Motorcycle tire

Abstract

The invention provides a motorcycle tire capable of suppressing burst damage of tread rubber caused by heat generation during high-speed driving. A tread portion of the motorcycle tire includes a crown region (Cr) traversing the equatorial plane of the tire, and a pair of shoulder regions (Sh) on the outer side of the crown region in the axial direction of the tire. The tread rubber (10) comprises: a surface layer (11) comprising a first rubber disposed on the outside in the radial direction of the tire; a bottom layer (13) comprising a third rubber disposed on the inside in the radial direction of the tire; and an intermediate layer (12) comprising a second rubber disposed between the surface layer and the bottom layer. The loss tangent tan [delta] of the second rubber at 100 DEG C is greater than the loss tangent tan [delta] of the first rubber at 100 DEG C and the loss tangent tan [delta] of the third rubber at 100 DEG C. The top layer and the bottom layer extend in a pair of shoulder regions and a crown region, and the intermediate layer (12) is configured from a pair extending in each of the pair of shoulder regions and is not disposed in the crown region. In the crown area, the surface layer and the bottom layer are directly connected.

Description

Technical Field

[0001] The present invention relates to a motorcycle tire. Background Art

[0002] Patent Document 1 below describes a motorcycle tire having a multi-layered tread rubber. The tread rubber includes a cap rubber forming the tread surface and a base rubber disposed radially inward of the tread surface. The cap rubber is configured to have a loss tangent tanδ smaller than that of the base rubber.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 7056227 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] Compared to motorcycle tires with a single-structure tread rubber, motorcycle tires with this multi-layered tread rubber structure offer both improved wear resistance and handling stability during high-speed driving. Consequently, multi-layered tread rubber has been increasingly adopted in many motorcycle tires in recent years. In particular, in motorcycle tires designed for sports such as racing, attempts are being made to position a rubber layer with a high loss tangent (tan δ) on the inner side of the tread rubber to maximize grip.

[0008] However, rubber with a high loss tangent tanδ is prone to heat generation due to high hysteresis losses, and thus easily reaches high temperatures during continuous high-speed driving. Furthermore, if the rubber layer with a high loss tangent tanδ is covered by the cap rubber, cooling by traveling air becomes difficult. Consequently, in such a multi-layered tread rubber, there is a risk of tread rubber bursting due to heat generation.

[0009] Furthermore, in racing, high grip is most needed during cornering, where the vehicle body is tilted to impart camber to the tires, particularly during intermediate lean (during acceleration) and full lean (during cornering), where the shoulder area of ​​the tread rubber is in contact. Therefore, it is desirable for motorcycle tires to have improved grip during cornering.

[0010] On the other hand, when traveling straight ahead, if the grip of the tread rubber is too high, there is also a problem of suppressing the maximum speed due to energy loss of the rubber.

[0011] The present invention has been developed in response to the aforementioned problems. Its primary objective is to provide a motorcycle tire that can suppress tread rubber burst damage caused by heat generation during high-speed driving. Furthermore, in a preferred embodiment, the present invention aims to improve grip during cornering. Furthermore, in a preferred embodiment, the present invention aims to increase the maximum speed during straight-ahead driving.

[0012] Technical solutions to problems

[0013] The present invention is a motorcycle tire comprising: a tread portion having a pair of tread ends; a pair of sidewall portions; a pair of bead portions; a carcass arranged between the pair of bead portions; a tread reinforcement layer arranged on the tire radially outer side of the carcass and having a reinforcing cord; and a tread rubber arranged on the tire radially outer side of the tread reinforcement layer, the tread portion comprising a crown region crossing the tire equatorial plane and a pair of shoulder regions on the tire axially outer side of the crown region, the pair of shoulder regions including the pair of tread ends, the tread rubber comprising a surface layer composed of a first rubber arranged on the tire radially outer side, a bottom layer composed of a third rubber arranged on the tire radially inner side layer, and an intermediate layer composed of a second rubber arranged between the surface layer and the bottom layer, the loss tangent tanδ of the second rubber at 100°C is greater than the loss tangent tanδ of the first rubber at 100°C and the loss tangent tanδ of the third rubber at 100°C, the surface layer and the bottom layer extend from one side of the pair of shoulder areas through the crown area to the other side of the pair of shoulder areas, the intermediate layer is composed of a pair of layers extending respectively in the pair of shoulder areas, and are interrupted at the inner end of the tire axial direction in a manner not arranged in the crown area, and in the crown area, the surface layer is directly connected to the bottom layer.

[0014] Effects of the Invention

[0015] The motorcycle tire of the present invention can suppress the bursting damage of the tread rubber caused by heat during high-speed running. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a cross-sectional view of a motorcycle tire according to the present embodiment in a dimensioned state.

[0017] Figure 2 yes Figure 1 A partial enlarged view of the tread portion.

[0018] Description of Reference Numerals

[0019] 1 motorcycle tire

[0020] 2. Tread

[0021] 2a Grounding outline

[0022] 3 sidewalls

[0023] 4 Bead part

[0024] 6 carcasses

[0025] 7 tread reinforcement layer

[0026] 10 tread rubber

[0027] 11 Surface

[0028] 12 middle layer

[0029] 12i inner end

[0030] 13 bottom floor

[0031] 20 Transition Area

[0032] 21 constant regions

[0033] C Tire equatorial plane

[0034] Cr crown area

[0035] Sh shoulder area DETAILED DESCRIPTION

[0036] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0037] It should be understood that, to facilitate understanding of the present invention, the drawings may include exaggerated representations or representations of dimensional ratios that differ from the actual structure. Furthermore, in the case of multiple embodiments, identical or common elements will be designated by the same reference numerals throughout the specification, and duplicate descriptions will be omitted. Furthermore, the specific structures illustrated in the embodiments and drawings are provided for understanding the content of the present invention, and the present invention is not limited to the specific structures illustrated.

[0038] Figure 1 This is a cross-sectional view of a motorcycle tire (hereinafter sometimes referred to as "tire") according to this embodiment. The tire 1 of this embodiment is suitable for use in, for example, racing on a circular track. Because such a tire 1 is used for both straight and cornering at relatively high speeds, it requires a high top speed and excellent grip during cornering. However, the tire of the present invention is not limited to such racing.

[0039] The motorcycle tire of this embodiment is a pneumatic tire. Figure 1 The sizing state is shown in FIG. In this specification, the sizing state refers to a state in which the shape of the tire 1 is determined, wherein the tire 1 is mounted on a standard rim (not shown) and the internal pressure is adjusted to 10 kPa in an unloaded state. Unless otherwise specified, the tire 1 is in this sizing state.

[0040] In this specification, "standard rim" refers to a rim specified for each tire in the specification system including the specifications on which the tire 1 is based, for example, "standard rim" in the case of JATMA, "Design Rim" in the case of TRA, and "Measuring Rim" in the case of ETRTO.

[0041] like Figure 1 As shown, the tire 1 includes: a tread portion 2 having a pair of tread ends Te, a pair of sidewall portions 3, a pair of bead portions 4 in which bead cores 5 are embedded, a carcass 6 extending between the pair of bead portions 4, a tread reinforcement layer 7 arranged on the radially outer side of the carcass 6 and having reinforcing cords, and a tread rubber 10 arranged on the radially outer side of the tread reinforcement layer 7.

[0042] In the present embodiment, the ground contact profile (determined to be without grooves in the case of grooves) 2a, which is the profile of the outer surface of the tread portion 2, is, for example, an arc shape convex to the outside in the radial direction of the tire. In addition, in the tire 1 of the present embodiment, the tire axial distance between a pair of tread ends Te, Te, that is, the tread width TW, constitutes the maximum width of the tire (tire cross-sectional width). In this way, the tread portion 2 of the present embodiment has a structure unique to motorcycle tires that turns by giving the tire a camber angle by tilting the vehicle body significantly. In addition, Figure 1 Here, H is the tire cross-sectional height measured from the bead base line BL. The tread end Te of the present embodiment is positioned further inward in the tire radial direction than the center position of the tire cross-sectional height H.

[0043] The tread portion 2 of the present embodiment includes a crown region Cr extending across the tire equatorial plane C, and a pair of shoulder regions Sh on the outer sides of the crown region Cr in the tire axial direction.

[0044] The crown region Cr primarily contacts the road surface during straight-ahead travel with a camber angle close to or substantially zero. As an example, the crown region Cr is within a range of 30 mm or greater, preferably 40 mm or greater, centered on the tire's equatorial plane C. Alternatively, the crown region Cr is within a range of 90 mm or less, preferably 80 mm or less, centered on the tire's equatorial plane C.

[0045] The radius of curvature R of the contact patch profile 2a of the crown region Cr is preferably less than 95% of the tire cross-sectional width, for example. For convenience, when the "nominal" cross-sectional width is displayed on the sidewall portion 3, the tire cross-sectional width is defined as the dimension expressed in millimeters. However, when the tire cross-sectional width is not displayed on the sidewall portion 3, the tire cross-sectional width is actually measured under the aforementioned sizing conditions.

[0046] When the radius of curvature R of the contact patch 2a of the crown region Cr is set small as described above, the motorcycle can be leaned more easily at the start of a turn, improving maneuverability in the initial stages of the turn. From this perspective, the radius of curvature R of the contact patch 2a of the crown region Cr is preferably 80% or less of the tire's cross-sectional width. However, if the radius of curvature R of the contact patch 2a of the crown region Cr is too small, stability during straight-ahead driving may be reduced. From this perspective, the radius of curvature R of the contact patch 2a of the crown region Cr can be, for example, 40% or more, preferably 50% or more, of the tire's cross-sectional width.

[0047] The pair of shoulder regions Sh are regions extending from the crown region Cr to respective tread ends Te. The shoulder regions Sh are regions that come into contact with the road surface during cornering with a camber angle applied to the tire 1 .

[0048] The carcass 6 is composed of at least one, in this embodiment, one, carcass ply 6A.

[0049] The carcass ply 6A of this embodiment is a ply material composed of a plurality of aligned carcass cords and a topping rubber covering them. The carcass ply 6A includes a main portion 6a extending annularly between the bead cores of a pair of bead sections 4, and a folded portion 6b folded back around the bead core 5 in each bead section 4 from the axially inner side to the outer side of the tire. In this embodiment, the outer end of the folded portion 6b is terminated radially inward of the tread end Te.

[0050] The carcass 6 of this embodiment has, for example, a radial structure, with the carcass cords arranged at an angle of, for example, 75 to 90 degrees relative to the tire equatorial plane C. The carcass cords can be made of organic fiber cords such as polyester, nylon, rayon, and aromatic polyamide. Alternatively, a bias-ply structure can be used as the carcass 6 .

[0051] In the bead portion 4 of this embodiment, a bead apex rubber 4a is disposed between the main portion 6a and the folded portion 6b of the carcass ply 6A. The bead apex rubber 4a extends, for example, in a tapered shape from the outer surface of the bead core 5 toward the outer side in the tire radial direction. The bead apex rubber 4a is formed of hard rubber and increases the flexural rigidity of the bead portion 4.

[0052] like Figure 2 As shown, the tread reinforcement layer 7 of this embodiment includes a belt layer 8. The belt layer 8 includes, for example, two belt layers 8A and 8B. The belt layers 8A and 8B have, for example, reinforcing cords arranged at an angle of 15 to 45 degrees relative to the tire equatorial plane C. The belt layers 8A and 8B overlap in the tire radial direction so that the reinforcing cords intersect each other. Steel cords are preferably used as the reinforcing cords of the belt layer 8.

[0053] The tread reinforcement layer 7 of the present embodiment also includes a cord layer 9 as an optional element. The cord layer 9 is arranged on the outer side of the belt layer 8 in the tire radial direction. The cord layer 9 of the present embodiment includes an endless cord layer 9A, which is formed by spirally winding a narrow strip of reinforcing cords covered with rubberized rubber multiple times on the outer side of the belt layer 8. The endless cord layer 9A has reinforcing cords arranged at an angle of, for example, 5° or less relative to the tire circumferential direction. Such a cord layer 9 helps to firmly fasten the belt layer 8 and improve the high-speed durability of the tire 1. The reinforcing cords of the cord layer 9 can be organic fiber cords such as nylon, rayon, polyester, and aromatic polyamide.

[0054] Furthermore, the tread reinforcing layer 7 may be composed of the belt layer 8 or the carcass layer 9 .

[0055] Reference Figure 1 , the tread rubber 10 of the present embodiment extends from one tread end Te across the tire equatorial plane C to the other tread end Te. In addition, the tread rubber 10 of the present embodiment has a multi-layer structure in which a plurality of rubbers are stacked in the radial direction of the tire. Specifically, the tread rubber 10 includes a surface layer 11 composed of a first rubber arranged on the radially outer side of the tire, a bottom layer 13 composed of a third rubber arranged on the radially inner side of the tire, and an intermediate layer 12 composed of a second rubber arranged between the surface layer 11 and the bottom layer 13. Moreover, the loss tangent tanδ of the second rubber at 100°C is greater than the loss tangent tanδ of the first rubber at 100°C and the loss tangent tanδ of the third rubber at 100°C (hereinafter, the mark of the temperature 100°C of tanδ is sometimes omitted).

[0056] In this specification, the loss tangent tan δ of each rubber is a value measured under the following conditions using a viscoelasticity spectrometer such as the "EPLEXOR (registered trademark)" manufactured by GABO Corporation on a test piece collected from the tread rubber 10 of the tire 1. The test piece has a shape with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm, with the long side in the tire circumferential direction being the long side.

[0057] Measuring temperature: 100°C

[0058] Frequency: 5Hz

[0059] Initial tensile strain: 10%

[0060] Amplitude of dynamic strain: ±2.5%

[0061] In the tread rubber 10, the surface layer 11 and the base layer 13 extend from one of the pair of shoulder regions Sh to the other of the pair of shoulder regions Sh through the crown region Cr. In this embodiment, the surface layer 11 and the base layer 13 extend continuously from one end to the other end of the tread rubber 10 in the tire axial direction.

[0062] Meanwhile, the intermediate layer 12 is composed of a pair of layers extending in each of the pair of shoulder regions Sh. Furthermore, the intermediate layer 12 is interrupted at each axially inner end 12i, so as not to be positioned in the crown region Cr. Furthermore, in the crown region Cr, the surface layer 11 and the base layer 13 are directly connected at the inner end 12i of the intermediate layer 12.

[0063] [Functions and Effects of the Tire of the Present Embodiment]

[0064] During the rigorous and continuous driving of a race, the tread rubber 10 of the tire 1 gradually heats up. In motorcycle tires, the area most susceptible to heat accumulation is the crown region Cr, which is most affected by high-speed, straight-ahead driving. In the tire 1 of this embodiment, the crown region Cr is not equipped with the intermediate layer 12 composed of the second rubber, which has the highest loss tangent tanδ in the tread rubber 10. As a result, the tire 1 of this embodiment can suppress burst damage in the crown region Cr, where heat accumulation is most severe.

[0065] When cornering at a large camber angle, an intermediate layer 12 composed of a second rubber with a high tanδ is required to improve grip. However, when driving straight ahead at high speeds, such high grip is not required. Therefore, in the crown region Cr, an intermediate layer 12 composed of a second rubber with a high tanδ is not important. Rather, an intermediate layer 12 composed of a second rubber with a high tanδ may suppress the maximum speed when driving straight ahead because it increases energy loss and rolling resistance. In the tire 1 of this embodiment, the crown region Cr does not have an intermediate layer 12 composed of a second rubber, which reduces the energy loss and rolling resistance of the tread rubber 10 when driving straight ahead. Therefore, the tire 1 of this embodiment can increase the maximum speed when driving straight ahead.

[0066] Furthermore, in the tread rubber 10 of this embodiment, the intermediate layer 12 composed of the second rubber having a large tan δ is arranged in the shoulder region Sh that contacts the road surface during cornering. Therefore, the tire 1 of this embodiment can exhibit high grip during cornering.

[0067] Hereinafter, a more preferable aspect of the tire 1 of the present embodiment will be described.

[0068] like Figure 2 As shown, the shoulder regions Sh of this embodiment each include a transition region 20 on their axially inner sides. The transition region 20 is a region where the thickness of the surface layer 11 increases toward the crown region Cr, and the thickness of the intermediate layer 12 decreases toward the crown region Cr. In the transition region 20 of this embodiment, the thickness of the intermediate layer 12 continuously decreases toward its axially inner end 12i. Similarly, in the transition region 20, the thickness of the surface layer 11 continuously increases until the inner end 12i of the intermediate layer 12.

[0069] In this transition region 20, the physical properties of the tread rubber 10 gradually change between the crown region Cr and the shoulder region Sh. This not only achieves the aforementioned benefits, but also suppresses abrupt changes in handling between straight driving and cornering, thereby enabling excellent steering stability. To more effectively achieve this benefit, the length L of the transition region 20 (the circumference along the contact patch profile 2a) is preferably greater than the total thickness T1 of the tread rubber 10 in the crown region Cr, and is particularly preferably at least 1.2 times, or even at least 1.5 times, this total thickness T1. In this specification, the total thickness T1 of the tread rubber 10 in the crown region Cr refers to the total thickness of the surface layer 11 and base layer 13 in the crown region Cr. When this total thickness varies, it refers to the maximum thickness.

[0070] Furthermore, the shoulder region Sh includes a constant region 21 extending axially outward of the transition region 20, where each of the surface layer 11, the intermediate layer 12, and the base layer 13 has a constant thickness. In this specification, the term "constant thickness" regarding rubber thickness is defined to take into account the tolerances inherent in rubber molded products such as pneumatic tires. Specifically, a constant thickness is defined when the difference between the maximum and minimum thicknesses is approximately 10% of the maximum thickness. This constant region 21 ensures that the physical properties of the shoulder region Sh are constant in the axial direction of the tire, thereby ensuring stable cornering performance.

[0071] [Rubber thickness, etc.]

[0072] In the crown region Cr, the total thickness T1 of the tread rubber 10 is preferably within a range of, for example, 5.0 to 9.0 mm.

[0073] By setting the total thickness T1 of the tread rubber 10 in the crown region Cr to 5.0 mm or greater, sufficient grip can be ensured in the crown region Cr. This improves straight-line stability during running on a circular track and also ensures sufficient rearward braking force during upright braking. From this perspective, the total thickness T1 of the tread rubber 10 in the crown region Cr is preferably 5.5 mm or greater, for example.

[0074] By setting the total thickness T1 of the tread rubber 10 in the crown region Cr to 9.0 mm or less, a good balance between burst damage resistance and grip can be achieved in the crown region Cr. From this perspective, the total thickness T1 of the tread rubber 10 in the crown region Cr is preferably 8.5 mm or less, for example.

[0075] In each shoulder region Sh, the total thickness T2 of the tread rubber 10 is preferably determined within a range of, for example, 5.0 to 9.0 mm. The total thickness T2 of the tread rubber 10 in the shoulder region Sh is the total thickness of the surface layer 11, the intermediate layer 12, and the base layer 13 in the shoulder region Sh. When this total thickness varies, it represents the maximum thickness.

[0076] In each shoulder region Sh, the thickness t2 of the intermediate layer 12 is preferably at least 10% of the total thickness T2 of the tread rubber 10. By setting the thickness t2 of the intermediate layer 12 at least 10% of the total thickness T2, the grip in the shoulder region Sh is improved, thereby enhancing propulsion when exiting a curve. From this perspective, the thickness t2 of the intermediate layer 12 is more preferably at least 20% of the total thickness T2 of the tread rubber 10, for example.

[0077] In each shoulder region Sh, the thickness t2 of the intermediate layer 12 is preferably 60% or less of the total thickness T2 of the tread rubber 10. By setting the thickness t2 of the intermediate layer 12 to 60% or less of the total thickness T2, excessive heat accumulation in the shoulder region Sh can be suppressed. From this perspective, the thickness t2 of the intermediate layer 12 is more preferably 50% or less of the total thickness T2, for example.

[0078] In the crown region Cr and the pair of shoulder regions Sh, the thickness t3 of the base layer 13 is preferably at least 5% of the combined thickness of the surface layer 11 and the intermediate layer 12 (the maximum combined thickness when varying). Typically, a high tan δ second rubber contains a large amount of oil. When this oil migrates to the reinforcing cords on the inner side of the tire, not only does it reduce the grip-enhancing function of the intermediate layer 12, but it also deteriorates the physical properties of the reinforcing cords. By specifying the thickness t3 of the base layer 13, as in this embodiment, the base layer 13 acts as a barrier, effectively preventing the oil in the second rubber from migrating to the tread reinforcement layer 7, thereby maintaining the high tan δ physical properties of the second rubber over a long period of time. From this perspective, it is more preferable that the thickness t3 of the base layer 13 be at least 10% of the combined thickness of the surface layer 11 and the intermediate layer 12.

[0079] In the crown region Cr and the pair of shoulder regions Sh, the thickness t3 of the base layer 13 is preferably no greater than 30% of the combined thickness of the surface layer 11 and the intermediate layer 12. Given the constraints imposed by the total thickness of the tread rubber 10, increasing the thickness t3 of the base layer 13 reduces the thickness of the surface layer 11 and the intermediate layer 12, potentially impairing grip and wear resistance. From this perspective, the thickness t3 of the base layer 13 is more preferably no greater than 20% of the combined thickness of the surface layer 11 and the intermediate layer 12.

[0080] [Loss tangent tanδ]

[0081] To achieve high grip during cornering, the loss tangent tanδ of the second rubber can be, for example, 0.30 or greater, preferably 0.35 or greater, and more preferably 0.40 or greater. On the other hand, if the loss tangent tanδ of the second rubber is too high, energy loss may increase. From this perspective, the loss tangent tanδ of the second rubber can be, for example, 0.60 or less, preferably 0.55 or less, and more preferably 0.50 or less, in combination with any of the above lower limits.

[0082] To more effectively suppress burst damage caused by heat accumulation during high-speed straight driving, the loss tangent tanδ of the first rubber forming the surface layer 11 may be, for example, 0.40 or less, preferably 0.35 or less, and more preferably 0.32 or less. Furthermore, to suppress a significant decrease in grip during high-speed straight driving, the loss tangent tanδ of the first rubber may be, for example, 0.20 or greater, preferably 0.25 or greater, and more preferably 0.27 or greater, in combination with any of the aforementioned upper limits.

[0083] To more effectively prevent burst damage caused by heat accumulation during high-speed straight driving, the third rubber forming the base layer 13 preferably has a loss tangent tanδ at 100°C that is smaller than the loss tangent tanδ of the second rubber at 100°C. Specifically, the loss tangent tanδ of the third rubber at 100°C can be, for example, 0.35 or less, preferably 0.30 or less, and more preferably 0.28 or less. Furthermore, to prevent a significant decrease in grip during straight driving, the loss tangent tanδ of the third rubber, in combination with any of the aforementioned upper limits, can be, for example, 0.15 or greater, preferably 0.20 or greater, and more preferably 0.23 or greater.

[0084] [300% modulus of the first rubber]

[0085] The 300% modulus at 100°C of the first rubber forming the surface layer 11 (hereinafter, the reference to the temperature of 100°C may be omitted) is preferably greater than the 300% modulus at 100°C of the second rubber forming the intermediate layer 12. While this first rubber may have inferior grip to the second rubber forming the intermediate layer 12, it exhibits superior wear resistance. Consequently, excellent wear resistance is achieved throughout the crown region Cr and shoulder regions Sh.

[0086] In this specification, the 300% modulus is the modulus when the rubber test piece is elongated by 300%, and is the tensile stress (MPa) M300 at 300% elongation measured at 100°C in accordance with JIS-K6251 "Rubber, vulcanized and thermoplastic rubber - Methods for determining tensile properties".

[0087] To effectively exhibit the aforementioned wear resistance, the 300% modulus of the first rubber may be, for example, 3.0 (MPa) M300 or greater, preferably 3.5 (MPa) M300 or greater, and more preferably 4.3 (MPa) M300 or greater. Furthermore, to prevent a significant decrease in grip, the 300% modulus of the first rubber may be, for example, 7.0 (MPa) M300 or less, preferably 6.0 (MPa) M300 or less, and more preferably 5.0 (MPa) M300 or less.

[0088] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific disclosures above, and can be implemented with various modifications within the scope of the technical concept described in the claims.

[0089] [Note]

[0090] The present invention includes the following aspects.

[0091] [Present invention 1]

[0092] A motorcycle tire, comprising:

[0093] a tread portion having a pair of tread ends;

[0094] a pair of sidewalls;

[0095] a pair of bead portions;

[0096] a carcass disposed between the pair of bead portions;

[0097] a tread reinforcement layer disposed on the outer side of the carcass in the tire radial direction and having reinforcing cords; and

[0098] a tread rubber disposed on the outer side of the tread reinforcement layer in the tire radial direction;

[0099] The tread portion includes a crown region that crosses the tire equatorial plane and a pair of shoulder regions on the axially outer sides of the crown region.

[0100] The pair of shoulder regions include the pair of tread ends,

[0101] The tread rubber includes a surface layer composed of a first rubber disposed on the outer side of the tire in the radial direction, a base layer composed of a third rubber disposed on the inner side of the tire in the radial direction, and an intermediate layer composed of a second rubber disposed between the surface layer and the base layer.

[0102] The loss tangent tanδ of the second rubber at 100°C is greater than the loss tangent tanδ of the first rubber at 100°C and the loss tangent tanδ of the third rubber at 100°C.

[0103] The surface layer and the base layer extend from one of the pair of shoulder regions through the crown region to the other of the pair of shoulder regions.

[0104] The intermediate layer is composed of a pair of layers extending in the pair of shoulder regions, and is interrupted at the inner end of the tire axial direction so as not to be arranged in the crown region.

[0105] In the crown region, the surface layer is directly connected to the base layer.

[0106] [Present invention 2]

[0107] According to the motorcycle tire of Invention 1, the pair of shoulder regions respectively include transition regions in which the thickness of the surface layer increases toward the crown region and the thickness of the intermediate layer decreases toward the crown region.

[0108] [Present invention 3]

[0109] According to the motorcycle tire of Invention 2, the pair of shoulder regions respectively include constant regions where the surface layer, the middle layer, and the base layer extend with a constant thickness on the axially outer side of the transition region.

[0110] [Present invention 4]

[0111] In the motorcycle tire according to any one of Inventions 1 to 3, the base layer has a constant thickness in the crown region and the pair of shoulder regions.

[0112] [Present invention 5]

[0113] In the motorcycle tire according to any one of Inventions 1 to 4, a 300% modulus of the first rubber at 100°C is greater than a 300% modulus of the second rubber at 100°C.

[0114] [Present invention 6]

[0115] The motorcycle tire according to any one of Inventions 1 to 5, wherein in an unloaded dimensional state where the tire is mounted on a standard rim and the internal pressure is adjusted to 10 kPa, the radius of curvature of the contact patch profile of the crown region is less than 95% of the tire cross-sectional width.

[0116] [Present invention 7]

[0117] In the motorcycle tire according to any one of Inventions 1 to 6, the crown region is within a range of 30 to 90 mm centered on the tire equatorial plane.

[0118] [Present invention 8]

[0119] The motorcycle tire according to any one of Inventions 1 to 7, wherein in the crown region, the total thickness of the tread rubber is within a range of 5.0 to 9.0 mm.

[0120] [Present invention 9]

[0121] According to any one of the present inventions 1 to 8, in the motorcycle tire, in each of the pair of shoulder regions, the total thickness of the tread rubber is within a range of 5.0 to 9.0 mm.

[0122] The thickness of the intermediate layer is 10% to 60% of the total thickness of the tread rubber.

[0123] [Present invention 10]

[0124] In the motorcycle tire according to any one of Inventions 1 to 9, in the crown region and the pair of shoulder regions, the thickness of the base layer is 5% to 30% of the total thickness of the surface layer and the intermediate layer.

Claims

1. A motorcycle tire, characterized in that: include: a tread portion having a pair of tread ends; a pair of sidewalls; a pair of bead portions; a carcass disposed between the pair of bead portions; a tread reinforcement layer disposed on the outer side of the carcass in the tire radial direction and having reinforcing cords; and a tread rubber disposed on the outer side of the tread reinforcement layer in the tire radial direction; The tread portion includes a crown region that crosses the tire equatorial plane and a pair of shoulder regions on the axially outer sides of the crown region. The pair of shoulder regions include the pair of tread ends, The tread rubber includes a surface layer composed of a first rubber disposed on the outer side of the tire in the radial direction, a base layer composed of a third rubber disposed on the inner side of the tire in the radial direction, and an intermediate layer composed of a second rubber disposed between the surface layer and the base layer. The loss tangent tanδ of the second rubber at 100°C is greater than the loss tangent tanδ of the first rubber at 100°C and the loss tangent tanδ of the third rubber at 100°C. The surface layer and the base layer extend from one of the pair of shoulder regions through the crown region to the other of the pair of shoulder regions. The intermediate layer is composed of a pair of layers extending in the pair of shoulder regions, and is interrupted at the inner end of the tire axial direction so as not to be arranged in the crown region. In the crown region, the surface layer is directly connected to the base layer.

2. The motorcycle tire according to claim 1, characterized in that: The pair of shoulder regions respectively include transition regions in which a thickness of the surface layer increases toward the crown region and a thickness of the intermediate layer decreases toward the crown region.

3. The motorcycle tire according to claim 2, characterized in that: The pair of shoulder regions respectively include constant regions where the surface layer, the middle layer, and the base layer extend with a constant thickness on the outer side of the transition region in the tire axial direction.

4. The motorcycle tire according to claim 3, characterized in that: The underlayer has a constant thickness in the crown region and the pair of shoulder regions.

5. The motorcycle tire according to any one of claims 1 to 4, characterized in that: The 300% modulus of the first rubber at 100°C is greater than the 300% modulus of the second rubber at 100°C.

6. The motorcycle tire according to any one of claims 1 to 4, characterized in that In an unloaded dimensional state mounted on a standard rim and with the internal pressure adjusted to 10 kPa, the radius of curvature of the contact patch profile of the crown region is less than 95% of the tire cross-sectional width.

7. The motorcycle tire according to any one of claims 1 to 4, characterized in that The crown region is within a range of 30 to 90 mm centered on the tire equatorial plane.

8. The motorcycle tire according to any one of claims 1 to 4, characterized in that In the crown region, the total thickness of the tread band is within a range of 5.0 to 9.0 mm.

9. The motorcycle tire according to any one of claims 1 to 4, characterized in that: In each of the pair of shoulder regions, the total thickness of the tread rubber is within a range of 5.0 to 9.0 mm. The thickness of the intermediate layer is 10% to 60% of the total thickness of the tread rubber.

10. The motorcycle tire according to any one of claims 1 to 4, characterized in that In the crown region and the pair of shoulder regions, the thickness of the base layer is 5% to 30% of the total thickness of the surface layer and the intermediate layer.

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