JP2010126046A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of compatibly realizing controllability and stability performance during high-speed travel on a dry road surface and controllability and stability performance during travel on a wet road surface; in particular, to provide a pneumatic tire suitable for a pickup truck of which the high-speed movement is required. <P>SOLUTION: A rib-shaped land part with a large number of blocks being arrayed is formed by demarcating right and left land parts 3B, 3B located on the outermost side of the tire width direction out of three or two land parts demarcated in main grooves 2A, 2B formed on a tread face 1 by narrow small grooves 4 arranged at the predetermined spacing in the tire circumferential direction, and a bottom-raised part 5 is formed in a center area of the tire width direction of the small grooves 4, which has the length of 50-70% of the length of the small grooves 4 and the height of 30-50% of the depth of the small grooves 4. A sipe 6 is formed, which is refracted in the tire circumferential direction inwardly in the tire width direction from the main groove 2B adjacent to the blocks on the outer side in the tire width direction, and in the tire circumferential direction within the blocks, and opened in the bottom-raised part 5 in the small grooves 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire. More specifically, the present invention relates to a pneumatic tire that can achieve both a steering stability performance during high-speed driving on a dry road surface and a steering stability performance on a wet road surface. The present invention relates to a pneumatic tire suitable for a truck.

  Conventionally, a tread surface of a pneumatic tire for a small truck used for a delivery vehicle traveling in an urban area, as illustrated in FIG. 9, in order to ensure steering stability performance at high speed traveling on a dry road surface. In order to form a plurality of land portions extending in the tire circumferential direction, and to secure the steering stability performance on the wet road surface, the width of the two land portions arranged in the central region of the tread among these plurality of land portions Many tread patterns that are divided into lug grooves R that are inclined in the direction and formed into block rows, and sipe Qs are formed on the surface of each block, and the arrangement density and arrangement angle of these sipe Qs are variously changed. It has been.

  However, with the recent progress of road maintenance, demands for increasing the load weight on the vehicle and increasing the vehicle speed have gradually increased. As a result, the block formed on the tread surface is damaged depending on the running conditions.

In order to avoid such a situation, conventionally, there have been many proposals relating to a tread pattern that improves drainage while ensuring a high level of tread rigidity (see, for example, Patent Document 1). However, none of these proposals have been able to fully meet the recent demand for high-speed movement, and there is still room for improvement.
JP 7-89303 A

  An object of the present invention is to eliminate the above-mentioned conventional problems, and a pneumatic tire, particularly a high-speed tire, capable of achieving both steering stability performance during high-speed driving on a dry road surface and steering stability performance on a wet road surface. It is an object of the present invention to provide a pneumatic tire suitable for a small truck that requires movement.

  In order to achieve the above object, the pneumatic tire of the present invention is provided with four or three main grooves extending in the tire circumferential direction on the tread surface, and is defined between the main grooves in a central region of the tread surface. In the pneumatic tire in which two or two land portions are formed, left and right land portions located on the outermost side in the tire width direction among the land portions are each set to have a groove width of 10 to 40% of the groove width of the main groove. And a rib-like land portion in which a large number of blocks are arrayed by being partitioned by narrow grooves obliquely crossing at a predetermined interval in the tire circumferential direction, and at the center region in the tire width direction of the narrow grooves A bottom raised portion having a length corresponding to 50 to 70% of the length of the narrow groove and having a height set to 30 to 50% of the maximum depth of the narrow groove is formed, and the tire width direction is formed on the block. From the main groove adjacent to the outside toward the inside in the tire width direction, and the block It is characterized in that the formation of the sipes is refracted in the tire circumferential direction open to the bottom raising portion of the narrow groove in the inner.

Moreover, in the structure mentioned above, it is preferable to comprise as described in (1)-(7) below.
(1) The position where the sipe opens at the bottom raised portion of the narrow groove is set within a range of ± 10% of the width of the rib-like land portion with respect to the center line in the tire width direction of the rib-like land portion.
(2) The maximum depth of the narrow groove is 60 to 90% of the depth of the main groove.
(3) The depth of the sipe is 20 to 50% of the depth of the main groove.
(4) A notch that cuts in the tire width direction is formed on the inner side wall of the block in the rib-like land portion in the tire width direction, and the depth of the notch from the tread surface is shallower than the depth of the main groove. . In this case, the land portion is composed of three pieces, the land portion located in the center is formed in a rib continuous in the tire circumferential direction, and the notch portion that bites into both side walls of the rib in the tire width direction is formed in the tire circumference. Are formed intermittently in the direction, and these notches are arranged alternately offset in the tire circumferential direction with respect to the notches of the blocks in the rib-like land adjacent to both sides of the rib, or the land It is good to make it the arrangement which consists of two rib-like land parts, and the above-mentioned notch formed in these two rib-like land parts is alternately offset in the tire peripheral direction. Furthermore, the biting width of the notch is preferably 3 to 15% of the width of the rib-like land.
(5) The main groove is composed of four, and the center line of the two main grooves on the inner side in the tire width direction is arranged at a position of 15 to 30% of the tire ground contact width centering on the tire equator, The center line of the outer two main grooves is arranged at a position of 55 to 75% of the tire ground contact width centering on the tire equator, and the land portion defined by the two main grooves on the inner side in the tire width direction is a tire. It is formed in a rib continuous in the circumferential direction.
(6) The hardness of the rubber constituting the tread surface is set to 65 to 80 according to JIS A type.
(7) A small truck tire having a maximum air pressure defined by ETRTO of 575 kPa or less, or a small truck tire having a maximum air pressure defined by JATMA of 650 kPa or less.

  According to the present invention, the left and right land portions positioned on the outermost side in the tire width direction among the three or two land portions partitioned by the main groove formed on the tread surface are each 10 to 10 times the groove width of the main groove. The groove has a groove width of 40% and is formed in a rib-like land portion in which a large number of blocks are arrayed by being partitioned by narrow grooves obliquely crossing at a predetermined interval in the tire circumferential direction. Since the bottom raised portion having a length corresponding to 50 to 70% of the length of the narrow groove and having a height set to 30 to 50% of the depth of the narrow groove is formed in the central region in the width direction. Drainability can be ensured by forming a narrow groove without substantially reducing the rigidity of the rib-like land part by setting the width and forming the bottom raised part, so steering stability performance and wetness at high speed traveling on dry road surface It is possible to balance the steering stability performance on the road with a good balance.

  Furthermore, a sipe that is refracted in the tire circumferential direction from the main groove adjacent to the outer side in the tire width direction on the block partitioned by the narrow groove and that is refracted in the tire circumferential direction in the block is formed in the block. Therefore, it becomes possible to maintain the rigidity of the rib-like land portion uniformly, improve uneven wear resistance, and at the same time, drain the water by forming a sipe without substantially reducing the rigidity of the rib-like land portion. Therefore, it is possible to improve the steering stability performance at the time of high speed traveling on a dry road surface and the steering stability performance on a wet road surface in a more balanced manner.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a plan view corresponding to FIG. 1 according to another embodiment of the present invention.

  As will be described in detail below, the tread surface of the pneumatic tire of the present invention is provided with four or three main grooves extending in the tire circumferential direction, and is partitioned between these main grooves in the central region of the tread surface. Three or two land portions are formed.

  In FIG. 1, four main grooves 2B, 2A, 2A, 2B are provided on the tread surface 1, and three land portions 3B defined by the main grooves 2B, 2A, 2A, 2B in the central area of the tread surface 1 are illustrated. FIG. 2 shows a case where three main grooves 2B, 2A and 2B are provided on the tread surface 1, and these main grooves 2B, 2A and 2B are provided in the central area of the tread surface 1. The case where the two land parts 3B and 3B divided are formed is shown.

  And in the pneumatic tire of the present invention, the left and right land portions 3B, 3B located on the outermost side in the tire width direction among the land portions 3B, 3A, 3B shown in FIG. 1 or the land portions 3B, 3B shown in FIG. Each of the main grooves 2A and 2B has a groove width of 10 to 40%, preferably 15 to 35%, and is partitioned by narrow grooves 4 that obliquely cross the tire circumferential direction at a predetermined interval. It is formed in a rib-like land portion in which a large number of blocks 3b are arranged.

  Here, the land portions 3B and 3B are formed in the rib-like land portions because the narrow grooves 4 that divide the land portions 3B and 3B greatly reduce the groove width as compared with the lug grooves in the usual tires. As will be described later, and by forming the bottom raised portion 5 in the center region in the tire width direction of the narrow groove 4, the land portions 3B and 3B themselves have substantially the same rigidity as the rib. Because it is.

  That is, in the center region in the tire width direction of the narrow groove 4 described above, as shown in FIGS. 3 and 4, a length corresponding to 50 to 70%, preferably 55 to 65% of the length L of the narrow groove 4. The height h of the bottom raised portion 5 is 30 to 50%, preferably 35 to 45% of the depth H of the narrow groove 4. Thereby, drainage can be ensured by forming the narrow groove 4 without substantially reducing the rigidity of the rib-like land portion by setting the width of the narrow groove 4 and forming the bottom raised portion 5, so that on the dry road surface It is possible to balance the steering stability performance during high-speed traveling with the steering stability performance on a wet road in a balanced manner.

  Further, the block 3b defined by the narrow groove 4 is refracted in the tire width direction from the main groove 2B adjacent to the outer side in the tire width direction and in the tire circumferential direction in the block 3b, and is a raised portion of the narrow groove 4 A sipe 6 opening to 5 is formed. This makes it possible to maintain the rigidity of the rib-like land portion uniformly, improve the uneven wear resistance, and at the same time, form the sipe 6 without substantially reducing the rigidity of the rib-like land portion. Therefore, the drainage performance can be further improved, so that the steering stability performance at the time of high speed traveling on the dry road surface and the steering stability performance on the wet road surface can be improved in a more balanced manner.

  When the groove width of the narrow groove 4 described above is less than 10% of the groove width of the main grooves 2A and 2B, the drainage performance is deteriorated and the steering stability performance on the wet road surface is deteriorated, and when it exceeds 40%, The rigidity of the rib-like land portion is insufficient, and the steering stability performance during high speed traveling on a dry road surface is reduced.

  Further, the length of the bottom raised portion 5 formed in the narrow groove 4 is less than 50% of the length L of the narrow groove 4, or the height h of the bottom raised portion 5 is less than 30% of the depth H of the narrow groove 4. Then, the rigidity of the rib-like land portion cannot be ensured, and the steering stability performance at the time of high speed traveling on a dry road surface becomes a factor. On the other hand, the length of the bottom raised portion 5 formed in the narrow groove 4 exceeds 70% of the length L of the narrow groove 4, or the height h of the bottom raised portion 5 exceeds 50% of the depth H of the narrow groove 4. If it becomes, drainage property will deteriorate and the steering stability performance on a wet road surface will fall.

  In the embodiment of FIG. 1 described above, the land portion 3A continuous in the tire circumferential direction is disposed in the central region of the tread surface 1, and the tread rigidity can be ensured at a high level. It is preferably employed for pneumatic tires that place importance on steering stability performance during traveling.

  In the present invention, the position P (see FIG. 3) that opens to the bottom raised portion 5 of the narrow groove 4 of the sipe 6 formed in the block 3b is the width S of the rib-shaped land portion with respect to the center line in the tire width direction of the rib-shaped land portion. It is good to set within the range of ± 10% of. As a result, uneven wear in the vicinity of the opening position P of the rib-like land portion can be prevented, and a decrease in the rigidity of the block 3b can be efficiently prevented.

In the pneumatic tire of the present invention, the depth H (see FIG. 4) of the narrow groove 4 described above may be set to 60 to 90%, preferably 70 to 85% of the depth H ₀ of the main grooves 2A and 2B. As a result, the rigidity of the land portion 3B can be ensured at a high level, and the steering stability performance during high-speed traveling can be reliably improved.

More preferably, the depth H _x of the sipe 6 is set to 20 to 50%, preferably 25 to 40% of the depth H ₀ of the main grooves 2A and 2B. Thereby, drainage can be improved, ensuring the rigidity of the block 3b at a high level. If the depth H _x of the sipe 6 is less than 20% of the depth H ₀ of the main grooves 2A and 2B, the drainage performance will deteriorate and the steering stability performance on wet roads will deteriorate, and if it exceeds 50%, the block 3b Stiffness is lowered, and the steering stability performance at high speed traveling on a dry road surface deteriorates.

  In the present invention, more preferably, a notch 8 that cuts in the tire width direction is formed on the inner side wall of the block 3b in the tire width direction, and the depth (not shown) of the notch 8 from the tread surface 1 is set to the main groove 2A. It is good to form shallower than this depth. Accordingly, pattern noise can be suppressed while efficiently suppressing uneven wear in the vicinity of the notch 8, and at the same time, the steering stability performance on the wet road surface can be efficiently improved by the edge effect of the notch 8.

  In the present invention, when three land portions 3B, 3A, 3B are formed on the tread surface 1 as in the embodiment of FIG. 1, the land portion 3A located at the center of the land portions 3A is a rib that continues in the tire circumferential direction. In addition, the notches 8 are formed intermittently in the tire circumferential direction on both side walls of the ribs in the tire circumferential direction, and these notches 8 are formed with respect to the notches 8 of the block 3b adjacent to both sides of the ribs. It is good to arrange it alternately offset in the tire circumferential direction. Thereby, while ensuring the tread rigidity at a high level, the pattern noise can be further suppressed, and the steering stability performance on the wet road surface can be further improved by the edge effect of the notch 8.

  When the two land portions 3B and 3B are formed on the tread surface 1 as in the embodiment of FIG. 2, the notch portions 8 formed in the two land portions 3B and 3B are alternately arranged in the tire circumferential direction. It is good to arrange to offset. Thereby, while suppressing pattern noise efficiently, the steering stability performance on a wet road surface can be improved by the edge effect of the notch part 8. FIG.

  In the present invention, the biting width W0 (see FIG. 3) of the notch 8 described above may be set to 3 to 15%, preferably 5 to 10% of the width S of the rib-like land portion. As a result, the pattern noise can be reliably suppressed, and at the same time, the steering stability performance on a wet road surface can be reliably improved by the edge effect of the notch 8.

  In the pneumatic tire of the present invention, the pattern configuration in the land portions on both shoulder sides partitioned by the main groove 2B is not particularly limited, but ensures the steering stability performance at the time of high speed traveling on a dry road surface. From the viewpoint of ensuring good steering stability performance on a wet road surface, as shown in FIG. 1 and FIG. 2, it is preferable to partition by a narrow groove 4 ′ inclined in the tire width direction as in the adjacent rib-like land portion.

  In the case described above, the inclination direction of the narrow groove 4 ′ formed in the land portion on the shoulder side is different from the narrow groove 4 in the adjacent rib-shaped land portion as illustrated in the embodiment of FIGS. 1 and 2. Can be tilted in the direction. FIG. 5 shows a tread surface 1 according to another embodiment of the present invention. In this embodiment, a narrow groove is formed between the shoulder-side land portion and the adjacent rib-like land portion in the embodiment of FIG. The case where the inclination direction is made different and the arrangement position of the sipe 6 formed in the rib-like land portion is changed with respect to the tire circumferential direction is shown.

  In the present invention, when the main groove is composed of four as in the embodiment shown in FIGS. 1 and 5, the center line of the two main grooves 2A, 2A on the tire equator CL side is centered on the tire equator CL. As 15 to 30% of the tire ground contact width W, and the center line of the two main grooves 2B and 2B on the tire shoulder side is located at 55 to 75% of the tire ground contact width W around the tire equator CL. In addition to the arrangement, the land portion 3A defined by the two main grooves 2A, 2A on the tire equator CL side may be formed as a rib extending continuously in the tire circumferential direction.

  Thereby, drainage can be improved efficiently, ensuring tread rigidity at a high level. In this case, a sipe 7 can be formed on the land portion 3A as illustrated in FIG. 1 and FIG.

  In the pneumatic tire of the present invention, the hardness of the rubber constituting the tread surface 1 may be set to 65 to 80 in JIS A type. Thereby, the steering stability performance at the time of high-speed driving | running | working on a dry road surface and the steering stability performance on a wet road surface can be made to make it compatible with a high level with sufficient balance.

  As described above, the pneumatic tire according to the present invention includes the left and right land portions positioned on the outermost side in the tire width direction among the three or two land portions defined in the main groove formed on the tread surface. Formed in a rib-like land portion in which a large number of blocks are arrayed by being divided by narrow narrow grooves arranged at predetermined intervals in the direction, and a bottom raised portion having a predetermined height is formed in the central area of the narrow groove In addition, a dry road surface is formed by forming a sipe that extends inward in the tire width direction from the main groove adjacent to the block on the outer side in the tire width direction and that is refracted in the tire circumferential direction in the block and opens to the bottom raised portion of the narrow groove. The balance between steering stability performance during high-speed driving and steering stability performance on wet roads in a well-balanced manner, and can fully support the increase in vehicle loading weight and vehicle speed. weight Big VAN tires, in particular maximum air pressure is less light truck tire 575kPa defined by ETRTO or maximum air pressure defined by the JATMA, it is preferably applied to the following light truck tires 650 kPa.

<Examples 1-3, Comparative Examples 1-4>
The tire size is 235 / 65R16C 115 / 113R, the basic form of the tread surface is FIG. 1 or FIG. 5, and the tread pattern, the presence or absence of the bottom raised portion in the narrow groove and the length of the bottom raised portion relative to the length of the narrow groove (in Table 1, The tires of the present invention (Examples 1 to 3) and comparative tires (Comparative Examples 1 to 4) were produced by varying the length ratio) and the presence or absence of sipes in the blocks as shown in Table 1, respectively.

  In each tire, the width of the narrow groove is 25% of the groove width of the main groove, the depth of the narrow groove is 75% of the depth of the main groove, the height of the bottom is 40% of the depth of the narrow groove, and sipe Was made common with 30% of the depth of the main groove, and the total sum of the sipe lengths formed in each block was made the same.

  For these seven types of tires, the following test methods were used to evaluate the handling stability during high speed running on dry road surfaces and the handling stability on wet road surfaces. It was written together. The larger the value, the better.

[Maneuvering stability at high speed on dry road] (referred to as steering stability at high speed in Table 1)
Each tire is mounted on a rim (16 × 6.5J), the filling air pressure is set to 300 kPa at the front wheel, and 480 kPa at the rear wheel, and the maximum loading capacity is set to the front and rear wheels of a VAN made in Europe with 2.0 tons, The load was set to 1.0 ton, and a test course consisting of a dry asphalt road surface was run while changing the speed within a range of 0 to 200 km / h, and sensory evaluation was performed by a skilled test driver.

[Maneuvering stability on wet road surface]
Each tire is mounted on a rim (16 × 6.5J), the filling air pressure is set to 300 kPa at the front wheel, and 480 kPa at the rear wheel, and the maximum loading capacity is set to the front and rear wheels of a VAN made in Europe with 2.0 tons, The load was set to 1.0 ton, and a test course consisting of an asphalt road surface with a water depth of 2 ± 1 mm was run while changing the speed within a range of 0 to 100 km / h, and sensory evaluation was performed by a skilled test driver.

  From Table 1, it can be seen that the tire of the present invention balances the steering stability at the time of high speed running on a dry road surface and the steering stability on a wet road surface in comparison with the comparative tire. In Comparative Example 2, since the bottom raised portion was not formed in the narrow groove, the rigidity of the rib-like land portion was insufficient, and the steering stability at the time of high speed traveling on the dry road surface was comparable to Comparative Example 1, Furthermore, since the sipe was not formed on the block, the handling stability on the wet road surface was deteriorated.

  Further, in Comparative Example 3, since the bottom raised portion was formed in the narrow groove, the rigidity of the rib-like land portion was ensured, and the handling stability during high speed running on the dry road surface was slightly improved compared to Comparative Example 1. However, since the sipe was not formed on the block, the handling stability on the wet road surface was greatly deteriorated in combination with the raised bottom portion formed in the narrow groove.

  Further, in Comparative Example 4, since the bottom raised portion is formed in the narrow groove, similarly to Comparative Example 3, the rigidity of the rib-like land portion is ensured, and the driving stability at high speed traveling on the dry road surface is compared with Comparative Example 1. Although it was slightly improved, the sipe formed on the block was terminated in the block, so that the steering stability on the wet road surface deteriorated in combination with the raised bottom formed on the narrow groove.

<Examples 4 and 5 and Comparative Examples 5 to 7>
The tire size is 235 / 65R16C 115 / 113R, the basic form of the tread surface is shown in FIG. 2, and the tread pattern, the presence / absence of the bottom raised portion in the narrow groove and the length of the bottom raised portion relative to the length of the narrow groove (in Table 2, The tires of the present invention (Examples 4 and 5) and comparative tires (Comparative Examples 5 to 7) were produced by differentiating the presence / absence of sipes in the blocks and the presence or absence of sipes in the blocks as shown in Table 2, respectively.

  In each tire, the width of the narrow groove is 25% of the groove width of the main groove, the depth of the narrow groove is 75% of the depth of the main groove, the height of the bottom is 40% of the depth of the narrow groove, and sipe Was made common with 30% of the depth of the main groove, and the total sum of the sipe lengths formed in each block was made the same.

  For these five types of tires, as in the test method described above, the steering stability during high speed running on a dry road surface and the steering stability on a wet road surface were evaluated, and the results were indexed with Comparative Example 5 as 100. Are also shown in Table 2. The larger the value, the better.

  From Table 2, it can be seen that the tire of the present invention balances the steering stability during high-speed driving on a dry road surface and the steering stability on a wet road surface in comparison with the comparative tire. In Comparative Example 6, since the bottom raised portion was not formed in the narrow groove, the rigidity of the rib-like land portion was insufficient, and the steering stability at the time of high-speed traveling on the dry road surface was comparable to Comparative Example 5, Furthermore, since the sipe was not formed on the block, the steering stability on the wet road surface was deteriorated.

  Moreover, since the comparative example 7 formed the bottom raising part in the narrow groove, like the comparative example 6, the rigidity of a rib-like land part is ensured and the steering stability at the time of high-speed driving | running | working on a dry road surface is the comparative example 5. Although it was slightly improved, the sipe was not formed on the block, so that the steering stability on the wet road surface was greatly deteriorated in combination with the bottom raised portion formed in the narrow groove.

1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. FIG. 6 is a plan view corresponding to FIG. 1 according to another embodiment of the present invention. It is an enlarged view which takes out and shows a part of rib-like land part in the tread surface of FIG. It is XX arrow sectional drawing of FIG. FIG. 6 is a plan view corresponding to FIG. 1 according to still another embodiment of the present invention. It is a top view which shows the tread surface used as the reference | standard of evaluation in an Example. It is a top view which shows the tread surface made into the evaluation object in an Example. It is a top view which shows the tread surface used as the reference | standard of evaluation in an Example. It is a top view which shows an example of the tread surface of the conventional tire.

Explanation of symbols

1 Tread surface 2A, 2B Main groove 3A, 3B Land part 4 Narrow groove 5 Bottom raising part 6, 7 Sipe 8 Notch

Claims (12)

In a pneumatic tire in which four or three main grooves extending in the tire circumferential direction are provided on the tread surface, and three or two land portions defined between the main grooves are formed in a central region of the tread surface.
The left and right land portions located on the outermost side in the tire width direction among the land portions have a groove width of 10 to 40% of the groove width of the main groove, and are inclined at a predetermined interval in the tire circumferential direction. And is formed in a rib-like land portion in which a large number of blocks are arrayed by being partitioned by narrow grooves that cross each other, and a length corresponding to 50 to 70% of the length of the narrow grooves in the center region in the tire width direction of the narrow grooves And a bottom raised portion whose height is set to 30 to 50% of the maximum depth of the narrow groove, from the main groove adjacent to the block in the tire width direction toward the inner side in the tire width direction, and A pneumatic tire having a sipe that is refracted in the tire circumferential direction in the block and opens to a bottom-up portion of the narrow groove.   The position at which the sipe opens at the bottom-up portion of the narrow groove is set within a range of ± 10% of the width of the rib-shaped land portion with respect to the center line in the tire width direction of the rib-shaped land portion. Pneumatic tires.   The pneumatic tire according to claim 1 or 2, wherein a maximum depth of the narrow groove is 60 to 90% of a depth of the main groove.   The pneumatic tire according to any one of claims 1 to 3, wherein a depth of the sipe is 20 to 50% of a depth of the main groove.   The notch part which cuts in the tire width direction is formed in the side wall inside the tire width direction of the block in the rib-like land part, and the depth from the tread surface of the notch part is formed shallower than the depth of the main groove. The pneumatic tire of any one of -4.   The land portion is composed of three pieces, and the land portion located at the center is formed in a rib continuous in the tire circumferential direction, and the notch portions that bite into both side walls of the rib in the tire width direction are intermittent in the tire circumferential direction. The pneumatic tire according to claim 5, wherein the cutout portions are alternately offset in the tire circumferential direction with respect to the cutout portions of the blocks in the rib-like land portions adjacent to both sides of the rib.   The pneumatic tire according to claim 5, wherein the land portion is constituted by two rib-like land portions, and the cutout portions formed in the two rib-like land portions are alternately offset in the tire circumferential direction. .   The pneumatic tire according to any one of claims 5 to 7, wherein a cut-in width of the notch portion is 3 to 15% of a width of the rib-like land portion.   The main groove is composed of four, and the center line of the two main grooves on the inner side in the tire width direction is arranged at a position of 15 to 30% of the tire ground contact width centering on the tire equator, and 2 on the outer side in the tire width direction. The center line of the main groove is disposed at a position of 55 to 75% of the tire ground contact width centering on the tire equator, and the land portion defined by the two main grooves on the inner side in the tire width direction is the tire circumferential direction. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed in a continuous rib.   The pneumatic tire according to any one of claims 1 to 9, wherein the hardness of the rubber constituting the tread surface is 65 to 80 according to JIS A type.   The pneumatic tire according to any one of claims 1 to 10, which is a small truck tire having a maximum air pressure defined by ETRTO of 575 kPa or less.   The pneumatic tire according to any one of claims 1 to 10, which is a small truck tire having a maximum air pressure defined by JATMA of 650 kPa or less.

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