JP2022012310A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which improves traveling performance on an unpaved road without deteriorating uniformity.SOLUTION: A high block 23H and a low block 23L whose protruded heights are different are provided as side blocks 23 disposed in a side region, and when the side blocks are a block pair B comprising the high block 23H and the low block 23L adjacent to each other in a tire circumferential direction, a protruded part extending along the tire circumferential direction toward the low block 23L included in the block pair B which is the same as the high block 23H included in the block pair B is provided. The protruded part includes an overlapped region surrounded by the low block 23L in three directions by overlapping the low block 23L included in the same block pair B, and the ratio of the area of the overlapped region to the total area of a top surface of the block pair B is set to be 20-40%.SELECTED DRAWING: Figure 3

Description

The present invention relates to a pneumatic tire suitable as a tire for traveling on unpaved roads, and more particularly to a pneumatic tire provided with a side block in a side region outside the shoulder block in the tire width direction.

Pneumatic tires intended for driving on unpaved roads such as rough terrain, muddy terrain, snowy roads, sandy terrain, and rocky terrain generally have a tread pattern mainly composed of rug grooves and blocks with many edge components. Those with a large area are adopted. Further, a side block is provided in a side region further outside in the tire width direction of the shoulder block located on the outermost side in the tire width direction of the tread portion. In such tires, mud, snow, sand, stones, rocks, etc. on the road surface due to the unevenness of grooves and blocks provided in the tread and side areas (hereinafter, these are collectively referred to as "mud, etc."). The tires are caught in the tire to obtain traction performance, and the large groove area prevents mud and the like from being clogged in the groove, thereby improving the running performance on unpaved roads (see, for example, Patent Documents 1 and 2).

Comparing the tires of Patent Documents 1 and 2, it can be said that the tire of Patent Document 1 is a type of tire having a relatively small groove area and considering running performance on a paved road. On the other hand, it can be said that the tire of Patent Document 2 is a type of tire having a large groove area and a large individual block, and is specialized for running performance on unpaved roads. Therefore, the former tends to have lower running performance on unpaved roads than the latter, and the latter tends to have lower running performance during normal running than the former. In recent years, the required performance of tires has been diversified, and tires for unpaved roads having intermediate level performance between these two types of tires are also required. Therefore, for example, in the side region, there is a demand for measures for optimizing the shapes of grooves and blocks to efficiently improve the running performance on unpaved roads. In addition, if a large number of grooves or blocks are provided in the side area, the tire uniformity may be affected. Therefore, in order to improve the running performance on the above-mentioned unpaved road, it is also required to maintain good uniformity. ing.

Japanese Unexamined Patent Publication No. 2016-007861 Japanese Unexamined Patent Publication No. 2013-119277

An object of the present invention is to provide a pneumatic tire having improved running performance on unpaved roads without reducing uniformity.

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 on the inner side in the tire radial direction, a side region adjacent to the inner side in the tire radial direction at the boundary between the tread portion and the sidewall portion is along the tire radial direction. A plurality of side grooves extending vertically and a plurality of side blocks partitioned by the side grooves and raised from the outer surface of the sidewall portion are provided, and the side blocks have a relatively large raised height. It contains two types of blocks, a high block and a low block with a relatively small ridge height, and these high blocks and low blocks are arranged alternately in the tire circumferential direction, and the high block and the low block adjacent to each other in the tire circumferential direction. When the block is a block pair, the high block included in the block pair has a protrusion extending along the tire circumferential direction toward the low block included in the same block pair, and the protrusion is the same. It includes an overlapping region that overlaps with the low block included in the block pair and is surrounded by the low block in three directions, and the ratio of the area of the overlapping region to the total area of the top surface of the block pair is 20% to 40%. It is characterized by being.

In the present invention, in order to provide a side block in the side region to improve the running performance on an unpaved road, as described above, the difference in the height of the ridge between the side blocks (high block and low block) adjacent to each other in the tire circumferential direction is provided. And by overlapping these high blocks and low blocks to make these blocks function as substantially one large block (block pair), the block rigidity is improved and the top of the block (block pair) is provided. Since an excellent edge effect can be ensured by the unevenness of the surface, it is possible to improve the running performance on an unpaved road. In particular, since the protruding part (overlapping area) of the high block is surrounded by the low block and the unevenness of the top surface of the block pair is complicated, mud etc. can be effectively scraped and the running performance on unpaved road is improved. It can be increased efficiently. At this time, since the area of the overlapping region is set to an appropriate range, it is possible to maintain good uniformity. Through these collaborations, it is possible to improve the running performance on unpaved roads without reducing the uniformity.

In the present invention, the ratio of the area of the overlapping region to the area of the top surface of the high block is 20% to 30%, and the ratio of the area of the overlapping region to the area of the top surface of the low block is 20% to 25%. Is preferable. By setting the relationship between the top surface of each block and the area of the overlapping area in this way, the balance between the high block, the low block, and the overlapping area becomes good, and both uniformity and running performance on unpaved roads are compatible. Will be advantageous.

In the present invention, it is preferable that the ridge height of the high block is 4 mm to 6 mm and the ridge height of the low block is 2 mm to 3 mm. As a result, the shape of the unevenness composed of the top surface of the high block and the top surface of the low block becomes good, which is advantageous for improving the running performance on unpaved roads.

In the present invention, the ratio A / SH of the vertical distance A from the maximum outer diameter position of the tire to the inner end in the tire radial direction of the side block and the tire cross-sectional height SH is 10% to 30%, and the block pair of tires. The radial length is preferably 40 mm to 50 mm. By appropriately setting the arrangement and size of the side blocks in this way, it is advantageous to achieve both uniformity and running performance on unpaved roads. In particular, since the ratio A / SH is in an appropriate range, when the tires are buried in mud or the like when driving on unpaved roads, the side blocks come into good contact with the road surface, and the driving performance on unpaved roads is effective. It will be possible to increase to.

In the present invention, of the boundary lines between the high block and the low block in the overlapping region, the angle formed by the upper side located on the outermost side in the tire radial direction and the lower side located on the innermost side in the tire radial direction with respect to the tire circumferential direction is 0, respectively. The temperature is preferably ° to 10 °, and the length of the upper side is preferably 50% to 70% of the length of the lower side. As a result, the shape of the side block becomes good, which is advantageous in achieving both uniformity and running performance on unpaved roads.

In the present invention, when the length measured along the outer surface of the tire from the equator of the tire to the bead portion is defined as the profile line length, the overlapping region is arranged at a position of 35% to 45% of the length of the profile line from the equator of the tire. Is preferable.

In the present invention, the "ground contact end" is the tire axial direction of the ground contact region formed when a tire is rim-assembled on a regular rim, placed vertically on a flat surface with a regular internal pressure applied, and a regular load is applied. Both ends of. 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, "DesignRim" 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. The maximum value described in "COLD INFLATION PRESSURES" is "INFLATION PRESSURE" for ETRTO, but 180 kPa when the tires are for passenger cars. "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 LOAD LIMITS AT VARIOUS". The maximum value described in "COLD INFRATION PRESSURES" is "LOAD CAPACITY" in the case of ETRTO, but when the tire is for a passenger car, the load is equivalent to 88% of the above load.

It is a meridian 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 explanatory drawing which magnified and shows the main part of the pneumatic tire which comprises embodiment of this invention. It is explanatory drawing which shows the block pair 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 arranged inside the tread portion 1, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and the sidewall portion 2 in the tire radial direction. It is provided with a pair of bead portions 3. In FIG. 1, reference numeral CL indicates a tire equator, and reference numeral E indicates a ground contact end. Although FIG. 1 is a cross-sectional view of the meridian, 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, whereby the pneumatic tire is formed. The toroidal basic structure of is constructed. Hereinafter, the description using FIG. 1 is basically based on the illustrated meridian cross-sectional shape, 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 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 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 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 to, for example, in the range of 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 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 a pneumatic tire having such a general cross-sectional structure, but the basic structure thereof is not limited to that described above.

Since the present invention relates to the shoulder region and the side region (particularly the side region) described later, if the detailed shape of the tread portion 1 is a tread pattern mainly composed of blocks suitable for unpaved roads, FIG. Not limited to the example of.

On the surface of the tread portion 1 of the pneumatic tire shown in FIG. 2, a pair of main grooves 10 extending along the tire circumferential direction are formed on both sides of the tire equator CL. These main grooves 10 have a maximum width of, for example, 9 mm to 20 mm and a groove depth of 10 mm to 18 mm. As will be described later, these main grooves 10 have a zigzag shape in which portions that go straight in a predetermined direction are connected via bending points.

The three rows of land portions divided by the main grooves 10 are further divided into blocks 20 by various grooves, and the entire tread pattern is a block pattern based on the block 20. In the illustrated example, the shoulder block 21 is partitioned on the outer side of the pair of main grooves 10 in the tire width direction among the plurality of blocks 20, and the center block 22 is partitioned between the pair of main grooves. The shoulder block 21 is partitioned by a shoulder lug groove 31 extending from the main groove 10 beyond the ground contact end E, and a plurality of shoulder blocks 21 are arranged in the tire circumferential direction. The center block 22 is partitioned by a center lug groove 32a extending in the tire width direction and an auxiliary groove 32b connecting the center lug grooves 32a adjacent to each other in the tire circumferential direction. In particular, in the illustrated example, two types of center lug grooves 32a having different end positions are alternately arranged in the tire circumferential direction, and the auxiliary grooves 32b connect the end portions of the center lug grooves extending to the vicinity of the tire equatorial CL. The one that connects the middle part of the center lug groove that extends to the vicinity of the tire equatorial CL, and the one that connects the end of the center lug groove that terminates without reaching the vicinity of the tire equatorial CL and extends to the vicinity of the tire equatorial CL. Includes those that connect to the end of the center lug groove. A sipe 41 or a narrow groove 42 may be optionally provided on the tread of the center block 22, the tread of the shoulder block 21, and the outer side surface in the tire width direction.

Of the lug grooves that further divide the land portion partitioned by the main groove 10 into blocks 20, the shoulder lug groove 31 may have a groove width of, for example, 9 mm to 20 mm and a groove depth of, for example, 12 mm to 17 mm. The center lug groove 32a may have a groove width of, for example, 7 mm to 13 mm and a groove depth of, for example, 11 mm to 14 mm. In particular, the shoulder lug groove 31 may have the same groove depth as the main groove 10. Further, the auxiliary groove 32b may have a groove width of, for example, 7 mm to 10 mm and a groove depth of, for example, 9 mm to 12 mm. Further, the arbitrarily formed sipe 41 is a fine groove having a groove width of, for example, 0.5 mm to 2.0 mm and a groove depth of, for example, 2 mm to 15 mm, and is an arbitrarily formed fine groove 42. The groove width and groove depth are sufficiently smaller than those of the main groove 10 and the lug groove, and the groove width is, for example, 0.5 mm to 4.0 mm, and the groove depth is, for example, 2 mm to 15 mm.

As shown in FIGS. The land portion is further divided into a plurality of side blocks 23 by the side grooves 33. In the illustrated example, at the boundary between the outer side surface of the shoulder block 21 in the tire width direction and the top surface of the side block 23 (the boundary between the shoulder region and the side region), the tire is raised from the side surface and the top surface and is the entire circumference of the tire. There is a ridge 24 that extends all over. Therefore, from a different point of view, the shoulder area is adjacent to the inside of the ridge 24 (the boundary between the shoulder area and the side area) in the tire width direction, and the side area is the tire of the ridge 24 (the boundary between the shoulder area and the side area). Adjacent to the inner side in the radial direction, the shoulder block 21 and the side block 23 described above are provided in these shoulder regions and side regions, respectively.

It is preferable that the side groove 33 for partitioning the side block 23 is located on the extension line of the shoulder lug groove 31 and extends substantially continuously as shown in the illustrated example. Further, it is preferable that the side block 23 is arranged at an extension position outside the tire width direction of each shoulder block 21 based on the positional relationship between the grooves. When viewed from the tread side of the tread portion 1 as shown in FIG. 2, the side block 23 and the side groove 33 are located outside the shoulder block 21 and the shoulder lug groove 31 in the tire width direction, as shown in FIG. When viewed from the sidewall portion 2 side, the side block 23 and the side groove 33 are located inside the shoulder block 21 and the shoulder lug groove 31 in the tire radial direction. The fact that the grooves are located on the extension line means that at least a part of the virtual grooves extending from each of the target grooves overlaps in the groove width direction.

In the present invention, the side block 23 includes two types of blocks, a high block 23H having a relatively large uplift height and a low block 23L having a relatively small uplift height. These high blocks 23H and low blocks 23L are arranged alternately in the tire circumferential direction. When the high block 23H and the low block 23L adjacent to each other in the tire circumferential direction are set as block vs. B, a part of the high block 23H and the low block 23L included in the block vs. B overlaps with each other, thereby blocking the block vs. B. The tire radial inner end of the side groove 33 located between the high block 23H and the low block 23L included in is closed. Hereinafter, the side groove 33 in which the inner end in the tire radial direction is closed is the closed groove 33A, and the side groove 33 in which the inner end in the tire radial direction is opened located between the blocks adjacent to each other in the tire circumferential direction is the open groove 33B. May be said.

As shown in FIG. 4 for simplification of the top surface of block vs. B, in one block vs. B, the high block 23H has a protrusion extending along the tire circumferential direction toward the low block 23L. A part of the protruding part overlaps with the low block 23L. When the portion where the high block 23H (protruding portion) overlaps with the low block 23L is an overlapping region O (hatched portion in FIG. 4A), this overlapping region O is in three directions (inside in the tire radial direction and outside in the tire radial direction). , One side in the tire circumferential direction) is surrounded by the low block 23L.

In this way, the side blocks 23 (high block 23H and low block 23L) adjacent to each other in the tire circumferential direction are overlapped to make these blocks substantially function as one large block (block vs. B), thereby increasing the block rigidity. Can be improved. Further, by providing a difference in the height of the ridge between the high block 23H and the low block 23L, unevenness is formed on the top surface of the block (block vs. B), thereby ensuring an excellent edge effect. can. Through these collaborations, driving performance on unpaved roads can be improved. In particular, since the protruding portion (overlapping region O) of the high block 23H is surrounded by the low block 23L and the unevenness of the top surface of the block vs. B is complicated, it is possible to effectively scrape mud and the like, and the unpaved road. It is possible to efficiently improve the running performance in.

At this time, if the area of the overlapping region O is small, the block rigidity cannot be sufficiently increased, and if the area of the overlapping region O is large, the uniformity may decrease. Therefore, the ratio of the area of the overlapping region to the total area of the top surface of the block to B is set to 20% to 40%, preferably 25% to 30%. The "total area of the top surface of the block vs. B" is the total area of the top surface of the high block 23H and the top surface of the low block 23L (the area of the shaded area in FIG. 4B). Further, the "area of the overlapping region O" refers to the boundary line between the high block 23H and the low block 23L in the overlapping region O, and the intersection of the inner and outer contour lines of the protruding portion in the tire radial direction and the low block 23L. It is the area of the portion surrounded by the connected straight line (broken line in FIG. 4A) (the area of the shaded portion in FIG. 4A). If the ratio of the area of the overlapping region O to the total area of the top surface of the block to B is less than 20%, the block rigidity cannot be sufficiently increased. If the ratio of the area of the overlapping region O to the total area of the top surface of the block to B exceeds 40%, the uniformity may decrease.

Further, in order to achieve both uniformity and running performance on unpaved roads, it is preferable to improve the balance between the high block 23H, the low block 23L and the overlapping region O. Specifically, the ratio of the area of the overlapping region O to the area of the top surface of the high block 23H (the area of the shaded area in FIG. 4C) is preferably 20% to 30%, more preferably 23% to 26%. It is good to set to. Further, the ratio of the area of the overlapping region O to the area of the top surface of the low block 23L (the area of the shaded area in FIG. 4D) is preferably set to 20% to 25%, more preferably 22% to 23%. good. If the ratio of the area of the overlapping region O to the area of the top surface of the high block 23H is less than 20%, the effect of improving the block rigidity is limited. If the ratio of the area of the overlapping region O to the area of the top surface of the high block 23H exceeds 30%, the uniformity may be affected. If the ratio of the area of the overlapping region O to the area of the top surface of the low block 23L is less than 20%, the effect of improving the block rigidity is limited. If the ratio of the area of the overlapping region O to the area of the top surface of the low block 23L exceeds 25%, the uniformity may be affected. The relationship between the area of the top surface of the high block 23H and the area of the top surface of the low block 23L is not particularly limited, but the area of the top surface of the high block 23H is preferably 80% to 85% of the area of the top surface of the low block 23L. It is good to set it to%.

The height of the ridge of the side block 23 can be set to, for example, 2 mm to 6 mm. As a result, when traveling on an unpaved road, the side block 23 appropriately comes into contact with the road surface, and the traveling performance of the side block 23 can be satisfactorily exhibited. In particular, the raised height of the high block 23H is preferably 4 mm to 6 mm, and the raised height of the low block 23L is preferably 2 mm to 3 mm. Further, the difference in the height of the ridge between the high block 23H and the low block 23L is preferably set to 2 mm to 4 mm. As a result, the shape of the unevenness composed of the top surface of the high block 23H and the top surface of the low block 23L becomes good, which is advantageous for improving the running performance on unpaved roads. If the raised height of the high block 23H is less than 4 mm, the side block 23 becomes smaller as a whole, so that it becomes difficult to secure sufficient block rigidity, and the effect of improving the running performance on unpaved roads is limited. Become. Further, since the difference in the height of the ridge between the high block 23H and the low block 23L becomes small, the edge effect due to the unevenness formed on these top surfaces cannot be sufficiently expected. If the raised height of the high block 23H exceeds 6 mm, the side block 23 becomes excessive and the influence on uniformity becomes large. If the raised height of the low block 23L is less than 2 mm, the low block 23L is too small and it becomes difficult to sufficiently secure the block rigidity. When the ridge height of the low block 23L exceeds 3 mm, the difference in ridge height between the high block 23H and the low block 23L becomes small, so that the edge effect due to the unevenness formed on these top surfaces cannot be sufficiently expected.

As described above, the high block 23H has a protruding portion protruding toward the low block 23L, and a part thereof is an overlapping region O. The shape of the protruding portion is not particularly limited, but it is preferable that the protruding portion extends along the tire circumferential direction as shown in the figure. In particular, since the overlapping region O is surrounded by the low block 23L in three directions, the boundary line between the high block 23H and the low block 23L in the overlapping region O has at least three sides (L1, L2, L3 in the figure). If the outermost side in the tire radial direction is the upper side L1 and the innermost side in the tire radial direction is the lower side L2, the angles formed by the upper side L1 and the lower side L2 with respect to the tire circumferential direction are preferable. Is preferably 0 ° to 10 °, more preferably 4 ° to 6 °. Further, the length of the upper side L1 is preferably 50% to 70%, more preferably 57% to 63% of the length of the lower side L2. As a result, the shape of the side block 23 becomes good, which is advantageous in achieving both uniformity and running performance on unpaved roads. When the angle formed by the upper side L1 and the lower side L2 with respect to the tire circumferential direction deviates from the above range, the edge formed by the protruding portion (overlapping region O) is greatly inclined with respect to the tire collecting direction, so that a good edge effect is obtained. It becomes difficult to secure. Further, if the length of the upper side L1 is less than 50% of the length of the lower side L2, the upper side L1 is too short and it becomes difficult to sufficiently secure the edge effect. If the length of the upper side L1 exceeds 70% of the length of the lower side L2, it becomes difficult to maintain good uniformity.

In the illustrated example, the inclination directions of the upper side L1 and the lower side L2 are different, but the angle between the upper side L1 and the lower side L2 is an absolute value of each angle. Further, as shown in the illustrated example, the upper side L1 is inclined in a direction away from the tread portion 1 toward the overlapping region O, and the lower side L2 is inclined in a direction approaching the tread portion 1 toward the overlapping region O and protrudes. It is preferable that the entire portion has a tapered shape that tapers toward the overlapping region O. In such a shape, if the relationship between the angle and the length of the upper side L1 and the lower side L2 is satisfied, the shape of the protruding portion (overlapping region O) becomes good, so that the uniformity and running performance on unpaved roads can be improved. It is possible to achieve both in a particularly well-balanced manner.

It is preferable that the side block 23 is arranged in an appropriate region in the tire radial direction so as to appropriately contact the road surface when the tire is buried in mud or the like while traveling on an unpaved road. Specifically, the ratio A / SH of the vertical distance A from the maximum outer diameter position of the tire to the inner end in the tire radial direction of the side block 23 and the tire cross-sectional height SH is preferably 10% to 30%, more preferably 20. It should be% to 23%. If the ratio A / SH is less than 10%, the side block 23 is arranged in a narrow area on the tread portion 1 side, and it becomes difficult to secure a sufficient size of the side block 23, which may reduce the edge effect. .. When the ratio A / SH exceeds 30%, the side block 23 becomes large, so that the influence on uniformity becomes large.

By setting the ratio A / SH described above, the size of the side block 23 in the tire radial direction is limited to an appropriate range, but specifically, the tire of the side block 23 (block vs. B). The radial length BL is preferably 40 mm to 50 mm, more preferably 40 mm to 45 mm. The tire radial length BL of the side block 23 (block vs. B) is the tire from the outermost point in the tire radial direction of the two side blocks 23 (high block 23H and low block 23L) constituting the block vs. B. It is the length along the tire radial direction up to the innermost point in the radial direction. By setting the size of the side block appropriately in this way, it is advantageous to achieve both uniformity and running performance on unpaved roads. If the tire radial length BL of the side block 23 (block vs. B) is less than 40 mm, it becomes difficult to secure a sufficient size of the side block 23, and the edge effect may be reduced. When the tire radial length BL of the side block 23 (block vs. B) exceeds 50 mm, the side block 23 becomes large, so that the influence on uniformity becomes large.

In arranging the side blocks 23 (block vs. B) as described above, the position of the overlapping region O is particularly important in order to achieve both uniformity and running performance on unpaved roads. When the length measured along the outer surface of the tire from the tire equatorial CL to the bead portion 3 (bead toe) is defined as the profile line length PL, the overlapping region O is preferably 35 from the tire equatorial CL to the profile line length PL. It is preferable to place it at a position of% to 45%, more preferably 39% to 41%. In other words, the distance measured along the outer surface of the tire from the tire equatorial CL to the outermost point in the tire radial direction of the overlapping region O, and the tire from the tire equatorial CL to the innermost point in the tire radial direction of the overlapping region O. The distance measured along the outer surface is preferably in the range of preferably 35% to 45%, more preferably 40% to 43% of the above-mentioned profile line length PL, respectively. By arranging the overlapping region O at such a position, the position of the overlapping region O in the entire tire is optimized, which is advantageous in achieving both uniformity and running performance on unpaved roads. If the position of the overlapping area O deviates from the above range, the balance of the position of the overlapping area O becomes poor, so that the effect of achieving both uniformity and running performance on unpaved roads may be limited.

As shown in the figure, one of the pair of shoulder blocks 21 located inside the block vs. B in the tire width direction is processed into a concave shape on the outer edge portion in the tire width direction of one block in the tire width direction of the other block. A hollowed portion 21a recessed inward in the tire width direction from the outer edge portion may be provided. This complicates the shape of the edge portion of the shoulder block 21 along the tire circumferential direction, which is advantageous for improving the running performance on unpaved roads.

As shown in the illustrated example, when the narrow groove 42 is provided on the outer side surface of the shoulder block 21 in the tire width direction, it is preferable to provide the fine groove 42 on the top surface of the side block 23 as well. The narrow groove 42 provided in the side block 23 may extend inward in the tire radial direction from the position of the inner end portion in the tire radial direction of the fine groove 42 provided on the outer side surface of the shoulder block 21 in the tire width direction. .. As a result, soil texture and edge effect can be added by the fine groove 42, which is advantageous for improving the running performance on unpaved roads.

A linear convex portion 50 having a width of, for example, 0.5 mm to 2.0 mm and a protrusion height from the block top surface of, for example, 0.5 mm to 1.5 mm can be provided on the top surface of the side block 23. In the illustrated example, the linear convex portion 50 extending along the contour line of each side block 23 at a distance of 5 mm to 20 mm from the contour line, and the side block 23 having one end connected to the narrow groove 42. A linear convex portion 50 extending so as to pass through an intermediate position of a pair of contour lines on both sides of the side block 23 in the tire circumferential direction is provided at the center position in the tire circumferential direction. Since such a linear convex portion 50 also functions as an edge component, it is advantageous for improving running performance on unpaved roads.

As shown in FIG. 2, if the above-mentioned side block 23 is provided in at least one side region (the right side region in the illustrated example) of the side regions on both sides in the tire width direction, the above-mentioned effect can be exhibited. Can be done. Of course, the above-mentioned side block 23 can also be applied to both side regions on both sides in the tire width direction. Further, as shown in FIG. 2, by applying the above-mentioned side block 23 to one side region and adopting a different shape for the other side region, one side region and the other side in the tire width direction can be used. It is also possible to specialize the side area to different performance.

The tire size is LT265 / 70R17 121Q, it has the basic structure illustrated in FIG. 1, and based on the tread pattern of FIG. 2, the presence or absence of overlap (overlap) between high blocks and low blocks adjacent to each other in the tire circumferential direction in the block pair. Presence / absence of area), ratio of the area of the overlapping area to the total area of the top surface of the block pair, the ratio of the area of the top surface of the overlapping area to the area of the top surface of the high block, and the ratio of the overlapping area to the area of the top surface of the low block. The ratio of the area of the top surface, the height of each of the high block and the low block, the ratio A / SH of the vertical distance A from the maximum outer diameter position of the tire to the inner end of the side block in the tire radial direction and the tire cross-sectional height SH. , The tire radial length of the block pair, the angle formed by the upper side of the boundary line between the high block and the low block in the overlapping area with respect to the tire circumferential direction, and the lower side of the boundary line between the high block and the low block in the overlapping area is the tire. Conventionally, the angle formed in the circumferential direction, the ratio of the upper side length to the lower side length, and the distance from the tire equatorial line to the overlapping region (ratio to the profile line length) are set as shown in Tables 1 to 3, respectively. Pneumatic tires of Example 1, Comparative Examples 1 to 4, and Examples 1 to 24 were produced.

Regarding the column of "presence or absence of overlapping area" in Tables 1 to 3, the case where the high block and the low block adjacent to each other in the tire circumferential direction overlap in the block pair as shown in FIG. 3 is displayed as "Yes". On the contrary, when there is no overlapping area and all the side grooves are released inward in the radial direction of the tire without being blocked (not shown), "None" is displayed. In the conventional example 1, although the side block is not provided, the column of the raised height is displayed as “0 mm” and the column of the presence / absence of the overlapping area is displayed as “none” for convenience. Even when there is no difference in the height of the uplift as in Comparative Examples 1 and 2, the block at the position corresponding to the high block in FIG. 3 is regarded as a high block for convenience, and the block corresponding to the low block in FIG. 3 is regarded as a high block. For convenience, it was regarded as a low block. Regarding the columns of "Distance from the tire equatorial line to the overlapping area" in Tables 1 to 3, the distance measured along the outer surface of the tire from the tire equatorial CL to the outermost point in the tire radial direction of the overlapping area is shown in the upper row. The distance measured along the outer surface of the tire from the tire equatorial CL to the innermost point in the tire radial direction of the overlapping region is described in the lower row.

These pneumatic tires were evaluated for uniformity, off-road running performance, and startability on unpaved roads by the following evaluation methods, and the results are also shown in Tables 1 to 3.

Uniformity Each test tire was subjected to a radial force variation test (RFV test) under the conditions conforming to JIS D4233, and the radial force variation (RFV) was measured. The evaluation result is shown by an exponent in which the reciprocal of the value of the conventional example is 100. The larger this index value is, the better the uniformity is. If the exponential value is "95" or more, it means that a good uniformity equivalent to that of the conventional level is obtained.

Off-road running performance Each test tire is attached to a wheel with a rim size of 17 × 8J, and the air pressure is set to 350kPa and mounted on a test vehicle (four-wheel drive SUV). Was evaluated by a test driver. The evaluation result is shown by an index with the value of Conventional Example 1 as 100. The larger this index value is, the better the off-road running performance is.

Startability on unpaved roads Each test tire is attached to a wheel with a rim size of 17 x 8J, and the air pressure is set to 350 kPa and mounted on a test vehicle (four-wheel drive SUV) on a test road consisting of unpaved roads (gravel road surface). A sensory evaluation was performed by a test driver for the startability. The evaluation result is shown by an index with the value of Comparative Example 1 as 100. The larger this index value is, the better the startability on unpaved roads.

As is clear from Tables 1 to 3, all of Examples 1 to 24 effectively maintain off-road driving performance and startability on unpaved roads while maintaining good uniformity as compared with Conventional Example 1. Improved. Although only the off-road running performance and startability on the gravel road surface were evaluated, the tire of the present invention can be used on the road surface even when traveling on other unpaved roads (mud roads, rocky areas, snowy roads, etc.). Since it works effectively against mud, rocks, snow, etc., it can demonstrate excellent performance.

On the other hand, in Comparative Example 1, since the raised height of the side block was uniform and there was no overlapping region, the effect of improving off-road running performance and starting performance could not be sufficiently obtained. In Comparative Example 2, the uplift height of the side block was uniform and there was no overlapping region as in Comparative Example 1, but the uplift height of the side block was large, so that the uniformity was deteriorated. In Comparative Example 3, since the area of the overlapping region was small, the effect of improving off-road running performance and starting performance could not be sufficiently obtained. In Comparative Example 4, since the area of the overlapping region is large, the uniformity is deteriorated.

1 Tread part 2 Side wall part 3 Bead part 4 Carcus layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 10 Main groove 20 Block 21 Shoulder block 21a Scooping part 22 Center block 23 Side block 24 Protrusion 31 Shoulder lug groove 32a Center lug groove 32b Auxiliary groove 33 Side groove 41 Sipe 42 Fine groove 50 Linear convex part B Block vs. O Overlapping area CL Tire equatorial E Grounding end

Claims (6)

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 side grooves extending along the tire radial direction in a side region adjacent to the inner side of the boundary between the tread portion and the sidewall portion in the tire radial direction, and the sidewall portion partitioned by the side grooves. There are multiple side blocks that rise from the outer surface of the tire,
The side block includes two types of blocks, a high block having a relatively large uplift height and a low block having a relatively small uplift height, and these high blocks and low blocks are arranged alternately in the tire circumferential direction. When the high block and the low block adjacent to each other in the tire circumferential direction are used as a block pair,
The high block included in the block pair has a protrusion extending along the tire circumferential direction toward the low block included in the same block pair, and the protrusion includes the low block included in the same block pair. Air including an overlapping region surrounded by the low blocks in three directions overlapping with the above, and the ratio of the area of the overlapping region to the total area of the top surface of the block pair is 20% to 40%. Tires with tires. The ratio of the area of the top surface of the overlapping region to the area of the top surface of the high block is 20% to 30%, and the ratio of the area of the top surface of the overlapping region to the area of the top surface of the low block is 20%. The pneumatic tire according to claim 1, wherein the content is -25%. The pneumatic tire according to claim 1 or 2, wherein the high block has a raised height of 4 mm to 6 mm, and the low block has a raised height of 2 mm to 3 mm. The ratio A / SH of the vertical distance A from the maximum outer diameter position of the tire to the inner end in the tire radial direction of the side block and the tire cross-sectional height SH is 10% to 30%, and the tire radial direction of the block pair. The pneumatic tire according to any one of claims 1 to 3, wherein the tire has a length of 40 mm to 50 mm. Of the boundary line between the high block and the low block in the overlapping region, the angle formed by the upper side located on the outermost side in the tire radial direction and the lower side located on the innermost side in the tire radial direction with respect to the tire circumferential direction is 0 °, respectively. The pneumatic tire according to any one of claims 1 to 4, wherein the temperature is about 10 ° and the length of the upper side is 50% to 70% of the length of the lower side. When the length measured along the outer surface of the tire from the tire equator to the bead portion is defined as the profile line length, the overlapping region is arranged at a position 35% to 45% of the profile line length from the tire equator. The pneumatic tire according to any one of claims 1 to 5.

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