Motorcycle tires

Abstract

To provide a motorcycle tire capable of achieving both turning performance and durability performance.SOLUTION: A motorcycle tire 1 includes a carcass 6 and a tread reinforcement layer 7 arranged outside in a tire radial direction of the carcass 6 in a tread part 2. The tread reinforcement layer 7 includes: a belt layer 8 where a plurality of belt cords 8a are arranged; and a band layer 9 where a plurality of band cords 9a are arranged. The belt layer 8 is composed of one inside belt ply 8A arranged in adjacency to the carcass 6; and one outside belt ply 8B arranged outside in the tire radial direction of the inside belt ply 8A. The band layer 9 is composed of at least one band ply 9A arranged adjacent to the inner belt ply 8A and the outside belt ply 8B between the inner belt ply 8A and the outside belt ply 8B in a tire radial direction. A development width W1 of the outside belt ply 8B is larger than a development width W2 of the inside belt ply 8A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a motorcycle tire capable of achieving both turning performance and durability performance.

Background Art

[0002] Conventionally, in order to improve turning performance, a motorcycle tire including a tread reinforcing layer in a tread portion is known. For example, Patent Document 1 below proposes a motorcycle tire in which the tread reinforcing layer is composed of two belt plies arranged on the outer side in the tire radial direction of the carcass and one band ply arranged on the outer side in the tire radial direction of the two belt plies.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the motorcycle tire of Patent Document 1 tends to generate a large cornering force due to the tag effect of the two belt plies, and the force that tries to lift the motorcycle when the centrifugal force is small, such as in a slow turning state from a straight-ahead state, becomes large. For this reason, further improvement in turning performance when the centrifugal force is small is desired for the motorcycle tire of Patent Document 1, and improvement in durability performance is also desired.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object is to provide a motorcycle tire capable of achieving both turning performance and durability performance.

Means for Solving the Problems

[0006] This disclosure relates to 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, wherein the tread reinforcing layer comprises a belt layer with a plurality of belt cords arranged thereon and a band layer with a plurality of band cords arranged thereon, wherein the belt layer consists of one inner belt ply disposed adjacent to the carcass and one outer belt ply disposed radially outer of the inner belt ply, and the band layer is arranged radially in the tire direction with respect to the inner belt ply and A motorcycle tire comprising at least one band ply positioned adjacent to the inner belt ply and the outer belt ply, wherein the inner belt ply has its belt cords arranged at a first angle greater than 5° with respect to the tire circumferential direction, the outer belt ply has its belt cords arranged at a second angle greater than 5° with respect to the tire circumferential direction, and the band ply has its band cords arranged at an angle of 5° or less with respect to the tire circumferential direction, and the unfolded width of the outer belt ply is greater than the unfolded width of the inner belt ply. [Effects of the Invention]

[0007] The motorcycle tire of this disclosure, by having the above-described configuration, can achieve both cornering performance and durability. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing one embodiment of a motorcycle tire according to the present disclosure. [Figure 2] This is a diagram showing the tread reinforcement layer. [Figure 3] This is a magnified cross-sectional view of the tread area. [Modes for carrying out the invention]

[0009] One form of implementation of this disclosure will be described in detail below with reference to the drawings. Figure 1 is a meridian cross-sectional view of the motorcycle tire 1 (hereinafter sometimes simply referred to as "tire 1") of this embodiment in its normal state.

[0010] Here, "normal condition" refers to a state in which tire 1 is mounted on a normal rim, adjusted to the normal internal pressure, and under no load. Unless otherwise specified in this specification, the dimensions of each part of tire 1 are values ​​measured under the normal condition.

[0011] Furthermore, a "standard rim" is the rim defined for each tire within the standard system that includes the standard on which the tire is based. For example, it is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0012] Furthermore, "standard internal pressure" refers to the air pressure specified for each tire by each standard within the standards system, including the standard on which the tire is based. For JATMA, this is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0013] As shown in Figure 1, the 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. A bead core 5 is embedded in each of the pair of bead portions 4, for example.

[0014] The tread surface 2s, which is the outer surface of the tread portion 2, extends in a curved arc shape that is convex outward in the radial direction of the tire, for example, from the tire equator C to the tread edge Te. In this embodiment, the position of the tread edge Te is the position of the tire's maximum width. Such a tire 1 can be turned with a large camber angle.

[0015] Here, the tread edge Te is the tire axial direction edge of the tread portion 2. The tire equator C is the axial center of the tire between the tread edges Te. Also, the length measured along the tread surface 2s between the tread edges Te is the tread width TWe.

[0016] The tire 1 of the present embodiment includes a carcass 6 that extends from the 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-back portion 6b that is continuous with the main body portion 6a and is folded back around the bead core 5.

[0017] The carcass 6 includes at least one, and in this embodiment, two carcass plies 6A and 6B. Each of the carcass plies 6A and 6B includes, for example, carcass cords arranged at an angle of 75 to 90° with respect to the tire circumferential direction.

[0018] The tire 1 of the present 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 the present embodiment includes a belt layer 8 and a band layer 9.

[0019] FIG. 2 is an exploded view of the tread reinforcing layer 7 of the present embodiment. As shown in FIGS. 1 and 2, it is desirable that the belt layer 8 is formed by arranging a plurality of belt cords 8a. It is desirable that the band layer 9 is formed by arranging a plurality of band cords 9a.

[0020] The belt layer 8 of the present embodiment is composed of one inner belt ply 8A disposed adjacent to the carcass 6 and one outer belt ply 8B disposed on the outer side in the tire radial direction of the inner belt ply 8A.

[0021] In the inner belt ply 8A of the present embodiment, the belt cords 8a are arranged at a first angle θ1 greater than 5° with respect to the tire circumferential direction. In the outer belt ply 8B of the present embodiment, the belt cords 8a are arranged at a second angle θ2 greater than 5° with respect to the tire circumferential direction. Such a belt layer 8 helps to improve the rigidity of the tread portion 2 and generate a large cornering force due to the tagging effect between the inner belt ply 8A and the outer belt ply 8B.

[0022] Here, the turning of the motorcycle is performed by tilting the motorcycle. At this time, the lateral force generated in the tire 1 is expressed as the sum of the camber thrust generated by tilting the tire 1 and the cornering force generated by the slip angle of the tire 1. When the lateral force generated in this tire 1 and the centrifugal force of the motorcycle are balanced, the motorcycle can turn stably and can be said to have excellent turning performance.

[0023] The centrifugal force of the motorcycle, for example, is small in the gentle turning state from the straight-ahead state and large in the sharp turning state. Therefore, the tire 1 can improve the turning performance from the straight-ahead state to the sharp turning state by suppressing the generation of the cornering force in the gentle turning state from the straight-ahead state and increasing the cornering force in the sharp turning state.

[0024] Since the tire 1 of the present embodiment can increase the cornering force by the belt layer 8, the lateral force acting on the tire 1 also increases, and the turning performance when the centrifugal force is large, such as in the sharp turning state, can be improved.

[0025] The developed width W1 of the outer belt ply 8B of the present embodiment is larger than the developed width W2 of the inner belt ply 8A. Such a belt layer 8 can suppress the occurrence of breaker edge ruffle where the belt cords 8a peel off at the ends of the ply, and can improve the durability performance. Here, the developed width of the ply is the length measured along the outer surface of the ply between the ends in the tire axial direction of the ply.

[0026] The band layer 9 consists of at least one band ply 9A, in this embodiment one band ply, in which the band cords 9a are arranged at an angle of 5° or less with respect to the circumferential direction of the tire. In this embodiment, the band ply 9A is arranged in the radial direction of the tire between the inner belt ply 8A and the outer belt ply 8B, adjacent to the inner belt ply 8A and the outer belt ply 8B.

[0027] Such a tire 1 can mitigate the binding effect between the inner belt ply 8A and the outer belt ply 8B, thereby suppressing the generation of excessive cornering force when centrifugal force is small, such as when moving straight or making a gentle turn. Therefore, the tire 1 of this embodiment can achieve both cornering performance and durability.

[0028] In a more preferred embodiment, the second angle θ2 of the belt cord 8a of the outer belt ply 8B with respect to the tire circumferential direction is different from the first angle θ1 of the belt cord 8a of the inner belt ply 8A with respect to the tire circumferential direction. Such a belt layer 8 can more reliably exert the binding effect between the inner belt ply 8A and the outer belt ply 8B.

[0029] In this embodiment, the second angle θ2 is greater 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 large with respect to the tire circumferential direction, which can improve the rigidity of the tread portion 2 and help generate greater cornering force.

[0030] 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 exerted. When the difference (θ2-θ1) is 40° or less, the difference in the magnitude of the cornering force due to the presence or absence of the band ply 9A can be reduced, and the transient characteristics at the boundary position of the band ply 9A can be improved.

[0031] The first angle θ1 is preferably 50 to 80°. A first angle θ1 of 50° or more suppresses excessive binding effect, generates good cornering force, and improves turning performance. A first angle θ1 of 80° or less ensures a reliable angle difference between the outer belt ply 8B and the belt cord 8a, thereby enabling the binding effect.

[0032] The second angle θ2 is preferably 70 to 90°. A second angle θ2 of 70° or more suppresses excessive hooping effect, generates good cornering force, and improves turning performance. A second angle θ2 of 90° or less ensures that the inclination direction of the inner belt ply 8A is the same as that of the belt cord 8a, thereby reducing placement errors during manufacturing.

[0033] In this embodiment, the deployed width W3 of the band ply 9A is smaller than the deployed width W2 of the inner belt ply 8A. Such a tread reinforcement layer 7 mitigates the binding effect between the inner belt ply 8A and the outer belt ply 8B from a straight-ahead state to a gentle turn state, while allowing the binding effect to be exerted in a sharp turn state.

[0034] Therefore, the tire 1 of this embodiment can suppress the generation of excessive cornering force from a straight-ahead state to a gentle turn, and generate a large cornering force in a sharp turn, thereby improving turning performance from a straight-ahead state to a sharp turn.

[0035] The deployed width W3 of the band ply 9A is preferably 30% to 90% of the tread deployed width TWe. By having a deployed width W3 of 30% or more of the tread deployed width TWe, the band ply 9A can be reliably included in the contact area even when the tread portion 2 deforms during braking in a straight line, thereby reducing the cornering force. From this viewpoint, it is more preferable that the deployed width W3 of the band ply 9A is 35% or more of the tread deployed width TWe, and even more preferable that it is 40% or more.

[0036] By ensuring that the deployment width W3 of the band ply 9A is 90% or less of the tread deployment width TWe, the binding effect during sharp turns can be reliably achieved, thereby increasing the cornering force. From this perspective, it is more preferable that the deployment width W3 of the band ply 9A is 85% or less of the tread deployment width TWe, and even more preferable that it is 80% or less.

[0037] The difference (W1-W2) between the unfolded width W1 of the outer belt ply 8B and the unfolded width W2 of the inner belt ply 8A is preferably 10 mm or more. That is, in this embodiment, the distance L1 between the tire axial end of the outer belt ply 8B and the tire axial end of the inner belt ply 8A is 5 mm or more on both sides in the tire axial direction. Such a belt layer 8 can more reliably suppress the occurrence of breaker edge looseness and improve durability.

[0038] Figure 3 is an enlarged cross-sectional view of the tread portion 2 of this embodiment. As shown in Figures 1 to 3, the tread portion 2 of this embodiment includes a rubber layer 10 arranged on the outer side of the band ply 9A in the tire axial direction. Preferably, the rubber layer 10 is arranged on both sides of the band ply 9A in the tire axial direction. Each rubber layer 10 consists of at least one rubber sheet 10A, and in this embodiment, one rubber sheet 10A.

[0039] Here, the state including the rubber layer 10 made of rubber sheet 10A means that the distance between the members arranged on either side of this rubber layer 10 is kept approximately constant. In this specification, "approximately constant distance" means that the variation of the average value of that distance is within ±15%.

[0040] In this tread section 2, the torsional rigidity is improved by the rubber sheet 10A, which increases the cornering force in sharp turns. Therefore, the tire 1 of this embodiment can improve the turning performance in sharp turns. Note that if the rubber layer 10 consists of multiple rubber sheets 10A, the rubber sheets 10A may be arranged in the radial direction of the tire, or they may be arranged in the axial direction of the tire.

[0041] In this embodiment, the rubber layer 10 is positioned between the inner belt ply 8A and the outer belt ply 8B. The distance t between the inner belt ply 8A and the outer belt ply 8B at the position where the rubber layer 10 is positioned 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.

[0042] A distance t of 0.5 mm or more ensures that the torsional effect is reliably exerted, and the cornering force in sharp turns can be increased. A distance t of 3.0 mm or less suppresses excessive cornering force and improves transient characteristics in the region with the band ply 9A.

[0043] In this embodiment, the sum of the unfolded width W4 of the rubber layers 10 on both sides and the unfolded width W3 of the band ply 9A (W3 + 2 × W4) is smaller than the unfolded width W2 of the inner belt ply 8A. Such rubber layers 10 can further improve the torsional rigidity of the tread portion 2.

[0044] The complex modulus of elasticity G* of the rubber layer 10 at 70°C is preferably 500 kPa or higher. Such a rubber layer 10 can more reliably exert a torsional effect and increase the cornering force in sharp turns.

[0045] Here, the complex modulus G* of rubber layer 10 at 70°C is the value measured using a GABO dynamic viscoelasticity measuring device (Iplexer series) under the following conditions, in accordance with the provisions of JIS-K6394. Initial strain: 10% Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: Tension Measurement temperature: 70℃

[0046] While particularly preferred embodiments of this disclosure have been described in detail above, this disclosure is not limited to the embodiments described above and can be implemented in various modified forms. [Examples]

[0047] A motorcycle tire with the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1. As Comparative Example 1, a motorcycle tire with a band layer positioned radially outside the belt layer was prototyped. The prototype tires were mounted on the front and rear wheels of a test motorcycle to test their turning performance, and the durability of the prototype rear tire was also tested. The main common points and test methods are as follows.

[0048] <Common matters> Front tire size: 120 / 70R17 Front tire pressure: 250kPa Rear tire size: 200 / 60R17 Rear tire pressure: 290kPa Test motorcycle: Large motorcycle

[0049] <Turning performance> Using a test motorcycle fitted with prototype tires, the smooth turning performance from an upright position to a gentle turn, the sharp turning performance in a sharp turn, and the transient characteristics from a gentle turn to a sharp turn were evaluated subjectively by a test driver. The results are expressed as an index with Comparative Example 1 set to 100, where a higher value indicates superior smooth turning performance, sharp turning performance, and transient characteristics. The sum of smooth turning performance, sharp turning performance, and transient characteristics is shown as the turning performance.

[0050] <Durability> A prototype rear tire was mounted on a drum-type test bench and tested for breaker edge looseness over 7,000 km under conditions of a load of 5.5 kN, a speed of 80 km / h, and a camber angle of 0°. The results showed that tires exhibiting breaker edge looseness were marked as "fail," while those without breaker edge looseness were marked as "pass." The pass rating indicates superior durability.

[0051] The test results are shown in Table 1. [Table 1]

[0052] The test results showed that the tire in the example demonstrated improved cornering performance while also exhibiting superior durability compared to the comparative example, confirming that it is possible to achieve both high cornering performance and durability.

[0053] [Note] This disclosure is as follows:

[0054] [Disclosure 1] 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, wherein the tread reinforcing layer comprises a belt layer with a plurality of belt cords arranged thereon and a band layer with a plurality of band cords arranged thereon, wherein the belt layer consists of one inner belt ply disposed adjacent to the carcass and one outer belt ply disposed radially outer of the inner belt ply, and the band layer is arranged radially between the inner belt ply and the front A motorcycle tire comprising at least one band ply positioned adjacent to the inner belt ply and the outer belt ply, wherein the inner belt ply has its belt cords arranged at a first angle greater than 5° with respect to the tire circumferential direction, the outer belt ply has its belt cords arranged at a second angle greater than 5° with respect to the tire circumferential direction, and the band ply has its band cords arranged at an angle of 5° or less with respect to the tire circumferential direction, and the unfolded width of the outer belt ply is greater than the unfolded width of the inner belt ply.

[0055] [Disclosure 2] The motorcycle tire according to Disclosure 1, wherein the difference between the unfolded width of the outer belt ply and the unfolded width of the inner belt ply is 10 mm or more.

[0056] [Disclosure 3] The motorcycle tire according to disclosure 1 or 2, wherein the deployed width of the band ply is smaller than the deployed width of the inner belt ply.

[0057] [Disclosure 4] The motorcycle tire according to any one of disclosures 1 to 3, wherein the width of the band ply is 30% to 90% of the tread width.

[0058] [Disclosure 5] The motorcycle tire according to any one of disclosures 1 to 4, wherein the second angle is different from the first angle.

[0059] [Disclosure 6] The motorcycle tire according to Disclosure 5, wherein the second angle is greater than the first angle.

[0060] [Disclosure 7] The motorcycle tire according to disclosure 6, wherein the difference between the second angle and the first angle is 10 to 40°.

[0061] [Disclosure 8] A motorcycle tire according to disclosure 7, wherein the first angle is 50 to 80° and the second angle is 70 to 90°.

[0062] [Disclosure 9] The tread portion includes a rubber layer disposed on the tire axial side of the band ply, the rubber layer is disposed 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 disposed is substantially constant between 0.5 and 3.0 mm, as described in any one of disclosures 1 to 8.

[0063] [Disclosure 10] The motorcycle tire according to disclosure 9, wherein the complex modulus of elasticity of the rubber layer at 70°C is 500 kPa or more. [Explanation of Symbols]

[0064] 1. Motorcycle tires 2 Tread section 6 Carcass 7. Tread reinforcement layer 8 Belt Layer 8A Inner Belt Ply 8B Outer Belt Ply 8a Belt cord 9-band layer 9A Bandply 9a Bandcode

Claims

1. Motorcycle tires, The carcass includes a tread portion, a pair of sidewall portions, and 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 reinforcement 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 consists of one inner belt ply positioned adjacent to the carcass and one outer belt ply positioned radially outward of the inner belt ply. The band layer consists of at least one band ply arranged adjacent to the inner belt ply and the outer belt ply in the radial direction of the tire, between the inner belt ply and the outer belt ply. The inner belt ply is configured such that the belt cords are arranged at a first angle greater than 5° with respect to the circumferential direction of the tire. The outer belt ply is arranged such that the belt cords are arranged at a second angle greater than 5° with respect to the circumferential direction of the tire. The band ply is such that the band cords are arranged at an angle of 5° or less with respect to the circumferential direction of the tire. The unfolded width of the outer belt ply is greater than the unfolded width of the inner belt ply. The tread portion includes a rubber layer positioned on the outer side of the band ply in the tire axial direction, The rubber layer is disposed between the inner belt ply and the outer belt ply. The distance between the inner belt ply and the outer belt ply at the position where the rubber layer is arranged is approximately constant between 0.5 and 3.0 mm. Motorcycle tires.

2. The motorcycle tire according to claim 1, wherein the complex modulus of elasticity of the rubber layer at 70°C is 500 kPa or more.

3. The motorcycle tire according to claim 1 or 2, wherein the second angle is different from the first angle.

4. The motorcycle tire according to claim 3, wherein the second angle is greater than the first angle.

5. A tire for a motorcycle, The carcass includes a tread portion, a pair of sidewall portions, and 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 reinforcement 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 consists of one inner belt ply positioned adjacent to the carcass and one outer belt ply positioned radially outward of the inner belt ply. The band layer consists of at least one band ply arranged adjacent to the inner belt ply and the outer belt ply in the radial direction of the tire, between the inner belt ply and the outer belt ply. The inner belt ply is configured such that the belt cords are arranged at a first angle greater than 5° with respect to the circumferential direction of the tire. The outer belt ply is arranged such that the belt cords are arranged at a second angle greater than 5° with respect to the circumferential direction of the tire. The band ply is such that the band cords are arranged at an angle of 5° or less with respect to the circumferential direction of the tire. The unfolded width of the outer belt ply is greater than the unfolded width of the inner belt ply. The second angle is greater than the first angle. Motorcycle tires.

6. The difference between the second angle and the first angle is 10 to 40°, the motorcycle tire according to claim 4 or 5.

7. The aforementioned first angle is 50 to 80°, The motorcycle tire according to claim 6, wherein the second angle is 70 to 90°.

8. The difference between the unfolded width of the outer belt ply and the unfolded width of the inner belt ply is 10 mm or more, as described in any one of claims 1 to 7, for a motorcycle tire.

9. The motorcycle tire according to any one of claims 1 to 8, wherein the deployed width of the band ply is smaller than the deployed width of the inner belt ply.

10. The motorcycle tire according to any one of claims 1 to 9, wherein the deployed width of the band ply is 30% to 90% of the deployed width of the tread.

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