire radial direction over the entire width of the belt layer and arranged substantially parallel to the tire circumferential direction; and / or arranged at both ends region of the belt layer, Ri Na by layer layer made of rubberized layer of substantially non-metallic cord arranged in parallel are arranged with respect to the tire circumferential direction,
The dc and the ds are represented by the following formulas (II) to (IV),
dc <ds (II)
0.20 ≦ dc ≦ 0.32 (III)
0.27 ≦ ds ≦ 0.43 (IV)
A pneumatic tire characterized by satisfying the relationship represented by: The pneumatic tire of claim 1 wherein the thickness of the belt layer is 1.30Mm～1.65Mm. The pneumatic tire according to claim 1 or 2, wherein a twist pitch of the sheath filament is 18 mm or less. The pneumatic tire according to any one of claims 1 to 3 , wherein the rubber-coated steel cord cut out from the tire has a tensile elastic modulus of 190 GPa or more. The pneumatic tire according to any one of claims 1 to 4 , wherein a short diameter of the steel cord is 0.85 mm to 1.05 mm. The pneumatic tire according to any one of claims 1 to 5 , wherein an interval between adjacent steel cords in the belt layer is 0.50 mm to 1.40 mm.

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