JP6672814B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In pneumatic tires, grooves are formed on the tread surface mainly to ensure drainage, but if there are too many grooves, the rigidity of the land decreases and steering stability and wear resistance decrease. Some conventional pneumatic tires improve the conflicting performance by devising the arrangement of grooves. For example, in the pneumatic tire described in Patent Literature 1, four circumferential grooves extending in a zigzag shape along the tire circumferential direction are arranged side by side in the tire width direction. By providing a lug groove formed in a crank shape between the two inner circumferential grooves in the direction, traction and wear resistance on a wet road surface are improved.

JP 2006-111122 A

  Here, the pneumatic tire changes its grounding characteristics depending on the weight of the vehicle when traveling, but especially in trucks and buses where the difference between the weight when no cargo is loaded and the weight when the cargo is full is large. In addition, the change in the grounding characteristics due to the change in the weight of the vehicle has become remarkable. For example, in a truck or a bus, a vehicle mounted with a plurality of wheels stacked on each other has an empty pneumatic tire in which no cargo is loaded, compared to a loaded vehicle in which cargo is loaded. The contact area to the road surface is reduced, and only the vicinity of the center area is contacted. As described above, when the ground contact area becomes small, a slip easily occurs between the tread surface and the road surface of the pneumatic tire. Therefore, in order to prevent the slip, it is better to reduce the groove area ratio near the center region. However, when the groove area ratio is reduced, the drainage performance is reduced, and the wet performance is reduced. As described above, pneumatic tires mounted on trucks, buses, etc., achieve both steering stability during dry driving and wet performance regardless of the loaded state of cargo, that is, regardless of whether the vehicle is empty or loaded. It was very difficult to do.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire that can improve both dry performance and wet performance.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention includes a pair of pneumatic tires disposed on both sides of the tire equatorial plane in the tire width direction with respect to the tire equatorial plane and extending in the tire circumferential direction. Inner circumferential groove, and a pair of outer circumferential grooves disposed outside each of the pair of inner circumferential grooves in the tire width direction and extending in the tire circumferential direction, and a pair of inner circumferential grooves at both ends. A plurality of lug grooves having a circumferential extension extending in the tire circumferential direction by being bent at a plurality of positions while being connected, and land portions defined by the lug grooves and the inner circumferential groove. A center block, one end of which is connected to the lug groove, the other end of which is terminated in the center block, and has a notch bent at at least one position, and the center block in the tire width direction is provided. Tsu about the center of the click, and wherein the contact area ratio of the center region is 10% of the region having a width in the tire width direction of the center block is 70% or less than 30%.

  Further, in the pneumatic tire, it is preferable that the circumferentially extending portion is located in the center region.

  In the pneumatic tire, a length of the center block in the tire circumferential direction of a portion of the center block located in the center region is at least 25% of a length of the center block in a tire circumferential direction. It is preferably 40% or less.

  In the pneumatic tire, it is preferable that a length of the circumferentially extending portion in a circumferential direction of the tire is not less than 50% and not more than 70% of a length of the center region.

  Further, in the pneumatic tire, two notches are connected to one lug groove, and the two notches are provided on a side of an end that terminates in the center block from a bent portion. It is preferable that the located portions bend in directions opposite to each other in the tire circumferential direction.

  In the pneumatic tire, it is preferable that the notch bends at a position outside the center region in the tire width direction.

  Further, in the pneumatic tire, the inner circumferential groove extends in the tire circumferential direction while oscillating in the tire width direction, and an overlapping amount of the opposing groove walls when viewed in the tire circumferential direction is 0 mm or more. It is preferably 5 mm or less.

  Further, in the pneumatic tire, the outer circumferential groove extends in the tire circumferential direction while oscillating in the tire width direction, and the overlapping amount of the opposed groove walls when viewed in the tire circumferential direction is 1 mm or more. It is preferably 5 mm or less.

  Further, in the pneumatic tire, the inner circumferential groove and the outer circumferential groove extend in the tire circumferential direction while both oscillating in the tire width direction, and are formed between opposed groove walls of the inner circumferential groove. The overlap amount L1 when viewed in the tire circumferential direction and the overlap amount L2 between the opposing groove walls of the outer circumferential groove when viewed in the tire circumferential direction satisfy the relationship of L1 ≦ L2. preferable.

  In the pneumatic tire, the relation between the groove width W1 of the inner circumferential groove and the groove width W2 of the outer circumferential groove in the inner circumferential groove and the outer circumferential groove is 0.5 ≦ ( (W2 / W1) ≦ 0.9.

  In the pneumatic tire, the width of the center block in the tire width direction is preferably 20% or more and 40% or less of the tread development width.

  In the pneumatic tire, the center block preferably has a ratio of a length L in a tire circumferential direction and a width W in a tire width direction satisfying 0.9 ≦ (L / W) ≦ 1.1. .

  Further, in the pneumatic tire, a shoulder block that is a land portion whose inner portion in the tire width direction is partitioned by the outer circumferential groove is provided outside the outer circumferential groove in the tire width direction, The area of the shoulder block is preferably 40% or more and 60% or less of the area of the center block.

  The pneumatic tire is preferably used for a heavy-duty pneumatic tire.

  The pneumatic tire according to the present invention has an effect that both dry performance and wet performance can be improved.

FIG. 1 is a meridional sectional view showing a main part of the pneumatic tire according to the embodiment. FIG. 2 is a view taken along the line AA in FIG. FIG. 3 is a detailed view of a portion B in FIG. FIG. 4 is a detailed view of a portion C in FIG. FIG. 5 is a detailed view of the center block shown in FIG. FIG. 6A is a table showing the results of performance tests on pneumatic tires. FIG. 6B is a table showing the results of performance tests on pneumatic tires. FIG. 6C is a table showing the results of performance tests on pneumatic tires. FIG. 6D is a chart showing the results of the performance test of the pneumatic tire. FIG. 6E is a chart showing the results of performance tests on pneumatic tires.

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

  In the following description, the tire width direction refers to a direction parallel to the rotation axis of the pneumatic tire, and the inside in the tire width direction is the direction toward the tire equatorial plane in the tire width direction, and the outside in the tire width direction is It refers to the direction opposite to the direction toward the tire equator in the tire width direction. Further, the tire radial direction refers to a direction orthogonal to the tire rotation axis, the tire radial direction inward refers to the direction toward the tire rotation axis in the tire radial direction, and the tire radial direction outward refers to the tire rotation in the tire radial direction. The direction away from the axis. The tire circumferential direction refers to a direction in which the tire rotates around the tire rotation axis.

  FIG. 1 is a meridional sectional view showing a main part of the pneumatic tire according to the embodiment. In a pneumatic tire 1 shown in FIG. 1, when viewed in a meridional cross-sectional view, a tread portion 2 is disposed at the outermost portion in the tire radial direction, and the surface of the tread portion 2, that is, the air A portion that comes into contact with a road surface when a vehicle (not shown) to which the tire 1 is mounted travels is formed as a tread surface 3. A plurality of circumferential grooves 20 extending in the tire circumferential direction are formed on the tread surface 3, and a plurality of lug grooves 30 (see FIG. 2) intersecting with the circumferential grooves 20 are formed. A plurality of land portions 10 are defined on the tread surface 3 by the plurality of circumferential grooves 20 and the lug grooves 30.

  Both ends of the tread portion 2 in the tire width direction are formed as shoulder portions 4, and a sidewall portion 5 is provided 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 provided at two places on both sides of the pneumatic tire 1 in the tire width direction.

  Further, bead portions 50 are located on the radially inner side 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, similarly to the sidewall portions 5. Has been established. That is, a pair of bead portions 50 are provided on both sides of the tire equatorial plane CL in the tire width direction. A bead core 51 is provided in each of the pair of bead portions 50, and a bead filler 55 is provided outside each bead core 51 in the tire radial direction. 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 described later at the position of the bead core 51 outward in the tire width direction.

  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, 73, and 74 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 coat rubber. It is constructed by rolling. The belts 71, 72, 73, and 74 have different belt cords defined as an inclination angle of the belt cord in the fiber direction with respect to the tire circumferential direction, and are stacked with the fiber directions of the belt cords intersecting each other. , A so-called cross-ply structure.

  On the inner side in the tire radial direction of the belt layer 7 and on the side of the sidewall portion 5 on the tire equatorial plane CL side, a carcass 6 including a cord of a radial ply is continuously provided. The carcass 6 has a single-layer structure made up of one carcass ply or a multilayer structure made up of a plurality of carcass plies, and is toroidally bridged between bead cores 51 arranged on both sides in the tire width direction. It is passed and constitutes the skeleton of the tire. More 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 surrounds the bead core 51 and the bead filler 55. The bead portion 50 is wound outward along the bead core 51 in the tire width direction. The carcass ply of the carcass 6 arranged in this manner uses a steel cord, which is a carcass cord made of a steel material, and is formed by rolling a plurality of steel cords with coat rubber. That is, the carcass 6 is configured using a steel carcass material.

  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 a view taken along the line AA in FIG. A pair of inner circumferential grooves 21 disposed on both sides of the tire equatorial plane CL in the tire width direction across the tire equatorial plane CL and extending in the tire circumferential direction, as the circumferential grooves 20 formed on the tread surface 3; A pair of outer circumferential grooves 25 are provided outside each 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. The two inner circumferential grooves 21 are arranged on both sides in the tire width direction with the two inner circumferential grooves 21 interposed therebetween in the width direction. The inner circumferential groove 21 and the outer circumferential groove 25 are formed to extend in the tire circumferential direction while oscillating in the tire width direction. The inner circumferential groove 21 has a groove width in a range of 6 mm to 11 mm and a groove depth in a range of 10 mm to 18 mm. The outer circumferential groove 25 has a groove width in a range of 4 mm or more and 9 mm or less, and a groove depth in a range of 10 mm or more and 18 mm or less.

  FIG. 3 is a detailed view of a portion B in FIG. The inner circumferential groove 21 extending in the tire circumferential direction while oscillating in the tire width direction is the innermost in the tire width direction among the groove walls 22 located on the outer side in the tire width direction among the groove walls 22 of the inner circumferential groove 21. The portion located on the side is located on the inner side in the tire width direction than the portion located on the outermost side in the tire width direction among the groove walls 22 located on the inner side in the tire width direction. That is, the groove walls 22 facing each other when viewed in the tire circumferential direction of the inner circumferential groove 21 overlap each other, and are not see-through in the tire circumferential direction. Similarly, the outer circumferential groove 25 that extends in the tire circumferential direction while oscillating in the tire width direction is the outermost circumferential groove wall 26 of the outer circumferential groove 25. The part located on the inner side in the tire width direction is located on the inner side in the tire width direction than the part located on the outer side in the tire width direction among the groove walls 26 located on the inner side in the tire width direction. That is, in the outer circumferential groove 25, the groove walls 26 facing each other when viewed in the tire circumferential direction overlap each other, and are not see-through in the tire circumferential direction.

  The width of the inner circumferential groove 21 and the outer circumferential groove 25 is such that when the outer circumferential groove 25 is viewed in the tire circumferential direction, the opposed groove walls 26 of the outer circumferential groove 25 overlap in the tire width direction. When the inner circumferential groove 21 is viewed in the tire circumferential direction, the width of the opposing groove walls 22 of the inner circumferential groove 21 is greater than or equal to the width overlapping in the tire width direction. In other words, the inner circumferential groove 21 and the outer circumferential groove 25 are formed by an overlapping amount L1 between the facing groove walls 22 of the inner circumferential groove 21 when viewed in the tire circumferential direction, and an opposing position of the outer circumferential groove 25. The overlapping amount L2 of the groove walls 26 when viewed in the tire circumferential direction satisfies the relationship of L1 ≦ L2. Of the overlap amounts L1 and L2 between the groove walls 22 and 26 of the inner circumferential groove 21 and the outer circumferential groove 25, the overlap amount L1 of the groove walls 22 of the inner circumferential groove 21 is 0 mm or more and 5 mm or less. The overlapping amount L2 between the groove walls 26 of the outer circumferential groove 25 is 1 mm or more and 5 mm or less.

  Further, in the inner circumferential groove 21 and the outer circumferential groove 25, the groove width W1 of the inner circumferential groove 21 is larger than the groove width W2 of the outer circumferential groove 25. Specifically, in the inner circumferential groove 21 and the outer circumferential groove 25, the relationship between the groove width W1 of the inner circumferential groove 21 and the groove width W2 of the outer circumferential groove 25 is 0.5 ≦ (W2 / W1) ≦ 0.9, that is, (W2 / W1) is 0.5 or more and 0.9 or less. Further, the relationship between the groove width W1 of the inner circumferential groove 21 and the groove width W2 of the outer circumferential groove 25 is preferably in the range of 0.6 ≦ (W2 / W1) ≦ 0.8.

  In addition to the circumferential groove 20, a plurality of lug grooves 30 extending in the tire width direction are provided on the tread surface 3. As the lug groove 30, a center lug groove 31, an intermediate lug groove 35, and a shoulder lug groove 36 are provided. Of these, the center lug groove 31 is disposed between the pair of inner circumferential grooves 21 in the tire width direction, and the lug groove 30 is connected at both ends 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 are connected to the inner circumferential groove 21 and the outer circumferential groove 25. Lug groove 30. The shoulder lug groove 36 is disposed outside the outer circumferential groove 25 in the tire width direction, and serves as a lug groove 30 having one end connected to the outer circumferential groove 25. A plurality of each 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 a range from 4 mm to 9 mm, and a groove depth in a range from 10 mm to 18 mm. The intermediate lug groove 35 has a groove width in a range from 4 mm to 9 mm, and a groove depth in a range from 2 mm to 16 mm. The shoulder lug groove 36 has a groove width in the range of 8 mm to 16 mm and a groove depth in the range of 2 mm to 16 mm.

  The center lug groove 31 and the intermediate lug groove 35 are connected to the common inner circumferential groove 21, but the position in the tire circumferential direction of the portion connected to the inner circumferential groove 21 is the center lug groove 31 and the intermediate lug It differs from the groove 35. Similarly, the intermediate lug groove 35 and the shoulder lug groove 36 are connected to the common outer circumferential groove 25, but the position in the tire circumferential direction of the portion connected to the outer circumferential groove 25 is the intermediate lug groove 35. And the shoulder lug groove 36 are different.

  In the land portion 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 the land portion 10 defined by the adjacent center lug groove 31 and the pair of inner circumferential grooves 21, whereby the center block 11 is placed on the tire equatorial plane CL. positioned. The intermediate block 12 is a land portion 10 defined by adjacent inner circumferential grooves 21 and outer circumferential grooves 25 and adjacent intermediate lug grooves 35. Further, the shoulder block 13 is provided outside the outer circumferential groove 25 in the tire width direction, is defined by the adjacent shoulder lug groove 36, and has an inner portion in the tire width direction defined by the outer circumferential groove 25. It is part 10. A plurality of each of the center block 11, the intermediate block 12, and the shoulder block 13 are provided side by side in the tire circumferential direction.

  FIG. 4 is a detailed view of a portion C in FIG. The center lug groove 31 among the lug grooves 30 defining the land portion 10 has a circumferentially extending portion 33 extending in the tire circumferential direction by bending at a plurality of positions. Specifically, one center lug groove 31 has two bent portions 32, which are bent portions, and is formed in a crank shape by bending at the two bent portions 32. The center lug groove 31 is formed as a circumferentially extending portion 33 at a position sandwiched between the two bent portions 32. The circumferentially extending portion 33 is formed on the tire equatorial plane CL. The circumferentially extending portion 33 may be inclined in the tire width direction with respect to the tire circumferential direction, or may be inclined in the tire width direction within a range of ± 10 ° with respect to the tire circumferential direction. .

  Further, in the center lug groove 31, a portion connecting the end of the circumferentially extending portion 33 and the inner circumferential groove 21, that is, a portion connecting the bent portion 32 and the inner circumferential groove 21 is extended in the width direction. It is the existing part 34. The width direction extending portions 34 are provided at two places of each center lug groove 31, and the two width direction extending portions 34 are different from each other in a bent portion 32 and a pair of inner circumferential grooves 21. The inner circumferential groove 21 is connected. The two widthwise extending portions 34 extend in the tire width direction and are inclined in the same direction in the tire circumferential direction. The inclination angles of the two width-direction extending portions 34 with respect to the tire width direction are substantially the same.

  A cutout 40 is connected to the center lug groove 31 near the bent portion 32. The notch 40 has one end connected to the center lug groove 31 and the other end terminated in the center block 11. Different notches 40 are connected to each of the two bent portions 41 in the center lug groove 31, whereby two notches 40 are connected to one center lug groove 31. Specifically, the cutout portion 40 extends from the bent portion 41 in the tire width direction opposite to the direction in which the width direction extending portion 34 extends from the bent portion 41 in the tire width direction. That is, the notch 40 is bent in the direction of the inner circumferential groove 21 different from the inner circumferential groove 21 to which the widthwise extending portion 34 extending from the bent portion 41 to which the notch 40 is connected is connected. It extends from the part 41. At that time, the notch portion 40 is formed in the tire circumferential direction in the same direction as the direction in which the width direction extending portion 34 is inclined in the tire circumferential direction while extending in the tire width direction from the bent portion 41 toward the inner circumferential groove 21. , And is inclined while extending from the bent portion 41 in the tire width direction.

  The notch 40 is bent toward the tire circumferential direction at a predetermined position extending in the tire width direction from the bent portion 32 of the center lug groove 31. Specifically, the two notches 40 connected to one center lug groove 31 extend from the bent portions 41, which are the bent portions of the respective notches 40, in directions extending in mutually opposite directions in the tire circumferential direction. It is bent. In other words, the two notch portions 40 are bent at the portions located on the side of the end portion 42 terminating in the center block 11 from the bent portion 41 in directions opposite to each other in the tire circumferential direction.

  In the notch portion 40, the circumferentially extending portion 43, which is a portion between the end portion 42 and the bent portion 41 that terminates in the center block 11, has an inclination angle in the tire width direction with respect to the tire circumferential direction. , 0 ° or more and 20 ° or less. Further, the direction in which the circumferentially extending portion 43 of the notch portion 40 is inclined in the tire width direction is preferably inclined in the direction from the bent portion 41 to the outside in the tire width direction. Note that the notch 40 may be bent at two or more positions, as long as one notch 40 is bent at at least one position.

  The pneumatic tire 1 according to the present embodiment has a ground contact area ratio in a center area CA in which the center block 11 and the center lug groove 31 are mainly defined by the center lug grooves 31 on both sides in the tire circumferential direction. Is formed in the range of 30% or more and 70% or less. The center area CA in this case is an area of 10% of the width W of the center block 11 in the tire width direction with the center block center BC being the center of the center block 11 in the tire width direction. That is, the center area CA is an area that is 5% of the width W of the center block 11 in the tire width direction on both sides in the tire width direction from the center block center BC.

  Further, the center block center BC in this case refers to the center position in the tire width direction between the outermost portions in the tire width direction on both sides of the center block 11 in the tire width direction. In the pneumatic tire according to the present embodiment, the center block center BC is located on the tire equatorial plane CL, and the center block center BC has the same position in the tire width direction as the tire equatorial plane CL. ing. The width W of the center block 11 is the distance in the tire width direction between the outermost portions in the tire width direction on both sides of the center block 11 in the tire width direction.

  The ground contact area ratio refers to the area of the tread surface 3 that actually touches the area of the center area CA. The circumferentially extending portion 33 of the center lug groove 31 is located in the center area CA, and the notch 40 has a bent portion 41 located outside the center area CA in the tire width direction. It is bent at a position outside the center area CA in the width direction. When the pneumatic tire 1 actually touches the ground, the pneumatic tire 1 is touched at any position on the tire circumferential direction, and the contact area ratio is different for each contacted portion. Also, the ground contact surface ratio in the center area CA is in the range of 30% or more and 70% or less. Further, it is preferable that the ground contact surface ratio in the center region CA is preferably in a range of 40% or more and 60% or less.

  FIG. 5 is a detailed view of the center block shown in FIG. In the center block 11, the center area length AL, which is the length of the portion of the center block 11 located in the center area CA in the tire circumferential direction, is at least 25% of the length L of the center block 11 in the tire circumferential direction. It is formed within a range of 40% or less. In this case, the center area length AL is the distance in the tire circumferential direction between the most distant parts in the tire circumferential direction of the part located in the center area CA in the center block 11. Further, the length L of the center block 11 is a distance in the tire circumferential direction between portions of the center block 11 that are farthest apart in the tire circumferential direction.

  The circumferential extension 33 of the center lug groove 31 has a length GL in the tire circumferential direction within a range of 50% or more and 70% or less of the center area length AL. The length GL of the circumferentially extending portion 33 is a distance in the tire circumferential direction between both ends of the circumferentially extending portion 33 in the tire circumferential direction regardless of the inclination angle of the circumferentially extending portion 33 with respect to the tire circumferential direction. It has become.

  The center block 11 is formed such that the width W in the tire width direction is in the range of 20% or more and 40% or less of the tread development width TW. In this case, the tread development width TW is the tread portion 2 when the pneumatic tire 1 is rim-assembled into a specified rim, air is filled into the pneumatic tire 1 at a specified internal pressure, and no load is applied. It refers to the linear distance between both ends in the tire width direction in the developed view.

  The specified rim refers to an “applied rim” specified by JATMA, a “Design Rim” specified by TRA, or a “Measuring Rim” specified by ETRTO. The specified internal pressure refers to the “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. The width W of the center block 11 in the tire width direction is preferably in the range of 25% to 35% of the tread development width TW.

  The center block 11 is formed such that the ratio of the length L in the tire circumferential direction to the width W in the tire width direction is within a range of 0.9 ≦ (L / W) ≦ 1.1. That is, the center block 11 is formed in a shape in which the length L in the tire circumferential direction is 0.9 times or more and 1.1 times or less the width W in the tire width direction.

  The area of the center block 11 is larger than the areas of the intermediate block 12 and the shoulder block 13. In other words, the intermediate block 12 and the shoulder block 13 have a smaller area than the center block 11. For example, the shoulder block 13 has an area within a range of 40% to 60% of the area of the center block 11. It is formed. The area of the shoulder block 13 with respect to the area of the center block 11 is preferably 45% or more and 55% or less.

  The center block 11 is formed such that the width W in the tire width direction is in the range of 25% to 45% of the maximum belt width BW which is the maximum width of the belt layer 7 in the tire width direction. Here, the maximum belt width BW is such that the position in the tire width direction is the outermost side at each end on both sides in the tire width direction of the plurality of belts 71, 72, 73, 74 constituting the belt layer 7. It is the distance between the ends in the tire width direction. The width W of the center block 11 in the tire width direction with respect to the maximum belt width BW is preferably within a range of 30% or more and 40% or less.

  The pneumatic tire 1 according to the present embodiment configured as described above is used for a heavy-duty pneumatic tire. When the pneumatic tire 1 is mounted on a vehicle, the pneumatic tire 1 is mounted on the vehicle in a state where the rim is assembled with a rim wheel and inflated. The pneumatic tire 1 mounted on a rim wheel is mounted on a large vehicle such as a truck or a bus and used.

  When the vehicle equipped with the pneumatic tire 1 travels, the pneumatic tire 1 rotates while the tread surface 3 located below the tread surface 3 contacts the road surface. The vehicle travels by transmitting a driving force or a braking force to the road surface or generating a turning force by a frictional force between the tread surface 3 and the road surface. For this reason, the contact area in the contact area of the pneumatic tire 1 is an important factor for the steering stability during running of the vehicle. On the other hand, when traveling on a wet road surface in rainy weather or the like, it is necessary to drain the water between the tread surface 3 and the road surface by the circumferential grooves 20 and the lug grooves 30 to secure the grounding property of the tread surface 3. Therefore, the groove area in the ground region is also an important factor.

  In a large vehicle such as a truck or a bus, the total weight of the vehicle changes greatly depending on the loading state of the cargo, and accordingly, the load acting on the pneumatic tire 1 also changes greatly. When the load acting on the pneumatic tire 1 changes greatly, the shape of the contact area of the pneumatic tire 1 changes, and the contact area increases as the load increases. That is, as the load acting on the pneumatic tire 1 increases, the contact area of the pneumatic tire 1 increases in both the tire width direction and the tire circumferential direction.

  However, the vicinity of the center of the tread surface 3 in the tire width direction, that is, the vicinity of the tire equatorial plane CL on the tread surface 3 is in contact with the ground when the vehicle runs, regardless of the magnitude of the load acting on the pneumatic tire 1. In the pneumatic tire 1 according to the present embodiment, the inner circumferential grooves 21 are provided on both sides of the tire equatorial plane CL, and the center block 11 is located on the tire equatorial plane CL. The area is secured. Thereby, irrespective of the magnitude of the load acting on the pneumatic tire 1, steering stability when traveling on a dry road surface can be ensured.

  In addition, since the center lug groove 31 has the circumferentially extending portion 33 on the tire equatorial plane CL by bending at a plurality of positions, drainage near the tire equatorial plane CL is ensured. Thereby, regardless of the magnitude of the load acting on the pneumatic tire 1, it is possible to ensure drainage when traveling on a wet road surface. Further, since the circumferential extension portion 33 is formed in the center lug groove 31 and the circumferential extension portion 43 is also formed in the notch portion 40 connected to the center lug groove 31, the vicinity of the tire equatorial plane CL , The edge component in the tire width direction can be increased. Thereby, the skid of the pneumatic tire 1 with respect to the slip at the time of acceleration can be reduced, and the steering stability when traveling on a wet road surface can be improved.

  Furthermore, since the tread surface 3 has a contact area ratio of 30% or more and 70% or less in the center area CA, regardless of the magnitude of the load acting on the pneumatic tire 1, the tread surface 3 travels on a dry road surface. An area can be ensured and drainage can be ensured. In other words, when the contact area ratio in the center area CA is less than 30%, the contact area when the load is small becomes small, so that it becomes difficult to ensure steering stability, and the contact area ratio in the center area CA becomes 70%. %, The groove area becomes small when the load is small, and it becomes difficult to ensure drainage. On the other hand, in the pneumatic tire 1 according to the present embodiment, the load acting on the pneumatic tire 1 is small because the contact area ratio in the center area CA is formed in the range of 30% or more and 70% or less. In this case, it is possible to secure drainage while securing a ground contact area. As a result, both dry performance and wet performance can be improved regardless of the loading state of cargo, that is, regardless of whether the vehicle is empty or loaded, and in particular, the dry performance and wet performance when the vehicle is empty are improved. be able to.

  Further, since the circumferentially extending portion 33 of the center lug groove 31 is located in the center area CA, the groove area in the center area CA is secured when the center block 11 located on the tire equatorial plane CL is provided. can do. Thereby, when the center block 11 is disposed on the tire equatorial plane CL, the dry performance when the vehicle is empty is ensured, and the drainage when the vehicle is empty can be ensured. As a result, both dry performance and wet performance can be more reliably improved.

  Also, since the center area length AL of the center block 11 is not less than 25% and not more than 40% of the length L of the center block in the tire circumferential direction, it is necessary to secure a desired contact area in the center area CA. Accordingly, the ground area ratio in the center area CA can be more reliably set in the range of 30% or more and 70% or less. As a result, both dry performance and wet performance can be more reliably improved.

  Further, since the length GL in the circumferential direction of the tire is 50% or more and 70% or less of the center area length AL of the center block 11, the circumferentially extending portion 33 of the center block 11 reduces the groove area in the center area CA. A desired size can be ensured, and the ground contact area ratio in the center region CA can be more reliably set in the range of 30% or more and 70% or less. As a result, both dry performance and wet performance can be more reliably improved.

  In the two notches 40 connected to one center lug groove 31, the portions located on the side of the end portion 42 that terminates in the center block 11 from the bent portion 41 are opposite to each other in the tire circumferential direction. , The drainage by the notch portion 40 can be ensured regardless of the rotation direction of the pneumatic tire 1. As a result, the wet performance when the vehicle is empty can be improved regardless of the rotation direction of the pneumatic tire 1.

  In addition, since the notch portion 40 is bent at a position outside the center region CA in the tire width direction, it is possible to secure drainage while suppressing a decrease in the ground contact area of the center region CA. As a result, both dry performance and wet performance can be more reliably improved.

  Further, since the inner circumferential groove 21 extends in the tire circumferential direction while oscillating in the tire width direction, the groove area near the end in the tire width direction of the ground contact area in the empty condition is secured while maintaining the groove area in the tire width direction. And the contact area with respect to both the tire and the tire circumferential direction can be improved. Further, the inner circumferential groove 21 is formed such that the overlapping amount L1 of the opposing groove walls 22 when viewed in the tire circumferential direction is 0 mm or more and 5 mm or less. Can be more reliably improved. As a result, dry performance and wet performance when the vehicle is empty can be more reliably improved.

  Further, since the outer circumferential groove 25 extends in the tire circumferential direction while oscillating in the tire width direction, the tire width in the ground contact area in the loading condition or when the pneumatic tire 1 is mounted on the front wheel side of the vehicle. The edge component and the contact area in both the tire width direction and the tire circumferential direction can be improved while securing the groove area near the end in the direction. Further, since the outer circumferential groove 25 is formed such that the overlapping amount L2 of the opposed groove walls 26 when viewed in the tire circumferential direction is 1 mm or more and 5 mm or less, the outer circumferential groove 25 is formed in the tire width direction and the tire circumferential direction. Can be more reliably improved. As a result, the dry performance and the wet performance during loading can be more reliably improved.

  In addition, the inner circumferential groove 21 and the outer circumferential groove 25 have an overlapping amount L1 between opposing groove walls 22 of the inner circumferential groove 21 and an overlapping amount L2 between opposing groove walls 26 of the outer circumferential groove 25. Are formed so as to satisfy the relationship of L1 ≦ L2, so that drainage at a position near the center area CA can be ensured. As a result, it is possible to more reliably improve the wet performance when the vehicle is empty while improving the dry performance.

  Further, the relationship between the groove width W1 of the inner circumferential groove 21 and the groove width W2 of the outer circumferential groove 25 is 0.5 ≦ (W2 / W1) ≦ 0 between the inner circumferential groove 21 and the outer circumferential groove 25. 9, the groove area near the center area CA can be ensured, and the drainage property can be sufficiently exhibited. As a result, it is possible to more reliably improve the wet performance when the vehicle is empty while improving the dry performance.

  Further, since the center block 11 is formed so that the width W in the tire width direction is equal to or more than 20% and equal to or less than 40% of the tread development width TW, the area of the center block 11 is secured while ensuring the groove area of the center area CA. Can be greatly increased. As a result, it is possible to more reliably improve the dry performance while ensuring the wet performance.

  The center block 11 is formed so that the ratio of the length L in the tire circumferential direction to the width W in the tire width direction is within a range of 0.9 ≦ (L / W) ≦ 1.1. The rigidity of the block 11 can be secured, and the steering stability can be secured. That is, if (L / W) is less than 0.9 or larger than 1.1, the rigidity of the center block 11 in the tire circumferential direction and the rigidity in the tire width direction may be too low. 11 is likely to fall, and the effective ground contact area of the center block 11 may be reduced. On the other hand, by setting the ratio of the length L in the tire circumferential direction of the center block 11 to the width W in the tire width direction to fall within a range of 0.9 ≦ (L / W) ≦ 1.1, Since the rigidity of the center block 11 can be ensured, a decrease in the effective ground contact area of the center block 11 can be suppressed. As a result, both dry performance and wet performance can be more reliably improved.

  Further, since the area of the shoulder block 13 is formed within a range of 40% or more and 60% or less of the area of the center block 11, when the vehicle is vacant, the frequency of contact with the shoulder area is lower than that of the center area CA. The groove area can be secured, and drainage can be secured. In addition, by increasing the area of the center block 11 with respect to the area of the shoulder block 13, the rigidity of the center block 11 can be ensured. Thereby, it is possible to suppress a decrease in the effective contact area of the center block 11 due to the low rigidity of the center block 11. As a result, both dry performance and wet performance can be more reliably improved.

  Further, since the center block 11 is formed such that the width W in the tire width direction is in the range of 25% to 45% of the maximum belt width BW, the center block 11 is centered on the center area CA in the tire width direction. The width of the belt layer 7 can be optimized in a region where the ground pressure is high. Thereby, the rigidity of the tread portion 2 in the tire width direction can be made uniform. As a result, the steering stability can be improved regardless of the traveling state of the vehicle.

  Further, since a steel carcass material is used for the carcass 6, the rigidity of the entire pneumatic tire 1 can be ensured. As a result, the steering stability can be improved regardless of the traveling state of the vehicle.

  Also, by using the pneumatic tire 1 according to the present embodiment as a heavy-duty pneumatic tire, even when the load acting on the pneumatic tire 1 changes greatly depending on the loaded state of the cargo, regardless of the magnitude of the load, Both dry performance and wet performance can be improved. As a result, the running performance of the vehicle when the pneumatic tire 1 according to the present embodiment is mounted on a large vehicle such as a truck or a bus can be improved.

〔Example〕
6A to 6E are tables showing the results of performance tests on pneumatic tires. Hereinafter, performance evaluation tests performed on the above-described pneumatic tire 1 with respect to the conventional pneumatic tire 1 and the pneumatic tire 1 according to the present invention will be described. The performance evaluation test was conducted on a test on dry acceleration performance, which is acceleration performance on a dry road surface, and on a test on wet acceleration performance, which is acceleration performance on a wet road surface.

  In these performance evaluation tests, a pneumatic tire 1 with a nominal size of 275 / 80R22.5 and a load index of 151 J specified by JATMA was assembled on a rim wheel of a specified rim specified by JATMA, and the air pressure was reduced. The test was performed by adjusting to the maximum air pressure specified by JATMA, and mounted on a 2-D test vehicle (tractor head) for test running.

  Regarding the evaluation method of each test item, the dry acceleration performance was evaluated by measuring acceleration in a speed section of 5 to 40 km / h on a dry road surface and indexing the average acceleration. The larger the value, the better the dry acceleration performance. The wet acceleration performance was evaluated by measuring acceleration in a speed section of 5 to 40 km / h on a wet road surface having a depth of 2 mm and indexing the average acceleration. The higher the value, the better the wet acceleration performance. Further, when the dry acceleration performance and the wet acceleration performance each have an index of 105 or more, it is assumed that they have effective performance.

  The evaluation test was conducted on the pneumatic tires 1 of Conventional Examples 1 to 5 which are examples of the conventional pneumatic tire 1 and the 26 types of pneumatic tires 1 of Examples 1 to 21 which are the pneumatic tires 1 according to the present invention. went. These pneumatic tires 1 are provided in the center block 11 as to whether the center lug groove 31 is bent, whether the circumferential groove 20 is oscillating in the tire width direction, the contact area ratio in the center area CA, and the center block 11. The shapes of the notches 40 are different from each other. Among them, in the pneumatic tires 1 of Conventional Examples 1 to 5, the center lug groove 31 is not bent, the circumferential groove 20 is not oscillated, or the ground contact area ratio in the center area CA is 30% or more and 70% or more. % Or less, or the notch 40 is formed without bending.

  In contrast, in Examples 1 to 21 which are examples of the pneumatic tire 1 according to the present invention, the center lug groove 31 is bent, the circumferential groove 20 is oscillated, and the ground contact area ratio in the center area CA is reduced. It is in the range of 30% or more and 70% or less, and the notch portion 40 is formed to be bent. Further, the pneumatic tire 1 according to Examples 1 to 21 has the ratio of the length GL of the circumferentially extending portion 33 of the center lug groove 31 to the center area length AL, the bent position of the notch 40, and the inner circumference. Of the overlapping amount L1, L2 of the respective groove walls 22, 26 when the direction groove 21 and the outer circumferential groove 25 are viewed in the tire circumferential direction, and the widths W1, W2 of the inner circumferential groove 21 and the outer circumferential groove 25. Relative relationship, ratio of width W of center block 11 to tread development width TW, aspect ratio of center block 11, ratio of area of shoulder block 13 to area of center block 11, ratio of width W of center block to maximum belt width BW But each is different.

  As a result of an evaluation test performed using these pneumatic tires 1, as shown in FIGS. And the wet acceleration performance were both improved. That is, the pneumatic tire 1 according to Examples 1 to 21 can improve both dry performance and wet 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 8 Inner liner 10 Land part 11 Center block 12 Intermediate block 13 Shoulder block 20 Circumferential groove 21 Inner circumferential groove 22, 26 groove Wall 25 outer circumferential groove 30 lug groove 31 center lug groove 32 bent portion 33 circumferentially extending portion 34 widthwise extending portion 35 intermediate lug groove 36 shoulder lug groove 40 notch portion 41 bent portion 42 end portion 43 circumferentially extending Existing part 50 Bead part CL Tire Equatorial plane CA Center area

Claims (14)

A pair of inner circumferential grooves disposed on both sides of the tire equatorial plane in the tire width direction with the tire equatorial plane interposed therebetween and extending in the tire circumferential direction;
A pair of outer circumferential grooves disposed outside each of the pair of inner circumferential grooves in the tire width direction and extending in the tire circumferential direction,
A plurality of lug grooves having both ends connected to the pair of inner circumferential grooves and having a circumferentially extending portion extending in the tire circumferential direction by bending at a plurality of positions,
A center block that is a land portion defined by the lug groove and the inner circumferential groove,
A notch portion having one end connected to the lug groove, the other end terminating in the center block, and bending at least one place;
With
The center area of the center block in the tire width direction is the center, and the contact area ratio in the center region, which is a region of 10% of the width of the center block in the tire width direction, is 30% or more and 70% or less. Pneumatic tire.   The pneumatic tire according to claim 1, wherein the circumferentially extending portion is located in the center region.   The center region length, which is the length of the portion of the center block located in the center region in the tire circumferential direction, is 25% or more and 40% or less of the length of the center block in the tire circumferential direction. Or the pneumatic tire according to 2.   The pneumatic tire according to claim 3, wherein the circumferential extension has a length in the tire circumferential direction of 50% or more and 70% or less of the length of the center region. Two notches are connected to one lug groove,
5. The two notch portions, wherein portions located on the end side ends in the center block from the bent portion are bent in directions opposite to each other in the tire circumferential direction. 6. The pneumatic tire according to any one of the preceding claims.   The pneumatic tire according to any one of claims 1 to 5, wherein the notch is bent at a position outside the center region in a tire width direction.   The inner circumferential groove extends in the tire circumferential direction while oscillating in the tire width direction, and an overlapping amount of the opposed groove walls when viewed in the tire circumferential direction is 0 mm or more and 5 mm or less. 7. The pneumatic tire according to any one of 6.   The outer circumferential groove extends in the tire circumferential direction while oscillating in the tire width direction, and an amount of overlap between opposed groove walls when viewed in the tire circumferential direction is 1 mm or more and 5 mm or less. The pneumatic tire according to any one of claims 7 to 10. The inner circumferential groove and the outer circumferential groove both extend in the tire circumferential direction while oscillating in the tire width direction,
An overlapping amount L1 of the opposed groove walls of the inner circumferential groove when viewed in the tire circumferential direction;
The overlap amount L2 between the opposed groove walls of the outer circumferential groove when viewed in the tire circumferential direction is:
The pneumatic tire according to any one of claims 1 to 8, which satisfies a relationship of L1 ≦ L2.   The relationship between the groove width W1 of the inner circumferential groove and the groove width W2 of the outer circumferential groove is 0.5 ≦ (W2 / W1) ≦ 0.9 between the inner circumferential groove and the outer circumferential groove. The pneumatic tire according to any one of claims 1 to 9, wherein   The pneumatic tire according to any one of claims 1 to 10, wherein the center block has a width in a tire width direction of 20% or more and 40% or less of a tread development width.   12. The center block according to claim 1, wherein a ratio of a length L in a tire circumferential direction and a width W in a tire width direction is 0.9 ≦ (L / W) ≦ 1.1. 13. The pneumatic tire as described. Outside the outer circumferential groove in the tire width direction, a shoulder block that is a land portion whose inner portion in the tire width direction is partitioned by the outer circumferential groove is provided.
The pneumatic tire according to any one of claims 1 to 12, wherein an area of the shoulder block is 40% or more and 60% or less of an area of the center block.   The pneumatic tire according to any one of claims 1 to 13, wherein the pneumatic tire is used for a heavy load pneumatic tire.

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