JP2008087494A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire 2 for a motorcycle, superior in disturbance absorption property and turning stability. <P>SOLUTION: This tire 2 has a tread 4, a belt 12 and a pair of reinforcing layers 14 separately arranged in the axial direction. This belt 12 has a first belt ply 34 and a second belt ply 36 laminated on this first belt ply 34. This first belt ply 34 has a first cord. This first cord is set to 65° to 80° in an absolute value of an angle formed to an equatorial surface. This second belt ply 36 has a second cord substantially spirally wound in the peripheral direction. The ratio of the peripheral length of this reinforcing layer 14 to the peripheral length of this first belt ply 34, is set to 0.3 to 0.4. The thickness of this reinforcing layer 14 is set to 0.5 mm to 1.0 mm. Hardness of this reinforcing layer 14 measured under condition of being 100 °C in the temperature, is set to 30 to 40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

The performance improvement of the vehicle is remarkable, and the improvement of the performance is also demanded for the tire mounted on the vehicle. A motorcycle tire that can achieve both high-speed stability and turning performance is disclosed in Japanese Patent Laid-Open No. 7-108803. In this tire, a rubber layer is provided between the belt layer and the carcass. This rubber layer is made of a rubber composition containing carbon black and short fibers.
JP-A-7-108803

  In the tire of the above publication, the rubber layer is disposed in a region from the center to the shoulder. This tire has high rigidity. This tire is excellent in turning stability. On the other hand, there is a problem that this tire is inferior in disturbance absorption.

  An object of the present invention is to provide a motorcycle tire excellent in disturbance absorption and turning stability.

  The motorcycle tire according to the present invention includes a tread whose outer surface forms a tread surface, a belt positioned radially inward of the tread, and further radially inward of the belt and spaced apart in the axial direction. And a pair of reinforcing layers to be disposed. The belt includes a first belt ply and a second belt ply laminated on the first belt ply. The first belt ply includes a first cord. The absolute value of the angle formed by the first cord with respect to the equator plane is 65 ° or more and 80 ° or less. The second belt ply includes a second cord that is spirally wound substantially along the circumferential direction. The ratio of the circumferential length of the reinforcing layer to the circumferential length of the first belt ply is 0.3 or more and 0.4 or less. The thickness of this reinforcing layer is 0.5 mm or greater and 1.0 mm or less. The hardness of the reinforcing layer measured at a temperature of 100 ° C. is 30 or more and 40 or less.

  Preferably, in this tire, the complex elastic modulus of the reinforcing layer is 3.5 MPa or more and 4.0 MPa or less. The loss coefficient of this reinforcing layer is 0.05 or more and 0.12 or less.

  The tire includes a pair of reinforcing layers that are located on the inner side in the radial direction of the belt and are spaced apart in the axial direction. This reinforcing layer can contribute to the rigidity of the shoulder of the tire. This tire is excellent in turning stability. In this tire, the width, thickness and hardness of the reinforcing layer are adjusted to optimize the contribution of the reinforcing layer to the tire stiffness. Therefore, this tire is also excellent in disturbance absorption.

  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, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. 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, a reinforcing layer 14, an inner liner 16 and a chafer 18. The tire 2 is a tubeless type. The tire 2 is a pneumatic tire mainly used for racing.

  The tread 4 is made of a crosslinked rubber having excellent wear resistance. The tread 4 has a shape protruding outward in the radial direction. The outer surface of the tread 4 forms a tread surface 20. The tread surface 20 is in contact with the road surface. In the tire 2, no groove is formed in the tread surface 20. The tire 2 is a slick tire. In addition, a groove may be engraved on the tread surface 20 to form a tread pattern.

  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 substantially inward of the sidewall 6 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. The core 22 includes a plurality of non-stretchable wires (typically steel wires). The apex 24 is tapered outward in the radial direction. The apex 24 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a first carcass ply 26 and a second carcass ply 28. The first carcass ply 26 and the second carcass ply 28 are spanned between the beads 8 on both sides, and are along the inside of the tread 4 and the sidewall 6. The first carcass ply 26 is folded around the core 22 from the inner side to the outer side in the axial direction. The second carcass ply 28 is located outside the first carcass ply 26. The second carcass ply 28 is not folded back around the core 22. The end 30 of the second carcass ply 28 is connected to the tip 32 of the apex 24. The end 30 is located on the inner side in the axial direction of the first carcass ply 26 folded back by the core 22.

  Although not shown in figure, the 1st carcass ply 26 and the 2nd carcass ply 28 consist of many parallel cords and topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 10 having a bias structure may be employed.

  The belt 12 is located on the inner side in the radial direction of the tread 4. The belt 12 is located outside the carcass 10 in the radial direction. The belt 12 reinforces the carcass 10. The belt 12 includes a first belt ply 34 and a second belt ply 36. The second belt ply 36 is laminated on the first belt ply 34. In the tire 2, the second belt ply 36 is located outside the first belt ply 34. In the tire 2, the axial width of the second belt ply 36 is wider than the axial width of the first belt ply 34. The second belt ply 36 covers the first belt ply 34.

  Although not shown, the first belt ply 34 is composed of a plurality of first cords arranged in parallel and a topping rubber. The first cord is inclined with respect to the equator plane. The absolute value of the angle formed by the first cord with respect to the equator plane is 65 ° or more and 80 ° or less. Examples of preferable materials for the first cord include steel and organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  Although not shown, the second belt ply 36 includes a second cord and a topping rubber. The second cord is spirally wound substantially along the circumferential direction. The carcass 10 and the first belt ply 34 are restrained by the second cord. The tire 2 is excellent in straight running stability during high speed running. The absolute value of the angle formed by the second cord with respect to the equator plane is 5 ° or less, particularly 2 ° or less. In the present invention, the direction in which the absolute value of the angle formed with respect to the equator plane is 5.0 ° or less is the “substantially circumferential direction”. The belt 12 has a so-called jointless structure. Examples of the material of the second cord include nylon fiber, aramid fiber, polyethylene naphthalate fiber, polyester fiber, rayon fiber, glass fiber, carbon fiber, and steel. The second cord having a high elastic modulus and high strength contributes to the straight running stability of the tire 2. From this viewpoint, as the second cord, aramid fiber and steel are particularly preferable. From the viewpoint of reducing the weight of the tire, the aramid fiber is particularly preferable as the second cord.

  The inner liner 16 is joined to the inner peripheral surface of the carcass 10. 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 chafer 18 is located in the vicinity of the bead 8. When the tire 2 is incorporated into the rim, the chafer 18 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected. The chafer 18 is usually made of cloth and rubber impregnated in the cloth. A chafer made of a single rubber may be used.

  The reinforcing layer 14 is located on the inner side in the radial direction of the belt 12. The reinforcing layer 14 is located on the radially outer side of the carcass 10. The reinforcing layer 14 is located between the caste and the belt 12. The left and right reinforcing layers 14 are spaced apart in the axial direction. The reinforcing layer 14 is located on the shoulder 38. The outer end 40 of the reinforcing layer 14 coincides with the end 42 of the first belt ply 34. The outer end 40 of the reinforcing layer 14 is located inside the end 42 of the first belt ply 34 in the axial direction.

  When turning, the rider tilts the motorcycle inward. Therefore, when turning (particularly full bank), the tread surface 20 located on the shoulder 38 side is mainly grounded. As described above, the reinforcing layer 14 is disposed on the shoulder 38 of the tire 2. The reinforcing layer 14 increases the rigidity of the shoulder 38 of the tire 2. In the tire 2, the reinforcing layer 14 contributes to the grip force during turning. The tire 2 is excellent in turning stability.

  When traveling straight, the tread surface 20 located at the center 44 of the tire 2 is grounded. In the tire 2, the reinforcing layer 14 is not provided at the center 44. In the tire 2, the rigidity at the center 44 is low. The tire 2 is excellent in disturbance absorption during straight traveling.

  In the tire 2, as will be described later, the width, thickness, and hardness of the reinforcing layer 14 are adjusted, and the contribution of the reinforcing layer 14 to the tire stiffness is optimized. The tire 2 is excellent in disturbance absorption without impairing turning stability. The tire 2 is excellent in ride comfort.

  In FIG. 1, the double arrow line L0 is the circumferential length of the first belt ply 34. The double arrow line L1 is the circumferential length of the reinforcing layer 14. A double arrow line TA represents the thickness of the reinforcing layer 14.

  In the tire 2, the ratio of the circumferential length L1 to the circumferential length L0 is 0.3 or more and 0.4 or less. The rigidity of the shoulder 38 of the tire 2 in which this ratio is set to 0.3 or more is high. The tire 2 is excellent in turning stability. In this respect, the ratio is more preferably equal to or greater than 0.32, and particularly preferably equal to or greater than 0.34. By setting this ratio to 0.4 or less, excessive rigidity of the tire 2 can be suppressed. The tire 2 can maintain disturbance absorption. In this respect, the ratio is more preferably equal to or less than 0.38, and particularly preferably equal to or less than 0.36.

  The rigidity of the tire 2 depends on the thickness TA of the reinforcing layer 14. As described above, the reinforcing layer 14 is located on the shoulder 38. Therefore, the tire 2 having a large thickness of the reinforcing layer 14 has high rigidity at the shoulder 38. The tire 2 is excellent in turning stability. From this viewpoint, this thickness is 0.5 mm or more. The tire 2 having an excessive thickness of the reinforcing layer 14 is inferior in disturbance absorption. From this viewpoint, the thickness is 1.0 mm or less.

  In the tire 2, the hardness (durometer A hardness) measured under the condition that the temperature is 100 ° C. of the reinforcing layer 14 is 30 or more and 40 or less. The reinforcing layer 14 having the hardness set to 30 or more appropriately increases the rigidity of the tire 2. The tire 2 is excellent in turning stability. From this viewpoint, the hardness is more preferably 32 or more, and particularly preferably 34 or more. By setting the hardness to 40 or less, excessive rigidity of the tire 2 can be suppressed. The tire 2 can maintain disturbance absorption. In this respect, the hardness is more preferably equal to or less than 38, and particularly preferably equal to or less than 36. In addition, it is preferable that the hardness (type A durometer) of this reinforcement layer 14 measured on the conditions whose temperature is 25 degreeC is 65-75.

  In the present invention, the hardness is measured by a type A durometer according to JIS-K6253. This hardness is measured by stacking three sheet-like test pieces having a thickness of 1.0 mm cut out from the tire 2. This hardness is measured under conditions where the temperature is 25 ° C. and 100 ° C. When the hardness is measured at 100 ° C., the test piece is held in an environment of 100 ° C. for 2 hours or more prior to measurement. For this measurement, a test piece formed by crosslinking the rubber composition may be used. In this case, this test piece is obtained by holding the rubber composition in a mold having a temperature of 160 ° C. for 10 minutes.

  In the tire 2, the complex elastic modulus (E *) of the reinforcing layer 14 is preferably 3.5 MPa or more and 4.0 MPa or less. The reinforcing layer 14 having the complex elastic modulus set to 3.5 MPa or more appropriately increases the rigidity of the tire 2. The tire 2 is excellent in turning stability. In this respect, the complex elastic modulus is more preferably equal to or greater than 3.6 MPa. By setting the complex elastic modulus to 4.0 MPa or less, excessive rigidity of the tire 2 can be suppressed. The tire 2 can maintain disturbance absorption. From this viewpoint, the complex elastic modulus is preferably 3.9 MPa or less.

  In the tire 2, the loss coefficient (tan δ) of the reinforcing layer 14 is preferably 0.05 or more and 0.12 or less. By setting the loss factor to be 0.05 or more, the reinforcing layer 14 can effectively contribute to disturbance absorption. In this respect, the loss factor is more preferably 0.06 or more, and particularly preferably 0.07 or more. By setting the loss factor to 0.12 or less, the reinforcing layer 14 can effectively contribute to the turning stability. From this viewpoint, the loss factor is more preferably 0.11 or less, and particularly preferably 0.10 or less.

In the present invention, the complex elastic modulus and loss factor of the reinforcing layer 14 are based on viscoelasticity spectrometer (“VES · F−” of Iwamoto Seisakusho Co., Ltd.) under the conditions shown below in accordance with the provisions of “JIS-K 6394”. Type 3 ").
Initial strain: 10%
Amplitude: 2%
Frequency: 10Hz
Deformation mode: Tensile
Starting temperature: -100 ° C
End temperature: 100 ° C
Temperature rising temperature: 3 ° C / min
Measurement temperature: 70 ° C

  The test piece used for the measurement by a viscoelastic spectrometer is plate shape, the length is 45 mm, the width is 4 mm, and the thickness is 2 mm. Measurement is performed by chucking both ends of the test piece. The length of the displacement part of the test piece is 30 mm. This test piece is cut out from the tire 2.

  In the tire 2, the reinforcing layer 14 is formed by crosslinking a rubber composition containing a base rubber, carbon black as a filler, and a softening agent. The reinforcing layer 14 is a crosslinked rubber. This rubber composition contains chemicals such as a crosslinking agent, a vulcanization accelerator, and an anti-aging agent in addition to the base rubber, carbon black and softening agent. In consideration of the workability and performance of the tire 2, an optimal chemical is blended in the rubber composition in an optimal amount. In the tire 2, the carbon black is a seast 3 manufactured by Tokai Carbon Corporation. The softener is X140 manufactured by Japan Energy Corporation. In the tire 2, the rubber composition constituting the reinforcing layer 14 does not contain short fibers.

  As the base rubber of the reinforcing layer 14, natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene copolymer, polychloroprene, acrylonitrile-butadiene copolymer, and isobutylene-isoprene copolymer are used. Is exemplified. In the tire 2, the base rubber of the reinforcing layer 14 is preferably made of natural rubber and a styrene-butadiene copolymer. Particularly preferably, the base rubber is blended so that the blend ratio of natural rubber and styrene-butadiene copolymer ((natural rubber) / (styrene-butadiene copolymer)) is 70/30. It is constituted by. In the tire 2, the natural rubber is RSS # 3. This styrene-butadiene copolymer is JSR1502 manufactured by Nippon Synthetic Rubber Co., Ltd.

  In the tire 2, the hardness, the complex elastic modulus, and the loss coefficient of the reinforcing layer 14 are adjusted by optimizing the amounts of carbon black and softening agent.

  In the tire 2, the amount of carbon black contained in the rubber composition constituting the reinforcing layer 14 is preferably 30 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of the base rubber. The reinforcing layer 14 whose blending amount is set to 30 parts by mass or more is highly rigid. The tire 2 provided with the reinforcing layer 14 is excellent in turning stability. In this respect, the amount is more preferably equal to or greater than 35 parts by weight, and particularly preferably equal to or greater than 40 parts by weight. By setting the blending amount to 55 parts by mass or less, the rigidity of the reinforcing layer 14 can be appropriately maintained. In the tire 2, disturbance absorbability can be maintained. In this respect, the amount is more preferably equal to or less than 50 parts by weight, and particularly preferably equal to or less than 45 parts by weight.

  In the tire 2, the blending amount of the softening agent contained in the rubber composition constituting the reinforcing layer 14 is preferably 15 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the base rubber. By setting the blending amount to 15 parts by mass or more, excessive rigidity of the reinforcing layer 14 can be prevented. The tire 2 can maintain disturbance absorption. In the production of the rubber composition, good processability can be maintained. In this respect, the amount is more preferably equal to or greater than 20 parts by weight. By setting the blending amount to 30 parts by mass or less, the rigidity of the reinforcing layer 14 can be appropriately maintained. The tire 2 is excellent in turning stability. In this respect, the amount is more preferably equal to or less than 25 parts by mass.

  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.

  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.

[Adjustment of rubber composition A]
70 parts by mass of natural rubber, 30 parts by mass of a styrene-butadiene copolymer, 65 parts by mass of carbon black and 10 parts by mass of a softening agent were kneaded in a closed kneader to obtain a rubber composition A. . The natural rubber is RSS # 3. The styrene-butadiene copolymer is JSR1502 manufactured by Nippon Synthetic Rubber Co., Ltd. Carbon black is a seast 3 made by Tokai Carbon Co., Ltd. The softener is X140 manufactured by Japan Energy Corporation. The reinforcing layer obtained by crosslinking the rubber composition A has a hardness measured under conditions where the temperature is 100 ° C. and a complex elastic modulus and a loss coefficient measured under conditions where the temperature is 70 ° C. It was measured. The measurement results are shown in Table 1 below.

[Adjustment of rubber compositions B, C, D and E]
Rubber compositions B, C, D and E were obtained in the same manner as the rubber composition A, except that the blending amounts of carbon black and softener were as shown in Table 1 below.

[Example 1]
A motorcycle tire of Example 1 having the basic configuration shown in FIG. 1 and having the specifications shown in Table 2 below was obtained. The first cord of the first belt ply is made of an aramid fiber. The absolute value of the angle formed by the first cord with respect to the equator plane is 70 °. The second cord of the second belt ply is made of an aramid fiber. The absolute value of the angle formed by the second cord with respect to the equator plane is 0 °. The reinforcing layer is formed by crosslinking the rubber composition D. The thickness TA of this reinforcing layer is 0.5 mm. A ratio L1 / L0 of the circumferential length L1 of the reinforcing layer to the circumferential length L0 of the first belt ply is 0.35. The hardness of the reinforcing layer measured at a temperature of 100 ° C. is 35. The complex elastic modulus measured under the condition where the temperature is 70 ° C. is 4 MPa. The loss factor measured under conditions where the temperature is 70 ° C. is 0.06.

[Comparative Examples 4 and 5 and Example 4]
Tires were obtained in the same manner as in Example 1 except that the ratio L1 / L0 was as shown in Tables 2 and 3 below.

[Comparative Examples 1, 2, and 3 and Examples 2, 3, and 5]
A tire was obtained in the same manner as in Example 1 except that the rubber composition constituting the reinforcing layer and the ratio L1 / L0 were as shown in Tables 2 and 3 below.

[Comparative Examples 11 and 12 and Example 9]
A tire was obtained in the same manner as in Example 1 except that the thickness TA of the reinforcing layer was as shown in Table 4 below.

[Comparative Examples 9 and 10 and Example 8]
A tire was obtained in the same manner as in Example 1 except that the thickness TA and the ratio L1 / L0 of the reinforcing layer were as shown in Tables 3 and 4 below.

[Comparative Examples 6, 7, and 8 and Examples 6, 7, and 10]
A tire was obtained in the same manner as in Example 1 except that the rubber composition constituting the reinforcing layer, the thickness TA of the reinforcing layer, and the ratio L1 / L0 were as shown in Tables 3 and 4 below.

[Comparative Example 13]
It is a conventional tire that is commercially available. This tire is not provided with a reinforcing layer.

[Real car evaluation]
Prototype tires were mounted on the rear wheels of a super sports car (4-cylinder) with a displacement of 1000 cm ³ . The tire size for the rear wheels is 200 / 65R420. The rim is MT 6.25 × 420. The air pressure inside the tire is 170 kPa. Commercial tires are mounted on the front wheels. The tire size for the front wheels is 125 / 80R420. The rim is MT3.50 × 420. The tire air pressure is 200 kPa. Riders performed sensory evaluations by running on a circuit course (international course) composed of dry asphalt roads. The number of laps of the course is 10 laps. Evaluation items are braking, disturbance absorption, traction performance, and turning stability. The average value of the data regarding these items is described as an actual vehicle score. A score of 10 is a perfect score, and the larger this value, the better. The evaluation results are shown in Table 2, Table 3, and Table 4.

  As shown in Tables 2, 3 and 4, the tires of the examples are excellent in disturbance absorption and turning stability. 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 showing a part of a motorcycle tire according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Tire 4 ... Tread 6 ... Side wall 8 ... Bead 10 ... Carcass 12 ... Belt 14 ... Reinforcement layer 16 ... Inner liner 18 ... Chafer 20 ... Tread surface 22 ... Core 24 ... Apex 26 ... First carcass ply 28 ... Second carcass ply 30, 42 ... End 32 ... Tip 34 ... First Belt ply 36 ... Second belt ply 38 ... Shoulder 40 ... Outer end 44 ... Center

Claims (2)

A tread whose outer surface forms a tread surface, a belt positioned radially inward of the tread, and a pair of reinforcing layers positioned further radially inward of the belt and spaced apart in the axial direction And
The belt includes a first belt ply and a second belt ply laminated on the first belt ply,
This first belt ply has a first cord,
The absolute value of the angle formed by the first cord with respect to the equator plane is 65 ° or more and 80 ° or less,
The second belt ply includes a second cord spirally wound substantially along the circumferential direction,
The ratio of the circumference of the reinforcing layer to the circumference of the first belt ply is 0.3 or more and 0.4 or less,
The thickness of this reinforcing layer is 0.5 mm or more and 1.0 mm or less,
A tire for a motorcycle, wherein the hardness of the reinforcing layer measured at 100 ° C is not less than 30 and not more than 40. The complex elastic modulus of the reinforcing layer is 3.5 MPa or more and 4.0 MPa or less,
The tire according to claim 1, wherein a loss coefficient of the reinforcing layer is 0.05 or more and 0.12 or less.

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