JP2007182098A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire 2 for a motorcycle having excellent driving performance and turning performance. <P>SOLUTION: A belt 12 of a tire has a first belt ply 26 and a second belt ply 28. The first belt ply 26 comprises a first cord 30 and a topping rubber 32. The first belt ply 26 is obtained by spirally winding a ribbon consisting of one or a plurality of longitudinally extending first cords 30 and the topping rubber 32. The first cord 30 extends substantially in the circumferential direction. The second belt ply 28 comprises a second cord 34 and a topping rubber 36. The second cord 34 is substantially arc-shaped in plan view. The angle of the second cord 34 with respect to the circumferential direction is gradually reduced from the equator to the end. The angle of the second cord 34 with respect to the circumferential direction at the equator CL is substantially 90°. The angle of the second cord 34 with respect to the circumferential direction is ≥5° and ≤50°. <P>COPYRIGHT: (C)2007,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 belts.

  The motorcycle turns while facing the centrifugal force by the camber thrust generated by the inward inclination of the vehicle. From the viewpoint of turning performance, motorcycle tires are required to have high lateral rigidity.

  Conventional radial tires for motorcycles include a belt between the carcass and the tread. This belt consists of two cut plies. Each cut ply includes a cord inclined at an angle of 15 ° to 40 ° with respect to the circumferential direction. The cord of the first cut ply is inclined in the opposite direction to the equator plane with respect to the cord of the second cut ply. With this belt, lateral rigidity is imparted to the tire. A tire provided with this belt is excellent in turning performance. However, the driving performance of this tire during straight running is not sufficient.

  There is also a radial tire provided with a belt having a so-called jointless structure. The belt has a cord wound spirally and extending substantially in the circumferential direction. This belt contributes to driving performance during straight running. However, the spirally wound cord has a small contribution to the lateral rigidity. The turning performance of the tire provided with this belt is not sufficient.

Japanese Patent Application Laid-Open No. 2005-254992 discloses a belt in which the angle with respect to the circumferential direction gradually changes from the equator toward the end. This belt contributes to both driving performance and turning performance.
JP 2005-254992 A

  Recent motorcycles have high performance and can run at high speed. Especially in racing, motorcycles go straight at high speed and turn at high speed. Further improvement in driving performance and turning performance is desired. An object of the present invention is to provide a motorcycle tire excellent in driving performance and turning performance.

  A motorcycle tire according to the present invention has a tread whose outer surface forms a tread surface, a pair of sidewalls extending substantially inward in the radial direction from an end of the tread, and a radially inner side with respect to the sidewall. A pair of beads, a carcass bridged between both beads along the inside of the tread and the sidewall, and a belt laminated with the carcass on the radially inner side of the tread. The carcass includes a carcass cord having an angle with respect to the circumferential direction of 40 ° or more and 90 ° or less. The belt includes a first belt ply and a second belt ply located on the radially outer side of the first belt ply. The first belt ply includes a first cord wound spirally and extending substantially in the circumferential direction. The second belt ply includes a second cord whose angle with respect to the circumferential direction gradually decreases from the equator toward the end. The angle with respect to the circumferential direction of the second cord at the equator is substantially 90 °, and the angle with respect to the circumferential direction of the second cord at the end is not less than 5 ° and not more than 50 °.

  Preferably, the width of the first belt ply is not less than 80% and not more than 100% of the width of the tread, and the width of the second belt ply is not less than 80% and not more than 100% of the width of the first belt ply.

  In this tire, the first belt ply contributes to driving performance during straight traveling, and the second belt ply contributes to turning performance. In this tire, extremely excellent driving performance and extremely excellent turning performance are achieved.

  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 motorcycle 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 horizontal 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 symmetrical shape with the equator CL as the center. 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 tread 4 forms a tread surface 18 that contacts the road surface. A groove may be carved in the tread surface 18.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. 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 is located radially inward with respect to the sidewall 6. The bead 8 includes a core 20 and an apex 22 that extends radially outward from the core 20. The core 20 is ring-shaped and includes a plurality of non-stretchable wires (typically steel wires). The apex 22 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 24. The carcass ply 24 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 24 is wound around the core 20 from the inner side toward the outer side in the axial direction. Although not shown, the carcass ply 24 includes a cord and a topping rubber. The absolute value of the angle formed by the cord with respect to the circumferential direction is 40 ° (degree) to 90 °, particularly 75 ° to 90 °. The carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include nylon fibers, polyethylene naphthalate fibers, polyester fibers, rayon fibers, and aramid fibers. Nylon fibers and polyethylene naphthalate fibers are preferred from the viewpoint of shock absorption and steering response.

  The belt 12 is located on the radially outer side of the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes a first belt ply 26 and a second belt ply 28. The second belt ply 28 is located on the outer side in the radial direction of the first belt ply 26.

  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.

  FIG. 2 is an enlarged exploded perspective view showing a part of the belt 12 of the tire 2 of FIG. In FIG. 2, what is indicated by a double arrow A is the circumferential direction of the tire 2. FIG. 2 shows the first belt ply 26 and the second belt ply 28.

  The first belt ply 26 includes a first cord 30 and a topping rubber 32. The first belt ply 26 is obtained by winding a ribbon in a spiral shape. The ribbon includes one or more first cords 30 and a topping rubber 32 extending in the longitudinal direction. The first cord 30 extends substantially in the circumferential direction. The angle of the first cord 30 with respect to the circumferential direction is 5 ° or less, particularly 2 ° or less. The first cord 30 has a so-called jointless structure. The first code 30 contributes to driving performance during straight traveling. The first cord 30 further contributes to stability performance and braking performance during straight traveling. Preferable materials for the first cord 30 include nylon fiber, aramid fiber, polyethylene naphthalate fiber, polyester fiber, rayon fiber, glass fiber, carbon fiber, and steel.

  From the viewpoint of driving performance, the fineness of the first cord 30 is preferably 1500 dtex or more, and particularly preferably 1500/2 dtex or more. From the viewpoint of turning performance, the fineness of the first cord 30 is preferably 1670/3 dtex or less, and particularly preferably 1670/2 dtex or less. From the viewpoint of driving performance, the density of the first cord 30 is preferably 25 ends / 5 cm or more. From the viewpoint of turning performance, the density of the first cord 30 is preferably 70 ends / 5 cm or less.

  The second belt ply 28 includes a second cord 34 and a topping rubber 36. Preferable materials for the first cord 30 include nylon fiber, aramid fiber, polyethylene naphthalate fiber, polyester fiber, rayon fiber, glass fiber, carbon fiber, and steel.

  FIG. 3 is a development view showing the tire 2 of FIG. 1. In FIG. 3, the tread surface 18 is shown. In FIG. 3, the second cord 34 is exposed by cutting out a part of the tread 4. In FIG. 4, one second code 34 is shown. In FIG. 4, the vertical direction is the circumferential direction of the tire 2. As apparent from FIGS. 3 and 4, the planar shape of the second cord 34 is a curved line. In this example, the planar shape of the second cord 34 is substantially an arc. The second cord 34 may have a shape other than an arc. The shape of the second cord 34 is symmetric with respect to the equator CL. The shape of the second cord 34 is convex with respect to the traveling direction of the tire 2. The shape of the second cord 34 may be concave with respect to the traveling direction of the tire 2.

  In FIG. 4, what is indicated by a double arrow α is the angle of the second cord 34 with respect to the circumferential direction. The angle α gradually decreases from the equator CL toward the end 40. In FIG. 4, the angle α at the equator CL is indicated by the symbol α1, and the angle α at the end 40 is indicated by the symbol α2.

  As is apparent from FIG. 4, the angle α1 is 90 °. When traveling straight, the vicinity of the equator CL of the tire 2 is grounded. The second cord 34 having the angle α1 of 90 ° does not reduce the contact area during straight traveling. The second code 34 does not hinder driving performance. The angle α1 may be substantially 90 °. Specifically, the angle α1 is not less than 80 ° and not more than 100 °, particularly not less than 85 ° and not more than 95 °.

  As is apparent from FIG. 4, the angle α2 is smaller than the angle α1. The second cord 34 having a small angle α2 increases the lateral rigidity of the tire 2. At the time of turning, the vicinity (that is, the shoulder) of the end 40 of the second cord 34 is grounded. The second cord 34 having a small angle α2 contributes to the turning performance. From the viewpoint of turning performance, the angle α2 is preferably 50 ° or less, more preferably 40 ° or less, and particularly preferably 35 ° or less. From the viewpoint of turning performance, the angle α2 is preferably 5 ° or more, and more preferably 15 ° or more.

  In order to obtain the tire 2, the carcass ply 24 is first wound around the former in the preforming step. Next, the first belt ply 26 is wound around the carcass 10. Next, a second belt ply 28 having a large number of second cords 34 extending in the axial direction is prepared. Next, only the vicinity of the center of the second belt ply 28 is attached to the first belt ply 26. Next, a tension in the circumferential direction is applied to the end of the second belt ply 28, and the vicinity of the end is attached to the first belt ply 26. Tension can be applied by rotation of the former. Due to this tension, the second cord 34 is curved in an arc shape. The second belt ply 28 having the arc-shaped second cord 34 may be prepared from the beginning.

  In the tire 2, the first belt ply 26 contributes to the driving performance when the vicinity of the equator CL is grounded and travels straight. At this time, the second belt ply 28 does not hinder driving performance. In the tire 2, the second belt ply 28 contributes to rigidity when the shoulder turns and turns. In the tire 2, extremely excellent driving performance and extremely excellent turning performance are compatible.

  From the viewpoint of turning performance, the fineness of the second cord 34 is preferably 1500 dtex or more, and particularly preferably 1500/2 dtex or more. From the viewpoint of driving performance, the fineness of the second cord 34 is preferably 1670/3 dtex or less, and particularly preferably 1670/2 dtex or less. From the viewpoint of turning performance, the density of the second cord 34 is preferably 25 ends / 5 cm or more. From the viewpoint of driving performance, the density of the second cord 34 is preferably 70 ends / 5 cm or less.

  In FIG. 1, the width of the tread 4 is indicated by the arrow Wt, the width of the belt 12 is indicated by the arrow W1, and the second belt ply is indicated by the double arrow W2. 28 width. The width W1 is also the width of the first belt ply 26. The width Wt, the width W1, and the width W2 are measured along the axial direction. From the viewpoint of driving performance, the ratio of the width W1 of the first belt ply 26 to the width Wt of the tread 4 is preferably 80% or more, and more preferably 85% or more. The upper limit of this ratio is 100%. From the viewpoint of turning performance, the ratio of the width W2 of the second belt ply 28 to the width W1 of the first belt ply 26 is preferably 80% or more, and more preferably 85% or more. The upper limit of this ratio is 120%.

  In the present invention, the dimensions and angles 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 the JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “INFLATION PRESSURE” in the 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 radial tire for a motorcycle having the structure shown in FIGS. 1 to 4 was manufactured. The size of this tire is “195 / 50ZR17”. The carcass is provided with a cord made of nylon fiber and having an angle of 90 ° with respect to the circumferential direction. The first belt ply includes a first cord made of aramid fiber and spirally wound. The fineness of the first cord is 1500/2 dtex. The density of the first cord is 50 ends / 5 cm. The second belt ply includes a second cord made of nylon fiber and arranged in an arc shape. The fineness of the second cord is 1400/2 dtex. The density of the second cord is 28 ends / 5 cm. The angle α with respect to the circumferential direction of the second cord gradually decreases from the equator toward the end. The angle α1 at the equator is 90 °, and the angle α2 at the end is 35 °. The ratio of the width W1 to the width Wt is 90%. The ratio of the width W2 to the width W1 is 90%.

[Examples 2 to 5]
Tires of Examples 2 to 5 were obtained in the same manner as Example 1 except that the angle α2 at the end was as shown in Table 1 below.

[Example 6]
A tire of Example 6 was obtained in the same manner as Example 1 except that the material of the second cord was aramid fiber.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that cut plies including cords made of aramid fibers were used as the first belt ply and the second belt ply. The absolute value of the angle of the cord in the first belt ply and the second belt ply with respect to the circumferential direction is 25 °. The direction of inclination of the cord of the first belt ply is opposite to the direction of inclination of the cord of the second belt ply.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1 except that the belt was composed only of the first belt ply in which the cord was spirally wound.

[Comparative Examples 3 and 4]
Tires of Comparative Examples 3 and 4 were obtained in the same manner as in Example 1 except that the belt was composed of the first belt ply and the second belt ply made of cut ply and the third belt ply in which the cord was spirally wound. .

[Comparative Examples 5 and 6]
Tires of Comparative Examples 5 and 6 were obtained in the same manner as in Example 1 except that the belt was composed of the first belt ply and the second belt ply in which the cords were arranged in an arc.

[Running test]
The tires were assembled on a “17 × MT 6.0” rim. The tire was filled with air so that the internal pressure was 290 kPa. The tire and rim were attached as a rear wheel to a motorcycle having a displacement of 1000 cm ³ . A conventional tire having a size of “120 / 70ZR17” was attached to the front wheel. The motorcycle was run on a race circuit course and the lap time was measured. At the same time, the rider was asked to evaluate the driving performance and turning performance. The results are shown in Tables 1 and 2 below. The evaluation values in Tables 1 and 2 are indices when Comparative Example 1 is set to 100. The driving performance and turning performance are preferably larger. The lap time is preferably smaller.

  As shown in Tables 1 and 2, the tire of the example has a shorter lap time than the tire of the comparative example. The reason is that the tires of the examples are excellent in driving performance and turning performance. 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. This tire is particularly suitable for racing motorcycles.

FIG. 1 is a cross-sectional view showing a part of a motorcycle tire according to an embodiment of the present invention. FIG. 2 is an enlarged exploded perspective view showing a part of the belt of the tire of FIG. FIG. 3 is a development view showing the tire of FIG. 1. FIG. 4 is a schematic view showing a second cord of the tire of FIG.

Explanation of symbols

2 ... Tire for motorcycle 4 ... Tread 6 ... Side wall 8 ... Bead 10 ... Carcass 12 ... Belt 14 ... Inner liner 16 ... Chafer 24 ... Carcass ply 26 ... first belt ply 28 ... second belt ply 30 ... first cord 34 ... second cord

Claims (2)

A tread whose outer surface forms a tread surface, a pair of sidewalls extending substantially inward in the radial direction from the end of the tread, a pair of beads positioned radially inward with respect to the sidewall, and a tread and sidewalls A carcass spanned between both beads along the inner side, and a belt laminated with the carcass on the inner side in the radial direction of the tread;
The carcass includes a carcass cord having an angle with respect to the circumferential direction of 40 ° or more and 90 ° or less,
The belt includes a first belt ply and a second belt ply located on the radially outer side of the first belt ply,
The first belt ply includes a first cord wound spirally and extending substantially in the circumferential direction,
The second belt ply includes a second cord whose angle with respect to the circumferential direction gradually decreases from the equator toward the end,
A motorcycle tire in which an angle with respect to a circumferential direction of a second cord on the equator is substantially 90 °, and an angle with respect to a circumferential direction of the second cord at an end is 5 ° or more and 50 ° or less.   The width of the first belt ply is 80% or more and 100% or less of the width of the tread, and the width of the second belt ply is 80% or more and 100% or less of the width of the first belt ply. tire.

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