JP2014234145A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that secures ride quality without deteriorating abrasion resistance.SOLUTION: A pneumatic tire includes protrusive blocks that are formed on a tread surface and that are disposed in a tire circumference direction by being partitioned with a plurality of circumferential grooves elongated in the tire circumference direction and a plurality of width-direction grooves elongated in a tire width direction, and thin-walled parts that are formed at the tire-width-direction of the block at predetermined intervals in the tire circumference direction and that decrease the height of the block.

Description

  The present invention relates to a pneumatic tire.

  The tread surface of the pneumatic tire has convex blocks that are partitioned by a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction. There is a pneumatic tire in which an inclined surface in which the height of the block gradually decreases toward the circumferential groove is formed at the end of the block in the tire width direction over the entire circumference of the tire (for example, Patent Document 1).

  When an inclined surface is provided at the end of the block in the tire width direction, the block follows the unevenness of the road surface and falls down in the tire width direction, so that an impact from the road surface is released in the tire width direction and riding comfort is improved. However, if an inclined surface is provided over the entire circumference of the tire, the block rigidity is lowered and the wear resistance may be impaired.

JP 2002-46425 A

  An object of the present invention is to provide a pneumatic tire that secures riding comfort without impairing wear resistance in consideration of the above matters.

  The pneumatic tire according to claim 1 is formed on a tread surface, and is partitioned by a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction, and arranged in the tire circumferential direction. Convex blocks, and end portions in the tire width direction facing the circumferential grooves of the blocks have thin portions formed with a height lower than the surface of the blocks at intervals in the tire circumferential direction. .

  In the pneumatic tire according to claim 1, convex blocks defined by a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of width grooves extending in the tire width direction are arranged in the tire circumferential direction. . Moreover, the thin part whose height is lower than the surface of a block is formed in the edge part of the tire width direction of a block. As a result, the convex portion on the road surface easily enters the circumferential groove, the block follows the irregularities on the road surface and falls down in the tire width direction, and the impact in the tire radial direction received from the convex portion on the road surface is in the tire width direction. To escape. For this reason, the impact on the vehicle is reduced and the ride comfort can be secured.

  The thin portions are formed at predetermined intervals in the tire circumferential direction. Thereby, compared with the case where the thin part is formed over the whole tire periphery, since the fall of block rigidity is suppressed, the abrasion resistance of a tire is not impaired.

  The pneumatic tire according to claim 2 is the pneumatic tire according to claim 1, wherein the block has at least one extending in a tire width direction between the circumferential grooves with a narrower width than the width direction grooves. It is comprised by the small block divided by the above fine groove, The said thin part is formed only in one of the said small blocks adjacent on both sides of the said fine groove, It is characterized by the above-mentioned.

  In the pneumatic tire according to claim 2, the block is configured by a small block defined by at least one narrow groove extending in the tire width direction with a narrower width than the width direction groove, and sandwiching the narrow groove. A thin portion is formed only in one of the adjacent small blocks. Thereby, compared with the case where the thin part is formed in the small block of the both sides of a narrow groove, the fall of block rigidity can be suppressed. Moreover, since each small block deform | transforms independently, steering stability can be improved.

  The pneumatic tire according to claim 3 is the pneumatic tire according to claim 2, wherein the blocks are arranged in two rows in the center portion of the tread surface in the tire width direction, and the thin portion is The small block is formed only at one end in the tire width direction.

  In the pneumatic tire according to claim 3, the blocks are arranged in two rows at the center portion of the tread surface in the tire width direction. Moreover, the thin part is formed only in the one end part of the tire width direction of the small block which comprises a block. That is, since the thin part is not formed in the other end part of the tire width direction of a small block, the fall of block rigidity can be suppressed.

  The pneumatic tire according to claim 4 is the pneumatic tire according to claim 3, wherein the small block extends from the circumferential groove in the tire width direction and terminates in the small block. The thin section is formed only in one of the small blocks adjacent to each other with the center lug groove interposed therebetween.

  In the pneumatic tire according to claim 4, a center lug groove extending in the tire width direction from the circumferential groove and terminating in the small block is formed. Thus, since the center lug groove | channel is terminated in the block, a part of adjacent small block is connected on both sides of the center lug groove. Thereby, it can suppress that the rigidity of a small block falls. Moreover, since the thin part is formed in one of the small blocks adjacent on both sides of the center lug groove, the ride comfort can be ensured.

  The pneumatic tire according to claim 5 is the pneumatic tire according to any one of claims 2 to 4, wherein the thin portion is every other small block arranged in a tire circumferential direction. It is provided in.

  In the pneumatic tire according to claim 5, since the thin portion is provided every other small block arranged in the tire circumferential direction, the small blocks having the thin portion are not adjacent to each other. Thereby, block rigidity can be made uniform over the tire perimeter.

  The pneumatic tire according to claim 6 is the pneumatic tire according to any one of claims 2 to 5, wherein the circumferential groove is a center circumferential groove formed on a tire equatorial plane. A shoulder circumferential groove formed on both sides of the center circumferential groove in the tire width direction, and the thin portion is formed at an end of the small block on the shoulder circumferential groove side. Features.

  In the pneumatic tire according to claim 6, a center circumferential groove formed on the tire equatorial plane and a shoulder circumferential groove formed on both sides of the center circumferential groove in the tire width direction are formed. Moreover, the thin part is formed in the edge part by the side of the shoulder circumferential direction groove | channel of a small block. As a result, the convex portion on the road surface easily enters the two shoulder circumferential grooves, so that the block is less than the case where the thin portion is formed only at the end of the small block on the center circumferential groove side. It becomes easy to fall down in the tire radial direction, and riding comfort is improved.

  The pneumatic tire according to claim 7 is the pneumatic tire according to any one of claims 1 to 6, wherein the thin portion is disposed at an end of the block in a tire width direction, and the circumferential direction. An inclined surface in which the height of the block gradually decreases toward the groove is formed.

  In the pneumatic tire according to claim 7, an inclined surface in which the height of the block gradually decreases toward the circumferential groove is formed. Thereby, when the convex part on a road surface contacts the inclined surface of a block, since the force of a tire width direction acts with respect to a block, a block will fall easily in a tire width direction.

  The pneumatic tire according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein a height of a lowest portion of the thin portion is a groove bottom of the circumferential groove. To 80% to 90% of the height from the surface of the block to the surface of the block.

  In the pneumatic tire according to claim 8, the height of the thinnest portion of the thin portion is 80% to 90% of the height from the groove bottom of the circumferential groove to the surface of the block. When the height of the thinnest part is lower than 80% of the height from the groove bottom of the circumferential groove to the surface of the block, the block rigidity of the tire is lowered and the wear resistance is impaired. Also, if the height of the thinnest part is higher than 90% of the height from the groove bottom to the surface of the block in the circumferential groove, the effect of the thin part cannot be obtained sufficiently, ensuring riding comfort Can not. For this reason, by setting the height of the thinnest portion within the above range, the ride comfort can be ensured without impairing the wear resistance.

  The pneumatic tire according to claim 9 is the pneumatic tire according to any one of claims 1 to 8, wherein the width of the thin portion is a groove of the circumferential groove adjacent to the thin portion. The width is 5% to 10% of the width.

  In the pneumatic tire according to claim 9, the width of the thin portion is 5% to 10% of the width of the circumferential groove adjacent to the thin portion. When the width of the thin portion is narrower than 5% of the groove width of the circumferential groove, the effect of the thin portion cannot be obtained sufficiently, and thus the riding comfort cannot be ensured. In addition, when the width of the thin portion is larger than 10% of the groove width of the circumferential groove, the area of the block that comes into contact with the road surface is reduced, and the block rigidity is lowered. By setting the range, the ride comfort can be ensured without reducing the block rigidity.

  Since the present invention has the above-described configuration, it is possible to provide a pneumatic tire that secures riding comfort without impairing wear resistance.

It is an expanded view showing the tread surface of the pneumatic tire concerning a 1st embodiment of the present invention. (A) It is the sectional view on the AA line of FIG. (B) It is a BB sectional drawing of FIG. It is a principal part expanded sectional view which shows the state which the pneumatic tire which concerns on 1st Embodiment of this invention is grounding on the uneven | corrugated road surface during driving | running | working. The main part expansion which shows the state where the small block in which the inclined surface was formed fell down in the tire width direction in the state which the pneumatic tire concerning a 1st embodiment of the present invention touches an uneven road surface while driving. It is sectional drawing. (A) It is a principal part expanded sectional view which shows the small block concerning 2nd Embodiment of this invention. (B) It is a principal part expanded sectional view which shows the small block concerning 3rd Embodiment of this invention. It is an expanded view which shows the tread surface of the pneumatic tire which concerns on 4th Embodiment of this invention. It is an expanded view which shows the tread surface of the pneumatic tire which concerns on 5th Embodiment of this invention.

  A pneumatic tire 10 (hereinafter referred to as a tire 10) according to a first embodiment of the present invention will be described with reference to the drawings. In the figure, an arrow TW indicates the width direction of the tire 10, an arrow TC indicates the circumferential direction of the tire 10, and a symbol CL indicates the equator plane of the tire 10.

  As shown in FIG. 1, a center circumferential groove 14 extending in the tire circumferential direction on the tire equator plane is formed on the tread surface 12 of the pneumatic tire 10 according to the present embodiment. Further, shoulder circumferential grooves 16 extending in the tire circumferential direction are formed on both sides of the center circumferential groove 14 in the tire width direction. The center circumferential groove 14 and the shoulder circumferential groove 16 are formed in parallel to each other, and the groove width D1 of the center circumferential groove 14 is, for example, 10 mm. Further, the groove width D2 of the shoulder circumferential groove 16 is, for example, 5 mm.

  A plurality of widthwise grooves 18 extending in the tire width direction are formed between the center circumferential groove 14 and the two shoulder circumferential grooves 16. The width direction groove | channel 18 is formed in the tire circumferential direction at equal intervals, and the groove width D3 of the width direction groove | channel 18 is formed with 3 mm as an example. Further, the width direction groove 18 on the left side in the figure from the tire equator plane is convexly curved upward in the figure as it goes to the center circumferential direction groove 14, and the width direction groove 18 on the right side in the figure from the tire equator plane is As it goes to the center circumferential groove 14, it is convexly curved downward in the figure.

  The groove width D1 of the center circumferential groove 14, the groove width D2 of the shoulder circumferential groove 16, and the groove width D3 of the width groove 18 are not particularly limited to the above dimensions. Further, the groove width D1 of the center circumferential groove 14 and the groove width D2 of the shoulder circumferential groove 16 may be formed so as to periodically change along the tire circumferential direction.

  A longitudinal sipe 20 extending in the tire circumferential direction is formed outside the shoulder circumferential groove 16 in the tire width direction, and a lateral sipe 22 extending in the tire width direction is formed between the shoulder circumferential groove 16 and the longitudinal sipe 20. Are formed at equal intervals in the tire circumferential direction. Further, a shoulder width direction groove 26 extending in the tire width direction is formed in the shoulder portion 24 outside the vertical sipe 20 in the tire width direction.

  At the center of the tread surface 12 in the tire width direction, a center circumferential groove 14, a shoulder circumferential groove 16, and a width groove 18 are partitioned, and convex blocks 28 are arranged in two rows in the tire circumferential direction. ing.

  The blocks 28 are arranged point-symmetrically with respect to the tire equatorial plane, and each block 28 is narrower than the widthwise grooves 18 and is divided by at least one narrow groove 30 extending in the tire width direction. The block 32 is constituted. In the present embodiment, as an example, two narrow grooves 30 having a groove width of about 1 mm and parallel to each other are formed for each block 28.

  Of the small blocks 32 defined by the narrow grooves 30, the middle small block 32 in the tire circumferential direction extends from the shoulder circumferential groove 16 to the center circumferential groove 14 and terminates in the small block 32. The center lug groove 34 partitions the two small blocks 32A and 32B. That is, the block 28 is composed of a total of four small blocks 32. Further, the center lug groove 34 of the present embodiment extends slightly from the center of the small block 32 to the center circumferential groove 14 side, and the groove width of the center lug groove 34 is the same width (3 mm) as the width direction groove. It has become.

  As shown in FIG. 2A, the height H from the groove bottom of the center circumferential groove 14 to the surface of the small block 32 (depth H of the center circumferential groove 14) is a no-load filled with normal internal pressure. In the state, it is 20 mm. Further, the height from the shoulder circumferential groove 16 to the surface of the small block 32 is also the same height. Furthermore, the depth (not shown) of the narrow groove 30 and the center lug groove 34 is formed shallower than the center circumferential groove 14, and is 15 mm as an example in this embodiment. In the figure, for convenience of explanation, the surface of the small block 32 is drawn flat. However, since the tread surface 12 of the tire 10 filled with the internal pressure is curved, the surface shape of the small block 32 is the center circumference. Curved so that the height gradually decreases from the direction groove 14 toward the shoulder circumferential groove 16.

  As shown in FIG. 1, among the small blocks 32 that are adjacent to each other with the narrow groove 30 interposed therebetween, the small block 32 is directed toward the shoulder circumferential groove 16 at the end on the shoulder circumferential groove 16 side of one small block 32. An inclined surface 36 is formed as a thin portion where the height of the thin film gradually decreases. The inclined surface 36 is also formed on one of the adjacent small blocks 32 with the center lug groove 34 interposed therebetween. For this reason, paying attention to one block 28, the small blocks 32 in which the inclined surfaces 36 are formed and the small blocks 32 in which the inclined surfaces 36 are not formed are arranged every other in the tire circumferential direction.

  Further, the inclined surface 36 is formed only in one small block 32 adjacent to the width direction groove 18. For this reason, the small block 32 in which the inclined surface 36 was formed, and the small block 32 in which the inclined surface 36 was not formed are arranged every other in the tire circumferential direction over the entire circumference of the tire 10.

  As shown in FIG. 2B, the lowest portion (lowest position LP) of the inclined surface 36 is formed at a height of 80% to 90% of the height H to the surface of the block 28. In this embodiment, as an example, the height to the surface of the block 28 is 80% (0.8H). That is, the distance from the groove bottom of the shoulder circumferential groove 16 to the lowest position LP is 16 mm. Here, when the height from the groove bottom of the shoulder circumferential groove 16 to the lowest position LP is lower than 16 mm (0.8 H), the block rigidity is lowered and the wear resistance of the tire 10 is impaired. Further, when the height from the groove bottom of the shoulder circumferential groove 16 to the lowest position LP is higher than 18 mm (0.9H), the action by the inclined surface 36 is not sufficiently obtained, and the riding comfort cannot be ensured.

  The width of the inclined surface 36 is 5% to 10% of the groove width D2 of the shoulder circumferential groove 16 adjacent to the inclined surface 36. In the present embodiment, as an example, the width is 10% (0.1D2). That is, the width is 0.5 mm. Here, when the width of the inclined surface 36 is narrower than 0.25 mm (0.05D2), the effect of forming the inclined surface 36 is not sufficiently obtained, and riding comfort cannot be ensured. Further, when the width of the inclined surface 36 is wider than 0.5 mm (0.1D2), the contact area of the small block 32 that contacts the road surface is reduced, and the block rigidity is lowered. For convenience of explanation, the inclined surface 36 is exaggerated.

  In this embodiment, the inclined surface 36 is formed only at the outer end of the small block 32 in the tire width direction. However, the present invention is not limited to this, and the inclined surface 36 is formed only at the inner end of the small block 32 in the tire width direction. Alternatively, the inclined surfaces 36 may be formed at both ends of the small block 32.

  Next, the operation of the tire 10 according to this embodiment will be described. Since the tread surface 12 of the tire 10 according to the present embodiment is formed point-symmetrically with respect to one point on the tire equatorial plane, it is necessary to specify the rotation direction of the tire 10 when attaching the tire 10 to the rim. There is no. Further, the tire 10 can be freely rotated in accordance with the wear state of the tire 10.

  Moreover, since the block 28 is divided into the small blocks 32 by the narrow grooves 30, the small blocks 32 that are in contact with the road surface can be independently deformed following the shape of the road surface. Thereby, steering stability can be improved.

  Further, since the inclined surface 36 is formed on the small block 32, the ride comfort can be ensured without impairing the wear resistance of the tire 10. This action will be described in detail with reference to the drawings. As shown in FIG. 3, when the vehicle to which the tire 10 according to this embodiment is attached is traveling, the vehicle weight and the weight of the occupant are acting on the tire 10. For this reason, the tread surface 12 is pressed against the road surface 100 and is deformed in accordance with the unevenness of the road surface 100.

  Here, in the state where the small block 32 in which the inclined surface 36 is not formed and the road surface 100 are in contact, the opening width of the shoulder circumferential groove 16 opened on the surface of the tire 10 is the shoulder circumferential groove 16. Therefore, the convex portion on the road surface 100 is unlikely to enter the shoulder circumferential groove 16. For this reason, since the small block 32 is hard to be deformed in the tire width direction, the block rigidity is not lowered and the wear resistance is not impaired.

  Next, as shown in FIG. 4, when the small block 32 on which the inclined surface 36 is formed and the road surface 100 are in contact, the opening width of the shoulder circumferential groove 16 opened on the surface of the tire 10. Is wider than the width of the shoulder circumferential groove 16, so that the convex portion on the road surface 100 can easily enter the shoulder circumferential groove 16.

  Here, since the convex part on the road surface 100 that has entered the shoulder circumferential groove 16 is in contact with the inclined surface 36, the small block 32 receives a force in the tire width direction. Thereby, the small block 32 falls in the tire width direction, and the impact in the tire radial direction received from the convex portion on the road surface 100 can be released in the tire width direction. Therefore, the impact on the vehicle is reduced and the ride comfort can be secured.

  In addition, in this embodiment, although the inclined surface 36 was formed in the edge part by the side of the shoulder circumferential direction groove | channel 16 of the small block 32, not only this but another shape may be sufficient. For example, as shown in FIG. 5A, the end of the small block 32 on the shoulder circumferential groove 16 side may be a chamfered portion 40 and may have an R shape. In this case, since there are no corners, the impact received from the road surface 100 can be dispersed without being concentrated in one place.

  Further, as shown in FIG. 5B, a stepped portion 42 having a low height may be formed at the end of the small block 32 on the shoulder circumferential groove 16 side. In this case, the opening width of the shoulder circumferential groove 16 opening on the surface of the tire 10 can be easily widened. In addition, the present invention can be implemented in various shapes without departing from the gist of the present invention. For example, a shape in which the corner of the small block 32 is recessed may be used. Of course, the shapes described above may be combined.

  Next, a tire 50 according to a fourth embodiment of the present invention will be described. In addition, about the structure same as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. As shown in FIG. 6, a block 52 defined by a center circumferential groove 14, a shoulder circumferential groove 16, and a width direction groove 18 is formed on the tread surface 12 of the tire 50 according to the present embodiment.

  The block 52 is divided into three small blocks 54 by narrow grooves 30 extending in the tire width direction with a narrower width than the width direction groove 18. Further, the center lug groove 34 according to the first embodiment is not formed.

  An inclined surface 56 in which the height of the block 52 gradually decreases toward the shoulder circumferential groove 16 is formed at the end portion on the shoulder circumferential groove 16 side of one small block 54 across the narrow groove 30. Further, the inclined surface 56 is formed only on one small block 54 among the small blocks 54 adjacent in the tire circumferential direction over the entire circumference of the tire. That is, every other small block 54 in which the inclined surface 56 is formed and every other small block 54 in which the inclined surface 56 is not formed are formed in the tire circumferential direction. The depth and width of the inclined surface 56 are the same as those in the first embodiment. Other configurations are the same as those of the tire 10 of the first embodiment.

  Next, the operation of the tire 50 according to this embodiment will be described. In the tire 50 according to the present embodiment, the center lug groove 34 is not formed, so that the block rigidity is improved as compared with the tire 10 according to the first embodiment. Further, since the small blocks 54 formed with the inclined surfaces 36 and every other small block 54 formed with no inclined surfaces are formed over the entire circumference of the tire, the wear resistance of the tire 50 is impaired. It is possible to ensure a comfortable ride without any problems.

  Next, a tire 60 according to a fifth embodiment of the present invention will be described. In addition, about the structure same as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. As shown in FIG. 7, blocks 62 </ b> A and 62 </ b> B defined by a center circumferential groove 14, a shoulder circumferential groove 16, and a width direction groove 18 are formed on the tread surface 12 of the tire 60 according to the present embodiment. Yes.

  The blocks 62A and 62B are not partitioned into small blocks as in the first embodiment. Further, every other block 62A and block 62B are formed in the tire circumferential direction, and the height gradually decreases toward the shoulder circumferential groove 16 at the end of the block 62A on the shoulder circumferential groove 16 side. An inclined surface 64 is formed. Other configurations are the same as those of the first embodiment.

  In the tire 60 according to the present embodiment, since every other block 62A in which the inclined surface 64 is formed and every other block 62B in which the inclined surface 64 is not formed, the wear resistance of the tire 60 is impaired. It is possible to ensure a comfortable ride without any problems. Further, since the blocks 62A and B are not defined by the narrow groove 30 and the center lug groove 34, the block rigidity can be improved as compared with the tire 10 of the first embodiment and the tire 50 of the fourth embodiment.

  The first to fifth embodiments of the present invention have been described above, but the present invention is not limited to such embodiments, and can be implemented in various modes without departing from the gist of the present invention. Of course. For example, the tread surface 12 may be configured by combining the block 28 according to the first embodiment, the block 52 according to the fourth embodiment, and the block 62 according to the fifth embodiment. In this case, the block rigidity can be set finely by changing the combination of the blocks constituting the tread surface 12.

(Test example)
In order to confirm the effect of the present invention, a test was carried out using the tire of the example and the tires of comparative examples 1 and 2. The tires used in the test are as follows, and the tire sizes were all 215 / 60R17.
Example: Tire according to the first embodiment of the present invention.
Comparative Example 1: A tire having the same tread pattern as that of the example and in which the inclined surface 36 is not formed at the end of the block.
Comparative Example 2: A tire having the same tread pattern as that of the example, and an inclined surface 36 having the same shape as that of the example formed at the end of the block on the shoulder circumferential groove 16 side over the entire circumference of the tire.

Test 1: A tire width generated in a block when a three-dimensional model of the tire of the example and the tires of comparative examples 1 and 2 is manufactured on a computer and the vehicle to which each tire is attached is traveling at 100 km / h. After calculating the amount of displacement (block stiffness) in the direction by simulation, the block stiffness of Comparative Example 1 was displayed as an index with 100 as the block stiffness.
Test 2: The tires of the examples and the tires of Comparative Examples 1 and 2 were each attached to a passenger car, filled with appropriate internal pressure, and then actually run on a test course to evaluate the ride comfort by feeling the driver. The evaluation results are shown as an index with the riding comfort of Comparative Example 1 as 100. The larger the value, the better the ride comfort.
Test 3: The tire of Example and the tires of Comparative Examples 1 and 2 were each attached to a passenger car, and the amount of wear of the tire after running for 1000 km was also measured. The smaller the value, the smaller the amount of wear and the better the wear resistance.

  As shown in Table 1, in Comparative Example 2, since the inclined surface 36 was formed over the entire circumference of the tire, the block rigidity was low and the riding comfort was the best, but conversely the wear resistance was I know it ’s bad. That is, the tire replacement frequency is increased.

  On the other hand, the tire of the example is more comfortable to ride than the tire of comparative example 1 in which the inclined surface 36 is not formed, and the wear resistance is equivalent to that of comparative example 1. Therefore, it was confirmed that the tires of the examples can ensure the ride comfort without impairing the wear resistance.

10 Pneumatic tire 12 Tread surface 14 Center circumferential groove 16 Shoulder circumferential groove 18 Width direction groove 28 Block 30 Narrow groove 32 Small block 32A Small block 32B Small block 34 Center lug groove 36 Inclined surface (thin part)
40 Chamfered part (thin part)
42 Stepped part (thin part)
50 Tire 52 Block 54 Small block 56 Inclined surface (thin part)
60 Tire 62A Block 62B Block 64 Inclined surface (thin part)

Claims (9)

Convex blocks formed on the tread surface, partitioned by a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction, and arranged in the tire circumferential direction;
An end portion in the tire width direction facing the circumferential groove of the block has a thin portion formed with a height lower than the surface of the block at intervals in the tire circumferential direction;
Pneumatic tire having The block is composed of small blocks defined by at least one narrow groove extending in the tire width direction between the circumferential grooves with a narrower width than the width direction groove,
The pneumatic tire according to claim 1, wherein the thin portion is formed only on one of the small blocks adjacent to each other with the narrow groove interposed therebetween.   The block is arranged in two rows at the tire width direction central portion of the tread surface, and the thin portion is formed only at one end portion of the small block in the tire width direction. Pneumatic tire described in 2. The small block extends in the tire width direction from the circumferential groove, and is divided into two small blocks by a center lug groove that terminates in the small block,
The pneumatic tire according to claim 3, wherein the thin portion is formed only on one of the small blocks adjacent to each other across the center lug groove.   The pneumatic tire according to any one of claims 2 to 4, wherein the thin portion is provided every other one of the small blocks arranged in a tire circumferential direction. The circumferential groove is a center circumferential groove formed on the tire equatorial plane;
Shoulder circumferential grooves formed on both sides in the tire width direction of the center circumferential grooves;
Have
The pneumatic tire according to any one of claims 2 to 5, wherein the thin portion is formed at an end of the small block on the shoulder circumferential groove side.   The thin portion is formed by forming an inclined surface in which the height of the block gradually decreases toward the circumferential groove at an end of the block in the tire width direction. The pneumatic tire according to any one of the above.   The height of the lowest part of the thin part is 80% to 90% of the height from the groove bottom of the circumferential groove to the surface of the block. The pneumatic tire according to item.   The pneumatic according to any one of claims 1 to 8, wherein a width of the thin portion is 5% to 10% of a width of the circumferential groove adjacent to the thin portion. tire.

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