Tire for two-wheeled motor vehicle

Abstract

The present invention provides a tire for a two-wheeled motor vehicle, which suppresses the occurrence of buckling when braking is applied during straight travel and improves braking performance. A tire for a two-wheeled motor vehicle is a tire (10) for a front wheel of a two-wheeled motor vehicle, in which a carcass (1) extending annularly across a pair of bead sections (13) is used as a skeleton, and a spiral belt (2) formed by helically winding a belt cord in the circumferential direction of the tire is provided 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 0.3-0.85% 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 front 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 tires for motor vehicles using a spiral belt, for example, Patent Document 1 discloses a pneumatic radial tire for motor vehicles in which a single spiral belt uses steel cords having a specific tensile breaking strength, and the arrangement density of the steel cords at the shoulder 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 layers arranged at both ends thereof is limited to a predetermined amount.

[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, conventional front wheel tires using spiral belts may have insufficient braking performance when the motorcycle is traveling straight ahead. This is because a phenomenon called buckling occurs when the ground contact pressure decreases during braking.

[0009] In contrast, buckling can be improved to a certain extent by reducing the arrangement density of the cords of the spiral belt in the center portion by using a technique of locally reducing the arrangement density in the tire width direction as disclosed in Patent Document 1. However, reducing the arrangement density of the cords will lead to a decrease in durability and rigidity, so buckling deformation cannot be significantly reduced with this technique.

[0010] Therefore, an object of the present invention is to provide a motorcycle tire that suppresses the occurrence of buckling when the brakes are applied during straight-ahead driving and improves braking performance.

[0011] Solutions for solving problems

[0012] As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by limiting the elongation of a belt cord used in a spiral belt of a front wheel 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 the front 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 of 0.3% to 0.85% 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 23 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 110 mm to 150 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 the occurrence of buckling when the brakes are applied during straight-ahead driving and improves the braking 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 tire for the front wheel of 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 tire for a two-wheeled vehicle 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 50N is applied is 0.3% to 0.85%. In the tire of the present invention, by using such a belt cord with high elasticity, the occurrence of buckling can be suppressed. Therefore, in the tire of the present invention, sufficient braking force can be obtained. In addition, according to the present invention, the durability and rigidity will not be reduced as in the case where the arrangement density of the cord is reduced in the center.

[0029] 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 3The 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.

[0030] In the present invention, the belt cord used as the spiral belt 2 needs to have an elongation of 0.3% to 0.85%, preferably 0.4% to 0.7% when a load of 50 N is applied to the belt cord taken out of the tire. If the elongation is less than 0.3%, the occurrence of buckling cannot be suppressed, and if the elongation is greater than 0.85%, the rigidity decreases, so the desired effect of the present invention cannot be obtained.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 .

[0035] 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.

[0036] 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.

[0037] In the present invention, the arrangement density of the belt cords in the spiral belt 2 is preferably 10 to 23 cords / 25 mm, more preferably 11 to 21 cords / 25 mm. If the arrangement density of the belt cords is too small, durability and rigidity may be insufficient.

[0038] 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.

[0039] 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.

[0040] The spiral belt 2 can be configured with at least one, or more than two. In the example shown in the figure, one spiral belt 2 is configured. In addition, the belt width of the spiral belt measured along the tire surface is preferably 110 mm to 150 mm, and more preferably 120 mm to 145 mm. By setting the belt width to such a width, the effect of the present invention can be more appropriately obtained.

[0041] Although not shown in the figure, in the present invention, two or more inclined belt layers may be arranged in a manner that the cord direction is interlaced between layers in addition to the spiral belt 2. As the reinforcing material constituting the inclined belt layer, 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.

[0042] 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.

[0043] The tire 10 shown in the figure can be applied to any tire of a radial structure or a bias structure.

[0044] Description of Reference Numerals

[0045] 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 the front 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 of 0.3% to 0.85% 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 23 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 110 mm to 150 mm.

Images