Tire for two-wheeled vehicle

Abstract

To provide a tire for a two-wheeled vehicle, capable of improving stability during braking and turning performance.SOLUTION: A tire 1 for a two-wheeled vehicle includes a tread part 2, sidewall parts 3, bead parts 4, and a carcass 6. The tread part 2 includes a tread reinforcing layer 9 and tread rubber 12. The tread reinforcing layer 9 includes a belt layer 7 and a band layer 8. A development width of the band layer 8 is smaller than a development width of the belt layer 7. The tread rubber 12 includes crown rubber 13 and shoulder rubber 14. A hardness at 100°C of the shoulder rubber 14 is higher than a hardness at 100°C of the crown rubber 13. A complex elastic modulus at 100°C of the shoulder rubber 14 is higher than a complex elastic modulus at 100°C of the crown rubber 13. A 300% modulus at 100°C of the shoulder rubber 14 is higher than a 300% modulus at 100°C of the crown rubber 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 below proposes a motorcycle tire having a tread reinforcing layer in the tread portion. This tire is expected to improve cornering performance by specifying the angle of the belt cords included in the tread reinforcing layer with respect to the tire circumferential direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6946646 Summary of the Invention [Problem to be solved by the invention]

[0004] 2. Description of the Related Art In recent years, with improvements in the performance of motorcycles and the like, there has been a demand for improved cornering performance and stability during braking for motorcycle tires.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire for a two-wheeled vehicle that can improve stability during braking and cornering performance. [Means for solving the problem]

[0006] The present invention relates to a tire for a motorcycle, comprising a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass extending between the pair of bead portions, the tread portion comprising a tread reinforcing layer disposed on the tire radially outer side of the carcass, and a tread rubber disposed on the tire radially outer side of the tread reinforcing layer, the tread reinforcing layer comprising a belt layer including a plurality of belt cords inclined with respect to a tire circumferential direction, and a band layer disposed on the tire radially outer side of the belt layer and including at least one band cord wound spirally in the tire circumferential direction, the developed width of the band layer being equal to or larger than the width of the bead portion, a developed width of the tread layer that is smaller than the developed width of the tread layer, the tread rubber including a crown rubber arranged in a region including the tire equator, and a shoulder rubber arranged axially outboard of the crown rubber in a region including a tread edge, the hardness of the shoulder rubber at 100°C being greater than the hardness of the crown rubber at 100°C, the complex modulus of elasticity of the shoulder rubber at 100°C being greater than the complex modulus of elasticity of the crown rubber at 100°C, and the 300% modulus of the shoulder rubber at 100°C being greater than the 300% modulus of the crown rubber at 100°C. Effect of the Invention

[0007] The motorcycle tire of the present invention employs the above-mentioned configuration, thereby making it possible to improve stability during braking and cornering performance. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing one embodiment of a motorcycle tire of the present invention. [Diagram 2] FIG. 2 is an enlarged perspective view showing an inner material of the tire of FIG. 1. [Diagram 3] FIG. 2 is a development view of the tread rubber and the tread reinforcing layer of FIG. 1. [Figure 4] This is the profile of the tread at 10 kPa. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a tire meridian cross-sectional view including a tire rotation axis of a motorcycle tire 1 (hereinafter, sometimes simply referred to as "tire") of this embodiment in a normal state. The tire 1 of this embodiment is a tire for the front wheel of a motorcycle suitable for on-road sports driving. However, the tire of the present invention is not limited to this embodiment.

[0010] In the case of a pneumatic tire for which various standards are established, the "normal state" refers to a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal state refers to a standard usage state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state. In addition, the dimensions of components that cannot be measured in the normal state (for example, the internal materials of tire 1) are values ​​measured with tire 1 in a state as close as possible to the normal state.

[0011] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0012] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0013] As shown in Fig. 1, a tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 are continuous with both sides of the tread portion 2 in the tire axial direction. The bead portions 4 are continuous with the sidewall portions 3 on the inner side in the tire radial direction. In the tread portion 2, a contact surface 2s between one tread edge Te and the other tread edge Te is curved in an arc shape that is convex toward the outer side in the tire radial direction so that a sufficient contact area can be obtained even during cornering with a large camber angle. A bead core 5 is embedded in the bead portion 4.

[0014] The tread edge Te corresponds to an end of the contact surface 2s of the tread portion 2, and comes into contact with the road surface at least when turning at the maximum camber angle.

[0015] The tire 1 includes a carcass 6 extending between a pair of bead portions 4 .

[0016] The carcass 6 includes, for example, a carcass ply 6A including a plurality of carcass cords. The carcass 6 in this embodiment is configured with one carcass ply 6A, but may be one in which a plurality of carcass plies are overlapped. The carcass ply 6A includes a main body portion 6a and a turn-up portion 6b. The main body portion 6a extends from the tread portion 2 through the sidewall portions 3 on both sides to the bead cores 5 of the bead portions 4 on both sides. The turn-up portions 6b are connected to the main body portion 6a, and are turned up around the bead cores 5 from the inside to the outside in the tire axial direction.

[0017] The tread portion 2 includes a tread reinforcing layer 9 disposed on the radially outer side of the carcass 6, and a tread rubber 12 disposed on the radially outer side of the tread reinforcing layer 9. The tread reinforcing layer 9 includes a belt layer 7 and a band layer 8 disposed on the radially outer side of the belt layer 7. Fig. 2 shows an enlarged perspective view conceptually illustrating the internal material of the tire, and Fig. 3 shows a development view in which the tread rubber 12 and the tread reinforcing layer 9 are developed on a plane.

[0018] As shown in FIG. 2, the belt layer 7 is disposed adjacent to the carcass 6 on the outer side in the tire radial direction. The belt layer 7 is disposed so as to reinforce substantially the entire tread portion 2. As shown in FIG. 3, the belt layer 7 includes a plurality of belt cords 15 inclined with respect to the tire circumferential direction. The angle of these belt cords 15 with respect to the tire circumferential direction is, for example, 10 to 40 degrees. The belt layer 7 of this embodiment includes a first belt ply 10 disposed adjacent to the carcass 6 and a second belt ply 11 disposed on the outer side of the first belt ply 10 in the tire radial direction. In a more preferable embodiment, the belt layer 7 is composed of only these two belt plies.

[0019] The band layer 8 is disposed in the center of the tread portion 2 in the tire axial direction, and is disposed so as to straddle at least the tire equator C. The band layer 8 includes at least one band cord 20 wound in a spiral shape in the tire circumferential direction. The band layer 8 may be wound with a plurality of band cords 20. The band layer 8 may be wound with a band cord 20 covered with a topping rubber, or may be wound with a rubber-uncovered band cord 20 on a rubber sheet. The band layer 8 of this embodiment is configured as a jointless band in which, for example, four band cords 20 covered with a topping rubber are wound in a spiral shape. In the present invention, the development width W3 of the band layer 8 is smaller than the development width W2 of the belt layer 7. In this embodiment, the development width W6 of the second belt ply 11 corresponds to the development width W2 of the belt layer 7. The development width means the length in the tire axial direction when the band layer 8 or the belt layer 7 is developed on a plane. The same applies to the following description of this specification.

[0020] As shown in Fig. 1, the tread rubber 12 includes a crown rubber 13 and a shoulder rubber 14. The crown rubber 13 is disposed in an area including the tire equator C. The shoulder rubber 14 is disposed in an area including the tread edge Te on the axially outer side of the crown rubber 13. In a preferred embodiment, the shoulder rubber 14 is continuous with the crown rubber 13. The shoulder rubber 14 is also continuous with a sidewall rubber 18.

[0021] Generally, the temperature of the tread rubber 12 during running varies depending on various factors such as the running speed, the load on the tire 1, the road surface temperature, etc. For example, when the running speed is fast, when the load on the tire 1 is large, or when the road surface temperature is high, the temperature of the tread rubber 12 may rise to about 100°C.

[0022] In consideration of such circumstances, in the tire 1 of the present invention, the crown rubber 13 and the shoulder rubber 14 have the following relationships among the rubber hardness H, complex modulus E*, and 300% modulus M300 at 100°C. The hardness Hs of the shoulder rubber 14 at 100°C is greater than the hardness Hc of the crown rubber 13 at 100°C. The complex modulus E*s of the shoulder rubber 14 at 100°C is greater than the complex modulus E*c of the crown rubber 13 at 100°C. The 300% modulus M300s of the shoulder rubber 14 at 100°C is greater than the 300% modulus M300c of the crown rubber 13 at 100°C.

[0023] The hardness H of rubber is a value measured using a durometer type A in accordance with JIS-K6253.

[0024] The complex elastic modulus E* is a value measured in accordance with JIS-K6394 using a viscoelasticity spectrometer such as "IPLEXER (registered trademark)" manufactured by GABO under the conditions shown below. Initial distortion: 10% Amplitude: ±2.5% Frequency: 10Hz Deformation mode: tension

[0025] The 300% modulus M300 is the modulus at 300% elongation, and is a value measured in accordance with JIS-K6251 "Vulcanized rubber and thermoplastic rubber -- Determination of tensile properties."

[0026] The tire 1 of the present invention, by adopting the above-mentioned configuration, can improve stability during braking and cornering performance for the following reasons.

[0027] In the present invention, the above-mentioned band layer 8 increases the rigidity of the tread portion 2 in the tire circumferential direction. This effectively suppresses the outer diameter growth in the region where the crown rubber 13 is arranged, so that the band layer 8 improves stability during braking when traveling straight and the tread rubber 12 (in this example, the crown rubber 13) in the region where the band layer 8 is arranged touches the ground. On the other hand, in the present invention, the belt layer 7 increases the rigidity of the tread portion 2 in the tire axial direction in the region outside the band layer 8 in the tire axial direction. This allows the belt layer 7 to exert a large cornering force during cornering and provides excellent cornering performance when the tread rubber (in this example, the shoulder rubber 14) in the region where the band layer 8 is not arranged touches the ground.

[0028] Furthermore, the inventors discovered that stability and cornering performance during braking can be improved by making the rigidity of the shoulder rubber 14 greater than that of the crown rubber 13. That is, by making the rigidities of the rubbers different as described above, the crown rubber 13 exerts a high vibration absorbing effect during braking, improving stability during braking. Also, the shoulder rubber 14, which constitutes the contact surface, provides a large reaction force during cornering, improving cornering performance.

[0029] Generally, the rigidity of rubber can be specified by the complex modulus of elasticity E*. However, as a result of various experiments, it has been found that by simply specifying the complex modulus of elasticity E* for the rigidity of the shoulder rubber 14 and the crown rubber 13, the above-mentioned effects cannot be sufficiently obtained in driving conditions where the deformation of the tread rubber 12 is small (for example, low-speed driving on general roads) or driving conditions where the deformation of the tread rubber 12 is large (for example, limit driving on a circuit, etc.).

[0030] In the present invention, not only the complex elastic modulus E* but also the hardness Hc at 100°C of the crown rubber 13 constituting the contact surface 2s during straight running is specified, so that sufficient stability during braking can be obtained even in a running state in which the deformation amount of the tread rubber 12 is small. In addition, in the present invention, the 300% modulus M300 at 100°C is also specified, so that sufficient cornering performance can be obtained even in a running state in which the deformation amount of the tread rubber 12 constituting the contact surface 2s is large due to heat generation caused by friction with the road surface during cornering. In this way, the tire 1 of the present invention can improve stability during braking and cornering performance in various situations.

[0031] A more detailed configuration of this embodiment will be described below. Each configuration described below shows a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configuration described below. In addition, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0032] [Belt Layer Details] As shown in FIG. 3, the developed width W5 of the first belt ply 10 and the developed width W6 of the second belt ply 11 are 80% to 100% of the developed width W4 of the tread portion 2 (shown in FIG. 1), and preferably 90% to 95%. The developed width W6 of the second belt ply 11 is preferably larger than the developed width W5 of the first belt ply 10. This suppresses damage originating from the end of the first belt ply 10, and improves the durability of the area where the shoulder rubber 14 (shown in FIG. 1) is arranged. The developed width W4 of the tread portion 2 corresponds to the axial distance from one tread edge Te to the other tread edge Te when the ground contact surface 2s of the tread portion 2 is developed into a plane.

[0033] As shown in Fig. 3, the first belt ply 10 of this embodiment includes a plurality of first belt cords 16 inclined in a first direction (downward to the right in Fig. 3) with respect to the tire circumferential direction. The second belt ply 11 includes a plurality of second belt cords 17 inclined in a second direction (upward to the right in Fig. 3) opposite to the first direction with respect to the tire circumferential direction. Such an arrangement of the belt cords strongly reinforces the tread portion 2, and excellent cornering performance is exhibited.

[0034] The average angle θ1 of the first belt cord 16 with respect to the tire circumferential direction is 10 to 40°. The average angle θ1 corresponds to a value obtained by dividing the first belt cord 16 into a plurality of minute regions of the same length, and dividing the sum of the angles of each minute region with respect to the tire circumferential direction by the number of the minute regions. The same applies to the rest of the description in this specification. The length of one minute region is preferably 5 mm or less. In this embodiment, the first belt cord 16 is angled as described above, thereby improving straight-line stability and cornering performance in a well-balanced manner.

[0035] The maximum angle of the first belt cord 16 at the end of the first belt ply 10 in the tire axial direction with respect to the tire circumferential direction is larger than the maximum angle of the first belt cord 16 on the tire equator C with respect to the tire circumferential direction. In a more preferable embodiment, the average angle of the first belt cords 16 with respect to the tire circumferential direction in the region where the shoulder rubber 14 is arranged is larger than the average angle of the first belt cords 16 with respect to the tire circumferential direction in the region where the crown rubber 13 is arranged. By arranging the first belt cords 16 in this way, the rigidity in the tire circumferential direction is improved in the region where the crown rubber 13 is arranged, and the rigidity in the tire axial direction is improved in the region where the shoulder rubber 14 is arranged. Therefore, straight running stability and cornering performance are improved in a well-balanced manner.

[0036] The average of the angles θ2 of the second belt cords 17 with respect to the tire circumferential direction is 10 to 40°. The maximum angle of the second belt cords 17 with respect to the tire circumferential direction at the end of the second belt ply 11 in the tire axial direction is larger than the maximum angle of the second belt cords 17 with respect to the tire circumferential direction on the tire equator C. In a more preferable embodiment, the average of the angles of the second belt cords 17 with respect to the tire circumferential direction in the region where the shoulder rubber 14 is arranged is larger than the average of the angles of the second belt cords 17 with respect to the tire circumferential direction in the region where the crown rubber 13 is arranged. Such an arrangement of the second belt cords 17 improves straight running stability and cornering performance in a well-balanced manner.

[0037] The material of the first belt cord 16 and the second belt cord 17 is not particularly limited, but for example, organic fibers such as polyester fibers, nylon fibers, or aramid fibers are used.

[0038] The first belt cord 16 and the second belt cord 17 of the present embodiment are formed of a single cord that is not twisted. Such belt cords are less likely to elongate than twisted cords. Therefore, it is easier to generate a large linear reaction force during cornering, and the steering stability can be improved.

[0039] [Band Layer Details] The developed width W3 of the band layer 8 is, for example, 20% to 80% of the developed width W4 of the tread portion 2. The developed width W3 of the band layer 8 is 20% to 60% of the developed width W2 of the belt layer 7. On the other hand, from the viewpoint of exerting a large cornering force even at a relatively small camber angle, it is preferable that the developed width W3 of the band layer 8 is relatively small. From this viewpoint, the developed width W3 of the band layer 8 is preferably 20% to 50% of the developed width W2 of the belt layer 7, and more preferably 20% to 40%.

[0040] The breaking strength of the band cord 20 (maximum stress at break) is desirably greater than the breaking strength of the belt cord 15. From this perspective, the band cord 20 is desirably a steel cord. This reliably improves straight-line stability even when the developed width W3 of the band layer 8 is small.

[0041] [Crown rubber details] The developed width W7 of the ground contact surface 21 of the crown rubber 13 is preferably 80 to 120% of the developed width W3 of the band layer 8. If the developed width W7 of the ground contact surface 21 of the crown rubber 13 is 80% or more of the developed width W3 of the band layer 8, the band layer 8 improves stability during braking when traveling straight, and the crown rubber 13 constituting the ground contact surface 2s can exhibit a high vibration absorption effect, so that stability during braking can be improved more effectively. If the developed width W7 of the ground contact surface 21 of the crown rubber 13 is 120% or less of the developed width W3 of the band layer 8, the rubber volume of the shoulder rubber 14 can be sufficiently secured, and cornering performance can be further improved.

[0042] From the viewpoint of more effectively improving stability during braking, it is preferable that the developed width W7 of the ground contact surface 21 of the crown rubber 13 is larger than the developed width W3 of the band layer 8. If the developed width W7 is larger than the developed width W3, the ground contact surface 2s is composed of only the ground contact surface 21 of the crown rubber 13 during straight driving. That is, the ground contact surface 2s is composed of one rubber. Therefore, for example, as in the case where the ground contact surface 2s is composed of two rubbers, the crown rubber 13 and the shoulder rubber 14, there is no boundary between the rubbers on the ground contact surface 2s (in this example, the boundary 23 between the crown rubber 13 and the shoulder rubber 14, which will be described later), and therefore distortion is less likely to occur on the ground contact surface 2s during braking, improving stability during braking.

[0043] From the viewpoint of adjusting the circumferential rigidity of the crown rubber 13 within an appropriate range, the hardness Hc of the crown rubber 13 at 100° C. is preferably 38 degrees or more, more preferably 39 degrees or more, and is preferably 42 degrees or less, and more preferably 41 degrees or less. The crown rubber 13 having such hardness Hc has an appropriate deformation at 100° C. and has a rigidity adjusted within an appropriate range, so that the braking force is effectively exerted and a high vibration absorbing effect is exhibited.

[0044] From the same viewpoint, the complex elastic modulus E*c of the crown rubber 13 at 100°C is preferably 2.1 MPa or more, more preferably 2.3 MPa or more, and is preferably 2.7 MPa or less, and more preferably 2.5 MPa or less. The crown rubber 13 having such a complex elastic modulus E*c has an appropriate elasticity at 100°C and a rigidity adjusted to an appropriate range, thereby exerting the same effects as those described above.

[0045] From the same viewpoint, the 300% modulus M300c of the crown rubber 13 at 100°C is preferably 4.0 MPa or more, more preferably 4.2 MPa or more, and is preferably 4.8 MPa or less, and more preferably 4.6 MPa or less. The crown rubber 13 having such a 300% modulus M300c has a suitable flexibility at 100°C and a rigidity adjusted to an appropriate range, thereby exerting the same effects as those described above.

[0046] As described above, the temperature of the tread rubber 12 during running generally varies depending on the running speed, the load on the tire, the road surface temperature, etc. For example, when the running speed is slow, the load on the tire is small, or the road surface temperature is low, the temperature of the tread rubber 12 may be about 50° C. Therefore, it is more desirable to specify the performance at 50° C. for each part of the tread rubber 12.

[0047] From the above viewpoints, the hardness Hc of the crown rubber 13 at 50° C. is preferably 44 degrees or more, more preferably 45 degrees or more, and is preferably 48 degrees or less, and more preferably 47 degrees or less. The crown rubber 13 having such hardness Hc has its rigidity adjusted to an appropriate range even at 50° C., so that it effectively exerts braking force and exerts a high vibration absorbing effect.

[0048] From the same viewpoint, the complex elastic modulus E*c of the crown rubber 13 at 50°C is preferably 3.2 MPa or more, more preferably 3.4 MPa or more, and is preferably 3.8 MPa or less, and more preferably 3.6 MPa or less. This provides appropriate elasticity at 50°C and adjusts the rigidity to an appropriate range, so that the above-mentioned effects can be expected.

[0049] [Shoulder rubber details] 3, the developed width W8 of the contact surface 22 of the shoulder rubber 14 is preferably 60 to 90% of the developed width W7 of the crown rubber 13. This makes it possible to improve stability during braking and cornering performance in a well-balanced manner.

[0050] From the viewpoint of adjusting the axial stiffness of the shoulder rubber 14 at 100° C. to an appropriate range, the hardness Hs of the shoulder rubber 14 at 100° C. is desirably 40 degrees or more, more desirably 41 degrees or more, and desirably 44 degrees or less, more desirably 43 degrees or less. This makes it possible to obtain the above-mentioned effects and also improve the controllability during cornering.

[0051] From the same viewpoint, the complex modulus E*s of the shoulder rubber 14 at 100°C is preferably 2.4 MPa or more, more preferably 2.6 MPa or more, and preferably 3.0 MPa or less, and more preferably 2.8 MPa or less. Also, the 300% modulus M300s of the shoulder rubber 14 at 100°C is preferably 4.7 MPa or more, more preferably 4.9 MPa or more, and preferably 5.5 MPa or less, and more preferably 5.3 MPa or less. This allows the rigidity of the shoulder rubber 14 to be adjusted within an appropriate range, and the above-mentioned effects are reliably exhibited.

[0052] As described above, from the viewpoint of adjusting the axial stiffness of the shoulder rubber 14 at 50°C within an appropriate range, the hardness of the shoulder rubber 14 at 50°C is preferably 47 degrees or more, more preferably 48 degrees or more, and preferably 51 degrees or less, and more preferably 50 degrees or less. When the temperature of the shoulder rubber 14 is about 50°C, which is a relatively low temperature, such a shoulder rubber 14 provides an appropriate deformation and the stiffness is adjusted within an appropriate range, thereby achieving the same effect as that described above.

[0053] From the same viewpoint, the complex elastic modulus E*s of the shoulder rubber 14 at 50° C. is preferably 4.0 MPa or more, more preferably 4.2 MPa or more, and is preferably 4.6 MPa or less, and more preferably 4.4 MPa or less. When the temperature of the shoulder rubber 14 is about 50° C., which is a relatively low temperature, such a shoulder rubber 14 has an appropriate elasticity and its rigidity is adjusted to an appropriate range, thereby exerting the same effects as those described above.

[0054] [Relationship between crown rubber and shoulder rubber] As described above, in order to adjust the rigidity of the crown rubber 13 and the shoulder rubber 14 to an appropriate range when the load on the tire is relatively low, it is preferable that the rubber hardness H, the complex modulus E*, and the 300% modulus M300 at 50°C have the following relationship. The hardness Hs of the shoulder rubber 14 at 50°C is greater than the hardness Hc of the crown rubber 13 at 50°C. The complex modulus E*s of the shoulder rubber 14 at 50°C is greater than the complex modulus E*c of the crown rubber 13 at 50°C. The 300% modulus M300s of the shoulder rubber 14 at 50°C is greater than the 300% modulus M300c of the crown rubber 13 at 50°C. Such a tire 1 can improve stability and cornering performance during braking not only at a relatively high temperature of about 100°C during driving, but also at a relatively low temperature of about 50°C during driving. Therefore, such a tire 1 can exhibit the above-mentioned effects in response to changes in the running speed, the load on the tire, the road surface temperature, and the like.

[0055] From the viewpoint of adjusting the rigidity of the crown rubber 13 and the shoulder rubber 14 at 100° C. within an appropriate range, the hardness Hs of the shoulder rubber 14 at 100° C. is desirably 105% or more, more desirably 110% or more, and desirably 125% or less, more desirably 120% or less of the hardness Hc of the crown rubber 13 at 100° C. Such crown rubber 13 and shoulder rubber 14 have an appropriate balance of rigidity, and therefore stability during braking and cornering performance are improved in a well-balanced manner.

[0056] From the same viewpoint, the complex modulus E*s of the shoulder rubber 14 at 100° C. is preferably 105% or more, more preferably 110% or more, and preferably 150% or less, more preferably 140% or less of the complex modulus E*c of the crown rubber 13 at 100° C. Such crown rubber 13 and shoulder rubber 14 have an appropriate balance of rigidity, and therefore stability during braking and cornering performance are improved in a well-balanced manner.

[0057] From the same viewpoint, the 300% modulus M300s at 100° C. of the shoulder rubber 14 is preferably 105% or more, more preferably 110% or more, and preferably 150% or less, more preferably 140% or less of the 300% modulus M300c at 100° C. of the crown rubber 13. Such crown rubber 13 and shoulder rubber 14 have an appropriate balance of rigidity, and therefore stability during braking and cornering performance are improved in a well-balanced manner.

[0058] From the viewpoint of adjusting the rigidity of the crown rubber 13 and the shoulder rubber 14 at 50° C. within an appropriate range, the hardness Hs of the shoulder rubber 14 at 50° C. is preferably 105% or more, more preferably 110% or more, and preferably 125% or less, more preferably 120% or less of the hardness Hc of the crown rubber 13 at 50° C. Such crown rubber 13 and shoulder rubber 14 have an appropriate balance of rigidity, and therefore stability during braking and cornering performance are improved in a well-balanced manner.

[0059] From the same viewpoint, the complex modulus E*s of the shoulder rubber 14 at 50° C. is preferably 105% or more, more preferably 110% or more, and preferably 150% or less, more preferably 140% or less of the complex modulus E*c of the crown rubber 13 at 50° C. Such crown rubber 13 and shoulder rubber 14 have an appropriate balance of rigidity, and therefore stability during braking and cornering performance are improved in a well-balanced manner.

[0060] From the same viewpoint, the 300% modulus M300s at 50° C. of the shoulder rubber 14 is preferably 105% or more, more preferably 110% or more, and preferably 150% or less, more preferably 140% or less of the 300% modulus M300c at 50° C. of the crown rubber 13. Such crown rubber 13 and shoulder rubber 14 have an appropriate balance of rigidity, and therefore stability during braking and cornering performance are improved in a well-balanced manner.

[0061] It is generally known that rubber with a large loss tangent tanδ has excellent heat generation and can exert a large grip. Based on these technical matters, it is preferable that the loss tangent tanδs of the shoulder rubber 14 at 100°C is larger than the loss tangent tanδc of the crown rubber 13 at 100°C. Such a shoulder rubber 14 can exert a large grip and maintain driving stability even if the temperature of the shoulder rubber 14 rises to about 100°C due to friction with the road surface during cornering. In addition, such a crown rubber 13 appropriately suppresses heat generation and maintains high stability during high-speed driving.

[0062] The loss tangent tan δ is a value measured in accordance with the provisions of JIS-K6394 using the above-mentioned viscoelasticity spectrometer under the conditions shown below. Initial strain: 5% Amplitude: ±1% Frequency: 10Hz Deformation mode: Stretch

[0063] The loss tangent tanδs of the shoulder rubber 14 at 50° C. is preferably larger than the loss tangent tanδc of the crown rubber 13 at 50° C. Such a shoulder rubber 14 can exert a large grip and maintain driving stability even when the temperature of the shoulder rubber 14 rises to only about 50° C. due to friction with the road surface during cornering. In addition, such a crown rubber 13 appropriately suppresses heat generation, and maintains high stability during high-speed driving.

[0064] The characteristics of each rubber described above can be obtained by appropriately combining known rubber materials and known manufacturing methods.

[0065] From the viewpoint of making the rigidity of the shoulder rubber 14 greater than that of the crown rubber 13, it is preferable that the amount of carbon added to the crown rubber 13 is less than the amount of carbon added to the shoulder rubber 14. Such a tire 1 can improve stability during braking and cornering performance.

[0066] [Boundary Detail] As shown in FIG. 1, the crown rubber 13 of this embodiment extends with a substantially constant thickness in the region on the outer side of the band layer 8 in the tire radial direction. The shoulder rubber 14 of this embodiment extends with a substantially constant thickness on the outer side of the first belt ply 10 in the tire radial direction. The tread rubber 12, the crown rubber 13, and the shoulder rubber 14 are not limited to such an embodiment, and for example, the shoulder rubber 14 may extend so that the thickness becomes thinner as it approaches the tread edge Te. Note that extending with a substantially constant thickness allows for unavoidable errors in rubber products such as tires, and includes an embodiment in which the difference between the maximum value and the minimum value of the thickness of the rubber layer is 5% or less of the maximum value.

[0067] In this embodiment, in the tire meridian cross section, the boundary 23 between the crown rubber 13 and the shoulder rubber 14 has a straight line shape along the tire radial direction. The boundary 23 extends in the tire circumferential direction while maintaining this shape. It is preferable that the boundary 23 is inclined with respect to the tire normal line perpendicular to the ground contact surface 2s. The angle θ3 of the boundary 23 with respect to the tire normal line is preferably 20 to 70°, more preferably 20 to 40°. If the angle θ3 is 20 to 70°, the cross-sectional length of the boundary 23 can be secured to be large, and the crown rubber 13 and the shoulder rubber 14 can be suppressed from peeling off. If the angle θ3 is 20 to 40°, when traveling straight, the ground contact surface 2s is composed of only the ground contact surface 21 of the crown rubber 13, and the boundary 23 is not arranged on the ground contact surface 2s. As a result, distortion is less likely to occur in the ground contact surface 2s during braking, and stability during braking is improved. Note that the boundary 23 is not limited to such a form, and may have a curved shape, for example.

[0068] Boundaries 23 between the crown rubber 13 and the shoulder rubber 14 are formed on both sides of the tire equator C. These two boundaries 23 are preferably disposed symmetrically with respect to the tire equator C. Such a tire 1 has excellent balance performance when turning left and right, and can further improve cornering performance.

[0069] In this embodiment, the boundary 23 between the crown rubber 13 and the shoulder rubber 14 is located closer to the tread edge Te than the axial end 8a of the band layer 8. Such an arrangement of the boundary 23 allows the crown rubber 13 to cover the entire band layer 8, further improving stability during braking.

[0070] [Base rubber] The tread portion 2 of the present embodiment includes a base rubber 24 disposed between the tread reinforcing layer 9 and the tread rubber 12. The base rubber 24 is adjacent to each of the crown rubber 13 and the shoulder rubber 14.

[0071] The hardness of the base rubber 24 at 100° C. is desirably greater than the hardness Hc of the crown rubber 13 at 100° C. and less than the hardness Hs of the shoulder rubber 14 at 100° C. This makes the adhesion of the tread rubber 12 uniform, and makes it possible to suppress the tread rubber 12 from peeling off from the tread reinforcing layer 9.

[0072] From the same viewpoint, it is preferable that the complex modulus of elasticity of the base rubber 24 at 100°C is larger than the complex modulus of elasticity E*c of the crown rubber 13 at 100°C and smaller than the complex modulus of elasticity E*s of the shoulder rubber 14 at 100°C. Also, it is preferable that the 300% modulus of the base rubber 24 at 100°C is larger than the 300% modulus M300c of the crown rubber 13 at 100°C and smaller than the 300% modulus M300s of the shoulder rubber 14 at 100°C.

[0073] Profile Curvature Radius Fig. 4 shows a profile of the tread portion 2 in a tire meridian cross section in a 10 kPa state where the tire 1 is mounted on a regular rim and inflated with an internal pressure of 10 kPa. As shown in Fig. 4, in the 10 kPa state, the radius of curvature Rc of the ground contact surface 21 of the crown rubber 13 (shown in Fig. 1) is less than 95% of the tire cross-sectional width W1 (shown in Fig. 1), and the radius of curvature Rb of the ground contact surface 22 of the shoulder rubber 14 (shown in Fig. 1) is larger than the radius of curvature Rc. The tire cross-sectional width W1 corresponds to the axial width of the tire in the regular state.

[0074] As described above, the profile of the tread portion 2 is defined at 10 kPa, and the radius of curvature Rc of the contact surface 21 of the crown rubber 13 is relatively small. In such a tire 1, even when the normal internal pressure is filled and the outer diameter of the region where the shoulder rubber 14 is arranged grows, the change in the radius of curvature of the contact surface 2s of the tread portion 2 occurs mainly in the region where the crown rubber 13 is arranged, and the radius of curvature Rb of the contact surface 22 of the shoulder rubber 14 is unlikely to change. Therefore, the radius of curvature Rb of the contact surface 22 of the shoulder rubber 14 is appropriately maintained without becoming excessively large, and cornering performance can be maintained.

[0075] Although a motorcycle tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above and can be modified and carried out in various aspects. EXAMPLES

[0076] A motorcycle tire (front tire) of size 120 / 70ZR17 having the basic structure of FIG. 1 was manufactured based on the specifications in Table 1. In addition, as a comparative example, a tire was prototyped in which there was no distinction between crown rubber and shoulder rubber in the tread portion, and only one type of rubber was arranged as the tread rubber (in Table 1, the hardness, complex modulus of elasticity, and 300% modulus of the crown rubber and shoulder rubber are the same). The comparative tire has substantially the same configuration as the example tire, except for the above-mentioned points. Stability during braking and cornering performance were evaluated for each test tire. The common specifications and test methods for each test tire are as follows: Rim size: MT3.50×17 Tire pressure: 250kPa Test vehicle: Displacement 1000cc First belt ply development width W5: 140mm Second belt ply development width W6: 150mm Band layer deployment width W3: 60mm

[0077] <Stability during braking> The test vehicle was used to evaluate stability during braking when full braking was applied while traveling straight on an asphalt road at 220km / h. The results were shown as a score based on the comparative example being 100, with a higher score indicating better stability during braking.

[0078] <Turning performance> The test vehicle was evaluated for cornering performance when it was driven on an asphalt mountain road. The cornering performance was evaluated by comprehensively assessing the turning ability in corners, the degree of freedom when turning, the degree of front wheel cutting, etc. The results are shown as a score with the comparative example being 100, and the higher the score, the better the evaluation items. The test results are shown in Table 1.

[0079] [Table 1]

[0080] As a result of the test, it was confirmed that the tire of the embodiment can improve stability during braking and cornering performance.

[0081] [Note] The present invention includes the following aspects.

[0082] [Invention 1] A tire for a motorcycle, A tread portion; A pair of sidewall portions; A pair of bead portions; a carcass extending between the pair of bead portions, The tread portion includes a tread reinforcing layer disposed on the outer side of the carcass in the tire radial direction, and a tread rubber disposed on the outer side of the tread reinforcing layer in the tire radial direction, The tread reinforcing layer includes a belt layer including a plurality of belt cords inclined with respect to the tire circumferential direction, and a band layer disposed on the tire radial outer side of the belt layer and including at least one band cord wound spirally in the tire circumferential direction, The developed width of the band layer is smaller than the developed width of the belt layer, The tread rubber includes a crown rubber disposed in an area including a tire equator, and a shoulder rubber disposed axially outboard of the crown rubber in an area including a tread edge, The hardness of the shoulder rubber at 100°C is greater than the hardness of the crown rubber at 100°C, The shoulder rubber has a complex elastic modulus at 100°C greater than the complex elastic modulus at 100°C of the crown rubber, The 300% modulus of the shoulder rubber at 100°C is greater than the 300% modulus of the crown rubber at 100°C. Tires for motorcycles. [Invention 2] The motorcycle tire according to the first aspect of the present invention, wherein a loss tangent of the shoulder rubber at 100°C is greater than a loss tangent of the crown rubber at 100°C. [Invention 3] The hardness of the shoulder rubber at 50°C is greater than the hardness of the crown rubber at 50°C, The shoulder rubber has a complex elastic modulus at 50°C greater than the complex elastic modulus at 50°C of the crown rubber, 3. The motorcycle tire according to claim 1 or 2, wherein the 300% modulus at 50°C of the shoulder rubber is greater than the 300% modulus at 50°C of the crown rubber. [Invention 4] 4. A motorcycle tire according to any one of claims 1 to 3, wherein a loss tangent at 50°C of the shoulder rubber is greater than a loss tangent at 50°C of the crown rubber. [Invention 5] The hardness of the crown rubber at 100°C is 38 to 42 degrees, The complex modulus of the crown rubber at 100°C is 2.1 to 2.7 MPa, 5. The tire for a motorcycle according to any one of Inventions 1 to 4, wherein the 300% modulus of the crown rubber at 100° C. is 4.0 to 4.8 MPa. [Invention 6] The hardness of the shoulder rubber at 100°C is 40 to 44 degrees, The shoulder rubber has a complex elastic modulus of 2.4 to 3.0 MPa at 100°C. 6. The tire for a motorcycle according to any one of Inventions 1 to 5, wherein the shoulder rubber has a 300% modulus at 100° C. of 4.7 to 5.5 MPa. [Invention 7] The hardness of the crown rubber at 50°C is 44 to 48 degrees, 7. The tire for a motorcycle according to any one of Inventions 1 to 6, wherein the complex modulus of the crown rubber at 50° C. is 3.2 to 3.8 MPa. [Invention 8] The hardness of the shoulder rubber at 50°C is 47 to 51 degrees, The motorcycle tire according to any one of Inventions 1 to 7, wherein the shoulder rubber has a complex modulus of elasticity at 50° C. of 4.0 to 4.6 MPa. [The present invention 9] At the meridian cross section of a tire mounted on a regular rim and inflated to an internal pressure of 10 kPa, The radius of curvature Rc of the contact surface of the crown rubber is less than 95% of the tire cross-sectional width, The motorcycle tire according to any one of claims 1 to 8, wherein a radius of curvature Rb of the contact surface of the shoulder rubber is larger than the radius of curvature Rc. [The present invention 10] 10. The tire for a motorcycle according to any one of claims 1 to 9, wherein the developed width of the ground contact surface of the crown rubber is 80 to 120% of the developed width of the band layer. [The present invention 11] 10. The motorcycle tire according to any one of claims 1 to 9, wherein the developed width of the contact surface of the crown rubber is larger than the developed width of the band layer. [Explanation of symbols]

[0083] 1. Motorcycle tires 2 Tread section 3 Sidewall 4 Bead section 6. Carcass 7 Belt layer 8 Band Layer 9 Tread reinforcement layer 12 Tread rubber 13 Crown rubber 14 Shoulder rubber C Tire Equator Te tread edge

Claims

1. A tire for a motorcycle, A tread portion; A pair of sidewall portions; A pair of bead portions; a carcass extending between the pair of bead portions, The tread portion includes a tread reinforcing layer disposed on the outer side of the carcass in the tire radial direction, and a tread rubber disposed on the outer side of the tread reinforcing layer in the tire radial direction, The tread reinforcing layer includes a belt layer including a plurality of belt cords inclined with respect to the tire circumferential direction, and a band layer disposed on the tire radial outer side of the belt layer and including at least one band cord wound spirally in the tire circumferential direction, The developed width of the band layer is smaller than the developed width of the belt layer, The tread rubber includes a crown rubber disposed in an area including a tire equator, and a shoulder rubber disposed axially outboard of the crown rubber in an area including a tread edge, The hardness of the shoulder rubber at 100° C. is greater than the hardness of the crown rubber at 100° C., The shoulder rubber has a complex elastic modulus at 100° C. that is greater than the complex elastic modulus at 100° C. of the crown rubber, The 300% modulus at 100°C of the shoulder rubber is greater than the 300% modulus at 100°C of the crown rubber. Tires for motorcycles.

2. The motorcycle tire according to claim 1 , wherein a loss tangent at 100° C. of the shoulder rubber is greater than a loss tangent at 100° C. of the crown rubber.

3. The hardness of the shoulder rubber at 50° C. is greater than the hardness of the crown rubber at 50° C., The shoulder rubber has a complex elastic modulus at 50° C. that is greater than the complex elastic modulus at 50° C. of the crown rubber, 3. The motorcycle tire according to claim 1, wherein a 300% modulus at 50° C. of the shoulder rubber is greater than a 300% modulus at 50° C. of the crown rubber.

4. The motorcycle tire according to claim 3 , wherein a loss tangent at 50° C. of the shoulder rubber is greater than a loss tangent at 50° C. of the crown rubber.

5. The hardness of the crown rubber at 100°C is 38 to 42 degrees, The complex modulus of the crown rubber at 100° C. is 2.1 to 2.7 MPa, The motorcycle tire according to claim 1 or 2, wherein the crown rubber has a 300% modulus at 100° C. of 4.0 to 4.8 MPa.

6. The hardness of the shoulder rubber at 100°C is 40 to 44 degrees, The shoulder rubber has a complex elastic modulus of 2.4 to 3.0 MPa at 100°C. The motorcycle tire according to claim 5, wherein the shoulder rubber has a 300% modulus at 100° C. of 4.7 to 5.5 MPa.

7. The hardness of the crown rubber at 50° C. is 44 to 48 degrees, The motorcycle tire according to claim 3, wherein the crown rubber has a complex modulus of elasticity at 50° C. of 3.2 to 3.8 MPa.

8. The hardness of the shoulder rubber at 50°C is 47 to 51 degrees, The motorcycle tire according to claim 7, wherein the shoulder rubber has a complex modulus of elasticity at 50° C. of 4.0 to 4.6 MPa.

9. In the meridian cross section of a tire mounted on a regular rim and inflated with an internal pressure of 10 kPa, The radius of curvature Rc of the contact surface of the crown rubber is less than 95% of the tire cross-sectional width, The motorcycle tire according to claim 1 or 2, wherein a radius of curvature Rb of the contact surface of the shoulder rubber is larger than the radius of curvature Rc.

10. 3. The motorcycle tire according to claim 1, wherein a developed width of the contact surface of the crown rubber is 80 to 120% of a developed width of the band layer.

11. The motorcycle tire according to claim 1 or 2, wherein a developed width of the ground contact surface of the crown rubber is larger than a developed width of the band layer.

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