JP4733502B2 - Pneumatic tire for running on rough terrain - Google Patents

Description

  The present invention relates to a pneumatic tire for running on rough terrain, which can effectively improve driving performance on rough terrain, particularly driving force on road surfaces with different soil properties in the depth direction.

  For example, in the case of a motorcycle for rough terrain traveling for motorcycles, which is made exclusively for rough terrain traveling such as motocross, trial and / or off-road, in order to ensure driving force and soil removal performance on rough terrain, A block pattern in which a plurality of blocks are relatively sparsely spaced is employed (see, for example, Patent Documents 1 and 2 below). In these conventional pneumatic tires for running on rough terrain, the blocks disposed in the tread portion are made substantially the same height.

JP 2002-36823 A JP 2003-72318 A

  By the way, conventional pneumatic tires for rough terrain are lined up in multiple types optimally tuned according to the hardness of the road surface. Usually, they include those for hard road surfaces, soft road surfaces, medium road surfaces having intermediate hardness, and the like.

  However, in recent years, a so-called composite road surface in which a hard soil surface is covered with soft earth or the like tends to be frequently used in a motocross course or the like. Such a composite road surface has a characteristic not found in conventional road surfaces in that the hardness of the soil is greatly different in the depth direction. For this reason, the conventional rough terrain tire has a drawback that a sufficient driving force cannot be obtained. Accordingly, fine tuning is required for tire patterns or blocks, which can also be applied to these road surfaces.

  The present invention has been devised in view of the above circumstances, and based on the inclusion of at least two types of blocks having different heights in the tread portion, sufficient driving on rough terrain, particularly the above-described composite road surface. An object of the present invention is to provide a pneumatic tire for running on rough terrain that can exert its power.

The invention according to claim 1 of the present invention is a pneumatic tire for running on uneven terrain having a land-sea ratio of 10 to 70% in which a plurality of blocks are provided in a tread portion, and the rim is assembled to a regular rim. In a tire cross section including a tire rotating shaft in a normal state in which no normal load is filled with a normal internal pressure, the tread portion is normal to a base surface formed by a circular arc that connects between the outer surface ends of the sidewall portion and has a smooth outer surface. A plurality of the blocks protruding at a height of 10.0 to 35.0 mm in the direction, and the blocks include a high block having the largest height and a low block having a smaller height than the high block. The low block on the inner side in the tire radial direction from the virtual tread surface that is formed of a smooth arc that passes through the height position of the high block and is symmetric with respect to the tire equator. The provided ground surface, yet the tread portion, the tread and the crown region having a developed width of 1/3 of the developed width, the tread width from the tread edge to the inner side in the tire axial direction around the tire equator 1 / When the virtual region is virtually divided into a shoulder region having an unfolded width of 6 and a middle region that is an area between the shoulder region and the crown region, only the low block is arranged in the middle region, and the high region block is characterized Rukoto disposed in the crown region and the shoulder region.

The invention according to claim 2 is a pneumatic tire for running on uneven terrain having a land-sea ratio of 10 to 70% in which a plurality of blocks are provided in a tread portion, and is assembled to a regular rim and has a regular internal pressure. In a tire cross section including a tire rotating shaft in a normal state that is filled with no load, the tread portion extends from the base surface formed by an arc that connects between the outer surface ends of the sidewall portion and has a smooth outer surface in the normal direction. A plurality of blocks raised at a height of 0.0 to 35.0 mm, and the blocks include a high block having the largest height and a low block having a height smaller than the high block. Thus, the ground contact of the low block on the inner side in the tire radial direction from the virtual tread surface that is formed of a smooth arc that passes through the height position of the high block and is line-symmetrical at the tire equator. The tread portion is provided with a crown region having a developed width of 1/3 of the tread developed width centered on the tire equator, and 1/6 of the tread developed width inward in the tire axial direction from the tread end. When virtually divided into a shoulder region having an unfolded width and a middle region that is an area between the shoulder region and the crown region, only the high block is arranged in the middle region, and the low block is , And is arranged only in the crown region and the shoulder region.

According to a third aspect of the present invention, the tread portion includes a first block arrangement in which at least three blocks including at least one high block and at least one low block are adjacent in the tread width direction. Or it is a pneumatic tire for rough terrain travel according to 2.

In the invention according to claim 4 , the tread portion includes a second block arrangement in which at least two high blocks are adjacent in the tread width direction, and at least two low blocks are adjacent in the tread width direction. The pneumatic tire for rough terrain travel according to any one of claims 1 to 3, wherein the block arrangement is provided alternately in the tire circumferential direction.

According to a fifth aspect of the present invention, the high block and / or the low block have a trapezoidal grounding surface, and the upper and lower bases of the grounding surface are arranged substantially parallel to the tread width direction. The lower bottom having a large length is a pneumatic tire for running on uneven terrain according to any one of claims 1 to 4 , which is 1.2 to 3.0 times the upper bottom.

  The pneumatic tire for running on rough terrain of the present invention includes a high block and a low block having different heights, so that the ground contact surface of the low block is more than the virtual tread surface passing through the ground contact surface of the high block It is provided inside the direction. In such a block pattern, the contact pressure of the high block is locally higher than that of the low block. For this reason, for example, when traveling on the above-mentioned composite road surface, the high block can deeply bite into the soft layer on the surface layer side of the road surface and splash it so that the low block can be brought into contact with the hard ground. Therefore, high traction performance can be obtained on the composite road surface. In particular, since the reaction force when splashing earth and sand acts as a driving force on the side surface of the block, high traction performance due to the high block is exhibited.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire for rough terrain travel (hereinafter sometimes simply referred to as “tire”) according to the present embodiment, and FIG. 2 is a non-development corresponding to the AA position. FIG. 3 is a cross-sectional view at the BB position.

  The pneumatic tire 1 is assembled to a tread portion 2, a pair of sidewall portions 3 and 3 extending inward in the tire radial direction from both sides thereof, and a rim (not shown) connected to the inside of the sidewall portion 3. In this embodiment, a tire for traveling on rough terrain for a motorcycle that is used in a motocross competition is shown.

  The pneumatic tire 1 includes, for example, a toroidal carcass 6 and a tread reinforcing layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and on the inner side of the tread portion 2.

  The carcass 6 includes at least one carcass ply 6A. The carcass ply 6A is preferably made of a carcass cord made of an organic fiber cord. In the present embodiment, the body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal shape, and the bead core 5 connected to the body portion 6a. And a folded portion 6b folded from the inner side to the outer side in the tire axial direction. The carcass 6 preferably has a bias structure in which two or more carcass plies 6A are used, but may have a radial structure.

  Further, the tread reinforcing cord layer 7 is made of an organic fiber cord, and in the present embodiment, is constituted by a plurality of reinforcing plies stacked in the tire radial direction. This helps to increase the rigidity of the tread portion 2 and improve the cut resistance.

  As shown in FIGS. 2 to 3, the tread portion 2 includes a plurality of blocks 10 protruding from the base surface 9 in the normal direction.

  The base surface 9 is formed of a smooth arc Cb that connects between the outer surface ends 3t and 3t that are outer ends in the tire radial direction of the outer surfaces of the sidewall portions 3 and 3 in the tire cross section including the tire rotation axis in a normal state. In the present embodiment, the arc Cb forming the base surface 9 has a substantially single radius of curvature Rb having a center O1 on the tire equator C. Therefore, the tire equator C is symmetric. The base surface 9 serves as a reference surface for determining the base portion of the block 10, in other words, the height Bh of the block 10. The base surface 9 includes a portion exposed between the blocks 10 and a virtual portion inside the block.

  Further, the “normal state” refers to a no-load state in which the tire 1 is assembled on a normal rim (not shown) and filled with a normal internal pressure. In addition, the regular rim is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, and ETRTO. For example, "Measuring Rim". In addition, “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. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars. In addition, when the corresponding standard does not exist, a manufacturer recommended value is adopted.

  In addition, the rough tire traveling pneumatic tire 1 according to the present embodiment is used at a relatively low internal pressure, for example, a low internal pressure of about 75 to 120 kPa.

  In addition, the base surface 9 of the present embodiment is formed with a single curvature radius Rb, but may be, for example, a compound arc formed by connecting two or more arcs having different curvature radii. In this case, it is desirable that the composite arc is line symmetric with respect to the tire equator C.

  The blocks 10 are provided relatively sparsely. Such a sparsely distributed arrangement of the blocks 10 increases the contact pressure of each block 10 as a whole, acquires a large amount of block biting into the road surface on soft earth or mud even on rough terrain, and has a high driving force. Demonstrated. Further, since the base surface 9 is formed in a large area between the blocks 10 and 10 due to the sparse block arrangement, clogging of mud between the blocks 10 and 10 is prevented.

  The block 10 is arranged so that the land sea ratio of the tread portion 2 is 10 to 70%. The land sea ratio is a ratio of the land area S1 to the sea area Ss of the tread portion 2, that is, a percentage of the ratio (Sl / Ss). The land area S1 is the sum of the contact surface areas of all the blocks 10. In addition, the sea area Ss is a tread area other than the land area, and specifically obtained by the product of the tread deployment width TW and the tread circumference LT passing through the tire equator C (the circumference at the tire maximum outer diameter). It is obtained by subtracting the land area from the virtual tread area (TW · LA).

  Here, when the land sea ratio is remarkably reduced, the driving force on the hard road surface is reduced. On the contrary, when the land sea ratio is remarkably increased, the driving force on the soft road surface is reduced. From such a viewpoint, the land sea ratio is preferably 5% or more, more preferably 10% or more, further preferably 15% or more, and the upper limit is preferably 95% or less, more preferably 80%. % Or less, more preferably 70% or less.

  Each block 10 has a height Bh of 10.0 to 35.0 mm. The height Bh is measured in the normal direction from the base surface 9 (or its virtual extension surface). 4 shows a part of the cross section of the tread portion 2 along the circumferential direction. For example, when the height is not constant in one block 10, the maximum height Bh1 and the minimum height are shown. The average value with Bh2 is defined as the height of the block.

  When the height Bh of the block is less than 10.0 mm, the driving force tends to decrease on a soft road surface. Conversely, when the height exceeds 35.0 mm, a very large bending moment is applied to the base portion of the block 10 during driving or braking. Acts, and the durability of the block 10 and the driving force on a hard road surface are likely to decrease. From such a viewpoint, the height Bh of the block is preferably 10 mm or more, more preferably 15 mm or more, further preferably 20 mm or more, and the upper limit is preferably 35 mm or less, more preferably 30 mm or less, Preferably it is 25 mm or less.

  In the present embodiment, the block 10 includes a plurality of high blocks 11 having the largest height Bh and low blocks 12 having a smaller height than the high block 11. As a result, the ground contact surface 12c of the low block 12 is provided on the inner side in the tire radial direction from the virtual tread surface VT formed of the smooth arc Ct that passes through the ground contact surface 11c of the high block 11 and is line symmetric with respect to the tire equator C. For easy understanding in FIG. 1, the high block 11 is colored in gray.

  The virtual tread surface VT is a virtual curved surface obtained by continuously rotating a smooth arc Ct in the tire cross section 360 ° around the tire rotation axis. In the present embodiment, the arc Ct is formed with a single radius of curvature Rt having the center O2 on the tire equator C. However, the arc Ct may be a composite arc formed by connecting two or more arcs having different curvature radii. . In this case, it is desirable that the composite arc is line symmetric with respect to the tire equator C.

  In such a block pattern, the ground pressure of the high block 11 is relatively larger than the ground pressure of the low block 12. For this reason, when traveling on the above-described composite road surface, the high block 11 can be removed effectively by splashing the soft layer on the road surface layer side. As a result, the hard ground can be exposed to the surface, and the low block 12 can be brought into contact therewith to obtain a frictional force. Thereby, the tire 1 of this embodiment can obtain high traction performance on the composite road surface.

  On the other hand, in the conventional block pattern in which all the block heights are the same, the above-mentioned significant difference in relative ground pressure does not occur between the blocks. Accordingly, the overall ability to splash the soft layer is insufficient. As a result, it becomes difficult to bring the ground contact surface of the block into contact with the deep hard road surface, and sufficient driving force on the composite road surface cannot be obtained.

  In order to effectively express the above-described action, the difference Δh between the height of the high block 11 and the height of the low block 12 is preferably 1.0 mm or more, more preferably 2.0 mm or more. On the other hand, when the difference in height is remarkably large, the low block is difficult to contact the road surface, so that a sufficient driving force may not be obtained. From such a viewpoint, the height difference Δh is preferably 5.0 mm or less, more preferably 4.0 mm or less.

  In the present embodiment, the tread portion 2 includes a first block array P1 including at least one high block 11 and at least one low block 12 and three or more blocks 10 adjacent in the tread width direction. . Here, the blocks adjacent to each other in the tread width direction mean that each block has an overlapping portion in the tire circumferential direction, in other words, it is sufficient if the first block array P1 as described above appears in the tire cross section. is there.

  As is apparent from FIG. 1, in the present embodiment, the first block array P1 in which three to five blocks are adjacent in the tread width direction is spaced apart at a substantially constant pitch in the tire circumferential direction. Since the first block array P1 includes the high block 11 and the low block 12 in one row in the tread width direction, the low block 12 exists in the depth direction. The opportunity to contact a hard road surface can be increased. Therefore, an effective driving force can be obtained on the composite road surface.

Further, in the present embodiment, the tread portion 2 includes a crown region Cr having a developed width of 1/3 of the tread developed width TW centering on the tire equator C, and the tread developed width from the tread end 2e toward the tire axial direction inside. 1/6 and shoulder region Sh having developed width of, when virtual divided into a middle region Md is a region between the shoulder regions Sh and the crown region Cr, only the low block 12 in the middle region Md is distribution together with the high block 11 is coordinating the crown region Cr and the shoulder regions Sh. In the illustrated embodiment, both the high block 11 and the low block 12 are included in the crown region Cr, and the high block 12 is not included in the middle region Md.

  The arrangement area of the blocks 10 is determined based on which area the center of gravity (centroid) of the ground contact surface of each block 10 belongs.

  In such a block pattern, when traveling on the composite road surface, the high block 11 disposed in the crown region Cr that is most likely to have the highest ground pressure during straight traveling can more effectively scrape the soft surface layer. Therefore, a very excellent driving force can be exhibited. In addition, when the vehicle travels straight, excessively lowering of the contact pressure can be suppressed by arranging the high block 11 in the shoulder region Sh where the contact pressure is likely to decrease. Therefore, such a block arrangement can effectively increase the driving force and shorten the lap time especially in a high-speed motocross course having a long straight traveling distance.

On the other hand, FIGS. 5 to 7 show block pattern configurations opposite to those described above. FIG. 5 is a development view of the tread portion 2, and FIGS. 6 and 7 are partial cross-sectional views at positions AA and BB (the internal structure is omitted). In this embodiment, with only the high block 11 is arranged in the middle region Md of the tread portion 2, the low block 12 is coordinating the crown region Cr and the shoulder regions Sh. In this embodiment, both the high block 11 and the low block 12 are included in the crown region Cr. Other than that, one block is arranged in each area.

  In such a block pattern, when traveling on the composite road surface, the high block 11 disposed in the middle region Md where the contact pressure tends to be high during turning can more effectively scrape the soft surface layer. The low blocks 12 respectively disposed on both sides thereof, that is, the crown region Cr and the shoulder region Sh can be effectively brought into contact with the hard road surface. Thereby, a very excellent driving force is exhibited during turning. Therefore, such a block arrangement can effectively increase the driving force and shorten the lap time particularly in a technical type motocross course having many corners.

  In each of the above embodiments, the low block 12 can be configured not only by one type but also by two or more types. However, when the number of types of the low blocks 12 increases, the difference in height between the blocks tends to be small, and a sufficient driving force tends not to be obtained. For this reason, the number of types of the low blocks 12 is preferably 3 or less.

  FIG. 8 is a developed view of the tread portion 2 as still another embodiment of the present invention. FIG. 9 is an end view of the AA position, and FIG. 10 is an end view of the BB position.

  In the present embodiment, the tread portion 2 includes a second block array P2 in which at least two high blocks 11 are adjacent in the tread width direction, and a third block array in which at least two low blocks 12 are adjacent in the tread width direction. P3 and the tire circumferential direction are provided alternately and at a substantially constant pitch. Such a block pattern can exhibit a very high driving force as a result of more effective repetition of the soft road removing action by the high block 11 and the contact action with the hard road by the low block 12 on the composite road surface. Particularly preferred in terms. In particular, it is particularly desirable that at least three high blocks 11 or low blocks 12 are adjacent to each other in each of the second and third block arrays P2 and P3.

  In each of the above embodiments, the crown region Cr has the highest chance of contacting the road surface, including when going straight and turning. Therefore, it is preferable to arrange the most blocks 10 in the crown region Cr in each block pattern.

  Further, in each of the above embodiments, the ratio of the high block 11 among all the blocks 10 is not particularly limited. However, if the ratio is too small, the effect of eliminating the soft layer on the composite road surface tends to decrease, and conversely, If the ratio is too large, the opportunity to bring the low block 12 into contact with the hard road surface after the soft layer is removed tends to be impaired. From such a viewpoint, the number of high blocks 11 with respect to the total number of blocks is preferably 30% or more, more preferably 50% or more, and the upper limit is preferably 80% or less, more preferably 70% or less. Is desirable.

In each of the above embodiments, the area of the ground contact surface 10c of each block 10 is preferably 1.0 cm ² or more, more preferably 2.0 cm ² or more, and even more preferably 3.0 cm ² or more, and the upper limit is preferably 10.0 cm ² or less, more preferably 8.0 cm ² or less, more preferably 5.0 cm ² or less.

  In each of the above embodiments, the high block 11 and / or the low block 12 has trapezoidal ground surfaces 11c and 12c, and parallel sides of the trapezoidal ground surface (in other words, upper and lower sides). Is along the tire circumferential direction. Instead of such an embodiment, for example, as shown in FIG. 11, the upper base 13 and the lower base 14 of the ground surface 10c may be arranged substantially parallel to the tread width direction. In particular, it is desirable that the length Lb of the lower base 14 having a large length is 1.2 to 3.0 times the length La of the upper base 13. With the above configuration, the characteristics of the driving force and the braking force can be made asymmetric. For example, it is preferable that a tire using a block with a large side on the rotational direction first arrival side is for a rear wheel, and a tire using a block with a large side on the rotation direction rear arrival side is for a front wheel. As a result, the rear wheel tire can sufficiently exhibit the driving force, and the front wheel tire effectively exhibits the braking force.

  Further, as shown in FIG. 12 (A), with respect to the tire 1a attached to the non-drive wheel (the front wheel in the case of a motorcycle tire), the height of the block 10 is changed from the first arrival side to the rear arrival side in the rotational direction. It is desirable to incline the grounding surface 10c so as to increase toward. That is, as relative, a small height Bh2 is set on the first arrival side in the rotational direction, and a large height Bh1 (> Bh2) is set on the second arrival side. Thereby, the block 10 deform | transforms so that it may bite into a road surface like a wedge at the time of braking, and a braking capability can be improved.

  Further, as shown in FIG. 12B, with respect to the tire 1b mounted on the driving wheel (rear wheel in the case of a motorcycle tire), the height of the block 10 is changed from the rotational first arrival side to the rear arrival side. It is desirable to incline the grounding surface 10c so as to decrease toward. That is, as a relative thing, a large height Bh1 is set on the first arrival side in the rotation direction, and a small height Bh2 (<Bh1) is set on the second arrival side. Thereby, the block 10 acts like a wedge at the time of driving, and the driving ability can be improved.

  As described above in detail, it goes without saying that the pneumatic tire of the present invention can be implemented not only for motorcycles but also for three-wheel buggy vehicles and four-wheel vehicles. In addition, the specific block patterns are all symmetrical with respect to the tire equator, but the blocks 10 may be non-linearly symmetric and are implemented in various modifications without being limited to the illustrated embodiment.

  Based on the use of Table 1, a plurality of types of pneumatic tires for running on rough terrain (Landsea ratio: 20%) having a size of 120 / 80-19 were manufactured and their traction performance was evaluated.

For traction performance, vehicles with each test tire mounted on the rear wheels under the following conditions were used. General rough roads (hard road surface), deep muddy ground (soft road surface), and hard soil were about 40 mm thick. Each of the three motocross courses on the composite road covered with soft soil was run by a professional test driver, and the degree of transmission of driving force to each road was evaluated by the feeling of 10 drivers. The results are evaluated by a 10-point method (average value of n = 5). The larger the value, the better. The rims, vehicles, etc. were as follows, and common tires (size 90 / 90-18) were used for the front wheels.
Rims: 19 x 2.15
Internal pressure: 80 kPa
Vehicle: Motocross motorcycle with a displacement of 450 cc Test tire wearing wheel: Rear wheel Table 1 shows the test results.

  As a result of the test, it can be confirmed that the tires of the examples have improved traction performance on the road surfaces of the mud road and the composite road while maintaining the performance on the hard road.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is sectional drawing of the AA position. It is sectional drawing of the BB position. It is a fragmentary sectional view along the tire peripheral direction of a tread part. It is an expanded view of the tread part which shows other embodiment of this invention. It is sectional drawing of the AA position. It is sectional drawing of the BB position. It is an expanded view of the tread part of a comparative example . It is an end elevation of the AA position. It is an end elevation of the BB position. It is a top view which shows the grounding surface of the block of other embodiment. It is sectional drawing along the tire circumferential direction explaining the ground-contact surface of a block as other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rough-pneumatic pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Tread reinforcement cord layer 10 Block 11 High block 12 Low block P1 1st block arrangement P2 2nd block arrangement P3 3rd Block arrangement Cr Crown area Md Middle area Sh Shoulder area

Claims (5)

A pneumatic tire for running on uneven terrain having a land-sea ratio of 10 to 70% in which a plurality of blocks are provided in a tread portion,
In the tire cross section including the tire rotation shaft in the normal state in which the rim is assembled to the normal rim and the normal internal pressure is filled, and in an unloaded state,
The tread portion includes a plurality of the blocks protruding from the base surface formed by a circular arc having a smooth outer surface between the outer surface ends of the sidewall portion at a height of 10.0 to 35.0 mm in the normal direction. ,And,
The block includes a high block having the largest height and a low block having a height smaller than the high block,
The ground contact surface of the low block is provided on the inner side in the tire radial direction than the virtual tread surface that is formed of a smooth arc that passes through the height position of the high block and is line-symmetrical at the tire equator ,
Moreover, the tread portion has a crown region having a developed width of 1/3 of the tread developed width centered on the tire equator, and a shoulder having a developed width of 1/6 of the tread developed width from the tread end to the inside in the tire axial direction. When the area is virtually divided into a middle area that is an area between the shoulder area and the crown area,
With low block only is disposed in the middle region, the high block, the crown region and an off-road pneumatic tire according to claim Rukoto disposed in the shoulder region. A pneumatic tire for running on uneven terrain having a land-sea ratio of 10 to 70% in which a plurality of blocks are provided in a tread portion,
In the tire cross section including the tire rotation shaft in the normal state in which the rim is assembled to the normal rim and the normal internal pressure is filled, and in an unloaded state,
The tread portion includes a plurality of the blocks protruding from the base surface formed by a circular arc having a smooth outer surface between the outer surface ends of the sidewall portion at a height of 10.0 to 35.0 mm in the normal direction. ,And,
The block includes a high block having the largest height and a low block having a height smaller than the high block,
The ground contact surface of the low block is provided on the inner side in the tire radial direction than the virtual tread surface that is formed of a smooth arc that passes through the height position of the high block and is line-symmetrical at the tire equator,
Moreover, the tread portion has a crown region having a developed width of 1/3 of the tread developed width centered on the tire equator, and a shoulder having a developed width of 1/6 of the tread developed width from the tread end to the inside in the tire axial direction. When the area is virtually divided into a middle area that is an area between the shoulder area and the crown area,
The pneumatic tire for rough terrain travel , wherein only the high block is disposed in the middle region, and the low block is disposed only in the crown region and the shoulder region . The rough tread traveling air according to claim 1 or 2, wherein the tread portion includes a first block arrangement in which at least three blocks including at least one high block and at least one low block are adjacent in the tread width direction. Tires. The tread portion includes a second block arrangement in which at least two high blocks are adjacent in the tread width direction;
The pneumatic tire for rough terrain travel according to any one of claims 1 to 3, wherein at least two of the low blocks are alternately provided in the tire circumferential direction with a third block array adjacent in the tread width direction . The high block and / or low block has a trapezoidal ground surface;
The upper and lower bases of the grounding surface are disposed substantially parallel to the tread width direction;
The pneumatic tire for running on uneven terrain according to any one of claims 1 to 4, wherein the lower bottom having a large length is 1.2 to 3.0 times the upper bottom .

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