JP2010083462A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To spectacularly improve on-ice performance by optimizing a tread pattern. <P>SOLUTION: In the pneumatic tire, a block group G<SB>B</SB>composed by mutually densely arranging a plurality of independent blocks 3 partitioned by grooves is provided on at least one part of a tread part 1. When assuming that the reference pitch length of the block 3 of the block group G<SB>B</SB>is P (mm), the width of the group G<SB>B</SB>is W (mm), the number of the blocks 3 existing in the reference zone Z of the block group G<SB>B</SB>partitioned by the reference pitch length P and the width W is (a) (piece), and a negative rate in the reference zone Z is N (%), the block number density S per unit actual ground contact area of the block group G<SB>B</SB>given by a/äP×W×(1-N/100)} is within the range of 0.003 pieces/mm<SP>2</SP>-0.04 pieces/mm<SP>2</SP>. The blocks 3 are respectively formed into a hexagonal shape and mutually the same size. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire provided with a block formed by a groove in a tread portion, and more specifically, proposes a technique that brings about a dramatic improvement in performance on ice.

  Conventionally, in a pneumatic tire, for the purpose of improving the performance on ice by enhancing the edge effect, as shown in FIG. 3, the tread portion 100 has a longitudinal groove 101 extending in the tread circumferential direction and a tread width direction. In general, it is widely performed that the block 103 is partitioned by the extending lateral groove 102 and a plurality of sipes 104 are added to the formed block 103. In such a conventional pneumatic tire, a large number of sipes 104 are arranged in the block 103 under the requirements of higher driving, braking and turning performance, and in particular, on-ice performance is ensured for a large ground contact area. Therefore, the number of block rows in the tread surface is reduced from 3 to 9, and each block 103 has a vertically long shape in the tread circumferential direction.

  However, in the conventional pneumatic tire as described above, the rigidity of the divided block portion 103a partitioned by the sipe 104 is too low, and the divided block portion 103a falls down at the time of ground contact, so that the grounding property is deteriorated. It has been difficult to obtain sufficient on-ice performance commensurate with recent improvements in vehicle performance. Also, the size of each block 103 is large, and in the central area of the block 103, the formation of the sipe 104 alone can sufficiently remove the water film between the ice surface and the tire during braking on ice. In view of this, it has been difficult to dramatically improve the performance on ice.

  Therefore, an object of the present invention is to solve these problems, and an object thereof is to dramatically improve the performance on ice by optimizing the tread pattern.

In order to achieve the above object, a pneumatic tire according to the present invention is an air in which a group of blocks each including a plurality of independent blocks partitioned by grooves are arranged densely at least in a tread portion. A reference pitch length of the block in the block group is P (mm), a width of the block group is W (mm), and is divided by the reference pitch length P and the width W, When the number of the blocks existing in the reference area of the block group is a (piece) and the negative rate in the reference area is N (%), a / (P × W × (1−N / 100) The given block number density S per unit actual ground area of the block group is in the range of 0.003 / mm ^{2 to} 0.04 / mm ² , and the blocks are each formed in a hexagonal shape. And the same size A pneumatic tire characterized by being formed.

  The “reference pitch length of the block” here refers to the minimum unit of the repeated pattern of the block in one block row constituting the block group. For example, one block and a groove partitioning the block are used. When the pattern repeat pattern is specified, the reference pitch length of the block is the sum of the tread circumferential length of one block and the tread circumferential length of one groove adjacent to this block in the tread circumferential direction. It becomes.

  Further, the “block group width W” refers to the length in the tread width direction of the block group formed by densely arranging the blocks. For example, when the block group is present in the entire tread, it indicates the tread ground contact width. .

  The “actual contact area” of the block group shall mean the total surface area of all the blocks in the reference area of the block group, in other words, defined by the product of the reference pitch length P and the width W. This refers to the area obtained by subtracting the area of the groove defining each block from the area of the reference area.

In the pneumatic tire of the present invention, the blocks partitioned by the grooves are densely arranged so that the block number density S is in the range of 0.003 to 0.04 / mm ² . The total edge length of the block is increased, and an edge effect higher than that of sipe is obtained. Further, the surface area per block is reduced, and the grounding property of each block is improved. Furthermore, since the distance from the central area of the block to the peripheral edge of the block is reduced, the water film in the central area of the block is efficiently removed when the block is grounded. In the pneumatic tire of the present invention, each block is formed in a hexagonal shape and the same size, so that the contact pressure in the block arrangement range can be made substantially uniform. Further, the grounding property can be further improved. Furthermore, by making the block hexagonal, each corner of the block can be obtuse, and the ground contact property can be further improved by increasing the block rigidity. Furthermore, by making the blocks hexagonal, adjacent blocks can be arranged so as to overlap each other when viewed along the tread surface, that is, the density of the blocks can be increased. The total edge length of the block can be further increased easily compared to the case where the square is a square. In addition, the hexagonal block has less anisotropy of the block rigidity with respect to the input of force from all directions during steering of the tire, and the cornering property is particularly improved because the edge of the block works effectively.

  Therefore, according to the pneumatic tire of the present invention, it is possible to dramatically improve the performance on ice by ensuring excellent grounding property and edge effect and efficiently removing the water film by the block.

  In addition, although the block group is more effective for the performance on ice if it is provided on the entire tread, it can be balanced with other performances such as steering stability and uneven wear resistance by applying to a limited area. .

  Moreover, in the pneumatic tire of this invention, it is preferable that the blocks of the block group are arranged in a staggered manner in the tread circumferential direction.

  Furthermore, in the pneumatic tire according to the present invention, the block group includes at least two blocks that are adjacent to each other in the tread circumferential direction and each have first and second sides parallel to the tread width direction. Of the at least two blocks, the groove width between the first side of one block and the second side of the other block is adjacent to a side other than the first and second sides. It is preferable that the width is set larger than the groove width of all the grooves.

  Furthermore, in the pneumatic tire according to the present invention, it is preferable that the block group includes blocks having first and second sides parallel to the tread circumferential direction.

  Moreover, in the pneumatic tire of the present invention, the block group preferably includes a block in which one or more sipes are disposed.

  According to the pneumatic tire of the present invention, it is possible to remarkably improve the performance on ice by ensuring excellent grounding property and edge effect and efficiently removing the water film by the block.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial development view showing a tread pattern of a pneumatic tire (hereinafter referred to as “tire”) according to an embodiment of the present invention. In the drawing, the vertical direction indicates the tread circumferential direction, and the horizontal direction (direction perpendicular to the equator plane C) indicates the tread width direction.

  Although the tire of this embodiment is not illustrated, a carcass extending in a toroid shape between a pair of left and right bead cores, a belt disposed on the outer side in the tire radial direction of the crown portion of the carcass, and an outer side in the tire radial direction of the belt It has a tire structure in accordance with the conventional practice including a tread portion arranged, and has the tread pattern shown in FIG. 1 in the tread portion.

として表される、ブロック群Ｇ_Ｂの単位実接地面積当りのブロック個数密度Ｓ（個／ｍｍ^２）は、０．００３個／ｍｍ^２以上０．０４個／ｍｍ^２以下の範囲内にある。なお、ブロック群の基準区域Ｚ内のブロック３の個数ａをカウントするに際して、ブロック３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、ブロック３の表面積に対する、基準区域内に残ったブロック３の残存面積の比率を用いて数えることとする。例えば、図１に符号Ｂ１で示すブロックのように、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の場合は、１／２個と数えることができる。 This tire, as shown in FIG. 1 has a tread portion 1, and defined by grooves 2, independent from each other is densely plurality of blocks 3 are made block group G _B. Block group G _B is present throughout the tread portion 1. Here, the blocks 3 are each formed in a hexagonal shape (a shape having a hexagonal column shape and a surface contour shape being a hexagonal shape) and are formed in the same size as each other, and in a zigzag shape in the tread circumferential direction. Has been placed. The block 3 of the block group G _B is arranged so as to be adjacent to each other in the tread circumferential direction, each of blocks 3 includes a first and second sides ST1, ST2 are parallel to the tread width direction, Of the blocks 3 adjacent to each other in the tread circumferential direction, the groove width of the lateral groove 2T extending in the tread width direction sandwiched between the first side ST1 of one block 3 and the second side ST2 of the other block 3 WT is set larger than the groove width WI of all the other inclined grooves 2I adjacent to the sides other than the first and second sides ST1, ST2, and the blocks 3 adjacent in the tread width direction, 3 is arranged so as to overlap each other in the tread circumferential direction and the tread width direction as seen along the tread surface. And in this tire, a reference pitch length of the block 3 in the block group G _B P (mm), the width W (mm) (this embodiment of the block group G _B, block 3 in the entire tread portion 1 because it is arranged equal to the tread width TW.), it is defined by the said reference pitch length P and the width W, in the reference zone Z of the block group G _B (area shown in FIG hatching) When the number of existing blocks 3 is a (pieces) and the negative rate in the reference zone Z is N (%),

Represented as the block number per unit actual ground contact area of the block group _{G B} Density S (pieces / mm ²⁾ is 0.003 pieces / mm ² or more 0.04 / mm ² within the following ranges. When counting the number a of the blocks 3 in the reference area Z of the block group, if the block 3 exists across the reference area Z and cannot be counted as one, the surface area of the block 3 is It is counted using the ratio of the remaining area of the block 3 remaining in the reference area. For example, in the case of a block that spans the inside and outside of the reference zone Z and only half of the block exists in the reference zone Z, such as a block indicated by reference numeral B1 in FIG.

In the tire of this embodiment, the blocks 3 partitioned by the grooves 2 are densely arranged so that the block number density S is in the range of 0.003 to 0.04 / mm ^2. The total edge length of the block 3 is increased, and an edge effect higher than that of the sipe is obtained. Further, the surface area per block is reduced, and the grounding property of each block is improved. Furthermore, since the distance from the central area of the block 3 to the block periphery becomes small, the water film in the central area of the block 3 is efficiently removed when the block is grounded. In the tire of this embodiment, since each block 3 is formed in a hexagonal shape and the same size, the contact pressure in the arrangement range of the blocks 3 can be made substantially uniform. It is possible to further improve the ground contact. Furthermore, by making the block 3 hexagonal, each corner of the block can be obtuse, and the ground contact property can be further improved by increasing the block rigidity. Furthermore, by making the blocks 3 hexagonal, adjacent blocks 3 can be arranged so as to overlap each other when viewed along the tread surface, that is, the density of the blocks 3 can be increased. For example, the total edge length of the block 3 can be further increased more easily than when the block is rectangular. In addition, the hexagonal block 3 has less anisotropy of the block rigidity with respect to the input of force from all directions during the steering of the tire, and the cornering performance is particularly improved because the edge of the block 3 works effectively.

  Therefore, according to the pneumatic tire of this embodiment, it is possible to dramatically improve the performance on ice by ensuring excellent grounding performance and edge effect and efficiently removing the water film by the block 3. it can.

  Moreover, according to the tire of this embodiment, since the blocks 3 are arranged in a zigzag shape in the tread circumferential direction, each edge can be caused to act sequentially while forming more blocks 3 during rolling of the tire. Therefore, the edge effect can be more effectively exhibited. Further, by arranging the blocks 3 in a zigzag manner in the tread circumferential direction, the timing of contact with the road surface can be shifted between the blocks 3 adjacent in the tread width direction, and pattern noise can also be reduced. Further, by arranging the blocks 3 in a staggered manner in this way, a high-density arrangement of the blocks 3 can be easily realized.

  Furthermore, according to the tire of this embodiment, the sides ST1 and ST2 of the block 3 set parallel to the tread width direction exhibit an excellent edge effect when the tire rotates, and particularly brake (braking) performance on ice. In addition, the traction (driving) performance can be remarkably improved. Further, the groove width WT of the transverse groove 2T sandwiched between the sides ST1 and ST2 of the block 3 and extending in the tread width direction is made larger than the groove widths WI of all the other inclined grooves 2I around the block 3, and By arranging the blocks 3 adjacent to each other in the tread width direction so as to overlap each other in the tread circumferential direction and the tread width direction as seen along the tread surface, It is possible to increase the rigidity of the block 3 by exerting a support effect between the blocks 3 when the block 3 is deformed. On the other hand, in the lateral groove 2T having a relatively large groove width, As a result, it is possible to secure a high performance on ice and snow.

Incidentally, in the present invention, negative ratio N of the block group _{G B} is preferably 5% to 50%. If negative ratio N of the block group G _B is less than 5%, except that the insufficient drainage groove area is too small, the present invention becomes too large the size of each one block is where the aim This is because it is difficult to realize the edge effect. On the other hand, if it exceeds 50%, the ground contact area becomes too small and the steering stability may be lowered. Also, if the number density S of the blocks 3 in the block group G _B is less than 0.003 (pieces / mm ^2), without the formation of a large number of sipes it is difficult to realize a high edge effect, whereas, the block 3 If the number density S exceeds 0.04 (pieces / mm ² ), the block 3 becomes too small and it is difficult to achieve the required block rigidity. Further, the number density S of the blocks 3 in the block group _{G B,} if within the range of 0.0035 to 0.03 piece / mm ^2, to achieve a higher level of compatibility between the block rigidity and the edge effect it can.

  Next, another embodiment according to the present invention will be described. FIG. 2 is a partial development view showing a tread pattern of a tire according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the element similar to the tire shown in previous FIG. 1, and the description is abbreviate | omitted.

In the tire, sipes 4 extending in the tread width direction in block 3 of the block group G _B is provided two each. The sipe 4 has a linear shape and is disposed along the tread width direction.

  By providing the sipe 4 in the block 3 in this way, the edge effect and the water removal effect can be further improved, so that higher performance on ice can be obtained and, for example, adjustment with performance other than the performance on ice can be performed. From the standpoint of achieving this, even if the block number density S is made smaller than when the sipe 4 is not formed, the excellent on-ice performance that the present invention aims at can be obtained.

  The shape of the sipe 4 is not limited to the example shown in the figure, and from the viewpoint of further improving the performance on ice by suppressing excessive deformation of the block 3, the middle portion thereof is refracted in a zigzag shape toward the tread circumferential direction. However, it can be a so-called three-dimensional sipe extending in the tread width direction or refracting in the tire radial direction. Further, in the illustrated example, the sipe 4 is open to the groove 2 that partitions the block 3 at both ends thereof, but is not limited to this, so-called blind sipe formed by terminating one end or both ends within the block 3. According to this, it is possible to suppress a decrease in the rigidity of the block 3, which is particularly advantageous when a plurality of sipes 4 are provided in the block 3. In the present invention, it is not necessary to provide the sipes 4 in all the blocks 3, and a predetermined effect can be obtained if they are provided in the plurality of blocks 3. When a higher edge effect or the like is required, it is preferable to provide the sipe 4 in approximately three or more blocks 3 of each block group.

The number of sipes 4 provided for each block is not limited to two, but can be three or one by adjusting the block rigidity and the required edge length (edge effect). More specifically, for example, when it is required to make the block 3 relatively large for the purpose of balancing with other performance such as steering stability and wear resistance, the block number density S is set to 0.00. It is preferable that the number of sipes 4 provided in the block 3 is ^two or more within a range of 003 / mm ² or more and 0.01 pieces / mm ² or less. In this way, the required edge effect can be obtained while balancing with other performances. When a plurality of sipes 4 are arranged in the block 3 in this way, it is preferable that the sipes 4 in the same block 3 are arranged in parallel to each other. By arranging the sipes 4 in the same block 3 in parallel in this way, the shape of the divided block portion between the sipes can be made uniform, and the strength of the block rigidity can be eliminated, thereby further improving the performance on ice. Because it can. Further, eliminating partial strength of block rigidity is also advantageous for uneven wear resistance. Note that the block number density S is more preferably 0.003 / mm ² or more and 0.008 / mm ² or less under the requirement of higher block rigidity.

On the other hand, when it is required to form the block 3 relatively small for the purpose of balancing with other performances such as steering stability and wear resistance, the block number density S is set to 0.005 / mm. It is preferable that the number of sipes 4 provided in each block 3 is one in a range of ² or more and 0.02 pieces / mm ² or less. In this way, the required edge effect can be obtained while balancing with other performances. Note that the block number density S is more preferably 0.007 / mm ² or more and 0.015 / mm ² or less under the demand for higher edge effect.

  Further, the extending direction of the sipe 4 is not limited to that in FIG. 2 and can be arbitrarily set in relation to the required edge length. For example, when emphasizing traction performance and braking performance, it can be set along the tread width direction. On the other hand, when emphasizing lateral input (cornering performance), tilt it in the tread width direction. Can be set. Although not shown, performance can be adjusted more effectively by partially changing the sipe direction in units of blocks in the tread. If it does in this way, these can be improved efficiently, aiming at the good balance of traction performance, brake performance, and cornering performance.

  Next, still another embodiment according to the present invention will be described. FIG. 3 is a partial development view showing a tread pattern of a tire according to another embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the element similar to the tire shown in previous FIG. 1, and the description is abbreviate | omitted.

In the tire, each of the blocks 3 of the block group G _B, has a first side SL1 and second sides SL2 parallel to the tread circumferential direction, and vertical grooves 2L is formed by these sides SL1 and SL2 Yes. Thus, by arranging the blocks 3 and forming the longitudinal grooves 2L extending in parallel with the tread circumferential direction, the edge effect can be enhanced, and steering stability on ice is particularly improved.

  In the embodiment shown in FIGS. 1 and 3, the block 3 having the sides ST1 and ST2 or the block 3 having the sides SL1 and SL2 is arranged over the entire tread portion 1, but the present invention is not limited to this. Can be provided in a part of the tread portion 1, and for example, includes both the block 3 shown in FIGS. 1 and 3, that is, the block 3 having the sides ST1 and ST2 and the block 3 having the sides SL1 and SL2. It is also possible to provide both the blocks 3 together in the same tread portion 1 to effectively improve the performance on ice while adjusting with other performance such as block rigidity.

  Next, tires of Examples 1 to 3 according to the present invention, tires of Conventional Example 1 according to the prior art, and tires of Comparative Examples 1 to 3 were respectively prototyped and performance evaluations on ice performance were performed.

The tires of Examples 1 to 3 are 205 / 55R16 size radial tires for passenger cars having the tread pattern shown in FIGS. These tires have the entire tread portion was partitioned and formed by a groove, a block group G _B composed by densely independent multiple blocks. Each block is formed in a regular hexagon and the same size as each other, and is arranged in a staggered manner in the tread circumferential direction. Tread circumferential length BL (mm), tread width length BW (mm), height (height from groove bottom) BH (mm), distance between adjacent blocks BGL (WT) Table 1 shows the distance BGW (mm) between blocks adjacent to each other in the tread width direction, and the distance BGO (WI) (mm) between blocks adjacent to each other in the oblique direction with respect to the tread circumferential direction. Also in each tire, the reference pitch length P of the block (mm), the width W of the block group (mm), is defined by the width W of the reference pitch length P and the block group of the block, the reference block group G _B negative ratio in zone Z N (%), the number a (number) of the blocks existing in the reference zone Z, a block number per unit actual ground contact area of the block group density S (pieces / mm ^2), the block group G _B Table 1 shows the number of blocks (columns) counted in the tread width direction. The tire of Example 2 is different from the tire of Example 1 in that each block has two sipes extending in the tread width direction in each block. The tire of Example 3 is implemented in the arrangement direction of each block. This is different from the tire of Example 1.

  For comparison, a 205 / 55R16 size radial tire for passenger cars, the negative rate of the tread portion shown in FIG. 4 having a negative rate of 31.9% in the entire tread portion, and the negative rate of the entire tread portion is shown in FIG. A tire of Comparative Example 1 having a tread pattern shown in FIG. In the tire of Conventional Example 1, a plurality of rectangular blocks are partitioned and formed in the tread portion by vertical grooves extending in the tread circumferential direction and horizontal grooves extending orthogonally to the vertical grooves. The longitudinal groove has a width of 3 mm and a depth of 8.5 mm, and the transverse groove has a width of 7.9 mm and a depth of 8.5 mm. Each block has three sipes extending linearly. In the tire of Comparative Example 1, a plurality of rectangular blocks are defined in the tread portion by vertical grooves extending in the tread circumferential direction and horizontal grooves extending orthogonally to the vertical grooves. The longitudinal groove has a width of 1.2 mm and a depth of 8.5 mm, and the transverse groove has a width of 4.5 mm and a depth of 8.5 mm. Each block has two sipes extending linearly. Other specifications are shown in Table 1.

Further, for comparison, tires of Comparative Examples 2 and 3 which are 205 / 55R16 size radial tires for passenger cars and have a tread pattern shown in FIGS. The tires of Comparative Examples 2 and 3 have substantially the same configuration as the tire of Example 1 except that the block number density S is outside the range of 0.003 to 0.04 / mm ^2. Table 1 shows the specifications of the tire of the comparative example.

(Performance evaluation)
About each said test tire, it assembled | attached to the rim of size 6.5Jx16, and it mounted | worn with the vehicle as internal pressure 220kPa (relative pressure), and performed the following tests and evaluated the performance.

(1) Brake performance evaluation test on ice The braking 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 the index of the tires of Examples 1 to 3 and Comparative Examples 1 to 3 with the result of Conventional Example 1 being 100, and the larger the value, the better the braking performance on ice. Indicates that

(2) Driving performance evaluation test on ice The driving performance on ice was evaluated from the measured time by fully accelerating the road surface on ice and measuring the time required to reach a distance of 20 m. 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 tires of Comparative Examples 1 to 3 with the result of Conventional Example 1 being 100. The larger the value, the better the driving performance on ice. Indicates that

(3) Steering stability evaluation test on ice Steering stability performance on ice is a combination of braking, acceleration, straightness and cornering by a test driver when driving on a test course on an ice plate in various driving modes. This was done by evaluating the feeling. 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 tires of Comparative Examples 1 to 3 with the result of Conventional Example 1 being 100, and the larger the value, the more the steering stability on ice. Shows good.

  From the evaluation results shown in Table 2, the tires of Examples 1 to 3 show superior performance in all of the braking performance on ice, the driving performance on ice, and the steering stability performance on ice compared to the tire of Conventional Example 1. In addition, the tire of Example 3 shows better performance than the tires of Examples 1 and 2 particularly in terms of steering stability on ice.

  According to the present invention, it is possible to dramatically improve the performance on ice by ensuring excellent grounding property and edge effect and efficiently removing the water film by the block.

It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 1) of one Embodiment according to this invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of Example 2) of other embodiment according to this invention. FIG. 10 is a partial development view showing a tread pattern of a pneumatic tire according to still another embodiment (tire of Example 3) according to the present invention. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the prior art example 1) of a prior art. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the comparative example 1) as a comparison. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the comparative example 2) as a comparison. It is the partial expanded view which showed the tread pattern of the pneumatic tire (tire of the comparative example 3) as a comparison.

Explanation of symbols

1 tread portion 2 grooves 2I inclined grooves 2L longitudinal grooves 2T lateral grooves 3 blocks 4 sipes C equatorial plane ST1, ST2 tread width direction parallel sides SL1, SL2 reference pitch of the tread peripheral G _B block group P blocks parallel to a direction Length W Block group width WT, WI Groove width Z Reference area

Claims (5)

A group of blocks formed by densely arranging a plurality of independent blocks partitioned by grooves is a pneumatic tire provided in at least a part of the tread portion,
In the reference area of the block group, the reference pitch length of the block in the block group is defined as P (mm), the width of the block group is defined as W (mm), and the reference pitch length P and the width W are defined. The block group is given by a / (P × W × (1−N / 100), where a is the number of the blocks existing in the reference area and N is the negative rate in the reference area. The block number density S per unit actual ground contact area is in the range of 0.003 / mm ^{2 to} 0.04 / mm ² ,
The pneumatic tire is characterized in that the blocks are each formed in a hexagonal shape and have the same size.   The pneumatic tire according to claim 1, wherein the blocks of the block group are arranged in a zigzag shape in the tread circumferential direction. The block group includes at least two blocks having first and second sides that are adjacent to each other in the tread circumferential direction and parallel to the tread width direction, respectively.
Of the at least two blocks, the groove width between the first side of one block and the second side of the other block is equal to the side other than the first and second sides. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is set to be larger than groove widths of all adjacent grooves.   The pneumatic tire according to any one of claims 1 to 3, wherein the block group includes a block having first and second sides parallel to a tread circumferential direction.   The pneumatic tire according to claim 1, wherein the block group includes a block in which one or more sipes are disposed.

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