JP2005231420A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for reducing noises and also restraining eccentric abrasion when a rotational direction is designated. <P>SOLUTION: This pneumatic radial tire with a rotational direction R designated comprises a thin groove 4 connected in a peripheral direction minced in a shoulder area SH of a tread 1, horizontal grooves 2, 3 communicated with the thin groove 4, and a land part 11 demarcated by the thin groove 4 and the horizontal groove 2, 3. Depth of the thin groove 4 on a kick-out side 5 of the land part 11 is constituted deeper than depth of the thin groove 4 of a step-in side 6 of the land pat 11. Also, the depth of the thin groove 4 on the kick-out side 5 of the land 11 is 1.2-5 times as deep as the depth of the thin groove 4 of the step-in side 6 of the land part 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly to noise reduction and suppression of uneven wear.

  In a pneumatic radial tire having a land portion divided into lateral grooves, a difference in friction energy expressed by accumulation in the contact process of the product of pressure and displacement occurs on the stepping side and the kicking side of the land portion. As a result, circumferential uneven step wear (toe and heel uneven wear) occurs, and is particularly noticeable in the shoulder region where the pressure increases during braking. Moreover, when the land part divided by the horizontal groove is provided, the striking sound at the contact step is increased. Therefore, a narrow groove continuous in the circumferential direction is provided in the shoulder region to suppress uneven wear and reduce noise performance.

For example, in the pneumatic tire disclosed in Patent Document 1, longitudinal sub-grooves are cut in the shoulder region to suppress uneven wear.
JP-A-6-87303

  During braking, it is known that uneven wear on the kicking side tends to occur because the frictional energy on the kicking side is higher than that on the stepping side, and wear on the kicking side becomes large. However, if the direction of rotation of the tire is specified, the kicking side and the stepping side remain fixed until the tire is replaced. For this reason, uneven uneven wear is likely to occur, and noise performance is also deteriorated.

  An object of the present invention is to provide a pneumatic radial tire that achieves both noise reduction and uneven wear suppression when a rotational direction is specified.

As a result of intensive studies to solve the above-mentioned problems, the invention according to claim 1 is a pneumatic radial tire in which a rotation direction is specified, and a narrow groove continuous in a circumferential direction carved in a shoulder region of a tread; A lateral groove communicating with the narrow groove, and a land portion defined by the narrow groove and the lateral groove, the depth of the narrow groove on the kicking side of the land portion being the depth of the narrow groove on the stepping side of the land portion Pneumatic radial tire characterized by being deeper than depth.
It was.

  Since the horizontal groove that divides the land portion communicates with the narrow groove that is continuous in the circumferential direction, the hitting sound of the land portion is alleviated and the noise performance is reduced. Moreover, since the depth of the narrow groove on the kicking side of the land portion is deeper than that on the stepping side, the rigidity on the kicking side of the land portion is reduced. As a result, on the kicking side, the pressure in the land portion is reduced, slippage is suppressed, and the friction energy is reduced. On the other hand, on the stepping side, the pressure in the land portion increases, slipping occurs, and the friction energy increases. Accordingly, the frictional energy of the land portion on the kicking side and the stepping side is made uniform, so that uneven wear in the land portion is suppressed.

  In addition, it is preferable that the depth of the narrow groove gradually increases from the stepping side of the land portion to the kicking side of the land portion. Further, the depth of the narrow groove may change for each land portion, and the depth of the narrow groove may change within a plurality of continuous land portions.

  According to a second aspect of the present invention, the depth of the narrow groove on the kicking side of the land portion is 1.2 to 5 times the depth of the narrow groove on the stepping side of the land portion. The pneumatic radial tire described in 1 was obtained.

  In particular, when the depth of the narrow groove on the kicking side of the land portion is 1.2 to 5 times the depth of the narrow groove on the stepping side of the land portion, the suppression of uneven uneven wear increases. If the depth ratio is less than 1.2 times, the frictional energy between the kicking side and the stepping side cannot be made uniform, and the effect of suppressing uneven wear cannot be obtained. On the other hand, if it exceeds five times, the rigidity on the kicking side of the land portion is excessively decreased, the friction energy is excessively decreased, and the friction energy cannot be made uniform.

  In the pneumatic radial tire of the present invention, the lateral grooves that define the land portion communicate with the narrow grooves that are continuous in the circumferential direction, so that the impact sound of the land portion is alleviated and the noise performance is reduced. In addition, since the depth of the narrow groove on the kicking side of the land portion is deeper than that on the stepping side, the frictional energy of the land portion on the kicking side and stepping side is made uniform, and uneven wear in the land portion is uneven. Is suppressed.

  Hereinafter, embodiments of a pneumatic radial tire according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a pattern of a pneumatic radial tire according to the present invention. In the figure, a narrow groove 4 continuous in the circumferential direction is carved in the shoulder region SH of the tread 1. The lateral grooves 2 and 3 communicate with the narrow groove 4, and the land portion 11 is defined by the lateral grooves 2 and 3 and the narrow groove 4. A main groove 10 is carved in the center region CE. The tire rotation direction R is specified.

  Since the lateral grooves 2 and 3 that divide the land portion 11 communicate with the narrow grooves 4 that are continuous in the circumferential direction, the striking sound of the land portion 11 is alleviated and the noise performance is reduced. Furthermore, since the depth of the narrow groove 4 carved in the shoulder region SH has changed and the depth of the kicking side 5 of the land portion 11 is deeper than that of the stepping side 6 of the land portion 11, The rigidity of the kicking side 5 of the part 11 is lowered. As a result, on the kick-out side 5, the pressure of the land portion 11 is reduced, slippage is suppressed, and the friction energy is reduced. On the other hand, on the stepping side 6, the pressure of the land portion 11 rises to cause a slip, and the friction energy increases. Accordingly, the frictional energy of the land portion 11 on the kicking side 5 and the stepping side 6 is made uniform, so that uneven uneven wear in the land portion 11 is suppressed. Moreover, since the striking sound at the grounding stepping edge of the land portion 11 is reduced, the noise performance is also reduced.

  FIG. 2B shows a Y1-Y2 cross section of FIG. In the drawing, the depth of the narrow groove 4 is gradually increased from d2 on the stepping side 6 to d1 on the kicking side 5 for each land portion 11 partitioned into the lateral grooves 2 and 3. 2 (c) and 2 (d), the depth of the narrow groove 4 gradually increases from d2 on the stepping side 6 to d1 on the kicking side 5 in two and three consecutive land portions 11, respectively. It is the structure which becomes. In FIG. 2 (e), the depth of the narrow groove 4 is deepened in three stages from d2 on the stepping side 6 to d1 on the kicking side 5 for each land portion 11. When the depth of the structure is changed stepwise, the wear progresses and the depth of the narrow groove 4 changes abruptly. Therefore, a structure in which the depth is gradually changed is more preferable.

  The depth of the narrow groove 4 on the kicking side 5 of the land portion 11 is preferably 1.2 to 5 times the depth of the narrow groove 4 on the stepping side 6 of the land portion 11. The depth of the stepping side 6 of the shallowest land portion 11 is preferably 1 mm or more. If it is less than 1 mm, the impact sound mitigating effect is small and noise cannot be reduced. Moreover, although the width | variety of the narrow groove 4 is not specifically limited, 0.5 mm-3 mm are preferable.

  The shoulder region SH is a region on both sides of a region obtained by dividing the ground contact width TW into three equal parts in the tire width direction. Here, the contact width TW is the maximum width that is grounded in the tire width direction when it is incorporated in a normal rim conforming to the ETRTO standard, filled with normal internal pressure, and a load of 70% of the design maximum load is applied on the flat plate. It is.

  As an example, a pneumatic radial tire according to the present invention and a pneumatic radial tire according to a comparative example were prototyped and performance evaluation was performed. Example and Comparative Example 2 are tires having the pattern shown in FIG. As shown in Table 1, the depth of the narrow groove of the example is changing, but the depth of the narrow groove of Comparative Example 2 is constant. Comparative Example 1 is a tire having the pattern shown in FIG. 3, and does not have a narrow groove, and the lateral grooves 12 and 13 are closed on the center side in the tire width direction in the land portion 11. The tire size was 225 / 45ZR17, the air pressure was set to 220 kPa, and it was mounted on a 2500 cc passenger car, and performance evaluation was performed under the load condition of two passengers.

  In the wear evaluation, the reciprocal of the uneven uneven wear amount after traveling 10,000 km is represented by an index with Comparative Example 1 as 100. In the noise evaluation, the sensory evaluation value of noise in the four speed modes (40 km / h, 80 km / h, 120 km / h, and 40 km to 0 km) is indicated by an index with Comparative Example 1 at the time of new article as 100. Therefore, in any evaluation, it shows that performance is so good that a numerical value is large.

  According to the results shown in Table 1, uneven wear on the step is suppressed in the pneumatic radial tire according to the present invention as compared with Comparative Examples 1 and 2. Although the noise performance is slightly deteriorated as compared with Comparative Example 2 at the time of a new article, the deterioration of the noise performance is not remarkable even when the wear progresses. Therefore, it was possible to achieve both noise reduction and suppression of uneven uneven wear.

It is a pattern development view of a pneumatic radial tire according to the present invention. It is a figure which shows the cross section of a narrow groove. 2 is a pattern development view of a pneumatic radial tire according to Comparative Example 1. FIG.

Explanation of symbols

1 Tread 2, 3 Horizontal groove 4 Narrow groove 10 Main groove 11 Land

Claims (2)

In pneumatic radial tires with specified rotation direction,
A narrow groove continuous in the circumferential direction carved in a shoulder region of the tread, a lateral groove communicating with the narrow groove, and a land portion defined by the narrow groove and the lateral groove, the land portion on the kicking side of the land portion A pneumatic radial tire characterized in that the depth of the narrow groove is deeper than the depth of the narrow groove on the stepping side of the land portion. 2. The pneumatic radial tire according to claim 1, wherein a depth of the narrow groove on a kicking side of the land portion is 1.2 to 5 times a depth of the narrow groove on a stepping side of the land portion.

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