JP5018981B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable for winter use, and more particularly to a pneumatic tire that can improve performance on ice and performance on snow in a well-balanced manner.

  Conventionally, in winter pneumatic tires represented by studless tires, a tread portion is provided with a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction. A plurality of blocks are partitioned, and a plurality of sipes extending in the tire width direction are provided in each block (see, for example, Patent Document 1).

  In such a pneumatic tire for winter, both performance on ice and performance on snow are required. In general, when improving performance on ice, a tread pattern in which the groove area ratio in the tread portion is lowered to increase the actual ground contact area is employed. However, if the groove area ratio in the tread portion is simply lowered, the performance on snow is reduced accordingly. That is, the performance on ice and the performance on snow have a trade-off relationship, and it is extremely difficult to achieve both.

JP 2009-96220 A

  An object of the present invention is to provide a pneumatic tire capable of improving the performance on ice and the performance on snow in a balanced manner.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A plurality of longitudinal grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction are provided on the tread portion, and the longitudinal grooves and the lateral grooves are provided. In the pneumatic tire which divides a plurality of block rows composed of a plurality of blocks, one end of each of the plurality of blocks included in the block row located between the block row of the tire shoulder and the block row on the tire equator At least one first closed groove whose one end is adjacent to the block and the other end is closed in the block, and the other end adjacent to the block is the other. At least three closed groove end open type opening to the other end comprising at least two second closed groove is closed in the block provided on the groove, the shoulder side of the block in which a closed-groove The first closing groove and the second closing groove are arranged in each block provided with the first closing groove, and the second closing groove is arranged on the tire equator side of each block provided with the closing groove. Two or more kinds of angles are set as the inclination angles of the closed groove with respect to the tire width direction by making the inclination directions of the groove different with respect to the tire width direction.

In the present invention, each of the plurality of blocks included in the block row located between the block row of the tire shoulder and the block row on the tire equator , instead of the lateral groove that extends in the tire width direction and subdivides the block, At least three closing grooves of one end opening type are provided. In general, increasing the number of lateral grooves that subdivide the block to improve the performance on snow reduces the handling stability on the dry road surface and wet road surface by reducing the block rigidity, and further reduces the contact area. There is a tendency for braking performance on ice to decrease. However, when the one-end opening type closing groove as described above is provided, it is possible to avoid a decrease in steering stability on a dry road surface and a wet road surface due to a decrease in block rigidity and a decrease in braking performance on ice due to a decrease in contact area. It becomes possible to improve performance. As a result, in winter pneumatic tires represented by studless tires, it is possible to improve on-ice performance and on-snow performance in a balanced manner.

  In addition, since two or more kinds of angles are set as inclination angles with respect to the tire width direction of the closing groove in each block, there are two or more falling directions of the block in one block, and the portions that cause the falling Will support each other. Therefore, this structure also contributes to an increase in block rigidity. Further, by setting two or more angles as the inclination angles of the closing grooves with respect to the tire width direction in each block, it is possible to improve the handling stability during cornering on snow.

In the present invention, the inclination directions of the first closing groove and the second closing groove with respect to the tire width direction are different from each other in each block provided with the closing groove . As a result, sufficient block rigidity can be ensured, so that it is possible to prevent a decrease in steering stability on the dry road surface and a wet road surface, and further it is possible to prevent a decrease in performance on ice due to the collapse of the block.

In the present invention, each of the plurality of blocks included in the block row located between the block row of the tire shoulder and the block row on the tire equator is provided with the above-described closing groove, and each block provided with the closing groove is provided. At least one first closing groove is arranged on the shoulder side, and at least two second closing grooves are arranged on the tire equator side of each block provided with the closing groove . Normally, in a pneumatic tire, the driving performance on snow is demonstrated in the tire equator area of the tread, and the braking performance on ice is demonstrated in the shoulder area of the tread. Driving performance on snow is improved by arranging a relatively large number of closed grooves on the tire equator side, while block rigidity is secured by placing relatively few closed grooves on the shoulder side to ensure block rigidity. The braking performance can be improved.

  When at least two second closing grooves are arranged on the tire equator side of each block provided with the closing grooves, it is preferable that the change width of the inclination angle of the second closing grooves with respect to the tire width direction is 10 ° or less. As a result, the direction in which the snow clogged in the second closing groove is discharged becomes constant and the snow removal performance is improved, so that the performance on snow can be improved.

  In each block provided with a closing groove, the crossing angle between the first closing groove and the second closing groove is preferably 110 ° or more and 170 ° or less. Thereby, the steering stability at the time of cornering on snow can be improved, suppressing the fall of block rigidity and avoiding the fall of performance on ice.

  In the present invention, each of the plurality of blocks included in the block row adjacent to the tire shoulder block row is provided with the above-mentioned closing groove, and at least one closing groove is a transverse groove that divides the block of the tire shoulder block row; It is preferable to arrange in a communicating position. Thereby, since snow removal performance improves, on-snow performance can be improved.

  In the present invention, the above-mentioned closing groove is provided in each of the plurality of blocks included in the block row adjacent to the block row on the tire equator, and at least one closing groove is provided as a block row block on the tire equator. It is preferable to arrange at a position communicating with the transverse groove to be partitioned. Thereby, since snow removal performance improves, on-snow performance can be improved.

  It is preferable to provide a plurality of sipes extending in the tire width direction in each of the plurality of blocks included in the plurality of block rows. Thereby, favorable on-ice performance can be exhibited as a pneumatic tire for winter.

  Here, when each block provided with the closing groove is partitioned into at least three regions in the tire circumferential direction, it is preferable that the inclination directions of the sipes in these regions with respect to the tire width direction are alternately changed. Thereby, the steering stability at the time of cornering on ice can be improved.

  Also, in the tire circumferential direction both end regions of each block provided with the closing groove, the difference between the inclination angle of the sipe with respect to the tire width direction and the inclination angle with respect to the tire width direction of the lateral groove defining the block is set to 10 ° or less, and the closing groove is The difference between the inclination angle of the sipe with respect to the tire width direction and the inclination angle with respect to the tire width direction of the closing groove that inclines in the opposite direction to the lateral groove defining the block in the center region in the tire circumferential direction of each provided block is 10 ° or less. It is preferable to do. Thus, by optimizing the inclination angle of the sipe according to the inclination angle of the lateral groove and the closing groove, the sipe can be arranged at a high density and the performance on ice can be improved.

  It is preferable that the block pitch of the block row located on the tire equator side with respect to the tire shoulder block row is twice the block pitch of the tire shoulder block row. Thereby, sufficient performance on ice can be ensured.

  The present invention can be applied to a pneumatic tire in which the mounting direction of the tire front and back with respect to the vehicle is not specified, but can also be applied to a pneumatic tire having an asymmetric tread pattern in which the mounting direction of the tire front and back with respect to the vehicle is specified. is there. In a pneumatic tire having an asymmetric tread pattern in which a tire front and back mounting direction with respect to a vehicle is specified, the above-described closing groove is formed in each of a plurality of blocks included in a block row located inside the vehicle from the block row on the tire equator. Is preferably provided. Thereby, on-snow performance can be improved based on the closing grooves formed in the blocks of the block row located inside the vehicle without reducing the block rigidity on the outside of the vehicle.

  In the present invention, the closed groove is defined as a groove having a maximum groove width of 2 mm to 10 mm (preferably 3 mm to 7 mm) and a maximum groove depth of 5 mm to 10 mm. On the other hand, sipe is defined as a groove having a groove width of 1 mm or less. Further, the end of the closing groove is closed in the block, but it is allowed that a sipe having a width of 1 mm or less communicates with the closed end. Such a narrow sipe does not substantially impair the effect of occlusion.

1 is a perspective view showing a pneumatic tire according to an embodiment of the present invention. It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a top view which expands and shows the principal part of the tread pattern of the pneumatic tire of FIG. It is a top view which expands and shows the principal part of the tread pattern of the pneumatic tire of FIG. It is a top view which expands and shows the principal part of the tread pattern of the pneumatic tire of FIG. It is an expanded view which shows the tread pattern of the pneumatic tire which consists of other embodiment of this invention. It is an expanded view which shows the tread pattern of a test tire (Example 2). It is an expanded view which shows the tread pattern of a test tire (Example 4). It is an expanded view which shows the tread pattern of a test tire (comparative example 1). It is an expanded view which shows the tread pattern of a test tire (comparative example 2). It is an expanded view which shows the tread pattern of a test tire (comparative example 3). It is an expanded view which shows the tread pattern of a test tire (comparative example 4).

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show a pneumatic tire according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the pneumatic tire of the present embodiment includes a tread portion 101 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions that are disposed on both sides of the tread portion 101. 102 and a pair of bead portions 103 disposed inside the sidewall portions 102 in the tire radial direction.

  Between the pair of bead portions 103, 103, a two-layer carcass layer 104 is mounted. These carcass layers 104 include a plurality of reinforcing cords extending in the tire radial direction, and are folded back from the inside of the tire to the outside around the bead cores 105 disposed in each bead portion 103. A bead filler 106 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 105.

  On the other hand, a plurality of belt layers 107 are embedded on the outer peripheral side of the carcass layer 104 in the tread portion 101. These belt layers 107 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 107, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of 10 ° to 40 °, for example. For the purpose of improving high-speed durability, at least one belt cover layer 108 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 107. Yes.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  FIG. 3 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIGS. The pneumatic tire of the present embodiment has an asymmetric tread pattern in which the mounting direction of the front and back of the tire with respect to the vehicle is specified, IN is the inside of the vehicle, and OUT is the outside of the vehicle.

  As shown in FIG. 3, the tread portion 101 has a plurality of longitudinal grooves 1a, 1b, 1c, 1d, and 1e extending in the tire circumferential direction and a plurality of lateral grooves 2a, 2b, 2c, 2d, and 2e extending in the tire width direction. , 2f are formed, and a plurality of block rows 10, 20, 30, 40, 50, 60 are sequentially partitioned from the vehicle inner side toward the vehicle outer side by the vertical grooves 1a to 1e and the horizontal grooves 2a to 2f. The groove width and groove depth of the longitudinal groove 1 are not particularly limited. For example, the groove width is set in a range of 2 mm to 13 mm, and the groove depth is set in a range of 8 mm to 10 mm.

  The block row 10 located on the tire shoulder inside the vehicle includes a plurality of blocks 11 defined by the vertical grooves 1a and the horizontal grooves 2a. Each block 11 extends in the tire width direction and has a plurality of zigzags on the tread surface. The sipe 12 is formed.

  The block row 20 adjacent to the block row 10 includes a plurality of blocks 21 defined by the vertical grooves 1a, 1b and the horizontal grooves 2b. Each block 21 extends in the tire width direction and has a plurality of zigzag shapes on the tread surface. The sipe 22 is formed. Each block 21 is formed with three closing grooves 23a, 23b, and 23c. The closing groove 23 a (first closing groove) has one end opened to one longitudinal groove 1 a adjacent to the block 21 and the other end closed in the block 21. One end of each of the closing grooves 23 b and 23 c (second closing groove) is opened in one longitudinal groove 1 b adjacent to the block 21, and the other end is closed in the block 21. Further, each block 21 is formed with two sipes 24 that extend in the tire width direction from the ends of the closing grooves 23b and 23c and form a linear shape on the tread surface. In each block 21, two or more types of angles are set as the inclination angles of the closing grooves 23 a to 23 c with respect to the tire width direction.

  That is, as shown in FIG. 4, two or more kinds of inclination angles θa, θb, and θc with respect to the tire width direction of the closing grooves 23a to 23c are set. The inclination angles θa to θc are preferably set in the range of 10 ° to 45 ° or in the range of −10 ° to −45 °. Note that a positive value means a case of inclination to one side, and a negative value means a case of inclination to the other side. In addition, the inclination angles θa to θc are specified based on a straight line passing through both ends of the longer groove wall surface of each of the closing grooves 23a to 23c.

  The block row 30 located on the tire equator CL includes a plurality of blocks 31 defined by the longitudinal grooves 1b and 1c and the lateral grooves 2c. Each block 31 extends in the tire width direction and has a zigzag shape on the tread surface. A book sipe 32 is formed.

  The block row 40 adjacent to the block row 30 includes a plurality of blocks 41 defined by the vertical grooves 1c and 1d and the horizontal grooves 2d. Each block 41 extends in the tire width direction and has a plurality of zigzag shapes on the tread surface. The sipe 42 is formed. Each block 41 is formed with one closing groove 43. The closing groove 43 has one end opened to the longitudinal groove 1 c adjacent to the block 41 and the other end closed within the block 41.

  The block row 50 adjacent to the block row 40 includes a plurality of blocks 51 defined by the vertical grooves 1d and 1e and the horizontal grooves 2e. Each block 51 extends in the tire width direction and has a plurality of zigzag shapes on the tread surface. The sipe 52 is formed. Each block 51 is formed with one closing groove 53. The closing groove 53 has one end opened to the longitudinal groove 1 e adjacent to the block 51 and the other end closed within the block 51.

  The block row 60 located on the tire shoulder outside the vehicle includes a plurality of blocks 61 defined by the vertical grooves 1e and the horizontal grooves 2f, and each block 61 extends in the tire width direction and has a plurality of zigzag shapes on the tread surface. The sipe 62 is formed.

  In the pneumatic tire described above, each of the plurality of blocks 21 included in the block row 20 is provided with at least three closing grooves 23a to 23c that are closed on one side. The on-snow performance can be improved by the closed grooves 23a to 23c firmly capturing the snow surface while avoiding a decrease in on-ice braking performance due to a decrease in steering stability on a wet road surface and a decrease in the contact area.

  Moreover, since two or more types of angles are set as inclination angles with respect to the tire width direction of the closing grooves 23a to 23c in each block 21, there are two or more falling directions of the block 21 in one block. The portions that cause the collapses come to support each other, contributing to an increase in the rigidity of the block 21. Furthermore, by setting two or more kinds of angles as the inclination angles of the closing grooves 23a to 23c with respect to the tire width direction in each block 21, it is possible to improve steering stability during cornering on snow.

  In the pneumatic tire, in each block 21, the inclination directions of the first closing groove 23a and the second closing grooves 23b, 23c with respect to the tire width direction are different from each other. That is, in FIG. 3, the first closing groove 23 a rises to the right and the second closing grooves 23 b and 23 c rise to the left. In this case, the falling direction of the block 21 is equal to or more than two directions across the tire circumferential direction, and the portions that cause the falling down firmly support each other, so that the rigidity of the block 21 can be effectively increased. Therefore, it is possible to prevent the steering stability from being lowered on the dry road surface and the wet road surface, and further, it is possible to prevent the on-ice performance from being lowered due to the collapse of the block 21.

  In the pneumatic tire, each of the plurality of blocks 21 included in the block row 20 positioned between the block row 10 of the tire shoulder and the block row 30 on the tire equator CL is formed with the above-described closing grooves 23a to 23c. In addition, at least one first closing groove 23a is disposed on the shoulder side of each block 21, and at least two second closing grooves 23b and 23c are disposed on the tire equator CL side of each block 21. As described above, by disposing relatively many closing grooves 23b and 23c on the tire equator CL side of each block 21, driving performance on snow can be improved. On the other hand, by arranging relatively few closing grooves 23a on the shoulder side of each block 21, the rigidity of the block 21 can be ensured and the braking performance on ice can be improved.

  When at least two second closing grooves 23b and 23c are arranged on the tire equator CL side of each block 21, the change widths of the inclination angles θb and θc with respect to the tire width direction of the second closing grooves 23b and 23c are 10 ° or less. There should be (see FIG. 4). That is, it is preferable that | θb−θc | ≦ 10 °. As a result, the direction in which the snow clogged in the second closing grooves 23b and 23c is discharged becomes the same, and the snow discharging performance is improved, so that the performance on snow can be improved. Moreover, if the change width of the inclination angles θb and θc of the second closing grooves 23b and 23c is too large, the effect of improving the snow removal performance becomes insufficient.

  In each block 21, as shown in FIG. 5, the crossing angle α between the first closing groove 23a and the second closing grooves 23b, 23c is preferably 110 ° to 170 °. Thereby, the steering stability at the time of cornering on snow can be improved, suppressing the fall of the rigidity of the block 21 and avoiding the fall of performance on ice. In particular, a remarkable effect is obtained when the crossing angle α is set to 140 ° or more and 160 ° or less. If the crossing angle α between the first closing groove 23a and the second closing grooves 23b, 23c is too small, the performance on the ice will be reduced due to a decrease in the rigidity of the block 21, and conversely if too large, the steering stability during cornering on snow will be reduced. The effect to improve becomes insufficient.

  In the pneumatic tire, the above-described closing grooves 23a to 23c are provided in each of the plurality of blocks 21 included in the block row 20 adjacent to the block row 10 of the tire shoulder. In this case, as shown in FIG. In addition, at least one closing groove 23a may be disposed at a position communicating with the lateral groove 2a that defines the block 11 of the block row 10 of the tire shoulder. Thereby, it becomes possible for the snow clogged in the closing groove 23a to move to the side groove 2a side, and the snow drainage performance is improved, so that the performance on snow can be improved.

  Further, in the pneumatic tire described above, the above-described closing grooves 23a to 23c are provided in each of the plurality of blocks 21 included in the block row 20 adjacent to the block row 30 on the tire equator CL. As shown in FIG. 3, at least one closing groove 23b may be disposed at a position communicating with the lateral groove 2c that defines the block 31 of the block row 30 on the tire equator CL. Thereby, the snow clogged in the closing groove 23b can be moved to the lateral groove 2c side, and the snow discharging performance is improved, so that the performance on snow can be improved.

  In the pneumatic tire described above, a plurality of sipes 12, 22, 32, 42, 52 extending in the tire width direction in each of the blocks 11, 21, 31, 41, 51, 61 in order to exhibit good on-ice performance. 62 for the blocks 21 provided with the closing grooves 23a to 23c, the arrangement of the sipes 22 may be set as follows. That is, when each block 21 is partitioned into at least three regions in the tire circumferential direction, the inclination direction of the sipe 22 with respect to the tire width direction in these regions may be alternately changed. In FIG. 6, the block 21 is divided into three regions based on the extension lines of the closing grooves 23b and 23c, and sipes 22a, 22b, and 22c in which the inclination directions with respect to the tire width direction are alternately changed in these three regions. It is arranged. This makes it possible to exert an edge effect against forces from different directions based on the sipes 22a to 22c tilted in different directions, so that it is possible to improve steering stability during cornering on ice. .

  Here, the difference between the inclination angles βa and βc of the sipes 22a and 22c with respect to the tire width direction and the inclination angles γa and γc with respect to the tire width direction of the lateral grooves 2b that define the blocks 21 in the tire circumferential direction both end regions of each block 21 respectively. The tire width of the closing groove 23b (or 23c) that is 10 ° or less and is inclined in the opposite direction to the inclination angle βb of the sipe 22b with respect to the tire width direction of the sipe 22b and the lateral groove 2b that defines the block 21 in the central region in the tire circumferential direction of each block 21 The difference from the inclination angle θb (or θc) with respect to the direction is preferably 10 ° or less. That is, | βa−γa | ≦ 10 °, | βc−γc | ≦ 10 °, | βb−θb | ≦ 10 ° (or | βb−θc | ≦ 10 °).

  In this way, by optimizing the inclination angles βa to βc of the sipes 22a to 22c in accordance with the inclination angles of the lateral groove 2b and the closing groove 23b (or 23c), it becomes possible to arrange the sipes 22a to 22c at a high density. As a result, the performance on ice can be improved. If the above-described difference in inclination angle is too large, it becomes difficult to arrange the sipes 22a to 22c at a high density. Note that the inclination angles βa to βc are specified based on straight lines passing through both ends of the sipes 22a to 22c. Further, the inclination angles γa and γc are specified based on straight lines passing through both ends of the groove wall surface of each lateral groove 2b.

  In the pneumatic tire described above, the block pitch in the tire circumferential direction of the block rows 20, 30, 40, 50 located on the tire equator CL side with respect to the tire shoulder block rows 10, 60 is the same as that of the tire shoulder block rows 10, 60. It is twice the block pitch in the tire circumferential direction. That is, subdivision of the blocks 21, 31, 41, 51 is avoided in the center region of the tread portion 101. As a result, sufficient performance on ice can be ensured, and furthermore, steering stability on the dry road surface and the wet road surface can be sufficiently ensured.

  FIG. 7 shows a tread pattern of a pneumatic tire according to another embodiment of the present invention. The pneumatic tire of the present embodiment has a tread pattern in which the mounting direction of the tire front and back with respect to the vehicle is not specified.

  In this embodiment, the block rows 10, 20, and 30 in the embodiment of FIG. 3 are arranged substantially symmetrically with the tire equator CL interposed therebetween. Also in this case, since each of the plurality of blocks 21 included in the block row 20 is provided with at least three closing grooves 23a to 23c that are closed on one side, on the dry road surface and the wet road surface due to a decrease in rigidity of the block 21. It is possible to improve on-snow performance while avoiding a decrease in braking performance on ice due to a decrease in steering stability and a decrease in contact area.

  In each of the embodiments described above, the case where the above-described closing groove is provided in a block included in a specific block row has been described. However, in the present invention, the above-described closing groove can be provided in a block included in any block row. It is. Even when at least three closed grooves are provided in any block, it is possible to improve the performance on snow based on these closed grooves, and it is not accompanied by a significant decrease in block rigidity, so that it can be used on dry road surfaces and wet road surfaces. The steering stability of the vehicle is not substantially lowered, and the on-ice performance is not substantially lowered because the ground contact area is not significantly reduced.

  A pneumatic tire having an asymmetric tread pattern in which the tire size is 215 / 60R16 and the mounting direction of the tire front and back with respect to the vehicle is specified, and a plurality of longitudinal grooves extending in the tire circumferential direction in the tread portion and in the tire width direction In a pneumatic tire provided with a plurality of lateral grooves extending and partitioning a plurality of block rows composed of a plurality of blocks by the longitudinal grooves and the lateral grooves, a block row of tire shoulders inside the vehicle and a block row on the tire equator Each of the plurality of blocks included in the block row positioned between each has one first closing groove and one end that opens in a longitudinal groove on the shoulder side adjacent to the block and the other end closes in the block Three closed grooves including two second closed grooves that are open in a longitudinal groove on the tire equator side adjacent to the block and whose other end is closed in the block Provided, to produce a tire of Examples 1, 2 is set two kinds of angle as the inclination angle with respect to the tire width direction of the closed grooves in each block provided with these closed grooves.

  The tire of Example 1 has the tread pattern of FIG. 3, the inclination angle θa of the first closing groove 23a is −17 °, and the inclination angles θb and θc of the second closing grooves 23b and 23c are + 15 °, respectively. Is. The tire of Example 2 has the tread pattern of FIG. 8, except that the first closing groove 23 a is arranged at a position shifted in the tire circumferential direction from the lateral groove 2 a that defines the block 11 of the tire shoulder block row 10. Has the same configuration as that of the first embodiment.

  For comparison, tires of Comparative Examples 1 and 2 having a tread pattern similar to FIG. 3 were prepared. That is, the tire of Comparative Example 1 has the tread pattern of FIG. 10, and instead of providing the closing grooves 23 a to 23 c in each block 21, lateral grooves crossing each block 21 are provided, and each block 21 is subdivided in the tire circumferential direction. Except for having been changed, it has the same configuration as the first embodiment. The tire of Comparative Example 2 has the tread pattern of FIG. 11 and has the same configuration as that of Example 1 except that the closing grooves 23a to 23c are eliminated from each block 21.

  These test tires were evaluated for their braking performance on snow, steering stability on snow, steering stability on wet road surfaces, and braking performance on ice by the following evaluation methods, and the results are shown in Table 1.

Brake performance on snow:
Each test tire was mounted on a wheel with a rim size of 16 × 7 J and mounted on a test vehicle with an air pressure of 230 kPa, braked from a running state at a speed of 40 km / h on snow, and the braking distance until the vehicle completely stopped was measured. . The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on snow.

Steering stability on snow:
Each test tire was assembled on a wheel with a rim size of 16 × 7 J and mounted on a test vehicle with an air pressure of 230 kPa, and sensory evaluation was performed on the snow by a test driver. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the handling stability on snow.

Steering stability on wet surfaces:
Each test tire was mounted on a wheel having a rim size of 16 × 7 J and mounted on a test vehicle with an air pressure of 230 kPa, and sensory evaluation was performed by a test driver on a wet road surface. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the steering stability in the wet state.

Brake performance on ice:
Each test tire was assembled on a wheel with a rim size of 16 × 7J and mounted on a test vehicle with an air pressure of 230 kPa. The test was braked from a running state at a speed of 40 km / h on ice, and the braking distance until the vehicle completely stopped was measured . The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on ice.

  As is clear from Table 1, the tires of Examples 1 and 2 were superior in braking performance on snow and braking performance on ice as compared with Comparative Example 1 in which the blocks were subdivided with lateral grooves. In particular, the tire of Example 1 showed an improvement effect on the handling stability on snow and the handling stability on the wet road surface. On the other hand, since the tire of Comparative Example 2 was not provided with a closing groove, braking performance on snow, steering stability on snow, and steering stability on wet road surfaces were deteriorated.

  Next, the tire size is 215 / 60R16, and a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction are provided in the tread portion, and a plurality of blocks are formed by the vertical grooves and the horizontal grooves. In a pneumatic tire having a plurality of block rows, one end of each of the plurality of blocks included in the block row located between the block row of the tire shoulder and the block row on the tire equator is adjacent to the block. One first closing groove that opens to the vertical groove on the shoulder side and the other end closes within the block, and one end opens to the vertical groove on the tire equator side adjacent to the block and the other end within the block Three closing grooves including two second closing grooves to be closed are provided, and in each block provided with these closing grooves, there are two kinds of angles as inclination angles of the closing grooves with respect to the tire width direction. The tires of the set Examples 3 and 4 were prepared.

  The tire of Example 3 has the tread pattern of FIG. 7, the inclination angle θa of the first closing groove 23a is −17 °, and the inclination angles θb and θc of the second closing grooves 23b and 23c are each + 15 °. Is. The tire of Example 4 has the tread pattern of FIG. 9, except that the first closing groove 23 a is arranged at a position shifted in the tire circumferential direction from the lateral groove 2 a that defines the block 11 of the tire shoulder block row 10. Has the same configuration as that of the third embodiment.

  For comparison, tires of Comparative Examples 3 and 4 having a tread pattern similar to FIG. 7 were prepared. That is, the tire of Comparative Example 3 has the tread pattern of FIG. 12, and instead of providing the closing grooves 23 a to 23 c in each block 21, lateral grooves crossing each block 21 are provided, and each block 21 is subdivided in the tire circumferential direction. The configuration is the same as that of the third embodiment except that the configuration is changed. The tire of Comparative Example 4 has the tread pattern of FIG. 13 and has the same configuration as that of Example 3 except that the closing grooves 23a to 23c are eliminated from each block 21.

  These test tires were evaluated for the braking performance on snow, steering stability on snow, steering stability on wet road surfaces, and braking performance on ice by the above-described evaluation methods, and the results are shown in Table 2. However, the evaluation criteria for each evaluation item was Comparative Example 3.

  As is apparent from Table 2, the tires of Examples 3 and 4 were superior in braking performance on snow and braking performance on ice as compared with Comparative Example 3 in which the blocks were subdivided with lateral grooves. In particular, the tire of Example 3 was also improved in steering stability on snow and steering stability on wet road surfaces. On the other hand, since the tire of Comparative Example 4 was not provided with a closing groove, braking performance on snow, steering stability on snow, and steering stability on wet road surfaces were deteriorated.

1a, 1b, 1c, 1d, 1e Vertical groove 2a, 2b, 2c, 2d, 2e, 2f Horizontal groove 10, 20, 30, 40, 50, 60 Block row 11, 21, 31, 41, 51, 61 Block 12, 22, 32, 42, 52, 62 Sipe 23a, 23b, 23c Closing groove 101 Tread part

Claims (10)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. Provided with a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction in the tread portion, and a plurality of block rows composed of a plurality of blocks are defined by the vertical grooves and the horizontal grooves. In the entering tire, each of the plurality of blocks included in the block row located between the block row of the tire shoulder and the block row on the tire equator has one end opened to one vertical groove adjacent to the block. At least one first closing groove whose end is closed in the block and at least one other vertical groove adjacent to the block and the other end closed in the block. The two least three closed groove end opening type and a second closed groove provided, the first closed groove is arranged on the shoulder side of the block having a said closed groove, provided said closed groove The second closing groove is disposed on the tire equator side of each block, and in each block provided with the closing groove, the first closing groove and the second closing groove are inclined differently from each other in the tire width direction. A pneumatic tire characterized in that two or more kinds of angles are set as inclination angles with respect to the tire width direction of the groove. 2. The pneumatic tire according to claim 1 , wherein a change width of an inclination angle of the second closing groove with respect to a tire width direction is 10 ° or less. Air according to any one of claims 1 to 2, wherein the crossing angle between the first closed groove and the second closed groove in each block provided with the closed grooves is less than 110 ° 170 ° or less Enter tire. The closing groove is provided in each of a plurality of blocks included in a block row adjacent to the tire shoulder block row, and at least one closing groove is disposed at a position communicating with a lateral groove defining a block of the tire shoulder block row. The pneumatic tire according to any one of claims 1 to 3 , wherein A position where each of a plurality of blocks included in a block row adjacent to the block row on the tire equator is provided with the closing groove, and at least one closing groove communicates with a lateral groove that defines a block of the block row on the tire equator The pneumatic tire according to any one of claims 1 to 4 , wherein The pneumatic tire according to any one of claims 1 to 5, characterized in that a plurality of sipes extending in the tire width direction in each of the plurality of blocks included in block row multi-column. The block according to claim 6 , wherein when each block provided with the closing groove is partitioned into at least three regions in the tire circumferential direction, the inclination directions of the sipe in these regions with respect to the tire width direction are alternately changed. Pneumatic tire. The difference between the inclination angle of the sipe with respect to the tire width direction and the inclination angle with respect to the tire width direction of the transverse groove defining the block is 10 ° or less in the tire circumferential direction both end regions of each block provided with the closing groove, and the closing groove is The difference between the inclination angle of the sipe with respect to the tire width direction and the inclination angle with respect to the tire width direction of the closing groove that inclines in the opposite direction to the lateral groove defining the block in the center region in the tire circumferential direction of each provided block is 10 ° or less. The pneumatic tire according to claim 7 , wherein The pneumatic according to any one of claims 1 to 8 , wherein the block pitch of the block row located on the tire equator side with respect to the tire shoulder block row is twice the block pitch of the tire shoulder block row. tire. In a pneumatic tire having an asymmetric tread pattern in which a tire front and back mounting direction with respect to a vehicle is specified, the closing groove is provided in each of a plurality of blocks included in a block row located inside the vehicle from the block row on the tire equator. The pneumatic tire according to any one of claims 1 to 9 , wherein

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