Two-wheeled vehicle tire pair

Abstract

The present invention provides a tire pair for a two-wheeled motor vehicle, which can improve the turning performance of the vehicle. The tire pair is composed of a front tire (2) and a rear tire. Based on the contour line (TLf) of the tread surface (16) of the front tire (2) and the contour line of the tread surface of the rear tire, a central arc index (Ac), an intermediate arc index (Am), and a shoulder arc index (As) are obtained. In the tire pair, the intermediate arc index (Am) is greater than the central arc index (Ac), and the shoulder arc index (As) is greater than the intermediate arc index (Am).

Description

Technical Field

[0001] The present invention relates to a pair of tires for two-wheeled vehicles. Background Art

[0002] Motorcycles turn with their bodies tilted. The tread surface of a tire mounted on a motorcycle has rounded corners. During straight driving, the equatorial portion of the tread primarily contacts the road surface. During cornering, the axially outer portion of the tread primarily contacts the road surface.

[0003] In motorcycle tires, attempts have been made to define the curvature radius of the tread surface according to the region of the tread surface in order to improve performance such as cornering and agility (for example, see Patent Document 1 below).

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-216135

[0005] In a two-wheeled vehicle, even if the front tires' turning force is increased, if the rear tires do not have sufficient turning force, the steering characteristics will tend to oversteer. Even if the front tires have high turning performance, if the rear tires have higher turning performance than the front tires, the steering characteristics will tend to understeer.

[0006] For example, even if measures are taken to improve the turning performance of the front tires, the measures taken for the front tires may not be fully effective depending on the rear tires used. To improve the performance of a vehicle, not only the front tires but also the rear tires need to be adjusted. Summary of the Invention

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pair of tires for a motorcycle that can improve the turning performance of the vehicle.

[0008] One embodiment of the present invention is a pair of tires for a two-wheeled vehicle, comprising a front tire and a rear tire. The front tire and the rear tire each comprise: a pair of beads; a carcass spanned between a first bead and a second bead of the pair of beads; a cap band located radially outward of the carcass; and a tread located radially outward of the cap band. The carcass includes a plurality of carcass cords arranged in parallel, each carcass cord being inclined relative to the equatorial plane. The cap band includes cap band cords extending substantially in the circumferential direction. The tread has a tread surface that contacts the road surface. In a meridian cross-section of each of the front tire and the rear tire, the contour line of the tread surface is divided into five parts by dividing the contour line into five equal parts. The five parts are a central portion including the equator, a pair of middle portions connected to the central portion, and a pair of shoulder portions connected to the middle portion. The arc passing through the equator and both ends of the central portion is a first arc, the arc passing through the inner and outer ends of the intermediate portion and the center of the intermediate portion is a second arc, and the arc passing through the inner and outer ends of the shoulder portion and the center of the shoulder portion is a third arc. The ratio (R1f / R1r) of the radius R1f of the first arc of the front tire to the radius R1r of the first arc of the rear tire is a central arc index, the ratio (R2f / R2r) of the radius R2f of the second arc of the front tire to the radius R2r of the second arc of the rear tire is a central arc index, and the ratio (R3f / R3r) of the radius R3f of the third arc of the front tire to the radius R3r of the third arc of the rear tire is a shoulder arc index. The central arc index is greater than the central arc index, and the shoulder arc index is greater than the central arc index.

[0009] Preferably, in this motorcycle tire pair, the center arc index is 0.40 or more and 0.60 or less, and the shoulder arc index is 0.70 or more and 1.10 or less.

[0010] Preferably, in this pair of motorcycle tires, the radial distance from the equator to the end of the tread surface is the tread height. In the front tire, the ratio of the tread height to the nominal cross-sectional width is 35% or more and 45% or less. In the rear tire, the ratio of the tread height to the nominal cross-sectional width is 30% or more and 35% or less.

[0011] Preferably, in this pair of motorcycle tires, in the front tire, a ratio of a radius R1f of the first circular arc to a nominal cross-sectional width is 45% or more and 55% or less. In the rear tire, a ratio of a radius R1r of the first circular arc to a nominal cross-sectional width is 45% or more and 65% or less.

[0012] Preferably, in this pair of motorcycle tires, no grooves intersecting the equator are engraved on the tread surface.

[0013] Preferably, in this pair of motorcycle tires, the angle formed by the carcass cords with respect to the equatorial plane is 20 degrees or more and 65 degrees or less.

[0014] More preferably, in the pair of motorcycle tires, the carcass cords are cords composed of organic fibers.

[0015] According to the present invention, a pair of motorcycle tires capable of improving the turning performance of the vehicle can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a cross-sectional view showing a portion of a front tire constituting a pair of motorcycle tires according to one embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram illustrating the structure of the carcass and cap band in a front tire.

[0018] Figure 3 This is a cross-sectional view illustrating the outline of the tread surface of the front tire.

[0019] Figure 4 It is a development view showing a modified example of the tread surface.

[0020] Figure 5 This is a cross-sectional view showing a portion of a rear tire constituting a pair of motorcycle tires according to one embodiment of the present invention.

[0021] Figure 6 This is a schematic diagram illustrating the structure of the carcass and cap band in a rear tire.

[0022] Figure 7 This is a cross-sectional view illustrating the outline of the tread surface of the rear tire.

[0023] Description of labels

[0024] 2: front tire; 4, 44: tread; 8, 48: bead; 10, 50: carcass; 12, 52: cap band; 22, 62: carcass ply; 24, 64: carcass cord; 28, 68: cap band cord; 42: rear tire. DETAILED DESCRIPTION

[0025] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0026] The tire is assembled to the rim. Air is filled inside the tire to adjust the internal pressure of the tire. In the present disclosure, the tire assembled to the rim is a tire-rim assembly. The tire-rim assembly includes a rim and a tire assembled to the rim.

[0027] In the present disclosure, a state in which a tire is assembled on a regular rim, the internal pressure of the tire is adjusted to a regular internal pressure, and no load is applied to the tire is referred to as a regular state.

[0028] In this disclosure, unless otherwise specified, the dimensions and angles of various tire components are measured under normal conditions. Dimensions and angles of various components in a meridian cross-section of a tire that cannot be measured with the tire assembled on a normal rim are measured using a cross-section obtained by cutting the tire along a plane containing the axis of rotation, with the distance between the left and right beads aligned with the distance between the beads of a tire assembled on a normal rim.

[0029] A "regular rim" is a rim specified in the tire's specifications. JATMA's "standard rim," TRA's "design rim," and ETRTO's "measuring rim" are all considered "regular rims." Unless otherwise specified, the term "rim" in this disclosure refers to a "regular rim."

[0030] The normal internal pressure refers to the internal pressure specified in the tire's standards. The normal internal pressures include the "maximum air pressure" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" section of the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard.

[0031] The normal load refers to the load specified in the tire's standards. The normal loads include the "maximum load capacity" in the JATMA standards, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" section of the TRA standards, and the "LOAD CAPACITY" section of the ETRTO standards.

[0032] In the present disclosure, the “nominal section width” is the “nominal section width” included in the “nominal tire” specified in JIS D4203 “Motorcycle Tires—Nominal Methods and Standards”.

[0033] In this disclosure, the tread portion of a tire refers to the part of the tire that contacts the road surface. The bead portion is the part of the tire that engages the wheel rim. The sidewall portion is the portion of the tire that spans between the tread and bead portions. A tire includes a tread portion, a pair of bead portions, and a pair of sidewall portions.

[0034] A motorcycle tire pair according to one embodiment of the present invention comprises a front tire mounted on the front wheel of a motorcycle (not shown) and a rear tire mounted on the rear wheel.

[0035] [Front tire]

[0036] Figure 1 A portion of a cross section (hereinafter also referred to as a meridian cross section) of the front tire 2 (hereinafter referred to as the tire 2) along a plane including the rotation axis of the tire 2 is shown. Figure 1 In FIG, 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. Figure 1 The direction perpendicular to the paper is the circumferential direction of the tire 2. Figure 1 In FIG, a dashed line ELf is the equatorial plane of the tire 2 .

[0037] exist Figure 1 In the embodiment, the tire 2 is assembled on the rim Rf (regular rim). Air is filled in the interior of the tire 2 to adjust the internal pressure of the tire 2.

[0038] The tire 2 includes a tread 4 , a pair of sidewalls 6 , a pair of beads 8 , a carcass 10 , a cap band 12 , and an inner liner 14 .

[0039] The tread 4 is made of cross-linked rubber. The tread 4 is located radially outward of the cap band 12. The tread 4 has a tread surface 16 that contacts the road surface. The tire 2 contacts the road surface on the tread surface 16. Figure 1 As shown, in a meridian cross section, the tread surface 16 is curved in such a manner that a portion of its equatorial plane projects toward the radially outer side.

[0040] There are no grooves on the tread 4 of the tire 2. The tire 2 is a racing tire.

[0041] exist Figure 1 The position indicated by reference symbol Ef in FIG. 1 is the intersection of the tread surface 16 and the equatorial plane. Intersection Ef is the equator of the tire 2. When the grooves are located on the equatorial plane, the equator Ef is determined based on an imaginary outer surface (tread profile line TLf, described later) assuming no grooves. The equator Ef is also the radially outer end of the tire 2.

[0042] exist Figure 1The position indicated by the reference symbol Fe in the figure is the end of the tread surface 16. The length indicated by the double-headed arrow TWf is the width of the tread surface 16. The width TWf of the tread surface 16 is represented by the axial distance from the first end Fe to the second end Fe of the tread surface 16. The end Fe of the tread surface 16 of the tire 2 is the axially outer end of the tire 2. The width TWf of the tread surface 16 of the tire 2 is also referred to as the total width (see JATMA, etc.).

[0043] Each sidewall 6 is made of cross-linked rubber and is connected to the end of the tread 4. The sidewall 6 is located radially inward of the tread 4.

[0044] Each bead 8 is located radially inward of the sidewall 6. Each bead 8 includes a core 18 and an apex 20. Although not shown, the core 18 is made of a steel wire rod. The apex 20 is located radially outward of the core 18. The apex 20 tapers outward. The apex 20 is made of highly rigid cross-linked rubber.

[0045] The carcass 10 is located inside the tread 4 and the pair of sidewalls 6. The carcass 10 is laid between the first bead 8 and the second bead 8 of the pair of beads 8.

[0046] The carcass 10 includes at least one carcass ply 22. The carcass 10 of the tire 2 is composed of one carcass ply 22.

[0047] The carcass ply 22 includes a ply main body 22 a spanning between the first core 18 and the second core 18 , and a pair of folded portions 22 b connected to the ply main body 22 a and folded around each core 18 from the axial inside toward the outside.

[0048] exist Figure 2 , the structure of the carcass 10 is shown together with the cap band 12 described later. Figure 2 , 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 paper is the radial direction of the tire 2. The front side of the paper is the radial outer side, and the back side is the radial inner side.

[0049] like Figure 2 As shown, the carcass ply 22 constituting the carcass 10 includes a plurality of carcass cords 24 arranged in parallel. Figure 2 In FIG. 1 , for convenience of explanation, the carcass cords 24 are indicated by solid lines, but the carcass cords 24 are covered by a topping rubber 26 .

[0050] Each carcass cord 24 is inclined relative to the equatorial plane. Figure 2 In FIG. 2 , the angle θf is the angle (inclination angle θf) formed by the carcass cords 24 in the carcass ply 22 relative to the equatorial plane. In the tire 2 , the inclination angle θf of the carcass cords 24 is 20 degrees or more and 65 degrees or less.

[0051] This tire 2 can use cords made of organic fibers (organic fiber cords) as the carcass cords 24. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In this tire 2, the carcass cords 24 can also be cords made of inorganic fibers. In this case, examples of the inorganic fibers include glass fibers and carbon fibers.

[0052] In the tire 2 , the carcass cords 24 are preferably organic fiber cords from the viewpoint of being able to adjust the strength and steering stability in a balanced manner.

[0053] The cap band 12 is located radially outside the carcass 10. The cap band 12 is laminated on the carcass 10 radially inside the tread 4. The cap band 12 is located between the tread 4 and the carcass 10.

[0054] The cap band 12 includes a cap band cord 28 wound in a spiral shape. Figure 2 For ease of explanation, the band cord 28 is indicated by a solid line; however, the band cord 28 is covered by a topping rubber 30. In this tire 2, the band cord 28 substantially extends in the circumferential direction. Specifically, the angle formed by the band cord 28 with respect to the circumferential direction is 5° or less. The band 12 is also referred to as a seamless band.

[0055] The tire 2 can use cords made of organic fibers (organic fiber cords) as the band cords 28. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In the tire 2, the band cords 28 may also be cords made of inorganic fibers. In this case, examples of the inorganic fibers include glass fibers and carbon fibers. The band cords 28 may also be steel cords.

[0056] exist Figure 1 In the tire 2, the position indicated by reference symbol Bf is the end of the band 12. The length indicated by the double-headed arrow BWf is the width of the band 12. The width BWf of the band 12 is represented by the axial distance from the first end Bf to the second end Bf of the band 12. In this tire 2, the ratio (BWf / TWf) of the width BWf of the band 12 to the width TWf of the tread surface 16 is 0.80 or more and 0.95 or less.

[0057] The inner liner 14 is located inside the carcass 10 and forms the inner surface of the tire 2. The inner liner 14 is made of a cross-linked rubber having a low gas permeability coefficient and maintains the internal pressure of the tire 2.

[0058] exist Figure 1 The length indicated by the reference numeral Hf is the tread height. The tread height Hf is the radial distance from the equator Ef to the end Fe of the tread surface 16.

[0059] In the tire 2 , the ratio of the tread height Hf to the nominal cross-sectional width is preferably 35% or more and 45% or less.

[0060] By setting this ratio to 35% or more, sufficient cornering force can be obtained in the tire 2. From this viewpoint, this ratio is more preferably 37% or more, and even more preferably 39% or more.

[0061] By setting the ratio to 45% or less, sufficient rigidity can be obtained in the sidewall portion of the tire 2. From this viewpoint, the ratio is more preferably 43% or less, and even more preferably 42% or less.

[0062] exist Figure 3 2 shows the outline of the tire 2 in a meridian cross section. The outline of the tire 2 is obtained by measuring the outer surface shape of the tire 2 in a normal state using a displacement sensor, for example.

[0063] The portion of the contour line extending from the first end Fe to the second end Fe of the tread surface 16 is the contour line TLf (hereinafter referred to as the tread contour line TLf) of the tread surface 16. For example, when the tread 4 is grooved, the contour line of the grooved portion is represented by an imaginary contour line obtained without the grooves.

[0064] The contour line of the tread surface of the rear tire described later is also obtained in the same manner as the contour line TLf.

[0065] exist Figure 3 In the tire 2, the tread outline TLf has a symmetrical shape with respect to the equatorial plane. In the tire 2, the tread outline TLf is divided into five parts by dividing the tread outline TLf into five equal parts.

[0066] The axially central portion of the five sections is the central section CLf. The central section CLf includes the equator Ef. The section axially outward of the central section CLf is the middle section MLf. The middle section MLf is connected to the central section CLf. The section axially outward of the middle section MLf is the shoulder section SLf. The shoulder section SLf is connected to the middle section MLf.

[0067] The five parts are a central portion CLf including the equator Ef, a pair of middle portions MLf connected to the central portion CLf, and a pair of shoulder portions SLf connected to the middle portions MLf.

[0068] exist Figure 3The position denoted by the reference numeral CMf is the boundary between the center portion CLf and the middle portion MLf. The boundary CMf is the end of the center portion CLf and the inner end of the middle portion MLf. The position denoted by the reference numeral MSf is the boundary between the middle portion MLf and the shoulder portion SLf. The boundary MSf is the outer end of the middle portion MLf and the inner end of the shoulder portion SLf. The outer end of the shoulder portion SLf is the end portion Fe of the tread surface 16. The shoulder portion SLf includes the end portion Fe of the tread surface 16.

[0069] In the tire 2, the arc passing through the equator Ef and both ends CMf of the center portion CLf is the first arc. Figure 3 In FIG, arrow R1f is the radius of the first arc. Although not shown, the center of the first arc is located on the equatorial plane.

[0070] The arc passing through the inner end CMf and the outer end MSf of the middle part MLf and the center of the middle part MLf is the second arc. Figure 3 In FIG, arrow R2f is the radius of the second arc. The center of the middle portion MLf is the intersection of the middle portion MLf and the perpendicular bisector of the line segment connecting the inner end CMf and the outer end MSf.

[0071] The arc passing through the inner end MSf and outer end Fe of the shoulder portion SLf and the center of the shoulder portion SLf is the third arc. Figure 3 The center of the shoulder portion SLf is the intersection of the perpendicular bisector of the line segment connecting the inner end MSf and the outer end Fe and the shoulder portion SLf.

[0072] In the tire 2 , the ratio of the radius R1f of the first arc to the nominal cross-sectional width is preferably 45% or more and 55% or less.

[0073] By setting the ratio to 45% or more, it is possible to suppress the tire 2 from cutting in at the initial stage of turning. From this viewpoint, the ratio is more preferably 48% or more.

[0074] By setting the ratio to 55% or less, initial responsiveness can be improved. From this viewpoint, the ratio is more preferably 52% or less.

[0075] In the tire 2 , the ratio of the radius R2f of the second arc to the radius R1f of the first arc ( R2f / R1f ) is preferably 0.88 or more and 1.49 or less.

[0076] By setting the ratio (R2f / R1f) to 0.88 or more, it is possible to effectively suppress the tire 2 from cutting in at the initial stage of turning. From this viewpoint, the ratio (R2f / R1f) is more preferably 0.98 or more.

[0077] By setting the ratio (R2f / R1f) to 1.49 or less, sufficient cornering force can be obtained in the tire 2. From this viewpoint, the ratio (R2f / R1f) is more preferably 1.30 or less.

[0078] In the tire 2 , the ratio of the radius R3f of the third arc to the radius R2f of the second arc ( R3f / R2f ) is preferably 0.96 or more and 2.07 or less.

[0079] By setting the ratio (R3f / R2f) to 0.96 or more, it is possible to effectively suppress the tire 2 from cutting in at the initial stage of turning. From this viewpoint, the ratio (R3f / R2f) is more preferably 0.98 or more.

[0080] By setting the ratio (R3f / R2f) to 2.07 or less, sufficient cornering force can be obtained in the tire 2. From this viewpoint, the ratio (R3f / R2f) is more preferably 1.33 or less, and even more preferably 1.23 or less.

[0081] As described above, no grooves are engraved on the tread surface 16 of the tire 2. No grooves intersecting the equator Ef are engraved on the tread surface 16.

[0082] This tire 2 has higher rigidity in the equatorial plane portion that primarily contacts the road surface during straight travel than tires with grooves intersecting the equator. This tire 2 can quickly transition from straight travel to cornering, fully utilizing the tire's excellent cornering performance.

[0083] Figure 4 FIG. 1 shows a modified example of the tread surface 16. Figure 4 As shown, the tire 2 can be grooved on the tread surface 16. By grooves being carved on the tread surface 16, for example, Figure 4 Tread pattern as shown.

[0084] exist Figure 4 In FIG, 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. Figure 4 The direction perpendicular to the paper surface is the radial direction of the tire 2 .

[0085] exist Figure 4 In FIG. 1 , arrow A is the direction of rotation of the tire 2. The tread surface 16 is Figure 4 The upper side of the paper is facing the lower side and contacts the road surface. The upper side of the paper is the side that touches the ground first, and the lower side of the paper is the side that touches the ground later.

[0086] Figure 4 The tread pattern of is an example of a tread pattern that can be engraved on the tread surface 16 of the tire 2. Figure 4 A tread pattern that can be engraved on the tread surface 16 of the tire 2 will be described.

[0087] exist Figure 4 The tread surface 16 shown has an inclined groove 34 as the groove 32. The inclined groove 34 is inclined relative to the circumferential direction. The leading end 36a of the inclined groove 34 is located on the end Fe side of the tread surface 16. The trailing end 36b of the inclined groove 34 is located on the equator Ef side.

[0088] The inclined grooves 34 include a first inclined groove 34a carved between the equator Ef and the first end Fea of ​​the tread surface 16; and a second inclined groove 34b carved between the equator Ef and the second end Feb of the tread surface 16. A plurality of first inclined grooves 34a are arranged circumferentially at regular intervals on the tread surface 16. A plurality of second inclined grooves 34b are arranged circumferentially at regular intervals. The first inclined grooves 34a and the second inclined grooves 34b are arranged alternately in the circumferential direction.

[0089] like Figure 4 As shown, the entire first inclined groove 34a is located between the equator Ef and the end Fea of ​​the tread surface 16. The entire second inclined groove 34b is also located between the equator Ef and the end Feb of the tread surface 16.

[0090] The tread surface 16 also lacks grooves that intersect the equator (Ef). Therefore, in this case, the tire 2 has higher rigidity in the portion of the equatorial plane that primarily contacts the road surface during straight travel than tires with grooves that intersect the equator. This tire 2 can quickly transition from straight travel to cornering, fully utilizing its excellent cornering performance.

[0091] From the viewpoint of contributing to improved turning performance of the vehicle, in the tire 2 , it is preferable that no grooves intersecting the equator Ef are engraved on the tread surface 16 .

[0092] [Rear tire]

[0093] Figure 5 A portion of a cross section (hereinafter also referred to as a meridian cross section) of the rear tire 42 (hereinafter referred to as the tire 42) along a plane including the rotation axis of the tire 42 is shown. Figure 5 In FIG, the left-right direction is the axial direction of the tire 42, and the up-down direction is the radial direction of the tire 42. Figure 5 The direction perpendicular to the paper is the circumferential direction of the tire 42. Figure 5 In FIG, the one-dot chain line ELr is the equatorial plane of the tire 42 .

[0094] exist Figure 5 In FIG. 4 , the tire 42 is assembled to the rim Rr (regular rim). The interior of the tire 42 is filled with air to adjust the internal pressure of the tire 42.

[0095] The tire 42 includes a tread 44 , a pair of sidewalls 46 , a pair of beads 48 , a carcass 50 , a cap band 52 , and an inner liner 54 .

[0096] The tread 44 is made of cross-linked rubber. The tread 44 is located radially outward of the cap band 52. The tread 44 has a tread surface 56 that contacts the road surface. The tire 42 contacts the road surface on the tread surface 56. Figure 5 As shown, in a meridian cross section, the tread surface 56 is curved such that a portion of its equatorial plane projects radially outward.

[0097] There are no grooves on the tread 44 of the tire 42. The tire 42 is a racing tire.

[0098] exist Figure 5 The position indicated by the symbol Er in FIG is the intersection of the tread surface 56 and the equatorial plane. The intersection Er is the equator of the tire 42. When the groove is located on the equatorial plane, the equator Er is determined based on the tread profile line TLr described later. The equator Er is also the radially outer end of the tire 42.

[0099] exist Figure 5 The position indicated by the reference symbol Re in the figure is the end of the tread surface 56. The length indicated by the double-headed arrow TWr is the width of the tread surface 56. The width TWr of the tread surface 56 is represented by the axial distance from the first end Re to the second end Re of the tread surface 56. The end Re of the tread surface 56 of the tire 42 is the axially outer end of the tire 42. The width TWr of the tread surface 56 of the tire 42 is also referred to as the total width (see JATMA, etc.).

[0100] Each sidewall 46 is made of cross-linked rubber and is connected to the end of the tread 44. The sidewall 46 is located radially inward of the tread 44.

[0101] Each bead 48 is located radially inward of the sidewall 46. Each bead 48 includes a core 58 and an apex 60. Although not shown, the core 58 is made of a steel wire rod. The apex 60 is located radially outward of the core 58. The apex 60 tapers outward. The apex 60 is made of highly rigid cross-linked rubber.

[0102] The carcass 50 is located inside the tread 44 and the pair of sidewalls 46. The carcass 50 is spanned between the first bead 48 and the second bead 48 of the pair of beads 48.

[0103] The carcass 50 includes at least one carcass ply 62. The carcass 50 of the tire 42 is composed of one carcass ply 62.

[0104] The carcass ply 22 includes a ply main body 62 a spanning between the first core 58 and the second core 58 , and a pair of folded portions 62 b connected to the ply main body 62 a and folded around each core 58 from the axial inside toward the outside.

[0105] exist Figure 6 , the structure of the carcass 50 is shown together with the cap band 52 described later. Figure 6 , the left-right direction is the axial direction of the tire 42, and the up-down direction is the circumferential direction of the tire 42. The direction perpendicular to the paper is the radial direction of the tire 42. The front side of the paper is the radial outer side, and the back side is the radial inner side.

[0106] like Figure 6 As shown, the carcass ply 62 constituting the carcass 50 includes a plurality of carcass cords 64 arranged in parallel. Figure 6 In FIG. 5 , for convenience of explanation, the carcass cords 64 are indicated by solid lines, but the carcass cords 64 are covered by the topping rubber 66 .

[0107] Each carcass cord 64 is inclined relative to the equatorial plane. Figure 6 In FIG. 4 , the angle denoted by symbol θr is the angle (inclination angle θr) formed by the carcass cords 64 in the carcass ply 62 relative to the equatorial plane. In the tire 42, the inclination angle θr of the carcass cords 64 is 20 degrees or more and 65 degrees or less.

[0108] The tire 42 can use cords made of organic fibers (organic fiber cords) as the carcass cords 64. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In the tire 42, the carcass cords 64 can also be cords made of inorganic fibers. In this case, examples of the inorganic fibers include glass fibers and carbon fibers.

[0109] In the tire 42 , the carcass cords 64 are preferably organic fiber cords from the viewpoint of being able to adjust the strength and steering stability in a balanced manner.

[0110] The cap band 52 is located radially outside the carcass 50. The cap band 52 is laminated on the carcass 50 radially inside the tread 44. The cap band 52 is located between the tread 44 and the carcass 50.

[0111] The cap band 52 includes a cap band cord 68 wound in a spiral shape. Figure 6 For ease of explanation, the band cord 68 is indicated by a solid line and is covered with a topping rubber 70. In this tire 42, the band cord 68 extends substantially in the circumferential direction. Specifically, the angle formed by the band cord 68 with respect to the circumferential direction is 5° or less. The band 52 is also referred to as a seamless band.

[0112] The tire 42 can use cords made of organic fibers (organic fiber cords) as the band cords 68. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In the tire 42, the band cords 68 may also be cords made of inorganic fibers. In this case, examples of the inorganic fibers include glass fibers and carbon fibers. The band cords 68 may also be steel cords.

[0113] exist Figure 5 The position indicated by the symbol Br in the figure is the end of the band 52. The length indicated by the double-headed arrow BWr is the width of the band 52. The width BWf of the band 52 is represented by the axial distance from the first end Br to the second end Br of the band 52. In this tire 42, the ratio (BWr / TWr) of the width BWr of the band 52 to the width TWr of the tread surface 56 is 0.80 or more and 0.95 or less.

[0114] The inner liner 54 is located inside the carcass 50. The inner liner 54 forms the inner surface of the tire 42. The inner liner 54 is made of a cross-linked rubber having a low gas permeability coefficient. The inner liner 54 maintains the internal pressure of the tire 2.

[0115] exist Figure 5 The length indicated by the symbol Hr is the tread height. The tread height Hr is the radial distance from the equator Er to the end Re of the tread surface 56.

[0116] In the tire 42 , the ratio of the tread height Hr to the nominal cross-sectional width is preferably 30% or more and 35% or less.

[0117] By setting this ratio to 30% or more, sufficient cornering force can be obtained in the tire 42. From this viewpoint, the ratio is more preferably 32% or more.

[0118] By setting the ratio to 35% or less, sufficient rigidity can be obtained in the side portion of the tire 42. From this viewpoint, the ratio is more preferably 34% or less.

[0119] exist Figure 7 , the outline of the rear tire 42 in a meridian cross section is shown. Figure 7 A portion of the illustrated outline from the first end Re to the second end Re of the tread surface 56 is a outline TLr of the tread surface 56 (hereinafter referred to as a tread outline TLr).

[0120] exist Figure 7 In the tire 42 , the tread outline TLr has a symmetrical shape with respect to the equatorial plane. In the tire 42 , the tread outline TLr is divided into five parts by dividing the tread outline TLr into five equal parts.

[0121] The axially central portion of the five sections is the center section CLr. The center section CLr includes the equator Er. The section axially outward of the center section CLr is the middle section MLr. The middle section MLr is connected to the center section CLr. The section axially outward of the middle section MLr is the shoulder section SLr. The shoulder section SLr is connected to the middle section MLr.

[0122] The five parts are a center portion CLr including the equator Er, a pair of middle portions MLr connected to the center portion CLr, and a pair of shoulder portions SLr connected to the middle portions MLr.

[0123] exist Figure 7 The position denoted by the symbol CMr is the boundary between the center portion CLr and the middle portion MLr. The boundary CMr is the end of the center portion CLr and the inner end of the middle portion MLr. The position denoted by the symbol MSr is the boundary between the middle portion MLr and the shoulder portion SLr. The boundary MSr is the outer end of the middle portion MLr and the inner end of the shoulder portion SLr. The outer end of the shoulder portion SLr is the end Re of the tread surface 56. The shoulder portion SLr includes the end Re of the tread surface 56.

[0124] In the tire 42, the arc passing through the equator Er and both ends CMr of the center portion CLr is the first arc. Figure 7 In FIG, arrow R1r is the radius of the first arc. Although not shown, the center of the first arc is located on the equatorial plane.

[0125] The arc passing through the inner end CMr and the outer end MSr of the middle portion MLr and the center of the middle portion MLr is the second arc. Figure 7 The center of the middle portion MLr is the intersection of the middle portion MLr and the perpendicular bisector of the line segment connecting the inner end CMr and the outer end MSr.

[0126] The arc passing through the inner end MSr and the outer end Re of the shoulder portion SLr and the center of the shoulder portion SLr is the third arc. Figure 7 The center of the shoulder portion SLr is the intersection of the perpendicular bisector of the line segment connecting the inner end MSr and the outer end Re and the shoulder portion SLr.

[0127] In the tire 42 , the ratio of the radius R1r of the first arc to the nominal cross-sectional width is preferably 45% or more and 65% or less.

[0128] By setting this ratio to 45% or more, it is possible to suppress the rear tire 42 from cutting in at the initial stage of turning. From this viewpoint, the ratio is more preferably 54% or more.

[0129] By setting this ratio to 65% or less, initial responsiveness can be improved. From this viewpoint, it is more preferably 62% or less.

[0130] In the tire 42 , the ratio of the radius R2r of the second arc to the radius R1r of the first arc ( R2r / R1r ) is preferably 0.81 or more and 1.36 or less.

[0131] By setting the ratio (R2r / R1r) to 0.81 or more, it is possible to effectively suppress the tire 42 from cutting in at the initial stage of turning. From this viewpoint, the ratio (R2r / R1r) is more preferably 0.83 or more.

[0132] By setting the ratio (R2r / R1r) to 1.36 or less, sufficient cornering force can be obtained in the tire 42. From this viewpoint, the ratio (R2r / R1r) is more preferably 1.09 or less, and even more preferably 0.92 or less.

[0133] In the tire 42 , the ratio of the radius R3r of the third arc to the radius R2r of the second arc ( R3r / R2r ) is preferably 0.62 or more and 1.26 or less.

[0134] By setting the ratio (R3r / R2r) to 0.62 or more, it is possible to effectively suppress the tire 42 from cutting in at the initial stage of turning. From this viewpoint, the ratio (R3r / R2r) is more preferably 0.81 or more.

[0135] By setting the ratio (R3r / R2r) to 1.26 or less, sufficient cornering force can be obtained in the tire 42. From this viewpoint, the ratio (R3r / R2r) is more preferably 1.08 or less, and even more preferably 0.96 or less.

[0136] As described above, no grooves are engraved on the tread surface 56 of the tire 42. No grooves intersecting the equator Er are engraved on the tread surface 56.

[0137] The tire 42 has higher rigidity in the equatorial plane portion that primarily contacts the road surface during straight travel than a tire with grooves intersecting the equator. This tire 42 can quickly transition from straight travel to cornering, fully utilizing its excellent cornering performance.

[0138] This tire 42 can also have grooves on its tread surface 56, similar to the tread surface 16 of the front tire 2 described above. In this case, the tread pattern (not shown) is constructed so as to not include grooves intersecting the equator Er, similar to the tread surface 16. This tire 42 has higher rigidity than tires with grooves intersecting the equator in the portion of the equatorial plane that primarily contacts the road surface during straight travel. This tire 42 allows for a quick transition from straight travel to cornering, fully utilizing its excellent cornering performance.

[0139] In the tire 42 , it is preferable that no grooves intersecting the equator Er are engraved on the tread surface 56 from the viewpoint of contributing to improved cornering performance of the vehicle.

[0140] [Tire pair]

[0141] The tire pair according to one embodiment of the present invention is composed of the front tire 2 and the rear tire 42 described above. In order to effectively contribute to improving the turning performance of the vehicle, the tread profile line TLf of the front tire 2 and the tread profile line TLr of the rear tire 42 are primarily set in an excellent balance.

[0142] In order to appropriately set the tread profile line TLf and the tread profile line TLr in this tire pair, the center arc index Ac, the middle arc index Am, and the shoulder arc index As shown below are used.

[0143] The central arc index Ac is a ratio (R1f / R1r) of the radius R1f of the first arc of the front tire 2 to the radius R1r of the first arc of the rear tire 42 .

[0144] The intermediate arc index Am is a ratio (R2f / R2r) of the radius R2f of the second arc of the front tire 2 to the radius R2r of the second arc of the rear tire 42 .

[0145] The shoulder arc index As is a ratio (R3f / R3r) of the radius R3f of the third arc of the front tire 2 to the radius R3r of the third arc of the rear tire 42 .

[0146] In this tire pair, the middle arc index Am is greater than the central arc index Ac, and the shoulder arc index As is greater than the middle arc index Am.

[0147] In this tire pair, at the beginning of a turn, the camber thrust of the rear tire 42 decreases. This tire pair makes it easy to change the direction of the vehicle body.

[0148] At the beginning of the turn, the front tires 2 turn first because the turning performance of the front tires 2 is higher than that of the rear tires 42. The vehicle can maintain its turning performance without showing an oversteering tendency in its turning characteristics.

[0149] In the secondary turn, the difference in turning performance between the front tire 2 and the rear tire 42 is suppressed to be small. In this tire pair, good stability can be maintained.

[0150] Since the vehicle body can be oriented sufficiently at the initial stage of a turn, the vehicle can ensure sufficient turning performance and compensate for the lack of turning force in the secondary turn.

[0151] With this tire pair, the cornering force at the initial stage of cornering is improved, and the cornering performance and stability in secondary cornering are enhanced.

[0152] This tire pair can improve the cornering performance of the vehicle.

[0153] In this tire pair, the central arc index Ac is preferably 0.40 or higher and 0.60 or lower. This improves cornering force in the initial stage of cornering and enhances turning performance and stability during secondary cornering. This tire pair can enhance vehicle turning performance. From this perspective, the central arc index Ac is more preferably 0.50 or higher, and even more preferably 0.51 or higher. The central arc index Ac is more preferably 0.58 or lower.

[0154] In this tire pair, the shoulder arc index As is preferably 0.70 or greater and 1.10 or less. This improves cornering force in the initial phase of cornering and enhances turning performance and stability during secondary cornering. This tire pair can enhance vehicle turning performance. From this perspective, the shoulder arc index As is more preferably 0.80 or greater, and even more preferably 0.83 or greater. The shoulder arc index As is more preferably 0.88 or less.

[0155] In this tire pair, from the viewpoint of improving the turning performance of the vehicle, the center arc index Ac is 0.40 to 0.60, and the shoulder arc index As is more preferably 0.70 to 1.10.

[0156] As described above, the ratio of the tread height Hf to the nominal cross-sectional width is preferably 35% to 45% in the front tire 2. The ratio of the tread height Hr to the nominal cross-sectional width is preferably 30% to 35% in the rear tire 42.

[0157] In this tire pair, from the perspective of being able to improve the turning performance of the vehicle, in the front tire 2, the ratio of the tread height Hf to the nominal cross-sectional width is greater than 35% and less than 45%, and in the rear tire 42, the ratio of the tread height Hf to the nominal cross-sectional width is more preferably greater than 30% and less than 35%.

[0158] As described above, in the front tire 2, the ratio of the radius R1f of the first arc to the nominal cross-sectional width is preferably 45% to 55%. In the rear tire 42, the ratio of the radius R1r of the first arc to the nominal cross-sectional width is preferably 45% to 65%.

[0159] In this tire pair, from the perspective of improving the turning performance of the vehicle, in the front tire 2, the ratio of the radius R1f of the first arc to the nominal cross-sectional width is greater than 45% and less than 55%, and in the rear tire 42, the ratio of the radius R1r of the first arc to the nominal cross-sectional width is more preferably greater than 45% and less than 65%.

[0160] As described above, according to the present invention, a pair of motorcycle tires capable of improving the turning performance of the vehicle can be obtained.

[0161] [Example]

[0162] Hereinafter, the present invention will be described in further detail with reference to Examples and the like, but the present invention is not limited to these Examples.

[0163] [Example 1]

[0164] The following two-wheeled vehicle tire pair is obtained, wherein the two-wheeled vehicle tire pair is composed of Figure 1 The basic structure shown in Table 1 below has a front tire (120 / 70ZR17) and a Figure 4 The basic structure shown in the figure is composed of rear tires (190 / 55ZR17) with the specifications shown in the following Table 1. The nominal cross-section width Wf of the front tire is 120, and the nominal cross-section width Wr of the rear tire is 190.

[0165] The front and rear tires of Example 1 are sliding tires. Grooves intersecting the equator are not engraved on the tread surfaces of the front and rear tires. This is indicated by "Y" in the "Groove" column of Table 1.

[0166] [Examples 2-9 and Comparative Examples 1-4]

[0167] Adjust the radius R1f of the first arc, the radius R2f of the second arc, the radius R3f of the third arc, and the tread height Hf of the front tire, and the radius R1r of the first arc, the radius R2r of the second arc, the radius R3r of the third arc, the nominal section width Wr, and the tread height Hr of the rear tire so that the ratio (R2f / R1f), the ratio (R3f / R2f), the ratio (R1f / Wf), the ratio (Hf / Wf), the ratio (R2r / R1r), the ratio (R3r / R2r), the ratio (R1r / Wr), the ratio (Hr / Wr), the central arc index Ac, the intermediate arc index Am, and the shoulder arc index As are as shown in Tables 1 and 2 below, to obtain tire pairs of Examples 2-9 and Comparative Examples 1-4.

[0168] Grooves intersecting the equator are provided on the tread surfaces of Examples 2, 8, and 9 and Comparative Examples 1 and 4. This is indicated by "N" in the "Groove" column of Tables 1 and 2.

[0169] The tire size of the rear tires of Examples 3 and 4 and Comparative Example 1 is 200 / 55ZR17. The tire size of the rear tire of Comparative Example 4 is 180 / 55ZR17.

[0170] Except for the structures shown in Tables 1 and 2, the same structure as that of Example 1 was adopted.

[0171] [Performance Evaluation]

[0172] Assemble the front and rear tires on regular rims, fill them with air, and adjust the tire internal pressure to the regular pressure.

[0173] Front and rear tires were mounted on a large motorcycle (displacement = 1000 cc). The motorcycle was driven on a test course on a dry asphalt road surface, and sensory evaluation (10-point scale) was performed by a test rider.

[0174] Evaluation items include initial turning performance, transition characteristics, and turning performance and stability during secondary turning.

[0175] The evaluation results are expressed as indices in the following Tables 1 and 2. The larger the numerical value, the better.

[0176] [Table 1]

[0177]

[0178] [Table 2]

[0179]

[0180] As shown in Table 1-2, it was confirmed that the tire pair of the embodiment can contribute to improving the turning performance of the vehicle. The superiority of the present invention is obvious from this evaluation result.

[0181] Industrial applicability

[0182] The above-described technology that can contribute to improving the turning performance of a vehicle can also be applied to tire pairs for various motorcycles.

Claims

1. A tire pair for a two-wheeled motor vehicle, comprising a front tire and a rear tire, wherein: The front tire and the rear tire each have: a pair of tire beads; a carcass mounted between a first bead and a second bead of the pair of beads; a cap band located radially outward of the carcass; and a tread located radially outward of the cap band, The carcass comprises a plurality of carcass cords arranged in parallel, each carcass cord being inclined relative to the equatorial plane. The band includes a band cord extending substantially in the circumferential direction, wherein the angle formed by the band cord with respect to the circumferential direction is 5° or less. The tread has a tread surface that contacts the road surface, In the meridian cross section, the contour line of the tread surface is divided into five parts by dividing the contour line into five equal parts. The five parts are a central portion including the equator, a pair of middle portions connected to the central portion, and a pair of shoulder portions connected to the middle portions. The arc passing through the equator and both ends of the central portion is a first arc. The arc passing through the inner and outer ends of the middle portion and the center of the middle portion is a second arc, The arc passing through the inner and outer ends of the shoulder portion and the center of the shoulder portion is a third arc. The ratio of the radius R1f of the first circular arc of the front tire to the radius R1r of the first circular arc of the rear tire is a central circular arc index. The ratio of the radius R2f of the second circular arc of the front tire to the radius R2r of the second circular arc of the rear tire is the intermediate circular arc index, The ratio of the radius R3f of the third circular arc of the front tire to the radius R3r of the third circular arc of the rear tire is the shoulder arc index. The middle arc index is greater than the central arc index, and the shoulder arc index is greater than the middle arc index.

2. The tire pair for a two-wheeled vehicle according to claim 1, wherein: The central arc index is greater than or equal to 0.40 and less than or equal to 0.60, The shoulder arc index is greater than or equal to 0.70 and less than or equal to 1.

10.

3. The tire pair for a motorcycle according to claim 1 or 2, wherein: The radial distance from the equator to the end of the tread surface is the tread height, In the front tire, the ratio of the tread height to the nominal cross-sectional width is 35% or more and 45% or less, In the rear tire, a ratio of the tread height to a nominal cross-sectional width is 30% or more and 35% or less.

4. The tire pair for a motorcycle according to claim 1 or 2, wherein: In the front tire, a ratio of a radius R1f of the first arc to a nominal cross-sectional width is 45% or more and 55% or less, In the rear tire, a ratio of a radius R1r of the first arc to a nominal cross-sectional width is 45% or more and 65% or less.

5. The tire pair for a motorcycle according to claim 1 or 2, wherein: No grooves crossing the equator are engraved on the tread surface.

6. The tire pair for a motorcycle according to claim 1 or 2, wherein: The angle formed by the carcass cord with respect to the equatorial plane is 20 degrees or more and 65 degrees or less.

7. The tire pair for a two-wheeled vehicle according to claim 6, wherein: The carcass cords are cords composed of organic fibers.

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