Motorcycle tires

Abstract

To provide a tire for a motor cycle that can exert excellent steering performance even when centrifugal force is small during transfer from a straight travelling state to a slow turning state.SOLUTION: A carcass 6 includes at least one carcass ply 6B in which carcass cords 6c are arranged. A tread reinforcement layer 7 includes one belt ply 8A in which belt cords 8a are arranged, and at least one band ply 9A in which band cords 9a are arranged. The belt ply 8A is arranged adjacently to outside in a tire radial direction of the carcass ply 6B. The band ply 9A is arranged adjacently to outside in the tire radial direction of the belt ply 8A. A difference |θ2-θ1| between an angle θ1 of the belt cords 8a arranged adjacently in the tire radial direction with respect to a tire circumferential direction and an angle θ2 of the carcass cords 6c with respect to the tire circumferential direction is 10-60°. The band cords 9a are arranged at angles θ3 of 5°or less with respect to the tire circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire for a motorcycle that can exhibit excellent cornering performance. [Background technology]

[0002] Conventionally, motorcycle tires that include a tread reinforcing layer in the tread portion to improve cornering performance have been known. For example, Patent Document 1 below proposes a motorcycle tire in which the tread reinforcing layer is composed of two belt plies arranged radially outward of the carcass and one band ply arranged radially outward of the two belt plies. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-111375 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 right 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 of the motorcycle tire of Patent Document 1 when the centrifugal force is small is desired.

[0005] The present invention was devised in view of the above-described circumstances, and its main object is 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-ahead state to a gentle turn. [Means for solving the problem]

[0006] The present disclosure relates to a motorcycle tire including: a carcass extending from a tread portion through a pair of sidewall portions to a pair of bead portions; and a tread reinforcing layer arranged on the radially outer side of the carcass in the tread portion, wherein the carcass includes at least one carcass ply having carcass cords arranged therein; the tread reinforcing layer includes one belt ply having belt cords arranged therein and at least one band ply having band cords arranged therein; the belt ply is arranged adjacent to the radially outer side of the carcass ply; the band ply is arranged adjacent to the radially outer side of the belt ply; a difference between an angle of the belt cords adjacent to each other in the tire radial direction with respect to the tire circumferential direction and an angle of the carcass cord with respect to the tire circumferential direction is 10 to 60°; and the band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction. [Effects of the Invention]

[0007] By virtue of having the above-described configuration, the motorcycle tire of the present disclosure can exhibit excellent cornering performance even when the centrifugal force is small, such as when going from a straight-ahead state to a gentle cornering state. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an embodiment of a motorcycle tire of the present disclosure. [Figure 2] FIG. 2 is a schematic development view of a carcass and a tread reinforcing layer. [Figure 3] FIG. 2 is a schematic development view of an inner carcass ply. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure 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.

[0010] 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.

[0011] Furthermore, a "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0012] In addition, the "normal internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standard on which tire 1 is based, and is the "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO.

[0013] 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.

[0014] 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 edge Te, curving in an arc shape that is convex outward in the tire radial direction. In this embodiment, the position of the tread edge Te is the tire's maximum width position. Such a tire 1 can be cornered by applying a large camber angle.

[0015] In addition, when making gentle turns, it is desirable for a motorcycle tire 1 to obtain turning force from camber thrust, which increases according to the camber angle, and when making sharp turns, it is desirable for the tire 1 to obtain turning force by adding the cornering force generated by the slip angle to the camber thrust.

[0016] Here, the tread edges Te are the axial ends of the tread portion 2. The tire equator C is the axial center between the tread edges Te. The length measured along the tread surface 2s between the tread edges Te is the tread developed width TWe.

[0017] 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 turned-up portion 6b that is continuous with the main body portion 6a and is turned up around the bead cores 5. The tire 1 desirably includes a tread reinforcing layer 7 that is disposed radially outward of the carcass 6 in the tread portion 2.

[0018] Fig. 2 is a schematic development view of the carcass 6 and the tread reinforcing layer 7. As shown in Fig. 1 and Fig. 2, the carcass 6 includes at least one carcass ply 6A, in this embodiment, two carcass plies 6A, 6B in which carcass cords 6c are arranged. The carcass plies 6A, 6B include, for example, an inner carcass ply 6A arranged on the inner side in the tire radial direction in the tread portion 2, and an outer carcass ply 6B arranged on the outer side in the tire radial direction of the inner carcass ply 6A.

[0019] The tread reinforcing layer 7 of this embodiment includes a belt layer 8 and a band layer 9. The belt layer 8 of this embodiment includes one belt ply 8A in which belt cords 8a are arranged. The belt ply 8A is disposed adjacent to the carcass ply 6B, in this embodiment, the outer carcass ply 6B, on the outer side in the tire radial direction.

[0020] The difference |θ2-θ1| between the angle θ1 of the belt cords 8a adjacent in the tire radial direction to the tire circumferential direction and the angle θ2 of the carcass cord 6c to the tire circumferential direction is preferably 10 to 60°. When the angle difference |θ2-θ1| between the belt cords 8a and the carcass cord 6c is 10° or more, the hoop effect in the shoulder region can be improved and the cornering force during sharp turns can be increased. Herein, the cord angle is measured as an angle less than or equal to a right angle to the tire circumferential direction.

[0021] By setting the angle difference |θ2-θ1| between the belt cord 8a and the carcass cord 6c to 60° or less, an excessive increase in cornering force can be suppressed, the transition from a gentle turning state to a sharp turning state can be smoothed, and the transient characteristics of the tire 1 during cornering can be improved.

[0022] The band layer 9 includes at least one band ply 9A, in this embodiment one band ply 9A, in which band cords 9a are arranged. The band ply 9A is preferably arranged adjacent to the belt ply 8A on the radially outer side of the tire. In this embodiment, the band cords 9a are arranged at an angle θ3 of 5° or less with respect to the tire circumferential direction. The band ply 9A is preferably a so-called jointless band in which one band cord 9a is wound spirally.

[0023] Such a band ply 9A can mitigate the hoop effect of the belt cord 8a and the carcass cord 6c, and can reduce the cornering force during gentle turning. Therefore, the tire 1 of this embodiment can exhibit excellent cornering performance even when the centrifugal force is small, such as when going from a straight state to a gentle turning state.

[0024] In a more preferred embodiment, the carcass cords 6c of the inner carcass ply 6A and the carcass cords 6c of the outer carcass ply 6B are inclined in opposite directions relative to the tire circumferential direction. The carcass cords 6c may be arranged, for example, at an angle θ2 of 90° relative to the tire circumferential direction. In this case, the carcass cords 6c of the inner carcass ply 6A and the carcass cords 6c of the outer carcass ply 6B extend parallel to each other.

[0025] The carcass cords 6c are preferably arranged at an angle θ2 of 30 to 90° with respect to the tire circumferential direction. The angle θ2 of the carcass cords 6c of the inner carcass ply 6A and the angle θ2 of the carcass cords 6c of the outer carcass ply 6B are preferably equal to each other. By setting the angle θ2 of the carcass cords 6c to 30° or more, it is possible to prevent the hoop effect from becoming excessively large.

[0026] FIG. 3 is a schematic view of the inner carcass ply 6A in development. Although not shown, it is desirable that the outer carcass ply 6B also has carcass cords 6c similar to those in the inner carcass ply 6A. As shown in FIG. 3, the carcass plies 6A and 6B may have different angles θ2 of the carcass cords 6c in the tread portion 2, θ4 of the carcass cords 6c in the main body portion 6a in the sidewall portion 3, and θ5 of the carcass cords 6c in the turned-up portion 6b. Even in this case, it is desirable that the angles θ2, θ4, and θ5 are all within a range of 30 to 90 degrees relative to the tire circumferential direction. Here, each angle of the carcass cords 6c is measured in a state where the carcass cords 6c are developed on a plane.

[0027] In this case, it is desirable that the angle θ2 of the carcass cord 6c in the tread portion 2 be larger than the angle θ5 of the carcass cord 6c in the turned-up portion 6b. Such carcass plies 6A, 6B can improve the hoop effect in the tread portion 2 while suppressing a decrease in rigidity in the bead portions 4, which helps to improve the cornering performance of the tire 1.

[0028] Additionally, it is desirable that the angle θ4 of the carcass cords 6c of the main body 6a in the sidewall portion 3 is larger than the angle θ2 of the carcass cords 6c in the tread portion 2. Such carcass plies 6A, 6B make it easier for the sidewall portion 3 to bend, improving ground contact during sharp turns and improving the cornering performance of the tire 1.

[0029] That is, it is desirable that the angles θ2, θ4, and θ5 of the carcass cords 6c satisfy the following formula (1). θ5 < θ2 < θ4 …(1)

[0030] 1 and 2, the developed width W1 of the band ply 9A is preferably smaller than the developed width W2 of the belt ply 8A. Such a band ply 9A reduces the hoop effect of the belt cords 8a and the carcass cords 6c when traveling straight or when making gentle turns, and also enables the hoop effect of the belt cords 8a and the carcass cords 6c to be exerted when making sharp turns.

[0031] The developed width W1 of the band ply 9A is preferably 25% to 85% of the developed tread width TWe. By making the developed width W1 of the band ply 9A 30% or more of the developed tread width TWe, the band ply 9A can be reliably contained in the ground contact area even when the tread portion 2 deforms during braking while traveling straight, thereby reducing the cornering force.

[0032] By setting the developed width W1 of the band ply 9A to 90% or less of the developed tread width TWe, the hoop effect can be reliably exhibited in sharp cornering conditions, and the cornering force can be increased. Therefore, the tire 1 of this embodiment can reliably improve cornering performance from straight running conditions to sharp cornering conditions.

[0033] The developed width W2 of the belt ply 8A is preferably 90% to 100% of the developed tread width TWe. When the developed width W2 of the belt ply 8A is 90% or more of the developed tread width TWe, the rigidity of the tread portion 2 can be improved over a wide range, which helps to improve the cornering performance of the tire 1 in sharp cornering conditions.

[0034] The belt cords 8a of the belt ply 8A are desirably inclined to the same side as the carcass cords 6c of the outer carcass ply 6B. When the carcass cords 6c of the outer carcass ply 6B are arranged at an angle θ2 of 90° with respect to the tire circumferential direction, the belt cords 8a may be inclined in any direction.

[0035] The belt cords 8a are preferably arranged at an angle θ1 of 30 to 80° with respect to the tire circumferential direction. Such belt cords 8a suppress excessive cornering force and are useful for improving the cornering performance of the tire 1 from a straight traveling state to a gentle cornering state.

[0036] The tread portion 2 includes a rubber layer 10 disposed on the outer side of the band ply 9A in the tire axial direction. The rubber layer 10 is preferably disposed on both sides of the band ply 9A in the tire axial direction. Each rubber layer 10 is made of at least one rubber sheet 10A, and in this embodiment, one rubber sheet 10A.

[0037] Here, the state including the rubber layer 10 made of the rubber sheet 10A means that the distance between the members arranged on either side of the rubber layer 10 is kept substantially constant. In this specification, the term "substantially constant distance" means that the variation of the distance from the average value is within ±15%.

[0038] 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 cornering performance during sharp turns. When the rubber layer 10 is made up of multiple rubber sheets 10A, the rubber sheets 10A may be arranged in the tire radial direction or the tire axial direction.

[0039] As shown in Fig. 1, the rubber layer 10 of this embodiment is disposed radially outward of the belt ply 8A. The thickness t of the rubber layer 10 is preferably approximately constant, ranging from 0.5 to 3.0 mm. The thickness t of the rubber layer 10 is preferably approximately equal to the thickness of the band ply 9A. In this specification, "approximately equal thickness" means that the difference in thickness is within ±15%.

[0040] By setting the thickness t to 0.5 mm or more, the torsional effect can be reliably exerted and the cornering force during sharp turns can be increased. By setting the thickness t to 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.

[0041] 2, in this embodiment, the sum of the developed width W3 of the rubber layers 10 on both sides and the developed width W1 of the band ply 9A (W1 + 2 × W3) is smaller than the developed width W2 of the belt ply 8A. Such rubber layers 10 are useful for improving the torsional rigidity of the tread portion 2.

[0042] 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 torsional effect and increase the cornering force during sharp turns.

[0043] 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 using a dynamic viscoelasticity measuring device (Iplexer series) manufactured by GABO under the following conditions: Initial distortion: 10% Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 70℃

[0044] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments and can be modified and implemented in various forms. [Example]

[0045] A prototype motorcycle tire having the basic structure shown in Figure 1 was manufactured based on the specifications in Table 1. The prototype tires were mounted on the front and rear wheels of a test motorcycle, and the test driver evaluated the gentle turning performance from an upright position to a gentle turning position, the sharp turning performance in a sharp turning position, and the transient characteristics from a gentle turning position to a sharp turning position through sensory evaluation. The results are expressed as an index, with the comparative example being set at 100, and a higher index indicates better gentle turning performance, sharp turning performance, and transient characteristics. The main common features are as follows:

[0046] <Common matters> Front tire size: 120 / 70R17 Front tire pressure: 250kPa Rear tire size: 200 / 60R17 Rear tire pressure: 290kPa Test motorcycle: Large motorcycle

[0047] The test results are shown in Table 1. [Table 1]

[0048] As a result of the test, it was confirmed that the tires of the example had improved gentle turning performance while maintaining sharp turning performance compared to the comparative example, and were able to exhibit excellent turning performance even when the centrifugal force was small, such as when going from a straight line to a gentle turn.

[0049] [Note] The present disclosure is as follows.

[0050] [Disclosure 1] 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 radially outward of the carcass in the tread portion, wherein the carcass includes at least one carcass ply having arranged carcass cords, and the tread reinforcing layer includes one belt ply having arranged belt cords and at least one band ply having arranged band cords, the belt ply being disposed adjacent to the carcass ply on the radially outer side of the tire, and the band ply being disposed adjacent to the belt ply on the radially outer side of the tire, a difference between an angle of the belt cords adjacent to each other in the tire radial direction with respect to the tire circumferential direction and an angle of the carcass cord with respect to the tire circumferential direction is 10 to 60°, and the band cords are disposed at an angle of 5° or less with respect to the tire circumferential direction.

[0051] [Disclosure 2] The motorcycle tire according to Disclosure 1, wherein the developed width of the band ply is smaller than the developed width of the belt ply.

[0052] [Disclosure 3] The motorcycle tire according to Disclosure 1 or 2, wherein the developed width of the band ply is 25% to 85% of the developed width of the tread.

[0053] [Disclosure 4] The motorcycle tire according to any one of Disclosures 1 to 3, wherein the belt cords are arranged at an angle of 30 to 80° with respect to the circumferential direction of the tire.

[0054] [Disclosure 5] The motorcycle tire according to any one of Disclosures 1 to 4, wherein the carcass cords are arranged at an angle of 30 to 90° with respect to the circumferential direction of the tire.

[0055] [Disclosure 6] The motorcycle tire according to any one of Disclosures 1 to 5, wherein the tread portion includes a rubber layer arranged axially outward of the band ply, and the rubber layer is arranged adjacent to the belt ply in the tire radial direction.

[0056] [Disclosure 7] The motorcycle tire according to Disclosure 6, wherein the rubber layer has a complex modulus of elasticity at 70°C of 500 kPa or more. [Explanation of symbols]

[0057] 6. Carcass 6B carcass ply 7 Tread reinforcement layer 8A Belt Ply 8a Belt cord 9A Band Ply 9a Band Cord

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 the outer side of the carcass in the tread portion in the tire radial direction, The carcass includes at least one carcass ply in which carcass cords are arranged, the tread reinforcing layer includes one belt ply in which belt cords are arranged and at least one band ply in which band cords are arranged, The belt ply is disposed adjacent to the carcass ply on the outer side in the tire radial direction, The band ply is disposed adjacent to the belt ply on the outer side in the tire radial direction, a difference between an angle of the belt cords adjacent to each other in the tire radial direction with respect to the tire circumferential direction and an angle of the carcass cord with respect to the tire circumferential direction is 10 to 60 degrees; The band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction, The tread portion includes rubber layers disposed on both sides of the band ply in the tire axial direction, The rubber layer is disposed adjacent to the belt ply in the tire radial direction, The sum of the developed width of the rubber layers on both sides and the developed width of the band ply is smaller than the developed width of the belt ply. Tires for motorcycles.

2. The motorcycle tire according to claim 1 , wherein the developed width of the band ply is smaller than the developed width of the belt ply.

3. 3. The motorcycle tire according to claim 1, wherein the developed width of the band ply is 25% to 85% of the developed width of the tread.

4. 4. The motorcycle tire according to claim 1, wherein the belt cords are arranged at an angle of 30 to 80 degrees with respect to the circumferential direction of the tire.

5. 5. The motorcycle tire according to claim 1, wherein the carcass cords are arranged at an angle of 30 to 90 degrees with respect to the circumferential direction of the tire.

6. A motorcycle tire as described in any one of claims 1 to 5, wherein the complex modulus of elasticity of the rubber layer at 70°C is 500 kPa or more.

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