JP5160242B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire provided with three or more main grooves extending along a tire circumferential direction on a tread surface.

  For pneumatic tires with multiple main grooves extending along the tire circumferential direction, many blocks on the tread surface for the purpose of improving traction performance and WET performance (driving performance on wet roads) May be partitioned. Such pneumatic tires, particularly heavy duty pneumatic tires used for trucks, buses and the like, have a problem that uneven wear tends to occur.

  Various forms of uneven wear are known, but during straight running or driving, the ground pressure in the center area is relatively high and the deformation of the block increases, so the center area wears preferentially. In many cases, center wear is a problem. It is also important to suppress not only center wear but also shoulder wear (shoulder fall wear) in which the shoulder region wears preferentially so that uneven wear does not occur on the entire tread surface. The center region and the shoulder region are based on the outermost main groove in the tire width direction.

Patent Documents 1 to 3 below disclose techniques for suppressing uneven wear. However, the methods described in Patent Documents 1 and 2 below are for exclusively suppressing shoulder wear, and there is no disclosure about a method for suppressing center wear. Moreover, in the method of suppressing uneven wear by the groove bottom raised portion provided in the circumferential groove as in Patent Document 3 below, the groove depth of the circumferential groove is reduced, so that the WET performance tends to be lowered. .
JP 2000-177326 A JP 2007-99047 A JP 2006-123786 A

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which can suppress uneven wear, without reducing WET performance.

The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire in which three or more main grooves extending along the tire circumferential direction are provided on the tread surface, and the tire width direction is more than the outermost main groove in the tire width direction. Inside, a pair of center land portions extending along the tire circumferential direction are provided across the tire equator, and each of the center land portions is inclined with respect to the tire width direction, and only the inner end in the tire width direction is A first lateral groove that opens in the main groove, and a second lateral groove that extends in the same direction as the first lateral groove, and that only the outer end in the tire width direction opens in the main groove and is provided alternately with the first lateral groove; The center circumferential direction narrow groove that extends incline with respect to the tire circumferential direction and connects the first lateral groove and the second lateral groove adjacent to each other in the tire circumferential direction is partitioned into two block rows, The first lateral groove and the second lateral groove With the projection overlap each other in the tire meridian, a groove depth of the first lateral grooves and the second groove depth of the lateral groove gradually decreases with increasing distance from the open end of the main groove, the first transverse grooves and the second transverse groove Is 50% or less of the depth of the main groove in the region closer to the closing side than half of the length .

  In the pneumatic tire of the present invention, a pair of center land portions are partitioned into two block rows by the first lateral groove, the second lateral groove, and the center circumferential narrow groove as described above. And the 1st transverse groove and the 2nd transverse groove which are arranged alternately extend inclining with respect to the tire width direction, respectively, open one end portion to the main groove and close the other end portion in the land portion. Thus, deformation of the center land portion during braking / driving can be suppressed while securing the ridge line length of the lateral groove and suppressing slippage with the road surface. In addition, the projections of the first lateral groove and the second lateral groove on the tire meridian overlap each other, and the groove depth of the first lateral groove and the second lateral groove gradually decreases as the distance from the opening end of the main groove increases. Since the lateral groove becomes shallow in the central region, the block rigidity of the center land portion provided with the lateral groove can be secured and the center wear can be suppressed. As described above, according to the present invention, uneven wear can be suppressed without lowering the WET performance.

  In addition, when a longitudinal force or lateral force is applied to the block, the stress tends to concentrate on the groove bottom edge of the lateral groove that defines the block, and the ground pressure tends to be high during straight running and driving. According to the present invention, the groove depth of the first lateral groove and the second lateral groove gradually decreases with increasing distance from the opening end of the main groove, thereby causing a groove bottom edge. The stress acting on the part can be dispersed to prevent the block from being damaged.

  In the above, a pair of shoulder land portions extending along the tire circumferential direction is provided on the outer side in the tire width direction than the outermost main groove in the tire width direction, and each of the shoulder land portions is inclined with respect to the tire width direction. A third lateral groove whose only inner end in the tire width direction is open to the main groove, and an inclination extending in the same direction as the third lateral groove, the inner end in the tire width direction is closed, and the outer end in the tire width direction is grounded A fourth lateral groove that reaches the end and is provided alternately with the third lateral groove, and a shoulder that extends incline with respect to the tire circumferential direction and communicates the third lateral groove and the fourth lateral groove adjacent to each other in the tire circumferential direction. And the third transverse groove and the fourth transverse groove incline in the opposite direction to the first transverse groove and the second transverse groove, and the shoulder circumferential direction. The narrow groove is the center Preferably those inclined in the opposite direction to the direction narrow groove.

  In the above-described configuration of the present invention, a pair of shoulder land portions are arranged outside the pair of center land portions, and each of them is partitioned into two block rows. The third horizontal groove and the fourth horizontal groove are inclined in the opposite direction to the first horizontal groove and the second horizontal groove, and the shoulder circumferential narrow groove is inclined in the opposite direction to the central circumferential narrow groove. The direction in which the block that constitutes the block easily falls and the direction in which the block that constitutes the shoulder land portion tends to fall are opposite to each other, and excessive deformation of the block can be suppressed over the entire tread surface during braking and turning. As a result, the deformation of the block during braking / driving can be suppressed over the entire tread surface, and the effect of suppressing uneven wear can be enhanced.

  In the above, the ratio of the maximum width of the shoulder land portion with respect to the maximum width of the center land portion is 0.8 to 1.2, and among the row of blocks constituting the center land portion and the shoulder land portion, the shoulder The maximum width of each block row located on the inner side in the tire width direction with respect to the circumferential narrow groove has a ratio of the maximum value to the minimum value of 1.0 to 1.4. It is preferable that the ratio of the maximum width of the block row located on the outer side in the tire width direction with respect to the maximum width of each block row located on the inner side in the width direction is 1.1 or more.

  According to the above configuration, uneven wear is effectively reduced by balancing the rigidity balance between the center land portion and the shoulder land portion, and the rigidity balance of each block row located on the inner side in the tire width direction than the shoulder circumferential narrow groove. Can be suppressed. In addition, by setting the maximum width of the block row located on the outer side in the tire width direction from the shoulder circumferential direction narrow groove, it is set larger than the other block rows, so that the block rigidity at the place where the load due to the lateral force tends to increase is increased. It can raise and can suppress shoulder wear.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic tire according to the present invention. 2 and 3 are cross-sectional views taken along arrows AA and BB in FIG. 1, respectively. In the pneumatic tire of the present invention, three or more main grooves extending along the tire circumferential direction are provided on the tread surface. In this embodiment, as shown in FIG. 1, an example in which three main grooves 1 a to 1 c extending in a zigzag shape along the tire circumferential direction is provided.

  The land portion of the tread surface is partitioned into a pair of center land portions 2 and a pair of shoulder land portions 3 by main grooves 1a to 1c. That is, a pair of center land portions 2 extending along the tire circumferential direction is provided on the inner side in the tire width direction with respect to the main grooves 1a and 1c which are the outermost sides in the tire width direction, with the tire equator C interposed therebetween, and the main grooves 1a and 1c. A pair of shoulder land portions 3 extending along the tire circumferential direction are provided on the outer side in the tire width direction. As will be described later, each of the center land portion 2 and the shoulder land portion 3 is partitioned into two block rows.

  The ground contact edge E is the outermost position in the tire axial direction where a tire, which is assembled with a normal rim and filled with a normal internal pressure, contacts the flat road surface when a normal load is applied by placing the tire perpendicular to the flat road surface. The normal load and the normal internal pressure are the maximum load (design normal load in the case of passenger car tires) specified in the standard corresponding to the place of use and manufacturing place of the tire, such as JATMA, TRA, ETRTO, etc. Appropriate air pressure is used, and the regular rim is a standard rim defined in JATMA, TRA, ETRTO, etc. in principle.

  Each of the pair of center land portions 2 is divided into two block rows 21 and 22 by a first lateral groove 4, a second lateral groove 5, and a center circumferential direction narrow groove 6. In FIG. 1, the left block row 21 and the right block row 21 are point-symmetric with each other, and the center of symmetry is located on the tire equator C. The same applies to the block row 22 and block rows 31 and 32 described later.

  The first lateral groove 4 extends inclined with respect to the tire width direction, only the inner end in the tire width direction opens into the main groove 1b, and the outer end in the tire width direction closes in the land portion. The second lateral grooves 5 are provided alternately with the first lateral grooves 4 and extend while inclining with respect to the tire width direction. Only the outer ends in the tire width direction open to the main grooves 1a and 1c, and the inner ends in the tire width direction land. It is blocked in the department. The second horizontal groove 5 only needs to be inclined in the same direction as the first horizontal groove 4 (in the present embodiment, the upward direction in FIG. 1). In this embodiment, the first horizontal groove 4 and the second horizontal groove 5 have the same angle. However, they may be different from each other. The center circumferential direction narrow groove 6 extends inclining with respect to the tire circumferential direction, and connects the first lateral groove 4 and the second lateral groove 5 adjacent to each other in the tire circumferential direction. With such a configuration, deformation of the center land portion 2 during braking / driving can be suppressed while securing the ridge line length of the first horizontal groove 4 and the second horizontal groove 5 and suppressing slippage with the road surface.

  Moreover, the 1st horizontal groove 4 and the 2nd horizontal groove 5 are extended so that the projection to a tire meridian may mutually overlap. Although not shown, the tire meridian is a virtual line extending in the left-right direction in FIG. As shown in FIGS. 2 and 3, the groove depths of the first lateral groove 4 and the second lateral groove 5 are formed so as to gradually decrease as the distance from the opening ends 4 a and 5 a to the main groove increases. In the present embodiment, an example is shown in which the groove bottoms 4b and 5b of the first horizontal groove 4 and the second horizontal groove 5 are formed in a tapered shape. With this configuration, it is possible to secure the block rigidity of the center land portion 2 provided with the first lateral grooves 4 and the second lateral grooves 5, and to suppress center wear.

  In addition, the stress acting on the bottom edge portions of the first lateral groove 4 and the second lateral groove 5 is dispersed by gradually decreasing the groove depth of the first lateral groove 4 and the second lateral groove 5 away from the opening ends 4a and 5a. Thus, damage to the blocks constituting the center land portion 2 can be prevented. In addition, since the groove bottoms 4b and 5b are gradually exposed as the wear progresses, the wear promoting points are hard to be revealed compared to the case where the groove depth is reduced stepwise, and the appearance of the tread surface during the wear process is reduced. It becomes good.

  The length L4 in the tire width direction of the first lateral groove 4 and the length L5 in the tire width direction of the second lateral groove 5 are preferably 50 to 85% of the maximum width W1 of the center land portion 2, respectively. When the lengths L4 and L5 are less than 50% of the maximum width W1, the ridge line length of the lateral groove is reduced and the edge effect is reduced, so that the WET performance tends to be lowered. On the other hand, when the lengths L4 and L5 exceed 85% of the maximum width W1, the block rigidity in the center land portion 2 is reduced, so that the uneven wear suppression effect tends to be reduced.

The groove depths of the first lateral grooves 4 and the second lateral grooves 5 are 50% or less of the main groove depth D in the region closer to the closing side than half of the lengths L4 and L5 . As a result, the block rigidity of the center land portion 2 where the ground pressure tends to be high can be reliably increased, and uneven wear can be effectively suppressed. Moreover, it is preferable that the groove depth of the deepest part of the 1st horizontal groove 4 and the 2nd horizontal groove 5 is 80 to 100% of the main groove depth D. FIG.

  As described above, the first lateral groove 4 and the second lateral groove 5 are projected on the tire meridian, but the tire width direction length of the overlapping region is an average of the length L4 and the length L5. It is preferable that it is 5 to 60% with respect to the value. If this is less than 5%, it becomes difficult to ensure the length of the ridge line of the lateral groove, and thus the effect of improving the WET performance tends to be small. On the other hand, if this exceeds 60%, the block rigidity in the center land portion 2 is lowered, so that the effect of suppressing uneven wear tends to be reduced.

  The groove depth of the center circumferential narrow groove 6 is preferably 10 to 70% or more of the main groove depth D. If this is less than 10%, drainage tends to be reduced and WET performance tends to be lowered. On the other hand, when this exceeds 70%, the block rigidity in the center land portion 2 is lowered, and uneven wear resistance performance tends to be lowered.

  In the present embodiment, the center circumferential narrow groove 6 is configured by alternately arranging the wide portions 6 a and the narrow portions 6 b via the first lateral grooves 4 and the second lateral grooves 5. The wide portion 6a has a groove width wider than that of the narrow portion 6b, so that it is possible to ensure snow drainage particularly at the initial stage of wear. When such a wide portion 6a is formed, there is a concern that block deformation during turning increases, but since the narrow portion 6b is also formed, block deformation during turning is suppressed and block rigidity is increased. It can be secured.

  The wide portion 6a preferably has a groove width 1.2 to 2.0 times that of the narrow portion 6b from the viewpoint of achieving both uneven wear resistance and WET performance. That is, when this is less than 1.2 times, not only the effect of improving snow drainage is reduced, but also the movement of the block is excessively suppressed and the WET performance tends to be lowered. On the other hand, if this exceeds 2.0 times, the block near the wide portion 6a moves too much, and the effect of suppressing uneven wear tends to be small.

  The wide portion 6a is provided with a groove depth wider than that of the narrow portion 6b and a groove depth shallower than that of the narrow portion 6b. As a result, the rigidity balance between the periphery of the wide portion 6a and the periphery of the narrow portion 6b becomes good, which can contribute to suppression of uneven wear. The groove depth of the wide portion 6a is 10 to 30% of the main groove depth D, and the groove depth of the narrow portion 6b is 50 to 70% of the main groove depth D.

  It is preferable to form one or more sipes along the extending direction of the center circumferential narrow groove 6 at the groove bottom of the wide portion 6a. As a result, the traction performance can be enhanced when the wear progresses and the groove bottom of the wide portion 6a appears on the tread surface, so that the WET performance in the middle stage of wear can be ensured. Examples of the sipe formed in the wide portion 6a include those having a width of 0.7 to 1.0 mm and a maximum depth position of 75% or less of the main groove depth D from the tread surface.

  Each of the pair of shoulder land portions 3 is divided into two block rows 31 and 32 by the third lateral groove 7, the fourth lateral groove 8, and the shoulder circumferential narrow groove 9. The third lateral groove 7 extends while being inclined with respect to the tire width direction, and only the inner end in the tire width direction opens into the main grooves 1a and 1c, and the outer end in the tire width direction is closed in the land portion. The fourth lateral grooves 8 are provided alternately with the third lateral grooves 7, extend inclining with respect to the tire width direction, the inner end in the tire width direction is closed in the land portion, and the outer end in the tire width direction reaches the ground contact E. ing. The fourth horizontal groove 8 only needs to be inclined in the same direction as the third horizontal groove 7 (downward direction in FIG. 1). In the present embodiment, the third horizontal groove 7 and the fourth horizontal groove 8 are inclined at the same angle. However, they may be different from each other. The shoulder circumferential narrow groove 9 extends while inclining with respect to the tire circumferential direction, and communicates the third lateral groove 7 and the fourth lateral groove 8 adjacent to each other in the tire circumferential direction.

  As shown in FIG. 1, the third lateral groove 7 and the fourth lateral groove 8 are inclined in the opposite direction to the first lateral groove 4 and the second lateral groove 5. Further, the shoulder circumferential narrow groove 9 and the center circumferential narrow groove 6 are inclined in opposite directions with respect to the tire circumferential direction. With this configuration, the direction in which the block constituting the center land portion 2 is likely to fall and the direction in which the block constituting the shoulder land portion 3 is likely to fall are opposite to each other. And the effect of suppressing uneven wear can be enhanced.

  In the present embodiment, the ratio W2 / W1 of the maximum width W2 of the shoulder land portion 3 to the maximum width W1 of the center land portion 2 is 0.8 to 1.2. Further, the maximum widths W21, W22, W31 of the respective block rows 21, 22, 31 located on the inner side in the tire width direction from the shoulder circumferential narrow groove 9 have a ratio of the maximum value to the minimum value of 1.0 to 1. For example, if W21 <W31 <W22, the ratio W22 / W21 is within the above range. Thereby, the rigidity balance of the center land part 2 and the shoulder land part 3, and the rigidity balance of the block row | line | columns 21, 22, and 31 can be taken, and partial wear can be suppressed effectively.

  Furthermore, in the present embodiment, the ratio of the maximum width W32 of the block row 32 to the maximum widths W21, W22, W31 of the block rows 21, 22, 31 is 1.1 or more. That is, all of the ratio W32 / W21, the ratio W32 / W22, and the ratio W32 / W31 are set to 1.1 or more. Thus, by setting the maximum width W32 of the block row 32 to be larger than that of the other block rows 21, 22, 31, the rigidity of the block row 32 that tends to increase the load due to the lateral force is increased, and the shoulder wear is increased. Can be effectively suppressed. The maximum width W2 and the maximum width W32 are based on the ground contact E.

  The length L7 of the third lateral groove 7 in the tire width direction is preferably 30 to 50% of the maximum width W2 of the shoulder land portion 3. When the length L7 is less than 30% of the maximum width W2, the ridge line length of the lateral groove is reduced and the edge effect is reduced, so that the WET performance tends to be lowered. On the other hand, when the length L7 exceeds 50% of the maximum width W2, the block rigidity in the shoulder land portion 3 is lowered, so that the uneven wear suppression effect tends to be reduced.

  The length L8 in the tire width direction of the fourth lateral groove 8 with respect to the ground contact end E is preferably 50 to 85% of the maximum width W2 of the shoulder land portion 3. When the length L8 is less than 50% of the maximum width W2, the ridge line length of the lateral groove is reduced and the edge effect is reduced, so that the WET performance tends to be lowered. On the other hand, when the length L8 exceeds 85% of the maximum width W2, the block rigidity in the shoulder land portion 3 is lowered, so that the uneven wear suppression effect tends to be reduced.

  The groove width of the first horizontal groove 4 and the second horizontal groove 5 in the center land portion 2 is 30 to 90% of the wider groove width of the third horizontal groove 7 and the fourth horizontal groove 8 in the shoulder land portion 3. preferable. If this is less than 30%, the rigidity difference between the center land portion 2 and the shoulder land portion 3 becomes large, so the effect of suppressing uneven wear tends to be small. On the other hand, if this exceeds 90%, the rigidity of the center land portion 2 decreases, and therefore, the effect of suppressing uneven wear in the center region where the contact pressure tends to be high tends to be reduced.

  In this embodiment, the lengths L6a and L6b along the extending direction of the wide portion 6a and the narrow portion 6b constituting the center circumferential direction narrow groove 6 are approximately 1 of the block lengths L21 and L22 along the same direction. / 2, and the length L9 along the extending direction of the shoulder circumferential narrow groove 9 is 1.5 to 2.5 times the lengths L6a and L6b of the center circumferential narrow groove 6. If this is less than 1.5 times, heel and toe wear tends to occur at the shoulder land portion 3 and the steering stability tends to be lowered. On the other hand, if this exceeds 2.5 times, the WET performance tends to decrease.

  Further, the groove width of the center circumferential narrow groove 6 is preferably 15% or less of the maximum width W1 of the center land portion 2, and the groove width of the shoulder circumferential narrow groove 9 is the maximum width W2 of the shoulder land portion 3. Is preferably 15% or less. If these exceed 15% of the maximum width W2, the ratio of grooves to each land portion increases, so that the rigidity of the land portion decreases and the effect of suppressing uneven wear tends to decrease.

  The maximum lengths L31 and L32 of the blocks constituting the shoulder land portion 3 are preferably 0.80 to 0.95 with respect to the maximum lengths L21 and L22 of the blocks constituting the center land portion 2, respectively. If this is less than 0.80, the block rigidity in the shoulder land portion 3 is lowered, and therefore, there is a tendency that shoulder fall wear and toe and heel wear tend to occur. On the other hand, when this exceeds 0.95, the effect of suppressing uneven wear at the center land portion 2 where the contact pressure tends to be high is lowered. The lengths L21 and L22 are lengths along the extending direction of the center circumferential narrow groove 6, and the lengths L31 and L32 are lengths along the extending direction of the shoulder circumferential narrow groove 9.

  As described above, it is preferable to set the maximum width of the block row 32 to be larger than the block rows 21, 22, 31, thereby increasing the rigidity of the block row 32, which tends to increase the load due to the lateral force, Wear can be suppressed. On the other hand, in the above, by making the maximum lengths L21 and L22 of the blocks constituting the center land portion 2 larger than the maximum lengths L31 and L32 of the blocks constituting the shoulder land portion 3, it depends on the longitudinal force. It is possible to increase the rigidity of the center land portion 2 that tends to increase the load, and to suppress center wear.

  In the present embodiment, the shoulder circumferential narrow groove 9 intersects the third lateral groove 7 so as to form a T shape. As a result, the rigidity of the block row 32 that tends to increase the load due to the lateral force can be increased, and this can contribute particularly to the suppression of shoulder wear.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread pattern as described above, and the materials, shapes, structures, manufacturing methods, etc. of conventionally known pneumatic tires are all within the scope of the present invention. Can be adopted.

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. Therefore, for example, four main grooves 11a to 11d as shown in FIG. 4 are provided, and the land portion of the tread surface is extended to the rib 10 extending on the tire equator C, the pair of center land portions 20, and the pair of shoulder lands. It may be divided into parts 30. In this case, the ratio W3 / W4 of the maximum width W3 of the rib 10 to the maximum width W4 of the center land portion 20 is preferably 0.3 to 0.8.

  In the above-described embodiment, an example in which the main groove extends in a zigzag shape along the tire circumferential direction has been described. However, in the present invention, the main groove may extend in a straight shape along the tire circumferential direction. Furthermore, in the above-described embodiment, the example in which the first lateral grooves 4 and the second lateral grooves 5 change the groove depth uniformly as shown in FIGS. 2 and 3 is shown, but the present invention is not limited to this, The gradient of the groove bottom may be changed in the middle, or the groove bottom may have a curvature.

  Examples that specifically show the structure and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) WET performance Index braking was performed with Example 1 set to 100 with respect to the braking distance from the running speed of 40 km / h on a wet road surface until the vehicle was stopped. The larger the index, the shorter the braking distance and the better the WET performance.

(2) Uneven wear resistance performance Index evaluation was performed with Example 1 as 100 with respect to the difference in wear amount between the stepping side portion and the kicking side portion of the block of the shoulder land portion after running at 50,000 km. The higher the index is, the smaller the height difference is, which indicates that the uneven wear resistance performance is excellent with respect to heel and toe wear. Further, index evaluation was performed with Example 1 as 100 for the wear amount in the center region (amount of decrease in groove depth) and the wear amount in the shoulder region after traveling the distance. The larger the index, the smaller the wear amount, and the better the uneven wear resistance with respect to center wear and shoulder wear.

(3) Steering stability performance With respect to the sensory test regarding the steering stability performance of an actual vehicle, the index evaluation was performed with Example 1 as 100. The larger the index, the better the steering stability.

Comparative Examples and Examples 1-8
In the tire of size 11R22.5 having the tread pattern shown in FIG. 1, W21 = W22 = W31 and W2 / W1, W32 / W21, L9 / L6a are set to the values shown in Table 1, respectively, and Comparative Example and Example It was set as Examples 1-8. In the comparative example, the groove depths of the first lateral groove and the second lateral groove are not changed, and are uniformly equal to the main groove depth. As tire specifications, the tread width is 228 mm, the main groove depth is 14.5 mm, the center main groove width is 11.5 mm, the shoulder main groove width is 12.5 mm, and the lateral groove width is 10.5 mm. The results are shown in Table 1.

  From Table 1, compared with a comparative example, in Examples 1-8, all can suppress uneven wear, ensuring WET performance. Further, compared to Examples 1 to 3, there is a tendency for shoulder wear in Example 4, and there is a tendency for center wear in Example 5, so W2 / W1 is preferably 0.8 to 1.2. I understand. Furthermore, since there is a tendency for shoulder wear in Example 6 as compared with Examples 1-3, it can be seen that the ratio of W32 to W21, W22, and W31 is preferably 1.1 or more. And compared with Examples 1-3, in Example 7, there exists a tendency of heel and toe wear, and steering stability is falling, and since WET performance is falling in Example 8, L9 / L6a is 1 It can be seen that .5 to 2.5 is preferable.

The top view which shows an example of the tread pattern of the pneumatic tire which concerns on this invention AA arrow sectional view of FIG. BB arrow sectional view of FIG. The top view which shows the modification of the tread pattern of the pneumatic tire which concerns on this invention

Explanation of symbols

1a to 1c Main groove 2 Center land portion 21, 22 Block row 3 Shoulder land portion 31, 32 Block row 4 First lateral groove 4a Open end 5 with main groove Second lateral groove 5a Open end 6 with main groove Groove 6a Wide part 6b Narrow part 7 Third lateral groove 8 Fourth lateral groove 9 Shoulder circumferential direction narrow groove

Claims (3)

In the pneumatic tire in which three or more main grooves extending along the tire circumferential direction are provided on the tread surface,
A pair of center land portions extending along the tire circumferential direction are provided across the tire equator on the inner side in the tire width direction from the outermost main groove in the tire width direction,
Each of the center land portions extends while inclining with respect to the tire width direction, a first lateral groove having only an inner end in the tire width direction opening in the main groove, and an inclination extending in the same direction as the first lateral groove. Only the width direction outer side end is opened to the main groove, the second lateral groove provided alternately with the first lateral groove, the first lateral groove adjacent to the circumferential direction of the tire, A center circumferential narrow groove that communicates with the second lateral groove, and is divided into two block rows;
The projections of the first lateral groove and the second lateral groove on the tire meridian overlap each other, and the depths of the first lateral groove and the second lateral groove gradually decrease as the distance from the opening end of the main groove increases . A pneumatic tire characterized in that the groove depth of the lateral groove and the second lateral groove is 50% or less of the main groove depth in a region closer to the closing side than half the length thereof .
A pair of shoulder land portions extending along the tire circumferential direction are provided on the outer side in the tire width direction than the outermost main groove in the tire width direction,
Each of the shoulder land portions extends while inclining with respect to the tire width direction, a third lateral groove having only an inner end in the tire width direction opening in the main groove, and an inclination extending in the same direction as the third lateral groove. The inner end in the width direction is closed and the outer end in the tire width direction reaches the ground contact end, and extends in a slanted manner with respect to the tire circumferential direction, with the fourth lateral grooves provided alternately with the third lateral grooves, and adjacent to the tire circumferential direction. The third circumferential groove and the fourth lateral groove that fit together are partitioned into two block rows by a shoulder circumferential narrow groove that communicates with each other;
The third lateral groove and the fourth lateral groove are inclined in the opposite direction to the first lateral groove and the second lateral groove, and the shoulder circumferential direction narrow groove is inclined in the opposite direction to the center circumferential direction narrow groove. The pneumatic tire according to 1. The ratio of the maximum width of the shoulder land portion to the maximum width of the center land portion is 0.8 to 1.2,
Among the block rows constituting the center land portion and the shoulder land portion, the maximum width of each block row located on the inner side in the tire width direction from the shoulder circumferential narrow groove is a ratio of the maximum value to the minimum value thereof. 1.0 to 1.4,
The ratio of the maximum width of the block row positioned on the outer side in the tire width direction from the shoulder circumferential narrow groove to the maximum width of each block row located on the inner side in the tire width direction from the shoulder circumferential narrow groove is 1.1 or more The pneumatic tire according to claim 2.

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