JP2017140936A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can make both on-snow and on-ice performance and dry performance compatible.SOLUTION: When an area in which is positioned a block 10 arranged on a tire equator surface CL or an area in which are positioned blocks 10, arranged at both sides in a tire width direction of a circumferential groove 20, arranged on the tire equator surface CL, adjacently to the circumferential groove 20 is set as a center area CA, and an area in which is positioned a block 10 arranged adjacently to an outer side in a tire width direction of the block 10 positioned at the center area CA through the circumferential groove 20 is set as an outer area OA, the outer area is formed so that a density D2 of a sipe 40 in the outer area OA is larger than a density D1 of the sipe 40 in the center area CA, a depth H2 of a lug groove 30 in the outer area OA is shallower than a depth H1 of a lug groove 30 in the center area CA, a thickness G2 of an under tread 62 positioned in the outer area OA is thicker than a thickness G1 of the under tread 62 positioned in the center area CA.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  In conventional pneumatic tires, sipes are formed on the tread surface for the purpose of improving snow / ice performance, which is the performance on snowy roads and frozen roads, and wet performance, which is the performance on wet roads. There is something that has been. For example, in the pneumatic tire described in Patent Document 1, a sipe is provided so that the density of the center region is higher than that of the shoulder region, and the center region is thinner than the shoulder region of the undertread. This ensures hydroplaning performance, dry braking performance, and wear resistance.

  In the pneumatic tire described in Patent Document 2, the rubber hardness of the under tread in the shoulder region is harder than the rubber hardness of the under tread in the center region, and the density in the center region is higher than that in the shoulder region. By installing a sipe, both dry maneuverability and snow maneuverability are achieved. Further, in the pneumatic tire described in Patent Document 3, the type of sipe is made different between the inner region and the outer region in the vehicle mounting direction, and the rubber of the under tread in the outer region is more than the rubber hardness of the under tread in the inner region. By making the hardness harder, the thickness of the undertread in the outer region is thicker than the thickness of the undertread in the inner region, and the sipe density in the inner region is higher than the sipe density in the outer region. , To achieve both dry maneuverability and snow maneuverability.

Special table 2014-523836 gazette JP 2013-79016 A JP 2013-252840 A

  Here, in order to improve the snow and ice performance, it is effective to increase the edge component due to the groove or the like in the region on the outer side in the tire width direction from the center region rather than the edge component in the center region. Thus, as one of the methods for making the edge component different depending on the region in the tire width direction, it is possible to make the sipe density different. By increasing the edge component in the region outside the tire width direction from the center region by making the sipe density different, by increasing the sipe density in the region outside the tire width direction from the center region Realize.

  However, an increase in sipe density leads to a decrease in block rigidity, and a decrease in block rigidity leads to a decrease in dry performance, which is steering stability on a dry road surface. For this reason, when the sipe density is increased in order to improve the snow and ice performance, the dryness may decrease due to the block rigidity being lowered, and improving the snow and ice performance without reducing the dry performance It was very difficult.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can make snow-ice performance and dry performance compatible.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention is formed by laminating a cap tread and an under tread made of rubber harder than rubber constituting the cap tread. A tread portion, a plurality of circumferential grooves formed in the cap tread and extending in the tire circumferential direction; a plurality of lug grooves formed in the cap tread and extending in the tire width direction; the circumferential grooves and the lug grooves; A region in the tire width direction where the land portion located on the tire equatorial plane is located, or a plurality of the circumferential grooves Region in the tire width direction where the land portions located on both sides in the tire width direction of the circumferential groove are adjacent to the circumferential groove located on the tire equatorial plane. Is the center region, and the region in the tire width direction where the land portion adjacent to the land portion located in the tire region in the tire region in the tire width direction is located in the tire width direction is defined as the outer region. The density D2 of the sipe located in the outer region is larger than the density D1 of the sipe located in the center region, and the depth H2 of the lug groove located in the outer region is located in the center region. A thickness G2 of the undertread located in the outer region that is shallower than a depth H1 of the lug groove is greater than a thickness G1 of the undertread located in the center region.

  In the pneumatic tire, in the sipe, the density D1 of the sipe located in the center region and the density D2 of the sipe located in the outer region satisfy a relationship of 1.1 ≦ (D2 / D1), In the lug groove, the depth H1 of the lug groove located in the center region and the depth H2 of the lug groove located in the outer region satisfy a relationship of 1.0 mm ≦ (H1−H2) ≦ 4.0 mm. In the undertread, a thickness G1 of the undertread located in the center region and a thickness G2 of the undertread located in the outer region satisfy a relationship of 1.2 ≦ (G2 / G1). Is preferred.

  In the pneumatic tire, when the index calculated from the density of the sipe, the depth of the sipe, the depth of the lug groove, and the hardness of the rubber is used as an index δ of the ease of falling of the land portion The index δ1 of the center area which is an index δ1 of the ease of falling of the land portion located in the center area and the index of the outer area which is an index δ of the ease of falling of the land part located in the outer area It is preferable that δ2 satisfies the relationship 0.7 ≦ (δ2 / δ1) ≦ 1.3.

  The pneumatic tire according to the present invention has an effect that both snow and ice performance and dry performance can be achieved.

FIG. 1 is a meridional cross-sectional view showing a main part of a pneumatic tire according to an embodiment. FIG. 2 is an AA arrow view of FIG. FIG. 3 is a schematic diagram for explaining values used in a formula for calculating an index of the ease of block collapse. FIG. 4 is a schematic diagram for explaining values used in a formula for calculating an index of the ease of block collapse. FIG. 5 is a meridional cross-sectional view showing a main part when a circumferential groove is located on the tire equatorial plane, which is a modification of the pneumatic tire according to the embodiment. 6 is a BB arrow view of FIG. FIG. 7A is a chart showing the results of a performance test of a pneumatic tire. FIG. 7B is a chart showing the results of the performance test of the pneumatic tire. FIG. 7C is a chart showing the results of the performance test of the pneumatic tire.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be replaced by those skilled in the art and can be easily conceived, or those that are substantially the same.

  In the following description, the tire width direction refers to the direction parallel to the rotation axis of the pneumatic tire, the inner side in the tire width direction is the direction toward the tire equatorial plane in the tire width direction, and the outer side in the tire width direction is The direction opposite to the direction toward the tire equatorial plane in the tire width direction. The tire radial direction means a direction orthogonal to the tire rotation axis, the tire radial inner direction means the direction toward the tire rotation axis in the tire radial direction, and the tire radial direction outer direction means that the tire rotates in the tire radial direction. The direction away from the axis. Further, the tire circumferential direction refers to a direction rotating around the tire rotation axis.

  FIG. 1 is a meridional cross-sectional view showing a main part of a pneumatic tire according to an embodiment. When the pneumatic tire 1 shown in FIG. 1 is seen in a meridional cross-sectional view, the tread portion 2 is disposed on the outermost side in the tire radial direction, and the tread portion 2 includes a cap tread 61, An under tread 62 and a wing tip 63 are provided. Among these, the cap tread 61 and the under tread 62 are laminated in the tire radial direction, and the under tread 62 is disposed on the inner side in the tire radial direction of the cap tread 61. The under tread 62 is made of rubber that is harder than the rubber constituting the cap tread 61, that is, the rubber hardness indicated by the JIS-A hardness in accordance with JIS-K6253 is lower than the rubber hardness of the cap tread 61. The rubber hardness of the tread 62 is high. Specifically, the cap tread 61 is made of rubber having a rubber hardness measured in a range of 45 to 70, measured under a condition of 20 ° C., and the under tread 62 is measured under a condition of 20 ° C. The rubber hardness is in the range of 53 to 78. Further, the wing tips 63 are disposed on both sides of the cap tread 61 in the tire width direction.

  The surface of the tread portion 2, that is, the portion that contacts the road surface when the vehicle (not shown) on which the pneumatic tire 1 is mounted is formed as a tread surface 3, and the tread surface 3 is formed by a cap tread 61. Has been. A plurality of circumferential grooves 20 extending in the tire circumferential direction and a plurality of lug grooves 30 extending in the tire width direction are formed on the tread surface 3. That is, the plurality of circumferential grooves 20 and lug grooves 30 are respectively formed on the cap tread 61 that constitutes the tread surface 3. A plurality of blocks 10 that are land portions are defined on the tread surface 3 by the plurality of circumferential grooves 20 and lug grooves 30.

  Both ends of the tread portion 2 in the tire width direction are formed as shoulder portions 4, and sidewall portions 5 are disposed from the shoulder portion 4 to a predetermined position on the inner side in the tire radial direction. That is, the sidewall portions 5 are disposed at two locations on both sides of the pneumatic tire 1 in the tire width direction.

  Furthermore, bead portions 50 are located on the inner side in the tire radial direction of the respective sidewall portions 5, and the bead portions 50 are arranged at two locations on both sides of the tire equatorial plane CL, like the sidewall portions 5. It is installed. That is, a pair of bead portions 50 is disposed on both sides of the tire equatorial plane CL in the tire width direction. Each of the pair of bead portions 50 is provided with a bead core 51, and a bead filler 55 is provided on the outer side of each bead core 51 in the tire radial direction. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 55 is a rubber material disposed in a space formed by folding an end portion in the tire width direction of the carcass 6 to be described later outward in the tire width direction at the position of the bead core 51.

  A belt layer 7 is provided inside the tread portion 2 in the tire radial direction. The belt layer 7 has a multilayer structure in which, for example, four layers of belts 71, 72, and 73 are laminated, and a plurality of belt cords made of steel or an organic fiber material such as polyester, rayon, or nylon are covered with a coat rubber and rolled. Processed and configured. The belts 71, 72, and 73 are different from each other in belt cords defined as inclination angles of the fiber direction of the belt cord with respect to the tire circumferential direction, and are laminated so that the fiber directions of the belt cord intersect with each other. Configured as a cross-ply structure.

  A carcass 6 including a radial ply cord is continuously provided on the inner side in the tire radial direction of the belt layer 7 and on the tire equatorial plane CL side of the sidewall portion 5. The carcass 6 has a single-layer structure composed of a single carcass ply or a multilayer structure formed by laminating a plurality of carcass plies, and is laid in a toroidal shape between bead cores 51 disposed on both sides in the tire width direction. Passed to form the tire skeleton. Specifically, the carcass 6 is disposed from one bead portion 50 to the other bead portion 50 of the pair of bead portions 50 located on both sides in the tire width direction, and wraps the bead core 51 and the bead filler 55. The bead portion 50 is wound back outward along the bead core 51 in the tire width direction. The carcass ply of the carcass 6 arranged in this way is configured by rolling a plurality of carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, rayon, etc. with a coat rubber.

  An inner liner 8 is formed along the carcass 6 on the inner side of the carcass 6 or on the inner side of the carcass 6 in the pneumatic tire 1.

  FIG. 2 is an AA arrow view of FIG. The circumferential grooves 20 formed in the tread surface 3 are disposed on both sides of the tire equatorial plane CL in the tire width direction across the tire equatorial plane CL, and a pair of inner circumferential grooves 21 extending in the tire circumferential direction. A pair of outer circumferential grooves 25 are provided on the outer sides of the pair of inner circumferential grooves 21 in the tire width direction and extend in the tire circumferential direction. That is, the inner circumferential groove 21 has two inner circumferential grooves 21 disposed on both sides of the tire equatorial plane CL in the tire width direction, and the outer circumferential groove 25 has two outer circumferential grooves 25 that are tires. The two inner circumferential grooves 21 are disposed on both sides of the two inner circumferential grooves 21 in the tire width direction across the two inner circumferential grooves 21 in the width direction. The inner circumferential groove 21 has a groove width in the range of 2 mm to 12 mm and a groove depth in the range of 6 mm to 10 mm. Further, the outer circumferential groove 25 has a groove width in the range of 2 mm to 12 mm, and a groove depth in the range of 6 mm to 10 mm. Further, the circumferential groove 20 may be inclined in the tire width direction while facing the tire circumferential direction, or may be formed to be curved or bent.

  As the lug groove 30 formed in the tread surface 3, a center lug groove 31, an intermediate lug groove 35, and a shoulder lug groove 36 are provided. Among these, the center lug groove 31 is disposed between the pair of inner circumferential grooves 21 in the tire width direction, and is a lug groove 30 whose both ends are connected to the pair of inner circumferential grooves 21. The intermediate lug groove 35 is disposed between the inner circumferential groove 21 and the outer circumferential groove 25 adjacent in the tire width direction, and both ends thereof are connected to the inner circumferential groove 21 and the outer circumferential groove 25. Lug groove 30 is formed. Further, the shoulder lug groove 36 is disposed on the outer side of the outer circumferential groove 25 in the tire width direction, and one end is a lug groove 30 connected to the outer circumferential groove 25. A plurality of the center lug groove 31, the intermediate lug groove 35, and the shoulder lug groove 36 are provided side by side in the tire circumferential direction.

  The center lug groove 31 has a groove width in the range of 2 mm to 8 mm and a groove depth in the range of 6 mm to 10 mm. The intermediate lug groove 35 has a groove width in the range of 2 mm or more and 8 mm or less, and a groove depth in the range of 6 mm or more and 10 mm or less. The shoulder lug groove 36 has a groove width in the range of 2 mm or more and 8 mm or less, and a groove depth in the range of 6 mm or more and 10 mm or less. The lug groove 30 may be inclined in the tire circumferential direction while facing the tire width direction, or may be formed by being bent or bent.

  In the block 10 formed on the tread surface 3, a center block 11, an intermediate block 12, and a shoulder block 13 are defined by the plurality of lug grooves 30 and the plurality of circumferential grooves 20. Of these, the center block 11 is a block 10 defined by adjacent center lug grooves 31 and a pair of inner circumferential grooves 21, whereby the center block 11 is positioned on the tire equatorial plane CL. doing. The intermediate block 12 is a block 10 defined by the adjacent inner circumferential groove 21 and outer circumferential groove 25 and the adjacent intermediate lug groove 35. The shoulder block 13 is provided on the outer side of the outer circumferential groove 25 in the tire width direction, is partitioned by the adjacent shoulder lug grooves 36, and the inner portion in the tire width direction is partitioned by the outer circumferential groove 25. The block 10 becomes. A plurality of the center block 11, the intermediate block 12, and the shoulder block 13 are provided side by side in the tire circumferential direction.

  In the block 10 formed as described above, a sipe 40 is formed. The sipe 40 has a groove width within a range of 0.5 mm to 1.5 mm and a groove depth of 4 mm to 9 mm. A plurality of sipes 40 formed in the block 10 are formed in each of the center block 11, the intermediate block 12, and the shoulder block 13. That is, a plurality of center sipes 41 are formed in the center block 11, a plurality of intermediate sipes 42 are formed in the intermediate block 12, and a plurality of shoulder sipes 43 are formed in the shoulder block 13. These sipes 40 are formed so as to extend in the tire width direction by being formed along the tire width direction or being inclined in the tire circumferential direction while extending in the tire width direction. Note that the sipe 40 formed in each block 10 may have an end portion connected to the lug groove 30 or the circumferential groove 20, and an end portion may terminate in the block 10.

  The sipes 40 provided as described above are provided with different densities depending on the blocks 10. Specifically, an area in the tire width direction where the block 10 located on the tire equatorial plane CL is located is defined as a center area CA, and a circumferential groove 20 is provided on the outer side in the tire width direction of the block 10 located in the center area CA. When the region in the tire width direction where the adjacent block 10 is located is the outer region OA, the density D2 of the sipe 40 located in the outer region OA is larger than the density D1 of the sipe 40 located in the center region CA. ing. That is, in the present embodiment, the region in the tire width direction where the center block 11 located on the tire equatorial plane CL is located is the center region CA, and the circumferential groove on the outer side in the tire width direction of the center block 11 A region in the tire width direction where the intermediate block 12 adjacent via 20 is located is an outer region OA.

  In the sipe 40, the density D2 of the sipe 40 located in the outer area OA is larger than the density D1 of the sipe 40 located in the center area CA, that is, the density D1 of the center sipe 41 formed in the center block 11. The density D2 of the intermediate sipe 42 formed in the intermediate block 12 is larger than that. Specifically, in the sipe 40, the ratio (D2 / D1) between the density D1 of the sipe 40 located in the center area CA and the density D2 of the sipe 40 located in the outer area OA satisfies 1.1 ≦ (D2 / D1). The relationship is satisfied, and it is preferable that the relationship of 1.3 ≦ (D2 / D1) ≦ 3.0 is satisfied.

  In this case, the density of the sipes 40 is a ratio of the lengths of all the sipes 40 provided in the block 10 to the area of the block 10 in which the sipes 40 are provided. That is, the density of the sipe 40 provided in one block 10 is (total length of the sipe 40 provided in the block 10 / area of the block 10 viewed in the tire radial direction). Further, the density D3 of the shoulder sipe 43 provided in the shoulder block 13 is approximately the same as the density D2 of the intermediate sipe 42.

  The depth of the lug groove 30 is different between the outer area OA and the center area CA, and the depth H2 of the lug groove 30 located in the outer area OA is the depth of the lug groove 30 located in the center area CA. It is shallower than H1. That is, the groove depth H2 of the intermediate lug groove 35 is shallower than the groove depth H1 of the center lug groove 31. Specifically, the lug groove 30 has a difference (H1−H2) between the depth H1 of the lug groove 30 located in the center area CA and the depth H2 of the lug groove 30 located in the outer area OA is 1.0 mm ≦ ( H1-H2) ≦ 4.0 mm is satisfied, and preferably, 2.0 mm ≦ (H1-H2) ≦ 3.0 mm is satisfied. Further, the groove depth H3 of the shoulder lug groove 36 is substantially the same as the groove depth H2 of the intermediate lug groove 35.

  Also, the thickness of the under tread 62 that constitutes the tread portion 2 together with the cap tread 61 is different between the outer area OA and the center area CA, and the thickness G2 of the under tread 62 located in the outer area OA is the center area. It is thicker than the thickness G1 of the undertread 62 located at CA. That is, the thickness of the under tread 62 in the stacking direction with the cap tread 61 is greater in the thickness G2 of the outer region OA than in the thickness G1 of the center region CA. Specifically, the undertread 62 has a ratio (G2 / G1) of the thickness G1 of the undertread 62 located in the center area CA to the thickness G2 of the undertread 62 located in the outer area OA is 1.2 ≦ ( G2 / G1) is satisfied, and it is preferable that the relationship of 1.3 ≦ (G2 / G1) ≦ 2.5 is satisfied.

  In this case, the thickness of the under tread 62 is the average thickness of the under tread 62 in each region. Further, the thickness G3 of the portion of the undertread 62 located in the region in the tire width direction where the shoulder block 13 is located is approximately the same as the thickness G2 of the undertread 62 located in the outer region OA. .

  In the present embodiment, the depth of the sipe 40, the depth of the lug groove 30, and the thickness of the undertread 62 are different between the center area CA and the outer area OA, respectively, so that the center area CA and the outer area OA are different. The ease of falling of the block 10 is about the same. In this case, the ease of falling of the block 10 is expressed by the following equation from the density D of the sipe 40, the depth S of the sipe 40, the depth H of the lug groove 30, and the hardness of the rubber constituting the undertread 62. The determination is made based on the index δ calculated by (1). The index δ indicates that the smaller the value, the easier the block 10 falls.

  FIG. 3 and FIG. 4 are schematic diagrams for explaining values used in an expression for calculating an index of the ease of falling of a block. In Equation (1), the lug groove depth H is the groove depth of the lug groove 30, and the sipe depth S is the groove depth of the sipe 40. CAP Ga is the thickness of the cap tread 61, UT Ga is the thickness of the under tread 62, and Total Ga is a thickness obtained by adding the laminated cap tread 61 and the under tread 62. It has become. Further, CAP Hs is the rubber hardness of the cap tread 61, and UT Hs is the rubber hardness of the under tread 62. That is, CAP Hs and UT Hs are represented by JIS-A hardness in accordance with JIS-K6253, and are rubber hardness measured under the condition of 20 ° C. Further, the denominator of the formula (1) represents the average hardness of the tread portion 2. Further, the ease of falling of the block 10 is affected not only by the lug grooves 30 but also by the grooves around the respective blocks 10, but the depth of the grooves other than the lug grooves 30 varies between the center area CA and the outer area OA. If not, the ease of falling of the block 10 can be determined by equation (1).

  When the ease of falling of the block 10 is represented by the index δ calculated by the expression (1), the pneumatic tire 1 according to the present embodiment is a center that is an index δ of the ease of falling of the block 10 located in the center area CA. The index δ1 of the area CA and the index δ2 of the outer area OA, which is an index δ of the ease of falling of the block 10 located in the outer area OA, satisfy the relationship of 0.7 ≦ (δ2 / δ1) ≦ 1.3. . That is, the ratio (δ2 / δ1) between the index δ1 of the ease of falling of the center block 11 and the index δ2 of the ease of falling of the intermediate block 12 has a relationship of 0.7 ≦ (δ2 / δ1) ≦ 1.3. Satisfies. The ratio (δ2 / δ1) between the index δ1 and the index δ2 preferably satisfies the relationship 0.8 ≦ (δ2 / δ1) ≦ 1.2.

  When the pneumatic tire 1 configured as described above is mounted on a vehicle and travels, the pneumatic tire 1 rotates while the tread surface 3 positioned below the tread surface 3 is in contact with the road surface. When driving on a dry road surface with a vehicle equipped with pneumatic tires 1, the driving force or braking force is transmitted to the road surface or the turning force is generated mainly by the frictional force between the tread surface 3 and the road surface. To drive. On the other hand, when traveling on a snowy road or a frozen road surface, the traveling is performed using the edge effect of the circumferential groove 20, the lug groove 30, and the sipe 40. For this reason, it is effective to increase the edge component in order to ensure the steering stability on the snow and ice road surface. Further, when the vehicle turns, a large load acts on the tread surface 3 of the pneumatic tire 1 on a portion located on the outer side in the vehicle width direction, that is, the tread surface 3 in the tire width direction. A large load acts on the portion located on the outer side.

  In the pneumatic tire 1 according to the present embodiment, since the density D2 of the sipe 40 located in the outer area OA is larger than the density D1 of the sipe 40 located in the center area CA, the tire width is larger than the center area CA. The edge component of the outer area OA located on the outer side in the direction is increased. For this reason, there are many edge components in a region where a large load is likely to act when the vehicle turns, and the turning effect is improved by using the edge effect of the sipe 40 located in the outer region OA when traveling on a snowy and ice road surface. be able to. Accordingly, it is possible to improve the steering stability on the snowy and ice road surface.

  It is effective to increase the density of the sipe 40 as described above when traveling on a snowy and ice road surface. However, if the density of the sipe 40 is increased, the rigidity of the block 10 provided with the sipe 40 is likely to decrease. Become. When the rigidity of the block 10 is reduced, the block 10 is likely to fall down, and therefore, when a large load is applied to the tread surface 3 when traveling on a dry road surface, the block 10 falls down and steering stability is likely to be lowered. .

  On the other hand, in the pneumatic tire 1 according to the present embodiment, the depth H2 of the lug groove 30 located in the outer region OA is shallower than the depth H1 of the lug groove 30 located in the center region CA. The height from the bottom of the lug groove 30 to the tread surface 3 is lower in the outer area OA than in the center area CA. For this reason, the rigidity of the block 10 located in the outer area OA is higher than the rigidity of the block 10 located in the center area CA. In other words, since the rubber capacity with respect to the entire outer area OA is larger than the rubber capacity with respect to the entire center area CA, the rigidity of the block 10 located in the outer area OA is that of the block 10 located in the center area CA. It is higher than the rigidity.

  In the pneumatic tire 1 according to this embodiment, the thickness G2 of the undertread 62 located in the outer area OA is thicker than the thickness G1 of the undertread 62 located in the center area CA. Since the under tread 62 is harder than the rubber composing the cap tread 61, the outer region OA where the thickness of the under tread 62 is thicker than the center region CA has the rigidity of the block 10. It is high.

  For these reasons, in the outer area OA, although the density of the sipe 40 is larger than that of the center area CA, the rigidity of the block 10 in the outer area OA is hardly lowered. That is, by increasing the density of the sipe 40 in the outer area OA, ensuring the steering stability on the snow and ice road surface, while suppressing the decrease in the rigidity of the block 10 located in the outer area OA, the dry road surface Steering stability can be ensured. As a result, both snow and ice performance and dry performance can be achieved.

  In the sipe 40, the ratio (D2 / D1) between the density D1 of the sipe 40 located in the center area CA and the density D2 of the sipe 40 located in the outer area OA satisfies a relationship of 1.1 ≦ (D2 / D1). Therefore, the edge effect in the outer area OA can be ensured more reliably, and the steering stability on the snow and ice road surface can be improved more reliably.

  The lug groove 30 has a difference (H1−H2) between the depth H1 of the lug groove 30 located in the center area CA and the depth H2 of the lug groove 30 located in the outer area OA is 1.0 mm ≦ (H1 -H2) Since the relationship of 4.0 mm is satisfied, the rigidity of the block 10 can be secured in a well-balanced manner. That is, when the difference (H1-H2) between the depth H1 of the lug groove 30 in the center area CA and the depth H2 of the lug groove 30 in the outer area OA is less than 1.0 mm, the lug groove in the center area CA Since the difference between the depth H1 of 30 and the depth H2 of the lug groove 30 in the outer region OA is too small, the rigidity of the block 10 in the outer region OA is effective when the density D2 of the sipe 40 in the outer region OA is increased. May not be secured. Further, when the difference (H1−H2) between the depth H1 of the lug groove 30 in the center area CA and the depth H2 of the lug groove 30 in the outer area OA is larger than 4.0 mm, the outer area OA There is a possibility that the rigidity of the block 10 in the center area CA becomes too low. In contrast, the difference (H1−H2) between the depth H1 of the lug groove 30 in the center area CA and the depth H2 of the lug groove 30 in the outer area OA is 1.0 mm ≦ (H1−H2) ≦ 4.0 mm. When the density D2 of the sipe 40 in the outer area OA is increased, the rigidity of the block 10 in the outer area OA and the rigidity of the block 10 in the center area CA can be ensured in a balanced manner. .

  The undertread 62 has a ratio (G2 / G1) of the thickness G1 of the undertread 62 located in the center area CA to the thickness G2 of the undertread 62 located in the outer area OA is 1.2 ≦ (G2 / G1) is satisfied, the rigidity of the block 10 in the outer area OA can be ensured more reliably when the density D2 of the sipe 40 in the outer area OA is increased, and steering stability on a dry road surface can be ensured. Sex can be ensured more reliably. As a result, snow / ice performance and dry performance can be more reliably achieved.

  Further, the ratio (δ2 / δ1) between the index δ1 of the ease of falling of the block 10 located in the center area CA and the index δ2 of the ease of falling of the block 10 located in the outer area OA is 0.7 ≦ (δ2). Since the relationship of /δ1)≦1.3 is satisfied, the rigidity of the block 10 can be ensured with a good balance. That is, when the ratio (δ2 / δ1) between the index δ1 of the center area CA and the index δ2 of the outer area OA is less than 0.7, the block 10 of the outer area OA is likely to fall over the center area CA. Therefore, when the density D2 of the sipe 40 in the outer area OA is increased, there is a possibility that the rigidity of the block 10 in the outer area OA cannot be effectively secured. When the ratio (δ2 / δ1) between the index δ1 of the center area CA and the index δ2 of the outer area OA is greater than 1.3, the rigidity of the block 10 of the center area CA is lower than the outer area OA. It may be too much. On the other hand, when the ratio (δ2 / δ1) between the index δ1 of the center area CA and the index δ2 of the outer area OA is within the range of 0.7 ≦ (δ2 / δ1) ≦ 1.3, the outer side When the density D2 of the sipe 40 in the area OA is increased, the rigidity of the block 10 in the outer area OA and the rigidity of the block 10 in the center area CA can be secured in a balanced manner. As a result, snow / ice performance and dry performance can be more reliably achieved.

  Further, the density D3 of the shoulder sipe 43 is approximately the same as the density D2 of the intermediate sipe 42, and the groove depth H3 of the shoulder lug groove 36 is approximately the same as the groove depth H2 of the intermediate lug groove 35. Since the thickness G3 of the under tread 62 located in the region where the shoulder block 13 is located is equal to the thickness G2 of the under tread 62 located in the outer region OA, the shoulder sipes 43 can also ensure the rigidity of the shoulder block 13 while improving the snow and ice performance. As a result, snow / ice performance and dry performance can be more reliably achieved.

  In the embodiment described above, the area in the tire width direction of the block 10 where the block is located on the tire equatorial plane CL is defined as the center area CA. However, the center area CA includes the block 10 located on the tire equatorial plane CL. It may be other than the located region. FIG. 5 is a meridional cross-sectional view showing a main part when a circumferential groove is located on the tire equatorial plane, which is a modification of the pneumatic tire according to the embodiment. 6 is a BB arrow view of FIG. Since the position of the circumferential groove 20 formed in the tread surface 3 differs for each tread pattern, the block 10 that is a land portion is not located on the tire equator surface CL depending on the tread pattern, and the circumferential groove 20 is not formed. May be located. In such a case, blocks 10 located on both sides in the tire width direction of the circumferential groove 20 are located adjacent to the circumferential groove 20 located on the tire equatorial plane CL among the plurality of circumferential grooves 20. The region in the tire width direction may be a center region CA.

  The pneumatic tire 1 shown in FIGS. 5 and 6 includes a center circumferential groove 26 that is a circumferential groove 20 located on the tire equatorial plane CL as a circumferential groove 20 and a center circumferential groove 26 in the tire width direction. Three of the two outer circumferential grooves 27 disposed on both sides are disposed. In addition, as the lug groove 30, a plurality of center lug grooves 37 disposed between the center circumferential groove 26 and the outer circumferential groove 27 and a plurality of lug grooves 30 on the outer side in the tire width direction of the outer circumferential groove 27 are arranged. A shoulder lug groove 38 is provided.

  As the block 10, a center block 16 and a shoulder block 17 are provided. Among these, the center block 16 is a block 10 defined by an adjacent center circumferential groove 26 and an outer circumferential groove 27 and an adjacent center lug groove 37. The shoulder block 17 is provided on the outer side of the outer circumferential groove 27 in the tire width direction, is partitioned by the adjacent shoulder lug grooves 38, and the inner portion in the tire width direction is partitioned by the outer circumferential groove 27. The block 10 becomes. These blocks 10 are each formed with a sipe 40, a center sipe 46 is formed on the center block 16, and a shoulder sipe 47 is formed on the shoulder block 17.

  As described above, when the center circumferential groove 26 is formed on the tire equatorial plane CL, the block 10 is located adjacent to the center circumferential groove 26 on both sides in the tire width direction of the center circumferential groove 26. A region in the tire width direction where the center block 16 is located is a center region CA. The outer region OA is a region in the tire width direction where the shoulder block 17 adjacent to the center block 16 located in the center region CA on the outer side in the tire width direction via the outer circumferential groove 27 is located. OA.

  Even when the center area CA and the outer area OA are provided as described above, the density D2 of the shoulder sipe 47 located in the outer area OA is larger than the density D1 of the center sipe 46 located in the center area CA. The depth H2 of the shoulder lug groove 38 located in OA is shallower than the depth H1 of the center lug groove 37 located in the center area CA, and the thickness G2 of the undertread 62 located in the outer area OA is located in the center area CA. It is sufficient that the thickness of the undertread 62 to be thickened is larger than the thickness G1. As a result, when the density of the sipe 40 in the outer region OA is increased while the edge component in the outer region OA located on the outer side in the tire width direction of the center region CA is increased to improve the steering stability on the snow and ice road surface. It is possible to suppress a decrease in rigidity of the block 10 and to secure steering stability on a dry road surface. As a result, both snow and ice performance and dry performance can be achieved.

  Further, the number of circumferential grooves 20 formed on the tread surface 3 may be other than four or three. Regardless of the number of circumferential grooves 20, the tire width of the circumferential groove 20 adjacent to the region where the block 10 located on the tire equatorial plane CL is located, or the circumferential groove 20 located on the tire equatorial plane CL. When the area where the blocks 10 located on both sides in the direction are defined as the center area CA, the density D2 of the sipe 40 in the outer area OA is larger than the density D1 of the sipe 40 in the center area CA, and the lug groove in the outer area OA The depth H2 of 30 is shallower than the depth H1 of the lug groove 30 in the center area CA, and the thickness G2 of the undertread 62 in the outer area OA is thicker than the thickness G1 of the undertread 62 in the center area CA. That's fine.

〔Example〕
7A to 7C are tables showing results of performance tests of pneumatic tires. Hereinafter, the performance evaluation test performed on the pneumatic tire 1 of the conventional example, the pneumatic tire 1 of the comparative example, and the pneumatic tire 1 according to the present invention will be described. The performance evaluation test was conducted with respect to a snow performance test that is a running performance on a snowy and ice road surface and a dry performance test that is a running performance on a dry road surface.

  In these evaluation tests, a 195 / 65R15 91Q size pneumatic tire 1 is assembled to a rim wheel of a 15 × 6.0J size JATMA standard rim, and the air pressure is adjusted to 230 kPa for the front wheel and 220 kPa for the rear wheel, and the front wheel of 1800 cc. The test was carried out by mounting it on a driving car. The evaluation method for each test item was performed for snow performance by running a test course on snow with a vehicle equipped with the pneumatic tire 1 to be subjected to the evaluation test and performing a sensory evaluation with a test driver. The snow performance is displayed with a score of 100 as a conventional example to be described later, and the larger the value, the better the snow performance. The dry performance was evaluated by running a test course on a dry road surface with a vehicle equipped with a pneumatic tire 1 to be evaluated and performing a sensory evaluation with a test driver. The dry performance is displayed with a score of 100 as a conventional example to be described later, and the larger the value, the better the dry performance.

  The evaluation test is a comparison with the conventional pneumatic tire 1 which is an example of the conventional pneumatic tire 1, the examples 1 to 13 which are the pneumatic tire 1 according to the present invention, and the pneumatic tire 1 according to the present invention. It performed about 20 types of pneumatic tires 1 of Comparative Examples 1-6 which are the pneumatic tires 1 to perform. In these pneumatic tires 1, sipes 40 are formed on the tread surface 3. Among these, in the conventional pneumatic tire 1, the density D1, D2 of the sipe 40, the depth of the lug groove 30, and the thickness of the undertread 62 are all constant in the center area CA and the outer area OA. . Further, in the pneumatic tires 1 of Comparative Examples 1 to 6, the density D2 of the sipe 40 in the outer area OA is larger than the density D1 of the sipe 40 in the center area CA, and the depth H2 of the lug groove 30 in the outer area OA. The depth H1 of the lug groove 30 in the center area CA is less than the depth H1, and the thickness G2 of the undertread 62 in the outer area OA is greater than the thickness G1 of the undertread 62 in the center area CA. It has not been.

  On the other hand, in Examples 1 to 13, which are examples of the pneumatic tire 1 according to the present invention, the density D2 of the sipe 40 in the outer area OA is larger than the density D1 of the sipe 40 in the center area CA, and the outer area OA. The depth H2 of the lug groove 30 is shallower than the depth H1 of the lug groove 30 in the center area CA, and the thickness G2 of the undertread 62 in the outer area OA is thicker than the thickness G1 of the undertread 62 in the center area CA. It has become. Moreover, the pneumatic tire 1 which concerns on Examples 1-13 is the density ratio (D2 / D1) of the sipe 40, the difference (H1-H2) of the depth of the lug groove 30, and the thickness ratio (G2) of the undertread 62. / G1) are different, and the ratio (δ2 / δ1) of the index of the ease of falling of the block 10 is also different.

  As a result of performing an evaluation test using these pneumatic tires 1, as shown in FIGS. 7A to 7C, the pneumatic tires 1 of Examples 1 to 13 are compared with the conventional examples and Comparative Examples 1 to 6. It was found that both snow performance and dry performance were improved. That is, the pneumatic tire 1 according to Examples 1 to 13 can achieve both snow and ice performance and dry performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Tread surface 4 Shoulder part 5 Side wall part 6 Carcass 7 Belt layer 10 Block (land part)
11, 16 Center block 12 Intermediate block 13, 17 Shoulder block 20 Circumferential groove 21 Inner circumferential groove 25, 27 Outer circumferential groove 26 Center circumferential groove 30 Lug groove 31, 37 Center lug groove 35 Intermediate lug groove 36, 38 Shoulder lug groove 40 Sipe 41, 46 Center sipe 42 Intermediate sipe 43, 47 Shoulder sipe 50 Bead section 61 Cap tread 62 Under tread CL Tire equatorial plane CA Center area OA Outer area

Claims (3)

A tread portion in which a cap tread and an under tread made of rubber harder than rubber constituting the cap tread are laminated;
A plurality of circumferential grooves formed in the cap tread and extending in the tire circumferential direction;
A plurality of lug grooves formed in the cap tread and extending in the tire width direction;
A plurality of land portions defined by the circumferential grooves and the lug grooves;
A sipe formed in the land,
With
An area in the tire width direction where the land portion located on the tire equatorial plane is located, or a tire width of the circumferential groove adjacent to the circumferential groove located on the tire equatorial plane among the plurality of circumferential grooves The region in the tire width direction where the land portion located on both sides in the direction is located as a center region
When the region in the tire width direction where the land portion adjacent to the land portion adjacent to the land portion in the tire width direction of the land region located in the center region is located as the outer region,
The density D2 of the sipe located in the outer region is larger than the density D1 of the sipe located in the center region,
A depth H2 of the lug groove located in the outer region is shallower than a depth H1 of the lug groove located in the center region;
A pneumatic tire characterized in that a thickness G2 of the undertread located in the outer region is thicker than a thickness G1 of the undertread located in the center region. In the sipe, a density D1 of the sipe located in the center region and a density D2 of the sipe located in the outer region satisfy a relationship of 1.1 ≦ (D2 / D1),
In the lug groove, a depth H1 of the lug groove located in the center region and a depth H2 of the lug groove located in the outer region satisfy a relationship of 1.0 mm ≦ (H1−H2) ≦ 4.0 mm. Meet,
In the undertread, a thickness G1 of the undertread located in the center region and a thickness G2 of the undertread located in the outer region satisfy a relationship of 1.2 ≦ (G2 / G1). The pneumatic tire according to 1. In the case where the index calculated from the density of the sipe, the depth of the sipe, the depth of the lug groove, and the hardness of the rubber is an index δ of the ease of falling of the land portion,
The index δ1 of the center area which is an index δ1 of the ease of falling of the land portion located in the center area, and the index δ2 of the outer area which is an index δ of the ease of falling of the land part located in the outer area. Is a pneumatic tire according to claim 1 or 2, satisfying a relationship of 0.7 ≦ (δ2 / δ1) ≦ 1.3.

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