JP2016159664A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire the on-snow performance and uneven wear resistance of which can be improved in a proper balance.SOLUTION: Long first shoulder lug grooves 41 and short second shoulder lug grooves 42 are alternately provided along a tire circumferential direction on shoulder land portions 40; shoulder sipes 44 are provided between the first shoulder lug grooves 41 and the second shoulder lug grooves 42; auxiliary sipes 46 communicating with major grooves are provided from the tip of each first shoulder lug groove 41; shoulder land portions 40 are divided into a plurality of block portions 47, and evenly divided regions A in which the maximum/minimum ratio of the circumferential lengths of the block portions 47 is 1.0 to 1.2 are each formed on the ground contact end side of the shoulder land portion 40 and on the major groove side; and the total sum of a width WA of the evenly divided region A of the ground contact end side and a width WB of the evenly divided region B on the major groove side is 50% or more of a width of the shoulder land portion 40 in the ground contact region thereof.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a pneumatic tire in which a lug groove is provided in a shoulder land portion, and more particularly, to a pneumatic tire that can improve performance on snow and uneven wear resistance in a well-balanced manner.

  Conventionally, in a pneumatic tire, a plurality of main grooves extending in the tire circumferential direction are formed in a tread portion, and a plurality of rows of land portions are partitioned by these main grooves. In addition, a lug groove extending in the tire width direction and a sipe extending in the tire width direction are formed in each land portion. In particular, pneumatic tires for all seasons are required to have excellent driving performance on snow in addition to excellent driving performance on dry roads, and therefore have a large number of lug grooves and sipes on the tread. (For example, refer to Patent Document 1).

  In such a pneumatic tire, by increasing the number of lug grooves and sipes, it is possible to improve the performance on snow based on the edge effect. However, if the number of lug grooves and sipes is increased, the wear amount differs between the stepped-in part and the kick-out part of the block due to a decrease in block rigidity, and step wear with different wear amounts in the width direction of the land part. There is a problem that is likely to occur. In particular, heel-and-wear and step wear appear remarkably in the shoulder land portion. Therefore, it is extremely difficult to achieve both high performance on snow and uneven wear resistance at a high level.

JP 2009-292252 A

  An object of the present invention is to provide a pneumatic tire that can improve performance on snow and uneven wear resistance in a well-balanced manner.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A pair of bead portions arranged on the inner side in the tire radial direction, and at least two main grooves extending in the tire circumferential direction are provided in the tread portion, and a plurality of rows of land portions including shoulder land portions are formed by the main grooves. In partitioned pneumatic tires,
A plurality of first shoulder lug grooves and a plurality of second shoulder lug grooves, which extend in the tire width direction so as to cross the ground contact edge in the shoulder land portion and are not in communication with the main groove, extend along the tire circumferential direction. Alternately, the length of the second shoulder lug groove in the ground contact region is smaller than the length of the first shoulder lug groove in the ground contact region;
A shoulder sipe that extends in the tire width direction and communicates with the main groove is provided between the first shoulder lug groove and the second shoulder lug groove, and from the tip of each first shoulder lug groove in the tire width direction. An auxiliary sipe that extends and communicates with the main groove is provided, and the shoulder land portion is divided into a plurality of block portions by the first shoulder lug groove, the second shoulder lug groove, the shoulder sipes and the auxiliary sipes,
An equal division region where the maximum and minimum ratio of the circumferential lengths of the plurality of block portions divided between the first shoulder lug grooves adjacent in the tire circumferential direction is 1.0 to 1.2 is grounded on the shoulder land portion. Formed respectively on the end side and the main groove side, the sum of the width of the equally divided area on the ground end side and the width of the equal divided area on the main groove side is 50% or more of the width W in the ground area of the shoulder land portion It is characterized by that.

  In the present invention, by providing the first shoulder lug groove, the second shoulder lug groove, the shoulder sipe, and the auxiliary sipe in the shoulder land portion, it is possible to exhibit excellent performance on snow based on the edge effect. In addition, by alternately arranging the relatively long first shoulder lug groove and the relatively short second shoulder lug groove in the shoulder land portion, the rigidity of the shoulder land portion changes extremely along the width direction. Since it avoids, generation | occurrence | production of step wear can be suppressed. In addition, an equal division region where the maximum and minimum ratios of the circumferential lengths of the plurality of block portions are 1.0 to 1.2 is formed on the grounding end side and the main groove side of the shoulder land portion, respectively, By making the sum of the width of the divided area and the width of the equally divided area on the main groove side 50% or more of the width W in the ground contact area of the shoulder land portion, the rigidity of each block portion is made uniform, and the heel and toe wear Can be suppressed. As a result, according to the present invention, on-snow performance and uneven wear resistance can be improved in a well-balanced manner.

  In the present invention, the width of the equally divided region on the main groove side is preferably 10% or more of the width W in the ground contact region of the shoulder land portion, or 3 mm or more. By sufficiently securing the width of the equally divided region on the main groove side, the occurrence of heel and toe wear can be effectively suppressed.

  The length R1 in the ground contact area of the first shoulder lug groove is 0.70 ≦ R1 / W ≦ 0.95 with respect to the width W in the ground contact area of the shoulder land portion, and the ground contact area of the second shoulder lug groove The inner length R2 is preferably 0.50 ≦ R2 / W ≦ 0.75 with respect to the width W in the ground contact area of the shoulder land portion. The difference between the length R1 and the length R2 is preferably (R1−R2) /W≧0.1 with respect to the width W. By setting the length R1 of the first shoulder lug groove and the length R2 of the second shoulder lug groove in the above ranges, it is possible to effectively improve on-snow performance and uneven wear resistance.

  Preferably, the shoulder sipe is raised at a portion communicating with the main groove, and the auxiliary sipe is raised relative to the first shoulder lug groove. In this way, the shoulder sipe is raised at the portion communicating with the main groove, and the auxiliary sipe connected to the first shoulder lug groove is raised, so that the rigidity of the block portion constituting the shoulder land portion is sufficiently secured in the vicinity of the main groove. In addition, heel and toe wear can be effectively suppressed.

  The depths of the first shoulder lug groove, the second shoulder lug groove, the shoulder sipe, and the auxiliary sipe are preferably defined along substantially the same groove bottom profile line in the ground contact region. Thereby, the rigidity of the block part which comprises a shoulder land part can be equalize | homogenized, and heel and toe wear can be suppressed effectively.

  It is preferable to provide the shoulder sipe with an intersecting portion intersecting the first shoulder lug groove or the second shoulder lug groove. By crossing the shoulder sipe with the first shoulder lug groove or the second shoulder lug groove in this way, skidding on the snow can be suppressed by the edge effect of the intersecting portion.

  Moreover, it is preferable to arrange | position the cross | intersection part with respect to the 1st shoulder lug groove or the 2nd shoulder lug groove of a shoulder sipe on the tire width direction outer side rather than a grounding end. When braking on snow, the ground contact width increases, and as a result, the intersecting part comes into contact with the snow surface.If this intersecting part is placed outside the grounding end, the gripping force increases during braking, It is possible to effectively suppress the side slip.

  In the present invention, the sipe means a groove having a groove width of 1.5 mm or less, and the lug groove is a groove having a groove width larger than that of the sipe. On the other hand, the main groove is a continuous groove in the tire circumferential direction, and the groove width is 5.0 mm or more, preferably 6.0 mm to 16.0 mm, and the groove depth is 6.5 mm or more. The groove is preferably in the range of 7.0 mm to 11.0 mm.

  Further, in the present invention, the contact area of the tread portion is the tire axial direction measured when a normal load is applied by placing the tire on a normal rim and filling the normal internal pressure with the normal internal pressure. Identified based on ground contact width. 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, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “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. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “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. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORMATION PRESURES”, “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 80% of the load.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a top view which shows the principal part of the tread pattern of the pneumatic tire of FIG. It is a top view which shows the principal part of the tread pattern of the pneumatic tire of FIG. It is sectional drawing which notched the shoulder land part along the longitudinal direction of the 1st shoulder lug groove.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 5 show a pneumatic tire according to an embodiment of the present invention. In addition, the pneumatic tire of this embodiment is a tire in which the rotation direction R is designated. 1 and 2, CL is a tire center line, and TCW is a ground contact width. A region on the tire circumference corresponding to the contact width TCW is a contact region.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A two-layer carcass layer 4 is mounted between the pair of bead portions 3 and 3. These carcass layers 4 include a plurality of reinforcing cords extending in the tire radial direction, and are folded back from the tire inner side to the outer side around bead cores 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIGS. 2 to 4, four main grooves 10 extending in the tire circumferential direction are formed in the tread portion 1. These main grooves 10 include a pair of inner main grooves 11 and 11 located on both sides of the tire center line CL, and a pair of outer main grooves 12 and 12 located on the outer side in the tire width direction with respect to the inner main grooves 11. doing. Accordingly, the tread portion 1 includes a center land portion 20 positioned on the tire center line CL, a pair of intermediate land portions 30 and 30 positioned on the outer side in the tire width direction from the center land portion 20, and the intermediate land. A pair of shoulder land portions 40, 40 located on the outer side in the tire width direction than the portion 30 are partitioned.

  In the center land portion 20, a plurality of sipes 21, 22, and 23 extending from edge portions on both sides toward the tire center line CL are disposed at intervals along the tire circumferential direction. Each of these sipes 21, 22, and 23 has one end communicating with the inner main groove 11 and the other end terminating in the center land portion 20. While the sipe 21 extends linearly, the sipe 22 has a shape bent in the middle. Further, the sipe 23 has a locally large groove width at the communication portion with the inner main groove 11.

  In the intermediate land portion 30, a plurality of intermediate lug grooves 31 extending while inclining in the direction opposite to the rotational direction R from the tire center line CL toward the outer side in the tire width direction are spaced along the tire circumferential direction. Arranged. Each intermediate lug groove 31 has one end communicating with the outer main groove 12 and the other end terminating in the intermediate land portion 30. The auxiliary sipe 32 extends in the tire width direction from the tip and communicates with the inner main groove 11. Is provided. A bottom raised portion 33 is formed at each longitudinal end portion of each intermediate lug groove 31. A chamfered portion 34 is locally formed at each portion of the intermediate land portion 30 where the auxiliary sipes 32 are disposed.

  In the intermediate land portion 30, a plurality of cross lug grooves 35 that intersect with at least two intermediate lug grooves 31 are repeatedly formed along the tire circumferential direction. Each cross lug groove 35 includes a main body portion 35a that extends while inclining with respect to the tire circumferential direction, a bent portion 35b that is folded back at the tip of the main body portion 35a, and a branch portion 35c that is branched from the middle of the main body portion 35a. And the tip of the branch portion 35 c and the tip of the bent portion 35 b are arranged so as to face each other without communicating with the intermediate lug groove 31. Further, a bottom raised portion 36 is formed at a portion where the cross lug groove 35 communicates with the intermediate lug groove 31. Further, a chamfered portion 37 is formed at the edge of the cross lug groove 35 so as to surround the cross lug groove 35.

  The shoulder land portion 40 includes a plurality of first shoulder lug grooves 41 extending in the tire width direction so as to cross the ground contact edge E and not communicating with the outer main groove 12, and a tire crossing the ground contact edge E. A plurality of second shoulder lug grooves 42 extending in the width direction and not communicating with the outer main groove 12 are alternately provided along the tire circumferential direction. The two first shoulder lug grooves 41 and one second shoulder lug groove 42 positioned between them are connected to each other by a vertical groove 43 extending in the tire circumferential direction on the outer side in the tire width direction from the ground contact end E. Has been. The length R2 of the second shoulder lug groove 42 in the ground contact region is set to be smaller than the length R1 of the first shoulder lug groove 41 in the ground contact region.

  A shoulder sipe 44 that extends in the tire width direction and communicates with the outer main groove 12 is disposed between the first shoulder lug groove 41 and the second shoulder lug groove 42. A pair of shoulder sipes 44, 44 located on both sides of the second shoulder lug groove 42 are connected to each other in a loop shape on the grounding end side to form an intersecting portion 45 intersecting the second shoulder lug groove 42. Yes. Further, the pair of shoulder sipes 44, 44 located on both sides of the second shoulder lug groove 42 are arranged so that the distance between them becomes narrow on the main groove side. Further, the shoulder land portion 40 is provided with an auxiliary sipe 46 that extends in the tire width direction from the tip of each first shoulder lug groove 41 and communicates with the outer main groove 12. The shoulder land portion 40 is divided into a plurality of block portions 47 by a first shoulder lug groove 41, a second shoulder lug groove 42, a shoulder sipe 44 and an auxiliary sipe 46. Further, a chamfered portion 48 is locally formed in each portion of the shoulder land portion 40 where the auxiliary sipes 46 are disposed.

  Here, as shown in FIG. 4, the circumferential lengths of the plurality of block portions 47 divided between the first shoulder lug grooves 41, 41 adjacent in the tire circumferential direction are measured at arbitrary positions in the tire width direction. When this is done, equally divided areas with a maximum to minimum ratio of 1.0 to 1.2 are formed on the ground contact end side and the main groove side of the shoulder land portion 40, respectively. More specifically, the circumferential lengths LA1, LA2, LA3, LA4 of the block portion 47 are measured on the ground contact end side of the shoulder land portion 40, and the circumferential lengths LA1, LA2, LA3, LA4 are measured. A region where the ratio of the maximum value to the minimum value is 1.0 to 1.2 is the equally divided region A. On the other hand, the circumferential lengths LB1, LB2, and LB3 of the block portion 47 are measured on the main groove side of the shoulder land portion 40. The ratio of the maximum value to the minimum value of the circumferential lengths LB1, LB2, and LB3 is as follows. The region that is 1.0 to 1.2 is the equally divided region B. The sum of the width WA of the equally divided area A on the ground contact end side and the width WB of the equally divided area B on the main groove side is set to 50% or more of the width W in the ground contact area of the shoulder land portion 40. In the equally divided areas A and B, when the circumferential length of the block portion 47 is measured at an arbitrary position in the tire width direction, the maximum / minimum ratio of the circumferential length of the block portion 47 in the entire tire circumferential direction is 1. It is desirable to be within the range of .0 to 1.7. That is, the variation in the circumferential length of the block portion 47 due to the pitch variation is allowed within the above range.

  According to the pneumatic tire described above, by providing the first shoulder lug groove 41, the second shoulder lug groove 42, the shoulder sipe 44, and the auxiliary sipe 46 in the shoulder land portion 40, excellent on-snow performance based on the edge effect. Can be demonstrated. Moreover, by alternately disposing the relatively long first shoulder lug groove 41 and the relatively short second shoulder lug groove 42 in the shoulder land portion 40, the rigidity of the shoulder land portion 40 is extremely increased along the width direction. Since it avoids changing, generation | occurrence | production of the step wear in the shoulder land part 40 can be suppressed. Further, equally divided areas A and B in which the maximum and minimum ratios of the circumferential lengths of the plurality of block portions 47 are 1.0 to 1.2 are formed on the ground contact end side and the main groove side of the shoulder land portion 40, respectively. By making the sum of the width WA of the equally divided area A on the ground contact side and the width WB of the equally divided area B on the main groove side 50% or more of the width W in the ground area of the shoulder land portion 40, each block portion The rigidity of 47 can be made uniform, and the occurrence of heel and toe wear in the shoulder land portion 40 can be suppressed. As a result, performance on snow and uneven wear resistance can be improved in a well-balanced manner.

  In particular, in the pneumatic tire, since the number of divisions of the block portion 47 on the ground contact end side is relatively large, it is possible to improve the performance on snow by selectively enhancing the edge effect at the relevant part when traveling on snow. On the other hand, since the number of divisions of the block portion 47 on the main groove side is relatively small, the rigidity of the shoulder land portion 40 in the tire width direction is reduced by increasing the block rigidity at the portion, and step wear is reduced. Generation | occurrence | production can be suppressed effectively.

  Here, if the maximum / minimum ratio of the circumferential lengths of the plurality of block portions 47 constituting the shoulder land portion 40 is out of the range of 1.0 to 1.2, heel and toe wear easily occurs, The sum of the widths WA and WB of the equally divided areas A and B in which the maximum and minimum ratio of the circumferential length of the block portion 47 is 1.0 to 1.2 is 50 of the width W in the ground contact area of the shoulder land portion 40. If it is smaller than%, heel and toe wear tends to occur. In particular, the sum of the width WA of the equally divided area A on the ground contact end side and the width WB of the equally divided area B on the main groove side may be 65% to 100% of the width W in the ground contact area of the shoulder land portion 40.

  In the pneumatic tire, the width WB of the equally divided region B on the main groove side is preferably 10% or more of the width W in the ground contact region of the shoulder land portion 40 or 3 mm or more. That is, the portion of the shoulder land portion 40 facing the outer main groove 12 has low rigidity, and the segmented block portion 47 is easily deformed, so that the width WB of the equally divided region B on the main groove side is sufficiently secured. In the equally divided region B, the occurrence of heel and wear can be effectively suppressed by reducing the difference in rigidity of the plurality of block portions 47 arranged in the tire circumferential direction. Here, if the width WB of the equally divided region B on the main groove side is less than 10% of the width W in the ground contact region of the shoulder land portion 40 and smaller than 3 mm, the effect of improving uneven wear resistance is lowered. .

  In the pneumatic tire, the length R1 of the first shoulder lug groove 41 in the ground contact region is 0.70 ≦ R1 / W ≦ 0.95 with respect to the width W of the shoulder land portion 40 in the ground contact region, The length R2 of the second shoulder lug groove 42 in the ground contact region is 0.50 ≦ R2 / W ≦ 0.75 with respect to the width W of the shoulder land portion 40 in the ground contact region. The difference from R2 is preferably (R1−R2) /W≧0.1 with respect to the width W (see FIG. 3). By setting the length R1 of the first shoulder lug groove 41 and the length R2 of the second shoulder lug groove 42 within the above ranges, it is possible to effectively improve on-snow performance and uneven wear resistance. Here, if the first shoulder lug groove 41 or the second shoulder lug groove 42 is too long, uneven wear tends to occur due to a decrease in rigidity, and conversely, if it is too short, the performance on snow will be lowered. Further, if the difference between the length R1 of the first shoulder lug groove 41 and the length R2 of the second shoulder lug groove 42 is too small, the change in rigidity in the width direction of the shoulder land portion 40 becomes large, and therefore, step wear is likely to occur. Become.

4 and 5, the shoulder sipe 44 is raised at a portion communicating with the outer main groove 12 to form a bottom raised portion 49, and the auxiliary sipe 46 connected to the first shoulder lug groove 41 is connected to the first shoulder lug groove 41. Is raised. The depth of the bottom raised portion 49 of the shoulder sipe 44 and the auxiliary sipe 46 may be set in a range of 15% to 50% of the depth of the outer main groove 12. The shoulder sipe 44 is raised at the portion communicating with the outer main groove 12 and the auxiliary sipe 46 connected to the first shoulder lug groove 41 is raised to increase the rigidity of the block portion 47 constituting the shoulder land portion 40 in the vicinity of the main groove. Can be sufficiently secured, and heel and toe wear can be effectively suppressed.

  Further, as shown in FIG. 5, the depths of the first shoulder lug groove 41, the second shoulder lug groove 42, the shoulder sipe 44, and the auxiliary sipe 46 are substantially along the same groove bottom profile line in the ground contact region. It is prescribed. That is, the first shoulder lug groove 41, the second shoulder lug groove 42, the shoulder sipe 44, and the auxiliary sipe 46 have the same depth at the same position in the tire width direction. FIG. 5 depicts an aspect in which the groove bottom profile lines of the second shoulder lug groove 42 and the shoulder sipe 44 are matched with the groove bottom profile lines of the first shoulder lug groove 41 and the auxiliary sipe 46. Thereby, the rigidity of the block part 47 which comprises the shoulder land part 40 can be equalize | homogenized, and heel and toe wear can be suppressed effectively.

  In the pneumatic tire described above, a pair of shoulder sipes 44 located on both sides of the second shoulder lug groove 42 are provided with intersecting portions 45 intersecting the second shoulder lug groove 42. By crossing with the second shoulder lug groove 42, skidding on snow can be suppressed by the edge effect of the crossing portion 45. In order to effectively prevent skidding on the snow, it is desirable that the crossing angle between the second shoulder lug groove 42 and the crossing portion 45 is 20 ° to 70 ° on the acute angle side. Further, in order to avoid a decrease in rigidity of the block portion 47, it is desirable that the depth at the intersecting portion 45 of the shoulder sipe 44 is 1 to 4 mm. The shoulder sipes 44 preferably intersect with the second shoulder lug grooves 42, but may intersect with the first shoulder lug grooves 41.

  Further, the intersection 45 of the shoulder sipe 44 is preferably arranged on the outer side in the tire width direction with respect to the ground contact end E. When the crossing portion 45 of the shoulder sipe 44 is disposed outside the ground contact E, the crossing portion 45 abuts against the snow surface during braking to increase the gripping force, and can effectively suppress a skid on the snow. . However, if the crossing portion 45 of the shoulder sipe 44 is too far away from the ground contact end E toward the outer side in the tire width direction, the crossing portion 45 is difficult to ground during braking. Therefore, it is desirable that the intersection 45 of the shoulder sipe 44 is disposed outside the ground contact edge E in the tire width direction and within a range 1.1 times the ground contact width TCW.

  Although the pneumatic tire in which the rotation direction R is designated has been described in the above-described embodiment, the present invention can also be applied to a pneumatic tire in which the rotation direction R is not designated.

  Moreover, although the embodiment mentioned above demonstrated the pneumatic tire which provided the four main grooves in the tread part, this invention is applicable to the pneumatic tire which provided the at least two main grooves in the tread part. In particular, an optimal effect is expected when the tread portion is provided with 2 to 6 main grooves. The pneumatic tire of the present invention is suitable for all season use.

  The tire size is 215 / 45R17 87W, and extends in the tire circumferential direction to form an annular tread portion, a pair of sidewall portions disposed on both sides of the tread portion, and the tire radial inner sides of these sidewall portions A pneumatic tire in which four main grooves extending in the tire circumferential direction are provided in the tread portion, and a plurality of rows of land portions including shoulder land portions are partitioned by the main grooves, As shown in FIG. 2, a long first shoulder lug groove and a short second shoulder lug groove are alternately provided along the tire circumferential direction in the shoulder land portion, and between the first shoulder lug groove and the second shoulder lug groove. A shoulder sipe that extends in the tire width direction and communicates with the main groove is provided, and an auxiliary sipe that communicates with the main groove from the tip of each first shoulder lug groove is provided. The shoulder land portion is divided into a plurality of block portions, and the equally divided region in which the maximum and minimum ratios of the circumferential lengths of the plurality of block portions are 1.0 to 1.2 is set to the grounding end side of the shoulder land portion and the main groove The sum of the width WA of the equally divided area A on the ground contact side and the width WB of the equally divided area B on the main groove side is 50% or more of the width W in the ground area of the shoulder land portion. Tires of Examples 1 to 7 were produced.

  In the first to seventh embodiments, the ratio of the sum of the width WA of the equally divided area A on the ground contact side and the width WB of the equally divided area B on the main groove side to the width W in the ground contact area of the shoulder land portion [(WA + WB) / W × 100%], the ratio of the width WB of the equally divided region B on the main groove side to the width W in the ground contact region of the shoulder land portion (WB / W × 100%), in the ground contact region of the shoulder land portion The ratio (R1 / W) of the length R1 of the first shoulder lug groove in the ground contact area to the width W, the length of the second shoulder lug groove in the ground contact area relative to the width W in the ground contact area of the shoulder land portion. The ratio of R2 (R2 / W), the presence / absence of raising the shoulder sipe and auxiliary sipe, and the presence / absence of the intersection of the shoulder sipe with the first shoulder lug groove were set as shown in Table 1. The depths of the first shoulder lug groove, the second shoulder lug groove, the shoulder sipe, and the auxiliary sipe were defined along substantially the same groove bottom profile line in the ground contact region. Furthermore, the intersection of the shoulder sipe was disposed slightly outside the ground contact end.

  For comparison, a tire of Comparative Example 1 was prepared in which the lengths of the first shoulder lug groove and the second shoulder lug groove were the same, and the shoulder sipes were eliminated. Moreover, the tire of the comparative example 2 which prepared the 2nd shoulder lug groove shorter than the 1st shoulder lug groove, and eliminated the shoulder sipe was prepared. Furthermore, although the 2nd shoulder lug groove was shortened rather than the 1st shoulder lug groove and the shoulder sipe was provided, the tire of the comparative example 3 which made the total width of the equally divided area | region 30% was prepared.

  These test tires were evaluated for braking performance on snow and uneven wear resistance by the following evaluation methods, and the results are also shown in Table 1.

Brake performance on snow:
Each test tire is mounted on a wheel with a rim size of 17 x 7 J, mounted on a test vehicle with a displacement of 1800 cc with an air pressure of 230 kPa, and the braking distance when braking from a running state of 40 km / h on snow is measured five times. The average value was obtained. The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on snow.

Uneven wear resistance:
Each test tire was mounted on a wheel with a rim size of 17 × 7 J and mounted on a test vehicle with a displacement of 1800 cc with an air pressure of 230 kPa. After running a real vehicle of 20000 km, the amount of uneven wear at the shoulder land was measured. Regarding the step wear, the difference in the amount of wear between the position on the main groove side of the shoulder land portion and the position on the ground contact end side was measured. For heel and toe wear, the difference in the amount of wear that occurred along the circumferential direction of the shoulder land was measured. The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

  As is clear from Table 1, the tires of Examples 1 to 7 were able to improve the performance on snow and the uneven wear resistance with a good balance in comparison with Comparative Example 1. On the other hand, in the tire of Comparative Example 2, the occurrence of step wear was suppressed by making the second shoulder lug groove shorter than the first shoulder lug groove, but the braking performance on snow was deteriorated. In the tire of Comparative Example 3, the second shoulder lug groove is made shorter than the first shoulder lug groove and at the same time a shoulder sipe is added. However, since the total width of the equally divided region is small, heel and toe wear is reduced. The outbreak was conducive.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 10 Main groove 11 Inner main groove 12 Outer main groove 20 Center land part 30 Middle land part 40 Shoulder land part 41 First shoulder lug groove 42 Second shoulder lug groove 44 Shoulder sipe 46 Auxiliary Sipe 47 block part

Claims (8)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the pneumatic tire in which at least two main grooves extending in the tire circumferential direction are provided in the tread portion, and a plurality of rows of land portions including shoulder land portions are partitioned by these main grooves,
A plurality of first shoulder lug grooves and a plurality of second shoulder lug grooves, which extend in the tire width direction so as to cross the ground contact edge in the shoulder land portion and are not in communication with the main groove, extend along the tire circumferential direction. Alternately, the length of the second shoulder lug groove in the ground contact region is smaller than the length of the first shoulder lug groove in the ground contact region;
A shoulder sipe that extends in the tire width direction and communicates with the main groove is provided between the first shoulder lug groove and the second shoulder lug groove, and from the tip of each first shoulder lug groove in the tire width direction. An auxiliary sipe that extends and communicates with the main groove is provided, and the shoulder land portion is divided into a plurality of block portions by the first shoulder lug groove, the second shoulder lug groove, the shoulder sipes and the auxiliary sipes,
An equal division region where the maximum and minimum ratio of the circumferential lengths of the plurality of block portions divided between the first shoulder lug grooves adjacent in the tire circumferential direction is 1.0 to 1.2 is grounded on the shoulder land portion. Formed respectively on the end side and the main groove side, the sum of the width of the equally divided area on the ground end side and the width of the equal divided area on the main groove side is 50% or more of the width W in the ground area of the shoulder land portion Pneumatic tire characterized by that.   The pneumatic tire according to claim 1, wherein the width of the equally divided region on the main groove side is 10% or more of the width W in the ground contact region of the shoulder land portion or 3 mm or more.   The length R1 of the first shoulder lug groove in the ground contact region is 0.70 ≦ R1 / W ≦ 0.95 with respect to the width W of the shoulder land portion in the ground contact region, and the second shoulder lug groove The length R2 in the ground contact area is 0.50 ≦ R2 / W ≦ 0.75 with respect to the width W in the ground contact area of the shoulder land portion. Pneumatic tires.   The pneumatic tire according to claim 3, wherein a difference between the length R1 and the length R2 is set to (R1-R2) /W≧0.1 with respect to the width W.   The pneumatic tire according to any one of claims 1 to 4, wherein the shoulder sipe is raised at a portion communicating with the main groove, and the auxiliary sipe is raised relative to the first shoulder lug groove. .   The depths of the first shoulder lug groove, the second shoulder lug groove, the shoulder sipe, and the auxiliary sipe are defined along substantially the same groove bottom profile line in the ground contact region. The pneumatic tire according to any one of 1 to 5.   The pneumatic tire according to claim 1, wherein the shoulder sipe is provided with an intersecting portion that intersects the first shoulder lug groove or the second shoulder lug groove.   The pneumatic tire according to claim 7, wherein an intersection of the shoulder sipe with the first shoulder lug groove or the second shoulder lug groove is disposed on the outer side in the tire width direction from the ground contact end.

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