JP2008143327A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire 2 for a motorcycle with excellent performances. <P>SOLUTION: The tire 2 is provided with a tread 4 and a belt 14. The tread 4 comprises one center region 22 and a pair of shoulder regions 24. During straight traveling, the center region 22 is mainly grounded. During turning, the shoulder regions 24 are mainly grounded. Each of the center region 22 and the shoulder regions 24 comprises a cross-linked rubber composition. The hardness Hc of the rubber composition in the center region 22 is set small, and the hardness Hs of the rubber composition in the shoulder region 24 is set large. A difference (Hs - Hc) between the hardness Hs and the hardness Hc is 3 or more. The belt 14 has a jointless structure. A cord of the belt 14 comprises aramid fiber or steel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire mounted on a motorcycle. In particular, the present invention relates to improvements in tire treads.

  Centrifugal force acts on the motorcycle when the motorcycle turns. For cornering, a cornering force that balances this centrifugal force is required. When turning, the rider tilts the motorcycle inward. Turning is achieved by the camber thrust generated by this inclination. For the purpose of easy turning, motorcycle tires have a tread with a small radius of curvature. When going straight, the center area of the tread is grounded. On the other hand, when turning, the shoulder region is grounded. Japanese Unexamined Patent Application Publication No. 2005-271760 discloses a tire in which the roles of the center region and the shoulder region are considered.

A belt having a so-called jointless structure is employed in recent radial tires to be mounted on a motorcycle. The belt includes a cord extending in the circumferential direction. The cord is spirally wound. The jointless belt suppresses kickback and shimmy. This tire is excellent in disturbance absorbing performance.
JP-A-2005-271760

  In a tire provided with a belt having a jointless structure, a large camber thrust is unlikely to occur. The turning performance of the tire is inferior to the turning performance of a tire provided with a belt having a bias structure. If a hard tread is used, a large camber thrust can occur. However, a hard tread hinders disturbance absorption performance.

  The turning performance is also affected by the grip performance of the tire. Low hardness tread contributes to grip performance. However, the low hardness tread is inferior in wear resistance. Furthermore, a low-tread tread impairs the stability performance when going straight.

  An object of the present invention is to provide a motorcycle tire excellent in various performances.

  A motorcycle tire according to the present invention includes a tread, a carcass having a radial structure, and a belt including a spirally wound cord. The tread includes a center region and a pair of shoulder regions positioned on the outer side in the axial direction than the center region. The center region and the shoulder region are made of a crosslinked rubber composition. The hardness Hc of the center region is different from the hardness Hs of the shoulder region. The absolute value of the difference (Hs−Hc) is 3 or more

  Preferably, the cord of the belt is made of aramid fiber or steel. In particular, a steel cord is preferable.

  Preferably, the ratio (Wc / Wt) of the half circumference Wc of the center region to the half circumference Wt of the tread is not less than 0.3 and not more than 0.7. Preferably, the ratio (Ws / Wt) of the circumference Ws of the shoulder region to the half circumference Wt of the tread is 0.3 or more and 0.7 or less.

  A tire having a hardness Hs larger than the hardness Hc is suitable for a front wheel of a motorcycle. A tire having a hardness Hc larger than the hardness Hs is suitable for a rear wheel of a motorcycle.

  The tire pair according to the present invention includes a front tire and a rear tire. Each of the front tire and the rear tire includes a tread, a carcass having a radial structure, and a belt including a spirally wound cord. The tread includes a center region and a pair of shoulder regions positioned on the outer side in the axial direction than the center region. The center region and the shoulder region are made of a crosslinked rubber composition. In the front tire, the hardness Hs of the shoulder region is larger than the hardness Hc of the center region. In the rear tire, the hardness Hc of the center region is larger than the hardness Hs of the shoulder region.

  In the motorcycle tire according to the present invention, various performances can be achieved by the jointless belt and the tread having the center region and the shoulder region.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a front tire 2 according to an embodiment of the present invention. In FIG. 1, the vertical direction is the radial direction, and the horizontal direction is the axial direction. The tire 2 has a substantially bilaterally symmetric shape with the one-dot chain line CL as the center. This alternate long and short dash line represents the equator plane. The tire 2 includes a tread 4, a wing 6, a sidewall 8, a bead 10, a carcass 12, a belt 14, an inner liner 16, and a chafer 18. The tire 2 is a tubeless type pneumatic tire. The tire 2 is attached to the front wheel of a motorcycle.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 20 that contacts the road surface. The tread 4 includes one center region 22 and a pair of shoulder regions 24. The center region 22 straddles the equator plane CL. The shoulder region 24 is located outside the center region 22 in the axial direction.

  The sidewall 8 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 8 is made of a crosslinked rubber composition. The sidewall 8 absorbs an impact from the road surface by bending. Further, the sidewall 8 prevents the carcass 12 from being damaged.

  The bead 10 extends from the sidewall 8 substantially inward in the radial direction. The bead 10 includes a core 26 and an apex 28 that extends radially outward from the core 26. The core 26 has a ring shape and includes a plurality of non-stretchable wires (typically steel wires). The apex 28 is tapered outward in the radial direction. The apex 28 is made of a crosslinked rubber composition. The apex 28 has a high hardness.

  The carcass 12 includes a first ply 30 and a second ply 32. The first ply 30 and the second ply 32 extend along the inner surfaces of the tread 4 and the sidewall 8. The first ply 30 is folded around the core 26 from the inner side to the outer side in the axial direction. By this folding, the main portion 34 and the folding portion 36 are formed in the first ply 30. The folded portion 36 is laminated on the outer surface of the main portion 34. The end 38 of the second ply 32 is in contact with the inner surface of the sidewall 8. This end 38 does not reach the bead 10.

  Although not shown, the first ply 30 and the second ply 32 are each made of a cord and a topping rubber. The absolute value of the angle formed by the cord with respect to the equator plane CL is 65 ° to 90 °. In other words, the tire 2 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 14 is located between the carcass 12 and the tread 4. The belt 14 includes a belt ply 40. Although not shown, the belt ply 40 is composed of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally. The belt 14 has a so-called jointless structure. This belt 14 suppresses kickback and shimmy. The tire 2 provided with the belt 14 is excellent in disturbance absorbing performance.

  The material of the cord of the belt 14 is steel or organic fiber. Specific examples of the organic fiber include aramid fiber, nylon fiber, polyester fiber, rayon fiber, and polyethylene naphthalate fiber. From the viewpoint of high restraining force and thus high rigidity, the preferred material of the cord is steel or aramid fiber. In particular, steel is preferred.

  The inner liner 16 is joined to the inner peripheral surface of the carcass 12. The inner liner 16 is made of a crosslinked rubber. For the inner liner 16, rubber having excellent air shielding properties is used. The inner liner 16 serves to maintain the internal pressure of the tire 2.

  The center region 22 and the shoulder region 24 are each made of a crosslinked rubber composition. The hardness Hc of the rubber composition in the center region 22 is small, and the hardness Hs of the rubber composition in the shoulder region 24 is large. In the tire 2, the center region 22 is mainly grounded when going straight. Due to the synergistic effect of the center region 22 having a small hardness and the belt 14 having a jointless structure, the tire 2 exhibits excellent disturbance absorbing performance. In the tire 2, the shoulder region 24 is mainly grounded when turning. Since the shoulder region 24 has a high hardness, a large camber thrust is generated even though the belt 14 having a jointless structure is used. In the tire 2, both disturbance absorption performance and turning performance are achieved.

  From the viewpoint of achieving both disturbance absorbing performance and turning performance, the difference between the hardness Hs and the hardness Hc (Hs−Hc) is preferably 3 or more, and more preferably 4 or more. From the viewpoint of transient characteristics, the difference (Hs−Hc) is preferably 7 or less, and more preferably 6 or less. From the viewpoint of disturbance absorbing performance, the hardness Hc is preferably 70 or less, and more preferably 68 or less. The hardness Hc is preferably 60 or more. From the viewpoint of turning performance, the hardness Hs is preferably 63 or more, and more preferably 65 or more. The hardness Hs is preferably 73 or less.

  Hardness Hc and Hs are JIS-A hardness. The hardnesses Hc and Hs are measured by pressing a type A durometer against the tire at room temperature.

  In FIG. 1, what is indicated by a double arrow Wt is the half circumference of the tread 4. The half circumference Wt is a distance from the equator CL to the tread 4 end, measured along the tread surface 20. What is indicated by a double-headed arrow Wc is the half circumference of the center region 22. The half circumference Wc is the distance from the equator CL to the end of the center region 22 measured along the tread surface 20. What is indicated by a double arrow Ws is the circumference of the shoulder region 24. The circumferential length Ws is a distance from one end of the shoulder region 24 to the other end measured along the tread surface 20. The circumferential lengths Wt, Wc and Ws are measured in a sample obtained by cutting the tire 2.

  From the viewpoint of disturbance absorbing performance when traveling straight, the ratio (Wc / Wt) is preferably 0.3 or more, and more preferably 0.4 or more. From the viewpoint of turning performance, the ratio (Wc / Wt) is preferably 0.7 or less, and more preferably 0.6 or less.

  From the viewpoint of turning performance, the ratio (Ws / Wt) is preferably 0.3 or more, and more preferably 0.4 or more. From the viewpoint of disturbance absorbing performance during straight travel, the ratio (Ws / Wt) is preferably 0.7 or less, and more preferably 0.6 or less.

  FIG. 2 is a cross-sectional view for explaining a manufacturing process of the tire 2 of FIG. In the manufacture of the tire 2, the inner liner 16, the first ply 30 and the second ply 32 are sequentially wound around a former (not shown). A ribbon 46 composed of a cord 42 and a topping rubber 44 is spirally wound on the second ply 32 to form a belt ply 40 having a jointless structure. The ribbon 46 extends substantially in the circumferential direction. A first strip 48 made of uncrosslinked rubber is wound on the belt ply 40 in a spiral shape. The first strip 48 extends substantially in the circumferential direction. The first strips 48 are sequentially stacked. When the first strip 48 has been wound, the second strip 50 made of uncrosslinked rubber is wound continuously with the first strip 48. The second strip 50 extends substantially in the circumferential direction. The second strips 50 are sequentially stacked. When the second strip 50 has been wound, the first strip 48 is further wound continuously with the second strip 50. A green tire is thus obtained. This green tire is put into a mold, and pressurized and heated. A cross-linking reaction occurs in the rubber by heating, and the tire 2 is obtained. A shoulder region 24 is obtained from the first strip 48. A center region 22 is obtained from the second strip 50. In the tire 2, since two types of strips 48 and 50 are used, the tread 4 including the center region 22 and the shoulder region 24 is easily formed. The tire 2 is easy to manufacture.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  FIG. 3 is a cross-sectional view showing a rear tire 52 according to an embodiment of the present invention. In FIG. 3, the vertical direction is the radial direction, and the horizontal direction is the axial direction. The tire 52 has a substantially bilaterally symmetric shape with the one-dot chain line CL as the center. This alternate long and short dash line represents the equator plane. The tire 52 includes a tread 54, a wing 56, a sidewall 58, a bead 60, a carcass 62, a belt 64, an inner liner 66, and a chafer 68. The tire 52 is a tubeless type pneumatic tire. The tire 52 is attached to the rear wheel of the motorcycle.

  The tread 54 has a shape protruding outward in the radial direction. The tread 54 forms a tread surface 70 that contacts the road surface. The tread 54 includes one center region 72 and a pair of shoulder regions 74. The center region 72 straddles the equator plane CL. The shoulder region 74 is located outside the center region 72 in the axial direction.

  The carcass 62 includes one carcass ply 76. The carcass ply 76 extends along the inner surfaces of the tread 54 and the sidewall 58. The carcass ply 76 is folded around the core 78 from the inner side to the outer side in the axial direction. By this folding, a main portion 80 and a folding portion 82 are formed in the carcass ply 76. The folded portion 82 is stacked on the outer surface of the main portion 80.

  Although not shown, the carcass ply 76 includes a cord and a topping rubber. The absolute value of the angle formed by the cord with respect to the equator plane CL is 65 ° to 90 °. In other words, the tire 52 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 64 is located between the carcass 62 and the tread 54. The belt 64 includes a belt ply 84. Although not shown, the belt ply 84 is made of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally. The belt 64 has a so-called jointless structure. The tire 52 including the belt 64 is excellent in stability performance when traveling straight.

  The material of the cord of the belt 64 is steel or organic fiber. Examples of preferable organic fibers include aramid fibers, nylon fibers, polyester fibers, rayon fibers, and polyethylene naphthalate fibers. From the viewpoint of high restraining force and thus high rigidity, the preferred material of the cord is steel or aramid fiber. In particular, steel is preferred.

  The configurations of the sidewalls 58, the beads 60, and the inner liner 66 of the tire 52 are the same as those of the tire 2 shown in FIG.

  The center region 72 and the shoulder region 74 are made of a crosslinked rubber composition. The hardness Hc of the rubber composition in the center region 72 is large, and the hardness Hs of the rubber composition in the shoulder region 74 is small. In the tire 52, the center region 72 is mainly grounded when going straight. Due to the synergistic effect of the center region 72 having a high hardness and the belt 64 having a jointless structure, the tire 52 exhibits excellent stability performance when traveling straight. In the tire 52, the shoulder region 74 is mainly grounded when turning. Since the hardness of the shoulder region 74 is small, excellent grip performance is exhibited during turning. This grip performance contributes to the turning performance. In the tire 52, both the stability performance during straight traveling and the turning performance are compatible.

  From the viewpoint of achieving both the straight running stability and the turning grip performance, the difference between the hardness Hc and the hardness Hs (Hc−Hs) is preferably 3 or more, and more preferably 4 or more. From the viewpoint of transient characteristics, the difference (Hc−Hs) is preferably 7 or less, and more preferably 6 or less. From the viewpoint of stability performance, the hardness Hc is preferably 63 or more, and more preferably 65 or more. The hardness Hc is preferably 73 or less. From the viewpoint of grip performance, the hardness Hs is preferably 70 or less, and more preferably 68 or less. The hardness Hs is preferably 60 or more.

  From the viewpoint of stable performance during straight traveling, the ratio (Wc / Wt) of the half circumference Wc of the center region 72 to the half circumference Wt of the tread 54 is preferably 0.3 or more, and more preferably 0.4 or more. In light of grip performance during turning, the ratio (Wc / Wt) is preferably equal to or less than 0.7, and more preferably equal to or less than 0.6.

  From the viewpoint of grip performance during turning, the ratio (Ws / Wt) of the circumferential length Ws of the shoulder region 74 to the half circumferential length Wt of the tread 54 is preferably 0.3 or more, and more preferably 0.4 or more. From the viewpoint of the stability performance during straight travel, the ratio (Ws / Wt) is preferably 0.7 or less, and more preferably 0.6 or less.

  The tread 54 is also formed by spirally winding the first strip 48 and the second strip 50 in the same manner as the tread 4 shown in FIG. The tire 52 is easy to manufacture.

  The tire pair according to the present invention includes the front tire 2 shown in FIG. 1 and the rear tire 52 shown in FIG. In a motorcycle equipped with this tire pair, when traveling straight, disturbance absorbing performance is exhibited by the front tire 2, and stability performance is exhibited by the rear tire 52. When turning, a large camber thrust is generated by the front tire 2, and excellent grip performance is exhibited by the rear tire 52. This tire pair is excellent in various performances.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A tire pair consisting of a front tire having the structure shown in FIG. 1 and a rear tire having the structure shown in FIG. 3 was obtained. The belt of the front tire has a cord made of steel. The tread of the front tire includes a center region and a pair of shoulder regions. The hardness Hc of the center region is 65, and the hardness Hs of the shoulder region is 68. In this front tire, the ratio (Wc / Wt) is 0.5, and the ratio (Ws / Wt) is 0.5. The size of the front tire is “120 / 70ZR17”. The belt of the rear tire has a cord made of steel. The rear tire tread includes a center region and a pair of shoulder regions. The hardness Hc of the center region is 68, and the hardness Hs of the shoulder region is 65. In this rear tire, the ratio (Wc / Wt) is 0.5, and the ratio (Ws / Wt) is 0.5. The size of the rear tire is “190 / 50ZR17”.

[Example 4]
A tire pair of Example 4 was obtained in the same manner as in Example 1 except that a belt cord made of an aramid fiber was used for the front tire.

[Examples 3 and 5]
In the front tire, tire pairs of Examples 3 and 5 were obtained in the same manner as in Example 1 except that the ratio (Wc / Wt) and the ratio (Ws / Wt) were as shown in Table 1 below.

[Examples 2 and 6]
A tire pair of Example 2 was obtained in the same manner as in Example 1 except that a tread composed of a single member having a hardness of 65 was formed on the front tire. A tire pair of Example 6 was obtained in the same manner as in Example 1 except that a tread composed of a single member having a hardness of 68 was formed on the front tire.

[Comparative Examples 1 and 2]
The tire pair of Comparative Example 1 was the same as Example 1 except that a tread composed of a single member having a hardness of 65 was molded on the front tire and a tread composed of a single member having a hardness of 65 was molded on the rear tire. Got. The tire pair of Comparative Example 2 was the same as Example 1 except that a tread composed of a single member having a hardness of 68 was molded on the front tire and a tread composed of a single member having a hardness of 68 was molded on the rear tire. Got.

[Example 9]
A tire pair of Example 9 was obtained in the same manner as Example 1 except that a belt cord made of an aramid fiber was used for the rear tire.

[Examples 8 and 10]
In the rear tire, tire pairs of Examples 8 and 10 were obtained in the same manner as Example 1 except that the ratio (Wc / Wt) and the ratio (Ws / Wt) were as shown in Table 2 below.

[Examples 7 and 11]
A tire pair of Example 7 was obtained in the same manner as Example 1 except that a tread composed of a single member having a hardness of 65 was formed on the rear tire. A tire pair of Example 11 was obtained in the same manner as in Example 1 except that a tread composed of a single member having a hardness of 68 was formed on the rear tire.

[sensory evaluation]
The tire pair was mounted on a motorcycle having a displacement of 1000 cc. This motorcycle was run on a racing circuit, and the rider was evaluated for turning performance and disturbance absorbing performance and stability performance when traveling straight. The results are shown in Tables 1 and 2 below as indices. The higher the number, the better.

  As shown in Tables 1 and 2, the tire pairs of the examples are excellent in various performances. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various motorcycles.

FIG. 1 is a cross-sectional view illustrating a front tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining a manufacturing process of the tire of FIG. FIG. 3 is a cross-sectional view illustrating a rear tire according to an embodiment of the present invention.

Explanation of symbols

2 ... Front tires 4, 54 ... Tread 8, 58 ... Side walls 10, 60 ... Beads 12, 62 ... Carcass 14, 64 ... Belts 16, 66 ... Inner liner 20, 70 ... Tread surface 22, 72 ... Center region 24, 74 ... Shoulder region 46 ... Ribbon 48 ... First strip 50 ... Second strip 52 ... Rear tire

Claims (7)

A tread, a carcass having a radial structure, and a belt including a spirally wound cord;
The tread includes a center region and a pair of shoulder regions positioned outside in the axial direction from the center region,
The center region and the shoulder region are made of a crosslinked rubber composition,
The hardness Hc of the center region is different from the hardness Hs of the shoulder region,
A motorcycle tire having an absolute value of a difference (Hs-Hc) of 3 or more.   The tire according to claim 1, wherein the cord is made of aramid fiber or steel.   The tire according to claim 2, wherein the cord is made of steel.   The ratio (Wc / Wt) of the center region half circumference Wc to the tread half circumference Wt is not less than 0.3 and not more than 0.7, and the ratio of the shoulder region circumference Ws to the tread half circumference Wt (Ws / The tire according to any one of claims 1 to 3, wherein Wt) is not less than 0.3 and not more than 0.7.   The tire according to any one of claims 1 to 4, wherein the hardness Hs is greater than the hardness Hc and is attached to a front wheel of a motorcycle.   The tire according to any one of claims 1 to 4, wherein the hardness Hc is larger than the hardness Hs and is attached to a rear wheel of a motorcycle. (1) A tread, a carcass having a radial structure, and a belt including a spirally wound cord,
The tread includes a center region and a pair of shoulder regions positioned outward in the axial direction from the center region.
The center region and the shoulder region are made of a crosslinked rubber composition,
A front tire having a shoulder region hardness Hs greater than a center region hardness Hc, and (2) a tread, a carcass having a radial structure, and a belt including a spirally wound cord.
The tread includes a center region and a pair of shoulder regions positioned outward in the axial direction from the center region.
The center region and the shoulder region are made of a crosslinked rubber composition,
A pair of motorcycle tires comprising a rear tire having a center region hardness Hc greater than a shoulder region hardness Hs.

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