JP6822186B2 - 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 has an angle of 80 ° or more and 100 ° or less with respect to the lug groove. A vertical hook consisting of two or more and four or less vertical hook-shaped blocks partitioned by at least one vertical bending groove having both ends communicating with the pair of lug grooves and having a bending portion in the middle. The shape block group and at least one vertical groove extending linearly at an angle of 80 ° or more and 100 ° or less with respect to the lug groove and having both ends communicating with the pair of lug grooves and communicating with the vertical groove. 4 or more and 8 or less lateral hooks that extend at an inclination angle of 5 ° or more and 15 ° or less with respect to the tire width direction and are partitioned by at least one lateral bending groove having a bending portion in the middle portion. Including a horizontal hook-shaped block group composed of shaped blocks, the vertical hook-shaped block group is arranged close to one side in the tire width direction in each land portion, and the horizontal hook-shaped block group is arranged on the other side in the tire width direction. The vertical hook-shaped block group and the horizontal hook-shaped block group are alternately arranged in the tire circumferential direction on one side and the other side in the tire width direction, respectively, and the tires of the vertical hook-shaped block group are arranged close to each other. The width direction length W1 satisfies the relationship of 0.4 TW ≦ W1 ≦ 0.5 TW with respect to the ground contact width TW, and the tire width direction length W2 of the horizontal hook-shaped block group is 0.4 TW ≦ with respect to the ground contact width TW. Satisfying the relationship of W2 ≦ 0.5 TW, the tire circumferential length L1 of the vertical hook-shaped block group and the tire circumferential length L2 of the horizontal hook-shaped block group are 20% or more and 50% or less of the ground contact length TL, respectively. It is characterized by being.

In the present invention, as described above, a plurality of vertical hook-shaped blocks (vertical hook-shaped block group), which are provided with linear lug grooves inclined at a predetermined angle and further partitioned by vertical bending grooves, vertical grooves and Since a plurality of horizontal hook-shaped blocks (horizontal hook-shaped block group) partitioned by the horizontal bending groove are provided in a sufficient range with respect to the ground contact area, the land rigidity (vertical hook-shaped block and horizontal hook-shaped block) is provided. Rigidity), while ensuring the edge effect of the slanted edge of the lug groove and the bent edge of the vertical hook-shaped block and the horizontal hook-shaped block, the drive control during straight running and the grip during turning Can be improved 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 vertical 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 vertical hook-shaped block and 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, the vertical hook-shaped block group and the horizontal hook-shaped block group are 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 have a vertical hook shape. In each of the block group and the horizontal hook-shaped block group, it is preferable that only one side of the end portion in the tire width direction 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 vertical hook-shaped block group. By setting the groove width W _C of the circumferential groove in this way, a good balance between the effect of providing the circumferential groove and the influence of providing the circumferential groove on the vertical hook-shaped block and the horizontal hook-shaped block is good. This is advantageous for improving 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 vertical 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.

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 FIG. 2, 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. In FIG. 2, the reference numeral A (the region surrounded by the broken line) schematically shows the ground contact region which is the basis of the ground contact width TW and the ground contact length TL described later. 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 is a horizontal hook composed of a vertical hook-shaped block group 10'described later and a horizontal hook-shaped block 20 described later. It always includes the shape block group 20'. Further, in the illustrated example, in addition to these blocks (block group), the outer block 30 described later is included. In the present invention, at least a vertical hook-shaped block 10 (vertical hook-shaped block group 10') and a horizontal hook-shaped block 20 (horizontal hook-shaped block group 20') may be provided, and other structures are not particularly limited. That is, a block or the like having another shape may be provided instead of the outer block 30. Alternatively, the entire land portion may be composed of a vertical hook-shaped block 10 (vertical hook-shaped block group 10') and a horizontal hook-shaped block 20 (horizontal hook-shaped block group 20').

The vertical hook-shaped block 10 is a block partitioned by at least one vertical bending groove 11 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 11, one other longitudinal 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 hook-shaped block 10 (when the vertical hook-shaped 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. Including). In the illustrated example, two vertical bending grooves 11 are provided to form two vertical hook-shaped blocks 10. Of these, the vertical hook-shaped 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, which will be described later, and has a vertical hook shape on the tire equator CL side. The block 10 is divided by two lug grooves 9 and two vertical bending grooves 11.

The vertical bending 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 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 11 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 11a and a bent portion 11b extending in the same direction as the lug groove 9 by connecting the ends of the pair of main portions in the land portion. The angle of the vertical bending groove 11 described above is the angle of the main portion 11a excluding the bending portion 11b.

The vertical hook-shaped block group 10'is a block group composed of the vertical hook-shaped blocks 10 formed as described above, and is composed of two or more and five or less vertical hook-shaped blocks 10 adjacent to each other in the tire width direction. It is composed. In the illustrated example, the vertical hook-shaped block group 10'is composed of two vertical hook-shaped blocks 10.

The horizontal hook-shaped block 20 is divided by at least one vertical groove 21 and at least one lateral bending groove 22 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 21, one other vertical groove 21, or a groove extending in the tire circumferential direction (for example, the above-mentioned vertical bending groove 11 and the later-described circumferential groove). The block partitioned by 31) and one lateral bending groove 22 is a horizontal hook-shaped block 20 (the horizontal hook-shaped block 20 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 21 and one lateral bending groove 22). In the illustrated example, one vertical groove 21 and two horizontal bending grooves 22 (one horizontal bending groove 22 located between the vertical groove 21 and the above-mentioned vertical bending groove 11, the vertical groove 21 and the vertical groove 21 will be described later. A single lateral bending groove 22) located between the circumferential groove 31 and the tire is provided to form a total of four horizontal hook-shaped blocks 20 having two rows in the tire circumferential direction and two rows in the tire width direction. Has been done. Of these, the two horizontal hook-shaped blocks 20 belonging to the row farthest from the tire equatorial CL have one lug groove 9, one vertical groove 21, one lateral bending groove 22, and one circumference described later, respectively. The two horizontal hook-shaped blocks 20 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 21, and one lateral bending groove 22, respectively. It is partitioned by the above-mentioned vertical bending groove 11 of the book.

The vertical groove 21 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 22 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 21 and the other end. It communicates with the vertical groove 21 on one end side and a groove extending along the tire circumferential direction adjacent to the tire circumferential direction (one of the other vertical groove 21, the above-mentioned vertical bending groove 11, or the later-described circumferential groove 31). 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 22 communicates with a groove having one end extending along the tire circumferential direction (one of the vertical groove 21, the above-mentioned vertical bending groove 21, and the later-described circumferential groove 31). A pair of main portions 22a extending at an angle of 5 ° or more and 15 ° or less with respect to the tire width direction, and a vertical groove 21 connecting the ends of the pair of main portions 22a in the land portion. It is composed of a bent portion 22b extending in the same direction. The angle of the lateral bending groove 22 described above is the angle of the main portion 22a excluding the bending portion 22b.

The horizontal hook-shaped block group 20'is a block group composed of the horizontal hook-shaped blocks 20 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 20. Preferably, the horizontal hook-shaped blocks 20 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 20'is composed of a total of four horizontal hook-shaped blocks 10 having two rows in the tire circumferential direction and two rows in the tire width direction as described above.

The vertical hook-shaped block group 10'and the horizontal hook-shaped block group 20'included in each land portion are arranged close to one side or the other side in the tire width direction, respectively, as shown in the drawing. Further, the vertical hook-shaped block group 10'and the horizontal hook-shaped block group 20'are alternately arranged in the tire circumferential direction on one side and the other side in the tire width direction, respectively. That is, focusing on the vertical hook-shaped block group 10', as shown in the figure, the vertical hook-shaped block group 10'arranged on one side in the tire width direction and the vertical hook-shaped block group 10'arranged on the other side in the tire width direction. The vertical hook-shaped block group 10'is arranged so as to be adjacent to each other in the tire circumferential direction. Focusing on the horizontal hook-shaped block group 20', as shown in the figure, the horizontal hook-shaped block group 20'and the tire width arranged closer to the other side in the tire width direction (opposite side of the vertical hook-shaped block group 10'). The horizontal hook-shaped block groups 20'arranged close to one side in the direction (opposite side of the vertical hook-shaped block group 10') are arranged so as to be adjacent to each other in the tire circumferential direction. That is, the vertical hook-shaped block group 10'and the horizontal hook-shaped block group 20'have a point-symmetrical relationship with respect to a point on the tire equatorial CL, and the tread pattern consisting of these block groups is omnidirectional and contrasting. It has a typical pattern.

In the present invention, the individual sizes of the vertical hook-shaped block 10 and the horizontal hook-shaped block 20 are not specified, but they are set to have a sufficient size as the vertical hook-shaped block group 10'or the horizontal hook-shaped block group 20'. Has been done. That is, the length W1 in the tire width direction of the vertical hook-shaped block group 10'satisfy the relationship of 0.4 TW ≤ W1 ≤ 0.5 TW with respect to the ground contact width TW, and the length in the tire width direction of the horizontal hook-shaped block group 20'. W2 satisfies the relationship of 0.4 TW ≤ W2 ≤ 0.5 TW with respect to the ground contact width TW, and the tire circumferential length L1 of the vertical hook-shaped block group 10'and the tire circumferential length of the horizontal hook-shaped block group 20'. L2 is set to 20% or more and 50% or less of the ground contact length TL, respectively. 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 vertical hook-shaped block group 10', and the length W2 is the distance in the tire width direction of the horizontal hook-shaped block group 20'. The distance between the end points in the tire width direction, the length L1 is the distance in the tire circumferential direction between the end points in the tire circumferential direction of the vertical hook-shaped block group 10', and the length L2 is the distance of the horizontal hook-shaped block group 20'. It is the distance in the tire circumferential direction between the end points in the tire circumferential direction.

As described above, since the vertical hook-shaped block 10 (vertical hook-shaped block group 10') and the horizontal hook-shaped block 20 (horizontal hook-shaped block group 20') are provided, the land rigidity (vertical hook-shaped block 10 and the vertical hook-shaped block 10'and While ensuring the rigidity of the horizontal hook-shaped block 20), the edge effect of the inclined edge of the lug groove 9 and the bent edge of the vertical hook-shaped block 10 and the horizontal hook-shaped block 20 is ensured to control the driving when traveling straight. It is possible to improve the performance and the grip during turning in a well-balanced manner. Further, since the tread pattern is a non-directional and symmetrical pattern as described above, it is not necessary to produce individual tires according to the mounting direction with respect to the vehicle, and the productivity can be improved.

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 angle of the vertical bending groove 11 deviates from the above range, it becomes difficult to maintain a good shape of the vertical hook-shaped block 10, and it becomes difficult to secure sufficient block rigidity. If the number of vertical hook-shaped blocks 10 included in the vertical hook-shaped block group 10'is less than 2, the effect of enhancing the driving control during straight running cannot be obtained, and if it exceeds 4, the grip during turning is not obtained. Decreases. Since the vertical hook-shaped block group 10'having a sufficient size in the tire width direction mainly contributes to the cornering performance, the length W1 in the tire width direction and the ground contact width TW of the vertical hook-shaped block group 10'are described above. If the relationship is not satisfied, it will be difficult to obtain good cornering performance. If the tire circumferential length L1 of the vertical 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 vertical hook-shaped block group 10'exceeds 50% of the ground contact length TL, the controllability during straight running is lowered.

If the angles of the vertical groove 21 and the lateral bending groove 22 deviate from the above range, it becomes difficult to maintain a good shape of the horizontal hook-shaped block 20, and it becomes difficult to sufficiently secure the block rigidity. If the number of the horizontal hook-shaped blocks 20 included in the horizontal hook-shaped block group 20'is less than 4, the effect of enhancing the driving control during straight running cannot be obtained, and if it exceeds 8, the grip during turning running is not obtained. Decreases. Since the horizontal hook-shaped block group 20'having a sufficient size in the tire width direction mainly contributes to the controllability during straight running, the horizontal hook-shaped block group 20' has a length W2 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 L2 of the horizontal hook-shaped block group 20'is less than 20% of the ground contact length TL, the grip system during turning is lowered. If the tire circumferential length L2 of the horizontal hook-shaped block group 20'exceeds 50% of the ground contact length TL, the controllability during straight running is lowered.

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 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 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, in addition to the vertical hook-shaped block 10 (vertical hook-shaped block group 10') and the horizontal hook-shaped block 20 (horizontal hook-shaped block group 20'), the outer side partitioned by the circumferential groove 31. A block 30 is provided. The circumferential groove 31 (and the outer block 30) is an arbitrary element in the present invention, but it is advantageous to use it because it is advantageous in improving the control drive property during straight running and the grip property during turning running. preferable.

The circumferential groove 31 is a groove that is arranged outside the vertical hook-shaped block group 10'and the horizontal hook-shaped block group 20'in the tire width direction 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 the end portion in the tire width direction of each of the vertical hook-shaped block group 10'and the horizontal hook-shaped block group 20'is in contact with the circumferential groove. In other words, of the vertical hook-shaped blocks 10 included in the vertical hook-shaped block group 10', the outer side of the vertical hook-shaped block 10 farthest from the tire equatorial CL in the tire width direction is in contact with the circumferential groove 31 and has a horizontal hook shape. Of the horizontal hook-shaped blocks 20 included in the block group 20', the outer side of the horizontal hook-shaped blocks 20 in the row farthest from the tire equatorial CL in the tire width direction is preferably in contact with the circumferential groove 31. 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 vertical hook-shaped block group 10'. As a result, the effect of providing the circumferential groove 31 and the vertical hook-shaped block 10 (vertical hook-shaped block group 10') and the horizontal hook-shaped block 20 (horizontal hook-shaped block group 20') by providing the circumferential groove 31 It is possible to improve the balance with the influence on the vehicle, which is advantageous for improving the controllability during straight running and the grip during turning running 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 hook-shaped block group 10', it becomes difficult to sufficiently improve the control driveability 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 vertical 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 vertical 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 vertical hook-shaped block group 10'and the horizontal hook-shaped block group 20', and to provide control driving property during straight running and gripping property during turning running. It is advantageous to improve in a well-balanced manner. 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 vertical 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 vertical hook-shaped block group 10', it becomes difficult to sufficiently improve the grip during turning.

In the present invention, it is preferable to provide recesses 41 and 42 having a depth of 2 mm or less on the treads of the vertical hook-shaped block 10 and the horizontal hook-shaped block 20. By providing the recesses 41 and 42 in this way, the edge effect due to the recesses 41 and 42 can be expected, which is advantageous for improving the controllability during straight running. If the depths of the dents 41 and 42 exceed 2 mm, the block rigidity decreases and it becomes difficult to sufficiently improve the grip during turning.

The shape of the recess 41 provided in the vertical hook-shaped block 10 is preferably a linear shape having a sufficient length at least in the tire circumferential direction. For example, as shown in the figure, the recess 41 has a bent shape corresponding to the shape of the vertical hook-shaped block 10, and is a straight portion extending linearly at an angle of 80 ° or more and 100 ° or less with respect to the lug groove 9. And a pair of bent portions extending in the same direction as the lug groove 9 at both ends thereof. Similarly, the shape of the recess 42 provided in the horizontal hook-shaped block 20 is preferably a linear shape having a sufficient length at least in the tire width direction. For example, as shown in the figure, the recess 42 has a bent shape corresponding to the shape of the horizontal hook-shaped block 20, and has a straight portion extending linearly in the same direction as the lug groove 9 and lug grooves 9 at both ends thereof. It is preferable that it is composed of a bent portion extending at an angle of 80 ° or more and 100 ° or less.

As shown in the illustrated example, the outer block 30 may be provided with a recess 43. 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 the recess 43 in this way, the edge effect due to the recess 43 can be expected, which is advantageous for improving the controllability during straight running. It is preferable to set the depth of the recess 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, has the basic structure illustrated in FIG. 1, and is based on the tread pattern of FIG. 2, the shape of the lug groove, the inclination angle α of the lug groove, and the tire circumferential direction of the vertical hook-shaped block group. the ratio of the width W _L of the lug groove to the length L1 W _L / L1, with respect to the longitudinal hook-shaped blocks, the number of longitudinal hook-shaped blocks included angle of the longitudinal curved groove for the lug grooves, the longitudinal hook-shaped blocks, ground contact width The ratio W1 / TW of the width W1 of the vertical hook-shaped block group to the TW, the ratio L1 / TL of the circumferential length L1 of the vertical hook-shaped block group to the ground contact length TL, and the vertical groove of the vertical hook-shaped block group to the lug groove. Angle, angle of lateral bending groove with respect to tire width direction, number of lateral hook-shaped blocks included in horizontal hook-shaped block group, arrangement of horizontal hook-shaped block group, ratio of width W1 of horizontal hook-shaped block group to ground contact width TW W1 / TW, ratio of the circumferential length L1 of the horizontal hook-shaped block group to the ground contact length TL L1 / TL, the presence or absence of dents on the treads of the vertical hook-shaped blocks and the horizontal hook-shaped blocks, the depth of the dents, the number of circumferential grooves , The positional relationship between the circumferential groove and the vertical hook-shaped block group, 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, and the outer block with respect to the width W1 of the vertical hook-shaped block group. 37 types of pneumatic tires of Conventional Example 1, Comparative Examples 1 to 12, and Examples 1 to 24 in which the ratio W3 / W1 of the width W3 was set as shown in Tables 1 to 4, respectively, 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 vertical hook-shaped block group composed of vertical hook-shaped blocks having the same shape as the present invention and a horizontal hook-shaped block group composed of horizontal hook-shaped blocks. In Conventional Example 1, the vertical hook-shaped block group is provided close to one side in the tire width direction (the outside of the vehicle, which is the outside of the vehicle when mounted on the vehicle), and the horizontal hook-shaped block group is provided on the other side in the tire width direction (the other side in the tire width direction). It is installed closer to the inside of the vehicle, which is inside the vehicle when it is mounted on the vehicle. The circumferential groove is provided adjacent to the horizontal hook-shaped block group only on the same side (inside the vehicle) as the horizontal hook-shaped block group. That is, the circumferential groove is provided only on the opposite side (inside the vehicle) of the vertical hook-shaped block group and not adjacent to the vertical hook-shaped block group. 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.

For these 37 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 shown in Tables 1 to 4.

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 4, all of Examples 1 to 24 have improved straight-ahead driveability and turning maneuvering stability as compared with Conventional Example 1. Further, since all of Examples 1 to 24 have a non-directional symmetric pattern as compared with the conventional example 1 having an asymmetric directional pattern as described above, less types of molds are required, and productivity is reduced. (Kold the mold manufacturing cost low).

On the other hand, in Comparative Example 1, the ratio W1 / TW was too small and the ratio W2 / TW was too large, and the width of the vertical hook-shaped block group could not be sufficiently secured, so that the steering stability during turning deteriorated. In Comparative Example 2, the ratio W1 / TW was excessive and the ratio W2 / TW was too small, and the width of the horizontal hook-shaped block group could not be sufficiently secured, so that the controllability at the time of going straight was deteriorated. In Comparative Example 3, the ratio W1 / TW was too small, and the width of the vertical hook-shaped block group could not be sufficiently secured, so that the steering stability during turning deteriorated. In Comparative Example 4, the ratio W2 / TW was too small, and the width of the horizontal hook-shaped block group could not be sufficiently secured, so that the controllability at the time of going straight was deteriorated.

In Comparative Example 5, since the inclination angle of the lug groove was too small, the steering stability at the time of turning was deteriorated. In Comparative Example 6, since the inclination angle of the lug groove was excessive, the controllability at the time of going straight was deteriorated. In Comparative Example 7, since the number of vertical hook-shaped blocks included in the vertical hook-shaped block group was too small, the steering stability during turning deteriorated. In Comparative Example 8, since the number of vertical hook-shaped blocks included in the vertical hook-shaped block group was excessive, the control driveability at the time of going straight was deteriorated. In Comparative Example 9, since the number of horizontal hook-shaped blocks included in the horizontal hook-shaped block group was too small, the control driveability at the time of going straight was deteriorated. In Comparative Example 10, 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 11, the ratio L1 / TL and the ratio L2 / TL are too small, and the longitudinal lengths of the vertical hook-shaped block group and the horizontal hook-shaped block group cannot be sufficiently secured, so that the steering stability during turning deteriorates. did. In Comparative Example 12, the ratio L1 / TL and the ratio L2 / TL were excessive, and the ratio of the vertical hook-shaped block group and the horizontal hook-shaped block group to the ground contact length was too large, so that the control driveability at the time of straight running deteriorated.

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 vertical hook-shaped block 10'vertical hook-shaped block group 11 vertical bending groove 20 horizontal hook-shaped block 20 ′ Horizontal hook-shaped block group 21 Vertical groove 22 Horizontal bending groove 30 Outer block 31 Circumferential groove 41, 42, 43 Depression 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 plurality 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.
The land portion partitioned between the pair of lug grooves adjacent to each other in the tire circumferential direction extends at an angle of 80 ° or more and 100 ° or less with respect to the lug groove, and both ends communicate with the pair of lug grooves. A group of vertical hook-shaped blocks composed of two or more and four or less vertical hook-shaped blocks partitioned by at least one vertical bending groove having a bent portion in the middle portion, and 80 ° or more and 100 ° with respect to the lug groove. At least one flute that extends linearly at an angle of ° or less and has both ends communicating with the pair of lug grooves and an inclination of 5 ° or more and 15 ° or less with respect to the tire width direction that communicates with the flute. Includes a group of horizontal hook-shaped blocks consisting of 4 to 8 horizontal hook-shaped blocks partitioned by at least one lateral bending groove extending at an angle and having a bent portion in the middle portion.
In each land portion, the vertical hook-shaped block group is arranged close to one side in the tire width direction, the horizontal hook-shaped block group is arranged close to the other side in the tire width direction, and one side in the tire width direction. The vertical hook-shaped block group and the horizontal hook-shaped block group are alternately arranged in the tire circumferential direction on and on the other side, respectively.
The length W1 in the tire width direction of the vertical hook-shaped block group satisfies the relationship of 0.4 TW ≦ W1 ≦ 0.5 TW with respect to the ground contact width TW, and the tire width direction length W2 of the horizontal hook-shaped block group is the ground contact width. Satisfying the relationship of 0.4 TW ≤ W2 ≤ 0.5 TW with respect to TW,
A pneumatic tire characterized in that the tire circumferential length L1 of the vertical hook-shaped block group and the tire circumferential length L2 of the horizontal hook-shaped block group are each 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 vertical hook-shaped blocks in the tire circumferential direction length L1. The pneumatic tire according to claim 1 or 2, wherein the treads of the vertical hook-shaped block and the horizontal hook-shaped block are provided with a recess having a depth of 2 mm or less. The vertical hook-shaped block group and the horizontal hook-shaped block group are 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. The pneumatic tire according to any one of claims 1 to 3, wherein each of the group and the horizontal hook-shaped block group is in contact with the circumferential groove only on one side of the end portion in the tire width direction. 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 vertical 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 vertical 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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