JP2010000993A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving ride comfort without the deterioration of driving stability. <P>SOLUTION: In the pneumatic tire, a plurality of carcass layers 4 are mounted between a pair of bead parts 3, and the total thickness T of a sidewall part 2 at the position of the maximum width of the tire is 5 to 8 mm. At least one belt layer 6 composed of a plurality of organic fiber cords tilting with respect to the tire circumferential direction is disposed on the periphery side of the carcass layers 4 in a tread part 1. A reinforced rubber layer 11 is disposed between the carcass layers 4 in the inside position in the tire radial direction of the belt layer 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a belt layer made of an organic fiber cord is disposed in a tread portion. More specifically, the present invention relates to a pneumatic tire that can improve riding comfort while avoiding a decrease in steering stability. .

  Conventionally, in pneumatic tires, it has been proposed to use a belt layer made of an organic fiber cord such as aramid instead of a belt layer made of steel cord for the purpose of improving riding comfort and reducing the weight (for example, Patent Literatures 1 to 3).

However, the belt layer made of organic fiber cord has lower out-of-plane bending rigidity than the belt layer made of steel cord. Therefore, when the belt layer made of organic fiber cord is arranged in the tread part, the tread during cornering under high load conditions There is a problem that a part of the surface is lifted, and the steering stability is lowered due to the reduction of the contact area.
Japanese Patent Laid-Open No. 5-278413 Japanese Patent Laid-Open No. 5-345502 JP-A-6-320904

  An object of the present invention is to provide a pneumatic tire that can improve ride comfort while avoiding a decrease in steering stability.

  In order to achieve the above object, the pneumatic tire of the present invention has a plurality of carcass layers mounted between a pair of bead portions, and the total thickness of the sidewall portions at the tire maximum width position is 5 mm to 8 mm. In the pneumatic tire, at least one belt layer made of a plurality of organic fiber cords inclined with respect to the tire circumferential direction is disposed on the outer peripheral side of the carcass layer in the tread portion, and the inner side in the tire radial direction of the belt layer A reinforcing rubber layer is disposed between the carcass layers at a position.

  In the present invention, the ride comfort can be improved by disposing a belt layer made of an organic fiber cord on the outer peripheral side of the carcass layer in the tread portion. In addition, by placing a reinforced rubber layer between the carcass layers at the inner side of the belt layer in the tire radial direction, the bending rigidity of the tread portion is increased, and the tread surface lift is suppressed during cornering under high load conditions. It is possible to avoid a decrease in steering stability. This makes it possible to achieve both ride comfort and handling stability.

  In the present invention, the ratio of the 100% modulus of the reinforcing rubber layer to the 100% modulus of the coat rubber of the carcass layer is preferably 1.1 to 3.5. This effectively suppresses the tread lift, while minimizing the difference in rigidity near the edge of the reinforced rubber layer, providing a good balance between handling stability and ride comfort and durability. Can be improved. The 100% modulus in the present invention is a tensile stress at 100% elongation defined by JIS K6251.

  The width of the reinforcing rubber layer is preferably 60% to 110% of the width of the narrowest belt layer in the tread portion. As a result, it is possible to effectively prevent the tread surface from being lifted, while ensuring an appropriate flex zone of the tread portion, and to improve steering stability, ride comfort and durability in a well-balanced manner. .

  The average thickness of the reinforcing rubber layer is preferably 0.5 mm to 2.0 mm. This effectively suppresses the tread lift, while minimizing the difference in rigidity near the edge of the reinforced rubber layer, providing a good balance between handling stability and ride comfort and durability. Can be improved.

  The present invention is directed to a pneumatic tire in which the total thickness of the sidewall portion at the tire maximum width position is set to 5 mm to 8 mm. That is, the pneumatic tire of the present invention is a high performance tire that emphasizes ride comfort and driving stability, unlike a tire having a thick sidewall portion like a run flat tire.

  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. The total thickness T of the sidewall portion 2 at the maximum tire width position is set to 5 mm to 8 mm. If the total thickness T of the sidewall portion 2 is less than 5 mm, it becomes difficult to exhibit excellent steering stability, and conversely, if it exceeds 8 mm, the riding comfort is deteriorated.

  As shown in FIG. 1, a plurality of carcass layers 4 including a plurality of aligned carcass cords are mounted between a pair of bead portions 3 and 3. As the carcass cord, an organic fiber cord such as rayon, polyester, nylon, or aramid is preferably used, but a steel cord can also be used. The cord angle of the carcass layer 4 with respect to the tire circumferential direction is not particularly limited, but it is preferably set in a range of 65 ° to 86 °, and the carcass cords cross each other between the layers. Such a configuration contributes to improved steering stability. These carcass layers 4 are wound up around the bead core 5 from the inside to the outside of the tire.

  On the other hand, a plurality of belt layers 6 are arranged on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. The cord angle of the belt layer 6 with respect to the tire circumferential direction is set in the range of 10 ° to 40 °, preferably in the range of 20 ° to 30 °. A belt cover layer 7 including a reinforcing cord oriented substantially at an angle of 0 ° with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 6.

  As the reinforcing cord of at least one layer of the belt layer 6, an organic fiber cord having a high elastic modulus is used. Thus, by disposing the belt layer 6 made of an organic fiber cord on the outer peripheral side of the carcass layer 4 in the tread portion 1, the riding comfort of the pneumatic tire can be improved and the weight can be reduced. As the organic fiber cord having a high elastic modulus, organic fiber cords such as aramid, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybenzoxazole (PBO), and polyolefin ketone (POK) are effective. From the viewpoint of improving ride comfort and reducing weight, it is desirable that all belt layers 6 are made of organic fiber cords. However, belt layers made of steel cords may be combined if necessary.

  In the pneumatic tire, a reinforcing rubber layer 11 is disposed between the carcass layers 4 at a position in the tire radial direction of the belt layer 6. Thus, by arranging the reinforcing rubber layer 11 between the carcass layers 4 at the inner side in the tire radial direction of the belt layer 6, the bending rigidity of the tread portion 1 is increased, and the tread surface of the tread surface during cornering under high load conditions is increased. Lifting can be suppressed. Therefore, even when the belt layer 6 made of an organic fiber cord is employed as described above, it is possible to avoid a decrease in steering stability.

  The reinforcing rubber layer 11 needs to be interposed between the layers of the carcass layer 4. That is, when the reinforcing rubber layer 11 is inserted between the belt layer 6 and the carcass layer 4, the drag force against the interlaminar shear force between the belt layer 6 and the carcass layer 4 is lowered and steering stability is impaired. Become. Further, when the reinforcing rubber layer 11 is arranged on the inner side in the tire radial direction than the carcass layer 4 (for example, when inserted between the carcass layer 4 and the inner liner layer), the effect of increasing the bending rigidity becomes insufficient. When the carcass layer 4 has, for example, a three-layer structure, it is possible to insert the reinforcing rubber layer 11 at both the interlayer positions of the inner two layers and the interlayer positions of the outer two layers. The reinforcing rubber layer 11 may be inserted into only one of them.

  Since the reinforcing rubber layer 11 increases the bending rigidity by separating the pair of carcass layers 4, the constituent material may be the same as the coating rubber of the carcass layer 4. However, the constituent material of the reinforcing rubber layer 11 is different from the coated rubber of the carcass layer 4, and the ratio of the 100% modulus of the reinforcing rubber layer 11 to the 100% modulus of the coated rubber of the carcass layer 4 is in the range of 1.1 to 3.5. It is good to make it. Thereby, while effectively suppressing the tread surface from being lifted, the difference in rigidity near the edge of the reinforcing rubber layer 11 can be minimized. If the modulus ratio is less than 1.1, the effect of suppressing the tread surface lift is reduced, so that the steering stability is reduced. Conversely, if the modulus ratio exceeds 3.5, the rigidity change near the edge of the reinforcing rubber layer 11 is changed. Riding comfort and durability are reduced due to the increased size. In order to obtain the above modulus ratio, the rubber component and the compounding agent may be appropriately selected to increase the 100% modulus of the reinforced rubber layer 11. It is also effective to mix short fibers with the reinforcing rubber layer 11.

  The width W1 of the reinforcing rubber layer 11 is preferably in the range of 60% to 110% of the width W0 of the narrowest belt layer 6 in the tread portion 1. Thereby, while suppressing the lifting of a tread surface effectively, the flex zone of the tread part 1 can be ensured appropriately. If the width W1 of the reinforcing rubber layer 11 is less than 60% of the width W0 of the narrowest belt layer 6, the effect of suppressing the tread surface from rising is reduced, so that the steering stability is lowered. Since the flex zone of the part 1 is reduced, ride comfort and durability are lowered. The reinforcing rubber layer 11 is preferably arranged symmetrically so that the center position in the width direction coincides with the tire equator, but it is allowed to be displaced due to a manufacturing error or the like.

  The average thickness of the reinforcing rubber layer 11 is preferably in the range of 0.5 mm to 2.0 mm. Thereby, while effectively suppressing the tread surface from being lifted, the difference in rigidity near the edge of the reinforcing rubber layer 11 can be minimized. If the average thickness of the reinforced rubber layer 11 is less than 0.5 mm, the effect of suppressing the tread surface from rising is reduced, so that the steering stability is lowered. Conversely, if it exceeds 2.0 mm, the vicinity of the edge of the reinforced rubber layer 11 is reduced. Rigidity at the road increases and ride comfort and durability are reduced.

  The present invention can be applied to various types of pneumatic tires. However, when the present invention is applied to a racing tire in which the thickness of the tread rubber is 3.0 mm to 5.0 mm, a remarkable effect can be obtained. That is, in a racing tire with a thin tread rubber, the belt layer made of an organic fiber cord has a significant effect on the rigidity of the tread portion, and the grounding property during cornering greatly affects the handling stability.

  With tire size 225 / 40R18, two carcass layers are mounted between a pair of bead portions, two belt layers are arranged on the outer periphery side of the carcass layer in the tread portion, and the sidewall at the tire maximum width position In a pneumatic tire having a total thickness of 12 mm, the material of the belt layer, the position of the reinforcing rubber layer, the 100% modulus of the reinforcing rubber layer at 20 ° C. of the coated rubber of the carcass layer at 20 ° C. The tires of conventional examples, comparative examples 1 and 2 and examples 1 to 12 in which the ratio and the average thickness of the reinforcing rubber layer were set as shown in Tables 1 and 2 were produced. The width of the narrowest belt layer in the tread portion is 200 mm.

  These test tires were evaluated for steering stability, riding comfort, and durability by the following test methods, and the results are also shown in Tables 1 and 2.

Steering stability:
The test tire was assembled on a wheel with a rim size of 18 × 8 JJ and mounted on a test vehicle, and a sensory evaluation was performed by a test driver on steering stability under the condition of an air pressure of 220 kPa. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

Ride comfort:
The test tire was assembled on a rim size 18 × 8 JJ wheel and mounted on a test vehicle, and a sensory evaluation was performed on the ride comfort by a test driver under the condition of an air pressure of 220 kPa. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the ride comfort.

durability:
The test tire is mounted on a wheel with a rim size of 18 x 8 JJ and mounted on a drum testing machine with a drum diameter of 1707 mm. Under the conditions of air pressure of 240 kPa and speed of 81 km / h, a load of 13% is applied every 88 hours from 88% of the maximum load capacity. After increasing and running for 32 hours, the test tire was cut, and the size of the separation portion of the carcass layer generated near the edge of the reinforcing rubber layer was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the durability.

  As shown in Tables 1 and 2, the tires of Examples 1 to 12 are improved in a balanced manner in terms of handling stability, riding comfort, and durability in comparison with the conventional examples including a belt layer made of a steel cord. It was. In particular, when the ratio of the 100% modulus of the reinforcing rubber layer to the 100% modulus of the coat rubber of the carcass layer is in the range of 1.1 to 3.5, the width of the reinforcing rubber layer is the width of the narrowest belt layer in the tread portion. Good results were obtained when it was in the range of 60% to 110% and when the average thickness of the reinforcing rubber layer was in the range of 0.5 mm to 2.0 mm.

  On the other hand, since the tire of Comparative Example 1 did not include the reinforcing rubber layer, the steering stability was lowered. The tire of Comparative Example 2 had poor steering stability because the position of the reinforcing rubber layer was between the belt layer and the carcass layer.

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 5 Bead core 6 Belt layer 7 Belt cover layer 11 Reinforcement rubber layer

Claims (4)

  In a pneumatic tire in which a plurality of carcass layers are mounted between a pair of bead portions and the total thickness of the sidewall portions at the tire maximum width position is 5 mm to 8 mm, the outer peripheral side of the carcass layer in the tread portion At least one belt layer made of a plurality of organic fiber cords inclined with respect to the tire circumferential direction is disposed, and a reinforcing rubber layer is disposed between the carcass layers at a position radially inward of the belt layer in the tire radial direction. Pneumatic tire characterized by.   2. The pneumatic tire according to claim 1, wherein the ratio of the 100% modulus of the reinforcing rubber layer to the 100% modulus of the coated rubber of the carcass layer is 1.1 to 3.5. 3.   The pneumatic tire according to claim 1 or 2, wherein a width of the reinforcing rubber layer is 60% to 110% of a width of the narrowest belt layer in the tread portion.   The pneumatic tire according to claim 1, wherein an average thickness of the reinforcing rubber layer is 0.5 mm to 2.0 mm.

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