JP2008105616A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving deterioration of a braking property and steering stability due to a main inclined groove without causing a problem of deterioration of durability. <P>SOLUTION: In this pneumatic tire, reinforced cords f1, f2 diagonally arranged in a tire peripheral direction T are embedded in rubber layers r1, r2 on an outer peripheral side of a carcass layer 4 of a tread part 1, and two belt layers 8, 9 crossing each other in a manner that a direction inclined to a tire peripheral direction T is made opposite between the reinforced cords f1, f2. A main inclined groove 12 diagonally extending in the tire peripheral direction T is provided on a tread face 1A, and a land part 13 is partitioned by the main inclined groove 12. In an inter-layer gauge defined at an interval between the reinforced cords f1, f2 of the two belt layers 8, 9, an inter-layer gauge t in a belt layer area A positioned on an inner peripheral side of the main inclined groove 12 is thicker than an inter-layer gauge α of a belt layer area B positioned on an inner peripheral side of the land part 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which a decrease in running performance due to an inclined main groove is improved.

  In order to ensure good drainage performance, a pneumatic tire is known in which inclined main grooves that are inclined and extend with respect to the tire circumferential direction on the tread surface are arranged at a predetermined pitch in the tire circumferential direction. In a pneumatic tire provided with such an inclined main groove, since the rigidity of the tread portion is lowered at the position where the inclined main groove is disposed, a buckling phenomenon occurs in the inclined main groove portion when the load is applied, As a result, as shown in FIG. 4, the front and rear ends of the portion 32 a of the land portion 32 adjacent to the inclined main groove 31 are not grounded (the portion indicated by the dotted line is not grounded), and the edge component of the land portion to be ground decreases. At the same time, the ground contact area is reduced. As a result, compared with the case where the front and rear ends of the land portion 32a are grounded, the braking performance during running on wet and dry road surfaces is lowered, and the steering stability is further lowered.

Conventionally, in order to improve the rigidity reduction of the tread portion at the main groove position, a rubber layer harder than the rubber layer is embedded in the tread rubber layer on the inner peripheral side of the main groove, thereby the tread rigidity at the main groove position. A technique is known in which the occurrence of a buckling phenomenon is suppressed and the occurrence of a buckling phenomenon is suppressed (see, for example, Patent Document 1). However, when different types of rubber layers having high hardness are arranged under the grooves as described above, there is a problem that cracks are easily generated at the bottom of the grooves and durability is lowered.
JP-A-7-9815

  An object of the present invention is to provide a pneumatic tire capable of improving the reduction in braking performance and steering stability caused by an inclined main groove without causing the problem of deterioration in durability.

  The pneumatic tire of the present invention that achieves the above-described object extends a carcass layer between the left and right bead parts, and embeds a reinforcing cord inclined in the tire circumferential direction on the outer circumferential side of the carcass layer of the tread part in the rubber layer. In addition, an inclined main groove in which the reinforcing cord is disposed between the layers so that at least two belt layers intersecting each other with the inclination direction with respect to the tire circumferential direction being opposite to each other and extending obliquely with respect to the tire circumferential direction on the tread surface In the pneumatic tire in which the land portion is sectioned by the inclined main groove, an interlayer gauge defined by an interval between reinforcing cords of the two belt layers is positioned on the inner peripheral side of the land portion. The belt layer region A located on the inner peripheral side of the inclined main groove is thicker than the layer region B.

  According to the present invention described above, the out-of-plane bending rigidity of the two belt layers can be increased in the belt layer region A by increasing the interlayer gauge t in the belt layer region A where the inclined main groove is located. Therefore, the tread rigidity is higher than that in the portion where the inclined main groove is disposed, and the difference in rigidity from the land portion can be reduced. Therefore, it is possible to suppress the occurrence of a buckling phenomenon in the inclined main groove portion at the time of grounding with a load and to ground the front and rear end portions of the land portion adjacent to the inclined main groove. As a result, it is possible to suppress a decrease in the edge component of the land portion to be grounded and to increase the ground contact area, thereby improving the braking performance at the time of running on a wet road surface and a dry road surface that is reduced due to the inclined main groove. As well as improved handling stability.

  Since it is not necessary to dispose a different type of hard rubber layer under the inclined main groove, it is possible to avoid the occurrence of cracks due to the different type of hard rubber layer at the bottom of the inclined main groove.

  In addition, since the deformation of the groove bottom of the inclined main groove can be suppressed by increasing the bending rigidity of the two belt layers in the belt layer region A, the occurrence of cracks at the groove bottom of the inclined main groove can be suppressed. This makes it possible to improve durability due to cracks at the bottom of the inclined main groove.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 show an embodiment of the pneumatic tire of the present invention, where 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion.

  The carcass layers 4, 5 are extended between the left and right bead parts 3, and both end parts 4 a of the inner carcass layer 4 are outside from the inside of the tire so that the bead filler 7 is sandwiched around the bead core 6 embedded in the bead part 3. It is folded back. Both ends 5a of the outer carcass layer 5 are wound around the bead core 6 from the tire outer side.

  Two belt layers 8 and 9 are disposed on the outer peripheral side of the carcass layers 4 and 5 of the tread portion 1. The inner first belt layer 8 adjacent to the outer peripheral side of the carcass layer 5 has a rubber layer in which reinforcing cords f1 extending obliquely in one direction with respect to the tire circumferential direction are arranged at predetermined intervals in the tire circumferential direction. The structure is embedded in r1.

  The outer second belt layer 9 disposed on the outer peripheral side of the first belt layer 8 has reinforcing cords f2 extending in an inclined direction in the tire circumferential direction and arranged at predetermined intervals in the tire circumferential direction. The reinforcing cords f1 and f2 of the two belt layers 8 and 9 intersect with each other with the inclination direction with respect to the tire circumferential direction reversed between the layers.

  A belt full cover layer 10 and a belt edge cover layer 11 are disposed on the outer peripheral side of the belt layers 8 and 9, respectively. On the tread surface 1A of the tread portion 1, inclined main grooves 12 that are inclined and extend with respect to the tire circumferential direction are arranged at a predetermined pitch in the tire circumferential direction, and the land portion 13 is divided by the inclined main grooves 12 Is formed. In addition, the inclination main groove 12 here is an inclination groove | channel which inclines and extends in a tire circumferential direction with a groove width of about 5.0-30.0 mm.

  As a tread pattern in which such inclined main grooves 12 are arranged, for example, the one shown in FIG. 3 can be cited. The tread pattern in FIG. 3 is a directional pattern in which the rotation direction of the tire is designated in the direction indicated by the arrow R, and CL is the tire equatorial plane. The tread surface 1A includes a plurality of left-side inclined groove groups 22 each including three left-side inclined main grooves 12 that are inclined in the anti-tire rotation direction with the tread center portion as a start end, and exit to the left shoulder end, and the tread center portion as the start end. Further, a plurality of right inclined groove groups 23 composed of three right inclined main grooves 12 which are inclined in the anti-tire rotation direction and come out to the right shoulder end are alternately arranged in the tire circumferential direction T.

  The left and right inclined main grooves 12 include a first groove portion X extending straight from the tread center portion to the tire contact end position while being inclined with respect to the tire width direction, and the tire outer side along the tire width direction from the first groove portion X. And a second groove portion Y extending in a straight shape. The groove width of the first groove portion X is wider than the groove width of the second groove portion Y.

  The tread surface 1A is provided with one main rib (land portion) 24 extending in a zigzag shape in the tire circumferential direction T by the left and right inclined main grooves 12 and the left and right inclined main grooves 12 from the main rib 24, respectively. Left and right secondary ribs (land portions) 25 are formed. Between each inclined main groove 12 adjacent to the tire circumferential direction T, one inclined narrow groove 26 that is inclined and extends with respect to the tire circumferential direction T is provided. Reference numeral 27 denotes a narrow groove formed in the portion 25 </ b> A of the sub-rib 25 divided by the inclined narrow groove 26.

  In the present invention, the rubber layer 14 is disposed between the two belt layers 8 and 9 in the belt layer region A located on the inner peripheral side of the inclined main groove 12, whereby the two belt layers 8 and 9. In the interlayer gauge defined by the interval between the reinforcing cords f1 and f2, the interlayer gauge t in the belt layer region A is thicker than the interlayer gauge α in the belt layer region B located on the inner peripheral side of the land portion 13. Yes. The rubber layer 14 may be a rubber layer made only of rubber or a rubber layer in which a reinforcing cord is embedded.

  Thus, by increasing the interlayer gauge t in the belt layer region A where the inclined main groove 12 is located, the out-of-plane bending rigidity of the laminated belt layers 8 and 9 can be increased in the belt layer region A. Therefore, the tread rigidity is increased at the portion where the inclined main groove 12 is disposed, and the difference in rigidity from the land portion 13 can be reduced. Therefore, the buckling phenomenon occurs at the portion of the inclined main groove 12 when a load is applied. Can be prevented, and the front and rear ends of the land portion adjacent to the inclined main groove 12 can be grounded. Accordingly, it is possible to suppress a decrease in the edge component of the land portion 13 to be grounded and to increase the ground contact area, thereby improving the braking performance at the time of running on a wet road surface and a dry road surface that is reduced due to the inclined main groove 12. Furthermore, the steering stability can be improved.

  Since it is not necessary to dispose a different type of hard rubber layer under the inclined main groove 12, cracks caused by the different type of hard rubber layer at the bottom of the inclined main groove 12 do not occur.

  In addition, since the deformation of the bottom of the inclined main groove 12 can be suppressed by increasing the bending rigidity of the belt layers 8 and 9 in the belt layer region A, the generation of cracks at the bottom of the inclined main groove 12 is suppressed. As a result, it is possible to improve durability resulting from cracks at the bottom of the inclined main groove 12.

  In the present invention, the interlayer gauge t of the belt layer region A located on the inner peripheral side of the inclined main groove 12 is 0.5-2 from the interlayer gauge α of the belt layer region B located on the inner peripheral side of the land portion 13. It is good to make it thick in the range of 0.0 mm. If the range in which the interlayer gauge t is thickened is less than 0.5 mm, the bending rigidity of the belt layers 8 and 9 in the belt layer region A cannot be effectively increased, so that it is difficult to obtain the above-described effect. If the range in which the interlayer gauge t is thicker exceeds 2.0 mm, the restraining force of the belt layers 8 and 9 with respect to the carcass layer 5 adjacent to the belt layer region A becomes too large, and thus the land portion 13 adjacent to the inclined main groove 12. As a result, it becomes difficult to achieve the above-described effects.

  The pneumatic tire according to the present invention is not limited to the two belt layers 8 and 9 described above, and the reinforcing cords f1 and f2 that are inclined and extend in the tire circumferential direction T are provided with an inclination direction with respect to the tire circumferential direction T between the layers. Any belt having at least two belt layers 8 and 9 crossing each other in the opposite direction may be used.

  In the tread pattern of FIG. 3, an example in which the inclined main grooves 12 are arranged at predetermined intervals in the tire circumferential direction T is shown, but the inclined main grooves 12 continuously extend while drawing a large zigzag shape in the circumferential direction. The inclined main groove 12 referred to here may be inclined in the tire circumferential direction. Moreover, it is not limited to a directional tread pattern, A non-directional tread pattern may be sufficient.

  As an example of increasing the interlayer gauge t in the belt layer region A, in the above-described embodiment, an example in which the rubber layer 14 is arranged has been described. It may be configured to intervene, or one or both of the belt layers 8 and 9 may be thickened in the belt layer region A.

  The present invention can be preferably used particularly for a pneumatic tire used in a passenger car. However, the present invention is not limited thereto, and may be a pneumatic tire for other uses.

  In the present invention tires 1 and 2 and the present invention tire 1 in which the tire size is 245 / 35R19, the tire structure is the same in FIG. 1, the tread pattern is common in FIG. 3, and the interlayer gauge t is thicker than the interlayer gauge α as shown in Table 1. Comparative tires without a rubber layer were prepared.

  Each of these test tires was assembled on a standard rim, the air pressure was set to 230 kPa, and an evaluation test of braking performance, steering stability, and durability was performed according to the following test methods. The results shown in Table 1 were obtained.

Braking performance Each test tire was mounted on a passenger car with a displacement of 2000 cc, full braking was applied at a speed of 100 km / h on wet and dry road test courses, and the distance until stopping was measured five times. The result of averaging the results is shown as an index value with the comparative tire as 100. The larger this value, the better the braking performance.

Steering stability Each test tire was mounted on a passenger car similar to the above, a feeling test by a test driver was performed on the test course, and the evaluation result was shown as an index value with a comparative tire as 100. The larger this value, the better the steering stability.

Durability Each test tire is mounted on a drum testing machine, and under the condition of a load of 4.55 kN, the test speed is increased to 0 to 170 km / h in 10 minutes, followed by running at 170 km / h for 10 minutes, and then 10 The test speed is increased every 10 minutes by 10 km / h up to 200 km / h, and after running for 10 minutes, the drum testing machine is once stopped. Immediately after stopping, the test speed is increased again to 0 to 210 km / h in 10 minutes, and then run at 210 km / h for 10 minutes. Then, the test speed is increased by 10 km / h every 10 minutes, and tire failure occurs. The test speed and time up to were measured. The evaluation results are shown as index values with the comparative tire as 100. The greater this value, the better the durability due to the cracks at the bottom of the inclined main groove.

  From Table 1, it can be seen that the tire of the present invention can improve the braking performance and the steering stability while improving the durability resulting from the cracks at the bottom of the inclined main groove.

It is a tire meridian principal part sectional view showing one embodiment of the pneumatic tire of the present invention. It is a partial expanded sectional view of the two belt layers of FIG. It is a partial development view of a tread surface showing an example of a tread pattern. It is the elements on larger scale which show the shape (footprint) of the grounding part of a tread surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 1A Tread surface 2 Side wall part 3 Bead part 4,5 Carcass layer 8,9, Belt layer 12 Inclined main groove 13 Land part 14 Rubber layer A, B Belt layer area T Tire circumferential direction f1, f2 Reinforcement cord t , Α Interlayer gauge

Claims (2)

A carcass layer is extended between the left and right bead portions, a reinforcing cord inclined in the tire circumferential direction is embedded in the outer circumferential side of the tread portion in the tire circumferential direction, and the reinforcing cord is inclined in the tire circumferential direction between the layers. At least two belt layers intersecting with each other in the opposite direction are arranged, and an inclined main groove extending obliquely with respect to the tire circumferential direction is provided on the tread surface, and the land portion is sectioned by the inclined main groove In a pneumatic tire
An interlayer gauge defined by a distance between reinforcing cords of the two belt layers is a belt layer region located on the inner peripheral side of the inclined main groove with respect to a belt layer region B located on the inner peripheral side of the land portion. Pneumatic tire thickened with A.   The pneumatic tire according to claim 1, wherein an interlayer gauge t in the belt layer region A is 0.5 to 2.0 mm thicker than an interlayer gauge α in the belt layer region B.

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