JP6822187B2 - Pneumatic tires - Google Patents

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 having improved traveling performance during straight running and turning traveling on rough terrain.

Tires for rough terrain used in rally competitions, in particular, have traction to reliably transmit driving force to rough terrain covered with mud, and cornering grip to prevent skidding during turning. It is required. Conventionally, as a tread pattern of a tire for running on rough terrain to satisfy both of these characteristics, a block having an edge component inclined in the tire circumferential direction is arranged on the outside of the vehicle in order to secure a lateral grip force during turning. , There is a proposal to arrange a block having an edge component extending in the tire width direction inside the vehicle in order to secure the straight-ahead drive performance (see, for example, Patent Document 1).

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

Japanese Unexamined Patent Publication No. 2008-037263

An object of the present invention is to provide a pneumatic tire having well-balanced improved running performance during straight running and turning running on rough terrain.

The pneumatic tire of the present invention for achieving the above object has a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged inside in the tire radial direction, a plurality of tires extending linearly on the tread portion at an inclination angle of 5 ° or more and 15 ° or less with respect to the tire width direction. The lug grooves are provided at intervals in the tire circumferential direction, and the land portion partitioned between the pair of the lug grooves adjacent to each other in the tire circumferential direction is at an angle of 80 ° or more and 100 ° or less with respect to the lug groove. At least one flute that extends linearly and has both ends communicating with the pair of lug grooves and that communicate with the flute and extend at an inclination angle of 5 ° or more and 15 ° or less with respect to the tire width direction. A tire width direction of the horizontal hook-shaped block group including a horizontal hook-shaped block group consisting of 4 or more and 8 or less horizontal hook blocks partitioned by at least one lateral bending groove having a bent portion in the middle portion. The length W1 satisfies the relationship of 0.5 TW <W1 ≤ 0.8 TW with respect to the ground contact width TW, and the tire circumferential length L1 of the horizontal hook-shaped block group is 20% or more and 50% or less of the ground contact length TL. It is characterized by that.

In the present invention, as described above, a linear lug groove inclined at a predetermined angle is provided, and a plurality of horizontal hook-shaped blocks (horizontal hook-shaped block group) partitioned by the vertical groove and the horizontal bending groove are grounded. Since it is provided in a sufficient range for the area, the edge effect due to the inclined edge of the lug groove and the bent edge of the horizontal hook-shaped block is secured while ensuring the land rigidity (rigidity of the horizontal hook-shaped block). Therefore, it is possible to improve the controllability during straight running and the grip during turning running in a well-balanced manner.

In the present invention, it is preferable groove width W _L of the lug grooves is 25% or less than 5% of the lateral 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 recess having a depth of 2 mm or less on the tread surface of the horizontal hook-shaped block. By providing the dent in this way, the edge effect due to the dent can be expected, which is advantageous for improving the controllability during straight running.

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 outside the tire width direction of the horizontal hook-shaped block group, and each of the horizontal hook-shaped block groups is a tire. It is preferable that only one side of the widthwise end is in contact with the circumferential groove. By providing the circumferential groove in this way, the edge effect due to the circumferential groove can be expected, which is advantageous for improving the grip during turning. In addition, since the effect of discharging water, gravel, etc. can be obtained by this circumferential groove, it is advantageous to improve the controllability during straight running.

At this time, it is preferable that the groove width W _C of the circumferential groove is 5% or more and 15% or less of the tire width direction length W1 of the horizontal hook-shaped 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 influence of providing the circumferential groove on the horizontal hook-shaped block. , It is advantageous to improve the controllability during straight running and the grip during turning running in a well-balanced manner.

Further, it is preferable that the tire width direction length W3 of the outer block partitioned outside the tire width direction of the circumferential groove is 15% or more and 45% or less of the tire width direction length W1 of the horizontal hook-shaped block group. By setting the tire width direction length W3 of the outer block in this way, the outer block can be made an appropriate size, and the position of the circumferential groove is also limited to the shoulder area on the outer side in the width direction of the tread portion. Therefore, it is advantageous to improve the controllability during straight running and the grip during turning running in a well-balanced manner.

The pneumatic tire of the present invention can be suitably used as a tire for traveling on rough terrain. That is, with the above-mentioned structure, the control drive property during straight running and the grip property during turning running are well balanced, so that good running performance can be obtained on rough terrain.

In the present invention, the "ground contact width" and "ground contact length" of the tread portion are when the tire is rim-assembled on the regular rim and placed vertically on a flat surface with the regular internal pressure applied, and a regular load is applied. The length of the ground contact area in the tire axial direction (ground contact width) and the length in the tire circumferential direction (ground contact length). A "regular rim" is a rim defined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATTA, a "Design Rim" for TRA, or ETRTO. If so, it is set to "Measuring Rim". "Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, and for TRA, the table "TIRE ROAD LIMITED AT VARIOUS". The maximum value described in "COLD INFLATION PRESSURES", which is "INFLATION PRESSURE" for ETRTO, but 180 kPa when the tire is a passenger car. "Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. If it is JATTA, it is the maximum load capacity, and if it is TRA, it is the table "TIRE ROAD LIMITED AT VARIOUS". The maximum value described in "COLD INFLATION PRESSURES" is "LOAD CAPACITY" in the case of ETRTO, but when the tire is a passenger car, the load is equivalent to 88% of the above load.

It is a meridian cross-sectional view of the pneumatic tire which comprises embodiment of this invention. It is a front view which shows the tread surface of the pneumatic tire which comprises embodiment of this invention. It is a front view which shows the tread surface of the pneumatic tire which comprises 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 extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and side surfaces. It is provided with a pair of bead portions 3 arranged 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 from the inside to the outside of the vehicle around the bead core 5 arranged in each bead portion 3. Further, a bead filler 6 is arranged on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by a main body portion and a 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 the reinforcing cords are arranged so as to intersect 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 the 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 covering the entire width of the belt layer and a pair of belt reinforcing layers 8 covering only the end portion of the belt layer 7) is provided. It is provided. The belt reinforcing layer 8 contains an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 8, the angle of the organic fiber cord with respect to the tire circumferential direction is 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 above-mentioned basic structure.

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 being inclined 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. Note that, in FIGS. The reference numeral E _W indicates the ground contact end (the end portion in the tire width direction of the ground contact region A), and the reference numeral E _C indicates the end portion in the tire circumferential direction of the ground 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 partitioned between a pair of lug grooves 9 adjacent to each other in the tire circumferential direction always includes a horizontal hook-shaped block group 10'consisting of a horizontal hook-shaped block 10 described later. Further, in the illustrated example, in addition to the horizontal hook-shaped block 10 (horizontal hook-shaped block group 10'), the vertical hook-shaped block group 20'consisting of the vertical hook-shaped block 20 described later and the outer block 30 described later are included. .. In the present invention, at least the horizontal hook-shaped block 10 (horizontal hook-shaped block group 10') may be provided, and other structures are not particularly limited. That is, instead of the vertical hook-shaped block 20 (vertical hook-shaped block group 20') and the outer block 30, a block having another shape or the like may be provided.

The horizontal hook-shaped block 10 is divided by at least one vertical groove 11 and at least one lateral bending groove 12 in each of the land portions partitioned between a pair of lug grooves 9 adjacent to each other in the tire circumferential direction. It is a block. In other words, one lug groove 9, one vertical groove 11, one other vertical groove 11, or a groove extending in the tire circumferential direction (for example, a vertical bending groove 21 described later or a circumferential groove described later). The block partitioned by 31) and one lateral bending groove 12 is a horizontal hook-shaped block 10 (the horizontal hook-shaped block 10 is located on the outermost side in the tire width direction, and one lug groove 9 and 1 Including the case where the book is partitioned by the vertical groove 11 and one lateral bending groove 12). In the illustrated example, two vertical grooves 11 and three lateral bending grooves 12 (one lateral bending groove 12, two located between one vertical groove 11 and the vertical bending groove 21 described later). One lateral bending groove 12 located between the vertical grooves 11 and one lateral bending groove 12) located between the other vertical groove 11 and the circumferential groove 31 described later are provided in the tire circumferential direction. A total of six horizontal hook-shaped blocks 10 are formed in two rows and three rows in the tire width direction. Of these, the two horizontal hook-shaped blocks 10 belonging to the row farthest from the tire equatorial CL have one lug groove 9, one vertical groove 11, one lateral bending groove 12, and one circumference described later, respectively. The two horizontal hook-shaped blocks 10 which are partitioned by the directional grooves 31 and belong to the row on the CL side of the tire equatorial line are one lug groove 9, one vertical groove 11, and one lateral bending groove 12, respectively. The two horizontal hook-shaped blocks 10 which are partitioned by the vertical bending grooves 21 described later in the book and belong to the row between them have one lug groove 9, two vertical grooves 11, and one horizontal bending groove, respectively. It is partitioned by 12.

The vertical groove 11 is a groove that extends linearly with respect to the lug groove 9 at an angle of 80 ° or more and 100 ° or less, and both ends communicate with the lug groove 9. The lateral bending groove 12 is inclined and extends at an angle of 5 ° or more and 15 ° or less (preferably the same angle as the lug groove 9) with respect to the tire width direction, one end communicating with the vertical groove 11 and the other end. It communicates with the vertical groove 11 on one end side and a groove extending along the tire circumferential direction adjacent to the tire circumferential direction (one of another vertical groove 11, a vertical bending groove 21 described later, or a circumferential groove 31 described later). It is a groove that is opened to the outside in the tire width direction and the middle part is bent. In particular, in the illustrated example, the lateral bending groove 12 communicates with a groove (one of the vertical groove 11, the vertical bending groove 21 described later, and the circumferential groove 31 described later) having one end extending along the tire circumferential direction. A pair of main portions 12a extending at an angle of 5 ° or more and 15 ° or less with respect to the tire width direction, and the vertical grooves 11 connecting the ends of the pair of main portions 12a in the land portion. It is composed of a bent portion 12b extending in the same direction. The angle of the lateral bending groove 12 described above is the angle of the main portion 12a excluding the bending portion 12b.

The horizontal hook-shaped block group 10'is a block group composed of the horizontal hook-shaped blocks 10 formed as described above, and has four or more and eight or less horizontal hooks adjacent to each other in the tire width direction or the tire circumferential direction. It is composed of a shape block 10. Preferably, the horizontal hook-shaped blocks 10 are provided in two rows in the tire circumferential direction and in two to four rows in the tire width direction. In the illustrated example, the horizontal hook-shaped block group 10'is composed of a total of six horizontal hook-shaped blocks 10 having two rows in the tire circumferential direction and three rows in the tire width direction as described above.

In the present invention, the individual size of the horizontal hook-shaped blocks 10 is not specified, but it is set to have a sufficient size as the horizontal hook-shaped block group 10'. That is, the length W1 of the horizontal hook-shaped block group 10'in the tire width direction satisfies the relationship of 0.5 TW <W1 ≤ 0.8 TW, preferably 0.6 TW ≤ W1 ≤ 0.7 TW with respect to the ground contact width TW, and is lateral. The tire circumferential length L1 of the hook-shaped block group 10'is set to be 20% or more and 50% or less of the ground contact length TL. As shown in the figure, the length W1 is the distance in the tire width direction between the end points in the tire width direction of the horizontal hook-shaped block group 10', and the length L1 is the tire circumferential direction of the horizontal hook-shaped block group 10'. It is the distance in the tire circumferential direction between the end points of.

Since the horizontal hook-shaped block 10 (horizontal hook-shaped block group 10') is provided in this way, the inclined edge of the lug groove 9 and the inclined edge of the lug groove 9 can be secured while ensuring the land rigidity (rigidity of the horizontal hook-shaped block 10). The edge effect due to the bent edge of the horizontal hook-shaped block 10 can be ensured, and the control drive property during straight running and the grip property during turning running can be improved in a well-balanced manner.

At this time, if the inclination angle α of the lug groove 9 is less than 5 °, the grip property (lateral grip force) during turning travel is reduced. If the inclination angle α of the lug groove 9 exceeds 15 °, the lug groove 9 is inclined too much and the controllability during straight running is lowered. If the angles of the vertical groove 11 and the lateral bending groove 12 deviate from the above range, it becomes difficult to maintain a good shape of the horizontal hook-shaped block 10, and it becomes difficult to sufficiently secure the block rigidity. If the number of the horizontal hook-shaped blocks 10 included in the horizontal hook-shaped block group 10'is less than 4, the effect of enhancing the control driveability during straight running cannot be obtained, and if it exceeds 8, the grip property during turning running is not obtained. Decreases. Since the horizontal hook-shaped block group 10'having a sufficient size in the tire width direction mainly contributes to the controllability during straight running, the horizontal hook-shaped block group 10' has a length W1 in the tire width direction and a ground contact width. If the TW does not satisfy the above relationship, it becomes difficult to obtain good traction performance. If the tire circumferential length L1 of the horizontal hook-shaped block group 10'is less than 20% of the ground contact length TL, the grip system during turning is lowered. If the tire circumferential length L1 of the horizontal hook-shaped block group 10'exceeds 50% of the ground contact length TL, the controllability during straight running is lowered.

As shown in the drawing, the horizontal hook-shaped block group 10'included in each land portion is preferably arranged close to one side or the other side in the tire width direction. For example, as shown in FIG. 2, a horizontal hook-shaped block group 10'arranged on one side in the tire width direction and a horizontal hook-shaped block group 10'arranged on the other side in the tire width direction are formed. It can be arranged so as to be adjacent to each other in the tire circumferential direction. Alternatively, as shown in FIG. 3, all the horizontal hook-shaped block groups 10'can be arranged close to one side (right side in the figure) in the tire width direction.

In the case of FIG. 2, since the horizontal hook-shaped block groups 10'adjacent in the tire circumferential direction have a point-symmetrical relationship with respect to the point on the tire equatorial CL, the tread pattern becomes a non-directional and symmetric pattern. .. Therefore, it is not necessary to produce individual tires according to the mounting direction on the vehicle, so that the productivity can be improved. In the case of FIG. 3, the tread pattern is asymmetrical, 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 lateral hook-shaped blocks 10 'L1 It is preferable that it is% 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 less than 5% and braking and driving at the time of straight running of the tire circumferential length L1 of the lateral 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 lateral hook-shaped blocks 10 '.

In the illustrated example, a vertical hook-shaped block 20 (vertical hook-shaped block group 20') is provided in addition to the horizontal hook-shaped block 10 (horizontal hook-shaped block group 10') as described above. The vertical hook-shaped block 20 (vertical hook-shaped block group 20') is an arbitrary 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 vertical hook-shaped block 20 (vertical hook-shaped block group 20'), the edge effect due to the block shape and the groove shape can be expected, so that the drive control property during straight running and the grip property during turning running can be expected. It is advantageous to improve the balance.

The vertical hook-shaped block 20 is a block partitioned by at least one vertical bending groove 21 in each of the land portions partitioned between a pair of lug grooves 9 adjacent to each other in the tire circumferential direction. In other words, two lug grooves 9, one longitudinal bending groove 21, one other longitudinal bending groove 21, or a groove extending in an arbitrary circumferential direction (for example, a circumferential groove 31 described later). The partitioned block is a vertical hook-shaped block 20 (when the vertical hook-shaped block 20 is located on the outermost side in the tire width direction and is partitioned by two lug grooves 9 and one vertical bending groove 21. Including). In the illustrated example, two vertical bending grooves 21 are provided to form two vertical hook-shaped blocks 20. Of these, the vertical hook-shaped block 20 on the tire equatorial side is partitioned by two lug grooves 9 and two vertical bending grooves 21, and the other vertical hook-shaped block 20 (vertical hook-shaped on the side separated from the tire equatorial CL). The block 20) is partitioned by two lug grooves 9, one vertical bending groove 21, and a circumferential groove 31, which will be described later.

The vertical bending groove 21 is a groove that extends at an angle of 80 ° or more and 100 ° or less with respect to the lug groove 9 and has both ends communicating with the lug groove 9 and the middle portion is bent. In particular, in the illustrated example, the longitudinal bending groove 21 communicates with any of the pair of lug grooves 9 adjacent to the land portion at one end and extends at an angle of 80 ° or more and 100 ° or less with respect to the lug groove 9. It is composed of a pair of main portions 21a and a bent portion 21b extending in the same direction as the lug groove 9 by connecting the ends of the pair of main portions 21a in the land portion. The angle of the vertical bending groove 21 described above is the angle of the main portion 21a excluding the bending portion 21b.

As shown in the figure, the vertical hook-shaped block group 20'included in each land portion is arranged close to the opposite side of the horizontal hook-shaped block group 10'in the tire width direction. Therefore, in FIG. 2, the vertical hook-shaped block group 20'arranged on one side in the tire width direction and the vertical hook-shaped block group 20'arranged on the other side in the tire width direction are arranged in the tire circumferential direction. They are arranged next to each other. Further, in FIG. 3, all the vertical hook-shaped block groups 20'are arranged close to one side (left side in the figure) in the tire width direction. In the examples of FIGS. 2 and 3, only the horizontal hook-shaped block group 10'and the vertical hook-shaped block group 20'are provided inside the circumferential groove 31 described later in the tire width direction.

In the illustrated example, in addition to the horizontal hook-shaped block 10 (horizontal hook-shaped block group 10') as described above, the outer block 30 partitioned by the circumferential groove 31 is provided. The circumferential groove 31 (and the outer block 30) is an arbitrary element in the present invention, but unlike the above-mentioned vertical hook-shaped block 20 (vertical hook-shaped block group 20'), it is preferable to use the groove 31 (and the outer block 30) when traveling straight. It is possible to effectively improve the controllability of the vehicle and the grip during turning.

The circumferential groove 31 is a groove that is arranged outside in the tire width direction of the horizontal hook-shaped block group 10'and extends linearly in the tire circumferential direction over the entire circumference of the tire. In particular, it is preferable that only one side of each end of the horizontal hook-shaped block group 10'in the tire width direction is in contact with the circumferential groove. In other words, of the horizontal hook-shaped blocks 10 included in the horizontal hook-shaped block group 10', the outer side of the horizontal hook-shaped blocks 10 in the row farthest from the tire equatorial CL in the tire width direction is in contact with the circumferential groove 31. Is preferable. By providing the circumferential groove 31 in this way, the edge effect due to the circumferential groove 31 can be expected, which is advantageous for improving the grip during turning. Further, since the effect of discharging water, gravel, etc. can be obtained by the circumferential groove 31, it is advantageous to improve the controllability during straight running.

When the circumferential groove 31 is provided, it is preferable to set the groove width W _C of the circumferential groove 31 to 5% or more and 15% or less of the tire width direction length W1 of the horizontal hook-shaped block group 10'. As a result, the balance between the effect of providing the circumferential groove 31 and the effect of providing the circumferential groove 31 on the horizontal hook-shaped block 10 (horizontal hook-shaped block group 10') can be improved, and the vehicle travels straight. It is advantageous to improve the controllability during running and the grip during turning 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 horizontal hook-shaped block group 10', it becomes difficult to sufficiently improve the controllability during straight running. If the groove width W _C of the circumferential groove 31 exceeds 15% of the tire width direction length W1 of the horizontal hook-shaped block group 10', it becomes difficult to sufficiently improve the grip during turning.

By providing the circumferential groove 31, the outer block 30 is partitioned outside the tire width direction of the circumferential groove 31 in the land portion partitioned between the pair of lug grooves 9. The tire width direction length W3 of the outer block 30 partitioned in this way is preferably 15% or more and 45% or less of the tire width direction length W1 of the horizontal hook-shaped block group 10'. By setting the tire width direction length W3 of the outer block 30 in this way, the outer block 30 can be made an appropriate size, and the position of the circumferential groove 31 is also outside the width direction of the tread portion 1. Since it is limited to the shoulder area, it is possible to secure a sufficient width of the horizontal hook-shaped block group 10', which is advantageous for improving the controllability during straight running and the grip during turning running in a well-balanced manner. Become. If the tire width direction length W3 of the outer block 30 is less than 15% of the tire width direction length W1 of the horizontal hook-shaped block group 10', it becomes difficult to sufficiently improve the control driveability during straight running. If the tire width direction length W3 of the outer block 30 exceeds 45% of the tire width direction length W1 of the horizontal hook-shaped block group 10', it becomes difficult to sufficiently improve the grip during turning.

In the present invention, it is preferable to provide a recess 41 having a depth of 2 mm or less on the tread surface of the horizontal hook-shaped block 10. The recess 41 provided in the horizontal hook-shaped block 10 is preferably a linear recess having a sufficient length at least in the tire width direction. In the illustrated example, the recess 41 has a bent shape corresponding to the shape of the horizontal hook-shaped block 10, and has a straight portion extending linearly in the same direction as the lug groove 9 and a straight portion extending linearly at both ends thereof with respect to the lug groove 9. It is composed of a bent portion extending at an angle of 80 ° or more and 100 ° or less. By providing such a recess 41, an edge effect due to the recess 41 can be expected, which is advantageous for improving the controllability during straight running. If the depth of the recess 41 exceeds 2 mm, the block rigidity decreases, and it becomes difficult to sufficiently improve the grip during turning.

As shown in the illustrated example, the vertical hook-shaped block 20 and the outer block 30 may also be provided with recesses 42 and 43. The recess 42 provided in the vertical hook-shaped block 20 is preferably a linear recess having a sufficient length at least in the tire circumferential direction. In the illustrated example, the recess 42 has a bent shape corresponding to the shape of the vertical hook-shaped block 20, and has a straight portion extending linearly at an angle of 80 ° or more and 100 ° or less with respect to the lug groove 9. It is composed of a pair of bent portions extending in the same direction as the lug groove 9 at both ends. The recess 43 provided in the outer block 30 is preferably a linear recess 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 recesses 42 and 43, the edge effect due to these recesses 42 and 43 can be expected, which is advantageous for improving the controllability during straight running. It is preferable to set the depths of these dents 42 and 43 to 2 mm or less in consideration of the influence on the grip during turning.

The present invention described above can be applied to various pneumatic tires, and can be particularly preferably used as a tire for traveling on rough terrain. Above all, it is preferable to use it as a tire for competitions running on rough terrain such as rallies and dirt trials. That is, with the above-mentioned structure, the control drive property during straight running and the grip property during turning running are well balanced, so that good running performance can be obtained on rough terrain.

The tire size is 205 / 65R15, and it has the basic structure illustrated in FIG. 1, based on the tread pattern of FIG. 2 or 3, the shape of the lug groove, the inclination angle α of the lug groove, and the horizontal hook-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 flutes relative to the lug grooves, the angle of the lateral curved groove with respect to the tire width direction, lateral hook-shaped blocks included in the horizontal hook-like blocks , The arrangement of the horizontal hook-shaped block group, the ratio W1 / TW of the width W1 of the horizontal hook-shaped block group to the ground contact width TW, the ratio L1 / TL of the circumferential length L1 of the horizontal hook-shaped block group to the ground contact length TL, Presence or absence of dents on the tread surface of the horizontal hook-shaped block, depth of dents, number of circumferential grooves, positional relationship between the circumferential groove and the horizontal hook-shaped block group, groove of the circumferential groove with respect to the width W1 of the horizontal hook-shaped block group. The ratio W _C / W1 of the width W _C and the ratio W3 / W1 of the width W3 of the outer block to the width W1 of the horizontal hook-shaped block group are set as shown in Tables 1 to 3, respectively, in Conventional Example 1 and Comparative Examples 1 to 8. , 32 types of pneumatic tires of Examples 1 to 23 were produced.

In Conventional Example 1, lug grooves curved and extending along the tire width direction are provided at intervals in the tire circumferential direction, and the land portion is partitioned between a pair of lug grooves adjacent to each other in the tire circumferential direction. This is an example including a group of horizontal hook-shaped blocks composed of horizontal hook-shaped blocks having the same shape as that of the present invention. In the conventional example 1, the horizontal hook-shaped block group is provided close to one side in the tire width direction (the inside of the vehicle which is inside the vehicle when mounted on the vehicle), and the circumferential groove is provided on the same side as the horizontal hook-shaped block group (the horizontal hook-shaped block group). It is provided adjacent to the horizontal hook-shaped block group only on the inside of the vehicle. Further, in the conventional example 1, the lug groove extends along the tire width direction in the region inside the vehicle, and is inclined toward the outside in the tire width direction in the region outside the vehicle in the direction opposite to the tire rotation direction. There is. That is, the tire of Conventional Example 1 is a tire having an asymmetrical tread pattern, and a pair of left and right tires is required.

The numbers in the figure are shown in the column of "Arrangement of horizontal hook-shaped block groups" in Tables 1 to 3, but this does not mean that each example has the pattern of the drawing, but the horizontal hook-shaped block group. It shows that the arrangement of is similar to the drawing. That is, as shown in FIG. 2, the horizontal hook-shaped block group arranged close to one side in the tire width direction and the horizontal hook-shaped block group arranged close to the other side in the tire width direction are arranged in the tire circumferential direction. As shown in FIG. 2 and FIG. 3, the case where the blocks are arranged alternately is shown as “FIG. 3” when all the horizontal hook-shaped block groups are arranged close to one side in the tire width direction.

For these 32 types of pneumatic tires, straight-ahead driveability, turning steering stability, and mold manufacturing cost were evaluated by the following evaluation methods, and the results are also shown in Tables 1 to 3.

Straight-ahead driveability and turning steering stability Each test tire is assembled on a wheel with a rim size of 15 x 7.0J, installed on a four-wheel drive vehicle (test vehicle) with a displacement of 2000cc with an air pressure of 200kPa, and a lap of 2km. A test driver runs three laps on a test course that imitates leveling (a course that includes an area covered with floating gravel and an area dug up), and the test driver explains the controllability when going straight and the steering stability when turning. A sensory evaluation was performed. The evaluation results are shown by indexes with the value of Conventional Example 1 as 100. The larger this index value is, the better the straight-ahead driveability and the turning steering stability are.

Productivity For each test tire, the mold manufacturing cost required to manufacture the tire to be mounted on the test vehicle was evaluated as an index of productivity. The evaluation result is shown by an index with the value of Conventional Example 1 as 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 23 have improved straight-ahead driveability and turning maneuvering stability as compared with Conventional Example 1. Further, since all of Examples 1 to 23 have a non-directional tread pattern as compared with the conventional example 1 having an asymmetric directional tread pattern as described above, less types of molds are required. , Productivity could be increased (mold production cost could be kept low).

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

Although not shown in Tables 1 to 3, all the horizontal hook-shaped block groups are arranged close to one side in the tire width direction as in Example 2, and other as in Examples 3 to 23. When the items were changed, the same results as in Examples 3 to 23 with respect to Example 1 were obtained with respect to Example 2.

1 Tread part 2 sidewall part 3 bead part 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcement layer 9 lug groove 10 horizontal hook-shaped block 10'horizontal hook-shaped block group 11 vertical groove 12 horizontal bending groove 20 vertical hook Shaped block 20'Vertical hook-shaped block group 21 Vertical and horizontal bending groove 30 Outer block 31 Circumferential groove 41, 42, 43 Recess CL Tire equatorial E _W Grounding end

Claims (7)

A tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged inside the tire radial direction of these sidewall portions. With pneumatic tires
A pair of lug grooves extending linearly 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 partitioned between the lug grooves extends linearly with respect to the lug groove at an angle of 80 ° or more and 100 ° or less, and both ends communicate with the pair of lug grooves. 4 partitioned by a groove and at least one laterally bent groove that communicates with the vertical groove and extends at an inclination angle of 5 ° or more and 15 ° or less with respect to the tire width direction and has a bent portion in the middle portion. A group of horizontal hook-shaped blocks composed of 8 or more horizontal hook-shaped blocks is included, and the length W1 of the horizontal hook-shaped block group in the tire width direction is 0.5 TW <W1 ≦ 0.8 TW with respect to the ground contact width TW. A pneumatic tire that satisfies the relationship and is characterized in that the tire circumferential length L1 of the horizontal hook-shaped block group is 20% or more and 50% or less of the ground contact length TL. 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 horizontal hook-shaped blocks in the tire circumferential direction length L1. The pneumatic tire according to claim 1 or 2, wherein the tread surface of the horizontal hook-shaped block is provided with a recess having a depth of 2 mm or less. The lateral hook-shaped block group is provided with at least one circumferential groove extending linearly in the tire circumferential direction over the entire circumference of the tire on the outer side in the tire width direction, and each of the horizontal hook-shaped block groups is provided 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 of the tire is in contact with the circumferential groove. The pneumatic tire according to claim 4, wherein the groove width W _C of the circumferential groove is 5% or more and 15% or less of the tire width direction length W1 of the horizontal hook-shaped block group. The tire width direction length W3 of the outer block partitioned outside the tire width direction of the circumferential groove is 15% or more and 45% or less of the tire width direction length W1 of the horizontal hook-shaped block group. The pneumatic tire according to claim 4 or 5. The pneumatic tire according to any one of claims 1 to 6, wherein the tire is for traveling on rough terrain.

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