Tire for two-wheeled motor vehicle

Abstract

The invention provides a tire for a two-wheeled motor vehicle, which has improved handling stability, particularly lodging feeling during roll. A directional pattern including at least one center main groove (11) is provided on a tread ground contact portion of the two-wheeled motor vehicle tire. The groove area ratio of the entire tread land portion is 10% or less, and the ratio (Gs / Gc) of the shear stiffness (Gs) measured in the tire width direction at a position of 1 / 4 of the tread width (TW) from the tread edge (TE) in the tread land portion to the shear stiffness (Gc) measured in the tire width direction at a position of 1 / 2 of the tread width (TW) from the tread edge (TE) is 95%-100%.

Description

Technical Field

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

[0002] Two-wheeled vehicle tires are different from four-wheeled vehicles such as cars, trucks, and buses. In order to realize the characteristics of two-wheeled vehicles that can turn by tilting the vehicle body, the tire crown portion has a smaller radius of curvature than four-wheeled vehicle tires and has a tire shape with a rounder cross section than four-wheeled vehicle tires. Therefore, in two-wheeled vehicle tires, the center portion of the main tread contacts the ground when the vehicle is driving straight, and the shoulder portion of the tread contacts the ground when turning.

[0003] As a prior art relating to the improvement of the tread pattern of a tire for a two-wheeled vehicle, for example, Patent Document 1 discloses a tire for a motor two-wheeled vehicle in which at least one of the groove walls on the side contacting the ground in the rotational direction and the groove walls on the side contacting the ground in the rotational direction of the main grooves provided in the tread portion is provided with two or more widening portions extending outward in the groove width direction, and at least one of the main grooves becomes shallower as it goes outward in the tread width direction.

[0004] In addition, Patent Document 2 discloses a motorcycle tire in which at least one of the groove walls on the first contact side in the rotation direction and the groove walls on the last contact side in the rotation direction of at least one main groove provided in the tread portion is provided with three or more widening portions extending outward in the groove width direction, and at least one portion has a portion where the extension length along the groove wall between the vertices of the adjacent widening portions is 0.3% to 50% longer than the length of the imaginary straight line connecting the vertices of the adjacent widening portions. The purpose of the technologies disclosed in Patent Documents 1 and 2 is to provide a motorcycle tire that improves drainage performance and takes both dry and wet performance into consideration.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-049837

[0008] Patent Document 2: Japanese Patent Application Publication No. 2021-049836 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] In the past, in tires for motorcycles, the rigidity of the center portion was set high and the rigidity of the shoulder portion was set low, and the handling stability, especially the feeling of falling during rolling, had room for improvement. In the tires disclosed in Patent Documents 1 and 2, this point has not been studied.

[0011] Therefore, an object of the present invention is to provide a tire for a motorcycle having improved steering stability, particularly improved squatting feeling during rolling.

[0012] Solutions for solving problems

[0013] The present inventors have found that the above problems can be solved by providing at least one central main groove in the tread contact surface and satisfying the following conditions in terms of the groove area ratio and shear rigidity in the tire width direction of the tread contact surface, thereby completing the present invention.

[0014] That is, the present invention is as follows.

[0015] (1) A motorcycle tire having a directional pattern including at least one center main groove on a tread contact surface, wherein:

[0016] The groove area ratio of the entire tread contact surface portion is 10% or less, and

[0017] In the tread contact portion, a ratio Gs / Gc of a shear stiffness Gs measured in the tire width direction at a position 1 / 4 of the tread width TW from the tread end to a shear stiffness Gc measured in the tire width direction at a position 1 / 2 of the tread width TW from the tread end is 95% to 100%.

[0018] (2) The motorcycle tire according to (1), wherein the center main groove is arranged so as not to cross the tire equatorial plane.

[0019] (3) A motorcycle tire according to (1) or (2), wherein, when the contact surface of the tread contact surface portion during straight driving is defined as a center region, and a pair of regions located outside the center region in the tire width direction are defined as shoulder regions, a ratio Nc / Ns of a groove area ratio Nc of the center region to a groove area ratio Ns of the shoulder region is 40% to 120%.

[0020] (4) The motorcycle tire according to any one of (1) to (3), wherein a distance d between the center main grooves disposed across the tire equatorial plane is 1% to 20% of the tread width TW.

[0021] (5) The motorcycle tire according to any one of (1) to (4), wherein an angle θ1 formed between an extending direction of the center main groove and the tire circumferential direction is 0° to 30°.

[0022] (6) A motorcycle tire according to any one of (1) to (5), wherein, when the point where a perpendicular line drawn at the midpoint 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 is set to X, an angle θ2 formed by two straight lines connecting point X and the tire circumferential ends of the center main groove is 0° to 40°.

[0023] (7) A tire for a motorcycle according to any one of (1) to (6), wherein at least one of the center main grooves has an expanded portion in which at least one of the two or more inner groove walls in the tire width direction and the outer groove walls in the tire width direction expands outward in the groove width direction, and when the maximum value of the groove width of the expanded portion is set to the maximum groove width W, the minimum value of the groove width of the narrowing portion formed between the expanded portions, i.e., the minimum groove width w, is 20% to 60% of the maximum groove width W.

[0024] (8) A motorcycle tire according to any one of (1) to (7), wherein the overlapping length in the tire circumferential direction of the center main grooves arranged across the tire equatorial plane is 10% to 90% of the tire circumferential length Lg of the center main grooves.

[0025] (9) A tire for a motorcycle according to any one of (1) to (8), wherein at least one of the center main grooves has one or more widening portions, the widening portion being formed by expanding at least one of the inner groove wall in the tire width direction and the outer groove wall in the tire width direction outward in the groove width direction, and a raised portion is provided at the groove bottom of the widening portion.

[0026] (10) A motorcycle tire according to any one of (1) to (9), wherein the tread contact surface portion further comprises a shoulder main groove, wherein an angle θ3 formed between an extending direction of the shoulder main groove and the tire circumferential direction is 20° to 60°.

[0027] (11) A motorcycle tire according to any one of (1) to (10), wherein the tread contact portion further comprises a shoulder main groove, wherein an angle θ3 formed between the extension direction of the shoulder main groove and the circumferential direction of the tire is greater than an angle θ1 formed between the extension direction of the center main groove and the circumferential direction of the tire.

[0028] Effects of the Invention

[0029] According to the present invention, by adopting the above-mentioned configuration, it is possible to realize a motorcycle tire having improved steering stability, particularly improved squatting feeling during rolling. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a partial development view showing a tread contact surface portion of a front wheel tire as an example of a motorcycle tire according to the present invention.

[0031] Figure 2 It is a partial development view showing a tread contact surface portion of a rear tire as another example of the motorcycle tire of the present invention.

[0032] Figure 3 It is another partial development view showing the contact surface portion of the tread of a rear tire as another example of the tire for a motorcycle according to the present invention.

[0033] Figure 4 It is a cross-sectional view in the width direction showing an example of the tire for a two-wheeled vehicle of the present invention.

[0034] Figure 5 It is a partial development view showing the tread contact surface portion of a front tire of a comparative example.

[0035] Figure 6 It is a partial development view showing a tread contact surface portion of a rear tire of a comparative example. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0037] Figure 1 It is a partial development view showing a tread contact surface portion of a front wheel tire as an example of a motorcycle tire according to the present invention. Figure 2 , Figure 3 It is a partial development view showing a tread contact surface portion of a rear tire as another example of the motorcycle tire of the present invention. Figure 1 to Figure 3 The arrow in the middle indicates the direction of tire rotation.

[0038] In the motorcycle tire of the present invention, a directional pattern including at least one center main groove is provided on the tread contact portion. Figure 1 In the front wheel tire 100 shown in the figure, a central main groove 11 is arranged on the tread contact surface. Figure 2 , Figure 3 In the rear wheel tire 200 shown, two center main grooves 21 and 22 are arranged on the tread contact surface. These center main grooves are arranged so as not to cross the tire equatorial plane CL. By setting the structure that the center main grooves do not cross the tire equatorial plane CL, the straight-ahead stability can be improved.

[0039] Here, in the present invention, the center main groove refers to a main groove that contains 80% or more of the groove area in the ground contact surface during straight-line driving. In addition, in the present invention, the ground contact surface during straight-line driving refers to the ground contact surface during straight-line driving in a state where the tire is mounted on an application rim, filled with a predetermined internal pressure, and loaded with a predetermined load.

[0040] In the above description, the application rim refers to a standard rim of an application size specified by an industrial standard effective in a region where the tire is produced and used, the specified internal pressure refers to an air pressure corresponding to the maximum load capacity of the application size / tire level specified by the above industrial standard, and the specified load refers to the maximum mass allowed to be loaded on the tire specified by the above industrial standard. In addition, the above industrial standards are, for example, the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Association) in Japan, the STANDARD MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association Inc.) in the United States.

[0041] In the present invention, specifically, the ground contact surface during straight running refers to a belt-shaped range centered on the tire equatorial plane CL and having a width of 20% to 40% of the tread width TW.

[0042] Here, the tread width TW refers to the distance in the tire width direction between the two tread ends TE measured along the tread surface in an unloaded state when the tire is mounted on the applicable rim and filled with a specified internal pressure. Similarly, unless otherwise specified, each dimension of the tire of the present invention refers to the value measured in an unloaded state when the tire is mounted on the applicable rim and filled with a specified internal pressure.

[0043] In the tire of the present invention, the groove area ratio of the entire tread contact portion is less than 10% and the ratio Gs / Gc of the shear stiffness Gs measured along the tire width direction at a position 1 / 4 of the tread width TW from the tread end TE in the tread contact portion to the shear stiffness Gc measured along the tire width direction at a position 1 / 2 of the tread width TW from the tread end TE, that is, on the tire equatorial plane CL, is expressed as a percentage of 95% to 100%.

[0044] Here, the groove area ratio is the ratio of the area of ​​the groove to the area of ​​the tread surface assuming that there is no groove, and refers to the ratio of the area of ​​the tread surface occupied by the groove portion other than the sipe.

[0045] In addition, in the present invention, the shear stiffness Gs and Gc of the tread contact surface portion are values ​​indicating the pattern stiffness determined by the tread pattern formed by the grooves, sipes, etc. provided on the tread contact surface portion, and are calculated using the finite element method (FEM). Specifically, a 3D model of only the tread pattern is made using a tetrahedral element with one side of about 3 mm, and the shear stiffness in the tire width direction is calculated for an area of ​​20 mm × the entire circumference of the tire in the tire width direction by FEM analysis, and the average value is obtained as the value of the shear stiffness at each tire width direction position.

[0046] In addition, parameters regarding the thickness direction and material can be appropriately set in conjunction with each tire.

[0047] In the tire of the present invention, by defining the value of the groove area ratio and the value of the shear rigidity ratio Gs / Gc as described above, the pattern rigidity can be made uniform in the tire width direction, and the steering stability, particularly the feeling of falling during rolling, can be improved.

[0048] Furthermore, in the tire of the present invention, from the viewpoint of ensuring steering stability during high-speed running, the groove area ratio of the entire tread contact surface portion can be preferably set to 4% to 9%.

[0049] In the tire of the present invention, it is important to configure at least one center main groove and preferably configure the center main groove so as not to cross the tire equatorial plane CL, and to define the value of the groove area ratio and the value of the shear stiffness ratio Gs / Gc as described above, thereby achieving the expected effect of the present invention. There are no particular restrictions on other aspects, but it is preferably configured as follows.

[0050] In the tire of the present invention, when the contact surface of the tread contact surface portion during straight driving is set as the center area, and a pair of areas located outside the center area in the tire width direction are respectively set as shoulder areas, the ratio Nc / Ns of the groove area ratio Nc of the center area to the groove area ratio Ns of the shoulder area is preferably 40% to 120% when expressed as a percentage. As a result, the pattern rigidity can be made more uniform in the tire width direction, and the steering stability, especially the feeling of falling during rollover, can be further improved. In the present invention, the ratio Nc / Ns of the groove area ratio is preferably 40% to 95%. In addition, especially when the present invention is applied to the front tire, the ratio Nc / Ns of the groove area ratio is preferably 40% to 43%, and when the present invention is applied to the rear tire, the ratio Nc / Ns of the groove area ratio is preferably 80% to 100%.

[0051] In addition, in the tire of the present invention, the distance d between the center main grooves arranged across the tire equatorial plane CL is preferably 1% to 20% of the tread width TW, and more preferably 10% to 15%. By setting the distance d within the above range, the shear stiffness can be made uniform and the feeling of falling during cornering can be improved. The distance d refers to the minimum value when measuring the distance in the tire width direction between the inner ends of the center main grooves arranged across the tire equatorial plane CL along the tread surface.

[0052] Furthermore, in the tire of the present invention, the angle θ1 formed by the extension direction of the center main groove and the tire circumferential direction is preferably 0° to 30°, and more preferably 10° to 15°. By setting the angle θ1 within the above range, the shear stiffness can be made uniform. In the present invention, the angle θ1 is defined as the angle formed by the straight line connecting the tire circumferential ends of the center main groove to each other and the tire circumferential direction.

[0053] exist Figure 1 In the front wheel tire 100 shown in the figure, the angle θ1 is an angle θ1-11 formed by a straight line connecting the tire circumferential ends 11a and 11b of one center main groove 11 and the tire circumferential direction. Figure 2 In the rear tire 200 shown, the angle θ1 is the angle θ1-21, θ1-22 formed by the straight line connecting the tire circumferential ends 21a, 21b and the tire circumferential ends 22a, 22b of the two center main grooves 21, 22, respectively, and the tire circumferential direction.

[0054] In addition, in the tire of the present invention, when the point where a perpendicular line drawn from the point M of the line segment connecting the tire circumferential ends of the center main groove intersects with the inner groove wall of the center main groove in the tire width direction is set as X, the angle θ2 formed by two straight lines connecting the point X and 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 set to a curved shape, and the pattern rigidity can be made more uniform in the tire width direction.

[0055] exist Figure 1 In the front wheel tire 100 shown in FIG. 1 , the angle θ2 is the angle θ2-11 formed by two straight lines connecting point X and the tire circumferential ends 11a, 11b of the center main groove 11, respectively, when the point where a perpendicular line drawn from the midpoint M of the 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 is set as X. Figure 3In the rear wheel tire 200 shown, the angle θ2 is the angle θ2-21, θ2-22 formed by two straight lines connecting the points X-1, X-2 and the tire circumferential ends 21a, 21b and tire circumferential ends 22a, 22b of the two center main grooves 21, 22, respectively, when the points where the perpendicular lines drawn from the midpoints M-1, M-2 intersect with the inner groove walls 21A, 22A in the tire width direction of the center main grooves 21, 22 are set to X-1, X-2, respectively.

[0056] In addition, in the tire of the present invention, it is preferred that at least one of the center main grooves has one or more widening portions, and the widening portions are formed by expanding at least one of the inner groove wall in the tire width direction and the outer groove wall in the tire width direction outward in the groove width direction, and it is also preferred that there are two or more widening portions. In the tire of the present invention, when the center main groove has two or more widening portions, a narrowing portion is formed between the widening portions. In this case, when the maximum value of the groove width of the widening portion of the center main groove is set to the maximum groove width W, the minimum value of the groove width of the narrowing 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 narrowing portion that meets the above conditions in the center main groove, the rigidity can be prevented from being excessively reduced.

[0057] In the present invention, the groove width of the widened portion and the groove width of the narrowed portion of the central main groove refer to the maximum and minimum values ​​of the groove width measured perpendicularly to the inner groove wall of the central main groove in the tire width direction.

[0058] exist Figure 1 In the front wheel tire 100 shown, the center main groove 11 has two widening parts 11W-1 and 11W-2, in which the outer groove wall 11B in the tire width direction expands outward in the groove width direction, and a narrowing part 11C is formed between the two widening parts 11W-1 and 11W-2. The maximum value of the groove width of the two widening parts 11W-1 and 11W-2 is the maximum groove width W11, and the minimum value of the groove width of the narrowing part 11C is the minimum groove width w11. Figure 2 In the rear wheel tire 200 shown, the center main groove 21 has two widened portions 21W-1 and 21W-2, both of which are the inner groove wall 21A in the tire width direction and the outer groove wall 21B in the tire width direction, and a narrowed portion 21C is formed between the two widened portions 21W-1 and 21W-2. The maximum groove width of the two widened portions 21W-1 and 21W-2 is the maximum groove width W21, and the minimum groove width of the narrowed portion 21C is the minimum groove width w21. Figure 2The center main groove 22 has one widened portion 22W in which the outer groove wall 22B in the tire width direction expands outward in the groove width direction, and has no narrowed portion.

[0059] In the present invention, it is preferred that the narrowed portion of the center main groove is provided at the center of the center main groove in the tire circumferential direction, for example, in the range of 40% to 60% of the center main groove length Lg in the tire circumferential direction.

[0060] In the tire of the present invention, when one or more widening portions are provided in the center main groove, it is preferred that a raised portion be provided at the groove bottom of the widening portion. This can improve drainage along the inner groove wall and the outer groove wall in the tire width direction, thereby improving drainage performance. In order to achieve such an effect, the shape of the raised portion is preferably a shape along the extension direction of the center main groove having the widening portion.

[0061] Furthermore, the raised portion may be provided in all the widened portions existing in one central main groove, or only in a part of the widened portions; furthermore, the raised portion may be provided in all the central main grooves having the widened portions, or only in a part of the central main grooves. In particular, in the present invention, it is preferred that one or two raised portions are provided for one central main groove.

[0062] exist Figure 3 In the rear tire 200 shown, one ridge is provided in each of the two widened portions 21W-1 and 21W-2 of the center main groove 21, and a total of two ridges 121-1 and 121-2 are provided, and one ridge 122 is provided in one widened portion 22W of the center main groove 22. Figure 1 In the front tire 100 shown, no raised portion is provided in the widened portions 11W- 1 and 11W- 2 of the center main groove 11 .

[0063] The height of the raised portion is not particularly limited as long as it is less than the depth of the central main groove with the widened portion, but is preferably less than 90% of the depth of the central main groove with the widened portion. In addition, the extended length of the raised portion is preferably 30% to 50% of the widened portion.

[0064] In the tire of the present invention, it is preferred that Figure 3As shown in the center main groove 21 of the rear tire 200, the inner groove wall 21A in the tire width direction and the outer groove wall 21B in the tire width direction have the same number of parts extending outward in the groove width direction, and the parts extending outward in the groove width direction of the inner groove wall 21A in the tire width direction and the outer groove wall 21B in the tire width direction are arranged in pairs, and the ridges 121-1 and 121-2 are provided at the groove bottoms of the expanded width parts 21W-1 and 21W-2 formed thereby. In this case, the ridges may be provided at all the expanded width parts or at part of the expanded width parts.

[0065] In addition, in the tire of the present invention, the overlapping length of the center main grooves arranged across the tire equatorial plane CL in the tire circumferential direction is preferably 10% to 90% of the tire circumferential length Lg of the center main groove, and more preferably 15% to 85%. As a result, the rigidity of the center portion can be reduced and the rigidity of the shoulder portion can be relatively increased, thereby improving the steering stability and the feeling of falling when rolling.

[0066] Here, the above-mentioned overlapping length refers to the overlapping length in the tire circumferential direction of the center main grooves arranged across the tire equatorial plane CL, and is the sum of the tire circumferential length of the parts of the center main grooves overlapping each other across the tire equatorial plane relative to each center main groove when viewed from the tire width direction.

[0067] In the tire of the present invention, a center main groove having a relatively large tire circumferential length is arranged in the center region of the tread contact surface close to the tire equatorial plane CL, and a shoulder main groove is arranged in the shoulder region outside the center region in the tire width direction. Here, in the present invention, the shoulder main groove refers to the main groove other than the center main groove. Figure 1 The front wheel tire 100 shown in the figure is provided with shoulder main grooves 31, 32, 33. Figure 2 , Figure 3 The rear wheel tire 200 shown is provided with shoulder main grooves 41, 42, 43.

[0068] Preferably, the shoulder main grooves are arranged at substantially equal intervals in the tire circumferential direction in the shoulder region. Here, substantially equal intervals means that the groove distances between the opening ends of the tire contact surface of each of the plurality of shoulder main grooves arranged are substantially the same in the tire circumferential direction.

[0069] exist Figure 1 In the front tire 100 shown in the figure, 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 among the three shoulder main grooves 31, 32 and 33 are set, L1≈L2≈L3 is satisfied. Figure 3In the rear wheel tire 200 shown, since one center main groove 22 extends to the shoulder area, 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 set to three shoulder main grooves 41, 42, 43 and the center main groove 22, respectively, L4≈L5≈L6≈L7 is satisfied.

[0070] In the present invention, the groove distance can be measured, for example, at the same tire width direction position where a plurality of shoulder main grooves are arranged overlappingly when viewed along the tire circumference. In addition, the groove distance being substantially the same means including manufacturing errors, for example, if it is within the error range of ±20% based on mm, it is substantially the same.

[0071] The angle θ3 formed by the extension direction of the shoulder main groove and the tire circumferential direction is preferably 20° to 60°, and more preferably 35° to 50°. By setting the angle θ3 within the above range, the shear stiffness can be made uniform. In the present invention, the angle θ3 is defined as the angle formed by the straight line connecting the tire circumferential ends of the shoulder main groove to each other and the tire circumferential direction.

[0072] exist Figure 1 In the front wheel tire 100 shown in the figure, the angle θ3 is the angle θ3-31, θ3-32, θ3-33 formed by the straight line connecting the tire circumferential ends 31a, 31b, 32a, 32b, and 33a, 33b of the three shoulder main grooves 31, 32, 33 and the tire circumferential direction. Figure 3 In the rear wheel tire 200 shown, the angle θ3 is the angle θ3-41, θ3-42, θ3-43 formed by the straight line connecting the tire circumferential ends 41a, 41b, 42a, 42b, and 43a, 43b of the three shoulder main grooves 41, 42, 43 respectively and the tire circumferential direction.

[0073] In this case, it is preferred that the angle θ3 formed by the extension direction of the shoulder main groove and the tire circumferential direction is larger than the angle θ1 formed by the extension direction of the center main groove and the tire circumferential direction. This can make the shear stiffness uniform and improve the drainage performance of the center portion when the tire is moving straight and the shoulder portion when the tire is tilted.

[0074] More specifically, in Figure 1 In the front tire 100 shown, the angle 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. Figure 2 , Figure 3In the rear tire 200 shown, the relationship between the angles of 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.

[0075] In the tire of the present invention, the groove depth of the center main groove and the groove depth of the shoulder main groove are not particularly limited, and can be generally set to 2.0 mm to 11 mm, preferably 3.5 mm to 6.5 mm.

[0076] In addition, as shown in the figure, in the present invention, a pattern consisting of a groove group consisting of a plurality of center main grooves and shoulder main grooves is substantially repeated in the tire circumferential direction in a shape symmetrical with respect to the tire equatorial plane CL and arranged at a staggered interval of 1 / 2. Here, in the present invention, the arrangement pitch of the pattern refers to a unit of repetition in the tire circumferential direction of the pattern formed by the center main grooves and shoulder main grooves provided in the tread contact surface portion. The arrangement pitch of the pattern of the present invention is not particularly limited, and can be set, for example, to about 1 / 20 to 1 / 5 of the entire circumferential length of the tire.

[0077] Figure 4 FIG. 2 is a cross-sectional view of a rear tire as an example of a tire for a motorcycle of the present invention in the width direction. Figure 4 As shown, the tire 200 of the present invention includes a tread portion 1 forming a ground contact portion, and a pair of sidewall portions 2 and a bead portion 3 extending from both ends of the tread portion 1 toward the inner side in the tire radial direction.

[0078] The tire 200 shown in the figure uses two carcass cords 4 extending in a ring shape across a pair of bead portions 3 as a skeleton. In the present invention, the carcass cords 4 are formed by arranging relatively highly elastic textile cords in parallel with each other, and the number of the carcass cords is at least one, and may be three or more. In addition, the two ends of the carcass cords 4 may be folded back from the inside to the outside of the tire at the bead portion 3 as shown in the figure, or may be clamped from both sides by bead wires, and any fixing method may be used.

[0079] In the tire 200 shown in the figure, a two-layer belt layer 6 is arranged on the outer side of the carcass cord 4 of the tread portion 1 in the radial direction of the tire. In the present invention, the belt layer 6 can be configured with at least one layer, and can be formed by two or more inclined belt layers arranged in a manner of interlacing between layers in the cord direction, or can also be formed by only one or more spiral belts, and the one or more spiral belts are composed of rubber-coated cords spirally wound in the circumferential direction of the tire. In addition, as reinforcing materials constituting the belt layer 6, nylon fiber, aromatic polyamide (trade name: ケブラー (registered trademark)), steel, etc. can be listed. Among them, aromatic polyamide and steel are reinforcing materials that do not stretch at high temperatures and can suppress the expansion of the tread portion.

[0080] Furthermore, in the tire 200 of the present invention, the bead strip 7 can be arranged outside the bead core 5 in the tire radial direction, and an inner liner (not shown) can be arranged in the innermost layer of the tire.

[0081] Furthermore, in the tire of the present invention, the ratio of the height SWH at the maximum width position of the tire to the tire cross-section height SH is preferably in the range of 40% to 75%. By setting the ratio SWH / SH of the tire cross-section height SH to the height SWH at the maximum width position of the tire in the range of 40% to 75% expressed as a percentage, a tire having an appropriate contact patch and excellent steering stability can be made. In addition, the steering stability in a tilted state can be improved, especially when a two-wheeled vehicle is turning. Here, the tire cross-section height SH refers to 1 / 2 of the difference between the outer diameter of the tire and the rim diameter of the rim specified by the above-mentioned industrial standard.

[0082] The tire of the present invention can be applied to any of the front wheel tires and the rear wheel tires of a motorcycle, and can also be applied to any tire of a radial structure and a bias structure. In addition, the tire of the present invention has improved handling stability, especially the feeling of falling when rolling, compared with the past, so it is useful as a sports tire.

[0083] Example

[0084] Hereinafter, the present invention will be described in more detail using specific examples.

[0085] (Example 1)

[0086] The tread contact surface is provided with Figure 1 A front wheel tire for a motorcycle having a directional pattern shown in FIG. 1 (tire size 120 / 70ZR17M / C) and a tread contact surface having a Figure 2 The rear tires (tire size 190 / 55ZR17M / C) had the directional pattern shown. These test tires met the following conditions.

[0087] The distance d between the center main grooves arranged across the tire equatorial plane is 5% of the tread width TW (for the front wheel) and 7% of the tread width TW (for the rear wheel).

[0088] The angle θ1-11 of the central main groove 11 is 17°, the angle θ1-21 of the central main groove 21 is 10°, and the angle θ1-22 of the central main groove 22 is 25°.

[0089] The angle θ2-11 of the central main groove 11 is 10°, the angle θ2-21 of the central main groove 21 is 5°, and the angle θ2-22 of the central main groove 22 is 6°.

[0090] The minimum groove width w11 of the central main groove 11 is 50% of the maximum groove width W11 , the minimum groove width w21 of the central main groove 21 is 50% of the maximum groove width W21 , and the minimum groove width w22 of the central main groove 22 is 39% of the maximum groove width W22 .

[0091] The overlapping length of the center main grooves arranged across the tire equatorial plane is: 40% of the tire circumferential length Lg of the center main groove 11 (front wheel), 15% of the tire circumferential length Lg of the center main groove 21 (rear wheel), and 82% of the tire circumferential length Lg of the center main groove 22.

[0092] Angle θ3-31 of the shoulder main groove 31: 35°, angle θ3-32 of the shoulder main groove 32: 45°, angle θ3-33 of the shoulder main groove 33: 35°, angle θ3-41 of the shoulder main groove 41: 45°, angle θ3-42 of the shoulder main groove 42: 45°, angle θ3-43 of the shoulder main groove 43: 30°.

[0093] The obtained front and rear tires were assembled on rims with rim sizes of MT3.50×17 and MT6.00×17, respectively, filled with internal pressures of 250kPa and 290kPa, respectively, and installed on commercially available motorized two-wheeled vehicles. Two test riders conducted a sensory evaluation of the motorized two-wheeled vehicle, scoring the yaw responsiveness and the feeling of falling when rolling, and calculating the average score. Specifically, the test riders drove at large and small corners, and evaluated the yaw responsiveness when turning and the feeling of falling when rolling with a full score of 10.

[0094] (Comparative Example 1)

[0095] In addition to being installed as front and rear tires, Figure 5 and Figure 6 Evaluation was performed in the same manner as in the examples except for the tires having the tread patterns shown, and the average score was calculated. Figure 5 , Figure 6 The arrow in the middle indicates the direction of tire rotation.

[0096] The comparative example was used as a reference, and the evaluation results were expressed as the difference in scores. The larger the evaluation score, the better the rider's evaluation. The results are shown in Table 1 below together with the shear stiffness ratio Gs / Gc, the groove area ratio of the entire tread contact surface, and the ratio of the groove area ratio Nc / Ns.

[0097] [Table 1]

[0098]

[0099] *1) is the value of the ratio Gs / Gc of the shear stiffness Gs measured along the tire width direction at a position 1 / 4 of the tread width TW from the tread end TE in the tread contact portion and the shear stiffness Gc measured along the tire width direction at a position 1 / 2 of the tread width TW from the tread end TE, obtained by FEM analysis.

[0100] *2) is the value of the ratio Nc / Ns of the groove area ratio Nc of the center region to the groove area ratio Ns of the shoulder region, when the contact patch of the tread contact portion during straight driving is defined as the center region and a pair of regions located outside the center region in the tire width direction are defined as shoulder regions.

[0101] As shown in the above table, it is clear that by satisfying the predetermined shear rigidity ratio and the groove area ratio, a motorcycle tire having improved steering stability, particularly improved squatting feeling during rolling, can be achieved.

[0102] Description of Reference Numerals

[0103] 1. Tread; 2. Sidewall; 3. Bead; 4. Carcass cord; 5. Bead core; 6. Belt; 7. Bead rubber strip; 11, 21, 22, center main groove; 11a, 11b, 21a, 21b, 22a, 22b, tire circumferential end of the center main groove; 11A, 21A, 22A, inner groove wall of the center main groove in the tire width direction; 11B, 21B, 22B, outer groove wall of the center main groove in the tire width direction; 11W-1, 1 1W-2, 21W-1, 21W-2, 22W, expanded portion; 11C, 21C, narrowed portion; 31, 32, 33, 41, 42, 43, shoulder main groove; 31a, 31b, 32a, 32b, 33a, 33b, 41a, 41b, 42a, 42b, 43a, 43b, tire circumferential end of the shoulder main groove; 100, front wheel tire; 121-1, 121-2, 122, raised portion; 200, rear wheel tire.

Claims

1. A motorcycle tire, wherein a directional pattern including at least one central main groove is provided on a tread contact surface portion, wherein: The groove area ratio of the entire tread contact surface portion is 10% or less, and In the tread contact portion, a ratio Gs / Gc of a shear stiffness Gs measured in the tire width direction at a position 1 / 4 of the tread width TW from the tread end to a shear stiffness Gc measured in the tire width direction at a position 1 / 2 of the tread width TW from the tread end is 95% to 100%.

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

3. The tire for a motorcycle according to claim 1 or 2, wherein: When the contact surface of the tread contact portion during straight driving is defined as a center region, and a pair of regions located outside the center region in the tire width direction are defined as shoulder regions, a ratio Nc / Ns of a groove area ratio Nc of the center region to a groove area ratio Ns of the shoulder region is 40% to 120%.

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

5. The tire for a motorcycle according to claim 1, wherein: An angle θ1 formed between the extending direction of the central main groove and the tire circumferential direction is 0° to 30°.

6. The tire for a motorcycle according to claim 1, wherein: When the point where a perpendicular line drawn at the midpoint 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 is set as X, the angle θ2 formed by two straight lines connecting point X and the tire circumferential ends of the center main groove is 0° to 40°.

7. The tire for a motorcycle according to claim 1, wherein: At least one of the center main grooves has an expansion portion in which at least one of the two or more inner groove walls in the tire width direction and the outer groove walls in the tire width direction expands outward in the groove width direction. When the maximum value of the groove width of the expansion portion is set to the maximum groove width W, the minimum value of the groove width of the narrowing portion formed between the expansion portions, that is, the minimum groove width w, is 20% to 60% of the maximum groove width W.

8. The tire for a motorcycle according to claim 1, wherein: The overlapping length in the tire circumferential direction of the center main grooves disposed across the tire equatorial plane is 10% to 90% of the tire circumferential direction length Lg of the center main grooves.

9. The tire for a motorcycle according to claim 1, wherein: At least one of the central main grooves has one or more widened portions, wherein at least one of the inner groove wall and the outer groove wall in the tire width direction is expanded outward in the groove width direction, and a raised portion is provided at the groove bottom of the widened portion.

10. The tire for a motorcycle according to claim 1, wherein: The tread contact surface portion further includes a shoulder main groove, and an angle θ3 formed between an extending direction of the shoulder main groove and the tire circumferential direction is 20° to 60°.

11. The tire for a motorcycle according to claim 1, wherein: The tread contact surface portion further includes a shoulder main groove, and an angle θ3 formed between an extending direction of the shoulder main groove and the tire circumferential direction is larger than an angle θ1 formed between an extending direction of the center main groove and the tire circumferential direction.

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