JP5909045B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having a block-based tread pattern in which each block is partitioned into block-like land portions by lateral sipes.

  To improve the running performance on snow and ice in a block-based tread pattern in which a plurality of blocks are defined by a plurality of circumferential grooves and width grooves, a plurality of horizontal sipes are formed on each block. Tires are known. An example of this tire is shown in FIG. In the tire 700, four circumferential grooves 71A, 71B, 72A, 72B and a plurality of widthwise grooves 73, 74A, 74B, 75A, 75B are arranged on the tread portion 70, and these are a total of five rows. Block groups 79, 80A, 80B, 81A, 81B are formed. Like the sipe 82, four horizontal sipes arranged in each block further partition each block into five block-like land portions. In the tire 700, the circumferential dimension, the width dimension, and the height dimension of all the block-shaped land portions are equal.

  As another example, in Patent Document 1, the sipe interval is narrow in the block in the tread central region, and the sipe interval is wide in the block in the tread side region. A compatible pneumatic tire is described. In Patent Document 2, the hardness of the rubber constituting the tread portion tread differs in the tread width direction position, and the tread portion where the rubber is hard has a higher sipe density than the tread portion where the rubber is soft, and performance on the snow. A pneumatic tire with improved performance is described.

Japanese Patent Laid-Open No. 3-186403 JP 2010-6107 A

  Generally, in tires, due to the difference in diameter between the vicinity of the tire equator and the vicinity of the tread end, the circumferential shear force acting on the tread portion during load rolling is greater in the tread central region than in the tread side region. For this reason, the wear energy in the tread central region tends to be larger than the wear energy in the tread side region. In particular, in the pneumatic tire as shown in FIG. 7, which has a block-tread tread pattern and each block is divided into block-like land portions by lateral sipes, the rigidity of the block land portions decreases as a result of providing sipes. Therefore, this tendency is remarkable. As a result, there has been a problem that so-called center wear tends to occur in the block in the center region, which wears faster than the block in the shoulder region.

  The tires described in Patent Document 1 and Patent Document 2 having different sipe intervals depending on the blocks are not designed with the recognition that center wear is suppressed, and still have a problem that center wear is likely to occur.

  Therefore, in view of the above problems, the present invention is a pneumatic tire having a block-based tread pattern and each block partitioned into block-like land portions by lateral sipes, and suppresses so-called center wear in the tread portion. An object of the present invention is to provide a pneumatic tire that can be used.

In view of the above problems, the gist of the present invention is as follows.
The pneumatic tire of the present invention is provided with a plurality of circumferential grooves extending along the tire circumferential direction and a plurality of widthwise grooves extending along the tire width direction in the tread portion, and the tire circumferential direction. Forming a block group of three or more rows composed of a plurality of blocks arranged in a row,
When dividing the tread portion into a central area and both side areas, among the three or more rows of block groups, one row of block groups is a central block row consisting of a plurality of central blocks located in the central region, Each of the other one-row block groups is a side block row composed of a plurality of side blocks located in both side areas,
The central block is further provided with a transverse sipe extending along the tire width direction until it is opened in two circumferential grooves, and the central block is further divided into a plurality of central block-shaped land portions,
A pneumatic tire, in which a lateral sipe extending along the tire width direction is disposed in the side block until it is opened at a circumferential groove and a tread end, and further divided into a plurality of side block land portions. Because
The following conditions 1 and 2 are satisfied.
Condition 1: The circumferential shear rigidity (Gxc) of the central block land portion is smaller than the circumferential shear rigidity (Gxs) of the side block land portion.
Condition 2: The compression rigidity (Ezc) of the central block land portion is larger than the compression rigidity (Ezs) of the side block land portion.

In the pneumatic tire of the present invention, the circumferential dimension of the central block land portion is Lc, the width dimension is Wc, the height dimension is Hc, and the circumferential dimension of the side block land portion is the same. Ls, width dimension Ws, height dimension Hs, the aspect ratio Axc and Axs of the central and side block land portion,
Axc = Lc / Hc
Axs = Ls / Hs
And define
The shape factors Shc and Shs of the central and side block land portions are
Shc = (Lc · Wc) / (2 × Hc (Lc + Wc))
Shs = (Ls · Ws) / (2 × Hs (Ls + Ws))
When defined as
The circumferential shear rigidity Gxc and Gxs of the central and side block land portions are:
(Here, E _0C and E _0S indicate the Young's modulus of rubber in the central and side block land portions, respectively.)
Defined as
The compression stiffness Ezc and Ezs of the central and side block land portions is:
When 1/3 ≦ Lc / Wc ≦ 3,
Ezc = E _0C × (1 + 2.19 · Shc ² ) Equation (2-1)
If Lc / Wc <1/3 or 3 <Lc / Wc,
Ezc = E _0C × (1.33 + 1.1 · Shc ² ) Equation (2-2)
When 1/3 ≦ Ls / Ws ≦ 3,
Ezs = E _0S × (1 + 2.19 · Shs ² ) Equation (2-3)
If Ls / Ws <1/3 or 3 <Ls / Ws,
Ezs = E _0S × (1.33 + 1.1 · Shs ² ) (2-4)
Can be defined.

Further, in the pneumatic tire of the present invention, E _0C = E _0S , and the central block-shaped land portion and the side block satisfy the condition 1: Gxc <Gxs and condition 2: Ezc> Ezs. It is preferable to set the circumferential dimensions Lc and Ls, the width dimensions Wc and Ws, and the height dimensions Hc and Hs of the land portion.

In the pneumatic tire of the present invention, G xc / Gxs is preferably 0.4 to 0.6, and Ezc / Ezs is preferably 1.1 to 1.3.

  In the pneumatic tire according to the present invention, it is preferable that three or more horizontal sipes are disposed in each of the plurality of blocks.

  In the pneumatic tire of the present invention, it is preferable that a vertical sipe extending along the tire circumferential direction and having both ends open to the widthwise groove is disposed in the side block land portion.

According to the present invention, the condition 1 in which the circumferential shear stiffness of the central block land portion is made smaller than the circumferential shear stiffness of the lateral block land portion, and the compression stiffness of the central block land portion is set to the side block. Center wear can be suppressed by designing each block-like land portion so as to satisfy both the condition 2 for making it larger than the compression rigidity of the land-like portion.

(A) is a developed view showing a part of a tread portion of the Hare follow the reference example air-filled tire 100 (Reference Embodiment 1) of the present invention, (b) it is a perspective of the central block 22 of the tire 100 FIG. 4C is a perspective view of the side block 26 </ b> A of the tire 100. Cormorant accordance with the present invention air-filled tire 200 is a development view illustrating a part of a tread portion of (Embodiment 2). It is an expanded view which shows a part of tread part of another pneumatic tire 300 (Embodiment 3) according to this invention. It is a graph explaining the tire width direction position dependence of the circumferential shear force at the time of free rolling and load rolling of a general tire. FIG. 2 is a circumferential cross-sectional view of a block portion of a general tire for explaining the lifting associated with bending deformation at the kicking-out portion of the block, (a) is a tire having a large circumferential dimension of the block, and (b) is a block. A tire with a small circumferential dimension is shown. It is a graph which shows the relationship between the aspect ratio (circumferential dimension / height dimension) and circumferential shear rigidity of a block in a general tire. FIG. 6 is a development view showing a part of a tread portion 70 of a conventional pneumatic tire 700.

  Hereinafter, the gist of the present invention will be clarified in more detail by describing a pneumatic tire (hereinafter simply referred to as “tire”) according to an embodiment of the present invention with reference to the drawings. In FIG. 1 to FIG. 3, the same components are denoted by the same reference numerals in principle and description thereof is omitted.

( Reference Embodiment 1)
A tire 100 according to a reference embodiment of the present invention will be described with reference to FIG. In the pneumatic tire of the present invention, the tire is provided with a plurality of circumferential grooves extending along the tire circumferential direction R and a plurality of widthwise grooves extending along the tire width direction W in the tread portion. A block group of three or more rows composed of a plurality of blocks arranged in the circumferential direction R is formed. In the tire 100 of the present embodiment shown in FIG. 1, four circumferential grooves 12A, 12B, 14A, and 14B and a plurality of widthwise grooves 16, 18A, 18B, 20A, and 20B are disposed on the tread portion 10, respectively. To do. The first circumferential grooves 12A and 12B and the second circumferential grooves 14A and 14B are arranged symmetrically with respect to the tire equator CL. The first and second circumferential grooves 12A, 12B, 14A, 14B are all linear in parallel to the tire circumferential direction R, and have the same groove width and groove depth. Each of the plurality of width direction grooves 16, 18A, 18B, 20A, and 20B is a straight line parallel to the tire width direction, and is arranged at equal intervals in the circumferential direction. Moreover, it has the same groove width and groove depth.

  In the pneumatic tire of the present invention, among the three or more rows of formed block groups, one row of block groups is a central block row composed of a plurality of central blocks located in the central region C, Each block group of one row is a side block row composed of a plurality of side blocks located in the both-side area S. Here, in the present specification, the “central area” of the tread means an area of 50% of the tread width around the tire equator CL. The “side area” of the tread means an area other than the central area 3 of the tread portion. “Tread width” is a distance in the tire width direction between the tread ends E.

  In the tire 100, among the four circumferential grooves, a plurality of first widthwise grooves 16 are disposed between the two first circumferential grooves 12A and 12B from the side closer to the tire equator CL, A central block row 28 composed of a plurality of central blocks 22 is partitioned. Further, a plurality of third width direction grooves 20A and 20B are disposed between the tread end E and the second circumferential grooves 14A and 14B closest to the tread end E, respectively, and a plurality of lateral sides are provided. Side block rows 32A and 32B made up of blocks 26A and 26B are partitioned. Further, in the tire 100, a plurality of second width direction grooves 18A and 18B are disposed between the first circumferential grooves 12A and 12B and the second circumferential grooves 12a and 12b, respectively. Intermediate block rows 30A and 30B composed of intermediate blocks 24A and 24B are partitioned.

  In the tire 100, each central block 22 is provided with a lateral sipe 34 extending along the tire width direction until it is opened in the two first circumferential grooves 12A and 12B. It is further divided into a land portion 36 (hereinafter referred to as “center portion 36”). Also, each side block 26A is provided with a second circumferential groove 14A and a lateral sipe 42A extending along the tire width direction until it opens at the tread end E. Further, two lateral grooves 20A adjacent to each other are provided in each lateral block 26A. A vertical sipe 44A having both ends opened is disposed, and the side block 26A is further partitioned into a plurality of side block land portions 46A (hereinafter referred to as “side portions 46A”). Similarly, the side block 26B is divided into a plurality of side block land portions 46B by the horizontal sipes 42B and the vertical sipes 44B. Further, in the tire 100, the horizontal blocks 38A and 38B are also provided in the intermediate blocks 24A and 24B, and further divided into a plurality of intermediate block land portions 40A and 40B.

  In this specification, “sipe” means a groove whose opening is closed when the tire is in contact with the ground, and generally means a groove having a width of 2 mm or less. It is something to support. “Block” means an island-like land portion defined by a circumferential groove or tread edge and a width-direction groove, and “block-like land portion” means that a sipe is provided in this block. Means the land portion in the block partitioned by

The characteristic configuration of the present invention is that the tire 100 satisfies both of the following two conditions.
Note 1: The circumferential shear stiffness of the central portion 36 is smaller than the circumferential shear stiffness of the side portions 46A and 46B.
Condition 2: The compression rigidity of the central portion 36 is larger than the compression rigidity of the side portions 46A and 46B.

  Hereinafter, the technical significance of adopting such a characteristic configuration will be described together with the effects. First, the reason why center wear is likely to occur in the conventional tire 700 shown in FIG. 7 will be described with reference to FIGS.

  First, as described above, in the general tire 700 (regardless of the sipe density), due to the difference in diameter between the vicinity of the tire equator CL and the vicinity of the tread end E, the circumference acting on the tread portion at the time of load rolling is reduced. The directional shear force is greater in the tread central area than the tread lateral area. This is due to the following reasons. As shown in FIG. 4, during free rolling, the shearing force in the driving direction is large in the tread central region having a large diameter, and the shearing force in the braking direction is large in the tread side region having a small diameter. Here, when a driving force is applied, a shearing force in the driving direction is generated on the entire ground surface. Therefore, the shear stress in the driving direction becomes larger in the tread central region, and the shearing force in the braking direction is canceled out in the tread side region, and the circumferential shear force becomes smaller. For this reason, the wear energy in the tread central region tends to be larger than the wear energy in the tread side region. In particular, in the tire 700 provided with sipes, this tendency is remarkable because the rigidity of the block land portion decreases.

  In addition, in a tire in which sipes are arranged in the block, the circumferential dimension of the block-shaped land portion is small, so that bending deformation is likely to occur. In particular, as shown in FIG. When the land part kicks out, it falls and deforms, and the ground contact surface rises partially. For this reason, when the part where the ground pressure is low increases, the slip amount of the block-like land part increases, and the wear energy increases. The collapse deformation is as follows: 1. When the amount of shear in the circumferential direction is large It increases when the amount of compressive deflection in the tire radial direction is large. Compared with a tire having a large block size in the circumferential direction as shown in FIG. 5 (a), a tire having a small block size in the circumferential direction as shown in FIG. 5 (b) has a small circumferential shear stiffness and radial compression stiffness. For this reason, the amount of circumferential shear and the amount of compressive deflection in the radial direction are increased, and the collapse deformation is increased. As described above, due to the difference in diameter, the central tread region has a larger amount of circumferential shear than the tread side region. For this reason, the wear energy is larger in the tread central region than in the tread side region, and therefore, center wear is more likely to occur in the pattern in which the circumferential dimension of the block land portion is reduced by sipes.

  Furthermore, the following reasons can be cited as causes of the center wear still being prone to occur after the wear has progressed. That is, when center wear occurs, the block-like land portion in the tread central area where the wear amount is large increases the circumferential shear rigidity, whereas the block land portion in the tread side area where the wear amount is small. Then, the circumferential shear stiffness does not change much. For this reason, the driving force generated at the time of load rolling becomes larger in the central region than in the tread side region, and as a result, the wear energy in the tread central region still tends to be larger than the wear energy in the tread side region. Here, FIG. 6 is a graph showing a relationship between an aspect ratio (circumferential dimension / height dimension) of a block and a circumferential shear rigidity in a general tire. From FIG. 6, it can be seen that the smaller the aspect ratio, the greater the change in the circumferential shear stiffness with respect to the change in the aspect ratio. That is, since the tire 700 provided with sipes has a small aspect ratio, the circumferential shear rigidity tends to change greatly when the aspect ratio changes due to wear. Therefore, the tendency that the wear energy in the central region of the tread tends to be larger than the wear energy in the side region of the tread becomes particularly remarkable.

  From such an analysis, the present inventors have found that the center wear can be suppressed by appropriately setting the circumferential shear stiffness and the compression stiffness of the block-shaped land portion in the central region and the lateral region, The present invention has been completed.

  As condition 1, in the tire 100, by reducing the circumferential shear rigidity of the central portion 36 to be smaller than the circumferential shear rigidity of the side portions 46A and 46B, the driving force burden in the central region is reduced, and the lateral region is reduced. Increase the driving force burden at Thereby, center abrasion can be suppressed.

  Further, as the condition 2, in the tire 100, by making the compression rigidity of the central portion 36 larger than the compression rigidity of the side portions 46A and 46B, the bending deformation of the central portion 36 in the central region is reduced, and the lateral region The bending deformation of the side portions 46A and 46B is increased. Thereby, center abrasion can be suppressed.

Condition 1 and condition 2 will be described in more detail. As shown in FIGS. 1B and 1C, the circumferential dimension of the central portion 36 is Lc, the width dimension is Wc, the height dimension is Hc, and the same applies to the side portions 46A (46B). ) Is defined as Ls, the width dimension as Ws, and the height dimension as Hs. Here, the aspect ratios Axc and Axs of the central portion 36 and the side portion 46A are expressed as follows:
Axc = Lc / Hc
Axs = Ls / Hs
It is defined as That is, the aspect ratio is a ratio of the circumferential dimension to the height dimension, and is a dimensionless value.
Further, the shape factors Shc and Shs of the central portion 36 and the side portion 46A are set as follows:
Shc = (Lc · Wc) / (2 × Hc (Lc + Wc))
Shs = (Ls · Ws) / (2 × Hs (Ls + Ws))
It is defined as That is, the shape factor is a dimensionless value obtained by dividing the pressurized cross-sectional area by the side area in the block land portion.

(Condition 1)
At this time, the circumferential shear stiffness Gxc [Pa] of the central portion 36 and the circumferential shear stiffness Gxs [Pa] of the side portion 46A are:
It can be expressed as. (Here, E _0C and E _0S represent the Young's modulus [Pa] of the central and side block land portions, respectively.) That is, the circumferential shear stiffness is the Young's modulus and aspect ratio of the rubber. This is a variable function. Condition 1 is Gxc <Gxs.

The method that satisfies condition 1 is not particularly limited. For example, rubber of the same material is used for the central portion 36 and the side portion 46A to equalize the Young's modulus (E _0C = E _0S ), and the aspect ratio is made smaller at the central portion 36 than at the side portion 46A. (Axc <Axs). In this case, for example, if the height dimension of the side part 46A and the central part 36 are made equal (Hc = Hs), the circumferential dimension of the side part 46A and the central part 36 may be in a relationship of Lc <Ls. As another method, the aspect ratio may be equal between the central portion 36 and the side portion 46A (Axc = Axs), and the Young's modulus may be E _0C <E _0S .

(Condition 2)
Next, the compression rigidity Ezc [Pa] of the central portion 36 is
When 1/3 ≦ Lc / Wc ≦ 3,
Ezc = E _0C × (1 + 2.19 · Shc ² ) Equation (2-1)
If Lc / Wc <1/3 or 3 <Lc / Wc,
Ezc = E _0C × (1.33 + 1.1 · Shc ² ) Equation (2-2)
It can be expressed as. The compression rigidity Ezs [Pa] of the side portion 46A is
When 1/3 ≦ Ls / Ws ≦ 3,
Ezs = E _0S × (1 + 2.19 · Shs ² ) Equation (2-3)
If Ls / Ws <1/3 or 3 <Ls / Ws,
Ezs = E _0S × (1.33 + 1.1 · Shs ² ) (2-4)
It can be expressed as. That is, the compression stiffness is a function with the Young's modulus and shape factor of rubber as variables. Condition 2 is Ezc> Ezs.

A method that satisfies condition 2 is not particularly limited. For example, rubber of the same material is used for the central portion 36 and the side portion 46A to make the Young's modulus equal (E _0C = E _0S ), and the shape factor is made larger at the central portion 36 than at the side portion 46A. (Shc> Shs). As described above, the shape factor is a function of the circumferential dimension, the width dimension, and the height dimension of the block-shaped land portion. Therefore, Lc, Wc, Hc, Ls, Ws, and Hs may be set so as to satisfy the relationship Shc> Shs. As another method, the central part 36 and the side part 46A may have the same shape factor (Shc = Shs), and the Young's modulus may be E _0C > E _0S .

  Here, the expressions (1-1), (1-2) and the expressions (2-1) to (2-4) are all established for the block-shaped land portion itself, and the situation around the portion Does not depend on Therefore, the same formula is established for a block in which both ends in the circumferential direction are sipes and a block in which one end in the circumferential direction is a groove in the width direction. The same applies to both ends in the width direction, which are circumferential grooves or vertical sipes. Therefore, in the present invention, it is only necessary to extract the arbitrary central portion 36 and the side portion 46A and satisfy at least one of the condition 1 and the condition 2.

  By doing in this way, the circumferential direction shear rigidity and compression rigidity of a block-shaped land part part can be set appropriately by a center area and a side area, and center wear can be suppressed.

With reference to FIGS. 1A, 1B, and 1C, the center portion 36 and the side portion 46A of the tire 100 are compared. In this embodiment, rubbers of the same material are used for both, and the Young's modulus is equal (E _0C = E _0S ). Further, like the tire 700 of FIG. 7, the circumferential dimension and the height dimension are both equal (Lc = Ls, Hc = Hs). Therefore, the aspect ratios are equal (Axc = Axs), and Condition 1 is not satisfied. However, as compared with the tire 700 in FIG. 7, the width direction dimension Wc of the central portion 36 in the central area is set large, and the width direction dimension Ws of the side portion 46A in the side area is set small. For this reason, the shape factor has a relationship of Shc> Shs and satisfies the condition 2: Ezc> Ezs.

Like the tire 100, regarding the Young's modulus of rubber, the relationship of E _0C = E _0S is set, and by setting Lc and Ls, Wc and Ws, Hc and Hs , both condition 1 and condition 2 are satisfied. It is preferable. This is because the tread rubber can be formed from a single material, and a tire with reduced center wear can be easily and inexpensively manufactured.

  In addition, Formula (1-1), (1-2) and Formula (2-1)-(2-4) are materialized when the ground-contacting surface shape of a block-shaped land part part is a rectangle. However, in the present invention, the shape is not limited to a strict rectangle as long as these expressions are satisfied, and may be a substantially rectangular shape. Specifically, the “substantially rectangular” is not only a perfect rectangle such as the central portion 36, but also a parallelogram having both ends of the central portion in the tire circumferential direction within ± 20 ° with respect to the tire width direction. But you can. That is, this is a case where the width direction groove and the lateral sipe are within ± 20 ° with respect to the tire width direction. In this case, the circumferential dimension L and the width dimension W are measured along the circumferential direction and the width direction of the tire, respectively. (That is, in the above example, the circumferential dimension L and the width dimension W are not changed in either the rectangle or the parallelogram.)

  When the depths of the four grooves or sipes surrounding the block land portion are different, the height of the block land portion is the depth of the deepest groove or sipe. In this way, the expressions (1-1) and (1-2) and the expressions (2-1) to (2-4) are substantially satisfied.

(Embodiment 2)
The tire 200 which is another embodiment of this invention is demonstrated using FIG. Note that differences from the tire 100 will be mainly described, and the others will be omitted. In the tire 200, the central portion 36 and the side portion 46A are compared. In this embodiment, rubbers of the same material are used for both, and the Young's modulus is equal (E _0C = E _0S ). Further, the circumferential dimension Lc of the central portion 36 in the central region was set smaller than that of the tire 700 in FIG. Therefore, the aspect ratio has a relationship of Axc <Axs, and the condition 1: the relationship of Gxc <Gxs is satisfied. In addition, as compared with the tire 700 of FIG. 7, the width direction dimension Wc of the central portion 36 in the central area is set wide, and the width direction dimension Ws of the side portion 46A in the side area is set narrow. For this reason, the shape factor is in a relationship of Shc> Shs, and the condition 2: Ezc> Ezs is also satisfied.

In the present invention, by satisfying this way both conditions 1 and 2, Ru can be suppressed more effectively center wear.

When the shapes of the central portion 36 and the side portion 46A are made equal (that is, the aspect ratio and the shape factor are made equal), the rubber Young's modulus E _0C and E _0S are made different so that both the conditions 1 and 2 are satisfied. Can't meet. Therefore, it is necessary to set Lc, Wc, Hc, Ls, Ws, and Hs so that both condition 1 and condition 2 are satisfied regardless of whether the Young's modulus E _0C and E _{0S of} the rubber are equal.

(Embodiment 3)
A tire 300, which is another embodiment of the present invention, will be described with reference to FIG. The differences from the tires 100 and 200 will be mainly described, and the others will be omitted. In the tire 300, the central portion 36 and the side portion 46A are compared. In this embodiment, rubbers of the same material are used for both, and the Young's modulus is equal (E _0C = E _0S ). Further, the circumferential dimension Lc of the central portion 36 in the central region was set smaller than that of the tire 700 in FIG. Therefore, the aspect ratio has a relationship of Axc <Axs, and the condition 1: the relationship of Gxc <Gxs is satisfied. In addition, as compared with the tire 700 of FIG. 7, the width direction dimension Wc of the central portion 36 in the central area is set wide, and the width direction dimension Ws of the side portion 46A in the side area is set narrow. In the side block 26 </ b> A, the longitudinal sipes 44 </ b> A are increased to three, and the width direction dimension Ws of the side portion 46 </ b> A in the side region is set narrower than the tire 200. For this reason, the shape factor is in a relationship of Shc> Shs, and the condition 2: Ezc> Ezs is also satisfied.

This embodiment also to satisfy both the conditions 1 and 2, Ru can be suppressed more effectively center wear.

(Other preferred embodiments)
In the present invention, G xc / Gxs is preferably 0.4 to 0.6, and Ezc / Ezs is preferably 1.1 to 1.3. When G xc / Gxs is less than 0.4, (1) the circumferential length of the central portion becomes extremely short, and buckling is complicated when loaded, and the necessary longitudinal and lateral forces required for the tire are exhibited. This is because (2) the circumferential length of the side portion becomes extremely long, and the amount of wear in the tread side region may increase so much that shoulder wear may occur, and G xc This is because if / Gxs exceeds 0.6, the deformation of the central portion and the side portion becomes close, and the effects of the present invention may not be sufficiently obtained. Further, if Ezc / Ezs is less than 1.1, deformation of the central part and the side part becomes close, and there is a possibility that the effects of the present invention cannot be sufficiently obtained, and Ezc / Ezs is 1.3. This is because the radial deflection of the side portion becomes larger than that of the central portion, and shoulder wear may occur.

  Moreover, it is preferable to arrange three or more horizontal sipes per block in each of the blocks 22, 24A, 24B, 26A, and 26B. If three or more horizontal sipes are installed, it is important for performance on ice and snow. (1) While ensuring the length of the block edge, (2) The block length is shortened and it is easy to bend and deform. This is because the contact pressure of the block edge can be increased.

  Furthermore, as shown in FIGS. 1 to 3, it is preferable that the side portion 46 </ b> A is provided with a vertical sipe 44 </ b> A that extends along the tire circumferential direction R and that has both ends opened to the width direction groove 20 </ b> A. The presence of the longitudinal sipe 44A makes it possible to reduce the compression rigidity without changing the circumferential shear rigidity of the side portion, and the Gcx / Gxs is 0.4 to 0.6 and the Ezc / Ezs is 1.1 to 1. This is because it is easy to design a pattern within the range of 3.

  The tire of the present invention can be used for tires of any application including tires for passenger cars, and the tire size is not limited. The tire of the present invention can be suitably used as a winter studless tire, particularly as a studless tire for passenger cars.

  In the present invention, the internal structure of the tire is not particularly limited, and can be applied to a pneumatic tire having an arbitrary tire structure. In addition, the matters other than those defined in the claims are not limited at all, and for example, various changes can be made to the tread pattern within the scope of the gist.

Next, in order to further clarify the effects of the present invention, comparative evaluations performed using tires according to the following examples , reference examples, and comparative examples will be described. The tire size of each tire was 195 / 65R15.

The conventional tire 700 described in FIG. 7 is referred to as Comparative Example 1, and the tires 100, 200, and 300 described in Embodiments 1 to 3 are referred to as Reference Example 1, Example 2, and Example 3 , respectively. Specific dimensions of the central portion 36 and the side portions 46A and 46B are shown in Table 1. Although the tread pattern is not shown, the same tires were used in Reference Example 4 and Reference Example 5 except that the specific dimensions of the central portion 36 and the side portions 46A and 46B were as shown in Table 1.

<Evaluation of wear performance>
Each tire was mounted on a rim (6 J × 15), filled with an internal pressure of 220 kPa, and mounted on the rear shaft, which is the drive shaft of a passenger car (drive system FR). At this time, the front wheel axle load was 3.7 kN. After traveling 10,000 km with a traveling speed in the range of 0 to 80 km / h, the wear amount of the circumferential grooves in the central region and the circumferential grooves in the lateral region was measured. In this test, since the wear amount of the circumferential groove in the central region exceeded the wear amount of the circumferential groove in the lateral region in any tire, the smaller the wear amount of the circumferential groove in the central region, Wear can be suppressed. Therefore, for each tire, the wear amount of the circumferential groove in the central region was indicated as an index with a comparative example being 100. That is, center wear can be suppressed as the index is smaller. The results are shown in Table 1.

From Table 1, it can be seen that , in Reference Example 1, Examples 2 and 3, and Reference Examples 4 and 5 , which satisfy at least one of Condition 1 and Condition 2, the center wear could be suppressed more than in the Comparative Example. In addition, it can be seen that, in Examples 2 and 3 that satisfy both Condition 1 and Condition 2, center wear could be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can suppress center wear can be provided.

10 tread portion 12A, 12B first circumferential groove 14A, 14B second circumferential groove 16 first width direction groove 18A, 18B second width direction groove 20A, 20B third width direction groove 22 central block 24A, 24B intermediate block 26A , 26B Side block 28 Central block row 30A, 30B Intermediate block row 32A, 32B Side block row 34 Horizontal sipe 36 Central block-shaped land portion 38A, 38B Horizontal sipe 40A, 40B Intermediate block-shaped land portion 42A, 42B Horizontal Sipe 44A, 44B Vertical sipe 46A, 46B Side block land portion 100, 200, 300 Pneumatic tire

Claims (6)

In the tread part,
Three or more rows of a plurality of blocks arranged in the tire circumferential direction by arranging a plurality of circumferential grooves extending along the tire circumferential direction and a plurality of widthwise grooves extending along the tire width direction Form a group of blocks,
When dividing the tread part into the central area and the bilateral areas,
Among the block groups of three or more rows, one row block group is a central block row composed of a plurality of central blocks located in the central region, and the other one row block groups are located in both side regions. A side block row consisting of a plurality of side blocks,
The central block is further provided with a transverse sipe extending along the tire width direction until it is opened in two circumferential grooves, and the central block is further divided into a plurality of central block-shaped land portions,
A pneumatic tire, in which a lateral sipe extending along the tire width direction is disposed in the side block until it is opened at a circumferential groove and a tread end, and further divided into a plurality of side block land portions. Because
A pneumatic tire characterized by satisfying both of the following conditions 1 and 2 .
Condition 1: The circumferential shear rigidity (Gxc) of the central block land portion is smaller than the circumferential shear rigidity (Gxs) of the side block land portion.
Condition 2: The compression rigidity (Ezc) of the central block land portion is larger than the compression rigidity (Ezs) of the side block land portion. The circumferential dimension of the central block land portion is Lc, the width dimension is Wc, and the height dimension is Hc.
The circumferential dimension of the side block land portion is Ls, the width dimension is Ws, and the height dimension is Hs.
The aspect ratios Axc and Axs of the central and side block land portions are as follows:
Axc = Lc / Hc
Axs = Ls / Hs
And define
The shape factors Shc and Shs of the central and side block land portions are
Shc = (Lc · Wc) / (2 × Hc (Lc + Wc))
Shs = (Ls · Ws) / (2 × Hs (Ls + Ws))
When defined as
The circumferential shear rigidity Gxc and Gxs of the central and side block land portions are:
(Here, E _0C and E _0S indicate the Young's modulus of rubber in the central and side block land portions, respectively.)
Defined as
The compression stiffness Ezc and Ezs of the central and side block land portions is:
When 1/3 ≦ Lc / Wc ≦ 3,
Ezc = E _0C × (1 + 2.19 · Shc ² ) Equation (2-1)
If Lc / Wc <1/3 or 3 <Lc / Wc,
Ezc = E _0C × (1.33 + 1.1 · Shc ² ) Equation (2-2)
When 1/3 ≦ Ls / Ws ≦ 3,
Ezs = E _0S × (1 + 2.19 · Shs ² ) Equation (2-3)
If Ls / Ws <1/3 or 3 <Ls / Ws,
Ezs = E _0S × (1.33 + 1.1 · Shs ² ) (2-4)
The pneumatic tire according to claim 1, defined as E _0C = E _0S
Condition 1: Gxc <Gxs and Condition 2: Ezc> Ezs so as to satisfy both of the center block land portion and the side block land portion circumferential direction dimensions Lc and Ls, width direction dimensions Wc and Ws, and The pneumatic tire according to claim 2, wherein the height dimensions Hc and Hs are set. The pneumatic tire according to claim 3 , wherein G xc / Gxs is 0.4 to 0.6 and Ezc / Ezs is 1.1 to 1.3. The pneumatic tire according to any one of claims 1 to 4 , wherein three or more horizontal sipes are disposed in each of the plurality of blocks. The pneumatic tire according to any one of claims 1 to 5 , wherein a longitudinal sipe extending along a tire circumferential direction and having both ends opened in the width direction groove is disposed in the side block land portion. .