Motorcycle tires

Abstract

To provide a tire for a motorcycle that can exert excellent steering performance, in states such as a direct advancing state and a slow turning state where centrifugal force is small.SOLUTION: A tire 1 for a motorcycle includes a carcass 6 and a tread reinforcement layer 7 arranged outside in a tire radial direction of the carcass 6. The tread reinforcement layer 7 includes a belt layer 8 and a band layer 9. The belt layer 8 is constituted of one inner belt ply 8A in which a belt cord 8a is arranged at a first angle θ1 and which is arranged adjacently to the carcass 6 and one outer belt ply 8B in which the belt cord 8a is arranged at a second angle θ2 different from the first angle θ1 and which is arranged outside in the tire radial direction of the inner belt ply 8A. The band layer 9 is constituted of at least one band ply 9A. The band ply 9A is arranged adjacently to the inner belt ply 8A and the outer belt play 8B, between the inner belt ply 8A and the outer belt ply 8B, in the tire radial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire for a motorcycle capable of exhibiting excellent cornering performance. [Background technology]

[0002] Conventionally, motorcycle tires including a tread reinforcing layer in the tread portion are known to improve cornering performance. For example, the following Patent Document 1 proposes a motorcycle tire in which the tread reinforcing layer is composed of two belt plies arranged on the radially outer side of the carcass and one band ply arranged on the radially outer side of the two belt plies. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-111375 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the motorcycle tire of Patent Document 1 generates a large cornering force due to the hoop effect of the two belt plies, and tends to increase the force that tries to raise the motorcycle when the centrifugal force is small, such as when going from a straight state to a gentle turn. For this reason, further improvement in the cornering performance when the centrifugal force is small is desired for the motorcycle tire of Patent Document 1.

[0005] The present invention has been devised in consideration of the above-mentioned circumstances, and has as its main object to provide a motorcycle tire that can exhibit excellent cornering performance even when the centrifugal force is small, such as when going from a straight line to a gentle cornering state. [Means for solving the problem]

[0006] The present invention provides a motorcycle tire, comprising: a carcass extending from a tread portion through a pair of sidewall portions to a pair of bead portions; and a tread reinforcing layer disposed on the radially outer side of the carcass in the tread portion, the tread reinforcing layer including a belt layer in which a plurality of belt cords are arranged, and a band layer in which a plurality of band cords are arranged, the belt layer including one inner belt ply disposed adjacent to the carcass and one outer belt ply disposed on the radially outer side of the inner belt ply, the inner belt ply being arranged such that the belt cords intersect with the tire circumferential direction at a first angle, and the outer belt ply being arranged such that the belt cords intersect with the tire circumferential direction at a second angle different from the first angle, the band layer including at least one band ply in which the band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction, and the band ply being disposed between the inner belt ply and the outer belt ply in the radial direction of the tire, adjacent to the inner belt ply and the outer belt ply.

[0007] In the motorcycle tire of the present invention, it is preferable that a developed width of the band ply is smaller than a developed width of the inner belt ply and a developed width of the outer belt ply.

[0008] In the motorcycle tire of the present invention, the developed width of the band ply is desirably 30% to 90% of the developed width of the tread.

[0009] In the motorcycle tire of the present invention, the first angle is preferably 50 to 80°.

[0010] In the motorcycle tire of the present invention, the second angle is preferably 70 to 90°.

[0011] In the motorcycle tire of the present invention, the difference between the second angle and the first angle is preferably 10 to 40°.

[0012] In the motorcycle tire of the present invention, it is preferable that the second angle is greater than the first angle.

[0013] In the motorcycle tire of the present invention, it is preferable that the tread portion includes a rubber layer disposed axially outward of the band ply, and the rubber layer is made of at least one rubber sheet.

[0014] In the motorcycle tire of the present invention, it is preferable that the tread portion includes a rubber layer arranged axially outward of the band ply, the rubber layer being arranged between the inner belt ply and the outer belt ply, and the distance between the inner belt ply and the outer belt ply at the position where the rubber layer is arranged is approximately constant and is 0.5 to 3.0 mm.

[0015] In the motorcycle tire of the present invention, the complex modulus of elasticity of the rubber layer at 70° C. is desirably 500 kPa or more. Effect of the Invention

[0016] In the motorcycle tire of the present invention, the band ply is disposed between the inner belt ply and the outer belt ply and adjacent to the inner belt ply and the outer belt ply in the tire radial direction.

[0017] Such a motorcycle tire can reduce the hoop effect between the inner belt ply and the outer belt ply, and can suppress the generation of excessive cornering force when the centrifugal force is small, such as when going from a straight traveling state to a gentle turning state. Therefore, the motorcycle tire of the present invention can exhibit excellent cornering performance even when the centrifugal force is small, such as when going from a straight traveling state to a gentle turning state. [Brief description of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing one embodiment of a motorcycle tire of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a tire meridian cross-sectional view of a motorcycle tire 1 (hereinafter sometimes simply referred to as "tire 1") according to this embodiment in a normal state.

[0020] Here, the "normal state" refers to a state in which the tire 1 is mounted on a normal rim, adjusted to a normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in the normal state.

[0021] In addition, a "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based, such as a "standard rim" in the case of JATMA, a "Design Rim" in the case of TRA, and a "Measuring Rim" in the case of ETRTO.

[0022] In addition, the "normal internal pressure" is the air pressure set for each tire by each standard in the standard system including the standard on which tire 1 is based, and 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," and in the case of ETRTO, it is the "INFLATION PRESSURE."

[0023] 1, a tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3 extending radially inward from both ends of the tread portion 2, and a pair of bead portions 4 located radially inward of the sidewall portions 3. For example, a bead core 5 is embedded in each of the pair of bead portions 4.

[0024] The tread surface 2s, which is the outer surface of the tread portion 2, extends, for example, from the tire equator C to the tread end Te, curving in an arc shape that is convex outward in the tire radial direction. In this embodiment, the position of the tread end Te is the maximum tire width position. Such a tire 1 can be turned with a large camber angle.

[0025] Here, the tread ends Te are the axial ends of the tread portion 2. The tire equator C is the axial center between the tread ends Te. The length measured along the tread surface 2s between the tread ends Te is the tread developed width TWe.

[0026] The tire 1 of this embodiment includes a carcass 6 that extends from a tread portion 2 through a pair of sidewall portions 3 to a pair of bead portions 4. The carcass 6 includes, for example, a main body portion 6a that spans between a pair of bead cores 5, and a folded-up portion 6b that is continuous with the main body portion 6a and that is folded back around the bead cores 5.

[0027] The carcass 6 includes at least one, and in this embodiment, two carcass plies 6A, 6B. Each of the carcass plies 6A, 6B includes carcass cords arranged at an angle of, for example, 75 to 90° with respect to the tire circumferential direction.

[0028] The tire 1 of this embodiment includes a tread reinforcing layer 7 disposed on the outer side in the tire radial direction of the carcass 6 in the tread portion 2. The tread reinforcing layer 7 of this embodiment includes a belt layer 8 and a band layer 9.

[0029] Fig. 2 is a development view of the tread reinforcing layer 7 of this embodiment. As shown in Fig. 1 and Fig. 2, the belt layer 8 is preferably one in which a plurality of belt cords 8a are arranged. The band layer 9 is preferably one in which a plurality of band cords 9a are arranged.

[0030] The belt layer 8 in this embodiment is composed of one inner belt ply 8A disposed adjacent to the carcass 6, and one outer belt ply 8B disposed outside the inner belt ply 8A in the tire radial direction.

[0031] In the present embodiment, the inner belt ply 8A is arranged such that the belt cords 8a intersect with the tire circumferential direction at a first angle θ1. In the present embodiment, the outer belt ply 8B is arranged such that the belt cords 8a intersect with the tire circumferential direction at a second angle θ2 different from the first angle θ1. Such a belt layer 8 improves the rigidity of the tread portion 2 by the hoop effect between the inner belt ply 8A and the outer belt ply 8B, and helps to generate a large cornering force.

[0032] Here, a motorcycle turns by leaning the motorcycle. At this time, the lateral force generated in the tire 1 is expressed as the sum of the camber thrust generated by the leaning of the tire 1 and the cornering force generated by the slip angle of the tire 1. When the lateral force generated in the tire 1 and the centrifugal force of the motorcycle are balanced, the motorcycle can turn stably and can be said to have excellent cornering performance.

[0033] The centrifugal force of a motorcycle is small when going from a straight-line state to a gentle turn and is large when turning sharply. Therefore, the tire 1 can improve cornering performance from a straight-line state to a sharp turn by suppressing the generation of cornering force when going from a straight-line state to a gentle turn and by increasing the cornering force when turning sharply.

[0034] In the tire 1 of this embodiment, the belt layer 8 can increase the cornering force, so that the lateral force acting on the tire 1 is also increased, thereby improving the cornering performance when the centrifugal force is large, such as in a sharp cornering state.

[0035] The band layer 9 is made of at least one band ply 9A, in this embodiment, one band ply 9A, in which band cords 9a are arranged at an angle of 5° or less with respect to the tire circumferential direction. The band ply 9A in this embodiment is disposed between the inner belt ply 8A and the outer belt ply 8B and adjacent to the inner belt ply 8A and the outer belt ply 8B in the tire radial direction.

[0036] Such a tire 1 can reduce the hoop effect between the inner belt ply 8A and the outer belt ply 8B and suppress the generation of excessive cornering force when the centrifugal force is small, such as when going from a straight running state to a gentle turning state. Therefore, the tire 1 of the present embodiment can exhibit excellent cornering performance even when the centrifugal force is small, such as when going from a straight running state to a gentle turning state.

[0037] In a more preferred embodiment, the developed width W1 of the band ply 9A is smaller than the developed width W2 of the inner belt ply 8A and the developed width W3 of the outer belt ply 8B. Such a tread reinforcing layer 7 reduces the hoop effect between the inner belt ply 8A and the outer belt ply 8B from a straight running state to a gentle turning state, and can exert the hoop effect in a sharp turning state.

[0038] Therefore, the tire 1 of the present embodiment can suppress the generation of excessive cornering force when going straight to a gentle turning state and can generate a large cornering force when turning sharply, thereby improving the cornering performance from a straight state to a sharp turning state. 。

[0039] The developed width W1 of the band ply 9A is preferably 30% to 90% of the developed tread width TWe. By setting the developed width W1 of the band ply 9A to 30% or more of the developed tread width TWe, the band ply 9A can be reliably included in the ground contact portion even when the tread portion 2 is deformed during braking in a straight-ahead state, and the cornering force can be reduced.

[0040] By setting the developed width W1 of the band ply 9A to 90% or less of the developed tread width TWe, the hoop effect in a sharp turning state can be reliably exhibited and the cornering force can be increased. Therefore, the tire 1 of the present embodiment can reliably improve the cornering performance from a straight running state to a sharp turning state.

[0041] The developed width W2 of the inner belt ply 8A is preferably 90% to 100% of the developed tread width TWe. The developed width W3 of the outer belt ply 8B is preferably 85% to 95% of the developed tread width TWe. The developed width W3 of the outer belt ply 8B in this embodiment is smaller than the developed width W2 of the inner belt ply 8A. Such a belt layer 8 can further improve the rigidity of the tread portion 2.

[0042] The first angle θ1 of the belt cord 8a of the inner belt ply 8A with respect to the tire circumferential direction is preferably 50 to 80°. When the first angle θ1 is 50° or more, an excessive hoop effect can be suppressed, a good cornering force can be generated, and the cornering performance can be improved. When the first angle θ1 is 80° or less, an angle difference can be reliably provided between the inner belt ply 8A and the belt cord 8a of the outer belt ply 8B, and the hoop effect can be exerted.

[0043] The second angle θ2 of the belt cord 8a of the outer belt ply 8B with respect to the tire circumferential direction is preferably 70 to 90°. When the second angle θ2 is 70° or more, an excessive hoop effect is suppressed, a good cornering force is generated, and the cornering performance can be improved. When the second angle θ2 is 90° or less, the inclination direction is the same as that of the belt cord 8a of the inner belt ply 8A, so that the arrangement error during manufacturing can be reduced.

[0044] The difference (|θ2-θ1|) between the second angle θ2 and the first angle θ1 is preferably 10 to 40°. When the difference (|θ2-θ1|) is 10° or more, the hoop effect of the inner belt ply 8A and the outer belt ply 8B can be exhibited. When the difference (|θ2-θ1|) is 40° or less, the difference in the magnitude of the cornering force depending on whether the band ply 9A is present or not can be reduced, and the transient characteristics at the boundary position of the band ply 9A can be improved.

[0045] The second angle θ2 in this embodiment is larger than the first angle θ1. In such a belt layer 8, the angle of the belt cord 8a of the outer belt ply 8B closer to the tread surface 2s is larger with respect to the tire circumferential direction, so that the rigidity of the tread portion 2 can be improved, which helps to generate a larger cornering force.

[0046] FIG. 3 is an enlarged cross-sectional view of the tread portion 2 of this embodiment. As shown in FIGS. 1 to 3, the tread portion 2 of this embodiment includes a rubber layer 10 arranged on the axially outer side of the band ply 9A. The rubber layer 10 is preferably arranged on both sides of the band ply 9A in the axial direction of the tire. Each rubber layer 10 is made of at least one rubber sheet 10A, one rubber sheet in this embodiment. Here, the state of including the rubber layer 10 made of the rubber sheet 10A indicates that the distance between the members arranged on either side of the rubber layer 10 is kept substantially constant. In this specification, the distance being substantially constant indicates that the variation of the average value of the distance is within ±15%.

[0047] In such a tread portion 2, the torsional rigidity is improved by the rubber sheet 10A, and the cornering force during sharp turns can be increased. Therefore, the tire 1 of this embodiment can improve the cornering performance during sharp turns. When the rubber layer 10 is made of a plurality of rubber sheets 10A, the rubber sheets 10A may be arranged in the tire radial direction or the tire axial direction.

[0048] The rubber layer 10 of this embodiment is disposed between the inner belt ply 8A and the outer belt ply 8B. A distance t between the inner belt ply 8A and the outer belt ply 8B at the position where the rubber layer 10 is disposed is preferably approximately constant at 0.5 to 3.0 mm. Here, the distance t between the inner belt ply 8A and the outer belt ply 8B is the shortest distance between the outer surface 8As of the inner belt ply 8A and the inner surface 8Bs of the outer belt ply 8B.

[0049] By making the distance t 0.5 mm or more, the torsional effect can be reliably exerted and the cornering force during sharp turns can be increased. By making the distance t 3.0 mm or less, the cornering force can be prevented from becoming excessively large and the transient characteristics with the area having the band ply 9A can be improved.

[0050] In this embodiment, the sum of the developed width W4 of the rubber layers 10 on both sides and the developed width W1 of the band ply 9A (W1+2×W4) is smaller than the developed width W2 of the inner belt ply 8A and larger than the developed width W3 of the outer belt ply 8B. Such a rubber layer 10 can further improve the torsional rigidity of the tread portion 2.

[0051] The complex modulus G* of the rubber layer 10 at 70° C. is preferably 500 kPa or more. Such a rubber layer 10 can more reliably exert the torsion effect and can further increase the cornering force during sharp turns.

[0052] Here, the complex modulus G* of the rubber layer 10 at 70° C. is a value measured in accordance with the provisions of JIS-K6394 under the following conditions using a dynamic viscoelasticity measuring device (Iplexer series) manufactured by GABO Corporation. Initial strain: 10% Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 70℃

[0053] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment and can be modified in various ways. EXAMPLES

[0054] A motorcycle tire having the basic structure of FIG. 1 was prototyped based on the specifications of Table 1. As a comparative example, a motorcycle tire in which a band layer was arranged on the radially outer side of the belt layer was prototyped. The prototype tires were mounted on the front and rear wheels of a test motorcycle, and the gentle turning performance from an upright state to a gentle turning state, the sharp turning performance in a sharp turning state, and the transient characteristics from a gentle turning state to a sharp turning state were evaluated by the test driver's senses. The results are expressed as an index with Comparative Example 1 being 100, and the larger the value, the more excellent the gentle turning performance, the sharp turning performance, and the transient characteristics. The main common points are as follows.

[0055] <Common matters> Front tire size: 120 / 70R17 Front tire pressure: 250kPa Rear tire size: 200 / 60R17 Rear tire pressure: 290kPa Test motorcycle: Large motorcycle

[0056] The results are shown in Table 1. [Table 1]

[0057] As a result of the test, it was confirmed that the tires of the embodiment example have improved gentle turning performance while maintaining sharp turning performance compared to the comparative example, and can exhibit excellent turning performance even when the centrifugal force is small, such as when going from a straight line to a gentle turn. [Explanation of symbols]

[0058] 6. Carcass 7 Tread reinforcement layer 8 Belt Layer 8A Inner Belt Ply 8B Outer belt ply 8a Belt cord 9 Band Layer 9A Band Ply

Claims

1. A tire for a motorcycle, a carcass extending from a tread portion through a pair of sidewall portions to a pair of bead portions; and a tread reinforcing layer disposed on an outer side of the carcass in the tread portion in the tire radial direction, The tread reinforcing layer includes a belt layer in which a plurality of belt cords are arranged, and a band layer in which a plurality of band cords are arranged, The belt layer includes one inner belt ply disposed adjacent to the carcass, and one outer belt ply disposed outside the inner belt ply in the tire radial direction, The inner belt ply is arranged such that the belt cords intersect at a first angle with respect to a tire circumferential direction, The outer belt ply is arranged such that the belt cords intersect with respect to the tire circumferential direction at a second angle larger than the first angle, The band layer is made up of at least one band ply in which the band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction, The band ply is disposed between the inner belt ply and the outer belt ply in the tire radial direction and adjacent to the inner belt ply and the outer belt ply, The developed width of the band ply is smaller than the developed width of the inner belt ply and the developed width of the outer belt ply. Tires for motorcycles.

2. 2. The motorcycle tire according to claim 1, wherein the developed width of the band ply is 30% to 90% of the developed width of the tread.

3. The motorcycle tire according to claim 1 or 2, wherein the first angle is from 50 to 80 degrees.

4. The motorcycle tire according to any one of claims 1 to 3, wherein the second angle is in the range of 70 to 90 degrees.

5. The motorcycle tire according to any one of claims 1 to 4, wherein a difference between the second angle and the first angle is in a range of 10 to 40 degrees.

6. The tread portion includes a rubber layer disposed axially outward of the band ply, The motorcycle tire according to claim 1 , wherein the rubber layer is made of at least one rubber sheet.

7. The tread portion includes a rubber layer disposed axially outward of the band ply, The rubber layer is disposed between the inner belt ply and the outer belt ply, 7. The motorcycle tire according to claim 1, wherein a distance between the inner belt ply and the outer belt ply at a position where the rubber layer is disposed is approximately constant and ranges from 0.5 to 3.0 mm.

8. The motorcycle tire according to claim 6 or 7, wherein the rubber layer has a complex modulus of elasticity at 70° C. of 500 kPa or more.

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