JP2005047441A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire ensuring run flat traveling performance equal to the conventional one while suppressing increase of mass and improving riding comfort at usual traveling. <P>SOLUTION: The pneumatic tire has a carcass layer 4 comprising at least one sheet of carcass ply 4A extending from a tread part 1 to a bead part 3 through a side wall part 2; and a belt layer 7 comprising at least two sheets of belt plies 7A, 7B arranged at the outside in a tire radial direction of the carcass layer 4 in the tread part 1. The side wall part 2 has a side reinforcement rubber layer 9 having cross section of crescent-like shape at the inside in an axial direction of the carcass ply 4A positioned at the innermost side in the tire axial direction. A high elasticity reinforcement layer 10 including a reinforcement cord having elasticity of 200MPa or higher is arranged between the side reinforcement rubber layer 9 and the carcass ply 4A from a lower part of the belt ply 7A at the innermost side in the tire radial direction to a lower end of a bead filler 6. The cord angle is made to 10° or smaller against the tire radial direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire having run-flat running performance. More specifically, the present invention secures run-flat running performance equivalent to that of a conventional tire while minimizing an increase in mass and improves riding comfort during normal running. It is related with the made pneumatic tire.

  Conventionally, as a pneumatic tire having run-flat running performance, a reinforcing rubber layer having a crescent-shaped cross section is provided in the sidewall portion, and the vertical deflection of the tire at the time of puncture is suppressed based on the rigidity of the reinforcing rubber layer. A pneumatic tire has been proposed in which destruction is prevented (see, for example, Patent Document 1).

In recent years, such run-flat tires have come to be mounted on vehicles as genuine parts, and are gradually attracting attention in the market. However, when a crescent-shaped reinforcing rubber layer is provided on the sidewall portion, there is a drawback that the mass is significantly increased as compared with a general pneumatic tire and the ride comfort is deteriorated due to an increase in the longitudinal spring. Therefore, there is a demand from the market to improve these disadvantages.
Japanese Patent Laid-Open No. 3-176213

  An object of the present invention is to provide a pneumatic tire that can secure a run-flat running performance equivalent to that of a conventional tire while minimizing an increase in mass and that can improve riding comfort during normal running. is there.

  In order to solve the above-described object, a pneumatic tire according to the present invention includes a carcass layer including at least one carcass ply extending from a tread portion through a sidewall portion to a bead portion, and the tire of the carcass layer in the tread portion. In the pneumatic tire having a belt layer composed of at least two belt plies arranged on the outer side in the radial direction, the sidewall portion has a crescent-shaped cross section on the inner side in the axial direction of the carcass ply located on the innermost side in the tire axial direction. A high elastic modulus reinforcing layer having a side reinforcing rubber layer and including a reinforcing cord having an elastic modulus of 200 MPa or more is provided between the side reinforcing rubber layer and the carcass ply from below the innermost belt ply in the tire radial direction. Arranged to the lower end, and the cord angle of the high elastic modulus reinforcing layer was 10 ° or less with respect to the tire radial direction It is an feature.

  In the present invention, in a pneumatic tire provided with a side reinforcing rubber layer having a crescent-shaped cross section, a portion (a portion from the end of the belt layer to the lower end of the bead filler) that receives the largest tensile stress during run-flat running has a high elastic modulus. Since the reinforcement is reinforced by the reinforcing layer, the run-flat running performance equivalent to the conventional one can be ensured while minimizing the volume of the side reinforcing rubber layer. In addition, the ride comfort during normal running can be improved by reducing the cord angle of the high elastic modulus reinforcing layer to 0 ° while minimizing the volume of the side reinforcing rubber layer. Furthermore, the increase in mass can be minimized by reducing the volume of the side reinforcing rubber layer.

  In the present invention, the following conditions are preferably satisfied in order to form a more effective reinforcing structure. That is, the maximum thickness position of the side reinforcing rubber layer is disposed between the maximum tire width position and the end of the belt layer, and the maximum thickness of the side reinforcing rubber layer is 40 to 60% of the total gauge on the tire side wall. In addition, the width of the side reinforcing rubber layer in the tire radial direction is preferably 55 to 75% of the tire cross-sectional height. Further, the rubber composition used for the side reinforcing rubber layer has a hardness (JIS-A) of 50 to 95, a loss tangent tan δ of 0.05 to 0.3, and a 100% modulus of 0.5 to 15. It is preferably 0 MPa.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Between the pair of left and right bead portions 3, 3, a carcass layer 4 including a single carcass ply 4 </ b> A including a plurality of reinforcing cords arranged in parallel is mounted. The carcass layer 4 is composed of at least one carcass ply, and the total number of carcass plies is preferably two or less from the viewpoint of weight reduction. The inclination angle of the reinforcing cord constituting the carcass layer 4 with respect to the tire circumferential direction is 70 to 90 °. The carcass ply 4A is folded around the bead core 5 disposed in the bead portion 3 from the tire inner side to the outer side. Further, the bead filler 6 arranged on the outer periphery of the bead core 5 is wrapped by the carcass ply 4A.

  A belt layer 7 including two belt plies 7A and 7B including a plurality of reinforcing cords arranged in parallel is embedded in the tire radial direction outer side of the carcass layer 4 in the tread portion 1. These belt plies 7A and 7B are disposed so that the reinforcing cords are inclined at 15 to 35 ° with respect to the tire circumferential direction, and the reinforcing cords cross each other between the layers. Further, on the outer side of the belt layer 7 in the tire radial direction, a belt cover layer 8 is provided in which reinforcing cords are oriented in the tire circumferential direction.

  In the sidewall portion 2, a side reinforcing rubber layer 9 having a crescent cross section is inserted on the inner side in the axial direction of the carcass ply 4 </ b> A located on the innermost side in the tire axial direction. The thickness of the side reinforcing rubber layer 9 is gradually reduced from the central portion in the tire radial direction toward the tread side and the bead side. The maximum thickness position of the side reinforcing rubber layer 9 is disposed between the tire maximum width position P and the end E of the belt ply 7A positioned at the innermost side in the tire radial direction, and the maximum thickness t is the total tire sidewall. It is set to 40 to 60% of the gauge T. Further, the width W in the tire radial direction of the side reinforcing rubber layer 9 is set to 55 to 75% of the tire cross-section height SH. By satisfying these dimensional requirements, the side reinforcing rubber layer 9 effectively supports the load in the puncture state, and run-flat running is possible. In addition, if the above dimensional requirements are not satisfied, durability during run-flat running is insufficient.

  Between the side reinforcing rubber layer 9 and the carcass ply 4A, a high elastic modulus reinforcing layer 10 including a high elastic modulus reinforcing cord is located below the belt ply 7A located at the innermost side in the tire radial direction from the lower end of the bead filler 6 ( The tire radial direction inner end) is arranged. More specifically, the high elastic modulus reinforcing layer 10 is disposed only in a portion corresponding to the side reinforcing rubber layer 9 without traversing the tread portion 1. The cord angle of the high elastic modulus reinforcing layer 10 is set to 10 ° or less with respect to the tire radial direction. However, the inclination direction of the reinforcing cord is not particularly limited. When the cord angle of the high elastic modulus reinforcing layer 10 with respect to the tire radial direction exceeds 10 °, the riding comfort during normal running is deteriorated.

  As the reinforcing cord of the high elastic modulus reinforcing layer 10, it is preferable to use an organic fiber cord having an elastic modulus of 200 to 600 MPa and a tensile strength of 5 to 20 MPa. Examples of such an organic fiber cord include an aramid fiber and a rayon fiber. Further, a steel cord can be used as the reinforcing cord of the high elastic modulus reinforcing layer 10. However, if the elastic modulus of the reinforcing cord used for the high elastic modulus reinforcing layer 10 is less than 200 MPa, durability during run flat running becomes insufficient.

  In the pneumatic tire configured as described above, the side wall portion 2 reinforced by the side reinforcing rubber layer 9 is deformed so as to protrude outward in the tire axial direction during run flat running. At this time, the portion from the end portion of the belt layer 7 to the lower end of the bead filler 6 receives a large tensile stress, but the innermost belt in the tire radial direction is interposed between the side reinforcing rubber layer 9 and the carcass ply 4A. Since the high elastic modulus reinforcing layer 10 is disposed from the bottom of the ply 7A to the lower end of the bead filler 6, the bending rigidity of the sidewall portion 2 can be efficiently increased. Therefore, even when the volume of the side reinforcing rubber layer 9 is reduced as compared with the conventional case, the run-flat running performance equivalent to the conventional one can be ensured.

  In addition, the ride comfort during normal running can be improved by reducing the volume of the side reinforcing rubber layer 9 to the minimum and making the cord angle of the high elastic modulus reinforcing layer 10 close to 0 °. Furthermore, since the side reinforcing rubber layer 9 can be made thinner by the addition of the high elastic modulus reinforcing layer 10, a pneumatic tire having run-flat running performance can be made lighter than before.

  The rubber composition used for the side reinforcing rubber layer 9 has a hardness (JIS-A) of 50 to 95, a loss tangent tan δ of 0.05 to 0.3, and a 100% modulus at 20 ° C. of 0.5 to It is preferably 15.0 MPa. However, the loss tangent tan δ is measured using a viscoelastic spectrometer under the conditions of a temperature of 20 ° C., a frequency of 20 Hz, an initial strain of 10%, and a dynamic strain of ± 2%. By defining the physical properties of the rubber composition used for the side reinforcing rubber layer 9 as described above, it is possible to obtain a good reinforcing effect without impairing the ride comfort.

  In the pneumatic tire of tire size 225 / 50R17, run-flat tires of conventional examples, comparative examples, and examples 1 and 2 in which the reinforcing structures in the sidewall portions were varied as described below were manufactured. Moreover, the normal tire (reference example) which is not classified into a run flat tire was prepared.

Conventional example A carcass layer composed of two carcass plies extending from the tread portion through the sidewall portion to the bead portion, and a belt layer composed of two belt plies disposed on the outer side in the tire radial direction of the carcass layer in the tread portion. A pneumatic tire having a side reinforcing rubber layer having a crescent-shaped cross section on the inner side in the axial direction of the carcass ply located at the innermost side in the tire axial direction is manufactured.

Comparative Example A high elastic modulus reinforcing layer including an aramid fiber cord is disposed between the side reinforcing rubber layer and the carcass ply from the bottom of the innermost belt ply in the tire radial direction to the lower end of the bead filler. A pneumatic tire having the same structure as the conventional example was manufactured except that the angle was set to 45 ° with respect to the tire radial direction and the cross-sectional area of the side reinforcing rubber layer was reduced from that of the conventional example.

Example 1
A high elastic modulus reinforcing layer including an aramid fiber cord is arranged between the side reinforcing rubber layer and the carcass ply from the bottom of the innermost belt ply in the tire radial direction to the lower end of the bead filler, and the cord angle of the high elastic modulus reinforcing layer is set. The structure is the same as that of the conventional example except that it is 0 ° with respect to the tire radial direction, the number of carcass plies constituting the carcass layer is one, and the cross-sectional area of the side reinforcing rubber layer is reduced from the conventional example. A pneumatic tire having the above was manufactured.

Example 2
A high elastic modulus reinforcing layer including an aramid fiber cord is arranged between the side reinforcing rubber layer and the carcass ply from the bottom of the innermost belt ply in the tire radial direction to the lower end of the bead filler, and the cord angle of the high elastic modulus reinforcing layer is set. A pneumatic tire having the same structure as that of the conventional example was manufactured except that the cross-sectional area of the side reinforcing rubber layer was reduced from that of the conventional example while being set to 0 ° with respect to the tire radial direction.

Reference Example A carcass layer composed of two carcass plies extending from the tread portion through the sidewall portion to the bead portion, and a belt layer composed of two belt plies disposed on the outer side in the tire radial direction of the carcass layer in the tread portion. A pneumatic tire having That is, this tire is a normal tire that is not classified as a run-flat tire.

  For these test tires, while measuring the tire mass, the run-flat mileage was measured to evaluate the ride comfort, and the results are shown in Table 1.

Run-flat mileage:
Each test tire is assembled on a wheel with a rim size of 17 × 7 1 / 2JJ, mounted on the right side of the front wheel of the rear wheel drive vehicle with the valve core removed and air pressure of 0 kPa, and the elliptical course is counterclockwise at a speed of 90 km / h We measured the distance until the test driver felt abnormal vibration due to a tire failure and stopped driving.

Ride comfort:
Each test tire was assembled on a wheel having a rim size of 17 × 7 1/2 JJ, mounted on all the wheels of the vehicle at an air pressure of 230 kPa, and a feeling test was performed by a test driver. The evaluation results are shown by the 5-point method. A larger evaluation score means better ride comfort.

この表１から判るように、実施例１〜２のタイヤは、従来例との比較において、質量増加を最小限に抑えながら、通常走行時の乗り心地を改善すると共に、ランフラット走行時の耐久性を向上することができた。一方、比較例のタイヤは、ランフラット走行時の耐久性が良好であるものの、通常走行時の乗り心地の悪化が顕著であった。

As can be seen from Table 1, the tires of Examples 1 and 2 improve the ride comfort during normal running and minimize the durability during run flat running while minimizing the increase in mass in comparison with the conventional example. I was able to improve. On the other hand, although the tire of the comparative example has good durability during run-flat running, the ride comfort during normal running was significantly deteriorated.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4A Carcass ply 5 Bead core 6 Bead filler 7 Belt layer 6A, 6B Belt ply 8 Belt cover layer 9 Side reinforcement rubber layer 10 High elastic modulus reinforcement layer

Claims (3)

A carcass layer composed of at least one carcass ply extending from the tread portion through the sidewall portion to the bead portion, and at least two belt plies disposed on the outer side in the tire radial direction of the carcass layer in the tread portion. In the pneumatic tire having a belt layer, the sidewall portion includes a side reinforcing rubber layer having a crescent-shaped cross section on the axially inner side of the carcass ply located on the innermost side in the tire axial direction, A high elastic modulus reinforcing layer including a reinforcing cord having an elastic modulus of 200 MPa or more is arranged between the carcass ply and the belt ply at the innermost side in the tire radial direction to the lower end of the bead filler, and the cord angle of the high elastic modulus reinforcing layer is set A pneumatic tire that is 10 ° or less with respect to the tire radial direction. The maximum thickness position of the side reinforcing rubber layer is disposed between the maximum tire width position and the end of the belt layer, and the maximum thickness of the side reinforcing rubber layer is 40 to 60% of the total gauge on the tire side wall. The pneumatic tire according to claim 1, wherein the width of the side reinforcing rubber layer in the tire radial direction is 55 to 75% of the tire cross-sectional height. The rubber composition used for the side reinforcing rubber layer has a hardness (JIS-A) of 50 to 95, a loss tangent tan δ of 0.05 to 0.3, and a 100% modulus of 0.5 to 15.0 MPa. The pneumatic tire according to claim 1 or 2 which is.

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