Motorcycle tire

Abstract

The present invention provides a motorcycle tire capable of suppressing water splashing forward for a long period of time. A motorcycle tire (1) has a circumferential groove (3). The circumferential groove (3) includes a plurality of first inclined portions (8) and a plurality of second inclined portions (9) that are inclined. The circumferential groove (3) includes a pair of groove walls (12). In a groove cross-section of the first inclined portion (8), each of the pair of groove walls (12) is inclined toward the first tread edge (T1) toward the inside in the tire radial direction with respect to a tread normal line (n). In a groove cross-section of the second inclined portion (9), each of the pair of groove walls (12) is inclined toward a second tread end (T2) toward the inside in the tire radial direction with respect to a tread normal (n).

Description

Technical Field

[0001] The invention relates to a tire for motorcycles. Background Art

[0002] The following Patent Document 1 describes a motorcycle tire having circumferential grooves formed on the tread portion. The circumferential grooves include curved portions arranged on one side and the other side of the tire equator, and connecting portions connecting the curved portions, extending in a zigzag shape. Such circumferential grooves are expected to have the effect of suppressing the poor vision of the rider caused by the water film being pushed forward in the traveling direction.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-165795 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] In recent years, motorcycle tires have been required to suppress poor visibility as described above, or the motorcycle or the rider from being splashed with water for a long period of time.

[0008] The present invention has been developed in view of the above-mentioned problems, and an object of the present invention is to provide a motorcycle tire that can suppress water splashing forward for a long period of time when running on a wet road.

[0009] [Technical means to solve the problem]

[0010] The present invention is a motorcycle tire having a tread portion, wherein the tread portion includes: a first tread end, a second tread end, a tread between the first tread end and the second tread end, and a circumferential groove extending continuously in the tread along the tire circumferential direction. The circumferential groove includes: a plurality of first inclined portions inclined in a first direction relative to the tire circumferential direction, and a plurality of second inclined portions inclined in a direction opposite to the first direction. The circumferential groove includes: a pair of groove walls extending from the tread to the inner side of the tire radial direction. In the groove section in the tire meridian direction of each of the plurality of first inclined portions, the pair of groove walls are inclined toward the first tread end side toward the inner side of the tire radial direction relative to the tread normal line standing at the groove edge. In the groove section in the tire meridian direction of each of the plurality of second inclined portions, the pair of groove walls are inclined toward the second tread end side toward the inner side of the tire radial direction relative to the tread normal line standing at the groove edge.

[0011] [Effects of the Invention]

[0012] The motorcycle tire of the present invention can suppress forward splashing of water for a long period of time by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a development view of a tread portion showing an embodiment of a motorcycle tire of the present invention.

[0014] Figure 2 is a plan view of the circumferential groove.

[0015] Figure 3 (A) is Figure 2 AA line section diagram, Figure 3 (B) is Figure 2 BB line cross-section diagram.

[0016] Figure 4 (A) is Figure 2 The CC line profile, Figure 4 (B) is Figure 4 A cross-sectional view of another embodiment of (A).

[0017] Figure 5 (A) is Figure 2 DD line profile, Figure 5 (B) is Figure 2 EE line profile.

[0018] Figure 6 (A) is Figure 2 FF line cross-section diagram, Figure 6 (B) is Figure 2 GG line profile.

[0019] Figure 7 It is a development view of the tread portion of the present embodiment.

[0020] Figure 8 is a plan view of the first inclined trough.

[0021] Fig. 9 is a plan view of the first inclined trough.

[0022] Fig.10 yes Figure 8 HH line profile.

[0023] Fig.11 is a plan view of the first small inclined trough.

[0024] [Explanation of Symbols]

[0025] 1: Motorcycle tires / tires

[0026] 3: Circumferential groove

[0027] 8: First inclined portion

[0028] 9: Second inclined portion

[0029] 12: Groove wall

[0030] n: tread normal

[0031] T1: First tread end

[0032] T2: Second tread end DETAILED DESCRIPTION

[0033] Hereinafter, an embodiment of the present invention will be described based on the accompanying drawings. The accompanying drawings contain exaggerated representations or representations with different dimensional ratios from the actual structure to help understand the present invention. In addition, when there are multiple embodiments, the same or common components are annotated with the same symbols throughout the specification, and repeated descriptions are omitted.

[0034] Figure 1 The present invention is a plan view of a tread portion 2 of a motorcycle tire (hereinafter sometimes referred to as a "tire") 1 according to an embodiment of the present invention. The present invention can be used for tires of so-called commuter bicycles (bikes) that are intended to be used on the street (comfort / safety is more important than speed). Such tires are more likely to be driven mainly at a small camber angle. In addition, the present invention can be suitably used for bias tires in which the carcass cords (not shown) of the carcass extend at an angle of 20 to 60 degrees relative to the tire circumferential direction.

[0035] like Figure 1 As shown, the tread portion 2 includes a first tread end T1 (left side in the figure), a second tread end T2 (right side in the figure), a tread surface 2a between the first tread end T1 and the second tread end T2, and a circumferential groove 3 extending continuously in the tread surface 2a along the tire circumference. The center of the tire axial direction between the first tread end T1 and the second tread end T2 is the tire equator C.

[0036] The first tread end T1 and the second tread end T2 are the ends forming the maximum width of the tread. In the case of a tire 1 whose maximum tread width is consistent with the total width (maximum width) of the tire, the first tread end T1 and the second tread end T2 are the outer ends of the tire 1 in the axial direction of the tire. In the case of a tire 1 whose maximum tread width is smaller than the total width of the tire, the first tread end T1 and the second tread end T2 are the two ends of the tire axial direction that are in contact with the plane when a normal load is applied to the tire 1 in a normal state and the camber angle is 30 degrees so that it is inclined to both sides of the tire axial direction and contacts the plane. The length along the tread 2a between the first tread end T1 and the second tread end T2 is the tread development width TWe. In addition, 50% of the tread development width TWe is the tread development half width TW. In addition, in this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in the normal state. The "normal state" is a state in which the tire 1 is hooped to a normal rim (not shown), adjusted to a normal internal pressure, and is unloaded. The "normal load" refers to the load specified for each tire in each specification in the specification system that includes the specifications on which the tire is based. If it is the Japan Automobile Tire Manufacturers Association (JATMA), it is set to the maximum load capacity; if it is the Tire and Rim Association (TRA), it is set to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; if it is the European Tire and Rim Technical Organization (ETRTO), it is set to "LOAD CAPACITY".

[0037] In addition, the "conventional rim" is a rim specified for each tire in the specification system that includes the specifications on which the tire 1 is based, for example, if it is JATMA, it is a "standard rim", if it is TRA, it is a "design rim (Design Rim)", and if it is ETRTO, it is a "measuring rim (Measuring Rim)".

[0038] In addition, "normal internal pressure" is the air pressure specified for each tire in each specification in the specification system including the specifications on which tire 1 is based. If it is JATMA, it is the "maximum air pressure"; if it is TRA, it is the maximum value recorded in the table "Tire load limits at various cold inflation pressures (TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES)"; if it is ETRTO, it is the "inflation pressure (INFLATION PRESSURE)".

[0039] Figure 2 is a plan view of the circumferential groove 3. Figure 2 As shown, the circumferential groove 3 includes a plurality of first inclined portions 8 inclined in a first direction relative to the tire circumference and a plurality of second inclined portions 9 inclined in a direction opposite to the first direction. Such a circumferential groove 3 has a larger groove volume than, for example, a circumferential groove (not shown) extending in a straight line along the tire circumference, thereby reducing the amount of water splashing. In addition, the first inclined portion 8 and the second inclined portion 9 make the water splashing when contacting the wet road surface form an angle to the left and right relative to the direction of travel, thereby reducing the water splashing forward. Therefore, the circumferential groove 3 of this embodiment has the basic performance of suppressing water splashing forward. In this embodiment, the first inclined portion 8 is inclined to the upper right side. In this embodiment, the second inclined portion 9 is inclined to the upper left side. In this embodiment, the first inclined portion 8 and the second inclined portion 9 are alternately arranged in the tire circumferential direction. In addition, the first inclined portion 8 may be inclined to the upper left side and the second inclined portion 9 may be inclined to the upper right side.

[0040] The circumferential groove 3 includes a pair of groove walls 12 extending from the tread surface 2a toward the inner side in the tire radial direction. Figure 3 (A) is Figure 2 AA line cross-section diagram. Figure 3 (A) is a groove cross section of each of the plurality of first inclined portions 8 in the tire meridian direction. Figure 3 As shown in (A), in each of the plurality of first inclined portions 8, the pair of groove walls 12 are inclined toward the first tread end T1 side toward the inner side in the tire radial direction relative to the tread normal line n standing at the groove edge 3e. Figure 3 (B) is Figure 2 BB line cross-section diagram. Figure 3 (B) is a groove cross section of each of the plurality of second inclined portions 9 in the tire meridian direction. Figure 3As shown in (B), in each of the plurality of second inclined portions 9, a pair of groove walls 12 are respectively inclined toward the second tread end T2 side inward in the tire radial direction relative to the tread normal line n standing upright at the groove edge 3e. By utilizing the inclination, the splashing water during the wet road running process can be further dispersed to the left and right. Furthermore, when the wear of the tread portion 2 intensifies, the first inclined portion 8 and the second inclined portion 9 have a portion where the inclination angle relative to the tire circumferential direction becomes larger. As a result, at the end of the wear when the groove volume becomes smaller, splashing water can be generated at a larger angle relative to the traveling direction, so that splashing water to the front can be suppressed for a long time.

[0041] like Figure 1 As shown, the tread portion 2 of the present embodiment is assigned a tire rotation direction R. The tread portion 2 contacts the road surface from the bottom to the top of the figure. In addition, in the present embodiment, the contour of the tread portion 2 (not shown) is curved in an arc shape convex to the outside in the radial direction of the tire (not shown).

[0042] In the present embodiment, the tread portion 2 includes a crown region Cr including the tire equator C. In the present embodiment, the crown region Cr is a region that contacts the plane when a normal load is applied to the tire 1 in a normal state and the camber angle is set to 0 degrees, and the region that contacts the road surface mainly when the tire is running straight. The "normal load" refers to the load specified for each tire in each specification in the specification system including the specifications to which the tire is based, and is set to the maximum load capacity in the case of JATMA, the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[0043] The circumferential groove 3 extends in a wave shape, for example. In the present embodiment, the circumferential groove 3 extends in a sinusoidal wave shape. Compared with a circumferential groove (not shown) extending in a sawtooth shape or a pseudo-sinusoidal wave shape, the flow of water in the circumferential groove 3 becomes smoother, and the amount of water splashed when contacting with a wet road surface is reduced without damaging the drainage performance of the tread surface 2a. The sinusoidal wave shape is of course a sine wave, including a form formed by multiple waves with different wavelengths and / or multiple waves with different amplitudes.

[0044] The ratio (λ / A) of the amplitude λ of the circumferential groove 3 to the half wavelength A is preferably 0.04 or more, more preferably 0.06 or more, and is preferably 0.12 or less, more preferably 0.10 or less. Since the ratio (λ / A) is 0.12 or less, the splashing water when contacting with the wet road surface can be made to form a large angle to the left and right relative to the direction of travel. Since the ratio (λ / A) is 0.04 or more, the flow of water in the circumferential groove 3 becomes smooth, and the amount of splashing water can be suppressed. The amplitude λ and the half wavelength A are specifically specified by the groove center line 3c of the circumferential groove 3. The groove center line 3c is specifically specified by the position on the tread 2a in the radial direction of the tire.

[0045] The circumferential groove 3 is disposed, for example, in the crown region Cr. The circumferential groove 3 is ideally located on the tire equator C. In the present embodiment, the center line 3k of the amplitude of the circumferential groove 3 is located on the tire equator C. This can suppress the splashing of water during straight travel, which is relatively high-speed travel.

[0046] The circumferential groove 3 further includes: a connecting portion 10 connecting the first inclined portion 8 and the second inclined portion 9 adjacent to each other in the tire circumferential direction. The connecting portion 10 includes a first connecting portion 10A located on the first tread end T1 side. The first connecting portion 10A is located, for example, closer to the first tread end T1 side than the tire equator C. In addition, the connecting portion 10 includes a second connecting portion 10B located on the second tread end T2 side. The second connecting portion 10B is located, for example, closer to the second tread end T2 side than the tire equator C.

[0047] Figure 4 (A) is Figure 2 CC line profile. Figure 4 (A) is a groove cross section of each of the plurality of connecting portions 10 in the tire meridian direction. Figure 4 (A) shows the groove cross section of the first connecting portion 10A in the tire meridian direction. Figure 4 As shown in (A), in the connection portion 10, a pair of groove walls 12 extend at an angle θ of 0 degrees relative to the tread normal line n standing upright at the groove edge 3e. In addition, in the connection portion 10, the pair of groove walls 12 may also extend inward in the radial direction of the tire in a tapered shape ( Figure 4 Such a connection portion 10 allows the water in the first inclined portion 8 and the second inclined portion 9 to flow smoothly, thereby reducing the amount of water splashing.

[0048] Figure 5 (A) is Figure 2 DD line profile. Figure 5 (B) is Figure 2 EE line profile. Figure 5 (A) Figure 5 (B) is a groove cross section of each of the plurality of first inclined portions 8 in the tire meridian direction. Figure 5 (A) Figure 5 The cross-section shown in each figure of (B) is the middle part 8c ( Figure 2 2 is a cross-section closer to the two ends 8e (connecting portion 10) of the first inclined portion 8. Figure 6 (A) is Figure 2 FF line cross-section diagram. Figure 6 (B) is Figure 2 GG line profile. Figure 6 (A) Figure 6 (B) is a groove cross section of each of the plurality of second inclined portions 9 in the tire meridian direction. Figure 6 (A) Figure 6 The cross-section shown in each figure of (B) is the middle part 9c ( Figure 2 1 is a cross section closer to the two ends 9e (connecting portion 10) of the second inclined portion 9.

[0049] In each of the plurality of first inclined portions 8, the angle θ1 ( Figure 3 (A) Figure 5 (A) Figure 5 (B) For example, the angle θ2 ( Figure 3 (B) Figure 6 (A) Figure 6 (B) For example, the first inclined portion 8 and the second inclined portion 9 are the same from one end 9e (connecting portion 10) side through the middle portion 9c to the other end 9e (connecting portion 10) side. Such first inclined portion 8 and second inclined portion 9 can reduce the change in the inclination angle of the first inclined portion 8 and the second inclined portion 9 relative to the tire circumference at the end of wear, thereby introducing a large amount of water into the circumferential groove 3, thereby suppressing splashing. In this specification, the middle portion 8c of the first inclined portion 8 refers to an area within 1 / 4 of the length Lx of the first inclined portion 8 in the tire circumferential direction, centered at the midpoint of the first inclined portion 8 in the tire circumferential direction. The middle portion 9c of the second inclined portion 9 is also defined in the same manner.

[0050] The angle θ1 ( Figure 3 (A) is at least the largest at the middle portion 8c in the longitudinal direction of each of the plurality of first inclined portions 8. In addition, the angle θ2 ( Figure 3(B) is at least the largest at the middle portion 9c in the length direction of each of the plurality of second inclined portions 9. Such middle portions 8c and 9c effectively play the role described above. In the present embodiment, between the EE line section and the FF line section adjacent in the tire circumferential direction across the first connecting portion 10A, the angle θ of each of the pair of groove walls 12 relative to the tread normal n changes. In addition, in the present embodiment, between the GG line section and the DD line section adjacent in the tire circumferential direction across the second connecting portion 10B, the angle θ of each of the pair of groove walls 12 relative to the tread normal n changes.

[0051] The maximum values ​​of the angles θ1 and θ2 of the pair of groove walls 12 relative to the tread normal line n are preferably 5 degrees or more, more preferably 7 degrees or more, and are preferably 15 degrees or less, more preferably 13 degrees or less. Since the maximum values ​​of the angles θ1 and θ2 are 5 degrees or more, splashing water can be generated at a larger angle relative to the traveling direction at the end of wear. Since the maximum values ​​of the angles θ1 and θ2 are 15 degrees or less, the change in rigidity of the tread portion 2 near the circumferential groove 3 can be maintained small. In addition, since the maximum values ​​of the angles θ1 and θ2 are 15 degrees or less, damage to the mold (not shown) used to manufacture the tire 1 when pulling it can be suppressed.

[0052] The pair of groove walls 12 of the circumferential groove 3 includes a first groove wall 12A on the first tread end T1 side and a second groove wall 12B on the second tread end T2 side. Figure 3 (A) and Figure 5 (A) Figure 5 As shown in (B), in each cross section of the tire meridian of the first inclined portion 8, the angle θ1a of the first groove wall 12A relative to the tread normal line n is preferably the same as the angle θ1b of the second groove wall 12B relative to the tread normal line n (the same absolute value). Figure 3 (B) and Figure 6 (A) Figure 6As shown in (B), in each cross section of the tire meridian of the second inclined portion 9, the angle θ2a of the first groove wall 12A relative to the tread normal n is preferably the same as the angle θ2b of the second groove wall 12B relative to the tread normal n (the same absolute value). In each cross section of the first inclined portion 8, the same angle means that the absolute value of the difference |θ1a-θ1b| between the angle θ1a of the first groove wall 12A and the angle θ1b of the second groove wall 12B is 0 degrees, including the case of 3 degrees or less. In addition, in each cross section of the second inclined portion 9, the absolute value of the difference |θ2a-θ2b| between the angle θ2a of the first groove wall 12A and the angle θ2b of the second groove wall 12B is 0 degrees, including the case of 3 degrees or less. In each cross section of the tire meridian of the first inclined portion 8, the first groove wall 12A forms an acute angle with the tread 2a, and the second groove wall 12B forms an obtuse angle with the tread 2a. In each transverse section of the second inclined portion 9 along the tire meridian, the first groove wall 12A forms an obtuse angle with the tread surface 2a, and the second groove wall 12B forms an acute angle with the tread surface 2a.

[0053] like Figure 4 As shown in (B), the circumferential groove 3 also includes a groove bottom 13 connected to a pair of groove walls 12. The pair of groove walls 12 extend in a straight line, for example. The straight line is of course extending in a straight line in the groove section in the meridian direction of the tire, including the case where it extends in an arc (omitted in the figure) with a curvature radius of more than 100 mm. The groove bottom 13 includes a groove bottom with the maximum groove depth, for example, formed in an arc shape. Such a groove bottom 13 allows the water in the circumferential groove 3 to flow smoothly, and disperses the stress generated in the groove bottom, thereby suppressing the occurrence of cracks in the groove bottom. In the present embodiment, the arc shape of course includes an arc with a single curvature radius, and also includes a form formed by an arc forming the groove bottom, and a pair of arcs connecting the arc to each groove wall 12 and having a smaller curvature radius than the arc of the groove bottom (omitted in the figure). In addition, the arc forming the groove bottom may also be a straight line.

[0054] The groove width W1 of the circumferential groove 3 is, for example, preferably 2% or more of the tread half width TW, more preferably 3% or more, and is preferably 7% or less, more preferably 6% or less. The groove depth d1 of the circumferential groove 3 is, for example, preferably 1.1 times or more of the groove width W1, more preferably 1.5 times or more, and is preferably 3.5 times or less, more preferably 3.0 times or less.

[0055] Figure 7 FIG. 2 is a development diagram of the tread portion 2 of the present embodiment. Figure 7As shown, in this embodiment, a plurality of first inclined grooves 15 and a plurality of second inclined grooves 16 are further provided in the tread portion 2. In addition, a plurality of first small inclined grooves 40 and a plurality of second small inclined grooves 41 are provided in the tread portion 2. Each inclined groove 15, 16 and each small inclined groove 40, 41 can make the splashing water when contacting with the wet road surface form an angle with respect to the traveling direction.

[0056] Each first inclined groove 15 has an inner end 15i separated from the circumferential groove 3 on the first tread end T1 side of the circumferential groove 3. The inner end 15i is, for example, the innermost end of the first inclined groove 15 in the tire axial direction. Each first inclined groove 15 extends, for example, from the inner end 15i to the first tread end T1 side. In addition, each second inclined groove 16 has an inner end 16i separated from the circumferential groove 3 on the second tread end T2 side of the circumferential groove 3. The inner end 16i is, for example, the innermost end of the second inclined groove 16 in the tire axial direction. Each second inclined groove 16 extends, for example, from the inner end 16i to the second tread end T2 side. In the present embodiment, the plurality of first inclined grooves 15 extend continuously toward the first tread end T1 side toward the rear ground contact side in the tire rotation direction R. In the present embodiment, the plurality of second inclined grooves 16 extend continuously toward the second tread end T2 side toward the rear ground contact side in the tire rotation direction R. The first inclined grooves 15 and the second inclined grooves 16 can smoothly drain water by utilizing the rotation of the tire 1. The first inclined grooves 15 and the second inclined grooves 16 are formed in a curved shape convex toward the rear ground contact side in the tire rotation direction R.

[0057] In addition, the inner end 15i of each of the plurality of first inclined grooves 15 is, for example, located at a position closer to the first tread end T1 than the first connecting portion 10A. In addition, in the present embodiment, the inner end 16i of each of the second inclined grooves 16 is located at a position closer to the second tread end T2 than the plurality of second connecting portions 10B. As a result, the excessive reduction in the rigidity of the tread portion 2 can be suppressed, and thus the occurrence of uneven wear can be suppressed. In addition, the split position of the mold (not shown) for manufacturing the tire 1 can be arranged between the circumferential groove 3 and the first inclined groove 15 or the second inclined groove 16, and thus the groove bottom crack (not shown) which tends to be generated due to the intersection of the split position and the groove can be suppressed. Although not particularly limited, the length Ls in the tire axial direction between the inner end 15i and the first connecting portion 10A (groove edge 3e) is preferably 5% or more of the tread half width TW, more preferably 7% or more, and is ideally 15% or less, more preferably 13% or less. The length Lt between the inner end 16i and the second connecting portion 10B (groove edge 3e) in the tire axial direction is preferably 5% or more, more preferably 7% or more, and is preferably 15% or less, more preferably 13% or less of the tread half width TW.

[0058] The inner ends 15i of the plurality of first inclined grooves 15 are located adjacent to the plurality of first inclined portions 8 in the tire axial direction. In the present embodiment, the inner ends 15i are closer to the first inclined portions 8 than to the second inclined portions 9. Figure 3 (A) Figure 5 (A) Figure 5 As shown in (B), the pair of groove walls 12 of the first inclined portion 8 are inclined toward the first tread end T1 side toward the inner side in the tire radial direction. As a result, the tread 2a of the tread portion 2 between the first inclined portion 8 and the inner end 15i is easily moved by the inner end 15i being adjacent to the first inclined portion 8, and the load generated in the inner end 15i can be dispersed and reduced, thereby suppressing the occurrence of local wear. In addition, the tread 2a adjacent to the second groove wall 12B on the second tread end T2 side of the first inclined portion 8 is accelerated to wear due to load concentration. Therefore, the difference in the amount of wear at both sides of the first inclined portion 8 in the tire axial direction becomes smaller, and the uneven wear resistance performance can be improved.

[0059] In addition, the inner ends 16i of the plurality of second inclined grooves 16 are located adjacent to the plurality of second inclined portions 9 in the tire axial direction. In the present embodiment, the inner ends 16i are closer to the second inclined portions 9 than to the first inclined portions 8. Figure 3 (B) Figure 6 (A) Figure 6 As shown in (B), the pair of groove walls 12 of the second inclined portion 9 are inclined toward the second tread end T2 side toward the inner side in the tire radial direction. As described above, the difference in the amount of wear of the tread surfaces 2a on both sides of the second inclined portion 9 is reduced.

[0060] The plurality of first inclined grooves 15 each include a pair of groove edges 15e extending in the longitudinal direction of the first inclined groove 15. The pair of groove edges 15e include a tapered portion 18, in which the pair of groove edges 15e extend in a tapered shape toward the inner end 15i. Such tapered portion 18 can smoothly guide the water film on the tread surface 2a into the first inclined groove 15. The length L1 of each tapered portion 18 in the tire circumferential direction is preferably 5% or more, more preferably 7% or more, and is preferably 13% or less, more preferably 11% or less of the length La of the first inclined groove 15 in the tire circumferential direction.

[0061] Each of the plurality of second inclined grooves 16 includes a pair of groove edges 16e extending in the longitudinal direction of the second inclined groove 16. The pair of groove edges 16e includes a tapered portion 19, and the pair of groove edges 16e extend in a tapered shape toward the inner end 16i in the tapered portion 19. The tapered portion 19 plays the same role as the tapered portion 18 of the first inclined groove 15. The length L2 of each tapered portion 19 in the tire circumferential direction is preferably 5% or more, more preferably 7% or more, and is preferably 13% or less, more preferably 11% or less of the length Lb of the second inclined groove 16 in the tire circumferential direction.

[0062] In the present embodiment, the second inclined groove 16 has the same shape (line symmetric shape) as the first inclined groove 15 inverted about the tire equator C. Therefore, in this specification, the first inclined groove 15 is described as a representative, and the second inclined groove 16 is described as having a structure different from the first inclined groove 15 .

[0063] Figure 8 is a plan view of the first inclined groove 15. Figure 8 As shown, the plurality of first inclined grooves 15 each include a first portion 20 where the groove width W2 decreases from the crown region Cr toward the first tread end T1 side, and a second portion 21 where the groove width W2 increases toward the first tread end T1 until reaching the first tread end T1. The first portion 20 reduces the amount of slippage on the outer side of the tire axial direction where the slippage is likely to increase, and reduces the difference in the amount of wear generated in the two groove edges 15e of the first portion 20, thereby improving the uneven wear resistance. In addition, during wet driving with a reduced camber angle, the reduction in the groove width W2 of the first inclined groove 15 in the area contacting the road surface is suppressed, so that the wet performance can be maintained. In addition, the second portion 21 makes the drainage from the first tread end T1 smooth, so that the wet performance can be maintained.

[0064] The first inclined groove 15 of the present embodiment is formed by a first portion 20, a second portion 21, and a tapered portion 18 (shadowless line). The groove width W2 is the length of the first inclined groove 15 in a direction perpendicular to the groove center line 15c. In addition, when the first inclined groove 15 is connected to a groove or cutout having a smaller groove depth than the first inclined groove 15, the groove width W2 is measured at the portion where the small groove or cutout is formed using an imaginary groove edge 15v obtained by filling the small groove or cutout. Figure 8 In the figure, for convenience, the first portion 20 and the second portion 21 are indicated by hatching in different directions. In addition, the imaginary groove edge 15v is indicated by a double-dot chain line.

[0065] The length L3 of the first portion 20 in the tire axial direction is preferably 50% or more, more preferably 55% or more, of the tread half width TW, and is preferably 75% or less, more preferably 70% or less. Since the length L3 of the first portion 20 is 50% or more of the tread half width TW, the uneven wear resistance can be improved. Since the length L3 of the first portion 20 is 75% or less of the tread half width TW, the excessive reduction of the flow of water in the first inclined groove 15 can be suppressed.

[0066] The length L4 of the second portion 21 in the tire axial direction is preferably 5% or more, more preferably 7% or more, and is preferably 15% or less, more preferably 13% or less. Since the length L4 of the second portion 21 is 5% or more of the tread half width TW, water can be drained smoothly. Since the length L4 of the second portion 21 is 15% or less of the tread half width TW, the rigidity near the first tread end T1 is suppressed from being excessively reduced, and the amount of slip can be suppressed from becoming excessively large.

[0067] In order to improve the uneven wear resistance while maintaining the wet performance, the maximum value W2a of the groove width W2 of the first portion 20 is preferably 5% or more, more preferably 7% or more, and is preferably 15% or less, more preferably 13% or less of the tread half width TW. In addition, the maximum value W2b of the groove width W2 of the second portion 21 is preferably 80% or more, more preferably 90% or more, and is preferably 120% or less, more preferably 110% or less of the maximum value W2a of the groove width W2 of the first portion 20.

[0068] The pair of groove edges 15e includes a leading land-contact-side inclined groove edge 22A located on the leading land-contact-side in the tire rotation direction R, and a rear land-contact-side inclined groove edge 22B located on the rear land-contact-side in the tire rotation direction R. In this specification, the leading land-contact-side inclined groove edge 22A and the rear land-contact-side inclined groove edge 22B refer to a form that includes the imaginary groove edge 15v and extends continuously between the inner end 15i and the first tread end T1.

[0069] The tread portion 2 includes at least one shallow groove 24 connected to the first inclined groove 15. Such shallow groove 24 removes the water film on the tread surface 2a to improve the ground contact with the road surface, and suppresses the reduction of the rigidity of the tread portion 2, thereby improving the wet performance while maintaining high uneven wear resistance. The shallow groove 24 has a groove depth d4 ( Fig.10 shown) is formed.

[0070] Fig. 9 is a plan view of the first inclined groove 15. Fig. 9 As shown, the shallow groove 24 includes an opening 26 connected to the first inclined groove 15. Water in the shallow groove 24 flows into the first inclined groove 15 through the opening 26 and is discharged to the outside of the tread 2a during running. The position of the opening 26 overlaps with the virtual groove edge 15v.

[0071] The shallow groove 24 includes a pair of groove edges 24e connected to the groove edge 15e of the first inclined groove 15. In the present embodiment, at least one of the pair of groove edges 24e is formed in a curved shape convex toward the rear ground contact side in the tire rotation direction R.

[0072] The tread surface 2a of the tread portion 2 includes an acute angle portion 28 sandwiched between one of the groove edges 15e of the first inclined groove 15 and one of the pair of groove edges 24e of the shallow groove 24. Moreover, in the acute angle portion 28, the groove edge 15e and the groove edge 24e are connected by the arc 27. As a result, the load carried by the connecting portion of the first inclined groove 15 and the shallow groove 24 is dispersed, thereby improving the uneven wear resistance. In the acute angle portion 28, the curvature radius r1 of the arc 27 is preferably 0.5 mm or more, and more preferably 0.7 mm or more. Since the curvature radius r1 is 0.5 mm or more, the uneven wear resistance can be improved. There is no particular limitation on the upper limit of the curvature radius r1 of the arc 27, but if the aesthetic design of the pattern is considered, it is preferably 1.5 mm or less, and more preferably 1.3 mm or less.

[0073] In addition, the tread surface 2a of the tread portion 2 includes an obtuse angle portion 29 sandwiched by one of the groove edges 15e of the first inclined groove 15 and one of the pair of groove edges 24e of the shallow groove 24. In addition, in the obtuse angle portion 29, the groove edge 24e is formed by an arc with a curvature radius r2. The curvature radius r2 is preferably 20 mm or more, more preferably 30 mm or more, and is preferably 100 mm or less, more preferably 90 mm or less.

[0074] The shallow groove 24 extends from the opening 26 toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1 side. In other words, a pair of groove edges 24e extend from the arc 27 toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1 side. Such shallow grooves 24 relatively reduce the amount of sliding during driving, thereby improving the uneven wear resistance. In addition, such shallow grooves 24 disperse and reduce the load generated near the first inclined groove 15, thereby improving the uneven wear resistance. In this embodiment, the shallow groove 24 has an end 24t that terminates at a position on the rear ground contact side in the tire rotation direction R.

[0075] The pair of groove edges 24e includes: a first groove edge 24a located on the rear ground contact side in the tire rotation direction R, and a second groove edge 24b located on the front ground contact side in the tire rotation direction R. Moreover, in the present embodiment, the first groove edge 24a defines an acute angle portion 28. In other words, the acute angle portion 28 is arranged on the rear ground contact side in the tire rotation direction R relative to the shallow groove 24. In addition, the second groove edge 24b defines an obtuse angle portion 29. In other words, the obtuse angle portion 29 is arranged on the front ground contact side in the tire rotation direction R relative to the shallow groove 24. Thus, the effect of relatively reducing the amount of slip during the driving can be effectively exerted.

[0076] The shallow groove 24 has a groove width W3 parallel to the opening width Wa of the opening portion 26. Moreover, the groove width W3 of the shallow groove 24 decreases, for example, as it moves away from the first inclined groove 15. As a result, it is possible to suppress an excessive decrease in the rigidity of the tread portion 2 (tread surface 2a). In this specification, "moving away from the first inclined groove 15" refers to a direction orthogonal to the opening width Wa.

[0077] Fig.10 yes Figure 8 HH line profile of. Fig.10 As shown, the groove depth d4 of the shallow groove 24 decreases as it moves away from the first inclined groove 15. This can suppress an excessive decrease in the rigidity of the tread 2a. The groove depth d4 of the shallow groove 24 is maximum at the opening 26 and minimum at the one end 24t.

[0078] The maximum groove depth d4a of the shallow groove 24 is ideally 0.3 times or more, more ideally 0.4 times or more, and ideally 0.7 times or less, more ideally 0.6 times or less of the groove depth d3 of the first inclined groove 15 at the position of the opening 26. Since the maximum groove depth d4a of the shallow groove 24 is at least 0.3 times the groove depth d3 of the first inclined groove 15, the effect of improving wet performance can be achieved. Since the maximum groove depth d4a of the shallow groove 24 is less than 0.7 times the groove depth d3 of the first inclined groove 15, an excessive reduction in the rigidity of the tread portion 2 can be suppressed. In the present specification, the first inclined groove 15 at the position of the opening 26 is an area A3 where the first inclined groove 15 intersects with a line segment that is orthogonal to the opening width Wa between a pair of groove edges 24e, 24e of the shallow groove 24. Fig. 9 In FIG. 1 , for convenience, area A3 is indicated by hatching.

[0079] like Fig. 9 As shown, the opening width Wa is preferably 1.0 times or more, more preferably 1.5 times or more, and is preferably 4.0 times or less, more preferably 3.5 times or less, of the groove width W2d of the first inclined groove 15 at the position of the opening 26 (area A3). Since the opening width Wa is 1.0 times or more of the groove width W2d of the first inclined groove 15, the effect of improving wet performance can be achieved. Since the opening width Wa is 4.0 times or less of the groove width W2d of the first inclined groove 15, excessive reduction in the rigidity of the tread portion 2 can be suppressed.

[0080] In the present embodiment, the shallow groove 24 includes: a first shallow groove 24A connected to the inclined groove edge 22A on the first ground contact side, and a second shallow groove 24B connected to the inclined groove edge 22B on the rear ground contact side. In the present embodiment, the first shallow groove 24A is located at a position closer to the inner end 15i side (the first ground contact side in the tire rotation direction R) than the second shallow groove 24B. In the present embodiment, the second shallow groove 24B includes: an inner second shallow groove 31 arranged at a position overlapping with the first shallow groove 24A in the tire axial direction; and an outer second shallow groove 32 located at a position closer to the first tread end T1 than the inner second shallow groove 31. In the present embodiment, the outer second shallow groove 32 is located at a position spanning the first portion 20 and the second portion 21. In the present embodiment, each shallow groove 24 is located at a position closer to the first tread end T1 than the crown region Cr.

[0081] One end 32e of the outer second shallow groove 32 on the rear ground contact side in the tire rotation direction R is located closer to the rear ground contact side in the tire rotation direction R than one end 15b of the first inclined groove 15 on the rear ground contact side in the tire rotation direction R. Such an outer second shallow groove 32 helps to collect a larger amount of water film on the tread surface 2a into the first inclined groove 15.

[0082] like Figure 7 As shown, in this embodiment, the second small inclined groove 41 has the same shape (line symmetric shape) as the shape obtained by inverting the first small inclined groove 40 about the tire equator C. Therefore, in this specification, the first small inclined groove 40 is described as a representative, and the second small inclined groove 41 is described as a structure different from the first small inclined groove 40.

[0083] The first small inclined groove 40 has an inner end 40i located closer to the first tread end T1 than the inner end 15i of the first inclined groove 15, and opens to the first tread end T1. The first small inclined groove 40 extends toward the first tread end T1 toward the rear ground contact side in the tire rotation direction R. In addition, the first small inclined groove 40 is formed, for example, in a curved shape convex toward the rear ground contact side in the tire rotation direction R. Furthermore, the first small inclined groove 40 of the present embodiment is located closer to the first tread end T1 than the crown region Cr.

[0084] Fig.11 is a plan view of the first small inclined groove 40. Fig.11 As shown, the first small inclined groove 40 has a pair of groove edges 40e extending from the inner end 40i to the first tread end T1. The pair of groove edges 40e includes a leading ground contact side small groove edge 43 located on the leading ground contact side in the tire rotation direction R, and a trailing ground contact side small groove edge 44 located on the trailing ground contact side in the tire rotation direction R.

[0085] In the present embodiment, the first small inclined groove 40 includes a first portion 48 whose groove width W4 decreases toward the first tread end T1 side, and a second portion 49 whose groove width W4 increases toward the first tread end T1 until reaching the first tread end T1. The first portion 48 reduces the amount of slippage on the outer side of the tire axial direction where the amount of slippage tends to increase, and reduces the difference in the amount of wear generated on both sides of the groove width direction of the first portion 48, thereby improving the uneven wear resistance. The second portion 49 makes drainage from the first tread end T1 smooth, thereby maintaining wet performance.

[0086] In addition, the tread portion 2 includes at least one small shallow groove 45 connected to the first small inclined groove 40. The small shallow groove 45 is formed with a groove depth smaller than the groove depth (not shown) of the first small inclined groove 40. In the present embodiment, the small shallow groove 45 has an opening 46 connected to the first small inclined groove 40 and an end 47 located on the rear ground contact side in the tire rotation direction R. The small shallow groove 45 extends from the opening 46 toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1 side.

[0087] The tread surface 2a of the tread portion 2 includes an acute angle portion 50 sandwiched between one of the groove edges 40e of the first small inclined groove 40 and one of the pair of groove edges 45e of the small shallow groove 45. In addition, the tread surface 2a of the tread portion 2 includes an obtuse angle portion 51 sandwiched between one of the groove edges 40e of the first small inclined groove 40 and one of the pair of groove edges 45e of the small shallow groove 45. In the present embodiment, the acute angle portion 50 is defined by the groove edge 45e on the rear ground contact side in the tire rotation direction R. In the present embodiment, the obtuse angle portion 51 is defined by the groove edge 45e on the front ground contact side in the tire rotation direction R.

[0088] The small shallow groove 45 includes a first small shallow groove 45A connected to the small groove edge 43 on the front ground contact side, and a second small shallow groove 45B connected to the small groove edge 44 on the rear ground contact side. The first small shallow groove 45A is located closer to the inner end 40i (front ground contact side in the tire rotation direction R) than the second small shallow groove 45B. One end 47t on the rear ground contact side in the tire rotation direction R of the second small shallow groove 45B is located closer to the rear ground contact side in the tire rotation direction R than one end 40b on the rear ground contact side in the tire rotation direction R of the first small inclined groove 40. Such a second small shallow groove 45B helps to collect a larger amount of water film on the tread portion 2 into the first small inclined groove 40.

[0089] The land ratio of the tread portion 2 is preferably 75% or more, more preferably 80% or more, and is preferably 95% or less, more preferably 90% or less. Since the land ratio is 75% or more and 95% or less, in this specification, the land ratio is represented by the ratio (A2 / A1) of the area A1 of the virtual tread surface obtained by filling all the grooves of the tread portion 2 to the area A2 of the tread surface 2a.

[0090] As mentioned above, although the particularly preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, and can be implemented in various modified forms.

[0091] [Example]

[0092] Based on the specifications in Table 1, a prototype with Figure 1 The basic pattern of motorcycle tires was tested. In addition, the water splash suppression performance, uneven wear resistance, wet performance and groove bottom crack resistance of the test tires were tested. The test methods and common specifications of each test tire are as follows.

[0093] Tire size: 100 / 90-10

[0094] <Water splash suppression performance / wet performance>

[0095] Each test tire is mounted on the front and rear wheels of a motorcycle. A test rider drives the motorcycle on a test route on a wet road. The water splash suppression performance is evaluated based on the amount of water splashed to the test rider while driving, and is represented by a score with the amount of water splashed in Comparative Example 1 being 100. In addition, the wet performance is evaluated based on the stability during driving or the ease of handling of the motorcycle, and is represented by a score with Comparative Example 1 being 100. The larger the numerical value, the better the water splash suppression performance and wet performance are considered to be. In addition, regarding the water splash suppression performance, it is performed until the end of the wear of the circumferential groove.

[0096] Internal pressure: 170kPa (front), 225kPa (rear)

[0097] Motorcycle: A small motorcycle with a displacement of 100cc (scooter)

[0098] <Uneven wear resistance>

[0099] The test rider drove the motorcycle on a test course of dry asphalt. After the driving, the occurrence of uneven wear was evaluated by the tester's visual inspection. The evaluation was expressed by a score with the occurrence of uneven wear in Comparative Example 1 as 100. The larger the value, the better the uneven wear resistance performance was considered to be.

[0100] <Resistance to groove bottom crack>

[0101] Each test tire was run on a smooth drum tester based on the durability test specified in the U.S. Department of Transportation's Motor Vehicle Safety Standard (FMVSS119). After the third stage of running, cracks in the groove bottoms of the circumferential grooves and each inclined groove were observed by the naked eye of the test personnel.

[0102] The test conditions are described below.

[0103] Drum diameter: 1.7m

[0104] Speed: 80km / h

[0105] Room temperature: 38±3℃

[0106] (Load)

[0107] Stage 1: Normal load (driving time 4 hours)

[0108] Stage 2: Normal load × 108% (driving time 6 hours)

[0109] Stage 3: Normal load × 117% (driving time 24 hours)

[0110] The results are shown in Table 1.

[0111] In Table 1, "T1" means that a pair of groove walls are inclined toward the first tread end side toward the inner side in the tire radial direction, and "T2" means that a pair of groove walls are inclined toward the second tread end side toward the inner side in the tire radial direction.

[0112] In addition, the expression “-” in θ1a, θ1b, θ2a, and θ2b means that the groove wall and the tread surface form an obtuse angle, and the expression without “-” means that the groove wall and the tread surface form an acute angle.

[0113] Furthermore, "A" in Table 1 means that the first inclined groove is inclined toward the rear ground contact side in the tire rotation direction and toward the first tread end, and "B" means that the first inclined groove is inclined toward the rear ground contact side in the tire rotation direction and toward the tire equator.

[0114] In addition, the "cone" in Table 1 is Figure 1 In the illustrated form, the arc shape refers to an arc having a curvature radius of 50% of W2a.

[0115] Furthermore, "C" in Table 1 means that the tread surface near the circumferential groove is damaged, and "D" means that a groove bottom crack is generated at the parting position of the die.

[0116] [Table 1]

[0117]

[0118] The test results show that the tires of the examples are superior to the tires of the comparative examples in terms of water splash suppression performance. In addition, it was confirmed that the tires of the examples have high uneven wear resistance, wet performance, and groove bottom crack resistance.

[0119] [Note]

[0120] The present invention includes the following embodiments.

[0121] [Present invention 1]

[0122] A motorcycle tire comprises a tread portion.

[0123] In the motorcycle tire,

[0124] The tread portion includes: a first tread end, a second tread end, a tread surface between the first tread end and the second tread end, and a circumferential groove extending continuously in the tread surface along the tire circumferential direction.

[0125] The circumferential groove includes: a plurality of first inclined portions inclined in a first direction relative to the tire circumferential direction and a plurality of second inclined portions inclined in a direction opposite to the first direction.

[0126] The circumferential groove includes: a pair of groove walls extending from the tread inwardly in the tire radial direction;

[0127] In the groove cross section in the tire meridian direction of each of the plurality of first inclined portions, the pair of groove walls are respectively inclined toward the first tread end side toward the inner side in the tire radial direction relative to the tread normal line standing at the groove edge,

[0128] In the groove cross section in the tire meridian direction of each of the plurality of second inclined portions, the pair of groove walls are inclined toward the second tread end side toward the inside in the tire radial direction relative to a tread normal line standing at the groove edge.

[0129] [Present invention 2]

[0130] According to the motorcycle tire of the first aspect of the present invention, the circumferential groove further comprises: a connecting portion connecting the first inclined portion and the second inclined portion adjacent to each other in the tire circumferential direction;

[0131] In the groove cross section of the connection portion in the tire meridian direction, the pair of groove walls extend in a tapered shape at 0 degrees or toward the inside in the tire radial direction with respect to a tread normal line standing upright at the groove edge.

[0132] [Present invention 3]

[0133] In the motorcycle tire according to Invention 1 or 2, the circumferential groove is located on the tire equator.

[0134] [Present invention 4]

[0135] According to any one of the motorcycle tires of the present invention 1 to 3, the angle of each of the pair of groove walls relative to the tread normal is maximum at the middle part of the length direction of each of the plurality of first inclined portions, or is maximum at the middle part of the length direction of each of the plurality of second inclined portions.

[0136] [Present invention 5]

[0137] According to the motorcycle tire of the fourth aspect of the present invention, a maximum value of an angle of each of the pair of groove walls relative to the tread normal line is 5 degrees to 15 degrees.

[0138] [Present invention 6]

[0139] According to the motorcycle tire of the fourth or fifth invention, in each of the plurality of first inclined portions, the angle of each of the pair of groove walls relative to the tread normal line continuously decreases from the middle portion in the length direction of the first inclined portion toward both ends of the first inclined portion, or

[0140] In each of the plurality of second inclined portions, an angle of each of the pair of groove walls relative to the tread normal line continuously decreases from a middle portion in a longitudinal direction of the second inclined portion toward both ends of the second inclined portion.

[0141] [Present invention 7]

[0142] According to any one of the present inventions 1 to 6, a motorcycle tire is provided with a plurality of first inclined grooves on the tread portion and further on the side of the first tread end of the circumferential groove, wherein the plurality of first inclined grooves extend from an inner end separated from the circumferential groove to the side of the first tread end.

[0143] The inner end of each of the plurality of first inclined grooves is located adjacent to the plurality of first inclined portions in the tire axial direction.

[0144] [Present invention 8]

[0145] According to the motorcycle tire of the seventh aspect of the present invention, the circumferential groove further comprises: a connecting portion connecting the first inclined portion and the second inclined portion adjacent to each other in the tire circumferential direction;

[0146] The connecting portion includes: a first connecting portion located on the side of the first tread end,

[0147] The inner end of each of the plurality of first inclined grooves is located closer to the first tread end than the first connecting portion.

[0148] [Present invention 9]

[0149] According to the motorcycle tire of the seventh or eighth aspect of the present invention, each of the plurality of first inclined grooves comprises: a pair of groove edges extending along the length direction of the first inclined groove;

[0150] The pair of groove edges include a tapered portion, in which the pair of groove edges extend in a tapered shape toward the inner end.

[0151] [Present invention 10]

[0152] According to any one of the present inventions 7 to 9, a motorcycle tire is provided with a plurality of second inclined grooves on the tread portion and further on the side of the second tread end of the circumferential groove, wherein the plurality of second inclined grooves extend from an inner end separated from the circumferential groove to the side of the second tread end.

[0153] The inner end of each of the plurality of second inclined grooves is located adjacent to the plurality of second inclined portions in the tire axial direction.

[0154] [Present invention 11]

[0155] According to the motorcycle tire of the present invention 10, the circumferential groove further comprises: a connecting portion connecting the first inclined portion and the second inclined portion adjacent to each other in the tire circumferential direction;

[0156] The connecting portion includes: a second connecting portion located on the side of the second tread end,

[0157] The inner end of each of the plurality of second inclined grooves is located closer to the second tread end than the second connecting portion.

[0158] [Present invention 12]

[0159] According to the motorcycle tire of the tenth or eleventh invention, the plurality of second inclined grooves respectively include: a pair of groove edges extending along the length direction of the second inclined groove;

[0160] The pair of groove edges include a tapered portion, in which the pair of groove edges extend in a tapered shape toward the inner end.

Claims

1. A motorcycle tire having a tread portion, characterized in that: In the motorcycle tire, The tread portion includes: a first tread end, a second tread end, a tread surface between the first tread end and the second tread end, and a circumferential groove extending continuously in the tread surface along the tire circumferential direction. The circumferential groove includes: a plurality of first inclined portions inclined in a first direction relative to the tire circumferential direction, and a plurality of second inclined portions inclined in a direction opposite to the first direction. The circumferential groove includes: a pair of groove walls extending from the tread inwardly in the tire radial direction; In the groove cross section in the tire meridian direction of each of the plurality of first inclined portions, the pair of groove walls are respectively inclined toward the first tread end side toward the inner side in the tire radial direction relative to the tread normal line standing at the groove edge, In the groove cross section in the tire meridian direction of each of the plurality of second inclined portions, the pair of groove walls are inclined toward the second tread end side toward the inside in the tire radial direction relative to a tread normal line standing at the groove edge.

2. The motorcycle tire according to claim 1, characterized in that: The circumferential groove further includes: a connecting portion connecting the first inclined portion and the second inclined portion adjacent to each other in the tire circumferential direction; In the groove cross section of the connection portion in the tire meridian direction, the pair of groove walls extend in a tapered shape at 0 degrees or toward the inside in the tire radial direction with respect to a tread normal line standing upright at the groove edge.

3. The motorcycle tire according to claim 1, characterized in that: The circumferential groove is located on the tire equator.

4. The motorcycle tire according to any one of claims 1 to 3, characterized in that: The angle of each of the pair of groove walls relative to the tread normal line is maximum at a middle portion in the longitudinal direction of each of the plurality of first inclined portions, or is maximum at a middle portion in the longitudinal direction of each of the plurality of second inclined portions.

5. The motorcycle tire according to claim 4, characterized in that: The maximum value of the angle of each of the pair of groove walls with respect to the tread normal line is 5 degrees to 15 degrees.

6. The motorcycle tire according to claim 4, characterized in that: In each of the plurality of first inclined portions, an angle of each of the pair of groove walls relative to the tread normal line continuously decreases from a middle portion in a longitudinal direction of the first inclined portion toward both ends of the first inclined portion, or In each of the plurality of second inclined portions, an angle of each of the pair of groove walls relative to the tread normal line continuously decreases from a middle portion in a longitudinal direction of the second inclined portion toward both ends of the second inclined portion.

7. The motorcycle tire according to any one of claims 1 to 3, characterized in that: A plurality of first inclined grooves are provided in the tread portion, further on the first tread end side of the circumferential groove, the plurality of first inclined grooves extending from an inner end separated from the circumferential groove to the first tread end side, The inner end of each of the plurality of first inclined grooves is located adjacent to the plurality of first inclined portions in the tire axial direction.

8. The motorcycle tire according to claim 7, characterized in that: The circumferential groove further includes: a connecting portion connecting the first inclined portion and the second inclined portion adjacent to each other in the tire circumferential direction; The connecting portion includes: a first connecting portion located on the side of the first tread end, The inner end of each of the plurality of first inclined grooves is located closer to the first tread end than the first connecting portion.

9. The motorcycle tire according to claim 7, characterized in that: The plurality of first inclined grooves respectively include: a pair of groove edges extending along the length direction of the first inclined groove; The pair of groove edges include a tapered portion, in which the pair of groove edges extend in a tapered shape toward the inner end.

10. The motorcycle tire according to claim 7, characterized in that: A plurality of second inclined grooves are provided in the tread portion, further on the second tread end side of the circumferential groove, the plurality of second inclined grooves extending from an inner end separated from the circumferential groove to the second tread end side, The inner end of each of the plurality of second inclined grooves is located adjacent to the plurality of second inclined portions in the tire axial direction.

11. The motorcycle tire according to claim 10, characterized in that: The circumferential groove further includes: a connecting portion connecting the first inclined portion and the second inclined portion adjacent to each other in the tire circumferential direction; The connecting portion includes: a second connecting portion located on the side of the second tread end, The inner end of each of the plurality of second inclined grooves is located closer to the second tread end than the second connecting portion.

12. The motorcycle tire according to claim 10, characterized in that: The plurality of second inclined grooves respectively include: a pair of groove edges extending along the length direction of the second inclined groove; The pair of groove edges include a tapered portion, in which the pair of groove edges extend in a tapered shape toward the inner end.

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