Motorcycle tires

Abstract

The present invention provides a pair of motorcycle tires capable of improving 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 center 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 equal to or greater than the center arc index (Ac), and the shoulder arc index (As) is less than the center arc index (Ac).

Description

Technical Field

[0001] The present invention relates to a pair of tires for motorcycles. Background Art

[0002] Motorcycles lean to turn. The tread surface of a motorcycle tire has rounded corners. During straight-ahead travel, 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 area of ​​the tread surface in order to improve performance such as cornering and lightness (for example, see Patent Document 1 below).

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

[0005] In a motorcycle, even if the front tire's turning force is increased, if the rear tire does not have sufficient turning force, the steering characteristics tend to oversteer. Even if the front tire has high turning performance, if the rear tire has higher turning performance than the front tire, the steering characteristics 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 utilized depending on the rear tires that are combined. In order to improve vehicle performance, in addition to the front tires, the rear tires also 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 motorcycle tires capable of improving the turning performance of the vehicle.

[0008] A motorcycle tire pair according to one embodiment of the present invention comprises a front tire and a rear tire. In the tire pair, the front tire and the rear tire each include: a pair of beads; a carcass spanned between a first bead and a second bead of the pair of beads; a band located radially outward of the carcass; and a tread located radially outward of the band. The carcass includes a plurality of carcass cords arranged in parallel, each carcass cord being inclined relative to the equatorial plane. The band includes band cords extending substantially in the circumferential direction. The tread includes a tread surface that contacts the road surface. In a meridian cross-section, the contour line of the tread surface is divided into five sections by dividing the portion from the equator to the end of the tread surface at a length ratio of 1:2:1. The five sections are a center portion including the equator, a pair of middle portions connected to the center portion, and a pair of shoulder portions connected to the middle portions. The arc passing through the equator and both ends of the center portion is the first arc, the arc passing through the inner and outer ends of the middle portion and its center is the second arc, and the arc passing through the inner and outer ends of the shoulder portion and its center is the 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 the center 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 the intermediate arc index. 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 the shoulder arc index. The intermediate arc index is equal to or greater than the center arc index. The shoulder arc index is less than the center arc index.

[0009] In the centering of the motorcycle tire, it is preferable that the middle arc index is 0.50 or greater, and the shoulder arc index is 0.35 or greater.

[0010] Preferably, in this motorcycle tire pair, 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 outer diameter is 5.0% to 10.0%, and in the rear tire, the ratio of the tread height to the outer diameter is 8.5% to 15.0%.

[0011] Preferably, in the motorcycle tire pair, in the front tire, the ratio of the radius R1f of the first arc to the outer diameter is greater than 8.0% and less than 13.0%, and in the rear tire, the ratio of the radius R1r of the first arc to the outer diameter is greater than 9.0% and less than 21.0%.

[0012] In the motorcycle tire, preferably, no grooves intersecting the equator are formed on the tread surface.

[0013] In the motorcycle tire pair, the angle formed by the carcass cord with respect to the equatorial plane is preferably not less than 20 degrees and not more than 65 degrees.

[0014] More preferably, in the motorcycle tire pair, 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 is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It 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 It 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 for explaining the structure of the carcass and cap band in the rear tire.

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

[0023] Description of Reference Numerals

[0024] 2...front tire; 4, 44...tread; 8, 48...bead; 10, 50...carcass; 12, 52...cap and band; 22, 62...carcass ply; 24, 64...carcass cord; 28, 68...cap and 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. The interior of the tire is filled with air, allowing for adjustment of the tire's internal pressure. In the present disclosure, the tire assembled to the rim is referred to as 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] Unless otherwise specified, the dimensions and angles of various tire components are measured in a normal state. Dimensions and angles of various components in a meridian cross-section of the tire, which cannot be measured when the tire is assembled on a normal rim, are measured by aligning the distance between the left and right beads in a cross-section of the tire obtained by cutting the tire along a plane containing the axis of rotation 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. These pressures include the "Maximum Air Pressure" in the JATMA standard, the "Maximum Value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLDINFLATION 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. These include the "maximum load capacity" 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 "LOADCAPACITY" in the ETRTO standard.

[0032] In this disclosure, the tire tread is the portion of the tire that contacts the road surface. The bead is the portion of the tire that engages the wheel rim. The sidewall is the portion of the tire that spans between the tread and bead. A tire includes a tread, a pair of bead portions, and a pair of sidewall portions.

[0033] 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.

[0034] [Front tire]

[0035] Figure 1 A portion of a cross section (hereinafter also referred to as a meridian cross section) of a front tire 2 (hereinafter referred to as tire 2 ) cut 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 surface is the circumferential direction of the tire 2 . Figure 1 In FIG, a dashed line ELf is the equatorial plane of the tire 2 .

[0036] Figure 1 In the embodiment, tire 2 is assembled on rim Rf (regular rim). Air is filled in the inside of tire 2 and the internal pressure of tire 2 can be adjusted.

[0037] 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 .

[0038] 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 at the tread surface 16. Figure 1 As shown, in a meridian cross section, the tread surface 16 is curved such that a portion of its equatorial plane projects radially outward.

[0039] No grooves are formed on the tread 4 of the tire 2. The tire 2 is a slick tire.

[0040] Figure 1 The position indicated by reference numeral Ef is the intersection of the tread surface 16 and the equatorial plane. Intersection Ef is the equator of the tire 2. When 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 the absence of grooves. The equator Ef is also the radially outer end of the tire 2.

[0041] Figure 1 The position indicated by reference numeral Fe 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The carcass 10 includes at least one carcass ply 22. The carcass 10 of the tire 2 is composed of one carcass ply 22.

[0046] The carcass ply 22 includes a ply main body 22 a spanning between the first and second cores 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.

[0047] Figure 2 The structures of the cap band 12 and the carcass 10 described later are shown. 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.

[0048] like Figure 2 As shown, the carcass fabric 22 constituting the carcass 10 includes a plurality of carcass cords 24 arranged in parallel. Figure 2 In the figure, for convenience of explanation, the carcass cords 24 are indicated by solid lines, but the carcass cords 24 are covered by the topping rubber 26.

[0049] Each carcass cord 24 is inclined with respect 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.

[0050] In this tire 2, the carcass cords 24 may be cords made of organic fibers (organic fiber cords). Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In this tire 2, the carcass cords 24 may also be cords made of inorganic fibers. In this case, examples of the inorganic fibers include glass fibers and carbon fibers.

[0051] In the tire 2 , from the viewpoint of being able to adjust the strength and steering stability in a balanced manner, the carcass cords 24 are preferably organic fiber cords.

[0052] 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.

[0053] The band 12 includes a band cord 28 wound in a spiral shape. Figure 2 For ease of explanation, the band cord 28 is shown as 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.

[0054] In this tire 2, the band cords 28 may be cords made of organic fibers (organic fiber cords). Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In this tire 2, the band cords 28 may also be cords made of inorganic fibers. In this case, examples of inorganic fibers include glass fibers and carbon fibers. The band cords 28 may also be steel cords.

[0055] Figure 1 The position indicated by reference numeral 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 greater and 0.95 or less.

[0056] The inner liner 14 is located inside the carcass 10. The inner liner 14 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. The inner liner 14 maintains the internal pressure of the tire 2.

[0057] Figure 1 The length indicated by the reference symbol 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.

[0058] The length indicated by reference symbol Df is the outer diameter of the tire 2. The outer diameter Df is measured for the tire 2 in a normal state.

[0059] In the tire 2 , the ratio of the tread height Hf to the outer diameter Df (Hf / Df) is preferably 5.0% or more and 10.0% or less.

[0060] By setting the ratio (Hf / Df) to 5.0% or more, sufficient cornering force can be obtained in the tire 2. From this viewpoint, the ratio (Hf / Df) is more preferably 7.0% or more, and even more preferably 8.2% or more.

[0061] By setting the ratio (Hf / Df) to 10.0% or less, sufficient rigidity can be obtained in the sidewall portion of the tire 2. From this viewpoint, the ratio (Hf / Df) is more preferably 9.0% or less, and even more preferably 8.5% or less.

[0062] Figure 3 1 shows the contour line of the tire 2 in a meridian cross section. The contour line of the tire 2 is obtained by measuring the outer surface shape of the tire 2 in a normal state using, for example, a displacement sensor.

[0063] The portion of the contour line 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 as if no grooves were formed.

[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] Figure 3 In the tire 2, the tread profile line TLf has a symmetrical shape with respect to the equatorial plane. In this tire 2, the tread profile line TLf is divided into five parts by dividing the portion from the equator Ef to the end Fe of the tread surface 16 at a length ratio of 1:2:1.

[0066] The axially central portion of the five sections is the center section CLf. The center section CLf includes the equator Ef. The section axially outward of the center section CLf is the middle section MLf. The middle section MLf is connected to the center 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 center portion CLf including the equator Ef, a pair of middle portions MLf connected to the center portion CLf, and a pair of shoulder portions SLf connected to the middle portions MLf.

[0068] Figure 3 In the tire 2, the position indicated by reference numeral CMf is the boundary between the center portion CLf and the middle portion MLf. Boundary CMf is the end of the center portion CLf and the inner end of the middle portion MLf. The position indicated by reference numeral MSf is the boundary between the middle portion MLf and the shoulder portion SLf. 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 of this tire 2 includes the end portion Fe of the tread surface 16.

[0069] In the tire 2, the length of the portion of the tread contour line TLf from the first boundary CMf to the second boundary CMf, i.e., the length of the center portion CLf, is 1 / 4 of the length of the tread surface 16 from the first end Fe to the second end Fe, i.e., the length of the tread contour line TLf.

[0070] The length of the portion of the tread outline TLf from the boundary CMf to the boundary MSf, that is, the length of the middle portion MLf is 1 / 4 of the length of the tread outline TLf.

[0071] The length of the portion of the tread outline TLf from the boundary MSf to the end Fe of the tread surface 16 , that is, the length of the shoulder portion SLf is 1 / 8 of the length of the tread outline TLf.

[0072] In the tire 2 , an arc passing through the equator Ef and both ends CMf of the center portion CLf is a first arc. Figure 3 The middle arrow R1f is the radius of the first arc. Although not shown, the center of the first arc is located on the equatorial plane.

[0073] An arc passing through the inner end CMf, the outer end MSf, and the center of the middle portion MLf is a second arc. Figure 3 The 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.

[0074] An arc passing through the inner end MSf, the outer end Fe, and the center of the shoulder portion SLf is a 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.

[0075] In the tire 2 , the ratio ( R1f / Df) of the radius R1f of the first arc to the outer diameter Df is preferably 8.0% or more and 13.0% or less.

[0076] By setting the ratio (R1f / Df) to 8.0% or more, understeering of the vehicle at the initial stage of turning is suppressed. From this viewpoint, the ratio (R1f / Df) is more preferably 9.0% or more, and even more preferably 9.7% or more.

[0077] By setting the ratio (R1f / Df) to 13.0% or less, initial responsiveness is improved. From this viewpoint, the ratio (R1f / Df) is more preferably 12.0% or less.

[0078] 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 0.99 or more and 1.22 or less.

[0079] By setting the ratio (R2f / R1f) to 0.99 or more, understeering of the vehicle at the initial stage of turning is suppressed.

[0080] By setting the ratio (R2f / R1f) to 1.22 or less, the tire 2 can obtain sufficient cornering force.

[0081] 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 0.79 or more and 1.06 or less.

[0082] By setting the ratio (R3f / R2f) to 0.79 or more, understeering of the vehicle at the initial stage of turning is suppressed. From this viewpoint, the ratio (R3f / R2f) is more preferably 1.01 or more.

[0083] By setting the ratio (R3f / R2f) to 1.06 or less, the tire 2 can obtain sufficient cornering force.

[0084] As described above, no grooves are formed on the tread surface 16 of the tire 2. No grooves are formed on the tread surface 16 that intersect the equator Ef.

[0085] The tire 2 has a higher rigidity at its equatorial plane, where it 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, and has excellent initial responsiveness.

[0086] Figure 4 FIG. 1 shows a modified example of the tread surface 16. Figure 4 As shown, the tire 2 can be provided with grooves on the tread surface 16. By providing grooves on the tread surface 16, for example, Figure 4 Tread pattern shown.

[0087] 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.

[0088] Figure 4 In FIG. 1 , arrow A indicates the direction of rotation of the tire 2. The tread surface 16 is Figure 4 The upper side of the paper is the first side to touch the ground, and the lower side of the paper is the last side to touch the ground.

[0089] Figure 4 The tread pattern is an example of a tread pattern that can be engraved on the tread surface 16 of the tire 2. Figure 4 , describing a tread pattern that can be engraved on the tread surface 16 of the tire 2 .

[0090] exist Figure 4 The tread surface 16 shown is provided with inclined grooves 34 as grooves 32. The inclined grooves 34 are inclined relative to the circumferential direction. The leading land end 36a of the inclined grooves 34 is located on the end Fe side of the tread surface 16. The trailing land end 36b of the inclined grooves 34 is located on the equator Ef side.

[0091] The inclined grooves 34 include: a first inclined groove 34a, which is engraved between the equator Ef and the first end Fea of ​​the tread surface 16; and a second inclined groove 34b, which is engraved between the equator Ef and the second end Feb of the tread surface 16. In the tread surface 16, a plurality of first inclined grooves 34a are arranged at regular intervals along the circumference. A plurality of second inclined grooves 34b are arranged at regular intervals along the circumference. The first inclined grooves 34a and the second inclined grooves 34b are arranged alternately along the circumference.

[0092] like Figure 4 As shown, the first inclined groove 34a is entirely located between the equator Ef and the end Fea of ​​the tread surface 16. The second inclined groove 34b is also entirely located between the equator Ef and the end Feb of the tread surface 16.

[0093] The tread surface 16 also lacks grooves intersecting the equator Ef. Therefore, even in this case, the equatorial portion of the tire 2, which primarily contacts the road surface during straight travel, exhibits higher rigidity than tires with grooves intersecting the equator. This tire 2 enables rapid transition from straight travel to cornering. This tire 2 exhibits excellent initial responsiveness.

[0094] From the viewpoint of obtaining good initial responsiveness, in the tire 2 , it is preferable that no grooves intersecting the equator Ef are engraved on the tread surface 16 .

[0095] [Rear tire]

[0096] Figure 5 This is 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 ) cut along a plane including the rotation axis of the tire 42 . Figure 5 , 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 surface 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 .

[0097] Figure 5 In the embodiment, the tire 42 is assembled to the rim Rr (regular rim). The inside of the tire 42 is filled with air, and the internal pressure of the tire 42 can be adjusted.

[0098] 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 .

[0099] 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 at the tread surface 56. Figure 5 As shown, in a meridian cross section, the tread surface 56 is curved so that a portion of its equatorial plane projects radially outward.

[0100] No grooves are carved on the tread 44 of the tire 42. The tire 42 is a slick tire.

[0101] Figure 5 In the figure, the position indicated by reference numeral Er is the intersection of the tread surface 56 and the equatorial plane. The intersection Er is the equator of the tire 42. When the grooves are 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.

[0102] Figure 5 The position indicated by the reference numeral Re 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.).

[0103] 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.

[0104] 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.

[0105] 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.

[0106] The carcass 50 includes at least one carcass ply 62. The carcass 50 of the tire 42 is composed of one carcass ply 62.

[0107] 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.

[0108] Figure 6 The structures of the cap band 52 and the carcass 50 described later are shown. 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.

[0109] 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. 1 , for convenience of explanation, the carcass cords 64 are indicated by solid lines, but the carcass cords 64 are covered with the topping rubber 66 .

[0110] Each carcass cord 64 is inclined with respect to the equatorial plane. Figure 6 In the figure, the angle indicated by reference 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 this tire 42, the inclination angle θr of the carcass cords 64 is 20 degrees or more and 65 degrees or less.

[0111] In the tire 42, the carcass cords 64 may be made of organic fibers (organic fiber cords). Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. In the tire 42, the carcass cords 64 may also be made of inorganic fibers. In this case, examples of the inorganic fibers include glass fibers and carbon fibers.

[0112] In the tire 42 , from the viewpoint of being able to adjust the strength and steering stability in a balanced manner, the carcass cords 64 are preferably organic fiber cords.

[0113] 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.

[0114] The band 52 includes a band cord 68 wound in a spiral shape. Figure 6 For ease of explanation, the band cord 68 is shown as a solid line; however, the band cord 68 is covered by a topping rubber 70. In this tire 42, the band cord 68 substantially extends 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.

[0115] In the tire 42, the band cords 68 may be cords made of organic fibers (organic fiber cords). 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 inorganic fibers include glass fibers and carbon fibers. The band cords 68 may also be steel cords.

[0116] Figure 5 In the tire 42, the position indicated by reference symbol Br 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 of the width BWr of the band 52 to the width TWr of the tread surface 56 (BWr / TWr) is 0.80 or more and 0.95 or less.

[0117] 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.

[0118] Figure 5 In FIG. 5 , the length indicated by reference 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 .

[0119] The length indicated by reference symbol Dr is the outer diameter of the tire 42. The outer diameter Dr is measured for the tire 42 in a normal state.

[0120] In the tire 42 , the ratio of the tread height Hr to the outer diameter Dr (Hr / Dr) is preferably 8.5% or more and 15.0% or less.

[0121] By setting the ratio (Hr / Dr) to 8.5% or more, sufficient cornering force can be obtained for the tire 42. From this viewpoint, the ratio (Hr / Dr) is more preferably 9.1% or more.

[0122] By setting the ratio (Hr / Dr) to 15.0% or less, sufficient rigidity can be obtained in the sidewall portion of the tire 42. From this viewpoint, the ratio (Hr / Dr) is more preferably 9.5% or less.

[0123] Figure 7 The outline of the rear tire 42 in a meridian cross section is shown. Figure 7 Of the outline shown, a portion from the first end portion Re to the second end portion Re of the tread surface 56 is a outline TLr of the tread surface 56 (hereinafter referred to as a tread outline TLr).

[0124] Figure 7 In the tire 42, the tread profile line TLr has a symmetrical shape with respect to the equatorial plane. In this tire 42, the tread profile line TLr is divided into five parts by dividing the portion from the equator Er to the end Re of the tread surface 56 at a length ratio of 1:2:1.

[0125] 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.

[0126] 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.

[0127] Figure 7 In the tire 42, the position indicated by reference numeral CMr is the boundary between the center portion CLr and the middle portion MLr. Boundary CMr is the end of the center portion CLr and the inner end of the middle portion MLr. The position indicated by reference numeral MSr is the boundary between the middle portion MLr and the shoulder portion SLr. 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 portion Re of the tread surface 56. The shoulder portion SLr of this tire 42 includes the end portion Re of the tread surface 56.

[0128] In the tire 42 , the length of the portion of the tread outline TLr from the first boundary CMr to the second boundary CMr, i.e., the length of the center portion CLr, is 1 / 4 of the length of the tread surface 56 from the first end Re to the second end Re, i.e., the length of the tread outline TLr.

[0129] The length of the portion of the tread outline TLr from the boundary CMr to the boundary MSr, that is, the length of the middle portion MLr is 1 / 4 of the length of the tread outline TLr.

[0130] The length of the portion of the tread contour line TLr from the boundary MSr to the end Re of the tread surface 56 , that is, the length of the shoulder portion SLr is 1 / 8 of the length of the tread contour line CLr.

[0131] In the tire 42 , an arc passing through the equator Er and both ends CMr of the center portion CLr is a 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.

[0132] An arc passing through the inner end CMr, the outer end MSr, and the center of the middle portion MLr is a second arc. Figure 7 The arrow R2r is the radius of the second arc. 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.

[0133] An arc passing through the inner end MSr, the outer end Re, and the center of the shoulder portion SLr is a 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.

[0134] In the tire 42 , the ratio of the radius R1r of the first arc to the outer diameter Dr (R1r / Dr) is preferably 9.0% or more and 21.0% or less.

[0135] By setting the ratio (R1r / Dr) to 9.0% or more, understeering of the vehicle at the initial stage of turning is suppressed. From this viewpoint, the ratio is more preferably 9.1% or more.

[0136] By setting this ratio to 21.0% or less, initial responsiveness is improved. From this viewpoint, it is more preferably 20.7% or less.

[0137] 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 0.84 or more and 1.19 or less.

[0138] By setting the ratio (R2r / R1r) to 0.84 or greater, understeering of the vehicle at the initial stage of turning is effectively suppressed. From this viewpoint, the ratio (R2r / R1r) is more preferably 0.94 or greater, and even more preferably 0.99 or greater.

[0139] By setting the ratio (R2r / R1r) to 1.19 or less, the tire 42 can obtain sufficient cornering force.

[0140] 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 0.81 or more and 1.44 or less.

[0141] By setting the ratio (R3r / R2r) to 0.81 or more, understeering of the vehicle at the initial stage of turning is effectively suppressed. From this viewpoint, the ratio (R3r / R2r) is more preferably 0.93 or more, and even more preferably 1.15 or more.

[0142] By setting the ratio (R3r / R2r) to 1.44 or less, the tire 42 can obtain sufficient cornering force.

[0143] As described above, no grooves are formed on the tread surface 56 of the tire 42. No grooves intersecting the equator Er are formed on the tread surface 56.

[0144] The tire 42 has a higher rigidity at its equatorial plane, where it 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. This tire 42 has excellent initial responsiveness.

[0145] This tire 42, like the tread surface 16 of the front tire 2 described above, can also have grooves carved into its tread surface 56. In this case, as with the tread surface 16, the tread pattern (not shown) is configured to not include grooves intersecting the equator Er. The equatorial portion of this tire 42, which primarily contacts the road surface during straight travel, has higher rigidity than tires with grooves carved into the equator. This tire 42 allows for rapid transitions from straight travel to cornering. This tire 42 exhibits excellent initial responsiveness.

[0146] In the tire 42 , from the viewpoint of obtaining good initial responsiveness, it is preferable that no grooves intersecting the equator Er are engraved on the tread surface 56 .

[0147] [Tire pair]

[0148] 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 set in perfect balance.

[0149] 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.

[0150] The center 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 .

[0151] 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 .

[0152] 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 .

[0153] In corners where the vehicle turns at high speed (hereinafter referred to as high-speed corners), portions of the tire's tread surface corresponding to the center and middle portions of the tread profile are used. Specifically, the tread surface 16 of the front tire 2 uses portions corresponding to the center CLf and middle portion MLf of the tread profile TLf, while the tread surface 56 of the rear tire 42 uses portions corresponding to the center CLr and middle portion MLr of the tread profile TLr.

[0154] In this tire pair, the middle arc index Am is equal to or greater than the center arc index Ac. At the beginning of a turn, the rear tire 42 of the tire pair generates a camber thrust that is smaller than the camber thrust generated by the front tire 2. This tire pair easily changes the direction of the vehicle. Since the turning performance of the front tire 2 is higher than that of the rear tire 42, the front tire 2 contributes to the turning of the vehicle before the rear tire 42. This tire pair will not oversteer and can maintain good turning performance. By making the turning force when the vehicle is overturned equal to or less than the turning force at the beginning of a turn, the vehicle can travel stably in high-speed corners. This tire pair has excellent cornering stability. This tire pair has excellent turning performance in high-speed corners. From this point of view, it is preferred that the middle arc index Am is greater than the center arc index Ac.

[0155] In corners where the vehicle turns at low or medium speeds (hereinafter referred to as low or medium speed corners), the portion from the equator to the end of the tread surface is used, that is, the portion corresponding to the center portion of the tread profile to the portion corresponding to the shoulder portion is used. Specifically, for the tread surface 16 of the front tire 2, the portion corresponding to the center portion CLf of the tread profile TLf to the portion corresponding to the shoulder portion SLf is used, and for the tread surface 56 of the rear tire 42, the portion corresponding to the center portion CLr of the tread profile TLr to the portion corresponding to the shoulder portion SLr is used.

[0156] When the vehicle is traveling at a low or medium speed corner, similar to the case of traveling at a high speed corner, the portions of the tire tread surface corresponding to the center and middle portions of the tread contour line are first used.

[0157] As described above, the intermediate arc index Am is equal to or greater than the center arc index Ac. By using this tire pair, the vehicle can easily change direction and can stably travel around corners at medium and low speeds.

[0158] The radius of curvature of low- and medium-speed corners is smaller than that of high-speed corners. When a vehicle is traveling through a low- and medium-speed corner, it may be traveling in a fully tilted state (i.e., fully banked). In this case, the portion of the tire's tread surface corresponding to the shoulder of the tread contour is used.

[0159] In this tire pair, the shoulder arc index As is smaller than the center arc index Ac. This tire pair allows the vehicle to maintain the required cornering force while cornering at low and medium speeds. While further leaning the vehicle might cause understeer, this tire pair effectively suppresses understeer. This tire pair exhibits excellent cornering performance at low and medium speeds.

[0160] In this tire pair, the middle arc index Am is equal to or greater than the center arc index Ac, and the shoulder arc index As is less than the center arc index Ac.

[0161] This tire pair can maintain good turning performance at high-speed corners and improve turning performance at medium and low-speed corners. This tire pair can improve the turning performance of the vehicle.

[0162] In this tire pair, from the viewpoint of further improving the turning performance of the vehicle, it is preferable that the middle arc index Am is larger than the center arc index Ac, and the shoulder arc index As is smaller than the center arc index Ac.

[0163] In this tire pair, the middle arc index Am is preferably 0.50 or greater. This prevents the rounded corners of the rear tire 42, as a whole, from becoming too small relative to the rounded corners of the front tire 2, as a whole, tread surface 56. During high-speed cornering using the portions of the tire's tread surface corresponding to the center and middle portions of the tread contour, the turning force of the front tire 2 is appropriately maintained. This tire pair can effectively prevent vehicle understeer. From this perspective, the middle arc index Am is more preferably 0.54 or greater. To maintain good cornering performance, the middle arc index Am is preferably 1.10 or less, and more preferably 1.03 or less.

[0164] In this tire pair, the shoulder arc index As is preferably 0.35 or greater. This prevents the overall rounding of the tread surface 56 of the rear tire 42 from becoming excessively large relative to the overall rounding of the tread surface 16 of the front tire 2. During full-tilt driving at low- and medium-speed corners using the portion of the tire's tread surface corresponding to the shoulder portion of the tread contour line, the contribution of the front tire 2 is prevented from becoming excessively greater than that of the rear tire 42. This tire pair can effectively prevent the vehicle from oversteering during full-tilt driving. From this perspective, a shoulder arc index As of 0.37 or greater is more preferable. To maintain good cornering performance, the shoulder arc index As is preferably 0.88 or less, and more preferably 0.68 or less.

[0165] In this tire pair, from the viewpoint of obtaining good cornering performance, it is more preferable that the middle arc index Am is 0.50 or greater and the shoulder arc index As is 0.35 or greater.

[0166] In this tire pair, it is further preferred that the middle arc index Am is equal to or greater than the center arc index Ac, the shoulder arc index As is less than the center arc index Ac, the middle arc index Am is greater than 0.50, and the shoulder arc index As is greater than 0.35.

[0167] As described above, the ratio of the tread height Hf to the outer diameter Df (Hf / Df) in the front tire 2 is preferably 5.0% or more and 10.0% or less. The ratio of the tread height Hr to the outer diameter Dr (Hr / Dr) in the rear tire 42 is preferably 8.5% or more and 15.0% or less.

[0168] In this tire pair, from the viewpoint of being able to improve the turning performance of the vehicle, it is more preferred that in the front tire 2, the ratio of the tread height Hf to the outer diameter Df (Hf / Df) is greater than 5.0% and less than 10.0%, and in the rear tire 42, the ratio of the tread height Hr to the outer diameter Dr (Hr / Dr) is greater than 8.5% and less than 15.0%.

[0169] As described above, in the front tire 2, the ratio of the radius R1f of the first arc to the outer diameter Df (R1f / Df) is preferably 8.0% or more and 13.0% or less. In the rear tire 42, the ratio of the radius R1r of the first arc to the outer diameter Dr (R1r / Dr) is preferably 9.0% or more and 21.0% or less.

[0170] In this tire pair, from the viewpoint of being able to improve the turning performance of the vehicle, it is more preferred that in the front tire 2, the ratio of the radius R1f of the first arc to the outer diameter Df (R1f / Df) is greater than 8.0% and less than 13.0%, and in the rear tire 42, the ratio of the radius R1r of the first arc to the outer diameter Dr (R1r / Dr) is greater than 9.0% and less than 21.0%.

[0171] As described above, according to the present invention, a pair of motorcycle tires capable of improving the turning performance of the vehicle is obtained.

[0172] Example

[0173] Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to these Examples.

[0174] [Example 1]

[0175] Prepare a pair of motorcycle tires, which consists of Figure 1 The basic structure shown in the following table 1 has a front tire (120 / 70ZR17) with a specification shown in the following table 1, and a Figure 4 The basic structure shown in the figure is provided with a rear tire (190 / 55ZR17) having the specifications shown in Table 1 below.

[0176] The front and rear tires of Example 1 were slick tires. No grooves intersecting the equator were engraved on the tread surfaces of the front and rear tires. This is indicated by "Y" in the "Groove" column of Table 1.

[0177] [Examples 2-4 and Comparative Examples 1-2]

[0178] Tire pairs of Examples 2 to 4 and Comparative Examples 1 to 2 were prepared, having the specifications shown in Table 1 below. The basic structure of each tire pair was the same as that of the tire pair of Example 1.

[0179] Grooves intersecting the equator are provided on the tread surfaces of Examples 2 and 3 and Comparative Example 1. This is indicated by "N" in the "Groove" column of Tables 1 and 2.

[0180] For either tire pair, the front tire size is 120 / 70ZR17 and the rear tire size is 190 / 55ZR17.

[0181] [Performance Evaluation]

[0182] Assemble the front and rear tires on regular rims, fill them with air, and adjust the tire internal pressure to the regular pressure.

[0183] Front and rear tires were mounted on a large motorcycle (displacement = 1000cc). 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.

[0184] Evaluation items include high-speed cornering, medium- and low-speed cornering, and initial responsiveness.

[0185] The evaluation results are shown by indexes in the following Table 1. A larger numerical value indicates a better result.

[0186] Table 1

[0187]

[0188] As shown in Table 1, it was confirmed that the tire pair of the Example can contribute to the improvement of the turning performance of the vehicle. The superiority of the present invention is clear from this evaluation result.

[0189] Industrial applicability

[0190] The technology described above that can contribute to improving the turning performance of a vehicle can also be applied to tire pairs for various motorcycles.

Claims

1. A motorcycle tire pair, the motorcycle tire pair being a tire pair consisting of a front tire and a rear tire, characterized in that: The front tire and the rear tire each include: a pair of 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 term "substantially" means that 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 a meridian cross section, the contour line of the tread surface is divided into five parts by dividing the portion from the equator to the end of the tread surface at a length ratio of 1:2:

1. The five parts are a center portion including the equator, a pair of middle portions connected to the center portion, and a pair of shoulder portions connected to the middle portions. The arc passing through the equator and both ends of the center is the first arc. The arc passing through the inner end, outer end and center of the middle part is the second arc. The arc passing through the inner end, outer end and center of the shoulder portion is the third arc. The ratio R1f / R1r 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 the center circular arc index. The ratio R2f / R2r 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 R3f / R3r 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 equal to or greater than the center arc index, and the shoulder arc index is less than the center arc index.

2. The motorcycle tire pair according to claim 1, characterized in that: The intermediate arc index is greater than 0.50, The shoulder arc index is greater than 0.

35.

3. The motorcycle tire pair according to claim 1 or 2, characterized in that: 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 outer diameter is 5.0% or more and 10.0% or less, In the rear tire, a ratio of the tread height to the outer diameter is 8.5% or more and 15.0% or less.

4. The motorcycle tire pair according to claim 1 or 2, characterized in that: In the front tire, a ratio of a radius R1f of the first arc to an outer diameter is 8.0% or more and 13.0% or less, In the rear tire, a ratio of a radius R1r of the first arc to an outer diameter is 9.0% or more and 21.0% or less.

5. The motorcycle tire pair according to claim 1 or 2, characterized in that: No grooves intersecting the equator are engraved on the tread surface.

6. The motorcycle tire pair according to claim 1 or 2, characterized in that: 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 motorcycle tire pair according to claim 6, wherein: The carcass cords are cords composed of organic fibers.

Images