JP6085317B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having excellent mud performance and wet performance.

  All-season tires and M + S type pneumatic tires for running on rough terrain are required to have so-called mud performance that exhibits sufficient traction and soil removal performance in muddy areas, for example. In order to improve the mud performance, a tire having a block pattern in which a plurality of blocks are provided in a tread portion has been proposed. In addition, for example, so-called wet performance having excellent drainage is also required on a paved road. In order to improve the wet performance, a tire having a large groove area ratio has been proposed.

Japanese Patent Application Laid-Open No. 09-300195

  However, conventional tires are prone to mud clogging in the grooves as they travel, and good mud performance has not been sustained. Further, since the conventional tire has a large groove area ratio, wear on the paved road was fast. In particular, there has been a problem that uneven wear tends to occur in the center block where a large contact pressure tends to act. Such uneven wear remarkably shortened the life of the tire and adversely affected the running of the vehicle such as noise and vibration.

  The present invention has been devised in view of the above situation, and based on improving the shape of the center block, it suppresses the occurrence of uneven wear and exhibits good mud performance and wet performance over a long period of time. The main objective is to provide a pneumatic tire that can be used.

  The present invention is a pneumatic tire in which a plurality of center blocks are provided on both sides of the tire equator of the tread portion, and the tread of each center block has an inner edge facing the tire equator side, and the inner edge Has a first inclined edge extending obliquely outward in the tire axial direction from the apex on the tire equator side, and a second inclined edge extending obliquely outward in the tire axial direction from the apex in the opposite direction to the first inclined edge. The end of the second inclined edge opposite to the apex is connected to an end edge that extends obliquely in the same direction as the first inclined edge on the outer side in the tire axial direction, and extends from the end edge to the groove bottom side. The groove wall surface extending toward the side includes a stepped portion.

  In the pneumatic tire according to the present invention, the end edge is preferably inclined at an angle of 15 degrees or more with respect to the tire axial direction.

  In the pneumatic tire according to the present invention, the length of the end edge is preferably 20% to 50% of the tire axial distance from the tire equator to the outer end of the center block in the tire axial direction.

  In the pneumatic tire according to the present invention, the stepped portion includes a horizontal portion having an angle of 15 degrees or less with respect to the tread surface and a rising portion extending at an angle larger than the horizontal portion in the cross section thereof. Is desirable.

  In the pneumatic tire according to the present invention, the stepped portion is a first corner that is a corner between the groove bottom and the rising portion, and a second corner that is a corner between the horizontal portion and the rising portion. Preferably, each corner is formed in an arc shape, and the radius of curvature of the first corner is greater than the radius of curvature of the second corner.

  In the pneumatic tire according to the present invention, the stepped portion includes an inner stepped portion including two or more horizontal portions provided on the tire equator side, and two or more of the stepped portions provided on the outer side in the tire axial direction. It is desirable to include an outer stepped portion including a horizontal portion, and a central stepped portion having one horizontal portion provided between the inner stepped portion and the outer stepped portion.

  In the pneumatic tire according to the present invention, the horizontal portion of the central stepped portion includes the horizontal portion closest to the groove bottom of the inner stepped portion and the horizontal portion closest to the groove bottom of the outer stepped portion. It is desirable that they be provided at the same height.

  In the pneumatic tire according to the present invention, it is desirable that a horizontal length of the horizontal portion is 15% or more of a length of the second inclined edge in a cross section of the central stepped portion.

  In the pneumatic tire according to the present invention, in the inner stepped portion and the outer stepped portion, the height from the groove bottom to the first horizontal portion is 30% to 40% of the maximum height of the center block. % The height from the horizontal portion of the first step to the horizontal portion of the second step is 30% to 35% of the maximum height of the center block, and the height from the horizontal portion of the second step to the tread surface. Is preferably 30% to 35% of the maximum height of the center block.

  In the pneumatic tire according to the present invention, the tread portion has a center region that is a region between outer ends in the tire axial direction of the center block on each side of the tire equator, and is a total of the treads of the plurality of center blocks. The area is preferably 50% to 60% of the area of the center region.

  In the pneumatic tire of the present invention, a plurality of center blocks are provided on both sides of the tire equator of the tread portion. The tread of each center block has an inner edge that faces the tire equator. The inner edge has a first inclined edge extending obliquely outward from the apex on the tire equator side in the tire axial direction, and a second inclined edge extending obliquely outward from the apex in the tire axial direction and opposite to the first inclined edge. doing. Since such a 1st inclination edge and a 2nd inclination edge have a tire axial direction component, they can exhibit a shear force with respect to mud and can improve traction. Further, when the center block contacts the mud road surface, mud is discharged to the outside in the tire axial direction along the inner edge of the center block.

  An end edge that extends obliquely in the same direction as the first inclined edge is connected to the outer side in the tire axial direction at the end opposite to the apex of the second inclined edge. Since the end edges extend obliquely, it is possible to avoid that all of the end edges simultaneously contact the road surface when the center block is grounded. For this reason, even in a tire having a large groove area ratio, wear at the end edge of the center block is suppressed, and the rigidity of the center block is maintained even in the late use of the tire. As a result, the wear of the first inclined edge located at the counter edge with the end edge is also suppressed, so that the uneven wear of the center block is suppressed.

  The end edge includes a stepped portion extending stepwise toward the groove bottom. Accordingly, when mud is clogged in the groove including the end edge, the stepped portion cracks the mud, and the mud is effectively discharged starting from the crack. Further, such a stepped portion is provided at the end edge extending obliquely, so that the mud in the groove near the end edge is effectively discharged. For this reason, the more excellent soil removal property is obtained.

  By the above effect | action, the pneumatic tire of this invention can exhibit the outstanding mud performance and wet performance, suppressing generation | occurrence | production of uneven wear.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. FIG. 2 is an enlarged view of a pair of adjacent center blocks in FIG. 1. It is a fragmentary perspective view of a center block. It is sectional drawing of the AA line of FIG. It is sectional drawing of the BB line of FIG.

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 1 showing an embodiment of the present invention. A pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is suitably used as an all-season tire for a four-wheel drive vehicle, for example.

  As shown in FIG. 1, the tread portion 2 includes a plurality of center blocks 3 disposed on both sides of the tire equator C, and a plurality of shoulder blocks 4 disposed on the tread end Te side with respect to the center block 3. A groove 5 extending around the center block 3 or the shoulder block 4 is provided. In the present embodiment, the center block 3 and the shoulder block 4 are arranged substantially symmetrically with respect to a point on the tire equator C except for the variable pitch, but are limited to such a mode. I don't mean.

  The “tread end” Te is the most when the normal load 1 is loaded with the normal rim and is loaded with the normal internal pressure, and the normal load is applied to the flat tire with a camber angle of 0 degree. It is determined as a contact position on the outer side in the tire axial direction. In the normal state, the distance in the tire axial direction between the tread ends Te and Te is determined as the tread contact width TW. When there is no notice in particular, the dimension of each part of the tire 1 is a value measured in a normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, ETRTO Then "Measuring Rim".

  “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. “JAMATA” is the “maximum air pressure”, TRA is the table “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO. When the tire is for a passenger car, the normal internal pressure is 180 kPa.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load.

  In order to improve the mud performance, the wet performance and the steering stability performance as an all-season tire in a well-balanced manner, the height of each of the center block 3 and the shoulder block 4 is preferably 12 to 18 mm. Similarly, in order to effectively discharge mud, water, etc., it is desirable that the groove width W1 of the groove 5 is determined in the range of 5% to 15% of the tread ground contact width TW.

  FIG. 2 is an enlarged view of a pair of adjacent center blocks 3 and 3 in FIG. As shown in FIG. 2, each center block 3 has an inner edge 6 facing the tire equator C side and an outer edge 7 facing the tread end Te (shown in FIG. 1). The inner edge 6 and the outer edge 7 are edges where the tread surface 3a of the center block 3 and the block wall surface 3b (shown in FIG. 3) intersect.

  The inner edge 6 extends obliquely from the apex 6a on the tire equator C side to the outer side in the tire axial direction and obliquely extends in the opposite direction to the first inclined edge 8 from the apex 6a to the outer side in the tire axial direction. It has a substantially V shape having two inclined edges 9. Since the first inclined edge 8 and the second inclined edge 9 have a tire axial direction component, they can exert a shearing force against mud and enhance traction. Further, when the center block 3 contacts the mud road surface, mud is discharged along the inner edge 6 to the outer side in the tire axial direction.

  The outer edge 7 includes a third inclined edge 10, an end edge 11, a fourth inclined edge 12 and a fifth inclined edge 13.

  The third inclined edge 10 extends obliquely in the direction opposite to the first inclined edge 8 outward from the outer end 8e, which is the end opposite to the apex 6a of the first inclined edge 8, in the tire axial direction. The end edge 11 extends obliquely in the same direction as the first inclined edge 8 outward from the outer end 9e, which is the end opposite to the apex 6a of the second inclined edge 9, in the tire axial direction. The fourth inclined edge 12 extends from the outer end 10 e of the third inclined edge 10 along the first inclined edge 8. The fifth inclined edge 13 extends from the inner end 12 i of the fourth inclined edge 12 along the second inclined edge 9. In this embodiment, the 4th inclination edge 12 and the 5th inclination edge 13 are arrange | positioned at the substantially V shape which makes the tire equator C side the vertex. In the present embodiment, the outer end 10 e of the third inclined edge 10 is the outer end of the center block 3 in the tire axial direction.

  The fourth inclined edge 12 includes a fourth gently inclined edge 12a inclined at a small angle with respect to the tire axial direction, and a fourth steeply inclined edge 12b inclined at a larger angle than the fourth gently inclined edge 12a. The fourth steeply inclined edge 12 b extends from the outer end 10 e of the third inclined edge 10. The fifth inclined edge 13 includes a fifth gently inclined edge 13a inclined at a small angle with respect to the tire axial direction, and a fifth steeply inclined edge 13b inclined at a larger angle than the fifth gently inclined edge 13a. The fifth gently inclined edge 13 a extends from the inner end 12 i of the fourth inclined edge 12.

  In FIG. 2, the first inclined edge 8 rises to the right and the second inclined edge 9 rises to the left, and each of them is inclined without changing its direction. The first inclined edge 8 is preferably inclined at an angle of 15 degrees or more with respect to the tire axial direction. On the other hand, the second inclined edge 9 is preferably inclined at an angle of 75 degrees or less with respect to the tire axial direction. Thereby, the load acts efficiently on the first inclined edge 8 and the second inclined edge 9, the center block 3 is smoothly deformed, mud can be effectively grasped between the center blocks 3, and excellent. Demonstrate mud performance.

  In the present embodiment, the end edge 11 is inclined substantially linearly continuously with respect to the tire axial direction. The end edge 11 is preferably inclined at an angle of 15 degrees or more with respect to the tire axial direction. Thereby, when the center block 3 is grounded, it is possible to avoid that all of the end edges 11 simultaneously contact the road surface. For this reason, the end edge 11 of the center block 3 is prevented from being worn, and the rigidity of the center block 3 is maintained even in the late use of the tire. As a result, since the wear of the first inclined edge 8 positioned opposite to the end edge 11 is also suppressed, uneven wear of the center block 3, particularly heel and toe wear (hereinafter referred to as “H / T wear”). It is suppressed.

  The length L1 of the first inclined edge 8 is larger than the length L2 of the second inclined edge 9, the length L3 of the third inclined edge 10, and the length L4 of the end edge 11. Here, the length L1 of the first inclined edge 8 is a linear distance from the vertex 6a to the outer end 8e of the first inclined edge 8. The length L2 of the second inclined edge 9 is a linear distance from the vertex 6a to the outer end 9e of the second inclined edge 9. The length L3 of the third inclined edge 10 is a linear distance from the outer end 8e of the first inclined edge 8 to the outer end 10e of the third inclined edge 10.

  As a result, a greater force from the road surface acts on the first inclined edge 8 than on the second inclined edge 9, so that the amount of deformation at the time of grounding increases. For this reason, when the center block 3 is deformed unbalanced at the time of ground contact, the mud grasped by the groove 5 adjacent to the center block 3 can be effectively discharged, and excellent soil removal performance can be obtained.

  In order to effectively exhibit this action, the lengths L1 to L3 of the first inclined edge 8 to the third inclined edge 10 and the length L4 of the end edge 11 are in the tire axial direction of the center block 3 from the tire equator C. It is desirable that the length is within a predetermined range with respect to the tire axial distance h to the outer end (the outer end 10e of the third inclined edge 10). For example, the length L1 of the first inclined edge 8 is desirably 110% to 130% of the tire axial distance h. The length L2 of the second inclined edge 9 is preferably 40% to 70% of the tire axial distance h. The length L3 of the third inclined edge 10 is preferably 20% to 50% of the tire axial distance h. Furthermore, the length L4 of the end edge 11 is preferably 20% to 50% of the tire axial distance h.

  In the present embodiment, the center block 3 is provided with a siping 14. The siping 14 effectively reduces the rigidity of the center block 3, promotes deformation of the center block 3 at the time of ground contact, and effectively grabs and discharges mud in the groove 5 between the center blocks 3 and 3.

  The siping 14 of the present embodiment includes an outer portion 15 provided on the outer side in the tire axial direction and an inner portion 16 provided on the inner side in the tire axial direction. Thereby, since the rigidity of the center block 3 is reduced substantially uniformly, the center block 3 is deformed as a whole, and mud can be gripped effectively. Moreover, the outer portion 15 and the inner portion 16 are separated from each other without overlapping in the tire axial direction and the tire circumferential direction. Thereby, the above-mentioned effect is further exhibited. Such a siping 14 preferably has a width of 1.0 mm or less, and a depth (not shown) of 9.0 to 14.0 mm.

  FIG. 3 is a partial perspective view of the center block 3. 4 is a cross-sectional view taken along line AA in FIG. 2, and FIG. 5 is a cross-sectional view taken along line BB in FIG. As shown in FIG. 3, the center block 3 has a groove wall surface 17 extending from the end edge 11 toward the groove bottom GB. The groove wall surface 17 is a wall surface extending from the end edge 11 in the block wall surface 3b.

  The groove wall surface 17 of the present embodiment includes a stepped portion 18 extending in a stepped manner. Such a groove wall surface 17 can cause the mud to crack at the stepped portion 18 where the thickness (depth) of the mud is reduced when the groove 5 in the vicinity of the groove wall surface 17 is clogged with mud. Mud can be discharged effectively from cracks. Moreover, mud can be discharged more effectively by providing the stepped portion 18 on the groove wall surface 17 where the deformation amount at the time of ground contact is small. For this reason, the more excellent soil removal property is obtained.

  The stepped portion 18 includes an inner stepped portion 18i provided on the tire equator C side of the groove wall surface 17, an outer stepped portion 18e provided on the outer side in the tire axial direction, an inner stepped portion 18i, and an outer stepped portion. And a central stepped portion 18c provided between 18e. Thereby, since cracks can be generated at two locations of the inner stepped portion 18i and the outer stepped portion 18e of the center block 3, the soil removal performance is further improved. Further, cracks originating from the inner stepped portion 18 i and the outer stepped portion 18 e are propagated to the mud in the groove 5 along the second inclined edge 9 and the fifth inclined edge 13 adjacent to the end edge 11. , Soil removal is further improved.

  As shown in FIG. 4, in the present embodiment, the inner stepped portion 18 i and the outer stepped portion 18 e have a horizontal portion 19 extending at an angle θ1 of 15 degrees or less with respect to the tread surface 3 a of the center block 3, and a horizontal portion 19. And a rising portion 20 extending at a larger angle θ2. In the present embodiment, the horizontal portions 19 of the inner stepped portion 18i and the outer stepped portion 18e are a first horizontal portion 19a provided on the groove bottom GB side, and an outer side in the tire radial direction than the first horizontal portion 19a. The second horizontal portion 19b provided in the first horizontal portion 19b. Such an inner stepped portion 18i and an outer stepped portion 18e can promote the generation of cracks in the region of the second horizontal portion 19b where the thickness of the mud is small while ensuring the groove volume. Sex and traction are improved in a well-balanced manner.

  In order to exhibit the above-described action more effectively, the height H1 from the groove bottom GB to the first horizontal portion 19a of the first stage is 30% to 40% of the maximum height Ha of the center block 3. desirable. Further, the height H2 from the first horizontal portion 19a of the first stage to the second horizontal portion 19b of the second stage is preferably 30% to 35% of the maximum height Ha of the center block 3. Further, the height H3 from the second horizontal portion 19b of the second stage to the tread surface 3a is preferably 30% to 35% of the maximum height Ha of the center block 3.

  In the present embodiment, it is desirable that the first corner portion 21 that is the corner between the groove bottom GB and the rising portion 20 is formed in an arc shape. In addition, it is desirable that the second corner portion 22 that is the corner between the horizontal portion 19 and the rising portion 20 is also formed in an arc shape. By forming the 1st corner 21 and the 2nd corner 22 in circular arc shape, it can suppress that stress concentrates and can maintain the rigidity of center block 3 over a long period of time.

  The radius of curvature R1 of the first corner 21 is preferably larger than the radius of curvature R2 of the second corner 22. The curvature radius R1 of the first corner portion 21 is as large as the curvature radius of the corner portion of the groove bottom GB and the other block wall surface 3b of the center block 3 so that the rigidity of the center block 3 as a whole is increased. Can be secured. On the other hand, since the radius of curvature R2 of the second corner portion 22 is relatively small, the area of the horizontal portion 19 can be secured widely, so that the soil removal performance is further improved.

  As shown in FIG. 5, in the present embodiment, the central stepped portion 18 c has a horizontal portion 19 extending at an angle θ1 of 15 degrees or less with respect to the tread surface 3 a of the center block 3, and an angle θ2 larger than the horizontal portion 19. And a rising portion 20 that extends. The horizontal portion 19 of the central stepped portion 18c is less than the number of the horizontal portions 19 of the inner stepped portion 18i and the outer stepped portion 18e, and in the present embodiment, is composed of one third horizontal portion 19c. Such a central stepped portion 18c suppresses an excessive decrease in the rigidity of the groove wall surface 17, and exerts a large shearing force on the mud.

  The horizontal length W of the third horizontal portion 19c of the central stepped portion 18c is desirably 15% or more of the length L2 (shown in FIG. 2) of the second inclined edge 9. If the horizontal length W of the third horizontal portion 19c is less than 15% of the length L2 of the second inclined edge 9, mud cracks are less likely to occur.

  In the present embodiment, the third horizontal portion 19c of the central stepped portion 18c includes the first horizontal portion 19a (shown in FIG. 4) closest to the groove bottom GB of the inner stepped portion 18i and the most groove of the outer stepped portion 18e. It is provided at the same height H1 as the first horizontal portion 19a (shown in FIG. 4) on the bottom GB side. That is, as shown in FIG. 3, the first horizontal portion 19a and the third horizontal portion 19c form the same plane. For this reason, since the rigidity of the groove wall surface 17 can be improved in a balanced manner, excessive deformation of the center block 3 at the time of grounding can be suppressed.

  As shown in FIG. 3, in the present embodiment, the horizontal portions 19 of the inner stepped portion 18i are formed in the same number as the horizontal portions 19 of the outer stepped portion 18e. Thereby, the rigidity in the vicinity of both end sides of the groove wall surface 17 is ensured in a well-balanced manner, and the occurrence of cracks is equalized.

  In the present embodiment, each of the inner stepped portion 18 i and the outer stepped portion 18 e has two horizontal portions 19, but may have more horizontal portions 19. In this case, the number of horizontal portions 19 may be increased for only one of the inner stepped portion 18i and the outer stepped portion 18e. By having many horizontal parts 19, since the thickness of the mud by the horizontal part 19 provided in the outermost side of a tire radial direction becomes small, and it becomes easy to generate | occur | produce a crack, soil removal property can further be improved.

  In the present embodiment, the center block 3 is provided with a recess 23 having a gentle slope 24 in which the block wall surface of the portion where the outer edge 7 is greatly recessed toward the tire equator C side is gently inclined toward the outer side in the tire axial direction. Yes. Such a recess 23 improves the mud performance because the gentle slope 24 can effectively discharge the mud in the recess 23. The concave portion 23 of the present embodiment is provided from the fourth gently inclined edge 12a and the fifth gently inclined edge 13a to the groove bottom GB.

  In the concave portion 23 of the present embodiment, the end edge 24a of the gentle slope 24 is located outside the groove bottom GB in the tire radial direction. Such a recess 23 can secure the rigidity of the center block 3, suppress excessive deformation of the center block 3, and increase the shear force of the first inclined edge 8 and the second inclined edge 9. In addition, the recessed part 23 is not limited to such an aspect, The depth may be smaller than the maximum height Ha of the center block 3, and a fixed aspect (illustration omitted).

  The maximum depth D1 of the recess 23 is preferably 50% to 80% of the maximum height Ha of the center block 3. When the maximum depth D1 of the recess 23 exceeds 80% of the maximum height Ha of the center block 3, the rigidity of the center block 3 may be excessively reduced, and traction may be reduced. Moreover, when the maximum depth D1 of the recessed part 23 is less than 50% of the maximum height Ha of the center block 3, there exists a possibility that mud cannot be grasped effectively.

  As shown in FIG. 1, in order to improve the mud performance, the wet performance and the steering stability performance in a well-balanced manner, the total area of the treads 3a (shown in FIG. 2) of the center block 3 excellent in soil removal is preferably It is desirable that it is 50% to 60% of the area of the center region Cf. Here, the center region Cf is a region between the outer ends (the outer ends 10e of the third inclined edges 10) of the center block 3 on each side of the tire equator C in the tire axial direction. Further, the area of the center region Cf is the area of the tread obtained when all the grooves 5 are filled.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to exemplary embodiment, and can be deform | transformed and implemented in a various aspect.

An all-season tire for a four-wheel drive vehicle having the basic pattern of FIG. 1 was prototyped based on the specifications shown in Table 1, and the wet performance, mud performance, and uneven wear performance of each sample tire were tested. The main common specifications and test methods for each sample tire are as follows.
Tread contact width TW: 240mm
Center block height: 15.6mm
Shoulder block height: 15.6mm
Tire size: 37 x 12.50R17
Rim: 9.0JJ
Internal pressure: 100kPa

<Wet performance>
Each sample tire was mounted on all wheels of a four-wheel drive vehicle, and a test driver ran a test course on a wet paved road. The driving characteristics related to the steering stability and drainage at this time were evaluated based on the test driver's sensuality. The result is displayed with a score of 100 as a comparative example. The larger the value, the better.

<Mad performance>
Each sample tire was mounted on all wheels of a four-wheel drive vehicle, and a test driver ran on a muddy road test course. The running characteristics related to traction and soil removal at this time were evaluated by the sensuality of test drivers. The result is displayed with a score of 100 as a comparative example. The larger the value, the better.

<Uneven wear performance>
Durability tests were carried out until each sample tire was mounted on a bench test machine and completely worn out. The degree of occurrence of uneven wear (H / T wear) at this time was evaluated by measuring the wear amount on the first and second wear sides. The results are displayed in five grades with the comparative example as 3. The higher the score, the better.

  Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example had improved wet performance and mud performance compared to the tire of the comparative example. Moreover, it was confirmed that the tires of the examples had a lower degree of occurrence of uneven wear (H / T wear) than the tires of the comparative examples.

1 Pneumatic tire 3 Center block 6 Inner edge
6a vertex 8 first inclined edge 9 second inclined edge 11 end edge 17 groove wall surface 18 stepped portion C tire equator

Claims (8)

A pneumatic tire in which a plurality of center blocks are provided on both sides of the tire equator of the tread portion,
Each tread of the center block has an inner edge facing the tire equator side,
The inner edge includes a first inclined edge extending obliquely outward in the tire axial direction from the apex on the tire equator side, and a second inclined edge extending obliquely outward in the tire axial direction from the apex in an opposite direction to the first inclined edge. And
The end opposite to the top of the second inclined edge is connected to an end edge extending obliquely in the same direction as the first inclined edge on the outer side in the tire axial direction,
The groove wall surface extending toward the groove bottom side from said end edge, viewed including the stepped portion,
The length of the end edge is 20% to 50% of the distance in the tire axial direction from the tire equator to the outer end of the center block in the tire axial direction . A pneumatic tire in which a plurality of center blocks are provided on both sides of the tire equator of the tread portion,
Each tread of the center block has an inner edge facing the tire equator side,
The inner edge includes a first inclined edge extending obliquely outward in the tire axial direction from the apex on the tire equator side, and a second inclined edge extending obliquely outward in the tire axial direction from the apex in an opposite direction to the first inclined edge. And
The end opposite to the top of the second inclined edge is connected to an end edge extending obliquely in the same direction as the first inclined edge on the outer side in the tire axial direction,
The groove wall surface extending from the end edge toward the groove bottom side includes a stepped portion,
The tread portion has a center region that is a region between outer ends in the tire axial direction of the center block on each side of the tire equator,
The total area of the treads of the plurality of center blocks is 50% to 60% of the area of the center region . A pneumatic tire in which a plurality of center blocks are provided on both sides of the tire equator of the tread portion,
Each tread of the center block has an inner edge facing the tire equator side,
The inner edge includes a first inclined edge extending obliquely outward in the tire axial direction from the apex on the tire equator side, and a second inclined edge extending obliquely outward in the tire axial direction from the apex in an opposite direction to the first inclined edge. And
The end opposite to the top of the second inclined edge is connected to an end edge extending obliquely in the same direction as the first inclined edge on the outer side in the tire axial direction,
The groove wall surface extending from the end edge toward the groove bottom side includes a stepped portion,
The stepped portion includes a horizontal portion having an angle of 15 degrees or less with respect to the tread surface in a cross section thereof, and a rising portion extending at an angle larger than the horizontal portion,
In the stepped portion, a first corner that is an entrance corner between the groove bottom and the rising portion, and a second corner that is an entrance corner between the horizontal portion and the rising portion are respectively arcuate. Formed,
The pneumatic tire according to claim 1, wherein a radius of curvature of the first corner is larger than a radius of curvature of the second corner . A pneumatic tire in which a plurality of center blocks are provided on both sides of the tire equator of the tread portion,
Each tread of the center block has an inner edge facing the tire equator side,
The inner edge includes a first inclined edge extending obliquely outward in the tire axial direction from the apex on the tire equator side, and a second inclined edge extending obliquely outward in the tire axial direction from the apex in an opposite direction to the first inclined edge. And
The end opposite to the top of the second inclined edge is connected to an end edge extending obliquely in the same direction as the first inclined edge on the outer side in the tire axial direction,
The groove wall surface extending from the end edge toward the groove bottom side includes a stepped portion,
The stepped portion includes a horizontal portion having an angle of 15 degrees or less with respect to the tread surface in a cross section thereof, and a rising portion extending at an angle larger than the horizontal portion,
The stepped portion is
An inner stepped portion including two or more horizontal portions provided on the tire equator side;
An outer stepped portion including two or more of the horizontal portions provided on the outer side in the tire axial direction;
A pneumatic tire comprising a central stepped portion having one horizontal portion provided between the inner stepped portion and the outer stepped portion . The horizontal portion of the central stepped portion is provided at the same height as the horizontal portion of the inner stepped portion closest to the groove bottom and the horizontal portion of the outer stepped portion closest to the groove bottom. Item 5. The pneumatic tire according to Item 4 . The pneumatic tire according to claim 4 or 5 , wherein a horizontal length of the horizontal portion is 15% or more of a length of the second inclined edge in a cross section of the central stepped portion. In the inner stepped portion and the outer stepped portion,
The height from the groove bottom to the first horizontal portion is 30% to 40% of the maximum height of the center block.
The height from the horizontal part of the first stage to the horizontal part of the second stage is 30% to 35% of the maximum height of the center block,
The pneumatic tire according to any one of claims 4 to 6 , wherein a height from the horizontal portion of the second stage to the tread surface is 30% to 35% of a maximum height of the center block. The pneumatic tire according to any one of claims 1 to 7, wherein the end edge is inclined at an angle of 15 degrees or more with respect to a tire axial direction.

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