tire

Abstract

To provide a tire 2 which can achieve enhancement of brake performance without accompanying significant increase in rolling resistance.SOLUTION: A tire 2 comprises a tread 4, a pair of side walls 6, a pair of beads 10 and a carcass 12. The bead 12 comprises a core 30 and an apex 32. Ratio (A / H) of height A of the apex 32 to cross section height H is 5% or more and 15% or less. In meridian cross section of the tire 2 with standard state, profile of side surface S containing maximum width position PW contains two circular arcs which adjoin each other in the maximum width position PW. One circular arc of the two circular arcs which positions inside of the maximum width position PW in a radial direction is a first circular arc and the other circular arc which positions outside of the maximum width position is a second circular arc. And then, ratio (R1 / R2) of radius R1 of the first circular arc to radius R2 of the second circular arc is 70% or more and 91% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, in the following Patent Document 1, tire performance such as durability, rolling resistance, and ride comfort is controlled by adjusting the contour from the shoulder portion of the tread to the sidewall, i.e., the contour of the side surface. In order to control tire performance, the tire contour may be adjusted in addition to the physical properties and arrangement of the elements constituting the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-121899 A Summary of the Invention [Problem to be solved by the invention]

[0004] Considering the impact on the environment, tires with low rolling resistance are in demand. Using low heat generation rubber in the tread reduces the rolling resistance of the tire. Using low heat generation rubber in the tread reduces the coefficient of friction of the tire. In this case, braking performance decreases. Increasing the coefficient of friction of the tire to improve braking performance increases the rolling resistance.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a tire that can achieve improved braking performance without a significant increase in rolling resistance. [Means for solving the problem]

[0006] A tire according to one aspect of the present invention includes a tread that comes into contact with a road surface, a pair of sidewalls that are connected to an end of the tread and positioned radially inward of the tread, a pair of beads that are positioned radially inward of the sidewalls, and a carcass that is positioned inward of the tread and the pair of sidewalls. The bead includes a core and an apex that is positioned radially outward of the core. The ratio of the height of the apex to the cross-sectional height is 5% to 15%. In a meridian cross section in a state in which the tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 250 kPa, and no load is applied to the tire, the contour of the side surface including the maximum width position includes two arcs that are tangent at the maximum width position, and of the two arcs, the arc positioned radially inward of the maximum width position is a first arc, and the arc positioned radially outward of the maximum width position is a second arc, and the ratio of the radius of the first arc to the radius of the second arc is 70% to 91%.

[0007] Preferably, in the tire, the radius of the first circular arc is equal to or greater than 50 mm and equal to or less than 65 mm.

[0008] Preferably, in the tire, the carcass includes a carcass ply. The carcass ply includes a ply body that spans between one bead and the other bead, and a pair of turn-up portions that are continuous with the ply body and turn up around the bead from the inside to the outside in the axial direction. A ratio of a radial distance from a bead base line to an end of the turn-up portion to a radial distance from the bead base line to the maximum width position is 48% or more and 68% or less.

[0009] Preferably, in the tire, a plurality of land portions are formed by cutting a plurality of circumferential grooves in the tread, and among the plurality of land portions, a land portion located on the outer side in the axial direction is a shoulder land portion, and a land portion located on the inner side of the shoulder land portion is a middle land portion. An outer surface of the middle land portion has an outwardly curved contour. The maximum height of the outer surface is 0.05 mm or more and 0.15 mm or less.

[0010] Preferably, in the tire, lateral sipes extending substantially in the axial direction are formed in the middle land portion, and edges of the lateral sipes are chamfered.

[0011] Preferably, in the tire, lateral grooves and lateral sipes extending substantially in the axial direction are formed in the shoulder land portion, and edges of the lateral grooves and the lateral sipes are chamfered. Effect of the Invention

[0012] According to the present invention, a tire can be obtained that can achieve improved braking performance without a significant increase in rolling resistance. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a part of a tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a bead portion of a tire. [Diagram 3] FIG. 3 is a development view showing the outer surface of the tread. [Figure 4] FIG. 4 is a cross-sectional view showing a portion of the tread. [Diagram 5] FIG. 5 is a cross-sectional view taken along line aa in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line bb in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0015] In this disclosure, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, and no load is applied to the tire is referred to as a standard state. A state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to 250 kPa, and no load is applied to the tire is referred to as a standard state.

[0016] In this disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a standard state. The dimensions and angles of each part in a meridian section of the tire that cannot be measured when the tire is mounted on a regular rim are measured by cutting the tire along a plane including the rotation axis, and the distance between the left and right beads in the tire section is measured so as to match the distance between the beads in the tire mounted on a regular rim.

[0017] A genuine rim is a rim that is specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are genuine rims.

[0018] Normal tire pressure means the internal pressure specified in the standard on which the tire is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0019] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0020] In this disclosure, the tread portion of a tire is the portion of the tire that comes into contact with the road surface, the bead portion is the portion of the tire that fits onto the rim, and the side portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire includes the following portions: a tread portion, a pair of bead portions, and a pair of side portions. The rim includes a seat and a flange. When the tire is mounted on the rim, the inner circumferential surface of the bead portion rests on the seat and the outer circumferential surface of the bead portion contacts the flange.

[0021] In the present disclosure, the loss tangent (also referred to as tan δ) at a temperature of 30°C of an element made of crosslinked rubber among the elements constituting a tire is measured in accordance with the provisions of JIS K6394 using a viscoelasticity spectrometer ("VES" manufactured by Iwamoto Seisakusho Co., Ltd.) under the following conditions. Initial distortion = 10% Dynamic strain = 2% Frequency = 10Hz Deformation mode = tension In this measurement, the test specimen is sampled from a tire. If it is not possible to sample the test specimen from a tire, the test specimen is sampled from a sheet-like crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressing and heating the rubber composition used to form the element to be measured at a temperature of 170°C for 12 minutes.

[0022] In the present disclosure, the hardness of an element made of crosslinked rubber among the elements constituting a tire is measured using a type A durometer at a temperature condition of 23° C. in accordance with the provisions of JIS K6253. When the hardness cannot be measured in a tire, a test piece made of crosslinked rubber obtained by pressing and heating the rubber composition used to form the element to be measured at a temperature of 170° C. for 12 minutes is used.

[0023] FIG 1 shows a part of a tire 2 according to one embodiment of the present invention. This tire 2 is a tire for passenger cars. In FIG 1, the tire 2 is mounted on a rim R. The rim R is a regular rim. Air is filled inside the tire 2, and the internal pressure of the tire 2 is adjusted. The tire 2 shown in FIG 1 is in a standard state.

[0024] The tire 2 mounted on the rim R is also referred to as a tire-rim assembly. The tire-rim assembly includes the rim R and the tire 2 mounted on the rim R.

[0025] 1 shows a part of a cross section (hereinafter also referred to as a meridian cross section) of the tire 2 taken along a plane including a rotation axis (not shown) of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. In FIG. 1, a dashed dotted line CL represents the equatorial plane of the tire 2.

[0026] In Fig. 1, the solid line BBL extending in the axial direction is the bead base line. This bead base line is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0027] In FIG. 1, the position indicated by the symbol PW is the axial outer end of the tire 2. If there is a decoration such as a pattern or lettering on the outer surface, the outer end PW is determined based on a virtual outer surface obtained by assuming that there is no decoration. The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 2, i.e., the cross-sectional width (see JATMA, etc.). The outer end PW is the position where the tire 2 shows its maximum width (hereinafter, the maximum width position). The maximum width position PW is determined for the tire 2 in a standard state.

[0028] The tire 2 includes a tread 4 , a pair of sidewalls 6 , a pair of clinches 8 , a pair of beads 10 , a carcass 12 , a belt 14 , a band 16 , a pair of chafers 18 , and an inner liner 20 .

[0029] The outer surface of the tread 4 comes into contact with the road surface. Grooves 22 are cut into the tread 4. This forms a tread pattern.

[0030] The grooves 22 constituting the tread pattern of the tire 2 include a circumferential groove 24 that extends continuously in the circumferential direction. In the tire 2, a plurality of circumferential grooves 24 arranged in parallel in the axial direction are cut into the tread 4. In the tire 2 shown in FIG. 1, three circumferential grooves 24 are cut into the tread 4. Of the three circumferential grooves 24, the circumferential groove 24 located on the outer side in the axial direction is the shoulder circumferential groove 24s. The circumferential groove 24 located on the inner side of the shoulder circumferential groove 24s in the axial direction is the middle circumferential groove 24m. In the tire 2, the middle circumferential groove 24m is located on the equatorial plane.

[0031] In this tire 2, there are no particular limitations on the arrangement, groove depth, and groove width of the circumferential grooves 24 engraved in the tread 4. General arrangement, groove depth, and groove width of the circumferential grooves 24 of the tire 2 are applied to this tread 4.

[0032] In Fig. 1, the position indicated by the symbol PC is the equator of the tire 2. The equator PC is the intersection point between the outer surface of the tread 4 and the equatorial plane. In this tire 2, the middle circumferential groove 24m is located on the equatorial plane, so the equator PC is determined based on a virtual outer surface obtained by assuming that the middle circumferential groove 24m does not exist.

[0033] 1, the length indicated by the symbol H is the section height (see JATMA, etc.) of the tire 2. The section height H is the radial distance from the bead base line to the equator PC. The section height H is measured with the tire 2 in a standard state.

[0034] The tread 4 has a base layer 26 and a cap layer 28. The base layer 26 covers the belt 14 and the band 16. The base layer 26 is made of a crosslinked rubber having low heat buildup. In the tire 2, the loss tangent of the base layer 26 at 30° C. is 0.11 or less.

[0035] The cap layer 28 is located radially outside the base layer 26. The cap layer 28 covers the entire base layer 26. The outer surface of the cap layer 28 is the outer surface of the tread 4. The cap layer 28 is made of a crosslinked rubber that takes into consideration abrasion resistance and grip performance. The loss tangent of the cap layer 28 is larger than that of the base layer. From the viewpoint of the contribution of the cap layer 28 to reducing rolling resistance, the loss tangent of the cap layer 28 is preferably 0.30 or less, and more preferably 0.20 or less.

[0036] Each sidewall 6 is continuous with an end of the tread 4. The sidewall 6 is located radially inward of the tread 4. The sidewall 6 extends from the end of the tread 4 toward the clinch 8 along the carcass 12. The sidewall 6 is made of crosslinked rubber in consideration of cut resistance.

[0037] Each clinch 8 is located radially inside the sidewall 6. The clinch 8 contacts the flange G of the rim R. The clinch 8 is made of crosslinked rubber in consideration of wear resistance.

[0038] Each bead 10 is located axially inside the clinch 8. Each bead 10 is located radially inside the sidewall 6. Each bead 10 includes a core 30 and an apex 32. Although not shown, the core 30 includes a steel wire.

[0039] The apex 32 is located radially outside the core 30. The apex 32 tapers outward. The apex 32 is made of crosslinked rubber having high rigidity. The hardness of the apex 32 is 80 or more and 98 or less. In FIG. 1, the position indicated by the symbol PA is the radial outer end (hereinafter also referred to as the tip) of the apex 32.

[0040] The carcass 12 is located on the inside of the tread 4, the pair of sidewalls 6, and the pair of clinches 8. The carcass 12 bridges between one bead 10 and the other bead 10. The carcass 12 has a radial structure.

[0041] The carcass 12 includes at least one carcass ply 34. From the viewpoint of reducing rolling resistance, the carcass 12 is preferably configured with one carcass ply 34.

[0042] The carcass 12 of the tire 2 is composed of one carcass ply 34. The carcass ply 34 includes a ply body 34a that spans between one bead 10 and the other bead 10, and a pair of turn-up portions 34b that are continuous with the ply body 34a and turn up around each bead 10 from the inside to the outside in the axial direction. In the radial direction, the end of the turn-up portion 34b is located inside the maximum width position PW. The end of the turn-up portion 34b is located between the ply body 34a and the sidewall 6. In the zone from the tip PA of the apex to the end of the turn-up portion 34b, the turn-up portion 34b is joined to the ply body 34a.

[0043] Although not shown, the carcass ply 34 includes a number of carcass cords arranged in parallel. Each carcass cord crosses the equator plane. The carcass cord is a cord made of an organic fiber. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0044] The belt 14 is located radially inside the tread 4. The belt 14 is laminated on the carcass 12 from the radially outside. In the tire 2, the axial width of the belt 14 is 65% or more and 85% or less of the cross-sectional width.

[0045] The belt 14 is composed of at least two layers 36 laminated in the radial direction. The belt 14 of the tire 2 is composed of two layers 36 laminated in the radial direction. Of the two layers 36, the layer 36 located on the inner side is the inner layer 36a, and the layer 36 located on the outer side is the outer layer 36b. As shown in FIG. 1, the inner layer 36a is wider than the outer layer 36b. The length from an end of the outer layer 36b to an end of the inner layer 36a is 3 mm or more and 10 mm or less.

[0046] Although not shown, each of the inner layer 36a and the outer layer 36b includes a number of belt cords arranged in parallel. Each belt cord is inclined with respect to the equator plane. The material of the belt cord is steel.

[0047] The band 16 is located between the tread 4 and the belt 14 in the radial direction. The band 16 is laminated on the belt 14 on the inside of the tread 4. The band 16 covers the entire belt 14. The band 16 is wider than the belt 14. The length from the end of the belt 14 to the end of the band 16 is 3 mm or more and 7 mm or less.

[0048] Although not shown, the band 16 includes a band cord wound in a spiral shape. The band cord extends substantially in the circumferential direction. Specifically, the angle that the band cord forms with the circumferential direction is 5° or less. The band 16 has a jointless structure. In the tire 2, a cord made of an organic fiber is used as the band cord. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0049] The band 16 of the tire 2 includes a full band 16F and a pair of edge bands 16E. The full band 16F has both ends facing each other across the equatorial plane. The ends of the full band 16F are located outside the ends of the belt 14 in the axial direction. The full band 16F is laminated on the belt 14. The full band 16F covers the entire belt 14 from the outside in the radial direction. The pair of edge bands 16E are arranged spaced apart in the axial direction across the equatorial plane. The edge band 16E is laminated on the full band 16F. The edge band 16E covers the ends of the full band 16F from the outside in the radial direction. The band 16 may be composed of the full band 16F or a pair of edge bands 16E.

[0050] Each chafer 18 is located radially inward of the bead 10. The chafer 18 contacts the seat E of the rim R. The chafer 18 of the tire 2 is made of a cloth and rubber impregnated into the cloth.

[0051] The inner liner 20 is positioned inside the carcass 12. The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of a crosslinked rubber having a low gas permeability coefficient. The inner liner 20 maintains the internal pressure of the tire 2.

[0052] The profile of the tire 2 is obtained, for example, by measuring the outer surface shape of the tire 2 in a standard state with a displacement sensor. In a meridian cross section, the profile of the outer surface of the tire 2 (hereinafter, tire outer surface TS) is formed by connecting multiple contour lines made of straight lines or circular arcs. In this disclosure, a contour line made of a straight line or a circular arc is simply referred to as a contour line. A contour line made of a straight line is referred to as a straight contour line, and a contour line made of a circular arc is referred to as a curved contour line.

[0053] The tire outer surface TS includes a tread surface T and a pair of side surfaces S connected to the ends of the tread surface T. In this disclosure, the contour of the tread surface T is described by the contour of a virtual outer surface (also referred to as a virtual tread surface) obtained assuming that there are no grooves. The tread surface T includes the above-mentioned equator PC. The contour of the side surfaces S is described by the contour of a virtual outer surface (also referred to as a virtual side surface) obtained assuming that there are no decorations such as patterns or letters. The side surfaces S include the above-mentioned maximum width position PW.

[0054] In the meridian cross section, the contour of the tread surface T includes a plurality of curved contour lines having different radii. In this tire 2, the curved contour line having the smallest radius among the plurality of curved contour lines included in the contour of the tread surface T is located at an end portion of the tread surface T and connects to the side surface S. In the meridian cross section, the contour of the tire outer surface TS includes a curved portion that is a curved contour line that is composed of an arc having the smallest radius among the plurality of curved contour lines included in the contour of the tread surface T and connects to the side surface S, at an end portion of the tread surface T. In FIG. 1, this curved portion is indicated by the symbol RS.

[0055] In the contour of the tire outer surface TS, the curved portion RS is tangent to a contour line adjacent to the axially inner side (hereinafter, referred to as an inner adjacent contour line NT) at a tangent point CT. This curved portion RS is tangent to a contour line constituting the contour of the side surface S adjacent to the axially outer side (hereinafter, referred to as an outer adjacent contour line NS) at a tangent point CS. This contour of the tire outer surface TS includes an inner adjacent contour line NT located axially inside the curved portion RS and tangent to the curved portion RS, and an outer adjacent contour line NS located axially outside the curved portion RS and tangent to the curved portion RS.

[0056] In FIG. 1, solid line LT is a tangent to curved portion RS at a tangent point CT between the inner adjacent contour line NT and curved portion RS. Solid line LS is a tangent to curved portion RS at a tangent point CS between the outer adjacent contour line NS and curved portion RS. The position indicated by the symbol PE is the intersection point between the tread surface T and a straight line extending in the radial direction that passes through the intersection point of the tangent line LT and the tangent line LS. In this tire 2, this intersection point PE is the tread reference edge. The tangent point CS is the boundary between the tread surface T and the side surface S.

[0057] In Fig. 1, the symbol B1 denotes a specific position on the side surface S. The solid line LG is a straight line that passes through the radial outer end of the flange G and extends in the radial direction. The specific position B1 is the intersection of this straight line LG and the side surface S. This specific position B1 is the flange reference position.

[0058] In FIG. 1, the symbol B2 is a specific position on the side surface S. The length indicated by the double arrow D is the radial distance from the bead baseline to the specific position B2. In this tire 2, the radial distance D is set to 0.77 times the section height H. The specific position B2 is a position on the side surface S where the radial distance D from the bead baseline is 0.77 times the section height H. This specific position B2 is the buttress reference position.

[0059] As described above, the side surface S includes the maximum width position PW. In a meridian cross section, the contour of the side surface S includes two curved contours, i.e., circular arcs, that are tangent at the maximum width position PW. Of the two circular arcs that are tangent at the maximum width position PW, the arc located inside the maximum width position PW in the radial direction is the first circular arc, and the arc located outside the maximum width position PW is the second circular arc. The curved contour consisting of the first circular arc is also referred to as the first curved contour, and the curved contour consisting of the second circular arc is also referred to as the second curved contour.

[0060] 1, the arrow indicated by the symbol R1 indicates the radius of the first circular arc, and the arrow indicated by the symbol R2 indicates the radius of the second circular arc. The center of the first circular arc and the center of the second circular arc are located on a straight line that passes through the maximum width position PW and extends in the axial direction.

[0061] In this tire 2, the radius R1 of the first circular arc is smaller than the radius R2 of the second circular arc. Specifically, the ratio (R1 / R2) of the radius R1 of the first circular arc to the radius R2 of the second circular arc is equal to or less than 91%. This allows the carcass 12 to be disposed further outward in the meridian cross section. Since a long carcass 12 is configured, the longitudinal stiffness of this tire 2 is effectively reduced. Since the longitudinal stiffness is low, the tire 2 can ensure a wide contact surface during braking when a large load is applied. From this viewpoint, the ratio (R1 / R2) is preferably equal to or less than 90%, more preferably equal to or less than 88%, and further preferably equal to or less than 86%.

[0062] In the tire 2, the ratio (R1 / R2) of the radius R1 of the first circular arc to the radius R2 of the second circular arc is 70% or more. This appropriately maintains the contact area between the bead portion and the flange G. Since the variation in friction and strain caused by repeated deformation and restoration of the bead portion during running is effectively suppressed, good durability is maintained. From this viewpoint, the ratio (R1 / R2) is preferably 75% or more, more preferably 78% or more, and even more preferably 80% or more.

[0063] 1, the position indicated by the symbol PM is the center of the axial width of the contact surface of the apex 32 with the core 30. The length indicated by the symbol A is the radial distance from the width center PM to the tip PA of the apex 32. In this tire 2, the radial distance A is the height of the apex 32.

[0064] In this tire 2, the ratio (A / H) of the height A of the apex 32 to the cross-sectional height H is 15% or less. This ratio (A / H) is usually set to about 20% or more. The height A of this apex 32 is low. The apex 32 having a low height A contributes to reducing the vertical stiffness. This apex 32 also contributes to positioning the carcass 12 further outward in the meridian cross section. In this tire 2, the vertical stiffness is effectively reduced. This apex 32 contributes to ensuring a large contact area. This apex 32 also contributes to reducing rolling resistance.

[0065] In this tire 2, the ratio (A / H) of the height A of the apex 32 to the cross-sectional height H is 5% or more. In this tire 2, the apex 32 is configured to have the required height A. This apex 32 effectively restrains the core 30 in the bead portion assembled to the rim R. Since the movement of the core 30 during running is suppressed, the tire 2 ensures the required durability.

[0066] In this tire 2, the ratio (R1 / R2) of the radius R1 of the first circular arc to the radius R2 of the second circular arc is 91% or less, and the ratio (A / H) of the height A of the apex 32 to the cross-sectional height H is 15% or less. In this tire 2, the contact width is wider and the contact area is increased. The increase in the contact area increases the friction coefficient of the tire 2. In this tire 2, good braking performance can be obtained even if low-heat-generating rubber is used in the tread 4. There is no need to use heat-generating rubber in the tread 4 that prioritizes grip in order to increase the friction coefficient. This tire 2 can achieve improved braking performance without a significant increase in rolling resistance.

[0067] In this tire 2, a ratio (R1 / R2) of a radius R1 of the first circular arc to a radius R2 of the second circular arc is 70% or more, and a ratio (A / H) of a height A of the apex 32 to a cross-sectional height H is 5% or more. In this tire 2, necessary durability is ensured.

[0068] In tire 2, the ratio (R1 / R2) of the radius R1 of the first circular arc to the radius R2 of the second circular arc is equal to or greater than 70% and equal to or less than 91%, and the ratio (A / H) of the height A of the apex 32 to the cross-sectional height H is equal to or greater than 5% and equal to or less than 15%. Tire 2 can achieve improved braking performance without a significant increase in rolling resistance or a significant decrease in durability.

[0069] In the tire 2, the radius R1 of the first circular arc is preferably 50 mm or more and 65 mm or less. By setting the radius R1 to 50 mm or more, the contact area between the bead portion and the flange G is appropriately maintained. Since the variation in friction and strain caused by the repeated deformation and restoration of the bead portion during running is effectively suppressed, good durability is maintained. From this viewpoint, the radius R1 is more preferably 53 mm or more, and further preferably 55 mm or more. By setting the radius R1 to 65 mm or less, the carcass 12 can be disposed further outward in the meridian cross section. Since a long carcass 12 is formed, the vertical rigidity of the tire 2 is effectively reduced. During braking when a large load is applied, the tire 2 can secure a wide contact surface. With the tire 2, good braking performance is obtained. From this viewpoint, the radius R1 is more preferably 62 mm or less, and further preferably 60 mm or less.

[0070] In Fig. 1, the position indicated by the reference character G1 is the end point of the first circular arc when the maximum width position PW is the start point of the first circular arc. The length indicated by the reference character C1 is the radial distance from the maximum width position PW to the end point G1. The length indicated by the reference character W1 is the radial distance from the maximum width position PW to the flange reference position B1.

[0071] In the tire 2, from the viewpoint that the portion of the side surface S represented by the first circular arc can effectively contribute to reducing the vertical stiffness, the ratio (C1 / W1) of the radial distance C1 from the maximum width position PW to the end point G1 of the first circular arc to the radial distance W1 from the maximum width position PW to the flange reference position B1 is preferably 0.70 or more, more preferably 0.80 or more, and even more preferably 0.90 or more. The ratio (C1 / W1) is particularly preferably 1.00.

[0072] In Fig. 1, the position indicated by the reference character G2 is the end point of the first circular arc when the maximum width position PW is the start point of the second circular arc. The length indicated by the reference character C2 is the radial distance from the maximum width position PW to the end point G2. The length indicated by the reference character W2 is the radial distance from the maximum width position PW to the buttress reference position B2.

[0073] In this tire 2, from the viewpoint that the portion of the side surface S represented by the second circular arc can effectively contribute to reducing the vertical stiffness, the ratio (C2 / W2) of the radial distance C2 from the maximum width position PW to the end point G2 of the second circular arc to the radial distance W2 from the maximum width position PW to the buttress reference position B2 is preferably 0.70 or more, more preferably 0.80 or more, and even more preferably 0.90 or more. It is particularly preferable that the ratio (C2 / W2) is 1.00.

[0074] Fig. 2 shows a part of the meridian cross section shown in Fig. 1. Fig. 2 shows a bead portion of the tire 2. In Fig. 2, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper surface of Fig. 2 is the circumferential direction of the tire 2.

[0075] In Fig. 2, the position indicated by the symbol PF is the end of the turn-up portion 34b. The length indicated by the symbol F is the radial distance from the bead baseline to the end PF of the turn-up portion 34b. This radial distance F is the height of the turn-up portion 34b. The length indicated by the symbol W is the radial distance from the bead baseline to the maximum width position PW. This radial distance W is the maximum width height.

[0076] In the tire 2, the ratio (F / W) of the height F of the folded-back portion 34b to the maximum width W is preferably equal to or greater than 48% and equal to or less than 68%.

[0077] By setting the ratio (F / W) to 48% or more, concentration of strain at the end PF of the turn-up portion 34b is suppressed when a force is applied to the bead portion. With this tire 2, good durability can be obtained. From this viewpoint, it is more preferable that the ratio (F / W) is 50% or more. By setting the ratio (F / W) to 68% or less, vertical rigidity can be effectively reduced, so that the tire 2 can ensure a wide contact surface during braking when a large load is applied. With this tire 2, good braking performance can be obtained. The low turn-up portion 34b also contributes to reducing rolling resistance. From this viewpoint, it is more preferable that the ratio (F / W) is 65% or less.

[0078] 2, a solid line LAM is a straight line passing through the tip PA and width center PM of the apex 32. A solid line LAF is a straight line passing through the tip PA and the end PF of the folded-back portion 34b of the apex 32. Angle θ is the angle between the straight line LAM and the straight line LAF.

[0079] In this tire 2, when the ratio (F / W) of the height F of the turn-back portion 34b to the maximum width height W is 48% or more and 68% or less, it is preferable that the angle θ between a straight line LAM passing through the tip PA of the apex 32 and the width center PM, and a straight line LAF passing through the tip PA of the apex 32 and the end PF of the turn-back portion 34b is 35 degrees or more and 50 degrees or less.

[0080] By setting the angle θ to 35 degrees or more, the carcass 12 can be disposed further outward in the meridian cross section. Since a long carcass 12 is formed, the vertical rigidity of the tire 2 is effectively reduced. From this viewpoint, the angle θ is more preferably 38 degrees or more, and more preferably 40 degrees or more. By setting the angle θ to 50 degrees or less, the contact area between the bead portion and the flange G is appropriately maintained. Since the variation in friction and distortion caused by repeated deformation and restoration of the bead portion during running is effectively suppressed, good durability is maintained. From this viewpoint, the angle θ is more preferably 48 degrees or less, and more preferably 45 degrees or less.

[0081] Fig. 3 shows a part of the outer surface of the tread 4. In Fig. 3, the left-right direction is the axial direction of the tire 2, and the up-down direction is the circumferential direction of the tire 2. The direction perpendicular to the plane of Fig. 2 is the radial direction of the tire 2. In Fig. 3, the tread reference edge PE located on the left side is the first tread reference edge PE1, and the tread reference edge PE located on the right side is the second tread reference edge PE2. When this tire 2 is mounted on a vehicle, the first tread reference edge PE1 is located outside the vehicle in the width direction.

[0082] As described above, the tread pattern is formed by cutting grooves 22 into the tread 4 of the tire 2. Of the grooves 22 that form the tread pattern, grooves having a groove width of 1.5 mm or less are called sipes.

[0083] In the present disclosure, a groove extending in a generally axial direction means that the angle that the groove makes with respect to the axial direction is 45 degrees or less. A sipe extending in a generally axial direction is also called a transverse sipe.

[0084] As described above, in this tire 2, a plurality of circumferential grooves 24 are cut into the tread 4. This forms a plurality of land portions 38. In this tire 2, three circumferential grooves 24 are cut into the tread 4, forming four land portions 38 arranged in parallel in the axial direction. Of the four land portions 38, the land portion 38 located on the outer side in the axial direction is the shoulder land portion 38s. The land portion 38 located on the inner side of the shoulder land portion 38s is the middle land portion 38m.

[0085] A lateral groove 40 is formed in the shoulder land portion 38s. The lateral groove 40 has a groove width of at least 2.0 mm or more. The lateral groove 40 has an end in the shoulder land portion 38s. The lateral groove 40 extends from this end toward the tread reference edge PE. The lateral groove 40 extends in a substantially axial direction. The inclination direction of the lateral groove 40 in the shoulder land portion 38s on the first tread reference edge PE1 side is the same as the inclination direction of the lateral groove 40 in the shoulder land portion 38s on the second tread reference edge PE2 side. A plurality of lateral grooves 40 are formed in the shoulder land portion 38s. These lateral grooves 40 are arranged at intervals in the circumferential direction.

[0086] In the shoulder land portion 38s, dead-end sipes 44 are formed as lateral sipes 42. The dead-end sipes 44 have ends within the shoulder land portion 38s. The dead-end sipes 44 extend from the ends toward the tread reference edge PE. The inclination direction of the dead-end sipes 44 is the same as the inclination direction of the lateral grooves 40. A plurality of dead-end sipes 44 are formed in the shoulder land portion 38s. In this tire 2, the lateral grooves 40 and the dead-end sipes 44 are alternately arranged in the circumferential direction.

[0087] In the shoulder land portion 38s on the second tread reference edge PE2 side, connecting sipes 46 are formed as the lateral sipes 42. The connecting sipes 46 bridge the shoulder circumferential groove 24s and the lateral groove 40. The inclination direction of the connecting sipes 46 is the same as the inclination direction of the lateral groove 40. In the shoulder land portion 38s, the same number of connecting sipes 46 as the number of lateral grooves 40 are formed.

[0088] In the middle land portion 38m, main dead-end sipes 48 are engraved as the lateral sipes 42. The main dead-end sipes 48 have ends within the middle land portion 38ms. The main dead-end sipes 48 extend from the ends toward the circumferential grooves 24. In the tire 2, the main dead-end sipes 48 connecting the ends and the shoulder circumferential groove 24s are outer main dead-end sipes 48s. The main dead-end sipes 48 connecting the ends and the middle circumferential groove 24m are inner main dead-end sipes 48u.

[0089] A plurality of outer main dead-end sipes 48s are formed in the middle land portion 38m. These outer main dead-end sipes 48s are arranged at intervals in the circumferential direction. A plurality of inner main dead-end sipes 48u are formed in the middle land portion 38m. These inner main dead-end sipes 48u are arranged at intervals in the circumferential direction. The pitch of the outer main dead-end sipes 48s and the pitch of the inner main dead-end sipes 48u are the same.

[0090] The inclination direction of the outer main dead-end sipe 48s is the same as the inclination direction of the inner main dead-end sipe 48u. The inclination direction of the inner main dead-end sipe 48u located on the first tread reference edge PE1 side is the same as the inclination direction of the inner main dead-end sipe 48u located on the second tread reference edge PE2 side.

[0091] In this tire 2, the inclination angle of the inner main dead-end sipe 48u is larger than the inclination angle of the outer main dead-end sipe 48s. The outer main dead-end sipe 48s and the inner main dead-end sipe 48u are arranged such that the inclination angle of the line segment connecting the end of the outer main dead-end sipe 48s and the end of the inner main dead-end sipe 48u is larger than the inclination angle of the outer main dead-end sipe 48s and smaller than the inclination angle of the inner main dead-end sipe 48u. In this tire 2, the combination of the outer main dead-end sipe 48s and the inner main dead-end sipe 48u adjacent to the outer main dead-end sipe 48s is also referred to as a pair sipe.

[0092] In the middle land portion 38m on the first tread reference edge PE1 side, sub-dead-end sipes 50 are engraved as the lateral sipes 42. The sub-dead-end sipes 50 have ends within the middle land portion 38m. The sub-dead-end sipes 50 extend from the ends toward the shoulder circumferential grooves 24s. The inclination direction of the sub-dead-end sipes 50 is the same as the inclination direction of the outer main dead-end sipes 48s. The sub-dead-end sipes 50 are longer than the outer main dead-end sipes 48s. A plurality of sub-dead-end sipes 50 are engraved in the middle land portion 38m. In the tire 2, the sub-dead-end sipes 50 and the outer dead-end sipes 44 are alternately arranged in the circumferential direction.

[0093] In the middle land portion 38m on the second tread reference end PE2 side, transverse sipes 52 are engraved as the lateral sipes 42. The transverse sipes 52 bridge the shoulder circumferential groove 24s and the middle circumferential groove 24m. The inclination direction of the part of the transverse sipes 52 on the shoulder circumferential groove 24s side is the same as the inclination direction of the outer main dead-end sipe 48s. The inclination direction of the part of the transverse sipes 52 on the middle circumferential groove 24m side is the same as the inclination direction of the inner main dead-end sipe 48u. A plurality of transverse sipes 52 are engraved in this middle land portion 38m. In the middle land portion 38m on the second tread reference end PE2 side, the transverse sipes 52 and the pair sipes are alternately arranged in the circumferential direction.

[0094] An enlarged cross-sectional view of the middle land portion 38m is shown in Fig. 4. In Fig. 4, a modified example of the middle land portion 38m is shown.

[0095] In Fig. 4, the two-dot chain line indicated by the symbol T is the above-mentioned tread surface T. The tread surface T passes through the left and right edges 54 of the middle land portion 38m. The tread surface T is a reference surface of the outer surface of the tread 4. An outer surface 56 of the middle land portion 38m shown in Fig. 4 is located outside the tread surface T in the radial direction.

[0096] 4, the outer surface 56 of the middle land portion 38m has an outwardly curved contour. In a meridian cross section, the contour of the outer surface 56 of the middle land portion 38m is represented by a circular arc passing through the left and right edges 54 and the apex 58.

[0097] In this tire 2, the outer surface 56 of the middle land portion 38m has an outwardly curved contour, which effectively suppresses an increase in ground pressure at the edge 54 of the middle land portion 38m. A ground pressure distribution with reduced differences in ground pressure is obtained, so that the tread 4 adheres sufficiently to the road surface. The friction coefficient of the tire 2 is increased, and good braking performance is obtained. From this viewpoint, in this tire 2, it is preferable that the outer surface 56 of the middle land portion 38m has an outwardly curved contour.

[0098] 4, the length indicated by the symbol DX is the maximum height of the outer surface 56 of the middle land portion 38m. This maximum height DX is represented by the shortest distance from the tread surface T to the peak 58.

[0099] In the tire 2, from the viewpoint of obtaining good braking performance, the maximum height DX of the outer surface 56 of the middle land portion 38m is preferably 0.05 mm or more, and more preferably 0.08 mm or more. From the viewpoint of appropriately maintaining the volume of the middle land portion 38m and suppressing an increase in rolling resistance, the maximum height DX is preferably 0.15 mm or less, and more preferably 0.12 mm or less.

[0100] 5 shows a cross section of a lateral groove 40 formed in the shoulder land portion 38s. In FIG. 5, a modified example of the lateral groove 40 is shown.

[0101] As described above, the lateral groove 40 extends in a substantially axial direction. The edge 60 of the lateral groove 40 also extends in a substantially axial direction. As shown in FIG. 5, the edge 60 of the lateral groove 40 is chamfered. This suppresses the concentration of strain on the edge 60 of the lateral groove 40 during braking. Since a ground pressure distribution with a suppressed difference in ground pressure is obtained, the tread 4 comes into sufficient contact with the road surface. The friction coefficient of the tire 2 is increased, and good braking performance is obtained. From this viewpoint, it is preferable that the edge 60 of the lateral groove 40 in the tire 2 is chamfered. In this case, it is more preferable that both edges 60 of the lateral groove 40 are chamfered from the viewpoint of allowing the tread 4 to come into more sufficient contact with the road surface and effectively increasing the friction coefficient of the tire 2. FIG. 5 shows an example in which the edge 60 of the lateral groove 40 is chamfered with a C-shape, but the edge 60 of the lateral groove 40 may be chamfered with a R-shape.

[0102] Fig. 6 shows a cross section of a dead-end sipe 44 engraved in a shoulder land portion 38s as an example of the lateral sipe 42 engraved in the land portion 38. Fig. 6 shows a modified example of the lateral sipe 42.

[0103] As described above, the lateral sipes 42 extend in a substantially axial direction. The edges 62 of the lateral sipes 42 also extend in a substantially axial direction. As shown in FIG. 6, the edges 62 of the lateral sipes 42 are chamfered. This suppresses the concentration of strain on the edges 62 of the lateral sipes 42 during braking. Since a ground pressure distribution with a suppressed difference in ground pressure is obtained, the tread 4 comes into sufficient contact with the road surface. The friction coefficient of the tire 2 is increased, and good braking performance is obtained. From this viewpoint, it is preferable that the edges 62 of the lateral sipes 42 in the tire 2 are chamfered. In this case, it is more preferable that both edges 62 of the lateral sipes 42 are chamfered from the viewpoint that the tread 4 can come into sufficient contact with the road surface and the friction coefficient of the tire 2 can be effectively increased. FIG. 6 shows an example in which the edges 62 of the lateral sipes 42 are C-chamfered, but the edges 62 of the lateral sipes 42 may be R-chamfered.

[0104] In Fig. 5, the double arrow Dg indicates the chamfer depth of the edge 60 of the lateral groove 40. The double arrow Wg indicates the chamfer width. In Fig. 6, the double arrow Ds indicates the chamfer depth of the edge 62 of the lateral sipe 42. The double arrow Ws indicates the chamfer width.

[0105] In the tire 2, the chamfer depth Dg of the edge 60 of the lateral groove 40 is preferably deeper than the chamfer depth Ds of the edge 62 of the lateral sipe 42. This effectively increases the friction coefficient of the tire 2. From this viewpoint, the chamfer depth Dg of the edge 60 of the lateral groove 40 is preferably 2.0 mm or greater and 3.0 mm or less, and the chamfer depth Ds of the edge 62 of the lateral sipe 42 is preferably 1.0 mm or greater and 2.0 mm or less.

[0106] In the tire 2, the chamfer width Wg of the edge 60 of the lateral groove 40 is preferably 1.0 mm or greater and 2.0 mm or less from the viewpoint of effectively increasing the friction coefficient of the tire 2. From the same viewpoint, the chamfer width Ws of the edge 62 of the lateral sipe 42 is preferably 1.0 mm or greater and 2.0 mm or less. In this case, the chamfer width Wg and the chamfer width Ws may be the same or different.

[0107] In this tire 2, from the viewpoint of effectively increasing the coefficient of friction, it is preferable that the lateral sipes 42 extending in a substantially axial direction are cut in the middle land portion 38m and the edges 62 of the lateral sipes 42 are chamfered. In this case, it is more preferable that both edges 62 of the lateral sipes 42 are chamfered. In this tire 2, when the outer surface 56 of the middle land portion 38m has an outwardly curved contour, the coefficient of friction is more effectively increased by cutting the lateral sipes 42 extending in a substantially axial direction in the middle land portion 38m and chamfering the edges 62 of the lateral sipes 42.

[0108] In the tire 2, from the viewpoint of effectively increasing the coefficient of friction, it is preferable that the shoulder land portion 38s is provided with lateral grooves 40 and lateral sipes 42 extending in a substantially axial direction, and that the edges 60 of the lateral grooves 40 and the edges 62 of the lateral sipes 42 are chamfered. In this case, it is more preferable that both edges 60 of the lateral grooves 40 and both edges 62 of the lateral sipes 42 are chamfered.

[0109] When lateral grooves 40 and lateral sipes 42 extending approximately in the axial direction are formed in the shoulder land portion 38s, and the edges 60 of the lateral grooves 40 and the edges 62 of the lateral sipes 42 are chamfered, it is preferable that the chamfer depth Dg of the edges 60 of the lateral grooves 40 is deeper than the chamfer depth Ds of the edges 62 of the lateral sipes 42, from the viewpoint of more effectively increasing the friction coefficient of the tire 2.

[0110] As described above, according to the present invention, a tire 2 is obtained that can achieve improved braking performance without a significant increase in rolling resistance. EXAMPLES

[0111] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0112] [Example 1] A pneumatic tire for passenger cars (tire size=205 / 60R16) having the basic structure shown in FIG. 1 and the specifications shown in Table 1 below was obtained. The ratio (R1 / R2) of the radius R1 of the first circular arc included in the profile of the side surface to the radius R2 of the second circular arc was 86%. The radius R1 was 55 mm. The ratio (A / H) of the apex height A to the cross-sectional height H was 10%. The carcass was composed of one carcass ply, and the ratio (F / W) of the height F of the turned-up portion to the maximum width W was 58%.

[0113] [Comparative Example 1] Comparative Example 1 is a conventional tire. In this Comparative Example 1, the ratio (R1 / R2) of the radius R1 of the first circular arc included in the profile of the side surface to the radius R2 of the second circular arc was 100%. The radius R1 was 70 mm. The ratio (A / H) of the apex height A to the cross-sectional height H was 20%. The carcass was composed of two carcass plies. Although not shown, the two carcass plies were turned up around the bead from the inside to the outside in the axial direction. The ratio of the height of the first turned up part located on the outside in the axial direction to the maximum width height was 65%. The ratio of the height of the second turned up part located on the inside of the first turned up part in the axial direction to the maximum width height was 20%.

[0114] [Examples 2-7 and Comparative Examples 2-4] Tires of Examples 2-7 and Comparative Examples 2-4 were obtained in the same manner as in Example 1, except that the radius R2 of the second circular arc was adjusted so that the radius R1 of the first circular arc and the ratio (R1 / R2) were as shown in Tables 1 and 2 below.

[0115] [Examples 8-9] Tires of Examples 8 and 9 were obtained in the same manner as in Example 1, except that the ratio (A / H) was set as shown in Table 3 below.

[0116] [Examples 10-11] Tires of Examples 10 and 11 were obtained in the same manner as in Example 1, except that the ratio (F / W) was set as shown in Table 3 below.

[0117] [Example 12] A tire of Example 12 was obtained in the same manner as Example 1, except that the middle land portion was changed to the middle land portion having the configuration shown in Fig. 4. The maximum height DX was set to 0.10 mm.

[0118] [Example 13] A tire of Example 13 was obtained in the same manner as Example 12, except that both edges of all lateral grooves and lateral sipes cut into the land portion were chamfered. The chamfer width Wg of the lateral grooves was 1.5 mm, and the chamfer depth Dg was 2.5 mm. The chamfer width Ws of the lateral sipes was 1.5 mm, and the chamfer depth Ds was 1.5 mm. The fact that chamfering was performed is indicated by "Y" in the chamfering column of Table 3 below. Note that "N" in the chamfering column of each table indicates that chamfering was not performed.

[0119] [Braking performance] The prototype tire was mounted on a rim (size = 16 x 6.5) and filled with air to adjust the tire's internal pressure to 250 kPa. The tire was mounted on a test vehicle (passenger car) and the test vehicle was driven on a test course for evaluating braking performance. The braking distance was measured from a speed of 110 km / h. The results are shown as an index in Table 1-3 below. The higher the value, the shorter the braking distance and the better the tire's braking performance.

[0120] [Rolling resistance coefficient (RRC)] Using a rolling resistance tester, the rolling resistance coefficient (RRC) of a prototype tire was measured when it was running on a drum at a speed of 80km / h under the following conditions. The results are shown as an index in Table 1-3 below. The higher the value, the lower the rolling resistance of the tire. In this evaluation, an index of 95 or more is acceptable as it does not indicate a significant increase in rolling resistance. Rim: 16×6.5J Internal pressure: 250kPa Vertical load: 5.43kN

[0121] [Achievement level] The total index obtained in the evaluation of braking performance and rolling resistance was calculated. The results are shown in the "Achievement" column of Table 1-3 below. The higher the value, the better.

[0122] [Durability] The prototype tire was mounted on a rim (size = 16 x 6.5) and filled with air to adjust the internal pressure of the tire to 250 kPa. A durability test was conducted using a drum testing machine with the step speed method in accordance with the load / speed performance test stipulated by ECE30. The distance traveled until the tire was destroyed was measured. The results are shown in the index in Table 1-3 below. The higher the value, the more durable the tire is. In this evaluation, an index of 95 or more is acceptable as it does not indicate a significant decrease in durability.

[0123] [Table 1]

[0124] [Table 2]

[0125] [Table 3]

[0126] As shown in Table 1-3, it has been confirmed that the examples can achieve an improvement in braking performance without a significant increase in rolling resistance. From these evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0127] The above-described technology capable of achieving improved braking performance without a significant increase in rolling resistance can be applied to various types of tires. [Explanation of symbols]

[0128] 2. Tires 4. Tread 6. Sidewall 10 Bead 12. Carcass 24, 24s, 24m...Circumferential groove 30 cores 32. Apex 34, 34a, 34b... Carcass ply 38, 38s, 38m...Land 40 Yokomizo 42 Horizontal sipes

Claims

1. The tire comprises a tread that comes into contact with a road surface, a pair of sidewalls that are connected to ends of the tread and positioned radially inward of the tread, a pair of beads that are positioned radially inward of the sidewalls, and a carcass that is positioned radially inward of the tread and the pair of sidewalls, The bead includes a core and an apex located radially outward of the core, The ratio of the height of the apex to the cross-sectional height is 5% or more and 15% or less, When mounted on a regular rim, the internal pressure is adjusted to 250 kPa, and no load is applied, the profile of the side surface including the maximum width position in a meridian cross section includes two circular arcs that are in contact at the maximum width position. Of the two arcs, the arc located inside the maximum width position in the radial direction is a first arc, and the arc located outside the maximum width position is a second arc, a ratio of a radius of the first circular arc to a radius of the second circular arc is 75% or more and 86% or less; The radius of the first circular arc is 53 mm or more and 65 mm or less. tire.

2. The carcass comprises a carcass ply; The carcass ply includes a ply body that spans between one bead and the other bead, and a pair of turn-up portions that are connected to the ply body and are turned up around the bead from the inside toward the outside in the axial direction, a ratio of a radial distance from a bead baseline to an end of the turned-up portion to a radial distance from the bead baseline to the maximum width position is 48% or more and 68% or less; 2. The tire of claim 1.

3. The angle between a line passing through the tip of the apex and the width center of the contact surface of the apex with the core and a line passing through the tip of the apex and the end of the folded-back portion is greater than or equal to 35 degrees and less than or equal to 50 degrees.

3. The tire of claim 2.

4. A plurality of land portions are formed by forming a plurality of circumferential grooves in the tread, Among the plurality of land portions, a land portion located on an outer side in an axial direction is a shoulder land portion, and a land portion located on an inner side of the shoulder land portion is a middle land portion, The outer surface of the middle land portion has an outwardly curved contour, The maximum height of the outer surface is 0.05 mm or more and 0.15 mm or less. A tire according to any one of claims 1 to 3.

5. A horizontal sipe extending substantially in the axial direction is formed in the middle land portion, The edges of the transverse sipes are chamfered.

5. The tire of claim 4.

6. A lateral groove and a lateral sipe extending in a substantially axial direction are formed in the shoulder land portion, The edges of the lateral grooves and lateral sipes are chamfered.

6. A tire according to claim 4 or 5.

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