Motorcycle tires

Abstract

To provide a motor cycle tire in which steering stability, particularly, a falling feeling at the time of rolling is improved.SOLUTION: Provided is a motor cycle tire in which a directional pattern including at least one center major groove 11 is provided in a tread part. A negative ratio in the entire tread part is equal to or less than 10%. In the tread part, a ratio Gs / Gc of shearing rigidity Gs measured in a tire width direction at a 1 / 4 position of a tread width TW from a tread end TE and shearing rigidity Gc measured in the tire width direction at a 1 / 2 position of the tread width TW from the tread end TE is 95% to 100%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a motorcycle tire (hereinafter also simply referred to as "tire"), and more particularly to a motorcycle tire with an improved tread pattern provided on the tread surface, and particularly to a pneumatic motorcycle tire. [Background technology]

[0002] Unlike passenger cars, trucks, buses, and other four-wheeled vehicles, motorcycles have a characteristic of leaning the body when turning, so the crown of motorcycle tires has a smaller radius of curvature than automobile tires, and the cross section of motorcycle tires is rounder than automobile tires.For this reason, with motorcycle tires, the center of the tread mainly comes into contact with the ground when the vehicle is traveling straight, and the shoulder of the tread comes into contact with the ground when cornering.

[0003] As an example of prior art relating to improvements in the tread pattern of motorcycle tires, Patent Document 1 discloses a motorcycle tire in which at least one of the main grooves provided in the tread portion has two or more widened portions that widen outward in the groove width direction on at least one of the leading groove wall and trailing groove wall in the rotational direction, and in which at least one main groove becomes shallower toward the outside in the tread width direction.

[0004] Patent Document 2 discloses a motorcycle tire in which at least one of the main grooves provided in the tread portion has three or more widened portions that widen outward in the groove width direction on at least one of the leading groove wall and trailing groove wall in the rotational direction of at least one main groove, and the extension length along the groove wall between the apexes of adjacent widened portions is 0.3 to 50% longer than the length of an imaginary line connecting the apexes of the adjacent widened portions.The technologies disclosed in Patent Documents 1 and 2 both aim to provide a motorcycle tire that improves drainage performance and achieves both dry and wet performance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-049837 [Patent Document 2] Patent Publication No. 2021-049836 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, some motorcycle tires have been designed with high rigidity in the center portion and low rigidity in the shoulder portion, leaving room for improvement in handling stability, particularly the feeling of tipping over during rolling. Even in the tires disclosed in Patent Documents 1 and 2, this point was not considered.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a motorcycle tire that is improved in handling stability, particularly in the feeling of tipping over during rolling. [Means for solving the problem]

[0008] As a result of extensive research, the inventors have found that the above-mentioned problems can be solved by providing at least one center main groove in the tread surface portion and by ensuring that the negative ratio of the tread surface portion and the shear rigidity in the tire width direction satisfy the following conditions, and have thus completed the present invention.

[0009] That is, the present invention provides a motorcycle tire having a directional pattern including at least one center main groove on a tread surface thereof, The negative ratio of the entire tread surface portion is 10% or less, and The tread surface portion is characterized in that the ratio Gs / Gc of the shear stiffness Gs measured in the tire width direction at a position 1 / 4 of the tread width TW from the tread edge to the shear stiffness Gc measured in the tire width direction at a position 1 / 2 of the tread width TW from the tread edge is 95% to 100%.

[0010] In the tire of the present invention, it is preferable that the center main groove is arranged so as not to cross the tire equatorial plane.

[0011] In addition, in the tire of the present invention, when the contact surface of the tread surface during straight-ahead driving is defined as the center region and a pair of regions located on the tire widthwise outer sides of the center region are defined as shoulder regions, it is preferable that the ratio Nc / Ns of the negative rate Nc of the center region to the negative rate Ns of the shoulder regions is 40% to 120%.

[0012] Furthermore, in the tire of the present invention, it is preferable that the distance d between the center main grooves arranged on either side of the tire equatorial plane is 1% to 20% of the tread width TW.

[0013] Furthermore, in the tire of the present invention, it is preferable that the angle θ1 formed by the extending direction of the center main groove with respect to the tire circumferential direction is 0° to 30°.

[0014] Furthermore, in the tire of the present invention, when the point at which a perpendicular line drawn to the midpoint of a line segment connecting the tire circumferential ends of the center main groove intersects with an inner groove wall in the tire width direction of the center main groove is defined as X, it is preferable that the angle θ2 formed by two straight lines connecting point X and each of the tire circumferential ends of the center main groove is 0° to 40°.

[0015] Furthermore, in the tire of the present invention, it is preferable that at least one of the center main grooves has two or more widened portions in which at least one of the tire width direction inner groove wall and the tire width direction outer groove wall widens outward in the groove width direction, and when the maximum value of the groove width in the widened portions is the maximum groove width W, the minimum value of the groove width in the constricted portion formed between the widened portions is the minimum groove width w, which is 20% to 60% of the maximum groove width W.

[0016] Furthermore, in the tire of the present invention, it is preferable that the overlap length in the tire circumferential direction between the center main grooves arranged on either side of the tire equatorial plane is 10% to 90% of the tire circumferential length Lg of the center main groove.

[0017] Furthermore, in the tire of the present invention, it is preferable that at least one of the center main grooves has one or more widened portions in which at least one of the inner groove wall in the tire width direction and the outer groove wall in the tire width direction widens outward in the groove width direction, and that a raised portion is provided at the groove bottom of the widened portion.

[0018] Furthermore, in the tire of the present invention, it is preferable that the tread surface portion further has shoulder main grooves, and the angle θ3 formed by the extending direction of the shoulder main grooves with respect to the tire circumferential direction is 20° to 60°.

[0019] Furthermore, in the tire of the present invention, it is preferable that the tread surface portion further has shoulder main grooves, and the angle θ3 formed by the extension direction of the shoulder main groove with respect to the tire circumferential direction is larger than the angle θ1 formed by the extension direction of the center main groove with respect to the tire circumferential direction. [Effects of the Invention]

[0020] According to the present invention, by adopting the above-mentioned configuration, it is possible to realize a motorcycle tire that has improved steering stability, in particular, improved feeling of tipping during rolling. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a partial development view showing a tread surface portion of a front tire that is an example of a motorcycle tire according to the present invention. [Figure 2] FIG. 2 is a partial development view showing a tread surface portion of a rear tire that is another example of a motorcycle tire according to the present invention. [Figure 3] FIG. 4 is another partial development view showing the tread surface of a rear tire that is another example of a motorcycle tire according to the present invention. [Figure 4] 1 is a widthwise cross-sectional view showing an example of a tire for a motorcycle of the present invention. [Figure 5] FIG. 2 is a partial development view showing a tread surface portion of a front tire of a comparative example. [Figure 6] FIG. 2 is a partial development view showing a tread surface portion of a rear tire of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a partial development view showing the tread surface of a front tire, which is an example of a motorcycle tire of the present invention. Figs. 2 and 3 are partial development views showing the tread surface of a rear tire, which is another example of a motorcycle tire of the present invention. Arrows in Figs. 1 to 3 indicate the tire rotation direction.

[0023] In the motorcycle tire of the present invention, a directional pattern including at least one center main groove is provided in the tread surface. In the front tire 100 shown in Fig. 1, one center main groove 11 is arranged in the tread surface, and in the rear tire 200 shown in Figs. 2 and 3, two center main grooves 21 and 22 are arranged in the tread surface. Neither of these center main grooves is arranged so as to not cross the tire equatorial plane CL. By configuring the center main groove so that it does not cross the tire equatorial plane CL, straight-line stability can be improved.

[0024] In the present invention, the center main groove refers to a main groove whose groove area is 80% or more within the contact patch during straight running. Also, in the present invention, the contact patch during straight running refers to the contact patch when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and run straight under a specified load.

[0025] In the above, "applicable rim" means the standard rim for the applicable size specified by the industry standard in effect in the region where the tire is produced and used, "specified internal pressure" means the air pressure corresponding to the maximum load capacity for the applicable size and ply rating specified by the industry standard, and "specified load" means the maximum mass allowed to be loaded on the tire specified by the industry standard. Examples of such industry standards include the JATMA Year Book of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the Standard Manual of the European Tire and Rim Technical Organization (ETRTO) in Europe, and the Year Book of the Tire and Rim Association Inc. (TRA) in the United States.

[0026] In the present invention, the contact patch during straight running specifically refers to a band-like area having a center on the tire equatorial plane CL and a width of 20% to 40% of the tread width TW.

[0027] Here, the tread width TW means the distance in the tire width direction between both tread ends TE measured along the tread surface when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and in an unloaded state. Similarly, unless otherwise specified, the tire dimensions in this invention refer to values ​​measured when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and in an unloaded state.

[0028] In the tire of the present invention, the negative ratio of the entire tread surface is 10% or less, and the ratio Gs / Gc of the shear stiffness Gs measured in the tire width direction at a position 1 / 4 of the tread width TW from the tread edge TE to the shear stiffness Gc measured in the tire width direction at a position 1 / 2 of the tread width TW from the tread edge TE, i.e., at the tire equatorial plane CL, is 95% to 100% as a percentage.

[0029] Here, the negative rate is the ratio of the area of ​​the grooves to the area of ​​the tread surface assuming there are no grooves, and means the ratio of the area of ​​the grooves excluding sipes to the area of ​​the tread surface.

[0030] In the present invention, the shear stiffnesses Gs and Gc of the tread surface are values ​​indicating the pattern stiffness determined by the tread pattern formed by grooves, sipes, etc. provided in the tread surface, and are calculated using the finite element method (FEM). Specifically, a three-dimensional model of only the tread pattern is created using tetrahedral elements with sides of approximately 3 mm, and the shear stiffness in the tire width direction is calculated using FEM analysis for an area of ​​20 mm in the tire width direction × the entire tire circumference, and the average value is calculated to be the shear stiffness value for each position in the tire width direction. The parameters relating to the thickness direction and material can be set appropriately in accordance with each individual tire.

[0031] In the tire of the present invention, by specifying the value of the negative rate and the value of the shear rigidity ratio Gs / Gc as described above, it is possible to make the pattern rigidity uniform in the tire width direction, and to improve the handling stability, in particular the feeling of collapse during rolling.

[0032] In the tire of the present invention, the negative ratio of the entire tread surface can be preferably set to 4% to 9% from the viewpoint of ensuring steering stability during high-speed running.

[0033] In the tire of the present invention, it is important that at least one center main groove is disposed, preferably so as not to cross the tire equatorial plane CL, and that the negative ratio value and the shear stiffness ratio Gs / Gc value are specified as described above, thereby achieving the desired effects of the present invention. Other points are not particularly limited, but the tire can preferably be configured as follows.

[0034] In the tire of the present invention, when the contact patch of the tread surface during straight running is defined as a center region and a pair of regions located on the outer sides of the center region in the tire width direction are defined as shoulder regions, the ratio Nc / Ns of the negative rate Nc of the center region to the negative rate Ns of the shoulder regions is preferably 40% to 120% expressed as a percentage. This makes it possible to make the pattern rigidity more uniform in the tire width direction, and to further improve steering stability, particularly the feeling of tipping during rolling. In the present invention, the negative rate ratio Nc / Ns is preferably 40% to 95%. Furthermore, particularly when the present invention is applied to a front tire, the negative rate ratio Nc / Ns is preferably 40% to 43%, and when applied to a rear tire, the negative rate ratio Nc / Ns is preferably 80% to 100%.

[0035] In the tire of the present invention, the distance d between the center main grooves arranged on either side of the tire equatorial plane CL is preferably 1% to 20%, and more preferably 10% to 15%, of the tread width TW. By setting the distance d within the above range, the shear stiffness can be made uniform, improving the feeling of leaning over when cornering. This distance d refers to the minimum value, measured along the tread surface, of the distance in the tire width direction between the inner ends of the center main grooves arranged on either side of the tire equatorial plane CL.

[0036] Furthermore, in the tire of the present invention, the angle θ1 formed by the extending direction of the center main groove with respect to the tire circumferential direction is preferably 0° to 30°, and more preferably 10° to 15°. By setting the angle θ1 within the above range, it is possible to make the shear rigidity uniform. In the present invention, the angle θ1 is defined as the angle formed by a line connecting the tire circumferential ends of the center main groove with respect to the tire circumferential direction.

[0037] In the front tire 100 shown in Figure 1, the angle θ1-11 is formed by a straight line connecting the tire circumferential ends 11a, 11b of one center main groove 11 with respect to the tire circumferential direction, and in the rear tire 200 shown in Figure 2, the angles θ1-21, θ1-22 are formed by straight lines connecting the tire circumferential ends 21a, 21b and 22a, 22b of two center main grooves 21, 22 with respect to the tire circumferential direction.

[0038] Furthermore, in the tire of the present invention, when a perpendicular line drawn to the midpoint M of a line segment connecting the tire circumferential ends of the center main groove intersects with the inner groove wall in the tire width direction of the center main groove at point X, the angle θ2 formed by the two lines connecting point X and each of the tire circumferential ends of the center main groove is preferably 0° to 40°, and more preferably 10° to 15°. By setting the angle θ2 within the above range, the center main groove can be made curved, and the pattern rigidity can be made more uniform in the tire width direction.

[0039] In the front tire 100 shown in FIG. 1, when a perpendicular line drawn to the midpoint M of a line segment connecting the tire circumferential ends 11a, 11b of one center main groove 11 intersects with the tire width direction inner groove wall 11A of the center main groove 11 at point X, the angle θ2-11 is formed by two straight lines connecting point X and each of the tire circumferential ends 11a, 11b of the center main groove 11. In the rear tire 200 shown in Figure 3, when the points X-1 and X-2 are defined as the intersections of perpendicular lines drawn to midpoints M-1 and M-2 of the line segments connecting the tire circumferential ends 21a, 21b and 22a, 22b of the two center main grooves 21, 22 and the tire widthwise inner groove walls 21A, 22A of the center main grooves 21, 22, respectively, the angles θ2-21 and θ2-22 are defined as the angles formed by the two straight lines connecting points X-1 and X-2 with the tire circumferential ends 21a, 21b and 22a, 22b of the center main grooves 21, 22, respectively.

[0040] Furthermore, in the tire of the present invention, at least one of the center main grooves preferably has one or more, and preferably two or more, widened portions in which at least one of the tire width direction inner groove wall and tire width direction outer groove wall widens outward in the groove width direction. In the tire of the present invention, when the center main groove has two or more widened portions, constricted portions are formed between the widened portions. In this case, when the maximum groove width of the widened portion of the center main groove is the maximum groove width W, the minimum groove width of the constricted portion, i.e., the minimum groove width w, is preferably 20% to 60% of the maximum groove width W, and more preferably 30% to 50%. By providing a constricted portion in the center main groove that satisfies the above conditions, it is possible to prevent the rigidity from becoming too low.

[0041] In the present invention, the groove widths of the widened portion and constricted portion of the center main groove refer to the maximum and minimum groove widths measured perpendicularly to the inner groove wall of the center main groove in the tire width direction.

[0042] In the front tire 100 shown in Fig. 1, the center main groove 11 has two widened portions 11W-1 and 11W-2, where the tire width direction inner groove wall 11A and the tire width direction outer groove wall 11B of the tire width direction outer groove wall 11B are widened outward in the groove width direction, and a narrowed portion 11C is formed between these two widened portions 11W-1 and 11W-2. The maximum groove width of the two widened portions 11W-1 and 11W-2 is the maximum groove width W11, and the minimum groove width of the narrowed portion 11C is the minimum groove width w11. In the rear tire 200 shown in Fig. 2, the center main groove 21 has two widened portions 21W-1 and 21W-2, where the tire width direction inner groove wall 21A and the tire width direction outer groove wall 21B are widened outward in the groove width direction, and a narrowed portion 21C is formed between these two widened portions 21W-1 and 21W-2. The maximum groove width in the two widened portions 21W-1, 21W-2 is the maximum groove width W21, and the minimum groove width in the constricted portion 21C is the minimum groove width w21. The center main groove 22 in Fig. 2 has one widened portion 22W in which the tire width direction outer groove wall 22B of the tire width direction inner groove wall 22A and the tire width direction outer groove wall 22B is widened outward in the groove width direction, and does not have a constricted portion.

[0043] In the present invention, the constricted portion of the center main groove is preferably provided in the center portion in the tire circumferential direction of the center main groove, for example, in the range of 40% to 60% of the tire circumferential length Lg of the center main groove.

[0044] In the tire of the present invention, when one or more widened portions are provided in the center main groove, it is preferable to provide a raised portion at the groove bottom of the widened portion. This improves drainage along the inner groove wall and the outer groove wall in the tire width direction, thereby improving drainage performance. To achieve this effect, it is preferable that the shape of the raised portion is a shape that follows the extension direction of the center main groove having the widened portion.

[0045] The raised portions may be provided on all or only some of the widened portions of a single center main groove, and may be provided on all or only some of the widened portions of a single center main groove. In particular, in the present invention, it is preferable to provide one or two raised portions per center main groove.

[0046] In the rear tire 200 shown in Fig. 3, two raised portions 121-1 and 121-2 are provided, one for each of the two widened portions 21W-1 and 21W-2 of the center main groove 21, and one raised portion 122 is provided in one widened portion 22W of the center main groove 22. In the front tire 100 shown in Fig. 1, no raised portions are provided in the widened portions 11W-1 and 11W-2 of the center main groove 11.

[0047] The height of the raised portion is not particularly limited as long as it is less than the depth of the widened center main groove, but is preferably 90% or less of the depth of the widened center main groove. The extension length of the raised portion is preferably 30 to 50% of the widened portion.

[0048] In the tire of the present invention, it is preferable that the tire width direction inner groove wall 21A and the tire width direction outer groove wall 21B have the same number of portions that widen outward in the groove width direction, and that the tire width direction inner groove wall 21A and the tire width direction outer groove wall 21B are arranged in pairs, and that raised portions 121-1 and 121-2 are provided at the groove bottoms of the widened portions 21W-1 and 21W-2 formed thereby, as in the center main groove 21 of the rear tire 200 shown in Fig. 3. In this case, raised portions may be provided in all or some of the widened portions.

[0049] Furthermore, in the tire of the present invention, the overlap length in the tire circumferential direction between the center main grooves arranged on either side of the tire equatorial plane CL is preferably 10% to 90%, and more preferably 15% to 85%, of the tire circumferential length Lg of the center main groove, which reduces the rigidity of the center portion and relatively increases the rigidity of the shoulder portions, thereby improving handling stability and the feeling of tilting during rolling.

[0050] Here, the overlap length refers to the circumferential overlap length of the center main grooves arranged on either side of the tire equatorial plane CL, and is the sum of the circumferential lengths of the overlapping portions of the center main grooves on either side of the tire equator when viewed in the tire width direction, per center main groove.

[0051] In the tire of the present invention, a center main groove having a large circumferential length is disposed in a center region of the tread surface close to the tire equatorial plane CL, and shoulder main grooves may be provided in shoulder regions on the tire widthwise outer side of the center region. Here, in the present invention, shoulder main grooves refer to main grooves other than the center main groove. The front tire 100 shown in Figure 1 has shoulder main grooves 31, 32, and 33. The rear tire 200 shown in Figures 2 and 3 has shoulder main grooves 41, 42, and 43.

[0052] The shoulder main grooves are preferably arranged at substantially equal intervals in the tire circumferential direction in the shoulder region, where "substantially equal intervals" means that the distance between the open ends of the shoulder main grooves in the tire tread portion is substantially the same in the tire circumferential direction.

[0053] In the front tire 100 shown in Fig. 1, when the groove distance L1 between the shoulder main grooves 31 and 32, the groove distance L2 between the shoulder main grooves 32 and 33, and the groove distance L3 between the shoulder main grooves 33 and 31 are defined as three shoulder main grooves 31, 32, and 33, L1 ≒ L2 ≒ L3 is satisfied. In the rear tire 200 shown in Fig. 3, since the single center main groove 22 extends to the shoulder region, when the groove distance L4 between the shoulder main grooves 41 and 42, the groove distance L5 between the shoulder main grooves 42 and 43, the groove distance L6 between the shoulder main groove 43 and the center main groove 22, and the groove distance L7 between the center main groove 22 and the shoulder main groove 41 are defined as three shoulder main grooves 41, 42, and 43 and the center main groove 22, L4 ≒ L5 ≒ L6 ≒ L7 is satisfied.

[0054] In the present invention, the groove distance can be measured, for example, at the same widthwise position of the tire where multiple shoulder main grooves are overlapped when viewed in the circumferential direction of the tire. Furthermore, "substantially the same groove distance" means that it includes manufacturing errors, and is considered to be substantially the same if it is within an error range of ±20% in mm, for example.

[0055] The angle θ3 formed by the extension direction of the shoulder main groove with respect to the tire circumferential direction is preferably 20° to 60°, and more preferably 35° to 50°. By setting the angle θ3 within the above range, it is possible to make the shear rigidity uniform. In the present invention, the angle θ3 is defined as the angle formed by a line connecting the tire circumferential ends of the shoulder main grooves with respect to the tire circumferential direction.

[0056] In the front tire 100 shown in Fig. 1, the angles θ3-31, θ3-32, and θ3-33 are defined by the angles formed with the tire circumferential direction by lines connecting the tire circumferential ends 31a, 31b, 32a, 32b, and 33a, 33b of the three shoulder main grooves 31, 32, and 33. In the rear tire 200 shown in Fig. 3, the angles θ3-41, θ3-42, and θ3-43 are defined by the angles formed with the tire circumferential direction by lines connecting the tire circumferential ends 41a, 41b, 42a, 42b, and 43a, 43b of the three shoulder main grooves 41, 42, and 43.

[0057] In this case, the angle θ3 between the extension direction of the shoulder main groove and the tire circumferential direction is preferably larger than the angle θ1 between the extension direction of the center main groove and the tire circumferential direction, which makes it possible to equalize the shear stiffness and improve drainage, particularly in the center region when traveling straight and in the shoulder regions when banking.

[0058] More specifically, in the front tire 100 shown in Fig. 1, the angular relationship between the one center main groove 11 and the three shoulder main grooves 31, 32, 33 preferably satisfies θ3-31 ≥ θ3-32 > θ3-33 > θ1-11. In the rear tire 200 shown in Figs. 2 and 3, the angular relationship between the two center main grooves 21, 22 and the three shoulder main grooves 41, 42, 43 preferably satisfies θ3-41 ≥ θ3-42 > θ3-43 > θ1-22 > θ1-21.

[0059] In the tire of the present invention, the groove depth of the center main groove and shoulder main groove is not particularly limited, but can usually be set to 2.0 to 11 mm, and preferably 3.5 to 6.5 mm.

[0060] As shown in the drawings, in the present invention, a pattern consisting of a groove group, each of which includes a plurality of center main grooves and shoulder main grooves, is arranged symmetrically about the tire equatorial plane CL, repeated in the tire circumferential direction, and shifted by half the arrangement pitch. Here, in the present invention, the arrangement pitch of the pattern means one unit of repetition in the tire circumferential direction of the design formed by the center main grooves and shoulder main grooves provided in the tread surface portion. The arrangement pitch of the pattern in the present invention is not particularly limited, but may be, for example, approximately 1 / 20 to 1 / 5 of the total circumference of the tire.

[0061] Fig. 4 is a widthwise cross-sectional view of a rear tire that is an example of a motorcycle tire of the present invention. As shown in Fig. 4, a tire 200 of the present invention has a tread portion 1 that forms a ground-contacting portion, and a pair of sidewall portions 2 and bead portions 3 that extend radially inward from both ends of the tread portion.

[0062] The illustrated tire 200 has a skeleton of two carcass plies 4 extending in a toroidal shape across a pair of bead portions 3. In the present invention, the carcass ply 4 is formed by arranging relatively highly elastic textile cords in parallel to each other, and the number of carcass plies 4 may be at least one, but may also be three or more. In addition, both ends of the carcass ply 4 may be fastened in the bead portions 3 by folding back from the inside to the outside of the tire around the bead core 5 as shown in the drawing, or by sandwiching the end with bead wires from both sides, and either fastening method may be used.

[0063] In the tire 200 shown in the figure, two belt layers 6 are arranged radially outward of the carcass ply 5 in the tread portion 1. In the present invention, the belt layer 6 can be arranged in at least one layer, and may be formed from two or more inclined belt layers arranged so that the cord directions intersect with each other between the layers, or may be formed only from one or more spiral belt layers made of rubber-coated cords wound spirally in the circumferential direction of the tire. Examples of reinforcing materials that constitute the belt layer 6 include nylon fiber, aromatic polyamide (trade name: Kevlar), and steel. Among these, aromatic polyamide and steel are reinforcing materials that can suppress expansion of the tread portion without elongating even at high temperatures.

[0064] In the tire 200 of the present invention, a bead filler 7 can be disposed on the outer side of the bead core 5 in the tire radial direction, and an inner liner (not shown) can be disposed in the innermost layer of the tire.

[0065] Furthermore, in the tire of the present invention, the ratio of the height (SWH) at the tire's maximum width position to the tire's section height (SH) is preferably within the range of 40% to 75%. By setting the ratio (SWH / SH) of the tire's section height (SH) to the tire's section height (SWH) at the tire's maximum width position within the range of 40% to 75% expressed as a percentage, a tire with an appropriate contact patch and excellent handling stability can be obtained. Furthermore, the handling stability can be improved, particularly when a motorcycle is cornering and the vehicle is banking. Here, the tire section height (SH) refers to half the difference between the outer diameter of the tire and the rim diameter of the rim as defined by the above-mentioned industry standard.

[0066] The tire of the present invention can be applied to both front and rear tires of motorcycles, and can be applied to both radial and bias tires. Furthermore, the tire of the present invention has improved handling stability, particularly the feeling of tipping during rolling, compared to conventional tires, making it useful as a sports tire. [Example]

[0067] The present invention will be described in more detail below using specific examples.

[0068] Example 1 A front tire for a motorcycle (tire size 120 / 70ZR17M / C) was manufactured with a directional pattern on the tread surface as shown in Figure 1, and a rear tire (tire size 190 / 55ZR17M / C) was manufactured with a directional pattern as shown in Figure 2. These test tires satisfied the following conditions.

[0069] Distance d between the center main grooves on either side of the tire equatorial plane: (front) 5% of the tread width TW, (rear) 7% of the tread width TW. · Angle of center main groove 11 θ1-11: 17°, angle of center main groove 21 θ1-21: 10°, angle of center main groove 22 θ1-22: 25°. The angle θ2-11 of the center main groove 11 is 10°, the angle θ2-21 of the center main groove 21 is 5°, and the angle θ2-22 of the center main groove 22 is 6°. The minimum groove width w11 of the center main groove 11 is 50% of the maximum groove width W11, the minimum groove width w21 of the center main groove 21 is 50% of the maximum groove width W21, and the minimum groove width w22 of the center main groove 22 is 39% of the maximum groove width W22. - Overlap length between center main grooves arranged on either side of the tire equatorial plane: (front) 40% of the circumferential length Lg of the center main groove 11, (rear) 15% of the circumferential length Lg of the center main groove 21, and 82% of the circumferential length Lg of the center main groove 22. · Angle of shoulder main groove 31 θ3-31: 35°, angle of shoulder main groove 32 θ3-32: 45°, angle of shoulder main groove 33 θ3-33: 35°, angle of shoulder main groove 41 θ3-41: 45°, angle of shoulder main groove 42 θ3-42: 45°, angle of shoulder main groove 43 θ3-43: 30°.

[0070] The resulting front and rear tires were mounted on rims with MT3.50 x 17 and MT6.00 x 17 sizes, respectively, and inflated to internal pressures of 250 kPa and 290 kPa, respectively, before being mounted on a commercially available motorcycle. Two test riders performed a sensory evaluation of the motorcycle, assigning scores to the yaw response and the feeling of leaning during roll, and calculating the average score. Specifically, the test riders drove the motorcycle through large and small corners, and evaluated the yaw response during cornering and the feeling of leaning during roll on a scale of 1 to 10.

[0071] (Comparative Example 1) The evaluation was carried out in the same manner as in the Examples, except that the front and rear tires had the tread patterns shown in Figures 5 and 6, respectively. The arrows in Figures 5 and 6 indicate the direction of tire rotation.

[0072] The evaluation results were shown as the difference in scores with the comparative example used as a control. The higher the evaluation score, the better the rider's evaluation. The results are shown in Table 1 below, along with the shear stiffness ratio Gs / Gc, the negative rate of the entire tread surface, and the negative rate ratio Nc / Ns.

[0073] [Table 1]

[0074] *1) Gs / Gc is the ratio of shear stiffness Gs measured in the tire width direction at a position 1 / 4 of the tread width TW from the tread edge TE on the tread surface, to shear stiffness Gc measured in the tire width direction at a position 1 / 2 of the tread width TW from the tread edge TE, calculated by FEM analysis. *2) When the contact patch of the tread surface during straight-ahead driving is defined as the center region, and the pair of regions located on the outer sides of the center region in the tire width direction are defined as shoulder regions, Nc / Ns is the ratio of the negative rate Nc of the center region to the negative rate Ns of the shoulder regions.

[0075] As shown in the above table, it is clear that by satisfying the predetermined shear stiffness ratio and negative rate, it is possible to realize a motorcycle tire with improved handling stability, in particular, improved feeling of tipping during rolling. [Explanation of symbols]

[0076] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass ply 5 bead core 6 Belt Layer 7 Bead Filler 11, 21, 22 Center main groove 11a, 11b, 21a, 21b, 22a, 22b Circumferential ends of center main grooves 11A, 21A, 22A: Center main groove inner groove wall in tire width direction 11B, 21B, 22B Outer groove wall in the tire width direction of the center main groove 11W-1, 11W-2, 21W-1, 21W-2, 22W Widened section 11C, 21C waist 31, 32, 33, 41, 42, 43 Shoulder main groove 31a, 31b, 32a, 32b, 33a, 33b, 41a, 41b, 42a, 42b, 43a, 43b Circumferential ends of shoulder main grooves 100 front tire 121-1,121-2,122 Ridge 200 rear tire

Claims

1. A motorcycle tire having a directional pattern including at least one center main groove on a tread surface thereof, The negative ratio of the entire tread surface portion is 10% or less, and A motorcycle tire characterized in that the ratio Gs / Gc of the shear stiffness Gs measured in the tire width direction at a position 1 / 4 of the tread width TW from the tread edge in the tread surface portion to the shear stiffness Gc measured in the tire width direction at a position 1 / 2 of the tread width TW from the tread edge is 95% to 100%.

2. 2. The motorcycle tire according to claim 1, wherein the center main groove is disposed so as not to cross the tire equatorial plane.

3. 3. The motorcycle tire according to claim 1, wherein, when the contact surface of the tread surface during straight-ahead running is defined as a center region and a pair of regions located on the outer sides of the center region in the tire width direction are defined as shoulder regions, the ratio Nc / Ns of the negative rate Nc of the center region to the negative rate Ns of the shoulder regions is 40% to 120%.

4. 2. The motorcycle tire according to claim 1, wherein a distance d between the center main grooves disposed on either side of the tire equatorial plane is 1% to 20% of a tread width TW.

5. 2. The motorcycle tire according to claim 1, wherein an angle θ1 formed by the extending direction of the center main groove with respect to the tire circumferential direction is 0° to 30°.

6. 2. The motorcycle tire according to claim 1, wherein when a point X is defined as an intersection between a line segment connecting the tire circumferential ends of the center main grooves and a perpendicular line drawn to the midpoint of the line segment and an inner groove wall of the center main groove in the tire width direction, an angle θ2 formed by two straight lines connecting point X and each of the tire circumferential ends of the center main groove is 0° to 40°.

7. 2. The motorcycle tire according to claim 1, wherein at least one of the center main grooves has two or more widened portions in which at least one of an inner groove wall in the tire width direction and an outer groove wall in the tire width direction widens outward in the groove width direction, and when the maximum value of the groove width in the widened portions is defined as a maximum groove width W, a minimum groove width w, which is the minimum value of the groove width in the constricted portions formed between the widened portions, is 20% to 60% of the maximum groove width W.

8. 2. The motorcycle tire according to claim 1, wherein an overlap length in the tire circumferential direction between the center main grooves arranged on either side of the tire equatorial plane is 10% to 90% of a circumferential length Lg of the center main groove.

9. 2. The motorcycle tire according to claim 1, wherein at least one of the center main grooves has one or more widened portions in which at least one of an inner groove wall in the tire width direction and an outer groove wall in the tire width direction widens outward in the groove width direction, and a raised portion is provided at the groove bottom of the widened portion.

10. 2. The motorcycle tire according to claim 1, wherein the tread surface portion further includes shoulder main grooves, and the angle θ3 between the extending direction of the shoulder main grooves and the circumferential direction of the tire is 20° to 60°.

11. 2. The motorcycle tire according to claim 1, wherein the tread surface portion further includes shoulder main grooves, and the angle θ3 formed by the extension direction of the shoulder main groove with respect to the tire circumferential direction is larger than the angle θ1 formed by the extension direction of the center main groove with respect to the tire circumferential direction.

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