Motorcycle tires

Abstract

To provide a tire for a motorcycle, the tire being capable of maintaining steering stability for many hours.SOLUTION: A tire 1 for a motorcycle is provided, comprising: a carcass 6 which extends between a pair of bead portions 4 via a tread portion 2 and a pair of side wall portions 3; and a pair of reinforcement rubbers 7 for reinforcing the pair of side wall portions 3. The carcass 6 includes at least one carcass ply 6A which has a body portion 6a extending between the pair of bead portions 4 and a folded portion 6b which follows the body portion 6a and is folded outward from inside a tire shaft direction around bead cores 5 of the bead portions 4. In the carcass ply 6A, a plurality of columns of carcass codes 8 where a plurality of filaments 10 are twisted are arranged. A proportion D / d of a cord average diameter D of the carcass cord 8 and an external diameter d of the filament 10 is 28 or more. The reinforcement rubbers 7 are arranged between the body portion 6a and the folded portion 6b in the respective side wall portions 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to tires for motorcycles. [Background technology]

[0002] Conventionally, motorcycle tires including a tread portion, a sidewall portion, and a bead portion have been known. For example, Patent Document 1 listed below proposes a motorcycle tire that improves cornering performance by using a bead apex rubber to reinforce almost the entire sidewall and increase side rigidity while suppressing an increase in tread rigidity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-108035 Summary of the Invention [Problem to be solved by the invention]

[0004] However, performance such as cornering performance and handling stability may deteriorate during driving, and further improvement was desired in order to maintain handling stability over a long period of time even in the motorcycle tire of Patent Document 1.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a motorcycle tire that can maintain steering stability for a long period of time. [Means for solving the problem]

[0006] The present disclosure relates to a motorcycle tire including a tread portion, a pair of sidewall portions extending radially inward from both sides of the tread portion, and a pair of bead portions located radially inward of the pair of sidewall portions, the tire including a carcass extending between the pair of bead portions via the tread portion and the pair of sidewall portions, and a pair of reinforcing rubber for reinforcing the pair of sidewall portions, the carcass including at least one carcass ply having a main portion extending between the pair of bead portions and a turned-up portion connected to the main portion and turned back around the bead core of the bead portion from the inside to the outside in the tire axial direction, the carcass ply having a plurality of carcass cords arranged in the carcass ply, the ratio D / d of the average cord diameter D of the carcass cord to the outer diameter d of the filament being 28 or greater, and the reinforcing rubber being arranged in each of the sidewall portions between the main portion and the turned-up portion. [Effects of the Invention]

[0007] The motorcycle tire of the present disclosure has the above-described configuration, and thus can maintain steering stability for a long period of time. [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. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a carcass cord. [Figure 4] FIG. 2 is an enlarged cross-sectional view of a sidewall portion. 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 showing a motorcycle tire 1 (hereinafter sometimes simply referred to as "tire 1") in a normal state according to this embodiment.

[0010] Here, "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. Unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in this normal state.

[0011] 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" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0012] "Normal internal pressure" is the air pressure set for each tire by 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 sides of the tread portion 2, and a pair of bead portions 4 located radially inward of the pair of sidewall portions 3. Each of the bead portions 4 of this embodiment has a bead core 5 extending circumferentially of the tire.

[0014] The tire 1 of this embodiment includes a carcass 6 extending between a pair of bead portions 4 via a tread portion 2 and a pair of sidewall portions 3, and a pair of reinforcing rubbers 7 for reinforcing the pair of sidewall portions 3. In such a tire 1, the carcass 6 and the reinforcing rubbers 7 can improve the rigidity of the sidewall portions 3.

[0015] The carcass 6 includes at least one carcass ply 6A, two in this embodiment. Each carcass ply 6A in this embodiment has a main body portion 6a extending between a pair of bead portions 4, and a turned-up portion 6b that is continuous with the main body portion 6a and is turned up around the bead core 5 of the bead portion 4 from the inside to the outside in the tire axial direction.

[0016] Fig. 2 is an enlarged perspective view of the carcass ply 6A of this embodiment. As shown in Fig. 2, the carcass ply 6A of this embodiment has a plurality of carcass cords 8 arranged therein. The carcass ply 6A preferably includes a topping rubber 9 that covers the carcass cords 8.

[0017] The carcass cords 8 of the carcass ply 6A are arranged, for example, inclined at an angle of 15 to 45° with respect to the tire circumferential direction. It is desirable that the carcass cords 8 of the two carcass plies 6A are arranged so that they are inclined in opposite directions with respect to the tire circumferential direction. For the carcass cords 8, organic fiber cords such as nylon, polyester, rayon, etc. are suitably used.

[0018] The carcass ply 6A preferably has an ends number, which is the number of carcass cords 8 included per 5 cm of ply width in a direction perpendicular to the carcass cords 8, of 40 to 60. Such a carcass ply 6A helps to improve the rigidity of the tire 1 while suppressing an increase in mass. From this perspective, the ends number of the carcass ply 6A is more preferably 45 to 55. The ends number of the carcass ply 6A can be measured in accordance with the provisions of JIS-L1017.

[0019] The fineness of one carcass cord 8 is preferably 2000 to 7000 dtex. Such a carcass cord 8 helps to improve the rigidity of the tire 1 while suppressing an increase in mass. From this viewpoint, the fineness of one carcass cord 8 is more preferably 2500 to 6500 dtex, and even more preferably 3000 to 6000 dtex. The fineness of the carcass cord 8 can be measured in accordance with the provisions of JIS-L1017.

[0020] Fig. 3 is an enlarged cross-sectional view of the carcass cord 8 of this embodiment. As shown in Fig. 3, each carcass cord 8 of this embodiment is configured by twisting together a plurality of filaments 10. The carcass cord 8 is configured by twisting together a plurality of first twist yarns 8a, for example, two first twist yarns in this embodiment, each first twist yarn 8a being configured by twisting together a plurality of filaments 10.

[0021] The carcass cord 8 is formed by, for example, twisting two first twist yarns 8a together, so that a portion 8b of the outer surface of the first twist yarn 8a is flattened. The flattened portion 8b of the outer surface of the first twist yarn 8a corresponds to, for example, the contact surface of the two first twist yarns 8a. As a result, the cross-sectional shape of the carcass cord 8 is a substantially ellipse with a narrower cross-sectional width at the center. However, the carcass cord 8 is not limited to this embodiment, and for example, the portions 8b of the outer surfaces of three or more first twist yarns 8a may be twisted together while contacting each other.

[0022] The fineness of one first twist yarn 8a is preferably 1000 to 3500 dtex. Such a first twist yarn 8a helps to improve the rigidity of the tire 1 while suppressing an increase in mass. From this perspective, the fineness of one first twist yarn 8a is more preferably 1500 to 3000 dtex. The fineness of the first twist yarn 8a can be measured in accordance with the provisions of JIS-L1017.

[0023] The ratio D / d of the average cord diameter D of the carcass cord 8 to the outer diameter d of the filament 10 is preferably equal to or greater than 28. When the ratio D / d is equal to or greater than 28, the carcass cord 8 becomes more easily stretchable even when a high load is applied, and breakage of the filament 10 can be suppressed.

[0024] As a result, the carcass cord 8 of the present embodiment can maintain high strength for a long period of time even in a situation where a high load is repeatedly applied, and can suppress deterioration in the steering stability of the tire 1. The carcass cord 8 having a ratio D / d of 28 or more can be manufactured by appropriately combining known manufacturing methods.

[0025] Here, the cord average diameter D is determined by the simple average of the major diameter D1 and minor diameter D2 in the cross section of the carcass cord 8. The major diameter D1 means the maximum diameter in the cross section of the carcass cord 8. The minor diameter D2 means the maximum diameter of the carcass cord 8 in the direction perpendicular to the major diameter D1 in the cross section of the carcass cord 8. The major diameter D1 and minor diameter D2 of the carcass cord 8 and the outer diameter d of the filament 10 can each be measured in accordance with the provisions of JIS-L1017.

[0026] Although the carcass cord 8 is exemplified as one that has a constant cross-sectional shape and extends in the length direction of the carcass cord 8, the cross-sectional shape or cross-sectional area of ​​the carcass cord 8 may change in the length direction of the carcass cord 8. In this case, the average cord diameter D is measured at a position where the cross-sectional area of ​​the carcass cord 8 is minimum. This is because the substantial tensile strength of the carcass cord 8 depends on the configuration of the carcass cord 8 at the position where the cross-sectional area of ​​the carcass cord 8 is minimum.

[0027] As shown in Fig. 1, the reinforcing rubber 7 of this embodiment is disposed between the main body portion 6a and the folded-up portion 6b in each sidewall portion 3. Such reinforcing rubber 7 can suppress the concentration of strain that occurs when a high load is applied to the tire 1, relieve stress that acts locally on the carcass ply 6A, and further suppress breakage of the filaments 10 (shown in Fig. 3). As a result, the tire 1 of this embodiment can maintain steering stability for a long period of time.

[0028] In a more preferred embodiment, the tire 1 is suitable for off-road riding, such as in off-road motorcycle races. The tread portion 2 of this embodiment is provided with a plurality of blocks 11. The blocks 11 include, for example, crown blocks 11A located at the tire equator C and shoulder blocks 11B that form the tread edge Te. It is desirable that the blocks 11 further include middle blocks 11C located axially between the crown blocks 11A and the shoulder blocks 11B.

[0029] Fig. 4 is an enlarged cross-sectional view of the sidewall portion 3. As shown in Fig. 4, the outer surface 2a of the tread portion 2 connected to the sidewall portion 3 has an arc portion 2b with a curvature radius R of 10 mm or more. By setting the curvature radius R to 10 mm or more, excessive deformation of the shoulder blocks 11B can be suppressed, even when a high load is applied or when making a sharp turn, and breakage of the filaments 10 of the carcass ply 6A near the shoulder blocks 11B can be suppressed.

[0030] The reinforcing rubber 7 of this embodiment extends radially outward from the radially outer end surface 5a of the bead core 5. The reinforcing rubber 7 includes, for example, an inner end 7a in contact with the radially outer end surface 5a of the bead core 5 and an outer end 7b on the radially outer side of the tire. Such reinforcing rubber 7 also suppresses strain concentration in the bead portion 4, and helps maintain the steering stability of the tire 1 for a long period of time.

[0031] The radially outer ends 7b of the reinforcing rubber 7 are located radially outward of the boundary 12 between the tread portion 2 and the sidewall portion 3. This type of reinforcing rubber 7 compensates for the rigidity of the shoulder blocks 11B, thereby suppressing excessive deformation of the shoulder blocks 11B, even when a heavy load is applied or a sharp turn is made. Furthermore, this type of reinforcing rubber 7 suppresses the concentration of strain in the carcass ply 6A near the shoulder blocks 11B, thereby suppressing breakage of the filaments 10 and suppressing a decrease in the steering stability of the tire 1.

[0032] Here, the boundary 12 between the tread portion 2 and the sidewall portion 3 is the innermost position in the tire radial direction of the arc portion 2b where the outer surface 2a of the tread portion 2 connects to the sidewall portion 3. In other words, the boundary 12 between the tread portion 2 and the sidewall portion 3 corresponds to the position of the base of the shoulder block 11B.

[0033] The reinforcing rubber 7 preferably has a thickness t of 0.5 mm or more in the range from the outer end surface 5a of the bead core 5 to the boundary 12. Having a thickness t of 0.5 mm or more of the reinforcing rubber 7 helps to improve the rigidity of the shoulder block 11B, suppresses breakage of the filaments 10, and further suppresses deterioration in the steering stability of the tire 1.

[0034] As shown in FIG. 1 , the radially outer end 7b of the reinforcing rubber 7 is preferably positioned radially outward of the intermediate position 13 of the radial height H from the outer end surface 5a of the bead core 5 to the maximum diameter portion of the tread portion 2. Such reinforcing rubber 7 compensates for the rigidity of the middle blocks 11C, thereby preventing excessive deformation of the middle blocks 11C, even when a heavy load is applied or during cornering. Furthermore, such reinforcing rubber 7 prevents strain concentration in the carcass ply 6A near the middle blocks 11C, preventing breakage of the filaments 10 and preventing a decrease in the steering stability of the tire 1.

[0035] The tire 1 may include, for example, at least one outer ply 14 disposed radially outward of the carcass 6 to reinforce the tread portion 2. The outer ply 14 extends, for example, between the pair of sidewall portions 3. In the outer ply 14, for example, a plurality of carcass cords 8 identical to those in the carcass ply 6A are arranged. The carcass cords 8 of the outer ply 14 are arranged, for example, at an angle of 15 to 45° with respect to the circumferential direction of the tire.

[0036] It is desirable that the radially inner end 14a of the outer ply 14 be located radially inward of the boundary 12 between the tread portion 2 and the sidewall portion 3. Such an outer ply 14 can suppress excessive deformation of the shoulder blocks 11B even when a high load is applied or when making a sharp turn.

[0037] 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]

[0038] A motorcycle tire with the internal structure shown in Figure 1 was prototyped based on the specifications in Table 1. The prototype tire was used to evaluate the durability of the motorcycle tire's handling stability. The main common specifications and test methods are as follows:

[0039] <Common specifications> Tire size: 120 / 80-19 Rim size: 2.15 x 19 Air pressure: 80kPa Test vehicle: 450cc off-road competition vehicle

[0040] <Sustained handling stability> The prototype tires were mounted on the rear wheels of test vehicles, and test riders drove the vehicles on an off-road course for 30 minutes, during which the handling stability was evaluated by the test riders' senses. The results were expressed as a score with the initial performance of each prototype tire's handling stability set at 100, and the closer the score is to 100, the smaller the difference from the initial performance and the better the durability of handling stability.

[0041] [Table 1]

[0042] As a result of the test, it was confirmed that the difference between the initial performance of the tires of the examples and that the handling stability can be maintained for a long period of time compared to the comparative example.

[0043] [Note] The present disclosure is as follows.

[0044] [Disclosure 1] a pair of bead portions located radially inward of the pair of sidewall portions in the tire radial direction, the tire for a motorcycle including a tread portion; a carcass extending between the pair of bead portions via the tread portion and the pair of sidewall portions; and a pair of reinforcing rubber for reinforcing the pair of sidewall portions, the carcass including at least one carcass ply having a main portion extending between the pair of bead portions and a turned-up portion connected to the main portion and turned back around a bead core of the bead portion from the inside to the outside in the tire axial direction, the carcass ply having a plurality of carcass cords arranged in the carcass ply, the carcass cords having a plurality of filaments twisted together, a ratio D / d of an average cord diameter D of the carcass cord to an outer diameter d of the filaments being 28 or greater, and the reinforcing rubber being arranged in each of the sidewall portions between the main portion and the turned-up portion.

[0045] [Disclosure 2] The motorcycle tire according to Disclosure 1, wherein the reinforcing rubber extends radially outward from an outer end surface of the bead core in the tire radial direction.

[0046] [Disclosure 3] The motorcycle tire according to Disclosure 2, wherein the radially outer end of the reinforcing rubber is located radially outward of the intermediate position in the height direction of the tire from the outer end surface of the bead core to the maximum diameter portion of the tread portion.

[0047] [Disclosure 4] The motorcycle tire according to Disclosure 2 or 3, wherein an outer end of the reinforcing rubber in the tire radial direction is positioned outer in the tire radial direction than a boundary between the tread portion and the sidewall portion.

[0048] [Disclosure 5] The motorcycle tire according to Disclosure 4, wherein the reinforcing rubber has a thickness of 0.5 mm or more in the range from the outer end surface of the bead core to the boundary.

[0049] [Disclosure 6] The motorcycle tire according to any one of Disclosures 1 to 5, wherein an outer surface of the tread portion connected to the sidewall portion has an arc portion with a curvature radius of 10 mm or more.

[0050] [Disclosure 7] The motorcycle tire according to any one of Disclosures 1 to 6, wherein the tread portion is provided with a plurality of blocks, and the blocks include shoulder blocks that form tread edges. [Explanation of symbols]

[0051] 1. Motorcycle tires 2 Tread section 3 Sidewall 4 Bead section 5 bead core 6. Carcass 6A carcass ply 6a Main body 6b Folded part 7 Reinforced rubber 8 Carcass Cord 10 filaments

Claims

1. A motorcycle tire including a tread portion, a pair of sidewall portions extending radially inward from both sides of the tread portion, and a pair of bead portions located radially inward of the pair of sidewall portions, a carcass extending between the pair of bead portions via the tread portion and the pair of sidewall portions; and a pair of reinforcing rubbers for reinforcing the pair of sidewall portions, the carcass includes at least one carcass ply having a main body portion extending between the pair of bead portions and a turned-up portion connected to the main body portion and turned up around the bead core of the bead portion from the inside to the outside in the tire axial direction, The carcass ply includes a plurality of carcass cords each formed by twisting together a plurality of filaments, a ratio D / d of an average cord diameter D of the carcass cord to an outer diameter d of the filament is 28 or more, the reinforcing rubber extends from an outer end surface of the bead core in the tire radial direction to an outer side in the tire radial direction between the main body portion and the turned-up portion in each of the sidewall portions, an outer end of the reinforcing rubber in the tire radial direction is located radially outward of an intermediate position in the height from the outer end surface of the bead core to a maximum diameter portion of the tread portion in the tire radial direction; Tires for motorcycles.

2. The motorcycle tire according to claim 1 , wherein the reinforcing rubber extends from an inner side in the tire axial direction of the outer end surface of the bead core to an outer side in the tire radial direction.

3. A motorcycle tire as described in claim 1 or 2, wherein the cross-sectional area of ​​the carcass cord changes in the length direction of the carcass cord.

4. The motorcycle tire according to claim 1 , wherein a radially outer end of the reinforcing rubber is located radially outward of a boundary between the tread portion and the sidewall portion.

5. 5. The motorcycle tire according to claim 4, wherein the reinforcing rubber has a thickness of 0.5 mm or more in the range from the outer end surface of the bead core to the boundary.

6. 6. The motorcycle tire according to claim 1, wherein an outer surface of the tread portion connected to the sidewall portion has an arc portion having a curvature radius of 10 mm or more.

7. The tread portion is provided with a plurality of blocks, The motorcycle tire according to claim 1 , wherein the blocks include shoulder blocks that form tread edges.

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