Tire for two-wheeled motor vehicle

Abstract

The present invention provides a tire for a two-wheeled motor vehicle, which suppresses a decrease in grip force in the lateral direction during drive turning and improves turning performance. The tire for a two-wheeled motor vehicle is a tire (10) for a rear wheel of a two-wheeled motor vehicle, which has a carcass (1) extending annularly across a pair of bead sections (13) as a skeleton, and is provided with a spiral belt (2) formed by helically winding a belt cord in the circumferential direction of the tire on the outside of the carcass in the radial direction of the tire. The belt cord has a 1 * N structure, and the belt cord removed from the tire has an elongation of greater than 0.3% and less than 0.7% when a load of 50 N is applied thereto.

Description

Technical Field

[0001] The present invention relates to a tire for a motorcycle (hereinafter also referred to as "tire"), and more particularly to a rear wheel tire for a motorcycle having an improved belt cord used in a spiral belt, particularly a pneumatic tire for a motorcycle. Background Art

[0002] In the past, as a belt to reinforce the tread contact portion of a motorcycle tire, two or more inclined belt layers are used in which the cord directions are staggered between layers, or one or more spiral belts composed of rubber-coated cords spirally wound in the circumferential direction of the tire are used.

[0003] As a prior art of a motorcycle tire using a spiral belt, for example, Patent Document 1 discloses a pneumatic radial tire for a motorcycle: a single spiral belt uses a steel cord having a specific tensile breaking strength, and the arrangement density of the single spiral belt at the shoulder portion is set to be smaller than the arrangement density at the tire equator, the arrangement width of the single spiral belt is set within a specific range, and the overlap amount of the single spiral belt and the fabric reinforcement layer arranged at both ends thereof is limited to a predetermined amount. The purpose of the technology described in Patent Document 1 is to provide a pneumatic radial tire for a motorcycle that solves the paradoxical problem of ground contact and lateral rigidity during cornering, and achieves a high level of both ground contact and lateral rigidity, thereby achieving improved stability during cornering.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2006 / 098112 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, in the conventional rear wheel tires using spiral belts, the turning performance of the motorcycle is sometimes insufficient when turning, especially in the initial stage of gradually raising the vehicle body from the fully tilted state where the vehicle body is tilted to the maximum extent, for example, in the range of camber angle 50° to 40°. It is believed that this is because when the accelerator is turned on and the driving force increases when turning, the contact area of ​​the rear wheel tire as the driving wheel decreases, and the lateral gripping force generated is insufficient. In the tire disclosed in Patent Document 1, such a point is not studied either.

[0009] Therefore, an object of the present invention is to provide a tire for a motorcycle that suppresses a decrease in lateral grip during drive cornering and improves cornering performance.

[0010] Solutions for solving problems

[0011] The present inventors have analyzed the contact state of the rear tire and found that during driving and turning, the spiral belt that contacts the ground surface applies a circumferential tensile input to the tire. The present inventors have conducted in-depth research and found that if the elongation of the spiral belt in the circumferential direction of the tire when the tensile input is applied can be increased, the contact surface will expand in the circumferential direction of the tire, and the contact area will expand, thereby achieving an increase in lateral force as a result.

[0012] Based on the above, the present inventors conducted further studies and found that the above-mentioned problems can be solved by limiting the elongation of the belt cord used in the spiral belt of the rear tire of a motorcycle to a predetermined value, thereby completing the present invention.

[0013] That is, the present invention is as follows.

[0014] (1) A tire for a motorcycle, which is a tire for a rear wheel of a motorcycle, comprising a carcass extending in a toroidal shape across a pair of bead portions as a frame, and a spiral belt formed by spirally winding belt cords in the tire circumferential direction on the outer side of the carcass in the tire radial direction, wherein the tire for a motorcycle is characterized in that:

[0015] The belt cord has a 1×N configuration, and the belt cord taken out from the tire has an elongation greater than 0.3% and less than 0.7% when a load of 50 N is applied.

[0016] (2) The motorcycle tire according to (1), wherein the belt cord is formed by twisting N steel wires, and a lay pitch of the belt cord not coated with rubber before vulcanization is 5.2 mm to 8.8 mm.

[0017] (3) The motorcycle tire according to (1) or (2), wherein the arrangement density of the belt cords in the spiral belt is 10 to 25 cords / 25 mm.

[0018] (4) The motorcycle tire according to any one of (1) to (3), wherein the belt width of the spiral belt measured along the tire surface is 100 mm to 240 mm.

[0019] Here, in the present invention, unless otherwise specified, each dimension of a tire refers to a value measured in a no-load state when the tire is assembled on a rim specified by an industrial standard effective in a region where the tire is produced and used and filled with an internal pressure specified in the industrial standard. In addition, the above industrial standards are, for example, the JATMA (Japan Automobile Tire Association) YEAR BOOK in Japan, the ETRTO (European Tyre and Rim Technical Organisation) STANDARD MANUAL in Europe, and the TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK in the United States.

[0020] Effects of the Invention

[0021] According to the present invention, by adopting the above-mentioned configuration, it is possible to realize a motorcycle tire that suppresses a decrease in lateral grip during drive turning and achieves improved turning performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view in the width direction showing an example of the motorcycle tire of the present invention.

[0023] Figure 2 This is a cross-sectional view in the width direction showing a configuration example of a belt cord used in the spiral belt of the present invention.

[0024] Figure 3 This is a graph (schematic diagram) showing an example of a stress-strain curve of a belt cord.

[0025] Figure 4 It is an explanatory diagram showing a state in which steel wires are arranged in an offset manner in a cord cross section. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0027] Figure 1 1 is a cross-sectional view showing an example of a motorcycle tire of the present invention. The motorcycle tire 10 shown in the figure is a rear wheel tire for a motorcycle, and includes a tread portion 11 formed in an annular shape, a pair of sidewall portions 12 and a bead portion 13 sequentially arranged on the inner side of the tread portion 11 in the tire radial direction. In addition, the motorcycle tire 10 shown in the figure uses a carcass 1 extending in an annular shape across the pair of bead portions 13 as a skeleton, and includes a spiral belt 2 formed by spirally winding belt cords in the tire circumferential direction on the outer side of the carcass 1 in the tire radial direction.

[0028] In the motorcycle tire of the present invention, as the belt cord used for the spiral belt 2, a material having a 1×N structure is used, and the elongation of the belt cord taken out of the tire when a load of 50 N is applied is greater than 0.3% and less than 0.7%. By using such a belt cord with high elasticity, when the spiral belt 2 that contacts the ground surface is subjected to a circumferential tensile input in the tire, the elongation of the spiral belt 2 in the tire circumferential direction can be increased.

[0029] According to the present invention, the contact surface is expanded in the tire circumferential direction during driving and turning, and the contact area is expanded, so as a result, the lateral force can be increased. In addition, in the tire of the present invention, the value of longitudinal stiffness / lateral stiffness can also be ensured to be equal to or higher than the conventional value.

[0030] exist Figure 3 An example of a stress-strain curve of a belt cord taken out of a tire is shown in a graph (schematic diagram). The belt cord of the present invention has excellent elasticity, and specifically, shows Figure 3 The stress-strain characteristics shown in the figure. The stress-strain curve shown in the figure has an inflection point P, and shows a relatively low elastic modulus in the low elastic modulus region from the origin to the inflection point P, and shows a relatively high elastic modulus in the high elastic modulus region exceeding the inflection point P. The elastic modulus mentioned here refers to the tensile modulus.

[0031] In the present invention, the belt cord used as the spiral belt 2 needs to have an elongation greater than 0.3% and less than 0.7% when a load of 50N is applied to the belt cord taken out of the tire. If the elongation is less than 0.3%, the effect of improving the lateral force cannot be obtained, and if it is greater than 0.7%, the rigidity of the tire decreases and the handling stability deteriorates, so the desired effect of the present invention cannot be obtained. By setting it within the above elongation range, it is possible to take into account both the increase in the contact area during driving and turning and good tire rigidity.

[0032] Here, in the present invention, the belt cord taken out from the tire means the belt cord cut from the inside of the vulcanized finished tire in a state where the rubber is attached.

[0033] In addition, in the present invention, as the belt cord used for the spiral belt 2, a 1×N structure (N=2 to 7) twisted cord formed by twisting N filaments, especially molded steel wires, with each other is used. In the present invention, the reason for using a 1×N structure single-twisted belt cord is that it is easier to obtain the above-mentioned cord characteristics with higher elasticity than a double-twisted cord of an N×M structure. As the belt cord of the present invention, it is most preferred that it can be used in Figure 2 , a steel cord 100 having a 1×5 structure formed by twisting five pressed steel wires 101 as shown in the cross-sectional structure.

[0034] The diameter of the belt cord of the present invention in the state of not being coated with rubber before vulcanization is preferably 0.59 mm to 0.71 mm, and more preferably 0.64 mm to 0.69 mm. By using such a belt cord, the effect of the present invention can be more appropriately obtained.

[0035] Furthermore, the lay pitch of the belt cord of the present invention in the state of not being coated with rubber before vulcanization is preferably 5.2 mm to 8.8 mm, more preferably 5.5 mm to 7.5 mm. If the lay pitch of the belt cord is too small, production stability deteriorates. On the other hand, if the lay pitch of the belt cord is too large, when it is necessary to ensure the required elongation, such as Figure 4 As shown, a defect occurs when the cord is manufactured, that is, the steel wires 201 are arranged unevenly but unevenly in the cross section of the steel cord 200 .

[0036] In the belt cord of the present invention, the mold height of the steel wire in the state of not being coated with rubber before vulcanization is preferably 0.70 mm to 0.80 mm, more preferably 0.71 mm to 0.74 mm. By using such a belt cord, the effects of the present invention can be more appropriately obtained.

[0037] In the motorcycle tire of the present invention, the belt cord satisfying the above conditions is used for the spiral belt 2. The spiral belt 2 is formed by spirally winding the belt cord in the tire circumferential direction, which is substantially parallel to the tire equatorial plane CL.

[0038] In the present invention, the arrangement density of the belt cords in the spiral belt 2 is preferably 10 to 25 cords / 25 mm, more preferably 16 to 24 cords / 25 mm. If the arrangement density of the belt cords is too small, durability and rigidity may be insufficient.

[0039] In the motorcycle tire of the present invention, the belt cords of the spiral belt 2 only need to satisfy the above conditions, and other tire structures and details of materials used are not particularly limited. For example, the tire can be constructed as follows.

[0040] The carcass 1 is composed of at least one carcass cord, which is formed by arranging relatively high elastic fiber cords in parallel with each other. The number of carcass cords can be one, two, or more than three. In the example shown in the figure, two carcass cords are configured. The two ends of the carcass cord can be folded back from the inside to the outside of the tire at the bead portion 13 around the bead core 3 buried in the bead portion 13 and fixed, or can be fixed by clamping from both sides using bead wires, and any fixing method can be used.

[0041] At least one spiral belt 2 may be arranged, and two or more spiral belts may be arranged. In the example shown in the figure, one spiral belt 2 is arranged. The belt width of the spiral belt measured along the tire surface is preferably 100 mm to 240 mm.

[0042] In addition, although not shown in the figure, in the present invention, in addition to the spiral belt 2, a width direction belt layer formed by rubber coating the reinforcing cords arranged in the tire width direction may be further arranged on the outer side of the spiral belt 2 in the tire radial direction, or two or more inclined belt layers may be arranged in a manner that the cord directions are interlaced between layers. As the reinforcing materials constituting these belt layers, nylon fiber, aromatic polyamide (trade name: Kevlar (registered trademark)), steel, etc. can be listed. Among them, aromatic polyamide and steel are reinforcing materials that do not stretch at high temperatures and can suppress the expansion of the tread portion.

[0043] Furthermore, in the motorcycle tire of the present invention, the bead rubber 4 can be arranged outside the bead core 3 in the tire radial direction, and an inner liner layer (not shown) can be arranged in the innermost layer of the tire.

[0044] The tire 10 shown in the figure can be applied to a tire of radial construction.

[0045] Example

[0046] Hereinafter, the present invention will be described in more detail using specific examples.

[0047] (Example)

[0048] A rear wheel tire for a motorcycle with a tire size of 200 / 655R17 was manufactured. The tire has a carcass 1 composed of two carcass plies as a skeleton, and has a spiral belt 2 formed by spirally winding belt cords satisfying the following conditions in the tire circumferential direction, and a width direction belt layer formed by rubber coating reinforcing cords arranged in the tire width direction.

[0049] Cord structure: A steel cord having a 1×5 structure formed by twisting five steel wires with a diameter of 0.21 mm.

[0050] The elongation of the belt cord taken out from the tire when a load of 50 N was applied: 0.5%.

[0051] The two carcass cords are reinforced by interlaced cords (material: nylon fiber) arranged at a cord angle of ±6° relative to the tire width direction. In addition, the belt width of the spiral belt measured along the tire surface is 185mm, and the arrangement density of the belt cords in the spiral belt is 20 / 25mm.

[0052] (Previous example)

[0053] A test tire of the conventional example was produced in the same manner as in the example except that the conditions of the belt cords used in the spiral belt were changed as shown below.

[0054] Cord structure: A steel cord having a 1×5 structure formed by twisting five steel wires with a diameter of 0.21 mm.

[0055] The elongation of the belt cord taken out from the tire when a load of 50 N was applied: 0.3%.

[0056] (Evaluation of longitudinal and lateral rigidity)

[0057] Each test tire was assembled on a rim of MT6.00×17, and the longitudinal and lateral rigidities were evaluated under the conditions of an internal pressure of 180 kPa and a load of 2 kN. The results are expressed as average values ​​at camber angles of 0° to 50°, with the conventional example being 100%.

[0058] (Dynamic grounding measurement)

[0059] Each test tire was assembled on a rim of MT6.00×17, filled with an internal pressure of 180 kPa and applied with a load of 1.5 kN, and the contact area of ​​each test tire during driving cornering was evaluated under the conditions of a camber angle of 47°, a slip angle of 0°, and a driving force of 0.9 kN. The results are shown as an index with the conventional example being 100.

[0060] (Friction circle test)

[0061] Each test tire was assembled on a rim with a rim size of MT6.00×17, filled with an internal pressure of 180 kPa and applied with a load of 1.5 kN, and driving force was continuously applied at a camber angle of 45° and a slip angle of 0° to evaluate the lateral force during driving cornering. The results are shown as the value when the driving force is 0.9 kN when the conventional example is set as 100%.

[0062] These results are shown in Table 1 below.

[0063] [Table 1]

[0064]

[0065] From the results shown in the above table, the test tires of the examples ensured values ​​equal to or higher than those of the test tires of the conventional examples in terms of both longitudinal rigidity and lateral rigidity.

[0066] In addition, in the test tire of the embodiment, the contact area is increased by about 4% compared with the test tire of the conventional example.

[0067] As is apparent from the above results, in the test tires of the examples, a decrease in the grip in the lateral direction during drive cornering is suppressed, and the cornering performance is improved.

[0068] Description of Reference Numerals

[0069] 1. carcass; 2. spiral belt; 3. bead core; 4. bead rubber strip; 10. tire for two-wheeled motor vehicle; 11. tread portion; 12. sidewall portion; 13. bead portion; 100, 200, steel cord; 101, 201, steel wire.

Claims

1. A tire for a motorcycle, which is a tire for a rear wheel of a motorcycle, comprising a carcass extending in a ring shape across a pair of bead portions as a frame, and a spiral belt formed by spirally winding belt cords in the tire circumferential direction on the outer side of the carcass in the tire radial direction, wherein the tire for a motorcycle is characterized in that: The belt cord has a 1×N configuration, and the belt cord taken out from the tire has an elongation greater than 0.3% and less than 0.7% when a load of 50 N is applied.

2. The tire for a motorcycle according to claim 1, wherein: The belt cord is formed by twisting N steel wires, and the lay length of the belt cord not coated with rubber before vulcanization is 5.2 mm to 8.8 mm.

3. The tire for a motorcycle according to claim 1, wherein: The arrangement density of the belt cords in the spiral belt is 10 to 25 cords / 25 mm.

4. The tire for a motorcycle according to claim 1, wherein: The belt width of the spiral belt measured along the tire surface is 100 mm to 240 mm.

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