JP2018127090A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in traveling performance during straight traveling and during turn traveling in traveling on an irregular ground, with good balance.SOLUTION: A plurality of lug grooves 9 extending linearly at inclination angles of 5° or more and 15° or less with respect to a tire width direction are provided at intervals in a tire circumferential direction in a tread part 1. Land parts partitioned between a pair of lug grooves 9 adjacent to each other in the tire circumferential direction are configured to include a vertical hook-shaped block group 10' constituted of two or more and five or less vertical hook-shaped blocks 10 partitioned by at least one vertical bent groove 11 which extends linearly at angles of 80° or more and 100° or less with respect to the lug grooves 9 and whose both ends communicate with a pair of the lug grooves 9 and which comprises a bent part 11b at a midway part thereof. A width W1 in the tire width direction of the vertical hook-shaped block group 10' satisfies a relational expression of 0.5TW<W1≤0.8TW with respect to a grounding width TW, and a length L1 in the tire circumferential direction of the vertical hook-shaped block group 10' is set to be equal to 20% or more and 50% or less of a grounding length TL.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire suitable as a tire for traveling on rough terrain, and more particularly to a pneumatic tire in which traveling performance during straight traveling and traveling during rough terrain traveling is improved in a well-balanced manner.

  Rough terrain tires used for rally competitions, in particular, have traction to reliably transmit driving force to rough terrain covered with mud and cornering grip to suppress side slip during turning. It is requested. Conventionally, as a tread pattern of a rough terrain tire for satisfying both of these characteristics, a block having an edge component inclined in the tire circumferential direction is arranged on the outer side of the vehicle in order to secure a lateral grip force during turning. There is a proposal in which a block having an edge component extending in the tire width direction is arranged on the inner side of the vehicle in order to ensure straight drive braking / driving performance (see, for example, Patent Document 1).

  However, in these proposals, the traction performance during straight running and the grip performance during cornering have not necessarily reached a level that can be satisfied at the same time, and further improvements have been required to achieve these performances simultaneously.

JP 2008-037263 A

  An object of the present invention is to provide a pneumatic tire in which traveling performance during straight traveling and turning traveling on rough terrain is improved in a well-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 tires linearly extending at an inclination angle of 5 ° or more and 15 ° or less with respect to the tire width direction in the pneumatic tire including a pair of bead portions disposed on the inner side in the tire radial direction of the tire The lug grooves are provided at intervals in the tire circumferential direction, and the land portion defined between the pair of lug grooves adjacent in the tire circumferential direction is at an angle of 80 ° to 100 ° with respect to the lug grooves. A vertical rod-like shape comprising two or more and five or less vertical rod-shaped blocks extending and having both ends communicating with the pair of lug grooves and defined by at least one vertical bending groove provided with a bent portion in the middle portion Including a group of blocks, The length W1 of the block group in the tire width direction satisfies the relationship of 0.5TW <W1 ≦ 0.8TW with respect to the ground contact width TW, and the tire circumferential direction length L1 of the vertical saddle block group is 20 which is the ground contact length TL. % Or more and 50% or less.

  In the present invention, as described above, a linear lug groove inclined at a predetermined angle is provided, and a plurality of vertical saddle-like blocks (vertical saddle-like block group) partitioned by vertical bending grooves are provided with respect to the grounding region. Since it is provided in a sufficient range, it ensures straightness while ensuring the edge effect due to the sloping edge of the lug groove and the bent edge of the vertical hook block while ensuring the rigidity of the land part (the rigidity of the vertical hook block) The braking / driving performance during traveling and the grip performance during turning can be improved in a well-balanced manner.

In the present invention, it is preferable groove width W _L of the lug groove is within 25% 5% or more longitudinal hook-shaped blocks in the tire circumferential direction length L1. By thus setting the groove width W _L of the lug groove becomes advantageous and grip property during turning and braking and driving of the straight running to improve well-balanced.

  In the present invention, it is preferable to provide a depression having a depth of 2 mm or less on the tread surface of the vertical saddle block. Providing the depression in this way is advantageous in improving braking / driving performance during straight traveling because the edge effect due to the depression can be expected.

  In the present invention, at least one circumferential groove extending linearly in the tire circumferential direction over the entire circumference of the tire is provided on the outer side in the tire width direction of the vertical saddle-like block group, and each of the vertical saddle-like block groups is a tire. It is preferable that only one side of the end portion in the width direction is in contact with the circumferential groove. By providing the circumferential groove in this way, an edge effect due to the circumferential groove can be expected, which is advantageous in improving the grip performance during cornering. In addition, since the effect of discharging water, gravel, and the like is obtained by the circumferential groove, it is advantageous for improving the braking / driving performance during straight traveling.

At this time, it is preferable that the groove width W _C of the circumferential groove is not less than 5% and not more than 15% of the tire width direction length W1 of the vertical saddle-like block group. By setting the groove width W _C of the circumferential groove in this way, it is possible to improve the balance between the effect of providing the circumferential groove and the effect on the vertical hook block by providing the circumferential groove. This is advantageous for improving the braking / driving performance during straight traveling and the grip performance during turning.

  Moreover, it is preferable that the tire width direction length W3 of the outer side block divided on the tire width direction outer side of the circumferential groove is 15% or more and 45% or less of the tire width direction length W1 of the vertical saddle-like block group. By setting the tire width direction length W3 of the outer block in this way, the outer block can be appropriately sized, and the position of the circumferential groove is also limited to the shoulder region on the outer side in the width direction of the tread portion. Therefore, it is advantageous to improve the braking / driving performance during straight traveling and the grip performance during turning traveling in a well-balanced manner.

  The pneumatic tire of the present invention can be suitably used as a rough terrain tire. In other words, with the above-described structure, the braking / driving performance during straight traveling and the grip performance during turning traveling are both balanced, so that it is possible to obtain good traveling performance on rough terrain.

  In the present invention, the “contact width” and “contact length” of the tread portion are defined as when a normal load is applied by placing the tire on a normal rim and placing the tire vertically on a plane in a state where normal internal pressure is filled. These are the length in the tire axial direction (contact width) and the length in the tire circumferential direction (contact length). The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a front view which shows the tread surface of the pneumatic tire which consists of embodiment of this invention. It is a front view which shows the tread surface of the pneumatic tire which consists of another embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the pneumatic tire of the present invention includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction. In FIG. 1, reference numeral CL denotes a tire equator, reference numeral E _W denotes a ground terminal (tire widthwise end portions of the contact patch).

  A carcass layer 4 (two carcass layers 4 in the illustrated example) is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in the illustrated example) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. Further, on the outer peripheral side of the belt layer 7, a belt reinforcing layer 8 (in the illustrated example, two layers of a belt reinforcing layer 8 that covers the entire width of the belt layer 7 and a pair of belt reinforcing layers 8 that cover only the end of the belt layer 7). Is provided. The belt reinforcing layer 8 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

As shown in FIGS. 2 and 3, a plurality of lug grooves 9 are provided on the outer surface of the tread portion 1 at intervals in the tire circumferential direction. The lug groove 9 extends linearly while inclining with respect to the tire width direction. The inclination angle α of the lug groove 9 is set to 5 ° or more and 15 ° or less. 2 and 3, a symbol A (a region surrounded by a broken line) schematically shows a grounding region that is a basis of a grounding width TW and a grounding length TL, which will be described later. Code E _W denotes a ground terminal (tire widthwise end portion of the ground area A), reference numeral E _C denotes a tire circumferential end of the contact region A. The ground contact width TW is the distance between the ground terminal E _W, the contact length TL is a distance between E tire circumferential end of the ground area A _C.

  The land portion defined between a pair of lug grooves 9 adjacent to each other in the tire circumferential direction necessarily includes a vertical rod-shaped block group 10 ′ including vertical rod-shaped blocks 10 described later. Further, in the illustrated example, in addition to the vertical saddle-like block 10 (vertical saddle-like block group 10 ′), a horizontal saddle-like block group 20 ′ including a horizontal saddle-like block 20 described later and an outer block 30 described later are included. . In the present invention, it suffices to have at least the vertical hook-shaped block 10 (vertical hook-shaped block group 10 '), and other structures are not particularly limited. That is, instead of the recumbent block 20 (recumbent block group 20 ′) and the outer block 30, blocks having other shapes may be provided.

  The vertical rod-shaped block 10 is a block defined by at least one vertical bending groove 11 in each of the land portions defined between a pair of lug grooves 9 adjacent in the tire circumferential direction. In other words, with two lug grooves 9, one vertical bending groove 11, and one other vertical bending groove 11 or a groove extending in an arbitrary circumferential direction (for example, a circumferential groove 31 described later). The partitioned block is a vertical saddle-like block 10 (when the vertical saddle-like block 10 is located on the outermost side in the tire width direction and is partitioned by two lug grooves 9 and one vertical bending groove 11 Also included). In the illustrated example, three vertical bending grooves 11 are provided, and three vertical rod-shaped blocks 10 are formed. Of these, the vertical saddle-like block 10 farthest from the tire equator CL is partitioned by two lug grooves 9, one vertical bending groove 11, and a circumferential groove 31 described later, and the other two vertical saddle-like blocks. 10 is defined by two lug grooves 9 and two longitudinal bending grooves 11.

  The longitudinally bent groove 11 is a groove that extends at an angle of 80 ° or more and 100 ° or less with respect to the lug groove 9, has both ends communicating with the lug groove 9, and a midway portion is bent. In particular, in the illustrated example, the longitudinally bent groove 11 communicates with one of the pair of lug grooves 9 adjacent to the land portion at one end and extends with respect to the lug groove 9 at an angle of 80 ° to 100 °. The pair of main portions 11a and the bent portions 11b extending in the same direction as the lug grooves 9 by connecting the end portions in the land portions of the pair of main portions. The angle of the longitudinal bending groove 11 described above is the angle of the main part 11a excluding the bending part 11b.

  The vertical saddle-like block group 10 'is a block group composed of the vertical saddle-like blocks 10 formed as described above. The vertical saddle-like block 10 includes two or more vertical saddle-like blocks 10 adjacent in the tire width direction. Composed. In the illustrated example, the vertical saddle-like block group 10 ′ is composed of three vertical saddle-like blocks 10.

  In the present invention, the individual size of the vertical rod-shaped block 10 is not specified, but is set to have a sufficient size as the vertical rod-shaped block group 10 '. That is, the length W1 of the vertical saddle-shaped block group 10 ′ in the tire width direction satisfies the relationship 0.5TW <W1 ≦ 0.8TW, preferably 0.6TW ≦ W1 ≦ 0.7TW, with respect to the ground contact width TW. The circumferential length L1 of the saddle-shaped block group 10 'is set to 20% or more and 50% or less of the contact length TL. As shown in the drawing, the length W1 is the distance in the tire width direction between the end points in the tire width direction of the vertical saddle block group 10 ', and the length L1 is the tire circumferential direction of the vertical saddle block group 10'. Is the distance in the tire circumferential direction between the end points.

  Thus, since the vertical hook-shaped block 10 (vertical hook-shaped block group 10 ′) is provided, the inclined edge of the lug groove 9 and the land portion rigidity (the rigidity of the vertical hook-shaped block 10) are secured. The edge effect by the bent edge of the vertical rod-shaped block 10 can be ensured, and the braking / driving performance during straight traveling and the grip performance during turning can be improved in a balanced manner.

  At this time, if the inclination angle α of the lug groove 9 is less than 5 °, the grip performance (lateral grip force) during cornering decreases. When the inclination angle α of the lug groove 9 exceeds 15 °, the lug groove 9 is excessively inclined and the braking / driving performance during straight traveling is lowered. If the angle of the longitudinally bent groove 11 deviates from the above range, it becomes difficult to keep the shape of the vertical saddle-shaped block 10 well, and it becomes difficult to ensure sufficient block rigidity. If the number of the vertical rod-shaped blocks 10 included in the vertical rod-shaped block group 10 'is less than 2, the effect of improving the braking / driving performance during straight traveling cannot be obtained. Decreases. Since the vertical saddle block group 10 'having a sufficient size in the tire width direction mainly contributes to cornering performance, the vertical width block group 10' has a tire width direction length W1 and a ground contact width TW described above. If the relationship is not satisfied, it is difficult to obtain good cornering performance. When the length L1 in the tire circumferential direction of the vertical saddle-shaped block group 10 'is less than 20% of the ground contact length TL, the grip system during cornering decreases. When the length L1 in the tire circumferential direction of the vertical saddle-shaped block group 10 'exceeds 50% of the ground contact length TL, the braking / driving performance during straight traveling is degraded.

  The vertical saddle-like block group 10 ′ included in each land portion is preferably arranged close to one side or the other side in the tire width direction as illustrated. For example, as shown in FIG. 2, a vertical saddle-like block group 10 ′ arranged close to one side in the tire width direction and a vertical saddle-like block group 10 ′ arranged close to the other side in the tire width direction. They can be arranged adjacent to each other in the tire circumferential direction. Alternatively, as shown in FIG. 3, all the vertical saddle-like block groups 10 ′ can be arranged close to one side in the tire width direction (left side in the figure).

  In the case of FIG. 2, the vertical saddle-like block groups 10 ′ adjacent to each other in the tire circumferential direction have a point-symmetrical relationship with respect to points on the tire equator CL, so that the tread pattern becomes a non-directional and symmetrical pattern. . Therefore, it is not necessary to produce individual tires according to the mounting direction with respect to the vehicle, so that productivity can be improved. In the case of FIG. 3, an asymmetric tread pattern is obtained, but since it is non-directional, productivity can be improved as compared with a pneumatic tire having a directional tread pattern.

Although the lug grooves 9 are grooves inclined at a predetermined angle with respect to the tire width direction as described above, 5 preferably, the groove width W _L is the tire circumferential direction length of the vertical hook-shaped blocks 10 'L1 % Or more and 25% or less. By thus setting the groove width W _L of the lug groove 9, which is advantageous in the grip property during turning and braking and driving of the straight running to improve well-balanced. It is difficult to groove width W _L of the lug grooves 9 are sufficiently improved to be less than 5% of braking and driving at the time of straight running of the tire circumferential length L1 of the vertical hook-shaped blocks 10 '. It is difficult to groove width W _L of the lug grooves 9 are sufficiently improve the grip performance during turning with more than 25% of the tire circumferential length L1 of the vertical hook-shaped blocks 10 '.

  In the illustrated example, as described above, the recumbent block 20 (recumbent block group 20 ') is provided in addition to the recumbent block 10 (recumbent block group 10'). The recumbent block 20 (recumbent block group 20 ') is an optional element in the present invention, and even if it is replaced with another block or the like, the effect of the present invention is not affected. Of course, by using the recumbent block 20 (recumbent block group 20 '), the edge effect due to the block shape and groove shape can be expected. It is advantageous to improve the balance.

  The recumbent block 20 is defined by at least one longitudinal groove 21 and at least one lateral bending groove 22 in each of the land portions defined between a pair of lug grooves 9 adjacent in the tire circumferential direction. Block. In other words, one lug groove 9, one vertical groove 21, one other vertical groove 21 or a groove extending in the tire circumferential direction (for example, a vertical bending groove 11 or a circumferential groove 31 described later). And a block defined by one laterally bent groove 22 is a horizontal saddle-like block 20 (the horizontal saddle-like block 20 is located on the outermost side in the tire width direction, and one lug groove 9 and one (Including the case where it is defined by the vertical groove 21 and one horizontal bending groove 22). In the illustrated example, one vertical groove 21, one horizontal bent groove 22 between the vertical groove 21 and the vertical bent groove 11, and one between the vertical groove 21 and a circumferential groove 31 described later. The laterally bent grooves 22 are provided to form a total of four horizontal saddle-like blocks 20 in two rows in the tire circumferential direction and two rows in the tire width direction. Of these, the two horizontal saddle-like blocks 20 belonging to the row farthest from the tire equator CL are composed of one lug groove 9, one vertical groove 21, one lateral bending groove 22, and one circumferential groove 31. The two horizontal saddle-shaped blocks 20 belonging to the row on the tire equator CL side are composed of one lug groove 9, one vertical bending groove 11, one vertical groove 21, and one horizontal bending groove. And 22.

  The vertical groove 21 is a groove extending at an angle of 80 ° or more and 100 ° or less with respect to the lug groove 9 and having both ends communicating with the lug groove 9. The lateral bending groove 22 is a land portion defined between grooves extending in the tire circumferential direction adjacent to the tire width direction (any of the vertical bending groove 11, the vertical groove 21, and a circumferential groove 31 described later). Provided at an angle of 5 ° to 15 ° with respect to the tire width direction and extending at both ends along the tire circumferential direction (longitudinal bending groove 11, vertical groove 21, described later) Any of the circumferential grooves 31) is a groove that is bent in the middle. In particular, in the illustrated example, the laterally bent groove 22 communicates with a groove (one of the vertically bent groove 11, the vertical groove 21, and a circumferential groove 31 described later) having one end extending along the tire circumferential direction. A pair of main portions 22a extending at an angle of 5 ° to 15 ° with respect to the width direction, and ends in the land portion of the pair of main portions 22a are connected to each other in the same direction as the longitudinal groove 21. It is comprised by the bending part 22b extended to. The angle of the lateral bending groove 22 is the angle of the main part 22a excluding the bending part 22b.

  As shown in the figure, the horizontal saddle-like block group 20 'included in each land portion is arranged close to the opposite side of the vertical saddle-like block group 10' in the tire width direction. Therefore, in FIG. 2, the recumbent block group 20 ′ arranged close to one side in the tire width direction and the recumbent block group 20 ′ arranged close to the other side in the tire width direction are the tire circumferential direction. Are arranged adjacent to each other. In FIG. 3, all of the recumbent block groups 20 ′ are arranged close to one side (right side in the figure) in the tire width direction. 2 and 3, only the vertical saddle-like block group 10 'and the horizontal saddle-like block group 20' are provided on the inner side in the tire width direction of a circumferential groove 31 to be described later.

  In the illustrated example, the outer block 30 defined by the circumferential groove 31 is provided in addition to the vertical hook block 10 (vertical hook block group 10 ') as described above. The circumferential groove 31 (and the outer block 30) is an optional element in the present invention, but is preferably employed and different from the above-mentioned horizontal saddle-shaped block 20 (horizontal horizontal block group 20 '). It is possible to effectively improve the braking / driving performance and the grip performance during turning.

  The circumferential groove 31 is a groove that is disposed on the outer side in the tire width direction of the vertical rod-shaped block group 10 ′ and linearly extends in the tire circumferential direction over the entire circumference of the tire. In particular, it is preferable that only one side of each end portion in the tire width direction of the vertical rod-shaped block group 10 ′ is in contact with the circumferential groove. In other words, of the vertical rod-shaped blocks 10 included in the vertical rod-shaped block group 10 ′, the outermost side in the tire width direction of the vertical rod-shaped block 10 farthest from the tire equator CL is in contact with the circumferential groove 31. preferable. By providing the circumferential groove 31 in this way, an edge effect by the circumferential groove 31 can be expected, which is advantageous in improving the grip performance during turning. Further, the circumferential groove 31 has an effect of discharging water, gravel and the like, which is advantageous for improving the braking / driving performance during straight traveling.

When the circumferential groove 31 is provided, the groove width W _C of the circumferential groove 31 is preferably set to 5% or more and 15% or less of the tire width direction length W1 of the vertical rod-shaped block group 10 ′. Thereby, the balance between the effect of providing the circumferential groove 31 and the influence on the vertical rod-shaped block 10 (vertical rod-shaped block group 10 ') by providing the circumferential groove 31 can be improved, and the vehicle goes straight. It is advantageous to improve the braking / driving performance during traveling and the grip performance during turning traveling in a well-balanced manner. If the groove width W _C of the circumferential groove 31 is less than 5% of the tire width direction length W1 of the vertical rod-shaped block group 10 ′, it becomes difficult to sufficiently improve the braking / driving performance during straight traveling. When the groove width W _C of the circumferential groove 31 exceeds 15% of the length W1 of the vertical saddle-shaped block group 10 ′, it becomes difficult to sufficiently improve the grip performance during cornering.

  By providing the circumferential groove 31, the outer block 30 is defined on the outer side in the tire width direction of the circumferential groove 31 in the land portion defined between the pair of lug grooves 9. The tire width direction length W3 of the outer block 30 thus partitioned is preferably 15% to 45% of the tire width direction length W1 of the vertical saddle-like block group 10 ′. Thus, by setting the tire width direction length W3 of the outer block 30, the outer block 30 can be appropriately sized, and the position of the circumferential groove 31 is also on the outer side in the width direction of the tread portion 1. Since it is limited to the shoulder region, the width of the vertical saddle-like block group 10 'can be sufficiently secured, and it is advantageous for improving the braking / driving performance during straight running and the grip performance during turning. Become. If the length W3 in the tire width direction of the outer block 30 is less than 15% of the length W1 in the tire width direction of the vertical rod-shaped block group 10 ′, it is difficult to sufficiently improve the braking / driving performance during straight traveling. If the length W3 in the tire width direction of the outer block 30 exceeds 45% of the length W1 in the tire width direction of the vertical saddle-shaped block group 10 ′, it becomes difficult to sufficiently improve the grip performance during cornering.

  In the present invention, it is preferable to provide a depression 41 having a depth of 2 mm or less on the tread surface of the vertical saddle block 10. The depression 41 provided in the vertical hook-shaped block 10 is preferably a linear depression having a sufficient length at least in the tire circumferential direction. In the illustrated example, the recess 41 has a bent shape corresponding to the shape of the vertical hook-shaped block 10, and linearly extends with respect to the lug groove 9 at an angle of 80 ° to 100 °, It is comprised by a pair of bending part extended in the same direction as the lug groove 9 at the both ends. By providing such a depression 41, an edge effect due to the depression 41 can be expected, which is advantageous for improving the braking / driving performance during straight traveling. When the depth of the recess 41 exceeds 2 mm, the block rigidity is lowered, and it becomes difficult to sufficiently improve the grip performance during turning.

  In addition, you may provide the dents 42 and 43 also in the recumbent block 20 and the outer side block 30 like the example of illustration. The depressions 42 provided in the recumbent block 20 are linear depressions having a sufficient length at least in the tire width direction. In the example shown in the drawing, the recess 42 has a bent shape corresponding to the shape of the recumbent block 20, a straight portion extending linearly in the same direction as the lug groove 9, and the lug groove 9 at both ends thereof. And a bent portion extending at an angle of 80 ° to 100 °. The depression 43 provided in the outer block 30 is a linear depression having a sufficient length at least in the tire circumferential direction. In the illustrated example, the recess 43 has a linear shape corresponding to the shape of the outer block 30. By providing these depressions 42 and 43, the edge effect by these depressions 42 and 43 can be expected, which is advantageous in improving braking / driving performance during straight traveling. The depths of these recesses 42 and 43 are preferably set to 2 mm or less in consideration of the influence on grip performance during turning.

  Although the above-mentioned present invention can be applied to various pneumatic tires, it can be suitably used as a tire for traveling on uneven terrain. Among them, it is preferable to use as a tire for competition running on rough terrain such as rally and dirt trial. In other words, with the above-described structure, the braking / driving performance during straight traveling and the grip performance during turning traveling are both balanced, so that it is possible to obtain good traveling performance on rough terrain.

The tire size is 205 / 65R15, has the basic structure illustrated in FIG. 1, and is based on the tread pattern of FIG. 2 or FIG. 3, and the shape of the lug groove, the inclination angle α of the lug groove, the vertical rod-shaped block group the ratio W _L / L1 of the width W _L of the lug grooves with respect to the tire circumferential direction length L1, the angle of the longitudinal curved groove for the lug grooves, the number of longitudinal hook-shaped blocks included in a vertical hook-shaped blocks, the vertical hook-shaped blocks Arrangement, ratio W1 / TW of the width W1 of the vertical hook block group to the contact width TW, ratio L1 / TL of the circumferential length L1 of the vertical hook block group to the contact length TL, the depression of the tread of the vertical hook block presence, depression depth, the number of the circumferential grooves, the positional relationship between the circumferential groove and the vertical hook-shaped blocks, the ratio of the groove width W _C of the circumferential groove to the width W1 of the vertical hook-shaped block group W _C / W1 The width W of the outer block relative to the width W1 of the vertical saddle-shaped block group The ratio W3 / W1 of the conventional example 1 was set as each table 1-3, Comparative Examples 1-8, were prepared 30 kinds of pneumatic tires of Examples 1 to 21.

  The conventional example 1 is a land portion in which lug grooves extending curvedly along the tire width direction are provided at intervals in the tire circumferential direction, and are defined between a pair of lug grooves adjacent in the tire circumferential direction. Is an example in which a vertical rod-shaped block group including vertical rod-shaped blocks having the same shape as the present invention is included. In Conventional Example 1, the vertical saddle-like block group is provided close to one side in the tire width direction (the vehicle outer side that is the outside of the vehicle when the vehicle is mounted), and the circumferential groove is opposite to the vertical saddle-like block group ( It is provided only on the inner side of the vehicle, which is the inner side of the vehicle when mounted on the vehicle, without being adjacent to the vertical saddle block group. In Conventional Example 1, the lug groove extends along the tire width direction in the vehicle inner region, and inclines toward the opposite side of the tire rotation direction toward the tire width direction outer side in the vehicle outer region. Yes. That is, the tire of Conventional Example 1 is a tire having an asymmetric directional tread pattern, and requires a pair of left and right tires.

  Although the number of the figure is shown in the column “arrangement of the vertical hook block group” in Tables 1 to 3, it does not indicate that each example has the pattern of the drawing, but the vertical hook block group Is the same as the drawing. That is, as shown in FIG. 2, a vertical saddle-like block group arranged close to one side in the tire width direction and a vertical saddle-like block group arranged close to the other side in the tire width direction are arranged in the tire circumferential direction. The case where they are arranged alternately is shown in FIG. 2 and the case where all the vertical saddle-like block groups are arranged close to one side in the tire width direction as shown in FIG. 3 is shown as “FIG. 3”.

  With respect to these 30 types of pneumatic tires, the straight driving controllability, the turning operation stability, and the mold production cost were evaluated by the following evaluation methods, and the results are also shown in Tables 1 to 3.

Straight drive control and turning maneuvering stability Each test tire is mounted on a wheel with a rim size of 15 x 7.0 J and mounted on a four-wheel drive vehicle (test vehicle) with a displacement of 2000 cc and an air pressure of 200 kPa. Drive a test course that simulates leveling (including the area where floating gravel is spread and the area that has been dug up) for three laps. Sensory evaluation was performed. The evaluation results are shown as indices with the value of Conventional Example 1 being 100. The larger the index value, the better the straight drive control and the turning operation stability.

Productivity For each test tire, the mold production cost required to manufacture the tire to be mounted on the test vehicle was evaluated as an index of productivity. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. The smaller the index value, the lower the mold manufacturing cost, and the higher the productivity.

  As is clear from Tables 1 to 3, all of Examples 1 to 21 were improved in straight drive control and turning control stability as compared with Conventional Example 1. Further, as compared with the conventional example 1 having the asymmetric directional pattern as described above, each of the examples 1 to 21 has the non-directional pattern, so that the number of necessary molds can be reduced and the productivity can be reduced. We were able to raise it (to keep mold production costs low).

  On the other hand, in Comparative Example 1, the steering stability at the time of turning deteriorated because the inclination angle of the lug groove was too small. In Comparative Example 2, since the inclination angle of the lug groove is excessive, the braking / driving performance during straight traveling deteriorated. In Comparative Example 3, since the number of the vertical hook-shaped blocks included in the vertical hook-shaped block group is too small, the braking / driving performance at the time of straight traveling deteriorated. In Comparative Example 4, since the number of the vertical hook-shaped blocks included in the vertical hook-shaped block group is excessive, the steering stability at the time of turning deteriorated. In Comparative Example 5, the ratio W1 / TW was too small, and the width of the vertical saddle-like block group could not be secured sufficiently, so that the steering stability during turning deteriorated. In Comparative Example 6, the ratio W1 / TW is excessive, and the ratio of the vertical saddle-like block group to the ground contact width is too large, so that the braking / driving performance during straight traveling is deteriorated. In Comparative Example 7, the ratio L1 / TL was too small, and the circumferential length of the vertical saddle-like block group could not be secured sufficiently, so that the steering stability during turning deteriorated. In Comparative Example 8, the ratio L1 / TL is excessive, and the ratio of the vertical saddle-like block group to the ground contact length is too large, so that the braking / driving performance during straight traveling is deteriorated.

  Although not shown in Tables 1 to 3, all the vertical saddle-like block groups are arranged close to one side in the tire width direction as in Example 2, and the other groups as in Examples 3 to 21 are arranged. When the items were changed, the same results as in Examples 3 to 21 for Example 1 were obtained for Example 2.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 9 Lug groove 10 Vertical hook-shaped block 10 'Vertical hook-shaped block group 11 Vertically bent groove 20 Horizontal hook-shaped block 20 'lateral hook-shaped blocks 21 vertical grooves 22 transverse curved groove 30 outer blocks 31 circumferential groove 41, 42, 43 recesses CL tire equator E _W ground terminal

Claims (7)

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. In the provided pneumatic tire,
A pair of lug grooves linearly extending at an inclination angle of 5 ° or more and 15 ° or less with respect to the tire width direction are provided in the tread portion at intervals in the tire circumferential direction, and are adjacent to each other in the tire circumferential direction. The land portion defined between the lug grooves extends at an angle of 80 ° or more and 100 ° or less with respect to the lug grooves, and both ends communicate with the pair of lug grooves and include bent portions in the middle. And a vertical saddle-like block group composed of 2 or more and 5 or less vertical saddle-like blocks partitioned by at least one vertical bending groove, and the tire width direction length W1 of the vertical saddle-like block group is a ground contact width TW. In which the relation of 0.5 TW <W1 ≦ 0.8 TW is satisfied, and the length L1 in the tire circumferential direction of the vertical saddle-like block group is 20% or more and 50% or less of the contact length TL tire. The pneumatic tire according to claim 1, wherein the groove width W _L of the lug grooves is 25% or less than 5% of the vertical hook-shaped blocks in the tire circumferential direction length L1.   The pneumatic tire according to claim 1 or 2, wherein a depression having a depth of 2 mm or less is provided on a tread surface of the vertical saddle block.   At least one circumferential groove extending linearly in the tire circumferential direction over the entire tire circumference is provided on the outer side in the tire width direction of the vertical saddle-shaped block group, and each of the vertical saddle-shaped block groups is in the tire width direction. The pneumatic tire according to any one of claims 1 to 3, wherein only one side of the end portion is in contact with the circumferential groove. The pneumatic tire according to claim 4, wherein a groove width W _C of the circumferential groove is 5% or more and 15% or less of a tire width direction length W 1 of the vertical saddle-like block group.   A tire width direction length W3 of the outer block partitioned outside in the tire width direction of the circumferential groove is 15% or more and 45% or less of a tire width direction length W1 of the vertical saddle-like block group. The pneumatic tire according to claim 4 or 5.   The pneumatic tire according to claim 1, wherein the pneumatic tire is a rough terrain tire.

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