Pneumatic tire

Abstract

To provide a pneumatic tire which can balance improvement of wandering performance with suppressing of rolling resistance.SOLUTION: A tread 30 of a pneumatic tire comprises: a tread surface 36 which contacts with a road surface; and a belt 31 which is embedded in the tread 30. A land 70 of the tread surface 36 includes a shoulder land 72 which is arranged at an end part of the tread surface 36 in a tire axial direction. A major groove 80 of the tread surface 36 includes a second major groove 82 as a shoulder major groove which is adjacent to the shoulder land 72 at an inner side in the tire axial direction. The shoulder land 72 includes a plurality of slits 77 which are extended in a direction crossing the tire circumferential direction and arrayed in the tire circumferential direction. When ground width of the tread surface 36 is C and width of the belt 31 is B, a ratio B / C is 105% or more and 110% or less at the time of 70% load of the maximum load based on the tire standard JATMA. An end 77a of the slit 77 at an inner side in the tire axial direction is not communicated with the second major groove 82 and is terminated in the shoulder land 72.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] When a vehicle equipped with pneumatic tires travels on a road, a phenomenon called wandering may occur in which the vehicle unintentionally sways due to ruts, bumps, and the like. It is known that one of the causes of wandering is that the wheels cannot smoothly overcome ruts or bumps when the camber thrust is small. Improvement of wandering performance that suppresses the occurrence of wandering is desirable because it leads to ensuring driving stability. Patent Document 1 discloses a pneumatic tire in which wandering performance is improved by extending the bead turn-up end of the carcass ply that forms the framework of the tire up to above the belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-10001 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional techniques for improving wandering performance, there is a concern that an increase in the mass of the carcass ply leads to an increase in tire mass, which in turn leads to a deterioration in rolling resistance.

[0005] An object of the present invention is to provide a pneumatic tire that exhibits a good balance between improved wandering performance and reduced rolling resistance. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread, the tread including a tread surface that contacts the road surface and a belt embedded in the tread, the tread surface including a plurality of lands extending in the tire circumferential direction and a plurality of main grooves that extend in the tire circumferential direction and divide the plurality of lands in the tire axial direction, the lands having shoulder lands arranged at the ends of the tread surface in the tire axial direction, the main groove having a shoulder main groove adjacent to the shoulder land on the axially inner side, the shoulder land having a plurality of slits extending in a direction intersecting the tire circumferential direction and aligned in the tire circumferential direction, a ratio B / C of a width B of the belt to a contact width C of the tread surface at a load of 70% of the maximum load in the JATMA tire standard is 105% or more and 110% or less, and the axially inner ends of the slits do not communicate with the shoulder main groove and terminate within the shoulder land. Effect of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire that exhibits a good balance between improved wandering performance and reduced rolling resistance. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a half cross section in an axial direction of a tire according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a partially enlarged plan view showing a tread surface of the tire according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing the internal structure of a tire 1, which is a pneumatic tire according to an embodiment, and shows a half cross section in the tire axial direction. FIG. 2 is a partially enlarged plan view of the tire 1 seen from above, showing a tread surface 36 of the tire 1 on which a tread pattern 39 is formed. The tire 1 according to the embodiment is, for example, a pneumatic tire for passenger cars. Note that the configuration of the tire 1 according to the embodiment can also be applied to tires for various vehicles such as light trucks, trucks, and buses.

[0010] First, the internal structure of a tire 1 will be described with reference to FIG. 1. The cross-sectional view in FIG. 1 is a half cross-sectional view in the axial direction of a tire in an unloaded state in which the tire 1 is mounted on a regular rim (not shown) and inflated to a regular internal pressure. The regular rim is a rim that is determined for each tire by a standard system including the standard on which the tire is based, for example, a standard rim for JATMA, and a "Measuring Rim" for TRA and ETRTO. The regular internal pressure is an air pressure that is determined for each tire by each standard in a standard system including the standard on which the tire is based, and in the case of tires for trucks and buses and tires for light trucks, it is the maximum air pressure for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. For tires for passenger cars, it is usually 180 kPa, but for tires marked "Extra Load" or "Reinforced", it is 220 kPa.

[0011] In FIG. 1, the symbol S1 indicates a tire equatorial plane perpendicular to the rotation axis of the tire 1. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and is located at the center in the tire axial direction. The basic internal structure of the tire 1 is symmetrical with respect to the tire equatorial plane S1. FIG. 1 shows a half cross section of the right half of the tire 1, and the left half (not shown) has the same structure. Note that FIG. 2 shows a tire equator S2 that corresponds to the tire equatorial plane S1 and extends in the tire circumferential direction on the tread surface 36. In addition, FIGS. 1 and 2 show a contact width C of the tread surface 36. The contact width C of the tread surface 36 is the axial distance of the tire where the tread surface 36 comes into contact with the road surface under a load of 70% of the maximum load in the tire standard JATMA.

[0012] In Fig. 1, the tire axial direction is indicated by arrow X, and the tire radial direction is indicated by arrow Y. The tire axial direction is a direction parallel to the tire rotation axis, and corresponds to the left-right direction on the page in Fig. 1. The tire axially inner side is a direction approaching the tire equatorial plane S1 in the tire axial direction, and corresponds to the left-hand side on the page in Fig. 1. The tire axially outer side is a direction away from the tire equatorial plane S1 in the tire axial direction, and corresponds to the right-hand side on the page in Fig. 1.

[0013] The tire radial direction is a direction perpendicular to the tire rotation axis, and is the up-down direction on the paper in Fig. 1. In Fig. 1, this is illustrated as tire radial direction Y. The outer side in the tire radial direction is a direction away from the tire rotation axis, and is the upper side on the paper in Fig. 1. The inner side in the tire radial direction is a direction approaching the tire rotation axis, and is the lower side on the paper in Fig. 1.

[0014] As shown in FIG. 1, the tire 1 includes a pair of beads 10, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a shoulder 40 which is a transition portion from the sidewalls 20 to the tread 30, a carcass ply 50 disposed spanning between the pair of beads 10, and an inner liner 60 disposed on the tire cavity side of the carcass ply 50.

[0015] The pair of beads 10 are disposed on both axial sides of the tire and on the inner ends in the tire radial direction. Each bead 10 has a bead core 11, a bead filler 12 extending from the bead core 11 to the outer side in the tire radial direction, and a rim strip rubber 13.

[0016] The bead core 11 is an annular member in which a rubber-coated metal bead wire is wound multiple times in the tire circumferential direction. The bead core 11 is a member that serves to fix the tire 1 filled with air to the rim. The bead filler 12 has a tapered shape that decreases in thickness as it extends from the tire radial inner side to the tire radial outer side. The bead filler 12 is joined to the tire radial outer surface of the bead core 11. The bead filler 12 is provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is made of, for example, rubber that is harder than the surrounding rubber members.

[0017] The rim strip rubber 13 is provided in such a manner that it further surrounds the outside of the carcass ply 50 which surrounds the bead core 11 and the bead filler 12. The rim strip rubber 13 has a rim line 13c that protrudes outward in the axial direction of the tire. The rim line 13c is an annular line that runs along the circumferential direction of the tire. The rim line 13c is a mark for matching the edge of the rim. The rim strip rubber 13 including the rim line 13c forms a rim protector 14 that is positioned to protrude outward in the axial direction of the tire beyond the rim.

[0018] The sidewall 20 includes a sidewall rubber 21 disposed axially outward of the carcass ply 50. The sidewall rubber 21 constitutes the outer surface of the tire 1. The sidewall rubber 21 is the portion that bends the most when the tire 1 performs its cushioning function, and flexible rubber having fatigue resistance is usually used for the sidewall rubber 21.

[0019] The sidewall rubber 21 is disposed in a region extending in the tire radial direction from the shoulder 40 to the tire radially outer portion of the bead 10. The tire radially outer end 21a of the sidewall rubber 21 covers the tire axially outer end 35a of a tread rubber 35 of the tread 30 described later. The tire radially inner side of the sidewall rubber 21 extends to the rim line 13c.

[0020] The tread 30 includes an endless belt 31, a cap ply 34, and a tread rubber 35. The belt 31 is disposed on the outer side of the carcass ply 50 in the tire radial direction. The cap ply 34 is disposed on the outer side of the belt 31 in the tire radial direction. The tread rubber 35 is disposed on the outer side of the cap ply 34 in the tire radial direction.

[0021] The belt 31 is a member that reinforces the tread 30. The belt 31 of the embodiment has a two-layer structure including an inner belt 32 arranged on the outer side of the inner liner 60 in the tire radial direction, and an outer belt 33 arranged on the outer side of the inner belt 32 in the tire radial direction. Both the inner belt 32 and the outer belt 33 have a structure in which a plurality of belt cords such as steel cords are covered with rubber.

[0022] The inner belt 32 is wider than the outer belt 33. An axially outer end 32a of the inner belt 32 is the axially outermost end of the belt 31. An outer surface 33a of the outer belt 33 is the surface of the belt 31 on the outer side in the tire radial direction. By providing the belt 31, the rigidity of the tire 1 is ensured, and the contact of the tread 30 with the road surface is improved. Note that the belt 31 is not limited to a two-layer structure, and may have a single layer structure, or a three-layer or more layer structure.

[0023] 1 shows the width B of the belt 31 together with the ground contact width C of the tread surface 36 of the tread 30 at a load of 70% of the maximum load in the JATMA tire standard. The width B of the belt 31 is the distance between both ends in the tire axial direction of the inner belt 32, which is the axially outermost end of the belt 31. In the tire 1 of the embodiment, the ratio B / C of the width B of the belt 31 to the ground contact width C of the tread surface 36 is preferably 105% or more and 110% or less.

[0024] The cap ply 34 is a member that reinforces the tread 30 together with the belt 31. The cap ply 34 has a structure in which a plurality of insulating organic fiber cords such as polyamide fiber are covered with rubber. The cap ply 34 covers the entire belt 31 from the tire outer surface side. The cap ply 34 has a folded portion 34a at the end on the outer side in the tire axial direction that is folded toward the tire cavity side to form a double layer. This folded portion 34a is configured to press the ends of the outer sides of the belts 32 and 33 of the belt 31 in the tire axial direction toward the tire cavity side. By providing the cap ply 34, it is possible to improve durability and reduce road noise during driving. Note that the cap ply 34 in the embodiment is a single layer, but may be a structure of two or more layers.

[0025] The tread rubber 35 is disposed on the outer side of the cap ply 34 in the tire radial direction. The tread rubber 35 is a member that constitutes a tread surface 36, which is the outer surface of the tread 30 and comes into contact with the road surface. An end 35a on the outer side of the tread rubber 35 in the tire axial direction extends beyond the folded portion 34a of the cap ply 34 to the outer side of the tire axial direction, and is curved inward in the tire radial direction. The end 35a on the outer side of the tread rubber 35 in the tire axial direction is covered by an end 21a on the outer side of the sidewall rubber 21 in the tire radial direction.

[0026] The tread surface 36 is provided with a tread pattern 39 as shown in Fig. 2. The tread pattern 39 will be described in detail later.

[0027] The shoulder 40 is a region where the tread 30 transitions to the sidewall 20. The shoulder 40 includes a region where an end 21a of the sidewall rubber 21 on the outer side in the tire radial direction covers an end 37a of the tread rubber 35 on the outer side in the tire axial direction.

[0028] The carcass ply 50 is laid between a pair of beads 10. The carcass ply 50 is embedded inside the tire 1 in a manner that the carcass ply 50 passes between the pair of beads 10, through a pair of sidewalls 20, a pair of shoulders 40, and the tire cavity side of the tread 30. In the tread 30, a belt 31 is disposed on the outer side of the carcass ply 50 in the tire radial direction.

[0029] The carcass ply 50 includes a plurality of ply cords (not shown) that form the framework of the tire 1. The plurality of ply cords extend, for example, along a plane along the tire axial direction, and are arranged side by side in the tire circumferential direction. The ply cords are made of insulating organic fiber cords such as polyester or polyamide. The carcass ply 50 is formed by covering the plurality of ply cords with rubber.

[0030] The carcass ply 50 includes a ply body 50A and a pair of turned-up portions 50B. The ply body 50A is a portion that extends from the tread 30 through a pair of shoulders 40 and a pair of sidewalls 20 to the axially inner side of each of the pair of beads 10. The pair of turned-up portions 50B are wound around each of the pair of bead cores 11 from the ply body 50A, and turn back radially outward from the pair of bead cores 11 to extend along the sidewalls 20. A tip 50b of the turned-up portion 50B is located radially inward of the maximum width position 20W of the tire 1. A portion of the turned-up portion 50B radially outward from the bead filler 12 overlaps the axially outer side of the ply body 50A.

[0031] The above-mentioned rim strip rubber 13 further surrounds the portion of the carcass ply 50 surrounding the bead core 11 and the bead filler 12 .

[0032] Although the carcass ply 50 in the embodiment has a single layer structure, the carcass ply 50 may have a two-layer or more multi-layer structure.

[0033] The inner liner 60 covers the inner surface of the ply body portion 50A of the carcass ply 50 and the axially inner portion of the rim strip rubber 13 between the pair of beads 10 to form the tire cavity surface. The inner liner 60 may have a single layer structure, or a two-layer or more layer structure. The inner liner 60 is made of air-permeable resistant rubber and prevents air in the tire cavity from leaking to the outside.

[0034] Here, the rubber used for the bead filler 12 has a hardness higher than at least the sidewall rubber 21 and the inner liner 60. The hardness of the rubber is a hardness measured by "JIS K6253-3:2012 durometer hardness type A".

[0035] For example, when the hardness of the sidewall rubber 21 is used as a standard, the hardness of the bead filler 12 is preferably about 1.2 to 2.3 times the hardness of the sidewall rubber 21. By setting the hardness at such a level, it is possible to ensure a balance between the flexibility of the tire and the rigidity in the vicinity of the bead 10. Moreover, the hardness of the tread rubber 35 is preferably relatively low from the viewpoint of good ground contact and low fuel consumption, and is preferably about 50 to 60 in terms of the above-mentioned durometer hardness type A.

[0036] The above is the internal structure of the tire 1 according to the embodiment. Next, the tread pattern 39 formed on the tread surface 36 will be described with reference to Fig. 2. Note that Fig. 2 shows the tire axial direction X and the tire circumferential direction G. The tread pattern 39 of the embodiment is a point-symmetric pattern that does not change even when rotated 180 degrees with respect to the center of the total width of the tire 1. In other words, the tread pattern 39 has a point-symmetric shape with respect to an arbitrary point on the tire equator S2 as the symmetric point.

[0037] The tread pattern 39 includes a plurality of lands 70 and a plurality of main grooves 80 between the lands 70. Each of the lands 70 is a rib-shaped protrusion extending in the circumferential direction of the tire, and each of the main grooves 80 is a circumferential groove extending in the circumferential direction of the tire.

[0038] The multiple lands 70 include a central land 71 arranged in the center of the tire axial direction, a pair of shoulder lands 72 on both sides of the tire axial direction, and a pair of intermediate lands 73 arranged between the central land 71 and each shoulder land 72. The multiple main grooves 80 include a pair of first main grooves 81 between the central land 71 and each intermediate land 73, and a pair of second main grooves 82 between each intermediate land 73 and each shoulder land 72. The pair of first main grooves 81 are the main grooves that are closest to the tire equator S2 in the tire axial direction among the multiple main grooves 80. The pair of second main grooves 82 are main grooves arranged axially outboard of each first main groove 81. The second main groove 82 of the embodiment is an example of a shoulder main groove of the present disclosure that is adjacent to the axially inner side of the shoulder land 72.

[0039] An auxiliary groove 83 is formed in the widthwise center of the central land 71. The auxiliary groove 83 is aligned along the tire equator S2.

[0040] A plurality of first notch grooves 75 communicating with the first main groove 81 are formed at intervals in the tire circumferential direction on both widthwise ends of the central land 71. The first notch grooves 75 are relatively short grooves with a groove width exceeding 1 mm. Each of the first notch grooves 75 extends from an opening base end communicating with the first main groove 81 at an incline with respect to the tire circumferential direction and terminates without reaching the sub-groove 83. The first notch groove 75 on one side (right side in FIG. 2) of both widthwise ends of the central land 71 and the first notch groove 75 on the other side (left side in FIG. 2) have inclination directions opposite to each other, and the first notch grooves 75 spaced apart in the widthwise direction are arranged to face each other as a pair. The intervals between the first notch grooves 75 arranged in the tire circumferential direction may be equal or unequal. The first notched groove 75 of the embodiment is an example of a groove that intersects with the tire circumferential direction and communicates with the main groove 80 (first main groove 81).

[0041] The axial length M1 of each of the first notched grooves 75 is preferably 70% or less of the width W1 of the central land 71 in which the first notched groove 75 is formed, and more preferably 15% to 70%.

[0042] A plurality of second notch grooves 76 communicating with the second main groove 82 are formed at intervals in the tire circumferential direction on each edge of the intermediate land 73 on the outer side in the tire width direction. The second notch grooves 76 are relatively short grooves with a groove width exceeding 1 mm. Each second notch groove 76 extends from an opening base end communicating with the second main groove 82 at an incline with respect to the tire circumferential direction and terminates near the center of the intermediate land 73 in the width direction. The second notch groove 76 of the intermediate land 73 on one side (right side in FIG. 2) and the second notch groove 76 of the intermediate land 73 on the other side (left side in FIG. 2) have inclination directions opposite to each other, and the second notch grooves 76 spaced apart in the tire axial direction are arranged to face each other as a pair. The intervals between the second notch grooves 76 arranged in the tire circumferential direction may be equal or unequal. The second notched groove 76 of the embodiment is an example of a groove that intersects with the tire circumferential direction and communicates with the main groove 80 (second main groove 82).

[0043] The axial length M2 of each of the second notched grooves 76 is preferably 70% or less of the width W2 of the intermediate land 73 in which the second notched groove 76 is formed, and more preferably 30% or more and 70% or less.

[0044] A plurality of slits 77 are formed in each shoulder land 72 at intervals in the tire circumferential direction, and further, composite grooves 78 are formed between each of the slits 77 .

[0045] The slit 77 is a groove with a groove width exceeding 1 mm. The slit 77 has an arc shape that is gently convex on one side in the tire circumferential direction, and generally extends in a direction intersecting the tire circumferential direction. The slit 77 extends from the tire radial outer end 21a of the sidewall 20 toward the second main groove 82 while drawing an arc, and terminates without reaching the second main groove 82. The axially outer end 77b of the slit 77 opens to the tire radial outer end 21a of the sidewall 20.

[0046] The axial length of the slit 77 is, for example, about 70% to 90% of the width of the shoulder land 72. The axial distance L1 between the axially inner end 77a of the slit 77 and the second main groove 82 is, for example, preferably 3% or more, and more preferably 3% to 10% of the contact width C of the tread surface 36. For example, it is preferable that the above L1 be 5 mm or more.

[0047] 1, when the maximum depth of the slit 77 is D2 and the depth of the second main groove 82 adjacent to the slit 77 is D1, it is preferable that D2 satisfies (D1-2.4)≦D2≦(D1-1.6). This is to ensure that the depth of the slit 77 is not too large and is appropriate. If the depth is too large, the rolling resistance increases, and if the depth is too small, the slit 77 is easily worn away, which may result in a poor appearance, for example.

[0048] The composite groove 78 includes an outer slit 78a on the outer side in the tire axial direction, and an inner sipe 78b on the inner side in the tire axial direction that communicates with the outer slit 78a. The outer slit 78a is a groove with a groove width exceeding 1 mm, for example, a groove width of 2.0 mm to 5.0 mm. The inner sipe 78b is a groove with a groove width of 1 mm or less, for example, a groove width of 0.8 mm or less. The composite groove 78 has an arc shape along the slit 77 as a whole. The composite groove 78 is formed between the second main groove 82 and the end 21a of the sidewall 20 on the outer side in the tire radial direction, and crosses the shoulder land 72. The outer slit 78a on the outer side in the tire axial direction is open to the sidewall 20, and the inner sipe on the inner side in the tire axial direction communicates with the second main groove 82.

[0049] The circumferential intervals of each of the slits 77 and each of the composite grooves 78 aligned in the tire circumferential direction may be equal or unequal.

[0050] In the tire 1 of the embodiment having the above-mentioned internal structure and tread pattern 39, as described above, when the relationship between the ground contact width C of the tread surface 36 of the tread 30 and the width B of the belt 31 at a load of 70% of the maximum load in the tire standard JATMA is 105% or more and 110% or less, both ends of the belt 31 on the outer side in the tire axial direction reach the vicinity of the shoulder 40, and the width of the belt 31 can be said to be relatively large. As a result, in the vicinity of the shoulder 40, the binding force by the belt 31 is large, the rigidity is improved, and distortion is less likely to occur. Therefore, the camber thrust force of the tire 1 is large, and as a result, the wandering performance is improved. Note that if B / C is less than 105%, the camber thrust force may be insufficient and the wandering performance may not be fully exhibited. On the other hand, if B / C is more than 110%, the width of the belt 31 is too large, which may cause design problems and make it practically impossible to manufacture.

[0051] Here, when the width B of the belt 31 is increased, the mass of the tire 1 also increases with the increase in the mass of the belt 31. The increase in tire mass leads to an increase in rolling resistance. Meanwhile, when grooves extending in a direction intersecting the tire circumferential direction are formed, the grooves also tend to increase the rolling resistance. Therefore, in the tire 1 of the embodiment, the increase in rolling resistance is suppressed by reducing the length of the multiple slits 77 formed in the shoulder land 72 so as to extend in a direction intersecting the tire circumferential direction and having a relatively large groove width.

[0052] As a means for reducing the length of the slits 77, as described above, the slits 77 are terminated without reaching the second main groove 82, and further, the axial distance L1 between the axially inner end 77a of the slits 77 and the second main groove 82 is set to 3% or more of the contact width C of the tread surface 36. This ensures a large flat area of ​​the shoulder land 72 even with the slits 77, resulting in reduced rolling resistance.

[0053] As described above, in the tire 1 of the embodiment, the ratio B / C of the width B of the belt 31 to the contact width C of the tread surface 36 of the tread 30 is 105% or more and 110% or less, and the axially inner end 77a of the slit 77 of the shoulder land 72 does not communicate with the second main groove 82 but terminates within the shoulder land 72, thereby achieving a good balance between improved wandering performance and reduced rolling resistance.

[0054] As described above, the axial length of the notched grooves 75 and 76 formed in the central land 71 and the intermediate land 73 is set to 70% or less of the width of each land 71, 72. This ensures that each land 71, 72 has as much flat area as possible, which contributes to suppressing rolling resistance.

[0055] The tire 1 of the above embodiment provides the following advantages.

[0056] (1) A tire 1 according to an embodiment is a pneumatic tire having a tread 30. The tread 30 includes a tread surface 36 that comes into contact with a road surface and a belt 31 embedded within the tread 30. The tread surface 36 includes a plurality of lands 70 extending in a tire circumferential direction and a plurality of main grooves 80 that extend in the tire circumferential direction and divide the plurality of lands 70 in the tire axial direction. The lands 70 have shoulder lands 72 that are disposed at ends of the tread surface 36 in the tire axial direction. The main grooves 80 are spaced apart from the shoulder lands 72. The shoulder land 72 has a second main groove 82 as a shoulder main groove adjacent to the axially inner side of the second main groove 82, and the shoulder land 72 has a plurality of slits 77 extending in a direction intersecting the circumferential direction of the tire and aligned in the circumferential direction of the tire, and a ratio B / C of a width B of the belt 31 to a contact width C of the tread surface 36 at a load of 70% of the maximum load in the JATMA tire standard is 105% or more and 110% or less, and an axially inner end 77a of the slit 77 does not communicate with the second main groove 82 and terminates within the shoulder land 72.

[0057] As a result, the tire 1 exhibits a good balance between improved wandering performance and reduced rolling resistance.

[0058] (2) In the tire 1 according to the embodiment (1) above, the axial distance L1 from the axially inner end 77a of the slit 77 to the second main groove 82 is preferably 3% or more of the contact width C.

[0059] This improves the effect of suppressing rolling resistance.

[0060] (3) In the tire 1 according to the above embodiments (1) and (2), the shoulder land 72 further has a plurality of composite grooves 78 extending in a direction intersecting the tire circumferential direction and aligned in the tire circumferential direction, and the composite grooves 78 have outer slits 78a arranged axially outward on the shoulder land 72, and inner sipes 78b arranged axially inward of the outer slits 78a, continuous with the outer slits 78a, and communicating with the shoulder main groove, and it is preferable that the width of the outer slits 78a is 2.0 mm or more and 5.0 mm or less, and the width of the inner sipes 78b is 0.8 mm or less.

[0061] This makes it possible to achieve both drainage performance provided by the outer slits 78a and grip performance provided by the inner sipes 78b.

[0062] (4) In the tire 1 according to the above embodiments (1) to (3), the multiple lands 70 further include a central land 71 arranged in the axial center of the tire, and an intermediate land 73 arranged between the central land 71 and the shoulder land 72, and each of the central land 71 and the intermediate land 73 has a first notched groove 75 and a second notched groove 76 as grooves that intersect in the tire circumferential direction and communicate with the main groove 80 (first main groove 81, second main groove 82), and it is preferable that the axial lengths M1, M2 of each of these notched grooves 75, 76 are 70% or less of the widths W1, W2 of the central land 71 and the intermediate land 73, respectively.

[0063] This ensures that each of the lands 71, 72 has a large flat area, improving the effect of suppressing rolling resistance.

[0064] (5) In the tire 1 according to the above embodiments (1) to (4), when the depth of the second main groove 82, which is the shoulder main groove, is D1 (mm), and the maximum depth of the slit 77 is D2 (mm), it is preferable that (D1-2.4)≦D2≦(D1-1.6).

[0065] This ensures that the depth of the slits 77 is not too large and is an appropriate depth, thereby suppressing an increase in rolling resistance, and suppressing the susceptibility of the slits 77 to wear and the deterioration of their appearance.

[0066] The present invention is not limited to the above-described embodiment, and even if modifications and improvements are made within the scope of the present invention, they will still be included in the scope of the present invention. EXAMPLES

[0067] Examples will be described below. Examples 1 to 3 having the same configuration as the above embodiment and varying the above B / C and the ratio of L1 to the contact width C of the tread surface 36 (L1 / contact width C) were actually manufactured, and the camber thrust force and RRC (rolling resistance coefficient) were measured. The tire air pressure during the measurement was 230 kPa and the load was 457 kgf. Meanwhile, tires were actually manufactured for Comparative Examples 1 to 3 in which either B / C or L1 / contact width C deviates from the present invention, and the camber thrust force and RRC (rolling resistance coefficient) were measured in the same manner. Table 1 shows the data of Examples 1 to 3 and Comparative Examples 1 to 3, and also lists the measurement results. The L1 / contact width C of Comparative Examples 1 and 2 being "0" means that the axially inner side of the slit 77 of the embodiment extends to the second main groove 82 and communicates, and does not terminate within the shoulder land 72.

[0068] RRC attached one tire to a drum-type tire testing machine and measured the rolling resistance coefficient. The method of measuring the camber thrust force was to give the tire a camber angle of 8 degrees and measure the lateral force generated during driving as the camber thrust force.

[0069] For the camber thrust force and RRC in Table 1, each value of Comparative Example 1 is assigned an index of 100, and the other values ​​are evaluated as an index in comparison with Comparative Example 1. For the camber thrust force, the larger the index evaluation value, the better the wandering performance is. For the RRC, the smaller the index evaluation value, the better the rolling resistance is.

[0070] [Table 1]

[0071] According to Table 1, as the ratio B / C of the width B of the belt 31 to the ground contact width C of the tread surface 36 increases, the camber thrust force increases and the anti-wandering performance improves, but on the other hand, the tire mass increases and the rolling resistance tends to deteriorate. Here, in Examples 1 to 3 where L1 / ground contact width C satisfies 3% or more, the rolling resistance also tends to be suppressed. Therefore, when B / C is 105% or more and 110% or less and L1 / ground contact width C is 3% or more, the improvement of the anti-wandering performance and the suppression of the rolling resistance are exhibited in a well-balanced manner. [Explanation of symbols]

[0072] 1...tire (pneumatic tire), 30...tread, 31...belt, 36...tread surface, 70...land, 71...center land, 72...shoulder land, 73...intermediate land, 75...first notched groove (groove), 76...second notched groove (groove), 77...slit, 77a...axially inner end of slit, 78...compound groove, 78a...outer slit, 78b...inner sipe, 80...main groove, 82...second main groove (shoulder main groove).

Claims

1. A pneumatic tire having a tread, The tread includes a tread surface that comes into contact with a road surface and a belt embedded in the tread, The tread surface includes a plurality of lands extending in a tire circumferential direction, and a plurality of main grooves extending in the tire circumferential direction and dividing the plurality of lands in the tire axial direction, The land has a shoulder land arranged at an end of the tread surface in the tire axial direction, The main groove includes a shoulder main groove adjacent to the shoulder land on the axially inner side of the tire, The shoulder land has a plurality of slits extending in a direction intersecting the tire circumferential direction and aligned in the tire circumferential direction, A ratio B / C of a width B of the belt to a contact width C of the tread surface when a load of 70% of the maximum load in the tire standard JATMA is 105% or more and 110% or less, The pneumatic tire has an axially inner end of the slit that does not communicate with the shoulder main groove and terminates within the shoulder land.

2. The pneumatic tire according to claim 1 , wherein an axial distance L1 between the axially inner end of the slit and the shoulder main groove is 3% or more of the contact width C.

3. The shoulder land further has a plurality of composite grooves extending in a direction intersecting the tire circumferential direction and aligned in the tire circumferential direction, The composite groove has an outer slit arranged axially outward of the shoulder land, and an inner sipe arranged axially inward of the outer slit, continuous with the outer slit, and communicating with the shoulder main groove, The pneumatic tire according to claim 1 or 2, wherein a width of the outer slit is equal to or greater than 2.0 mm and equal to or less than 5.0 mm, and a width of the inner sipe is equal to or less than 0.8 mm.

4. The plurality of lands further include a central land disposed at a center in the tire axial direction, and an intermediate land disposed between the central land and the shoulder land, Each of the central land and the intermediate land has a groove that intersects with the main groove in the tire circumferential direction, The pneumatic tire according to claim 1 , wherein axial lengths M1, M2 of the grooves are 70% or less of widths W1, W2 of the central land and intermediate land, respectively.

5. The pneumatic tire according to claim 1 or 2, wherein, when the depth of the shoulder main groove is D1 (mm) and the maximum depth of the slit is D2 (mm), (D1-2.4)≦D2≦(D1-1.6).

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