Pneumatic tire

Abstract

The invention relates to a pneumatic tire. Provided is a pneumatic tire having both uneven wear resistance and tractability. A pneumatic tire according to an embodiment is provided with a vehicle outside shoulder land portion (20), a vehicle inside shoulder land portion (30), a vehicle outside center land portion (40), and a vehicle inside center land portion (50), a main groove (11) between the vehicle outside shoulder land portion (20) and the vehicle outside center land portion (40) extending in a straight line. A main groove (12) between a vehicle-inside shoulder land portion (30) and a vehicle-inside center land portion (50) extends in a zigzag shape, the vehicle-outside center land portion is a rib portion extending in the tire circumferential direction, the vehicle-inside center land portion is a pattern block row, and the pattern block row is arranged on the two sides of the vehicle-outside center land portion in the tire axial direction. Slits (41) and recesses (42) are alternately formed in the circumferential direction of the tire as grooves that open in the main grooves (10, 11) and that are closed in the land portion.

Description

[0001] This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-070608 (filing date: April 24, 2024), and incorporates the entire contents of Japanese Patent Application No. 2024-070608. Technical Field

[0002] The present invention relates to a pneumatic tire. Background Art

[0003] As described in Patent Document 1, a pneumatic tire is known that includes, as land portions formed in the tread portion, the following: an outer shoulder land portion located on the outer side of the vehicle when assembled; an inner shoulder land portion located on the inner side of the vehicle when assembled; an outer center land portion adjacent to the outer shoulder land portion; and an inner center land portion adjacent to the inner shoulder land portion. The main groove between the outer shoulder land portion and the outer center land portion extends in a straight line, while the main groove between the inner shoulder land portion and the inner center land portion extends in a zigzag pattern. The pneumatic tire of Patent Document 1 aims to achieve both snow performance and noise performance.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-12510 Summary of the Invention

[0005] In the past, pneumatic tires have been developed that attempt to achieve a balance between two performance characteristics, as described in Patent Document 1. However, achieving both performance characteristics is sometimes difficult depending on the type of performance. Among the two performance characteristics that are difficult to achieve a balance between are uneven wear resistance and traction. This is because reducing the groove volume in the tread is effective in improving uneven wear resistance, but this reduction in groove volume degrades traction.

[0006] An object of the present invention is to provide a pneumatic tire that achieves both uneven wear resistance and traction, which have been difficult to achieve at the same time.

[0007] In the pneumatic tire according to the embodiment, as land portions formed in the tread portion, at least a vehicle-outer-side shoulder land portion which is a land portion located most outward in the vehicle, a vehicle-inner-side shoulder land portion which is a land portion located most inward in the vehicle, a vehicle-outer-side inner land portion which is adjacent to the vehicle-outer-side shoulder land portion, and a vehicle-inner-side inner land portion which is adjacent to the vehicle-inner-side shoulder land portion are provided, each of the land portions is separated by a main groove extending in the tire circumferential direction, the main groove between the vehicle-outer-side shoulder land portion and the vehicle-outer-side inner land portion extends in a straight line, and the main groove between the vehicle-inner-side shoulder land portion and the vehicle-inner-side inner land portion extends in a zigzag shape, characterized in that the vehicle-outer-side inner land portion is a rib portion extending continuously in the tire circumferential direction, and the vehicle-inner-side inner land portion is a block row in which a plurality of blocks separated by grooves are arranged in the tire circumferential direction, and in that, on both sides of the vehicle-outer-side inner land portion in the tire axial direction, a longer groove and a shorter groove are alternately formed in the tire circumferential direction as grooves which are open at the main groove and are closed in the land portion.

[0008] In the pneumatic tire according to the embodiment, the resistance to cornering wear and the traction are balanced. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A tread pattern of the embodiment is shown.

[0010] Figure 2 is an enlarged view of A portion of Figure 1

[0011] Figure 3 is an enlarged view of B portion of Figure 1

[0012] Figure 4 is an enlarged view of C portion of Figure 1

[0013] Figure 5 is an enlarged view of D portion of Figure 1

[0014] BRIEF DESCRIPTION OF REFERENCE NUMERALS

[0015] ​​​​10…Center main groove; 11…Outer shoulder main groove; 12…Inner shoulder main groove; 12a…First groove portion; 12b…Second groove portion; 20…Outer shoulder land portion; 21…Lug groove; 22…Slit; 23…Non-groove area; 24…Sipe; 25…Sipe; 30…Inner shoulder land portion; 31…Narrow groove; 31a…Curved portion; 31b…Curved portion; 32…Lug groove Groove; 33…slit; 34…outer tread block; 35…inner tread block; 36…sipe; 37…sipe; 40…outer central land portion; 41…slit; 42…recess; 43…connecting sipe; 44…long sipe; 45…short sipe; 50…inner central land portion; 51…inner central tread block; 52…inclined groove; 53…long sipe; 54…short sipe. DETAILED DESCRIPTION

[0016] In addition to the tread portion, the pneumatic tire of the embodiment has a normal cross-sectional structure as a pneumatic tire. Specifically, bead portions are provided on both axial sides of the tire (the bead portion refers to the portion consisting of the bead core and the bead outer rubber), and carcass ply is provided from the bead portion on one axial side of the tire to the bead portion on the other axial side. A belt is provided on the outer diameter side of the carcass ply, and a tread portion is provided on the outer diameter side of the belt. In addition, an inner liner is provided on the inner side of the carcass ply, and sidewall rubber is provided on both axial sides of the carcass ply. In addition to the above components, a plurality of rubber components are provided, thereby constituting a pneumatic tire.

[0017] The rubber tread is formed with Figure 1 The tread pattern shown. Figure 1 In the figure, the arrow X direction is the tire axial direction, and the arrow Y direction is the tire circumferential direction. In the tire axial direction, OUT represents the vehicle outer side when the vehicle is assembled, and IN represents the vehicle inner side.

[0018] about Figure 1 The tread pattern shown here consists of a central main groove 10 and two shoulder main grooves 11 and 12, which are relatively wide grooves extending in the tire's circumferential direction. The shoulder main grooves 11 and 12 are located on opposite sides of the tire's axial direction, with the central main groove 10 located between the two shoulder main grooves 11 and 12. These main grooves 10, 11, and 12 have the same depth. Although not shown, protrusions are provided at the bottoms of the main grooves 10, 11, and 12 to prevent stones from being caught in them.

[0019] The central main groove 10 and the shoulder main groove 11 on the vehicle outer side extend in a straight line in the tire circumferential direction. On the other hand, the shoulder main groove 12 on the vehicle inner side is zigzag. That is, with respect to the shoulder main groove 12 on the vehicle inner side, a first groove portion 12a extending obliquely with respect to the tire circumferential direction and a second groove portion 12b extending in the opposite direction to the first groove portion 12a with respect to the tire circumferential direction are alternately arranged in the tire circumferential direction. The first groove portion 12a is longer than the second groove portion 12b.

[0020] In the present embodiment, the tread portion is divided by the above-described main grooves 10, 11, 12 to form four land portions. In addition, in the present embodiment, the land portion refers to a portion divided by a main groove. Further, the main groove refers to a groove having a large width extending in the tire circumferential direction as described above, and in the present embodiment, the width is set to 9 mm or more.

[0021] The four land portions of the present embodiment refer to: a vehicle outer shoulder land portion 20 which is the land portion located most on the vehicle outer side when the tire is mounted on a vehicle; a vehicle inner shoulder land portion 30 which is the land portion located most on the vehicle inner side when the tire is mounted on a vehicle; a vehicle outer central land portion 40 which is a land portion located on the vehicle outer side and further on the tire equator CL side than the vehicle outer shoulder land portion 20 when the tire is mounted on a vehicle; and a vehicle inner central land portion 50 which is a land portion located on the vehicle inner side and further on the tire equator CL side than the vehicle inner shoulder land portion 30 when the tire is mounted on a vehicle. Here, the tire equator CL is a line passing through the center position in the tire axial direction and extending in a straight line in the tire circumferential direction. In the present embodiment, the vehicle outer central land portion 40 is a vehicle outer inner land portion, and the vehicle inner central land portion 50 is a vehicle inner inner land portion.

[0022] The vehicle inner central land portion 50 is wider in the tire axial direction than the vehicle outer central land portion 40. Here, the width of the land portion refers to the length of the land portion in the tire axial direction. Further, the center line of the central main groove 10 (the center line extending in the tire circumferential direction) is further on the vehicle outer side than the tire equator CL.

[0023] Figure 2 A portion of the vehicle outer shoulder land portion 20 is shown in an enlarged manner. In the vehicle outer shoulder land portion 20, a cross groove 21 extending from the tire axial end of the tread portion and closed within the vehicle outer shoulder land portion 20, and a slit 22 opening at the shoulder main groove 11 on the vehicle outer side and closed within the vehicle outer shoulder land portion 20 are provided. The cross groove 21 and the slit 22 are each one kind of groove. A plurality of cross grooves 21 and a plurality of slits 22 are alternately arranged in the tire circumferential direction.

[0024] Further, in the present embodiment, among the grooves extending in the tire axial direction or the grooves extending obliquely with respect to the tire axial direction, the groove extending from the tire axial end of the tread portion is referred to as a sipe groove, and the groove extending from the main groove is referred to as a slit. In addition, in the present embodiment, both the sipe groove and the slit are provided so as to be closed at one end in the land portion. In addition, in the case where grooves of different lengths exist in the same land portion as grooves extending from the main groove, the longer groove is referred to as a slit, and the shorter groove is referred to as a notch.

[0025] The sipe groove 21 and the slit 22 do not penetrate the tire axial direction in the vehicle outer side shoulder land portion 20, and therefore, the vehicle outer side shoulder land portion 20 is formed as a rib portion, that is, a land portion continuously in the tire circumferential direction without interruption.

[0026] In addition, the sipe groove 21 and the slit 22 do not have an overlapping portion in the tire circumferential direction. In detail, in the vehicle outer side shoulder land portion 20, the sipe groove 21 is positioned on the tire axial direction outer side, and the slit 22 is positioned on the tire axial direction inner side (tire equator CL side). Further, a groove-free region 23 in which no groove (but a wider groove having a width greater than that of the sipe groove) exists is formed in the tire axial direction center of the vehicle outer side shoulder land portion 20. The groove-free region 23 extends in the tire circumferential direction throughout the tire 1.

[0027] On the tire axial direction outer side in the vehicle outer side shoulder land portion 20, a plurality of sipe grooves 24 are provided at equal intervals between the sipe grooves 21. The lengths of the sipe grooves 24 are all the same. In addition, on the tire axial direction inner side in the vehicle outer side shoulder land portion 20, a plurality of sipe grooves 25 are provided at equal intervals between the slits 22. The lengths of the sipe grooves 25 are all the same. The above-described sipe grooves 24, 25 are wavy sipe grooves extending obliquely with respect to the tire axial direction. In addition, both ends of the extension direction of the above-described sipe grooves 24, 25 are closed in the vehicle outer side shoulder land portion 20. The sipe grooves 24, 25 are not present in the region in the tire axial direction center in the above-described groove-free region 23.

[0028] Further, the sipe groove refers to a groove having a width of 0.3 mm or more and less than 1.5 mm. Here, the width of the groove or the sipe groove refers to the length in the direction perpendicular to the extension direction of the groove or the sipe groove when viewed from the tire radial direction outer side.

[0029] Next, Figure 3 A portion of the vehicle inner side shoulder land portion 30 is shown in an enlarged manner. In the vehicle inner side shoulder land portion 30, a fine groove 31 extending in the tire circumferential direction throughout the tire 1 is formed. The width of the fine groove 31 is 1.5 mm or more and 3.0 mm or less. The width of the fine groove 31 is smaller than the widths of the main grooves 10, 11, 12. The fine groove 31 has an effect of resistance to lateral slip. Two kinds of curved portions 31a, 31b curved in opposite directions are alternately formed at equal intervals in the fine groove 31.

[0030] On the tire axial outer side of the vehicle inner shoulder land portion 30, a plurality of sipes 32 are provided at equal intervals in the tire circumferential direction. One end of each sipe 32 is opened at the fine groove 31, and the other end is opened at the tire axial end of the tread portion. Therefore, on the tire axial outer side of the vehicle inner shoulder land portion 30, specifically, more on the tire axial outer side than the fine groove 31, the blocks divided by the fine groove 31 and the two sipes 32 from the surroundings, that is, the outer blocks 34 are arranged at equal intervals in the tire circumferential direction.

[0031] In addition, on the tire axial inner side of the vehicle inner shoulder land portion 30, a plurality of slits 33 are provided at equal intervals in the tire circumferential direction. One end of each slit 33 is opened at the serrated shoulder main groove 12, and the other end is opened at the fine groove 31. Therefore, on the tire axial inner side of the vehicle inner shoulder land portion 30, specifically, more on the tire axial inner side than the fine groove 31, the blocks divided by the shoulder main groove 12, the fine groove 31, and the two slits 33 from the surroundings, that is, the inner blocks 35 are arranged at equal intervals in the tire circumferential direction.

[0032] In the vehicle inner shoulder land portion 30, the sipes 32 and the slits 33 are alternately arranged in the tire circumferential direction. Therefore, the plurality of outer blocks 34 and the plurality of inner blocks 35 are arranged in a staggered manner in the tire circumferential direction.

[0033] A plurality of sipes 36, 37 are provided at equal intervals in the tire circumferential direction in the outer blocks 34 and the inner blocks 35 of the vehicle inner shoulder land portion 30, respectively. In the outer blocks 34, the lengths of all the sipes 36 are the same. In addition, in the inner blocks 35, the lengths of all the sipes 37 are the same. The sipes 36, 37 described above are wavy sipes that extend slightly inclined with respect to the tire axial direction. In addition, both ends of the elongated direction of the sipes 36, 37 are not opened at the grooves or the like but are closed within the blocks 34, 35.

[0034] Next, Figure 4 A portion of the vehicle outer side center land portion 40 is shown in an enlarged manner. The vehicle outer side center land portion 40 is a rib portion, that is, a land portion that is continuously continuous in the tire circumferential direction without interruption. On both tire axial sides of the vehicle outer side center land portion 40, as grooves that are opened at the main grooves 10, 11 and closed within the vehicle outer side center land portion 40, a longer groove, that is, a slit 41, and a shorter groove than the slit 41, that is, a notch 42 are alternately provided in the tire circumferential direction.

[0035] The slits 41 and the notches 42 are inclined in the same direction with respect to the tire axial direction. The notches 42 extending from the shoulder main grooves 11 are on the extension line of the slits 41 extending from the center main groove 10, and the slits 41 extending from the shoulder main grooves 11 are on the extension line of the notches 42 extending from the center main groove 10. The slits 41 and the notches 42 on the same extension line are separated.

[0036] The extension line described above is provided with a link sipe 43 that links the slit 41 and the notch 42. One end of the link sipe 43 is open at the slit 41, and the other end of the link sipe 43 is open at the notch 42. The link sipe 43 is a wavy sipe.

[0037] The vehicle-outer-side center land portion 40 is a rib portion, and the link sipe 43 that links the slit 41 and the notch 42 is provided at a place where the width is reduced due to the slit 41 and the notch 42, and thus the traction is ensured. In addition, the link sipe 43 is closed when the pneumatic tire is grounded and a load is applied from above, and thus the vehicle-outer-side center land portion 40 can be regarded as a rib portion that is continuously continuous in the tire circumferential direction without interruption.

[0038] A plurality of long sipes 44 and short sipes 45 are alternately provided at constant intervals in the tire circumferential direction between the two link sipes 43, respectively. The long sipes 44 and the short sipes 45 are wavy sipes that are inclined and extend with respect to the tire axial direction. Both ends of the extension direction of the long sipes 44 and the short sipes 45 are closed within the vehicle-outer-side center land portion 40.

[0039] The long sipes 44 and the short sipes 45 contribute to the traction. In addition, the long sipes 44 and the short sipes 45 are alternately arranged in the tire circumferential direction, and thus the deviation of the rigidity within the vehicle-outer-side center land portion 40 is suppressed, the reduction of the rigidity of the entire vehicle-outer-side center land portion 40 is also suppressed, and in addition, the ground pressure within the vehicle-outer-side center land portion 40 is homogenized. As a result, uneven wear is difficult to occur.

[0040] The length L2 of the long sipes 44 in the tire axial direction is 50% or more and 80% or less of the length LI of the vehicle-outer-side center land portion 40 in the tire axial direction. As a result, the traction based on the long sipes 44 is sufficiently ensured, and the rigidity of the vehicle-outer-side center land portion 40 is also sufficiently ensured. In addition, the length L3 of the short sipes 45 in the tire axial direction is 50% or more and 90% or less of the length L2 of the long sipes 44 in the tire axial direction. As a result, the traction based on the short sipes 45 is sufficiently ensured, and the rigidity of the vehicle-outer-side center land portion 40 is also sufficiently ensured.

[0041] Next, Figure 5A portion of the vehicle inner side central land portion 50 is shown in an enlarged scale. The vehicle inner side central land portion 50 is a block row in which the vehicle inner side central blocks 51 and the inclined grooves 52 extending obliquely with respect to the tire axial direction are alternately arranged. The inclined grooves 52 open at one end in the central main groove 10 and at the other end in the serrated shoulder main groove 12. The vehicle inner side central blocks 51 are blocks partitioned by two main grooves 10, 12 and two inclined grooves 52 with respect to the surroundings.

[0042] The plurality of long sipe grooves 53 and the short sipe grooves 54 are alternately arranged at constant intervals in the tire circumferential direction in each of the vehicle inner side central blocks 51. The long sipe grooves 53 and the short sipe grooves 54 are wavy sipe grooves extending obliquely with respect to the tire axial direction. Both ends of the long sipe grooves 53 and the short sipe grooves 54 in the direction of extension are closed within the vehicle inner side central blocks 51.

[0043] Such long sipe grooves 53 and short sipe grooves 54 contribute to the traction property. In addition, the long sipe grooves 53 and the short sipe grooves 54 are alternately arranged in the tire circumferential direction, and therefore, the deviation of the rigidity in the vehicle inner side central land portion 50 is suppressed, the lowering of the rigidity of the entire vehicle inner side central land portion 50 is suppressed, and in addition, the uniformity of the ground contact pressure in the vehicle inner side central land portion 50 is achieved. As a result, uneven wear is difficult to occur.

[0044] The length L5 of the long sipe grooves 53 in the tire axial direction is 50% or more and 80% or less of the length L4 of the vehicle inner side central blocks 51 in the tire axial direction. As a result, the traction property based on the long sipe grooves 53 is sufficiently ensured, and the rigidity of the vehicle inner side central land portion 50 is also sufficiently ensured. In addition, the length L6 of the short sipe grooves 54 in the tire axial direction is 50% or more and 90% or less of the length L5 of the long sipe grooves 53 in the tire axial direction. As a result, the traction property based on the short sipe grooves 54 is sufficiently ensured, and the rigidity of the vehicle inner side central land portion 50 is also sufficiently ensured.

[0045] The number of the sipe grooves 24 between the two transverse grooves 21 of the vehicle outer side shoulder land portion 20 is the same as the number of the sipe grooves 36 of the one outer block 34 of the vehicle inner side shoulder land portion 30. In addition, the number of the sipe grooves 25 between the two slits 22 of the vehicle outer side shoulder land portion 20, the number of the sipe grooves 37 of the one inner block 35 of the vehicle inner side shoulder land portion 30, the number of the sipe grooves 44, 45 between the two connecting sipe grooves 43 of the vehicle outer side central land portion 40, and the number of the sipe grooves 53, 54 of the one vehicle inner side central block 51 are the same.

[0046] In addition, the number of sipes 24 between the two lateral grooves 21 of the vehicle-outer-side shoulder land portion 20 and the number of sipes 36 of the one outer block 34 of the vehicle-inner-side shoulder land portion 30 are each less than the number of sipes 25 between the two slits 22 of the vehicle-outer-side shoulder land portion 20, the number of sipes 37 of the one inner block 35 of the vehicle-inner-side shoulder land portion 30, the number of sipes 44, 45 between the two connecting sipes 43 of the vehicle-outer-side center land portion 40, and the number of sipes 53, 54 of the one vehicle-inner-side center block 51. In this way, the number of sipes 24, 36 is less on both sides in the tire axial direction, so the rigidity on both sides in the tire axial direction is ensured, and the eccentric wear on both sides in the tire axial direction, which is easily affected by the lateral force, is suppressed.

[0047] The depths of the lateral grooves 21, 32, the slits 22, 33, 41, the notches 42, and the inclined grooves 52 are 30% or more and 60% or less of the depths of the main grooves 10, 11, 12. Thus, the traction in the middle and end stages of wear is ensured, and the rigidity of each land portion 20, 30, 40, 50 is also ensured. In addition, the depth of the fine groove 31 is also 30% or more and 60% or less of the depths of the main grooves 10, 11, 12, and in addition, the widths of the slits 22, 33, 41 and the notches 42 are 4.0 mm or more and 8.0 mm or less.

[0048] In addition, the depths of the sipes 24, 25, 36, 37, 43, 44, 45, 53, 54 are 30% or more and 60% or less of the depths of the main grooves 10, 11, 12. Thus, the traction in the middle and end stages of wear is ensured, and the rigidity of each land portion 20, 30, 40, 50 is also ensured.

[0049] The pneumatic tire having the above features is a pneumatic tire that balances the eccentric wear resistance and the traction. This will be described below.

[0050] First, in the present embodiment, a vehicle-outer-side shoulder land portion 20 as the land portion closest to the vehicle-outer-side, a vehicle-inner-side shoulder land portion 30 as the land portion closest to the vehicle-inner-side, a vehicle-outer-side center land portion 40 (a vehicle-outer-side inner land portion) adjacent to the vehicle-outer-side shoulder land portion 20, and a vehicle-inner-side center land portion 50 (a vehicle-inner-side inner land portion) adjacent to the vehicle-inner-side shoulder land portion 30 are provided.

[0051] Further, the shoulder main groove 12 between the vehicle inner side shoulder land portion 30 and the vehicle inner side central land portion 50 is zigzag, and thus, the traction is ensured. Also, the vehicle outer side portion of a normal pneumatic tire is easily subjected to eccentric wear due to the influence of the lateral force, and thus, in the present embodiment, the shoulder main groove 11 between the vehicle outer side shoulder land portion 20 and the vehicle outer side central land portion 40 extends in a straight line, and the rigidity of the land portions on both sides of the shoulder main groove 11 is ensured, and thus, the eccentric wear is difficult to occur.

[0052] Further, the vehicle inner side central land portion 50 is a block row, and a plurality of vehicle inner side central blocks 51 are arranged in the tire circumferential direction, and thus, the traction is ensured. On the other hand, on the vehicle outer side, the vehicle outer side central land portion 40 is a rib portion extending in the tire circumferential direction, and thus, the rigidity is ensured and the eccentric wear is difficult to occur.

[0053] Further, on both sides of the vehicle outer side central land portion 40 in the tire axial direction, a slit 41 (longer groove) and a notch 42 (shorter groove) are provided as grooves which are opened at the main grooves 10, 11 and closed within the vehicle outer side central land portion 40. Thus, the traction is also generated from the vehicle outer side central land portion 40 which is a rib portion. Also, not only the longer slit 41 is provided, but the longer slit 41 and the shorter notch 42 are alternately provided, and thus, the rigidity of the vehicle outer side central land portion 40 is ensured and the traction is also ensured.

[0054] Thus, with regard to the pneumatic tire of the present embodiment, the configurations on the vehicle inner side and the vehicle outer side are different as described above, and thus, the eccentric wear resistance and the traction are both ensured.

[0055] The eccentric wear of a pneumatic tire is particularly likely to occur in the case of being fitted to the front side of a vehicle (when the lateral force is easily applied during turning on the front side), in the case of being fitted to an electric automobile (the torque of an electric automobile is large), but the pneumatic tire of the present embodiment is difficult to be subjected to the eccentric wear in the case of being fitted to the front side of a vehicle, in the case of being fitted to an electric automobile. Also, the traction of the pneumatic tire of the present embodiment is high, and thus, the grip required in the case of being fitted to an electric automobile (the torque of an electric automobile is large) is also ensured.

[0056] Also, in the present embodiment, as the grooves formed in the vehicle outer side shoulder land portion 20, a cross groove 21 extending from the tire axial end of the tread portion and closed within the land portion, and a slit 22 opened at the shoulder main groove 11 and closed within the land portion are provided, and the cross groove 21 and the slit 22 are alternately arranged in the tire circumferential direction. The traction is generated due to the cross groove 21 and the slit 22.

[0057] In addition, in the present embodiment, the vehicle-outer-side shoulder land portion 20 is formed as a rib portion that extends continuously in the tire circumferential direction. Therefore, the rigidity of the vehicle-outer-side shoulder land portion 20 is ensured. In addition, when the pneumatic tire is rolling, the load applied to a portion of the vehicle-outer-side shoulder land portion 20 is easily dispersed in the tire circumferential direction. Thus, in the present embodiment, uneven wear is less likely to occur in the vehicle-outer-side shoulder land portion 20. In particular, the sipe 21 and the slit 22 do not have an overlapping portion in the tire circumferential direction in the vehicle-outer-side shoulder land portion 20, and thus uneven wear is less likely to occur.

[0058] In addition, in the present embodiment, the vehicle-outer-side shoulder land portion 20 is a rib portion, and the volume of the rubber is easily increased on the vehicle-outer side as compared with the vehicle-inner side with respect to the shoulder land portion. In particular, in the present embodiment, the vehicle-inner-side shoulder land portion 30 is a block row, and thus the volume of the rubber is easily increased on the vehicle-outer side as compared with the vehicle-inner side with respect to the shoulder land portion.

[0059] On the other hand, with respect to the center land portion, the vehicle-inner-side center land portion 50 is wider in the tire axial direction than the vehicle-outer-side center land portion 40, and thus the volume of the rubber is easily increased on the vehicle-inner side as compared with the vehicle-outer side. Thus, when the entire tread portion is observed, the difference in the volume of the rubber between the vehicle-inner side and the vehicle-outer side is reduced. Therefore, uneven wear is less likely to occur.

[0060] Here, the reason why the width of the vehicle-inner-side center land portion 50 is increased instead of the width of the vehicle-inner-side shoulder land portion 30 in order to reduce the difference in the volume of the rubber between the vehicle-inner side and the vehicle-outer side is that the tire axial central region has a higher ground pressure than the tire axial both-side regions, and thus increasing the width of the vehicle-inner-side center land portion 50 can improve the traction as compared with increasing the width of the vehicle-inner-side shoulder land portion 30.

[0061] In addition, in the present embodiment, the vehicle-inner-side shoulder land portion 30 is configured to include a block row in which the outer blocks 34 are arranged in the tire circumferential direction, and a block row in which the inner blocks 35 are arranged in the tire circumferential direction, and thus the traction is improved. In addition, the fine groove 31 between the block row of the outer blocks 34 and the block row of the inner blocks 35 is thin, and thus when the pneumatic tire is grounded and a load is applied, the outer blocks 34 and the inner blocks 35 can support each other, and the rigidity of the vehicle-inner-side shoulder land portion 30 is ensured. Therefore, uneven wear is less likely to occur.

[0062] The above embodiment is merely an example, and various modifications can be made to the above embodiment. Embodiments obtained by appropriately modifying the above embodiment within the scope of the gist of the present application are also included in the scope of the present application.

[0063] For example, the number of the main grooves can be four or more. In the case where the number of the main grooves is four or more, the land portion adjacent to the vehicle-outer-side shoulder land portion is a vehicle-outer-side inner land portion, and the land portion adjacent to the vehicle-inner-side shoulder land portion is a vehicle-inner-side inner land portion.

[0064] In addition, in the case where the number of the main grooves is five or more, a land portion closest to the tire equator among the plurality of land portions on the vehicle-outer side than the tire equator (referred to as a "vehicle-outer-side central land portion" in this modification example) and a land portion closest to the tire equator among the plurality of land portions on the vehicle-inner side than the tire equator (referred to as a "vehicle-inner-side central land portion" in this modification example) are sometimes formed differently from the vehicle-outer-side inner land portion and the vehicle-inner-side inner land portion. In this case, it is preferable that the width of the vehicle-inner-side central land portion be larger than that of the vehicle-outer-side central land portion in the tire axial direction. Thereby, when the entire tread portion is observed, the difference in the volume of rubber between the vehicle-inner side and the vehicle-outer side is reduced. In addition, by expanding the width of the vehicle-inner-side central land portion in the tire axial direction central region where the ground pressure is high, the traction is improved.

Claims

1. A pneumatic tire, as land portions formed in a tread portion, at least a vehicle-outer-side shoulder land portion as a land portion most on a vehicle-outer-side, a vehicle-inner-side shoulder land portion as a land portion most on a vehicle-inner-side, a vehicle-outer-side inner land portion adjacent to the vehicle-outer-side shoulder land portion, and a vehicle-inner-side inner land portion adjacent to the vehicle-inner-side shoulder land portion are provided, each of the land portions being separated by a main groove extending in a tire-circumferential direction, the main groove between the vehicle-outer-side shoulder land portion and the vehicle-outer-side inner land portion extends in a straight line, and the main groove between the vehicle-inner-side shoulder land portion and the vehicle-inner-side inner land portion extends in a zigzag shape, characterized in that the vehicle-outer-side inner land portion is a rib portion extending continuously in the tire-circumferential direction, and the vehicle-inner-side inner land portion is a block row in which a plurality of blocks separated by grooves are arranged in the tire-circumferential direction, on both tire-axial sides of the vehicle-outer-side inner land portion, a longer groove and a shorter groove are alternately formed in the tire-circumferential direction as grooves opening at the main groove and being closed in the land portion.

2. The pneumatic tire according to claim 1, characterized in that as grooves formed in the vehicle-outer-side shoulder land portion, a cross groove extending from a tire-axial end of the tread portion and being closed in the land portion, and a slit opening at the main groove and being closed in the land portion are provided, the cross groove and the slit being alternately arranged in the tire-circumferential direction, the vehicle-outer-side shoulder land portion is formed as a rib portion extending continuously in the tire-circumferential direction, and the cross groove and the slit do not have an overlapping portion in the tire-circumferential direction.

3. The pneumatic tire according to claim 1 or 2, characterized in that the vehicle-inner-side inner land portion is wider in the tire-axial direction than the vehicle-outer-side inner land portion.

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