JP4851244B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire mainly used for a motorcycle.

  As the speed of vehicles increases, radial tires are used for tires mounted on motorcycles. This tire includes a belt made of a belt ply on the outer side in the radial direction of the carcass. The belt cord of the belt ply is inclined with respect to the circumferential direction. Such a belt structure is referred to as a cut (CUT) structure. This tire is excellent in turning performance.

A tire excellent in straight running performance and turning running performance is disclosed in Japanese Patent Laid-Open No. 5-178007. In this tire, a ply piece formed by spiral winding of a belt-like ply is disposed in the center region of the tread, and two cut plies are disposed in a superimposed manner in the shoulder region.
JP-A-5-178007

  In motorcycles, the performance of vehicles has been significantly improved. For this reason, the tire mounted on this vehicle is also required to further improve the high-speed running performance.

  A tire having a belt ply in which the belt cord is inclined with respect to the circumferential direction has a problem that sufficient straight running stability cannot be obtained during high-speed running.

  There is a tire provided with a belt ply in which the belt cord is spirally wound substantially along the circumferential direction. This tire is excellent in straight running stability during high speed running. On the other hand, with this tire, there is a problem that when the motorcycle is turned with the motorcycle tilted inward, the tire has insufficient rigidity and a sufficient camber thrust cannot be obtained. This tire is inferior in turning performance.

  An object of the present invention is to provide a pneumatic tire for a motorcycle that is excellent in straight running stability and turning performance.

  The pneumatic tire for a motorcycle according to the present invention includes a tread whose outer surface forms a tread surface, and a belt positioned on the inner side in the radial direction of the tread. This belt includes a center ply located in the center and a pair of side plies that are spaced apart in the axial direction. The center ply includes a center cord spirally wound substantially along the circumferential direction. The side ply includes a side cord. The absolute value of the angle formed by the side cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The side ply is folded back on the outside in the axial direction. The side ply includes a wide portion and a narrow portion whose axial width is narrower than the wide portion. A part of the center ply is laminated with the wide portion. The ratio of the axial width of the belt to the tread width is 90% or more and 95% or less. The ratio of the axial width of the center ply to the tread width is 65% or more and 85% or less. The ratio of the axial distance of the inner ends of the wide portions located on the left and right to the tread width is 40% or more and 60% or less.

  Preferably, in the tire, the narrow portion is located on the outer side in the axial direction of the center ply.

  The tire according to the present invention includes a center cord in which a center ply located at the center is substantially spirally wound in the circumferential direction. This tire is excellent in straight running stability during high speed running. The side ply is folded back on the outer side in the axial direction, and includes a side cord disposed to be inclined with respect to the circumferential direction. This side ply contributes to the grip force during turning. Since sufficient camber thrust is generated during turning, this tire is excellent in turning performance. In a tire including such a side ply, the end of the side cord is not disposed at the outer end of the belt. In this tire, damage due to repeated strain at the outer end of the belt is suppressed. This tire is also excellent in durability.

  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 showing a part of a pneumatic tire 2 according to an embodiment of the present invention. In FIG. 1, the vertical direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. The tire 2 has a substantially left-right symmetric shape centered on a one-dot chain line CL in FIG. This alternate long and short dash line CL represents the equator plane of the tire 2. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, an inner liner 14, and a chafer 16. The tire 2 is a tubeless type pneumatic tire.

  The tread 4 is made of a crosslinked rubber and has a shape protruding outward in the radial direction. The outer surface of the tread 4 forms a tread surface 18 that contacts the road surface. In addition, a groove may be cut in the tread surface 18 to form a tread pattern.

  The sidewall 6 extends from the end 20 of the tread 4 substantially inward in the radial direction. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, the sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 extends from the sidewall 6 substantially inward in the radial direction. The bead 8 includes a core 22 and an apex 24 that extends radially outward from the core 22. The core 22 has a ring shape and includes a plurality of non-stretchable wires (typically steel wires). The apex 24 has a tapered shape that tapers outward in the radial direction, and is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 26. The carcass ply 26 is bridged between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. The carcass ply 26 is wound around the core 22 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 26 includes a carcass cord and a topping rubber. The absolute value of the angle formed by the carcass cord with respect to the equator plane is usually 75 ° to 90 °. In other words, the tire 2 is a radial tire. The carcass cord is usually made of an organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 14 is joined to the inner peripheral surface of the carcass 10. The inner liner 14 is made of a crosslinked rubber. For the inner liner 14, a rubber having a low air permeability is used. The inner liner 14 plays a role of maintaining the internal pressure of the tire 2.

  The chafer 16 is located in the vicinity of the bead 8. When the tire 2 is incorporated into the rim, the chafer 16 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected. The chafer 16 is usually made of a cloth and a rubber impregnated in the cloth. A chafer 16 made of a single rubber may be used.

  The belt 12 is located on the inner side in the radial direction of the tread 4. The belt 12 is positioned on the outer side in the radial direction of the carcass 10 and is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes a center ply 28 located at the center and a pair of side plies 30.

  The center ply 28 is obtained by winding a long band in a spiral shape. Although not shown in the figure, this band is composed of one or more center cords extending in the longitudinal direction and a topping rubber. In other words, the center ply 28 includes a center cord spirally wound substantially along the circumferential direction. The angle formed with respect to the circumferential direction of the center cord is 5 ° or less, particularly 2 ° or less. The center ply 28 is a so-called “jointless belt ply (JLB ply)”. In the present invention, the direction in which the absolute value of the angle formed with respect to the circumferential direction is 5.0 ° or less is the “substantially circumferential direction”.

  The side ply 30 is disposed in the vicinity of the shoulder 32. The left and right side plies 30 are separated in the axial direction. Although not shown, the side ply 30 includes a side cord and a topping rubber. This side cord is inclined with respect to the circumferential direction. The absolute value of the angle formed by the side cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. In the tire 2, the angle formed by the side cord of one side ply 30 with respect to the circumferential direction is opposite to the angle formed by the side cord of the other side ply 30 with respect to the circumferential direction. The side ply 30 is a so-called “cut ply”. Examples of the side cord include nylon fiber, aramid fiber, polyethylene naphthalate fiber, polyester fiber, rayon fiber, glass fiber, carbon fiber, and steel.

  The side ply 30 is folded back on the outside in the axial direction. The side ply 30 includes a wide portion 34 and a narrow portion 36. The wide portion 34 and the narrow portion 36 extend substantially inward in the axial direction from the position where the side ply 30 is folded back. In the tire 2, in one side ply 30, the angle formed by the side cord of the wide portion 34 with respect to the circumferential direction is opposite to the angle formed by the side cord of the narrow portion 36 with respect to the circumferential direction. Such a structure of the side ply 30 is referred to as a “fold structure”.

  In the tire 2, the axial width of the narrow portion 36 is narrower than the axial width of the wide portion 34. As shown in FIG. 1, a part of the wide portion 34 is stacked on the narrow portion 36. The narrow portion 36 extends outward from the outer end 38 of the center ply 28 in the axial direction. The inner end 40 of the narrow portion 36 is connected to the outer end 38 of the center ply 28. The inner end 42 of the wide portion 34 is located inside the outer end 38 of the center ply 28 in the axial direction. As shown in FIG. 1, in the tire 2, a part of the center ply 28 is part of the wide portion 34 in the range from the inner end 40 of the narrow portion 36 to the inner end 42 of the wide portion 34. It is laminated on the outside in the radial direction. In the present specification, a region where the center ply 28 is laminated on the wide portion 34 is referred to as an intermediate region 44. In the intermediate region 44, the JLB ply and the cut ply coexist.

  In the tire 2, the center cord spirally wound substantially along the circumferential direction sufficiently restrains the carcass 10. The tire 2 is excellent in straight running stability during high speed running. Examples of the center cord include nylon fiber, aramid fiber, polyethylene naphthalate fiber, polyester fiber, rayon fiber, glass fiber, carbon fiber, and steel. The high elastic modulus and high strength cord contributes to the straight running stability of the tire 2. From this viewpoint, as the center cord, an aramid fiber and steel are particularly preferable.

  As described above, the side ply 30 is folded back on the outer side in the axial direction, and includes a side cord that is inclined with respect to the circumferential direction. The side ply 30 increases the rigidity of the shoulder 32 of the tire 2 and contributes to the grip force during turning. In the tire 2, sufficient camber thrust is generated during turning. The tire 2 is excellent in turning performance. In the tire 2, the end of the side cord is not disposed at the outer end 46 of the belt 12. Therefore, damage due to repeated strain at the outer end 46 of the belt 12 is suppressed. The tire 2 is excellent in durability.

  In the tire 2, the center 48 of the tread 4 is mainly grounded when traveling straight. When turning, the rider tilts the motorcycle inward. Therefore, the shoulder 32 of the tread 4 is mainly grounded during turning (particularly full bank). At the time of transition from straight traveling to turning traveling, the ground contact portion first transitions from the center 48 to the intermediate region 44, and further transitions from the intermediate region 44 to the shoulder 32. As described above, the JLB ply and the cut ply coexist in the intermediate region 44. For this reason, in the transition from the center 48 to the intermediate region 44, the characteristics do not change abruptly. Further, the characteristics do not change abruptly even when the transition from the intermediate region 44 to the shoulder 32 occurs. Such a tire 2 can smoothly transition from straight running to turning. The tire 2 can smoothly transition from turning to straight running. The tire 2 is also excellent in operability.

  In FIG. 1, a double arrow line WT is an axial distance between the ends 20 of the tread 4 located on the left and right. This axial distance WT is the tread width. A double arrow line WB is the axial width of the belt 12. A double arrow line WH is an axial width of the center ply 28. A double arrow line WF is an axial distance of the inner end 42 of the wide portion 34 located on the left and right. A double arrow line WL represents an axial distance between the inner end 40 of the narrow portion 36 and the outer end 46 of the belt 12. This axial distance WL represents the overlapping width of the narrow portion 36 and the wide portion 34. A double arrow line WS is an axial distance between the inner end 42 of the wide portion 34 and the outer end 38 of the center ply 28. This axial distance WS is the axial width of the intermediate region 44.

  In the tire 2, the ratio (WB / WT × 100) of the axial width WB of the belt 12 to the tread width WT is 90% or more and 95% or less. By setting this ratio to 90% or more, the belt 12 effectively increases the rigidity of the tire 2. Thereby, turning performance can be maintained. In this respect, the ratio is more preferably equal to or greater than 92%, and particularly preferably equal to or less than 94%. By setting this ratio to 95% or less, excessive rigidity of the tire 2 can be suppressed. Such tire 2 can maintain the riding comfort.

  In the tire 2, the ratio (WH / WT × 100) of the axial width WH of the center ply 28 to the tread width WT is 65% or more and 85% or less. By setting this ratio to 65% or more, the center ply 28 effectively restrains the carcass 10. The tire 2 is sufficiently in contact with the road surface when traveling straight ahead. The tire 2 is excellent in straight running stability. From this viewpoint, the ratio is more preferably 67% or more, and particularly preferably 70% or more. By setting this ratio to 85% or less, the side ply 30 effectively increases the rigidity of the shoulder 32 of the tread 4. In the tire 2, sufficient camber thrust is generated during turning. The tire 2 is excellent in turning performance. In this respect, the ratio is more preferably equal to or less than 80%, and particularly preferably equal to or less than 75%.

  In the tire 2, the ratio (WF / WT × 100) of the axial distance WF of the inner end 42 of the wide portion 34 positioned on the left and right to the tread width WT is 40% or more and 60% or less. By setting this ratio to 40% or more, excessive rigidity of the tire 2 can be suppressed. In the tire 2, riding comfort can be maintained. In this respect, the ratio is more preferably equal to or greater than 45%, and particularly preferably equal to or greater than 50%. By setting this ratio to 60% or less, the contribution of the side ply 30 to the grip force of the tire 2 can be maintained. In the tire 2, turning performance can be maintained. In this respect, the ratio is more preferably equal to or less than 57%, and particularly preferably equal to or less than 55%.

  In the tire 2, the ratio (WL / WT × 100) of the overlapping width WL between the narrow portion 36 and the wide portion 34 to the tread width WT is preferably 10% or more and 30% or less. By setting this ratio to 10% or more, the side ply 30 effectively increases the rigidity of the shoulder 32 of the tread 4. In the tire 2, sufficient camber thrust is generated during turning. The tire 2 is excellent in turning performance. From this viewpoint, the ratio is more preferably 15% or more, and particularly preferably 20% or more. By setting this ratio to 30% or less, an excessive rigidity of the tire 2 can be suppressed. Such tire 2 can maintain the riding comfort. In this respect, the ratio is more preferably equal to or less than 27%, and particularly preferably equal to or less than 25%.

  As described above, the presence of the intermediate region 44 suppresses a sudden change in characteristics between the center 48 and the shoulder 32 of the tread 4. In the tire 2, the ratio (WS) of the axial width WS of the intermediate region 44 to the tread width WT is maintained from the viewpoint that the transition from the straight traveling to the turning traveling and the smooth transition from the turning traveling to the straight traveling are maintained. / WT × 100) is more preferably 15% or more, further preferably 20% or more, and particularly preferably 25% or more. This ratio is more preferably 35% or less, still more preferably 33% or less, and particularly preferably 30% or less.

  The size and angle 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.

  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 pneumatic tire for a motorcycle of Example 1 having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained. The tire size is 185 / 55ZR17. The center cord of the center ply is an aramid fiber. The angle formed by the center cord with respect to the circumferential direction is substantially 0 °. The side cord of the side ply is nylon fiber. The angle formed by the side cord with respect to the circumferential direction is 50 °. The ratio of the belt axial width WB to the tread width WT (WB / WT × 100) is 95%. The ratio (WH / WT × 100) of the axial width WH of the center ply to the tread width WT is 75%. The ratio (WF / WT × 100) of the axial distance WF between the inner ends of the wide portions positioned on the left and right to the tread width WT is 50%.

[Comparative Examples 3 and 4 and Examples 4 and 5]
Tires were obtained in the same manner as in Example 1 except that the ratio (WH / WT × 100) was as shown in Table 1 below.

[Comparative Examples 2 and 5 and Examples 3 and 6]
A tire was obtained in the same manner as in Example 1 except that the ratio (WF / WT × 100) was as shown in Table 1 below.

[Comparative Example 1 and Example 2]
A tire was obtained in the same manner as in Example 1 except that the ratio (WB / WT × 100) was as shown in Table 1 below.

[Comparative Example 6]
Comparative Example 6 is a commercially available conventional tire. In this tire, the belt is composed of two belt plies. The two belt plies are laminated in the radial direction. The angle formed by the belt cord of the belt ply with respect to the circumferential direction is 20 °. This belt cord is a nylon fiber. This belt ply is a cut ply.

[Comparative Example 7]
Comparative Example 7 is a conventional tire that is commercially available. In this tire, the belt is composed of one belt ply. The belt ply includes a belt cord spirally wound substantially along the circumferential direction. The angle formed by the belt cord with respect to the circumferential direction is 0 °. This belt cord is an aramid fiber. This belt ply is a JLB ply.

[Real car evaluation]
A prototype tire was mounted on the rear wheel of a commercially available motorcycle (4 cycles) having a displacement of 600 cm ³ . The rim was MT 5.50 × 17, and the air pressure inside the tire was 290 kPa. The front wheels are equipped with commercially available conventional tires. The tire size of this front wheel is 120 / 70ZR17. The rim is MT3.50 × 17, and the tire has an internal air pressure of 250 kPa. Sensory evaluation by riders was conducted on a circuit course composed of dry asphalt roads. Turning at a speed of 100 km / h to 150 km / h and straight running at a maximum vehicle speed (about 280 km / h) from 250 km / h were performed, and the straight running stability and the grip force during turning were evaluated. The results are shown as index values in Table 1 below. A larger index value indicates better performance.

  As shown in Table 1, the tires of the examples are excellent in straight running stability and turning performance. From this evaluation result, the superiority of the present invention is clear.

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

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention.

Explanation of symbols

2 ... tyre 4 ... tread 6 ... side wall 8 ... bead 10 ... carcass 12 ... belt 14 ... inner liner 16 ... chafer 18 ... tread surface 20 ... End 22 ... Core 24 ... Apex 26 ... Carcass ply 28 ... Center ply 30 ... Side ply 32 ... Shoulder 34 ... Wide part 36 ... Narrow Part 38, 46 ... Outer end 40, 42 ... Inner end 44 ... Middle region 48 ... Center

Claims (1)

A tread whose outer surface forms a tread surface,
It is equipped with a belt located on the inner side in the radial direction of this tread,
The belt includes a center ply located in the center and a pair of side plies that are spaced apart in the axial direction.
The center ply includes a center cord spirally wound substantially along the circumferential direction,
This side ply has a side cord,
The absolute value of the angle formed by the side cord with respect to the circumferential direction is 10 ° to 80 °,
This side ply is folded back on the outside in the axial direction,
This side ply is composed of a wide part and a narrow part whose axial width is narrower than this wide part,
A part of this center ply is laminated with this wide part,
The ratio of the axial width of the belt to the tread width is 90% or more and 95% or less,
The ratio of the axial width of the center ply to the tread width is 65% or more and 85% or less,
The inner end axial distance of the wide portion positioned on the right and left, the ratio of the tread width state, and are 60% less 40%,
The narrow portion, the pneumatic tire for a motorcycle that is located axially outwardly of the center ply.

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