JP5437851B2 - Pneumatic tire - Google Patents

Description

  In the tread portion, a shoulder block row in which a plurality of shoulder blocks extending across the tread grounding end are arranged side by side in the tire circumferential direction, and the shoulder block row is disposed on the inner side in the tire width direction of the shoulder block row. In particular, a pneumatic tire including a plurality of circumferential main grooves extending in the region is intended to achieve both wet performance, on-ice performance, and uneven wear resistance.

  One of the important performances in terms of tire safety is wet performance and on-ice performance. As a technology to improve these wet performance and on-ice performance, sipe is engraved in the block land part that constitutes the block system pattern, and the pattern edge is formed. The thing which increased is known (for example, patent document 1).

  On the other hand, engraving sipes on the block land will lead to a decrease in block rigidity, which is effective for wet performance and on-ice performance, but adversely affects dry performance such as handling stability on dry roads. It will be.

  Therefore, the inventor diligently studied to achieve both of the conflicting performances, and by reducing the size of each block constituting the block pattern and consolidating a large number of them, the decrease in block rigidity is suppressed to some extent. The knowledge that the block edge can be increased was obtained.

JP-A-2005-145128

  However, when the inventor prototyped a pneumatic tire employing such a block pattern and repeated the experiment, it was confirmed that the wet performance and on-ice performance were significantly improved compared to the conventional sipe type block pattern, It was found that uneven wear of the block increased in the shoulder region of the tread portion.

  Therefore, the present invention is to provide a pneumatic tire capable of achieving both improvement in wet performance and on-ice performance due to increase in pattern edges due to dense arrangement of blocks, and prevention of uneven wear in the shoulder area of the tread portion. is there.

  The present invention has been made to solve the above-described problems, and in the pneumatic tire of the present invention, a plurality of shoulder blocks extending across the tread grounding end are arranged in the tire circumferential direction in the tread portion. A pneumatic tire comprising a shoulder block row and a plurality of circumferential main grooves disposed inward in the tire width direction of the shoulder block row and extending in the tire circumferential direction. Between the circumferential main groove located on the outer side and the shoulder block row, a plurality of circumferential sub-grooves having a groove width smaller than the circumferential main groove and extending in the tire circumferential direction intersect the circumferential sub-groove. A block group consisting of a plurality of rows of block rows in which blocks partitioned by a plurality of transverse grooves extending in the tire circumferential direction are provided, and the tie is formed via the circumferential sub-grooves. The distance between the blocks mutually adjacent in the width direction is characterized in that the tapering taken to toward the outer side in the tire width direction.

  Here, the “tread ground contact” is an industrial standard valid for the region where tires are produced or used, for example, “Year Book” of The Tire and Rim Association Inc. in the United States, and The European Tire and Rim Technical Organization in Europe. “Standard Manual” of Japan, and in Japan, tires are assembled to standard rims at the applicable size of the standard described in the “JATMA Year Book” of the Japan Automobile Association, and the maximum load (maximum load capacity) and maximum of the single wheel at the applicable size of such standard In the state where the air pressure corresponding to the load is applied, it is the outermost position in the tire width direction of the surface where the tire surface contacts the ground. In addition, the “distance between blocks” refers to a distance obtained by measuring the distance between blocks adjacent in the tire width direction along the tire width direction via the circumferential sub-groove.

  In such a pneumatic tire, the groove width is smaller than the circumferential main groove between the circumferential main groove located on the outermost side in the tire width direction of the circumferential main groove and the shoulder block row. A block group comprising a plurality of rows of block rows in which blocks defined by a plurality of circumferential sub-grooves extending in the tire circumferential direction and a plurality of lateral grooves extending across the circumferential sub-groove are arranged in the tire circumferential direction. Thus, the block edge can be increased while avoiding a decrease in block rigidity to some extent.

Here, the inventor repeated research on the cause of increased uneven wear in the shoulder region block of the tread portion, and the cause was the circumferential sub-groove that divides the blocks in the block group at the time of tire contact. It has been found that the groove closing amount increases toward the outer side in the tire width direction of the tread portion, and the shear deformation in the width direction of the block increases. The mechanism for closing the circumferential sub-groove when the tire contacts the ground is as follows. That is, as shown in FIG. 3, when the tire contacts the ground, vertical load F _P from the rim, the bead portion 4, is converted into a horizontal direction parallel to the road surface through the sidewall portion 3 and the shoulder portion 2, tire width in the vicinity direction of the tread ground contact end TE lateral force P _H is generated toward the tire width direction inner side. And this lateral force P _H is cause shear deformation of the block in the vicinity of the tread ground contact end TE. Therefore, the amount of shear deformation of the block adjacent to the circumferential sub-groove increases as it approaches the tread ground contact TE.

  Therefore, based on these findings, the inventor has adopted a configuration in which the groove width of the circumferential sub-groove in the block group is gradually reduced toward the outer side in the tire width direction. The effect of reducing the shear deformation in the width direction of the block due to the reduction of the amount or the contact (support) between the blocks adjacent to each other in the tire width direction becomes greater as it approaches the tread ground contact edge, so the uneven wear of the block in the shoulder area of the tread portion Can be effectively prevented.

  Therefore, according to the pneumatic tire of the present invention, the pattern edge increases due to the dense arrangement of the blocks, and the shear deformation in the width direction of the blocks is suppressed by controlling the closing of the grooves in the block group at the time of tire contact. Therefore, it is possible to achieve both improvement in wet performance and on-ice performance and prevention of uneven wear in the shoulder region of the tread portion.

In the pneumatic tire of the present invention, the width of the block group is W (mm), the reference pitch length of blocks in an arbitrary block row in the block group is PL (mm), and the width of the block group When the number of blocks existing in the reference area of the block group divided by W and the reference pitch length PL is a (number) and the negative rate in the reference area is N (%), S = a Block number density S (units / mm ² ) per unit actual contact area of the block group given by / {PL × W × (1−N / 100)} is within a range of 0.003 to 0.04. It is preferable to do.

  The “block group width” herein refers to the length of the block group along the tire width direction. The “reference pitch length of a block” refers to the minimum unit or a plurality of units of a repeating pattern in the tire circumferential direction in an arbitrary block row. For example, one block and a lateral groove adjacent to the block If a repeating pattern of the tire circumferential pattern is specified, the reference pitch length of the block may be the sum of the tire circumferential length of one block and the groove width of the lateral groove adjacent to this block. it can. Furthermore, the “block number density” represents the number of blocks existing as a density per actual ground contact area in the reference area (total surface area of all blocks in the reference area). In addition, “actual ground contact area” is an industrial standard effective in the region where tires are produced or used, for example, “Year Book” by The Tire and Rim Association Inc. in the United States, “European Tire and Rim Technical Organization“ Standard Manual ”, in Japan, tires are assembled to standard rims at the applicable size of the standard described in the Japan Automobile Association“ JATMA Year Book ”, and the maximum load (maximum load capacity) and maximum load of the single wheel at the applicable size of such standard This refers to the state when the corresponding air pressure is applied.

  According to the present invention, it is possible to provide a pneumatic tire capable of achieving both improvement in wet performance and on-ice performance due to an increase in pattern edges due to dense arrangement of blocks and prevention of uneven wear in the shoulder region of the tread portion. it can.

It is sectional drawing of the tire width direction which assembled | attached the pneumatic tire of embodiment according to this invention to the rim | limb, and applied the predetermined | prescribed internal pressure, (a) shows the state which is not grounding, (b) shows the state which grounded, respectively It is. It is the partial expanded view which showed the tread pattern of the tire of one Embodiment (Example 1 tire) according to this invention. It is sectional drawing of the tire width direction when the pneumatic tire which has a block in a shoulder area | region is assembled | attached to a rim, and a predetermined internal pressure is applied, (a) is the state which is not grounding, (b) is the state which grounded. Each is shown. It is the partial expanded view which expanded and showed a part of tread pattern of the pneumatic tire (tire of Example 2) of other embodiment according to this invention. It is the partial expanded view which expanded and showed a part of tread pattern of the pneumatic tire (tire of Example 3) of other embodiment according to this invention. It is the partial expanded view which expanded and showed a part of tread pattern of the pneumatic tire as a comparison (tire of the comparative example 1). It is the partial expanded view which showed the tread pattern of the pneumatic tire of the prior art (tire of the prior art example 1).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view in the tire width direction in which a pneumatic tire (hereinafter simply referred to as “tire”) according to an embodiment of the present invention is assembled to a rim and a predetermined internal pressure is applied, and (a) is grounded. FIG. 2 (b) shows a grounded state, and FIG. 2 is a partial development view showing a tread pattern of a tire according to an embodiment of the present invention.

  As shown in FIG. 1, the tire of this embodiment includes a tread portion 1 that forms a tread surface of the tire, a pair of sidewall portions 3 that are connected to the outer side in the width direction of the tread portion 1 via a shoulder portion 2, and these A carcass 5 that includes a pair of bead portions 4 disposed on the radially inner side of the sidewall portion 3 and extends in a toroidal shape between the pair of bead portions 4 and 4 inside the tire, and a radially outer side of the crown region of the carcass 5 And a belt layer 6 disposed on the tire.

  As shown in FIG. 2, the tire includes a shoulder block row L1 in which a plurality of shoulder blocks 8 extending across the tread grounding end TE are arranged in the tire circumferential direction on the tread portion 1, and the shoulder block row L1. And a plurality of circumferential main grooves 10 (one on each of the right and left sides in the tire width direction) disposed in the tire width direction and extending in the tire circumferential direction. The circumferential main groove 10 is preferably arranged at a position corresponding to 5 to 30% of the tread contact width with the tire equatorial plane C as the center. This is because if the area is smaller than 5%, the land area between the circumferential main grooves 10 is extremely small, so that the straight running stability cannot be sufficiently secured. This is because uneven wear of the shoulder block row L1 is likely to occur. The groove width of the circumferential main groove is preferably 2 to 15% of the tread ground contact width. This is because if the groove width is smaller than 2%, the groove volume of the circumferential main groove necessary for draining the tire cannot be secured sufficiently, and if it is larger than 15%, the ground pressure is concentrated on the land facing the circumferential main groove. This is because uneven wear tends to occur around the circumferential main groove.

  Further, the tire has a plurality of tires extending in the tire circumferential direction between the circumferential main groove 10 located on the outermost side in the tire width direction and the shoulder block row L1 and having a groove width smaller than that of the circumferential main groove 10. A block 16 defined by a circumferential sub-groove 12 (referred to as 12a, 12b, 12c in this order from the outer side in the tire width direction) and a plurality of lateral grooves 14 extending across the circumferential sub-grooves 12a, 12b, 12c is a tire. A block group G is provided that includes a plurality of block rows arranged in the circumferential direction (block rows L2, L3, and L4 in order from the outside in the tire width direction).

  The blocks 16 in the block group G can have any surface contour shape, but are preferably polygonal (here, approximately octagonal). By using a polygon, the so-called edge effect anisotropy of the block 16 can be reduced. In particular, by making the octagonal shape, the uniform grounding property of the block 16 can be enhanced. The height h of the block 16 in the block group G (measured in the tire radial direction from the groove bottom of the circumferential sub-groove 12 or the lateral groove 14 defining the block 16 to the block surface with the larger groove depth) The distance) is preferably set so that the block aspect ratio defined by “Wb / h” is 1.5 or more. Because, when “Wb / h” is less than 1.5, the shear rigidity of the block rapidly decreases, and the block tends to collapse (buckling). Because it ends up.

  Further, the blocks 16 in the block group G are arranged in a staggered manner. That is, the blocks 16 forming the block rows L2 to L4 adjacent in the tire width direction are arranged so that the phases are different in the tire circumferential direction. Here, “the phase is different in the tire circumferential direction” means that, for example, in the example of FIG. 2, the block 16 of the block row L2 and the block 16 of the block row L3 are shifted in the tire circumferential direction by a half pitch. Say that. By adopting such a staggered arrangement, the block number density described later in the block group G can be easily increased, and the grounding timing of the blocks 16 in the block group G can be shifted. Noise can also be reduced.

として表される、ブロック群Ｇの単位実接地面積当りのブロック個数密度Ｓは、０．００３（個／ｍｍ^２）以上０．０４（個／ｍｍ^２）以下である。ブロック個数密度Ｓは、ブロック群Ｇ内の全てのブロック１６の実接地面積（溝分を除いた面積）中の単位面積（ｍｍ^２）当りに何個のブロック１６があるかということを密度として表現したものである。ちなみに、例えば通常のスタッドレスタイヤの場合には、この密度Ｓは概ね０．００２以下となる。なお、ブロック群Ｇの基準区域Ｚ内のブロック１６の個数ａをカウントするに際して、ブロック１６が基準区域Ｚの内外に跨って存在し、１個として数えることができない場合は、基準区域Ｚを跨るブロック１６の表面積に対する、基準区域内に残った同ブロック１６の残存面積の比率を用いて数えることとする。例えば、基準区域Ｚの内外に跨り、基準区域Ｚ内にその半分しか存在しないブロック１６の場合は、１／２個と数えることができる。 The smaller the size of the blocks 16 in the block group G and the higher the density, the greater the block edges in the total pattern, but the preferred range of block number density is as follows. That is, the reference pitch length in the tire circumferential direction of the block 16 in any block row L2 to L4 of the block group G is PL (mm), the width of each block group G is W (mm), and these reference pitch lengths The number of blocks 16 existing in the reference zone Z (the region indicated by the slanted line in FIG. 2) partitioned by the length PL and the block group W is a (number), and the negative rate in each reference zone Z is N ( %)

The block number density S per unit actual ground contact area of the block group G is 0.003 (pieces / mm ² ) or more and 0.04 (pieces / mm ² ) or less. The block number density S is defined as the number of blocks 16 per unit area (mm ² ) in the actual ground contact area (area excluding the groove) of all the blocks 16 in the block group G. It is a representation. Incidentally, for example, in the case of a normal studless tire, this density S is approximately 0.002 or less. When counting the number a of the blocks 16 in the reference zone Z of the block group G, if the block 16 exists inside and outside the reference zone Z and cannot be counted as one, it crosses the reference zone Z. Counting is performed using the ratio of the remaining area of the block 16 remaining in the reference area to the surface area of the block 16. For example, in the case of the block 16 straddling the inside and outside of the reference zone Z and having only half of the block in the reference zone Z, it can be counted as 1/2.

When the block number density S in the block group G is less than 0.003 (pieces / mm ² ), it is difficult to increase the block edge without forming sipes, while the block number density S is 0.04. If it exceeds (pieces / mm ² ), the size of the block 16 becomes too small and it is difficult to achieve the required block rigidity. Further, if the block number density S in the block group G is in the range of 0.0035 to 0.03 / mm ² , it is possible to achieve both higher levels of block rigidity and increased block edge. it can.

  The negative rate N in the block group G is preferably 5% to 50%. When the negative rate N in the block group G is less than 5%, the groove area is too small and the drainage performance is insufficient, and the size of each block is too large and the block edge that the present invention aims at is On the other hand, if it exceeds 50%, the contact area becomes too small, and the steering stability may be lowered.

  And the feature of this tire is that the distances d1, d2, d3 between the blocks 16 adjacent to each other in the tire width direction via the circumferential sub-grooves 12a, 12b, 12c are increased toward the outer side in the tire width direction. That is, the configuration gradually decreases, that is, d3> d2> d1.

In the tire of this embodiment, the groove width is larger than the circumferential main groove 10 between the circumferential main groove 10 located on the outermost side in the tire width direction of the circumferential main groove and the shoulder block row L1. Is a block 16 defined by a plurality of circumferential sub-grooves 12a, 12b, 12c and a plurality of lateral grooves 14 that extend across the circumferential sub-grooves 12a, 12b, 12c. Since the block group G including the plurality of rows L2 to L4 of the block rows arranged in the direction is provided, the block edge can be increased while avoiding a decrease in block rigidity to some extent (that is, ensuring dry performance). And by making the block number density in the block group G 0.003 (pieces / mm ² ) or more and 0.04 (pieces / mm ² ) or less, the surface area of the blocks can be made sufficiently smaller than the conventional one. Therefore, while improving the ground contact property of each block, the distance from the central area to the peripheral edge on the surface of the block 16 can be reduced, and it is ensured that the water film in the central area of the block surface is efficiently removed when the block is grounded. It can be.

  Further, the distances d1, d2, and d3 between the blocks 16 adjacent in the tire width direction through the circumferential sub-grooves 12a, 12b, and 12c in the block group G are gradually reduced toward the outer side in the tire width direction. As shown in FIG. 3, compared with the case where these distances d1, d2, and d3 are constant, the effect of reducing the groove closing amount of the circumferential sub-grooves 12a, 12b, and 12c, that is, the tire width direction Since the effect of suppressing the shear deformation in the width direction of the blocks 16 due to the contact between the blocks 16 adjacent to each other can be increased toward the tread grounding end (see FIG. 1B), the blocks in the shoulder region of the tread portion 1 16 uneven wear can be effectively prevented. Here, the groove widths of the circumferential sub-grooves 12a, 12b, and 12c are preferably within 3 mm. Because, if the groove width of the circumferential sub-grooves 12a, 12b, 12c is larger than 3 mm, the wall surfaces of the blocks separated by the grooves at the time of grounding do not come into contact with each other, so that the effect of supporting the blocks is sufficiently exerted. Because it disappears.

  Therefore, according to this tire, it is possible to achieve both improvement in wet performance and on-ice performance due to increase in pattern edges due to dense arrangement of the blocks 16, and prevention of uneven wear in the shoulder region of the tread portion.

  Moreover, the tire provided with the block group G in the shoulder region is very advantageous for reducing rolling resistance. This is because by providing a large number of such relatively small blocks 16, the tread portion 1 in the vicinity of the belt end that is dominant in the rolling resistance can be subdivided (that is, the tread portion in the vicinity of the belt end can be made flexible), and the tire load This is because the energy loss of the tread portion 1 during rolling can be significantly reduced.

  Next, another embodiment of the present invention will be described with reference to FIGS. In the tire shown in FIG. 4, the distances d1, d2, and d3 between the blocks 16 adjacent in the tire width direction are gradually reduced through the circumferential sub grooves 12a, 12b, and 12c toward the outer side in the tire width direction. In the block row L2 to L4, the width (tire width direction length) Wb of the block row L2 adjacent to the shoulder block row L1 of the block row L1 is set to the width of the block 16 of the block row L3 adjacent to the block row L2. It is larger than the width Wb. According to this, the block rigidity (particularly the rigidity in the width direction) in the vicinity of the tread grounding end TE can be increased, and therefore, uneven wear of the shoulder region of the tread portion 1 due to the effect of suppressing shear deformation can be further prevented. it can.

  The tire shown in FIG. 5 has a pattern configuration on the outer side in the tire width direction from the circumferential main groove 10, but the groove width of the circumferential main groove 10 is set to the tread center side as compared with the tire of FIG. 2. It is an extension to. According to this, in addition to the effect of the tire of FIG. 2, the volume of the circumferential main groove 10 in the tread center region can be expanded, and in particular, drainage during straight running can be improved.

  Next, the tires of Examples 1 to 3 according to the present invention, the tire of Conventional Example 1 according to the prior art, and the tire of Comparative Example 1 were respectively prototyped and subjected to various performance evaluations. These tires are all radial tires for passenger cars having a tire size of 195 / 65R15.

  The tire of Example 1 has the tread pattern shown in FIG. 2 in the tread portion. One circumferential main groove 10 is provided on each of the left and right sides, and the circumferential main groove 10 is disposed at a position corresponding to 22% of the tread contact width with the tire equatorial plane C as the center. The groove width of the circumferential main groove is 7.0 mm, and the groove depth is 7.0 mm. The block width Wbs of the shoulder block 8 in the shoulder block row L1 is 22.0 mm, the block width Wb of the block 16 in the block rows L2 and L3 is 15.0 mm, and the block width of the block 16 in the block row L4 Wb is 8.0 mm. The block heights of the blocks 16 in the block group are all 5.0 mm. Further, the pattern on the inner side in the tire width direction from the circumferential main groove 10 is the distance d1, d2, d3 between the blocks adjacent to each other in the tire width direction via the circumferential sub grooves 12a, 12b, and 12c. > D2> d1 is satisfied. Other specifications are as shown in Table 1.

  The tire of Example 2 has the tread pattern shown in FIG. 4 in the tread portion. The configuration on the inner side in the tire width direction from the circumferential main groove 10 is substantially the same as that of the tire of the first embodiment, but the block width Wb of the blocks 16 in the block row L2 is larger than that of the first embodiment. The circumferential main groove 10 is disposed at a position corresponding to 22% of the tread contact width with the tire equatorial plane C as the center. The groove width of the circumferential main groove is 7.0 mm, and the groove depth is 7.0 mm. The block width Wbs of the shoulder block 8 in the shoulder block row L1 is 20.0 mm, the block width Wb of the block 16 in the block row L2 is 17.0 mm, and the block width Wb of the block 16 in L3 is 15.0 mm. The block width Wb of the block 16 in the block row L4 is 8.0 mm. The block heights of the blocks 16 in the block group are all 5.0 mm. Further, the distances d1, d2, and d3 between the blocks adjacent in the tire width direction via the circumferential sub-grooves 12a, 12b, and 12c satisfy the relationship of d3> d2> d1. Other specifications are as shown in Table 1.

  The tire of Example 3 has the tread pattern shown in FIG. The configuration on the inner side in the tire width direction from the circumferential main groove 10 is substantially the same as that of the tire of the first embodiment, but the groove width of the circumferential main groove 10 is larger than that of the first embodiment. The circumferential main groove 10 is disposed at a position corresponding to 22% of the tread contact width with the tire equatorial plane C as the center. The groove width of the circumferential main groove is 9.0 mm, and the groove depth is 7.0 mm. The block width Wbs of the shoulder block 8 in the shoulder block row L1 is 20.0 mm, the block width Wb of the block 16 in the block rows L2 and L3 is 15.0 mm, and the block width Wb of the block 16 in the block row L4 is 8.0 mm. The block heights of the blocks 16 in the block group are all 5.0 mm. Further, the distances d1, d2, and d3 between the blocks adjacent in the tire width direction via the circumferential sub-grooves 12a, 12b, and 12c satisfy the relationship of d3> d2> d1. Other specifications are as shown in Table 1.

  For comparison, a tire of Comparative Example 1 having the tread pattern shown in FIG. 6 in the tread portion and a tire of Conventional Example 1 having the tread pattern shown in FIG. In the tire of Comparative Example 1, the pattern configuration on the inner side in the tire width direction from the circumferential main groove 10 is substantially the same as that of the tire of Example 1, but adjacent to the tire width direction through the circumferential sub grooves 12a, 12b, and 12c. The distances d1, d2, and d3 between the blocks to be performed are configured to satisfy the relationship d3 = d2 = d1. The circumferential main groove 10 is disposed at a position corresponding to 22% of the tread contact width with the tire equatorial plane C as the center. The groove width of the circumferential main groove is 7.0 mm, and the groove depth is 7.0 mm. The block width Wbs of the shoulder block 8 in the shoulder block row L1 is 20.0 mm, the block width Wb of the block 16 in the block rows L2 and L3 is 15.0 mm, and the block width Wb of the block 16 in the block row L4 is 8.0 mm. The block heights of the blocks 16 in the block group are all 5.0 mm. Other specifications are as shown in Table 1.

  The tire of Conventional Example 1 has the tread pattern shown in FIG. In addition, in FIG. 7, the part shown with a satin is a groove | channel. The circumferential main groove 10 is disposed at a position corresponding to 22% of the tread contact width with the tire equatorial plane C as the center. The groove width of the circumferential main groove is 7.0 mm, and the groove depth is 7.0 mm. As for the block width of the shoulder portion, Wbs is 40 mm and Wb is 8 mm. Each block height is 5.0 mm. Other specifications are as shown in Table 1.

(Performance evaluation)
About each said test tire, the following tests were done and performance was evaluated.

(1) Test on Evaluation of Brake Performance on Ice Brake performance on ice was evaluated from the measured distance by measuring the braking distance when full braking was performed from 20 km / h on an ice plate road surface. The evaluation results are shown in Table 2. The evaluation in Table 2 is expressed as an index for the tires of Examples 1 to 3 and the tire of Comparative Example 1 with the result of Conventional Example 1 being 100, and the larger the value, the better the braking performance on ice. It shows that.

(2) Test on Steering Stability Evaluation on Wet Road Surface Wet sports on the circuit course in the wet state in various driving modes and evaluated by feeling of the test driver. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 3 and the tire of Comparative Example 1 with the result of Conventional Example 1 being 100, and the larger the value, the better the steering stability when wet. Indicates that there is.

(3) Test for evaluating the wear resistance of the shoulder region The vehicle travels on a general road in a dry state in various travel modes, measures the remaining groove depth near the tread edge when traveling at 5000 km, and determines the measured remaining groove depth. The index was evaluated. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 to 3 and the tire of Comparative Example 1 with the result of Conventional Example 1 being 100, and the larger the value, the higher the wear resistance of the shoulder area of the tread portion. Is good.

  From the results shown in Table 2, it can be seen that the application of the present invention can achieve both improvement in wet performance and on-ice performance and prevention of uneven wear in the shoulder region. In particular, it can be seen that uneven wear can be further prevented by increasing the block width of the block in the block row adjacent to the shoulder block row.

  Thus, according to the present invention, it is possible to achieve both improvement in wet performance and on-ice performance due to an increase in pattern edges due to dense block arrangement and prevention of uneven wear in the shoulder region of the tread portion.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Shoulder part 3 Side wall part 4 Bead part 5 Carcass 6 Belt layer 8 Shoulder block 10 Circumferential main groove 12a, 12b, 12c Circumferential subgroove 14 Lateral groove 16 block G Block group d1, d2, d3 Between blocks Distance of

Claims (2)

A shoulder block row in which a plurality of shoulder blocks extending across the tread grounding end are arranged side by side in the tire circumferential direction on the tread portion, and a plurality of shoulder blocks arranged in the tire width direction inside the shoulder block row and extending in the tire circumferential direction. In a pneumatic tire comprising a circumferential main groove,
Between the circumferential main groove located on the outermost side in the tire width direction among the circumferential main grooves and the shoulder block row, a plurality of circumferences having a groove width smaller than the circumferential main groove and extending in the tire circumferential direction. A block group composed of a plurality of rows of block rows in which blocks defined by a direction sub-groove and a plurality of lateral grooves extending across the circumferential sub-groove are arranged in the tire circumferential direction;
The pneumatic tire according to claim 1, wherein a distance between the blocks adjacent to each other in the tire width direction via the circumferential sub-groove gradually decreases toward the outer side in the tire width direction. The width of the block group is W (mm), the reference pitch length of blocks in an arbitrary block row constituting the block group is PL (mm), and the width W of the block group and the reference pitch length PL are S = a / {PL × W × (1−N) where a is the number of blocks existing in the reference area of the block group to be partitioned and N (%) is the negative rate in the reference area. / 100)}, the block number density S (pieces / mm ² ) per unit actual ground contact area of the block group is within the range of 0.003 to 0.04. tire.

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