JP2012056478A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that strikes a balance between on-ice performance and dry performance.SOLUTION: The pneumatic tire includes: a plurality of sipes arranged in a land part provided in a tread part; and a plurality of hole groups where at least one hole j exists in the hole groups to which the hole j itself belongs so as to satisfy dij≤(ri+rj)×2 regarding all holes j in terms of any of two holes i, j, and an area ratio of the holes to a total area of the land part is larger in each of two shoulder regions than in a center region in terms of the center region and the two shoulder regions, which are evenly divided into three regions in a tire width direction of a land width.

Description

  The present invention relates to a pneumatic tire. In particular, the present invention relates to a pneumatic tire having a tread surface in which sipes and hole groups are formed in a land portion provided in the tread portion.

  In order to improve the performance on ice, it is preferable to increase the edge length of the land portion of the tread pattern. On the other hand, in order to improve the tire performance (dry performance) on the dry road surface, it is preferable to increase the rigidity of the land portion. However, if the edge length of the land portion of the tread pattern is increased, the rigidity of the land portion is lowered, and therefore it is difficult to achieve both the increase of the edge length of the land portion and the improvement of the rigidity of the land portion.

  To date, many technologies have been developed to improve the rigidity of land while ensuring a scratching effect by pattern edges (hereinafter referred to as “edge effect” if necessary) to achieve both on-ice performance and dry performance. Has been. For example, a technique has been developed in which a large number of holes are provided on the tread surface to ensure the edge effect and to maintain the rigidity of the land portion. Specifically, the following techniques are listed.

  Patent Document 1 has a tread pattern based on a block pattern, and the block surface constituting the block pattern has a diameter of 0.5 mm to 2 mm and a depth of 50% to 100% of the main groove depth. A studless tire is disclosed in which a plurality of holes are opened so as to be 0.5% to 10% with respect to the block surface area. According to the tire, by providing a plurality of holes in the block surface, it is possible to improve the ground contact property of the tread surface mainly due to the occurrence of water absorption and to improve the running performance on icy and snowy roads.

  In Patent Document 2, a pair of sidewalls and a tread extending over both sidewalls are connected to the toroidal, a plurality of circumferential grooves extending in parallel to each other at predetermined intervals in the axial direction on the tread, and these circumferential grooves. And a plurality of lateral grooves arranged at substantially equal intervals in the circumferential direction and independent blocks partitioned by these groove groups, the tire is provided at least in the vicinity of an edge along the lateral groove of the block. There is disclosed a pneumatic tire that suppresses uneven wear by providing a plurality of small holes extending inward in the radial direction at predetermined intervals. According to the tire, the rigidity of the edge along the lateral groove of the block is reduced, and as a result, the entire block receives the shearing external force in the front-rear direction, and uneven wear in the block can be effectively suppressed. It is said that.

  In Patent Document 3, a pair of second sipes extending in a direction intersecting with the first sipes is disposed in at least one block land portion, and virtually partitioned by the extension lines of the first and second sipes. A pneumatic tire having a plurality of small holes in the sub-block land portion is disclosed. According to the tire, as a result of suppressing the bending deformation of the block land portion, the performance on ice and the performance on snow can be made compatible at a high level on the premise of maintaining the block rigidity of the tire.

  Patent Document 4 includes a plurality of sipes formed in a land portion and extending linearly or in a zigzag shape, and a plurality of fine holes formed in the land portion and extending inward in the tire radial direction from the tread surface. A pneumatic tire is disclosed in which the number of the fine holes with respect to the land portion increases from the center land portion located in the tread center portion toward the shoulder land portion located in the tread shoulder portion. According to the tire, it is possible to suppress a decrease in rigidity of the land portion compared to a pneumatic tire in which sipes are formed on the entire land portion, and in particular, it is possible to suppress a decrease in rigidity of the shoulder land portion. It is said that it is possible to ensure the running performance on the road surface.

Japanese Patent Laid-Open No. 03-208705 JP 04-85108 A JP 2008-30656 A JP 2009-274726 A

  The techniques disclosed in Patent Document 1 to Patent Document 4 are all provided with holes on the tread surface to improve various performances of the tire. For example, a hole is simply provided in the block edge along the directional groove. However, in these techniques, when a small number of holes are provided on the tread surface, the edge effect due to the pattern edge is insufficient. Moreover, when many holes are provided on the tread surface, the rigidity of the land portion is insufficient. For this reason, the techniques disclosed in Patent Document 1 to Patent Document 4 are difficult to achieve both high land rigidity and an edge effect, and as a result, there is a possibility that both on-ice performance and dry performance cannot be sufficiently achieved.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the pneumatic tire which aimed at coexistence with performance on ice and dry performance.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention includes a plurality of sipes disposed in a land portion provided in a tread portion, and three or more holes, and includes a tread. For any two holes i and j formed on the surface, in a plan view, the radius of the circumscribed circle Ci of the hole i is ri, the radius of the circumscribed circle Cj of the hole j is rj, and both the circumscribed circles Ci and Cj When the distance between the centers is dij, at least one hole j satisfying dij ≦ (ri + rj) × 2 exists in the hole group to which all holes i belong, and the contact width is set in the tire width direction. For one center region and two shoulder regions divided into three equal parts, the area ratio of the hole to the total area of the land portion is larger in each of the two shoulder regions than the center region A plurality of hole groups, and It is characterized in.

  In this pneumatic tire, a plurality of sipes are formed in a land portion provided on the tread surface, and a hole group is formed in a small block defined by the sipes. For this reason, according to this pneumatic tire, both the performance on ice and the dry performance can be achieved by the combined use of the sipe and the hole group.

  Specifically, this pneumatic tire has a plurality of hole groups composed of three or more holes, and the circumscribed circle Ci of the hole i for any two holes i and j in the hole group. When the radius is ri, the radius of the circumscribed circle Cj of the hole j is rj, and the distance between the centers of the circumscribed circles Ci and Cj is dij, all the holes i are included in the group of holes to which they belong. There is at least one hole j that satisfies ≦ (ri + rj) × 2. This means that for every hole i, there is at least one hole j at a relatively close position. As described above, when the holes i and j are concentrated in a narrow area, the individual holes i and j are compared with the case where one hole having the same volume as the total volume of the dense holes is formed. Has a small diameter and is not easily crushed, so that the collapse of the hole i and the hole j can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect, compared with the case where one hole having the same volume as the total volume of the densely packed holes is formed. Can be secured.

  Furthermore, in this pneumatic tire, the area ratio of the hole to the total area of the land portion is one center region and two shoulder regions divided by dividing the contact width into three in the tire width direction. Each of the two shoulder regions is larger than the center region. For this reason, according to this pneumatic tire, the water removal effect and the edge effect can be enhanced in the shoulder region, and the rigidity of the land portion can be sufficiently ensured in the center region. According to such a configuration, compared to a pneumatic tire in which sipes are simply arranged evenly in the center region and the shoulder region, the edge effect is maintained by the sipes in the center region, and the land portion in the shoulder region is maintained. Can be sufficiently secured.

  As described above, the pneumatic tire according to the present invention has at least one hole j at a relatively close position for all the holes i on the assumption that the sipe and the hole group are used together, and the total area of the land portion. The hole area ratio is completed by making it larger in the shoulder region than in the center region. For this reason, while being able to enhance the performance on ice by a high water removal effect, a water absorption effect, and an edge effect, it is possible to enhance the dry performance by sufficiently securing the rigidity of the land portion provided in the tread portion, As a result, both on-ice performance and dry performance can be achieved.

  In the pneumatic tire of the present invention, the ribs defined by the circumferential grooves extending in the tire circumferential direction, or the land portion rows defined by the circumferential grooves and having a plurality of land portions in the tire circumferential direction, The rib area in the rib or each land portion row or the area ratio of the hole to the total area of the land portion is the outer side in the tire width direction from the rib or land portion row on the tire equator surface or the rib or land portion row closest to the tire equator surface. It is desirable that the size gradually increases toward the rib or land section. When only sipes are evenly arranged in the center region and the shoulder region, the dry performance is insufficient because the rigidity of the land portion in the shoulder region is insufficient. However, according to this pneumatic tire, the hole groups are sequentially formed from the rib or land portion row on the tire equator surface or the rib or land portion row closest to the tire equator surface toward the rib or land portion row on the outer side in the tire width direction. A large amount is disposed, and the amount of sipes disposed on the ribs or land portion rows on the outer side in the tire width direction is suppressed accordingly. For this reason, in particular, by ensuring sufficient rigidity of the land portion in the shoulder region, it is possible to efficiently improve the dry performance, and as a result, it is possible to efficiently achieve both on-ice performance and dry performance. .

  In the pneumatic tire of the present invention, the length of the sipe per unit area is about 2 for one center region and two shoulder regions that are divided by dividing the contact width into three in the tire width direction. The center region is preferably larger than each of the two shoulder regions. According to this pneumatic tire, the edge effect can be sufficiently obtained in the center region, and the rigidity of the land portion can be sufficiently obtained in the shoulder region. For this reason, it is possible to efficiently ensure the edge effect and ensure the rigidity of the land portion, and as a result, it is possible to more efficiently achieve both on-ice performance and dry performance.

  Further, in the pneumatic tire according to the present invention, the sipes per unit area for a rib partitioned by a circumferential groove or a land portion row partitioned by the circumferential groove and having a plurality of land portions in the tire circumferential direction. It is desirable that the length of the tire gradually increases from the outermost rib or land portion row in the tire width direction toward the inner rib or land portion row in the tire width direction. According to this pneumatic tire, particularly, the edge effect in the center region and the land portion rigidity in the shoulder region can be efficiently performed. It is possible to more efficiently achieve both.

  In the pneumatic tire of the present invention, for all the holes i in the hole group, there may be at least two holes j satisfying dij ≦ (ri + rj) × 2 in the hole group to which the hole belongs. desirable. This means that for every hole i, there are at least two holes j at relatively close positions. According to this pneumatic tire, in the periphery of all the holes i, it is remarkably suppressed that the own hole or other holes are deformed and crushed. Thereby, the water removal effect and the rigidity of the tread land portion can be further enhanced, and as a result, the on-ice performance and the dry performance can be further enhanced.

  In the pneumatic tire of the present invention, it is desirable that the volume of at least one hole is different from the volume of other holes in at least one hole group. According to this pneumatic tire, when each hole is used as a reference, not only the water removal effect by each hole, but also the rigidity of the faithful tread rubber existing around each hole can be set as appropriate. For this reason, the water removal effect and the rigidity of the land part provided in the tread part can be locally increased or decreased. As a result, the balance between the water removal effect and the rigidity in the hole group can be adjusted efficiently, and consequently the balance between the performance on ice and the dry performance can be adjusted.

  In the pneumatic tire of the present invention, it is desirable that the radius of the circumscribed circle of all the holes in the hole group is 0.2 mm or more and 1.0 mm or less. According to this pneumatic tire, by setting the radius to 0.2 mm or more, it is possible to sufficiently suppress the crushing of each hole and enhance the water removal effect. Moreover, by making the said radius 1.0 mm or less, it can fully suppress that each hole deform | transforms and can suppress the fall of rigidity. As a result, the water removal effect and the rigidity of the land portion of the tread portion can be further increased, and consequently the performance on ice and the dry performance can be further increased.

In the pneumatic tire of the present invention, it is desirable that the total volume of the holes in the hole group is 10 mm ³ or less. According to this pneumatic tire, a large number of holes having a small volume can be arranged by reducing the volume of the entire hole group. For this reason, each hole can be sufficiently prevented from being deformed and crushed, the water removal effect and the rigidity of the tread land portion can be further enhanced, and the on-ice performance and the dry performance can be further enhanced. .

  In the pneumatic tire of the present invention, it is preferable that the hole group is disposed in at least one of a stepping side region and a kicking side region of the land portion when the tire rotates. According to this pneumatic tire, the water absorption effect at the time of tire rotation increases, and as a result, the performance on ice can be further enhanced.

  The pneumatic tire according to the present invention can achieve both on-ice performance and dry performance.

FIG. 1 is a plan view illustrating a main part of an example of a tread portion of the pneumatic tire according to the first embodiment. FIG. 2 is an enlarged perspective view of the hole group shown in FIG. FIG. 3A is a plan view illustrating a variation of an arrangement mode of holes constituting a hole group formed in a tread portion of the pneumatic tire according to the first embodiment. FIGS. 3-2 is a top view which shows the variation about the arrangement | positioning aspect of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 1. FIGS. FIG. 3-3 is a plan view illustrating a variation regarding an arrangement mode of holes constituting a hole group formed in the tread portion of the pneumatic tire according to the first embodiment. FIG. 4-1 is a plan view illustrating a variation of holes forming a hole group formed in the tread portion of the pneumatic tire according to the first embodiment, and a dotted line indicates a circumscribed circle of a solid line figure. FIG. 4-2 is a plan view illustrating a variation of the holes constituting the hole group formed in the tread portion of the pneumatic tire according to the first embodiment, and a dotted line indicates a circumscribed circle of a solid line figure. FIG. 4-3 is a plan view illustrating a variation of the holes constituting the hole group formed in the tread portion of the pneumatic tire according to the first embodiment, and a dotted line indicates a circumscribed circle of a solid line figure. FIGS. 4-4 is a top view which shows the variation of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 1, and a dotted line shows the circumscribed circle of a solid line figure. FIGS. 4-5 is a top view which shows the variation of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 1, and a dotted line shows the circumscribed circle of a solid line figure. FIGS. 4-6 is a top view which shows the variation of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 1, and a dotted line shows the circumscribed circle of a solid line figure. FIGS. 4-7 is a top view which shows the variation of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 1, and a dotted line shows the circumscribed circle of a solid line figure. FIG. 5 is an enlarged plan view of the hole group shown in FIG. FIG. 6 is a plan view illustrating a main part of an example of a tread portion of the pneumatic tire according to the second embodiment. FIG. 7 is an enlarged perspective view of the hole group shown in FIG. FIGS. 8-1 is a top view which shows the variation about the arrangement | positioning aspect of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 2. FIGS. FIGS. 8-2 is a top view which shows the variation about the arrangement | positioning aspect of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 2. FIGS. FIG. 9 is an enlarged plan view of the hole group shown in FIG. FIG. 10 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description. In addition, constituent elements in the following description include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Moreover, the structure disclosed below can be combined suitably. In the following description, the tire circumferential direction means a circumferential direction with the tire rotation axis as the central axis. The tire width direction means a direction parallel to the tire rotation axis, the tire width direction outer side means a side away from the tire equatorial plane, and the tire width direction inner side means a side toward the tire equatorial plane. . The tire radial direction means a direction orthogonal to the pneumatic tire rotation axis, the tire radial direction outer side means a side away from the tire rotation axis, and the tire radial direction inner side means a side toward the tire rotation axis. To do.

[Embodiment 1]
FIG. 1 is a plan view illustrating a main part of an example of a tread portion of the pneumatic tire according to the first embodiment. In the example shown in the figure, a plurality of circumferential grooves 2 (21, 22, 23, 24, 25, 26) extending substantially in the tire circumferential direction and two adjacent circumferential grooves 2 are formed in the tread portion 1. A plurality of lateral grooves 3 (31, 32, 33, 34, 35, 36, 37, 38) communicating with (21 to 26) are disposed. The lateral grooves 3 (31 to 38) extend from the outermost part in the tire width direction to the inner side in the tire width direction, and extend at an angle with respect to the tire width direction from the middle to extend toward the tire equatorial plane CL. Terminate before reaching. Further, in the vicinity of the tire equatorial plane CL, there are a plurality of lateral grooves 4 (41, 42) inclined in a direction opposite to the inclination direction of the lateral grooves 3 (31 to 38) with respect to the tire width direction on the basis of the tire width direction. It is arranged. As a result, a large number of land portions 5 (51, 52, 53, 54, 55, 56, 57) are defined in the tread portion 1.

  In the example shown in FIG. 1, a plurality of sipes 6 (61, 62, 63, 64, 65, 66, 67) extending across the tire circumferential direction are disposed on the land portion 5 (51-57). Thus, the land portion 5 (51-57) is divided into a plurality of small blocks 7 (71, 72, 73, 74, 75, 76, 77). For example, in the land portion 51, three sipes 61 are arranged, whereby the land portion 51 is divided into four small blocks 71.

  The sipe 6 (61 to 67) can be formed into a wave shape as shown in FIG. 1 or a linear shape or a three-dimensional shape.

  Of the land portions 5 (51 to 57) in which the small blocks 7 (71 to 77) are defined in this way, each of the land portions 51, 52, 53, 55, 56, and 57 has three or more holes. A plurality of hole groups 8 (81, 82, 83, 85, 86, 87) are formed. In the example shown in FIG. 1, the hole group 8 (81-83, 85-87) is composed of all three holes 8a, 8b, 8c, and becomes an equilateral triangle when the centers of the holes 8a-8c are connected. It is an arrangement shape.

  FIG. 2 is an enlarged perspective view of the hole group shown in FIG. As shown in FIG. 2, the holes 8a, 8b, 8c constituting the hole group 8 (81-83, 85-87) are all cylindrical in the tire radial direction outer side and tapered in the tire radial direction inner side. It has become. Further, the holes 8a to 8c are open on the tread surface and are bottomed on the inner side in the tire radial direction. Each of the holes 8a to 8c has a tapered shape in which the hole diameter is gradually reduced at the bottom portion, and is suitable for improving the rigidity of the bottom portion.

  In the example shown in FIG. 2, the holes 8a, 8b, 8c have the same tire radial depth. The depth in the tire radial direction of each hole 8a to 8c is preferably 2 mm or more in order to obtain a sufficient water removal effect. In addition, the tire radial depth of each of the holes 8a to 8c is less than the depth of the circumferential groove 2 where the groove bottom is close to the belt layer because excellent durability is obtained by the hole bottom not being close to the belt layer. It is preferable to do.

  In the example illustrated in FIG. 1, the arrangement mode of the holes 8 a, 8 b, and 8 c is a regular triangle in plan view, but the first embodiment is not limited to such a mode. FIGS. 3A to 3C are plan views illustrating variations of the arrangement mode of the holes constituting the hole group formed in the tread portion of the pneumatic tire according to the first embodiment.

  As for the arrangement | positioning aspect of the holes 8a, 8b, and 8c, as shown to FIGS. 3-1, the figure which tied the center of each hole 8a-8c is a triangle. Moreover, as shown to FIGS. 3-2, it can also be set as the aspect from which the figure which tied the center of each hole 8a-8c becomes a straight line. Moreover, as shown to FIGS. 3-3, the hole group 8 is comprised from four holes 8a, 8b, 8c, and 8d, and it can also be set as the aspect from which the figure which tied the center of each hole 8a-8d becomes a trapezoid. . In the example illustrated in FIG. 3C, the tire radial depth of each hole can be the same for the holes 8a to 8d.

  In the example shown in FIG. 1, the holes 8a, 8b, and 8c are all circular in a plan view, but the first embodiment is not limited to such a mode. FIGS. 4-1 to FIGS. 4-7 are plan views showing variations of the holes constituting the hole group formed in the tread portion of the pneumatic tire according to the first embodiment, and the dotted line shows a circumscribed circle of a solid line figure .

  As shown in these drawings, the shape of the holes constituting the hole group 8 is not only a circle as shown in FIG. 4-1, but also a quadrangle shown in FIG. 4-2, a pentagon shown in FIG. 4-3, And it can be set as the n-gon (n> = 3) containing the hexagon shown to FIGS. 4-4. Moreover, the shape of the hole which comprises the hole group 8 can also be made into the star shape shown to FIGS. 4-5, the eaves shape shown to FIGS. 4-6, and the ellipse shape shown to FIGS. 4-7. In the example shown in FIG. 1, the dimensions of the holes 8a, 8b, and 8c (the radius of the circumscribed circle) are all equal, but the first embodiment is not limited to such a form, and the dimensions of each hole are at least partially. Can be different. Here, the circumscribed circle means the circumscribed circle of the openings of the holes 8a to 8c.

  The hole group 8 (81-83, 85-87) further satisfies the following first requirement and second requirement on the premise of the arrangement mode, shape and dimensions of such holes. That is, the first requirement is that the radius of the circumscribed circle Ci of the hole i is ri and the hole j in plan view for any two holes i and hole j in the hole group 8 (81 to 83, 85 to 87). When the radius of the circumscribed circle Cj is rj and the distance between the centers of the circumscribed circles Ci and Cj is dij, for all holes i, dij ≦ (ri + rj) × 2 That is, there is at least one hole j to be filled. Here, the symbols i and j are identifiers for identifying arbitrary holes constituting the hole group 8 (81 to 83, 85 to 87), and do not indicate specific holes.

  Further, the second requirement is that the area ratio of the hole to the total area of the land portion 5 (51 to 57) with respect to one center region and two shoulder regions divided by dividing the ground contact width into three in the tire width direction. Is larger in each of the two shoulder regions than in the center region. Here, the total area of the land portion means the sum of the areas of all the land portions included in each region in a plan view when the tire is new, and excludes the area of the portion corresponding to the groove wall of the land portion. It is. Moreover, the area of a hole means the sum total of the area of the opening part of all the holes contained in each area | region by planar view at the time of a tire new article.

  First, the first requirement will be described in detail. In the pneumatic tire shown in FIG. 1, all the holes i have at least one hole j at a relatively close position in the hole group 8 (81-83, 85-87). Here, the relatively close position in the first requirement means that the center distance dij between the circumscribed circle Ci of the hole i and the circumscribed circle Cj of the hole j is the radius ri of the hole i and the radius rj of the hole j. The position of the hole j with respect to the hole i when satisfy | filling that it is 2 times or less of the sum is said.

  FIG. 5 is an enlarged plan view of the hole group 8 (81-83, 85-87) shown in FIG. As shown in FIG. 5, each of the hole groups 8 (81-83, 85-87) is composed of three holes 8a, 8b, 8c. Since the holes 8a, 8b, and 8c are all circular in a plan view, these circumscribed circles coincide with the outer shapes of the holes 8a, 8b, and 8c. Here, the radius of the circumscribed circle Ca of the hole 8a is ra, the radius of the circumscribed circle Cb of the hole 8b is rb, the radius of the circumscribed circle Cc of the hole 8c is rc, and the distance between the centers of the circumscribed circles Ca and Cb is dab. The distance between the centers of the circles Cb and Cc is dbc, and the distance between the centers of the circumscribed circles Cc and Ca is dca.

  When the hole i is the hole 8a and the hole j is the hole 8b and the hole 8c, as shown in FIG. 5, with respect to the hole 8a, in relation to the hole 8b and the hole 8c, dab ≦ (ra + rb) × 2 There is a hole 8b that satisfies the above condition, and a hole 8c that satisfies dca ≦ (rc + ra) × 2. When the hole i is the hole 8b and the hole j is the hole 8c and the hole 8a, the hole 8b similarly satisfies dbc ≦ (rb + rc) × 2 in the relationship between the hole 8c and the hole 8a. The hole 8c and the hole 8a satisfying dab ≦ (ra + rb) × 2 exist. Further, when the hole i is the hole 8c and the hole j is the hole 8a and the hole 8b, similarly, the hole 8c satisfies dca ≦ (rc + ra) × 2 in relation to the hole 8a and the hole 8b. The hole 8a and the hole 8b satisfying dbc ≦ (rb + rc) × 2 exist.

  A pneumatic tire having a tread surface in which such a group of holes 8 (81-83, 85-87) is formed has its own holes, and in the example shown in FIG. At least one hole exists at a relatively close position in the hole group 8 to which the hole group 8 belongs, and has the first requirement.

  Looking at the hole 8 a, the holes 8 b and 8 c are holes located at relatively close positions in the hole group 8. In this case, in terms of the relationship between the hole 8a and the hole 8b, as shown in FIG. 2, when the hole 8a and the hole 8b are closely packed in a narrow region, the total volume of the densely packed holes 8a and 8b is the same. Compared with the case of forming one hole having a volume of 1 mm, the diameter of each of the holes 8a and 8b is small, and the cylindrical surface having a small radius of curvature is not easily affected by an external force, and thus is not easily crushed. Here, the total volume of the holes 8a and 8b means the sum of the volume of the hole 8a and the volume of the hole 8b. For this reason, falling of the holes 8a and 8b can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 8a and 8b is formed. Can be secured. Further, in terms of the relationship between the holes 8a and 8c, as shown in FIG. 2, when the holes 8a and 8c are closely packed in a narrow region, the total volume of the densely packed holes 8a and 8c is the same. Compared to the case where one hole having a volume is formed, each of the holes 8a and 8c has a small diameter and is not easily crushed. For this reason, falling of the holes 8a and 8c can be suppressed. As a result, compared to the case where one hole having the same volume as the total volume of the dense holes 8a and 8c is formed, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect. Can be secured.

  Similarly, regarding the hole 8 b, the holes 8 c and 8 a are holes located at relatively close positions in the hole group 8. In this case, in terms of the relationship between the hole 8b and the hole 8c, as shown in FIG. 2, when the hole 8b and the hole 8c are closely packed in a narrow area, the total volume of the densely packed holes 8b and 8c is the same. Compared to the case of forming one hole having a volume of 1 mm, each of the holes 8b and 8c has a small diameter and is not easily crushed. For this reason, falling of the holes 8b and 8c can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 8b and 8c is formed. Can be secured. Further, in the relationship between the hole 8b and the hole 8a, as shown in FIG. 2, when the hole 8b and the hole 8a are closely packed in a narrow region, the total volume of the densely packed holes 8b and 8a is the same. Compared to the case where one hole having a volume is formed, each of the holes 8b and 8a has a small diameter and is not easily crushed. For this reason, the fall of the holes 8b and 8a can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 8b and 8a is formed. Can be secured.

  Similarly, regarding the hole 8 c, the holes 8 a and 8 b are holes located at relatively close positions in the hole group 8. In this case, in terms of the relationship between the hole 8c and the hole 8a, as shown in FIG. 2, when the hole 8c and the hole 8a are closely packed in a narrow region, the total volume of the densely packed holes 8c and 8a is the same. Compared to the case where one hole having a volume of 1 is formed, each of the holes 8c and 8a has a small diameter and is not easily crushed. For this reason, the fall of the holes 8c and 8a can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 8c and 8a is formed. Can be secured. Further, in terms of the relationship between the hole 8c and the hole 8b, as shown in FIG. 2, when the hole 8c and the hole 8b are densely packed in a narrow region, the total volume of the densely packed holes 8c and 8b is the same. Compared to the case where one hole with a volume is formed, each of the holes 8c and 8b has a small diameter and is not easily crushed. For this reason, falling of the holes 8c and 8b can be suppressed. As a result, compared to the case where one hole having the same volume as the total volume of the dense holes 8c and 8b is formed, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect. Can be secured.

  In this way, the collapse suppression unit (the unit composed of the hole 8a and the hole 8b, the unit composed of the hole 8b and the hole 8c, and the unit composed of the hole 8c and the hole 8a) constituted by the holes 8a to 8c being densely packed is When each hole 8a, 8b, 8c is used as a reference, at least one exists in a narrow area around each hole including each hole. In other words, in the example shown in FIG. 1, regarding the hole group 8 (81-83, 85-87), there are two collapse suppression units around each hole. As a result, in each collapse suppression unit in the hole group 8, the holes 8a to 8c are suppressed from being deformed and crushed.

  By the above, the pneumatic tire of Embodiment 1 has the 1st requirement regarding the positional relationship of the holes 8a-8c which comprise the hole group 8 (81-83, 85-87).

  Further, the second requirement will be described in detail. In the pneumatic tire shown in FIG. 1, the area of the hole with respect to the total area of the land portion in each of the center region and the two shoulder regions divided by dividing the contact width into three in the tire width direction. The ratio is larger in the shoulder region than in the center region. Here, the contact width means a linear distance between both ends of a tread pattern portion of a tire in a no-load state when a tire is mounted on an applicable rim, as specified in JATMA YEAR BOOK 2009 edition, with a specified air pressure. To do.

  In FIG. 1, dotted lines L1, L2, L3, and L4 are virtual dotted lines for dividing the ground contact width into three equal parts in the tire width direction, respectively. Hereinafter, the region between the virtual dotted line L2 and the virtual dotted line L3 is referred to as a center region, the region between the virtual dotted line L1 and the virtual dotted line L2 is referred to as a first shoulder region, and the virtual dotted line L3 and the virtual dotted line L4 The area in between is called the second shoulder area.

  As shown in FIG. 1, the water removal effect can be enhanced in both shoulder regions by increasing the area ratio of the hole to the total area of the land portion in the first shoulder region and the second shoulder region than in the center region. In addition, the rigidity of the land portion can be sufficiently secured in the center region. Here, the total area of the land portion means the sum of the areas of all the land portions included in each region in a plan view when the tire is new, and excludes the area of the portion corresponding to the groove wall of the land portion. It is. Moreover, the area of a hole means the sum total of the area of the opening part of all the holes contained in each area | region by planar view at the time of a tire new article.

  As described above, the pneumatic tire of Embodiment 1 has the second requirement regarding the area ratio of the holes to the total area of the land portion.

  As described above, the pneumatic tire of the first embodiment has at least one hole at a relatively close position for all the holes 8a, 8b, and 8c on the assumption that the sipe and the hole group are used in combination ( In addition to satisfying the first requirement, the ratio of the hole area to the total area of the land portion 5 is set to be larger in the shoulder region than in the center region (second requirement). For this reason, the first requirement and the second requirement are combined, and the performance on ice can be enhanced by the high water removal effect, the water absorption effect, and the edge effect, and sufficiently ensure the rigidity of the land portion provided in the tread portion. Can improve the dry performance. Therefore, according to this pneumatic tire, both on-ice performance and dry performance can be achieved.

  Here, the on-ice performance refers to various performances of the tire on the ice, and particularly means the driving performance and braking performance on the polished ice burn. The dry performance refers to various performances of the tire on the dry road surface, and particularly means driving performance and braking performance on the dry road surface.

  In addition, although the example shown in FIG. 5 is the arrangement | positioning mode of the hole from which the figure which tied the center of each hole 8a, 8b, 8c becomes an equilateral triangle, this embodiment is not restricted to this. The hole arrangement modes shown in FIGS. 3-1 to 3-3 also satisfy the first requirement and the second requirement. When all the hole groups shown in FIG. 1 are replaced with the hole group 8 shown in FIG. 3A, at least one hole satisfying dij ≦ (ri + rj) × 2 is present in the hole group to which the hole belongs. (For the hole 8a, the holes 8b and 8c, for the hole 8b, the hole 8a, for the hole 8c, the hole 8a) are present (having the first requirement). Moreover, since it is a requirement regarding the arrangement | positioning aspect of the hole group 8, about the 2nd requirement, it comprises similarly to the example shown in FIG.

  In addition, when all the hole groups shown in FIG. 1 are replaced with the hole group 8 shown in FIG. 3-2, for all the holes, holes satisfying dij ≦ (ri + rj) × 2 are included in the hole groups to which the holes belong. There is at least one (the hole 8b for the hole 8a, the holes 8a and 8c for the hole 8b, and the hole 8b for the hole 8c) (having the first requirement). Moreover, since it is a requirement regarding the arrangement | positioning aspect of the hole group 8, about the 2nd requirement, it comprises similarly to the example shown in FIG.

  Further, when all the hole groups shown in FIG. 1 are replaced with the hole group 8 shown in FIG. 3-3, for all the holes, holes satisfying dij ≦ (ri + rj) × 2 are included in the hole groups to which the holes belong. There is at least one (hole 8b for hole 8a, holes 8a and 8c for hole 8b, holes 8b and 8d for hole 8c, and hole 8c for hole 8d) (having the first requirement). Moreover, since it is a requirement regarding the arrangement | positioning aspect of the hole group 8, about the 2nd requirement, it comprises similarly to the example shown in FIG.

  For this reason, also about the example shown to FIGS. 3-1 to FIG. 3-3, while being able to improve performance on ice by a high water removal effect, a water absorption effect, and an edge effect, the rigidity of the land part provided in the tread part is improved. Dry performance can be improved by ensuring sufficient. Therefore, even with these pneumatic tires, both on-ice performance and dry performance can be achieved.

  In the pneumatic tire of the first embodiment, as described above, the shape of the holes constituting the hole group 8 is a circle or an n-gon (n ≧ 3) indicated by a solid line in FIGS. It may be a star shape, a saddle shape, an ellipse shape or the like shown in 4-5 to FIG. 4-7. Of these, a circular shape or a substantially circular shape is preferable. By making the shape of each hole circular or substantially circular, the water removal effect, water absorption effect, and edge effect can be more evenly exhibited in both the tire circumferential direction and the tire width direction, and the rigidity of the tread land portion Can be ensured more evenly, so that the performance on ice and the dry performance can be further enhanced.

  In the pneumatic tire of the first embodiment, as described above, the size and shape of the holes constituting the hole group 8 may be equalized for all the holes as shown in FIGS. 3-1 to 3-3. Alternatively, at least a part of the holes may be different, but it is preferable that all holes have the same size and shape. By making the size and shape of all the holes equal, the water removal effect, the water absorption effect, and the edge effect can be more evenly exhibited in both the tire circumferential direction and the tire width direction when viewed as the whole hole group 8. At the same time, since the rigidity of the tread land portion can be more evenly secured, the on-ice performance and the dry performance can be further enhanced.

  Further, in the pneumatic tire of the first embodiment, the distance between the centers of the holes constituting the hole group 8 may be made equal for all the holes as shown in FIG. As shown in FIG. 3, at least some of the holes may be different from each other, but it is preferable that the distances between the centers of all the holes are equal. By making the distance between the centers of all the holes equal, the hole group 8 as a whole exhibits the water removal effect, the water absorption effect, and the edge effect more evenly in both the tire circumferential direction and the tire width direction. In addition, the rigidity of the tread land portion can be more evenly secured, and the on-ice performance and the dry performance can be further enhanced.

  Moreover, in the pneumatic tire of Embodiment 1, it is preferable that (ri + rj) × 1.1 ≦ dij ≦ (ri + rj) × 1.9 in the first requirement. By setting (ri + rj) × 1.1 ≦ dij, it is possible to sufficiently secure the interval between the hole i and the hole j and sufficiently secure the rigidity of the land portion existing between these holes. In addition, by setting dj ≦ (ri + rj) × 1.9, the holes i and j are further densely packed in a narrow region so that the individual holes i and j are more difficult to collapse, and the holes i and j are collapsed. Can be suppressed. As a result, the distance between the holes is significantly shortened, compared with the case where one hole having the same volume as the total volume of the plurality of holes is formed, and the land provided in the tread portion is reduced without reducing the water removal effect. The rigidity of the part can be sufficiently secured. When the distance between the centers of the circumscribed circles of the hole i and the hole j is 0, the holes substantially coincide with each other, which is contrary to the technical idea of the first embodiment. Let 0 <dij. As described above, when the first requirement is further limited, the edge effect and the rigidity of the land portion provided in the tread portion can be further increased without deteriorating the water removal effect, and consequently the performance on ice and the dry performance. And can be further enhanced.

  In the pneumatic tire according to the first embodiment, the land portion is divided by the circumferential grooves 2 (21, 22, 23, 24, 25, 26) and the land portion row has a plurality of land portions in the tire circumferential direction. It is preferable that the area ratio of the holes to the total area of 5 gradually increases from the land portion row on the tire equatorial plane CL toward the land portion row on the outer side in the tire width direction. Here, the total area of the land portion means the sum of the areas of all the land portions included in each land portion row in a plan view when the tire is new, and the area of the portion corresponding to the groove wall of the land portion is It means to exclude. Moreover, the area of a hole means the sum total of the area of the opening part of all the holes contained in each land part row | line in planar view at the time of a tire new article. Hereinafter, as shown in FIG. 1, a land portion row that is located on the outer side in the tire width direction from the circumferential groove 21 and includes a plurality of land portions 51 is referred to as a land portion row A. A land portion row that is located between the circumferential groove 21 and the circumferential groove 22 and includes a plurality of land portions 52 is referred to as a land portion row B. A land portion row that is located between the circumferential groove 22 and the circumferential groove 23 and includes a plurality of land portions 53 is referred to as a land portion row C. A land portion row that is located between the circumferential groove 23 and the circumferential groove 24 and includes a plurality of land portions 54 is referred to as a land portion row D. A land portion row that is located between the circumferential groove 24 and the circumferential groove 25 and includes a plurality of land portions 55 is referred to as a land portion row C ′. A land portion row that is located between the circumferential groove 25 and the circumferential groove 26 and includes a plurality of land portions 56 is referred to as a land portion row B ′. A land portion row that is located outside the circumferential groove 26 in the tire width direction and includes a plurality of land portions 57 is referred to as a land portion row A ′.

  When only sipes are evenly arranged in the center region and the shoulder region, the dry performance is insufficient because the rigidity of the land portion in the shoulder region is insufficient. However, the area ratio of the holes was sequentially increased from the innermost side in the tire width direction toward the outer side row in the tire width direction for each of the land portion rows A, A ′, B, B ′, C, C ′, and D. In that case, the amount of sipe disposed in the land portion row on the outer side in the tire width direction is suppressed accordingly. For this reason, in particular, by ensuring sufficient rigidity of the land in the shoulder region, it is possible to efficiently improve the dry performance, and as a result, it is possible to efficiently achieve both on-ice performance and dry performance. It becomes. In addition, unlike the example shown in FIG. 1, when the land portion row does not exist on the tire equator plane, that is, when the circumferential groove is disposed on the tire equator plane, the above-mentioned area ratio is It is preferable to increase the size sequentially from the land portion row closest to the equator plane toward the land portion row on the outer side in the tire width direction.

  In the pneumatic tire according to the first embodiment, the length of the sipe per unit area of the one center region and the two shoulder regions divided by dividing the contact width into three in the tire width direction is the shoulder. The center region is preferably larger than the region. Here, the length of the sipe per unit area means a value obtained by dividing the sum of the lengths in the extending direction of all the sipes by the total area of the land portion in each of the center region and the two shoulder regions. To do. In this way, by making the sipe length per unit area larger in the center region than in the shoulder region, the edge effect can be sufficiently obtained in the center region, and the rigidity of the land portion is sufficiently obtained in the shoulder region. Obtainable. For this reason, it is possible to efficiently ensure the edge effect and the rigidity of the land portion, and as a result, it is possible to efficiently achieve both on-ice performance and dry performance.

  In the pneumatic tire according to the first embodiment, the length of the sipe per unit area is the outermost side in the tire width direction with respect to a land portion row that is partitioned by a circumferential groove and has a plurality of land portions in the tire circumferential direction. It is preferable that the size gradually increases from the land portion row toward the land portion row on the inner side in the tire width direction. Here, the length of the sipe per unit area means a value obtained by dividing the sum of the lengths in the extending direction of all the sipes by the total area of the ribs or land portions in each rib or each land portion row. To do.

  As described above, the length of the sipe is sequentially increased from the outermost side in the tire width direction toward the inner land portion row in the tire width direction for each of the land portion rows A, A ′, B, B ′, C, C ′, and D. By increasing the size, it is possible to efficiently secure the edge effect in the center region and the rigidity of the land portion in the shoulder region. As a result, it is more efficient to achieve both on-ice performance and dry performance. Can be performed automatically.

  In the pneumatic tire of the first embodiment, it is preferable that the volume of at least one hole is different from the volume of other holes in at least one hole group 8 (81-83, 85-87). For example, by changing the volume of each of the holes 8a to 8c for one hole group of the hole group 81, the land portion rigidity around each of the holes 8a to 8c and the water removal effect by each of the holes 8a to 8c The balance can be adjusted. When the volume of each of the holes 8a to 8c is increased, a high water removal effect is obtained, but the land portion rigidity around the holes 8a to 8c is reduced. On the other hand, when the volume of each hole 8a-8c is made small, the water removal effect will become low, but the surrounding land part rigidity will improve. The volume of each hole 8a-8c can be set by varying the area of the opening part of each hole 8a-8c and the tire radial direction length of each hole 8a-8c. Moreover, the volume of each hole 8a-8c can also be set by varying the three-dimensional shape.

  Moreover, in the pneumatic tire of Embodiment 1, the radius of the circumscribed circle of all the holes 8a, 8b, 8c in the hole group 8 (81-83, 85-87) is 0.2 mm or more and 1.0 mm or less. Preferably there is. By setting the radius of the circumscribed circle of all the holes 8a, 8b, and 8c to 0.2 mm or more, the holes 8a, 8b, and 8c can be sufficiently prevented from being crushed and the water removal effect can be enhanced. Moreover, by making the said radius 1.0 mm or less, it can suppress more fully that each hole 8a, 8b, 8c deform | transforms, and can suppress the fall of rigidity further. As a result, compared with the case where one hole having the same volume as the total volume of all the holes 8a to 8c included in the hole group 8 is formed, the water removal effect and the rigidity of the tread land portion are further improved, and on the ice. The performance and the dry performance can be further enhanced.

In the pneumatic tire of the first embodiment, the total volume of the holes 8a, 8b, 8c in the hole group 8 (81-83, 85-87) is preferably 10 mm ³ or less. Here, the total volume of the holes 8a, 8b, 8c in the hole group 8 (81-83, 85-87) means the sum of the volumes of all the holes 8a, 8b, 8c of the hole group 8. . As a result of setting the total volume of the holes 8a, 8b, and 8c to 10 mm ³ or less, a large number of holes having a small volume can be provided. For this reason, it can further suppress that each hole 8a, 8b, 8c deform | transforms and crushes, and further improves a water removal effect and the rigidity of a tread land part, and also improves on-ice performance and dry performance further. Is possible.

  Further, in the pneumatic tire of the first embodiment, at least one of the stepping side region and the kicking side region of the land portion 5 (51, 52, 53, 54, 55, 56, 57) when the tire rotates. Preferably there is. In the example shown in FIG. 1, the hole group 8 (81-83, 85-87) includes the stepping side region and the kicking side of the land portion 5 (51-53, 55-57) during tire rotation. It is formed in both areas. Here, the area on the stepping side when the tire rotates is an area where the tire first contacts when the tire is rotating in the forward direction, and in FIG. Area or lower end area). On the other hand, the area on the kick-out side when the tire rotates is an area where the tire comes into contact last when the tire rotates in the forward direction, and the other end area in the tire circumferential direction of the land portion 5 in FIG. It means the lower end area or the upper end area of the paper. Further, the forward rotation of the tire means tire rotation when the vehicle body equipped with the tire moves forward. On the other hand, the reverse rotation of the tire means the rotation of the tire when the vehicle body equipped with the tire moves backward.

  In the pneumatic tire in which the tread surface having such a configuration is formed, the water absorption effect at the time of tire rotation is increased, and as a result, the performance on ice can be further enhanced. In particular, in the example shown in FIG. 1, in any case where the tire rotates in the forward direction and in the reverse direction, the hole group 8 is formed in the first contact area and the last contact area. The water absorption effect is effectively exhibited both at the time and during the reverse rotation of the tire.

  The example shown in FIG. 1 is an example in which the hole group 8 is formed in both the stepping side and kicking side regions when the tire rotates, but the first embodiment is not limited to such a form. Includes a form formed only in one of the stepping side region and the kicking side region during tire rotation. In addition, when the hole group 8 is formed only in the stepping side region when the tire rotates, the water absorption effect when the tire rotates in the forward direction is increased, and as a result, the performance on ice is improved. On the other hand, when the hole group 8 is formed only in the area on the kick-out side when the tire rotates, the water absorption effect when the tire rotates in the reverse direction is increased, and as a result, the performance on ice is improved.

  In addition, although the pneumatic tire of Embodiment 1 is a case where each of the land part row | line | column divided by the circumferential direction groove | channel 2 has a some land part, this embodiment is not restricted to this. The present embodiment also includes a case in which at least one rib extending in the tire circumferential direction without a break is defined by the circumferential groove 2.

[Embodiment 2]
Next, the second embodiment will be described in detail. In the second embodiment, for all the holes i in the hole group 8 (81-83, 85-87), at least two holes j satisfying dij ≦ (ri + rj) × 2 exist in the hole group to which the hole belongs. This is different from the first embodiment.

  FIG. 6 is a plan view illustrating a main part of an example of a tread portion of the pneumatic tire according to the second embodiment. Hereinafter, only the difference between the example (embodiment 2) shown in FIG. 6 and the example (embodiment 1) shown in FIG. 1 will be described in detail. Note that among the elements denoted by the reference numerals in FIG. 6, the elements denoted by the same reference numerals in FIG. 1 indicate the same elements as the elements illustrated in FIG.

  In the example shown in FIG. 6, the configuration of the hole group 10 (101 to 103, 105 to 107) is different from the example shown in FIG. 1. That is, in the example shown in FIG. 6, the hole group 10 (101-103, 105-107) is comprised from four hole 10a, 10b, 10c, 10d circular by planar view. Moreover, the hole group 10 (101-103, 105-107) becomes the arrangement | positioning shape which becomes a square, if the center of each hole 10a-10d is tied.

  FIG. 7 is an enlarged perspective view of the hole group shown in FIG. As shown in FIG. 7, all of the holes 10a, 10b, 10c, and 10d constituting the hole group 10 have a cylindrical shape on the outer side in the tire radial direction and a tapered shape on the inner side in the tire radial direction. Each of the holes 10a to 10d is open on the tread surface and has a bottom on the inner side in the tire radial direction. Each of the holes 10a to 10d has a tapered shape in which the hole diameter is gradually reduced at the bottom portion, and thus is suitable for improving the rigidity of the bottom portion.

  In the example shown in FIG. 7, the holes 10a, 10b, 10c, and 10d have the same tire radial depth. The depth of each of the holes 10a to 10d is preferably 2 mm or more in order to obtain a sufficient water removal effect. In addition, the depth of each of the holes 10a to 10d is preferably set to be equal to or less than the depth of the circumferential groove 2 because excellent durability is obtained when the hole bottom does not approach the belt layer.

  In the example illustrated in FIG. 6, the arrangement mode of the holes 10 a, 10 b, 10 c, and 10 d is a square in plan view, but the second embodiment is not limited to such a configuration. FIGS. 8-1 and FIGS. 8-2 are top views which show the variation about the arrangement | positioning aspect of the hole which comprises the hole group formed in the tread part of the pneumatic tire which concerns on Embodiment 2. FIGS.

  As shown in FIG. 6, the arrangement of the holes 10a, 10b, 10c, and 10d can be such that the figure connecting the centers of the holes 10a to 10d is a square. Further, as shown in FIG. 8A, the hole group 10 is composed of five holes 10a, 10b, 10c, 10d, and 10e, and the figure connecting the centers of the holes 10a to 10e is a pentagon. Further, as shown in FIG. 8B, a figure formed by five holes 10a to 10e and connecting the centers of the holes 10a to 10e may be a trapezoid. In the example illustrated in FIGS. 8A and 8B, the holes 10a to 10e can have the same depth in the tire radial direction.

  The hole group 10 further satisfies the first requirement and the second requirement described above on the premise of such a hole arrangement mode. FIG. 9 is an enlarged plan view of the hole group 10 shown in FIG. As shown in FIG. 9, since the holes 10a, 10b, 10c, and 10d are all circular in a plan view, their circumscribed circles coincide with the outer shapes of the holes 10a to 10d. Here, the radius of the circumscribed circle Ca of the hole 10a is ra, the radius of the circumscribed circle Cb of the hole 10b is rb, the radius of the circumscribed circle Cc of the hole 10c is rc, the radius of the circumscribed circle Cd of the hole 10d is rd, and the circumscribed circle The distance between the centers of the circles Ca and Cc is dac, the distance between the centers of the circumscribed circles Ca and Cd is dad, the distance between the centers of the circumscribed circles Cb and Cc is dbc, and the distance between the centers of the circumscribed circles Cb and Cd is dbd.

  When the hole i in the first requirement is the hole 10a and the hole j is the holes 10c and 10d, as shown in FIG. 9, in relation to the hole 10c and the hole 10d, the hole 10a has dac ≦ (ra + rc) × 2 and a hole 10d satisfying dad ≦ (ra + rd) × 2. When the hole i is the hole 10b and the hole j is the hole 10c and the hole 10d, the hole 10b similarly satisfies dbc ≦ (rb + rc) × 2 in the relationship between the hole 10c and the hole 10d. There is a hole 10c and a hole 10d that satisfies dbd ≦ (rb + rd) × 2. Further, when the hole i is the hole 10c and the hole j is the hole 10a and the hole 10b, similarly, the hole 10c satisfies dac ≦ (ra + rc) × 2 in relation to the hole 10a and the hole 10b. A hole 10a and a hole 10b satisfying dbc ≦ (rb + rc) × 2 exist. In addition, when the hole i is the hole 10d and the hole j is the hole 10a and the hole 10b, similarly, regarding the hole 10d, in the relationship between the hole 10a and the hole 10b, dad ≦ (ra + rd) × 2 There is a hole 10a that fills and a hole 10b that satisfies dbd ≦ (rb + rd) × 2.

  In a pneumatic tire having a tread surface in which such a hole group 10 (101 to 103, 105 to 107) is formed, all the holes, in the example shown in FIG. 6, about the holes 10a, 10b, 10c, and 10d At least one hole exists in a relatively close position in the hole group 10 (101 to 103, 105 to 107) to which it belongs, and has the first requirement.

  Looking at the hole 10 a, the holes 10 c and 10 d are holes located at relatively close positions in the hole group 10. In this case, in terms of the relationship between the hole 10a and the hole 10c, as shown in FIG. 7, when the hole 10a and the hole 10c are closely packed in a narrow region, the total volume of the densely packed holes 10a and 10c is the same. Compared to the case where one hole having a volume of 1 is formed, each of the holes 10a and 10c has a small diameter and is not easily crushed. For this reason, falling of the holes 10a and 10c can be suppressed. As a result, compared to the case where one hole having the same volume as the total volume of the dense holes 10a and 10c is formed, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect. Can be secured. Further, in the relationship between the hole 10a and the hole 10d, as shown in FIG. 7, when the hole 10a and the hole 10d are closely packed in a narrow area, the total volume of the densely packed holes 10a and 10d is the same. Compared to the case where one hole having a volume is formed, each of the holes 10a and 10d has a small diameter and is not easily crushed. For this reason, falling of the holes 10a and 10d can be suppressed. As a result, compared with the case where one hole having the same volume as the total volume of the dense holes 10a and 10d is formed, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect. Can be secured.

  Similarly, regarding the hole 10 b, the holes 10 c and 10 d are holes located at relatively close positions in the hole group 10. In this case, in terms of the relationship between the hole 10b and the hole 10c, as shown in FIG. 7, when the hole 10b and the hole 10c are closely packed in a narrow region, the total volume of the plurality of holes 10b and 10c that are densely packed is the same. Compared to the case where one hole having a volume of 1 is formed, each of the holes 10b and 10c has a small diameter and is not easily crushed. For this reason, falling of the holes 10b and 10c can be suppressed. As a result, compared to the case where one hole having the same volume as the total volume of the dense holes 10b and 10c is formed, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect. Can be secured. Further, in the relationship between the hole 10b and the hole 10d, as shown in FIG. 7, when the hole 10b and the hole 10d are closely packed in a narrow region, the total volume of the densely packed holes 10b and 10d is the same. Compared to the case where one hole having a volume is formed, each of the holes 10b and 10d has a small diameter and is not easily crushed. For this reason, falling of the holes 10b and 10d can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 10b and 10d is formed. Can be secured.

  Similarly, regarding the hole 10 c, the holes 10 a and 10 b are holes located at relatively close positions in the hole group 10. In this case, in terms of the relationship between the hole 10c and the hole 10a, as shown in FIG. 7, when the hole 10c and the hole 10a are closely packed in a narrow area, the total volume of the densely packed holes 10c and 10a is the same. Compared to the case where one hole having a volume of 1 is formed, each of the holes 10c and 10a has a small diameter and is not easily crushed. For this reason, falling of the holes 10c and 10a can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 10c and 10a is formed. Can be secured. Further, in terms of the relationship between the hole 10c and the hole 10b, as shown in FIG. 7, when the hole 10c and the hole 10b are closely packed in a narrow area, the total volume of the plurality of holes 10c and 10b that are densely packed is the same. Compared to the case where one hole having a volume is formed, each of the holes 10c and 10b has a small diameter and is not easily crushed. For this reason, falling of the holes 10c and 10b can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without deteriorating the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 10c and 10b is formed. Can be secured.

  Similarly, regarding the hole 10d, the holes 10a and 10b are holes located in relatively close positions in the hole group 10. In this case, in terms of the relationship between the hole 10d and the hole 10a, as shown in FIG. 7, when the hole 10d and the hole 10a are closely packed in a narrow region, the total volume of the densely packed holes 10d and 10a is the same. Compared to the case where one hole having a volume of 1 is formed, each of the holes 10d and 10a has a small diameter and is not easily crushed. For this reason, falling of the holes 10d and 10a can be suppressed. As a result, compared with the case where one hole having the same volume as the total volume of the dense holes 10d and 10a is formed, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect. Can be secured. Further, in the relationship between the hole 10d and the hole 10b, as shown in FIG. 7, when the hole 10d and the hole 10b are closely packed in a narrow region, the total volume of the densely packed holes 10d and 10b is the same. Compared to the case where one hole having a volume is formed, each of the holes 10d and 10b has a small diameter and is not easily crushed. For this reason, falling of the holes 10d and 10b can be suppressed. As a result, the rigidity of the land portion provided in the tread portion is sufficiently reduced without reducing the water removal effect as compared with the case where one hole having the same volume as the total volume of the dense holes 10d and 10b is formed. Can be secured.

  In this way, the fall-down suppressing unit (the unit consisting of the hole 10a and the hole 10c, the unit consisting of the hole 10a and the hole 10d, the unit consisting of the hole 10b and the hole 10c, the hole 10b, In the case where each of the holes 10a, 10b, 10c, and 10d is used as a reference, there is at least one unit in the narrow area including the holes. In other words, in the example shown in FIG. 6, regarding the hole group 10, there are two collapse suppression units around each hole. As a result, in each collapse suppression unit in the hole group 10, the holes 10a to 10d are suppressed from being deformed and crushed.

  As described above, the pneumatic tire of the second embodiment includes the first requirement regarding the positional relationship between the holes 10a to 10d constituting the hole group 10 (101 to 103, 105 to 107).

  The second requirement is a requirement related to the arrangement mode of the hole group 10 (101 to 103, 105 to 107). For this reason, the example (Embodiment 2) shown in FIG. 6 has the second requirement as in the example (Embodiment 1) shown in FIG.

  As described above, the pneumatic tire according to the second embodiment has all the holes 10a, 10b, and 10c with respect to all the hole groups 10 (101 to 103, 105 to 107) on the assumption that the sipe and the hole group are used together. In addition to satisfying that at least one hole exists at a relatively close position for 10d (first requirement), the area ratio of the hole to the total area of the land portion 5 is made larger in the shoulder region than in the center region ( Satisfies the second requirement). For this reason, the first requirement and the second requirement are combined, and the performance on ice can be enhanced by the high water removal effect, the water absorption effect, and the edge effect, and sufficiently ensure the rigidity of the land portion provided in the tread portion. Can improve the dry performance. Therefore, according to this pneumatic tire, both on-ice performance and dry performance can be achieved.

  Furthermore, the example (Embodiment 2) illustrated in FIG. 6 satisfies the first requirement and the second requirement, and also satisfies the following third requirement. That is, the third requirement is that for all the holes 10a, 10b, 10c, and 10d in the hole group i (10), at least a hole j that satisfies dij ≦ (ri + rj) × 2 is included in the hole group to which the hole belongs. There are two. That is, when the hole i in the third requirement is the hole 10a and the hole j is the hole 10c and the hole 10d, the two holes 10c and 10d exist at positions relatively close to the hole 10a. When the hole i in the third requirement is the hole 10b, the hole j is the hole 10c, and the hole 10d, the two holes 10c and 10d exist at relatively close positions with respect to the hole 10b. When the hole i in the third requirement is the hole 10c and the hole j is the hole 10a and the hole 10b, the hole 10c has two holes 10a and 10b at relatively close positions. When the hole i in the third requirement is the hole 10d and the hole j is the hole 10a and the hole 10b, the hole 10d has two holes 10a and 10b at relatively close positions.

  As described above, the pneumatic tire according to the second embodiment satisfies all of the first requirement and the second requirement on the assumption that the sipe and the hole group are used in combination, and all the hole groups 10 (101 to 103, 105 to 105). 107), the fact that all the holes 10a, 10b, 10c, 10d have at least two holes at relatively close positions (third requirement) is satisfied. For this reason, the first requirement and the second requirement can be combined to achieve both on-ice performance and dry performance. In particular, the third requirement further enhances the water removal effect and the rigidity of the tread land portion. As a result, on-ice performance and dry performance can be further enhanced.

  In addition, although the example shown in FIG. 9 is the arrangement | positioning aspect of the hole from which the figure which connected the centerline of each hole 10a, 10b, 10c, 10d becomes a square, as above-mentioned, this embodiment is not restricted to this. . That is, the hole arrangement shown in FIGS. 8-1 and 8-2 also satisfies the first to third requirements. When all the hole groups shown in FIG. 6 are replaced with the hole group 10 shown in FIG. 8A, at least 2 holes satisfying dij ≦ (ri + rj) × 2 among all the hole groups to which the holes belong. (E.g., hole 10c, hole 10d for hole 10a) (having first and third requirements). Further, the second requirement is a requirement related to the arrangement mode of the hole group 10. For this reason, the example in which all the hole groups shown in FIG. 6 are replaced with the hole group 10 shown in FIG. 8A has the second requirement as in the example shown in FIG.

  When all the hole groups shown in FIG. 6 are replaced with the hole group 10 shown in FIG. 8B, for all the holes, holes satisfying dij ≦ (ri + rj) × 2 are included in the hole groups to which the holes belong. There are at least two (for example, hole 10c and hole 10d for hole 10a) (having the first requirement and the third requirement). Further, the second requirement is a requirement related to the arrangement mode of the hole group 10. For this reason, the example in which all the hole groups shown in FIG. 6 are replaced with the hole group 10 shown in FIG. 8B has the second requirement as in the example shown in FIG.

  For this reason, also in the examples shown in FIGS. 8A and 8B, high water removal effect, water absorption effect, edge effect, and high rigidity of the tread land portion can be obtained. It is possible to achieve both performance and performance. Moreover, also about the example shown to FIGS. 8-1 and FIGS. 8-2, especially by the 3rd requirement, the water removal effect and the rigidity of a tread land part can be improved further, and also on-ice performance and dry performance. Can be further enhanced.

  Pneumatic tires according to the present embodiment, conventional examples, and comparative examples were manufactured and evaluated. The embodiment according to the present embodiment is an example. The comparative example does not indicate a conventional example.

  In a pneumatic tire having a common tire size of 195 / 65R15, various items shown in FIG. 10 (hole arrangement mode, hole area ratio in each land portion row shown in FIG. 1, sipe in each land portion row) The hole or hole group satisfying the length, the volume of the hole in one hole group, and the volume of each hole) is provided on the entire circumference of the tire, and the configuration of the tread portion shown in FIG. 1 is adopted for the other configurations. The pneumatic tires of the conventional example, comparative examples 1 and 2 and examples 1 to 6 were manufactured. Here, the area ratio of the holes in each land section row means the area ratio of the holes to the total area of the land section, and the total area of the land section is each land section row in plan view when the tire is new. Means the sum of the areas of all the land parts included in, and excludes the area corresponding to the groove wall of the land parts. Moreover, the area of a hole means the sum total of the area of the opening part of all the holes contained in each land part row | line in planar view at the time of a tire new article.

  Each of these test tires was mounted on a rim having a rim size of 15 × 6 JJ, the air pressure was set to 230 kPa, and an evaluation test was performed on ice performance and dry performance under the following measurement conditions. The vehicle used was a 1500 cc class passenger car.

  Regarding the performance on ice, the braking stop distance from the initial speed of 40 km / h was measured in a polished ice burn (on the ice surface). Regarding the dry performance, on the test course and the circuit, the evaluation regarding the braking stop distance from the initial speed of 100 km / h was performed by feeling evaluation using a 10-point method by five test drivers.

  All of these performances were calculated as relative indices with the conventional pneumatic tire set to 100. About these indexes, it means that each performance is excellent, so that it is large. The above evaluation results are also shown in FIG.

  As can be seen from FIG. 10, for the pneumatic tires of Examples 1 to 6 within the scope of the present invention, excellent results exceeding 100 were obtained for any of the evaluation items on ice performance and dry performance. Yes. As for this, as for the pneumatic tire of Examples 1-6, as for all, on the premise of combined use with a sipe and a hole group, at least one other hole exists in a position comparatively near about all the holes, and a land part Since the area ratio of the hole to the total area is larger in the shoulder region than in the center region, the performance on ice can be enhanced by a high water removal effect, water absorption effect, and edge effect, and the land portion provided in the tread portion This is considered to be because the dry performance can be enhanced by sufficiently securing the rigidity.

  When the pneumatic tires of Examples 1 to 6 are individually viewed, the dry performance of the pneumatic tire of Example 2 is improved as compared to the pneumatic tire of Example 1. This is because the ratio of the area of the hole to the total area of the land portion increases gradually from the land portion row on the tire equatorial plane toward the land portion row on the outer side in the tire width direction. This is considered to be because the rigidity of the part was sufficiently secured.

  About the pneumatic tire of Example 3, the performance on ice and dry performance are improving compared with the pneumatic tire of Example 1. This is because the sipe length per unit area is larger in the center region than in the shoulder region, so that the edge effect can be sufficiently obtained in the center region, and the rigidity of the land portion is sufficient in the shoulder region. It is thought that it is because it can be obtained.

  About the pneumatic tire of Example 4, the dry performance is improving compared with the pneumatic tire of Example 3. This is because the ratio of the area of the hole to the total area of the land portion increases gradually from the land portion row on the tire equatorial plane toward the land portion row on the outer side in the tire width direction. This is considered to be because the rigidity of the part was sufficiently secured.

  About the pneumatic tire of Example 5, the performance on ice and dry performance are improving compared with the pneumatic tire of Example 4. This is because the length of the sipe per unit area gradually increases from the outermost land portion row in the tire width direction toward the inner land portion row in the tire width direction. This is probably because the effect and the rigidity of the land portion in the shoulder region could be efficiently performed.

  About the pneumatic tire of Example 6, the performance on ice and dry performance are improving compared with the pneumatic tire of Example 5. In the pneumatic tire of Example 6, the volume of at least one hole is different from the volume of other holes. For this reason, when each hole is used as a reference, not only the water removal effect by each hole, but also the rigidity of the faithful tread rubber existing around each hole can be set as appropriate. Therefore, in the pneumatic tire of Example 6, since the water removal effect and the rigidity of the land portion provided in the tread portion can be locally increased or decreased, the performance on ice and the dry performance are improved. It is considered a thing.

  On the other hand, in the pneumatic tires of Comparative Examples 1 and 2, the hole arrangement mode is not a hole group but a simple hole. For this reason, especially the pneumatic tire of the comparative examples 1 and 2 has not acquired the outstanding edge effect. As a result, the pneumatic tires of Comparative Examples 1 and 2 are considered to have degraded performance on ice as compared with the conventional pneumatic tire of the conventional example in which only the sipes are evenly arranged in all the land rows.

  As described above, the pneumatic tire according to the present invention is useful for achieving both on-ice performance and dry performance.

1 Tread portion 21, 22, 23, 24, 25, 26, circumferential groove 31, 32, 33, 34, 35, 36, 37, 38, 41, 42 transverse groove 51, 52, 53, 54, 55, 56, 57 Land part 61, 62, 63, 64, 65, 66, 67 Sipe 71, 72, 73, 74, 75, 76, 77 Small block 8, 81, 82, 83, 85, 86, 87, 10, 101, 102, 103, 105, 106, 107 Hole group 8a, 8b, 8c, 8d, 10a, 10b, 10c, 10d, 10e Hole CL Tire equatorial plane A, A ', B, B', C, C ', D Land Part row L1, L2, L3, L4 Virtual dotted line W Tire length in the tire circumferential direction

Claims (9)

A plurality of sipes arranged in a land portion provided in a tread portion;
Consists of three or more holes, formed on the tread surface,
For any two holes i and j, in plan view, the radius of the circumscribed circle Ci of the hole i is ri, the radius of the circumscribed circle Cj of the hole j is rj, and the distance between the centers of both the circumscribed circles Ci and Cj is In the case of dij, at least one hole j satisfying dij ≦ (ri + rj) × 2 exists in the hole group to which all holes i belong,
For one center region and two shoulder regions that are divided by dividing the ground contact width into three equal parts in the tire width direction, the area ratio of the hole to the total area of the land portion is more than the two shoulder regions than the center region. A plurality of hole groups that are larger in each direction,
A pneumatic tire characterized by including.   For ribs defined by circumferential grooves extending in the tire circumferential direction, or for land portion rows defined by the circumferential grooves and having a plurality of land portions in the tire circumferential direction, each rib or rib area in each land portion row Alternatively, as the area ratio of the hole to the total area of the land portion increases from the rib or land portion row on the tire equator surface or the rib or land portion row closest to the tire equator surface to the rib or land portion row on the outer side in the tire width direction. The pneumatic tire according to claim 1, which is gradually increased.   For one center region and two shoulder regions that are divided by dividing the ground contact width into three equal parts in the tire width direction, the length of the sipe per unit area is larger than that of each of the two shoulder regions. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is larger.   About the rib sectioned by the circumferential groove or the land section row partitioned by the circumferential groove and having a plurality of land sections in the tire circumferential direction, the length of the sipe per unit area is the outermost in the tire width direction. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire gradually increases from a rib or a land portion row toward a rib or a land portion row on an inner side in the tire width direction.   5. The method according to claim 1, wherein for all holes i in the hole group, at least two holes j satisfying dij ≦ (ri + rj) × 2 exist in the hole group to which the hole belongs. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 5, wherein the volume of at least one hole is different from the volume of other holes in at least one hole group.   The pneumatic tire according to any one of claims 1 to 6, wherein a radius of a circumscribed circle of all the holes in the hole group is 0.2 mm or more and 1.0 mm or less. The total volume of the holes in the hole group, the pneumatic tire according to any one of claims 1 to 7 is 10 mm ³ or less.   The pneumatic tire according to any one of claims 1 to 8, wherein a region where the hole group is disposed is at least one of a stepping side region and a kicking side region during tire rotation of the land portion.

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