JP2019142369A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which is improved in road holding performance on an unpaved road while maintaining good cut resistance.SOLUTION: In a side area on a tire width direction outer side of a shoulder land part 20, one side block 40 is provided for each of a pair of shoulder blocks (first block 21a and second block 21b) which are adjacent to each other in a tire circumferential direction. Each side block 40 includes three areas comprising a high level area 41, a middle level area 42 and a low level area 43 which have raised heights different from one another. The high level area 41 and the low level area 43 are located at respective extension positions of the first block 21a and the second block 21b, and the high level area 41 on the first block 21a side and the high level area 41 on the second block side 21b side are adjacent to each other with the middle level area 42, which is formed as a narrow groove having a width of 10 mm or less, interposed therebetween.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire suitable as a tire for traveling on an unpaved road, and more particularly to a pneumatic tire improved in running performance on an unpaved road while maintaining good cut resistance.

  Pneumatic tires intended for running on unpaved roads such as rough terrain, muddy ground, snowy roads, sandy terrain, and rocky terrain are generally tread patterns mainly composed of lug grooves and blocks with many edge components. A thing with a large area is adopted. In such tires, mud, snow, sand, stones, rocks, etc. on the road surface (hereinafter collectively referred to as “mud etc.”) get traction performance, and mud etc. It prevents clogging and improves running performance on unpaved roads. In particular, by providing blocks (side blocks) in the side area outside the tread shoulder area in the tire width direction (outside the ground contact edge in the tire width direction), it is proposed to improve driving performance on unpaved roads. (For example, see Patent Documents 1 and 2).

  Comparing these tires of Patent Documents 1 and 2, the tire of Patent Document 1 is a tire of a type that has a relatively small groove area, has relatively little unevenness in the side region, and takes into account the running performance on paved roads. It can be said that there is. On the other hand, the tire of Patent Document 2 has a large groove area, large individual blocks, and emphasized unevenness in the side region, and can be said to be a type of tire specialized in running performance on an unpaved road. Therefore, the former tends to have lower running performance on an unpaved road than the latter, and the latter tends to have lower performance during normal driving (such as noise performance) than the former. Further, in a tire having a side block, it is necessary to consider not only the land portion existing in the tread portion but also the wear and damage of the side block itself. In recent years, the demand performance for tires has been diversified, and there is also a demand for tires for running on unpaved roads that have an intermediate level of performance between these two types of tires. Therefore, there is a demand for measures for enhancing the durability and the durability (cut resistance) of the side block.

Japanese Unexamined Patent Publication No. 2016-150603 JP 2013-119277 A

  An object of the present invention is to provide a pneumatic tire with improved running performance on an unpaved road while maintaining good cut resistance.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of the tire, a pair of main grooves extending along the tire circumferential direction on both sides of the tire equator on the surface of the tread portion, The main body groove has a shoulder land portion partitioned on the outer side in the tire width direction and a plurality of shoulder lug grooves extending along the tire width direction, and the shoulder lug grooves are arranged at intervals in the tire circumferential direction. The shoulder land portion is partitioned into a plurality of shoulder blocks by the shoulder lug groove, and the side region adjacent to the outer side of the shoulder land portion in the tire width direction is A plurality of side blocks raised from the surface of the wall portion are formed at intervals in the tire circumferential direction one by one with respect to the pair of shoulder blocks adjacent in the tire circumferential direction, and each side block has a raised height. It includes three regions of different high-level region, middle-level region, and low-level region. The raised height H1 of the high-level region, the raised height H2 of the middle-level region, and the raised height H3 of the low-level region are , H1> H2> H3, and when one of the pair of shoulder blocks is a first block and the other is a second block, the first block and the second block are extended at the extended positions. A level region and the low level region exist, and the high level region on the first block side and the high level region on the second block side are formed as narrow grooves having a width of 10 mm or less. Characterized in that adjacent to each other with the middle-level area.

  In the present invention, since the side block is configured as described above, each region raised at different heights effectively acts on an unpaved road (road surface having an irregular uneven shape). The running performance (startability) can be improved. In particular, since the high-level area, the middle-level area, and the low-level area are arranged as described above, the balance of the positional relationship between these areas is improved, and the startability on the unpaved road can be effectively enhanced. it can. In addition, since one side block is provided for each of the two shoulder blocks, the size of each side block is sufficiently secured, and the block rigidity is sufficiently secured even when there is a region with a low raised height. The cut resistance can be maintained well.

  In the present invention, the line portion formed by the boundary between the low level region and the high level region when viewed from the top surface side of the side block has at least one bending point, and the line portions on both sides of the bending point are The formed angle is preferably 90 ° or more. Thereby, the edge part formed between the low level area | region and the high level area | region can fully be ensured, and it becomes advantageous to improving the running performance on an unpaved road.

  In the present invention, the difference ΔH between the height H1 of the high level region and the height H2 of the middle level region is preferably 0.5 mm or more. In this way, by making the medium level area arranged between the high level areas moderately deep with respect to the high level area, it is possible to improve the soil removal property by the medium level area (thin groove), in the unpaved road This is advantageous for improving running performance.

  In the present invention, in each side block, the total area S1 of the high level region is preferably larger than the total area S3 of the low level region. Furthermore, in each side block, the total area S1 of the high-level region is preferably 110% to 135% of the total area S3 of the low-level region. Thus, cut resistance can be improved by enlarging a high level area | region sufficiently and also setting the area to an appropriate range.

  In the present invention, in the extended position of the first block, the high level region is arranged on the tread portion side from the low level region, and in the extended position of the second block, the low level region is arranged on the tread portion side from the high level region, In addition, the area of the low level region on the second block side is preferably larger than the area of the low level region on the first block side. By setting the arrangement and size of each region in this way, the balance of rigidity of each portion becomes good, which is advantageous for improving cut resistance.

  In the present invention, it is preferable that the raised height H3 of the low level region is 0.5 mm or more. By sufficiently raising even the low level area with the lowest elevation height in this way, the elevation height of the entire side block can be secured sufficiently, and the running performance on the unpaved road is improved and the cut resistance is also improved. Can be increased.

  In the present invention, it is preferable that at least a part of each side block is connected to the side surface of the shoulder block. By connecting the side block and the shoulder block in this way, a series of edge components extending from the side surface of the shoulder block to the side block will act effectively on the road surface, and the driving performance on the unpaved road is improved. Will be advantageous.

  In the present invention, the term “contacting end” refers to the tire axial direction of the contact region formed when a normal load is applied by placing the tire on a normal rim and filling the normal internal pressure in a vertical state on a plane. It is the both ends of. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESSURE” in the case of ETRTO, is 180 kPa when the tire is for passenger cars. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORMATION PRESURES”, “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a front view which shows the tread surface of the pneumatic tire which consists of embodiment of this invention. It is explanatory drawing which expands and shows the principal part of this invention. It is xx arrow sectional drawing of FIG.

  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 is disposed on a tread portion 1, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and on the tire radial direction inner side of the sidewall portion 2. And a pair of bead portions 3. In FIG. 1, reference sign CL indicates a tire equator, and reference sign E indicates a ground contact end. Although FIG. 1 is a meridian cross-sectional view and is not depicted, the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction to form an annular shape. The toroidal basic structure is constructed. Hereinafter, the description using FIG. 1 is basically based on the meridian cross-sectional shape shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

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

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

  A pair of main grooves 10 extending along the tire circumferential direction on both sides of the tire equator CL are formed on the surface of the tread portion 1 of the pneumatic tire of the present invention. In particular, in the example of FIG. 2, the pair of main grooves 10 extend in a zigzag shape along the tire circumferential direction on both sides of the tire equator CL. Note that extending in a zigzag shape means that a portion that goes straight in a predetermined direction and a portion that goes straight in a different direction from this portion are alternately repeated and bent along the tire circumferential direction as shown in the example in the figure. Shape. The main groove 10 can have a groove width of, for example, 12 mm to 22 mm, and a groove depth of, for example, 12 mm to 18 mm. In addition, the groove width w1 and the groove depth d1 of the main groove 10 are values measured in the above-described straight traveling portion.

  In the present invention, the tread portion 1 includes a shoulder land portion 20 defined on the outer side in the tire width direction of the main groove 10 and a center land portion 30 defined between the pair of main grooves 10. And are formed. Further, a side block 40 is formed in a side region on the outer side in the tire width direction of the shoulder land portion 20. Hereinafter, the description will be made based on the embodiment of FIG. 2, but the present invention mainly relates to the side block 40, and therefore a specific tread pattern (particularly the structure of the center land portion 30) is not necessarily limited to the illustrated example. Is not to be done.

  A plurality of shoulder lug grooves 11 extending along the tire width direction are formed in the shoulder land portion 20. One end of the shoulder lug groove 11 communicates with the main groove 10, and the other end extends beyond the ground contact E to partition the shoulder land portion 20 into shoulder blocks 21. The width and depth of the shoulder lug groove 11 can be equal to or less than those of the main groove 10. Specifically, the groove width of the shoulder lug groove 11 at the opening position with respect to the main groove 10 is preferably 50% to 100% of the groove width of the main groove 10, and the groove depth of the shoulder lug groove 11 is the groove depth of the main groove 10. Preferably, it can be set to 75% to 100%. In the following description, one of the pair of shoulder blocks 21 adjacent to each other in the tire circumferential direction may be referred to as a first block 21a and the other as a second block 21b. In the example shown in the figure, a concave bend 22 is provided at a portion where the tread surface of the first block 21a and the side surface on the grounding end side are connected, and the edge on the grounding end E side of the first block 21a is It enters the inner side in the tire width direction from the ground contact end E (the edge on the ground contact end E side of the second block 21b).

  The center land portion 30 is formed with a plurality of center lug grooves 12 extending in an inclined manner with respect to the tire width direction. The center lug groove 12 has one end communicating with the main groove 10 and the other end terminating in the center land portion 30. In the illustrated example, the center lug groove 12 includes two types of the first center lug groove 12a and the second center lug groove 12b having different end positions in the center land portion 30. Specifically, the first center lug groove 12a reaches the tire equator CL and terminates, and the second center lug groove 12b terminates without reaching the tire equator CL. These first center lug grooves 12a and second center lug grooves 12b are alternately arranged in the tire circumferential direction. Any of the center lug grooves 12 (first center lug 12a, second center lug groove 12b) is inclined at an angle of, for example, 45 ° to 70 ° with respect to the tire width direction. The groove width of the center lug groove 12 can be made equal to or less than the groove width of the main groove 10. For example, the groove width of the center lug groove 12 at the center position in the longitudinal direction of the center lug groove 12 can be set to 50% to 100% of the groove width of the main groove 10. On the other hand, the groove depth of the center lug groove 12 may be set smaller than the groove depth of the main groove 10. Specifically, the groove depth of the center lug groove 12 can be set to preferably 60% to 85% of the groove depth of the main groove 10. The center lug groove 30 can further be provided with a connection groove 13 for connecting the center lug grooves 12 to each other. The groove width of the connection groove 13 is preferably smaller than the groove width of the center lug groove 12, and the groove depth of the connection groove 13 is preferably smaller than the groove depth of the center lug groove 12.

  The positional relationship between the shoulder lug groove 11 and the center lug groove 12 is not particularly limited. For example, a part of the main groove 10 extending in a zigzag shape is inclined in the same direction as the center lug groove 12 as shown in the example in the figure. This portion relays between the shoulder lug groove 11 and the center lug groove 12, and the shoulder lug groove 11, a part of the main groove 10 and the center lug groove 12 are smoothly continuous. It is preferable in terms of soil properties and edge effect.

  The shoulder land portion 20 and the center land portion 30 may be provided with a sipe S and a stud pin implantation hole P as shown in the example in order to further improve the running performance on an unpaved road. The shape of the sipe S and the position of the stud pin implantation hole P can be set according to the shape of each block, and are not particularly limited.

  The side blocks 40 are formed one by one in the tire circumferential direction with respect to a pair of shoulder blocks (first block 21a and second block 21b) adjacent in the tire circumferential direction. In other words, in the side region, a plurality of side blocks 40 protruding from the surface of the sidewall portion 2 and the shoulder lug groove 11 are continuously extended, and the groove bottom on the sidewall side is the sidewall portion 2. A plurality of side grooves 50 opened toward the sidewall portion 2 are provided so as to coincide with the surface, and the side blocks 40 and the side grooves 50 are alternately arranged. At this time, every other side groove 50 is provided with respect to the shoulder lug groove 11, and on the outer side in the tire width direction of a pair of shoulder blocks (first block 21a and second block 21b) adjacent in the tire circumferential direction. One side block 40 is arranged.

  As shown in FIGS. 3 and 4, each side block 40 includes three regions of a high level region 41, a middle level region 42, and a low level region 43 having different protruding heights, and the protruding height H <b> 1 of the high level region 41. The raised height H2 of the middle level region 42 and the raised height H3 of the low level region 43 satisfy the relationship of H1> H2> H3. In other words, the side block 40 of the present invention has a step-like unevenness on the top surface, and the highest surface (the portion that protrudes most from the surface of the sidewall portion 2) is a high level among the unevenness on the top surface. In the region 41, the second highest surface is the middle level region 42, and the third highest surface (lowest surface) is the low level region 43. For these areas, the high-level area 41 and the low-level area 42 always exist at the extended positions of the first block 21a and the second block 21b, and the high-level area 41 and the second block on the first block 21a side. The high level region 41 on the 21b side is adjacent to the middle level region 42 formed as a narrow groove having a width of 10 mm or less.

  By configuring the side block 40 in this way, each region (high-level region 41, middle-level region 42, low-level region 43) raised at different heights has an unpaved road, that is, an irregular uneven shape. Since it effectively acts on the road surface, the running performance (startability) on the unpaved road can be improved. In particular, since these three regions are arranged as described above, the balance of the positional relationship and the like of these regions becomes good, and startability on an unpaved road can be effectively enhanced. Further, since the side block 40 is provided at a ratio of one to the two shoulder blocks 20, the size of each side block 4 is sufficiently secured, and there is a region where the raised height is low (low level region 43). Even so, the block rigidity can be sufficiently secured, and the cut resistance can be maintained well.

  At this time, if there are two or less regions having different raised heights, the unevenness of the side block 40 is reduced, and the effect of improving the running performance on an unpaved road cannot be sufficiently obtained. In addition, when there are four or more types of regions having different raised heights, the area of each region is reduced and the effect of being caught on the road surface is reduced, so that the effect of improving the running performance on an unpaved road cannot be sufficiently obtained. . If the width of the narrow groove (intermediate level region 42) exceeds 10 mm, the area of the high level region 41 is relatively reduced, and it becomes difficult to maintain good block rigidity. Preferably, the width of the narrow groove (intermediate level region 42) is 3 mm to 9 mm.

  Each region can be arranged at any position as long as it satisfies the above-described structure, but by adopting the illustrated embodiment, the shape from the shoulder block 21 to the side block 40 is improved, and the effect of the present invention is further enhanced. Can do. Specifically, in the extended position of the first block 21 a, the high level area 41 is arranged closer to the tread portion 1 than the low level area 43, and in the extended position of the second block 21 b, the low level area 43 is higher than the high level area 41. Also, it may be arranged on the tread portion side. At this time, it is preferable that the intermediate level region 42 exists on the extended line of the shoulder lug groove 11 located between the first block 21a and the second block 21b.

  In addition, it is preferable that at least a part of each side block 40 is connected to the side surface of the shoulder block 21. By connecting the side block 40 and the shoulder block 21 in this way, a series of edge components extending from the side surface of the shoulder block 21 to the side block 40 effectively act on the road surface, and traveling on an unpaved road. It is advantageous to increase performance. In particular, in the illustrated example, the first block 21a provided with the bent portion 22 and the side block 40 (the high-level region 41 on the tread portion 1 side) are connected, but the first block 21 having no bent portion 22 is connected. The two blocks 21b are separated from the side block 40 (the low level region 43 on the tread portion 1 side). In this aspect, the rigidity of the first block 21a that is lowered by the bent portion 22 can be compensated by connecting to the side block 40 (high-level region 41), and the second block that does not have the bent portion 22 is provided. It can be avoided that the rigidity of the second block 21b is relatively increased by separating the block 21b and the side block 40, and the rigidity balance between the first block 21a and the second block 21b can be improved. it can.

  As shown in FIG. 3, the line formed by the boundary between the low level region 43 and the high level region 41 when viewed from the top surface side of the side block 40 may have at least one bending point A. The angle (bending angle) formed by the line portions on both sides of the point A is preferably 90 ° or more, and more preferably 85 ° to 180 °. For example, in the illustrated example, the bending angle θ1 at the boundary between the low level region 43 on the first block 21a side and the high level region 41 is 100 ° to 150 °, and the low level region 43 and the high level region on the second block 21b side. The bending angle θ2 at the boundary with 41 is set to 115 ° to 165 °. As a result, the edge formed between the low level region 43 and the high level region 41 can be sufficiently secured, which is advantageous for improving the running performance on an unpaved road. If the number of bending points A exceeds 4, the corners formed for each bending point A become thin, and the durability of the edge portion formed between the low level region 43 and the high level region 41 decreases. The number of bending points is preferably 1 to 3. In addition, even when the bending angle is less than 90 °, the corner portion is narrowed, and the durability of the edge portion formed between the low level region 43 and the high level region 41 is lowered.

  If the height of the entire side block 40 is small, the effect of the side block 40 cannot be fully expected. Therefore, the height H3 of the low level region 43 is preferably 0.5 mm or more. By sufficiently raising even the low level area with the lowest elevation height in this way, the elevation height of the entire side block can be secured sufficiently, and the running performance on the unpaved road is improved and the cut resistance is also improved. Can be increased. More preferably, the raised height H3 of the low level region 43 is 1 mm to 6 mm, the raised height H2 of the intermediate level region 42 is 2 mm to 7 mm, and the raised height H1 of the high level region 41 is 3 mm to 8 mm. Although these ranges overlap, as described above, the heights H1 to H3 always satisfy the magnitude relationship of H1> H2> H3.

Regarding the height of each region, the difference ΔH _1-2 between the raised height H1 of the high level region 41 and the raised height H2 of the middle level region 42 is preferably 0.5 mm or more. Thus, by appropriately deepening the intermediate level region 42 disposed between the high level regions 41 with respect to the high level region 41, it is possible to improve the soil removal by the intermediate level region 41 (thin grooves), This is advantageous for improving the running performance on an unpaved road. More preferably, the difference ΔH _1-2 between the raised height H1 of the high level region 41 and the raised height H2 of the middle level region 42 is ₁ mm to 3 mm, and the raised height H2 of the middle level region 42 and the lower level region 43 The difference ΔH _2-3 with the raised height H3 may be 1 mm to ₃ mm, and the difference ΔH _1-3 between the raised height H1 of the high level region 41 and the raised height H3 of the low level region 43 may be 1 mm to 5 mm.

  In each side block, the high-level region 41 and the low-level region 43 may have the same area, but preferably, the total area S1 of the high-level region 41 is larger than the total area S3 of the low-level region 43. . In particular, in each side block, the total area S1 of the high-level region 41 may be 110% to 135% of the total area S3 of the low-level region 43. Thus, by making the high level region 41 sufficiently large and further setting the area in an appropriate range, the cut resistance can be improved. At this time, if the total area S1 of the high-level region 41 is less than 110% of the total area S3 of the low-level region 43, the area difference between these regions becomes small, and the effect of widening the high-level region 41 is sufficient. Cannot be expected. If the total area S1 of the high-level region 41 exceeds 135% of the total area S3 of the low-level region 43, the low-level region 41 becomes relatively narrow, and it becomes difficult to function as an edge component of various heights. It becomes difficult to sufficiently improve the startability on the road.

  Furthermore, as shown in the example, the high level region 41 is arranged closer to the tread portion 1 than the low level region 43 at the extended position of the first block 21a, and the low level region 43 is high at the extended position of the second block 21b. When arranged on the tread portion 1 side with respect to the level region 41, the area of the low level region 43 on the second block 21b side (low level region 43 close to the tread portion 1) is the low level region on the first block 21a side. It is preferable that it is larger than the area of 43 (low level area | region 43 far from the tread part 1). That is, the area of the low level region 43 on the first block 21a side (low level region 43 far from the tread portion 1) is S3a, and the low level region 43 on the second block 21b side (low level region 43 close to the tread portion 1). If the area of S3b is S3b, it is preferable that these areas satisfy the relationship of S3a <S3b. More preferably, the area S3b is 110% to 140% of the area S3a. By setting the arrangement and size of the low-level region 43 in this manner, the balance of the rigidity of each part becomes good, which is advantageous for improving cut resistance.

The tire size is LT265 / 70R17 121Q, has the basic structure illustrated in FIG. 1, is based on the tread pattern of FIG. 2, and the side block has a high-level region and a low-level region (arrangement of each region), Presence / absence of middle level area, height H1 of the high level area, height H2 of the middle level area, height H3 of the low level area, difference ΔH _1-2 in the height of the height, medium level area (narrow groove) , The bending angle of the boundary between the low level region and the high level region, the ratio of the total area S1 of the high level region to the total area S3 of the low level region (S1 / S3 × 100%), the low level on the first block side The ratio of the area S3b of the low level region on the second block side to the area S3a of the region (S3b / S3a × 100%), the presence / absence of connection between the shoulder block and the side block (whether the shoulder / side is connected), respectively. Comparative Example 1-5 the set as to 3, to prepare a 26 types of pneumatic tires of Examples 1 to 21.

  Regarding the “arrangement column of each region” in Tables 1 to 3, the low-level regions (tables on the tread side and sidewall side in the extended position of the first block, and the tread side and sidewall side in the extended position of the second block, respectively) "Low" in the middle) or high-level area ("High" in the table). Comparative Example 1 is an example in which the entire side block has a uniform raised height, and is shown as an example in which only a low level region exists for convenience. Comparative Example 2 is an example in which the entire side block excluding the narrow groove (medium level region) has a uniform raised height, and as an example in which only the high level region and the middle level region (thin groove) exist for convenience. Indicated. Comparative Examples 3 and 4 are examples in which only the high level region and the low level region exist and do not have the intermediate level region (thin groove).

  These pneumatic tires were evaluated for cut resistance and startability by the following evaluation methods, and the results are also shown in Tables 1 to 3.

Cut resistance Each test tire is assembled on a wheel with a rim size of 17 x 8 J, mounted on a test vehicle (four-wheel drive SUV) with an air pressure of 350 kPa, and after running 1000 km on a test road consisting of an unpaved road, side blocks The cut length produced was measured. The evaluation results are shown as an index with the reciprocal of the measured value of Comparative Example 2 as 100. A larger index value means a shorter cut length and better cut resistance. If the index value is “97” or more, it means that good cut resistance equal to or higher than that of Comparative Example 2 as a reference was obtained.

Startability Each test tire is assembled to a wheel with a rim size of 17 × 8J, mounted on a test vehicle (SUV with four-wheel drive) at an air pressure of 350 kPa, and the startability is tested on a test road consisting of an unpaved road (gravel road surface). Sensory evaluation by a driver was performed. The evaluation results are shown as an index with the value of Comparative Example 1 as 100. A larger index value means better startability on an unpaved road. When the index value is “103” or less, it is equivalent to the conventional level, which means that the effect of improving startability is not substantially obtained.

  As is clear from Tables 1 to 3, each of Examples 1 to 21 was compared with Comparative Example 1 while ensuring good cut resistance at the same level as Comparative Example 2 in which the entire side block was significantly raised. Improved startability. Although only the startability on the gravel road surface was evaluated, the tire of the present invention can be used for mud and rocks on the road surface even when traveling on other unpaved roads (such as muddy roads, rocky places, and snowy roads). Since it acts effectively on snow and the like, it can exhibit excellent startability on any unpaved road.

  On the other hand, the pneumatic tire of Comparative Example 1 had poorer cut resistance than Comparative Example 2 because the height of the entire side block was uniform and small. The pneumatic tire of Comparative Example 2 did not have a low level region, and there were few unevenness on the side block top surface, so that the effect of improving startability could not be sufficiently obtained. The pneumatic tires of Comparative Examples 3 and 4 do not have an intermediate level region (thin groove), and the arrangement of the high level region and the low level region is inappropriate, so that the effect of improving startability is sufficiently obtained. I couldn't. In the pneumatic tire of Comparative Example 5, since the groove width of the intermediate level region (thin groove) is too large and has a wide area, the intermediate level region itself is easily damaged and the cut resistance is deteriorated.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 10 Main groove 11 Shoulder lug groove 12 Center lug groove 13 Connection groove 20 Shoulder land part 21 Shoulder block 21a First block 21b 2nd block 22 Bending part 30 Center land part 40 Side block 41 High level area 42 Middle level area 43 Low level area 50 Side groove S Sipe P Hole for stud pin installation CL Tire equator E Grounding end

Claims (8)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the provided pneumatic tire,
A pair of main grooves extending along the tire circumferential direction on both sides of the tire equator on the surface of the tread portion, a shoulder land portion defined on the outer side in the tire width direction of the main groove, and along the tire width direction A plurality of shoulder lug grooves extending, the shoulder lug grooves are arranged at intervals in the tire circumferential direction, the shoulder land portion is partitioned into a plurality of shoulder blocks by the shoulder lug grooves,
A plurality of side blocks raised from the surface of the sidewall portion in a side region adjacent to the outer side in the tire width direction of the shoulder land portion are tires one by one with respect to the pair of shoulder blocks adjacent in the tire circumferential direction. Formed at intervals in the circumferential direction,
Each side block includes three regions of a high level region, a medium level region, and a low level region having different heights. The high level region has a height H1, the medium level region has a height H2, and the low level region has a low level. The height H3 of the level region satisfies the relationship of H1>H2> H3,
When one of the pair of shoulder blocks is a first block and the other is a second block, the high-level region and the low-level region exist at the extended positions of the first block and the second block, respectively. The pneumatic tire is characterized in that the high-level region on the first block side and the high-level region on the second block side are adjacent to each other with a middle level region formed as a narrow groove having a width of 10 mm or less. .   When viewed from the top surface side of the side block, the line portion formed by the boundary between the low level region and the high level region has at least one bending point, and the line portions on both sides of the bending point are formed. The pneumatic tire according to claim 1, wherein the angle is 90 ° or more.   The pneumatic tire according to claim 1 or 2, wherein a difference between a height H1 of the high level region and a height H2 of the middle level region is 0.5 mm or more.   The pneumatic tire according to any one of claims 1 to 3, wherein a total area S1 of the high-level region is larger than a total area S3 of the low-level region in each side block.   The pneumatic tire according to any one of claims 1 to 4, wherein in each side block, the total area S1 of the high-level region is 110% to 135% of the total area S3 of the low-level region. In the extended position of the first block, the high level region is arranged closer to the tread portion than the low level region, and in the extended position of the second block, the low level region is closer to the tread portion than the high level region. And
The pneumatic tire according to any one of claims 1 to 5, wherein an area of the low level region on the second block side is larger than an area of the low level region on the first block side.   The pneumatic tire according to any one of claims 1 to 6, wherein a raised height H3 of the low-level region is 0.5 mm or more.   The pneumatic tire according to claim 1, wherein at least a part of each side block is connected to a side surface of the shoulder block.

Images