JP5424474B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run flat tire (hereinafter, also simply referred to as “tire”), and more particularly, to an improvement in a reinforcing cord layer in a side reinforcing type run flat tire.

  Conventionally, even in a state where the internal pressure of the tire has decreased due to puncture or the like, the tire can be safely traveled over a certain distance without losing its load supporting ability, so-called run flat tire, and the inside of the carcass in the sidewall portion On the other hand, a crescent-shaped side reinforcing rubber layer with a relatively high modulus is arranged to improve the rigidity of the side wall, so that the load can be borne without excessively increasing the deformation of the side wall when the internal pressure decreases. Various types of side-reinforced run-flat tires have been proposed.

  However, the conventional side-reinforced run-flat tire has a large deflection of the tire during run-flat running, and the sidewall portion becomes hot during run-flat running, and the rigidity of the sidewall portion is increased due to softening of rubber. Since the lowering and the bending become even larger, the main cause of the failure at the end of the run-flat travel was due to the cracking of the side reinforcing rubber layer having a crescent-shaped cross section. Therefore, the conventional side reinforcement type run flat tire has a problem that the durability distance in the run flat running is short.

  On the other hand, if the sidewall is reinforced by increasing the gauge of the side reinforcing rubber layer, etc., in order to extend the durability distance of the tire during run-flat running, the tire weight increases or the tire runs during normal running. There has been a problem that the ride comfort during normal driving deteriorates due to the vertical spring rising.

  In a run-flat tire, as a technique for achieving both run-flat durability performance and ride comfort, Patent Document 1, for example, in a side-reinforced type run-flat tire, the maximum width portion of the tire side portion from the belt end. A plurality of filament bundles made of polyketone are twisted on the reinforcing cord layer disposed in at least a part of the region A and the region B from the vicinity of the bead core to the bead filler, and the heat shrinkage stress σ and 25 at 177 ° C. A technique using a polyketone fiber cord in which an elastic modulus E at 49 N load at ° C satisfies a predetermined condition is disclosed. Here, the suitable angle with respect to the tire radial direction of the polyketone fiber cord in the reinforcing cord layer is supposed to be 0 to 85 °.

JP 2007-191154 A (Claims etc.)

  According to the technique according to Patent Document 1, it is possible to realize a run-flat tire that satisfactorily achieves both ride comfort during normal traveling and run-flat durability. However, with the recent improvement in required performance, it has been desired to establish a technology that can achieve both of these performances at a higher level.

  Accordingly, an object of the present invention is to provide a run-flat tire that solves the above-described problems and achieves a higher level of both ride comfort during normal driving and run-flat durability.

  As a result of intensive studies, the inventor has found that the above problems can be solved by using a cord that satisfies a specific material and physical property value as a cord of a reinforcing cord layer inserted into a specific portion, and completed the present invention. It came to do.

In other words, the run-flat tire of the present invention is arranged on a radial carcass composed of one or more carcass plies extending in a toroid shape between bead cores embedded in a pair of bead portions, and on the radially outer side of the radial carcass. A tread portion disposed at the outer side in the tire radial direction of the crown portion of the radial carcass, a pair of buttress portions located at both ends of the tread portion, and the buttress portion, A run-flat tire comprising a pair of side portions connecting between the bead portions and a pair of crescent-shaped side reinforcing rubber layers disposed inside the radial carcass extending from the buttress portion to the side portions. In
A reinforcing cord layer covering at least the belt end to the maximum width portion of the tire side portion is provided along the radial carcass, and the cord constituting the reinforcing cord layer has a cord angle of 85 to 90 ° with respect to the tire radial direction. Have
The cords drawn from the tire had a heat shrinkage stress σ (cN / dtex) at 177 ° C. and an elastic modulus E (cN / dtex) at a load of 10 N at 177 ° C. of σ + 0.025E ≧ 0.36, 40 ≧ E It satisfies the conditions of ≧ 8 and σ ≧ 0.05.

  Here, the heat shrinkage stress σ of the cord at 177 ° C. is obtained by heating a 25 cm length fixed sample of the cord before vulcanization subjected to a general dip treatment at a heating rate of 5 ° C./min. This is the stress that occurs in the cord at ℃ In addition, the elastic modulus E at a load of 10 N at 177 ° C. is a unit of cN / dtex calculated from a tangent at 10 N of the obtained SS curve by performing a JIS cord tensile test in a thermostatic chamber set at 177 ° C. Elastic modulus.

  In the present invention, the cord drawn from the tire has a heat shrinkage stress σ (cN / dtex) at 177 ° C. and an elastic modulus E (cN / dtex) at 177 ° C. under a load of 10 N of σ + 0.025E ≧ 0. It is preferable that the conditions of 36, 40 ≧ E ≧ 8 and σ ≧ 0.15 are satisfied. In the present invention, the cord constituting the reinforcing cord layer may be any one selected from the group consisting of nylon 66 cord, cellulosic fiber cord, and a hybrid fiber cord of aramid and nylon 66. preferable.

  Further, the number of cords constituting the reinforcing cord layer is preferably 40 to 60/50 mm. Furthermore, in the present invention, the reinforcing cord layer is preferably formed by winding a cord / rubber composite made of a cord having a width of 5 to 15 mm and rubber in the tire circumferential direction.

  According to the present invention, the above configuration makes it possible to realize a run-flat tire that achieves a higher level of both ride comfort and run-flat durability performance during normal driving than in the past. It was.

It is a width direction one side sectional view showing an example of the run flat tire of the present invention. It is a width direction one side sectional view showing other examples of the run flat tire of the present invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional side view of one example of the run-flat tire of the present invention in the width direction. The run-flat tire shown in the figure has a main body portion extending in a toroidal shape between bead cores 1 embedded in a pair of bead portions 11, and a windup wound around the bead core 1 from the inner side to the outer side in the tire width direction. A radial carcass 2 composed of one or more carcass plies composed of a portion, a tread portion 12 disposed on the outer side in the tire radial direction of the crown portion of the radial carcass 2, and a pair of buttress portions 13 located at both ends thereof, And a pair of side parts 14 connecting the buttress part 13 and the bead part 11, and a pair of crescent-shaped side reinforcing rubber layers 4 on the inner side of the radial carcass 2 extending from the buttress part 13 to the side part 14. Is provided.

  In the illustrated tire, a bead filler 6 is disposed between the main body portion and the folded portion of the radial carcass 2 and outside the bead core 1 in the tire radial direction, and the tire radius of the crown portion of the radial carcass 2 is On the outer side in the direction, a belt 3 composed of two belt layers, a belt reinforcing layer 7A that covers the entire belt 3, and a pair of belt reinforcing layers 7B that cover only both ends of the belt reinforcing layer 7A are sequentially arranged. Yes. Here, the belt layer is usually composed of a rubberized layer of a cord extending in an inclined manner with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord, and the two belt layers constitute each belt layer. The belt 3 is configured by laminating the cords so as to cross each other with the tire equator plane interposed therebetween. The belt reinforcing layers 7A and 7B are usually made of rubberized layers of cords arranged substantially parallel to the tire circumferential direction.

  The radial carcass 2 of the illustrated tire is composed of one carcass ply. However, in the present invention, the number of carcass plies constituting the radial carcass 2 is not limited to this and may be two or more. Further, the structure is not particularly limited. The locking structure of the radial carcass 2 in the bead portion is not limited to the structure in which the radial carcass 2 is wound around and locked around the bead core as shown in the figure, and may be a structure in which the end portion of the radial carcass is sandwiched between two layers of bead cores (not shown). ) In the present invention, as the cord constituting the carcass ply 2, any one selected from the group consisting of a cellulose fiber cord, a polyethylene terephthalate (PET) cord, and a polyethylene naphthalate (PEN) cord is preferably used. it can.

  The illustrated belt 3 includes two belt layers. However, in the present invention, the number of belt layers constituting the belt 3 is not limited to this. Further, the belt reinforcement layers 7A and 7B shown in the figure are composed of a single belt reinforcement layer 7A that covers the entire belt 3 and a pair of belt reinforcement layers 7B that cover only both ends thereof, so-called cap layer structure. However, in the present invention, it is not essential to dispose the belt reinforcing layers 7A and 7B, and a belt reinforcing layer having a different structure and number of layers can be disposed.

  The illustrated tire includes a rim guard 8 having a substantially triangular cross section outside the folded portion of the radial carcass 2 in the region extending from the side portion 13 to the bead portion 11 in the tire width direction. In the present invention, the rim guard 8 is provided. This arrangement is not essential, and rim guards of other shapes can be arranged. In the present invention, the maximum width portion of the tire side portion refers to the maximum width portion of the tire side portion when the rim guard 8 is not provided.

  In the present invention, along the radial carcass 2, in the example shown in FIG. 1, a reinforcing cord layer 5 that covers from the end of the belt 3 to the maximum width portion of the tire side portion is disposed on the outer side in the tire radial direction. . The reinforcing cord layer 5 may be any portion that covers at least the end portion of the belt 3 to the maximum width portion of the tire side portion as a portion where the tensile stress to the carcass ply is large during the run-flat running, thereby reducing the tire weight. The run-flat durability can be effectively improved without increasing it. Further, the reinforcing cord layer 5 may be disposed inside the radial carcass 2 in the tire radial direction, as shown in FIG. Further, the reinforcing cord layer 5 is arranged in one layer in the illustrated example, but may be two or more layers, and the number of layers is not particularly limited.

  The reinforcing cord layer 5 is disposed such that the constituent cords are at an angle of 85 to 90 ° with respect to the tire radial direction. By setting the cord angle of the reinforcing cord layer 5 to be substantially 90 ° with respect to the tire radial direction, it is possible to suppress the longitudinal spring during normal running and to maintain riding comfort as a result. The cord material of the reinforcing cord layer 5 is not particularly limited, but any one selected from the group consisting of nylon 66 cord, cellulosic fiber cord, and a hybrid fiber cord of aramid and nylon 66, It can be used suitably.

  In the present invention, it is necessary to use a cord that satisfies the following physical properties as the cord constituting the reinforcing cord layer 5. That is, first, as the cord pulled out from the tire, the cord has a heat shrinkage stress σ (cN / dtex) at 177 ° C. and an elastic modulus E (cN / dtex) at a load of 10 N at 177 ° C. of σ + 0.025E. The conditions of ≧ 0.36, 40 ≧ E ≧ 8, and σ ≧ 0.05 are satisfied. In the run flat tire at the time of run flat running, unlike normal tires for passenger cars, heat of 150 to 200 ° C. is generated in the vicinity of the reinforcing cord layer 5. By arranging the cord that can express the contraction stress, an effective tightening force can be expressed, the tire can be prevented from being bent, and the run-flat durability can be greatly improved.

Here, the formula σ + 0.025E ≧ 0.36 will be described. The force that supports the tire during run-flat running includes a drag F ₁ that passively develops against input of external force (load and strain) and a drag F ₂ that actively develops the side portion due to heat generation. . Of these, the main governing factor of F ₁ is the rigidity (elastic modulus) E _c of the reinforcing cord layer, and therefore F ₁ is expressed by the following equation.
F ₁ = aE _c (1)
(Wherein, a is the contribution ratio of rigidity to F ₁ , and a> 0)
The major controlling factors of F ₂ is the thermal shrinkage stress F _h of the reinforcing cord layer, thus F ₂ is represented by the following formula.
F ₂ = bF _h (2)
(Where b is the contribution of heat shrinkage stress to F ₂ and b> 0)
That is, in order to effectively support the run-flat running, the sum of F ₁ and F ₂ needs to be above a certain level. If the level is γ, the following equation is established.
F ₁ + F ₂ ≧ γ (3)
(Where γ is a reference amount determined by tire size and load, and γ> 0)
Substituting the formulas (1) and (2) into the above formula (3) leads to the following formula.
aE _c + bF _h ≧ γ
By dividing both sides of this equation by b, the following equation is obtained.
F _h + a / b × E _c ≧ γ / b
Based on the above formula, the formula σ + 0.025E ≧ 0.36 was derived.

  Here, the heat shrinkage stress σ is preferably σ ≧ 0.15, more preferably 1.5 ≧ σ ≧ 0.15. When the thermal shrinkage stress σ exceeds 1.5 cN / dtex, the shrinkage force during vulcanization becomes too large, resulting in the disorder of the cord inside the tire and the disorder of the rubber placement, resulting in deterioration of durability and uniformity. Will be invited. Further, the thermal contraction stress σ of the cord is preferably 0.20 cN / dtex or more from the viewpoint of sufficiently suppressing the deformation of the tire in the run-flat running, and the tire deformation in the run-flat running is surely suppressed. From the viewpoint, it is more preferably 0.30 cN / dtex or more, and even more preferably 0.4 cN / dtex.

  In the present invention, by arranging the reinforcing cord layer 5 using the cord satisfying the above physical property values, it is possible to improve the run flat durability performance while maintaining the vertical spring at the normal internal pressure, It has become possible to achieve both of these performances at a higher level than in the past. In particular, the run-flat tire of the present invention is excellent in cost performance because it can ensure performance equal to or higher than that of conventional polyketone fibers without using expensive polyketone fibers. Here, in the present invention, examples of the method for adjusting the physical property value of the cord include a method for controlling the number of twists of the cord and the tension or temperature during the dipping process. For example, regarding the dip treatment tension, the higher the treatment tension in the final normalizing zone, the higher the elastic modulus of the cord. However, it is not preferable to apply a processing tension exceeding 40 N / line because code breaks frequently occur during processing. The dip temperature basically has little influence on the cord elastic modulus and the heat shrinkage stress in the case of rayon or lyocell, that is, hardly changes even if the temperature is changed. In the case of other cords such as nylon 66 or a hybrid fiber cord of aramid and nylon 66, the elastic modulus is generally higher as the treatment temperature is higher. However, in order to prevent yarn breakage, the treatment is preferably performed at a temperature lower than the melting point by 5 ° C. or more. Furthermore, the smaller the number of twists, the higher the elastic modulus. However, if the number of twists is too small, the fatigue properties and adhesive strength of the cord are significantly reduced, which is not preferable. On the other hand, if the number of twists is too large, the cord strength is lowered and the cord elastic modulus is also lowered. In addition, the suitable range of the twist coefficient in a reinforcement cord layer is comparable as a normal carcass ply.

  The number of cords forming the reinforcing cord layer 5 is preferably 40 to 60/50 mm. If the number of implantations is too small or too large, there is a possibility that the effect of improving the run flat durability cannot be obtained sufficiently.

  A cord / rubber composite used for the reinforcing cord layer 5 can be obtained by coating a cord satisfying the above material and physical properties with a coating rubber at a predetermined number of driving. There is no restriction | limiting in particular as coating rubber used here, The coating rubber conventionally used for the cord / rubber composite for tires can be used. Prior to covering the cord with the coating rubber, the cord may be treated with an adhesive to improve the adhesion to the coating rubber. In this case, the reinforcing cord layer 5 is formed by winding a cord / rubber composite composed of a cord having a width of 5 to 15 mm and rubber in the tire circumferential direction one or more times, thereby further improving the tightening effect. The run flat durability performance can be remarkably improved, which is preferable.

  The run-flat tire of the present invention can be manufactured by a conventional method by arranging the reinforcing cord layer 5 so as to cover at least the belt end to the maximum width portion of the tire side portion. In the run-flat 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.
Fiber cords satisfying the conditions relating to the reinforcing cord layers shown in Tables 1 to 3 below are arranged in parallel by the number of drivings shown in each table, covered with coating rubber, and cords having the widths shown in each table / A rubber composite was prepared. The obtained cord / rubber composite is wound in the tire circumferential direction by the number of times shown in each table to form the reinforcing cord layer 5, and the side reinforcing type run of each embodiment having the structure shown in FIG. 1 or FIG. A flat tire was produced. The tire size was 245 / 45R19. The angles of the cords constituting the reinforcing cord layer 5 with respect to the tire radial direction are as shown in the table. In the table below, the thermal contraction stress σ at 177 ° C. and the elastic modulus E at 10 N load at 177 ° C. of the cords constituting the reinforcing cord layer are values measured for the cords pulled out from the tire.

  Moreover, the run flat tire of the comparative example 1 was produced by the same structure as an Example except not providing the reinforcement cord layer 5. FIG. Furthermore, run cord tires of Comparative Examples 2 to 5 were manufactured by changing the cord conditions of the reinforcing cord layer 5 as shown in the following table.

  About each obtained test tire, the run-flat durability and the vertical spring at the time of internal pressure filling were evaluated according to the following. The results are also shown in Tables 1 to 3 below.

(1) Run-flat durability Drum tests were performed in an environment with a load of 4.17kN, a speed of 89km / h, and a temperature of 38 ° C without filling each test tire with internal pressure. Was measured, and the travel distance until failure of the tire of Comparative Example 1 was taken as 100, which was displayed as an index. The larger the index value, the longer the distance traveled until failure, and the better the run-flat durability.

(2) Longitudinal spring when filling with internal pressure Measure the load-deflection curve of the test tire filled with an internal pressure of 230 kPa, and let the tangential slope at a certain load on the obtained load-deflection curve be the vertical spring constant for the load. The value of the longitudinal spring constant of the tire of Comparative Example 1 was expressed as an index with the value of 100. The smaller the index value is, the smaller the longitudinal spring constant is, and the better the riding comfort during normal driving.

  Here, the physical property values of the cords shown in Tables 1 to 3 above were adjusted by controlling the dip conditions (tension and temperature) and the number of twists. For example, the control conditions when the cord material is nylon 66 (1400/2) are shown in the following table (corresponding to Examples 1 to 4).

  As shown in Table 4 above, for Example 1, the heat shrinkage stress is significantly increased by significantly increasing the dip treatment tension in the normalizing zone and by greatly increasing the number of twists. . In Example 2, the heat shrinkage stress is increased by increasing the dip treatment tension in the normalizing zone and increasing the number of twists. Further, in Example 3, the number of twists was not changed, and the dip treatment tension in the normalizing zone was increased, so that the elastic modulus was increased and the heat shrinkage stress was increased. Furthermore, in Example 4, since the dip treatment tension in the normalizing zone was increased and the number of twists was decreased, the elastic modulus was significantly increased and the heat shrinkage stress was slightly increased.

  From the results of Tables 1 to 3, in the test tires of the examples that satisfy the conditions according to the present invention, the run-flat performance is improved while maintaining the longitudinal spring index, and the performance is improved as a whole. It turns out that the effect is acquired. On the other hand, in Comparative Example 2 in which the cord angle of the reinforcing cord layer is 80 °, the longitudinal spring at the time of filling with the internal pressure becomes large and the ride comfort is impaired.

  Further, in Comparative Examples 3 and 4 in which the elastic modulus and heat shrinkage stress are low and σ + 0.025E <0.36, sufficient elastic modulus and heat shrinkage stress are not exhibited during run-flat travel, so that the side reinforcing rubber layer Deflection could not be sufficiently suppressed, and run-flat durability could not be improved. Furthermore, in Comparative Example 5, the run-flat durability is improved, but the elastic modulus E becomes extremely high, so that the longitudinal spring at the time of filling with the internal pressure becomes large, and the riding comfort is deteriorated.

DESCRIPTION OF SYMBOLS 1 Bead core 2 Radial carcass 3 Belt 4 Side reinforcement rubber layer 5 Reinforcement cord layer 6 Bead filler 7A, 7B Belt reinforcement layer 8 Rim guard 11 Bead part 12 Tread part 13 Buttress part 14 Side part

Claims (5)

A radial carcass made of one or more carcass plies extending in a toroid shape between bead cores embedded in a pair of bead portions, respectively, and at least one belt disposed on the outer side in the tire radial direction of the radial carcass. And a pair of tread portions arranged on the outer side in the tire radial direction of the crown portion of the radial carcass, a pair of buttress portions located at both ends of the tread portion, and a pair connecting the buttress portion and the bead portion. In a run flat tire comprising a pair of crescent-shaped side reinforcing rubber layers disposed inside the radial carcass extending from the buttress portion to the side portion,
A reinforcing cord layer covering at least the belt end to the maximum width portion of the tire side portion is provided along the radial carcass, and the cord constituting the reinforcing cord layer has a cord angle of 85 to 90 ° with respect to the tire radial direction. Have
The cords drawn from the tire had a heat shrinkage stress σ (cN / dtex) at 177 ° C. and an elastic modulus E (cN / dtex) at a load of 10 N at 177 ° C. of σ + 0.025E ≧ 0.36, 40 ≧ E A run-flat tire characterized by satisfying the conditions of ≧ 8 and σ ≧ 0.05.   The cords drawn from the tire had a heat shrinkage stress σ (cN / dtex) at 177 ° C. and an elastic modulus E (cN / dtex) at 10 N load at 177 ° C. of σ + 0.025E ≧ 0.36, 40 ≧ E The run-flat tire according to claim 1, wherein the conditions of ≧ 8 and σ ≧ 0.15 are satisfied.   The run flat according to claim 1 or 2, wherein the cord constituting the reinforcing cord layer is selected from the group consisting of nylon 66 cord, cellulosic fiber cord, and hybrid fiber cord of aramid and nylon 66. tire.   The run-flat tire according to any one of claims 1 to 3, wherein a number of cords constituting the reinforcing cord layer is 40 to 60/50 mm.   The run-flat tire according to any one of claims 1 to 4, wherein the reinforcing cord layer is formed by winding a cord / rubber composite made of a cord having a width of 5 to 15 mm and rubber in a tire circumferential direction.

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