Motorcycle tires

Abstract

To provide a tire for a motorcycle which improves transient characteristics and a turning performance.SOLUTION: A tire 1 for a motorcycle has a breaker layer 7 on a tread part 2. The breaker layer 7 is composed of breaker plies 7p in which a plurality of breaker cords is arrayed. Each of the breaker cords has an angle relative to a tire circumferential direction of a crown region Cr, and an angle relative to a tire circumferential direction at a position separated from ends 7e of the breaker plies to inside in a tire axial direction by 5 mm. The breaker cords are gradually increased to a position angle separated to inside in a tire axial direction from the crown region angle by 5 mm, and its change rate is 15% or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire for a motorcycle. [Background technology]

[0002] Patent Document 1 below describes a motorcycle tire having a tread portion. The tread portion includes a center region, a shoulder region, and a middle region. In this motorcycle tire, the modulus of each rubber composition in the center region, the shoulder region, and the middle region is specified. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4566903 Summary of the Invention [Problem to be solved by the invention]

[0004] In motorcycle tires as described above, differences in rigidity occur at the boundaries between the regions of the tread portion, and so there is room for improvement in the transient characteristics when transitioning from straight traveling to cornering and when transitioning from cornering to straight traveling.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a motorcycle tire capable of improving transient characteristics and cornering performance. [Means for solving the problem]

[0006] The present invention provides a motorcycle tire having a tread portion, the tire including a carcass and a breaker layer disposed on the radial outside of the carcass and inside the tread portion, the tread portion including a pair of shoulder regions located on both axially outer sides of the tire when the tread developed width is divided into five equal parts, a pair of middle regions adjacent to the axially inner side of the pair of shoulder regions, and a crown region sandwiched between the pair of middle regions, the breaker layer being composed of a breaker ply in which a plurality of breaker cords are arranged, a pair of ends of the breaker ply being located in the pair of shoulder regions, respectively, the plurality of breaker cords having an angle θc with respect to the tire circumferential direction at a position Pc of an end of the crown region and an angle θs with respect to the tire circumferential direction at a position Ps spaced 5 mm axially inward from the end of the breaker ply on each side of the tire equator, the angle of the plurality of breaker cords gradually increasing from the angle θc to the angle θs, and the rate of change ((θs-θc) / θc) is 15% or more.

[0007] In the motorcycle tire according to the present invention, it is preferable that the tread portion has a bandless structure in which a tread rubber is disposed on the outer side of the breaker layer in the tire radial direction so as to be in direct contact with the breaker layer.

[0008] In the motorcycle tire according to the present invention, the rate of change ((θs−θc) / θc) is preferably 70% or less.

[0009] In the motorcycle tire according to the present invention, the rate of change ((θs−θc) / θc) is preferably 50% or less.

[0010] In the motorcycle tire according to the present invention, the rate of change ((θs−θc) / θc) is preferably 30% or more.

[0011] In the motorcycle tire according to the present invention, it is preferable that ends, which is the number of the breaker cords in the breaker ply per 50 mm width in a direction perpendicular to the breaker cords, decreases from the position Pc toward the outside in the tire axial direction.

[0012] In the motorcycle tire according to the present invention, it is preferable that the ends are 30 to 50 at the position Pc.

[0013] In the motorcycle tire according to the present invention, it is preferable that the end is 35 to 45 at the position Pc.

[0014] In the motorcycle tire according to the present invention, the breaker cord is preferably an organic fiber cord or a steel cord.

[0015] The motorcycle tire according to the present invention is preferably for use on a front wheel. Effect of the Invention

[0016] By employing the above-described configuration, the present invention can improve transient characteristics and cornering performance. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing one embodiment of a motorcycle tire of the present invention. [Diagram 2] FIG. 2 is a conceptual diagram showing the arrangement of breaker cords laid out on a plane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a tire meridian cross-sectional view of a motorcycle tire (hereinafter, sometimes simply referred to as "tire") 1 in a normal state, showing one embodiment of the present invention. The tire 1 of this embodiment is suitably used for on-road driving on dry asphalt roads, for example. However, the tire 1 of the present invention is not limited to such a usage mode.

[0019] The "normal state" refers to a state in which the tire 1 is mounted on a normal rim (not shown), inflated to normal internal pressure, and unloaded. Unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state.

[0020] A "genuine rim" is a rim that is defined for each tire by a standard system including the standard on which tire 1 is based, such as a standard rim in the case of JATMA, a "Design Rim" in the case of TRA, and a "Measuring Rim" in the case of ETRTO.

[0021] "Normal internal pressure" refers to the air pressure set 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 "INFLATION PRESSURE" in the case of ETRTO.

[0022] As shown in FIG. 1, a tread portion 2 of a tire 1 of this embodiment has an outer surface 2a that is curved in a convex arc shape radially outward in a tire meridian cross section.

[0023] The tread portion 2 includes a pair of shoulder regions Sh, a pair of middle regions Mi, and a crown region Cr when the tread developed width TWe is divided into five equal parts. The shoulder regions Sh are located on both outermost sides in the axial direction of the tire. The middle region Mi is adjacent to the shoulder regions Sh on the inner side in the axial direction of the tire. The crown region Cr is sandwiched between the pair of middle regions Mi. The tread developed width TWe is the axial distance between the tread ends Te when the tread portion 2 is developed on a plane.

[0024] The tire 1 of this embodiment includes a carcass 6 and a breaker layer 7 disposed on the outer side of the carcass 6 in the tire radial direction and inside the tread portion 2. The tire 1 also includes, for example, a tread rubber 10 disposed on the outer side of the breaker layer 7 in the tire radial direction.

[0025] The carcass 6 is formed of one or more carcass plies 6A, 6B in this embodiment, two carcass plies 6A, 6B having carcass cords 6c (shown in FIG. 2) arranged at an angle θ1 of, for example, 75 to 90° with respect to the tire circumferential direction. The carcass cords 6c are preferably, for example, organic fiber cords or steel cords.

[0026] The breaker layer 7 is formed as a breaker ply 7p in which a plurality of breaker cords 7c (shown in FIG. 2) are arranged. The inclination of the breaker cords 7c has a large effect on the rigidity of the tread portion 2. That is, when the breaker cords 7c are inclined at a small angle with respect to the tire circumferential direction, the rigidity of the tread portion 2 in the tire circumferential direction is large. On the other hand, when the breaker cords 7c are inclined at a large angle with respect to the tire circumferential direction, the rigidity of the tread portion 2 in the tire axial direction is large. A pair of end portions 7e of the breaker ply 7p are located in a pair of shoulder regions Sh, respectively.

[0027] FIG. 2 is a conceptual diagram showing the arrangement of the breaker cords 7c, developed on a plane. As shown in FIG. 2, the breaker cords 7c have an angle θc with respect to the tire circumferential direction at position Pc and an angle θs with respect to the tire circumferential direction at position Ps on each side of the tire equator C. Position Pc is the position of the end of the crown region Cr. Position Ps is a position 5 mm away from the end 7e of the breaker ply 7p toward the inside in the tire axial direction. Position Ps is a position where a relatively large ground pressure (load) acts during cornering with a large bank angle (hereinafter referred to as full bank running). Position Pc is a position where a relatively large ground pressure (load) acts during cornering with a bank angle between full bank running and straight running (hereinafter referred to as intermediate bank running). In addition, in a motorcycle, braking becomes smaller from intermediate bank running to full bank running, and therefore the load becomes smaller.

[0028] The angle of each breaker cord 7c gradually increases from the angle θc to the angle θs. As a result, the rigidity of the tread portion 2 in the tire circumferential direction gradually decreases from the position Pc to the position Ps, and therefore, in the motorcycle tire 1 of this embodiment, the transient characteristics from mid-bank running to full-bank running are improved.

[0029] Furthermore, the multiple breaker cords 7c have a rate of change ((θs-θc) / θc) between the angles θc and θs of 15% or more. This increases cornering power from position Pc to position Ps, improving cornering performance from mid-bank driving to full-bank driving. Therefore, the tire 1 of this embodiment has excellent transient characteristics and cornering performance. To further improve cornering performance from mid-bank driving to full-bank driving, it is desirable for the rate of change ((θs-θc) / θc) to be 30% or more.

[0030] If the rate of change ((θs-θc) / θc) becomes too large, the change in cornering power becomes too large, which may deteriorate the turning performance. Therefore, the rate of change ((θs-θc) / θc) is preferably 70% or less, and more preferably 50% or less.

[0031] Although not particularly limited, the angle θc is desirably 10 degrees or more, more desirably 15 degrees or more, desirably 50 degrees or less, more desirably 40 degrees or less, even more desirably 30 degrees or less, and even more desirably 20 degrees or less.

[0032] In this embodiment, the angle θ2 of each breaker cord 7c with respect to the tire circumferential direction gradually increases from the tire equator C to the position Pc. This improves the transient characteristics from straight running to middle bank running. Although not particularly limited, the angle θa of the breaker cord 7c at the tire equator C is preferably 10 degrees or more, more preferably 12 degrees or more, more preferably 40 degrees or less, even more preferably 30 degrees or less, and even more preferably 18 degrees or less. Note that the angle θ2 of each breaker cord 7c with respect to the tire circumferential direction gradually increases, for example, from the position Ps to the outer end 7E in the tire axial direction.

[0033] The ends E, which is the number of breaker cords 7c per 50 mm width in the direction perpendicular to the breaker cords 7c in the breaker ply 7p, desirably decreases from position Pc toward the outer side in the tire axial direction. This reduces the rigidity of the tread portion 2 from position Pc toward the outer side in the tire axial direction, and more effectively improves the transient characteristics from mid-bank running to running with a large bank angle. From this perspective, it is desirable for the ends E to decrease continuously from position Pc to position Ps. In this specification, the ends E of the breaker ply 7p at position Pc is referred to as "ends Ec."

[0034] The end Ec is preferably 30 to 50. Since the end Ec is 30 or more, the rigidity of the tread portion 2 is ensured and the cornering performance is maintained at a high level. Since the end Ec is 50 or less, an excessive increase in the rigidity of the tread portion 2 is suppressed and the ground contact feeling is maintained, thereby improving the transient characteristics. From this viewpoint, the end Ec is more preferably 35 or more, and even more preferably 45 or less.

[0035] In this embodiment, the end E gradually decreases from the tire equator C to the position Pc. This improves the transient characteristics when traveling from a straight line to a middle bank.

[0036] The breaker cord 7c is preferably an organic fiber cord or a steel cord. Such a breaker cord 7c maintains the rigidity of the breaker layer 7 and improves the turning performance. As the organic fiber cord, for example, polyester, nylon, rayon, aramid, etc. are preferably used.

[0037] 1, in this embodiment, the breaker layer 7 is formed of two breaker plies 7A and 7B overlapped on the inside and outside in the tire radial direction. In this embodiment, the inner breaker ply 7A has a smaller developed width than the outer breaker ply 7B. The developed width Wa between both end portions 7e of the outer breaker ply 7B is preferably 85% or more and 95% or less of the tread developed width TWe.

[0038] In this embodiment, the breaker cord 7c of both the inner breaker ply 7A and the outer breaker ply 7B gradually increases from the angle θc to the angle θs, and the rate of change ((θs-θc) / θc) is 15% or more. Note that the present invention is not limited to such an embodiment, and for example, the breaker layer 7 may be composed of one breaker ply 7p. Also, when the breaker layer 7 is composed of two breaker plies 7A and 7B, the breaker cord 7c of one of the breaker plies 7p may gradually increase from the angle θc to the angle θs, and the rate of change ((θs-θc) / θc) may be 15% or more.

[0039] The tread portion 2 of this embodiment has a bandless structure in which the tread rubber 10 is disposed on the outer side of the breaker layer 7 in the tire radial direction so as to be in direct contact with the breaker layer 7. In other words, the tread portion 2 of this embodiment does not have a band layer formed of a band ply having cords arranged at an angle of less than 15 degrees with respect to the tire circumferential direction. Such a tread portion 2 has excellent transient characteristics with excessive increase in rigidity suppressed.

[0040] Such a tire 1 is preferably applied to, for example, the front wheel. When a motorcycle turns, a large load is applied due to braking from straight ahead to the middle bank, and the load decreases as the brake is released from the middle bank to the full bank. The load acting on this tire 1 is larger on the front wheel than on the rear wheel. For this reason, applying the tire 1 of this embodiment to the front wheel enables stable cornering.

[0041] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, and can be modified and carried out in various forms. EXAMPLES

[0042] Motorcycle tires having the basic structure shown in Fig. 1 were prototyped. The transient characteristics and cornering performance of each prototype tire were tested. The common specifications and test methods for each prototype tire are as follows:

[0043] <Transient characteristics / turning performance> Each test tire was mounted on the front wheel of a motorcycle (engine displacement 1000cc) under the conditions listed below. A commercially available tire was mounted on the rear wheel under the conditions listed below. A test rider then drove the vehicle on a test course with a dry asphalt road surface, and evaluated each performance from mid-bank to full-bank by the test rider's senses. The results are shown on a 10-point scale, with 10 being the maximum score. The higher the value for each performance, the better it is. Test tire specifications (size, rim, internal pressure): 120 / 70ZR17, 17×3.5MT, 200kPa Rear tire specifications (size, rim, internal pressure): 180 / 55R17, 17×5.5MT, 200kPa

[0044] The test results are shown in Table 1.

[0045] [Table 1]

[0046] As a result of the tests, it is understood that the tires of the examples are superior in transient characteristics and cornering performance to the tires of the comparative examples.

[0047] 1. Motorcycle tires 2 Tread section 7 Breaker Layer 7p Breaker ply 7c Breaker Code 7e end Cr Crown region

Claims

1. A motorcycle tire having a tread portion, A carcass and a breaker layer disposed on an outer side of the carcass in the tire radial direction and inside the tread portion, The tread portion includes, when a tread developed width is divided into five equal parts, a pair of shoulder regions located on both axially outer sides of the tire, a pair of middle regions adjacent to the pair of shoulder regions on the axially inner sides of the tire, and a crown region sandwiched between the pair of middle regions, The breaker layer is made of a breaker ply in which a plurality of breaker cords are arranged, A pair of ends of the breaker ply are located in the pair of shoulder regions, respectively, the plurality of breaker cords have, on each side of the tire equator, an angle θc with respect to the tire circumferential direction at a position Pc of an end of the crown region, and an angle θs with respect to the tire circumferential direction at a position Ps spaced 5 mm axially inward from the end of the breaker ply, The angle of the plurality of breaker cords gradually increases from the angle θc to the angle θs, and the rate of change ((θs-θc) / θc) is 32% to 62%. Tires for motorcycles.

2. 2. The motorcycle tire according to claim 1, wherein the tread portion has a bandless structure in which a tread rubber is disposed on an outer side of the breaker layer in the tire radial direction so as to be in direct contact with the breaker layer.

3. The motorcycle tire according to claim 1 or 2, wherein the angle θc is 10 to 20 degrees.

4. A motorcycle tire as described in any one of claims 1 to 3, wherein the angle θa of the breaker cord at the tire equator position is 10 to 18 degrees.

5. The motorcycle tire according to any one of claims 1 to 4, wherein the rate of change ((θs-θc) / θc) is 47% to 62%.

6. The motorcycle tire according to claim 1 , wherein ends, which is the number of the breaker cords in the breaker ply per 50 mm width in a direction perpendicular to the breaker cords, decreases from the position Pc toward an outer side in the tire axial direction.

7. The motorcycle tire according to claim 6, wherein the ends are 30 to 50 at the position Pc.

8. The motorcycle tire according to claim 7, wherein the ends are 35 to 45 at the position Pc.

9. The motorcycle tire according to claim 1 , wherein the breaker cord is an organic fiber cord or a steel cord.

10. The motorcycle tire according to any one of claims 1 to 9, which is for a front wheel.

11. The motorcycle tire of claim 5, wherein the rate of change ((θs-θc) / θc) is 50% or less.

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