JP2008296800A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of effectively suppressing generation of uneven wear while sufficiently ensuring turning performance and ride comfort performance of a vehicle. <P>SOLUTION: In the pneumatic tire, a tread pattern constituted by a groove provided on a tread part 1 forms asymmetrical shape regarding a tire equator surface. In the tread part 1, a rubber of higher hardness than a vehicle inner side area IR is arranged at a vehicle outer side area ER while clamping the tire equator plane EP. In the tread pattern, ribs 4A and 4B are arranged at the vehicle outer side area ER while clamping the tire equator plane EP, and the tread pattern forms the asymmetric pattern where a block 5 is only arranged at the vehicle inner side area IR. Further, a recession groove 6 extending in a tire circumferential direction while opened toward a side of the tire is only provided on a buttress part 10 at the vehicle inner side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a tread pattern composed of grooves provided in a tread portion is asymmetric with respect to a tire equatorial plane.

  In general, when the vehicle turns, a large load is applied to the outer region of the vehicle that is outside when the tread portion of the tire is mounted on the vehicle, and uneven wear such as heel and toe wear tends to occur. In particular, minivans and one-box vehicles have a higher center of gravity and a heavier weight than sedan-type vehicles, which increases the load on the vehicle outer region of the tread portion, and the problem of uneven wear is significant.

  On the other hand, when the pattern rigidity of the entire tread pattern and the rubber rigidity of the entire tread portion are increased for the purpose of suppressing uneven wear, there is a problem that the flexibility of the entire tire is lowered and the riding performance is deteriorated.

  As a method for suppressing uneven wear of the tire, in Patent Document 1 below, the radius of curvature of the contour of the tread portion is asymmetric with respect to the tire equatorial plane, and the contact pressure in the vehicle outer region of the tread portion is increased and the tire is directed toward the tire side. It is described that uneven wear in the vehicle outer region of the tread portion is suppressed by providing a concave groove extending in the tire circumferential direction along the periphery of the shoulder portion only on the vehicle outer side.

  However, although this method has an effect of suppressing uneven wear in the vehicle outer region of the tread portion, since the groove is provided along the shoulder portion on the vehicle outer side, the vehicle outer side of the tread portion where a large load is applied when the vehicle turns. Stiffness in the area is reduced. As a result, the turning performance of the vehicle tends to decrease.

  Further, in Patent Documents 2 and 3, the tread pattern in the vehicle inner and outer regions is asymmetrical, and rubber materials having different rigidity are arranged asymmetrically in the vehicle inner and outer regions, so that the pattern rigidity and rubber in the vehicle outer region are arranged. It is described that the rigidity is increased, thereby suppressing uneven wear in the vehicle outer region of the tread portion.

In this method, by increasing the rigidity of the tread portion in the vehicle outer region, it is possible to effectively suppress uneven wear in the vehicle outer region of the tread portion while ensuring good vehicle turning performance. However, since the rigidity of the tread portion in the vehicle inner region is low, uneven wear such as heel and toe wear may occur in the vehicle inner region of the tread portion, and there is room for improving the uneven wear resistance.
Japanese Patent Laid-Open No. 5-139119 Japanese Patent Laid-Open No. 11-32237 JP 2003-326917 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire that can effectively suppress the occurrence of uneven wear while ensuring good vehicle turning performance and riding comfort performance. It is in.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire in which a tread pattern formed by grooves provided in the tread portion is asymmetric with respect to the tire equator surface, and the tread portion is a vehicle outer region across the tire equator surface. The tread pattern has an asymmetric pattern in which ribs are arranged in the vehicle outer area across the tire equator plane and only blocks are arranged in the vehicle inner area. Further, it is characterized in that only a buttress portion inside the vehicle is provided with a concave groove that opens in the tire lateral direction and extends in the tire circumferential direction.

  In the present invention, since the tread portion is provided with rubber having a hardness higher than that of the vehicle inner region in the vehicle outer region across the tire equatorial plane, in the vehicle outer region of the tread portion where a large load is applied when the vehicle turns. The rubber rigidity is increased. As a result, uneven wear in the vehicle outer region of the tread portion is effectively suppressed, and the turning performance of the vehicle can be ensured satisfactorily. In addition, the tread pattern is an asymmetric pattern in which ribs are arranged in the vehicle outer area across the tire equator plane, and only blocks are arranged in the vehicle inner area. Increases rigidity. Thereby, combined with the effect of the high-hardness rubber disposed in the vehicle outer region, it is possible to effectively suppress uneven wear in the vehicle outer region of the tread portion and to ensure good vehicle turning performance. Can do.

  In addition, by providing a concave groove extending in the tire circumferential direction while opening toward the tire side only in the buttress portion inside the vehicle, the tread portion and the side inside the vehicle are secured while ensuring the turning performance of the vehicle outside the vehicle. Interlocking with the wall portion can be suppressed, and the tread portion can have good flexibility. Thereby, since the absorbability with respect to the unevenness on the road surface of the tread portion and the ground contact property are improved, it is possible to effectively suppress uneven wear inside the vehicle while ensuring good riding comfort performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an example of a tire meridian cross-sectional view of a pneumatic tire according to the present invention, and FIG. 2 is an example of a development view of the tread pattern.

  In the pneumatic tire shown in FIG. 1, a pair of bead portions 8 each having a bead core 7, sidewall portions 9 extending outward from the bead portions 8 in the tire radial direction, and portions of the sidewall portions 9 on the outer side in the tire radial direction, The buttress part 10 which is a part that does not come into contact during normal running on a flat paved road, the tread part 1 connected to the buttress part 10, and both ends are folded back and locked by the bead core 7, and are attached to the inner periphery of the tire. A carcass 11 extending along the belt and a belt layer 12 disposed on the outer peripheral side of the tread portion 1 of the carcass 11 are provided.

  Further, as shown in FIG. 2, the pneumatic tire is provided with a plurality of main grooves 2 extending in the tire circumferential direction in the tread portion 1 and lateral grooves 3 extending so as to intersect the main grooves 2.

  In the present embodiment, as shown in FIG. 1, the tread pattern has a rib 4A divided by two main grooves 2 in the vehicle outer region ER across the tire equatorial plane EP, and a main groove located on the outermost side of the vehicle. On the other hand, the vehicle inner area IR has an asymmetric pattern in which only the blocks 5 divided by the two main grooves 2 and the lateral grooves 3 are arranged. As described above, the ribs 4A and 4B are arranged in the vehicle outer area ER across the tire equatorial plane EP, and only the block 5 is arranged in the vehicle inner area IR. Pattern rigidity is increased.

  Here, when the groove area in the vehicle outer region ER across the tire equatorial plane EP is S1, and the groove area in the vehicle inner region IR is S2, the smaller the groove area ratio (S1 / S2), the vehicle inner region. The pattern rigidity in the vehicle outer region ER is higher than IR, but considering adverse effects on other performances, S1 / S2 is 0.90 to 1.10, and further 0.90 to 0.97. In this case, it is preferable because the pattern rigidity in the vehicle outside region ER can be made higher than that in the vehicle inside region IR while minimizing the influence on other performance.

  Further, as shown in FIG. 1, the tread portion 1 is one in which rubber having a hardness higher than that of the vehicle inner region IR is arranged in the vehicle outer region ER across the tire equatorial plane EP. Specifically, for example, a high hardness rubber having a rubber hardness of 65 to 70 according to JISK6253 durometer hardness test (type A) is disposed in the vehicle outer region ER, and a rubber hardness of 55 to 60 is a low hardness. A rubber is arranged in the vehicle inner side region IR, and a rubber hardness difference between the two regions is 5 to 15.

  Here, when the ground contact width of the portion where the high hardness rubber is disposed is W and the tire ground contact width is Wo, the portion where the high hardness rubber is disposed so that 0.4 <W / Wo <0.6. And a boundary surface B between the portion where the low hardness rubber is arranged. FIG. 1 shows an example in which the boundary surface B is provided in the tire equatorial plane EP. The boundary surface B may be provided so as to be perpendicular to the tire rotation axis as shown in FIG. 1, or may be provided obliquely. When provided obliquely, the contact width W of the portion where the high hardness rubber is arranged from the boundary surface B at the center position in the thickness direction of the tread rubber is determined.

  Further, as shown in FIG. 1, in the present embodiment, only the buttress portion 10 on the vehicle inner side is provided with a concave groove 6 that opens in the tire lateral direction and extends in the tire circumferential direction. Thereby, the interlock | linkage with the tread part 1 and the sidewall part 9 inside a vehicle can be suppressed, the softness | flexibility of the tread part 1 can be ensured favorably, and absorptivity and grounding property can be improved. In order to appropriately exhibit such an effect, the size of the groove 6 is preferably 3 to 20 mm and a groove depth of 0.5 to 3 mm, but is not particularly limited.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

(1) Turning performance of vehicle A test tire (size 225 / 45R18 91W) is mounted on a rim with a wheel size of 7.5JJ on a domestic minivan, and it turns at a constant steering angle on a circular course with a radius of 57m under dry conditions. The speed was increased until the course was off and the limit speed was measured. The faster the limit speed, the better the turning performance of the vehicle.

(2) Ride Comfort Performance A test tire (size 225 / 45R18 91W) was mounted on a rim with a wheel size of 7.5JJ on a domestic minivan, and the ride performance was evaluated by sensory evaluation. The evaluation was made by index evaluation with Comparative Example 1 as 100. It shows that it is excellent in riding comfort performance, so that a numerical value is large.

(3) Uneven wear resistance After running 12,000km on a Japanese minivan car with test tires (size 225 / 45R18 91W) mounted on a rim with a wheel size of 7.5JJ, the height of the stepping side and kicking side of the block was high. The height was measured and the difference in height was evaluated as the heel and toe wear amount. It shows that it is excellent in uneven wear resistance, so that this amount of wear is small. The uneven wear resistance was evaluated in both the vehicle outer region and the vehicle inner region.

Example 1
A rubber having a rubber hardness of 67 according to JISK6253 durometer hardness test (type A) is arranged on the outer side of the tire with the tire equatorial plane in the tread, and a rubber having a rubber hardness of 58 is arranged on the inner side of the vehicle. The pneumatic tire shown in FIGS. 1-2 was produced and said evaluation was performed. The groove width of the concave groove is 5 mm, the groove depth is 1.5 mm, and the groove area ratio (S1 / S2) is 0.95.

Comparative Example 1
A pneumatic tire having the same configuration as that of Example 1 was prepared except that the concave groove was not provided in the buttress portion inside the vehicle, and the above evaluation was performed.

Comparative Example 2
The radius of curvature of the tread contour is asymmetrical in the vehicle inner and outer regions with respect to the tire equator plane, and rubber having a rubber hardness of 61 is disposed in the vehicle inner and outer regions of the tread portion, and further opens toward the tire side. However, a pneumatic tire provided with a concave groove extending in the tire circumferential direction only in the buttress portion outside the vehicle was produced, and the above evaluation was performed. The groove width of the concave groove is 5 mm, the groove depth is 1.5 mm, the curvature radius in the vehicle inner region is 850 mm, and the curvature radius in the vehicle outer region is 1100 mm.

Comparative Example 3
A pneumatic tire having the same configuration as that of Example 1 except that the concave grooves are provided in both the inside and outside buttress portions of the vehicle was produced, and the above evaluation was performed. The groove width of the recessed grooves provided in the buttress portions on the vehicle inner side and the vehicle outer side is 5 mm, and the groove depth is 1.5 mm. The results are shown in Table 1.

  From the results shown in Table 1, in Example 1, while ensuring good turning performance of the vehicle, the riding comfort performance was improved as compared with Comparative Example 1, and the uneven wear resistance inside the vehicle was further improved. On the other hand, in Comparative Example 2, by providing the concave groove in the buttress portion on the outside of the vehicle, the turning performance of the vehicle was greatly reduced as compared with Example 1, and the uneven wear resistance on the inside of the vehicle was further deteriorated. Further, in Comparative Example 3, the turning performance of the vehicle was greatly reduced by providing the concave groove on the buttress portion outside the vehicle.

An example of a tire meridian cross-sectional view of a pneumatic tire according to the present invention An example of a development view of a tread pattern of a pneumatic tire according to the present invention

Explanation of symbols

1 Tread 2 Main groove 3 Horizontal groove 4A, 4B Rib 5 Block 6 Concave groove
7 Bead core 8 Bead part 9 Side wall part 10 Buttress part 11 Carcass 12 Belt layer EP Tire equatorial plane B Interface ER Vehicle outer area IR Vehicle inner area

Claims (1)

In a pneumatic tire in which a tread pattern composed of grooves provided in the tread portion is asymmetric with respect to the tire equatorial plane,
The tread portion is a rubber having a higher hardness than the vehicle inner region in the vehicle outer region across the tire equator plane,
The tread pattern is an asymmetric pattern in which ribs are arranged in the vehicle outer area across the tire equator plane, and only the blocks are arranged in the vehicle inner area.
A pneumatic tire characterized in that a concave groove extending in the tire circumferential direction while opening toward the tire side is provided only in a buttress portion inside the vehicle.

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