JP4872273B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that is suitable when high-speed durability is required. More specifically, the present invention relates to a pneumatic tire that can improve high-speed durability while suppressing an increase in load dependency of cornering power. Regarding tires.

  In a pneumatic tire, in order to satisfy high-speed durability, it is common to provide a belt cover layer made of an organic fiber cord oriented in the tire circumferential direction on the outer side in the tire radial direction of the belt layer in the tread portion (for example, (See Patent Document 1 and Patent Document 2).

When such a reinforcing structure is adopted, there is a problem that the load dependency of the cornering power generated in the pneumatic tire increases while sufficient performance can be obtained for high-speed durability. Therefore, for example, when a pneumatic tire having the above-described reinforcing structure is mounted on a small FF vehicle, the cornering power of the front wheels becomes relatively larger than the cornering power of the rear wheels during cornering, which tends to oversteer. The steering stability during cornering may be reduced.
JP 2003-146014 A Japanese Patent Application Laid-Open No. 6-143917

  An object of the present invention is to provide a pneumatic tire that can improve high-speed durability while suppressing an increase in load dependency of cornering power.

In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which a belt layer is embedded in a tread portion, and the maximum inward in the tire width direction from the outermost end portion of the belt layer in the tread portion. A circumferential groove extending in the tire circumferential direction is provided in a region up to a position of 30% of the belt width, an annular reinforcing material is disposed at the groove bottom of the circumferential groove, and the reinforcing material is composed of organic fibers. To do.

  In the present invention, a circumferential groove extending in the tire circumferential direction is provided in a region from the outermost end portion of the belt layer in the tread portion to the position of 30% of the maximum belt width inward in the tire width direction, and the groove of the circumferential groove An annular reinforcing material is arranged at the bottom. Such a reinforcing material, unlike the reinforcing material embedded in the tread portion, can improve high-speed durability based on its tagging effect without substantially increasing the load dependency of cornering power. Therefore, the addition of the reinforcing material can improve the high speed durability without impairing the steering stability during cornering.

The reinforcing material is preferably coated with a rubber composition in order to ensure the damage resistance, and particularly preferably coated with a rubber composition having a crosslinking function. The reinforcing material is made of organic fibers in order to avoid an increase in the weight of the tire and to ensure rust prevention . As the organic fiber, it is preferable to select at least one organic fiber selected from the group consisting of nylon, aramid, and polyester.

  On the other hand, the groove width of the circumferential groove is preferably 5 mm or less, and the groove depth of the circumferential groove is preferably 80% or less of the main groove depth. Thereby, the rigidity of a tread part can be maintained. On the other hand, the width of the reinforcing material is preferably 90% or more of the groove bottom width of the circumferential groove. Thereby, high-speed durability can be improved while using a circumferential groove effectively.

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, and FIG. 2 shows the reinforcing material extracted. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between one bead portion 3 and the other bead portion (not shown), and an end portion of the carcass layer 4 is folded around the bead core 5 from the tire inner side to the outer side. On the outer peripheral side of the carcass layer 4 in the tread portion 1, two belt layers 6 are disposed over the entire circumference of the tire. These belt layers 6 include reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords cross each other between the layers.

  A plurality of main grooves 11 extending in the tire circumferential direction are formed in the tread portion 1. The main groove 11 is a groove with a wear indicator. Further, at least one circumferential groove 12 extending in the tire circumferential direction is formed in a region from the outermost end portion of the belt layer 6 in the tread portion 1 to a position of 30% of the maximum belt width W toward the inside in the tire width direction. Is formed. An annular reinforcing material 13 is disposed along the tire circumferential direction at the groove bottom of the circumferential groove 12.

  In the pneumatic tire, the circumferential groove 12 extending in the tire circumferential direction is provided in a region from the outermost end portion of the belt layer 6 in the tread portion 1 to the position of 30% of the maximum belt width W toward the inner side in the tire width direction. An annular reinforcing member 13 is formed at the groove bottom of the circumferential groove 12. Since this reinforcing material 13 is not embedded in the tread portion 1, it does not substantially increase the load dependency of the cornering power, but acts to enhance only the high-speed durability based on the tagging effect. Therefore, the addition of the reinforcing member 13 can improve the high speed durability without impairing the steering stability during cornering. Here, if the position of the circumferential groove 12 in which the reinforcing member 13 is disposed is closer to the tread center than the above region, the effect of reinforcing the belt end portion is insufficient, and the effect of improving the high-speed durability is insufficient.

The reinforcing material 13 can be made of organic fibers , but may be a monofilament or a cord formed by twisting a filament bundle. In particular, in order to avoid an increase in the weight of the tire and to ensure rust prevention, the reinforcing material 13 is made of organic fibers . Examples of the organic fiber include nylon, aramid, and polyester. That is, it is advantageous in terms of cost if a material generally used in the tire manufacturing industry is used. The reinforcing material 13 exhibits a reinforcing effect if a material having an elastic modulus of 200 kgf / mm ² or more and a total fineness of 1500 dtex or more is wound at least once. The cross-sectional shape of the reinforcing member 13 is not particularly limited, but it is preferable that the lateral direction (tire width direction) is wider than the longitudinal direction (tire radial direction).

  The reinforcing member 13 may be disposed in a state exposed to the outside of the groove bottom of the circumferential groove 12, but is coated with a rubber composition 14 as shown in FIG. It is good that it is in the state. The rubber composition 14 may be uncrosslinked or crosslinked. For example, the reinforcing material 13 coated with the unvulcanized rubber composition 14 is wound in the tire circumferential direction along the circumferential groove 12 to lock the both ends to leave the rubber composition 14 uncrosslinked. Alternatively, the rubber composition 14 may be cross-linked by electron beam irradiation or the like. When the rubber composition 14 covering the reinforcing material 13 contains a crosslinking agent and has a crosslinking function, the rubber composition 14 is crosslinked by, for example, heat generation during running of the tire even if the rubber composition 14 is left uncrosslinked. May progress naturally.

  The dimension of the circumferential groove 12 is not particularly limited, but the groove width measured on the tread surface is preferably 1 to 5 mm, and the groove depth is preferably 50 to 80% of the main groove depth. If the dimension of the circumferential groove 12 for arranging the reinforcing member 13 is too large, the rigidity of the tread portion 1 that is originally required becomes insufficient.

  On the other hand, the width of the reinforcing member 13 is preferably 90% or more of the groove bottom width of the circumferential groove 12. That is, by disposing the reinforcing material 13 over most of the groove bottom width of the circumferential groove 12, high-speed durability can be improved while effectively using the circumferential groove 12, but the width of the reinforcing material 13 is If it is less than 90% of the groove bottom width of 12, it is not possible to fully enjoy the effect of improving high-speed durability.

  In the embodiment described above, a circumferential groove shallower than the main groove is provided in a region from the outermost end portion of the belt layer in the tread portion to the position of 30% of the maximum belt width inward in the tire width direction. Reinforcement material is arranged at the groove bottom of the circumferential groove, but if there is a main groove continuous in the tire circumferential direction in the above region, it can also be used as a circumferential groove for arranging the reinforcement material It is.

  The above embodiment exemplifies a structure in which a belt cover layer made of an organic fiber cord oriented in the tire circumferential direction is not provided on the outer side in the tire radial direction of the belt layer. In the present invention, the belt layer or the belt cover layer is exemplified. The belt structure including is not particularly limited. In other words, when the above reinforcing structure is applied to a pneumatic tire in which a belt cover layer is embedded on the outer side in the tire radial direction of the belt layer in the tread portion for the purpose of improving high-speed durability as in the past, the load of the cornering power High-speed durability can be further improved while suppressing an increase in dependency. Of course, when the belt cover layer is positively removed, the load dependency of the cornering power can be reduced, and the steering stability during cornering can be greatly improved.

  In the pneumatic tires of the tire size 175 / 65R14, tires of Conventional Examples 1-2, Examples 1-2, and Comparative Example 1 in which only the tread portion reinforcement structure was varied were manufactured.

  In Conventional Example 1, a belt layer is embedded in the tread portion, and a circumferential groove is disposed at a position of 25% of the maximum belt width from the outermost end portion of the belt layer in the tread portion toward the inner side in the tire width direction. is there.

  In Conventional Example 2, a belt cover layer made of nylon cord covering the belt layer and both edges of the belt layer is embedded in the tread portion, and the outermost end portion of the belt layer in the tread portion is directed inward in the tire width direction. A circumferential groove is arranged at a position of 25% of the maximum belt width.

  In Example 1, a belt layer is embedded in the tread portion, and a circumferential groove is disposed at a position of 20% of the maximum belt width from the outermost end portion of the belt layer in the tread portion toward the inner side in the tire width direction. An annular reinforcing material formed by winding one nylon cord for one turn is disposed on the groove bottom of the circumferential groove.

  In Example 2, a belt layer is embedded in the tread portion, a circumferential groove is disposed at a position of 30% of the maximum belt width from the outermost end portion of the belt layer in the tread portion toward the inside in the tire width direction, An annular reinforcing material formed by winding one nylon cord for one turn is disposed on the groove bottom of the circumferential groove.

  In Comparative Example 1, a belt layer is embedded in the tread portion, a circumferential groove is arranged at a position of 40% of the maximum belt width from the outermost end portion of the belt layer in the tread portion toward the inside in the tire width direction, An annular reinforcing material formed by winding one nylon cord for one turn is disposed on the groove bottom of the circumferential groove.

  These test tires were evaluated for high-speed durability and rear stability by the following test methods, and the results are shown in Table 1.

High speed durability:
The test tire was subjected to an indoor high-speed endurance test in accordance with JIS-D4230, and then the speed was increased by 10 km / h every 10 minutes, and the travel distance until the tire failed was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. It means that high speed durability is excellent, so that this index value is large.

Rear stability:
The test tire was assembled on a wheel with a rim size of 14 × 5.5 J, mounted on a small FF sedan, and a tuck-in behavior test was performed. In other words, the gear was set to the second speed and the accelerator was released during cornering at a speed of 80 km / h, and the behavior of the vehicle was sensory evaluated. The evaluation result was expressed as a five-point score with the conventional example being 0 (reference). A negative value means that the rear stability is relatively bad, and a positive value means that the rear stability is relatively good.

  As shown in Table 1, although the tire of Conventional Example 2 to which the belt cover layer was added was superior in high speed durability as compared with Conventional Example 1, the rear stability was deteriorated. On the other hand, the tires of Examples 1 and 2 in which the reinforcing material was disposed at the groove bottom of the circumferential groove instead of the belt cover layer were superior in high-speed durability and good in rear stability compared to Conventional Example 1. Moreover, since the position of the circumferential groove was out of the specified range, the tire of Comparative Example 1 could not obtain the effect of improving the high speed durability.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a top view which extracts and shows the reinforcing material arrange | positioned at a circumferential groove.

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 11 Main groove 12 Circumferential groove 13 Reinforcement material 14 Rubber composition

Claims (6)

In a pneumatic tire in which a belt layer is embedded in a tread portion, in a tire circumferential direction in a region from the outermost end portion of the belt layer in the tread portion to a position of 30% of the maximum belt width inward in the tire width direction. A pneumatic tire in which an extending circumferential groove is provided, an annular reinforcing material is disposed at the groove bottom of the circumferential groove, and the reinforcing material is made of organic fibers .   The pneumatic tire according to claim 1, wherein the reinforcing material is coated with a rubber composition.   The pneumatic tire according to claim 1, wherein the reinforcing material is coated with a rubber composition having a crosslinking function.   The pneumatic tire according to any one of claims 1 to 3, wherein the reinforcing material is composed of at least one organic fiber selected from the group consisting of nylon, aramid, and polyester. The pneumatic tire according to any one of claims 1 to 4 , wherein a groove width of the circumferential groove is 5 mm or less, and a groove depth of the circumferential groove is 80% or less of a main groove depth. The pneumatic tire according to any one of claims 1 to 5 , wherein a width of the reinforcing material is 90% or more of a groove bottom width of the circumferential groove.

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