JP5265310B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To greatly improve the on-ice performance by achieving the adequate tread pattern. <P>SOLUTION: In a pneumatic tire, a small block group G<SB>B</SB>in which a plurality of independent small blocks 3 demarcated by grooves 2 are closely arranged to each other are provided at least in a part of a tread part 1, and a block row or a land row is formed of the small blocks 3 of the small block group G<SB>B</SB>. The small blocks 3 are formed in a single circular shape of the same size, and arc-shaped sipes 4 are formed in the small blocks 3. <P>COPYRIGHT: (C)2010,JPO&amp;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 divided block portion 103a partitioned by the sipe 104 becomes horizontally long and the rigidity becomes too low, and the divided block portion 103a falls down at the time of ground contact, and the grounding property is deteriorated. Therefore, it is 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, the pneumatic tire of the present invention is provided with a small block group in which a plurality of independent small blocks partitioned by grooves are densely arranged with each other in at least a part of the tread portion. A pneumatic tire in which a block row or a land portion row is formed by small blocks of the small block group, wherein the small blocks are each formed in a single circular shape and the same size, and the small blocks Arc-shaped sipes are formed , the reference pitch length of the small blocks in the small block group is P (mm), the width of the small block group is W (mm), the reference pitch length P and the width When the number of the small blocks existing in the reference area of the small block group divided by W is a (number) and the negative rate in the reference area is N (%), a / (P × W x (1-N / 100 )), The small block number density S per unit actual contact area of the small block group is in the range of 0.003 / mm ^{2 to} 0.04 / mm ² and is adjacent in the tread circumferential direction. The pneumatic tire is characterized in that a distance between the two small blocks is larger than a distance between the two small blocks adjacent to each other in a direction inclined with respect to a tread circumferential direction . Here, “sipe” refers to a thin notch cut into the tread surface that can be closed when grounded. In addition, the “reference pitch length of a small block” refers to a minimum unit of a repeated pattern of small blocks in one block row constituting a small block group. For example, one small block and the small block are partitioned. When the repeating pattern of the pattern is defined by the groove, the sum of the tread circumferential length of one small block and the tread circumferential length of one groove adjacent to the tread circumferential direction of this small block is small. This is the reference pitch length of the block. The “small block group width W” refers to the length in the tread width direction of the small block group formed by densely arranging the small blocks. For example, when the small block group exists in the entire tread, the tread grounding width is set. Shall point to. Moreover, the “actual ground contact area” of the small block group means the total surface area of all the small blocks in the reference area of the small block group, in other words, the product of the reference pitch length P and the width W. It refers to the area defined by subtracting the area of the groove defining each small block from the area of the reference area defined above.

  In the pneumatic tire according to the present invention, since the small blocks partitioned by the grooves are densely arranged with each other, the total edge length of the small blocks is increased, and an edge effect higher than that of the sipe is obtained. Moreover, since the surface area per small block is small, the grounding property of each block improves. In addition, since the distance from the central area of the small block to the periphery of the block is small, the water film in the central area of the small block is efficiently removed when the block is grounded. In the pneumatic tire of the present invention, since the small blocks are formed in a single shape and the same shape as each other, the contact pressure in the arrangement range of the small blocks can be made almost uniform, and the grounding property is improved. be able to. Furthermore, in the pneumatic tire according to the present invention, since the small block has a circular shape, it can be a tread pattern with a small anisotropy effect that can exhibit the edge effect equally in all directions. . Furthermore, the edge effect can be improved by providing a sipe in the small block, and the block rigidity is reduced by arranging the sipe as compared with the case where the sipe is made linear by making the shape arc. Since the length of the sipe (edge component length) can be increased while suppressing the above-mentioned, a higher edge effect can be exhibited.

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

  In addition, although the small block group is more effective for the performance on ice when it is provided on the entire tread, it can be applied to a limited area to balance with other performance such as steering stability and uneven wear resistance. it can.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the small blocks are arranged in a staggered manner in the tread circumferential direction.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the small block is formed in a perfect circular shape.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the arc-shaped sipes are arranged without a gap when viewed in the radial direction along the surface from the center of the surface of the small block. Here, the “surface of the small block” refers to a surface that comes into contact with the road surface when the tread portion contacts the ground.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the arc-shaped sipe is parallel to the contour shape of the surface of the small block.

  And in the pneumatic tire of this invention, it is preferable that the both ends of the arc-shaped sipe are terminated within the small block.

  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 with a small 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 E) indicates the tread width direction.

  Although the tire of this embodiment is not illustrated, a carcass extending in a toroidal 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.

This tire, as shown in FIG. 1 has a tread portion 1, and defined by grooves 2, the small block group G _B formed by each other is densely plurality of small blocks 3 independent. Small block group G _B is present throughout the tread portion 1. The small blocks 3 are arranged along the tread circumferential direction to form a block row. Each of the small blocks 3 has a circular shape (a cylindrical shape and a surface contour shape of a circular shape) and is formed to have the same size. The small blocks 3 are arranged in a zigzag pattern in the tread circumferential direction. An arc-shaped sipe 4 is formed in the small block 3. The arc-shaped sipe 4 is curved with a curvature that is parallel to the surface contour shape of the small block 3 (that is, the surface contour shape of the small block 3 and the arc-shaped sipe 4 have the same center C). Share.) Further, three arcuate sipes 4 are formed on the inner side in the radial direction and three on the outer side in the radial direction when viewed from the center C of the surface of the small block 3. These arc-shaped sipes 4 are terminated in the small block 3 at both ends in the longitudinal direction. The arc-shaped sipe 4 is disposed without a gap in the circumferential direction of the side surface of the small block 3 when viewed in the radial direction along the surface from the center C of the surface of the small block 3. The arc-shaped sipe 4 located at the radial direction and the arc-shaped sipe 4 located outside in the radial direction are arranged so as to overlap each other when viewed in the radial direction in the circumferential direction of the small block 3.

  In the tire of this embodiment, since the small blocks 3 partitioned by the grooves 2 are densely arranged with each other, the total edge length of the small blocks 3 is increased, and a high edge effect is obtained. Moreover, since the surface area per one small block 3 is small, the grounding property of each small block is improved. Further, since the distance from the central area of the small block 3 to the block periphery is small, the water film in the central area of the small block 3 is efficiently removed when the block is grounded. In the tire of this embodiment, since the small blocks 3 are formed in a single shape and the same shape as each other, the contact pressure in the arrangement range of the small blocks 3 can be made almost uniform, and the grounding property is improved. Can be made. Furthermore, in the tire according to this embodiment, since the surface contour shape of the small block 3 is circular, the tread pattern is less affected by anisotropy and can equally exhibit the edge effect in all directions. be able to. Further, the edge effect can be further improved by providing the sipe 4 in the small block 3, and the block by the sipe arrangement is formed by making the shape of the arc into a circular shape as compared with the case where the sipe is linear. Since the length of the sipe 4 (edge component length) can be increased while suppressing a decrease in rigidity, a higher edge effect can be exhibited.

  Therefore, according to the tire of this embodiment, 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 small block 3. .

  Further, according to the tire of this embodiment, since the small blocks 3 are arranged in a zigzag shape in the tread circumferential direction, the respective edges are sequentially acted upon when the tires roll and under the formation of more small blocks 3. Therefore, the edge effect can be more effectively exhibited. In addition, by arranging the small blocks 3 in a zigzag pattern in the tread circumferential direction, the timing of contact with the road surface can be shifted between the small blocks 3 adjacent in the tread width direction, and pattern noise can also be reduced. it can. Further, by arranging the small blocks 3 in a staggered manner in this manner, a high density arrangement of the small blocks 3 can be easily realized. In addition, when the small block number density S, which will be described later, is set high, the effect of supporting the blocks between the adjacent small blocks 3 when a high load is applied to the small blocks 3 can be exhibited. The rigidity of the block 3 can be increased, and the performance on ice can be further improved.

  Furthermore, if the small block 3 is formed in a perfect circle as in the tire of this embodiment, a tread pattern having no anisotropy that can exhibit the edge effect equally in any direction can be obtained.

  Furthermore, as in the tire of this embodiment, when the arc-shaped sipes 4 are arranged without gaps when viewed in the radial direction from the center C of the surface of the small block 3 along the surface, they are equal in all directions. It can be set as the tread pattern without anisotropy which can exhibit an edge effect.

  Furthermore, like the tire of this embodiment, if the arc-shaped sipe 4 is set to a curvature that is parallel to the contour shape of the surface of the small block 3, the shape of the divided block portion divided by the sipe 4 and Since the difference in size can be reduced, that is, the difference in rigidity between the divided block portions can be reduced, the intended edge effect can be exhibited while suppressing uneven wear.

  Moreover, if both ends in the longitudinal direction of the arc-shaped sipe 4 are terminated in the small block 3 as in the tire of this embodiment, the edge effect can be more effectively exhibited on the ice with high block rigidity. The performance can be further improved.

The number of arc-shaped sipes 4 provided for each small block 3 is not limited to the example shown in the figure, but can be changed as appropriate by adjusting the rigidity of the small block 3, the required edge length (edge effect), and the water removal effect. can do. More specifically, for example, when it is required to form the small blocks 3 relatively large for the purpose of balancing with other performance such as steering stability and wear resistance, the small block number density S is set. It is preferable that the number of arc-shaped sipes 4 provided in the small blocks 3 is 3 or more within a range of 0.005 pieces / mm ² or more and 0.012 pieces / mm ² or less. If it does in this way, a required edge effect and a water removal effect can be acquired, aiming at balance with other performance. In addition, under the demand for higher small block rigidity, it is more preferable that the small block number density S is 0.006 / mm ² or more and 0.012 / mm ² or less.

On the other hand, when it is required to form the small blocks 3 relatively small for the purpose of balancing with other performances such as steering stability and wear resistance, the small block number density S is set to 0.013. It is preferable that the number of arc-shaped sipes 4 provided in each of the small blocks 3 is three in a range of / mm ² or more and 0.02 pieces / mm ² or less. If it does in this way, a required edge effect and a water removal effect can be acquired, aiming at balance with other performance. In addition, under the request | requirement of a higher edge effect and the water removal effect, it is more preferable to make small block number density S 0.013 piece / mm < ² > or more and 0.018 piece / mm < ² > or less.

として表される、小ブロック群Ｇ_Ｂの単位実接地面積当りの小ブロック個数密度Ｓ（個／ｍｍ^２）は、０．００３個／ｍｍ^２以上０．０４個／ｍｍ^２以下とすることが好ましい。なお、小ブロック群Ｇ_Ｂの基準区域Ｚ内の小ブロック３の個数ａをカウントするに際して、小ブロック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、小ブロック３の表面積に対する、基準区域内に残った小ブロック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で示す小ブロックのように、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小ブロックの場合は、１／２個と数えることができる。小ブロック群Ｇ_Ｂにおける小ブロック３の個数密度Ｓが０．００３（個／ｍｍ^２）未満の場合は、サイプの形成なしには、高いエッジ効果の実現が難しく、一方、小ブロック３の個数密度Ｓが０．０４（個／ｍｍ^２）を超えると小ブロック３が小さくなり過ぎて所要の小ブロック剛性の実現が難しい。また、小ブロック群Ｇ_Ｂにおける小ブロック３の個数密度Ｓを、０．００３５〜０．０３個／ｍｍ^２の範囲内とすれば、小ブロック３の剛性とエッジ効果との両立をより高い次元で達成することができる。 By the way, in the present invention, the size of the small blocks 3 and the density thereof are smaller than those of the conventional pattern shown in FIG. 3, and the density is higher. The edge effect and the water removal effect can be enhanced as the size of the small blocks 3 is reduced and the density is increased. The preferred range is as follows. That is, the reference pitch length of the small block 3 in the small block group G _B P (mm), the width W (mm) (this embodiment of the small block group G _B, the small block 3 on the entire tread portion 1 since There are arranged equal to the tread width TW.), is defined by the said reference pitch length P and the width W, reference zone Z of the small block group G _B (region shown in FIG hatching) When the number of small blocks 3 existing in a is a (pieces) and the negative rate in the reference zone Z is N (%),

Expressed as the small block number density S per unit actual ground contact area of the small block group _{G B} (number / mm ²⁾ is to be 0.04 0.003 pieces / mm ² or more pieces / mm ² or less preferable. Note that when counting the number a of the small block 3 in the reference zone Z of the small block group G _B, if the small block 3 is present across the inside and outside of the reference zone Z, can not be counted as one is small Counting is performed using the ratio of the remaining area of the small block 3 remaining in the reference area to the surface area of the block 3. For example, in the case of a small block straddling the inside and outside of the reference zone Z and having only half of it in the reference zone Z, such as the small block indicated by B1 in FIG. 1, it can be counted as 1/2. If the number density S of the small block 3 in the small block group G _B is less than 0.003 (pieces / mm ^2), without the formation of sipes, it is difficult to realize a high edge effect, whereas, the number of small blocks 3 When the density S exceeds 0.04 (pieces / mm ² ), the small block 3 becomes too small and it is difficult to achieve the required small block rigidity. Further, the number density S of the small block 3 in the small block group _{G B,} if within the range of 0.0035 to 0.03 piece / mm ^2, higher level of compatibility between rigidity and the edge effect of the small block 3 Can be achieved.

Further, in the present invention, negative ratio N of the small block group _{G B} is preferably 5% to 50%. If negative ratio N is less than 5% in the small block group G _B, except that the insufficient drainage groove area is too small, the present invention is to aim too large small blocks every single size However, 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.

  Next, another embodiment according to the present invention will be described. FIG. 2 is a partially developed 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.

This tire, with arc-shaped sipes 4 are formed into small blocks 3 of the small block group G _B, the radiation sipes 5 extending in a radial direction from the center C or its vicinity of the small block 3 is formed. The radial sipe 5 is disposed inside the arc-shaped sipe 4 in the radial direction. Each of the radiation sipes 5 is connected at one end to one end of the arc-shaped sipe 4 (one end opens at one end of the arc-shaped sipe 4), and the other end joins at or near the center C of the small block 3. Yes. In this embodiment, there are three radial sipes 5, but the number is not limited to this and may be one or four or more. The radial direction 5 may not be connected to the arc-shaped sipe 4.

  Thus, by providing the small block 3 with the radial sipe 5 extending radially from the center C of the small block 3 or the vicinity thereof, the water film between the ice surface and the tire can be more reliably removed. In particular, drainage performance on ice can be further improved.

  The above description shows only some of the embodiments of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the arc-shaped sipe 4 has been described as having both ends terminated in the small block 3, but this is not limiting, and one end or both ends in the longitudinal direction define the small block 3. It may be an opening in the groove 2, or may be an annular sipe that extends continuously without interruption in the small block 3. Further, in the present invention, it is not necessary to provide the arc-shaped sipes 4 in all the small blocks 3, and a predetermined effect can be obtained if they are provided in the plurality of small blocks 3. When a higher edge effect or the like is required, it is preferable to provide an arc-shaped sipe 4 in approximately half or more of the small blocks 3 in each small block group. Further, in the above-described embodiment, the shape of the small block 3 is a perfect circle, but it may be oval. According to this, depending on the required performance (for example, cornering performance or traction / brake performance). This is advantageous because it can be handled by changing the aspect ratio of the small block 3. For example, when emphasizing traction / brake performance, the small block 3 may be oblong (long in the tread width direction) oval, and when emphasizing cornering, the small block 3 is vertically long (in the tread circumferential direction). (Long) is oval. Moreover, even if it tries to adjust other tire performances such as uneven wear resistance and steering stability by properly using a small circular block and an elliptical small block for each arbitrary range in the tread surface. good.

  Next, tires of Examples 1 and 2 according to the present invention, tires of Conventional Example 1 according to the prior art, and tires of Comparative Examples 1 and 2 were respectively prototyped and performance evaluations on ice performance were performed.

The tire of Example 1 is a 205 / 55R16 size passenger car radial tire having the tread pattern shown in FIG. 1 in the tread portion. These tires, the overall tread portion was partitioned and formed by a groove, having a small block group G _B composed by densely independent plurality of small blocks. Each small block is formed in a circular shape, is formed in the same size as each other, and is arranged in a staggered manner in the tread circumferential direction. Each small block is provided with six arc-shaped sipes, three of which are arranged on the radially outer side of the small block and the other three are arranged on the radially inner side of the small block. The arc-shaped sipe on the radially outer side and the arc-shaped sipe on the radially inner side overlap each other in the radial direction of the small block. Other specifications of the tire of Example 1 are as shown in Table 1.

The tire of Example 2 is a 205 / 55R16 size passenger car radial tire having the tread pattern shown in FIG. 2 in the tread portion. These tires, the overall tread portion was partitioned and formed by a groove, having a small block group G _B composed by densely independent plurality of small blocks. Each small block is formed in a circular shape, is formed in the same size as each other, and is arranged in a staggered manner in the tread circumferential direction. Each small block is provided with three arc-shaped sipes, each extending radially outward from the arc-shaped sipe and extending radially outward from the center of the small block. There are three radial sipes connected to each other. Other specifications of the tire of Example 2 are as shown in Table 1.

  For comparison, a 205 / 55R16 size radial tire for passenger cars, the negative rate of the tread portion shown in FIG. 3 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 small 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 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 small block has three sipes extending linearly. In the tire of Comparative Example 1, a plurality of rectangular small 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 small block has two sipes extending linearly. Other specifications are shown in Table 1.

  For comparison, a tire of Comparative Example 2 which is a 205 / 55R16 size passenger car radial tire and has a tread pattern shown in FIG. The tire of Comparative Example 2 is substantially the same as the tire of Example 1 except that no arc-shaped sipe is formed on the small block.

(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 Brake performance on ice was evaluated from the measured distance by measuring the braking distance when fully braking 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 and 2 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the braking performance on ice. Indicates that

(2) Traction performance evaluation test on ice The traction performance on ice was evaluated from the measured time by fully accelerating the road surface on ice and measuring the time 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 and 2 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the traction performance on ice. Indicates that

(3) Feeling evaluation test on ice Feeling evaluation on ice comprehensively includes braking performance, acceleration performance, straight travel performance and cornering performance by a test driver when traveling on a test course on an ice sheet in various driving modes. It 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 and 2 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the feeling on ice. Indicates that

(4) Drainage evaluation test Drainage was evaluated by measuring the limit speed at which a hydroplaning phenomenon occurred on a wet road surface having a water depth of 5 mm and measuring the limit speed. The evaluation results are shown in Table 2. The evaluation in Table 2 is the index of the tires of Examples 1 and 2 and the tires of Comparative Examples 1 and 2 with the result of Conventional Example 1 being 100. The larger the value, the better the drainage. Show.

  From the evaluation results shown in Table 2, the tires of Examples 1 and 2 showed superior performance in all of the brake performance on ice, the traction performance on ice, the feeling performance on ice, and the drainage performance as compared with the tire of Conventional Example 1. Yes. In addition, the tire of Example 2 having a radial sipe shows superior performance in terms of drainage performance compared to the tire of Example 2.

  According to the present invention, it is possible to dramatically improve the performance on ice by ensuring excellent grounding property and edge effect and realizing efficient removal of a water film by a small 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. 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). 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.

Explanation of symbols

1 reference pitch length of the tread portion 2 grooves 3 small block 4 arcuate sipe 5 radial sipes C small block of the surface of the center D small block diameter G _B small block group L radial sipe length P small block group W Width of small block group Z Reference area

Claims (6)

A small block group in which a plurality of independent small blocks partitioned by grooves are densely arranged mutually is provided in at least a part of the tread portion, and a block row or a land portion row is formed by the small blocks of the small block group A pneumatic tire,
The small blocks are each formed in a single circular shape and the same size as each other,
The small block is formed with an arc-shaped sipe ,
The small block group defined by P (mm) as the reference pitch length of the small block in the small block group, W (mm) as the width of the small block group, and the reference pitch length P and the width W. A / (P × W × (1−N / 100)) where a is the number of small blocks existing in the reference area, and N is the negative rate in the reference area. The small block number density S per unit actual ground contact area of the small block group is in the range of 0.003 / mm ^{2 to} 0.04 / mm ² ,
A pneumatic tire characterized in that a distance between two small blocks adjacent in the tread circumferential direction is larger than a distance between two small blocks adjacent in a direction inclined with respect to the tread circumferential direction . The pneumatic tire according to claim 1 , wherein the small blocks are arranged in a staggered manner in the tread circumferential direction. The small block is formed in a round shape, the pneumatic tire according to Claim 1 or 2. The pneumatic tire according to any one of claims 1 to 3 , wherein the arc-shaped sipes are arranged without a gap when viewed in a radial direction along the surface from the center of the surface of the small block. The pneumatic tire according to any one of claims 1 to 4 , wherein the arc-shaped sipe is parallel to a contour shape of a surface of the small block. The pneumatic tire according to any one of claims 1 to 5 , wherein both ends in the longitudinal direction of the arc-shaped sipe are terminated in the small block.

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