JP2019137088A - Pneumatic tire - Google Patents

Abstract

To improve the on-ice and on-snow performances of a pneumatic tire while maintaining uneven wear resistance.SOLUTION: A pneumatic tire includes: plural circumferential grooves provided to extend in a tire circumferential direction and to line in plural pieces in a tire width direction; plural lug grooves 24 provided to extend in a direction crossing with the circumferential groove and to line in the tire circumferential direction; and a block row partitioned by plural circumferential grooves. The block row has plural blocks B11 to B14 partitioned by plural lug grooves 24 and the circumferential grooves. The first-to-fourth blocks B11 to B14 lining continuously in the tire circumferential direction have notch parts BK11 to BK14, respectively, and the longitudinal direction of the notch parts BK11 to BK14 faces the tire circumferential direction. The plural blocks B11 to B14 having the notch parts BK11 to BK14 different from each other in size line in the circumferential direction alternately in the magnitude of the notch parts BK11 to BK14.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire.

  Patent Literature 1 is known as a pneumatic tire that improves the performance on ice and the performance on snow while suppressing the occurrence of uneven wear.

Japanese Patent No. 4510906

  The pneumatic tire described in Patent Document 1 is an adjustment of the ratio of the contact width of each land portion of the tread, and improves the balance between the performance on ice and the performance on snow while suppressing the occurrence of uneven wear. There is room for.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving the performance on ice and the performance on snow while maintaining the uneven wear resistance.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to an aspect of the present invention includes a plurality of circumferential grooves that extend in the tire circumferential direction and are arranged in the tire width direction, A plurality of lug grooves extending in a direction intersecting the circumferential groove and arranged in the tire circumferential direction; and a block row partitioned by the plurality of circumferential grooves, wherein the block row A plurality of blocks partitioned by the lug groove and the circumferential groove, wherein in the plurality of blocks, the first to fourth blocks arranged continuously in the tire circumferential direction each have a notch, A longitudinal direction of the notch portion is directed to the tire circumferential direction, the notch portion of the second block is larger than the notch portion of the first block, and the third block is not less than the notch portion of the second block. Notch in block It is small, it is larger in the notch of the third of the fourth block from the notch of the block.

  The ground area of the second block is smaller than the ground area of the first block, the ground area of the third block is larger than the ground area of the second block, and The ground contact area of the fourth block is preferably smaller than the ground contact area.

  The plurality of circumferential grooves preferably include a plurality of main grooves extending in the tire circumferential direction.

  The ratio of the maximum distance in the tire width direction between the block rows located on both sides of the main groove in the tire width direction to the see-through width of the main groove is 1.2 to 2.4, and the see-through width of the main groove Is 4 mm or more and 8 mm or less, and the ground contact area of the center block row located between the two main grooves closest to the tire equator plane and the space between the main groove closest to the tire ground contact edge and the tire ground contact edge The relationship between the ground contact area of the shoulder block row located at the center block row and the ground contact area of the middle block row located between the center block row and the shoulder block row is greater than the ground contact area of the middle block row. Preferably, the ground contact area is large, and the ground contact area of the center block row is larger than the ground contact area of the shoulder block row.

  The plurality of circumferential grooves preferably include two main grooves extending in the tire circumferential direction and narrow grooves provided between the two main grooves and extending in the tire circumferential direction.

  In the first and second block rows that are partitioned by the two main grooves and the narrow grooves and are adjacent in the tire width direction, lug grooves that partition each block of the first block row in the tire circumferential direction; and The lug groove that divides each block of the second block row in the tire circumferential direction extends in a different direction with respect to the tire width direction and is in a position shifted in the tire circumferential direction. Is preferred.

  Among the plurality of main grooves, a center block row positioned between two main grooves closest to the tire equatorial plane, and positioned between the main groove closest to the tire ground contact edge and the tire ground contact edge A shoulder block row, and a middle block row positioned between the center block row and the shoulder block row, wherein the plurality of lug grooves included in the center block row are in the same direction with respect to the tire width direction. The middle block row is provided between the two main grooves and is partitioned by narrow grooves extending in the tire circumferential direction and adjacent to each other in the tire width direction. In the block row, the lug groove that partitions each block of the first block row in the tire circumferential direction and the lug groove that partitions each block of the second block row in the tire circumferential direction are tire width directions It extends inclined in different directions with respect to, and is preferably in the position shifted in the tire circumferential direction.

  The inclination angle of the lug groove with respect to the tire width direction is preferably 10 degrees or more and 25 degrees or less.

  The narrow groove is preferably inclined with respect to the tire circumferential direction.

  The groove depth of the narrow groove is preferably 70% or more and 80% or less of the groove depth of the main groove.

  The groove depth of the lug groove is preferably 60% or more and 90% or less of the groove depth of the main groove.

  The notch has a step portion located between the tread tread surface and the bottom of the main groove in the tire meridional section, and the main groove with respect to the height from the bottom of the main groove to the tread tread It is preferable that the ratio of the height in the tire radial direction from the groove bottom to the step portion is from 0 to 0.7.

  The plurality of lug grooves include a first lug groove and a second lug groove having different groove widths, and the first lug grooves and the second lug grooves are alternately arranged in the tire circumferential direction. It is preferable.

  It is preferable that the block includes an open sipe and a closed sipe provided in a portion divided by the open sipe, and the open sipe has a three-dimensional shape.

  The open sipe has four or more bent portions in the tire width direction and four or more bent portions in the groove depth direction, and the groove depth of the open sipe is the groove of the main groove. It is preferably 50% or more and 70% or less of the depth.

  The open sipe includes a bent portion, a groove bottom portion, and a straight portion provided between the bent portion and the groove bottom portion, and the groove bottom portion has a wider groove width than the straight portion, The open sipe preferably has a linear shape when the bent portion disappears due to wear of the block, and the groove width becomes larger than the straight portion when further worn.

  It is preferable that the closed sipe has four or more bent portions in the tire width direction, and the groove depth of the closed sipe is shallower than the groove depth of the open sipe.

  The ratio of the groove width of the lug groove to the maximum circumferential length of the block is preferably 0.15 or more and 0.3 or less.

  The length in the tire width direction of each block row is preferably 10% or more and 25% or less with respect to the tread contact width.

  The pneumatic tire according to the present invention can improve on-ice performance and on-snow performance while maintaining more uneven wear resistance.

FIG. 1 is a meridional sectional view of a pneumatic tire according to this embodiment. FIG. 2 is a plan view showing a tread surface of the pneumatic tire according to the present embodiment. FIG. 3 is a diagram for explaining the size of each notch included in an adjacent block. FIG. 4A is a diagram illustrating the relationship between the groove depth of the main groove and the notch. FIG. 4B is a diagram illustrating the relationship between the groove depth of the main groove and the notch. FIG. 5 is a diagram showing the relationship between the distance between the block rows and the see-through width of the main groove. FIG. 6A is a diagram illustrating the inclination direction of the lug groove. FIG. 6B is a diagram illustrating an inclination direction of a lug groove of a comparative example. FIG. 7 is an enlarged view of the block. FIG. 8A is a diagram illustrating the shape of an open sipe. FIG. 8B is a diagram illustrating the shape of an open sipe. FIG. 9A is a diagram illustrating an example of changes in the tread surface due to wear of a block having an open sipe. FIG. 9B is a diagram illustrating an example of changes in the tread surface due to wear of a block having an open sipe. FIG. 9C is a diagram illustrating an example of changes in the tread surface due to wear of a block having an open sipe. FIG. 9D is a diagram illustrating an example of changes in the tread surface due to wear of a block having an open sipe. FIG. 10 is a diagram for explaining the relationship between the groove width of the lug groove and the maximum circumferential length of the block.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art. Some components may not be used.

  FIG. 1 is a meridional sectional view of a pneumatic tire 1 according to this embodiment. FIG. 2 is a plan view showing a tread surface of the pneumatic tire 1 according to the present embodiment.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction means the tire width direction. Is the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire 1 and that passes through the center of the tire width of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equator line is a line along the tire circumferential direction of the pneumatic tire 1 on the tire equator plane CL. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator line.

  As shown in FIG. 1, a pneumatic tire 1 according to the present embodiment includes a tread portion 2, shoulder portions 3 on both outer sides in the tire width direction, sidewall portions 4 and bead portions that are sequentially continuous from the shoulder portions 3. 5. The pneumatic tire 1 includes a carcass layer 6 and a belt layer 7.

  The tread portion 2 is made of a rubber material (tread rubber), is exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that contacts the road surface during traveling. The tread surface 21 is provided with a plurality of (four in this embodiment) main grooves 22 extending in the tire circumferential direction. The tread surface 21 extends along the tire circumferential direction by the plurality of main grooves 22, and a plurality of ribs (in the present embodiment, five in the present embodiment) are arranged in the rib-like land portions 20ce, 20m1, 20m2, 20s1 and 20s2 (hereinafter, collectively referred to as land portion 20) are formed. The land portion 20 has a narrow groove 26 extending in the tire circumferential direction.

  As shown in FIG. 2, the tread surface 21 is provided with lug grooves 24 and 25 extending in a direction intersecting with the main groove 22 extending in the tire circumferential direction in each land portion 20. Thereby, the land portion 20 is divided into a plurality of blocks B in the tire circumferential direction by the lug grooves 24, 25, and the block rows 23ce, 23m1, 23m2, 23s1, 23s2 (hereinafter collectively referred to as the block row 23). Is). For this reason, the land part 20 has the block row | line | column 23 divided by the circumferential groove | channel. In the block row 23, a plurality of blocks B defined by the plurality of lug grooves 24, 25 are arranged along the tire circumferential direction, and a plurality of the block rows 23 are arranged in the tire width direction. In addition, lug grooves 29 and 30 are provided in the rib-like land portions 20s1 and 20s2 provided on the outermost side in the tire width direction. The block row 23 is provided with narrow grooves 26 extending in the tire circumferential direction. The main groove 22 and the narrow groove 26 are circumferential grooves extending in the tire circumferential direction.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. Further, the sidewall portion 4 is exposed at the outermost side in the tire width direction of the pneumatic tire 1. The bead unit 5 includes a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is a rubber material arranged in a space formed by folding the end portion in the tire width direction of the carcass layer 6 outward in the tire width direction at the position of the bead core 51.

  The carcass layer 6 is configured such that each tire width direction end portion is folded back from the tire width direction inner side to the tire width direction outer side by a pair of bead cores 51 and is wound around in a toroidal shape in the tire circumferential direction. It is. The carcass layer 6 is formed by coating a plurality of carcass cords (not shown) arranged in parallel at an angle in the tire circumferential direction with an angle with respect to the tire circumferential direction being along the tire meridian direction. The carcass cord is made of steel or organic fiber (polyester, rayon, nylon, etc.).

  The belt layer 7 has, for example, a multilayer structure in which four layers of belts 71, 72, 73, and 74 are laminated. The belt layer 7 is disposed on the outer side in the tire radial direction that is the outer periphery of the carcass layer 6 in the tread portion 2. It covers in the circumferential direction. The belts 71, 72, 73, and 74 are formed by coating a plurality of cords (not shown) arranged in parallel at a predetermined angle with respect to the tire circumferential direction with a coat rubber. The cord is made of steel or organic fiber (polyester, rayon, nylon, etc.).

  This pneumatic tire 1 is applied as a studless tire. For this reason, a closed sipe 27 and an open sipe 28 are formed on the surface of the land portion 20 constituting the tread surface 21. The closed sipe 27 and the open sipe 28 are grooves having a width of less than 1 mm.

  In FIG. 2, a block row located between the two main grooves 22 closest to the tire equatorial plane CL is referred to as a center block row 23ce. The block rows located between the main groove 22 closest to the tire ground contact edge T and the tire ground contact edge T are referred to as shoulder block rows 23s1 and 23s2. The block rows located between the center block row 23ce and the shoulder block rows 23s1, 23s2 are referred to as middle block rows 23m1, 23m2.

  The relationship between the ground contact area of the center block row 23ce, the ground contact areas of the shoulder block rows 23s1 and 23s2, and the ground contact areas of the middle block rows 23m1 and 23m2 is preferably as follows. That is, it is preferable that the ground contact area of the shoulder block row 23s1 is larger than the ground contact area of the middle block row 23m1, and that the center block row 23ce is larger than the ground contact area of the shoulder block row 23s1. Further, it is preferable that the ground contact area of the shoulder block row 23s2 is larger than the ground contact area of the middle block row 23m2, and that the center block row 23ce is larger than the ground contact area of the shoulder block row 23s2.

  The ground contact area is calculated by using the ground contact width of each block row 23 as a width based on the maximum width position of the main groove 22. The ground contact area refers to the tire width direction and the tire circumferential direction in which the tread surface 21 contacts the road surface when the pneumatic tire 1 is assembled on a regular rim and filled with a regular internal pressure and 70% of the regular load is applied. Is the area of the region.

  Further, the width Wce in the tire width direction of the center block row 23ce, the widths Wm1 and Wm2 in the tire width direction of the middle block rows 23m1 and 23m2, and the widths Ws1 and Ws2 in the tire width direction of the shoulder block rows 23s1 and 23s2 are respectively treads. It is preferably 10% or more and 25% or less with respect to the ground contact width WH. When the widths Wce, Wm1, Wm2, Ws1, and Ws2 are less than 10% of the tread contact width WH, the performance on ice and the performance on snow are improved, but the uneven wear resistance is deteriorated. The wear performance is improved, but the performance on ice and the performance on snow are deteriorated. The end portions of the respective widths Wce, Wm1, Wm2, Ws1, and Ws2 are the maximum width position of the main groove 22. Each of the widths Wce, Wm1, Wm2, Ws1, and Ws2 is a width including the narrow groove 26.

  The tread contact width is the length in the tire width direction in the contact region. The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

(Notch)
Each of the blocks B shown in FIG. 2 has one side surface adjacent to the main groove 22 and the other side surface adjacent to the narrow groove 26 among the side surfaces on both sides in the tire width direction. Each block B has a notch BK on the side surface adjacent to the main groove 22. The end of each notch BK faces the main groove 22 side.

  FIG. 3 is a diagram for explaining the size of each notch included in an adjacent block. FIG. 3 shows the region 10 in FIG. 2 in an enlarged manner. As shown in FIG. 3, the middle block row 23m2 includes a plurality of blocks such as a block B11, a block B12, a block B13, and a block B14. The middle block row 23m2 includes a row of blocks B11, B12, B13, and B14 arranged in the tire circumferential direction on the tire equatorial plane direction across the narrow groove 26, and in the tire circumferential direction on the ground contact end direction side. There are rows of blocks B21, B22, B23, and B24 arranged side by side. Each block is partitioned in the tire circumferential direction by lug grooves 24, and is partitioned in the tire width direction by main grooves 22 and narrow grooves 26, that is, grooves extending in the tire circumferential direction. Block B11, block B12, block B13, block B14 and block B21, block B22, block B23, block B24 are arranged in a staggered manner in adjacent blocks with different positions in the tire width direction and the tire circumferential direction. Yes.

  Here, assuming that block B11 is the first block, block B12 is the second block, block B13 is the third block, and block B14 is the fourth block, the first, second, third, and fourth blocks Are arranged linearly and continuously in the tire circumferential direction. The first block B11, the second block B12, the third block B13, and the fourth block B14 are, respectively, a notch BK11, a notch BK12, a notch BK13, and a notch BK14 (hereinafter collectively referred to as a notch). May be called BK). The longitudinal direction of the notch BK11, the longitudinal direction of the notch BK12, the longitudinal direction of the notch BK13, and the longitudinal direction of the notch BK14 are oriented in the tire circumferential direction.

  The lengths in the tire circumferential direction of the notch BK11, the notch BK12, the notch BK13, and the notch BK14 are a length LBK1, a length LBK2, a length LBK3, and a length LBK4. At this time, the length LBK2 is larger than the length LBK1. Further, the length LBK3 is smaller than the length LBK2. Further, the length LBK4 is larger than the length LBK3. That is, the notch BK12 of the second block B12 is larger than the notch BK11 of the first block B11, the notch BK13 of the third block B13 is smaller than the notch BK12 of the second block B12, The notch BK14 of the fourth block B14 is larger than the notch BK13 of the third block B13. The length LBK1 and the length LBK3 may be the same size or different sizes. Further, the length LBK2 and the length LBK4 may be the same size or different sizes.

  Here, paying attention to the first block B11, the second block B12, and the third block B13, the cutout part BK11 of the first block B11, the third block rather than the cutout part BK12 of the second block B12. Both cutout portions BK13 of B13 are small. When attention is focused on the second block B12, the third block B13, and the fourth block B14, the cutout portion BK12 of the second block B12 and the fourth block B14 rather than the cutout portion BK13 of the third block B13. Both of the notch portions BK14 are large. Therefore, in the middle block row 23m2, it can be said that a plurality of blocks having cutout portions having different sizes are arranged in the tire circumferential direction alternately in the size of the cutout portion BK. By adjusting the size of the notch BK, the size relationship of the ground contact area of the block can be adjusted. The ground contact area can be reduced by increasing the notch BK. The ground contact area can be increased by reducing the notch BK. By fixing the groove width of the main groove 22 and adjusting the size of the notch BK, blocks with a large ground contact area and blocks with a small ground contact area can be alternately arranged in the tire circumferential direction. That is, the grounding area of the second block B12 is smaller than the grounding area of the first block B11, the grounding area of the third block B13 is larger than the grounding area of the second block B12, and the third The grounding area of the fourth block B14 can be made smaller than the grounding area of the block B13. Therefore, the blocks B12 and B14 having large notches and the blocks B11 and B13 having small notches are alternately arranged in the tire circumferential direction, thereby improving the performance on ice while maintaining the contact area, and the portions having large notches. Maintain performance on snow. For this reason, both can be improved while balancing the performance on ice and the performance on snow.

  The above is the case where the notches are arranged alternately in the size of the first block B11, the second block B12, the third block B13, and the fourth block B14, which are linearly continuously arranged in the tire circumferential direction. However, the notches may be arranged alternately in large and small sizes in blocks that are continuously arranged in a zigzag pattern in the tire circumferential direction. For example, in FIG. 3, the block B11, the block B21, the block B12, and the block B22 are arranged in a zigzag pattern in the tire circumferential direction. As described above, the block B11, the block B21, the block B12, and the block B22 that are continuously arranged in a zigzag pattern in the tire circumferential direction may have the notch portions alternately arranged in large and small sizes. This means that for the block rows adjacent in the tire width direction, the ground contact area of the other block row can be made larger or smaller than the ground contact area of one block row.

  The above description has been given for the case of the middle block row 23m2. Similarly, for the middle block row 23m1, a plurality of blocks having cutout portions having different sizes are arranged in the tire circumferential direction alternately in the size of the cutout portions. Yes. As described above, blocks having a large notch and blocks having a small notch are alternately arranged in the tire circumferential direction, thereby improving both of the performance on ice and the performance on snow.

  Further, similarly, in the other block rows 23, a plurality of blocks having notch portions having different sizes may be arranged alternately in the tire circumferential direction in terms of the size of the notch portions. If at least one block row 23 is alternately arranged in the tire circumferential direction with respect to the size of the notch, both can be improved while balancing the performance on ice and the performance on snow.

(Shape of notch)
4A and 4B are diagrams illustrating the relationship between the groove depth of the main groove 22 and the notch BK. 4A and 4B show an example of a side surface of the block B adjacent to the main groove 22 in an enlarged manner. 4A and 4B are views showing a tire meridian cross section.

  In FIG. 4A, the block B has a notch BK. The notch BK has a shape of step ST existing between the ground contact surface of the block B and the groove bottom 22BT of the main groove 22. Therefore, the notch BK is different from a chamfered portion that may be provided on the outermost radial direction of the main groove 22. A portion along the tire radial direction from the step ST to the groove bottom 22BT becomes a boundary SS between the notch BK and the main groove 22.

  Here, the distance in the tire radial direction from the ground contact surface of the block B to the groove bottom 22BT of the main groove 22, that is, the groove depth of the main groove 22 is defined as H22. Further, the distance in the tire radial direction from the groove bottom 22BT to the notch BK is HST. At this time, the ratio HST / H22 of the distance HST to the groove depth H22 is preferably 0 or more and 0.7 or less. The value of the ratio HST / H22 is more preferably 0.1 or more and 0.5 or less. In addition, the groove depth H22 of the main groove 22 is 16 mm or more and 22 mm or less, for example.

  FIG. 4B is a diagram showing a case where the value of the ratio HST / H22 is zero. As shown in FIG. 4B, when the ratio HST / H22 of the distance HST to the groove depth H22 is 0, the position in the tire radial direction of the step ST of the notch BK and the position of the groove bottom 22BT in the tire radial direction match. To do.

  FIG. 5 is a diagram showing the relationship between the distance between the block rows and the see-through width of the main groove. As shown in FIG. 5, block rows 23 are located on both sides of the main groove 22 in the tire width direction. The main groove 22 has a see-through structure.

  The see-through structure is a structure in which a continuous space is formed when the main groove 22 is projected in the tire circumferential direction. Even if the block row 23 exists on both sides of the main groove 22 in the tire width direction, the see-through portion remains at the center position in the tire width direction. The distance in the tire width direction of the see-through portion is the groove width of the main groove 22. The ratio W / Ws of the maximum distance W in the tire width direction between the block rows 23 to the distance in the tire width direction of the see-through portion, that is, the see-through width Ws of the main groove 22 is 1.2 or more and 2.4 or less. Is preferred. The see-through width Ws of the main groove 22 is preferably 4 mm or more and 8 mm or less. When the ratio and the value of the see-through width Ws of the main groove 22 are within the above ranges, the performance on ice and the performance on snow can be improved while maintaining the uneven wear resistance.

(Inclination of lug groove)
FIG. 6A is a diagram illustrating the inclination direction of the lug groove. FIG. 6A shows an enlarged part of the block row 23m2 of FIG. In FIG. 6A, the lug grooves 241 and 242 are located on both sides in the tire width direction with the narrow groove 26 interposed therebetween. The lug groove 241 is inclined at an angle θ1 with respect to the tire width direction and extends in a direction away from the narrow groove 26. Further, the lug groove 242 is inclined at an angle θ2 with respect to the tire width direction and extends in a direction away from the narrow groove 26. The angle θ1 and the angle θ2 have different inclination directions with respect to the tire width direction. That is, the lug groove 241 that is the first lug groove and the lug groove 242 that is the second lug groove extend in a different direction with respect to the tire width direction. Further, the lug groove 241 that is the first lug groove and the lug groove 242 that is the second lug groove are not located at the same position in the tire circumferential direction but are arranged at positions shifted in the tire circumferential direction. For this reason, there is no deviation in slipperiness on ice or snow. That is, there is no unevenness of slipperiness on ice or snow in the directions of arrows Y11, Y12, Y21, and Y22.

  Here, the angle θ1 and the angle θ2 with respect to the tire width direction are preferably 10 degrees or more and 25 degrees or less, and more preferably 14 degrees or more and 20 degrees or less. The ratio θ1 / θ2 between the angle θ1 and the angle θ2 is preferably 0.95 ≦ θ1 / θ2 ≦ 1.05.

  By the way, as shown in FIG. 2, the tread surface 21 has a non-directional pattern which is not specified in the rotation direction when the vehicle is mounted. In such a non-directional pattern, in the center block row 23ce, the plurality of lug grooves 24 extend in the same direction with respect to the tire width direction, and in the middle block rows 23m1, 23m2 on both sides thereof, The plurality of lug grooves 24 are inclined and extend in different directions with respect to the tire width direction. In this example, the middle block rows 23m1 and 23m2 employ lug grooves 241 and lug grooves 242, which have different inclination directions with respect to the tire width direction, as shown in FIG. 6A. There is no unevenness of thickness. For this reason, on-ice performance and on-snow performance can be improved while maintaining uneven wear resistance.

  FIG. 6B is a diagram illustrating an inclination direction of a lug groove of a comparative example. As in the case of the lug grooves 240a and 240b shown in FIG. 6B, if the inclination direction is the same even if the angle θ3 is inclined with respect to the tire width direction, the slipperiness on ice or snow is shifted. That is, it is easier to slip in the directions of the arrows Y12 and Y21 than in the directions of the arrows Y11 and Y22.

  As a means of improving the performance on ice and the performance on snow of the studless tire, the volume of the lug groove may be increased in order to increase the snow column shear force. However, when the volume of the lug groove is increased, the block rigidity is lowered and the heel and toe wear resistance performance is lowered. A method of inclining the lug groove so that the block is difficult to fall is conceivable. However, in this method, the peak angle of the snow column shear force in the block row is biased, and it may be easy to slip in a certain direction. Thus, in the present embodiment, as described above, by reversing the lug groove inclination direction in the block row, it is possible to realize both the performance on ice and the performance on snow and the heel and toe wear resistance.

(Blocks and sipes)
FIG. 7 is an enlarged view of the block B. As shown in FIG. 7, adjacent blocks B are partitioned in the tire width direction by narrow grooves 26 that are circumferential grooves. Since adjacent blocks B are partitioned by the narrow grooves 26 in the tire width direction and divided, the force applied to the blocks B at the time of ground contact is dispersed, and uneven wear resistance is improved.

  Each block B has an open sipe 28. The open sipe 28 has one end opened in the narrow groove 26 that is a circumferential groove, and the other end opened in the main groove 22 that is a circumferential groove. The open sipe 28 preferably has four or more bent portions in the tire width direction. The open sipe 28 is not preferable when the number of bent portions in the tire width direction is less than four (that is, three or less) because the effect of suppressing the block rigidity is low and the effect of increasing the edge component is low.

  Each block B is divided into a plurality of parts by the open sipes 28. In this example, it is divided into three parts Ba, Bb and Bc by two open sipes 28. Each of the portions Ba, Bb, and Bc divided into a plurality by the open sipe 28 has a closed sipe 27.

  The closed sipe 27 has four or more bent portions in the tire width direction. Since the closed sipe 27 is provided in each of the divided parts Ba, Bb, and Bc, the open sipe 28 and the closed sipe 27 having a three-dimensional shape maintain the uneven wear resistance performance on ice and on snow. Can be improved.

  Here, it is preferable that at least a part of the open sipe 28 has a three-dimensional shape. Here, the sipe having a three-dimensional shape means that the sipe extends by bending or the like in the groove depth direction. Since the open sipe 28 has a three-dimensional shape, the decrease in block rigidity can be suppressed and the edge component can be increased, so that it is possible to improve on-ice performance and on-snow performance while maintaining uneven wear resistance performance. it can.

(Open sipe)
8A and 8B are diagrams illustrating the shape of the open sipe 28. FIG. FIG. 8A is a diagram illustrating a cross-section of the AA portion of FIG. 7. FIG. 8B is a diagram showing a cross-section of the BB part of FIG. 7. As shown in FIG. 8A, the open sipe 28 has bent portions K11, K12, K13, K14, and K15 in the depth direction. As shown in FIG. 8B, the open sipe 28 has bent portions K21, K22, K23, K24, and K25 in the depth direction. As can be understood from FIGS. 8A and 8B, the bending portions K11 and K21 have bending directions opposite to each other. Similarly, the bending directions of the bending portions K12 and K22, the bending portions K13 and K23, the bending portions K14 and K24, and the bending portions K15 and K25 are opposite to each other. The open sipe 28 preferably has four or more bent portions in the groove depth direction. The open sipe 28 is not preferable when the number of bent portions in the groove depth direction is less than four (that is, three or less) because the effect of suppressing a decrease in block rigidity is low and the effect of increasing the edge component is low.

  Further, as shown in FIG. 8A, a portion deeper than the bent portion K15 of the open sipe 28 includes a straight portion T1 that does not bend with a constant width and a groove bottom portion R1 in which the groove volume is widened. As shown in FIG. 8B, a portion deeper than the bent portion K25 of the open sipe 28 includes a straight portion T2 that does not bend with a constant width and a groove bottom R2 in which the groove volume is expanded. If the straight line portion T1 and the straight line portion T2 have the same shape, the straight line portion T1 and the straight line portion T2 of the open sipe 28 are flat spaces. If the groove bottom portion R1 and the groove bottom portion R2 are circular in the same shape, the groove bottom portion R1 and the groove bottom portion R2 of the open sipe 28 are cylindrical spaces.

  As shown in FIGS. 8A and 8B, the open sipe 28 includes a bent region HK, a straight region HT, and a groove bottom region HR. Referring to FIG. 8A, the bent region HK includes bent portions K11, K12, K13, K14, and K15. The straight line region HT includes a straight line portion T1. The groove bottom region HR includes a groove bottom R1. Referring to FIG. 8B, the bent region HK includes bent portions K21, K22, K23, K24 and K25. The straight line region HT includes a straight line portion T2. The groove bottom region HR includes a groove bottom R2.

  The depth H28 of the open sipe 28 in the tire radial direction is preferably 50% or more and 70% or less with respect to the groove depth of the main groove 22. When the groove depth of the open sipe 28 is shallower than 50% of the groove depth of the main groove 22, the uneven wear resistance performance is improved, but the performance on ice and the performance on snow are deteriorated. When the groove depth of the open sipe 28 is deeper than 70% of the groove depth of the main groove 22, the performance on ice and the performance on snow are improved, but the uneven wear resistance is deteriorated.

  The bent region HK may be formed up to a groove depth of 50% with respect to the groove depth of the main groove 22, or the entire region up to the depth H28 may be used as the bent region HK. The ratio of the depth of the bent region HK, the straight region HT, and the groove bottom region HR to the depth H28 of the open sipe 28 is not limited to the case shown in FIGS. 8A and 8B. For example, the bending region HK may be 60% or more and 80% or less of the depth H28. Further, the straight region HT may be 0.5% or more and 2% or less of the depth H28. The total depth of the straight region HT and the groove bottom region HR may be 70% or more and 90% or less of the depth H28.

(Block wear)
9A to 9D are diagrams showing examples of changes in the tread due to wear of the block B having the open sipe 28 adopting the shape shown in FIGS. 7, 8A and 8B. FIG. 9A is a diagram showing a state in which the block B is worn by 0% or more and less than 40% with respect to the groove depth of the main groove 22. Referring to FIG. 9A, since the wear of the block B is in the initial stage, the shapes of both the open sipe 28 and the closed sipe 27 can be confirmed.

  FIG. 9B is a diagram showing a state in which the block B is worn by 40% or more and less than 50% with respect to the groove depth of the main groove 22. 9B, the shape of the open sipe 28 can be confirmed, but the shape of the closed sipe 27 cannot be confirmed. The groove depth of the closed sipe 27 is shallower than the groove depth of the open sipe 28, and when the groove bottom of the closed sipe 27 is worn, the shape of the closed sipe 27 cannot be confirmed as shown in FIG. 9B.

  FIG. 9C is a diagram showing a state in which the block B is worn by 50% or more and less than 55% with respect to the groove depth of the main groove 22. When wear progresses to the stage shown in FIG. 9C, the bent region HK of the open sipe 28 shown in FIGS. 8A and 8B is worn away and disappears. For this reason, at the stage shown in FIG. 9C, the open sipe 28 can confirm the straight line region HT shown in FIGS. 8A and 8B. The open sipe 28 can be confirmed not as a bent shape but as a straight shape.

  FIG. 9D is a diagram showing a state in which the block B is worn by 55% or more and 65% or less with respect to the groove depth of the main groove 22. When wear progresses to the stage shown in FIG. 9D, the open sipe 28 wears away in the straight line region HT shown in FIGS. 8A and 8B. For this reason, at the stage shown in FIG. 9D, the open sipe 28 can confirm the groove bottom region HR shown in FIGS. 8A and 8B. Since the groove bottom region HR has a groove width larger than that of the straight region HT, the open sipe 28 can be confirmed as a shape having a groove width wider than that in the stage shown in FIG. 9C.

  As described with reference to FIGS. 9A to 9D, the open sipe 28 has a linear shape when the bent portion disappears due to wear of the block B. When the open sipe 28 is further worn, the groove width becomes larger than the linear shape.

(Groove depth of open sipe and closed sipe)
If the groove depth of the closed sipe 27 is too shallow than the groove depth of the open sipe 28, the uneven wear resistance performance is improved, but the performance on ice and the performance on snow deteriorate. When the groove depth of the closed sipe 27 is too deeper than the groove depth of the open sipe 28, the performance on ice and the performance on snow are improved, but the uneven wear resistance performance is deteriorated. The groove depth of the closed sipe 27 is, for example, 5 mm or more and 15 mm or less. The groove depth of the open sipe 28 is, for example, 6 mm or more and 20 mm or less.

(Lug groove width and maximum circumferential length of block)
FIG. 10 is a diagram for explaining the relationship between the groove width of the lug groove 24 and the maximum circumferential length of the block B. FIG. In FIG. 10, the groove width of the lug groove 24 is WL, and among the plurality of blocks B, the length in the tire circumferential direction of the block having the maximum tire circumferential length, that is, the maximum circumferential length is LB. The ratio WL / LB of the groove width WL of the lug groove 24 to the maximum circumferential length LB of the block B is preferably 0.15 or more and 0.3 or less.

  When the ratio WL / LB is smaller than 0.15, the uneven wear resistance performance is improved, but the performance on ice and the performance on snow are deteriorated. When the ratio WL / LB is larger than 0.3, the performance on ice and the performance on snow are improved, but the uneven wear resistance is deteriorated. The lug groove width WL is preferably 5 mm or more and 9 mm or less.

(Narrow groove)
As shown in FIG. 10, the narrow groove 26 extends in the tire circumferential direction and partitions each block B in the tire width direction. The narrow groove 26 extends in the tire circumferential direction while changing its position in the tire width direction. That is, the narrow groove 26 extends in the tire circumferential direction while being bent in the left-right direction in the drawing. Since the narrow groove 26 is bent, it extends in the tire circumferential direction while alternately repeating a state inclined in one direction with respect to the tire circumferential direction and a state inclined in the other direction. Since the narrow grooves 26 are inclined with respect to the tire circumferential direction, an effect of supporting adjacent blocks with the narrow grooves 26 therebetween is generated, and the blocks are not easily displaced. Thereby, the uneven wear resistance performance is improved.

  The inclination angle θ of the narrow groove 26 with respect to the tire circumferential direction is preferably 10 degrees or more and 40 degrees or less. When the inclination angle θ is less than 10 degrees, the effect of supporting adjacent blocks decreases. When the inclination angle θ exceeds 40 degrees, the uneven wear resistance performance deteriorates.

  The narrow groove 26 has a groove width of, for example, 1 mm or more and 5 mm or less. The groove depth of the narrow groove 26 is preferably 70% to 80% of the main groove 22. The groove depth of the narrow groove 26 is, for example, not less than 14 mm and not more than 16 mm.

(Groove width and groove depth of lug groove)
The lug groove that divides each block included in the center block row 23ce includes a lug groove 24 having a wide groove width and a lug groove 25 having a narrow groove width. And the lug groove 24 with a wide groove width and the lug groove 25 with a narrow groove width are alternately arrange | positioned in the tire circumferential direction. The groove width of the lug groove 25 is narrower than the groove width of the lug groove 24. The groove width of the narrow lug groove 25 is approximately the same as the groove width of the narrow groove 26.

  The depth of the lug grooves 24 and 25 is preferably 60% or more and 90% or less, and more preferably 70% or more and 80% or less of the depth of the main groove 22. If the depth of the lug grooves 24 and 25 is shallower than 60% of the depth of the main groove 22, the uneven wear resistance performance is improved, but the performance on ice and the performance on snow are deteriorated. If the depth of the lug grooves 24 and 25 is deeper than 90% of the depth of the main groove 22, the performance on ice and the performance on snow are improved, but the uneven wear resistance performance is deteriorated.

(Summary)
On consecutive blocks in the block row of the tread surface of a pneumatic tire, by arranging the cutouts alternately in size and setting the contact area of each block appropriately, performance on ice and snow performance while maintaining uneven wear resistance And can be improved.

  In this example, performance tests on performance on snow (start performance on snow) and performance on ice (braking performance on ice) were performed on a plurality of types of pneumatic tires with different conditions (Tables 1 to 4). See). In all cases, pneumatic tires having four main grooves were used.

  In this performance test, a heavy-duty pneumatic tire having a tire size of 275 / 80R22.5 is assembled on a regular rim and filled with regular internal pressure, and a test vehicle of 2-D4 (front 2 wheels-rear 4 drive wheels) is tested. Attached to.

  In the performance test on snow, the above test vehicle is used to start and run on a snowy uphill road from a vehicle stopped state and evaluated with the feeling of a test driver. The evaluation result is based on a conventional pneumatic tire (100 ). The larger the index value, the better the performance on snow (start performance on snow).

  In the performance test for performance on ice, the above test vehicle is used to brake a flat surface on ice from 40 [km / h], and the braking distance from the position where the braking is applied to the position where the braking is stopped is measured. Based on this measurement result, index evaluation is performed with the conventional pneumatic tire as a reference (100). As the evaluation result is larger, the performance on ice (braking performance on ice) is better.

  For uneven wear resistance, a rim equipped with a pneumatic tire 1 was mounted on the drive shaft of the vehicle, and the amount of heel and toe wear after traveling 20,000 km was measured by a market monitor. The measurement results were indexed using a conventional pneumatic tire as a reference (100). The larger the index value, the better the performance.

  In Table 1, the tire of the conventional example is a tire in which the block does not have a notch, the ratio W / Ws = 1, and the positions of the lug grooves in the tire circumferential direction are all the same.

  In Table 1, in the tire of Comparative Example 1, the block does not have a notch, and the ratio W / Ws = 1. As described with reference to FIG. 6B, the tire of Comparative Example 1 has the same inclination direction with respect to the tire width direction of the lug groove in the block row of the center region and the middle region.

  In Table 1, in the tire of Comparative Example 2, each block has a cutout portion having the same size, and the ratio is W / Ws = 1. In the tire of Comparative Example 2, the inclination direction of the lug groove with respect to the tire width direction is the same in the block rows of the center region and the middle region. The tire of Comparative Example 2 has a narrow groove, but the narrow groove is not inclined with respect to the tire circumferential direction. In the tire of Comparative Example 2, the ratio of the groove depth of the narrow groove to the groove depth of the main groove is 60%, and the groove depth of the lug groove is 50% with respect to the groove depth of the main groove.

  The tire of Comparative Example 3 is a tire that is irregularly arranged rather than alternately arranged, although each block has a cutout portion having a different size. The tire of Comparative Example 3 has a ratio W / Ws = 1. In the tire of Comparative Example 3, the inclination direction of the lug groove with respect to the tire width direction is the same in the block row of the center region and the middle region. The tire of Comparative Example 3 has a narrow groove, but the narrow groove is not inclined with respect to the tire circumferential direction. In the tire of Comparative Example 3, the ratio of the groove depth of the narrow groove to the groove depth of the main groove is 60%, and the groove depth of the lug groove is 50% with respect to the groove depth of the main groove.

  Referring to Examples 1 to 47 in Tables 1 to 4, it can be seen that good results can be obtained when the cutouts are alternately arranged. Further, when the ratio W / Ws is 1.2 or more and 2.4 or less, when Ws is 4 mm or more and 8 mm or less, when the relationship of the contact area is center> shoulder> middle, the lug groove in the tire width direction is When the inclination direction is different, when the inclination angle of the lug groove with respect to the tire width direction is 10 degrees or more and 25 degrees or less, when the position of the lug groove in the tire circumferential direction is shifted, When there is an inclination, when the ratio of the fine groove depth to the depth of the main groove is 70% or more and 80% or less, when the ratio of the lug groove depth to the main groove depth is 60% or more and 90% or less, When the ratio of the height of the notch portion to the depth of the main groove is 0 or more and 0.7 or less, the groove width of the lug grooves is different and when they are alternately arranged, the shape of the open sipe is three-dimensional. If the open sipe has 4 bends If the ratio of the open sipe groove depth to the main groove depth is 50% or more and 70% or less, if the number of bent portions of the closed sipe is 4 or more, the closed sipe groove depth is larger than the open sipe groove depth. When the groove depth is shallow, when the ratio of the groove width of the lug groove to the maximum circumferential length of the block is 0.15 or more and 0.3 or less, the ratio of the width of the block row to the tread contact width is 10% or more and 25%. It can be seen that good results are obtained when

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Shoulder part 4 Side wall part 5 Bead part 6 Carcass layer 7 Belt layer 20 Land part 21 Tread surface 22 Main groove 23 Block row 24, 25 Lug groove 26 Narrow groove 27 Closed sipe 28 Open sipe 51 Bead core 52 Bead filler
71, 72, 73, 74 Belt B, B11-B14, B21-B24 Block BK, BK11-BK14 Notch

Claims (19)

A plurality of circumferential grooves provided in the tire circumferential direction and arranged in the tire width direction, and a plurality of lug grooves provided in the tire circumferential direction and extending in a direction intersecting the circumferential groove. And a row of blocks partitioned by the plurality of circumferential grooves,
The block row has a plurality of blocks partitioned by the plurality of lug grooves and the circumferential groove,
In the plurality of blocks, the first to fourth blocks arranged continuously in the tire circumferential direction each have a notch,
The longitudinal direction of the notch is directed to the tire circumferential direction,
The notch of the second block is larger than the notch of the first block,
The notch of the third block is smaller than the notch of the second block,
A pneumatic tire in which the cutout portion of the fourth block is larger than the cutout portion of the third block. The ground contact area of the second block is smaller than the ground contact area of the first block,
The ground contact area of the third block is larger than the ground contact area of the second block,
The pneumatic tire according to claim 1, wherein a contact area of the fourth block is smaller than a contact area of the third block.   The pneumatic tire according to claim 1, wherein the plurality of circumferential grooves include a plurality of main grooves extending in a tire circumferential direction. The ratio of the maximum distance in the tire width direction between the block rows located on both sides of the main groove in the tire width direction to the see-through width of the main groove is 1.2 to 2.4, and the see-through width of the main groove Is 4 mm or more and 8 mm or less,
The ground contact area of the center block row located between the two main grooves closest to the tire equatorial plane and the ground contact of the shoulder block row located between the main groove closest to the tire ground contact end and the tire ground contact end The relationship between the area and the ground contact area of the middle block row located between the center block row and the shoulder block row is such that the ground contact area of the shoulder block row is larger than the ground contact area of the middle block row. The pneumatic tire according to claim 3, wherein a ground contact area of the center block row is larger than a ground contact area of the row.   The plurality of circumferential grooves include two main grooves extending in the tire circumferential direction, and narrow grooves provided between the two main grooves and extending in the tire circumferential direction. 2. The pneumatic tire according to 2.   In the first and second block rows that are partitioned by the two main grooves and the narrow grooves and are adjacent in the tire width direction, lug grooves that partition each block of the first block row in the tire circumferential direction; and The lug groove that divides each block of the second block row in the tire circumferential direction extends in a different direction with respect to the tire width direction and is in a position shifted in the tire circumferential direction. Item 6. The pneumatic tire according to Item 5. Among the plurality of main grooves, a center block row positioned between two main grooves closest to the tire equatorial plane, and positioned between the main groove closest to the tire ground contact edge and the tire ground contact edge A shoulder block row, and a middle block row positioned between the center block row and the shoulder block row,
The plurality of lug grooves included in the center block row extend inclined in the same direction with respect to the tire width direction,
The middle block row is defined by a narrow groove provided between two main grooves and extending in the tire circumferential direction, and the first and second block rows adjacent to each other in the tire width direction. The lug groove that partitions each block of the block row in the tire circumferential direction and the lug groove that partitions each block of the second block row in the tire circumferential direction are inclined in different directions with respect to the tire width direction. The pneumatic tire according to claim 5, wherein the pneumatic tire is located at a position extending and deviating in the tire circumferential direction.   The pneumatic tire according to claim 7, wherein an inclination angle of the lug groove with respect to a tire width direction is 10 degrees or more and 25 degrees or less.   The pneumatic tire according to any one of claims 5 to 8, wherein the narrow groove is inclined with respect to a tire circumferential direction.   The pneumatic tire according to any one of claims 5 to 9, wherein a groove depth of the narrow groove is 70% or more and 80% or less of a groove depth of the main groove.   The pneumatic tire according to any one of claims 3 to 10, wherein a groove depth of the lug groove is 60% or more and 90% or less of a groove depth of the main groove.   The notch has a step portion located between the tread tread surface and the bottom of the main groove in the tire meridional section, and the main groove with respect to the height from the bottom of the main groove to the tread tread The pneumatic tire according to any one of claims 3 to 11, wherein a ratio of a height in a tire radial direction from the groove bottom to the step portion is 0 or more and 0.7 or less.   The plurality of lug grooves include a first lug groove and a second lug groove having different groove widths, and the first lug grooves and the second lug grooves are alternately arranged in the tire circumferential direction. The pneumatic tire according to any one of claims 3 to 12.   14. The block according to claim 3, wherein the block includes an open sipe and a closed sipe provided in a portion divided by the open sipe, and the open sipe has a three-dimensional shape. The described pneumatic tire. The open sipe has four or more bent portions in the tire width direction, and four or more bent portions in the groove depth direction,
The pneumatic tire according to claim 14, wherein the groove depth of the open sipe is 50% or more and 70% or less of the groove depth of the main groove. The open sipe includes a bent portion, a groove bottom portion, and a straight portion provided between the bent portion and the groove bottom portion, and the groove bottom portion has a wider groove width than the straight portion,
The pneumatic tire according to claim 15, wherein the open sipe becomes linear when the bent portion disappears due to wear of the block, and when further worn, the groove width becomes larger than the straight portion.   The closed sipe has four or more bent portions in the tire width direction, and the groove depth of the closed sipe is shallower than the groove depth of the open sipe. The described pneumatic tire.   The pneumatic tire according to any one of claims 3 to 15, wherein a ratio of a groove width of the lug groove to a maximum circumferential length of the block is 0.15 or more and 0.3 or less.   The pneumatic tire according to any one of claims 1 to 18, wherein a length of each block row in a tire width direction is 10% or more and 25% or less with respect to a tread contact width.

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