Tire and combination of tire and vehicle

Abstract

To provide a tire 2 which can achieve improvement in its handling performance on dry road surfaces and wet road surfaces, without deteriorating its uneven wear resistance.SOLUTION: An exterior surface TS of the tire 2 comprises a tread surface T and a pair of side surfaces S. A plurality of circular arcs representing a contour of the tread surface T includes a pair of crown arcs. A ratio of a radius CR1 of a first crown arc to a radius CR2 of a second crown arc is 1.10-1.70. A total groove capacity of a first circumferential groove 48 positioned in a zone from the equator to a first tread reference end TE1 is larger than a total groove capacity of a second circumferential groove 50 positioned in a zone from the equator to a second tread reference end TE2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire and a combination of a tire and a vehicle.

Background Art

[0002] When the tread pattern of a tire is configured as an asymmetric pattern, there is a possibility of improving handling stability and uneven wear resistance. In this case, it is considered to configure the contour of the tread surface in the meridian cross-section asymmetrically with respect to the equatorial plane, rather than symmetrically, so that the asymmetric pattern can fully exhibit its function (for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a tire is mounted on a high-output vehicle (hereinafter also referred to as a high-output vehicle) having a maximum output of 100 kW or more and considering driving at a speed of 160 km / h or more, the camber angle of the tire is set to a negative camber angle, specifically, an angle smaller than 0 degrees and larger than -2 degrees. A tire mounted on a high-output vehicle is required to exhibit good handling performance on a dry road surface or a wet road surface.

[0005] On the ground contact surface of a tire mounted on a vehicle with a negative camber angle, the area of the inner part of the equatorial plane is large and the area of the outer part is small. When the vehicle turns at high speed, the ground contact pressure tends to locally increase in the outer part. The local increase in the ground contact pressure causes a decrease in handling performance and uneven wear resistance. To suppress the local increase in the ground contact pressure, an increase in the ground contact area is required.

[0006] To improve handling performance on wet roads, it is necessary to ensure groove volume. As described above, on the contact surface of the tire mounted on the vehicle with a negative camber angle, the area of the outer portion of the equatorial plane is small. If the groove area of the groove is increased to ensure the groove volume, the contact area decreases and the contact pressure increases. By adopting a deep groove depth, the groove volume can be increased while suppressing the increase in contact pressure. In this case, it is necessary to consider the thickness of the tread.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a tire that can achieve improved handling performance on dry and wet roads without accompanying a decrease in uneven wear resistance.

Means for Solving the Problems

[0008] A tire according to an aspect of the present invention includes a tread in which a plurality of circumferential grooves arranged in parallel in the axial direction are engraved, the width of the tread is represented by the axial distance from a first tread reference end to a second tread reference end, and the first tread reference end is located on the outer side in the vehicle width direction. The outer surface of the tire includes a tread surface and a pair of side surfaces continuous with the ends of the tread surface. When the tire is mounted on a rim that is a normal rim, the internal pressure of the tire is adjusted to 230 kPa, and in the meridian cross section of the tire in a state where no load is applied to the tire, the contour of the tread surface is represented by a plurality of arcs arranged in parallel in the axial direction. The plurality of arcs include a pair of crown arcs that have centers on the equatorial plane of the tire and are in contact with the equator of the tire. The ratio of the radius of the crown arc located on the first tread reference end side to the radius of the crown arc located on the second tread reference end side is 1.10 or more and 1.70 or less. Among the plurality of circumferential grooves, the circumferential groove located in the zone from the equator to the first tread reference end is the first circumferential groove, and the circumferential groove located in the zone from the equator to the second tread reference end is the second circumferential groove. The total groove volume of the first circumferential groove is larger than the total groove volume of the second circumferential groove.

[0009] Preferably, in this tire, the position on the tread surface where the axial distance from the equatorial plane is 45% of the rim width of the rim is the drop reference position, and the radial distance from the equator to the drop reference position is the drop amount. The drop amount on the second tread reference end side is larger than the drop amount on the first tread reference end side, and the difference between the drop amount on the second tread reference end side and the drop amount on the first tread reference end side is 1.0 mm or more and 6.0 mm or less.

[0010] Preferably, in this tire, the plurality of arcs include a pair of shoulder arcs that are located axially outward and connected to the side surface. The ratio of the radius of the shoulder arc located on the first tread reference end side to the radius of the shoulder arc located on the second tread reference end side is 1.05 or more and 1.35 or less.

[0011] Preferably, in this tire, the ratio of the total groove volume of the first circumferential groove to the total groove volume of the second circumferential groove is 1.2 or more and 1.9 or less.

[0012] Preferably, in this tire, the second circumferential groove is shallower than the first circumferential groove.

[0013] Preferably, in this tire, the distance from the equator to the second circumferential groove close to the equator is longer than the distance from the equator to the first circumferential groove close to the equator.

[0014] Preferably, in this tire, the second circumferential groove includes an inner element and an outer element located axially outside the inner element. In the circumferential direction, the inner element and the outer element are alternately arranged.

[0015] Preferably, in this tire, inclined grooves inclined with respect to the circumferential direction are engraved on the tread. The inclined grooves bridge between the second circumferential groove and the first circumferential groove.

[0016] A combination of a tire and a vehicle according to one aspect of the present invention includes the aforementioned tire and a vehicle. The tire is mounted on the vehicle at a camber angle greater than -2 degrees and less than 0 degrees. The vehicle is a passenger car having a maximum output of 100 kW or more.

Advantages of the Invention

[0017] According to the present invention, a tire can be obtained that can achieve improved handling performance on dry and wet road surfaces without accompanying a decrease in uneven wear resistance.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0019] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0020] In the present 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 this 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 230 kPa, and no load is applied to this tire is referred to as a standard state.

[0021] In the present disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the standard state. The dimensions and angles of each part in the meridian cross-section of the tire that cannot be measured in the state where the tire is mounted on the standard rim are measured in the cross-section of the tire obtained by cutting the tire along a plane including the rotation axis, with the distance between the left and right beads being made to coincide with the distance between the beads in the tire mounted on the standard rim.

[0022] The standard rim means the rim defined in the standards on which the tire depends. The "Standard Rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are standard rims.

[0023] The standard internal pressure means the internal pressure defined in the standards on which the tire depends. The "Maximum Air Pressure" in the JATMA standard, the "Maximum Value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are standard internal pressures.

[0024] The standard load means the load defined in the standards on which the tire depends. The "Maximum Load Capacity" in the JATMA standard, the "Maximum Value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are standard loads.

[0025] In the present disclosure, the angle formed by the groove with respect to the circumferential direction or the axial direction (i.e., the inclination angle of the groove) is represented by the angle formed by the edge of the groove with respect to the circumferential direction or the axial direction. When the inclination angle obtained based on one edge of the groove is different from the inclination angle obtained based on the other edge, the inclination angle of the groove is represented by the average value of the two.

[0026] In the present disclosure, the groove width of the groove is represented by the length from one edge to the other edge measured along a line perpendicular to the center line of the groove. When the groove width changes in the length direction of the groove, the groove width is represented by the average value of the maximum width and the minimum width.

[0027] In the present disclosure, the camber angle is the angle formed between the plane perpendicular to the road surface and the equatorial plane of the tire when the tire is mounted on a vehicle. The state in which the tire is mounted on the vehicle with a negative camber angle means that when the tire is mounted on the vehicle, the upper side of the tire is located closer to the vehicle side than the lower side.

[0028] In the present disclosure, the speed symbol is, for example, a symbol defined in the JATMA standard and representing the maximum speed at which a tire can travel in a state where the tire is loaded with the mass indicated by its load index under specified conditions. A tire with a speed symbol of H or higher means a tire with a speed symbol of H, V, W, or Y.

[0029] In the present disclosure, the load index (LI) is, for example, an index defined in the JATMA standard and representing, in terms of an exponent, the maximum mass that can be allowed to be loaded on a tire under specified conditions, that is, the maximum load capacity.

[0030] FIG. 1 shows a part of a tire 2 according to an embodiment of the present invention. This tire 2 is a passenger car tire. In FIG. 1, the tire 2 is mounted on a rim R. The rim R is a standard rim. The inside of the tire 2 is filled with air and the internal pressure of the tire 2 is adjusted.

[0031] 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 this rim R.

[0032] FIG. 1 shows a part of a cross-section (hereinafter also referred to as a meridian cross-section) of the tire 2 along a plane including the 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 paper surface of FIG. 1 is the circumferential direction of the tire 2. In FIG. 1, the dashed-dotted line CL represents the equatorial plane of the tire 2.

[0033] In FIG. 1, the length indicated by the reference sign RW is the rim width (see JATMA, etc.). The rim width RW is the axial distance from one rim base line to the other rim base line.

[0034] In FIG. 1, the position indicated by the reference sign PW is the axial outer end of the tire 2. When there are decorations such as patterns and characters on the outer surface, the outer end PW is specified based on the virtual outer surface obtained assuming 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, that is, the section width (see JATMA, etc.). The outer end PW is the position where this tire 2 exhibits the maximum width (hereinafter, the maximum width position).

[0035] This tire 2 includes a tread 4, a pair of sidewalls 6, a pair of beads 8, a pair of clinchers 10, a carcass 12, a belt 14, a band 16, and an inner liner 18.

[0036] The tread 4 contacts the road surface on its outer surface. Grooves 20 are engraved in the tread 4. Thereby, a tread pattern is formed.

[0037] Although not shown, the tread 4 has a cap layer and a base layer. The cap layer constitutes the outer surface of the tread 4. The cap layer is made of crosslinked rubber in which wear resistance and grip performance are considered. The base layer is located radially inside the cap layer. The base layer is made of crosslinked rubber with low heat generation.

[0038] In FIG. 1, the position indicated by the reference sign PC is the equator of the tire 2. The equator PC is the intersection of the outer surface of the tread 4 and the equatorial plane. When a groove 20 is located on the equatorial plane, the equator PC is specified based on the virtual outer surface obtained assuming there is no such groove 20.

[0039] Each sidewall 6 is continuous with the edge of the tread 4. The sidewall 6 is located radially inside the tread 4. The sidewall 6 extends along the carcass 12 from the edge of the tread 4 towards the clinch 8. The sidewall 6 is made of cross-linked rubber considering cut resistance.

[0040] Each clinch 8 is located radially inside the sidewall 6. The clinch 8 contacts the rim R. The clinch 8 is made of cross-linked rubber considering wear resistance.

[0041] Each bead 10 is located axially inside the clinch 8. The bead 10 is located radially inside the sidewall 6. The bead 10 includes a core 22 and an apex 24.

[0042] Although not shown, the core 22 includes a steel wire. The apex 24 is located radially outside the core 22. The apex 24 tapers outward. The apex 24 is made of cross-linked rubber with high rigidity. Radially, the outer end of the apex 24 is located inside the maximum width position PW. The length of the apex 24 is appropriately set in the range of 20 mm to 40 mm.

[0043] The carcass 12 is located inside the tread 4, a pair of sidewalls 6 and a pair of clinches 8. The carcass 12 spans between one bead 10 and the other bead 10. The carcass 12 has a radial structure.

[0044] The carcass 12 includes at least one carcass ply 26. The carcass 12 of this tire 2 consists of two carcass plies 26. Radially inside the tread 4, the inner carcass ply 26 is the first carcass ply 28, and the carcass ply 26 located outside the first carcass ply 28 is the second carcass ply 30.

[0045] The first carcass ply 28 includes a first ply body 28a that spans between one bead 10 and the other bead 10, and a pair of first folded portions 28b that are continuous with the first ply body 28a and are folded back from the inner side to the outer side around each bead 10 in the axial direction. In the radial direction, the ends of the first folded portions 28b are located outside the maximum width position PW.

[0046] The second carcass ply 30 includes a second ply body 30a that spans between one bead 10 and the other bead 10, and a pair of second folded portions 30b that are continuous with the second ply body 30a and are folded back from the inner side to the outer side around each bead 10 in the axial direction. In the radial direction, the ends of the second folded portions 30b are located between the outer end of the apex 24 and the core 22.

[0047] Although not shown, the carcass ply 26 includes a number of carcass cords arranged in parallel. Each carcass cord intersects the equatorial plane. The carcass cord is a cord made of organic fiber. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0048] The belt 14 is located inside the tread 4 in the radial direction. The belt 14 is laminated on the carcass 12 from the outside in the radial direction. In this tire 2, the axial width of the belt 14 is 65% or more and 85% or less of the cross-sectional width.

[0049] The belt 14 is composed of at least two layers 32 laminated in the radial direction. The belt 14 of this tire 2 consists of two layers 32 laminated in the radial direction. Among the two layers 32, the layer 32 located inside is the inner layer 32a, and the layer 32 located outside is the outer layer 32b. As shown in FIG. 1, the inner layer 32a is wider than the outer layer 32b. The length from the end of the outer layer 32b to the end of the inner layer 32a is 3 mm or more and 10 mm or less.

[0050] Although not shown, the inner layer 32a and the outer layer 32b each include a number of parallel belt cords. Each belt cord is inclined with respect to the equatorial plane. The material of the belt cord is steel.

[0051] The band 16 is located radially between the tread 4 and the belt 14. The band 16 is laminated on the belt 14 inside 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.

[0052] Although not shown, the band 16 includes a band cord wound in a spiral. The band cord extends substantially in the circumferential direction. Specifically, the angle formed by the band cord with respect to the circumferential direction is 5° or less. The band 16 has a jointless structure. In this tire 2, a cord made of organic fiber is used as the band cord. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0053] The band 16 of this tire 2 includes a full band 34 and a pair of edge bands 36. The full band 34 covers the entire belt 14 from the outside in the radial direction. The pair of edge bands 36 are arranged axially spaced apart with the equatorial plane interposed therebetween. The edge band 36 covers the end of the full band 34 from the outside in the radial direction. This band 16 may be composed of the full band 34 or may be composed of the pair of edge bands 36.

[0054] The inner liner 18 is located inside the carcass 12. The inner liner 18 constitutes the inner surface of the tire 2. The inner liner 18 is made of a crosslinked rubber having a low gas permeability coefficient. The inner liner 18 retains the internal pressure of the tire 2.

[0055] Figure 2 shows the contour of the tire 2 shown in Figure 1. The contour of this tire 2 can be obtained by measuring the outer surface shape of the tire 2 in the standard state with, for example, a displacement sensor. In Figure 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 plane of this Figure 2 is the circumferential direction of the tire 2.

[0056] Figure 2 shows the contour of the outer surface (hereinafter referred to as the tire outer surface TS) of this tire 2 in the meridian cross-section of the tire 2 in the standard state. The contour of this tire outer surface TS is formed by connecting straight lines or arcs. The straight line or arc representing the contour is also referred to as a contour line.

[0057] The tire outer surface TS includes a tread surface T and a pair of side surfaces S. In Figure 2, the position indicated by the reference sign PE is the boundary between the tread surface T and the side surface S. The tread surface T is in contact with the side surface S at the boundary PE. The boundary PE is the end of the tread surface T and also the outer end of the side surface S.

[0058] The tread surface T forms the outer peripheral surface of the tire 2 that contacts the road surface. In the present 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 equator PC.

[0059] In the meridian cross-section, the contour of the tread surface T is represented by a plurality of arcs arranged in the axial direction. In the contour of the tread surface T, two adjacent arcs are in contact with each other. Between the equator PC and the end PE of the tread surface T, the radius of the arc located on the inner side in the axial direction is larger than the radius of the arc located on the outer side in the axial direction.

[0060] Among the plurality of arcs constituting the contour of the tread surface T, the arc located on the outer side in the axial direction and connected to the side surface S is the shoulder arc. In this tire 2, the shoulder arc has the smallest radius among the plurality of arcs constituting the contour of the tread surface T. In Figure 2, the arrow indicated by the reference sign SR is the radius of the shoulder arc.

[0061] In FIG. 2, the portion represented by the shoulder arc (hereinafter also referred to as the curved portion) is indicated by reference numeral RS. In the meridian cross-section, the contour of the outer surface TS of the tire includes, in the portion of the tread surface T, a curved portion RS formed by an arc having the smallest radius among a plurality of arcs included in the contour of the tread surface T and connected to the side surface S, in the portion of the end PE of the tread surface T.

[0062] Each side surface S is continuous with the end PE of the tread surface T. The side surface S is located inside the tread surface T in the radial direction. In the present disclosure, the contour of the side surface S is described by the contour of a virtual outer surface (also referred to as a virtual side surface) obtained assuming that there is no decoration such as a pattern or characters. The side surface S includes the maximum width position PW.

[0063] Although not described in detail, in the meridian cross-section, the contour of the side surface S includes a straight contour line and an upper arc. The straight contour line is a straight line that contacts the curved portion RS at the end PE of the tread surface T. The upper arc is an arc that is continuous with the straight contour line and passes through the maximum width position PW. Although not shown, the center of this upper arc is on a straight line passing through the maximum width position PW and extending in the axial direction. In this tire 2, the upper arc and the curved portion RS may be connected by an arc instead of a straight line. The upper arc and the curved portion RS may be directly connected.

[0064] In the contour of the outer surface TS of the tire, the aforementioned curved portion RS contacts the inner adjacent contour line (hereinafter referred to as the inner adjacent contour line NT) at the contact point CT adjacent to its inner side in the axial direction. This curved portion RS contacts the contour line (hereinafter referred to as the outer adjacent contour line NS) that constitutes the contour of the side surface S adjacent to its outer side in the axial direction at the contact point CS. The contour of the outer surface TS of this tire includes an inner adjacent contour line NT that is located inside the curved portion RS in the axial direction and contacts this curved portion RS, and an outer adjacent contour line NS that is located outside the curved portion RS in the axial direction and contacts this curved portion RS. In this tire 2, the contact point CS is the aforementioned boundary PE.

[0065] In FIG. 2, the solid line LT is the tangent line of the curved portion RS at the contact point CT between the inner adjacent contour line NT and the curved portion RS. The solid line LS is the tangent line of the curved portion RS at the contact point CS between the outer adjacent contour line NS and the curved portion RS. The position indicated by the reference numeral TE is the intersection point of the straight line extending radially through the intersection of the tangent line LT and the tangent line LS and the tread surface T. In this tire 2, this intersection point TE is the tread reference end. The tread reference end TE located on the left side in the plane of FIG. 2 is the first tread reference end TE1, and the tread reference end TE located on the right side is the second tread reference end TE2.

[0066] In FIG. 2, the length indicated by the reference numeral TW is the width of the tread 4. The width TW of the tread 4 is the axial distance from the first tread reference end TE1 to the second tread reference end TE2. The tread reference end TE is a reference position for specifying the width TW of the tread 4. In this tire 2, the ratio of the width TW of the tread 4 to the cross-sectional width is 70% or more and 90% or less.

[0067] As shown in FIG. 3, a part of the outer surface of the tread 4 is shown. 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. 3 is the radial direction of the tire 2. In FIG. 3, the direction indicated by the arrow A is the rotational direction of the tire 2. The lower side in the plane of FIG. 3 is the leading side in the rotational direction, and the upper side is the trailing side in the rotational direction.

[0068] As shown in FIG. 3, the tread pattern of this tire 2 is asymmetric with respect to the equatorial plane. This tread pattern is an asymmetric pattern. In this tire 2, the direction of the tread 4 when mounted on a vehicle is specified. This tire 2 is mounted on a vehicle such that the first tread reference end TE1 is located on the outer side in the vehicle width direction and the second tread reference end TE2 is located on the inner side in the vehicle width direction.

[0069] In this tire 2, the grooves 20 constituting the tread pattern include circumferential grooves 38 extending in the circumferential direction. In this tire 2, a plurality of circumferential grooves 38 arranged in parallel in the axial direction are engraved in the tread 4. As shown in FIG. 3, three circumferential grooves 38 are engraved in the tread 4 of this tire 2.

[0070] Among the three circumferential grooves 38, the circumferential groove 38 located on the outer side in the axial direction is the shoulder circumferential groove 38s. Among the two shoulder circumferential grooves 38s, the shoulder circumferential groove 38s located on the first tread reference end TE1 side is the first shoulder circumferential groove 38s1, and the shoulder circumferential groove 38s located on the second tread reference end TE2 side is the second shoulder circumferential groove 38s2.

[0071] The first shoulder circumferential groove 38s1 includes a plurality of straight elements 40. The angle formed by each straight element 40 with respect to the circumferential direction is 10 degrees or less. As shown in FIG. 3, the straight element 40 is slightly inclined with respect to the circumferential direction. The straight element 40 is engraved in the tread 4 such that the distance between the straight element 40 and the equatorial plane narrows from the rear side to the front side. In this tire 2, the first shoulder circumferential groove 38s1 is formed by connecting a plurality of straight elements 40. The first shoulder circumferential groove 38s1 extends continuously in the circumferential direction.

[0072] The second shoulder circumferential groove 38s2 includes a plurality of inner elements 42 and a plurality of outer elements 44. The angle formed by each inner element 42 with respect to the circumferential direction is 10 degrees or less. As shown in FIG. 3, the inner element 42 is slightly inclined with respect to the circumferential direction. The inner element 42 is engraved in the tread 4 such that the distance between the inner element 42 and the equatorial plane narrows from the rear side to the front side. Each outer element 44 is located axially outside the inner element 42. The angle formed by the outer element 44 with respect to the circumferential direction is 10 degrees or less. As shown in FIG. 3, the outer element 44 is slightly inclined with respect to the circumferential direction. The outer element 44 is engraved in the tread 4 such that the distance between the outer element 44 and the equatorial plane narrows from the trailing side toward the leading side. In this tire 2, the direction of inclination of the outer element 44 is the same as the direction of inclination of the inner element 42. In this tire 2, the inner element 42 and the outer element 44 are alternately arranged in the circumferential direction. The second shoulder circumferential groove 38s2 is formed by connecting the inner element 42 and the outer element 44 alternately. As described above, the outer element 44 is located axially outside the inner element 42. The second shoulder circumferential groove 38s2 extends intermittently in the circumferential direction.

[0073] Among the three circumferential grooves 38, the circumferential groove 38 located axially inside the shoulder circumferential groove 38s is the middle circumferential groove 38m.

[0074] The middle circumferential groove 38m includes a plurality of tapered elements 46. Each tapered element 46 extends in the circumferential direction. The tapered element 46 is an element configured such that its width narrows from the trailing side toward the leading side. The ratio of the width of the leading-side tapered element 46 to the width of the trailing-side tapered element 46 is 0.5 or more and 0.7 or less. In this tire 2, the middle circumferential groove 38m is formed by connecting a plurality of tapered elements 46. The middle circumferential groove 38m extends continuously in the circumferential direction.

[0075] In this tire 2, drainage and ensuring the contact area are considered. The groove width GS1 of the first shoulder circumferential groove 38s1 is set in the range of 4% or more and 8% or less of the width TW of the tread 4. The groove width GM of the middle circumferential groove 38m is narrower than the groove width GS1 of the first shoulder circumferential groove 38s1. The ratio (GM / GS1) of the groove width GM to the groove width GS1 is set in the range of 30% or more and 50% or less. The groove width GS2 of the second shoulder circumferential groove 38s2 is narrower than the groove width GS1 of the first shoulder circumferential groove 38s1 and wider than the groove width GM of the middle circumferential groove 38m. The ratio (GS2 / GS1) of the groove width GS2 to the groove width GS1 is set in the range of 55% or more and 75% or less.

[0076] As shown in FIG. 3, the middle circumferential groove 38m of this tire 2 is located axially between the equatorial plane and the first shoulder circumferential groove 38s1. This middle circumferential groove 38m is not located on the equatorial plane. This middle circumferential groove 38m is arranged offset from the equatorial plane toward the first tread reference end TE1 side.

[0077] In this tire 2, the first shoulder circumferential groove 38s1 and the middle circumferential groove 38m are located in the zone from the equator to the first tread reference end TE1 (hereinafter, the first zone). The first shoulder circumferential groove 38s1 and the middle circumferential groove 38m located in the first zone are also referred to as the first circumferential groove 48. The second shoulder circumferential groove 38s2 is located in the zone from the equator to the second tread reference end TE2 (hereinafter, the second zone). The second shoulder circumferential groove 38s2 located in the second zone is also referred to as the second circumferential groove 50.

[0078] In this tire 2, the total groove volume V1 of the first circumferential groove 48 is represented by the sum of the groove volume of the first shoulder circumferential groove 38s1 and the groove volume of the middle circumferential groove 38m. The total groove volume V2 of the second circumferential groove 50 is represented by the groove volume of the second shoulder circumferential groove 38s2.

[0079] In the present disclosure, the groove volume of the circumferential groove 38 is calculated using three-dimensional data regarding the outer surface shape of the tire, which is measured by, for example, a displacement sensor. When there is a transverse groove crossing the circumferential groove 38, the groove wall of the circumferential groove 38 located on the leading side of this transverse groove or the groove wall of the circumferential groove 38 located on the trailing side is virtually extended to block the transverse groove, and one circumferential groove 38 is specified.

[0080] In this tire 2, a plurality of land portions 52 are formed by cutting a plurality of circumferential grooves 38 in the tread 4. As shown in FIG. 3, in this tire 2, by cutting three circumferential grooves 38, four land portions 52 arranged in parallel in the axial direction are formed. Among the four land portions 52, in the axial direction, the land portion 52 located on the outside is the shoulder land portion 52s, and the land portion 52 located inside the shoulder land portion 52s is the middle land portion 52m. Among the two shoulder land portions 52s, the shoulder land portion 52s located on the first tread reference end TE1 side is the first shoulder land portion 52s1, and the shoulder land portion 52s located on the second tread reference end TE2 side is the second shoulder land portion 52s2. Among the two middle land portions 52m, the middle land portion 52m located on the first tread reference end TE1 side is the first middle land portion 52m1, and the middle land portion 52m located on the second tread reference end TE2 side is the second middle land portion 52m2.

[0081] A transverse groove 54 is cut in the first shoulder land portion 52s1. The transverse groove 54 spans between the first tread reference end TE1 and the first shoulder circumferential groove 38s1. The angle formed by the transverse groove 54 with respect to the axial direction is 10 degrees or less. As shown in FIG. 3, the transverse groove 54 is slightly inclined with respect to the axial direction. The transverse groove 54 is cut in the first shoulder land portion 52s1 such that the inner portion of the transverse groove 54 is located on the leading side of its outer portion in the axial direction.

[0082] The transverse groove 54 includes a wide portion 54a and a narrow portion 54b located inside this wide portion 54a. The groove width of the wide portion 54a is 3% or more and 5% or less of the width TW of the tread 4. The narrow portion 54b has a groove width that is 0.10 times to 0.20 times the groove width of the wide portion 54a.

[0083] In this tire 2, by forming a plurality of lateral grooves 54 in the first shoulder land portion 52s1, a plurality of blocks 56 are formed in the first shoulder land portion 52s1. These blocks 56 are continuous in the circumferential direction. A plurality of sipes 58 are formed in each block 56. The direction of inclination of the sipes 58 is the same as the direction of inclination of the lateral grooves 54.

[0084] Furthermore, fine grooves 60 are formed in the blocks 56 of the first shoulder land portion 52s1. The fine grooves 60 bridge between the front lateral groove 54 and the rear lateral groove 54. The direction of inclination of the fine grooves 60 is the same as the direction of inclination of the linear element 40 that constitutes the first shoulder circumferential groove 38s1. In this tire 2, by forming a plurality of fine grooves 60 in the block 56, a plurality of pieces 62 arranged in parallel in the axial direction are formed in this block. The fine grooves 60 have a groove width that is 0.15 times to 0.25 times the groove width of the wide portion 54a that forms a part of the lateral groove 54.

[0085] An inclined groove 64 is formed in the first middle land portion 52m1. The inclined groove 64 bridges between the first shoulder circumferential groove 38s1 and the middle circumferential groove 38m. The angle formed by the inclined groove 64 with respect to the axial direction is 20 degrees or more and 30 degrees or less. The inclined groove 64 is inclined with respect to the axial direction. The inclined groove 64 is formed in the first middle land portion 52m1 such that the outer portion of the inclined groove 64 is located on the front side with respect to the inner portion in the axial direction. The groove width of this inclined groove 64 is 1% or more and 3% or less of the width TW of the tread 4.

[0086] In this tire 2, by forming a plurality of inclined grooves 64 in the first middle land portion 52m1, a plurality of blocks 66 are formed in the first middle land portion 52m1. These blocks 66 are continuous in the circumferential direction. A plurality of sipes 68 are formed in each block 66. As shown in FIG. 3, the direction of inclination of the sipes 68 is opposite to the direction of inclination of the inclined groove 64.

[0087] In the second middle land portion 52m2, an inclined groove 70 is engraved. The inclined groove 70 bridges between the middle circumferential groove 38m and the second shoulder circumferential groove 38s2. The inclined groove 70 is inclined with respect to the axial direction. The inclined groove 70 is engraved in the second middle land portion 52m2 such that, in the axial direction, the inner portion of the inclined groove 70 is positioned on the leading side relative to its outer portion. The direction of inclination of the inclined groove 70 is the same as the direction of inclination of the inclined groove 64 engraved in the first middle land portion 52m1.

[0088] In this tire 2, the inclined groove 70 includes a steeply inclined portion 72 and a gently inclined portion 74. In the axial direction, the steeply inclined portion 72 is positioned on the inner side, and the gently inclined portion 74 is positioned on the outer side. The angle formed by the steeply inclined portion 72 with respect to the axial direction is 40 degrees or more and 50 degrees or less. The angle formed by the gently inclined portion 74 with respect to the axial direction is 10 degrees or more and 20 degrees or less. The inclination angle of the steeply inclined portion 72 is greater than the inclination angle of the gently inclined portion 74. The difference between the inclination angle of the steeply inclined portion 72 and the inclination angle of the gently inclined portion 74 is 20 degrees or more and 40 degrees or less.

[0089] The groove width of the gently inclined portion 74 is 2% or more and 4% or less of the width TW of the tread 4. The steeply inclined portion 72 is configured such that its groove width tapers from the boundary with the gently inclined portion 74 toward the middle circumferential groove 38m. Among the steeply inclined portions 72 of the inclined grooves 70 arranged in the circumferential direction, the steeply inclined portion 72a where the narrow-width block to be described later is positioned on the leading side and the wide-width block to be described later is positioned on the trailing side includes a wide portion 72aa and a narrow portion 72ab. The narrow portion 72ab has a groove width that is 0.10 times to 0.30 times the groove width of the wide portion 72aa.

[0090] In this tire 2, by engraving a plurality of inclined grooves 70 in the second middle land portion 52m2, a plurality of blocks 76 are formed in the second middle land portion 52m2. These blocks 76 are continuous in the circumferential direction.

[0091] As shown in FIG. 3, a fine groove 78 is engraved in each block 76. The fine groove 78 bridges between the leading-side inclined groove 70 and the trailing-side inclined groove 70. The fine groove 78 has a groove width that is 0.20 times to 0.50 times the groove width of the gently inclined portion 74 that forms part of the inclined groove.

[0092] In this tire 2, in the block 76 (hereinafter, wide block 80) located between the middle circumferential groove 38m and the outer element 44 of the second shoulder circumferential groove 38s2, as the narrow groove 78, an inclined narrow groove 78t1 and a straight narrow groove 78s are engraved. Thereby, an inner piece 80a, an intermediate piece 80b, and an outer piece 80c are formed in this wide block 80. The direction of inclination of the straight narrow groove 78s is the same as the direction of inclination of the outer element 44. The inclined narrow groove 78t1 is engraved in the wide block 80 such that the leading side is located axially outside the trailing side. The angle formed by the inclined narrow groove 78t1 with respect to the circumferential direction is 30 degrees or more and 40 degrees or less.

[0093] As shown in FIG. 3, in the inner piece 80a of the wide block 80, a plurality of inner side ribs 82u extending in the axial direction are engraved. In the intermediate piece 80b and the outer piece 80c, a plurality of outer side ribs 82s inclined slightly with respect to the axial direction are engraved.

[0094] In this tire 2, in the block 76 (hereinafter, narrow block 84) located between the middle circumferential groove 38m and the inner element 42 of the second shoulder circumferential groove 38s2, as the narrow groove 78, two inclined narrow grooves 78t2 are engraved. Thereby, an inner piece 84a, an intermediate piece 84b, and an outer piece 84c are formed in this narrow block 84. The direction of inclination of the inclined narrow groove 78t2 is the same as the direction of inclination of the inclined narrow groove 78t1 engraved in the wide block 80.

[0095] As shown in FIG. 3, in the inner piece 84a and the intermediate piece 84b of the narrow block 84, a plurality of inner side ribs 86u extending in the axial direction are engraved. In the outer piece 84c, a plurality of outer side ribs 86s inclined slightly with respect to the axial direction are engraved.

[0096] A transverse groove 88 is engraved on the second shoulder land portion 52s2. The transverse groove 88 spans between the second shoulder circumferential groove 38s2 and the second tread reference end TE2. The transverse groove 88 includes an inclined portion 88a and a straight portion 88b. The inclined portion 88a is inclined with respect to the axial direction. The inclined portion 88a is continuous with the gently inclined portion 74 of the inclined groove 70 engraved on the second middle land portion 52m2. The direction of inclination of the inclined portion 88a is the same as the direction of inclination of the gently inclined portion 74. The straight portion 88b extends in the axial direction. The groove width of the inclined portion 88a is the same as the groove width of the gently inclined portion 74 that forms part of the inclined groove 70 of the second middle land portion 52m2. The straight portion 88b has a groove width that is 1.1 to 1.3 times the groove width of the inclined portion 88a.

[0097] In this tire 2, by engraving a plurality of transverse grooves 88 in the second shoulder land portion 52s2, a plurality of blocks 90 are formed in the second shoulder land portion 52s2. These blocks 90 are continuous in the circumferential direction. A plurality of sipes 92 are engraved in each block 90. The sipes 92 extend in the axial direction.

[0098] As shown in FIG. 3, further, fine grooves 94 are engraved in the block 90 of the second shoulder land portion 52s2. The fine grooves 94 span between the transverse groove 88 on the leading side and the transverse groove 88 on the trailing side. The direction of inclination of the fine grooves 94 is the same as the direction of inclination of the inner element 42 or the outer element 44 that constitutes the second shoulder circumferential groove 38s2. The fine grooves 94 have a groove width that is 0.15 to 0.25 times the groove width of the inclined portion 88a that forms part of the transverse groove 88. In this tire 2, by engraving a plurality of fine grooves 94 in the block 90, a plurality of pieces 96 arranged in parallel in the axial direction are formed in this block 90.

[0099] In FIG. 1, the double arrow WS1 represents the width of the first shoulder land portion 52s1. This width WS1 is the axial distance from the edge of the first shoulder circumferential groove 38s1 to the first tread reference end TE1. The double arrow WM1 represents the width of the first middle land portion 52m1. This width WM1 is the axial distance from the edge of the first shoulder circumferential groove 38s1 to the edge of the middle circumferential groove 38m. The double arrow WM2 represents the width of the second middle land portion 52m2. This width WM2 is the axial distance from the edge of the middle circumferential groove 38m to the edge of the second shoulder circumferential groove 38s2. The double arrow WS2 represents the width of the second shoulder land portion 52s2. This width WS2 is the axial distance from the edge of the second shoulder circumferential groove 38s2 to the second tread reference end TE2. When the width of the land portion 52 changes in the circumferential direction, the average value of the maximum width and the minimum width is used as the width of this land portion 52.

[0100] In this tire 2, from the viewpoint of ensuring the contact area and drainage performance, the ratio (WS1 / TW) of the width WS1 of the first shoulder land portion 52s1 to the width TW of the tread 4 is set in the range of 20% or more and 30% or less. The ratio (WM1 / TW) of the width WM1 of the first middle land portion 52m1 to the width TW of the tread 4 is set in the range of 10% or more and 20% or less. The ratio (WM2 / TW) of the width WM2 of the second middle land portion 52m2 to the width TW of the tread 4 is set in the range of 30% or more and 40% or less. The ratio (WS2 / TW) of the width WS2 of the second shoulder land portion 52s2 to the width TW of the tread 4 is set in the range of 10% or more and 20% or less.

[0101] As described above, in the meridian cross-section of the tire 2 in the standard state, the contour of the tread surface T is represented by a plurality of arcs arranged in the axial direction. In this tire 2, the plurality of arcs representing the contour of the tread surface T include a pair of crown arcs that have centers on the equatorial plane of the tire 2 and are in contact with each other at the equator PC. Among the pair of crown arcs, the crown arc on the side of the first tread reference end TE1 is also referred to as the first crown arc. The crown arc on the side of the second tread reference end TE2 is also referred to as the second crown arc.

[0102] In FIG. 2, the arrow indicated by reference numeral CR1 is the radius of the first crown arc. The arrow indicated by reference numeral CR2 is the radius of the second crown arc. The position indicated by reference numeral P1 is a position on the tread surface T. The length indicated by reference numeral W10 is the axial distance from the equator PC to the position P1. In this tire 2, the ratio (W10 / RW) of the axial distance W10 to the rim width RW is 10%. The position P1 is a position on the tread surface T where the distance W10 from the equator corresponds to 10% of the rim width RW. This position P1 is the crown reference position for specifying the radius of the crown arc. The crown reference position P1 on the first tread reference end TE1 side is referred to as the first crown reference position P1a, and the reference position P1 on the second tread reference end TE2 side is referred to as the second crown reference position P1b.

[0103] In this tire 2, the radius CR1 of the first crown arc is represented by the radius of an arc having a center on the equatorial plane and passing through the equator PC and the first crown reference position P1a. The radius CR2 of the second crown arc is represented by the radius of an arc having a center on the equatorial plane and passing through the equator PC and the second crown reference position P1b.

[0104] When the radius CR of the crown arc is specified, the radii of the other arcs constituting the contour of the tread surface T are specified. Taking the case where there are two arcs between the crown arc and the shoulder arc as an example, the method for specifying the radii of the arcs will be described below. Of the two arcs located between the crown arc and the shoulder arc, the arc located on the crown arc side is referred to as the middle arc, and the arc on the shoulder arc side is referred to as the side arc. Without going into details, in this tire 2, there are a middle arc and a side arc between the crown arc and the shoulder arc. (1) The position where the arc of radius CR deviates from the tread surface T is specified as the outer end of the portion represented by the crown arc (hereinafter also referred to as the crown contour line). (2) The position on the tread surface T where the distance from the outer end of the crown contour line corresponds to 10% of the rim width RW is specified as the middle reference position. (3) It has a center on a straight line passing through the outer end of the crown contour line and the center of the crown arc, and the radius of the arc passing through the outer end of the crown contour line and the middle reference position is specified as the radius of the middle arc. (4) Similar to the outer end of the crown contour line, the outer end of the portion represented by the middle arc (hereinafter also referred to as the middle contour line) is specified. (5) The position on the tread surface T where the distance from the outer end of the middle contour line corresponds to 10% of the rim width RW is specified as the side reference position. (6) It has a center on a straight line passing through the outer end of the middle contour line and the center of the middle arc, and the radius of the arc passing through the outer end of the middle contour line and the side reference position is specified as the radius of the side arc. (7) Similar to the outer end of the crown contour line, the outer end of the portion represented by the side arc (hereinafter also referred to as the side contour line) is specified. (8) The position on the tread surface T where the distance from the equator corresponds to 50% of the rim width RW is specified as the shoulder reference position. (9) It has a center on a straight line passing through the outer end of the side contour line and the center of the side arc, and the radius of the arc passing through the outer end of the side contour line and the shoulder reference position is specified as the radius SR of the shoulder arc.

[0105] In this tire 2, the ratio (CR1 / CR2) of the radius CR1 of the first crown arc to the radius CR2 of the second crown arc is 1.10 or more and 1.70 or less.

[0106] Since the ratio (CR1 / CR2) is 1.10 or more, when this tire 2 is mounted on a vehicle, this tire 2 can effectively increase the contact area of the first zone located on the outer side in the width direction of this vehicle. In this tire 2, the handling performance and resistance to uneven wear on dry and wet road surfaces are effectively improved. From this perspective, this ratio (CR1 / CR2) is preferably 1.20 or more, and more preferably 1.30 or more.

[0107] Since the ratio (CR1 / CR2) is 1.70 or less, excessive load acting on the first zone located outside in the vehicle width direction is suppressed. This tire 2 can appropriately maintain good handling performance on dry and wet road surfaces and good resistance to uneven wear. From this viewpoint, this ratio (CR1 / CR2) is preferably 1.65 or less, more preferably 1.60 or less.

[0108] In this tire 2, the total groove volume V1 of the first circumferential direction grooves 48 is larger than the total groove volume V2 of the second circumferential direction grooves 50. In this tire 2, the drainage performance of the first zone located outside during high-speed cornering is improved. This tire 2 is excellent in handling performance on wet road surfaces.

[0109] In this tire 2, the ratio (CR1 / CR2) of the radius CR1 of the crown arc located on the first tread reference end TE1 side to the radius CR2 of the crown arc located on the second tread reference end TE2 side is 1.10 or more and 1.70 or less, and the total groove volume V1 of the first circumferential direction grooves 48 is larger than the total groove volume V2 of the second circumferential direction grooves 50. This tire 2 can achieve an improvement in handling performance on dry and wet road surfaces without accompanying a decrease in resistance to uneven wear.

[0110] As shown in FIG. 1, the tread surface T curves so that the portion of the equator PC protrudes outward. The radial distance from the equator PC to an arbitrary position on the tread surface T gradually increases toward the tread reference end TE from the equator PC. This radial distance represents the degree of depression of the tread surface T from the equator PC. This degree of depression affects the contact shape and contact pressure distribution.

[0111] In FIG. 1, reference sign PD indicates a specific position on the tread surface. The length indicated by reference sign W45 is the axial distance from the equatorial plane to the specific position PD. In this tire 2, the ratio (W45 / RW) of the axial distance W45 to the rim width RW is 45%. The position PD is a position on the tread surface T where the axial distance W45 from the equatorial plane is 45% of the rim width RW. In the present disclosure, this position PD is the drop reference position. The radial distance from the equator PC to the drop reference position PD is the drop amount, which is an index representing the degree of depression of the tread surface T. In FIG. 1, the length indicated by reference sign d1 is the drop amount on the first tread reference end TE1 side, and the length indicated by reference sign d2 is the drop amount on the second tread reference end TE2 side.

[0112] With the camber angle of the tire 2 in the standard state set to 0°, a load of 70% of the normal load is applied to this tire 2 as a vertical load, and the tire 2 is brought into contact with a road surface composed of a flat plane. The contact width of the contact surface obtained is controlled so as to be in the range of 70% or more and 90% or less of the width TW of the tread 4. The tire 2 has a tread 4 width TW approximately equal to the rim width RW. When the tire 2 contacts the road surface, the grounding end is located near the drop reference position PD. The drop amount at the drop reference position PD is an effective index for obtaining an appropriate grounding shape and grounding pressure distribution.

[0113] In this tire 2, preferably, the drop amount d2 on the second tread reference end TE2 side is larger than the drop amount d1 on the first tread reference end TE1 side, and the difference (d2 - d1) between the drop amount d2 on the second tread reference end TE2 side and the drop amount d1 on the first tread reference end TE1 side is 1.0 mm or more and 6.0 mm or less. In this tire 2, when this tire 2 is mounted on a vehicle, the contact area of the first zone located on the outer side in the width direction of this vehicle increases. Since the effective contact area during high-speed cornering increases, a local increase in the grounding pressure is suppressed. Since the tread 4 sufficiently contacts the road surface, the handling performance on a dry road surface is improved. Since the ground contact area of the first zone increases, the groove area of the first circumferential groove 48 included in this first zone can be increased. The increase in the groove area contributes to the increase in the groove volume, so the drainage performance is improved. In this tire 2, the handling performance on a wet road surface is also improved. And with respect to the ground contact length at a position corresponding to 80% of the ground contact width, the ground contact length on the outer side and the ground contact length on the inner side in the vehicle width direction are configured to be approximately the same. Since it is difficult for a bias to occur in the ground contact pressure distribution during straight running, in this tire 2, the resistance to uneven wear is improved. In this tire 2, from the viewpoint that the tire 2 can achieve an improvement in handling performance on a dry road surface and a wet road surface and an improvement in resistance to uneven wear, the difference (d2 - d1) is more preferably 2.0 mm or more, and even more preferably 2.5 mm or more. From the viewpoint that the tire 2 can appropriately maintain good handling performance on a dry road surface and a wet road surface and good resistance to uneven wear, this difference (d2 - d1) is more preferably 5.0 mm or less, and even more preferably 4.5 mm or less.

[0114] In this tire 2, preferably, the ratio (CR1 / CR2) of the radius CR1 of the crown arc located on the first tread reference end TE1 side to the radius CR2 of the crown arc located on the second tread reference end TE2 side is 1.10 or more and 1.70 or less, the drop amount d2 on the second tread reference end TE2 side is larger than the drop amount d1 on the first tread reference end TE1 side, and the difference (d2 - d1) between the drop amount d2 on the second tread reference end TE2 side and the drop amount d1 on the first tread reference end TE1 side is 1.0 mm or more and 6.0 mm or less, and the total groove volume V1 of the first circumferential groove 48 is larger than the total groove volume V2 of the second circumferential groove 50. This tire 2 can achieve an improvement in handling performance on a dry road surface and a wet road surface without accompanying a decrease in resistance to uneven wear.

[0115] In FIG. 2, the arrow SR1 is the radius of the shoulder arc (hereinafter, the first shoulder arc) located on the first tread reference end TE1 side. The arrow SR2 is the radius of the shoulder arc (hereinafter, the second shoulder arc) located on the second tread reference end TE2 side.

[0116] In this tire 2, the ratio (SR1 / SR2) of the radius SR1 of the first shoulder arc to the radius SR2 of the second shoulder arc is preferably 1.05 or more and 1.35 or less.

[0117] By setting the ratio (SR1 / SR2) to 1.05 or more, the portion of the first zone that is not in contact with the road surface during straight running can come into contact with the road surface during high-speed cornering. Since the contact surface expands outward, the effective contact area increases. This tire 2 can improve the handling performance on dry and wet road surfaces. From this perspective, this ratio (SR1 / SR2) is more preferably 1.10 or more, and even more preferably 1.15 or more.

[0118] By setting the ratio (SR1 / SR2) to 1.35 or less, it is possible to suppress an excessive load from acting on the first zone located on the outer side in the vehicle width direction. This tire 2 can appropriately maintain good handling performance and good resistance to uneven wear on dry and wet road surfaces. From this perspective, this ratio (SR1 / SR2) is more preferably 1.30 or less, and even more preferably 1.25 or less.

[0119] As described above, the total groove volume V1 of the first circumferential groove 48 is larger than the total groove volume V2 of the second circumferential groove 50. In this tire 2, the ratio (V1 / V2) of the total groove volume V1 of the first circumferential groove 48 to the total groove volume V2 of the second circumferential groove 50 is preferably 1.2 or more and 1.9 or less.

[0120] By setting the ratio (V1 / V2) to 1.2 or more, the drainage performance of the first zone located on the outer side during high-speed cornering is improved. This tire 2 is excellent in handling performance on wet road surfaces. From this perspective, this ratio (V1 / V2) is more preferably 1.3 or more, and even more preferably 1.4 or more.

[0121] By setting the ratio (V1 / V2) to 1.9 or less, the required rigidity in the tread 4 of the first zone is ensured. In this tire 2, good handling performance is maintained. From this viewpoint, this ratio (V1 / V2) is more preferably 1.8 or less, and even more preferably 1.7 or less.

[0122] In FIG. 1, the length indicated by the symbol DS1 is the groove depth of the first shoulder circumferential groove 38s1. The length indicated by the symbol DM is the groove depth of the middle circumferential groove 38m. The length indicated by the symbol DS2 is the groove depth of the second shoulder circumferential groove 38s2. The length indicated by the symbol A is the thickness of the tread 4. This thickness A is measured along the equatorial plane.

[0123] In this tire 2, the groove depth DS1 of the first shoulder circumferential groove 38s1 and the groove depth DM of the middle circumferential groove 38m are the same. The groove depth DS1 of the first shoulder circumferential groove 38s1 and the groove depth DM of the middle circumferential groove 38m may be different. As described above, the first shoulder circumferential groove 38s1 and the middle circumferential groove 38m are the first circumferential grooves 48. The groove depth D1 of this first circumferential groove 48 is represented by the average value of the groove depth DS1 of the first shoulder circumferential groove 38s1 and the groove depth DM of the middle circumferential groove 38m. In this tire 2, from the viewpoints of improving drainage performance and ensuring the rigidity of the tread, the ratio (D1 / A) of the groove depth D1 of the first circumferential groove 48 to the thickness A of the tread is preferably 0.70 or more and 0.95 or less.

[0124] As described above, in this tire 2, the second shoulder circumferential groove 38s2 is the second circumferential groove 50. The groove depth DS2 of the second shoulder circumferential groove 38s2 is the groove depth D2 of the second circumferential groove 50. When a plurality of circumferential grooves 38 are formed in the second zone, the groove depth D2 of the second circumferential groove 50 is represented by the average value of the groove depths of these circumferential grooves 38.

[0125] In this tire 2, the radius CR1 of the crown arc located on the first tread reference end TE1 side is larger than the radius CR2 of the crown arc located on the second tread reference end TE2 side, and the drop amount d1 on the first tread reference end TE1 side is smaller than the drop amount d2 on the second tread reference end TE2 side. In this tire 2, the volume of the tread 4 in the first zone is larger than the volume of the tread 4 in the second zone. Even if the first circumferential groove 48 deeper than the second circumferential groove 50 is engraved, the required rigidity in the tread 4 of the first zone is ensured.

[0126] In this tire 2, the second circumferential groove 50 is shallower than the first circumferential groove 48. The shallow second circumferential groove 50 contributes to ensuring the rigidity of the second zone. The deep first circumferential groove 48 contributes to improving the drainage performance during high-speed cornering. The deep first circumferential groove 48 can further contribute to an increase in the groove volume without expanding the groove area. This tire 2 can further improve the handling performance on dry and wet road surfaces. From this perspective, it is preferable that the second circumferential groove 50 is shallower than the first circumferential groove 48.

[0127] In this tire 2, from the perspective of improving the handling performance on dry and wet road surfaces, the ratio (D1 / D2) of the groove depth D1 of the first circumferential groove 48 to the groove depth D2 of the second circumferential groove 50 is preferably 1.3 or more, more preferably 1.4 or more, and even more preferably 1.5 or more. From the perspective of ensuring the required rigidity in the tread 4 of the first zone, this ratio (D1 / D2) is preferably 2.0 or less, more preferably 1.9 or less, and even more preferably 1.8 or less.

[0128] In FIG. 1, the length indicated by reference sign F1 is the axial distance from the equator PC to the middle circumferential groove 38m. The middle circumferential groove 38m is the first circumferential groove 48 closest to the equator in the first zone. This axial distance F1 is the distance from the equator to the first circumferential groove 48 close to this equator. The length indicated by reference sign F2 is the axial distance from the equator PC to the second shoulder circumferential groove 38s2. The second shoulder circumferential groove 38s2 is the second circumferential groove 50 closest to the equator in the second zone. This axial distance F2 is the distance from the equator to the second circumferential groove 50 close to this equator. When the axial distance F1 changes in the circumferential direction, the axial distance F1 is represented by the average value of the maximum value and the minimum value. The same applies to the axial distance F2.

[0129] In this tire 2, the axial distance F2 is longer than the axial distance F1. The long axial distance F2 contributes to securing the contact area in the second zone. The short axial distance F1 contributes to improving the drainage performance during high-speed cornering. This tire 2 can further improve the handling performance on dry and wet road surfaces. From this viewpoint, it is preferable that the axial distance F2 is longer than the axial distance F1.

[0130] From the viewpoint of improving the drainage performance during high-speed cornering, the ratio (F1 / TW) of the axial distance F1 to the width TW of the tread 4 is preferably 2% or more, and more preferably 3% or more. From the viewpoint of maintaining good resistance to uneven wear, this ratio (F1 / TW) is preferably 7% or less, and more preferably 6% or less.

[0131] From the viewpoint of improving the handling performance, the ratio (F2 / TW) of the axial distance F2 to the width TW of the tread 4 is preferably 25% or more, and more preferably 28% or more. From the viewpoint of maintaining good resistance to uneven wear, this ratio (F2 / TW) is preferably 35% or less, and more preferably 32% or less.

[0132] As shown in FIG. 3, the second middle land portion 52m2 of this tire 2 straddles the equatorial plane, and most of the second middle land portion 52m2 is located in the second zone. When this tire 2 is mounted on a vehicle at a negative camber angle, the tire 2 mainly contacts the road surface at this second middle land portion 52m2. This second middle land portion 52m2 is located between the middle circumferential groove 38m as the first circumferential groove 48 and the second shoulder circumferential groove 38s2 as the second circumferential groove 50.

[0133] As described above, the inclined groove 70 is engraved in the second middle land portion 52m2 of this tire 2, and the inclined groove 70 spans between the middle circumferential groove 38m and the second shoulder circumferential groove 38s2. Since the edge of the inclined groove 70 contributes to the generation of traction, good handling performance can be obtained with this tire 2. The middle circumferential groove 38m is the first circumferential groove 48 closest to the equator in the first zone. The second shoulder circumferential groove 38s2 is the second circumferential groove 50 closest to the equator in the second zone. In this tire 2, from the viewpoint of obtaining good handling performance, the inclined groove 70 inclined with respect to the circumferential direction is engraved in the tread 4, and it is preferable that this inclined groove 70 spans between the second circumferential groove 50 and the first circumferential groove 48.

[0134] In this tire 2, the second shoulder circumferential groove 38s2 is located between the second middle land portion 52m2 and the second shoulder land portion 52s2 in the second zone. In other words, the second shoulder circumferential groove 38s2 is a second circumferential groove 50 that is close to the equatorial PC but is arranged in the second zone farther from the equator than the first circumferential groove 48 close to the equator in the first zone. As described above, this second shoulder circumferential groove 38s2 includes an inner element 42 and an outer element 44, and in the circumferential direction, the inner element 42 and the outer element 44 are alternately arranged. Since the two edges of the inner element 42 and the two edges of the outer element 44 contribute to the generation of traction, good handling performance can be obtained in this tire 2. Since the outer element 44 is located outside the inner element 42 in the axial direction, the stress acting on the inner element 42 and the edges of the inner element 42 is effectively dispersed. Since damage such as chipping is unlikely to occur at the edges of the inner element 42 or the outer element 44, the second shoulder circumferential groove 38s can stably exhibit its function. From this perspective, in this tire 2, the second circumferential groove 50 that is close to the equatorial PC but is arranged in the second zone farther from the equator than the first circumferential groove 48 close to the equator in the first zone preferably includes an inner element 42 and an outer element 44 located outside the inner element 42 in the axial direction, and the inner element 42 and the outer element 44 are alternately arranged in the circumferential direction.

[0135] As described above, according to the present invention, a tire 2 can be obtained that can achieve an improvement in handling performance on dry and wet road surfaces without accompanying a decrease in uneven wear resistance. The present invention has a remarkable effect in a tire 2 with a load index of 100 or more and a speed symbol of H or more. The tire 2 of the present invention is preferably mounted on a vehicle at a negative camber angle, specifically, a camber angle greater than -2 degrees and less than 0 degrees. The tire 2 of the present invention is more preferably mounted on a vehicle having a maximum output of 100 kW or more at a camber angle greater than -2 degrees and less than 0 degrees. A vehicle equipped with the tire 2 of the present invention is a combination of a tire and a vehicle according to an aspect of the present invention. This combination includes the aforementioned tire 2 and a vehicle, and this tire 2 is mounted on the vehicle at a camber angle greater than -2 degrees and less than 0 degrees, and the vehicle is a passenger car having a maximum output of 100 kW or more.

Example

[0136] Hereinafter, the present invention will be described in more detail by way of examples and the like, but the present invention is not limited to such examples only.

[0137] [Example 1] A pneumatic tire for a passenger car (tire size = 245 / 45R18 100V) having the basic configuration shown in FIGS. 1-3 and the specifications shown in Table 1 below was obtained. In this Example 1, the ratio (CR1 / CR2) of the radius CR1 of the first crown arc to the radius CR2 of the second crown arc was 1.50. The ratio (SR1 / SR2) of the radius SR1 of the first shoulder arc to the radius SR2 of the second shoulder arc was 1.20. The difference (d2 - d1) between the drop amount d2 on the second tread reference end TE2 side and the drop amount d1 on the first tread reference end TE1 side was 3.5 mm. The ratio (V1 / V2) of the total groove volume V1 of the first circumferential groove to the total groove volume V2 of the second circumferential groove was 1.7. In this Example 1, the ratio (F1 / TW) of the axial distance F1 from the equator PC to the middle circumferential groove to the tread width TW was 4%. The ratio (F2 / TW) of the axial distance F2 from the equator PC to the second shoulder circumferential groove to the tread width TW was 30%. The ratio (D2 / D1) of the groove depth D1 of the first circumferential groove to the groove depth D2 of the second circumferential groove was 1.6. The ratio (D1 / A) of the groove depth D1 of the first circumferential groove to the tread thickness A was 0.93.

[0138] [Comparative Example 1] Comparative Example 1 is a conventional tire. The tread pattern of this Comparative Example 1 is a symmetric pattern, and the contour of the tread surface T is a symmetric profile.

[0139] [Comparative Examples 2-3] Tires of Comparative Examples 2-3 were obtained in the same manner as in Example 1, except that the radius CR1, the radius SR1, and the drop amount d1 were changed so that the ratio (CR1 / CR2), the ratio (SR1 / SR2), and the difference (d2 - d1) were as shown in Table 1 below.

[0140] [Example 3 and Comparative Example 4] The tires of Example 3 and Comparative Example 4 were obtained in the same manner as in Example 1, except that the groove width of the first shoulder circumferential groove was changed so that the ratio (V1 / V2) was as shown in Table 2 below.

[0141] [Example 2] The tires of Example 3 and Comparative Example 4 were obtained in the same manner as in Example 1, except that the ratio (SR1 / SR2) and the ratio (V1 / V2) were made as shown in Table 2 below by changing the radius SR1 and the groove width of the first shoulder circumferential groove.

[0142] [Example 4] The tire of Example 4 was obtained in the same manner as in Example 1, except that the ratio (SR1 / SR2) was made as shown in Table 2 below by changing the radius SR1.

[0143] [Handling Performance (WET)] The prototype tire was mounted on a rim (size = 18×8.0J), filled with air, and the internal pressure of the tire was adjusted to 230 kPa. The tire was mounted on a test vehicle (passenger car: maximum output = 135 kW) so that the first tread reference end was located on the outside in the vehicle width direction. The test vehicle was run on a test course on a wet road surface (water film thickness = 1.4 mm), and the driver was asked to evaluate the handling performance (sensory evaluation). The results are shown in Table 1 and 2 below in terms of an index. The larger the numerical value, the better the handling performance of the tire on a wet road surface.

[0144] [Handling Performance (DRY)] The prototype tire was mounted on a rim (size = 18×8.0J), filled with air, and the internal pressure of the tire was adjusted to 230 kPa. The tire was mounted on a test vehicle (passenger car: maximum output = 135 kW) so that the first tread reference end was located on the outside in the vehicle width direction. The test vehicle was run on a test course on a dry road surface, and the driver was asked to evaluate the handling performance (sensory evaluation). The results are shown in Table 1 and 2 below in terms of an index. The larger the numerical value, the better the handling performance of the tire on a dry road surface.

[0145] [Resistance to Uneven Wear] A prototype tire was mounted on a rim (size = 18×8.0J), filled with air, and the internal pressure of the tire was adjusted to 230 kPa. The tire was mounted on a test vehicle (passenger car: maximum output = 135 kW) such that the first tread reference end was located on the outside in the vehicle width direction. The test vehicle was driven on a test course on a dry road surface. After driving 30,000 km, the wear condition of the rear tire was checked. The wear amount at a position corresponding to 80% of the contact width was measured. The difference between the wear amount in the second zone arranged on the inner side in the vehicle width direction and the wear amount in the first zone arranged on the outer side in the vehicle width direction was measured. The results are shown in Table 1 below. The closer to 0, the more preferable. This evaluation was performed on the tires of Comparative Example 1 and Example 1.

[0146]

Table 1

[0147]

Table 2

[0148] As shown in Table 1-2, in the examples, it has been confirmed that the handling performance on dry and wet road surfaces can be improved without accompanying a decrease in uneven wear resistance. From this evaluation result, the superiority of the present invention is clear.

Industrial Applicability

[0149] The technology described above, which can achieve an improvement in handling performance on dry and wet road surfaces without accompanying a decrease in uneven wear resistance, can also be applied to various tires.

Explanation of Reference Numerals

[0150] 2 ··· Tire 4 ··· Tread 6 ··· Sidewall 8 ··· Clinch 10 ··· Bead 12 ··· Carcass 14 ··· Belt 16 ··· Band 18 ··· Inner Liner 20 ··· Groove 38, 38s, 38s1, 38s2, 38m ··· Circumferential Groove 48 ··· First Circumferential Groove 50 ··· Second Circumferential Groove 52, 52s, 52s1, 52s2, 52m1, 52m2 ··· Crest 70 ··· Inclined Groove of the Second Middle Crest 52m2 72 ··· Steep Inclined Portion of the Inclined Groove 70 74 ··· Gentle Inclined Portion of the Inclined Groove 70

Claims

1. A tire mounted on a vehicle, comprising a tread having a plurality of circumferential grooves engraved in parallel in the axial direction, the width of the tread being represented by an axial distance from a first tread reference end to a second tread reference end, and the first tread reference end being located on the outer side in the vehicle width direction, wherein an outer surface of the tire includes a tread surface and a pair of side surfaces continuous with ends of the tread surface, When assembled on a rim which is a standard rim and with the internal pressure adjusted to 230 kPa and no load applied, in the meridian cross section of the tire, the contour of the tread surface is represented by a plurality of arcs arranged in parallel in the axial direction, the plurality of arcs include a pair of crown arcs having centers on the equatorial plane of the tire and contacting at the equator of the tire, a ratio of a radius of the crown arc located on the first tread reference end side to a radius of the crown arc located on the second tread reference end side is 1.10 or more and 1.70 or less, among the plurality of circumferential grooves, the circumferential grooves located in a zone from the equator to the first tread reference end are first circumferential grooves, and the circumferential grooves located in a zone from the equator to the second tread reference end are second circumferential grooves, a total groove volume of the first circumferential grooves is larger than a total groove volume of the second circumferential grooves, a distance from the equator to the second circumferential groove adjacent to the equator is longer than a distance from the equator to the first circumferential groove adjacent to the equator, the second circumferential groove adjacent to the equator includes an inner element and an outer element located axially outside the inner element, in the circumferential direction, the inner element and the outer element are alternately arranged, the tire.

2. A position on the tread surface, where an axial distance from the equatorial plane is 45% of a rim width of the rim, is a drop reference position, and a radial distance from the equator to the drop reference position is a drop amount, The drop amount on the second tread reference end side is larger than the drop amount on the first tread reference end side, and the difference between the drop amount on the second tread reference end side and the drop amount on the first tread reference end side is 1.0 mm or more and 6.0 mm or less. The tire according to claim 1.

3. The plurality of arcs include a pair of shoulder arcs that are located on the outer side in the axial direction and connect to the side surface. The ratio of the radius of the shoulder arc located on the first tread reference end side to the radius of the shoulder arc located on the second tread reference end side is 1.05 or more and 1.35 or less. The tire according to claim 1 or 2.

4. Between the equatorial plane and the end of the tread surface, the shoulder arc has the smallest radius among the plurality of arcs that constitute the contour of the tread surface, and contacts the contour line that constitutes the contour of the side surface at the end of the tread surface. The tire according to claim 3.

5. The ratio of the total groove volume of the first circumferential groove to the total groove volume of the second circumferential groove is 1.2 or more and 1.9 or less. The tire according to any one of claims 1 to 4.

6. The second circumferential groove is shallower than the first circumferential groove. When a plurality of the circumferential grooves are formed in the zone from the equator to the first tread reference end, the groove depth of the first circumferential groove is represented by the average value of the groove depths of the plurality of the circumferential grooves formed in the zone from the equator to the first tread reference end. When a plurality of the circumferential grooves are formed in the zone from the equator to the second tread reference end, the groove depth of the second circumferential groove is represented by the average value of the groove depths of the plurality of the circumferential grooves formed in the zone from the equator to the second tread reference end. The tire according to any one of claims 1 to 5.

7. Inclined grooves that are inclined with respect to the circumferential direction are engraved on the tread. The inclined grooves bridge between the second circumferential groove close to the equator and the first circumferential groove close to the equator. The tire according to any one of claims 1 to 6.

8. The first circumferential groove close to the equator includes a plurality of tapered elements arranged in the circumferential direction. Each of the tapered elements is an element that extends in the circumferential direction and is configured such that its width narrows from the rear attachment side toward the front attachment side. The tire according to any one of claims 1 to 7.

9. A combination of a tire according to any one of claims 1 to 8 and a vehicle. The tire is mounted on the vehicle at a camber angle greater than -2 degrees and less than 0 degrees. The vehicle is a passenger car having a maximum output of 100 kW or more. A combination of a tire and a vehicle.

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